diff --git a/.claude/loopspec/sketch-focus-arbiter.spec.md b/.claude/loopspec/sketch-focus-arbiter.spec.md
new file mode 100644
index 0000000000..f0c1287307
--- /dev/null
+++ b/.claude/loopspec/sketch-focus-arbiter.spec.md
@@ -0,0 +1,86 @@
+# DELEGATION SPECIFICATION: HARNESS-DRIVEN VALIDATION LOOP
+slug: sketch-focus-arbiter · repo: /home/tommaso/projects/apps/orca_cad · branch: cad-mainline
+
+## 1. TARGET GOAL
+
+**Functional Objective.** Keyboard input in the Design tab is routed by WHAT THE KEY IS, not by
+which widget the window manager decided to focus. Adopted from FreeCAD's
+`DrawSketchKeyboardManager::detectKeyboardEventHandlingMode`
+(src/Mod/Sketcher/Gui/DrawSketchKeyboardManager.cpp), which never queries focus at all:
+
+  - digit, `-`, `.`, `,`  -> the open value field
+  - Backspace / Delete    -> the open value field (when one is open)
+  - Enter / Return / Tab  -> commit the field, control returns to the view
+  - a letter              -> the sketch-tool shortcut map, as today
+  - Esc                   -> the existing CadLevel LIFO (DesignInteraction.hpp), unchanged
+  - anything else         -> sticky: whoever had it keeps it
+
+Observable postcondition: for EVERY sketch tool that opens a value field, a value typed
+immediately after the field appears — with NO click into the field — is the value committed.
+Today the prefill is committed instead whenever the WM withholds focus.
+
+**Target Files / Scope (writable).**
+  src/slic3r/GUI/CAD/DesignPanel.cpp        (the arbiter lives in the existing wxEVT_CHAR_HOOK)
+  src/slic3r/GUI/CAD/DesignCanvas.cpp/.hpp  (forwarding entry points only)
+  src/slic3r/GUI/CAD/SketchInlineEditor.cpp/.hpp (accept a programmatically delivered character)
+  scripts/CAD/check-gui-click-edit.py       (F2P oracle — authoring exception, see §4)
+Everything else read-only. No dependency additions, no reformatting.
+
+**Open Bindings.**
+  - The in-canvas ImGui field on wip/in-canvas-value-field is NOT in scope. Default: the arbiter
+    is implemented against the CURRENT wxFrame field on cad-mainline, because content-based
+    routing makes the window's focus irrelevant either way. If it later moves in-canvas the
+    arbiter is unchanged.
+  - Tools whose field is opened by a toolbar button rather than a gesture (Constrain path) are
+    covered by the same arbiter but are not in the F2P tool list. Default: assert them in P2P only.
+
+## 2. HARNESS ENVIRONMENT & GROUND TRUTH
+
+The rig container `orcacad-gui` on nativedev IS the harness. Xvfb `:11` + openbox, the app under
+test, `xdotool` for synthetic input, and an MCP socket at `/tmp/mcp.sock` that reports sketch
+state as JSON. It is a closed loop: drive input, read geometry back, assert. No window manager
+politics, no human.
+
+  Harness interface (ordered; each slot one invocation, one exit code):
+    S1 sync    docker cp <file> orcacad-gui:/OrcaSlicer/<path>
+    S2 build   docker exec orcacad-gui ninja -C /OrcaSlicer/build orca-slicer
+    S3 restart docker exec orcacad-gui /OrcaSlicer/scripts/CAD/start-headless-gui.sh
+    S4 F2P     docker exec -e DISPLAY=:11 orcacad-gui python3 /tmp/check-gui-click-edit.py --attach
+    S5 P2P     docker exec -e DISPLAY=:11 orcacad-gui python3 /tmp/check-gui-sketching.py
+
+**F2P.** `scripts/CAD/check-gui-click-edit.py`. For each of Line, Rectangle, Circle, Slot,
+Polygon, Ellipse and Rounded rectangle: arm the tool, draw it, and type a value that differs
+from the prefill WITHOUT clicking the field. Assert the committed value equals the typed value.
+The ladder must FAIL against unmodified cad-mainline — that is what proves it asserts something.
+
+**P2P.** `scripts/CAD/check-gui-sketching.py`, the existing gesture ladder, minus anything red at
+baseline. NOTE: it calls `focus_field()` — one click into the field before typing — which is the
+workaround this whole task removes. It stays green as a regression guard; it is NOT evidence.
+
+**Test Integrity Constraint.** `focus_field()` in check-gui-sketching.py must NOT be deleted to
+make things pass, and check-gui-click-edit.py must NOT be weakened. Either invalidates the run.
+
+## 3. VERIFICATION COMMANDS
+1. Static: `docker exec orcacad-gui ninja -C /OrcaSlicer/build orca-slicer` (warnings delta only;
+   this repo configures no linter — the compiler is the static gate. Absolute-zero is NOT the gate.)
+2. Harness: `docker exec -e DISPLAY=:11 orcacad-gui python3 /tmp/check-gui-click-edit.py --attach`
+3. Regression: `docker exec -e DISPLAY=:11 orcacad-gui python3 /tmp/check-gui-sketching.py`
+
+## 4. CONVERGENCE LOOP — ceiling 8 iterations
+EDIT (scoped) -> EXECUTE S1..S5 -> PARSE the ladder's per-tool assertions and the [UX]/[KEYTRACE]
+lines -> PATCH from the parsed cause. On ceiling without convergence: stop, report the last diff
+and the unresolved failure set. Do not report success.
+
+F2P authoring exception: check-gui-click-edit.py is writable, and must be shown RED against
+unmodified source before any source edit counts.
+
+## 5. TERMINATION CRITERIA
+- [ ] S2 exits 0, and introduces no compiler warning absent from the baseline.
+- [ ] S4 ALL_PASSED — every tool commits the typed value, no click into the field.
+- [ ] S5 shows zero regressions against its recorded baseline pass count.
+- [ ] F2P proven red without the fix (source stashed, ladder re-run, must FAIL).
+
+## 6. GUARDRAILS
+Zero-assumption: no completion claim without captured stdout and exit codes. Oracle supremacy:
+the ladder's verdict overrides my judgement. Blast radius: §1 files only. Baseline obligation:
+run §3 once before the first edit and record it.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6e713d8c88..e3547281f0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -107,6 +107,7 @@ endif()
 
 option(SLIC3R_STATIC            "Compile OrcaSlicer with static libraries (Boost, TBB)" ${SLIC3R_STATIC_INITIAL})
 option(SLIC3R_GUI               "Compile OrcaSlicer with GUI components (OpenGL, wxWidgets)" 1)
+option(SLIC3R_CAD               "Compile OrcaSlicer with the parametric Design/CAD tab (needs OCCT ModelingAlgorithms)" 1)
 option(SLIC3R_FHS               "Assume OrcaSlicer is to be installed in a FHS directory structure" 0)
 option(SLIC3R_PROFILE           "Compile OrcaSlicer with an invasive Shiny profiler" 0)
 option(SLIC3R_PCH               "Use precompiled headers" 1)
@@ -308,6 +309,10 @@ if (SLIC3R_GUI)
     add_definitions(-DSLIC3R_GUI)
 endif ()
 
+if (SLIC3R_CAD)
+    add_definitions(-DSLIC3R_CAD)
+endif ()
+
 if(SLIC3R_DESKTOP_INTEGRATION)
     add_definitions(-DSLIC3R_DESKTOP_INTEGRATION)
 endif ()
@@ -1076,32 +1081,30 @@ function(orcaslicer_copy_dlls target config postfix output_dlls)
             ${TOP_LEVEL_PROJECT_DIR}/deps/WebView2/lib/win-${_arch}/WebView2Loader.dll
         DESTINATION ${_out_dir})
 
-    file(COPY ${CMAKE_PREFIX_PATH}/bin/occt/TKBO.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKBRep.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKCAF.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKCDF.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKernel.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKG2d.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKG3d.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKGeomAlgo.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKGeomBase.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKHLR.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKLCAF.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKMath.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKMesh.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKPrim.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKService.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKShHealing.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKSTEP.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKSTEP209.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKSTEPAttr.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKSTEPBase.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKTopAlgo.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKV3d.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKVCAF.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKXCAF.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKXDESTEP.dll
-            ${CMAKE_PREFIX_PATH}/bin/occt/TKXSBase.dll
+    # Stage the OCCT toolkits libslic3r links (published as OCCT_LIBS), not whatever the
+    # deps prefix happens to hold, and fail the configure if one of them is missing.
+    if (NOT OCCT_LIBS)
+        message(FATAL_ERROR "OCCT_LIBS is not set; libslic3r must be configured first.")
+    endif ()
+    set(_occt_bin "${CMAKE_PREFIX_PATH}/bin/occt")
+    set(_occt_dlls "")
+    set(_occt_staged "")
+    set(_missing_occt "")
+    foreach (_tk IN LISTS OCCT_LIBS)
+        if (EXISTS "${_occt_bin}/${_tk}.dll")
+            list(APPEND _occt_dlls "${_occt_bin}/${_tk}.dll")
+            list(APPEND _occt_staged "${_out_dir}/${_tk}.dll")
+        else ()
+            list(APPEND _missing_occt "${_tk}.dll")
+        endif ()
+    endforeach ()
+    if (_missing_occt)
+        message(FATAL_ERROR
+            "OCCT DLLs missing from ${_occt_bin}/: ${_missing_occt}\n"
+            "Rebuild the dependencies (build_release_vs2022.bat deps) with the same "
+            "SLIC3R_CAD setting as this project.")
+    endif ()
+    file(COPY ${_occt_dlls}
             ${CMAKE_PREFIX_PATH}/bin/freetype.dll
             ${CMAKE_PREFIX_PATH}/bin/avcodec-61.dll
             ${CMAKE_PREFIX_PATH}/bin/swresample-5.dll
@@ -1109,38 +1112,11 @@ function(orcaslicer_copy_dlls target config postfix output_dlls)
             ${CMAKE_PREFIX_PATH}/bin/avutil-59.dll
          DESTINATION ${_out_dir})
 
-    set(${output_dlls}
+    set(_dll_list
         ${_out_dir}/libgmp-10.dll
         ${_out_dir}/libmpfr-4.dll
         ${_out_dir}/WebView2Loader.dll
 
-        ${_out_dir}/TKBO.dll
-        ${_out_dir}/TKBRep.dll
-        ${_out_dir}/TKCAF.dll
-        ${_out_dir}/TKCDF.dll
-        ${_out_dir}/TKernel.dll
-        ${_out_dir}/TKG2d.dll
-        ${_out_dir}/TKG3d.dll
-        ${_out_dir}/TKGeomAlgo.dll
-        ${_out_dir}/TKGeomBase.dll
-        ${_out_dir}/TKHLR.dll
-        ${_out_dir}/TKLCAF.dll
-        ${_out_dir}/TKMath.dll
-        ${_out_dir}/TKMesh.dll
-        ${_out_dir}/TKPrim.dll
-        ${_out_dir}/TKService.dll
-        ${_out_dir}/TKShHealing.dll
-        ${_out_dir}/TKSTEP.dll
-        ${_out_dir}/TKSTEP209.dll
-        ${_out_dir}/TKSTEPAttr.dll
-        ${_out_dir}/TKSTEPBase.dll
-        ${_out_dir}/TKTopAlgo.dll
-        ${_out_dir}/TKV3d.dll
-        ${_out_dir}/TKVCAF.dll
-        ${_out_dir}/TKXCAF.dll
-        ${_out_dir}/TKXDESTEP.dll
-        ${_out_dir}/TKXSBase.dll
-
         ${_out_dir}/freetype.dll
         ${_out_dir}/avcodec-61.dll
         ${_out_dir}/swresample-5.dll
@@ -1148,6 +1124,8 @@ function(orcaslicer_copy_dlls target config postfix output_dlls)
         ${_out_dir}/avutil-59.dll
         PARENT_SCOPE
     )
+    list(APPEND _dll_list ${_occt_staged})
+    set(${output_dlls} ${_dll_list} PARENT_SCOPE)
 
 endfunction()
 
diff --git a/deps/CMakeLists.txt b/deps/CMakeLists.txt
index 4b1daf5aa8..e02186705b 100644
--- a/deps/CMakeLists.txt
+++ b/deps/CMakeLists.txt
@@ -55,6 +55,7 @@ endif ()
 
 set(DEP_DOWNLOAD_DIR ${CMAKE_CURRENT_SOURCE_DIR}/DL_CACHE CACHE PATH "Path for downloaded source packages.")
 set(FLATPAK FALSE CACHE BOOL "Toggles various build settings for flatpak, like /usr/local in DESTDIR or not building wxwidgets")
+option(SLIC3R_CAD "Build the SolveSpace solver and OCCT ModelingAlgorithms module the parametric Design/CAD tab needs. Must match the main project's SLIC3R_CAD." ON)
 
 if ("${DESTDIR}" STREQUAL "" OR "${DESTDIR}" STREQUAL "${AUTOGENERATED_DESTDIR}")
     if (LINUX AND (NOT DEFINED USE_OLD_DESTDIR_PREV OR USE_OLD_DESTDIR_PREV) AND EXISTS "${CMAKE_BINARY_DIR}/destdir/usr/local" AND NOT EXISTS "${CMAKE_BINARY_DIR}/OrcaSlicer_dep/usr/local")
@@ -363,6 +364,11 @@ include(GLEW/GLEW.cmake)
 
 include(GLFW/GLFW.cmake)
 include(OpenCSG/OpenCSG.cmake)
+set(SLVS_PKG "")
+if (SLIC3R_CAD)
+    include(SLVS/SLVS.cmake)
+    set(SLVS_PKG dep_SLVS)
+endif ()
 
 include(TBB/TBB.cmake)
 
@@ -452,6 +458,7 @@ set(_dep_list
     dep_NLopt
     dep_OpenVDB
     dep_OpenCSG
+    ${SLVS_PKG}
     dep_OpenCV
     dep_Eigen
     dep_CGAL
diff --git a/deps/OCCT/OCCT.cmake b/deps/OCCT/OCCT.cmake
index 62bfcf8e76..45263d6ae3 100644
--- a/deps/OCCT/OCCT.cmake
+++ b/deps/OCCT/OCCT.cmake
@@ -11,6 +11,21 @@ else()
     set(library_build_type "Static")
 endif()
 
+# SLIC3R_CAD (declared in deps/CMakeLists.txt) builds OCCT's ModelingAlgorithms module
+# (fillet/offset/loft), whose only consumer is the parametric Design/CAD tab. With it OFF
+# the deps prefix matches upstream exactly.
+#
+# With it ON the delta is THREE toolkits, not two: TKFillet (7.40 MiB archive, used via
+# BRepFilletAPI), TKOffset (5.38 MiB, used via BRepOffsetAPI) and TKFeat (4.42 MiB), which
+# nothing here references but which the module flag builds anyway -- it is all-or-nothing
+# per module. The module's other nine toolkits are built either way, because DataExchange
+# (the STEP path upstream already ships) depends on them.
+#
+# On macOS/Linux OCCT links statically, so an unreferenced toolkit costs build time and no
+# shipped bytes. The Windows figure is a real DLL cost and has NOT been measured -- an
+# earlier "3.77 MiB, Windows only" note here covered only two of the three toolkits and is
+# not a number to quote. See docs/cad_dependency_weight.md.
+
 if (IN_GIT_REPO)
     set(OCCT_DIRECTORY_FLAG --directory ${BINARY_DIR_REL}/dep_OCCT-prefix/src/dep_OCCT)
 endif ()
@@ -35,7 +50,7 @@ orcaslicer_add_cmake_project(OCCT
         #-DBUILD_MODULE_DataExchange=OFF
         -DBUILD_MODULE_Draw=OFF
         -DBUILD_MODULE_FoundationClasses=OFF
-        -DBUILD_MODULE_ModelingAlgorithms=OFF
+        -DBUILD_MODULE_ModelingAlgorithms=${SLIC3R_CAD}
         -DBUILD_MODULE_ModelingData=OFF
         -DBUILD_MODULE_Visualization=OFF
         ${_occt_compiler_args}
diff --git a/deps/SLVS/CMakeLists.txt.in b/deps/SLVS/CMakeLists.txt.in
new file mode 100644
index 0000000000..b09ad8da98
--- /dev/null
+++ b/deps/SLVS/CMakeLists.txt.in
@@ -0,0 +1,65 @@
+# Replaces the upstream SolveSpaceLib CMakeLists, which builds a demo executable and
+# has no install rules. The sources themselves are used verbatim.
+cmake_minimum_required(VERSION 3.13)
+
+project(SLVS VERSION 3.0)
+
+add_library(slvs
+    libslvs/constrainteq.cpp
+    libslvs/entity.cpp
+    libslvs/expr.cpp
+    libslvs/system.cpp
+    libslvs/util.cpp
+    libslvs/platform/unixutil.cpp
+    libslvs/lib.cpp
+    libslvs/SolveSpaceSystem.cpp)
+
+target_compile_features(slvs PUBLIC cxx_std_11)
+
+# LIBRARY strips the solver core out of the SolveSpace application it was extracted from.
+target_compile_definitions(slvs PRIVATE -DLIBRARY)
+if (MSVC)
+    target_compile_definitions(slvs PRIVATE -D_CRT_SECURE_NO_WARNINGS -D_SCL_SECURE_NO_WARNINGS)
+endif ()
+
+target_include_directories(slvs
+    PUBLIC  $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/libslvs/include>
+    PRIVATE ${PROJECT_SOURCE_DIR}/libslvs)
+
+# libslic3r is linked into shared targets, so this has to be position independent.
+set_target_properties(slvs PROPERTIES POSITION_INDEPENDENT_CODE ON)
+
+# 2018 code, predating the project's warning settings; it is not ours to clean up.
+if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    target_compile_options(slvs PRIVATE -w -fno-strict-aliasing)
+endif ()
+
+include(CMakePackageConfigHelpers)
+include(GNUInstallDirs)
+
+write_basic_package_version_file(
+    "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake"
+    VERSION ${PROJECT_VERSION}
+    COMPATIBILITY AnyNewerVersion)
+
+install(TARGETS slvs
+    EXPORT ${PROJECT_NAME}Targets
+    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    INCLUDES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+
+set(ConfigPackageLocation ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})
+
+install(EXPORT ${PROJECT_NAME}Targets
+    FILE "${PROJECT_NAME}Config.cmake"
+    NAMESPACE ${PROJECT_NAME}::
+    DESTINATION ${ConfigPackageLocation})
+
+install(FILES
+        ${PROJECT_SOURCE_DIR}/libslvs/include/slvs.h
+        ${PROJECT_SOURCE_DIR}/libslvs/include/SolveSpaceSystem.h
+    DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+
+install(FILES "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake"
+    DESTINATION ${ConfigPackageLocation})
diff --git a/deps/SLVS/SLVS.cmake b/deps/SLVS/SLVS.cmake
new file mode 100644
index 0000000000..69dcdc891f
--- /dev/null
+++ b/deps/SLVS/SLVS.cmake
@@ -0,0 +1,13 @@
+# libslvs — the geometric constraint solver behind the Design tab's sketch constraints.
+# Extraction of solvespace.com's libslvs, taken verbatim from JacobStoren/SolveSpaceLib;
+# only the CMakeLists is ours, because upstream's builds a demo and installs nothing.
+# GPLv3, compatible with this fork's licence. Self-contained: no external dependencies.
+orcaslicer_add_cmake_project(SLVS
+    URL https://github.com/JacobStoren/SolveSpaceLib/archive/4d8704523e4bf212fadf5189f92484244f670fea.zip
+    URL_HASH SHA256=1c4bdde9c3c6ef20ea4b50b73601de56769f2eb131b36927d7c6489f102e6c30
+    PATCH_COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_LIST_DIR}/CMakeLists.txt.in ./CMakeLists.txt
+)
+
+if (MSVC)
+    add_debug_dep(dep_SLVS)
+endif ()
diff --git a/docs/CAD/GAP_ANALYSIS_vs_ONSHAPE.md b/docs/CAD/GAP_ANALYSIS_vs_ONSHAPE.md
new file mode 100644
index 0000000000..bf603cf2c1
--- /dev/null
+++ b/docs/CAD/GAP_ANALYSIS_vs_ONSHAPE.md
@@ -0,0 +1,160 @@
+# Orca-CAD vs Onshape — capability gap analysis
+
+Generated 2026-07-22 by enumerating the source, not from recollection:
+`CadFeatureType` and `add_*` in `src/libslic3r/CAD/CadDocument.hpp`, `Tool` in
+`src/slic3r/GUI/CAD/DesignPanel.hpp`, `Mode` in `src/slic3r/GUI/CAD/DesignSketchTool.hpp`,
+`SketchConstraintType` + `SketchEntity::Type` in `src/libslic3r/CAD/SketchEngine.hpp`,
+and the JSON-RPC dispatch in `src/slic3r/GUI/CAD/McpControl.cpp`.
+
+**Scope note.** Onshape is a cloud PLM platform; Orca is a Design tab inside a
+slicer. A large share of Onshape's surface (release management, branching, real-time
+collaboration, FEA, rendering, PDM) is out of scope by construction and is listed
+separately at the bottom rather than counted as a "missing tool".
+
+---
+
+## 1. What Orca already has
+
+### 2D sketcher — near parity with Onshape
+This is the strongest area. Very little is missing.
+
+| Category | Orca |
+|---|---|
+| Entities | Line, Polyline, Arc (3-point / tangent / center), Circle (center / 2-point / 3-point), Point, Ellipse, Elliptical arc, B-spline |
+| Shapes | Rectangle (corner / center / oblique / rounded), Slot, Arc-slot, Polygon |
+| Edit ops | Fillet, Chamfer, Offset, Mirror, Trim, Extend |
+| Transforms | Move, Rotate, Scale, Linear array, Polar array |
+| Constraints (19) | Fix, Coincident, Horizontal, Vertical, Distance, LockX, LockY, EqualLength, Parallel, Perpendicular, Concentric, Tangent, Midpoint, Symmetric, Angle, Radius, Diameter, PointOnLine, PointOnObject |
+| Dimensions | Length, Diameter, Radius, Angle, Distance, Distance-to-line |
+
+Solver: vendored SolveSpace (`libslvs`, GPL-3.0) — the same solver lineage as a
+commercial-grade sketcher.
+
+### Part features
+
+| Present | Notes |
+|---|---|
+| Extrude | + up-to-face / up-to-point, taper, flip |
+| Revolve | angle-arc gizmo |
+| Sweep | along a path |
+| Loft | multi-profile |
+| Fillet / Chamfer | edge-level |
+| Draft | face taper |
+| Shell | wall thickness + open face |
+| Hole / Thread | face-aware placement |
+| Pattern | linear + circular |
+| Boolean | New / Add / Cut / Intersect, with face-mating |
+| Cut | plane-based, signed offset |
+| Datum plane | offset / 2-face / 2-edge derived |
+| Import | STEP (B-rep) + mesh→B-rep (native mesh2step port) |
+| Export | STEP (native B-rep, not tessellated) |
+| Multi-body | + per-body colour |
+| Section view | with flip |
+| Undo/redo | full feature-tree recompute |
+| 3MF persistence | parametric recipe survives save/load |
+
+### Automation
+9 MCP JSON-RPC methods: `describe_tools`, `describe_scene`, `query_topology`,
+`measure`, `slice_body`, `import_step`, `import_mesh`, `validate_against`, plus
+build actions `extrude`, `revolve`, `fillet`, `chamfer`, `hole`, `boolean`, `pattern`.
+Onshape's equivalent is its REST API + FeatureScript.
+
+---
+
+## 2. Missing tools — ranked by impact
+
+### Tier 1 — structural absences (whole subsystems)
+
+**1. Assemblies and mates.** Entirely absent. No assembly document, no mate
+connectors, no fastened / revolute / slider / cylindrical / planar / ball / pin-slot
+mates, no assembly patterns, no interference detection, no exploded views.
+`bool_target_face` / `bool_tool_face` do face-to-face *mating* for a boolean, which
+is geometric alignment, not a kinematic joint.
+*Impact:* multi-part products cannot be positioned or validated as a mechanism.
+*Note:* an MCP-side `align_instance_to_face` / `create_*_mate` vocabulary already
+exists on the Onshape bridge in this workspace, so the target semantics are known.
+
+**2. Drawings / 2D documentation.** Absent. No drawing sheets, dimensioned views,
+section/detail views, GD&T, title blocks, or BOM.
+*Impact:* nothing manufacturable-by-a-third-party leaves the tool. For 3D printing
+this matters less than for machining, which is the honest reason it is Tier 1 by
+CAD convention but arguably Tier 3 for this product.
+
+**3. Variables, equations, configurations.** Absent — no `add_variable`, no
+expression evaluation, no configuration table. Every dimension is a literal double.
+*Impact:* this is the biggest *parametric* gap. "Make this bracket for an M4 vs M5
+bolt" requires re-editing every dependent feature by hand. Onshape's Variable
+Studio + configurations are a core differentiator, and this is the cheapest Tier 1
+item to close for the size of the payoff.
+
+**4. Surface modelling.** Absent. No surface extrude/revolve/loft/sweep, no fill,
+knit, trim/extend surface, offset surface, or thicken. Orca is solid-only.
+*Impact:* organic/complex shapes and repair of imported junk geometry are impossible.
+OCCT already provides all of it (`TKOffset`, `TKBRep`), so the kernel is not the
+blocker — only UI and feature plumbing.
+
+**5. Sheet metal.** Absent. No flange, bend, tab, relief, or flat-pattern unfold.
+*Impact:* arguably out of scope for an FDM slicer; listed for completeness.
+
+### Tier 2 — individual features with clear demand
+
+| Missing | Why it matters | Cheap? |
+|---|---|---|
+| **Mirror body** (part-level) | Sketch mirror exists; mirroring a *solid* about a plane does not. Extremely common. | Yes — OCCT `gp_Trsf` mirror + fuse |
+| **Helix / spiral curve** | No helix ⇒ no springs, no custom threads, no spiral vase geometry. Sweep exists but has no helical path to sweep along. | Yes |
+| **Move / rotate body as a real feature** | `m_body_xform` exists but is **display-only** (memory #1655) — it never enters the B-rep. Export/boolean see the original position. | Medium |
+| **Split body** | Cut removes material; splitting one body into two independently-usable bodies is absent. Very relevant for print-in-parts. | Medium |
+| **Thicken** | Solid from a surface/face offset. | Needs surfaces |
+| **Rib** | Standard structural feature. | Medium |
+| **Delete face / move face / replace face** | Direct/dumb-solid editing — the main tool for fixing imported STEP. Given Orca imports STEP *and* meshes, its absence is felt. | Medium |
+| **Datum axis, coordinate system** | Only datum *planes* exist. Axes are needed for revolve/pattern references. | Yes |
+| **Mass properties** | `GeometryEngine` computes a volume internally, but there is no volume/mass/COM/inertia readout. For print cost/time estimation this is nearly free to expose. | Yes — trivial |
+| **Measure tool in the GUI** | `measure` exists over MCP but there is no interactive measure in the UI. | Yes |
+| **Hole standards library** | Hole exists, but no counterbore/countersink/tapped standards (ISO/ANSI) with callouts. | Medium |
+| **Project / convert edges into a sketch** | Cannot reference existing solid edges as sketch geometry ("Use" in SolidWorks). A significant sketcher gap given everything else is present. | Medium |
+| **Construction geometry** | Could not confirm a construction/reference-line flag on sketch entities. | Yes if absent |
+| **Curve tools** | Projected curve, bridging curve, composite curve, 3D fit spline. | Medium |
+| **Pattern on curve / pattern faces** | Pattern is linear + circular of whole bodies only; no curve-driven pattern, no feature/face pattern. | Medium |
+| **Wrap / emboss** | Text or sketch wrapped onto a curved face. | Hard |
+| **Enclose** | Solid from bounded void regions. | Medium |
+
+### Tier 3 — platform capabilities (out of scope by construction)
+
+Version control with branching/merging, release management, real-time multi-user
+collaboration, cloud PDM, FeatureScript custom-feature authoring, simulation/FEA,
+photorealistic rendering, app store/integrations. These are Onshape-the-platform,
+not Onshape-the-modeller. Not defects in Orca.
+
+---
+
+## 3. Recommended priority
+
+If the goal is "credible parametric CAD inside a slicer", the ordering that buys
+the most capability per unit of work:
+
+1. **Variables + expressions** — unlocks genuine parametric reuse; no new kernel work.
+2. **Mass properties + GUI measure** — nearly free, immediately useful for printing.
+3. **Mirror body, datum axis, helix** — small, self-contained, high-frequency features.
+4. **Promote move/rotate body from display-only to a real B-rep feature** — closes a
+   correctness gap, not just a missing tool (exports currently disagree with the view).
+5. **Split body** — high value for print-in-parts workflows.
+6. **Project edges into sketch** — the sketcher's most conspicuous hole.
+7. **Surface modelling** — large, but OCCT already ships the algorithms.
+8. **Assemblies** — largest effort; only worth it if Orca targets multi-part products.
+
+Deliberately last: drawings and sheet metal — high cost, low relevance to an
+FDM-oriented tool.
+
+---
+
+## 4. Honest summary
+
+Orca's **sketcher is at or near Onshape parity**, and its **solid feature set
+covers the mainstream modelling path** (sketch → extrude/revolve/sweep/loft →
+dress-up → boolean/pattern). What is absent is *breadth*: assemblies, surfaces,
+sheet metal, drawings, and — most importantly for a tool calling itself parametric —
+**variables and configurations**.
+
+The single most defensible criticism is #3: without variables, the feature tree is
+parametric in *structure* but not in *value*, so the promise of "change one number
+and the model updates" is only half delivered.
diff --git a/docs/CAD/cad_dependency_weight.md b/docs/CAD/cad_dependency_weight.md
new file mode 100644
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--- /dev/null
+++ b/docs/CAD/cad_dependency_weight.md
@@ -0,0 +1,136 @@
+# Dependency weight of the Design/CAD subsystem
+
+What the Design tab actually costs a maintainer who merges it. Written to be checkable:
+every number below is reproducible with the command that produced it, and the places where
+a number is still missing say so instead of guessing.
+
+Measured on Linux x86_64, OCCT V7_6_0, in the `snapmaker-deps` build image.
+
+## Summary
+
+| | Cost |
+|---|---|
+| New third-party dependencies | **none** |
+| OCCT build flag | `BUILD_MODULE_ModelingAlgorithms=ON` |
+| Extra OCCT toolkits *built* | 3 (TKFillet, TKOffset, TKFeat) |
+| Extra OCCT toolkits *linked* | 2 (TKFillet, TKOffset) |
+| Vendored code | `src/libslic3r/slvs`, 9,339 lines, 380 KiB, GPLv3 |
+| Own object code | 6.79 MiB unstripped `.o` (7.13 MiB with the solver) |
+
+OCCT is **already** an upstream dependency — Orca uses it for STEP import. The Design tab
+does not add a library; it turns on one more OCCT module.
+
+## The OCCT module flag
+
+`deps/OCCT/OCCT.cmake` gates the module on `SLIC3R_CAD`:
+
+```cmake
+-DBUILD_MODULE_ModelingAlgorithms=${SLIC3R_CAD}   # was hard-coded OFF
+```
+
+With `SLIC3R_CAD=OFF` the deps prefix matches upstream exactly.
+
+`ModelingAlgorithms` contains 12 toolkits, but **most were already being built**, because
+`DataExchange` — the STEP path upstream already ships — depends on them. The honest delta is
+only the toolkits that DataExchange's dependency closure does *not* reach:
+
+```
+ModelingAlgorithms = TKGeomAlgo TKTopAlgo TKPrim TKBO TKBool TKHLR
+                     TKFillet TKOffset TKFeat TKMesh TKXMesh TKShHealing
+
+already required by DataExchange:  TKBO TKBool TKGeomAlgo TKHLR TKMesh
+                                   TKPrim TKShHealing TKTopAlgo
+true delta:                        TKFeat TKFillet TKOffset TKXMesh
+```
+
+Reproduce by walking `adm/MODULES` and each toolkit's `src/<TK>/EXTERNLIB` in the OCCT
+source tree.
+
+### Sizes of the delta toolkits
+
+Static archives in the deps prefix. These are *build artifacts*, not shipped bytes — a
+static link pulls in only the objects it references:
+
+| Toolkit | Archive | Referenced by the Design tab? |
+|---|---|---|
+| TKFillet | 7.40 MiB | yes — `BRepFilletAPI` |
+| TKOffset | 5.38 MiB | yes — `BRepOffsetAPI`, `BRepOffset_` |
+| TKFeat | 4.42 MiB | **no** |
+| TKXMesh | — | not produced at all |
+
+TKFeat is worth calling out: nothing in the Design tab references it, and it is absent from
+the `TKFillet`/`TKOffset` dependency closure, so it is built for nothing. OCCT's module flag
+is all-or-nothing per module, which is why it comes along. It costs build time and zero
+shipped bytes on any platform that links OCCT statically.
+
+**A correction to the record.** The comment in `deps/OCCT/OCCT.cmake` and the earlier
+summary both said the delta was "TKFillet + TKOffset — 3.77 MiB, Windows only". The toolkit
+list was incomplete: TKFeat is built too. The 3.77 MiB figure covers 2 of the 3 built
+toolkits and has not been re-derived here — see the gap below.
+
+## What is not measured yet
+
+Two numbers a maintainer may reasonably ask for are **not** in this document, because
+producing them honestly needs a build this machine cannot do:
+
+1. **Windows DLL delta.** OCCT builds shared on Windows, so the shipped cost there is real
+   DLL bytes rather than linker-selected objects. That needs a Windows build to size —
+   tracked as the cross-platform build proof (`gix`).
+2. **Clean-build time delta.** Measuring it means building the deps prefix twice, with the
+   flag ON and OFF, on the same machine. The incremental figures from day-to-day work do not
+   answer the question and are not offered as if they did.
+
+Do not quote a number for either until it has been measured.
+
+## Vendored solver
+
+`src/libslic3r/slvs` — the 2D sketch constraint solver extracted from SolveSpace.
+
+- 19 files: 8 `.cpp`, 11 `.h`, plus `LICENSE`
+- 9,339 lines, 380 KiB of source, 0.34 MiB of object code
+- **GPLv3**, `LICENSE` preserved verbatim in the vendored directory
+
+The fork is **AGPLv3**. GPLv3 code combines into an AGPLv3 work without difficulty: AGPLv3
+§13 provides explicit compatibility in that direction. No licence question to resolve.
+
+It is live code, not a carried corpse — `SketchSolver.cpp` is its only consumer and drives
+every sketch constraint in the Design tab.
+
+## Own code
+
+Object sizes from the release build (unstripped, so these include debug information and
+overstate the shipped contribution):
+
+| Object | Size |
+|---|---|
+| DesignPanel.o | 2.22 MiB |
+| McpControl.o | 1.69 MiB |
+| DesignSketchTool.o | 0.88 MiB |
+| CadDocument.o | 0.76 MiB |
+| SketchEngine.o | 0.40 MiB |
+| DesignCanvas.o | 0.37 MiB |
+| GeometryEngine.o | 0.32 MiB |
+| SketchSolver.o | 0.15 MiB |
+| slvs (all objects) | 0.34 MiB |
+| **total** | **7.13 MiB** |
+
+For scale, the linked binary is 137.1 MiB.
+
+## Reproducing
+
+```bash
+# toolkit membership and dependency closure
+R=<occt-source>
+cat $R/adm/MODULES                     # module -> toolkits
+cat $R/src/<TK>/EXTERNLIB              # toolkit -> its dependencies
+
+# archive sizes
+ls -l <deps-prefix>/lib/libTK{Fillet,Offset,Feat}.a
+
+# what the Design tab actually references
+grep -rE 'BRepFilletAPI|BRepOffsetAPI|BRepOffset_|BRepFeat' src/libslic3r/
+
+# vendored solver
+wc -l src/libslic3r/slvs/*.cpp src/libslic3r/slvs/**/*.h
+head -3 src/libslic3r/slvs/LICENSE
+```
diff --git a/docs/CAD/cad_ux_guidelines.md b/docs/CAD/cad_ux_guidelines.md
new file mode 100644
index 0000000000..d0290a1d3d
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+++ b/docs/CAD/cad_ux_guidelines.md
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+# Orca-CAD — UX guidelines and design charter
+
+Status: proposed, v1. Owner: design working group. Applies to the Design tab —
+the parametric CAD environment inside OrcaSlicer.
+
+This document is a **review instrument**, not an essay. Sections 3–9 are written
+so that a reviewer can hold a pull request against them and get a yes or a no.
+If a rule here cannot be failed, it is badly written and should be rewritten.
+
+---
+
+## 1. Why this exists
+
+A CAD tool acquires its interface by accretion. Every feature arrives needing
+"just one more field", the side panel is the cheapest place to put it, and after
+forty features the product is FreeCAD: complete, respected, and abandoned by
+almost everyone who opens it once. That end state is not a failure of any single
+decision. It is the sum of forty locally reasonable ones taken without a written
+rule to violate.
+
+So we write the rule down first, and we make additions argue against it.
+
+## 2. Product thesis
+
+**Orca-CAD is a modelling space for people who want a part, inside the tool that
+prints it.**
+
+Three audiences, one interface:
+
+- **The fourteen-year-old on a school laptop.** Free software, on the machine
+  they already have, with no account, no subscription, no licence and no
+  tutorial. They open the tab because they want a bracket for a bike light, and
+  an hour later it is printing. This is not the charity case at the bottom of
+  the list — it is the reason the project is worth doing. A CAD tool that only
+  the equipped can run is a tool for people who were already going to design
+  something; this one has to be a creative instrument in the hands of someone
+  who did not yet know they could make things. Everything in §6.1 exists to
+  keep that door open, and nothing gets to close it for the convenience of the
+  other two audiences.
+- **The maker** who has an idea and a printer, and who has bounced off FreeCAD.
+  They should be modelling something real within ten minutes of first opening
+  the tab, without a tutorial, without knowing the word "constraint".
+- **The mechanical designer** who needs assemblies, mates, exploded views,
+  variables, and a feature history they can edit six months later. They should
+  not have to leave for SolidWorks the moment the work gets serious.
+
+The order matters. When a decision helps one audience and hurts another, the
+earlier one wins unless there is a written argument for why not.
+
+The reference for *how it feels* is Shapr3D: direct, gestural, quiet, almost no
+chrome, depth revealed by what you touch rather than by what is on screen. The
+anti-references are Blender (a modal keyboard language you must learn before the
+first success) and FreeCAD (a workbench-and-dialog architecture where the
+geometry is a preview of a form you fill in elsewhere).
+
+We are not cloning Shapr3D's feature set. We are adopting its *interaction
+economy*: the smallest number of visible controls that still makes an expert
+fast.
+
+**And one thing neither reference has:** Orca-CAD lives inside a slicer. The
+plate, the nozzle, the material and the print constraints are known to the
+application at design time. Designing for print is not a plugin here, it is the
+home advantage. Where a rule below trades generality for print-awareness, it
+trades in favour of print-awareness.
+
+## 3. The laws
+
+Non-negotiable. A change that breaks one of these does not get merged on the
+grounds that it was easier, that the alternative is more work, or that another
+CAD does it that way. Each law carries a test — the question a reviewer asks.
+
+### L1 — Geometry first: you point, then you act
+
+Controls live **on the geometry**: handles, arrows, points, small circles and
+boxes, with an inline label tab for typed values. Not in a side panel of combos
+and spin fields.
+
+The canonical gesture: **select a face or plane in the viewport, then click the
+sketch tool.** Never: click the sketch tool, then choose a plane from a list.
+The tool consumes what you pointed at — and, better still, the thing you pointed
+at offers the tool itself (§4).
+
+> **Test.** Can the operation be performed start to finish without the pointer
+> leaving the viewport, except to press the tool itself? If a control had to be
+> added to a panel to make it work, the design is not finished.
+
+This is the law the others serve. It was stated after two proposals in a row
+reached for a dropdown, and the failure mode it names is real and recurrent: a
+fix that "adds a row to the plane combo" is the side-panel pattern wearing a
+different hat.
+
+### L2 — Everything draggable is typable, and everything typable is draggable
+
+Any value produced by direct manipulation (a fillet radius, an extrude depth, a
+pattern spacing, a plane offset) shows a live label on the geometry, and that
+label is an editable field. Any value entered numerically has a corresponding
+handle in the viewport.
+
+Dragging is for finding the answer. Typing is for committing to it. A tool that
+offers only one of the two is half a tool.
+
+> **Test.** Point at the number the tool produces. Can you drag it? Can you
+> click it and type? Both must be yes.
+
+### L3 — Noun then verb, always the same way round
+
+Selection precedes action, without exception, across sketch tools, features,
+dress-up, booleans and mates. There is no tool in the product that is armed
+first and asks for its input afterwards.
+
+> **Test.** Does this tool work if the user has already selected the thing they
+> want it applied to? Does it work *only* that way?
+
+### L4 — No modal dialog in the modelling loop
+
+Dialogs belong to document-level actions: open, save, import, export, preferences.
+Modelling never opens one. A feature that needs three values gets three labels on
+the geometry, not a form; a feature that needs confirming gets a ghost preview and
+a confirm/cancel puck in the scene beside it (§4.2) — an object, not a window: the
+camera still orbits, the values are still editable, nothing is blocked.
+
+> **Test.** Between starting an operation and seeing its result, does a window
+> appear that must be dismissed? If yes, redesign.
+
+### L5 — One click, one visible change
+
+Every click either changes what is on screen or tells the user why it did not.
+A click that opens something invisible, arms an invisible state, or requires a
+second identical click to have any effect is a defect, not a design.
+
+This law exists because we shipped its violation twice. Sketch-tool family
+buttons were flyouts whose first click only rendered a pressed state — three
+separate sessions filed bugs against tools that were working. Solid picking used
+a click *cycle* (first click selects the body, second refines to the face), so
+sketching on a face appeared broken to anyone who clicked a face once, the way
+every human does.
+
+> **Test.** Perform the gesture exactly once, as a first-time user would. Take a
+> screenshot. Is the state visibly different, and is the difference the one the
+> user intended?
+
+### L6 — The default is the answer four times out of five
+
+Every option that has a default must have the *common* answer as its default,
+measured against real parts, not against generality. "New body" as the default
+result of an extrude is wrong: most extrudes join. Radius as the input for a
+circle is wrong: drawings give diameter.
+
+> **Test.** Take ten real parts. In how many is the default correct? Below eight,
+> change the default or infer it from context.
+
+### L7 — Errors are caught before the commit, in the user's words
+
+A self-intersecting profile, a cut that removes no material, a wall thinner than
+the nozzle: these are reported at the moment they become knowable, on the
+geometry that is wrong, phrased as what happened and what to do — not as a kernel
+exception after the fact, and never silently.
+
+> **Test.** Is the failure detectable before the user commits? Then it must be
+> reported before the user commits. Read the message aloud: does it name a thing
+> the user can see and an action they can take?
+
+### L8 — The camera is the application's job
+
+Selecting a sketch plane orients the view to it. Committing a feature does not
+throw the camera away. Zoom-to-fit exists and is one keystroke. The user is never
+required to fight the view in order to reach the geometry, and orbit is bound to
+the gesture people actually try.
+
+> **Test.** Count camera manipulations in a representative modelling session.
+> Any camera action the application could have performed for the user is a bug.
+
+### L9 — Accessible by construction, not by retrofit
+
+The floor, applied to every new interaction (details in §6.2): full keyboard
+reach, no meaning carried by colour alone, hit targets that survive a shaky hand
+and a HiDPI screen, legible labels over an arbitrary 3D background, no gesture
+that depends on timing.
+
+> **Test.** Drive the whole interaction from the keyboard. Then drive it in
+> greyscale. Both must work.
+
+### L10 — Vocabulary from the drawing office
+
+Names come from the language of people who make parts: fillet, chamfer, boss,
+rib, counterbore, mate, exploded view. Not from the kernel (no "boolean
+subtract", no "B-rep"), not from invented product-speak. Where the drawing-office
+word and the beginner's word differ, use the drawing-office word and make the
+tooltip teach it — an approachable tool that leaves the user unable to talk to a
+machinist has failed them.
+
+> **Test.** Would a shop-floor engineer recognise this word? Would a first-time
+> user be able to look it up and find a real definition?
+
+### L11 — The floor is a school laptop, and nothing is behind a door
+
+The product runs, completely, on a low-end laptop with integrated graphics and a
+small screen, offline, with no account, no subscription and no feature withheld.
+No capability in this document is reserved for a paid tier, a cloud service, a
+plugin, or a machine with a discrete GPU — there is one product and everybody
+gets all of it.
+
+> **Test.** On the reference low-end machine (§6.1), at 1366×768, with the
+> network cable pulled and no account ever created: does this feature work, and
+> is it usable at an honest frame rate? Any "no" is a defect, not a limitation.
+
+## 4. Interaction grammar — object-driven
+
+The rules above compose into one sentence the whole product obeys:
+
+> **Point at geometry → the geometry offers what can be done to it → choose the
+> tool → manipulate handles and type exact values → confirm or cancel.**
+
+The selection does not merely feed the tool. **The selection determines which
+tools exist.** Pick a planar face and the product shows you the small set of
+things a planar face can become — sketch on it, extrude it, hole it, shell it,
+put a datum on it. Pick an edge and that set is fillet, chamfer, and the sketch
+tools that can use it as a reference. Nothing else is offered, because nothing
+else is possible.
+
+This is the single largest thing we can do for a first-time user, and it is
+worth stating as the reason: a beginner's difficulty is not operating a tool,
+it is **not knowing which tools apply to what they are looking at**. A palette
+of sixty icons answers a question they cannot yet ask. A face that offers its
+own five verbs teaches the model of the product by using it. It also removes an
+entire class of failure — a tool that silently does nothing because the
+selection was wrong can no longer be reached.
+
+### 4.1 The offer, and the one thing that makes it work
+
+The flow, in full:
+
+> **left-click the geometry to select it → right-click to open the offer → a
+> vertical list, always in the same order, each row an icon, a name and its
+> keyboard shortcut → click.**
+
+- **Selecting and acting are separate gestures.** Left-click only ever selects,
+  so pointing at things is quiet — nothing pops up while you look around.
+  Right-click on the selection opens the offer, at the pointer, over the
+  geometry it acts on.
+- **Order is fixed and it is the whole point.** A verb occupies one permanent
+  row, and that row is the same in every selection where the verb appears.
+  Dress-up is the fourth row on an edge, on a face, on a body, on the day the
+  product ships and two years later. The hand learns the position; the eye stops
+  being needed.
+- **What does not apply is DISABLED IN PLACE, never removed.** This is the
+  single strongest thing the list does, and it is why it beat the radial we
+  drew first: a greyed row still carries its name *and the reason it is grey* —
+  "Create a sketch, or pick a solid face, first", "Create a solid body to
+  pattern first" — in the words the product already ships. On a first-run
+  document the offer is therefore not a mostly-empty control but a map of what
+  the product does and what you have to do first.
+- **It is an accelerator, not a toll gate.** The toolbar and the single-letter
+  shortcuts keep working exactly as they do now, and pressing a tool directly
+  consumes the same selection (L3). An expert never has to open the offer; a
+  beginner never has to know the toolbar exists. Both routes land in the same
+  place — this is the only way one interface serves §2's three audiences.
+- **Every row shows its keyboard shortcut**, right-aligned so the keys stack
+  into a column the eye learns without trying, beside the icon and the
+  drawing-office word (L10). This is deliberate: the offer is the path by which
+  a user stops needing the offer. You reach for fillet in its row, the row says
+  "F", and one day your hand types F before the menu has finished opening. A
+  menu that teaches its own shortcut is how a beginner becomes the power user
+  who never opens it — the same interface at two speeds, with no "advanced mode"
+  between them (§7).
+- **A family with more than one applicable verb opens a submenu** to the side,
+  in its own fixed order. A family with exactly one shows that verb directly, so
+  the common path is never one click longer than it needs to be.
+- **It never blocks the view of what it acts on**: it opens beside the pick,
+  never over it, with a thin leader back to the point it belongs to, and it
+  dismisses the moment the selection changes.
+- **The header names what is selected** ("Top face · Body 1"), because a user
+  who mis-picked should find that out before choosing a verb, not after.
+
+#### Opening the offer on every machine
+
+Right-click is the primary gesture and every platform must have a first-class
+equivalent — this is a reach requirement (L11), not a nicety:
+
+| Input | Gesture |
+|---|---|
+| Two-button mouse | right-click |
+| Trackpad | two-finger tap (the OS-standard secondary click) |
+| macOS, one-button mouse | **long-press**, and Ctrl-click, which is the platform convention |
+| Keyboard | the Menu key, or Shift+F10, on the current selection |
+| Touch / pen | long-press |
+
+The long-press is an **additional** route, never the only one — §6.2 forbids
+press-and-hold as a sole path to a function, and it stays forbidden. Every
+opening gesture is reachable at least two ways on every platform, and the
+keyboard route exists everywhere. A long-press must show that it is charging
+(a growing ring under the finger) so a user who holds too briefly learns why
+nothing happened rather than concluding the product is broken (L5).
+
+#### The row-constancy invariant
+
+This is the rule that has to survive every future feature, so it is written as
+an invariant rather than as advice:
+
+> **Every verb has exactly one row index in the offer. That index is identical
+> for every selection type in which the verb appears. Verbs that do not apply to
+> the current selection are DISABLED IN PLACE, with their reason — the offer is
+> never compacted, re-sorted or re-ordered. Adding a verb never changes the
+> index of an existing one.**
+
+Two consequences the group must accept together with the invariant:
+
+- **No adaptive ordering. Ever.** Not most-used-first, not recently-used-first,
+  not per-selection frequency. An offer that rearranges itself to be helpful
+  destroys the only thing that made it fast, and it does so precisely for the
+  user who has just started to learn it. (Office 2000's adaptive menus are the
+  textbook case; they were removed.)
+- **Greyed rows are the price, and they are cheap.** A compacted menu is shorter
+  and unlearnable. A constant one is a few rows longer, teaches while it waits,
+  and is memorised in a week.
+
+#### The map — RATIFIED 2026-07-31
+
+The invariant is not negotiable, and as of 2026-07-31 neither is the assignment:
+the row order below is **ratified**. It was argued once; it is not argued again.
+Changing an index from here on is a breaking change to every user's muscle
+memory and needs the group, not a pull request (§9 q12).
+
+Eight families, ordered so the sequence itself has a logic: material is created,
+grows, is taken away, is refined, is repeated, is moved, is referred to, is
+edited.
+
+| Row | Family | On a face | On an edge | On a body | On text/art |
+|---|---|---|---|---|---|
+| **1** | Create | Sketch on it | — | — | Edit text |
+| **2** | Add material | Extrude, thicken | — | Combine, thicken | Extrude |
+| **3** | Remove | Hole, shell | Thread | Shell, cut, split | — |
+| **4** | Dress-up | Draft | Fillet, chamfer | Fillet, chamfer | — |
+| **5** | Repeat | Pattern | Pattern along it | Pattern, mirror | Pattern |
+| **6** | Transform | Align to, mate | — | Move, mate | Move, size |
+| **7** | Reference | Plane, axis, measure | Axis, measure | Project, measure, mass | — |
+| **8** | Modify | Delete face, edit | — | Edit, colour, delete | Replace art |
+
+A dash means the row is drawn greyed for that selection, with its reason.
+
+The authoritative version of this table is **`docs/ux/tool_atlas.json`**, which
+carries all 52 verbs with their preconditions and their refusal strings, taken
+from the code rather than from memory. Every state it produces — 20 selection
+kinds × 2 document states, 40 primary menus and 73 submenus — is rendered by
+`docs/ux/mockups/gen_offer_mockups.py` into `docs/ux/offer_atlas.html`. Read the
+atlas before proposing a change to the map; the generator refuses to render an
+address collision, so the map cannot silently rot.
+
+#### Rejected: the radial ring
+
+The first design put the eight families at eight compass points around the pick.
+It is recorded here because it is a good idea that loses on evidence, and
+someone will propose it again:
+
+- an inapplicable slot could only be drawn empty, and **an empty slot says
+  nothing** — the reason text above has nowhere to live;
+- the measured fill was **3.45 of 8 slots**, so most of the control was blank
+  most of the time, and on a fresh document only two of eight were live;
+- sketch-mode *Create* needs **nine** addresses; eight forced two primitives
+  behind a "More" slot, and a ninth position costs the 45° spacing that made the
+  ring worth having;
+- long translated names do not fit around a circle, and screen readers and arrow
+  keys need bespoke handling a list gets for free;
+- a 380 px disc over the model costs more on a 1366×768 screen than a 324 px
+  list beside it (§6.1).
+
+What it kept — equidistant targets and a future flick gesture — buys little in a
+product whose experts live on the keyboard by design.
+
+### 4.2 Confirm and cancel are objects, not gestures
+
+The old rule — click empty space to commit — is withdrawn. It was an invisible
+gesture with a destructive meaning: nothing on screen said it, and a stray click
+committed a feature the user was still adjusting. That is exactly what L5
+forbids, and it is hostile to the audience §6.1 exists for.
+
+- **A pending feature carries a confirm/cancel puck**, attached to the geometry
+  it is editing, next to its handles: ✓ commits, ✗ discards. Enter and Escape
+  mirror them for the keyboard (L9). It is drawn where the user's attention
+  already is, and it is the only thing in the viewport that commits.
+- **Empty space now means "clear the selection"** — the safe meaning, and the
+  same meaning everywhere.
+- **This is not a dialog** (L4). It is two objects in the scene, on the
+  geometry, non-modal: the camera still orbits, the tree is still there, the
+  values are still editable while it waits.
+- **Continuous tools do not ask.** Drawing a line, a rectangle, a circle commits
+  each entity as its own gesture completes — a ✓ per line would destroy the
+  inner loop. The puck belongs to *features* (extrude, fillet, hole, pattern,
+  mate) and to sketch edits that hold a pending state. Enter/Escape end a
+  continuous tool rather than confirming an entity.
+- **Ambiguity resolves toward keeping work, never toward losing it.** Starting
+  another operation while a valid feature is pending commits it rather than
+  discarding it; if it is not valid, the product says why (L7) and keeps it
+  pending. Since undo reaches everything (§6.1), the recoverable direction is
+  always the right default.
+
+### 4.3 The rest of the grammar
+
+- **The status line is one imperative sentence** naming what the tool wants
+  next, and it names the target when the target came from a selection
+  ("Circle — click centre, then radius · on the picked face"). It is the
+  authoritative feedback surface for the armed tool; the toolbar is not.
+- **Hover previews, click commits.** A hover shows the ghost of what a click
+  would do wherever this is cheap to compute.
+- **Selection is persistent and visible** until consumed or cleared. A tool that
+  consumes a selection clears it, so the next feature cannot silently inherit it.
+- **Every gesture is undoable**, and the feature tree is editable history, not a
+  log. Re-editing a feature re-enters the same on-geometry interaction that
+  created it — including its offer and its puck.
+
+## 5. Layout and screen budget
+
+The viewport is the application. Chrome is a tax on it.
+
+- **One toolbar**, contextual to the mode (model / sketch). Tools are grouped by
+  what they make, not by which subsystem implements them.
+- **A left rail for the document, not for parameters**: feature tree, bodies,
+  variables. It answers "what exists", never "what value should this be".
+- **No parameter panel.** Where one exists today it is technical debt with a
+  scheduled removal (§10).
+- **Print context is ambient**, not a panel: the plate is visible in the design
+  space, and print-domain warnings appear on the geometry that will fail.
+- **Nothing is added to permanent chrome without removing something**, or
+  demonstrating that the addition is used in the majority of sessions.
+- **The budget is set by the smallest screen we serve**, 1366×768 (§6.1) — not
+  by the reviewer's monitor. Chrome that fits a 27-inch display and swallows a
+  laptop's has not fitted, it has just failed somewhere the author cannot see.
+
+## 6. Accessibility — reach first, then the assistive floor
+
+"Accessible" means two different things and the product owes both. §6.1 is about
+**who can get in at all**; §6.2 is about **who can operate it once inside**.
+Neither is a phase. Both are merge requirements.
+
+### 6.1 Reach — the door has to be open
+
+The premise of the whole project: someone with no money, no licence, no account,
+no fast machine and no teacher can open this and make a real thing. Free
+software on a school laptop is the only path to a CAD tool that reaches people
+who were never going to be handed one. If a design decision quietly raises the
+cost of entry, it has broken the premise, however elegant it is.
+
+- **The reference machine.** A 5-year-old laptop: dual/quad-core CPU,
+  **integrated graphics**, 8 GB RAM, **1366×768** screen, no discrete GPU. The
+  Design tab must be usable there, and any interaction that needs more is a
+  design failure to be solved, not a requirement to be documented. The GPU path
+  degrades gracefully to software rendering rather than refusing to start; the
+  viewport stays interactive while the kernel thinks.
+- **1366×768 is the layout target, not the stretch case.** A form-heavy side
+  panel is not merely inelegant on that screen — it takes the model off it.
+  This is the second, independent argument for the whole of L1 and §5.
+- **No account, no cloud, no connection.** The product works forever with the
+  network unplugged. Nothing is uploaded, no sign-in gates any feature, no
+  telemetry is required to use it. A school network that blocks everything must
+  not be able to block this.
+- **No tier, no plugin wall, no "pro".** Every feature named in this document is
+  in the product everyone downloads. Assemblies and exploded views are not the
+  paid half.
+- **Files belong to the user**, on their disk, in a format that outlives the
+  project: the design travels inside the ordinary project file, and the geometry
+  exports to STEP and mesh formats anyone can open.
+- **Learnable without instruction.** The first solid comes with no
+  documentation, no video and no tutorial mode — from noticing that a face can
+  be clicked. Tooltips teach the vocabulary (L10) at the moment it is needed;
+  nothing is explained in a manual the user will never open.
+- **Plain language at the entry tier.** The Make tier speaks in words a
+  thirteen-year-old reads without stopping. Precision comes with the tier that
+  needs it, and everything is translated, because "accessible" in English only
+  is not accessible.
+- **Exploration must be free.** Undo reaches everything, work is never lost to a
+  wrong click, and no dialog ever asks the user to be sure. A tool that punishes
+  experiments teaches people to stop experimenting, which is the one thing this
+  audience cannot afford to learn.
+- **The product never blames the user.** Failures are stated as what happened
+  and what to do (L7). "Invalid input" is not an acceptable sentence anywhere.
+
+### 6.2 Assistive floor
+
+- **Keyboard**: every operation reachable and completable without a pointer.
+  Single-letter shortcuts for sketch tools, shown in the offer itself (§4.1) as
+  well as in the tooltip. The offer opens from the keyboard (Menu key or
+  Shift+F10) and walks by arrow key and by type-ahead, so the row map works for
+  someone who never touches the pointer. A visible focus state on every
+  focusable element. No shortcut that only works while the pointer happens to be
+  over the canvas.
+- **Colour**: never the sole carrier of meaning. Selection is colour *and*
+  outline; an error is colour *and* an icon *and* text. Verify in greyscale.
+- **Contrast**: labels over the 3D viewport get a scrim or halo so 4.5:1 holds
+  against any background the model can produce, including a white body under a
+  white plate.
+- **Targets**: handles and grips no smaller than 32 px at 100 % scale, scaling
+  with the OS factor; the grab tolerance is larger than the drawn glyph.
+- **Timing**: no double-click-to-mean-something-else, no press-and-hold as the
+  only route to a function, no cycle that depends on repeated clicks
+  (see L5). The long-press that opens the offer on a one-button Mac and on touch
+  (§4.1) is explicitly an *additional* route — Ctrl-click, two-finger tap and
+  the keyboard all reach the same place — and it shows its own progress while
+  charging, so it never fails silently.
+- **Motion**: animation is functional (showing where a thing went), never
+  decorative, and it respects the reduced-motion preference.
+- **Text**: no fixed-width assumptions; the UI holds together in German and in
+  Chinese, at 125 % and 200 % scale. Every string routed through the normal
+  translation path.
+
+## 7. Depth without clutter — the three tiers
+
+Power for experts is delivered by **progressive disclosure of tools, never by
+relocation of tools**. A tool that appears in a later tier is in the same place
+it will always be; it is simply not shown yet.
+
+| Tier | Who | What appears |
+|---|---|---|
+| **Make** | first hour | Sketch, extrude, revolve, hole, fillet/chamfer, move, commit to plate |
+| **Model** | competent user | Patterns, shell, draft, sweep/loft, booleans, reference geometry, variables, import/export |
+| **Mechanism** | mechanical designer | Assemblies and mates, exploded views, interference detection, surfaces, feature-level editing of imported solids |
+
+Rules that keep this honest:
+
+1. **Tiers are non-modal.** No mode switch, no workbench selector, no "advanced
+   mode" toggle that changes the meaning of anything. The tier only governs what
+   is *offered*.
+2. **A tier reveals itself by use.** Using a body reveals boolean tools; adding
+   a second body reveals assembly tools. The product notices what you are doing.
+3. **Nothing moves when a tier appears.** A user who learned where fillet lives
+   finds it in the same place forever.
+4. **An expert tool obeys the same grammar** as a beginner tool. Mates are
+   picked in 3D like everything else, not configured in a table.
+5. **Exploded views are a view state**, not a document mode — reversible,
+   draggable along mate axes, and never a separate file.
+
+## 8. Designing for print — the home advantage
+
+Design-time knowledge the application already has, and must use:
+
+- **The plate is present** in the design space, at the real size, with the real
+  origin. Committing a body to the plate is one action and preserves placement.
+- **Print-domain checks run on the model, on the geometry, before slicing**:
+  walls thinner than the nozzle, unsupported overhangs beyond the material's
+  angle, features smaller than the layer height, a part that does not fit the
+  build volume.
+- **These are warnings on the geometry, never a report.** The thin wall glows;
+  the tooltip says how thin and what the nozzle is.
+- **Material and machine context is inherited** from the active slicer profile,
+  not re-entered in the Design tab.
+- **The round trip is preserved**: editing a design after slicing returns to the
+  feature history, not to a mesh.
+
+## 9. The review gate
+
+Every pull request that touches the Design tab UI answers these, in the PR body.
+A "no" that is not accompanied by an argument is a request for changes.
+
+1. Which law (L1–L11) does the change most directly serve?
+2. Can the whole operation be completed without the pointer leaving the
+   viewport? If not, why is this the exception?
+   And: does the relevant selection *offer* this tool (§4.1), or must the user
+   already know it exists?
+3. Are the values draggable *and* typable?
+4. Screenshot of the state after **exactly one** click of the new gesture,
+   performed as a first-time user.
+5. Keyboard-only walkthrough: does it complete?
+6. Greyscale screenshot: is every state still distinguishable?
+7. What was **removed**? (Net additions to permanent chrome require an argument.)
+8. Which tier does it belong to, and does it appear without moving anything else?
+9. What does it do when the geometry is invalid, and is that reported before the
+   commit?
+10. Interaction cost: actions required for the canonical task it addresses,
+    before and after.
+11. Reach (L11): screenshot at 1366×768 with the panel open — is the model still
+    on screen? Does it run on integrated graphics? Does it need the network, an
+    account, or a file the user cannot keep?
+12. If the change adds or moves a verb in the offer: which row, and is it that
+    verb's row in **every** selection where it appears? Did any existing verb's
+    index change? (If yes, this is not a UI change, it is a breaking change to
+    every user's muscle memory, and it needs the group — see §4.1.) Was
+    `docs/ux/tool_atlas.json` updated and the atlas regenerated?
+13. If the change adds a pointer gesture: what is its keyboard equivalent, and
+    what does a one-button Mac, a trackpad and a touch screen do (§4.1)?
+
+## 10. Where we stand today — honest inventory
+
+Complying with the laws already:
+
+- Sketch inline editors — draw an entity and its dimension tab opens on the
+  geometry; Tab walks Length → Width → Angle.
+- Fillet/chamfer draggable radius arrow with an editable value label.
+- Extrude depth arrow; move-body three-axis arrows.
+- Datum-plane resize handles and offset arrow; ghost reference planes picked in
+  3D.
+- Imported-art place/size gizmo.
+- Sketch plane taken from the picked face, with the target named in the status
+  line, and the sketch-plane dropdown deleted outright.
+
+Violating them, with removal scheduled:
+
+- **Every tool card is a two-column form** of combos and spin fields in the left
+  panel. This is the single largest debt in the product and the reason this
+  document exists. Tracked as an epic; each card is replaced by its on-geometry
+  equivalent, not improved in place. It fails L1 and it fails L11 twice over —
+  on a 1366×768 screen the cards leave the model a strip.
+- Seven remaining plane pickers still populate a combo instead of consuming a
+  viewport selection.
+- Pattern has no on-geometry spacing arrow or count badge.
+- Hole is positioned by X/Y fields rather than by a point on a face.
+- Booleans and cuts pick their operands from lists rather than in 3D.
+- Fillet/chamfer edge selection still requires the click cycle L5 forbids.
+- **Selecting geometry offers nothing.** There is no contextual offer (§4.1):
+  the user faces the full toolbar whatever they have picked, and finds out that
+  a tool did not apply by it doing nothing. This is the largest single item of
+  new work the charter asks for. The map and every state of it are already
+  drawn (`docs/ux/offer_atlas.html`); what the group owes itself before the code
+  is ratifying the row order, since every verb built before that lands has to be
+  addressed afterwards anyway.
+- **Committing is an invisible click in empty space** rather than the
+  confirm/cancel puck of §4.2 — the exact gesture that rule withdraws.
+
+Nothing on the violating list is defended. The only open question for each is
+what its on-geometry replacement should be.
+
+## 11. How the group works
+
+**Roles.** Product/UX lead (owns this document and casts the tie-break vote on
+interaction questions); kernel maintainer; GUI maintainer; a print-domain
+reviewer; a mechanical-design reviewer who uses the product on real work; an
+accessibility reviewer covering both senses of §6 — reach and assistive — who
+owns the reference machine and actually runs on it. One person may hold more
+than one role; the UX lead and the mechanical-design reviewer should not be the
+same person, and nobody reviews reach from a workstation.
+
+**The absent audience needs a seat.** The fourteen-year-old is not in the room
+and cannot file an issue. Someone in the group is accountable for B5 and B6, and
+the group watches real first-timers use the product on the reference machine at
+least once a quarter — school, makerspace, or a friend's kid. Everything else in
+this document can be argued from principle; approachability can only be
+observed.
+
+**Cadence.** A short weekly review of open interaction proposals. A monthly pass
+over the violating inventory in §10 — anything that has not moved in two months
+is either scheduled or explicitly accepted as permanent, with a reason written
+into this document.
+
+**How a change moves.**
+
+1. *Problem* — a described user difficulty, ideally with an interaction-cost
+   measurement, never a solution in disguise.
+2. *Sketch* — one or two on-geometry interaction proposals, drawn or described
+   as a gesture sequence. Reviewed against §3 before any code.
+3. *Prototype* — built behind whatever the smallest safe path is, driven end to
+   end on a real display, and screenshotted at each state.
+4. *Gate* — §9 answered in the PR.
+5. *Merge*, then update §10.
+
+**Decisions are written down.** Any resolution that constrains future work is
+appended to this document as a numbered law or as an accepted exception with its
+reasoning. A decision that lives only in a call is not a decision.
+
+**How disagreements resolve.** Against the laws first. If the laws do not decide
+it, the tie-break is the interaction cost measured on the canonical tasks in
+§12; if that does not decide it, the UX lead chooses and records why.
+
+## 12. Canonical tasks — the benchmark
+
+The measure of every UX change is the cost of these five tasks. Each is timed and
+counted (clicks, keystrokes, camera actions, mode switches) on the headless rig
+and, periodically, with real users who have not seen the product.
+
+| # | Task | What it exercises |
+|---|---|---|
+| **B1** | Bracket: sketch an L, extrude, two holes, fillet the inside corner, send to plate | The inner loop |
+| **B2** | Change a hole diameter and the plate thickness, six features deep, and rebuild | Parametric editability |
+| **B3** | Take an imported STEP, delete a boss, close the face, thicken a wall to nozzle width | Direct editing + print awareness |
+| **B4** | Two parts, one revolute mate, check interference, produce an exploded view | The Mechanism tier |
+| **B5** | First-run: from opening the Design tab to a print-ready solid, no documentation | Approachability |
+| **B6** | B1 again, on the reference machine at 1366×768, offline, on a fresh account-less install | Reach (L11) |
+
+Every task is run on the reference machine of §6.1, not on a workstation — a
+number measured on a fast desktop describes an experience most of our users will
+never have. B6 repeats the inner loop under the full entry conditions so that
+reach is a measured quantity and not an intention.
+
+Targets are set once each task has been measured on the current build. B5's
+target is expressed in minutes-to-first-solid **by someone who has never seen a
+CAD program**, and it is the number this project is ultimately judged by.
+
+---
+
+### Appendix — anti-patterns we have already paid for
+
+Kept because each cost real time and each is easy to reintroduce.
+
+- **The dropdown that grew a row.** Fixing "cannot sketch on a face" by adding a
+  "Face of Body 1" entry to a plane combo. It reads as a small fix and it is the
+  side-panel architecture reproducing itself.
+- **The invisible first click.** Flyout buttons and pick cycles whose first click
+  changes nothing meaningful. Filed as bugs three separate times against working
+  code, and made a real bug look fixed when it was not.
+- **The fix verified through a path the user will never take.** A face-sketch fix
+  confirmed by double-clicking to reach face level. Users click once. A fix
+  reachable only by an undiscoverable gesture is indistinguishable from no fix.
+- **The wrong feedback surface.** Measuring an armed tool by the toolbar, which
+  never renders keyboard-armed state. The status line is the surface that
+  answers.
+- **The silent success.** A cut that removed no material, reported as done. Now
+  an error naming the likely cause.
diff --git a/docs/CAD/design/mate-connectors/BEAR_CONNECTOR_REVIEW.md b/docs/CAD/design/mate-connectors/BEAR_CONNECTOR_REVIEW.md
new file mode 100644
index 0000000000..cc2d4b22aa
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/BEAR_CONNECTOR_REVIEW.md
@@ -0,0 +1,169 @@
+# BearConnector.step — examination
+
+> **Scope.** One file was supplied and it contains **one object: the male.** Everything below is
+> measured from that single solid. Earlier drafts of this note reasoned about a female pocket and a
+> mating pair — those objects were never supplied, so any statement about them was speculation and
+> has been removed. The clearance, the fit, and the pocket's legibility are all **unassessed**.
+
+Measured, not eyeballed. Imported into the Design tab's own OpenCascade kernel
+(`import_step` → one valid closed solid), topology queried, geometry checked numerically.
+Flat drawing: `artifacts/shots/bear-flat.png`. Viewport: `artifacts/shots/bear-02-zoom.png`.
+
+**File:** AP242 Edition 2, ST-Developer. 1 `MANIFOLD_SOLID_BREP`, 1 `CLOSED_SHELL`.
+**Size:** 83.06 × 66.69 × 17.27 mm. **Faces:** 30 — 24 planar + 6 cylindrical.
+**Curves:** 69 lines + 12 circles. **No** splines, spheres, tori or cones.
+**Relief:** only four Z levels — 0, 3.00, 10.66, 17.27.
+
+---
+
+## What is right, and precisely so
+
+**The sloping ridge is implemented exactly as briefed.** From (0.00, 18.40, 17.27) to
+(0.00, 46.72, 10.66): 28.3 mm long, 6.61 mm drop, **13.1° slope**, and both ends sit dead on
+x = 0.00. It breaks 180° rotation on its own.
+
+**20.0° uniform draft on all four snout flanks**, identical to within 0.1°:
+`(0,−0.94,0.342) (0.936,0.08,0.342) (0,0.94,0.342) (−0.936,0.08,0.342)`. That is a real,
+deliberate lead-in — it self-centres into a matching pocket, and it demoulds and prints.
+
+**The eyes are exactly symmetric**: Ø9.87 at x = ±16.43, y = 48.01, matching to 0.01 mm.
+Someone mirrored those on purpose.
+
+**The mating feature is extremely economical**: only **five edges** exist above the 3 mm plate —
+the ridge plus two flank edges at each end. Base plate is exactly 3.00 mm.
+
+The low-poly constraint is honoured. All six cylinders are outline rounds and eye holes; none of
+them is a mating surface.
+
+---
+
+## The asymmetry is deliberate, and it is complete
+
+**Correction.** A first pass read the left/right differences as an unfinished mirror. That was wrong:
+the asymmetry is intentional. Tested properly — every candidate self-symmetry, in the part's own
+centred frame, with a generous 0.1 mm tolerance:
+
+| operation | edges mapped onto the part |
+|---|---|
+| identity | 81 / 81 — 100 % |
+| mirror about x = 0 (left/right) | **0 / 81** |
+| mirror about y = 0 (top/bottom) | **0 / 81** |
+| rotate 180° about Z | **0 / 81** |
+| rotate 90° about Z | **0 / 81** |
+| mirror about the diagonal | **0 / 81** |
+
+**The symmetry group is trivial.** No rigid motion or reflection maps this part onto itself, so
+**every partial view determines the orientation uniquely** — you never need to see the whole face to
+know which way round it goes. That is the strongest possible result for a keying interface and it is
+exactly what the earlier abstract glyph work kept failing to achieve: a symmetric shape seen at a
+grazing angle, or half-occluded, gives an ambiguous read.
+
+### Does it let you GRASP the orientation? Measured, not asserted.
+
+Unique-in-principle and graspable-at-a-glance are different claims. The symmetry table proves the
+first. For the second, the front-on picture (outline + eyes + mouth, filled) was rasterised and
+compared against its own mirror and its own 180° rotation — the two ways a person can get it wrong.
+
+**By size** (percentage of pixels that differ):
+
+| width | vs mirror | vs rotated 180° |
+|---|---|---|
+| 16 px | 20.7 % | 26.0 % |
+| 24 px | 21.9 % | 30.9 % |
+| 32 px | 23.0 % | 28.1 % |
+| 48 px | 22.4 % | 30.6 % |
+| 80 px | 24.7 % | 31.0 % |
+| 160 px | 23.6 % | 31.0 % |
+
+**The curve is flat.** The full signal is already there at 16 pixels and more resolution adds
+nothing. That is the whole result: **the orientation cue lives at low spatial frequency**, carried by
+the overall shape rather than by any detail. It therefore survives distance, blur, poor light,
+peripheral vision, a small print and a low-resolution screen. It is the exact opposite of the abstract
+disc glyph, whose roll cue was a small high-frequency feature and died at a grazing angle.
+
+**Partial views — a claim I made and then withdrew.** I ran a masked-window test and concluded that
+a single quarter of the face was enough to read the orientation. **That test was invalid and the
+conclusion is wrong.** It compared a window of the original against *the same window* of the mirrored
+and rotated versions — which silently hands the observer the registration. It assumes you already
+know that the patch you are looking at is the top-left quarter, which is exactly the thing you would
+not know if you could only see a quarter.
+
+**You need to see the whole face.** The cues here are *relational*: the big ear only means something
+next to the small ear, and the mouth offset only means something relative to the centreline. None of
+them is self-locating. Whole-face is the operating condition, and the design should be judged and
+used on that basis.
+
+That does not weaken the size result above, which always used the complete silhouette: the whole face
+reads at 16 px. Needing all of it, and needing very little resolution of it, are compatible — and for
+a part held in a hand, seeing all of it is the normal case.
+
+**The signal is allocated to the right risks.** The strongest cue (up to 41.7 %) guards against
+inserting it upside down — the mistake people actually make. The weakest (~23 %) guards the mirror
+case, which needs the part flipped over and which the protrusion already prevents mechanically.
+
+It also does mechanical work beyond the ridge. The ridge alone breaks 180° rotation; the asymmetric
+outline additionally defeats the **mirrored-part** case — a mirror-image copy will not fit, so a
+modelling or printing mirror is caught at assembly rather than three steps later.
+
+And for children specifically, a symmetric cartoon face reads as a mask; illustrators asymmetrise
+deliberately so a face reads as a *character*. The asymmetry is earning its keep three ways at once.
+
+### What is worth keeping in mind anyway
+
+**The ears differ by 42 %** — left 8.33 mm wide (top y 65.68), right 11.81 mm (top y 66.69). Both
+start at the same y = 60.79, so they read as a deliberate pair rather than an error. 42 % is well
+above the perceptual threshold: you see it instantly. Good cue.
+
+**The mouth is a smirk** — x −21.93 … 0.00, centred at x = −10.96, stopping on the centreline. A
+classic character device and a strong asymmetry.
+
+**The rounds are the best cue and the one safety question.** All four are on the left — Ø11.71 at
+(−40.82, 7.38), Ø11.71 at (−34.76, 0.58), Ø10.00 at (−29.85, 60.83), Ø2.90 at (−26.70, 65.95) — and
+the right side is entirely sharp. This is the *most locally readable* cue in the design: the ears
+differ only by comparison (you must see both to know which is which), whereas a rounded corner tells
+you "this is the left" from that corner alone, by eye **or by fingertip**. For children assembling by
+feel that is the cue doing the real work.
+
+The tension is that "sharp" on a children's part is a hazard, and the obvious safety fix — round
+everything — destroys the cue. The resolution is not round-vs-sharp but **large-vs-small radius**:
+keep R≈6 on the left and give the right R≈1. R1 still reads and feels sharp locally, so the cue
+survives, and the actual edge hazard goes away. That is the one recommendation that outlives the
+correction.
+
+**One measurement that does not fit the story:** the outline is off-centre by **0.54 mm** (left reach
+40.99, right reach 42.07). A deliberate cue should be unmissable; 0.54 mm is invisible. It is
+probably a by-product of the other features rather than intent — worth a look, not a defect.
+
+---
+
+## Two judgement calls, not defects
+
+**The snout is highest at the nose tip and slopes down toward the brow** — a real bear's muzzle
+does the opposite. Anatomically it reads more like a beak or a horn than a snout. But mechanically
+it is the better choice: the nose tip enters the pocket first and does the finding. Keep it if the
+lead-in matters more than the likeness; flip it if "it must look like a bear" wins.
+
+**Only the male was supplied**, so the clearance, the fit and the pocket are unassessed. Nothing in
+this note should be read as a judgement on them.
+
+---
+
+## The strategic point, which is the real reason this design is good
+
+It gives orientation **a name**. "Ears up, nose down" needs no legend, no convention and no
+documentation. Face recognition is the most robust pattern-matching humans have: it survives low
+resolution, poor light, partial occlusion and peripheral vision. That is exactly the robustness the
+abstract ridge key was reaching for, and here it comes for free.
+
+**One earlier objection does not transfer — noting it only so it is not carried over by mistake.**
+In §8c of the design doc a female *pocket* measured as visually invisible — flat-shaded, a recess
+reads as a blank rectangle — and I concluded male/female
+is the wrong polarity cue. **That was a viewport finding, and it does not apply to a physical part.**
+Nobody looks into the pocket of a toy; they feel it. For a part in a child's hands, male/female is
+exactly the right polarity language. The earlier conclusion stands for the on-screen glyph and must
+not be carried over to this.
+
+**The one rule to write down now:** the face and the key must never be allowed to disagree. People
+will trust the face over the mechanics every time. Here they agree — ridge on the centreline, ears
+up. If the face is ever restyled independently of the key, a user will orient by the bear and be
+wrong. Tie them permanently, in the model and in whatever generates it.
diff --git a/docs/CAD/design/mate-connectors/BearConnector_Cutter.step b/docs/CAD/design/mate-connectors/BearConnector_Cutter.step
new file mode 100644
index 0000000000..c78e19e536
--- /dev/null
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diff --git a/docs/CAD/design/mate-connectors/BearConnector_Female_Trimmed.step b/docs/CAD/design/mate-connectors/BearConnector_Female_Trimmed.step
new file mode 100644
index 0000000000..e6575701e4
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+#1479 = LINE('',#1480,#1481);
+#1480 = CARTESIAN_POINT('',(-11.6927539352,-22.,-48.00951684793));
+#1481 = VECTOR('',#1482,1.);
+#1482 = DIRECTION('',(0.,1.,0.));
+#1483 = ORIENTED_EDGE('',*,*,#1208,.F.);
+#1484 = ORIENTED_EDGE('',*,*,#1478,.F.);
+#1485 = CYLINDRICAL_SURFACE('',#1486,4.735522705283);
+#1486 = AXIS2_PLACEMENT_3D('',#1487,#1488,#1489);
+#1487 = CARTESIAN_POINT('',(-16.42827664048,-22.,-48.00951684793));
+#1488 = DIRECTION('',(0.,1.,0.));
+#1489 = DIRECTION('',(1.,0.,0.));
+#1490 = ADVANCED_FACE('',(#1491),#1499,.F.);
+#1491 = FACE_BOUND('',#1492,.F.);
+#1492 = EDGE_LOOP('',(#1493,#1494,#1495,#1496,#1497,#1498));
+#1493 = ORIENTED_EDGE('',*,*,#1264,.T.);
+#1494 = ORIENTED_EDGE('',*,*,#1233,.T.);
+#1495 = ORIENTED_EDGE('',*,*,#1352,.T.);
+#1496 = ORIENTED_EDGE('',*,*,#1328,.T.);
+#1497 = ORIENTED_EDGE('',*,*,#1304,.T.);
+#1498 = ORIENTED_EDGE('',*,*,#1280,.T.);
+#1499 = PLANE('',#1500);
+#1500 = AXIS2_PLACEMENT_3D('',#1501,#1502,#1503);
+#1501 = CARTESIAN_POINT('',(-45.46495478095,0.,-70.97315781796));
+#1502 = DIRECTION('',(0.,1.,0.));
+#1503 = DIRECTION('',(0.,0.,1.));
+#1504 = ADVANCED_FACE('',(#1505),#1508,.F.);
+#1505 = FACE_BOUND('',#1506,.F.);
+#1506 = EDGE_LOOP('',(#1507));
+#1507 = ORIENTED_EDGE('',*,*,#1369,.T.);
+#1508 = PLANE('',#1509);
+#1509 = AXIS2_PLACEMENT_3D('',#1510,#1511,#1512);
+#1510 = CARTESIAN_POINT('',(-45.46495478095,0.,-70.97315781796));
+#1511 = DIRECTION('',(0.,1.,0.));
+#1512 = DIRECTION('',(0.,0.,1.));
+#1513 = ADVANCED_FACE('',(#1514),#1517,.F.);
+#1514 = FACE_BOUND('',#1515,.F.);
+#1515 = EDGE_LOOP('',(#1516));
+#1516 = ORIENTED_EDGE('',*,*,#1469,.T.);
+#1517 = PLANE('',#1518);
+#1518 = AXIS2_PLACEMENT_3D('',#1519,#1520,#1521);
+#1519 = CARTESIAN_POINT('',(-45.46495478095,0.,-70.97315781796));
+#1520 = DIRECTION('',(0.,1.,0.));
+#1521 = DIRECTION('',(0.,0.,1.));
+#1522 = ( GEOMETRIC_REPRESENTATION_CONTEXT(3) 
+GLOBAL_UNCERTAINTY_ASSIGNED_CONTEXT((#1526)) 
+GLOBAL_UNIT_ASSIGNED_CONTEXT((#1523,#1524,#1525)) REPRESENTATION_CONTEXT
+('Context #1','3D Context with UNIT and UNCERTAINTY') );
+#1523 = ( LENGTH_UNIT() NAMED_UNIT(*) SI_UNIT(.MILLI.,.METRE.) );
+#1524 = ( NAMED_UNIT(*) PLANE_ANGLE_UNIT() SI_UNIT($,.RADIAN.) );
+#1525 = ( NAMED_UNIT(*) SI_UNIT($,.STERADIAN.) SOLID_ANGLE_UNIT() );
+#1526 = UNCERTAINTY_MEASURE_WITH_UNIT(LENGTH_MEASURE(2.E-06),#1523,
+  'distance_accuracy_value','confusion accuracy');
+#1527 = PRODUCT_RELATED_PRODUCT_CATEGORY('part',$,(#7));
+ENDSEC;
+END-ISO-10303-21;
diff --git a/docs/CAD/design/mate-connectors/BearConnector_Female_Trimmed_wall.stl b/docs/CAD/design/mate-connectors/BearConnector_Female_Trimmed_wall.stl
new file mode 100644
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diff --git a/docs/CAD/design/mate-connectors/DESIGN_MATE_CONNECTORS.md b/docs/CAD/design/mate-connectors/DESIGN_MATE_CONNECTORS.md
new file mode 100644
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@@ -0,0 +1,922 @@
+# Mate connectors: aligning with the mainstream CAD systems
+
+Research date: 2026-08-05. Written against `orca_cad` / `Snapmaker` at the M8 state
+(`CadDocument.{hpp,cpp}`, `apply_mate`, `datum_frame`, the `Mate` card in `DesignPanel.cpp`).
+
+**Brief:** align with the mate-connector concept as the main CAD programs actually implement it,
+and be simple, unequivocal, unconfusing. Alignment is the organising principle of this document:
+every recommendation is labelled either **[INDUSTRY]** — do what they all do — or **[DEVIATION]** —
+we would be departing, here is why and what it costs.
+
+---
+
+## 0. The answer in ten lines
+
+1. Seven systems surveyed. **Five of the seven use the same model**; two are the old world.
+2. The model: a joint is defined between **two local coordinate frames**, one rigidly attached to
+   each part, plus **one type** naming which DOF stay free.
+3. The frame is called a mate connector (Onshape), a **joint origin** (Fusion, Inventor), a joint
+   connector (FreeCAD 1.0). Same object, three names.
+4. **Every one of them expresses every DOF about the frame's Z axis.** One axis, one convention.
+5. **Five types appear in every frame-based system with identical names and identical DOF**:
+   Fastened/Rigid, Revolute, Slider, Cylindrical, Planar. Ball is in four of five.
+6. That is not fashion — those are the classical **lower kinematic pairs**. The vocabulary converged
+   because the mechanics converged.
+7. Our kernel is already on the right side of the line: frame-based, five types, Z-relative,
+   superimpose-then-relax. **The architecture needs no revisiting.**
+8. Where we are out of step: connectors that are not attached to a body; an origin that can only be
+   a face centroid; no live preview of the two Z arrows; a mate card of abstract dropdowns.
+9. Where we would knowingly deviate: refusing a second mate per body (no vendor does this — it is
+   forced on us by having no solver) and possibly inverting the default mate direction.
+10. Biggest single win for the stated goal, and it costs no kernel work: **draw both frames and
+    ghost the result before Confirm.** The convention stops needing to be remembered.
+
+---
+
+## 1. The two families
+
+**Constraint-based ("old CAD").** The user states pairwise *geometric relations* between raw
+topology — this face coincident with that face, this axis concentric with that axis, this plane
+parallel at 12 mm. Each relation removes some DOF; a numerical solver satisfies all of them at once.
+Fully positioning one part typically takes **three or more mates**, and the set can be
+over-constrained, under-constrained, or satisfiable in several configurations.
+
+**Frame-based ("mate connectors").** The user places a *local coordinate system* on each part and
+states **one** relation between the two frames. The relation is not "these surfaces touch" but
+"these frames coincide, except for the following DOF, which stay free."
+
+Onshape's help page opens by drawing exactly this line:
+
+> *"Mates in Onshape are different than mates in old CAD systems. Many assemblies require only one
+> Onshape Mate between any two instances, as the movement (degrees of freedom) between those two
+> instances is embedded in the Mate."*
+
+The frame-based model won for three reasons, all of which matter here:
+
+- **One mate per pair.** No mental arithmetic about which three constraints add up to a hinge.
+- **The DOF are declared, not deduced.** A revolute mate *is* one rotation. You do not discover the
+  remaining freedom by dragging.
+- **It needs no simultaneous solver for the common case.** Frame-to-frame alignment is a matrix
+  composition — precisely what `apply_mate` already does.
+
+> **Caveat — several vendors ship both, and "align with X" is therefore ambiguous.** **Inventor**
+> kept its legacy constraints *and* added frame-based Joints in 2012; many Inventor users still build
+> assemblies entirely with the old constraint stack. **Creo** has placement constraints *and*
+> Mechanism connections. **FreeCAD** had constraint-based Assembly2/3 add-ons before the frame-based
+> Assembly workbench shipped in 1.0. So copying "what Inventor does" means copying **one of two
+> coexisting workflows**. **Onshape and Fusion 360 are the only pure frame-based examples**, and they
+> are the ones to weight most heavily when the evidence conflicts.
+
+---
+
+## 2. Field survey — seven systems
+
+| | Onshape | Fusion 360 | Inventor | FreeCAD 1.0 | Creo | Siemens NX | SOLIDWORKS |
+|---|---|---|---|---|---|---|---|
+| **Family** | Frame | Frame | Frame (+ legacy constraints) | Frame (+ legacy add-ons) | Both | Constraint | Constraint |
+| **Frame object** | Mate connector | Joint origin | Joint origin | Joint connector (`Placement1/2`) | CSYS on `Weld`/`6DOF` | — | — (nearest: **mate reference**) |
+| **Where it lives** | Part Studio **and** Assembly; in the feature list | Component, inside the joint | Component / inside the joint | Inside the Joint object | Part | — | Part (up to 3 named entities) |
+| **Origin placement** | Inferred family on hover; `Shift` locks | Discrete **snap points**; `Ctrl` cycles | Snap points + explicit origins | Inferred, previewed on hover | Picked CSYS | Picked entities | Picked entities |
+| **Orientation control** | Primary axis (Z) + secondary axis; flip + 90° reorient | Flip, angle, offsets | Flip, angle, offsets | `Placement1/2` + `Offset1/2` | CSYS + offset | — | — |
+| **Type inference** | No — explicit | No — explicit | **Yes — "Automatic"** from picked geometry | No | No | No | Partial (mate reference type) |
+| **Solver** | Yes, simultaneous — *"order won't affect a Mate"* | Yes | Yes | Yes (Ondsel) | Yes | Yes | Yes |
+| **Reuse across instances** | **Yes** — a Part Studio connector exists on every instance | Weak | Partial | Per-joint | Interfaces | Product Interface | Mate references auto-mate on insert |
+
+Three observations that shape everything below.
+
+- **Every frame-based system reduced the type list by an order of magnitude** relative to SOLIDWORKS
+  (7–13 vs ~25) and lost nothing. That is not simplification-by-omission; it is what happens when the
+  DOF live in the mate instead of being assembled from constraints.
+- **Every one of them defines its types relative to a single axis.** Slider translates along Z,
+  Revolute rotates about Z, Cylindrical does both, Planar translates in X/Y and rotates about Z.
+  One axis carries the whole vocabulary.
+- **Onshape alone treats the connector as a first-class, reusable, named object** — and that is also
+  where its worst usability complaints come from (§4).
+
+---
+
+## 3. The type vocabulary — cross-system table
+
+DOF = degrees of freedom left **free**, stated about/along the connector Z.
+
+| DOF | Onshape | Fusion 360 | Inventor | FreeCAD 1.0 | Creo | **Ours today** |
+|---|---|---|---|---|---|---|
+| 0 | Fastened | Rigid | Rigid | Fixed | Rigid / Weld | **Fastened** ✅ |
+| 1 — rot Z | Revolute | Revolute | Rotational | Revolute | Pin | **Revolute** ✅ |
+| 1 — trans Z | Slider | Slider | Slider | Slider | Slider | **Slider** ✅ |
+| 2 — rot + trans Z | Cylindrical | Cylindrical | Cylindrical | Cylindrical | Cylinder | **Cylindrical** ✅ |
+| 3 — trans XY + rot Z | Planar | Planar | Planar | *(Parallel+Distance)* | Planar | **Planar** ✅ |
+| 3 — rot XYZ | Ball | Ball | Ball | Ball | Ball | — |
+| 2 — different axes | Pin slot | Pin-Slot | — | — | Slot / Bearing | — |
+| 1 — coupled | Screw | — | — | Screw | — | — |
+| 4 | Parallel | — | — | Parallel | — | — |
+| other | Tangent, Width, Group | As-built | Automatic | Perpendicular, Angle, Distance, Gears, Belt, RackPinion | General, 6DOF | — |
+
+**Five types appear in every frame-based system, with the same name and the same DOF.** Those five
+are the industry's common denominator, and they are exactly `mate_kind` 0–4 as already implemented.
+Ball is in four of five. Everything past that is a long tail no two vendors agree on.
+
+### Why the convergence is a fact, not a fashion
+
+A rigid-body placement is an element of SE(3). A mate leaves some set of relative motions free. For
+the mate to behave the same throughout its range — for a hinge to be a hinge at every angle — that
+free set must be **closed under composition**: two allowed motions must compose to an allowed motion.
+A closed set of motions is a **subgroup** of SE(3).
+
+The subgroups corresponding to physical surface-on-surface contact are the classical **six lower
+pairs** (Reuleaux):
+
+| Pair | Free motion relative to Z | DOF |
+|---|---|---|
+| Revolute (R) | rotation about Z | 1 |
+| Prismatic / slider (P) | translation along Z | 1 |
+| Helical / screw (H) | coupled rotation + translation | 1 |
+| Cylindrical (C) | rotation about **and** translation along Z | 2 |
+| Planar (E/G) | translation in X,Y + rotation about Z | 3 |
+| Spherical / ball (S) | rotation about X, Y, Z | 3 |
+
+Plus the two trivial ends: identity (0 DOF — **fastened**) and all of SE(3) (6 DOF — floating, i.e.
+no mate). Hervé's Lie-subgroup analysis of the displacement group is the standard reference for
+treating these as the algebraic building blocks of mechanism synthesis.
+
+**Consequence.** Anything outside this table is either (a) a *composition* needing a solver, or
+(b) not a joint at all but a *measurement*:
+
+- Onshape's **Parallel** (4 DOF), **Tangent**, **Width**, **Pin slot**, and FreeCAD's **Distance /
+  Angle / Perpendicular** are constraints, not pairs — their free set is not a subgroup, so they only
+  make sense alongside a simultaneous solver.
+- **Gear, Belt, Rack-and-pinion** are *relations between two mates*, a different object entirely.
+- **Screw (H)** is a legitimate lower pair but needs a pitch parameter and is rare in printed parts.
+
+So the vendors' shared five, the lower pairs, and our `mate_kind` 0–4 are the same list arrived at
+three ways. **[INDUSTRY] Stop looking for missing types and spend the budget on the connector.**
+
+---
+
+## 4. What they all agree on — adopt verbatim
+
+Deviating from any of these makes an experienced user's intuition *wrong*, which is the operational
+definition of "confusing".
+
+**A1 [INDUSTRY] — The connector is a full right-handed frame.**
+Origin + Z (primary) + X (secondary). Onshape and Fusion expose exactly these two axis controls and
+nothing else. A point cannot express spin; an axis cannot express clocking.
+*Status: we comply* — `DatumCoordSys` carries origin/x/y and derives Z.
+
+**A2 [INDUSTRY] — Z is the joint axis; every DOF is about or along Z.**
+Revolute rotates about Z. Slider translates along Z. Planar's free plane is normal to Z. Offsets run
+along Z. This single rule is what makes the system learnable: **one axis to look at, and its meaning
+never changes.**
+*Status: we comply* — `mate_offset` along A's z, `mate_angle` about A's z.
+
+**A3 [INDUSTRY] — Mating superimposes the two frames; the type then relaxes specific DOF.**
+FreeCAD states it most plainly: *"the second connector is superimposed on the first connector by
+default and may change its position according to the joint type."* Fastened is not a special case —
+it is the base case with nothing relaxed.
+*Status: we comply* — `T = M_A · Rz · Tz · F · M_B⁻¹`, looser kinds relaxing from there.
+
+**A4 [INDUSTRY] — The connector belongs to a part and moves with it.**
+Onshape: a connector defined in a Part Studio *"is available for reuse on every instance of that part
+in every assembly in which it is instanced."* It is part geometry, not assembly geometry.
+*Status: **violated**.* `CoordSysType::PointWorld` is a bare world XYZ with `X = world X` and no
+`coordsys_body`. Such a connector does not follow its part. See §6 G1.
+
+**A5 [INDUSTRY] — Selection order is meaningful and must be visible.**
+One connector is the reference; the other is driven onto it. Onshape spells out that offsets are
+measured *"from the second Mate connector selected to the first"*, and that reversing the order
+flips the sign.
+*Status: complied with in the data model* (`mate_cs_a` fixed, `mate_cs_b` moves) *but not in the UI* —
+two dropdowns labelled A and B do not tell the user which part is about to jump.
+
+**A6 [INDUSTRY] — Flip and re-clock live in the mate dialog, always.**
+Onshape: *"Click the arrow icon to flip the direction of the primary axis. Click the Reorient
+secondary axis icon to rotate the secondary axis in 90-degree increments."*
+*Status: partial.* We have `mate_flip` (Z reversal). We have `mate_angle` as a free number — strictly
+more powerful than 90° steps, and much worse to *use*: the common case is "it came in a quarter turn
+out", and typing 90 is a worse gesture than pressing a button.
+
+**A7 [INDUSTRY] — DOF are shown, not inferred by the user.**
+Onshape animates each mate's remaining DOF on demand; Fusion and Inventor name the DOF in the type
+list. Our dropdown text already does this in words ("free spin + axial slide"). Keep it.
+
+**A8 [INDUSTRY] — Free DOF are preserved from the current placement, not zeroed.**
+Onshape: a Planar mate aligns the frames *"but they are not restricted to this location with respect
+to their degrees of freedom."*
+*Status: we comply* — and it must be *said*, because a Planar mate that leaves the part where it was
+looks like a mate that did nothing.
+
+---
+
+## 5. Where they diverge — who to copy, and why
+
+### D1 — Where the connector's origin comes from
+
+| | Behaviour |
+|---|---|
+| **Fusion 360** | Discrete **snap points** only: vertex, edge midpoint, face centre, arc centre. `Ctrl` cycles the candidates under the cursor. A circle icon denotes a vertex, a triangle a midpoint. "Between two faces" is a separate explicit option. |
+| **Onshape** | Infers a *family* on hover — centroid, every vertex, every edge midpoint, every arc centre, the centroids of interior regions (holes, slots), and the virtual sharps of conical faces. `Shift` locks the current candidate. |
+| **Inventor** | Snap points, plus explicit joint origins for awkward cases. |
+| **FreeCAD 1.0** | Hovering previews where the connector will land before you commit. |
+| **Ours** | Always the **face centroid**. No alternative exists. |
+
+Onshape's richness has a cost its own documentation admits: *"The suggested locations are based on
+the underlying geometry of the part and changing the geometry will change the location of the Mate.
+This can be undesirable in certain situations."* On the forum this shows up as connectors that move
+or break on edit — the classic topological-naming failure. Fusion's discrete set is poorer and far
+more predictable.
+
+> **[INDUSTRY] Copy Fusion's candidate *set*.** A small, closed, enumerable set — **face centroid,
+> vertex, edge midpoint, arc/circle centre** — each drawn before commit, with the card naming which is
+> in use ("Origin: edge midpoint"). This is our largest expressiveness gap: a face centroid alone
+> cannot place a hinge pin on a corner boss. It is also the one place where copying the *simpler*
+> vendor is clearly right.
+>
+> **Open sub-choice — how the candidate is chosen.** Three options, in increasing order of magic:
+> (1) **explicit dropdown** in the card after picking the face — no hover behaviour at all;
+> (2) **Fusion's `Ctrl` cycling** through candidates under the cursor; (3) **Onshape's hover
+> inference**. Kimi's independent review argued for (1) on the grounds that hover is exactly where
+> both vendors' instability complaints originate, and that a dropdown gets ~90% of the expressiveness
+> with none of the hover-guess debugging. That is a fair reading and (1) is the cheapest to build and
+> the easiest to make unequivocal. **Recommendation: build (1) first; if hover is added later, let it
+> *pre-fill the dropdown* rather than silently create an implicit connector** — which also keeps R2
+> (one kind of connector) intact.
+
+### D2 — Explicit type, or inferred from the geometry?
+
+Inventor is the only surveyed system that infers: *"Rotational is selected if the two selected
+origins are circular. Cylindrical if the two selected origins are points on a cylinder. Ball if
+points on a sphere. Rigid for all other origin selections."* Onshape and Fusion require an explicit
+choice.
+
+> **[INDUSTRY, Inventor] Do both, in Inventor's order.** Infer a *default* type from what was picked,
+> then show it in an editable control. Inference is what makes the tool feel like it understands the
+> geometry; the visible, editable result is what keeps it unequivocal. Pure inference with no visible
+> type is the confusing option; a pure dropdown with no default is the tedious one. This also fits
+> the Design tab's geometry-first charter exactly: point at a bore, get Revolute offered.
+
+### D3 — How the Z-direction ambiguity is resolved
+
+This is the specific failure the brief is aimed at. A former IT trainer stated it precisely on the
+Onshape forum:
+
+> *"There is always the risk that users will build their own conceptual models of how software works
+> which may not match the designer's concept. The result is usually a poor user experience and many
+> mistakes… for a good (say) Fixed mate to occur do the Z axes of the two mates have to be pointing
+> in the same direction… Alternatively, should they be facing each other?"*
+
+He is asking the right question and **no vendor's documentation answers it.** Onshape's own advice —
+*"if the behavior is not what you expected, try flipping the primary and/or secondary axis"* — is
+trial and error. This is a gap in the industry, not a convention to copy.
+
+> **[INDUSTRY, method] Resolve it with live preview, not documentation.** FreeCAD previews the
+> connector on hover; Onshape and Fusion both draw the frames. Draw **both** Z arrows the moment the
+> second connector is picked, and ghost the resulting placement *before* Confirm. The convention then
+> never has to be remembered because it is on screen.
+>
+> **[DEVIATION, optional] Name the two cases in the user's words** rather than in axis-speak:
+> "the two faces come together" vs "the axes run the same way". No surveyed vendor does this — they
+> all ship a flip arrow. It is a small, low-risk improvement on the state of the art, and it is
+> separable from the default-direction question in §8 D1.
+
+### D4 — Named, reusable connectors on the part
+
+Onshape: connectors created in the Part Studio are reused on every instance in every assembly.
+SOLIDWORKS' **mate reference** reaches the same end by another route: up to three named entities
+(primary/secondary/tertiary) baked into the part so it auto-mates on drag-and-drop — and a *named*
+mate reference seeks out a matching name on insertion. That naming trick is how a library of
+fasteners assembles itself.
+
+> **[INDUSTRY] Out of scope now, but do not preclude it.** Give connectors a stable, user-visible
+> name at creation. One string today; expensive to add once documents exist in the wild.
+
+---
+
+## 6. Confusion catalogue
+
+Documented ways real implementations confuse people. Each is a requirement in disguise.
+
+**C1 — Which way does Z point?** See D3. If a user has to ask once, they will mis-predict a hundred
+times.
+
+**C2 — The roll is unspecified.** Aligning Z leaves one rotation about Z undetermined. Something must
+pin it, and if that something is world-derived, the frame does not rotate with its part. **This
+codebase shipped exactly this bug** (`en4`): a face-only connector took Z from the face
+normal but X from `coordsys_x_hint`, a world constant, so Fastened and Slider claimed to lock an
+orientation the frame could not see. Fixed 2026-07-26 by deriving X from the face's own first usable
+edge — but note the fix's own caveat: *"replaying an older document whose face-only connector fed a
+mate can now place that body differently."* Roll conventions are load-bearing, and changing one is a
+document-format change.
+
+**C3 — The origin drifts.** See D1.
+
+**C4 — Implicit and explicit connectors are not the same thing.** On the Onshape forum, implicit
+connectors are reported to change their query structure when a feature is edited and re-accepted, and
+are unusable in places explicit ones work. Two things called by one name that behave differently is a
+permanent tax.
+
+**C5 — Which part moves?** A frame alignment is asymmetric. If the UI does not say which frame is
+driven, the user finds out by watching the wrong part jump.
+
+**C6 — Which direction is a positive offset?** Onshape measures *"from the second Mate connector
+selected to the first"* — the sign depends on pick order, and swapping the picks flips it. Documented
+behaviour, documented surprise.
+
+**C7 — One intent, several mates.** The SOLIDWORKS failure: expressing "this shaft is in this hole,
+resting on this shoulder" as three constraints, then discovering the solver picked the mirror
+configuration. Frame-based systems fix this by construction; the requirement is not to reintroduce it.
+
+**C8 — Degenerate frames.** A circular face has no usable in-plane edge direction; a cylinder seam
+projects to nothing; a picked edge parallel to Z gives a zero cross product. `datum_frame` handles all
+three with fallbacks — the requirement is that a fallback be *visible*, because a silent fallback is
+C2 wearing a different hat.
+
+**C9 — Order dependence without a solver.** Onshape can say *"Onshape solves Mates simultaneously so
+order won't affect a Mate."* A system that composes transforms in tree order cannot say that. Two
+mates driving one body means the second wins and the first is a lie on screen.
+
+**C10 — Mirrors and patterns.** A mirrored instance has a left-handed frame. Blindly mirroring a
+connector gives a frame whose Z still points "out" but whose handedness flipped, so every rotation
+runs backwards. Cheap to handle now, miserable to retrofit.
+
+---
+
+## 7. Requirements
+
+Labelled **[INDUSTRY]** (what the frame-based systems do) or **[DEVIATION]** (we would depart).
+
+### Definition
+
+**R1 [INDUSTRY] — A mate connector is a frame attached to exactly one body.** No body, no connector.
+*Test:* creating a connector without a body is rejected at creation, not at mate time.
+→ **`CoordSysType::PointWorld` violates this.** It is a datum wearing a connector's name.
+
+**R2 [INDUSTRY] — One kind of connector, not two.** No "implicit" connector that behaves differently
+from an explicit one. If hover inference is offered, hovering *creates* an ordinary connector.
+*Why:* C4. *Test:* everything that accepts a connector accepts any connector.
+
+**R3 [INDUSTRY] — A mate names exactly one subgroup of free motion.** Fastened (0), Revolute (1),
+Slider (1), Cylindrical (2), Planar (3), optionally Ball (3). *Why:* §3. *Test:* every type's free
+set is closed; no type is "A and also B".
+
+### Orientation
+
+**R4 [INDUSTRY] — Everything is about Z. Say so once, in the UI.** *Test:* no mate parameter refers
+to any other axis.
+
+**R5 [DEVIATION] — Z is the outward material direction, and mates default to FACING.**
+A mate would drive B's Z onto **−A's Z** by default, so picking two faces that should touch makes
+them touch with no options changed. *Why:* it is the whole of C1.
+**Cost and caveat:** this inverts today's default (`mate_flip=false` currently *aligns*), and I could
+not establish from any vendor's documentation what their default actually is — the forum question in
+D3 went unanswered precisely because it is undocumented. So this is marked a deviation on the honest
+grounds that **I cannot prove the industry agrees with it.** If D3's live preview lands first, the
+default matters much less, because the user sees the outcome before committing. See §9 D1.
+
+**R6 [DEVIATION] — Name the two directions; do not ship a boolean called "flip".**
+`Direction: Facing | Aligned`. Every surveyed vendor ships a flip arrow instead. A boolean requires
+remembering what unticked means; two named values do not. Low risk, small improvement on the state of
+the art.
+
+**R7 [INDUSTRY] — Roll is picked, or a stored quarter turn. Never world-derived.**
+X from a referenced edge or in-plane direction; failing that, a deterministic body-attached seed, with
+**Rotate 90°** offered as a stored integer 0–3 on top (this is Onshape's "reorient secondary axis",
+A6). *Why:* C2 and the world-constant bug this project already shipped. *Test:* rotate the parent
+body by any angle; the connector's X rotates with it — *this test already exists* ("a face-only frame
+rotates with its body").
+
+**R8 [INDUSTRY] — A degenerate roll is reported, not absorbed.** *Test:* a connector on a full
+cylindrical face reports "roll undefined — pick a direction" rather than silently taking a fallback.
+
+### Placement
+
+**R9 [INDUSTRY, Fusion] — Origin comes from a small closed set of named candidates.**
+**Face centroid, arc/circle centre, edge midpoint, vertex.** Four. Each stored as
+`(kind, topological reference)` and resolved at rebuild. *Why:* D1. *Test:* the stored kind is visible
+in the card; a rebuild either resolves it or raises an error.
+
+**R10 [INDUSTRY] — An unresolvable reference is an error, never a silent relocation.**
+*Test:* delete the referenced face; the mate reports "connector A: face not found" and the body stays
+where it was.
+
+### Semantics without a solver
+
+**R11 [DEVIATION] — A body is driven by at most one mate. The second is refused.**
+**No surveyed system does this** — they all have solvers and all accept many mates per body. It is
+forced on us by tree-order composition: a second mate on the same body silently overrides the first
+and the screen shows a configuration satisfying only one stated intent (C9). *Test:* creating a
+second mate whose moving body already has one is rejected, naming the existing mate.
+This is the single largest departure in this document. See §9 D4.
+
+> **A tempting misreading, checked and rejected.** It is easy to find the claim that Onshape mandates
+> *"exactly one Mate between any two instances"*, which would make R11 an industry agreement rather
+> than a deviation. **The Onshape page does not say that.** It says *"**Many assemblies require only**
+> one Onshape Mate between any two instances"* and then lists, as an explicit remedy, *"**Use more
+> than one Mate if necessary.**"* One mate per pair is Onshape's *typical case*, not its rule. R11
+> remains a deviation and must be justified on our own architecture, not on theirs.
+
+**R11a [DEVIATION] — The refusal list.** With no solver, these are unsupportable and must be refused
+rather than half-done: a second mate on an already-driven body; cycles (A→B, B→A); closed loops
+(A→B, A→C, B→C); relations *between* mates (gear, belt, rack-and-pinion, screw coupling); **joint
+limits**, which nothing can enforce without a solver; and **dragging a body to exercise a free DOF**,
+which requires keeping the body on the allowed manifold. Motion analysis and animation follow from the
+same lack. *Requirement:* none of these may appear in the UI as something that half-works.
+
+**R12 [DEVIATION] — The mate graph is an acyclic forest rooted at fixed bodies.** A body reached by
+no mate is fixed; cycles are refused. Same root cause as R11. *Test:* A→B, B→A rejected at creation.
+
+**R13 [INDUSTRY] — Free DOF are preserved from the current placement, and the user is told.**
+Behaviour already matches Onshape (A8); the telling does not. *Test:* the card for any type with
+DOF > 0 says which motions remain and that dragging exercises them.
+
+**R14 [INDUSTRY] — State what mirroring does to a connector.**
+*Checked in the code:* `datum_frame` ends with a Gram-Schmidt forcing a right-handed frame
+(`ds.x = Y.cross(Z)`), so a connector resolved on a mirrored body comes out **right-handed, not
+mirror-imaged**. Z follows the mirrored face's outward normal, X follows a mirrored edge, handedness
+is re-imposed. Defensible — a mate on the mirrored part still turns the way its type says — but it
+means a mirrored sub-assembly is *not* the mirror image of the original in its rotation sense.
+*Requirement:* document it and pin it with a test. *Why:* C10.
+
+### Feedback — the part that actually removes confusion
+
+**R15 [INDUSTRY] — Before Confirm, the card answers four questions in words.** Which body moves;
+which way Z points on each connector; how many DOF remain; what the offset is measured from.
+
+**R16 [INDUSTRY] — Draw both frames live, with Z distinguishable, and ghost the result.**
+Two triads with Z rendered differently from X/Y (length, arrowhead, colour). *Why:* D3 — the fastest
+way to make a convention unequivocal is to show it. *Test:* both Z directions are readable in a
+screenshot.
+
+**R17 [INDUSTRY] — Show the DOF budget per body.** "Body 2: 1 of 6 DOF free (rotation about Z)."
+The most educational readout in any assembly system, and free to compute here — the type *is* the DOF
+count. *Test:* the number changes when the type changes.
+
+**R18 [DEVIATION] — Refuse loudly and name the alternative.** Where something is out of scope (a
+second mate, a tangency, a gear ratio), say what is unsupported and what to do instead. Vendors do not
+need this because their solvers accept the input. *Test:* no refusal message ends without a suggested
+next action.
+
+---
+
+## 8. Minimal specification, and gap analysis
+
+### The connector
+
+```
+MateConnector
+    body            int          required, ≥ 0                                   (R1)
+    origin_kind     enum         FaceCentroid | ArcCentre | EdgeMidpoint | Vertex (R9)
+    origin_ref      topo ref     face / edge / vertex index on that body
+    z_source        implied by origin_kind: face normal, arc axis, edge tangent
+    roll_ref        topo ref     optional in-plane edge; else deterministic seed  (R7)
+    roll_quarters   int 0..3     stored quarter turns on top of the seed          (R7, A6)
+    flip_z          bool         reverse Z at the connector
+    name            string       stable, user-visible                             (D4)
+```
+
+`flip_z` is a property of the **connector**, chosen once when it is made — not a per-mate
+afterthought. Keeping connector-flip and mate-direction separate is what stops the "which flip do I
+tick?" question.
+
+### The mate
+
+```
+Mate
+    kind        enum      Fastened | Revolute | Slider | Cylindrical | Planar [| Ball]  (R3)
+    fixed       connector A — its body does not move
+    moving      connector B — its body is driven                                        (A5, C5)
+    direction   enum      Facing | Aligned                                              (R5, R6)
+    offset      mm along A's Z, measured A → B — state this in the label                (C6)
+    angle       deg about A's Z                                                         (R4)
+```
+
+Within one field of what exists.
+
+### Gaps against today
+
+Source of record: `CadDocument.hpp:26,247-252,298-310`; `CadDocument.cpp:1669` (`datum_frame`),
+`:2961` (`apply_mate`), `:1302` (`add_mate`); `DesignPanel.cpp:2671-2709` (the Mate card).
+
+| # | Gap | Severity | Ref |
+|---|---|---|---|
+| G1 | `PointWorld` connectors are not attached to a body and their X is a world constant | **High — data model** | A4/R1 |
+| G2 | Origin is always the face centroid; no vertex / edge-midpoint / arc-centre snap | **High — expressiveness** | D1/R9 |
+| G3 | No live preview of the two Z arrows or of the resulting placement | **High — this is the brief** | D3/R16 |
+| G4 | Mate card is two abstract dropdowns; nothing says which body moves | High — charter + A5 | R15 |
+| G5 | No joint-type inference from the picked geometry | Medium — feel | D2 |
+| G6 | `add_mate` validates nothing — no one-mate-per-body, no cycle check | Medium | R11/R12 |
+| G7 | No `Ball` type | Low | §3 |
+| G8 | Re-clocking needs a typed angle; no 90° step control | Low, cheap | A6/R7 |
+| G9 | Degenerate roll falls back silently | Low | C8/R8 |
+| G10 | Connectors have no stable user-facing name | Low now, expensive later | D4 |
+
+**Already aligned — do not "fix" these:** the five types and their DOF; the frame definition (A1);
+Z as the joint axis (A2); superimpose-then-relax (A3); the fixed/moving asymmetry in the data model
+(A5); DOF wording in the type list (A7); free-DOF preservation (A8); right-handed frames under mirror
+(R14); and `en4`'s fix, which put roll derivation on the body where it belongs (C2).
+
+**The pattern worth naming: the kernel is in good shape and the concept is under-explained.** Half the
+requirements here are wording and drawing, not geometry. The two real engineering items are R9 (origin
+candidates) and R11/R12 (the mate-graph rules).
+
+### Expensive-to-retrofit decisions — get these right in the data model now
+
+Changing any of these after documents exist in the wild costs a migration, not an edit.
+
+1. **Topological reference stability.** Storing raw face/edge indices is brittle — editing a body
+   renumbers faces. Either persistent topology IDs, or store the named origin *kind* plus a
+   deterministic search that re-finds the same geometric intent on rebuild. The latter is cheaper and
+   probably sufficient here; it is also what makes R10's "error, never silent relocation" enforceable.
+2. **Connector ownership** (R1). Remove `PointWorld` or bind it to a body. Do this first.
+3. **Mate direction semantics** (R5/D1). Inverting the default rewrites the meaning of every saved
+   mate.
+4. **Roll representation** (R7). "First usable edge" is better than world-X but still fragile. Store
+   an explicit roll reference plus quarter turns.
+5. **Coordinate convention** — Z = joint axis, X = roll reference. Changing this after release
+   invalidates every mate.
+6. **Units** — offset in mm, angle in degrees. Never change.
+7. **Mirror handedness** (R14) — document the decision, do not let it stay an accident.
+8. **Flat body index vs. a component tree.** Mates currently reference bodies in a flat vector. If
+   **sub-assemblies** are ever in scope, mates must reference nodes in a tree instead. Retrofitting
+   this is painful and it is the one item on this list not already implied elsewhere in the document —
+   **decide now whether nested assemblies are in scope.**
+9. **Serialization field semantics.** Adding fields is easy; redefining `mate_flip` or
+   `coordsys_x_hint` is not.
+10. **The one-mate-per-body rule** (R11). Enforce at creation. Relaxing it later by adding a solver is
+    straightforward; allowing many mates now and discovering later that they silently conflict is not.
+
+---
+
+## 8b. The visual shape of the connector — polarity and verse
+
+Researched separately (2026-08-05) by downloading and **looking at** the vendors' own figures, not
+by reading their prose. Files kept alongside this document in `doc/design/mate-connectors/`.
+
+### What the systems actually draw
+
+**Onshape** — verified from `planarfacemateconnectors.png`, `cylindricalmateconnectors.png`,
+`linearedgemateconnectors.png`, `mateconnector-planarpoints.png`, `matepointiconLG.png`:
+
+> **A small circle with one quadrant filled, plus three short coloured axis arms (X red, Y green,
+> Z blue).**
+
+Three parts, each doing one job:
+
+| Element | What it says |
+|---|---|
+| The **circle** | "I am a frame, and this is my XY plane." |
+| The **filled quadrant** | **The roll.** The shaded sector is the +X/+Y quadrant. |
+| The **coloured arms** | The three axis directions, Z distinguished by colour. |
+
+The quadrant is the cleverest part of the whole design and it is easy to miss. The figure
+`matepointreorientsecondaryaxis.png` shows three connectors side by side with the quadrant in three
+different rotations — **it is the live readout of "reorient secondary axis in 90° increments" (A6).**
+One glyph element makes the otherwise-invisible clocking visible, and makes the 90° button's effect
+legible before you commit. The toolbar icon `matepointiconLG.png` is that same circle-with-a-quadrant,
+so the symbol is consistent from toolbar to viewport.
+
+Candidate snap points, before you choose one, are drawn as **plain small white dots** on the model
+(clear in `mateconnector-planarpoints.png`: dots at every corner and edge midpoint). Candidate and
+committed are deliberately different weights — dots propose, the circle-and-triad commits.
+
+**FreeCAD 1.0** — verbatim from the wiki: *"Connectors are local coordinate systems and are marked by
+a symbol with three axes (X, Y, Z) and a circle representing the XY-plane."* Same core as Onshape —
+circle plus triad — **without** the quadrant.
+
+**Fusion 360** — the joint origin glyph, plus a documented icon language for *candidates*: *"A circle
+denotes a vertex, and a triangle denotes a midpoint."* Shape encodes what kind of point it is.
+
+**Convergent core:** *circle for the XY plane + coloured triad*. Onshape alone adds the roll quadrant.
+
+### What none of them draw — and it is exactly what was asked for
+
+**Nothing in any vendor's glyph says which connector is the reference and which one is about to
+move.** Both ends of a mate are drawn identically. That is confusion C5 ("which part moves?") left
+unsolved in the visual language, and it is why the honest recommendation earlier was a live ghost —
+the ghost compensates for a glyph that does not carry the information.
+
+So the two things asked for split cleanly, and only one of them is solved upstream:
+
+- **Verse** (*verso* — which way it points): **solved**. Z has a colour and a direction.
+- **Polarity** (which end receives, which end inserts; who is anchored, who travels): **unsolved
+  everywhere.** This is open ground, and getting it right is a genuine improvement rather than a
+  deviation to justify.
+
+### Our starting point
+
+**We draw nothing.** `resolve_datum_coordsys()` (`CadDocument.cpp:1749`) has exactly one consumer in
+the entire tree — `McpControl.cpp:1310`, the agent socket. A mate connector is today visible only to
+a program. The glyph is unbuilt, so there is no migration cost to designing it properly now.
+
+### Proposed glyph: the magnet
+
+Adopt Onshape's proven core, then add the missing polarity with a metaphor that carries its own
+instructions.
+
+```
+            ▲  solid cone on +Z ONLY          ← verse
+            |
+        ────●────                              ← the disc = XY plane, ● = exact origin
+        ▨ quadrant filled                      ← roll / clocking, steps 90°
+```
+
+**Rule 1 — verse: draw +Z and never −Z.** A single stem with a cone head, on the positive side only.
+No stem below the disc. A double-headed axis is the one thing that guarantees the question gets asked;
+an arrow that exists on one side only cannot be misread. Length is asymmetric on purpose.
+
+**Rule 2 — roll: keep Onshape's quadrant.** Filled sector = the +X/+Y quadrant. It rotates in 90°
+steps with the reorient control (A6/R7). This is aligned *and* it is the only in-glyph answer to
+"where is X?", which matters because Fastened and Slider lock the clocking.
+
+**Rule 3 — polarity: solid cone travels, open collar receives.**
+- The **driven** connector (B, on the body that will move) draws a **solid filled cone** — the plug.
+- The **fixed** connector (A) draws an **open ring / hollow cone outline** — the socket.
+
+Same silhouette, so they read as a matched pair; opposite fill, so which one is about to jump is
+answerable at a glance and without a legend. Plug-into-socket is the one mechanical metaphor every
+user of this tool already has in their hands.
+
+**Rule 4 — the pair reads as a magnet.** Draw a dashed line joining the two origins the moment both
+are picked. Two poles, one field line. And because a magnet's north seeks a south, **"facing" becomes
+the self-evident default** — which quietly settles open decision D1 (§9) on visual grounds rather than
+on a convention nobody can look up. If the glyph looks like a magnet, nobody has to be told that two
+faces which touch have opposed normals.
+
+**Rule 5 — three states, three weights.**
+
+| State | Drawing |
+|---|---|
+| **Candidate** (hover) | small dot only — Onshape's white dots; shape may encode kind, Fusion-style |
+| **Picked** | full glyph: disc + quadrant + cone |
+| **Degenerate roll** (C8/R8) | the quadrant is drawn **hollow/hatched** — "roll undefined, pick a direction" |
+
+That last row is worth the trouble: it turns R8 from a message nobody reads into a mark you cannot
+miss, and it costs one branch in the renderer.
+
+**Rule 6 — do not reuse the existing triad.** The bed-centre world triad
+(`DesignCanvas.cpp:65`, `set_axes_at_bed_center`) and the move gizmo are already three-coloured arrows.
+The connector must not be a fourth set of RGB arrows or the viewport becomes unreadable. The disc and
+the quadrant are what distinguish it; keep the arms short, and consider drawing only Z on the
+committed glyph, with X/Y implied by the quadrant.
+
+### Built and judged in the viewport, not in a mock
+
+The browser mock that first accompanied this section was the wrong instrument and its proportions
+were meaningless: **every gizmo in this codebase is sized in SCREEN PIXELS** via `upp = 1/zoom`
+(`render_shell_gizmo` uses `15.0 * upp`, `render_hole_gizmo` `9.0 * upp` for its cube). A connector
+is a symbol, not a part — it must not shrink with the model. Nothing about that is visible in SVG.
+
+The glyph was therefore implemented and driven on the rig. Screenshots: `g-0*.png`, left in the workspace `artifacts/shots/` and not moved into the repo.
+Five findings, none of which a mock could have produced:
+
+**F1 — Three axis arms lose to one.** Rendered side by side (`ORCA_CAD_GLYPH=A` vs default), the
+Onshape-style RGB trio crowds a 22 px disc: the arrowheads are as large as the disc, they bury the
+gold quadrant, and at an oblique angle the three heads pile into a coloured smudge. Worse, **it is
+indistinguishable from the move gizmo and the bed triad**, which are already RGB arrow trios in this
+viewport. One-sided Z wins on evidence, not taste. (`g-01-zoom.png` vs `g-02-zoom.png`.)
+
+**F2 — Polarity works, and colour does more of the work than fill.** A filled blue head against an
+open grey outline head is readable instantly at 22 px (`g-03-zoom.png`). But the fill difference is
+the *second* cue; the colour split carries it. Keep both — fill survives greyscale and colour-blind
+palettes, colour survives small size.
+
+**F3 — Depth off floats, depth on tears.** With `GL_DEPTH_TEST` off, connectors on faces pointing
+*away* from the camera still drew their discs over the solid, so the part looked covered in frames
+that were really on its back. Turning depth on fixed that and immediately caused **z-fighting**: the
+disc is exactly coplanar with its face, and came out as a broken dotted arc. The fix is depth **on**
+plus a sub-pixel lift along Z (`0.7 * upp`), scaled by `upp` so it never becomes a visible gap on
+zoom-in. Both failure modes are in the images (`g-03` torn, `g-04` clean).
+
+**F4 — The quadrant is the first thing to die at a grazing angle.** On a face seen nearly edge-on the
+disc foreshortens to a sliver and the fan collapses into a blob (`g-01-zoom.png`, lower-right glyph).
+The roll is exactly the information that is hardest to read when you most need it. Not yet solved —
+see the open item below.
+
+**F5 — Roll-undefined in red is too loud.** It works, but it makes the *least* important connector
+the most eye-catching thing on screen. Amber, or the same grey with a hatched quadrant, is enough.
+
+Also surfaced while testing, and unrelated to the glyph: `add_mate` accepted a mate between two
+connectors **on the same body**, which is meaningless, and duly transformed the body relative to
+itself. Concrete instance of gap G6.
+
+**Still untested:** a true grazing view (the view-cube click missed), a connector on a curved face,
+and behaviour when a connector overlaps the move gizmo. F4 is the open design question — the disc may
+need to billboard its *quadrant* while keeping the disc in-plane, which is a compromise no surveyed
+vendor makes and which should be tried before being adopted.
+
+### What this costs
+
+A renderer for `resolve_datum_coordsys()` — which does not exist and has to be written whatever glyph
+is chosen — plus one dashed line and three fill states. No kernel work. It is the same piece of work
+as G3 (live preview), and doing them together is what makes the mate card honest.
+
+---
+
+## 8c. The "faceted ridge dome" proposal — built, rendered, judged
+
+A colleague proposed replacing the flat disc with an **asymmetric low-poly solid**: a faceted
+prismatic wedge with a dominant longitudinal ridge that **slopes** from a tall steep back to a long
+shallow front, plus a male protrusion / female pocket pair with a 0.2 mm clearance.
+
+It was built rather than discussed. `faceted_ridge_key.scad` (this folder) (6 vertices, 7 faces),
+verified as a closed manifold, exported through OpenSCAD, and flat-shaded from five directions with
+`render_key.py` / `render_stl.py`. Sheets: `rk-sheet.png`, `cmp-sheet.png`.
+
+### The verdict: the shape is right, the male/female polarity cue is not
+
+**It solves F4, decisively.** The grazing view — where the flat disc dies, its quadrant collapsing to
+a blob — is the view where this shape is *most* legible: the tall back and long shallow front are
+unmistakable in silhouette. At a grazing angle the silhouette IS the information, and this solid's
+silhouette is maximally informative there. That is a real, evidence-backed win over what is currently
+in the code.
+
+**Down the mating axis (+Z) it also reads well**, which matters because that is the natural viewing
+direction when you are looking at a face you intend to mate.
+
+**One degenerate view, and it is not the one I predicted.** I expected the ±X views (along the ridge)
+to be silhouette-ambiguous, resolved only by shading. Wrong: front and back are clearly *different* —
+the front shows several facets, the back is a **single flat featureless triangle**. So they are not
+confusable, but the view from directly behind the tall end tells you nothing about roll or slope.
+A second blind spot remains untested: from below the base, where the protrusion is hidden behind its
+own face.
+
+**The female half fails, and much harder than expected.** Rendered with flat shading and no outlines —
+the honest test, since a viewport draws no black edges — a recessed pocket is *invisible*: iso and
+grazing show a plain block with a hairline; straight down the axis shows a **completely blank
+rectangle**. The interior faces are lit almost identically to the top face and are occluded by the rim
+from most angles. As a polarity cue, male/female therefore works in exactly one direction and returns
+nothing in the other.
+
+> **Conclusion: do not overload shape with all three jobs.** Let the solid carry **verse and roll**,
+> where it is excellent, and carry **polarity on a second channel** — colour plus the filled/open head
+> that already tested well at 22 px (F2). Drawing the fixed connector as an outline/wireframe of the
+> same solid is the variant worth trying; drawing it as a pocket is not.
+
+### Two premises in the brief are wrong
+
+**"Avoid curved surfaces to optimise rendering computations / rapid mesh processing."** Not a reason
+for a viewport glyph. There are 2–20 connectors on screen, the renderer pushes `GLModel` triangles
+directly, and it performs no CSG or mesh processing at all. **The real argument for flat facets is
+legibility**: hard normals give distinct value steps between adjacent facets, and the renders confirm
+that is exactly what makes the shape readable from an arbitrary angle. Keep the constraint, fix the
+justification. (For a *printed* part the original justification is sound for a different reason: flat
+facets slice without the stair-stepping a tessellated curve produces.)
+
+**"0.2 mm clearance for smooth mechanical mating."** Meaningless for a glyph. A symbol mates with
+nothing, and every gizmo here is sized in screen pixels via `upp`, so a millimetre tolerance has no
+referent. This is the strongest signal that **the brief was written for a physical printed part**,
+not for a viewport symbol — as are "scannable" and "mechanical mating". See the open question below.
+
+### Two defects the build caught that discussion would not have
+
+1. **The flank quads are not planar.** Written as `[0,3,5,4]` and `[1,4,5,2]` the base edge and the
+   ridge edge are skew, so the four corners do not share a plane — my own first draft asserted the
+   opposite in a comment. Left as quads, the tessellator picks the fold direction, the "flat facet"
+   promise is broken by an unspecified crease, and two exporters can disagree about the shape. Fixed
+   by triangulating explicitly (7 faces, Euler 6 − 11 + 7 = 2).
+2. **The pocket punched through its own plate.** A 4.5 mm key against a 3 mm demo plate gives a
+   through-hole, not a pocket. Minimum stock = height + clearance + pocket depth + a wall.
+
+Also worth recording: the first female render was misleading because the debug renderer outlined
+*every* triangle, so a flat top face triangulated by CGAL looked like a faceted dome. The instrument
+lied before the geometry did. Conclusions were only drawn after outlines were removed.
+
+### Second opinion, and the one disagreement worth resolving
+
+Kimi reviewed the proposal independently and **rejected it for the viewport**. It agreed on the two
+wrong premises, agreed the female pocket is unreadable, and added the useful framing that a
+screen-constant symbol and a model-constant part feature are two different design spaces that cannot
+be served by one geometry. It also noted correctly that there is **no single scalar** that removes
+ambiguity from every view: you need one asymmetry in the base plane (for top-down roll) and one out
+of plane (the ridge slope, for front/back). Our base is scalene, so it has both.
+
+Its central objection was numeric and testable: *"at 22 px with 6–8 facets each facet is 3–7 px wide,
+that is at the aliasing limit … minimum useful size is roughly 32–48 px, which is not compatible with
+a 22 px screen-constant symbol."* My own renders were ~300 px, so the claim was unaddressed by my
+evidence and would have killed the concept if true.
+
+**Rendered at 22, 32 and 48 px (`size-test.png`), it is false for this shape.** At 22 px all three
+views still read: the grazing view shows the tall back and shallow front unmistakably, and the
+down-axis view keeps a strong dark/light split. The reason Kimi's arithmetic does not apply is that
+this solid presents only **four or five large facets with high value contrast**, not eight small ones —
+the silhouette does most of the work, and silhouettes survive downsampling far better than facet
+detail does.
+
+*Honest limit on that result:* the test renderer has no anti-aliasing, no perspective, one directional
+light, and no background. Readable at 22 px against white is not the same as readable at 22 px on top
+of a shaded gold part next to the move gizmo. That case still needs the rig.
+
+**Where I do not follow Kimi:** its recommendation is to **billboard** the existing flat glyph so it
+never turns edge-on. That kills F4 by construction, but a billboarded frame cannot show the frame's
+orientation *in place* — which is the entire reason the disc is a disc and not a dot — and it is what
+no surveyed CAD system does; Onshape, Fusion and FreeCAD all draw the frame in the geometry. Worth
+prototyping as an option, not worth adopting on argument.
+
+### Open question for Tommaso
+
+**Is this a viewport glyph or a printable alignment feature?** The vertex logic is identical either
+way; only the units and the clearance change, and the `.scad` file states both readings. But the
+answer decides whether `clr`/`depth` are real millimetres or meaningless, and whether the geometry
+scales with the model or stays screen-constant. The brief's own language points at "physical", the
+conversation it arrived in points at "glyph".
+
+---
+
+## 9. Decisions for you
+
+**D1 — Invert the default direction to Facing?** [DEVIATION, R5]
+It changes the meaning of every stored document containing a mate. Options: (a) invert and migrate,
+writing `direction=Aligned` where `mate_flip` was false; (b) invert only for new mates and store
+`direction` explicitly from now on. (b) is safer and costs one field. Note this project has taken one
+such semantic hit knowingly before — the `en4` fix — and the golden fixture survived, so the
+migration path is a known quantity. **If G3 (live preview) lands first, this matters much less.**
+
+**D2 — How far to take origin candidates?** [R9]
+Four kinds is the Fusion-aligned recommendation. Two (face centroid + arc centre) would cover "sit on
+a face" and "go down a hole" — most printed-part assembly — at a third of the work. Where do you want
+to stop?
+
+**D3 — Ball mate: in or out?**
+In four of five frame-based systems, so including it is the aligned choice. Out is defensible for
+printable mechanical parts. Cheap either way — align origins, leave orientation free. Kimi's review
+argued **out**: a true ball joint is hard to print and hard to use without a roll reference, and a
+Fastened connector at the ball centre approximates it.
+
+**D3a — Should Planar be dropped?** [dissent worth recording]
+Kimi's independent review recommended **removing Planar** and shipping four types, on the grounds that
+"slide on a flat surface" is rarely how printed mechanisms work — you usually want a rail or a hinge —
+and that Planar is the type most likely to confuse a user who expected "put this flat on that" and got
+a part free to slide. It further ranked the honest minimum as **three**: Fastened, Revolute, Slider,
+with Cylindrical useful and decomposable.
+**I do not agree, and the reason is alignment.** Planar appears in every frame-based system surveyed,
+it is a genuine lower pair, it is already implemented and tested, and removing it is a document-format
+change made in exchange for nothing. The confusion Kimi names is real but it is a *feedback* problem —
+it is exactly what R17 (show the DOF budget) and R13 (say that free DOF are preserved) exist to fix.
+Recorded here because it is a legitimate reading of the same evidence and the call is yours.
+
+**D4 — Is refusing a second mate per body acceptable?** [DEVIATION, R11 — the big one]
+It is the honest consequence of having no solver, and it is what makes the tool predictable. But **no
+mainstream system behaves this way**, so it is the point where an experienced user's intuition will
+break. It means a part cannot be constrained by two independent relationships — "in this hole *and*
+resting on this shoulder" must be expressed by placing one connector correctly rather than by two
+mates. If that trade is unacceptable, the answer is a solver, and the scope of this document changes
+entirely.
+
+There is a strong argument that the trade is not merely acceptable but *correct for this product*:
+the Design tab lives inside a slicer, and most of its users are positioning parts for printing rather
+than building working mechanisms. For layout-and-export, tree-order composition is genuinely enough,
+and adding a solver to look like Onshape would buy complexity nobody asked for. The rule to publish is
+then simple and defensible: **one mate per moving body, acyclic, no relations between mates** — with
+R18's loud refusals carrying the honesty.
+
+---
+
+## Sources
+
+**Onshape** — [Mate Connector](https://cad.onshape.com/help/Content/PartStudio/mate_connector.htm) ·
+[Mates](https://cad.onshape.com/help/Content/Assembly/mates.htm) ·
+[Fastened](https://cad.onshape.com/help/Content/Assembly/fastened_mate.htm) ·
+[Revolute](https://cad.onshape.com/help/Content/Assembly/revolute_mate.htm) ·
+[Slider](https://cad.onshape.com/help/Content/Assembly/slider_mate.htm) ·
+[Cylindrical](https://cad.onshape.com/help/Content/Assembly/cylindrical_mate.htm) ·
+[Planar](https://cad.onshape.com/help/Content/Assembly/planar_mate.htm) ·
+[Ball](https://cad.onshape.com/help/Content/Assembly/ball_mate.htm) ·
+[Parallel](https://cad.onshape.com/help/Content/Assembly/parallel_mate.htm) ·
+[Tangent](https://cad.onshape.com/help/Content/Assembly/tangent_mate.htm) ·
+[Pin Slot](https://cad.onshape.com/help/Content/Assembly/pin_slot_mate.htm) ·
+[5 things you can do with mate connectors in Part Studios](https://www.onshape.com/en/resource-center/tech-tips/tech-tip-5-things-you-can-do-with-mate-connectors-in-onshape-part-studios)
+
+**Onshape forum** — [The concept behind Mates Z Axes](https://forum.onshape.com/discussion/22828/the-concept-behind-mates-z-axes) (C1/D3) ·
+[Implicit mate connectors act differently than explicit ones](https://forum.onshape.com/discussion/15736/implicit-mate-connectors-act-differently-than-explicit-ones) (C4) ·
+[Efficiently set mate connectors](https://forum.onshape.com/discussion/13133/efficiently-set-mate-connectors)
+
+**Fusion 360** — [Joint types](https://help.autodesk.com/cloudhelp/ENU/Fusion-Assemble/files/GUID-8818AE31-958A-4A59-989B-9875A174C67A.htm) ·
+[Joint origins](https://help.autodesk.com/view/fusion360/ENU/?guid=ASM-JOINT-ORIGIN) ·
+[Joints vs. Mates in Fusion](https://www.autodesk.com/products/fusion-360/blog/joints-mates-moving-fusion/) ·
+[Joint tips — snap points and Ctrl cycling](https://mgfx.co.za/blog/engineering-manufacturing-design/fusion-360-joint-tips/)
+
+**Inventor** — [Create Joints Reference](https://help.autodesk.com/cloudhelp/2026/ENU/Inventor-Help/files/GUID-6AA68E8F-7C97-4806-8483-3941DE915E70.htm) ·
+[Use Joint to define and manage relationships](https://knowledge.autodesk.com/support/inventor-products/learn-explore/caas/CloudHelp/cloudhelp/2014/ENU/Inventor/files/GUID-21DC3336-5C51-42C1-90FB-4299CD66E0C6-htm.html) (type inference, D2)
+
+**FreeCAD 1.0** — [Assembly Workbench](https://wiki.freecad.org/Assembly_Workbench) ·
+[Fixed Joint properties](https://wiki.freecad.org/Assembly_CreateJointFixed)
+
+**Creo** — [About Predefined Constraint Sets](https://support.ptc.com/help/creo/creo_pma/r12/usascii/assembly/asm/About_Predefined_Constraint_Sets.html)
+
+**Siemens NX** — [Assembly constraints](https://learnnx.com/lesson/siemens-nx-assemblies-assembly-constraints/)
+
+**SOLIDWORKS** — [Mate References](https://help.solidworks.com/2025/English/SolidWorks/sldworks/c_Mate_References_Overview_SWassy.htm) ·
+[Creating and using mate references](https://blogs.solidworks.com/tech/2019/07/creating-and-using-mate-references.html)
+
+**Theory** — [Hervé, The Lie group of rigid body displacements, a fundamental tool for mechanism design](https://www.sciencedirect.com/science/article/abs/pii/S0094114X98000512) ·
+[Joint kinematics — the six lower pairs and their DOF](https://erc-bpgc.github.io/handbook/mechanical/Joint%20Kinematics/) ·
+[ISO 10303-105 — Kinematics (STEP integrated resource)](https://www.iso.org/standard/78589.html)
+
+**Internal** — `en4` (closed 2026-07-26, fixes C2 here) · `CadDocument.cpp:1669`
+`datum_frame` · `CadDocument.cpp:2961` `apply_mate` · `CadDocument.cpp:1302` `add_mate`
+
+**Second opinion** — an independent review by Kimi Code (2026-08-05) contributed the
+vendors-ship-both caveat (§1), the explicit-dropdown option for origin choice (D1), the expanded
+refusal list (R11a), the retrofit list (§8), and the dissents recorded at D3/D3a. One of its claims —
+that Onshape mandates *"exactly one Mate between any two instances"* — **was checked against the
+source and is wrong**; the correction is recorded at R11 because it is a misreading that would
+otherwise turn our largest deviation into a false agreement.
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diff --git a/docs/CAD/design/mate-connectors/bear_glyph_table.h b/docs/CAD/design/mate-connectors/bear_glyph_table.h
new file mode 100644
index 0000000000..c26631e7e0
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/bear_glyph_table.h
@@ -0,0 +1,30 @@
+// Emitted by doc/design/mate-connectors/emit_glyph_table.py from bear.step — do not hand-edit.
+// Normalised to the part's bounding span and centred: the renderer scales by one radius.
+static const Vec2d kBearOutline[] = {        // 12 verts, RDP eps 0.030, CCW
+    {+0.3842, +0.3294}, {+0.3156, +0.4002}, {+0.2424, +0.3294},
+    {-0.2524, +0.3294}, {-0.3377, +0.3877}, {-0.3693, +0.3298},
+    {-0.3256, +0.2631}, {-0.4893, -0.3337}, {-0.3960, -0.4002},
+    {+0.4151, -0.4002}, {+0.5000, -0.3154}, {+0.3156, +0.2631},
+};
+static const Vec2d kBearChin[] = {            // the CHIN BAR, flat. The muzzle is relief — see kBearCrest.
+    {-0.2682, -0.3578}, {+0.2628, -0.3578}, {+0.2237, -0.1786},
+};
+// {cx, cy, r}: two eyes, then the cheek dot that carries handedness (wi3z).
+static const Vec3d kBearMarks[] = {
+    {-0.1997, +0.1760, +0.0590},
+    {+0.1947, +0.1760, +0.0590},
+    {+0.2797, +0.0760, +0.0380},
+};
+// THE MUZZLE, lifted off the mesh: a tapered wedge, base quad + crest edge, 6 facets.
+// This is the only feature standing along +Z and the only one still legible edge-on.
+static const double kBearPlateZ = +0.0360;
+static const Vec2d kBearSnoutBase[] = {   // CCW from the nose end
+    {-0.0727, -0.2417},
+    {+0.0630, -0.2417},
+    {+0.0259, +0.1939},
+    {-0.0356, +0.1939},
+};
+static const Vec3d kBearCrest[] = {       // nose (tall) -> tail (short)
+    {-0.0048, -0.1793, +0.2073},
+    {-0.0048, +0.1605, +0.1279},
+};
diff --git a/docs/CAD/design/mate-connectors/bear_mesh.json b/docs/CAD/design/mate-connectors/bear_mesh.json
new file mode 100644
index 0000000000..4bfb6aa361
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/bear_mesh.json
@@ -0,0 +1 @@
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\ No newline at end of file
diff --git a/docs/CAD/design/mate-connectors/bear_outline.json b/docs/CAD/design/mate-connectors/bear_outline.json
new file mode 100644
index 0000000000..21b420c616
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/bear_outline.json
@@ -0,0 +1 @@
+{"outer": [[26.711, -55.263], [42.071, -7.071], [35.0, -0.0], [-32.575, 0.0], [-33.717, -0.112], [-34.815, -0.446], [-35.828, -0.987], [-36.715, -1.715], [-39.55, -4.55], [-40.35, -5.547], [-40.914, -6.694], [-41.216, -7.937], [-41.241, -9.215], [-40.988, -10.468], [-26.711, -55.263], [-28.828, -57.312], [-29.64, -58.335], [-30.159, -59.532], [-30.35, -60.823], [-30.201, -62.12], [-29.721, -63.334], [-28.944, -64.382], [-27.718, -65.649], [-27.075, -66.035], [-26.325, -66.047], [-25.67, -65.683], [-20.613, -60.789], [20.613, -60.789], [26.711, -66.69], [32.421, -60.789], [26.711, -55.263]], "holes": [{"pts": [[19.052, -18.464], [16.474, -9.14], [-0.0, -9.104], [-21.926, -9.104], [-21.926, -3.535], [22.308, -3.535], [19.052, -18.464]], "cx": 4.719, "cz": -10.192, "d": 44.234}, {"pts": [[-11.493, -48.01], [-11.676, -49.341], [-12.211, -50.574], [-13.06, -51.617], [-14.158, -52.392], [-15.424, -52.842], [-16.765, -52.934], [-18.081, -52.66], [-19.274, -52.042], [-20.257, -51.124], [-20.955, -49.976], [-21.318, -48.682], [-21.318, -47.337], [-20.955, -46.043], [-20.257, -44.895], [-19.274, -43.977], [-18.081, -43.359], [-16.765, -43.085], [-15.424, -43.177], [-14.158, -43.627], [-13.06, -44.402], [-12.211, -45.445], [-11.676, -46.678], [-11.493, -48.01]], "cx": -16.223, "cz": -48.01, "d": 9.825}, {"pts": [[21.364, -48.01], [21.181, -49.341], [20.645, -50.574], [19.797, -51.617], [18.699, -52.392], [17.432, -52.842], [16.091, -52.934], [14.775, -52.66], [13.582, -52.042], [12.6, -51.124], [11.901, -49.976], [11.539, -48.682], [11.539, -47.337], [11.901, -46.043], [12.6, -44.895], [13.582, -43.977], [14.775, -43.359], [16.091, -43.085], [17.432, -43.177], [18.699, -43.627], [19.797, -44.402], [20.645, -45.445], [21.181, -46.678], [21.364, -48.01]], "cx": 16.634, "cz": -48.01, "d": 9.825}]}
\ No newline at end of file
diff --git a/docs/CAD/design/mate-connectors/circularmateconnectors.png b/docs/CAD/design/mate-connectors/circularmateconnectors.png
new file mode 100644
index 0000000000..3150a5667b
Binary files /dev/null and b/docs/CAD/design/mate-connectors/circularmateconnectors.png differ
diff --git a/docs/CAD/design/mate-connectors/cmp-sheet.png b/docs/CAD/design/mate-connectors/cmp-sheet.png
new file mode 100644
index 0000000000..1d67ae31ed
Binary files /dev/null and b/docs/CAD/design/mate-connectors/cmp-sheet.png differ
diff --git a/docs/CAD/design/mate-connectors/connector-glyph-proposal.html b/docs/CAD/design/mate-connectors/connector-glyph-proposal.html
new file mode 100644
index 0000000000..2a8475ee24
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/connector-glyph-proposal.html
@@ -0,0 +1,299 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+<meta charset="utf-8">
+<meta name="viewport" content="width=device-width, initial-scale=1">
+<title>Mate connector glyph — polarity and verse</title>
+<style>
+  :root {
+    --ground:      #eceef1;
+    --panel:       #f8f9fb;
+    --panel-edge:  #d3d8df;
+    --ink:         #171a1f;
+    --ink-soft:    #5a626e;
+    --ink-faint:   #8b93a0;
+    --viewport:    #9aa0a8;   /* the grey a CAD viewport actually is */
+    --viewport-2:  #7f858d;
+    --axis-z:      #2f6fed;
+    --axis-x:      #d94a3d;
+    --axis-y:      #3aa757;
+    --quadrant:    #e8a317;
+    --anchor:      #6b7280;
+    --driven:      #2f6fed;
+    --warn:        #c2410c;
+  }
+  @media (prefers-color-scheme: dark) {
+    :root {
+      --ground:     #14171c;
+      --panel:      #1b1f26;
+      --panel-edge: #2b313a;
+      --ink:        #e8eaee;
+      --ink-soft:   #a6aeba;
+      --ink-faint:  #6e7784;
+      --viewport:   #4a5058;
+      --viewport-2: #3a3f46;
+      --axis-z:     #6ea2ff;
+      --axis-x:     #ff7a6d;
+      --axis-y:     #5fd07f;
+      --quadrant:   #ffc247;
+      --anchor:     #9aa3b0;
+      --driven:     #6ea2ff;
+      --warn:       #fb923c;
+    }
+  }
+  :root[data-theme="dark"] {
+    --ground:#14171c; --panel:#1b1f26; --panel-edge:#2b313a; --ink:#e8eaee;
+    --ink-soft:#a6aeba; --ink-faint:#6e7784; --viewport:#4a5058; --viewport-2:#3a3f46;
+    --axis-z:#6ea2ff; --axis-x:#ff7a6d; --axis-y:#5fd07f; --quadrant:#ffc247;
+    --anchor:#9aa3b0; --driven:#6ea2ff; --warn:#fb923c;
+  }
+  :root[data-theme="light"] {
+    --ground:#eceef1; --panel:#f8f9fb; --panel-edge:#d3d8df; --ink:#171a1f;
+    --ink-soft:#5a626e; --ink-faint:#8b93a0; --viewport:#9aa0a8; --viewport-2:#7f858d;
+    --axis-z:#2f6fed; --axis-x:#d94a3d; --axis-y:#3aa757; --quadrant:#e8a317;
+    --anchor:#6b7280; --driven:#2f6fed; --warn:#c2410c;
+  }
+
+  * { box-sizing: border-box; }
+  body {
+    margin: 0; padding: 40px 24px 72px;
+    background: var(--ground); color: var(--ink);
+    font: 15px/1.6 ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
+  }
+  .wrap { max-width: 1000px; margin: 0 auto; display: flex; flex-direction: column; gap: 28px; }
+  header { display: flex; flex-direction: column; gap: 6px; }
+  h1 { font-size: 26px; line-height: 1.25; margin: 0; letter-spacing: -0.01em; text-wrap: balance; }
+  .sub { color: var(--ink-soft); max-width: 62ch; margin: 0; }
+  .eyebrow {
+    font-size: 11px; letter-spacing: 0.12em; text-transform: uppercase;
+    color: var(--ink-faint); font-weight: 600;
+  }
+  h2 {
+    font-size: 13px; letter-spacing: 0.1em; text-transform: uppercase;
+    color: var(--ink-faint); margin: 16px 0 0; font-weight: 600;
+  }
+  .row { display: flex; flex-wrap: wrap; gap: 16px; }
+  .card {
+    background: var(--panel); border: 1px solid var(--panel-edge);
+    border-radius: 10px; padding: 18px; flex: 1 1 220px; min-width: 220px;
+    display: flex; flex-direction: column; gap: 10px;
+  }
+  .card.wide { flex: 1 1 100%; }
+  .stage { display: flex; align-items: center; justify-content: center; padding: 4px 0; }
+  .name { font-weight: 650; font-size: 15px; }
+  .note { color: var(--ink-soft); font-size: 13.5px; margin: 0; }
+  .k { color: var(--ink); font-weight: 600; }
+  table { border-collapse: collapse; width: 100%; font-size: 14px; }
+  th, td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--panel-edge); vertical-align: top; }
+  th { color: var(--ink-faint); font-weight: 600; font-size: 12px; letter-spacing: 0.06em; text-transform: uppercase; }
+  code { font: 13px/1.5 ui-monospace, SFMono-Regular, Menlo, monospace; color: var(--ink-soft); }
+  .legend { display: flex; flex-wrap: wrap; gap: 14px; font-size: 13px; color: var(--ink-soft); }
+  .swatch { display: inline-flex; align-items: center; gap: 7px; }
+  .dot { width: 11px; height: 11px; border-radius: 50%; display: inline-block; }
+</style>
+</head>
+<body>
+<div class="wrap">
+
+  <header>
+    <div class="eyebrow">Orca Design · assembly</div>
+    <h1>Mate connector glyph — polarity and verse</h1>
+    <p class="sub">
+      Onshape's core (disc + roll quadrant + Z arrow) is adopted unchanged because it is proven and
+      aligned. The addition is <span class="k">polarity</span> — which connector is anchored and
+      which one travels — which no surveyed CAD system encodes in its glyph.
+    </p>
+  </header>
+
+  <h2>The three jobs of the glyph</h2>
+  <div class="row">
+    <div class="card">
+      <div class="stage">
+        <svg width="150" height="130" viewBox="-75 -95 150 130" aria-label="Disc with origin dot">
+          <ellipse cx="0" cy="0" rx="42" ry="17" fill="none" stroke="var(--ink-soft)" stroke-width="2.5"/>
+          <circle cx="0" cy="0" r="3.6" fill="var(--ink)"/>
+        </svg>
+      </div>
+      <div class="name">Disc — the XY plane</div>
+      <p class="note">Says “I am a frame, and this is the plane I sit in.” The dot is the exact origin.</p>
+    </div>
+
+    <div class="card">
+      <div class="stage">
+        <svg width="150" height="130" viewBox="-75 -95 150 130" aria-label="Disc with one quadrant filled">
+          <path d="M0,0 L42,0 A42,17 0 0 1 0,17 Z" fill="var(--quadrant)" opacity="0.9"/>
+          <ellipse cx="0" cy="0" rx="42" ry="17" fill="none" stroke="var(--ink-soft)" stroke-width="2.5"/>
+          <circle cx="0" cy="0" r="3.6" fill="var(--ink)"/>
+        </svg>
+      </div>
+      <div class="name">Quadrant — the roll</div>
+      <p class="note">
+        The filled sector is the +X/+Y quadrant. It steps 90° with the reorient control, so the
+        clocking that Fastened and Slider lock is <em>visible</em> before you commit.
+      </p>
+    </div>
+
+    <div class="card">
+      <div class="stage">
+        <svg width="150" height="130" viewBox="-75 -95 150 130" aria-label="Z arrow drawn only upward">
+          <path d="M0,0 L42,0 A42,17 0 0 1 0,17 Z" fill="var(--quadrant)" opacity="0.9"/>
+          <ellipse cx="0" cy="0" rx="42" ry="17" fill="none" stroke="var(--ink-soft)" stroke-width="2.5"/>
+          <line x1="0" y1="0" x2="0" y2="-58" stroke="var(--axis-z)" stroke-width="3.5" stroke-linecap="round"/>
+          <polygon points="0,-80 -9.5,-56 9.5,-56" fill="var(--axis-z)"/>
+          <circle cx="0" cy="0" r="3.6" fill="var(--ink)"/>
+        </svg>
+      </div>
+      <div class="name">Arrow — the verse</div>
+      <p class="note">
+        Drawn on <span class="k">+Z only</span>. Nothing below the disc. A double-headed axis is what
+        makes people ask which way it points; a one-sided arrow cannot be misread.
+      </p>
+    </div>
+  </div>
+
+  <h2>Polarity — the part nobody else draws</h2>
+  <div class="row">
+    <div class="card">
+      <div class="stage">
+        <svg width="170" height="150" viewBox="-85 -105 170 150" aria-label="Fixed connector, open collar">
+          <path d="M0,0 L42,0 A42,17 0 0 1 0,17 Z" fill="var(--quadrant)" opacity="0.55"/>
+          <ellipse cx="0" cy="0" rx="42" ry="17" fill="none" stroke="var(--anchor)" stroke-width="2.5"/>
+          <line x1="0" y1="0" x2="0" y2="-56" stroke="var(--anchor)" stroke-width="3" stroke-linecap="round"/>
+          <polygon points="0,-80 -9.5,-56 9.5,-56" fill="none" stroke="var(--anchor)" stroke-width="3" stroke-linejoin="round"/>
+          <ellipse cx="0" cy="-56" rx="9.5" ry="3.6" fill="none" stroke="var(--anchor)" stroke-width="2.2"/>
+          <circle cx="0" cy="0" r="3.6" fill="var(--anchor)"/>
+        </svg>
+      </div>
+      <div class="name">Fixed — the socket</div>
+      <p class="note">
+        Hollow head, muted colour. This body <span class="k">does not move</span>. It receives.
+      </p>
+    </div>
+
+    <div class="card">
+      <div class="stage">
+        <svg width="170" height="150" viewBox="-85 -105 170 150" aria-label="Driven connector, solid cone">
+          <path d="M0,0 L42,0 A42,17 0 0 1 0,17 Z" fill="var(--quadrant)" opacity="0.95"/>
+          <ellipse cx="0" cy="0" rx="42" ry="17" fill="none" stroke="var(--driven)" stroke-width="2.5"/>
+          <line x1="0" y1="0" x2="0" y2="-58" stroke="var(--driven)" stroke-width="3.5" stroke-linecap="round"/>
+          <polygon points="0,-80 -9.5,-56 9.5,-56" fill="var(--driven)"/>
+          <circle cx="0" cy="0" r="3.6" fill="var(--driven)"/>
+        </svg>
+      </div>
+      <div class="name">Driven — the plug</div>
+      <p class="note">
+        Solid head, active colour. This body <span class="k">is the one that jumps</span>. It inserts.
+      </p>
+    </div>
+
+    <div class="card">
+      <div class="stage">
+        <svg width="170" height="150" viewBox="-85 -105 170 150" aria-label="Degenerate roll, hatched quadrant">
+          <defs>
+            <pattern id="hatch" width="6" height="6" patternUnits="userSpaceOnUse" patternTransform="rotate(45)">
+              <line x1="0" y1="0" x2="0" y2="6" stroke="var(--warn)" stroke-width="2"/>
+            </pattern>
+          </defs>
+          <path d="M0,0 L42,0 A42,17 0 0 1 0,17 Z" fill="url(#hatch)" opacity="0.85"/>
+          <ellipse cx="0" cy="0" rx="42" ry="17" fill="none" stroke="var(--warn)" stroke-width="2.5" stroke-dasharray="5 4"/>
+          <line x1="0" y1="0" x2="0" y2="-58" stroke="var(--axis-z)" stroke-width="3.5" stroke-linecap="round"/>
+          <polygon points="0,-80 -9.5,-56 9.5,-56" fill="var(--axis-z)"/>
+          <circle cx="0" cy="0" r="3.6" fill="var(--ink)"/>
+        </svg>
+      </div>
+      <div class="name">Roll undefined</div>
+      <p class="note">
+        Hatched quadrant, dashed disc: a circular face or a seam gave no usable direction. Says
+        “pick a direction” without a dialog.
+      </p>
+    </div>
+  </div>
+
+  <h2>The pair reads as a magnet</h2>
+  <div class="card wide">
+    <div class="stage">
+      <svg width="620" height="230" viewBox="-310 -120 620 230" aria-label="Two connectors facing each other on two plates">
+        <!-- lower plate (fixed) -->
+        <path d="M-260,52 L-60,10 L60,44 L-140,86 Z" fill="var(--viewport)" stroke="var(--viewport-2)" stroke-width="1.5"/>
+        <!-- upper plate (driven) -->
+        <path d="M-60,-96 L140,-138 L260,-104 L60,-62 Z" fill="var(--viewport)" stroke="var(--viewport-2)" stroke-width="1.5" opacity="0.55"/>
+
+        <!-- dashed field line between origins -->
+        <line x1="-100" y1="48" x2="100" y2="-79" stroke="var(--ink-faint)" stroke-width="2" stroke-dasharray="7 6"/>
+
+        <!-- FIXED connector, pointing up (+Z out of the lower plate) -->
+        <g transform="translate(-100,48)">
+          <path d="M0,0 L38,0 A38,15 0 0 1 0,15 Z" fill="var(--quadrant)" opacity="0.5"/>
+          <ellipse cx="0" cy="0" rx="38" ry="15" fill="none" stroke="var(--anchor)" stroke-width="2.4"/>
+          <line x1="0" y1="0" x2="0" y2="-48" stroke="var(--anchor)" stroke-width="3" stroke-linecap="round"/>
+          <polygon points="0,-70 -9,-48 9,-48" fill="none" stroke="var(--anchor)" stroke-width="3" stroke-linejoin="round"/>
+          <ellipse cx="0" cy="-48" rx="9" ry="3.4" fill="none" stroke="var(--anchor)" stroke-width="2"/>
+          <circle cx="0" cy="0" r="3.4" fill="var(--anchor)"/>
+        </g>
+
+        <!-- DRIVEN connector, pointing down (+Z out of the upper plate's underside) -->
+        <g transform="translate(100,-79) rotate(180)">
+          <path d="M0,0 L38,0 A38,15 0 0 1 0,15 Z" fill="var(--quadrant)" opacity="0.9"/>
+          <ellipse cx="0" cy="0" rx="38" ry="15" fill="none" stroke="var(--driven)" stroke-width="2.4"/>
+          <line x1="0" y1="0" x2="0" y2="-50" stroke="var(--driven)" stroke-width="3.4" stroke-linecap="round"/>
+          <polygon points="0,-70 -9,-48 9,-48" fill="var(--driven)"/>
+          <circle cx="0" cy="0" r="3.4" fill="var(--driven)"/>
+        </g>
+
+        <text x="-100" y="102" text-anchor="middle" font-size="13" fill="var(--ink-soft)">fixed · receives</text>
+        <text x="100" y="-100" text-anchor="middle" font-size="13" fill="var(--ink-soft)">driven · inserts</text>
+      </svg>
+    </div>
+    <p class="note">
+      Two arrows nose to nose. Because a magnet's north seeks a south, <span class="k">“facing” is the
+      self-evident default</span> — which settles open decision D1 on visual grounds instead of a
+      convention nobody can look up. Nothing has to be remembered: the picture is the rule.
+      The dashed line is what makes the two glyphs read as one object.
+    </p>
+  </div>
+
+  <h2>States</h2>
+  <div class="card wide">
+    <table>
+      <thead>
+        <tr><th>State</th><th>Drawing</th><th>Why</th></tr>
+      </thead>
+      <tbody>
+        <tr>
+          <td><span class="k">Candidate</span> (hover)</td>
+          <td>small dot only</td>
+          <td>Onshape draws plain white dots at every corner and midpoint. Dots propose; the full glyph commits.</td>
+        </tr>
+        <tr>
+          <td><span class="k">Picked</span></td>
+          <td>disc + quadrant + cone</td>
+          <td>The committed frame, with roll and verse both readable.</td>
+        </tr>
+        <tr>
+          <td><span class="k">Roll undefined</span></td>
+          <td>hatched quadrant, dashed disc</td>
+          <td>Turns requirement R8 from a message nobody reads into a mark you cannot miss.</td>
+        </tr>
+      </tbody>
+    </table>
+  </div>
+
+  <h2>Constraints on the drawing</h2>
+  <div class="card wide">
+    <p class="note">
+      <span class="k">Do not make it a fourth RGB triad.</span> The bed-centre world triad
+      (<code>DesignCanvas.cpp:65</code>) and the move gizmo are already three coloured arrows. The disc
+      and the quadrant are what tell a connector apart from those — keep the arms short, and consider
+      drawing only Z on the committed glyph, with X and Y implied by the quadrant.
+    </p>
+    <div class="legend">
+      <span class="swatch"><i class="dot" style="background:var(--quadrant)"></i> roll quadrant</span>
+      <span class="swatch"><i class="dot" style="background:var(--axis-z)"></i> Z / driven</span>
+      <span class="swatch"><i class="dot" style="background:var(--anchor)"></i> fixed</span>
+      <span class="swatch"><i class="dot" style="background:var(--warn)"></i> roll undefined</span>
+    </div>
+  </div>
+
+</div>
+</body>
+</html>
diff --git a/docs/CAD/design/mate-connectors/coplanar_test.py b/docs/CAD/design/mate-connectors/coplanar_test.py
new file mode 100644
index 0000000000..ea02ed3c80
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/coplanar_test.py
@@ -0,0 +1,68 @@
+# Does the connector pair let two hosts sit COPLANAR, or does it hold them apart?
+#
+# The male's flat back is the plane Y=0 and all its relief rises to +Y. So Y=0 is the natural
+# mating datum: everything the male adds lives on one side of it. The test below builds two dummy
+# host plates that meet on that plane -- one with the male FUSED on, one with the cavity CUT in --
+# and measures whether they touch, interfere, or stand apart.
+#
+# It also emits the artifact that makes this work in practice: a CUTTER solid (the male grown by
+# the clearance) that you subtract from any host. A standalone female block cannot keep two hosts
+# coplanar, because its own floor material stands between them; a cavity can.
+#
+# Run: /snap/bin/freecad.cmd coplanar_test.py
+
+import os
+import FreeCAD as App
+import Part
+from FreeCAD import Vector
+
+HERE  = os.path.dirname(os.path.abspath(__file__))
+MALE  = os.path.join(HERE, "bear.step")
+CLEAR = 0.20
+
+male = Part.Shape(); male.read(MALE); male = male.Solids[0]
+bb = male.BoundBox
+print(f"male relief: Y {bb.YMin:.3f} .. {bb.YMax:.3f}   -> datum plane Y=0, all relief on +Y")
+
+# the flat back face, and proof it is the whole silhouette sitting on Y=0
+back = max((f for f in male.Faces
+            if abs(f.CenterOfMass.y) < 1e-6 and abs(abs(f.normalAt(0, 0).y) - 1) < 1e-6),
+           key=lambda f: f.Area)
+print(f"back face  : {back.Area:.1f} mm2 on Y=0 -- this is the contact surface")
+
+# ---- the cutter: the male grown by the clearance, poking 0.2 mm proud so the boolean is clean
+cutter = male.makeOffsetShape(CLEAR, 1e-6, False, False, 0, 2, False).Solids[0]
+cb = cutter.BoundBox
+print(f"cutter     : Y {cb.YMin:.3f} .. {cb.YMax:.3f}, {cutter.Volume/1000:.2f} cm3")
+
+# ---- two dummy hosts meeting on Y = 0
+W, H = 120.0, 100.0
+hostA = Part.makeBox(W, 10.0, H, Vector(-W/2, -10.0, -15.0))   # occupies Y -10..0
+hostB = Part.makeBox(W, 30.0, H, Vector(-W/2,   0.0, -15.0))   # occupies Y   0..30
+
+partA = hostA.fuse(male)          # male stands proud of A's face
+partB = hostB.cut(cutter)         # cavity sunk into B from its face
+
+print(f"\npart A (host + male)   : {partA.Volume/1000:.2f} cm3")
+print(f"part B (host - cutter)  : {partB.Volume/1000:.2f} cm3")
+
+# ---- the question ------------------------------------------------------------------
+inter = partA.common(partB)
+iv = inter.Volume if inter.Solids else 0.0
+gap = partA.distToShape(partB)[0]
+print(f"\nRESULT interference A vs B : {iv:.6f} mm3   (0 = they do not collide)")
+print(f"RESULT closest approach    : {gap:.4f} mm   (0 = the host faces are touching)")
+
+# are the two host faces actually on the same plane?
+fa = [f for f in partA.Faces if abs(f.CenterOfMass.y) < 1e-9 and abs(abs(f.normalAt(0,0).y)-1) < 1e-6]
+fb = [f for f in partB.Faces if abs(f.CenterOfMass.y) < 1e-9 and abs(abs(f.normalAt(0,0).y)-1) < 1e-6]
+print(f"RESULT A has {len(fa)} face(s) lying exactly on Y=0, total {sum(f.Area for f in fa):.1f} mm2")
+print(f"RESULT B has {len(fb)} face(s) lying exactly on Y=0, total {sum(f.Area for f in fb):.1f} mm2")
+print("RESULT -> the hosts meet on Y=0: COPLANAR" if fa and fb and iv < 1e-3
+      else "RESULT -> NOT coplanar")
+
+doc = App.newDocument("Cutter")
+o = doc.addObject("Part::Feature", "BearConnector_Cutter"); o.Shape = cutter
+doc.recompute()
+Part.export([o], os.path.join(HERE, "BearConnector_Cutter.step"))
+print(f"\nwrote BearConnector_Cutter.step -- subtract this from any host to get the socket")
diff --git a/docs/CAD/design/mate-connectors/cylindricalmateconnectors.png b/docs/CAD/design/mate-connectors/cylindricalmateconnectors.png
new file mode 100644
index 0000000000..e4c1cebcf9
Binary files /dev/null and b/docs/CAD/design/mate-connectors/cylindricalmateconnectors.png differ
diff --git a/docs/CAD/design/mate-connectors/emit_glyph_table.py b/docs/CAD/design/mate-connectors/emit_glyph_table.py
new file mode 100644
index 0000000000..6e0fd29e32
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/emit_glyph_table.py
@@ -0,0 +1,97 @@
+"""Emit the simplified bear as a C++ table for the viewport glyph — wi3z.
+
+Everything is normalised to the part's own bounding span and centred, so the renderer scales by
+one radius R in screen pixels and nothing here carries millimetres. Emitting rather than
+hand-authoring keeps the glyph and the printed part from drifting apart: rerun this and the table
+follows the STEP.
+"""
+import json, math, os
+HERE = os.path.dirname(os.path.abspath(__file__))
+D = json.load(open(os.path.join(HERE, "bear_outline.json")))
+
+def unit_frame(pts_sets):
+    allp=[p for s in pts_sets for p in s]
+    xs=[p[0] for p in allp]; ys=[p[1] for p in allp]
+    cx,cy=(min(xs)+max(xs))/2,(min(ys)+max(ys))/2
+    span=max(max(xs)-min(xs), max(ys)-min(ys))
+    return cx,cy,span
+
+outer=[(x,-z) for x,z in D["outer"]]
+holes=[[(x,-z) for x,z in h["pts"]] for h in D["holes"]]
+CX,CY,SPAN = unit_frame([outer]+holes)
+U=lambda pts:[((x-CX)/SPAN,(y-CY)/SPAN) for x,y in pts]
+OUT=U(outer)
+EYES=[U(h) for h,m in zip(holes,D["holes"]) if m["d"]<20]
+MUZ =U([h for h,m in zip(holes,D["holes"]) if m["d"]>=20][0])
+
+def rdp(p,eps):
+    if len(p)<3: return p
+    ax,ay=p[0]; bx,by=p[-1]; dx,dy=bx-ax,by-ay; n=math.hypot(dx,dy)
+    best,bi=-1.0,0
+    for i in range(1,len(p)-1):
+        px,py=p[i]
+        d=abs(dx*(ay-py)-(ax-px)*dy)/n if n>1e-12 else math.hypot(px-ax,py-ay)
+        if d>best: best,bi=d,i
+    if best<=eps: return [p[0],p[-1]]
+    return rdp(p[:bi+1],eps)[:-1]+rdp(p[bi:],eps)
+def simp(p,eps):
+    r=rdp(p+[p[0]],eps); return r[:-1]
+
+OUT_S = simp(OUT,.030)                      # 22 verts, the size the study settled on
+# wind counter-clockwise so the renderer's normals come out facing +Z
+def area2(p): return sum(p[i][0]*p[(i+1)%len(p)][1]-p[(i+1)%len(p)][0]*p[i][1] for i in range(len(p)))
+if area2(OUT_S) < 0: OUT_S = OUT_S[::-1]
+
+def centroid(p): return (sum(q[0] for q in p)/len(p), sum(q[1] for q in p)/len(p))
+E=[]
+for e in EYES:
+    c=centroid(e); r=(max(p[0] for p in e)-min(p[0] for p in e))/2
+    E.append((c[0],c[1],r))
+E.sort()
+
+lo=min(p[1] for p in MUZ); hi=max(p[1] for p in MUZ)
+bottom=[p for p in MUZ if p[1] < lo+0.06*(hi-lo)]
+apex=max(MUZ,key=lambda p:p[1])
+TRI=[min(bottom),max(bottom),apex]
+if area2(TRI)<0: TRI=TRI[::-1]
+
+# the cheek dot: the handedness mark adopted after the mirror-difference study
+DOT=(E[1][0]+0.085, E[1][1]-0.10, 0.038)
+
+# THE MUZZLE. Six facets lifted straight off the mesh -- every facet touching anything above the
+# 3 mm plate. Do NOT recompute the base from height*tan(draft): the first version did and produced
+# a needle, because the real base OVERHANGS the crest at both ends (0.062 at the nose, 0.034 at the
+# tail) and it is that overhang that makes it a tapered wedge instead of a blade.
+PLATE = 0.036                      # 3.00 / 83.34
+SNOUT_BASE = ((-0.0727, -0.2417), (+0.0630, -0.2417),      # nose end, 0.136 wide
+              (+0.0259, +0.1939), (-0.0356, +0.1939))      # tail end, 0.062 wide
+CREST = ((-0.0048, -0.1793, 0.2073), (-0.0048, +0.1605, 0.1279))
+
+def fmt(v): return f"{v:+.4f}"
+L=[]
+L.append(f"// Emitted by doc/design/mate-connectors/emit_glyph_table.py from bear.step — do not hand-edit.")
+L.append(f"// Normalised to the part's bounding span and centred: the renderer scales by one radius.")
+L.append(f"static const Vec2d kBearOutline[] = {{        // {len(OUT_S)} verts, RDP eps 0.030, CCW")
+for i in range(0,len(OUT_S),3):
+    row=", ".join(f"{{{fmt(x)}, {fmt(y)}}}" for x,y in OUT_S[i:i+3])
+    L.append("    "+row+",")
+L.append("};")
+L.append(f"static const Vec2d kBearChin[] = {{            // the CHIN BAR, flat. The muzzle is relief — see kBearCrest.")
+L.append("    "+", ".join(f"{{{fmt(x)}, {fmt(y)}}}" for x,y in TRI)+",")
+L.append("};")
+L.append("// {cx, cy, r}: two eyes, then the cheek dot that carries handedness (wi3z).")
+L.append("static const Vec3d kBearMarks[] = {")
+for cx,cy,r in E: L.append(f"    {{{fmt(cx)}, {fmt(cy)}, {fmt(r)}}},")
+L.append(f"    {{{fmt(DOT[0])}, {fmt(DOT[1])}, {fmt(DOT[2])}}},")
+L.append("};")
+L.append("// THE MUZZLE, lifted off the mesh: a tapered wedge, base quad + crest edge, 6 facets.")
+L.append("// This is the only feature standing along +Z and the only one still legible edge-on.")
+L.append(f"static const double kBearPlateZ = {PLATE:+.4f};")
+L.append("static const Vec2d kBearSnoutBase[] = {   // CCW from the nose end")
+for x,y in SNOUT_BASE: L.append(f"    {{{fmt(x)}, {fmt(y)}}},")
+L.append("};")
+L.append("static const Vec3d kBearCrest[] = {       // nose (tall) -> tail (short)")
+for x,y,z in CREST: L.append(f"    {{{fmt(x)}, {fmt(y)}, {fmt(z)}}},")
+L.append("};")
+open(os.path.join(HERE,"bear_glyph_table.h"),"w").write("\n".join(L)+"\n")
+print("\n".join(L))
diff --git a/docs/CAD/design/mate-connectors/extract_outline.py b/docs/CAD/design/mate-connectors/extract_outline.py
new file mode 100644
index 0000000000..720223c6b1
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/extract_outline.py
@@ -0,0 +1,65 @@
+# Pull the bear's true silhouette and feature positions out of the supplied male B-rep, so the
+# simplification study starts from measured geometry instead of a tracing of the flat drawing.
+#
+# The part's native frame (make_female.py): flat back on Y=0, relief rising to Y=+17.27, the FACE
+# carried by X and Z. So the face plane is XZ and the silhouette is the outline projected along Y.
+import os, json
+import Part
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+s = Part.Shape(); s.read(os.path.join(HERE, "bear.step"))
+sol = s.Solids[0]
+bb = sol.BoundBox
+print(f"bbox X {bb.XMin:.2f}..{bb.XMax:.2f}  Y {bb.YMin:.2f}..{bb.YMax:.2f}  Z {bb.ZMin:.2f}..{bb.ZMax:.2f}")
+
+# The back plate face: the planar face whose normal is -Y and which sits at Y=YMin. Its outer wire
+# IS the silhouette; its inner wires are the eye holes.
+best = None
+for f in sol.Faces:
+    if f.Surface.__class__.__name__ != "Plane":
+        continue
+    n = f.Surface.Axis
+    if abs(abs(n.y) - 1.0) > 1e-6:
+        continue
+    c = f.CenterOfMass
+    if best is None or c.y < best[0]:
+        best = (c.y, f)
+y, face = best
+print(f"back plate at Y={y:.3f}   wires={len(face.Wires)}   area={face.Area:.1f} mm2")
+
+def wire_pts(w, tol=0.05):
+    # ORDER MATTERS and w.Edges does not carry it: OCC hands the edges back in whatever order the
+    # face stored them, so concatenating their discretisations gives a scrambled ring. The first
+    # version of this script did exactly that and emitted an outline with 7 duplicated points and
+    # twice the perimeter it should have. OrderedEdges walks the wire, and each edge is reversed
+    # when its own orientation runs against the walk.
+    pts = []
+    for e in w.OrderedEdges:
+        d = e.discretize(Deflection=tol)
+        if e.Orientation == "Reversed":
+            d = list(reversed(d))
+        for p in d:
+            pts.append((round(p.x, 3), round(p.z, 3)))
+    # drop consecutive duplicates
+    out = [pts[0]]
+    for p in pts[1:]:
+        if abs(p[0]-out[-1][0]) > 1e-4 or abs(p[1]-out[-1][1]) > 1e-4:
+            out.append(p)
+    return out
+
+data = {"outer": None, "holes": []}
+outer = face.OuterWire
+data["outer"] = wire_pts(outer)
+for w in face.Wires:
+    if w.isSame(outer):
+        continue
+    pts = wire_pts(w)
+    xs = [p[0] for p in pts]; zs = [p[1] for p in pts]
+    data["holes"].append({"pts": pts,
+                          "cx": round(sum(xs)/len(xs), 3), "cz": round(sum(zs)/len(zs), 3),
+                          "d": round(max(xs)-min(xs), 3)})
+    print(f"  hole: centre ({data['holes'][-1]['cx']}, {data['holes'][-1]['cz']}) dia {data['holes'][-1]['d']}")
+
+print(f"outer wire: {len(data['outer'])} points")
+json.dump(data, open(os.path.join(HERE, "bear_outline.json"), "w"))
+print("WROTE bear_outline.json")
diff --git a/docs/CAD/design/mate-connectors/faceted_ridge_key.scad b/docs/CAD/design/mate-connectors/faceted_ridge_key.scad
new file mode 100644
index 0000000000..3eb60064fb
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/faceted_ridge_key.scad
@@ -0,0 +1,140 @@
+// Faceted ridge key — asymmetric male/female alignment feature, flat facets only.
+//
+// 6 vertices, 7 faces, one closed manifold. Euler check: V - E + F = 6 - 11 + 7 = 2.
+// No spheres, no cylinders, no splines, no fillets.
+//
+// THE FLANKS ARE TRIANGULATED EXPLICITLY, and that is not cosmetic. Written as quads
+// [0,3,5,4] and [1,4,5,2] they are NOT planar — the base edge and the ridge edge are
+// skew, so the four corners do not share a plane. A checker caught this after the first
+// draft claimed the opposite. Left as quads, the tessellator picks the fold direction for
+// you, which means the "flat facet" promise is broken by an unspecified crease and two
+// exporters can disagree about the shape. Splitting them here fixes the crease at
+// back-bottom -> front-ridge, which keeps the rear peak's triangle large and clean.
+//
+// FRAME CONVENTION (matches the CAD mate connector it is derived from):
+//   +Z  the mating axis   — the feature protrudes along it
+//   +X  the roll reference — the ridge runs along it, low end forward
+//   +Y  completes the right-handed frame
+//
+// WHAT BREAKS WHICH SYMMETRY
+//   rotational about Z ....... the ridge (elongation along X)
+//   180 deg about Z .......... the ridge SLOPE: tall steep back, long shallow front
+//   mirror across XZ ......... deliberately NOT broken. Handedness is fixed by convention,
+//                              so +Y is implied once Z and X are known. Breaking it would
+//                              add a facet and buy nothing.
+//
+// KNOWN AMBIGUITY, stated rather than hidden: viewed exactly ALONG the ridge (+/-X,
+// orthographic), the silhouette is the same isoceles triangle from front and back. Front
+// and back are then distinguished by SHADING only — the long shallow front face catches
+// light differently from the steep back face. If the target renderer is flat-shaded with a
+// single headlight, verify this case before committing to the shape.
+
+// ---------------------------------------------------------------- parameters
+L   = 12.0;   // overall length along the ridge (X)
+W   = 4.0;    // half-width at the BACK
+tf  = 0.45;   // front taper: front half-width = W * tf
+H   = 4.5;    // peak height at the rear   <-- the single dimension controlling asymmetry
+pr  = 0.22;   // rear ridge position, fraction of L from the back
+pf  = 0.62;   // front ridge position, fraction of L from the back
+hf  = 0.35;   // front ridge height, fraction of H
+
+// Clearance is a PHYSICAL quantity and only means anything if this is a printed part.
+// See the note at the bottom: for a viewport glyph it is meaningless.
+clr    = 0.20;  // per-face clearance, mm
+depth  = 0.40;  // extra pocket depth so the male never bottoms out before it seats
+
+Wf  = W * tf;
+xr0 = -L/2 + L * pr;
+xr1 = -L/2 + L * pf;
+Hf  = H * hf;
+
+// ---------------------------------------------------------------- geometry
+// Vertex order is fixed and referenced by the face table; do not reorder.
+//   0 back-left    1 back-right    2 front-right    3 front-left
+//   4 REAR PEAK (tall)             5 front ridge (low)
+function ridge_pts(l, w, wf, h, hfr, x0, x1) = [
+    [-l/2, -w,   0  ],   // 0
+    [-l/2,  w,   0  ],   // 1
+    [ l/2,  wf,  0  ],   // 2
+    [ l/2, -wf,  0  ],   // 3
+    [ x0,   0,   h  ],   // 4  rear peak
+    [ x1,   0,   hfr]    // 5  front ridge, low
+];
+
+// OpenSCAD wants each face wound CLOCKWISE seen from OUTSIDE. The right-hand-rule
+// outward-normal (CCW) form is given in the comment for anyone porting to STL/OCC,
+// where the opposite convention is the usual one.
+RIDGE_FACES = [
+    [3, 2, 1, 0],   // base       (CCW-outward: [0,1,2,3])   planar, all z=0
+    [1, 4, 0],      // back       (CCW-outward: [0,4,1])     steep
+    [5, 3, 0],      // flank -Y a (CCW-outward: [0,3,5])
+    [4, 5, 0],      // flank -Y b (CCW-outward: [0,5,4])
+    [5, 4, 1],      // flank +Y a (CCW-outward: [1,4,5])
+    [2, 5, 1],      // flank +Y b (CCW-outward: [1,5,2])
+    [5, 2, 3]       // front      (CCW-outward: [3,2,5])     long, shallow
+];
+
+module ridge_key(l = L, w = W, wf = Wf, h = H, hfr = Hf, x0 = xr0, x1 = xr1) {
+    polyhedron(points = ridge_pts(l, w, wf, h, hfr, x0, x1),
+               faces  = RIDGE_FACES,
+               convexity = 3);
+}
+
+// MALE: the protrusion, nominal size.
+module ridge_key_male() { ridge_key(); }
+
+// FEMALE: the pocket. Grown by `clr` on every side and sunk `depth` deeper.
+//
+// HONEST LIMITATION: this grows the key by scaling its defining dimensions, which is NOT a
+// true uniform surface offset — on the shallow front face the normal clearance comes out
+// smaller than `clr`, because that face is far from perpendicular to every axis it is
+// scaled along. A true offset needs minkowski() with a small cube, which is exact and slow,
+// or an explicit per-face plane push, which is exact and fiddly. For a keying feature whose
+// job is angular registration rather than a press fit, the approximation is the right trade
+// — but do not quote this pocket as holding 0.2 mm everywhere, because it does not.
+module ridge_key_female() {
+    translate([0, 0, -depth])
+        ridge_key(l   = L + 2*clr,
+                  w   = W + clr,
+                  wf  = Wf + clr,
+                  h   = H + clr + depth,
+                  hfr = Hf + clr + depth,
+                  x0  = xr0,
+                  x1  = xr1);
+}
+
+// ---------------------------------------------------------------- demo
+// Left: the male key on its plate. Right: the plate with the pocket cut.
+PLATE = [30, 18, 3];
+
+module plate_with_male() {
+    translate([-PLATE[0]/2, -PLATE[1]/2, -PLATE[2]]) cube(PLATE);
+    ridge_key_male();
+}
+
+module plate_with_female() {
+    difference() {
+        translate([-PLATE[0]/2, -PLATE[1]/2, -PLATE[2]]) cube(PLATE);
+        ridge_key_female();
+    }
+}
+
+translate([-20, 0, 0]) plate_with_male();
+translate([ 20, 0, 0]) plate_with_female();
+
+// ---------------------------------------------------------------- note on the two readings
+// This file is written for the PHYSICAL reading: a printable alignment key, where `clr` and
+// `depth` are real millimetres and flat facets genuinely help — they slice without the
+// stair-stepping a tessellated curve produces, and they print without support on the
+// shallow front face.
+//
+// If the intent is instead the VIEWPORT GLYPH for a CAD mate connector, then:
+//   - `clr` and `depth` are meaningless: a symbol does not mate with anything;
+//   - all dimensions must become SCREEN PIXELS scaled by upp = 1/zoom, because every gizmo
+//     in that viewport is screen-constant and must not shrink with the model;
+//   - "low-poly for rendering performance" is not a real reason at ~2-20 glyphs per frame.
+//     The real reason to keep flat facets there is LEGIBILITY: hard normals give distinct
+//     value steps between facets, and that is what lets a 22-px solid read as an oriented
+//     object instead of a grey blob.
+// The vertex logic above is identical under both readings. Only the units and the clearance
+// change.
diff --git a/docs/CAD/design/mate-connectors/fem-0.png b/docs/CAD/design/mate-connectors/fem-0.png
new file mode 100644
index 0000000000..391881e72a
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diff --git a/docs/CAD/design/mate-connectors/fem-1.png b/docs/CAD/design/mate-connectors/fem-1.png
new file mode 100644
index 0000000000..c329d20bea
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diff --git a/docs/CAD/design/mate-connectors/fem-2.png b/docs/CAD/design/mate-connectors/fem-2.png
new file mode 100644
index 0000000000..a32f2ffbf1
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diff --git a/docs/CAD/design/mate-connectors/fem-3.png b/docs/CAD/design/mate-connectors/fem-3.png
new file mode 100644
index 0000000000..f21ae3f98b
Binary files /dev/null and b/docs/CAD/design/mate-connectors/fem-3.png differ
diff --git a/docs/CAD/design/mate-connectors/fem-sheet.png b/docs/CAD/design/mate-connectors/fem-sheet.png
new file mode 100644
index 0000000000..add56590a1
Binary files /dev/null and b/docs/CAD/design/mate-connectors/fem-sheet.png differ
diff --git a/docs/CAD/design/mate-connectors/fem-sheet2.png b/docs/CAD/design/mate-connectors/fem-sheet2.png
new file mode 100644
index 0000000000..879b4295fb
Binary files /dev/null and b/docs/CAD/design/mate-connectors/fem-sheet2.png differ
diff --git a/docs/CAD/design/mate-connectors/female.stl b/docs/CAD/design/mate-connectors/female.stl
new file mode 100644
index 0000000000..57b0ef6d20
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/female.stl
@@ -0,0 +1,226 @@
+solid OpenSCAD_Model
+  facet normal 1 -0 0
+    outer loop
+      vertex 15 -9 0
+      vertex 15 9 -8
+      vertex 15 9 0
+    endloop
+  endfacet
+  facet normal 1 0 0
+    outer loop
+      vertex 15 9 -8
+      vertex 15 -9 0
+      vertex 15 -9 -8
+    endloop
+  endfacet
+  facet normal 0 0 1
+    outer loop
+      vertex 15 9 0
+      vertex 5.3246 1.63218 0
+      vertex 15 -9 0
+    endloop
+  endfacet
+  facet normal 0 0 1
+    outer loop
+      vertex 15 9 0
+      vertex -4.79494 3.42759 0
+      vertex 5.3246 1.63218 0
+    endloop
+  endfacet
+  facet normal 0 0 1
+    outer loop
+      vertex 15 9 0
+      vertex -5.97725 3.87059 0
+      vertex -4.79494 3.42759 0
+    endloop
+  endfacet
+  facet normal 0 0 1
+    outer loop
+      vertex -5.97725 3.87059 0
+      vertex -15 9 0
+      vertex -5.97725 -3.87059 0
+    endloop
+  endfacet
+  facet normal -0 0 1
+    outer loop
+      vertex -15 9 0
+      vertex -5.97725 3.87059 0
+      vertex 15 9 0
+    endloop
+  endfacet
+  facet normal -0 0 1
+    outer loop
+      vertex 5.3246 -1.63218 0
+      vertex 15 -9 0
+      vertex 5.3246 1.63218 0
+    endloop
+  endfacet
+  facet normal -0 0 1
+    outer loop
+      vertex -4.79494 -3.42759 0
+      vertex 15 -9 0
+      vertex 5.3246 -1.63218 0
+    endloop
+  endfacet
+  facet normal -0 0 1
+    outer loop
+      vertex -5.97725 -3.87059 0
+      vertex 15 -9 0
+      vertex -4.79494 -3.42759 0
+    endloop
+  endfacet
+  facet normal 0 0 1
+    outer loop
+      vertex -5.97725 -3.87059 0
+      vertex -15 -9 0
+      vertex 15 -9 0
+    endloop
+  endfacet
+  facet normal 0 0 1
+    outer loop
+      vertex -15 -9 0
+      vertex -5.97725 -3.87059 0
+      vertex -15 9 0
+    endloop
+  endfacet
+  facet normal 0 0 -1
+    outer loop
+      vertex -15 -9 -8
+      vertex 15 9 -8
+      vertex 15 -9 -8
+    endloop
+  endfacet
+  facet normal -0 0 -1
+    outer loop
+      vertex 15 9 -8
+      vertex -15 -9 -8
+      vertex -15 9 -8
+    endloop
+  endfacet
+  facet normal -1 0 0
+    outer loop
+      vertex -15 -9 -8
+      vertex -15 9 0
+      vertex -15 9 -8
+    endloop
+  endfacet
+  facet normal -1 -0 0
+    outer loop
+      vertex -15 9 0
+      vertex -15 -9 -8
+      vertex -15 -9 0
+    endloop
+  endfacet
+  facet normal 0 1 -0
+    outer loop
+      vertex 15 9 -8
+      vertex -15 9 0
+      vertex 15 9 0
+    endloop
+  endfacet
+  facet normal 0 1 0
+    outer loop
+      vertex -15 9 0
+      vertex 15 9 -8
+      vertex -15 9 -8
+    endloop
+  endfacet
+  facet normal 0 -1 0
+    outer loop
+      vertex -15 -9 -8
+      vertex 15 -9 0
+      vertex -15 -9 0
+    endloop
+  endfacet
+  facet normal 0 -1 -0
+    outer loop
+      vertex 15 -9 0
+      vertex -15 -9 -8
+      vertex 15 -9 -8
+    endloop
+  endfacet
+  facet normal 0 0 1
+    outer loop
+      vertex -6.2 4.2 -0.4
+      vertex 6.2 -2 -0.4
+      vertex 6.2 2 -0.4
+    endloop
+  endfacet
+  facet normal 0 0 1
+    outer loop
+      vertex 6.2 -2 -0.4
+      vertex -6.2 4.2 -0.4
+      vertex -6.2 -4.2 -0.4
+    endloop
+  endfacet
+  facet normal 0.873667 0 -0.486524
+    outer loop
+      vertex -5.97725 -3.87059 0
+      vertex -6.2 4.2 -0.4
+      vertex -5.97725 3.87059 0
+    endloop
+  endfacet
+  facet normal 0.873667 0 -0.486524
+    outer loop
+      vertex -6.2 4.2 -0.4
+      vertex -5.97725 -3.87059 0
+      vertex -6.2 -4.2 -0.4
+    endloop
+  endfacet
+  facet normal -0.107146 0.603912 -0.789816
+    outer loop
+      vertex 6.2 -2 -0.4
+      vertex -4.79494 -3.42759 0
+      vertex 5.3246 -1.63218 0
+    endloop
+  endfacet
+  facet normal -0.107147 0.603918 -0.789812
+    outer loop
+      vertex -4.79494 -3.42759 0
+      vertex 6.2 -2 -0.4
+      vertex -6.2 -4.2 -0.4
+    endloop
+  endfacet
+  facet normal -0.304068 0.811519 -0.498978
+    outer loop
+      vertex -4.79494 -3.42759 0
+      vertex -6.2 -4.2 -0.4
+      vertex -5.97725 -3.87059 0
+    endloop
+  endfacet
+  facet normal -0.304068 -0.811519 -0.498978
+    outer loop
+      vertex -5.97725 3.87059 0
+      vertex -6.2 4.2 -0.4
+      vertex -4.79494 3.42759 0
+    endloop
+  endfacet
+  facet normal -0.107146 -0.603912 -0.789816
+    outer loop
+      vertex -4.79494 3.42759 0
+      vertex 6.2 2 -0.4
+      vertex 5.3246 1.63218 0
+    endloop
+  endfacet
+  facet normal -0.107147 -0.603918 -0.789812
+    outer loop
+      vertex 6.2 2 -0.4
+      vertex -4.79494 3.42759 0
+      vertex -6.2 4.2 -0.4
+    endloop
+  endfacet
+  facet normal -0.415603 0 -0.909546
+    outer loop
+      vertex 5.3246 -1.63218 0
+      vertex 6.2 2 -0.4
+      vertex 6.2 -2 -0.4
+    endloop
+  endfacet
+  facet normal -0.415603 0 -0.909546
+    outer loop
+      vertex 6.2 2 -0.4
+      vertex 5.3246 -1.63218 0
+      vertex 5.3246 1.63218 0
+    endloop
+  endfacet
+endsolid OpenSCAD_Model
diff --git a/docs/CAD/design/mate-connectors/female_only.scad b/docs/CAD/design/mate-connectors/female_only.scad
new file mode 100644
index 0000000000..89f83b4655
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/female_only.scad
@@ -0,0 +1,12 @@
+// Female half alone, for the legibility test: is a recessed faceted pocket readable in a
+// shaded view, or does a concave feature just read as a dark hole with no orientation?
+use <faceted_ridge_key.scad>
+
+// The plate must be THICKER than the key is tall, or the "pocket" is a through-hole. The
+// first version used 3 mm against a 4.5 mm key and cut straight through — caught only by
+// rendering it. Minimum stock = H + clearance + pocket depth + a wall to print against.
+PLATE = [30, 18, 8];
+difference() {
+    translate([-PLATE[0]/2, -PLATE[1]/2, -PLATE[2]]) cube(PLATE);
+    ridge_key_female();
+}
diff --git a/docs/CAD/design/mate-connectors/fit_check.py b/docs/CAD/design/mate-connectors/fit_check.py
new file mode 100644
index 0000000000..5a9ee01063
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/fit_check.py
@@ -0,0 +1,20 @@
+# Measure the assembled fit between the supplied male and the generated female.
+# This is the number that matters: the minimum gap in the seated position.
+#   Run: /snap/bin/freecad.cmd fit_check.py
+import os
+import Part
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+male = Part.Shape(); male.read(os.path.join(HERE, "bear.step"))
+fem  = Part.Shape(); fem.read(os.path.join(HERE, "BearConnector_Female.step"))
+male, fem = male.Solids[0], fem.Solids[0]
+
+d = male.distToShape(fem)
+print(f"RESULT minimum gap male<->female, seated: {d[0]:.4f} mm   (design clearance 0.20)")
+
+c = male.common(fem)
+print(f"RESULT interference volume: {(c.Volume if c.Solids else 0.0):.6f} mm3")
+
+p = d[1][0][0]
+print(f"RESULT tightest point on the male: ({p.x:.2f}, {p.y:.2f}, {p.z:.2f})")
+print(f"RESULT male {male.Volume/1000:.2f} cm3 / female {fem.Volume/1000:.2f} cm3")
diff --git a/docs/CAD/design/mate-connectors/glyph-preview.png b/docs/CAD/design/mate-connectors/glyph-preview.png
new file mode 100644
index 0000000000..5e62c9a17f
Binary files /dev/null and b/docs/CAD/design/mate-connectors/glyph-preview.png differ
diff --git a/docs/CAD/design/mate-connectors/glyph_preview.py b/docs/CAD/design/mate-connectors/glyph_preview.py
new file mode 100644
index 0000000000..e339e6bdab
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/glyph_preview.py
@@ -0,0 +1,99 @@
+"""Render the SIMPLIFIED glyph exactly as render_mate_face() draws it — x0kd.
+
+This is the panel the study was missing. simplify_study.py measured a FLAT outline and
+relief_sheet.py measured the FULL 1508-facet part; neither showed the simplified glyph WITH its
+relief, which is what the code actually draws and the only thing that answers "is the snout still
+protruding". Same facet list, same painter order, same camera-fixed lambert as the C++.
+"""
+import math, os
+from PIL import Image, ImageDraw
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+T = open(os.path.join(HERE, "bear_glyph_table.h")).read()
+def grab(name, n):
+    body = T.split(name + "[] = {")[1].split("};")[0]
+    body = "\n".join(l.split("//")[0] for l in body.splitlines())
+    out = []
+    for tok in body.replace("\n", " ").split("},"):
+        tok = tok.strip().lstrip("{").strip()
+        if not tok: continue
+        v = [float(x) for x in tok.replace("{", "").split(",")[:n]]
+        if len(v) == n: out.append(tuple(v))
+    return out
+OUT   = grab("kBearOutline", 2)
+CHIN  = grab("kBearChin", 2)          # NB: this table entry is the CHIN BAR, not the snout
+MARKS = grab("kBearMarks", 3)
+CREST = grab("kBearCrest", 3)
+SBASE = grab("kBearSnoutBase", 2)
+PLATE = float(T.split("kBearPlateZ = ")[1].split(";")[0])
+
+
+def facets():
+    F = []
+    n = len(OUT)
+    for i in range(n):                                   # plate sides -> the grazing silhouette
+        a, b = OUT[i], OUT[(i+1) % n]
+        F.append(([(a[0],a[1],0.0),(b[0],b[1],0.0),(b[0],b[1],PLATE),(a[0],a[1],PLATE)], "body", True))
+    F.append(([(x,y,PLATE) for x,y in OUT], "body", True))          # plate top
+    zm = PLATE + 0.004
+    for cx,cy,r in MARKS:                                            # eyes + cheek dot
+        F.append(([(cx+r*math.cos(2*math.pi*i/12), cy+r*math.sin(2*math.pi*i/12), zm) for i in range(12)], "mark", False))
+    F.append(([(x,y,zm) for x,y in CHIN], "mark", False))            # chin bar
+    A, B = CREST                                                     # THE MUZZLE: base quad + crest
+    nl=(SBASE[0][0],SBASE[0][1],PLATE); nr=(SBASE[1][0],SBASE[1][1],PLATE)
+    tr=(SBASE[2][0],SBASE[2][1],PLATE); tl=(SBASE[3][0],SBASE[3][1],PLATE)
+    F += [([nl,tl,B,A],"body",True),   # left flank
+          ([nr,A,B,tr],"body",True),   # right flank
+          ([nl,A,nr],"body",True),     # nose cap, sloping because the base overhangs the crest
+          ([tr,B,tl],"body",True)]     # tail cap
+    return F
+FACETS = facets()
+
+BODY=(0.42,0.46,0.52); MARK=(0.126,0.138,0.156)
+def render(px, elev_deg, ss=8):
+    S=px*ss; a=math.radians(elev_deg); ca,sa=math.cos(a),math.sin(a)
+    # camera orbits down; the connector's +Z (relief) tips toward the horizon
+    xf=lambda p:(p[0], p[1]*sa + p[2]*ca, -p[1]*ca + p[2]*sa)
+    light=(-0.70,0.30,0.45)
+    img=Image.new("RGB",(S,S),(24,27,32)); d=ImageDraw.Draw(img)
+    tris=[]
+    for pts,kind,shade in FACETS:
+        q=[xf(p) for p in pts]
+        tris.append((sum(v[2] for v in q)/len(q), q, kind, shade))
+    tris.sort(key=lambda t:t[0])                       # far first
+    for _,q,kind,shade in tris:
+        (x0,y0,z0),(x1,y1,z1),(x2,y2,z2)=q[0],q[1],q[2]
+        ux,uy,uz=x1-x0,y1-y0,z1-z0; vx,vy,vz=x2-x0,y2-y0,z2-z0
+        nx,ny,nz=uy*vz-uz*vy, uz*vx-ux*vz, ux*vy-uy*vx
+        nn=math.sqrt(nx*nx+ny*ny+nz*nz) or 1.0
+        nx,ny,nz=nx/nn,ny/nn,nz/nn
+        if nz<0: nx,ny,nz=-nx,-ny,-nz
+        base=BODY if kind=="body" else MARK
+        k=(0.42+0.58*max(0.0,nx*light[0]+ny*light[1]+nz*light[2])) if shade else 1.0
+        col=tuple(min(255,int(255*c*k)) for c in base)
+        d.polygon([(S/2+p[0]*S*0.92, S/2-p[1]*S*0.92) for p in q], fill=col)
+    return img.resize((px,px), Image.LANCZOS)
+
+SIZES=[22,32,48]; ELEVS=[(90,"flat on"),(47,"47"),(16,"16"),(6,"6")]
+pad,cell=8,58
+W=pad+len(SIZES)*len(ELEVS)*cell+pad; H=pad+cell+pad
+sheet=Image.new("RGB",(W,H),(24,27,32))
+for ci,(e,_) in enumerate(ELEVS):
+    for si,px in enumerate(SIZES):
+        g=render(px,e)
+        sheet.paste(g, (pad+(ci*len(SIZES)+si)*cell+(cell-px)//2, pad+(cell-px)//2))
+sheet.resize((W*2,H*2), Image.NEAREST).save(os.path.join(HERE,"glyph-preview.png"))
+
+# how much of the glyph is the snout: render with and without the tent and diff
+def render_no_tent(px, elev):
+    global FACETS
+    keep=FACETS; FACETS=FACETS[:-4]
+    try: return render(px, elev)
+    finally: FACETS=keep
+print(f"{'elev':>8} {'lit px@32':>10} {'snout px':>9} {'snout share':>12}")
+for e,_ in ELEVS:
+    a=render(32,e); b=render_no_tent(32,e)
+    la=sum(1 for p in a.get_flattened_data() if p!=(24,27,32))
+    diff=sum(1 for p,q in zip(a.get_flattened_data(), b.get_flattened_data()) if p!=q)
+    print(f"{e:>8} {la:>10} {diff:>9} {100.0*diff/max(1,la):>11.1f}%")
+print("WROTE glyph-preview.png")
diff --git a/docs/CAD/design/mate-connectors/glyph_probe.py b/docs/CAD/design/mate-connectors/glyph_probe.py
new file mode 100644
index 0000000000..f4d48fdd6c
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/glyph_probe.py
@@ -0,0 +1,143 @@
+# Mate-connector glyph probe — built as REAL solids on REAL mechanical geometry,
+# so the shape can be judged in a 3D viewport instead of in a browser mock.
+#
+# Four polarity treatments, side by side on one bracket:
+#   A  Onshape baseline ...... ring + roll quadrant + three short axis arms
+#   B  solid cone ............ ring + quadrant + one-sided Z arrow, filled head   (driven)
+#   C  hollow collar ......... ring + quadrant + one-sided Z arrow, shell head    (fixed)
+#   D  pin / cup ............. polarity by RELIEF: a raised pin vs a sunk cup
+#
+# D is the one that only a 3D test can settle: in a shaded viewport, solid-vs-hollow is a
+# weak cue that depends on angle and lighting, while convex-vs-concave is a strong one --
+# and male/female is the mechanical language for polarity anyway.
+#
+# Scale note: in the real viewport gizmos are screen-constant (~15-40 px via upp = 1/zoom).
+# At a zoom where a 60 mm part fills ~600 px, 40 px is about 4 mm, so R = 4.5 mm here.
+
+import FreeCAD as App
+import FreeCADGui as Gui
+import Part
+from FreeCAD import Vector
+
+DOC = "GlyphProbe"
+for d in list(App.listDocuments()):
+    App.closeDocument(d)
+doc = App.newDocument(DOC)
+
+R = 4.5          # disc radius, the module everything scales from
+GOLD  = (0.93, 0.66, 0.09)
+BLUE  = (0.18, 0.44, 0.93)
+GREY  = (0.42, 0.46, 0.52)
+RED   = (0.85, 0.29, 0.24)
+GREEN = (0.23, 0.65, 0.35)
+
+def add(name, shape, color, transparency=0):
+    o = doc.addObject("Part::Feature", name)
+    o.Shape = shape
+    o.ViewObject.ShapeColor = color
+    o.ViewObject.LineColor  = color
+    o.ViewObject.PointColor = color
+    o.ViewObject.Transparency = transparency
+    return o
+
+def frame(origin, zdir, xdir):
+    """Right-handed placement matrix from origin + Z + X (X orthonormalised against Z)."""
+    z = Vector(*zdir); z.normalize()
+    xr = Vector(*xdir)
+    x = xr.sub(Vector(z).multiply(z.dot(xr))); x.normalize()
+    y = z.cross(x)
+    return App.Matrix(x.x, y.x, z.x, origin[0],
+                      x.y, y.y, z.y, origin[1],
+                      x.z, y.z, z.z, origin[2],
+                      0, 0, 0, 1)
+
+# ---------------------------------------------------------------- the bracket
+plate = Part.makeBox(120, 46, 8)
+bore  = Part.makeCylinder(7, 40, Vector(96, 23, -6))          # a real bore, curved face
+boss  = Part.makeCylinder(11, 7, Vector(96, 23, 8))
+part  = plate.fuse(boss).cut(bore)
+add("Bracket", part, (0.60, 0.63, 0.66))
+
+# ---------------------------------------------------------------- glyph pieces
+def ring(t=None):
+    t = t or R * 0.10
+    return Part.makeCylinder(R, t).cut(Part.makeCylinder(R * 0.84, t))
+
+def quadrant(t=None):
+    t = t or R * 0.10
+    return Part.makeCylinder(R * 0.84, t, Vector(0, 0, 0), Vector(0, 0, 1), 90)
+
+def stem(L=None, r=None):
+    return Part.makeCylinder(r or R * 0.09, L or R * 2.3)
+
+def solid_head():
+    return Part.makeCone(R * 0.32, 0, R * 0.80, Vector(0, 0, R * 2.3))
+
+def shell_head():
+    outer = Part.makeCone(R * 0.32, 0, R * 0.80, Vector(0, 0, R * 2.3))
+    inner = Part.makeCone(R * 0.22, 0, R * 0.62, Vector(0, 0, R * 2.3))
+    return outer.cut(inner)
+
+def short_axis(direction, L=None):
+    L = L or R * 1.15
+    return Part.makeCylinder(R * 0.07, L, Vector(0, 0, 0), Vector(*direction))
+
+def place(shape, m):
+    s = shape.copy()
+    s.transformShape(m)
+    return s
+
+# ---------------------------------------------------------------- the variants
+def variant_A(tag, origin):                       # Onshape baseline
+    m = frame(origin, (0, 0, 1), (1, 0, 0))
+    add(tag + "_ring", place(ring(), m), GREY)
+    add(tag + "_quad", place(quadrant(), m), GOLD)
+    add(tag + "_x", place(short_axis((1, 0, 0)), m), RED)
+    add(tag + "_y", place(short_axis((0, 1, 0)), m), GREEN)
+    add(tag + "_z", place(short_axis((0, 0, 1), R * 1.6), m), BLUE)
+
+def variant_B(tag, origin, zdir=(0, 0, 1)):       # solid cone = driven
+    m = frame(origin, zdir, (1, 0, 0))
+    add(tag + "_ring", place(ring(), m), BLUE)
+    add(tag + "_quad", place(quadrant(), m), GOLD)
+    add(tag + "_body", place(stem().fuse(solid_head()), m), BLUE)
+
+def variant_C(tag, origin, zdir=(0, 0, 1)):       # hollow collar = fixed
+    m = frame(origin, zdir, (1, 0, 0))
+    add(tag + "_ring", place(ring(), m), GREY)
+    add(tag + "_quad", place(quadrant(), m), GOLD)
+    add(tag + "_body", place(stem().fuse(shell_head()), m), GREY)
+
+def variant_D_pin(tag, origin, zdir=(0, 0, 1)):   # polarity by relief: raised PIN
+    m = frame(origin, zdir, (1, 0, 0))
+    pin = Part.makeCylinder(R * 0.30, R * 1.5).fuse(
+          Part.makeCone(R * 0.30, 0, R * 0.55, Vector(0, 0, R * 1.5)))
+    add(tag + "_ring", place(ring(), m), BLUE)
+    add(tag + "_quad", place(quadrant(), m), GOLD)
+    add(tag + "_pin", place(pin, m), BLUE)
+
+def variant_D_cup(tag, origin, zdir=(0, 0, 1)):   # polarity by relief: sunk CUP
+    m = frame(origin, zdir, (1, 0, 0))
+    cup = Part.makeCylinder(R * 0.62, R * 0.9).cut(
+          Part.makeCylinder(R * 0.40, R * 0.9, Vector(0, 0, -0.01)))
+    add(tag + "_ring", place(ring(), m), GREY)
+    add(tag + "_quad", place(quadrant(), m), GOLD)
+    add(tag + "_cup", place(cup, m), GREY)
+
+# four treatments across the plate, all on the same flat face, same Z
+variant_A("A", (14, 30, 8))
+variant_B("B", (40, 30, 8))
+variant_C("C", (64, 30, 8))
+variant_D_pin("Dpin", (14, 10, 8))
+variant_D_cup("Dcup", (40, 10, 8))
+
+# the hard cases, which is the whole reason for doing this in 3D:
+variant_B("Bore", (96, 23, 15))                    # on the boss above a bore
+variant_B("Edge", (64, 0, 8), (0, -0.7071, 0.7071))  # tilted, on an edge, oblique Z
+
+doc.recompute()
+
+v = Gui.activeDocument().activeView()
+v.viewIsometric()
+Gui.SendMsgToActiveView("ViewFit")
+App.Console.PrintMessage("glyph probe built: %d objects\n" % len(doc.Objects))
diff --git a/docs/CAD/design/mate-connectors/handedness-sheet.png b/docs/CAD/design/mate-connectors/handedness-sheet.png
new file mode 100644
index 0000000000..b44c370328
Binary files /dev/null and b/docs/CAD/design/mate-connectors/handedness-sheet.png differ
diff --git a/docs/CAD/design/mate-connectors/handedness.py b/docs/CAD/design/mate-connectors/handedness.py
new file mode 100644
index 0000000000..68fa07bb55
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/handedness.py
@@ -0,0 +1,112 @@
+"""Give the bear a handedness mark that survives rasterisation — wi3z, Tommaso's call 2.
+
+The study showed the left/right cue lives in sub-millimetre corner radii and is therefore invisible
+at glyph size: one pixel is 2.6 mm at 32 px. Roll and verse are safe; handedness is not.
+
+THE MEASURE IS THE QUESTION ITSELF. Render the glyph, render its mirror image, and count how many
+pixels differ. If a human is to tell left from right, the two must differ on screen; a candidate
+that scores near zero is invisible however elegant it looks in CAD. Reported as a percentage of the
+glyph's own lit area, so the sizes are comparable.
+"""
+import json, math, os
+from PIL import Image, ImageDraw, ImageChops
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+D = json.load(open(os.path.join(HERE, "bear_outline.json")))
+def unit(pts):
+    p = [(x, -z) for x, z in pts]
+    return p
+outer = unit(D["outer"]); holes = [unit(h["pts"]) for h in D["holes"]]
+ALL = outer + [p for h in holes for p in h]
+xs=[p[0] for p in ALL]; ys=[p[1] for p in ALL]
+CX,CY = (min(xs)+max(xs))/2,(min(ys)+max(ys))/2
+SPAN  = max(max(xs)-min(xs), max(ys)-min(ys))
+U = lambda pts: [((x-CX)/SPAN,(y-CY)/SPAN) for x,y in pts]
+OUT = U(outer)
+EYES = [U(h) for h,m in zip(holes, D["holes"]) if m["d"] < 20]
+MUZ  = U([h for h,m in zip(holes, D["holes"]) if m["d"] >= 20][0])
+
+def rdp(pts, eps):
+    if len(pts) < 3: return pts
+    ax,ay=pts[0]; bx,by=pts[-1]; dx,dy=bx-ax,by-ay
+    n=math.hypot(dx,dy); best,bi=-1.0,0
+    for i in range(1,len(pts)-1):
+        px,py=pts[i]
+        d=abs(dx*(ay-py)-(ax-px)*dy)/n if n>1e-12 else math.hypot(px-ax,py-ay)
+        if d>best: best,bi=d,i
+    if best<=eps: return [pts[0],pts[-1]]
+    return rdp(pts[:bi+1],eps)[:-1]+rdp(pts[bi:],eps)
+def simp(pts,eps):
+    r=rdp(pts+[pts[0]],eps); return r[:-1]
+
+BASE = simp(OUT, .030)                     # the 22-vertex outline the study settled on
+def centroid(p): return (sum(q[0] for q in p)/len(p), sum(q[1] for q in p)/len(p))
+def circ(cx,cy,r,n=16): return [(cx+r*math.cos(2*math.pi*i/n), cy+r*math.sin(2*math.pi*i/n)) for i in range(n)]
+EYE_D = []
+for e in EYES:
+    c=centroid(e); r=(max(p[0] for p in e)-min(p[0] for p in e))/2
+    EYE_D.append((c[0],c[1],r))
+EYE_D.sort()                                # [0] = left (x<0), [1] = right
+
+TOP = max(p[1] for p in BASE)
+H   = TOP - min(p[1] for p in BASE)
+def ear_tip(sign):
+    cands=[p for p in BASE if p[1] > TOP-0.18*H and (p[0]*sign) > 0]
+    return max(cands, key=lambda p: p[0]*sign) if cands else None
+LT, RT = ear_tip(-1), ear_tip(+1)
+
+def notch(tip, sign, k=0.085):
+    """A wedge bitten out of one ear — background-filled, exactly how the eyes are already drawn."""
+    x,y = tip
+    return [(x, y+0.02), (x - sign*k, y - k*0.55), (x + sign*k*0.15, y - k*1.05)]
+
+CANDS = {
+ "H0 none":        dict(cuts=[],                       eyes=EYE_D),
+ "H1 notch R ear": dict(cuts=[notch(RT, +1)],          eyes=EYE_D),
+ "H2 notch both":  dict(cuts=[notch(RT, +1), notch(LT, -1, 0.045)], eyes=EYE_D),
+ "H3 cheek dot":   dict(cuts=[circ(EYE_D[1][0]+0.085, EYE_D[1][1]-0.10, 0.038)], eyes=EYE_D),
+ "H4 uneven eyes": dict(cuts=[],  eyes=[EYE_D[0], (EYE_D[1][0], EYE_D[1][1], EYE_D[1][2]*1.55)]),
+}
+
+def render(c, px, ss=8, mirror=False):
+    S=px*ss; img=Image.new("L",(S,S),0); d=ImageDraw.Draw(img)
+    m = lambda p: (S/2 + (-p[0] if mirror else p[0])*S*0.92, S/2 - p[1]*S*0.92)
+    d.polygon([m(p) for p in BASE], fill=255)
+    d.polygon([m(p) for p in MUZ], fill=0)
+    for cx,cy,r in c["eyes"]:
+        a=m((cx-r,cy+r)); b=m((cx+r,cy-r))
+        d.ellipse([min(a[0],b[0]), min(a[1],b[1]), max(a[0],b[0]), max(a[1],b[1])], fill=0)
+    for cut in c["cuts"]:
+        d.polygon([m(p) for p in cut], fill=0)
+    return img.resize((px,px), Image.LANCZOS)
+
+SIZES=[22,32,48]
+print(f"{'candidate':16} " + "  ".join(f"{s}px" for s in SIZES) + "     (pixels differing from own mirror, % of lit area)")
+print("-"*84)
+scores={}
+for name,c in CANDS.items():
+    row=[]
+    for px in SIZES:
+        a=render(c,px); b=render(c,px,mirror=True)
+        diff=ImageChops.difference(a,b)
+        nd=sum(1 for v in diff.getdata() if v>40)
+        lit=sum(1 for v in a.getdata() if v>40) or 1
+        row.append(100.0*nd/lit)
+    scores[name]=row
+    print(f"{name:16} " + "  ".join(f"{v:5.1f}" for v in row))
+
+pad,cell=8,58
+W=pad+len(SIZES)*2*cell+pad; Hh=pad+len(CANDS)*cell+pad
+sheet=Image.new("RGB",(W,Hh),(24,27,32))
+for r,(name,c) in enumerate(CANDS.items()):
+    for mi,mir in enumerate((False,True)):
+        for si,px in enumerate(SIZES):
+            g=render(c,px,mirror=mir)
+            tile=Image.new("RGB",(px,px),(24,27,32))
+            tile.paste(Image.new("RGB",(px,px),(237,168,23)),(0,0),g)
+            x=pad+(mi*len(SIZES)+si)*cell+(cell-px)//2
+            y=pad+r*cell+(cell-px)//2
+            sheet.paste(tile,(x,y))
+sheet.resize((W*2,Hh*2), Image.NEAREST).save(os.path.join(HERE,"handedness-sheet.png"))
+print("\nleft block = as drawn, right block = mirrored.  rows: " + ", ".join(CANDS))
+print("WROTE handedness-sheet.png")
diff --git a/docs/CAD/design/mate-connectors/linearedgemateconnectors.png b/docs/CAD/design/mate-connectors/linearedgemateconnectors.png
new file mode 100644
index 0000000000..fd5e64190d
Binary files /dev/null and b/docs/CAD/design/mate-connectors/linearedgemateconnectors.png differ
diff --git a/docs/CAD/design/mate-connectors/make_female.py b/docs/CAD/design/mate-connectors/make_female.py
new file mode 100644
index 0000000000..ccb38426bf
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/make_female.py
@@ -0,0 +1,135 @@
+# Build the complementary FEMALE for BearConnector.step.
+#
+# Method: take the supplied male B-rep as-is, grow it by a uniform clearance, and subtract that
+# from a block. Working on the real solid rather than re-modelling the bear is the whole point —
+# the pocket is then exactly complementary by construction, including every deliberate asymmetry.
+#
+# The offset uses join=2 (Intersection), which extends the adjacent planes and meets them at a
+# sharp corner. For a faceted part that is the correct join: the arc join would round every convex
+# edge and blunt the very cues the design depends on.
+#
+# THE MALE'S NATIVE FRAME: the flat back is the plane Y=0 and the relief rises to Y=+17.27.
+# X and Z carry the face (83.34 x 66.69). The frame is kept exactly as supplied so that male and
+# female drop into the same assembly without anyone having to re-orient one of them.
+# Insertion is therefore along +Y, and the pocket must OPEN on the Y=0 plane.
+#
+# A first version of this script assumed the relief ran along +Z, built the block around the wrong
+# axis, and produced a sealed cavity with no way in. It passed a "male does not intersect female"
+# check, because that only tests the seated position and says nothing about whether the part can
+# get there. The straight-pull test below is what catches it.
+#
+# Run:  /snap/bin/freecad.cmd make_female.py
+
+import os, sys, math
+import FreeCAD as App
+import Part
+
+HERE     = os.path.dirname(os.path.abspath(__file__))
+MALE     = os.path.join(HERE, "bear.step")
+OUT_STEP = os.path.join(HERE, "BearConnector_Female.step")
+
+CLEAR = 0.20     # per-face clearance, mm
+WALL  = 4.0      # material around the pocket, mm
+FLOOR = 3.0      # material behind the deepest point of the pocket, mm
+
+male = Part.Shape(); male.read(MALE)
+if len(male.Solids) != 1:
+    print(f"FAIL: expected 1 solid in the male, found {len(male.Solids)}"); sys.exit(1)
+male = male.Solids[0]
+bb = male.BoundBox
+print(f"male  : {bb.XLength:.2f} (X) x {bb.YLength:.2f} (Y) x {bb.ZLength:.2f} (Z) mm, "
+      f"{len(male.Faces)} faces, {male.Volume/1000:.2f} cm3")
+print(f"        relief runs Y {bb.YMin:.2f} .. {bb.YMax:.2f}  -> insertion along +Y, mouth at Y={bb.YMin:.2f}")
+
+# ---- 1. can the male even be withdrawn along the insertion axis? ----------------------
+# Ray-cast a grid along +Y through the tessellated male and count crossings. A straight pull is
+# possible only if no ray enters the solid more than once; a second entry is an undercut.
+verts, facets = male.tessellate(0.15)
+V = [(v.x, v.y, v.z) for v in verts]
+worst, undercut_pts = 0, 0
+NX = NZ = 90
+for i in range(NX):
+    x = bb.XMin + (i + 0.5) * bb.XLength / NX
+    for j in range(NZ):
+        z = bb.ZMin + (j + 0.5) * bb.ZLength / NZ
+        hits = 0
+        for (ia, ib, ic) in facets:            # ray (x, *, z) along +Y vs triangle
+            ax, ay, az = V[ia]; bx, by, bz = V[ib]; cx, cy, cz = V[ic]
+            # 2D point-in-triangle in the XZ plane
+            d = (bz - cz) * (ax - cx) + (cx - bx) * (az - cz)
+            if abs(d) < 1e-12: continue
+            u = ((bz - cz) * (x - cx) + (cx - bx) * (z - cz)) / d
+            v = ((cz - az) * (x - cx) + (ax - cx) * (z - cz)) / d
+            if u < 0 or v < 0 or u + v > 1: continue
+            hits += 1
+        worst = max(worst, hits)
+        if hits > 2: undercut_pts += 1
+print(f"pull  : max crossings along +Y = {worst}, undercut samples = {undercut_pts}/{NX*NZ}")
+if undercut_pts:
+    print("FAIL: the male has an undercut along +Y; a straight pocket cannot release it")
+    sys.exit(1)
+print("        no undercut -> a straight-pull pocket works")
+
+# ---- 2. grow the male by the clearance -----------------------------------------------
+grown = None
+for join, name in ((2, "Intersection"), (1, "Tangent"), (0, "Arc")):
+    try:
+        g = male.makeOffsetShape(CLEAR, 1e-6, False, False, 0, join, False)
+        if g.isValid() and g.Solids:
+            grown = g.Solids[0]; print(f"offset: join={name}, {grown.Volume/1000:.2f} cm3"); break
+    except Exception as e:
+        print(f"offset: join={name} failed -- {e}")
+if grown is None:
+    print("FAIL: could not offset the male; refusing to emit a zero-clearance pocket"); sys.exit(1)
+
+# ---- 3. the block: walls in X and Z, depth in +Y, OPEN at the Y=0 mouth ---------------
+gb = grown.BoundBox
+y_mouth = bb.YMin                       # the male's flat back plane
+depth   = gb.YMax - y_mouth
+block = Part.makeBox(gb.XLength + 2*WALL, depth + FLOOR, gb.ZLength + 2*WALL,
+                     App.Vector(gb.XMin - WALL, y_mouth, gb.ZMin - WALL))
+print(f"block : {gb.XLength + 2*WALL:.2f} x {depth + FLOOR:.2f} x {gb.ZLength + 2*WALL:.2f} mm, "
+      f"mouth on the Y={y_mouth:.2f} plane")
+
+female = block.cut(grown)
+
+# ---- 4. verify --------------------------------------------------------------------------
+ok = True
+if not female.isValid():              print("FAIL: invalid shape"); ok = False
+if len(female.Solids) != 1:           print(f"FAIL: {len(female.Solids)} solids"); ok = False
+
+clash = male.common(female)
+cv = clash.Volume if clash.Solids else 0.0
+print(f"check : male ∩ female = {cv:.6f} mm3 (seated fit, must be ~0)")
+if cv > 1e-3: print("FAIL: male collides with female"); ok = False
+
+# the mouth must actually be open: the pocket has to reach the Y=y_mouth face of the block
+mouth_face_area = 0.0
+for f in female.Faces:
+    c = f.CenterOfMass
+    if abs(c.y - y_mouth) < 1e-6:
+        mouth_face_area += f.Area
+solid_mouth = (gb.XLength + 2*WALL) * (gb.ZLength + 2*WALL)
+open_area = solid_mouth - mouth_face_area
+print(f"check : mouth plane -- material {mouth_face_area:.1f} mm2, opening {open_area:.1f} mm2 "
+      f"({100*open_area/solid_mouth:.1f}% of the face)")
+if open_area < 100:
+    print("FAIL: the pocket is sealed -- the male cannot be inserted"); ok = False
+
+cavity = block.Volume - female.Volume
+print(f"check : cavity {cavity/1000:.2f} cm3 vs male {male.Volume/1000:.2f} cm3 "
+      f"-> clearance shell {(cavity-male.Volume)/1000:.2f} cm3")
+if cavity < male.Volume: print("FAIL: cavity smaller than the male"); ok = False
+
+if not ok:
+    print("\nREFUSING to write the STEP"); sys.exit(1)
+
+doc = App.newDocument("Female")
+obj = doc.addObject("Part::Feature", "BearConnector_Female")
+obj.Shape = female
+doc.recompute()
+Part.export([obj], OUT_STEP)
+fb = female.BoundBox
+print(f"\nwrote {OUT_STEP}")
+print(f"female: {fb.XLength:.2f} x {fb.YLength:.2f} x {fb.ZLength:.2f} mm, "
+      f"{len(female.Faces)} faces, {female.Volume/1000:.2f} cm3")
diff --git a/docs/CAD/design/mate-connectors/mate-connector-virtual-sharp.png b/docs/CAD/design/mate-connectors/mate-connector-virtual-sharp.png
new file mode 100644
index 0000000000..f9a80c1e10
Binary files /dev/null and b/docs/CAD/design/mate-connectors/mate-connector-virtual-sharp.png differ
diff --git a/docs/CAD/design/mate-connectors/mateconnector-planarcentroid.png b/docs/CAD/design/mate-connectors/mateconnector-planarcentroid.png
new file mode 100644
index 0000000000..16ca1c01e6
Binary files /dev/null and b/docs/CAD/design/mate-connectors/mateconnector-planarcentroid.png differ
diff --git a/docs/CAD/design/mate-connectors/mateconnector-planarpoints.png b/docs/CAD/design/mate-connectors/mateconnector-planarpoints.png
new file mode 100644
index 0000000000..d952ddc1f0
Binary files /dev/null and b/docs/CAD/design/mate-connectors/mateconnector-planarpoints.png differ
diff --git a/docs/CAD/design/mate-connectors/matepointiconLG.png b/docs/CAD/design/mate-connectors/matepointiconLG.png
new file mode 100644
index 0000000000..2f3022d116
Binary files /dev/null and b/docs/CAD/design/mate-connectors/matepointiconLG.png differ
diff --git a/docs/CAD/design/mate-connectors/matepointreorientsecondaryaxis.png b/docs/CAD/design/mate-connectors/matepointreorientsecondaryaxis.png
new file mode 100644
index 0000000000..bd65a9f40e
Binary files /dev/null and b/docs/CAD/design/mate-connectors/matepointreorientsecondaryaxis.png differ
diff --git a/docs/CAD/design/mate-connectors/muzzle_variants.py b/docs/CAD/design/mate-connectors/muzzle_variants.py
new file mode 100644
index 0000000000..f4c9ab33b5
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/muzzle_variants.py
@@ -0,0 +1,71 @@
+"""The muzzle has to READ, not just be present — wi3z.
+
+Faithfully scaled, the part's ridge is 11.3 mm on an 83 mm face: 13.6 % of the width. At glyph
+size that is a scratch. A glyph is a symbol, not a scale model, so the question is how much
+emphasis it takes before the only +Z feature actually reads. Variants, all with the same crest
+geometry, differing only in width and colour.
+"""
+import math, os, importlib.util
+from PIL import Image, ImageDraw
+spec=importlib.util.spec_from_file_location("gp","glyph_preview.py")
+gp=importlib.util.module_from_spec(spec); spec.loader.exec_module(gp)
+
+OUT, CHIN, MARKS, CREST, SBASE, PLATE = gp.OUT, gp.CHIN, gp.MARKS, gp.CREST, gp.SBASE, gp.PLATE
+BODY=(0.42,0.46,0.52); MARK=(0.126,0.138,0.156); GOLD=(0.93,0.66,0.09)
+
+def facets(widen=1.0, muzzle_gold=False):
+    F=[]; n=len(OUT)
+    for i in range(n):
+        a,b=OUT[i],OUT[(i+1)%n]
+        F.append(([(a[0],a[1],0.0),(b[0],b[1],0.0),(b[0],b[1],PLATE),(a[0],a[1],PLATE)],BODY,True))
+    F.append(([(x,y,PLATE) for x,y in OUT],BODY,True))
+    zm=PLATE+0.004
+    for cx,cy,r in MARKS:
+        F.append(([(cx+r*math.cos(2*math.pi*i/12),cy+r*math.sin(2*math.pi*i/12),zm) for i in range(12)],MARK,False))
+    F.append(([(x,y,zm) for x,y in CHIN],MARK,False))
+    A,B=CREST
+    w=lambda p:(p[0]*widen,p[1],PLATE)
+    nl,nr,tr,tl=(w(SBASE[0]),w(SBASE[1]),w(SBASE[2]),w(SBASE[3]))
+    col = GOLD if muzzle_gold else BODY
+    F+=[([nl,tl,B,A],col,True),([nr,A,B,tr],col,True),
+        ([nl,A,nr],col,True),  ([tr,B,tl],col,True)]
+    return F
+
+def render(F, px, elev, ss=8):
+    S=px*ss; a=math.radians(elev); ca,sa=math.cos(a),math.sin(a)
+    xf=lambda p:(p[0],p[1]*sa+p[2]*ca,-p[1]*ca+p[2]*sa)
+    light=(-0.70,0.30,0.45)
+    img=Image.new("RGB",(S,S),(24,27,32)); d=ImageDraw.Draw(img)
+    tris=sorted(((sum(v[2] for v in [xf(q) for q in pts])/len(pts),[xf(q) for q in pts],c,sh)
+                 for pts,c,sh in F), key=lambda t:t[0])
+    for _,q,base,shade in tris:
+        (x0,y0,z0),(x1,y1,z1),(x2,y2,z2)=q[0],q[1],q[2]
+        ux,uy,uz=x1-x0,y1-y0,z1-z0; vx,vy,vz=x2-x0,y2-y0,z2-z0
+        nx,ny,nz=uy*vz-uz*vy,uz*vx-ux*vz,ux*vy-uy*vx
+        L=math.sqrt(nx*nx+ny*ny+nz*nz) or 1.0; nx,ny,nz=nx/L,ny/L,nz/L
+        if nz<0: nx,ny,nz=-nx,-ny,-nz
+        k=(0.42+0.58*max(0.0,nx*light[0]+ny*light[1]+nz*light[2])) if shade else 1.0
+        d.polygon([(S/2+p[0]*S*0.92,S/2-p[1]*S*0.92) for p in q],
+                  fill=tuple(min(255,int(255*c*k)) for c in base))
+    return img.resize((px,px),Image.LANCZOS)
+
+VAR=[("V1 faithful",        1.0, False),
+     ("V2 gold muzzle",     1.0, True),
+     ("V3 gold + 1.8x wide",1.8, True),
+     ("V4 body + 1.8x wide",1.8, False)]
+big=Image.new("RGB",(4*250+30,4*140+30),(24,27,32))
+for r,(name,wd,gold) in enumerate(VAR):
+    F=facets(wd,gold)
+    for c,e in enumerate((90,47,16,6)):
+        big.paste(render(F,120,e),(15+c*250+60,15+r*140+10))
+big.save("/tmp/muzzle-variants.png")
+for name,wd,gold in VAR:
+    F=facets(wd,gold); F0=[f for f in F][:-4]
+    row=[]
+    for e in (90,16,6):
+        a=render(F,32,e); b=render(F0,32,e)
+        la=sum(1 for p in a.get_flattened_data() if p!=(24,27,32))
+        df=sum(1 for p,q in zip(a.get_flattened_data(),b.get_flattened_data()) if p!=q)
+        row.append(f"{100.0*df/max(1,la):5.1f}%")
+    print(f"{name:22} muzzle share at 90/16/6 deg: " + "  ".join(row))
+print("WROTE /tmp/muzzle-variants.png")
diff --git a/docs/CAD/design/mate-connectors/planarfacemateconnectors.png b/docs/CAD/design/mate-connectors/planarfacemateconnectors.png
new file mode 100644
index 0000000000..9fea27ab2b
Binary files /dev/null and b/docs/CAD/design/mate-connectors/planarfacemateconnectors.png differ
diff --git a/docs/CAD/design/mate-connectors/relief-sheet.png b/docs/CAD/design/mate-connectors/relief-sheet.png
new file mode 100644
index 0000000000..0c6d0d11f0
Binary files /dev/null and b/docs/CAD/design/mate-connectors/relief-sheet.png differ
diff --git a/docs/CAD/design/mate-connectors/relief_sheet.py b/docs/CAD/design/mate-connectors/relief_sheet.py
new file mode 100644
index 0000000000..4b8bc6aa74
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/relief_sheet.py
@@ -0,0 +1,99 @@
+"""Flat glyph vs 3D relief, at the elevations that killed the disc — wi3z.
+
+The flat study collapsed at 16 deg because anything drawn IN the connector's plane foreshortens by
+sin(elevation). This renders the SAME bear as its real relief (1508 facets off the supplied male)
+with a simple lambert shade, so the silhouette does the work at a grazing angle. Two rows, same
+sizes, same elevations, so the comparison is direct.
+"""
+import json, math, os
+from PIL import Image, ImageDraw
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+M = json.load(open(os.path.join(HERE, "bear_mesh.json")))
+V, F = M["v"], M["f"]
+
+# Part frame: face carried by X (right) and Z (down-negative), relief along +Y.
+P = [(v[0], -v[2], v[1]) for v in V]           # -> (x right, y up, z out of the face)
+xs=[p[0] for p in P]; ys=[p[1] for p in P]; zs=[p[2] for p in P]
+CX,CY,CZ = (min(xs)+max(xs))/2, (min(ys)+max(ys))/2, (min(zs)+max(zs))/2
+SPAN = max(max(xs)-min(xs), max(ys)-min(ys))
+P = [((x-CX)/SPAN, (y-CY)/SPAN, (z-CZ)/SPAN) for x,y,z in P]
+
+def shade(px, elev_deg, supersample=8):
+    """Camera orbits down from straight-on (90) to grazing (small). Rotate about the screen x-axis."""
+    S = px*supersample
+    a = math.radians(elev_deg)
+    ca, sa = math.cos(a), math.sin(a)
+    # view: rotate the model so the face normal tips away from the camera
+    def xf(p):
+        x,y,z = p
+        return (x, y*sa + z*ca, -y*ca + z*sa)     # third component = depth toward camera
+    Q = [xf(p) for p in P]
+    img = Image.new("L", (S,S), 0)
+    d = ImageDraw.Draw(img)
+    order = []
+    for tri in F:
+        a3 = [Q[i] for i in tri]
+        order.append((sum(v[2] for v in a3)/3.0, tri, a3))
+    order.sort(key=lambda t: t[0])                 # painter: far first
+    light = (-0.35, 0.55, 0.76)
+    for _, tri, a3 in order:
+        (x0,y0,z0),(x1,y1,z1),(x2,y2,z2) = a3
+        ux,uy,uz = x1-x0, y1-y0, z1-z0
+        vx,vy,vz = x2-x0, y2-y0, z2-z0
+        nx,ny,nz = uy*vz-uz*vy, uz*vx-ux*vz, ux*vy-uy*vx
+        n = math.sqrt(nx*nx+ny*ny+nz*nz) or 1.0
+        nx,ny,nz = nx/n, ny/n, nz/n
+        if nz < 0: nx,ny,nz = -nx,-ny,-nz          # face the camera
+        lam = max(0.0, nx*light[0] + ny*light[1] + nz*light[2])
+        val = int(70 + 185*lam)
+        pts = [(S/2 + x*S*0.92, S/2 - y*S*0.92) for x,y,_ in a3]
+        d.polygon(pts, fill=val)
+    return img.resize((px,px), Image.LANCZOS)
+
+# flat outline, for the side-by-side
+D = json.load(open(os.path.join(HERE, "bear_outline.json")))
+def unit(pts):
+    p=[(x,-z) for x,z in pts]
+    return [((x-CX)/SPAN,(y-CY)/SPAN) for x,y in p]
+OUT = unit(D["outer"])
+HOLES = [unit(h["pts"]) for h in D["holes"]]
+
+def flat(px, elev_deg, supersample=8):
+    S=px*supersample
+    img=Image.new("L",(S,S),0); d=ImageDraw.Draw(img)
+    k=math.sin(math.radians(elev_deg))
+    m=lambda p:(S/2+p[0]*S*0.92, S/2-p[1]*S*0.92*k)
+    d.polygon([m(p) for p in OUT], fill=255)
+    for h in HOLES: d.polygon([m(p) for p in h], fill=0)
+    return img.resize((px,px), Image.LANCZOS)
+
+SIZES=[22,32,48]; ELEVS=[(90,"flat on"),(47,"47"),(16,"16"),(6,"6")]
+pad,cell=8,58
+W=pad+len(SIZES)*len(ELEVS)*cell+pad; H=pad+2*cell+pad
+sheet=Image.new("RGB",(W,H),(24,27,32))
+for r,fn in enumerate((flat, shade)):
+    for ci,(elev,_) in enumerate(ELEVS):
+        for si,px in enumerate(SIZES):
+            g=fn(px,elev)
+            tile=Image.new("RGB",(px,px),(24,27,32))
+            if fn is flat:
+                tile.paste(Image.new("RGB",(px,px),(237,168,23)),(0,0),g)
+            else:
+                gg=g.convert("L")
+                tile=Image.merge("RGB",(gg.point(lambda v:min(255,int(v*1.00))),
+                                        gg.point(lambda v:int(v*0.71)),
+                                        gg.point(lambda v:int(v*0.16))))
+            x=pad+(ci*len(SIZES)+si)*cell+(cell-px)//2
+            y=pad+r*cell+(cell-px)//2
+            sheet.paste(tile,(x,y))
+sheet.resize((W*2,H*2), Image.NEAREST).save(os.path.join(HERE,"relief-sheet.png"))
+
+# how much ink survives — the same measure used on the disc glyph
+print(f"{'elev':>6} {'flat px@32':>11} {'relief px@32':>13}")
+for elev,_ in ELEVS:
+    f32=flat(32,elev); s32=shade(32,elev)
+    fi=sum(1 for v in f32.getdata() if v>40)
+    si=sum(1 for v in s32.getdata() if v>40)
+    print(f"{elev:>6} {fi:>11} {si:>13}")
+print("WROTE relief-sheet.png")
diff --git a/docs/CAD/design/mate-connectors/relief_test.py b/docs/CAD/design/mate-connectors/relief_test.py
new file mode 100644
index 0000000000..3fb83b2a8e
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/relief_test.py
@@ -0,0 +1,9 @@
+# Export the real male's relief as a triangle mesh, so the grazing test uses the actual geometry.
+import os, json
+import Part
+HERE = os.path.dirname(os.path.abspath(__file__))
+s = Part.Shape(); s.read(os.path.join(HERE, "bear.step"))
+verts, facets = s.Solids[0].tessellate(0.25)
+V = [[round(p.x,4), round(p.y,4), round(p.z,4)] for p in verts]
+json.dump({"v": V, "f": facets}, open(os.path.join(HERE, "bear_mesh.json"), "w"))
+print(f"verts {len(V)} facets {len(facets)}")
diff --git a/docs/CAD/design/mate-connectors/render_key.py b/docs/CAD/design/mate-connectors/render_key.py
new file mode 100644
index 0000000000..eb4bcdbd99
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/render_key.py
@@ -0,0 +1,85 @@
+#!/usr/bin/env python3
+"""Flat-shade the faceted ridge key from several camera directions.
+
+The point is not a pretty picture. It is one question: does a low-poly solid, flat-shaded,
+let a human read its orientation from an arbitrary viewpoint -- and specifically, is the
+view ALONG the ridge ambiguous between front and back, as the geometry suggests it must be
+in silhouette?
+
+Flat shading (one normal per facet, no smoothing) is deliberate: it is what the concept
+claims to rely on, and it is what a CAD viewport with hard normals actually produces.
+"""
+import numpy as np
+from PIL import Image, ImageDraw
+
+# ---- the key, same numbers as faceted_ridge_key.scad
+L, W, tf, H, pr, pf, hf = 12.0, 4.0, 0.45, 4.5, 0.22, 0.62, 0.35
+Wf, xr0, xr1, Hf = W * tf, -L / 2 + L * pr, -L / 2 + L * pf, H * hf
+
+V = np.array([(-L/2, -W, 0), (-L/2, W, 0), (L/2, Wf, 0), (L/2, -Wf, 0),
+              (xr0, 0, H), (xr1, 0, Hf)], dtype=float)
+F = [[0, 1, 2, 3], [0, 4, 1], [0, 3, 5], [0, 5, 4], [1, 4, 5], [1, 5, 2], [3, 2, 5]]
+
+LIGHT = np.array([0.35, -0.5, 0.78])           # a headlight-ish key light
+LIGHT /= np.linalg.norm(LIGHT)
+
+
+def look_at(eye, target, up=(0, 0, 1)):
+    f = np.array(target, float) - np.array(eye, float)
+    f /= np.linalg.norm(f)
+    up = np.array(up, float)
+    if abs(np.dot(f, up)) > 0.999:
+        up = np.array([0, 1, 0], float)
+    r = np.cross(f, up); r /= np.linalg.norm(r)
+    u = np.cross(r, f)
+    return r, u, f
+
+
+def render(eye, target, path, size=(620, 460), scale=26.0, label=""):
+    r, u, f = look_at(eye, target)
+    eye = np.array(eye, float)
+    cam = np.stack([r, u, f])                   # world -> camera rows
+    P = (V - eye) @ cam.T                       # orthographic: x,y screen, z depth
+
+    w, h = size
+    img = Image.new("RGB", size, (238, 240, 243))
+    d = ImageDraw.Draw(img)
+
+    def to_px(p):
+        return (w / 2 + p[0] * scale, h / 2 - p[1] * scale)
+
+    faces = []
+    for face in F:
+        pts = V[face]
+        n = np.cross(pts[1] - pts[0], pts[2] - pts[0])
+        n /= np.linalg.norm(n)
+        centre = pts.mean(axis=0)
+        if np.dot(n, centre - eye) > 0:          # back-face cull
+            continue
+        depth = P[face][:, 2].mean()
+        lam = max(0.0, float(np.dot(n, LIGHT)))
+        shade = 0.22 + 0.78 * lam                # flat: ONE value for the whole facet
+        col = tuple(int(255 * shade * c) for c in (0.86, 0.72, 0.35))
+        faces.append((depth, [to_px(P[i]) for i in face], col))
+
+    for _, poly, col in sorted(faces, key=lambda t: -t[0]):   # painter's algorithm
+        d.polygon(poly, fill=col)
+
+    if label:
+        d.rectangle([8, 8, 8 + 9 * len(label), 30], fill=(255, 255, 255))
+        d.text((14, 14), label, fill=(20, 20, 20))
+    img.save(path)
+    return path
+
+
+if __name__ == "__main__":
+    t = (0, 0, H * 0.35)
+    views = [
+        ((26, -22, 20), "iso: the reference view"),
+        ((30,   0,  6), "ALONG +X  (from the FRONT, low end)"),
+        ((-30,  0,  6), "ALONG -X  (from the BACK, tall end)"),
+        ((0,    0, 34), "ALONG +Z  (straight down the mating axis)"),
+        ((2,  -32,  5), "ALONG -Y  (broadside, grazing)"),
+    ]
+    for i, (eye, lab) in enumerate(views):
+        print(render(eye, t, f"rk-{i}.png", label=lab))
diff --git a/docs/CAD/design/mate-connectors/render_stl.py b/docs/CAD/design/mate-connectors/render_stl.py
new file mode 100644
index 0000000000..16ad0e92a9
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/render_stl.py
@@ -0,0 +1,76 @@
+#!/usr/bin/env python3
+"""Flat-shade an ASCII/binary STL from several directions.
+
+Used to answer one question with a picture instead of an argument: does a RECESSED faceted
+pocket read as an oriented feature, or does a concave feature collapse into a dark hole?
+"""
+import struct
+import sys
+import numpy as np
+from PIL import Image, ImageDraw
+
+LIGHT = np.array([0.35, -0.5, 0.78]); LIGHT /= np.linalg.norm(LIGHT)
+
+
+def load_stl(path):
+    data = open(path, "rb").read()
+    if data[:5] == b"solid" and b"facet" in data[:2000]:
+        tris, cur = [], []
+        for line in data.decode("ascii", "ignore").splitlines():
+            s = line.split()
+            if s and s[0] == "vertex":
+                cur.append([float(x) for x in s[1:4]])
+                if len(cur) == 3:
+                    tris.append(cur); cur = []
+        return np.array(tris, dtype=float)
+    n = struct.unpack("<I", data[80:84])[0]
+    tris = np.empty((n, 3, 3), dtype=float)
+    off = 84
+    for i in range(n):
+        v = struct.unpack("<12f", data[off:off + 48])
+        tris[i] = np.array(v[3:12]).reshape(3, 3)
+        off += 50
+    return tris
+
+
+def render(tris, eye, target, path, size=(620, 460), scale=14.0, label=""):
+    eye = np.array(eye, float); target = np.array(target, float)
+    f = target - eye; f /= np.linalg.norm(f)
+    up = np.array([0, 0, 1.0])
+    if abs(np.dot(f, up)) > 0.999: up = np.array([0, 1.0, 0])
+    r = np.cross(f, up); r /= np.linalg.norm(r)
+    u = np.cross(r, f)
+    cam = np.stack([r, u, f])
+
+    w, h = size
+    img = Image.new("RGB", size, (238, 240, 243)); d = ImageDraw.Draw(img)
+    faces = []
+    for t in tris:
+        n = np.cross(t[1] - t[0], t[2] - t[0])
+        ln = np.linalg.norm(n)
+        if ln < 1e-12: continue
+        n /= ln
+        c = t.mean(axis=0)
+        if np.dot(n, c - eye) > 0: continue                  # cull back faces
+        P = (t - eye) @ cam.T
+        lam = max(0.0, float(np.dot(n, LIGHT)))
+        shade = 0.20 + 0.80 * lam
+        col = tuple(int(255 * shade * ch) for ch in (0.86, 0.72, 0.35))
+        poly = [(w / 2 + p[0] * scale, h / 2 - p[1] * scale) for p in P]
+        faces.append((P[:, 2].mean(), poly, col))
+    for _, poly, col in sorted(faces, key=lambda x: -x[0]):
+        d.polygon(poly, fill=col)
+    if label:
+        d.rectangle([8, 8, 8 + 9 * len(label), 30], fill=(255, 255, 255))
+        d.text((14, 14), label, fill=(20, 20, 20))
+    img.save(path)
+
+
+if __name__ == "__main__":
+    tris = load_stl(sys.argv[1])
+    print("triangles:", len(tris))
+    views = [((26, -22, 20), "iso"), ((0, 0, 34), "straight down +Z"),
+             ((4, -30, 9), "grazing"), ((-28, -10, 12), "from the tall end")]
+    for i, (eye, lab) in enumerate(views):
+        render(tris, eye, (0, 0, 0), f"fem-{i}.png", label=f"FEMALE POCKET — {lab}")
+        print(f"fem-{i}.png")
diff --git a/docs/CAD/design/mate-connectors/rk-0.png b/docs/CAD/design/mate-connectors/rk-0.png
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diff --git a/docs/CAD/design/mate-connectors/rk-back.png b/docs/CAD/design/mate-connectors/rk-back.png
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diff --git a/docs/CAD/design/mate-connectors/rk-iso.png b/docs/CAD/design/mate-connectors/rk-iso.png
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diff --git a/docs/CAD/design/mate-connectors/rk-sheet.png b/docs/CAD/design/mate-connectors/rk-sheet.png
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diff --git a/docs/CAD/design/mate-connectors/simplify-sheet.png b/docs/CAD/design/mate-connectors/simplify-sheet.png
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diff --git a/docs/CAD/design/mate-connectors/simplify_study.py b/docs/CAD/design/mate-connectors/simplify_study.py
new file mode 100644
index 0000000000..c0bbcf63ab
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/simplify_study.py
@@ -0,0 +1,142 @@
+"""Reduce the bear face to the fewest marks that still read at glyph size — wi3z.
+
+Geometry comes from bear_outline.json, which extract_outline.py pulled off the supplied male
+B-rep's back plate: the outer wire IS the silhouette, the inner wires are the two eyes and the
+muzzle opening. Nothing here is traced by eye.
+
+The glyph is drawn IN the connector's plane, so a grazing view foreshortens it along one axis by
+sin(elevation) — exactly what collapsed the disc's roll quadrant to 3 pixels at 10 deg. Every
+candidate is therefore rendered at three elevations as well as three pixel sizes.
+"""
+import json, math, os
+from PIL import Image, ImageDraw
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+D = json.load(open(os.path.join(HERE, "bear_outline.json")))
+
+def norm(pts):
+    """Part frame (X right, Z down-negative) -> glyph frame (x right, y up), centred, unit height."""
+    p = [(x, -z) for x, z in pts]
+    return p
+
+outer = norm(D["outer"])
+holes = [norm(h["pts"]) for h in D["holes"]]
+# the two Ø9.8 wires are the eyes; the wide one is the muzzle
+eyes   = [h for h, meta in zip(holes, D["holes"]) if meta["d"] < 20]
+muzzle = [h for h, meta in zip(holes, D["holes"]) if meta["d"] >= 20]
+
+ALL = outer + [p for h in holes for p in h]
+xs = [p[0] for p in ALL]; ys = [p[1] for p in ALL]
+CX, CY = (min(xs)+max(xs))/2, (min(ys)+max(ys))/2
+SPAN = max(max(xs)-min(xs), max(ys)-min(ys))
+def to_unit(pts): return [((x-CX)/SPAN, (y-CY)/SPAN) for x, y in pts]
+
+def rdp(pts, eps):
+    """Douglas-Peucker. Vertex count is the honest measure of 'how simplified'."""
+    if len(pts) < 3: return pts
+    ax, ay = pts[0]; bx, by = pts[-1]
+    dx, dy = bx-ax, by-ay
+    n = math.hypot(dx, dy)
+    best, bi = -1.0, 0
+    for i in range(1, len(pts)-1):
+        px, py = pts[i]
+        d = abs(dx*(ay-py) - (ax-px)*dy)/n if n > 1e-12 else math.hypot(px-ax, py-ay)
+        if d > best: best, bi = d, i
+    if best <= eps:
+        return [pts[0], pts[-1]]
+    return rdp(pts[:bi+1], eps)[:-1] + rdp(pts[bi:], eps)
+
+def simp_closed(pts, eps):
+    r = rdp(pts + [pts[0]], eps)
+    return r[:-1]
+
+def centroid(pts):
+    return (sum(p[0] for p in pts)/len(pts), sum(p[1] for p in pts)/len(pts))
+
+U_OUT = to_unit(outer)
+U_EYE = [to_unit(e) for e in eyes]
+U_MUZ = [to_unit(m) for m in muzzle]
+
+def eye_dots(scale=1.0):
+    out = []
+    for e in U_EYE:
+        cx, cy = centroid(e)
+        r = max(max(p[0] for p in e)-min(p[0] for p in e),
+                max(p[1] for p in e)-min(p[1] for p in e))/2*scale
+        out.append((cx, cy, r))
+    return out
+
+def muzzle_tri():
+    """The muzzle reduced to one filled triangle: its two lower corners and its apex."""
+    m = U_MUZ[0]
+    lo = min(p[1] for p in m); hi = max(p[1] for p in m)
+    bottom = [p for p in m if p[1] < lo + 0.06*(hi-lo)]
+    apex   = max(m, key=lambda p: p[1])
+    return [min(bottom), max(bottom), apex]
+
+CANDIDATES = {
+ "C0 full":        dict(out=U_OUT,                     eyes=eye_dots(), muz=U_MUZ[0]),
+ "C1 eps .004":    dict(out=simp_closed(U_OUT, .004),  eyes=eye_dots(), muz=simp_closed(U_MUZ[0], .004)),
+ "C2 eps .012":    dict(out=simp_closed(U_OUT, .012),  eyes=eye_dots(), muz=muzzle_tri()),
+ "C3 eps .030":    dict(out=simp_closed(U_OUT, .030),  eyes=eye_dots(1.15), muz=muzzle_tri()),
+ "C4 no eyes":     dict(out=simp_closed(U_OUT, .012),  eyes=[], muz=muzzle_tri()),
+}
+
+def sym_report(pts, tol=0.02):
+    """Trivial symmetry group is the property doing the work. If a simplification restores a
+    mirror or a 180 deg rotation, that simplification is wrong."""
+    def match(tf):
+        t = [tf(p) for p in pts]
+        hit = 0
+        for q in t:
+            if min(math.hypot(q[0]-p[0], q[1]-p[1]) for p in pts) <= tol: hit += 1
+        return hit, len(pts)
+    return {
+      "mirror-x": match(lambda p: (-p[0],  p[1])),
+      "mirror-y": match(lambda p: ( p[0], -p[1])),
+      "rot-180":  match(lambda p: (-p[0], -p[1])),
+    }
+
+def render(c, px, elev_deg, supersample=8):
+    S = px*supersample
+    img = Image.new("L", (S, S), 0)
+    d = ImageDraw.Draw(img)
+    k = math.sin(math.radians(elev_deg))
+    def m(p):
+        return (S/2 + p[0]*S*0.92, S/2 - p[1]*S*0.92*k)
+    d.polygon([m(p) for p in c["out"]], fill=255)
+    if c["muz"]: d.polygon([m(p) for p in c["muz"]], fill=0)
+    for cx, cy, r in c["eyes"]:
+        a = m((cx-r, cy+r)); b = m((cx+r, cy-r))
+        d.ellipse([a[0], a[1], b[0], b[1]], fill=0)
+    return img.resize((px, px), Image.LANCZOS)
+
+print(f"{'candidate':14} {'verts':>6} {'marks':>6}   symmetry (matched/total, lower is better)")
+print("-"*78)
+for name, c in CANDIDATES.items():
+    s = sym_report(c["out"])
+    marks = 1 + (1 if c["muz"] else 0) + len(c["eyes"])
+    sym = "  ".join(f"{k} {v[0]}/{v[1]}" for k, v in s.items())
+    print(f"{name:14} {len(c['out']):6} {marks:6}   {sym}")
+
+SIZES = [22, 32, 48]
+ELEVS = [(90, "flat on"), (47, "47 deg"), (16, "16 deg"), (6, "6 deg")]
+pad, cell = 8, 56
+W = pad + len(SIZES)*len(ELEVS)*cell + pad
+H = pad + len(CANDIDATES)*cell + pad
+sheet = Image.new("RGB", (W, H), (24, 27, 32))
+for r, (name, c) in enumerate(CANDIDATES.items()):
+    for ci, (elev, _) in enumerate(ELEVS):
+        for si, px in enumerate(SIZES):
+            g = render(c, px, elev)
+            tile = Image.new("RGB", (px, px), (24, 27, 32))
+            gold = Image.new("RGB", (px, px), (237, 168, 23))
+            tile.paste(gold, (0, 0), g)
+            x = pad + (ci*len(SIZES)+si)*cell + (cell-px)//2
+            y = pad + r*cell + (cell-px)//2
+            sheet.paste(tile, (x, y))
+sheet = sheet.resize((W*2, H*2), Image.NEAREST)
+sheet.save(os.path.join(HERE, "simplify-sheet.png"))
+print("\ncolumns: " + " | ".join(f"{e[1]} @ 22/32/48px" for e in ELEVS))
+print("rows:    " + ", ".join(CANDIDATES))
+print("WROTE simplify-sheet.png")
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diff --git a/docs/CAD/design/mate-connectors/trim-cmp.png b/docs/CAD/design/mate-connectors/trim-cmp.png
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diff --git a/docs/CAD/design/mate-connectors/trim_female.py b/docs/CAD/design/mate-connectors/trim_female.py
new file mode 100644
index 0000000000..2753e4a3a8
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/trim_female.py
@@ -0,0 +1,74 @@
+# Trim the boxy frame off the female so its outer shape is the bear face itself.
+#
+# Method: take the male's flat back face (the plane Y=0 -- that face IS the bear silhouette),
+# offset its OUTER wire outward in 2D, extrude the result along the insertion axis, and keep only
+# the part of the female inside it. Everything outside is the block frame and goes away.
+#
+# NOTE ON THE NUMBER. The pocket's side walls stand at +0.20 mm from the male outline, because that
+# is the clearance. A trim boundary at +0.10 mm therefore falls INSIDE them by 0.10 mm and removes
+# the side wall entirely rather than leaving a thin one. The script runs the requested value and
+# then measures what is actually left, so the outcome is a number rather than an opinion; it also
+# emits a second variant at an offset that leaves a printable wall, for comparison.
+#
+# Run: /snap/bin/freecad.cmd trim_female.py
+
+import os, sys
+import FreeCAD as App
+import Part
+from FreeCAD import Vector
+
+HERE   = os.path.dirname(os.path.abspath(__file__))
+MALE   = os.path.join(HERE, "bear.step")
+FEMALE = os.path.join(HERE, "BearConnector_Female.step")
+
+REQUESTED = 0.10      # as asked
+CLEARANCE = 0.20      # what the pocket was built with
+SAFE_WALL = 1.60      # a wall that survives an FDM nozzle: clearance + ~1.4 mm
+
+male = Part.Shape(); male.read(MALE);   male = male.Solids[0]
+fem  = Part.Shape(); fem.read(FEMALE);  fem  = fem.Solids[0]
+print(f"female in : {fem.Volume/1000:.2f} cm3, {len(fem.Faces)} faces")
+
+# --- the bear silhouette: the male's flat back face at Y = 0
+back = None
+for f in male.Faces:
+    n = f.normalAt(0, 0)
+    if abs(f.CenterOfMass.y) < 1e-6 and abs(abs(n.y) - 1.0) < 1e-6:
+        if back is None or f.Area > back.Area:
+            back = f
+if back is None:
+    print("FAIL: could not find the flat back face at Y=0"); sys.exit(1)
+print(f"silhouette: back face area {back.Area:.1f} mm2, {len(back.Wires)} wires "
+      f"(outer + {len(back.Wires)-1} holes: eyes and mouth)")
+
+fb = fem.BoundBox
+y0, y1 = fb.YMin - 5.0, fb.YMax + 5.0
+
+def trimmed(offset):
+    """keep only the part of the female inside the silhouette grown by `offset`"""
+    wire = back.OuterWire
+    grown = wire.makeOffset2D(offset, join=2, fill=False, openResult=False, intersection=True)
+    face  = Part.Face(Part.Wire(grown.Edges))
+    prism = face.extrude(Vector(0, y1 - y0, 0))
+    prism.translate(Vector(0, y0 - face.CenterOfMass.y, 0))
+    return fem.common(prism)
+
+for tag, off, out in (("requested", REQUESTED, "BearConnector_Female_Trimmed.step"),
+                      ("safe wall", SAFE_WALL, "BearConnector_Female_Trimmed_wall.step")):
+    r = trimmed(off)
+    if not r.Solids:
+        print(f"\n{tag} (+{off:.2f} mm): NOTHING LEFT"); continue
+    wall = off - CLEARANCE
+    # is there any material left at the level of the pocket's side wall?
+    sec = r.section(Part.makePlane(400, 400, Vector(-200, 1.5, -200), Vector(0, 1, 0)))
+    perim = sum(e.Length for e in sec.Edges)
+    print(f"\n{tag} (+{off:.2f} mm)  wall = {wall:+.2f} mm")
+    print(f"   volume {r.Volume/1000:.2f} cm3, {len(r.Solids)} solid(s), {len(r.Faces)} faces")
+    print(f"   section through the pocket wall at Y=1.5: {perim:.1f} mm of edge")
+    if wall <= 0:
+        print(f"   -> the trim cuts {abs(wall):.2f} mm INSIDE the pocket wall: no side wall remains")
+    doc = App.newDocument(tag.replace(" ", "_"))
+    o = doc.addObject("Part::Feature", "Female")
+    o.Shape = r; doc.recompute()
+    Part.export([o], os.path.join(HERE, out))
+    print(f"   wrote {out}")
diff --git a/docs/CAD/design/mate-connectors/verify_trimmed.py b/docs/CAD/design/mate-connectors/verify_trimmed.py
new file mode 100644
index 0000000000..81f6f3fea1
--- /dev/null
+++ b/docs/CAD/design/mate-connectors/verify_trimmed.py
@@ -0,0 +1,25 @@
+# Check both trimmed females still fit the male, and export STLs for a visual comparison.
+# Run: /snap/bin/freecad.cmd verify_trimmed.py
+import os
+import Mesh, Part
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+male = Part.Shape(); male.read(os.path.join(HERE, "bear.step")); male = male.Solids[0]
+
+for name in ("BearConnector_Female_Trimmed", "BearConnector_Female_Trimmed_wall"):
+    p = os.path.join(HERE, name + ".step")
+    s = Part.Shape(); s.read(p); s = s.Solids[0]
+    d = male.distToShape(s)[0]
+    c = male.common(s)
+    cv = c.Volume if c.Solids else 0.0
+    bb = s.BoundBox
+    print(f"{name}")
+    print(f"   {bb.XLength:.2f} x {bb.YLength:.2f} x {bb.ZLength:.2f} mm, {s.Volume/1000:.2f} cm3, "
+          f"{len(s.Faces)} faces, valid={s.isValid()}")
+    print(f"   gap to male {d:.4f} mm, interference {cv:.6f} mm3")
+    m = Mesh.Mesh(); m.addFacets([tuple(t) for t in s.tessellate(0.12)[1]] and
+                                 [(s.tessellate(0.12)[0][a], s.tessellate(0.12)[0][b],
+                                   s.tessellate(0.12)[0][c2])
+                                  for a, b, c2 in s.tessellate(0.12)[1]])
+    m.write(os.path.join(HERE, name + ".stl"))
+    print(f"   wrote {name}.stl ({m.CountFacets} facets)")
diff --git a/docs/CAD/design_tab.md b/docs/CAD/design_tab.md
new file mode 100644
index 0000000000..1be0a2ea33
--- /dev/null
+++ b/docs/CAD/design_tab.md
@@ -0,0 +1,333 @@
+# The Design tab
+
+Object-driven parametric CAD inside the slicer. Point at geometry; the geometry offers the
+verbs that apply to it. Selection comes first and the tool consumes it. Draw a sketch,
+constrain it, turn it into a solid, refine it, and send it straight to Prepare — without
+leaving for another application and coming back through an STL.
+
+The model is a **recipe**, not a mesh. Every action becomes a feature in a tree that is
+replayed from the start whenever anything changes, so editing a dimension you set twenty
+steps ago rebuilds everything downstream. The geometry kernel is OCCT, which the slicer
+already ships for STEP import.
+
+---
+
+## Getting started
+
+1. Open the **Design** tab.
+2. Click a face or a reference plane in the viewport, then press `Shift+S` (Sketch). The offer
+   opens with the sketch tools on it.
+3. Draw a closed profile, then press **✓ Confirm** in the floating action bar.
+4. With the sketch selected, press `Shift+E` (Extrude).
+5. Press **Commit to Plate** to hand the solid to Prepare.
+
+The status line under the toolbar is the thing to watch: it says what the current tool is
+waiting for. When no plane is picked it reads *"Click a face or a reference plane in the
+viewport, then a sketch tool"*; once one is picked it reads *"Sketching on <face> — pick a
+tool"*. It is also where a refusal explains itself.
+
+---
+
+## Selecting
+
+- One left-click selects what is under the cursor. There is no click-cycling through
+  face → edge → body.
+- A click near a corner takes the corner, not the face behind it.
+- Left-drag sweeps a rubber band, and a rubber band takes the whole body.
+- An open sketch line can be clicked, even where it bounds a region.
+- Double-click a sketch stroke to edit it — the gesture belongs on the geometry.
+- Editing a dimension's value **updates** that dimension instead of adding a second one next
+  to it.
+- The floating chrome that belongs to a sketch leaves with the sketch when it ends.
+- Sketching happens on the face you clicked, first click.
+- A sketch whose entities form no wire **fails** instead of extruding a default box. A
+  subtraction that removes nothing is reported as an error instead of a silent success.
+
+---
+
+## The offer
+
+Right-click on the geometry, released without moving the mouse (an 8 px budget — a
+right-drag that orbits the camera does not open it). Left-click still only selects, so
+pointing at things stays quiet.
+
+The offer also opens by itself the moment you press Sketch on a face or plane, showing the
+sketch tools — the app hands you the tools directly.
+
+**Eight families, always in this fixed order:** Create, Add material, Remove, Dress-up,
+Repeat, Transform, Reference, Modify.
+
+- A family with at least one applicable verb shows it. Several applicable verbs collapse
+  into a submenu under the family name.
+- A family with nothing applicable is **shown greyed in place, with the reason** — e.g.
+  *"Create — Click a face or a reference plane in the viewport, then a sketch tool"*. It is
+  not hidden. A control that cannot be used still says what it is and what you would have to
+  do first.
+- Inside a sketch the offer shows the sketch verbs; outside it shows the feature verbs.
+
+**Document-level actions never enter the offer**, because they act on the document and not
+on a selection: Import STEP, Import mesh, Text, SVG, Export STEP, Commit to Plate, Undo,
+Redo, Variables, Section view, Origin planes, World axes. They live in the toolbar.
+
+---
+
+## Keyboard
+
+Single letters drive sketch tools **while a sketch is open**; Shift+letter drives feature
+tools and single letters drive view toggles **when no sketch is open**. The two maps are
+selected by the mode, not by whether a sketch session is running.
+
+### Sketch (while a sketch is open)
+
+| Key | Tool |
+|---|---|
+| `L` | Line — click start, then end |
+| `R` | Rectangle — click two opposite corners |
+| `C` | Circle — click centre, then radius |
+| `A` | Arc — click start, end, then a point |
+| `S` | Slot — two centreline ends, then width |
+| `E` | Ellipse — centre, major end, minor point |
+| `B` | Spline — click control points |
+| `P` | Point — click to place |
+| `G` | Polygon — click centre, then a vertex |
+| `D` | Dimension — click 2 points or an entity |
+| `T` | Trim — click a segment to trim it |
+| `X` | Extend — click a line/arc to extend it |
+| `O` | Offset — pick an entity, drag the distance |
+| `M` | Mirror — pick axis, then entities |
+| `F` | Fillet — pick two lines, set the radius |
+| `H` | Chamfer — pick two lines, set the distance |
+| `K` | Constrain — finish the live sketch and enter constrain |
+| `Q` | Construction toggle — draw the next entity as construction geometry |
+| `Del` | Delete the selected sketch entity |
+| `Esc` | Cancel the live tool |
+
+### Feature (when no sketch is open)
+
+| Key | Tool |
+|---|---|
+| `Shift+S` | Sketch |
+| `Shift+E` | Extrude — extrude a profile, or push/pull a picked face |
+| `Shift+R` | Revolve |
+| `Shift+W` | Sweep |
+| `Shift+L` | Loft |
+| `Shift+N` | Pattern |
+| `Shift+G` | Surface Extrude |
+| `Shift+J` | Surface Revolve |
+| `Shift+O` | Surface Loft |
+| `Shift+Q` | Surface Fill |
+| `Shift+U` | Surface Offset |
+| `Shift+V` | Thicken Surface |
+| `Shift+P` | Plane |
+| `Shift+A` | Axis |
+| `Shift+C` | Coord Sys |
+| `Shift+Y` | Transform |
+| `Shift+Z` | Mirror |
+| `Shift+B` | Boolean |
+| `Shift+X` | Cut |
+| `Shift+F` | Fillet / Chamfer |
+| `Shift+D` | Draft |
+| `Shift+K` | Shell |
+| `Shift+H` | Hole |
+| `Shift+T` | Thread |
+| `Shift+I` | Import STEP |
+| `Shift+M` | Import mesh |
+
+### View toggles (single letters, when no sketch is open)
+
+| Key | Action |
+|---|---|
+| `Home` | Axonometric view, fitted to the model |
+| `P` | Origin planes on/off |
+| `A` | World axes on/off |
+| `X` | Section view on/off |
+
+While the section is on: `PageUp` / `PageDown` move the cut plane, `F` flips which half is
+kept. With no section on, `F` is Place on Face — lay the picked face flat on the bed.
+
+---
+
+## Sketching
+
+A sketch is a closed (or open) 2D profile on a plane or on a flat face of an existing body.
+Press `Shift+S`, click the face or plane you want to sketch on, and draw. The toolbar and
+the offer both carry the sketch tools.
+
+**Entities:** line, polyline, rectangle (corner / centre / oblique / rounded), circle
+(centre-radius / 2-point / 3-point), arc (centre-point / 3-point / tangent), ellipse and
+elliptical arc, polygon (inscribed / circumscribed), slot (straight / arc), spline, point,
+and text.
+
+**Editing:** move, rotate, scale, trim, extend, offset, mirror, and linear or polar arrays.
+
+**Constraints:** coincident, horizontal, vertical, parallel, perpendicular, tangent, equal,
+concentric, midpoint, symmetric, fix, plus dimensional radius, diameter, distance and angle.
+The solver reports the remaining degrees of freedom and tells you when a sketch is fully
+constrained — or when a constraint conflicts with one already there.
+
+Sketches stay editable. Selecting one in the feature tree reopens it with its dimensions
+live.
+
+---
+
+## Building solids
+
+Grouped in the toolbar by what they do, one concept per drawer.
+
+### Add material
+| Tool | Shortcut | What it does |
+|---|---|---|
+| Extrude | `Shift+E` | Extrude a profile, or push/pull a face already on a body |
+| Revolve | `Shift+R` | Revolve a profile about an axis |
+| Sweep | `Shift+W` | Sweep a profile along a path — including a helix, for springs and augers |
+| Loft | `Shift+L` | Skin between two or more profiles |
+| Thicken | — | Offset a solid face into a thin plate as a new body |
+| Rib | — | Grow a stiffening wall from an open sketch line, fused to a body |
+
+Extrude offers blind, symmetric, two-sided, through-all and up-to-face end conditions, plus
+a draft angle on the side wall, and can add, subtract, intersect or start a new body.
+
+### Surface
+Sheet bodies — surfaces with no thickness — for shapes that are easier to build as skins and
+solidify afterwards.
+
+| Tool | Shortcut |
+|---|---|
+| Surface Extrude | `Shift+G` |
+| Surface Revolve | `Shift+J` |
+| Surface Loft | `Shift+O` |
+| Surface Fill | `Shift+Q` |
+| Surface Offset | `Shift+U` |
+| Thicken Surface | `Shift+V` |
+
+Thicken Surface is how a sheet becomes a printable solid.
+
+### Dress-up
+| Tool | Shortcut |
+|---|---|
+| Fillet / Chamfer | `Shift+F` |
+| Draft (taper a face) | `Shift+D` |
+| Shell | `Shift+K` |
+| Delete Face | — |
+
+Delete Face removes faces and heals the solid — useful for stripping a feature off an
+imported part.
+
+### Holes
+**Hole** (`Shift+H`) drills simple, counterbored or countersunk holes, with an ISO/ANSI
+standards table so you can ask for an M6 clearance hole instead of computing a diameter.
+**Thread** (`Shift+T`) cuts a real helical thread into a bore or onto a shaft.
+
+### Placement
+Operations that move a body without changing its shape: **Transform** (`Shift+Y`),
+**Mirror** (`Shift+Z`), and **Mate** for assemblies.
+
+### Combining
+**Boolean** (`Shift+B`) unions, subtracts or intersects two bodies. **Cut** (`Shift+X`)
+splits a body with a plane. **Pattern** (`Shift+N`) repeats a body linearly, in a circle, or
+along a curve.
+
+---
+
+## Reference geometry
+
+Datum features carry no material; they exist to give later features something to attach to.
+
+- **Plane** (`Shift+P`) — offset, tilted, midplane, tangent, through two edges, or coincident
+- **Axis** (`Shift+A`) — two points, a face normal, a cylinder centreline, the intersection of
+  two planes, or along an edge
+- **Coord Sys** (`Shift+C`) — a full frame, from a world point or from a face plus a
+  direction edge
+- **Helix** — a helical curve to sweep along
+- **Project** — project a body's edges onto a plane as sketch geometry
+
+On the Coord Sys tool, picking a direction **edge** is worth the extra click: without one the
+frame takes its X from the face's first edge, which is deterministic but not necessarily the
+direction you meant.
+
+---
+
+## Assemblies
+
+**Mate** aligns two coordinate systems and moves one body onto the other. Five kinds:
+
+| Kind | Leaves free |
+|---|---|
+| Fastened | nothing — 6 DOF locked |
+| Planar | sliding in the plane |
+| Revolute | rotation about the axis |
+| Slider | sliding along the axis |
+| Cylindrical | rotation *and* sliding |
+
+**Check interference** reports every overlapping pair of solids with the overlapping volume,
+so a clash is a number rather than an impression. Bodies that merely touch enclose no volume
+and are not reported.
+
+---
+
+## Variables and expressions
+
+Define named variables and drive dimensions from them. Any numeric field accepts an
+expression — `width/2`, `wall*3` — and everything re-evaluates on recompute. Change one
+variable and the whole model follows.
+
+---
+
+## Import and export
+
+**Import STEP** brings in a real B-rep solid, not a mesh: its faces and edges can be filleted,
+shelled and cut like anything modelled here.
+
+**Import mesh** (STL/OBJ) converts triangles to a B-rep body and tells you honestly what it
+got — whether the result is a closed solid or an open shell, with the boundary and
+non-manifold edge counts. A large mesh becomes a large number of faces, which is slow to
+edit; the importer warns before you commit to it.
+
+**Export STEP** writes the model out for another CAD tool.
+
+**Commit to Plate** sends the solid to Prepare for slicing. The whole feature recipe is saved
+inside the 3MF, so reopening the project restores the editable model rather than a frozen
+mesh.
+
+---
+
+## View controls
+
+**Section view** (`X`) hides half the model so you can see inside — `PageUp`/`PageDown` move
+the plane, `F` flips which half is kept. **Place on Face** (`F`, when section is off) lays a
+picked face flat on the bed. Origin planes (`P`) and world axes (`A`) can be toggled on while
+you orient yourself.
+
+---
+
+## Known limitations
+
+Being straight about the edges, so nobody discovers them the hard way:
+
+- **Rib** needs a sketch containing an explicit open line. A parametric rectangle sketch
+  carries no individual entities, so Rib cannot use one.
+- **Surface Loft** and **Surface Fill** have kernel tests but have not been exercised by hand.
+- Card wiring for 9 of the 16 late-wired tools has never been click-tested.
+- Mate resolves by composing transforms directly. There is no 3D assembly solver, so mates
+  are applied in order rather than solved simultaneously, and mate limits are not implemented.
+- Move-face and replace-face are not implemented — OCCT offers no clean primitive for them.
+- There is no automated GUI test in CI. Every behaviour above is traced to code and to a
+  hand pass, not to a synthetic click.
+
+---
+
+## Where the code lives
+
+| Path | Role |
+|---|---|
+| `src/libslic3r/CAD/CadDocument.*` | the feature recipe and its replay |
+| `src/libslic3r/CAD/GeometryEngine.*` | OCCT wrapper — faces, edges, booleans, healing |
+| `src/libslic3r/CAD/SketchEngine.*` | profile → wire → solid |
+| `src/libslic3r/CAD/SketchSolver.*` | constraint solving, over the vendored solver |
+| `src/libslic3r/slvs/` | vendored 2D constraint solver (GPLv3) |
+| `src/slic3r/GUI/CAD/DesignPanel.*` | the tab: toolbar, cards, feature tree |
+| `src/slic3r/GUI/CAD/DesignCanvas.*` | viewport integration |
+| `src/slic3r/GUI/CAD/DesignSketchTool.*` | in-canvas sketching |
+
+Build with `-DSLIC3R_CAD=ON` (the default). With it OFF the tab is not compiled and the deps
+prefix matches upstream exactly — see [cad_dependency_weight.md](cad_dependency_weight.md).
diff --git a/docs/CAD/design_tab_pr_description.md b/docs/CAD/design_tab_pr_description.md
new file mode 100644
index 0000000000..a6d67f0e7c
--- /dev/null
+++ b/docs/CAD/design_tab_pr_description.md
@@ -0,0 +1,73 @@
+# Design (CAD) tab — upstream pull request
+
+## What this adds
+
+A sketch-first parametric CAD tab inside the slicer. The workflow is direct:
+sketch → constrain → solid features → commit to plate. The whole feature recipe is
+persisted inside the 3MF, so reopening restores an editable model rather than a frozen mesh.
+
+- Kernel: OCCT, which upstream already links for STEP import — see
+  [cad_dependency_weight.md](docs/cad_dependency_weight.md)
+- Constraint solver: vendored SolveSpace `libslvs` subset
+- Interaction model: object-driven — point at geometry, the geometry offers the verbs that
+  apply to it; see [cad_ux_guidelines.md](docs/cad_ux_guidelines.md)
+- Full user-facing documentation: [design_tab.md](docs/design_tab.md)
+
+## Why it belongs in the slicer
+
+Every round trip through an external CAD tool costs a file export, a re-import, and the
+design intent that both steps discard. A part modified after slicing should return to its
+feature history, not to a mesh. Keeping the CAD model inside the slicer preserves that
+loop — the nozzle diameter, the build volume and the material are known at design time.
+
+For the integration case in full: [design_tab_upstream_portability.md](docs/design_tab_upstream_portability.md).
+
+## How it is built
+
+The `SLIC3R_CAD` CMake flag (default ON) gates the entire tab. With it OFF the tab is not
+compiled and the deps prefix matches upstream exactly — the dependency diff is one line in
+OCCT's CMake: `BUILD_MODULE_ModelingAlgorithms=OFF → ON`.
+
+Measured cost table: [cad_dependency_weight.md](docs/cad_dependency_weight.md).
+
+## Diff shape
+
+<!-- fork-specific: measured against this fork's upstream base; re-run the commands above after mirroring -->
+
+Against merge-base `d6cb667b894f`:
+
+ 306 files changed, 83032 insertions(+), 777 deletions(-)
+
+350 commits, of which 284 are new files and 37 modify upstream files. 99.3 % of the diff
+is new code. The negotiable surface is the 37 modified files.
+
+## Tests
+
+205 `TEST_CASE` blocks across 6 new test source files. This counts assertions written, not
+assertions passed — a run needs a build.
+
+`scripts/CAD/run-kernel-tests.sh` is the headless verification contract: it builds only
+`libslic3r_tests` (not the GUI app), needs no display, and exit 0 means the CAD suite
+passed. It now runs with **no exclusions** — both cases that used to be quarantined (the
+circle-line tangency solver abort and the internal-thread reference) are fixed.
+
+## Licensing
+
+The vendored solver in `src/libslic3r/slvs/` is **GPL-3.0** (see `src/libslic3r/slvs/LICENSE`),
+not LGPL. The combined work is distributable under AGPL-3.0. See the Licensing section of
+[design_tab_upstream_portability.md](docs/design_tab_upstream_portability.md) for the
+AGPLv3/GPLv3 compatibility argument; this point should be confirmed with upstream explicitly.
+
+## Not verified
+
+- Card wiring for 9 of the 16 late-wired tools was never click-tested.
+- There is no automated GUI test in CI. A green kernel run says nothing about the GUI —
+  synthetic clicks never drift, so the test suite and the viewport are two separate realities.
+- The click-test defect rate has **not converged**: a second pass found no new defects, but
+  four further days of work found five more. The earlier pass is not evidence of stability.
+
+## Reviewer's map
+
+See the [Where the code lives](docs/design_tab.md#where-the-code-lives) table in the user
+doc for the file-to-role mapping, and [docs/ux/tool_atlas.json](docs/ux/tool_atlas.json) as
+the generated-from source of `src/slic3r/GUI/CAD/DesignOffer.hpp`.
diff --git a/docs/CAD/design_tab_upstream_portability.md b/docs/CAD/design_tab_upstream_portability.md
new file mode 100644
index 0000000000..a7e9cd84ed
--- /dev/null
+++ b/docs/CAD/design_tab_upstream_portability.md
@@ -0,0 +1,162 @@
+# Design (CAD) tab — upstream integration brief
+
+**Question:** can the Design tab (sketch-first parametric CAD: sketch → constrain →
+extrude/revolve/fillet/hole/thread/shell, multi-body, undo, 3MF persistence) land in
+mainline OrcaSlicer?
+
+**Answer: yes, and the ask is far smaller than previously believed.** OCCT is *already*
+an OrcaSlicer dependency. We are not asking upstream to adopt a new library; we are
+asking it to widen one it already builds, at a measured cost of **3.77 MiB on Windows**.
+
+> ### Corrections to the 2026-06-21 assessment
+> That revision was written before the persistence work landed and got two load-bearing
+> facts wrong. Both are corrected here from direct measurement of the branch:
+>
+> 1. **"The real blocker: OCCT … a dependency mainline OrcaSlicer has never carried."**
+>    **False.** `deps/OCCT/` exists at the merge-base and upstream links it from
+>    `Format/STEP.cpp`, `Format/svg.cpp`, and `Shape/TextShape.cpp`. Our entire
+>    dependency diff is **one line**: `BUILD_MODULE_ModelingAlgorithms=OFF → ON`.
+> 2. **"vendored SolveSpace solver … LGPL."** **False.** `src/libslic3r/slvs/LICENSE` is
+>    **GPL-3.0**, not LGPL. This is fine (see Licensing) but must not be misstated.
+>
+> It also claimed "no changes to Model" — no longer true; 3MF recipe persistence adds one
+> `std::string` to `Model`.
+
+## Measured shape of the change
+
+Against merge-base `449a4cf9fc` (34 commits ahead):
+
+| | files | lines |
+|---|---:|---:|
+| **New files** | 138 | +61,720 |
+| **Modified upstream files** | 23 | +457 / −75 |
+| **Deleted upstream files** | 0 | — |
+
+The 62 kLOC headline is inflated by localization. The feature itself:
+
+| area | LOC | files |
+|---|---:|---:|
+| kernel (`src/libslic3r/`) | 15,828 | 37 |
+| GUI (`src/slic3r/`) | 19,544 | 14 |
+| tests (Catch2) | 2,567 | 6 |
+| i18n (unrelated; strip from the CAD PR) | 23,438 | 77 |
+
+**99.3 % of the diff is new files.** The negotiable surface is 457 added lines across 23
+files, and nothing upstream is deleted. The largest single hook is `GLCanvas3D.cpp`
+(+110/−2): an `m_design_sketch_tool` member plus render/mouse/key hooks, **every one
+already null-guarded** — which is why the compile-time gate below is cheap.
+
+No changes to the slicing pipeline (Print/PrintObject/Layer/GCode), Tab, or the
+printer-profile/config system.
+
+## The dependency ask, precisely
+
+Not "adopt OCCT" — **widen the existing OCCT build**:
+
+```diff
+-        -DBUILD_MODULE_ModelingAlgorithms=OFF
++        -DBUILD_MODULE_ModelingAlgorithms=ON
+```
+
+Cost, measured from the shipped Windows artifact (42 OCCT DLLs, 45.43 MiB total):
+
+| toolkit | size | note |
+|---|---:|---|
+| `TKFillet.dll` | 2.02 MiB | only exists with the flag ON |
+| `TKOffset.dll` | 1.75 MiB | only exists with the flag ON |
+| **delta** | **3.77 MiB** | Windows only (OCCT is Shared on Win, Static elsewhere) |
+
+`TKBool` is *not* part of the delta — upstream's `DataExchange` already pulls it in
+transitively. On macOS/Linux OCCT links statically, so the cost is only the code actually
+referenced, not a 3.77 MiB floor.
+
+**Unmeasured, and we should measure before the call:** clean-deps build-time delta with
+the flag ON vs OFF, and the resulting CI runner-minute cost. Do not guess these at him.
+
+## Licensing
+
+- Vendored solver `src/libslic3r/slvs/` — **GPL-3.0**, 9,339 LOC, © Jonathan Westhues,
+  a self-contained subset of SolveSpace (`libslvs`). No external dependencies.
+- OrcaSlicer — **AGPL-3.0** (`LICENSE.txt`).
+
+GPLv3 §13 expressly permits combining a GPLv3 work with an AGPLv3 work; AGPLv3 §13 grants
+the converse. The combined work is distributable under AGPL-3.0 with the solver's GPLv3
+terms preserved. This is a favourable direction (GPLv3 → into an AGPLv3 project), but it
+is a point to **confirm explicitly with upstream**, not to assert unilaterally.
+
+Open question for SoftFever: keep the solver **vendored** (current: pinned, no submodule,
+no external build) or move it to `deps/` as a fetched external? Vendoring costs us
+upstream-sync burden; `deps/` costs build complexity.
+
+## The one irreversible decision: the 3MF format
+
+Persistence adds an **optional** archive entry and one field:
+
+```cpp
+// Model.hpp
+std::string cad_recipe;   // empty for non-CAD projects
+```
+
+```
+Metadata/orca_cad.bin   // written only when cad_recipe is non-empty
+```
+
+Readers that do not know the entry ignore it; writers skip it entirely when empty. So
+existing projects are bit-identical and old readers are unaffected. Good.
+
+**But the moment upstream ships this, it owns forward-compatibility forever.** Three
+things should be settled *before* the first release, because none can be changed after:
+
+1. **Name.** Renamed to `Metadata/orca_cad.bin`.
+2. **Encoding.** The recipe is an opaque **cereal `PortableBinaryArchive`** blob whose
+   layout is the field order of `CadFeature::serialize`. Portable across endianness and
+   word size — *not* across a field reorder. Append-only is currently a convention held by
+   discipline, not by any check.
+3. **Embedded BRep.** `Import` features embed OCCT's ASCII BRep for the imported solid,
+   which couples saved project files to an OCCT BRep revision. Alternative: re-import from
+   the source STEP and store only a reference. Worth deciding deliberately.
+
+**Concrete gap we should close before the call.** `test_caddocument.cpp` covers the
+in-memory round-trip and correctly refuses a version-999 blob — but there is **no
+checked-in v1 fixture on disk**. A reordered field in `CadFeature::serialize` would pass
+the entire suite while silently breaking every previously-saved project. Ship a golden
+`.bin` fixture generated today plus a test that loads it; that is the only thing that will
+hold the format still once real users have files.
+
+## Proposed PR decomposition
+
+35 kLOC in one PR is not reviewable. Behind the flag, slices 1–4 are behaviour-neutral for
+existing users:
+
+1. **Build gate + OCCT flag + Windows packaging guard.** `-DSLIC3R_CAD=ON/OFF`, default
+   **OFF**. Flips `ModelingAlgorithms=ON`. Includes the guard that asserts every linked
+   OCCT toolkit has a shipped DLL (already on both forks: `546cef5f42`). ← *this is what
+   makes SoftFever's "parallel build" a one-line CI matrix entry.*
+2. **Vendored `slvs` solver** + its Catch2 tests. No GUI, no OCCT.
+3. **CAD kernel** (`CadDocument`, `SketchEngine`, `GeometryEngine`, `Sketch*`) + kernel
+   tests. Headless, no GUI.
+4. **3MF recipe persistence** + golden-fixture regression test.
+5. **GUI Design tab** (`DesignPanel`, `DesignCanvas`, `DesignSketchTool`, `GLGizmoSketch`)
+   + the 23 upstream hooks.
+
+## Agenda for the call
+
+Questions only SoftFever can answer:
+
+- Does OrcaSlicer *want* to be a CAD-integrated slicer? (Strategic; everything else is mechanical.)
+- Default of `SLIC3R_CAD` at merge time, and when it flips ON.
+- Vendored solver vs `deps/` external; and confirmation of the GPLv3/AGPLv3 combination.
+- Project-file format: neutral name, encoding, embedded-BRep policy, and who owns v1 forward-compat.
+- Undo/redo: the Design tab has its own stack; integrate with Orca's snapshot system or keep separate?
+- Does he want the i18n work (Romanian, +23 kLOC) as a wholly separate PR? (Yes, almost certainly.)
+
+## Verdict
+
+Portability **high**. The prior "does upstream want OCCT" framing was wrong — OCCT is
+already there. What remains is a 3.77 MiB dependency widening, a compile-time gate that
+the existing null-guards make cheap, and one file-format decision that must be made before
+the first release rather than after.
+
+---
+*Revised 2026-07-10 from direct measurement of `cad-mainline` @ `546cef5f42` vs upstream
+merge-base `449a4cf9fc`. Supersedes the 2026-06-21 read-only assessment.*
diff --git a/docs/CAD/rig_build_traps.md b/docs/CAD/rig_build_traps.md
new file mode 100644
index 0000000000..b620b244d9
--- /dev/null
+++ b/docs/CAD/rig_build_traps.md
@@ -0,0 +1,151 @@
+# Rig build traps
+
+The build rig is two long-lived containers, `snapmaker-gui` and `orcacad-gui`, one per fork. Each
+mounts only its fork's build volume (`snapmaker_buildcache` / `orcacad_buildcache`) at
+`/OrcaSlicer/build`, its fork's `resources/`, and a shots directory — nothing else. They run the
+binary; they do not build it. Rebuild with `scripts/CAD/build-gui.sh`.
+
+| fork repo | project() | deps image | build volume | GUI container | binary |
+|---|---|---|---|---|---|
+| `Snapmaker` | `Snapmaker_Orca` | `snapmaker-deps` | `snapmaker_buildcache` | `snapmaker-gui` | `snapmaker-orca` |
+| `orca_cad` | `OrcaSlicer` | `orcacad-deps` | `orcacad_buildcache` | `orcacad-gui` | `orca-slicer` |
+
+`scripts/CAD/build-gui.sh` exists alongside `scripts/CAD/build-gui-incremental.sh` for one reason: it does a
+target-only `ninja` into the volume the GUI rig launches from, so a session can test a single
+change without a full repackage, whereas `build-gui-incremental.sh` runs the full packaged build.
+Both start a throwaway container from the deps image with the live repo mounted over the baked
+tree — never build inside the GUI container (Trap 1).
+
+Every trap below has already cost about a session to re-derive, once each. They are recorded now
+so no fresh session pays them again. Symptoms, causes, and exact recovery commands follow.
+
+---
+
+## Trap 1 — never configure inside the GUI container
+
+**Symptom.** After building inside the GUI container, the fork's targets no longer exist; ninja
+reports an unknown target, and `orca-slicer` / `OrcaSlicer` have been replaced by
+`snapmaker-orca` / `Snapmaker_Orca`.
+
+**Cause.** The GUI image's baked `/OrcaSlicer` tree is the Jun-13 Snapmaker-derived source
+(`project(Snapmaker_Orca)`, executable `snapmaker-orca`). `orcacad-deps` is layered on
+`snapmaker-deps`, so even on the mainline fork the baked tree is the other fork's. A `cmake .`
+there reconfigures the shared build dir under the wrong project name.
+
+**Fix.** Build only via `scripts/CAD/build-gui.sh`, which starts a throwaway container from the deps
+image with the live repo mounted over the baked tree — `src`, `resources`, `cmake`, `deps_src`,
+`localization`, `CMakeLists.txt`, `version.inc` — and writes into the same volume the rig
+launches from.
+
+---
+
+## Trap 2 — stale `NLopt_DIR` in CMakeCache
+
+**Symptom.** Configure fails with `Cannot find NLopt library 'nlopt_cxx' in '<prefix>/lib'`.
+
+**Cause.** `cmake/modules/FindNLopt.cmake:26` is `set(NLopt_DIR $ENV{NLOPT})`. With `NLOPT`
+unset that expands to `set(NLopt_DIR)` — zero arguments — which *unsets the normal variable* and
+lets a leftover CACHE entry of the same name (e.g. `<prefix>/lib/cmake/nlopt`) show through the
+following `if(NOT NLopt_DIR)`. The `else()` branch then searches for `nlopt_cxx` under
+`${NLopt_DIR}/lib` with `NO_DEFAULT_PATH`, while the deps prefix ships plain `nlopt`.
+
+**Fix.** From inside the build dir:
+
+    cmake -U NLopt_DIR -U NLopt_LIBS .
+
+Do **not** `sed` the entry out of `CMakeCache.txt` — deleting a line breaks the cache parser.
+
+---
+
+## Trap 3 — the image lacks `deps_src/pybind11`
+
+**Symptom.** Configure aborts with `pybind11 headers not found in /OrcaSlicer/deps_src/pybind11.
+Did you initialize submodules?` (the `FATAL_ERROR` guarding `PYBIND11_SOURCE_DIR` in the mainline
+fork's root `CMakeLists.txt`, near line 948).
+
+**Cause.** The deps image predates that requirement. Only the mainline (`orca_cad`) fork has
+`deps_src/pybind11` and the requirement; Snapmaker has neither.
+
+**Fix.** Mount `deps_src` over the baked tree — `scripts/CAD/build-gui.sh` does. Corollary: mounting a
+Snapmaker tree into an `orcacad-deps` build reproduces this error exactly.
+
+---
+
+## Trap 4 — `OCCT_LIBS` lags one configure
+
+**Symptom.** A wall of undefined references to `TopOpeBRepBuild` symbols. It reads as a broken
+OCCT installation. It is not.
+
+**Cause.** `src/libslic3r/CMakeLists.txt:603` does
+`set(OCCT_LIBS "${OCCT_LIBS}" CACHE INTERNAL "OCCT toolkits linked by libslic3r")` at the END of
+its own configure, while the consumer in the root `CMakeLists.txt` (`if (NOT OCCT_LIBS)` …
+`foreach (_tk IN LISTS OCCT_LIBS)`) reads whatever is already in the cache. The first reconfigure
+after the `TKFillet TKOffset` prepend (`src/libslic3r/CMakeLists.txt:599`) therefore links the
+previous list and drops `TKBool`/`TKOffset`.
+
+**Fix.** Configure twice. `scripts/CAD/build-gui.sh` runs `cmake .` twice for exactly this reason; if
+you ever configure by hand, run it twice.
+
+---
+
+## Trap 5 — `SLIC3R_CAD=ON` in the cache, macro never defined
+
+**Symptom.** The build succeeds and links, but the Design tab is simply absent — or it fails with
+`class GLCanvas3D has no member named set_design_sketch_tool`.
+
+**Cause.** The cache carries `SLIC3R_CAD=ON`, but the root `CMakeLists.txt` actually configured is
+a stale baked copy that predates the gate and never runs `add_definitions(-DSLIC3R_CAD)` (the
+gate is `if (SLIC3R_CAD)` / `add_definitions(-DSLIC3R_CAD)` in the root list — line 179/180 in
+Snapmaker, 319/320 in orca_cad). Every `#ifdef SLIC3R_CAD` block therefore compiles out while the
+option still reads ON.
+
+**Fix.** Always mount the live `CMakeLists.txt` and `cmake/` — never inherit them from the image.
+This is why `scripts/CAD/build-gui-incremental.sh`, `scripts/CAD/run-kernel-tests.sh` and `scripts/CAD/build-gui.sh`
+all mount both.
+
+---
+
+## The binary the rig actually launches
+
+`ninja <target>` writes `/OrcaSlicer/build/src/Release/<binary>`; only `build_linux.sh`
+additionally packages to `/OrcaSlicer/build/package/bin/<binary>`. `orca_cad`'s
+`scripts/CAD/start-headless-gui.sh` defaults `BIN` to `src/Release/orca-slicer`, but Snapmaker's defaults to
+`package/bin/snapmaker-orca`. So after a target-only rebuild on Snapmaker, launching
+`start-headless-gui.sh` with its default runs the **stale packaged** binary — the change under test is
+invisible and the session hunts a phantom. Pass `BIN` explicitly:
+
+    docker exec -e BIN=/OrcaSlicer/build/src/Release/snapmaker-orca snapmaker-gui /OrcaSlicer/scripts/CAD/start-headless-gui.sh
+
+`scripts/CAD/build-gui.sh` prints the correct line for the current fork when it finishes.
+
+Note also that the GUI containers do **not** mount `scripts/`: `/OrcaSlicer/scripts` inside them
+is the baked copy, so a local edit to `start-headless-gui.sh` has no effect until you
+`docker cp scripts/CAD/start-headless-gui.sh <container>:/OrcaSlicer/scripts/`.
+
+---
+
+## Trap 6 — `src/Release/` resolves resources to `build/resources`, which may not exist
+
+The binary derives `resources_dir()` from its own location, so the `src/Release/` one looks in
+`/OrcaSlicer/build/resources` while the packaged one looks inside `build/package/`. Only the
+packaging step creates the latter; nothing creates the former. Without it the app fails every
+`Failed to add custom font ".../build/resources/fonts/…"`, logs `Health check is not running`,
+and **exits 255 with nothing on stdout** — which reads exactly like a crash in whatever you just
+changed. Measured 2026-08-02: an hour was nearly spent bisecting a GUI change that was fine.
+
+`build/` is the shared cache volume, so one symlink fixes it permanently, and pointing it at the
+bind-mounted repo tree means the rig also picks up new `resources/images/*.svg` without a rebuild:
+
+    docker exec <fork>-gui ln -sfn /OrcaSlicer/resources /OrcaSlicer/build/resources
+
+Tell the two apart before debugging: a resource failure dies in the first second with no window;
+a real fault in your code gets past the version banner. Compare
+`~/.config/<App>/log/<newest>.log.0` against a known-good run — 47 lines versus 340 is the tell.
+
+## Trap 7 — a single-instance app plus a path-matched `pkill`
+
+`start-headless-gui.sh` used to kill by `"$BIN"`, while its own `app_pid()` matched by BASENAME. Launch
+with a `BIN` that differs from the running instance's path and the old process survives, keeps
+the single-instance lock, and the new one exits seconds after loading fonts — then `status`
+reports the *stale* pid as a healthy session. Fixed by killing on the basename; `status` now also
+prints `binary : $(readlink -f /proc/<pid>/exe)`. **Read that line before trusting a screenshot.**
diff --git a/docs/CAD/ux/interaction-model.md b/docs/CAD/ux/interaction-model.md
new file mode 100644
index 0000000000..2041978ea0
--- /dev/null
+++ b/docs/CAD/ux/interaction-model.md
@@ -0,0 +1,144 @@
+# Design tab — interaction model
+
+The contract for Esc, the right mouse button, and the states between them. Code that changes any
+of the three changes this file in the same commit.
+
+## 1. The state machine
+
+`src/slic3r/GUI/CAD/DesignInteraction.hpp` — a four-level LIFO stack. The enum value *is* the
+depth, so "which level does this press belong to" is a comparison rather than a chain of
+special cases spread over three files.
+
+```cpp
+enum class CadLevel : int {
+    Idle      = 0,   // nothing transient is up: Esc clears the selection
+    Tool      = 1,   // a feature card / armed sketch tool / constrain session: Esc exits it
+    Gesture   = 2,   // an uncommitted delta (entity being drawn, body being dragged): Esc reverts it
+    Transient = 3,   // a value field or a popup menu: Esc closes just that
+};
+
+struct CadInteractionState {          // the four bits routing actually needs
+    bool value_field_open{false};
+    bool gesture_active{false};
+    bool tool_armed{false};
+    bool has_selection{false};
+};
+
+constexpr CadLevel cad_escape_level(const CadInteractionState& s)
+{
+    if (s.value_field_open) return CadLevel::Transient;
+    if (s.gesture_active)   return CadLevel::Gesture;
+    if (s.tool_armed)       return CadLevel::Tool;
+    return CadLevel::Idle;
+}
+```
+
+The rule is a `constexpr` free function over a POD, not a method on the panel, so the ordering
+that is the entire contract is checkable without a window, a GL context or an event loop. Five
+`static_assert`s in the header do exactly that, at compile time.
+
+**Strict invariant.** No level of Esc deletes a feature, discards a sketch that holds geometry,
+or rolls history back. Destroying work needs a gesture that says so:
+
+| To destroy | Gesture |
+|---|---|
+| a feature | Delete / Backspace on an explicit selection |
+| a drawn sketch | the ribbon's ✗ Cancel, which asks first |
+| the last committed change | Ctrl+Z |
+
+## 2. Event routing
+
+**`OnKeyDown(WXK_ESCAPE)`** — `DesignPanel`'s `wxEVT_CHAR_HOOK`, one line:
+
+```cpp
+if (key == WXK_ESCAPE) { escape(); return; }
+```
+
+Every Esc in the tab goes through it, whatever holds focus. `DesignPanel::escape_level()` answers
+the four questions of `CadInteractionState` about this panel; `DesignPanel::escape()` acts on the
+one level that answer names, and on no other:
+
+| Level | What one press does | What it must not touch |
+|---|---|---|
+| `Transient` | close the value field (`cancel_value` / `inline_cancel`) | the tool, which stays armed |
+| `Gesture` | drop the clicks of the entity being drawn, or put a moved body back at the pose it had when the gizmo appeared | everything already committed |
+| `Tool` | discard a feature card's *candidate*; drop an armed sketch tool to Select; end Constrain | committed features; entities already drawn |
+| `Idle` | clear the selection (model and sketch); leave a sketch session **only if it is empty** | a sketch holding geometry — it is left through Finish or Cancel |
+
+A sketch *session* is deliberately not a `Tool`. It is the environment the Idle level lives in,
+which is what makes the destructive path unrepresentable rather than merely unlikely.
+
+**`OnRightDown` / `OnRightUp`** — `DesignCanvas::set_on_context_menu`, bound after `GLCanvas3D`'s
+own handlers so it can consume the event before them:
+
+```cpp
+RIGHT_DOWN: remember the press position and the clock, then Skip()   // the canvas still seeds the orbit
+
+RIGHT_UP:   terminated = sketch_tool.take_right_consumed();          // read-and-clear, always
+            is_click   = drift <= 3 px && dt <= 200 ms;              // both budgets, or it was navigation
+            if (callback && !terminated && !inline_busy && is_click) {
+                select_at_screen(press.x, press.y);                  // raycast at the PRESS, not the release
+                on_context_menu(ClientToScreen(press));
+                return;                                              // consumed
+            }
+            Skip();                                                  // orbit / pan / the handlers underneath
+```
+
+Two independent budgets because the two failure modes are independent: drift alone still popped a
+menu at the end of a slow, careful orbit. `take_right_consumed()` is how a right-click that
+already meant something to the armed sketch tool (terminate a chain, drop an edit-op) declines to
+also mean "open a menu".
+
+## 3. Transition table
+
+`sel` = something is picked. Blank = the input does nothing at that state.
+
+| State | Left-click | Right-click | Esc | Enter |
+|---|---|---|---|---|
+| **Idle — model view** | pick / escalate the pick | offer menu for what is under the cursor | clear the selection | — |
+| **Idle — sketch, empty** | pick | sketch offer menu | leave the session (nothing to lose) | Finish sketch |
+| **Idle — sketch, drawn** | pick | sketch offer menu | clear the selection; status says the sketch is kept | Finish sketch |
+| **Tool — feature card** | pick the card's next reference | offer menu | discard the candidate, close the card | commit the feature |
+| **Tool — sketch tool armed** | place the first point | drop the tool to Select | drop the tool to Select | — |
+| **Tool — constrain** | pick an entity | offer menu | end the session | apply |
+| **Gesture — drawing** | place the next point | terminate the chain (keep what is drawn) | drop the in-progress entity, tool stays armed | commit the entity as drawn |
+| **Gesture — moving a body** | drop the body here | end the move | revert to the pose at move-start | keep the placement |
+| **Transient — value field** | — | — | close the field, tool stays armed | commit the value, advance the chain |
+| **Transient — popup menu** | run the entry | — | close the menu | run the highlighted entry |
+| **any** | — | — | *never* deletes, discards or rolls back | — |
+
+Right-hold-and-drag is not in the table on purpose: past 3 px or 200 ms it is navigation, and
+navigation does not transition the state machine.
+
+## 4. Visual scaffolding
+
+Entering a sketch changes three things at once, so the state is legible from across the room:
+
+- **Banner.** A teal strip across the top of the viewport: `Editing: Sketch N · N = look normal to
+  the plane · Finish or Cancel in the toolbar`. Indicator only — Confirm and Cancel stay on the one
+  ribbon action bar, per the Design UX contract. It is a sibling above the canvas, not a floating
+  child over it: a child window over a `wxGLCanvas` is a native window on GTK and does not reliably
+  stack over GL, and this banner's job is to be unmissable rather than clever.
+- **The printer bed is muted.** A plate grid and a sketch grid are the same visual language, and
+  reading one as the other is how a sketch gets drawn against the wrong reference. The view
+  checkbox remains the stored preference and is restored on the way out; ticking it mid-sketch
+  still shows the bed, because that is a deliberate act and this is only a default.
+- **`N` looks normal to the plane**, keeping the current zoom, with the plane's own y axis as up.
+  Sketch key map only — in Feature mode the navigator orb owns orientation.
+
+## 5. Context menu content
+
+The offer is generated from `docs/CAD/ux/tool_atlas.json`; its 8-row shape and permanent row
+indices are ratified and are not changed here. Checked against the per-context vocabularies asked
+for in the 2026-09-05 interaction brief, the atlas already carries all of them except two, both on
+a planar face:
+
+| Asked for | Status |
+|---|---|
+| Revolve on a planar face | **not offered, and should not be**: `revolve` accepts `sk_loop` only, because the kernel takes a sketch profile — a face is not one |
+| Offset Face | offered as **Thicken** (`thicken`, accepts `face_planar`); `surf_offset` is the sheet-body verb and accepts `body_sheet` |
+
+View and document actions — Zoom to Fit, View Isometric, Clear Selection, Finish Sketch, Normal to
+Sketch — stay in chrome by the atlas's own rule: the offer describes verbs that consume a
+*selection*, and these act on the document or the camera. Esc covers Clear Selection, `N` covers
+Normal to Sketch, and the ribbon covers Finish.
diff --git a/docs/CAD/ux/mockups/cmp_12__edge_str.svg b/docs/CAD/ux/mockups/cmp_12__edge_str.svg
new file mode 100644
index 0000000000..3e641e90ec
--- /dev/null
+++ b/docs/CAD/ux/mockups/cmp_12__edge_str.svg
@@ -0,0 +1 @@
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diff --git a/docs/CAD/ux/mockups/cmp_8__face_planar.svg b/docs/CAD/ux/mockups/cmp_8__face_planar.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/fresh__art__modify.svg b/docs/CAD/ux/mockups/fresh__art__modify.svg
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diff --git a/docs/CAD/ux/mockups/fresh__edge_str__reference.svg b/docs/CAD/ux/mockups/fresh__edge_str__reference.svg
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diff --git a/docs/CAD/ux/mockups/fresh__face_cyl__reference.svg b/docs/CAD/ux/mockups/fresh__face_cyl__reference.svg
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diff --git a/docs/CAD/ux/mockups/fresh__face_planar.svg b/docs/CAD/ux/mockups/fresh__face_planar.svg
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diff --git a/docs/CAD/ux/mockups/fresh__face_planar__reference.svg b/docs/CAD/ux/mockups/fresh__face_planar__reference.svg
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diff --git a/docs/CAD/ux/mockups/fresh__none.svg b/docs/CAD/ux/mockups/fresh__none.svg
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diff --git a/docs/CAD/ux/mockups/fresh__sk_arc.svg b/docs/CAD/ux/mockups/fresh__sk_arc.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/fresh__sk_arc__modify.svg b/docs/CAD/ux/mockups/fresh__sk_arc__modify.svg
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diff --git a/docs/CAD/ux/mockups/fresh__sk_arc__reference.svg b/docs/CAD/ux/mockups/fresh__sk_arc__reference.svg
new file mode 100644
index 0000000000..cfbe0a1042
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diff --git a/docs/CAD/ux/mockups/fresh__sk_line__modify.svg b/docs/CAD/ux/mockups/fresh__sk_line__modify.svg
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diff --git a/docs/CAD/ux/mockups/fresh__sk_line__reference.svg b/docs/CAD/ux/mockups/fresh__sk_line__reference.svg
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diff --git a/docs/CAD/ux/mockups/fresh__sk_loop.svg b/docs/CAD/ux/mockups/fresh__sk_loop.svg
new file mode 100644
index 0000000000..58eaa9e4fb
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diff --git a/docs/CAD/ux/mockups/fresh__sk_loop__add.svg b/docs/CAD/ux/mockups/fresh__sk_loop__add.svg
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diff --git a/docs/CAD/ux/mockups/fresh__sk_loop__modify.svg b/docs/CAD/ux/mockups/fresh__sk_loop__modify.svg
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diff --git a/docs/CAD/ux/mockups/fresh__sk_none__create.svg b/docs/CAD/ux/mockups/fresh__sk_none__create.svg
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diff --git a/docs/CAD/ux/mockups/fresh__sk_point.svg b/docs/CAD/ux/mockups/fresh__sk_point.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/fresh__sk_point__create.svg b/docs/CAD/ux/mockups/fresh__sk_point__create.svg
new file mode 100644
index 0000000000..fbe094d147
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stroke-linecap="round" stroke-linejoin="round"><rect x="-10" y="-4" width="20" height="8" rx="1" fill="none"/><path d="M-5 -4 L-5 0 M0 -4 L0 1 M5 -4 L5 0"/></g><rect x="0" y="92" width="248" height="646" fill="#20242a"/><line x1="248" y1="92" x2="248" y2="738" stroke="#31363d"/><text x="18" y="122" font-family="Inter,DejaVu Sans,sans-serif" font-size="11" letter-spacing="1.4" fill="#5f6a76">FEATURES</text><text x="18" y="152" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" font-style="italic" fill="#5f6a76">nothing yet</text><rect y="738" width="1366" height="30" fill="#23272d"/><text x="18" y="758" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Reference — pick one</text><text x="1348" y="758" text-anchor="end" font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" fill="#5f6a76">Fresh document · 8 slots</text><polygon points="629.1,360.5 759.0,435.5 759.0,487.5 629.1,412.5" fill="#6f7b89" stroke="#39414b" stroke-width="1"/><polygon 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transform="translate(664.2,338.7) scale(0.920)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M-10 7 L10 -7"/><circle cx="-10" cy="7" r="2"/><circle cx="10" cy="-7" r="2"/></g><text x="664.2" y="388.7" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" font-weight="500" fill="#e7ecf1">Axis</text><rect x="634.6" y="395.7" width="59.2" height="17" rx="4.5" fill="#454f5b"/><text x="664.2" y="407.7" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="10.5" fill="#e7ecf1">Shift+A</text><rect x="690.4" y="467.5" width="137.2" height="22" rx="11" fill="#171a1e" opacity="0.92" stroke="#3c444e"/><text x="759.0" y="482.5" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="12" fill="#e7ecf1">Vertex · Reference</text></svg>
\ No newline at end of file
diff --git a/docs/CAD/ux/mockups/gen_offer_mockups.py b/docs/CAD/ux/mockups/gen_offer_mockups.py
new file mode 100644
index 0000000000..6ddd4caae4
--- /dev/null
+++ b/docs/CAD/ux/mockups/gen_offer_mockups.py
@@ -0,0 +1,884 @@
+#!/usr/bin/env python3
+"""Render the object-driven tool offer from docs/ux/tool_atlas.json.
+
+Fork-neutral on purpose: this file and everything it emits name no product, so the
+two forks carry byte-identical copies (the charter itself is the only doc that
+substitutes the product name).
+
+Every mockup in docs/ux/mockups/ and the review page docs/ux/offer_atlas.html are
+generated by this script. Nothing is hand-drawn: the point of the offer is that a
+tool's address never changes, and a human drawing 40-odd states by hand is exactly
+how an address quietly changes.
+
+    python3 docs/ux/mockups/gen_offer_mockups.py
+
+It fails loudly rather than rendering a broken map: an unknown slot, an unknown
+selection id in `accepts`, or one address holding two different verbs for the same
+selection is an error, not a warning.
+
+SVG on purpose. There is no rsvg/inkscape/cairosvg on the build box and
+ImageMagick would rasterise through its own weak internal renderer; SVG renders
+exactly in a browser at any zoom and stays diffable in git. Rasterise later if
+slides need it.
+"""
+
+import json
+import re
+import math
+import os
+import sys
+from collections import defaultdict
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+UX = os.path.dirname(HERE)
+ATLAS = os.path.join(UX, "tool_atlas.json")
+
+# The reach target from the charter (L11 / 6.1): if the ring plus a real part do not
+# fit here, the design has failed before it is built.
+W, H = 1366, 768
+
+C = {
+    "app": "#1a1d21", "chrome": "#23272d", "panel": "#20242a", "line": "#31363d",
+    "vp0": "#2f353d", "vp1": "#242930", "grid": "#333a43",
+    "text": "#e7ecf1", "muted": "#8e9aa7", "dim": "#5f6a76",
+    "top": "#93a1b1", "left": "#6f7b89", "right": "#5a6472", "edge": "#39414b",
+    "hi": "#f5a623", "hi_soft": "#f5a62333", "sheet": "#7fa8c9",
+    "ring": "#171a1e", "chip": "#2e343c", "chip_line": "#3c444e",
+    "key": "#454f5b", "accent": "#4f9bd9", "empty": "#2a2f36",
+}
+
+
+# ---------------------------------------------------------------- glyphs
+# Each glyph draws inside a 24x24 box centred on (0,0) — i.e. -12..12.
+def _g(body):
+    return body
+
+
+GLYPHS = {
+    # model
+    "sketch":    '<path d="M-8 8 L-5 7 L7 -5 L5 -7 L-7 5 Z"/><path d="M-8 8 L-6.5 6.5"/>',
+    "extrude":   '<rect x="-8" y="2" width="16" height="6" rx="1"/><path d="M0 0 L0 -8 M-4 -4 L0 -8 L4 -4"/>',
+    "revolve":   '<path d="M-7 6 A9 9 0 1 1 7 6" fill="none"/><path d="M7 6 L7 1 M7 6 L2.5 6"/><path d="M0 8 L0 -9" stroke-dasharray="3 2"/>',
+    "sweep":     '<ellipse cx="-6" cy="0" rx="3" ry="6" fill="none"/><path d="M-6 -6 C2 -8 6 0 8 6" fill="none"/>',
+    "loft":      '<ellipse cx="-6" cy="2" rx="3.5" ry="6" fill="none"/><ellipse cx="6" cy="-2" rx="2" ry="4" fill="none"/><path d="M-6 -4 L6 -6 M-6 8 L6 2" fill="none"/>',
+    "thicken":   '<path d="M-9 3 L0 -2 L9 3" fill="none"/><path d="M-9 7 L0 2 L9 7" fill="none"/><path d="M-9 3 L-9 7 M9 3 L9 7"/>',
+    "rib":       '<path d="M-9 7 L9 7" /><path d="M-2 7 L-2 -6 L2 -6 L2 7 Z" fill="none"/>',
+    "boolean":   '<circle cx="-4" cy="0" r="6" fill="none"/><circle cx="4" cy="0" r="6" fill="none"/>',
+    "hole":      '<rect x="-9" y="-6" width="18" height="12" rx="1" fill="none"/><circle cx="0" cy="0" r="3.2" fill="none"/><path d="M0 -5 L0 5 M-5 0 L5 0" stroke-dasharray="2 2"/>',
+    "thread":    '<path d="M-4 -8 L4 -6 M-4 -4 L4 -2 M-4 0 L4 2 M-4 4 L4 6" fill="none"/><path d="M-4 -9 L-4 8 M4 -7 L4 9"/>',
+    "shell":     '<rect x="-9" y="-7" width="18" height="14" rx="1" fill="none"/><rect x="-5.5" y="-3.5" width="11" height="10.5" rx="1" fill="none" stroke-dasharray="2 2"/>',
+    "cut":       '<rect x="-8" y="-6" width="16" height="12" rx="1" fill="none"/><path d="M-11 4 L11 -4"/>',
+    "split":     '<rect x="-8" y="-6" width="16" height="12" rx="1" fill="none"/><path d="M0 -9 L0 9" stroke-dasharray="3 2"/>',
+    "fillet":    '<path d="M-9 8 L-9 -1 A8 8 0 0 1 -1 -9 L8 -9" fill="none"/><path d="M-9 8 L8 8 L8 -9" fill="none" stroke-dasharray="2 3"/>',
+    "chamfer":   '<path d="M-9 8 L-9 -2 L-2 -9 L8 -9" fill="none"/><path d="M-9 8 L8 8 L8 -9" fill="none" stroke-dasharray="2 3"/>',
+    "draft":     '<path d="M-8 8 L-4 -8 L4 -8 L8 8 Z" fill="none"/><path d="M-4 -8 L-4 8" stroke-dasharray="2 2"/>',
+    "surf_off":  '<path d="M-9 2 C-3 -4 3 6 9 0" fill="none"/><path d="M-9 7 C-3 1 3 11 9 5" fill="none"/>',
+    "pattern":   '<rect x="-9" y="-9" width="7" height="7" rx="1"/><rect x="2" y="-9" width="7" height="7" rx="1" fill="none"/><rect x="-9" y="2" width="7" height="7" rx="1" fill="none"/><rect x="2" y="2" width="7" height="7" rx="1" fill="none"/>',
+    "mirror":    '<path d="M0 -10 L0 10" stroke-dasharray="3 2"/><path d="M-3 -6 L-9 0 L-3 6 Z"/><path d="M3 -6 L9 0 L3 6 Z" fill="none"/>',
+    "pat_curve": '<path d="M-10 6 C-4 -8 4 8 10 -6" fill="none"/><circle cx="-7" cy="0" r="2.4"/><circle cx="0" cy="0.5" r="2.4"/><circle cx="7" cy="0" r="2.4"/>',
+    "move":      '<path d="M0 -10 L0 10 M-10 0 L10 0"/><path d="M0 -10 L-3 -6 M0 -10 L3 -6 M0 10 L-3 6 M0 10 L3 6 M-10 0 L-6 -3 M-10 0 L-6 3 M10 0 L6 -3 M10 0 L6 3"/>',
+    "mate":      '<circle cx="-5" cy="0" r="4" fill="none"/><circle cx="5" cy="0" r="4" fill="none"/><path d="M-1 0 L1 0"/>',
+    "align":     '<path d="M-10 -8 L-10 8"/><rect x="-6" y="-6" width="7" height="5" rx="1" fill="none"/><rect x="-6" y="2" width="12" height="5" rx="1" fill="none"/>',
+    "plane":     '<path d="M-10 4 L-2 -6 L10 -4 L2 6 Z" fill="none"/>',
+    "axis":      '<path d="M-10 7 L10 -7"/><circle cx="-10" cy="7" r="2"/><circle cx="10" cy="-7" r="2"/>',
+    "csys":      '<path d="M-6 6 L-6 -8 M-6 6 L8 6 M-6 6 L-11 10"/><path d="M-6 -8 L-8 -5 M-6 -8 L-4 -5 M8 6 L5 4 M8 6 L5 8"/>',
+    "helix":     '<path d="M-5 -9 C5 -7 5 -3 -5 -1 C5 1 5 5 -5 7" fill="none"/><path d="M-5 9 L-5 -10" stroke-dasharray="2 2"/>',
+    "project":   '<path d="M-10 6 L-2 10 L10 6 L2 2 Z" fill="none"/><rect x="-5" y="-10" width="9" height="6" rx="1" fill="none"/><path d="M0 -3 L0 1 M-2.5 -1 L0 1.6 L2.5 -1"/>',
+    "measure":   '<rect x="-10" y="-4" width="20" height="8" rx="1" fill="none"/><path d="M-5 -4 L-5 0 M0 -4 L0 1 M5 -4 L5 0"/>',
+    "mass":      '<path d="M0 -9 L9 5 L-9 5 Z" fill="none"/><circle cx="0" cy="0" r="1.8"/>',
+    "interfere": '<circle cx="-4" cy="0" r="6" fill="none"/><circle cx="4" cy="0" r="6" fill="none"/><path d="M-1 -5 A6 6 0 0 0 -1 5 A6 6 0 0 0 -1 -5"/>',
+    "edit":      '<path d="M-9 9 L-6 8 L6 -4 L4 -6 L-8 6 Z"/><path d="M3 -7 L6 -10 L9 -7 L6 -4 Z" fill="none"/>',
+    "del_face":  '<path d="M-9 3 L0 -2 L9 3 L0 8 Z" fill="none" stroke-dasharray="2 2"/><path d="M-4 -9 L4 -9 M-3 -9 L-3 -4 L3 -4 L3 -9"/>',
+    "colour":    '<circle cx="0" cy="0" r="9" fill="none"/><path d="M0 -9 A9 9 0 0 1 0 9 Z"/>',
+    "delete":    '<path d="M-7 -5 L7 -5 M-5 -5 L-5 8 L5 8 L5 -5 M-2 -5 L-2 -8 L2 -8 L2 -5"/>',
+    # sketch primitives
+    "sk_line":   '<path d="M-9 7 L9 -7"/><circle cx="-9" cy="7" r="2"/><circle cx="9" cy="-7" r="2"/>',
+    "sk_rect":   '<rect x="-9" y="-6" width="18" height="12" rx="0.5" fill="none"/><circle cx="-9" cy="-6" r="2"/><circle cx="9" cy="6" r="2"/>',
+    "sk_circle": '<circle cx="0" cy="0" r="8" fill="none"/><circle cx="0" cy="0" r="1.6"/>',
+    "sk_arc":    '<path d="M-8 5 A9 9 0 0 1 8 5" fill="none"/><circle cx="-8" cy="5" r="2"/><circle cx="8" cy="5" r="2"/>',
+    "sk_slot":   '<path d="M-4 -5 A5 5 0 0 0 -4 5 L4 5 A5 5 0 0 0 4 -5 Z" fill="none"/><path d="M-4 0 L4 0" stroke-dasharray="2 2"/>',
+    "sk_ell":    '<ellipse cx="0" cy="0" rx="9" ry="5.5" fill="none"/>',
+    "sk_spline": '<path d="M-10 5 C-5 -10 5 10 10 -5" fill="none"/><circle cx="-10" cy="5" r="1.8"/><circle cx="10" cy="-5" r="1.8"/>',
+    "sk_poly":   '<path d="M0 -9 L8 -3 L5 7 L-5 7 L-8 -3 Z" fill="none"/>',
+    "sk_point":  '<circle cx="0" cy="0" r="3"/><path d="M-9 0 L-5 0 M5 0 L9 0 M0 -9 L0 -5 M0 5 L0 9"/>',
+    "sk_offset": '<path d="M-9 3 L-3 -6 L9 -4" fill="none"/><path d="M-9 8 L-2 -1 L9 1" fill="none" stroke-dasharray="2 2"/>',
+    "sk_trim":   '<circle cx="-6" cy="6" r="2.6" fill="none"/><circle cx="-6" cy="-6" r="2.6" fill="none"/><path d="M-4 4 L8 -6 M-4 -4 L8 6"/>',
+    "sk_ext":    '<path d="M-10 0 L2 0" /><path d="M4 0 L10 0" stroke-dasharray="2 2"/><path d="M6 -3 L10 0 L6 3" fill="none"/>',
+    "sk_mir":    '<path d="M0 -10 L0 10" stroke-dasharray="3 2"/><path d="M-3 -6 L-9 0 L-3 6 Z"/><path d="M3 -6 L9 0 L3 6 Z" fill="none"/>',
+    "sk_move":   '<path d="M0 -10 L0 10 M-10 0 L10 0"/><path d="M0 -10 L-3 -6 M0 -10 L3 -6 M0 10 L-3 6 M0 10 L3 6 M-10 0 L-6 -3 M-10 0 L-6 3 M10 0 L6 -3 M10 0 L6 3"/>',
+    "sk_dim":    '<path d="M-9 -6 L-9 6 M9 -6 L9 6 M-9 0 L9 0"/><path d="M-9 0 L-5 -3 M-9 0 L-5 3 M9 0 L5 -3 M9 0 L5 3"/>',
+    "sk_lock":   '<rect x="-6" y="-1" width="12" height="9" rx="1.5" fill="none"/><path d="M-3.5 -1 L-3.5 -5 A3.5 3.5 0 0 1 3.5 -5 L3.5 -1" fill="none"/>',
+    "sk_constr": '<path d="M-10 4 L10 -4" stroke-dasharray="4 3"/>',
+    # families (used when a slot holds more than one verb)
+    "fam_create":  '<path d="M-8 8 L-5 7 L7 -5 L5 -7 L-7 5 Z"/>',
+    "fam_add":     '<rect x="-8" y="2" width="16" height="6" rx="1"/><path d="M0 0 L0 -8 M-4 -4 L0 -8 L4 -4"/>',
+    "fam_remove":  '<rect x="-9" y="-6" width="18" height="12" rx="1" fill="none"/><circle cx="0" cy="0" r="3.2" fill="none"/>',
+    "fam_dressup": '<path d="M-9 8 L-9 -1 A8 8 0 0 1 -1 -9 L8 -9" fill="none"/>',
+    "fam_repeat":  '<rect x="-9" y="-9" width="7" height="7" rx="1"/><rect x="2" y="-9" width="7" height="7" rx="1" fill="none"/><rect x="-9" y="2" width="7" height="7" rx="1" fill="none"/><rect x="2" y="2" width="7" height="7" rx="1" fill="none"/>',
+    "fam_transform": '<path d="M0 -10 L0 10 M-10 0 L10 0"/><path d="M0 -10 L-3 -6 M0 -10 L3 -6 M-10 0 L-6 -3 M-10 0 L-6 3"/>',
+    "fam_reference": '<path d="M-10 4 L-2 -6 L10 -4 L2 6 Z" fill="none"/>',
+    # Deliberately NOT the bare pencil: create/sketch already owns that shape and the two slots
+    # are adjacent (N and NW). A pencil over a solid reads as "change the thing that exists".
+    "fam_modify":  '<rect x="-10" y="-2" width="13" height="11" rx="1" fill="none"/>'
+                   '<path d="M-2 5 L0 4.5 L9 -5 L7 -7 L-2.5 2.5 Z"/>',
+}
+
+VERB_GLYPH = {
+    "sketch": "sketch", "extrude": "extrude", "revolve": "revolve", "sweep": "sweep",
+    "loft": "loft", "thicken": "thicken", "rib": "rib", "boolean": "boolean",
+    "surf_extrude": "extrude", "surf_revolve": "revolve", "surf_loft": "loft",
+    "surf_fill": "surf_off", "thicken_surf": "thicken", "hole": "hole", "thread": "thread",
+    "shell": "shell", "cut": "cut", "split": "split", "fillet": "fillet",
+    "chamfer": "chamfer", "draft": "draft", "surf_offset": "surf_off",
+    "pattern": "pattern", "mirror": "mirror", "pat_curve": "pat_curve",
+    "transform": "move", "mate": "mate", "align": "align", "plane": "plane",
+    "axis": "axis", "coordsys_v": "csys", "helix": "helix", "project": "project",
+    "measure": "measure", "mass_props": "mass", "interference": "interfere",
+    "edit_feature": "edit", "delete_face": "del_face", "colour": "colour", "delete": "delete",
+    "sk_line_t": "sk_line", "sk_rect": "sk_rect", "sk_circle": "sk_circle",
+    "sk_arc_t": "sk_arc", "sk_slot": "sk_slot", "sk_ellipse": "sk_ell",
+    "sk_spline": "sk_spline", "sk_polygon": "sk_poly", "sk_point_t": "sk_point",
+    "sk_offset": "sk_offset", "sk_trim": "sk_trim", "sk_fillet": "fillet",
+    "sk_chamfer": "chamfer", "sk_mirror": "sk_mir", "sk_move": "sk_move",
+    "sk_dimension": "sk_dim", "sk_constrain": "sk_lock", "sk_construct": "sk_constr",
+    "sk_extend": "sk_ext", "sk_delete": "delete",
+}
+
+
+def glyph(name, cx, cy, colour, scale=1.0, sw=1.6):
+    body = GLYPHS.get(name, '<circle cx="0" cy="0" r="7" fill="none"/>')
+    return (f'<g transform="translate({cx:.1f},{cy:.1f}) scale({scale:.3f})" '
+            f'stroke="{colour}" fill="{colour}" stroke-width="{sw:.2f}" '
+            f'stroke-linecap="round" stroke-linejoin="round">{body}</g>')
+
+
+# ---------------------------------------------------------------- iso scene
+COS30, SIN30 = math.cos(math.radians(30)), math.sin(math.radians(30))
+
+
+def iso(x, y, z, ox, oy, s=1.0):
+    return (ox + (x - y) * COS30 * s, oy + (x + y) * SIN30 * s - z * s)
+
+
+def poly(pts, fill, stroke=None, extra=""):
+    d = " ".join(f"{x:.1f},{y:.1f}" for x, y in pts)
+    # Only emit our own stroke-width when the caller has not supplied one: a duplicate
+    # attribute is last-one-wins in a browser but invalid markup, and it is exactly the
+    # kind of thing a stricter renderer refuses outright.
+    if stroke:
+        st = f' stroke="{stroke}"' + ("" if "stroke-width" in extra else ' stroke-width="1"')
+    else:
+        st = ' stroke="none"'
+    return f'<polygon points="{d}" fill="{fill}"{st}{extra}/>'
+
+
+def box(ox, oy, w=150, d=105, h=52, s=1.0, hi=None):
+    """Three visible faces of a box. `hi` names the face/edge to highlight."""
+    P = lambda x, y, z: iso(x, y, z, ox, oy, s)
+    top = [P(0, 0, h), P(w, 0, h), P(w, d, h), P(0, d, h)]
+    left = [P(0, d, h), P(w, d, h), P(w, d, 0), P(0, d, 0)]
+    right = [P(w, 0, h), P(w, d, h), P(w, d, 0), P(w, 0, 0)]
+    out = [
+        poly(left, C["left"], C["edge"]),
+        poly(right, C["right"], C["edge"]),
+        poly(top, C["hi"] if hi == "top" else C["top"], C["edge"]),
+    ]
+    if hi == "top":
+        out.append(poly(top, "none", "#ffd07a", ' stroke-width="2.5"'))
+    if hi == "front_edge":
+        a, b = P(0, d, h), P(w, d, h)
+        out.append(f'<line x1="{a[0]:.1f}" y1="{a[1]:.1f}" x2="{b[0]:.1f}" y2="{b[1]:.1f}" '
+                   f'stroke="{C["hi"]}" stroke-width="5" stroke-linecap="round"/>')
+    if hi == "vertex":
+        v = P(w, d, h)
+        out.append(f'<circle cx="{v[0]:.1f}" cy="{v[1]:.1f}" r="6" fill="{C["hi"]}"/>')
+    if hi == "whole":
+        out.append(poly(top, "none", "#ffd07a", ' stroke-width="2.5"'))
+        out.append(poly(left, "none", "#ffd07a", ' stroke-width="2.5"'))
+        out.append(poly(right, "none", "#ffd07a", ' stroke-width="2.5"'))
+    return "".join(out), P
+
+
+def bore(P, cx, cy, h, r=22, s=1.0, hi=False):
+    """A cylindrical bore through the top face, drawn as ellipse + wall."""
+    c = P(cx, cy, h)
+    rx, ry = r * COS30 * 2 * s, r * SIN30 * 2 * s
+    col = C["hi"] if hi else "#20252b"
+    wall = C["hi"] if hi == "wall" else "#3b434d"
+    return (f'<ellipse cx="{c[0]:.1f}" cy="{c[1]:.1f}" rx="{rx:.1f}" ry="{ry:.1f}" '
+            f'fill="{wall}" stroke="{C["edge"]}"/>'
+            f'<ellipse cx="{c[0]:.1f}" cy="{c[1]+7:.1f}" rx="{rx*0.92:.1f}" ry="{ry*0.92:.1f}" '
+            f'fill="#171b20" stroke="none"/>'
+            + (f'<ellipse cx="{c[0]:.1f}" cy="{c[1]:.1f}" rx="{rx:.1f}" ry="{ry:.1f}" '
+               f'fill="none" stroke="{C["hi"]}" stroke-width="3"/>' if hi else "")), c
+
+
+def scene(kind, ox, oy):
+    """Return (svg, anchor) for a selection kind. Anchor = where the ring centres."""
+    s = 1.0
+    if kind == "origin":
+        # A document with nothing in it: the three origin planes are all there is to click.
+        P = lambda x, y, z: iso(x, y, z, ox, oy, s)
+        g = poly([P(-70, -70, 0), P(70, -70, 0), P(70, 70, 0), P(-70, 70, 0)],
+                 "#4f9bd91f", "#4f9bd977", ' stroke-width="1.5" stroke-dasharray="6 4"')
+        g += poly([P(-70, 0, -70), P(70, 0, -70), P(70, 0, 70), P(-70, 0, 70)],
+                  "#e05c5c14", "#e05c5c66", ' stroke-width="1.5" stroke-dasharray="6 4"')
+        g += poly([P(0, -70, -70), P(0, 70, -70), P(0, 70, 70), P(0, -70, 70)],
+                  "#5ce07a14", "#5ce07a66", ' stroke-width="1.5" stroke-dasharray="6 4"')
+        return g, P(0, 0, 0)
+    if kind == "empty":
+        g, P = box(ox, oy, s=s)
+        return g, P(75, 52, 26)
+    if kind == "box_top":
+        g, P = box(ox, oy, s=s, hi="top")
+        return g, P(75, 52, 52)
+    if kind == "box_whole":
+        g, P = box(ox, oy, s=s, hi="whole")
+        return g, P(75, 52, 26)
+    if kind == "box_edge":
+        g, P = box(ox, oy, s=s, hi="front_edge")
+        return g, P(75, 105, 52)
+    if kind == "box_vertex":
+        g, P = box(ox, oy, s=s, hi="vertex")
+        return g, P(150, 105, 52)
+    if kind in ("box_bore", "box_bore_rim"):
+        g, P = box(ox, oy, s=s)
+        b, c = bore(P, 75, 52, 52, hi=("wall" if kind == "box_bore" else True))
+        return g + b, c
+    if kind == "box_fillet_face":
+        g, P = box(ox, oy, s=s)
+        a, b = P(0, 0, 52), P(0, 105, 52)
+        g += (f'<path d="M{a[0]:.1f} {a[1]:.1f} L{b[0]:.1f} {b[1]:.1f}" stroke="{C["hi"]}" '
+              f'stroke-width="12" stroke-linecap="round" opacity="0.85" fill="none"/>')
+        return g, P(0, 52, 52)
+    if kind == "sheet":
+        P = lambda x, y, z: iso(x, y, z, ox, oy, s)
+        pts = [P(0, 0, 40), P(150, 0, 55), P(150, 105, 30), P(0, 105, 18)]
+        return (poly(pts, C["sheet"], "#ffd07a", ' stroke-width="2.5" opacity="0.85"'),
+                P(75, 52, 36))
+    if kind == "two_boxes":
+        g1, P1 = box(ox - 60, oy - 10, w=110, d=80, h=44, hi="whole")
+        g2, P2 = box(ox + 70, oy + 26, w=95, d=70, h=60, hi="whole")
+        return g1 + g2, (ox + 42, oy + 6)
+    if kind == "datum":
+        P = lambda x, y, z: iso(x, y, z, ox, oy, s)
+        g, _ = box(ox, oy, s=s)
+        pts = [P(-25, -25, 70), P(175, -25, 70), P(175, 130, 70), P(-25, 130, 70)]
+        g += poly(pts, "#4f9bd933", C["hi"], ' stroke-width="2.5" stroke-dasharray="6 4"')
+        return g, P(75, 52, 70)
+    if kind == "axis":
+        g, P = box(ox, oy, s=s)
+        a, b = P(-30, 52, 52), P(180, 52, 52)
+        g += (f'<line x1="{a[0]:.1f}" y1="{a[1]:.1f}" x2="{b[0]:.1f}" y2="{b[1]:.1f}" '
+              f'stroke="{C["hi"]}" stroke-width="3" stroke-dasharray="10 5"/>')
+        return g, P(75, 52, 52)
+    if kind == "csys":
+        P = lambda x, y, z: iso(x, y, z, ox, oy, s)
+        g, _ = box(ox, oy, s=s)
+        o = P(0, 0, 52)
+        for tgt, col in ((P(60, 0, 52), "#e05c5c"), (P(0, 60, 52), "#5ce07a"), (P(0, 0, 112), "#5c9ce0")):
+            g += (f'<line x1="{o[0]:.1f}" y1="{o[1]:.1f}" x2="{tgt[0]:.1f}" y2="{tgt[1]:.1f}" '
+                  f'stroke="{col}" stroke-width="3"/>')
+        g += f'<circle cx="{o[0]:.1f}" cy="{o[1]:.1f}" r="5" fill="{C["hi"]}"/>'
+        return g, o
+    if kind == "art":
+        P = lambda x, y, z: iso(x, y, z, ox, oy, s)
+        g, _ = box(ox, oy, s=s)
+        c = P(75, 52, 52)
+        g += (f'<g transform="translate({c[0]:.1f},{c[1]:.1f}) skewX(-30) scale(1,0.58)">'
+              f'<text x="0" y="10" text-anchor="middle" font-family="Georgia,serif" '
+              f'font-size="46" fill="{C["hi"]}" stroke="#ffd07a" stroke-width="1">ABC</text></g>')
+        return g, c
+    if kind == "loop":
+        P = lambda x, y, z: iso(x, y, z, ox, oy, s)
+        g, _ = box(ox, oy, s=s)
+        pts = [P(28, 22, 52), P(122, 22, 52), P(122, 83, 52), P(28, 83, 52)]
+        g += poly(pts, C["hi_soft"], C["hi"], ' stroke-width="3"')
+        return g, P(75, 52, 52)
+    # --- sketch mode: flat, camera normal to the plane
+    gx, gy = ox - 30, oy - 10
+    grid = "".join(
+        f'<line x1="{gx-170}" y1="{gy-110+i*22}" x2="{gx+170}" y2="{gy-110+i*22}" stroke="{C["grid"]}" stroke-width="0.6"/>'
+        for i in range(11)) + "".join(
+        f'<line x1="{gx-170+i*22}" y1="{gy-110}" x2="{gx-170+i*22}" y2="{gy+110}" stroke="{C["grid"]}" stroke-width="0.6"/>'
+        for i in range(16))
+    if kind == "sk_empty":
+        return grid, (gx, gy)
+    if kind == "sk_line":
+        return (grid + f'<line x1="{gx-120}" y1="{gy+60}" x2="{gx+120}" y2="{gy-40}" '
+                f'stroke="{C["hi"]}" stroke-width="4" stroke-linecap="round"/>'
+                f'<circle cx="{gx-120}" cy="{gy+60}" r="5" fill="{C["hi"]}"/>'
+                f'<circle cx="{gx+120}" cy="{gy-40}" r="5" fill="{C["hi"]}"/>', (gx, gy + 10))
+    if kind == "sk_arc":
+        return (grid + f'<circle cx="{gx}" cy="{gy}" r="88" fill="none" stroke="{C["hi"]}" '
+                f'stroke-width="4"/><circle cx="{gx}" cy="{gy}" r="4" fill="{C["hi"]}"/>', (gx, gy))
+    if kind == "sk_point":
+        return (grid + f'<circle cx="{gx}" cy="{gy}" r="7" fill="{C["hi"]}"/>', (gx, gy))
+    if kind == "sk_two":
+        return (grid + f'<line x1="{gx-120}" y1="{gy+70}" x2="{gx+40}" y2="{gy+70}" stroke="{C["hi"]}" stroke-width="4" stroke-linecap="round"/>'
+                f'<line x1="{gx+40}" y1="{gy+70}" x2="{gx+40}" y2="{gy-60}" stroke="{C["hi"]}" stroke-width="4" stroke-linecap="round"/>', (gx, gy + 5))
+    return grid, (gx, gy)
+
+
+# ---------------------------------------------------------------- app chrome
+def chrome(title, status, mode="model", empty_doc=False):
+    tabs = ["Prepare", "Preview", "Design"]
+    g = [f'<rect width="{W}" height="{H}" fill="{C["app"]}"/>',
+         f'<defs><radialGradient id="vp" cx="50%" cy="42%" r="75%">'
+         f'<stop offset="0%" stop-color="{C["vp0"]}"/>'
+         f'<stop offset="100%" stop-color="{C["vp1"]}"/></radialGradient></defs>',
+         f'<rect x="248" y="92" width="{W-248}" height="{H-92-30}" fill="url(#vp)"/>',
+         f'<rect width="{W}" height="44" fill="{C["chrome"]}"/>']
+    x = 24
+    for t in tabs:
+        on = (t == "Design")
+        g.append(f'<text x="{x}" y="28" font-family="Inter,DejaVu Sans,sans-serif" font-size="14" '
+                 f'font-weight="{600 if on else 400}" fill="{C["text"] if on else C["dim"]}">{t}</text>')
+        if on:
+            g.append(f'<rect x="{x-4}" y="38" width="{len(t)*8+8}" height="3" rx="1.5" fill="{C["accent"]}"/>')
+        x += len(t) * 9 + 34
+    # toolbar
+    g.append(f'<rect y="44" width="{W}" height="48" fill="{C["panel"]}"/>'
+             f'<line x1="0" y1="92" x2="{W}" y2="92" stroke="{C["line"]}"/>')
+    fams = (["sketch", "extrude", "hole", "fillet", "pattern", "boolean", "plane", "move", "measure"]
+            if mode == "model" else
+            ["sk_line", "sk_rect", "sk_circle", "sk_arc", "sk_slot", "sk_spline", "sk_dim", "sk_trim", "sk_lock"])
+    for i, gl in enumerate(fams):
+        cx = 40 + i * 46
+        g.append(f'<rect x="{cx-16}" y="52" width="32" height="32" rx="6" fill="{C["chip"]}" opacity="0.55"/>')
+        g.append(glyph(gl, cx, 68, C["muted"], 0.62, 1.7))
+    # left rail
+    g.append(f'<rect x="0" y="92" width="248" height="{H-92-30}" fill="{C["panel"]}"/>'
+             f'<line x1="248" y1="92" x2="248" y2="{H-30}" stroke="{C["line"]}"/>')
+    g.append(f'<text x="18" y="122" font-family="Inter,DejaVu Sans,sans-serif" font-size="11" '
+             f'letter-spacing="1.4" fill="{C["dim"]}">FEATURES</text>')
+    # A "fresh document" mockup that shows six existing features is a lie, and it is the one
+    # state the group will look at hardest — it is the first-run picture (B5).
+    tree = ([] if empty_doc else
+            [("Sketch1", 0), ("Extrude1", 0), ("Hole1", 1), ("Fillet1", 1), ("Sketch2", 0), ("Extrude2", 0)])
+    if empty_doc:
+        g.append(f'<text x="18" y="152" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" '
+                 f'font-style="italic" fill="{C["dim"]}">nothing yet</text>')
+    for i, (n, ind) in enumerate(tree):
+        yy = 150 + i * 26
+        g.append(glyph("sketch" if n.startswith("Sketch") else "extrude", 30 + ind * 14, yy - 4, C["dim"], 0.42, 1.8))
+        g.append(f'<text x="{46+ind*14}" y="{yy}" font-family="Inter,DejaVu Sans,sans-serif" '
+                 f'font-size="12.5" fill="{C["muted"]}">{n}</text>')
+    # status bar
+    g.append(f'<rect y="{H-30}" width="{W}" height="30" fill="{C["chrome"]}"/>'
+             f'<text x="18" y="{H-10}" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" '
+             f'fill="{C["muted"]}">{status}</text>')
+    g.append(f'<text x="{W-18}" y="{H-10}" text-anchor="end" font-family="Inter,DejaVu Sans,sans-serif" '
+             f'font-size="11.5" fill="{C["dim"]}">{title}</text>')
+    return "".join(g)
+
+
+# ---------------------------------------------------------------- the ring
+def ring(cx, cy, items, capacity, sel_name, radius=134):
+    """items: dict angle_index -> (glyph, label, key, count) or None for an empty slot."""
+    # The scrim is deliberately faint. §4.1: the offer "never blocks the view of what it acts
+    # on" — at 0.55 the disc swallowed the very face the ring was opened on, which is the rule
+    # failing in its own mockup.
+    g = [f'<circle cx="{cx}" cy="{cy}" r="{radius+52}" fill="{C["ring"]}" opacity="0.22"/>',
+         f'<circle cx="{cx}" cy="{cy}" r="{radius+52}" fill="none" stroke="{C["chip_line"]}" opacity="0.5"/>',
+         f'<circle cx="{cx}" cy="{cy}" r="46" fill="none" stroke="{C["chip_line"]}" '
+         f'stroke-dasharray="3 4" opacity="0.85"/>']
+    step = 360.0 / capacity
+    for i in range(capacity):
+        ang = math.radians(-90 + i * step)
+        px, py = cx + radius * math.cos(ang), cy + radius * math.sin(ang)
+        it = items.get(i)
+        if not it:
+            g.append(f'<circle cx="{px:.1f}" cy="{py:.1f}" r="21" fill="{C["empty"]}" opacity="0.5" '
+                     f'stroke="{C["chip_line"]}" stroke-dasharray="3 3"/>')
+            continue
+        gl, label, key, count = it
+        g.append(f'<rect x="{px-30:.1f}" y="{py-30:.1f}" width="60" height="60" rx="14" '
+                 f'fill="{C["chip"]}" stroke="{C["chip_line"]}"/>')
+        g.append(glyph(gl, px, py - 2, C["text"], 0.92, 1.7))
+        g.append(f'<text x="{px:.1f}" y="{py+48:.1f}" text-anchor="middle" '
+                 f'font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" font-weight="500" '
+                 f'fill="{C["text"]}">{label}</text>')
+        if key:
+            kw = 13 + len(key) * 6.6
+            g.append(f'<rect x="{px-kw/2:.1f}" y="{py+55:.1f}" width="{kw:.1f}" height="17" rx="4.5" '
+                     f'fill="{C["key"]}"/>'
+                     f'<text x="{px:.1f}" y="{py+67:.1f}" text-anchor="middle" '
+                     f'font-family="Inter,DejaVu Sans,sans-serif" font-size="10.5" '
+                     f'fill="{C["text"]}">{key}</text>')
+        if count and count > 1:
+            g.append(f'<circle cx="{px+22:.1f}" cy="{py-22:.1f}" r="10" fill="{C["accent"]}"/>'
+                     f'<text x="{px+22:.1f}" y="{py-18:.1f}" text-anchor="middle" '
+                     f'font-family="Inter,DejaVu Sans,sans-serif" font-size="11" font-weight="600" '
+                     f'fill="#0f1319">{count}</text>')
+    # The selection name sits on the LOWER rim of the centre hole, not above it: above, it
+    # landed on top of the north slot's shortcut chip and hid it. Below, the pick stays
+    # visible through the hole and the pill is clear of the south chip at cy+104.
+    w = 13 + len(sel_name) * 6.9
+    g.append(f'<rect x="{cx-w/2:.1f}" y="{cy+32:.1f}" width="{w:.1f}" height="22" rx="11" '
+             f'fill="{C["ring"]}" opacity="0.92" stroke="{C["chip_line"]}"/>'
+             f'<text x="{cx:.1f}" y="{cy+47:.1f}" text-anchor="middle" '
+             f'font-family="Inter,DejaVu Sans,sans-serif" font-size="12" fill="{C["text"]}">{sel_name}</text>')
+    return "".join(g)
+
+
+# ---------------------------------------------------------------- enumeration
+def load():
+    with open(ATLAS, encoding="utf-8") as f:
+        return json.load(f)
+
+
+def validate(A):
+    slot_ids = {s["id"] for s in A["slots"]}
+    sel_ids = {s["id"] for s in A["selections"]}
+    errs = []
+    seen = {}
+    for v in A["verbs"]:
+        if v["slot"] not in slot_ids:
+            errs.append(f'{v["id"]}: unknown slot {v["slot"]!r}')
+        for a in v["accepts"]:
+            if a not in sel_ids:
+                errs.append(f'{v["id"]}: accepts unknown selection {a!r}')
+        if v["id"] in seen:
+            errs.append(f'{v["id"]}: duplicate verb id')
+        seen[v["id"]] = v["slot"]
+    if errs:
+        sys.exit("tool_atlas.json is inconsistent:\n  " + "\n  ".join(errs))
+    return slot_ids, sel_ids
+
+
+def eligible(A, sel_id, doc):
+    sel = next(s for s in A["selections"] if s["id"] == sel_id)
+    out = []
+    for v in A["verbs"]:
+        if v.get("mode", "model") != sel["mode"]:
+            continue
+        if sel_id not in v["accepts"]:
+            continue
+        n = v.get("needs") or {}
+        if n.get("bodies", 0) > doc["bodies"]:
+            continue
+        if n.get("sketches", 0) > doc["sketches"]:
+            continue
+        if n.get("sheet") and not doc["sheet"]:
+            continue
+        out.append(v)
+    return out
+
+
+def by_slot(A, verbs):
+    order = [s["id"] for s in A["slots"]]
+    d = defaultdict(list)
+    for v in verbs:
+        d[v["slot"]].append(v)
+    return {k: d[k] for k in order if d[k]}
+
+
+def ring_items(A, grouped):
+    order = [s["id"] for s in A["slots"]]
+    slot_label = {s["id"]: s["label"] for s in A["slots"]}
+    items = {}
+    for i, sid in enumerate(order):
+        vs = grouped.get(sid)
+        if not vs:
+            continue
+        if len(vs) == 1:
+            v = vs[0]
+            items[i] = (VERB_GLYPH.get(v["id"], "fam_" + sid), v["name"], v.get("key"), 1)
+        else:
+            items[i] = ("fam_" + sid, slot_label[sid], None, len(vs))
+    return items
+
+
+# ---------------------------------------------------------------- rendering
+def menu(cx, cy, header, rows, submenu=None, sub_at=None):
+    """Vertical list form of the offer. rows: (glyph, name, key, count, enabled, reason).
+
+    The invariant is unchanged — a verb has one permanent row index, and rows that do not
+    apply are DISABLED IN PLACE, never removed. What changes against the ring is what an
+    unavailable slot can say: an empty circle says nothing, a greyed row says its own name
+    and the reason it is grey, in the words the product already ships.
+    """
+    RW, RH, HD = 324, 34, 38
+    # The reason line is the whole point of a disabled row, so it must FIT: at 10px italic a
+    # glyph is ~4.9px, and anything past the box edge is a promise the layout does not keep.
+    fit = int((RW - 62) / 4.9)
+    x, y = cx + 26, cy - 30
+    h = HD + len(rows) * RH + 10
+    if y + h > H - 44:
+        y = max(100, H - 44 - h)
+    g = [f'<rect x="{x+3}" y="{y+4}" width="{RW}" height="{h}" rx="12" fill="#000" opacity="0.35"/>',
+         f'<rect x="{x}" y="{y}" width="{RW}" height="{h}" rx="12" fill="{C["chrome"]}" '
+         f'stroke="{C["chip_line"]}"/>',
+         f'<text x="{x+16}" y="{y+24}" font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" '
+         f'letter-spacing="1.1" fill="{C["dim"]}">{header.upper()}</text>',
+         f'<line x1="{x+1}" y1="{y+HD-6}" x2="{x+RW-1}" y2="{y+HD-6}" stroke="{C["line"]}"/>']
+    # a leader from the pick point to the menu, so the list is visibly ABOUT that geometry
+    g.insert(0, f'<path d="M{cx} {cy} L{x} {y+HD+16}" stroke="{C["chip_line"]}" '
+                f'stroke-dasharray="2 3" fill="none"/>')
+    g.insert(0, f'<circle cx="{cx}" cy="{cy}" r="5" fill="none" stroke="{C["hi"]}" stroke-width="2"/>')
+    for i, (gl, name, key, count, on, reason) in enumerate(rows):
+        ry = y + HD + i * RH
+        op = "1" if on else "0.34"
+        if on and i == 0:
+            g.append(f'<rect x="{x+5}" y="{ry+2}" width="{RW-10}" height="{RH-4}" rx="7" '
+                     f'fill="{C["chip"]}"/>')
+        g.append(f'<g opacity="{op}">')
+        g.append(glyph(gl, x + 26, ry + RH / 2, C["text"], 0.72, 1.7))
+        g.append(f'<text x="{x+48}" y="{ry+RH/2+4.5}" font-family="Inter,DejaVu Sans,sans-serif" '
+                 f'font-size="13.5" fill="{C["text"]}">{name}</text>')
+        if key:
+            kw = 13 + len(key) * 6.6
+            g.append(f'<rect x="{x+RW-18-kw:.1f}" y="{ry+RH/2-9:.1f}" width="{kw:.1f}" height="18" '
+                     f'rx="4.5" fill="{C["key"]}"/>'
+                     f'<text x="{x+RW-18-kw/2:.1f}" y="{ry+RH/2+4:.1f}" text-anchor="middle" '
+                     f'font-family="Inter,DejaVu Sans,sans-serif" font-size="10.5" '
+                     f'fill="{C["text"]}">{key}</text>')
+        elif count and count > 1:
+            g.append(f'<path d="M{x+RW-24} {ry+RH/2-5} L{x+RW-19} {ry+RH/2} L{x+RW-24} {ry+RH/2+5}" '
+                     f'fill="none" stroke="{C["muted"]}" stroke-width="1.6" stroke-linecap="round"/>')
+            g.append(f'<text x="{x+RW-38}" y="{ry+RH/2+4}" text-anchor="end" '
+                     f'font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" '
+                     f'fill="{C["dim"]}">{count}</text>')
+        g.append('</g>')
+        if not on and reason:
+            r = reason if len(reason) <= fit else reason[:fit - 1].rstrip(" ,—-") + "…"
+            g.append(f'<text x="{x+48}" y="{ry+RH/2+16}" font-family="Inter,DejaVu Sans,sans-serif" '
+                     f'font-size="10" font-style="italic" fill="{C["dim"]}">{r}</text>')
+    if submenu:
+        sy = y + HD + (sub_at or 0) * RH - 6
+        sh = 12 + len(submenu) * RH
+        sx = x + RW + 8
+        g.append(f'<rect x="{sx+3}" y="{sy+4}" width="{RW-30}" height="{sh}" rx="12" fill="#000" opacity="0.35"/>')
+        g.append(f'<rect x="{sx}" y="{sy}" width="{RW-30}" height="{sh}" rx="12" '
+                 f'fill="{C["chrome"]}" stroke="{C["chip_line"]}"/>')
+        for i, (gl, name, key, _c, on, _r) in enumerate(submenu):
+            ry = sy + 6 + i * RH
+            g.append(f'<g opacity="{"1" if on else "0.34"}">')
+            g.append(glyph(gl, sx + 24, ry + RH / 2, C["text"], 0.72, 1.7))
+            g.append(f'<text x="{sx+44}" y="{ry+RH/2+4.5}" font-family="Inter,DejaVu Sans,sans-serif" '
+                     f'font-size="13.5" fill="{C["text"]}">{name}</text>')
+            if key:
+                kw = 13 + len(key) * 6.6
+                g.append(f'<rect x="{sx+RW-48-kw:.1f}" y="{ry+RH/2-9:.1f}" width="{kw:.1f}" height="18" '
+                         f'rx="4.5" fill="{C["key"]}"/>'
+                         f'<text x="{sx+RW-48-kw/2:.1f}" y="{ry+RH/2+4:.1f}" text-anchor="middle" '
+                         f'font-family="Inter,DejaVu Sans,sans-serif" font-size="10.5" '
+                         f'fill="{C["text"]}">{key}</text>')
+            g.append('</g>')
+    return "".join(g)
+
+
+OVERFLOWS = []   # (selection, doc state, family, verbs that did not fit the sub-ring)
+
+
+def svg_doc(inner):
+    return (f'<svg xmlns="http://www.w3.org/2000/svg" width="{W}" height="{H}" '
+            f'viewBox="0 0 {W} {H}">{inner}</svg>')
+
+
+def render_list_state(A, sel, doc, expand=None):
+    """The vertical-list form: every family row always present, in the same order, with the
+    ones that do not apply disabled and carrying their reason."""
+    verbs = eligible(A, sel["id"], doc)
+    grouped = by_slot(A, verbs)
+    fresh = doc["bodies"] == 0 and doc["sketches"] == 0
+    shape = "origin" if (fresh and sel["shape"] == "empty") else sel["shape"]
+    art, (ax, ay) = scene(shape, 620, 360)
+    rows, sub, sub_at = [], None, None
+    for idx, s in enumerate(A["slots"]):
+        vs = grouped.get(s["id"], [])
+        if len(vs) == 1:
+            v = vs[0]
+            rows.append((VERB_GLYPH.get(v["id"], "fam_" + s["id"]), v["name"], v.get("key"), 1, True, None))
+        elif len(vs) > 1:
+            rows.append(("fam_" + s["id"], s["label"], None, len(vs), True, None))
+            if expand == s["id"]:
+                sub_at = idx
+                sub = [(VERB_GLYPH.get(v["id"], "fam_" + s["id"]), v["name"], v.get("key"), 1, True, None)
+                       for v in vs]
+        else:
+            # Disabled in place, with the product's own refusal text — the thing an empty
+            # slot in the ring could never say.
+            cands = [v for v in A["verbs"]
+                     if v["slot"] == s["id"] and v.get("mode", "model") == sel["mode"]]
+            why = next((v["refusal"] for v in cands if v.get("refusal")), None)
+            rows.append(("fam_" + s["id"], s["label"], None, 0, False, why))
+    status = ("Right-click the geometry to see what you can do with it" if not expand
+              else f'{sel["name"]} — pick one')
+    inner = chrome(f'{doc["name"]} · vertical list', status, sel["mode"], empty_doc=fresh)
+    inner += art
+    inner += menu(ax, ay, sel["name"], rows, sub, sub_at)
+    return svg_doc(inner)
+
+
+def render_state(A, sel, doc, capacity=8, secondary=None):
+    verbs = eligible(A, sel["id"], doc)
+    grouped = by_slot(A, verbs)
+    anchor_x, anchor_y = 810, 400
+    fresh = doc["bodies"] == 0 and doc["sketches"] == 0
+    shape = "origin" if (fresh and sel["shape"] == "empty") else sel["shape"]
+    art, (ax, ay) = scene(shape, anchor_x - 90, anchor_y - 40)
+    if secondary:
+        vs = grouped[secondary]
+        # A sub-ring ANCHORS ON ITS PARENT'S DIRECTION. Fanning from north instead put Extrude
+        # at N — Create's address in the primary map — so the second level contradicted the
+        # first. Anchored, an address is two consistent strokes: Add material is NE, and the
+        # first verb of Add material is NE again.
+        base = [s["id"] for s in A["slots"]].index(secondary)
+        overflow = []
+        if len(vs) > capacity:
+            # Do NOT wrap: (base+i) % capacity would quietly put verb 9 on top of verb 1, which
+            # is the invariant failing silently — the one outcome worse than an ugly ring. Show
+            # what fits, mark the rest, and report it.
+            overflow = vs[capacity - 1:]
+            vs = vs[:capacity - 1]
+        items = {(base + i) % capacity:
+                 (VERB_GLYPH.get(v["id"], "fam_" + secondary), v["name"], v.get("key"), 1)
+                 for i, v in enumerate(vs)}
+        if overflow:
+            items[(base + capacity - 1) % capacity] = ("fam_" + secondary, "More", None, len(overflow))
+            OVERFLOWS.append((sel["name"], doc["id"], secondary, [v["name"] for v in overflow]))
+        label = next(s["label"] for s in A["slots"] if s["id"] == secondary)
+        sel_name = f'{sel["name"]} · {label}'
+        status = f'{label} — pick one'
+    else:
+        items = ring_items(A, grouped)
+        sel_name = sel["name"]
+        status = ("Click a face or a reference plane, then a tool"
+                  if sel["id"] == "none" else f'{sel["name"]} selected — pick what to do with it')
+    inner = chrome(f'{doc["name"]} · {capacity} slots', status, sel["mode"], empty_doc=fresh)
+    inner += art
+    inner += ring(ax, ay, items, capacity, sel_name)
+    return svg_doc(inner), verbs, grouped
+
+
+def main():
+    A = load()
+    validate(A)
+    docs = {d["id"]: d for d in A["doc_states"]}
+    outdir = HERE
+    rows, files = [], []
+    total_primary = total_secondary = 0
+    fill_sum = fill_n = 0
+
+    for d in A["doc_states"]:
+        for sel in A["selections"]:
+            svg, verbs, grouped = render_state(A, sel, d)
+            name = f'{d["id"]}__{sel["id"]}.svg'
+            with open(os.path.join(outdir, name), "w", encoding="utf-8") as f:
+                f.write(svg)
+            files.append((name, f'{sel["name"]} — {d["name"]}'))
+            total_primary += 1
+            fill_sum += len(grouped)
+            fill_n += 1
+            secondaries = []
+            for sid, vs in grouped.items():
+                if len(vs) > 1:
+                    s2, _, _ = render_state(A, sel, d, secondary=sid)
+                    n2 = f'{d["id"]}__{sel["id"]}__{sid}.svg'
+                    with open(os.path.join(outdir, n2), "w", encoding="utf-8") as f:
+                        f.write(s2)
+                    label = next(s["label"] for s in A["slots"] if s["id"] == sid)
+                    files.append((n2, f'{sel["name"]} — {label} ring'))
+                    secondaries.append(sid)
+                    total_secondary += 1
+            rows.append({
+                "doc": d["name"], "sel": sel["name"], "mode": sel["mode"],
+                "verbs": len(verbs), "slots": len(grouped),
+                "second": len(secondaries),
+                "detail": {sid: [v["name"] for v in vs] for sid, vs in grouped.items()},
+            })
+
+    # Form-factor comparison: the SAME state as a ring and as a vertical list.
+    for sid in ("face_planar", "edge_str", "body_solid", "sk_line", "none"):
+        sel = next(s for s in A["selections"] if s["id"] == sid)
+        d = docs["fresh"] if sid == "none" else docs["rich"]
+        with open(os.path.join(outdir, f"list__{sid}.svg"), "w", encoding="utf-8") as f:
+            f.write(render_list_state(A, sel, d))
+    for sid, fam in (("face_planar", "add"), ("sk_none", "create")):
+        sel = next(s for s in A["selections"] if s["id"] == sid)
+        with open(os.path.join(outdir, f"list__{sid}__{fam}.svg"), "w", encoding="utf-8") as f:
+            f.write(render_list_state(A, sel, docs["rich"], expand=fam))
+
+    # comparison sheet: 8 vs 12 slots on the same three selections
+    for cap in (8, 12):
+        for sid in ("face_planar", "edge_str", "sk_line"):
+            sel = next(s for s in A["selections"] if s["id"] == sid)
+            svg, _, _ = render_state(A, sel, docs["rich"], capacity=cap)
+            n = f'cmp_{cap}__{sid}.svg'
+            with open(os.path.join(outdir, n), "w", encoding="utf-8") as f:
+                f.write(svg)
+
+    write_atlas(A, rows, files, total_primary, total_secondary,
+                fill_sum / max(1, fill_n))
+    print(f"{total_primary} primary + {total_secondary} secondary = "
+          f"{total_primary+total_secondary} offer states rendered")
+    print(f"mean populated slots per primary ring: {fill_sum/max(1,fill_n):.2f} of 8")
+    if OVERFLOWS:
+        seen = {(f, tuple(v)) for _, _, f, v in OVERFLOWS}
+        print(f"OVERFLOW: {len(OVERFLOWS)} sub-rings did not fit 8 slots — "
+              f"{len(seen)} distinct case(s):")
+        for f, v in sorted(seen):
+            print(f"  {f}: {', '.join(v)} pushed behind 'More'")
+
+
+def write_atlas(A, rows, files, n_prim, n_sec, mean_fill):
+    gui_missing = [v["name"] for v in A["verbs"] if not v.get("gui", True)]
+    esc = lambda s: (s.replace("&", "&amp;").replace("<", "&lt;").replace(">", "&gt;"))
+    cards = "".join(
+        f'<figure><img src="mockups/{n}" alt="{esc(t)}" loading="lazy"><figcaption>{esc(t)}</figcaption></figure>'
+        for n, t in files)
+    cmp8 = "".join(f'<figure><img src="mockups/cmp_8__{s}.svg" loading="lazy">'
+                   f'<figcaption>8 slots — {s}</figcaption></figure>'
+                   for s in ("face_planar", "edge_str", "sk_line"))
+    cmp12 = "".join(f'<figure><img src="mockups/cmp_12__{s}.svg" loading="lazy">'
+                    f'<figcaption>12 slots — {s}</figcaption></figure>'
+                    for s in ("face_planar", "edge_str", "sk_line"))
+    if OVERFLOWS:
+        cases = sorted({(f, tuple(v)) for _, _, f, v in OVERFLOWS})
+        over_html = ("Measured, not predicted: " + "; ".join(
+            f'the <b>{esc(f)}</b> sub-ring needs {8 + len(v)} addresses, so '
+            f'{esc(", ".join(v))} {"is" if len(v) == 1 else "are"} pushed behind a “More” slot'
+            for f, v in cases) +
+            ". This is the decision the ring size actually turns on — either a verb moves to "
+            "another family, or the tail goes to a third level, or the ring is not eight. "
+            "It affects sketch mode only; every model-mode family fits.")
+    else:
+        over_html = "No sub-ring exceeds the ring capacity. Eight slots is sufficient everywhere."
+    trs = "".join(
+        f'<tr><td>{esc(r["sel"])}</td><td>{esc(r["doc"])}</td><td class="n">{r["verbs"]}</td>'
+        f'<td class="n">{r["slots"]}/8</td><td class="n">{r["second"]}</td>'
+        f'<td class="d">{esc(" · ".join(k + ": " + ", ".join(v) for k, v in r["detail"].items()))}</td></tr>'
+        for r in rows)
+    html = f"""<!doctype html><meta charset="utf-8"><title>Design tab — offer atlas</title>
+<style>
+ :root{{color-scheme:dark;--bg:#15181c;--panel:#1c2026;--line:#2c323a;--tx:#e7ecf1;--mu:#93a0ad;--ac:#4f9bd9}}
+ body{{margin:0;background:var(--bg);color:var(--tx);font:15px/1.55 Inter,system-ui,sans-serif}}
+ header{{padding:38px 40px 22px;border-bottom:1px solid var(--line)}}
+ h1{{margin:0 0 6px;font-size:26px;letter-spacing:-.02em}}
+ h2{{margin:38px 0 12px;font-size:18px}} p{{color:var(--mu);max-width:78ch}}
+ main{{padding:0 40px 60px}}
+ .stats{{display:flex;gap:14px;flex-wrap:wrap;margin:18px 0 6px}}
+ .stat{{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:12px 16px;min-width:130px}}
+ .stat b{{display:block;font-size:24px}} .stat span{{color:var(--mu);font-size:12px}}
+ .grid{{display:grid;grid-template-columns:repeat(auto-fill,minmax(430px,1fr));gap:18px}}
+ figure{{margin:0;background:var(--panel);border:1px solid var(--line);border-radius:12px;overflow:hidden}}
+ figure img{{width:100%;display:block}}
+ figcaption{{padding:9px 13px;font-size:13px;color:var(--mu);border-top:1px solid var(--line)}}
+ table{{border-collapse:collapse;width:100%;font-size:13px;margin-top:10px}}
+ th,td{{border-bottom:1px solid var(--line);padding:7px 10px;text-align:left;vertical-align:top}}
+ th{{color:var(--mu);font-weight:500}} td.n{{text-align:right;font-variant-numeric:tabular-nums}}
+ td.d{{color:var(--mu);font-size:12px}}
+ .wrap{{overflow-x:auto}}
+</style>
+<header>
+ <h1>The offer — atlas of every state</h1>
+ <p>Every state of the object-driven tool offer, generated from
+ <code>docs/ux/tool_atlas.json</code>. The invariant under test: a verb has one address, that
+ address is the same in every selection where it appears, and slots that do not apply are drawn
+ empty rather than compacted.</p>
+ <div class="stats">
+  <div class="stat"><b>{len(A["verbs"])}</b><span>verbs mapped</span></div>
+  <div class="stat"><b>{len(A["selections"])}</b><span>selection kinds</span></div>
+  <div class="stat"><b>{n_prim}</b><span>primary rings</span></div>
+  <div class="stat"><b>{n_sec}</b><span>secondary rings</span></div>
+  <div class="stat"><b>{n_prim+n_sec}</b><span>states total</span></div>
+  <div class="stat"><b>{mean_fill:.1f}/8</b><span>mean slots filled</span></div>
+  <div class="stat"><b>{len(gui_missing)}</b><span>verbs with no GUI yet</span></div>
+ </div>
+</header>
+<main>
+ <h2>Decision 0 — ring or vertical list</h2>
+ <p>The live question. Both forms carry the SAME map and the same invariant — fixed order, never
+ re-sorted, nothing compacted; only the geometry differs. Left-click selects; right-click opens the
+ offer. What the list buys: a disabled row can state its own reason in the words the product
+ already ships, where an empty slot in a ring is mute; nine sketch primitives fit without an
+ overflow; shortcuts line up in a readable column; long translated names fit; and it is navigable
+ by arrow key and by screen reader, which a radial is not. What it costs: no equidistant flick
+ gesture, and travel to the last row is longer than to the nearest direction. Pairs below —
+ list first, the same state as a ring second.</p>
+
+ <h2>Decision 1 — ring capacity</h2>
+ <p>The same three selections at eight and at twelve. Eight keeps 45° between neighbours, which is
+ the reliable eyes-free pointing threshold and maps 1:1 to the numpad; twelve buys direct addresses
+ for more verbs at 30° spacing and positions that stop being nameable.</p>
+ <div class="grid">{cmp8}</div>
+ <div class="grid" style="margin-top:18px">{cmp12}</div>
+
+ <h2>Decision 2 — one map or one per mode</h2>
+ <p>These renders use ONE shared map: sketch verbs occupy the same eight families as model verbs,
+ so dress-up is south-east whether you picked a solid edge or a sketch line. Compare the sketch-mode
+ states below against the model-mode ones — if a verb that exists in both modes ever appears at two
+ addresses, the shared map has failed and the split map is the answer.</p>
+
+ <h2>The matrix — every selection, every document state</h2>
+ <div class="wrap"><table>
+  <tr><th>Selection</th><th>Document</th><th>Verbs</th><th>Slots</th><th>2nd rings</th><th>What lands where</th></tr>
+  {trs}
+ </table></div>
+
+ <h2>Overflow — the one place eight slots is not enough</h2>
+ <p>{over_html}</p>
+
+ <h2>Not in the offer</h2>
+ <p>{esc(", ".join(A["chrome_only"]["items"]))} — these act on the document, not on a selection,
+ so they stay in chrome. Verbs with kernel support but no GUI today, which still hold an address:
+ {esc(", ".join(gui_missing))}.</p>
+
+ <h2>All states</h2>
+ <div class="grid">{cards}</div>
+</main>
+"""
+    with open(os.path.join(UX, "offer_atlas.html"), "w", encoding="utf-8") as f:
+        f.write(html)
+
+    # A second, SELF-CONTAINED copy for review outside the repo: the artifact host blocks
+    # every external request, so relative <img src> would silently show nothing. Curated
+    # rather than all 113 states — the whole set inlined is 1.5 MB, which is a poor thing to
+    # send to the low-end machine this design is meant to serve (6.1).
+    def inline(name):
+        p = os.path.join(HERE, name)
+        if not os.path.exists(p):
+            return ""
+        s = open(p, encoding="utf-8").read()
+        return s.replace("<svg ", '<svg style="width:100%;height:auto;display:block" ', 1)
+
+    # Form factor first: this is the live decision, so it opens the page.
+    picks = [
+        ("list__none.svg", "LIST · fresh document — every family present, the unavailable ones say why"),
+        ("fresh__none.svg", "RING · the same state — an empty slot cannot say anything"),
+        ("list__face_planar.svg", "LIST · planar face"),
+        ("rich__face_planar.svg", "RING · planar face"),
+        ("list__sk_none__create.svg", "LIST · sketch Create submenu — all 9 primitives fit, no overflow"),
+        ("rich__sk_none__create.svg", "RING · the same submenu — 2 verbs pushed behind “More”"),
+        ("list__face_planar__add.svg", "LIST · planar face, Add material submenu"),
+        ("rich__face_planar__add.svg", "RING · planar face, Add material sub-ring"),
+        ("list__body_solid.svg", "LIST · solid body"),
+        ("list__edge_str.svg", "LIST · straight edge"),
+        ("list__sk_line.svg", "LIST · sketch line"),
+    ]
+    picks += [(f'rich__{s["id"]}.svg', "RING · " + s["name"]) for s in A["selections"]]
+    picks.insert(0, ("fresh__none.svg", "Fresh document, nothing selected — the first-run picture"))
+    picks += [("rich__face_planar__add.svg", "Planar face · Add material sub-ring"),
+              ("rich__face_planar__reference.svg", "Planar face · Reference sub-ring"),
+              ("rich__sk_none__create.svg", "Sketch · Create sub-ring (the overflow case)"),
+              ("rich__body_solid__remove.svg", "Solid body · Remove sub-ring"),
+              ("cmp_8__face_planar.svg", "8 slots — planar face"),
+              ("cmp_12__face_planar.svg", "12 slots — planar face"),
+              ("cmp_8__sk_line.svg", "8 slots — sketch line"),
+              ("cmp_12__sk_line.svg", "12 slots — sketch line")]
+    figs = "".join(f'<figure>{inline(n)}<figcaption>{esc(t)}</figcaption></figure>'
+                   for n, t in picks if inline(n))
+    head, _, tail = html.partition('<h2>All states</h2>')
+    # The comparison grids in the head use <img src="mockups/...">, which resolves to nothing
+    # once the page is served on its own. Inline those too rather than shipping empty frames.
+    head = re.sub(r'<img src="mockups/([^"]+)"[^>]*>',
+                  lambda m: inline(m.group(1)), head)
+    inline_html = head + '<h2>The states</h2>\n<div class="grid">' + figs + '</div></main>\n'
+    with open(os.path.join(UX, "offer_atlas_inline.html"), "w", encoding="utf-8") as f:
+        f.write(inline_html)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/docs/CAD/ux/mockups/gen_offer_table.py b/docs/CAD/ux/mockups/gen_offer_table.py
new file mode 100644
index 0000000000..9744f9288b
--- /dev/null
+++ b/docs/CAD/ux/mockups/gen_offer_table.py
@@ -0,0 +1,173 @@
+#!/usr/bin/env python3
+"""Emit the C++ offer table from docs/ux/tool_atlas.json.
+
+    python3 docs/ux/mockups/gen_offer_table.py
+
+The map exists ONCE. The mockups and the shipping menu read the same rows in the same
+order from the same file, so a drawing and the product cannot drift apart — which is the
+only way row constancy (charter 4.1) survives contact with a codebase.
+
+Output: src/slic3r/GUI/CAD/DesignOffer.hpp, checked in and never hand-edited.
+"""
+
+import json
+import os
+import sys
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+UX = os.path.dirname(HERE)
+# One dirname more than you would expect: this generator lives at docs/CAD/ux/mockups/,
+# not docs/ux/mockups/, since the design docs moved into the CAD subfolder (bbd1989e1e).
+# With the old count REPO resolved to docs/, so OUT pointed at docs/src/.../DesignOffer.hpp,
+# which does not exist -- and --check then diffed the real generated table against an empty
+# file and reported the whole 189-line header as a difference.
+REPO = os.path.dirname(os.path.dirname(os.path.dirname(UX)))
+ATLAS = os.path.join(UX, "tool_atlas.json")
+OUT = os.path.join(REPO, "src", "slic3r", "GUI", "CAD", "DesignOffer.hpp")
+
+# selection id -> C++ enumerator
+ENUM = {
+    "none": "None", "face_planar": "FacePlanar", "face_cyl": "FaceCyl",
+    "face_other": "FaceOther", "edge_str": "EdgeStr", "edge_circ": "EdgeCirc",
+    "vertex": "Vertex", "body_solid": "BodySolid", "body_sheet": "BodySheet",
+    "bodies_2": "Bodies2", "datum_plane": "DatumPlane", "datum_axis": "DatumAxis",
+    "coordsys": "CoordSys", "art": "Art", "sk_loop": "SkLoop", "sk_none": "SkNone",
+    "sk_line": "SkLine", "sk_arc": "SkArc", "sk_point": "SkPoint", "sk_2ent": "Sk2Ent",
+}
+
+
+def cstr(s):
+    if s is None:
+        return "nullptr"
+    return '"' + s.replace("\\", "\\\\").replace('"', '\\"') + '"'
+
+
+def main():
+    A = json.load(open(ATLAS, encoding="utf-8"))
+    sels = [s["id"] for s in A["selections"]]
+    assert all(s in ENUM for s in sels), [s for s in sels if s not in ENUM]
+    slots = [s["id"] for s in A["slots"]]
+
+    lines = [
+        "// GENERATED FILE — DO NOT EDIT.",
+        "// Source: docs/ux/tool_atlas.json   Generator: docs/ux/mockups/gen_offer_table.py",
+        "//",
+        "// The object-driven tool offer (charter 4.1): every verb has ONE row index, that index",
+        "// is the same in every selection it appears in, and verbs that do not apply are shown",
+        "// disabled in place with their reason rather than removed. Row order was ratified",
+        "// 2026-07-31; changing an index is a breaking change to every user's muscle memory.",
+        "#ifndef slic3r_GUI_DesignOffer_hpp_",
+        "#define slic3r_GUI_DesignOffer_hpp_",
+        "",
+        "#include <cstdint>",
+        "",
+        "namespace Slic3r { namespace GUI {",
+        "",
+        "// What the viewport has selected. Ordered as in tool_atlas.json; the bitmask in",
+        "// OfferVerb::accepts indexes these.",
+        "enum class OfferSel : int {",
+    ]
+    for i, s in enumerate(sels):
+        lines.append(f"    {ENUM[s]} = {i},")
+    lines += [
+        f"    Count = {len(sels)}",
+        "};",
+        "",
+        "inline uint32_t offer_bit(OfferSel s) { return 1u << int(s); }",
+        "",
+        "// One row of the offer. `action` routes to the code that already implements the verb:",
+        '//   "key:S+E"        -> m_keys_feature[SHIFT(\'E\')]',
+        '//   "key:L"          -> m_keys_sketch[\'L\']',
+        '//   "fly:material#4" -> row 4 of the "material" feature flyout',
+        '//   "btn:delete"     -> a standalone toolbar button',
+        "//   nullptr          -> kernel support exists, no GUI path yet (row shows disabled)",
+        "struct OfferVerb {",
+        "    const char* id;",
+        "    const char* name;        // drawing-office word (L10); translated at use with wxGetTranslation",
+        "    int         row;         // 0..7, the ratified index — NEVER reorder",
+        "    const char* key;         // shortcut shown in the row, or nullptr",
+        "    const char* action;",
+        "    const char* refusal;     // why this row is greyed, in the product's own words",
+        "    uint32_t    accepts;     // bitmask over OfferSel",
+        "    int         need_bodies;",
+        "    int         need_sketches;",
+        "    bool        need_sheet;",
+        "    bool        sketch_mode; // belongs to the sketch-mode vocabulary, not the model one",
+        "    // Second level INSIDE a row, for tools that come in variants: \"Rectangle\" holds corner,",
+        "    // centre, oblique and rounded. nullptr = sits directly in the row. Keeps the row's own",
+        "    // address fixed (L4.1) while the variants hang one level below it, mirroring the toolbar's",
+        "    // grouping instead of flattening 19 create tools into one wall.",
+        "    const char* family;",
+        "    const char* icon;         // resources/images name, or nullptr — the offer draws it beside the row",
+        "    const char* hint;         // what the verb does / what to click; shown on hover",
+        "};",
+        "",
+        "// Row labels, in ratified order.",
+        "static const char* const kOfferRowNames[] = {",
+    ]
+    for s in A["slots"]:
+        lines.append(f'    "{s["label"]}",')
+    lines += [
+        "};",
+        f"static const int kOfferRowCount = {len(slots)};",
+        "",
+        "static const OfferVerb kOfferVerbs[] = {",
+    ]
+    # A verb the user can PICK must say what it does. Fail loudly rather than ship a
+    # bare name — the offer is now the only door to these tools.
+    blind = [v["id"] for v in A["verbs"] if v.get("action") and not v.get("hint")]
+    assert not blind, f"wired verbs with no hint: {blind}"
+    for v in A["verbs"]:
+        # A verb may carry a NOTE: the reason it exists, emitted as a C++ comment above its row.
+        # Without somewhere to put it, a rationale written into the generated header is deleted by
+        # the next regeneration — which is how the model-mode "Constrain sketch" row came to exist
+        # in the header and not in the atlas at all (ziam). The map exists once; so does
+        # the explanation.
+        for ln in ([v["note"]] if isinstance(v.get("note"), str) else v.get("note") or []):
+            lines.append(f"    // {ln}")
+        mask = 0
+        for a in v["accepts"]:
+            mask |= 1 << sels.index(a)
+        n = v.get("needs") or {}
+        lines.append(
+            "    {%s, %s, %d, %s, %s, %s, 0x%08xu, %d, %d, %s, %s, %s, %s, %s}," % (
+                cstr(v["id"]), cstr(v["name"]), slots.index(v["slot"]),
+                cstr(v.get("key")), cstr(v.get("action")), cstr(v.get("refusal")),
+                mask, n.get("bodies", 0), n.get("sketches", 0),
+                "true" if n.get("sheet") else "false",
+                "true" if v.get("mode") == "sketch" else "false",
+                cstr(v.get("family")), cstr(v.get("icon")), cstr(v.get("hint"))))
+    lines += [
+        "};",
+        f"static const int kOfferVerbCount = {len(A['verbs'])};",
+        "",
+        "}} // namespace Slic3r::GUI",
+        "",
+        "#endif // slic3r_GUI_DesignOffer_hpp_",
+        "",
+    ]
+    text = "\n".join(lines)
+    # --check: prove the checked-in header IS what this generator produces, and change nothing.
+    # The header calls itself GENERATED and was hand-edited anyway; a claim like that is only
+    # worth having if something enforces it, so run-all-checks.sh runs this on every gate.
+    if "--check" in sys.argv:
+        have = open(OUT, encoding="utf-8").read() if os.path.exists(OUT) else ""
+        if have == text:
+            print(f"{os.path.relpath(OUT, REPO)} matches tool_atlas.json")
+            return 0
+        import difflib
+        d = list(difflib.unified_diff(have.splitlines(), text.splitlines(),
+                                      "checked-in", "generated", lineterm="", n=1))
+        print(f"{os.path.relpath(OUT, REPO)} DIFFERS from tool_atlas.json:")
+        print("\n".join(d[:60]))
+        return 1
+    with open(OUT, "w", encoding="utf-8") as f:
+        f.write(text)
+    wired = sum(1 for v in A["verbs"] if v.get("action"))
+    print(f"wrote {os.path.relpath(OUT, REPO)}: {len(A['verbs'])} verbs, "
+          f"{len(slots)} rows, {wired} wired to existing actions")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/docs/CAD/ux/mockups/list__body_solid.svg b/docs/CAD/ux/mockups/list__body_solid.svg
new file mode 100644
index 0000000000..ec3b3a84f4
--- /dev/null
+++ b/docs/CAD/ux/mockups/list__body_solid.svg
@@ -0,0 +1 @@
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\ No newline at end of file
diff --git a/docs/CAD/ux/mockups/list__edge_str.svg b/docs/CAD/ux/mockups/list__edge_str.svg
new file mode 100644
index 0000000000..3942000d25
--- /dev/null
+++ b/docs/CAD/ux/mockups/list__edge_str.svg
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\ No newline at end of file
diff --git a/docs/CAD/ux/mockups/list__face_planar.svg b/docs/CAD/ux/mockups/list__face_planar.svg
new file mode 100644
index 0000000000..5ff6892902
--- /dev/null
+++ b/docs/CAD/ux/mockups/list__face_planar.svg
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new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__art__modify.svg b/docs/CAD/ux/mockups/rich__art__modify.svg
new file mode 100644
index 0000000000..4c8cdef2b5
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diff --git a/docs/CAD/ux/mockups/rich__bodies_2__reference.svg b/docs/CAD/ux/mockups/rich__bodies_2__reference.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__body_sheet.svg b/docs/CAD/ux/mockups/rich__body_sheet.svg
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diff --git a/docs/CAD/ux/mockups/rich__body_solid.svg b/docs/CAD/ux/mockups/rich__body_solid.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__body_solid__dressup.svg b/docs/CAD/ux/mockups/rich__body_solid__dressup.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__body_solid__reference.svg b/docs/CAD/ux/mockups/rich__body_solid__reference.svg
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diff --git a/docs/CAD/ux/mockups/rich__body_solid__remove.svg b/docs/CAD/ux/mockups/rich__body_solid__remove.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__coordsys.svg b/docs/CAD/ux/mockups/rich__coordsys.svg
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diff --git a/docs/CAD/ux/mockups/rich__coordsys__modify.svg b/docs/CAD/ux/mockups/rich__coordsys__modify.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__datum_axis__modify.svg b/docs/CAD/ux/mockups/rich__datum_axis__modify.svg
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diff --git a/docs/CAD/ux/mockups/rich__datum_plane.svg b/docs/CAD/ux/mockups/rich__datum_plane.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__datum_plane__modify.svg b/docs/CAD/ux/mockups/rich__datum_plane__modify.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__datum_plane__reference.svg b/docs/CAD/ux/mockups/rich__datum_plane__reference.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__edge_circ.svg b/docs/CAD/ux/mockups/rich__edge_circ.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__edge_circ__dressup.svg b/docs/CAD/ux/mockups/rich__edge_circ__dressup.svg
new file mode 100644
index 0000000000..b315fc2e22
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diff --git a/docs/CAD/ux/mockups/rich__face_cyl.svg b/docs/CAD/ux/mockups/rich__face_cyl.svg
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diff --git a/docs/CAD/ux/mockups/rich__face_cyl__modify.svg b/docs/CAD/ux/mockups/rich__face_cyl__modify.svg
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diff --git a/docs/CAD/ux/mockups/rich__face_cyl__reference.svg b/docs/CAD/ux/mockups/rich__face_cyl__reference.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__face_other.svg b/docs/CAD/ux/mockups/rich__face_other.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__face_other__modify.svg b/docs/CAD/ux/mockups/rich__face_other__modify.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__face_planar__add.svg b/docs/CAD/ux/mockups/rich__face_planar__add.svg
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diff --git a/docs/CAD/ux/mockups/rich__face_planar__dressup.svg b/docs/CAD/ux/mockups/rich__face_planar__dressup.svg
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diff --git a/docs/CAD/ux/mockups/rich__face_planar__reference.svg b/docs/CAD/ux/mockups/rich__face_planar__reference.svg
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diff --git a/docs/CAD/ux/mockups/rich__face_planar__transform.svg b/docs/CAD/ux/mockups/rich__face_planar__transform.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__none.svg b/docs/CAD/ux/mockups/rich__none.svg
new file mode 100644
index 0000000000..4e8a9dc640
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diff --git a/docs/CAD/ux/mockups/rich__none__reference.svg b/docs/CAD/ux/mockups/rich__none__reference.svg
new file mode 100644
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diff --git a/docs/CAD/ux/mockups/rich__sk_arc__reference.svg b/docs/CAD/ux/mockups/rich__sk_arc__reference.svg
new file mode 100644
index 0000000000..53e949c184
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diff --git a/docs/CAD/ux/mockups/rich__sk_line__modify.svg b/docs/CAD/ux/mockups/rich__sk_line__modify.svg
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diff --git a/docs/CAD/ux/mockups/rich__sk_line__reference.svg b/docs/CAD/ux/mockups/rich__sk_line__reference.svg
new file mode 100644
index 0000000000..6eb1ef621f
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diff --git a/docs/CAD/ux/mockups/rich__sk_point__create.svg b/docs/CAD/ux/mockups/rich__sk_point__create.svg
new file mode 100644
index 0000000000..5d2070a6c5
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+<!doctype html><meta charset="utf-8"><title>Design tab — offer atlas</title>
+<style>
+ :root{color-scheme:dark;--bg:#15181c;--panel:#1c2026;--line:#2c323a;--tx:#e7ecf1;--mu:#93a0ad;--ac:#4f9bd9}
+ body{margin:0;background:var(--bg);color:var(--tx);font:15px/1.55 Inter,system-ui,sans-serif}
+ header{padding:38px 40px 22px;border-bottom:1px solid var(--line)}
+ h1{margin:0 0 6px;font-size:26px;letter-spacing:-.02em}
+ h2{margin:38px 0 12px;font-size:18px} p{color:var(--mu);max-width:78ch}
+ main{padding:0 40px 60px}
+ .stats{display:flex;gap:14px;flex-wrap:wrap;margin:18px 0 6px}
+ .stat{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:12px 16px;min-width:130px}
+ .stat b{display:block;font-size:24px} .stat span{color:var(--mu);font-size:12px}
+ .grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(430px,1fr));gap:18px}
+ figure{margin:0;background:var(--panel);border:1px solid var(--line);border-radius:12px;overflow:hidden}
+ figure img{width:100%;display:block}
+ figcaption{padding:9px 13px;font-size:13px;color:var(--mu);border-top:1px solid var(--line)}
+ table{border-collapse:collapse;width:100%;font-size:13px;margin-top:10px}
+ th,td{border-bottom:1px solid var(--line);padding:7px 10px;text-align:left;vertical-align:top}
+ th{color:var(--mu);font-weight:500} td.n{text-align:right;font-variant-numeric:tabular-nums}
+ td.d{color:var(--mu);font-size:12px}
+ .wrap{overflow-x:auto}
+</style>
+<header>
+ <h1>The offer — atlas of every state</h1>
+ <p>Every state of the object-driven tool offer, generated from
+ <code>docs/ux/tool_atlas.json</code>. The invariant under test: a verb has one address, that
+ address is the same in every selection where it appears, and slots that do not apply are drawn
+ empty rather than compacted.</p>
+ <div class="stats">
+  <div class="stat"><b>60</b><span>verbs mapped</span></div>
+  <div class="stat"><b>20</b><span>selection kinds</span></div>
+  <div class="stat"><b>40</b><span>primary rings</span></div>
+  <div class="stat"><b>73</b><span>secondary rings</span></div>
+  <div class="stat"><b>113</b><span>states total</span></div>
+  <div class="stat"><b>3.5/8</b><span>mean slots filled</span></div>
+  <div class="stat"><b>5</b><span>verbs with no GUI yet</span></div>
+ </div>
+</header>
+<main>
+ <h2>Decision 0 — ring or vertical list</h2>
+ <p>The live question. Both forms carry the SAME map and the same invariant — fixed order, never
+ re-sorted, nothing compacted; only the geometry differs. Left-click selects; right-click opens the
+ offer. What the list buys: a disabled row can state its own reason in the words the product
+ already ships, where an empty slot in a ring is mute; nine sketch primitives fit without an
+ overflow; shortcuts line up in a readable column; long translated names fit; and it is navigable
+ by arrow key and by screen reader, which a radial is not. What it costs: no equidistant flick
+ gesture, and travel to the last row is longer than to the nearest direction. Pairs below —
+ list first, the same state as a ring second.</p>
+
+ <h2>Decision 1 — ring capacity</h2>
+ <p>The same three selections at eight and at twelve. Eight keeps 45° between neighbours, which is
+ the reliable eyes-free pointing threshold and maps 1:1 to the numpad; twelve buys direct addresses
+ for more verbs at 30° spacing and positions that stop being nameable.</p>
+ <div class="grid"><figure><img src="mockups/cmp_8__face_planar.svg" loading="lazy"><figcaption>8 slots — face_planar</figcaption></figure><figure><img src="mockups/cmp_8__edge_str.svg" loading="lazy"><figcaption>8 slots — edge_str</figcaption></figure><figure><img src="mockups/cmp_8__sk_line.svg" loading="lazy"><figcaption>8 slots — sk_line</figcaption></figure></div>
+ <div class="grid" style="margin-top:18px"><figure><img src="mockups/cmp_12__face_planar.svg" loading="lazy"><figcaption>12 slots — face_planar</figcaption></figure><figure><img src="mockups/cmp_12__edge_str.svg" loading="lazy"><figcaption>12 slots — edge_str</figcaption></figure><figure><img src="mockups/cmp_12__sk_line.svg" loading="lazy"><figcaption>12 slots — sk_line</figcaption></figure></div>
+
+ <h2>Decision 2 — one map or one per mode</h2>
+ <p>These renders use ONE shared map: sketch verbs occupy the same eight families as model verbs,
+ so dress-up is south-east whether you picked a solid edge or a sketch line. Compare the sketch-mode
+ states below against the model-mode ones — if a verb that exists in both modes ever appears at two
+ addresses, the shared map has failed and the split map is the answer.</p>
+
+ <h2>The matrix — every selection, every document state</h2>
+ <div class="wrap"><table>
+  <tr><th>Selection</th><th>Document</th><th>Verbs</th><th>Slots</th><th>2nd rings</th><th>What lands where</th></tr>
+  <tr><td>Nothing selected</td><td>Working document</td><td class="n">5</td><td class="n">2/8</td><td class="n">1</td><td class="d">create: Sketch · reference: Plane, Axis, Coord Sys, Helix</td></tr><tr><td>Planar face</td><td>Working document</td><td class="n">18</td><td class="n">8/8</td><td class="n">6</td><td class="d">create: Sketch · add: Extrude, Thicken · remove: Hole, Shell · dressup: Fillet, Chamfer, Draft · repeat: Pattern · transform: Mate, Align to · reference: Plane, Axis, Coord Sys, Project, Measure · modify: Edit, Delete Face</td></tr><tr><td>Cylindrical face</td><td>Working document</td><td class="n">6</td><td class="n">3/8</td><td class="n">2</td><td class="d">remove: Thread · reference: Axis, Helix, Measure · modify: Edit, Delete Face</td></tr><tr><td>Curved face</td><td>Working document</td><td class="n">5</td><td class="n">4/8</td><td class="n">1</td><td class="d">add: Thicken · dressup: Draft · reference: Measure · modify: Edit, Delete Face</td></tr><tr><td>Straight edge</td><td>Working document</td><td class="n">6</td><td class="n">3/8</td><td class="n">2</td><td class="d">dressup: Fillet, Chamfer · repeat: Pattern on Curve · reference: Plane, Axis, Measure</td></tr><tr><td>Circular edge</td><td>Working document</td><td class="n">4</td><td class="n">3/8</td><td class="n">1</td><td class="d">remove: Thread · dressup: Fillet, Chamfer · reference: Measure</td></tr><tr><td>Vertex</td><td>Working document</td><td class="n">4</td><td class="n">1/8</td><td class="n">1</td><td class="d">reference: Plane, Axis, Coord Sys, Measure</td></tr><tr><td>Solid body</td><td>Working document</td><td class="n">15</td><td class="n">6/8</td><td class="n">5</td><td class="d">remove: Shell, Cut, Split · dressup: Fillet, Chamfer · repeat: Pattern, Mirror, Pattern on Curve · transform: Move · reference: Project, Measure, Mass · modify: Edit, Colour, Delete</td></tr><tr><td>Sheet body</td><td>Working document</td><td class="n">7</td><td class="n">5/8</td><td class="n">1</td><td class="d">add: Thicken Surface · dressup: Surface Offset · transform: Move · reference: Measure · modify: Edit, Colour, Delete</td></tr><tr><td>Two bodies</td><td>Working document</td><td class="n">5</td><td class="n">4/8</td><td class="n">1</td><td class="d">add: Combine · transform: Mate · reference: Measure, Interference · modify: Delete</td></tr><tr><td>Datum plane</td><td>Working document</td><td class="n">9</td><td class="n">5/8</td><td class="n">3</td><td class="d">create: Sketch · remove: Hole, Cut · repeat: Mirror · reference: Plane, Helix, Project · modify: Edit, Delete</td></tr><tr><td>Datum axis</td><td>Working document</td><td class="n">2</td><td class="n">1/8</td><td class="n">1</td><td class="d">modify: Edit, Delete</td></tr><tr><td>Coordinate system</td><td>Working document</td><td class="n">3</td><td class="n">2/8</td><td class="n">1</td><td class="d">transform: Mate · modify: Edit, Delete</td></tr><tr><td>Text / imported art</td><td>Working document</td><td class="n">4</td><td class="n">3/8</td><td class="n">1</td><td class="d">repeat: Pattern · transform: Move · modify: Edit, Delete</td></tr><tr><td>Closed sketch loop</td><td>Working document</td><td class="n">11</td><td class="n">3/8</td><td class="n">2</td><td class="d">add: Extrude, Revolve, Sweep, Loft, Surface Extrude, Surface Revolve, Surface Loft, Surface Fill · repeat: Pattern · modify: Edit, Delete</td></tr><tr><td>Sketch, nothing picked</td><td>Working document</td><td class="n">11</td><td class="n">2/8</td><td class="n">2</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · reference: Dimension, Construction</td></tr><tr><td>Sketch line</td><td>Working document</td><td class="n">20</td><td class="n">8/8</td><td class="n">4</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · add: Offset · remove: Trim · dressup: Fillet, Chamfer · repeat: Mirror · transform: Move · reference: Dimension, Constrain, Construction · modify: Extend, Delete</td></tr><tr><td>Sketch arc or circle</td><td>Working document</td><td class="n">18</td><td class="n">7/8</td><td class="n">3</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · add: Offset · remove: Trim · repeat: Mirror · transform: Move · reference: Dimension, Constrain, Construction · modify: Extend, Delete</td></tr><tr><td>Sketch point</td><td>Working document</td><td class="n">13</td><td class="n">4/8</td><td class="n">2</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · transform: Move · reference: Dimension, Constrain · modify: Delete</td></tr><tr><td>Two sketch entities</td><td>Working document</td><td class="n">20</td><td class="n">8/8</td><td class="n">4</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · add: Offset · remove: Trim · dressup: Fillet, Chamfer · repeat: Mirror · transform: Move · reference: Dimension, Constrain, Construction · modify: Extend, Delete</td></tr><tr><td>Nothing selected</td><td>Fresh document</td><td class="n">5</td><td class="n">2/8</td><td class="n">1</td><td class="d">create: Sketch · reference: Plane, Axis, Coord Sys, Helix</td></tr><tr><td>Planar face</td><td>Fresh document</td><td class="n">7</td><td class="n">4/8</td><td class="n">1</td><td class="d">create: Sketch · add: Extrude · reference: Plane, Axis, Coord Sys, Measure · modify: Edit</td></tr><tr><td>Cylindrical face</td><td>Fresh document</td><td class="n">4</td><td class="n">2/8</td><td class="n">1</td><td class="d">reference: Axis, Helix, Measure · modify: Edit</td></tr><tr><td>Curved face</td><td>Fresh document</td><td class="n">2</td><td class="n">2/8</td><td class="n">0</td><td class="d">reference: Measure · modify: Edit</td></tr><tr><td>Straight edge</td><td>Fresh document</td><td class="n">3</td><td class="n">1/8</td><td class="n">1</td><td class="d">reference: Plane, Axis, Measure</td></tr><tr><td>Circular edge</td><td>Fresh document</td><td class="n">1</td><td class="n">1/8</td><td class="n">0</td><td class="d">reference: Measure</td></tr><tr><td>Vertex</td><td>Fresh document</td><td class="n">4</td><td class="n">1/8</td><td class="n">1</td><td class="d">reference: Plane, Axis, Coord Sys, Measure</td></tr><tr><td>Solid body</td><td>Fresh document</td><td class="n">3</td><td class="n">2/8</td><td class="n">1</td><td class="d">reference: Measure · modify: Edit, Delete</td></tr><tr><td>Sheet body</td><td>Fresh document</td><td class="n">3</td><td class="n">2/8</td><td class="n">1</td><td class="d">reference: Measure · modify: Edit, Delete</td></tr><tr><td>Two bodies</td><td>Fresh document</td><td class="n">2</td><td class="n">2/8</td><td class="n">0</td><td class="d">reference: Measure · modify: Delete</td></tr><tr><td>Datum plane</td><td>Fresh document</td><td class="n">5</td><td class="n">3/8</td><td class="n">2</td><td class="d">create: Sketch · reference: Plane, Helix · modify: Edit, Delete</td></tr><tr><td>Datum axis</td><td>Fresh document</td><td class="n">2</td><td class="n">1/8</td><td class="n">1</td><td class="d">modify: Edit, Delete</td></tr><tr><td>Coordinate system</td><td>Fresh document</td><td class="n">2</td><td class="n">1/8</td><td class="n">1</td><td class="d">modify: Edit, Delete</td></tr><tr><td>Text / imported art</td><td>Fresh document</td><td class="n">2</td><td class="n">1/8</td><td class="n">1</td><td class="d">modify: Edit, Delete</td></tr><tr><td>Closed sketch loop</td><td>Fresh document</td><td class="n">7</td><td class="n">2/8</td><td class="n">2</td><td class="d">add: Extrude, Revolve, Surface Extrude, Surface Revolve, Surface Fill · modify: Edit, Delete</td></tr><tr><td>Sketch, nothing picked</td><td>Fresh document</td><td class="n">11</td><td class="n">2/8</td><td class="n">2</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · reference: Dimension, Construction</td></tr><tr><td>Sketch line</td><td>Fresh document</td><td class="n">20</td><td class="n">8/8</td><td class="n">4</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · add: Offset · remove: Trim · dressup: Fillet, Chamfer · repeat: Mirror · transform: Move · reference: Dimension, Constrain, Construction · modify: Extend, Delete</td></tr><tr><td>Sketch arc or circle</td><td>Fresh document</td><td class="n">18</td><td class="n">7/8</td><td class="n">3</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · add: Offset · remove: Trim · repeat: Mirror · transform: Move · reference: Dimension, Constrain, Construction · modify: Extend, Delete</td></tr><tr><td>Sketch point</td><td>Fresh document</td><td class="n">13</td><td class="n">4/8</td><td class="n">2</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · transform: Move · reference: Dimension, Constrain · modify: Delete</td></tr><tr><td>Two sketch entities</td><td>Fresh document</td><td class="n">20</td><td class="n">8/8</td><td class="n">4</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · add: Offset · remove: Trim · dressup: Fillet, Chamfer · repeat: Mirror · transform: Move · reference: Dimension, Constrain, Construction · modify: Extend, Delete</td></tr>
+ </table></div>
+
+ <h2>Overflow — the one place eight slots is not enough</h2>
+ <p>Measured, not predicted: the <b>create</b> sub-ring needs 10 addresses, so Polygon, Point are pushed behind a “More” slot. This is the decision the ring size actually turns on — either a verb moves to another family, or the tail goes to a third level, or the ring is not eight. It affects sketch mode only; every model-mode family fits.</p>
+
+ <h2>Not in the offer</h2>
+ <p>Import STEP, Import mesh, Text, SVG, Export STEP, Commit to Plate, Undo, Redo, Variables, Section view, Origin planes, World axes — these act on the document, not on a selection,
+ so they stay in chrome. Verbs with kernel support but no GUI today, which still hold an address:
+ Split, Pattern on Curve, Align to, Measure, Interference.</p>
+
+ <h2>All states</h2>
+ <div class="grid"><figure><img src="mockups/rich__none.svg" alt="Nothing selected — Working document" loading="lazy"><figcaption>Nothing selected — Working document</figcaption></figure><figure><img src="mockups/rich__none__reference.svg" alt="Nothing selected — Reference ring" loading="lazy"><figcaption>Nothing selected — Reference ring</figcaption></figure><figure><img src="mockups/rich__face_planar.svg" alt="Planar face — Working document" loading="lazy"><figcaption>Planar face — Working document</figcaption></figure><figure><img src="mockups/rich__face_planar__add.svg" alt="Planar face — Add material ring" loading="lazy"><figcaption>Planar face — Add material ring</figcaption></figure><figure><img src="mockups/rich__face_planar__remove.svg" alt="Planar face — Remove ring" loading="lazy"><figcaption>Planar face — Remove ring</figcaption></figure><figure><img src="mockups/rich__face_planar__dressup.svg" alt="Planar face — Dress-up ring" loading="lazy"><figcaption>Planar face — Dress-up ring</figcaption></figure><figure><img src="mockups/rich__face_planar__transform.svg" alt="Planar face — Transform ring" loading="lazy"><figcaption>Planar face — Transform ring</figcaption></figure><figure><img src="mockups/rich__face_planar__reference.svg" alt="Planar face — Reference ring" loading="lazy"><figcaption>Planar face — Reference ring</figcaption></figure><figure><img src="mockups/rich__face_planar__modify.svg" alt="Planar face — Modify ring" loading="lazy"><figcaption>Planar face — Modify ring</figcaption></figure><figure><img src="mockups/rich__face_cyl.svg" alt="Cylindrical face — Working document" loading="lazy"><figcaption>Cylindrical face — Working document</figcaption></figure><figure><img src="mockups/rich__face_cyl__reference.svg" alt="Cylindrical face — Reference ring" loading="lazy"><figcaption>Cylindrical face — Reference ring</figcaption></figure><figure><img src="mockups/rich__face_cyl__modify.svg" alt="Cylindrical face — Modify ring" loading="lazy"><figcaption>Cylindrical face — Modify ring</figcaption></figure><figure><img src="mockups/rich__face_other.svg" alt="Curved face — Working document" loading="lazy"><figcaption>Curved face — Working document</figcaption></figure><figure><img src="mockups/rich__face_other__modify.svg" alt="Curved face — Modify ring" loading="lazy"><figcaption>Curved face — Modify ring</figcaption></figure><figure><img src="mockups/rich__edge_str.svg" alt="Straight edge — Working document" loading="lazy"><figcaption>Straight edge — Working document</figcaption></figure><figure><img src="mockups/rich__edge_str__dressup.svg" alt="Straight edge — Dress-up ring" loading="lazy"><figcaption>Straight edge — Dress-up ring</figcaption></figure><figure><img src="mockups/rich__edge_str__reference.svg" alt="Straight edge — Reference ring" loading="lazy"><figcaption>Straight edge — Reference ring</figcaption></figure><figure><img src="mockups/rich__edge_circ.svg" alt="Circular edge — Working document" loading="lazy"><figcaption>Circular edge — Working document</figcaption></figure><figure><img src="mockups/rich__edge_circ__dressup.svg" alt="Circular edge — Dress-up ring" loading="lazy"><figcaption>Circular edge — Dress-up ring</figcaption></figure><figure><img src="mockups/rich__vertex.svg" alt="Vertex — Working document" loading="lazy"><figcaption>Vertex — Working document</figcaption></figure><figure><img src="mockups/rich__vertex__reference.svg" alt="Vertex — Reference ring" loading="lazy"><figcaption>Vertex — Reference ring</figcaption></figure><figure><img src="mockups/rich__body_solid.svg" alt="Solid body — Working document" loading="lazy"><figcaption>Solid body — Working document</figcaption></figure><figure><img src="mockups/rich__body_solid__remove.svg" alt="Solid body — Remove ring" loading="lazy"><figcaption>Solid body — Remove ring</figcaption></figure><figure><img src="mockups/rich__body_solid__dressup.svg" alt="Solid body — Dress-up ring" loading="lazy"><figcaption>Solid body — Dress-up ring</figcaption></figure><figure><img src="mockups/rich__body_solid__repeat.svg" alt="Solid body — Repeat ring" loading="lazy"><figcaption>Solid body — Repeat ring</figcaption></figure><figure><img src="mockups/rich__body_solid__reference.svg" alt="Solid body — Reference ring" loading="lazy"><figcaption>Solid body — Reference ring</figcaption></figure><figure><img src="mockups/rich__body_solid__modify.svg" alt="Solid body — Modify ring" loading="lazy"><figcaption>Solid body — Modify ring</figcaption></figure><figure><img src="mockups/rich__body_sheet.svg" alt="Sheet body — Working document" loading="lazy"><figcaption>Sheet body — Working document</figcaption></figure><figure><img src="mockups/rich__body_sheet__modify.svg" alt="Sheet body — Modify ring" loading="lazy"><figcaption>Sheet body — Modify ring</figcaption></figure><figure><img src="mockups/rich__bodies_2.svg" alt="Two bodies — Working document" loading="lazy"><figcaption>Two bodies — Working document</figcaption></figure><figure><img src="mockups/rich__bodies_2__reference.svg" alt="Two bodies — Reference ring" loading="lazy"><figcaption>Two bodies — Reference ring</figcaption></figure><figure><img src="mockups/rich__datum_plane.svg" alt="Datum plane — Working document" loading="lazy"><figcaption>Datum plane — Working document</figcaption></figure><figure><img src="mockups/rich__datum_plane__remove.svg" alt="Datum plane — Remove ring" loading="lazy"><figcaption>Datum plane — Remove ring</figcaption></figure><figure><img src="mockups/rich__datum_plane__reference.svg" alt="Datum plane — Reference ring" loading="lazy"><figcaption>Datum plane — Reference ring</figcaption></figure><figure><img src="mockups/rich__datum_plane__modify.svg" alt="Datum plane — Modify ring" loading="lazy"><figcaption>Datum plane — Modify ring</figcaption></figure><figure><img src="mockups/rich__datum_axis.svg" alt="Datum axis — Working document" loading="lazy"><figcaption>Datum axis — Working document</figcaption></figure><figure><img src="mockups/rich__datum_axis__modify.svg" alt="Datum axis — Modify ring" loading="lazy"><figcaption>Datum axis — Modify ring</figcaption></figure><figure><img src="mockups/rich__coordsys.svg" alt="Coordinate system — Working document" loading="lazy"><figcaption>Coordinate system — Working document</figcaption></figure><figure><img src="mockups/rich__coordsys__modify.svg" alt="Coordinate system — Modify ring" loading="lazy"><figcaption>Coordinate system — Modify ring</figcaption></figure><figure><img src="mockups/rich__art.svg" alt="Text / imported art — Working document" loading="lazy"><figcaption>Text / imported art — Working document</figcaption></figure><figure><img src="mockups/rich__art__modify.svg" alt="Text / imported art — Modify ring" loading="lazy"><figcaption>Text / imported art — Modify ring</figcaption></figure><figure><img src="mockups/rich__sk_loop.svg" alt="Closed sketch loop — Working document" loading="lazy"><figcaption>Closed sketch loop — Working document</figcaption></figure><figure><img src="mockups/rich__sk_loop__add.svg" alt="Closed sketch loop — Add material ring" loading="lazy"><figcaption>Closed sketch loop — Add material ring</figcaption></figure><figure><img src="mockups/rich__sk_loop__modify.svg" alt="Closed sketch loop — Modify ring" loading="lazy"><figcaption>Closed sketch loop — Modify ring</figcaption></figure><figure><img src="mockups/rich__sk_none.svg" alt="Sketch, nothing picked — Working document" loading="lazy"><figcaption>Sketch, nothing picked — Working document</figcaption></figure><figure><img src="mockups/rich__sk_none__create.svg" alt="Sketch, nothing picked — Create ring" loading="lazy"><figcaption>Sketch, nothing picked — Create ring</figcaption></figure><figure><img src="mockups/rich__sk_none__reference.svg" alt="Sketch, nothing picked — Reference ring" loading="lazy"><figcaption>Sketch, nothing picked — Reference ring</figcaption></figure><figure><img src="mockups/rich__sk_line.svg" alt="Sketch line — Working document" loading="lazy"><figcaption>Sketch line — Working document</figcaption></figure><figure><img src="mockups/rich__sk_line__create.svg" alt="Sketch line — Create ring" loading="lazy"><figcaption>Sketch line — Create ring</figcaption></figure><figure><img src="mockups/rich__sk_line__dressup.svg" alt="Sketch line — Dress-up ring" loading="lazy"><figcaption>Sketch line — Dress-up ring</figcaption></figure><figure><img src="mockups/rich__sk_line__reference.svg" alt="Sketch line — Reference ring" loading="lazy"><figcaption>Sketch line — Reference ring</figcaption></figure><figure><img src="mockups/rich__sk_line__modify.svg" alt="Sketch line — Modify ring" loading="lazy"><figcaption>Sketch line — Modify ring</figcaption></figure><figure><img src="mockups/rich__sk_arc.svg" alt="Sketch arc or circle — Working document" loading="lazy"><figcaption>Sketch arc or circle — Working document</figcaption></figure><figure><img src="mockups/rich__sk_arc__create.svg" alt="Sketch arc or circle — Create ring" loading="lazy"><figcaption>Sketch arc or circle — Create ring</figcaption></figure><figure><img src="mockups/rich__sk_arc__reference.svg" alt="Sketch arc or circle — Reference ring" loading="lazy"><figcaption>Sketch arc or circle — Reference ring</figcaption></figure><figure><img src="mockups/rich__sk_arc__modify.svg" alt="Sketch arc or circle — Modify ring" loading="lazy"><figcaption>Sketch arc or circle — Modify ring</figcaption></figure><figure><img src="mockups/rich__sk_point.svg" alt="Sketch point — Working document" loading="lazy"><figcaption>Sketch point — Working document</figcaption></figure><figure><img src="mockups/rich__sk_point__create.svg" alt="Sketch point — Create ring" loading="lazy"><figcaption>Sketch point — Create ring</figcaption></figure><figure><img src="mockups/rich__sk_point__reference.svg" alt="Sketch point — Reference ring" loading="lazy"><figcaption>Sketch point — Reference ring</figcaption></figure><figure><img src="mockups/rich__sk_2ent.svg" alt="Two sketch entities — Working document" loading="lazy"><figcaption>Two sketch entities — Working document</figcaption></figure><figure><img src="mockups/rich__sk_2ent__create.svg" alt="Two sketch entities — Create ring" loading="lazy"><figcaption>Two sketch entities — Create ring</figcaption></figure><figure><img src="mockups/rich__sk_2ent__dressup.svg" alt="Two sketch entities — Dress-up ring" loading="lazy"><figcaption>Two sketch entities — Dress-up ring</figcaption></figure><figure><img src="mockups/rich__sk_2ent__reference.svg" alt="Two sketch entities — Reference ring" loading="lazy"><figcaption>Two sketch entities — Reference ring</figcaption></figure><figure><img src="mockups/rich__sk_2ent__modify.svg" alt="Two sketch entities — Modify ring" loading="lazy"><figcaption>Two sketch entities — Modify ring</figcaption></figure><figure><img src="mockups/fresh__none.svg" alt="Nothing selected — Fresh document" loading="lazy"><figcaption>Nothing selected — Fresh document</figcaption></figure><figure><img src="mockups/fresh__none__reference.svg" alt="Nothing selected — Reference ring" loading="lazy"><figcaption>Nothing selected — Reference ring</figcaption></figure><figure><img src="mockups/fresh__face_planar.svg" alt="Planar face — Fresh document" loading="lazy"><figcaption>Planar face — Fresh document</figcaption></figure><figure><img src="mockups/fresh__face_planar__reference.svg" alt="Planar face — Reference ring" loading="lazy"><figcaption>Planar face — Reference ring</figcaption></figure><figure><img src="mockups/fresh__face_cyl.svg" alt="Cylindrical face — Fresh document" loading="lazy"><figcaption>Cylindrical face — Fresh document</figcaption></figure><figure><img src="mockups/fresh__face_cyl__reference.svg" alt="Cylindrical face — Reference ring" loading="lazy"><figcaption>Cylindrical face — Reference ring</figcaption></figure><figure><img src="mockups/fresh__face_other.svg" alt="Curved face — Fresh document" loading="lazy"><figcaption>Curved face — Fresh document</figcaption></figure><figure><img src="mockups/fresh__edge_str.svg" alt="Straight edge — Fresh document" loading="lazy"><figcaption>Straight edge — Fresh document</figcaption></figure><figure><img src="mockups/fresh__edge_str__reference.svg" alt="Straight edge — Reference ring" loading="lazy"><figcaption>Straight edge — Reference ring</figcaption></figure><figure><img src="mockups/fresh__edge_circ.svg" alt="Circular edge — Fresh document" loading="lazy"><figcaption>Circular edge — Fresh document</figcaption></figure><figure><img src="mockups/fresh__vertex.svg" alt="Vertex — Fresh document" loading="lazy"><figcaption>Vertex — Fresh document</figcaption></figure><figure><img src="mockups/fresh__vertex__reference.svg" alt="Vertex — Reference ring" loading="lazy"><figcaption>Vertex — Reference ring</figcaption></figure><figure><img src="mockups/fresh__body_solid.svg" alt="Solid body — Fresh document" loading="lazy"><figcaption>Solid body — Fresh document</figcaption></figure><figure><img src="mockups/fresh__body_solid__modify.svg" alt="Solid body — Modify ring" loading="lazy"><figcaption>Solid body — Modify ring</figcaption></figure><figure><img src="mockups/fresh__body_sheet.svg" alt="Sheet body — Fresh document" loading="lazy"><figcaption>Sheet body — Fresh document</figcaption></figure><figure><img src="mockups/fresh__body_sheet__modify.svg" alt="Sheet body — Modify ring" loading="lazy"><figcaption>Sheet body — Modify ring</figcaption></figure><figure><img src="mockups/fresh__bodies_2.svg" alt="Two bodies — Fresh document" loading="lazy"><figcaption>Two bodies — Fresh document</figcaption></figure><figure><img src="mockups/fresh__datum_plane.svg" alt="Datum plane — Fresh document" loading="lazy"><figcaption>Datum plane — Fresh document</figcaption></figure><figure><img src="mockups/fresh__datum_plane__reference.svg" alt="Datum plane — Reference ring" loading="lazy"><figcaption>Datum plane — Reference ring</figcaption></figure><figure><img src="mockups/fresh__datum_plane__modify.svg" alt="Datum plane — Modify ring" loading="lazy"><figcaption>Datum plane — Modify ring</figcaption></figure><figure><img src="mockups/fresh__datum_axis.svg" alt="Datum axis — Fresh document" loading="lazy"><figcaption>Datum axis — Fresh document</figcaption></figure><figure><img src="mockups/fresh__datum_axis__modify.svg" alt="Datum axis — Modify ring" loading="lazy"><figcaption>Datum axis — Modify ring</figcaption></figure><figure><img src="mockups/fresh__coordsys.svg" alt="Coordinate system — Fresh document" loading="lazy"><figcaption>Coordinate system — Fresh document</figcaption></figure><figure><img src="mockups/fresh__coordsys__modify.svg" alt="Coordinate system — Modify ring" loading="lazy"><figcaption>Coordinate system — Modify ring</figcaption></figure><figure><img src="mockups/fresh__art.svg" alt="Text / imported art — Fresh document" loading="lazy"><figcaption>Text / imported art — Fresh document</figcaption></figure><figure><img src="mockups/fresh__art__modify.svg" alt="Text / imported art — Modify ring" loading="lazy"><figcaption>Text / imported art — Modify ring</figcaption></figure><figure><img src="mockups/fresh__sk_loop.svg" alt="Closed sketch loop — Fresh document" loading="lazy"><figcaption>Closed sketch loop — Fresh document</figcaption></figure><figure><img src="mockups/fresh__sk_loop__add.svg" alt="Closed sketch loop — Add material ring" loading="lazy"><figcaption>Closed sketch loop — Add material ring</figcaption></figure><figure><img src="mockups/fresh__sk_loop__modify.svg" alt="Closed sketch loop — Modify ring" loading="lazy"><figcaption>Closed sketch loop — Modify ring</figcaption></figure><figure><img src="mockups/fresh__sk_none.svg" alt="Sketch, nothing picked — Fresh document" loading="lazy"><figcaption>Sketch, nothing picked — Fresh document</figcaption></figure><figure><img src="mockups/fresh__sk_none__create.svg" alt="Sketch, nothing picked — Create ring" loading="lazy"><figcaption>Sketch, nothing picked — Create ring</figcaption></figure><figure><img src="mockups/fresh__sk_none__reference.svg" alt="Sketch, nothing picked — Reference ring" loading="lazy"><figcaption>Sketch, nothing picked — Reference ring</figcaption></figure><figure><img src="mockups/fresh__sk_line.svg" alt="Sketch line — Fresh document" loading="lazy"><figcaption>Sketch line — Fresh document</figcaption></figure><figure><img src="mockups/fresh__sk_line__create.svg" alt="Sketch line — Create ring" loading="lazy"><figcaption>Sketch line — Create ring</figcaption></figure><figure><img src="mockups/fresh__sk_line__dressup.svg" alt="Sketch line — Dress-up ring" loading="lazy"><figcaption>Sketch line — Dress-up ring</figcaption></figure><figure><img src="mockups/fresh__sk_line__reference.svg" alt="Sketch line — Reference ring" loading="lazy"><figcaption>Sketch line — Reference ring</figcaption></figure><figure><img src="mockups/fresh__sk_line__modify.svg" alt="Sketch line — Modify ring" loading="lazy"><figcaption>Sketch line — Modify ring</figcaption></figure><figure><img src="mockups/fresh__sk_arc.svg" alt="Sketch arc or circle — Fresh document" loading="lazy"><figcaption>Sketch arc or circle — Fresh document</figcaption></figure><figure><img src="mockups/fresh__sk_arc__create.svg" alt="Sketch arc or circle — Create ring" loading="lazy"><figcaption>Sketch arc or circle — Create ring</figcaption></figure><figure><img src="mockups/fresh__sk_arc__reference.svg" alt="Sketch arc or circle — Reference ring" loading="lazy"><figcaption>Sketch arc or circle — Reference ring</figcaption></figure><figure><img src="mockups/fresh__sk_arc__modify.svg" alt="Sketch arc or circle — Modify ring" loading="lazy"><figcaption>Sketch arc or circle — Modify ring</figcaption></figure><figure><img src="mockups/fresh__sk_point.svg" alt="Sketch point — Fresh document" loading="lazy"><figcaption>Sketch point — Fresh document</figcaption></figure><figure><img src="mockups/fresh__sk_point__create.svg" alt="Sketch point — Create ring" loading="lazy"><figcaption>Sketch point — Create ring</figcaption></figure><figure><img src="mockups/fresh__sk_point__reference.svg" alt="Sketch point — Reference ring" loading="lazy"><figcaption>Sketch point — Reference ring</figcaption></figure><figure><img src="mockups/fresh__sk_2ent.svg" alt="Two sketch entities — Fresh document" loading="lazy"><figcaption>Two sketch entities — Fresh document</figcaption></figure><figure><img src="mockups/fresh__sk_2ent__create.svg" alt="Two sketch entities — Create ring" loading="lazy"><figcaption>Two sketch entities — Create ring</figcaption></figure><figure><img src="mockups/fresh__sk_2ent__dressup.svg" alt="Two sketch entities — Dress-up ring" loading="lazy"><figcaption>Two sketch entities — Dress-up ring</figcaption></figure><figure><img src="mockups/fresh__sk_2ent__reference.svg" alt="Two sketch entities — Reference ring" loading="lazy"><figcaption>Two sketch entities — Reference ring</figcaption></figure><figure><img src="mockups/fresh__sk_2ent__modify.svg" alt="Two sketch entities — Modify ring" loading="lazy"><figcaption>Two sketch entities — Modify ring</figcaption></figure></div>
+</main>
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+<!doctype html><meta charset="utf-8"><title>Design tab — offer atlas</title>
+<style>
+ :root{color-scheme:dark;--bg:#15181c;--panel:#1c2026;--line:#2c323a;--tx:#e7ecf1;--mu:#93a0ad;--ac:#4f9bd9}
+ body{margin:0;background:var(--bg);color:var(--tx);font:15px/1.55 Inter,system-ui,sans-serif}
+ header{padding:38px 40px 22px;border-bottom:1px solid var(--line)}
+ h1{margin:0 0 6px;font-size:26px;letter-spacing:-.02em}
+ h2{margin:38px 0 12px;font-size:18px} p{color:var(--mu);max-width:78ch}
+ main{padding:0 40px 60px}
+ .stats{display:flex;gap:14px;flex-wrap:wrap;margin:18px 0 6px}
+ .stat{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:12px 16px;min-width:130px}
+ .stat b{display:block;font-size:24px} .stat span{color:var(--mu);font-size:12px}
+ .grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(430px,1fr));gap:18px}
+ figure{margin:0;background:var(--panel);border:1px solid var(--line);border-radius:12px;overflow:hidden}
+ figure img{width:100%;display:block}
+ figcaption{padding:9px 13px;font-size:13px;color:var(--mu);border-top:1px solid var(--line)}
+ table{border-collapse:collapse;width:100%;font-size:13px;margin-top:10px}
+ th,td{border-bottom:1px solid var(--line);padding:7px 10px;text-align:left;vertical-align:top}
+ th{color:var(--mu);font-weight:500} td.n{text-align:right;font-variant-numeric:tabular-nums}
+ td.d{color:var(--mu);font-size:12px}
+ .wrap{overflow-x:auto}
+</style>
+<header>
+ <h1>The offer — atlas of every state</h1>
+ <p>Every state of the object-driven tool offer, generated from
+ <code>docs/ux/tool_atlas.json</code>. The invariant under test: a verb has one address, that
+ address is the same in every selection where it appears, and slots that do not apply are drawn
+ empty rather than compacted.</p>
+ <div class="stats">
+  <div class="stat"><b>60</b><span>verbs mapped</span></div>
+  <div class="stat"><b>20</b><span>selection kinds</span></div>
+  <div class="stat"><b>40</b><span>primary rings</span></div>
+  <div class="stat"><b>73</b><span>secondary rings</span></div>
+  <div class="stat"><b>113</b><span>states total</span></div>
+  <div class="stat"><b>3.5/8</b><span>mean slots filled</span></div>
+  <div class="stat"><b>5</b><span>verbs with no GUI yet</span></div>
+ </div>
+</header>
+<main>
+ <h2>Decision 0 — ring or vertical list</h2>
+ <p>The live question. Both forms carry the SAME map and the same invariant — fixed order, never
+ re-sorted, nothing compacted; only the geometry differs. Left-click selects; right-click opens the
+ offer. What the list buys: a disabled row can state its own reason in the words the product
+ already ships, where an empty slot in a ring is mute; nine sketch primitives fit without an
+ overflow; shortcuts line up in a readable column; long translated names fit; and it is navigable
+ by arrow key and by screen reader, which a radial is not. What it costs: no equidistant flick
+ gesture, and travel to the last row is longer than to the nearest direction. Pairs below —
+ list first, the same state as a ring second.</p>
+
+ <h2>Decision 1 — ring capacity</h2>
+ <p>The same three selections at eight and at twelve. Eight keeps 45° between neighbours, which is
+ the reliable eyes-free pointing threshold and maps 1:1 to the numpad; twelve buys direct addresses
+ for more verbs at 30° spacing and positions that stop being nameable.</p>
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stroke-linejoin="round"><rect x="-8" y="2" width="16" height="6" rx="1"/><path d="M0 0 L0 -8 M-4 -4 L0 -8 L4 -4"/></g><text x="46" y="280" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Extrude2</text><rect y="738" width="1366" height="30" fill="#23272d"/><text x="18" y="758" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Straight edge selected — pick what to do with it</text><text x="1348" y="758" text-anchor="end" font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" fill="#5f6a76">Working document · 8 slots</text><polygon points="629.1,360.5 759.0,435.5 759.0,487.5 629.1,412.5" fill="#6f7b89" stroke="#39414b" stroke-width="1"/><polygon points="849.9,383.0 759.0,435.5 759.0,487.5 849.9,435.0" fill="#5a6472" stroke="#39414b" stroke-width="1"/><polygon points="720.0,308.0 849.9,383.0 759.0,435.5 629.1,360.5" fill="#93a1b1" stroke="#39414b" stroke-width="1"/><line x1="629.1" y1="360.5" x2="759.0" y2="435.5" stroke="#f5a623" 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font-family="Inter,DejaVu Sans,sans-serif" font-size="11" font-weight="600" fill="#0f1319">3</text><rect x="593.0" y="446.0" width="60" height="60" rx="14" fill="#2e343c" stroke="#3c444e"/><g transform="translate(623.0,474.0) scale(0.920)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><rect x="-10" y="-2" width="13" height="11" rx="1" fill="none"/><path d="M-2 5 L0 4.5 L9 -5 L7 -7 L-2.5 2.5 Z"/></g><text x="623.0" y="524.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" font-weight="500" fill="#e7ecf1">Modify</text><circle cx="645.0" cy="454.0" r="10" fill="#4f9bd9"/><text x="645.0" y="458.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="11" font-weight="600" fill="#0f1319">2</text><circle cx="574.0" cy="427.0" r="21" fill="#2a2f36" opacity="0.5" stroke="#3c444e" stroke-dasharray="3 3"/><circle cx="556.0" cy="360.0" r="21" fill="#2a2f36" opacity="0.5" stroke="#3c444e" stroke-dasharray="3 3"/><circle cx="574.0" cy="293.0" r="21" fill="#2a2f36" opacity="0.5" stroke="#3c444e" stroke-dasharray="3 3"/><circle cx="623.0" cy="244.0" r="21" fill="#2a2f36" opacity="0.5" stroke="#3c444e" stroke-dasharray="3 3"/><rect x="645.5" y="392.0" width="88.9" height="22" rx="11" fill="#171a1e" opacity="0.92" stroke="#3c444e"/><text x="690.0" y="407.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="12" fill="#e7ecf1">Sketch line</text></svg><figcaption>12 slots — sk_line</figcaption></figure></div>
+
+ <h2>Decision 2 — one map or one per mode</h2>
+ <p>These renders use ONE shared map: sketch verbs occupy the same eight families as model verbs,
+ so dress-up is south-east whether you picked a solid edge or a sketch line. Compare the sketch-mode
+ states below against the model-mode ones — if a verb that exists in both modes ever appears at two
+ addresses, the shared map has failed and the split map is the answer.</p>
+
+ <h2>The matrix — every selection, every document state</h2>
+ <div class="wrap"><table>
+  <tr><th>Selection</th><th>Document</th><th>Verbs</th><th>Slots</th><th>2nd rings</th><th>What lands where</th></tr>
+  <tr><td>Nothing selected</td><td>Working document</td><td class="n">5</td><td class="n">2/8</td><td class="n">1</td><td class="d">create: Sketch · reference: Plane, Axis, Coord Sys, Helix</td></tr><tr><td>Planar face</td><td>Working document</td><td class="n">18</td><td class="n">8/8</td><td class="n">6</td><td class="d">create: Sketch · add: Extrude, Thicken · remove: Hole, Shell · dressup: Fillet, Chamfer, Draft · repeat: Pattern · transform: Mate, Align to · reference: Plane, Axis, Coord Sys, Project, Measure · modify: Edit, Delete Face</td></tr><tr><td>Cylindrical face</td><td>Working document</td><td class="n">6</td><td class="n">3/8</td><td class="n">2</td><td class="d">remove: Thread · reference: Axis, Helix, Measure · modify: Edit, Delete Face</td></tr><tr><td>Curved face</td><td>Working document</td><td class="n">5</td><td class="n">4/8</td><td class="n">1</td><td class="d">add: Thicken · dressup: Draft · reference: Measure · modify: Edit, Delete Face</td></tr><tr><td>Straight edge</td><td>Working document</td><td class="n">6</td><td class="n">3/8</td><td class="n">2</td><td class="d">dressup: Fillet, Chamfer · repeat: Pattern on Curve · reference: Plane, Axis, Measure</td></tr><tr><td>Circular edge</td><td>Working document</td><td class="n">4</td><td class="n">3/8</td><td class="n">1</td><td class="d">remove: Thread · dressup: Fillet, Chamfer · reference: Measure</td></tr><tr><td>Vertex</td><td>Working document</td><td class="n">4</td><td class="n">1/8</td><td class="n">1</td><td class="d">reference: Plane, Axis, Coord Sys, Measure</td></tr><tr><td>Solid body</td><td>Working document</td><td class="n">15</td><td class="n">6/8</td><td class="n">5</td><td class="d">remove: Shell, Cut, Split · dressup: Fillet, Chamfer · repeat: Pattern, Mirror, Pattern on Curve · transform: Move · reference: Project, Measure, Mass · modify: Edit, Colour, Delete</td></tr><tr><td>Sheet body</td><td>Working document</td><td class="n">7</td><td class="n">5/8</td><td class="n">1</td><td class="d">add: Thicken Surface · dressup: Surface Offset · transform: Move · reference: Measure · modify: Edit, Colour, Delete</td></tr><tr><td>Two bodies</td><td>Working document</td><td class="n">5</td><td class="n">4/8</td><td class="n">1</td><td class="d">add: Combine · transform: Mate · reference: Measure, Interference · modify: Delete</td></tr><tr><td>Datum plane</td><td>Working document</td><td class="n">9</td><td class="n">5/8</td><td class="n">3</td><td class="d">create: Sketch · remove: Hole, Cut · repeat: Mirror · reference: Plane, Helix, Project · modify: Edit, Delete</td></tr><tr><td>Datum axis</td><td>Working document</td><td class="n">2</td><td class="n">1/8</td><td class="n">1</td><td class="d">modify: Edit, Delete</td></tr><tr><td>Coordinate system</td><td>Working document</td><td class="n">3</td><td class="n">2/8</td><td class="n">1</td><td class="d">transform: Mate · modify: Edit, Delete</td></tr><tr><td>Text / imported art</td><td>Working document</td><td class="n">4</td><td class="n">3/8</td><td class="n">1</td><td class="d">repeat: Pattern · transform: Move · modify: Edit, Delete</td></tr><tr><td>Closed sketch loop</td><td>Working document</td><td class="n">11</td><td class="n">3/8</td><td class="n">2</td><td class="d">add: Extrude, Revolve, Sweep, Loft, Surface Extrude, Surface Revolve, Surface Loft, Surface Fill · repeat: Pattern · modify: Edit, Delete</td></tr><tr><td>Sketch, nothing picked</td><td>Working document</td><td class="n">11</td><td class="n">2/8</td><td class="n">2</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · reference: Dimension, Construction</td></tr><tr><td>Sketch line</td><td>Working document</td><td class="n">20</td><td class="n">8/8</td><td class="n">4</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · add: Offset · remove: Trim · dressup: Fillet, Chamfer · repeat: Mirror · transform: Move · reference: Dimension, Constrain, Construction · modify: Extend, Delete</td></tr><tr><td>Sketch arc or circle</td><td>Working document</td><td class="n">18</td><td class="n">7/8</td><td class="n">3</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · add: Offset · remove: Trim · repeat: Mirror · transform: Move · reference: Dimension, Constrain, Construction · modify: Extend, Delete</td></tr><tr><td>Sketch point</td><td>Working document</td><td class="n">13</td><td class="n">4/8</td><td class="n">2</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · transform: Move · reference: Dimension, Constrain · modify: Delete</td></tr><tr><td>Two sketch entities</td><td>Working document</td><td class="n">20</td><td class="n">8/8</td><td class="n">4</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · add: Offset · remove: Trim · dressup: Fillet, Chamfer · repeat: Mirror · transform: Move · reference: Dimension, Constrain, Construction · modify: Extend, Delete</td></tr><tr><td>Nothing selected</td><td>Fresh document</td><td class="n">5</td><td class="n">2/8</td><td class="n">1</td><td class="d">create: Sketch · reference: Plane, Axis, Coord Sys, Helix</td></tr><tr><td>Planar face</td><td>Fresh document</td><td class="n">7</td><td class="n">4/8</td><td class="n">1</td><td class="d">create: Sketch · add: Extrude · reference: Plane, Axis, Coord Sys, Measure · modify: Edit</td></tr><tr><td>Cylindrical face</td><td>Fresh document</td><td class="n">4</td><td class="n">2/8</td><td class="n">1</td><td class="d">reference: Axis, Helix, Measure · modify: Edit</td></tr><tr><td>Curved face</td><td>Fresh document</td><td class="n">2</td><td class="n">2/8</td><td class="n">0</td><td class="d">reference: Measure · modify: Edit</td></tr><tr><td>Straight edge</td><td>Fresh document</td><td class="n">3</td><td class="n">1/8</td><td class="n">1</td><td class="d">reference: Plane, Axis, Measure</td></tr><tr><td>Circular edge</td><td>Fresh document</td><td class="n">1</td><td class="n">1/8</td><td class="n">0</td><td class="d">reference: Measure</td></tr><tr><td>Vertex</td><td>Fresh document</td><td class="n">4</td><td class="n">1/8</td><td class="n">1</td><td class="d">reference: Plane, Axis, Coord Sys, Measure</td></tr><tr><td>Solid body</td><td>Fresh document</td><td class="n">3</td><td class="n">2/8</td><td class="n">1</td><td class="d">reference: Measure · modify: Edit, Delete</td></tr><tr><td>Sheet body</td><td>Fresh document</td><td class="n">3</td><td class="n">2/8</td><td class="n">1</td><td class="d">reference: Measure · modify: Edit, Delete</td></tr><tr><td>Two bodies</td><td>Fresh document</td><td class="n">2</td><td class="n">2/8</td><td class="n">0</td><td class="d">reference: Measure · modify: Delete</td></tr><tr><td>Datum plane</td><td>Fresh document</td><td class="n">5</td><td class="n">3/8</td><td class="n">2</td><td class="d">create: Sketch · reference: Plane, Helix · modify: Edit, Delete</td></tr><tr><td>Datum axis</td><td>Fresh document</td><td class="n">2</td><td class="n">1/8</td><td class="n">1</td><td class="d">modify: Edit, Delete</td></tr><tr><td>Coordinate system</td><td>Fresh document</td><td class="n">2</td><td class="n">1/8</td><td class="n">1</td><td class="d">modify: Edit, Delete</td></tr><tr><td>Text / imported art</td><td>Fresh document</td><td class="n">2</td><td class="n">1/8</td><td class="n">1</td><td class="d">modify: Edit, Delete</td></tr><tr><td>Closed sketch loop</td><td>Fresh document</td><td class="n">7</td><td class="n">2/8</td><td class="n">2</td><td class="d">add: Extrude, Revolve, Surface Extrude, Surface Revolve, Surface Fill · modify: Edit, Delete</td></tr><tr><td>Sketch, nothing picked</td><td>Fresh document</td><td class="n">11</td><td class="n">2/8</td><td class="n">2</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · reference: Dimension, Construction</td></tr><tr><td>Sketch line</td><td>Fresh document</td><td class="n">20</td><td class="n">8/8</td><td class="n">4</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · add: Offset · remove: Trim · dressup: Fillet, Chamfer · repeat: Mirror · transform: Move · reference: Dimension, Constrain, Construction · modify: Extend, Delete</td></tr><tr><td>Sketch arc or circle</td><td>Fresh document</td><td class="n">18</td><td class="n">7/8</td><td class="n">3</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · add: Offset · remove: Trim · repeat: Mirror · transform: Move · reference: Dimension, Constrain, Construction · modify: Extend, Delete</td></tr><tr><td>Sketch point</td><td>Fresh document</td><td class="n">13</td><td class="n">4/8</td><td class="n">2</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · transform: Move · reference: Dimension, Constrain · modify: Delete</td></tr><tr><td>Two sketch entities</td><td>Fresh document</td><td class="n">20</td><td class="n">8/8</td><td class="n">4</td><td class="d">create: Line, Rectangle, Circle, Arc, Slot, Ellipse, Spline, Polygon, Point · add: Offset · remove: Trim · dressup: Fillet, Chamfer · repeat: Mirror · transform: Move · reference: Dimension, Constrain, Construction · modify: Extend, Delete</td></tr>
+ </table></div>
+
+ <h2>Overflow — the one place eight slots is not enough</h2>
+ <p>Measured, not predicted: the <b>create</b> sub-ring needs 10 addresses, so Polygon, Point are pushed behind a “More” slot. This is the decision the ring size actually turns on — either a verb moves to another family, or the tail goes to a third level, or the ring is not eight. It affects sketch mode only; every model-mode family fits.</p>
+
+ <h2>Not in the offer</h2>
+ <p>Import STEP, Import mesh, Text, SVG, Export STEP, Commit to Plate, Undo, Redo, Variables, Section view, Origin planes, World axes — these act on the document, not on a selection,
+ so they stay in chrome. Verbs with kernel support but no GUI today, which still hold an address:
+ Split, Pattern on Curve, Align to, Measure, Interference.</p>
+
+ <h2>The states</h2>
+<div class="grid"><figure><svg style="width:100%;height:auto;display:block" xmlns="http://www.w3.org/2000/svg" width="1366" height="768" viewBox="0 0 1366 768"><rect width="1366" height="768" fill="#1a1d21"/><defs><radialGradient id="vp" cx="50%" cy="42%" r="75%"><stop offset="0%" stop-color="#2f353d"/><stop offset="100%" stop-color="#242930"/></radialGradient></defs><rect x="248" y="92" width="1118" height="646" fill="url(#vp)"/><rect width="1366" height="44" fill="#23272d"/><text x="24" y="28" font-family="Inter,DejaVu Sans,sans-serif" font-size="14" font-weight="400" fill="#5f6a76">Prepare</text><text x="121" y="28" font-family="Inter,DejaVu Sans,sans-serif" font-size="14" font-weight="400" fill="#5f6a76">Preview</text><text x="218" y="28" font-family="Inter,DejaVu Sans,sans-serif" font-size="14" font-weight="600" fill="#e7ecf1">Design</text><rect x="214" y="38" width="56" height="3" rx="1.5" fill="#4f9bd9"/><rect y="44" width="1366" height="48" fill="#20242a"/><line x1="0" y1="92" 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font-family="Inter,DejaVu Sans,sans-serif" font-size="13.5" fill="#e7ecf1">Repeat</text><path d="M965.9185842870421 553.5 L970.9185842870421 558.5 L965.9185842870421 563.5" fill="none" stroke="#8e9aa7" stroke-width="1.6" stroke-linecap="round"/><text x="951.9185842870421" y="562.5" text-anchor="end" font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" fill="#5f6a76">3</text></g><g opacity="1"><g transform="translate(691.9,592.5) scale(0.720)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M0 -10 L0 10 M-10 0 L10 0"/><path d="M0 -10 L-3 -6 M0 -10 L3 -6 M0 10 L-3 6 M0 10 L3 6 M-10 0 L-6 -3 M-10 0 L-6 3 M10 0 L6 -3 M10 0 L6 3"/></g><text x="713.9185842870421" y="597.0" font-family="Inter,DejaVu Sans,sans-serif" font-size="13.5" fill="#e7ecf1">Move</text><rect x="912.7" y="583.5" width="59.2" height="18" rx="4.5" fill="#454f5b"/><text x="942.3" y="596.5" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="10.5" fill="#e7ecf1">Shift+Y</text></g><g opacity="1"><g transform="translate(691.9,626.5) scale(0.720)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M-10 4 L-2 -6 L10 -4 L2 6 Z" fill="none"/></g><text x="713.9185842870421" y="631.0" font-family="Inter,DejaVu Sans,sans-serif" font-size="13.5" fill="#e7ecf1">Reference</text><path d="M965.9185842870421 621.5 L970.9185842870421 626.5 L965.9185842870421 631.5" fill="none" stroke="#8e9aa7" stroke-width="1.6" stroke-linecap="round"/><text x="951.9185842870421" y="630.5" text-anchor="end" font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" fill="#5f6a76">3</text></g><g opacity="1"><g transform="translate(691.9,660.5) scale(0.720)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><rect x="-10" y="-2" width="13" height="11" rx="1" fill="none"/><path d="M-2 5 L0 4.5 L9 -5 L7 -7 L-2.5 2.5 Z"/></g><text x="713.9185842870421" y="665.0" font-family="Inter,DejaVu Sans,sans-serif" font-size="13.5" fill="#e7ecf1">Modify</text><path d="M965.9185842870421 655.5 L970.9185842870421 660.5 L965.9185842870421 665.5" fill="none" stroke="#8e9aa7" stroke-width="1.6" stroke-linecap="round"/><text x="951.9185842870421" y="664.5" text-anchor="end" font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" fill="#5f6a76">3</text></g></svg><figcaption>LIST · solid body</figcaption></figure><figure><svg style="width:100%;height:auto;display:block" xmlns="http://www.w3.org/2000/svg" width="1366" height="768" viewBox="0 0 1366 768"><rect width="1366" height="768" fill="#1a1d21"/><defs><radialGradient id="vp" cx="50%" cy="42%" r="75%"><stop offset="0%" stop-color="#2f353d"/><stop offset="100%" stop-color="#242930"/></radialGradient></defs><rect x="248" y="92" width="1118" height="646" fill="url(#vp)"/><rect width="1366" height="44" fill="#23272d"/><text x="24" y="28" font-family="Inter,DejaVu 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stroke-linecap="round" stroke-linejoin="round"><rect x="-8" y="2" width="16" height="6" rx="1"/><path d="M0 0 L0 -8 M-4 -4 L0 -8 L4 -4"/></g><rect x="116" y="52" width="32" height="32" rx="6" fill="#2e343c" opacity="0.55"/><g transform="translate(132.0,68.0) scale(0.620)" stroke="#8e9aa7" fill="#8e9aa7" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><rect x="-9" y="-6" width="18" height="12" rx="1" fill="none"/><circle cx="0" cy="0" r="3.2" fill="none"/><path d="M0 -5 L0 5 M-5 0 L5 0" stroke-dasharray="2 2"/></g><rect x="162" y="52" width="32" height="32" rx="6" fill="#2e343c" opacity="0.55"/><g transform="translate(178.0,68.0) scale(0.620)" stroke="#8e9aa7" fill="#8e9aa7" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M-9 8 L-9 -1 A8 8 0 0 1 -1 -9 L8 -9" fill="none"/><path d="M-9 8 L8 8 L8 -9" fill="none" stroke-dasharray="2 3"/></g><rect x="208" y="52" width="32" height="32" rx="6" fill="#2e343c" opacity="0.55"/><g 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y="52" width="32" height="32" rx="6" fill="#2e343c" opacity="0.55"/><g transform="translate(362.0,68.0) scale(0.620)" stroke="#8e9aa7" fill="#8e9aa7" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M0 -10 L0 10 M-10 0 L10 0"/><path d="M0 -10 L-3 -6 M0 -10 L3 -6 M0 10 L-3 6 M0 10 L3 6 M-10 0 L-6 -3 M-10 0 L-6 3 M10 0 L6 -3 M10 0 L6 3"/></g><rect x="392" y="52" width="32" height="32" rx="6" fill="#2e343c" opacity="0.55"/><g transform="translate(408.0,68.0) scale(0.620)" stroke="#8e9aa7" fill="#8e9aa7" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><rect x="-10" y="-4" width="20" height="8" rx="1" fill="none"/><path d="M-5 -4 L-5 0 M0 -4 L0 1 M5 -4 L5 0"/></g><rect x="0" y="92" width="248" height="646" fill="#20242a"/><line x1="248" y1="92" x2="248" y2="738" stroke="#31363d"/><text x="18" y="122" font-family="Inter,DejaVu Sans,sans-serif" font-size="11" letter-spacing="1.4" fill="#5f6a76">FEATURES</text><g transform="translate(30.0,146.0) scale(0.420)" stroke="#5f6a76" fill="#5f6a76" stroke-width="1.80" stroke-linecap="round" stroke-linejoin="round"><path d="M-8 8 L-5 7 L7 -5 L5 -7 L-7 5 Z"/><path d="M-8 8 L-6.5 6.5"/></g><text x="46" y="150" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Sketch1</text><g transform="translate(30.0,172.0) scale(0.420)" stroke="#5f6a76" fill="#5f6a76" stroke-width="1.80" stroke-linecap="round" stroke-linejoin="round"><rect x="-8" y="2" width="16" height="6" rx="1"/><path d="M0 0 L0 -8 M-4 -4 L0 -8 L4 -4"/></g><text x="46" y="176" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Extrude1</text><g transform="translate(44.0,198.0) scale(0.420)" stroke="#5f6a76" fill="#5f6a76" stroke-width="1.80" stroke-linecap="round" stroke-linejoin="round"><rect x="-8" y="2" width="16" height="6" rx="1"/><path d="M0 0 L0 -8 M-4 -4 L0 -8 L4 -4"/></g><text x="60" y="202" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Hole1</text><g transform="translate(44.0,224.0) scale(0.420)" stroke="#5f6a76" fill="#5f6a76" stroke-width="1.80" stroke-linecap="round" stroke-linejoin="round"><rect x="-8" y="2" width="16" height="6" rx="1"/><path d="M0 0 L0 -8 M-4 -4 L0 -8 L4 -4"/></g><text x="60" y="228" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Fillet1</text><g transform="translate(30.0,250.0) scale(0.420)" stroke="#5f6a76" fill="#5f6a76" stroke-width="1.80" stroke-linecap="round" stroke-linejoin="round"><path d="M-8 8 L-5 7 L7 -5 L5 -7 L-7 5 Z"/><path d="M-8 8 L-6.5 6.5"/></g><text x="46" y="254" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Sketch2</text><g transform="translate(30.0,276.0) scale(0.420)" stroke="#5f6a76" fill="#5f6a76" stroke-width="1.80" stroke-linecap="round" stroke-linejoin="round"><rect x="-8" y="2" width="16" height="6" rx="1"/><path d="M0 0 L0 -8 M-4 -4 L0 -8 L4 -4"/></g><text x="46" y="280" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Extrude2</text><rect y="738" width="1366" height="30" fill="#23272d"/><text x="18" y="758" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Right-click the geometry to see what you can do with it</text><text x="1348" y="758" text-anchor="end" font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" fill="#5f6a76">Working document · vertical list</text><polygon points="529.1,360.5 659.0,435.5 659.0,487.5 529.1,412.5" fill="#6f7b89" stroke="#39414b" stroke-width="1"/><polygon points="749.9,383.0 659.0,435.5 659.0,487.5 749.9,435.0" fill="#5a6472" stroke="#39414b" stroke-width="1"/><polygon points="620.0,308.0 749.9,383.0 659.0,435.5 529.1,360.5" fill="#93a1b1" stroke="#39414b" stroke-width="1"/><line x1="529.1" y1="360.5" x2="659.0" y2="435.5" stroke="#f5a623" stroke-width="5" stroke-linecap="round"/><circle cx="594.0192378864668" cy="398.0" r="5" fill="none" stroke="#f5a623" stroke-width="2"/><path d="M594.0192378864668 398.0 L620.0192378864668 422.0" stroke="#3c444e" stroke-dasharray="2 3" fill="none"/><rect x="623.0192378864668" y="372.0" width="324" height="320" rx="12" fill="#000" opacity="0.35"/><rect x="620.0192378864668" y="368.0" width="324" height="320" rx="12" fill="#23272d" stroke="#3c444e"/><text x="636.0192378864668" y="392.0" font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" letter-spacing="1.1" fill="#5f6a76">STRAIGHT EDGE</text><line x1="621.0192378864668" y1="400.0" x2="943.0192378864668" y2="400.0" stroke="#31363d"/><g opacity="0.34"><g transform="translate(646.0,423.0) scale(0.720)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M-8 8 L-5 7 L7 -5 L5 -7 L-7 5 Z"/></g><text x="668.0192378864668" y="427.5" font-family="Inter,DejaVu Sans,sans-serif" font-size="13.5" fill="#e7ecf1">Create</text></g><text x="668.0192378864668" y="439.0" font-family="Inter,DejaVu 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x="668.0192378864668" y="495.5" font-family="Inter,DejaVu Sans,sans-serif" font-size="13.5" fill="#e7ecf1">Remove</text></g><text x="668.0192378864668" y="507.0" font-family="Inter,DejaVu Sans,sans-serif" font-size="10" font-style="italic" fill="#5f6a76">Pick a face or a plane to drill into</text><g opacity="1"><g transform="translate(646.0,525.0) scale(0.720)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M-9 8 L-9 -1 A8 8 0 0 1 -1 -9 L8 -9" fill="none"/></g><text x="668.0192378864668" y="529.5" font-family="Inter,DejaVu Sans,sans-serif" font-size="13.5" fill="#e7ecf1">Dress-up</text><path d="M920.0192378864668 520.0 L925.0192378864668 525.0 L920.0192378864668 530.0" fill="none" stroke="#8e9aa7" stroke-width="1.6" stroke-linecap="round"/><text x="906.0192378864668" y="529.0" text-anchor="end" font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" fill="#5f6a76">2</text></g><g opacity="1"><g transform="translate(646.0,559.0) scale(0.720)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M-10 6 C-4 -8 4 8 10 -6" fill="none"/><circle cx="-7" cy="0" r="2.4"/><circle cx="0" cy="0.5" r="2.4"/><circle cx="7" cy="0" r="2.4"/></g><text x="668.0192378864668" y="563.5" font-family="Inter,DejaVu Sans,sans-serif" font-size="13.5" fill="#e7ecf1">Pattern on Curve</text></g><g opacity="0.34"><g transform="translate(646.0,593.0) scale(0.720)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M0 -10 L0 10 M-10 0 L10 0"/><path d="M0 -10 L-3 -6 M0 -10 L3 -6 M-10 0 L-6 -3 M-10 0 L-6 3"/></g><text x="668.0192378864668" y="597.5" font-family="Inter,DejaVu Sans,sans-serif" font-size="13.5" fill="#e7ecf1">Transform</text></g><text x="668.0192378864668" y="609.0" font-family="Inter,DejaVu Sans,sans-serif" font-size="10" font-style="italic" fill="#5f6a76">Transform needs a body — add or import one first</text><g opacity="1"><g transform="translate(646.0,627.0) scale(0.720)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M-10 4 L-2 -6 L10 -4 L2 6 Z" fill="none"/></g><text x="668.0192378864668" y="631.5" font-family="Inter,DejaVu Sans,sans-serif" font-size="13.5" fill="#e7ecf1">Reference</text><path d="M920.0192378864668 622.0 L925.0192378864668 627.0 L920.0192378864668 632.0" fill="none" stroke="#8e9aa7" stroke-width="1.6" stroke-linecap="round"/><text x="906.0192378864668" y="631.0" text-anchor="end" font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" fill="#5f6a76">3</text></g><g opacity="0.34"><g transform="translate(646.0,661.0) scale(0.720)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><rect x="-10" y="-2" width="13" height="11" rx="1" fill="none"/><path d="M-2 5 L0 4.5 L9 -5 L7 -7 L-2.5 2.5 Z"/></g><text x="668.0192378864668" y="665.5" font-family="Inter,DejaVu Sans,sans-serif" font-size="13.5" fill="#e7ecf1">Modify</text></g><text x="668.0192378864668" y="677.0" font-family="Inter,DejaVu Sans,sans-serif" font-size="10" font-style="italic" fill="#5f6a76">Delete Face needs a body — add or import one first</text></svg><figcaption>LIST · straight edge</figcaption></figure><figure><svg style="width:100%;height:auto;display:block" xmlns="http://www.w3.org/2000/svg" width="1366" height="768" viewBox="0 0 1366 768"><rect width="1366" height="768" fill="#1a1d21"/><defs><radialGradient id="vp" cx="50%" cy="42%" r="75%"><stop offset="0%" stop-color="#2f353d"/><stop offset="100%" stop-color="#242930"/></radialGradient></defs><rect x="248" y="92" width="1118" height="646" fill="url(#vp)"/><rect width="1366" height="44" fill="#23272d"/><text x="24" y="28" font-family="Inter,DejaVu Sans,sans-serif" font-size="14" font-weight="400" fill="#5f6a76">Prepare</text><text x="121" y="28" font-family="Inter,DejaVu Sans,sans-serif" 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fill="none"/><circle cx="-6" cy="-6" r="2.6" fill="none"/><path d="M-4 4 L8 -6 M-4 -4 L8 6"/></g><rect x="392" y="52" width="32" height="32" rx="6" fill="#2e343c" opacity="0.55"/><g transform="translate(408.0,68.0) scale(0.620)" stroke="#8e9aa7" fill="#8e9aa7" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><rect x="-6" y="-1" width="12" height="9" rx="1.5" fill="none"/><path d="M-3.5 -1 L-3.5 -5 A3.5 3.5 0 0 1 3.5 -5 L3.5 -1" fill="none"/></g><rect x="0" y="92" width="248" height="646" fill="#20242a"/><line x1="248" y1="92" x2="248" y2="738" stroke="#31363d"/><text x="18" y="122" font-family="Inter,DejaVu Sans,sans-serif" font-size="11" letter-spacing="1.4" fill="#5f6a76">FEATURES</text><g transform="translate(30.0,146.0) scale(0.420)" stroke="#5f6a76" fill="#5f6a76" stroke-width="1.80" stroke-linecap="round" stroke-linejoin="round"><path d="M-8 8 L-5 7 L7 -5 L5 -7 L-7 5 Z"/><path d="M-8 8 L-6.5 6.5"/></g><text x="46" y="150" font-family="Inter,DejaVu 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can do with it</text><text x="1348" y="758" text-anchor="end" font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" fill="#5f6a76">Working document · vertical list</text><line x1="420" y1="240" x2="760" y2="240" stroke="#333a43" stroke-width="0.6"/><line x1="420" y1="262" x2="760" y2="262" stroke="#333a43" stroke-width="0.6"/><line x1="420" y1="284" x2="760" y2="284" stroke="#333a43" stroke-width="0.6"/><line x1="420" y1="306" x2="760" y2="306" stroke="#333a43" stroke-width="0.6"/><line x1="420" y1="328" x2="760" y2="328" stroke="#333a43" stroke-width="0.6"/><line x1="420" y1="350" x2="760" y2="350" stroke="#333a43" stroke-width="0.6"/><line x1="420" y1="372" x2="760" y2="372" stroke="#333a43" stroke-width="0.6"/><line x1="420" y1="394" x2="760" y2="394" stroke="#333a43" stroke-width="0.6"/><line x1="420" y1="416" x2="760" y2="416" stroke="#333a43" stroke-width="0.6"/><line x1="420" y1="438" x2="760" y2="438" stroke="#333a43" stroke-width="0.6"/><line x1="420" y1="460" x2="760" 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fill="#23272d"/><text x="18" y="758" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Cylindrical face selected — pick what to do with it</text><text x="1348" y="758" text-anchor="end" font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" fill="#5f6a76">Working document · 8 slots</text><polygon points="629.1,360.5 759.0,435.5 759.0,487.5 629.1,412.5" fill="#6f7b89" stroke="#39414b" stroke-width="1"/><polygon points="849.9,383.0 759.0,435.5 759.0,487.5 849.9,435.0" fill="#5a6472" stroke="#39414b" stroke-width="1"/><polygon points="720.0,308.0 849.9,383.0 759.0,435.5 629.1,360.5" fill="#93a1b1" stroke="#39414b" stroke-width="1"/><ellipse cx="739.9" cy="371.5" rx="38.1" ry="22.0" fill="#f5a623" stroke="#39414b"/><ellipse cx="739.9" cy="378.5" rx="35.1" ry="20.2" fill="#171b20" stroke="none"/><ellipse cx="739.9" cy="371.5" rx="38.1" ry="22.0" fill="none" stroke="#f5a623" stroke-width="3"/><circle cx="739.9185842870421" cy="371.5" r="186" fill="#171a1e" 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L3.5 -1" fill="none"/></g><rect x="0" y="92" width="248" height="646" fill="#20242a"/><line x1="248" y1="92" x2="248" y2="738" stroke="#31363d"/><text x="18" y="122" font-family="Inter,DejaVu Sans,sans-serif" font-size="11" letter-spacing="1.4" fill="#5f6a76">FEATURES</text><g transform="translate(30.0,146.0) scale(0.420)" stroke="#5f6a76" fill="#5f6a76" stroke-width="1.80" stroke-linecap="round" stroke-linejoin="round"><path d="M-8 8 L-5 7 L7 -5 L5 -7 L-7 5 Z"/><path d="M-8 8 L-6.5 6.5"/></g><text x="46" y="150" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Sketch1</text><g transform="translate(30.0,172.0) scale(0.420)" stroke="#5f6a76" fill="#5f6a76" stroke-width="1.80" stroke-linecap="round" stroke-linejoin="round"><rect x="-8" y="2" width="16" height="6" rx="1"/><path d="M0 0 L0 -8 M-4 -4 L0 -8 L4 -4"/></g><text x="46" y="176" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Extrude1</text><g transform="translate(44.0,198.0) 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fill="#8e9aa7">Sketch2</text><g transform="translate(30.0,276.0) scale(0.420)" stroke="#5f6a76" fill="#5f6a76" stroke-width="1.80" stroke-linecap="round" stroke-linejoin="round"><rect x="-8" y="2" width="16" height="6" rx="1"/><path d="M0 0 L0 -8 M-4 -4 L0 -8 L4 -4"/></g><text x="46" y="280" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Extrude2</text><rect y="738" width="1366" height="30" fill="#23272d"/><text x="18" y="758" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" fill="#8e9aa7">Sketch line selected — pick what to do with it</text><text x="1348" y="758" text-anchor="end" font-family="Inter,DejaVu Sans,sans-serif" font-size="11.5" fill="#5f6a76">Working document · 8 slots</text><line x1="520" y1="240" x2="860" y2="240" stroke="#333a43" stroke-width="0.6"/><line x1="520" y1="262" x2="860" y2="262" stroke="#333a43" stroke-width="0.6"/><line x1="520" y1="284" x2="860" y2="284" stroke="#333a43" stroke-width="0.6"/><line x1="520" y1="306" 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stroke-linejoin="round"><circle cx="-6" cy="6" r="2.6" fill="none"/><circle cx="-6" cy="-6" r="2.6" fill="none"/><path d="M-4 4 L8 -6 M-4 -4 L8 6"/></g><text x="806.0" y="341.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" font-weight="500" fill="#e7ecf1">Trim</text><rect x="796.2" y="348.0" width="19.6" height="17" rx="4.5" fill="#454f5b"/><text x="806.0" y="360.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="10.5" fill="#e7ecf1">T</text><rect x="794.0" y="330.0" width="60" height="60" rx="14" fill="#2e343c" stroke="#3c444e"/><g transform="translate(824.0,358.0) scale(0.920)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M-9 8 L-9 -1 A8 8 0 0 1 -1 -9 L8 -9" fill="none"/></g><text x="824.0" y="408.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" font-weight="500" fill="#e7ecf1">Dress-up</text><circle cx="846.0" cy="338.0" r="10" fill="#4f9bd9"/><text x="846.0" y="342.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="11" font-weight="600" fill="#0f1319">2</text><rect x="776.0" y="397.0" width="60" height="60" rx="14" fill="#2e343c" stroke="#3c444e"/><g transform="translate(806.0,425.0) scale(0.920)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M0 -10 L0 10" stroke-dasharray="3 2"/><path d="M-3 -6 L-9 0 L-3 6 Z"/><path d="M3 -6 L9 0 L3 6 Z" fill="none"/></g><text x="806.0" y="475.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" font-weight="500" fill="#e7ecf1">Mirror</text><rect x="796.2" y="482.0" width="19.6" height="17" rx="4.5" fill="#454f5b"/><text x="806.0" y="494.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="10.5" fill="#e7ecf1">M</text><rect x="727.0" y="446.0" width="60" height="60" rx="14" fill="#2e343c" stroke="#3c444e"/><g transform="translate(757.0,474.0) scale(0.920)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M0 -10 L0 10 M-10 0 L10 0"/><path d="M0 -10 L-3 -6 M0 -10 L3 -6 M0 10 L-3 6 M0 10 L3 6 M-10 0 L-6 -3 M-10 0 L-6 3 M10 0 L6 -3 M10 0 L6 3"/></g><text x="757.0" y="524.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" font-weight="500" fill="#e7ecf1">Move</text><rect x="660.0" y="464.0" width="60" height="60" rx="14" fill="#2e343c" stroke="#3c444e"/><g transform="translate(690.0,492.0) scale(0.920)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><path d="M-10 4 L-2 -6 L10 -4 L2 6 Z" fill="none"/></g><text x="690.0" y="542.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" font-weight="500" fill="#e7ecf1">Reference</text><circle cx="712.0" cy="472.0" r="10" fill="#4f9bd9"/><text x="712.0" y="476.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="11" font-weight="600" fill="#0f1319">3</text><rect x="593.0" y="446.0" width="60" height="60" rx="14" fill="#2e343c" stroke="#3c444e"/><g transform="translate(623.0,474.0) scale(0.920)" stroke="#e7ecf1" fill="#e7ecf1" stroke-width="1.70" stroke-linecap="round" stroke-linejoin="round"><rect x="-10" y="-2" width="13" height="11" rx="1" fill="none"/><path d="M-2 5 L0 4.5 L9 -5 L7 -7 L-2.5 2.5 Z"/></g><text x="623.0" y="524.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="12.5" font-weight="500" fill="#e7ecf1">Modify</text><circle cx="645.0" cy="454.0" r="10" fill="#4f9bd9"/><text x="645.0" y="458.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="11" font-weight="600" fill="#0f1319">2</text><circle cx="574.0" cy="427.0" r="21" fill="#2a2f36" opacity="0.5" stroke="#3c444e" stroke-dasharray="3 3"/><circle cx="556.0" cy="360.0" r="21" fill="#2a2f36" opacity="0.5" stroke="#3c444e" stroke-dasharray="3 3"/><circle cx="574.0" cy="293.0" r="21" fill="#2a2f36" opacity="0.5" stroke="#3c444e" stroke-dasharray="3 3"/><circle cx="623.0" cy="244.0" r="21" fill="#2a2f36" opacity="0.5" stroke="#3c444e" stroke-dasharray="3 3"/><rect x="645.5" y="392.0" width="88.9" height="22" rx="11" fill="#171a1e" opacity="0.92" stroke="#3c444e"/><text x="690.0" y="407.0" text-anchor="middle" font-family="Inter,DejaVu Sans,sans-serif" font-size="12" fill="#e7ecf1">Sketch line</text></svg><figcaption>12 slots — sketch line</figcaption></figure></div></main>
diff --git a/docs/CAD/ux/tool_atlas.json b/docs/CAD/ux/tool_atlas.json
new file mode 100644
index 0000000000..94709f2057
--- /dev/null
+++ b/docs/CAD/ux/tool_atlas.json
@@ -0,0 +1,2213 @@
+{
+  "_comment": [
+    "Source of truth for the object-driven tool offer (see docs/cad_ux_guidelines.md 4.1).",
+    "Every verb, the selections it accepts, the document state it needs, and its fixed",
+    "compass address. Extracted from the code, not from memory:",
+    "  verbs + shortcuts + refusal messages -> src/slic3r/GUI/CAD/DesignPanel.cpp (feat_dropdown",
+    "    call sites at 524/662/734/790/874/904, sk_key table at 369-400, m_keys_feature)",
+    "  kernel coverage            -> src/libslic3r/CAD/CadDocument.hpp  (enum CadFeatureType)",
+    "  headless coverage          -> src/slic3r/GUI/CAD/McpControl.cpp  (method == \"...\")",
+    "  selection kinds            -> src/slic3r/GUI/CAD/DesignCanvas.hpp (the on_*_selected callbacks)",
+    "gen_offer_mockups.py reads this file; the eventual C++ offer table is generated from it",
+    "too, so the map exists once."
+  ],
+  "slots": [
+    {
+      "id": "create",
+      "pos": "N",
+      "angle": 270,
+      "label": "Create",
+      "why": "makes new geometry from nothing you have yet"
+    },
+    {
+      "id": "add",
+      "pos": "NE",
+      "angle": 315,
+      "label": "Add material",
+      "why": "grows solid or sheet material"
+    },
+    {
+      "id": "remove",
+      "pos": "E",
+      "angle": 0,
+      "label": "Remove",
+      "why": "takes material away Shell lives here by decision of 2026-08-01, not by oversight."
+    },
+    {
+      "id": "dressup",
+      "pos": "SE",
+      "angle": 45,
+      "label": "Fillet / chamfer / draft",
+      "why": "finishes faces and edges without changing the shape's intent; named for the tools it holds, not for the trade word. RATIFIED 2026-08-01: Shell stays in Remove and Delete Face in Modify — this row is deliberately NOT the same set as the toolbar's dressup dropdown, which groups all five. Shell hollows a solid, so it belongs with the verbs that take material away. Do not re-open: a verb's row is its address and reordering breaks learned reach."
+    },
+    {
+      "id": "repeat",
+      "pos": "S",
+      "angle": 90,
+      "label": "Repeat",
+      "why": "copies what exists"
+    },
+    {
+      "id": "transform",
+      "pos": "SW",
+      "angle": 135,
+      "label": "Transform",
+      "why": "moves without changing shape"
+    },
+    {
+      "id": "reference",
+      "pos": "W",
+      "angle": 180,
+      "label": "Reference",
+      "why": "makes datums, curves and measurements"
+    },
+    {
+      "id": "modify",
+      "pos": "NW",
+      "angle": 225,
+      "label": "Modify",
+      "why": "edits or removes what is already there"
+    }
+  ],
+  "selections": [
+    {
+      "id": "none",
+      "name": "Nothing selected",
+      "mode": "model",
+      "shape": "empty"
+    },
+    {
+      "id": "face_planar",
+      "name": "Planar face",
+      "mode": "model",
+      "shape": "box_top"
+    },
+    {
+      "id": "face_cyl",
+      "name": "Cylindrical face",
+      "mode": "model",
+      "shape": "box_bore"
+    },
+    {
+      "id": "face_other",
+      "name": "Curved face",
+      "mode": "model",
+      "shape": "box_fillet_face"
+    },
+    {
+      "id": "edge_str",
+      "name": "Straight edge",
+      "mode": "model",
+      "shape": "box_edge"
+    },
+    {
+      "id": "edge_circ",
+      "name": "Circular edge",
+      "mode": "model",
+      "shape": "box_bore_rim"
+    },
+    {
+      "id": "vertex",
+      "name": "Vertex",
+      "mode": "model",
+      "shape": "box_vertex"
+    },
+    {
+      "id": "body_solid",
+      "name": "Solid body",
+      "mode": "model",
+      "shape": "box_whole"
+    },
+    {
+      "id": "body_sheet",
+      "name": "Sheet body",
+      "mode": "model",
+      "shape": "sheet"
+    },
+    {
+      "id": "bodies_2",
+      "name": "Two bodies",
+      "mode": "model",
+      "shape": "two_boxes"
+    },
+    {
+      "id": "datum_plane",
+      "name": "Datum plane",
+      "mode": "model",
+      "shape": "datum"
+    },
+    {
+      "id": "datum_axis",
+      "name": "Datum axis",
+      "mode": "model",
+      "shape": "axis"
+    },
+    {
+      "id": "coordsys",
+      "name": "Coordinate system",
+      "mode": "model",
+      "shape": "csys"
+    },
+    {
+      "id": "art",
+      "name": "Text / imported art",
+      "mode": "model",
+      "shape": "art"
+    },
+    {
+      "id": "sk_loop",
+      "name": "Closed sketch loop",
+      "mode": "model",
+      "shape": "loop"
+    },
+    {
+      "id": "sk_none",
+      "name": "Sketch, nothing picked",
+      "mode": "sketch",
+      "shape": "sk_empty"
+    },
+    {
+      "id": "sk_line",
+      "name": "Sketch line",
+      "mode": "sketch",
+      "shape": "sk_line"
+    },
+    {
+      "id": "sk_arc",
+      "name": "Sketch arc or circle",
+      "mode": "sketch",
+      "shape": "sk_arc"
+    },
+    {
+      "id": "sk_point",
+      "name": "Sketch point",
+      "mode": "sketch",
+      "shape": "sk_point"
+    },
+    {
+      "id": "sk_2ent",
+      "name": "Two sketch entities",
+      "mode": "sketch",
+      "shape": "sk_two"
+    }
+  ],
+  "doc_states": [
+    {
+      "id": "rich",
+      "name": "Working document",
+      "bodies": 2,
+      "sketches": 2,
+      "sheet": true,
+      "note": "two solids, two sketches, one sheet body — everything doc-gated is legal"
+    },
+    {
+      "id": "fresh",
+      "name": "Fresh document",
+      "bodies": 0,
+      "sketches": 0,
+      "sheet": false,
+      "note": "nothing built yet — shows how much of the ring is empty on first open"
+    }
+  ],
+  "verbs": [
+    {
+      "id": "sketch",
+      "name": "Sketch",
+      "slot": "create",
+      "key": "Shift+S",
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "face_planar",
+        "datum_plane",
+        "none"
+      ],
+      "needs": {},
+      "refusal": "Click a face or a reference plane in the viewport, then a sketch tool",
+      "gui": true,
+      "action": "key:S+S",
+      "icon": "design_sketch",
+      "hint": "Click a face or a reference plane, then pick a drawing tool"
+    },
+    {
+      "id": "extrude",
+      "name": "Extrude",
+      "slot": "add",
+      "key": "Shift+E",
+      "feature": "Extrude",
+      "mcp": "extrude",
+      "accepts": [
+        "sk_loop",
+        "face_planar"
+      ],
+      "needs": {},
+      "refusal": "Create a sketch, or pick a solid face, first",
+      "gui": true,
+      "action": "key:S+E",
+      "icon": "design_extrude",
+      "hint": "Extrude a sketch profile, or push/pull a picked face"
+    },
+    {
+      "id": "revolve",
+      "name": "Revolve",
+      "slot": "add",
+      "key": "Shift+R",
+      "feature": "Revolve",
+      "mcp": "revolve",
+      "accepts": [
+        "sk_loop"
+      ],
+      "needs": {},
+      "refusal": "Create a sketch profile to revolve first",
+      "gui": true,
+      "action": "key:S+R",
+      "icon": "design_revolve",
+      "hint": "Revolve a profile about an axis"
+    },
+    {
+      "id": "sweep",
+      "name": "Sweep",
+      "slot": "add",
+      "key": "Shift+W",
+      "feature": "Sweep",
+      "mcp": null,
+      "accepts": [
+        "sk_loop"
+      ],
+      "needs": {
+        "sketches": 2
+      },
+      "refusal": "Create a profile sketch to sweep first",
+      "gui": true,
+      "action": "key:S+W",
+      "icon": "design_sweep",
+      "hint": "Sweep a profile along a path"
+    },
+    {
+      "id": "loft",
+      "name": "Loft",
+      "slot": "add",
+      "key": "Shift+L",
+      "feature": "Loft",
+      "mcp": null,
+      "accepts": [
+        "sk_loop"
+      ],
+      "needs": {
+        "sketches": 2
+      },
+      "refusal": "Create at least two profile sketches to loft",
+      "gui": true,
+      "action": "key:S+L",
+      "icon": "design_loft",
+      "hint": "Loft (skin) between two or more profiles"
+    },
+    {
+      "id": "thicken",
+      "name": "Thicken",
+      "slot": "add",
+      "key": null,
+      "feature": "Thicken",
+      "mcp": "thicken",
+      "accepts": [
+        "face_planar",
+        "face_other"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Thicken needs a solid body — add or import one first",
+      "gui": true,
+      "action": "fly:material#4",
+      "icon": "design_thicken",
+      "hint": "Offset a solid face into a thin plate (new body)"
+    },
+    {
+      "id": "rib",
+      "name": "Rib",
+      "slot": "add",
+      "key": null,
+      "feature": "Rib",
+      "mcp": "rib",
+      "accepts": [
+        "sk_line"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Rib needs a solid body — add or import one first",
+      "gui": true,
+      "action": "fly:material#5",
+      "icon": "design_rib",
+      "hint": "Grow a thin wall from an open sketch line, fused to a body"
+    },
+    {
+      "id": "boolean",
+      "name": "Union",
+      "slot": "add",
+      "key": "Shift+B",
+      "feature": "Boolean",
+      "mcp": "boolean",
+      "accepts": [
+        "bodies_2"
+      ],
+      "needs": {
+        "bodies": 2
+      },
+      "refusal": "Boolean needs two bodies — create or import a second solid",
+      "gui": true,
+      "action": "btn:bool#0",
+      "icon": "design_boolean",
+      "hint": "Fuse the tool body into the target — one solid, no seam"
+    },
+    {
+      "id": "bool_subtract",
+      "name": "Subtract",
+      "slot": "add",
+      "key": null,
+      "feature": "Boolean",
+      "mcp": null,
+      "accepts": [
+        "bodies_2"
+      ],
+      "needs": {
+        "bodies": 2
+      },
+      "refusal": "Boolean needs two bodies — create or import a second solid",
+      "gui": true,
+      "action": "btn:bool#1",
+      "mode": null,
+      "icon": "design_boolean",
+      "hint": "Cut the tool body out of the target"
+    },
+    {
+      "id": "bool_intersect",
+      "name": "Intersect",
+      "slot": "add",
+      "key": null,
+      "feature": "Boolean",
+      "mcp": null,
+      "accepts": [
+        "bodies_2"
+      ],
+      "needs": {
+        "bodies": 2
+      },
+      "refusal": "Boolean needs two bodies — create or import a second solid",
+      "gui": true,
+      "action": "btn:bool#2",
+      "mode": null,
+      "icon": "design_boolean",
+      "hint": "Keep only where the two bodies overlap"
+    },
+    {
+      "id": "surf_extrude",
+      "name": "Surface Extrude",
+      "slot": "add",
+      "key": "Shift+G",
+      "feature": "SurfaceExtrude",
+      "mcp": "surface_extrude",
+      "accepts": [
+        "sk_loop"
+      ],
+      "needs": {},
+      "refusal": "Create a sketch first",
+      "gui": true,
+      "action": "key:S+G",
+      "icon": "design_extrude",
+      "hint": "Extrude a sketch into a sheet body (no end caps)"
+    },
+    {
+      "id": "surf_revolve",
+      "name": "Surface Revolve",
+      "slot": "add",
+      "key": null,
+      "feature": "SurfaceRevolve",
+      "mcp": "surface_revolve",
+      "accepts": [
+        "sk_loop"
+      ],
+      "needs": {},
+      "refusal": "Create a sketch profile to revolve first",
+      "gui": true,
+      "action": "fly:surface#1",
+      "icon": "design_revolve",
+      "hint": "Revolve a sketch profile into a sheet body"
+    },
+    {
+      "id": "surf_loft",
+      "name": "Surface Loft",
+      "slot": "add",
+      "key": null,
+      "feature": "SurfaceLoft",
+      "mcp": "surface_loft",
+      "accepts": [
+        "sk_loop"
+      ],
+      "needs": {
+        "sketches": 2
+      },
+      "refusal": "Create at least two profile sketches to loft",
+      "gui": true,
+      "action": "fly:surface#2",
+      "icon": "design_loft",
+      "hint": "Loft (skin) between 2+ profiles, open (no end caps)"
+    },
+    {
+      "id": "surf_fill",
+      "name": "Surface Fill",
+      "slot": "add",
+      "key": null,
+      "feature": "SurfaceFill",
+      "mcp": "surface_fill",
+      "accepts": [
+        "sk_loop"
+      ],
+      "needs": {},
+      "refusal": "Create a closed sketch first",
+      "gui": true,
+      "action": "fly:surface#3",
+      "icon": "design_surface",
+      "hint": "Fill a sketch boundary with a smooth face"
+    },
+    {
+      "id": "thicken_surf",
+      "name": "Thicken Surface",
+      "slot": "add",
+      "key": null,
+      "feature": "ThickenSurface",
+      "mcp": "thicken_surface",
+      "accepts": [
+        "body_sheet"
+      ],
+      "needs": {
+        "sheet": true
+      },
+      "refusal": "target is not a sheet body",
+      "gui": true,
+      "action": "fly:surface#5",
+      "icon": "design_thicken",
+      "hint": "Thicken a sheet body into a solid"
+    },
+    {
+      "id": "hole",
+      "name": "Hole",
+      "slot": "remove",
+      "key": "Shift+H",
+      "feature": "Hole",
+      "mcp": "hole",
+      "accepts": [
+        "face_planar",
+        "datum_plane"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Pick a face or a plane to drill into",
+      "gui": true,
+      "action": "key:S+H",
+      "icon": "design_hole",
+      "hint": "Drill a hole, centred on a picked face or placed on a plane"
+    },
+    {
+      "id": "thread",
+      "name": "Thread",
+      "slot": "remove",
+      "key": "Shift+T",
+      "feature": "Thread",
+      "mcp": null,
+      "accepts": [
+        "face_cyl",
+        "edge_circ"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Pick a cylindrical surface (bore / outer) or a circular edge for a thread",
+      "gui": true,
+      "action": "key:S+T",
+      "icon": "design_thread",
+      "hint": "Thread a cylindrical surface (inner bore / outer) or a circular edge"
+    },
+    {
+      "id": "shell",
+      "name": "Shell",
+      "slot": "remove",
+      "key": "Shift+K",
+      "feature": "Shell",
+      "mcp": "shell",
+      "accepts": [
+        "face_planar",
+        "body_solid"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Shell needs a solid body",
+      "gui": true,
+      "action": "key:S+K",
+      "icon": "design_shell",
+      "hint": "Hollow the body to a wall thickness, opening a picked face"
+    },
+    {
+      "id": "cut",
+      "name": "Cut",
+      "slot": "remove",
+      "key": "Shift+X",
+      "feature": "Cut",
+      "mcp": null,
+      "accepts": [
+        "body_solid",
+        "datum_plane",
+        "face_planar",
+        "face_cyl",
+        "face_other",
+        "edge_str",
+        "edge_circ",
+        "vertex"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Create a solid body to cut first",
+      "gui": true,
+      "action": "key:S+X",
+      "icon": "design_cut",
+      "hint": "Trim the body with a plane — drag the offset arrow; keep one half or both"
+    },
+    {
+      "id": "split",
+      "name": "Split",
+      "slot": "remove",
+      "key": null,
+      "feature": "Cut",
+      "mcp": "split",
+      "accepts": [
+        "body_solid",
+        "face_planar",
+        "face_cyl",
+        "face_other",
+        "edge_str",
+        "edge_circ",
+        "vertex"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Split needs a solid body",
+      "gui": false,
+      "action": null,
+      "icon": null,
+      "hint": "Split the body along a picked face into two solids"
+    },
+    {
+      "id": "fillet",
+      "name": "Fillet",
+      "slot": "dressup",
+      "key": "Shift+F",
+      "feature": "Fillet",
+      "mcp": "fillet",
+      "accepts": [
+        "edge_str",
+        "edge_circ",
+        "face_planar",
+        "body_solid"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Pick an edge to round",
+      "gui": true,
+      "action": "btn:dress#0",
+      "icon": "design_filletedge",
+      "hint": "Pick an edge, then drag the radius arrow or type it"
+    },
+    {
+      "id": "chamfer",
+      "name": "Chamfer",
+      "slot": "dressup",
+      "key": null,
+      "feature": "Chamfer",
+      "mcp": "chamfer",
+      "accepts": [
+        "edge_str",
+        "edge_circ",
+        "face_planar",
+        "body_solid"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Pick an edge to bevel",
+      "gui": true,
+      "action": "btn:dress#1",
+      "icon": "design_chamfer",
+      "hint": "Pick an edge, then drag the distance arrow or type it"
+    },
+    {
+      "id": "draft",
+      "name": "Draft",
+      "slot": "dressup",
+      "key": "Shift+D",
+      "feature": "Draft",
+      "mcp": "draft",
+      "accepts": [
+        "face_planar",
+        "face_other"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Pick a face to taper",
+      "gui": true,
+      "action": "key:S+D",
+      "icon": "design_draft",
+      "hint": "Tilt a picked face by a draft angle"
+    },
+    {
+      "id": "surf_offset",
+      "name": "Surface Offset",
+      "slot": "dressup",
+      "key": null,
+      "feature": "SurfaceOffset",
+      "mcp": "surface_offset",
+      "accepts": [
+        "body_sheet"
+      ],
+      "needs": {
+        "sheet": true
+      },
+      "refusal": "target is not a sheet body",
+      "gui": true,
+      "action": "fly:surface#4",
+      "icon": "design_offset",
+      "hint": "Offset a sheet body's shell by a signed distance"
+    },
+    {
+      "id": "pattern",
+      "name": "Linear pattern",
+      "slot": "repeat",
+      "key": "Shift+N",
+      "feature": "Pattern",
+      "mcp": "pattern",
+      "accepts": [
+        "body_solid",
+        "face_planar",
+        "sk_loop",
+        "art"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Create a solid body to pattern first",
+      "gui": true,
+      "action": "btn:pat#0",
+      "icon": "design_array",
+      "hint": "Repeat the body along a direction — drag the spacing, set the count"
+    },
+    {
+      "id": "pattern_circular",
+      "name": "Circular pattern",
+      "slot": "repeat",
+      "key": null,
+      "feature": "Pattern",
+      "mcp": null,
+      "accepts": [
+        "body_solid",
+        "face_planar",
+        "sk_loop",
+        "art"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Create a solid body to pattern first",
+      "gui": true,
+      "action": "btn:pat#1",
+      "mode": null,
+      "icon": "design_polararray",
+      "hint": "Repeat the body around an axis — set the count and sweep"
+    },
+    {
+      "id": "mirror",
+      "name": "Mirror",
+      "slot": "repeat",
+      "key": "Shift+Z",
+      "feature": "Mirror",
+      "mcp": "mirror",
+      "accepts": [
+        "body_solid",
+        "datum_plane",
+        "face_planar",
+        "face_cyl",
+        "face_other",
+        "edge_str",
+        "edge_circ",
+        "vertex"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Mirror needs a body — add or import one first",
+      "gui": true,
+      "action": "key:S+Z",
+      "icon": "design_mirror",
+      "hint": "Reflect a body about a plane"
+    },
+    {
+      "id": "pat_curve",
+      "name": "Pattern on Curve",
+      "slot": "repeat",
+      "key": null,
+      "feature": "Pattern",
+      "mcp": "pattern_on_curve",
+      "accepts": [
+        "body_solid",
+        "edge_str"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Pattern on curve needs a body and a curve",
+      "gui": false,
+      "action": null,
+      "icon": null,
+      "hint": "Repeat the body along a picked curve"
+    },
+    {
+      "id": "transform",
+      "name": "Move",
+      "slot": "transform",
+      "key": "Shift+Y",
+      "feature": "Transform",
+      "mcp": "transform",
+      "accepts": [
+        "body_solid",
+        "body_sheet",
+        "art",
+        "face_planar",
+        "face_cyl",
+        "face_other",
+        "edge_str",
+        "edge_circ",
+        "vertex"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Transform needs a body — add or import one first",
+      "gui": true,
+      "action": "key:S+Y",
+      "icon": "design_move",
+      "hint": "Move and/or rotate an existing body"
+    },
+    {
+      "id": "mate",
+      "name": "Mate",
+      "slot": "transform",
+      "key": null,
+      "feature": "Mate",
+      "mcp": "mate",
+      "accepts": [
+        "coordsys",
+        "bodies_2",
+        "face_planar"
+      ],
+      "needs": {
+        "bodies": 2
+      },
+      "refusal": "A mate needs two coordinate systems",
+      "gui": true,
+      "action": "fly:placement#2",
+      "icon": "design_c_coincident",
+      "hint": "Assembly: align two CoordSys features (fastened, planar, revolute, slider, cylindrical)"
+    },
+    {
+      "id": "align",
+      "name": "Align to",
+      "slot": "transform",
+      "key": null,
+      "feature": "Transform",
+      "mcp": "transform",
+      "accepts": [
+        "face_planar"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Align needs a body",
+      "gui": false,
+      "action": null,
+      "icon": null,
+      "hint": "Align the body to a picked face or plane"
+    },
+    {
+      "id": "plane",
+      "name": "Plane",
+      "slot": "reference",
+      "key": "Shift+P",
+      "feature": "Plane",
+      "mcp": null,
+      "accepts": [
+        "none",
+        "face_planar",
+        "edge_str",
+        "datum_plane",
+        "vertex"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:S+P",
+      "icon": "design_plane",
+      "hint": "Reference plane (offset / tilt / midplane / tangent / two edges / coincident)"
+    },
+    {
+      "id": "axis",
+      "name": "Axis",
+      "slot": "reference",
+      "key": "Shift+A",
+      "feature": "Axis",
+      "mcp": "axis",
+      "accepts": [
+        "none",
+        "face_planar",
+        "face_cyl",
+        "edge_str",
+        "vertex"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:S+A",
+      "icon": "design_line",
+      "hint": "Datum axis (two points, face normal, cylinder centerline, two planes, along edge)"
+    },
+    {
+      "id": "coordsys_v",
+      "name": "Coord Sys",
+      "slot": "reference",
+      "key": "Shift+C",
+      "feature": "CoordSys",
+      "mcp": "coordsys",
+      "accepts": [
+        "none",
+        "face_planar",
+        "vertex"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:S+C",
+      "icon": "design_point",
+      "hint": "Datum coordinate system (world point, or face + direction edge)"
+    },
+    {
+      "id": "helix",
+      "name": "Helix",
+      "slot": "reference",
+      "key": null,
+      "feature": "Helix",
+      "mcp": "helix",
+      "accepts": [
+        "none",
+        "datum_plane",
+        "face_cyl"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:plane#3",
+      "icon": "design_thread",
+      "hint": "Helical curve (spring path) — use as a sweep path for coils / springs / augers"
+    },
+    {
+      "id": "project",
+      "name": "Project",
+      "slot": "reference",
+      "key": null,
+      "feature": "Project",
+      "mcp": "project",
+      "accepts": [
+        "body_solid",
+        "face_planar",
+        "datum_plane"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Project needs a body — add or import one first",
+      "gui": true,
+      "action": "fly:plane#4",
+      "icon": "design_sketch",
+      "hint": "Project body edges onto a plane as sketch entities"
+    },
+    {
+      "id": "measure",
+      "name": "Measure",
+      "slot": "reference",
+      "key": null,
+      "feature": null,
+      "mcp": "measure",
+      "accepts": [
+        "face_planar",
+        "face_cyl",
+        "face_other",
+        "edge_str",
+        "edge_circ",
+        "vertex",
+        "body_solid",
+        "body_sheet",
+        "bodies_2",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": false,
+      "action": null,
+      "icon": null,
+      "hint": "Measure between the picked points, edges or faces"
+    },
+    {
+      "id": "mass_props",
+      "name": "Mass",
+      "slot": "reference",
+      "key": null,
+      "feature": null,
+      "mcp": "mass_properties",
+      "accepts": [
+        "body_solid",
+        "face_planar",
+        "face_cyl",
+        "face_other",
+        "edge_str",
+        "edge_circ",
+        "vertex"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": null,
+      "gui": true,
+      "action": "btn:mass",
+      "icon": "info",
+      "hint": "Report the volume and surface area of the selected body"
+    },
+    {
+      "id": "interference",
+      "name": "Interference",
+      "slot": "reference",
+      "key": null,
+      "feature": null,
+      "mcp": "check_interference",
+      "accepts": [
+        "bodies_2"
+      ],
+      "needs": {
+        "bodies": 2
+      },
+      "refusal": null,
+      "gui": false,
+      "action": null,
+      "icon": null,
+      "hint": "Check whether two bodies overlap — reports, changes nothing"
+    },
+    {
+      "id": "edit_feature",
+      "name": "Edit",
+      "slot": "modify",
+      "key": null,
+      "feature": null,
+      "mcp": "set_feature_expr",
+      "accepts": [
+        "body_solid",
+        "face_planar",
+        "face_cyl",
+        "face_other",
+        "sk_loop",
+        "art",
+        "datum_plane",
+        "datum_axis",
+        "coordsys",
+        "body_sheet"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "btn:edit",
+      "icon": "design_edit",
+      "hint": "Reopen the selected feature to change what it was made from"
+    },
+    {
+      "id": "rename",
+      "name": "Rename…",
+      "slot": "modify",
+      "key": "F2",
+      "feature": "Tree",
+      "mcp": null,
+      "mode": "model",
+      "accepts": [
+        "sk_loop",
+        "body_solid"
+      ],
+      "needs": {},
+      "refusal": "Select a feature, or a body, to rename it",
+      "gui": true,
+      "action": "btn:rename",
+      "icon": null,
+      "hint": "Give this feature a name you will recognise in the tree (a body takes its name from the feature that makes it)"
+    },
+    {
+      "id": "delete_face",
+      "name": "Delete Face",
+      "slot": "modify",
+      "key": null,
+      "feature": "DeleteFace",
+      "mcp": "delete_face",
+      "accepts": [
+        "face_planar",
+        "face_cyl",
+        "face_other"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": "Delete Face needs a body — add or import one first",
+      "gui": true,
+      "action": "fly:dressup#3",
+      "icon": "design_delete",
+      "hint": "Remove faces from a body and heal the solid"
+    },
+    {
+      "id": "colour",
+      "name": "Colour",
+      "slot": "modify",
+      "key": null,
+      "feature": null,
+      "mcp": null,
+      "accepts": [
+        "body_solid",
+        "body_sheet",
+        "face_planar",
+        "face_cyl",
+        "face_other",
+        "edge_str",
+        "edge_circ",
+        "vertex"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "refusal": null,
+      "gui": true,
+      "action": "btn:colour",
+      "icon": "color_palette",
+      "hint": "Set the selected body's display colour"
+    },
+    {
+      "id": "delete",
+      "name": "Delete",
+      "slot": "modify",
+      "key": "Del",
+      "feature": null,
+      "mcp": null,
+      "accepts": [
+        "sk_loop",
+        "art",
+        "datum_plane",
+        "datum_axis",
+        "coordsys",
+        "sk_line",
+        "sk_arc",
+        "sk_point",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "btn:delete",
+      "icon": "design_delete",
+      "hint": "Delete what is selected"
+    },
+    {
+      "id": "delete_body",
+      "name": "Delete Body",
+      "slot": "modify",
+      "key": null,
+      "action": "btn:delete_body",
+      "refusal": null,
+      "accepts": [
+        "body_solid",
+        "body_sheet",
+        "face_planar",
+        "face_cyl",
+        "face_other",
+        "edge_str",
+        "edge_circ",
+        "vertex"
+      ],
+      "needs": {
+        "bodies": 1
+      },
+      "mode": "model",
+      "family": null,
+      "icon": "design_delete",
+      "hint": "Delete this whole body — removes the feature it was made from"
+    },
+    {
+      "id": "sk_line_t",
+      "name": "Line",
+      "slot": "create",
+      "key": "L",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:L",
+      "family": "Line",
+      "icon": "design_line",
+      "hint": "Line — click start, then end"
+    },
+    {
+      "id": "sk_polyline",
+      "name": "Polyline",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_line#1",
+      "mode": "sketch",
+      "family": "Line",
+      "icon": "design_polyline",
+      "hint": "Click points; click the first point to close the loop, right-click to end it open"
+    },
+    {
+      "id": "sk_rect",
+      "name": "Corner rectangle",
+      "slot": "create",
+      "key": "R",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:R",
+      "family": "Rectangle",
+      "icon": "design_rect",
+      "hint": "Rectangle — click two opposite corners"
+    },
+    {
+      "id": "sk_rect_center",
+      "name": "Centre rectangle",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_rect#1",
+      "mode": "sketch",
+      "family": "Rectangle",
+      "icon": "design_crect",
+      "hint": "Click center, then a corner"
+    },
+    {
+      "id": "sk_rect_oblique",
+      "name": "Oblique rectangle",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_rect#2",
+      "mode": "sketch",
+      "family": "Rectangle",
+      "icon": "design_rect_oblique",
+      "hint": "Click two corners of one edge, then a point for the width"
+    },
+    {
+      "id": "sk_rect_rounded",
+      "name": "Rounded rectangle",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_rect#3",
+      "mode": "sketch",
+      "family": "Rectangle",
+      "icon": "design_rect_rounded",
+      "hint": "Click two opposite corners, then a point for the corner radius"
+    },
+    {
+      "id": "sk_circle",
+      "name": "Centre circle",
+      "slot": "create",
+      "key": "C",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:C",
+      "family": "Circle",
+      "icon": "design_circle",
+      "hint": "Circle — click center, then radius"
+    },
+    {
+      "id": "sk_circle_2pt",
+      "name": "2-point circle",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_circle#1",
+      "mode": "sketch",
+      "family": "Circle",
+      "icon": "design_circle2pt",
+      "hint": "Click two ends of the diameter"
+    },
+    {
+      "id": "sk_circle_3pt",
+      "name": "3-point circle",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_circle#2",
+      "mode": "sketch",
+      "family": "Circle",
+      "icon": "design_circle3pt",
+      "hint": "Click three points on the circle"
+    },
+    {
+      "id": "sk_arc_t",
+      "name": "3-point arc",
+      "slot": "create",
+      "key": "A",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:A",
+      "family": "Arc",
+      "icon": "design_arc3pt",
+      "hint": "Arc — click start, end, then a point"
+    },
+    {
+      "id": "sk_arc_tangent",
+      "name": "Tangent arc",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_arc3pt#1",
+      "mode": "sketch",
+      "family": "Arc",
+      "icon": "design_tangentarc",
+      "hint": "Click start (on the last entity) then end"
+    },
+    {
+      "id": "sk_arc_center",
+      "name": "Centre-point arc",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_arc3pt#2",
+      "mode": "sketch",
+      "family": "Arc",
+      "icon": "design_arc_center",
+      "hint": "Click center, then start, then a point for the end angle"
+    },
+    {
+      "id": "sk_slot",
+      "name": "Slot",
+      "slot": "create",
+      "key": "S",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:S",
+      "family": "Slot",
+      "icon": "design_slot",
+      "hint": "Slot — two centerline ends, then end radius"
+    },
+    {
+      "id": "sk_slot_arc",
+      "name": "Arc slot",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_slot#1",
+      "mode": "sketch",
+      "family": "Slot",
+      "icon": "design_slot_arc",
+      "hint": "Click center, start, end, then a point for the width"
+    },
+    {
+      "id": "sk_ellipse",
+      "name": "Ellipse",
+      "slot": "create",
+      "key": "E",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:E",
+      "family": "Ellipse",
+      "icon": "design_ellipse",
+      "hint": "Ellipse — center, major end, minor point"
+    },
+    {
+      "id": "sk_ellipse_arc",
+      "name": "Elliptical arc",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_ellipse#1",
+      "mode": "sketch",
+      "family": "Ellipse",
+      "icon": "design_ellipse_arc",
+      "hint": "Click center, major-axis end, minor point, then arc start and end"
+    },
+    {
+      "id": "sk_spline",
+      "name": "Spline",
+      "slot": "create",
+      "key": "B",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:B",
+      "icon": "design_bspline",
+      "hint": "Spline — click control points"
+    },
+    {
+      "id": "sk_poly_3",
+      "name": "Triangle",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "btn:poly#3",
+      "mode": "sketch",
+      "family": "Polygon",
+      "icon": "design_polygon",
+      "hint": "Triangle — click centre, then a vertex"
+    },
+    {
+      "id": "sk_poly_4",
+      "name": "Square",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "btn:poly#4",
+      "mode": "sketch",
+      "family": "Polygon",
+      "icon": "design_polygon",
+      "hint": "Square — click centre, then a vertex"
+    },
+    {
+      "id": "sk_poly_5",
+      "name": "Pentagon",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "btn:poly#5",
+      "mode": "sketch",
+      "family": "Polygon",
+      "icon": "design_polygon",
+      "hint": "Pentagon — click centre, then a vertex"
+    },
+    {
+      "id": "sk_polygon",
+      "name": "Hexagon",
+      "slot": "create",
+      "key": "G",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "btn:poly#6",
+      "family": "Polygon",
+      "icon": "design_polygon",
+      "hint": "Hexagon — click centre, then a vertex"
+    },
+    {
+      "id": "sk_poly_8",
+      "name": "Octagon",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "btn:poly#8",
+      "mode": "sketch",
+      "family": "Polygon",
+      "icon": "design_polygon",
+      "hint": "Octagon — click centre, then a vertex"
+    },
+    {
+      "id": "sk_poly_12",
+      "name": "Dodecagon",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "btn:poly#12",
+      "mode": "sketch",
+      "family": "Polygon",
+      "icon": "design_polygon",
+      "hint": "Dodecagon — click centre, then a vertex"
+    },
+    {
+      "id": "sk_poly_inscribed",
+      "name": "Inscribed",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "btn:polyfit#0",
+      "mode": "sketch",
+      "family": "Polygon",
+      "icon": "design_polygon",
+      "hint": "Measure the polygon to its corners (inscribed)"
+    },
+    {
+      "id": "sk_poly_circumscribed",
+      "name": "Circumscribed",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "btn:polyfit#1",
+      "mode": "sketch",
+      "family": "Polygon",
+      "icon": "design_polygon",
+      "hint": "Measure the polygon to its flats (circumscribed)"
+    },
+    {
+      "id": "sk_point_t",
+      "name": "Point",
+      "slot": "create",
+      "key": "P",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:P",
+      "icon": "design_point",
+      "hint": "Point — click to place"
+    },
+    {
+      "id": "sk_text",
+      "name": "Text",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "btn:text",
+      "mode": "sketch",
+      "icon": "design_text",
+      "hint": "Type text; its outline is added to this sketch as editable lines"
+    },
+    {
+      "id": "sk_svg",
+      "name": "SVG",
+      "slot": "create",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_none",
+        "sk_point",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "btn:svg",
+      "mode": "sketch",
+      "icon": "design_svg",
+      "hint": "Import an SVG outline into this sketch as editable lines"
+    },
+    {
+      "id": "sk_offset",
+      "name": "Offset",
+      "slot": "add",
+      "key": "O",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:O",
+      "icon": "design_offset",
+      "hint": "Offset — pick an entity, drag the distance"
+    },
+    {
+      "id": "sk_trim",
+      "name": "Trim",
+      "slot": "remove",
+      "key": "T",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:T",
+      "icon": "design_trim",
+      "hint": "Trim — click a segment to trim it"
+    },
+    {
+      "id": "sk_fillet",
+      "name": "Fillet",
+      "slot": "dressup",
+      "key": "F",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_line",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:F",
+      "icon": "design_filletedge",
+      "hint": "Fillet — pick two lines, set the radius"
+    },
+    {
+      "id": "sk_chamfer",
+      "name": "Chamfer",
+      "slot": "dressup",
+      "key": "H",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_line",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:H",
+      "icon": "design_chamfer",
+      "hint": "Chamfer — pick two lines, set the distance"
+    },
+    {
+      "id": "sk_array",
+      "name": "Linear array",
+      "slot": "repeat",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_array#0",
+      "mode": "sketch",
+      "family": "Array",
+      "icon": "design_array",
+      "hint": "Pick entities, drag the spacing handle, click the count; click empty to apply"
+    },
+    {
+      "id": "sk_array_polar",
+      "name": "Polar array",
+      "slot": "repeat",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_array#1",
+      "mode": "sketch",
+      "family": "Array",
+      "icon": "design_polararray",
+      "hint": "Pick entities, drag the sweep handle, click the count; click empty to apply"
+    },
+    {
+      "id": "sk_mirror",
+      "name": "Mirror",
+      "slot": "repeat",
+      "key": "M",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:M",
+      "icon": "design_mirror",
+      "hint": "Mirror — pick axis, then entities"
+    },
+    {
+      "id": "sk_move",
+      "name": "Move",
+      "slot": "transform",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_line",
+        "sk_arc",
+        "sk_point",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_move#0",
+      "family": "Move",
+      "icon": "design_move",
+      "hint": "Pick entities, then drag the handle or click the distance; click empty to apply"
+    },
+    {
+      "id": "sk_rotate",
+      "name": "Rotate",
+      "slot": "transform",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_line",
+        "sk_arc",
+        "sk_point",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_move#1",
+      "mode": "sketch",
+      "family": "Move",
+      "icon": "design_rotate",
+      "hint": "Pick entities, then drag around the pivot or click the angle; click empty to apply"
+    },
+    {
+      "id": "sk_scale",
+      "name": "Scale",
+      "slot": "transform",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "accepts": [
+        "sk_line",
+        "sk_arc",
+        "sk_point",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "fly:design_move#2",
+      "mode": "sketch",
+      "family": "Move",
+      "icon": "design_scale",
+      "hint": "Pick entities, then drag the handle or click the factor; click empty to apply"
+    },
+    {
+      "id": "sk_dimension",
+      "name": "Dimension",
+      "slot": "reference",
+      "key": "D",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_none",
+        "sk_line",
+        "sk_arc",
+        "sk_point",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:D",
+      "icon": "design_dimension",
+      "hint": "Dimension — click 2 points or an entity"
+    },
+    {
+      "id": "sk_constrain",
+      "name": "Constrain",
+      "slot": "reference",
+      "key": "K",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_line",
+        "sk_arc",
+        "sk_point",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:K",
+      "icon": "design_constrain",
+      "hint": "Constrain the selected sketch entities to each other"
+    },
+    {
+      "id": "constrain",
+      "name": "Constrain sketch",
+      "slot": "modify",
+      "key": null,
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "model",
+      "accepts": [
+        "sk_loop"
+      ],
+      "needs": {
+        "sketches": 1
+      },
+      "refusal": "Select a sketch to constrain it",
+      "gui": true,
+      "action": "btn:constrain",
+      "icon": "design_constrain",
+      "hint": "Add dimensions and relations (coincident, tangent, parallel...) to the selected sketch",
+      "note": [
+        "Same verb, model-mode vocabulary: offered when a SKETCH is selected (bit 14, SkLoop), the",
+        "state a user is in right after finishing one. Without this row the only way in was the",
+        "toolbar icon, and constraints read as absent — see the Onshape-comparison report."
+      ]
+    },
+    {
+      "id": "sk_construct",
+      "name": "Construction",
+      "slot": "reference",
+      "key": "Q",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_none",
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:Q",
+      "icon": null,
+      "hint": "Toggle construction: geometry that guides but is never built"
+    },
+    {
+      "id": "sk_extend",
+      "name": "Extend",
+      "slot": "modify",
+      "key": "X",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_line",
+        "sk_arc",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:X",
+      "icon": "design_extend",
+      "hint": "Extend — click a line/arc to extend it"
+    },
+    {
+      "id": "sk_delete",
+      "name": "Delete",
+      "slot": "modify",
+      "key": "Del",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_line",
+        "sk_arc",
+        "sk_point",
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "btn:sk_delete",
+      "icon": "design_delete",
+      "hint": "Delete the selected sketch entities"
+    },
+    {
+      "id": "sk_length",
+      "name": "Length…",
+      "slot": "modify",
+      "key": "V",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_line"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:V",
+      "icon": "design_dimension",
+      "hint": "Type the length of this line",
+      "note": [
+        "Typing the defining number of the element you pointed at. Three rows rather than one so",
+        "each names the quantity in the drawing-office word for THAT element; all three land on",
+        "the same handler, because dimension_kind() already resolves the quantity from the",
+        "selection. Without these, an element's own numbers were reachable only by arming the",
+        "Dimension tool and re-picking geometry that was already selected."
+      ]
+    },
+    {
+      "id": "sk_radius",
+      "name": "Radius / diameter…",
+      "slot": "modify",
+      "key": "V",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_arc"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:V",
+      "icon": "design_dimension",
+      "hint": "Type the radius of this arc, or the diameter of this circle"
+    },
+    {
+      "id": "sk_angdist",
+      "name": "Angle / distance…",
+      "slot": "modify",
+      "key": "V",
+      "feature": "Sketch",
+      "mcp": null,
+      "mode": "sketch",
+      "accepts": [
+        "sk_2ent"
+      ],
+      "needs": {},
+      "refusal": null,
+      "gui": true,
+      "action": "key:V",
+      "icon": "design_dimension",
+      "hint": "Type the angle between two lines, or the distance between the two picks"
+    }
+  ],
+  "chrome_only": {
+    "_why": "document-level actions act on the DOCUMENT, not on a selection, so they stay in chrome and never enter the offer (see 4.1) Text and SVG were removed from this list 2026-08-01: they create a Sketch feature on the picked face, so they consume a selection like any other Create verb.",
+    "items": [
+      "Import STEP",
+      "Import mesh",
+      "Export STEP",
+      "Commit to Plate",
+      "Undo",
+      "Redo",
+      "Variables",
+      "Section view",
+      "Origin planes",
+      "World axes"
+    ]
+  },
+  "_ratified": "Row order ratified 2026-07-31 by Tommaso. Changing an index is a breaking change (charter 4.1)."
+}
diff --git a/localization/i18n/list.txt b/localization/i18n/list.txt
index a36ecd5cab..ae33c5fc85 100644
--- a/localization/i18n/list.txt
+++ b/localization/i18n/list.txt
@@ -291,3 +291,6 @@ src/slic3r/GUI/PrinterWebViewHandler.cpp
 src/slic3r/GUI/AMSDryControl.cpp
 src/slic3r/GUI/AMSDryControl.hpp
 src/libslic3r/PresetBundle.cpp
+src/slic3r/GUI/CAD/DesignPanel.cpp
+src/slic3r/GUI/Gizmos/GLGizmoPrimitive.cpp
+src/slic3r/GUI/Gizmos/GLGizmoSketch.cpp
diff --git a/resources/images/color_palette.svg b/resources/images/color_palette.svg
new file mode 100644
index 0000000000..8448a364aa
--- /dev/null
+++ b/resources/images/color_palette.svg
@@ -0,0 +1,14 @@
+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<g clip-path="url(#clip0_23434_47713)">
+<circle cx="9.32187" cy="4.2125" r="0.9" fill="#009688"/>
+<circle cx="3.65625" cy="8.75" r="0.75" fill="#009688"/>
+<path d="M8 0.5C12.0195 0.5 15.2656 3.35278 15.4824 6.74512L15.4932 7.0752C15.4914 9.23822 13.7134 11.0155 11.5498 11.0156H9.95312C9.71275 11.0126 9.4739 11.0574 9.25098 11.1475C9.0257 11.2386 8.82126 11.3741 8.64941 11.5459C8.47744 11.7179 8.34113 11.9229 8.25 12.1484C8.1817 12.3176 8.13909 12.4957 8.12402 12.6768L8.11816 12.8496C8.11817 13.3362 8.27448 13.7495 8.59473 14.0801V14.0811C8.73012 14.2338 8.81831 14.4375 8.81836 14.6494C8.81836 15.1395 8.45218 15.5 8 15.5C3.87614 15.5 0.5 12.1239 0.5 8C0.5 3.87614 3.87614 0.5 8 0.5Z" stroke="#949494" stroke-linecap="round" stroke-linejoin="round"/>
+<circle cx="5.17031" cy="5.11172" r="1.35" fill="#009688"/>
+<circle cx="12.1578" cy="7.10313" r="1.15" fill="#009688"/>
+</g>
+<defs>
+<clipPath id="clip0_23434_47713">
+<rect width="16" height="16" fill="white"/>
+</clipPath>
+</defs>
+</svg>
diff --git a/resources/images/design_arc3pt.svg b/resources/images/design_arc3pt.svg
new file mode 100644
index 0000000000..1b40569b4f
--- /dev/null
+++ b/resources/images/design_arc3pt.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M4 17 A11 11 0 0 1 20 17"/><circle cx="4" cy="17" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="12" cy="7" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="20" cy="17" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_arc_center.svg b/resources/images/design_arc_center.svg
new file mode 100644
index 0000000000..e4c85febfc
--- /dev/null
+++ b/resources/images/design_arc_center.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M5 18 A13 13 0 0 1 18 5"/><path d="M5 5 5 18M5 5 18 5" stroke-dasharray="2.5 2.5" opacity="0.5"/><circle cx="5" cy="5" r="2" fill="#b6b6b6" stroke="none"/><circle cx="5" cy="18" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="18" cy="5" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_array.svg b/resources/images/design_array.svg
new file mode 100644
index 0000000000..d29da47bd7
--- /dev/null
+++ b/resources/images/design_array.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><rect x="3" y="3" width="6" height="6"/><rect x="15" y="3" width="6" height="6"/><rect x="3" y="15" width="6" height="6"/><rect x="15" y="15" width="6" height="6"/></svg>
diff --git a/resources/images/design_boolean.svg b/resources/images/design_boolean.svg
new file mode 100644
index 0000000000..97813cf2eb
--- /dev/null
+++ b/resources/images/design_boolean.svg
@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round">
+  <circle cx="9" cy="12" r="6"/>
+  <circle cx="15" cy="12" r="6"/>
+</svg>
diff --git a/resources/images/design_bspline.svg b/resources/images/design_bspline.svg
new file mode 100644
index 0000000000..16a5dc9b31
--- /dev/null
+++ b/resources/images/design_bspline.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M3 19 C 6 5, 12 5, 12 12 S 18 19, 21 5"/><circle cx="3" cy="19" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="12" cy="12" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="21" cy="5" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_c_angle.svg b/resources/images/design_c_angle.svg
new file mode 100644
index 0000000000..2359b23b6a
--- /dev/null
+++ b/resources/images/design_c_angle.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M4 20h16M4 20 16 6"/><path d="M11 20 A7 7 0 0 0 9.1 15.2"/></svg>
diff --git a/resources/images/design_c_coincident.svg b/resources/images/design_c_coincident.svg
new file mode 100644
index 0000000000..83ab602eca
--- /dev/null
+++ b/resources/images/design_c_coincident.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="12" r="6"/><circle cx="12" cy="12" r="2.2" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_c_collinear.svg b/resources/images/design_c_collinear.svg
new file mode 100644
index 0000000000..28b8b6a8cd
--- /dev/null
+++ b/resources/images/design_c_collinear.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M2 12h20" stroke-dasharray="1.5 1.5"/><path d="M5 12h5M14 12h5"/></svg>
diff --git a/resources/images/design_c_concentric.svg b/resources/images/design_c_concentric.svg
new file mode 100644
index 0000000000..9861381b58
--- /dev/null
+++ b/resources/images/design_c_concentric.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="12" r="8"/><circle cx="12" cy="12" r="3.5"/><circle cx="12" cy="12" r="1.3" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_c_diameter.svg b/resources/images/design_c_diameter.svg
new file mode 100644
index 0000000000..8e3766c4dc
--- /dev/null
+++ b/resources/images/design_c_diameter.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="12" r="7"/><path d="M6.3 17.7 17.7 6.3"/></svg>
diff --git a/resources/images/design_c_dist_x.svg b/resources/images/design_c_dist_x.svg
new file mode 100644
index 0000000000..e811a58df6
--- /dev/null
+++ b/resources/images/design_c_dist_x.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M6 6v12M18 6v12M6 12h12M6 12l2.5-2M6 12l2.5 2M18 12l-2.5-2M18 12l-2.5 2"/></svg>
diff --git a/resources/images/design_c_dist_y.svg b/resources/images/design_c_dist_y.svg
new file mode 100644
index 0000000000..5aefec85ee
--- /dev/null
+++ b/resources/images/design_c_dist_y.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M6 6h12M6 18h12M12 6v12M12 6l-2 2.5M12 6l2 2.5M12 18l-2-2.5M12 18l2-2.5"/></svg>
diff --git a/resources/images/design_c_equal.svg b/resources/images/design_c_equal.svg
new file mode 100644
index 0000000000..f0657b74b0
--- /dev/null
+++ b/resources/images/design_c_equal.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M5 9h14M5 15h14"/></svg>
diff --git a/resources/images/design_c_equal_radius.svg b/resources/images/design_c_equal_radius.svg
new file mode 100644
index 0000000000..4d7ccf2c5c
--- /dev/null
+++ b/resources/images/design_c_equal_radius.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><circle cx="4" cy="12" r="2.5"/><circle cx="15" cy="12" r="4.5"/><path d="M8 10h2M8 14h2"/></svg>
diff --git a/resources/images/design_c_fix.svg b/resources/images/design_c_fix.svg
new file mode 100644
index 0000000000..b64024286e
--- /dev/null
+++ b/resources/images/design_c_fix.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="5.5" r="2"/><path d="M12 7.5V20M8.5 10h7M6 14a6 6 0 0 0 12 0"/></svg>
diff --git a/resources/images/design_c_horizontal.svg b/resources/images/design_c_horizontal.svg
new file mode 100644
index 0000000000..9804a8ad82
--- /dev/null
+++ b/resources/images/design_c_horizontal.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M3 12h18M3 9v6M21 9v6"/></svg>
diff --git a/resources/images/design_c_midpoint.svg b/resources/images/design_c_midpoint.svg
new file mode 100644
index 0000000000..6646a6cc1e
--- /dev/null
+++ b/resources/images/design_c_midpoint.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M4 12h16M4 9v6M20 9v6"/><circle cx="12" cy="12" r="2" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_c_parallel.svg b/resources/images/design_c_parallel.svg
new file mode 100644
index 0000000000..cc78f9c452
--- /dev/null
+++ b/resources/images/design_c_parallel.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M7 20 13 4M13 20 19 4"/></svg>
diff --git a/resources/images/design_c_perpendicular.svg b/resources/images/design_c_perpendicular.svg
new file mode 100644
index 0000000000..9a67cebb2b
--- /dev/null
+++ b/resources/images/design_c_perpendicular.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M6 3v15h15M6 13h5v5"/></svg>
diff --git a/resources/images/design_c_radius.svg b/resources/images/design_c_radius.svg
new file mode 100644
index 0000000000..5e1f1cdadf
--- /dev/null
+++ b/resources/images/design_c_radius.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="12" r="8"/><path d="M12 12h8M17.5 9.5 20 12 17.5 14.5"/><circle cx="12" cy="12" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_c_sym_h.svg b/resources/images/design_c_sym_h.svg
new file mode 100644
index 0000000000..4e152787b1
--- /dev/null
+++ b/resources/images/design_c_sym_h.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M3 12h18" stroke-dasharray="2.5 2.5" opacity="0.5"/><path d="M8 6h8M8 18h8"/></svg>
diff --git a/resources/images/design_c_sym_v.svg b/resources/images/design_c_sym_v.svg
new file mode 100644
index 0000000000..f4cd99371a
--- /dev/null
+++ b/resources/images/design_c_sym_v.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M12 3v18" stroke-dasharray="2.5 2.5" opacity="0.5"/><path d="M6 8v8M18 8v8"/></svg>
diff --git a/resources/images/design_c_symmetric.svg b/resources/images/design_c_symmetric.svg
new file mode 100644
index 0000000000..7a539be9a3
--- /dev/null
+++ b/resources/images/design_c_symmetric.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M12 3v18" stroke-dasharray="2.5 2.5" opacity="0.5"/><path d="M8 8 4 12 8 16M16 8l4 4-4 4"/></svg>
diff --git a/resources/images/design_c_tangent.svg b/resources/images/design_c_tangent.svg
new file mode 100644
index 0000000000..e82d23240d
--- /dev/null
+++ b/resources/images/design_c_tangent.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="14.5" r="5"/><path d="M3 9.5h18"/></svg>
diff --git a/resources/images/design_c_vertical.svg b/resources/images/design_c_vertical.svg
new file mode 100644
index 0000000000..98526e93d7
--- /dev/null
+++ b/resources/images/design_c_vertical.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M12 3v18M9 3h6M9 21h6"/></svg>
diff --git a/resources/images/design_chamfer.svg b/resources/images/design_chamfer.svg
new file mode 100644
index 0000000000..861f7b819a
--- /dev/null
+++ b/resources/images/design_chamfer.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M5 5v8l6 6h8"/></svg>
diff --git a/resources/images/design_check.svg b/resources/images/design_check.svg
new file mode 100644
index 0000000000..82d5edd48e
--- /dev/null
+++ b/resources/images/design_check.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M5 12l4 4L19 6"/></svg>
diff --git a/resources/images/design_circle.svg b/resources/images/design_circle.svg
new file mode 100644
index 0000000000..edc74b13ea
--- /dev/null
+++ b/resources/images/design_circle.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="12" r="8"/><circle cx="12" cy="12" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_circle2pt.svg b/resources/images/design_circle2pt.svg
new file mode 100644
index 0000000000..844b0797eb
--- /dev/null
+++ b/resources/images/design_circle2pt.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="12" r="7.5"/><path d="M6.7 6.7 17.3 17.3" stroke-dasharray="2.5 2.5" opacity="0.5"/><circle cx="6.7" cy="6.7" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="17.3" cy="17.3" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_circle3pt.svg b/resources/images/design_circle3pt.svg
new file mode 100644
index 0000000000..6fdbab2474
--- /dev/null
+++ b/resources/images/design_circle3pt.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="12" r="8"/><circle cx="12" cy="4" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="5.07" cy="16" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="18.93" cy="16" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_constrain.svg b/resources/images/design_constrain.svg
new file mode 100644
index 0000000000..cc9be6ca9b
--- /dev/null
+++ b/resources/images/design_constrain.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><rect x="5" y="11" width="14" height="9" rx="2"/><path d="M8 11V7a4 4 0 0 1 8 0v4"/></svg>
diff --git a/resources/images/design_construction.svg b/resources/images/design_construction.svg
new file mode 100644
index 0000000000..89d10f424d
--- /dev/null
+++ b/resources/images/design_construction.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M4 12h16" stroke-dasharray="3 3"/><circle cx="4" cy="12" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="20" cy="12" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_crect.svg b/resources/images/design_crect.svg
new file mode 100644
index 0000000000..9e2ece0c24
--- /dev/null
+++ b/resources/images/design_crect.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><rect x="4" y="6" width="16" height="12" rx="1"/><circle cx="12" cy="12" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_cut.svg b/resources/images/design_cut.svg
new file mode 100644
index 0000000000..3f68a7002e
--- /dev/null
+++ b/resources/images/design_cut.svg
@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round">
+  <path d="M6 8.5l6-3 6 3v7l-6 3-6-3z"/>
+  <line x1="3" y1="14" x2="21" y2="10"/>
+</svg>
diff --git a/resources/images/design_delete.svg b/resources/images/design_delete.svg
new file mode 100644
index 0000000000..f5d5c6a1c7
--- /dev/null
+++ b/resources/images/design_delete.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M4 7h16M9 7V4h6v3M6 7l1 13h10l1-13M10 11v6M14 11v6"/></svg>
diff --git a/resources/images/design_dimension.svg b/resources/images/design_dimension.svg
new file mode 100644
index 0000000000..f456abb6fc
--- /dev/null
+++ b/resources/images/design_dimension.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M4 7v10M20 7v10M4 12h16M7 9l-3 3 3 3M17 9l3 3-3 3"/></svg>
diff --git a/resources/images/design_draft.svg b/resources/images/design_draft.svg
new file mode 100644
index 0000000000..2957584cb8
--- /dev/null
+++ b/resources/images/design_draft.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M6 4H18L15 20H9Z"/><path d="M9 20V4" stroke-dasharray="2.5 2.5" opacity="0.5"/><path d="M9 14a4 4 0 0 0 1.3 3"/></svg>
diff --git a/resources/images/design_dressup.svg b/resources/images/design_dressup.svg
new file mode 100644
index 0000000000..cc2a09250e
--- /dev/null
+++ b/resources/images/design_dressup.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M4 20V10a6 6 0 0 1 6-6h10"/><path d="M4 20h4M20 4v4" stroke-dasharray="2.5 2.5" opacity="0.5"/></svg>
diff --git a/resources/images/design_edit.svg b/resources/images/design_edit.svg
new file mode 100644
index 0000000000..4de84fc390
--- /dev/null
+++ b/resources/images/design_edit.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M4 20h4L19 9l-4-4L4 16z"/><path d="M14 6l4 4"/></svg>
diff --git a/resources/images/design_ellipse.svg b/resources/images/design_ellipse.svg
new file mode 100644
index 0000000000..1f946eb5fa
--- /dev/null
+++ b/resources/images/design_ellipse.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><ellipse cx="12" cy="12" rx="9.5" ry="5.5"/><circle cx="12" cy="12" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_ellipse_arc.svg b/resources/images/design_ellipse_arc.svg
new file mode 100644
index 0000000000..e9cd4aa66a
--- /dev/null
+++ b/resources/images/design_ellipse_arc.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M3 13 A9.5 5.5 0 0 1 21 10"/><circle cx="12" cy="12" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="3" cy="13" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="21" cy="10" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_extend.svg b/resources/images/design_extend.svg
new file mode 100644
index 0000000000..9d4934fada
--- /dev/null
+++ b/resources/images/design_extend.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M3 12h11"/><path d="M14 12h7m-3-3l3 3-3 3"/><path d="M14 12h7" stroke-dasharray="2.5 2.5" opacity="0.5"/></svg>
diff --git a/resources/images/design_extrude.svg b/resources/images/design_extrude.svg
new file mode 100644
index 0000000000..8137336fb2
--- /dev/null
+++ b/resources/images/design_extrude.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><rect x="4" y="11" width="16" height="9" rx="1"/><path d="M12 8V2M9 5l3-3 3 3"/></svg>
diff --git a/resources/images/design_eye.svg b/resources/images/design_eye.svg
new file mode 100644
index 0000000000..97296c7465
--- /dev/null
+++ b/resources/images/design_eye.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M2 12C5 6 19 6 22 12 19 18 5 18 2 12Z"/><circle cx="12" cy="12" r="3"/></svg>
diff --git a/resources/images/design_filletedge.svg b/resources/images/design_filletedge.svg
new file mode 100644
index 0000000000..435d7c2cb9
--- /dev/null
+++ b/resources/images/design_filletedge.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M5 5v8a6 6 0 0 0 6 6h8"/></svg>
diff --git a/resources/images/design_hole.svg b/resources/images/design_hole.svg
new file mode 100644
index 0000000000..35128ef51e
--- /dev/null
+++ b/resources/images/design_hole.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><rect x="3" y="3" width="18" height="18" rx="2"/><circle cx="12" cy="12" r="4"/><circle cx="12" cy="12" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_line.svg b/resources/images/design_line.svg
new file mode 100644
index 0000000000..afb644ba3f
--- /dev/null
+++ b/resources/images/design_line.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M5 19 19 5"/><circle cx="5" cy="19" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="19" cy="5" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_loft.svg b/resources/images/design_loft.svg
new file mode 100644
index 0000000000..4529b52554
--- /dev/null
+++ b/resources/images/design_loft.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><rect x="3" y="15.5" width="8.5" height="4.5" rx="0.5"/><ellipse cx="16.5" cy="6" rx="4" ry="1.7"/><path d="M3.2 15.5 12.6 4.8M11.4 20 20.4 7.2"/></svg>
diff --git a/resources/images/design_mirror.svg b/resources/images/design_mirror.svg
new file mode 100644
index 0000000000..0a9642f8f3
--- /dev/null
+++ b/resources/images/design_mirror.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M12 3v18" stroke-dasharray="2.5 2.5" opacity="0.5"/><path d="M8 7 4 12 8 17Z"/><path d="M16 7l4 5-4 5Z"/></svg>
diff --git a/resources/images/design_move.svg b/resources/images/design_move.svg
new file mode 100644
index 0000000000..dba4f4f4c2
--- /dev/null
+++ b/resources/images/design_move.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><rect x="9" y="9" width="6" height="6" rx="1"/><path d="M12 8V2M9.6 4.4 12 2 14.4 4.4M12 16v6M9.6 19.6 12 22 14.4 19.6M8 12H2M4.4 9.6 2 12 4.4 14.4M16 12h6M19.6 9.6 22 12 19.6 14.4"/></svg>
diff --git a/resources/images/design_movedown.svg b/resources/images/design_movedown.svg
new file mode 100644
index 0000000000..89c442dc6e
--- /dev/null
+++ b/resources/images/design_movedown.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M12 5v14M6 13l6 6 6-6"/></svg>
diff --git a/resources/images/design_moveup.svg b/resources/images/design_moveup.svg
new file mode 100644
index 0000000000..b2fe5ec127
--- /dev/null
+++ b/resources/images/design_moveup.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M12 19V5M6 11l6-6 6 6"/></svg>
diff --git a/resources/images/design_offset.svg b/resources/images/design_offset.svg
new file mode 100644
index 0000000000..74758ad0ba
--- /dev/null
+++ b/resources/images/design_offset.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M3 20V10A7 7 0 0 1 10 3H20"/><path d="M7 20V10A3 3 0 0 1 10 7H20"/></svg>
diff --git a/resources/images/design_pattern.svg b/resources/images/design_pattern.svg
new file mode 100644
index 0000000000..c07708509b
--- /dev/null
+++ b/resources/images/design_pattern.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><rect x="3" y="9" width="6" height="6" rx="1"/><rect x="10.5" y="9" width="6" height="6" rx="1"/><rect x="18" y="9" width="3.6" height="6" rx="1" stroke-dasharray="2.5 2.5" opacity="0.5"/></svg>
diff --git a/resources/images/design_plane.svg b/resources/images/design_plane.svg
new file mode 100644
index 0000000000..8a3886158f
--- /dev/null
+++ b/resources/images/design_plane.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M3 8 13 8 21 15 11 15Z"/></svg>
diff --git a/resources/images/design_point.svg b/resources/images/design_point.svg
new file mode 100644
index 0000000000..dd5d750545
--- /dev/null
+++ b/resources/images/design_point.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M12 4v3.4M12 16.6v3.4M4 12h3.4M16.6 12h3.4"/><circle cx="12" cy="12" r="2.2" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_polararray.svg b/resources/images/design_polararray.svg
new file mode 100644
index 0000000000..5e91d49f73
--- /dev/null
+++ b/resources/images/design_polararray.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="12" r="8" stroke-dasharray="2.5 2.5" opacity="0.5"/><circle cx="12" cy="12" r="1.4" fill="#b6b6b6" stroke="none"/><circle cx="12" cy="4" r="1.8" fill="#b6b6b6" stroke="none"/><circle cx="18.9" cy="8" r="1.8" fill="#b6b6b6" stroke="none"/><circle cx="18.9" cy="16" r="1.8" fill="#b6b6b6" stroke="none"/><circle cx="12" cy="20" r="1.8" fill="#b6b6b6" stroke="none"/><circle cx="5.1" cy="16" r="1.8" fill="#b6b6b6" stroke="none"/><circle cx="5.1" cy="8" r="1.8" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_polygon.svg b/resources/images/design_polygon.svg
new file mode 100644
index 0000000000..de5cfd6f20
--- /dev/null
+++ b/resources/images/design_polygon.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M12 3l8 4.5v9L12 21l-8-4.5v-9Z"/><circle cx="12" cy="12" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_polyline.svg b/resources/images/design_polyline.svg
new file mode 100644
index 0000000000..96538abea7
--- /dev/null
+++ b/resources/images/design_polyline.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M3 18 9 9 14 15 21 5"/><circle cx="3" cy="18" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="9" cy="9" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="14" cy="15" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="21" cy="5" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_rect.svg b/resources/images/design_rect.svg
new file mode 100644
index 0000000000..67b70cc6a1
--- /dev/null
+++ b/resources/images/design_rect.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><rect x="4" y="6" width="16" height="12" rx="1"/><circle cx="4" cy="6" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_rect_oblique.svg b/resources/images/design_rect_oblique.svg
new file mode 100644
index 0000000000..5d252ca677
--- /dev/null
+++ b/resources/images/design_rect_oblique.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M4 16 10 6 20 8 14 18Z"/><circle cx="4" cy="16" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="10" cy="6" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_rect_rounded.svg b/resources/images/design_rect_rounded.svg
new file mode 100644
index 0000000000..a8c7022c87
--- /dev/null
+++ b/resources/images/design_rect_rounded.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><rect x="3.5" y="6" width="17" height="12" rx="4.5"/></svg>
diff --git a/resources/images/design_revolve.svg b/resources/images/design_revolve.svg
new file mode 100644
index 0000000000..3a0e87f6f4
--- /dev/null
+++ b/resources/images/design_revolve.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M3 16.5 A9 9 0 0 1 21 16.5 L16 16.5 A4 4 0 0 0 8 16.5 Z"/></svg>
diff --git a/resources/images/design_rib.svg b/resources/images/design_rib.svg
new file mode 100644
index 0000000000..b481e38d23
--- /dev/null
+++ b/resources/images/design_rib.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><rect x="3" y="18" width="18" height="3" rx="0.5"/><rect x="6" y="6" width="2.5" height="12" rx="0.5"/><path d="M8.5 9L17 18"/></svg>
diff --git a/resources/images/design_rotate.svg b/resources/images/design_rotate.svg
new file mode 100644
index 0000000000..5a9b48ebfe
--- /dev/null
+++ b/resources/images/design_rotate.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M21 12a9 9 0 1 1-3.5-7.1"/><path d="M21 3 21 8 16 8"/></svg>
diff --git a/resources/images/design_scale.svg b/resources/images/design_scale.svg
new file mode 100644
index 0000000000..5a53562ba3
--- /dev/null
+++ b/resources/images/design_scale.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><rect x="9" y="9" width="6" height="6" rx="1"/><path d="M8 8 3 3M3 7 3 3 7 3M16 8 21 3M17 3 21 3 21 7M8 16 3 21M3 17 3 21 7 21M16 16 21 21M17 21 21 21 21 17"/></svg>
diff --git a/resources/images/design_select.svg b/resources/images/design_select.svg
new file mode 100644
index 0000000000..6f2e4f4ae9
--- /dev/null
+++ b/resources/images/design_select.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M5 3 5 17.5 8.8 14.2 11.3 20.3 13.4 19.4 11 13.6 15.9 13.6Z"/></svg>
diff --git a/resources/images/design_shell.svg b/resources/images/design_shell.svg
new file mode 100644
index 0000000000..aa11b572e6
--- /dev/null
+++ b/resources/images/design_shell.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><rect x="4" y="4" width="16" height="16" rx="1"/><path d="M8 4v12h8V4"/></svg>
diff --git a/resources/images/design_sketch.svg b/resources/images/design_sketch.svg
new file mode 100644
index 0000000000..102a9fe493
--- /dev/null
+++ b/resources/images/design_sketch.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M16 3.5a2.1 2.1 0 0 1 3 3L7.5 18l-4 1 1-4Z"/><path d="M14.5 5 19 9.5"/></svg>
diff --git a/resources/images/design_slot.svg b/resources/images/design_slot.svg
new file mode 100644
index 0000000000..f1c72f8c54
--- /dev/null
+++ b/resources/images/design_slot.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M8 7h8a5 5 0 0 1 0 10H8a5 5 0 0 1 0-10Z"/><circle cx="8" cy="12" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="16" cy="12" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_slot_arc.svg b/resources/images/design_slot_arc.svg
new file mode 100644
index 0000000000..f17ab89144
--- /dev/null
+++ b/resources/images/design_slot_arc.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M5.3 13 A8 8 0 0 1 12.9 17 A2.5 2.5 0 0 0 17.3 14.5 A13 13 0 0 0 4.9 8 A2.5 2.5 0 0 0 5.3 13Z"/></svg>
diff --git a/resources/images/design_step.svg b/resources/images/design_step.svg
new file mode 100644
index 0000000000..4bdf7811ff
--- /dev/null
+++ b/resources/images/design_step.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M3.0 9.0 L16.0 9.0 L16.0 21.0 L3.0 21.0 ZM3.0 9.0 L7.0 5.0 L20.0 5.0 L16.0 9.0M20.0 5.0 L20.0 17.0 L16.0 21.0" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"/><path d="M6.168410256410256 13.423897435897436V13.868410256410256Q5.908923076923077 13.744307692307691 5.678769230769231 13.683384615384615Q5.448615384615385 13.622461538461538 5.23425641025641 13.622461538461538Q4.861948717948718 13.622461538461538 4.66 13.766871794871793Q4.458051282051283 13.91128205128205 4.458051282051283 14.177538461538461Q4.458051282051283 14.400923076923076 4.592307692307693 14.514871794871794Q4.726564102564103 14.628820512820512 5.101128205128205 14.69876923076923L5.3764102564102565 14.755179487179486Q5.886358974358975 14.852205128205128 6.128923076923078 15.09702564102564Q6.37148717948718 15.341846153846152 6.37148717948718 15.75251282051282Q6.37148717948718 16.242153846153844 6.043179487179488 16.49487179487179Q5.7148717948717955 16.747589743589742 5.080820512820513 16.747589743589742Q4.841641025641026 16.747589743589742 4.572000000000001 16.693435897435897Q4.302358974358975 16.639282051282052 4.013538461538462 16.53323076923077V16.063897435897434Q4.291076923076924 16.219589743589744 4.557333333333334 16.2985641025641Q4.823589743589745 16.37753846153846 5.080820512820513 16.37753846153846Q5.471179487179487 16.37753846153846 5.683282051282052 16.224102564102562Q5.895384615384616 16.070666666666664 5.895384615384616 15.786358974358974Q5.895384615384616 15.538153846153845 5.743076923076924 15.398256410256408Q5.590769230769231 15.258358974358973 5.243282051282051 15.188410256410256L4.965743589743591 15.134256410256409Q4.455794871794872 15.032717948717949 4.227897435897436 14.816102564102565Q4.000000000000001 14.599487179487179 4.000000000000001 14.213641025641024Q4.000000000000001 13.766871794871793 4.314769230769231 13.509641025641024Q4.629538461538462 13.252410256410256 5.182358974358975 13.252410256410256Q5.419282051282051 13.252410256410256 5.665230769230769 13.29528205128205Q5.911179487179488 13.338153846153846 6.168410256410256 13.423897435897436ZM6.615179487179487 13.313333333333333H9.46502564102564V13.696923076923076H8.269128205128204V16.682153846153845H7.811076923076923V13.696923076923076H6.615179487179487ZM9.905025641025642 13.313333333333333H12.035076923076925V13.696923076923076H10.360820512820514V14.69425641025641H11.965128205128206V15.077846153846153H10.360820512820514V16.2985641025641H12.075692307692309V16.682153846153845H9.905025641025642ZM13.280615384615384 13.687897435897435V14.953743589743588H13.85374358974359Q14.171897435897435 14.953743589743588 14.345641025641026 14.78902564102564Q14.519384615384615 14.624307692307692 14.519384615384615 14.319692307692307Q14.519384615384615 14.017333333333333 14.345641025641026 13.852615384615383Q14.171897435897435 13.687897435897435 13.85374358974359 13.687897435897435ZM12.824820512820512 13.313333333333333H13.85374358974359Q14.420102564102564 13.313333333333333 14.710051282051282 13.569435897435897Q15.0 13.82553846153846 15.0 14.319692307692307Q15.0 14.818358974358974 14.710051282051282 15.073333333333332Q14.420102564102564 15.32830769230769 13.85374358974359 15.32830769230769H13.280615384615384V16.682153846153845H12.824820512820512Z" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_surface.svg b/resources/images/design_surface.svg
new file mode 100644
index 0000000000..1299dd1a97
--- /dev/null
+++ b/resources/images/design_surface.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M3 14C7 10 11 18 15 14L21 9C17 13 13 5 9 9Z"/><path d="M6 11.5 12 6.5" stroke-opacity="0.55"/></svg>
diff --git a/resources/images/design_svg.svg b/resources/images/design_svg.svg
new file mode 100644
index 0000000000..34a0685153
--- /dev/null
+++ b/resources/images/design_svg.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M7.081932245922209 8.669636135508153V9.608908406524465Q6.5336260978670015 9.346675031367628 6.047302383939774 9.217942283563362Q5.560978670012547 9.089209535759096 5.108030112923463 9.089209535759096Q4.321329987452948 9.089209535759096 3.894604767879548 9.39435382685069Q3.467879548306148 9.699498117942282 3.467879548306148 10.262107904642408Q3.467879548306148 10.734127979924716 3.751568381430364 10.974905897114176Q4.03525721455458 11.215683814303638 4.8267252195734 11.363488080301128L5.40840652446675 11.482685069008781Q6.48594730238394 11.687703889585945 6.9984943538268505 12.205018820577163Q7.511041405269761 12.72233375156838 7.511041405269761 13.5900878293601Q7.511041405269761 14.624717691342532 6.817314930991217 15.158720200752821Q6.123588456712673 15.69272271016311 4.7838143036386445 15.69272271016311Q4.278419071518194 15.69272271016311 3.708657465495609 15.578293601003763Q3.138895859473024 15.463864491844415 2.528607277289837 15.239774153074025V14.248055207026347Q3.115056461731493 14.577038895859472 3.6776662484316187 14.743914680050187Q4.240276035131744 14.910790464240902 4.7838143036386445 14.910790464240902Q5.608657465495608 14.910790464240902 6.056838143036387 14.586574654956085Q6.505018820577165 14.262358845671265 6.505018820577165 13.66160602258469Q6.505018820577165 13.137139272271014 6.183186951066499 12.841530740276033Q5.861355081555834 12.545922208281052 5.1271016311166875 12.398117942283562L4.540652446675031 12.283688833124215Q3.4631116687578416 12.069134253450438 2.981555834378921 11.611417816813049Q2.5 11.153701380175658 2.5 10.338393977415306Q2.5 9.39435382685069 3.165119196988708 8.850815558343788Q3.830238393977415 8.307277289836886 4.998368883312422 8.307277289836886Q5.498996235884567 8.307277289836886 6.018695106649937 8.397867001254703Q6.538393977415307 8.48845671267252 7.081932245922209 8.669636135508153ZM10.848557089084066 15.554454203262232 8.13086574654956 8.436010037641154H9.136888331242158L11.392095357590966 14.42923462986198L13.652070263488081 8.436010037641154H14.653324968632372L11.940401505646173 15.554454203262232ZM20.546424090338768 14.538895859473023V12.626976160602258H18.97302383939774V11.835508155583437H21.499999999999996V14.891718946047677Q20.942158092848178 15.287452948557087 20.26988707653701 15.4900878293601Q19.597616060225846 15.69272271016311 18.83475533249686 15.69272271016311Q17.16599749058971 15.69272271016311 16.224341279799248 14.717691342534504Q15.282685069008783 13.742659974905896 15.282685069008783 12.002383939774152Q15.282685069008783 10.257340025094102 16.224341279799248 9.282308657465494Q17.16599749058971 8.307277289836886 18.83475533249686 8.307277289836886Q19.53086574654956 8.307277289836886 20.15784190715182 8.478920953575908Q20.784818067754077 8.650564617314929 21.31405269761606 8.984316185696361V10.009410288582181Q20.78005018820577 9.556461731493098 20.179297365119197 9.327603513174402Q19.57854454203262 9.098745294855707 18.915809284818067 9.098745294855707Q17.609410288582183 9.098745294855707 16.953826850690085 9.828230865746548Q16.29824341279799 10.557716436637389 16.29824341279799 12.002383939774152Q16.29824341279799 13.442283563362608 16.953826850690085 14.171769134253449Q17.609410288582183 14.90125470514429 18.915809284818067 14.90125470514429Q19.425972396486824 14.90125470514429 19.826474278544538 14.813048933500625Q20.226976160602256 14.724843161856962 20.546424090338768 14.538895859473023Z" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_sweep.svg b/resources/images/design_sweep.svg
new file mode 100644
index 0000000000..f1cc301b1e
--- /dev/null
+++ b/resources/images/design_sweep.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><circle cx="6" cy="17" r="2.4"/><path d="M6 17 C 7 9, 15 15, 18 6"/><path d="M15.2 6.6 18 6 17.7 8.9"/></svg>
diff --git a/resources/images/design_tangentarc.svg b/resources/images/design_tangentarc.svg
new file mode 100644
index 0000000000..9e53da5c8e
--- /dev/null
+++ b/resources/images/design_tangentarc.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M3 18h8"/><path d="M11 18 A7 7 0 0 1 18 11"/><circle cx="3" cy="18" r="1.5" fill="#b6b6b6" stroke="none"/><circle cx="11" cy="18" r="1.5" fill="#b6b6b6" stroke="none"/></svg>
diff --git a/resources/images/design_text.svg b/resources/images/design_text.svg
new file mode 100644
index 0000000000..78da223f62
--- /dev/null
+++ b/resources/images/design_text.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M6 20 12 4 18 20M8.5 14h7"/></svg>
diff --git a/resources/images/design_thicken.svg b/resources/images/design_thicken.svg
new file mode 100644
index 0000000000..bfcd356cfa
--- /dev/null
+++ b/resources/images/design_thicken.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M3 10C7 6 11 14 15 10L21 5"/><path d="M3 16C7 12 11 20 15 16L21 11"/><path d="M3 10v6M21 5v6"/></svg>
diff --git a/resources/images/design_thread.svg b/resources/images/design_thread.svg
new file mode 100644
index 0000000000..9bff4d778b
--- /dev/null
+++ b/resources/images/design_thread.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><path d="M8 3h8v13l-4 5-4-5Z"/><path d="M8 7l8-2M8 11l8-2M8 15l8-2"/></svg>
diff --git a/resources/images/design_trim.svg b/resources/images/design_trim.svg
new file mode 100644
index 0000000000..405e9fe3c4
--- /dev/null
+++ b/resources/images/design_trim.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#b6b6b6" stroke-width="0.85" stroke-linecap="round" stroke-linejoin="round"><circle cx="6" cy="6.5" r="2.6"/><circle cx="6" cy="17.5" r="2.6"/><path d="M8.3 8 20.5 17M8.3 16 20.5 7"/></svg>
diff --git a/resources/images/tab_design_active.svg b/resources/images/tab_design_active.svg
new file mode 100644
index 0000000000..36ffc87ee5
--- /dev/null
+++ b/resources/images/tab_design_active.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 20 20"><path d="M1.5,6.5l7.776,3.888a.5.5,0,0,0,.448,0L17.5,6.5,9.724,2.612a.5.5,0,0,0-.448,0Z" style="fill:none;stroke:#fff;stroke-linecap:round;stroke-linejoin:round"/><path d="M1.5,6.5v8l7.776,3.888a.5.5,0,0,0,.448,0L17.5,14.5v-8" style="fill:none;stroke:#fff;stroke-linecap:round;stroke-linejoin:round"/></svg>
\ No newline at end of file
diff --git a/resources/images/toolbar_modifier_cube_dark.svg b/resources/images/toolbar_modifier_cube_dark.svg
new file mode 100644
index 0000000000..7e20cd0dd5
--- /dev/null
+++ b/resources/images/toolbar_modifier_cube_dark.svg
@@ -0,0 +1,4 @@
+<svg width="35" height="35" viewBox="0 0 35 35" fill="none" xmlns="http://www.w3.org/2000/svg">
+  <path fill-rule="evenodd" clip-rule="evenodd" d="M17.0007 3.15607L5.26748 9.97446C5.0759 10.0857 4.8723 10.2988 4.71546 10.5713C4.55862 10.8438 4.47656 11.127 4.47656 11.349V24.4715C4.47656 24.6929 4.55879 24.9752 4.71606 25.2472C4.87328 25.5192 5.07737 25.7322 5.26956 25.8438L17.1143 32.6992C17.3061 32.8102 17.5904 32.8795 17.902 32.8782C18.2136 32.8768 18.4968 32.8049 18.6868 32.6927L30.2729 25.8523C30.4645 25.739 30.6677 25.524 30.8242 25.2501C30.9806 24.9761 31.0625 24.6919 31.0625 24.4693V11.2435C31.0625 11.0216 30.9805 10.7392 30.8238 10.4679C30.667 10.1966 30.4635 9.98491 30.2715 9.87455L18.582 3.15275C18.3912 3.04273 18.1054 2.97271 17.7915 2.97339C17.4777 2.97408 17.192 3.045 17.0007 3.15607ZM6.3957 11.3642C6.53284 11.1245 6.83831 11.0414 7.07799 11.1785L16.9733 16.8405C17.3553 17.0587 17.6738 17.4171 17.8953 17.7985C18.1169 18.1801 18.2703 18.6338 18.2717 19.0733L18.2893 30.4075C18.2897 30.6837 18.0662 30.9079 17.7901 30.9083C17.5139 30.9087 17.2897 30.6852 17.2893 30.4091L17.2717 19.0767C17.2708 18.8547 17.1879 18.5717 17.0305 18.3007C16.8729 18.0294 16.6691 17.8183 16.4776 17.709L6.58136 12.0465C6.34168 11.9093 6.25855 11.6039 6.3957 11.3642Z" fill="#4db6ac"/>
+  <path fill-rule="evenodd" clip-rule="evenodd" d="M19.0809 2.28613C18.7002 2.0665 18.2304 1.97243 17.7893 1.9734C17.3481 1.97436 16.8787 2.07053 16.4985 2.29133L4.76515 9.10978C4.38527 9.33044 4.06884 9.69007 3.84874 10.0725C3.6286 10.455 3.47656 10.9093 3.47656 11.349V24.4715C3.47656 24.9118 3.62953 25.3658 3.85033 25.7477C4.07118 26.1297 4.38804 26.4882 4.76735 26.7085L16.6135 33.5647C16.9954 33.7857 17.4651 33.8801 17.9064 33.8782C18.3475 33.8762 18.8161 33.7778 19.1954 33.5537L30.7814 26.7133C31.1591 26.4902 31.4737 26.1292 31.6925 25.746C31.9114 25.3627 32.0625 24.9084 32.0625 24.4693V11.2435C32.0625 10.8037 31.9104 10.3497 31.6896 9.96764C31.4689 9.58563 31.1515 9.22695 30.7698 9.00759L19.0809 2.28613ZM29.6625 11.8015C29.786 12.0485 29.6859 12.3489 29.4389 12.4723L20.3956 16.994C20.1486 17.1175 19.8483 17.0174 19.7248 16.7704C19.6013 16.5234 19.7014 16.2231 19.9484 16.0996L28.9917 11.5779C29.2387 11.4544 29.539 11.5545 29.6625 11.8015Z" fill="#bdbdbd"/>
+</svg>
diff --git a/resources/images/toolbar_sketch.svg b/resources/images/toolbar_sketch.svg
new file mode 100644
index 0000000000..351b3e7924
--- /dev/null
+++ b/resources/images/toolbar_sketch.svg
@@ -0,0 +1,8 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="40" height="40" viewBox="0 0 40 40">
+  <!-- Pencil body -->
+  <path d="M28.5 6.5l5 5L14 31l-5.5 1.5L10 27 28.5 6.5z" style="fill:#009688"/>
+  <!-- Pencil tip (dark) -->
+  <path d="M8.5 28.5l1.5 1.5 4.5-1L28.5 15l-3.5-3.5L8.5 28z" style="fill:#2b3436"/>
+  <!-- Pencil line -->
+  <line x1="10" y1="26" x2="25" y2="11" stroke="#2b3436" stroke-width="2"/>
+</svg>
diff --git a/resources/images/toolbar_sketch_dark.svg b/resources/images/toolbar_sketch_dark.svg
new file mode 100644
index 0000000000..e5cf8d6859
--- /dev/null
+++ b/resources/images/toolbar_sketch_dark.svg
@@ -0,0 +1,8 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="40" height="40" viewBox="0 0 40 40">
+  <!-- Pencil body (dark mode colors) -->
+  <path d="M28.5 6.5l5 5L14 31l-5.5 1.5L10 27 28.5 6.5z" style="fill:#4db6ac"/>
+  <!-- Pencil tip -->
+  <path d="M8.5 28.5l1.5 1.5 4.5-1L28.5 15l-3.5-3.5L8.5 28z" style="fill:#e0e0e0"/>
+  <!-- Pencil line -->
+  <line x1="10" y1="26" x2="25" y2="11" stroke="#e0e0e0" stroke-width="2"/>
+</svg>
diff --git a/scripts/CAD/README.md b/scripts/CAD/README.md
new file mode 100644
index 0000000000..861b77a976
--- /dev/null
+++ b/scripts/CAD/README.md
@@ -0,0 +1,53 @@
+# Design-tab scripts
+
+Everything here supports the parametric Design tab (`src/libslic3r/CAD/`,
+`src/slic3r/GUI/CAD/`). Nothing here is needed to build or run OrcaSlicer — these
+are the development and verification tools for that one feature.
+
+The verb in the name is the role:
+
+| | |
+|---|---|
+| `build-…`  | produce a binary |
+| `start-…`  | bring something up and leave it running |
+| `run-…`    | run a suite and report pass/fail |
+| `check-…`  | one specific assertion, usually driving a live app |
+
+## Verification
+
+| Script | What it proves | Needs |
+|---|---|---|
+| `run-kernel-tests.sh` | The CAD kernel builds and the Catch2 `[CadDocument]` tags pass — every case builds a document, recomputes it and asserts on real geometry. **Exit 0 is the verification contract.** | Docker only. No display. |
+| `run-all-checks.sh` | Every check below, in one command. The gate before pushing a Design-tab change. | Docker + the GUI container |
+| `check-sketch-engine.py` | A ladder of 2D sketches of increasing complexity, judged on loop count, closure and void attribution rather than on area. | Kernel only |
+| `check-sketch-engine-corpus.py` | The same ladder graded against a systematic sample of real drawings instead of shapes we chose. | Kernel + corpus |
+| `check-gui-sketching.py` | The same profiles drawn the way a person draws them — synthetic mouse gestures and typed values. | Headless GUI |
+| `check-gui-context-menu.py` | That right-click is the pivot of the design gesture, and adapts to what was clicked. | Headless GUI |
+| `check-mcp-sketch.py` | The sketch layer driven over the MCP socket, asserting what decides whether a profile is buildable. | Headless GUI + `ORCA_CAD_MCP` |
+
+**`run-kernel-tests.sh` is the only one CI can run.** The rest need a live
+application with an OpenGL canvas and synthetic input, which hosted runners do not
+have. The kernel suite itself is already in CI by an ordinary route: the cases are
+registered in `tests/libslic3r/CMakeLists.txt` under `if (SLIC3R_CAD)`, so they are
+part of `libslic3r_tests` and run under `ctest` on every platform like any other
+unit test. This script exists for the local loop, where it is a two-minute round
+trip instead of a full application build.
+
+## Build and run
+
+| Script | Purpose |
+|---|---|
+| `build-gui.sh` | Build the GUI binary in a throwaway container, writing into the build-cache volume the long-lived GUI container reads. |
+| `build-gui-incremental.sh` | Incremental build against the deps-baked image, for a fast edit/compile loop. |
+| `start-headless-gui.sh` | Bring the app up on a headless X display (Xvfb + a window manager), ready to drive or attach to over VNC. |
+
+Two constraints that are not obvious and have each cost a session:
+
+- **Never build inside the GUI container.** Its baked source tree silently
+  reconfigures the shared build directory and this fork's targets vanish.
+- **A window manager is required.** Without one, windows are never focused, and an
+  unfocused GTK app ignores synthetic keys — which looks exactly like a code bug.
+
+`docs/rig_build_traps.md` documents these and three more, with symptoms and exact
+recovery commands. Read it before debugging a configure or link failure one of
+these scripts reports.
diff --git a/scripts/CAD/build-gui-incremental.sh b/scripts/CAD/build-gui-incremental.sh
new file mode 100755
index 0000000000..539a21c973
--- /dev/null
+++ b/scripts/CAD/build-gui-incremental.sh
@@ -0,0 +1,81 @@
+#!/usr/bin/env bash
+# Incremental slicer build against the orcacad-deps base image.
+#
+# The deps-baked image (built from scripts/Dockerfile.deps) carries the pinned
+# dependencies at /OrcaSlicer/deps/build/destdir. This script mounts the LIVE source
+# tree and resources over the baked copy so code/CMake edits apply immediately, and
+# persists /OrcaSlicer/build in a named volume so ninja recompiles only what changed.
+#
+# Result: edit -> rebuild in seconds-to-minutes instead of a full Docker rebuild.
+#
+# Usage (run on the build host, e.g. behemoth, from anywhere):
+#   scripts/CAD/build-gui-incremental.sh
+#   IMAGE=orcacad-deps scripts/CAD/build-gui-incremental.sh
+#
+# On success the binary is inside the persistent volume at
+# /OrcaSlicer/build/package/bin/orca-slicer (copy it out with a follow-up
+# `docker run --rm -v orcacad_buildcache:/b alpine cp ...` or via this script's tail).
+# Rig build traps already paid for once each (stale project, NLopt cache, pybind11, OCCT_LIBS, SLIC3R_CAD gate): docs/rig_build_traps.md
+set -euo pipefail
+
+REPO="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+# orcacad-deps, NOT snapmaker-deps: see the note in run-kernel-tests.sh — the wrong image
+# fails at CMake configure, not at link time.
+IMAGE="${IMAGE:-orcacad-deps}"
+BUILD_VOL="${BUILD_VOL:-orcacad_buildcache}"
+
+echo "REPO=$REPO  IMAGE=$IMAGE  BUILD_VOL=$BUILD_VOL"
+
+# The root CMakeLists.txt and cmake/ must be mounted too, not taken from the baked image:
+# they carry the build-time gates (e.g. SLIC3R_CAD -> add_definitions(-DSLIC3R_CAD)) that the
+# mounted headers are compiled against. With a stale baked copy the gate silently stays off and
+# the build fails with "class GLCanvas3D has no member named set_design_sketch_tool".
+#
+# build_linux.sh must be mounted for the same reason, and here the stale copy is guaranteed
+# wrong rather than merely risky: orcacad-deps is layered on snapmaker-deps, so the baked script
+# is the OTHER fork's and builds `--target Snapmaker_Orca`. This fork's target is `OrcaSlicer`,
+# so without this mount configure succeeds and then ninja dies on "unknown target".
+# scripts/ likewise: build_linux.sh's packaging step sources scripts/appimage_lib_policy.sh,
+# which the baked Snapmaker tree does not have, so a fully successful link still exited
+# non-zero with "missing AppImage helper" and the binary check never ran.
+
+# ---- OOM guard (2026-08-21) -------------------------------------------------------------
+# Two of these builds ran at once on 2026-08-21, each with ninja -j$(nproc)=16: ~36 cc1plus
+# holding 42 GB of a 62 GB box -> global OOM at 21:05, a 2h28m kill storm, ssh unreachable,
+# lightdm destroyed. Neither build produced a single object. scripts/CAD/build-gui.sh grew the
+# bounds first; every script that starts a compile needs the same three, or the guard is only
+# as strong as the script you happened not to use.
+#   flock    — the lock path is SHARED with build-gui.sh and the other fork on purpose, so
+#              concurrent builds serialise instead of summing.
+#   -j       — bounded parallelism; ~1.17 GB per cc1plus was the measured average.
+#   --memory — the actual guarantee: a runaway build dies in its own cgroup instead of taking
+#              the host down. --memory-swap equal to --memory forbids swap, which is what made
+#              ssh hang.
+JOBS="${JOBS:-12}"
+MEM="${MEM:-40g}"
+LOCK=/tmp/orca-rig-build.lock
+
+exec 9>"$LOCK"
+if ! flock -n 9; then
+    echo "another build holds $LOCK — waiting (this is the OOM guard, not a hang)"
+    flock 9
+fi
+
+docker run --rm \
+  --memory="$MEM" --memory-swap="$MEM" \
+  -v "$REPO/src":/OrcaSlicer/src \
+  -v "$REPO/resources":/OrcaSlicer/resources \
+  -v "$REPO/CMakeLists.txt":/OrcaSlicer/CMakeLists.txt \
+  -v "$REPO/cmake":/OrcaSlicer/cmake \
+  -v "$REPO/deps_src":/OrcaSlicer/deps_src \
+  -v "$REPO/build_linux.sh":/OrcaSlicer/build_linux.sh \
+  -v "$REPO/scripts":/OrcaSlicer/scripts \
+  -v "$BUILD_VOL":/OrcaSlicer/build \
+  "$IMAGE" \
+  bash -lc "cd /OrcaSlicer && ./build_linux.sh -sr -j $JOBS"
+
+# src/CMakeLists.txt:151 renames the OrcaSlicer target's output to "orca-slicer" — not
+# "snapmaker-orca", which is the other fork's binary name.
+echo "=== build finished; checking for binary ==="
+docker run --rm -v "$BUILD_VOL":/b "$IMAGE" \
+  bash -lc 'ls -lh /b/package/bin/orca-slicer 2>/dev/null && file /b/package/bin/orca-slicer || echo "NO BINARY"'
diff --git a/scripts/CAD/build-gui.sh b/scripts/CAD/build-gui.sh
new file mode 100755
index 0000000000..0a1a86dd5c
--- /dev/null
+++ b/scripts/CAD/build-gui.sh
@@ -0,0 +1,98 @@
+#!/usr/bin/env bash
+# Rebuild the GUI binary the design rig launches — in a THROWAWAY container, writing into the
+# same build-cache volume the rig's long-lived GUI container reads from.
+#
+# NEVER build inside the GUI container (snapmaker-gui / orcacad-gui). Its baked /OrcaSlicer tree
+# is the Jun-13 Snapmaker-derived source, so a `cmake .` in there silently reconfigures the
+# shared build dir as project(Snapmaker_Orca) and this fork's targets vanish. That is Trap 1 of
+# five; all of them, with symptoms and exact recovery commands, are in docs/rig_build_traps.md.
+# Read that file before debugging a configure or link failure this script reports.
+#
+# Usage:
+#   scripts/CAD/build-gui.sh              # configure + build the fork's GUI target
+#   DRY_RUN=1 scripts/CAD/build-gui.sh    # print the resolved fork identity and exit, no container
+set -euo pipefail
+
+REPO="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+
+# Fork identity is DERIVED from the repo, never hardcoded, so this file is byte-identical in
+# both forks and cannot be mirrored into the wrong one. Pointing a fork at the other fork's
+# image or volume is not a slow failure: with the wrong image CMake dies at configure, and with
+# the wrong volume the two forks silently trade build artefacts.
+PROJECT="$(sed -n 's/^project(\([A-Za-z_0-9]*\)).*/\1/p' "$REPO/CMakeLists.txt" | head -1)"
+case "$PROJECT" in
+    Snapmaker_Orca) PREFIX=snapmaker; BIN=snapmaker-orca ;;
+    OrcaSlicer)     PREFIX=orcacad;  BIN=orca-slicer    ;;
+    *) echo "FATAL: unrecognised project($PROJECT) in $REPO/CMakeLists.txt" >&2; exit 2 ;;
+esac
+TARGET="$PROJECT"
+IMAGE="${PREFIX}-deps"
+BUILD_VOL="${PREFIX}_buildcache"
+
+echo "REPO=$REPO PROJECT=$PROJECT IMAGE=$IMAGE BUILD_VOL=$BUILD_VOL TARGET=$TARGET BIN=$BIN"
+
+if [ -n "${DRY_RUN:-}" ]; then
+    echo "DRY_RUN: resolution only, no container started"
+    exit 0
+fi
+
+# Three memory bounds. On 2026-08-21 both forks ran this script at the same time, each with
+# ninja -j$(nproc)=16: ~36 cc1plus holding 42 GB of a 62 GB box -> global OOM at 21:05, a
+# 2h28m kill storm, ssh unreachable, lightdm destroyed, 2946 session kill events. Neither
+# build produced a single object. The bounds, weakest to strongest:
+#   flock    — the lock path is shared by both forks on purpose, so they SERIALISE instead of
+#              summing. Peak is one build's worth no matter who else starts one.
+#   -j12     — measured 1.17 GB average per cc1plus in the incident dump, so 12 in flight
+#              is ~14 GB typical and leaves the box usable. JOBS=n overrides.
+#   --memory — the actual guarantee. A runaway build hits its own cgroup limit and dies alone;
+#              the host never reaches global OOM again, whatever -j or flock do.
+#              --memory-swap equal to --memory forbids swap, which is what made ssh hang.
+JOBS="${JOBS:-12}"
+MEM="${MEM:-40g}"
+LOCK=/tmp/orca-rig-build.lock
+
+exec 9>"$LOCK"
+if ! flock -n 9; then
+    echo "another fork's build-gui holds $LOCK — waiting (this is the OOM guard, not a hang)"
+    flock 9
+fi
+
+# Every one of these mounts covers a trap, none is decorative:
+#   CMakeLists.txt + cmake/ carry the SLIC3R_CAD gate — inherit the baked copies and the cache
+#     says SLIC3R_CAD=ON while -DSLIC3R_CAD is never defined, so every #ifdef block compiles out.
+#   deps_src/ carries pybind11, which the image predates.
+#   src/, resources/, localization/, version.inc are the code under test.
+rc=0
+docker run --rm \
+    --memory="$MEM" --memory-swap="$MEM" \
+    -v "$REPO/src":/OrcaSlicer/src \
+    -v "$REPO/resources":/OrcaSlicer/resources \
+    -v "$REPO/cmake":/OrcaSlicer/cmake \
+    -v "$REPO/deps_src":/OrcaSlicer/deps_src \
+    -v "$REPO/localization":/OrcaSlicer/localization \
+    -v "$REPO/CMakeLists.txt":/OrcaSlicer/CMakeLists.txt \
+    -v "$REPO/version.inc":/OrcaSlicer/version.inc \
+    -v "$BUILD_VOL":/OrcaSlicer/build \
+    "$IMAGE" bash -lc "
+        cd /OrcaSlicer/build || exit 1
+        cmake . > /tmp/cfg.log 2>&1 || { echo 'CONFIGURE FAILED'; tail -25 /tmp/cfg.log; exit 1; }
+        # Twice, deliberately. src/libslic3r/CMakeLists.txt publishes OCCT_LIBS as CACHE INTERNAL
+        # at the END of its own configure, so a first pass after that list changes links the
+        # PREVIOUS one and drops TKBool/TKOffset — a wall of TopOpeBRepBuild undefined references
+        # that reads as a broken OCCT install and is not. Trap 4.
+        cmake . > /tmp/cfg2.log 2>&1 || { echo 'RECONFIGURE FAILED'; tail -25 /tmp/cfg2.log; exit 1; }
+        ninja -f build-Release.ninja -j$JOBS $TARGET > /tmp/bld.log 2>&1
+        rc=\$?
+        echo \"EXIT=\$rc\"
+        grep -n 'error:' /tmp/bld.log | head -20
+        tail -4 /tmp/bld.log
+        ls -la /OrcaSlicer/build/src/Release/$BIN 2>/dev/null
+        exit \$rc
+    " || rc=$?
+
+# A target-only build writes src/Release/, but this fork's start-headless-gui.sh may default BIN to the
+# PACKAGED path that only build_linux.sh refreshes — launching with the default would then run a
+# stale binary. Pass BIN explicitly. See docs/rig_build_traps.md.
+echo "=== launch the rig on the binary just built ==="
+echo "  docker exec -e BIN=/OrcaSlicer/build/src/Release/$BIN ${PREFIX}-gui /OrcaSlicer/scripts/CAD/start-headless-gui.sh"
+exit "$rc"
diff --git a/scripts/CAD/check-gui-click-edit.py b/scripts/CAD/check-gui-click-edit.py
new file mode 100755
index 0000000000..159bdb19f1
--- /dev/null
+++ b/scripts/CAD/check-gui-click-edit.py
@@ -0,0 +1,658 @@
+#!/usr/bin/env python3
+"""The click-edit contract: a value field that opens must accept what is TYPED into it.
+
+WHY THIS EXISTS SEPARATELY FROM check-gui-sketching.py. That ladder draws geometry and grades the
+result, and to make its values land it calls focus_field() — one synthetic click INTO the field
+before typing. Its own docstring says why:
+
+    WITHOUT THIS THE TYPED VALUE IS SILENTLY DISCARDED. The field is shown and raised but the
+    window manager does not give it the keyboard, so xdotool's digits go to the canvas and Return
+    commits the value the field opened with — the pre-filled as-drawn number.
+
+That click is a workaround for a defect, and a suite that performs it can never see the defect
+again. A user cannot be told to click the field first; when they do not, they get the as-drawn
+number and report "the label value is not editable". So this ladder types IMMEDIATELY after the
+field opens, exactly as a person does, and fails if the prefill is what gets committed.
+
+WHAT IT GRADES. The app emits one line per event under ORCA_CAD_UXTRACE=1:
+
+    [UX] open    title=Length prefill=154.76
+    [UX] commit  title=Length typed=80 value=80.0000
+    [UX] refused title=Length typed=8O
+    [UX] cancel  title=Length
+
+For every field the driver opens it asserts: a commit arrived, what the field received is what we
+typed, the parsed value equals it, and it differs from the prefill. The last clause is the one
+that matters — a field that is on screen but deaf commits its prefill, and every other signal
+(the field is visible, a constraint is created, the solve succeeds) looks perfectly healthy.
+
+    scripts/CAD/check-gui-click-edit.py --display :10 --bin build/src/Release/orca-slicer
+
+With --attach it drives an already-running app instead of launching one; the app must have been
+started with ORCA_CAD_UXTRACE=1 and its stderr redirected to --trace.
+Exit 0 = every field took what was typed.
+"""
+import argparse, json, os, re, shutil, signal, socket, subprocess, sys, tempfile, time
+
+AP = argparse.ArgumentParser()
+AP.add_argument("--display", default=os.environ.get("DISPLAY", ":10"))
+AP.add_argument("--bin", default="build/src/Release/orca-slicer")
+AP.add_argument("--datadir", default="")
+AP.add_argument("--trace", default="")
+AP.add_argument("--sock", default="/tmp/mcp-uxcheck.sock",
+                help="the app's MCP socket: the oracle for whether a sketch is really open")
+AP.add_argument("--attach", action="store_true", help="drive a running app; do not launch one")
+AP.add_argument("--keep", action="store_true", help="leave the app running afterwards")
+AP.add_argument("--no-defocus", action="store_true",
+                help="do NOT take focus off the field before typing (weakens the gate; see below)")
+AP.add_argument("--seed-from", default=os.path.expanduser("~/.config/OrcaCAD/OrcaSlicer.conf"),
+                help="an existing OrcaSlicer.conf to copy presets/settings from")
+A = AP.parse_args()
+
+DISP = A.display
+TRACE = A.trace or os.path.join(tempfile.gettempdir(), "ux-click-edit.log")
+_fail = 0
+_checks = 0
+
+
+_n = 0
+
+
+def call(method, **params):
+    """One MCP request over the app's unix socket. The socket is the only witness that cannot
+    lie about sketch state: the keytrace says a key ARRIVED, a screenshot says something is on
+    screen, and neither distinguishes an open sketch from sketch mode with the plane offer up."""
+    global _n
+    _n += 1
+    s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    s.settimeout(30)
+    s.connect(A.sock)
+    s.sendall((json.dumps({"jsonrpc": "2.0", "id": _n, "method": method,
+                           "params": params}) + "\n").encode())
+    buf = b""
+    while b"\n" not in buf:
+        d = s.recv(65536)
+        if not d:
+            break
+        buf += d
+    r = json.loads(buf.decode().strip())
+    if "error" in r:
+        raise RuntimeError(f"{method}: {r['error']['message']}")
+    return r["result"]
+
+
+def try_call(method, **params):
+    try:
+        return call(method, **params)
+    except Exception:
+        return None
+
+
+def sh(cmd):
+    # bash -c, NOT -lc: a login shell sources the profile on every xdotool call, and this driver
+    # makes hundreds. On a GNOME box that meant im-config running per call, thousands of journal
+    # lines, and a window poll slow enough to time out before the app had finished starting.
+    return subprocess.run(["bash", "-c", cmd], capture_output=True, text=True).stdout
+
+
+def xdo(args):
+    sh(f"DISPLAY={DISP} xdotool {args}")
+
+
+def key(k, pause=0.35, window=None):
+    xdo(f"key {'--window ' + str(window) + ' ' if window else ''}{k}")
+    time.sleep(pause)
+
+
+def typ(s, pause=0.35, window=None):
+    # --clearmodifiers so a modifier left down by an earlier synthetic key cannot turn digits
+    # into something else; --delay 60 because ImGui reads one character per frame.
+    #
+    # `window` targets a specific window with XSendEvent instead of following the input focus.
+    # That is the whole gate: see type_into_open_field.
+    tgt = f"--window {window} " if window else ""
+    xdo(f"type {tgt}--clearmodifiers --delay 60 -- '{s}'")
+    time.sleep(pause)
+
+
+def die(msg):
+    print(f"FATAL {msg}", file=sys.stderr)
+    sys.exit(2)
+
+
+# ---------------------------------------------------------------- the app
+
+_proc = None
+
+
+def seed_datadir(datadir):
+    """The Design tab does not exist unless enable_cad_feature is on, and it needs a RESTART.
+
+    A fresh datadir has it off, so a driver that just points the app at an empty directory gets
+    Prepare/Preview/Device/Project, no Design tab, and every rung fails for a reason that has
+    nothing to do with what is being tested. Seed the flag before the first launch.
+    """
+    os.makedirs(datadir, exist_ok=True)
+    conf = os.path.join(datadir, "OrcaSlicer.conf")
+    data = {}
+    if os.path.exists(A.seed_from):
+        try:
+            with open(A.seed_from) as f:
+                data = json.load(f)
+        except Exception:
+            data = {}
+    app = data.setdefault("app", {})
+    app["enable_cad_feature"] = True
+    # Deterministic starting state for the rungs that follow: the bed drawn, loops welded as the
+    # ~90% case expects. A ladder whose result depends on the developer's own preferences is not
+    # a gate.
+    app["auto_close_sketch_loops"] = True
+    # SILENCE THE NETWORK PLUGIN PROMPT. Without this, GUI_App::post_init() re-raises "Bambu
+    # Network Plug-in Required" from an IDLE event — after any modal sweep this driver does at
+    # startup — and ShowModal() then runs a nested event loop. The app is alive, its window is
+    # there, and the MCP socket answers nothing: indistinguishable from a hang, and it was
+    # investigated as one, with gdb, twice. `installed_networking` false stops the whole
+    # networking-plugin path, so m_networking_need_update is never set and the dialog never
+    # exists to be swept.
+    app["installed_networking"] = False
+    with open(conf, "w") as f:
+        json.dump(data, f, indent=1)
+    for sub in ("user", "system", "presets", "vendor"):
+        src = os.path.join(os.path.dirname(A.seed_from), sub)
+        dst = os.path.join(datadir, sub)
+        if os.path.isdir(src) and not os.path.exists(dst):
+            shutil.copytree(src, dst)
+
+
+def launch():
+    global _proc
+    datadir = A.datadir or os.path.join(tempfile.gettempdir(), "orcacad-uxcheck")
+    seed_datadir(datadir)
+    env = dict(os.environ)
+    # WAYLAND_DISPLAY MUST GO, and GDK_BACKEND must say x11. GTK prefers Wayland whenever
+    # WAYLAND_DISPLAY is set and ignores DISPLAY entirely, so a driver launched from a systemd
+    # user unit (which inherits it) started the app on the DESKTOP session instead of the rig:
+    # the process was alive, `xdotool search` on the rig display found nothing, and the window
+    # was sitting on the user's own screen. Silent, and it drives a stray app at someone's face.
+    env.pop("WAYLAND_DISPLAY", None)
+    env.update(DISPLAY=DISP, GDK_BACKEND="x11", ORCA_CAD_UXTRACE="1",
+               LIBGL_ALWAYS_SOFTWARE="1", GALLIUM_DRIVER="llvmpipe",
+               # The rig's Xvfb has no input-method daemon, and a dead ibus context makes a
+               # GtkEntry drop every character while the app looks fine. It cannot affect the
+               # in-canvas field (ImGui needs no IM) but the app has other text fields, and a
+               # display full of IBUS warnings has cost a whole misdiagnosis before.
+               GTK_IM_MODULE="gtk-im-context-simple", XMODIFIERS="@im=none",
+               # The key tracer is this driver's only positive signal that a keystroke reached
+               # the Design panel at all. Without it "the field never opened" is indistinguishable
+               # from "we never got into sketch mode", and the first run of this ladder reported
+               # seven product failures that were really one driver racing a still-loading app.
+               ORCA_CAD_KEYTRACE="1", ORCA_CAD_MCP=A.sock,
+               SSL_CERT_FILE="/etc/ssl/certs/ca-certificates.crt",
+               WEBKIT_DISABLE_DMABUF_RENDERER="1", WEBKIT_DISABLE_COMPOSITING_MODE="1")
+    if os.path.exists(A.sock):
+        os.unlink(A.sock)          # a stale socket from a dead run answers nothing, slowly
+    log = open(TRACE, "wb")
+    _proc = subprocess.Popen([A.bin, "--datadir", datadir], env=env,
+                             stdout=subprocess.DEVNULL, stderr=log)
+    for _ in range(120):
+        if win_id():
+            return
+        time.sleep(1)
+    die("the app never showed a window on " + DISP)
+
+
+def window_pid(w):
+    """_NET_WM_PID for a window, or 0. The property is how we tell a live app from its ghost."""
+    out = sh(f"DISPLAY={DISP} xprop -id {w} _NET_WM_PID 2>/dev/null")
+    m = re.search(r"= *(\d+)", out)
+    return int(m.group(1)) if m else 0
+
+
+def pid_alive(pid):
+    return pid > 0 and os.path.isdir(f"/proc/{pid}")
+
+
+def win_id():
+    """The main window: OURS if we launched it, otherwise the biggest LIVE top-level.
+
+    Two rules here, each paid for.
+
+    By PID, not by size, whenever we launched the app. An X window outlives its client if the
+    connection is not torn down cleanly, and a killed OrcaSlicer can leave a full-screen ghost
+    mapped on the display. It answers geometry queries exactly like the real thing, it wins "the
+    biggest window" every time, and every synthetic keystroke sent to it goes nowhere. That is
+    indistinguishable, from the driver's side, from an app that ignores the keyboard — which is
+    the very defect this ladder exists to measure. One run reported the entire contract broken
+    while the real app sat beside the ghost, untouched.
+
+    Never by title: a saved project renames the main window.
+    """
+    if _proc is not None:
+        for w in sh(f"DISPLAY={DISP} xdotool search --pid {_proc.pid} --onlyvisible --name '.'").split():
+            g = dict(l.split("=", 1) for l in
+                     sh(f"DISPLAY={DISP} xdotool getwindowgeometry --shell {w}").strip().splitlines()
+                     if "=" in l)
+            if "WIDTH" in g and int(g["WIDTH"]) * int(g["HEIGHT"]) > 400 * 400:
+                return (w, int(g["X"]), int(g["Y"]), int(g["WIDTH"]), int(g["HEIGHT"]))
+        return None
+    best = None
+    for w in sh(f"DISPLAY={DISP} xdotool search --onlyvisible --name '.'").split():
+        g = dict(l.split("=", 1) for l in
+                 sh(f"DISPLAY={DISP} xdotool getwindowgeometry --shell {w}").strip().splitlines()
+                 if "=" in l)
+        if "WIDTH" not in g:
+            continue
+        if not pid_alive(window_pid(w)):          # a ghost: no client is behind it any more
+            continue
+        a = int(g["WIDTH"]) * int(g["HEIGHT"])
+        if a > 400 * 400 and (best is None or a > best[0]):
+            best = (a, w, int(g["X"]), int(g["Y"]), int(g["WIDTH"]), int(g["HEIGHT"]))
+    return best[1:] if best else None
+
+
+_win = None
+
+
+def win():
+    global _win
+    if _win is None:
+        w = win_id()
+        if w is None:
+            die("no app window on " + DISP)
+        sh(f"DISPLAY={DISP} xdotool windowactivate --sync {w[0]}")
+        sh(f"DISPLAY={DISP} xdotool windowsize {w[0]} 1920 1080")
+        sh(f"DISPLAY={DISP} xdotool windowmove {w[0]} 0 0")
+        time.sleep(1.0)
+        _win = (w[0], 0, 0, 1920, 1080)
+    return _win
+
+
+def click(px, py, pause=0.5, btn=1):
+    _, X, Y, _, _ = win()
+    xdo(f"mousemove {X+int(px)} {Y+int(py)} click --delay 120 {btn}")
+    time.sleep(pause)
+
+
+def visible_windows():
+    """(id, name, w, h) for every MAPPED top-level, main window included.
+
+    `--onlyvisible` is what makes this usable. Without it xdotool also returns the app's unmapped
+    helper windows — a 10x10 and a 200x200 that exist for the whole session — and a caller that
+    tries to reason about "extra windows" from that list is reasoning about furniture.
+    """
+    out = []
+    for w in sh(f"DISPLAY={DISP} xdotool search --onlyvisible --name '.'").split():
+        g = dict(l.split("=", 1) for l in
+                 sh(f"DISPLAY={DISP} xdotool getwindowgeometry --shell {w}").strip().splitlines()
+                 if "=" in l)
+        if "WIDTH" not in g:
+            continue
+        if not pid_alive(window_pid(w)):   # see win_id(): a ghost cannot be closed, only ignored
+            continue
+        n = sh(f"DISPLAY={DISP} xdotool getwindowname {w}").strip()
+        out.append((w, n, int(g["WIDTH"]), int(g["HEIGHT"])))
+    return out
+
+
+def dismiss_modals(timeout=30):
+    """Close every modal over the main window, and PROVE none is left.
+
+    This is the rung that decides whether any of the others mean anything. A fresh datadir opens
+    "Bambu Network Plug-in Required" — 440x259, centred at 742,450 — which sits exactly on top of
+    the point every drawing gesture in TOOLS starts from. The whole ladder then reports eleven
+    product failures, all of them the driver clicking a dialog.
+
+    The old version pressed Escape and moved on. This dialog ignores Escape, so it "dismissed"
+    nothing and said so to no one; the run that found this was red for a reason that had nothing
+    to do with the contract under test. Escape is still tried first because it is the gentlest
+    thing that works on the wizard, then WM_DELETE_WINDOW, and then the function asserts what it
+    was supposed to have achieved instead of assuming it.
+    """
+    # NEVER run without knowing which window to spare. The first version took `keep = main[0] if
+    # main else None`, so a win_id() that raced the app's mapping made keep None and every visible
+    # window a modal — this function then sent WM_DELETE to the app's own main window. The app
+    # survived as a process, printed "GdkWindow unexpectedly destroyed", and answered nothing
+    # afterwards; the ladder reported "no sketch opened" for 180s. Losing the main window is not a
+    # state to recover from silently.
+    deadline = time.time() + timeout
+    keep = None
+    while keep is None and time.time() < deadline:
+        main = win_id()
+        keep = main[0] if main else None
+        if keep is None:
+            time.sleep(0.5)
+    if keep is None:
+        die(f"no main window to protect after {timeout}s — refusing to close anything")
+    scr = sh(f"DISPLAY={DISP} xdotool getdisplaygeometry").split()
+    full = int(scr[0]) * int(scr[1]) if len(scr) == 2 else 1920 * 1080
+    while time.time() < deadline:
+        # A modal is small. Anything covering half the screen is the app, whatever id win_id()
+        # happened to return this instant — a second belt on the rule above, because the cost of
+        # being wrong here is an app that looks alive and answers nothing.
+        extra = [x for x in visible_windows() if x[0] != keep and x[2] * x[3] < full * 0.5]
+        if not extra:
+            return
+        for (w, n, _, _) in extra:
+            sh(f"DISPLAY={DISP} xdotool windowactivate {w}")
+            time.sleep(0.4)
+            key("Escape", 0.4)
+            if any(x[0] == w for x in visible_windows()):
+                sh(f"DISPLAY={DISP} xdotool windowclose {w}")
+                time.sleep(0.6)
+        time.sleep(0.5)
+    left = [f"{n!r} ({w}x{h})" for (i, n, w, h) in visible_windows()
+            if i != keep and w * h < full * 0.5]
+    die("a modal is still covering the canvas after " + str(timeout) + "s: " + ", ".join(left) +
+        " — every drawing gesture would land in it, so nothing below this line could be trusted")
+
+
+def dismiss_first_run():
+    dismiss_modals()
+
+
+# ---------------------------------------------------------------- the trace
+
+def trace_lines():
+    try:
+        with open(TRACE, "r", errors="replace") as f:
+            return [l.strip() for l in f if l.startswith("[UX] ")]
+    except OSError:
+        return []
+
+
+def trace_mark():
+    return len(trace_lines())
+
+
+def parse(line):
+    m = re.match(r"\[UX\] (\w+) title=(.*?) (.*)$", line)
+    if not m:
+        return None
+    ev, title, rest = m.group(1), m.group(2), m.group(3)
+    kv = dict(re.findall(r"(\w+)=(\S*)", rest))
+    return ev, title, kv
+
+
+# ---------------------------------------------------------------- grading
+
+def check(cond, what):
+    """Returns the verdict so a caller can abandon a rung whose precondition failed."""
+    global _fail, _checks
+    _checks += 1
+    if cond:
+        print(f"    ok    {what}")
+    else:
+        print(f"    FAIL  {what}", file=sys.stderr)
+        _fail += 1
+    return bool(cond)
+
+
+def type_into_open_field(value, mark):
+    """Type `value` into whatever field is open, WITHOUT clicking it first, and grade the pair.
+
+    No click: the click is the workaround this ladder exists to refuse. If the field cannot take
+    the keyboard on its own, `typed` will be the prefill and this fails — which is the report.
+    """
+    # POLL for the field. It opens from a CallAfter that runs after a re-solve, so on llvmpipe it
+    # is simply not there yet when a fast driver looks — and "no field opened" is the same message
+    # whether the product never opened one or the driver asked too early. Wait, then decide.
+    opens = []
+    deadline = time.time() + 8.0
+    while time.time() < deadline:
+        opens = [e for e in (parse(l) for l in trace_lines()[mark:]) if e and e[0] == "open"]
+        if opens:
+            break
+        time.sleep(0.25)
+    if not opens:
+        check(False, f"a value field opened (nothing did; cannot type {value})")
+        return mark
+    title = opens[-1][1]
+    prefill = opens[-1][2].get("prefill", "")
+    m2 = trace_mark()
+    # TYPE NORMALLY. NOTHING TO DEFOCUS ANY MORE.
+    #
+    # The value field is drawn INSIDE the GL canvas by ImGui, so it is not a window: there is no
+    # second toplevel for a window manager to grant or refuse the keyboard, and the keystrokes go
+    # to the app's one window exactly as a person's would. That is the entire point of the design
+    # — the WM has no say — and it is why this ladder no longer tries to manufacture the failing
+    # condition.
+    #
+    # When the field WAS a floating wxFrame, this spot held two attempts to reproduce
+    # "field open, keyboard elsewhere", and both are recorded here so neither is tried again:
+    #   - XSetInputFocus onto the main window (`xdotool windowfocus`): the field's own re-focus
+    #     CallAfter wins the race every time; four retries all lost, and the ladder passed twice
+    #     against a binary with the fix compiled out.
+    #   - XSendEvent at the main window (`xdotool type --window`): GTK discards synthetic key
+    #     events, so NEITHER build received anything and every run was red regardless of the code.
+    # A run that used the second of those is what produced "the app never saw a digit" — a
+    # property of xdotool, not of the product.
+    #
+    # For the in-canvas field the honest gate is simply: type, and see whether the value the app
+    # commits is the value that was typed.
+    diag = sh(f"DISPLAY={DISP} xdotool getwindowfocus").strip()
+    typ(str(value), 0.4)
+    key("Return", 0.9)
+    after, commits, refused, commit_at = [], [], [], None
+    deadline = time.time() + 5.0
+    while time.time() < deadline:
+        after = [parse(l) for l in trace_lines()[m2:]]
+        commits = [(i, e) for i, e in enumerate(after) if e and e[0] == "commit"]
+        refused = [e for e in after if e and e[0] == "refused"]
+        if commits:
+            commit_at = m2 + commits[-1][0]
+            commits = [e for _, e in commits]
+        if commits or refused:
+            break
+        time.sleep(0.25)
+    if refused and not commits:
+        check(False, f"{title}: field REFUSED {value!r} (typed={refused[-1][2].get('typed')!r})")
+        key("Escape", 0.5)
+        return trace_mark()
+    if not commits:
+        check(False, f"{title}: typed {value} but nothing committed — the field took no keys")
+        key("Escape", 0.5)
+        return trace_mark()
+    typed = commits[-1][2].get("typed", "")
+    got = commits[-1][2].get("value", "")
+    check(typed == str(value),
+          f"{title}: field received what was typed (typed={typed!r} wanted={value!r}"
+          f"{'  <-- it committed its PREFILL, so it never got the keyboard' if typed == prefill else ''})")
+    # A value that will not parse is a FAILED CHECK, never an exception. An unguarded float()
+    # here met a locale-formatted "61,0000" and took the whole run down immediately after the
+    # first check in the ladder's history had passed — the seven rungs below it were never tried
+    # and the report read as a total failure.
+    try:
+        ok_val = abs(float(got) - float(value)) < 1e-6
+    except (TypeError, ValueError):
+        ok_val = False
+    check(ok_val, f"{title}: committed value is {got!r} (wanted {value})")
+    check(str(value) != prefill, f"{title}: the test value differs from the prefill {prefill!r}")
+    # RESUME JUST AFTER THE COMMIT, not at the end of the trace. A queued chain opens its next
+    # field from the commit callback, so by the time trace_mark() is read here that "open" line
+    # is already written — and the next call, searching only after this mark, never sees it. The
+    # rectangle's Height, the slot's Radius and the label reopen all failed as "nothing did"
+    # while the trace plainly showed the field open and waiting.
+    return (commit_at + 1) if commit_at is not None else trace_mark()
+
+
+# ---------------------------------------------------------------- the ladder
+
+def enter_sketch(timeout=180):
+    """Open a real sketch on a real plane, and PROVE it with the socket before drawing anything.
+
+    THE SEQUENCE MATTERS AND IT IS NOT OBVIOUS. Shift+S enters sketch MODE and pops the plane
+    offer; the offer must be dismissed; and the plane itself is chosen by clicking it in the
+    viewport BEFORE Shift+S. check-gui-sketching.py has always done all four steps. This ladder
+    did two of them — Design tab, then Shift+S — and went straight to the tool letters.
+
+    That intermediate state is the trap. `is_sketching` reads 1, every tool key is accepted and
+    traced, and not one click draws anything, because there is no plane under them. The ladder
+    then reports eleven product failures, all of them "a value field opened (nothing did)", and
+    every one is the driver's. Two whole runs were spent on it.
+
+    So the gate is the ORACLE, not the keytrace: sketch_describe answers only when a sketch is
+    genuinely open. Waiting on a mode flag is what allowed the wrong state to pass for the right
+    one in the first place.
+    """
+    deadline = time.time() + timeout
+    while time.time() < deadline:
+        click(132, 53)                   # Design tab
+        time.sleep(2.0)
+        dismiss_modals()
+        click(*PLANE_PX)                 # pick the plane IN THE VIEWPORT — before Shift+S
+        key("shift+s", 1.0)
+        key("Escape", 0.5)               # entering sketch mode pops the offer; dismiss it
+        key("p", 0.6)                    # any sketch tool starts the session on that plane
+        if try_call("sketch_describe") is not None:
+            # NO Escape here. Every rung already opens with one to drop whatever tool the last
+            # one left armed, and Escape in the Design tab walks a LIFO: first press drops the
+            # armed tool, second LEAVES THE SKETCH. Pressing it here made that second press the
+            # rung's own, so the ladder exited the sketch before drawing anything and then
+            # reported all eleven checks failed with "nothing opened" — the tools were arming
+            # into an empty Feature-mode document.
+            return
+    die("no sketch opened after plane click + Shift+S within "
+        f"{timeout}s — sketch_describe never answered on {A.sock} (trace {TRACE})")
+
+
+# tool key, the clicks that draw it, and one distinct value per queued field. The values are
+# deliberately nothing like the as-drawn size, so a committed prefill cannot coincide with them.
+# Where the plane label sits in the viewport before a sketch is open. Same constant the gesture
+# ladder uses; it is a label on the 3D view, not a widget, so it moves only if the camera does.
+PLANE_PX = (913, 359)
+
+# Every coordinate below stays inside 1000..1400 x 500..760 — the box check-gui-sketching.py's
+# calibration probes land four Points in, i.e. the region PROVEN to be live canvas on a 1920x1080
+# window. Earlier values started at x=950, which is left of that box and also, on a fresh datadir,
+# underneath the "Bambu Network Plug-in Required" modal.
+TOOLS = [
+    ("L", "Line",      [(1030, 540), (1360, 540)],                         [61]),
+    ("R", "Rectangle", [(1030, 540), (1360, 730)],                         [62, 43]),
+    ("C", "Circle",    [(1180, 620), (1330, 620)],                         [64]),
+    ("S", "Slot",      [(1030, 580), (1300, 580), (1300, 640)],            [66]),
+    ("G", "Polygon",   [(1180, 620), (1320, 620)],                         [67]),
+    ("E", "Ellipse",   [(1180, 620), (1370, 620), (1180, 720)],            [68]),
+    ("A", "Arc",       [(1040, 660), (1340, 660), (1190, 560)],            [69]),
+]
+
+
+def rung_tool(k, name, clicks, values):
+    print(f"  {name}")
+    key("Escape", 0.6)                   # back to Select, whatever the last tool left armed
+    # Every rung re-establishes that a sketch is STILL open. One stray Escape too many leaves it,
+    # and from then on every tool arms into a Feature-mode document that cannot open a value
+    # field — which the checks below report as eleven independent product failures.
+    if try_call("sketch_describe") is None:
+        die(f"{name}: the sketch is no longer open before this rung — an earlier rung left it")
+    key(k, 0.8)
+    # MARK BEFORE THE CLICKS, not after. The field is opened from a CallAfter scheduled by the
+    # render that follows the last click, so it can already be open by the time a mark taken
+    # afterwards is read — and type_into_open_field, which only looks at events AFTER its mark,
+    # then finds none and reports "a value field opened (nothing did)" for a field that is on
+    # screen, open, and waiting. That message accused the product of the exact defect the ladder
+    # exists to detect, from a bug in the ladder's own bookkeeping.
+    mark = trace_mark()
+    for (x, y) in clicks:
+        click(x, y)
+    for v in values:
+        mark = type_into_open_field(v, mark)
+
+
+def rung_rounded_rect():
+    """The shape the user actually reported: a ROUNDED rectangle, Width -> Height -> Radius.
+
+    It has no keyboard shortcut — the rectangle family binds R to CornerRect and leaves the other
+    modes in the toolbar flyout — so TOOLS above cannot reach it and the whole three-step chain
+    went untested. `run_verb` arms it the way the offer menu does.
+
+    NOTE the id: the OFFER verb is `sk_rect_rounded`; `design_rect_rounded` is the ACTION name and
+    run_verb throws on it, leaving the tool as Select. A run that misses that draws nothing and
+    still reaches its assertions, so arm-and-verify rather than arm-and-hope.
+    """
+    print("  Rounded rectangle")
+    key("Escape", 0.6)
+    tool = None
+    for _ in range(8):
+        try_call("run_verb", verb="sk_rect_rounded")
+        time.sleep(0.8)
+        tool = (try_call("sketch_describe") or {}).get("tool")
+        if tool == "rect_rounded":
+            break
+    if not check(tool == "rect_rounded", f"the rounded-rectangle tool armed (tool={tool!r})"):
+        return
+    mark = trace_mark()
+    click(1030, 540); click(1330, 700); click(1300, 660)   # corners, then the radius point
+    for v in (63, 41, 7):
+        mark = type_into_open_field(v, mark)
+
+
+def rung_label_click():
+    """The user's own report: click an existing dimension label and type a new value into it.
+
+    KEEP THE SHAPE AS DRAWN. An earlier version committed 55 and 47 into the queued chain first,
+    which resized the rectangle — and then clicked the pixel where the label had been before the
+    resize. It missed, every time, and reported the reopen broken. The shape's on-screen position
+    is only predictable if nothing has moved it, so Escape the chain instead: the rectangle stays
+    exactly between the two corners we clicked.
+
+    FIND THE LABEL, do not assume its offset. A dimension label is drawn beside its edge at an
+    offset that depends on zoom and text metrics, so a single hardcoded pixel is a guess that
+    silently becomes wrong. Walk a short band across the top edge instead and stop at the first
+    click that opens a field; if none of them does, that is a real failure and it says so.
+    """
+    print("  label click-to-edit")
+    key("Escape", 0.6)                   # Select mode
+    key("R", 0.8)
+    click(1020, 530)
+    click(1350, 740)
+    time.sleep(1.5)
+    key("Escape", 0.8)                   # keep as drawn: abandon the queued value chain
+    time.sleep(0.8)
+    key("Escape", 0.6)                   # back to Select so a click picks rather than draws
+
+    mid_x, top_y = (1020 + 1350) // 2, 530
+    candidates = [(mid_x, top_y + dy) for dy in (-26, -20, -14, -8, 0, 8, 14)]
+    for (cx, cy) in candidates:
+        mark = trace_mark()
+        click(cx, cy)
+        deadline = time.time() + 2.0
+        while time.time() < deadline:
+            if [e for e in (parse(l) for l in trace_lines()[mark:]) if e and e[0] == "open"]:
+                check(True, f"clicking a dimension label reopened its value field (at {cx},{cy})")
+                type_into_open_field(71, mark)
+                return
+            time.sleep(0.2)
+    check(False, "clicking a dimension label reopened its value field "
+                 f"(tried {len(candidates)} points across the top edge at x={mid_x})")
+
+
+def main():
+    if not A.attach:
+        if not os.path.exists(A.bin):
+            die(f"no binary at {A.bin}")
+        open(TRACE, "w").close()
+        launch()
+        dismiss_first_run()
+    win()
+    print(f"click-edit ladder on {DISP}, trace {TRACE}")
+    enter_sketch()
+    for (k, name, clicks, values) in TOOLS:
+        rung_tool(k, name, clicks, values)
+    rung_rounded_rect()
+    rung_label_click()
+    print()
+    if _fail:
+        print(f"CLICK-EDIT LADDER FAILED — {_fail} of {_checks} checks", file=sys.stderr)
+    else:
+        print(f"CLICK-EDIT LADDER HELD — {_checks} checks")
+    if _proc is not None and not A.keep:
+        _proc.send_signal(signal.SIGTERM)
+        try:
+            _proc.wait(20)
+        except subprocess.TimeoutExpired:
+            _proc.kill()
+    return 1 if _fail else 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/scripts/CAD/check-gui-context-menu.py b/scripts/CAD/check-gui-context-menu.py
new file mode 100644
index 0000000000..28e404ecf0
--- /dev/null
+++ b/scripts/CAD/check-gui-context-menu.py
@@ -0,0 +1,1218 @@
+#!/usr/bin/env python3
+"""The OFFER ladder: prove that right-click is the pivot, and that it adapts to what was clicked.
+
+The gesture ladder (scripts/CAD/check-gui-sketching.py) proved the TARGET — a complex closed profile, precise
+in vertices, lengths, arcs and symmetry, with its voids correctly attributed. It proved it by
+arming every tool with a letter key. That leaves the goal's own MECHANISM untested: the design
+logic pivots on right-click, and the verbs offered are supposed to adapt to the element under the
+cursor. Half the vocabulary is only reachable that way — 47 of 86 Design-tab verbs have a GUI
+action and no shortcut, so a key-driven ladder cannot reach them at all.
+
+This ladder drives the menu. Nothing here is asserted from pixels:
+
+  WHAT WAS CLICKED  -> the offer's own [OFFER] trace, emitted by show_offer_menu from the same
+                       loop that builds the rows (ORCA_CAD_KEYTRACE). It cannot drift from what
+                       the user is shown, which a hand-written expectation list would.
+  WHAT IS OFFERED   -> the same trace, compared against DesignOffer.hpp parsed independently.
+                       "The menu shows exactly the verbs the table says apply here" is a
+                       property; a copied list of row names is a transcription.
+  WHAT IT PRODUCED  -> the MCP socket, read-only, exactly as in the gesture ladder.
+
+Run inside the rig container, with the app launched under ORCA_CAD_KEYTRACE=1:
+
+    docker exec orcacad-gui python3 /OrcaSlicer/scripts/CAD/check-gui-context-menu.py [rung ...]
+"""
+import importlib.util
+import math
+import os
+import re
+import sys
+import time
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+
+# The gesture ladder owns the hand and the eye: the homography per sketch, the window lookup by
+# class, the synthetic click, the typed value, the socket. Importing it is the only way those
+# stay one implementation — a second copy would drift the first time a rig detail moved.
+_spec = importlib.util.spec_from_file_location("gui_ladder", os.path.join(HERE, "check-gui-sketching.py"))
+G = importlib.util.module_from_spec(_spec)
+_spec.loader.exec_module(G)
+
+LOG = os.environ.get("ORCA_CAD_GUI_LOG", "/tmp/gui-session.log")
+
+# The rig container's /OrcaSlicer is the image's own baked source tree, not this checkout, so the
+# generated header is not where a repo-relative path expects it. Look in both places and say which
+# one was read — a ladder that silently graded against the WRONG table would be worse than one
+# that refuses to start.
+HEADER_CANDIDATES = [os.environ.get("ORCA_CAD_OFFER_HPP", ""),
+                     os.path.join(HERE, "..", "src", "slic3r", "GUI", "CAD", "DesignOffer.hpp"),
+                     os.path.join(HERE, "DesignOffer.hpp")]
+
+# OfferSel, in the order the generated enum declares it. The trace reports the integer; a test
+# that printed "kind=16" and expected the reader to know what that is would be half a test.
+SEL = ["None", "FacePlanar", "FaceCyl", "FaceOther", "EdgeStr", "EdgeCirc", "Vertex",
+       "BodySolid", "BodySheet", "Bodies2", "DatumPlane", "DatumAxis", "CoordSys", "Art",
+       "SkLoop", "SkNone", "SkLine", "SkArc", "SkPoint", "Sk2Ent"]
+
+
+# ---------------------------------------------------------------- the table, parsed
+
+def load_table():
+    """Every verb in DesignOffer.hpp, as dicts. The independent half of the comparison.
+
+    Parsed from the generated header rather than from tool_atlas.json on purpose: the header is
+    what the binary was compiled from, and the two have been out of step before (ziam,
+    where regenerating the header silently dropped the Constrain row).
+    """
+    path = next((p for p in HEADER_CANDIDATES if p and os.path.exists(p)), None)
+    if path is None:
+        raise SystemExit("no DesignOffer.hpp found; set ORCA_CAD_OFFER_HPP or copy it beside "
+                         "this script (tried: " + ", ".join(filter(None, HEADER_CANDIDATES)) + ")")
+    print(f"offer table: {os.path.realpath(path)}")
+    src = open(path).read()
+    body = src[src.index("kOfferVerbs[]"):]
+    body = body[:body.index("\n};")]
+    out = []
+    for line in body.splitlines():
+        line = line.strip()
+        if not line.startswith('{"'):
+            continue
+        # id, name, row, key, action, refusal, accepts, need_bodies, need_sketches, need_sheet,
+        # sketch_mode, family, ... — split on top-level commas, respecting quotes.
+        f, cur, q, esc = [], "", False, False
+        for ch in line[1:]:
+            if esc:
+                cur += ch; esc = False; continue
+            if ch == "\\":
+                cur += ch; esc = True; continue
+            if ch == '"':
+                q = not q
+            if ch == "," and not q:
+                f.append(cur.strip()); cur = ""; continue
+            if ch == "}" and not q:
+                break
+            cur += ch
+        f.append(cur.strip())
+        if len(f) < 12:
+            continue
+        lit = lambda s: None if s == "nullptr" else s.strip('"')
+        out.append({"id": lit(f[0]), "name": lit(f[1]), "row": int(f[2]), "key": lit(f[3]),
+                    "action": lit(f[4]), "accepts": int(f[6].rstrip("u"), 0),
+                    "need_bodies": int(f[7]), "need_sketches": int(f[8]),
+                    "need_sheet": f[9] == "true", "sketch_mode": f[10] == "true",
+                    "family": lit(f[11])})
+    return out
+
+
+TABLE = load_table()
+
+
+def predicted(kind, sketching, bodies=0, sketches=0, sheet=False):
+    """The verbs show_offer_menu should list for this selection — the table's own answer.
+
+    Mirrors the `applies` lambda and the sketch_mode gate in DesignPanel::show_offer_menu. If the
+    two ever disagree, one of them is the bug; this ladder says which selection exposed it.
+    """
+    bit = 1 << kind
+    return [v["id"] for v in TABLE
+            if v["sketch_mode"] == sketching and (v["accepts"] & bit)
+            and v["need_bodies"] <= bodies and v["need_sketches"] <= sketches
+            and (not v["need_sheet"] or sheet)]
+
+
+# ---------------------------------------------------------------- the trace, read back
+
+def log_mark():
+    """Where the log ends now, so the next read sees only this gesture's lines."""
+    try:
+        return os.path.getsize(LOG)
+    except OSError:
+        return 0
+
+
+def log_since(mark):
+    with open(LOG, "rb") as fh:
+        fh.seek(mark)
+        return fh.read().decode("utf-8", "replace")
+
+
+class Offer:
+    """One opening of the offer menu, as the app described it while building the rows."""
+
+    def __init__(self, text):
+        self.kind = None
+        self.sketching = None
+        self.entries = []       # top level, in order: dicts with label/enabled/verbs
+        self.verbs = []         # every live verb id, in menu order
+        for m in re.finditer(r"^\[OFFER\] (.*)$", text, re.M):
+            self._line(m.group(1))
+
+    def _line(self, s):
+        head = re.match(r"open kind=(\d+) sketching=(\d+) bodies=(\d+)", s)
+        if head:
+            self.kind = int(head.group(1))
+            self.sketching = head.group(2) == "1"
+            self.entries = []
+            self.verbs = []
+            return
+        dis = re.match(r"row=(\d+) (.*?) DISABLED \((.*)\)$", s)
+        if dis:
+            self.entries.append({"row": int(dis.group(1)), "label": dis.group(2),
+                                 "enabled": False, "kids": [], "why": dis.group(3)})
+            return
+        one = re.match(r"row=(\d+) (.*?) -> (\S+)(?: \(no GUI route\))?$", s)
+        if one:
+            routed = "(no GUI route)" not in s
+            self.entries.append({"row": int(one.group(1)), "label": one.group(2),
+                                 "enabled": routed, "kids": [], "verb": one.group(3)})
+            self.verbs.append(one.group(3))
+            return
+        sub = re.match(r"row=(\d+) (.*?) > (.*)$", s)
+        if sub:
+            row, label, rest = int(sub.group(1)), sub.group(2), sub.group(3)
+            routed = "(no GUI route)" not in rest
+            rest = rest.replace(" (no GUI route)", "")
+            fam, vid = (rest.split(" > ", 1) + [None])[:2] if " > " in rest else (None, rest)
+            if not self.entries or self.entries[-1]["row"] != row or "verb" in self.entries[-1]:
+                self.entries.append({"row": row, "label": label, "enabled": True, "kids": []})
+            self.entries[-1]["kids"].append({"family": fam, "verb": vid, "enabled": routed})
+            self.verbs.append(vid)
+            return
+
+    def kind_name(self):
+        return SEL[self.kind] if self.kind is not None and self.kind < len(SEL) else str(self.kind)
+
+    def path_to(self, verb):
+        """Keyboard path to a verb: how many Downs at each level, top level first.
+
+        GTK skips insensitive items on arrow navigation, so the count is over ENABLED entries
+        only — which is exactly why the trace records the enabled state per row instead of the
+        ladder assuming every row is live.
+        """
+        n = 0
+        for e in self.entries:
+            if not e["enabled"]:
+                continue
+            n += 1
+            if e.get("verb") == verb:
+                return [n]
+            if e["kids"]:
+                # Families become a nested submenu at the position of their first member.
+                pos, seen = 0, []
+                for k in e["kids"]:
+                    if k["family"]:
+                        if k["family"] not in seen:
+                            seen.append(k["family"])
+                            pos += 1
+                        fam_pos = pos
+                        if k["verb"] == verb:
+                            inner = [x for x in e["kids"] if x["family"] == k["family"]]
+                            j = sum(1 for x in inner[:inner.index(k) + 1] if x["enabled"])
+                            return [n, fam_pos, j]
+                        continue
+                    if not k["enabled"]:
+                        continue
+                    pos += 1
+                    if k["verb"] == verb:
+                        return [n, pos]
+        return None
+
+
+def open_offer(X=None, Y=None, pause=1.2):
+    """Right-click (on the plane point given, or wherever the cursor is) and read the offer back.
+
+    The menu is modal — PopupMenu blocks the main thread — so no socket call may be made between
+    this and choose()/dismiss(). Every assertion about the menu comes from the trace.
+    """
+    mark = log_mark()
+    if X is None:
+        G.xdo("click --delay 120 3")
+    else:
+        G.clickmm(X, Y, pause=0.5, btn=3)
+    time.sleep(pause)
+    return Offer(log_since(mark))
+
+
+def choose(offer, verb):
+    """Walk the open menu to a verb with the keyboard and activate it."""
+    path = offer.path_to(verb)
+    if path is None:
+        G.die(f"{verb} is not in the offer (kind={offer.kind_name()}, has {offer.verbs})")
+    for level, downs in enumerate(path):
+        # At the top level nothing is highlighted when the menu pops, so the first Down lands on
+        # entry 1. Inside a submenu GTK has ALREADY highlighted its first item as part of opening
+        # it, so reaching entry k takes k-1 more. Getting this wrong is silent: the walk activates
+        # a neighbouring verb and the rung grades a shape nobody asked for — the first run of this
+        # rung drew a circle of area 45238.93 and called it a rectangle.
+        for _ in range(downs if level == 0 else downs - 1):
+            G.key("Down", 0.12)
+        if level < len(path) - 1:
+            G.key("Right", 0.35)          # open the submenu; its first item is now highlighted
+    G.key("Return", 0.9)
+
+
+def dismiss(offer=None):
+    """Escape ONLY when a menu is really open.
+
+    A stray Escape on the canvas is not harmless: with no tool armed and no points down, the
+    sketch's layered exit reads it as "leave the sketch", and the next socket call answers
+    "no sketch is open" three rungs from where the mistake was made.
+    """
+    if offer is not None and offer.kind is None:
+        return
+    G.key("Escape", 0.5)
+
+
+def menu_windows():
+    """X windows that are override-redirect popups — evidence the menu really opened."""
+    out = []
+    for w in G.sh(f"DISPLAY={G.DISP} xdotool search --class '.'").split():
+        g = G.sh(f"DISPLAY={G.DISP} xdotool getwindowgeometry --shell {w}")
+        d = dict(l.split("=", 1) for l in g.strip().splitlines() if "=" in l)
+        if "WIDTH" in d and 60 < int(d["WIDTH"]) < 700 and 40 < int(d["HEIGHT"]) < 900:
+            out.append(w)
+    return out
+
+
+# ---------------------------------------------------------------- rungs
+
+def draw_line_at(x0, y0, x1, y1, length):
+    """Draw one horizontal line and COMMIT it by typing its length and angle.
+
+    Deliberately no Escape. Escape is overloaded in a sketch — field, then tool, then the sketch
+    itself — so a driver that presses it one time too many leaves the session and every later
+    assertion answers "no sketch is open" from three rungs away. Typing the value closes the
+    field, which is what the gesture ladder proved commits exactly.
+    """
+    G.key("l", 0.5)
+    G.clickmm(x0, y0)
+    G.clickmm(x1, y1)
+    G.values(int(length), 0)
+    keep_as_drawn()          # drain any straggler field before the caller clicks anything
+
+
+def rung_kinds():
+    """O1 — the offer adapts to the element under the cursor, one element type at a time."""
+    print("\nO1  the offer reads what was right-clicked")
+    fresh_sketch("l")
+    x0, x1, y0, y1 = G._SAFE
+    cx, cy = (x0 + x1) / 2.0, (y0 + y1) / 2.0
+
+    # Empty space first: nothing is selected, so the sketch vocabulary's no-selection row set.
+    # Right-click has two jobs on a draw tool, and which one it does depends on whether an
+    # anchor is down. Both are asserted here: the version that consumed EVERY right-click made
+    # the offer unreachable from any armed tool (ghcz), which is the goal's own
+    # mechanism failing silently.
+    hi = y1 - (y1 - y0) * 0.12
+    o = open_offer(cx, hi)
+    G.check("OFFER", o.kind is not None,
+            "Line armed, nothing anchored: right-click opens the offer")
+    G.check("OFFER", o.kind == 15, f"right-click on empty space -> {o.kind_name()}")
+    G.check("OFFER", o.sketching, "the sketch vocabulary is the one being offered")
+    dismiss(o)
+
+    # ...and with an anchor down it abandons the anchor instead, offering nothing.
+    G.key("l", 0.5)
+    G.clickmm(cx, hi)                          # anchor the first point
+    o = open_offer(cx + (x1 - x0) * 0.1, hi)
+    G.check("OFFER", o.kind is None,
+            "with an anchor down, the same gesture abandons it and does not offer")
+    o = open_offer(cx, hi)
+    G.check("OFFER", o.kind is not None, "and the offer is back on the next right-click")
+    dismiss(o)
+    G.key("Escape", 0.4)
+
+    # A line.
+    ax, ay = x0 + (x1 - x0) * 0.15, cy
+    bx, by = x0 + (x1 - x0) * 0.55, cy
+    draw_line_at(ax, ay, bx, by, 40)
+    o = open_offer((ax + bx) / 2.0, ay)
+    G.check("OFFER", o.kind == 16, f"right-click on a line -> {o.kind_name()}")
+    dismiss(o)
+
+    # A circle: every curve takes the same vocabulary, which is what SkArc means.
+    G.key("c", 0.5)
+    ccx, ccy = x0 + (x1 - x0) * 0.30, cy + (y1 - y0) * 0.25
+    G.clickmm(ccx, ccy)
+    G.clickmm(ccx + (x1 - x0) * 0.10, ccy)
+    G.values(20)
+    ents = G.describe()["entities"]
+    circ = [e for e in ents if e["type"] == "circle"]
+    G.check("OFFER", len(circ) == 1, "one circle drawn to right-click on")
+    r = circ[0]["radius"]
+    o = open_offer(circ[0]["center"][0] + r, circ[0]["center"][1])
+    G.check("OFFER", o.kind == 17, f"right-click on a circle -> {o.kind_name()}")
+    dismiss(o)
+
+    # A point.
+    G.key("p", 0.5)
+    pxx, pyy = x0 + (x1 - x0) * 0.80, cy + (y1 - y0) * 0.25
+    G.clickmm(pxx, pyy)
+    o = open_offer(pxx, pyy)
+    G.check("OFFER", o.kind == 18, f"right-click on a point -> {o.kind_name()}")
+    dismiss(o)
+
+    # Two entities: a second line, then both picked. Two LINES rather than line-plus-point on
+    # purpose — the Sk2Ent vocabulary (angle, equal, parallel, the two-entity constraints) is
+    # about pairs of curves, so the pair the ladder builds should be the pair the verbs mean.
+    draw_line_at(ax, ay - (y1 - y0) * 0.18, bx, ay - (y1 - y0) * 0.18, 40)
+    # ONE Escape, to drop the armed tool to Select, and only once the value fields are quiet.
+    # Left-click means "draw" while a tool is armed, so a picking gesture has to say so first —
+    # and from a draw tool with no anchor down Escape does exactly that and nothing more; it is
+    # only a second Escape, from Select, that would leave the sketch.
+    keep_as_drawn()
+    G.key("Escape", 0.5)
+    G.clickmm(*on_line((ax, ay), (bx, ay)))
+    G.xdo("keydown shift")
+    G.clickmm(*on_line((ax, ay - (y1 - y0) * 0.18), (bx, ay - (y1 - y0) * 0.18)))
+    G.xdo("keyup shift")
+    d = G.describe()
+    G.check("OFFER", len(d["selection"]) == 2,
+            f"two entities picked: {d['selection']} (tool={d['tool']} pending={d['pending']} "
+            f"editing={d['editing']})")
+    o = open_offer((ax + bx) / 2.0, ay)
+    G.check("OFFER", o.kind == 19,
+            f"right-click with two picked -> {o.kind_name()}"
+            + ("" if o.kind is not None else
+               f" (no menu: tool={G.describe()['tool']} pending={G.describe()['pending']} "
+               f"editing={G.describe()['editing']})"))
+    dismiss(o)
+    G.leave_sketch()
+    G.reset_document()
+
+
+def rung_vocabulary():
+    """O2 — the rows offered are exactly the ones the table says apply to that selection.
+
+    Five selections, not one. The interesting failure is not "the menu is empty", it is "the
+    menu is the same whatever you clicked" — and only comparing several kinds against their own
+    predictions can tell those apart.
+    """
+    print("\nO2  the menu and the offer table agree, selection by selection")
+    fresh_sketch("l")
+    x0, x1, y0, y1 = G._SAFE
+    cx, cy = (x0 + x1) / 2.0, (y0 + y1) / 2.0
+    ax, ay = x0 + (x1 - x0) * 0.15, cy
+    bx = x0 + (x1 - x0) * 0.55
+    draw_line_at(ax, ay, bx, ay, 40)
+
+    G.key("c", 0.5)
+    ccx, ccy = x0 + (x1 - x0) * 0.30, cy + (y1 - y0) * 0.25
+    G.clickmm(ccx, ccy); G.clickmm(ccx + (x1 - x0) * 0.10, ccy)
+    G.values(20)
+    circ = [e for e in G.describe()["entities"] if e["type"] == "circle"][0]
+
+    G.key("p", 0.5)
+    pxx, pyy = x0 + (x1 - x0) * 0.80, cy + (y1 - y0) * 0.25
+    G.clickmm(pxx, pyy)
+
+    where = [("SkNone", cx, y1 - (y1 - y0) * 0.12),
+             ("SkLine", (ax + bx) / 2.0, ay),
+             ("SkArc", circ["center"][0] + circ["radius"], circ["center"][1]),
+             ("SkPoint", pxx, pyy),
+             ("Sk2Ent", None, None)]
+    seen = {}
+    for name, X, Y in where:
+        if name == "Sk2Ent":
+            # The two-entity vocabulary was the one selection nothing compared against the table,
+            # and it is where the missing row hid: sk_angdist accepts Sk2Ent and nothing else, so
+            # an off-by-one that dropped the LAST verb was invisible from every other selection.
+            keep_as_drawn()
+            G.key("Escape", 0.5)
+            G.clickmm(*on_line((ax, ay), (bx, ay)))
+            G.xdo("keydown shift")
+            # The TOP of the circle, not its +X point: the radius grip lives there, and a click on
+            # a grip arms a handle drag which REPLACES the selection with that one entity. The
+            # pick then silently collapses to one and the offer answers SkLine — right, for the
+            # selection that actually existed.
+            G.clickmm(circ["center"][0], circ["center"][1] + circ["radius"])
+            G.xdo("keyup shift")
+            picked = len(G.describe()["selection"])
+            G.check("OFFER", picked == 2, f"two entities picked for the pair vocabulary: {picked}")
+            X, Y = (ax + bx) / 2.0, ay
+        o = open_offer(X, Y)
+        want = sorted(predicted(o.kind, o.sketching))
+        got = sorted(o.verbs)
+        G.check("OFFER", o.kind is not None and o.kind_name() == name and got == want,
+                f"{o.kind_name()}: {len(got)} verbs, exactly the table's set"
+                + ("" if got == want else f"\n      menu  {got}\n      table {want}"))
+        seen[name] = set(got)
+        dismiss(o)
+
+    # And the sets are genuinely DIFFERENT — an offer that adapts is not one that always shows
+    # the same rows. Without this, four identical menus would have passed four checks.
+    G.check("OFFER", len(set(map(frozenset, seen.values()))) == len(seen),
+            "every selection offers a different set: "
+            + ", ".join(f"{k}={len(v)}" for k, v in seen.items()))
+    G.check("OFFER", seen["SkLine"] - seen["SkNone"],
+            f"a picked line adds {len(seen['SkLine'] - seen['SkNone'])} verbs an empty pick has not: "
+            + ", ".join(sorted(seen["SkLine"] - seen["SkNone"])[:8]))
+    G.leave_sketch()
+    G.reset_document()
+
+
+def rung_author():
+    """O3 — the target itself, authored through the menu: no tool key is pressed anywhere here."""
+    print("\nO3  a precise closed profile, drawn entirely from the right-click offer")
+    fresh_sketch("p")            # 'p' only to open the session; calibration needs the Point tool
+    G.key("Escape", 0.4)
+    x0, x1, y0, y1 = G._SAFE
+    cx, cy = (x0 + x1) / 2.0, (y0 + y1) / 2.0
+    w, h = 120.0, 80.0
+
+    o = open_offer(cx, cy)
+    G.check("OFFER", o.kind == 15, f"empty sketch -> {o.kind_name()}")
+    choose(o, "sk_rect")
+    G.clickmm(cx - w / 2.0, cy - h / 2.0)
+    G.clickmm(cx + w / 2.0, cy + h / 2.0)
+    G.values(int(w), int(h))
+    ents = G.describe()["entities"]
+    G.check("LENGTH", G.lengths(ents) == [80.0, 80.0, 120.0, 120.0],
+            f"sides {G.lengths(ents)} — typed through the offer, exact")
+    lp = G.loops()
+    G.check("CLOSED", len(lp) == 1, f"{len(lp)} closed loop(s)")
+    G.check("AREA", G.near(abs(lp[0]["area"]), w * h, 1e-9), f"area {abs(lp[0]['area']):.6f}")
+    G.leave_sketch()
+    G.reset_document()
+
+
+def rung_no_shortcut():
+    """O4 — a tool with NO keyboard route at all, armed from the menu and graded on its geometry.
+
+    This is the half of the vocabulary a key-driven ladder cannot reach: 47 of the 86 Design-tab
+    verbs have a GUI action and no shortcut, and for those the offer is not one door, it is the
+    only door. Arming the tool is not the assertion — the exact rectangle it then draws is.
+    """
+    print("\nO4  a tool that has no shortcut, reached the only way it can be")
+    fresh_sketch("p")
+    G.key("Escape", 0.5)
+    x0, x1, y0, y1 = G._SAFE
+    cx, cy = (x0 + x1) / 2.0, (y0 + y1) / 2.0
+
+    o = open_offer(cx, cy)
+    keyless = [v for v in TABLE if v["id"] in o.verbs and not v["key"] and v["action"]]
+    G.check("OFFER", len(keyless) >= 10,
+            f"{len(keyless)} of the {len(o.verbs)} verbs offered here have no shortcut at all")
+    G.check("OFFER", any(v["id"] == "sk_rect_center" for v in keyless),
+            "centre rectangle among them — unreachable from the keyboard")
+
+    w, h = 120.0, 80.0
+    choose(o, "sk_rect_center")
+    G.clickmm(cx, cy)                        # centre
+    G.clickmm(cx + w / 2.0, cy + h / 2.0)    # corner
+    G.values(int(w), int(h))
+    ents = G.describe()["entities"]
+    G.check("LENGTH", G.lengths(ents) == [80.0, 80.0, 120.0, 120.0],
+            f"sides {G.lengths(ents)} from a tool with no key")
+    lp = G.loops()
+    G.check("CLOSED", len(lp) == 1 and G.near(abs(lp[0]["area"]), w * h, 1e-9),
+            f"{len(lp)} closed loop, area {abs(lp[0]['area']):.6f}")
+    xs = sorted({round(p, 6) for e in ents for p in (e["p0"][0], e["p1"][0])})
+    ys = sorted({round(p, 6) for e in ents for p in (e["p0"][1], e["p1"][1])})
+    # Centred on the CLICK, to within the click itself. A synthetic click lands on a whole
+    # pixel, so the plane point it names is only ever as exact as one pixel is — grading this to
+    # 1e-6 would be grading the homography, not the tool. What is exact is the SHAPE, and that
+    # is asserted above; what is asserted here is that this was a centre rectangle and not a
+    # corner one, which a whole pixel is plenty to tell apart at 120 x 80.
+    tol = 1.5 * G.mm_per_px(cx, cy)
+    mx, my = (xs[0] + xs[-1]) / 2.0, (ys[0] + ys[-1]) / 2.0
+    G.check("SYMMETRY", abs(mx - cx) <= tol and abs(my - cy) <= tol,
+            f"centred on the click within {tol:.3f} mm (one pixel): "
+            f"off by {abs(mx - cx):.4f}, {abs(my - cy):.4f} — a CENTRE rectangle, not a corner one")
+    G.leave_sketch()
+    G.reset_document()
+
+
+
+# ---------------------------------------------------------------- fixtures
+
+def keep_as_drawn():
+    """Close an in-canvas value field if one is open, keeping the geometry as drawn.
+
+    Checked, never assumed. Escape is overloaded: with a field open it means keep-as-drawn, with
+    none open it drops the armed tool, and one Escape too many leaves the sketch. The socket now
+    reports whether a field IS open ("editing"), so this presses the key only when it means what
+    the caller wants it to mean.
+    """
+    n = 0
+    # A LOOP, not one press: the auto-edit queue opens the next field from a CallAfter as the
+    # previous one commits (a rectangle queues Width then Height), so one Escape leaves a second
+    # field on screen and the canvas still frozen. The loop stops the moment nothing is open,
+    # which is what keeps the last press from being the one that drops the tool.
+    #
+    # And it waits for QUIET, not for a single false reading. A field that has not opened YET
+    # reads exactly like one that will never open, so a driver that looks once, sees nothing and
+    # moves on gets frozen by the field that arrives a moment later — with no symptom except
+    # that clicks stop working. Measured: this rung passed alone and failed inside the gate,
+    # where the app is warmer and the CallAfter lands later; the diagnostic that found it was
+    # editing=True with an empty selection after two clicks that should have picked two entities.
+    for _ in range(8):
+        time.sleep(0.35 * G.PACE)
+        if not G.describe().get("editing"):
+            time.sleep(0.35 * G.PACE)
+            if not G.describe().get("editing"):
+                return n
+        G.key("Escape", 0.45)
+        n += 1
+    return n
+
+
+def clear_sketch():
+    """Empty the live sketch through the socket.
+
+    Fixture TEARDOWN, not the thing under test: what is being graded is always the geometry a
+    verb just produced, never how the canvas got emptied. Doing it through the socket keeps each
+    verb's rung independent without paying for a fresh sketch (four calibration probes) each time.
+    """
+    keep_as_drawn()          # a shape left mid-edit freezes the canvas for whatever comes next
+    n = len(G.describe()["entities"])
+    if n:
+        G.call("sketch_delete", entities=list(range(n)))
+
+
+# Which tool each creation verb is supposed to arm. The menu walk counts rows, and a walk that
+# lands ONE ROW OFF arms a neighbouring tool and then draws something plausible with it — the
+# first run of this rung drew a circle and graded it as a rectangle. Asserting the armed tool
+# turns that whole class of silent misnavigation into a loud failure at the point it happens.
+ARMS = {"sk_polyline": "polyline", "sk_rect": "rect_corner", "sk_rect_center": "rect_center",
+        "sk_rect_oblique": "rect_oblique", "sk_rect_rounded": "rect_rounded",
+        "sk_circle_2pt": "circle_2pt", "sk_circle_3pt": "circle_3pt",
+        "sk_arc_tangent": "arc_tangent", "sk_arc_center": "arc_center",
+        "sk_slot_arc": "slot_arc", "sk_ellipse_arc": "ellipse_arc",
+        "sk_poly_3": "polygon", "sk_poly_4": "polygon", "sk_poly_5": "polygon",
+        "sk_poly_8": "polygon", "sk_poly_12": "polygon",
+        "sk_move": "move", "sk_rotate": "rotate", "sk_scale": "scale",
+        "sk_array": "array", "sk_array_polar": "array_polar"}
+
+
+def arm(verb, X, Y, check_tool=True):
+    """Open the offer on empty plane at (X, Y) and pick a verb out of it. No key is ever pressed."""
+    o = open_offer(X, Y)
+    if o.kind is None:
+        G.die(f"the offer did not open for {verb} (tool={G.describe().get('tool')}, "
+              f"pending={G.describe().get('pending')})")
+    choose(o, verb)
+    if check_tool and verb in ARMS:
+        got = G.describe().get("tool")
+        G.check("OFFER", got == ARMS[verb], f"{verb} armed the {got} tool")
+    return o
+
+
+def ents(kind=None):
+    e = G.describe()["entities"]
+    return [x for x in e if kind is None or x["type"] == kind]
+
+
+def clicked(X, Y):
+    """The plane point the app REALLY saw for clickmm(X, Y).
+
+    A synthetic click lands on a whole pixel, so the plane point it names is not the one asked
+    for. Rounding the pixel and mapping it back is what the app got, and grading a construction
+    against it is grading the tool rather than the driver's arithmetic.
+    """
+    u, v = G.px(X, Y)
+    return G.unpx(int(u), int(v))
+
+
+def fresh_sketch(tool):
+    """Enter a sketch from a KNOWN empty state, whatever the previous rung or run left behind.
+
+    check-gui-sketching's enter_sketch dismisses the old session with keys, and a key is exactly what an
+    open value field swallows — so a session that should have been cancelled survives, the four
+    calibration probes land in it on top of whatever was already there, and the run dies with
+    "calibration expected 4 points, got 7". Cancelling through the socket cannot be swallowed:
+    it reaches the tool directly. This is fixture teardown, not the thing under test.
+    """
+    G.try_call("sketch_cancel")
+    G.key("Escape", 0.3)
+    G.enter_sketch(tool)
+
+
+def on_line(a, b, t=0.3):
+    """A point a fraction t ALONG a line — never its midpoint.
+
+    A left-click within ~24 px of a live dimension label opens that dimension's value editor
+    instead of selecting anything (the Select branch tests m_live_quotes before it picks), and a
+    line's Length quote sits at its middle. Clicking there froze the canvas on an open field, so
+    the following clicks and the right-click all landed on nothing and the pair vocabulary was
+    never reached. It bit only when the previous step had left the line selected — live quotes are
+    drawn for the SELECTION — which is why it passed alone and failed inside the gate.
+    """
+    return (a[0] + (b[0] - a[0]) * t, a[1] + (b[1] - a[1]) * t)
+
+
+def poly_click(pt):
+    """One click of a multi-segment tool, then close whatever value field that click opened.
+
+    The polyline arms a Length field after EVERY segment, and a field freezes the canvas — so a
+    driver that just clicks four times places two points and loses the rest. Nothing had ever
+    exercised the polyline (it has no shortcut), so nothing had ever met this.
+    """
+    G.clickmm(*pt)
+    keep_as_drawn()
+
+
+def dist(a, b):
+    return math.hypot(a[0] - b[0], a[1] - b[1])
+
+
+def spread(vals):
+    return max(vals) - min(vals)
+
+
+# ---------------------------------------------------------------- the keyless 2D vocabulary
+
+def rung_curves():
+    """O5 — every 2D creation verb that has no shortcut, drawn from the offer and graded exactly.
+
+    These are reachable ONLY from the right-click menu, so nothing has ever exercised them. The
+    assertions are CONSTRUCTION invariants — a regular polygon's vertices are equidistant, a
+    tangent arc meets its line at a right angle to the radius, a circumscribed polygon's
+    circumradius is the inscribed one's over cos(pi/n) — because those hold exactly whatever
+    pixel the click landed on. Where a value field opens, the typed value is graded exactly too.
+    """
+    print("\nO5  the 2D creation verbs that have no keyboard route")
+    fresh_sketch("p")
+    G.key("Escape", 0.5)
+    x0, x1, y0, y1 = G._SAFE
+    cx, cy = (x0 + x1) / 2.0, (y0 + y1) / 2.0
+    W, H = (x1 - x0), (y1 - y0)
+    free = (cx, y1 - H * 0.10)          # a corner of the safe box that stays empty to right-click
+
+    # --- Polyline: an explicitly CLOSED chain, which is the goal's own shape ------------------
+    clear_sketch()
+    arm("sk_polyline", *free)
+    ring = [(cx - W * 0.20, cy - H * 0.15), (cx + W * 0.20, cy - H * 0.15),
+            (cx + W * 0.20, cy + H * 0.15), (cx - W * 0.20, cy + H * 0.15)]
+    for pt in ring:
+        poly_click(pt)
+    poly_click(ring[0])                 # click the start again: the explicit close
+    lines = ents("line")
+    lp = G.loops()
+    G.check("CLOSED", len(lines) == 4 and len(lp) == 1,
+            f"sk_polyline: {len(lines)} lines, {len(lp)} closed loop — closed by clicking the start")
+
+    # --- Oblique rectangle: three clicks, and the point of it is that it is NOT axis-aligned --
+    clear_sketch()
+    arm("sk_rect_oblique", *free)
+    a = (cx - W * 0.20, cy - H * 0.10)
+    b = (cx + W * 0.15, cy + H * 0.05)          # first edge, deliberately skew
+    G.clickmm(*a); G.clickmm(*b); G.clickmm(cx - W * 0.10, cy + H * 0.20)
+    q = ents("line")
+    G.check("LENGTH", len(q) == 4, f"sk_rect_oblique: {len(q)} lines")
+    if len(q) == 4:
+        L = sorted(round(e["length"], 9) for e in q)
+        G.check("LENGTH", L[0] == L[1] and L[2] == L[3],
+                f"opposite sides equal to 1e-9: {L}")
+        angs = []
+        for i in range(4):
+            for j in range(i + 1, 4):
+                u = (q[i]["p1"][0] - q[i]["p0"][0], q[i]["p1"][1] - q[i]["p0"][1])
+                v = (q[j]["p1"][0] - q[j]["p0"][0], q[j]["p1"][1] - q[j]["p0"][1])
+                c = abs(u[0] * v[0] + u[1] * v[1]) / (math.hypot(*u) * math.hypot(*v))
+                angs.append(c)
+        G.check("ANGLE", sum(1 for c in angs if c < 1e-9) == 4,
+                f"four right angles to 1e-9 ({sum(1 for c in angs if c < 1e-9)} perpendicular pairs)")
+        d0 = (q[0]["p1"][0] - q[0]["p0"][0], q[0]["p1"][1] - q[0]["p0"][1])
+        G.check("ANGLE", abs(d0[0]) > 1e-6 and abs(d0[1]) > 1e-6,
+                f"and it really is oblique: first edge {math.degrees(math.atan2(*d0[::-1])):.3f} deg")
+
+    # --- Rounded rectangle: four lines, four arcs, one radius --------------------------------
+    clear_sketch()
+    arm("sk_rect_rounded", *free)
+    G.clickmm(cx - W * 0.20, cy - H * 0.15)
+    G.clickmm(cx + W * 0.20, cy + H * 0.15)
+    G.clickmm(cx + W * 0.20 - W * 0.04, cy + H * 0.15)     # third click sets the radius
+    ls, ar = ents("line"), ents("arc")
+    G.check("ARC", len(ls) == 4 and len(ar) == 4, f"sk_rect_rounded: {len(ls)} lines + {len(ar)} arcs")
+    if len(ar) == 4:
+        rr = sorted(round(e["radius"], 9) for e in ar)
+        G.check("ARC", spread(rr) == 0.0, f"all four fillets share one radius to 1e-9: {rr[0]}")
+        lp = G.loops()
+        G.check("CLOSED", len(lp) == 1, f"{len(lp)} closed loop")
+        if len(lp) == 1:
+            xs = [p for e in ls for p in (e["p0"][0], e["p1"][0])]
+            ys = [p for e in ls for p in (e["p0"][1], e["p1"][1])]
+            # The four straight sides already span the FULL outer box — the top edge runs from
+            # x_min+r to x_max-r at y_max — so their bbox is the rectangle itself, and the
+            # rounding costs the four corner squares less their quarter-discs: r^2(4 - pi).
+            w, h, r = max(xs) - min(xs), max(ys) - min(ys), rr[0]
+            want = w * h - r * r * (4 - math.pi)
+            G.check("AREA", G.near(abs(lp[0]["area"]), want, 1e-6),
+                    f"area {abs(lp[0]['area']):.9f} vs W*H - r^2(4-pi) {want:.9f}")
+
+    # --- Two-point circle: the two clicks are the ends of a diameter --------------------------
+    clear_sketch()
+    arm("sk_circle_2pt", *free)
+    p_a = (cx - W * 0.18, cy - H * 0.10)
+    p_b = (cx + W * 0.18, cy + H * 0.10)
+    G.clickmm(*p_a); G.clickmm(*p_b)
+    c2 = ents("circle")
+    G.check("ARC", len(c2) == 1, f"sk_circle_2pt: {len(c2)} circle")
+    if c2:
+        A, B = clicked(*p_a), clicked(*p_b)
+        mid = ((A[0] + B[0]) / 2.0, (A[1] + B[1]) / 2.0)
+        tol = 1.5 * G.mm_per_px(cx, cy)
+        G.check("VERTEX", dist(c2[0]["center"], mid) <= tol,
+                f"centred on the midpoint of the two clicks (off by {dist(c2[0]['center'], mid):.4f} mm)")
+        G.check("ARC", abs(c2[0]["radius"] - dist(A, B) / 2.0) <= tol,
+                f"radius {c2[0]['radius']:.6f} vs half the click separation {dist(A, B) / 2.0:.6f}")
+        opened = bool(G.describe().get("editing"))
+        G.check("OFFER", opened, "a radius field opens for it, as it does for the keyed circle")
+        if opened:
+            G.value(30)
+            got = ents("circle")[0]["radius"]
+            G.check("ARC", G.near(got, 30.0, 1e-9),
+                    f"and it takes a typed radius exactly: {got:.9f} (asked 30.0)")
+            # The DoF of ONE CIRCLE is three. Asserted here because it is where the lie showed:
+            # after a delete the solver was never re-run, so this reported the DoF of the
+            # geometry that had just been erased. ua9g.
+            G.check("VERTEX", G.describe()["dof"] == 2,
+                    f"and the sketch reports the DoF of what is actually in it: {G.describe()['dof']}")
+
+    # --- Three-point circle: all three clicks lie on it ---------------------------------------
+    clear_sketch()
+    arm("sk_circle_3pt", *free)
+    three = [(cx - W * 0.18, cy), (cx, cy + H * 0.18), (cx + W * 0.16, cy - H * 0.06)]
+    for pt in three:
+        G.clickmm(*pt)
+    c3 = ents("circle")
+    G.check("ARC", len(c3) == 1, f"sk_circle_3pt: {len(c3)} circle")
+    if c3:
+        ds = [dist(clicked(*pt), c3[0]["center"]) for pt in three]
+        tol = 1.5 * G.mm_per_px(cx, cy)
+        G.check("ARC", spread(ds) <= tol and abs(ds[0] - c3[0]["radius"]) <= tol,
+                f"all three clicks lie on it: distances {[round(d, 4) for d in ds]} "
+                f"vs radius {c3[0]['radius']:.4f}")
+
+    # --- Centre arc: centre, start, end -------------------------------------------------------
+    clear_sketch()
+    arm("sk_arc_center", *free)
+    C = (cx, cy)
+    G.clickmm(*C); G.clickmm(cx + W * 0.15, cy); G.clickmm(cx, cy + H * 0.15)
+    aa = ents("arc")
+    G.check("ARC", len(aa) == 1, f"sk_arc_center: {len(aa)} arc")
+    if aa:
+        tol = 1.5 * G.mm_per_px(cx, cy)
+        G.check("VERTEX", dist(aa[0]["center"], clicked(*C)) <= tol,
+                f"centred on the first click (off by {dist(aa[0]['center'], clicked(*C)):.4f} mm)")
+        for nm, pt in (("start", aa[0]["p0"]), ("end", aa[0]["p1"])):
+            G.check("ARC", abs(dist(pt, aa[0]["center"]) - aa[0]["radius"]) < 1e-9,
+                    f"its {nm} sits exactly on the radius, to 1e-9")
+
+    # --- Tangent arc: the construction property, exact whatever the click ---------------------
+    clear_sketch()
+    G.key("l", 0.5)                              # fixture: one line for the arc to leave tangentially
+    la, lb = (cx - W * 0.20, cy - H * 0.05), (cx + W * 0.05, cy - H * 0.05)
+    G.clickmm(*la); G.clickmm(*lb)
+    G.values(40, 0)
+    line = ents("line")[0]
+    G.key("Escape", 0.5)
+    arm("sk_arc_tangent", *free)
+    G.clickmm(*lb)                               # start snaps onto the line's endpoint
+    G.clickmm(cx + W * 0.12, cy + H * 0.12)
+    ta = ents("arc")
+    G.check("ARC", len(ta) == 1, f"sk_arc_tangent: {len(ta)} arc off the line's endpoint")
+    if ta:
+        end = min((ta[0]["p0"], ta[0]["p1"]), key=lambda q: dist(q, line["p1"]))
+        rad = (end[0] - ta[0]["center"][0], end[1] - ta[0]["center"][1])
+        d = (line["p1"][0] - line["p0"][0], line["p1"][1] - line["p0"][1])
+        cosang = abs(rad[0] * d[0] + rad[1] * d[1]) / (math.hypot(*rad) * math.hypot(*d))
+        G.check("TANGENT", cosang < 1e-9,
+                f"its radius at the shared end is perpendicular to the line to 1e-9 (cos={cosang:.2e})")
+
+    # --- Arc slot: two concentric arcs, one width --------------------------------------------
+    clear_sketch()
+    arm("sk_slot_arc", *free)
+    G.clickmm(cx - W * 0.15, cy)                 # start
+    G.clickmm(cx, cy - H * 0.10)                 # centre
+    G.clickmm(cx + W * 0.15, cy)                 # end direction
+    G.clickmm(cx + W * 0.15, cy + H * 0.04)      # width
+    sa = ents("arc")
+    G.check("ARC", len(sa) >= 2, f"sk_slot_arc: {len(sa)} arcs")
+    if len(sa) >= 2:
+        # Group by centre rather than by size: an arc slot is two RAILS about a common centre
+        # plus two end caps about their own, and "the two biggest arcs" is not the same set —
+        # it picked a rail and a cap and called them non-concentric.
+        groups = {}
+        for e in sa:
+            k = (round(e["center"][0], 9), round(e["center"][1], 9))
+            groups.setdefault(k, []).append(e["radius"])
+        rails = max(groups.values(), key=len)
+        G.check("ARC", len(rails) == 2,
+                f"two rails share one centre to 1e-9 (radii {[round(r, 6) for r in sorted(rails)]}), "
+                f"{len(groups) - 1} cap centre(s) besides")
+
+    # --- Ellipse arc: five clicks, and now the socket can actually see its parameters ---------
+    clear_sketch()
+    arm("sk_ellipse_arc", *free)
+    G.clickmm(cx, cy)
+    G.clickmm(cx + W * 0.18, cy)
+    G.clickmm(cx, cy + H * 0.10)
+    G.clickmm(cx + W * 0.18, cy)
+    G.clickmm(cx, cy + H * 0.10)
+    ea = ents("ellipse_arc")
+    G.check("ARC", len(ea) == 1, f"sk_ellipse_arc: {len(ea)} ellipse arc")
+    if ea and "radius" in ea[0]:
+        G.check("ARC", ea[0]["radius"] > ea[0]["rminor"] > 0,
+                f"semi-axes a={ea[0]['radius']:.6f} b={ea[0]['rminor']:.6f}, a > b > 0")
+        for nm, pt in (("start", ea[0]["p0"]), ("end", ea[0]["p1"])):
+            X = (pt[0] - ea[0]["center"][0], pt[1] - ea[0]["center"][1])
+            ph = ea[0]["rotation"]
+            u = (X[0] * math.cos(ph) + X[1] * math.sin(ph)) / ea[0]["radius"]
+            v = (-X[0] * math.sin(ph) + X[1] * math.cos(ph)) / ea[0]["rminor"]
+            G.check("ARC", abs(u * u + v * v - 1.0) < 1e-9,
+                    f"its {nm} satisfies (x/a)^2+(y/b)^2 = 1 to 1e-9")
+
+    # --- The five fixed-count polygons: regular, to 1e-9 --------------------------------------
+    for verb, n in (("sk_poly_3", 3), ("sk_poly_4", 4), ("sk_poly_5", 5),
+                    ("sk_poly_8", 8), ("sk_poly_12", 12)):
+        clear_sketch()
+        arm(verb, *free)
+        G.clickmm(cx, cy)
+        G.clickmm(cx + W * 0.15, cy)
+        q = ents("line")
+        if len(q) != n:
+            G.check("LENGTH", False, f"{verb}: {len(q)} sides, expected {n}")
+            continue
+        L = [round(e["length"], 9) for e in q]
+        ctr = clicked(cx, cy)
+        R = [dist(e["p0"], ctr) for e in q]
+        G.check("LENGTH", spread(L) == 0.0 and spread(R) < 1.5 * G.mm_per_px(cx, cy),
+                f"{verb}: {n} equal sides to 1e-9 ({L[0]:.9f}), all vertices on one circle")
+
+    # --- Inscribed vs circumscribed: the exact ratio between them -----------------------------
+    radii = {}
+    for verb, fit in (("sk_poly_inscribed", "inscribed"), ("sk_poly_circumscribed", "circumscribed")):
+        clear_sketch()
+        arm(verb, *free)                          # a tool PARAMETER, chosen from the menu
+        arm("sk_poly_5", *free)
+        G.clickmm(cx, cy)
+        G.clickmm(cx + W * 0.15, cy)
+        q = ents("line")
+        ctr = clicked(cx, cy)
+        radii[fit] = dist(q[0]["p0"], ctr) if q else 0.0
+    want = 1.0 / math.cos(math.pi / 5.0)
+    got = (radii["circumscribed"] / radii["inscribed"]) if radii["inscribed"] else 0.0
+    G.check("ARC", G.near(got, want, 1e-6),
+            f"circumscribed/inscribed circumradius = {got:.9f} vs 1/cos(pi/5) = {want:.9f} "
+            "— the two fits are genuinely different constructions")
+    G.leave_sketch()
+    G.reset_document()
+
+
+def tf_fixture(cx, cy, W, L=40):
+    """One horizontal line of exactly L mm, drawn by key. Fixture, not the thing under test.
+
+    Horizontal and exactly L because every transform assertion below is derived from it: the
+    gizmo seeds its parameters from the target's own size (pivot = the line's midpoint, handle
+    radius = half its length), so knowing the line exactly is what makes the handle and its value
+    label land on a computable pixel instead of a guessed one.
+    """
+    G.key("l", 0.5)
+    G.clickmm(cx - W * 0.10, cy)
+    G.clickmm(cx + W * 0.10, cy)
+    G.values(L, 0)
+    e = ents("line")[0]
+    G.key("Escape", 0.5)
+    return e
+
+
+def tf_label(pivot, handle, at):
+    """Where the gizmo prints its value — the same formula render_tf_gizmo uses.
+
+    label = handle + outward * 1.2 * max(15 px, 1e-4), outward = the pivot -> handle direction.
+    Recomputing it here rather than hunting for it in pixels is what keeps this a click on a
+    control and not a search: if the formula ever moves, this rung fails loudly instead of
+    clicking somewhere harmless.
+    """
+    th = max(15.0 * G.mm_per_px(*at), 1e-4)
+    d = (handle[0] - pivot[0], handle[1] - pivot[1])
+    n = math.hypot(*d) or 1.0
+    return (handle[0] + d[0] / n * th * 1.2, handle[1] + d[1] / n * th * 1.2)
+
+
+def rung_transforms():
+    """O6 — Move, Rotate, Scale, Array and Polar array: five verbs, none with a shortcut.
+
+    Each is a gizmo, so the whole gesture is menu -> pick -> click the value label -> type ->
+    click empty to apply, with no keyboard route anywhere in it. The assertions are the exact
+    ones the operation promises: a translation moves every point by the typed amount and nothing
+    else, a rotation turns the direction by the typed angle and leaves the length alone, a scale
+    multiplies the length and leaves the direction alone.
+    """
+    print("\nO6  the 2D transforms — gizmo verbs, none of them on the keyboard")
+    fresh_sketch("p")
+    G.key("Escape", 0.5)
+    x0, x1, y0, y1 = G._SAFE
+    cx, cy = (x0 + x1) / 2.0, (y0 + y1) / 2.0
+    W, H = (x1 - x0), (y1 - y0)
+    free = (cx, y1 - H * 0.10)
+    away = (x0 + W * 0.03, y0 + H * 0.03)        # empty plane: the click that applies a gizmo
+    L = 40.0
+    half = L / 2.0
+    step = max(half * 1.5, 1.0)
+
+    def pivot_of(e):
+        return ((e["p0"][0] + e["p1"][0]) / 2.0, (e["p0"][1] + e["p1"][1]) / 2.0)
+
+    def direction(e):
+        return math.degrees(math.atan2(e["p1"][1] - e["p0"][1], e["p1"][0] - e["p0"][0]))
+
+    # --- Move: 25 mm along +X, and nothing else changes --------------------------------------
+    clear_sketch()
+    before = tf_fixture(cx, cy, W, L)
+    # The transforms are offered for a SELECTION, not for empty space — so the right-click that
+    # opens the menu happens ON the line, which is also what selects it. Then one more click
+    # picks it as the gizmo's target: choosing the verb sets the mode, it does not carry a pick.
+    arm("sk_move", *pivot_of(before))
+    G.clickmm(*pivot_of(before))                  # pick the line
+    piv = pivot_of(before)
+    G.clickmm(*tf_label(piv, (piv[0] + step, piv[1]), (cx, cy)))
+    G.value(25)
+    G.clickmm(*away)                              # empty click applies
+    after = ents("line")
+    G.check("VERTEX", len(after) == 1, f"sk_move: {len(after)} line after the transform")
+    if len(after) == 1:
+        dx = [after[0]["p0"][0] - before["p0"][0], after[0]["p1"][0] - before["p1"][0]]
+        dy = [after[0]["p0"][1] - before["p0"][1], after[0]["p1"][1] - before["p1"][1]]
+        G.check("LENGTH", all(abs(v - 25.0) < 1e-9 for v in dx) and all(abs(v) < 1e-9 for v in dy),
+                f"every point moved by exactly +25.000000000 in X and 0 in Y: dx={dx} dy={dy}")
+
+    # --- Rotate: 30 degrees about the centroid, length untouched ------------------------------
+    clear_sketch()
+    before = tf_fixture(cx, cy, W, L)
+    # The transforms are offered for a SELECTION, not for empty space — so the right-click that
+    # opens the menu happens ON the line, which is also what selects it. Then one more click
+    # picks it as the gizmo's target: choosing the verb sets the mode, it does not carry a pick.
+    arm("sk_rotate", *pivot_of(before))
+    G.clickmm(*pivot_of(before))
+    piv = pivot_of(before)
+    h = (piv[0] + half * math.cos(math.pi / 4), piv[1] + half * math.sin(math.pi / 4))
+    G.clickmm(*tf_label(piv, h, (cx, cy)))
+    G.value(30)
+    G.clickmm(*away)
+    after = ents("line")
+    G.check("VERTEX", len(after) == 1, f"sk_rotate: {len(after)} line")
+    if len(after) == 1:
+        turned = (direction(after[0]) - direction(before)) % 360.0
+        G.check("ANGLE", min(abs(turned - 30.0), abs(turned - 210.0)) < 1e-9,
+                f"turned by exactly {turned:.9f} deg")
+        G.check("LENGTH", abs(after[0]["length"] - before["length"]) < 1e-9,
+                f"and its length is untouched: {after[0]['length']:.9f}")
+
+    # --- Scale: x3 about the centroid, direction untouched ------------------------------------
+    clear_sketch()
+    before = tf_fixture(cx, cy, W, L)
+    # The transforms are offered for a SELECTION, not for empty space — so the right-click that
+    # opens the menu happens ON the line, which is also what selects it. Then one more click
+    # picks it as the gizmo's target: choosing the verb sets the mode, it does not carry a pick.
+    arm("sk_scale", *pivot_of(before))
+    G.clickmm(*pivot_of(before))
+    piv = pivot_of(before)
+    G.clickmm(*tf_label(piv, (piv[0] + 2.0 * half, piv[1]), (cx, cy)))
+    G.value(3)
+    G.clickmm(*away)
+    after = ents("line")
+    G.check("VERTEX", len(after) == 1, f"sk_scale: {len(after)} line")
+    if len(after) == 1:
+        G.check("LENGTH", abs(after[0]["length"] - 3.0 * before["length"]) < 1e-9,
+                f"length {before['length']:.9f} -> {after[0]['length']:.9f}, exactly x3")
+        G.check("ANGLE", abs(direction(after[0]) - direction(before)) < 1e-9,
+                "and its direction is untouched to 1e-9")
+
+    # --- Linear array: 4 copies at an exact pitch ---------------------------------------------
+    clear_sketch()
+    before = tf_fixture(cx, cy, W, L)
+    # The transforms are offered for a SELECTION, not for empty space — so the right-click that
+    # opens the menu happens ON the line, which is also what selects it. Then one more click
+    # picks it as the gizmo's target: choosing the verb sets the mode, it does not carry a pick.
+    arm("sk_array", *pivot_of(before))
+    G.clickmm(*pivot_of(before))
+    piv = pivot_of(before)
+    # A single LINE target seeds the spacing PERPENDICULAR to it, which for a horizontal line
+    # is +Y. That is the tool's own rule, not an assumption: see tf_pick's Array branch.
+    G.clickmm(*tf_label(piv, (piv[0], piv[1] + step), (cx, cy)))
+    G.value(20)
+    th = max(15.0 * G.mm_per_px(cx, cy), 1e-4)
+    G.clickmm(piv[0] + th * 1.5, piv[1] + th * 1.5)      # the "xN" count label
+    G.value(4)
+    G.clickmm(*away)
+    rows = sorted(ents("line"), key=lambda e: e["p0"][1])
+    G.check("VERTEX", len(rows) == 4, f"sk_array: {len(rows)} lines (1 original + 3 copies)")
+    if len(rows) == 4:
+        pitch = [round(rows[i + 1]["p0"][1] - rows[i]["p0"][1], 9) for i in range(3)]
+        G.check("LENGTH", pitch == [20.0, 20.0, 20.0], f"pitch exactly {pitch} mm")
+        G.check("LENGTH", spread([round(e["length"], 9) for e in rows]) == 0.0,
+                "and every copy is the same length to 1e-9")
+
+    # --- Polar array: 6 copies, 60 degrees apart, sharing one centre --------------------------
+    clear_sketch()
+    before = tf_fixture(cx, cy, W, L)
+    # The transforms are offered for a SELECTION, not for empty space — so the right-click that
+    # opens the menu happens ON the line, which is also what selects it. Then one more click
+    # picks it as the gizmo's target: choosing the verb sets the mode, it does not carry a pick.
+    arm("sk_array_polar", *pivot_of(before))
+    G.clickmm(*pivot_of(before))
+    piv = pivot_of(before)
+    G.clickmm(*tf_label(piv, (piv[0] + half, piv[1]), (cx, cy)))
+    G.value(360)
+    th = max(15.0 * G.mm_per_px(cx, cy), 1e-4)
+    G.clickmm(piv[0] + th * 1.5, piv[1] + th * 1.5)
+    G.value(6)
+    G.clickmm(*away)
+    spokes = ents("line")
+    G.check("VERTEX", len(spokes) == 6, f"sk_array_polar: {len(spokes)} lines")
+    if len(spokes) == 6:
+        mids = [((e["p0"][0] + e["p1"][0]) / 2.0, (e["p0"][1] + e["p1"][1]) / 2.0) for e in spokes]
+        G.check("VERTEX", max(dist(m, mids[0]) for m in mids) < 1e-9,
+                "all six share one centre to 1e-9 — rotated about the pivot, not scattered")
+        # mod 360, not 180. A line carries an orientation, and folding the six directions into a
+        # half-turn collapses opposite spokes onto each other: a perfectly even star then reads
+        # as gaps of [0, 60, 0, 60, 0] and the rung fails on its own arithmetic.
+        angs = sorted(direction(e) % 360.0 for e in spokes)
+        gaps = [round(angs[(i + 1) % 6] - angs[i], 9) % 360.0 for i in range(6)]
+        G.check("ANGLE", all(abs(g - 60.0) < 1e-9 for g in gaps),
+                f"and they are 60 deg apart all the way round: {gaps}")
+    G.leave_sketch()
+    G.reset_document()
+
+
+def rung_art():
+    """O7 — Text and SVG: the last two 2D verbs, and the only two that open a dialog.
+
+    Both are keyless, so the offer is their only door; both also leave the canvas for a modal
+    window, which is why nothing that drives the canvas had ever reached them. The properties
+    graded are the ones that survive a change of font or of importer scale: how many CLOSED loops
+    came back, and the exact aspect ratio of a shape whose proportions are known.
+    """
+    print("\nO7  Text and SVG — the two verbs that go through a dialog")
+    fresh_sketch("p")
+    G.key("Escape", 0.5)
+    x0, x1, y0, y1 = G._SAFE
+    cx, cy = (x0 + x1) / 2.0, (y0 + y1) / 2.0
+    H = y1 - y0
+    free = (cx, y1 - H * 0.10)
+
+    # --- Text ---------------------------------------------------------------------------------
+    clear_sketch()
+    o = open_offer(*free)
+    G.check("OFFER", "sk_text" in o.verbs, "sk_text is offered on an empty sketch")
+    choose(o, "sk_text")
+    time.sleep(1.5)
+    names = G.sh(f"DISPLAY={G.DISP} xdotool search --name '.' getwindowname %@").split("\n")
+    G.check("OFFER", any(n.strip() == "Text" for n in names),
+            "choosing it opens the Text dialog")
+    G.typ("LT", 0.4)
+    G.key("Return", 2.5)
+    lp = G.loops()
+    G.check("CLOSED", len(lp) == 2 and all(l["closed"] for l in lp),
+            f"two letters came back as {len(lp)} closed loops")
+    G.check("VERTEX", all(abs(l["area"]) > 1.0 for l in lp),
+            f"both enclose real area: {[round(abs(l['area']), 3) for l in lp]}")
+
+    # --- SVG ----------------------------------------------------------------------------------
+    # A file whose proportions are known EXACTLY, so the assertion does not depend on what the
+    # importer decides a user unit is: a 40 x 20 path is 2:1 at any scale.
+    # FILLED, not stroked. A stroked path imports as its stroke OUTLINE — two loops, an outer and
+    # an inner, each inflated by half the stroke width — so the shape that comes back is 8 lines
+    # at 1.952 : 1 and the assertion would be grading the pen, not the importer.
+    svg = "/tmp/offer-ladder-2to1.svg"
+    G.sh("cat > %s <<'EOF'\n<svg xmlns=\"http://www.w3.org/2000/svg\" width=\"40\" height=\"20\" "
+         "viewBox=\"0 0 40 20\"><path d=\"M0,0 L40,0 L40,20 L0,20 Z\" fill=\"black\"/>"
+         "</svg>\nEOF" % svg)
+    clear_sketch()
+    o = open_offer(*free)
+    G.check("OFFER", "sk_svg" in o.verbs, "sk_svg is offered too")
+    choose(o, "sk_svg")
+    time.sleep(2.0)
+    G.key("ctrl+l", 0.6)            # GTK's own "type a path" entry: never guess at the file list
+    G.typ(svg, 0.5)
+    G.key("Return", 3.0)
+    ls = ents("line")
+    lp = G.loops()
+    G.check("CLOSED", len(lp) == 1 and len(ls) == 4,
+            f"the imported path is {len(ls)} lines and {len(lp)} closed loop")
+    if ls:
+        xs = [p for e in ls for p in (e["p0"][0], e["p1"][0])]
+        ys = [p for e in ls for p in (e["p0"][1], e["p1"][1])]
+        w, h = max(xs) - min(xs), max(ys) - min(ys)
+        # 1e-6, not 1e-9, and the reason is measured rather than tuned away: the imported box is
+        # 10.583333000 x 5.291667000 where 40 and 20 user units at 25.4/96 are 10.58333333... and
+        # 5.29166666..., so the SVG path coordinates arrive ROUNDED TO SIX DECIMAL PLACES (both
+        # numbers are exactly 6 dp, one rounded down and one up — which is also why the ratio is
+        # 1.999999811 rather than 2). Everything the sketcher itself draws is exact to 1e-9; this
+        # 1e-6 belongs to the import path alone, and it is the band the assertion allows.
+        G.check("LENGTH", abs(w / h - 2.0) < 1e-6,
+                f"and its proportions survived the import: {w:.9f} x {h:.9f} = {w / h:.9f} : 1 "
+                f"(the import rounds coordinates to 1e-6 mm)")
+    G.leave_sketch()
+    G.reset_document()
+
+
+# Every 2D verb this ladder drives from the menu, by id. Kept as data so the coverage claim can
+# be CHECKED rather than asserted in prose: rung_coverage compares it against the offer table and
+# fails the moment a keyless sketch verb exists that nothing here exercises.
+DRIVEN = {
+    "sk_rect_center",                                           # O4
+    "sk_polyline", "sk_rect_oblique", "sk_rect_rounded",        # O5
+    "sk_circle_2pt", "sk_circle_3pt", "sk_arc_center", "sk_arc_tangent",
+    "sk_slot_arc", "sk_ellipse_arc",
+    "sk_poly_3", "sk_poly_4", "sk_poly_5", "sk_poly_8", "sk_poly_12",
+    "sk_poly_inscribed", "sk_poly_circumscribed",
+    "sk_move", "sk_rotate", "sk_scale", "sk_array", "sk_array_polar",   # O6
+    "sk_text", "sk_svg",                                        # O7
+}
+
+
+def rung_coverage():
+    """O8 — the coverage claim, checked against the table instead of written in a comment.
+
+    "Every 2D verb with no keyboard route is exercised" is the whole point of the rungs above, and
+    a claim like that rots the day someone adds a verb. Here it is arithmetic: the set of keyless
+    sketch verbs in DesignOffer.hpp, minus the set this file drives, must be empty.
+    """
+    print("\nO8  coverage — every keyless 2D verb, checked against the table")
+    sk = [v for v in TABLE if v["sketch_mode"]]
+    keyless = {v["id"] for v in sk if v["action"] and not v["key"]}
+    keyed = {v["id"] for v in sk if v["key"]}
+    dead = {v["id"] for v in sk if not v["action"]}
+    missing = keyless - DRIVEN
+    G.check("OFFER", not missing,
+            f"all {len(keyless)} keyless 2D verbs are driven from the menu"
+            + ("" if not missing else f" — MISSING: {sorted(missing)}"))
+    G.check("OFFER", not (DRIVEN - keyless - keyed),
+            f"and nothing is driven that is not in the table: {sorted(DRIVEN - keyless - keyed)}")
+    G.check("OFFER", not dead,
+            f"no 2D verb is a dead row: {len(sk)} sketch verbs, {len(keyed)} with a shortcut, "
+            f"{len(keyless)} without, {len(dead)} with no GUI route at all")
+
+
+RUNGS = {"kinds": rung_kinds, "vocabulary": rung_vocabulary,
+         "author": rung_author, "no_shortcut": rung_no_shortcut,
+         "curves": rung_curves, "transforms": rung_transforms,
+         "art": rung_art, "coverage": rung_coverage}
+
+
+def main():
+    if not os.path.exists(LOG):
+        G.die(f"no {LOG} — launch the app through scripts/CAD/start-headless-gui.sh")
+    if "[OFFER]" not in open(LOG, errors="replace").read()[-400000:]:
+        print(f"note: no [OFFER] lines in {LOG} yet — the app must run with ORCA_CAD_KEYTRACE=1")
+    want = sys.argv[1:] or list(RUNGS)
+    # TWICE. From a cold launch the app shows the Home page over the Design tab, and the first
+    # click only selects the tab — the second is what brings the viewport forward. A ladder that
+    # clicked once drew its whole first rung into a webview.
+    G.go_design(); G.go_design()
+    G.key("Escape", 0.4)
+    G.reset_document()
+    for name in want:
+        if name not in RUNGS:
+            G.die(f"unknown rung {name}; have {' '.join(RUNGS)}")
+        RUNGS[name]()
+    print(f"\n{G._checks - G._fail}/{G._checks} properties held")
+    sys.exit(1 if G._fail else 0)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/scripts/CAD/check-gui-sketching.py b/scripts/CAD/check-gui-sketching.py
new file mode 100644
index 0000000000..d4ebd1f1ca
--- /dev/null
+++ b/scripts/CAD/check-gui-sketching.py
@@ -0,0 +1,2024 @@
+#!/usr/bin/env python3
+"""A ladder of sketches drawn the way a person draws them: mouse gestures and typed values.
+
+WHY THIS EXISTS, next to scripts/CAD/check-sketch-engine.py. That ladder proves the ENGINE — it feeds
+geometry through the MCP socket's add_entities_scripted and grades what comes back. The socket
+path skips everything the goal actually rests on: gesture state, the auto-edit queue, snapping,
+inference at gesture tolerance, and the right-click offer. A ladder that only drives the socket
+cannot say the Design tab meets its goal. This one draws with synthetic clicks and types the
+values into the in-canvas field, then reads the result back through the socket, which is used
+here ONLY as an instrument, never as an author.
+
+Runs INSIDE the headless rig container (Xvfb :10 + openbox + the app with ORCA_CAD_MCP set):
+
+    docker cp scripts/CAD/check-gui-sketching.py orcacad-gui:/tmp/ && \
+    docker exec orcacad-gui python3 /tmp/check-gui-sketching.py [rung ...]
+
+With no arguments every rung runs. Exit 0 = every property held.
+"""
+import json, math, os, re, socket, subprocess, sys, time
+
+SOCK  = os.environ.get("ORCA_CAD_MCP", "/tmp/mcp.sock")
+DISP  = os.environ.get("DISPLAY", ":10")
+_n = 0
+_fail = 0
+_checks = 0
+
+# ---------------------------------------------------------------- the instrument (read-only)
+
+def call(method, **params):
+    global _n
+    _n += 1
+    s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    s.settimeout(30)
+    s.connect(SOCK)
+    s.sendall((json.dumps({"jsonrpc": "2.0", "id": _n, "method": method,
+                           "params": params}) + "\n").encode())
+    buf = b""
+    while b"\n" not in buf:
+        d = s.recv(65536)
+        if not d:
+            break
+        buf += d
+    r = json.loads(buf.decode().strip())
+    if "error" in r:
+        raise RuntimeError(f"{method}: {r['error']['message']}")
+    return r["result"]
+
+
+def try_call(method, **params):
+    try:
+        return call(method, **params)
+    except Exception:
+        return None
+
+
+def describe():
+    return call("sketch_describe")
+
+
+# ---------------------------------------------------------------- the hand (synthetic input)
+
+_win = None
+
+def win():
+    """The app window's id and origin. Asked fresh once per run: a relaunch changes the id."""
+    global _win
+    # BY SIZE, never by title. Saving a project renames the window to the file, and a driver
+    # that hunts for "Untitled" then reports "no app window" for an app that is running fine —
+    # which is a false negative in the one place a false negative is most expensive.
+    if _win is None:
+        best = None
+        # --class, not --name: after a project is opened the main window can come back with no
+        # WM_NAME at all, and a name search then does not list it — the driver picks a 200x200
+        # helper and every click lands on nothing.
+        for w in sh(f"DISPLAY={DISP} xdotool search --class '.'").split():
+            g = sh(f"DISPLAY={DISP} xdotool getwindowgeometry --shell {w}")
+            d = dict(l.split("=", 1) for l in g.strip().splitlines() if "=" in l)
+            if "WIDTH" not in d:
+                continue
+            a = int(d["WIDTH"]) * int(d["HEIGHT"])
+            if best is None or a > best[0]:
+                best = (a, w, int(d["X"]), int(d["Y"]), int(d["WIDTH"]), int(d["HEIGHT"]))
+        if best is None:
+            die("no app window on " + DISP)
+        sh(f"DISPLAY={DISP} xdotool windowactivate --sync {best[1]}")
+        _win = best[1:]
+    return _win
+
+
+def sh(cmd):
+    return subprocess.run(["bash", "-lc", cmd], capture_output=True, text=True).stdout
+
+
+def xdo(args):
+    sh(f"DISPLAY={DISP} xdotool {args}")
+
+
+def key(k, pause=0.35):
+    xdo(f"key {k}")
+    time.sleep(pause)
+
+
+def typ(s, pause=0.35):
+    xdo(f"type --delay 40 -- '{s}'")
+    time.sleep(pause)
+
+
+def click(px, py, pause=0.45, btn=1):
+    _, X, Y, _, _ = win()
+    xdo(f"mousemove {X+int(px)} {Y+int(py)} click --delay 120 {btn}")
+    time.sleep(pause)
+
+
+def click_ctrl(px, py, pause=0.45):
+    """Ctrl+click: EXTEND the sketch selection instead of replacing it.
+
+    A plain second click clears the first pick (DesignSketchTool's Select branch only keeps
+    one entity unless `extend` is set), so a two-entity constraint driven by two plain clicks
+    silently arrives with one pick and is rejected for the wrong reason.
+    """
+    _, X, Y, _, _ = win()
+    xdo(f"keydown ctrl mousemove {X+int(px)} {Y+int(py)} click --delay 120 1 keyup ctrl")
+    time.sleep(pause)
+
+
+def move(px, py, pause=0.2):
+    _, X, Y, _, _ = win()
+    xdo(f"mousemove {X+int(px)} {Y+int(py)}")
+    time.sleep(pause)
+
+
+def shot(path):
+    w, X, Y, W, H = win()
+    sh(f"DISPLAY={DISP} import -window root -crop {W}x{H}+{X}+{Y} +repage {path}")
+
+
+# ---------------------------------------------------------------- pixels <-> plane
+
+# The viewport is a perspective camera looking at the sketch plane, so pixel -> plane is a
+# HOMOGRAPHY, not a scale: the same pixel span covers more millimetres at the far edge than at
+# the near one. Four measured correspondences determine it exactly. Measuring beats assuming —
+# the camera can be anywhere, and a wrong constant silently puts every click somewhere else.
+_H = None            # plane -> pixel, row-major 3x3
+_SAFE = None         # (xmin, xmax, ymin, ymax) of the plane region the probes covered
+
+
+def _solve(A, b):
+    """Tiny dense solve; no numpy in the rig container."""
+    n = len(A)
+    M = [row[:] + [b[i]] for i, row in enumerate(A)]
+    for c in range(n):
+        p = max(range(c, n), key=lambda r: abs(M[r][c]))
+        if abs(M[p][c]) < 1e-12:
+            die("calibration is degenerate — the four probe points are not in general position")
+        M[c], M[p] = M[p], M[c]
+        for r in range(n):
+            if r == c:
+                continue
+            f = M[r][c] / M[c][c]
+            for k in range(c, n + 1):
+                M[r][k] -= f * M[c][k]
+    return [M[i][n] / M[i][i] for i in range(n)]
+
+
+def fit_homography(pairs):
+    """pairs: [((X_mm, Y_mm), (u_px, v_px)), ...] -> 3x3 plane->pixel with h22 = 1."""
+    A, b = [], []
+    for (X, Y), (u, v) in pairs:
+        A.append([X, Y, 1, 0, 0, 0, -u * X, -u * Y]); b.append(u)
+        A.append([0, 0, 0, X, Y, 1, -v * X, -v * Y]); b.append(v)
+    h = _solve(A, b)
+    return [h[0], h[1], h[2], h[3], h[4], h[5], h[6], h[7], 1.0]
+
+
+def px(X, Y):
+    """Plane millimetres -> window pixels."""
+    h = _H
+    w = h[6] * X + h[7] * Y + h[8]
+    return ((h[0] * X + h[1] * Y + h[2]) / w, (h[3] * X + h[4] * Y + h[5]) / w)
+
+
+def unpx(u, v):
+    """Window pixels -> plane millimetres (the homography inverted, by hand)."""
+    h = _H
+    A = [[h[0] - u * h[6], h[1] - u * h[7]], [h[3] - v * h[6], h[4] - v * h[7]]]
+    b = [u * h[8] - h[2], v * h[8] - h[5]]
+    return tuple(_solve(A, b))
+
+
+def mm_per_px(X, Y):
+    """The viewport's local scale at a plane point — what the tool calls unit_per_px."""
+    u, v = px(X, Y)
+    a = unpx(u, v)
+    b = unpx(u + 1.0, v)
+    return math.dist(a, b)
+
+
+def clickmm(X, Y, pause=0.45, btn=1):
+    u, v = px(X, Y)
+    click(u, v, pause, btn)
+
+
+def movemm(X, Y, pause=0.2):
+    u, v = px(X, Y)
+    move(u, v, pause)
+
+
+# ---------------------------------------------------------------- session control
+
+def leave_sketch():
+    """Back to a clean Feature-mode document, whatever state the last rung left behind."""
+    try_call("sketch_cancel")
+    for _ in range(4):
+        key("Escape", 0.25)
+    time.sleep(0.5)
+
+
+# EVERY absolute chrome coordinate below is written in the Snapmaker fork's layout and then
+# shifted by CHROME_DY, because this fork keeps mainline OrcaSlicer's top row (File / save /
+# undo / redo / Calibration, with the document title) which that fork does not have. The whole
+# chrome — tab strip, sketch toolbar, confirm button — sits 26 px lower here.
+#
+# Getting this wrong does not look like a coordinate problem. At the unshifted y the Design tab
+# click landed in that toolbar, the app stayed on the Home page, and the first rung reported
+# "no sketch opened after plane click + Shift+S"; the unshifted Construction checkbox reported
+# "0 construction axis". Both name the wrong subsystem. Canvas coordinates are immune because
+# clickmm() derives them from the live canvas geometry — only the chrome constants need this.
+CHROME_DY = int(os.environ.get("ORCA_CAD_CHROME_DY", "26"))
+
+DESIGN_TAB = (128, 29 + CHROME_DY)
+
+# Feature-tree rows, measured on the rig at 1920x1080: first row centre, then 23 px apart.
+# x=300, not the label: a second click ON the label opens the inline rename, and Delete then
+# edits the text instead of removing the feature.
+#
+# CHROME_DY applies here too, and this was the one chrome constant that did not carry it. The
+# unshifted click lands 26 px BELOW the first row -- just past its 23 px height -- so the row is
+# never selected, Delete does nothing, and reset_document spends 40 rounds on it before dying
+# with "could not empty the feature tree". That names the feature tree, which is not the fault.
+TREE_ROW0 = (300, 215 + CHROME_DY)
+
+
+def go_design():
+    """Make sure the Design tab is in front — loading a project lands on Prepare."""
+    click(*DESIGN_TAB, pause=1.0)
+
+
+def reset_document():
+    """Delete every committed feature, by picking its tree row and pressing Delete.
+
+    A rung that ends in Constrain COMMITS its sketch, and the next rung's Constrain resolves
+    'the last sketch' — which is then the PREVIOUS rung's. That is how D2 first read a rectangle
+    of exactly 120 x 80 back from a sketch it had drawn at 120.020087: it was grading a sketch
+    left behind by an earlier run. The document is part of the fixture; reset it like one.
+    """
+    go_design()
+    leave_sketch()
+    for _ in range(40):
+        if not call("describe_scene")["features"]:
+            return
+        click(*TREE_ROW0, pause=0.35)
+        key("Delete", 0.5)
+    die("could not empty the feature tree")
+
+
+def enter_sketch(tool_key, plane_px=(913, 359)):
+    """Enter a sketch the way the design law says: pick the plane in the viewport, then the tool.
+
+    Shift+S enters sketch MODE and pops the offer; Escape dismisses it; the tool letter then
+    starts the session on the plane the click selected. All four steps are real input — nothing
+    here goes through the socket.
+    """
+    leave_sketch()
+    click(*plane_px)
+    key("shift+s", 0.8)
+    key("Escape", 0.4)          # entering sketch mode pops the offer; dismiss it
+    key("p", 0.6)
+    if try_call("sketch_describe") is None:
+        shot("/shots/gl-enter-failed.png")
+        die("no sketch opened after plane click + Shift+S (see /shots/gl-enter-failed.png)")
+    calibrate_here()            # THIS sketch's own camera map, on THIS sketch's own plane
+    key(tool_key, 0.6)
+
+
+def calibrate_here():
+    """Place four Points in the sketch that is already open, solve the map, then undo them.
+
+    PER SKETCH, not once per run. The camera is wherever the previous rung left it — reopening a
+    sketch and loading a project both move it — and the plane label the entry click lands on
+    moves with it, so a later sketch can end up on XZ while the map was solved on XY. Both of
+    those turn into clicks that land somewhere else, and geometry that looks drawn but is not
+    where it was asked for. Four points cost about four seconds and remove the whole class.
+    """
+    global _H
+    probes = [(1000, 500), (1400, 500), (1400, 760), (1000, 760)]
+    for u, v in probes:
+        click(u, v)
+    ents = describe()["entities"]
+    if len(ents) != 4 or any(e["type"] != "point" for e in ents):
+        die(f"calibration expected 4 points, got {[e['type'] for e in ents]}")
+    _H = fit_homography([((e["p"][0], e["p"][1]), probes[i]) for i, e in enumerate(ents)])
+    # Prove the fit by round-tripping the probes: a homography through its own four points is
+    # exact, so anything but a sub-pixel residual means the points came back mismatched.
+    for i, e in enumerate(ents):
+        u, v = px(e["p"][0], e["p"][1])
+        if abs(u - probes[i][0]) > 0.5 or abs(v - probes[i][1]) > 0.5:
+            die(f"calibration residual too large at probe {i}: {(u, v)} vs {probes[i]}")
+    global _SAFE
+    xs = [e["p"][0] for e in ents]; ys = [e["p"][1] for e in ents]
+    _SAFE = (min(xs), max(xs), min(ys), max(ys))
+    for _ in range(len(probes)):
+        key("ctrl+z", 0.5)                 # the probes are scaffolding, not geometry
+    left = describe()["entities"]
+    if left:
+        die(f"{len(left)} calibration probes survived the undo")
+
+
+# ---------------------------------------------------------------- typed values
+
+# How long to wait for the in-canvas field to appear and to settle after a commit. The queue
+# opens each field from a CallAfter that runs AFTER a re-solve, so on a heavy sketch the field is
+# simply not there yet when a fast driver starts typing — the digits go nowhere and the value
+# stays as drawn. Rungs that work on a thousand entities raise this.
+PACE = 1.0
+
+
+def field_open():
+    """Is a sketch value field open? Asked of the APP, not of the window list.
+
+    It used to be answered by hunting for a small top-level window, because the field WAS one.
+    It is not any more — it is drawn by ImGui inside the GL canvas precisely so that no window
+    manager gets a vote on whether it may hold the keyboard. Enumerating windows now always
+    answers "no field", which turns every check built on it into one that cannot fail.
+
+    sketch_describe's `editing` is DesignSketchTool::value_field_open(), i.e. the app's own
+    answer to the same question.
+    """
+    d = try_call("sketch_describe")
+    return bool(d and d.get("editing"))
+
+
+def focus_field():
+    """Deliberately nothing.
+
+    This used to click into the value field before typing, and its old docstring explained why:
+    "WITHOUT THIS THE TYPED VALUE IS SILENTLY DISCARDED ... the window manager does not give it
+    the keyboard, so xdotool's digits go to the canvas". That was a workaround for the field
+    being a separate top-level window, and it is also what made this ladder blind to the very
+    defect the user reported — a suite that clicks the field first can never see that typing
+    without clicking is broken.
+
+    The field is now inside the canvas and the canvas has the keyboard, so typing just works and
+    there is nothing to click. Kept as a no-op so the call sites still read in order.
+    """
+    return True
+
+
+def value(v, pause=0.6):
+    """Type one number into the open in-canvas field and commit it.
+
+    Select-all first: the field opens pre-filled with the as-drawn value and pre-selected, but a
+    pre-selection that a synthetic click has disturbed would otherwise leave the typed digits
+    appended to it.
+    """
+    time.sleep(0.25 * PACE)
+    focus_field()
+    key("ctrl+a", 0.15)
+    typ(str(v), 0.25)
+    key("Return", pause * PACE)
+
+
+def values(*vs):
+    for v in vs:
+        value(v)
+
+
+# ---------------------------------------------------------------- grading
+
+def say(msg):
+    print(f"  {msg}")
+
+
+def check(kind, cond, what):
+    global _fail, _checks
+    _checks += 1
+    if cond:
+        print(f"    {kind:9s} ok    {what}")
+    else:
+        print(f"    {kind:9s} FAIL  {what}", file=sys.stderr)
+        _fail += 1
+
+
+def near(a, b, tol=1e-6):
+    return abs(a - b) <= tol
+
+
+def die(msg):
+    print(f"    FATAL {msg}", file=sys.stderr)
+    sys.exit(2)
+
+
+def lengths(ents):
+    return sorted(round(e["length"], 6) for e in ents if e["type"] == "line")
+
+
+def loops():
+    return describe()["closed_loops"]
+
+
+# =================================================================== LADDER A — one tool each
+# Every 2D tool draws its primitive by gesture, then takes its exact value from the keyboard.
+# The click only has to be roughly right; the typed number is what must come back exactly.
+
+def rung_rect():
+    print("\nA1  rectangle — two corners, typed 120 x 80")
+    enter_sketch("r")
+    clickmm(-60, -40); clickmm(60, 40)
+    values(120, 80)
+    d = describe()
+    ls = lengths(d["entities"])
+    check("LENGTH", ls == [80.0, 80.0, 120.0, 120.0], f"sides {ls}")
+    lp = d["closed_loops"]
+    check("CLOSED", len(lp) == 1 and lp[0]["closed"], f"{len(lp)} closed loop(s)")
+    check("AREA", near(abs(lp[0]["area"]), 9600.0, 1e-6), f"area {abs(lp[0]['area']):.6f}")
+    check("VERTEX", all(near(abs(e["p1"][0] - e["p0"][0]), 0, 1e-9)
+                        or near(abs(e["p1"][1] - e["p0"][1]), 0, 1e-9)
+                        for e in d["entities"]), "every side axis-aligned")
+    leave_sketch()
+
+
+def rung_circle():
+    print("\nA2  circle — centre then rim, typed radius 25")
+    enter_sketch("c")
+    clickmm(0, 0); clickmm(30, 0)
+    values(25)
+    d = describe()
+    e = [x for x in d["entities"] if x["type"] == "circle"]
+    check("ARC", len(e) == 1 and near(e[0]["radius"], 25.0), f"radius {e[0]['radius'] if e else None}")
+    check("VERTEX", len(e) == 1 and near(e[0]["center"][0], 0.0, 0.6) and near(e[0]["center"][1], 0.0, 0.6),
+          f"centre {e[0]['center'] if e else None} at the clicked origin")
+    lp = d["closed_loops"]
+    check("CLOSED", len(lp) == 1 and lp[0]["closed"], f"{len(lp)} closed loop(s)")
+    check("AREA", len(lp) == 1 and near(abs(lp[0]["area"]), math.pi * 625.0, 1e-6),
+          f"area {abs(lp[0]['area']):.6f} vs pi r^2 {math.pi*625:.6f}")
+    leave_sketch()
+
+
+def rung_line():
+    print("\nA3  line — two clicks, typed length 50 and angle 30")
+    enter_sketch("l")
+    clickmm(-40, -20); clickmm(10, 5)
+    values(50, 30)
+    d = describe()
+    e = [x for x in d["entities"] if x["type"] == "line"]
+    check("LENGTH", len(e) == 1 and near(e[0]["length"], 50.0), f"length {e[0]['length'] if e else None}")
+    if e:
+        a = math.degrees(math.atan2(e[0]["p1"][1] - e[0]["p0"][1], e[0]["p1"][0] - e[0]["p0"][0])) % 360.0
+        check("ANGLE", near(a, 30.0, 1e-9), f"angle {a:.9f} deg")
+    leave_sketch()
+
+
+def rung_arc():
+    print("\nA4  three-point arc — typed radius 40 and sweep 90")
+    enter_sketch("a")
+    clickmm(-40, 0); clickmm(40, 0); clickmm(0, 40)
+    values(40, 90)
+    d = describe()
+    e = [x for x in d["entities"] if x["type"] == "arc"]
+    check("ARC", len(e) == 1 and near(e[0]["radius"], 40.0), f"radius {e[0]['radius'] if e else None}")
+    if e:
+        sw = abs(e[0]["end_angle"] - e[0]["start_angle"]) * 180.0 / math.pi
+        # 1e-7 deg, not exact: the sweep is READ BACK as end_angle - start_angle, two atan2
+        # results, where the line's angle is STORED as the direction it was given. A 1e-9 deg
+        # residual here is 7e-10 mm at r=40 — float round-trip, not a defect.
+        check("ANGLE", near(sw, 90.0, 1e-7), f"sweep {sw:.9f} deg")
+        ch = math.dist(e[0]["p0"], e[0]["p1"])
+        check("VERTEX", near(ch, 40.0 * math.sqrt(2.0), 1e-6),
+              f"chord {ch:.6f} vs r*sqrt2 {40*math.sqrt(2):.6f}")
+    leave_sketch()
+
+
+def rung_slot():
+    print("\nA5  slot — typed centre distance 60, radius 10, angle 0")
+    enter_sketch("s")
+    clickmm(-30, 0); clickmm(30, 0); clickmm(30, 12)
+    values(60, 10, 0)
+    d = describe()
+    arcs = [x for x in d["entities"] if x["type"] == "arc"]
+    lns  = [x for x in d["entities"] if x["type"] == "line"]
+    check("ARC", len(arcs) == 2 and all(near(a["radius"], 10.0) for a in arcs),
+          f"two end radii {[round(a['radius'], 9) for a in arcs]}")
+    check("LENGTH", len(lns) == 2 and all(near(l["length"], 60.0) for l in lns),
+          f"two flanks {[round(l['length'], 9) for l in lns]}")
+    lp = d["closed_loops"]
+    check("CLOSED", len(lp) == 1 and lp[0]["closed"], f"{len(lp)} closed loop(s)")
+    check("AREA", len(lp) == 1 and near(abs(lp[0]["area"]), 60 * 20 + math.pi * 100, 1e-6),
+          f"area {abs(lp[0]['area']):.6f} vs 60*20+pi*100 {60*20+math.pi*100:.6f}")
+    leave_sketch()
+
+
+def rung_polygon():
+    print("\nA6  polygon — typed side 30, angle 0")
+    enter_sketch("g")
+    clickmm(0, 0); clickmm(35, 0)
+    values(30, 0)
+    d = describe()
+    e = [x for x in d["entities"] if x["type"] == "line"]
+    ls = lengths(d["entities"])
+    check("LENGTH", len(e) >= 3 and all(near(l, 30.0, 1e-9) for l in ls),
+          f"{len(e)} equal sides {set(ls)}")
+    lp = d["closed_loops"]
+    check("CLOSED", len(lp) == 1 and lp[0]["closed"], f"{len(lp)} closed loop(s)")
+    if e:
+        n = len(e)
+        want = n * 30.0 ** 2 / (4.0 * math.tan(math.pi / n))
+        check("AREA", near(abs(lp[0]["area"]), want, 1e-6),
+              f"area {abs(lp[0]['area']):.6f} vs regular {n}-gon {want:.6f}")
+    leave_sketch()
+
+
+def rung_ellipse():
+    print("\nA7  ellipse — typed major 50, minor 20")
+    enter_sketch("e")
+    clickmm(0, 0); clickmm(40, 0); clickmm(0, 15)
+    values(50, 20)
+    d = describe()
+    e = [x for x in d["entities"] if x["type"] == "ellipse"]
+    check("ARC", len(e) == 1, f"{len(e)} ellipse")
+    lp = d["closed_loops"]
+    check("CLOSED", len(lp) == 1 and lp[0]["closed"], f"{len(lp)} closed loop(s)")
+    check("AREA", len(lp) == 1 and near(abs(lp[0]["area"]), math.pi * 50 * 20, 2e-2),
+          f"area {abs(lp[0]['area']):.4f} vs pi*a*b {math.pi*1000:.4f}")
+    leave_sketch()
+
+
+def rung_point():
+    print("\nA8  point — one click, no value to type")
+    enter_sketch("p")
+    clickmm(20, 10)
+    d = describe()
+    e = [x for x in d["entities"] if x["type"] == "point"]
+    check("VERTEX", len(e) == 1 and near(e[0]["p"][0], 20.0, 0.6) and near(e[0]["p"][1], 10.0, 0.6),
+          f"placed at {[round(v, 3) for v in e[0]['p']] if e else None}")
+    leave_sketch()
+
+
+def rung_spline():
+    print("\nA9  spline — click control points, right-click to end")
+    enter_sketch("b")
+    for p in [(-40, 0), (-15, 30), (15, -30), (40, 0)]:
+        clickmm(*p)
+    clickmm(40, 0, btn=3)
+    d = describe()
+    e = [x for x in d["entities"] if x["type"] == "spline"]
+    check("VERTEX", len(e) == 1, f"{len(e)} spline from 4 control points")
+    leave_sketch()
+
+
+# =================================================================== LADDER B — voids by hand
+# The strategic target itself: one closed outer loop with internal voids, every one of them
+# drawn by gesture in a single sketch and given its size from the keyboard.
+
+def rung_voids():
+    print("\nB1  closed profile with two internal voids, all by gesture")
+    enter_sketch("r")
+    clickmm(-60, -40); clickmm(60, 40)          # outer 120 x 80
+    values(120, 80)
+    key("r", 0.6)                                # same tool again, from the keyboard
+    clickmm(-45, -15); clickmm(-5, 15)           # void 1: 40 x 30
+    values(40, 30)
+    key("c", 0.6)
+    clickmm(30, 0); clickmm(42, 0)               # void 2: circle r 10
+    values(10)
+    d = describe()
+    ls = lengths(d["entities"])
+    check("LENGTH", ls == [30.0, 30.0, 40.0, 40.0, 80.0, 80.0, 120.0, 120.0], f"sides {ls}")
+    lp = d["closed_loops"]
+    check("CLOSED", len(lp) == 3 and all(l["closed"] for l in lp), f"{len(lp)} closed loops")
+    check("CLOSED", d["buildable"] and not d["open_ends"], "buildable, nothing dangling")
+    # The void attribution is the property under test: the outer loop must OWN both inner ones,
+    # and neither inner loop may claim a hole of its own.
+    outer = max(range(len(lp)), key=lambda i: abs(lp[i]["area"]))
+    holes = sorted(lp[outer]["holes"])
+    check("VOID", holes == sorted(i for i in range(len(lp)) if i != outer),
+          f"outer loop {outer} owns holes {holes}")
+    check("VOID", all(not lp[i]["holes"] for i in range(len(lp)) if i != outer),
+          "neither void claims a hole of its own")
+    a = {i: abs(lp[i]["area"]) for i in range(len(lp))}
+    check("AREA", near(a[outer], 9600.0, 1e-6), f"outer {a[outer]:.6f}")
+    inner = sorted(a[i] for i in a if i != outer)
+    check("AREA", near(inner[0], math.pi * 100, 1e-6) and near(inner[1], 1200.0, 1e-6),
+          f"voids {inner[0]:.6f} (pi*100) and {inner[1]:.6f} (40*30)")
+    net = a[outer] - sum(v for i, v in a.items() if i != outer)
+    check("AREA", near(net, 9600.0 - 1200.0 - math.pi * 100, 1e-6), f"net material {net:.6f}")
+    leave_sketch()
+
+
+# =================================================================== LADDER C — combining
+# Mirror, offset, trim, extend, fillet and chamfer, each driven by the same picks and the same
+# on-geometry value label a person would use. The label's place is COMPUTED from the geometry
+# the tool itself derives (render_op_gizmo: tip = anchor + dir * value, label = tip + dir * 1.2
+# * max(15 * unit_per_px, 1e-4)) rather than hunted for in the pixels — the tool's own formula
+# is the only thing that can be right by construction.
+
+def op_label_mm(anchor, direction, value, at):
+    th = max(15.0 * mm_per_px(*at), 1e-4)
+    d = (direction[0] / math.hypot(*direction), direction[1] / math.hypot(*direction))
+    tip = (anchor[0] + d[0] * value, anchor[1] + d[1] * value)
+    return (tip[0] + d[0] * th * 1.2, tip[1] + d[1] * th * 1.2)
+
+
+def mid(e):
+    return ((e["p0"][0] + e["p1"][0]) / 2.0, (e["p0"][1] + e["p1"][1]) / 2.0)
+
+
+def corner_of(a, b):
+    """The shared endpoint of two adjacent lines, and the bisector pointing into their wedge."""
+    C = min(((pa, pb) for pa in (a["p0"], a["p1"]) for pb in (b["p0"], b["p1"])),
+            key=lambda t: math.dist(t[0], t[1]))[0]
+    def away(e):
+        f = e["p1"] if math.dist(e["p0"], C) < math.dist(e["p1"], C) else e["p0"]
+        n = math.dist(f, C)
+        return ((f[0] - C[0]) / n, (f[1] - C[1]) / n)
+    ua, ub = away(a), away(b)
+    bis = (ua[0] + ub[0], ua[1] + ub[1])
+    return tuple(C), bis
+
+
+def draw_rect(w, h, x0, y0):
+    clickmm(x0, y0); clickmm(x0 + w, y0 + h)
+    values(w, h)
+
+
+def rung_fillet():
+    print("\nC1  fillet — pick two legs, type radius 8 on the label")
+    enter_sketch("r")
+    draw_rect(120, 80, -60, -40)
+    d0 = describe()["entities"]
+    a, b = corner_pair(d0)
+    key("f", 0.6)
+    clickmm(*mid(a)); clickmm(*mid(b))
+    C, bis = corner_of(a, b)
+    v0 = 0.2 * min(a["length"], b["length"])
+    clickmm(*op_label_mm(C, bis, v0, C))
+    values(8)
+    d = describe()
+    arcs = [x for x in d["entities"] if x["type"] == "arc"]
+    check("ARC", len(arcs) == 1 and near(arcs[0]["radius"], 8.0), f"radius {arcs[0]['radius'] if arcs else None}")
+    lp = d["closed_loops"]
+    check("CLOSED", len(lp) == 1 and lp[0]["closed"], f"{len(lp)} closed loop(s)")
+    want = 9600.0 - 64.0 * (1.0 - math.pi / 4.0)
+    check("AREA", len(lp) == 1 and near(abs(lp[0]["area"]), want, 1e-6),
+          f"area {abs(lp[0]['area']):.6f} vs 9600 - r^2(1-pi/4) {want:.6f}")
+    if arcs:
+        # TANGENT: the arc centre must sit exactly r from each surviving leg's line.
+        legs = [x for x in d["entities"] if x["type"] == "line"]
+        ds = sorted(point_line_dist(arcs[0]["center"], l) for l in legs)[:2]
+        check("TANGENT", all(near(x, 8.0, 1e-9) for x in ds), f"centre stands off both legs by {ds}")
+    leave_sketch()
+
+
+def rung_chamfer():
+    print("\nC2  chamfer — pick two legs, type distance 10 on the label")
+    enter_sketch("r")
+    draw_rect(120, 80, -60, -40)
+    d0 = describe()["entities"]
+    a, b = corner_pair(d0)
+    key("h", 0.6)
+    clickmm(*mid(a)); clickmm(*mid(b))
+    C, bis = corner_of(a, b)
+    clickmm(*op_label_mm(C, bis, 0.2 * min(a["length"], b["length"]), C))
+    values(10)
+    d = describe()
+    lp = d["closed_loops"]
+    check("CLOSED", len(lp) == 1 and lp[0]["closed"], f"{len(lp)} closed loop(s)")
+    check("LENGTH", len(lp) == 1 and len(lp[0]["entities"]) == 5,
+          f"{len(lp[0]['entities'])} sides after the cut")
+    ls = sorted(e["length"] for e in d["entities"] if e["type"] == "line")
+    check("LENGTH", any(near(x, 10.0 * math.sqrt(2.0), 1e-9) for x in ls),
+          f"the new face is d*sqrt2 = {10*math.sqrt(2):.9f}; sides {[round(x,9) for x in ls]}")
+    check("LENGTH", near(ls[1], 70.0, 1e-9) and near(ls[3], 110.0, 1e-9),
+          "both legs shortened by exactly d")
+    check("AREA", len(lp) == 1 and near(abs(lp[0]["area"]), 9600.0 - 50.0, 1e-6),
+          f"area {abs(lp[0]['area']):.6f} vs 9600 - d^2/2")
+    leave_sketch()
+
+
+def rung_offset():
+    print("\nC3  offset — pick a circle, type 5 on the label")
+    enter_sketch("c")
+    clickmm(0, 0); clickmm(30, 0)
+    values(25)
+    key("o", 0.6)
+    clickmm(25, 0)                                  # pick the rim
+    # Circle offset anchors at centre + (r, 0) and grows along +x; the starting value is 0.1 * 2r.
+    clickmm(*op_label_mm((25.0, 0.0), (1.0, 0.0), 0.1 * 50.0, (25.0, 0.0)))
+    values(5)
+    d = describe()
+    cs = sorted(x["radius"] for x in d["entities"] if x["type"] == "circle")
+    # The gizmo's arrow starts on the +x side, so the typed 5 lands OUTWARD; what the goal cares
+    # about is that the separation is exactly the number typed, on whichever side it was given.
+    check("ARC", len(cs) == 2 and near(cs[0], 25.0) and near(cs[1] - cs[0], 5.0),
+          f"radii {cs} — separated by exactly {cs[1]-cs[0] if len(cs)==2 else None}")
+    lp = d["closed_loops"]
+    check("CLOSED", len(lp) == 2 and all(l["closed"] for l in lp), f"{len(lp)} closed loops")
+    check("VOID", any(l["holes"] for l in lp), "the inner circle is read as a void of the outer")
+    leave_sketch()
+
+
+def cross(a, b):
+    """Where two lines' infinite supports meet."""
+    (x1, y1), (x2, y2) = a["p0"], a["p1"]
+    (x3, y3), (x4, y4) = b["p0"], b["p1"]
+    d = (x2 - x1) * (y4 - y3) - (y2 - y1) * (x4 - x3)
+    t = ((x3 - x1) * (y4 - y3) - (y3 - y1) * (x4 - x3)) / d
+    return (x1 + t * (x2 - x1), y1 + t * (y2 - y1))
+
+
+def mid_of(a, b):
+    return ((a[0] + b[0]) / 2.0, (a[1] + b[1]) / 2.0)
+
+
+def point_line_dist(p, l):
+    (x0, y0), (x1, y1) = l["p0"], l["p1"]
+    dx, dy = x1 - x0, y1 - y0
+    n = math.hypot(dx, dy)
+    return abs((p[0] - x0) * dy - (p[1] - y0) * dx) / n
+
+
+def corner_pair(ents):
+    """Two adjacent lines of a rectangle: the first line and the one sharing an endpoint."""
+    ls = [e for e in ents if e["type"] == "line"]
+    a = ls[0]
+    for b in ls[1:]:
+        if min(math.dist(pa, pb) for pa in (a["p0"], a["p1"]) for pb in (b["p0"], b["p1"])) < 1e-6:
+            return a, b
+    die("no adjacent pair in what should be a rectangle")
+
+
+CONSTRUCTION_CHECKBOX = (419, 75 + CHROME_DY)
+
+
+def draw_line(x0, y0, x1, y1, length, angle):
+    clickmm(x0, y0); clickmm(x1, y1)
+    values(length, angle)
+
+
+def rung_mirror():
+    print("\nC4  mirror — a half profile reflected about a construction axis")
+    enter_sketch("l")
+    click(*CONSTRUCTION_CHECKBOX)                    # the axis is reference, not material
+    key("l", 0.6)
+    draw_line(0, -40, 0, 40, 80, 90)                 # the axis, on x = 0
+    click(*CONSTRUCTION_CHECKBOX)                    # back to real geometry
+    key("l", 0.6)
+    draw_line(0, -40, 50, -40, 50, 0)
+    key("l", 0.6)
+    draw_line(50, -40, 50, 40, 80, 90)
+    key("l", 0.6)
+    draw_line(50, 40, 0, 40, 50, 180)
+    d0 = describe()["entities"]
+    axis = [e for e in d0 if e.get("construction")]
+    check("VERTEX", len(axis) == 1, f"{len(axis)} construction axis")
+    half = [e for e in d0 if e["type"] == "line" and not e.get("construction")]
+    check("LENGTH", len(half) == 3, f"{len(half)} lines in the half profile")
+    key("m", 0.6)
+    clickmm(*mid(axis[0]))
+    for e in half:
+        clickmm(*mid(e))
+    clickmm(-90, 60)                                 # empty space confirms
+    d = describe()
+    real = [e for e in d["entities"] if e["type"] == "line" and not e.get("construction")]
+    check("LENGTH", len(real) == 6, f"{len(real)} lines after the reflection")
+    lp = [l for l in d["closed_loops"]]
+    check("CLOSED", len(lp) == 1 and lp[0]["closed"], f"{len(lp)} closed loop(s)")
+    # Graded against the geometry ACTUALLY DRAWN, not against the coordinates I aimed at. A
+    # synthetic click lands on a whole pixel, so the half profile sits a few tenths of a
+    # millimetre off the origin; the typed values fix its lengths and angles, not its anchor.
+    # Demanding 8000.000000 here would grade my aim, and the mirror is what is under test.
+    far = max(half, key=lambda e: e["length"])            # the edge parallel to the axis
+    w   = point_line_dist(mid(far), axis[0])
+    want = 2.0 * w * far["length"]
+    check("AREA", len(lp) == 1 and near(abs(lp[0]["area"]), want, 1e-6),
+          f"area {abs(lp[0]['area']):.6f} vs 2 x {w:.6f} x {far['length']:.6f} = {want:.6f}")
+    # SYMMETRY is the property this rung exists for: every vertex must have its exact reflection
+    # ABOUT THE AXIS THAT WAS DRAWN.
+    vs = [tuple(p) for e in real for p in (e["p0"], e["p1"])]
+    def refl(q):
+        (ax, ay), (bx, by) = axis[0]["p0"], axis[0]["p1"]
+        dx, dy = bx - ax, by - ay
+        n = dx * dx + dy * dy
+        t = ((q[0] - ax) * dx + (q[1] - ay) * dy) / n
+        fx, fy = ax + t * dx, ay + t * dy
+        return (2 * fx - q[0], 2 * fy - q[1])
+    missing = [v for v in vs if not any(math.dist(refl(v), o) < 1e-9 for o in vs)]
+    check("SYMMETRY", not missing,
+          f"every one of {len(vs)} vertices has its exact reflection about the drawn axis")
+    leave_sketch()
+
+
+def rung_trim():
+    print("\nC5  trim — cut one arm off a crossing")
+    enter_sketch("l")
+    draw_line(-50, 0, 50, 0, 100, 0)
+    key("l", 0.6)
+    draw_line(0, -50, 0, 50, 100, 90)
+    d0 = describe()["entities"]
+    horiz = min(d0, key=lambda e: abs(e["p1"][1] - e["p0"][1]))
+    vert  = max(d0, key=lambda e: abs(e["p1"][1] - e["p0"][1]))
+    X = cross(horiz, vert)
+    left = min(horiz["p0"], horiz["p1"])              # the end that must survive
+    want = math.dist(left, X)
+    key("t", 0.6)
+    clickmm(*mid_of(X, max(horiz["p0"], horiz["p1"])))   # the arm on the far side of the crossing
+    d = describe()
+    ls = sorted(round(e["length"], 9) for e in d["entities"] if e["type"] == "line")
+    check("LENGTH", len(ls) == 2 and near(ls[1], vert["length"], 1e-9) and near(ls[0], want, 1e-9),
+          f"lengths {ls} — the picked arm is gone at the crossing (expected {want:.9f}), "
+          f"the other line untouched")
+    ends = [tuple(p) for e in d["entities"] if e["type"] == "line" for p in (e["p0"], e["p1"])]
+    check("VERTEX", any(math.dist(X, q) < 1e-9 for q in ends), "the cut lands exactly on the crossing")
+    leave_sketch()
+
+
+def rung_extend():
+    print("\nC6  extend — reach a line to the one it stops short of")
+    enter_sketch("l")
+    draw_line(-50, 0, -10, 0, 40, 0)
+    key("l", 0.6)
+    draw_line(0, -50, 0, 50, 100, 90)
+    d0 = describe()["entities"]
+    short = min(d0, key=lambda e: e["length"])
+    vert  = max(d0, key=lambda e: e["length"])
+    X = cross(short, vert)
+    far = min((short["p0"], short["p1"]), key=lambda q: q[0])   # the end that stays put
+    near_end = max((short["p0"], short["p1"]), key=lambda q: q[0])
+    want = math.dist(far, X)
+    key("x", 0.6)
+    clickmm(*mid_of(near_end, mid_of(far, near_end)))           # click the end that must grow
+    d = describe()
+    ls = sorted(round(e["length"], 9) for e in d["entities"] if e["type"] == "line")
+    check("LENGTH", len(ls) == 2 and near(ls[0], want, 1e-9),
+          f"lengths {ls} — {short['length']:.6f} grew to exactly {want:.9f}")
+    ends = [tuple(p) for e in d["entities"] if e["type"] == "line" for p in (e["p0"], e["p1"])]
+    check("VERTEX", any(math.dist(X, q) < 1e-9 for q in ends),
+          "the new end sits exactly on the target line")
+    leave_sketch()
+
+
+# =================================================================== LADDER D — dimensions
+# A drawn shape with no numbers on it, then numbers put on it by hand: the Dimension tool for a
+# value, the Constrain buttons for a relation. Both must hold the value they were given AND take
+# the degrees of freedom away — a dimension that moves the geometry but leaves the DoF standing
+# has not constrained anything, it has only nudged it.
+
+# Constrain-mode toolbar, measured off the rig at 1920x1080 (icon centres, 42 px apart).
+#
+# THIS LIST MIRRORS THE cbtn() SEQUENCE IN DesignPanel.cpp AND HAS TO BE UPDATED WHEN A BUTTON
+# IS INSERTED. Positions are computed by index, so inserting a button shifts every entry after
+# it and the map silently points at the wrong icon -- a rung then applies some OTHER constraint
+# and fails with a geometric message that says nothing about buttons.
+#
+# It has already happened once, undetected: equal_radius and collinear (after "equal"), sym_v
+# and sym_h (after "symmetric") and dist_x and dist_y (after "fix") were added while this list
+# still had 14 names. Everything from index 6 on was wrong in both forks. Nothing caught it
+# because the ladder only ever clicks "perpendicular" (3) and "equal" (5), both of which sit
+# before the first insertion. The next rung to use "tangent" would have clicked "collinear".
+CON_BTN_Y = 76 + CHROME_DY
+CON_BTN = {n: (449 + 42 * i, CON_BTN_Y) for i, n in enumerate(
+    ["horizontal", "vertical", "parallel", "perpendicular", "coincident", "equal",
+     "equal_radius", "collinear", "concentric", "tangent", "midpoint", "symmetric",
+     "sym_v", "sym_h", "angle", "radius", "diameter", "fix", "dist_x", "dist_y"])}
+
+# The SAME twenty buttons, at their SKETCH-mode x. Constraining during a sketch put the group
+# after the (wide) sketch toolbar instead of at the start of an otherwise empty row, so every
+# button sits 228 px further right. Measured, not derived: the strip was screenshotted in sketch
+# mode and the icon columns detected — first centre 677, pitch 42, twenty of them. Deriving it
+# from the Constrain-mode map is exactly how this table drifted the last time.
+# NOTE FOR THIS FORK: 677 was measured on the OTHER fork's rig. Y is safe (it rides CON_BTN_Y,
+# which already carries CHROME_DY), but the X start depends on how wide the sketch toolbar to the
+# left of this group renders, and this fork keeps mainline's top row. Re-measure before trusting
+# D11 here: screenshot in sketch mode and detect the icon columns, do not derive it by offset.
+CON_BTN_SKETCH = {n: (677 + 42 * i, CON_BTN_Y) for i, n in enumerate(
+    ["horizontal", "vertical", "parallel", "perpendicular", "coincident", "equal",
+     "equal_radius", "collinear", "concentric", "tangent", "midpoint", "symmetric",
+     "sym_v", "sym_h", "angle", "radius", "diameter", "fix", "dist_x", "dist_y"])}
+
+
+def draw_rect_undimensioned():
+    """A rectangle by two clicks, with both queued value fields dismissed (Esc keeps it as drawn)."""
+    clickmm(-60, -40); clickmm(60, 40)
+    key("Escape", 0.7)      # Width  — keep as drawn
+    key("Escape", 0.7)      # Height — keep as drawn
+
+
+def rung_dimension():
+    print("\nD1  dimension — put a length on a side that had none")
+    enter_sketch("r")
+    draw_rect_undimensioned()
+    d0 = describe()
+    dof0 = d0["dof"]
+    check("VERTEX", dof0 > 0, f"the undimensioned rectangle has {dof0} degrees of freedom")
+    side = max((e for e in d0["entities"] if e["type"] == "line"), key=lambda e: e["length"])
+    key("d", 0.6)
+    clickmm(*mid(side))
+    values(90)
+    d = describe()
+    ls = sorted(round(e["length"], 9) for e in d["entities"] if e["type"] == "line")
+    check("LENGTH", any(near(x, 90.0, 1e-9) for x in ls), f"the dimensioned side reads {ls}")
+    check("VERTEX", d["dof"] < dof0, f"degrees of freedom {dof0} -> {d['dof']}")
+    check("CLOSED", d["solve_ok"] and len(d["closed_loops"]) == 1, "still one closed, solved loop")
+    leave_sketch()
+
+
+CONFIRM_BTN = (1751, 75 + CHROME_DY)
+
+
+def confirm_and_reopen():
+    """(see reopen_sketch below — same two steps, kept together for the constrain rungs)"""
+    """Leave Constrain with the action bar's tick, then re-open the sketch for editing.
+
+    THE DoF HAS TO BE READ HERE, not in Constrain mode. While constraining, sketch_describe
+    reports the LIVE tool's dof and constraint count, which the constrain session does not
+    touch — it works on the committed feature's own entity_constraints, and the panel computes
+    its readout from those. Reading during the session says 4 -> 4 for a constraint that really
+    did land; reading after the round trip says 4 -> 3, and proves the constraint was persisted
+    rather than merely previewed.
+    """
+    click(*CONFIRM_BTN, pause=1.5)
+    w, X, Y, _, _ = win()
+    sh(f"DISPLAY={DISP} xdotool mousemove {X+TREE_ROW0[0]} {Y+TREE_ROW0[1]} "
+       f"click --repeat 2 --delay 120 1")
+    time.sleep(2.0)
+    return describe()
+
+
+def rung_constrain():
+    reset_document()
+    print("\nD2  constrain — Equal length on two adjacent sides, from the Constrain toolbar")
+    enter_sketch("r")
+    draw_rect_undimensioned()
+    a, b = corner_pair(describe()["entities"])
+    check("LENGTH", not near(a["length"], b["length"], 1e-6),
+          f"the two sides start unequal: {a['length']:.6f} vs {b['length']:.6f}")
+    key("k", 1.5)                              # finish the sketch and enter Constrain
+    # Re-read the picks from the COMMITTED sketch: finish_sketch repackages the entities, so an
+    # index taken before Constrain is not the same index afterwards.
+    d1 = describe()
+    a, b = corner_pair(d1["entities"])
+    dof0 = 4                                   # an undimensioned rectangle: position + size
+    ia, ib = d1["entities"].index(a), d1["entities"].index(b)
+    clickmm(*mid(a)); clickmm(*mid(b))
+    click(*CON_BTN["equal"])
+    time.sleep(1.0)
+    d = describe()
+    la, lb = d["entities"][ia]["length"], d["entities"][ib]["length"]
+    check("LENGTH", near(la, lb, 1e-9), f"the two sides are now equal: {la:.9f} and {lb:.9f}")
+    d2 = confirm_and_reopen()
+    check("VERTEX", d2["dof"] == dof0 - 1, f"degrees of freedom {dof0} -> {d2['dof']} after the round trip")
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    ls2 = sorted(round(e["length"], 9) for e in d2["entities"] if e["type"] == "line")
+    check("LENGTH", near(ls2[0], la, 1e-9) and near(ls2[-1], la, 1e-9),
+          f"the geometry came back unchanged: {ls2}")
+    leave_sketch()
+
+
+def rung_perpendicular():
+    reset_document()
+    print("\nD3  constrain — two free lines made exactly perpendicular")
+    enter_sketch("l")
+    clickmm(-50, -30); clickmm(30, -18)
+    key("Escape", 0.7); key("Escape", 0.7)
+    key("l", 0.6)
+    # 56 degrees off the first line, not 3. The original second point put the pair within
+    # inference's perpendicular tolerance, so on a rig whose camera maps the click a pixel
+    # differently the two lines arrive ALREADY at exactly 90.000000 -- inference did the job the
+    # rung exists to test, and the precondition failed while every later check passed. Held on
+    # one fork and failed on the other from the same source, which is the signature of a rung
+    # that depends on luck. Start well outside any snap tolerance so the button has real work.
+    clickmm(30, -18); clickmm(55, 35)
+    key("Escape", 0.7); key("Escape", 0.7)
+    d0 = describe()
+    check("ANGLE", abs(angle_between(d0["entities"][0], d0["entities"][1]) - 90.0) > 1e-3,
+          f"they start at {angle_between(d0['entities'][0], d0['entities'][1]):.6f} deg")
+    key("k", 1.5)
+    d1 = describe()
+    clickmm(*mid(d1["entities"][0])); clickmm(*mid(d1["entities"][1]))
+    click(*CON_BTN["perpendicular"])
+    time.sleep(1.0)
+    d = describe()
+    ang = angle_between(d["entities"][0], d["entities"][1])
+    # 1e-6 deg, which is 1.7e-8 radians: the LIVE solve converges to its own tolerance and lands
+    # at 89.999999991 from a 51 deg start. The old 1e-9 held only because the pair began 3 deg
+    # from square, so the correction was tiny -- it was measuring how little work the solver had
+    # to do, not whether the lines came out perpendicular. The round-trip check below still
+    # demands exactly 90: the committed feature re-solves from scratch and gets there.
+    check("ANGLE", near(ang, 90.0, 1e-6), f"now {ang:.9f} deg")
+    d2 = confirm_and_reopen()
+    ang2 = angle_between(d2["entities"][0], d2["entities"][1])
+    check("ANGLE", near(ang2, 90.0, 1e-9), f"still {ang2:.9f} deg after the round trip")
+    check("CLOSED", d2["constraints"] > 0 and d2["solve_ok"],
+          f"{d2['constraints']} constraints survived, dof {d2['dof']}")
+    leave_sketch()
+
+
+def angle_between(a, b):
+    va = (a["p1"][0] - a["p0"][0], a["p1"][1] - a["p0"][1])
+    vb = (b["p1"][0] - b["p0"][0], b["p1"][1] - b["p0"][1])
+    c = (va[0] * vb[0] + va[1] * vb[1]) / (math.hypot(*va) * math.hypot(*vb))
+    return math.degrees(math.acos(max(-1.0, min(1.0, c))))
+
+
+def parallel_gap(a, b):
+    """How far from parallel, in degrees. Parallel reads 0 or 180; both mean parallel."""
+    ang = angle_between(a, b)
+    return min(ang, 180.0 - ang)
+
+
+def rung_parallel():
+    reset_document()
+    print("\nD10 constrain — two divergent lines made parallel (the button had no rung at all)")
+    enter_sketch("l")
+    clickmm(-50, -30); clickmm(30, -18)
+    key("Escape", 0.7); key("Escape", 0.7)
+    key("l", 0.6)
+    # Well outside inference's 3 deg snap, for the same reason D3 starts at 56: a pair that
+    # arrives already parallel would let a dead button pass the rung.
+    clickmm(30, -18); clickmm(55, 35)
+    key("Escape", 0.7); key("Escape", 0.7)
+    d0 = describe()
+    g0 = parallel_gap(d0["entities"][0], d0["entities"][1])
+    check("ANGLE", g0 > 1e-3, f"they start {g0:.6f} deg from parallel")
+    key("k", 1.5)
+    d1 = describe()
+    clickmm(*mid(d1["entities"][0])); clickmm(*mid(d1["entities"][1]))
+    click(*CON_BTN["parallel"])
+    time.sleep(1.0)
+    d = describe()
+    g = parallel_gap(d["entities"][0], d["entities"][1])
+    check("ANGLE", near(g, 0.0, 1e-6), f"now {g:.9f} deg from parallel")
+    check("LENGTH", d["entities"][0]["length"] > 1.0 and d["entities"][1]["length"] > 1.0,
+          f"neither line collapsed: {d['entities'][0]['length']:.6f}, {d['entities'][1]['length']:.6f}")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["constraints"] > 0 and d2["solve_ok"],
+          f"{d2['constraints']} constraints survived the commit, dof {d2['dof']}")
+    leave_sketch()
+
+
+def rung_live_constrain():
+    reset_document()
+    print("\nD11 constrain WHILE SKETCHING — no commit, no tree pick, no padlock")
+    enter_sketch("l")
+    clickmm(-50, -30); clickmm(30, -18)
+    key("Escape", 0.7); key("Escape", 0.7)
+    key("l", 0.6)
+    clickmm(30, -18); clickmm(55, 35)
+    # Two Escapes only: the first clears the polyline's pending point, the second drops the
+    # tool to Select. The session stays LIVE -- that is the whole point of this rung.
+    key("Escape", 0.7); key("Escape", 0.7)
+    d0 = describe()
+    check("VERTEX", len(d0["entities"]) == 2, f"{len(d0['entities'])} entities in the live sketch")
+    g0 = parallel_gap(d0["entities"][0], d0["entities"][1])
+    check("ANGLE", g0 > 1e-3, f"they start {g0:.6f} deg from parallel")
+    # Pick both in the LIVE session, then press the button. No "k": pressing Constrain is
+    # exactly the step this rung exists to prove is no longer necessary.
+    clickmm(*mid(d0["entities"][0]))
+    cx, cy = mid(d0["entities"][1])
+    click_ctrl(*px(cx, cy))
+    click(*CON_BTN_SKETCH["parallel"])
+    time.sleep(1.2)
+    d = describe()
+    g = parallel_gap(d["entities"][0], d["entities"][1])
+    check("ANGLE", near(g, 0.0, 1e-6), f"parallel without ever leaving the sketch: {g:.9f} deg")
+    check("LENGTH", d["entities"][0]["length"] > 1.0 and d["entities"][1]["length"] > 1.0,
+          f"neither line collapsed: {d['entities'][0]['length']:.6f}, {d['entities'][1]['length']:.6f}")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["constraints"] > 0 and d2["solve_ok"],
+          f"{d2['constraints']} constraints survived the commit, dof {d2['dof']}")
+    leave_sketch()
+
+
+# ---- the eleven buttons no rung had ever pressed ------------------------------------------
+# Twenty constraint buttons, nine of them exercised. The other eleven were "implemented" in the
+# sense that the kernel builds the right def for them -- which is exactly what was true of
+# Parallel this morning, right up until a user pressed it. What a kernel test cannot see: that
+# the BUTTON is wired to the index its name claims. CON_BTN is 449 + 42*i over a hand-written
+# name list and it has drifted once already, unnoticed for months, because nothing pressed
+# anything past index 5. These rungs press the rest.
+
+def rung_vertical():
+    reset_document()
+    print("\nD12 constrain — Vertical on one line, from a line that is not")
+    enter_sketch("l")
+    clickmm(-20, -35); clickmm(5, 30)
+    key("Escape", 0.7); key("Escape", 0.7)
+    d0 = describe()
+    dx0 = abs(d0["entities"][0]["p1"][0] - d0["entities"][0]["p0"][0])
+    check("VERTEX", dx0 > 1.0, f"it starts off-plumb by {dx0:.6f} mm")
+    key("k", 1.5)
+    d1 = describe()
+    clickmm(*mid(d1["entities"][0]))
+    click(*CON_BTN["vertical"])
+    time.sleep(1.0)
+    d = describe()
+    e = d["entities"][0]
+    dx = abs(e["p1"][0] - e["p0"][0])
+    check("VERTEX", near(dx, 0.0, 1e-6), f"now plumb: dx = {dx:.9f}")
+    check("LENGTH", e["length"] > 1.0, f"and it did not collapse: {e['length']:.6f}")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    leave_sketch()
+
+
+def rung_equal_radius_button():
+    reset_document()
+    print("\nD13 constrain — the equal_radius button ITSELF (index 6: past where the map drifted)")
+    # D4 proves the SHARED Equal button promotes on two circles. This presses design_c_equal_radius,
+    # the first button after the six that were once inserted without updating this table.
+    enter_sketch("c")
+    clickmm(-35, 0); clickmm(-20, 0); key("Escape", 0.7)
+    key("c", 0.6)
+    clickmm(35, 0); clickmm(60, 0); key("Escape", 0.7)
+    d0 = describe()
+    cs = [e for e in d0["entities"] if e["type"] == "circle"]
+    check("ARC", len(cs) == 2 and not near(cs[0]["radius"], cs[1]["radius"], 1e-6),
+          f"they start unequal: {[round(c['radius'], 6) for c in cs]}")
+    key("k", 1.5)
+    d1 = describe()
+    cs = [e for e in d1["entities"] if e["type"] == "circle"]
+    ia, ib = d1["entities"].index(cs[0]), d1["entities"].index(cs[1])
+    clickmm(*rim(cs[0])); clickmm(*rim(cs[1]))
+    click(*CON_BTN["equal_radius"])
+    time.sleep(1.0)
+    d = describe()
+    ra, rb = d["entities"][ia]["radius"], d["entities"][ib]["radius"]
+    check("ARC", near(ra, rb, 1e-9), f"equal by the dedicated button: {ra:.9f} and {rb:.9f}")
+    check("ARC", ra > 1e-6, f"and not equal at zero: {ra:.9f}")
+    leave_sketch()
+
+
+def rung_concentric():
+    reset_document()
+    print("\nD14 constrain — Concentric puts two circles on one centre, radii untouched")
+    enter_sketch("c")
+    clickmm(-30, -10); clickmm(-14, -10); key("Escape", 0.7)
+    key("c", 0.6)
+    clickmm(28, 14); clickmm(52, 14); key("Escape", 0.7)
+    d0 = describe()
+    cs = [e for e in d0["entities"] if e["type"] == "circle"]
+    gap0 = math.dist(cs[0]["center"], cs[1]["center"])
+    r_before = sorted(round(c["radius"], 9) for c in cs)
+    check("ARC", gap0 > 1.0, f"centres start {gap0:.6f} mm apart")
+    key("k", 1.5)
+    d1 = describe()
+    cs = [e for e in d1["entities"] if e["type"] == "circle"]
+    ia, ib = d1["entities"].index(cs[0]), d1["entities"].index(cs[1])
+    clickmm(*rim(cs[0])); clickmm(*rim(cs[1]))
+    click(*CON_BTN["concentric"])
+    time.sleep(1.0)
+    d = describe()
+    gap = math.dist(d["entities"][ia]["center"], d["entities"][ib]["center"])
+    check("ARC", near(gap, 0.0, 1e-6), f"centres now coincide: {gap:.9f} mm apart")
+    # Concentric is about centres only. A solve that also equalised the radii would be wrong.
+    r_after = sorted(round(d["entities"][i]["radius"], 9) for i in (ia, ib))
+    check("ARC", all(near(a, b, 1e-6) for a, b in zip(r_before, r_after)),
+          f"radii untouched: {r_before} -> {r_after}")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    leave_sketch()
+
+
+def rung_tangent():
+    reset_document()
+    print("\nD15 constrain — Tangent brings a line to touch a circle exactly once")
+    enter_sketch("c")
+    clickmm(0, 0); clickmm(20, 0); key("Escape", 0.7)
+    key("l", 0.6)
+    # A line that clearly MISSES the circle: its perpendicular distance from the centre is well
+    # above the radius, so tangency has real work to do in the direction of shrinking the gap.
+    clickmm(-45, 38); clickmm(45, 44)
+    key("Escape", 0.7); key("Escape", 0.7)
+    d0 = describe()
+    c0 = next(e for e in d0["entities"] if e["type"] == "circle")
+    l0 = next(e for e in d0["entities"] if e["type"] == "line")
+    d_before = point_line_distance(c0["center"], l0)
+    check("ARC", d_before > c0["radius"] + 1.0,
+          f"the line misses by {d_before - c0['radius']:.6f} mm")
+    key("k", 1.5)
+    d1 = describe()
+    c1 = next(e for e in d1["entities"] if e["type"] == "circle")
+    l1 = next(e for e in d1["entities"] if e["type"] == "line")
+    ic, il = d1["entities"].index(c1), d1["entities"].index(l1)
+    clickmm(*rim(c1)); clickmm(*mid(l1))
+    click(*CON_BTN["tangent"])
+    time.sleep(1.2)
+    d = describe()
+    cc, ll = d["entities"][ic], d["entities"][il]
+    dist = point_line_distance(cc["center"], ll)
+    check("ARC", near(dist, cc["radius"], 1e-6),
+          f"centre-to-line {dist:.9f} == radius {cc['radius']:.9f}")
+    check("ARC", cc["radius"] > 1e-6, f"and the circle did not collapse: r = {cc['radius']:.9f}")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    leave_sketch()
+
+
+def rung_midpoint():
+    reset_document()
+    print("\nD16 constrain — Midpoint drops a free point onto the middle of a line")
+    enter_sketch("l")
+    clickmm(-50, -20); clickmm(40, 26)
+    key("Escape", 0.7); key("Escape", 0.7)
+    key("p", 0.6)
+    clickmm(10, -35)
+    d0 = describe()
+    l0 = next(e for e in d0["entities"] if e["type"] == "line")
+    p0 = next(e for e in d0["entities"] if e["type"] == "point")
+    mid0 = ((l0["p0"][0] + l0["p1"][0]) / 2.0, (l0["p0"][1] + l0["p1"][1]) / 2.0)
+    check("VERTEX", math.dist(p0["p"], mid0) > 1.0,
+          f"the point starts {math.dist(p0['p'], mid0):.6f} mm off the midpoint")
+    key("k", 1.5)
+    d1 = describe()
+    l1 = next(e for e in d1["entities"] if e["type"] == "line")
+    p1 = next(e for e in d1["entities"] if e["type"] == "point")
+    il, ip = d1["entities"].index(l1), d1["entities"].index(p1)
+    # Point first, then the line: Midpoint binds a POINT role on ea and a whole segment on eb.
+    clickmm(*p1["p"]); clickmm(*mid(l1))
+    click(*CON_BTN["midpoint"])
+    time.sleep(1.2)
+    d = describe()
+    ll, pp = d["entities"][il], d["entities"][ip]
+    m = ((ll["p0"][0] + ll["p1"][0]) / 2.0, (ll["p0"][1] + ll["p1"][1]) / 2.0)
+    check("VERTEX", near(math.dist(pp["p"], m), 0.0, 1e-6),
+          f"the point sits on the midpoint: off by {math.dist(pp['p'], m):.9f}")
+    check("LENGTH", ll["length"] > 1.0, f"and the line did not collapse: {ll['length']:.6f}")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    leave_sketch()
+
+
+def rung_symmetric_line_axis():
+    reset_document()
+    print("\nD17 constrain — Symmetric about a PICKED axis line (the three-pick form)")
+    # D7 covers the implicit-axis buttons. This is the plain Symmetric: two entities AND an axis
+    # entity, three picks, the only constraint on the bar that needs a third.
+    enter_sketch("l")
+    clickmm(0, -40); clickmm(0, 40)          # the axis: a real line on x = 0
+    key("Escape", 0.7); key("Escape", 0.7)
+    key("p", 0.6)
+    clickmm(-38, 12)
+    key("p", 0.6)
+    clickmm(14, 12)
+    d0 = describe()
+    ps = [e for e in d0["entities"] if e["type"] == "point"]
+    check("VERTEX", not near(abs(ps[0]["p"][0]), abs(ps[1]["p"][0]), 1e-3),
+          f"they start unmirrored: x = {ps[0]['p'][0]:.6f}, {ps[1]['p'][0]:.6f}")
+    key("k", 1.5)
+    d1 = describe()
+    ps = [e for e in d1["entities"] if e["type"] == "point"]
+    ax = next(e for e in d1["entities"] if e["type"] == "line")
+    ia, ib = d1["entities"].index(ps[0]), d1["entities"].index(ps[1])
+    iax = d1["entities"].index(ax)
+    clickmm(*ps[0]["p"]); clickmm(*ps[1]["p"]); clickmm(*mid(ax))
+    click(*CON_BTN["symmetric"])
+    time.sleep(1.2)
+    d = describe()
+    # Measure against the axis WHERE IT NOW IS, not against x = 0. All three entities are free,
+    # so the solver is entitled to satisfy the mirror by moving the AXIS instead of the points --
+    # and it does: the pair came out symmetric about x = -8.18, which is a correct solution and
+    # which an "xa == -xb" assertion calls a failure. That was this rung being wrong, not the app.
+    ax_now = d["entities"][iax]
+    sa = signed_point_line_distance(d["entities"][ia]["p"], ax_now)
+    sb = signed_point_line_distance(d["entities"][ib]["p"], ax_now)
+    ya, yb = d["entities"][ia]["p"][1], d["entities"][ib]["p"][1]
+    check("VERTEX", near(sa, -sb, 1e-6),
+          f"mirrored about the picked line: {sa:.9f} and {sb:.9f} from it")
+    check("VERTEX", abs(sa) > 1e-6, f"and not both collapsed onto it: |d| = {abs(sa):.9f}")
+    check("VERTEX", near(ya, yb, 1e-6), f"y untouched on both: {ya:.6f}, {yb:.6f}")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    leave_sketch()
+
+
+def rung_symmetric_h():
+    reset_document()
+    print("\nD18 constrain — symmetric about the HORIZONTAL axis (sym_h, the twin of D7)")
+    enter_sketch("p")
+    clickmm(20, -34)
+    key("p", 0.6)
+    clickmm(20, 9)
+    d0 = describe()
+    ps = [e for e in d0["entities"] if e["type"] == "point"]
+    check("VERTEX", not near(abs(ps[0]["p"][1]), abs(ps[1]["p"][1]), 1e-3),
+          f"they start unmirrored: y = {ps[0]['p'][1]:.6f}, {ps[1]['p'][1]:.6f}")
+    key("k", 1.5)
+    d1 = describe()
+    ps = [e for e in d1["entities"] if e["type"] == "point"]
+    ia, ib = d1["entities"].index(ps[0]), d1["entities"].index(ps[1])
+    clickmm(*ps[0]["p"]); clickmm(*ps[1]["p"])
+    click(*CON_BTN["sym_h"])
+    time.sleep(1.0)
+    d = describe()
+    xa, xb = d["entities"][ia]["p"][0], d["entities"][ib]["p"][0]
+    ya, yb = d["entities"][ia]["p"][1], d["entities"][ib]["p"][1]
+    check("VERTEX", near(ya, -yb, 1e-9), f"mirrored across y = 0: {ya:.9f} and {yb:.9f}")
+    check("VERTEX", abs(ya) > 1e-6, f"and not both collapsed onto the axis: |y| = {abs(ya):.9f}")
+    check("VERTEX", near(xa, xb, 1e-6), f"x untouched on both: {xa:.6f}, {xb:.6f}")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    leave_sketch()
+
+
+def rung_radius():
+    reset_document()
+    print("\nD19 constrain — a typed Radius drives the circle to exactly that radius")
+    enter_sketch("c")
+    clickmm(0, 0); clickmm(31, 0); key("Escape", 0.7)
+    d0 = describe()
+    c0 = next(e for e in d0["entities"] if e["type"] == "circle")
+    check("ARC", not near(c0["radius"], 22.0, 1e-3), f"it starts at r = {c0['radius']:.6f}")
+    key("k", 1.5)
+    d1 = describe()
+    c1 = next(e for e in d1["entities"] if e["type"] == "circle")
+    ic = d1["entities"].index(c1)
+    ctr = list(c1["center"])
+    clickmm(*rim(c1))
+    click(*CON_BTN["radius"])
+    time.sleep(0.8)
+    values(22)
+    d = describe()
+    cc = d["entities"][ic]
+    check("ARC", near(cc["radius"], 22.0, 1e-6), f"radius driven to {cc['radius']:.9f}")
+    # A Radius constraint moves the RIM, never the centre.
+    check("ARC", near(math.dist(cc["center"], ctr), 0.0, 1e-6),
+          f"and the centre stayed put: moved {math.dist(cc['center'], ctr):.9f}")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    leave_sketch()
+
+
+def rung_diameter():
+    reset_document()
+    print("\nD20 constrain — a typed Diameter is a diameter, not a radius")
+    # The failure this exists for is a factor of two: Diameter wired to the Radius handler gives
+    # a circle of r = 30 for a typed 30, and nothing about the sketch looks wrong.
+    enter_sketch("c")
+    clickmm(0, 0); clickmm(19, 0); key("Escape", 0.7)
+    key("k", 1.5)
+    d1 = describe()
+    c1 = next(e for e in d1["entities"] if e["type"] == "circle")
+    ic = d1["entities"].index(c1)
+    clickmm(*rim(c1))
+    click(*CON_BTN["diameter"])
+    time.sleep(0.8)
+    values(30)
+    d = describe()
+    r = d["entities"][ic]["radius"]
+    check("ARC", near(r, 15.0, 1e-6), f"typed diameter 30 gives radius {r:.9f}, not 30")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    leave_sketch()
+
+
+def rung_fix():
+    reset_document()
+    print("\nD21 constrain — Fix anchors a point, and the anchor is what the solver moves around")
+    # Fix on its own is unfalsifiable: nothing moved, so nothing proves it did anything. The
+    # property only becomes observable when a SECOND constraint would otherwise have moved the
+    # fixed point -- so drive the pair apart and see which end travels.
+    enter_sketch("p")
+    clickmm(-25, 0)
+    key("p", 0.6)
+    clickmm(15, 0)
+    key("k", 1.5)
+    d1 = describe()
+    ps = [e for e in d1["entities"] if e["type"] == "point"]
+    ia, ib = d1["entities"].index(ps[0]), d1["entities"].index(ps[1])
+    anchor = list(ps[0]["p"])
+    clickmm(*ps[0]["p"])
+    click(*CON_BTN["fix"])
+    time.sleep(1.0)
+    d = describe()
+    check("VERTEX", near(math.dist(d["entities"][ia]["p"], anchor), 0.0, 1e-9),
+          "the fixed point did not move when it was fixed")
+    # Now demand a horizontal gap far from the current one. Only the FREE point may travel.
+    clickmm(*d["entities"][ia]["p"]); clickmm(*d["entities"][ib]["p"])
+    click(*CON_BTN["dist_x"])
+    time.sleep(0.8)
+    values(70)
+    d = describe()
+    moved_a = math.dist(d["entities"][ia]["p"], anchor)
+    gap = abs(d["entities"][ib]["p"][0] - d["entities"][ia]["p"][0])
+    check("LENGTH", near(gap, 70.0, 1e-6), f"the gap was driven to {gap:.9f}")
+    check("VERTEX", near(moved_a, 0.0, 1e-6),
+          f"and the anchored point held station: moved {moved_a:.9f}")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 1,
+          f"{d2['constraints']} constraints survived the commit")
+    leave_sketch()
+
+
+def rung_distance_y():
+    reset_document()
+    print("\nD22 constrain — vertical distance, and it is not the straight-line one either")
+    enter_sketch("p")
+    clickmm(-22, -18)
+    key("p", 0.6)
+    clickmm(19, 24)
+    key("k", 1.5)
+    d1 = describe()
+    ps = [e for e in d1["entities"] if e["type"] == "point"]
+    ia, ib = d1["entities"].index(ps[0]), d1["entities"].index(ps[1])
+    dx_before = d1["entities"][ib]["p"][0] - d1["entities"][ia]["p"][0]
+    clickmm(*ps[0]["p"]); clickmm(*ps[1]["p"])
+    click(*CON_BTN["dist_y"])
+    time.sleep(0.8)
+    values(35)
+    d = describe()
+    gy = abs(d["entities"][ib]["p"][1] - d["entities"][ia]["p"][1])
+    gx = d["entities"][ib]["p"][0] - d["entities"][ia]["p"][0]
+    check("LENGTH", near(gy, 35.0, 1e-6), f"vertical gap driven to {gy:.9f}")
+    check("VERTEX", near(gx, dx_before, 1e-6),
+          f"the horizontal gap is untouched at {gx:.9f} — this is not a straight-line distance")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    leave_sketch()
+
+
+def signed_point_line_distance(p, line):
+    """Perpendicular distance with a SIGN, so the two sides of a mirror are distinguishable."""
+    x0, y0 = line["p0"]; x1, y1 = line["p1"]
+    dx, dy = x1 - x0, y1 - y0
+    n = math.hypot(dx, dy)
+    return (dy * (p[0] - x0) - dx * (p[1] - y0)) / n
+
+
+def point_line_distance(p, line):
+    """Perpendicular distance from a point to the INFINITE line through a segment."""
+    x0, y0 = line["p0"]; x1, y1 = line["p1"]
+    dx, dy = x1 - x0, y1 - y0
+    n = math.hypot(dx, dy)
+    return abs(dy * (p[0] - x0) - dx * (p[1] - y0)) / n
+
+
+# =================================================================== DURABILITY
+# Exactness that does not survive an undo or a save is not exactness.
+
+def rim(e, deg=135.0):
+    """A point on a circle's rim, away from +X.
+
+    NOT the +X point: a click there grabs the RADIUS GRIP instead of selecting the circle,
+    and a grip click REPLACES the selection with that one entity — so the second pick of a
+    two-entity constraint silently discards the first.
+    """
+    a = math.radians(deg)
+    return (e["center"][0] + e["radius"] * math.cos(a),
+            e["center"][1] + e["radius"] * math.sin(a))
+
+
+def rung_equal_radius():
+    reset_document()
+    print("\nD4  constrain — Equal on two CIRCLES means equal radius, not equal length")
+    # The dead end this fixed: two circles + Equal used to emit EQUAL_LENGTH_LINES, which
+    # constrains nothing on a curve. The user got a silent no-op with no error and no way to
+    # tell why. One Equal button, two meanings — lines get length, curves get radius.
+    # NOT dimensioned: a typed radius is a DRIVING Radius constraint, and EqualRadius on two
+    # circles pinned to 15 and 25 is genuinely inconsistent -- the kernel refuses the addition
+    # and is right to. Draw them at different sizes and leave the radius free.
+    enter_sketch("c")
+    clickmm(-35, 0); clickmm(-20, 0); key("Escape", 0.7)
+    key("c", 0.6)
+    clickmm(35, 0); clickmm(60, 0); key("Escape", 0.7)
+    d0 = describe()
+    cs = [e for e in d0["entities"] if e["type"] == "circle"]
+    check("ARC", len(cs) == 2 and not near(cs[0]["radius"], cs[1]["radius"], 1e-6),
+          f"they start unequal: {[round(c['radius'], 6) for c in cs]}")
+    key("k", 1.5)
+    d1 = describe()
+    cs = [e for e in d1["entities"] if e["type"] == "circle"]
+    ia, ib = d1["entities"].index(cs[0]), d1["entities"].index(cs[1])
+    clickmm(*rim(cs[0])); clickmm(*rim(cs[1]))
+    click(*CON_BTN["equal"])          # the SHARED Equal button, not design_c_equal_radius
+    time.sleep(1.0)
+    d = describe()
+    ra, rb = d["entities"][ia]["radius"], d["entities"][ib]["radius"]
+    check("ARC", near(ra, rb, 1e-9), f"the two radii are now equal: {ra:.9f} and {rb:.9f}")
+    check("ARC", ra > 1e-6, f"and not equal at zero: {ra:.9f}")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    rs = sorted(round(e["radius"], 9) for e in d2["entities"] if e["type"] == "circle")
+    check("ARC", len(rs) == 2 and near(rs[0], rs[-1], 1e-9),
+          f"still equal after the round trip: {rs}")
+    leave_sketch()
+
+
+def rung_collinear():
+    reset_document()
+    print("\nD5  constrain — two offset lines brought onto one infinite line")
+    # Oblique on purpose: axis-aligned segments pick up an auto Horizontal at draw time, and
+    # this rung is about Collinear, not about interacting with inference.
+    enter_sketch("l")
+    clickmm(-60, -14); clickmm(-12, -6)
+    key("Escape", 0.7); key("Escape", 0.7)
+    key("l", 0.6)
+    clickmm(12, 14); clickmm(60, 22)
+    key("Escape", 0.7); key("Escape", 0.7)
+    d0 = describe()
+    ls = [e for e in d0["entities"] if e["type"] == "line"]
+    check("VERTEX", len(ls) == 2 and abs(ls[0]["p0"][1] - ls[1]["p0"][1]) > 1.0,
+          f"they start on different lines, dy = {abs(ls[0]['p0'][1] - ls[1]['p0'][1]):.6f}")
+    key("k", 1.5)
+    d1 = describe()
+    ls = [e for e in d1["entities"] if e["type"] == "line"]
+    ia, ib = d1["entities"].index(ls[0]), d1["entities"].index(ls[1])
+    clickmm(*mid(ls[0])); clickmm(*mid(ls[1]))
+    click(*CON_BTN["collinear"])
+    time.sleep(1.0)
+    d = describe()
+    A, B = d["entities"][ia], d["entities"][ib]
+    ax, ay = A["p0"]
+    dx, dy = A["p1"][0] - ax, A["p1"][1] - ay
+    cross = [dx * (q[1] - ay) - dy * (q[0] - ax) for q in (B["p0"], B["p1"])]
+    check("VERTEX", all(abs(c) < 1e-6 for c in cross),
+          f"both ends of the second line lie on the first: cross {[round(c, 9) for c in cross]}")
+    # A line collapsed to a point is trivially collinear with anything, so the cross products
+    # above pass on a degenerate solve. Both lines have to survive.
+    check("LENGTH", A["length"] > 1.0 and B["length"] > 1.0,
+          f"neither line collapsed: {A['length']:.6f}, {B['length']:.6f}")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    leave_sketch()
+
+
+def rung_distance_xy():
+    reset_document()
+    print("\nD6  constrain — horizontal distance, and accepting its own value moves nothing")
+    enter_sketch("p")
+    clickmm(-30, -20)
+    key("p", 0.6)
+    clickmm(25, 18)
+    # A THIRD point, placed now while the point tool is still armed. The typed half of this rung
+    # needs a pair that carries no dimension yet, and pressing "p" again once the constrain tool
+    # has taken over does not re-arm the point tool -- the click is consumed as a pick and no
+    # point appears, which read as an IndexError three lines later rather than as what it was.
+    key("p", 0.6)
+    clickmm(5, 5)
+    d0 = describe()
+    ps = [e for e in d0["entities"] if e["type"] == "point"]
+    check("VERTEX", len(ps) == 3, f"three points placed: {len(ps)}")
+    key("k", 1.5)
+    d1 = describe()
+    ps = [e for e in d1["entities"] if e["type"] == "point"]
+    ia, ib = d1["entities"].index(ps[0]), d1["entities"].index(ps[1])
+    ic = d1["entities"].index(ps[2])
+
+    # THE NO-OP PROPERTY, which is the one a unit test cannot reach: the field opens pre-filled
+    # with the current projected gap, and pressing Return must change nothing. The constraint is
+    # SIGNED — (pB - pA).dot(axis) — so if the refs were ordered to show |delta| while the real
+    # delta is negative, accepting the number on screen teleports the point across its anchor.
+    before = [list(d1["entities"][ia]["p"]), list(d1["entities"][ib]["p"])]
+    clickmm(*ps[0]["p"]); clickmm(*ps[1]["p"])
+    click(*CON_BTN["dist_x"])
+    time.sleep(0.8)
+    key("Return", 1.2)                 # accept the pre-filled value, type nothing
+    d = describe()
+    after = [list(d["entities"][ia]["p"]), list(d["entities"][ib]["p"])]
+    moved = max(abs(a - b) for pa, pb in zip(before, after) for a, b in zip(pa, pb))
+    # 5 microns, not zero: the field shows two decimals, so accepting what it shows commits a
+    # ROUNDED value and the geometry legitimately shifts by up to half a displayed unit. The
+    # defect this guards is a sign flip, which moves the point by twice the gap — tens of
+    # millimetres. A 1e-6 tolerance here failed on a 0.96 micron rounding step, which is the
+    # instrument disagreeing with the display, not the app misbehaving.
+    check("VERTEX", moved < 5e-3,
+          f"accepting the shown value moved nothing (max {moved:.9f})")
+    # "nothing moved" passes just as happily when the constraint was never applied at all --
+    # which is exactly how the phantom-endpoint bug hid. The gap has to be REAL and driveable,
+    # so prove the mechanism works before trusting the no-op above.
+    check("LENGTH", abs(d["entities"][ib]["p"][0] - d["entities"][ia]["p"][0]) > 1.0,
+          "and the two points still have a real horizontal gap to dimension")
+
+    # Now drive it with a TYPED value, on a FRESH pair. Not on the pair just dimensioned: that
+    # one already carries its DistanceX, the button rightly refuses to dimension it twice, and no
+    # field opens — so the digits went nowhere and the gap kept the value the no-op step had
+    # accepted. A green "gap is 54.94" for a rung that typed 40 is the rung's fault, not the app's.
+    dy_before = d["entities"][ic]["p"][1] - d["entities"][ia]["p"][1]
+    clickmm(*d["entities"][ia]["p"]); clickmm(*d["entities"][ic]["p"])
+    click(*CON_BTN["dist_x"])
+    time.sleep(0.8)
+    values(40)
+    d = describe()
+    gx = abs(d["entities"][ic]["p"][0] - d["entities"][ia]["p"][0])
+    gy = d["entities"][ic]["p"][1] - d["entities"][ia]["p"][1]
+    check("LENGTH", near(gx, 40.0, 1e-6), f"horizontal gap driven to {gx:.9f}")
+    check("VERTEX", near(gy, dy_before, 1e-6),
+          f"the vertical gap is untouched at {gy:.9f} — this is not a straight-line distance")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    leave_sketch()
+
+
+def rung_coincident_points():
+    reset_document()
+    print("\nD8  constrain — Coincident on two POINTS actually joins them")
+    # The regression this exists for: the closest-pair search used to enumerate {P0,p0},{P1,p1}
+    # on both entities, and a Point's p1 reads (0,0). For two points the phantom pair is at
+    # distance 0, which ALWAYS wins, so the constraint was added against a role the solver
+    # cannot resolve and dropped in silence -- constraints=0, the points never moved, no error.
+    # Two points is the simplest possible use of the button and it did nothing on every press.
+    enter_sketch("p")
+    clickmm(-30, -20)
+    key("p", 0.6)
+    clickmm(25, 18)
+    key("k", 1.5)
+    d1 = describe()
+    ps = [e for e in d1["entities"] if e["type"] == "point"]
+    ia, ib = d1["entities"].index(ps[0]), d1["entities"].index(ps[1])
+    gap0 = math.dist(ps[0]["p"], ps[1]["p"])
+    check("VERTEX", gap0 > 1.0, f"they start apart: {gap0:.6f}")
+    clickmm(*ps[0]["p"]); clickmm(*ps[1]["p"])
+    click(*CON_BTN["coincident"])
+    time.sleep(1.2)
+    d = describe()
+    gap = math.dist(d["entities"][ia]["p"], d["entities"][ib]["p"])
+    check("VERTEX", gap < 1e-6, f"and are now joined: gap {gap:.9f}")
+    # The count has to be read AFTER the round trip, never during the session: while
+    # constraining, sketch_describe reports the LIVE tool's constraints, which the constrain
+    # session never touches -- it writes the committed feature's entity_constraints. Reading it
+    # here says 0 for a constraint that really did land. Same trap the D2 rung documents.
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit — a dropped one leaves this at 0")
+    ps2 = [e for e in d2["entities"] if e["type"] == "point"]
+    check("VERTEX", math.dist(ps2[0]["p"], ps2[1]["p"]) < 1e-6,
+          "and they are still joined after the round trip")
+    leave_sketch()
+
+
+def rung_symmetric_axis():
+    reset_document()
+    print("\nD7  constrain — symmetric about the vertical axis, with no construction line")
+    # Plain Symmetric needs a third pick for the mirror axis, so being symmetric about the
+    # sketch's own vertical axis used to mean drawing a construction line first. This button
+    # uses the implicit axis: two picks, no axis entity.
+    enter_sketch("p")
+    clickmm(-40, 15)
+    key("p", 0.6)
+    clickmm(12, 15)
+    key("k", 1.5)
+    d1 = describe()
+    ps = [e for e in d1["entities"] if e["type"] == "point"]
+    ia, ib = d1["entities"].index(ps[0]), d1["entities"].index(ps[1])
+    check("VERTEX", not near(abs(ps[0]["p"][0]), abs(ps[1]["p"][0]), 1e-3),
+          f"they start unmirrored: x = {ps[0]['p'][0]:.6f}, {ps[1]['p'][0]:.6f}")
+    clickmm(*ps[0]["p"]); clickmm(*ps[1]["p"])
+    click(*CON_BTN["sym_v"])
+    time.sleep(1.0)
+    d = describe()
+    xa, xb = d["entities"][ia]["p"][0], d["entities"][ib]["p"][0]
+    ya, yb = d["entities"][ia]["p"][1], d["entities"][ib]["p"][1]
+    check("VERTEX", near(xa, -xb, 1e-9), f"mirrored across x = 0: {xa:.9f} and {xb:.9f}")
+    # Both collapsing onto the axis satisfies the mirror trivially.
+    check("VERTEX", abs(xa) > 1e-6, f"and not both collapsed onto the axis: |x| = {abs(xa):.9f}")
+    check("VERTEX", near(ya, yb, 1e-6), f"y untouched on both: {ya:.6f}, {yb:.6f}")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["solve_ok"] and d2["constraints"] > 0,
+          f"{d2['constraints']} constraints survived the commit")
+    leave_sketch()
+
+
+def rung_type_guards():
+    reset_document()
+    print("\nD9  constrain — a button that cannot apply must SAY so, not store a dead constraint")
+    # Both halves were live defects found by reviewing the DistanceX/Y fix for its class.
+    #
+    # Horizontal on a lone Point: P1 is a role the solver cannot resolve, so the constraint was
+    # dropped at ref_ok -- but still STORED. Measured before the fix: constraints 0 -> 1 after the
+    # commit, point unmoved. A constraint listed in the panel that can never do anything is worse
+    # than a refusal, because the panel then claims the sketch is constrained when it is not.
+    enter_sketch("p")
+    clickmm(-30, -20)
+    key("k", 1.5)
+    d = describe()
+    ps = [e for e in d["entities"] if e["type"] == "point"]
+    ia = d["entities"].index(ps[0])
+    clickmm(*ps[0]["p"])
+    click(*CON_BTN["horizontal"])
+    time.sleep(1.0)
+    d = describe()
+    check("VERTEX", near(d["entities"][ia]["p"][0], ps[0]["p"][0], 1e-9) and
+                    near(d["entities"][ia]["p"][1], ps[0]["p"][1], 1e-9),
+          "Horizontal on a point moved nothing, as it must")
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["constraints"] == 0,
+          f"and stored NO constraint: {d2['constraints']} (a dead stored one reads 1)")
+    leave_sketch()
+
+    # Angle on two circles: p1-p0 on a circle is (0,0)-centre, so the field used to pre-fill with
+    # the angle between the two centre POSITION VECTORS -- 178.83 deg for two circles on the x
+    # axis -- and committing it fed SLVS_C_ANGLE two circle prims, which are not directions.
+    reset_document()
+    enter_sketch("c")
+    clickmm(-35, 0); clickmm(-20, 0); key("Escape", 0.7)
+    key("c", 0.6)
+    clickmm(35, 0); clickmm(60, 0); key("Escape", 0.7)
+    key("k", 1.5)
+    d = describe()
+    cs = [e for e in d["entities"] if e["type"] == "circle"]
+    clickmm(*rim(cs[0])); clickmm(*rim(cs[1]))
+    click(*CON_BTN["angle"])
+    time.sleep(1.0)
+    check("ANGLE", not field_open(),
+          "Angle on two circles opened no value field")
+    key("Escape", 0.6)
+    d2 = confirm_and_reopen()
+    check("CLOSED", d2["constraints"] == 0,
+          f"and stored no angle: {d2['constraints']}")
+    leave_sketch()
+
+
+def rung_undo():
+    print("\nE1  undo — the last entity goes, the rest do not move")
+    enter_sketch("l")
+    draw_line(-50, -30, 0, -30, 50, 0)
+    key("l", 0.6); draw_line(0, -30, 0, 20, 50, 90)
+    key("l", 0.6); draw_line(0, 20, -40, 20, 40, 180)
+    before = describe()["entities"]
+    check("LENGTH", len(before) == 3, f"{len(before)} entities drawn")
+    key("ctrl+z", 1.0)
+    after = describe()["entities"]
+    check("VERTEX", len(after) == 2, f"{len(after)} entities after one undo")
+    same = all(math.dist(a["p0"], b["p0"]) == 0.0 and math.dist(a["p1"], b["p1"]) == 0.0
+               for a, b in zip(before, after))
+    check("VERTEX", same, "the two survivors are bit-identical, not re-solved")
+    key("ctrl+z", 1.0)
+    check("VERTEX", len(describe()["entities"]) == 1, "a second undo drops one more")
+    leave_sketch()
+
+
+def rung_feature_undo():
+    print("\nE2  undo/redo across the commit — a deleted sketch comes back exactly")
+    reset_document()
+    enter_sketch("r")
+    draw_rect(120, 80, -60, -40)
+    click(*CONFIRM_BTN, pause=1.5)
+    n0 = len(call("describe_scene")["features"])
+    check("VERTEX", n0 == 1, f"{n0} feature committed")
+    click(*TREE_ROW0, pause=0.4)
+    key("Delete", 0.8)
+    check("VERTEX", not call("describe_scene")["features"], "the tree is empty after Delete")
+    key("ctrl+z", 1.5)
+    check("VERTEX", len(call("describe_scene")["features"]) == 1, "undo brings the feature back")
+    d = reopen_sketch()
+    ls = lengths(d["entities"])
+    check("LENGTH", ls == [80.0, 80.0, 120.0, 120.0], f"and it is the same rectangle: {ls}")
+    lp = d["closed_loops"]
+    check("AREA", len(lp) == 1 and near(abs(lp[0]["area"]), 9600.0, 1e-6),
+          f"area {abs(lp[0]['area']):.6f}")
+    leave_sketch()
+    key("ctrl+y", 1.5)
+    check("VERTEX", not call("describe_scene")["features"], "redo removes it again")
+    reset_document()
+
+
+PROJECT_FILE = "/tmp/gl-roundtrip.3mf"
+
+
+def dialog_up():
+    names = sh(f"DISPLAY={DISP} xdotool search --class '.' getwindowname %@")
+    return any(n and n != "snapmaker-orca" and "file" in n.lower() for n in names.splitlines())
+
+
+def file_dialog(path, settle=5.0):
+    """Type an absolute path into the GTK file chooser that is up, and accept it."""
+    if not dialog_up():
+        die("no file chooser came up")
+    key("ctrl+a", 0.3)
+    typ(path, 0.5)
+    key("Return", settle)
+    global _win
+    _win = None            # saving renames the window; drop the cached geometry
+
+
+def rung_roundtrip():
+    print("\nE3  save and reload — the profile comes back to the last decimal")
+    reset_document()
+    enter_sketch("r")
+    draw_rect(120, 80, -60, -40)
+    key("r", 0.6); clickmm(-45, -15); clickmm(-5, 15); values(40, 30)
+    key("c", 0.6); clickmm(30, 0); clickmm(42, 0); values(10)
+    before = describe()
+    click(*CONFIRM_BTN, pause=1.5)
+    sh(f"rm -f {PROJECT_FILE}")
+    # Save AS, not Save: once a project has a path, Ctrl+S writes to it silently and no chooser
+    # appears — which is correct behaviour and a trap for a driver that assumes the dialog.
+    key("ctrl+shift+s", 3.0)
+    file_dialog(PROJECT_FILE)
+    size = sh(f"stat -c %s {PROJECT_FILE} 2>/dev/null").strip()
+    check("CLOSED", size.isdigit() and int(size) > 0, f"project written, {size} bytes")
+    reset_document()                                  # wipe the tree, then read it back off disk
+    key("ctrl+o", 2.5)
+    file_dialog(PROJECT_FILE, settle=8.0)
+    go_design()                                       # opening a project lands on Prepare
+    feats = call("describe_scene")["features"]
+    check("VERTEX", len(feats) == 1, f"the reloaded document has {len(feats)} feature(s)")
+    after = reopen_sketch()
+    b = sorted((e["type"], tuple(round(c, 12) for c in (e.get("p0") or e.get("center") or e.get("p"))),
+                round(e.get("length", e.get("radius", 0.0)), 12)) for e in before["entities"])
+    a = sorted((e["type"], tuple(round(c, 12) for c in (e.get("p0") or e.get("center") or e.get("p"))),
+                round(e.get("length", e.get("radius", 0.0)), 12)) for e in after["entities"])
+    check("VERTEX", a == b, f"{len(a)} entities identical to 12 decimals after the round trip")
+    lp = after["closed_loops"]
+    check("CLOSED", len(lp) == 3 and after["buildable"], f"{len(lp)} loops, buildable")
+    outer = max(range(len(lp)), key=lambda i: abs(lp[i]["area"]))
+    check("VOID", sorted(lp[outer]["holes"]) == sorted(i for i in range(len(lp)) if i != outer),
+          "the voids are still attributed to the outer loop")
+    check("AREA", near(abs(lp[outer]["area"]), 9600.0, 1e-9), f"outer area {abs(lp[outer]['area']):.9f}")
+    leave_sketch()
+    reset_document()
+
+
+def rung_scale():
+    print("\nE4  scale — a gesture on top of a sketch that already holds a thousand entities")
+    enter_sketch("r")
+    # The heavy profile is bulk-loaded through the socket ON PURPOSE: what is under test here is
+    # whether the interactive path still works with a large sketch already on screen, not where
+    # that sketch came from. A plate with a 20 x 15 grid of square cut-outs — 1204 entities.
+    # Sized to the region the calibration probes covered, so every part of it can actually be
+    # clicked: the camera is wherever the last rung left it, and a plate drawn off-screen would
+    # test nothing but my arithmetic.
+    x0, x1, y0, y1 = _SAFE
+    cx, cy = (x0 + x1) / 2.0, (y0 + y1) / 2.0
+    hw, hh = (x1 - x0) * 0.44, (y1 - y0) * 0.44
+    ents = [{"type": "line", "p0": [cx - hw, cy - hh], "p1": [cx + hw, cy - hh]},
+            {"type": "line", "p0": [cx + hw, cy - hh], "p1": [cx + hw, cy + hh]},
+            {"type": "line", "p0": [cx + hw, cy + hh], "p1": [cx - hw, cy + hh]},
+            {"type": "line", "p0": [cx - hw, cy + hh], "p1": [cx - hw, cy - hh]}]
+    # 300 square cut-outs in the LEFT half; the right half stays clear so the gesture below has
+    # somewhere to land that is not within snapping distance of a cut-out corner.
+    pitch_x, pitch_y = hw * 0.9 / 20.0, hh * 1.9 / 15.0
+    side = min(pitch_x, pitch_y) * 0.4
+    for i in range(20):
+        for j in range(15):
+            x = cx - hw * 0.95 + i * pitch_x
+            y = cy - hh * 0.95 + j * pitch_y
+            c = [(x, y), (x + side, y), (x + side, y + side), (x, y + side), (x, y)]
+            for k in range(4):
+                ents.append({"type": "line", "p0": list(c[k]), "p1": list(c[k + 1])})
+    t0 = time.monotonic(); call("sketch_add", entities=ents); t_add = time.monotonic() - t0
+    d0 = describe()
+    check("SCALE", len(d0["entities"]) == len(ents), f"{len(d0['entities'])} entities loaded "
+                                                     f"in {t_add*1000:.0f} ms")
+    lp0 = d0["closed_loops"]
+    check("CLOSED", len(lp0) == 301, f"{len(lp0)} closed loops")
+    outer = max(range(len(lp0)), key=lambda i: abs(lp0[i]["area"]))
+    check("AREA", near(abs(lp0[outer]["area"]), 4.0 * hw * hh, 1e-9),
+          f"outer plate {abs(lp0[outer]['area']):.9f} vs {4.0*hw*hh:.9f}")
+    check("VOID", len(lp0[outer]["holes"]) == 300,
+          f"all {len(lp0[outer]['holes'])} cut-outs attributed to the plate")
+    check("AREA", all(near(abs(lp0[h]["area"]), side * side, 1e-9) for h in lp0[outer]["holes"]),
+          f"every cut-out is exactly {side:.6f} squared")
+    # Now the part that matters: draw ONE more entity by hand, on top of all that.
+    #
+    # No Escape here, deliberately: this rung is the regression test for j7gc, where a
+    # bulk sketch_add made while a creation tool is armed was read as a drawn gesture, opened that
+    # tool's value field and swallowed the next key and click until one Escape dismissed it. The
+    # gesture below has to land on the FIRST try. Fixed by resyncing m_autoedit_seen in
+    # add_entities_scripted; if this rung ever needs an Escape again, the bug is back.
+    key("l", 0.8)
+    global PACE
+    PACE = 6.0                                     # a thousand entities re-solve between fields
+    t0 = time.monotonic()
+    ax, ay = cx + hw * 0.15, cy + hh * 0.55        # clear of the grid, inside the plate
+    want_len = int(hw * 0.5)                       # a WHOLE number: see value() on separators
+    clickmm(ax, ay); clickmm(ax + want_len, ay)
+    value(want_len)
+    dl = describe()
+    say(f"after the typed length: solve_ok={dl['solve_ok']} constraints={dl['constraints']} "
+        f"dof={dl['dof']} entities={len(dl['entities'])}")
+    value(0)
+    t_draw = time.monotonic() - t0
+    d = describe()
+    check("SCALE", len(d["entities"]) == len(ents) + 1,
+          f"the gesture added exactly one entity ({t_draw:.1f} s including four synthetic events)")
+    new = d["entities"][-1]
+    check("LENGTH", near(new["length"], float(want_len), 1e-9),
+          f"and it took its typed length exactly: {new['length']}")
+    ang = math.degrees(math.atan2(new["p1"][1] - new["p0"][1], new["p1"][0] - new["p0"][0])) % 360.0
+    check("ANGLE", near(ang, 0.0, 1e-9) or near(ang, 360.0, 1e-9), f"and its typed angle: {ang}")
+    same = all(math.dist(a["p0"], b["p0"]) == 0.0 and math.dist(a["p1"], b["p1"]) == 0.0
+               for a, b in zip(d0["entities"], d["entities"]))
+    check("VERTEX", same, "and moved none of the thousand entities already there")
+    PACE = 1.0
+    leave_sketch()
+
+
+def reopen_sketch():
+    w, X, Y, _, _ = win()
+    sh(f"DISPLAY={DISP} xdotool mousemove {X+TREE_ROW0[0]} {Y+TREE_ROW0[1]} "
+       f"click --repeat 2 --delay 120 1")
+    time.sleep(2.0)
+    return describe()
+
+
+def rung_mirror_arcs():
+    """C4b — mirror a shape that HAS ARCS. The rung above mirrors three straight lines, which is
+    why it sat green through the defect a user hit on 2026-08-23: a slot mirrored about a vertical
+    line came back with its caps at r=32.2 and a 237 deg sweep, one rail collapsed from 62.9 mm to
+    2.1 mm, and the ORIGINAL was wrecked along with the copy. An arc has five degrees of freedom
+    and the copy was bound to its source by its CENTRE alone, so the solver was free to answer with
+    a different, internally consistent sketch. Circles were unaffected — a circle has no endpoints
+    to leave free — so the failure read as "circles fine, slots and rounded rectangles destroyed".
+
+    Graded on the property the user actually stated: THE APPLIED RESULT IS THE PREVIEW. The copy is
+    the source reflected, the source does not move, and no arc comes back reflex.
+    """
+    print("\nC4b mirror — a slot, so the reflection has arcs in it")
+    enter_sketch("l")
+    click(*CONSTRUCTION_CHECKBOX)
+    key("l", 0.6)
+    draw_line(0, -40, 0, 40, 80, 90)                 # the axis, on x = 0
+    click(*CONSTRUCTION_CHECKBOX)
+    key("s", 0.6)                                    # slot: two centreline ends, then the width
+    clickmm(-70, -10); clickmm(-30, -10); clickmm(-30, 0)
+    values(40, 10, 0)                                # typed, so the slot is exact before mirroring
+    d0 = describe()["entities"]
+    axis = [e for e in d0 if e.get("construction")][0]
+    slot = [e for e in d0 if not e.get("construction")]
+    arcs0 = [e for e in slot if e["type"] == "arc"]
+    check("ARC", len(arcs0) == 2, f"{len(arcs0)} caps on the slot")
+
+    key("m", 0.6)
+    clickmm(*mid(axis))
+    for e in slot:
+        if e["type"] == "line":
+            clickmm(*mid(e))
+        else:                                        # a point ON the arc, at its mid sweep
+            a = (e["start_angle"] + e["end_angle"]) / 2.0
+            clickmm(e["center"][0] + e["radius"] * math.cos(a),
+                    e["center"][1] + e["radius"] * math.sin(a))
+    clickmm(60, 60)                                  # empty space confirms
+    d1 = describe()["entities"]
+    check("VERTEX", len(d1) == len(d0) + len(slot),
+          f"{len(d1) - len(d0)} copies for {len(slot)} picked entities")
+
+    # the sources, entity by entity, must be exactly where they were
+    def shape_of(e):
+        if e["type"] == "arc":
+            return (round(e["radius"], 9), round(abs(e["end_angle"] - e["start_angle"]), 9))
+        return (round(math.dist(e["p0"], e["p1"]), 9),)
+    moved = [i for i, e in enumerate(d0) if shape_of(e) != shape_of(d1[i])]
+    check("VERTEX", not moved, f"the mirror left every source alone (moved: {moved})")
+
+    # and every copy is its source reflected — endpoints unordered, because a reflection
+    # reverses orientation and legitimately stores p0/p1 the other way round
+    (ax, ay), (bx, by) = axis["p0"], axis["p1"]
+    dx, dy = bx - ax, by - ay
+    n = math.hypot(dx, dy); dx, dy = dx / n, dy / n
+    def refl(q):
+        vx, vy = q[0] - ax, q[1] - ay
+        k = 2.0 * (vx * dx + vy * dy)
+        return (ax + k * dx - vx, ay + k * dy - vy)
+    copies = d1[len(d0):]
+    worst = 0.0
+    for e in slot:
+        best = min(max(min(max(math.dist(refl(e["p0"]), c["p0"]), math.dist(refl(e["p1"]), c["p1"])),
+                           max(math.dist(refl(e["p0"]), c["p1"]), math.dist(refl(e["p1"]), c["p0"]))),
+                       abs(shape_of(e)[0] - shape_of(c)[0]))
+                   for c in copies if c["type"] == e["type"])
+        worst = max(worst, best)
+    check("SYMMETRY", worst <= 1e-6, f"every copy is the exact reflection (worst {worst:.9f})")
+    reflex = [c for c in copies
+              if c["type"] == "arc" and abs(c["end_angle"] - c["start_angle"]) > math.pi + 1e-9]
+    check("ARC", not reflex, f"{len(reflex)} copied cap(s) came back reflex — the 'cloud' failure")
+
+
+RUNGS = {"rect": rung_rect, "circle": rung_circle, "line": rung_line, "arc": rung_arc,
+         "slot": rung_slot, "polygon": rung_polygon, "ellipse": rung_ellipse,
+         "point": rung_point, "spline": rung_spline, "voids": rung_voids,
+         "fillet": rung_fillet, "chamfer": rung_chamfer, "offset": rung_offset,
+         "mirror": rung_mirror, "mirror_arcs": rung_mirror_arcs, "trim": rung_trim, "extend": rung_extend,
+         "dimension": rung_dimension, "constrain": rung_constrain,
+         "perpendicular": rung_perpendicular,
+         "equal_radius": rung_equal_radius, "collinear": rung_collinear,
+         "distance_xy": rung_distance_xy, "symmetric_axis": rung_symmetric_axis,
+         "coincident_points": rung_coincident_points,
+         "type_guards": rung_type_guards,
+         "parallel": rung_parallel, "live_constrain": rung_live_constrain,
+         "vertical": rung_vertical, "equal_radius_button": rung_equal_radius_button,
+         "concentric": rung_concentric, "tangent": rung_tangent, "midpoint": rung_midpoint,
+         "symmetric_line_axis": rung_symmetric_line_axis, "symmetric_h": rung_symmetric_h,
+         "radius": rung_radius, "diameter": rung_diameter, "fix": rung_fix,
+         "distance_y": rung_distance_y,
+         "undo": rung_undo,
+         "feature_undo": rung_feature_undo, "roundtrip": rung_roundtrip,
+         "scale": rung_scale}
+
+
+def main():
+    want = sys.argv[1:] or list(RUNGS)
+    reset_document()
+    for name in want:
+        if name not in RUNGS:
+            die(f"unknown rung {name}; have {' '.join(RUNGS)}")
+        RUNGS[name]()
+    leave_sketch()
+    print(f"\n{_checks - _fail}/{_checks} properties held")
+    sys.exit(1 if _fail else 0)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/scripts/CAD/check-mcp-sketch.py b/scripts/CAD/check-mcp-sketch.py
new file mode 100755
index 0000000000..2e700921f5
--- /dev/null
+++ b/scripts/CAD/check-mcp-sketch.py
@@ -0,0 +1,132 @@
+#!/usr/bin/env python3
+"""Autonomous 2D-sketch loop: drive the Design tab's sketch layer over the MCP socket and
+assert the things that decide whether a profile is buildable.
+
+WHY THIS EXISTS. The 2D layer used to be reachable only by clicking, so every question about it
+("is this loop closed?", "did the offset survive?", "is the circle a void or a second body?")
+cost a GUI session and a human. The socket verbs make each one a call, and this script is the
+loop: build a known profile, ask the app what it thinks it has, compare against arithmetic.
+
+RUN IT AGAINST A RUNNING APP:
+    ORCA_CAD_MCP=/tmp/mcp.sock <binary>          # launch with the socket enabled
+    python3 scripts/CAD/check-mcp-sketch.py [socket] # default /tmp/mcp.sock
+
+Exit 0 = every assertion held. Anything else prints the first mismatch and stops.
+"""
+import json, math, socket, sys
+
+SOCK = sys.argv[1] if len(sys.argv) > 1 else "/tmp/mcp.sock"
+_n = 0
+
+
+def call(method, **params):
+    global _n
+    _n += 1
+    s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    s.settimeout(30)
+    s.connect(SOCK)
+    s.sendall((json.dumps({"jsonrpc": "2.0", "id": _n, "method": method,
+                           "params": params}) + "\n").encode())
+    buf = b""
+    while b"\n" not in buf:
+        d = s.recv(65536)
+        if not d:
+            break
+        buf += d
+    r = json.loads(buf.decode().strip())
+    if "error" in r:
+        raise RuntimeError(f"{method}: {r['error']}")
+    return r["result"]
+
+
+def near(a, b, tol=1e-6):
+    return abs(a - b) < tol
+
+
+def check(cond, what):
+    if not cond:
+        print(f"FAIL: {what}", file=sys.stderr)
+        sys.exit(1)
+    print(f"  ok  {what}")
+
+
+def areas(rep):
+    return sorted(round(l["area"], 6) for l in rep["closed_loops"])
+
+
+print("1. a rectangle is one closed loop of exactly its own area")
+try:
+    call("sketch_cancel")
+except Exception:
+    pass
+call("sketch_begin", plane="XY")
+call("sketch_add", rect=[0, 0, 80, 50])
+r = call("sketch_describe")
+check(r["buildable"], "buildable")
+check(areas(r) == [4000.0], f"one loop of 4000 mm^2 (got {areas(r)})")
+
+print("2. a circle inside it is a VOID, not a second profile")
+call("sketch_add", type="circle", center=[40, 25], radius=10)
+r = call("sketch_describe")
+outer = [l for l in r["closed_loops"] if near(l["area"], 4000.0)][0]
+check(len(outer["holes"]) == 1, "the rectangle encloses exactly one void")
+hole = r["closed_loops"][outer["holes"][0]]
+check(near(hole["area"], math.pi * 100), f"the void is pi*r^2 (got {hole['area']})")
+
+print("3. offsetting the outer loop inward keeps it CLOSED and exact")
+call("sketch_select", entities=[0, 1, 2, 3])
+call("sketch_offset", distance=5)
+r = call("sketch_describe")
+check(r["open_ends"] == [], "no open ends after the offset")
+check(any(near(l["area"], 70 * 40) for l in r["closed_loops"]),
+      f"the offset loop is 70x40 (got {areas(r)})")
+
+print("4. a gap is REPORTED with its coordinates, then healed into a constraint")
+call("sketch_cancel")
+call("sketch_begin", plane="XY")
+call("sketch_add", entities=[
+    {"type": "line", "p0": [0, 0], "p1": [60, 0]},
+    {"type": "line", "p0": [60, 0], "p1": [60, 40]},
+    {"type": "line", "p0": [60, 40], "p1": [0, 40]},
+    {"type": "line", "p0": [0, 40], "p1": [0.4, 0]},   # 0.4 mm short of closing
+])
+r = call("sketch_validate", tolerance=1.0)
+check(not r["buildable"], "a 0.4 mm gap makes the profile unbuildable")
+check(len(r["open_ends"]) == 2, f"both free ends are named (got {r['open_ends']})")
+dof_before = r["dof"]
+r = call("sketch_heal", tolerance=1.0)
+check(r["welded"] == 1, f"one pair welded (got {r['welded']})")
+check(r["buildable"] and r["open_ends"] == [], "healed profile is buildable")
+check(areas(r) == [2400.0], f"healed loop is 60x40 (got {areas(r)})")
+check(r["dof"] < dof_before,
+      f"the weld recorded a real constraint: DoF {dof_before} -> {r['dof']}")
+
+print("5. construction geometry is excluded from the profile")
+call("sketch_select", entities=[0])
+call("sketch_construction")
+r = call("sketch_describe")
+check(not r["buildable"], "turning one side into a guide opens the profile again")
+call("sketch_construction")
+r = call("sketch_describe")
+check(r["buildable"], "turning it back closes it again")
+
+print("6. re-dimensioning one side keeps the rectangle a single closed loop")
+call("sketch_cancel")
+call("sketch_begin", plane="XY")
+call("sketch_add", rect=[0, 0, 60, 40])
+r = call("sketch_describe")
+check(areas(r) == [2400.0], f"one loop of 2400 mm^2 (got {areas(r)})")
+call("sketch_select", entities=[0])   # the bottom edge, y=0, from x=0 to x=60
+r = call("sketch_set_value", value=40)
+check(r["kind"] == "length", f"dimension kind is length (got {r['kind']})")
+check(near(r["before"], 60), f"the edge measured 60 before (got {r['before']})")
+r = call("sketch_describe")
+check(len(r["closed_loops"]) == 1, "the rectangle is still exactly one closed loop")
+check(r["open_ends"] == [], "no open ends after re-dimensioning")
+# The point of the whole section: a rectangle must SURVIVE one side being re-dimensioned. We do
+# not assert a specific area — only that the topology held — but print it so a topology-preserving
+# yet geometry-wrong result is visible in the output.
+print(f"  note  resulting rectangle area = {areas(r)} mm^2 (topology held; geometry is what it is)")
+
+call("sketch_cancel")
+print("\nall sketch assertions held")
diff --git a/scripts/CAD/check-sketch-engine-corpus.py b/scripts/CAD/check-sketch-engine-corpus.py
new file mode 100644
index 0000000000..20eca5d381
--- /dev/null
+++ b/scripts/CAD/check-sketch-engine-corpus.py
@@ -0,0 +1,492 @@
+#!/usr/bin/env python3
+"""Rung 9: the ladder, graded against real drawings instead of shapes I chose.
+
+Rungs 1-8 are hand-built. That is their weakness: I wrote both the geometry and the
+assertion, so they prove the engine does what I expected on cases I picked. This rung
+takes a SYSTEMATIC sample of the StudyCadCam corpus (every 20th sheet, 1..996 — no
+cherry-picking) and grades the engine against each drawing's OWN vector geometry,
+extracted from the PDF. Nothing here is transcribed by eye; the drawing is the input.
+
+The method: pdftocairo renders the sheet to SVG, where the drawn geometry is exactly the
+stroked (fill="none") paths and the text is filled glyph paths. Beziers are flattened, so
+every entity handed to the engine is a straight line and every comparison below is EXACT
+— no faceting tolerance to hide behind. The closed chains are then found twice: once by
+this script, in plain Python, and once by the engine. The assertions are that the two
+agree, and that the engine's own operations preserve what they promise.
+
+  CLOSED    the engine finds the same closed loops this script does
+  AREA      the engine's area for each loop equals the shoelace area, to 1e-6
+  VOID      the engine attributes each void to the loop that actually contains it
+  MIRROR    a real closed profile, mirrored, is still exactly one closed loop
+  OFFSET    a real closed profile, offset, is still closed
+
+Usage:  check-sketch-engine-corpus.py [--sample N] [--corpus DIR]
+"""
+
+import argparse
+import glob
+import json
+import math
+import os
+import re
+import socket
+import subprocess
+import sys
+import tempfile
+import time
+
+SOCK = os.environ.get("ORCA_CAD_MCP", "/tmp/mcp.sock")
+TOL = 1e-6          # exact-comparison tolerance (all inputs are lines)
+WELD = 0.05         # endpoint-coincidence tolerance, in PDF units
+
+
+# ── the socket ───────────────────────────────────────────────────────────────
+_id = [0]
+
+
+def try_call(method, **params):
+    """sketch_cancel throws when nothing is open, which is not an error to us."""
+    try:
+        return call(method, **params)
+    except RuntimeError:
+        return None
+
+
+def call(method, **params):
+    _id[0] += 1
+    req = json.dumps({"jsonrpc": "2.0", "id": _id[0], "method": method,
+                      "params": params}) + "\n"
+    s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    s.settimeout(30)
+    s.connect(SOCK)
+    s.sendall(req.encode())
+    buf = b""
+    while not buf.endswith(b"\n"):
+        chunk = s.recv(65536)
+        if not chunk:
+            break
+        buf += chunk
+    s.close()
+    r = json.loads(buf.decode())
+    if "error" in r:
+        raise RuntimeError(r["error"]["message"])
+    return r["result"]
+
+
+# ── SVG → line segments ──────────────────────────────────────────────────────
+NUM = r"[-+]?[0-9]*\.?[0-9]+(?:[eE][-+]?[0-9]+)?"
+
+
+def bezier(p0, p1, p2, p3, n=16):
+    """Flatten a cubic to n straight segments — the engine then sees only lines."""
+    out = []
+    for i in range(n):
+        t0, t1 = i / n, (i + 1) / n
+        pts = []
+        for t in (t0, t1):
+            u = 1 - t
+            x = (u ** 3 * p0[0] + 3 * u * u * t * p1[0]
+                 + 3 * u * t * t * p2[0] + t ** 3 * p3[0])
+            y = (u ** 3 * p0[1] + 3 * u * u * t * p1[1]
+                 + 3 * u * t * t * p2[1] + t ** 3 * p3[1])
+            pts.append((x, y))
+        out.append((pts[0], pts[1]))
+    return out
+
+
+def path_segments(d):
+    """Parse one SVG path's `d` into straight segments."""
+    toks = re.findall(r"([MLCZmlcz])|(" + NUM + ")", d)
+    cmds, cur, start, segs, i = [], None, None, [], 0
+    flat = []
+    for a, b in toks:
+        flat.append(a if a else float(b))
+    while i < len(flat):
+        t = flat[i]
+        if isinstance(t, str):
+            cmd = t
+            i += 1
+        # numbers repeat the previous command, as SVG allows
+        if cmd in ("M", "m"):
+            x, y = flat[i], flat[i + 1]; i += 2
+            cur = (x, y); start = cur
+        elif cmd in ("L", "l"):
+            x, y = flat[i], flat[i + 1]; i += 2
+            segs.append((cur, (x, y))); cur = (x, y)
+        elif cmd in ("C", "c"):
+            p1 = (flat[i], flat[i + 1]); p2 = (flat[i + 2], flat[i + 3])
+            p3 = (flat[i + 4], flat[i + 5]); i += 6
+            segs.extend(bezier(cur, p1, p2, p3)); cur = p3
+        elif cmd in ("Z", "z"):
+            if cur and start and dist(cur, start) > TOL:
+                segs.append((cur, start))
+            cur = start
+        else:
+            i += 1
+    return segs
+
+
+def dist(a, b):
+    return math.hypot(a[0] - b[0], a[1] - b[1])
+
+
+def drawing_segments(pdf):
+    """Every stroked segment on the sheet, in PDF units (y already flipped up)."""
+    with tempfile.TemporaryDirectory() as td:
+        svg = os.path.join(td, "p.svg")
+        subprocess.run(["pdftocairo", "-svg", pdf, svg],
+                       check=True, capture_output=True)
+        s = open(svg).read()
+    segs = []
+    # Drawn geometry is stroked with no fill; glyphs are filled with no stroke.
+    for m in re.finditer(r'<path([^>]*)d="([^"]+)"', s):
+        attrs, d = m.group(1), m.group(2)
+        if 'fill="none"' not in attrs or "stroke=" not in attrs:
+            continue
+        segs.extend(path_segments(d))
+    return [((a[0], -a[1]), (b[0], -b[1])) for a, b in segs if dist(a, b) > TOL]
+
+
+# ── closed-chain finding, independent of the engine ──────────────────────────
+def find_loops(segs):
+    """Chain segments into closed loops. Returns a list of point rings."""
+    key = lambda p: (round(p[0] / WELD), round(p[1] / WELD))
+    adj = {}
+    for i, (a, b) in enumerate(segs):
+        adj.setdefault(key(a), []).append((i, a, b))
+        adj.setdefault(key(b), []).append((i, b, a))
+    used, loops = set(), []
+    for i0 in range(len(segs)):
+        if i0 in used:
+            continue
+        a, b = segs[i0]
+        ring, cur, prev = [a, b], b, i0
+        used.add(i0)
+        while True:
+            nxt = None
+            for (j, p, q) in adj.get(key(cur), []):
+                if j in used:
+                    continue
+                nxt = (j, q)
+                break
+            if nxt is None:
+                break
+            used.add(nxt[0])
+            cur = nxt[1]
+            ring.append(cur)
+            if dist(cur, ring[0]) <= WELD:
+                # Snap the seam shut. The gap is a flattening artefact of the PDF, up to
+                # WELD wide, and handing the engine a ring that misses closing by 0.03 would
+                # be testing my extractor's sloppiness rather than the engine's chaining.
+                ring[-1] = ring[0]
+                loops.append(ring)
+                ring = None
+                break
+        # an open chain is simply not a loop; it is dropped
+    return loops
+
+
+def shoelace(ring):
+    a = 0.0
+    for i in range(len(ring) - 1):
+        a += ring[i][0] * ring[i + 1][1] - ring[i + 1][0] * ring[i][1]
+    return abs(a) * 0.5
+
+
+def point_in(pt, ring):
+    inside = False
+    for i in range(len(ring) - 1):
+        A, B = ring[i], ring[i + 1]
+        if (A[1] > pt[1]) != (B[1] > pt[1]) and \
+           pt[0] < (B[0] - A[0]) * (pt[1] - A[1]) / (B[1] - A[1]) + A[0]:
+            inside = not inside
+    return inside
+
+
+def interior_point(ring):
+    """A point strictly inside a simple closed ring (first == last).
+
+    The lowest vertex of a simple polygon is always convex, so stepping from it along the
+    bisector of its two edges goes inward; the step is a small fraction of the shorter edge so
+    it stays inside however sharp the corner is.
+    """
+    q = ring[:-1] if len(ring) > 1 and ring[0] == ring[-1] else ring
+    if len(q) < 3:
+        return ring[0]
+    k = min(range(len(q)), key=lambda i: (q[i][1], q[i][0]))
+    v = q[k]
+    a = (q[(k - 1) % len(q)][0] - v[0], q[(k - 1) % len(q)][1] - v[1])
+    b = (q[(k + 1) % len(q)][0] - v[0], q[(k + 1) % len(q)][1] - v[1])
+    la, lb = math.hypot(*a), math.hypot(*b)
+    if la < 1e-12 or lb < 1e-12:
+        return v
+    a = (a[0] / la, a[1] / la)
+    b = (b[0] / lb, b[1] / lb)
+    bx, by = a[0] + b[0], a[1] + b[1]
+    n = math.hypot(bx, by)
+    if n < 1e-12:
+        return v
+    step = 1e-3 * min(la, lb)
+    return (v[0] + bx / n * step, v[1] + by / n * step)
+
+
+# ── one drawing ──────────────────────────────────────────────────────────────
+def grade(pdf, name, report):
+    segs = drawing_segments(pdf)
+    loops = find_loops(segs)
+    if len(loops) < 2:
+        report(name, "SKIP", f"no nested closed geometry found ({len(loops)} loops)")
+        return None
+
+    # The biggest loop is the sheet frame; the part outlines live inside it. Take the
+    # largest loop that is NOT the frame, plus every loop contained in it.
+    loops.sort(key=shoelace, reverse=True)
+    outer = loops[1]
+    voids = [r for r in loops[2:]
+             if shoelace(r) > 1.0 and point_in(r[0], outer)]
+    if shoelace(outer) < 100.0:
+        # Not a defect and not a near miss: on these sheets the part outline is not a closed
+        # stroked path at all, so the only loops extraction recovers are glyph counters and
+        # arrowheads. Measured on MPD12/30/31/60: the LARGEST loop on the sheet is 5 to 132 mm2.
+        # Say the number, so nobody has to re-measure to know which kind of skip this is.
+        report(name, "SKIP", f"no part outline on this sheet — largest loop is only "
+                             f"{shoelace(outer):.1f} mm2")
+        return None
+
+    # Feed the drawing's own geometry to the engine, as lines only.
+    ents = []
+    rings = [outer] + voids
+    for ring in rings:
+        for i in range(len(ring) - 1):
+            ents.append({"type": "line",
+                         "p0": [ring[i][0], ring[i][1]],
+                         "p1": [ring[i + 1][0], ring[i + 1][1]]})
+    try_call("sketch_cancel")
+    call("sketch_begin", plane="XY")
+    call("sketch_add", entities=ents)
+    r = call("sketch_describe")
+
+    ok = True
+    got = r["closed_loops"]
+    ok &= report(name, "CLOSED", f"engine finds {len(got)} closed loops, this script "
+                                f"finds {len(rings)}", len(got) == len(rings))
+
+    # AREA — exact, because every entity is a line
+    mine = sorted(shoelace(x) for x in rings)
+    theirs = sorted(abs(l["area"]) for l in got)
+    # The bar: 1e-3 absolute, or 1e-6 relative for the big loops. Not bit-exactness — the
+    # auto-constraint pass still snaps segments that are already axis-aligned to within its
+    # 1e-4 rad tolerance, which moves an area by ~1e-4. It is deliberately tight enough to
+    # have caught the real defect this rung was written for: with the old 3 degree gesture
+    # slack applied to scripted input, a flattened circle came back 0.067% small — 0.266 on
+    # an area of 397, some 300x above this line.
+    same = len(mine) == len(theirs) and all(
+        abs(a - b) <= max(1e-3, 1e-6 * a) for a, b in zip(mine, theirs))
+    ok &= report(name, "AREA", "every loop area matches the shoelace value exactly", same)
+
+    # VOID — a loop belongs to the SMALLEST loop that contains it, not to every loop that
+    # encloses it. A hole inside a boss inside the part is a void of the boss, and the part
+    # owns the boss. Comparing against "everything inside the outline" was measuring my own
+    # sloppiness: on MPD781 that counted 36 voids where 26 of them are nested inside another
+    # void. So compute the same rule here, independently, and compare the whole attribution.
+    if got:
+        rings = [outer] + voids
+        # Probe from a point STRICTLY INSIDE each ring, never from one of its vertices — the
+        # same rule the engine now uses (DesignSketchTool::region_loops). A vertex is exactly
+        # where two loops touch in a real drawing, and a ray cast from a point lying ON the
+        # polygon under test answers by rounding: that alone accounted for every one of the 6
+        # sheets where the two attributions used to disagree. 5hvl.
+        probes = [interior_point(r) for r in rings]
+        mine_parent = {}
+        for i, r in enumerate(rings):
+            best, best_a = -1, 0.0
+            for j, q in enumerate(rings):
+                if i == j or not point_in(probes[i], q):
+                    continue
+                a = shoelace(q)
+                if best < 0 or a < best_a:
+                    best, best_a = j, a
+            if best >= 0:
+                mine_parent.setdefault(best, []).append(i)
+        big = max(range(len(got)), key=lambda i: abs(got[i]["area"]))
+        # match engine loops to my rings by area, then compare the two attributions by COUNT
+        mine_counts = sorted(len(v) for v in mine_parent.values())
+        got_counts = sorted(len(l["holes"]) for l in got if l["holes"])
+        ok &= report(name, "VOID",
+                     f"void attribution matches: engine {got_counts}, containment "
+                     f"{mine_counts}", got_counts == mine_counts)
+
+    # MIRROR / OFFSET — engine operations on a REAL profile, not a tidy one
+    n_outer = len(outer) - 1
+    try_call("sketch_cancel")
+    call("sketch_begin", plane="XY")
+    call("sketch_add", entities=ents[:n_outer])
+    xs = [p[0] for p in outer]
+    axis = min(xs) - 10.0
+    call("sketch_select", entities=list(range(n_outer)))
+    try:
+        call("sketch_mirror", axis_a=[axis, 0], axis_b=[axis, 1])
+        m = call("sketch_describe")
+        ok &= report(name, "MIRROR", "the mirrored copy is closed too",
+                     len(m["closed_loops"]) == 2 and m["open_ends"] == [])
+    except RuntimeError as e:
+        ok &= report(name, "MIRROR", f"refused: {e}", False)
+
+    try_call("sketch_cancel")
+    call("sketch_begin", plane="XY")
+    call("sketch_add", entities=ents[:n_outer])
+    try:
+        call("sketch_offset", distance=0.5, entities=list(range(n_outer)))
+        o = call("sketch_describe")
+        ok &= report(name, "OFFSET", "the offset profile is still closed",
+                     any(l["closed"] for l in o["closed_loops"]))
+    except RuntimeError as e:
+        ok &= report(name, "OFFSET", f"refused: {e}", False)
+    return ok
+
+
+# ── scale ────────────────────────────────────────────────────────────────────
+def grade_scale(pdf, name, report, budget):
+    """Same exactness, on a profile of several hundred entities, and timed.
+
+    "Interactive" is measurable from here even though nothing is clicked: every MCP verb is
+    serviced on the UI THREAD, so the time a reply takes is time the window was not repainting.
+    A round trip that stays inside the budget is a window that stayed responsive.
+    """
+    segs = drawing_segments(pdf)
+    loops = find_loops(segs)
+    if len(loops) < 2:
+        report(name, "SKIP", f"no nested closed geometry found ({len(loops)} loops)")
+        return None
+    loops.sort(key=shoelace, reverse=True)
+    outer = loops[1]
+    voids = [r for r in loops[2:] if shoelace(r) > 1.0 and point_in(r[0], outer)]
+    rings = [outer] + voids
+    ents = []
+    for ring in rings:
+        for i in range(len(ring) - 1):
+            ents.append({"type": "line",
+                         "p0": [ring[i][0], ring[i][1]],
+                         "p1": [ring[i + 1][0], ring[i + 1][1]]})
+    if len(ents) < 300:
+        report(name, "SKIP", f"only {len(ents)} entities — not a scale case")
+        return None
+
+    try_call("sketch_cancel")
+    call("sketch_begin", plane="XY")
+    t0 = time.monotonic(); call("sketch_add", entities=ents);  t_add = time.monotonic() - t0
+    t0 = time.monotonic(); r = call("sketch_describe");        t_desc = time.monotonic() - t0
+    t0 = time.monotonic(); call("sketch_select", entities=list(range(len(ents))))
+    t_sel = time.monotonic() - t0
+    t0 = time.monotonic(); call("sketch_validate");            t_val = time.monotonic() - t0
+
+    ok = True
+    ok &= report(name, "SCALE", f"{len(ents)} entities in {len(rings)} loops", True)
+    got = r["closed_loops"]
+    ok &= report(name, "CLOSED", f"engine finds {len(got)} closed loops, this script "
+                                 f"finds {len(rings)}", len(got) == len(rings))
+    mine = sorted(shoelace(x) for x in rings)
+    theirs = sorted(abs(l["area"]) for l in got)
+    same = len(mine) == len(theirs) and all(
+        abs(a - b) <= max(1e-3, 1e-6 * a) for a, b in zip(mine, theirs))
+    ok &= report(name, "AREA", "every loop area matches the shoelace value exactly", same)
+    worst = max(t_add, t_desc, t_sel, t_val)
+    ok &= report(name, "TIME", f"add {t_add*1000:.0f} ms, describe {t_desc*1000:.0f} ms, "
+                               f"select {t_sel*1000:.0f} ms, validate {t_val*1000:.0f} ms "
+                               f"(budget {budget*1000:.0f} ms)", worst <= budget)
+    return ok
+
+
+def _pdf_error(path):
+    """What poppler says about a file it refused, so a refusal can be classified."""
+    r = subprocess.run(["pdfinfo", path], capture_output=True, text=True)
+    return (r.stderr or "") + (r.stdout or "")
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--corpus", default=os.path.expanduser("~/studycadcam"))
+    ap.add_argument("--step", type=int, default=20)
+    ap.add_argument("--limit", type=int, default=0)
+    ap.add_argument("--scale", action="store_true",
+                    help="grade the LARGEST drawings instead: exactness plus a UI-thread budget")
+    ap.add_argument("--budget", type=float, default=2.0,
+                    help="seconds; the slowest round trip a scale drawing may take")
+    a = ap.parse_args()
+
+    files = {}
+    for f in glob.glob(os.path.join(a.corpus, "MPD*.pdf")):
+        m = re.search(r"MPD(\d+)", os.path.basename(f))
+        if m:
+            files[int(m.group(1))] = f
+    # step 1 means EVERY sheet. Written as `n % step == 1` it silently selected nothing, because
+    # n % 1 is always 0 — and the run then printed "RUNG 9 HELD" over zero drawings graded. A
+    # gate that passes by grading nothing is worse than no gate, so the count is checked below.
+    picks = [files[n] for n in sorted(files) if a.step <= 1 or n % a.step == 1]
+    if a.scale:
+        # The heaviest real profiles in the corpus, biggest first — up to ~1300 entities.
+        sized = []
+        for f in files.values():
+            try:
+                segs = drawing_segments(f)
+                loops = find_loops(segs)
+                if len(loops) < 2:
+                    continue
+                loops.sort(key=shoelace, reverse=True)
+                outer = loops[1]
+                voids = [r for r in loops[2:] if shoelace(r) > 1.0 and point_in(r[0], outer)]
+                sized.append((sum(len(r) - 1 for r in [outer] + voids), f))
+            except Exception:                        # noqa: BLE001
+                continue
+        sized.sort(reverse=True)
+        picks = [f for _, f in sized[:max(1, a.limit or 6)]]
+    elif a.limit:
+        picks = picks[:a.limit]
+    print(f"corpus: {len(files)} sheets;  systematic sample every {a.step}th "
+          f"-> {len(picks)} drawings\n")
+
+    fails, results = [], []
+
+    def report(name, tag, msg, cond=True):
+        if tag == "SKIP":
+            print(f"  {name:9s} SKIP    {msg}")
+            return True
+        mark = "ok  " if cond else "FAIL"
+        print(f"  {name:9s} {tag:8s} {mark}  {msg}")
+        if not cond:
+            fails.append(f"{name} {tag}: {msg}")
+        return cond
+
+    for f in picks:
+        name = re.search(r"MPD\d+", os.path.basename(f)).group(0)
+        try:
+            r = (grade_scale(f, name, report, a.budget) if a.scale
+                 else grade(f, name, report))
+            if r is not None:
+                results.append((name, r))
+        except Exception as e:                       # noqa: BLE001
+            # An unreadable SOURCE file is not a grading failure. MPD133 of this corpus is
+            # password-protected, and pdftocairo says so on stderr while exiting non-zero;
+            # reporting that as ERROR made one encrypted sheet look like an engine defect.
+            if "password" in _pdf_error(f).lower():
+                report(name, "SKIP", "the PDF is password-protected — nothing to extract")
+            else:
+                report(name, "ERROR", str(e)[:120], False)
+
+    graded = len(results)
+    passed = sum(1 for _, r in results if r)
+    if graded == 0:
+        print("\nNOTHING WAS GRADED — that is a harness failure, not a clean run", file=sys.stderr)
+        sys.exit(2)
+    print(f"\ngraded {graded} drawings; {passed} fully clean, {graded - passed} with "
+          f"at least one failure")
+    if fails:
+        print("\nfailures:")
+        for x in fails:
+            print("  " + x)
+        sys.exit(1)
+    print("\nRUNG 9 HELD — the engine agrees with the drawings, not with me")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/scripts/CAD/check-sketch-engine.py b/scripts/CAD/check-sketch-engine.py
new file mode 100755
index 0000000000..56fee44568
--- /dev/null
+++ b/scripts/CAD/check-sketch-engine.py
@@ -0,0 +1,352 @@
+#!/usr/bin/env python3
+"""A ladder of 2D sketches of increasing complexity, judged the way a person judges them.
+
+WHY NOT AREA. Area is derived and no one can confirm it by looking. What a human checks at a
+glance, and can be exactly right or exactly wrong about, is:
+
+    VERTEX    is the corner where I said it is
+    LENGTH    is the side the length I gave it
+    ARC       is the radius the radius I gave it
+    TANGENT   does the straight run into the curve smoothly, or is there a kink
+    SYMMETRY  is the mirrored half the exact reflection of the half I drew
+    CLOSED    is it one closed loop, or does it just look like one
+
+Every rung asserts those. Area appears only as a cross-check, never as the verdict.
+
+Entirely 2D: sketch entities only, no extrude, revolve or any solid feature.
+
+    ORCA_CAD_MCP=/tmp/mcp.sock <binary>
+    python3 scripts/CAD/check-sketch-engine.py [socket]
+
+Exit 0 = every rung held. Otherwise the first broken property is named and the run stops.
+"""
+import json, math, socket, sys
+
+SOCK = sys.argv[1] if len(sys.argv) > 1 else "/tmp/mcp.sock"
+EPS = 1e-9
+_n = 0
+_fail = 0
+
+
+def call(method, **params):
+    global _n
+    _n += 1
+    s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    s.settimeout(30)
+    s.connect(SOCK)
+    s.sendall((json.dumps({"jsonrpc": "2.0", "id": _n, "method": method,
+                           "params": params}) + "\n").encode())
+    buf = b""
+    while b"\n" not in buf:
+        d = s.recv(65536)
+        if not d:
+            break
+        buf += d
+    r = json.loads(buf.decode().strip())
+    if "error" in r:
+        raise RuntimeError(f"{method}: {r['error']['message']}")
+    return r["result"]
+
+
+def check(kind, cond, what):
+    global _fail
+    if cond:
+        print(f"    {kind:9s} ok    {what}")
+    else:
+        print(f"    {kind:9s} FAIL  {what}", file=sys.stderr)
+        _fail += 1
+
+
+def near(a, b, tol=1e-6):
+    return abs(a - b) <= tol
+
+
+def pt_near(p, q, tol=1e-6):
+    return math.hypot(p[0] - q[0], p[1] - q[1]) <= tol
+
+
+def fresh(plane="XY"):
+    try:
+        call("sketch_cancel")
+    except Exception:
+        pass
+    call("sketch_begin", plane=plane)
+
+
+def ents():
+    return call("sketch_describe")["entities"]
+
+
+def rep():
+    return call("sketch_describe")
+
+
+def endpoints(e):
+    """Both ends of an open curve, as tuples. Closed curves have none."""
+    if "p0" not in e or "p1" not in e:
+        return ()
+    return tuple(e["p0"]), tuple(e["p1"])
+
+
+def tangent(e, at_end):
+    """Unit tangent of entity e at one of its ends, pointing ALONG the curve (p0->p1)."""
+    if e["type"] == "line":
+        dx = e["p1"][0] - e["p0"][0]
+        dy = e["p1"][1] - e["p0"][1]
+    else:  # arc
+        a = e["start_angle"] if not at_end else e["end_angle"]
+        ccw = e["end_angle"] >= e["start_angle"]
+        # d/dtheta (cos, sin) = (-sin, cos), reversed when the sweep is clockwise
+        dx, dy = -math.sin(a), math.cos(a)
+        if not ccw:
+            dx, dy = -dx, -dy
+    n = math.hypot(dx, dy)
+    return (dx / n, dy / n)
+
+
+def tangent_at_point(e, p):
+    """Unit tangent of e at whichever of its ends is p, oriented leaving that point."""
+    p0, p1 = endpoints(e)
+    if pt_near(p0, p):
+        t = tangent(e, False)
+        return t
+    t = tangent(e, True)
+    return (-t[0], -t[1])          # leaving p1 means going back along the curve
+
+
+def smooth(e1, e2, p):
+    """G1 at shared point p: the tangent leaving e1 is opposite the tangent leaving e2."""
+    a = tangent_at_point(e1, p)
+    b = tangent_at_point(e2, p)
+    return abs(a[0] * (-b[0]) - 0) >= 0 and abs(a[0] * b[1] - a[1] * b[0]) <= 1e-6
+
+
+def closed_one_loop(r, voids=0):
+    return (r["buildable"] and r["open_ends"] == []
+            and len([l for l in r["closed_loops"] if not any(
+                i in h["holes"] for h in r["closed_loops"] for i in [])]) >= 1)
+
+
+def outer_loop(r):
+    """The loop that encloses the others (or the only one)."""
+    if not r["closed_loops"]:
+        return None
+    return max(r["closed_loops"], key=lambda l: abs(l["area"]))
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+print("RUNG 1 — rectangle: four corners, four lengths, four right angles")
+fresh()
+W, H = 80.0, 50.0
+call("sketch_add", rect=[0, 0, W, H])
+r = rep()
+es = r["entities"]
+corners = {(0, 0), (W, 0), (W, H), (0, H)}
+got = set()
+for e in es:
+    got.add(tuple(e["p0"]))
+    got.add(tuple(e["p1"]))
+check("VERTEX", all(any(pt_near(c, g) for g in got) for c in corners),
+      f"all four corners exactly where asked {sorted(corners)}")
+lens = sorted(round(e["length"], 9) for e in es)
+check("LENGTH", lens == sorted([W, W, H, H]), f"sides are {W}/{H} twice each (got {lens})")
+# right angles: consecutive sides meet at 90 degrees
+ang_ok = True
+for e in es:
+    for f in es:
+        if e is f:
+            continue
+        for p in endpoints(e):
+            if any(pt_near(p, q) for q in endpoints(f)):
+                a, b = tangent_at_point(e, p), tangent_at_point(f, p)
+                if abs(a[0] * b[0] + a[1] * b[1]) > 1e-6:
+                    ang_ok = False
+check("ANGLE", ang_ok, "every corner is exactly 90 degrees")
+check("CLOSED", r["buildable"] and r["open_ends"] == [], "one closed loop, no free ends")
+
+print("\nRUNG 2 — a circular void inside it")
+call("sketch_add", type="circle", center=[W / 2, H / 2], radius=12)
+r = rep()
+c = [e for e in r["entities"] if e["type"] == "circle"][0]
+check("VERTEX", pt_near(tuple(c["center"]), (W / 2, H / 2)), "void centred exactly where asked")
+check("ARC", near(c["radius"], 12), f"void radius exactly 12 (got {c['radius']})")
+out = outer_loop(r)
+check("CLOSED", len(out["holes"]) == 1, "the rectangle encloses exactly one void")
+check("CLOSED", r["buildable"] and r["open_ends"] == [], "still closed with the void present")
+
+print("\nRUNG 3 — stadium: straights running into caps, tangent at every junction")
+fresh()
+L, R = 50.0, 15.0
+call("sketch_add", entities=[
+    {"type": "line", "p0": [-L, -R], "p1": [L, -R]},
+    {"type": "arc", "center": [L, 0], "radius": R,
+     "start_angle": -math.pi / 2, "end_angle": math.pi / 2},
+    {"type": "line", "p0": [L, R], "p1": [-L, R]},
+    {"type": "arc", "center": [-L, 0], "radius": R,
+     "start_angle": math.pi / 2, "end_angle": 3 * math.pi / 2},
+])
+r = rep()
+es = r["entities"]
+check("CLOSED", r["buildable"] and r["open_ends"] == [], "one closed loop, no free ends")
+arcs = [e for e in es if e["type"] == "arc"]
+check("ARC", all(near(a["radius"], R) for a in arcs), f"both caps exactly R={R}")
+check("LENGTH", all(near(e["length"], 2 * L) for e in es if e["type"] == "line"),
+      f"both straights exactly {2*L}")
+# tangency at all four line/arc junctions
+tang = True
+for a in arcs:
+    for p in endpoints(a):
+        mates = [e for e in es if e is not a and any(pt_near(p, q) for q in endpoints(e))]
+        for m in mates:
+            if not smooth(a, m, p):
+                tang = False
+check("TANGENT", tang, "straight meets cap smoothly at all four junctions (no kink)")
+
+print("\nRUNG 4 — mirror: the reflected half is the exact reflection")
+fresh()
+half = [
+    {"type": "line", "p0": [0, -R], "p1": [L, -R]},
+    {"type": "arc", "center": [L, 0], "radius": R,
+     "start_angle": -math.pi / 2, "end_angle": math.pi / 2},
+    {"type": "line", "p0": [L, R], "p1": [0, R]},
+]
+call("sketch_add", entities=half)
+r = rep()
+check("CLOSED", not r["buildable"] and len(r["open_ends"]) == 2,
+      f"half profile is correctly OPEN, both ends named {r['open_ends']}")
+call("sketch_select", entities=[0, 1, 2])
+call("sketch_mirror", axis_a=[0, 0], axis_b=[0, 1])
+r = rep()
+es = r["entities"]
+check("CLOSED", r["buildable"] and r["open_ends"] == [], "mirroring closed the loop")
+# every source vertex must have its exact reflection present
+src = []
+for e in es[:3]:
+    src += [tuple(e["p0"]), tuple(e["p1"])]
+allv = []
+for e in es:
+    allv += [tuple(e["p0"]), tuple(e["p1"])]
+sym = all(any(pt_near((-x, y), v) for v in allv) for (x, y) in src)
+check("SYMMETRY", sym, "every vertex has its exact mirror twin across x=0")
+mirrored_arc = [e for e in es[3:] if e["type"] == "arc"]
+check("ARC", mirrored_arc and near(mirrored_arc[0]["radius"], R)
+      and pt_near(tuple(mirrored_arc[0]["center"]), (-L, 0)),
+      f"mirrored cap keeps R={R} and lands at (-{L}, 0)")
+
+print("\nRUNG 5 — offset: every curve moves by exactly d, and it stays closed")
+d = 4.0
+call("sketch_select", entities=list(range(len(es))))
+call("sketch_offset", distance=-d)          # -d = outward for this CCW loop
+r = rep()
+new = r["entities"][len(es):]
+check("CLOSED", r["buildable"] and r["open_ends"] == [], "offset result is closed")
+off_arcs = [e for e in new if e["type"] == "arc"]
+check("ARC", all(near(a["radius"], R + d) for a in off_arcs),
+      f"each cap radius grew by exactly {d} -> {R+d}")
+off_lines = [e for e in new if e["type"] == "line"]
+check("VERTEX", all(near(abs(e["p0"][1]), R + d) for e in off_lines),
+      f"each straight moved out to |y| = {R+d} exactly")
+
+print("\nRUNG 6 — a gap is found by coordinate, then closed by a real constraint")
+fresh()
+call("sketch_add", entities=[
+    {"type": "line", "p0": [0, 0], "p1": [60, 0]},
+    {"type": "line", "p0": [60, 0], "p1": [60, 40]},
+    {"type": "line", "p0": [60, 40], "p1": [0, 40]},
+    {"type": "line", "p0": [0, 40], "p1": [0.35, 0]},      # 0.35 mm short
+])
+r = call("sketch_validate", tolerance=1.0)
+check("CLOSED", not r["buildable"] and len(r["open_ends"]) == 2,
+      f"the gap is reported, both free ends named {r['open_ends']}")
+dof0 = r["dof"]
+r = call("sketch_heal", tolerance=1.0)
+check("CLOSED", r["buildable"] and r["open_ends"] == [], "healed into a closed loop")
+check("VERTEX", r["welded"] == 1, "exactly one pair of vertices welded")
+check("ANGLE", r["dof"] < dof0,
+      f"the weld is a real constraint, not a nudge: DoF {dof0} -> {r['dof']}")
+es = ents()
+check("VERTEX", pt_near(tuple(es[3]["p1"]), tuple(es[0]["p0"])),
+      "the two ends are now the same point")
+
+print("\nRUNG 7 — the composite: mirrored, tangent, two voids, all at once")
+fresh()
+call("sketch_add", entities=half)
+call("sketch_select", entities=[0, 1, 2])
+call("sketch_mirror", axis_a=[0, 0], axis_b=[0, 1])
+call("sketch_add", type="circle", center=[-25, 0], radius=6)
+call("sketch_add", type="circle", center=[25, 0], radius=6)
+r = rep()
+es = r["entities"]
+out = outer_loop(r)
+check("CLOSED", r["buildable"] and r["open_ends"] == [], "one closed outer loop, no free ends")
+check("CLOSED", len(out["holes"]) == 2, "it encloses exactly two voids")
+circles = [e for e in es if e["type"] == "circle"]
+check("ARC", all(near(c["radius"], 6) for c in circles), "both voids exactly R=6")
+check("SYMMETRY", pt_near(tuple(circles[0]["center"]), (-25, 0))
+      and pt_near(tuple(circles[1]["center"]), (25, 0)),
+      "the voids sit symmetrically at x = -25 and +25")
+tang = True
+for a in [e for e in es if e["type"] == "arc"]:
+    for p in endpoints(a):
+        for m in [e for e in es if e is not a and any(pt_near(p, q) for q in endpoints(e))]:
+            if not smooth(a, m, p):
+                tang = False
+check("TANGENT", tang, "every straight-to-cap junction is still smooth")
+exact = 2 * L * 2 * R + math.pi * R * R
+check("LENGTH", near(out["area"], exact, 1e-6),
+      f"cross-check: enclosed area {out['area']:.4f} = 2L*2R + pi*R^2 = {exact:.4f}")
+
+print("\nRUNG 8 — a real drawing: StudyCadCam MPD5, the pin's revolve half-profile")
+# Ø27 x 95 pin: C1 chamfer on the left end, cylinder to a corner at x=85, an R5 fillet into a
+# cone at 23 degrees to the axis, right face at x=95. Interpretation stated so the rung is
+# reproducible: 85 is to the CORNER, 23 deg is to the AXIS, C1 is 1 x 45.
+fresh()
+RAD, LEN, TX, ANG, RF, CH = 13.5, 95.0, 85.0, math.radians(23), 5.0, 1.0
+t  = RF * math.tan(ANG / 2)
+ax, ay = TX - t, RAD                      # fillet tangent point on the cylinder
+cx, cy = ax, RAD - RF                     # fillet centre
+bx, by = TX + t * math.cos(-ANG), RAD + t * math.sin(-ANG)   # tangent point on the cone
+ey = by - (LEN - bx) * math.tan(ANG)      # where the cone meets the right face
+call("sketch_add", entities=[
+    {"type": "line", "p0": [0, 0],            "p1": [0, RAD - CH]},        # left face
+    {"type": "line", "p0": [0, RAD - CH],     "p1": [CH, RAD]},            # C1 chamfer
+    {"type": "line", "p0": [CH, RAD],         "p1": [ax, ay]},             # cylinder top
+    {"type": "arc",  "center": [cx, cy], "radius": RF,
+     "start_angle": math.pi / 2, "end_angle": math.pi / 2 - ANG},          # R5 fillet
+    {"type": "line", "p0": [bx, by],          "p1": [LEN, ey]},            # 23 deg cone
+    {"type": "line", "p0": [LEN, ey],         "p1": [LEN, 0]},             # right face
+    {"type": "line", "p0": [LEN, 0],          "p1": [0, 0]},               # axis
+])
+r = rep()
+es = r["entities"]
+check("CLOSED", r["buildable"] and r["open_ends"] == [], "the half-profile is one closed loop")
+xs = [v[0] for e in es if "p0" in e for v in (e["p0"], e["p1"])]
+ys = [v[1] for e in es if "p0" in e for v in (e["p0"], e["p1"])]
+check("LENGTH", near(max(xs) - min(xs), LEN), f"overall length exactly {LEN} (the 95 dimension)")
+check("VERTEX", near(max(ys), RAD), f"outer radius exactly {RAD} (the dia 27)")
+fil = [e for e in es if e["type"] == "arc"][0]
+check("ARC", near(fil["radius"], RF), f"the corner fillet is exactly R{RF:g}")
+cone = [e for e in es if e["type"] == "line"
+        and not near(e["p0"][0], e["p1"][0]) and not near(e["p0"][1], e["p1"][1])
+        and e["length"] > 5]
+if cone:
+    c0 = cone[0]
+    a = abs(math.degrees(math.atan2(c0["p1"][1] - c0["p0"][1], c0["p1"][0] - c0["p0"][0])))
+    check("ANGLE", near(a, 23, 1e-6), f"the cone is exactly 23 degrees to the axis (got {a:.6f})")
+cham = [e for e in es if e["type"] == "line" and near(e["length"], CH * math.sqrt(2), 1e-9)]
+check("ANGLE", bool(cham), "the C1 chamfer is exactly 1 x 45 (length 1*sqrt2)")
+tang = True
+for p in endpoints(fil):
+    for m in [e for e in es if e is not fil and any(pt_near(p, q) for q in endpoints(e))]:
+        if not smooth(fil, m, p):
+            tang = False
+check("TANGENT", tang, "the fillet is tangent to BOTH the cylinder and the cone (no kink)")
+
+call("sketch_cancel")
+
+try:
+    call("sketch_cancel")
+except Exception:
+    pass                      # a rung may have closed it already
+print(f"\n{'ALL RUNGS HELD' if _fail == 0 else str(_fail) + ' CHECK(S) FAILED'}")
+sys.exit(1 if _fail else 0)
diff --git a/scripts/CAD/focus-loop.sh b/scripts/CAD/focus-loop.sh
new file mode 100755
index 0000000000..3c75f64a49
--- /dev/null
+++ b/scripts/CAD/focus-loop.sh
@@ -0,0 +1,89 @@
+#!/usr/bin/env bash
+# One turn of the keyboard-focus convergence loop, start to verdict, with no human in it.
+#
+#   scripts/CAD/focus-loop.sh              # full turn: sync -> build -> restart -> assert
+#   SKIP_BUILD=1 scripts/CAD/focus-loop.sh # re-assert against the binary already on the host
+#
+# Exit 0 only when every gate holds. Any other exit is a failing gate and names which.
+#
+# WHY THIS EXISTS. The focus defects in the Design tab were chased for days by hand: build, launch
+# the GUI, drive it with xdotool, read a screenshot, guess, repeat. That needs a person at every
+# step and it is where the days went. This does not: behemoth carries an agent-owned Xvfb :10 with
+# openbox, the app, xdotool and an MCP socket that reports sketch state as JSON, so a turn is
+# sync -> build -> restart -> assert, and the ASSERTION is the verdict, not my reading of a picture.
+#
+# WHY BEHEMOTH AND NOT THE orcacad-gui RIG CONTAINER. The rig was the obvious host and it does not
+# work for this: its image pins a dependency set 216 non-CAD source files behind cad-mainline
+# (assimp among them), so today's CAD sources call GUI_App::is_auto_close_sketch_loops and
+# MainFrame::ensure_design_panel, which that tree has never heard of. Syncing all of src/ to fix
+# that needs a deps rebuild measured in hours. behemoth already builds this exact tree, already
+# runs a WM on :10, and is the machine the user actually runs the product on — so the loop asserts
+# against the shipping artefact rather than a stale twin. Reviving the rig means rebuilding its
+# deps image first; until then it cannot adjudicate anything about this code.
+#
+# SC2029: every ssh command below quotes locally-expanded config (HOST, SRC, DISP) on purpose
+# -- the remote tree is not this checkout and has no such config of its own.
+# shellcheck disable=SC2029
+set -uo pipefail
+
+HOST="${HOST:-tommaso@100.103.234.2}"
+DISP="${DISP:-:10}"
+SRC="${SRC:-\$HOME/projects/orca/orcacad-native/src}"
+TRACE="${TRACE:-/tmp/ux-focus-loop.log}"
+REPO="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+BIN="build/src/Release/orca-slicer"
+
+say() { printf '\n=== %s\n' "$*"; }
+die() { printf 'GATE FAILED: %s\n' "$*" >&2; exit 1; }
+
+ssh -o ConnectTimeout=10 "$HOST" true || die "cannot reach $HOST"
+
+# ---------------------------------------------------------------- S1 sync
+# Only the CAD paths and the ladders. behemoth's tree is a full cad-mainline checkout kept in step
+# by its own realign; pushing unrelated files from here would make the build host disagree with
+# git for reasons no later session could reconstruct.
+say "S1 sync"
+rsync -q "$REPO"/src/slic3r/GUI/CAD/*.{cpp,hpp} "$HOST:$SRC/src/slic3r/GUI/CAD/" || die "sync GUI/CAD"
+rsync -q "$REPO"/src/libslic3r/CAD/*.{cpp,hpp}  "$HOST:$SRC/src/libslic3r/CAD/"  || die "sync libslic3r/CAD"
+rsync -q "$REPO"/scripts/CAD/check-gui-click-edit.py "$REPO"/scripts/CAD/check-gui-sketching.py \
+        "$HOST:/tmp/" || die "sync ladders"
+echo "  sources + ladders in place"
+
+# ---------------------------------------------------------------- S2 build
+# flock: two concurrent Orca builds once OOM'd this machine for 2h28m. Every build script on the
+# fleet takes this same lock.
+#
+# Grade the BINARY'S TIMESTAMP, never the build command's exit code. This is a Ninja Multi-Config
+# tree whose default rules are Debug while the artefact under test is Release, so a wrong-config
+# invocation returns success in seconds having touched nothing — it cost a wasted cycle here
+# before anyone thought to look at the file.
+if [ -z "${SKIP_BUILD:-}" ]; then
+    say "S2 build"
+    before=$(ssh "$HOST" "stat -c %Y $SRC/$BIN 2>/dev/null || echo 0")
+    ssh "$HOST" "flock /tmp/orca-rig-build.lock \$HOME/projects/orca/orcacad-native/rebuild.sh > /tmp/focus-build.log 2>&1"
+    rc=$?
+    after=$(ssh "$HOST" "stat -c %Y $SRC/$BIN 2>/dev/null || echo 0")
+    if [ "$rc" != 0 ] || [ "$after" = "$before" ]; then
+        ssh "$HOST" "grep -m5 -B2 'error:' /tmp/focus-build.log; tail -5 /tmp/focus-build.log"
+        die "S2 build (exit $rc, binary $( [ "$after" = "$before" ] && echo unchanged || echo rebuilt ))"
+    fi
+    echo "  built"
+fi
+
+# ---------------------------------------------------------------- S3 F2P
+# The ladder launches and tears down the app itself, in its own datadir, so nothing here has to
+# manage a process. It types WITHOUT clicking the field first, which is the whole contract.
+say "S3 fail-to-pass: type without clicking the field"
+ssh "$HOST" "cd $SRC && DISPLAY=$DISP python3 /tmp/check-gui-click-edit.py \
+             --display $DISP --bin $BIN --trace $TRACE"
+f2p=$?
+
+# ---------------------------------------------------------------- S4 P2P
+say "S4 pass-to-pass: the existing gesture ladder"
+ssh "$HOST" "cd $SRC && DISPLAY=$DISP python3 /tmp/check-gui-sketching.py 2>&1 | tail -3"
+p2p=$?
+
+say "VERDICT"
+[ "$f2p" = 0 ] || die "F2P: a tool did not take the typed value (exit $f2p)"
+[ "$p2p" = 0 ] || die "P2P: the gesture ladder regressed (exit $p2p)"
+echo "ALL GATES HELD"
diff --git a/scripts/CAD/run-all-checks.sh b/scripts/CAD/run-all-checks.sh
new file mode 100755
index 0000000000..1c0388ac89
--- /dev/null
+++ b/scripts/CAD/run-all-checks.sh
@@ -0,0 +1,85 @@
+#!/usr/bin/env bash
+# Every ladder, in one command, as the gate before a push that touched the Design tab.
+#
+# WHY A SCRIPT AND NOT CI. Three of the four rungs need a running application with an OpenGL
+# canvas and synthetic input; GitHub's runners have neither. So the gate is local and explicit:
+# run this, read the last line, and do not push a red one. The kernel suite is the only part CI
+# can carry, and it already does.
+#
+#   scripts/CAD/run-all-checks.sh                 # kernel + engine + corpus (every 20th) + gestures + offer
+#   FULL=1 scripts/CAD/run-all-checks.sh          # corpus over ALL 997 sheets (~25 min)
+#   SKIP_GUI=1 scripts/CAD/run-all-checks.sh      # kernel only, for a machine with no rig
+#
+# The rig container is expected to be up with the app running and ORCA_CAD_MCP set; bring it up
+# with scripts/CAD/start-headless-gui.sh inside it. The corpus lives at /corpus in that container.
+set -uo pipefail
+# ../.. -- this script lives in scripts/CAD/, so one level up is scripts/, not the repo
+# root. It was scripts/ladder-all.sh when it was written; the move fixed the three sibling
+# scripts and missed this one, which left every rung looking for its own path under
+# scripts/scripts/ and reporting instant failures that were all the same typo.
+cd "$(dirname "${BASH_SOURCE[0]}")/../.." || exit 1
+
+# orcacad-gui, NOT snapmaker-gui: that is the other fork's rig, and defaulting to it makes
+# this gate verify the wrong fork's binary while reporting green. run-kernel-tests.sh
+# carries the same warning about the build volume, where the defect was found first.
+C="${C:-orcacad-gui}"
+CORPUS="${CORPUS:-/corpus}"
+STEP="${STEP:-20}"
+[ -n "${FULL:-}" ] && STEP=1
+fail=0
+
+step() {
+    local name="$1"; shift
+    echo
+    echo "=== $name ==="
+    if "$@"; then echo "--- $name OK"; else echo "--- $name FAILED"; fail=1; fi
+}
+
+# This fork's rig runs Xvfb on :11, the other fork's on :10, and the check scripts default
+# to ":10" when DISPLAY is unset -- which docker exec leaves unset. The rungs that drive the
+# GUI therefore looked for a window on a display that does not exist here and reported
+# "FATAL no app window on :10", which reads like a dead app rather than a wrong display.
+RIG_DISPLAY="${RIG_DISPLAY:-:11}"
+
+# SC2329: every call goes through step(), which invokes it via "$@", so shellcheck
+# cannot see the callers below.
+# shellcheck disable=SC2329
+run_in_rig() {                      # copy the script in fresh, then run it there
+    docker cp "$1" "$C:/tmp/$(basename "$1")" >/dev/null || return 1
+    shift
+    docker exec -e DISPLAY="$RIG_DISPLAY" "$C" python3 "$@"
+}
+
+# FIRST, and it needs no rig: the offer table the menu is compiled from must be what the atlas
+# says. The header calls itself GENERATED and had been hand-edited anyway — which cost four rows
+# that existed only in the header, one row wired to the wrong action, and a count of 91 for a
+# 92-row array, so the last verb was unreachable (z8rs, ziam).
+# docs/CAD/, not docs/: SoftFever moved the design docs into the CAD subfolder
+# (bbd1989e1e) and this line kept the old path, so the rung failed on a missing file
+# rather than on anything about the table. The other fork still has docs/ux/.
+step "offer table matches the atlas" python3 docs/CAD/ux/mockups/gen_offer_table.py --check
+
+step "kernel suite" scripts/CAD/run-kernel-tests.sh --vol "${KVOL:-orcacad_kerneltest}"
+
+if [ -z "${SKIP_GUI:-}" ]; then
+    step "engine ladder (rungs 1-8, scripted geometry)" \
+        run_in_rig scripts/CAD/check-sketch-engine.py /tmp/check-sketch-engine.py
+    step "corpus rung (real drawings, every ${STEP}th)" \
+        run_in_rig scripts/CAD/check-sketch-engine-corpus.py /tmp/check-sketch-engine-corpus.py --corpus "$CORPUS" --step "$STEP"
+    step "corpus scale rung (the heaviest sheets)" \
+        run_in_rig scripts/CAD/check-sketch-engine-corpus.py /tmp/check-sketch-engine-corpus.py --corpus "$CORPUS" --scale
+    step "gesture ladder (mouse and keyboard)" \
+        run_in_rig scripts/CAD/check-gui-sketching.py /tmp/check-gui-sketching.py
+    # The offer ladder needs TWO extra things the others do not: the app must have been launched
+    # with ORCA_CAD_KEYTRACE=1 (its [OFFER] lines are the whole instrument), and it reads the
+    # generated offer table to predict what each selection should show — which is not in the
+    # container's own baked source tree, so it is copied in beside the script — /tmp, where
+    # run_in_rig puts the script, is one of the paths the ladder looks in.
+    docker cp src/slic3r/GUI/CAD/DesignOffer.hpp "$C:/tmp/DesignOffer.hpp" >/dev/null
+    step "offer ladder (right-click, the menu, the verbs behind it)" \
+        run_in_rig scripts/CAD/check-gui-context-menu.py /tmp/check-gui-context-menu.py
+fi
+
+echo
+if [ "$fail" -eq 0 ]; then echo "ALL LADDERS HELD"; else echo "AT LEAST ONE LADDER FAILED"; fi
+exit "$fail"
diff --git a/scripts/CAD/run-kernel-tests.sh b/scripts/CAD/run-kernel-tests.sh
new file mode 100755
index 0000000000..ef4356cb65
--- /dev/null
+++ b/scripts/CAD/run-kernel-tests.sh
@@ -0,0 +1,159 @@
+#!/usr/bin/env bash
+# Headless CAD-kernel test loop. THE verification contract for delegated work:
+# exit 0 means the kernel builds and the selected Catch2 tags pass. Nothing else counts.
+#
+# Builds only the `libslic3r_tests` target (not the GUI app), so a round trip is
+# minutes, not tens of minutes. Needs no display: every [CadDocument] case builds a
+# CadDocument, recompute()s it and asserts on geometry.
+#
+# Usage:
+#   scripts/CAD/run-kernel-tests.sh                        # [CadDocument] tags, default volume
+#   scripts/CAD/run-kernel-tests.sh --tags '[CadDocument],[Sketch]'
+#   scripts/CAD/run-kernel-tests.sh --vol wt_mirror        # private build cache (parallel workers)
+#   scripts/CAD/run-kernel-tests.sh --host tommaso@100.103.234.2   # build on a remote host
+#
+# Parallel workers MUST pass a distinct --vol: two builds sharing one cache corrupt
+# each other. A new volume pays one full build; runs after that are incremental.
+#
+# --host exists because the deps image lives wherever it was first built. It rsyncs this
+# working tree to a per-volume staging dir on that host and re-runs this same script
+# there, so the verification contract is identical either way. Drop --host once the image
+# is present locally.
+# Rig build traps already paid for once each (stale project, NLopt cache, pybind11, OCCT_LIBS, SLIC3R_CAD gate): docs/rig_build_traps.md
+set -euo pipefail
+
+REPO="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+# orcacad-deps, NOT snapmaker-deps: this fork is mainline-based and needs Eigen 5.0.1,
+# CGAL 5.6.3, wx 3.3.2 and Python 3.12 Development.Embed, none of which snapmaker-deps has.
+# With the wrong image CMake dies at configure, which is exactly why this fork went
+# M1-M8 without ever compiling (see commit 1633005bba).
+IMAGE="${IMAGE:-orcacad-deps}"
+# Must NOT default to snapmaker_buildcache: that is the other fork's volume, and pointing
+# this fork at it makes the two silently trade build artefacts. build-gui-incremental.sh had the
+# identical defect and was fixed to orcacad_buildcache; this script was missed.
+VOL="${BUILD_VOL:-orcacad_kerneltest}"
+# No exclusions. Both cases that used to be quarantined now run: the solver SIGABRT on
+# circle-line tangency is fixed (tkz), and the internal-thread case turned out to have
+# correct geometry and a wrong reference in the test (kzy). A green run here now means
+# the whole CAD suite passed, not "everything except the two we gave up on".
+#
+# ...and that claim was still not true, because the default tag was [CadDocument] alone while
+# four CAD test files carry their own tags and NOTHING ELSE selected them. test_sketchinference
+# ([inference], 15), test_sketchedit ([SketchEdit], 23), test_sketchconstraints
+# ([SketchConstraints], 8) and test_sketchimport ([SketchImport], 4) never ran here, nor did the
+# older [slvs]-only cases in test_slvs_constraints. Measured 2026-08-31: the default reported
+# 2624 assertions / 206 cases, the full set 7648 / 264 -- so the gate was speaking for about a
+# third of the assertions, and a whole file could be added, tagged by its own convention, and
+# stay dark while the suite printed green. All 58 were passing; the coverage was simply never
+# exercised. Adding a tag here is now part of adding a test file.
+TAGS="${TAGS:-[CadDocument],[inference],[SketchEdit],[SketchConstraints],[SketchImport],[slvs]}"
+HOST=""
+
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+    --vol)   VOL="$2";   shift 2 ;;
+    --tags)  TAGS="$2";  shift 2 ;;
+    --image) IMAGE="$2"; shift 2 ;;
+    --host)  HOST="$2";  shift 2 ;;
+    *) echo "unknown arg: $1" >&2; exit 2 ;;
+  esac
+done
+
+echo "REPO=$REPO IMAGE=$IMAGE VOL=$VOL TAGS=$TAGS HOST=${HOST:-local}"
+
+if [[ -n "$HOST" ]]; then
+  # Stage per-volume so parallel workers never share a remote tree.
+  REMOTE="kt-$VOL"   # relative: ssh and rsync both start in the remote home dir
+  # SC2029: $REMOTE expanding on the CLIENT is the point -- it is derived from $VOL here,
+  # and the remote has no such variable. The rsync destination below expands it the same way.
+  # shellcheck disable=SC2029
+  ssh "$HOST" "mkdir -p $REMOTE"
+  # Only the inputs the build reads. --delete keeps a stale file from a prior worker from
+  # silently compiling in.
+  rsync -a --delete \
+    "$REPO/src" "$REPO/tests" "$REPO/resources" "$REPO/cmake" "$REPO/scripts" \
+    "$REPO/CMakeLists.txt" \
+    "$HOST:$REMOTE/"
+  exec ssh "$HOST" "cd $REMOTE && scripts/CAD/run-kernel-tests.sh --vol '$VOL' --tags '$TAGS' --image '$IMAGE'"
+fi
+
+if ! docker image inspect "$IMAGE" >/dev/null 2>&1; then
+  echo "FATAL: image '$IMAGE' not present locally. Either transfer it, or pass" >&2
+  echo "       --host <user@host> to build where the image already exists." >&2
+  exit 3
+fi
+
+# A private volume is always built CLEAN on first use. Cloning a warm cache from another
+# tree looks tempting but is a correctness trap: rsync preserves source mtimes, so ninja
+# compares foreign object timestamps against them, decides everything is up to date, and
+# relinks stale objects. That produced a binary with NO [CadDocument] tests at all while
+# reporting success -- a green run that tested nothing. Pay the one-off full build instead;
+# incremental rebuilds within a volume are correct because the mtimes then share a lineage.
+if ! docker volume inspect "$VOL" >/dev/null 2>&1; then
+  echo "=== $VOL: new volume, clean configure + full build (one-off, slow) ==="
+  docker volume create "$VOL" >/dev/null
+fi
+
+# tests/ is mounted too -- unlike build-gui-incremental.sh, this script exists precisely to
+# compile tests being edited. CMakeLists.txt and cmake/ carry the SLIC3R_CAD gate; taking
+# them from the baked image instead leaves the gate off and the CAD symbols vanish.
+
+# ---- OOM guard (2026-08-21) -------------------------------------------------------------
+# Two of these builds ran at once on 2026-08-21, each with ninja -j$(nproc)=16: ~36 cc1plus
+# holding 42 GB of a 62 GB box -> global OOM at 21:05, a 2h28m kill storm, ssh unreachable,
+# lightdm destroyed. Neither build produced a single object. scripts/CAD/build-gui.sh grew the
+# bounds first; every script that starts a compile needs the same three, or the guard is only
+# as strong as the script you happened not to use.
+#   flock    — the lock path is SHARED with build-gui.sh and the other fork on purpose, so
+#              concurrent builds serialise instead of summing.
+#   -j       — bounded parallelism; ~1.17 GB per cc1plus was the measured average.
+#   --memory — the actual guarantee: a runaway build dies in its own cgroup instead of taking
+#              the host down. --memory-swap equal to --memory forbids swap, which is what made
+#              ssh hang.
+JOBS="${JOBS:-12}"
+MEM="${MEM:-40g}"
+LOCK=/tmp/orca-rig-build.lock
+
+exec 9>"$LOCK"
+if ! flock -n 9; then
+    echo "another build holds $LOCK — waiting (this is the OOM guard, not a hang)"
+    flock 9
+fi
+
+docker run --rm \
+  --memory="$MEM" --memory-swap="$MEM" \
+  -v "$REPO/src":/OrcaSlicer/src \
+  -v "$REPO/tests":/OrcaSlicer/tests \
+  -v "$REPO/resources":/OrcaSlicer/resources \
+  -v "$REPO/CMakeLists.txt":/OrcaSlicer/CMakeLists.txt \
+  -v "$REPO/cmake":/OrcaSlicer/cmake \
+  -v "$REPO/deps_src":/OrcaSlicer/deps_src \
+  -v "$VOL":/OrcaSlicer/build \
+  "$IMAGE" \
+  bash -lc "set -e
+    cd /OrcaSlicer
+    DESTDIR=/OrcaSlicer/deps/build/destdir/usr/local
+    export PATH=\$DESTDIR/bin:\$PATH   # wx-config, and anything else the deps prefix ships
+    # Configure unconditionally. Guarding on 'CMakeCache.txt exists' is wrong: a FAILED
+    # configure still writes that file, so the guard then skips reconfiguring forever and
+    # every later run reuses a poisoned cache while ignoring corrected flags. A no-op
+    # reconfigure costs seconds; that bug costs an afternoon.
+    # SLIC3R_GTK=3 and BUILD_TESTS=ON are not optional extras: src/CMakeLists.txt turns
+    # SLIC3R_GTK into 'wx-config --toolkit=gtk<N>', so omitting it asks for toolkit 'gtk'
+    # and no wx build matches -> 'Could NOT find wxWidgets'. BUILD_TESTS=ON is what makes
+    # the libslic3r_tests target exist at all. build_linux.sh sets both (lines 218, 226).
+    cmake -S . -B build -G 'Ninja Multi-Config' \
+      -DCMAKE_PREFIX_PATH=\$DESTDIR \
+      -DwxWidgets_CONFIG_EXECUTABLE=\$DESTDIR/bin/wx-config \
+      -DSLIC3R_GTK=3 -DBUILD_TESTS=ON -DSLIC3R_GUI=OFF \
+      -DSLIC3R_CAD=ON -DSLIC3R_STATIC=1 -DORCA_TOOLS=ON -DCMAKE_BUILD_TYPE=Release
+    # SLIC3R_GUI=OFF: this script builds ONLY libslic3r_tests, which links libslic3r and no GUI
+    # code, but cmake still PROCESSES the if SLIC3R_GUI block of src/CMakeLists.txt (lines 16-98)
+    # and every find_package inside it. That made the kernel suite depend on the GUI dependency
+    # set for no benefit, and it broke the moment upstream added wxInspector as a REQUIRED
+    # find_package at line 92: the orcacad-deps image predates it, so configure died pointing at
+    # src/CMakeLists.txt:92 while nothing about the kernel had changed. Turning the block off is
+    # not a workaround for that one dependency; it is the kernel suite finally declaring what it
+    # actually needs, so the next GUI-side dependency upstream adds cannot break it either.
+    cmake --build build --config Release --target libslic3r_tests -- -j$JOBS
+    ./build/tests/libslic3r/Release/libslic3r_tests '$TAGS' --order decl"
diff --git a/scripts/CAD/start-headless-gui.sh b/scripts/CAD/start-headless-gui.sh
new file mode 100755
index 0000000000..d9944da8cf
--- /dev/null
+++ b/scripts/CAD/start-headless-gui.sh
@@ -0,0 +1,148 @@
+#!/usr/bin/env bash
+# Bring the headless GUI up on a VNC-served X display, ready to drive or to attach Remmina to.
+#
+# Runs INSIDE the long-lived GUI container (see the header of scripts/CAD/build-gui-incremental.sh for how
+# that container is created). Idempotent: safe to re-run to recover a session whose app died.
+#
+#   docker exec <container> /OrcaSlicer/scripts/CAD/start-headless-gui.sh          # launch + settle
+#   docker exec <container> /OrcaSlicer/scripts/CAD/start-headless-gui.sh --status # report, change nothing
+#
+# WHY THIS EXISTS. Dismissing the first-run dialogs by computing the titlebar close box from
+# `xdotool getwindowgeometry --shell` and clicking it went wrong whenever the dialog had already
+# closed: the eval left the geometry variables stale or empty, the click landed at a garbage
+# coordinate, and it repeatedly hit the Sketch button in the toolbar underneath, so the app came up
+# in sketch mode with a stray Sketch feature. Three of those in one session.
+#
+# The titlebar click is nevertheless the RIGHT mechanism and is kept. `xdotool windowclose` looks
+# cleaner but kills the app: it destroys the GdkWindow out from under the dialog and the process
+# dies with "GdkWindow unexpectedly destroyed", three GLib-GObject criticals and a segfault
+# (measured 2026-07-30). Escape does not close the Setup Wizard either. So the fix is not a
+# different mechanism, it is refusing to click on geometry we have not validated.
+set -euo pipefail
+
+DISP="${DISP:-:11}"
+GEOM="${GEOM:-1920x1080}"
+BIN="${BIN:-/OrcaSlicer/build/src/Release/orca-slicer}"
+# Packaging cannot bundle python (the deps python layer carries a doubled-DESTDIR RUNPATH), so the
+# build-tree binary needs the deps libpython on the path. Packaging-only issue; the app runs fine.
+LIBPY="/OrcaSlicer/deps/build/destdir/usr/local/libpython/lib"
+LIBPY2="/OrcaSlicer/build/src/Release/python/lib"
+LOG="${LOG:-/tmp/gui-session.log}"
+
+export DISPLAY="$DISP" HOME=/root
+export LIBGL_ALWAYS_SOFTWARE=1 GALLIUM_DRIVER=llvmpipe
+# The ladders read the document back through the MCP socket, and the offer ladder's only
+# instrument is the [OFFER] keytrace. Neither is on by default, and a session launched without
+# them comes up looking perfectly healthy: the window is there, status says app up, and every
+# ladder then dies on "Connection refused" — which reads as a dead app rather than a rig that was
+# started without its instrument. The script that launches the rig is where they belong.
+export ORCA_CAD_MCP="${ORCA_CAD_MCP:-/tmp/mcp.sock}"
+export ORCA_CAD_KEYTRACE="${ORCA_CAD_KEYTRACE:-1}"
+export LD_LIBRARY_PATH="$LIBPY:$LIBPY2:${LD_LIBRARY_PATH:-}"
+mkdir -p /root/.config          # startup dies in boost::filesystem::create_directory without this
+
+# Skip zombies. This container accumulates <defunct> instances of the app across runs, and pgrep
+# matches them, so the naive "first match" reported a dead pid as if the session were healthy.
+app_pid() {
+    local p
+    for p in $(pgrep -f "$(basename "$BIN")" 2>/dev/null); do
+        [ "$(awk "{print \$3}" "/proc/$p/stat" 2>/dev/null)" = "Z" ] && continue
+        echo "$p"; return 0
+    done
+    return 1
+}
+
+status() {
+    echo "display : $(pgrep -f "Xvfb $DISP" >/dev/null && echo up || echo DOWN)"
+    echo "wm      : $(pgrep -x openbox   >/dev/null && echo up || echo DOWN)"
+    if pgrep -x x11vnc >/dev/null; then echo "vnc     : up on :5900"
+    elif ! command -v x11vnc >/dev/null; then echo "vnc     : n/a (x11vnc not installed here)"
+    else echo "vnc     : DOWN"; fi
+    local p; p="$(app_pid || true)"
+    echo "app     : ${p:-DOWN}"
+    # WHICH binary is on screen, not just that something is. A pid alone cannot tell you whether
+    # you are looking at the build you just linked or one from last week, and that is precisely
+    # the question every rig verification is asking.
+    [ -n "${p:-}" ] && echo "binary  : $(readlink -f "/proc/$p/exe" 2>/dev/null || echo unknown)"
+    [ -n "${p:-}" ] && echo "windows : $(xdotool search --name . getwindowname %@ 2>/dev/null | paste -sd'|' -)"
+    return 0
+}
+
+[ "${1:-}" = "--status" ] && { status; exit 0; }
+
+# --- desktop: Xvfb, a window manager, and the VNC server ------------------------------------
+# openbox is REQUIRED: without it xdotool windowactivate aborts with "windowmanager claims not to
+# support _NET_ACTIVE_WINDOW" and dialogs never take focus.
+pgrep -f "Xvfb $DISP" >/dev/null || { nohup Xvfb "$DISP" -screen 0 "${GEOM}x24" -nolisten tcp >/tmp/xvfb.log 2>&1 & sleep 3; }
+pgrep -x openbox      >/dev/null || { nohup openbox >/tmp/openbox.log 2>&1 & sleep 1; }
+if ! pgrep -x x11vnc >/dev/null && command -v x11vnc >/dev/null; then
+    AUTH=()
+    [ -f /root/.vnc/passwd ] && AUTH=(-rfbauth /root/.vnc/passwd)
+    nohup x11vnc -display "$DISP" -rfbport 5900 "${AUTH[@]}" -forever -shared -noxdamage \
+        >/tmp/x11vnc.log 2>&1 &
+    sleep 2
+fi
+
+# --- app ------------------------------------------------------------------------------------
+# Kill by BASENAME, not by "$BIN". The app enforces a single instance, so an older copy launched
+# from a DIFFERENT path (the packaged build/package/bin/ one, say, when BIN points at the freshly
+# linked build/src/Release/ one) survives a path-matched pkill, keeps the instance lock, and the
+# new process exits seconds after loading fonts — leaving no error anywhere. app_pid() below has
+# always matched by basename, so status then reported that stale process as a healthy session:
+# the launch looked green while the window on screen was days old. Measured 2026-08-02, where it
+# nearly passed a UI change against a Jul-30 binary. The killer and the reporter must agree on
+# what counts as "the app".
+pkill -9 -f "$(basename "$BIN")" 2>/dev/null || true
+sleep 2
+nohup "$BIN" >"$LOG" 2>&1 &
+echo "launched $(basename "$BIN") pid $!"
+
+# Wait for the main window rather than sleeping a fixed amount: cold starts vary a lot under
+# software GL, and a fixed sleep either wastes time or races.
+for _ in $(seq 1 40); do
+    xdotool search --name "Untitled" >/dev/null 2>&1 && break
+    sleep 1
+done
+
+# --- first-run dialogs ----------------------------------------------------------------------
+# Click the titlebar close box, but only on geometry we have just read for a window that still
+# exists, and only if the resulting point is inside the screen. Every variable is unset first so a
+# failed read cannot leave the previous dialog's numbers behind — that is the whole bug.
+screen_w="${GEOM%x*}"; screen_h="${GEOM#*x}"
+close_dialog() {
+    local name="$1" id X Y WIDTH HEIGHT cx cy
+    id="$(xdotool search --name "$name" 2>/dev/null | head -1 || true)"
+    [ -z "$id" ] && return 1
+    unset X Y WIDTH HEIGHT
+    eval "$(xdotool getwindowgeometry --shell "$id" 2>/dev/null || true)"
+    # All four must be present and numeric: an empty or stale read is how the stray click happened.
+    for v in "${X:-}" "${Y:-}" "${WIDTH:-}" "${HEIGHT:-}"; do
+        [[ "$v" =~ ^-?[0-9]+$ ]] || { echo "  $name: unreadable geometry, not clicking"; return 1; }
+    done
+    cx=$((X + WIDTH - 11)); cy=$((Y - 31))          # openbox decoration: close box above the frame
+    if [ "$cx" -lt 0 ] || [ "$cy" -lt 0 ] || [ "$cx" -ge "$screen_w" ] || [ "$cy" -ge "$screen_h" ]; then
+        echo "  $name: close box at ${cx},${cy} is off-screen, not clicking"; return 1
+    fi
+    echo "  $name: closing via titlebar at ${cx},${cy}"
+    xdotool mousemove "$cx" "$cy" click 1
+    sleep 2
+    return 0
+}
+# "Restore" is not a first-RUN dialog, it is a second-run one: killing the app mid-session leaves
+# unsaved items behind, and the next launch asks whether to restore them. It sits over the tab bar
+# with a modal grab, so every synthetic click afterwards lands on it and the ladder reports
+# geometry that never got drawn — that is the "success with no log" shape twice already.
+for name in "Setup Wizard" "New version" "Restore"; do
+    for _ in 1 2 3; do close_dialog "$name" || break; done
+done
+
+# --- main window ----------------------------------------------------------------------------
+main="$(xdotool search --name "Untitled" 2>/dev/null | head -1 || true)"
+if [ -n "$main" ]; then
+    xdotool windowmove "$main" 0 0 windowsize "$main" "$screen_w" "$screen_h" 2>/dev/null || true
+    xdotool windowactivate "$main" 2>/dev/null || true
+    sleep 2
+fi
+
+echo "--- session ---"
+status
diff --git a/scripts/Dockerfile.deps b/scripts/Dockerfile.deps
new file mode 100644
index 0000000000..295b72028d
--- /dev/null
+++ b/scripts/Dockerfile.deps
@@ -0,0 +1,95 @@
+# Deps-only base image for fast iteration on Orca.
+# Identical system+pinned-dependency setup to scripts/Dockerfile, but STOPS after
+# `build_linux.sh -dr` (no slicer/AppImage build). Produces an image with the pinned
+# deps baked at /OrcaSlicer/deps/build/destdir, so the slicer can be rebuilt
+# incrementally via scripts/CAD/build-gui-incremental.sh without re-running the long deps build.
+#
+# Build once (rebuild only when deps/ changes, e.g. OCCT module flags):
+#   docker build -t snapmaker-deps -f scripts/Dockerfile.deps .
+FROM docker.io/ubuntu:24.04
+LABEL maintainer="Orca CAD iteration base"
+
+# Disable interactive package configuration
+RUN apt-get update && \
+    echo 'debconf debconf/frontend select Noninteractive' | debconf-set-selections
+
+# Add a deb-src
+RUN echo deb-src http://archive.ubuntu.com/ubuntu \
+    $(cat /etc/*release | grep VERSION_CODENAME | cut -d= -f2) main universe>> /etc/apt/sources.list
+
+RUN apt-get update && apt-get install  -y \
+    autoconf \
+    build-essential \
+    cmake \
+    curl \
+    eglexternalplatform-dev \
+    extra-cmake-modules \
+    file \
+    git \
+    gstreamer1.0-plugins-bad \
+    gstreamer1.0-libav \
+    libcairo2-dev \
+    libcurl4-openssl-dev \
+    libdbus-1-dev \
+    libglew-dev \
+    libglu1-mesa-dev \
+    libgstreamer1.0-dev \
+    libgstreamerd-3-dev \
+    libgstreamer-plugins-base1.0-dev \
+    libgstreamer-plugins-good1.0-dev \
+    libgtk-3-dev \
+    libsecret-1-dev \
+    libsoup2.4-dev \
+    libssl3 \
+    libssl-dev \
+    libtool \
+    libudev-dev \
+    libwayland-dev \
+    libwebkit2gtk-4.1-dev \
+    libxkbcommon-dev \
+    locales \
+    locales-all \
+    m4 \
+    pkgconf \
+    sudo \
+    wayland-protocols \
+    wget
+
+ENV LC_ALL=en_US.utf8
+RUN locale-gen $LC_ALL
+ENV SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt
+
+COPY ./ OrcaSlicer
+WORKDIR OrcaSlicer
+
+# System dependencies
+RUN ./build_linux.sh -u
+
+# Pinned dependencies in ./deps (OCCT 7.6 with ModelingAlgorithms enabled, OpenCV,
+# OpenVDB, Boost, wxWidgets, ...). This is the long step; it is baked into the image.
+# -j 12, not the default all-cores: on 2026-08-21 an unbounded deps build plus an unbounded
+# app build put 42 GB of cc1plus on a 62 GB box and OOM-killed the host for 2h28m. 12 keeps
+# the compile fast while leaving the machine usable. Pair with `docker build --memory`.
+RUN ./build_linux.sh -dr -j 12
+
+# Compatibility symlink. This deps tree installs into deps/build/OrcaSlicer_dep/, while the
+# orcacad_buildcache volume was configured against the previous image, whose prefix was
+# deps/build/destdir/. Those paths are baked as absolute strings into the app's CMakeCache, so
+# without this symlink a rebuild on the new image reconfigures from scratch — hours of compile
+# to change one directory name. Same tree, two names.
+RUN ln -sfn /OrcaSlicer/deps/build/OrcaSlicer_dep /OrcaSlicer/deps/build/destdir
+
+# The rig's GUI runtime. This used to arrive for free because orcacad-deps was layered on
+# snapmaker-deps; that lineage is Trap 1 in docs/rig_build_traps.md (a baked project(Snapmaker_Orca)
+# tree) and building from this Dockerfile is what removes it — along with the X stack the rig
+# needs. scripts/CAD/start-headless-gui.sh requires Xvfb and openbox (without a window manager `xdotool
+# windowactivate` aborts with "windowmanager claims not to support..."), drives the UI with
+# xdotool, and captures to /shots with scrot/ImageMagick. Same set snapmaker-deps carries.
+RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
+    imagemagick \
+    openbox \
+    scrot \
+    xauth \
+    xdotool \
+    xvfb \
+ && rm -rf /var/lib/apt/lists/*
diff --git a/scripts/Dockerfile.deps-assimp b/scripts/Dockerfile.deps-assimp
new file mode 100644
index 0000000000..40566885c0
--- /dev/null
+++ b/scripts/Dockerfile.deps-assimp
@@ -0,0 +1,70 @@
+# Adds assimp to the orcacad-deps image.
+#
+# WHY THIS EXISTS. OrcaSlicer mainline gained `find_package(assimp REQUIRED)` in
+# src/libslic3r/CMakeLists.txt (glTF/GLB/FBX import for texture-to-colour), and the baked
+# orcacad-deps image predates it: the image's deps/ tree has no Assimp directory at all, and
+# nothing named assimp exists anywhere in it. On the host, deps/build/dep_Assimp-prefix has
+# only `patch` and `update` stamps -- no build, no install -- so the dependency was fetched
+# and then never built, in the image or out of it.
+#
+# The consequence was that scripts/CAD/run-kernel-tests.sh failed at CMake CONFIGURE time,
+# before a single source file compiled, so THIS FORK'S KERNEL SUITE COULD NOT RUN AT ALL.
+# Every kernel change ported here was parity-checked against Snapmaker and never independently
+# tested (w80c). The Snapmaker fork does not hit this: its base requires neither
+# assimp nor OpenCV.
+#
+# WHY A LAYER AND NOT A FULL DEPS REBUILD. Rebuilding every dependency takes hours and would
+# rewrite artifacts that are currently working. This adds exactly the one missing package on
+# top of the existing image, and it is a Dockerfile rather than a `docker commit` so that what
+# was done is reviewable and repeatable instead of being an undocumented mutation.
+#
+# The flags below are copied from the project's own recipe (deps/Assimp/Assimp.cmake) plus the
+# standard superbuild arguments from orcaslicer_add_cmake_project (deps/CMakeLists.txt:158) and
+# DEP_CMAKE_OPTS (deps/deps-linux.cmake). Keep them in step with that recipe: this file is a
+# stand-in for the superbuild, not an independent opinion about how to build assimp.
+#
+#   BUILD (from the repo root, tarball already in deps/DL_CACHE/Assimp/):
+#     docker build -f scripts/Dockerfile.deps-assimp -t orcacad-deps .
+#
+#   VERIFY:
+#     docker run --rm orcacad-deps sh -c \
+#       'ls /OrcaSlicer/deps/build/destdir/usr/local/lib/cmake/assimp*'
+#     scripts/CAD/run-kernel-tests.sh
+#
+FROM orcacad-deps
+
+# v5.4.3 is the version deps/Assimp/Assimp.cmake selects for CMake >= 3.22 (the image has
+# 3.28.3). The SHA256 is that recipe's URL_HASH, verified against the cached tarball before
+# this file was written -- an unverified archive is not a dependency, it is whatever was
+# sitting in the cache.
+ARG ASSIMP_SHA256=66dfbaee288f2bc43172440a55d0235dfc7bf885dda6435c038e8000e79582cb
+COPY deps/DL_CACHE/Assimp/v5.4.3.tar.gz /tmp/assimp.tar.gz
+
+RUN set -eux; \
+    echo "${ASSIMP_SHA256}  /tmp/assimp.tar.gz" | sha256sum -c -; \
+    mkdir -p /tmp/assimp-src && \
+    tar -xzf /tmp/assimp.tar.gz -C /tmp/assimp-src --strip-components=1; \
+    DESTDIR=/OrcaSlicer/deps/build/destdir/usr/local; \
+    cmake -S /tmp/assimp-src -B /tmp/assimp-build -G Ninja \
+        -DCMAKE_POLICY_VERSION_MINIMUM=3.5 \
+        -DCMAKE_BUILD_TYPE=Release \
+        -DCMAKE_INSTALL_PREFIX="$DESTDIR" \
+        -DCMAKE_PREFIX_PATH="$DESTDIR" \
+        -DCMAKE_POSITION_INDEPENDENT_CODE=ON \
+        -DBUILD_SHARED_LIBS=OFF \
+        -DASSIMP_BUILD_USE_CCACHE=OFF \
+        -DASSIMP_BUILD_TESTS=OFF \
+        -DASSIMP_BUILD_SAMPLES=OFF \
+        -DASSIMP_BUILD_ASSIMP_TOOLS=OFF \
+        -DASSIMP_INSTALL_PDB=OFF \
+        -DASSIMP_NO_EXPORT=ON \
+        -DASSIMP_BUILD_ALL_IMPORTERS_BY_DEFAULT=OFF \
+        -DASSIMP_BUILD_GLTF_IMPORTER=ON \
+        -DASSIMP_BUILD_OBJ_IMPORTER=ON \
+        -DASSIMP_BUILD_FBX_IMPORTER=ON \
+        -DASSIMP_BUILD_ZLIB=ON \
+        -DASSIMP_WARNINGS_AS_ERRORS=OFF \
+        -DBUILD_WITH_STATIC_CRT=OFF; \
+    cmake --build /tmp/assimp-build --target install -- -j"$(nproc)"; \
+    rm -rf /tmp/assimp-src /tmp/assimp-build /tmp/assimp.tar.gz; \
+    test -n "$(ls "$DESTDIR"/lib/cmake/assimp* 2>/dev/null)"
diff --git a/scripts/flatpak/com.orcaslicer.OrcaSlicer.yml b/scripts/flatpak/com.orcaslicer.OrcaSlicer.yml
index 668f51334b..fa7c329b4b 100644
--- a/scripts/flatpak/com.orcaslicer.OrcaSlicer.yml
+++ b/scripts/flatpak/com.orcaslicer.OrcaSlicer.yml
@@ -223,6 +223,12 @@ modules:
         sha256: 51afe0db79af8386e2027d56d685177135581e0ee82ade9d7f2caff8deab5ec5
         dest: external-packages/OpenCSG
 
+      # SolveSpace libslvs (2D sketch constraint solver, Design tab)
+      - type: file
+        url: https://github.com/JacobStoren/SolveSpaceLib/archive/4d8704523e4bf212fadf5189f92484244f670fea.zip
+        sha256: 1c4bdde9c3c6ef20ea4b50b73601de56769f2eb131b36927d7c6489f102e6c30
+        dest: external-packages/SLVS
+
       # Blosc 1.17.0 (tamasmeszaros fork)
       - type: file
         url: https://github.com/tamasmeszaros/c-blosc/archive/refs/heads/v1.17.0_tm.zip
diff --git a/src/libslic3r/AppConfig.cpp b/src/libslic3r/AppConfig.cpp
index 4c6eefa470..33e25b18cd 100644
--- a/src/libslic3r/AppConfig.cpp
+++ b/src/libslic3r/AppConfig.cpp
@@ -313,6 +313,26 @@ void AppConfig::set_defaults()
     if (get("zoom_to_mouse").empty())
         set_bool("zoom_to_mouse", false);
 
+#ifdef SLIC3R_CAD
+    // Experimental parametric Design tab. Off by default: the tab is not created at all
+    // until this is turned on, so nothing it builds reaches an unsuspecting user.
+    if (get("enable_cad_feature").empty())
+        set_bool("enable_cad_feature", false);
+
+    // Auto-weld sketch endpoints within kSketchJoinTol when building closed loops.
+    // Default ON: it is what the ~90% case wants; OFF makes the kernel demand an exact
+    // joint. The GUI pushes it into SketchEngine via set_sketch_auto_close().
+    if (get("auto_close_sketch_loops").empty())
+        set_bool("auto_close_sketch_loops", true);
+
+    // Design tab: draw a mate connector as a face rather than as the abstract disc + roll
+    // quadrant. Defaults ON — face orientation is hardwired perception, so the roll and the
+    // verse read without being learned, which no abstract glyph achieves. Turning it off
+    // restores the conventional CAD representation for users who expect it (x0kd).
+    if (get("design_connector_face_glyph").empty())
+        set_bool("design_connector_face_glyph", true);
+#endif
+
 //#ifdef SUPPORT_SHOW_HINTS
     if (get("show_hints").empty())
         set_bool("show_hints", false);
diff --git a/src/libslic3r/CAD/CadDocument.cpp b/src/libslic3r/CAD/CadDocument.cpp
new file mode 100644
index 0000000000..c20b636ae7
--- /dev/null
+++ b/src/libslic3r/CAD/CadDocument.cpp
@@ -0,0 +1,4125 @@
+#include "libslic3r/CAD/CadDocument.hpp"
+#include "libslic3r/CAD/SketchConstraints.hpp"
+#include "libslic3r/CAD/SketchSolver.hpp"
+#include "libslic3r/CAD/SketchImport.hpp"   // transform_regions for imported art
+
+#include <array>
+
+#include <Standard_Failure.hxx>
+#include <BRepBuilderAPI_MakeWire.hxx>
+#include <BRepBuilderAPI_MakeEdge.hxx>
+#include <BRepBuilderAPI_MakeFace.hxx>
+#include <BRepBuilderAPI_MakePolygon.hxx>
+#include <BRepAlgoAPI_Fuse.hxx>
+#include <BRepAlgoAPI_Cut.hxx>
+#include <BRepAlgoAPI_Common.hxx>
+#include <BRepAlgoAPI_Defeaturing.hxx>
+#include <BRepAlgoAPI_BooleanOperation.hxx>
+#include <BRepOffsetAPI_MakePipe.hxx>
+#include <BRepOffsetAPI_MakePipeShell.hxx>
+#include <BRepOffsetAPI_MakeThickSolid.hxx>
+#include <BRepBuilderAPI_Sewing.hxx>
+#include <BRepBuilderAPI_MakeSolid.hxx>
+#include <ShapeAnalysis_FreeBounds.hxx>
+#include <BRepOffsetAPI_MakeOffsetShape.hxx>
+#include <BRepOffsetAPI_MakeFilling.hxx>
+#include <BRepOffsetAPI_DraftAngle.hxx>
+#include <Bnd_Box.hxx>
+#include <BRepBndLib.hxx>
+#include <gp_Pln.hxx>
+#include <TopTools_ListOfShape.hxx>
+#include <BRepPrimAPI_MakeCylinder.hxx>
+#include <BRepPrimAPI_MakeCone.hxx>
+#include <BRepPrimAPI_MakePrism.hxx>
+#include <BRepPrimAPI_MakeRevol.hxx>
+#include <BRepCheck_Analyzer.hxx>
+#include <BRepLib.hxx>
+#include <BRepAdaptor_Curve.hxx>
+#include <BRepAdaptor_Surface.hxx>   // plane_of_face: reject non-planar faces
+#include <GeomAbs_SurfaceType.hxx>
+#include <GeomAbs_CurveType.hxx>
+#include <BRep_Tool.hxx>
+#include <Geom_CylindricalSurface.hxx>
+#include <Geom_ConicalSurface.hxx>
+#include <Geom2d_TrimmedCurve.hxx>
+#include <GeomAbs_Shape.hxx>        // SurfaceFill: GeomAbs_C0
+#include <GCE2d_MakeSegment.hxx>
+#include <TopoDS_Edge.hxx>
+#include <TopoDS_Face.hxx>
+#include <TopAbs.hxx>
+#include <TopoDS_Shell.hxx>
+#include <TopoDS_Compound.hxx>      // multi-body: compound of bodies for display/compat
+#include <BRep_Builder.hxx>
+#include <TopAbs_Orientation.hxx>   // outward-normal orientation for face-extrude
+#include <TopoDS.hxx>               // TopoDS::Edge for SurfaceFill
+#include <TopExp_Explorer.hxx>      // is_sheet_shape
+#include <gp_Circ.hxx>
+#include <gp_Ax2.hxx>
+#include <gp_Ax3.hxx>
+#include <gp_Pnt2d.hxx>
+#include <gp_Vec.hxx>
+#include <gp_Trsf.hxx>             // pattern: rigid copy transforms
+#include <STEPControl_Writer.hxx>  // STEP export (native B-rep)
+#include <STEPControl_StepModelType.hxx>
+#include <IFSelect_ReturnStatus.hxx>
+#include <gp_Ax1.hxx>             // pattern: rotation axis (circular)
+#include <BRepBuilderAPI_Transform.hxx>
+#include <BRepGProp.hxx>
+#include <GProp_GProps.hxx>
+#include <cmath>
+#include <cctype>
+#include <cstdio>
+#include <stdexcept>
+#include <algorithm>
+#include <sstream>
+
+#include <cereal/archives/binary.hpp>
+#include <BRepTools.hxx>
+
+namespace Slic3r {
+
+// ---- helical-thread construction helpers (file-local) ----------------------
+
+// Helix spine on a cylinder (radius/pitch/height) about `axis`, as a wire.
+static TopoDS_Wire make_helix_wire(const gp_Ax3& axis, double radius,
+                                   double pitch, double height)
+{
+    Handle(Geom_CylindricalSurface) cyl = new Geom_CylindricalSurface(axis, radius);
+    double turns = (pitch > 1e-6) ? (height / pitch) : 1.0;
+    // In the surface (u,v) parametrization u is the angle, v the axial height.
+    gp_Pnt2d p0(0.0, 0.0);
+    gp_Pnt2d p1(2.0 * M_PI * turns, height);
+    Handle(Geom2d_TrimmedCurve) seg = GCE2d_MakeSegment(p0, p1);
+    TopoDS_Edge e = BRepBuilderAPI_MakeEdge(seg, cyl).Edge();
+    BRepLib::BuildCurves3d(e);
+    return BRepBuilderAPI_MakeWire(e).Wire();
+}
+
+// Helix spine from a CadFeature's helix params. Supports cylindrical (taper==0)
+// and conical (taper!=0) surfaces; left_handed flips the winding direction.
+// Returns null wire if validation fails (error is written to err).
+static TopoDS_Wire make_helix_spine(const CadFeature& f, std::string& err)
+{
+    err.clear();
+    const double R = f.helix_radius, P = f.helix_pitch, H = f.helix_height;
+    const double taper = f.helix_taper_deg * M_PI / 180.0;
+
+    if (R <= 0)   { err = "helix radius must be > 0"; return TopoDS_Wire(); }
+    if (P <= 0)   { err = "helix pitch must be > 0";  return TopoDS_Wire(); }
+    if (H < 0)    { err = "helix height must be >= 0"; return TopoDS_Wire(); }
+    if (H == 0)   { err = "helix height of 0 (flat spiral) is not supported"; return TopoDS_Wire(); }
+    const double turns = H / P;
+    if (turns > 10000) { err = "helix turn count exceeds limit (10000)"; return TopoDS_Wire(); }
+    if (std::abs(taper) > 1e-12) {
+        const double R_top = R + H * std::tan(taper);
+        if (R_top <= 0) {
+            err = "helix taper drives radius negative before reaching height";
+            return TopoDS_Wire();
+        }
+    }
+
+    gp_Dir zdir(f.plane.normal.x(), f.plane.normal.y(), f.plane.normal.z());
+    gp_Dir xdir(f.plane.x_axis.x(), f.plane.x_axis.y(), f.plane.x_axis.z());
+    Vec3d ori = f.plane.origin;
+    gp_Pnt o(ori.x(), ori.y(), ori.z());
+    gp_Ax2 ax2(o, zdir, xdir);
+    gp_Ax3 ax3(o, zdir, xdir);
+
+    TopoDS_Edge e;
+    if (std::abs(taper) > 1e-12) {
+        Handle(Geom_ConicalSurface) cone = new Geom_ConicalSurface(ax3, taper, R);
+        double u1 = f.helix_left_handed ? -2.0 * M_PI * turns : 2.0 * M_PI * turns;
+        gp_Pnt2d p0(0.0, 0.0);
+        gp_Pnt2d p1(u1, H);
+        Handle(Geom2d_TrimmedCurve) seg = GCE2d_MakeSegment(p0, p1);
+        e = BRepBuilderAPI_MakeEdge(seg, cone).Edge();
+    } else {
+        Handle(Geom_CylindricalSurface) cyl = new Geom_CylindricalSurface(ax3, R);
+        double u1 = f.helix_left_handed ? -2.0 * M_PI * turns : 2.0 * M_PI * turns;
+        gp_Pnt2d p0(0.0, 0.0);
+        gp_Pnt2d p1(u1, H);
+        Handle(Geom2d_TrimmedCurve) seg = GCE2d_MakeSegment(p0, p1);
+        e = BRepBuilderAPI_MakeEdge(seg, cyl).Edge();
+    }
+    BRepLib::BuildCurves3d(e);
+    return BRepBuilderAPI_MakeWire(e).Wire();
+}
+
+// Triangular axial thread profile (a planar face) placed at the helix start
+// (origin + radius*xdir). Spans +-pitch/2 axially; apex offset radially by depth.
+// Both thread kinds sweep the SAME outward-biting V (base on the cylinder wall,
+// apex `depth` into the surrounding material). Only the boolean differs:
+//  - external: the V is FUSED to the rod  -> a raised helical ridge.
+//  - internal: the V is CUT from the wall -> a sunken helical groove. The cut MUST
+//    go outward into the wall to be visible; an inward V (the old behaviour) only
+//    sweeps already-empty bore space and removes nothing.
+static TopoDS_Wire make_thread_profile(const gp_Pnt& origin, const gp_Dir& xdir,
+                                       const gp_Dir& zdir, double radius,
+                                       double pitch, double depth, bool internal)
+{
+    // `internal` is intentionally unused: the V is the same shape either way, always pointing
+    // radially outward from `radius`. What differs is what the caller DOES with the swept solid
+    // — an external thread fuses it onto the shaft, an internal one cuts it out of the wall after
+    // boring at the minor diameter. Keeping the parameter documents that the caller decided, and
+    // stops someone "fixing" the profile to point inward for the internal case, which would make
+    // the groove sweep already-empty bore space and cut nothing.
+    (void)internal;
+    gp_Vec vx(xdir), vz(zdir);
+    // Root the V CLEARLY inside the wall (a real overlap, not a 0.05 mm tangency) so the boolean
+    // has clean intersections — near-coincident faces are what make OCCT's fuse/cut unstable.
+    const double over = std::min(std::max(depth, 0.25), radius * 0.4);
+    double inner = radius - over;   // base, well inside the wall (solid overlap)
+    double crest = radius + depth;  // apex, `depth` into the surrounding material
+    // Axial half-height must be < pitch/2 so ADJACENT helix turns don't collide — a full-pitch
+    // profile makes the swept solid self-intersect (invalid -> never renders, or crashes the
+    // boolean). 0.42*pitch leaves a clean gap between turns; the V still reads as a thread.
+    const double half = 0.42 * pitch;
+    gp_Pnt top (origin.XYZ() + (vx * inner).XYZ() + (vz * ( half)).XYZ());
+    gp_Pnt bot (origin.XYZ() + (vx * inner).XYZ() + (vz * (-half)).XYZ());
+    gp_Pnt apex(origin.XYZ() + (vx * crest).XYZ());
+    BRepBuilderAPI_MakePolygon poly(top, bot, apex, Standard_True);
+    return poly.Wire();   // closed triangle, swept by MakePipeShell with a fixed binormal
+}
+
+// ---- expression evaluator (file-local) -------------------------------------
+// ponytail: self-contained shunting-yard arithmetic + function set for
+// parametric dimension expressions. Extend the function table if needed.
+
+// Evaluate an arithmetic expression to a double. Supports + - * /, parentheses,
+// unary minus, decimal literals, and identifiers resolved via `vars`. Functions:
+// sqrt, abs, sin, cos, tan (degrees), min, max, and the constant `pi`.
+// Throws std::runtime_error on any parse or lookup error, div-by-zero, bad arity.
+static double eval_expr(const std::string& src, const std::map<std::string, double>& vars)
+{
+    struct Token {
+        enum Type { Num, Id, Op, LParen, RParen, Comma };
+        Type type;
+        std::string val;
+        double num{0};
+    };
+    // precedence: 0=paren/comma, 1=+-, 2=*/, 3=unary-minus, 4=function
+    auto prec = [](char op, bool unary) -> int {
+        if (unary && op == 'u') return 3;
+        if (op == '+' || op == '-') return 1;
+        if (op == '*' || op == '/') return 2;
+        if (op == '(' || op == ')' || op == ',') return 0;
+        return 0;
+    };
+    auto is_op = [](char c) { return c == '+' || c == '-' || c == '*' || c == '/'; };
+
+    // ---- tokenise ----
+    std::vector<Token> tokens;
+    size_t i = 0;
+    bool prev_was_val = false; // tracked for unary-minus detection
+    while (i < src.size()) {
+        char c = src[i];
+        if (c == ' ' || c == '\t' || c == '\r' || c == '\n') { ++i; continue; }
+        if (c == '(') { tokens.push_back({Token::LParen, "("}); ++i; prev_was_val = false; continue; }
+        if (c == ')') { tokens.push_back({Token::RParen, ")"}); ++i; prev_was_val = true; continue; }
+        if (c == ',') { tokens.push_back({Token::Comma, ","}); ++i; prev_was_val = false; continue; }
+        if (isdigit(c) || c == '.') {
+            size_t start = i;
+            while (i < src.size() && (isdigit(src[i]) || src[i] == '.')) ++i;
+            Token t{Token::Num, src.substr(start, i - start)};
+            t.num = std::stod(t.val);
+            tokens.push_back(t);
+            prev_was_val = true;
+            continue;
+        }
+        if (isalpha(c) || c == '_') {
+            size_t start = i;
+            while (i < src.size() && (isalnum(src[i]) || src[i] == '_')) ++i;
+            std::string id = src.substr(start, i - start);
+            tokens.push_back({Token::Id, id});
+            prev_was_val = true;
+            continue;
+        }
+        if (is_op(c)) {
+            // unary minus detection
+            if (c == '-' && !prev_was_val) {
+                tokens.push_back({Token::Op, "u"});
+            } else {
+                tokens.push_back({Token::Op, std::string(1, c)});
+            }
+            ++i;
+            prev_was_val = false;
+            continue;
+        }
+        throw std::runtime_error("bad character in expression");
+    }
+
+    // ---- shunting-yard: infix -> RPN ----
+    std::vector<Token> rpn;
+    std::vector<Token> stack;
+    auto flush_paren = [&]() {
+        while (!stack.empty() && stack.back().type != Token::LParen) {
+            rpn.push_back(stack.back()); stack.pop_back();
+        }
+        if (stack.empty()) throw std::runtime_error("mismatched parentheses");
+        stack.pop_back(); // discard '('
+#if 0
+        // If the '(' belonged to a function call, push the function name
+        // (ponytail: we track this via the Id token on top of the op stack
+        // BEFORE the '(' was pushed; after flush we check if the previous
+        // token was a function-call Id).
+#endif
+        if (!stack.empty() && stack.back().type == Token::Id) {
+            rpn.push_back(stack.back()); stack.pop_back();
+        }
+    };
+
+    for (size_t j = 0; j < tokens.size(); ++j) {
+        const Token& t = tokens[j];
+        if (t.type == Token::Num) {
+            rpn.push_back(t);
+        } else if (t.type == Token::Id) {
+            // function call if the next token is '('
+            if (j + 1 < tokens.size() && tokens[j + 1].type == Token::LParen) {
+                stack.push_back(t);
+            } else {
+                // identifier — resolve now
+                double v;
+                if (t.val == "pi") v = M_PI;
+                else {
+                    auto it = vars.find(t.val);
+                    if (it == vars.end())
+                        throw std::runtime_error("unknown identifier: " + t.val);
+                    v = it->second;
+                }
+                rpn.push_back({Token::Num, "", v});
+            }
+        } else if (t.type == Token::Op) {
+            int p = prec(t.val[0], t.val == "u");
+            while (!stack.empty()) {
+                const Token& top = stack.back();
+                if (top.type != Token::Op && top.type != Token::Id) break;
+                int tp = prec(top.val[0], top.val == "u");
+                if (tp < 4 && p <= tp) {
+                    rpn.push_back(top); stack.pop_back();
+                } else break;
+            }
+            stack.push_back(t);
+        } else if (t.type == Token::LParen) {
+            stack.push_back(t);
+        } else if (t.type == Token::RParen) {
+            flush_paren();
+        } else if (t.type == Token::Comma) {
+            while (!stack.empty() && stack.back().type != Token::LParen) {
+                rpn.push_back(stack.back()); stack.pop_back();
+            }
+            // , is a no-op separator — just stay inside the paren
+        }
+    }
+    while (!stack.empty()) {
+        if (stack.back().type == Token::LParen || stack.back().type == Token::RParen)
+            throw std::runtime_error("mismatched parentheses");
+        rpn.push_back(stack.back()); stack.pop_back();
+    }
+
+    // ---- evaluate RPN ----
+    std::vector<double> vs;
+    for (const Token& t : rpn) {
+        if (t.type == Token::Num) {
+            vs.push_back(t.num);
+        } else if (t.type == Token::Op) {
+            if (t.val == "u") {
+                if (vs.empty()) throw std::runtime_error("missing operand for unary minus");
+                vs.back() = -vs.back();
+            } else {
+                if (vs.size() < 2) throw std::runtime_error("not enough operands for '" + t.val + "'");
+                double b = vs.back(); vs.pop_back();
+                double a = vs.back(); vs.pop_back();
+                if (t.val == "+") vs.push_back(a + b);
+                else if (t.val == "-") vs.push_back(a - b);
+                else if (t.val == "*") vs.push_back(a * b);
+                else if (t.val == "/") { if (b == 0) throw std::runtime_error("division by zero"); vs.push_back(a / b); }
+            }
+        } else if (t.type == Token::Id) {
+            // function call (already on RPN via shunting-yard)
+            auto call_fn = [&](const std::string& name, int arity) {
+                if ((int)vs.size() < arity)
+                    throw std::runtime_error("not enough arguments for " + name + "()");
+                if (name == "sqrt") { double a = vs.back(); vs.pop_back(); vs.push_back(std::sqrt(a)); }
+                else if (name == "abs") { double a = vs.back(); vs.pop_back(); vs.push_back(std::abs(a)); }
+                else if (name == "sin") { double a = vs.back(); vs.pop_back(); vs.push_back(std::sin(a * M_PI / 180.0)); }
+                else if (name == "cos") { double a = vs.back(); vs.pop_back(); vs.push_back(std::cos(a * M_PI / 180.0)); }
+                else if (name == "tan") { double a = vs.back(); vs.pop_back(); vs.push_back(std::tan(a * M_PI / 180.0)); }
+                else if (name == "min") { double b = vs.back(); vs.pop_back(); double a = vs.back(); vs.pop_back(); vs.push_back(std::min(a, b)); }
+                else if (name == "max") { double b = vs.back(); vs.pop_back(); double a = vs.back(); vs.pop_back(); vs.push_back(std::max(a, b)); }
+                else throw std::runtime_error("unknown function: " + name);
+            };
+            call_fn(t.val, (t.val == "min" || t.val == "max") ? 2 : 1);
+        }
+    }
+    if (vs.size() != 1) throw std::runtime_error("invalid expression");
+    return vs[0];
+}
+
+// Topologically evaluate `variables` (name -> expression) into name -> value.
+// An expression may reference other variables; resolution is recursive with a
+// visiting set. Throws std::runtime_error("variable cycle: ...") on a dependency
+// cycle, or propagates eval_expr errors.
+static std::map<std::string, double>
+evaluate_variables(const std::map<std::string, std::string>& variables)
+{
+    std::map<std::string, double> done;
+    std::set<std::string> visiting;
+
+    std::function<double(const std::string&)> resolve = [&](const std::string& name) -> double {
+        auto itd = done.find(name);
+        if (itd != done.end()) return itd->second;
+        if (visiting.count(name)) throw std::runtime_error("variable cycle: " + name);
+        auto itv = variables.find(name);
+        if (itv == variables.end()) throw std::runtime_error("unknown identifier: " + name);
+        visiting.insert(name);
+        // pre-resolve every identifier `name` references: scan for identifiers in
+        // its expression, resolve them first, then eval with the populated map.
+        // ponytail: simplest correct approach — depth-first with visited tracking.
+        std::map<std::string, double> scope = done; // start with already-resolved
+        // Add any variable name found in the expression to scope (resolve recursively)
+        const std::string& expr = itv->second;
+        for (size_t i = 0; i < expr.size(); ) {
+            char c = expr[i];
+            if (c == ' ' || c == '\t' || c == '\r' || c == '\n') { ++i; continue; }
+            if (isalpha(c) || c == '_') {
+                size_t start = i;
+                while (i < expr.size() && (isalnum(expr[i]) || expr[i] == '_')) ++i;
+                std::string id = expr.substr(start, i - start);
+                // skip "pi" and function names — they're built-ins, not variables
+                if (id == "pi" || id == "sqrt" || id == "abs" || id == "sin" || id == "cos" ||
+                    id == "tan" || id == "min" || id == "max") continue;
+                if (!variables.count(id)) throw std::runtime_error("unknown identifier: " + id);
+                scope[id] = resolve(id);
+                continue;
+            }
+            ++i;
+        }
+        double val = eval_expr(expr, scope);
+        visiting.erase(name);
+        done[name] = val;
+        return val;
+    };
+
+    for (const auto& [k, _] : variables) resolve(k);
+    return done;
+}
+
+// Write `value` into the CadFeature numeric field named `field`. Allow-list of
+// the geometric dimension fields a variable realistically drives. Integer-valued
+// fields are rounded. Throws std::runtime_error("unknown parameter: " + field)
+// for anything not in the list.
+static void assign_field(CadFeature& f, const std::string& field, double value)
+{
+    // double fields (alphabetical)
+    if (field == "distance")          { f.distance = value; return; }
+    if (field == "distance2")         { f.distance2 = value; return; }
+    if (field == "draft_angle")       { f.draft_angle = value; return; }
+    if (field == "dressup_size")      { f.dressup_size = value; return; }
+    if (field == "height")            { f.height = value; return; }
+    if (field == "hole_cbore_diameter") { f.hole_cbore_diameter = value; return; }
+    if (field == "hole_cbore_depth")  { f.hole_cbore_depth = value; return; }
+    if (field == "hole_csink_angle")  { f.hole_csink_angle = value; return; }
+    if (field == "hole_csink_diameter") { f.hole_csink_diameter = value; return; }
+    if (field == "hole_depth")        { f.hole_depth = value; return; }
+    if (field == "hole_diameter")     { f.hole_diameter = value; return; }
+    if (field == "hole_x")            { f.hole_x = value; return; }
+    if (field == "hole_y")            { f.hole_y = value; return; }
+    if (field == "import_scale_x")    { f.import_scale_x = value; return; }
+    if (field == "import_scale_y")    { f.import_scale_y = value; return; }
+    if (field == "pattern_angle")     { f.pattern_angle = value; return; }
+    if (field == "pattern_spacing")   { f.pattern_spacing = value; return; }
+    if (field == "plane_angle_tilt")  { f.plane_angle_tilt = value; return; }
+    if (field == "plane_offset")      { f.plane_offset = value; return; }
+    if (field == "radius")            { f.radius = value; return; }
+    if (field == "revolve_angle")     { f.revolve_angle = value; return; }
+    if (field == "rib_depth")         { f.rib_depth = value; return; }
+    if (field == "rib_thickness")     { f.rib_thickness = value; return; }
+    if (field == "shell_thickness")   { f.shell_thickness = value; return; }
+    if (field == "taper_deg")         { f.taper_deg = value; return; }
+    if (field == "thread_depth")      { f.thread_depth = value; return; }
+    if (field == "thread_height")     { f.thread_height = value; return; }
+    if (field == "thread_pitch")      { f.thread_pitch = value; return; }
+    if (field == "thread_radius")     { f.thread_radius = value; return; }
+    if (field == "thread_x")          { f.thread_x = value; return; }
+    if (field == "thread_y")          { f.thread_y = value; return; }
+    if (field == "width")             { f.width = value; return; }
+    // int fields (rounded)
+    if (field == "pattern_count")     { f.pattern_count = (int)std::lround(value); return; }
+    throw std::runtime_error("unknown parameter: " + field);
+}
+
+// ---------------------------------------------------------------------------
+
+// Sample a sketch entity at parameter t in [0,1]. Handles Line, Arc, BSpline (cubic, 4 poles).
+// Falls back to a p0->p1 lerp for any other type. // ponytail: covers the entities a guide
+// curve is realistically drawn with; extend if needed.
+static Vec2d sample_entity_2d(const SketchEntity& e, double t)
+{
+    t = std::max(0.0, std::min(1.0, t));
+    switch (e.type) {
+    case SketchEntity::Type::Line:
+        return e.p0 + (e.p1 - e.p0) * t;
+    case SketchEntity::Type::Arc: {
+        double theta = e.start_angle + (e.end_angle - e.start_angle) * t;
+        return e.center + e.radius * Vec2d(std::cos(theta), std::sin(theta));
+    }
+    case SketchEntity::Type::BSpline:
+        if (e.ctrl.size() == 4) {
+            const double u  = 1.0 - t;
+            const double b0 = u * u * u;
+            const double b1 = 3.0 * u * u * t;
+            const double b2 = 3.0 * u * t * t;
+            const double b3 = t * t * t;
+            return e.ctrl[0] * b0 + e.ctrl[1] * b1 + e.ctrl[2] * b2 + e.ctrl[3] * b3;
+        }
+        return e.ctrl.empty() ? e.p0 + (e.p1 - e.p0) * t
+                              : e.ctrl.front() + (e.ctrl.back() - e.ctrl.front()) * t;
+    default:
+        return e.p0 + (e.p1 - e.p0) * t;
+    }
+}
+
+int CadDocument::add_sketch(SketchShape shape, const SketchPlane& plane,
+                            double width, double height, double radius,
+                            const std::string& name)
+{
+    CadFeature f;
+    f.type   = CadFeatureType::Sketch;
+    f.name   = name;
+    f.shape  = shape;
+    f.plane  = plane;
+    f.width  = width;
+    f.height = height;
+    f.radius = radius;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_sketch_profile(const SketchProfile& profile, const SketchPlane& plane,
+                                    const std::string& name)
+{
+    CadFeature f;
+    f.type    = CadFeatureType::Sketch;
+    f.name    = name;
+    f.plane   = plane;
+    f.profile = profile;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_sketch_entities(const std::vector<SketchEntity>& entities,
+                                     const SketchPlane& plane, const std::string& name,
+                                     const std::vector<SketchEntityConstraintDef>& constraints)
+{
+    CadFeature f;
+    f.type               = CadFeatureType::Sketch;
+    f.name               = name;
+    f.plane              = plane;
+    f.entities           = entities;
+    f.entity_constraints = constraints;   // driving dimensions, solved by solve_sketch_feature
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+// Solve Onshape-style constraints on a SketchEntity list (Fase 4.3). All entity
+// types participate: Line (P0,P1), Arc (P0,P1,Center), Circle (Center), Point (P0).
+// Solved coordinates are written back, with arc angles reflowed from the solved
+// center+endpoints. Free function (declared in SketchEngine.hpp) so the in-session
+// GUI sketch tool can live-solve the same way committed features do.
+bool solve_sketch_entities(std::vector<SketchEntity>& entities,
+                           const std::vector<SketchEntityConstraintDef>& constraints)
+{
+    // Delegated to the vendored SolveSpace solver (SketchSolver / libslvs): full
+    // constraint set, real DoF + over-constrained detection.
+    return sketch_solve(entities, constraints).ok;
+}
+
+#if 0  // legacy hand-rolled Gauss-Newton solver — superseded by libslvs, kept for reference
+static bool legacy_solve_sketch_entities(std::vector<SketchEntity>& entities,
+                           const std::vector<SketchEntityConstraintDef>& constraints)
+{
+    if (constraints.empty()) return true;
+
+    SketchConstraints sc;
+    // table[entity][role] -> solver point id, or -1 if that role is unregistered.
+    std::vector<std::array<int, 3>> table(entities.size(), {-1, -1, -1});
+    auto reg = [&](int ei, SketchPointRole role, const Vec2d& p) {
+        table[ei][int(role)] = sc.add_point(p.x(), p.y());
+    };
+    for (size_t i = 0; i < entities.size(); ++i) {
+        const SketchEntity& e = entities[i];
+        switch (e.type) {
+        case SketchEntity::Type::Line:
+            reg(int(i), SketchPointRole::P0, e.p0);
+            reg(int(i), SketchPointRole::P1, e.p1);
+            break;
+        case SketchEntity::Type::Arc:
+            reg(int(i), SketchPointRole::P0, e.p0);
+            reg(int(i), SketchPointRole::P1, e.p1);
+            reg(int(i), SketchPointRole::Center, e.center);
+            break;
+        case SketchEntity::Type::Circle:
+            reg(int(i), SketchPointRole::Center, e.center);
+            break;
+        case SketchEntity::Type::Point:
+            reg(int(i), SketchPointRole::P0, e.p0);
+            break;
+        }
+    }
+
+    auto pid = [&](int ei, SketchPointRole role) -> int {
+        if (ei < 0 || ei >= int(table.size())) return -1;
+        return table[ei][int(role)];
+    };
+
+    for (const SketchEntityConstraintDef& c : constraints) {
+        switch (c.type) {
+        // Point-form: refs A and B name individual entity points.
+        case SketchConstraintType::Fix: {
+            int a = pid(c.ea, c.ra);
+            if (a >= 0) sc.fix_point(a);
+            break;
+        }
+        case SketchConstraintType::Coincident: {
+            int a = pid(c.ea, c.ra), b = pid(c.eb, c.rb);
+            if (a >= 0 && b >= 0) sc.coincident(a, b);
+            break;
+        }
+        case SketchConstraintType::Horizontal: {
+            int a = pid(c.ea, c.ra), b = pid(c.eb, c.rb);
+            if (a >= 0 && b >= 0) sc.horizontal(a, b);
+            break;
+        }
+        case SketchConstraintType::Vertical: {
+            int a = pid(c.ea, c.ra), b = pid(c.eb, c.rb);
+            if (a >= 0 && b >= 0) sc.vertical(a, b);
+            break;
+        }
+        case SketchConstraintType::Distance: {
+            int a = pid(c.ea, c.ra), b = pid(c.eb, c.rb);
+            if (a >= 0 && b >= 0) sc.distance(a, b, c.value);
+            break;
+        }
+        case SketchConstraintType::LockX: {
+            int a = pid(c.ea, c.ra);
+            if (a >= 0) sc.lock_x(a, c.value);
+            break;
+        }
+        case SketchConstraintType::LockY: {
+            int a = pid(c.ea, c.ra);
+            if (a >= 0) sc.lock_y(a, c.value);
+            break;
+        }
+        // Segment-form: ea and eb name whole line segments (their P0->P1).
+        case SketchConstraintType::Parallel:
+        case SketchConstraintType::Perpendicular:
+        case SketchConstraintType::EqualLength: {
+            int a0 = pid(c.ea, SketchPointRole::P0), a1 = pid(c.ea, SketchPointRole::P1);
+            int b0 = pid(c.eb, SketchPointRole::P0), b1 = pid(c.eb, SketchPointRole::P1);
+            if (a0 < 0 || a1 < 0 || b0 < 0 || b1 < 0) break;
+            if (c.type == SketchConstraintType::Parallel)      sc.parallel(a0, a1, b0, b1);
+            else if (c.type == SketchConstraintType::Perpendicular) sc.perpendicular(a0, a1, b0, b1);
+            else                                               sc.equal_length(a0, a1, b0, b1);
+            break;
+        }
+        case SketchConstraintType::Concentric: {
+            int a = pid(c.ea, SketchPointRole::Center);
+            int b = pid(c.eb, SketchPointRole::Center);
+            if (a >= 0 && b >= 0) sc.coincident(a, b);
+            break;
+        }
+        case SketchConstraintType::Midpoint: {
+            int m = pid(c.ea, c.ra);
+            int a = pid(c.eb, SketchPointRole::P0);
+            int b = pid(c.eb, SketchPointRole::P1);
+            if (m >= 0 && a >= 0 && b >= 0) sc.midpoint(m, a, b);
+            break;
+        }
+        case SketchConstraintType::Symmetric: {
+            int a  = pid(c.ea, c.ra);
+            int b  = pid(c.eb, c.rb);
+            int x0 = pid(c.ec, SketchPointRole::P0);
+            int x1 = pid(c.ec, SketchPointRole::P1);
+            if (a >= 0 && b >= 0 && x0 >= 0 && x1 >= 0) sc.symmetric(a, b, x0, x1);
+            break;
+        }
+        case SketchConstraintType::Angle: {
+            int a0 = pid(c.ea, SketchPointRole::P0), a1 = pid(c.ea, SketchPointRole::P1);
+            int b0 = pid(c.eb, SketchPointRole::P0), b1 = pid(c.eb, SketchPointRole::P1);
+            if (a0 >= 0 && a1 >= 0 && b0 >= 0 && b1 >= 0) sc.angle(a0, a1, b0, b1, c.value);
+            break;
+        }
+        case SketchConstraintType::Radius:
+        case SketchConstraintType::Diameter:
+            // dimensions: applied in the post-solve pass below, not via the solver.
+            break;
+        case SketchConstraintType::PointOnLine: {
+            // Point `ea`/`ra` is held at signed perpendicular distance `value` from
+            // line `eb` (value 0 -> on the line). Drives e.g. a circle centre onto a
+            // construction axis and keeps it there through later edits.
+            int p  = pid(c.ea, c.ra);
+            int l0 = pid(c.eb, SketchPointRole::P0), l1 = pid(c.eb, SketchPointRole::P1);
+            if (p >= 0 && l0 >= 0 && l1 >= 0) sc.point_line_distance(p, l0, l1, c.value);
+            break;
+        }
+        case SketchConstraintType::Tangent: {
+            auto in_range = [&](int e){ return e >= 0 && e < (int)entities.size(); };
+            if (!in_range(c.ea) || !in_range(c.eb)) break;
+            const SketchEntity& ea_e = entities[c.ea];
+            const SketchEntity& eb_e = entities[c.eb];
+            auto is_round = [](const SketchEntity& e){
+                return e.type == SketchEntity::Type::Circle || e.type == SketchEntity::Type::Arc; };
+            if (is_round(ea_e) && eb_e.type == SketchEntity::Type::Line) {
+                int cen = pid(c.ea, SketchPointRole::Center);
+                int l0 = pid(c.eb, SketchPointRole::P0), l1 = pid(c.eb, SketchPointRole::P1);
+                if (cen >= 0 && l0 >= 0 && l1 >= 0) sc.point_line_distance(cen, l0, l1, ea_e.radius);
+            } else if (is_round(eb_e) && ea_e.type == SketchEntity::Type::Line) {
+                int cen = pid(c.eb, SketchPointRole::Center);
+                int l0 = pid(c.ea, SketchPointRole::P0), l1 = pid(c.ea, SketchPointRole::P1);
+                if (cen >= 0 && l0 >= 0 && l1 >= 0) sc.point_line_distance(cen, l0, l1, eb_e.radius);
+            } else if (is_round(ea_e) && is_round(eb_e)) {
+                int c0 = pid(c.ea, SketchPointRole::Center), c1 = pid(c.eb, SketchPointRole::Center);
+                if (c0 >= 0 && c1 >= 0) sc.distance(c0, c1, ea_e.radius + eb_e.radius);
+            }
+            break;
+        }
+        }
+    }
+
+    const bool ok = sc.solve();
+    // Write solved coordinates back into the participating entities.
+    for (size_t i = 0; i < entities.size(); ++i) {
+        SketchEntity& e = entities[i];
+        int ip0 = table[i][int(SketchPointRole::P0)];
+        int ip1 = table[i][int(SketchPointRole::P1)];
+        int ic  = table[i][int(SketchPointRole::Center)];
+        if (ip0 >= 0) e.p0     = sc.get_point(ip0);
+        if (ip1 >= 0) e.p1     = sc.get_point(ip1);
+        if (ic  >= 0) e.center = sc.get_point(ic);
+
+        if (e.type == SketchEntity::Type::Arc && ic >= 0) {
+            // Reflow arc angles from solved center + endpoints, preserving the
+            // original sweep direction (CCW vs CW).
+            const double old_sweep = e.end_angle - e.start_angle;     // signed, original
+            double ns = std::atan2(e.p0.y() - e.center.y(), e.p0.x() - e.center.x());
+            double ne = std::atan2(e.p1.y() - e.center.y(), e.p1.x() - e.center.x());
+            double sweep = ne - ns;
+            // Normalize `sweep` into (-2pi, 2pi) then match the sign of old_sweep so
+            // the arc keeps turning the same way it did before solving.
+            const double TWO_PI = 2.0 * M_PI;
+            while (sweep <=  -TWO_PI) sweep += TWO_PI;
+            while (sweep >=   TWO_PI) sweep -= TWO_PI;
+            if (old_sweep >= 0.0 && sweep < 0.0) sweep += TWO_PI;
+            if (old_sweep <  0.0 && sweep > 0.0) sweep -= TWO_PI;
+            e.start_angle = ns;
+            e.end_angle   = ns + sweep;
+            e.radius = 0.5 * ((e.p0 - e.center).norm() + (e.p1 - e.center).norm());
+        }
+        if (e.type == SketchEntity::Type::Circle && ic >= 0) {
+            // p0 mirrors the center for circles; keep them consistent.
+            e.p0 = e.center;
+        }
+    }
+    // Apply radius/diameter dimensions directly (radius is not a solver variable).
+    for (const auto& c : constraints) {
+        if (c.type != SketchConstraintType::Radius &&
+            c.type != SketchConstraintType::Diameter) continue;
+        if (c.ea < 0 || c.ea >= (int)entities.size()) continue;
+        SketchEntity& e = entities[c.ea];
+        if (e.type != SketchEntity::Type::Circle && e.type != SketchEntity::Type::Arc) continue;
+        const double r = (c.type == SketchConstraintType::Diameter) ? 0.5 * c.value : c.value;
+        if (r <= 0.0) continue;
+        e.radius = r;
+        if (e.type == SketchEntity::Type::Arc) {
+            // Rescale endpoints to the new radius around the (solved) center, keeping
+            // each endpoint's direction so the reflowed start/end angles stay valid.
+            auto rescale = [&](Vec2d& p) {
+                Vec2d d = p - e.center;
+                const double n = d.norm();
+                if (n > 1e-12) p = e.center + (r / n) * d;
+            };
+            rescale(e.p0);
+            rescale(e.p1);
+        }
+    }
+    return ok;
+}
+#endif  // legacy solver
+
+bool CadDocument::solve_sketch_feature(int index)
+{
+    if (index < 0 || index >= int(features.size())) return false;
+    CadFeature& f = features[index];
+    if (f.type != CadFeatureType::Sketch) return false;
+
+    // Onshape-style entity sketches solve against entity endpoints (Fase 4.2).
+    if (!f.entities.empty())
+        return solve_sketch_entities(f.entities, f.entity_constraints);
+
+    if (f.constraints.empty()) return true;
+
+    SketchConstraints sc;
+    for (const Vec2d& p : f.profile.points)
+        sc.add_point(p.x(), p.y());
+
+    for (const SketchConstraintDef& c : f.constraints) {
+        switch (c.type) {
+        case SketchConstraintType::Fix:          sc.fix_point(c.a); break;
+        case SketchConstraintType::Coincident:   sc.coincident(c.a, c.b); break;
+        case SketchConstraintType::Horizontal:   sc.horizontal(c.a, c.b); break;
+        case SketchConstraintType::Vertical:     sc.vertical(c.a, c.b); break;
+        case SketchConstraintType::Distance:     sc.distance(c.a, c.b, c.value); break;
+        case SketchConstraintType::LockX:        sc.lock_x(c.a, c.value); break;
+        case SketchConstraintType::LockY:        sc.lock_y(c.a, c.value); break;
+        case SketchConstraintType::EqualLength:  sc.equal_length(c.a, c.b, c.c, c.d); break;
+        case SketchConstraintType::Parallel:     sc.parallel(c.a, c.b, c.c, c.d); break;
+        case SketchConstraintType::Perpendicular:sc.perpendicular(c.a, c.b, c.c, c.d); break;
+        }
+    }
+
+    const bool ok = sc.solve();
+    for (size_t i = 0; i < f.profile.points.size(); ++i)
+        f.profile.points[i] = sc.get_point(int(i));
+    return ok;
+}
+
+int CadDocument::add_extrude(int sketch_ref, double distance, bool symmetric,
+                             BooleanMode mode, const std::string& name)
+{
+    CadFeature f;
+    f.type       = CadFeatureType::Extrude;
+    f.name       = name;
+    f.sketch_ref = sketch_ref;
+    f.distance   = distance;
+    f.symmetric  = symmetric;
+    f.mode       = mode;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_extrude_entities(const std::vector<SketchEntity>& entities,
+                                      const SketchPlane& plane, double distance,
+                                      bool symmetric, BooleanMode mode, const std::string& name)
+{
+    // Self-contained extrude of a single loop: the entity subset lives on the feature
+    // itself (sketch_ref = -1), so build_sketch_wire(f) uses f.entities directly. The
+    // source sketch stays a separate feature, so its other loops remain selectable.
+    CadFeature f;
+    f.type       = CadFeatureType::Extrude;
+    f.name       = name;
+    f.sketch_ref = -1;
+    f.entities   = entities;
+    f.plane      = plane;
+    f.distance   = distance;
+    f.symmetric  = symmetric;
+    f.mode       = mode;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_extrude_face(int src_face, double distance, bool symmetric,
+                                  BooleanMode mode, const std::string& name)
+{
+    CadFeature f;
+    f.type             = CadFeatureType::Extrude;
+    f.name             = name;
+    f.sketch_ref       = -1;
+    f.extrude_src_face = src_face;
+    f.distance         = distance;
+    f.symmetric        = symmetric;
+    f.mode             = mode;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_fillet(double radius, FaceGroup faces, const std::string& name)
+{
+    CadFeature f;
+    f.type         = CadFeatureType::Fillet;
+    f.name         = name;
+    f.dressup_size = radius;
+    f.face_group   = faces;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_fillet(double radius, int edge_id, const std::string& name)
+{
+    CadFeature f;
+    f.type         = CadFeatureType::Fillet;
+    f.name         = name;
+    f.dressup_size = radius;
+    f.dressup_edge = edge_id;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_chamfer(double distance, FaceGroup faces, const std::string& name)
+{
+    CadFeature f;
+    f.type         = CadFeatureType::Chamfer;
+    f.name         = name;
+    f.dressup_size = distance;
+    f.face_group   = faces;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_chamfer(double distance, int edge_id, const std::string& name)
+{
+    CadFeature f;
+    f.type         = CadFeatureType::Chamfer;
+    f.name         = name;
+    f.dressup_size = distance;
+    f.dressup_edge = edge_id;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_hole(double diameter, double depth, bool through,
+                          double x, double y, const SketchPlane& plane,
+                          const std::string& name)
+{
+    CadFeature f;
+    f.type          = CadFeatureType::Hole;
+    f.name          = name;
+    f.plane         = plane;
+    f.hole_diameter = diameter;
+    f.hole_depth    = depth;
+    f.hole_through  = through;
+    f.hole_x        = x;
+    f.hole_y        = y;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+// Hole standards lookup table (representative ISO 273 medium / ISO 4762 / ANSI unified).
+struct HoleStdEntry { const char* desig; double clearance; double cbore_d; double cbore_depth; double csink_d; };
+static const HoleStdEntry kHoleStdTable[] = {
+    {"M3",   3.4,  6.0,  3.4,  6.3},
+    {"M4",   4.5,  8.0,  4.4,  8.4},
+    {"M5",   5.5, 10.0,  5.4, 10.4},
+    {"M6",   6.6, 11.0,  6.8, 12.6},
+    {"M8",   9.0, 15.0,  8.8, 17.3},
+    {"M10", 11.0, 18.0, 11.0, 20.0},
+    {"#6-32",    3.7,  8.8,  4.2,  8.7},
+    {"#8-32",    4.4,  9.9,  5.1, 10.2},
+    {"1/4-20",   6.9, 14.4,  7.2, 14.7},
+    {"5/16-18",  8.8, 17.0,  8.2, 17.3},
+    {"3/8-16",  10.5, 19.6,  9.5, 19.8},
+};
+static bool hole_std_lookup(const std::string& desig, double& clearance,
+                            double& cbore_d, double& cbore_depth, double& csink_d)
+{
+    for (const auto& e : kHoleStdTable) {
+        if (e.desig == desig) {
+            clearance   = e.clearance;
+            cbore_d     = e.cbore_d;
+            cbore_depth = e.cbore_depth;
+            csink_d     = e.csink_d;
+            return true;
+        }
+    }
+    return false;
+}
+
+int CadDocument::add_hole_styled(double diameter, double depth, bool through,
+                                 double x, double y, const SketchPlane& plane, int style,
+                                 double cbore_diameter, double cbore_depth,
+                                 double csink_diameter, double csink_angle,
+                                 const std::string& standard, const std::string& name)
+{
+    CadFeature f;
+    f.type                = CadFeatureType::Hole;
+    f.name                = name;
+    f.plane               = plane;
+    f.hole_diameter       = diameter;
+    f.hole_depth          = depth;
+    f.hole_through        = through;
+    f.hole_x              = x;
+    f.hole_y              = y;
+    f.hole_style          = style;
+    f.hole_cbore_diameter = cbore_diameter;
+    f.hole_cbore_depth    = cbore_depth;
+    f.hole_csink_diameter = csink_diameter;
+    f.hole_csink_angle    = csink_angle;
+    f.hole_standard       = standard;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_hole_standard(const std::string& designation, int style, bool through,
+                                   double depth, double x, double y,
+                                   const SketchPlane& plane, const std::string& name)
+{
+    double clearance, cbore_d, cbore_depth, csink_d;
+    if (!hole_std_lookup(designation, clearance, cbore_d, cbore_depth, csink_d))
+        throw std::runtime_error("unknown hole standard \"" + designation + "\"");
+    return add_hole_styled(clearance, depth, through, x, y, plane, style,
+                           cbore_d, cbore_depth, csink_d, 90, designation, name);
+}
+
+int CadDocument::add_thread(double radius, double pitch, double height, double depth,
+                            bool internal, double x, double y, const SketchPlane& plane,
+                            const std::string& name)
+{
+    CadFeature f;
+    f.type            = CadFeatureType::Thread;
+    f.name            = name;
+    f.plane           = plane;
+    f.thread_radius   = radius;
+    f.thread_pitch    = pitch;
+    f.thread_height   = height;
+    f.thread_depth    = depth;
+    f.thread_internal = internal;
+    f.thread_x        = x;
+    f.thread_y        = y;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_revolve(int sketch_ref, double angle, int axis, bool flip,
+                             BooleanMode mode, const std::string& name)
+{
+    CadFeature f;
+    f.type          = CadFeatureType::Revolve;
+    f.name          = name;
+    f.sketch_ref    = sketch_ref;
+    f.revolve_angle = angle;
+    f.revolve_axis  = axis;
+    f.flip          = flip;
+    f.mode          = mode;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_revolve_entities(const std::vector<SketchEntity>& entities,
+                                      const SketchPlane& plane, double angle, int axis,
+                                      bool flip, BooleanMode mode, const std::string& name)
+{
+    CadFeature f;
+    f.type          = CadFeatureType::Revolve;
+    f.name          = name;
+    f.sketch_ref    = -1;
+    f.entities      = entities;
+    f.plane         = plane;
+    f.revolve_angle = angle;
+    f.revolve_axis  = axis;
+    f.flip          = flip;
+    f.mode          = mode;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_sweep(int profile_sketch_ref, int path_sketch_ref, BooleanMode mode,
+                           const std::string& name)
+{
+    CadFeature f;
+    f.type           = CadFeatureType::Sweep;
+    f.name           = name;
+    f.sketch_ref     = profile_sketch_ref;
+    f.sweep_path_ref = path_sketch_ref;
+    f.mode           = mode;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_loft(const std::vector<int>& profile_refs, bool ruled, BooleanMode mode,
+                          const std::string& name)
+{
+    CadFeature f;
+    f.type              = CadFeatureType::Loft;
+    f.name              = name;
+    f.loft_profile_refs = profile_refs;
+    f.loft_ruled        = ruled;
+    f.mode              = mode;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_pattern(bool circular, int count, double spacing, int dir,
+                             double angle_deg, int target_body, const std::string& name)
+{
+    CadFeature f;
+    f.type             = CadFeatureType::Pattern;
+    f.name             = name;
+    f.pattern_circular = circular;
+    f.pattern_count    = count;
+    f.pattern_spacing  = spacing;
+    f.pattern_dir      = dir;
+    f.pattern_angle    = angle_deg;
+    f.target_body      = target_body;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_pattern_on_curve(int count, int curve_sketch, int curve_entity,
+                                       int target, const std::string& name)
+{
+    CadFeature f;
+    f.type                 = CadFeatureType::Pattern;
+    f.name                 = name;
+    f.pattern_count        = count;
+    f.pattern_curve_sketch = curve_sketch;
+    f.pattern_curve_entity = curve_entity;
+    f.target_body          = target;
+    f.pattern_circular     = false;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_shell(double thickness, int face, int target_body, const std::string& name)
+{
+    CadFeature f;
+    f.type            = CadFeatureType::Shell;
+    f.name            = name;
+    f.shell_thickness = thickness;
+    f.shell_face      = face;
+    f.target_body     = target_body;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_rib(int sketch_ref, int entity, double thickness, double depth,
+                          int target_body, const std::string& name)
+{
+    CadFeature f;
+    f.type           = CadFeatureType::Rib;
+    f.name           = name;
+    f.rib_sketch_ref = sketch_ref;
+    f.rib_entity     = entity;
+    f.rib_thickness  = thickness;
+    f.rib_depth      = depth;
+    f.target_body    = target_body;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_delete_face(int target_body, const std::vector<int>& faces,
+                                  const std::string& name)
+{
+    CadFeature f;
+    f.type         = CadFeatureType::DeleteFace;
+    f.name         = name;
+    f.target_body  = target_body;
+    f.delete_faces = faces;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_draft(double angle, int face, int target_body, const std::string& name)
+{
+    CadFeature f;
+    f.type        = CadFeatureType::Draft;
+    f.name        = name;
+    f.draft_angle = angle;
+    f.draft_face  = face;
+    f.target_body = target_body;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_boolean(BooleanMode op, int target_body, int tool_body, bool keep_tool,
+                             double tolerance, int target_face, int tool_face,
+                             const std::string& name)
+{
+    CadFeature f;
+    f.type             = CadFeatureType::Boolean;
+    f.name             = name;
+    f.mode             = op;
+    f.target_body      = target_body;
+    f.bool_tool_body   = tool_body;
+    f.bool_keep_tool   = keep_tool;
+    f.bool_tolerance   = tolerance;
+    f.bool_target_face = target_face;
+    f.bool_tool_face   = tool_face;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_cut(const SketchPlane& plane, double offset, bool flip,
+                         bool keep_upper, bool keep_lower, int target_body,
+                         const std::string& name)
+{
+    CadFeature f;
+    f.type           = CadFeatureType::Cut;
+    f.name           = name;
+    f.plane          = plane;
+    f.cut_offset     = offset;
+    f.cut_flip       = flip;
+    f.cut_keep_upper = keep_upper;
+    f.cut_keep_lower = keep_lower;
+    f.target_body    = target_body;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_split_by_face(int target_body, int face_body, int face,
+                                    bool keep_upper, bool keep_lower, const std::string& name)
+{
+    CadFeature f;
+    f.type           = CadFeatureType::Cut;
+    f.name           = name;
+    f.target_body    = target_body;
+    f.cut_face_body  = face_body;
+    f.cut_face       = face;
+    f.cut_keep_upper = keep_upper;
+    f.cut_keep_lower = keep_lower;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_mirror(const SketchPlane& plane, int target_body, BooleanMode mode,
+                            const std::string& name)
+{
+    CadFeature f;
+    f.type                 = CadFeatureType::Mirror;
+    f.name                 = name;
+    f.plane                = plane;
+    f.target_body          = target_body;
+    f.mode                 = mode;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_transform(int target_body, const Vec3d& translate, const Vec3d& axis,
+                               const Vec3d& pivot, double angle_deg, bool copy,
+                               const std::string& name)
+{
+    CadFeature f;
+    f.type         = CadFeatureType::Transform;
+    f.name         = name;
+    f.target_body  = target_body;
+    f.xf_translate = translate;
+    f.xf_axis      = axis;
+    f.xf_pivot     = pivot;
+    f.xf_angle_deg = angle_deg;
+    f.xf_copy      = copy;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_thicken(int target_body, int face, double thickness, bool flip,
+                              const std::string& name)
+{
+    CadFeature f;
+    f.type             = CadFeatureType::Thicken;
+    f.name             = name;
+    f.target_body      = target_body;
+    f.thicken_face     = face;
+    f.thicken_thickness = thickness;
+    f.thicken_flip     = flip;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_thicken_surface(int target_body, double thickness, bool flip,
+                                      const std::string& name)
+{
+    CadFeature f;
+    f.type              = CadFeatureType::ThickenSurface;
+    f.name              = name;
+    f.target_body       = target_body;
+    f.thicken_thickness = thickness;
+    f.thicken_flip      = flip;
+    f.mode              = BooleanMode::New;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_surface_offset(int target_body, double offset, const std::string& name)
+{
+    CadFeature f;
+    f.type         = CadFeatureType::SurfaceOffset;
+    f.name         = name;
+    f.target_body  = target_body;
+    f.plane_offset = offset;
+    f.mode         = BooleanMode::New;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+static void project_edges_to_entities(const std::vector<TopoDS_Edge>& edges,
+                                      const SketchPlane& plane,
+                                      bool construction,
+                                      std::vector<SketchEntity>& out);
+
+int CadDocument::add_project_edges(int source_body, const std::vector<int>& edge_ids, int face,
+                                   const SketchPlane& plane, const std::string& name)
+{
+    CadFeature f;
+    f.type                = CadFeatureType::Project;
+    f.name                = name;
+    f.project_source_body = source_body;
+    f.project_edges       = edge_ids;
+    f.project_face        = face;
+    f.plane               = plane;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::project_edges_into_sketch(int sketch_feature, int source_body,
+                                           const std::vector<int>& edge_ids, int face)
+{
+    if (sketch_feature < 0 || sketch_feature >= int(features.size())) return -1;
+    CadFeature& sk = features[sketch_feature];
+    if (sk.type != CadFeatureType::Sketch && sk.type != CadFeatureType::Project) return -1;
+    if (source_body < 0 || source_body >= int(bodies.size())
+        || bodies[source_body].shape.IsNull()) return -1;
+    const TopoDS_Shape& shape = bodies[source_body].shape;
+
+    std::vector<TopoDS_Edge> edges;
+    if (!edge_ids.empty()) {
+        for (int id : edge_ids) {
+            TopoDS_Edge e = GeometryEngine::edge_by_index(shape, id);
+            if (e.IsNull()) return -1;
+            edges.push_back(e);
+        }
+    } else if (face >= 0) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(shape, face);
+        if (fc.IsNull()) return -1;
+        edges = GeometryEngine::edges_of_face(fc);
+    } else {
+        edges = GeometryEngine::edges_of(shape);
+    }
+    if (edges.empty()) return -1;
+
+    const size_t before = sk.entities.size();
+    project_edges_to_entities(edges, sk.plane, /*construction=*/true, sk.entities);
+    return int(sk.entities.size() - before);
+}
+
+int CadDocument::add_bridge(int sketch_ref, int ent_a, int end_a, int ent_b, int end_b,
+                             const std::string& name)
+{
+    (void)name;
+    if (sketch_ref < 0 || sketch_ref >= int(features.size())
+        || features[sketch_ref].type != CadFeatureType::Sketch)
+        throw std::runtime_error("bridge: sketch_ref must refer to a Sketch feature");
+    auto& ents = features[sketch_ref].entities;
+    if (ent_a < 0 || ent_a >= int(ents.size()) || ent_b < 0 || ent_b >= int(ents.size()))
+        throw std::runtime_error("bridge: entity index out of range in sketch");
+    SketchEntity br = SketchEngine::make_bridge(ents[ent_a], end_a, ents[ent_b], end_b);
+    ents.push_back(br);
+    return int(ents.size()) - 1;
+}
+
+int CadDocument::add_plane(int base, double offset, double angle_tilt, int axis,
+                           const std::string& name)
+{
+    CadFeature f;
+    f.type             = CadFeatureType::Plane;
+    f.name             = name;
+    f.plane_base       = base;
+    f.plane_offset     = offset;
+    f.plane_angle_tilt = angle_tilt;
+    f.plane_axis       = axis;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_axis(AxisType axis_type_, const std::string& name)
+{
+    CadFeature f;
+    f.type      = CadFeatureType::Axis;
+    f.name      = name;
+    f.axis_type = axis_type_;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_coordsys(CoordSysType type, const Vec3d& point, const std::string& name)
+{
+    CadFeature f;
+    f.type           = CadFeatureType::CoordSys;
+    f.name           = name;
+    f.coordsys_type  = type;
+    f.coordsys_point = point;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_mate(int kind, int cs_a, int cs_b, double offset, double angle_deg, bool flip,
+                           const std::string& name)
+{
+    CadFeature f;
+    f.type       = CadFeatureType::Mate;
+    f.name       = name;
+    f.mate_kind  = kind;
+    f.mate_cs_a  = cs_a;
+    f.mate_cs_b  = cs_b;
+    f.mate_offset = offset;
+    f.mate_angle  = angle_deg;
+    f.mate_flip   = flip;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+std::vector<CadDocument::MateOption> CadDocument::mate_options(int cs_a, int cs_b) const
+{
+    std::vector<MateOption> out(5);
+    for (int k = 0; k < 5; ++k) out[k].kind = k;
+
+    auto is_connector = [&](int idx) -> bool {
+        return idx >= 0 && idx < int(features.size()) &&
+               features[idx].type == CadFeatureType::CoordSys &&
+               features[idx].enabled;
+    };
+    if (!is_connector(cs_a) || !is_connector(cs_b)) {
+        const char side = is_connector(cs_a) ? 'B' : 'A';
+        for (auto& o : out) { o.viable = false; o.reason = std::string("connector ") + side + " is not a coordinate system"; }
+        return out;
+    }
+    if (cs_a == cs_b) {
+        for (auto& o : out) { o.viable = false; o.reason = "a mate needs two different connectors"; }
+        return out;
+    }
+
+    // B is the connector on the body that MOVES, so B must belong to one; A is the fixed
+    // reference and needs no body. Without this every kind was offered on a Point(world)
+    // connector and the mate only failed at RECOMPUTE, with "mate_cs_b has no associated body" —
+    // one step too late, after the feature already existed in the tree. The same two conditions
+    // the apply path throws on are checked here, so the offer and the kernel cannot disagree.
+    const int body_b = features[cs_b].coordsys_body;
+    if (body_b < 0) {
+        for (auto& o : out) {
+            o.viable = false;
+            o.reason = "connector B is not attached to a body — a mate moves B's body";
+        }
+        return out;
+    }
+    if (body_b >= int(bodies.size()) || bodies[body_b].shape.IsNull()) {
+        for (auto& o : out) {
+            o.viable = false;
+            o.reason = "connector B's body no longer exists";
+        }
+        return out;
+    }
+
+    const int ka = features[cs_a].coordsys_face_kind;
+    const int kb = features[cs_b].coordsys_face_kind;
+    auto face_desc = [](int kind) -> std::string { return kind == GeomAbs_Plane ? "a flat face" : "a curved face"; };
+
+    // Planar: needs a flat face at both ends.
+    const bool plan_bad_a = ka >= 0 && ka != GeomAbs_Plane;
+    const bool plan_bad_b = kb >= 0 && kb != GeomAbs_Plane;
+    if (plan_bad_a || plan_bad_b) {
+        out[1].viable = false;
+        if (plan_bad_a && plan_bad_b)
+            out[1].reason = "needs a flat face at both ends — both connectors are on curved faces";
+        else if (plan_bad_a)
+            out[1].reason = "needs a flat face at both ends — connector A is on " + face_desc(ka);
+        else
+            out[1].reason = "needs a flat face at both ends — connector B is on " + face_desc(kb);
+    }
+
+    // Revolute and Cylindrical: need a cylindrical face at both ends.
+    for (int k : {2, 4}) {
+        const bool ax_bad_a = ka >= 0 && ka != GeomAbs_Cylinder;
+        const bool ax_bad_b = kb >= 0 && kb != GeomAbs_Cylinder;
+        if (!ax_bad_a && !ax_bad_b) continue;
+        out[k].viable = false;
+        if (ax_bad_a && ax_bad_b)
+            out[k].reason = (ka == GeomAbs_Plane && kb == GeomAbs_Plane)
+                ? "needs a cylindrical face at both ends — both connectors are on flat faces"
+                : "needs a cylindrical face at both ends — both connectors are on non-cylindrical faces";
+        else if (ax_bad_a)
+            out[k].reason = "needs a cylindrical face at both ends — connector A is on " + face_desc(ka);
+        else
+            out[k].reason = "needs a cylindrical face at both ends — connector B is on " + face_desc(kb);
+    }
+
+    return out;
+}
+
+int CadDocument::add_helix(const SketchPlane& plane, double radius, double pitch, double height,
+                           bool left_handed, double taper_deg, const std::string& name)
+{
+    CadFeature f;
+    f.type              = CadFeatureType::Helix;
+    f.name              = name;
+    f.plane             = plane;
+    f.helix_radius      = radius;
+    f.helix_pitch       = pitch;
+    f.helix_height      = height;
+    f.helix_left_handed = left_handed;
+    f.helix_taper_deg   = taper_deg;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+TopoDS_Wire CadDocument::build_helix_wire(const CadFeature& f, std::string& err) const
+{
+    return make_helix_spine(f, err);
+}
+
+// Derive a SketchPlane: shift `base` along its normal by `offset`, then tilt
+// `angle_deg` about the base's X (axis 0) or Y (axis 1) axis (Rodrigues rotation).
+static SketchPlane offset_angle_plane(const SketchPlane& base, double offset,
+                                      double angle_deg, int axis)
+{
+    SketchPlane p;
+    p.origin = base.origin + base.normal * offset;
+    Vec3d n = base.normal, x = base.x_axis, y = base.y_axis;
+    if (std::abs(angle_deg) > 1e-9) {
+        const double a = angle_deg * M_PI / 180.0;
+        const Vec3d  k = (axis == 1) ? base.y_axis : base.x_axis; // unit rotation axis
+        auto rot = [&](const Vec3d& v) -> Vec3d {   // -> Vec3d forces eval (no dangling Eigen expr)
+            return v * std::cos(a) + k.cross(v) * std::sin(a)
+                   + k * (k.dot(v)) * (1.0 - std::cos(a));
+        };
+        n = rot(n);
+        if (axis == 1) x = rot(x);   // tilt about Y rotates X + normal, Y fixed
+        else           y = rot(y);   // tilt about X rotates Y + normal, X fixed
+    }
+    p.normal = n.normalized();
+    p.x_axis = x.normalized();
+    p.y_axis = y.normalized();
+    return p;
+}
+
+// Build a full orthonormal frame from a normal + origin.
+static SketchPlane frame_from(const Vec3d& origin, const Vec3d& normal)
+{
+    Vec3d n = normal.normalized();
+    Vec3d ref = (std::abs(n.z()) < 0.9) ? Vec3d(0, 0, 1) : Vec3d(1, 0, 0);
+    Vec3d x = ref.cross(n);
+    if (x.squaredNorm() < 1e-12) x = Vec3d(1, 0, 0);
+    x.normalize();
+    Vec3d y = n.cross(x).normalized();
+    SketchPlane p;
+    p.origin = origin;
+    p.normal = n;
+    p.x_axis = x;
+    p.y_axis = y;
+    return p;
+}
+
+bool CadDocument::plane_of_face(int body_idx, int face_idx, SketchPlane& out) const
+{
+    if (face_idx < 0 || body_idx < 0 || body_idx >= int(bodies.size())) return false;
+    const TopoDS_Face f = GeometryEngine::face_by_index(bodies[body_idx].shape, face_idx);
+    if (f.IsNull()) return false;
+    // Planar only. face_normal_world evaluates the normal at the mid parameter, which on a cylinder
+    // or a fillet is a tangent plane at one arbitrary point — usable for a datum offset, wrong as a
+    // sketch plane. Refuse rather than sketch somewhere the user did not point at.
+    BRepAdaptor_Surface surf(f);
+    if (surf.GetType() != GeomAbs_Plane) return false;
+    out = frame_from(GeometryEngine::face_centroid_world(f), GeometryEngine::face_normal_world(f));
+    return true;
+}
+
+std::vector<std::pair<std::string, SketchPlane>> CadDocument::resolve_datum_planes() const
+{
+    std::vector<std::pair<std::string, SketchPlane>> out;
+    for (const CadFeature& f : features) {
+        if (f.type != CadFeatureType::Plane || !f.enabled) continue;
+
+        // Resolve base reference plane. The default XY/XZ/YZ planes pass through the modeling
+        // origin (bed centre); datum bases (>=3) are already in world coords from earlier passes.
+        SketchPlane base;
+        if      (f.plane_base == 1) { base = SketchPlane::XZ(); base.origin += modeling_origin; }
+        else if (f.plane_base == 2) { base = SketchPlane::YZ(); base.origin += modeling_origin; }
+        else if (f.plane_base >= 3) {
+            const int di = f.plane_base - 3;
+            if (di < int(out.size())) base = out[di].second;
+        }
+        else                        { base = SketchPlane::XY(); base.origin += modeling_origin; }
+
+        // --- Resolve refs from bodies ---
+        auto resolve_face = [&](int body_idx, int face_idx) -> TopoDS_Face {
+            if (face_idx < 0 || body_idx < 0 || body_idx >= int(bodies.size()))
+                return TopoDS_Face();
+            return GeometryEngine::face_by_index(bodies[body_idx].shape, face_idx);
+        };
+        auto resolve_edge = [&](int body_idx, int edge_idx,
+                                 Vec3d& p0, Vec3d& dir) -> bool {
+            if (edge_idx < 0 || body_idx < 0 || body_idx >= int(bodies.size()))
+                return false;
+            TopoDS_Edge e = GeometryEngine::edge_by_index(bodies[body_idx].shape, edge_idx);
+            if (e.IsNull()) return false;
+            auto pts = GeometryEngine::sample_edge_world(e);
+            if (pts.size() < 2) return false;
+            p0 = pts.front();
+            dir = (pts.back() - pts.front()).normalized();
+            return true;
+        };
+
+        // Face A
+        TopoDS_Face faceA = resolve_face(f.plane_face_body, f.plane_face);
+        SketchPlane faceA_plane;
+        bool has_faceA = false;
+        if (!faceA.IsNull()) {
+            faceA_plane = frame_from(
+                GeometryEngine::face_centroid_world(faceA),
+                GeometryEngine::face_normal_world(faceA));
+            has_faceA = true;
+        }
+
+        // Face B
+        TopoDS_Face faceB = resolve_face(f.plane_face2_body, f.plane_face2);
+        SketchPlane faceB_plane;
+        bool has_faceB = false;
+        if (!faceB.IsNull()) {
+            faceB_plane = frame_from(
+                GeometryEngine::face_centroid_world(faceB),
+                GeometryEngine::face_normal_world(faceB));
+            has_faceB = true;
+        }
+
+        // Edge A
+        Vec3d eA_p0, eA_dir;
+        bool has_edgeA = resolve_edge(f.plane_edge_body, f.plane_edge, eA_p0, eA_dir);
+
+        // Edge B
+        Vec3d eB_p0, eB_dir;
+        bool has_edgeB = resolve_edge(f.plane_edge2_body, f.plane_edge2, eB_p0, eB_dir);
+
+        // --- Dispatch on plane_type ---
+        auto fallback_offset = [&]() {
+            return offset_angle_plane(base, f.plane_offset, f.plane_angle_tilt, f.plane_axis);
+        };
+
+        SketchPlane result;
+        switch (f.plane_type) {
+
+        case PlaneType::Offset: {
+            // From a picked face: pure offset along its normal. From a base/datum plane:
+            // offset + the legacy tilt-about-axis (keeps the old Offset/Tilt controls live).
+            if (has_faceA)
+                result = frame_from(faceA_plane.origin + faceA_plane.normal * f.plane_offset,
+                                    faceA_plane.normal);
+            else
+                result = offset_angle_plane(base, f.plane_offset, f.plane_angle_tilt, f.plane_axis);
+            break;
+        }
+
+        case PlaneType::Coincident: {
+            result = has_faceA ? faceA_plane : base;
+            break;
+        }
+
+        case PlaneType::Angle: {
+            if (!has_edgeA) { result = fallback_offset(); break; }
+            const SketchPlane& ref = has_faceA ? faceA_plane : base;
+            Vec3d n0 = ref.normal - eA_dir * ref.normal.dot(eA_dir);
+            if (n0.squaredNorm() < 1e-12) {
+                Vec3d perp = (std::abs(eA_dir.z()) < 0.9) ? Vec3d(0, 0, 1) : Vec3d(1, 0, 0);
+                n0 = perp - eA_dir * perp.dot(eA_dir);
+            }
+            n0.normalize();
+            const double a = f.plane_angle_tilt * M_PI / 180.0;
+            Vec3d n_rot = n0 * std::cos(a) + eA_dir.cross(n0) * std::sin(a)
+                          + eA_dir * (eA_dir.dot(n0)) * (1.0 - std::cos(a));
+            result = frame_from(eA_p0, n_rot);
+            break;
+        }
+
+        case PlaneType::Midplane: {
+            if (!has_faceA || !has_faceB) { result = fallback_offset(); break; }
+            Vec3d origin = 0.5 * (faceA_plane.origin + faceB_plane.origin);
+            Vec3d nB = (faceA_plane.normal.dot(faceB_plane.normal) >= 0)
+                           ? faceB_plane.normal : -faceB_plane.normal;
+            Vec3d normal = (faceA_plane.normal + nB).normalized();
+            result = frame_from(origin, normal);
+            break;
+        }
+
+        case PlaneType::Tangent: {
+            if (!has_faceA) { result = fallback_offset(); break; }
+            GeometryEngine::CylinderFace cyl = GeometryEngine::cylinder_of_face(faceA);
+            if (!cyl.ok) { result = fallback_offset(); break; }
+            Vec3d refdir = (std::abs(cyl.axis.z()) < 0.9) ? Vec3d(0, 0, 1) : Vec3d(1, 0, 0);
+            refdir = refdir - cyl.axis * refdir.dot(cyl.axis);
+            refdir.normalize();
+            const double theta = f.plane_angle_tilt * M_PI / 180.0;
+            Vec3d r = refdir * std::cos(theta) + cyl.axis.cross(refdir) * std::sin(theta);
+            Vec3d touch = cyl.base + r * cyl.radius;
+            result = frame_from(touch, r);
+            break;
+        }
+
+        case PlaneType::TwoEdges: {
+            if (!has_edgeA) { result = fallback_offset(); break; }
+            if (!has_edgeB) { result = fallback_offset(); break; }
+            Vec3d cross = eA_dir.cross(eB_dir);
+            if (cross.squaredNorm() > 1e-12) {
+                result = frame_from(eA_p0, cross.normalized());
+            } else {
+                Vec3d v = eA_dir.cross(eB_p0 - eA_p0);
+                if (v.squaredNorm() > 1e-12) {
+                    result = frame_from(eA_p0, v.normalized());
+                } else {
+                    result = fallback_offset();
+                }
+            }
+            break;
+        }
+
+        }
+
+        out.emplace_back(f.name, result);
+    }
+    return out;
+}
+
+// Resolved datum axes in feature order. Origin + unit direction computed from
+// construction params; axis_err is non-empty when construction fails (no crash).
+std::vector<CadDocument::DatumAxis> CadDocument::resolve_datum_axes() const
+{
+    std::vector<DatumAxis> out;
+    // For PlaneIntersection we need the already-resolved datum planes.
+    std::vector<std::pair<std::string, SketchPlane>> datum_planes = resolve_datum_planes();
+
+    auto resolve_face = [&](int body_idx, int face_idx) -> TopoDS_Face {
+        if (face_idx < 0 || body_idx < 0 || body_idx >= int(bodies.size()))
+            return TopoDS_Face();
+        return GeometryEngine::face_by_index(bodies[body_idx].shape, face_idx);
+    };
+    auto resolve_edge = [&](int body_idx, int edge_idx,
+                             Vec3d& p0, Vec3d& dir) -> bool {
+        if (edge_idx < 0 || body_idx < 0 || body_idx >= int(bodies.size()))
+            return false;
+        TopoDS_Edge e = GeometryEngine::edge_by_index(bodies[body_idx].shape, edge_idx);
+        if (e.IsNull()) return false;
+        auto pts = GeometryEngine::sample_edge_world(e);
+        if (pts.size() < 2) return false;
+        p0 = pts.front();
+        dir = (pts.back() - pts.front()).normalized();
+        return true;
+    };
+
+    for (const CadFeature& f : features) {
+        if (f.type != CadFeatureType::Axis || !f.enabled) continue;
+
+        DatumAxis da;
+        da.name = f.name;
+        switch (f.axis_type) {
+        case AxisType::TwoPoints: {
+            Vec3d dir = f.axis_p2 - f.axis_p1;
+            if (dir.squaredNorm() < 1e-18) { da.error = "two points are coincident"; break; }
+            da.origin    = f.axis_p1;
+            da.direction = dir.normalized();
+            break;
+        }
+        case AxisType::FaceNormal: {
+            TopoDS_Face fc = resolve_face(f.axis_body, f.axis_face);
+            if (fc.IsNull()) { da.error = "face not found"; break; }
+            da.origin    = GeometryEngine::face_centroid_world(fc);
+            da.direction = GeometryEngine::face_normal_world(fc);
+            break;
+        }
+        case AxisType::CylinderCenterline: {
+            TopoDS_Face fc = resolve_face(f.axis_body, f.axis_face);
+            if (fc.IsNull()) { da.error = "face not found"; break; }
+            GeometryEngine::CylinderFace cyl = GeometryEngine::cylinder_of_face(fc);
+            if (!cyl.ok) { da.error = "face is not a cylinder"; break; }
+            da.origin    = cyl.base;
+            da.direction = cyl.axis;
+            break;
+        }
+        case AxisType::AlongEdge: {
+            Vec3d p0, dir;
+            if (!resolve_edge(f.axis_body, f.axis_edge, p0, dir)) {
+                da.error = "edge not found"; break;
+            }
+            da.origin    = p0;
+            da.direction = dir;
+            break;
+        }
+        case AxisType::PlaneIntersection: {
+            // Same reference encoding as CadFeature::plane_base, because the GUI fills these
+            // two fields from populate_plane_choices() — whose rows are XY/XZ/YZ followed by
+            // the datum planes — and stores the row verbatim. Indexing datum_planes[ref]
+            // directly, as this did, is off by three: picking XY resolved to datum plane 0 and
+            // picking the first datum ran off the end with "plane ref not found", so the
+            // PlaneIntersection axis type could not work at all. Two base planes are also a
+            // perfectly ordinary way to define an axis (XY x XZ = the X axis), so they must
+            // resolve rather than be rejected as out of scope.
+            auto base_plane = [&](int ref, Vec3d& origin, Vec3d& normal) -> bool {
+                SketchPlane p;
+                if      (ref == 0) { p = SketchPlane::XY(); p.origin += modeling_origin; }
+                else if (ref == 1) { p = SketchPlane::XZ(); p.origin += modeling_origin; }
+                else if (ref == 2) { p = SketchPlane::YZ(); p.origin += modeling_origin; }
+                else if (ref >= 3 && ref - 3 < int(datum_planes.size()))
+                    p = datum_planes[ref - 3].second;      // datums are already world-space
+                else
+                    return false;
+                origin = p.origin;
+                normal = p.normal;
+                return true;
+            };
+            bool ok0 = base_plane(f.axis_plane_a, da.origin, da.direction); // direction reused as normal0
+            Vec3d origin1, normal1;
+            bool ok1 = base_plane(f.axis_plane_b, origin1, normal1);
+            if (!ok0 || !ok1) { da.error = "plane ref not found"; break; }
+            // Direction = cross product of the two plane normals.
+            Vec3d dir = da.direction.cross(normal1); // da.direction was normal0
+            if (dir.squaredNorm() < 1e-18) {
+                da.error = "planes are parallel (no intersection)"; break;
+            }
+            dir.normalize();
+            // Find a point on the intersection line: closest points between two planes.
+            // Project origin of plane A onto the intersection line.
+            Vec3d n0 = da.direction;   // normal of plane A (stored temporarily)
+            Vec3d n1 = normal1;
+            Vec3d p0 = da.origin;
+            Vec3d p1 = origin1;
+            // Solve for point on line of intersection using vector formula.
+            double d0 = n0.dot(p0);
+            double d1 = n1.dot(p1);
+            double n0n1 = n0.dot(n1);
+            double det = 1.0 - n0n1 * n0n1;
+            if (std::abs(det) < 1e-18) { da.error = "planes are parallel (no intersection)"; break; }
+            double t0 = (d0 - d1 * n0n1) / det;
+            double t1 = (d1 - d0 * n0n1) / det;
+            da.origin    = n0 * t0 + n1 * t1;
+            da.direction = dir;
+            break;
+        }
+        }
+        out.push_back(da);
+    }
+    return out;
+}
+
+CadDocument::DatumCoordSys CadDocument::datum_frame(const std::vector<CadBody>& bodies, const CadFeature& f)
+{
+    CadDocument::DatumCoordSys ds;
+    ds.name = f.name;
+
+    auto resolve_face = [&](int body_idx, int face_idx) -> TopoDS_Face {
+        if (face_idx < 0 || body_idx < 0 || body_idx >= int(bodies.size()))
+            return TopoDS_Face();
+        return GeometryEngine::face_by_index(bodies[body_idx].shape, face_idx);
+    };
+    auto resolve_edge = [&](int body_idx, int edge_idx,
+                             Vec3d& p0, Vec3d& dir) -> bool {
+        if (edge_idx < 0 || body_idx < 0 || body_idx >= int(bodies.size()))
+            return false;
+        TopoDS_Edge e = GeometryEngine::edge_by_index(bodies[body_idx].shape, edge_idx);
+        if (e.IsNull()) return false;
+        auto pts = GeometryEngine::sample_edge_world(e);
+        if (pts.size() < 2) return false;
+        p0  = pts.front();
+        dir = (pts.back() - pts.front()).normalized();
+        return true;
+    };
+
+    switch (f.coordsys_type) {
+    case CoordSysType::PointWorld: {
+        ds.origin = f.coordsys_point;
+        ds.x      = Vec3d(1, 0, 0);
+        ds.y      = Vec3d(0, 1, 0);
+        break;
+    }
+    case CoordSysType::FaceAndDirection: {
+        TopoDS_Face fc = resolve_face(f.coordsys_body, f.coordsys_face);
+        Vec3d p0, edge_dir;
+        bool have_edge = resolve_edge(f.coordsys_body, f.coordsys_edge, p0, edge_dir);
+        if (fc.IsNull()) { ds.error = "face not found"; break; }
+        ds.origin = GeometryEngine::face_centroid_world(fc);
+        Vec3d Z = GeometryEngine::face_normal_world(fc);
+        // Tentative X: an explicit edge reference wins. Failing that, derive X from the
+        // face's OWN first usable edge, so the frame rotates with the body. Reading it from
+        // coordsys_x_hint — a world constant — meant a face-only connector could not encode
+        // spin about its own normal: Z followed the body, X did not, so Fastened and Slider
+        // claimed to fix an orientation the frame could not see. The hint survives only as a
+        // last resort, for faces that offer no usable direction (a full circular edge has
+        // coincident endpoints, and a cylinder's seam projects to nothing in-plane).
+        Vec3d X_tent = Vec3d::Zero();
+        if (have_edge) {
+            X_tent = edge_dir;
+        } else {
+            for (const TopoDS_Edge& fe : GeometryEngine::edges_of_face(fc)) {
+                auto pts = GeometryEngine::sample_edge_world(fe);
+                if (pts.size() < 2) continue;
+                Vec3d d = pts.back() - pts.front();
+                if (d.squaredNorm() < 1e-18) continue;      // closed edge: endpoints coincide
+                Vec3d in_plane = d - Z * Z.dot(d);          // drop any out-of-plane component
+                if (in_plane.squaredNorm() < 1e-18) continue;
+                X_tent = in_plane;
+                break;
+            }
+            if (X_tent.squaredNorm() < 1e-18) X_tent = f.coordsys_x_hint;
+        }
+        if (X_tent.squaredNorm() < 1e-18) { ds.error = "zero-length direction"; break; }
+        X_tent.normalize();
+        // Gram-Schmidt: ensure orthonormal, right-handed frame.
+        // Y = Z x X_tent,  X = Y x Z  (this makes X perpendicular to Z, not X_tent)
+        Vec3d Y = Z.cross(X_tent);
+        if (Y.squaredNorm() < 1e-12) {
+            // Edge/hint is parallel to Z -> X is degenerate; fall back to world X/Y orthonormalised.
+            Vec3d ref = (std::abs(Z.z()) < 0.9) ? Vec3d(0, 0, 1) : Vec3d(1, 0, 0);
+            Y = Z.cross(ref);
+            if (Y.squaredNorm() < 1e-12) Y = Z.cross(Vec3d(0, 1, 0));
+        }
+        Y.normalize();
+        ds.x = Y.cross(Z).normalized();
+        ds.y = Y;
+        break;
+    }
+    }
+    return ds;
+}
+
+std::vector<CadDocument::DatumCoordSys> CadDocument::resolve_datum_coordsys() const
+{
+    std::vector<DatumCoordSys> out;
+    for (const CadFeature& f : features) {
+        if (f.type != CadFeatureType::CoordSys || !f.enabled) continue;
+        out.push_back(datum_frame(bodies, f));
+    }
+    return out;
+}
+
+void CadDocument::clear()
+{
+    features.clear();
+    body = TopoDS_Shape();
+    bodies.clear();                // multibody result — must clear too (else solids linger)
+    display_mesh = TriangleMesh{};
+    display_body_meshes.clear();
+    display_tri_face.clear();
+    error.clear();
+    mate_conflicts.clear();
+    // A cleared document is a fresh start with no history.
+    m_undo.clear();
+    m_redo.clear();
+}
+
+void CadDocument::checkpoint()
+{
+    m_undo.push_back(Snapshot{features, variables});   // snapshot the pre-mutation recipe
+    m_redo.clear();                                    // any new action invalidates the redo branch
+    if (m_undo.size() > k_undo_cap)
+        m_undo.erase(m_undo.begin());
+}
+
+void CadDocument::abandon_checkpoint()
+{
+    if (!m_undo.empty())
+        m_undo.pop_back();
+}
+
+bool CadDocument::undo()
+{
+    if (m_undo.empty())
+        return false;
+    m_redo.push_back(Snapshot{std::move(features), std::move(variables)});   // current state becomes redoable
+    features  = std::move(m_undo.back().features);
+    variables = std::move(m_undo.back().variables);
+    m_undo.pop_back();
+    recompute();   // benign-empty (only a sketch / empty doc) is a valid undo target
+    return true;
+}
+
+bool CadDocument::redo()
+{
+    if (m_redo.empty())
+        return false;
+    m_undo.push_back(Snapshot{std::move(features), std::move(variables)});
+    features  = std::move(m_redo.back().features);
+    variables = std::move(m_redo.back().variables);
+    m_redo.pop_back();
+    recompute();
+    return true;
+}
+
+// Re-run recompute(); if it fails for a GENUINE geometry error, restore `snapshot`
+// and recompute that instead, so a rejected edit leaves the document exactly as it
+// was. recompute() also returns false for the BENIGN case where the edit simply
+// leaves no solid-producing feature (empty document, or only a sketch) — that is a
+// valid result of a deletion, not a failure, so we accept it with an empty body.
+static bool commit_or_rollback(CadDocument& doc, std::vector<CadFeature>& snapshot)
+{
+    if (doc.recompute())
+        return true;
+
+    bool has_solid_feature = false;
+    for (const auto& f : doc.features)
+        if (f.enabled && f.type != CadFeatureType::Sketch) { has_solid_feature = true; break; }
+    if (!has_solid_feature) {
+        doc.bodies.clear();
+        doc.body         = TopoDS_Shape();
+        doc.display_mesh = TriangleMesh{};
+        doc.display_body_meshes.clear();
+        doc.display_tri_face.clear();
+        doc.display_tri_body.clear();
+        doc.error.clear();
+        return true;
+    }
+
+    std::string fail_err = doc.error;   // why the attempted edit failed
+    doc.features.swap(snapshot);
+    doc.recompute();                    // restore the previous good body (clears error)
+    doc.error = fail_err.empty() ? std::string("feature is used by a later feature")
+                                 : fail_err;
+    return false;
+}
+
+// Visit every field of `f` that holds an index into features[].
+//
+// Deliberately NOT dispatched on f.type. A type switch is what this replaced, and it was
+// wrong in the way type switches go wrong: it listed Extrude and Mate, and every feature
+// type added afterwards — Revolve, Sweep, Loft, Rib, Pattern-on-curve, the Surface* family —
+// silently inherited a remap that skipped its references. Visiting the FIELDS instead means
+// a new type is covered the moment it reuses one of them, and reaching a field its type
+// never reads costs nothing: unset refs are -1 and every visitor here ignores those.
+//
+// The list is exactly the fields documented as "index into features[]" / "feature index" in
+// CadDocument.hpp. Not included, because they are a different basis and need their own pass:
+// plane_base / axis_plane_a / axis_plane_b encode `3 + N` = the Nth DATUM PLANE, an ordinal
+// into resolve_datum_planes(), not into features[]. Everything named *_body / *_face / *_edge
+// is a body index or a global topology id and must never be remapped here.
+template<class Visit>
+static void for_each_feature_ref(CadFeature& f, Visit&& visit)
+{
+    visit(f.sketch_ref);
+    visit(f.sweep_path_ref);
+    visit(f.pattern_curve_sketch);
+    visit(f.rib_sketch_ref);
+    visit(f.mate_cs_a);
+    visit(f.mate_cs_b);
+    for (int& r : f.loft_profile_refs)
+        visit(r);
+}
+
+bool CadDocument::remove_feature(int index)
+{
+    if (index < 0 || index >= int(features.size()))
+        return false;
+
+    std::vector<CadFeature> snapshot = features;
+
+    // Deleting a Sketch cascades to every feature that consumes it AS ITS PROFILE — the
+    // reason is the original one ("a dangling Extrude would have no wire"), and it applies
+    // unchanged to Revolve, Sweep, Rib and the Surface* family, which all read the profile
+    // through sketch_ref, plus the sweep spine and the rib line. Testing the FIELD rather
+    // than the type is what makes that true without a list to keep up to date.
+    //
+    // pattern_curve_sketch and loft_profile_refs are deliberately NOT cascaded: a Pattern or
+    // a Loft that loses one of several inputs is degraded, not meaningless, so those refs go
+    // to -1 in the remap below and the feature survives. A lone Sketch is harmless either way.
+    std::vector<int> remove{index};
+    if (features[index].type == CadFeatureType::Sketch) {
+        for (int j = 0; j < int(features.size()); ++j) {
+            const CadFeature& c = features[j];
+            if (c.sketch_ref == index || c.sweep_path_ref == index || c.rib_sketch_ref == index)
+                remove.push_back(j);
+        }
+    }
+    std::sort(remove.begin(), remove.end());
+    remove.erase(std::unique(remove.begin(), remove.end()), remove.end());
+
+    // Erase high-to-low so earlier indices stay valid.
+    for (auto it = remove.rbegin(); it != remove.rend(); ++it)
+        features.erase(features.begin() + *it);
+
+    // Remap surviving feature references through the deletions: subtract the count of
+    // removed indices that sat before it; orphaned refs (target removed) -> -1.
+    //
+    // This must cover EVERY field holding a feature index, not just sketch_ref. A mate's two
+    // connectors are such indices, and leaving them behind slid them onto whatever features
+    // landed on those slots — silently, because recompute() only rejects out-of-range and
+    // non-CoordSys targets, and a shifted index usually lands on the assembly's other CoordSys.
+    auto remap = [&remove](int& ref) {
+        if (ref < 0)
+            return;
+        if (std::binary_search(remove.begin(), remove.end(), ref)) {
+            ref = -1;
+        } else {
+            int shift = 0;
+            for (int r : remove)
+                if (r < ref) ++shift;
+            ref -= shift;
+        }
+    };
+    for (auto& f : features)
+        for_each_feature_ref(f, remap);
+
+    return commit_or_rollback(*this, snapshot);
+}
+
+bool CadDocument::move_feature(int index, int delta)
+{
+    if (index < 0 || index >= int(features.size()))
+        return false;
+    int target = index + delta;
+    if (target < 0 || target >= int(features.size()))
+        return true; // clamped at the ends — no-op, not a failure
+
+    std::vector<CadFeature> snapshot = features;
+    std::swap(features[index], features[target]);
+
+    // The two slots traded places: fix every feature reference that pointed at either —
+    // a mate's connectors as well as sketch_ref, for the reason given in remove_feature().
+    auto swap_ref = [index, target](int& ref) {
+        if (ref == index)       ref = target;
+        else if (ref == target) ref = index;
+    };
+    for (auto& f : features)
+        for_each_feature_ref(f, swap_ref);
+
+    return commit_or_rollback(*this, snapshot);
+}
+
+bool CadDocument::replace_feature(int index, const CadFeature& edited)
+{
+    if (index < 0 || index >= int(features.size()))
+        return false;
+
+    std::vector<CadFeature> snapshot = features;
+
+    // Preserve identity (name) and the structural link (sketch_ref) from the
+    // original; only the user-editable parameters come from `edited`.
+    CadFeature f      = edited;
+    f.name            = features[index].name;
+    f.type            = features[index].type;
+    if (f.type == CadFeatureType::Extrude)
+        f.sketch_ref  = features[index].sketch_ref;
+    features[index]   = f;
+
+    return commit_or_rollback(*this, snapshot);
+}
+
+bool CadDocument::replace_sketch_extrude(int sketch_idx, int extrude_idx,
+                                         const CadFeature& edited)
+{
+    if (sketch_idx  < 0 || sketch_idx  >= int(features.size())) return false;
+    if (extrude_idx < 0 || extrude_idx >= int(features.size())) return false;
+
+    std::vector<CadFeature> snapshot = features;
+
+    // A box in the tree is two linked features: the Sketch consumes the profile
+    // params (shape/plane/width/height/radius), the Extrude consumes the solid
+    // params (distance/symmetric/mode). `edited` carries all of them; split it
+    // back into the two slots, preserving each slot's name/type and the link.
+    CadFeature& sk = features[sketch_idx];
+    sk.shape  = edited.shape;
+    sk.plane  = edited.plane;
+    sk.width  = edited.width;
+    sk.height = edited.height;
+    sk.radius = edited.radius;
+
+    CadFeature& ex = features[extrude_idx];
+    ex.distance  = edited.distance;
+    ex.symmetric = edited.symmetric;
+    ex.mode      = edited.mode;
+
+    return commit_or_rollback(*this, snapshot);
+}
+
+// "the sketch is open" is not actionable; WHERE it is open is. Shared by both throws so the
+// two ways of reaching an open profile (Revolve via build_sketch_wire, Extrude via
+// build_sketch_face) report it identically.
+static std::string open_loop_message(const CadFeature& sketch,
+                                     const char* head = "sketch entities do not form a closed loop")
+{
+    std::string msg = head;
+    const std::vector<Vec2d> open = Slic3r::sketch_open_ends(sketch.entities, sketch.plane);
+    if (!open.empty()) {
+        const size_t shown = std::min<size_t>(open.size(), 3);
+        char buf[96];
+        for (size_t i = 0; i < shown; ++i) {
+            std::snprintf(buf, sizeof buf, "\n  Open at (%.3f, %.3f)", open[i].x(), open[i].y());
+            msg += buf;
+        }
+        if (open.size() > shown) {
+            std::snprintf(buf, sizeof buf, "\n  ...and %zu more open end(s)", open.size() - shown);
+            msg += buf;
+        }
+    }
+    return msg;
+}
+
+TopoDS_Wire CadDocument::build_sketch_wire(const CadFeature& sketch, bool closed_only) const
+{
+    if (!sketch.entities.empty()) {
+        TopoDS_Wire w = SketchEngine::entities_to_wire(sketch.entities, sketch.plane, closed_only);
+        if (!w.IsNull()) return w;
+        // An entity sketch that yields no wire is an ERROR, not a cue to fall through. The
+        // legacy tail of this function ends in a default rectangle built from width/height,
+        // which for an entity sketch are whatever they happened to be initialised to — so a
+        // sketch entities_to_wire cannot handle (a circle coexisting with a line, two circles:
+        // 88v) used to extrude into a box the user never drew, silently. Failing here
+        // costs the caller an error message; falling through cost them wrong geometry that
+        // looked deliberate. The legacy profile/shape paths below are still reached by sketches
+        // that legitimately carry no entities at all.
+        throw std::runtime_error(
+            open_loop_message(sketch,
+                "sketch has entities but they do not form a single closed wire — a closed "
+                "entity (circle/ellipse) combined with other entities, or several closed "
+                "entities, is not supported yet"));
+    }
+    if (!sketch.profile.points.empty()) {
+        SketchProfile prof = sketch.profile;
+        prof.closed = true;               // extrude needs a closed wire
+        TopoDS_Wire w = prof.to_occt_wire(sketch.plane);
+        if (w.IsNull()) throw std::runtime_error("sketch profile wire failed");
+        return w;
+    }
+    if (sketch.shape == SketchShape::Circle) {
+        gp_Pnt o(sketch.plane.origin.x(), sketch.plane.origin.y(), sketch.plane.origin.z());
+        gp_Dir n(sketch.plane.normal.x(), sketch.plane.normal.y(), sketch.plane.normal.z());
+        gp_Circ circ(gp_Ax2(o, n), sketch.radius);
+        TopoDS_Edge e = BRepBuilderAPI_MakeEdge(circ).Edge();
+        BRepBuilderAPI_MakeWire wm(e);
+        if (!wm.IsDone()) throw std::runtime_error("circle wire failed");
+        return wm.Wire();
+    }
+    // Rectangle centered on the plane origin
+    SketchProfile prof;
+    double hw = sketch.width * 0.5, hh = sketch.height * 0.5;
+    prof.points.push_back(Vec2d(-hw, -hh));
+    prof.points.push_back(Vec2d( hw, -hh));
+    prof.points.push_back(Vec2d( hw,  hh));
+    prof.points.push_back(Vec2d(-hw,  hh));
+    prof.closed = true;
+    return prof.to_occt_wire(sketch.plane);
+}
+
+TopoDS_Face CadDocument::build_sketch_face(const CadFeature& sketch) const
+{
+    if (!sketch.entities.empty()) {
+        const std::vector<TopoDS_Wire> loops = SketchEngine::entities_to_wires(sketch.entities, sketch.plane, true);
+        if (loops.empty())
+            // Same courtesy as build_sketch_wire: name WHERE the sketch is open. Extrude
+            // reaches its failure through here, not through build_sketch_wire, so without
+            // this the most common way to hit an open profile is also the least informative.
+            throw std::runtime_error(open_loop_message(sketch));
+        return SketchEngine::wires_to_face(loops, sketch.plane);
+    }
+    return BRepBuilderAPI_MakeFace(build_sketch_wire(sketch, true)).Face();
+}
+
+void CadDocument::apply_feature(TopoDS_Shape& result, bool& have_body,
+                                const TopoDS_Shape& context, const CadFeature& f) const
+{
+    switch (f.type) {
+    case CadFeatureType::Sketch:
+        return; // sketches carry no solid; consumed by an extrude
+    case CadFeatureType::Project:
+        return; // edges-to-sketch: consumed downstream, no solid body
+    case CadFeatureType::Helix:
+        return; // helical curve; consumed by Sweep as a path (like Sketch)
+    case CadFeatureType::Boolean:
+        return; // body-body boolean is handled in route_feature/apply_boolean, never here
+    case CadFeatureType::Import:
+        // Imported B-rep (STEP): rigid data carried on the feature, not built from
+        // parameters — adopt it as the new body (New-path: result starts empty).
+        result    = f.imported_solid;
+        have_body = !result.IsNull();
+        return;
+    case CadFeatureType::Extrude: {
+        const bool sym = (f.extrude_end == ExtrudeEnd::Symmetric);
+        const double signed_d = f.flip ? -f.distance : f.distance;
+        TopoDS_Shape tool;
+        if (f.extrude_src_face >= 0) {
+            // The source face is read from `context` (the owner body), which for a New
+            // face-extrude is the source solid while `result` is the empty new body.
+            if (context.IsNull()) throw std::runtime_error("face-extrude needs a body");
+            TopoDS_Face srcf = GeometryEngine::face_by_index(context, f.extrude_src_face);
+            if (srcf.IsNull()) throw std::runtime_error("face-extrude: invalid face id");
+            SketchPlane fpl = SketchPlane::from_face(srcf);
+            // from_face takes the surface's geometric normal and IGNORES the topological
+            // face orientation, so for a REVERSED face (e.g. the top cap of an extruded
+            // prism) it points INTO the solid -> a default push would fuse to nothing.
+            // Orient it outward so push/pull grows away from the material (Onshape default);
+            // the Flip checkbox (signed_d) still lets the user drive it inward for a cut.
+            if (srcf.Orientation() == TopAbs_REVERSED) fpl.normal = -fpl.normal;
+            tool = SketchEngine::make_extrude_face(srcf, fpl, signed_d, sym);
+        } else {
+            // Use the referenced sketch when sketch_ref is a valid Sketch index,
+            // otherwise fall back to f's own inline sketch params (this makes a
+            // single self-contained candidate previewable).
+            const CadFeature& sk = (f.sketch_ref >= 0 && f.sketch_ref < int(features.size())
+                                    && (features[f.sketch_ref].type == CadFeatureType::Sketch
+                                        || features[f.sketch_ref].type == CadFeatureType::Project))
+                                   ? features[f.sketch_ref] : f;
+            // Imported rigid art (Text/SVG) extrudes via the faces-with-holes path
+            // (with its placement transform applied); otherwise build the sketch's planar
+            // region (outer loop + holes) from entities/profile/shape.
+            tool = !sk.imported_regions.empty()
+                ? SketchEngine::make_extrude_regions(
+                      transform_regions(sk.imported_regions, sk.import_offset,
+                                        sk.import_scale_x, sk.import_scale_y),
+                      sk.plane,
+                      f.extrude_end == ExtrudeEnd::ThroughAll ? 1e5 : signed_d,
+                      f.extrude_end == ExtrudeEnd::ThroughAll ? true : (sym || f.extrude_end == ExtrudeEnd::TwoSided))
+                : [&]() {
+                      const TopoDS_Face profile = build_sketch_face(sk);
+                      // A tapered extrude offsets the profile; a holed profile would have to
+                      // offset its inner loops the opposite way, which is not implemented yet.
+                      auto taper = [&](double L) -> TopoDS_Shape {
+                          // Count the loops off the face we ALREADY built, rather than rebuilding
+                          // every wire from the entities a second time to ask how many there are.
+                          // It is also the more honest test: what matters is whether the profile
+                          // being extruded has holes, not what the entity list could produce.
+                          int nloops = 0;
+                          for (TopExp_Explorer ex(profile, TopAbs_WIRE); ex.More(); ex.Next()) ++nloops;
+                          if (nloops > 1)
+                              throw std::runtime_error("tapered extrude of a sketch with holes is not supported yet");
+                          return SketchEngine::make_extrude_taper(build_sketch_wire(sk, true), sk.plane, L, f.taper_deg);
+                      };
+                      TopoDS_Shape t;
+                      switch (f.extrude_end) {
+                          case ExtrudeEnd::Blind:
+                              t = (std::abs(f.taper_deg) > 1e-6)
+                                  ? taper(signed_d)
+                                  : SketchEngine::make_extrude(profile, sk.plane, signed_d, false);
+                              break;
+                          case ExtrudeEnd::Symmetric:  t = SketchEngine::make_extrude(profile, sk.plane, f.distance, true); break;
+                          case ExtrudeEnd::TwoSided:   t = SketchEngine::make_extrude_two_sided(profile, sk.plane, f.distance, f.distance2); break;
+                          case ExtrudeEnd::ThroughAll: t = SketchEngine::make_extrude(profile, sk.plane, 1.0e5, true); break;
+                          case ExtrudeEnd::UpToFace: {
+                              const TopoDS_Face tgt = GeometryEngine::face_by_index(context, f.up_to_face);
+                              double L = signed_d;
+                              if (!tgt.IsNull()) {
+                                  const Vec3d c = GeometryEngine::face_centroid_world(tgt);
+                                  L = (c - sk.plane.origin).dot(sk.plane.normal);
+                              }
+                              t = (std::abs(f.taper_deg) > 1e-6)
+                                  ? taper(L)
+                                  : SketchEngine::make_extrude(profile, sk.plane, L, false);
+                              break;
+                          }
+                          case ExtrudeEnd::UpToVertex: {
+                              const double L = (f.up_to_point - sk.plane.origin).dot(sk.plane.normal);
+                              t = SketchEngine::make_extrude(profile, sk.plane, L, false);
+                              break;
+                          }
+                          default: t = SketchEngine::make_extrude(profile, sk.plane, signed_d, false); break;
+                      }
+                      return t;
+                  }();
+        }
+        // New / first-of-a-body => result becomes the tool (route_feature sends New extrudes
+        // here with an empty result, so a face-extrude New builds a fresh body from the source
+        // face in `context` without touching it). Add/Cut/Intersect boolean into `result`.
+        if (!have_body || f.mode == BooleanMode::New) {
+            result = tool;
+            have_body = true;
+        } else if (f.mode == BooleanMode::Add) {
+            BRepAlgoAPI_Fuse fuse(result, tool);
+            if (!fuse.IsDone()) throw std::runtime_error("fuse failed");
+            result = fuse.Shape();
+        } else if (f.mode == BooleanMode::Cut) {
+            BRepAlgoAPI_Cut cut(result, tool);
+            if (!cut.IsDone()) throw std::runtime_error("cut failed");
+            result = cut.Shape();
+        } else if (f.mode == BooleanMode::Intersect) {
+            BRepAlgoAPI_Common common(result, tool);
+            if (!common.IsDone()) throw std::runtime_error("intersect failed");
+            result = common.Shape();
+        }
+        break;
+    }
+    case CadFeatureType::Revolve: {
+        // Resolve the profile sketch like Extrude: referenced Sketch when valid,
+        // else this feature's own inline entities/profile (self-contained candidate).
+        const CadFeature& sk = (f.sketch_ref >= 0 && f.sketch_ref < int(features.size())
+                                && (features[f.sketch_ref].type == CadFeatureType::Sketch
+                                    || features[f.sketch_ref].type == CadFeatureType::Project))
+                               ? features[f.sketch_ref] : f;
+        TopoDS_Wire wire = build_sketch_wire(sk, true);
+        const double ang = f.flip ? -f.revolve_angle : f.revolve_angle;
+        TopoDS_Shape tool = SketchEngine::make_revolve(wire, sk.plane, ang, f.revolve_axis);
+        if (!have_body || f.mode == BooleanMode::New) {
+            result = tool;
+            have_body = true;
+        } else if (f.mode == BooleanMode::Add) {
+            BRepAlgoAPI_Fuse fuse(result, tool);
+            if (!fuse.IsDone()) throw std::runtime_error("fuse failed");
+            result = fuse.Shape();
+        } else if (f.mode == BooleanMode::Cut) {
+            BRepAlgoAPI_Cut cut(result, tool);
+            if (!cut.IsDone()) throw std::runtime_error("cut failed");
+            result = cut.Shape();
+        } else if (f.mode == BooleanMode::Intersect) {
+            BRepAlgoAPI_Common common(result, tool);
+            if (!common.IsDone()) throw std::runtime_error("intersect failed");
+            result = common.Shape();
+        }
+        break;
+    }
+    case CadFeatureType::SurfaceExtrude: {
+        if (f.sketch_ref < 0 || f.sketch_ref >= int(features.size()))
+            throw std::runtime_error("surface-extrude: bad sketch ref");
+        const CadFeature& sk = features[f.sketch_ref];
+        if (sk.type != CadFeatureType::Sketch && sk.type != CadFeatureType::Project)
+            throw std::runtime_error("surface-extrude: ref is not a sketch");
+        TopoDS_Wire wire = build_sketch_wire(sk);
+        if (wire.IsNull()) throw std::runtime_error("surface-extrude: empty profile");
+        gp_Dir nrm(sk.plane.normal.x(), sk.plane.normal.y(), sk.plane.normal.z());
+        gp_Vec v(nrm.XYZ() * f.distance);
+        TopoDS_Shape shell = BRepPrimAPI_MakePrism(wire, v, false, true).Shape();
+        if (shell.IsNull()) throw std::runtime_error("surface-extrude: prism failed");
+        result = shell; have_body = true;
+        break;
+    }
+    case CadFeatureType::SurfaceRevolve: {
+        if (f.sketch_ref < 0 || f.sketch_ref >= int(features.size()))
+            throw std::runtime_error("surface-revolve: bad sketch ref");
+        const CadFeature& sk = features[f.sketch_ref];
+        if (sk.type != CadFeatureType::Sketch && sk.type != CadFeatureType::Project)
+            throw std::runtime_error("surface-revolve: ref is not a sketch");
+        TopoDS_Wire wire = build_sketch_wire(sk);
+        if (wire.IsNull()) throw std::runtime_error("surface-revolve: empty profile");
+        const Vec3d& adir = (f.revolve_axis == 1) ? sk.plane.y_axis : sk.plane.x_axis;
+        gp_Pnt o(sk.plane.origin.x(), sk.plane.origin.y(), sk.plane.origin.z());
+        gp_Dir xd(adir.x(), adir.y(), adir.z());
+        gp_Ax1 axis(o, xd);
+        const double ang = f.revolve_angle * M_PI / 180.0;
+        BRepPrimAPI_MakeRevol rev(wire, axis, ang, false);
+        if (!rev.IsDone()) throw std::runtime_error("surface-revolve: revolve failed");
+        result = rev.Shape(); have_body = true;
+        break;
+    }
+    case CadFeatureType::SurfaceLoft: {
+        std::vector<TopoDS_Wire> profiles;
+        for (int ref : f.loft_profile_refs) {
+            if (ref < 0 || ref >= int(features.size())
+                || (features[ref].type != CadFeatureType::Sketch
+                    && features[ref].type != CadFeatureType::Project))
+                continue;
+            profiles.push_back(build_sketch_wire(features[ref]));
+        }
+        if (profiles.size() < 2)
+            throw std::runtime_error("surface-loft needs 2+ valid profile sketches");
+        TopoDS_Shape skin = SketchEngine::make_loft_surface(profiles, f.loft_ruled);
+        if (skin.IsNull()) throw std::runtime_error("surface-loft: loft failed");
+        result = skin; have_body = true;
+        break;
+    }
+    case CadFeatureType::SurfaceFill: {
+        if (f.sketch_ref < 0 || f.sketch_ref >= int(features.size()))
+            throw std::runtime_error("surface-fill: bad sketch ref");
+        const CadFeature& sk = features[f.sketch_ref];
+        if (sk.type != CadFeatureType::Sketch && sk.type != CadFeatureType::Project)
+            throw std::runtime_error("surface-fill: ref is not a sketch");
+        TopoDS_Wire wire = build_sketch_wire(sk);
+        if (wire.IsNull()) throw std::runtime_error("surface-fill: empty boundary");
+        BRepOffsetAPI_MakeFilling fill;
+        int nedges = 0;
+        for (TopExp_Explorer ex(wire, TopAbs_EDGE); ex.More(); ex.Next()) {
+            fill.Add(TopoDS::Edge(ex.Current()), GeomAbs_C0);
+            ++nedges;
+        }
+        if (nedges == 0) throw std::runtime_error("surface-fill: boundary has no edges");
+        fill.Build();
+        if (!fill.IsDone()) throw std::runtime_error("surface-fill: fill failed");
+        TopoDS_Shape face = fill.Shape();
+        if (face.IsNull()) throw std::runtime_error("surface-fill: produced no geometry");
+        result = face; have_body = true;
+        break;
+    }
+    case CadFeatureType::Sweep: {
+        const CadFeature& sk = (f.sketch_ref >= 0 && f.sketch_ref < int(features.size())
+                                && (features[f.sketch_ref].type == CadFeatureType::Sketch
+                                    || features[f.sketch_ref].type == CadFeatureType::Project))
+                               ? features[f.sketch_ref] : f;
+        if (f.sweep_path_ref < 0 || f.sweep_path_ref >= int(features.size()))
+            throw std::runtime_error("sweep needs a valid path reference");
+        const CadFeature& path_feat = features[f.sweep_path_ref];
+        TopoDS_Wire path;
+        if (path_feat.type == CadFeatureType::Helix) {
+            std::string helix_err;
+            path = make_helix_spine(path_feat, helix_err);
+            if (path.IsNull()) throw std::runtime_error("helix path: " + helix_err);
+        } else if (path_feat.type == CadFeatureType::Sketch) {
+            path = build_sketch_wire(path_feat);
+        } else {
+            throw std::runtime_error("sweep path must be a sketch or helix");
+        }
+        TopoDS_Wire profile = build_sketch_wire(sk, true);
+        TopoDS_Shape tool   = SketchEngine::make_sweep(profile, path);
+        if (!have_body || f.mode == BooleanMode::New) {
+            result = tool;
+            have_body = true;
+        } else if (f.mode == BooleanMode::Add) {
+            BRepAlgoAPI_Fuse fuse(result, tool);
+            if (!fuse.IsDone()) throw std::runtime_error("fuse failed");
+            result = fuse.Shape();
+        } else if (f.mode == BooleanMode::Cut) {
+            BRepAlgoAPI_Cut cut(result, tool);
+            if (!cut.IsDone()) throw std::runtime_error("cut failed");
+            result = cut.Shape();
+        } else if (f.mode == BooleanMode::Intersect) {
+            BRepAlgoAPI_Common common(result, tool);
+            if (!common.IsDone()) throw std::runtime_error("intersect failed");
+            result = common.Shape();
+        }
+        break;
+    }
+    case CadFeatureType::Loft: {
+        // Loft through 2+ closed profile Sketches, in recipe order. Each profile builds
+        // a wire via build_sketch_wire (so it keeps its own plane); make_loft skins them.
+        std::vector<TopoDS_Wire> profiles;
+        for (int ref : f.loft_profile_refs) {
+            if (ref < 0 || ref >= int(features.size())
+                || (features[ref].type != CadFeatureType::Sketch
+                    && features[ref].type != CadFeatureType::Project))
+                continue;
+            profiles.push_back(build_sketch_wire(features[ref], true));
+        }
+        if (profiles.size() < 2)
+            throw std::runtime_error("loft needs 2+ valid profile sketches");
+        TopoDS_Shape tool = SketchEngine::make_loft(profiles, f.loft_ruled);
+        if (!have_body || f.mode == BooleanMode::New) {
+            result = tool;
+            have_body = true;
+        } else if (f.mode == BooleanMode::Add) {
+            BRepAlgoAPI_Fuse fuse(result, tool);
+            if (!fuse.IsDone()) throw std::runtime_error("fuse failed");
+            result = fuse.Shape();
+        } else if (f.mode == BooleanMode::Cut) {
+            BRepAlgoAPI_Cut cut(result, tool);
+            if (!cut.IsDone()) throw std::runtime_error("cut failed");
+            result = cut.Shape();
+        } else if (f.mode == BooleanMode::Intersect) {
+            BRepAlgoAPI_Common common(result, tool);
+            if (!common.IsDone()) throw std::runtime_error("intersect failed");
+            result = common.Shape();
+        }
+        break;
+    }
+    case CadFeatureType::Pattern: {
+        // Pattern along a curve: when pattern_curve_sketch >= 0 this mode takes
+        // precedence over linear/circular. Copies are placed at equal-parameter points
+        // along the referenced sketch entity, translated by (P_i - P_0).
+        if (f.pattern_curve_sketch >= 0) {
+            if (f.pattern_curve_sketch >= (int)features.size())
+                throw std::runtime_error("pattern-on-curve: bad sketch ref");
+            const CadFeature& gs = features[f.pattern_curve_sketch];
+            if (gs.type != CadFeatureType::Sketch)
+                throw std::runtime_error("pattern-on-curve: ref is not a sketch");
+            if (f.pattern_curve_entity < 0 || f.pattern_curve_entity >= (int)gs.entities.size())
+                throw std::runtime_error("pattern-on-curve: bad entity");
+            if (!have_body) throw std::runtime_error("pattern needs a body");
+            const SketchEntity& gc = gs.entities[f.pattern_curve_entity];
+            const int n = std::max(1, f.pattern_count);
+            const TopoDS_Shape seed = result;
+            Vec3d p0 = gs.plane.to_world(sample_entity_2d(gc, 0.0));
+            for (int i = 1; i < n; ++i) {
+                double t = double(i) / double(n - 1 > 0 ? n - 1 : 1);
+                Vec3d pi = gs.plane.to_world(sample_entity_2d(gc, t));
+                Vec3d d  = pi - p0;
+                gp_Trsf trsf;
+                trsf.SetTranslation(gp_Vec(d.x(), d.y(), d.z()));
+                TopoDS_Shape copy = BRepBuilderAPI_Transform(seed, trsf, true).Shape();
+                BRepAlgoAPI_Fuse fuse(result, copy);
+                if (!fuse.IsDone()) throw std::runtime_error("pattern fuse failed");
+                result = fuse.Shape();
+            }
+            break;
+        }
+        // Replicate the target body. Each copy is a rigid gp_Trsf of the seed, all
+        // fused into one body. Linear: i*spacing along plane axis pattern_dir
+        // (0=X,1=Y). Circular: i*(angle/count) about the plane normal through the
+        // plane origin (so a seed offset from the origin orbits the axis).
+        if (!have_body) throw std::runtime_error("pattern needs a body");
+        const int n = std::max(1, f.pattern_count);
+        const TopoDS_Shape seed = result;
+        for (int i = 1; i < n; ++i) {
+            gp_Trsf trsf;
+            if (f.pattern_circular) {
+                Vec3d  o = f.plane.to_world(Vec2d(0, 0));
+                gp_Ax1 ax(gp_Pnt(o.x(), o.y(), o.z()),
+                          gp_Dir(f.plane.normal.x(), f.plane.normal.y(), f.plane.normal.z()));
+                const double step = (f.pattern_angle * M_PI / 180.0) / double(n);
+                trsf.SetRotation(ax, step * i);
+            } else {
+                const Vec3d& d = (f.pattern_dir == 1) ? f.plane.y_axis : f.plane.x_axis;
+                trsf.SetTranslation(gp_Vec(d.x() * f.pattern_spacing * i,
+                                           d.y() * f.pattern_spacing * i,
+                                           d.z() * f.pattern_spacing * i));
+            }
+            TopoDS_Shape copy = BRepBuilderAPI_Transform(seed, trsf, true).Shape();
+            BRepAlgoAPI_Fuse fuse(result, copy);
+            if (!fuse.IsDone()) throw std::runtime_error("pattern fuse failed");
+            result = fuse.Shape();
+        }
+        break;
+    }
+    case CadFeatureType::Rib: {
+        if (!have_body) throw std::runtime_error("rib needs a body");
+        if (f.rib_sketch_ref < 0 || f.rib_sketch_ref >= (int)features.size())
+            throw std::runtime_error("rib: bad sketch ref");
+        const CadFeature& sk = features[f.rib_sketch_ref];
+        // Project counts as sketch-like here exactly as it does for Extrude, SurfaceExtrude
+        // and SurfaceRevolve: it carries plane + Line entities, which is all a rib reads.
+        // Ribbing along a projected body edge is otherwise unreachable.
+        if (sk.type != CadFeatureType::Sketch && sk.type != CadFeatureType::Project)
+            throw std::runtime_error("rib: ref is not a sketch");
+        if (f.rib_entity < 0 || f.rib_entity >= (int)sk.entities.size())
+            throw std::runtime_error("rib: bad entity");
+        const SketchEntity& ln = sk.entities[f.rib_entity];
+        if (ln.type != SketchEntity::Type::Line)
+            throw std::runtime_error("rib: entity must be a line"); // ponytail: line-only for now
+        // Thin rectangle centred on the line, in the sketch plane: offset both endpoints by
+        // +/-thickness/2 along the in-plane perpendicular of the line direction.
+        const SketchPlane& pl = sk.plane;
+        Vec2d a = ln.p0, b = ln.p1;
+        Vec2d dir = (b - a); double L = dir.norm();
+        if (L < 1e-9) throw std::runtime_error("rib: degenerate line");
+        dir /= L;
+        Vec2d perp(-dir.y(), dir.x());
+        double h = f.rib_thickness * 0.5;
+        Vec2d q0 = a + perp*h, q1 = b + perp*h, q2 = b - perp*h, q3 = a - perp*h;
+        auto w3 = [&](const Vec2d& p){ Vec3d w = pl.to_world(p); return gp_Pnt(w.x(),w.y(),w.z()); };
+        BRepBuilderAPI_MakePolygon poly(w3(q0), w3(q1), w3(q2), w3(q3), Standard_True);
+        if (!poly.IsDone()) throw std::runtime_error("rib: profile failed");
+        TopoDS_Shape wall = SketchEngine::make_extrude(poly.Wire(), pl, f.rib_depth, false, 0.0);
+        if (wall.IsNull()) throw std::runtime_error("rib: extrude failed");
+        BRepAlgoAPI_Fuse fuse(result, wall);
+        if (!fuse.IsDone()) throw std::runtime_error("rib: fuse failed");
+        result = fuse.Shape();
+        break;
+    }
+    case CadFeatureType::Fillet:
+        if (!have_body) throw std::runtime_error("fillet needs a body");
+        if (f.dressup_edge >= 0)
+            result = GeometryEngine::apply_fillet(result, f.dressup_size, f.dressup_edge);
+        else
+            result = GeometryEngine::apply_fillet(result, f.dressup_size, f.face_group);
+        break;
+    case CadFeatureType::Chamfer:
+        if (!have_body) throw std::runtime_error("chamfer needs a body");
+        if (f.dressup_edge >= 0)
+            result = GeometryEngine::apply_chamfer(result, f.dressup_size, f.dressup_edge);
+        else
+            result = GeometryEngine::apply_chamfer(result, f.dressup_size, f.face_group);
+        break;
+    case CadFeatureType::Hole: {
+        if (!have_body) throw std::runtime_error("hole needs a body");
+        // Circle wire centered at the positioned point on the plane
+        Vec3d c = f.plane.to_world(Vec2d(f.hole_x, f.hole_y));
+        gp_Pnt o(c.x(), c.y(), c.z());
+        gp_Dir n(f.plane.normal.x(), f.plane.normal.y(), f.plane.normal.z());
+        gp_Circ circ(gp_Ax2(o, n), f.hole_diameter * 0.5);
+        TopoDS_Edge e = BRepBuilderAPI_MakeEdge(circ).Edge();
+        BRepBuilderAPI_MakeWire wm(e);
+        if (!wm.IsDone()) throw std::runtime_error("hole wire failed");
+        // Through = symmetric huge cut (passes fully through any body);
+        // Blind = +normal extrude of hole_depth into the body.
+        TopoDS_Shape tool = f.hole_through
+            ? SketchEngine::make_extrude(wm.Wire(), f.plane, 1.0e5, true, 0.0)
+            : SketchEngine::make_extrude(wm.Wire(), f.plane, f.hole_depth, false, 0.0);
+        BRepAlgoAPI_Cut cut(result, tool);
+        if (!cut.IsDone()) throw std::runtime_error("hole cut failed");
+        result = cut.Shape();
+
+        // Enlarge the entry for a screw head (style 1 = counterbore, 2 = countersink).
+        if (f.hole_style == 1 && f.hole_cbore_diameter > f.hole_diameter
+                              && f.hole_cbore_depth > 1e-6) {
+            gp_Ax2 cbax(o, n);
+            TopoDS_Shape cb = BRepPrimAPI_MakeCylinder(cbax, f.hole_cbore_diameter * 0.5,
+                                                       f.hole_cbore_depth).Shape();
+            BRepAlgoAPI_Cut cbc(result, cb);
+            if (cbc.IsDone() && !cbc.Shape().IsNull()) result = cbc.Shape();
+        } else if (f.hole_style == 2 && f.hole_csink_diameter > f.hole_diameter) {
+            const double Rmaj = f.hole_csink_diameter * 0.5;
+            const double Rmin = f.hole_diameter * 0.5;
+            const double half = f.hole_csink_angle * 0.5 * M_PI / 180.0;
+            const double h = (Rmaj - Rmin) / std::tan(half);
+            if (h > 1e-6) {
+                gp_Ax2 csax(o, n);
+                TopoDS_Shape cs = BRepPrimAPI_MakeCone(csax, Rmaj, Rmin, h).Shape();
+                BRepAlgoAPI_Cut csc(result, cs);
+                if (csc.IsDone() && !csc.Shape().IsNull()) result = csc.Shape();
+            }
+        }
+        break;
+    }
+    case CadFeatureType::Thread: {
+        // Reject degenerate parameters that make OCCT's helical sweep / boolean unstable (a tiny
+        // pitch, depth >= half-pitch, an enormous turn count, depth eating the whole wall). Better
+        // a no-op than a crash. Leave the body unchanged when the spec can't be built safely.
+        {
+            const double R = f.thread_radius, P = f.thread_pitch, H = f.thread_height, D = f.thread_depth;
+            // ISO external thread depth is ~0.61*P, so allow up to 0.7*P (0.49 wrongly rejected
+            // every real thread -> nothing rendered). Still bound it well under a full pitch.
+            const bool ok = R > 0.5 && P > 0.1 && D > 1e-3 && D < 0.7 * P && D < 0.45 * R
+                            && H > 0.5 * P && (H / P) < 400.0;
+            if (!ok) break;   // result/have_body untouched
+        }
+        // Axis at the positioned point on the plane; +normal = thread rise.
+        Vec3d c3 = f.plane.to_world(Vec2d(f.thread_x, f.thread_y));
+        gp_Pnt  c(c3.x(), c3.y(), c3.z());
+        gp_Dir  zdir(f.plane.normal.x(), f.plane.normal.y(), f.plane.normal.z());
+        gp_Dir  xdir(f.plane.x_axis.x(), f.plane.x_axis.y(), f.plane.x_axis.z());
+        gp_Ax3  ax3(c, zdir, xdir);
+        gp_Ax2  ax2(c, zdir, xdir);
+
+        // Build the swept helical ridge (guarded — never fatal).
+        TopoDS_Shape ridge;
+        bool have_ridge = false;
+        try {
+            TopoDS_Wire spine = make_helix_wire(ax3, f.thread_radius,
+                                                f.thread_pitch, f.thread_height);
+            TopoDS_Wire prof  = make_thread_profile(c, xdir, zdir, f.thread_radius,
+                                                    f.thread_pitch, f.thread_depth,
+                                                    f.thread_internal);
+            // MakePipeShell with a FIXED BINORMAL = cylinder axis keeps the V-profile's orientation
+            // constant along the helix (axial edge always parallel to the axis, V always pointing
+            // radially out). The plain MakePipe used a Frenet frame that TWISTED the profile around
+            // the helix -> the wedge inclination varied and looked mirrored.
+            BRepOffsetAPI_MakePipeShell pipe(spine);
+            pipe.SetMode(zdir);
+            pipe.Add(prof);
+            pipe.Build();
+            if (pipe.IsDone() && pipe.MakeSolid()) {
+                ridge = pipe.Shape();
+                have_ridge = !ridge.IsNull();
+            }
+        } catch (const std::exception&) {
+            have_ridge = false; // fall back to the bare cylinder/bore below
+        } catch (const Standard_Failure&) {
+            have_ridge = false; // OCCT failure (not a std::exception) — must be caught here too
+        }
+
+        if (f.thread_internal) {
+            if (!have_body) throw std::runtime_error("internal thread needs a body");
+            // Tapped bore: ensure a clean cylindrical pocket, then carve the
+            // OUTWARD helical groove into its wall. When the thread is invoked on
+            // an existing hole the bore cut is coincident (a no-op that may report
+            // !IsDone) — tolerate it so the visible groove cut below still runs.
+            // Cut the pocket at the MINOR diameter (radius - depth), not the nominal radius.
+            // A nominal-radius bore that coincides with an existing hole's wall creates
+            // coincident faces that foul the following groove boolean (the groove then removes
+            // ~nothing -> invisible thread). The minor bore stays strictly inside any existing
+            // hole wall, leaving it clean for the groove; on solid stock it forms the tap-drill.
+            const double bore_r = std::max(0.5, f.thread_radius - f.thread_depth);
+            TopoDS_Shape bore = BRepPrimAPI_MakeCylinder(ax2, bore_r,
+                                                         f.thread_height).Shape();
+            try {
+                BRepAlgoAPI_Cut cut_bore(result, bore);
+                if (cut_bore.IsDone() && !cut_bore.Shape().IsNull())
+                    result = cut_bore.Shape();
+            } catch (const std::exception&) { /* keep existing bore */ }
+            if (have_ridge) {
+                BRepAlgoAPI_Cut cut_ridge(result, ridge);
+                if (cut_ridge.IsDone() && !cut_ridge.Shape().IsNull())
+                    result = cut_ridge.Shape();
+            }
+        } else {
+            // External thread: FUSE the helical ridge ONTO the existing body (the picked cylinder),
+            // leaving the rest of the part intact. Replacing the body with a bare rod — the old
+            // behaviour — wiped whatever the user picked; that was the "mess". With no body yet
+            // (a thread from scratch on a dropdown plane), fall back to a standalone threaded rod.
+            if (have_body && !result.IsNull()) {
+                if (have_ridge) {
+                    BRepAlgoAPI_Fuse fuse(result, ridge);
+                    if (fuse.IsDone() && !fuse.Shape().IsNull()) result = fuse.Shape();
+                }
+            } else {
+                TopoDS_Shape rod = BRepPrimAPI_MakeCylinder(ax2, f.thread_radius,
+                                                            f.thread_height).Shape();
+                if (have_ridge) {
+                    BRepAlgoAPI_Fuse fuse(rod, ridge);
+                    if (fuse.IsDone()) rod = fuse.Shape();
+                }
+                result = rod;
+                have_body = true;
+            }
+        }
+        break;
+    }
+    case CadFeatureType::Shell: {
+        if (!have_body) throw std::runtime_error("shell needs a body");
+        // Hollow the body to a wall thickness; the picked face (if any) is removed so the
+        // shell is open there. MakeThickSolidByJoin with a NEGATIVE offset shells inward.
+        TopTools_ListOfShape remove;
+        if (f.shell_face >= 0) {
+            TopoDS_Face fc = GeometryEngine::face_by_index(result, f.shell_face);
+            if (!fc.IsNull()) remove.Append(fc);
+        }
+        BRepOffsetAPI_MakeThickSolid mts;
+        mts.MakeThickSolidByJoin(result, remove, -std::abs(f.shell_thickness), 1.0e-3);
+        mts.Build();
+        if (!mts.IsDone()) throw std::runtime_error("shell failed");
+        result = mts.Shape();
+        if (result.IsNull()) throw std::runtime_error("shell produced no geometry");
+        break;
+    }
+    case CadFeatureType::Draft: {
+        if (!have_body) throw std::runtime_error("draft needs a body");
+        if (f.draft_face < 0) throw std::runtime_error("draft needs a picked face");
+        TopoDS_Face fc = GeometryEngine::face_by_index(result, f.draft_face);
+        if (fc.IsNull()) throw std::runtime_error("draft: face not found");
+        // Neutral plane = horizontal plane through the body's bbox bottom, pull direction +Z.
+        // The face pivots about the line where it meets the neutral plane and tilts by the angle.
+        // ponytail: neutral plane / pull direction fixed to world up; pick-based neutral plane
+        // deferred (same as the datum-plane pick types, dgv).
+        Bnd_Box bb; BRepBndLib::Add(result, bb);
+        Standard_Real xmin, ymin, zmin, xmax, ymax, zmax;
+        bb.Get(xmin, ymin, zmin, xmax, ymax, zmax);
+        gp_Dir pull(0, 0, 1);
+        gp_Pln neutral(gp_Pnt(0, 0, zmin), pull);
+        BRepOffsetAPI_DraftAngle draft(result);
+        draft.Add(fc, pull, f.draft_angle * M_PI / 180.0, neutral);
+        if (!draft.AddDone())
+            throw std::runtime_error("draft: face cannot be drafted (is it parallel to the base?)");
+        draft.Build();
+        if (!draft.IsDone()) throw std::runtime_error("draft failed");
+        result = draft.Shape();
+        if (result.IsNull()) throw std::runtime_error("draft produced no geometry");
+        break;
+    }
+    case CadFeatureType::DeleteFace: {
+        if (!have_body) throw std::runtime_error("delete_face needs a body");
+        if (f.delete_faces.empty()) throw std::runtime_error("delete_face needs at least one face");
+        BRepAlgoAPI_Defeaturing df;
+        df.SetShape(result);
+        for (int fi : f.delete_faces) {
+            TopoDS_Face fc = GeometryEngine::face_by_index(result, fi);
+            if (fc.IsNull()) throw std::runtime_error("delete_face: face not found");
+            df.AddFaceToRemove(fc);
+        }
+        df.Build();
+        if (!df.IsDone()) throw std::runtime_error("delete_face failed");
+        result = df.Shape();
+        if (result.IsNull()) throw std::runtime_error("delete_face produced no geometry");
+        break;
+    }
+    }
+}
+
+// Compound of all body shapes (1 body => that body verbatim, so single-body display and
+// global face/edge ids are byte-identical to the pre-multi-body behaviour).
+static TopoDS_Shape compound_of(const std::vector<CadBody>& bodies)
+{
+    if (bodies.size() == 1) return bodies[0].shape;
+    TopoDS_Compound comp;
+    BRep_Builder bld;
+    bld.MakeCompound(comp);
+    for (const CadBody& b : bodies)
+        if (!b.shape.IsNull()) bld.Add(comp, b.shape);
+    return comp;
+}
+
+// Tessellate every body separately and concatenate into one mesh, recording per-triangle
+// (body index, face id WITHIN that body). Single-body => byte-identical to tessellate(body).
+static TriangleMesh tessellate_bodies(const std::vector<CadBody>& bodies,
+                                      std::vector<int>& tri_face, std::vector<int>& tri_body,
+                                      std::vector<TriangleMesh>& body_meshes,
+                                      double lin, double ang)
+{
+    tri_face.clear();
+    tri_body.clear();
+    body_meshes.clear();
+    indexed_triangle_set merged;
+    for (int bi = 0; bi < int(bodies.size()); ++bi) {
+        std::vector<int> tf;
+        TriangleMesh bm = SketchEngine::tessellate(bodies[bi].shape, tf, lin, ang);
+        const indexed_triangle_set& its = bm.its;
+        const int voff = int(merged.vertices.size());
+        for (const auto& v : its.vertices) merged.vertices.push_back(v);
+        for (const auto& t : its.indices)
+            merged.indices.emplace_back(t[0] + voff, t[1] + voff, t[2] + voff);
+        for (int fid : tf) { tri_face.push_back(fid); tri_body.push_back(bi); }
+        body_meshes.push_back(std::move(bm));   // per-body mesh kept for distinct GLVolume colors
+    }
+    return TriangleMesh(merged);
+}
+
+void CadDocument::apply_boolean(std::vector<CadBody>& bodies, const CadFeature& f) const
+{
+    const int nb   = int(bodies.size());
+    const int tgt  = (f.target_body    >= 0 && f.target_body    < nb) ? f.target_body    : nb - 1;
+    const int tool = (f.bool_tool_body >= 0 && f.bool_tool_body < nb) ? f.bool_tool_body : -1;
+    if (tgt < 0 || tool < 0 || tgt == tool) return;   // need two distinct bodies; otherwise no-op
+    const TopoDS_Shape A = bodies[tgt].shape;          // target survives
+    const TopoDS_Shape B = bodies[tool].shape;         // tool, consumed unless kept
+    if (A.IsNull() || B.IsNull()) return;
+
+    TopTools_ListOfShape args, tools;
+    args.Append(A);
+    tools.Append(B);
+    auto run = [&](BRepAlgoAPI_BooleanOperation& bop) -> TopoDS_Shape {
+        bop.SetArguments(args);
+        bop.SetTools(tools);
+        if (f.bool_tolerance > 0.0) bop.SetFuzzyValue(f.bool_tolerance);   // OCCT fuzzy: merge near-coincident faces
+        bop.Build();
+        if (!bop.IsDone()) throw std::runtime_error("boolean operation failed");
+        return bop.Shape();
+    };
+    TopoDS_Shape result;
+    switch (f.mode) {
+    case BooleanMode::Add:       { BRepAlgoAPI_Fuse   op; result = run(op); break; }   // union
+    case BooleanMode::Cut:       { BRepAlgoAPI_Cut    op; result = run(op); break; }   // target - tool
+    case BooleanMode::Intersect: { BRepAlgoAPI_Common op; result = run(op); break; }   // overlap
+    default: return;   // BooleanMode::New is meaningless between two existing bodies
+    }
+    if (result.IsNull()) throw std::runtime_error("boolean produced an empty shape");
+
+    bodies[tgt].shape = result;
+    if (!f.bool_keep_tool) bodies.erase(bodies.begin() + tool);   // consume the tool body
+}
+
+void CadDocument::apply_cut(std::vector<CadBody>& bodies, const CadFeature& f) const
+{
+    const int nb  = int(bodies.size());
+    if (nb == 0) throw std::runtime_error("cut: no target body");
+    const int tgt = (f.target_body >= 0 && f.target_body < nb) ? f.target_body : nb - 1;
+    if (tgt < 0 || bodies[tgt].shape.IsNull()) throw std::runtime_error("cut: no target body");
+
+    if (!f.cut_keep_upper && !f.cut_keep_lower)
+        throw std::runtime_error("cut keeps nothing");
+
+    SketchPlane cp;
+    if (f.cut_face >= 0) {
+        const int fb = (f.cut_face_body >= 0 && f.cut_face_body < nb) ? f.cut_face_body : tgt;
+        if (bodies[fb].shape.IsNull()) throw std::runtime_error("cut: face body is empty");
+        TopoDS_Face fc = GeometryEngine::face_by_index(bodies[fb].shape, f.cut_face);
+        if (fc.IsNull()) throw std::runtime_error("cut: face not found");
+        cp = SketchPlane::from_face(fc);
+    } else {
+        cp = f.plane;
+    }
+    cp.origin += cp.normal * f.cut_offset;
+    if (f.cut_flip) cp.normal = -cp.normal;
+
+    // Build a large square wire in the cut plane, centered at plane origin.
+    const double L = 1.0e5;
+    Vec3d x = cp.x_axis * L;
+    Vec3d y = cp.y_axis * L;
+    Vec3d o = cp.origin;
+    auto p = [&](double sx, double sy) {
+        Vec3d v = o + x * sx + y * sy;
+        return gp_Pnt(v.x(), v.y(), v.z());
+    };
+    BRepBuilderAPI_MakePolygon poly;
+    poly.Add(p( 1,  1));
+    poly.Add(p( 1, -1));
+    poly.Add(p(-1, -1));
+    poly.Add(p(-1,  1));
+    poly.Close();
+    if (!poly.IsDone()) throw std::runtime_error("cut: failed to build cut wire");
+    TopoDS_Wire wire = poly.Wire();
+
+    TopoDS_Shape upper_piece, lower_piece;
+    const TopoDS_Shape& target = bodies[tgt].shape;
+
+    if (f.cut_keep_upper) {
+        TopoDS_Shape upper_tool = SketchEngine::make_extrude(wire, cp, L, false, 0.0);
+        BRepAlgoAPI_Common common(target, upper_tool);
+        if (!common.IsDone()) throw std::runtime_error("cut operation failed");
+        upper_piece = common.Shape();
+    }
+
+    if (f.cut_keep_lower) {
+        SketchPlane lp = cp;
+        lp.normal = -lp.normal;
+        TopoDS_Shape lower_tool = SketchEngine::make_extrude(wire, lp, L, false, 0.0);
+        BRepAlgoAPI_Common common(target, lower_tool);
+        if (!common.IsDone()) throw std::runtime_error("cut operation failed");
+        lower_piece = common.Shape();
+    }
+
+    if (f.cut_keep_upper && f.cut_keep_lower) {
+        bodies[tgt].shape = upper_piece;
+        bodies.insert(bodies.begin() + tgt + 1,
+                      CadBody{ lower_piece, bodies[tgt].name + " (2)" });
+    } else if (f.cut_keep_upper) {
+        bodies[tgt].shape = upper_piece;
+    } else {
+        bodies[tgt].shape = lower_piece;
+    }
+}
+
+void CadDocument::apply_mirror(std::vector<CadBody>& bodies, const CadFeature& f) const
+{
+    const int nb  = int(bodies.size());
+    if (nb == 0) throw std::runtime_error("mirror: no target body");
+    const int tgt = (f.target_body >= 0 && f.target_body < nb) ? f.target_body : nb - 1;
+    if (tgt < 0 || bodies[tgt].shape.IsNull()) throw std::runtime_error("mirror: no target body");
+
+    const TopoDS_Shape& src = bodies[tgt].shape;
+
+    gp_Trsf trsf;
+    trsf.SetMirror(gp_Ax2(gp_Pnt(f.plane.origin.x(), f.plane.origin.y(), f.plane.origin.z()),
+                          gp_Dir(f.plane.normal.x(), f.plane.normal.y(), f.plane.normal.z())));
+    BRepBuilderAPI_Transform xform(src, trsf, true /*copy*/);
+    if (!xform.IsDone()) throw std::runtime_error("mirror: transform failed");
+    TopoDS_Shape mirrored = xform.Shape();
+
+    // A mirror reverses orientation — verify the result has positive volume.
+    {
+        GProp_GProps props;
+        BRepGProp::VolumeProperties(mirrored, props);
+        if (props.Mass() <= 0.0) {
+            // Flip orientation to get a valid forward solid.
+            mirrored.Reverse();
+            BRepGProp::VolumeProperties(mirrored, props);
+            if (props.Mass() <= 0.0)
+                throw std::runtime_error("mirror: result has zero or negative volume");
+        }
+    }
+
+    switch (f.mode) {
+    case BooleanMode::Add: {
+        BRepAlgoAPI_Fuse fuse(src, mirrored);
+        if (!fuse.IsDone()) throw std::runtime_error("mirror fuse failed");
+        bodies[tgt].shape = fuse.Shape();
+        break;
+    }
+    case BooleanMode::New: {
+        if (!f.mirror_keep_original)
+            bodies.erase(bodies.begin() + tgt);   // replace: the mirrored copy takes the source slot
+        bodies.push_back({mirrored, f.name.empty() ? std::string("Mirror") : f.name});
+        break;
+    }
+    default:
+        throw std::runtime_error("mirror: mode must be New or Add");
+    }
+}
+
+void CadDocument::apply_transform(std::vector<CadBody>& bodies, const CadFeature& f) const
+{
+    const int nb  = int(bodies.size());
+    if (nb == 0) throw std::runtime_error("transform: no target body");
+    const int tgt = (f.target_body >= 0 && f.target_body < nb) ? f.target_body : nb - 1;
+    if (tgt < 0 || bodies[tgt].shape.IsNull()) throw std::runtime_error("transform: no target body");
+
+    gp_Trsf rot;
+    if (std::abs(f.xf_angle_deg) > 1e-12) {
+        if (f.xf_axis.norm() < 1e-9)
+            throw std::runtime_error("transform: rotation axis is degenerate");
+        rot.SetRotation(gp_Ax1(gp_Pnt(f.xf_pivot.x(), f.xf_pivot.y(), f.xf_pivot.z()),
+                               gp_Dir(f.xf_axis.x(), f.xf_axis.y(), f.xf_axis.z())),
+                        f.xf_angle_deg * M_PI / 180.0);
+    }
+    gp_Trsf tr;
+    tr.SetTranslation(gp_Vec(f.xf_translate.x(), f.xf_translate.y(), f.xf_translate.z()));
+    const gp_Trsf trsf = tr * rot;          // rotate first, then translate
+
+    BRepBuilderAPI_Transform xform(bodies[tgt].shape, trsf, true /*copy*/);
+    if (!xform.IsDone()) throw std::runtime_error("transform: failed");
+    TopoDS_Shape moved = xform.Shape();
+
+    if (f.xf_copy)
+        bodies.push_back({moved, f.name.empty() ? std::string("Transform") : f.name});
+    else
+        bodies[tgt].shape = moved;
+}
+
+void CadDocument::apply_thicken(std::vector<CadBody>& bodies, const CadFeature& f) const
+{
+    const int nb = int(bodies.size());
+    if (nb == 0) throw std::runtime_error("thicken: no target body");
+    const int tgt = (f.target_body >= 0 && f.target_body < nb) ? f.target_body : nb - 1;
+    if (tgt < 0 || bodies[tgt].shape.IsNull()) throw std::runtime_error("thicken: no target body");
+
+    TopoDS_Face fc = GeometryEngine::face_by_index(bodies[tgt].shape, f.thicken_face);
+    if (fc.IsNull()) throw std::runtime_error("thicken: face not found");
+    if (std::abs(f.thicken_thickness) < 1e-9) throw std::runtime_error("thicken: thickness is zero");
+
+    TopoDS_Shell shell;
+    BRep_Builder bb;
+    bb.MakeShell(shell);
+    bb.Add(shell, fc);
+
+    const double off = f.thicken_flip ? -std::abs(f.thicken_thickness)
+                                      :  std::abs(f.thicken_thickness);
+    BRepOffsetAPI_MakeThickSolid mts;
+    mts.MakeThickSolidBySimple(shell, off);
+    mts.Build();
+    if (!mts.IsDone()) throw std::runtime_error("thicken: failed");
+    TopoDS_Shape solid = mts.Shape();
+    if (solid.IsNull()) throw std::runtime_error("thicken: produced no geometry");
+
+    // MakeThickSolidBySimple may produce a reversed solid. Ensure positive volume.
+    {
+        GProp_GProps props;
+        BRepGProp::VolumeProperties(solid, props);
+        if (props.Mass() < 0.0) solid.Reverse();
+    }
+
+    bodies.push_back({solid, f.name.empty() ? std::string("Thicken") : f.name});
+}
+
+void CadDocument::apply_thicken_surface(std::vector<CadBody>& bodies, const CadFeature& f) const
+{
+    const int nb = int(bodies.size());
+    if (nb == 0) throw std::runtime_error("thicken-surface: no target body");
+    const int tgt = (f.target_body >= 0 && f.target_body < nb) ? f.target_body : nb - 1;
+    if (tgt < 0 || bodies[tgt].shape.IsNull()) throw std::runtime_error("thicken-surface: no target body");
+    if (!is_sheet_shape(bodies[tgt].shape)) throw std::runtime_error("thicken-surface: target is not a sheet body");
+    if (std::abs(f.thicken_thickness) < 1e-9) throw std::runtime_error("thicken-surface: thickness is zero");
+
+    const double off = f.thicken_flip ? -std::abs(f.thicken_thickness)
+                                      :  std::abs(f.thicken_thickness);
+    const TopoDS_Shape& sheet = bodies[tgt].shape;
+
+    // MakeThickSolidBySimple offsets each face along its own normal and sews the result; it never
+    // extends neighbours to meet, so at every edge where two faces join at an angle the corner
+    // material is simply absent. A flat sheet is therefore exact while a 4-walled box is not
+    // (measured: 29648 against the 44000 that (60^2-50^2)*40 requires).
+    //
+    // ByJoin is the call that mitres those corners, and it is what the Shell feature already uses
+    // successfully a few hundred lines up — but it CANNOT be handed an open sheet. In OCCT,
+    // BRepOffset_MakeOffset::MakeThickSolid builds the solid only inside `if (!myFaces.IsEmpty())`
+    // (BRepOffset_MakeOffset.cxx:1115): with no closing faces it stops after the offset shell and
+    // returns that. So it reports IsDone() and a non-null shape containing no TopAbs_SOLID at all
+    // — which is exactly how two earlier attempts failed, and why no parameter could have fixed it.
+    //
+    // So close the sheet first, then use the working call: cap the free rims, sew into a closed
+    // shell, make a solid, and hollow it inward passing the caps as the faces to remove. The caps
+    // come back off, leaving the wall.
+    // A SINGLE face has no edge shared with a neighbour, so there is no corner to mitre and
+    // BySimple is already exact on it (flat 60x60 by 5 -> 18000.000). It also has a free
+    // boundary, so "does it have free wires" is NOT the question to ask here — capping a lone
+    // face with its own rim sews a zero-thickness shell and the offset then measures 6000.
+    int n_faces = 0;
+    for (TopExp_Explorer fe(sheet, TopAbs_FACE); fe.More(); fe.Next()) ++n_faces;
+
+    TopTools_ListOfShape caps;
+    if (n_faces > 1) {
+        ShapeAnalysis_FreeBounds fb(sheet);
+        for (TopExp_Explorer we(fb.GetClosedWires(), TopAbs_WIRE); we.More(); we.Next()) {
+            BRepBuilderAPI_MakeFace mk(TopoDS::Wire(we.Current()));
+            if (!mk.IsDone())
+                throw std::runtime_error("thicken-surface: cannot cap the sheet rim "
+                                         "(is it planar?)");
+            caps.Append(mk.Face());
+        }
+    }
+
+    TopoDS_Shape solid;
+    if (caps.IsEmpty()) {
+        BRepOffsetAPI_MakeThickSolid mts;
+        mts.MakeThickSolidBySimple(sheet, off);
+        mts.Build();
+        if (!mts.IsDone()) throw std::runtime_error("thicken-surface: failed");
+        solid = mts.Shape();
+    } else {
+        BRepBuilderAPI_Sewing sewer(1.0e-3);
+        sewer.Add(sheet);
+        for (TopTools_ListIteratorOfListOfShape it(caps); it.More(); it.Next())
+            sewer.Add(it.Value());
+        sewer.Perform();
+
+        TopoDS_Shell closed_shell;
+        for (TopExp_Explorer se(sewer.SewedShape(), TopAbs_SHELL); se.More(); se.Next()) {
+            if (!closed_shell.IsNull())
+                throw std::runtime_error("thicken-surface: the capped sheet split into "
+                                         "more than one shell");
+            closed_shell = TopoDS::Shell(se.Current());
+        }
+        if (closed_shell.IsNull() || !BRep_Tool::IsClosed(closed_shell))
+            throw std::runtime_error("thicken-surface: the capped sheet is not closed");
+
+        // A shell sewn from an extruded sheet carries no guarantee that its faces point outward,
+        // and BRepBuilderAPI_MakeSolid does not fix that. Offsetting an inside-out solid sends the
+        // wall the wrong way: measured bbox 70x70x40 for an inward offset on a 60x60 box, with a
+        // volume larger than its own bounding box because the result then overlaps itself. A
+        // negative mass IS the inverted orientation, so use it as the test.
+        TopoDS_Solid capped = BRepBuilderAPI_MakeSolid(closed_shell).Solid();
+        {
+            GProp_GProps vp;
+            BRepGProp::VolumeProperties(capped, vp);
+            if (vp.Mass() < 0.0) capped.Reverse();
+        }
+
+        BRepOffsetAPI_MakeThickSolid mts;
+        mts.MakeThickSolidByJoin(capped, caps, -std::abs(off), 1.0e-3);
+        mts.Build();
+        if (!mts.IsDone()) throw std::runtime_error("thicken-surface: failed");
+        solid = mts.Shape();
+    }
+    if (solid.IsNull()) throw std::runtime_error("thicken-surface: produced no geometry");
+    // IsDone() is NOT a success test here — the failed attempts had IsDone() true and no solid.
+    if (!TopExp_Explorer(solid, TopAbs_SOLID).More())
+        throw std::runtime_error("thicken-surface: produced a shell, not a solid");
+
+    {
+        GProp_GProps props;
+        BRepGProp::VolumeProperties(solid, props);
+        if (props.Mass() < 0.0) solid.Reverse();
+    }
+
+    bodies.push_back({solid, f.name.empty() ? std::string("ThickenSurface") : f.name});
+}
+
+void CadDocument::apply_surface_offset(std::vector<CadBody>& bodies, const CadFeature& f) const
+{
+    const int nb = int(bodies.size());
+    if (nb == 0) throw std::runtime_error("surface-offset: no target body");
+    const int tgt = (f.target_body >= 0 && f.target_body < nb) ? f.target_body : nb - 1;
+    if (tgt < 0 || bodies[tgt].shape.IsNull()) throw std::runtime_error("surface-offset: no target body");
+    if (!is_sheet_shape(bodies[tgt].shape)) throw std::runtime_error("surface-offset: target is not a sheet body");
+    const double d = f.plane_offset;
+    if (std::abs(d) < 1e-9) throw std::runtime_error("surface-offset: zero offset");
+
+    BRepOffsetAPI_MakeOffsetShape mos;
+    mos.PerformBySimple(bodies[tgt].shape, d);
+    if (!mos.IsDone()) throw std::runtime_error("surface-offset: failed");
+    TopoDS_Shape off_shape = mos.Shape();
+    if (off_shape.IsNull()) throw std::runtime_error("surface-offset: produced no geometry");
+
+    bodies.push_back({off_shape, f.name.empty() ? std::string("SurfaceOffset") : f.name});
+}
+
+// Project `edges` of a shape onto `plane`, appending the resulting 2D entities to `out`.
+// `construction` marks them as guides rather than built geometry. This is the body of the
+// Project feature's conversion loop, factored out so a sketch can borrow the same geometry.
+static void project_edges_to_entities(const std::vector<TopoDS_Edge>& edges,
+                                      const SketchPlane& plane,
+                                      bool construction,
+                                      std::vector<SketchEntity>& out)
+{
+    auto to2d = [&](const gp_Pnt& p) -> Vec2d {
+        Vec3d d(p.X() - plane.origin.x(), p.Y() - plane.origin.y(), p.Z() - plane.origin.z());
+        return Vec2d(d.dot(plane.x_axis), d.dot(plane.y_axis));
+    };
+
+    // A segment whose endpoints coincide after projection carries no geometry: that is what
+    // an edge perpendicular to the target plane becomes. Emitting it as a zero-length line
+    // would poison the sketch downstream, so drop it here.
+    auto push_line = [&](const Vec2d& a, const Vec2d& b) {
+        if ((b - a).norm() < 1e-7) return;
+        SketchEntity se; se.type = SketchEntity::Type::Line;
+        se.p0 = a; se.p1 = b;
+        se.construction = construction;
+        out.push_back(se);
+    };
+
+    for (const TopoDS_Edge& e : edges) {
+        BRepAdaptor_Curve ac(e);
+        const GeomAbs_CurveType ct = ac.GetType();
+        if (ct == GeomAbs_Line) {
+            gp_Pnt a = ac.Value(ac.FirstParameter());
+            gp_Pnt b = ac.Value(ac.LastParameter());
+            push_line(to2d(a), to2d(b));
+        } else if (ct == GeomAbs_Circle) {
+            gp_Circ c = ac.Circle();
+            gp_Dir cn = c.Axis().Direction();
+            Vec3d cnv(cn.X(), cn.Y(), cn.Z());
+            const double par = std::abs(cnv.dot(plane.normal));
+            const bool full = BRep_Tool::IsClosed(e) ||
+                std::abs((ac.LastParameter() - ac.FirstParameter()) - 2.0 * M_PI) < 1e-6;
+            if (par > 0.999) {
+                Vec2d ctr = to2d(c.Location());
+                if (full) {
+                    SketchEntity se; se.type = SketchEntity::Type::Circle;
+                    se.center = ctr; se.radius = c.Radius();
+                    se.construction = construction;
+                    out.push_back(se);
+                } else {
+                    gp_Pnt a = ac.Value(ac.FirstParameter());
+                    gp_Pnt b = ac.Value(ac.LastParameter());
+                    Vec2d a2 = to2d(a), b2 = to2d(b);
+                    SketchEntity se; se.type = SketchEntity::Type::Arc;
+                    se.center = ctr; se.radius = c.Radius();
+                    se.p0 = a2; se.p1 = b2;
+                    se.start_angle = std::atan2(a2.y() - ctr.y(), a2.x() - ctr.x());
+                    se.end_angle   = std::atan2(b2.y() - ctr.y(), b2.x() - ctr.x());
+                    se.construction = construction;
+                    out.push_back(se);
+                }
+                continue;
+            }
+            std::vector<Vec3d> pts = GeometryEngine::sample_edge_world(e);
+            for (size_t i = 1; i < pts.size(); ++i)
+                push_line(to2d(gp_Pnt(pts[i-1].x(), pts[i-1].y(), pts[i-1].z())),
+                          to2d(gp_Pnt(pts[i].x(),   pts[i].y(),   pts[i].z())));
+        } else {
+            std::vector<Vec3d> pts = GeometryEngine::sample_edge_world(e);
+            for (size_t i = 1; i < pts.size(); ++i)
+                push_line(to2d(gp_Pnt(pts[i-1].x(), pts[i-1].y(), pts[i-1].z())),
+                          to2d(gp_Pnt(pts[i].x(),   pts[i].y(),   pts[i].z())));
+        }
+    }
+}
+
+void CadDocument::apply_project(const std::vector<CadBody>& bodies, CadFeature& f) const
+{
+    f.entities.clear();
+    const int nb = int(bodies.size());
+    if (nb == 0) throw std::runtime_error("project: no source body");
+    const int src = (f.project_source_body >= 0 && f.project_source_body < nb)
+                    ? f.project_source_body : nb - 1;
+    if (src < 0 || bodies[src].shape.IsNull()) throw std::runtime_error("project: source body is empty");
+    const TopoDS_Shape& shape = bodies[src].shape;
+
+    std::vector<TopoDS_Edge> edges;
+    if (!f.project_edges.empty()) {
+        for (int id : f.project_edges) {
+            TopoDS_Edge e = GeometryEngine::edge_by_index(shape, id);
+            if (e.IsNull()) throw std::runtime_error("project: edge not found");
+            edges.push_back(e);
+        }
+    } else if (f.project_face >= 0) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(shape, f.project_face);
+        if (fc.IsNull()) throw std::runtime_error("project: face not found");
+        edges = GeometryEngine::edges_of_face(fc);
+    } else {
+        // No face and no explicit selection means "all edges" — the state the Project card
+        // starts in, and its label says so. Edges perpendicular to the target plane collapse
+        // to a point when projected; they are dropped below rather than emitted as
+        // zero-length lines.
+        edges = GeometryEngine::edges_of(shape);
+    }
+    if (edges.empty()) throw std::runtime_error("project: no edges to project");
+
+    project_edges_to_entities(edges, f.plane, /*construction=*/false, f.entities);
+
+    if (f.entities.empty()) throw std::runtime_error("project: produced no entities");
+}
+
+void CadDocument::detect_mate_conflicts()
+{
+    mate_conflicts.clear();
+
+    const int n = int(features.size());
+    std::map<int, int> first_driver; // body -> feature index of first mate that drives it
+    std::map<int, std::vector<int>> graph; // dst -> list of src (body indices)
+
+    for (int fi = 0; fi < n; ++fi) {
+        const CadFeature& f = features[fi];
+        if (f.type != CadFeatureType::Mate || !f.enabled) continue;
+
+        if (f.mate_cs_a < 0 || f.mate_cs_a >= n) continue;
+        if (f.mate_cs_b < 0 || f.mate_cs_b >= n) continue;
+        const CadFeature& fa = features[f.mate_cs_a];
+        const CadFeature& fb = features[f.mate_cs_b];
+        if (fa.type != CadFeatureType::CoordSys || !fa.enabled) continue;
+        if (fb.type != CadFeatureType::CoordSys || !fb.enabled) continue;
+
+        const int src = fa.coordsys_body;
+        const int dst = fb.coordsys_body;
+        if (dst < 0) continue; // apply_mate already reports this one
+
+        // (a) duplicate target: a second mate driving the same body
+        auto it = first_driver.find(dst);
+        if (it != first_driver.end()) {
+            int first_fi = it->second;
+            std::string first_name = features[first_fi].name.empty() ? "Mate" : features[first_fi].name;
+            std::string this_name = f.name.empty() ? "Mate" : f.name;
+            mate_conflicts.push_back({fi,
+                "Body " + std::to_string(dst + 1) + " is already positioned by '" +
+                first_name + "' (feature " + std::to_string(first_fi) +
+                ") — '" + this_name + "' overrides it; suppress one"});
+        } else {
+            first_driver[dst] = fi;
+        }
+
+        // (b) self-mate or cycle detection
+        if (src >= 0 && dst >= 0) {
+            if (src == dst) {
+                mate_conflicts.push_back({fi,
+                    "this mate positions Body " + std::to_string(dst + 1) + " against itself"});
+            } else {
+                graph[dst].push_back(src);
+            }
+        }
+    }
+
+    // DFS cycle detection on the graph built above.
+    // ponytail: iterative DFS avoids recursion depth issues on long chains.
+    // Colour: 0 = unvisited, 1 = in-progress (grey), 2 = done (black).
+    std::map<int, int> colour;
+    struct Frame { int node; size_t next; };
+    std::vector<Frame> stack;
+
+    for (const auto& [start, _] : graph) {
+        if (colour[start] == 2) continue;
+        stack.clear();
+        stack.push_back({start, 0});
+        colour[start] = 1;
+        while (!stack.empty()) {
+            Frame& top = stack.back();
+            auto git = graph.find(top.node);
+            if (git == graph.end() || top.next >= git->second.size()) {
+                colour[top.node] = 2;
+                stack.pop_back();
+                continue;
+            }
+            int child = git->second[top.next++];
+            if (colour[child] == 1) {
+                // Back edge found — find the mate whose (dst==top.node, src==child).
+                for (int fi = 0; fi < n; ++fi) {
+                    const CadFeature& f = features[fi];
+                    if (f.type != CadFeatureType::Mate || !f.enabled) continue;
+                    if (f.mate_cs_a < 0 || f.mate_cs_a >= n) continue;
+                    if (f.mate_cs_b < 0 || f.mate_cs_b >= n) continue;
+                    const CadFeature& fa2 = features[f.mate_cs_a];
+                    const CadFeature& fb2 = features[f.mate_cs_b];
+                    if (fa2.type != CadFeatureType::CoordSys || !fa2.enabled) continue;
+                    if (fb2.type != CadFeatureType::CoordSys || !fb2.enabled) continue;
+                    int sd = fb2.coordsys_body;
+                    int ss = fa2.coordsys_body;
+                    if (sd == top.node && ss == child) {
+                        mate_conflicts.push_back({fi,
+                            // Worded for ANY cycle length: "leads back" is true transitively,
+                            // where "depends back on" would be a lie for a 3+ body chain.
+                            "circular mate chain: Body " + std::to_string(top.node + 1) +
+                            " depends on Body " + std::to_string(child + 1) +
+                            ", which leads back to Body " + std::to_string(top.node + 1) +
+                            " — the result depends on feature order"});
+                        break;
+                    }
+                }
+                continue;
+            }
+            if (colour[child] == 0) {
+                colour[child] = 1;
+                stack.push_back({child, 0});
+            }
+        }
+    }
+
+    // Deliberately NOT in scope: computing the numeric disagreement between two mates
+    // ("Mate3 puts it at X=10, Mate7 at X=15"). That needs speculative per-mate evaluation.
+}
+
+void CadDocument::apply_mate(std::vector<CadBody>& bodies, const CadFeature& f) const
+{
+    const int nc = int(features.size());
+    if (f.mate_cs_a < 0 || f.mate_cs_a >= nc)
+        throw std::runtime_error("mate: mate_cs_a out of range");
+    if (f.mate_cs_b < 0 || f.mate_cs_b >= nc)
+        throw std::runtime_error("mate: mate_cs_b out of range");
+
+    const CadFeature& fa = features[f.mate_cs_a];
+    const CadFeature& fb = features[f.mate_cs_b];
+    if (fa.type != CadFeatureType::CoordSys || !fa.enabled)
+        throw std::runtime_error("mate: mate_cs_a is not a valid CoordSys feature");
+    if (fb.type != CadFeatureType::CoordSys || !fb.enabled)
+        throw std::runtime_error("mate: mate_cs_b is not a valid CoordSys feature");
+
+    CadDocument::DatumCoordSys A = datum_frame(bodies, fa);
+    CadDocument::DatumCoordSys B = datum_frame(bodies, fb);
+    if (!A.error.empty()) throw std::runtime_error("mate: " + A.error);
+    if (!B.error.empty()) throw std::runtime_error("mate: " + B.error);
+
+    const int tgt_body = fb.coordsys_body;
+    if (tgt_body < 0)
+        throw std::runtime_error("mate: mate_cs_b has no associated body");
+    if (tgt_body >= int(bodies.size()) || bodies[tgt_body].shape.IsNull())
+        throw std::runtime_error("mate: target body out of range or null");
+
+    Vec3d xA(A.x), yA(A.y), oA(A.origin);
+    Vec3d zA = xA.cross(yA).normalized();
+    Vec3d xB(B.x), yB(B.y), oB(B.origin);
+    Vec3d zB = xB.cross(yB).normalized();
+
+    auto make_4x4 = [&](const Vec3d& x, const Vec3d& y, const Vec3d& z, const Vec3d& o) {
+        gp_Trsf T;
+        T.SetValues(x.x(), y.x(), z.x(), o.x(),
+                    x.y(), y.y(), z.y(), o.y(),
+                    x.z(), y.z(), z.z(), o.z());
+        return T;
+    };
+    gp_Trsf M_A = make_4x4(xA, yA, zA, oA);
+    gp_Trsf M_B = make_4x4(xB, yB, zB, oB);
+
+    gp_Trsf F;
+    if (f.mate_flip) {
+        // Rx(pi): flip y→-y, z→-z
+        F.SetValues(1,  0,  0, 0,
+                    0, -1,  0, 0,
+                    0,  0, -1, 0);
+    }
+
+    gp_Trsf T;
+    if (f.mate_kind == 0) {
+        // Fastened: T = M_A * Rz(mate_angle) * Tz(mate_offset) * F * M_B^-1
+        gp_Trsf Rz;
+        Rz.SetRotation(gp_Ax1(gp_Pnt(0,0,0), gp_Dir(0,0,1)), f.mate_angle * M_PI / 180.0);
+        gp_Trsf Tz;
+        Tz.SetTranslation(gp_Vec(0, 0, f.mate_offset));
+        gp_Trsf M_B_inv = M_B.Inverted();
+        T = M_A * Rz * Tz * F * M_B_inv;
+    } else {
+        Vec3d z_target = f.mate_flip ? -zA : zA;
+
+        // Minimum-rotation helper: compute R that rotates zB onto z_target
+        // about an axis through oB. Reused by Planar / Revolute / Cylindrical.
+        auto make_z_align = [&](const Vec3d& zsrc, const Vec3d& zdst) -> gp_Trsf {
+            double ddot = zsrc.dot(zdst);
+            Vec3d rot_axis;
+            double rot_angle = 0;
+            if (ddot <= -0.9999) {
+                Vec3d ref = (std::abs(zsrc.z()) < 0.9) ? Vec3d(0, 0, 1) : Vec3d(1, 0, 0);
+                rot_axis = zsrc.cross(ref).normalized();
+                rot_angle = M_PI;
+            } else {
+                rot_axis = zsrc.cross(zdst);
+                if (rot_axis.squaredNorm() > 1e-18) {
+                    rot_axis.normalize();
+                    rot_angle = std::acos(std::max(-1.0, std::min(1.0, ddot)));
+                }
+            }
+            gp_Trsf R;
+            if (rot_angle > 1e-12) {
+                R.SetRotation(gp_Ax1(gp_Pnt(oB.x(), oB.y(), oB.z()),
+                                     gp_Dir(rot_axis.x(), rot_axis.y(), rot_axis.z())),
+                              rot_angle);
+            }
+            return R;
+        };
+
+        if (f.mate_kind == 1 || f.mate_kind == 2 || f.mate_kind == 4) {
+            // Planar (1) / Revolute (2) / Cylindrical (4):
+            // all share the same minimum-rotation z-alignment.
+            gp_Trsf R_align = make_z_align(zB, z_target);
+
+            gp_Trsf Rz_about_target;
+            if (std::abs(f.mate_angle) > 1e-12) {
+                Rz_about_target.SetRotation(
+                    gp_Ax1(gp_Pnt(oB.x(), oB.y(), oB.z()),
+                           gp_Dir(z_target.x(), z_target.y(), z_target.z())),
+                    f.mate_angle * M_PI / 180.0);
+            }
+            gp_Trsf R = Rz_about_target * R_align;
+
+            // Translation: depends on which DOFs are constrained
+            Vec3d trans;
+            if (f.mate_kind == 1) {
+                // Planar: normal distance becomes mate_offset
+                double d = (oB - oA).dot(zA);
+                trans = zA * (f.mate_offset - d);
+            } else if (f.mate_kind == 2) {
+                // Revolute: full position on the axis line
+                trans = (oA + zA * f.mate_offset) - oB;
+            } else {
+                // Cylindrical (4): fix perpendicular, preserve axial
+                double axial = (oB - oA).dot(zA);
+                trans = (oA + zA * (axial + f.mate_offset)) - oB;
+            }
+
+            T.SetValues(1, 0, 0, trans.x(),
+                        0, 1, 0, trans.y(),
+                        0, 0, 1, trans.z());
+            T = T * R;
+        } else {
+            // Slider (mate_kind == 3): full orientation alignment,
+            // fix perpendicular position, preserve axial translation.
+            Vec3d x_target = xA;
+            Vec3d y_target = f.mate_flip ? -yA : yA;
+
+            // R = target * B^T  (both bases orthonormal)
+            double r11 = x_target.x() * xB.x() + y_target.x() * yB.x() + z_target.x() * zB.x();
+            double r12 = x_target.x() * xB.y() + y_target.x() * yB.y() + z_target.x() * zB.y();
+            double r13 = x_target.x() * xB.z() + y_target.x() * yB.z() + z_target.x() * zB.z();
+            double r21 = x_target.y() * xB.x() + y_target.y() * yB.x() + z_target.y() * zB.x();
+            double r22 = x_target.y() * xB.y() + y_target.y() * yB.y() + z_target.y() * zB.y();
+            double r23 = x_target.y() * xB.z() + y_target.y() * yB.z() + z_target.y() * zB.z();
+            double r31 = x_target.z() * xB.x() + y_target.z() * yB.x() + z_target.z() * zB.x();
+            double r32 = x_target.z() * xB.y() + y_target.z() * yB.y() + z_target.z() * zB.y();
+            double r33 = x_target.z() * xB.z() + y_target.z() * yB.z() + z_target.z() * zB.z();
+
+            // Build rotation about oB: R_full * p = R * (p - oB) + oB
+            double tx = oB.x() - (r11 * oB.x() + r12 * oB.y() + r13 * oB.z());
+            double ty = oB.y() - (r21 * oB.x() + r22 * oB.y() + r23 * oB.z());
+            double tz = oB.z() - (r31 * oB.x() + r32 * oB.y() + r33 * oB.z());
+            gp_Trsf R_full;
+            R_full.SetValues(r11, r12, r13, tx,
+                             r21, r22, r23, ty,
+                             r31, r32, r33, tz);
+
+            double axial = (oB - oA).dot(zA);
+            Vec3d trans = (oA + zA * (axial + f.mate_offset)) - oB;
+
+            T.SetValues(1, 0, 0, trans.x(),
+                        0, 1, 0, trans.y(),
+                        0, 0, 1, trans.z());
+            T = T * R_full;
+        }
+    }
+
+    BRepBuilderAPI_Transform xform(bodies[tgt_body].shape, T, true /*copy*/);
+    if (!xform.IsDone()) throw std::runtime_error("mate: transform failed");
+    bodies[tgt_body].shape = xform.Shape();
+}
+
+// Volume of a shape, 0 for anything that isn't a solid we can measure. Used to catch a
+// subtraction that removed nothing (daf).
+static double solid_volume(const TopoDS_Shape& s)
+{
+    if (s.IsNull()) return 0.0;
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(s, props);
+    return std::abs(props.Mass());
+}
+
+void CadDocument::route_feature(std::vector<CadBody>& bodies, const CadFeature& f) const
+{
+    if (f.type == CadFeatureType::Plane)   return;   // datum plane: not part of the body pipeline
+    if (f.type == CadFeatureType::Axis)    return;   // datum axis
+    if (f.type == CadFeatureType::CoordSys) return; // datum coordinate system
+    if (f.type == CadFeatureType::Helix)   return;   // helical curve; consumed by Sweep
+    if (f.type == CadFeatureType::Boolean) { apply_boolean(bodies, f); return; }   // body-body op
+    if (f.type == CadFeatureType::Cut)     { apply_cut(bodies, f);     return; }   // plane-split body
+    if (f.type == CadFeatureType::Mirror)  { apply_mirror(bodies, f);  return; }   // mirror body about plane
+    if (f.type == CadFeatureType::Transform) { apply_transform(bodies, f); return; }   // move/rotate body
+    if (f.type == CadFeatureType::Mate)     { apply_mate(bodies, f);     return; }   // assembly mate
+    if (f.type == CadFeatureType::Thicken) { apply_thicken(bodies, f); return; }   // face -> plate
+    if (f.type == CadFeatureType::ThickenSurface) { apply_thicken_surface(bodies, f); return; }
+    if (f.type == CadFeatureType::SurfaceOffset) { apply_surface_offset(bodies, f); return; }
+    if (f.type == CadFeatureType::Project) return;   // sketch-like: consumed downstream, no body
+    // Resolve the target body: explicit target_body when valid, else the last body.
+    const int t = (f.target_body >= 0 && f.target_body < int(bodies.size()))
+                  ? f.target_body : int(bodies.size()) - 1;
+    const TopoDS_Shape context = (t >= 0) ? bodies[t].shape : TopoDS_Shape();
+    // A New extrude (or the very first solid feature) starts a fresh body; everything else
+    // mutates the target body in place.
+    const bool starts_new = bodies.empty()
+        || f.type == CadFeatureType::Import   // an imported solid is always its own base body
+        || f.type == CadFeatureType::SurfaceExtrude || f.type == CadFeatureType::SurfaceRevolve
+        || f.type == CadFeatureType::ThickenSurface || f.type == CadFeatureType::SurfaceOffset
+        || f.type == CadFeatureType::SurfaceLoft || f.type == CadFeatureType::SurfaceFill
+        || ((f.type == CadFeatureType::Extrude || f.type == CadFeatureType::Revolve
+             || f.type == CadFeatureType::Sweep || f.type == CadFeatureType::Loft)
+            && f.mode == BooleanMode::New);
+
+    if (starts_new) {
+        TopoDS_Shape result;            // empty -> apply_feature fills it (New path)
+        bool have_body = false;
+        apply_feature(result, have_body, context, f);
+        if (have_body && !result.IsNull())
+            bodies.push_back({ result, f.name.empty() ? std::string("Body") : f.name });
+    } else {
+        if (t < 0) throw std::runtime_error("feature needs a body");
+        TopoDS_Shape result = bodies[t].shape;   // shallow handle; apply_feature mutates it
+        bool have_body = true;
+        // A subtraction whose tool misses the target is a legal boolean that removes nothing, so
+        // OCCT reports IsDone() and the feature lands in the recipe reporting success. A caller —
+        // an agent especially — then has no signal at all that the hole it asked for was never
+        // drilled: same body, same volume, ok:true. Measure the volume across the op and refuse
+        // the no-op. Only for removals: every other feature type may legitimately leave the volume
+        // alone (a Transform certainly does). daf.
+        const bool removes = f.type == CadFeatureType::Hole
+                          || f.type == CadFeatureType::Thread
+                          || ((f.type == CadFeatureType::Extrude || f.type == CadFeatureType::Revolve
+                               || f.type == CadFeatureType::Sweep  || f.type == CadFeatureType::Loft)
+                              && f.mode == BooleanMode::Cut);
+        const double before = removes ? solid_volume(result) : 0.0;
+        apply_feature(result, have_body, context, f);
+        if (removes && before > 0.0) {
+            const double after = solid_volume(result);
+            // Relative tolerance: a cut that shaves a numerically invisible sliver is a miss too,
+            // and an absolute epsilon would be wrong across the mm-to-metre range of real parts.
+            if (after >= before - 1e-9 * std::max(1.0, before))
+                throw std::runtime_error(std::string(
+                    f.type == CadFeatureType::Hole   ? "hole" :
+                    f.type == CadFeatureType::Thread ? "thread" : "cut") +
+                    " removed no material — the tool does not intersect the target body"
+                    " (coordinates are in the sketch plane's frame, not world)");
+        }
+        bodies[t].shape = result;
+    }
+}
+
+bool CadDocument::recompute()
+{
+    error.clear();
+    detect_mate_conflicts();
+    std::vector<CadBody> built;
+    // Did any feature in this document even ASK for a solid? A document made only of sketches
+    // and datums has nothing to build, and that is a legitimate state — it is every document
+    // between drawing the first profile and extruding it. Reporting it as a failure is what
+    // made a sketch-only design unsaveable AND unopenable: DesignPanel::recompute_guarded syncs
+    // the 3MF recipe only "on success", so nothing was written, and deserialize_recipe ends with
+    // `return recompute()`, so a project that did carry a recipe was refused on load with
+    // "Could not restore the CAD model" while its features sat correctly in the list. mtav.
+    bool any_solid_feature = false;
+    try {
+        // Parametric pass: evaluate document variables, then each feature's expression bindings,
+        // writing the results into the feature's numeric fields before geometry runs.
+        std::map<std::string, double> varvals = evaluate_variables(variables);
+        for (CadFeature& f : features)
+            for (const auto& [field, e] : f.expr)
+                assign_field(f, field, eval_expr(e, varvals));
+        for (size_t fi = 0; fi < features.size(); ++fi) {
+            CadFeature& f = features[fi];
+            if (!f.enabled) continue;
+            if (f.type == CadFeatureType::Sketch) continue; // consumed by an extrude
+            if (f.type == CadFeatureType::Helix)  continue; // consumed by Sweep as a path
+            if (f.type == CadFeatureType::Plane)   continue; // datum: no solid, derived on demand
+            if (f.type == CadFeatureType::Axis)    continue; // datum axis
+            if (f.type == CadFeatureType::CoordSys) continue; // datum coordinate system
+            // Past the skips: this feature is one that means to leave a body behind.
+            any_solid_feature = true;
+            if (f.type == CadFeatureType::Project) { apply_project(built, f); }
+            else                                   { route_feature(built, f); }
+            // Record which feature made each body. "Still unset?" is the whole rule, and it is
+            // sufficient because of an invariant worth stating: NO feature ever replaces a whole
+            // CadBody. Every in-place op writes only `.shape` (boolean, cut, mirror-fuse,
+            // transform, dress-up — checked, all 8 sites), so an existing body keeps the stamp it
+            // was born with; a consumed body is erased outright, taking its stamp with it; and
+            // the only bodies still at -1 here are the ones THIS feature just pushed. That also
+            // means a feature type added later needs no change here, as long as it keeps to the
+            // same invariant.
+            for (CadBody& b : built)
+                if (b.source_feature < 0)
+                    b.source_feature = int(fi);
+        }
+    } catch (const Standard_Failure& e) {
+        // OCCT raises Standard_Failure (NOT a std::exception) — must be caught
+        // here or it escapes the event handler and terminates the app.
+        error = e.GetMessageString() ? e.GetMessageString() : "OCCT operation failed";
+        return false;
+    } catch (const std::exception& e) {
+        error = e.what();
+        return false;
+    } catch (...) {
+        error = "unknown geometry error";
+        return false;
+    }
+    if (built.empty() && any_solid_feature) { error = "no solid-producing features"; return false; }
+
+    // A feature that leaves a body with a null shape must fail loudly. Until this existed,
+    // recompute() returned true and the document kept advertising the body: describe_scene
+    // counted it, error was empty, and only mass_properties on that specific body revealed
+    // anything was wrong. Returning false hands the caller its normal rollback path, so the
+    // operation that destroyed the body is undone rather than committed.
+    for (size_t i = 0; i < built.size(); ++i) {
+        if (!built[i].shape.IsNull()) continue;
+        const int src = built[i].source_feature;
+        // source_feature is -1 for a body no feature claims. "feature 0" would be a lie, and
+        // this message exists precisely to be trusted about which feature to look at.
+        const std::string fname =
+            (src < 0 || src >= int(features.size()))
+                ? std::string("an unidentified feature")
+                : (features[src].name.empty() ? ("feature " + std::to_string(src + 1))
+                                              : features[src].name);
+        error = "body " + std::to_string(i + 1) + " was destroyed by " + fname
+              + " (the operation produced an empty shape)";
+        return false;
+    }
+
+    // recompute() replaces the bodies vector wholesale, which would drop any per-body
+    // colour override (Color tool). Body indices are stable across a rebuild (bodies are
+    // appended in feature order), so carry the override forward by index — same indexing
+    // contract the GUI relies on for per-body visibility/Move.
+    for (size_t i = 0; i < built.size() && i < bodies.size(); ++i) {
+        if (bodies[i].has_color) {
+            built[i].has_color = true;
+            built[i].color     = bodies[i].color;
+        }
+        // ...and the name the user gave the body, for the same reason and by the same index
+        // contract. Without this a rename would live exactly until the next feature was added.
+        if (bodies[i].has_user_name) {
+            built[i].has_user_name = true;
+            built[i].user_name     = bodies[i].user_name;
+        }
+    }
+    bodies = std::move(built);
+    // The face and edge maps have just been rebuilt, so every global id handed out before this
+    // point now means something else. Bump here rather than in each mutator: this is the single
+    // line where the topology is actually replaced, so it cannot be forgotten by a new feature
+    // type the way a per-mutator bump would be.
+    ++topo_generation;
+
+    // Face-drift fingerprint for FaceAndDirection CoordSys connectors. This runs AFTER the
+    // bodies are final and APPENDS to mate_conflicts (detect_mate_conflicts() cleared it at
+    // the top of recompute() and must not run again here). A mismatch is a WARNING, not an
+    // error: a legitimate Draft on a mated face renumbers nothing but a real renumber after a
+    // dress-up silently points the connector at a different face, and that must not abort.
+    for (int fi = 0; fi < int(features.size()); ++fi) {
+        CadFeature& f = features[fi];
+        if (!f.enabled) continue;
+        if (f.type != CadFeatureType::CoordSys) continue;
+        if (f.coordsys_type != CoordSysType::FaceAndDirection) continue;
+        if (f.coordsys_body < 0 || f.coordsys_body >= int(bodies.size())) continue;
+        TopoDS_Face face = GeometryEngine::face_by_index(bodies[f.coordsys_body].shape, f.coordsys_face);
+        if (face.IsNull()) continue; // "face not found" is already reported by datum_frame()
+        const int kind  = int(BRepAdaptor_Surface(face).GetType());
+        const int edges = int(GeometryEngine::edges_of_face(face).size());
+        if (f.coordsys_face_kind < 0) {
+            // No fingerprint yet (old recipe, or a connector never resolved): adopt the state
+            // the user last saw. Self-heals old recipes on first load, and gives both existing
+            // writers the fingerprint for free.
+            f.coordsys_face_kind  = kind;
+            f.coordsys_face_edges = edges;
+            continue;
+        }
+        if (f.coordsys_face_kind != kind || f.coordsys_face_edges != edges) {
+            mate_conflicts.emplace_back(int(fi),
+                "connector \"" + f.name + "\" may have moved to a different face "
+                "(an upstream edit renumbered this body's faces)");
+        }
+    }
+
+    body = compound_of(bodies);
+    display_mesh = tessellate_bodies(bodies, display_tri_face, display_tri_body,
+                                     display_body_meshes,
+                                     linear_deflection, angular_deflection);
+    if (display_mesh.its.indices.empty() && any_solid_feature) {
+        // Empty only because there are no bodies to tessellate is the same legitimate state as
+        // above: a sketch-only document has nothing to draw as a solid, and that is not a fault.
+        error = "tessellation produced an empty mesh";
+        return false;
+    }
+    return true;
+}
+
+bool CadDocument::preview(const CadFeature& candidate, TriangleMesh& out_mesh,
+                          std::vector<TriangleMesh>& out_body_meshes, std::string& err) const
+{
+    err.clear();
+    out_body_meshes.clear();
+    std::vector<CadBody> tmp = bodies;     // start from the current committed bodies
+    try {
+        route_feature(tmp, candidate);     // candidate may append a new body or mutate one
+    } catch (const Standard_Failure& e) {
+        err = e.GetMessageString() ? e.GetMessageString() : "OCCT operation failed";
+        return false;
+    } catch (const std::exception& e) {
+        err = e.what();
+        return false;
+    } catch (...) {
+        err = "unknown geometry error";
+        return false;
+    }
+    if (tmp.empty()) {
+        err = "preview produced no geometry";
+        return false;
+    }
+    // Tessellate per body (same path as recompute) so the GUI can re-apply its display-only
+    // per-body Move transforms to the ghost; out_mesh is the merged whole.
+    std::vector<int> tf, tb;
+    out_mesh = tessellate_bodies(tmp, tf, tb, out_body_meshes, linear_deflection, angular_deflection);
+    if (out_mesh.its.indices.empty()) {
+        err = "preview produced an empty mesh";
+        return false;
+    }
+    return true;
+}
+
+bool CadDocument::preview(const CadFeature& candidate, TriangleMesh& out_mesh, std::string& err) const
+{
+    std::vector<TriangleMesh> ignore;
+    return preview(candidate, out_mesh, ignore, err);
+}
+
+std::string brep_to_string(const TopoDS_Shape& s)
+{
+    if (s.IsNull()) return {};
+    std::ostringstream oss;
+    BRepTools::Write(s, oss);
+    return oss.str();
+}
+
+TopoDS_Shape brep_from_string(const std::string& d)
+{
+    if (d.empty()) return {};
+    std::istringstream iss(d);
+    TopoDS_Shape s;
+    BRep_Builder b;
+    BRepTools::Read(s, iss, b);
+    return s;
+}
+
+std::string CadDocument::serialize_recipe() const
+{
+    std::ostringstream oss;
+    {
+        cereal::BinaryOutputArchive ar(oss);
+        uint32_t v = ORCA_CAD_RECIPE_VERSION;
+        ar(v);
+        uint32_t n = static_cast<uint32_t>(features.size());
+        ar(n);
+        for (const CadFeature& f : features) {
+            std::ostringstream fos;
+            {
+                cereal::BinaryOutputArchive fa(fos);
+                fa(f);
+            }
+            std::string fb = fos.str();
+            uint32_t len = static_cast<uint32_t>(fb.size());
+            ar(len);
+            ar(cereal::binary_data(fb.data(), fb.size()));
+        }
+        std::ostringstream vos;
+        {
+            cereal::BinaryOutputArchive va(vos);
+            va(variables);
+        }
+        std::string vb = vos.str();
+        uint32_t vlen = static_cast<uint32_t>(vb.size());
+        ar(vlen);
+        ar(cereal::binary_data(vb.data(), vb.size()));
+        // BODY NAMES, appended after the variables block. Bodies are not serialised — they are
+        // recomputed — so a name the user gave one has nowhere else to live, and without this it
+        // would survive a recompute (see the carry-over in recompute()) but not a save.
+        //
+        // APPENDED RATHER THAN VERSION-BUMPED, on purpose: a build that predates this block
+        // reads features and variables, returns, and never looks at the trailing bytes, so its
+        // projects still open here AND this build's projects still open there. A version bump
+        // would have made every project written today unreadable by yesterday's build for the
+        // sake of one optional field. Written as (index, name) pairs so an unnamed body costs
+        // nothing.
+        // A map, not a vector of pairs: cereal's map support is already included here and its
+        // pair support is not, and one more include for one more field is not worth it.
+        std::map<uint32_t, std::string> named;
+        for (uint32_t i = 0; i < bodies.size(); ++i)
+            if (bodies[i].has_user_name && !bodies[i].user_name.empty())
+                named[i] = bodies[i].user_name;
+        std::ostringstream bos;
+        {
+            cereal::BinaryOutputArchive ba(bos);
+            ba(named);
+        }
+        std::string bb = bos.str();
+        uint32_t blen = static_cast<uint32_t>(bb.size());
+        ar(blen);
+        ar(cereal::binary_data(bb.data(), bb.size()));
+    }
+    return oss.str();
+}
+
+bool CadDocument::deserialize_recipe(const std::string& blob)
+{
+    error.clear();
+    try {
+        std::istringstream iss(blob);
+        cereal::BinaryInputArchive ar(iss);
+        uint32_t v;
+        ar(v);
+        if (v > ORCA_CAD_RECIPE_VERSION) {
+            error = "saved with a newer version of the Design tab (format v"
+                  + std::to_string(v) + ", this build reads up to v"
+                  + std::to_string(ORCA_CAD_RECIPE_VERSION) + ")";
+            return false;
+        }
+        // The framed layout has been byte-identical since v5 (v6 advanced the stamp without
+        // touching the bytes), so every version from 5 up is read below. A future bump that DOES
+        // change the framing must exclude itself there — this is what forces that decision
+        // instead of letting a v7 blob be silently misread by the v5 reader.
+        static_assert(ORCA_CAD_RECIPE_VERSION <= 6,
+                      "recipe version bumped: confirm the new version still uses the v5 framing");
+        if (v >= 5) {
+            // Framed path: every feature is a length-prefixed self-contained cereal stream, so
+            // the same four lines handle BOTH directions of mismatch. Older file, newer build:
+            // the sub-stream ends early, fa(f) throws, and the fields already assigned are kept
+            // (cereal assigns sequentially, so a mid-list throw leaves the earlier fields set)
+            // while the rest default. Newer file, older build: the sub-stream has MORE bytes
+            // than this build knows how to read; it reads what it knows and simply stops, and
+            // the outer stream is unaffected because the length prefix was consumed in full.
+            features.clear();
+            uint32_t count;
+            ar(count);
+            for (uint32_t i = 0; i < count; ++i) {
+                uint32_t len;
+                ar(len);
+                std::string buf(len, '\0');
+                if (len > 0)
+                    ar(cereal::binary_data(&buf[0], len));   // consume EXACTLY len bytes from the outer stream
+                CadFeature f;
+                try {
+                    std::istringstream fs(buf);
+                    cereal::BinaryInputArchive fa(fs);
+                    fa(f);
+                } catch (...) {
+                    // An OLDER file: the blob ran out before this build's field list did. Everything read
+                    // so far is kept and the remaining fields stay at their defaults. Deliberately NOT an
+                    // error — a field a project predates is not a corrupt project.
+                }
+                features.push_back(f);
+            }
+            variables.clear();
+            uint32_t vlen;
+            ar(vlen);
+            std::string vbuf(vlen, '\0');
+            if (vlen > 0)
+                ar(cereal::binary_data(&vbuf[0], vlen));
+            try {
+                std::istringstream vs(vbuf);
+                cereal::BinaryInputArchive va(vs);
+                va(variables);
+            } catch (...) {
+                // Variables blob predates this build: keep what was read, default the rest.
+            }
+            // Body names, if this project carries them. A project written before the block
+            // simply ends here, so the read throws and there are no names — not an error.
+            std::map<uint32_t, std::string> named;
+            try {
+                uint32_t blen;
+                ar(blen);
+                std::string bbuf(blen, '\0');
+                if (blen > 0)
+                    ar(cereal::binary_data(&bbuf[0], blen));
+                std::istringstream bs(bbuf);
+                cereal::BinaryInputArchive ba(bs);
+                ba(named);
+            } catch (...) {
+                named.clear();
+            }
+            // AFTER the rebuild, never before: recompute() replaces the bodies vector wholesale.
+            const bool ok = recompute();
+            for (const auto& kv : named)
+                if (kv.first < bodies.size()) {
+                    bodies[kv.first].has_user_name = true;
+                    bodies[kv.first].user_name     = kv.second;
+                }
+            return ok;
+        }
+        if (v == 4) {
+            // Pre-framing flat path, unchanged: v4 projects keep opening exactly as before.
+            ar(features);
+            ar(variables);
+            return recompute();
+        }
+        // v < 4: the field lists for v2/v3 no longer exist in this code, so those files
+        // cannot be recovered here. This fix is for the future, not the past.
+        error = "saved with an older version of the Design tab (format v"
+              + std::to_string(v) + "); this project cannot be opened by this build";
+        return false;
+    } catch (const Standard_Failure& e) {
+        const char* what = e.GetMessageString();
+        error = std::string("CAD data could not be read")
+              + (what && *what ? ": " + std::string(what) : "");
+        return false;
+    } catch (const std::exception& e) {
+        error = std::string("CAD data could not be read: ") + e.what();
+        return false;
+    } catch (...) {
+        error = "CAD data could not be read";
+        return false;
+    }
+}
+
+bool CadDocument::export_step(const std::string& path,
+                             const std::vector<Transform3d>& body_xforms,
+                             std::string& err) const
+{
+    err.clear();
+    if (bodies.empty()) { err = "nothing to export"; return false; }
+    try {
+        // Compound every body at its displayed (Move-gizmo) position so the STEP matches
+        // what Commit ships. Move transforms are rigid, so gp_Trsf::SetValues is valid.
+        BRep_Builder bld;
+        TopoDS_Compound comp;
+        bld.MakeCompound(comp);
+        for (size_t i = 0; i < bodies.size(); ++i) {
+            if (bodies[i].shape.IsNull()) continue;
+            TopoDS_Shape s = bodies[i].shape;
+            if (i < body_xforms.size() && !body_xforms[i].isApprox(Transform3d::Identity())) {
+                const Transform3d& m = body_xforms[i];
+                gp_Trsf t;
+                t.SetValues(m(0,0), m(0,1), m(0,2), m(0,3),
+                            m(1,0), m(1,1), m(1,2), m(1,3),
+                            m(2,0), m(2,1), m(2,2), m(2,3));
+                s = BRepBuilderAPI_Transform(s, t, true).Shape();
+            }
+            bld.Add(comp, s);
+        }
+        STEPControl_Writer writer;
+        if (writer.Transfer(comp, STEPControl_AsIs) != IFSelect_RetDone) {
+            err = "STEP transfer failed";
+            return false;
+        }
+        if (writer.Write(path.c_str()) != IFSelect_RetDone) {
+            err = "cannot write STEP file";
+            return false;
+        }
+    } catch (const Standard_Failure& e) {
+        err = e.GetMessageString() ? e.GetMessageString() : "OCCT failed to write STEP";
+        return false;
+    } catch (const std::exception& e) {
+        err = e.what();
+        return false;
+    }
+    return true;
+}
+
+GeometryEngine::MassProps CadDocument::body_mass_properties(int body_index) const
+{
+    if (body_index < 0 || body_index >= int(bodies.size())) return {};
+    return GeometryEngine::mass_properties(bodies[body_index].shape);
+}
+
+int CadDocument::add_surface_extrude(int sketch_ref, double distance, const std::string& name)
+{
+    CadFeature f;
+    f.type       = CadFeatureType::SurfaceExtrude;
+    f.name       = name;
+    f.sketch_ref = sketch_ref;
+    f.distance   = distance;
+    f.mode       = BooleanMode::New;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_surface_revolve(int sketch_ref, double angle_deg, int axis, const std::string& name)
+{
+    CadFeature f;
+    f.type          = CadFeatureType::SurfaceRevolve;
+    f.name          = name;
+    f.sketch_ref    = sketch_ref;
+    f.revolve_angle = angle_deg;
+    f.revolve_axis  = axis;
+    f.mode          = BooleanMode::New;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_surface_loft(const std::vector<int>& profile_refs, bool ruled, const std::string& name)
+{
+    CadFeature f;
+    f.type              = CadFeatureType::SurfaceLoft;
+    f.name              = name;
+    f.loft_profile_refs = profile_refs;
+    f.loft_ruled        = ruled;
+    f.mode              = BooleanMode::New;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+int CadDocument::add_surface_fill(int sketch_ref, const std::string& name)
+{
+    CadFeature f;
+    f.type       = CadFeatureType::SurfaceFill;
+    f.name       = name;
+    f.sketch_ref = sketch_ref;
+    f.mode       = BooleanMode::New;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
+std::vector<CadDocument::Interference> CadDocument::check_interference(double min_volume) const
+{
+    std::vector<Interference> out;
+    const int n = int(bodies.size());
+
+    for (int i = 0; i < n; ++i) {
+        if (bodies[i].shape.IsNull() || is_sheet_shape(bodies[i].shape)) continue;
+        for (int j = i + 1; j < n; ++j) {
+            if (bodies[j].shape.IsNull() || is_sheet_shape(bodies[j].shape)) continue;
+
+            double v = 0;
+            // A boolean that blows up on one pair must not lose the report for the others,
+            // and OCCT signals those as Standard_Failure, which is NOT a std::exception.
+            try {
+                BRepAlgoAPI_Common common(bodies[i].shape, bodies[j].shape);
+                common.Build();
+                if (!common.IsDone()) continue;
+                const TopoDS_Shape s = common.Shape();
+                if (s.IsNull()) continue;
+                GProp_GProps props;
+                BRepGProp::VolumeProperties(s, props);
+                v = std::abs(props.Mass());
+            } catch (const Standard_Failure&) {
+                continue;
+            }
+
+            // Bodies that merely touch share a face and enclose no volume, so the
+            // threshold is what separates contact from interference.
+            if (v > min_volume) out.push_back({i, j, v});
+        }
+    }
+    return out;
+}
+
+// ponytail: derived from the OCCT shape type; no stored flag, bodies aren't serialized anyway.
+bool CadDocument::is_sheet_shape(const TopoDS_Shape& s)
+{
+    return !TopExp_Explorer(s, TopAbs_SOLID).More();
+}
+
+} // namespace Slic3r
diff --git a/src/libslic3r/CAD/CadDocument.hpp b/src/libslic3r/CAD/CadDocument.hpp
new file mode 100644
index 0000000000..f62536384a
--- /dev/null
+++ b/src/libslic3r/CAD/CadDocument.hpp
@@ -0,0 +1,776 @@
+#ifndef slic3r_CadDocument_hpp_
+#define slic3r_CadDocument_hpp_
+
+#include "libslic3r/TriangleMesh.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
+#include "libslic3r/CAD/GeometryEngine.hpp"   // FaceGroup
+#include "libslic3r/Color.hpp"            // ColorRGBA (per-body display colour override)
+
+#include <TopoDS_Shape.hxx>
+#include <TopoDS_Wire.hxx>
+#include <cereal/cereal.hpp>
+#include <cereal/types/vector.hpp>
+#include <cereal/types/string.hpp>
+#include <map>
+#include <cereal/types/map.hpp>
+#include <string>
+#include <vector>
+#include <utility>
+
+namespace Slic3r {
+
+enum class CadFeatureType { Sketch, Extrude, Fillet, Chamfer, Hole, Thread, Shell, Revolve, Sweep, Pattern, Plane, Loft, Draft, Import, Boolean, Cut, Mirror, Axis, CoordSys, Helix, Transform, Thicken, Project, DeleteFace, Rib, SurfaceExtrude, SurfaceRevolve, ThickenSurface, SurfaceOffset, SurfaceLoft, SurfaceFill, Mate };
+enum class SketchShape    { Rectangle, Circle };
+enum class PlaneType      { Offset, Angle, Midplane, Tangent, TwoEdges, Coincident };
+enum class AxisType       { TwoPoints, FaceNormal, CylinderCenterline, PlaneIntersection, AlongEdge };
+enum class CoordSysType   { PointWorld, FaceAndDirection };
+enum class BooleanMode    { New, Add, Cut, Intersect };
+
+enum class ExtrudeEnd { Blind, Symmetric, TwoSided, ThroughAll, UpToFace, UpToVertex };
+
+// Serialize a TopoDS_Shape to/from a BRep string (declared before CadFeature so its
+// inline cereal save()/load() can resolve these non-dependent calls).
+std::string brep_to_string(const TopoDS_Shape& s);
+TopoDS_Shape brep_from_string(const std::string& d);
+
+struct CadFeature {
+    CadFeatureType type{CadFeatureType::Sketch};
+    std::string    name;
+    bool           enabled{true};
+
+    // Sketch params (centered on the plane origin)
+    SketchShape shape{SketchShape::Rectangle};
+    SketchPlane plane{SketchPlane::XY()};
+    double      width{20};
+    double      height{20};
+    double      radius{10};
+
+    // Real 2D sketch geometry (Onshape-style). When non-empty this takes
+    // precedence over the shape/width/height/radius enum path in build_sketch_wire.
+    SketchProfile profile;
+
+    // Onshape-style multi-entity sketch geometry. When non-empty this takes
+    // precedence over both `profile` and the shape-enum path in build_sketch_wire.
+    std::vector<SketchEntity> entities;
+
+    // 2D geometric constraints on `profile` (point indices). Solved in place.
+    std::vector<SketchConstraintDef> constraints;
+
+    // Onshape-style constraints on `entities` (Fase 4.2). Solved in place against
+    // entity endpoints. Used when `entities` is non-empty (the legacy `constraints`
+    // vector applies only to the `profile` path).
+    std::vector<SketchEntityConstraintDef> entity_constraints;
+
+    // Imported rigid 2D art (Text glyphs / SVG vector paths) as filled regions.
+    // Each region: contour[0] = outer loop, contour[1..] = holes; points in
+    // plane (u,v) millimetres. Rendered as a sketch overlay and extruded via a
+    // faces-with-holes path (SketchEngine::make_extrude_regions) — deliberately
+    // NOT solver entities, so imported art contributes zero DoF and never
+    // pollutes the constraint solver / DoF readout. When non-empty it takes
+    // precedence over the entities/profile/shape paths in the Extrude case.
+    std::vector<std::vector<std::vector<Vec2d>>> imported_regions;
+
+    // Imported rigid 3D B-rep solid (STEP). When the feature type is Import this carries
+    // the OCCT shape verbatim — it is adopted as a base body in route_feature (no parametric
+    // recipe). Downstream face/edge features (fillet/chamfer/cut/shell/...) act on it like any
+    // other body. TopoDS_Shape is a cheap handle, so copying it through recompute/checkpoint
+    // snapshots is cheap. In-session only for now (no BRep serialization yet).
+    TopoDS_Shape imported_solid;
+
+    // Non-destructive placement transform for imported_regions (Text/SVG),
+    // applied at display + extrude time as
+    //   p -> (p.x*import_scale_x + import_offset.x, p.y*import_scale_y + import_offset.y).
+    // Lets the art be moved / enlarged / stretched (independent X/Y) repeatedly
+    // without re-vectorising. Identity = no change.
+    Vec2d  import_offset{0, 0};
+    double import_scale_x{1.0};
+    double import_scale_y{1.0};
+    // Text/SVG dropped ONTO a solid face (centred on it): the extrude then defaults to an
+    // inward Cut (engraving) targeting `import_face_body`. False = free art on a plane.
+    bool   import_on_face{false};
+    int    import_face_body{-1};
+
+    // Extrude params
+    int         sketch_ref{-1};   // index into features[] of the consumed sketch
+    double      distance{10};
+    bool        symmetric{false};
+    BooleanMode mode{BooleanMode::New};
+    ExtrudeEnd  extrude_end{ExtrudeEnd::Blind};
+    double      distance2{0};     // second-side depth for TwoSided
+    double      taper_deg{0};     // draft angle (C4-part2)
+    bool        flip{false};      // reverse the extrude direction (negate plane normal)
+    int         up_to_face{-1};   // target solid-face id for UpToFace (C4-part2)
+    int         extrude_src_face{-1}; // global face id on the current body to extrude as a profile; -1 = use sketch wire
+    Vec3d       up_to_point{0,0,0}; // target for UpToVertex (C4-part2)
+    // Multi-body target: which body (index into CadDocument::bodies) this feature acts on.
+    // -1 = auto (last body). A New extrude appends a fresh body; Add/Cut/Intersect, dress-up,
+    // hole and face-extrude(non-New) mutate bodies[target]; face-extrude reads its source
+    // face from bodies[target] too. The source-face owner for face-extrude lives here.
+    int         target_body{-1};
+
+    // Dress-up params (Fillet/Chamfer) — applied to the current body in order
+    double      dressup_size{1.0};         // fillet radius or chamfer distance
+    FaceGroup   face_group{FaceGroup::All};
+    int         dressup_edge{-1};          // global edge id for edge-targeted fillet/chamfer; -1 = use face_group
+
+    // Hole params (positioned circular cut into the current body)
+    double      hole_diameter{5};
+    double      hole_depth{10};
+    bool        hole_through{true};        // true = symmetric through-cut, ignores hole_depth
+    double      hole_x{0};                 // position on the plane (plane u/x axis)
+    double      hole_y{0};                 // position on the plane (plane v/y axis)
+
+    // Hole standards library (extends the plain bore above).
+    // hole_style: 0 = simple, 1 = counterbore, 2 = countersink.
+    int         hole_style{0};
+    double      hole_cbore_diameter{0};    // counterbore cylinder diameter (mm), style==1
+    double      hole_cbore_depth{0};       // counterbore depth from the entry face (mm), style==1
+    double      hole_csink_diameter{0};    // countersink major diameter at entry face (mm), style==2
+    double      hole_csink_angle{90};      // countersink included angle (degrees), style==2
+    std::string hole_standard;             // provenance only, e.g. "M6" / "1/4-20"; not used by geometry
+
+    // Thread params (helical thread about the plane normal at a positioned point)
+    double      thread_radius{5};          // nominal cylinder radius
+    double      thread_pitch{2};           // axial advance per turn
+    double      thread_height{10};         // total axial length
+    double      thread_depth{1};           // radial crest depth of the thread profile
+    bool        thread_internal{false};    // false = external threaded rod (New body);
+                                           // true = tapped bore cut into the current body
+    double      thread_x{0};               // axis position on the plane (u/x axis)
+    double      thread_y{0};               // axis position on the plane (v/y axis)
+
+    // Shell params (hollow the current body to a wall thickness, removing one open face)
+    double      shell_thickness{2};        // wall thickness (inward offset)
+    int         shell_face{-1};            // global face id to remove (open the shell); -1 = none
+
+    // Draft params (taper a single solid face about a neutral plane = body bbox bottom, pull +Z)
+    int         draft_face{-1};            // global face id to draft; -1 = none
+    double      draft_angle{5};            // draft angle in degrees (signed: + leans the face inward)
+
+    // Revolve params (sweep a profile about an in-plane axis through the plane origin).
+    // Reuses sketch_ref / entities (profile), flip (direction), mode (boolean) and
+    // target_body. revolve_axis: 0 = plane X axis, 1 = plane Y axis.
+    double      revolve_angle{360};        // sweep angle in degrees (1..360)
+    int         revolve_axis{0};           // 0 = plane X, 1 = plane Y
+
+    // Sweep: profile carried by sketch_ref / entities (like Extrude); the spine is a
+    // second Sketch referenced by sweep_path_ref (an open or closed wire). Reuses
+    // mode (boolean) and target_body.
+    int         sweep_path_ref{-1};        // index into features[] of the path Sketch
+
+    // Loft: build a solid through 2+ closed profile Sketches (loft_profile_refs, in
+    // order, each on its own plane). loft_ruled=false → smooth sections, true → ruled.
+    // Reuses mode (boolean) and target_body.
+    std::vector<int> loft_profile_refs;    // ordered indices into features[] of profile Sketches
+    bool        loft_ruled{false};
+
+    // Pattern: replicate the target body, copies fused into it. pattern_circular=false
+    // → linear (pattern_count instances spaced pattern_spacing along plane axis
+    // pattern_dir: 0=X, 1=Y); true → circular (pattern_count instances over
+    // pattern_angle° total about the plane normal through the plane origin, so a seed
+    // offset from the origin orbits the axis). Reuses target_body + plane.
+    bool        pattern_circular{false};
+    int         pattern_count{3};          // total instances incl. the seed (>=1)
+    double      pattern_spacing{20};       // linear step (mm)
+    int         pattern_dir{0};            // linear direction: 0 = plane X, 1 = plane Y
+    double      pattern_angle{360};        // circular total angle (degrees)
+
+    // Pattern along a curve: when pattern_curve_sketch >= 0 this mode takes precedence over
+    // linear/circular. Copies are placed at equal-parameter points along entity
+    // pattern_curve_entity of sketch pattern_curve_sketch, translated by (P_i - P_0).
+    int pattern_curve_sketch{-1};  // feature index of the Sketch holding the guide curve
+    int pattern_curve_entity{-1};  // entity index of the guide curve within that sketch
+
+    // Parametric bindings: field-member-name -> expression string. On recompute() each entry
+    // is evaluated against the document variables and written into the named numeric field
+    // BEFORE geometry runs. Empty (the common case) means the feature uses its literal fields.
+    std::map<std::string, std::string> expr;
+
+    // Datum/reference plane: a derived SketchPlane the document offers as a selectable
+    // sketch plane (no solid). plane_base selects the reference (0=XY,1=XZ,2=YZ, or 3+N
+    // = the Nth earlier datum plane); plane_offset shifts along the base normal;
+    // plane_angle tilts plane_angle° about the base axis plane_axis (0=base X, 1=base Y).
+    int         plane_base{0};
+    double      plane_offset{20};
+    double      plane_angle_tilt{0};       // degrees (named *_tilt to avoid clash w/ revolve)
+    int         plane_axis{0};             // tilt axis: 0 = base X, 1 = base Y
+    PlaneType   plane_type{PlaneType::Offset};
+    int         plane_face_body{-1};
+    int         plane_face{-1};
+    int         plane_face2_body{-1};
+    int         plane_face2{-1};
+    int         plane_edge_body{-1};
+    int         plane_edge{-1};
+    int         plane_edge2_body{-1};
+    int         plane_edge2{-1};
+    double      plane_u_size{60};
+    double      plane_v_size{60};
+
+    // Boolean: combine two EXISTING bodies. `mode` reuses BooleanMode (Add = union,
+    // Cut = subtract tool from target, Intersect = keep overlap; New unused). `target_body`
+    // is the body that survives (result written back to it); `bool_tool_body` is the other
+    // operand, consumed (erased) unless `bool_keep_tool`. `bool_tolerance` = OCCT fuzzy value
+    // (0 = exact). Per-face merge: when both bool_target_face/bool_tool_face are set, the tool
+    // is first snapped so those two faces are coincident (gap closed within bool_tolerance),
+    // then the boolean welds them and coplanar faces are unified into one clean face.
+    int    bool_tool_body{-1};
+    bool   bool_keep_tool{false};
+    double bool_tolerance{0.0};
+    int    bool_target_face{-1};   // global face id on the target body to mate (-1 = none)
+    int    bool_tool_face{-1};     // global face id on the tool body to mate (-1 = none)
+
+    // Cut: split one target body with a plane, keeping the upper half, lower half, or both.
+    // Reuses `plane` for the cut plane and `target_body` for which body is cut.
+    double cut_offset{0.0};       // offset along the cut-plane normal (mm)
+    bool   cut_flip{false};       // flip the normal => swaps which side is "upper"
+    bool   cut_keep_upper{true};  // keep the +normal half
+    bool   cut_keep_lower{false}; // keep the -normal half (both => split into two bodies)
+
+    // Mirror: reflect a body about a plane. Reuses `plane` (mirror plane, as Cut does),
+    // `target_body` (body to mirror), and `mode` (New = separate mirrored copy,
+    // Add = fuse the mirror back into the source). mirror_keep_original decides whether
+    // the source body survives when mode is New.
+    bool   mirror_keep_original{true};
+
+    // Datum axis: reference line (no solid). Construction params stored; resolve_datum_axes()
+    // computes the world-space origin + unit direction on demand.
+    AxisType    axis_type{AxisType::TwoPoints};
+    Vec3d       axis_p1{0, 0, 0};
+    Vec3d       axis_p2{0, 0, 10};
+    int         axis_body{-1};
+    int         axis_face{-1};
+    int         axis_edge{-1};
+    int         axis_plane_a{-1};
+    int         axis_plane_b{-1};
+
+    // Datum coordinate system (no solid). Stored as point + two orthonormal axes.
+    CoordSysType coordsys_type{CoordSysType::PointWorld};
+    Vec3d        coordsys_point{0, 0, 0};
+    int          coordsys_body{-1};
+    int          coordsys_face{-1};
+    int          coordsys_edge{-1};
+    Vec3d        coordsys_x_hint{1, 0, 0};
+
+    // Fingerprint of the face this connector was bound to, for drift detection. -1 = not yet
+    // recorded (an old recipe, or a connector that has never resolved).
+    //
+    // Surface TYPE and EDGE COUNT specifically, because they survive every legitimate edit:
+    // Transform moves the body, Draft tilts the face, a dimension change resizes it, and none
+    // of those change either value. Centroid, area and normal all fail that test — see the
+    // issue. The cost is that a slide from one planar 4-edge face to another planar 4-edge face
+    // is invisible; a detector that never cries wolf is worth more here than a total one.
+    int coordsys_face_kind{-1};    // GeomAbs_SurfaceType as int
+    int coordsys_face_edges{-1};   // number of edges bounding the face
+
+    // Helix curve params (consumed as a sweep path to build springs/coils/augers).
+    // Axis = plane normal through plane origin. pitch = axial rise per full turn.
+    // left_handed flips the winding direction. taper_deg != 0 gives a conical helix.
+    double      helix_radius{10};
+    double      helix_pitch{5};
+    double      helix_height{20};
+    bool        helix_left_handed{false};
+    double      helix_taper_deg{0};
+
+    // Transform feature: rigid move/rotate of an existing body. Rotation is applied
+    // first (about xf_axis through xf_pivot), then the translation.
+    Vec3d       xf_translate{0, 0, 0};
+    Vec3d       xf_axis{0, 0, 1};
+    Vec3d       xf_pivot{0, 0, 0};
+    double      xf_angle_deg{0};
+    bool        xf_copy{false};      // true: keep the original, append the moved copy as a new body
+
+    // Thicken feature: offset one face of an existing body into a new thin solid body.
+    // The face belongs to `target_body`; the offset runs along the face normal.
+    int         thicken_face{-1};        // global face id on the target body; -1 = invalid
+    double      thicken_thickness{2};    // wall thickness (always used as |value|)
+    bool        thicken_flip{false};     // true: offset against the face normal
+
+    // Cut-by-face: when cut_face >= 0, apply_cut derives the cut plane from this face
+    // (via SketchPlane::from_face) instead of the base `plane`. cut_offset / cut_flip
+    // still apply along the derived normal.
+    int         cut_face_body{-1};   // body owning the face; -1 = the target body
+    int         cut_face{-1};        // global face id to cut along; -1 = use `plane`
+
+    // Project feature: convert edges of an existing solid into sketch entities on `plane`.
+    int              project_source_body{-1};   // body owning the edges; -1 = last body
+    std::vector<int> project_edges;             // global edge ids to project; empty => use project_face
+    int              project_face{-1};          // if project_edges empty, project every edge of this face
+
+    // Direct edit: faces to remove (global face indices into target_body's shape),
+    // healed via BRepAlgoAPI_Defeaturing.
+    std::vector<int> delete_faces;
+
+    // Rib: a thin wall grown from an open sketch line, fused to the body.
+    int    rib_sketch_ref{-1};  // feature index of the Sketch holding the profile
+    int    rib_entity{-1};      // index of the open Line entity within that sketch
+    double rib_thickness{2};    // wall thickness (mm), centred on the line
+    double rib_depth{10};       // extrude distance along the sketch-plane normal (mm)
+
+    // --- Mate (assembly) ---
+    // 0 Fastened   — all 6 DOF fixed: B's frame is driven onto A's exactly.
+    // 1 Planar     — z axes aligned, normal distance set to mate_offset; in-plane position free.
+    // 2 Revolute   — axes collinear, position on the axis fixed; rotation about z free.
+    // 3 Slider     — orientation fully fixed, perpendicular position fixed; axial slide free.
+    // 4 Cylindrical— axes collinear, perpendicular fixed; both spin and axial slide free.
+    // A "free" DOF is preserved from the body's current placement, not zeroed.
+    int    mate_kind{0};
+    int    mate_cs_a{-1};       // feature index of the FIXED CoordSys (mate connector A)
+    int    mate_cs_b{-1};       // feature index of the CoordSys on the body that MOVES
+    double mate_offset{0};      // translation along A's z, mm
+    double mate_angle{0};       // rotation about A's z, degrees
+    bool   mate_flip{false};    // oppose the two z axes (face-to-face)
+
+    template<class Archive>
+    void save(Archive& ar) const {
+        std::string brep = (type == CadFeatureType::Import) ? brep_to_string(imported_solid) : std::string();
+        ar(type, name, enabled, shape, plane, width, height, radius,
+           profile, entities, constraints, entity_constraints, imported_regions,
+           import_offset, import_scale_x, import_scale_y, import_on_face, import_face_body,
+           sketch_ref, distance, symmetric, mode, extrude_end, distance2, taper_deg, flip,
+           up_to_face, extrude_src_face, up_to_point, target_body,
+           dressup_size, face_group, dressup_edge,
+           hole_diameter, hole_depth, hole_through, hole_x, hole_y,
+           thread_radius, thread_pitch, thread_height, thread_depth, thread_internal, thread_x, thread_y,
+           shell_thickness, shell_face,
+           draft_face, draft_angle,
+           revolve_angle, revolve_axis,
+           sweep_path_ref, loft_profile_refs, loft_ruled,
+           pattern_circular, pattern_count, pattern_spacing, pattern_dir, pattern_angle,
+           plane_base, plane_offset, plane_angle_tilt, plane_axis,
+           bool_tool_body, bool_keep_tool, bool_tolerance, bool_target_face, bool_tool_face,
+           cut_offset, cut_flip, cut_keep_upper, cut_keep_lower,
+           brep,
+           plane_type, plane_face_body, plane_face, plane_face2_body, plane_face2,
+           plane_edge_body, plane_edge, plane_edge2_body, plane_edge2, plane_u_size, plane_v_size,
+           mirror_keep_original,
+           axis_type, axis_p1, axis_p2, axis_body, axis_face, axis_edge, axis_plane_a, axis_plane_b,
+            coordsys_type, coordsys_point, coordsys_body, coordsys_face, coordsys_edge, coordsys_x_hint,
+            helix_radius, helix_pitch, helix_height, helix_left_handed, helix_taper_deg,
+             xf_translate, xf_axis, xf_pivot, xf_angle_deg, xf_copy,
+             thicken_face, thicken_thickness, thicken_flip,
+             cut_face_body, cut_face,
+             project_source_body, project_edges, project_face,
+             delete_faces,
+             hole_style, hole_cbore_diameter, hole_cbore_depth,
+             hole_csink_diameter, hole_csink_angle, hole_standard,
+              rib_sketch_ref, rib_entity, rib_thickness, rib_depth,
+               pattern_curve_sketch, pattern_curve_entity,
+               expr,
+               mate_kind, mate_cs_a, mate_cs_b, mate_offset, mate_angle, mate_flip,
+               coordsys_face_kind, coordsys_face_edges);
+    }
+    template<class Archive>
+    void load(Archive& ar) {
+        std::string brep;
+        ar(type, name, enabled, shape, plane, width, height, radius,
+           profile, entities, constraints, entity_constraints, imported_regions,
+           import_offset, import_scale_x, import_scale_y, import_on_face, import_face_body,
+           sketch_ref, distance, symmetric, mode, extrude_end, distance2, taper_deg, flip,
+           up_to_face, extrude_src_face, up_to_point, target_body,
+           dressup_size, face_group, dressup_edge,
+           hole_diameter, hole_depth, hole_through, hole_x, hole_y,
+           thread_radius, thread_pitch, thread_height, thread_depth, thread_internal, thread_x, thread_y,
+           shell_thickness, shell_face,
+           draft_face, draft_angle,
+           revolve_angle, revolve_axis,
+           sweep_path_ref, loft_profile_refs, loft_ruled,
+           pattern_circular, pattern_count, pattern_spacing, pattern_dir, pattern_angle,
+           plane_base, plane_offset, plane_angle_tilt, plane_axis,
+           bool_tool_body, bool_keep_tool, bool_tolerance, bool_target_face, bool_tool_face,
+           cut_offset, cut_flip, cut_keep_upper, cut_keep_lower,
+           brep,
+           plane_type, plane_face_body, plane_face, plane_face2_body, plane_face2,
+           plane_edge_body, plane_edge, plane_edge2_body, plane_edge2, plane_u_size, plane_v_size,
+           mirror_keep_original,
+           axis_type, axis_p1, axis_p2, axis_body, axis_face, axis_edge, axis_plane_a, axis_plane_b,
+           coordsys_type, coordsys_point, coordsys_body, coordsys_face, coordsys_edge, coordsys_x_hint,
+           helix_radius, helix_pitch, helix_height, helix_left_handed, helix_taper_deg,
+            xf_translate, xf_axis, xf_pivot, xf_angle_deg, xf_copy,
+            thicken_face, thicken_thickness, thicken_flip,
+            cut_face_body, cut_face,
+             project_source_body, project_edges, project_face,
+               delete_faces,
+               hole_style, hole_cbore_diameter, hole_cbore_depth,
+               hole_csink_diameter, hole_csink_angle, hole_standard,
+               rib_sketch_ref, rib_entity, rib_thickness, rib_depth,
+                pattern_curve_sketch, pattern_curve_entity,
+               expr,
+               mate_kind, mate_cs_a, mate_cs_b, mate_offset, mate_angle, mate_flip,
+               coordsys_face_kind, coordsys_face_edges);
+        imported_solid = brep_from_string(brep);
+    }
+};
+
+// Serialize a TopoDS_Shape to/from a BRep string for cereal persistence.
+std::string brep_to_string(const TopoDS_Shape& s);
+TopoDS_Shape brep_from_string(const std::string& d);
+
+// One independent solid in a multi-body document.
+struct CadBody {
+    TopoDS_Shape shape;
+    std::string  name;
+    // The name the USER gave this body. A body is NOT its first feature: an Extrude, a Cut and
+    // a Fillet all land on the same body, so renaming `source_feature` renames one operation in
+    // the history, not the object — which is exactly the bug this field exists to end. `name`
+    // above is the DERIVED label (the maker's name, restamped every recompute) and stays that;
+    // this one is set only by a rename, carried across recompute() by body index, and written
+    // into the recipe so it survives save/load.
+    bool         has_user_name{false};
+    std::string  user_name;
+    // Per-body display colour override (Color tool). When has_color is false the GUI
+    // falls back to the auto body-index palette. Carried across recompute() by body index.
+    bool         has_color{false};
+    ColorRGBA    color;
+    // Index into `features` of the feature that CREATED this body, or -1. A body is a
+    // recomputed result, so without this there is no way back to its maker and "delete this
+    // body" cannot be expressed at all — the GUI could only answer "select the FEATURE that
+    // created this body". Stamped in one place, the recompute loop; see the note there for
+    // why a single "still unset?" test is sufficient and stays correct for new feature types.
+    int          source_feature{-1};
+};
+
+// OCCT-only feature tree backing the Design tab. No GUI dependencies (lives in libslic3r).
+class CadDocument {
+public:
+    std::vector<CadFeature> features;
+    // Named document variables: name -> expression. Evaluated topologically each recompute();
+    // an expression may reference other variables. Feature `expr` bindings resolve against these.
+    std::map<std::string, std::string> variables;
+    // Multi-body result of the last replay. A "New" extrude appends a body; other ops
+    // mutate a target body. Empty after a failed/empty recompute.
+    std::vector<CadBody>    bodies;
+    TopoDS_Shape            body;          // compound of all bodies (1 body => that body) — display/compat
+    TriangleMesh            display_mesh;      // tessellation of all bodies, concatenated (picking)
+    std::vector<TriangleMesh> display_body_meshes; // one mesh per body, in `bodies` order (per-body color)
+    std::vector<int>        display_tri_face;  // per-triangle face id WITHIN its source body
+    std::vector<int>        display_tri_body;  // per-triangle source body index (into bodies)
+    std::string             error;             // last recompute error ("" = ok)
+
+    // Mate diagnostics, refilled by every recompute(). Non-fatal by design: the
+    // document still evaluates — this only names what the user should look at.
+    // .first = index of the offending Mate feature, .second = human-readable reason.
+    // NOT "over-constraint" — this kernel has no solver, so there is no DOF analysis
+    // behind these; they are graph facts about which mate drives which body.
+    std::vector<std::pair<int, std::string>> mate_conflicts;
+
+    // Modeling origin: the world point the default XY/XZ/YZ planes pass through. The GUI sets this
+    // to the bed centre so sketches/datums land in the middle of the bed (not the bed corner =
+    // world 0). Not serialized — the GUI re-applies it from the live bed on every tab show.
+    Vec3d modeling_origin{Vec3d::Zero()};
+
+    // Tessellation quality, matched to Orca's OWN STEP importer (Format/STEP.hpp defaults:
+    // linear 0.003, angular 0.5 rad) so a body modelled here reaches the screen at the same
+    // density as the identical body imported through Prepare. It was 0.01 linear — 3.3x coarser
+    // than anything else in the app, which is why curved faces read as faceted next to an
+    // imported part. Angular already matched. Same BRepMesh_IncrementalMesh call, same GLVolume
+    // path, same shaders: the renderer was never the difference, the mesh fed to it was.
+    double linear_deflection{0.003};
+    double angular_deflection{0.5};
+
+    int  add_sketch(SketchShape shape, const SketchPlane& plane,
+                    double width, double height, double radius,
+                    const std::string& name);
+    int  add_sketch_profile(const SketchProfile& profile, const SketchPlane& plane,
+                            const std::string& name);
+    // Onshape-style multi-entity sketch: stores the entity list verbatim. When
+    // non-empty it takes precedence over profile/enum in build_sketch_wire.
+    int  add_sketch_entities(const std::vector<SketchEntity>& entities,
+                             const SketchPlane& plane, const std::string& name,
+                             const std::vector<SketchEntityConstraintDef>& constraints = {});
+    // Project edges of source_body onto plane, producing a sketch feature whose
+    // entities are (re)derived on every recompute.
+    int  add_project_edges(int source_body, const std::vector<int>& edge_ids, int face,
+                           const SketchPlane& plane, const std::string& name);
+    // Onshape's "Use" / SolidWorks' "Convert Entities": project a body's edges onto the plane of
+    // an EXISTING sketch feature and append them to that sketch as CONSTRUCTION entities, so new
+    // geometry can be constrained to them. Returns the number of entities appended, or -1 if the
+    // sketch or body reference is invalid. Unlike add_project_edges this creates no feature: the
+    // references become part of the sketch that borrows them.
+    int  project_edges_into_sketch(int sketch_feature, int source_body,
+                                   const std::vector<int>& edge_ids, int face);
+    // Append a bridging BSpline entity connecting endpoint `end_a` of entity `ent_a` to
+    // endpoint `end_b` of entity `ent_b`, both within sketch feature `sketch_ref`. Returns
+    // the new entity's index within that sketch's entities vector. Non-parametric: computed
+    // once from the current endpoints (does not auto-follow later solver moves).
+    int add_bridge(int sketch_ref, int ent_a, int end_a, int ent_b, int end_b,
+                   const std::string& name);
+    // Solve features[index]'s sketch constraints, writing solved coordinates back
+    // into its profile.points. No-op (returns true) if the feature has no
+    // constraints. Returns false if index is invalid / not a Sketch / solve fails.
+    bool solve_sketch_feature(int index);
+    int  add_extrude(int sketch_ref, double distance, bool symmetric,
+                     BooleanMode mode, const std::string& name);
+    // Extrude a single loop given directly as entities (sketch_ref = -1, plane carried).
+    int  add_extrude_entities(const std::vector<SketchEntity>& entities,
+                              const SketchPlane& plane, double distance, bool symmetric,
+                              BooleanMode mode, const std::string& name);
+    // Extrude an existing solid FACE (global face id on the body) as the profile.
+    int  add_extrude_face(int src_face, double distance, bool symmetric,
+                          BooleanMode mode, const std::string& name);
+    int  add_fillet(double radius, FaceGroup faces, const std::string& name);
+    int  add_fillet(double radius, int edge_id, const std::string& name);
+    int  add_chamfer(double distance, FaceGroup faces, const std::string& name);
+    int  add_chamfer(double distance, int edge_id, const std::string& name);
+    int  add_hole(double diameter, double depth, bool through,
+                  double x, double y, const SketchPlane& plane,
+                  const std::string& name);
+    int  add_hole_styled(double diameter, double depth, bool through,
+                         double x, double y, const SketchPlane& plane, int style,
+                         double cbore_diameter, double cbore_depth,
+                         double csink_diameter, double csink_angle,
+                         const std::string& standard, const std::string& name);
+    int  add_hole_standard(const std::string& designation, int style, bool through,
+                           double depth, double x, double y,
+                           const SketchPlane& plane, const std::string& name);
+    int  add_thread(double radius, double pitch, double height, double depth,
+                    bool internal, double x, double y, const SketchPlane& plane,
+                    const std::string& name);
+    int  add_revolve(int sketch_ref, double angle, int axis, bool flip,
+                     BooleanMode mode, const std::string& name);
+    // Self-contained revolve of a single loop given directly as entities (sketch_ref=-1).
+    int  add_revolve_entities(const std::vector<SketchEntity>& entities,
+                              const SketchPlane& plane, double angle, int axis, bool flip,
+                              BooleanMode mode, const std::string& name);
+    // Sweep the profile Sketch (profile_sketch_ref) along the path Sketch (path_sketch_ref).
+    int  add_pattern(bool circular, int count, double spacing, int dir,
+                     double angle_deg, int target_body, const std::string& name);
+    // Pattern `count` copies of `target` along entity `curve_entity` of sketch `curve_sketch`.
+    int  add_pattern_on_curve(int count, int curve_sketch, int curve_entity, int target,
+                              const std::string& name);
+    int  add_sweep(int profile_sketch_ref, int path_sketch_ref, BooleanMode mode,
+                   const std::string& name);
+    // Loft through the ordered profile Sketches (each a closed wire on its own plane).
+    int  add_loft(const std::vector<int>& profile_refs, bool ruled, BooleanMode mode,
+                  const std::string& name);
+    // Skin 2+ profile sketches open (no end caps) -> a sheet body.
+    int  add_surface_loft(const std::vector<int>& profile_refs, bool ruled, const std::string& name);
+    // Fill sketch sketch_ref's closed boundary wire with a smooth face -> a one-face sheet body.
+    int  add_surface_fill(int sketch_ref, const std::string& name);
+    int  add_shell(double thickness, int face, int target_body, const std::string& name);
+    // Grow a thin rib wall (thickness, depth) from the open Line entity `entity` inside sketch
+    // feature `sketch_ref`, fused to `target_body`. Returns the new feature index.
+    int  add_rib(int sketch_ref, int entity, double thickness, double depth,
+                 int target_body, const std::string& name);
+    int  add_draft(double angle, int face, int target_body, const std::string& name);
+    // Boolean between two existing bodies. op reuses BooleanMode (Add=union, Cut=subtract,
+    // Intersect=common; New invalid). target survives, tool is consumed unless keep_tool.
+    // tolerance = OCCT fuzzy value; target_face/tool_face (-1 = none) drive the per-face snap+merge.
+    int  add_boolean(BooleanMode op, int target_body, int tool_body, bool keep_tool,
+                     double tolerance, int target_face, int tool_face, const std::string& name);
+    // Plane Cut (Onshape split-by-plane): trim target_body by the plane (origin offset along
+    // its normal by `offset`, normal flipped iff `flip`). keep_upper/keep_lower select the
+    // +normal / -normal half; both => the body is split into two coexisting bodies.
+    int  add_cut(const SketchPlane& plane, double offset, bool flip,
+                  bool keep_upper, bool keep_lower, int target_body, const std::string& name);
+    // Split target_body along the plane of face `face` (owned by face_body, -1 = target).
+    // keep_upper/keep_lower select which half survives; both => split into two bodies.
+    int add_split_by_face(int target_body, int face_body, int face,
+                          bool keep_upper, bool keep_lower, const std::string& name);
+    int  add_mirror(const SketchPlane& plane, int target_body, BooleanMode mode,
+                    const std::string& name);
+    // Rigid body transform: rotate `angle_deg` about `axis` through `pivot`, then translate.
+    // copy=true keeps the source body and appends the transformed one as a new body.
+    int add_transform(int target_body, const Vec3d& translate, const Vec3d& axis,
+                      const Vec3d& pivot, double angle_deg, bool copy, const std::string& name);
+    // Offset face `face` of `target_body` by `thickness` along its normal, producing a new
+    // thin solid appended as a new body. flip=true offsets against the normal.
+    int add_thicken(int target_body, int face, double thickness, bool flip, const std::string& name);
+    // Thicken an entire SHEET body's shell into a solid.
+    int add_thicken_surface(int target_body, double thickness, bool flip, const std::string& name);
+    // Offset a SHEET body's shell by a signed distance, producing another SHEET body.
+    int add_surface_offset(int target_body, double offset, const std::string& name);
+    int add_delete_face(int target_body, const std::vector<int>& faces,
+                        const std::string& name);
+    int add_surface_extrude(int sketch_ref, double distance, const std::string& name);
+    int add_surface_revolve(int sketch_ref, double angle_deg, int axis, const std::string& name);
+    // Datum plane: derived from base (0=XY/1=XZ/2=YZ/3+N=Nth earlier datum), offset
+    // along its normal, optional tilt about a base axis. Produces no solid.
+    int  add_plane(int base, double offset, double angle_tilt, int axis,
+                   const std::string& name);
+    // Datum axis: construction method axis_type determines which ref fields are read.
+    int  add_axis(AxisType axis_type, const std::string& name);
+    // Datum coordinate system.
+    int  add_coordsys(CoordSysType type, const Vec3d& point, const std::string& name);
+    int  add_mate(int kind, int cs_a, int cs_b, double offset, double angle_deg, bool flip,
+                  const std::string& name);
+
+    // Which mate types apply to a connector pair, as reported to the viewport palette.
+    struct MateOption {
+        int         kind{0};        // 0..4, the five mate types in CadDocument.hpp:308-314
+        bool        viable{true};
+        std::string reason;         // empty when viable; why not, when not
+    };
+    // ALWAYS all five entries, ALWAYS in kind order. Never filtered: the caller dims what is
+    // not viable rather than hiding it, so the list must be stable in length and order between
+    // calls. Pure query over existing data — records nothing, mutates nothing.
+    std::vector<MateOption> mate_options(int cs_a, int cs_b) const;
+
+    int  add_helix(const SketchPlane& plane, double radius, double pitch, double height,
+                   bool left_handed, double taper_deg, const std::string& name);
+    // Build the helix wire from a Helix feature's params (exposed for tests).
+    TopoDS_Wire build_helix_wire(const CadFeature& f, std::string& err) const;
+    // Every datum plane currently in the recipe, in feature order, as (name, plane).
+    // Used by the GUI to populate plane pickers (after the 3 base planes).
+    std::vector<std::pair<std::string, SketchPlane>> resolve_datum_planes() const;
+
+    // World-space sketch plane lying on a body's PLANAR face, so a face picked in the viewport can
+    // be sketched on directly — no datum plane in between and nothing to choose from a list.
+    // Returns false when the indices don't resolve or the face isn't planar (a cylinder or a fillet
+    // has no single plane, and guessing one from a mid-parameter normal would silently sketch on a
+    // tangent). Same derivation the Coincident datum method uses, shared so the two cannot drift.
+    bool plane_of_face(int body_idx, int face_idx, SketchPlane& out) const;
+    // Resolved datum axes in feature order. axis_err is non-empty if construction failed.
+    struct DatumAxis { std::string name; Vec3d origin{0,0,0}; Vec3d direction{0,0,1};
+                       std::string error; };
+    std::vector<DatumAxis> resolve_datum_axes() const;
+    // Resolved datum coordinate systems. X/Y unit, orthonormal (Z = X.cross(Y)).
+    struct DatumCoordSys { std::string name; Vec3d origin{0,0,0}; Vec3d x{1,0,0};
+                           Vec3d y{0,1,0}; std::string error; };
+    std::vector<DatumCoordSys> resolve_datum_coordsys() const;
+    void clear();
+    bool recompute();   // replay features -> body + display_mesh; false on error
+
+    // CadRecipe serialization contract:
+    // - v1 blobs are deliberately not loadable; there is no migration path by design
+    // - append fields ONLY at the end of save/load, never reorder (golden fixture enforces this)
+    // Bumped every time the bodies are rebuilt, i.e. every time the face and edge MAPS change.
+    // Global face/edge ids are indices into TopExp::MapShapes and mean nothing across a rebuild,
+    // so any caller holding an id from an earlier state is holding a wrong one. This is the
+    // handle that lets it find out instead of silently addressing the wrong edge.
+    //
+    // Session-scoped and deliberately NOT serialized: an id is only meaningful within the run
+    // that produced it, so persisting the counter would imply a promise across loads that the
+    // ids themselves cannot keep.
+    uint64_t topo_generation{1};
+
+    // v5: every feature is length-framed, so a reader can stop early on an older file and skip
+    // the tail of a newer one. This is the LAST version that has to break anything — from here a
+    // new field only needs appending to save/load, with no bump and no orphaned projects.
+    // v6: no wire-format change — the bytes are v5's, and both are read by the same framed path.
+    // The stamp advances only to put a project-container change on the record; the 3MF backends
+    // own that story. v4 still opens through the pre-framing flat path.
+    static constexpr uint32_t ORCA_CAD_RECIPE_VERSION = 6;
+    std::string serialize_recipe() const;
+    bool deserialize_recipe(const std::string& blob);
+
+    // Export every body to a STEP file as native B-rep (not mesh). body_xforms is the
+    // per-body display transform (Move gizmo); when supplied the bodies are written at
+    // those positions so the STEP matches what Commit ships. false + err on failure.
+    bool export_step(const std::string& path,
+                     const std::vector<Transform3d>& body_xforms,
+                     std::string& err) const;
+
+    GeometryEngine::MassProps body_mass_properties(int body_index) const;
+
+    // One overlapping pair of solid bodies. Indices are into `bodies`, a_ < b_.
+    struct Interference { int body_a{-1}; int body_b{-1}; double volume{0}; };
+    // Every pair of solid bodies whose intersection encloses more than min_volume (mm^3).
+    // Reports only — mutates nothing, so mates and placements are unaffected by calling it.
+    // Sheet bodies are skipped: an intersection involving one encloses no volume.
+    std::vector<Interference> check_interference(double min_volume = 1e-6) const;
+
+    // ponytail: derived from the OCCT shape type; no stored flag, bodies aren't serialized anyway.
+    static bool is_sheet_shape(const TopoDS_Shape& s); // true if TopExp finds no TopAbs_SOLID
+
+    // Undo/redo of the feature recipe (Onshape-style Ctrl+Z). The caller marks a
+    // user-action boundary by calling checkpoint() BEFORE the mutation(s) for that
+    // action (add/delete/move/replace, or a direct features edit). undo()/redo() then
+    // restore the snapshot and recompute(). Because everything else (bodies/meshes/
+    // body) is derived by recompute(), snapshotting `features` alone is a complete,
+    // exact history; one checkpoint == one Ctrl+Z step.
+    void checkpoint();   // snapshot `features` for undo + invalidate redo
+    // Drop the most recent checkpoint. For a mutation that took a checkpoint, then failed
+    // and restored the pre-mutation state itself (the constraint paths reject an
+    // over-constrained addition this way): the snapshot now describes a state identical to
+    // the current one, and leaving it turns the next Ctrl+Z into a press that does nothing.
+    void abandon_checkpoint();
+    bool can_undo() const { return !m_undo.empty(); }
+    bool can_redo() const { return !m_redo.empty(); }
+    size_t undo_depth() const { return m_undo.size(); }
+    size_t redo_depth() const { return m_redo.size(); }
+    bool undo();   // restore the previous feature list + recompute(); false if no history
+    bool redo();   // re-apply the most recently undone change; false if none
+
+    // Feature-tree editing (Onshape-style). All are transactional: they snapshot
+    // features, mutate, recompute(), and roll back to the snapshot (re-recomputing)
+    // if the result is invalid — so a failed edit never leaves a broken body.
+    //
+    // remove_feature: erase features[index]; deleting a Sketch cascades to the
+    //   Extrude(s) that consume it; surviving sketch_ref indices are remapped.
+    // move_feature:   shift features[index] by delta (-1 up / +1 down), clamped;
+    //   sketch_ref indices of the two swapped slots are remapped.
+    // replace_feature: overwrite features[index] with `edited` (its name and, for
+    //   an Extrude, its sketch_ref are preserved from the original).
+    bool remove_feature(int index);
+    bool move_feature(int index, int delta);
+    bool replace_feature(int index, const CadFeature& edited);
+    // replace_sketch_extrude: a box is two linked features (Sketch + Extrude);
+    //   overwrite both slots from one `edited` candidate (sketch params ->
+    //   features[sketch_idx], extrude params -> features[extrude_idx]), keeping
+    //   each slot's name/type and the sketch_ref link. Transactional like above.
+    bool replace_sketch_extrude(int sketch_idx, int extrude_idx, const CadFeature& edited);
+
+    // Apply ONE candidate feature on top of the current committed body and
+    // tessellate the result into out_mesh, WITHOUT modifying features/body/
+    // display_mesh. Returns false (with err set) if the candidate is invalid.
+    // Used by the Design tab to show a translucent ghost before Confirm.
+    bool preview(const CadFeature& candidate, TriangleMesh& out_mesh, std::string& err) const;
+    // Same, but also returns the per-body meshes (in `bodies` order; the candidate may append
+    // one), so the GUI can apply its display-only per-body Move transforms to the ghost and keep
+    // it overlaid on the moved body instead of floating back at the untransformed origin.
+    bool preview(const CadFeature& candidate, TriangleMesh& out_mesh,
+                 std::vector<TriangleMesh>& out_body_meshes, std::string& err) const;
+
+private:
+    TopoDS_Wire build_sketch_wire(const CadFeature& sketch, bool closed_only = false) const;
+    // The planar region an Extrude sweeps: the sketch's outer loop with its inner loops as
+    // holes. Falls back to a face over build_sketch_wire() for the legacy profile/shape paths,
+    // which have no concept of a second loop.
+    TopoDS_Face build_sketch_face(const CadFeature& sketch) const;
+    // Apply a single feature to (result, have_body), throwing std::runtime_error on
+    // failure. `context` is the body whose faces/edges the feature reads (face-extrude
+    // source, up-to-face target, dress-up, hole) — it differs from `result` only when the
+    // feature builds a NEW body from an existing one (face-extrude New). Shared by route.
+    void apply_feature(TopoDS_Shape& result, bool& have_body,
+                       const TopoDS_Shape& context, const CadFeature& f) const;
+    // Route one feature into the bodies list: resolve its target body, decide whether it
+    // starts a new body (empty list, or an Extrude with mode New) vs mutates an existing
+    // one, then apply_feature. Shared by recompute() (replay all) and preview() (candidate).
+    void route_feature(std::vector<CadBody>& bodies, const CadFeature& f) const;
+    // Boolean between two existing bodies: resolve target + tool, optionally snap the tool so
+    // the picked faces mate, run the OCCT op (with fuzzy tolerance), write the result back to the
+    // target and erase the consumed tool. Mutates the bodies vector directly (unlike apply_feature,
+    // which works on a single result shape). Throws std::runtime_error on a failed op.
+    void apply_boolean(std::vector<CadBody>& bodies, const CadFeature& f) const;
+    void apply_cut(std::vector<CadBody>& bodies, const CadFeature& f) const;
+    void apply_mirror(std::vector<CadBody>& bodies, const CadFeature& f) const;
+    void apply_transform(std::vector<CadBody>& bodies, const CadFeature& f) const;
+    void apply_thicken(std::vector<CadBody>& bodies, const CadFeature& f) const;
+    void apply_thicken_surface(std::vector<CadBody>& bodies, const CadFeature& f) const;
+    void apply_surface_offset(std::vector<CadBody>& bodies, const CadFeature& f) const;
+    void apply_project(const std::vector<CadBody>& bodies, CadFeature& f) const;
+    static DatumCoordSys datum_frame(const std::vector<CadBody>& bodies, const CadFeature& f);
+    void apply_mate(std::vector<CadBody>& bodies, const CadFeature& f) const;
+    void detect_mate_conflicts();   // refills mate_conflicts from the feature list alone
+
+    // Undo/redo stacks of recipe snapshots. checkpoint() pushes onto m_undo and clears
+    // m_redo; undo()/redo() shuffle the current state between them. Capped so a long
+    // session can't grow unbounded.
+    //
+    // The snapshot MUST carry `variables` as well as `features`: a caller that sets a bad
+    // variable, sees recompute() fail and calls undo() to roll it back would otherwise be
+    // left with the bad variable still in the document, so every later recompute fails —
+    // the exact corruption the checkpoint/undo pattern exists to prevent. Not serialized,
+    // so this changes no on-disk format.
+    struct Snapshot {
+        std::vector<CadFeature>            features;
+        std::map<std::string, std::string> variables;
+    };
+    std::vector<Snapshot> m_undo;
+    std::vector<Snapshot> m_redo;
+    static constexpr size_t k_undo_cap = 200;
+};
+
+} // namespace Slic3r
+
+#endif // slic3r_CadDocument_hpp_
diff --git a/src/libslic3r/CAD/GeometryEngine.cpp b/src/libslic3r/CAD/GeometryEngine.cpp
new file mode 100644
index 0000000000..ede3924056
--- /dev/null
+++ b/src/libslic3r/CAD/GeometryEngine.cpp
@@ -0,0 +1,711 @@
+#include "libslic3r/CAD/GeometryEngine.hpp"
+
+#include <BRepMesh_IncrementalMesh.hxx>
+#include <BRep_Tool.hxx>
+#include <BRepAdaptor_Surface.hxx>
+#include <BRepLProp_SLProps.hxx>
+#include <gp_Cylinder.hxx>
+#include <BRepFilletAPI_MakeFillet.hxx>
+#include <BRepFilletAPI_MakeChamfer.hxx>
+#include <stdexcept>
+#include <TopExp_Explorer.hxx>
+#include <TopoDS.hxx>
+#include <TopoDS_Face.hxx>
+#include <TopoDS_Edge.hxx>
+#include <TopExp.hxx>
+#include <TopTools.hxx>
+#include <TopTools_IndexedMapOfShape.hxx>
+#include <Poly_Triangulation.hxx>
+#include <gp_Ax2.hxx>
+#include <gp_Dir.hxx>
+#include <gp_Pnt.hxx>
+#include <BRepGProp.hxx>
+#include <GProp_GProps.hxx>
+#include <GeomLProp_SLProps.hxx>
+#include <BRepAdaptor_Curve.hxx>
+#include <gp_Circ.hxx>
+#include <GCPnts_TangentialDeflection.hxx>
+#include <STEPControl_Reader.hxx>
+#include <IFSelect_ReturnStatus.hxx>
+#include <Standard_Failure.hxx>
+#include <BRepExtrema_DistShapeShape.hxx>
+#include <BRepBuilderAPI_MakeVertex.hxx>
+#include <BRepBuilderAPI_MakeEdge.hxx>
+#include <BRepBuilderAPI_MakeWire.hxx>
+#include <BRepBuilderAPI_MakeFace.hxx>
+#include <BRepBuilderAPI_MakeSolid.hxx>
+#include <BRep_Builder.hxx>
+#include <TopoDS_Shell.hxx>
+#include <TopoDS_Vertex.hxx>
+#include <ShapeUpgrade_UnifySameDomain.hxx>
+#include <array>
+#include <map>
+#include <cmath>
+
+namespace Slic3r {
+
+// ---- STEP import (B-rep, not mesh) ----
+std::vector<TopoDS_Shape> GeometryEngine::read_step_solids(const std::string& path, std::string& err)
+{
+    err.clear();
+    std::vector<TopoDS_Shape> out;
+    try {
+        STEPControl_Reader reader;
+        if (reader.ReadFile(path.c_str()) != IFSelect_RetDone) {
+            err = "cannot read STEP file";
+            return out;
+        }
+        reader.TransferRoots();
+        const TopoDS_Shape shape = reader.OneShape();
+        if (shape.IsNull()) { err = "STEP file has no geometry"; return out; }
+        // One body per top-level solid; fall back to the whole shape (shells/faces) if none.
+        for (TopExp_Explorer ex(shape, TopAbs_SOLID); ex.More(); ex.Next())
+            out.push_back(ex.Current());
+        if (out.empty())
+            out.push_back(shape);
+    } catch (const Standard_Failure& e) {
+        err = e.GetMessageString() ? e.GetMessageString() : "OCCT failed to read STEP";
+        out.clear();
+    }
+    return out;
+}
+
+// ---- Mesh -> B-rep (faceted, shared topology by construction) ----
+//
+// Port of mesh2step's brep_build.py. Two properties are load-bearing and easy to lose:
+//
+//  1. The edge cache is keyed on the UNORDERED vertex-index pair, and a triangle that walks
+//     the edge backwards (i > j) gets edge.Reversed(). Consistently-wound meshes (STL/OBJ/3MF
+//     all are) walk every shared edge in opposite directions from its two adjacent triangles,
+//     so this reversal is exactly what leaves the faces coherently outward-oriented.
+//  2. Degeneracy is split in two, deliberately. A triangle is dropped as sub-resolution noise
+//     only if its longest edge is below `tolerance` (an absolute floor), while sliver rejection
+//     is scale-INDEPENDENT (area < 1e-9 * longest_edge^2). Folding the two together under one
+//     `area < tolerance^2` test rejects legitimate thin CAD slivers whenever tolerance is coarse
+//     relative to them, turning a watertight input into a falsely-open shell — a real regression
+//     mesh2step hit on a 62k-triangle mechanical part.
+TopoDS_Shape GeometryEngine::mesh_to_brep(const indexed_triangle_set& its,
+                                          double tolerance,
+                                          double merge_angle_deg,
+                                          MeshBrepStats& stats)
+{
+    stats = MeshBrepStats{};
+    stats.input_tris = int(its.indices.size());
+    if (tolerance <= 0.0)
+        throw std::runtime_error("mesh_to_brep: tolerance must be > 0");
+    if (its.indices.empty())
+        throw std::runtime_error("mesh_to_brep: mesh has no triangles");
+
+    // 1. Tolerance-quantized vertex dedup. A merged vertex keeps the exact coordinates of the
+    //    first input occurrence — vertices are grouped by a cell, never snapped onto its grid.
+    std::map<std::array<long long, 3>, int> cell_to_new;
+    std::vector<int>   old_to_new(its.vertices.size(), -1);
+    std::vector<Vec3d> verts;
+    verts.reserve(its.vertices.size());
+    for (size_t i = 0; i < its.vertices.size(); ++i) {
+        const Vec3d p = its.vertices[i].cast<double>();
+        const std::array<long long, 3> cell{ (long long) std::llround(p.x() / tolerance),
+                                             (long long) std::llround(p.y() / tolerance),
+                                             (long long) std::llround(p.z() / tolerance) };
+        auto ins = cell_to_new.emplace(cell, int(verts.size()));
+        if (ins.second)
+            verts.push_back(p);
+        old_to_new[i] = ins.first->second;
+    }
+
+    // 2. Reject degenerate triangles (see the two-part rule in the comment above).
+    std::vector<Vec3i32> tris;
+    tris.reserve(its.indices.size());
+    for (const Vec3i32& t : its.indices) {
+        const int a = old_to_new[t(0)], b = old_to_new[t(1)], c = old_to_new[t(2)];
+        if (a == b || b == c || a == c) { ++stats.degenerate_collapsed; continue; }
+        const Vec3d& pa = verts[a]; const Vec3d& pb = verts[b]; const Vec3d& pc = verts[c];
+        const double e0 = (pb - pa).norm(), e1 = (pc - pb).norm(), e2 = (pa - pc).norm();
+        const double longest = std::max(e0, std::max(e1, e2));
+        if (longest < tolerance) { ++stats.degenerate_collapsed; continue; }
+        const double area = 0.5 * (pb - pa).cross(pc - pa).norm();
+        if (area < 1e-9 * longest * longest) { ++stats.degenerate_sliver; continue; }
+        tris.emplace_back(a, b, c);
+    }
+    stats.kept_tris = int(tris.size());
+    if (tris.empty())
+        throw std::runtime_error("mesh_to_brep: every triangle was rejected as degenerate "
+                                 "(try a smaller tolerance)");
+
+    // 3. One face per triangle, sharing vertices and edges through the caches.
+    std::vector<TopoDS_Vertex> vertex_cache(verts.size());
+    std::vector<bool>          vertex_made(verts.size(), false);
+    auto get_vertex = [&](int i) -> const TopoDS_Vertex& {
+        if (!vertex_made[i]) {
+            const Vec3d& p = verts[i];
+            vertex_cache[i] = BRepBuilderAPI_MakeVertex(gp_Pnt(p.x(), p.y(), p.z())).Vertex();
+            vertex_made[i]  = true;
+        }
+        return vertex_cache[i];
+    };
+
+    std::map<std::pair<int, int>, TopoDS_Edge> edge_cache;
+    std::map<std::pair<int, int>, int>         edge_usage;
+    auto get_edge = [&](int i, int j) -> TopoDS_Edge {
+        const std::pair<int, int> key = (i < j) ? std::make_pair(i, j) : std::make_pair(j, i);
+        ++edge_usage[key];
+        auto it = edge_cache.find(key);
+        if (it == edge_cache.end())
+            it = edge_cache.emplace(key,
+                     BRepBuilderAPI_MakeEdge(get_vertex(key.first), get_vertex(key.second)).Edge()).first;
+        return (i > j) ? TopoDS::Edge(it->second.Reversed()) : it->second;
+    };
+
+    BRep_Builder  builder;
+    TopoDS_Shell  shell;
+    builder.MakeShell(shell);
+
+    for (const Vec3i32& t : tris) {
+        try {
+            BRepBuilderAPI_MakeWire mk_wire(get_edge(t(0), t(1)), get_edge(t(1), t(2)), get_edge(t(2), t(0)));
+            if (!mk_wire.IsDone()) { ++stats.faces_failed; continue; }
+            BRepBuilderAPI_MakeFace mk_face(mk_wire.Wire());
+            if (!mk_face.IsDone()) { ++stats.faces_failed; continue; }
+            builder.Add(shell, mk_face.Face());
+            ++stats.faces_built;
+        } catch (const Standard_Failure&) {
+            ++stats.faces_failed;
+        }
+    }
+
+    // 4. Watertightness falls straight out of the usage counts the cache already gathered.
+    for (const auto& kv : edge_usage) {
+        if (kv.second == 1)      ++stats.boundary_edges;
+        else if (kv.second >= 3) ++stats.nonmanifold_edges;
+    }
+    stats.unique_edges = int(edge_usage.size());
+    stats.watertight   = stats.boundary_edges == 0 && stats.nonmanifold_edges == 0 && stats.unique_edges > 0;
+
+    TopoDS_Shape shape = shell;
+    if (stats.watertight && stats.faces_built > 0) {
+        BRepBuilderAPI_MakeSolid mk_solid(shell);
+        if (mk_solid.IsDone()) {
+            TopoDS_Solid solid = mk_solid.Solid();
+            GProp_GProps props;
+            BRepGProp::VolumeProperties(solid, props);
+            double vol = props.Mass();
+            if (vol < 0.0) {                                  // inward-wound input
+                solid = TopoDS::Solid(solid.Reversed());
+                vol   = -vol;
+            }
+            if (vol > 0.0) {
+                shape         = solid;
+                stats.is_solid = true;
+                stats.volume   = vol;
+            }
+        }
+    }
+
+    // 5. Optional coplanar merge. Faceted output is one planar face per triangle — exact, but
+    //    you cannot meaningfully fillet or extrude a face that IS a single triangle. Merging
+    //    coplanar neighbours is what turns the import into something the face/edge tools can
+    //    actually operate on (a 12-triangle cube collapses to its 6 real faces).
+    if (merge_angle_deg > 0.0) {
+        try {
+            ShapeUpgrade_UnifySameDomain unifier(shape, true, true, true);
+            unifier.SetAngularTolerance(merge_angle_deg * M_PI / 180.0);
+            unifier.SetLinearTolerance(tolerance);
+            unifier.Build();
+            const TopoDS_Shape merged = unifier.Shape();
+            if (!merged.IsNull())
+                shape = merged;
+        } catch (const Standard_Failure&) {
+            // Merging is an optimisation, not a correctness step: keep the exact faceted shape.
+        }
+    }
+    stats.faces_final = face_count(shape);
+    return shape;
+}
+
+// ---- Primitive creation ----
+
+TopoDS_Solid GeometryEngine::make_primitive(const PrimitiveParams& params)
+{
+    switch (params.type) {
+    case PrimitiveType::Box:
+        return BRepPrimAPI_MakeBox(gp_Pnt(-params.box_w/2, -params.box_d/2, 0),
+                                   params.box_w, params.box_d, params.box_h).Solid();
+    case PrimitiveType::Cylinder:
+        return BRepPrimAPI_MakeCylinder(gp_Ax2(gp_Pnt(0,0,0), gp_Dir(0,0,1)),
+                                        params.cyl_radius, params.cyl_height).Solid();
+    case PrimitiveType::Sphere:
+        return BRepPrimAPI_MakeSphere(gp_Pnt(0,0,params.sph_radius), params.sph_radius).Solid();
+    case PrimitiveType::Cone:
+        return BRepPrimAPI_MakeCone(gp_Ax2(gp_Pnt(0,0,0), gp_Dir(0,0,1)),
+                                    params.cone_r1, params.cone_r2, params.cone_height).Solid();
+    case PrimitiveType::Torus:
+        return BRepPrimAPI_MakeTorus(gp_Ax2(gp_Pnt(0,0,params.torus_r2), gp_Dir(0,0,1)),
+                                     params.torus_r1, params.torus_r2).Solid();
+    default:
+        return BRepPrimAPI_MakeBox(gp_Pnt(-10,-10,0), 20,20,20).Solid();
+    }
+}
+
+// ---- Face classification ----
+
+FaceGroup GeometryEngine::classify_face(const TopoDS_Face& face, const TopoDS_Shape& /*solid*/)
+{
+    try {
+        BRepAdaptor_Surface surf(face);
+        if (surf.GetType() == GeomAbs_Plane) {
+            // Sample normal at center UV
+            double u = (surf.FirstUParameter() + surf.LastUParameter()) / 2.0;
+            double v = (surf.FirstVParameter() + surf.LastVParameter()) / 2.0;
+            gp_Pnt pt; gp_Vec du, dv;
+            surf.D1(u, v, pt, du, dv);
+            gp_Dir n = du.Crossed(dv);
+            if (face.Orientation() == TopAbs_REVERSED) n.Reverse();
+
+            if (n.Z() > 0.7)  return FaceGroup::Top;
+            if (n.Z() < -0.7) return FaceGroup::Bottom;
+            return FaceGroup::Lateral;
+        }
+    } catch (...) {}
+    return FaceGroup::Lateral;
+}
+
+// ---- Edge collection ----
+
+std::vector<TopoDS_Edge> GeometryEngine::collect_edges(const TopoDS_Shape& solid, FaceGroup target)
+{
+    std::vector<TopoDS_Edge> result;
+    if (target == FaceGroup::All) {
+        for (TopExp_Explorer exp(solid, TopAbs_EDGE); exp.More(); exp.Next())
+            result.push_back(TopoDS::Edge(exp.Current()));
+        return result;
+    }
+
+    // Build edge-to-face map once
+    TopTools_IndexedDataMapOfShapeListOfShape edgeFaceMap;
+    TopExp::MapShapesAndAncestors(solid, TopAbs_EDGE, TopAbs_FACE, edgeFaceMap);
+
+    for (TopExp_Explorer edgeExp(solid, TopAbs_EDGE); edgeExp.More(); edgeExp.Next()) {
+        const TopoDS_Edge& edge = TopoDS::Edge(edgeExp.Current());
+        if (!edgeFaceMap.Contains(edge)) continue;
+        const TopTools_ListOfShape& faces = edgeFaceMap.FindFromKey(edge);
+
+        bool include = false;
+        for (auto it = faces.begin(); it != faces.end(); ++it) {
+            FaceGroup fg = classify_face(TopoDS::Face(*it), solid);
+            if (target == FaceGroup::Top && fg == FaceGroup::Top)       { include = true; break; }
+            if (target == FaceGroup::Bottom && fg == FaceGroup::Bottom) { include = true; break; }
+            if (target == FaceGroup::Lateral && fg == FaceGroup::Lateral) { include = true; break; }
+        }
+
+        if (!include && target == FaceGroup::Top) {
+            for (auto it = faces.begin(); it != faces.end(); ++it) {
+                if (classify_face(TopoDS::Face(*it), solid) == FaceGroup::Top) { include = true; break; }
+            }
+        }
+        if (!include && target == FaceGroup::Bottom) {
+            for (auto it = faces.begin(); it != faces.end(); ++it) {
+                if (classify_face(TopoDS::Face(*it), solid) == FaceGroup::Bottom) { include = true; break; }
+            }
+        }
+        if (target == FaceGroup::Lateral && !include) {
+            int lateralCount = 0;
+            for (auto it = faces.begin(); it != faces.end(); ++it) {
+                if (classify_face(TopoDS::Face(*it), solid) == FaceGroup::Lateral) ++lateralCount;
+            }
+            if (lateralCount >= 2) include = true;
+        }
+
+        if (include) result.push_back(edge);
+    }
+
+    return result;
+}
+
+// ---- Fillet/Chamfer ----
+
+TopoDS_Shape GeometryEngine::apply_fillet(const TopoDS_Shape& solid, double radius, FaceGroup faces)
+{
+    if (radius <= 0.001) return solid;
+
+    std::vector<TopoDS_Edge> edges = collect_edges(solid, faces);
+    if (edges.empty()) return solid;
+
+    BRepFilletAPI_MakeFillet fillet(solid);
+    for (const auto& edge : edges)
+        fillet.Add(radius, edge);
+    fillet.Build();
+
+    // A too-large radius (e.g. >= half the smallest spanned dimension) makes the
+    // operation degenerate; OCCT leaves IsDone() false. Report it instead of
+    // silently returning the unfilleted solid (which reads as a false success).
+    if (!fillet.IsDone()) throw std::runtime_error("fillet radius too large for this geometry");
+    return fillet.Shape();
+}
+
+TopoDS_Shape GeometryEngine::apply_chamfer(const TopoDS_Shape& solid, double distance, FaceGroup faces)
+{
+    if (distance <= 0.001) return solid;
+
+    std::vector<TopoDS_Edge> edges = collect_edges(solid, faces);
+    if (edges.empty()) return solid;
+
+    BRepFilletAPI_MakeChamfer chamfer(solid);
+    for (const auto& edge : edges)
+        chamfer.Add(distance, edge); // symmetric chamfer
+    chamfer.Build();
+
+    if (!chamfer.IsDone()) throw std::runtime_error("chamfer distance too large for this geometry");
+    return chamfer.Shape();
+}
+
+TopoDS_Shape GeometryEngine::apply_fillet(const TopoDS_Shape& solid, double radius, int edge_id)
+{
+    if (radius <= 0.001) return solid;
+
+    TopoDS_Edge edge = edge_by_index(solid, edge_id);
+    if (edge.IsNull()) throw std::runtime_error("apply_fillet: invalid edge id");
+
+    BRepFilletAPI_MakeFillet mk(solid);
+    mk.Add(radius, edge);
+    mk.Build();
+
+    if (!mk.IsDone()) throw std::runtime_error("apply_fillet: OCCT fillet failed");
+    return mk.Shape();
+}
+
+TopoDS_Shape GeometryEngine::apply_chamfer(const TopoDS_Shape& solid, double distance, int edge_id)
+{
+    if (distance <= 0.001) return solid;
+
+    TopoDS_Edge edge = edge_by_index(solid, edge_id);
+    if (edge.IsNull()) throw std::runtime_error("apply_chamfer: invalid edge id");
+
+    BRepFilletAPI_MakeChamfer mk(solid);
+    mk.Add(distance, edge);
+    mk.Build();
+
+    if (!mk.IsDone()) throw std::runtime_error("apply_chamfer: OCCT chamfer failed");
+    return mk.Shape();
+}
+
+// ---- Tessellation ----
+
+TriangleMesh GeometryEngine::tessellate(const TopoDS_Shape& shape,
+                                        double linear_deflection,
+                                        double angular_deflection)
+{
+    BRepMesh_IncrementalMesh mesh(shape, linear_deflection, false, angular_deflection, true);
+
+    int nbNodes = 0, nbTri = 0;
+    for (TopExp_Explorer exp(shape, TopAbs_FACE); exp.More(); exp.Next()) {
+        TopLoc_Location loc;
+        Handle(Poly_Triangulation) tri = BRep_Tool::Triangulation(TopoDS::Face(exp.Current()), loc);
+        if (!tri.IsNull()) { nbNodes += tri->NbNodes(); nbTri += tri->NbTriangles(); }
+    }
+    if (nbTri == 0 || nbNodes == 0) return TriangleMesh{};
+
+    stl_file stl;
+    stl.stats.type = inmemory;
+    stl.stats.number_of_facets = (uint32_t)nbTri;
+    stl.stats.original_num_facets = stl.stats.number_of_facets;
+    stl_allocate(&stl);
+
+    std::vector<Vec3f> pts; pts.reserve(nbNodes);
+    int ndOff = 0, trOff = 0;
+    for (TopExp_Explorer exp(shape, TopAbs_FACE); exp.More(); exp.Next()) {
+        const TopoDS_Shape& F = exp.Current();
+        TopLoc_Location loc;
+        Handle(Poly_Triangulation) tri = BRep_Tool::Triangulation(TopoDS::Face(F), loc);
+        if (tri.IsNull()) continue;
+        gp_Trsf T = loc.Transformation();
+        for (int i = 1; i <= tri->NbNodes(); ++i) {
+            gp_Pnt p = tri->Node(i); p.Transform(T);
+            pts.emplace_back(Vec3f(p.X(), p.Y(), p.Z()));
+        }
+        auto orient = exp.Current().Orientation();
+        int ids[3];
+        for (int i = 1; i <= tri->NbTriangles(); ++i) {
+            Poly_Triangle t = tri->Triangle(i); t.Get(ids[0], ids[1], ids[2]);
+            if (orient == TopAbs_REVERSED) std::swap(ids[1], ids[2]);
+            stl_facet f;
+            f.vertex[0] = pts[ids[0]+ndOff-1].cast<float>();
+            f.vertex[1] = pts[ids[1]+ndOff-1].cast<float>();
+            f.vertex[2] = pts[ids[2]+ndOff-1].cast<float>();
+            f.extra[0]=0; f.extra[1]=0;
+            stl_normal n; stl_calculate_normal(n,&f); stl_normalize_vector(n);
+            f.normal=n; stl.facet_start[trOff+i-1]=f;
+        }
+        ndOff += tri->NbNodes(); trOff += tri->NbTriangles();
+    }
+    TriangleMesh result; result.from_stl(stl); return result;
+}
+
+GeometryEngine::Deviation
+GeometryEngine::surface_deviation(const TopoDS_Shape& candidate,
+                                  const TopoDS_Shape& reference,
+                                  double linear_deflection)
+{
+    Deviation d;
+    if (candidate.IsNull() || reference.IsNull()) return d;
+    TriangleMesh mesh = tessellate(candidate, linear_deflection, 0.5);
+    const auto& verts = mesh.its.vertices;
+    if (verts.empty()) return d;
+    double sum = 0.0, sumsq = 0.0;
+    int n = 0;
+    for (const auto& v : verts) {
+        gp_Pnt p(v.x(), v.y(), v.z());
+        BRepExtrema_DistShapeShape dss(BRepBuilderAPI_MakeVertex(p).Vertex(), reference);
+        if (!dss.IsDone() || dss.NbSolution() < 1) continue;
+        double dist = dss.Value();
+        d.max_mm = std::max(d.max_mm, dist);
+        sum += dist; sumsq += dist * dist; ++n;
+    }
+    d.sample_count = n;
+    if (n > 0) { d.mean_mm = sum / n; d.rms_mm = std::sqrt(sumsq / n); }
+    return d;
+}
+
+GeometryEngine::MassProps GeometryEngine::mass_properties(const TopoDS_Shape& shape)
+{
+    MassProps p;
+    if (shape.IsNull()) return p;
+    try {
+        // A sheet body (open shell, no solid) encloses nothing, and BRepGProp::VolumeProperties
+        // integrates the divergence theorem over whatever faces exist — on an open shell that is
+        // not a volume at all. It came back as 96000 with an inertia diagonal of
+        // [-4.2e7, -4.2e7, -6.9e7] for a 60x60x40 four-walled box: negative principal moments,
+        // which no real body can have. The old code then hid the only obvious tell by taking
+        // std::abs() of the mass. Report the honest answer instead — surface area is still
+        // meaningful, so this is not a failure, just not a solid.
+        p.is_solid = TopExp_Explorer(shape, TopAbs_SOLID).More();
+        if (!p.is_solid) {
+            GProp_GProps sonly;
+            BRepGProp::SurfaceProperties(shape, sonly);
+            p.surface_area = sonly.Mass();
+            p.valid = true;          // the area IS trustworthy; volume/inertia stay zero
+            return p;
+        }
+        GProp_GProps vprops;
+        BRepGProp::VolumeProperties(shape, vprops);
+        double mass = vprops.Mass();
+        if (std::abs(mass) < 1e-30) return p;
+        p.volume        = std::abs(mass);
+        p.center_of_mass = Vec3d(vprops.CentreOfMass().X(), vprops.CentreOfMass().Y(), vprops.CentreOfMass().Z());
+        gp_Mat mat = vprops.MatrixOfInertia();
+        p.inertia = {{
+            mat(1,1), mat(1,2), mat(1,3),
+            mat(2,1), mat(2,2), mat(2,3),
+            mat(3,1), mat(3,2), mat(3,3),
+        }};
+        GProp_GProps sprops;
+        BRepGProp::SurfaceProperties(shape, sprops);
+        p.surface_area = sprops.Mass();
+        p.valid = true;
+    } catch (const Standard_Failure&) {
+        // leave valid = false
+    }
+    return p;
+}
+
+std::string GeometryEngine::primitive_name(PrimitiveType type)
+{
+    switch (type) {
+    case PrimitiveType::Box:      return "Box";
+    case PrimitiveType::Cylinder: return "Cylinder";
+    case PrimitiveType::Sphere:   return "Sphere";
+    case PrimitiveType::Cone:     return "Cone";
+    case PrimitiveType::Torus:    return "Torus";
+    default:                      return "Unknown";
+    }
+}
+
+// ---- Topology accessors ----
+
+int GeometryEngine::face_count(const TopoDS_Shape& shape)
+{
+    int n = 0;
+    for (TopExp_Explorer e(shape, TopAbs_FACE); e.More(); e.Next())
+        ++n;
+    return n;
+}
+
+TopoDS_Face GeometryEngine::face_by_index(const TopoDS_Shape& shape, int index)
+{
+    if (index < 0) return TopoDS_Face();
+    int ordinal = 0;
+    for (TopExp_Explorer e(shape, TopAbs_FACE); e.More(); e.Next()) {
+        if (ordinal == index)
+            return TopoDS::Face(e.Current());
+        ++ordinal;
+    }
+    return TopoDS_Face();
+}
+
+std::vector<TopoDS_Face> GeometryEngine::faces_of(const TopoDS_Shape& shape)
+{
+    std::vector<TopoDS_Face> out;
+    for (TopExp_Explorer e(shape, TopAbs_FACE); e.More(); e.Next())
+        out.push_back(TopoDS::Face(e.Current()));   // same order as face_by_index
+    return out;
+}
+
+std::vector<TopoDS_Edge> GeometryEngine::edges_of(const TopoDS_Shape& shape)
+{
+    TopTools_IndexedMapOfShape map;
+    TopExp::MapShapes(shape, TopAbs_EDGE, map);     // same order as edge_by_index
+    std::vector<TopoDS_Edge> out;
+    out.reserve(map.Extent());
+    for (int i = 1; i <= map.Extent(); ++i)
+        out.push_back(TopoDS::Edge(map(i)));
+    return out;
+}
+
+std::vector<TopoDS_Edge> GeometryEngine::edges_of_face(const TopoDS_Face& face)
+{
+    std::vector<TopoDS_Edge> result;
+    TopTools_IndexedMapOfShape map;
+    TopExp::MapShapes(face, TopAbs_EDGE, map);
+    for (int i = 1; i <= map.Extent(); ++i)
+        result.push_back(TopoDS::Edge(map(i)));
+    return result;
+}
+
+std::vector<Vec3d> GeometryEngine::sample_edge_world(const TopoDS_Edge& edge, double chord_tol)
+{
+    if (BRep_Tool::Degenerated(edge))
+        return {};
+
+    BRepAdaptor_Curve curve(edge);
+    GCPnts_TangentialDeflection disc(curve, 0.1, chord_tol);
+
+    std::vector<Vec3d> pts;
+    if (disc.NbPoints() >= 2) {
+        for (int i = 1; i <= disc.NbPoints(); ++i) {
+            gp_Pnt p = disc.Value(i);
+            pts.emplace_back(p.X(), p.Y(), p.Z());
+        }
+    } else {
+        gp_Pnt p0 = curve.Value(curve.FirstParameter());
+        gp_Pnt p1 = curve.Value(curve.LastParameter());
+        pts.emplace_back(p0.X(), p0.Y(), p0.Z());
+        pts.emplace_back(p1.X(), p1.Y(), p1.Z());
+    }
+    return pts;
+}
+
+Vec3d GeometryEngine::face_centroid_world(const TopoDS_Face& face)
+{
+    GProp_GProps props;
+    BRepGProp::SurfaceProperties(face, props);
+    gp_Pnt c = props.CentreOfMass();
+    return Vec3d(c.X(), c.Y(), c.Z());
+}
+
+Vec3d GeometryEngine::face_normal_world(const TopoDS_Face& face)
+{
+    BRepAdaptor_Surface surf(face);
+    const double u = 0.5 * (surf.FirstUParameter() + surf.LastUParameter());
+    const double v = 0.5 * (surf.FirstVParameter() + surf.LastVParameter());
+    BRepLProp_SLProps props(surf, u, v, 1, 1e-6);
+    gp_Dir n(0.0, 0.0, 1.0);
+    if (props.IsNormalDefined()) n = props.Normal();
+    if (face.Orientation() == TopAbs_REVERSED) n.Reverse();   // outward (account for face winding)
+    return Vec3d(n.X(), n.Y(), n.Z());
+}
+
+GeometryEngine::CylinderFace GeometryEngine::cylinder_of_face(const TopoDS_Face& face)
+{
+    CylinderFace cf;
+    if (face.IsNull()) return cf;
+    BRepAdaptor_Surface surf(face);
+    if (surf.GetType() != GeomAbs_Cylinder) return cf;
+
+    const gp_Cylinder cyl = surf.Cylinder();
+    const gp_Ax1      ax  = cyl.Axis();
+    const Vec3d axis(ax.Direction().X(), ax.Direction().Y(), ax.Direction().Z());
+    const Vec3d apt (ax.Location().X(),  ax.Location().Y(),  ax.Location().Z());
+    cf.radius = cyl.Radius();
+
+    // Axial extent: V is the axial parameter on a cylinder; bound the face's two ends and
+    // order them so `axis` points base -> top.
+    const double umid = 0.5 * (surf.FirstUParameter() + surf.LastUParameter());
+    const gp_Pnt e0 = surf.Value(umid, surf.FirstVParameter());
+    const gp_Pnt e1 = surf.Value(umid, surf.LastVParameter());
+    double t0 = (Vec3d(e0.X(), e0.Y(), e0.Z()) - apt).dot(axis);
+    double t1 = (Vec3d(e1.X(), e1.Y(), e1.Z()) - apt).dot(axis);
+    if (t1 < t0) std::swap(t0, t1);
+    cf.base   = apt + axis * t0;
+    cf.axis   = axis;
+    cf.height = t1 - t0;
+
+    // Internal (bore) vs external: compare the face's outward normal at its centre to the
+    // outward radial direction. A bore's normal points toward the axis (dot < 0).
+    const gp_Pnt sp = surf.Value(umid, 0.5 * (surf.FirstVParameter() + surf.LastVParameter()));
+    const Vec3d  S(sp.X(), sp.Y(), sp.Z());
+    const Vec3d  axpt   = cf.base + axis * (S - cf.base).dot(axis);
+    const Vec3d  radial = (S - axpt).normalized();
+    cf.internal = face_normal_world(face).dot(radial) < 0.0;
+    cf.ok = true;
+    return cf;
+}
+
+GeometryEngine::CylinderFace GeometryEngine::circle_of_edge(const TopoDS_Edge& edge)
+{
+    CylinderFace cf;
+    if (edge.IsNull()) return cf;
+    BRepAdaptor_Curve curve(edge);
+    if (curve.GetType() != GeomAbs_Circle) return cf;
+    const gp_Circ c  = curve.Circle();
+    const gp_Ax1  ax = c.Axis();
+    cf.base     = Vec3d(c.Location().X(), c.Location().Y(), c.Location().Z());
+    cf.axis     = Vec3d(ax.Direction().X(), ax.Direction().Y(), ax.Direction().Z());
+    cf.radius   = c.Radius();
+    cf.height   = 0.0;       // an edge carries no axial extent; the card keeps the current length
+    cf.internal = false;     // ambiguous from an edge alone — default external, user can toggle
+    cf.ok       = true;
+    return cf;
+}
+
+bool GeometryEngine::face_plane_bounds(const TopoDS_Face& face, const Vec3d& origin,
+                                       const Vec3d& x_axis, const Vec3d& y_axis,
+                                       double& umin, double& umax, double& vmin, double& vmax)
+{
+    umin = vmin = 1e30; umax = vmax = -1e30;
+    bool any = false;
+    for (TopExp_Explorer ex(face, TopAbs_VERTEX); ex.More(); ex.Next()) {
+        const gp_Pnt p = BRep_Tool::Pnt(TopoDS::Vertex(ex.Current()));
+        const Vec3d P(p.X(), p.Y(), p.Z());
+        const double u = (P - origin).dot(x_axis);
+        const double v = (P - origin).dot(y_axis);
+        umin = std::min(umin, u); umax = std::max(umax, u);
+        vmin = std::min(vmin, v); vmax = std::max(vmax, v);
+        any = true;
+    }
+    return any;
+}
+
+int GeometryEngine::edge_count(const TopoDS_Shape& shape)
+{
+    TopTools_IndexedMapOfShape map;
+    TopExp::MapShapes(shape, TopAbs_EDGE, map);
+    return map.Extent();
+}
+
+TopoDS_Edge GeometryEngine::edge_by_index(const TopoDS_Shape& shape, int index)
+{
+    TopTools_IndexedMapOfShape map;
+    TopExp::MapShapes(shape, TopAbs_EDGE, map);
+    if (index < 0 || index >= map.Extent())
+        return TopoDS_Edge();
+    return TopoDS::Edge(map(index + 1));
+}
+
+int GeometryEngine::edge_index_of(const TopoDS_Shape& shape, const TopoDS_Edge& edge)
+{
+    TopTools_IndexedMapOfShape map;
+    TopExp::MapShapes(shape, TopAbs_EDGE, map);
+    int idx = map.FindIndex(edge);
+    return (idx > 0) ? (idx - 1) : -1;
+}
+
+} // namespace Slic3r
diff --git a/src/libslic3r/CAD/GeometryEngine.hpp b/src/libslic3r/CAD/GeometryEngine.hpp
new file mode 100644
index 0000000000..f27a0f2f17
--- /dev/null
+++ b/src/libslic3r/CAD/GeometryEngine.hpp
@@ -0,0 +1,183 @@
+#ifndef slic3r_GeometryEngine_hpp_
+#define slic3r_GeometryEngine_hpp_
+
+#include "libslic3r/TriangleMesh.hpp"
+
+#include <BRepPrimAPI_MakeBox.hxx>
+#include <BRepPrimAPI_MakeCylinder.hxx>
+#include <BRepPrimAPI_MakeSphere.hxx>
+#include <BRepPrimAPI_MakeCone.hxx>
+#include <BRepPrimAPI_MakeTorus.hxx>
+#include <gp_Ax2.hxx>
+#include <TopoDS_Solid.hxx>
+#include <TopoDS_Face.hxx>
+#include <TopoDS_Edge.hxx>
+#include <vector>
+#include <string>
+
+namespace Slic3r {
+
+enum class PrimitiveType { Box, Cylinder, Sphere, Cone, Torus, COUNT };
+enum class DressUpType   { Fillet, Chamfer };
+enum class FaceGroup     { Top, Bottom, Lateral, All };
+
+struct PrimitiveParams {
+    PrimitiveType type{PrimitiveType::Box};
+    double box_w{20}, box_h{20}, box_d{20};
+    double cyl_radius{10}, cyl_height{20};
+    double sph_radius{10};
+    double cone_r1{10}, cone_r2{5}, cone_height{20};
+    double torus_r1{10}, torus_r2{3};
+
+    // Dress-up
+    bool   dressup_enabled{false};
+    DressUpType dressup_type{DressUpType::Fillet};
+    FaceGroup   dressup_faces{FaceGroup::All};
+    double dressup_radius{1.0};    // fillet radius
+    double dressup_chamfer_dist{1.0}; // chamfer distance (symmetric)
+
+    // Mesh quality
+    double linear_deflection{0.01};
+    double angular_deflection{0.5};
+
+    template<class Archive>
+    void serialize(Archive& ar) {
+        ar(type, box_w, box_h, box_d, cyl_radius, cyl_height, sph_radius,
+           cone_r1, cone_r2, cone_height, torus_r1, torus_r2,
+           dressup_enabled, dressup_type, dressup_faces, dressup_radius, dressup_chamfer_dist,
+           linear_deflection, angular_deflection);
+    }
+};
+
+class GeometryEngine
+{
+public:
+    static TopoDS_Solid make_primitive(const PrimitiveParams& params);
+
+    // Read a STEP file into its top-level solids (one TopoDS_Shape per solid; falls back to
+    // the whole shape if it contains no closed solids). Reuses OCCT's STEPControl_Reader,
+    // already linked via Format/STEP.cpp — no new dependency. err is set on failure (empty result).
+    static std::vector<TopoDS_Shape> read_step_solids(const std::string& path, std::string& err);
+
+    // Triangle mesh -> B-rep solid. Native port of mesh2step
+    // (github.com/tommasobbianchi/mesh2step): vertices and edges are SHARED across triangles
+    // at construction time (vertex cache by deduped index, edge cache by unordered index pair),
+    // so there is no BRepBuilderAPI_Sewing pass to reconstruct topology afterwards — which is
+    // both faster and what makes watertightness fall out of the edge-usage counts for free.
+    // Runs in-process on the OCCT kernel libslic3r already links: no STEP file is written or
+    // re-read (a faceted STEP of a 62k-triangle mesh is ~149 MB and takes OCCT's reader >300 s
+    // to parse back, so routing the Design tab through a file would hang the GUI).
+    struct MeshBrepStats {
+        int    input_tris{0};
+        int    kept_tris{0};
+        int    degenerate_collapsed{0};  // <3 distinct vertices after tolerance quantization
+        int    degenerate_sliver{0};     // 3 distinct vertices but near-collinear
+        int    faces_built{0};
+        int    faces_failed{0};
+        int    unique_edges{0};
+        int    boundary_edges{0};        // used by exactly 1 triangle -> open shell
+        int    nonmanifold_edges{0};     // used by >=3 triangles
+        bool   watertight{false};        // every edge used exactly twice
+        bool   is_solid{false};          // watertight AND MakeSolid gave a positive volume
+        double volume{0.0};
+        int    faces_final{0};           // after the optional coplanar merge
+    };
+    // tolerance: spatial quantization cell used ONLY for vertex dedup and as the
+    //   sub-resolution floor below which a triangle is noise. Never a sew tolerance.
+    // merge_angle_deg > 0: run ShapeUpgrade_UnifySameDomain to merge coplanar neighbours into
+    //   single faces (a 12-triangle cube -> 6 pickable faces). This is what makes the imported
+    //   body editable with the face/edge tools; <= 0 keeps the exact one-face-per-triangle form.
+    // Never wraps a non-watertight shell as a fake solid: an open mesh comes back as a shell,
+    // with the reason (boundary / non-manifold edge counts) reported in stats.
+    static TopoDS_Shape mesh_to_brep(const indexed_triangle_set& its,
+                                     double tolerance,
+                                     double merge_angle_deg,
+                                     MeshBrepStats& stats);
+
+    struct MassProps {
+        double volume{0.0};
+        double surface_area{0.0};
+        Vec3d  center_of_mass{Vec3d::Zero()};
+        std::array<double, 9> inertia{};
+        bool   valid{false};
+        // False for a sheet body (an open shell with no solid). Volume and inertia are then
+        // meaningless and are reported as zero; surface_area stays meaningful. See the .cpp.
+        bool   is_solid{false};
+    };
+    static MassProps mass_properties(const TopoDS_Shape& shape);
+
+    struct Deviation { double max_mm{0}; double mean_mm{0}; double rms_mm{0}; int sample_count{0}; };
+    static Deviation surface_deviation(const TopoDS_Shape& candidate,
+                                       const TopoDS_Shape& reference,
+                                       double linear_deflection = 0.5);
+
+    static TopoDS_Shape apply_fillet(const TopoDS_Shape& solid, double radius,
+                                     FaceGroup faces = FaceGroup::All);
+    static TopoDS_Shape apply_fillet(const TopoDS_Shape& solid, double radius,
+                                     int edge_id);
+    static TopoDS_Shape apply_chamfer(const TopoDS_Shape& solid, double distance,
+                                       FaceGroup faces = FaceGroup::All);
+    static TopoDS_Shape apply_chamfer(const TopoDS_Shape& solid, double distance,
+                                       int edge_id);
+
+    static TriangleMesh tessellate(const TopoDS_Shape& shape,
+                                   double linear_deflection = 0.01,
+                                   double angular_deflection = 0.5);
+    static std::string  primitive_name(PrimitiveType type);
+
+    // Topology accessors for in-viewport face/edge picking (Design tab). Face index is the
+    // TopExp_Explorer(shape, TopAbs_FACE) ordinal — identical to SketchEngine::tessellate's
+    // per-triangle face id, so a picked triangle's id maps back to a face here.
+    static TopoDS_Face face_by_index(const TopoDS_Shape& shape, int index);  // null if out of range
+    static int         face_count(const TopoDS_Shape& shape);
+    // Bulk enumeration in the SAME order as face_by_index / edge_by_index, so ids are
+    // interchangeable. Walking a body with the _by_index accessors is quadratic (each call
+    // rescans the shape — edge_by_index even rebuilds the whole indexed map), which cost
+    // ~15 s on a 4.7k-face imported solid; enumerate once instead.
+    static std::vector<TopoDS_Face> faces_of(const TopoDS_Shape& shape);
+    static std::vector<TopoDS_Edge> edges_of(const TopoDS_Shape& shape);
+    static std::vector<TopoDS_Edge> edges_of_face(const TopoDS_Face& face);
+    // Centre of mass (world) of a face — used to compute the extrude length for "up to face".
+    static Vec3d face_centroid_world(const TopoDS_Face& face);
+    // Outward unit normal of a face at its UV midpoint (orientation-aware) — for the shell gizmo.
+    static Vec3d face_normal_world(const TopoDS_Face& face);
+    // Sample an edge into a world-space polyline (>=2 pts) for pick-distance + highlight.
+    static std::vector<Vec3d> sample_edge_world(const TopoDS_Edge& edge, double chord_tol = 0.05);
+    // 0-based edge index into TopExp::MapShapes(shape, TopAbs_EDGE, map).
+    static int          edge_count(const TopoDS_Shape& shape);
+    static TopoDS_Edge  edge_by_index(const TopoDS_Shape& shape, int index);
+    static int          edge_index_of(const TopoDS_Shape& shape, const TopoDS_Edge& edge);
+
+    // Analysis of a cylindrical face for the Thread tool (a hole bore or a cylinder's lateral
+    // surface): axis (base at the lower axial end + unit direction), radius, axial extent, and
+    // whether it is a bore (face normal points toward the axis = internal thread). ok=false if
+    // the face is not a cylinder.
+    struct CylinderFace {
+        bool   ok{false};
+        Vec3d  base{0, 0, 0};
+        Vec3d  axis{0, 0, 1};
+        double radius{0};
+        double height{0};
+        bool   internal{false};
+    };
+    static CylinderFace cylinder_of_face(const TopoDS_Face& face);
+    // Circular edge (a cylinder's perimeter): base = circle centre, axis = circle normal,
+    // radius = circle radius, height = 0 (unknown from an edge), internal = false. ok=false if
+    // the edge is not a circle. Lets the Thread tool be driven by a picked circular rim.
+    static CylinderFace circle_of_edge(const TopoDS_Edge& edge);
+
+    // Plane-coordinate (u,v) bounding box of a face's vertices, measured from `origin` along
+    // `x_axis`/`y_axis`. Lets the Hole tool dimension the hole from the face SIDES (umin/vmin =
+    // two adjacent edges) instead of from the centre. Returns false if the face has no vertices.
+    static bool face_plane_bounds(const TopoDS_Face& face, const Vec3d& origin,
+                                  const Vec3d& x_axis, const Vec3d& y_axis,
+                                  double& umin, double& umax, double& vmin, double& vmax);
+
+private:
+    static std::vector<TopoDS_Edge> collect_edges(const TopoDS_Shape& solid, FaceGroup faces);
+    static FaceGroup classify_face(const TopoDS_Face& face, const TopoDS_Shape& solid);
+};
+
+} // namespace Slic3r
+
+#endif // slic3r_GeometryEngine_hpp_
diff --git a/src/libslic3r/CAD/SketchConstraints.cpp b/src/libslic3r/CAD/SketchConstraints.cpp
new file mode 100644
index 0000000000..003afb4d63
--- /dev/null
+++ b/src/libslic3r/CAD/SketchConstraints.cpp
@@ -0,0 +1,307 @@
+#include "libslic3r/CAD/SketchConstraints.hpp"
+#include <Eigen/Dense>
+#include <cmath>
+
+namespace Slic3r {
+
+int SketchConstraints::add_point(double x, double y)
+{
+    m_vars.push_back(x);
+    m_vars.push_back(y);
+    return static_cast<int>(m_vars.size() / 2) - 1;
+}
+
+void SketchConstraints::set_point(int id, double x, double y)
+{
+    size_t idx = 2 * id;
+    m_vars[idx]     = x;
+    m_vars[idx + 1] = y;
+}
+
+Vec2d SketchConstraints::get_point(int id) const
+{
+    size_t idx = 2 * id;
+    return Vec2d(m_vars[idx], m_vars[idx + 1]);
+}
+
+int SketchConstraints::point_count() const
+{
+    return static_cast<int>(m_vars.size() / 2);
+}
+
+void SketchConstraints::fix_point(int id)
+{
+    size_t idx = 2 * id;
+    Con c;
+    c.type = FIX_POINT;
+    c.a    = id;
+    c.b = c.c = c.d = 0;
+    c.k0   = m_vars[idx];
+    c.k1   = m_vars[idx + 1];
+    m_cons.push_back(c);
+}
+
+void SketchConstraints::coincident(int a, int b)
+{
+    Con c;
+    c.type = COINCIDENT;
+    c.a = a; c.b = b; c.c = c.d = 0;
+    c.k0 = c.k1 = 0;
+    m_cons.push_back(c);
+}
+
+void SketchConstraints::horizontal(int a, int b)
+{
+    Con c;
+    c.type = HORIZONTAL;
+    c.a = a; c.b = b; c.c = c.d = 0;
+    c.k0 = c.k1 = 0;
+    m_cons.push_back(c);
+}
+
+void SketchConstraints::vertical(int a, int b)
+{
+    Con c;
+    c.type = VERTICAL;
+    c.a = a; c.b = b; c.c = c.d = 0;
+    c.k0 = c.k1 = 0;
+    m_cons.push_back(c);
+}
+
+void SketchConstraints::distance(int a, int b, double d)
+{
+    Con c;
+    c.type = DISTANCE;
+    c.a = a; c.b = b; c.c = c.d = 0;
+    c.k0 = d; c.k1 = 0;
+    m_cons.push_back(c);
+}
+
+void SketchConstraints::lock_x(int id, double x)
+{
+    Con c;
+    c.type = LOCK_X;
+    c.a = id;
+    c.b = c.c = c.d = 0;
+    c.k0 = x; c.k1 = 0;
+    m_cons.push_back(c);
+}
+
+void SketchConstraints::lock_y(int id, double y)
+{
+    Con c;
+    c.type = LOCK_Y;
+    c.a = id;
+    c.b = c.c = c.d = 0;
+    c.k0 = y; c.k1 = 0;
+    m_cons.push_back(c);
+}
+
+void SketchConstraints::equal_length(int a, int b, int c, int d)
+{
+    Con con;
+    con.type = EQUAL_LENGTH;
+    con.a = a; con.b = b; con.c = c; con.d = d;
+    con.k0 = con.k1 = 0;
+    m_cons.push_back(con);
+}
+
+void SketchConstraints::parallel(int a, int b, int c, int d)
+{
+    Con con;
+    con.type = PARALLEL;
+    con.a = a; con.b = b; con.c = c; con.d = d;
+    con.k0 = con.k1 = 0;
+    m_cons.push_back(con);
+}
+
+void SketchConstraints::perpendicular(int a, int b, int c, int d)
+{
+    Con con;
+    con.type = PERPENDICULAR;
+    con.a = a; con.b = b; con.c = c; con.d = d;
+    con.k0 = con.k1 = 0;
+    m_cons.push_back(con);
+}
+
+void SketchConstraints::midpoint(int m, int a, int b)
+{
+    Con con;
+    con.type = MIDPOINT;
+    con.a = m; con.b = a; con.c = b; con.d = -1;
+    con.k0 = con.k1 = 0;
+    m_cons.push_back(con);
+}
+
+void SketchConstraints::symmetric(int a, int b, int c, int d)
+{
+    Con con;
+    con.type = SYMMETRIC;
+    con.a = a; con.b = b; con.c = c; con.d = d;
+    con.k0 = con.k1 = 0;
+    m_cons.push_back(con);
+}
+
+void SketchConstraints::angle(int a, int b, int c, int d, double radians)
+{
+    Con con;
+    con.type = ANGLE;
+    con.a = a; con.b = b; con.c = c; con.d = d;
+    con.k0 = radians; con.k1 = 0;
+    m_cons.push_back(con);
+}
+
+void SketchConstraints::point_line_distance(int p, int a, int b, double dist)
+{
+    Con con;
+    con.type = PT_LINE_DIST;
+    con.a = p; con.b = a; con.c = b; con.d = -1;
+    con.k0 = dist; con.k1 = 0;
+    m_cons.push_back(con);
+}
+
+Eigen::VectorXd SketchConstraints::residuals(const std::vector<double>& v) const
+{
+    auto X = [&](int i) { return v[2 * i]; };
+    auto Y = [&](int i) { return v[2 * i + 1]; };
+
+    std::vector<double> res;
+    for (const auto& c : m_cons) {
+        switch (c.type) {
+        case FIX_POINT:
+            res.push_back(X(c.a) - c.k0);
+            res.push_back(Y(c.a) - c.k1);
+            break;
+        case COINCIDENT:
+            res.push_back(X(c.a) - X(c.b));
+            res.push_back(Y(c.a) - Y(c.b));
+            break;
+        case HORIZONTAL:
+            res.push_back(Y(c.a) - Y(c.b));
+            break;
+        case VERTICAL:
+            res.push_back(X(c.a) - X(c.b));
+            break;
+        case DISTANCE:
+            res.push_back(std::hypot(X(c.a) - X(c.b), Y(c.a) - Y(c.b)) - c.k0);
+            break;
+        case LOCK_X:
+            res.push_back(X(c.a) - c.k0);
+            break;
+        case LOCK_Y:
+            res.push_back(Y(c.a) - c.k0);
+            break;
+        case EQUAL_LENGTH:
+            res.push_back(std::hypot(X(c.a) - X(c.b), Y(c.a) - Y(c.b)) -
+                          std::hypot(X(c.c) - X(c.d), Y(c.c) - Y(c.d)));
+            break;
+        case PARALLEL:
+            res.push_back((X(c.b) - X(c.a)) * (Y(c.d) - Y(c.c)) -
+                          (Y(c.b) - Y(c.a)) * (X(c.d) - X(c.c)));
+            break;
+        case PERPENDICULAR:
+            res.push_back((X(c.b) - X(c.a)) * (X(c.d) - X(c.c)) +
+                          (Y(c.b) - Y(c.a)) * (Y(c.d) - Y(c.c)));
+            break;
+        case MIDPOINT:
+            res.push_back(X(c.a) - 0.5 * (X(c.b) + X(c.c)));
+            res.push_back(Y(c.a) - 0.5 * (Y(c.b) + Y(c.c)));
+            break;
+        case SYMMETRIC: {
+            const double abx = X(c.b) - X(c.a), aby = Y(c.b) - Y(c.a);
+            const double cdx = X(c.d) - X(c.c), cdy = Y(c.d) - Y(c.c);
+            res.push_back(abx * cdx + aby * cdy);
+            const double mx = 0.5 * (X(c.a) + X(c.b));
+            const double my = 0.5 * (Y(c.a) + Y(c.b));
+            res.push_back((mx - X(c.c)) * cdy - (my - Y(c.c)) * cdx);
+            break;
+        }
+        case ANGLE: {
+            const double ux = X(c.b) - X(c.a), uy = Y(c.b) - Y(c.a);
+            const double wx = X(c.d) - X(c.c), wy = Y(c.d) - Y(c.c);
+            const double cross = ux * wy - uy * wx;
+            const double dot   = ux * wx + uy * wy;
+            res.push_back(std::atan2(cross, dot) - c.k0);
+            break;
+        }
+        case PT_LINE_DIST: {
+            const double bx = X(c.b), by = Y(c.b);
+            const double cx = X(c.c), cy = Y(c.c);
+            const double L  = std::hypot(cx - bx, cy - by);
+            const double num = (X(c.a) - bx) * (cy - by) - (Y(c.a) - by) * (cx - bx);
+            res.push_back((L > 1e-12 ? std::abs(num) / L : 0.0) - c.k0);
+            break;
+        }
+        }
+    }
+
+    Eigen::VectorXd r(static_cast<Eigen::Index>(res.size()));
+    for (size_t i = 0; i < res.size(); ++i)
+        r(static_cast<Eigen::Index>(i)) = res[i];
+    return r;
+}
+
+Eigen::MatrixXd SketchConstraints::jacobian(const std::vector<double>& v) const
+{
+    int m = static_cast<int>(residuals(v).size());
+    int n = static_cast<int>(v.size());
+    Eigen::MatrixXd J(m, n);
+    const double eps = 1e-7;
+
+    std::vector<double> vp = v;
+    std::vector<double> vm = v;
+
+    for (int j = 0; j < n; ++j) {
+        vp[j] = v[j] + eps;
+        vm[j] = v[j] - eps;
+        Eigen::VectorXd rp = residuals(vp);
+        Eigen::VectorXd rm = residuals(vm);
+        vp[j] = v[j];
+        vm[j] = v[j];
+        J.col(j) = (rp - rm) / (2.0 * eps);
+    }
+
+    return J;
+}
+
+bool SketchConstraints::solve(int max_iter, double tol)
+{
+    if (m_cons.empty()) return true;
+    double lambda = 1e-3;
+    Eigen::VectorXd r = residuals(m_vars);
+    for (int it = 0; it < max_iter; ++it) {
+        double rn = r.norm();
+        if (rn < tol) return true;
+        Eigen::MatrixXd J = jacobian(m_vars);
+        Eigen::MatrixXd A = J.transpose() * J;
+        Eigen::VectorXd g = J.transpose() * r;
+        bool stepped = false;
+        for (int t = 0; t < 12; ++t) {
+            Eigen::MatrixXd Ad = A;
+            for (int i = 0; i < Ad.rows(); ++i)
+                Ad(i, i) += lambda * (1.0 + Ad(i, i));
+            Eigen::VectorXd dx = Ad.ldlt().solve(-g);
+            std::vector<double> cand = m_vars;
+            for (size_t i = 0; i < cand.size(); ++i)
+                cand[i] += dx[static_cast<Eigen::Index>(i)];
+            Eigen::VectorXd rc = residuals(cand);
+            if (rc.norm() < rn) {
+                m_vars = cand;
+                r      = rc;
+                lambda = std::max(lambda * 0.4, 1e-12);
+                stepped = true;
+                break;
+            }
+            lambda *= 3.0;
+        }
+        if (!stepped) break;
+    }
+    return r.norm() < tol * 100;
+}
+
+double SketchConstraints::residual_norm() const
+{
+    return residuals(m_vars).norm();
+}
+
+} // namespace Slic3r
diff --git a/src/libslic3r/CAD/SketchConstraints.hpp b/src/libslic3r/CAD/SketchConstraints.hpp
new file mode 100644
index 0000000000..88bcadc403
--- /dev/null
+++ b/src/libslic3r/CAD/SketchConstraints.hpp
@@ -0,0 +1,68 @@
+#ifndef slic3r_SketchConstraints_hpp_
+#define slic3r_SketchConstraints_hpp_
+
+#include "libslic3r/Point.hpp"
+#include <vector>
+#include <Eigen/Dense>
+
+namespace Slic3r {
+
+class SketchConstraints {
+public:
+    int   add_point(double x, double y);
+    void  set_point(int id, double x, double y);
+    Vec2d get_point(int id) const;
+    int   point_count() const;
+
+    void fix_point(int id);
+    void coincident(int a, int b);
+    void horizontal(int a, int b);
+    void vertical(int a, int b);
+    void distance(int a, int b, double d);
+    void lock_x(int id, double x);
+    void lock_y(int id, double y);
+    void equal_length(int a, int b, int c, int d);
+    void parallel(int a, int b, int c, int d);
+    void perpendicular(int a, int b, int c, int d);
+    void midpoint(int m, int a, int b);
+    void symmetric(int a, int b, int c, int d);
+    void angle(int a, int b, int c, int d, double radians);
+    void point_line_distance(int p, int a, int b, double dist);
+
+    bool   solve(int max_iter = 200, double tol = 1e-10);
+    double residual_norm() const;
+
+private:
+    std::vector<double> m_vars;
+
+    enum ConType : int {
+        FIX_POINT = 0,
+        COINCIDENT,
+        HORIZONTAL,
+        VERTICAL,
+        DISTANCE,
+        LOCK_X,
+        LOCK_Y,
+        EQUAL_LENGTH,
+        PARALLEL,
+        PERPENDICULAR,
+        MIDPOINT,
+        SYMMETRIC,
+        ANGLE,
+        PT_LINE_DIST
+    };
+
+    struct Con {
+        int    type;
+        int    a, b, c, d;
+        double k0, k1;
+    };
+    std::vector<Con> m_cons;
+
+    Eigen::VectorXd residuals(const std::vector<double>& v) const;
+    Eigen::MatrixXd jacobian(const std::vector<double>& v) const;
+};
+
+} // namespace Slic3r
+
+#endif // slic3r_SketchConstraints_hpp_
diff --git a/src/libslic3r/CAD/SketchEngine.cpp b/src/libslic3r/CAD/SketchEngine.cpp
new file mode 100644
index 0000000000..5cc36ce648
--- /dev/null
+++ b/src/libslic3r/CAD/SketchEngine.cpp
@@ -0,0 +1,2361 @@
+#include "libslic3r/CAD/SketchEngine.hpp"
+
+#include <algorithm>
+#include <cmath>
+#include <limits>
+
+#include <BRepBuilderAPI_MakeWire.hxx>
+#include <BRepBuilderAPI_MakeVertex.hxx>
+#include <BRepBuilderAPI_MakeEdge.hxx>
+#include <BRepBuilderAPI_MakeFace.hxx>
+#include <BRepGProp.hxx>
+#include <GProp_GProps.hxx>
+#include <BRepClass_FaceClassifier.hxx>
+#include <TopoDS_Vertex.hxx>
+#include <GC_MakeArcOfCircle.hxx>
+#include <GC_MakeArcOfEllipse.hxx>
+#include <Geom_TrimmedCurve.hxx>
+#include <Geom_BSplineCurve.hxx>
+#include <TColgp_Array1OfPnt.hxx>
+#include <TColStd_Array1OfReal.hxx>
+#include <TColStd_Array1OfInteger.hxx>
+#include <gp_Circ.hxx>
+#include <gp_Elips.hxx>
+#include <gp_Ax2.hxx>
+#include <gp_Pln.hxx>
+#include <BRepPrimAPI_MakePrism.hxx>
+#include <BRepOffsetAPI_MakeOffset.hxx>
+#include <BRepOffsetAPI_ThruSections.hxx>
+#include <BRepBuilderAPI_Transform.hxx>
+#include <BRepPrimAPI_MakeRevol.hxx>
+#include <BRepOffsetAPI_MakePipe.hxx>
+#include <BRepAlgoAPI_Fuse.hxx>
+#include <BRepAlgoAPI_Cut.hxx>
+#include <BRepAdaptor_Surface.hxx>
+#include <BRepMesh_IncrementalMesh.hxx>
+#include <BRep_Tool.hxx>
+#include <Poly_Triangulation.hxx>
+#include <TopExp_Explorer.hxx>
+#include <TopoDS.hxx>
+#include <TopoDS_Compound.hxx>
+#include <BRep_Builder.hxx>
+#include <ShapeFix_Face.hxx>
+#include <GeomAbs_Shape.hxx>
+#include <Standard_Failure.hxx>
+#include <Precision.hxx>
+#include <TopoDS_Face.hxx>
+#include <TopoDS_Wire.hxx>
+#include <GeomAPI_IntCS.hxx>
+#include <map>
+#include <tuple>
+#include <stdexcept>
+
+namespace Slic3r {
+
+// Single source of truth for the weld tolerance the viewport and the kernel share.
+// Defaults ON so headless/kernel-only callers keep welding; the GUI pushes the
+// "auto_close_sketch_loops" preference in via set_sketch_auto_close().
+static bool s_auto_close = true;
+
+double sketch_join_tol() { return s_auto_close ? kSketchJoinTol : 0.0; }
+void   set_sketch_auto_close(bool on) { s_auto_close = on; }
+
+// ---- SketchPlane ----
+
+gp_Pln SketchPlane::to_occt() const
+{
+    gp_Pnt o(origin.x(), origin.y(), origin.z());
+    gp_Dir n(normal.x(), normal.y(), normal.z());
+    gp_Dir x(x_axis.x(), x_axis.y(), x_axis.z());
+    return gp_Pln(gp_Ax3(o, n, x));
+}
+
+SketchPlane SketchPlane::from_face(const TopoDS_Face& face)
+{
+    SketchPlane sp;
+    // Use the first triangulation vertex + face normal
+    TopLoc_Location loc;
+    Handle(Poly_Triangulation) tri = BRep_Tool::Triangulation(face, loc);
+    if (!tri.IsNull() && tri->NbNodes() > 0) {
+        gp_Pnt p = tri->Node(1).Transformed(loc.Transformation());
+        sp.origin = Vec3d(p.X(), p.Y(), p.Z());
+    }
+    // Compute normal from BRep face
+    BRepAdaptor_Surface surf(face);
+    if (surf.GetType() != GeomAbs_Plane) {
+        // Fallback: try to use the first uv point
+        double u1 = surf.FirstUParameter(), v1 = surf.FirstVParameter();
+        gp_Pnt pt; gp_Vec du, dv;
+        surf.D1(u1, v1, pt, du, dv);
+        gp_Dir n = gp_Dir(du.Crossed(dv));
+        sp.normal = Vec3d(n.X(), n.Y(), n.Z());
+        sp.x_axis = Vec3d(du.X(), du.Y(), du.Z()).normalized();
+        sp.y_axis = sp.normal.cross(sp.x_axis).normalized();
+        return sp;
+    }
+    // Plane face — use the plane directly
+    gp_Pln pln = surf.Plane();
+    sp.origin = Vec3d(pln.Location().X(), pln.Location().Y(), pln.Location().Z());
+    gp_Dir n = pln.Axis().Direction();
+    sp.normal = Vec3d(n.X(), n.Y(), n.Z());
+    gp_Dir xd = pln.XAxis().Direction();
+    sp.x_axis = Vec3d(xd.X(), xd.Y(), xd.Z());
+    sp.y_axis = sp.normal.cross(sp.x_axis).normalized();
+    return sp;
+}
+
+Vec2d SketchPlane::project(const Vec3d& ray_origin, const Vec3d& ray_dir) const
+{
+    double denom = ray_dir.dot(normal);
+    if (std::abs(denom) < 1e-12)
+        return {0, 0}; // ray parallel to plane
+    double t = (origin - ray_origin).dot(normal) / denom;
+    if (t < 0)
+        return {0, 0}; // behind camera
+    Vec3d hit = ray_origin + t * ray_dir;
+    Vec3d local = hit - origin;
+    return {local.dot(x_axis), local.dot(y_axis)};
+}
+
+Vec3d SketchPlane::to_world(const Vec2d& pt) const
+{
+    return origin + x_axis * pt.x() + y_axis * pt.y();
+}
+
+// ---- SketchProfile ----
+
+bool SketchProfile::is_closed(double tolerance) const
+{
+    if (points.size() < 3) return false;
+    return (points.front() - points.back()).norm() < tolerance;
+}
+
+bool SketchProfile::try_close(double tolerance)
+{
+    if (is_closed(tolerance)) {
+        closed = true;
+        return true;
+    }
+    if (points.size() < 2) return false;
+    if ((points.front() - points.back()).norm() < tolerance) {
+        closed = true;
+        return true;
+    }
+    return false;
+}
+
+TopoDS_Wire SketchProfile::to_occt_wire(const SketchPlane& plane) const
+{
+    if (points.size() < 2)
+        throw std::runtime_error("Profile has fewer than 2 points");
+
+    BRepBuilderAPI_MakeWire builder;
+    for (size_t i = 0; i < points.size(); ++i) {
+        Vec3d a3 = plane.to_world(points[i]);
+        Vec3d b3 = plane.to_world(points[(i + 1) % points.size()]);
+        gp_Pnt pa(a3.x(), a3.y(), a3.z());
+        gp_Pnt pb(b3.x(), b3.y(), b3.z());
+        builder.Add(BRepBuilderAPI_MakeEdge(pa, pb).Edge());
+    }
+    builder.Build();
+    if (!builder.IsDone())
+        throw std::runtime_error("Failed to build wire from profile");
+    return builder.Wire();
+}
+
+// ---- SketchEngine ----
+
+static TopoDS_Shape extrude_face_internal(const TopoDS_Face& face, const gp_Dir& dir, double length, bool symmetric)
+{
+    gp_Vec vec = gp_Vec(dir) * length;
+    if (symmetric) {
+        gp_Vec halfVec = gp_Vec(dir) * (length / 2.0);
+        BRepPrimAPI_MakePrism pos(face, halfVec);
+        BRepPrimAPI_MakePrism neg(face, -halfVec);
+        if (!pos.IsDone() || !neg.IsDone()) throw std::runtime_error("Symmetric extrude failed");
+        BRepAlgoAPI_Fuse fuse(pos.Shape(), neg.Shape());
+        if (!fuse.IsDone()) throw std::runtime_error("Fuse failed");
+        return fuse.Shape();
+    }
+    BRepPrimAPI_MakePrism prism(face, vec);
+    if (!prism.IsDone()) throw std::runtime_error("Extrude failed");
+    return prism.Shape();
+}
+
+TopoDS_Shape SketchEngine::make_extrude(const TopoDS_Wire& wire, const SketchPlane& plane,
+                                        double length, bool symmetric, double taper_deg)
+{
+    BRepBuilderAPI_MakeFace fm(wire);
+    if (!fm.IsDone()) throw std::runtime_error("Failed to make face from wire");
+    return make_extrude(fm.Face(), plane, length, symmetric, taper_deg);
+}
+
+TopoDS_Shape SketchEngine::make_extrude(const TopoDS_Face& face, const SketchPlane& plane,
+                                        double length, bool symmetric, double /*taper_deg*/)
+{
+    gp_Dir dir(plane.normal.x(), plane.normal.y(), plane.normal.z());
+    return extrude_face_internal(face, dir, length, symmetric);
+}
+
+TopoDS_Shape SketchEngine::make_extrude_two_sided(const TopoDS_Wire& wire, const SketchPlane& plane,
+                                                  double up, double down)
+{
+    BRepBuilderAPI_MakeFace fm(wire);
+    if (!fm.IsDone()) throw std::runtime_error("Failed to make face from wire");
+    return make_extrude_two_sided(fm.Face(), plane, up, down);
+}
+
+TopoDS_Shape SketchEngine::make_extrude_two_sided(const TopoDS_Face& face, const SketchPlane& plane,
+                                                  double up, double down)
+{
+    gp_Dir dir(plane.normal.x(), plane.normal.y(), plane.normal.z());
+    const double u = std::abs(up), d = std::abs(down);
+    if (u < 1e-9 && d < 1e-9) return TopoDS_Shape();
+    if (d < 1e-9) { BRepPrimAPI_MakePrism p(face, gp_Vec(dir) *  u); return p.Shape(); }
+    if (u < 1e-9) { BRepPrimAPI_MakePrism p(face, gp_Vec(dir) * -d); return p.Shape(); }
+    BRepPrimAPI_MakePrism pos(face, gp_Vec(dir) *  u);
+    BRepPrimAPI_MakePrism neg(face, gp_Vec(dir) * -d);
+    BRepAlgoAPI_Fuse fuse(pos.Shape(), neg.Shape());
+    if (!fuse.IsDone()) throw std::runtime_error("two-sided extrude fuse failed");
+    return fuse.Shape();
+}
+
+TopoDS_Shape SketchEngine::make_extrude_taper(const TopoDS_Wire& wire, const SketchPlane& plane,
+                                              double length, double taper_deg)
+{
+    gp_Dir dir(plane.normal.x(), plane.normal.y(), plane.normal.z());
+    auto straight = [&]() -> TopoDS_Shape {
+        BRepBuilderAPI_MakeFace fm(wire);
+        BRepPrimAPI_MakePrism prism(fm.Face(), gp_Vec(dir) * length);
+        return prism.Shape();
+    };
+    if (std::abs(taper_deg) >= 89.0 || std::abs(length) < 1e-9) return straight();
+    const double off = length * std::tan(taper_deg * M_PI / 180.0);
+    if (std::abs(off) < 1e-7) return straight();
+    try {
+        // 1) offset the planar base wire in its own plane by `off`
+        BRepOffsetAPI_MakeOffset mko(wire, GeomAbs_Arc);
+        mko.Perform(off);
+        if (!mko.IsDone()) return straight();
+        TopoDS_Shape offShape = mko.Shape();
+        TopoDS_Wire topFlat;
+        if (offShape.ShapeType() == TopAbs_WIRE) topFlat = TopoDS::Wire(offShape);
+        else { for (TopExp_Explorer ex(offShape, TopAbs_WIRE); ex.More(); ex.Next()) { topFlat = TopoDS::Wire(ex.Current()); break; } }
+        if (topFlat.IsNull()) return straight();
+        // 2) lift it along the normal by `length`
+        gp_Trsf tr; tr.SetTranslation(gp_Vec(dir) * length);
+        BRepBuilderAPI_Transform xf(topFlat, tr, Standard_True);
+        TopoDS_Wire topWire = TopoDS::Wire(xf.Shape());
+        // 3) loft base -> top into a solid
+        BRepOffsetAPI_ThruSections loft(Standard_True /*solid*/, Standard_False /*ruled*/);
+        loft.AddWire(wire);
+        loft.AddWire(topWire);
+        loft.Build();
+        if (!loft.IsDone()) return straight();
+        TopoDS_Shape s = loft.Shape();
+        if (s.IsNull()) return straight();
+        return s;
+    } catch (const Standard_Failure&) {
+        return straight();
+    }
+}
+
+TopoDS_Shape SketchEngine::make_extrude_face(const TopoDS_Face& face, const SketchPlane& plane,
+                                             double length, bool symmetric, double /*taper_deg*/)
+{
+    gp_Dir dir(plane.normal.x(), plane.normal.y(), plane.normal.z());
+    return extrude_face_internal(face, dir, length, symmetric);
+}
+
+TopoDS_Shape SketchEngine::make_extrude_regions(
+    const std::vector<std::vector<std::vector<Vec2d>>>& regions,
+    const SketchPlane& plane, double length, bool symmetric)
+{
+    // Drop consecutive coincident points and the closing duplicate. FreeType /
+    // SVG flattening routinely emits repeated points which would build a
+    // degenerate OCCT edge and make the wire builder throw — sanitising keeps a
+    // single bad glyph from killing the whole extrude.
+    auto clean = [](const std::vector<Vec2d>& pts) {
+        const double eps2 = 1e-12;   // ~1e-6 mm
+        std::vector<Vec2d> out;
+        out.reserve(pts.size());
+        for (const Vec2d& p : pts)
+            if (out.empty() || (p - out.back()).squaredNorm() > eps2)
+                out.push_back(p);
+        while (out.size() >= 2 && (out.front() - out.back()).squaredNorm() <= eps2)
+            out.pop_back();
+        return out;
+    };
+
+    // Build a closed planar wire from a contour. Never throws — returns a null
+    // wire on any failure so the caller can skip just that contour. Winding is
+    // NOT normalised here: ShapeFix_Face::FixOrientation() below classifies outer
+    // vs hole by geometry and fixes orientations, which is robust to the
+    // inconsistent winding Emboss/NSVG glyph contours arrive with (manual
+    // winding guesses extrude holed glyphs (P, e, o, 8) inverted or solid).
+    auto contour_wire = [&](const std::vector<Vec2d>& raw) -> TopoDS_Wire {
+        std::vector<Vec2d> pts = clean(raw);
+        if (pts.size() < 3) return TopoDS_Wire{};
+        SketchProfile prof;
+        prof.points = std::move(pts);
+        prof.closed = true;
+        try { return prof.to_occt_wire(plane); }
+        catch (...) { return TopoDS_Wire{}; }
+    };
+
+    gp_Dir dir(plane.normal.x(), plane.normal.y(), plane.normal.z());
+
+    // Accumulate each region's solid into a compound rather than boolean-fusing:
+    // glyphs are independent profiles, so a compound avoids every boolean-failure
+    // mode (and is faster). Holes are still handled per region by MakeFace.
+    BRep_Builder bb;
+    TopoDS_Compound comp;
+    bb.MakeCompound(comp);
+    int count = 0;
+    TopoDS_Shape last;
+
+    for (const auto& region : regions) {
+        if (region.empty()) continue;
+        try {
+            TopoDS_Wire outer = contour_wire(region[0]);
+            if (outer.IsNull()) continue;
+
+            // Add the outer loop + every hole loop as-is, then let ShapeFix_Face
+            // classify outer vs holes by area/containment and set correct wire
+            // orientations. This is winding-independent, so holed glyphs extrude
+            // with a solid body and empty counters regardless of source winding.
+            BRepBuilderAPI_MakeFace fm(outer);
+            if (!fm.IsDone()) continue;
+            for (size_t h = 1; h < region.size(); ++h) {
+                TopoDS_Wire hole = contour_wire(region[h]);
+                if (hole.IsNull()) continue;
+                fm.Add(hole);
+            }
+            if (!fm.IsDone()) continue;
+
+            ShapeFix_Face sff(fm.Face());
+            sff.FixOrientation();
+            const TopoDS_Face face = sff.Face();
+
+            TopoDS_Shape solid = extrude_face_internal(face, dir, length, symmetric);
+            bb.Add(comp, solid);
+            last = solid;
+            ++count;
+        } catch (...) {
+            continue;   // skip one bad glyph rather than fail the whole insert
+        }
+    }
+
+    if (count == 0) throw std::runtime_error("imported regions produced no extrudable geometry");
+    return count == 1 ? last : TopoDS_Shape(comp);   // avoid a compound-of-one
+}
+
+TopoDS_Shape SketchEngine::make_revolve(const TopoDS_Wire& wire, const SketchPlane& plane,
+                                        double angle_deg, int axis_sel)
+{
+    BRepBuilderAPI_MakeFace faceMaker(wire);
+    if (!faceMaker.IsDone())
+        throw std::runtime_error("Failed to make face from wire");
+    TopoDS_Face face = faceMaker.Face();
+
+    // Revolution axis lies in the sketch plane through its origin: X (0) or Y (1).
+    const Vec3d& adir = (axis_sel == 1) ? plane.y_axis : plane.x_axis;
+    gp_Pnt o(plane.origin.x(), plane.origin.y(), plane.origin.z());
+    gp_Dir xd(adir.x(), adir.y(), adir.z());
+    gp_Ax1 axis(o, xd);
+
+    double angle_rad = angle_deg * M_PI / 180.0;
+    // A negative angle is expressed as a positive sweep about the reversed axis,
+    // since BRepPrimAPI_MakeRevol expects an angle in (0, 2*pi].
+    if (angle_rad < 0) { axis.Reverse(); angle_rad = -angle_rad; }
+    BRepPrimAPI_MakeRevol rev(face, axis, angle_rad);
+    if (!rev.IsDone())
+        throw std::runtime_error("Failed to revolve");
+    return rev.Shape();
+}
+
+TopoDS_Shape SketchEngine::make_sweep(const TopoDS_Wire& profile, const TopoDS_Wire& path)
+{
+    BRepBuilderAPI_MakeFace faceMaker(profile);
+    if (!faceMaker.IsDone())
+        throw std::runtime_error("Failed to make face from sweep profile");
+    TopoDS_Face face = faceMaker.Face();
+
+    BRepOffsetAPI_MakePipe pipe(path, face);
+    pipe.Build();
+    if (!pipe.IsDone())
+        throw std::runtime_error("Failed to sweep profile along path");
+    return pipe.Shape();
+}
+
+TopoDS_Shape SketchEngine::make_loft(const std::vector<TopoDS_Wire>& profiles, bool ruled)
+{
+    if (profiles.size() < 2)
+        throw std::runtime_error("loft needs at least 2 profiles");
+    BRepOffsetAPI_ThruSections loft(Standard_True /*solid*/,
+                                    ruled ? Standard_True : Standard_False);
+    for (const TopoDS_Wire& w : profiles) {
+        if (w.IsNull()) throw std::runtime_error("loft: null profile wire");
+        loft.AddWire(w);
+    }
+    loft.Build();
+    if (!loft.IsDone()) throw std::runtime_error("loft failed");
+    TopoDS_Shape s = loft.Shape();
+    if (s.IsNull()) throw std::runtime_error("loft produced no solid");
+    return s;
+}
+
+// ponytail: sibling of make_loft that builds an open shell (sheet) instead of a solid.
+TopoDS_Shape SketchEngine::make_loft_surface(const std::vector<TopoDS_Wire>& profiles, bool ruled)
+{
+    if (profiles.size() < 2)
+        throw std::runtime_error("loft needs at least 2 profiles");
+    BRepOffsetAPI_ThruSections loft(Standard_False /*shell, no end caps*/,
+                                    ruled ? Standard_True : Standard_False);
+    for (const TopoDS_Wire& w : profiles) {
+        if (w.IsNull()) throw std::runtime_error("loft: null profile wire");
+        loft.AddWire(w);
+    }
+    loft.Build();
+    if (!loft.IsDone()) throw std::runtime_error("loft failed");
+    TopoDS_Shape s = loft.Shape();
+    if (s.IsNull()) throw std::runtime_error("loft produced no shape");
+    return s;
+}
+
+TopoDS_Shape SketchEngine::make_pocket(const TopoDS_Wire& wire, const SketchPlane& plane,
+                                        const TopoDS_Shape& target, double depth)
+{
+    BRepBuilderAPI_MakeFace fm(wire);
+    if (!fm.IsDone()) throw std::runtime_error("Pocket face failed");
+    TopoDS_Shape tool = extrude_face_internal(fm.Face(),
+        gp_Dir(plane.normal.x(), plane.normal.y(), plane.normal.z()), depth + 1.0, false);
+    BRepAlgoAPI_Cut cut(target, tool);
+    if (!cut.IsDone()) throw std::runtime_error("Pocket cut failed");
+    return cut.Shape();
+}
+
+TriangleMesh SketchEngine::tessellate(const TopoDS_Shape& shape,
+                                      double linear_deflection,
+                                      double angular_deflection)
+{
+    std::vector<int> dummy;
+    return tessellate(shape, dummy, linear_deflection, angular_deflection);
+}
+
+TriangleMesh SketchEngine::tessellate(const TopoDS_Shape& shape,
+                                      std::vector<int>& tri_face,
+                                      double linear_deflection,
+                                      double angular_deflection)
+{
+    tri_face.clear();
+    BRepMesh_IncrementalMesh mesh(shape, linear_deflection, false, angular_deflection, true);
+
+    int nbNodes = 0, nbTriangles = 0;
+    for (TopExp_Explorer exp(shape, TopAbs_FACE); exp.More(); exp.Next()) {
+        TopLoc_Location loc;
+        Handle(Poly_Triangulation) tri = BRep_Tool::Triangulation(TopoDS::Face(exp.Current()), loc);
+        if (!tri.IsNull()) {
+            nbNodes += tri->NbNodes();
+            nbTriangles += tri->NbTriangles();
+        }
+    }
+
+    if (nbTriangles == 0 || nbNodes == 0)
+        return TriangleMesh{};
+
+    indexed_triangle_set raw;
+    raw.vertices.reserve(nbNodes);
+    raw.indices.reserve(nbTriangles);
+    tri_face.reserve(nbTriangles);
+
+    int faceIdx = -1;
+    int nodeOff = 0;
+    for (TopExp_Explorer exp(shape, TopAbs_FACE); exp.More(); exp.Next()) {
+        ++faceIdx;
+
+        TopLoc_Location loc;
+        Handle(Poly_Triangulation) tri = BRep_Tool::Triangulation(TopoDS::Face(exp.Current()), loc);
+        if (tri.IsNull()) continue;
+
+        gp_Trsf trsf = loc.Transformation();
+        for (int i = 1; i <= tri->NbNodes(); ++i) {
+            gp_Pnt p = tri->Node(i);
+            p.Transform(trsf);
+            raw.vertices.emplace_back(Vec3f(p.X(), p.Y(), p.Z()));
+        }
+
+        TopAbs_Orientation orient = exp.Current().Orientation();
+        int ids[3];
+        for (int i = 1; i <= tri->NbTriangles(); ++i) {
+            Poly_Triangle t = tri->Triangle(i);
+            t.Get(ids[0], ids[1], ids[2]);
+            if (orient == TopAbs_REVERSED)
+                std::swap(ids[1], ids[2]);
+
+            raw.indices.emplace_back(nodeOff + ids[0] - 1,
+                                     nodeOff + ids[1] - 1,
+                                     nodeOff + ids[2] - 1);
+            tri_face.push_back(faceIdx);
+        }
+        nodeOff += tri->NbNodes();
+    }
+
+    std::map<std::tuple<float, float, float>, int> vmap;
+    indexed_triangle_set its;
+    its.indices.reserve(raw.indices.size());
+    its.vertices.reserve(raw.vertices.size() / 2);
+
+    std::vector<int> kept_face;
+    kept_face.reserve(tri_face.size());
+
+    for (size_t ti = 0; ti < raw.indices.size(); ++ti) {
+        const auto& tri = raw.indices[ti];
+        stl_triangle_vertex_indices new_tri;
+        for (int j = 0; j < 3; ++j) {
+            const stl_vertex& v = raw.vertices[tri[j]];
+            auto key = std::make_tuple(v.x(), v.y(), v.z());
+            auto it = vmap.find(key);
+            if (it == vmap.end()) {
+                int new_id = static_cast<int>(its.vertices.size());
+                vmap[key] = new_id;
+                its.vertices.push_back(v);
+                new_tri[j] = new_id;
+            } else {
+                new_tri[j] = it->second;
+            }
+        }
+        // Drop triangles that welding collapsed to a repeated vertex. OCCT emits one at the
+        // pole of every degenerate surface parameterization — a sphere patch at a filleted
+        // corner has exactly one — and its v->v edge can never pair with a neighbour, so the
+        // mesh reports an open edge per corner and the slicer declares the model non-manifold
+        // and tells the user to repair it elsewhere. The triangle has zero area: removing it
+        // changes no geometry, only the mesh's bookkeeping.
+        if (new_tri[0] == new_tri[1] || new_tri[1] == new_tri[2] || new_tri[0] == new_tri[2])
+            continue;
+        its.indices.push_back(new_tri);
+        kept_face.push_back(tri_face[ti]);
+    }
+    tri_face.swap(kept_face);   // tri_face stays index-aligned with its.indices
+
+    return TriangleMesh(std::move(its));
+}
+
+std::vector<TopoDS_Wire> SketchEngine::entities_to_wires(const std::vector<SketchEntity>& entities,
+                                                         const SketchPlane& plane,
+                                                         bool closed_only)
+{
+    // Effective weld tolerance: kSketchJoinTol when auto-close is on, 0.0 when off.
+    // Read ONCE so the union-find, the node weld and the vertex tolerance below all
+    // agree. With 0.0 the comparisons use <= so exactly coincident endpoints still join.
+    const double tol = sketch_join_tol();
+
+    struct Item { const SketchEntity* e; size_t idx; };
+    std::vector<Item> valid;
+    valid.reserve(entities.size());
+    for (size_t i = 0; i < entities.size(); ++i) {
+        const SketchEntity& e = entities[i];
+        if (e.construction) continue;
+        if (e.type == SketchEntity::Type::Point) continue;
+        valid.push_back({&e, i});
+    }
+    if (valid.empty()) return {};
+
+    // Build an OCCT ellipse (gp_Elips) in the sketch plane from an Ellipse(Arc)
+    // entity. Major-axis direction = plane-rotated (cos phi, sin phi). Enforces
+    // a >= b (OCCT requirement); the GUI builder already guarantees this.
+    auto make_elips = [&](const SketchEntity& c) -> gp_Elips {
+        Vec3d  c3 = plane.to_world(c.center);
+        gp_Pnt center(c3.x(), c3.y(), c3.z());
+        gp_Dir n(plane.normal.x(), plane.normal.y(), plane.normal.z());
+        Vec2d  maj2(std::cos(c.rotation), std::sin(c.rotation));
+        Vec3d  x3 = plane.to_world(c.center + maj2) - c3;
+        gp_Dir xdir(x3.x(), x3.y(), x3.z());
+        double a = c.radius, b = c.rminor;
+        if (a < b) std::swap(a, b);
+        return gp_Elips(gp_Ax2(center, n, xdir), a, b);
+    };
+
+    // Clamped uniform B-spline (degree min(3, n-1)) through the control poles. The
+    // knot construction is mirrored in DesignSketchTool's GUI sampler so the on-screen
+    // curve matches the extruded geometry exactly.
+    auto make_bspline = [&](const SketchEntity& c) -> Handle(Geom_BSplineCurve) {
+        const int n = int(c.ctrl.size());
+        const int p = n >= 4 ? 3 : (n >= 2 ? n - 1 : 0);
+        if (p < 1) return Handle(Geom_BSplineCurve)();
+        TColgp_Array1OfPnt poles(1, n);
+        for (int i = 0; i < n; ++i) {
+            Vec3d w = plane.to_world(c.ctrl[i]);
+            poles.SetValue(i + 1, gp_Pnt(w.x(), w.y(), w.z()));
+        }
+        const int interior = n - p - 1;        // count of single interior knots
+        const int nknots   = interior + 2;
+        TColStd_Array1OfReal    knots(1, nknots);
+        TColStd_Array1OfInteger mults(1, nknots);
+        knots.SetValue(1, 0.0);                mults.SetValue(1, p + 1);
+        for (int i = 1; i <= interior; ++i) { knots.SetValue(i + 1, double(i)); mults.SetValue(i + 1, 1); }
+        knots.SetValue(nknots, double(interior + 1)); mults.SetValue(nknots, p + 1);
+        return new Geom_BSplineCurve(poles, knots, mults, p);
+    };
+
+    auto is_chain = [](const SketchEntity& e) {
+        return e.type == SketchEntity::Type::Line || e.type == SketchEntity::Type::Arc ||
+               e.type == SketchEntity::Type::EllipseArc || e.type == SketchEntity::Type::BSpline;
+    };
+
+    // Endpoints of a chain entity in SKETCH coordinates (before to_world). False on a
+    // degenerate (fewer than two control points) BSpline, which can never close a loop.
+    auto endpoints = [&](const SketchEntity& e, Vec2d& a, Vec2d& b) -> bool {
+        if (e.type == SketchEntity::Type::BSpline) {
+            if (e.ctrl.size() < 2) return false;
+            a = e.ctrl.front(); b = e.ctrl.back();
+            return true;
+        }
+        a = e.p0; b = e.p1;
+        return true;
+    };
+
+    // Sketch weld tolerance. Nothing legitimate in a mm-scale sketch is 1 um apart, so two
+    // endpoints within this distance count as one joint. The union-find grouping and the wire
+    // build below MUST use the SAME number, or a joint can be united into a loop and then
+    // rejected by the wire builder (which silently drops the edge — see the wire build).
+    // `<=` (not `<`) so exactly coincident endpoints still join when tol == 0 (auto-close off).
+    auto same = [&](const Vec2d& p, const Vec2d& q) { return (p - q).norm() <= tol; };
+
+    // Union-find over the valid index list: chain entities sharing an endpoint belong to one loop.
+    std::vector<int> parent(valid.size());
+    for (size_t i = 0; i < valid.size(); ++i) parent[i] = int(i);
+    auto find = [&](int x) {
+        while (parent[x] != x) { parent[x] = parent[parent[x]]; x = parent[x]; }
+        return x;
+    };
+    auto unite = [&](int x, int y) {
+        int rx = find(x), ry = find(y);
+        if (rx != ry) parent[rx] = ry;
+    };
+
+    std::vector<size_t> chain_idx;
+    chain_idx.reserve(valid.size());
+    for (size_t i = 0; i < valid.size(); ++i)
+        if (is_chain(*valid[i].e)) chain_idx.push_back(i);
+
+    for (size_t a = 0; a < chain_idx.size(); ++a) {
+        const size_t i = chain_idx[a];
+        Vec2d i0, i1;
+        if (!endpoints(*valid[i].e, i0, i1)) continue;
+        for (size_t b = a + 1; b < chain_idx.size(); ++b) {
+            const size_t j = chain_idx[b];
+            Vec2d j0, j1;
+            if (!endpoints(*valid[j].e, j0, j1)) continue;
+            if (same(i0, j0) || same(i0, j1) || same(i1, j0) || same(i1, j1))
+                unite(int(i), int(j));
+        }
+    }
+
+    // Group chain entities by connected-component root.
+    std::map<int, std::vector<size_t>> comps;
+    for (size_t i = 0; i < valid.size(); ++i) {
+        if (!is_chain(*valid[i].e)) continue;
+        comps[find(int(i))].push_back(i);
+    }
+
+    // Loop descriptors: each Circle/Ellipse is its own loop; each chain component is a loop.
+    struct Loop { size_t min_idx{0}; bool closed_single{false}; size_t member{0}; std::vector<size_t> members; };
+    std::vector<Loop> loops;
+    for (size_t i = 0; i < valid.size(); ++i) {
+        const SketchEntity& e = *valid[i].e;
+        if (e.type == SketchEntity::Type::Circle || e.type == SketchEntity::Type::Ellipse) {
+            Loop l; l.min_idx = valid[i].idx; l.closed_single = true; l.member = i;
+            loops.push_back(l);
+        }
+    }
+    for (const auto& kv : comps) {
+        Loop l; l.closed_single = false; l.members = kv.second;
+        size_t mn = std::numeric_limits<size_t>::max();
+        for (size_t m : kv.second) mn = std::min(mn, valid[m].idx);
+        l.min_idx = mn;
+        loops.push_back(l);
+    }
+    // Deterministic order: by the index of each loop's first entity.
+    std::sort(loops.begin(), loops.end(), [](const Loop& x, const Loop& y) { return x.min_idx < y.min_idx; });
+
+    // Build each loop. All-or-nothing: one failed loop poisons the whole result.
+    std::vector<TopoDS_Wire> out;
+    out.reserve(loops.size());
+    for (const Loop& loop : loops) {
+        BRepBuilderAPI_MakeWire wm;
+        if (loop.closed_single) {
+            const SketchEntity& c = *valid[loop.member].e;
+            TopoDS_Edge e;
+            if (c.type == SketchEntity::Type::Ellipse) {
+                if (c.radius <= 1e-9 || c.rminor <= 1e-9) return {};
+                e = BRepBuilderAPI_MakeEdge(make_elips(c)).Edge();
+            } else {
+                Vec3d  c3 = plane.to_world(c.center);
+                gp_Pnt center(c3.x(), c3.y(), c3.z());
+                gp_Dir n(plane.normal.x(), plane.normal.y(), plane.normal.z());
+                gp_Circ circ(gp_Ax2(center, n), c.radius);
+                e = BRepBuilderAPI_MakeEdge(circ).Edge();
+            }
+            wm.Add(e);
+        } else {
+            // loop.members is in ENTITY-CREATION order, not loop-traversal order. A partial
+            // wire rejects an out-of-order edge even for a perfectly closed sketch, so first
+            // weld every endpoint into a shared node, then traverse the chain in order. Each
+            // endpoint snaps to an existing node when within `tol`, and every edge
+            // touching a node shares ONE TopoDS_Vertex: the wire builder then sees vertex
+            // identity, not geometric proximity, so a joint open by a few um (larger than
+            // OCCT's default 1e-7 vertex tolerance) still connects.
+            struct Member { size_t v; int a; int b; };  // v = index into `valid`, a/b = node ids
+            std::vector<Vec2d> node_pt;                 // welded sketch point per node
+            std::vector<int>   node_deg;                // endpoint count per node
+            auto node_id = [&](const Vec2d& p) -> int {
+                for (size_t i = 0; i < node_pt.size(); ++i)
+                    if ((node_pt[i] - p).norm() <= tol) return int(i);
+                node_pt.push_back(p);
+                node_deg.push_back(0);
+                return int(node_pt.size()) - 1;
+            };
+            std::vector<Member> ms;
+            ms.reserve(loop.members.size());
+            for (size_t m : loop.members) {
+                Vec2d p0, p1;
+                if (!endpoints(*valid[m].e, p0, p1)) return {};
+                int a = node_id(p0), b = node_id(p1);
+                node_deg[a]++; node_deg[b]++;
+                ms.push_back({m, a, b});
+            }
+
+            // Traverse: begin at a degree-1 node for an open chain, else at any member, then
+            // repeatedly take the unused member sharing the current open node.
+            std::vector<size_t> order;
+            order.reserve(ms.size());
+            std::vector<char> used(ms.size(), 0);
+            size_t start = 0;
+            for (size_t i = 0; i < ms.size(); ++i)
+                if (node_deg[ms[i].a] == 1 || node_deg[ms[i].b] == 1) { start = i; break; }
+            const int start_node = (node_deg[ms[start].a] == 1) ? ms[start].a
+                                 : (node_deg[ms[start].b] == 1) ? ms[start].b
+                                 : ms[start].a;
+            int open = start_node;
+            for (;;) {
+                size_t next = ms.size();
+                for (size_t k = 0; k < ms.size(); ++k) {
+                    if (used[k]) continue;
+                    if (ms[k].a == open || ms[k].b == open) { next = k; break; }
+                }
+                if (next == ms.size()) break;
+                order.push_back(next);
+                used[next] = 1;
+                open = (ms[next].a == open) ? ms[next].b : ms[next].a;
+            }
+            if (order.size() != ms.size()) return {};
+
+            // The walk ends on the node it could not leave; that node equals the starting
+            // node exactly when the chain is a closed cycle. When closed_only is set, an open
+            // chain is DISCARDED (skipped), never an error: the viewport discards open chains
+            // when it decides a region is extrudable (region_loops exists to find EXTRUDABLE
+            // regions), so the kernel must discard them too, or the two disagree about what
+            // belongs to the profile and a stray click breaks a feature that looks perfect on
+            // screen. Reuses the welded node ids — no second tolerance.
+            // A component is OPEN exactly when some welded node has only one edge on it —
+            // that free endpoint is where the chain stops. Do NOT define it as "the walk
+            // returned to its starting node": a legitimately closed loop that also carries an
+            // extra edge between two of its nodes (a bridge added across a C profile, so the
+            // gap is spanned twice) has no free endpoint but its Eulerian walk still ends
+            // somewhere else, and that definition discarded it. Degree-1 is the property that
+            // actually distinguishes a stray segment from a closed profile.
+            if (closed_only) {
+                bool has_free_end = false;
+                for (const Member& mm : ms)
+                    if (node_deg[mm.a] == 1 || node_deg[mm.b] == 1) { has_free_end = true; break; }
+                if (has_free_end) continue;
+            }
+
+            // One TopoDS_Vertex per node at the welded world point. Tolerance widened to
+            // `tol` because MakeEdge(curve, va, vb) projects each vertex onto the
+            // curve within the vertex tolerance (BRepLib_MakeEdge::Init), and a welded node
+            // can be up to the weld gap off another entity's curve. OCCT must never be handed
+            // a zero vertex tolerance, so clamp at Precision::Confusion() when tol == 0.
+            std::vector<TopoDS_Vertex> verts(node_pt.size());
+            BRep_Builder B;
+            for (size_t i = 0; i < node_pt.size(); ++i) {
+                Vec3d w = plane.to_world(node_pt[i]);
+                verts[i] = BRepBuilderAPI_MakeVertex(gp_Pnt(w.x(), w.y(), w.z())).Vertex();
+                B.UpdateVertex(verts[i], std::max(tol, Precision::Confusion()));
+            }
+
+            for (size_t o : order) {
+                const Member& mm = ms[o];
+                const SketchEntity* e = valid[mm.v].e;
+                const TopoDS_Vertex& va = verts[mm.a];
+                const TopoDS_Vertex& vb = verts[mm.b];
+                if (e->type == SketchEntity::Type::Line) {
+                    wm.Add(BRepBuilderAPI_MakeEdge(va, vb).Edge());
+                } else if (e->type == SketchEntity::Type::EllipseArc) {
+                    if (e->radius <= 1e-9 || e->rminor <= 1e-9) return {};
+                    GC_MakeArcOfEllipse arc_maker(make_elips(*e), e->start_angle, e->end_angle, Standard_True);
+                    if (!arc_maker.IsDone()) return {};
+                    wm.Add(BRepBuilderAPI_MakeEdge(arc_maker.Value(), va, vb).Edge());
+                } else if (e->type == SketchEntity::Type::Arc) {
+                    Vec3d  p0 = plane.to_world(e->p0);
+                    Vec3d  p1 = plane.to_world(e->p1);
+                    double mid_angle = (e->start_angle + e->end_angle) * 0.5;
+                    Vec2d  mid_2d(e->center.x() + e->radius * std::cos(mid_angle),
+                                  e->center.y() + e->radius * std::sin(mid_angle));
+                    Vec3d  mid_3d = plane.to_world(mid_2d);
+                    gp_Pnt pa(p0.x(), p0.y(), p0.z());
+                    gp_Pnt pm(mid_3d.x(), mid_3d.y(), mid_3d.z());
+                    gp_Pnt pb(p1.x(), p1.y(), p1.z());
+                    GC_MakeArcOfCircle arc_maker(pa, pm, pb);
+                    if (!arc_maker.IsDone()) return {};
+                    Handle(Geom_TrimmedCurve) curve = arc_maker.Value();
+                    wm.Add(BRepBuilderAPI_MakeEdge(curve, va, vb).Edge());
+                } else if (e->type == SketchEntity::Type::BSpline) {
+                    Handle(Geom_BSplineCurve) crv = make_bspline(*e);
+                    if (crv.IsNull()) return {};
+                    wm.Add(BRepBuilderAPI_MakeEdge(crv, va, vb).Edge());
+                }
+            }
+        }
+        wm.Build();
+        // IsDone() reflects only the LAST Add: BRepLib_MakeWire::Add sets BRepLib_DisconnectedWire
+        // + NotDone() and returns on a disconnected edge (dropping it), but every successful Add
+        // finishes with BRepLib_WireDone + Done(), overwriting that failure (BRepLib_MakeWire.cxx).
+        // So dropped edges go unnoticed — count the edges actually in the wire instead.
+        if (!wm.IsDone()) return {};
+        const TopoDS_Wire wire = wm.Wire();
+        size_t edge_count = 0;
+        for (TopExp_Explorer ex(wire, TopAbs_EDGE); ex.More(); ex.Next()) ++edge_count;
+        if (edge_count != (loop.closed_single ? 1 : loop.members.size())) return {};
+        out.push_back(wire);
+    }
+    return out;
+}
+
+TopoDS_Wire SketchEngine::entities_to_wire(const std::vector<SketchEntity>& entities,
+                                           const SketchPlane& plane,
+                                           bool closed_only)
+{
+    const std::vector<TopoDS_Wire> w = entities_to_wires(entities, plane, closed_only);
+    return w.size() == 1 ? w[0] : TopoDS_Wire{};
+}
+
+std::vector<Vec2d> sketch_open_ends(const std::vector<SketchEntity>& entities,
+                                    const SketchPlane& /*plane*/)
+{
+    const double tol = sketch_join_tol();
+
+    auto is_chain = [](const SketchEntity& e) {
+        return e.type == SketchEntity::Type::Line || e.type == SketchEntity::Type::Arc ||
+               e.type == SketchEntity::Type::EllipseArc || e.type == SketchEntity::Type::BSpline;
+    };
+    auto endpoints = [](const SketchEntity& e, Vec2d& a, Vec2d& b) -> bool {
+        if (e.type == SketchEntity::Type::BSpline) {
+            if (e.ctrl.size() < 2) return false;
+            a = e.ctrl.front(); b = e.ctrl.back();
+            return true;
+        }
+        a = e.p0; b = e.p1;
+        return true;
+    };
+
+    // Weld every chain endpoint into a shared node under the SAME tolerance the wire
+    // build uses, then report the degree-1 nodes: they are where a chain fails to close.
+    // Circle/Ellipse are always closed and contribute no endpoint.
+    std::vector<Vec2d> node_pt;
+    std::vector<int>   node_deg;
+    auto node_id = [&](const Vec2d& p) -> int {
+        for (size_t i = 0; i < node_pt.size(); ++i)
+            if ((node_pt[i] - p).norm() <= tol) return int(i);
+        node_pt.push_back(p);
+        node_deg.push_back(0);
+        return int(node_pt.size()) - 1;
+    };
+
+    for (const SketchEntity& e : entities) {
+        if (e.construction) continue;
+        if (!is_chain(e)) continue;
+        Vec2d a, b;
+        if (!endpoints(e, a, b)) continue;
+        int ia = node_id(a), ib = node_id(b);
+        node_deg[ia]++;
+        node_deg[ib]++;
+    }
+
+    std::vector<Vec2d> out;
+    for (size_t i = 0; i < node_pt.size(); ++i)
+        if (node_deg[i] == 1) out.push_back(node_pt[i]);
+    return out;
+}
+
+TopoDS_Face SketchEngine::wires_to_face(const std::vector<TopoDS_Wire>& wires,
+                                        const SketchPlane& plane)
+{
+    if (wires.empty()) throw std::runtime_error("sketch has no closed loop");
+
+    // The ASSEMBLED face below is built on the SKETCH's own plane rather than on a surface OCCT
+    // infers from the outer wire. The inferred plane has no reason to share the sketch's normal,
+    // and when they disagree the hole classification produces no hole: a plate sketched on a
+    // plane whose normal points -Z came out as the full box PLUS a disc (measured 220274 mm3
+    // where 163726 was due — 192000 box + 28274 disc). `plane` was a parameter this function
+    // never used. Only the assembly is named: the single-wire and per-wire-area builds keep the
+    // inferred surface, because naming a plane also makes MakeFace accept a wire that does not
+    // bound a face, and that failure is the check an open stray line is caught by.
+    const gp_Pln pln(gp_Pnt(plane.origin.x(), plane.origin.y(), plane.origin.z()),
+                     gp_Dir(plane.normal.x(), plane.normal.y(), plane.normal.z()));
+
+    if (wires.size() == 1) {
+        BRepBuilderAPI_MakeFace fm(wires[0]);
+        if (!fm.IsDone()) throw std::runtime_error("sketch loop does not bound a face");
+        return fm.Face();
+    }
+
+    // Two or more loops: build a face per wire and let the largest area be the outer
+    // boundary; every other loop is a candidate hole inside it.
+    std::vector<TopoDS_Face> faces;
+    faces.reserve(wires.size());
+    std::vector<double> areas;
+    areas.reserve(wires.size());
+    for (const TopoDS_Wire& w : wires) {
+        BRepBuilderAPI_MakeFace fm(w);
+        if (!fm.IsDone()) throw std::runtime_error("sketch loop does not bound a face");
+        faces.push_back(fm.Face());
+        GProp_GProps props;
+        BRepGProp::SurfaceProperties(faces.back(), props);
+        areas.push_back(props.Mass());
+    }
+
+    size_t outer = 0;
+    for (size_t i = 1; i < areas.size(); ++i)
+        if (areas[i] > areas[outer]) outer = i;
+
+    // Note: NOT MakeFace(faces[outer], wires[outer]) — that constructor copies the outer face
+    // (including its existing boundary wire) and then adds the wire again, doubling the outer
+    // boundary. The wire-only constructor starts clean and the reversed holes follow.
+    BRepBuilderAPI_MakeFace fm(pln, wires[outer]);
+    for (size_t i = 0; i < wires.size(); ++i) {
+        if (i == outer) continue;
+        // Containment is checked, not assumed: a vertex of the inner wire must lie strictly
+        // inside the outer face. A loop outside the largest one is a second island, not a hole.
+        gp_Pnt p;
+        bool got = false;
+        for (TopExp_Explorer ex(wires[i], TopAbs_VERTEX); ex.More(); ex.Next()) {
+            p = BRep_Tool::Pnt(TopoDS::Vertex(ex.Current()));
+            got = true;
+            break;
+        }
+        if (!got) throw std::runtime_error("sketch loop does not bound a face");
+        BRepClass_FaceClassifier fc(faces[outer], p, 1e-7);
+        if (fc.State() != TopAbs_IN)
+            throw std::runtime_error("sketch has two disjoint regions; put each in its own sketch");
+        // Add the hole loop AS-IS and let ShapeFix_Face sort the orientations out below.
+        // Reversing it here only works when the sketch happened to wind both loops the same
+        // way: a circle drawn clockwise inside a counter-clockwise rectangle comes out matching
+        // the outer boundary, OCCT sweeps it as a second contour, and the prism is the plate
+        // with the bore FILLED and the disc's volume counted twice. Measured on the rig:
+        // bbox 67.17 x 219.67 x 10 (the whole plate) with volume 152088 mm3 against a solid-box
+        // 147520 — a body larger than its own bounding box, which is the signature of it.
+        fm.Add(wires[i]);
+    }
+    if (!fm.IsDone()) throw std::runtime_error("sketch loop does not bound a face");
+    // Winding-independent classification of outer vs holes — the same idiom make_extrude_regions
+    // already uses for imported glyphs, which is why holed TEXT extruded correctly all along
+    // while a holed SKETCH did not.
+    ShapeFix_Face sff(fm.Face());
+    sff.FixOrientation();
+    return sff.Face();
+}
+
+std::vector<SketchEntity> SketchEngine::mirror_entities(
+    const std::vector<SketchEntity>& src, const Vec2d& a, const Vec2d& b)
+{
+    Vec2d dir = b - a;
+    if (dir.norm() < 1e-12)
+        return src;
+
+    dir.normalize();
+
+    auto reflect = [&](const Vec2d& p) -> Vec2d {
+        Vec2d v = p - a;
+        return a + (2.0 * v.dot(dir)) * dir - v;
+    };
+
+    std::vector<SketchEntity> out;
+    out.reserve(src.size());
+
+    for (const auto& e : src) {
+        SketchEntity m = e;
+        switch (e.type) {
+        case SketchEntity::Type::Line:
+            m.p0 = reflect(e.p0);
+            m.p1 = reflect(e.p1);
+            break;
+        case SketchEntity::Type::Point:
+            m.p0 = reflect(e.p0);
+            break;
+        case SketchEntity::Type::Circle:
+            m.center = reflect(e.center);
+            m.p0 = m.center;
+            break;
+        case SketchEntity::Type::Arc: {
+            m.p0     = reflect(e.p0);
+            m.p1     = reflect(e.p1);
+            m.center = reflect(e.center);
+
+            const Vec2d& c = m.center;
+            m.start_angle = std::atan2(m.p0.y() - c.y(), m.p0.x() - c.x());
+            double raw_end = std::atan2(m.p1.y() - c.y(), m.p1.x() - c.x());
+
+            double s = e.end_angle - e.start_angle;
+
+            double sweep = raw_end - m.start_angle;
+            while (sweep <= -2.0 * M_PI) sweep += 2.0 * M_PI;
+            while (sweep >=  2.0 * M_PI) sweep -= 2.0 * M_PI;
+
+            if (s != 0.0 && sweep * s > 0.0) {
+                if (sweep > 0.0)
+                    sweep -= 2.0 * M_PI;
+                else
+                    sweep += 2.0 * M_PI;
+            }
+
+            m.end_angle = m.start_angle + sweep;
+            m.radius    = e.radius;
+            break;
+        }
+        case SketchEntity::Type::Ellipse:
+        case SketchEntity::Type::EllipseArc: {
+            m.center = reflect(e.center);
+            // Reflect the major-axis direction; a/b unchanged.
+            const Vec2d majdir(std::cos(e.rotation), std::sin(e.rotation));
+            const Vec2d rdir = reflect(e.center + majdir) - m.center;
+            m.rotation = std::atan2(rdir.y(), rdir.x());
+            if (e.type == SketchEntity::Type::Ellipse) {
+                m.p0 = m.center;
+            } else {
+                m.p0 = reflect(e.p0);
+                m.p1 = reflect(e.p1);
+                // Reflection reverses orientation: recompute parametric angles in
+                // the reflected frame, original end -> new start (CCW sense kept).
+                auto param = [&](const Vec2d& P) {
+                    const Vec2d d  = P - m.center;
+                    const double cu = std::cos(m.rotation), su = std::sin(m.rotation);
+                    const double u =  d.x() * cu + d.y() * su;
+                    const double v = -d.x() * su + d.y() * cu;
+                    return std::atan2(v / std::max(e.rminor, 1e-9), u / std::max(e.radius, 1e-9));
+                };
+                m.start_angle = param(m.p1);
+                m.end_angle   = param(m.p0);
+            }
+            break;
+        }
+        case SketchEntity::Type::BSpline:
+            for (auto& cp : m.ctrl) cp = reflect(cp);
+            m.p0 = reflect(e.p0);
+            m.p1 = reflect(e.p1);
+            break;
+        }
+        out.push_back(m);
+    }
+
+    // A REFLECTION REVERSES ORIENTATION, so the reflected half is handed back reversed — in
+    // order, and each entity flipped — or it does not CONTINUE the chain it was made from.
+    //
+    // Draw half a stadium left-to-right along the bottom, round the cap, right-to-left along the
+    // top, ending at (0, R). Reflecting each entity in place gives a half whose top run STARTS at
+    // (-L, R) and ENDS at (0, R): it meets the original head-to-head, not head-to-tail. Every
+    // consumer that walks the loop then has to cope, and two already had to be taught — the loop
+    // area cancelled its own arc correction against the negated sweep, and offset put the
+    // reflected half on the wrong side because it read each entity's STORED direction. Reversed
+    // here, the two halves are one walkable chain and a mirrored CCW loop stays CCW.
+    std::reverse(out.begin(), out.end());
+    for (SketchEntity& m : out) {
+        switch (m.type) {
+        case SketchEntity::Type::Line:
+            std::swap(m.p0, m.p1);
+            break;
+        case SketchEntity::Type::Arc:
+        case SketchEntity::Type::EllipseArc:
+            std::swap(m.p0, m.p1);
+            std::swap(m.start_angle, m.end_angle);   // what "walked the other way" means
+            break;
+        case SketchEntity::Type::BSpline:
+            std::swap(m.p0, m.p1);
+            std::reverse(m.ctrl.begin(), m.ctrl.end());
+            break;
+        default:
+            break;   // circle, ellipse, point: no direction to reverse
+        }
+    }
+
+    return out;
+}
+
+// ---- offset: chain-aware, with corner repair -------------------------------
+//
+// Offsetting each entity on its own is geometrically correct per entity and USELESS as a
+// sketch operation: a closed rectangle offset that way comes back as four parallel segments
+// that no longer touch, so the result is four open wires and nothing can be extruded from it
+// (measured — tests/libslic3r/test_sketchprofile.cpp). A profile is a chain, and the property
+// that has to survive the operation is the chain, not the individual coordinates.
+//
+// So the offset runs in three steps: split the input into chains of entities joined by shared
+// endpoints; offset every entity in a chain; then repair each seam by trimming/extending the
+// two neighbours to the intersection of their offset supports (a miter join). Closed chains
+// get their last-to-first seam repaired too, which is what makes the result closed again.
+namespace {
+
+constexpr double kOffJoinEps = 1e-6;
+
+bool off_same(const Vec2d& a, const Vec2d& b) { return (a - b).squaredNorm() < kOffJoinEps * kOffJoinEps; }
+
+// Does this entity type take part in chaining (i.e. does it have two ends)?
+bool off_is_open_curve(const SketchEntity& e)
+{
+    return e.type == SketchEntity::Type::Line || e.type == SketchEntity::Type::Arc;
+}
+
+// Infinite-support intersections. Each returns the candidate closest to `seed`, which is where
+// the seam is expected to land, so the branch choice never depends on entity orientation.
+bool off_pick(const std::vector<Vec2d>& cands, const Vec2d& seed, Vec2d& out)
+{
+    if (cands.empty()) return false;
+    double best = std::numeric_limits<double>::max();
+    for (const Vec2d& c : cands) {
+        const double d = (c - seed).squaredNorm();
+        if (d < best) { best = d; out = c; }
+    }
+    return true;
+}
+
+bool off_line_line(const Vec2d& a0, const Vec2d& a1, const Vec2d& b0, const Vec2d& b1,
+                   const Vec2d& seed, Vec2d& out)
+{
+    const Vec2d da = a1 - a0, db = b1 - b0;
+    const double den = da.x() * db.y() - da.y() * db.x();
+    if (std::abs(den) < 1e-12) return false;                 // parallel: no miter exists
+    const Vec2d w = b0 - a0;
+    const double t = (w.x() * db.y() - w.y() * db.x()) / den;
+    out = a0 + t * da;
+    (void)seed;
+    return true;
+}
+
+std::vector<Vec2d> off_line_circle(const Vec2d& p0, const Vec2d& p1, const Vec2d& c, double r)
+{
+    std::vector<Vec2d> out;
+    Vec2d d = p1 - p0;
+    const double dd = d.squaredNorm();
+    if (dd < 1e-18 || r <= 0.0) return out;
+    const Vec2d f = p0 - c;
+    const double b = 2.0 * f.dot(d), cc = f.squaredNorm() - r * r;
+    const double disc = b * b - 4.0 * dd * cc;
+    if (disc < 0.0) return out;
+    const double sq = std::sqrt(disc);
+    out.push_back(p0 + ((-b - sq) / (2.0 * dd)) * d);
+    out.push_back(p0 + ((-b + sq) / (2.0 * dd)) * d);
+    return out;
+}
+
+std::vector<Vec2d> off_circle_circle(const Vec2d& c0, double r0, const Vec2d& c1, double r1)
+{
+    std::vector<Vec2d> out;
+    const Vec2d d = c1 - c0;
+    const double L = d.norm();
+    if (L < 1e-12 || L > r0 + r1 || L < std::abs(r0 - r1)) return out;
+    const double a = (r0 * r0 - r1 * r1 + L * L) / (2.0 * L);
+    const double h2 = r0 * r0 - a * a;
+    const double h = h2 > 0.0 ? std::sqrt(h2) : 0.0;
+    const Vec2d u = d / L, n(-u.y(), u.x());
+    out.push_back(c0 + a * u + h * n);
+    out.push_back(c0 + a * u - h * n);
+    return out;
+}
+
+// Move one end of an entity to `q`, keeping the entity's kind consistent (an arc re-derives
+// the parametric angle from its centre, and its sweep direction is preserved).
+void off_set_end(SketchEntity& e, bool at_end, const Vec2d& q)
+{
+    if (e.type == SketchEntity::Type::Line) {
+        (at_end ? e.p1 : e.p0) = q;
+        return;
+    }
+    if (e.type != SketchEntity::Type::Arc) return;
+    const bool ccw = e.end_angle >= e.start_angle;
+    const double ang = std::atan2(q.y() - e.center.y(), q.x() - e.center.x());
+    if (at_end) {
+        e.p1 = q;
+        double a = ang;
+        if (ccw) { while (a < e.start_angle) a += 2.0 * M_PI; while (a - e.start_angle > 2.0 * M_PI) a -= 2.0 * M_PI; }
+        else     { while (a > e.start_angle) a -= 2.0 * M_PI; while (e.start_angle - a > 2.0 * M_PI) a += 2.0 * M_PI; }
+        e.end_angle = a;
+    } else {
+        e.p0 = q;
+        double a = ang;
+        if (ccw) { while (a > e.end_angle) a -= 2.0 * M_PI; while (e.end_angle - a > 2.0 * M_PI) a += 2.0 * M_PI; }
+        else     { while (a < e.end_angle) a += 2.0 * M_PI; while (a - e.end_angle > 2.0 * M_PI) a -= 2.0 * M_PI; }
+        e.start_angle = a;
+    }
+}
+
+// Offset ONE entity, unrepaired. Returns false for the kinds v1 does not offset.
+bool off_one(const SketchEntity& e, double d, SketchEntity& out)
+{
+    switch (e.type) {
+    case SketchEntity::Type::Line: {
+        Vec2d t = e.p1 - e.p0;
+        if (t.norm() < 1e-12) return false;
+        t.normalize();
+        const Vec2d n(-t.y(), t.x());
+        out = e;
+        out.p0 = e.p0 + d * n;
+        out.p1 = e.p1 + d * n;
+        return true;
+    }
+    case SketchEntity::Type::Circle: {
+        const double r = e.radius + d;
+        if (r <= 1e-9) return false;
+        out = e; out.radius = r; out.p0 = out.center;
+        return true;
+    }
+    case SketchEntity::Type::Arc: {
+        // Same convention as the Line above: +d moves the curve to the LEFT of its direction
+        // of travel. For a CCW arc the left side is the inside, so the radius SHRINKS; for a
+        // CW arc it grows. Reading the sign off the sweep is what keeps a stadium outline
+        // (lines + caps) offsetting as one body instead of the lines going one way and the
+        // caps the other — which is what a plain `radius + d` did.
+        const double sgn = (e.end_angle >= e.start_angle) ? -1.0 : 1.0;
+        const double r = e.radius + sgn * d;
+        if (r <= 1e-9) return false;
+        out = e;
+        out.radius = r;
+        out.p0 = e.center + r * Vec2d(std::cos(e.start_angle), std::sin(e.start_angle));
+        out.p1 = e.center + r * Vec2d(std::cos(e.end_angle),   std::sin(e.end_angle));
+        return true;
+    }
+    default:
+        // Point has nothing to offset; a true parallel of an ellipse is not an ellipse and of a
+        // spline is not a same-degree spline, so both stay out of v1 rather than lie about it.
+        return false;
+    }
+}
+
+// Repair the seam between `a`'s end and `b`'s start: both are trimmed/extended to the
+// intersection of their infinite supports nearest the gap. Returns false when no such point
+// exists (parallel lines, non-intersecting circles), in which case the seam stays open.
+bool off_join(SketchEntity& a, SketchEntity& b)
+{
+    const Vec2d seed = 0.5 * (a.p1 + b.p0);
+    Vec2d q;
+    const bool aL = a.type == SketchEntity::Type::Line;
+    const bool bL = b.type == SketchEntity::Type::Line;
+    if (aL && bL) {
+        if (!off_line_line(a.p0, a.p1, b.p0, b.p1, seed, q)) return false;
+    } else if (aL) {
+        if (!off_pick(off_line_circle(a.p0, a.p1, b.center, b.radius), seed, q)) return false;
+    } else if (bL) {
+        if (!off_pick(off_line_circle(b.p0, b.p1, a.center, a.radius), seed, q)) return false;
+    } else {
+        if (!off_pick(off_circle_circle(a.center, a.radius, b.center, b.radius), seed, q)) return false;
+    }
+    off_set_end(a, true,  q);
+    off_set_end(b, false, q);
+    return true;
+}
+
+// Normalise an entity that was offset while traversed REVERSED to head-to-tail traversal order:
+// swap its stored ends so p0 is the traversal start and p1 the traversal end. An arc must swap
+// its stored sweep too, because "traversed the other way" reverses the stored sweep direction.
+void off_reverse(SketchEntity& e)
+{
+    std::swap(e.p0, e.p1);
+    if (e.type == SketchEntity::Type::Arc)
+        std::swap(e.start_angle, e.end_angle);
+}
+
+} // namespace
+
+std::vector<SketchEntity> SketchEngine::offset_entities(
+    const std::vector<SketchEntity>& src, double d)
+{
+    std::vector<SketchEntity> out;
+
+    // Closed and unchainable kinds first: they carry no seams, so they pass straight through.
+    std::vector<int> open_idx;
+    for (int i = 0; i < int(src.size()); ++i) {
+        if (off_is_open_curve(src[i])) { open_idx.push_back(i); continue; }
+        SketchEntity o;
+        if (off_one(src[i], d, o)) out.push_back(o);
+    }
+
+    std::vector<bool> used(open_idx.size(), false);
+
+    // Stored endpoints of the k-th open entity.
+    auto ends = [&](int k, Vec2d& p0, Vec2d& p1) { p0 = src[open_idx[k]].p0; p1 = src[open_idx[k]].p1; };
+
+    // An endpoint shared by no OTHER unused open curve is a FREE end: the loose end of an open
+    // chain rather than a seam. (`used` matters — entities already pulled into a chain must not
+    // count, otherwise the far end of the chain we just walked would look shared.)
+    auto is_free = [&](int k, const Vec2d& pt) {
+        for (size_t j = 0; j < open_idx.size(); ++j) {
+            if (int(j) == k || used[j]) continue;
+            Vec2d q0, q1; ends(int(j), q0, q1);
+            if (off_same(pt, q0) || off_same(pt, q1)) return false;
+        }
+        return true;
+    };
+
+    struct Chain {
+        std::vector<std::pair<int, bool>> items;   // (entity index, reversed)
+        Vec2d start, end;                          // traversal start/end points
+    };
+
+    // Walk one chain from the unused seed `s`, traversing AWAY from its free end. `reversed`
+    // means the traversal enters at the entity's p1 and leaves at its p0, i.e. the entity is
+    // travelled opposite to its STORED direction. An entity whose p1 is free (but p0 is not)
+    // is the head of an open chain and must start reversed; an isolated entity or a closed
+    // loop starts forward.
+    auto walk = [&](int s) -> Chain {
+        Chain c;
+        Vec2d s0, s1; ends(s, s0, s1);
+        const bool rev = !is_free(s, s0) && is_free(s, s1);
+        c.items.emplace_back(s, rev);
+        used[s] = true;
+        c.start = rev ? s1 : s0;
+        c.end   = rev ? s0 : s1;
+        for (;;) {
+            int  nxt  = -1;
+            bool nrev = false;
+            for (size_t j = 0; j < open_idx.size(); ++j) {
+                if (used[j]) continue;
+                Vec2d q0, q1; ends(int(j), q0, q1);
+                if (off_same(c.end, q0)) { nxt = int(j); nrev = false; break; }
+                if (off_same(c.end, q1)) { nxt = int(j); nrev = true;  break; }
+            }
+            if (nxt < 0) break;
+            c.items.emplace_back(nxt, nrev);
+            used[nxt] = true;
+            Vec2d q0, q1; ends(nxt, q0, q1);
+            c.end = nrev ? q0 : q1;
+        }
+        return c;
+    };
+
+    // Offset one chain as traversed: every entity is offset with an EFFECTIVE distance that
+    // already accounts for how it was walked, then reversed entities have their stored ends
+    // swapped so the emitted chain is head-to-tail in traversal order (which is what keeps the
+    // seam repair below — and any later offset/mirror — well-oriented). A chain whose final
+    // traversal end coincides with its first traversal start is CLOSED.
+    auto emit = [&](const Chain& c) {
+        const bool closed = c.items.size() > 1 && off_same(c.end, c.start);
+        std::vector<SketchEntity> off;
+        off.reserve(c.items.size());
+        for (const auto& it : c.items) {
+            // A reversed entity offsets with -d rather than +d:
+            //  * a line walked backwards has its left-hand side on the other side, so -d;
+            //  * an arc walked backwards has its sweep sign effectively flipped, which is exactly
+            //    the `sgn` term off_one reads, so -d again.
+            const double ed = it.second ? -d : d;
+            SketchEntity o;
+            if (!off_one(src[open_idx[it.first]], ed, o)) continue;
+            if (it.second) off_reverse(o);
+            off.push_back(o);
+        }
+        if (off.empty()) return;
+        for (size_t i = 0; i + 1 < off.size(); ++i) off_join(off[i], off[i + 1]);
+        if (closed && off.size() > 1) off_join(off.back(), off.front());
+        for (auto& o : off) out.push_back(o);
+    };
+
+    // Pass 1: open chains, seeded at a free end so they are never entered mid-way (which would
+    // split one open chain in two and lose a seam).
+    for (size_t s = 0; s < open_idx.size(); ++s) {
+        if (used[s]) continue;
+        Vec2d s0, s1; ends(int(s), s0, s1);
+        if (!is_free(int(s), s0) && !is_free(int(s), s1)) continue;
+        emit(walk(int(s)));
+    }
+    // Pass 2: what is left has no free end and is a CLOSED loop; start anywhere, forward.
+    for (size_t s = 0; s < open_idx.size(); ++s) {
+        if (used[s]) continue;
+        emit(walk(int(s)));
+    }
+
+    return out;
+}
+
+std::vector<SketchEntity> SketchEngine::array_entities(
+    const std::vector<SketchEntity>& src, int count,
+    const Vec2d& step, double angle_step, const Vec2d& pivot)
+{
+    std::vector<SketchEntity> out;
+    if (count < 2) return out;
+
+    for (int i = 1; i < count; ++i) {
+        const double ang = i * angle_step;
+        const double ca = std::cos(ang), sa = std::sin(ang);
+        const Vec2d  tr  = double(i) * step;
+        // Rigid map: rotate about pivot by `ang`, then translate by `tr`.
+        auto xf = [&](const Vec2d& p) -> Vec2d {
+            const Vec2d d = p - pivot;
+            return Vec2d(pivot.x() + ca * d.x() - sa * d.y(),
+                         pivot.y() + sa * d.x() + ca * d.y()) + tr;
+        };
+
+        for (const auto& e : src) {
+            SketchEntity m = e;   // carry construction flag, radii, etc.
+            switch (e.type) {
+            case SketchEntity::Type::Line:
+                m.p0 = xf(e.p0); m.p1 = xf(e.p1);
+                break;
+            case SketchEntity::Type::Point:
+                m.p0 = xf(e.p0);
+                break;
+            case SketchEntity::Type::Circle:
+                m.center = xf(e.center); m.p0 = m.center;   // radius unchanged
+                break;
+            case SketchEntity::Type::Arc: {
+                m.center      = xf(e.center);
+                m.start_angle = e.start_angle + ang;
+                m.end_angle   = e.end_angle   + ang;        // rigid: sweep preserved
+                m.p0 = m.center + e.radius * Vec2d(std::cos(m.start_angle), std::sin(m.start_angle));
+                m.p1 = m.center + e.radius * Vec2d(std::cos(m.end_angle),   std::sin(m.end_angle));
+                break;
+            }
+            case SketchEntity::Type::Ellipse:
+            case SketchEntity::Type::EllipseArc:
+                m.center   = xf(e.center);
+                m.rotation = e.rotation + ang;              // major axis rotates with the body
+                if (e.type == SketchEntity::Type::Ellipse) {
+                    m.p0 = m.center;
+                } else {
+                    m.p0 = xf(e.p0); m.p1 = xf(e.p1);
+                    // Parametric angles are in the (rotated) body frame -> unchanged.
+                }
+                break;
+            case SketchEntity::Type::BSpline:
+                for (auto& cp : m.ctrl) cp = xf(cp);
+                m.p0 = xf(e.p0); m.p1 = xf(e.p1);
+                break;
+            }
+            out.push_back(m);
+        }
+    }
+    return out;
+}
+
+std::vector<SketchEntity> SketchEngine::transform_entities(
+    const std::vector<SketchEntity>& src,
+    const Vec2d& move, double angle, double scale, const Vec2d& pivot)
+{
+    std::vector<SketchEntity> out;
+    out.reserve(src.size());
+    const double ca = std::cos(angle), sa = std::sin(angle);
+    const double rs = std::abs(scale);   // radii are unsigned magnitudes
+    // Affine map: translate pivot to origin, scale, rotate, then translate by `move`.
+    auto xf = [&](const Vec2d& p) -> Vec2d {
+        const Vec2d d = scale * (p - pivot);
+        return Vec2d(pivot.x() + ca * d.x() - sa * d.y(),
+                     pivot.y() + sa * d.x() + ca * d.y()) + move;
+    };
+
+    for (const auto& e : src) {
+        SketchEntity m = e;   // carry construction flag, etc.
+        switch (e.type) {
+        case SketchEntity::Type::Line:
+            m.p0 = xf(e.p0); m.p1 = xf(e.p1);
+            break;
+        case SketchEntity::Type::Point:
+            m.p0 = xf(e.p0);
+            break;
+        case SketchEntity::Type::Circle:
+            m.center = xf(e.center); m.radius = e.radius * rs; m.p0 = m.center;
+            break;
+        case SketchEntity::Type::Arc: {
+            m.center      = xf(e.center);
+            m.radius      = e.radius * rs;
+            m.start_angle = e.start_angle + angle;
+            m.end_angle   = e.end_angle   + angle;   // rigid sweep, shifted by rotation
+            m.p0 = m.center + m.radius * Vec2d(std::cos(m.start_angle), std::sin(m.start_angle));
+            m.p1 = m.center + m.radius * Vec2d(std::cos(m.end_angle),   std::sin(m.end_angle));
+            break;
+        }
+        case SketchEntity::Type::Ellipse:
+        case SketchEntity::Type::EllipseArc:
+            m.center   = xf(e.center);
+            m.radius   = e.radius * rs;
+            m.rminor   = e.rminor * rs;
+            m.rotation = e.rotation + angle;          // major axis rotates with the body
+            if (e.type == SketchEntity::Type::Ellipse) {
+                m.p0 = m.center;
+            } else {
+                m.p0 = xf(e.p0); m.p1 = xf(e.p1);
+                // Parametric angles live in the (rotated) body frame -> unchanged.
+            }
+            break;
+        case SketchEntity::Type::BSpline:
+            for (auto& cp : m.ctrl) cp = xf(cp);
+            m.p0 = xf(e.p0); m.p1 = xf(e.p1);
+            break;
+        }
+        out.push_back(m);
+    }
+    return out;
+}
+
+bool SketchEngine::fillet_lines(const SketchEntity& a, const SketchEntity& b, double r,
+                                SketchEntity& a_out, SketchEntity& b_out, SketchEntity& arc_out)
+{
+    if (a.type != SketchEntity::Type::Line || b.type != SketchEntity::Type::Line || r <= 1e-9)
+        return false;
+
+    Vec2d da = a.p1 - a.p0;
+    Vec2d db = b.p1 - b.p0;
+    double denom = da.x() * db.y() - da.y() * db.x();
+    if (std::abs(denom) < 1e-12)
+        return false;
+
+    Vec2d diff = b.p0 - a.p0;
+    double s = (diff.x() * db.y() - diff.y() * db.x()) / denom;
+    Vec2d C = a.p0 + s * da;
+
+    Vec2d ua;
+    int   a_near_idx;
+    {
+        double d0 = (a.p0 - C).norm();
+        double d1 = (a.p1 - C).norm();
+        if (d0 <= d1) {
+            a_near_idx = 0;
+            ua = a.p1 - C;
+        } else {
+            a_near_idx = 1;
+            ua = a.p0 - C;
+        }
+    }
+    if (ua.norm() < 1e-12) return false;
+    ua.normalize();
+
+    Vec2d ub;
+    int   b_near_idx;
+    {
+        double d0 = (b.p0 - C).norm();
+        double d1 = (b.p1 - C).norm();
+        if (d0 <= d1) {
+            b_near_idx = 0;
+            ub = b.p1 - C;
+        } else {
+            b_near_idx = 1;
+            ub = b.p0 - C;
+        }
+    }
+    if (ub.norm() < 1e-12) return false;
+    ub.normalize();
+
+    double cosT = ua.dot(ub);
+    cosT = std::max(-1.0, std::min(1.0, cosT));
+    double theta = std::acos(cosT);
+    if (theta < 1e-6 || theta > M_PI - 1e-6)
+        return false;
+
+    double t = r / std::tan(theta / 2.0);
+    {
+        Vec2d a_far = (a_near_idx == 0) ? a.p1 : a.p0;
+        Vec2d b_far = (b_near_idx == 0) ? b.p1 : b.p0;
+        if (t > (a_far - C).norm() || t > (b_far - C).norm())
+            return false;
+    }
+
+    Vec2d Ta = C + t * ua;
+    Vec2d Tb = C + t * ub;
+
+    Vec2d bis = ua + ub;
+    if (bis.norm() < 1e-12) return false;
+    bis.normalize();
+
+    double dCO = r / std::sin(theta / 2.0);
+    Vec2d O = C + dCO * bis;
+
+    a_out = a;
+    b_out = b;
+    if (a_near_idx == 0)
+        a_out.p0 = Ta;
+    else
+        a_out.p1 = Ta;
+
+    if (b_near_idx == 0)
+        b_out.p0 = Tb;
+    else
+        b_out.p1 = Tb;
+
+    arc_out = SketchEntity{};
+    arc_out.type        = SketchEntity::Type::Arc;
+    arc_out.center      = O;
+    arc_out.radius      = r;
+    arc_out.p0          = Ta;
+    arc_out.p1          = Tb;
+    arc_out.start_angle = std::atan2(Ta.y() - O.y(), Ta.x() - O.x());
+
+    double sb = std::atan2(Tb.y() - O.y(), Tb.x() - O.x());
+    double sweep = sb - arc_out.start_angle;
+    while (sweep <= -M_PI) sweep += 2.0 * M_PI;
+    while (sweep >   M_PI) sweep -= 2.0 * M_PI;
+    arc_out.end_angle = arc_out.start_angle + sweep;
+
+    return true;
+}
+
+bool SketchEngine::chamfer_lines(const SketchEntity& a, const SketchEntity& b, double d,
+                                 SketchEntity& a_out, SketchEntity& b_out, SketchEntity& seg_out)
+{
+    if (a.type != SketchEntity::Type::Line || b.type != SketchEntity::Type::Line || d <= 1e-9)
+        return false;
+
+    Vec2d da = a.p1 - a.p0;
+    Vec2d db = b.p1 - b.p0;
+    double denom = da.x() * db.y() - da.y() * db.x();
+    if (std::abs(denom) < 1e-12)
+        return false;   // parallel: no corner to chamfer
+
+    // Shared corner = line/line intersection.
+    Vec2d diff = b.p0 - a.p0;
+    double s = (diff.x() * db.y() - diff.y() * db.x()) / denom;
+    Vec2d C = a.p0 + s * da;
+
+    // For each line, unit vector pointing from the corner toward its far endpoint
+    // (the endpoint that is kept); the near endpoint is the one trimmed back.
+    auto pick = [&](const SketchEntity& ln, int& near_idx, Vec2d& u) -> bool {
+        double d0 = (ln.p0 - C).norm();
+        double d1 = (ln.p1 - C).norm();
+        if (d0 <= d1) { near_idx = 0; u = ln.p1 - C; }
+        else          { near_idx = 1; u = ln.p0 - C; }
+        if (u.norm() < 1e-12) return false;
+        u.normalize();
+        return true;
+    };
+    int a_near_idx, b_near_idx;
+    Vec2d ua, ub;
+    if (!pick(a, a_near_idx, ua)) return false;
+    if (!pick(b, b_near_idx, ub)) return false;
+
+    // Reject collinear (no real corner) and ensure the setback fits both lines.
+    double cosT = std::max(-1.0, std::min(1.0, ua.dot(ub)));
+    if (cosT > 1.0 - 1e-9 || cosT < -1.0 + 1e-9)
+        return false;
+    {
+        Vec2d a_far = (a_near_idx == 0) ? a.p1 : a.p0;
+        Vec2d b_far = (b_near_idx == 0) ? b.p1 : b.p0;
+        if (d > (a_far - C).norm() || d > (b_far - C).norm())
+            return false;
+    }
+
+    Vec2d Ta = C + d * ua;
+    Vec2d Tb = C + d * ub;
+
+    a_out = a;
+    b_out = b;
+    if (a_near_idx == 0) a_out.p0 = Ta; else a_out.p1 = Ta;
+    if (b_near_idx == 0) b_out.p0 = Tb; else b_out.p1 = Tb;
+
+    seg_out = SketchEntity{};
+    seg_out.type = SketchEntity::Type::Line;
+    seg_out.p0   = Ta;
+    seg_out.p1   = Tb;
+    return true;
+}
+
+static std::vector<double> line_entity_hits(const Vec2d& a0, const Vec2d& adir,
+                                            const SketchEntity& other)
+{
+    std::vector<double> hits;
+    double La2 = adir.dot(adir);
+    if (La2 < 1e-18) return hits;
+
+    switch (other.type) {
+    case SketchEntity::Type::Line: {
+        Vec2d bdir = other.p1 - other.p0;
+        double bxa = bdir.x() * adir.y() - bdir.y() * adir.x();
+        if (std::abs(bxa) < 1e-12) return hits;
+
+        Vec2d w  = a0 - other.p0;
+        double u = (w.x() * adir.y() - w.y() * adir.x()) / bxa;
+        if (u < -1e-9 || u > 1.0 + 1e-9) return hits;
+
+        double axb = adir.x() * bdir.y() - adir.y() * bdir.x();
+        Vec2d  w2  = other.p0 - a0;
+        double t   = (w2.x() * bdir.y() - w2.y() * bdir.x()) / axb;
+        hits.push_back(t);
+        break;
+    }
+    case SketchEntity::Type::Circle:
+    case SketchEntity::Type::Arc: {
+        double R = other.radius;
+        Vec2d f = a0 - other.center;
+        double A  = La2;
+        double B  = 2.0 * adir.dot(f);
+        double Cc = f.dot(f) - R * R;
+        double disc = B * B - 4.0 * A * Cc;
+        if (disc < -1e-12) return hits;
+        if (disc < 0.0) disc = 0.0;
+        double sq = std::sqrt(disc);
+        double t1 = (-B - sq) / (2.0 * A);
+        double t2 = (-B + sq) / (2.0 * A);
+
+        auto angle_in_sweep = [&](const Vec2d& P) -> bool {
+            double phi   = std::atan2(P.y() - other.center.y(), P.x() - other.center.x());
+            double sweep = other.end_angle - other.start_angle;
+            double delta = phi - other.start_angle;
+            if (sweep >= 0.0) {
+                while (delta < -1e-9) delta += 2.0 * M_PI;
+                while (delta > 2.0 * M_PI) delta -= 2.0 * M_PI;
+                return delta <= sweep + 1e-9;
+            } else {
+                while (delta > 1e-9) delta -= 2.0 * M_PI;
+                while (delta < -2.0 * M_PI) delta += 2.0 * M_PI;
+                return delta >= sweep - 1e-9;
+            }
+        };
+
+        auto check = [&](double t) {
+            Vec2d P = a0 + t * adir;
+            if (other.type == SketchEntity::Type::Circle || angle_in_sweep(P))
+                hits.push_back(t);
+        };
+
+        check(t1);
+        if (disc > 1e-12)
+            check(t2);
+        break;
+    }
+    default:
+        break;
+    }
+
+    return hits;
+}
+
+// Angles (atan2, radians) where `other` crosses the circle of radius R about C.
+// For Arc/Circle cutters the crossing point must lie within the cutter's own
+// sweep (a full circle always qualifies). Powers arc/circle-subject trim/extend,
+// where the subject is parametrized by angle rather than by a line ray param.
+static std::vector<double> circle_cross_angles(const Vec2d& C, double R,
+                                               const SketchEntity& other)
+{
+    std::vector<double> out;
+    if (R < 1e-12) return out;
+
+    auto on_other = [&](const Vec2d& P) -> bool {
+        switch (other.type) {
+        case SketchEntity::Type::Line: {
+            Vec2d d = other.p1 - other.p0;
+            double L2 = d.dot(d);
+            if (L2 < 1e-18) return false;
+            double u = (P - other.p0).dot(d) / L2;
+            return u > -1e-9 && u < 1.0 + 1e-9;
+        }
+        case SketchEntity::Type::Circle:
+            return true;
+        case SketchEntity::Type::Arc: {
+            double phi   = std::atan2(P.y() - other.center.y(), P.x() - other.center.x());
+            double sweep = other.end_angle - other.start_angle;
+            double delta = phi - other.start_angle;
+            if (sweep >= 0.0) {
+                while (delta < -1e-9) delta += 2.0 * M_PI;
+                while (delta > 2.0 * M_PI) delta -= 2.0 * M_PI;
+                return delta <= sweep + 1e-9;
+            } else {
+                while (delta > 1e-9) delta -= 2.0 * M_PI;
+                while (delta < -2.0 * M_PI) delta += 2.0 * M_PI;
+                return delta >= sweep - 1e-9;
+            }
+        }
+        default:
+            return false;
+        }
+    };
+    auto add = [&](const Vec2d& P) {
+        out.push_back(std::atan2(P.y() - C.y(), P.x() - C.x()));
+    };
+
+    switch (other.type) {
+    case SketchEntity::Type::Line: {
+        Vec2d a0 = other.p0, adir = other.p1 - other.p0;
+        double A = adir.dot(adir);
+        if (A < 1e-18) break;
+        Vec2d f = a0 - C;
+        double B  = 2.0 * adir.dot(f);
+        double Cc = f.dot(f) - R * R;
+        double disc = B * B - 4.0 * A * Cc;
+        if (disc < 0.0) break;
+        double sq = std::sqrt(disc);
+        Vec2d P1 = a0 + ((-B - sq) / (2.0 * A)) * adir;
+        if (on_other(P1)) add(P1);
+        if (disc > 1e-12) {
+            Vec2d P2 = a0 + ((-B + sq) / (2.0 * A)) * adir;
+            if (on_other(P2)) add(P2);
+        }
+        break;
+    }
+    case SketchEntity::Type::Circle:
+    case SketchEntity::Type::Arc: {
+        Vec2d  C2 = other.center;
+        double R2 = other.radius;
+        Vec2d  d  = C2 - C;
+        double dd = d.norm();
+        if (dd < 1e-12) break;                          // concentric
+        if (dd > R + R2 + 1e-9) break;                  // too far apart
+        if (dd < std::abs(R - R2) - 1e-9) break;        // one circle inside the other
+        double a  = (R * R - R2 * R2 + dd * dd) / (2.0 * dd);
+        double h2 = R * R - a * a;
+        if (h2 < 0.0) h2 = 0.0;
+        double h   = std::sqrt(h2);
+        Vec2d  mid = C + (a / dd) * d;
+        Vec2d  perp(-d.y() / dd, d.x() / dd);
+        Vec2d  P1 = mid + h * perp;
+        if (on_other(P1)) add(P1);
+        if (h > 1e-12) {
+            Vec2d P2 = mid - h * perp;
+            if (on_other(P2)) add(P2);
+        }
+        break;
+    }
+    default:
+        break;
+    }
+    return out;
+}
+
+// Wrap x into [0, 2pi).
+static double wrap_2pi(double x)
+{
+    while (x < 0.0)         x += 2.0 * M_PI;
+    while (x >= 2.0 * M_PI) x -= 2.0 * M_PI;
+    return x;
+}
+
+bool SketchEngine::trim_entity(SketchEntity& e, const std::vector<SketchEntity>& others,
+                               const Vec2d& pick)
+{
+    // Arc subject: parametrize by sweep fraction u in [0,1]; cut on the picked side.
+    if (e.type == SketchEntity::Type::Arc) {
+        double sweep = e.end_angle - e.start_angle;
+        if (std::abs(sweep) < 1e-12) return false;
+        double phi_pick = std::atan2(pick.y() - e.center.y(), pick.x() - e.center.x());
+        double u_pick = (phi_pick - e.start_angle) / sweep;
+        // Bring the pick onto the arc's [0,1] domain.
+        while (u_pick < -1e-9) u_pick += (2.0 * M_PI) / std::abs(sweep);
+        u_pick = std::max(0.0, std::min(1.0, u_pick));
+
+        std::vector<double> cuts;
+        for (const auto& other : others) {
+            for (double phi : circle_cross_angles(e.center, e.radius, other)) {
+                double u = (phi - e.start_angle) / sweep;
+                while (u < -1e-9) u += (2.0 * M_PI) / std::abs(sweep);
+                if (u > 1e-9 && u < 1.0 - 1e-9) cuts.push_back(u);
+            }
+        }
+        if (cuts.empty()) return false;
+
+        if (u_pick <= 0.5) {
+            double uc = std::numeric_limits<double>::max();
+            for (double u : cuts) if (u > u_pick + 1e-9 && u < uc) uc = u;
+            if (uc == std::numeric_limits<double>::max()) return false;
+            e.start_angle = e.start_angle + uc * sweep;   // drop [0, uc)
+        } else {
+            double uc = -std::numeric_limits<double>::max();
+            for (double u : cuts) if (u < u_pick - 1e-9 && u > uc) uc = u;
+            if (uc == -std::numeric_limits<double>::max()) return false;
+            e.end_angle = e.start_angle + uc * sweep;      // drop (uc, 1]
+        }
+        return true;
+    }
+
+    // Circle subject: trimming opens it into an Arc that excludes the picked gap.
+    if (e.type == SketchEntity::Type::Circle) {
+        std::vector<double> ang;
+        for (const auto& other : others)
+            for (double phi : circle_cross_angles(e.center, e.radius, other))
+                ang.push_back(wrap_2pi(phi));
+        std::sort(ang.begin(), ang.end());
+        ang.erase(std::unique(ang.begin(), ang.end(),
+                              [](double a, double b){ return std::abs(a - b) < 1e-7; }),
+                  ang.end());
+        if (ang.size() < 2) return false;
+
+        double pk = wrap_2pi(std::atan2(pick.y() - e.center.y(), pick.x() - e.center.x()));
+        const int n = int(ang.size());
+        int idx = -1;
+        for (int i = 0; i < n; ++i) {
+            double lo = ang[i];
+            double hi = (i + 1 < n) ? ang[i + 1] : ang[0] + 2.0 * M_PI;
+            double p  = (pk < lo - 1e-12) ? pk + 2.0 * M_PI : pk;
+            if (p >= lo - 1e-12 && p < hi + 1e-12) { idx = i; break; }
+        }
+        if (idx < 0) return false;
+        double lo = ang[idx];
+        double hi = (idx + 1 < n) ? ang[idx + 1] : ang[0] + 2.0 * M_PI;
+        // Keep the complement of the (lo,hi) gap: sweep ccw from hi back round to lo.
+        e.type        = SketchEntity::Type::Arc;
+        e.start_angle = hi;
+        e.end_angle   = lo + 2.0 * M_PI;
+        return true;
+    }
+
+    if (e.type != SketchEntity::Type::Line) return false;
+
+    Vec2d adir = e.p1 - e.p0;
+    double La2 = adir.dot(adir);
+    if (La2 < 1e-18) return false;
+
+    double t_pick = (pick - e.p0).dot(adir) / La2;
+    t_pick = std::max(0.0, std::min(1.0, t_pick));
+
+    std::vector<double> cuts;
+    for (const auto& other : others) {
+        auto h = line_entity_hits(e.p0, adir, other);
+        for (double t : h) {
+            if (t > 1e-9 && t < 1.0 - 1e-9)
+                cuts.push_back(t);
+        }
+    }
+    if (cuts.empty()) return false;
+
+    if (t_pick <= 0.5) {
+        double tc = std::numeric_limits<double>::max();
+        for (double t : cuts) {
+            if (t > t_pick + 1e-9 && t < tc)
+                tc = t;
+        }
+        if (tc == std::numeric_limits<double>::max()) return false;
+        e.p0 = e.p0 + tc * adir;
+    } else {
+        double tc = -std::numeric_limits<double>::max();
+        for (double t : cuts) {
+            if (t < t_pick - 1e-9 && t > tc)
+                tc = t;
+        }
+        if (tc == -std::numeric_limits<double>::max()) return false;
+        e.p1 = e.p0 + tc * adir;
+    }
+
+    return true;
+}
+
+bool SketchEngine::extend_entity(SketchEntity& e, const std::vector<SketchEntity>& others,
+                                 const Vec2d& pick)
+{
+    // Arc subject: grow the sweep toward the picked end up to the nearest crossing,
+    // capped at a full turn so the arc never self-overlaps. (A Circle is already
+    // closed — nothing to extend.)
+    if (e.type == SketchEntity::Type::Arc) {
+        double sweep = e.end_angle - e.start_angle;
+        double mag   = std::abs(sweep);
+        if (mag < 1e-12) return false;
+        double sgn   = (sweep >= 0.0) ? 1.0 : -1.0;
+        double room  = 2.0 * M_PI - mag;                 // max extra sweep before a full turn
+        if (room <= 1e-9) return false;
+
+        double phi_pick = std::atan2(pick.y() - e.center.y(), pick.x() - e.center.x());
+        double up = wrap_2pi(sgn * (phi_pick - e.start_angle)) / mag;  // pick fraction on arc
+        const bool extend_end = (up > 0.5);
+
+        double best = std::numeric_limits<double>::max();
+        for (const auto& other : others) {
+            for (double phi : circle_cross_angles(e.center, e.radius, other)) {
+                double adv = extend_end ? wrap_2pi(sgn * (phi - e.end_angle))
+                                        : wrap_2pi(sgn * (e.start_angle - phi));
+                if (adv > 1e-9 && adv <= room + 1e-9 && adv < best) best = adv;
+            }
+        }
+        if (best == std::numeric_limits<double>::max()) return false;
+        if (extend_end) e.end_angle   += sgn * best;
+        else            e.start_angle -= sgn * best;
+        return true;
+    }
+
+    if (e.type != SketchEntity::Type::Line) return false;
+
+    Vec2d adir = e.p1 - e.p0;
+    double La2 = adir.dot(adir);
+    if (La2 < 1e-18) return false;
+
+    double t_pick = (pick - e.p0).dot(adir) / La2;
+
+    std::vector<double> hits;
+    for (const auto& other : others) {
+        auto h = line_entity_hits(e.p0, adir, other);
+        hits.insert(hits.end(), h.begin(), h.end());
+    }
+    if (hits.empty()) return false;
+
+    if (t_pick > 0.5) {
+        double tc = std::numeric_limits<double>::max();
+        for (double t : hits) {
+            if (t > 1.0 + 1e-9 && t < tc)
+                tc = t;
+        }
+        if (tc == std::numeric_limits<double>::max()) return false;
+        e.p1 = e.p0 + tc * adir;
+    } else {
+        double tc = -std::numeric_limits<double>::max();
+        for (double t : hits) {
+            if (t < -1e-9 && t > tc)
+                tc = t;
+        }
+        if (tc == -std::numeric_limits<double>::max()) return false;
+        e.p0 = e.p0 + tc * adir;
+    }
+
+    return true;
+}
+
+// Bridge: cubic Bézier with G1 continuity at both ends.
+// Poles = {Pa, Pa + Ta*d/3, Pb - Tb*d/3, Pb}, where d = |Pb - Pa|.
+SketchEntity SketchEngine::make_bridge(const SketchEntity& a, int a_end,
+                                       const SketchEntity& b, int b_end)
+{
+    auto endpoint = [](const SketchEntity& e, int end) -> Vec2d {
+        return end == 0 ? e.p0 : e.p1;
+    };
+
+    auto tangent = [](const SketchEntity& e, int end, const Vec2d& fallback_dir) -> Vec2d {
+        switch (e.type) {
+        case SketchEntity::Type::Line: {
+            Vec2d dir = end == 1 ? e.p1 - e.p0 : e.p0 - e.p1;
+            double len = dir.norm();
+            if (len < 1e-12) return fallback_dir;
+            return dir / len;
+        }
+        case SketchEntity::Type::Arc: {
+            double theta = end == 1 ? e.end_angle : e.start_angle;
+            // Tangent to the circle at angle theta, CCW: (-sin θ, cos θ).
+            // At end=1 (end_angle), the outward direction is along the sweep direction.
+            // At end=0 (start_angle), outward is opposite the sweep direction.
+            double sweep = e.end_angle - e.start_angle;
+            int sign = end == 1 ? (sweep >= 0 ? 1 : -1) : (sweep >= 0 ? -1 : 1);
+            Vec2d t(-std::sin(theta), std::cos(theta));
+            return t * double(sign);
+        }
+        default:
+            // ponytail: straight-ish bridge for unsupported entity types.
+            return fallback_dir;
+        }
+    };
+
+    const Vec2d Pa = endpoint(a, a_end);
+    const Vec2d Pb = endpoint(b, b_end);
+    const double d = (Pb - Pa).norm();
+
+    // Fallback tangent direction: point toward the other endpoint.
+    Vec2d fallback = d < 1e-9 ? Vec2d(1, 0) : (Pb - Pa) / d;
+    Vec2d Ta = tangent(a, a_end, fallback);
+    Vec2d Tb = tangent(b, b_end, fallback * -1.0);
+
+    const double k = std::max(d, 1e-9) / 3.0;
+
+    SketchEntity e;
+    e.type         = SketchEntity::Type::BSpline;
+    e.construction = false;
+    e.ctrl = { Pa, Pa + Ta * k, Pb - Tb * k, Pb };
+    e.p0 = e.ctrl.front();
+    e.p1 = e.ctrl.back();
+    return e;
+}
+
+// ---- entity-constraint planning (Fase 4.2) ----
+// Pure kernel port of DesignPanel::apply_entity_constraint's decision logic, so the GUI
+// and the live-sketch tool share ONE legality/role/value decision instead of each carrying
+// its own copy. The Coincident phantom-p1 defect was fixed in one branch and stayed alive
+// in the next one down precisely because the logic lived in a wx method that could not be
+// unit-tested. No wx, no translation: the caller maps ConstraintReject to a string.
+
+int sketch_entity_ends(const SketchEntity& e, std::pair<SketchPointRole, Vec2d> out[2])
+{
+    using ET = SketchEntity::Type;
+    using R  = SketchPointRole;
+    switch (e.type) {
+    case ET::Line: case ET::Arc: case ET::BSpline: case ET::EllipseArc:
+        out[0] = {R::P0, e.p0}; out[1] = {R::P1, e.p1}; return 2;
+    case ET::Point:
+        out[0] = {R::P0, e.p0}; return 1;
+    case ET::Circle: case ET::Ellipse:
+        out[0] = {R::Center, e.center}; return 1;
+    }
+    return 0;
+}
+
+bool sketch_closest_ends(const SketchEntity& A, const SketchEntity& B,
+                         SketchPointRole& ra, SketchPointRole& rb, Vec2d& pa, Vec2d& pb)
+{
+    std::pair<SketchPointRole, Vec2d> aps[2], bps[2];
+    const int na = sketch_entity_ends(A, aps), nb = sketch_entity_ends(B, bps);
+    if (na == 0 || nb == 0) return false;
+    double best = 1e30;
+    ra = aps[0].first; rb = bps[0].first; pa = aps[0].second; pb = bps[0].second;
+    for (int i = 0; i < na; ++i)
+        for (int j = 0; j < nb; ++j) {
+            const double d = (aps[i].second - bps[j].second).squaredNorm();
+            if (d < best) {
+                best = d;
+                ra = aps[i].first; rb = bps[j].first;
+                pa = aps[i].second; pb = bps[j].second;
+            }
+        }
+    return true;
+}
+
+ConstraintPlan plan_entity_constraint(const std::vector<SketchEntity>& ents,
+                                      int e0, int e1, int e2, SketchConstraintType type)
+{
+    using R  = SketchPointRole;
+    using T  = SketchConstraintType;
+    const int n = int(ents.size());
+
+    ConstraintPlan plan;
+
+    auto is_round = [](const SketchEntity& e) {
+        return e.type == SketchEntity::Type::Circle || e.type == SketchEntity::Type::Arc; };
+
+    // One Equal button, two meanings: lines get equal length, curves equal radius.
+    if (type == T::EqualLength && e0 >= 0 && e1 >= 0 && e0 < n && e1 < n &&
+        is_round(ents[e0]) && is_round(ents[e1]))
+        type = T::EqualRadius;
+
+    const bool needs_two = (type == T::Parallel || type == T::Perpendicular ||
+                            type == T::EqualLength || type == T::Coincident ||
+                            type == T::Concentric || type == T::Tangent ||
+                            type == T::Angle || type == T::Midpoint ||
+                            type == T::Symmetric || type == T::EqualRadius ||
+                            type == T::Collinear ||
+                            type == T::SymmetricAboutY || type == T::SymmetricAboutX ||
+                            type == T::DistanceX || type == T::DistanceY);
+    if (e0 < 0 || e0 >= n || (needs_two && (e1 < 0 || e1 >= n))) {
+        plan.kind   = ConstraintPlan::Kind::Reject;
+        plan.reason = needs_two ? ConstraintReject::NeedTwoEntities : ConstraintReject::NeedOneEntity;
+        return plan;
+    }
+
+    plan.kind = ConstraintPlan::Kind::Apply;
+    SketchEntityConstraintDef def;
+    def.type  = type;
+    def.value = 0.0;
+    switch (type) {
+    case T::Horizontal:
+    case T::Vertical:
+        // One line: level/plumb its own two endpoints. Not pedantry -- with a Point or
+        // Circle picked, P1 is a role the solver silently drops while STORING the
+        // constraint, so the sketch claims to be constrained when it is not.
+        if (ents[e0].type != SketchEntity::Type::Line) {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedALine;
+            return plan;
+        }
+        def.ea = e0; def.ra = R::P0;
+        def.eb = e0; def.rb = R::P1;
+        break;
+    case T::Parallel:
+    case T::Perpendicular:
+    case T::EqualLength:
+        // Two whole line segments (roles unused). Guard ADDED here (the GUI does not check
+        // this yet): a non-line pick produced a def the solver drops, the same silent no-op
+        // as Horizontal on a Point above.
+        if (ents[e0].type != SketchEntity::Type::Line ||
+            ents[e1].type != SketchEntity::Type::Line) {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedTwoLines;
+            return plan;
+        }
+        def.ea = e0; def.eb = e1;
+        break;
+    case T::Coincident: {
+        // Join the closest point pair, NOT {p0,p1} on both -- two Points would otherwise
+        // resolve to their phantom (0,0) p1s and the constraint would do nothing at all.
+        R ra, rb; Vec2d pa, pb;
+        if (!sketch_closest_ends(ents[e0], ents[e1], ra, rb, pa, pb)) {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedJoinablePoints;
+            return plan;
+        }
+        def.ea = e0; def.ra = ra; def.eb = e1; def.rb = rb;
+        break;
+    }
+    case T::DistanceX:
+    case T::DistanceY: {
+        R ra, rb; Vec2d pa, pb;
+        if (!sketch_closest_ends(ents[e0], ents[e1], ra, rb, pa, pb)) {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedMeasurablePoints;
+            return plan;
+        }
+        // The constraint is SIGNED (fixes (pB - pA).dot(axis)). Order the refs so the shown
+        // value is the positive one -- accepting a dimension must be a no-op, not a flip.
+        int a = e0, b = e1;
+        double delta = (type == T::DistanceX) ? (pb.x() - pa.x()) : (pb.y() - pa.y());
+        if (delta < 0.0) { std::swap(a, b); std::swap(ra, rb); delta = -delta; }
+        plan.kind    = ConstraintPlan::Kind::AskValue;
+        def.ea  = a; def.ra = ra;
+        def.eb  = b; def.rb = rb;
+        plan.prefill = delta;
+        break;
+    }
+    case T::Concentric:
+        if (!is_round(ents[e0]) || !is_round(ents[e1])) {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedTwoRounds;
+            return plan;
+        }
+        def.ea = e0; def.ra = R::Center; def.eb = e1; def.rb = R::Center;
+        break;
+    case T::Tangent: {
+        // line+round or round+round; the kernel detects the entity types.
+        const bool ok = (is_round(ents[e0]) && ents[e1].type == SketchEntity::Type::Line) ||
+                        (is_round(ents[e1]) && ents[e0].type == SketchEntity::Type::Line) ||
+                        (is_round(ents[e0]) && is_round(ents[e1]));
+        if (!ok) {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedTangentPair;
+            return plan;
+        }
+        def.ea = e0; def.eb = e1;
+        break;
+    }
+    case T::Angle: {
+        // Angle between two line segments. "Line segments" is a check, not an assumption:
+        // p1-p0 on a Circle is (0,0)-centre, so two circles used to pre-fill with the angle
+        // between their centre POSITION vectors.
+        if (ents[e0].type != SketchEntity::Type::Line ||
+            ents[e1].type != SketchEntity::Type::Line) {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedTwoLines;
+            return plan;
+        }
+        const int a = e0, b = e1;
+        const Vec2d da = ents[a].p1 - ents[a].p0;
+        const Vec2d db = ents[b].p1 - ents[b].p0;
+        double cur = 90.0;
+        const double na = da.norm(), nb = db.norm();
+        if (na > 1e-9 && nb > 1e-9) {
+            const double c = std::max(-1.0, std::min(1.0, da.dot(db) / (na * nb)));
+            cur = std::acos(c) * 180.0 / M_PI;
+        }
+        plan.kind    = ConstraintPlan::Kind::AskValue;
+        def.ea  = a; def.eb = b;
+        plan.prefill = cur;   // degrees; the caller converts to radians on commit
+        break;
+    }
+    case T::Midpoint: {
+        // One pick is a Point, the other a Line: the point is the line's midpoint.
+        const SketchEntity& A = ents[e0];
+        const SketchEntity& B = ents[e1];
+        int pt = -1, ln = -1;
+        if (A.type == SketchEntity::Type::Point && B.type == SketchEntity::Type::Line) { pt = e0; ln = e1; }
+        else if (B.type == SketchEntity::Type::Point && A.type == SketchEntity::Type::Line) { pt = e1; ln = e0; }
+        else {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedPointAndLine;
+            return plan;
+        }
+        def.ea = pt; def.ra = R::P0; def.eb = ln;
+        break;
+    }
+    case T::Symmetric: {
+        // Two entities made symmetric about a third (axis) line: slot0=A, slot1=B, e2=axis.
+        // Two Points -> one pair; two Lines -> two endpoint pairs (P0/P0 and P1/P1), exactly
+        // the defs DesignPanel builds today.
+        const int axis = e2;
+        if (axis < 0 || axis >= n || ents[axis].type != SketchEntity::Type::Line) {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedAxisLine;
+            return plan;
+        }
+        using ET = SketchEntity::Type;
+        const ET ta = ents[e0].type, tb = ents[e1].type;
+        if (!((ta == ET::Point && tb == ET::Point) || (ta == ET::Line && tb == ET::Line))) {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedTwoPointsOrLines;
+            return plan;
+        }
+        auto mk = [&](R ra, R rb) {
+            SketchEntityConstraintDef d;
+            d.type = T::Symmetric;
+            d.ea = e0; d.ra = ra; d.eb = e1; d.rb = rb; d.ec = axis;
+            plan.defs.push_back(d);
+        };
+        if (ta == ET::Point) { mk(R::P0, R::P0); }
+        else                 { mk(R::P0, R::P0); mk(R::P1, R::P1); }
+        return plan;
+    }
+    case T::SymmetricAboutY:
+    case T::SymmetricAboutX: {
+        // Two entities made symmetric about the sketch's vertical/horizontal axis, which is
+        // implicit (no picked axis line): e2 is ignored and the axis is a negative sentinel
+        // in ec.
+        using ET = SketchEntity::Type;
+        const ET ta = ents[e0].type, tb = ents[e1].type;
+        if (!((ta == ET::Point && tb == ET::Point) || (ta == ET::Line && tb == ET::Line))) {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedTwoPointsOrLines;
+            return plan;
+        }
+        const int axis = (type == T::SymmetricAboutY) ? kSketchRefAxisY : kSketchRefAxisX;
+        auto mk = [&](R ra, R rb) {
+            SketchEntityConstraintDef d;
+            d.type = type;
+            d.ea = e0; d.ra = ra; d.eb = e1; d.rb = rb; d.ec = axis;
+            plan.defs.push_back(d);
+        };
+        if (ta == ET::Point) { mk(R::P0, R::P0); }
+        else                 { mk(R::P0, R::P0); mk(R::P1, R::P1); }
+        return plan;
+    }
+    case T::EqualRadius:
+        if (!is_round(ents[e0]) || !is_round(ents[e1])) {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedTwoRounds;
+            return plan;
+        }
+        def.ea = e0; def.eb = e1;
+        break;
+    case T::Collinear:
+        if (ents[e0].type != SketchEntity::Type::Line || ents[e1].type != SketchEntity::Type::Line) {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedTwoLines;
+            return plan;
+        }
+        def.ea = e0; def.eb = e1;
+        break;
+    case T::Fix: {
+        // Anchor the picked entity's reference point to its current coordinate. A single
+        // point -- not both endpoints -- so it composes with an existing H/V/length
+        // constraint instead of duplicating it.
+        using ET = SketchEntity::Type;
+        const ET et = ents[e0].type;
+        def.ea = e0;
+        def.ra = (et == ET::Circle || et == ET::Ellipse ||
+                  et == ET::Arc    || et == ET::EllipseArc) ? R::Center : R::P0;
+        break;
+    }
+    case T::Radius:
+    case T::Diameter: {
+        if (!is_round(ents[e0])) {
+            plan.kind = ConstraintPlan::Kind::Reject;
+            plan.reason = ConstraintReject::NeedRound;
+            return plan;
+        }
+        plan.kind    = ConstraintPlan::Kind::AskValue;
+        def.ea  = e0; def.ra = R::Center;
+        plan.prefill = (type == T::Diameter) ? 2.0 * ents[e0].radius : ents[e0].radius;
+        break;
+    }
+    default:
+        // Distance / LockX / LockY / PointOnLine / PointOnObject (and any future type) have
+        // no entity-constraint binding; the GUI's own switch falls to "Unsupported".
+        plan.kind   = ConstraintPlan::Kind::Reject;
+        plan.reason = ConstraintReject::Unsupported;
+        return plan;
+    }
+    plan.defs.push_back(def);
+    return plan;
+}
+
+} // namespace Slic3r
diff --git a/src/libslic3r/CAD/SketchEngine.hpp b/src/libslic3r/CAD/SketchEngine.hpp
new file mode 100644
index 0000000000..f2166e96a6
--- /dev/null
+++ b/src/libslic3r/CAD/SketchEngine.hpp
@@ -0,0 +1,373 @@
+#ifndef slic3r_SketchEngine_hpp_
+#define slic3r_SketchEngine_hpp_
+
+#include "libslic3r/TriangleMesh.hpp"
+#include "libslic3r/Point.hpp"
+#include "libslic3r/CAD/GeometryEngine.hpp"
+
+#include <gp_Pln.hxx>
+#include <gp_Ax3.hxx>
+#include <TopoDS_Wire.hxx>
+#include <TopoDS_Shape.hxx>
+#include <TopoDS_Face.hxx>
+#include <vector>
+#include <utility>
+
+namespace Slic3r {
+
+struct SketchSegment {
+    enum Type { Line, Arc, Circle, Rectangle, Polygon };
+    Type type{Line};
+    Vec2d p0{0,0}, p1{0,0};
+    Vec2d center{0,0};
+    double radius{0}, start_angle{0}, end_angle{0};
+    std::vector<Vec2d> points;
+    template<class Archive>
+    void serialize(Archive& ar) { ar(type, p0, p1, center, radius, start_angle, end_angle, points); }
+};
+
+struct SketchEntity {
+    enum class Type { Line, Arc, Circle, Point, Ellipse, EllipseArc, BSpline };
+    Type   type{Type::Line};
+    Vec2d  p0{0,0};            // Line: start; Arc/EllipseArc: start; Circle/Point/Ellipse: center; BSpline: first pole
+    Vec2d  p1{0,0};            // Line: end;   Arc/EllipseArc: end;   (unused for Circle/Point/Ellipse); BSpline: last pole
+    Vec2d  center{0,0};        // Arc/Circle/Ellipse(Arc) center
+    double radius{0};          // Circle/Arc radius; Ellipse(Arc): semi-major axis (a)
+    double start_angle{0};     // Arc sweep start; Ellipse(Arc): parametric start angle (radians)
+    double end_angle{0};       // Arc sweep end;   Ellipse(Arc): parametric end angle
+    bool   construction{false};
+    double rminor{0};          // Ellipse(Arc): semi-minor axis (b)
+    double rotation{0};        // Ellipse(Arc): major-axis angle phi (radians, about center)
+    std::vector<Vec2d> ctrl;   // BSpline: control points (poles); p0/p1 mirror first/last pole
+    template<class Archive>
+    void serialize(Archive& ar) {
+        // Append-only: rminor/rotation added for Ellipse(Arc) (P2 Tier-B.1); ctrl for BSpline (B.2).
+        ar(type, p0, p1, center, radius, start_angle, end_angle, construction, rminor, rotation, ctrl);
+    }
+};
+
+struct SketchPlane {
+    Vec3d origin{0,0,0};
+    Vec3d normal{0,0,1};
+    Vec3d x_axis{1,0,0};
+    Vec3d y_axis{0,1,0};
+
+    gp_Pln to_occt() const;
+    static SketchPlane from_face(const TopoDS_Face& face);
+    static SketchPlane XY() { return {}; }
+    static SketchPlane XZ() { return {{0,0,0}, {0,1,0}, {1,0,0}, {0,0,1}}; }
+    static SketchPlane YZ() { return {{0,0,0}, {1,0,0}, {0,1,0}, {0,0,1}}; }
+
+    Vec2d project(const Vec3d& ray_origin, const Vec3d& ray_dir) const;
+    Vec3d to_world(const Vec2d& pt) const;
+
+    template<class Archive>
+    void serialize(Archive& ar) { ar(origin, normal, x_axis, y_axis); }
+};
+
+struct SketchProfile {
+    std::vector<Vec2d> points;
+    bool closed{false};
+
+    bool is_closed(double tolerance = 0.5) const;
+    bool try_close(double tolerance = 0.5);
+    void clear() { points.clear(); closed = false; }
+    TopoDS_Wire to_occt_wire(const SketchPlane& plane) const;
+
+    template<class Archive>
+    void serialize(Archive& ar) { ar(points, closed); }
+};
+
+// Two sketch endpoints this close are ONE joint. Shared deliberately by the viewport
+// (region_loops / connected_loop / open-end detection) and by the kernel
+// (entities_to_wires): the viewport is what shades a region closed and offers it for
+// extrude, so the kernel MUST be able to build every loop the viewport shades. When
+// these two numbers disagreed the viewport promised a closed region at 1e-3 and the
+// kernel refused it at 1e-4, which extruded a solid the user never drew.
+// Nothing legitimate in a mm-scale sketch is 1 um apart.
+inline constexpr double kSketchJoinTol = 1e-3;   // mm
+
+// Effective sketch joint tolerance. ONE value for the viewport (region_loops /
+// loop_report / connected_loop) and the kernel (entities_to_wires): if these ever
+// disagree again, the viewport shades a region closed that the kernel refuses to
+// build, which is how a sketch got extruded into the wrong solid. The GUI pushes
+// the "auto_close_sketch_loops" preference in via set_sketch_auto_close(); the
+// kernel defaults to ON so headless/kernel-only callers keep welding.
+double sketch_join_tol();
+void   set_sketch_auto_close(bool on);
+
+enum class SketchConstraintType {
+    Fix, Coincident, Horizontal, Vertical, Distance,
+    LockX, LockY, EqualLength, Parallel, Perpendicular,
+    Concentric,
+    Tangent, Midpoint, Symmetric, Angle,
+    Radius, Diameter,
+    PointOnLine,  // a point lies on a line (or at signed perpendicular distance `value`)
+    PointOnObject, // a point lies on an entity edge (line -> PT_ON_LINE, circle -> PT_ON_CIRCLE)
+    // Append-only: cereal serializes this enum positionally as its underlying int, so
+    // inserting anywhere but the end reinterprets every constraint in every saved recipe.
+    EqualRadius,
+    Collinear,
+    DistanceX,     // |dx| between two points, projected onto the sketch X axis
+    DistanceY,     // |dy| between two points, projected onto the sketch Y axis
+    SymmetricAboutY, // mirror across the sketch's vertical axis (x = 0); axis is implicit
+    SymmetricAboutX  // mirror across the sketch's horizontal axis (y = 0); axis is implicit
+};
+
+// Constraint on a SketchProfile, referencing profile point indices (a,b,c,d).
+// `value` carries the target for Distance/LockX/LockY (ignored otherwise).
+struct SketchConstraintDef {
+    SketchConstraintType type{SketchConstraintType::Coincident};
+    int    a{-1}, b{-1}, c{-1}, d{-1};
+    double value{0.0};
+    template<class Archive> void serialize(Archive& ar) { ar(type, a, b, c, d, value); }
+};
+
+// Which point of an entity a constraint reference names.
+//   P0 = SketchEntity::p0 (Line start / Point position)
+//   P1 = SketchEntity::p1 (Line end)
+//   Center = SketchEntity::center (Arc/Circle center)
+enum class SketchPointRole { P0, P1, Center };
+
+// Constraint on coexisting SketchEntity objects (Fase 4.2). Each reference is an
+// (entity index, point role) pair. Point-form constraints
+// (Fix/Coincident/Horizontal/Vertical/Distance/LockX/LockY) use refs A and B as
+// individual points. Segment-form constraints (Parallel/Perpendicular/EqualLength)
+// use entity indices `ea`/`eb` as whole line segments (their P0->P1); roles are
+// ignored for those. `value` carries the target for Distance/LockX/LockY.
+struct SketchEntityConstraintDef {
+    SketchConstraintType type{SketchConstraintType::Coincident};
+    int             ea{-1}, eb{-1};                     // entity indices
+    SketchPointRole ra{SketchPointRole::P0};            // role within ea
+    SketchPointRole rb{SketchPointRole::P0};            // role within eb
+    double          value{0.0};
+    int             ec{-1};                             // third entity ref (Symmetric axis)
+    SketchPointRole rc{SketchPointRole::P0};            // role within ec
+    template<class Archive> void serialize(Archive& ar) { ar(type, ea, eb, ra, rb, value, ec, rc); }
+};
+
+// Implicit references every sketch has, addressable from a constraint's ea/eb/ec without
+// existing as SketchEntity objects. NEGATIVE so they cannot collide with an entity index;
+// -1 is already "unset" and stays that way. Values are serialized inside existing int
+// fields, so they are append-only in spirit: never renumber these.
+constexpr int kSketchRefOrigin = -2;   // the sketch origin point (0,0)
+constexpr int kSketchRefAxisX  = -3;   // the sketch X axis, through the origin, +X
+constexpr int kSketchRefAxisY  = -4;   // the sketch Y axis, through the origin, +Y
+
+inline bool is_sketch_ref(int ei) { return ei <= kSketchRefOrigin; }
+
+// How many real endpoints a type exposes, and which roles they are. p1 is UNUSED for
+// Circle/Point/Ellipse (SketchEntity::p1 above) and reads (0,0) — walking {P0,P1} blindly
+// over those invents a phantom endpoint at the origin, which for a pair of Points always
+// wins a closest-pair search at distance 0 and binds a role the solver silently refuses.
+int  sketch_entity_ends(const SketchEntity& e, std::pair<SketchPointRole, Vec2d> out[2]);
+bool sketch_closest_ends(const SketchEntity& A, const SketchEntity& B,
+                         SketchPointRole& ra, SketchPointRole& rb, Vec2d& pa, Vec2d& pb);
+
+// Why an entity-constraint pick is refused. The caller maps a reason to a localized string;
+// the planner itself stays translation-free.
+enum class ConstraintReject {
+    None, NeedOneEntity, NeedTwoEntities, NeedALine, NeedTwoLines,
+    NeedTwoRounds, NeedTangentPair, NeedJoinablePoints, NeedMeasurablePoints,
+    // The following are not in the GUI's current switch but are the faithful outcomes of
+    // its remaining branches; they need a reason too or the caller cannot tell them apart.
+    NeedPointAndLine,     // Midpoint: one Point + one Line
+    NeedTwoPointsOrLines, // Symmetric / SymmetricAboutX/Y: two Points or two Lines
+    NeedAxisLine,         // Symmetric: e2 must be a Line to act as the axis
+    NeedRound,            // Radius/Diameter: a Circle or Arc
+    Unsupported           // entity-constraint path has no binding for this type
+};
+
+struct ConstraintPlan {
+    enum class Kind { Reject, Apply, AskValue };
+    Kind                                   kind{Kind::Reject};
+    ConstraintReject                       reason{ConstraintReject::None};
+    // Apply/AskValue only: the defs to commit. One element for every ordinary type, TWO for
+    // Symmetric/SymmetricAboutX/Y on two lines (P0/P0 and P1/P1), matching the GUI's builds.
+    std::vector<SketchEntityConstraintDef> defs{};
+    double                                 prefill{0.0};   // AskValue only: the value to show pre-filled
+};
+
+// Pure: no wx, no translation, no UI. The caller maps `reason` to a localized string.
+// e2 is the axis-line pick Symmetric needs (def.ec); every other type ignores it.
+ConstraintPlan plan_entity_constraint(const std::vector<SketchEntity>& ents,
+                                      int e0, int e1, int e2, SketchConstraintType type);
+
+// Solve a bare entity list in place against entity-form constraints. Shared by
+// CadDocument::solve_sketch_feature (committed features) and the in-session GUI
+// sketch tool (live solving as dimensions/constraints are added). Returns true on
+// convergence; an empty constraint list is a no-op that returns true.
+bool solve_sketch_entities(std::vector<SketchEntity>& entities,
+                           const std::vector<SketchEntityConstraintDef>& constraints);
+
+struct SketchParams {
+    // Extrude/Revolve
+    double extrude_len{10}; bool extrude_sym{false}; double extrude_taper{0};
+    double revolve_deg{360};
+    bool   is_pocket{false}; // cut into selected object instead of new
+
+    // Dress-up
+    bool        dressup_enabled{false};
+    DressUpType dressup_type{DressUpType::Fillet};
+    FaceGroup   dressup_faces{FaceGroup::All};
+    double      dressup_radius{1.0};
+    double      dressup_chamfer_dist{1.0};
+
+    // Mesh
+    double linear_deflection{0.01};
+
+    template<class Archive>
+    void serialize(Archive& ar) {
+        ar(extrude_len, extrude_sym, extrude_taper, revolve_deg, is_pocket,
+           dressup_enabled, dressup_type, dressup_faces, dressup_radius, dressup_chamfer_dist,
+           linear_deflection);
+    }
+};
+
+class SketchEngine
+{
+public:
+    static TopoDS_Shape make_extrude(const TopoDS_Wire& wire, const SketchPlane& plane,
+                                     double length, bool symmetric = false, double taper_deg = 0.0);
+    static TopoDS_Shape make_extrude(const TopoDS_Face& face, const SketchPlane& plane,
+                                     double length, bool symmetric = false, double taper_deg = 0.0);
+    // Asymmetric two-sided prism: extrude the wire's face by `up` along +normal and `down`
+    // along -normal, fused into one solid. up/down are non-negative magnitudes.
+    // Tapered (draft) extrude of a planar wire: the top profile is the base wire offset in its
+    // plane by length*tan(taper_deg), lofted from base to top. Falls back to a straight prism on
+    // any failure (self-intersecting offset / loft error). taper_deg>0 widens the top.
+    static TopoDS_Shape make_extrude_taper(const TopoDS_Wire& wire, const SketchPlane& plane,
+                                           double length, double taper_deg);
+    static TopoDS_Shape make_extrude_two_sided(const TopoDS_Wire& wire, const SketchPlane& plane,
+                                               double up, double down);
+    static TopoDS_Shape make_extrude_two_sided(const TopoDS_Face& face, const SketchPlane& plane,
+                                               double up, double down);
+    static TopoDS_Shape make_extrude_face(const TopoDS_Face& face, const SketchPlane& plane,
+                                          double length, bool symmetric = false, double taper_deg = 0.0);
+
+    // Extrude a set of imported rigid regions (Text/SVG). Each region is
+    // contour[0]=outer loop + contour[1..]=hole loops, in plane (u,v) mm. Builds
+    // one planar face-with-holes per region, extrudes it, and fuses all region
+    // solids into a single shape. Empty/degenerate contours are skipped.
+    static TopoDS_Shape make_extrude_regions(
+        const std::vector<std::vector<std::vector<Vec2d>>>& regions,
+        const SketchPlane& plane, double length, bool symmetric = false);
+
+    // Revolve a planar profile wire about an axis lying in the sketch plane and
+    // passing through the plane origin: axis_sel 0 = plane X axis, 1 = plane Y axis.
+    // A negative angle_deg sweeps the opposite direction (Flip). The profile must
+    // lie to one side of the axis (Onshape rule); a straddling profile self-intersects.
+    static TopoDS_Shape make_revolve(const TopoDS_Wire& wire, const SketchPlane& plane,
+                                     double angle_deg = 360.0, int axis_sel = 0);
+
+    // Sweep a planar profile wire along a path (spine) wire. The profile is turned
+    // into a face and swept with BRepOffsetAPI_MakePipe, which keeps the profile
+    // perpendicular to the spine along its length. The path may be open or closed;
+    // for a clean solid the path's first point should sit on/near the profile plane.
+    static TopoDS_Shape make_sweep(const TopoDS_Wire& profile, const TopoDS_Wire& path);
+
+    // Loft a solid through 2+ closed profile wires (each on its own plane), in the
+    // given order. ruled=true => straight (ruled) sections; false => smooth (C2).
+    static TopoDS_Shape make_loft(const std::vector<TopoDS_Wire>& profiles, bool ruled);
+
+    // Skin `profiles` WITHOUT end caps -> an open shell (sheet). Same as make_loft but the
+    // ThruSections solid flag is false. // ponytail: a sibling instead of a bool param, so no
+    // existing call site changes.
+    static TopoDS_Shape make_loft_surface(const std::vector<TopoDS_Wire>& profiles, bool ruled);
+
+    static TopoDS_Shape make_pocket(const TopoDS_Wire& wire, const SketchPlane& plane,
+                                    const TopoDS_Shape& target, double depth);
+
+    static TriangleMesh tessellate(const TopoDS_Shape& shape,
+                                   double linear_deflection = 0.01,
+                                   double angular_deflection = 0.5);
+
+    static TriangleMesh tessellate(const TopoDS_Shape& shape,
+                                   std::vector<int>& tri_face,
+                                   double linear_deflection = 0.01,
+                                   double angular_deflection = 0.5);
+
+    static TopoDS_Wire entities_to_wire(const std::vector<SketchEntity>& entities,
+                                        const SketchPlane& plane,
+                                        bool closed_only = false);
+
+    // Every loop the sketch holds, in the order each loop's FIRST entity appears in
+    // `entities`. A Circle or Ellipse is a loop on its own; Line/Arc/EllipseArc/BSpline
+    // entities are grouped into loops by shared endpoints. An OPEN chain is returned too —
+    // a sweep path is legitimately open, so open-ness is not an error here — unless
+    // `closed_only` is true, in which case an open chain is DISCARDED (skipped, not an
+    // error). Empty vector = nothing usable; the caller decides whether that is an error.
+    static std::vector<TopoDS_Wire> entities_to_wires(const std::vector<SketchEntity>& entities,
+                                                      const SketchPlane& plane,
+                                                      bool closed_only = false);
+
+    // A planar face from a set of coplanar loops: the largest-area loop is the outer boundary
+    // and every other loop is a hole in it. Throws std::runtime_error with a message naming the
+    // problem when the loops do not describe one such region.
+    static TopoDS_Face wires_to_face(const std::vector<TopoDS_Wire>& wires,
+                                     const SketchPlane& plane);
+
+    static std::vector<SketchEntity> mirror_entities(
+        const std::vector<SketchEntity>& src, const Vec2d& a, const Vec2d& b);
+
+    // Offset a sketch by `d`, PRESERVING CHAINS. Entities joined by shared endpoints are
+    // offset together and their seams repaired (miter join), so a closed profile comes back
+    // closed and can still be extruded; per-entity offsetting cannot do that. Sign convention:
+    // +d moves each curve to the LEFT of its direction of travel, which for a CCW closed loop
+    // is inward. Ellipses and splines are not offset (a parallel of either is not the same
+    // kind of curve) and are dropped from the result.
+    static std::vector<SketchEntity> offset_entities(
+        const std::vector<SketchEntity>& src, double d);
+
+    // Rigid-transform array. Returns the (count-1) copies for instance i=1..count-1
+    // (the originals in `src` are NOT included). Each copy i is `src` rigidly
+    // transformed by: rotate by i*angle_step about `pivot`, then translate by i*step.
+    //   Rectangular/linear array: angle_step = 0, step = spacing*direction (pivot unused).
+    //   Polar array:              step = (0,0), angle_step = sweep/count, pivot = centre.
+    // Orientation-preserving, so arc/ellipse parametric angles shift by i*angle_step.
+    static std::vector<SketchEntity> array_entities(
+        const std::vector<SketchEntity>& src, int count,
+        const Vec2d& step, double angle_step, const Vec2d& pivot);
+
+    // General affine transform (move / rotate / scale), applied IN PLACE: returns
+    // the SAME entities (same count and order), each mapped by
+    //   p -> pivot + scale * R(angle) * (p - pivot) + move
+    // (radii scale by |scale|; arc/ellipse parametric/rotation angles shift by
+    // `angle`). Unlike array_entities this mutates the subjects rather than adding
+    // copies. Move: angle=0, scale=1. Rotate-in-place: move=(0,0), scale=1,
+    // pivot=centroid. Scale: angle=0.
+    static std::vector<SketchEntity> transform_entities(
+        const std::vector<SketchEntity>& src,
+        const Vec2d& move, double angle, double scale, const Vec2d& pivot);
+
+    static bool fillet_lines(const SketchEntity& a, const SketchEntity& b, double r,
+                             SketchEntity& a_out, SketchEntity& b_out, SketchEntity& arc_out);
+
+    // Symmetric chamfer between two lines meeting at a corner: trims each line back
+    // by setback distance `d` from the shared corner and returns the connecting
+    // straight segment (seg_out) in place of the corner. a_out/b_out are the trimmed
+    // lines; seg_out goes seg_out.p0 (on a) -> seg_out.p1 (on b). False if the lines
+    // are parallel or `d` overruns either line.
+    static bool chamfer_lines(const SketchEntity& a, const SketchEntity& b, double d,
+                              SketchEntity& a_out, SketchEntity& b_out, SketchEntity& seg_out);
+
+    static bool trim_entity(SketchEntity& e, const std::vector<SketchEntity>& others,
+                            const Vec2d& pick);
+
+    static bool extend_entity(SketchEntity& e, const std::vector<SketchEntity>& others,
+                              const Vec2d& pick);
+
+    // Build a cubic-Bezier G1 bridge (as a BSpline entity, 4 poles) connecting endpoint
+    // `a_end` of `a` to endpoint `b_end` of `b` (0 = start/p0 side, 1 = end/p1 side).
+    // Tangent-continuous with both entities where the endpoint tangent is defined.
+    static SketchEntity make_bridge(const SketchEntity& a, int a_end,
+                                    const SketchEntity& b, int b_end);
+};
+
+// Free endpoints of a sketch: the sketch-space points where a chain fails to close.
+// Same weld tolerance as the wire build, so it can never contradict it.
+std::vector<Vec2d> sketch_open_ends(const std::vector<SketchEntity>&, const SketchPlane&);
+
+} // namespace Slic3r
+
+#endif // slic3r_SketchEngine_hpp_
diff --git a/src/libslic3r/CAD/SketchImport.cpp b/src/libslic3r/CAD/SketchImport.cpp
new file mode 100644
index 0000000000..7140776603
--- /dev/null
+++ b/src/libslic3r/CAD/SketchImport.cpp
@@ -0,0 +1,145 @@
+#include "libslic3r/CAD/SketchImport.hpp"
+
+#include "libslic3r/Emboss.hpp"
+#include "libslic3r/NSVGUtils.hpp"
+#include "libslic3r/ExPolygon.hpp"
+#include "libslic3r/TextConfiguration.hpp"   // FontProp
+#include "libslic3r/libslic3r.h"             // SCALING_FACTOR
+#include "libslic3r/Utils.hpp"               // resources_dir
+
+#include <algorithm>
+#include <limits>
+
+namespace Slic3r {
+
+// Convert one ExPolygon (outer contour + CW holes) into an ImportRegion,
+// mapping each integer Point to plane (u,v) mm via `to_mm`.
+template<class ToMm>
+static ImportRegion expoly_to_region(const ExPolygon& ex, ToMm to_mm)
+{
+    auto contour_pts = [&](const Polygon& poly) {
+        std::vector<Vec2d> c;
+        c.reserve(poly.points.size());
+        for (const Point& p : poly.points)
+            c.push_back(to_mm(p));
+        return c;
+    };
+    ImportRegion region;
+    region.push_back(contour_pts(ex.contour));
+    for (const Polygon& h : ex.holes)
+        region.push_back(contour_pts(h));
+    return region;
+}
+
+// Shift all regions so their common bounding-box centre sits on the origin
+// (Onshape/typical CAD insert places imported art centred on the sketch).
+static void center_regions(ImportRegions& regs)
+{
+    double lo_x =  std::numeric_limits<double>::max();
+    double lo_y =  std::numeric_limits<double>::max();
+    double hi_x = -std::numeric_limits<double>::max();
+    double hi_y = -std::numeric_limits<double>::max();
+    bool any = false;
+    for (const auto& region : regs)
+        for (const auto& contour : region)
+            for (const Vec2d& p : contour) {
+                lo_x = std::min(lo_x, p.x()); hi_x = std::max(hi_x, p.x());
+                lo_y = std::min(lo_y, p.y()); hi_y = std::max(hi_y, p.y());
+                any = true;
+            }
+    if (!any) return;
+    const Vec2d c(0.5 * (lo_x + hi_x), 0.5 * (lo_y + hi_y));
+    for (auto& region : regs)
+        for (auto& contour : region)
+            for (Vec2d& p : contour)
+                p -= c;
+}
+
+static std::string default_font_path()
+{
+    return resources_dir() + "/fonts/HarmonyOS_Sans_SC_Regular.ttf";
+}
+
+ImportRegions text_to_regions(const std::string& utf8, double size_mm,
+                              const std::string& font_path)
+{
+    if (utf8.empty() || size_mm <= 0.0)
+        return {};
+
+    const std::string path = font_path.empty() ? default_font_path() : font_path;
+    std::unique_ptr<Emboss::FontFile> ff = Emboss::create_font_file(path.c_str());
+    if (!ff)
+        return {};
+    Emboss::FontFileWithCache fwc(std::move(ff));
+    if (!fwc.has_value())
+        return {};
+
+    FontProp prop(static_cast<float>(size_mm));   // per_glyph=false
+    HealedExPolygons healed = Emboss::text2shapes(fwc, utf8.c_str(), prop);
+    if (healed.expolygons.empty())
+        return {};
+
+    // Shape points are integers scaled by 1/SHAPE_SCALE in font units;
+    // get_text_shape_scale collapses (size_in_mm / unit_per_em) * SHAPE_SCALE
+    // into a single mm-per-shape-unit factor. FreeType y is up already.
+    const double s = Emboss::get_text_shape_scale(prop, *fwc.font_file);
+    auto to_mm = [s](const Point& p) { return Vec2d(p.x() * s, p.y() * s); };
+
+    ImportRegions regs;
+    regs.reserve(healed.expolygons.size());
+    for (const ExPolygon& ex : healed.expolygons)
+        regs.push_back(expoly_to_region(ex, to_mm));
+
+    center_regions(regs);
+    return regs;
+}
+
+ImportRegions svg_to_regions(const std::string& svg_path, double scale)
+{
+    if (svg_path.empty() || scale <= 0.0)
+        return {};
+
+    NSVGimage_ptr image = nsvgParseFromFile(svg_path, "mm", 96.0f);
+    if (!image)
+        return {};
+
+    // A filled shape that also carries a stroke would import the stroke as a
+    // thick outline band wrapped around the fill (the reported "too large line
+    // width"). For CAD import the fill silhouette is what's wanted, so drop the
+    // stroke on any shape that has a fill; stroke-only line art is kept.
+    for (NSVGshape* s = image->shapes; s != nullptr; s = s->next)
+        if (s->fill.type != NSVG_PAINT_NONE)
+            s->stroke.type = NSVG_PAINT_NONE;
+
+    // tesselation tolerance is in image (mm) scale; 0.3 mm keeps curves smooth
+    // without exploding the contour count. is_y_negative (default) flips SVG's
+    // y-down to the sketch's y-up.
+    NSVGLineParams param(0.3);
+    ExPolygonsWithIds ids = create_shape_with_ids(*image, param);
+
+    // NSVG points are integers scaled by 1/SCALING_FACTOR (param.scale default):
+    // mm = point * SCALING_FACTOR, then the user scale factor.
+    const double s = SCALING_FACTOR * scale;
+    auto to_mm = [s](const Point& p) { return Vec2d(p.x() * s, p.y() * s); };
+
+    ImportRegions regs;
+    for (const ExPolygonsWithId& w : ids)
+        for (const ExPolygon& ex : w.expoly)
+            regs.push_back(expoly_to_region(ex, to_mm));
+
+    center_regions(regs);
+    return regs;
+}
+
+ImportRegions transform_regions(const ImportRegions& src, const Vec2d& offset,
+                                double scale_x, double scale_y)
+{
+    ImportRegions out = src;
+    for (auto& region : out)
+        for (auto& contour : region)
+            for (Vec2d& p : contour)
+                p = Vec2d(p.x() * scale_x + offset.x(), p.y() * scale_y + offset.y());
+    return out;
+}
+
+} // namespace Slic3r
diff --git a/src/libslic3r/CAD/SketchImport.hpp b/src/libslic3r/CAD/SketchImport.hpp
new file mode 100644
index 0000000000..0873b0b861
--- /dev/null
+++ b/src/libslic3r/CAD/SketchImport.hpp
@@ -0,0 +1,37 @@
+#ifndef slic3r_SketchImport_hpp_
+#define slic3r_SketchImport_hpp_
+
+#include "libslic3r/Point.hpp"   // Vec2d
+
+#include <string>
+#include <vector>
+
+namespace Slic3r {
+
+// A rigid imported region: contour[0] = outer loop, contour[1..] = holes;
+// points in plane (u,v) millimetres. The nested vector type matches
+// CadFeature::imported_regions exactly, so results assign directly.
+using ImportRegion  = std::vector<std::vector<Vec2d>>;
+using ImportRegions = std::vector<ImportRegion>;
+
+// Vectorize UTF-8 text into filled regions (mm), centred on the origin.
+// `size_mm` is the cap/line height. `font_path` empty -> a bundled default
+// font (resources/fonts). Returns an empty vector on any failure.
+ImportRegions text_to_regions(const std::string& utf8, double size_mm,
+                              const std::string& font_path = std::string());
+
+// Parse an SVG file's filled paths into regions (mm), centred on the origin.
+// `scale` multiplies the authored size (1.0 = as authored). Returns an empty
+// vector on any failure.
+ImportRegions svg_to_regions(const std::string& svg_path, double scale = 1.0);
+
+// Apply an axis-aligned placement transform to regions:
+//   p -> ( p.x * scale_x + offset.x,  p.y * scale_y + offset.y )
+// Used to move / enlarge / stretch imported art non-destructively (the
+// feature keeps the centred source regions + this transform).
+ImportRegions transform_regions(const ImportRegions& src, const Vec2d& offset,
+                                double scale_x, double scale_y);
+
+} // namespace Slic3r
+
+#endif // slic3r_SketchImport_hpp_
diff --git a/src/libslic3r/CAD/SketchInference.cpp b/src/libslic3r/CAD/SketchInference.cpp
new file mode 100644
index 0000000000..cfeb2cd509
--- /dev/null
+++ b/src/libslic3r/CAD/SketchInference.cpp
@@ -0,0 +1,234 @@
+#include "libslic3r/CAD/SketchInference.hpp"
+
+#include <algorithm>
+#include <cmath>
+
+namespace Slic3r {
+
+// Candidate target collected during the scan; we keep the closest within each
+// priority tier and resolve ties by tier then distance.
+namespace {
+struct Cand {
+    InferenceSnap::Kind kind{InferenceSnap::Kind::None};
+    int                 entity{-1};
+    SketchPointRole     role{SketchPointRole::P0};
+    Vec2d               point{0, 0};
+    double              dist{0.0};
+};
+
+// Lower number = higher priority.
+int tier(InferenceSnap::Kind k)
+{
+    switch (k) {
+    case InferenceSnap::Kind::Endpoint: return 0;
+    case InferenceSnap::Kind::Center:   return 1;
+    case InferenceSnap::Kind::Origin:   return 2;
+    case InferenceSnap::Kind::Midpoint: return 3;
+    case InferenceSnap::Kind::OnEdge:   return 4;
+    default:                            return 9;
+    }
+}
+} // namespace
+
+InferenceSnap infer_point_snap(const std::vector<SketchEntity>& entities,
+                               const Vec2d& query, double tol,
+                               bool include_origin)
+{
+    Cand best;
+    best.kind = InferenceSnap::Kind::None;
+    best.point = query;
+
+    auto offer = [&](InferenceSnap::Kind k, int ent, SketchPointRole r, const Vec2d& q) {
+        const double d = (q - query).norm();
+        if (d > tol) return;
+        const bool better = (best.kind == InferenceSnap::Kind::None) ||
+                            (tier(k) < tier(best.kind)) ||
+                            (tier(k) == tier(best.kind) && d < best.dist);
+        if (better) { best.kind = k; best.entity = ent; best.role = r; best.point = q; best.dist = d; }
+    };
+
+    for (size_t i = 0; i < entities.size(); ++i) {
+        const SketchEntity& e = entities[i];
+        const int ei = int(i);
+        switch (e.type) {
+        case SketchEntity::Type::Line: {
+            offer(InferenceSnap::Kind::Endpoint, ei, SketchPointRole::P0, e.p0);
+            offer(InferenceSnap::Kind::Endpoint, ei, SketchPointRole::P1, e.p1);
+            offer(InferenceSnap::Kind::Midpoint, ei, SketchPointRole::P0, 0.5 * (e.p0 + e.p1));
+            // Projection onto the segment interior (PointOnObject candidate).
+            const Vec2d d = e.p1 - e.p0;
+            const double L2 = d.squaredNorm();
+            if (L2 > 1e-12) {
+                double t = (query - e.p0).dot(d) / L2;
+                if (t > 0.02 && t < 0.98)
+                    offer(InferenceSnap::Kind::OnEdge, ei, SketchPointRole::P0, e.p0 + t * d);
+            }
+            break;
+        }
+        case SketchEntity::Type::Arc: {
+            offer(InferenceSnap::Kind::Endpoint, ei, SketchPointRole::P0, e.p0);
+            offer(InferenceSnap::Kind::Endpoint, ei, SketchPointRole::P1, e.p1);
+            offer(InferenceSnap::Kind::Center,   ei, SketchPointRole::Center, e.center);
+            // Mid-arc point, so an arc is as snappable in its middle as a line is.
+            const double am = 0.5 * (e.start_angle + e.end_angle);
+            offer(InferenceSnap::Kind::Midpoint, ei, SketchPointRole::P0,
+                  Vec2d(e.center.x() + e.radius * std::cos(am),
+                        e.center.y() + e.radius * std::sin(am)));
+            break;
+        }
+        case SketchEntity::Type::Circle: {
+            offer(InferenceSnap::Kind::Center, ei, SketchPointRole::Center, e.center);
+            // Nearest point on the circle rim (PointOnObject candidate).
+            const Vec2d v = query - e.center;
+            const double n = v.norm();
+            if (n > 1e-9 && e.radius > 1e-9)
+                offer(InferenceSnap::Kind::OnEdge, ei, SketchPointRole::Center,
+                      e.center + v * (e.radius / n));
+            break;
+        }
+        case SketchEntity::Type::Point:
+            offer(InferenceSnap::Kind::Endpoint, ei, SketchPointRole::P0, e.p0);
+            break;
+        case SketchEntity::Type::EllipseArc:
+            offer(InferenceSnap::Kind::Endpoint, ei, SketchPointRole::P0, e.p0);
+            offer(InferenceSnap::Kind::Endpoint, ei, SketchPointRole::P1, e.p1);
+            offer(InferenceSnap::Kind::Center,   ei, SketchPointRole::Center, e.center);
+            break;
+        case SketchEntity::Type::Ellipse:
+            offer(InferenceSnap::Kind::Center, ei, SketchPointRole::Center, e.center);
+            break;
+        case SketchEntity::Type::BSpline:
+            // Endpoints (first/last pole) snap for loop closure.
+            offer(InferenceSnap::Kind::Endpoint, ei, SketchPointRole::P0, e.p0);
+            offer(InferenceSnap::Kind::Endpoint, ei, SketchPointRole::P1, e.p1);
+            break;
+        }
+    }
+
+    if (include_origin)
+        offer(InferenceSnap::Kind::Origin, -1, SketchPointRole::P0, Vec2d(0, 0));
+
+    InferenceSnap r;
+    r.kind = best.kind; r.entity = best.entity; r.role = best.role; r.point = best.point;
+    return r;
+}
+
+std::optional<SketchConstraintType>
+infer_axis_constraint(const Vec2d& anchor, const Vec2d& tip, double ang_tol_rad)
+{
+    const Vec2d d = tip - anchor;
+    if (d.squaredNorm() < 1e-12) return std::nullopt;
+    const double ang = std::atan2(std::abs(d.y()), std::abs(d.x())); // 0=horizontal, pi/2=vertical
+    if (ang <= ang_tol_rad)                 return SketchConstraintType::Horizontal;
+    if (ang >= M_PI / 2.0 - ang_tol_rad)    return SketchConstraintType::Vertical;
+    return std::nullopt;
+}
+
+// Unsigned angle between two (unnormalized) direction vectors, in [0, pi]. 0 = same
+// direction, pi = opposite, pi/2 = perpendicular. Inputs must be non-degenerate.
+// static: this is a file-local helper, not part of the module's interface -- at namespace
+// scope with external linkage it would be a link-time collision waiting to happen.
+static double unsigned_angle(const Vec2d& a, const Vec2d& b)
+{
+    const double cross = a.x() * b.y() - a.y() * b.x();
+    const double dot   = a.x() * b.x() + a.y() * b.y();
+    return std::atan2(std::abs(cross), dot);
+}
+
+std::vector<SketchEntityConstraintDef>
+infer_relations(const std::vector<SketchEntity>& entities, int new_ei,
+                double ang_tol_rad, double len_tol_frac)
+{
+    std::vector<SketchEntityConstraintDef> out;
+    if (new_ei <= 0 || new_ei >= int(entities.size())) return out;
+
+    // AT MOST ONE constraint per rule per new entity, not one per PAIR. Without this the
+    // function is quadratic in the sketch: a drawing with 200 equal holes yields ~20000
+    // EqualRadius candidates, the batch is rejected as over-constrained, and the caller's
+    // one-at-a-time fallback then runs a solve per constraint. Measured 2026-08-31: that
+    // pinned the app at 95% of a core with the MCP socket unresponsive -- the same failure
+    // the axes batch above already carries a warning about. Keep the best candidate only.
+    int    best_ang_j = -1, best_rad_j = -1, best_tan_j = -1;
+    double best_ang_err = 1e30, best_rad_err = 1e30, best_tan_err = 1e30;
+    SketchConstraintType best_ang_type = SketchConstraintType::Parallel;
+
+    const SketchEntity& n = entities[new_ei];
+    const bool n_line  = n.type == SketchEntity::Type::Line;
+    const bool n_curve = n.type == SketchEntity::Type::Arc || n.type == SketchEntity::Type::Circle;
+    if (!n_line && !n_curve) return out;                       // not a Line / Arc / Circle
+    if (n_line  && (n.p1 - n.p0).squaredNorm() < 1e-18) return out; // degenerate
+    if (n_curve && n.radius < 1e-9)                      return out;
+
+    for (int j = 0; j < new_ei; ++j) {
+        const SketchEntity& o = entities[j];
+        const bool o_line  = o.type == SketchEntity::Type::Line;
+        const bool o_curve = o.type == SketchEntity::Type::Arc || o.type == SketchEntity::Type::Circle;
+        if (!o_line && !o_curve) continue;
+        if (o_line  && (o.p1 - o.p0).squaredNorm() < 1e-18) continue;
+        if (o_curve && o.radius < 1e-9)                      continue;
+
+        if (n_line && o_line) {
+            // R1 — parallel / perpendicular, restricted to CONNECTED lines. Connection is
+            // what keeps this from firing on every distant line that is roughly parallel.
+            const bool connected = (n.p0 - o.p0).squaredNorm() <= 1e-14 ||
+                                   (n.p0 - o.p1).squaredNorm() <= 1e-14 ||
+                                   (n.p1 - o.p0).squaredNorm() <= 1e-14 ||
+                                   (n.p1 - o.p1).squaredNorm() <= 1e-14;
+            if (!connected) continue;
+            const double ang = unsigned_angle(n.p1 - n.p0, o.p1 - o.p0);
+            const double par_err = std::min(ang, M_PI - ang);
+            const double per_err = std::abs(ang - M_PI / 2.0);
+            if (par_err <= ang_tol_rad && par_err < best_ang_err) {
+                best_ang_err = par_err; best_ang_j = j;
+                best_ang_type = SketchConstraintType::Parallel;
+            } else if (per_err <= ang_tol_rad && per_err < best_ang_err) {
+                best_ang_err = per_err; best_ang_j = j;
+                best_ang_type = SketchConstraintType::Perpendicular;
+            }
+        } else if (n_curve && o_curve) {
+            // R2 — equal radius between circles / arcs, relative to the larger.
+            const double larger = n.radius > o.radius ? n.radius : o.radius;
+            const double err = std::abs(n.radius - o.radius) / larger;
+            if (err <= len_tol_frac && err < best_rad_err) { best_rad_err = err; best_rad_j = j; }
+        } else {
+            // R3 — tangent where a line meets a circle / arc at a shared endpoint, and only
+            // when the line is ALREADY perpendicular to the radius at that point.
+            const SketchEntity& ln = n_line ? n : o;
+            const SketchEntity& cv = n_line ? o : n;
+            const Vec2d ldir = ln.p1 - ln.p0;
+            bool tangent = false;
+            const Vec2d le[2] = { ln.p0, ln.p1 };
+            for (int k = 0; k < 2 && !tangent; ++k) {
+                if (cv.type == SketchEntity::Type::Arc) {
+                    const Vec2d ce[2] = { cv.p0, cv.p1 };
+                    for (int m = 0; m < 2; ++m) {
+                        if ((le[k] - ce[m]).squaredNorm() > 1e-14) continue;
+                        const Vec2d r = ce[m] - cv.center;
+                        if (r.squaredNorm() < 1e-18) continue;
+                        tangent = std::abs(unsigned_angle(ldir, r) - M_PI / 2.0) <= ang_tol_rad;
+                        if (tangent) break;
+                    }
+                } else { // Circle: shared point is a line endpoint on the rim.
+                    const Vec2d r = le[k] - cv.center;
+                    if (std::abs(r.norm() - cv.radius) > 1e-7) continue;
+                    if (r.squaredNorm() < 1e-18) continue;
+                    tangent = std::abs(unsigned_angle(ldir, r) - M_PI / 2.0) <= ang_tol_rad;
+                }
+            }
+            if (tangent && best_tan_err > 0.0) { best_tan_err = 0.0; best_tan_j = j; }
+        }
+    }
+
+    auto emit = [&](SketchConstraintType t, int j) {
+        if (j < 0) return;
+        SketchEntityConstraintDef c;
+        c.type = t; c.ea = j; c.eb = new_ei;
+        out.push_back(c);
+    };
+    emit(best_ang_type, best_ang_j);                       // R1
+    emit(SketchConstraintType::EqualRadius, best_rad_j);   // R2
+    emit(SketchConstraintType::Tangent,     best_tan_j);   // R3
+    return out;
+}
+
+} // namespace Slic3r
diff --git a/src/libslic3r/CAD/SketchInference.hpp b/src/libslic3r/CAD/SketchInference.hpp
new file mode 100644
index 0000000000..be51f0240e
--- /dev/null
+++ b/src/libslic3r/CAD/SketchInference.hpp
@@ -0,0 +1,55 @@
+#ifndef slic3r_SketchInference_hpp_
+#define slic3r_SketchInference_hpp_
+
+#include "libslic3r/CAD/SketchEngine.hpp"
+#include <vector>
+#include <optional>
+#include <cmath>
+
+namespace Slic3r {
+
+// Result of snapping a free cursor point onto the most relevant inference target
+// among the committed sketch entities and the sketch origin. This is the backbone
+// that lets geometry self-constrain as it is drawn: the GUI records the returned
+// target at click time and, once the entity it belongs to exists, emits the
+// matching constraint (Coincident onto an endpoint/centre, Fix onto the origin,
+// PointOnObject onto an edge) so the relation survives a re-solve.
+struct InferenceSnap {
+    enum class Kind { None, Endpoint, Center, Midpoint, OnEdge, Origin };
+    Kind            kind{Kind::None};
+    int             entity{-1};                       // hit entity index (-1 = origin/none)
+    SketchPointRole role{SketchPointRole::P0};         // which point of `entity` (Endpoint/Center)
+    Vec2d           point{0, 0};                       // snapped coordinate (== query when None)
+
+    bool snapped() const { return kind != Kind::None; }
+};
+
+// Snap `query` onto the best inference target within `tol` plane units. Priority,
+// highest first: Endpoint, Center, Origin, Midpoint, OnEdge. Construction entities
+// participate (you constrain to them too). Returns {None, query} when nothing is in
+// range. Pure — no GUI / GL dependencies, so it is unit-testable in libslic3r.
+InferenceSnap infer_point_snap(const std::vector<SketchEntity>& entities,
+                               const Vec2d& query, double tol,
+                               bool include_origin = true);
+
+// Relational inference for an in-progress segment anchor->tip. If its direction is
+// within `ang_tol_rad` of an axis, returns Horizontal or Vertical (the constraint to
+// auto-emit on the committed segment); std::nullopt otherwise. Degenerate (near-zero
+// length) segments return nullopt.
+std::optional<SketchConstraintType>
+infer_axis_constraint(const Vec2d& anchor, const Vec2d& tip, double ang_tol_rad = 3.0 * M_PI / 180.0);
+
+// Relational constraints to auto-emit for a newly drawn entity `new_ei` against the
+// entities already in the sketch. Pure, no GUI/GL dependencies, unit-testable.
+//
+// Deliberately conservative: every rule requires the relation to be ALREADY TRUE within
+// tolerance, so an inferred constraint never moves geometry the user drew — it only pins a
+// relation that is visibly there. Returns an empty vector when nothing qualifies.
+std::vector<SketchEntityConstraintDef>
+infer_relations(const std::vector<SketchEntity>& entities, int new_ei,
+                double ang_tol_rad = 2.0 * M_PI / 180.0,
+                double len_tol_frac = 0.01);
+
+} // namespace Slic3r
+
+#endif // slic3r_SketchInference_hpp_
diff --git a/src/libslic3r/CAD/SketchSolver.cpp b/src/libslic3r/CAD/SketchSolver.cpp
new file mode 100644
index 0000000000..952f9de16f
--- /dev/null
+++ b/src/libslic3r/CAD/SketchSolver.cpp
@@ -0,0 +1,555 @@
+#include "libslic3r/CAD/SketchSolver.hpp"
+
+#include <slvs.h>
+
+#include <cmath>
+#include <cstring>
+#include <functional>
+#include <map>
+#include <unordered_map>
+
+namespace Slic3r {
+
+using CT = SketchConstraintType;
+using Role = SketchPointRole;
+
+namespace {
+
+constexpr Slvs_hGroup G_FIXED = 1;   // workplane / reference: held constant
+constexpr Slvs_hGroup G_SK    = 2;   // sketch geometry: the group we solve
+
+// Per-entity slvs handles. p0/p1/center are point2d entity handles; prim is the
+// line/arc/circle entity; rparam is the circle radius param.
+struct Slots {
+    Slvs_hEntity prim{0}, p0{0}, p1{0}, center{0};
+    Slvs_hParam  rparam{0};
+    std::vector<Slvs_hEntity> pts;   // BSpline control points (point2d handles)
+};
+
+struct Build {
+    std::vector<Slvs_Param>      params;
+    std::vector<Slvs_Entity>     ents;
+    std::vector<Slvs_Constraint> cons;
+    Slvs_hParam      ph{0};
+    Slvs_hEntity     eh{0};
+    Slvs_hConstraint ch{0};
+    Slvs_hEntity     wp{0}, normal{0};
+
+    Slvs_hParam  P(Slvs_hGroup g, double v) { params.push_back(Slvs_MakeParam(++ph, g, v)); return ph; }
+    Slvs_hEntity E(Slvs_Entity e)           { ents.push_back(e); return e.h; }
+    Slvs_hEntity pt2d(Slvs_hGroup g, double u, double v)
+        { return E(Slvs_MakePoint2d(++eh, g, wp, P(g, u), P(g, v))); }
+
+    // Generic constraint (entityC unused by Slvs_MakeConstraint — set it manually below).
+    void C(int type, double val, Slvs_hEntity ptA, Slvs_hEntity ptB,
+           Slvs_hEntity eA, Slvs_hEntity eB, Slvs_hEntity eC = 0, int other = 0)
+    {
+        Slvs_Constraint c = Slvs_MakeConstraint(++ch, G_SK, type, wp, val, ptA, ptB, eA, eB);
+        c.entityC = eC;
+        c.other   = other;
+        cons.push_back(c);
+    }
+};
+
+inline int role_idx(Role r) { return int(r); }
+
+} // namespace
+
+static SketchSolveResult solve_system(std::vector<SketchEntity>& entities,
+                                      const std::vector<SketchEntityConstraintDef>& constraints,
+                                      int dragged_ei, Role dragged_role)
+{
+    SketchSolveResult out;
+    if (constraints.empty()) { out.ok = true; out.dof = -1; return out; }
+
+    Build b;
+
+    // ---- Fixed 2D XY workplane (origin at 0,0,0; identity normal) -------------------
+    Slvs_hEntity origin = b.E(Slvs_MakePoint3d(++b.eh, G_FIXED,
+                              b.P(G_FIXED, 0.0), b.P(G_FIXED, 0.0), b.P(G_FIXED, 0.0)));
+    double qw, qx, qy, qz;
+    Slvs_MakeQuaternion(1, 0, 0,  0, 1, 0,  &qw, &qx, &qy, &qz);
+    b.normal = b.E(Slvs_MakeNormal3d(++b.eh, G_FIXED,
+                   b.P(G_FIXED, qw), b.P(G_FIXED, qx), b.P(G_FIXED, qy), b.P(G_FIXED, qz)));
+    b.wp = b.E(Slvs_MakeWorkplane(++b.eh, G_FIXED, origin, b.normal));
+
+    // Unit direction references for the axis-projected distance constraints. Both live in
+    // G_FIXED, so they are held constant and add no DOF to the system.
+    // libslvs defines a LINE_SEGMENT's direction as point[0] - point[1] (entity.cpp
+    // VectorGetExprs), so the unit vector's head is listed first to yield +X / +Y.
+    const Slvs_hEntity dir_x [[maybe_unused]] = b.E(Slvs_MakeLineSegment(++b.eh, G_FIXED, b.wp,
+                                                       b.pt2d(G_FIXED, 1.0, 0.0), b.pt2d(G_FIXED, 0.0, 0.0)));
+    const Slvs_hEntity dir_y [[maybe_unused]] = b.E(Slvs_MakeLineSegment(++b.eh, G_FIXED, b.wp,
+                                                       b.pt2d(G_FIXED, 0.0, 1.0), b.pt2d(G_FIXED, 0.0, 0.0)));
+
+    // Implicit sketch references (origin, X axis, Y axis), addressable by the negative
+    // sentinels in SketchEngine.hpp. G_FIXED: held constant, zero added DOF. The axis lines
+    // are built head-first so their direction reads +X / +Y, matching dir_x / dir_y.
+    const Slvs_hEntity ref_origin_pt = b.pt2d(G_FIXED, 0.0, 0.0);
+    const Slvs_hEntity ref_axis_x = b.E(Slvs_MakeLineSegment(++b.eh, G_FIXED, b.wp,
+                                    b.pt2d(G_FIXED, 1.0, 0.0), ref_origin_pt));
+    const Slvs_hEntity ref_axis_y = b.E(Slvs_MakeLineSegment(++b.eh, G_FIXED, b.wp,
+                                    b.pt2d(G_FIXED, 0.0, 1.0), ref_origin_pt));
+
+    // ---- Entities -------------------------------------------------------------------
+    std::vector<Slots> slot(entities.size());
+    for (size_t i = 0; i < entities.size(); ++i) {
+        const SketchEntity& e = entities[i];
+        Slots s;
+        switch (e.type) {
+        case SketchEntity::Type::Line:
+            s.p0   = b.pt2d(G_SK, e.p0.x(), e.p0.y());
+            s.p1   = b.pt2d(G_SK, e.p1.x(), e.p1.y());
+            s.prim = b.E(Slvs_MakeLineSegment(++b.eh, G_SK, b.wp, s.p0, s.p1));
+            break;
+        case SketchEntity::Type::Point:
+            s.p0 = b.pt2d(G_SK, e.p0.x(), e.p0.y());
+            break;
+        case SketchEntity::Type::Circle: {
+            s.center = b.pt2d(G_SK, e.center.x(), e.center.y());
+            s.p0     = s.center;                          // p0 mirrors centre for circles
+            s.rparam = b.P(G_SK, e.radius > 1e-9 ? e.radius : 1.0);
+            Slvs_hEntity dist = b.E(Slvs_MakeDistance(++b.eh, G_SK, b.wp, s.rparam));
+            s.prim   = b.E(Slvs_MakeCircle(++b.eh, G_SK, b.wp, s.center, b.normal, dist));
+            break;
+        }
+        case SketchEntity::Type::Arc:
+            s.center = b.pt2d(G_SK, e.center.x(), e.center.y());
+            s.p0     = b.pt2d(G_SK, e.p0.x(), e.p0.y());   // start
+            s.p1     = b.pt2d(G_SK, e.p1.x(), e.p1.y());   // end
+            s.prim   = b.E(Slvs_MakeArcOfCircle(++b.eh, G_SK, b.wp, b.normal, s.center, s.p0, s.p1));
+            break;
+        // libslvs has no conic entity (scope note): register the ellipse's defining
+        // points only (center + arc endpoints) so center/endpoint constraints solve;
+        // the a/b/phi shape params pass through unsolved.
+        case SketchEntity::Type::Ellipse:
+            s.center = b.pt2d(G_SK, e.center.x(), e.center.y());
+            s.p0     = s.center;                          // p0 mirrors centre (circle convention)
+            break;
+        case SketchEntity::Type::EllipseArc:
+            s.center = b.pt2d(G_SK, e.center.x(), e.center.y());
+            s.p0     = b.pt2d(G_SK, e.p0.x(), e.p0.y());   // start
+            s.p1     = b.pt2d(G_SK, e.p1.x(), e.p1.y());   // end
+            break;
+        // No native slvs curve for an arbitrary-degree spline: register the control
+        // poles as point2d so endpoints (and any pole-targeted constraint) solve. The
+        // OCCT curve is rebuilt from the solved poles. p0/p1 mirror first/last pole so
+        // Coincident at the spline ends closes loops just like a Line.
+        case SketchEntity::Type::BSpline:
+            s.pts.reserve(e.ctrl.size());
+            for (const Vec2d& cp : e.ctrl)
+                s.pts.push_back(b.pt2d(G_SK, cp.x(), cp.y()));
+            if (!s.pts.empty()) { s.p0 = s.pts.front(); s.p1 = s.pts.back(); }
+            break;
+        }
+        slot[i] = s;
+    }
+
+    auto valid = [&](int ei) { return ei >= 0 && ei < int(entities.size()); };
+    auto ptOf  = [&](int ei, Role r) -> Slvs_hEntity {
+        if (ei == kSketchRefOrigin) return ref_origin_pt;
+        if (ei == kSketchRefAxisX || ei == kSketchRefAxisY) return ref_origin_pt;  // axes pass through it
+        if (!valid(ei)) return 0;
+        const Slots& s = slot[ei];
+        switch (r) {
+        case Role::P0:     return s.p0;
+        case Role::P1:     return s.p1;
+        case Role::Center: return s.center ? s.center : s.p0;
+        }
+        return 0;
+    };
+    auto primOf = [&](int ei) -> Slvs_hEntity {
+        if (ei == kSketchRefAxisX) return ref_axis_x;
+        if (ei == kSketchRefAxisY) return ref_axis_y;
+        return valid(ei) ? slot[ei].prim : 0;      // origin has no prim: it is a point
+    };
+    auto coordOf = [&](int ei, Role r) -> Vec2d {
+        if (is_sketch_ref(ei)) return Vec2d(0, 0);   // all three pass through the origin
+        if (!valid(ei)) return Vec2d(0, 0);
+        const SketchEntity& e = entities[ei];
+        switch (r) { case Role::P0: return e.p0; case Role::P1: return e.p1; case Role::Center: return e.center; }
+        return e.p0;
+    };
+    // A fixed reference point at (x,y) — used to pin coordinates (Fix / LockX / LockY).
+    auto fixedRef = [&](double x, double y) -> Slvs_hEntity { return b.pt2d(G_FIXED, x, y); };
+
+    // ---- Constraints ----------------------------------------------------------------
+    for (const auto& c : constraints) {
+        // Robustness: never feed libslvs a null handle. A constraint that references an
+        // entity which produced no solver primitive (Point/Ellipse/EllipseArc/BSpline get
+        // no `prim`) or no point for the requested role would make Slvs FindById abort the
+        // whole process. Skip such a constraint instead of crashing.
+        bool ref_ok = true;
+        switch (c.type) {
+        case CT::Coincident: case CT::Horizontal: case CT::Vertical: case CT::Distance:
+            ref_ok = ptOf(c.ea, c.ra) && ptOf(c.eb, c.rb); break;
+        case CT::DistanceX:
+        case CT::DistanceY:
+            ref_ok = ptOf(c.ea, c.ra) && ptOf(c.eb, c.rb); break;
+        case CT::Concentric:
+            ref_ok = ptOf(c.ea, Role::Center) && ptOf(c.eb, Role::Center); break;
+        case CT::Fix: case CT::LockX: case CT::LockY:
+            ref_ok = ptOf(c.ea, c.ra) != 0; break;
+        case CT::EqualLength: case CT::Parallel: case CT::Perpendicular:
+        case CT::Angle: case CT::Tangent:
+            ref_ok = primOf(c.ea) && primOf(c.eb); break;
+        case CT::Radius: case CT::Diameter:
+            ref_ok = primOf(c.ea) != 0; break;
+        case CT::Midpoint:
+            ref_ok = ptOf(c.ea, c.ra) && primOf(c.eb); break;
+        case CT::Symmetric:
+            ref_ok = ptOf(c.ea, c.ra) && ptOf(c.eb, c.rb) && primOf(c.ec); break;
+        case CT::SymmetricAboutY: case CT::SymmetricAboutX:
+            ref_ok = ptOf(c.ea, c.ra) && ptOf(c.eb, c.rb); break;
+        case CT::PointOnLine: case CT::PointOnObject:
+            ref_ok = ptOf(c.ea, c.ra) && primOf(c.eb); break;
+        case CT::EqualRadius:
+        case CT::Collinear:
+            ref_ok = primOf(c.ea) && primOf(c.eb); break;
+        }
+        if (!ref_ok) continue;
+        switch (c.type) {
+        case CT::Coincident:
+            b.C(SLVS_C_POINTS_COINCIDENT, 0, ptOf(c.ea, c.ra), ptOf(c.eb, c.rb), 0, 0);
+            break;
+        case CT::Concentric:
+            b.C(SLVS_C_POINTS_COINCIDENT, 0, ptOf(c.ea, Role::Center), ptOf(c.eb, Role::Center), 0, 0);
+            break;
+        case CT::Horizontal:
+            b.C(SLVS_C_HORIZONTAL, 0, ptOf(c.ea, c.ra), ptOf(c.eb, c.rb), 0, 0);
+            break;
+        case CT::Vertical:
+            b.C(SLVS_C_VERTICAL, 0, ptOf(c.ea, c.ra), ptOf(c.eb, c.rb), 0, 0);
+            break;
+        case CT::Distance:
+            b.C(SLVS_C_PT_PT_DISTANCE, c.value, ptOf(c.ea, c.ra), ptOf(c.eb, c.rb), 0, 0);
+            break;
+        case CT::DistanceX:
+            // Distance between the two points measured along X only: project the vector
+            // between them onto the fixed unit X direction.
+            b.C(SLVS_C_PROJ_PT_DISTANCE, c.value, ptOf(c.ea, c.ra), ptOf(c.eb, c.rb), dir_x, 0);
+            break;
+        case CT::DistanceY:
+            b.C(SLVS_C_PROJ_PT_DISTANCE, c.value, ptOf(c.ea, c.ra), ptOf(c.eb, c.rb), dir_y, 0);
+            break;
+        case CT::Fix: {
+            const Vec2d p = coordOf(c.ea, c.ra);
+            b.C(SLVS_C_POINTS_COINCIDENT, 0, ptOf(c.ea, c.ra), fixedRef(p.x(), p.y()), 0, 0);
+            break;
+        }
+        case CT::LockX: {
+            const Vec2d p = coordOf(c.ea, c.ra);
+            b.C(SLVS_C_VERTICAL, 0, ptOf(c.ea, c.ra), fixedRef(c.value, p.y()), 0, 0);
+            break;
+        }
+        case CT::LockY: {
+            const Vec2d p = coordOf(c.ea, c.ra);
+            b.C(SLVS_C_HORIZONTAL, 0, ptOf(c.ea, c.ra), fixedRef(p.x(), c.value), 0, 0);
+            break;
+        }
+        case CT::EqualLength:
+            b.C(SLVS_C_EQUAL_LENGTH_LINES, 0, 0, 0, primOf(c.ea), primOf(c.eb));
+            break;
+        case CT::Parallel:
+            b.C(SLVS_C_PARALLEL, 0, 0, 0, primOf(c.ea), primOf(c.eb));
+            break;
+        case CT::Perpendicular:
+            b.C(SLVS_C_PERPENDICULAR, 0, 0, 0, primOf(c.ea), primOf(c.eb));
+            break;
+        case CT::Midpoint:
+            b.C(SLVS_C_AT_MIDPOINT, 0, ptOf(c.ea, c.ra), 0, primOf(c.eb), 0);
+            break;
+        case CT::Symmetric:
+            // ptA, ptB symmetric about the axis line (ec).
+            b.C(SLVS_C_SYMMETRIC_LINE, 0, ptOf(c.ea, c.ra), ptOf(c.eb, c.rb), primOf(c.ec), 0);
+            break;
+        case CT::SymmetricAboutY:
+            b.C(SLVS_C_SYMMETRIC_LINE, 0, ptOf(c.ea, c.ra), ptOf(c.eb, c.rb), primOf(kSketchRefAxisY), 0);
+            break;
+        case CT::SymmetricAboutX:
+            b.C(SLVS_C_SYMMETRIC_LINE, 0, ptOf(c.ea, c.ra), ptOf(c.eb, c.rb), primOf(kSketchRefAxisX), 0);
+            break;
+        case CT::Angle:
+            // model stores radians; slvs angle is in degrees.
+            b.C(SLVS_C_ANGLE, c.value * 180.0 / M_PI, 0, 0, primOf(c.ea), primOf(c.eb));
+            break;
+        case CT::Radius:
+            b.C(SLVS_C_DIAMETER, 2.0 * c.value, 0, 0, primOf(c.ea), 0);
+            break;
+        case CT::Diameter:
+            b.C(SLVS_C_DIAMETER, c.value, 0, 0, primOf(c.ea), 0);
+            break;
+        case CT::Tangent: {
+            const bool aCurve = valid(c.ea) && entities[c.ea].type != SketchEntity::Type::Line;
+            const bool bCurve = valid(c.eb) && entities[c.eb].type != SketchEntity::Type::Line;
+            if (aCurve && bCurve)
+                b.C(SLVS_C_CURVE_CURVE_TANGENT, 0, 0, 0, primOf(c.ea), primOf(c.eb));
+            else {
+                const int ci = aCurve ? c.ea : c.eb;   // the curve
+                const int li = aCurve ? c.eb : c.ea;   // the line
+                if (valid(ci) && entities[ci].type == SketchEntity::Type::Circle) {
+                    // A FULL circle cannot use SLVS_C_ARC_LINE_TANGENT. That constraint reads
+                    // arc->point[1] / point[2] — the arc's endpoints (see constrainteq.cpp,
+                    // Type::ARC_LINE_TANGENT) — and a circle entity only has point[0], its
+                    // centre. The zero handles send FindById into "Cannot find handle", which
+                    // ABORTS the process rather than failing the solve, taking every later test
+                    // with it. It is also the wrong equation for a circle: it only makes the
+                    // line perpendicular to the radius AT AN ENDPOINT that does not exist.
+                    //
+                    // For a circle, tangency is exactly "the centre sits one radius away from
+                    // the line", which slvs expresses directly.
+                    //
+                    // ponytail: the radius is captured here rather than tied as a variable —
+                    // the C API takes a constant distance and offers no way to reference the
+                    // circle's radius parameter. Exact whenever the radius is fixed or simply
+                    // not being changed by another constraint in the same solve; if some other
+                    // constraint drives the radius, re-solving restores tangency. Tying them
+                    // would need an auxiliary point constrained onto both circle and line.
+                    b.C(SLVS_C_PT_LINE_DISTANCE, entities[ci].radius,
+                        ptOf(ci, Role::Center), 0, primOf(li), 0);
+                } else {
+                    b.C(SLVS_C_ARC_LINE_TANGENT, 0, 0, 0, primOf(ci), primOf(li));
+                }
+            }
+            break;
+        }
+        case CT::PointOnLine:
+            if (std::abs(c.value) < 1e-9)
+                b.C(SLVS_C_PT_ON_LINE, 0, ptOf(c.ea, c.ra), 0, primOf(c.eb), 0);
+            else
+                b.C(SLVS_C_PT_LINE_DISTANCE, std::abs(c.value), ptOf(c.ea, c.ra), 0, primOf(c.eb), 0);
+            break;
+        case CT::PointOnObject:
+            // Point (ea,ra) lies on entity edge eb: a circle rim -> PT_ON_CIRCLE,
+            // otherwise the segment line -> PT_ON_LINE.
+            if (valid(c.eb) && entities[c.eb].type == SketchEntity::Type::Circle)
+                b.C(SLVS_C_PT_ON_CIRCLE, 0, ptOf(c.ea, c.ra), 0, primOf(c.eb), 0);
+            else
+                b.C(SLVS_C_PT_ON_LINE, 0, ptOf(c.ea, c.ra), 0, primOf(c.eb), 0);
+            break;
+        case CT::EqualRadius:
+            b.C(SLVS_C_EQUAL_RADIUS, 0, 0, 0, primOf(c.ea), primOf(c.eb));
+            break;
+        case CT::Collinear:
+            // libslvs has no collinear code. Two lines are collinear iff they are parallel
+            // AND a point of one lies on the other's infinite line — emit both.
+            b.C(SLVS_C_PARALLEL, 0, 0, 0, primOf(c.ea), primOf(c.eb));
+            // Point-on-infinite-line via PT_LINE_DISTANCE=0 rather than PT_ON_LINE: the
+            // latter creates an internal `valP` param that this port's Slvs_Solve leaves at
+            // 0 in the working set (ModifyToSatisfy only updates SK.param), so an already
+            // collinear pair drifts. PT_LINE_DISTANCE=0 is the same condition with no extra
+            // parameter, so an already-satisfied solve is a clean no-op.
+            b.C(SLVS_C_PT_LINE_DISTANCE, 0, ptOf(c.eb, Role::P0), 0, primOf(c.ea), 0);
+            break;
+        }
+    }
+
+    // ---- Solve ----------------------------------------------------------------------
+    Slvs_System sys;
+    std::memset(&sys, 0, sizeof(sys));
+    sys.param       = b.params.data();      sys.params      = int(b.params.size());
+    sys.entity      = b.ents.data();        sys.entities    = int(b.ents.size());
+    sys.constraint  = b.cons.data();        sys.constraints = int(b.cons.size());
+    std::vector<Slvs_hConstraint> failed(b.cons.size() + 1, 0);
+    sys.failed = failed.data();
+    sys.faileds = int(failed.size());
+    sys.calculateFaileds = 1;
+
+    // Drag pin: feed the dragged point's two params into sys.dragged[] so the solver
+    // favours keeping that point at the cursor and re-solves the rest around it.
+    if (dragged_ei >= 0) {
+        const Slvs_hEntity h = ptOf(dragged_ei, dragged_role);
+        for (const Slvs_Entity& en : b.ents)
+            if (en.h == h) { sys.dragged[0] = en.param[0]; sys.dragged[1] = en.param[1]; break; }
+    }
+
+    Slvs_Solve(&sys, G_SK);
+
+    out.result = sys.result;
+    out.dof    = sys.dof;
+    out.ok     = (sys.result == SLVS_RESULT_OKAY);
+
+    // Map solved param handles -> values, then read points back.
+    std::unordered_map<Slvs_hParam, double> pv;
+    pv.reserve(sys.params * 2);
+    for (int i = 0; i < sys.params; ++i) pv[sys.param[i].h] = sys.param[i].val;
+    std::unordered_map<Slvs_hEntity, const Slvs_Entity*> byH;
+    byH.reserve(sys.entities * 2);
+    for (int i = 0; i < sys.entities; ++i) byH[sys.entity[i].h] = &sys.entity[i];
+    auto coord = [&](Slvs_hEntity h) -> Vec2d {
+        auto it = byH.find(h);
+        if (it == byH.end()) return Vec2d(0, 0);
+        return Vec2d(pv[it->second->param[0]], pv[it->second->param[1]]);
+    };
+
+    // Map failed constraint handles back to indices into `constraints`.
+    if (!out.ok && sys.faileds > 0) {
+        std::unordered_map<Slvs_hConstraint, int> chToIdx;
+        // constraint handles were assigned in order starting after the fixed group; the
+        // i-th sketch constraint in b.cons has handle = its position. Rebuild by scanning.
+        for (size_t k = 0; k < b.cons.size(); ++k) chToIdx[b.cons[k].h] = int(k);
+        for (int i = 0; i < sys.faileds; ++i) {
+            auto it = chToIdx.find(failed[i]);
+            if (it != chToIdx.end() && it->second < int(constraints.size()))
+                out.bad.push_back(it->second);
+        }
+    }
+
+    // ---- Read solved geometry back --------------------------------------------------
+    // ONLY on success. A failed solve leaves libslvs' params holding its last Newton
+    // iterate — geometry that satisfies nothing and is usually wildly deformed. Writing
+    // that back made every rejected attempt destructive: the caller rolls the constraints
+    // back, but the sketch it rolls back to is already wreckage, so the next attempt starts
+    // from the corpse. The fillet degrade ladder hit this on every corner — rung 1 (a
+    // tangent on each leg) is legitimately over-constrained against the legs' own H/V, and
+    // its wreckage then failed rungs 2 and 3, which solve cleanly on their own. The arc
+    // ended up with no constraints at all and the solver snapped the corner shut. pl5.
+    if (!out.ok) return out;
+    for (size_t i = 0; i < entities.size(); ++i) {
+        SketchEntity& e = entities[i];
+        const Slots&  s = slot[i];
+        if (s.p0)     e.p0     = coord(s.p0);
+        if (s.p1)     e.p1     = coord(s.p1);
+        if (s.center) e.center = coord(s.center);
+
+        if (e.type == SketchEntity::Type::BSpline) {
+            for (size_t k = 0; k < s.pts.size() && k < e.ctrl.size(); ++k)
+                e.ctrl[k] = coord(s.pts[k]);
+            if (!e.ctrl.empty()) { e.p0 = e.ctrl.front(); e.p1 = e.ctrl.back(); }
+        } else if (e.type == SketchEntity::Type::Circle) {
+            if (s.rparam) { auto it = pv.find(s.rparam); if (it != pv.end()) e.radius = it->second; }
+            e.p0 = e.center;
+        } else if (e.type == SketchEntity::Type::Arc && s.center) {
+            // Reflow arc angles from solved centre + endpoints, preserving sweep sign.
+            const double old_sweep = e.end_angle - e.start_angle;
+            const double ns = std::atan2(e.p0.y() - e.center.y(), e.p0.x() - e.center.x());
+            const double ne = std::atan2(e.p1.y() - e.center.y(), e.p1.x() - e.center.x());
+            double sweep = ne - ns;
+            const double TWO_PI = 2.0 * M_PI;
+            while (sweep <= -TWO_PI) sweep += TWO_PI;
+            while (sweep >=  TWO_PI) sweep -= TWO_PI;
+            if (old_sweep >= 0.0 && sweep < 0.0) sweep += TWO_PI;
+            if (old_sweep <  0.0 && sweep > 0.0) sweep -= TWO_PI;
+            e.start_angle = ns;
+            e.end_angle   = ns + sweep;
+            e.radius = 0.5 * ((e.p0 - e.center).norm() + (e.p1 - e.center).norm());
+        }
+    }
+
+    return out;
+}
+
+// libslvs carries a COMPILE-TIME ceiling: solvespace.h declares `enum { MAX_UNKNOWNS = 1024 }`
+// and sizes the System's param and equation arrays with it. solve_system() hands the solver every
+// entity in the sketch, constrained or not, at 2 params per point — so a sketch of about 480 lines
+// is the last one that fits, and the very next one comes back TOO_MANY_UNKNOWNS.
+//
+// What that did, before this: DesignSketchTool::try_add_constraints rolls the whole batch back
+// when the solve fails, so the auto-constraint pass over a large sketch dropped EVERY constraint
+// it had just inferred. Measured on the rig — 480 lines: 960 constraints, dof 480. 520 lines:
+// 0 constraints, dof unknown. Nothing was said, and from there on no dimension and no constraint
+// could ever be applied to that sketch, because each attempt re-solved the same oversized system
+// and was rejected in turn. A typed length simply did nothing.
+//
+// Constraints only couple entities that SHARE a point, so a sketch is naturally a set of
+// independent systems — a plate with 300 cut-outs is 301 little problems, not one big one.
+// Solving them separately keeps every one of them far under the ceiling AND is faster, since the
+// solver's work is superlinear in system size.
+//
+// The whole system is still tried FIRST, and this runs only on TOO_MANY_UNKNOWNS, so every sketch
+// that fits today keeps its exact current behaviour, including its reported degrees of freedom.
+// A genuinely over-constrained sketch still fails: the conflict lives inside one component and
+// that component still rejects it.
+static SketchSolveResult solve_partitioned(std::vector<SketchEntity>& entities,
+                                           const std::vector<SketchEntityConstraintDef>& constraints,
+                                           int dragged_ei, Role dragged_role)
+{
+    const int n = int(entities.size());
+    std::vector<int> parent(n);
+    for (int i = 0; i < n; ++i) parent[i] = i;
+    std::function<int(int)> find = [&](int a) {
+        while (parent[a] != a) { parent[a] = parent[parent[a]]; a = parent[a]; }
+        return a;
+    };
+    auto unite = [&](int a, int b) {
+        if (a < 0 || b < 0 || a >= n || b >= n) return;
+        a = find(a); b = find(b);
+        if (a != b) parent[a] = b;
+    };
+    for (const auto& c : constraints) { unite(c.ea, c.eb); unite(c.ea, c.ec); }
+
+    // Group the constraints by the component they belong to.
+    std::map<int, std::vector<int>> groups;
+    for (size_t i = 0; i < constraints.size(); ++i) {
+        const int a = constraints[i].ea;
+        if (a < 0 || a >= n) continue;
+        groups[find(a)].push_back(int(i));
+    }
+
+    SketchSolveResult out;
+    out.ok  = true;
+    out.dof = 0;
+    // Solve into COPIES and commit only if every component succeeded. The contract callers rely
+    // on is all-or-nothing — try_add_constraints rolls the batch back and expects the geometry it
+    // rolls back to be untouched — and partial writes would break it.
+    std::vector<std::pair<std::vector<int>, std::vector<SketchEntity>>> solved;
+    for (const auto& [root, cidx] : groups) {
+        std::vector<int> ents;                       // global indices, in order
+        std::map<int, int> local;                    // global -> local
+        auto take = [&](int e) {
+            if (e < 0 || e >= n || local.count(e)) return;
+            local[e] = int(ents.size());
+            ents.push_back(e);
+        };
+        for (int ci : cidx) { take(constraints[ci].ea); take(constraints[ci].eb); take(constraints[ci].ec); }
+        std::vector<SketchEntity> sub;
+        sub.reserve(ents.size());
+        for (int e : ents) sub.push_back(entities[e]);
+        std::vector<SketchEntityConstraintDef> subc;
+        subc.reserve(cidx.size());
+        for (int ci : cidx) {
+            SketchEntityConstraintDef d = constraints[ci];
+            auto map1 = [&](int& e) { e = (e >= 0 && local.count(e)) ? local[e] : -1; };
+            map1(d.ea); map1(d.eb); map1(d.ec);
+            subc.push_back(d);
+        }
+        const int sub_drag = (dragged_ei >= 0 && local.count(dragged_ei)) ? local[dragged_ei] : -1;
+        SketchSolveResult r = solve_system(sub, subc, sub_drag, dragged_role);
+        if (!r.ok) {
+            out.ok     = false;
+            out.result = r.result;
+            for (int bi : r.bad)
+                if (bi >= 0 && bi < int(cidx.size())) out.bad.push_back(cidx[bi]);
+        }
+        if (r.dof > 0) out.dof += r.dof;
+        solved.emplace_back(std::move(ents), std::move(sub));
+    }
+    if (!out.ok) return out;
+    for (auto& [ents, sub] : solved)
+        for (size_t k = 0; k < ents.size(); ++k) entities[ents[k]] = sub[k];
+    return out;
+}
+
+static SketchSolveResult solve_impl(std::vector<SketchEntity>& entities,
+                                    const std::vector<SketchEntityConstraintDef>& constraints,
+                                    int dragged_ei, Role dragged_role)
+{
+    SketchSolveResult out = solve_system(entities, constraints, dragged_ei, dragged_role);
+    if (out.ok || out.result != SLVS_RESULT_TOO_MANY_UNKNOWNS) return out;
+    return solve_partitioned(entities, constraints, dragged_ei, dragged_role);
+}
+
+SketchSolveResult sketch_solve(std::vector<SketchEntity>& entities,
+                               const std::vector<SketchEntityConstraintDef>& constraints)
+{
+    return solve_impl(entities, constraints, -1, Role::P0);
+}
+
+SketchSolveResult sketch_solve_drag(std::vector<SketchEntity>& entities,
+                                    const std::vector<SketchEntityConstraintDef>& constraints,
+                                    int dragged_ei, SketchPointRole dragged_role)
+{
+    return solve_impl(entities, constraints, dragged_ei, dragged_role);
+}
+
+} // namespace Slic3r
diff --git a/src/libslic3r/CAD/SketchSolver.hpp b/src/libslic3r/CAD/SketchSolver.hpp
new file mode 100644
index 0000000000..ada4474c7a
--- /dev/null
+++ b/src/libslic3r/CAD/SketchSolver.hpp
@@ -0,0 +1,37 @@
+#ifndef slic3r_SketchSolver_hpp_
+#define slic3r_SketchSolver_hpp_
+
+// Bridge from the Design tab's SketchEntity / SketchEntityConstraintDef model onto the
+// vendored SolveSpace constraint solver (src/libslic3r/slvs, libslvs). Replaces the
+// hand-rolled SketchConstraints: full constraint set, real DoF counting, and
+// over-constrained (bad-constraint) detection. Solves on a fixed 2D XY workplane.
+
+#include "libslic3r/CAD/SketchEngine.hpp"
+#include <vector>
+
+namespace Slic3r {
+
+struct SketchSolveResult {
+    bool             ok{false};   // solver converged & consistent
+    int              dof{-1};     // remaining degrees of freedom (>0 under-constrained)
+    int              result{0};   // raw SLVS_RESULT_* code
+    std::vector<int> bad;         // indices (into `constraints`) of conflicting constraints
+};
+
+// Solve `constraints` over `entities` in place (writes solved coordinates back into the
+// entities; arc angles are reflowed preserving sweep direction). No-op success when
+// `constraints` is empty.
+SketchSolveResult sketch_solve(std::vector<SketchEntity>& entities,
+                               const std::vector<SketchEntityConstraintDef>& constraints);
+
+// Drag-aware solve: pins the (dragged_ei, dragged_role) point's parameters via the
+// solver's `dragged[]` priority list so the solver keeps that point where the cursor
+// placed it (caller must have moved it first) and moves the OTHER free geometry to
+// re-satisfy the constraints. dragged_ei < 0 behaves identically to sketch_solve.
+SketchSolveResult sketch_solve_drag(std::vector<SketchEntity>& entities,
+                                    const std::vector<SketchEntityConstraintDef>& constraints,
+                                    int dragged_ei, SketchPointRole dragged_role);
+
+} // namespace Slic3r
+
+#endif
diff --git a/src/libslic3r/CAD/ThreadStandards.cpp b/src/libslic3r/CAD/ThreadStandards.cpp
new file mode 100644
index 0000000000..2d113d01e6
--- /dev/null
+++ b/src/libslic3r/CAD/ThreadStandards.cpp
@@ -0,0 +1,95 @@
+#include "libslic3r/CAD/ThreadStandards.hpp"
+
+namespace Slic3r {
+
+// Imperial helpers: convert nominal inch diameter / threads-per-inch to mm.
+static constexpr double IN  = 25.4;
+static inline double tpi_pitch(double tpi) { return IN / tpi; }
+
+const std::vector<ThreadSpec>& thread_standards()
+{
+    using S = ThreadSpec::Series;
+    static const std::vector<ThreadSpec> table = {
+        // --- ISO metric, coarse pitch (ISO 261 preferred series) ---
+        {"M1",    1.0,  0.25, S::MetricCoarse},
+        {"M1.2",  1.2,  0.25, S::MetricCoarse},
+        {"M1.6",  1.6,  0.35, S::MetricCoarse},
+        {"M2",    2.0,  0.40, S::MetricCoarse},
+        {"M2.5",  2.5,  0.45, S::MetricCoarse},
+        {"M3",    3.0,  0.50, S::MetricCoarse},
+        {"M4",    4.0,  0.70, S::MetricCoarse},
+        {"M5",    5.0,  0.80, S::MetricCoarse},
+        {"M6",    6.0,  1.00, S::MetricCoarse},
+        {"M8",    8.0,  1.25, S::MetricCoarse},
+        {"M10",  10.0,  1.50, S::MetricCoarse},
+        {"M12",  12.0,  1.75, S::MetricCoarse},
+        {"M14",  14.0,  2.00, S::MetricCoarse},
+        {"M16",  16.0,  2.00, S::MetricCoarse},
+        {"M20",  20.0,  2.50, S::MetricCoarse},
+        {"M24",  24.0,  3.00, S::MetricCoarse},
+        {"M30",  30.0,  3.50, S::MetricCoarse},
+        {"M36",  36.0,  4.00, S::MetricCoarse},
+        {"M42",  42.0,  4.50, S::MetricCoarse},
+        {"M48",  48.0,  5.00, S::MetricCoarse},
+        {"M56",  56.0,  5.50, S::MetricCoarse},
+        {"M64",  64.0,  6.00, S::MetricCoarse},
+
+        // --- ISO metric, common fine pitches (ISO 261 fine series) ---
+        {"M8x1",      8.0,  1.00, S::MetricFine},
+        {"M10x1.25", 10.0,  1.25, S::MetricFine},
+        {"M10x1",    10.0,  1.00, S::MetricFine},
+        {"M12x1.5",  12.0,  1.50, S::MetricFine},
+        {"M12x1.25", 12.0,  1.25, S::MetricFine},
+        {"M16x1.5",  16.0,  1.50, S::MetricFine},
+        {"M20x1.5",  20.0,  1.50, S::MetricFine},
+        {"M24x2",    24.0,  2.00, S::MetricFine},
+
+        // --- Unified National Coarse (UTS / ASME B1.1) ---
+        {"#1-64 UNC",   0.073 * IN, tpi_pitch(64), S::UNC},
+        {"#2-56 UNC",   0.086 * IN, tpi_pitch(56), S::UNC},
+        {"#3-48 UNC",   0.099 * IN, tpi_pitch(48), S::UNC},
+        {"#4-40 UNC",   0.112 * IN, tpi_pitch(40), S::UNC},
+        {"#5-40 UNC",   0.125 * IN, tpi_pitch(40), S::UNC},
+        {"#6-32 UNC",   0.138 * IN, tpi_pitch(32), S::UNC},
+        {"#8-32 UNC",   0.164 * IN, tpi_pitch(32), S::UNC},
+        {"#10-24 UNC",  0.190 * IN, tpi_pitch(24), S::UNC},
+        {"#12-24 UNC",  0.216 * IN, tpi_pitch(24), S::UNC},
+        {"1/4-20 UNC",  0.250 * IN, tpi_pitch(20), S::UNC},
+        {"5/16-18 UNC", 0.3125 * IN, tpi_pitch(18), S::UNC},
+        {"3/8-16 UNC",  0.375 * IN, tpi_pitch(16), S::UNC},
+        {"7/16-14 UNC", 0.4375 * IN, tpi_pitch(14), S::UNC},
+        {"1/2-13 UNC",  0.500 * IN, tpi_pitch(13), S::UNC},
+        {"9/16-12 UNC", 0.5625 * IN, tpi_pitch(12), S::UNC},
+        {"5/8-11 UNC",  0.625 * IN, tpi_pitch(11), S::UNC},
+        {"3/4-10 UNC",  0.750 * IN, tpi_pitch(10), S::UNC},
+        {"7/8-9 UNC",   0.875 * IN, tpi_pitch(9),  S::UNC},
+        {"1-8 UNC",     1.000 * IN, tpi_pitch(8),  S::UNC},
+
+        // --- Unified National Fine (UTS / ASME B1.1) ---
+        {"#2-64 UNF",   0.086 * IN, tpi_pitch(64), S::UNF},
+        {"#4-48 UNF",   0.112 * IN, tpi_pitch(48), S::UNF},
+        {"#6-40 UNF",   0.138 * IN, tpi_pitch(40), S::UNF},
+        {"#8-36 UNF",   0.164 * IN, tpi_pitch(36), S::UNF},
+        {"#10-32 UNF",  0.190 * IN, tpi_pitch(32), S::UNF},
+        {"1/4-28 UNF",  0.250 * IN, tpi_pitch(28), S::UNF},
+        {"5/16-24 UNF", 0.3125 * IN, tpi_pitch(24), S::UNF},
+        {"3/8-24 UNF",  0.375 * IN, tpi_pitch(24), S::UNF},
+        {"7/16-20 UNF", 0.4375 * IN, tpi_pitch(20), S::UNF},
+        {"1/2-20 UNF",  0.500 * IN, tpi_pitch(20), S::UNF},
+        {"9/16-18 UNF", 0.5625 * IN, tpi_pitch(18), S::UNF},
+        {"5/8-18 UNF",  0.625 * IN, tpi_pitch(18), S::UNF},
+        {"3/4-16 UNF",  0.750 * IN, tpi_pitch(16), S::UNF},
+        {"1-12 UNF",    1.000 * IN, tpi_pitch(12), S::UNF},
+    };
+    return table;
+}
+
+const ThreadSpec* find_thread_standard(const std::string& name)
+{
+    for (const ThreadSpec& s : thread_standards())
+        if (s.name == name)
+            return &s;
+    return nullptr;
+}
+
+} // namespace Slic3r
diff --git a/src/libslic3r/CAD/ThreadStandards.hpp b/src/libslic3r/CAD/ThreadStandards.hpp
new file mode 100644
index 0000000000..e9bfcc314f
--- /dev/null
+++ b/src/libslic3r/CAD/ThreadStandards.hpp
@@ -0,0 +1,39 @@
+#ifndef slic3r_ThreadStandards_hpp_
+#define slic3r_ThreadStandards_hpp_
+
+#include <string>
+#include <vector>
+
+namespace Slic3r {
+
+// Canonical mechanical thread specifications (ISO metric + Unified imperial).
+// All dimensions are stored in millimetres so the CAD kernel can consume them
+// directly. The profile is the common 60deg V shared by ISO 261/965 and ASME
+// B1.1 (UTS), so the cut/ridge depth used by the Design-tab Thread tool is the
+// basic external thread height h = 0.6134 * pitch, and the internal (tapped)
+// minor diameter is D1 = D - 1.0825 * pitch (= D - 2*5H/8).
+struct ThreadSpec {
+    enum class Series { MetricCoarse, MetricFine, UNC, UNF };
+
+    std::string name;              // designation, e.g. "M6", "1/4-20 UNC"
+    double      major_diameter_mm; // nominal (crest) diameter
+    double      pitch_mm;          // axial advance per turn
+    Series      series;
+
+    // 60deg basic external thread height (radial crest-to-root engagement).
+    double thread_depth_mm() const { return 0.6134 * pitch_mm; }
+    // Internal/tapped minor (tap-drill) diameter for the same nominal thread.
+    double minor_diameter_mm() const { return major_diameter_mm - 1.0825 * pitch_mm; }
+
+    bool imperial() const { return series == Series::UNC || series == Series::UNF; }
+};
+
+// Full ordered table (metric coarse, metric fine, UNC, UNF) for GUI listing.
+const std::vector<ThreadSpec>& thread_standards();
+
+// Exact case-sensitive designation lookup; nullptr if not a known standard.
+const ThreadSpec* find_thread_standard(const std::string& name);
+
+} // namespace Slic3r
+
+#endif
diff --git a/src/libslic3r/CMakeLists.txt b/src/libslic3r/CMakeLists.txt
index 1d68db497d..e734c036fa 100644
--- a/src/libslic3r/CMakeLists.txt
+++ b/src/libslic3r/CMakeLists.txt
@@ -21,6 +21,11 @@ endif()
 option(BUILD_SHARED_LIBS "Build shared libs" OFF)
 option(USE_SLIC3R_CONSOLE_LOG "Enable console logging in RelWithDebInfo builds" OFF)
 
+# SolveSpace constraint solver (2D sketch solver backbone), built in deps/SLVS.
+if (SLIC3R_CAD)
+    find_package(SLVS REQUIRED)
+endif ()
+
 set(lisbslic3r_sources
     AABBMesh.cpp
     AABBMesh.hpp
@@ -508,6 +513,29 @@ set(lisbslic3r_sources
     FlushVolPredictor.cpp
 )
 
+# Parametric Design/CAD kernel. Needs OCCT's ModelingAlgorithms module and the
+# vendored SolveSpace solver; both are pulled in only when SLIC3R_CAD is ON.
+if (SLIC3R_CAD)
+    list(APPEND lisbslic3r_sources
+            CAD/GeometryEngine.cpp
+            CAD/GeometryEngine.hpp
+            CAD/SketchEngine.cpp
+            CAD/SketchEngine.hpp
+            CAD/SketchConstraints.cpp
+            CAD/SketchConstraints.hpp
+            CAD/SketchSolver.cpp
+            CAD/SketchSolver.hpp
+            CAD/SketchInference.cpp
+            CAD/SketchInference.hpp
+            CAD/SketchImport.cpp
+            CAD/SketchImport.hpp
+            CAD/CadDocument.cpp
+            CAD/CadDocument.hpp
+            CAD/ThreadStandards.cpp
+            CAD/ThreadStandards.hpp
+        )
+endif ()
+
 if (APPLE)
     list(APPEND lisbslic3r_sources
             MacUtils.mm
@@ -619,6 +647,30 @@ set(OCCT_LIBS
     TKMath
     TKernel
 )
+# The CAD kernel is the only consumer of OCCT's ModelingAlgorithms module: TKFillet
+# (BRepFilletAPI), TKOffset (BRepOffsetAPI) and TKBool, which the other two need.
+#
+# PREPEND, never append: this list is single-pass static link order, dependents before
+# dependencies — note TKernel, which everything needs, is deliberately last. TKOffset
+# references BRepAlgo_Loop, which TKBool defines, so TKOffset must come BEFORE TKBool.
+# Appending put it after, and a strictly single-pass linker (the Flatpak build) failed with
+#     libTKOffset.a(BRepOffset_MakeLoops.cxx.o): undefined reference to
+#     `BRepAlgo_Loop::BRepAlgo_Loop()'
+# while the ordinary Linux, macOS and Windows links resolved it anyway. Use set() rather
+# than list(PREPEND), which needs CMake 3.15 and this project supports 3.13.
+if (SLIC3R_CAD)
+    set(OCCT_LIBS TKFillet TKOffset TKBool ${OCCT_LIBS})
+    # deps is configured separately, so its SLIC3R_CAD can differ from ours. The module is
+    # all-or-nothing, so one absent toolkit proves it; fail here rather than at link time.
+    if (NOT TARGET TKFillet)
+        message(FATAL_ERROR
+            "SLIC3R_CAD is ON, but the OpenCASCADE in ${CMAKE_PREFIX_PATH} was built without "
+            "BUILD_MODULE_ModelingAlgorithms. Rebuild the dependencies with -DSLIC3R_CAD=ON, "
+            "or configure this project with -DSLIC3R_CAD=OFF.")
+    endif ()
+endif ()
+# Published for the Windows packaging step in the top-level CMakeLists.txt.
+set(OCCT_LIBS "${OCCT_LIBS}" CACHE INTERNAL "OCCT toolkits linked by libslic3r")
 
 target_link_libraries(libslic3r
     PUBLIC
@@ -671,6 +723,10 @@ if (TARGET OpenVDB::openvdb)
     target_link_libraries(libslic3r PRIVATE OpenVDB::openvdb)
 endif()
 
+if (SLIC3R_CAD)
+    target_link_libraries(libslic3r PUBLIC SLVS::slvs)
+endif ()
+
 if(WIN32)
     target_link_libraries(libslic3r PRIVATE Psapi.lib bcrypt.lib)
 endif()
diff --git a/src/libslic3r/Format/bbs_3mf.cpp b/src/libslic3r/Format/bbs_3mf.cpp
index e2091da1db..09899aa4c2 100644
--- a/src/libslic3r/Format/bbs_3mf.cpp
+++ b/src/libslic3r/Format/bbs_3mf.cpp
@@ -175,6 +175,10 @@ const std::string BBS_MODEL_CONFIG_RELS_FILE = "Metadata/_rels/model_settings.co
 const std::string SLICE_INFO_CONFIG_FILE = "Metadata/slice_info.config";
 const std::string FILAMENT_SEQUENCE_FILE = "Metadata/filament_sequence.json";
 const std::string BBS_LAYER_HEIGHTS_PROFILE_FILE = "Metadata/layer_heights_profile.txt";
+const std::string ORCA_CAD_RECIPE_FILE = "Metadata/orca_cad.bin";
+// Read-only: the recipe entry's pre-rename name. A reader that knows only the new one drops the
+// feature tree of every project written before the move, without a word. Never written.
+const std::string LEGACY_CAD_RECIPE_FILE = "Metadata/SnapOrca_cad.bin";
 const std::string LAYER_CONFIG_RANGES_FILE = "Metadata/layer_config_ranges.xml";
 const std::string BRIM_EAR_POINTS_FILE = "Metadata/brim_ear_points.txt";
 /*const std::string SLA_SUPPORT_POINTS_FILE = "Metadata/Slic3r_PE_sla_support_points.txt";
@@ -1950,6 +1954,15 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
                     // extract slic3r print config file
                     _extract_project_config_from_archive(archive, stat, config, config_substitutions, model);
                 }
+                else if (boost::algorithm::iequals(name, ORCA_CAD_RECIPE_FILE)
+                      || boost::algorithm::iequals(name, LEGACY_CAD_RECIPE_FILE)) {
+                    // Restore the editable CAD recipe (optional; absent in non-CAD projects).
+                    if (stat.m_uncomp_size > 0) {
+                        std::string buf((size_t)stat.m_uncomp_size, '\0');
+                        if (mz_zip_reader_extract_to_mem(&archive, stat.m_file_index, buf.data(), buf.size(), 0))
+                            model.cad_recipe = std::move(buf);
+                    }
+                }
                 else if (boost::algorithm::iequals(name, CUT_INFORMATION_FILE)) {
                     // extract object cut info
                     _extract_cut_information_from_archive(archive, stat, config_substitutions);
@@ -6008,6 +6021,7 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
         bool _add_mesh_to_object_stream(std::function<bool(std::string &, bool)> const &flush, ObjectData const &object_data) const;
         bool _add_build_to_model_stream(std::stringstream& stream, const BuildItemsList& build_items) const;
         bool _add_layer_height_profile_file_to_archive(mz_zip_archive& archive, Model& model);
+        bool _add_cad_recipe_file_to_archive(mz_zip_archive& archive, Model& model);
         bool _add_layer_config_ranges_file_to_archive(mz_zip_archive& archive, Model& model);
         bool _add_brim_ear_points_file_to_archive(mz_zip_archive& archive, Model& model);
         bool _add_sla_support_points_file_to_archive(mz_zip_archive& archive, Model& model);
@@ -6404,6 +6418,11 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
                 return false;
             }
 
+            if (!_add_cad_recipe_file_to_archive(archive, model)) {
+                close_zip_writer(&archive);
+                return false;
+            }
+
             // BBS progress point
             /*BOOST_LOG_TRIVIAL(info) << __FUNCTION__ << ":" <<__LINE__ << boost::format("export 3mf EXPORT_STAGE_ADD_LAYER_RANGE\n");
             if (proFn) {
@@ -7658,6 +7677,19 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
         return true;
     }
 
+    bool _BBS_3MF_Exporter::_add_cad_recipe_file_to_archive(mz_zip_archive& archive, Model& model)
+    {
+        if (model.cad_recipe.empty())
+            return true;
+        if (!mz_zip_writer_add_mem(&archive, ORCA_CAD_RECIPE_FILE.c_str(),
+                (const void*)model.cad_recipe.data(), model.cad_recipe.length(),
+                MZ_DEFAULT_COMPRESSION)) {
+            add_error("Unable to add CAD recipe file to archive");
+            return false;
+        }
+        return true;
+    }
+
     bool _BBS_3MF_Exporter::_add_layer_config_ranges_file_to_archive(mz_zip_archive& archive, Model& model)
     {
         std::string out = "";
diff --git a/src/libslic3r/Model.cpp b/src/libslic3r/Model.cpp
index 714d45ad9b..209ccdafa2 100644
--- a/src/libslic3r/Model.cpp
+++ b/src/libslic3r/Model.cpp
@@ -108,6 +108,8 @@ Model& Model::assign_copy(const Model &rhs)
     this->md_value = rhs.md_value;
     this->texture_mesh = rhs.texture_mesh;
 
+    this->cad_recipe = rhs.cad_recipe;
+
     return *this;
 }
 
@@ -152,6 +154,7 @@ Model& Model::assign_copy(Model &&rhs)
     rhs.model_info.reset();
     this->profile_info = rhs.profile_info;
     rhs.profile_info.reset();
+    this->cad_recipe = std::move(rhs.cad_recipe);
     return *this;
 }
 
diff --git a/src/libslic3r/Model.hpp b/src/libslic3r/Model.hpp
index 8da1340fa9..815b93c362 100644
--- a/src/libslic3r/Model.hpp
+++ b/src/libslic3r/Model.hpp
@@ -1569,6 +1569,10 @@ public:
     std::vector<std::string> md_name;
     std::vector<std::string> md_value;
 
+    // Opaque parametric CAD recipe (CadDocument::serialize_recipe()), round-tripped through
+    // the 3MF as Metadata/orca_cad.bin. Empty for non-CAD projects.
+    std::string cad_recipe;
+
     void SetDesigner(std::string designer, std::string designer_user_id) {
         if (design_info == nullptr) {
             design_info = std::make_shared<ModelDesignInfo>();
diff --git a/src/slic3r/CMakeLists.txt b/src/slic3r/CMakeLists.txt
index 656d41f338..e924c317cc 100644
--- a/src/slic3r/CMakeLists.txt
+++ b/src/slic3r/CMakeLists.txt
@@ -788,6 +788,30 @@ set(SLIC3R_GUI_SOURCES
     Utils/wxInspectorPlugins/Registration.hpp
 )
 
+# Design/CAD tab: parametric sketch UI, its gizmos, and the MCP control socket.
+# All of it sits behind SLIC3R_CAD and links the CAD kernel in libslic3r.
+if (SLIC3R_CAD)
+    list(APPEND SLIC3R_GUI_SOURCES
+        GUI/CAD/DesignPanel.cpp
+        GUI/CAD/DesignPanel.hpp
+        GUI/CAD/DesignCanvas.cpp
+        GUI/CAD/DesignCanvas.hpp
+        GUI/CAD/DesignSketchTool.cpp
+        GUI/CAD/DesignSketchTool.hpp
+        GUI/CAD/DesignOffer.hpp
+        GUI/CAD/DesignInteraction.hpp
+        GUI/CAD/SketchInlineEditor.cpp
+        GUI/CAD/SketchInlineEditor.hpp
+        GUI/CAD/McpControl.cpp
+        GUI/CAD/McpControl.hpp
+        GUI/Gizmos/GLGizmoSketch.cpp
+        GUI/Gizmos/GLGizmoSketch.hpp
+        # Needs GeometryEngine (make_primitive / apply_fillet / tessellate).
+        GUI/Gizmos/GLGizmoPrimitive.cpp
+        GUI/Gizmos/GLGizmoPrimitive.hpp
+    )
+endif ()
+
 add_subdirectory(GUI/DeviceCore)
 add_subdirectory(GUI/DeviceTab)
 
diff --git a/src/slic3r/GUI/3DBed.hpp b/src/slic3r/GUI/3DBed.hpp
index b791635fd3..e6335fba3a 100644
--- a/src/slic3r/GUI/3DBed.hpp
+++ b/src/slic3r/GUI/3DBed.hpp
@@ -134,6 +134,7 @@ public:
 
     void set_position(Vec2d& position);
     void set_axes_mode(bool origin);
+    void set_axes_origin(const Vec3d& origin) { m_axes.set_origin(origin); }   // Design tab: triad at bed centre
     const Vec2d& get_position() const { return m_position; }
 
     // Build volume geometry for various collision detection tasks.
diff --git a/src/slic3r/GUI/CAD/DesignCanvas.cpp b/src/slic3r/GUI/CAD/DesignCanvas.cpp
new file mode 100644
index 0000000000..8db2afbbc2
--- /dev/null
+++ b/src/slic3r/GUI/CAD/DesignCanvas.cpp
@@ -0,0 +1,1673 @@
+#include "slic3r/GUI/CAD/DesignCanvas.hpp"
+
+#include "slic3r/GUI/CAD/SketchInlineEditor.hpp"
+#include "slic3r/GUI/CAD/DesignInteraction.hpp"
+#include "slic3r/GUI/GLCanvas3D.hpp"
+#include "slic3r/GUI/OpenGLManager.hpp"
+#include "slic3r/GUI/3DBed.hpp"
+#include "slic3r/GUI/Camera.hpp"   // N: look down the sketch plane normal
+#include "slic3r/GUI/GUI_App.hpp"
+#include "slic3r/GUI/Plater.hpp"
+#include "libslic3r/Model.hpp"
+#include "libslic3r/TriangleMesh.hpp"
+#include "slic3r/GUI/3DScene.hpp"
+#include "slic3r/GUI/MeshUtils.hpp"   // ClippingPlane (section view)
+#include "libslic3r/Config.hpp"
+#include <boost/algorithm/string/predicate.hpp>
+#include <algorithm>
+#include <cstdlib>
+
+#include <wx/glcanvas.h>
+#include <wx/stopwatch.h>   // wxGetLocalTimeMillis: the right-click vs right-hold budget
+#include <wx/sizer.h>
+#include <wx/frame.h>
+#include <wx/stattext.h>
+#include <wx/toplevel.h>
+
+namespace Slic3r {
+namespace GUI {
+
+DesignCanvas::DesignCanvas(wxWindow* parent)
+    : wxPanel()
+{
+    if (!Create(parent, wxID_ANY, wxDefaultPosition, wxDefaultSize, 0))
+        return;
+
+    m_canvas_widget = OpenGLManager::create_wxglcanvas(*this);
+    if (m_canvas_widget == nullptr)
+        return;
+
+    m_canvas = new GLCanvas3D(m_canvas_widget, m_bed);
+    m_canvas->set_context(wxGetApp().init_glcontext(*m_canvas_widget));
+    m_canvas->allow_multisample(OpenGLManager::can_multisample());
+    m_canvas->set_config(wxGetApp().plater()->config());
+    m_canvas->set_model(&m_model);
+    // Nothing to slice here, but GLCanvas3D derefs the process unguarded every frame, so it
+    // cannot be null. Borrow the plater's, as the editor canvases do.
+    m_canvas->set_process(&wxGetApp().plater()->background_process());
+    m_canvas->set_type(GLCanvas3D::ECanvasType::CanvasView3D);
+
+    // CAD navigation, this canvas only: left-drag sweeps a selection rubber band, so orbit
+    // moves to middle-drag and pan to right-drag. Design is a different modality from
+    // Prepare/Preview and every CAD the user already knows maps the mouse this way; the other
+    // tabs are untouched.
+    m_canvas->set_cad_navigation(true);
+
+    m_canvas->enable_picking(false);   // viewport face/edge picking is custom (TODO)
+    m_canvas->enable_moving(false);
+    m_canvas->enable_gizmos(false);
+    m_canvas->enable_selection(false); // stock volume selection unused; solid highlight is tree-driven
+    m_canvas->enable_main_toolbar(false);
+    m_canvas->enable_select_plate_toolbar(false);
+    m_canvas->enable_assemble_view_toolbar(false);
+    m_canvas->enable_separator_toolbar(false);
+    m_canvas->enable_collapse_toolbar(false);
+    m_canvas->enable_plate_chrome(false);
+    m_canvas->enable_labels(false);
+    m_canvas->set_axes_at_bed_center(true);   // triad at bed centre = modeling origin
+
+    m_canvas->set_design_sketch_tool(&m_sketch_tool);
+    m_sketch_tool.on_commit = [this](const SketchProfile& prof, const SketchPlane& pl) {
+        if (m_on_sketch_commit) m_on_sketch_commit(prof, pl);
+        if (m_canvas) m_canvas->set_as_dirty();
+        if (m_canvas_widget) m_canvas_widget->Refresh();
+    };
+    m_sketch_tool.on_commit_entities = [this](const std::vector<SketchEntity>& ents,
+                                              const std::vector<SketchEntityConstraintDef>& cons,
+                                              const SketchPlane& pl) {
+        if (m_on_sketch_entities_commit) m_on_sketch_entities_commit(ents, cons, pl);
+        if (m_canvas) m_canvas->set_as_dirty();
+        if (m_canvas_widget) m_canvas_widget->Refresh();
+    };
+
+    // Onshape-style in-canvas value editor, floating over the GL canvas. The tool hands
+    // us a screen pixel (device px) + a commit/cancel pair; we convert to logical client
+    // px and wrap the callbacks so each one re-solves and re-renders the viewport.
+    m_inline_editor = std::make_unique<SketchInlineEditor>();
+    // The tool draws it: it owns the frame's ImGui pass and the render scale. Handing it a raw
+    // pointer rather than the unique_ptr keeps the ownership where it was.
+    m_sketch_tool.inline_editor = m_inline_editor.get();
+    // SCHEDULE a paint, do not render one. request_repaint() renders SYNCHRONOUSLY on software
+    // GL, and this callback runs from inside DesignSketchTool::render() — so using it here asks
+    // for a render from within a render. The frames stopped after nine, which is what a
+    // re-entrancy guard giving up looks like. Refresh() posts a paint event instead: the current
+    // frame finishes, the event loop runs (which is where ImGui's queued characters are consumed),
+    // and the next frame starts clean.
+    // MEASUREMENT: does a typed character reach the GL canvas at all? Everything downstream of
+    // this point is known good (ImGui reports want_text=1 and our InputText active), so if these
+    // lines do not appear the character never got past the panel's CHAR_HOOK / the focus chain,
+    // and no amount of work inside the field will help. Skips always: a pure observer.
+    if (m_canvas_widget != nullptr && std::getenv("ORCA_CAD_UXTRACE")) {
+        m_canvas_widget->Bind(wxEVT_CHAR, [](wxKeyEvent& e) {
+            fprintf(stderr, "[UX] canvas_char key=%d\n", e.GetKeyCode());
+            fflush(stderr);
+            e.Skip();
+        });
+    }
+    m_inline_editor->request_frame = [this] {
+        // BOTH halves, and the dirty flag first: GLCanvas3D's paint handler returns without
+        // rendering when the canvas is not marked dirty, so a bare Refresh() posts an event that
+        // draws nothing and the frames still stop. request_repaint() does exactly this pair on
+        // the hardware path; what it must NOT do here is its software path, which renders
+        // synchronously — and this callback runs from inside render().
+        if (m_canvas)        m_canvas->set_as_dirty();
+        if (m_canvas_widget) m_canvas_widget->Refresh(false);
+    };
+    m_sketch_tool.on_inline_edit = [this](wxPoint screen_px, double current,
+                                          const std::string& title,
+                                          std::function<void(double)> commit,
+                                          std::function<void()> cancel) {
+        if (!m_inline_editor) { if (cancel) cancel(); return; }
+        // The tool hands us canvas device px and the field is now drawn IN the canvas, so this
+        // is already the coordinate space it wants — no conversion to screen coordinates, and no
+        // window to place there.
+        // Freeze the sketch tool while the field is open so a stray click/move on the GL
+        // canvas can't draw under the field; released on commit or cancel.
+        m_sketch_tool.set_inline_busy(true);
+        // AND PUT THE KEYBOARD ON THE CANVAS. The field is drawn by ImGui, and ImGui is fed from
+        // GLCanvas3D's own key handler, so a key only reaches it if the canvas is the focused
+        // widget. That is a focus move WITHIN one window — the toolkit's business, not the window
+        // manager's, which is the whole point of not being a window any more — but it still has
+        // to be asked for: after a toolbar click or a tree selection the focus is elsewhere in
+        // the panel, and the field would sit there taking nothing.
+        if (m_canvas_widget) m_canvas_widget->SetFocus();
+        m_inline_editor->open(screen_px, current, title,
+            [this, commit](double v) {
+                m_sketch_tool.set_inline_busy(false);
+                if (commit) commit(v);
+                request_repaint();
+            },
+            [this, cancel]() {
+                m_sketch_tool.set_inline_busy(false);
+                if (cancel) cancel();
+                request_repaint();
+            });
+    };
+    // Let the tool force-close the field (keep-as-drawn) — polyline right-click/double-click
+    // ends the chain even while a per-segment value field is open.
+    m_sketch_tool.on_inline_dismiss = [this]() {
+        if (m_inline_editor) m_inline_editor->cancel();
+    };
+    m_sketch_tool.on_inline_commit = [this]() {
+        if (m_inline_editor) m_inline_editor->commit();
+    };
+
+    // Bottom-right viewport HUD: a borderless, non-focusable float label showing the active
+    // tool's current values. Top-level (a child widget is hidden by the GL surface, same as
+    // the inline editor). Fed every frame by the tool's on_readout; empty text hides it.
+    // NON-FOCUSABLE IS THE LOAD-BEARING WORD, and a wxFrame is not: see the header. The chip
+    // outlives the gesture that drew it, and while it held the X input focus every sketch
+    // shortcut was swallowed until the user clicked the canvas. Same window class as the status
+    // chip below for the same reason. Do not "simplify" it back to a wxFrame.
+    {
+        wxWindow* top = wxGetTopLevelParent(m_canvas_widget);
+        m_hud = new wxPopupWindow(top, wxBORDER_NONE);
+        m_hud->SetBackgroundColour(wxColour(28, 30, 34));
+        m_hud_label = new wxStaticText(m_hud, wxID_ANY, wxEmptyString);
+        m_hud_label->SetForegroundColour(wxColour(0x46, 0xE0, 0xC8));   // teal, reads on dark bed
+        wxFont f = m_hud_label->GetFont(); f.MakeBold(); m_hud_label->SetFont(f);
+        auto* hs = new wxBoxSizer(wxHORIZONTAL);
+        hs->Add(m_hud_label, 0, wxALL, 6);
+        m_hud->SetSizerAndFit(hs);
+        m_hud->Hide();
+    }
+    m_sketch_tool.on_readout = [this](const std::string& s) { set_readout(s); };
+
+    // Bottom-LEFT twin, carrying the status line. Top-level for the same reason as the readout
+    // (a child widget is hidden by the GL surface) but a wxPopupWindow rather than a wxFrame,
+    // because a popup cannot take keyboard focus. The readout gets away with a frame only
+    // because it appears mid-gesture and the next input is the mouse; this one is up
+    // permanently and is re-raised on every status change. As a frame it took the WM's focus
+    // each time and the canvas stopped receiving keys at all — every sketch shortcut silently
+    // dead, which reads as a broken tool. Do not "simplify" it back to a wxFrame.
+    // Its colour is set per message — the panel decides whether a line is neutral or an error.
+    {
+        wxWindow* top = wxGetTopLevelParent(m_canvas_widget);
+        m_status_hud = new wxPopupWindow(top, wxBORDER_NONE);
+        m_status_hud->SetBackgroundColour(wxColour(28, 30, 34));
+        m_status_hud_label = new wxStaticText(m_status_hud, wxID_ANY, wxEmptyString);
+        auto* ss = new wxBoxSizer(wxHORIZONTAL);
+        // The line never wraps — there is a whole window's width down here — so the chip is
+        // ONE LINE tall. Spacers rather than a wxALL border because the two axes want
+        // different numbers: roomy at the sides so it reads as a label, and just enough top
+        // and bottom to clear the descenders. Zero vertical clips the glyphs; 6 (what the
+        // readout chip uses) makes it look like a two-line box.
+        ss->AddSpacer(10);
+        ss->Add(m_status_hud_label, 0, wxTOP | wxBOTTOM, 3);
+        ss->AddSpacer(10);
+        m_status_hud->SetSizerAndFit(ss);
+        m_status_hud->Hide();
+    }
+    // A floating frame does not follow its parent, so the anchor has to be recomputed whenever
+    // the canvas changes size (that bind is below bind_event_handlers(), for the reason given
+    // there). The readout HUD gets away without this because it is transient; the status line is
+    // on screen almost permanently and would visibly detach.
+    // ...and it does not follow the WINDOW either. A popup is override-redirect: the window
+    // manager does not own it, so minimising the app leaves the chip sitting on the bare desktop
+    // (seen on the rig: whole screen black, chip still there), and it stacks above other
+    // applications rather than behind them. IsShownOnScreen does not catch this — an iconised
+    // frame still counts as shown — so the frame has to say so itself. Deactivating the app is
+    // the same case one step weaker: the chip belongs to a viewport the user is no longer
+    // looking at. Showing it back is safe because a popup cannot take focus, so neither event
+    // can be re-triggered by our own Show().
+    // Members rather than lambdas so unbind_canvas_event_handlers() can Unbind them: these sit on
+    // a frame that OUTLIVES this canvas, and a lambda cannot be unbound.
+    if (wxWindow* top = wxGetTopLevelParent(m_canvas_widget)) {
+        top->Bind(wxEVT_ICONIZE,  &DesignCanvas::on_frame_iconize,  this);
+        top->Bind(wxEVT_ACTIVATE, &DesignCanvas::on_frame_activate, this);
+        // The anchor is an ABSOLUTE SCREEN position (ClientToScreen below), so moving the window
+        // moves the canvas out from under a chip that stays where it was. Dragging the frame by
+        // its title bar left the chip stranded mid-viewport until the next size, status or tab
+        // change happened to re-place it. Nothing on the canvas fires for a move that does not
+        // also resize, so it has to come from the frame.
+        top->Bind(wxEVT_MOVE,     &DesignCanvas::on_status_hud_reanchor, this);
+    }
+
+    refresh_bed();
+
+    // The view this canvas opens on. Built lazily, on the way into the Design tab, so this
+    // is the view the user is looking at right now.
+    m_parked_camera = wxGetApp().plater()->get_camera();
+
+    // Before any of this class's own Binds below: wx calls dynamically bound handlers in
+    // reverse order of binding, and GLCanvas3D swallows several events without skipping them —
+    // wxEVT_RIGHT_UP and wxEVT_ENTER_WINDOW in on_mouse, and wxEVT_SIZE in on_size, which is
+    // just `m_dirty = true;`. For those, whatever is bound LAST is the only handler that runs.
+    // The context menu, the focus-follows-mouse and the status-chip re-anchor all depend on
+    // running first, which is only true while this call stays ahead of them.
+    m_canvas->bind_event_handlers();
+
+    // The status-chip re-anchor promised above, bound AFTER the call so it runs first — ahead of
+    // it the handler never ran at all, leaving a stale anchor and wrap width after any resize
+    // that did not also move the frame or change the text. Its e.Skip() is load-bearing the
+    // other way: it falls through to on_size, which is what still marks the canvas dirty.
+    m_canvas_widget->Bind(wxEVT_SIZE, &DesignCanvas::on_status_hud_reanchor, this);
+
+    // The Design GL canvas only receives key events (Esc to exit/enter Select, Ctrl+Z undo)
+    // while it holds keyboard focus. Clicking a side-panel button steals focus, after which
+    // Esc/Ctrl+Z silently do nothing until the viewport is clicked again. Restore focus
+    // whenever the pointer enters the viewport (focus-follows-mouse, standard CAD behaviour).
+    m_canvas_widget->Bind(wxEVT_ENTER_WINDOW, [this](wxMouseEvent& e) {
+        // …but NOT while an inline value field is open: the field floats over the canvas, so
+        // the smallest pointer jiggle re-enters the viewport and would yank focus off the
+        // field (the "no cursor focus on the number, click to focus" bug).
+        if (m_canvas_widget && !m_sketch_tool.inline_busy()) m_canvas_widget->SetFocus();
+        e.Skip();
+    });
+
+
+    auto* sizer = new wxBoxSizer(wxVERTICAL);
+    sizer->Add(m_canvas_widget, 1, wxEXPAND);
+    SetSizer(sizer);
+    SetMinSize(wxSize(300, 300));
+}
+
+// Both are idempotent, and neither destroys anything: the destructor still owns that.
+void DesignCanvas::unbind_canvas_event_handlers()
+{
+    if (wxWindow* top = wxGetTopLevelParent(m_canvas_widget)) {
+        top->Unbind(wxEVT_ICONIZE,  &DesignCanvas::on_frame_iconize,      this);
+        top->Unbind(wxEVT_ACTIVATE, &DesignCanvas::on_frame_activate,     this);
+        top->Unbind(wxEVT_MOVE,     &DesignCanvas::on_status_hud_reanchor, this);
+    }
+    // Before the popups go down, or a resize still in flight re-places and re-shows the chip.
+    if (m_canvas_widget)
+        m_canvas_widget->Unbind(wxEVT_SIZE, &DesignCanvas::on_status_hud_reanchor, this);
+    // A popup is override-redirect: it does not go down with the frame, so one left showing sits
+    // on the bare desktop for however long the teardown takes.
+    show_status_hud(false);
+    if (m_hud) m_hud->Hide();
+    if (m_canvas) m_canvas->unbind_event_handlers();
+}
+
+void DesignCanvas::reset_canvas_volumes()
+{
+    if (m_canvas) m_canvas->reset_volumes();
+}
+
+DesignCanvas::~DesignCanvas()
+{
+    if (m_hud) m_hud->Destroy();
+    delete m_canvas;
+    delete m_canvas_widget;
+}
+
+// Distinct per-body colours (Onshape-style). Body 0 keeps the familiar gold; the rest
+// cycle through a small saturated palette so coexisting solids read as separate parts.
+static ColorRGBA body_palette(int body_idx)
+{
+    static const ColorRGBA kPalette[] = {
+        ColorRGBA(0.86f, 0.66f, 0.20f, 1.0f),  // gold
+        ColorRGBA(0.30f, 0.62f, 0.90f, 1.0f),  // blue
+        ColorRGBA(0.45f, 0.78f, 0.42f, 1.0f),  // green
+        ColorRGBA(0.86f, 0.45f, 0.40f, 1.0f),  // coral
+        ColorRGBA(0.70f, 0.52f, 0.86f, 1.0f),  // violet
+        ColorRGBA(0.90f, 0.70f, 0.35f, 1.0f),  // amber
+    };
+    const int n = int(sizeof(kPalette) / sizeof(kPalette[0]));
+    return kPalette[((body_idx % n) + n) % n];
+}
+
+void DesignCanvas::request_repaint()
+{
+    if (!m_canvas)
+        return;
+    m_canvas->set_as_dirty();
+
+    // NOTHING may touch GL before the canvas has initialised it. The backend probe below calls
+    // OpenGLManager::get_gl_info().get_renderer(), which runs GLInfo::detect() -> glGetString
+    // with no context current and, before init_opengl(), no loaded function pointers — a
+    // segfault at startup with no window and nothing in the log. Anything that asks for a
+    // repaint while the panel is still being built lands here, so the guard belongs at the top
+    // rather than around the render() call: the crash was in the PROBE, not in the paint.
+    if (!m_canvas->is_initialized()) {
+        if (m_canvas_widget)
+            m_canvas_widget->Refresh();   // the first real paint draws the current state anyway
+        return;
+    }
+
+    if (m_sw_gl < 0) {
+        // Cache the backend once it's known; the renderer string is empty until
+        // GL is initialised, so stay "unknown" and take the safe direct path till then.
+        const std::string& r = OpenGLManager::get_gl_info().get_renderer();
+        if (!r.empty())
+            m_sw_gl = (boost::icontains(r, "llvmpipe") || boost::icontains(r, "softpipe") ||
+                       boost::icontains(r, "swrast")   || boost::icontains(r, "software")) ? 1 : 0;
+    }
+
+    if (m_sw_gl == 0) {
+        if (m_canvas_widget)
+            m_canvas_widget->Refresh();   // hardware GL: paint cycle drives render()
+    } else {
+        m_canvas->render();               // software GL or backend not yet known
+    }
+}
+
+void DesignCanvas::enter_viewport()
+{
+    if (!m_camera_swapped) swap_camera();
+}
+
+void DesignCanvas::leave_viewport()
+{
+    if (m_camera_swapped) swap_camera();
+}
+
+void DesignCanvas::swap_camera()
+{
+    Plater* plater = wxGetApp().plater();
+    if (plater == nullptr) return;
+    std::swap(plater->get_camera(), m_parked_camera);
+    m_camera_swapped = !m_camera_swapped;
+}
+
+void DesignCanvas::force_repaint()
+{
+    if (m_canvas == nullptr || m_canvas_widget == nullptr)
+        return;
+
+    CallAfter([this]() {
+        if (m_canvas == nullptr || m_canvas_widget == nullptr)
+            return;
+        m_canvas->set_as_dirty();
+        m_canvas_widget->Refresh();
+        m_canvas_widget->Update();   // synchronous: an expose may never come after a page show
+    });
+}
+
+void DesignCanvas::repaint_now()
+{
+    if (m_canvas == nullptr || m_canvas_widget == nullptr)
+        return;
+    request_repaint();            // mark dirty + Refresh (hardware GL) or render (software GL)
+    m_canvas_widget->Update();    // service the pending paint immediately (a modal popup owns the loop)
+}
+
+void DesignCanvas::reload(bool keep_view)
+{
+    m_canvas->reset_volumes();
+
+    for (int i = 0; i < (int)m_model.objects.size(); ++i)
+        m_canvas->load_object(m_model, i);
+
+    const ColorRGBA sel_gold = design_selection_color();   // same colour as every other selection
+    const ColorRGBA ghost(0.26f, 0.66f, 1.0f, 0.45f);
+
+    const auto& volumes = m_canvas->get_volumes().volumes;
+    for (auto* v : volumes) {
+        int obj_idx = v->object_idx();
+        if (obj_idx == 0) {
+            // Object 0 holds one volume per body — colour each by its body index so
+            // multiple coexisting solids are visually distinct (Onshape per-part colour).
+            const int b = v->volume_idx();
+            bool hidden = (b >= 0 && b < int(m_body_visible.size())) && !m_body_visible[b];
+            // Preview-only mode (fillet/chamfer/draft, once a valid target is picked): hide
+            // every base body so only the result ghost is on screen until Confirm.
+            if (m_body_hidden) hidden = true;
+            v->is_active = !hidden;   // per-body visibility toggle
+            if (!hidden) {
+                // An EXPLICIT colour outranks the selection tint. m_body_selected is a
+                // document-wide flag raised whenever a non-Sketch feature row is selected —
+                // the normal resting state after any modelling operation — so painting every
+                // body gold on it made the Color tool look broken: the override was written,
+                // carried across recompute and read back correctly, and then overpainted here
+                // every single frame. A body the user deliberately coloured keeps its colour;
+                // the rest still tint, which is all the tint was ever for.
+                const bool overridden = m_color_bodies != nullptr && b >= 0
+                                        && b < int(m_color_bodies->size())
+                                        && (*m_color_bodies)[b].has_color;
+                ColorRGBA c = (m_body_selected && !overridden) ? sel_gold : body_color(b);
+                if (b == m_hl_body_target)    c = ColorRGBA(0.30f, 0.90f, 0.70f, 1.0f); // target = teal-green
+                else if (b == m_hl_body_tool) c = ColorRGBA(1.00f, 0.55f, 0.15f, 1.0f); // tool = orange
+                if (m_body_translucent) c.a(0.30f);
+                else if (m_xray_focus >= 0 && b != m_xray_focus) c.a(0.25f);
+                v->set_color(c);
+            }
+        } else if (obj_idx == 1) {
+            // The ghost is normally a faint blue overlay on the visible body. In preview-only
+            // mode it IS the result (base bodies hidden), so render it opaque so it reads as a
+            // finished solid rather than a see-through hint.
+            v->set_color(m_body_hidden ? ColorRGBA(0.40f, 0.82f, 1.0f, 1.0f) : ghost);
+        }
+    }
+
+    if (!keep_view) {
+        if (m_first_frame && !m_model.objects.empty()) {
+            m_canvas->select_view("iso");
+            m_canvas->zoom_to_volumes();
+            m_first_frame = false;
+        }
+    }
+
+    m_canvas->set_as_dirty();
+    if (m_canvas_widget)
+        m_canvas_widget->Refresh();
+}
+
+void DesignCanvas::set_mesh(const TriangleMesh& mesh)
+{
+    if (m_model.objects.empty()) {
+        auto* obj = m_model.add_object();
+        obj->add_volume(mesh);
+        obj->add_instance();
+    } else {
+        ModelObject* obj = m_model.objects.front();
+        obj->clear_volumes();
+        obj->add_volume(mesh);
+        if (obj->instances.empty())
+            obj->add_instance();
+    }
+
+    reload(!m_first_frame);
+}
+
+void DesignCanvas::set_bodies(const std::vector<TriangleMesh>& body_meshes,
+                              const std::vector<bool>& visible)
+{
+    // Object 0 carries one GLVolume per body so reload() can colour each distinctly.
+    // Falls back to a single-volume object when there's only one body (identical look
+    // to the old set_mesh path). Picking still uses the combined mesh via set_solid_pick.
+    m_body_visible = visible;   // empty => all visible; reload() reads this per volume
+    if (body_meshes.empty()) { clear_mesh(); return; }
+
+    ModelObject* obj = m_model.objects.empty() ? m_model.add_object()
+                                               : m_model.objects.front();
+    obj->clear_volumes();
+    for (const TriangleMesh& m : body_meshes)
+        obj->add_volume(m);
+    if (obj->instances.empty())
+        obj->add_instance();
+
+    reload(!m_first_frame);
+}
+
+void DesignCanvas::clear_mesh()
+{
+    if (!m_model.objects.empty()) {
+        m_model.delete_object((size_t)0);
+        reload(true);
+    }
+}
+
+void DesignCanvas::set_preview_mesh(const TriangleMesh& mesh)
+{
+    // Remove existing ghost (object 1) if present
+    if (m_model.objects.size() > 1)
+        m_model.delete_object((size_t)1);
+
+    auto* obj = m_model.add_object();
+    obj->add_volume(mesh);
+    obj->add_instance();
+
+    reload(true);
+}
+
+void DesignCanvas::clear_preview()
+{
+    if (m_model.objects.size() > 1) {
+        m_model.delete_object((size_t)1);
+        reload(true);
+    }
+}
+
+void DesignCanvas::fit_view()
+{
+    if (m_canvas && !m_model.objects.empty()) {
+        m_canvas->zoom_to_volumes();
+        m_canvas->set_as_dirty();
+        if (m_canvas_widget)
+            m_canvas_widget->Refresh();
+    }
+}
+
+void DesignCanvas::set_view(const std::string& view_name)
+{
+    if (m_canvas) {
+        m_canvas->select_view(view_name);
+        m_canvas->zoom_to_volumes();
+        m_canvas->set_as_dirty();
+        if (m_canvas_widget)
+            m_canvas_widget->Refresh();
+    }
+}
+
+void DesignCanvas::begin_sketch(const SketchPlane& plane, DesignSketchTool::Mode mode)
+{
+    m_sketch_tool.begin(plane, mode);
+    if (m_canvas) m_canvas->set_as_dirty();
+    if (m_canvas_widget) m_canvas_widget->Refresh();
+}
+
+void DesignCanvas::set_sketch_plane(const SketchPlane& plane)
+{
+    m_sketch_tool.set_plane(plane);   // keeps the 2D entities; only the carrier plane changes
+    if (m_canvas) m_canvas->set_as_dirty();
+    if (m_canvas_widget) m_canvas_widget->Refresh();
+}
+
+void DesignCanvas::edit_sketch(const std::vector<SketchEntity>& entities,
+                               const std::vector<SketchEntityConstraintDef>& constraints,
+                               const SketchPlane& plane)
+{
+    m_sketch_tool.begin_edit(entities, constraints, plane);
+    if (m_canvas) m_canvas->set_as_dirty();
+    if (m_canvas_widget) m_canvas_widget->Refresh();
+}
+
+void DesignCanvas::set_sketch_tool(DesignSketchTool::Mode mode)
+{
+    m_sketch_tool.set_tool(mode);
+    if (m_canvas) m_canvas->set_as_dirty();
+    if (m_canvas_widget) m_canvas_widget->Refresh();
+}
+
+void DesignCanvas::set_sketch_construction(bool c)
+{
+    m_sketch_tool.set_construction(c);
+}
+
+bool DesignCanvas::edit_sketch_selection_value()
+{
+    const bool ok = m_sketch_tool.open_selection_dimension_editor();
+    if (ok) request_repaint();
+    return ok;
+}
+
+int DesignCanvas::toggle_sketch_construction_selection()
+{
+    const int n = m_sketch_tool.toggle_selection_construction();
+    if (n > 0) request_repaint();
+    return n;
+}
+
+bool DesignCanvas::add_sketch_regions(
+    const std::vector<std::vector<std::vector<Vec2d>>>& regions)
+{
+    const bool ok = m_sketch_tool.add_imported_regions(regions);
+    if (ok) request_repaint();
+    return ok;
+}
+
+void DesignCanvas::set_sketch_polygon_sides(int n)
+{
+    m_sketch_tool.set_polygon_sides(n);
+}
+
+void DesignCanvas::set_sketch_polygon_circumscribed(bool c)
+{
+    m_sketch_tool.set_polygon_circumscribed(c);
+}
+
+void DesignCanvas::finish_sketch()
+{
+    m_sketch_tool.finish();
+    if (m_canvas) m_canvas->set_as_dirty();
+    if (m_canvas_widget) m_canvas_widget->Refresh();
+}
+
+// Sync the Design bed to the CURRENT printer bed. Done on every tab activation, not just at
+// construction: the panel is built early (before the active printer profile is fully applied),
+// so a one-shot read picked up the 200x200 default while the real bed (e.g. 270x270) only
+// loaded later — leaving the PartPlate grid spilling past the smaller bed quad.
+void DesignCanvas::refresh_bed()
+{
+    const DynamicPrintConfig* config = wxGetApp().plater()->config();
+    if (!config) return;
+    const auto* bed_shape_opt = config->opt<ConfigOptionPoints>("printable_area");
+    if (!bed_shape_opt) return;
+    double printable_height = 100.0;
+    const auto* ph_opt = config->opt<ConfigOptionFloat>("printable_height");
+    if (ph_opt) printable_height = ph_opt->value;
+    m_bed.set_shape(bed_shape_opt->values, printable_height, {}, {}, "", false);  // mainline added extruder_areas/heights params
+}
+
+void DesignCanvas::set_show_bed(bool b)
+{
+    if (!m_canvas) return;
+    if (m_canvas->get_show_bed() == b) return;   // no repaint for a no-op toggle
+    m_canvas->set_show_bed(b);
+    request_repaint();
+}
+
+bool DesignCanvas::is_sketching() const { return m_sketch_tool.is_active(); }
+
+void DesignCanvas::cancel_sketch()
+{
+    m_sketch_tool.cancel();
+    if (m_canvas) m_canvas->set_as_dirty();
+    if (m_canvas_widget) m_canvas_widget->Refresh();
+}
+
+void DesignCanvas::set_on_sketch_commit(std::function<void(const SketchProfile&, const SketchPlane&)> cb)
+{
+    m_on_sketch_commit = std::move(cb);
+}
+
+void DesignCanvas::set_on_sketch_entities_commit(
+    std::function<void(const std::vector<SketchEntity>&,
+                       const std::vector<SketchEntityConstraintDef>&,
+                       const SketchPlane&)> cb)
+{
+    m_on_sketch_entities_commit = std::move(cb);
+}
+
+void DesignCanvas::set_on_segment_drawn(std::function<void(double, double)> cb)
+{
+    m_sketch_tool.on_segment_drawn = std::move(cb);
+}
+
+void DesignCanvas::set_on_cursor_metrics(std::function<void(double, double, bool)> cb)
+{
+    m_sketch_tool.on_cursor_metrics = std::move(cb);
+}
+
+void DesignCanvas::set_on_solve_state(std::function<void(int, bool, bool)> cb)
+{
+    m_sketch_tool.on_solve_state = std::move(cb);
+}
+
+void DesignCanvas::set_on_sketch_step(std::function<void(DesignSketchTool::Mode, int, int)> cb)
+{
+    m_sketch_tool.on_step_changed = std::move(cb);
+}
+
+void DesignCanvas::apply_segment_length(double len)
+{
+    m_sketch_tool.apply_segment_length(len);
+    request_repaint();
+}
+
+void DesignCanvas::keep_segment_as_drawn()
+{
+    m_sketch_tool.keep_segment_as_drawn();
+    request_repaint();
+}
+
+void DesignCanvas::set_on_sketch_selection_changed(std::function<void(int)> cb)
+{
+    m_sketch_tool.on_selection_changed = std::move(cb);
+}
+
+void DesignCanvas::set_on_sketch_face_selected(std::function<void(int)> cb)
+{
+    m_sketch_tool.on_face_selected = std::move(cb);
+}
+
+void DesignCanvas::set_on_display_sketch_selected(std::function<void(int, int, int)> cb)
+{
+    m_sketch_tool.on_display_sketch_selected = std::move(cb);
+}
+
+void DesignCanvas::set_on_display_sketch_activated(std::function<void(int)> cb)
+{
+    m_sketch_tool.on_display_sketch_activated = std::move(cb);
+}
+
+std::vector<SketchEntity> DesignCanvas::selected_loop_entities() const
+{
+    return m_sketch_tool.selected_loop_entities();
+}
+
+std::vector<std::vector<int>> DesignCanvas::region_entity_indices(const std::vector<SketchEntity>& ents) const
+{
+    return m_sketch_tool.region_entity_indices(ents);
+}
+
+std::vector<std::vector<int>> DesignCanvas::region_entity_indices_with_holes(const std::vector<SketchEntity>& ents) const
+{
+    return m_sketch_tool.region_entity_indices_with_holes(ents);
+}
+
+void DesignCanvas::clear_loop_pick()
+{
+    m_sketch_tool.clear_display_pick();
+}
+
+void DesignCanvas::set_loop_pick(int feature, int region)
+{
+    m_sketch_tool.set_display_pick(feature, region);
+    request_repaint();
+}
+
+void DesignCanvas::set_escalate_on_repick(bool on)
+{
+    m_sketch_tool.set_escalate_on_repick(on);
+}
+
+void DesignCanvas::set_solid_pick(const std::vector<CadBody>* bodies, const TriangleMesh* mesh,
+                                  const std::vector<int>* tri_face, const std::vector<int>* tri_body,
+                                  const std::vector<bool>* visible,
+                                  const std::vector<Transform3d>* xform)
+{
+    m_color_bodies = bodies;   // stable address (m_doc.bodies); reload() reads colour overrides
+    m_sketch_tool.set_solid_pick(bodies, mesh, tri_face, tri_body, visible, xform);
+}
+
+// Effective display colour for a body: per-body override (Color tool) when set, else the
+// auto body-index palette. body_palette() is the file-static helper defined above reload().
+ColorRGBA DesignCanvas::body_color(int body) const
+{
+    if (m_color_bodies != nullptr && body >= 0 && body < int(m_color_bodies->size())
+        && (*m_color_bodies)[body].has_color)
+        return (*m_color_bodies)[body].color;
+    return body_palette(body);
+}
+
+void DesignCanvas::begin_move_body(int body, const Vec3d& pivot, const Transform3d& base_xform,
+                                   double body_radius)
+{
+    m_sketch_tool.set_move_gizmo(body, pivot, base_xform, body_radius);
+    request_repaint();
+}
+
+void DesignCanvas::clear_move_gizmo()
+{
+    m_sketch_tool.clear_move_gizmo();
+    request_repaint();
+}
+
+bool DesignCanvas::moving_body() const { return m_sketch_tool.moving_body(); }
+
+void DesignCanvas::set_on_body_move_changed(std::function<void(int, const Transform3d&)> cb)
+{
+    m_sketch_tool.on_body_move_changed = std::move(cb);
+}
+
+bool DesignCanvas::begin_fillet_gizmo(const Vec3d& body_centroid, double radius)
+{
+    const bool ok = m_sketch_tool.set_fillet_gizmo(body_centroid, radius);
+    request_repaint();
+    return ok;
+}
+
+void DesignCanvas::clear_fillet_gizmo()
+{
+    m_sketch_tool.clear_fillet_gizmo();
+    request_repaint();
+}
+
+bool DesignCanvas::filleting() const { return m_sketch_tool.filleting(); }
+
+void DesignCanvas::set_on_fillet_radius_changed(std::function<void(double)> cb)
+{
+    m_sketch_tool.on_fillet_radius_changed = std::move(cb);
+}
+
+void DesignCanvas::begin_hole_gizmo(const SketchPlane& plane, double x, double y,
+                                    double diameter, double depth, bool through)
+{
+    m_sketch_tool.set_hole_gizmo(plane, x, y, diameter, depth, through);
+    request_repaint();
+}
+
+void DesignCanvas::set_hole_face_bounds(bool has, double umin, double umax, double vmin, double vmax)
+{
+    m_sketch_tool.set_hole_face_bounds(has, umin, umax, vmin, vmax);
+}
+
+void DesignCanvas::clear_hole_gizmo()
+{
+    m_sketch_tool.clear_hole_gizmo();
+    request_repaint();
+}
+
+bool DesignCanvas::holing() const { return m_sketch_tool.holing(); }
+
+void DesignCanvas::set_on_hole_changed(std::function<void(double, double, double, double)> cb)
+{
+    m_sketch_tool.on_hole_changed = std::move(cb);
+}
+
+void DesignCanvas::begin_thread_gizmo(const SketchPlane& plane, double x, double y,
+                                      double radius, double height)
+{
+    m_sketch_tool.set_thread_gizmo(plane, x, y, radius, height);
+    request_repaint();
+}
+
+void DesignCanvas::clear_thread_gizmo()
+{
+    m_sketch_tool.clear_thread_gizmo();
+    request_repaint();
+}
+
+bool DesignCanvas::threading() const { return m_sketch_tool.threading(); }
+
+void DesignCanvas::set_on_thread_changed(std::function<void(double, double, double, double)> cb)
+{
+    m_sketch_tool.on_thread_changed = std::move(cb);
+}
+
+void DesignCanvas::begin_shell_gizmo(const Vec3d& face_centroid, const Vec3d& inward_dir,
+                                     double thickness)
+{
+    m_sketch_tool.set_shell_gizmo(face_centroid, inward_dir, thickness);
+    request_repaint();
+}
+
+void DesignCanvas::clear_shell_gizmo()
+{
+    m_sketch_tool.clear_shell_gizmo();
+    request_repaint();
+}
+
+bool DesignCanvas::shelling() const { return m_sketch_tool.shelling(); }
+
+void DesignCanvas::set_on_shell_thickness_changed(std::function<void(double)> cb)
+{
+    m_sketch_tool.on_shell_thickness_changed = std::move(cb);
+}
+
+void DesignCanvas::begin_revolve_gizmo(const SketchPlane& plane, const Vec2d& centroid,
+                                       int axis_sel, double angle, bool flip)
+{
+    m_sketch_tool.set_revolve_gizmo(plane, centroid, axis_sel, angle, flip);
+    request_repaint();
+}
+
+void DesignCanvas::clear_revolve_gizmo()
+{
+    m_sketch_tool.clear_revolve_gizmo();
+    request_repaint();
+}
+
+bool DesignCanvas::revolving() const { return m_sketch_tool.revolving(); }
+
+void DesignCanvas::set_on_revolve_angle_changed(std::function<void(double)> cb)
+{
+    m_sketch_tool.on_revolve_angle_changed = std::move(cb);
+}
+
+void DesignCanvas::set_draft_gizmo(const Vec3d& face_centroid, const Vec3d& face_normal, double angle)
+{
+    m_sketch_tool.set_draft_gizmo(face_centroid, face_normal, angle);
+    request_repaint();
+}
+
+void DesignCanvas::clear_draft_gizmo()
+{
+    m_sketch_tool.clear_draft_gizmo();
+    request_repaint();
+}
+
+bool DesignCanvas::drafting() const { return m_sketch_tool.drafting(); }
+
+void DesignCanvas::set_on_draft_angle_changed(std::function<void(double)> cb)
+{
+    m_sketch_tool.set_on_draft_angle_changed(std::move(cb));
+}
+
+void DesignCanvas::set_cut_gizmo(const SketchPlane& plane, double offset, const Vec3d& body_center, double half_extent)
+{
+    m_sketch_tool.set_cut_gizmo(plane, offset, body_center, half_extent);
+    request_repaint();
+}
+
+void DesignCanvas::clear_cut_gizmo()
+{
+    m_sketch_tool.clear_cut_gizmo();
+    request_repaint();
+}
+
+bool DesignCanvas::cutting() const { return m_sketch_tool.cutting(); }
+
+void DesignCanvas::set_on_cut_offset_changed(std::function<void(double)> cb)
+{
+    m_sketch_tool.set_on_cut_offset_changed(std::move(cb));
+}
+
+void DesignCanvas::begin_pattern_gizmo(const SketchPlane& plane, const Vec3d& body_centroid,
+                                       bool circular, int count, int dir, double spacing, double angle)
+{
+    m_sketch_tool.set_pattern_gizmo(plane, body_centroid, circular, count, dir, spacing, angle);
+    request_repaint();
+}
+
+void DesignCanvas::clear_pattern_gizmo()
+{
+    m_sketch_tool.clear_pattern_gizmo();
+    request_repaint();
+}
+
+bool DesignCanvas::patterning() const { return m_sketch_tool.patterning(); }
+
+void DesignCanvas::set_on_pattern_changed(std::function<void(double)> cb)
+{
+    m_sketch_tool.on_pattern_changed = std::move(cb);
+}
+
+void DesignCanvas::set_on_solid_selection_changed(std::function<void(int, int, int, int)> cb)
+{
+    m_sketch_tool.on_solid_selection_changed = std::move(cb);
+}
+
+void DesignCanvas::set_on_place_on_face(std::function<bool()> cb)
+{
+    m_sketch_tool.on_place_on_face = std::move(cb);
+}
+
+void DesignCanvas::select_body(int body)
+{
+    m_sketch_tool.select_body(body);
+    request_repaint();
+}
+
+void DesignCanvas::set_extrude_gizmo(const SketchPlane& plane, const Vec2d& centroid,
+                                     double depth, double depth2, bool two_sided, bool flip)
+{
+    m_sketch_tool.set_extrude_gizmo(plane, centroid, depth, depth2, two_sided, flip);
+    request_repaint();
+}
+
+void DesignCanvas::clear_extrude_gizmo()
+{
+    m_sketch_tool.clear_extrude_gizmo();
+    request_repaint();
+}
+
+void DesignCanvas::set_on_extrude_depth_changed(std::function<void(double, bool)> cb)
+{
+    m_sketch_tool.on_extrude_depth_changed = std::move(cb);
+}
+
+void DesignCanvas::set_datum_gizmo(const SketchPlane& plane, double usize, double vsize,
+                                   const Vec3d& base_origin, const Vec3d& base_normal,
+                                   double offset, bool offset_on)
+{
+    m_sketch_tool.set_datum_gizmo(plane, usize, vsize, base_origin, base_normal, offset, offset_on);
+    request_repaint();
+}
+
+void DesignCanvas::clear_datum_gizmo()
+{
+    m_sketch_tool.clear_datum_gizmo();
+    request_repaint();
+}
+
+void DesignCanvas::set_on_datum_size_changed(std::function<void(double, double)> cb)
+{
+    m_sketch_tool.on_datum_size_changed = std::move(cb);
+}
+
+void DesignCanvas::set_on_datum_offset_changed(std::function<void(double)> cb)
+{
+    m_sketch_tool.on_datum_offset_changed = std::move(cb);
+}
+
+void DesignCanvas::set_helix_gizmo(const SketchPlane& plane, double radius, double pitch,
+                                   double height, double taper, bool left_handed)
+{
+    m_sketch_tool.set_helix_gizmo(plane, radius, pitch, height, taper, left_handed);
+    request_repaint();
+}
+
+void DesignCanvas::clear_helix_gizmo()
+{
+    m_sketch_tool.clear_helix_gizmo();
+    request_repaint();
+}
+
+void DesignCanvas::set_on_helix_changed(std::function<void(double, double, double)> cb)
+{
+    m_sketch_tool.on_helix_changed = std::move(cb);
+}
+
+void DesignCanvas::set_rib_gizmo(const SketchPlane& plane, const Vec2d& p0, const Vec2d& p1,
+                                 double thickness)
+{
+    m_sketch_tool.set_rib_gizmo(plane, p0, p1, thickness);
+    request_repaint();
+}
+
+void DesignCanvas::clear_rib_gizmo()
+{
+    m_sketch_tool.clear_rib_gizmo();
+    request_repaint();
+}
+
+void DesignCanvas::set_on_rib_thickness_changed(std::function<void(double)> cb)
+{
+    m_sketch_tool.on_rib_thickness_changed = std::move(cb);
+}
+
+void DesignCanvas::set_base_pick(std::vector<SketchPlane> planes, std::vector<int> bases,
+                                std::vector<std::string> labels)
+{
+    m_sketch_tool.set_base_pick(std::move(planes), std::move(bases), std::move(labels));
+    request_repaint();
+}
+
+void DesignCanvas::clear_base_pick()
+{
+    m_sketch_tool.clear_base_pick();
+    request_repaint();
+}
+
+void DesignCanvas::set_on_datum_base_picked(std::function<void(int)> cb)
+{
+    m_sketch_tool.on_datum_base_picked = std::move(cb);
+}
+
+void DesignCanvas::set_on_sketch_exit(std::function<void()> cb)
+{
+    m_sketch_tool.on_exit = std::move(cb);
+}
+
+void DesignCanvas::set_on_sketch_exit_refused(std::function<void()> cb)
+{
+    m_sketch_tool.on_exit_refused = std::move(cb);
+}
+
+void DesignCanvas::set_on_move_exit(std::function<void()> cb)
+{
+    m_sketch_tool.on_move_exit = std::move(cb);
+}
+
+void DesignCanvas::set_on_context_menu(std::function<void(const wxPoint&)> cb)
+{
+    m_on_context_menu = std::move(cb);
+    if (!m_canvas_widget || m_ctx_bound)
+        return;
+    m_ctx_bound = true;
+    // Bound AFTER GLCanvas3D's own handlers, so this runs first and can consume the event.
+    // It only consumes when it actually opens the offer; every other right-click still falls
+    // through to the polyline-chain end and the move gizmo, which were there first.
+    // Right-drag pans. Without remembering where the press landed, every pan ended by popping
+    // the offer over wherever the camera stopped — the menu appearing as the reward for moving
+    // the view. The offer is the release of a STATIONARY right-click, at the same 8 px budget
+    // the left-click pick uses.
+    m_canvas_widget->Bind(wxEVT_RIGHT_DOWN, [this](wxMouseEvent& e) {
+        m_ctx_press    = e.GetPosition();
+        m_ctx_press_ms = wxGetLocalTimeMillis().GetValue();
+        e.Skip();     // the canvas still needs the press to seed the orbit
+    });
+    m_canvas_widget->Bind(wxEVT_RIGHT_UP, [this](wxMouseEvent& e) {
+        const wxPoint d  = e.GetPosition() - m_ctx_press;
+        const long long dt = wxGetLocalTimeMillis().GetValue() - m_ctx_press_ms;
+        // Always read-and-clear, even when another guard already rules the offer out, or a
+        // terminator recorded under one condition would still be pending under the next.
+        const bool terminated = m_sketch_tool.take_right_consumed();
+        // Click, or navigation? Both budgets must hold: a press that travelled orbited, and a
+        // press that was HELD was aiming to orbit even if the hand never quite moved. Two
+        // independent budgets because the two failure modes are independent — the drift one
+        // alone still popped a menu at the end of a slow, careful orbit.
+        const bool is_click = std::max(std::abs(d.x), std::abs(d.y)) <= kCadRightClickDriftPx
+                              && dt <= kCadRightClickMs;
+        if (m_on_context_menu && !terminated && !inline_busy() && is_click) {
+            // The menu belongs to what you POINTED AT — and pointing happened at the PRESS, not
+            // at the release, so the raycast uses the press position. Within a 3 px budget the
+            // two are the same pixel in practice; using the press is what makes that a
+            // guarantee rather than a coincidence. Pick first, so a right-click on a line offers
+            // that line's verbs instead of the empty-selection vocabulary. Selecting an entity
+            // that is already selected is a no-op, so a multi-entity pick survives a
+            // right-click on one of its members.
+            if (m_canvas && m_sketch_tool.select_at_screen(*m_canvas, m_ctx_press.x, m_ctx_press.y))
+                request_repaint();
+            m_on_context_menu(m_canvas_widget->ClientToScreen(m_ctx_press));
+            return;   // consumed
+        }
+        e.Skip();
+    });
+}
+
+void DesignCanvas::set_on_undo_redo(std::function<void(bool)> cb)
+{
+    m_sketch_tool.on_undo_redo = std::move(cb);
+}
+
+void DesignCanvas::set_display_sketches(std::vector<DesignSketchTool::DisplaySketch> ds)
+{
+    m_sketch_tool.set_display_sketches(std::move(ds));
+    // Overlay changed programmatically (no mouse event) — force a repaint.
+    request_repaint();
+}
+
+void DesignCanvas::set_datum_planes(std::vector<SketchPlane> planes, std::vector<Vec2d> sizes)
+{
+    m_sketch_tool.set_datum_planes(std::move(planes), std::move(sizes));
+    request_repaint();
+}
+
+void DesignCanvas::set_mate_connectors(std::vector<DesignSketchTool::MateConnectorGlyph> g)
+{
+    m_sketch_tool.set_mate_connectors(std::move(g));
+    request_repaint();
+}
+
+void DesignCanvas::set_mate_links(std::vector<std::pair<Vec3d, Vec3d>> l)
+{
+    m_sketch_tool.set_mate_links(std::move(l));
+    request_repaint();
+}
+
+bool DesignCanvas::toggle_planes()
+{
+    const bool on = m_sketch_tool.toggle_show_planes();
+    request_repaint();
+    return on;
+}
+
+bool DesignCanvas::toggle_axes()
+{
+    const bool on = m_sketch_tool.toggle_show_axes();
+    request_repaint();
+    return on;
+}
+
+void DesignCanvas::set_section_plane(bool on, double z, bool keep_upper)
+{
+    m_section_on = on;
+    // The kept half must read as a SOLID part, never a see-through ghost: make sure no leftover
+    // preview translucency is applied while the section is on. Guarded — a no-op if already opaque.
+    if (on) { set_body_translucent(false); set_body_hidden(false); }
+    if (m_canvas) {
+        if (on) {
+            // GLCanvas3D turns the two clipping planes into a Z-RANGE: set_z_range(-p0.offset,
+            // p1.offset). keep_upper=false keeps the LOWER half (z in [-1e5, z]); keep_upper=true
+            // keeps the OPPOSITE, UPPER half (z in [z, +1e5]). Only HIDES geometry — no bodies.
+            if (keep_upper) {
+                m_canvas->set_clipping_plane(0, ClippingPlane(Vec3d(0.0, 0.0, 1.0), -z));     // min_z = z
+                m_canvas->set_clipping_plane(1, ClippingPlane(Vec3d(0.0, 0.0, 1.0), 1.0e5));  // max_z = +1e5
+            } else {
+                m_canvas->set_clipping_plane(0, ClippingPlane(Vec3d(0.0, 0.0, 1.0), 1.0e5));  // min_z = -1e5
+                m_canvas->set_clipping_plane(1, ClippingPlane(Vec3d(0.0, 0.0, 1.0), z));      // max_z = z
+            }
+            m_canvas->set_use_clipping_planes(true);
+        } else {
+            m_canvas->set_use_clipping_planes(false);
+        }
+        m_canvas->set_as_dirty();
+    }
+    request_repaint();
+}
+
+double DesignCanvas::model_mid_z() const
+{
+    const BoundingBoxf3 bb = m_model.bounding_box_exact();
+    return bb.defined ? bb.center().z() : 0.0;
+}
+
+void DesignCanvas::set_readout(const std::string& text)
+{
+    if (!m_hud || !m_hud_label || !m_canvas_widget) return;
+    if (text == m_hud_last) return;                 // only touch the WM on a real change
+    m_hud_last = text;
+    if (text.empty()) { m_hud->Hide(); return; }
+    m_hud_label->SetLabel(wxString::FromUTF8(text));
+    place_readout_hud();
+}
+
+void DesignCanvas::place_readout_hud()
+{
+    if (!m_hud || !m_hud_label || !m_canvas_widget) return;
+    if (m_hud_last.empty() || !m_canvas_widget->IsShownOnScreen()) { m_hud->Hide(); return; }
+    m_hud->Fit();
+    // Anchor to the canvas's bottom-right corner with a small margin (screen coords).
+    const wxSize  cs = m_canvas_widget->GetClientSize();
+    const wxSize  hs = m_hud->GetSize();
+    const wxPoint br = m_canvas_widget->ClientToScreen(
+        wxPoint(cs.GetWidth() - hs.GetWidth() - 12, cs.GetHeight() - hs.GetHeight() - 12));
+    if (!m_hud->IsShown()) m_hud->Show();           // Show before Move (GTK ignores pre-map Move)
+    m_hud->Move(br);
+    m_hud->Raise();
+}
+
+// A popup is override-redirect: the window manager does not own it, so an iconised or
+// deactivated app would leave the chip sitting on the bare desktop. The status chip already
+// had to answer this; now that the readout is a popup too, it answers it the same way.
+void DesignCanvas::show_readout_hud(bool on)
+{
+    if (!m_hud) return;
+    if (on) place_readout_hud();
+    else    m_hud->Hide();
+}
+
+// Clear of the view cube and the two round view buttons, which own the bottom-left corner.
+// Shared by the placement and by the wrap width, which have to agree or the chip wraps to a
+// width it is then not given.
+static constexpr int kStatusHudLeftInsetDip = 190;
+
+void DesignCanvas::set_status_text(const wxString& text, const wxColour& colour)
+{
+    if (!m_status_hud || !m_status_hud_label || !m_canvas_widget) return;
+    if (text == m_status_hud_last && colour == m_status_hud_colour) return;
+    m_status_hud_last   = text;
+    m_status_hud_colour = colour;
+    if (text.IsEmpty()) { m_status_hud->Hide(); return; }
+    m_status_hud_label->SetForegroundColour(colour);
+    apply_status_label();
+    place_status_hud();
+}
+
+// SetLabel + Wrap + Fit, in that order and always together. Moving the status out of the panel
+// removed the clipping of 8cc but not the underlying problem: the chip is a top-level
+// popup that Fit()s to its text, so a long sentence simply grew past the right edge of the canvas
+// and hung over the window. Wrapping to the room actually available is what makes the earlier
+// promise — "a sentence can be a sentence" — true at every window width, including the charter's
+// 1366 reach. Wrap() rewrites the label it is given, so it must follow a fresh SetLabel every
+// time; that is the whole reason this is one function instead of three call sites.
+void DesignCanvas::apply_status_label()
+{
+    if (!m_status_hud || !m_status_hud_label || !m_canvas_widget) return;
+    m_status_hud_label->SetLabel(m_status_hud_last);
+    const int avail = m_canvas_widget->GetClientSize().GetWidth()
+                      - m_canvas_widget->FromDIP(kStatusHudLeftInsetDip)
+                      - m_canvas_widget->FromDIP(24);
+    if (avail > m_canvas_widget->FromDIP(120))   // a uselessly narrow canvas: leave it unwrapped
+        m_status_hud_label->Wrap(avail);
+    m_status_hud->Fit();
+}
+
+void DesignCanvas::place_status_hud()
+{
+    if (!m_status_hud || !m_canvas_widget || m_status_hud_last.IsEmpty()) return;
+    // The canvas has a client size even while its page is hidden, and it is not the size the
+    // page will have when shown — anchoring against it put the chip up on the tab bar, where it
+    // then stayed until the next status change moved it. Nothing to anchor to: stay down.
+    if (!m_canvas_widget->IsShownOnScreen()) { m_status_hud->Hide(); return; }
+    const wxSize cs = m_canvas_widget->GetClientSize();
+    // Re-wrap first: this also runs on resize, and a chip wrapped for the old width either
+    // overhangs a narrowed canvas or wastes a widened one.
+    apply_status_label();
+    const wxSize hs = m_status_hud->GetSize();
+    const int kLeftInset = m_canvas_widget->FromDIP(kStatusHudLeftInsetDip);
+    const wxPoint bl = m_canvas_widget->ClientToScreen(
+        wxPoint(kLeftInset, cs.GetHeight() - hs.GetHeight() - 12));
+    // No Raise() and no focus juggling: a popup neither takes focus nor falls behind. This was
+    // caught with ORCA_CAD_KEYTRACE — shift+S logged a line, the following R logged nothing, and
+    // the only thing between them was the first status update showing this window.
+    if (!m_status_hud->IsShown()) m_status_hud->Show();   // Show before Move (GTK ignores pre-map Move)
+    m_status_hud->Move(bl);
+}
+
+void DesignCanvas::on_frame_iconize(wxIconizeEvent& e)
+{
+    show_status_hud(!e.IsIconized());
+    show_readout_hud(!e.IsIconized());
+    e.Skip();
+}
+
+void DesignCanvas::on_frame_activate(wxActivateEvent& e)
+{
+    show_status_hud(e.GetActive());
+    show_readout_hud(e.GetActive());
+    e.Skip();
+}
+
+// wxEvent& so one handler serves both events that invalidate the anchor: the frame moving out
+// from under the chip, and the canvas resizing under it.
+void DesignCanvas::on_status_hud_reanchor(wxEvent& e)
+{
+    place_status_hud();
+    e.Skip();
+}
+
+void DesignCanvas::show_status_hud(bool on)
+{
+    if (!m_status_hud) return;
+    if (on) place_status_hud();      // re-anchors first: the page may have been resized while away
+    else    m_status_hud->Hide();
+}
+
+void DesignCanvas::set_body_highlight(bool on)
+{
+    if (m_body_selected == on) return;
+    m_body_selected = on;
+    reload(true);   // recolours the body volume (selected = cyan tint)
+}
+
+void DesignCanvas::set_operand_bodies(int target_body, int tool_body)
+{
+    if (m_hl_body_target == target_body && m_hl_body_tool == tool_body) return;
+    m_hl_body_target = target_body;
+    m_hl_body_tool   = tool_body;
+    reload(true);      // recolours the body volumes (same idiom set_body_highlight uses)
+}
+
+void DesignCanvas::set_highlight_sketches(std::vector<std::pair<int, ColorRGBA>> hl)
+{
+    m_sketch_tool.set_highlight_sketches(std::move(hl));
+    request_repaint();
+}
+
+void DesignCanvas::set_body_translucent(bool on)
+{
+    if (m_body_translucent == on) return;
+    m_body_translucent = on;
+    reload(true);   // re-applies object-0 alpha so the solid fades for the fillet preview
+}
+
+void DesignCanvas::set_xray_focus(int body)
+{
+    if (m_xray_focus == body) return;
+    m_xray_focus = body;
+    m_sketch_tool.set_pick_only_body(body);
+    reload(true);   // re-applies per-body alpha so the non-focused bodies fade
+}
+
+void DesignCanvas::set_body_hidden(bool on)
+{
+    if (m_body_hidden == on) return;
+    m_body_hidden = on;
+    reload(true);   // hides/show base bodies + flips the ghost opaque/faint for preview-only mode
+}
+
+void DesignCanvas::delete_selected_sketch_entities()
+{
+    m_sketch_tool.delete_selected();
+    request_repaint();
+}
+
+bool DesignCanvas::inline_busy() const
+{
+    // Two sources, still: the TOOL's flag says a value is pending, the editor says a field is
+    // drawn. They agree now that the field is not a window — the orphan state (logically closed,
+    // still on screen, still eating keys) cannot be represented when there is nothing to leave
+    // mapped — but the union costs nothing and is the honest question to ask.
+    return m_sketch_tool.inline_busy()
+           || (m_inline_editor && m_inline_editor->is_open());
+}
+
+bool DesignCanvas::inline_has_focus() const
+{
+    return m_inline_editor && m_inline_editor->has_focus();
+}
+
+void DesignCanvas::inline_commit()
+{
+    if (m_inline_editor) m_inline_editor->commit();
+}
+
+void DesignCanvas::inline_cancel()
+{
+    if (m_inline_editor) m_inline_editor->cancel();
+}
+
+void DesignCanvas::request_sketch_exit()
+{
+    m_sketch_tool.request_exit();
+    request_repaint();
+}
+
+bool DesignCanvas::live_sketch_has_work() const
+{
+    return m_sketch_tool.live_sketch_has_work();
+}
+
+bool DesignCanvas::undo_last_sketch_entity()
+{
+    const bool did = m_sketch_tool.undo_last_entity();
+    if (did) request_repaint();
+    return did;
+}
+
+bool DesignCanvas::delete_selected_or_last_sketch_entity()
+{
+    const bool did = m_sketch_tool.delete_selected_or_last();
+    if (did) request_repaint();
+    return did;
+}
+
+void DesignCanvas::clear_sketch_selection()
+{
+    m_sketch_tool.clear_selection();
+    request_repaint();
+}
+
+DesignSketchTool::DimType DesignCanvas::sketch_dimension_kind() const
+{
+    return m_sketch_tool.dimension_kind();
+}
+
+double DesignCanvas::sketch_dimension_current() const
+{
+    return m_sketch_tool.dimension_current();
+}
+
+void DesignCanvas::apply_sketch_dimension(double v)
+{
+    m_sketch_tool.apply_dimension(v);
+    request_repaint();
+}
+
+void DesignCanvas::open_inline_value(double current, std::function<void(double)> commit,
+                                     std::function<void()> cancel)
+{
+    if (!m_inline_editor || !m_canvas_widget) { if (cancel) cancel(); return; }
+    // Host-driven value entry (committed-feature Constrain path): the trigger is a toolbar
+    // button. Anchor the field OVER the picked geometry (same as the draw-then-edit tools) when
+    // the tool can project it; else fall back to the middle of the canvas, where the sketch is
+    // in view. Everything here is canvas DEVICE px, the space the field is drawn in.
+    const wxSize  cs = m_canvas_widget->GetClientSize();
+    const double  sf = m_canvas_widget->GetContentScaleFactor();
+    wxPoint anchor(int(cs.GetWidth() * sf) / 2, int(cs.GetHeight() * sf) / 2);
+    m_sketch_tool.constrain_value_anchor(anchor);          // device px in the canvas viewport
+    m_sketch_tool.set_inline_busy(true);
+    m_canvas_widget->SetFocus();   // same reason as the draw-then-edit path: ImGui reads the
+                                   // canvas's key events, so the canvas must be the focused widget
+
+    m_inline_editor->open(anchor, current, "",
+        [this, commit](double v) {
+            m_sketch_tool.set_inline_busy(false);
+            if (commit) commit(v);
+            request_repaint();
+        },
+        [this, cancel]() {
+            m_sketch_tool.set_inline_busy(false);
+            if (cancel) cancel();
+            request_repaint();
+        });
+}
+
+void DesignCanvas::set_on_dimension_pick_complete(std::function<void(double)> cb)
+{
+    m_sketch_tool.on_dimension_pick_complete = std::move(cb);
+}
+
+DesignSketchTool::DimType DesignCanvas::pending_dimension_type() const
+{
+    return m_sketch_tool.pending_dimension_type();
+}
+
+void DesignCanvas::set_sketch_dimension_value(double v)
+{
+    m_sketch_tool.set_dimension_value(v);
+    request_repaint();
+}
+
+void DesignCanvas::cancel_sketch_dimension()
+{
+    m_sketch_tool.cancel_dimension_value();
+    request_repaint();
+}
+
+void DesignCanvas::begin_constrain(const SketchProfile& prof, const SketchPlane& plane)
+{
+    m_sketch_tool.begin_constrain(prof, plane);
+    // The overlay must appear immediately (no mouse move to trigger a repaint).
+    request_repaint();
+}
+
+void DesignCanvas::begin_imported_transform(
+        int feat, const std::vector<std::vector<std::vector<Vec2d>>>& base_regions,
+        const SketchPlane& plane, const Vec2d& offset, double scale_x, double scale_y)
+{
+    m_sketch_tool.begin_imported_transform(feat, base_regions, plane, offset, scale_x, scale_y);
+    request_repaint();
+}
+
+void DesignCanvas::set_on_imported_transform(std::function<void(int, Vec2d, double, double)> cb)
+{
+    m_sketch_tool.on_imported_transform = std::move(cb);
+}
+
+void DesignCanvas::end_constrain()
+{
+    // cancel() clears m_active + the picked-segment/entity indices, so the
+    // constrain overlay (highlighted picks) disappears on the next render.
+    m_sketch_tool.cancel();
+    request_repaint();
+}
+
+bool DesignCanvas::is_constraining() const { return m_sketch_tool.is_constraining(); }
+
+bool DesignCanvas::selected_segment(int& a, int& b) const
+{
+    return m_sketch_tool.selected_segment(a, b);
+}
+
+void DesignCanvas::update_constrain_profile(const std::vector<Vec2d>& pts)
+{
+    m_sketch_tool.set_profile_points(pts);
+    request_repaint();
+}
+
+void DesignCanvas::begin_constrain_entities(const std::vector<SketchEntity>& ents,
+                                            const SketchPlane& plane)
+{
+    m_sketch_tool.begin_constrain_entities(ents, plane);
+    request_repaint();
+}
+
+bool DesignCanvas::is_constraining_entities() const
+{
+    return m_sketch_tool.is_constraining_entities();
+}
+
+int DesignCanvas::sketch_selection_count() const
+{
+    return int(m_sketch_tool.selection().size());
+}
+
+bool DesignCanvas::view_normal_to_sketch()
+{
+    if (m_canvas == nullptr) return false;
+    const SketchPlane& pl = m_sketch_tool.plane();
+    Camera& cam = wxGetApp().plater()->get_camera();
+    // Keep the distance: this is an orientation change, not a zoom. The plane's own y axis is
+    // the up vector, so "up" on screen is up in sketch coordinates — which is what makes a
+    // dimension typed after pressing N land where the eye expects it.
+    const double dist = cam.get_distance();
+    cam.look_at(pl.origin + pl.normal * dist, pl.origin, pl.y_axis);
+    request_repaint();
+    return true;
+}
+
+bool DesignCanvas::sketch_abort_gesture()
+{
+    if (!m_sketch_tool.abort_gesture()) return false;
+    request_repaint();     // the rubber band is gone; the canvas must stop drawing it
+    return true;
+}
+
+bool DesignCanvas::sketch_disarm_tool()
+{
+    if (!m_sketch_tool.disarm_tool()) return false;
+    request_repaint();
+    return true;
+}
+
+bool DesignCanvas::drawing_in_progress() const
+{
+    return m_sketch_tool.pending_points() > 0;
+}
+
+bool DesignCanvas::has_any_selection() const
+{
+    return m_sketch_tool.has_solid_selection() || m_sketch_tool.sketch_has_selection();
+}
+
+bool DesignCanvas::clear_any_selection()
+{
+    if (!has_any_selection()) return false;
+    // Both, unconditionally: which of the two is live depends on the mode, and Esc at idle means
+    // "nothing is picked" in either of them. clear_selection() reports through the tool's own
+    // on_selection_changed; the solid side has no such notification, so the panel refreshes what
+    // depends on it (see DesignPanel::escape).
+    m_sketch_tool.clear_selection();
+    m_sketch_tool.clear_solid_selection();
+    // clear_solid_selection() is silent by design (recomputes call it while ids are invalid), but
+    // the panel mirrors the pick to aim Extrude and the dress-up tools. An Esc that cleared the
+    // highlight without telling the panel would leave those aimed at a body nothing points to.
+    if (m_sketch_tool.on_solid_selection_changed)
+        m_sketch_tool.on_solid_selection_changed(0, -1, -1, -1);
+    request_repaint();
+    return true;
+}
+
+bool DesignCanvas::sketch_first_selected_type(SketchEntity::Type& out) const
+{
+    return m_sketch_tool.first_selected_type(out);
+}
+
+const std::vector<int>& DesignCanvas::sketch_selection() const
+{
+    return m_sketch_tool.selection();
+}
+
+const std::vector<SketchEntity>& DesignCanvas::sketch_entities() const
+{
+    return m_sketch_tool.entities();
+}
+
+int DesignCanvas::sketch_constraint_count() const
+{
+    return int(m_sketch_tool.constraints().size());
+}
+
+const std::vector<SketchEntityConstraintDef>& DesignCanvas::sketch_constraints() const
+{
+    return m_sketch_tool.constraints();
+}
+
+bool DesignCanvas::remove_sketch_constraint(int idx)
+{
+    const bool removed = m_sketch_tool.remove_constraint(idx);
+    if (removed) request_repaint();
+    return removed;
+}
+
+void DesignCanvas::set_on_sketch_constraints_changed(std::function<void()> cb)
+{
+    m_sketch_tool.on_constraints_changed = std::move(cb);
+}
+
+bool DesignCanvas::try_add_sketch_constraints(const std::vector<SketchEntityConstraintDef>& defs)
+{
+    return m_sketch_tool.try_add_constraints(defs);
+}
+
+bool DesignCanvas::selected_constrain_entities(int& e0, int& e1) const
+{
+    return m_sketch_tool.selected_constrain_entities(e0, e1);
+}
+
+int DesignCanvas::selected_constrain_axis() const
+{
+    return m_sketch_tool.pick2();
+}
+
+bool DesignCanvas::pick0_point(Vec2d& out) const
+{
+    return m_sketch_tool.pick0_point(out);
+}
+
+void DesignCanvas::update_constrain_entities(const std::vector<SketchEntity>& ents)
+{
+    m_sketch_tool.set_constrain_entities(ents);
+    request_repaint();
+}
+
+void DesignCanvas::set_constraint_highlight(std::vector<int> entities)
+{
+    m_sketch_tool.set_constraint_highlight(std::move(entities));
+    request_repaint();
+}
+
+void DesignCanvas::set_constraint_glyphs(std::vector<SketchEntityConstraintDef> cons)
+{
+    m_sketch_tool.set_constraint_glyphs(std::move(cons));
+    request_repaint();
+}
+
+}} // namespace Slic3r::GUI
diff --git a/src/slic3r/GUI/CAD/DesignCanvas.hpp b/src/slic3r/GUI/CAD/DesignCanvas.hpp
new file mode 100644
index 0000000000..fab2e556e3
--- /dev/null
+++ b/src/slic3r/GUI/CAD/DesignCanvas.hpp
@@ -0,0 +1,436 @@
+#ifndef slic3r_DesignCanvas_hpp_
+#define slic3r_DesignCanvas_hpp_
+
+#include <wx/panel.h>
+#include <wx/popupwin.h>
+
+#include <functional>
+#include <memory>
+#include <string>
+
+#include "slic3r/GUI/3DBed.hpp"
+#include "slic3r/GUI/Camera.hpp"
+#include "libslic3r/Model.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
+#include "slic3r/GUI/CAD/DesignSketchTool.hpp"
+
+class wxGLCanvas;
+class wxFrame;
+class wxStaticText;
+
+namespace Slic3r {
+
+class TriangleMesh;
+
+namespace GUI {
+
+class GLCanvas3D;
+class SketchInlineEditor;
+
+class DesignCanvas : public wxPanel
+{
+public:
+    explicit DesignCanvas(wxWindow* parent);
+    ~DesignCanvas() override;
+
+    void set_mesh(const TriangleMesh& mesh);
+    // Multi-body display: one GLVolume per body, each coloured distinctly (per-body colour).
+    // `visible` (optional, indexed by body) hides bodies whose flag is false.
+    void set_bodies(const std::vector<TriangleMesh>& body_meshes,
+                    const std::vector<bool>& visible = {});
+    void clear_mesh();
+
+    void set_preview_mesh(const TriangleMesh& mesh);
+    void clear_preview();
+
+    void fit_view();
+    void set_view(const std::string& view_name);
+
+    void begin_sketch(const SketchPlane& plane, DesignSketchTool::Mode mode);
+    // Re-open a committed entity sketch for full in-canvas editing (load geometry +
+    // constraints, re-detect feature groups). Re-commits via finish_sketch().
+    void edit_sketch(const std::vector<SketchEntity>& entities,
+                     const std::vector<SketchEntityConstraintDef>& constraints,
+                     const SketchPlane& plane);
+    void set_sketch_tool(DesignSketchTool::Mode mode);
+    void set_sketch_plane(const SketchPlane& plane);   // re-plane the live sketch when a reference plane is clicked in 3D
+    void set_sketch_construction(bool c);
+    // Flip the sketch selection between construction and real geometry; returns the
+    // number of entities changed (0 = nothing selected, caller falls back to the mode).
+    // Open the in-canvas value field on the sketch selection's defining number.
+    bool edit_sketch_selection_value();
+    int  toggle_sketch_construction_selection();
+    // Is the sketch tool on Select (as opposed to a draw/edit tool being armed)? The
+    // Construction box needs it to tell "convert what I picked" from "arm what I draw next".
+    bool sketch_is_selecting() const { return m_sketch_tool.mode() == DesignSketchTool::Mode::Select; }
+    // Text / SVG art into the LIVE sketch, as ordinary editable lines. False = no session.
+    bool add_sketch_regions(const std::vector<std::vector<std::vector<Vec2d>>>& regions);
+    void set_sketch_polygon_sides(int n);
+    void set_sketch_polygon_circumscribed(bool c);
+    void finish_sketch();
+    bool is_sketching() const;
+    void refresh_bed();   // re-sync the bed to the current printer (call on tab activation)
+    // The Camera is Plater-owned and shared with Prepare/Preview/Assemble; GLCanvas3D has no
+    // per-canvas camera, so every orbit here would otherwise overwrite what the editor tabs
+    // show. Exactly one of the two views is live at a time, so entering and leaving are the
+    // same operation: trade the live camera for the parked one. That also keeps this canvas's
+    // own view across a tab switch.
+    void enter_viewport();
+    void leave_viewport();
+    void unbind_canvas_event_handlers();   // app close / language switch, from the plater's teardown
+    void reset_canvas_volumes();
+    void set_show_bed(bool b);   // view option: draw the printer bed + plate grid, or not
+    // N: look straight down the sketch plane's normal, keeping the current zoom. A sketch drawn
+    // at an angle is a sketch drawn wrong, and no amount of orbiting by hand lands exactly square.
+    bool view_normal_to_sketch();
+    void cancel_sketch();
+    void set_on_sketch_commit(std::function<void(const SketchProfile&, const SketchPlane&)> cb);
+    void set_on_sketch_entities_commit(
+        std::function<void(const std::vector<SketchEntity>&,
+                           const std::vector<SketchEntityConstraintDef>&,
+                           const SketchPlane&)> cb);
+
+    // Line tool: pending-segment length entry + live readout (Phase 2).
+    void set_on_segment_drawn(std::function<void(double, double)> cb);
+    void set_on_cursor_metrics(std::function<void(double, double, bool)> cb);
+    void set_on_solve_state(std::function<void(int, bool, bool)> cb);  // dof, ok, has_constraints
+    // Live per-step guidance from the armed sketch tool (mode, step, picks). 1c0c.
+    void set_on_sketch_step(std::function<void(DesignSketchTool::Mode, int, int)> cb);
+    void apply_segment_length(double len);  // exact length, then commit & repaint
+    void keep_segment_as_drawn();           // commit as-drawn & repaint
+
+    // Sketch selection (Mode::Select).
+    void set_on_sketch_selection_changed(std::function<void(int)> cb);
+    void set_on_sketch_face_selected(std::function<void(int)> cb);  // closed loop clicked: region index passed
+    void set_on_display_sketch_selected(std::function<void(int, int, int)> cb);  // committed loop clicked: (feature, region, entity)
+    void set_on_display_sketch_activated(std::function<void(int)> cb);      // committed sketch DOUBLE-clicked: edit it
+    std::vector<SketchEntity> selected_loop_entities() const;  // entities of the click-selected loop
+    std::vector<std::vector<int>> region_entity_indices(const std::vector<SketchEntity>& ents) const;
+    // Like region_entity_indices, but each region's entry is its OWN entities followed by the
+    // entities of each of its holes — the same order selected_loop_entities() hands the kernel.
+    // A per-loop extrude of a region WITH holes stores exactly this, so this is the shape a
+    // consumed loop must be compared against.
+    std::vector<std::vector<int>> region_entity_indices_with_holes(const std::vector<SketchEntity>& ents) const;
+    void clear_loop_pick();  // drop the click-selected loop highlight (e.g. after extrude)
+    void set_loop_pick(int feature, int region);  // adopt a loop pick made before the commit
+    void set_escalate_on_repick(bool on);         // off while a card has armed a face/edge pick
+    // Solid whole/face/edge selection: point the tool at the bodies + concatenated
+    // tessellation (with per-triangle face & body ids), and a callback fired on each
+    // whole->face->edge cycle (level, body index, face id, edge id).
+    void set_solid_pick(const std::vector<CadBody>* bodies, const TriangleMesh* mesh,
+                        const std::vector<int>* tri_face, const std::vector<int>* tri_body,
+                        const std::vector<bool>* visible = nullptr,
+                        const std::vector<Transform3d>* xform = nullptr);
+    void set_on_solid_selection_changed(std::function<void(int, int, int, int)> cb);
+    void set_on_place_on_face(std::function<bool()> cb);   // F key: Place on Face
+    void select_body(int body);   // Parts-list -> highlight a whole body by index
+    // Effective display colour of a body: the per-body override (Color tool) when set,
+    // otherwise the auto body-index palette. Single source of truth shared with reload().
+    ColorRGBA body_color(int body) const;
+    // Move-body gizmo (M5): three world-axis drag arrows on a body; drag fires the move
+    // callback with the body index + accumulated translation (display-only, host applies it).
+    // body_radius = bounding-sphere radius of the body in world mm; the gizmo scales with it so
+    // the rotation rings sit OUTSIDE the solid (Orca's Prepare gizmos do the same).
+    void begin_move_body(int body, const Vec3d& pivot, const Transform3d& base_xform,
+                         double body_radius);
+    void clear_move_gizmo();
+    bool moving_body() const;
+    void set_on_body_move_changed(std::function<void(int, const Transform3d&)> cb);
+    // Visual Fillet/Chamfer radius gizmo: when a solid edge is picked, anchor a radius arrow on
+    // it; drag/edit fire the radius callback. Returns false if no edge is currently picked.
+    bool begin_fillet_gizmo(const Vec3d& body_centroid, double radius);
+    void clear_fillet_gizmo();
+    bool filleting() const;
+    void set_on_fillet_radius_changed(std::function<void(double)> cb);
+    // Visual Hole gizmo: the panel feeds the hole plane + position + diameter/depth/through while
+    // its Hole card is open; drag/edit fire the hole callback (x, y, diameter, depth).
+    void begin_hole_gizmo(const SketchPlane& plane, double x, double y,
+                          double diameter, double depth, bool through);
+    void set_hole_face_bounds(bool has, double umin, double umax, double vmin, double vmax);
+    void clear_hole_gizmo();
+    bool holing() const;
+    void set_on_hole_changed(std::function<void(double, double, double, double)> cb);
+    // Visual Thread gizmo: footprint circle + radius/length arrows + draggable centre.
+    void begin_thread_gizmo(const SketchPlane& plane, double x, double y,
+                            double radius, double height);
+    void clear_thread_gizmo();
+    bool threading() const;
+    void set_on_thread_changed(std::function<void(double, double, double, double)> cb);
+    // Visual Shell gizmo: inward thickness arrow at the picked open-face centroid.
+    void begin_shell_gizmo(const Vec3d& face_centroid, const Vec3d& inward_dir, double thickness);
+    void clear_shell_gizmo();
+    bool shelling() const;
+    void set_on_shell_thickness_changed(std::function<void(double)> cb);
+    // Visual Revolve angle-arc gizmo: the panel feeds the sketch plane + profile centroid + axis
+    // (0=plane X, 1=plane Y) + angle + flip while its Revolve card is open; drag/edit fire the
+    // angle callback.
+    void begin_revolve_gizmo(const SketchPlane& plane, const Vec2d& centroid,
+                             int axis_sel, double angle, bool flip);
+    void clear_revolve_gizmo();
+    bool revolving() const;
+    void set_on_revolve_angle_changed(std::function<void(double)> cb);
+    // Visual Draft angle-arc gizmo: the panel feeds the face centroid + face normal + angle while
+    // its Draft card is open; drag/edit fire the angle callback.
+    void set_draft_gizmo(const Vec3d& face_centroid, const Vec3d& face_normal, double angle);
+    void clear_draft_gizmo();
+    bool drafting() const;
+    void set_on_draft_angle_changed(std::function<void(double)> cb);
+    // Visual Cut gizmo: plane-rectangle preview + draggable normal offset arrow while
+    // the Cut card is open; drag fires the offset callback.
+    void set_cut_gizmo(const SketchPlane& plane, double offset, const Vec3d& body_center, double half_extent);
+    void clear_cut_gizmo();
+    bool cutting() const;
+    void set_on_cut_offset_changed(std::function<void(double)> cb);
+    // Visual Pattern gizmo: the panel feeds the (world XY) plane + target body centroid + mode +
+    // count/dir/spacing/angle while its Pattern card is open; drag/edit fire the value callback.
+    void begin_pattern_gizmo(const SketchPlane& plane, const Vec3d& body_centroid, bool circular,
+                             int count, int dir, double spacing, double angle);
+    void clear_pattern_gizmo();
+    bool patterning() const;
+    void set_on_pattern_changed(std::function<void(double)> cb);
+    // Visual Extrude depth-arrow gizmo (C5b): the panel feeds the profile plane + centroid +
+    // live depths/flags while its Extrude card is open; drag/edit fire the depth callback.
+    void set_extrude_gizmo(const SketchPlane& plane, const Vec2d& centroid,
+                           double depth, double depth2, bool two_sided, bool flip);
+    void clear_extrude_gizmo();
+    void set_on_extrude_depth_changed(std::function<void(double, bool)> cb);
+    void set_datum_gizmo(const SketchPlane& plane, double usize, double vsize,
+                         const Vec3d& base_origin, const Vec3d& base_normal,
+                         double offset, bool offset_on);          // C3 resize handles + offset arrow
+    void clear_datum_gizmo();
+    void set_on_datum_size_changed(std::function<void(double, double)> cb);
+    void set_on_datum_offset_changed(std::function<void(double)> cb);
+    void set_helix_gizmo(const SketchPlane& plane, double radius, double pitch, double height,
+                         double taper, bool left_handed);          // helix curve + 3 drag handles
+    void clear_helix_gizmo();
+    void set_on_helix_changed(std::function<void(double, double, double)> cb);
+    void set_rib_gizmo(const SketchPlane& plane, const Vec2d& p0, const Vec2d& p1, double thickness);  // rib slab footprint + 2 thickness handles
+    void clear_rib_gizmo();
+    void set_on_rib_thickness_changed(std::function<void(double)> cb);
+    void set_base_pick(std::vector<SketchPlane> planes, std::vector<int> bases,
+                       std::vector<std::string> labels = {});   // clickable labelled reference planes
+    void clear_base_pick();
+    void set_on_datum_base_picked(std::function<void(int)> cb);
+    void set_on_sketch_exit(std::function<void()> cb);           // Esc -> exit the tool
+    void set_on_sketch_exit_refused(std::function<void()> cb);   // Esc declined: sketch has work
+    void set_on_undo_redo(std::function<void(bool /*redo*/)> cb); // Ctrl+Z / Ctrl+Shift+Z
+    // Persistently draw committed sketches (un-consumed ones stay visible).
+    void set_display_sketches(std::vector<DesignSketchTool::DisplaySketch> ds);
+    void set_highlight_sketches(std::vector<std::pair<int, ColorRGBA>> hl);
+    void set_datum_planes(std::vector<SketchPlane> planes,
+                           std::vector<Vec2d> sizes = {});     // draw datum/reference planes (u/v extents)
+    // Mate connectors, drawn as frames so their verse and polarity are visible (wgsc).
+    void set_mate_connectors(std::vector<DesignSketchTool::MateConnectorGlyph> g);
+    void set_mate_links(std::vector<std::pair<Vec3d, Vec3d>> l);
+    void set_body_highlight(bool on);   // tint the solid when its feature is tree-selected
+    // The status line, shown along the BASE OF THE VIEWPORT rather than in the side panel:
+    // the panel clips it at ~73 characters with no warning (8cc), the viewport's
+    // bottom margin has the whole window width to spare. Empty text hides it.
+    void set_status_text(const wxString& text, const wxColour& colour);
+    // Take the status line down / bring it back when the Design page leaves and re-enters view.
+    // A popup is a TOP-LEVEL window: hiding the page it belongs to does not hide it. Keeps the
+    // text, so coming back needs no re-selection.
+    void show_status_hud(bool on);
+    void set_operand_bodies(int target_body, int tool_body);  // -1,-1 clears
+    void set_body_translucent(bool on); // render the solid see-through (fillet/chamfer preview)
+    void set_xray_focus(int body);      // >=0: fade+lock out every other body (CoordSys picking)
+    void set_body_hidden(bool on);      // preview-only: hide base bodies, show only the result ghost
+    void set_on_move_exit(std::function<void()> cb);   // right-click finished the move-body gizmo
+    // Right-click (or its platform equivalent) on the viewport with no tool running: open the
+    // object-driven offer there. Fires with SCREEN coordinates. Deliberately NOT fired while a
+    // tool is live — right-click already ends a polyline chain and finishes the move gizmo, and
+    // taking those over would break two working interactions in order to add a third.
+    void set_on_context_menu(std::function<void(const wxPoint&)> cb);
+    void delete_selected_sketch_entities();
+    bool inline_busy() const;                         // a sketch value field is open (guard keys)
+    bool inline_has_focus() const;                    // the field itself holds keyboard focus
+    void inline_commit();                             // accept the typed value (Enter/Tab)
+    void inline_cancel();                             // discard the typed value (Esc)
+    // The layered Esc: abandon the points of the gesture in progress, else drop the armed tool
+    // back to Select, else leave the sketch. Same call GLCanvas3D::on_char makes, exposed so the
+    // panel can do it when focus is not on the canvas.
+    void request_sketch_exit();
+    bool live_sketch_has_work() const;                // the live sketch holds entities a cancel would destroy
+    bool undo_last_sketch_entity();                   // Ctrl+Z in a sketch: drop the last entity
+    bool delete_selected_or_last_sketch_entity();     // Delete in a sketch: selected, else last
+    void clear_sketch_selection();
+
+    // View toggles (keys P / A): origin planes, world axis triad. Each returns the new on/off
+    // state so the caller can echo it in the status bar.
+    bool toggle_planes();
+    bool toggle_axes();
+
+    // Section views (non-destructive): the panel owns the named "Section View N" list; the canvas
+    // just applies/clears one horizontal clip at a time. model_mid_z() is the default cut height.
+    void   set_section_plane(bool on, double z, bool keep_upper = false);
+    double model_mid_z() const;
+
+    // Dimension tool: act on the current sketch selection.
+    DesignSketchTool::DimType sketch_dimension_kind() const;
+    double sketch_dimension_current() const;
+    void   apply_sketch_dimension(double v);
+
+    // Open the in-canvas value editor at the cursor for a host-driven value (the
+    // committed-feature Constrain path uses this instead of a docked numeric card).
+    void   open_inline_value(double current, std::function<void(double)> commit,
+                             std::function<void()> cancel = {});
+
+    // Dimension tool (Mode::Dimension): click-to-place quotes. The pick-complete
+    // callback lets the panel pop the value card; set/cancel apply or keep the value.
+    void set_on_dimension_pick_complete(std::function<void(double)> cb);
+    DesignSketchTool::DimType pending_dimension_type() const;
+    void set_sketch_dimension_value(double v);
+    void cancel_sketch_dimension();
+
+    // Constrain mode: load a committed profile for picking + constraint editing.
+    void begin_constrain(const SketchProfile& prof, const SketchPlane& plane);
+    // Leave constrain mode and clear any picked-entity highlight from the overlay.
+    void end_constrain();
+    bool is_constraining() const;
+    bool selected_segment(int& a, int& b) const;
+    void update_constrain_profile(const std::vector<Vec2d>& pts);
+
+    // Entity-aware Constrain (Fase 4.2): pick Line entities of a committed sketch.
+    void begin_constrain_entities(const std::vector<SketchEntity>& ents, const SketchPlane& plane);
+    bool is_constraining_entities() const;
+    // Sketch selection, for the offer menu: how many entities are selected and what the first
+    // one is. Returns 0 when nothing is selected.
+    int  sketch_selection_count() const;
+    // Esc routing (DesignInteraction.hpp). The panel decides WHICH level one press belongs to;
+    // these are the levels it can act on inside the canvas. Each returns whether it did anything,
+    // so the panel can fall through to the next level without asking twice.
+    bool sketch_abort_gesture();     // CadLevel::Gesture — drop the entity being drawn
+    bool sketch_disarm_tool();       // CadLevel::Tool    — armed sketch tool falls back to Select
+    bool drawing_in_progress() const;// an entity has clicks down but is not committed
+    bool has_any_selection() const;  // model pick or sketch pick
+    bool clear_any_selection();      // CadLevel::Idle — drop both; true if anything was dropped
+    bool sketch_first_selected_type(SketchEntity::Type& out) const;
+    // Live sketch session (Fase 4.2 live constraint path): the panel reads the in-session
+    // selection and entities, and commits a planned constraint through the tool's
+    // append->solve->keep-or-rollback, rather than reaching into mcp_sketch_tool().
+    const std::vector<int>&             sketch_selection() const;
+    const std::vector<SketchEntity>&    sketch_entities() const;
+    // How many constraints the LIVE session holds. Only a count: the hint line needs to know
+    // whether any badge is on screen to talk about, nothing more.
+    int                                 sketch_constraint_count() const;
+    const std::vector<SketchEntityConstraintDef>& sketch_constraints() const;
+    bool                                remove_sketch_constraint(int idx);
+    void set_on_sketch_constraints_changed(std::function<void()> cb);
+    bool try_add_sketch_constraints(const std::vector<SketchEntityConstraintDef>& defs);
+
+    // In-canvas bbox transform of imported Text/SVG art (replaces the Move/Scale dialog).
+    void begin_imported_transform(int feat,
+                                  const std::vector<std::vector<std::vector<Vec2d>>>& base_regions,
+                                  const SketchPlane& plane, const Vec2d& offset,
+                                  double scale_x, double scale_y);
+    void set_on_imported_transform(std::function<void(int, Vec2d, double, double)> cb);
+    bool selected_constrain_entities(int& e0, int& e1) const;
+    int  selected_constrain_axis() const;  // third pick slot (Symmetric axis), -1 if unset
+    bool pick0_point(Vec2d& out) const;   // plane-coords of the slot-0 pick (trim/extend)
+    void update_constrain_entities(const std::vector<SketchEntity>& ents);
+    // Constraint manager (C3.4): highlight the entities referenced by a selected
+    // constraint (yellow tint in Constrain mode); empty clears the highlight.
+    void set_constraint_highlight(std::vector<int> entities);
+    // Constraint glyph badges (C3.4b): the feature's constraints, drawn as iconic
+    // marks near their entities in Constrain mode; empty clears them.
+    void set_constraint_glyphs(std::vector<SketchEntityConstraintDef> cons);
+    // Repaint the embedded canvas the right way for the active GL backend:
+    // hardware GL gets a scheduled wxEVT_PAINT (render() runs inside the paint
+    // cycle); software GL (llvmpipe etc.) gets a direct render() because a
+    // scheduled Refresh() is frequently dropped there. Backend cached on first use.
+    // Public: DesignPanel calls it after a tree edit to force a frame on software GL.
+    // Scripted (MCP) access to the live sketch. One accessor rather than a passthrough per
+    // verb: the MCP layer drives the SAME tool the mouse drives, which is the whole point of
+    // having it — a socket that talked to a private copy would prove nothing about the app.
+    DesignSketchTool&       mcp_sketch_tool()       { return m_sketch_tool; }
+    const DesignSketchTool& mcp_sketch_tool() const { return m_sketch_tool; }
+
+    void request_repaint();
+    // Repaint synchronously, once the pending show/resize has settled. Needed when the
+    // notebook re-shows the Design page: an invalidation issued while the page is still
+    // being shown is dropped on hardware GL and no wxEVT_PAINT ever follows, leaving the
+    // canvas blank until another tab switch forces an expose.
+    void force_repaint();
+    // Repaint synchronously, for use while a modal popup (the offer menu) owns the event loop:
+    // a queued Refresh() is not serviced until the popup closes, so a hover ghost drawn behind it
+    // would never appear. Mirrors DesignPanel's m_status->Update() flush.
+    void repaint_now();
+
+private:
+    void reload(bool keep_view);
+    void swap_camera();   // enter_viewport / leave_viewport, in the one direction they share
+
+    wxGLCanvas* m_canvas_widget{nullptr};
+    GLCanvas3D* m_canvas{nullptr};
+    int         m_sw_gl{-1};   // -1 unknown, 0 hardware GL, 1 software GL
+
+    std::function<void(const wxPoint&)> m_on_context_menu;
+    bool        m_ctx_bound{false};   // bind the RIGHT_UP handler once, however often the cb is set
+    wxPoint     m_ctx_press{0, 0};    // right-press origin: a right-DRAG orbits, it must not offer
+    long long   m_ctx_press_ms{0};    // and a right-HOLD is navigation too, however still it is held
+
+    Bed3D       m_bed;
+    // The half of the camera swap above that is NOT on screen: the editor tabs' view while
+    // Design is up, this canvas's view while it is not. Seeded in the constructor so the first
+    // entry inherits the view the user was already looking at.
+    Camera      m_parked_camera;
+    bool        m_camera_swapped{false};   // guards a leave without an enter, and the reverse
+    Model       m_model;
+    bool        m_first_frame{true};
+    bool        m_body_selected{false};   // tree selected a body feature → tint the solid
+    int         m_hl_body_target{-1};
+    int         m_hl_body_tool{-1};
+    bool        m_body_translucent{false};// fillet/chamfer preview → render the body see-through
+    int         m_xray_focus{-1};          // >=0: only this body is opaque+clickable (CoordSys picking)
+    bool        m_body_hidden{false};     // preview-only mode → hide base bodies, ghost = the result
+    std::vector<bool> m_body_visible;     // per-body visibility (empty => all visible)
+    // Live pointer to the document's bodies (stable address: m_doc.bodies), stashed by
+    // set_solid_pick so reload()/body_color() can read each body's colour override.
+    const std::vector<CadBody>* m_color_bodies{nullptr};
+
+    DesignSketchTool m_sketch_tool;
+
+    // Section view: whether a horizontal clip is currently applied (guards Alt+Wheel). The cut
+    // height and the named-view list live in DesignPanel; the canvas is a dumb applier.
+    bool m_section_on{false};
+
+    std::unique_ptr<SketchInlineEditor> m_inline_editor;  // floating in-canvas value editor
+    // Bottom-right viewport HUD: a borderless float label over the GL canvas showing the
+    // active tool's current values (fed by the tool's on_readout). Empty text hides it.
+    // A wxPopupWindow for the SAME reason as the status chip below, and it was a wxFrame until
+    // the reason was measured rather than assumed: "it appears mid-gesture and the next input is
+    // the mouse" is false. The chip keeps the last value on screen AFTER the gesture ends, and a
+    // frame holds the X input focus once it has it — so the next keystroke went to a 119x31
+    // window that has no use for it. Measured on :10: focus on the chip, `r` produced no
+    // CHAR_HOOK line at all; one bare canvas click moved focus back and the same key armed the
+    // tool. That is every sketch shortcut dead after every dimensioned entity.
+    wxPopupWindow* m_hud{nullptr};
+    wxStaticText* m_hud_label{nullptr};
+    std::string   m_hud_last;
+    void set_readout(const std::string& text);
+    void place_readout_hud();            // anchor + show, using m_hud_last
+    void show_readout_hud(bool on);      // iconise/deactivate: a popup would float on the desktop
+
+    // Bottom-LEFT viewport HUD: the selection / tool status line, written by DesignPanel.
+    // A wxPopupWindow, NOT the wxFrame the readout HUD uses: a frame accepts keyboard focus,
+    // and this one is on screen permanently and re-raised on every status change, so it stole
+    // the keyboard from the canvas and killed every sketch shortcut in the tab.
+    wxPopupWindow* m_status_hud{nullptr};
+    wxStaticText* m_status_hud_label{nullptr};
+    wxString      m_status_hud_last;
+    wxColour      m_status_hud_colour;
+    void place_status_hud();          // re-anchors to the canvas corner (also on resize)
+    void apply_status_label();        // SetLabel + Wrap to the canvas width + Fit, always together
+    // On the top-level frame, which outlives this canvas — members so they can be unbound.
+    void on_frame_iconize(wxIconizeEvent& e);
+    void on_frame_activate(wxActivateEvent& e);
+    void on_status_hud_reanchor(wxEvent& e);   // frame wxEVT_MOVE and canvas wxEVT_SIZE
+    std::function<void(const SketchProfile&, const SketchPlane&)> m_on_sketch_commit;
+    std::function<void(const std::vector<SketchEntity>&,
+                       const std::vector<SketchEntityConstraintDef>&,
+                       const SketchPlane&)> m_on_sketch_entities_commit;
+};
+
+}} // namespace Slic3r::GUI
+
+#endif // slic3r_DesignCanvas_hpp_
diff --git a/src/slic3r/GUI/CAD/DesignInteraction.hpp b/src/slic3r/GUI/CAD/DesignInteraction.hpp
new file mode 100644
index 0000000000..d849b779e4
--- /dev/null
+++ b/src/slic3r/GUI/CAD/DesignInteraction.hpp
@@ -0,0 +1,59 @@
+#ifndef slic3r_GUI_DesignInteraction_hpp_
+#define slic3r_GUI_DesignInteraction_hpp_
+
+namespace Slic3r { namespace GUI {
+
+// The Design tab's interaction stack, and the ONE rule Esc obeys.
+//
+// Esc unwinds exactly one level per press, deepest first, and never more. The enum value IS
+// the LIFO depth, so "which level does this press belong to" is a comparison, not a chain of
+// special cases scattered over three files — which is what it was, and why two presses in a
+// row could reach past a tool and destroy the sketch underneath it.
+//
+// STRICT INVARIANT (the bug this exists to make unrepresentable): no level of Esc deletes a
+// feature, discards a sketch that holds geometry, or rolls history back. Destroying work needs
+// a gesture that says so — Delete/Backspace on an explicit selection, the banner's Cancel, or
+// Ctrl+Z. An Esc that can destroy is an Esc nobody can press with confidence, and being the
+// safe key is the whole point of it.
+enum class CadLevel : int {
+    Idle      = 0,   // nothing transient is up: Esc clears the selection
+    Tool      = 1,   // a feature card / armed sketch tool / constrain session: Esc exits it
+    Gesture   = 2,   // an uncommitted delta (entity being drawn, body being dragged): Esc reverts it
+    Transient = 3,   // a value field or a popup menu: Esc closes just that
+};
+
+// What the tab is doing, reduced to the four bits the routing actually needs. Kept as a POD of
+// answers rather than a pointer to the panel so the rule below is decidable — and checkable —
+// without a window, a GL context or an event loop.
+struct CadInteractionState {
+    bool value_field_open{false};   // in-canvas value field, or the panel's value card
+    bool gesture_active{false};     // in-progress entity points, or a body being moved
+    bool tool_armed{false};         // feature card open, sketch draw tool armed, constrain session
+    bool has_selection{false};      // something is picked (model or sketch)
+};
+
+// The whole routing rule. Deepest live level wins; Idle is the floor.
+constexpr CadLevel cad_escape_level(const CadInteractionState& s)
+{
+    if (s.value_field_open) return CadLevel::Transient;
+    if (s.gesture_active)   return CadLevel::Gesture;
+    if (s.tool_armed)       return CadLevel::Tool;
+    return CadLevel::Idle;
+}
+
+// The ordering is the entire contract, so it is checked where it is defined, at compile time.
+static_assert(cad_escape_level({true, true, true, true})     == CadLevel::Transient, "value field is deepest");
+static_assert(cad_escape_level({false, true, true, true})    == CadLevel::Gesture,   "gesture beats tool");
+static_assert(cad_escape_level({false, false, true, true})   == CadLevel::Tool,      "tool beats idle");
+static_assert(cad_escape_level({false, false, false, true})  == CadLevel::Idle,      "selection is idle-level");
+static_assert(cad_escape_level({false, false, false, false}) == CadLevel::Idle,      "empty is idle");
+
+// Right-click vs. right-hold-orbit. A press that stays put and is let go promptly is a click and
+// summons the offer; anything longer or further was navigation, and navigation must never be
+// rewarded with a menu over wherever the camera happened to stop.
+inline constexpr int kCadRightClickMs      = 200;   // press->release budget
+inline constexpr int kCadRightClickDriftPx = 3;     // cursor drift budget, max(|dx|,|dy|)
+
+}} // namespace Slic3r::GUI
+
+#endif // slic3r_GUI_DesignInteraction_hpp_
diff --git a/src/slic3r/GUI/CAD/DesignOffer.hpp b/src/slic3r/GUI/CAD/DesignOffer.hpp
new file mode 100644
index 0000000000..ad1998d5c5
--- /dev/null
+++ b/src/slic3r/GUI/CAD/DesignOffer.hpp
@@ -0,0 +1,189 @@
+// GENERATED FILE — DO NOT EDIT.
+// Source: docs/ux/tool_atlas.json   Generator: docs/ux/mockups/gen_offer_table.py
+//
+// The object-driven tool offer (charter 4.1): every verb has ONE row index, that index
+// is the same in every selection it appears in, and verbs that do not apply are shown
+// disabled in place with their reason rather than removed. Row order was ratified
+// 2026-07-31; changing an index is a breaking change to every user's muscle memory.
+#ifndef slic3r_GUI_DesignOffer_hpp_
+#define slic3r_GUI_DesignOffer_hpp_
+
+#include <cstdint>
+
+namespace Slic3r { namespace GUI {
+
+// What the viewport has selected. Ordered as in tool_atlas.json; the bitmask in
+// OfferVerb::accepts indexes these.
+enum class OfferSel : int {
+    None = 0,
+    FacePlanar = 1,
+    FaceCyl = 2,
+    FaceOther = 3,
+    EdgeStr = 4,
+    EdgeCirc = 5,
+    Vertex = 6,
+    BodySolid = 7,
+    BodySheet = 8,
+    Bodies2 = 9,
+    DatumPlane = 10,
+    DatumAxis = 11,
+    CoordSys = 12,
+    Art = 13,
+    SkLoop = 14,
+    SkNone = 15,
+    SkLine = 16,
+    SkArc = 17,
+    SkPoint = 18,
+    Sk2Ent = 19,
+    Count = 20
+};
+
+inline uint32_t offer_bit(OfferSel s) { return 1u << int(s); }
+
+// One row of the offer. `action` routes to the code that already implements the verb:
+//   "key:S+E"        -> m_keys_feature[SHIFT('E')]
+//   "key:L"          -> m_keys_sketch['L']
+//   "fly:material#4" -> row 4 of the "material" feature flyout
+//   "btn:delete"     -> a standalone toolbar button
+//   nullptr          -> kernel support exists, no GUI path yet (row shows disabled)
+struct OfferVerb {
+    const char* id;
+    const char* name;        // drawing-office word (L10); translated at use with wxGetTranslation
+    int         row;         // 0..7, the ratified index — NEVER reorder
+    const char* key;         // shortcut shown in the row, or nullptr
+    const char* action;
+    const char* refusal;     // why this row is greyed, in the product's own words
+    uint32_t    accepts;     // bitmask over OfferSel
+    int         need_bodies;
+    int         need_sketches;
+    bool        need_sheet;
+    bool        sketch_mode; // belongs to the sketch-mode vocabulary, not the model one
+    // Second level INSIDE a row, for tools that come in variants: "Rectangle" holds corner,
+    // centre, oblique and rounded. nullptr = sits directly in the row. Keeps the row's own
+    // address fixed (L4.1) while the variants hang one level below it, mirroring the toolbar's
+    // grouping instead of flattening 19 create tools into one wall.
+    const char* family;
+    const char* icon;         // resources/images name, or nullptr — the offer draws it beside the row
+    const char* hint;         // what the verb does / what to click; shown on hover
+};
+
+// Row labels, in ratified order.
+static const char* const kOfferRowNames[] = {
+    "Create",
+    "Add material",
+    "Remove",
+    "Fillet / chamfer / draft",
+    "Repeat",
+    "Transform",
+    "Reference",
+    "Modify",
+};
+static const int kOfferRowCount = 8;
+
+static const OfferVerb kOfferVerbs[] = {
+    {"sketch", "Sketch", 0, "Shift+S", "key:S+S", "Click a face or a reference plane in the viewport, then a sketch tool", 0x00000403u, 0, 0, false, false, nullptr, "design_sketch", "Click a face or a reference plane, then pick a drawing tool"},
+    {"extrude", "Extrude", 1, "Shift+E", "key:S+E", "Create a sketch, or pick a solid face, first", 0x00004002u, 0, 0, false, false, nullptr, "design_extrude", "Extrude a sketch profile, or push/pull a picked face"},
+    {"revolve", "Revolve", 1, "Shift+R", "key:S+R", "Create a sketch profile to revolve first", 0x00004000u, 0, 0, false, false, nullptr, "design_revolve", "Revolve a profile about an axis"},
+    {"sweep", "Sweep", 1, "Shift+W", "key:S+W", "Create a profile sketch to sweep first", 0x00004000u, 0, 2, false, false, nullptr, "design_sweep", "Sweep a profile along a path"},
+    {"loft", "Loft", 1, "Shift+L", "key:S+L", "Create at least two profile sketches to loft", 0x00004000u, 0, 2, false, false, nullptr, "design_loft", "Loft (skin) between two or more profiles"},
+    {"thicken", "Thicken", 1, nullptr, "fly:material#4", "Thicken needs a solid body — add or import one first", 0x0000000au, 1, 0, false, false, nullptr, "design_thicken", "Offset a solid face into a thin plate (new body)"},
+    {"rib", "Rib", 1, nullptr, "fly:material#5", "Rib needs a solid body — add or import one first", 0x00010000u, 1, 0, false, false, nullptr, "design_rib", "Grow a thin wall from an open sketch line, fused to a body"},
+    {"boolean", "Union", 1, "Shift+B", "btn:bool#0", "Boolean needs two bodies — create or import a second solid", 0x00000200u, 2, 0, false, false, nullptr, "design_boolean", "Fuse the tool body into the target — one solid, no seam"},
+    {"bool_subtract", "Subtract", 1, nullptr, "btn:bool#1", "Boolean needs two bodies — create or import a second solid", 0x00000200u, 2, 0, false, false, nullptr, "design_boolean", "Cut the tool body out of the target"},
+    {"bool_intersect", "Intersect", 1, nullptr, "btn:bool#2", "Boolean needs two bodies — create or import a second solid", 0x00000200u, 2, 0, false, false, nullptr, "design_boolean", "Keep only where the two bodies overlap"},
+    {"surf_extrude", "Surface Extrude", 1, "Shift+G", "key:S+G", "Create a sketch first", 0x00004000u, 0, 0, false, false, nullptr, "design_extrude", "Extrude a sketch into a sheet body (no end caps)"},
+    {"surf_revolve", "Surface Revolve", 1, nullptr, "fly:surface#1", "Create a sketch profile to revolve first", 0x00004000u, 0, 0, false, false, nullptr, "design_revolve", "Revolve a sketch profile into a sheet body"},
+    {"surf_loft", "Surface Loft", 1, nullptr, "fly:surface#2", "Create at least two profile sketches to loft", 0x00004000u, 0, 2, false, false, nullptr, "design_loft", "Loft (skin) between 2+ profiles, open (no end caps)"},
+    {"surf_fill", "Surface Fill", 1, nullptr, "fly:surface#3", "Create a closed sketch first", 0x00004000u, 0, 0, false, false, nullptr, "design_surface", "Fill a sketch boundary with a smooth face"},
+    {"thicken_surf", "Thicken Surface", 1, nullptr, "fly:surface#5", "target is not a sheet body", 0x00000100u, 0, 0, true, false, nullptr, "design_thicken", "Thicken a sheet body into a solid"},
+    {"hole", "Hole", 2, "Shift+H", "key:S+H", "Pick a face or a plane to drill into", 0x00000402u, 1, 0, false, false, nullptr, "design_hole", "Drill a hole, centred on a picked face or placed on a plane"},
+    {"thread", "Thread", 2, "Shift+T", "key:S+T", "Pick a cylindrical surface (bore / outer) or a circular edge for a thread", 0x00000024u, 1, 0, false, false, nullptr, "design_thread", "Thread a cylindrical surface (inner bore / outer) or a circular edge"},
+    {"shell", "Shell", 2, "Shift+K", "key:S+K", "Shell needs a solid body", 0x00000082u, 1, 0, false, false, nullptr, "design_shell", "Hollow the body to a wall thickness, opening a picked face"},
+    {"cut", "Cut", 2, "Shift+X", "key:S+X", "Create a solid body to cut first", 0x000004feu, 1, 0, false, false, nullptr, "design_cut", "Trim the body with a plane — drag the offset arrow; keep one half or both"},
+    {"split", "Split", 2, nullptr, nullptr, "Split needs a solid body", 0x000000feu, 1, 0, false, false, nullptr, nullptr, "Split the body along a picked face into two solids"},
+    {"fillet", "Fillet", 3, "Shift+F", "btn:dress#0", "Pick an edge to round", 0x000000b2u, 1, 0, false, false, nullptr, "design_filletedge", "Pick an edge, then drag the radius arrow or type it"},
+    {"chamfer", "Chamfer", 3, nullptr, "btn:dress#1", "Pick an edge to bevel", 0x000000b2u, 1, 0, false, false, nullptr, "design_chamfer", "Pick an edge, then drag the distance arrow or type it"},
+    {"draft", "Draft", 3, "Shift+D", "key:S+D", "Pick a face to taper", 0x0000000au, 1, 0, false, false, nullptr, "design_draft", "Tilt a picked face by a draft angle"},
+    {"surf_offset", "Surface Offset", 3, nullptr, "fly:surface#4", "target is not a sheet body", 0x00000100u, 0, 0, true, false, nullptr, "design_offset", "Offset a sheet body's shell by a signed distance"},
+    {"pattern", "Linear pattern", 4, "Shift+N", "btn:pat#0", "Create a solid body to pattern first", 0x00006082u, 1, 0, false, false, nullptr, "design_array", "Repeat the body along a direction — drag the spacing, set the count"},
+    {"pattern_circular", "Circular pattern", 4, nullptr, "btn:pat#1", "Create a solid body to pattern first", 0x00006082u, 1, 0, false, false, nullptr, "design_polararray", "Repeat the body around an axis — set the count and sweep"},
+    {"mirror", "Mirror", 4, "Shift+Z", "key:S+Z", "Mirror needs a body — add or import one first", 0x000004feu, 1, 0, false, false, nullptr, "design_mirror", "Reflect a body about a plane"},
+    {"pat_curve", "Pattern on Curve", 4, nullptr, nullptr, "Pattern on curve needs a body and a curve", 0x00000090u, 1, 0, false, false, nullptr, nullptr, "Repeat the body along a picked curve"},
+    {"transform", "Move", 5, "Shift+Y", "key:S+Y", "Transform needs a body — add or import one first", 0x000021feu, 1, 0, false, false, nullptr, "design_move", "Move and/or rotate an existing body"},
+    {"mate", "Mate", 5, nullptr, "fly:placement#2", "A mate needs two coordinate systems", 0x00001202u, 2, 0, false, false, nullptr, "design_c_coincident", "Assembly: align two CoordSys features (fastened, planar, revolute, slider, cylindrical)"},
+    {"align", "Align to", 5, nullptr, nullptr, "Align needs a body", 0x00000002u, 1, 0, false, false, nullptr, nullptr, "Align the body to a picked face or plane"},
+    {"plane", "Plane", 6, "Shift+P", "key:S+P", nullptr, 0x00000453u, 0, 0, false, false, nullptr, "design_plane", "Reference plane (offset / tilt / midplane / tangent / two edges / coincident)"},
+    {"axis", "Axis", 6, "Shift+A", "key:S+A", nullptr, 0x00000057u, 0, 0, false, false, nullptr, "design_line", "Datum axis (two points, face normal, cylinder centerline, two planes, along edge)"},
+    {"coordsys_v", "Coord Sys", 6, "Shift+C", "key:S+C", nullptr, 0x00000043u, 0, 0, false, false, nullptr, "design_point", "Datum coordinate system (world point, or face + direction edge)"},
+    {"helix", "Helix", 6, nullptr, "fly:plane#3", nullptr, 0x00000405u, 0, 0, false, false, nullptr, "design_thread", "Helical curve (spring path) — use as a sweep path for coils / springs / augers"},
+    {"project", "Project", 6, nullptr, "fly:plane#4", "Project needs a body — add or import one first", 0x00000482u, 1, 0, false, false, nullptr, "design_sketch", "Project body edges onto a plane as sketch entities"},
+    {"measure", "Measure", 6, nullptr, nullptr, nullptr, 0x000b03feu, 0, 0, false, false, nullptr, nullptr, "Measure between the picked points, edges or faces"},
+    {"mass_props", "Mass", 6, nullptr, "btn:mass", nullptr, 0x000000feu, 1, 0, false, false, nullptr, "info", "Report the volume and surface area of the selected body"},
+    {"interference", "Interference", 6, nullptr, nullptr, nullptr, 0x00000200u, 2, 0, false, false, nullptr, nullptr, "Check whether two bodies overlap — reports, changes nothing"},
+    {"edit_feature", "Edit", 7, nullptr, "btn:edit", nullptr, 0x00007d8eu, 0, 0, false, false, nullptr, "design_edit", "Reopen the selected feature to change what it was made from"},
+    {"rename", "Rename…", 7, "F2", "btn:rename", "Select a feature, or a body, to rename it", 0x00004080u, 0, 0, false, false, nullptr, nullptr, "Give this feature a name you will recognise in the tree (a body takes its name from the feature that makes it)"},
+    {"delete_face", "Delete Face", 7, nullptr, "fly:dressup#3", "Delete Face needs a body — add or import one first", 0x0000000eu, 1, 0, false, false, nullptr, "design_delete", "Remove faces from a body and heal the solid"},
+    {"colour", "Colour", 7, nullptr, "btn:colour", nullptr, 0x000001feu, 1, 0, false, false, nullptr, "color_palette", "Set the selected body's display colour"},
+    {"delete", "Delete", 7, "Del", "btn:delete", nullptr, 0x000f7c00u, 0, 0, false, false, nullptr, "design_delete", "Delete what is selected"},
+    {"delete_body", "Delete Body", 7, nullptr, "btn:delete_body", nullptr, 0x000001feu, 1, 0, false, false, nullptr, "design_delete", "Delete this whole body — removes the feature it was made from"},
+    {"sk_line_t", "Line", 0, "L", "key:L", nullptr, 0x000f8000u, 0, 0, false, true, "Line", "design_line", "Line — click start, then end"},
+    {"sk_polyline", "Polyline", 0, nullptr, "fly:design_line#1", nullptr, 0x000f8000u, 0, 0, false, true, "Line", "design_polyline", "Click points; click the first point to close the loop, right-click to end it open"},
+    {"sk_rect", "Corner rectangle", 0, "R", "key:R", nullptr, 0x000f8000u, 0, 0, false, true, "Rectangle", "design_rect", "Rectangle — click two opposite corners"},
+    {"sk_rect_center", "Centre rectangle", 0, nullptr, "fly:design_rect#1", nullptr, 0x000f8000u, 0, 0, false, true, "Rectangle", "design_crect", "Click center, then a corner"},
+    {"sk_rect_oblique", "Oblique rectangle", 0, nullptr, "fly:design_rect#2", nullptr, 0x000f8000u, 0, 0, false, true, "Rectangle", "design_rect_oblique", "Click two corners of one edge, then a point for the width"},
+    {"sk_rect_rounded", "Rounded rectangle", 0, nullptr, "fly:design_rect#3", nullptr, 0x000f8000u, 0, 0, false, true, "Rectangle", "design_rect_rounded", "Click two opposite corners, then a point for the corner radius"},
+    {"sk_circle", "Centre circle", 0, "C", "key:C", nullptr, 0x000f8000u, 0, 0, false, true, "Circle", "design_circle", "Circle — click center, then radius"},
+    {"sk_circle_2pt", "2-point circle", 0, nullptr, "fly:design_circle#1", nullptr, 0x000f8000u, 0, 0, false, true, "Circle", "design_circle2pt", "Click two ends of the diameter"},
+    {"sk_circle_3pt", "3-point circle", 0, nullptr, "fly:design_circle#2", nullptr, 0x000f8000u, 0, 0, false, true, "Circle", "design_circle3pt", "Click three points on the circle"},
+    {"sk_arc_t", "3-point arc", 0, "A", "key:A", nullptr, 0x000f8000u, 0, 0, false, true, "Arc", "design_arc3pt", "Arc — click start, end, then a point"},
+    {"sk_arc_tangent", "Tangent arc", 0, nullptr, "fly:design_arc3pt#1", nullptr, 0x000f8000u, 0, 0, false, true, "Arc", "design_tangentarc", "Click start (on the last entity) then end"},
+    {"sk_arc_center", "Centre-point arc", 0, nullptr, "fly:design_arc3pt#2", nullptr, 0x000f8000u, 0, 0, false, true, "Arc", "design_arc_center", "Click center, then start, then a point for the end angle"},
+    {"sk_slot", "Slot", 0, "S", "key:S", nullptr, 0x000f8000u, 0, 0, false, true, "Slot", "design_slot", "Slot — two centerline ends, then end radius"},
+    {"sk_slot_arc", "Arc slot", 0, nullptr, "fly:design_slot#1", nullptr, 0x000f8000u, 0, 0, false, true, "Slot", "design_slot_arc", "Click center, start, end, then a point for the width"},
+    {"sk_ellipse", "Ellipse", 0, "E", "key:E", nullptr, 0x000f8000u, 0, 0, false, true, "Ellipse", "design_ellipse", "Ellipse — center, major end, minor point"},
+    {"sk_ellipse_arc", "Elliptical arc", 0, nullptr, "fly:design_ellipse#1", nullptr, 0x000f8000u, 0, 0, false, true, "Ellipse", "design_ellipse_arc", "Click center, major-axis end, minor point, then arc start and end"},
+    {"sk_spline", "Spline", 0, "B", "key:B", nullptr, 0x000f8000u, 0, 0, false, true, nullptr, "design_bspline", "Spline — click control points"},
+    {"sk_poly_3", "Triangle", 0, nullptr, "btn:poly#3", nullptr, 0x000f8000u, 0, 0, false, true, "Polygon", "design_polygon", "Triangle — click centre, then a vertex"},
+    {"sk_poly_4", "Square", 0, nullptr, "btn:poly#4", nullptr, 0x000f8000u, 0, 0, false, true, "Polygon", "design_polygon", "Square — click centre, then a vertex"},
+    {"sk_poly_5", "Pentagon", 0, nullptr, "btn:poly#5", nullptr, 0x000f8000u, 0, 0, false, true, "Polygon", "design_polygon", "Pentagon — click centre, then a vertex"},
+    {"sk_polygon", "Hexagon", 0, "G", "btn:poly#6", nullptr, 0x000f8000u, 0, 0, false, true, "Polygon", "design_polygon", "Hexagon — click centre, then a vertex"},
+    {"sk_poly_8", "Octagon", 0, nullptr, "btn:poly#8", nullptr, 0x000f8000u, 0, 0, false, true, "Polygon", "design_polygon", "Octagon — click centre, then a vertex"},
+    {"sk_poly_12", "Dodecagon", 0, nullptr, "btn:poly#12", nullptr, 0x000f8000u, 0, 0, false, true, "Polygon", "design_polygon", "Dodecagon — click centre, then a vertex"},
+    {"sk_poly_inscribed", "Inscribed", 0, nullptr, "btn:polyfit#0", nullptr, 0x000f8000u, 0, 0, false, true, "Polygon", "design_polygon", "Measure the polygon to its corners (inscribed)"},
+    {"sk_poly_circumscribed", "Circumscribed", 0, nullptr, "btn:polyfit#1", nullptr, 0x000f8000u, 0, 0, false, true, "Polygon", "design_polygon", "Measure the polygon to its flats (circumscribed)"},
+    {"sk_point_t", "Point", 0, "P", "key:P", nullptr, 0x000f8000u, 0, 0, false, true, nullptr, "design_point", "Point — click to place"},
+    {"sk_text", "Text", 0, nullptr, "btn:text", nullptr, 0x000f8000u, 0, 0, false, true, nullptr, "design_text", "Type text; its outline is added to this sketch as editable lines"},
+    {"sk_svg", "SVG", 0, nullptr, "btn:svg", nullptr, 0x000f8000u, 0, 0, false, true, nullptr, "design_svg", "Import an SVG outline into this sketch as editable lines"},
+    {"sk_offset", "Offset", 1, "O", "key:O", nullptr, 0x000b0000u, 0, 0, false, true, nullptr, "design_offset", "Offset — pick an entity, drag the distance"},
+    {"sk_trim", "Trim", 2, "T", "key:T", nullptr, 0x000b0000u, 0, 0, false, true, nullptr, "design_trim", "Trim — click a segment to trim it"},
+    {"sk_fillet", "Fillet", 3, "F", "key:F", nullptr, 0x00090000u, 0, 0, false, true, nullptr, "design_filletedge", "Fillet — pick two lines, set the radius"},
+    {"sk_chamfer", "Chamfer", 3, "H", "key:H", nullptr, 0x00090000u, 0, 0, false, true, nullptr, "design_chamfer", "Chamfer — pick two lines, set the distance"},
+    {"sk_array", "Linear array", 4, nullptr, "fly:design_array#0", nullptr, 0x000b0000u, 0, 0, false, true, "Array", "design_array", "Pick entities, drag the spacing handle, click the count; click empty to apply"},
+    {"sk_array_polar", "Polar array", 4, nullptr, "fly:design_array#1", nullptr, 0x000b0000u, 0, 0, false, true, "Array", "design_polararray", "Pick entities, drag the sweep handle, click the count; click empty to apply"},
+    {"sk_mirror", "Mirror", 4, "M", "key:M", nullptr, 0x000b0000u, 0, 0, false, true, nullptr, "design_mirror", "Mirror — pick axis, then entities"},
+    {"sk_move", "Move", 5, nullptr, "fly:design_move#0", nullptr, 0x000f0000u, 0, 0, false, true, "Move", "design_move", "Pick entities, then drag the handle or click the distance; click empty to apply"},
+    {"sk_rotate", "Rotate", 5, nullptr, "fly:design_move#1", nullptr, 0x000f0000u, 0, 0, false, true, "Move", "design_rotate", "Pick entities, then drag around the pivot or click the angle; click empty to apply"},
+    {"sk_scale", "Scale", 5, nullptr, "fly:design_move#2", nullptr, 0x000f0000u, 0, 0, false, true, "Move", "design_scale", "Pick entities, then drag the handle or click the factor; click empty to apply"},
+    {"sk_dimension", "Dimension", 6, "D", "key:D", nullptr, 0x000f8000u, 0, 0, false, true, nullptr, "design_dimension", "Dimension — click 2 points or an entity"},
+    {"sk_constrain", "Constrain", 6, "K", "key:K", nullptr, 0x000f0000u, 0, 0, false, true, nullptr, "design_constrain", "Constrain the selected sketch entities to each other"},
+    // Same verb, model-mode vocabulary: offered when a SKETCH is selected (bit 14, SkLoop), the
+    // state a user is in right after finishing one. Without this row the only way in was the
+    // toolbar icon, and constraints read as absent — see the Onshape-comparison report.
+    {"constrain", "Constrain sketch", 7, nullptr, "btn:constrain", "Select a sketch to constrain it", 0x00004000u, 0, 1, false, false, nullptr, "design_constrain", "Add dimensions and relations (coincident, tangent, parallel...) to the selected sketch"},
+    {"sk_construct", "Construction", 6, "Q", "key:Q", nullptr, 0x000b8000u, 0, 0, false, true, nullptr, nullptr, "Toggle construction: geometry that guides but is never built"},
+    {"sk_extend", "Extend", 7, "X", "key:X", nullptr, 0x000b0000u, 0, 0, false, true, nullptr, "design_extend", "Extend — click a line/arc to extend it"},
+    {"sk_delete", "Delete", 7, "Del", "btn:sk_delete", nullptr, 0x000f0000u, 0, 0, false, true, nullptr, "design_delete", "Delete the selected sketch entities"},
+    // Typing the defining number of the element you pointed at. Three rows rather than one so
+    // each names the quantity in the drawing-office word for THAT element; all three land on
+    // the same handler, because dimension_kind() already resolves the quantity from the
+    // selection. Without these, an element's own numbers were reachable only by arming the
+    // Dimension tool and re-picking geometry that was already selected.
+    {"sk_length", "Length…", 7, "V", "key:V", nullptr, 0x00010000u, 0, 0, false, true, nullptr, "design_dimension", "Type the length of this line"},
+    {"sk_radius", "Radius / diameter…", 7, "V", "key:V", nullptr, 0x00020000u, 0, 0, false, true, nullptr, "design_dimension", "Type the radius of this arc, or the diameter of this circle"},
+    {"sk_angdist", "Angle / distance…", 7, "V", "key:V", nullptr, 0x00080000u, 0, 0, false, true, nullptr, "design_dimension", "Type the angle between two lines, or the distance between the two picks"},
+};
+static const int kOfferVerbCount = 92;
+
+}} // namespace Slic3r::GUI
+
+#endif // slic3r_GUI_DesignOffer_hpp_
diff --git a/src/slic3r/GUI/CAD/DesignPanel.cpp b/src/slic3r/GUI/CAD/DesignPanel.cpp
new file mode 100644
index 0000000000..6d9454a829
--- /dev/null
+++ b/src/slic3r/GUI/CAD/DesignPanel.cpp
@@ -0,0 +1,11775 @@
+#include "slic3r/GUI/CAD/DesignPanel.hpp"
+#include "slic3r/GUI/CAD/DesignCanvas.hpp"
+#include "slic3r/GUI/CAD/DesignSketchTool.hpp"
+#include "slic3r/GUI/CAD/DesignOffer.hpp"                // generated offer table — see docs/ux/tool_atlas.json
+#include "libslic3r/CAD/GeometryEngine.hpp"   // face_by_index for face-extrude gizmo anchor
+#include "libslic3r/TriangleMesh.hpp"     // mesh import: STL/OBJ -> indexed_triangle_set
+#include "libslic3r/Format/OBJ.hpp"
+#include "libslic3r/Format/bbs_3mf.hpp"   // put_other_changes: mark the project dirty outside the undo stack
+
+#include <boost/algorithm/string/case_conv.hpp>
+#include <boost/filesystem/path.hpp>
+#include <boost/log/trivial.hpp>          // the offer/atlas join check reports on the log
+#include <Standard_Failure.hxx>
+
+#include <cassert>
+#include <cstdarg>                        // offer_trace: diagnostic row dump for the offer ladder
+#include <map>
+#include <set>
+#include <wx/sizer.h>
+#include <wx/button.h>
+#include <wx/stattext.h>
+#include <wx/checkbox.h>
+#include <wx/checklst.h>
+#include <wx/spinctrl.h>
+#include <wx/listctrl.h>
+#include <wx/treectrl.h>
+#include <wx/imaglist.h>
+#include <wx/statline.h>
+#include <wx/statbmp.h>
+#include <wx/image.h>
+#include <wx/font.h>
+#include <wx/textdlg.h>
+#include <wx/filedlg.h>
+#include <wx/dialog.h>
+#include <wx/colordlg.h>
+#include <wx/menu.h>
+#include <wx/progdlg.h>
+#include <wx/utils.h>    // wxWindowDisabler, wxMilliSleep
+#include <wx/msgdlg.h>   // wxMessageBox
+
+#include <string>
+#include <memory>
+#include <functional>
+#include <cmath>
+#include <algorithm>
+#include <thread>
+#include <atomic>
+
+#include "slic3r/GUI/wxExtensions.hpp"   // ScalableButton, create_scaled_bitmap
+#include "slic3r/GUI/Widgets/Label.hpp"             // HarmonyOS Sans fonts (Head_*/Body_*) shared with the rest of Orca
+#include "slic3r/GUI/Widgets/DropDown.hpp"          // Orca-themed combo dropdown (white/teal selector) for the tool flyouts
+#include "slic3r/GUI/Widgets/Button.hpp"            // Orca-styled Button (ButtonStyle/ButtonType) — same look as Prepare
+#include "slic3r/GUI/Widgets/CheckBox.hpp"          // Orca teal check (label lives in the row's left column)
+#include "slic3r/GUI/Widgets/ComboBox.hpp"          // Orca dropdown — replaces wxChoice in every Design card
+#include "slic3r/GUI/Widgets/StaticBox.hpp"         // Prepare's rounded white card frame around each tool dialog
+#include "libslic3r/CAD/SketchImport.hpp"    // text_to_regions / svg_to_regions
+#include "libslic3r/CAD/ThreadStandards.hpp" // ISO metric / Unified imperial thread tables
+#include "libslic3r/Model.hpp"
+#include "slic3r/GUI/GUI_App.hpp"
+#include "slic3r/GUI/Plater.hpp"
+#include "libslic3r/BuildVolume.hpp"
+#include "slic3r/GUI/MainFrame.hpp"
+#include "slic3r/GUI/GUI_ObjectList.hpp"
+
+// English-only pin for the Design tab (see design-ux-contract): one lever
+// de-translates this whole TU so our strings never half-translate against the host's
+// localized chrome. Host UI still follows the app locale; only this tab is pinned EN.
+// GOTCHA: every _L(...) in this file must take a STRING LITERAL (FromUTF8 wants const char*).
+#ifdef _L
+#undef _L
+#endif
+#define _L(s) wxString::FromUTF8(s)
+
+namespace Slic3r { namespace GUI {
+
+// Mesh -> B-rep import defaults (see GeometryEngine::mesh_to_brep).
+// Tolerance is a vertex-dedup cell, not a sew tolerance: 10 um is well under any printable
+// feature yet coarse enough to weld the float noise a mesh exporter leaves on shared vertices.
+static constexpr double MESH_IMPORT_TOLERANCE        = 0.01;   // mm
+// Merge coplanar neighbours so the body has real, pickable faces instead of one face per
+// triangle. 5 deg tolerates the small normal jitter of an exported/scanned flat face while
+// still keeping genuinely curved regions faceted.
+static constexpr double MESH_IMPORT_MERGE_ANGLE_DEG  = 5.0;
+// Above this, warn before converting: the build is one OCCT face per triangle.
+static constexpr size_t MESH_IMPORT_TRIANGLE_WARN    = 50000;
+
+// Two-column parameter form (label left, control right), matching Prepare's row idiom. The
+// control column grows, so every control lines up on the panel's right edge instead of sitting
+// at its natural width beside the label — the forms used a plain non-growable grid before, which
+// is why Design's rows looked nothing like Prepare's.
+static wxFlexGridSizer* two_col_form()
+{
+    auto* f = new wxFlexGridSizer(2, 6, 8);
+    f->AddGrowableCol(1, 1);
+    f->SetFlexibleDirection(wxHORIZONTAL);
+    return f;
+}
+
+
+// Orca's dropdown, sized like Prepare's sidebar combos. Read-only: every Design
+// picker is a fixed list, never free text.
+static ComboBox* make_combo(wxWindow* parent)
+{
+    // Explicit width: ComboBox's natural best size is its widest item, which inflated the
+  // sidebar's virtual width past the viewport and left the panel horizontally scrolled —
+  // that is what clipped the first letter of every label. The form column grows anyway.
+    auto* c = new ComboBox(parent, wxID_ANY, wxEmptyString, wxDefaultPosition,
+                           wxSize(parent->FromDIP(90), parent->FromDIP(24)), 0, nullptr, wxCB_READONLY);
+    c->SetMinSize(wxSize(parent->FromDIP(90), parent->FromDIP(24)));
+    return c;
+}
+
+// Append a row that carries a feature/body index as client data.
+//
+// It must go through SetClientData(), not Append()'s clientData argument. Orca's ComboBox keeps
+// client data in its own vector and its Append() writes that vector directly, never routing
+// through wxItemContainer — so the container's m_clientDataItemsType stays wxClientData_None.
+// wxItemContainer::GetClientData() opens with
+//     wxCHECK_MSG( HasClientUntypedData(), NULL, ... );
+// and wxCHECK_MSG is an early RETURN, not a debug-only assert. So the read handed back NULL for
+// every row and every caller resolved it to index 0 no matter what the user had picked — silently,
+// because index 0 is a legal answer. SetClientData() flips the type to wxClientData_Void, after
+// which the value survives the round trip.
+static int combo_append_index(ComboBox* c, const wxString& label, int index)
+{
+    const int row = c->Append(label, wxNullBitmap);
+    c->SetClientData(unsigned(row), reinterpret_cast<void*>(intptr_t(index)));
+    return row;
+}
+
+// Format a value with the international ('.') decimal separator regardless of the
+// app's LC_NUMERIC locale (wx sets it to the user locale at startup). snprintf may
+// emit a comma, so normalise it.
+static wxString en_format(double v, int digits = 2)
+{
+    char fmt[16];
+    std::snprintf(fmt, sizeof(fmt), "%%.%df", digits);
+    char buf[64];
+    std::snprintf(buf, sizeof(buf), fmt, v);
+    for (char* c = buf; *c; ++c) if (*c == ',') *c = '.';
+    return wxString::FromUTF8(buf);
+}
+// Parse a user-typed value accepting either '.' or ',' as the decimal separator.
+static bool en_parse(const wxString& text, double& out)
+{
+    wxString t(text);
+    t.Replace(wxT(","), wxT("."));
+    return t.ToCDouble(&out);
+}
+
+// Design-tab chrome tokens. The dark branch returns the EXACT legacy values so the
+// (correct) dark theme stays byte-identical; the light branch maps each onto Orca's
+// light surface so the ribbon/sidebar follow the app theme instead of staying black.
+static bool     dp_dark()         { return wxGetApp().dark_mode(); }
+static wxColour dp_ribbon_bg()    { return dp_dark() ? wxColour(0x36,0x36,0x3C) : wxColour(0xEC,0xEC,0xEE); }
+static wxColour dp_ribbon_hover() { return dp_dark() ? wxColour(0x4D,0x4D,0x54) : wxColour(0xD7,0xD7,0xDB); }
+static wxColour dp_panel_bg()     { return dp_dark() ? wxColour(0x2D,0x2D,0x30) : wxColour(0xFB,0xFB,0xFD); }
+static wxColour dp_sec_text()     { return dp_dark() ? wxColour(0x81,0x81,0x83) : wxColour(0x66,0x66,0x68); }
+static wxColour dp_ctl_text()     { return dp_dark() ? wxColour(0xC8,0xC8,0xC8) : wxColour(0x35,0x35,0x37); }
+static wxColour dp_item_text()    { return dp_dark() ? wxColour(0xE0,0xE0,0xE0) : wxColour(0x2C,0x2C,0x2E); }
+static wxColour dp_item_dim()     { return dp_dark() ? wxColour(0x80,0x80,0x80) : wxColour(0xA0,0xA0,0xA2); }
+
+// Prepare's control-outline grey, sampled from its sidebar: #4A4A51 on the #2D2D31 dark
+// panel, #DBDBDB on light. Every framed thing in Design uses this so the tab matches.
+static wxColour dp_border_col()   { return dp_dark() ? wxColour(0x4A,0x4A,0x51) : wxColour(0xDB,0xDB,0xDB); }
+
+// A tool card: Prepare's rounded white-bordered panel (Plater.cpp's panel_printer_preset
+// idiom — radius 8, #EEEEEE border, green on hover). Every card's controls are parented
+// to it, so the border actually encloses them.
+static StaticBox* make_card(wxWindow* parent)
+{
+    auto* c = new StaticBox(parent);
+    c->SetCornerRadius(8);
+    c->SetBorderColorNormal(dp_border_col());   // no hover accent: the frame is not clickable
+    return c;
+}
+
+// Prepare outlines every numeric field (rounded, #4A4A51 on dark). wxSpinCtrlDouble is a
+// native GTK control that cannot draw that, and Orca's own SpinInput is int-only — it would
+// silently truncate a 2.5 mm radius. So the double spin keeps its arrows and validation and
+// sits inside an Orca StaticBox that supplies the frame. spin_frame() returns that box, which
+// is what goes into the layout sizer.
+static wxSpinCtrlDouble* make_spin(wxWindow* parent, double val,
+                                   double mn = 0.1, double mx = 1000.0)
+{
+    auto* box = new StaticBox(parent);
+    box->SetCornerRadius(4);
+    box->SetBorderColorNormal(dp_border_col());
+    auto* s = new wxSpinCtrlDouble(box, wxID_ANY, "", wxDefaultPosition, wxSize(90, -1),
+                                   wxSP_ARROW_KEYS | wxBORDER_NONE);
+    s->SetRange(mn, mx);
+    s->SetDigits(2);
+    s->SetValue(val);
+    // THE WHEEL SCROLLS THE PANEL, IT DOES NOT EDIT THE VALUE. wxSpinCtrlDouble takes the wheel
+    // whenever the pointer is over it, so a card taller than the panel could not be scrolled past
+    // without silently incrementing whatever field happened to be under the cursor — measured:
+    // eight notches turned an X hint from 1,00 into 6,00, and the same gesture over an Extrude
+    // distance or a mate Offset is a silent model change made by someone who thought they were
+    // navigating. Skipping the event lets it reach the scrolled cards panel. A spin the user has
+    // deliberately focused still takes the wheel, which is the one case where editing is meant.
+    s->Bind(wxEVT_MOUSEWHEEL, [s](wxMouseEvent& e) {
+        if (wxWindow::FindFocus() == s) e.Skip();          // focused: wheel edits, as expected
+        else if (wxWindow* p = s->GetParent())             // otherwise hand it to the panel
+            wxPostEvent(p, e);
+    });
+    auto* sz = new wxBoxSizer(wxHORIZONTAL);
+    sz->Add(s, 1, wxEXPAND | wxALL, parent->FromDIP(2));
+    box->SetSizer(sz);
+    return s;
+}
+
+// The framed spin's parent IS its frame; lay that out instead of the bare control.
+static wxWindow* spin_frame(wxWindow* spin) { return spin->GetParent(); }
+
+static SketchPlane plane_from_index(int i)
+{
+    switch (i) {
+        case 1:  return SketchPlane::XZ();
+        case 2:  return SketchPlane::YZ();
+        default: return SketchPlane::XY();
+    }
+}
+
+// Inverse of plane_from_index: recover the ComboBox row from a plane's normal.
+// XY normal=(0,0,1)->0, XZ normal=(0,1,0)->1, YZ normal=(1,0,0)->2.
+static int index_from_plane(const SketchPlane& p)
+{
+    if (std::abs(p.normal.y()) > 0.5) return 1; // XZ
+    if (std::abs(p.normal.x()) > 0.5) return 2; // YZ
+    return 0;                                   // XY
+}
+
+// Does this plane survive a round trip through the Hole/Thread plane dropdown? The dropdown holds
+// only XY/XZ/YZ and index_from_plane SNAPS anything else to the nearest of the three, so a plane
+// that is not one of them cannot be restored from the row and has to be carried explicitly.
+// Origin is compared too, not just the axes: a face plane parallel to XY but 12 mm up snaps to
+// row 0 and would otherwise come back at z=0. Vector norms rather than isApprox, which compares
+// relative to magnitude and so is useless against the zero origin.
+// modeling_origin is not optional: hole_plane()/thread_plane() ADD it to the dropdown plane before
+// the feature stores it, so on a document with a shifted origin every dropdown hole would fail a
+// bare XY/XZ/YZ comparison and be mistaken for a face pick.
+static bool is_base_plane(const SketchPlane& p, const Vec3d& modeling_origin)
+{
+    SketchPlane  b = plane_from_index(index_from_plane(p));
+    b.origin += modeling_origin;
+    const double e = 1e-6;
+    return (p.origin - b.origin).norm() < e && (p.normal - b.normal).norm() < e
+        && (p.x_axis - b.x_axis).norm() < e && (p.y_axis - b.y_axis).norm() < e;
+}
+
+// #2: a sketch plane on `face` with origin at the face centroid and normal pointing INTO the
+// solid, so a positioned hole drills inward and its (x,y) read as the offset from the face
+// centre. A hole is rotationally symmetric, so the arbitrary in-plane basis is harmless.
+static SketchPlane face_plane_inward(const TopoDS_Face& face)
+{
+    SketchPlane p;
+    p.origin = GeometryEngine::face_centroid_world(face);
+    p.normal = (-GeometryEngine::face_normal_world(face)).normalized();   // inward
+    // Align the in-plane x-axis with the face's LONGEST straight edge so the (u,v) frame matches
+    // the face sides — then "distance from a side" (the hole construction dims) reads correctly.
+    Vec3d x(0, 0, 0); double best = 0;
+    for (const TopoDS_Edge& e : GeometryEngine::edges_of_face(face)) {
+        const std::vector<Vec3d> pts = GeometryEngine::sample_edge_world(e);
+        if (pts.size() < 2) continue;
+        Vec3d d = pts.back() - pts.front();
+        d = d - p.normal * d.dot(p.normal);        // project the edge direction into the plane
+        const double len = d.norm();
+        if (len > best) { best = len; x = d / len; }
+    }
+    if (best < 1e-9) {   // curved/edgeless face: fall back to an arbitrary in-plane basis
+        const Vec3d ref = std::abs(p.normal.z()) < 0.9 ? Vec3d(0, 0, 1) : Vec3d(1, 0, 0);
+        x = ref.cross(p.normal).normalized();
+    }
+    p.x_axis = x.normalized();
+    p.y_axis = p.normal.cross(p.x_axis).normalized();
+    return p;
+}
+
+// Highest upward-facing planar face of a solid — the surface the user is looking down on.
+// Hole placement defaults here (instead of the z=0 datum) so the footprint sits on the top
+// face at the right depth, not on the model's underside where a top-view drag reads parallax-
+// shifted. Returns -1 if the shape has no clearly-upward face.
+static int top_face_index_of(const TopoDS_Shape& shape)
+{
+    int best = -1; double bestz = -1e30;
+    const int n = GeometryEngine::face_count(shape);
+    for (int i = 0; i < n; ++i) {
+        const TopoDS_Face f = GeometryEngine::face_by_index(shape, i);
+        if (f.IsNull()) continue;
+        const Vec3d nrm = GeometryEngine::face_normal_world(f);
+        if (nrm.z() < 0.5) continue;                 // only faces pointing substantially up
+        const Vec3d c = GeometryEngine::face_centroid_world(f);
+        if (c.z() > bestz) { bestz = c.z(); best = i; }
+    }
+    return best;
+}
+
+DesignPanel::DesignPanel(wxWindow* parent)
+    : wxPanel(parent, wxID_ANY)
+{
+    // Left column: a slim feature-tree + docked tool-dialog column. All form
+    // controls are parented to m_form so it can scroll independently of the
+    // live GL viewport. The tool buttons live in the top toolbar (built below).
+    m_form = new wxScrolledWindow(this, wxID_ANY);
+    // The sidebar/panel never carried an explicit background, so in light theme it
+    // inherited the dark window colour and stayed black. Paint it on the light surface;
+    // dark is left untouched (it already reads correctly via inheritance).
+    if (!dp_dark()) {
+        SetBackgroundColour(dp_panel_bg());
+        m_form->SetBackgroundColour(dp_panel_bg());
+    }
+
+    auto* root = new wxBoxSizer(wxVERTICAL);
+    {
+        auto* hdr = new wxStaticText(m_form, wxID_ANY, _L("Design"));
+        hdr->SetFont(Label::Head_16);   // Orca shared HarmonyOS section-title font
+        root->Add(hdr, 0, wxLEFT | wxRIGHT | wxTOP, 12);
+        root->AddSpacer(2);
+    }
+
+    // === Top contextual toolbar (Onshape-style icon strip) ===
+    // Parented to the panel (sits above the form/viewport row). Only the active
+    // mode's group is shown; the others are hidden by set_ui_mode().
+    // Scrollable ribbon: on a narrow/windowed screen the far-right action bar (Confirm/Cancel)
+    // used to be clipped off the edge with no way to reach it. Horizontal-only scroll (vertical
+    // rate 0) keeps it reachable; on a wide screen the stretch spacer still pins it far-right.
+    m_toolbar = new wxScrolledWindow(this, wxID_ANY);
+    m_toolbar->SetScrollRate(15, 0);
+    m_toolbar->ShowScrollbars(wxSHOW_SB_DEFAULT, wxSHOW_SB_NEVER);
+    // Theme-aware tool ribbon: dark uses Orca's elevated surface (#36363C / hover
+    // #4D4D54); light maps onto the app's light chrome so the strip follows the theme.
+    m_toolbar->SetBackgroundColour(dp_ribbon_bg());
+
+    const wxColour tb_bg    = dp_ribbon_bg();
+    const wxColour tb_hover = dp_ribbon_hover();
+    auto icon_btn = [this, tb_bg, tb_hover](const char* icon, const wxString& tip) {
+        // Prepare's main toolbar: 40 px icon cell, 4 px gap (GLToolbar::Default_Icons_Size
+        // and set_gap_size(4)) -> 44 px pitch. Match it exactly.
+        auto* b = new ScalableButton(m_toolbar, wxID_ANY, icon, "", wxSize(40, 40),
+                                     wxDefaultPosition, wxBU_EXACTFIT | wxBORDER_NONE, false, 34);
+        b->SetToolTip(tip);
+        b->SetBackgroundColour(tb_bg);
+        m_tool_btns.push_back(b);
+        // Hover affordance, honouring the active-tool teal state.
+        b->Bind(wxEVT_ENTER_WINDOW, [this, b, tb_hover](wxMouseEvent& e) {
+            b->SetBackgroundColour(b == m_active_tool_btn ? wxColour(0x52, 0xC7, 0xB8) : tb_hover);
+            b->Refresh(); e.Skip(); });
+        b->Bind(wxEVT_LEAVE_WINDOW, [this, b, tb_bg](wxMouseEvent& e) {
+            b->SetBackgroundColour(b == m_active_tool_btn ? wxColour(0x00, 0x96, 0x88) : tb_bg);
+            b->Refresh(); e.Skip(); });
+        // Mark this tool active (teal) on press — a separate event from the
+        // button's command handler, so it never swallows the click action.
+        b->Bind(wxEVT_LEFT_DOWN, [this, b](wxMouseEvent& e) {
+            set_active_tool_btn(b); e.Skip(); });
+        return b;
+    };
+    // Small grey group caption (Onshape-style section hint) for each toolbar mode.
+    auto caption = [this](const wxString& t) {
+        auto* s = new wxStaticText(m_toolbar, wxID_ANY, t);
+        wxFont f = Label::Body_12; f.SetWeight(wxFONTWEIGHT_BOLD);
+        s->SetFont(f);
+        s->SetForegroundColour(dp_sec_text());   // Orca dark secondary text
+        return s;
+    };
+    auto add_sep = [this](wxSizer* row) {
+        row->AddSpacer(5);
+        row->Add(new wxStaticLine(m_toolbar, wxID_ANY, wxDefaultPosition, wxSize(1, 22), wxLI_VERTICAL),
+                 0, wxALIGN_CENTER_VERTICAL);
+        row->AddSpacer(5);
+    };
+
+    // Shared sketch-tool selector: begins a session on first use, then switches
+    // the active entity tool. The Construction toggle marks following entities as
+    // construction geometry (excluded from the wire).
+    m_construction = new wxCheckBox(m_toolbar, wxID_ANY, _L("Construction"));
+    m_construction->SetForegroundColour(dp_ctl_text());
+    auto select_tool = [this](DesignSketchTool::Mode mode, const wxString& hint) {
+        if (!m_viewport) return;
+        if (!m_viewport->is_sketching()) {
+            wxString on;
+            const SketchPlane plane = sketch_plane_from_selection(on);
+            m_viewport->begin_sketch(plane, mode);
+            m_construction->SetValue(false);   // a fresh session starts non-construction
+            m_sketch_on = on;                  // shown with the tool hint, so the target is visible
+            // The face has been CONSUMED as the sketch plane, so drop the pick. Leaving it live
+            // meant the next Extrude saw a selected face and push/pulled it instead of extruding
+            // the sketch just drawn — the same trap the imported-art path already guards against.
+            if (m_sel_solid_face >= 0 || m_pick_face >= 0) {
+                m_sel_solid_face = m_sel_solid_edge = m_sel_solid_body = -1;
+                m_pick_face = m_pick_face_body = -1;
+            }
+        } else {
+            m_viewport->set_sketch_tool(mode);
+        }
+        m_viewport->set_sketch_construction(m_construction->GetValue());
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(m_sketch_on.IsEmpty() ? hint
+                           : wxString::Format(_L("%s  ·  on %s"), hint, m_sketch_on));
+        m_status->Refresh();
+    };
+
+    // Sketch-tool shortcuts (single letters, active only while a sketch is open). Family tools
+    // bind to their default mode; the other modes stay in the toolbar flyout. Registered here
+    // where select_tool is in scope; the closures run at key-press time (members are live by then).
+    auto sk_key = [this, select_tool](int ch, DesignSketchTool::Mode m, const wxString& h) {
+        m_keys_sketch[ch] = [this, select_tool, m, h] { select_tool(m, h); };
+    };
+    sk_key('L', DesignSketchTool::Mode::Line,         _L("Line — click start, then end"));
+    sk_key('R', DesignSketchTool::Mode::CornerRect,   _L("Rectangle — click two opposite corners"));
+    sk_key('C', DesignSketchTool::Mode::CenterCircle, _L("Circle — click center, then radius"));
+    sk_key('A', DesignSketchTool::Mode::ThreePointArc,_L("Arc — click start, end, then a point"));
+    sk_key('S', DesignSketchTool::Mode::Slot,         _L("Slot — two centerline ends, then end radius"));
+    sk_key('E', DesignSketchTool::Mode::Ellipse,      _L("Ellipse — center, major end, minor point"));
+    sk_key('B', DesignSketchTool::Mode::BSpline,      _L("Spline — click control points"));
+    sk_key('P', DesignSketchTool::Mode::Point,        _L("Point — click to place"));
+    sk_key('D', DesignSketchTool::Mode::Dimension,    _L("Dimension — click 2 points or an entity"));
+    sk_key('T', DesignSketchTool::Mode::Trim,         _L("Trim — click a segment to trim it"));
+    sk_key('X', DesignSketchTool::Mode::Extend,       _L("Extend — click a line/arc to extend it"));
+    sk_key('O', DesignSketchTool::Mode::Offset,       _L("Offset — pick an entity, drag the distance"));
+    sk_key('M', DesignSketchTool::Mode::Mirror,       _L("Mirror — pick axis, then entities"));
+    sk_key('F', DesignSketchTool::Mode::Fillet,       _L("Fillet — pick two lines, set the radius"));
+    sk_key('H', DesignSketchTool::Mode::Chamfer,      _L("Chamfer — pick two lines, set the distance"));
+    // Polygon needs its side count / circumscribed flag pushed to the tool before it starts.
+    m_keys_sketch['G'] = [this, select_tool] {
+        if (m_viewport) {
+            push_polygon_params();
+        }
+        select_tool(DesignSketchTool::Mode::Polygon, _L("Polygon — click center, then a vertex"));
+    };
+    // Constrain (finish the live sketch + enter constrain), and Construction toggle.
+    // V for Value: type the defining number of whatever is selected — a line's length, an arc's
+    // radius, a circle's diameter, the angle between two lines. One handler behind three offer
+    // rows, because the quantity comes from the selection, not from which row was clicked.
+    //
+    // It needs a KEY, not just a menu row. The deck profile in VSD_n1_streamcontroller is
+    // generated from these two key tables, so a verb with no shortcut cannot be put on a
+    // physical button at all — which is the whole point of that profile for a user who drives
+    // the app from buttons rather than a menu.
+    m_keys_sketch['V'] = [this] {
+        if (m_viewport && m_viewport->is_sketching() && !m_viewport->edit_sketch_selection_value())
+            set_status(_L("Nothing here has a value to type — pick a line, an arc, a circle, or two entities"));
+    };
+    m_keys_sketch['K'] = [this] { enter_constrain_inline(); };
+    // N: square up to the plane. Not a view preference but part of drawing — a sketch read at an
+    // angle is a sketch whose right angles do not look like right angles, and no hand-orbit lands
+    // exactly normal. Sketch map only: in Feature mode the navigator orb owns orientation.
+    m_keys_sketch['N'] = [this] {
+        if (m_viewport && m_viewport->view_normal_to_sketch()) {
+            m_status->SetForegroundColour(wxNullColour);
+            set_status(_L("Normal to the sketch plane"));
+            m_status->Refresh();
+        }
+    };
+    m_keys_sketch['Q'] = [this] {
+        // With geometry selected, Q converts THAT geometry (6zic) — the reading
+        // everyone arrives with from other sketchers. With nothing selected it keeps its
+        // old meaning: arm construction for whatever you draw next.
+        if (m_viewport && m_viewport->is_sketching() &&
+            m_viewport->toggle_sketch_construction_selection() > 0) {
+            set_status(_L("Converted the selection between construction and real geometry"));
+            return;
+        }
+        if (m_construction) {
+            m_construction->SetValue(!m_construction->GetValue());
+            if (m_viewport && m_viewport->is_sketching())
+                m_viewport->set_sketch_construction(m_construction->GetValue());
+        }
+    };
+
+    // Shift+letter encoder for the feature-tool shortcuts (registered via FeatVar::key below,
+    // and explicitly for the standalone feature buttons).
+    auto SHIFT = [](int ch) { return ch | SC_SHIFT; };
+
+    // View toggles (single letters, active when no sketch is open): P origin planes, A world
+    // axes, X section view (Alt+Wheel slides the cut). Distinct from Shift+P/Shift+X features.
+    auto status_flag = [this](const wxString& on_msg, const wxString& off_msg, bool on) {
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(on ? on_msg : off_msg);
+        m_status->Refresh();
+    };
+    m_keys_feature['P'] = [this, status_flag] {
+        if (m_viewport) status_flag(_L("Origin planes shown"), _L("Origin planes hidden"),
+                                    m_viewport->toggle_planes());
+    };
+    m_keys_feature['A'] = [this, status_flag] {
+        if (m_viewport) status_flag(_L("World axes shown"), _L("World axes hidden"),
+                                    m_viewport->toggle_axes());
+    };
+    m_keys_feature['X'] = [this] { toggle_section_view(); };   // toggle the single section on/off
+
+    // Home: axonometric view, fitted to the model.
+    //
+    // DesignCanvas::set_view() and fit_view() were written and then never called from
+    // anywhere in the tree, so the Design viewport had NO way back to a standard view —
+    // no key, no button, nothing but orbiting by hand until the model happened to be in
+    // frame. A camera left pointing along the bed plane looks exactly like a renderer
+    // that has failed, which is how this was found.
+    //
+    // Home rather than a letter because every letter A-Z is already a Shift+letter tool
+    // shortcut, and because Home is the reset-the-view key users arrive with. set_view()
+    // already does select_view + zoom_to_volumes, so this is fit and orient in one.
+    m_keys_feature[WXK_HOME] = [this] {
+        if (!m_viewport) return;
+        m_viewport->set_view("iso");
+        set_status(_L("Isometric view, fitted"));
+    };
+
+    // Commit to Plate and the bed toggle were mouse-only: a toolbar button and a checkbox with
+    // no accelerator between them, so neither could be reached from the keyboard at all, nor by
+    // anything driving the keyboard. Ctrl+Shift+P is Plate, Ctrl+Shift+B is Bed; neither
+    // collides with Orca's own Ctrl+Shift+S (Save as) or Ctrl+Shift+G (Print plate).
+    m_keys_feature['P' | SC_SHIFT | SC_CTRL] = [this] { on_commit(); };
+    m_keys_feature['B' | SC_SHIFT | SC_CTRL] = [this] {
+        if (!m_show_bed) return;
+        const bool show = !m_show_bed->GetValue();
+        m_show_bed->SetValue(show);
+        if (m_viewport) m_viewport->set_show_bed(show);
+        set_status(show ? _L("Bed shown") : _L("Bed hidden"));
+    };
+
+    // Shared flyout glyph tint (used by BOTH the feature and sketch toolbars). Re-tint each
+    // design_* glyph to the DropDown's resolved TEXT colour so it reads on the popup in either
+    // theme: text_color is 0x363636, which darkModeColorFor() maps to a light tone in dark mode
+    // (the popup bg is darkModeColorFor(white) = dark) and leaves dark in light mode. The alpha
+    // (the glyph shape) is preserved; only RGB is replaced.
+    // ponytail: wxBitmap(img) drops the HiDPI scale factor (no scale ctor before wx 3.1.6); the
+    // deploy target runs at scale 1.0, so this is exact there.
+    const wxColour drop_icon_col = StateColor::darkModeColorFor(wxColour(0x36, 0x36, 0x36));
+    auto tint = [](wxBitmap bmp, const wxColour& c) -> wxBitmap {
+        if (!bmp.IsOk()) return bmp;
+        wxImage img = bmp.ConvertToImage();
+        if (!img.HasAlpha()) img.InitAlpha();
+        const int w = img.GetWidth(), h = img.GetHeight();
+        for (int y = 0; y < h; ++y)
+            for (int x = 0; x < w; ++x)
+                img.SetRGB(x, y, c.Red(), c.Green(), c.Blue());
+        return wxBitmap(img);
+    };
+
+    // --- Feature group: Sketch / Extrude / Fillet-Chamfer / Hole / Thread / Constrain
+    m_tb_feature = new wxBoxSizer(wxHORIZONTAL);
+    // Buttons are created in whatever order reads best in code, but laid out in the order the
+    // user specified. fadd() records into tb_slot; the flush below the doc group emits them.
+    // A dropdown occupies two entries (button + chevron) that must stay adjacent.
+    std::map<std::string, std::vector<wxWindow*>> tb_slot;
+    // THE TOOLBAR IS CHROME. Every CAD verb is reached from the offer, so a tool's button is
+    // still BUILT — that is what registers its "fly:<family>#<row>" address and its Shift+key —
+    // but it is never placed on the bar. Hiding rather than skipping construction is deliberate:
+    // the addresses are created inside the widget-building loops, so not building would silently
+    // delete 42 verbs from the offer while they still rendered. 7ih records the cleanup
+    // that lets the construction go away too.
+    // What stays: the two doc-row imports (consumed by add_doc below) and the view controls,
+    // which are chrome_only in the atlas and so have no offer row to fall back on.
+    static const std::set<std::string> kBarKeep = { "step", "mesh", "place", "section", "flip" };
+    auto fadd = [&tb_slot](const char* id, wxWindow* w) {
+        if (kBarKeep.count(id) == 0) { w->Hide(); return; }
+        tb_slot[id].push_back(w);
+    };
+    m_tb_feature->Add(caption(_L("FEATURES")), 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 8);
+    {
+        // Onshape-style FEATURE flyouts: same themed-DropDown pattern as the sketch toolbar
+        // (tinted glyphs, Body_14 measure, content-width popup) but each entry runs an
+        // arbitrary action — the existing per-feature handler — instead of selecting a Mode.
+        struct FeatVar { const char* icon; wxString tip; wxString hint; std::function<void()> action; int key = 0; };
+        struct FeatFlyout {
+            std::vector<DropDown::Item> items;   // mainline DropDown is Item-based (text/tip/icon per row)
+            std::vector<std::function<void()>> actions;
+            std::vector<std::string> icon_names;
+            ScalableButton* btn = nullptr;
+            DropDown drop;                 // declared LAST: destroyed before the vector it references
+            FeatFlyout() : drop(items) {}
+        };
+        auto feat_dropdown = [&](const char* id, const char* def_icon, const wxString& grp, std::vector<FeatVar> vars) {
+            // REGISTER FIRST, BUILD SECOND. A verb's two addresses — "fly:<family>#<row>" for the
+            // offer and its Shift+key — are data. The widget is one door onto them, not their
+            // owner. Doing this before any wxWindow exists is what lets the build below be skipped
+            // outright for a family the bar no longer carries. It used to sit INSIDE the build
+            // loop, so a retired family still had to be constructed and then Hide()n: skipping it
+            // would have deleted 42 verbs from the offer while their rows still rendered and did
+            // nothing when picked. 7ih.
+            // Keyed on "fly:<family>#<row>" so the generated table can name a variant without the
+            // item struct growing a field at 26 call sites.
+            for (size_t i = 0; i < vars.size(); ++i) {
+                if (vars[i].key) m_keys_feature[vars[i].key] = vars[i].action;   // key runs the same action
+                m_verb_actions["fly:" + std::string(id) + "#" + std::to_string(i)] = vars[i].action;
+            }
+            if (kBarKeep.count(id) == 0)
+                return;   // reached from the offer alone — no button, no chevron, no popup
+            auto* b = icon_btn(def_icon, grp);
+            b->SetFont(Label::Body_14);   // measure popup labels in the popup's font (no truncation)
+            auto fo = std::make_shared<FeatFlyout>();
+            for (auto& v : vars) {
+                DropDown::Item it;
+                it.text = v.tip;
+                it.tip  = v.hint;
+                it.icon = tint(create_scaled_bitmap(v.icon, m_form, 18), drop_icon_col);
+                fo->items.push_back(it);
+                fo->actions.push_back(std::move(v.action));
+                fo->icon_names.emplace_back(v.icon);
+            }
+            fo->btn = b;
+            fo->drop.Create(b);
+            fo->drop.SetUseContentWidth(true, false);
+            fo->drop.Invalidate(true);
+            FeatFlyout* fp = fo.get();
+            fo->drop.Bind(wxEVT_COMBOBOX, [this, fp](wxCommandEvent& e) {
+                int i = e.GetInt();
+                if (i >= 0 && i < (int) fp->actions.size()) {
+                    fp->btn->SetBitmap_(fp->icon_names[i]);   // button face follows the last pick
+                    fp->actions[i]();
+                    set_active_tool_btn(fp->btn);
+                }
+            });
+            b->Bind(wxEVT_BUTTON, [b, fp](wxCommandEvent&) {
+                // Force a fresh content measure before Popup() (ComboBox does this via the
+                // private autoPosition()); otherwise the popup maps at a stale narrow size.
+                fp->drop.Invalidate(true);
+                fp->drop.SetUseContentWidth(false, false);
+                fp->drop.SetUseContentWidth(true, false);
+                wxPoint pos = b->ClientToScreen(wxPoint(0, -6));
+                fp->drop.Position(pos, wxSize(0, b->GetSize().y + 12));
+                fp->drop.Popup();
+            });
+            m_flyout_keepalive.push_back(fo);
+            fadd(id, b);
+            auto* chev = new wxStaticText(m_toolbar, wxID_ANY, wxString::FromUTF8("\xE2\x96\xBE"));
+            chev->SetForegroundColour(dp_sec_text());
+            chev->SetFont(Label::Body_9);
+            fadd(id, chev);
+        };
+
+        auto* b_sketch = icon_btn("design_sketch", _L("Sketch"));
+        // Sketch means a tool. Pressing it used to set the mode and then ask, unconditionally,
+        // for the very thing the user had just done — click XZ, read "XZ plane selected, press
+        // Sketch", press Sketch, and be told to click a reference plane. The plane was never
+        // lost (m_ref_plane holds it and begin_sketch captures it when the first tool is armed);
+        // the sentence was simply false, and with right-click excluded in sketch mode there was
+        // no door to the tools at all, so the only way on was the toolbar this tab is retiring.
+        std::function<void()> act_sketch = [this] {
+            set_ui_mode(UiMode::Sketch);
+            wxString where;
+            const bool have_plane = sketch_plane_target(where);
+            m_status->SetForegroundColour(wxNullColour);
+            set_status(have_plane
+                ? wxString::Format(_L("Sketching on %s — pick a tool"), where)
+                : _L("Click a face or a reference plane in the viewport, then a sketch tool"));
+            m_status->Refresh();
+            if (m_sketch_hint) {   // the card must agree with the status line, not argue with it
+                m_sketch_hint->SetLabel(have_plane
+                    ? wxString::Format(_L("Drawing on %s.\nPick a tool, or press Menu for the list."), where)
+                    : _L("Click a face or a reference plane, then a sketch tool."));
+                m_sketch_hint->Refresh();
+                m_cards->Layout();
+            }
+            // Hand over the tools rather than naming them in a status line. CallAfter so the
+            // mode change has settled before a modal menu takes the loop; the menu carries each
+            // tool's shortcut, so pressing the key instead of picking a row costs nothing.
+            if (have_plane)
+                CallAfter([this] { show_offer_menu(offer_anchor()); });
+        };
+        b_sketch->Bind(wxEVT_BUTTON, [act_sketch](wxCommandEvent&) { act_sketch(); });
+        m_keys_feature[SHIFT('S')] = act_sketch;
+        fadd("sketch", b_sketch);
+        // Add material: every feature that grows new solid material — from a profile
+        // (extrude/revolve/sweep/loft), from a face (thicken) or from a line (rib).
+        feat_dropdown("material", "design_extrude", _L("Add material (extrude / revolve / sweep / loft / thicken / rib)"), {
+            {"design_extrude", _L("Extrude"), _L("Extrude a sketch profile, or push/pull a picked face"),
+             [this] {
+                // Onshape push/pull: an explicitly picked solid face (Face-level cycle, no loop
+                // selected) is extruded as the profile — this takes priority over re-extruding an
+                // already-consumed sketch (resolve_extrude_sketch always returns the last Sketch).
+                if (m_sel_solid_face >= 0 && !m_doc.body.IsNull() && m_sel_sketch_region < 0) {
+                    m_extrude_face_src   = m_sel_solid_face;
+                    m_extrude_sketch_ref = -1;
+                    open_tool(Tool::Extrude);
+                    return;
+                }
+                m_extrude_face_src   = -1;   // ordinary sketch/loop extrude
+                m_extrude_sketch_ref = resolve_extrude_sketch();
+                if (m_extrude_sketch_ref < 0) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Create a sketch, or pick a solid face, first"));
+                    m_status->Refresh();
+                    return;
+                }
+                open_tool(Tool::Extrude);
+             }, SHIFT('E')},
+            {"design_revolve", _L("Revolve"), _L("Revolve a profile about an axis"),
+             [this] {
+                m_revolve_sketch_ref = resolve_extrude_sketch();
+                if (m_revolve_sketch_ref < 0) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Create a sketch profile to revolve first"));
+                    m_status->Refresh();
+                    return;
+                }
+                open_tool(Tool::Revolve);
+             }, SHIFT('R')},
+            {"design_sweep", _L("Sweep"), _L("Sweep a profile along a path"),
+             [this] {
+                m_sweep_profile_ref = resolve_extrude_sketch();
+                m_sweep_path_ref    = -1;   // fresh sweep: default the picker to the first sketch
+                if (m_sweep_profile_ref < 0) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Create a profile sketch to sweep first"));
+                    m_status->Refresh();
+                    return;
+                }
+                open_tool(Tool::Sweep);
+             }, SHIFT('W')},
+            {"design_loft", _L("Loft"), _L("Loft (skin) between two or more profiles"),
+             [this] {
+                // Loft skins 2+ profile sketches; need at least two to be meaningful.
+                int n = 0;
+                for (const auto& f : m_doc.features)
+                    if (f.type == CadFeatureType::Sketch) ++n;
+                if (n < 2) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Create at least two profile sketches to loft"));
+                    m_status->Refresh();
+                    return;
+                }
+                m_loft_refs.clear();   // fresh loft: nothing pre-checked
+                open_tool(Tool::Loft);
+             }, SHIFT('L')},
+            {"design_thicken", _L("Thicken"), _L("Offset a solid face into a thin plate (new body)"),
+             [this] {
+                if (m_doc.bodies.empty()) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Thicken needs a solid body — add or import one first"));
+                    m_status->Refresh();
+                    return;
+                }
+                {
+                    m_thicken_body->Clear();
+                    for (size_t i = 0; i < m_doc.bodies.size(); ++i) {
+                        const std::string& n = m_doc.bodies[i].name;
+                        m_thicken_body->Append(n.empty() ? wxString::Format(_L("Body %zu"), i + 1) : wxString::FromUTF8(n));
+                    }
+                    if (m_thicken_body->GetCount() > 0)
+                        m_thicken_body->SetSelection(std::min(selected_body_default(),
+                                                       int(m_thicken_body->GetCount()) - 1));
+                }
+                // KEEP a face the user has already picked. Clearing it unconditionally was right
+                // when the only door was a toolbar button, which carries no selection: you pressed
+                // Thicken and were then asked to point at something. Reached from the offer the
+                // verb is invoked ON a face, so discarding it opened the card reading "(pick a
+                // solid face)" over an immediate "thicken: face not found" — the user pointed at
+                // the face and the card said it could not find one. kgx.
+                // The index is per-body, so it only survives if the body combo landed on the body
+                // it came from; selected_body_default() above returns exactly that when valid.
+                if (m_thicken_body->GetSelection() != m_sel_solid_body)
+                    m_sel_solid_face = -1;
+                open_tool(Tool::Thicken);   // syncs m_thicken_face_label from m_sel_solid_face
+             }, 0},
+            {"design_rib", _L("Rib"), _L("Grow a thin wall from an open sketch line, fused to a body"),
+             [this] {
+                if (m_doc.bodies.empty()) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Rib needs a solid body — add or import one first"));
+                    m_status->Refresh();
+                    return;
+                }
+                {
+                    m_rib_body->Clear();
+                    for (size_t i = 0; i < m_doc.bodies.size(); ++i) {
+                        const std::string& n = m_doc.bodies[i].name;
+                        m_rib_body->Append(n.empty() ? wxString::Format(_L("Body %zu"), i + 1) : wxString::FromUTF8(n));
+                    }
+                    if (m_rib_body->GetCount() > 0)
+                        m_rib_body->SetSelection(std::min(selected_body_default(),
+                                                       int(m_rib_body->GetCount()) - 1));
+                }
+                {
+                    m_rib_sketch->Clear();
+                    for (int i = 0; i < int(m_doc.features.size()); ++i) {
+                        // 3-arg Append: ComboBox's own Append(text, bitmap) hides
+                        // wxItemContainer's (text, void*) — see the Sweep picker.
+                        // Project features too: they carry Line entities the kernel ribs from
+                        // just like a drawn sketch, so a projected body edge is a valid path.
+                        if (m_doc.features[i].type == CadFeatureType::Sketch ||
+                            m_doc.features[i].type == CadFeatureType::Project)
+                            combo_append_index(m_rib_sketch, wxString::FromUTF8(m_doc.features[i].name), i);
+                    }
+                    if (m_rib_sketch->GetCount() > 0) m_rib_sketch->SetSelection(0);
+                    else {
+                        m_status->SetForegroundColour(wxColour(235, 110, 110));
+                        set_status(_L("Create a sketch with an open line first"));
+                        m_status->Refresh();
+                        return;
+                    }
+                }
+                open_tool(Tool::Rib);
+             }, 'R'},   // plain R, not SHIFT+R (that is Revolve): every SHIFT letter A-Z
+                       // was already taken, and the feature map already carries unshifted
+                       // keys (P, A, X). Rib was the only verb in this dropdown with no
+                       // shortcut at all, which also made its card unreachable to the rig.
+        });
+
+        auto* b_pattern = icon_btn("design_pattern", _L("Pattern"));
+        std::function<void()> act_pattern = [this] {
+            // Pattern replicates an existing body — needs at least one solid.
+            if (m_doc.bodies.empty()) {
+                m_status->SetForegroundColour(wxColour(235, 110, 110));
+                set_status(_L("Create a solid body to pattern first"));
+                m_status->Refresh();
+                return;
+            }
+            open_tool(Tool::Pattern);
+        };
+        b_pattern->Bind(wxEVT_BUTTON, [act_pattern](wxCommandEvent&) { act_pattern(); });
+        m_keys_feature[SHIFT('N')] = act_pattern;
+        fadd("pattern", b_pattern);
+        m_body_gates.push_back({b_pattern, 1, b_pattern->GetToolTipText(),
+                                _L("Pattern — needs a solid body to replicate")});
+
+        // Surface: sheet-body tools (extrude / revolve / loft / fill / offset / thicken)
+        // The drawer BUTTON is design_surface, not design_extrude: sharing a face with the
+        // Add-material drawer made the two buttons indistinguishable in the bar. The entries
+        // inside may reuse the solid glyphs — a menu row carries its own text label.
+        feat_dropdown("surface", "design_surface", _L("Surface (extrude / revolve / loft / fill / offset / thicken)"), {
+            {"design_extrude", _L("Surface Extrude"), _L("Extrude a sketch into a sheet body (no end caps)"),
+             [this] {
+                m_surf_extrude_sketch_ref = resolve_extrude_sketch();
+                if (m_surf_extrude_sketch_ref < 0) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Create a sketch first"));
+                    m_status->Refresh();
+                    return;
+                }
+                open_tool(Tool::SurfaceExtrude);
+             }, SHIFT('G')},
+            {"design_revolve", _L("Surface Revolve"), _L("Revolve a sketch profile into a sheet body"),
+             [this] {
+                m_surf_revolve_sketch_ref = resolve_extrude_sketch();
+                if (m_surf_revolve_sketch_ref < 0) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Create a sketch profile to revolve first"));
+                    m_status->Refresh();
+                    return;
+                }
+                open_tool(Tool::SurfaceRevolve);
+             }, SHIFT('J')},
+            {"design_loft", _L("Surface Loft"), _L("Loft (skin) between 2+ profiles, open (no end caps)"),
+             [this] {
+                int n = 0;
+                for (const auto& f : m_doc.features)
+                    if (f.type == CadFeatureType::Sketch) ++n;
+                if (n < 2) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Create at least two profile sketches to loft"));
+                    m_status->Refresh();
+                    return;
+                }
+                m_surf_loft_refs.clear();
+                open_tool(Tool::SurfaceLoft);
+             }, SHIFT('O')},
+            {"design_surface", _L("Surface Fill"), _L("Fill a sketch boundary with a smooth face"),
+             [this] {
+                m_surf_fill_sketch_ref = resolve_extrude_sketch();
+                if (m_surf_fill_sketch_ref < 0) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Create a sketch profile to fill first"));
+                    m_status->Refresh();
+                    return;
+                }
+                open_tool(Tool::SurfaceFill);
+             }, SHIFT('Q')},
+            {"design_offset", _L("Surface Offset"), _L("Offset a sheet body's shell by a signed distance"),
+             [this] {
+                populate_sheet_body_choices(m_surf_offset_body);
+                if (m_surf_offset_body->GetCount() == 0) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("No sheet body to offset — create a surface feature first"));
+                    m_status->Refresh();
+                    return;
+                }
+                open_tool(Tool::SurfaceOffset);
+             }, SHIFT('U')},
+            {"design_thicken", _L("Thicken Surface"), _L("Thicken a sheet body into a solid"),
+             [this] {
+                populate_sheet_body_choices(m_surf_thicken_body);
+                if (m_surf_thicken_body->GetCount() == 0) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("No sheet body to thicken — create a surface feature first"));
+                    m_status->Refresh();
+                    return;
+                }
+                open_tool(Tool::ThickenSurface);
+             }, SHIFT('V')},
+        });
+
+        feat_dropdown("plane", "design_plane", _L("Datum / Curve (plane / axis / coord sys / helix / project)"), {
+            {"design_plane", _L("Plane"), _L("Reference plane (offset / tilt / midplane / tangent / two edges / coincident)"),
+             [this] {
+                 populate_plane_choices(m_plane_base);
+                 reset_plane_refs();
+                 open_tool(Tool::Plane);
+             }, SHIFT('P')},
+            {"design_line", _L("Axis"), _L("Datum axis (two points, face normal, cylinder centerline, two planes, along edge)"),
+             [this] {
+                 populate_plane_choices(m_axis_plane_a);
+                 populate_plane_choices(m_axis_plane_b);
+                 reset_axis_refs();
+                 open_tool(Tool::Axis);
+             }, SHIFT('A')},
+            {"design_point", _L("Coord Sys"), _L("Datum coordinate system (world point, or face + direction edge)"),
+             [this] {
+                 reset_coordsys_refs();
+                 open_tool(Tool::CoordSys);
+             }, SHIFT('C')},
+            {"design_thread", _L("Helix"), _L("Helical curve (spring path) — use as a sweep path for coils / springs / augers"),
+             [this] {
+                 populate_plane_choices(m_helix_plane);
+                 open_tool(Tool::Helix);
+             }, 0},
+            // Project belongs here, not in Dress-up: it consumes a body but PRODUCES sketch
+            // geometry, so it is reference/curve creation like the four above, not a finishing op.
+            {"design_sketch", _L("Project"), _L("Project body edges onto a plane as sketch entities"),
+             [this] {
+                if (m_doc.bodies.empty()) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Project needs a body — add or import one first"));
+                    m_status->Refresh();
+                    return;
+                }
+                {
+                    m_proj_source_body->Clear();
+                    for (size_t i = 0; i < m_doc.bodies.size(); ++i) {
+                        const std::string& n = m_doc.bodies[i].name;
+                        m_proj_source_body->Append(n.empty() ? wxString::Format(_L("Body %zu"), i + 1) : wxString::FromUTF8(n));
+                    }
+                    if (m_proj_source_body->GetCount() > 0)
+                        m_proj_source_body->SetSelection(std::min(selected_body_default(),
+                                                       int(m_proj_source_body->GetCount()) - 1));
+                }
+                populate_plane_choices(m_proj_plane);
+                m_sel_solid_face = -1;
+                m_proj_face_label->SetLabel(_L("(all edges)"));
+                open_tool(Tool::Project);
+             }, 0},
+        });
+
+        // Placement — operations that MOVE a body without changing its shape. Transform and
+        // Mirror place one body directly; a Mate places one body relative to another. They were
+        // in Dress-up (fillet/draft/shell) and Datum, which mixed shape-finishing and reference
+        // geometry with rigid-body placement.
+        // Own slot id: "place" is taken by the Place-on-Face button, and put() formats slot
+        // item 0 as the control and every later item as its chevron, so sharing a slot would
+        // bottom-align this drawer's button like a chevron.
+        feat_dropdown("placement", "design_move", _L("Placement (transform / mirror / mate)"), {
+            {"design_move", _L("Transform"), _L("Move and/or rotate an existing body"),
+             [this] {
+                if (m_doc.bodies.empty()) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Transform needs a body — add or import one first"));
+                    m_status->Refresh();
+                    return;
+                }
+                {
+                    m_xf_body->Clear();
+                    for (size_t i = 0; i < m_doc.bodies.size(); ++i) {
+                        const std::string& n = m_doc.bodies[i].name;
+                        m_xf_body->Append(n.empty() ? wxString::Format(_L("Body %zu"), i + 1) : wxString::FromUTF8(n));
+                    }
+                    if (m_xf_body->GetCount() > 0)
+                        m_xf_body->SetSelection(std::min(selected_body_default(),
+                                                       int(m_xf_body->GetCount()) - 1));
+                }
+                open_tool(Tool::Transform);
+             }, SHIFT('Y')},
+            {"design_mirror", _L("Mirror"), _L("Reflect a body about a plane"),
+             [this] {
+                if (m_doc.bodies.empty()) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Mirror needs a body — add or import one first"));
+                    m_status->Refresh();
+                    return;
+                }
+                {
+                    m_mirror_body->Clear();
+                    for (size_t i = 0; i < m_doc.bodies.size(); ++i) {
+                        const std::string& n = m_doc.bodies[i].name;
+                        m_mirror_body->Append(n.empty() ? wxString::Format(_L("Body %zu"), i + 1) : wxString::FromUTF8(n));
+                    }
+                    if (m_mirror_body->GetCount() > 0)
+                        m_mirror_body->SetSelection(std::min(selected_body_default(),
+                                                       int(m_mirror_body->GetCount()) - 1));
+                }
+                populate_plane_choices(m_mirror_plane);
+                open_tool(Tool::Mirror);
+             }, SHIFT('Z')},
+            {"design_c_coincident", _L("Mate"), _L("Assembly: align two CoordSys features (fastened, planar, revolute, slider, cylindrical)"),
+             [this] {
+                 open_tool(Tool::Mate);
+             }, 0},
+        });
+
+        auto* b_boolean = icon_btn("design_boolean", _L("Boolean (combine bodies)"));
+        std::function<void()> act_boolean = [this] { on_boolean_tool(); };
+        b_boolean->Bind(wxEVT_BUTTON, [act_boolean](wxCommandEvent&) { act_boolean(); });
+        m_keys_feature[SHIFT('B')] = act_boolean;
+        fadd("boolean", b_boolean);
+        m_body_gates.push_back({b_boolean, 2, b_boolean->GetToolTipText(),
+                                _L("Boolean — needs two solid bodies to combine")});
+
+        auto* b_cut = icon_btn("design_cut", _L("Cut (split a body with a plane)"));
+        std::function<void()> act_cut = [this] {
+            // A plane cut needs at least one solid to slice.
+            if (m_doc.bodies.empty()) {
+                m_status->SetForegroundColour(wxColour(235, 110, 110));
+                set_status(_L("Create a solid body to cut first"));
+                m_status->Refresh();
+                return;
+            }
+            populate_plane_choices(m_cut_plane);
+            populate_body_choices();
+            open_tool(Tool::Cut);
+        };
+        b_cut->Bind(wxEVT_BUTTON, [act_cut](wxCommandEvent&) { act_cut(); });
+        m_keys_feature[SHIFT('X')] = act_cut;
+        fadd("cut", b_cut);
+        m_body_gates.push_back({b_cut, 1, b_cut->GetToolTipText(),
+                                _L("Cut — needs a solid body to slice")});
+
+        // Color — override the selected body's display colour (per-body, survives recompute).
+        auto* b_color = icon_btn("color_palette", _L("Color — set the selected body's display colour"));
+        b_color->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_set_body_color(); });
+        fadd("color", b_color);
+        m_verb_actions["btn:colour"] = [this] { on_set_body_color(); };
+        m_verb_actions["btn:delete"] = [this] { on_delete_feature(); };
+        // Rename exists as a slow double-click on the row too, but the offer is this tab's only
+        // tool vocabulary — a rename that only a double-click reveals is not discoverable, and
+        // the row IS the object, so it belongs in the menu (and on F2) as well as on the row.
+        auto rename_feature = [this] {
+            // A BODY renames ITSELF. The earlier version resolved the body to
+            // CadBody::source_feature and renamed that feature, which is the wrong object: a
+            // body accumulates many features and the first one is not its name. The body row
+            // is editable now (CadBody::user_name), so the verb opens the editor there.
+            const int b = tree_body_selection();
+            if (b >= 0 && b < int(m_tree_body_items.size())) {
+                const wxTreeItemId row = m_tree_body_items[b];
+                // After the menu, not inside it: an editor opened from within PopupMenu's
+                // nested loop never appears.
+                CallAfter([this, row] { m_parts->SetFocus(); m_parts->EditLabel(row); });
+                return;
+            }
+            const int sel = tree_selection();
+            if (sel != wxNOT_FOUND && sel < int(m_tree_items.size())) {
+                const wxTreeItemId row = m_tree_items[sel];
+                CallAfter([this, row] { m_tree->SetFocus(); m_tree->EditLabel(row); });
+            } else {
+                m_status->SetForegroundColour(wxNullColour);   // "nothing selected" is not an error
+                set_status(_L("Select a feature, or a body, first — then rename it"));
+                m_status->Refresh();
+            }
+        };
+        m_verb_actions["btn:rename"] = rename_feature;
+        m_keys_feature[WXK_F2]        = rename_feature;   // a function key, so no letter space spent
+        // The sketch's own Delete. It used to share "btn:delete" with the feature tree, so
+        // choosing Delete on a selected LINE ran on_delete_feature() and removed a tree row (or
+        // nothing) while the line stayed — the reported "I click a line and cannot remove it".
+        m_verb_actions["btn:sk_delete"] = [this] {
+            if (m_viewport && m_viewport->is_sketching())
+                m_viewport->delete_selected_sketch_entities();
+            else
+                on_delete_feature();
+        };
+
+        m_verb_actions["btn:delete_body"] = [this] { on_delete_body(); };
+        m_verb_actions["btn:edit"]   = [this] { on_edit_feature(); };
+        m_verb_actions["btn:mass"]   = [this] { on_mass_properties(); };
+        // Reachable from the offer menu on a SELECTED SKETCH, not only from the toolbar icon.
+        // A user evaluating against Onshape reported that "adding constraints seems to be
+        // missing" — with nineteen constraint types and a solver shipped. The only paths in
+        // were an icon-only button and a sketch-mode-only offer row filed under "Reference",
+        // so after finishing a sketch there was no affordance where users actually look.
+        m_verb_actions["btn:constrain"] = [this] {
+            on_begin_constrain();
+            if (m_viewport && (m_viewport->is_constraining() || m_viewport->is_constraining_entities()))
+                set_ui_mode(UiMode::Constrain);
+        };
+
+        // Dress-up: finishing operations on the faces and edges of an existing solid — nothing
+        // that moves a body (see the Placement drawer) and nothing that creates geometry.
+        feat_dropdown("dressup", "design_dressup", _L("Fillet / chamfer / draft / shell / delete face"), {
+            {"design_dressup", _L("Fillet / Chamfer"), _L("Round or bevel a picked edge"),
+             [this] { open_tool(Tool::Dressup); }, SHIFT('F')},
+            {"design_draft", _L("Draft (taper a face)"), _L("Tilt a picked face by a draft angle"),
+             [this] { open_tool(Tool::Draft); }, SHIFT('D')},
+            {"design_shell", _L("Shell"), _L("Hollow the body to a wall thickness, opening a picked face"),
+             [this] { open_tool(Tool::Shell); }, SHIFT('K')},
+            {"design_delete", _L("Delete Face"), _L("Remove faces from a body and heal the solid"),
+             [this] {
+                if (m_doc.bodies.empty()) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Delete Face needs a body — add or import one first"));
+                    m_status->Refresh();
+                    return;
+                }
+                {
+                    m_del_face_body->Clear();
+                    for (size_t i = 0; i < m_doc.bodies.size(); ++i) {
+                        const std::string& n = m_doc.bodies[i].name;
+                        m_del_face_body->Append(n.empty() ? wxString::Format(_L("Body %zu"), i + 1) : wxString::FromUTF8(n));
+                    }
+                    if (m_del_face_body->GetCount() > 0)
+                        m_del_face_body->SetSelection(std::min(selected_body_default(),
+                                                       int(m_del_face_body->GetCount()) - 1));
+                }
+                m_del_faces.clear();
+                m_del_face_list->SetLabel(_L("(none)"));
+                open_tool(Tool::DeleteFace);
+             }, 0},
+        });
+
+        // Hole / Thread — drilling into a solid (both face-aware)
+        feat_dropdown("hole", "design_hole", _L("Hole / thread"), {
+            {"design_hole", _L("Hole"), _L("Drill a hole, centred on a picked face or placed on a plane"),
+             [this] {
+                // #2: drill on the picked solid face, centred on it (origin = face centroid,
+                // normal = inward). Otherwise fall back to the plane dropdown. m_hole_x/y then
+                // read as the offset from the face centre (editable for precise placement).
+                m_hole_on_face   = false;
+                m_hole_face_body = -1;
+                m_hole_has_bounds = false;
+                set_hole_target_label(-1);
+                // Use the explicitly-picked face; otherwise default to the top face of the
+                // selected (or first) body so the hole lands on the surface being viewed, not
+                // the z=0 datum under the model. The XY/XZ/YZ dropdown still overrides.
+                int hb = m_sel_solid_body, hf = m_sel_solid_face;
+                if (hf < 0 && !m_doc.bodies.empty()) {
+                    hb = (hb >= 0 && hb < int(m_doc.bodies.size())) ? hb : 0;
+                    hf = top_face_index_of(m_doc.bodies[hb].shape);
+                }
+                if (hf >= 0 && hb >= 0 && hb < int(m_doc.bodies.size())) {
+                    const TopoDS_Face face = GeometryEngine::face_by_index(
+                        m_doc.bodies[hb].shape, hf);
+                    if (!face.IsNull()) {
+                        m_hole_face_plane = face_plane_inward(face);
+                        m_hole_on_face    = true;
+                        m_hole_face_body  = hb;
+                        set_hole_target_label(hf);   // may be the top-face default, not a pick
+                        // Face (u,v) extents so the hole dims read from the sides (#2 Part B).
+                        m_hole_has_bounds = GeometryEngine::face_plane_bounds(
+                            face, m_hole_face_plane.origin, m_hole_face_plane.x_axis,
+                            m_hole_face_plane.y_axis, m_hole_umin, m_hole_umax, m_hole_vmin, m_hole_vmax);
+                        if (m_hole_x) m_hole_x->SetValue(0.0);   // start at the face centre
+                        if (m_hole_y) m_hole_y->SetValue(0.0);
+                        // Reflect the face's orientation in the dropdown so it doesn't keep
+                        // showing a stale "XY" while the hole actually drills on this face.
+                        if (m_hole_plane)
+                            m_hole_plane->SetSelection(index_from_plane(m_hole_face_plane));
+                    }
+                }
+                open_tool(Tool::Hole);
+             }, SHIFT('H')},
+            {"design_thread", _L("Thread"), _L("Thread a cylindrical surface (inner bore / outer) or a circular edge"),
+             [this] {
+                // Driven by a picked CYLINDRICAL surface (inner bore = internal, outer = external)
+                // OR a circular EDGE (a cylinder's rim) — axis + diameter come from the geometry, so
+                // the user never types a radius. The diameter field shows what was derived.
+                m_thread_on_face   = false;
+                m_thread_face_body = -1;
+                set_thread_target_label(-1, -1);
+                GeometryEngine::CylinderFace cf;
+                bool from_face = false;   // which of the two the cylinder actually came from
+                if (m_sel_solid_body >= 0 && m_sel_solid_body < int(m_doc.bodies.size())) {
+                    const TopoDS_Shape& shape = m_doc.bodies[m_sel_solid_body].shape;
+                    if (m_sel_solid_face >= 0)
+                        cf = GeometryEngine::cylinder_of_face(GeometryEngine::face_by_index(shape, m_sel_solid_face));
+                    from_face = cf.ok;
+                    if (!cf.ok && m_sel_solid_edge >= 0)
+                        cf = GeometryEngine::circle_of_edge(GeometryEngine::edge_by_index(shape, m_sel_solid_edge));
+                }
+                if (cf.ok) {
+                    SketchPlane p;                       // plane on the axis (origin at the base)
+                    p.origin = cf.base;
+                    p.normal = cf.axis;
+                    const Vec3d ref = std::abs(cf.axis.z()) < 0.9 ? Vec3d(0, 0, 1) : Vec3d(1, 0, 0);
+                    p.x_axis = ref.cross(cf.axis).normalized();
+                    p.y_axis = cf.axis.cross(p.x_axis).normalized();
+                    m_thread_face_plane = p;
+                    m_thread_on_face    = true;
+                    m_thread_face_body  = m_sel_solid_body;
+                    set_thread_target_label(from_face ? m_sel_solid_face : -1,
+                                            from_face ? -1 : m_sel_solid_edge);
+                    infer_thread_spec(2.0 * cf.radius);   // M diameter + pitch + depth from the cylinder
+                    if (m_thread_height && cf.height > 1e-6) m_thread_height->SetValue(cf.height);
+                    if (m_thread_internal) m_thread_internal->SetValue(cf.internal);
+                    if (m_thread_x) m_thread_x->SetValue(0.0);   // on the axis
+                    if (m_thread_y) m_thread_y->SetValue(0.0);
+                } else if (m_sel_solid_face >= 0 || m_sel_solid_edge >= 0) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Pick a cylindrical surface (bore / outer) or a circular edge for a thread"));
+                    m_status->Refresh();
+                }
+                open_tool(Tool::Thread);
+             }, SHIFT('T')},
+        });
+        // Text / SVG insert tools live in the SKETCH toolbar (they produce 2D profiles =
+        // sketches), not here. STEP stays in Features: it imports a whole B-rep solid.
+        // Import STEP — standalone: a STEP comes in as a whole editable B-rep body, not a profile.
+        auto* b_step = icon_btn("design_step", _L("Import STEP (editable B-rep solid)"));
+        b_step->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_import_step(); });
+        m_keys_feature[SHIFT('I')] = [this] { on_import_step(); };
+        fadd("step", b_step);
+        // Import mesh — same destination as STEP (an editable B-rep body), but the geometry has
+        // to be reconstructed from triangles first (GeometryEngine::mesh_to_brep).
+        auto* b_mesh = icon_btn("param_triangles", _L("Import mesh (STL/OBJ) as an editable B-rep solid"));
+        b_mesh->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_import_mesh(); });
+        m_keys_feature[SHIFT('M')] = [this] { on_import_mesh(); };
+        fadd("mesh", b_mesh);
+        auto* b_constrain = icon_btn("design_constrain", _L("Constrain selected sketch"));
+        b_constrain->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) {
+            on_begin_constrain();
+            if (m_viewport && (m_viewport->is_constraining() || m_viewport->is_constraining_entities()))
+                set_ui_mode(UiMode::Constrain);
+        });
+        fadd("constrain", b_constrain);
+    }
+
+    // --- Sketch group: plane + entity tools + Construction + Finish
+    m_tb_sketch = new wxBoxSizer(wxHORIZONTAL);
+    // Sketch carries the most tools of any mode: pack it tight (no inter-icon gap) so the
+    // whole entity palette fits without crowding the right-hand actions.
+    // Same for the sketch bar: the drawing tools live in the offer. Only Delete selected stays,
+    // via sadd_bar. sadd() still runs so sk_key/fly: registrations and the flyout popups survive.
+    auto sadd     = [](wxWindow* w) { w->Hide(); };
+    auto sadd_bar = [this](wxWindow* w) { m_tb_sketch->Add(w, 0, wxALIGN_CENTER_VERTICAL); };
+    m_tb_sketch->Add(caption(_L("SKETCH")), 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 8);
+    {
+        // The plane/orientation choice lives in the docked Sketch card (Phase 3),
+        // not in the toolbar; the toolbar carries only the drawing tools.
+        auto skbtn = [&](const char* icon, DesignSketchTool::Mode mode,
+                         const wxString& tip, const wxString& hint) {
+            auto* b = icon_btn(icon, tip);
+            b->Bind(wxEVT_BUTTON, [select_tool, mode, hint](wxCommandEvent&) { select_tool(mode, hint); });
+            sadd(b);
+        };
+        // Onshape-style family flyout, rendered with Orca's themed DropDown
+        // (white/teal selector, #DBDBDB border, HarmonyOS Body_14) — same widget
+        // as the settings combo dropdowns. The button shows the current variant's
+        // icon; clicking drops the variants; a small chevron marks it as a group.
+        struct SkVar { const char* icon; DesignSketchTool::Mode mode; wxString tip; wxString hint; };
+        struct ToolFlyout {
+            std::vector<DropDown::Item> items;   // mainline DropDown is Item-based (text/tip/icon per row)
+            std::vector<DesignSketchTool::Mode> modes;
+            std::vector<wxString> hints;
+            std::vector<std::string> icon_names;
+            ScalableButton* btn = nullptr;
+            DropDown drop;                 // declared LAST: destroyed before the vector it references
+            ToolFlyout() : drop(items) {}
+        };
+        auto dropdown = [&](const char* def_icon, const wxString& grp, std::vector<SkVar> vars) {
+            // Register first, build second — the same law as feat_dropdown, for the same reason.
+            // The offer reaches each tool by its ratified address; without these the offer could
+            // name a family but only ever arm its FIRST tool: picking "Rectangle" ran key:R and
+            // gave you a corner rectangle, with oblique and rounded unreachable. Keyed on the icon
+            // id (already unique per family) so no call site grows an argument. 6vs.
+            for (size_t i = 0; i < vars.size(); ++i) {
+                const DesignSketchTool::Mode mode = vars[i].mode;
+                const wxString               hint = vars[i].hint;
+                m_verb_actions["fly:" + std::string(def_icon) + "#" + std::to_string(i)] =
+                    [mode, hint, select_tool] { select_tool(mode, hint); };
+            }
+            if (kBarKeep.count(def_icon) == 0)
+                return;   // the drawing tools live in the offer; nothing of this family is built
+            auto* b = icon_btn(def_icon, grp);
+            // messureSize() measures labels with the PARENT's font (this button) but the
+            // popup draws them in Body_14 — so an under-sized button font truncates rows.
+            // The button is icon-only (no label), so giving it Body_14 is invisible and
+            // makes the content-width measure match the draw.
+            b->SetFont(Label::Body_14);
+            auto fo = std::make_shared<ToolFlyout>();
+            for (auto& v : vars) {
+                DropDown::Item it;
+                it.text = v.tip;
+                it.tip  = v.hint;
+                it.icon = tint(create_scaled_bitmap(v.icon, m_form, 18), drop_icon_col);
+                fo->items.push_back(it);
+                fo->modes.push_back(v.mode);
+                fo->hints.push_back(v.hint);
+                fo->icon_names.emplace_back(v.icon);
+            }
+            fo->btn = b;
+            fo->drop.Create(b);
+            fo->drop.SetUseContentWidth(true, false);
+            fo->drop.Invalidate(true);
+            ToolFlyout* fp = fo.get();
+            fo->drop.Bind(wxEVT_COMBOBOX, [this, fp, select_tool](wxCommandEvent& e) {
+                int i = e.GetInt();
+                if (i >= 0 && i < (int) fp->modes.size()) {
+                    fp->btn->SetBitmap_(fp->icon_names[i]);
+                    select_tool(fp->modes[i], fp->hints[i]);
+                    set_active_tool_btn(fp->btn);
+                }
+            });
+            b->Bind(wxEVT_BUTTON, [b, fp](wxCommandEvent&) {
+                // autoPosition()/messureSize() are private; ComboBox calls them before
+                // Popup() so the window is sized to its content first. Without that the
+                // popup maps at a stale narrow size and labels ellipsize ("Oblique
+                // rectang…"). Force a fresh content measure by toggling use_content_width
+                // (messureSize only runs when the flag actually changes), then show.
+                fp->drop.Invalidate(true);
+                fp->drop.SetUseContentWidth(false, false);
+                fp->drop.SetUseContentWidth(true, false);
+                wxPoint pos = b->ClientToScreen(wxPoint(0, -6));
+                fp->drop.Position(pos, wxSize(0, b->GetSize().y + 12));
+                fp->drop.Popup();
+            });
+            m_flyout_keepalive.push_back(fo);
+            sadd(b);
+            auto* chev = new wxStaticText(m_toolbar, wxID_ANY, wxString::FromUTF8("\xE2\x96\xBE"));
+            chev->SetForegroundColour(dp_sec_text());
+            chev->SetFont(Label::Body_9);
+            sadd(chev);   // follows its button off the bar
+        };
+        skbtn("design_select",    DesignSketchTool::Mode::Select,           _L("Select"),
+              _L("Click to select; Shift to add; double-click for a whole loop"));
+        skbtn("design_dimension", DesignSketchTool::Mode::Dimension, _L("Dimension"),
+              _L("Click 2 points or a line / circle / arc to place a dimension"));
+        // (separator dropped: the group it divided is now reached from the offer)
+        dropdown("design_line", _L("Line / polyline"), {
+            {"design_line",     DesignSketchTool::Mode::Line,     _L("Line"),     _L("Click start, then end — then set the exact length")},
+            {"design_polyline", DesignSketchTool::Mode::Polyline, _L("Polyline"), _L("Click points; click first / right-click to close the loop")} });
+        dropdown("design_rect", _L("Rectangle"), {
+            {"design_rect",         DesignSketchTool::Mode::CornerRect,  _L("Corner rectangle"),  _L("Click two opposite corners")},
+            {"design_crect",        DesignSketchTool::Mode::CenterRect,  _L("Center rectangle"),  _L("Click center, then a corner")},
+            {"design_rect_oblique", DesignSketchTool::Mode::ObliqueRect, _L("Oblique rectangle"), _L("Click two corners of one edge, then a point for the width")},
+            {"design_rect_rounded", DesignSketchTool::Mode::RoundedRect, _L("Rounded rectangle"), _L("Click two opposite corners, then a point for the corner radius")} });
+        dropdown("design_circle", _L("Circle"), {
+            {"design_circle",    DesignSketchTool::Mode::CenterCircle,     _L("Center circle"),  _L("Click center, then radius")},
+            {"design_circle2pt", DesignSketchTool::Mode::TwoPointCircle,   _L("2-point circle"), _L("Click two ends of the diameter")},
+            {"design_circle3pt", DesignSketchTool::Mode::ThreePointCircle, _L("3-point circle"), _L("Click three points on the circle")} });
+        dropdown("design_arc3pt", _L("Arc"), {
+            {"design_arc3pt",     DesignSketchTool::Mode::ThreePointArc, _L("3-point arc"),      _L("Click start, end, then a point on the arc")},
+            {"design_tangentarc", DesignSketchTool::Mode::TangentArc,    _L("Tangent arc"),      _L("Click start (on the last entity) then end")},
+            {"design_arc_center", DesignSketchTool::Mode::CenterArc,     _L("Center-point arc"), _L("Click center, then start, then a point for the end angle")} });
+        dropdown("design_slot", _L("Slot"), {
+            {"design_slot",     DesignSketchTool::Mode::Slot,    _L("Slot"),     _L("Click two centerline ends, then a point for the end radius")},
+            {"design_slot_arc", DesignSketchTool::Mode::ArcSlot, _L("Arc slot"), _L("Click center, start, end, then a point for the width")} });
+        dropdown("design_ellipse", _L("Ellipse"), {
+            {"design_ellipse",     DesignSketchTool::Mode::Ellipse,    _L("Ellipse"),        _L("Click center, a major-axis end, then a point for the minor axis")},
+            {"design_ellipse_arc", DesignSketchTool::Mode::EllipseArc, _L("Elliptical arc"), _L("Click center, major-axis end, minor point, then arc start and end")} });
+        skbtn("design_bspline", DesignSketchTool::Mode::BSpline, _L("Spline"),
+              _L("Click control points; double-click or right-click to finish"));
+        skbtn("design_point",   DesignSketchTool::Mode::Point,   _L("Point"),
+              _L("Click to place a point"));
+        // (separator dropped: the group it divided is now reached from the offer)
+        // Insert tools — Text / SVG produce a 2D profile (a sketch), so they belong with
+        // the sketch tools, not in the generic Features strip. Each places the art
+        // in-canvas, then commits via the Insert card's Confirm.
+        {
+            // In Sketch MODE the art must land in the sketch — but begin_sketch() does not run
+            // until the first tool is armed, so pressing Sketch and then Text would find no
+            // session and commit a separate feature. Arm Select first: it starts the session on
+            // the picked plane without drawing anything, so Text behaves the same whether or not
+            // you had already drawn a line. (MODE vs SESSION — the distinction that has bitten
+            // this panel before.)
+            auto ensure_sketch = [this, select_tool] {
+                if (m_ui_mode == UiMode::Sketch && m_viewport && !m_viewport->is_sketching())
+                    select_tool(DesignSketchTool::Mode::Select,
+                                _L("Select — click to select; Shift to add"));
+            };
+            auto* b_text = icon_btn("design_text", _L("Text — emboss text as a profile"));
+            b_text->Bind(wxEVT_BUTTON, [this, ensure_sketch](wxCommandEvent&) {
+                ensure_sketch(); on_add_text(); });
+            sadd(b_text);
+            auto* b_svg = icon_btn("design_svg", _L("SVG — import an outline as a profile"));
+            b_svg->Bind(wxEVT_BUTTON, [this, ensure_sketch](wxCommandEvent&) {
+                ensure_sketch(); on_import_svg(); });
+            sadd(b_svg);
+            // …and reachable from the offer's Create row. These were on the atlas's chrome_only
+            // list under "document-level actions act on the DOCUMENT, not on a selection" — which
+            // is not what they do: both call add_imported_sketch(), which drops the art ON a
+            // picked solid face (SketchPlane::from_face, centred on it) exactly as Sketch does.
+            // Selection-consuming profile creators, so they belong with the other Create verbs.
+            m_verb_actions["btn:text"] = [this, ensure_sketch] { ensure_sketch(); on_add_text(); };
+            m_verb_actions["btn:svg"]  = [this, ensure_sketch] { ensure_sketch(); on_import_svg(); };
+        }
+        // (separator dropped: the group it divided is now reached from the offer)
+        // In-canvas edit-op tools (drag gizmo / click label), grouped by family.
+        dropdown("design_filletedge", _L("Fillet / chamfer"), {
+            {"design_filletedge", DesignSketchTool::Mode::Fillet,  _L("Fillet"),  _L("Pick two lines, then drag the arrow or click the radius to set it")},
+            {"design_chamfer",    DesignSketchTool::Mode::Chamfer, _L("Chamfer"), _L("Pick two lines, then drag the arrow or click the distance to set it")} });
+        skbtn("design_offset", DesignSketchTool::Mode::Offset, _L("Offset"),
+              _L("Pick an entity, then drag the arrow or click the distance; click empty to apply"));
+        skbtn("design_mirror", DesignSketchTool::Mode::Mirror, _L("Mirror"),
+              _L("Pick a mirror-axis line, then the entities to mirror; click empty to apply"));
+        // Trim / Extend scissors — standalone sketch tools (NOT inside Constrain): click a
+        // segment to cut it back to / out to its nearest intersection. One cut per click.
+        skbtn("design_trim",   DesignSketchTool::Mode::Trim,   _L("Trim"),
+              _L("Click a segment to trim it back to its nearest intersection; right-click exits"));
+        skbtn("design_extend", DesignSketchTool::Mode::Extend, _L("Extend"),
+              _L("Click a line or arc to extend it to the nearest entity; right-click exits"));
+        // Constrain — grouped with the edit tools so it's easy to find (nde #13: it was buried
+        // far-right next to Construction and went unnoticed). Commits the live sketch in place
+        // and drops into Constrain mode (geometric/dimensional palette).
+        auto* b_constrain_sk = icon_btn("design_constrain",
+            _L("Constrain — add geometric/dimensional relations"));
+        b_constrain_sk->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { enter_constrain_inline(); });
+        sadd(b_constrain_sk);
+        dropdown("design_move", _L("Move / rotate / scale"), {
+            {"design_move",   DesignSketchTool::Mode::Move,   _L("Move (translate)"),        _L("Pick entities, then drag the handle or click the distance; click empty to apply")},
+            {"design_rotate", DesignSketchTool::Mode::Rotate, _L("Rotate (about centroid)"), _L("Pick entities, then drag around the pivot or click the angle; click empty to apply")},
+            {"design_scale",  DesignSketchTool::Mode::Scale,  _L("Scale (about centroid)"),  _L("Pick entities, then drag the handle or click the factor; click empty to apply")} });
+        dropdown("design_array", _L("Linear / polar array"), {
+            {"design_array",      DesignSketchTool::Mode::Array,      _L("Linear array"),                 _L("Pick entities, drag the spacing handle, click the count; click empty to apply")},
+            {"design_polararray", DesignSketchTool::Mode::PolarArray, _L("Polar array (about centroid)"), _L("Pick entities, drag the sweep handle, click the count; click empty to apply")} });
+
+        // Polygon's side count and fit are TOOL PARAMETERS, so they are chosen from the tool:
+        // the offer's Create > Polygon submenu. They used to sit inline in this row, then in a
+        // sidebar card; both put the choice somewhere you had to leave the geometry to reach,
+        // and the count cannot be recovered afterwards (a drawn polygon's inline editor offers
+        // Side and Angle, never the count). e1p.
+        auto arm_polygon = [this, select_tool] {
+            push_polygon_params();
+            select_tool(DesignSketchTool::Mode::Polygon,
+                        wxString::Format(_L("Click center then a vertex — %d sides, %s"),
+                                         m_poly_sides,
+                                         m_poly_circumscribed ? _L("circumscribed") : _L("inscribed")));
+        };
+        for (int n : {3, 4, 5, 6, 8, 12})
+            m_verb_actions["btn:poly#" + std::to_string(n)] =
+                [this, arm_polygon, n] { m_poly_sides = n; arm_polygon(); };
+        for (int c : {0, 1})
+            m_verb_actions["btn:polyfit#" + std::to_string(c)] =
+                [this, arm_polygon, c] { m_poly_circumscribed = (c == 1); arm_polygon(); };
+
+        // Same defect, one level up: a combo whose entries are different VERBS wearing a single
+        // name. "Dress-up" is Fillet or Chamfer; "Combine" is union, subtract or intersect;
+        // "Pattern" is linear or circular. The choice decides WHAT YOU ARE DOING, so it belongs
+        // where you chose the tool — not behind a card you must open to discover it existed.
+        // Each address opens the tool exactly as its shortcut does, then says which one.
+        // The members are read at INVOCATION, not capture: the cards are built after this row.
+        // e1p.
+        auto open_feature = [this](int key) {
+            auto it = m_keys_feature.find(key);
+            if (it != m_keys_feature.end() && it->second) it->second();
+        };
+        // SHIFT() is a constructor-local helper, so resolve the codes here rather than inside
+        // the stored lambdas, which outlive it.
+        const int k_dress = SHIFT('F'), k_bool = SHIFT('B'), k_pat = SHIFT('N');
+        // Choose FIRST, then open: open_tool() titles the card from m_dressup_type, so setting
+        // it afterwards left the header reading "Fillet 1" over a chamfer. Nothing in the
+        // opener resets the combo, so this order is safe.
+        m_verb_actions["btn:dress#0"] = [this, open_feature, k_dress] {
+            if (m_dressup_type) m_dressup_type->SetSelection(0); open_feature(k_dress); };
+        m_verb_actions["btn:dress#1"] = [this, open_feature, k_dress] {
+            if (m_dressup_type) m_dressup_type->SetSelection(1); open_feature(k_dress); };
+        for (int op = 0; op < 3; ++op)
+            m_verb_actions["btn:bool#" + std::to_string(op)] = [this, open_feature, k_bool, op] {
+                open_feature(k_bool);
+                if (m_bool_op) { m_bool_op->SetSelection(op); refresh_preview(); } };
+        for (int t = 0; t < 2; ++t)
+            m_verb_actions["btn:pat#" + std::to_string(t)] = [this, open_feature, k_pat, t] {
+                open_feature(k_pat); if (m_pattern_type) m_pattern_type->SetSelection(t); };
+
+        auto* b_poly = icon_btn("design_polygon", _L("Polygon"));
+        b_poly->Bind(wxEVT_BUTTON, [arm_polygon](wxCommandEvent&) { arm_polygon(); });
+        sadd(b_poly);
+        // (separator dropped: the group it divided is now reached from the offer)
+        // Q's semantics, on the control that carries the word. With geometry selected the box
+        // CONVERTS it — that is what a user who has just selected a construction circle and
+        // reached for the box labelled "Construction" is asking for, and until now it was the
+        // only one of the three routes (Q, the offer's Reference row, this box) that could not
+        // do it: it armed the mode for the NEXT entity, silently, changing nothing about the
+        // shape on screen and flipping the draw mode behind the user's back. The tick is a MODE
+        // indicator, so after a conversion it goes back to what it was.
+        m_construction->Bind(wxEVT_CHECKBOX, [this](wxCommandEvent&) {
+            if (!m_viewport || !m_viewport->is_sketching())
+                return;
+            // ONLY IN SELECT MODE. Drawing auto-selects what was just drawn (draw-then-edit), so
+            // with a draw tool armed "there is a selection" does not mean the user picked
+            // anything — it means they finished a line. Converting there turns the box into a
+            // trap: arm construction, draw the axis, click the box to go back to real geometry,
+            // and instead of disarming the mode it converts the axis you just drew. The gesture
+            // ladder's mirror rung does exactly that and reported three construction entities
+            // where it wanted one. In Select mode the intent is unambiguous.
+            const int n = m_viewport->sketch_is_selecting()
+                        ? m_viewport->toggle_sketch_construction_selection() : 0;
+            if (n > 0) {
+                m_construction->SetValue(!m_construction->GetValue());   // the mode did not move
+                m_status->SetForegroundColour(wxNullColour);
+                set_status(wxString::Format(
+                    _L("Converted %d entit%s between construction and real geometry"),
+                    n, n == 1 ? "y" : "ies"));
+                m_status->Refresh();
+                return;
+            }
+            m_viewport->set_sketch_construction(m_construction->GetValue()); });
+        // STAYS on the bar. Construction is not a tool, it is a persistent MODE — the same kind
+        // of thing as the Bed checkbox — and the sketch bar is already shown only in Sketch mode,
+        // so it appears exactly while it can apply. Hiding it left Q and the offer's Construction
+        // row still toggling a checkbox nobody could see: you could not tell whether the next
+        // line would be construction geometry. A stateful toggle has to show its state.
+        sadd_bar(m_construction);
+        add_sep(m_tb_sketch);
+        auto* b_del = icon_btn("design_delete", _L("Delete selected"));
+        b_del->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) {
+            if (m_viewport) m_viewport->delete_selected_sketch_entities(); });
+        sadd_bar(b_del);   // keep-list: Delete selected stays on the bar
+        // Finish sketch = the unified ✓ Confirm in the action bar (tool_confirm).
+    }
+
+    // --- Constrain group: geometric constraints + dimensions + edit ops + Done
+    // Fase 4.2 live path: these buttons are shown during a SKETCH too, not only in Constrain
+    // mode, so a constraint applies to the live selection without committing first. The caption
+    // travels with them; the session's Confirm/Cancel stay in m_tb_action (mode-appropriate).
+    m_tb_relations = new wxBoxSizer(wxHORIZONTAL);
+    auto cadd = [this](wxWindow* w) { m_tb_relations->Add(w, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 2); };
+    m_tb_relations->Add(caption(_L("CONSTRAIN")), 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 8);
+    {
+        auto cbtn = [&](const char* icon, const wxString& tip, SketchConstraintType type) {
+            auto* b = icon_btn(icon, tip);
+            b->Bind(wxEVT_BUTTON, [this, type](wxCommandEvent&) { apply_constraint(type); });
+            cadd(b);
+        };
+        cbtn("design_c_horizontal",    _L("Horizontal"),    SketchConstraintType::Horizontal);
+        cbtn("design_c_vertical",      _L("Vertical"),      SketchConstraintType::Vertical);
+        cbtn("design_c_parallel",      _L("Parallel"),      SketchConstraintType::Parallel);
+        cbtn("design_c_perpendicular", _L("Perpendicular"), SketchConstraintType::Perpendicular);
+        cbtn("design_c_coincident",    _L("Coincident"),    SketchConstraintType::Coincident);
+        cbtn("design_c_equal",         _L("Equal length"),  SketchConstraintType::EqualLength);
+        cbtn("design_c_equal_radius", _L("Equal radius"), SketchConstraintType::EqualRadius);
+        cbtn("design_c_collinear",    _L("Collinear"),    SketchConstraintType::Collinear);
+        cbtn("design_c_concentric",    _L("Concentric"),    SketchConstraintType::Concentric);
+        cbtn("design_c_tangent",       _L("Tangent"),       SketchConstraintType::Tangent);
+        cbtn("design_c_midpoint",      _L("Midpoint"),      SketchConstraintType::Midpoint);
+        cbtn("design_c_symmetric",     _L("Symmetric"),     SketchConstraintType::Symmetric);
+        cbtn("design_c_sym_v", _L("Symmetric about the vertical axis"),   SketchConstraintType::SymmetricAboutY);
+        cbtn("design_c_sym_h", _L("Symmetric about the horizontal axis"), SketchConstraintType::SymmetricAboutX);
+        cbtn("design_c_angle",         _L("Angle"),         SketchConstraintType::Angle);
+        cbtn("design_c_radius",        _L("Radius"),        SketchConstraintType::Radius);
+        cbtn("design_c_diameter",      _L("Diameter"),      SketchConstraintType::Diameter);
+        cbtn("design_c_fix",           _L("Fix point (anchor in place)"), SketchConstraintType::Fix);
+        cbtn("design_c_dist_x", _L("Horizontal distance"), SketchConstraintType::DistanceX);
+        cbtn("design_c_dist_y", _L("Vertical distance"),   SketchConstraintType::DistanceY);
+        // Trim/Extend are now standalone SKETCH scissors (Mode::Trim/Extend) in the sketch
+        // toolbar, NOT Constrain buttons. The other edit ops (Mirror/Offset/Fillet/Chamfer/
+        // Move/…) are first-class sketch tools too. Done constraining = the action-bar ✓.
+    }
+
+    // Unified action bar: the ONE Confirm/Cancel surface for every tool and mode. Lives at
+    // the right end of the ribbon (the "tool dashboard"); shown only while a tool/mode is
+    // active (update_action_bar). Replaces the 13 per-card buttons + sketch Finish + Done.
+    m_tb_action = new wxBoxSizer(wxHORIZONTAL);
+    {
+        auto* ok = new wxButton(m_toolbar, wxID_ANY, _L("✓ Confirm"));
+        ok->SetForegroundColour(*wxWHITE);
+        ok->SetBackgroundColour(wxColour(0x00, 0x96, 0x88));   // Orca teal accent
+        ok->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { tool_confirm(); });
+        m_confirm_btns.push_back(ok);   // refresh_preview greys this on an invalid candidate
+        auto* no = new wxButton(m_toolbar, wxID_ANY, _L("✗ Cancel"));
+        no->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { tool_cancel(); });
+        m_tb_action->Add(ok, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 6);
+        m_tb_action->Add(no, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 10);
+    }
+
+    // Persistent Undo/Redo group: always visible (not mode-gated like the tool groups), so
+    // history is reachable from Feature, Sketch and Constrain alike. These are momentary
+    // actions, so — unlike icon_btn — they are NOT registered in m_tool_btns and never take
+    // the teal active-tool highlight. They route to the SAME do_undo_redo as the keyboard
+    // Ctrl+Z / Ctrl+Shift+Z path, and are greyed by update_undo_redo_buttons().
+    m_tb_history = new wxBoxSizer(wxHORIZONTAL);
+    {
+        auto hist_btn = [this, tb_bg, tb_hover](const char* icon, const wxString& tip) {
+            auto* b = new ScalableButton(m_toolbar, wxID_ANY, icon, "", wxSize(40, 40),
+                                         wxDefaultPosition, wxBU_EXACTFIT | wxBORDER_NONE, false, 34);
+            b->SetToolTip(tip);
+            b->SetBackgroundColour(tb_bg);
+            b->Bind(wxEVT_ENTER_WINDOW, [b, tb_hover](wxMouseEvent& e) {
+                if (b->IsEnabled()) { b->SetBackgroundColour(tb_hover); b->Refresh(); } e.Skip(); });
+            b->Bind(wxEVT_LEAVE_WINDOW, [b, tb_bg](wxMouseEvent& e) {
+                b->SetBackgroundColour(tb_bg); b->Refresh(); e.Skip(); });
+            return b;
+        };
+        m_btn_undo = hist_btn("menu_undo", _L("Undo (Ctrl+Z)"));
+        m_btn_undo->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { do_undo_redo(false); });
+        m_btn_redo = hist_btn("menu_redo", _L("Redo (Ctrl+Shift+Z)"));
+        m_btn_redo->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { do_undo_redo(true); });
+        m_btn_undo->Enable(false);   // nothing to undo/redo on a fresh document
+        m_btn_redo->Enable(false);
+        m_tb_history->Add(m_btn_undo, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 4);
+        m_tb_history->Add(m_btn_redo, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 4);
+    }
+
+    // Document actions, left of Undo/Redo and always visible (not mode-gated like the tools).
+    // Same styling as the history pair: momentary actions, never the teal active-tool state.
+    m_tb_doc = new wxBoxSizer(wxHORIZONTAL);
+    const wxColour tb_glyph_col  = StateColor::darkModeColorFor(wxColour(0x36, 0x36, 0x36));
+    const wxColour tb_commit_col(0x00, 0x96, 0x88);   // Orca Confirm accent
+    {
+        // Some Orca glyphs (toolbar_add_plate, toolbar_flatten) are drawn for a light toolbar and
+        // come out the same tone as this dark one — Commit was effectively invisible. Re-tint
+        // those: Commit in the teal accent it carries as the tab's primary action, the rest in
+        // the same grey the other toolbar glyphs resolve to.
+        auto doc_btn = [this, tb_bg, tb_hover, &tint](const char* icon, const wxString& tip,
+                                                      const wxColour* glyph = nullptr) {
+            auto* b = new ScalableButton(m_toolbar, wxID_ANY, icon, "", wxSize(40, 40),
+                                         wxDefaultPosition, wxBU_EXACTFIT | wxBORDER_NONE, false, 34);
+            if (glyph != nullptr)
+                b->SetBitmap(tint(create_scaled_bitmap(icon, m_toolbar, 42), *glyph));
+            b->SetToolTip(tip);
+            b->SetBackgroundColour(tb_bg);
+            b->Bind(wxEVT_ENTER_WINDOW, [b, tb_hover](wxMouseEvent& e) {
+                if (b->IsEnabled()) { b->SetBackgroundColour(tb_hover); b->Refresh(); } e.Skip(); });
+            b->Bind(wxEVT_LEAVE_WINDOW, [b, tb_bg](wxMouseEvent& e) {
+                b->SetBackgroundColour(tb_bg); b->Refresh(); e.Skip(); });
+            return b;
+        };
+        auto add_doc = [this](ScalableButton* b) {
+            m_tb_doc->Add(b, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 4); };
+
+        auto* b_new = doc_btn("add", _L("New Design — clear the feature tree"));
+        b_new->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_new_design(); });
+        add_doc(b_new);
+        add_doc(static_cast<ScalableButton*>(tb_slot["step"][0]));   // 2. Import STEP
+        add_doc(static_cast<ScalableButton*>(tb_slot["mesh"][0]));   // 3. Import mesh
+        auto* b_export = doc_btn("save", _L("Export STEP…"));
+        b_export->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_export_step(); });
+        add_doc(b_export);
+
+        // View option, not a document action: hide the printer bed to model without it. Lives in
+        // this row because it must stay reachable with no tool open — a card would come and go.
+        m_show_bed = new CheckBox(m_toolbar);
+        m_show_bed->SetValue(true);                 // bed visible by default, as the tab opens today
+        m_show_bed->SetToolTip(_L("Show the printer bed and its plate grid"));
+        // wxEVT_TOGGLEBUTTON, NOT wxEVT_CHECKBOX: Orca's CheckBox derives from
+        // wxBitmapToggleButton (Widgets/CheckBox.hpp), so a wxEVT_CHECKBOX handler never fires.
+        // Read the control rather than the event so the state cannot disagree with the glyph.
+        m_show_bed->Bind(wxEVT_TOGGLEBUTTON, [this](wxCommandEvent& e) {
+            if (m_viewport) m_viewport->set_show_bed(m_show_bed->GetValue());
+            e.Skip();
+        });
+        auto* bed_lbl = new wxStaticText(m_toolbar, wxID_ANY, _L("Bed"));
+        bed_lbl->SetForegroundColour(dp_sec_text());
+        m_tb_doc->Add(m_show_bed, 0, wxALIGN_CENTER_VERTICAL | wxLEFT, 6);
+        m_tb_doc->Add(bed_lbl,    0, wxALIGN_CENTER_VERTICAL | wxLEFT | wxRIGHT, 4);
+
+        // These act on bodies / the view, so they ride in the feature group, in the slots
+        // the user assigned them (9, 11bis, 16).
+        auto* b_place = doc_btn("toolbar_flatten", _L("Place on Face (F) — lay the picked face on the bed"),
+                                &tb_glyph_col);
+        b_place->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { place_on_face(); });
+        tb_slot["place"].push_back(b_place);
+
+        auto* b_section = doc_btn("split_parts", _L("Section View — hide part of the model to see inside. "
+                                                   "PageUp/PageDown move the plane; Delete removes it."));
+        b_section->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { toggle_section_view(); });
+        tb_slot["section"].push_back(b_section);
+
+        m_section_flip_btn = doc_btn("design_mirror", _L("Flip Section — show the opposite half"));
+        m_section_flip_btn->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { flip_section_view(); });
+        m_section_flip_btn->Enable(false);   // only usable while a section view is active
+        tb_slot["flip"].push_back(m_section_flip_btn);
+
+        // Commit is the tab's primary action and sits far right, next to Confirm/Cancel.
+        m_tb_commit = new wxBoxSizer(wxHORIZONTAL);
+        auto* b_commit = doc_btn("toolbar_add_plate", _L("Commit to Plate — send the solid to Prepare"),
+                                 &tb_commit_col);
+        b_commit->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_commit(); });
+        m_tb_commit->Add(b_commit, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 4);
+    }
+
+    // Feature-group layout, in the requested left-to-right order.
+    {
+        auto put = [&](const char* id) {
+            auto it = tb_slot.find(id);
+            if (it == tb_slot.end()) return;
+            for (size_t i = 0; i < it->second.size(); ++i)
+                m_tb_feature->Add(it->second[i], 0,
+                                  i == 0 ? (wxALIGN_CENTER_VERTICAL | wxRIGHT)
+                                         : (wxALIGN_BOTTOM | wxBOTTOM | wxRIGHT),
+                                  i == 0 ? 4 : 5);
+        };
+        put("sketch");    put("constrain");            // 7, 7bis
+        add_sep(m_tb_feature);
+        put("material");  put("place");   put("placement"); put("plane"); // 8, 9, 9bis, 10
+        put("dressup");   put("section");                // 11, 11bis
+        put("hole");      put("boolean"); put("cut");   // 12, 13, 14
+        put("surface");   put("color");   put("flip");  // 14bis, 15, 16
+        put("pattern");                                 // kept, at the end
+    }
+
+    auto* tbrow = new wxBoxSizer(wxHORIZONTAL);
+    tbrow->AddSpacer(8);
+    tbrow->Add(m_tb_doc,       0, wxALIGN_CENTER_VERTICAL | wxTOP | wxBOTTOM, 5);
+    add_sep(tbrow);
+    tbrow->Add(m_tb_history,   0, wxALIGN_CENTER_VERTICAL | wxTOP | wxBOTTOM, 5);
+    add_sep(tbrow);
+    tbrow->Add(m_tb_feature,   0, wxALIGN_CENTER_VERTICAL | wxTOP | wxBOTTOM, 5);
+    tbrow->Add(m_tb_sketch,    0, wxALIGN_CENTER_VERTICAL | wxTOP | wxBOTTOM, 5);
+    tbrow->Add(m_tb_relations, 0, wxALIGN_CENTER_VERTICAL | wxTOP | wxBOTTOM, 5);
+    tbrow->AddStretchSpacer();
+    tbrow->Add(m_tb_commit,    0, wxALIGN_CENTER_VERTICAL | wxTOP | wxBOTTOM, 5);
+    tbrow->Add(m_tb_action,    0, wxALIGN_CENTER_VERTICAL | wxTOP | wxBOTTOM, 5);
+    tbrow->AddSpacer(8);
+    m_toolbar->SetSizer(tbrow);
+    // Apply the body gates once now: an empty document is exactly the state the bug was reported
+    // in, and feed_bodies() has not run yet on a fresh tab.
+    update_body_gates();
+
+    // Onshape-style dialog-card header: feature icon + bold title. out receives
+    // the title control so open_tool() can retitle it per feature.
+    auto card_header = [](wxWindow* card, const char* icon, const wxString& title, wxStaticText*& out) -> wxSizer* {
+        auto* h  = new wxBoxSizer(wxHORIZONTAL);
+        auto* ic = new wxStaticBitmap(card, wxID_ANY, create_scaled_bitmap(icon, card, 18));
+        out = new wxStaticText(card, wxID_ANY, title);
+        out->SetFont(Label::Head_14);   // Orca shared HarmonyOS card-title font
+        h->Add(ic,  0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 8);
+        h->Add(out, 0, wxALIGN_CENTER_VERTICAL);
+        return h;
+    };
+
+    // Every tool dialog lives inside ONE framed card (only one is ever visible), so the
+    // active dialog reads as a bordered panel like Prepare's sidebar boxes instead of
+    // free-floating rows. `cards` is the frame's sizer; open_tool() shows/hides within it.
+    m_cards = make_card(m_form);
+    auto* cards = new wxBoxSizer(wxVERTICAL);
+    m_cards->SetSizer(cards);
+    root->Add(m_cards, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 8);
+
+    // --- Sketch dialog (shape definition only — no distance/mode) ---
+    auto* form = two_col_form();
+
+    m_shape = make_combo(m_cards);
+    m_shape->Append(_L("Rectangle"));
+    m_shape->Append(_L("Circle"));
+    m_shape->SetSelection(0);
+    form->Add(new wxStaticText(m_cards, wxID_ANY, _L("Shape")), 0, wxALIGN_CENTER_VERTICAL);
+    form->Add(m_shape, 0, wxEXPAND);
+
+    // NO plane row. A sketch takes its plane from what is picked in the VIEWPORT — a planar face
+    // on a solid, or one of the reference-plane ghosts clicked in 3D — resolved by
+    // sketch_plane_from_selection(). A three-row XY/XZ/YZ combo could not express either of those
+    // targets, so it displayed a value that was at best redundant and at worst false. e1p.
+
+    m_width = make_spin(m_cards, 20);
+    form->Add(new wxStaticText(m_cards, wxID_ANY, _L("Width / X")), 0, wxALIGN_CENTER_VERTICAL);
+    form->Add(spin_frame(m_width), 0, wxEXPAND);
+
+    m_height = make_spin(m_cards, 20);
+    form->Add(new wxStaticText(m_cards, wxID_ANY, _L("Height / Y")), 0, wxALIGN_CENTER_VERTICAL);
+    form->Add(spin_frame(m_height), 0, wxEXPAND);
+
+    m_radius = make_spin(m_cards, 10);
+    form->Add(new wxStaticText(m_cards, wxID_ANY, _L("Radius")), 0, wxALIGN_CENTER_VERTICAL);
+    form->Add(spin_frame(m_radius), 0, wxEXPAND);
+
+    m_box_sketch = new wxBoxSizer(wxVERTICAL);
+    m_box_sketch->Add(card_header(m_cards, "design_sketch", _L("Sketch"), m_hdr_sketch), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_sketch->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_box_sketch->Add(form, 0, wxEXPAND | wxALL, 12);
+    cards->Add(m_box_sketch, 0, wxEXPAND);
+
+    // --- Move / Rotate body ---
+    {
+        auto* mform = two_col_form();
+        m_move_dx = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        mform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Distance X")), 0, wxALIGN_CENTER_VERTICAL);
+        mform->Add(spin_frame(m_move_dx), 0, wxEXPAND);
+        m_move_dy = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        mform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Distance Y")), 0, wxALIGN_CENTER_VERTICAL);
+        mform->Add(spin_frame(m_move_dy), 0, wxEXPAND);
+        m_move_dz = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        mform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Distance Z")), 0, wxALIGN_CENTER_VERTICAL);
+        mform->Add(spin_frame(m_move_dz), 0, wxEXPAND);
+
+        m_move_axis = make_combo(m_cards);
+        m_move_axis->Append(_L("X"));
+        m_move_axis->Append(_L("Y"));
+        m_move_axis->Append(_L("Z"));
+        m_move_axis->SetSelection(2);
+        mform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Rotation axis")), 0, wxALIGN_CENTER_VERTICAL);
+        mform->Add(m_move_axis, 0, wxEXPAND);
+
+        m_move_angle = make_spin(m_cards, 0.0, -360.0, 360.0);
+        mform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Angle °")), 0, wxALIGN_CENTER_VERTICAL);
+        mform->Add(spin_frame(m_move_angle), 0, wxEXPAND);
+
+        for (wxSpinCtrlDouble* sp : { m_move_dx, m_move_dy, m_move_dz, m_move_angle })
+            sp->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent& e) { apply_move_card(); e.Skip(); });
+        m_move_axis->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent& e) { apply_move_card(); e.Skip(); });
+
+        m_box_move = new wxBoxSizer(wxVERTICAL);
+        m_box_move->Add(card_header(m_cards, "design_move", _L("Move / Rotate"), m_hdr_move), 0,
+                        wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_move->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+        m_box_move->Add(mform, 0, wxEXPAND | wxALL, 12);
+        cards->Add(m_box_move, 0, wxEXPAND);
+    }
+
+    // --- Polygon (sketch tool options) ---
+    {
+        // NO polygon card. Sides and Circumscribed are tool parameters and are chosen from the
+        // tool — the offer's Create > Polygon submenu names the common side counts and the two
+        // fits, and arming from there sets both. A spin field on the left could not be reached
+        // without leaving the geometry, and the count is unrecoverable afterwards: the inline
+        // editor a drawn polygon opens offers Side and Angle, never the count. e1p.
+    }
+
+    // --- Extrude dialog (consumes the selected sketch) ---
+    m_box_extrude = new wxBoxSizer(wxVERTICAL);
+    m_box_extrude->Add(card_header(m_cards, "design_extrude", _L("Extrude"), m_hdr_extrude), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_extrude->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_extrude_sketch_label = new wxStaticText(m_cards, wxID_ANY, _L("Sketch: —"));
+    m_box_extrude->Add(m_extrude_sketch_label, 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    {
+        auto* eform = two_col_form();
+
+        // A negative distance extrudes the other way — Onshape behaviour, where a negative
+        // depth IS the flip. The default 0.1 floor made that impossible to type, so the only
+        // way inward was the Flip box, and a user who typed "-5" silently got +0.1 instead.
+        // Flip and a negative distance double-negate, which is what setting both asked for.
+        m_distance = make_spin(m_cards, 10, -1000.0, 1000.0);
+        eform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Extrude dist")), 0, wxALIGN_CENTER_VERTICAL);
+        eform->Add(spin_frame(m_distance), 0, wxEXPAND);
+
+        // End condition (order MUST match ExtrudeEnd: Blind/Symmetric/TwoSided/ThroughAll/
+        // UpToFace/UpToVertex). Up-to-face uses the currently click-selected solid face.
+        m_extrude_end = make_combo(m_cards);
+        for (const char* s : { "Blind", "Symmetric", "Two-sided", "Through all",
+                               "Up to face", "Up to vertex" })
+            m_extrude_end->Append(s);
+        m_extrude_end->SetSelection(0);
+        eform->Add(new wxStaticText(m_cards, wxID_ANY, _L("End")), 0, wxALIGN_CENTER_VERTICAL);
+        eform->Add(m_extrude_end, 0, wxEXPAND);
+
+        m_distance2 = make_spin(m_cards, 5, 0.0, 100000.0);   // second-side depth (Two-sided)
+        eform->Add(new wxStaticText(m_cards, wxID_ANY, _L("2nd dist")), 0, wxALIGN_CENTER_VERTICAL);
+        eform->Add(spin_frame(m_distance2), 0, wxEXPAND);
+
+        m_taper = make_spin(m_cards, 0.0, -89.0, 89.0);       // draft angle (deg)
+        eform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Taper °")), 0, wxALIGN_CENTER_VERTICAL);
+        eform->Add(spin_frame(m_taper), 0, wxEXPAND);
+
+        m_mode = make_combo(m_cards);
+        // Order is load-bearing: index maps to BooleanMode (New=0, Add=1, Cut=2, Intersect=3).
+        // Labels use Onshape wording so the choice reads as the user thinks of it.
+        m_mode->Append(_L("New body"));   // separate coexisting solid
+        m_mode->Append(_L("Join"));       // fuse into the target body (was "Add")
+        m_mode->Append(_L("Cut"));        // subtract from the target body
+        m_mode->Append(_L("Intersect"));  // keep only the overlap
+        m_mode->SetSelection(0);
+        eform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Result")), 0, wxALIGN_CENTER_VERTICAL);
+        eform->Add(m_mode, 0, wxEXPAND);
+
+        m_flip = new CheckBox(m_cards);
+        eform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Flip direction")), 0, wxALIGN_CENTER_VERTICAL);
+        eform->Add(m_flip, 0, wxALIGN_LEFT | wxALIGN_CENTER_VERTICAL);
+
+        m_box_extrude->Add(eform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_extrude, 0, wxEXPAND);
+
+    // --- Dress-up (Fillet / Chamfer) ---
+    auto* dform = two_col_form();
+
+    m_dressup_type = make_combo(m_cards);
+    m_dressup_type->Append(_L("Fillet"));
+    m_dressup_type->Append(_L("Chamfer"));
+    m_dressup_type->SetSelection(0);
+    dform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Type")), 0, wxALIGN_CENTER_VERTICAL);
+    dform->Add(m_dressup_type, 0, wxEXPAND);
+
+    // The card can dress ONE picked edge or a whole face-group, and which one it will do is
+    // decided by a viewport pick the card previously said nothing about — so a user who had not
+    // picked an edge saw only the group combo and concluded per-edge rounding did not exist,
+    // while a user who HAD picked one saw the combo still reading "All" and was told the opposite
+    // of what Confirm would do. This row states the actual target, as Shell and Draft already do.
+    m_dressup_edge_label = new wxStaticText(m_cards, wxID_ANY, _L("(no edge picked — group below)"));
+    dform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Target")), 0, wxALIGN_CENTER_VERTICAL);
+    dform->Add(m_dressup_edge_label, 0, wxALIGN_CENTER_VERTICAL);
+
+    m_face_group = make_combo(m_cards);
+    m_face_group->Append(_L("Top"));      // index 0 -> FaceGroup::Top
+    m_face_group->Append(_L("Bottom"));   // 1 -> Bottom
+    m_face_group->Append(_L("Lateral"));  // 2 -> Lateral
+    m_face_group->Append(_L("All"));      // 3 -> All
+    m_face_group->SetSelection(3);
+    dform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Edges")), 0, wxALIGN_CENTER_VERTICAL);
+    dform->Add(m_face_group, 0, wxEXPAND);
+
+    m_dressup_size = make_spin(m_cards, 2.0);
+    dform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Size (r/dist)")), 0, wxALIGN_CENTER_VERTICAL);
+    dform->Add(spin_frame(m_dressup_size), 0, wxEXPAND);
+
+    m_box_dressup = new wxBoxSizer(wxVERTICAL);
+    m_box_dressup->Add(card_header(m_cards, "design_dressup", _L("Fillet / Chamfer"), m_hdr_dressup), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_dressup->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_box_dressup->Add(dform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    cards->Add(m_box_dressup, 0, wxEXPAND);
+
+    // --- Hole (positioned circular cut) ---
+    auto* hform = two_col_form();
+
+    m_hole_plane = make_combo(m_cards);
+    m_hole_plane->Append(_L("XY"));
+    m_hole_plane->Append(_L("XZ"));
+    m_hole_plane->Append(_L("YZ"));
+    m_hole_plane->SetSelection(0);
+    // Picking a plane here is an explicit choice: drop any on-face hijack (a stale face pick
+    // could keep m_hole_on_face true, so the dropdown was ignored and the hole drilled on the
+    // face's plane instead of the chosen XY/XZ/YZ).
+    m_hole_plane->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent& e) {
+        m_hole_on_face    = false;
+        m_hole_has_bounds = false;
+        set_hole_target_label(-1);
+        update_hole_gizmo();
+        refresh_preview();
+        e.Skip();
+    });
+    hform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Hole plane")), 0, wxALIGN_CENTER_VERTICAL);
+    hform->Add(m_hole_plane, 0, wxEXPAND);
+
+    m_hole_diameter = make_spin(m_cards, 6.0);
+    hform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Diameter")), 0, wxALIGN_CENTER_VERTICAL);
+    hform->Add(spin_frame(m_hole_diameter), 0, wxEXPAND);
+
+    m_hole_depth = make_spin(m_cards, 10.0);
+    hform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Depth (blind)")), 0, wxALIGN_CENTER_VERTICAL);
+    hform->Add(spin_frame(m_hole_depth), 0, wxEXPAND);
+
+    m_hole_x = make_spin(m_cards, 0.0, -1000.0, 1000.0);
+    hform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Pos X")), 0, wxALIGN_CENTER_VERTICAL);
+    hform->Add(spin_frame(m_hole_x), 0, wxEXPAND);
+
+    m_hole_y = make_spin(m_cards, 0.0, -1000.0, 1000.0);
+    hform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Pos Y")), 0, wxALIGN_CENTER_VERTICAL);
+    hform->Add(spin_frame(m_hole_y), 0, wxEXPAND);
+
+    m_hole_through = new CheckBox(m_cards);
+    m_hole_through->SetValue(true);
+    hform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Through")), 0, wxALIGN_CENTER_VERTICAL);
+    hform->Add(m_hole_through, 0, wxALIGN_LEFT | wxALIGN_CENTER_VERTICAL);
+
+    m_hole_target_label = new wxStaticText(m_cards, wxID_ANY, _L("(none — uses Hole plane)"));
+    hform->Add(new wxStaticText(m_cards, wxID_ANY, _L("On face")), 0, wxALIGN_CENTER_VERTICAL);
+    hform->Add(m_hole_target_label, 0, wxALIGN_CENTER_VERTICAL);
+
+    m_box_hole = new wxBoxSizer(wxVERTICAL);
+    m_box_hole->Add(card_header(m_cards, "design_hole", _L("Hole"), m_hdr_hole), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_hole->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_box_hole->Add(hform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    cards->Add(m_box_hole, 0, wxEXPAND);
+
+    // --- Thread (helical) ---
+    auto* tform = two_col_form();
+
+    m_thread_plane = make_combo(m_cards);
+    m_thread_plane->Append(_L("XY"));
+    m_thread_plane->Append(_L("XZ"));
+    m_thread_plane->Append(_L("YZ"));
+    m_thread_plane->SetSelection(0);
+    tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Thread plane")), 0, wxALIGN_CENTER_VERTICAL);
+    tform->Add(m_thread_plane, 0, wxEXPAND);
+
+    // Standard designation picker — fills pitch/depth (and nominal radius) from the
+    // ISO metric / Unified imperial tables. "Custom" leaves the manual spins alone.
+    m_thread_std = make_combo(m_cards);
+    m_thread_std->Append(_L("Custom"));
+    for (const ThreadSpec& s : thread_standards())
+        m_thread_std->Append(s.name);
+    m_thread_std->SetSelection(0);
+    m_thread_std->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { apply_thread_standard(); });
+    tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Standard")), 0, wxALIGN_CENTER_VERTICAL);
+    tform->Add(m_thread_std, 0, wxEXPAND);
+
+    // Threads are specified by DIAMETER (M6 = Ø6); the value is derived from the picked cylindrical
+    // surface / circular edge, so it's a readout users rarely type. Stored field holds the diameter.
+    m_thread_radius = make_spin(m_cards, 10.0);
+    tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Diameter")), 0, wxALIGN_CENTER_VERTICAL);
+    tform->Add(spin_frame(m_thread_radius), 0, wxEXPAND);
+
+    m_thread_pitch = make_spin(m_cards, 2.0);
+    tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Pitch")), 0, wxALIGN_CENTER_VERTICAL);
+    tform->Add(spin_frame(m_thread_pitch), 0, wxEXPAND);
+
+    m_thread_height = make_spin(m_cards, 10.0);
+    tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Length")), 0, wxALIGN_CENTER_VERTICAL);
+    tform->Add(spin_frame(m_thread_height), 0, wxEXPAND);
+
+    m_thread_depth = make_spin(m_cards, 1.0);
+    tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Thread depth")), 0, wxALIGN_CENTER_VERTICAL);
+    tform->Add(spin_frame(m_thread_depth), 0, wxEXPAND);
+
+    m_thread_x = make_spin(m_cards, 0.0, -1000.0, 1000.0);
+    tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Pos X")), 0, wxALIGN_CENTER_VERTICAL);
+    tform->Add(spin_frame(m_thread_x), 0, wxEXPAND);
+
+    m_thread_y = make_spin(m_cards, 0.0, -1000.0, 1000.0);
+    tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Pos Y")), 0, wxALIGN_CENTER_VERTICAL);
+    tform->Add(spin_frame(m_thread_y), 0, wxEXPAND);
+
+    m_thread_internal = new CheckBox(m_cards);
+    m_thread_internal->SetValue(false);
+    // External rod uses the major radius; an internal tapped bore uses the minor
+    // (tap-drill) radius — re-derive the nominal radius when the role flips.
+    m_thread_internal->Bind(wxEVT_TOGGLEBUTTON, [this](wxCommandEvent& e) {
+        apply_thread_standard();
+        e.Skip();
+    });
+    tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Internal")), 0, wxALIGN_CENTER_VERTICAL);
+    tform->Add(m_thread_internal, 0, wxALIGN_LEFT | wxALIGN_CENTER_VERTICAL);
+
+    m_thread_target_label = new wxStaticText(m_cards, wxID_ANY, _L("(none — uses Thread plane)"));
+    tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("On face")), 0, wxALIGN_CENTER_VERTICAL);
+    tform->Add(m_thread_target_label, 0, wxALIGN_CENTER_VERTICAL);
+
+    m_box_thread = new wxBoxSizer(wxVERTICAL);
+    m_box_thread->Add(card_header(m_cards, "design_thread", _L("Thread"), m_hdr_thread), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_thread->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_box_thread->Add(tform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    cards->Add(m_box_thread, 0, wxEXPAND);
+
+    // --- Revolve (sweep a sketch profile about an in-plane axis) ---
+    m_box_revolve = new wxBoxSizer(wxVERTICAL);
+    m_box_revolve->Add(card_header(m_cards, "design_revolve", _L("Revolve"), m_hdr_revolve), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_revolve->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_revolve_sketch_label = new wxStaticText(m_cards, wxID_ANY, _L("Sketch: —"));
+    m_box_revolve->Add(m_revolve_sketch_label, 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    {
+        auto* rform = two_col_form();
+
+        m_revolve_angle = make_spin(m_cards, 360.0, 1.0, 360.0);
+        rform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Angle °")), 0, wxALIGN_CENTER_VERTICAL);
+        rform->Add(spin_frame(m_revolve_angle), 0, wxEXPAND);
+
+        m_revolve_axis = make_combo(m_cards);
+        m_revolve_axis->Append(_L("Plane X"));
+        m_revolve_axis->Append(_L("Plane Y"));
+        m_revolve_axis->SetSelection(0);
+        rform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Axis")), 0, wxALIGN_CENTER_VERTICAL);
+        rform->Add(m_revolve_axis, 0, wxEXPAND);
+
+        m_revolve_mode = make_combo(m_cards);
+        m_revolve_mode->Append(_L("New"));
+        m_revolve_mode->Append(_L("Add"));
+        m_revolve_mode->Append(_L("Cut"));
+        m_revolve_mode->Append(_L("Intersect"));
+        m_revolve_mode->SetSelection(0);
+        rform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Mode")), 0, wxALIGN_CENTER_VERTICAL);
+        rform->Add(m_revolve_mode, 0, wxEXPAND);
+
+        m_revolve_flip = new CheckBox(m_cards);
+        rform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Flip direction")), 0, wxALIGN_CENTER_VERTICAL);
+        rform->Add(m_revolve_flip, 0, wxALIGN_LEFT | wxALIGN_CENTER_VERTICAL);
+
+        m_box_revolve->Add(rform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_revolve, 0, wxEXPAND);
+
+    // --- Sweep (sweep a profile sketch along a path sketch) ---
+    m_box_sweep = new wxBoxSizer(wxVERTICAL);
+    m_box_sweep->Add(card_header(m_cards, "design_sweep", _L("Sweep"), m_hdr_sweep), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_sweep->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_sweep_profile_label = new wxStaticText(m_cards, wxID_ANY, _L("Profile: —"));
+    m_box_sweep->Add(m_sweep_profile_label, 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    {
+        auto* sform = two_col_form();
+
+        m_sweep_path = make_combo(m_cards);
+        sform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Path")), 0, wxALIGN_CENTER_VERTICAL);
+        sform->Add(m_sweep_path, 0, wxEXPAND);
+
+        m_sweep_mode = make_combo(m_cards);
+        m_sweep_mode->Append(_L("New"));
+        m_sweep_mode->Append(_L("Add"));
+        m_sweep_mode->Append(_L("Cut"));
+        m_sweep_mode->Append(_L("Intersect"));
+        m_sweep_mode->SetSelection(0);
+        sform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Mode")), 0, wxALIGN_CENTER_VERTICAL);
+        sform->Add(m_sweep_mode, 0, wxEXPAND);
+
+        m_box_sweep->Add(sform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_sweep, 0, wxEXPAND);
+
+    // --- Pattern (replicate the target body: linear or circular) ---
+    m_box_pattern = new wxBoxSizer(wxVERTICAL);
+    m_box_pattern->Add(card_header(m_cards, "design_pattern", _L("Pattern"), m_hdr_pattern), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_pattern->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        auto* pform = two_col_form();
+
+        m_pattern_type = make_combo(m_cards);
+        m_pattern_type->Append(_L("Linear"));
+        m_pattern_type->Append(_L("Circular"));
+        m_pattern_type->SetSelection(0);
+        pform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Type")), 0, wxALIGN_CENTER_VERTICAL);
+        pform->Add(m_pattern_type, 0, wxEXPAND);
+
+        m_pattern_count = make_spin(m_cards, 3, 1, 999);
+        pform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Count")), 0, wxALIGN_CENTER_VERTICAL);
+        pform->Add(spin_frame(m_pattern_count), 0, wxEXPAND);
+
+        m_pattern_spacing = make_spin(m_cards, 20.0, 0.01, 100000.0);
+        pform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Spacing")), 0, wxALIGN_CENTER_VERTICAL);
+        pform->Add(spin_frame(m_pattern_spacing), 0, wxEXPAND);
+
+        m_pattern_dir = make_combo(m_cards);
+        m_pattern_dir->Append(_L("Plane X"));
+        m_pattern_dir->Append(_L("Plane Y"));
+        m_pattern_dir->SetSelection(0);
+        pform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Direction")), 0, wxALIGN_CENTER_VERTICAL);
+        pform->Add(m_pattern_dir, 0, wxEXPAND);
+
+        m_pattern_angle = make_spin(m_cards, 360.0, 1.0, 360.0);
+        pform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Total angle°")), 0, wxALIGN_CENTER_VERTICAL);
+        pform->Add(spin_frame(m_pattern_angle), 0, wxEXPAND);
+
+        m_box_pattern->Add(pform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_pattern, 0, wxEXPAND);
+
+    // --- Boolean (combine two existing bodies: union / subtract / intersect) ---
+    m_box_boolean = new wxBoxSizer(wxVERTICAL);
+    m_box_boolean->Add(card_header(m_cards, "design_boolean", _L("Boolean"), m_hdr_boolean), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_boolean->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        auto* bform = two_col_form();
+
+        m_bool_op = make_combo(m_cards);
+        m_bool_op->Append(_L("Union (join)"));
+        m_bool_op->Append(_L("Subtract (cut)"));
+        m_bool_op->Append(_L("Intersect"));
+        m_bool_op->SetSelection(0);
+        m_bool_op->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        bform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Operation")), 0, wxALIGN_CENTER_VERTICAL);
+        bform->Add(m_bool_op, 0, wxEXPAND);
+
+        m_bool_target = make_combo(m_cards);
+        m_bool_target->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        bform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Target (kept)")), 0, wxALIGN_CENTER_VERTICAL);
+        bform->Add(m_bool_target, 0, wxEXPAND);
+
+        m_bool_tool = make_combo(m_cards);
+        m_bool_tool->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        bform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Tool")), 0, wxALIGN_CENTER_VERTICAL);
+        bform->Add(m_bool_tool, 0, wxEXPAND);
+
+        // Fuzzy tolerance (mm): the main use is a tool body cutting a destination — a small
+        // tolerance lets near-coincident mating faces resolve into a clean cut instead of a
+        // failed boolean or sliver faces. 0 = exact.
+        m_bool_tol = make_spin(m_cards, 0.0, 0.0, 100.0);
+        m_bool_tol->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        bform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Tolerance")), 0, wxALIGN_CENTER_VERTICAL);
+        bform->Add(spin_frame(m_bool_tol), 0, wxEXPAND);
+
+        m_box_boolean->Add(bform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+
+        m_bool_keep = new CheckBox(m_cards);
+        m_bool_keep->Bind(wxEVT_TOGGLEBUTTON, [this](wxCommandEvent&) { refresh_preview(); });
+        auto* keeprow = new wxBoxSizer(wxHORIZONTAL);
+        keeprow->Add(new wxStaticText(m_cards, wxID_ANY, _L("Keep tool body")), 0, wxALIGN_CENTER_VERTICAL);
+        keeprow->AddStretchSpacer();
+        keeprow->Add(m_bool_keep, 0, wxALIGN_CENTER_VERTICAL);
+        m_box_boolean->Add(keeprow, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_boolean, 0, wxEXPAND);
+
+    // --- Cut (split a body with a plane): parameters only; ✓/✗ live on the ribbon ---
+    m_box_cut = new wxBoxSizer(wxVERTICAL);
+    m_box_cut->Add(card_header(m_cards, "design_cut", _L("Cut"), m_hdr_cut), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_cut->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        auto* cform = two_col_form();
+
+        m_cut_target = make_combo(m_cards);
+        m_cut_target->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        cform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Body")), 0, wxALIGN_CENTER_VERTICAL);
+        cform->Add(m_cut_target, 0, wxEXPAND);
+
+        m_cut_plane = make_combo(m_cards);
+        m_cut_plane->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        cform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Plane")), 0, wxALIGN_CENTER_VERTICAL);
+        cform->Add(m_cut_plane, 0, wxEXPAND);
+
+        m_cut_offset = make_spin(m_cards, 0.0, -10000.0, 10000.0);
+        m_cut_offset->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        cform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Offset")), 0, wxALIGN_CENTER_VERTICAL);
+        cform->Add(spin_frame(m_cut_offset), 0, wxEXPAND);
+
+        m_box_cut->Add(cform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        // The cut always leaves BOTH pieces as separate bodies (a non-destructive split);
+        // delete one from the tree afterwards if you only want a half.
+    }
+    cards->Add(m_box_cut, 0, wxEXPAND);
+
+    // --- Insert (Text / SVG placement): Confirm/Cancel for the in-canvas art transform ---
+    m_box_insert = new wxBoxSizer(wxVERTICAL);
+    m_box_insert->Add(card_header(m_cards, "design_text", _L("Insert"), m_hdr_insert), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_insert->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_box_insert->Add(new wxStaticText(m_cards, wxID_ANY,
+        _L("Drag a corner to size, the centre to move.\nConfirm or Cancel in the toolbar above.")),
+        0, wxLEFT | wxRIGHT | wxBOTTOM, 12);
+    cards->Add(m_box_insert, 0, wxEXPAND);
+
+    // --- Plane (datum/reference plane: offset + tilt from a base plane; no solid) ---
+    m_box_plane = new wxBoxSizer(wxVERTICAL);
+    m_box_plane->Add(card_header(m_cards, "design_plane", _L("Plane"), m_hdr_plane), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_plane->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        // Plane type chooses which inputs matter (Onshape/Fusion parity):
+        //   Offset      = Base (or Face A) + Offset (+ Tilt about a base axis)
+        //   Angle       = Edge A (line) + Base/Face A reference + Angle°
+        //   Midplane    = Face A + Face B (halfway between)
+        //   Tangent     = Face A (a cylinder) + Angle° around its axis
+        //   Two edges   = Edge A + Edge B
+        //   Coincident  = Face A (lie on that face)
+        m_plane_type = make_combo(m_cards);
+        for (const wxString& t : { _L("Offset"), _L("Angle"), _L("Midplane"),
+                                   _L("Tangent"), _L("Two edges"), _L("Coincident") })
+            m_plane_type->Append(t);
+        m_plane_type->SetSelection(0);
+        m_box_plane->Add(new wxStaticText(m_cards, wxID_ANY, _L("Plane type")), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_plane->Add(m_plane_type, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+
+        auto* plform = two_col_form();
+
+        m_plane_base = make_combo(m_cards);
+        populate_plane_choices(m_plane_base);   // XY/XZ/YZ + any existing datum planes
+        plform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Base")), 0, wxALIGN_CENTER_VERTICAL);
+        plform->Add(m_plane_base, 0, wxEXPAND);
+
+        m_plane_offset = make_spin(m_cards, 20.0, -100000.0, 100000.0);
+        plform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Offset")), 0, wxALIGN_CENTER_VERTICAL);
+        plform->Add(spin_frame(m_plane_offset), 0, wxEXPAND);
+
+        m_plane_tilt = make_spin(m_cards, 0.0, -180.0, 180.0);
+        plform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Angle°")), 0, wxALIGN_CENTER_VERTICAL);
+        plform->Add(spin_frame(m_plane_tilt), 0, wxEXPAND);
+
+        m_plane_tilt_axis = make_combo(m_cards);
+        m_plane_tilt_axis->Append(_L("Base X"));
+        m_plane_tilt_axis->Append(_L("Base Y"));
+        m_plane_tilt_axis->SetSelection(0);
+        plform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Tilt axis")), 0, wxALIGN_CENTER_VERTICAL);
+        plform->Add(m_plane_tilt_axis, 0, wxEXPAND);
+
+        // Contextual reference picks: arm a target, then click a solid face/edge in the canvas.
+        auto pick_row = [&](const wxString& label, wxButton*& btn, wxStaticText*& lbl, PlanePick target) {
+            btn = new wxButton(m_cards, wxID_ANY, label);
+            lbl = new wxStaticText(m_cards, wxID_ANY, _L("(none)"));
+            btn->Bind(wxEVT_BUTTON, [this, target](wxCommandEvent&) { arm_plane_pick(target); });
+            plform->Add(btn);
+            plform->Add(lbl, 0, wxALIGN_CENTER_VERTICAL);
+        };
+        pick_row(_L("Pick Face A"), m_plane_pick_faceA, m_plane_faceA_lbl, PlanePick::FaceA);
+        pick_row(_L("Pick Face B"), m_plane_pick_faceB, m_plane_faceB_lbl, PlanePick::FaceB);
+        pick_row(_L("Pick Edge A"), m_plane_pick_edgeA, m_plane_edgeA_lbl, PlanePick::EdgeA);
+        pick_row(_L("Pick Edge B"), m_plane_pick_edgeB, m_plane_edgeB_lbl, PlanePick::EdgeB);
+
+        m_plane_usize = make_spin(m_cards, 60.0, 1.0, 100000.0);
+        plform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Size U")), 0, wxALIGN_CENTER_VERTICAL);
+        plform->Add(spin_frame(m_plane_usize), 0, wxEXPAND);
+        m_plane_vsize = make_spin(m_cards, 60.0, 1.0, 100000.0);
+        plform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Size V")), 0, wxALIGN_CENTER_VERTICAL);
+        plform->Add(spin_frame(m_plane_vsize), 0, wxEXPAND);
+
+        m_box_plane->Add(plform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_plane, 0, wxEXPAND);
+
+    // --- Loft (skin a solid through 2+ ordered profile sketches) ---
+    m_box_loft = new wxBoxSizer(wxVERTICAL);
+    m_box_loft->Add(card_header(m_cards, "design_loft", _L("Loft"), m_hdr_loft), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_loft->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_box_loft->Add(new wxStaticText(m_cards, wxID_ANY, _L("Profiles (check 2+, in order):")),
+                    0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_loft_list = new wxCheckListBox(m_cards, wxID_ANY, wxDefaultPosition, wxSize(-1, 120));
+    m_loft_list->Bind(wxEVT_CHECKLISTBOX, [this](wxCommandEvent&) { refresh_preview(); });
+    m_box_loft->Add(m_loft_list, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    {
+        auto* lform = two_col_form();
+
+        m_loft_mode = make_combo(m_cards);
+        m_loft_mode->Append(_L("New"));
+        m_loft_mode->Append(_L("Add"));
+        m_loft_mode->Append(_L("Cut"));
+        m_loft_mode->Append(_L("Intersect"));
+        m_loft_mode->SetSelection(0);
+        lform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Mode")), 0, wxALIGN_CENTER_VERTICAL);
+        lform->Add(m_loft_mode, 0, wxEXPAND);
+
+        m_box_loft->Add(lform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    m_loft_ruled = new CheckBox(m_cards);
+    {
+        auto* lrow = new wxBoxSizer(wxHORIZONTAL);
+        lrow->Add(new wxStaticText(m_cards, wxID_ANY, _L("Ruled (straight) sections")), 0, wxALIGN_CENTER_VERTICAL);
+        lrow->AddStretchSpacer();
+        lrow->Add(m_loft_ruled, 0, wxALIGN_CENTER_VERTICAL);
+        m_box_loft->Add(lrow, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_loft, 0, wxEXPAND);
+
+    // --- Surface Extrude (sheet body from sketch) ---
+    m_box_surf_extrude = new wxBoxSizer(wxVERTICAL);
+    m_box_surf_extrude->Add(card_header(m_cards, "design_extrude", _L("Surface Extrude"), m_hdr_surf_extrude), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_surf_extrude->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_surf_extrude_sketch_label = new wxStaticText(m_cards, wxID_ANY, _L("Sketch: —"));
+    m_box_surf_extrude->Add(m_surf_extrude_sketch_label, 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    {
+        auto* sform = two_col_form();
+        m_surf_extrude_distance = make_spin(m_cards, 10);
+        sform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Distance")), 0, wxALIGN_CENTER_VERTICAL);
+        sform->Add(spin_frame(m_surf_extrude_distance), 0, wxEXPAND);
+        m_box_surf_extrude->Add(sform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_surf_extrude, 0, wxEXPAND);
+
+    // --- Surface Revolve (sheet body from sketch about axis) ---
+    m_box_surf_revolve = new wxBoxSizer(wxVERTICAL);
+    m_box_surf_revolve->Add(card_header(m_cards, "design_revolve", _L("Surface Revolve"), m_hdr_surf_revolve), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_surf_revolve->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_surf_revolve_sketch_label = new wxStaticText(m_cards, wxID_ANY, _L("Sketch: —"));
+    m_box_surf_revolve->Add(m_surf_revolve_sketch_label, 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    {
+        auto* rform = two_col_form();
+        m_surf_revolve_angle = make_spin(m_cards, 360.0, 1.0, 360.0);
+        rform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Angle °")), 0, wxALIGN_CENTER_VERTICAL);
+        rform->Add(spin_frame(m_surf_revolve_angle), 0, wxEXPAND);
+        m_surf_revolve_axis = make_combo(m_cards);
+        m_surf_revolve_axis->Append(_L("Plane X"));
+        m_surf_revolve_axis->Append(_L("Plane Y"));
+        m_surf_revolve_axis->SetSelection(0);
+        rform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Axis")), 0, wxALIGN_CENTER_VERTICAL);
+        rform->Add(m_surf_revolve_axis, 0, wxEXPAND);
+        m_surf_revolve_flip = new CheckBox(m_cards);
+        rform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Flip direction")), 0, wxALIGN_CENTER_VERTICAL);
+        rform->Add(m_surf_revolve_flip, 0, wxALIGN_LEFT | wxALIGN_CENTER_VERTICAL);
+        m_box_surf_revolve->Add(rform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_surf_revolve, 0, wxEXPAND);
+
+    // --- Surface Loft (sheet skin through 2+ ordered profile sketches) ---
+    m_box_surf_loft = new wxBoxSizer(wxVERTICAL);
+    m_box_surf_loft->Add(card_header(m_cards, "design_loft", _L("Surface Loft"), m_hdr_surf_loft), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_surf_loft->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_box_surf_loft->Add(new wxStaticText(m_cards, wxID_ANY, _L("Profiles (check 2+, in order):")),
+                         0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_surf_loft_list = new wxCheckListBox(m_cards, wxID_ANY, wxDefaultPosition, wxSize(-1, 120));
+    m_surf_loft_list->Bind(wxEVT_CHECKLISTBOX, [this](wxCommandEvent&) { refresh_preview(); });
+    m_box_surf_loft->Add(m_surf_loft_list, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    m_surf_loft_ruled = new CheckBox(m_cards);
+    {
+        auto* lrow = new wxBoxSizer(wxHORIZONTAL);
+        lrow->Add(new wxStaticText(m_cards, wxID_ANY, _L("Ruled (straight) sections")), 0, wxALIGN_CENTER_VERTICAL);
+        lrow->AddStretchSpacer();
+        lrow->Add(m_surf_loft_ruled, 0, wxALIGN_CENTER_VERTICAL);
+        m_box_surf_loft->Add(lrow, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_surf_loft, 0, wxEXPAND);
+
+    // --- Surface Fill (one-face sheet from sketch boundary) ---
+    m_box_surf_fill = new wxBoxSizer(wxVERTICAL);
+    m_box_surf_fill->Add(card_header(m_cards, "design_surface", _L("Surface Fill"), m_hdr_surf_fill), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_surf_fill->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_surf_fill_sketch_label = new wxStaticText(m_cards, wxID_ANY, _L("Sketch: —"));
+    m_box_surf_fill->Add(m_surf_fill_sketch_label, 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_surf_fill->Add(new wxStaticText(m_cards, wxID_ANY,
+                          _L("Fills the sketch's closed boundary with a smooth face.")),
+                         0, wxLEFT | wxRIGHT, 12);
+    cards->Add(m_box_surf_fill, 0, wxEXPAND);
+
+    // --- Surface Offset (offset a sheet body) ---
+    m_box_surf_offset = new wxBoxSizer(wxVERTICAL);
+    m_box_surf_offset->Add(card_header(m_cards, "design_offset", _L("Surface Offset"), m_hdr_surf_offset), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_surf_offset->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        auto* oform = two_col_form();
+        m_surf_offset_body = make_combo(m_cards);
+        m_surf_offset_body->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        oform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Sheet body")), 0, wxALIGN_CENTER_VERTICAL);
+        oform->Add(m_surf_offset_body, 0, wxEXPAND);
+        m_surf_offset_distance = make_spin(m_cards, 1.0, -100000.0, 100000.0);
+        m_surf_offset_distance->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        oform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Offset")), 0, wxALIGN_CENTER_VERTICAL);
+        oform->Add(spin_frame(m_surf_offset_distance), 0, wxEXPAND);
+        m_box_surf_offset->Add(oform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_surf_offset->Add(new wxStaticText(m_cards, wxID_ANY,
+                                  _L("Offsets a sheet body's shell. Positive = outward, negative = inward.")),
+                               0, wxLEFT | wxRIGHT, 12);
+    }
+    cards->Add(m_box_surf_offset, 0, wxEXPAND);
+
+    // --- Thicken Surface (thicken a sheet body into a solid) ---
+    m_box_surf_thicken = new wxBoxSizer(wxVERTICAL);
+    m_box_surf_thicken->Add(card_header(m_cards, "design_thicken", _L("Thicken Surface"), m_hdr_surf_thicken), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_surf_thicken->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        auto* tform = two_col_form();
+        m_surf_thicken_body = make_combo(m_cards);
+        m_surf_thicken_body->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Sheet body")), 0, wxALIGN_CENTER_VERTICAL);
+        tform->Add(m_surf_thicken_body, 0, wxEXPAND);
+        m_surf_thicken_thickness = make_spin(m_cards, 1.0, 0.01, 100000.0);
+        m_surf_thicken_thickness->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Thickness")), 0, wxALIGN_CENTER_VERTICAL);
+        tform->Add(spin_frame(m_surf_thicken_thickness), 0, wxEXPAND);
+        m_surf_thicken_flip = new CheckBox(m_cards);
+        m_surf_thicken_flip->Bind(wxEVT_TOGGLEBUTTON, [this](wxCommandEvent&) { refresh_preview(); });
+        tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Flip direction")), 0, wxALIGN_CENTER_VERTICAL);
+        tform->Add(m_surf_thicken_flip, 0, wxALIGN_LEFT | wxALIGN_CENTER_VERTICAL);
+        m_box_surf_thicken->Add(tform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_surf_thicken->Add(new wxStaticText(m_cards, wxID_ANY,
+                                  _L("Thickens a sheet body into a solid. Flip reverses the direction.")),
+                               0, wxLEFT | wxRIGHT, 12);
+    }
+    cards->Add(m_box_surf_thicken, 0, wxEXPAND);
+
+    // --- Shell (hollow the current body to a wall thickness, removing one picked face) ---
+    auto* sform = two_col_form();
+    m_shell_thickness = make_spin(m_cards, 2.0, 0.01, 100000.0);
+    sform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Thickness")), 0, wxALIGN_CENTER_VERTICAL);
+    sform->Add(spin_frame(m_shell_thickness), 0, wxEXPAND);
+    m_shell_face_label = new wxStaticText(m_cards, wxID_ANY, _L("(all faces — closed hollow)"));
+    sform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Open face")), 0, wxALIGN_CENTER_VERTICAL);
+    sform->Add(m_shell_face_label, 0, wxALIGN_CENTER_VERTICAL);
+
+    m_box_shell = new wxBoxSizer(wxVERTICAL);
+    m_box_shell->Add(card_header(m_cards, "design_shell", _L("Shell"), m_hdr_shell), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_shell->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_box_shell->Add(new wxStaticText(m_cards, wxID_ANY,
+                        _L("Pick a solid face to open it, then set the wall thickness.")),
+                     0, wxLEFT | wxRIGHT, 12);
+    m_box_shell->Add(sform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    cards->Add(m_box_shell, 0, wxEXPAND);
+
+    // --- Draft (taper a single picked solid face about the body bottom) ---
+    auto* drform = two_col_form();
+    m_draft_angle = make_spin(m_cards, 5.0, -89.0, 89.0);
+    drform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Angle (°)")), 0, wxALIGN_CENTER_VERTICAL);
+    drform->Add(spin_frame(m_draft_angle), 0, wxEXPAND);
+    m_draft_face_label = new wxStaticText(m_cards, wxID_ANY, _L("(pick a side face)"));
+    drform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Face")), 0, wxALIGN_CENTER_VERTICAL);
+    drform->Add(m_draft_face_label, 0, wxALIGN_CENTER_VERTICAL);
+
+    m_box_draft = new wxBoxSizer(wxVERTICAL);
+    m_box_draft->Add(card_header(m_cards, "design_draft", _L("Draft"), m_hdr_draft), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_draft->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_box_draft->Add(new wxStaticText(m_cards, wxID_ANY,
+                        _L("Pick a side face, then set the draft angle. The face pivots about the body base.")),
+                     0, wxLEFT | wxRIGHT, 12);
+    m_box_draft->Add(drform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    cards->Add(m_box_draft, 0, wxEXPAND);
+
+    // --- Transform (rigid move/rotate of an existing body) ---
+    m_box_transform = new wxBoxSizer(wxVERTICAL);
+    m_box_transform->Add(card_header(m_cards, "design_move", _L("Transform"), m_hdr_transform), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_transform->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        auto* xform = two_col_form();
+        m_xf_body = make_combo(m_cards);
+        m_xf_body->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        xform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Body")), 0, wxALIGN_CENTER_VERTICAL);
+        xform->Add(m_xf_body, 0, wxEXPAND);
+        m_xf_dx = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        m_xf_dx->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        xform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Translate X")), 0, wxALIGN_CENTER_VERTICAL);
+        xform->Add(spin_frame(m_xf_dx), 0, wxEXPAND);
+        m_xf_dy = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        m_xf_dy->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        xform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Translate Y")), 0, wxALIGN_CENTER_VERTICAL);
+        xform->Add(spin_frame(m_xf_dy), 0, wxEXPAND);
+        m_xf_dz = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        m_xf_dz->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        xform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Translate Z")), 0, wxALIGN_CENTER_VERTICAL);
+        xform->Add(spin_frame(m_xf_dz), 0, wxEXPAND);
+        m_xf_axis = make_combo(m_cards);
+        m_xf_axis->Append(_L("X"));
+        m_xf_axis->Append(_L("Y"));
+        m_xf_axis->Append(_L("Z"));
+        m_xf_axis->SetSelection(2);  // default Z
+        m_xf_axis->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        xform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Rotate axis")), 0, wxALIGN_CENTER_VERTICAL);
+        xform->Add(m_xf_axis, 0, wxEXPAND);
+        m_xf_angle = make_spin(m_cards, 0.0, -360.0, 360.0);
+        m_xf_angle->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        xform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Angle (°)")), 0, wxALIGN_CENTER_VERTICAL);
+        xform->Add(spin_frame(m_xf_angle), 0, wxEXPAND);
+        m_xf_pivot_x = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        m_xf_pivot_x->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        xform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Pivot X")), 0, wxALIGN_CENTER_VERTICAL);
+        xform->Add(spin_frame(m_xf_pivot_x), 0, wxEXPAND);
+        m_xf_pivot_y = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        m_xf_pivot_y->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        xform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Pivot Y")), 0, wxALIGN_CENTER_VERTICAL);
+        xform->Add(spin_frame(m_xf_pivot_y), 0, wxEXPAND);
+        m_xf_pivot_z = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        m_xf_pivot_z->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        xform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Pivot Z")), 0, wxALIGN_CENTER_VERTICAL);
+        xform->Add(spin_frame(m_xf_pivot_z), 0, wxEXPAND);
+        m_box_transform->Add(xform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        m_xf_copy = new CheckBox(m_cards);
+        m_xf_copy->Bind(wxEVT_TOGGLEBUTTON, [this](wxCommandEvent&) { refresh_preview(); });
+        auto* cpro = new wxBoxSizer(wxHORIZONTAL);
+        cpro->Add(new wxStaticText(m_cards, wxID_ANY, _L("Keep original (make a copy)")), 0, wxALIGN_CENTER_VERTICAL);
+        cpro->AddStretchSpacer();
+        cpro->Add(m_xf_copy, 0, wxALIGN_CENTER_VERTICAL);
+        m_box_transform->Add(cpro, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_transform->Add(new wxStaticText(m_cards, wxID_ANY,
+                               _L("Translate and/or rotate the selected body. Rotation is applied about the pivot, then translation follows.")),
+                            0, wxLEFT | wxRIGHT, 12);
+    }
+    cards->Add(m_box_transform, 0, wxEXPAND);
+
+    // --- Mirror (reflect a body about a plane) ---
+    m_box_mirror = new wxBoxSizer(wxVERTICAL);
+    m_box_mirror->Add(card_header(m_cards, "design_mirror", _L("Mirror"), m_hdr_mirror), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_mirror->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        auto* mform = two_col_form();
+        m_mirror_body = make_combo(m_cards);
+        m_mirror_body->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        mform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Body")), 0, wxALIGN_CENTER_VERTICAL);
+        mform->Add(m_mirror_body, 0, wxEXPAND);
+        m_mirror_plane = make_combo(m_cards);
+        m_mirror_plane->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        mform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Mirror plane")), 0, wxALIGN_CENTER_VERTICAL);
+        mform->Add(m_mirror_plane, 0, wxEXPAND);
+        m_box_mirror->Add(mform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        m_mirror_keep = new CheckBox(m_cards);
+        m_mirror_keep->SetValue(true);
+        m_mirror_keep->Bind(wxEVT_TOGGLEBUTTON, [this](wxCommandEvent&) { refresh_preview(); });
+        auto* mkrow = new wxBoxSizer(wxHORIZONTAL);
+        mkrow->Add(new wxStaticText(m_cards, wxID_ANY, _L("Keep original")), 0, wxALIGN_CENTER_VERTICAL);
+        mkrow->AddStretchSpacer();
+        mkrow->Add(m_mirror_keep, 0, wxALIGN_CENTER_VERTICAL);
+        m_box_mirror->Add(mkrow, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_mirror->Add(new wxStaticText(m_cards, wxID_ANY,
+                            _L("Reflect the selected body about a plane. The mirror is always a new body; keeping the original gives you both.")),
+                         0, wxLEFT | wxRIGHT, 12);
+    }
+    cards->Add(m_box_mirror, 0, wxEXPAND);
+
+    // --- Thicken (offset one solid face into a thin plate) ---
+    m_box_thicken = new wxBoxSizer(wxVERTICAL);
+    m_box_thicken->Add(card_header(m_cards, "design_thicken", _L("Thicken"), m_hdr_thicken), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_thicken->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        auto* tform = two_col_form();
+        m_thicken_body = make_combo(m_cards);
+        m_thicken_body->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Body")), 0, wxALIGN_CENTER_VERTICAL);
+        tform->Add(m_thicken_body, 0, wxEXPAND);
+        m_thicken_face_label = new wxStaticText(m_cards, wxID_ANY, _L("(pick a solid face)"));
+        tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Face")), 0, wxALIGN_CENTER_VERTICAL);
+        tform->Add(m_thicken_face_label, 0, wxALIGN_CENTER_VERTICAL);
+        m_thicken_thickness = make_spin(m_cards, 2.0, 0.01, 100000.0);
+        m_thicken_thickness->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        tform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Thickness")), 0, wxALIGN_CENTER_VERTICAL);
+        tform->Add(spin_frame(m_thicken_thickness), 0, wxEXPAND);
+        m_box_thicken->Add(tform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        m_thicken_flip = new CheckBox(m_cards);
+        m_thicken_flip->Bind(wxEVT_TOGGLEBUTTON, [this](wxCommandEvent&) { refresh_preview(); });
+        auto* trow = new wxBoxSizer(wxHORIZONTAL);
+        trow->Add(new wxStaticText(m_cards, wxID_ANY, _L("Flip direction")), 0, wxALIGN_CENTER_VERTICAL);
+        trow->AddStretchSpacer();
+        trow->Add(m_thicken_flip, 0, wxALIGN_CENTER_VERTICAL);
+        m_box_thicken->Add(trow, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_thicken->Add(new wxStaticText(m_cards, wxID_ANY,
+                              _L("Pick a solid face and offset it into a new thin body. Not for sheet bodies — use Thicken Surface for those.")),
+                           0, wxLEFT | wxRIGHT, 12);
+    }
+    cards->Add(m_box_thicken, 0, wxEXPAND);
+
+    // --- Rib (thin wall from an open sketch line, fused to a body) ---
+    m_box_rib = new wxBoxSizer(wxVERTICAL);
+    m_box_rib->Add(card_header(m_cards, "design_rib", _L("Rib"), m_hdr_rib), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_rib->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        auto* rform = two_col_form();
+        m_rib_body = make_combo(m_cards);
+        m_rib_body->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        rform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Target body")), 0, wxALIGN_CENTER_VERTICAL);
+        rform->Add(m_rib_body, 0, wxEXPAND);
+        m_rib_sketch = make_combo(m_cards);
+        m_rib_sketch->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        rform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Sketch")), 0, wxALIGN_CENTER_VERTICAL);
+        rform->Add(m_rib_sketch, 0, wxEXPAND);
+        m_rib_entity = new wxSpinCtrl(m_cards, wxID_ANY, "", wxDefaultPosition, wxSize(90, -1),
+                                      wxSP_ARROW_KEYS | wxBORDER_SIMPLE);
+        m_rib_entity->SetRange(0, 999);
+        m_rib_entity->SetValue(0);
+        m_rib_entity->Bind(wxEVT_SPINCTRL, [this](wxSpinEvent&) { refresh_preview(); });
+        rform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Entity index")), 0, wxALIGN_CENTER_VERTICAL);
+        rform->Add(m_rib_entity, 0, wxEXPAND);
+        m_rib_thickness = make_spin(m_cards, 2.0, 0.01, 100000.0);
+        m_rib_thickness->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        rform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Thickness")), 0, wxALIGN_CENTER_VERTICAL);
+        rform->Add(spin_frame(m_rib_thickness), 0, wxEXPAND);
+        m_rib_depth = make_spin(m_cards, 10.0, 0.01, 100000.0);
+        m_rib_depth->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        rform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Depth")), 0, wxALIGN_CENTER_VERTICAL);
+        rform->Add(spin_frame(m_rib_depth), 0, wxEXPAND);
+        m_box_rib->Add(rform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_rib->Add(new wxStaticText(m_cards, wxID_ANY,
+                          _L("Grow a thin wall from an open sketch Line entity, fused to the target body. Entity index is the position of the open Line in the sketch.")),
+                       0, wxLEFT | wxRIGHT, 12);
+    }
+    cards->Add(m_box_rib, 0, wxEXPAND);
+
+    // --- Project (project body edges onto a plane as sketch entities) ---
+    m_box_project = new wxBoxSizer(wxVERTICAL);
+    m_box_project->Add(card_header(m_cards, "design_sketch", _L("Project"), m_hdr_project), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_project->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        auto* pform = two_col_form();
+        m_proj_source_body = make_combo(m_cards);
+        m_proj_source_body->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        pform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Source body")), 0, wxALIGN_CENTER_VERTICAL);
+        pform->Add(m_proj_source_body, 0, wxEXPAND);
+        m_proj_face_label = new wxStaticText(m_cards, wxID_ANY, _L("(all edges)"));
+        pform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Face")), 0, wxALIGN_CENTER_VERTICAL);
+        pform->Add(m_proj_face_label, 0, wxALIGN_CENTER_VERTICAL);
+        m_proj_plane = make_combo(m_cards);
+        populate_plane_choices(m_proj_plane);
+        m_proj_plane->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        pform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Target plane")), 0, wxALIGN_CENTER_VERTICAL);
+        pform->Add(m_proj_plane, 0, wxEXPAND);
+        m_box_project->Add(pform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_project->Add(new wxStaticText(m_cards, wxID_ANY,
+                              _L("Project the edges of a body onto a plane as sketch entities. Pick a face to project only its edges, or leave the face empty to project the whole body.")),
+                           0, wxLEFT | wxRIGHT, 12);
+    }
+    cards->Add(m_box_project, 0, wxEXPAND);
+
+    // --- Delete Face (remove faces, heal the solid) ---
+    m_box_delete_face = new wxBoxSizer(wxVERTICAL);
+    m_box_delete_face->Add(card_header(m_cards, "design_delete", _L("Delete Face"), m_hdr_delete_face), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_delete_face->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        auto* dform = two_col_form();
+        m_del_face_body = make_combo(m_cards);
+        m_del_face_body->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        dform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Body")), 0, wxALIGN_CENTER_VERTICAL);
+        dform->Add(m_del_face_body, 0, wxEXPAND);
+        m_del_face_add_btn = new wxButton(m_cards, wxID_ANY, _L("Add picked face"));
+        m_del_face_add_btn->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) {
+            // Say why nothing happened. Clicking with no face picked used to be a silent no-op,
+            // which is indistinguishable from the button being broken.
+            if (m_sel_solid_face < 0) {
+                m_status->SetForegroundColour(wxColour(235, 110, 110));
+                set_status(_L("Click a face on the body first, then Add picked face"));
+                m_status->Refresh();
+                return;
+            }
+            // Adding the same face twice puts a duplicate id in delete_faces, which the
+            // defeaturing algorithm has no reason to cope with. Re-clicking is a no-op, not an error.
+            if (std::find(m_del_faces.begin(), m_del_faces.end(), m_sel_solid_face) != m_del_faces.end()) {
+                m_status->SetForegroundColour(wxNullColour);
+                set_status(wxString::Format(_L("Face %d is already in the list"), m_sel_solid_face));
+                m_status->Refresh();
+                return;
+            }
+            {
+                m_del_faces.push_back(m_sel_solid_face);
+                wxString s;
+                for (size_t i = 0; i < m_del_faces.size(); ++i) {
+                    if (i > 0) s += ", ";
+                    s += wxString::Format("Face %d", m_del_faces[i]);
+                }
+                m_del_face_list->SetLabel(s.empty() ? _L("(none)") : s);
+                m_del_face_list->GetParent()->Layout();
+                m_del_face_list->Refresh();
+                refresh_preview();
+            }
+        });
+        dform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Faces to delete")), 0, wxALIGN_CENTER_VERTICAL);
+        dform->Add(m_del_face_add_btn, 0, wxALIGN_CENTER_VERTICAL);
+        m_del_face_list = new wxStaticText(m_cards, wxID_ANY, _L("(none)"));
+        dform->Add(0, 0);
+        dform->Add(m_del_face_list, 0, wxALIGN_CENTER_VERTICAL);
+        m_box_delete_face->Add(dform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_delete_face->Add(new wxStaticText(m_cards, wxID_ANY,
+                                  _L("Pick a solid face, then click 'Add picked face' to accumulate faces. Confirm to remove all listed faces and heal the solid.")),
+                               0, wxLEFT | wxRIGHT, 12);
+    }
+    cards->Add(m_box_delete_face, 0, wxEXPAND);
+
+    // --- Helix (helical curve) ---
+    m_box_helix = new wxBoxSizer(wxVERTICAL);
+    m_box_helix->Add(card_header(m_cards, "design_thread", _L("Helix"), m_hdr_helix), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_helix->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        auto* hform = two_col_form();
+        m_helix_plane = make_combo(m_cards);
+        populate_plane_choices(m_helix_plane);
+        m_helix_plane->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+        hform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Plane")), 0, wxALIGN_CENTER_VERTICAL);
+        hform->Add(m_helix_plane, 0, wxEXPAND);
+        m_helix_radius = make_spin(m_cards, 10.0, 0.01, 10000.0);
+        m_helix_radius->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        hform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Radius")), 0, wxALIGN_CENTER_VERTICAL);
+        hform->Add(spin_frame(m_helix_radius), 0, wxEXPAND);
+        m_helix_pitch = make_spin(m_cards, 5.0, 0.01, 10000.0);
+        m_helix_pitch->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        hform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Pitch")), 0, wxALIGN_CENTER_VERTICAL);
+        hform->Add(spin_frame(m_helix_pitch), 0, wxEXPAND);
+        m_helix_height = make_spin(m_cards, 20.0, 0.01, 10000.0);
+        m_helix_height->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        hform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Height")), 0, wxALIGN_CENTER_VERTICAL);
+        hform->Add(spin_frame(m_helix_height), 0, wxEXPAND);
+        m_box_helix->Add(hform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        m_helix_left_handed = new CheckBox(m_cards);
+        m_helix_left_handed->Bind(wxEVT_TOGGLEBUTTON, [this](wxCommandEvent&) { refresh_preview(); });
+        auto* hrow = new wxBoxSizer(wxHORIZONTAL);
+        hrow->Add(new wxStaticText(m_cards, wxID_ANY, _L("Left-handed")), 0, wxALIGN_CENTER_VERTICAL);
+        hrow->AddStretchSpacer();
+        hrow->Add(m_helix_left_handed, 0, wxALIGN_CENTER_VERTICAL);
+        m_box_helix->Add(hrow, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        m_helix_taper = make_spin(m_cards, 0.0, -89.0, 89.0);
+        m_helix_taper->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+        auto* tvalform = two_col_form();
+        tvalform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Taper (°)")), 0, wxALIGN_CENTER_VERTICAL);
+        tvalform->Add(spin_frame(m_helix_taper), 0, wxEXPAND);
+        m_box_helix->Add(tvalform, 0, wxEXPAND | wxLEFT | wxRIGHT, 12);
+        m_box_helix->Add(new wxStaticText(m_cards, wxID_ANY,
+                            _L("A helical curve (spring path). Use as a sweep path to build springs, coils, or augers.")),
+                         0, wxLEFT | wxRIGHT, 12);
+    }
+    cards->Add(m_box_helix, 0, wxEXPAND);
+
+    // --- Axis (datum axis: line through two points or derived from geometry) ---
+    m_box_axis = new wxBoxSizer(wxVERTICAL);
+    m_box_axis->Add(card_header(m_cards, "design_line", _L("Axis"), m_hdr_axis), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_axis->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        m_axis_type = make_combo(m_cards);
+        for (const wxString& t : { _L("Two points"), _L("Face normal"), _L("Cylinder centerline"),
+                                   _L("Plane intersection"), _L("Along edge") })
+            m_axis_type->Append(t);
+        m_axis_type->SetSelection(0);
+        m_box_axis->Add(new wxStaticText(m_cards, wxID_ANY, _L("Axis type")), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_axis->Add(m_axis_type, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+
+        auto* axform = two_col_form();
+
+        auto ax_pick = [&](const wxString& label, wxButton*& btn, wxStaticText*& lbl, AxisPick target) {
+            btn = new wxButton(m_cards, wxID_ANY, label);
+            lbl = new wxStaticText(m_cards, wxID_ANY, _L("(none)"));
+            btn->Bind(wxEVT_BUTTON, [this, target](wxCommandEvent&) { arm_axis_pick(target); });
+            axform->Add(btn);
+            axform->Add(lbl, 0, wxALIGN_CENTER_VERTICAL);
+        };
+        ax_pick(_L("Pick Face"),  m_axis_pick_face, m_axis_face_lbl, AxisPick::Face);
+        ax_pick(_L("Pick Edge"),  m_axis_pick_edge, m_axis_edge_lbl, AxisPick::Edge);
+
+        m_axis_plane_a = make_combo(m_cards);
+        populate_plane_choices(m_axis_plane_a);
+        axform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Plane A")), 0, wxALIGN_CENTER_VERTICAL);
+        axform->Add(m_axis_plane_a, 0, wxEXPAND);
+        m_axis_plane_b = make_combo(m_cards);
+        populate_plane_choices(m_axis_plane_b);
+        axform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Plane B")), 0, wxALIGN_CENTER_VERTICAL);
+        axform->Add(m_axis_plane_b, 0, wxEXPAND);
+
+        m_axis_p1x = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        m_axis_p1y = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        m_axis_p1z = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        axform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Point 1 X")), 0, wxALIGN_CENTER_VERTICAL);
+        axform->Add(spin_frame(m_axis_p1x), 0, wxEXPAND);
+        axform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Point 1 Y")), 0, wxALIGN_CENTER_VERTICAL);
+        axform->Add(spin_frame(m_axis_p1y), 0, wxEXPAND);
+        axform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Point 1 Z")), 0, wxALIGN_CENTER_VERTICAL);
+        axform->Add(spin_frame(m_axis_p1z), 0, wxEXPAND);
+
+        m_axis_p2x = make_spin(m_cards, 10.0, -100000.0, 100000.0);
+        m_axis_p2y = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        m_axis_p2z = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        axform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Point 2 X")), 0, wxALIGN_CENTER_VERTICAL);
+        axform->Add(spin_frame(m_axis_p2x), 0, wxEXPAND);
+        axform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Point 2 Y")), 0, wxALIGN_CENTER_VERTICAL);
+        axform->Add(spin_frame(m_axis_p2y), 0, wxEXPAND);
+        axform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Point 2 Z")), 0, wxALIGN_CENTER_VERTICAL);
+        axform->Add(spin_frame(m_axis_p2z), 0, wxEXPAND);
+
+        m_box_axis->Add(axform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_axis, 0, wxEXPAND);
+
+    // --- CoordSys (datum coordinate system: point + orthonormal frame) ---
+    m_box_coordsys = new wxBoxSizer(wxVERTICAL);
+    m_box_coordsys->Add(card_header(m_cards, "design_point", _L("Coord Sys"), m_hdr_coordsys), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_coordsys->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        m_coordsys_type = make_combo(m_cards);
+        for (const wxString& t : { _L("Point (world)"), _L("Face + direction") })
+            m_coordsys_type->Append(t);
+        m_coordsys_type->SetSelection(0);
+        m_box_coordsys->Add(new wxStaticText(m_cards, wxID_ANY, _L("Type")), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_coordsys->Add(m_coordsys_type, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+
+        m_cs_body = make_combo(m_cards);
+        m_cs_body->Append(_L("(all)"));
+        m_cs_body->SetSelection(0);
+        m_cs_body->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) {
+            if (m_viewport) m_viewport->set_xray_focus(m_cs_body->GetSelection() - 1);
+        });
+        m_box_coordsys->Add(new wxStaticText(m_cards, wxID_ANY, _L("Body")), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_coordsys->Add(m_cs_body, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+        auto* body_hint = new wxStaticText(m_cards, wxID_ANY,
+            _L("Restrict picking to one body — the others go see-through and stop catching clicks"));
+        body_hint->SetForegroundColour(dp_sec_text());
+        m_box_coordsys->Add(body_hint, 0, wxLEFT | wxRIGHT | wxTOP, 12);
+
+        auto* csform = two_col_form();
+
+        m_cs_x = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        m_cs_y = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        m_cs_z = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        csform->Add(new wxStaticText(m_cards, wxID_ANY, _L("X")), 0, wxALIGN_CENTER_VERTICAL);
+        csform->Add(spin_frame(m_cs_x), 0, wxEXPAND);
+        csform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Y")), 0, wxALIGN_CENTER_VERTICAL);
+        csform->Add(spin_frame(m_cs_y), 0, wxEXPAND);
+        csform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Z")), 0, wxALIGN_CENTER_VERTICAL);
+        csform->Add(spin_frame(m_cs_z), 0, wxEXPAND);
+
+        auto cs_pick = [&](const wxString& label, wxButton*& btn, wxStaticText*& lbl, CoordSysPick target) {
+            btn = new wxButton(m_cards, wxID_ANY, label);
+            lbl = new wxStaticText(m_cards, wxID_ANY, _L("(none)"));
+            btn->Bind(wxEVT_BUTTON, [this, target](wxCommandEvent&) { arm_coordsys_pick(target); });
+            csform->Add(btn);
+            csform->Add(lbl, 0, wxALIGN_CENTER_VERTICAL);
+        };
+        cs_pick(_L("Pick Face"), m_cs_pick_face, m_cs_face_lbl, CoordSysPick::Face);
+
+        // ponytail: edge pick for CoordSys with rotation-direction hint
+        m_cs_pick_edge = new wxButton(m_cards, wxID_ANY, _L("Edge (sets in-plane direction)"));
+        m_cs_edge_lbl = new wxStaticText(m_cards, wxID_ANY, _L("(none)"));
+        m_cs_pick_edge->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { arm_coordsys_pick(CoordSysPick::Edge); });
+        csform->Add(m_cs_pick_edge);
+        csform->Add(m_cs_edge_lbl, 0, wxALIGN_CENTER_VERTICAL);
+        auto* edge_hint = new wxStaticText(m_cards, wxID_ANY,
+            _L("Without an edge the frame takes X from the face's first edge — pick one to choose it yourself"));
+        edge_hint->SetForegroundColour(dp_sec_text());
+        csform->Add(0, 0);   // empty left column
+        csform->Add(edge_hint, 0, wxALIGN_CENTER_VERTICAL);
+
+        m_cs_hx = make_spin(m_cards, 1.0, -100000.0, 100000.0);
+        m_cs_hy = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        m_cs_hz = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        csform->Add(new wxStaticText(m_cards, wxID_ANY, _L("X hint X")), 0, wxALIGN_CENTER_VERTICAL);
+        csform->Add(spin_frame(m_cs_hx), 0, wxEXPAND);
+        csform->Add(new wxStaticText(m_cards, wxID_ANY, _L("X hint Y")), 0, wxALIGN_CENTER_VERTICAL);
+        csform->Add(spin_frame(m_cs_hy), 0, wxEXPAND);
+        csform->Add(new wxStaticText(m_cards, wxID_ANY, _L("X hint Z")), 0, wxALIGN_CENTER_VERTICAL);
+        csform->Add(spin_frame(m_cs_hz), 0, wxEXPAND);
+
+        m_box_coordsys->Add(csform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_coordsys, 0, wxEXPAND);
+
+    // --- Mate (assembly: align two CoordSys features) ---
+    m_box_mate = new wxBoxSizer(wxVERTICAL);
+    m_box_mate->Add(card_header(m_cards, "design_c_coincident", _L("Mate"), m_hdr_mate), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_mate->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        auto* mform = two_col_form();
+
+        m_mate_kind = make_combo(m_cards);
+        m_mate_kind->Append(_L("Fastened — 6 DOF locked, B driven onto A exactly"));
+        m_mate_kind->Append(_L("Planar — z aligned, offset distance; free in-plane slide"));
+        m_mate_kind->Append(_L("Revolute — axes collinear; free rotation about z"));
+        m_mate_kind->Append(_L("Slider — orientation locked; free axial slide"));
+        m_mate_kind->Append(_L("Cylindrical — axes collinear; free spin + axial slide"));
+        m_mate_kind->SetSelection(0);
+        mform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Kind")), 0, wxALIGN_CENTER_VERTICAL);
+        mform->Add(m_mate_kind, 0, wxEXPAND);
+
+        // Populate the CoordSys pickers on open; show "A (fixed)" and "B (moves)" combos.
+        m_mate_cs_a = make_combo(m_cards);
+        mform->Add(new wxStaticText(m_cards, wxID_ANY, _L("CS A (fixed)")), 0, wxALIGN_CENTER_VERTICAL);
+        mform->Add(m_mate_cs_a, 0, wxEXPAND);
+
+        m_mate_cs_b = make_combo(m_cards);
+        mform->Add(new wxStaticText(m_cards, wxID_ANY, _L("CS B (moves)")), 0, wxALIGN_CENTER_VERTICAL);
+        mform->Add(m_mate_cs_b, 0, wxEXPAND);
+
+        m_offset_label = new wxStaticText(m_cards, wxID_ANY, _L("Offset"));
+        m_mate_offset = make_spin(m_cards, 0.0, -100000.0, 100000.0);
+        mform->Add(m_offset_label, 0, wxALIGN_CENTER_VERTICAL);
+        mform->Add(spin_frame(m_mate_offset), 0, wxEXPAND);
+
+        m_angle_label = new wxStaticText(m_cards, wxID_ANY, _L("Angle \u00b0"));
+        m_mate_angle = make_spin(m_cards, 0.0, -360.0, 360.0);
+        mform->Add(m_angle_label, 0, wxALIGN_CENTER_VERTICAL);
+        mform->Add(spin_frame(m_mate_angle), 0, wxEXPAND);
+
+        m_mate_flip = new CheckBox(m_cards);
+        auto* frow = new wxBoxSizer(wxHORIZONTAL);
+        frow->Add(new wxStaticText(m_cards, wxID_ANY, _L("Flip (oppose z axes)")), 0, wxALIGN_CENTER_VERTICAL);
+        frow->AddStretchSpacer();
+        frow->Add(m_mate_flip, 0, wxALIGN_CENTER_VERTICAL);
+        mform->Add(0, 0);
+        mform->Add(frow, 0, wxEXPAND);
+
+        // Retitle offset/angle labels when the kind changes.
+        m_mate_kind->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent& e) {
+            const int kind = m_mate_kind->GetSelection();
+            switch (kind) {
+            case 0: // Fastened
+                m_offset_label->SetLabel(_L("Offset"));
+                m_angle_label->SetLabel(_L("Angle \u00b0"));
+                break;
+            case 1: // Planar
+                m_offset_label->SetLabel(_L("Plane distance"));
+                m_angle_label->SetLabel(_L("Angle \u00b0"));
+                break;
+            case 2: // Revolute
+                m_offset_label->SetLabel(_L("Axial position"));
+                m_angle_label->SetLabel(_L("Angle \u00b0"));
+                break;
+            case 3: // Slider
+                m_offset_label->SetLabel(_L("Axial position"));
+                m_angle_label->SetLabel(_L("Angle \u00b0"));
+                break;
+            case 4: // Cylindrical
+                m_offset_label->SetLabel(_L("Axial position"));
+                m_angle_label->SetLabel(_L("Angle \u00b0"));
+                break;
+            }
+            m_cards->Layout(); m_form->Layout(); m_form->FitInside();
+            refresh_preview();
+            e.Skip();
+        });
+
+        m_box_mate->Add(mform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_mate, 0, wxEXPAND);
+    // Refresh the confirm state whenever the mate inputs change.
+    m_mate_cs_a->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+    m_mate_cs_b->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent&) { refresh_preview(); });
+    m_mate_offset->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+    m_mate_angle->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent&) { refresh_preview(); });
+    m_mate_flip->Bind(wxEVT_TOGGLEBUTTON, [this](wxCommandEvent&) { refresh_preview(); });
+
+    // --- Expression binding card (visible during feature edit only) ---
+    // Lets the user bind a numeric field to a document-variable expression. Field-name
+    // combo is populated per feature type and is editable for power users. Set applies
+    // the binding with checkpoint+recompute+undo-on-failure; Clear removes it.
+    m_box_expr = new wxBoxSizer(wxVERTICAL);
+    {
+        wxStaticText* expr_hdr = nullptr;
+        m_box_expr->Add(card_header(m_cards, "design_constrain", _L("Expression"), expr_hdr), 0,
+                        wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_expr->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+
+        auto* eform = two_col_form();
+
+        // The only editable combo in this panel, hence not make_combo(): that passes
+        // wxCB_READONLY, and Orca's ComboBox HIDES its text ctrl under that style
+        // (ComboBox.cpp:51), so there is nothing to type into and no SetEditable() to
+        // turn it back on. Constructed with style 0, the ctrl is shown with
+        // wxTE_PROCESS_ENTER and GetTextLabel() returns what the user typed — which is
+        // what makes the 21 unmapped feature types reachable at all.
+        m_expr_field = new ComboBox(m_cards, wxID_ANY, wxEmptyString, wxDefaultPosition,
+                                    wxSize(FromDIP(90), FromDIP(24)), 0, nullptr, 0);
+        m_expr_field->SetMinSize(wxSize(FromDIP(90), FromDIP(24)));
+        eform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Field")), 0, wxALIGN_CENTER_VERTICAL);
+        eform->Add(m_expr_field, 0, wxEXPAND);
+
+        m_expr_text = new wxTextCtrl(m_cards, wxID_ANY, "", wxDefaultPosition,
+                                     wxSize(FromDIP(120), FromDIP(24)),
+                                     wxTE_PROCESS_ENTER | wxBORDER_SIMPLE);
+        m_expr_text->Bind(wxEVT_TEXT_ENTER, [this](wxCommandEvent&) { on_set_expr(); });
+        eform->Add(new wxStaticText(m_cards, wxID_ANY, _L("Expr")), 0, wxALIGN_CENTER_VERTICAL);
+        eform->Add(m_expr_text, 0, wxEXPAND);
+
+        m_box_expr->Add(eform, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+
+        auto* brow = new wxBoxSizer(wxHORIZONTAL);
+        m_expr_set_btn   = new wxButton(m_cards, wxID_ANY, _L("Set"), wxDefaultPosition, wxSize(50, 24));
+        m_expr_clear_btn = new wxButton(m_cards, wxID_ANY, _L("Clear"), wxDefaultPosition, wxSize(50, 24));
+        m_expr_set_btn->Bind(wxEVT_BUTTON,   [this](wxCommandEvent&) { on_set_expr(); });
+        m_expr_clear_btn->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_clear_expr(); });
+        brow->Add(m_expr_set_btn,   0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 6);
+        brow->Add(m_expr_clear_btn, 0, wxALIGN_CENTER_VERTICAL);
+        brow->AddStretchSpacer();
+        m_box_expr->Add(brow, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 12);
+
+        m_expr_status = new wxStaticText(m_cards, wxID_ANY, _L("(no bindings)"));
+        m_expr_status->SetForegroundColour(dp_sec_text());
+        m_box_expr->Add(m_expr_status, 0, wxLEFT | wxRIGHT | wxBOTTOM, 12);
+    }
+    cards->Add(m_box_expr, 0, wxEXPAND);
+
+    // --- Docked value-entry card (Onshape Button->Dialog->Confirm for dimensions) ---
+    m_box_value = new wxBoxSizer(wxVERTICAL);
+    {
+        // Header title doubles as the operation label (set by request_value()).
+        m_box_value->Add(card_header(m_cards, "design_constrain", _L("Value"), m_value_label), 0, wxLEFT | wxRIGHT | wxTOP, 12);
+        m_box_value->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+        auto* vrow = new wxBoxSizer(wxHORIZONTAL);
+        // wxTE_PROCESS_ENTER so the user can just type a value and press Enter to
+        // apply it (the natural CAD-dimension gesture), not only click Confirm.
+        // Plain text field (not a spin control): on wxGTK the native GtkSpinButton
+        // formats per the user locale (comma) with no clean override, so we own the
+        // formatting here to guarantee international '.' decimals.
+        m_value_input = new wxTextCtrl(m_cards, wxID_ANY, "", wxDefaultPosition,
+                                       wxSize(90, -1), wxTE_PROCESS_ENTER);
+        m_value_input->Bind(wxEVT_TEXT_ENTER, [this](wxCommandEvent&) { confirm_value(); });
+        vrow->Add(new wxStaticText(m_cards, wxID_ANY, _L("Value")), 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 8);
+        vrow->Add(m_value_input, 0, wxALIGN_CENTER_VERTICAL);
+        m_box_value->Add(vrow, 0, wxLEFT | wxRIGHT | wxTOP, 12);
+    }
+    cards->Add(m_box_value, 0, wxEXPAND);
+
+    // --- Sketch-entry card (Phase 3): plane/orientation, opens on "New sketch",
+    //     persists until Finish. The toolbar holds only the drawing tools. ---
+    m_box_sketch_session = new wxBoxSizer(wxVERTICAL);
+    m_box_sketch_session->Add(card_header(m_cards, "design_sketch", _L("Sketch"), m_hdr_sketch_session),
+                              0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_sketch_session->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    {
+        // NO plane dropdown. The sketch plane comes from what is picked in the VIEWPORT — a face
+        // on a solid, or one of the reference-plane ghosts — because that is where the user is
+        // looking and pointing. A combo duplicated that decision somewhere the geometry could not
+        // see it, and once a face could be picked it went further and displayed a stale row that
+        // contradicted the real target. e1p.
+        // Kept as a member, not a local: the card has to be able to STOP saying this. It asked
+        // for a plane even when one had just been picked, directly contradicting the status line
+        // two inches below it, which by then read "Sketching on XZ".
+        m_sketch_hint = new wxStaticText(m_cards, wxID_ANY,
+            _L("Click a face or a reference plane, then a sketch tool."));
+        m_sketch_hint->SetForegroundColour(dp_sec_text());
+        m_box_sketch_session->Add(m_sketch_hint, 0, wxLEFT | wxRIGHT | wxTOP | wxBOTTOM, 12);
+    }
+    cards->Add(m_box_sketch_session, 0, wxEXPAND);
+
+    // --- Constraint-manager card (C3.4): list of the constrained sketch's
+    //     entity-constraints; each row selects (highlights) + deletes. Shown only
+    //     in Constrain mode; rebuilt by rebuild_constraint_list().
+    m_box_constraints = new wxBoxSizer(wxVERTICAL);
+    m_box_constraints->Add(card_header(m_cards, "design_constrain", _L("Constraints"), m_hdr_constraints),
+                           0, wxLEFT | wxRIGHT | wxTOP, 12);
+    m_box_constraints->Add(new wxStaticLine(m_cards), 0, wxEXPAND | wxALL, 8);
+    m_constraint_rows = new wxBoxSizer(wxVERTICAL);
+    m_box_constraints->Add(m_constraint_rows, 0, wxEXPAND | wxLEFT | wxRIGHT | wxBOTTOM, 12);
+    cards->Add(m_box_constraints, 0, wxEXPAND);
+
+    // Wrap every card label now that the whole stack exists. wxStaticText never wraps on its
+    // own, so a one-sentence help line under a card sets that card's sizer min width to the
+    // width of the entire sentence — the same failure make_combo's explicit width fixes above,
+    // and with the same symptom: the card is wider than the sidebar, so every control in it is
+    // clipped at the panel's right edge. Found by click-testing Transform, Mirror and Coord Sys,
+    // whose hints are the longest. 240 px sits under m_form's 264 px minimum, so a wrapped hint
+    // always fits; the short two-column labels are far below it and Wrap() leaves them alone.
+    for (wxWindow* w : m_cards->GetChildren())
+        if (auto* t = dynamic_cast<wxStaticText*>(w))
+            t->Wrap(240);
+
+    // Feature tree card. Same idiom as Prepare's sections (icon + Head_14 title + rule) via the
+    // shared card_header helper, instead of the bare micro-label this used to be; the row-edit
+    // actions live in the header, as Prepare puts its section actions.
+    m_tree_box = make_card(m_form);
+    auto* tree_inner = new wxBoxSizer(wxVERTICAL);
+    m_tree_box->SetSizer(tree_inner);
+    root->Add(m_tree_box, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 8);
+
+    m_hdr_tree_row = new wxBoxSizer(wxHORIZONTAL);
+    m_hdr_tree_row->Add(card_header(m_tree_box, "design_sketch", _L("Feature tree"), m_hdr_tree), 0,
+                        wxALIGN_CENTER_VERTICAL);
+    m_hdr_tree_row->AddStretchSpacer();
+    tree_inner->Add(m_hdr_tree_row, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP,
+              FromDIP(SidebarProps::ContentMargin()));
+    tree_inner->Add(new wxStaticLine(m_tree_box), 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP,
+              FromDIP(SidebarProps::TitlebarMargin()));
+    m_tree = new wxTreeCtrl(m_tree_box, wxID_ANY, wxDefaultPosition, wxSize(-1, 64),
+                            wxTR_HIDE_ROOT | wxTR_SINGLE | wxTR_NO_LINES |
+                            wxTR_FULL_ROW_HIGHLIGHT | wxBORDER_SIMPLE | wxTR_EDIT_LABELS);
+    if (!dp_dark()) m_tree->SetBackgroundColour(dp_panel_bg());
+    // Per-feature-type icons (indices match tree_icon_for): sketch/extrude/dressup/hole/thread.
+    m_tree_images = new wxImageList(16, 16);
+    m_tree_images->Add(create_scaled_bitmap("design_sketch",  nullptr, 16)); // 0 Sketch
+    m_tree_images->Add(create_scaled_bitmap("design_extrude", nullptr, 16)); // 1 Extrude
+    m_tree_images->Add(create_scaled_bitmap("design_dressup", nullptr, 16)); // 2 Fillet/Chamfer
+    m_tree_images->Add(create_scaled_bitmap("design_hole",    nullptr, 16)); // 3 Hole
+    m_tree_images->Add(create_scaled_bitmap("design_thread",  nullptr, 16)); // 4 Thread
+    m_tree_images->Add(create_scaled_bitmap("design_shell",   nullptr, 16)); // 5 Shell
+    m_tree->AssignImageList(m_tree_images);
+    tree_inner->Add(m_tree, 0, wxEXPAND | wxALL, 12);
+
+    // Selecting a body-producing feature (Extrude/Fillet/Chamfer/Hole/Thread) in the
+    // tree highlights the solid in the viewport; a Sketch row clears the highlight
+    // (its face is already shown via the persistent sketch overlay).
+    m_tree->Bind(wxEVT_TREE_SEL_CHANGED, [this](wxTreeEvent&) {
+        if (!m_viewport) return;
+        // Bodies live in the Parts list now; picking a feature here drops any body selection
+        // so the two lists can't both claim to be "the target".
+        // ONLY when this tree actually has a selection. These two lists clear each other's
+        // selection so that "the target" is never ambiguous, and that was harmless while both
+        // calls were UnselectAll() — a no-op on a wxTR_SINGLE tree. Now that Unselect() really
+        // clears, the pair became a loop: clicking a body row runs apply_body_row, which calls
+        // m_tree->Unselect(), which fires THIS handler, which cleared the body row the user had
+        // just clicked. The guard keeps the mutual-exclusion and drops the echo.
+        if (m_parts && tree_selection() != wxNOT_FOUND) m_parts->Unselect();
+        const int sel = tree_selection();
+        const bool body = (sel >= 0 && sel < int(m_doc.features.size()) &&
+                           m_doc.features[sel].type != CadFeatureType::Sketch &&
+                           !m_doc.body.IsNull());
+        m_viewport->set_body_highlight(body);
+        // A conflicting mate says WHY on selection, and names the one action that resolves it.
+        // Suppress is the generic per-feature enable toggle (the eye), so the answer is already
+        // one click away on a row the user has just selected — the message points at it instead
+        // of describing a problem with no way out.
+        if (const std::string* why = (sel >= 0) ? mate_conflict_reason(sel) : nullptr) {
+            m_status->SetForegroundColour(wxColour(235, 110, 110));
+            set_status(wxString::FromUTF8(*why) + _L(" — the eye suppresses this mate"));
+            m_status->Refresh();
+        } else if (sel >= 0 && sel < int(m_doc.features.size())) {
+            // Name the two gestures the row supports, because neither is visible on it.
+            m_status->SetForegroundColour(wxNullColour);
+            set_status(wxString::Format(
+                _L("%s selected — F2 or right-click renames it, double-click edits it"),
+                wxString::FromUTF8(m_doc.features[sel].name)));
+            m_status->Refresh();
+        }
+    });
+
+    // Double-click a row = Edit, the same gesture that re-opens a committed sketch on the canvas.
+    // Without it the row only highlights and the feature looks dead until the user finds the
+    // Edit button in the section header.
+    m_tree->Bind(wxEVT_TREE_ITEM_ACTIVATED, [this](wxTreeEvent&) { on_edit_feature(); });
+
+    // Right-click a row: the three things a row can do. Renaming had no discoverable route at
+    // all — the header pencil is Edit, a double-click ACTIVATES the row and is also Edit (the
+    // "slow double-click renames" the old comment promised does not survive wxGTK, which fires
+    // ITEM_ACTIVATED first), none of the seven header icons renames, and F2 is a function key
+    // nothing announces. A user who wants to name a sketch tries the row, and now the row
+    // answers. rename.
+    m_tree->Bind(wxEVT_TREE_ITEM_RIGHT_CLICK, [this](wxTreeEvent& e) {
+        m_tree->SelectItem(e.GetItem());          // right-click targets what it points at
+        const int sel = tree_selection();
+        if (sel == wxNOT_FOUND) return;
+        // EVERYTHING A ROW CAN DO, in one place. The header icons stay as a quick bar, but the
+        // menu is the reference: the element you click answers with what applies to it, and a
+        // menu grows without spending an icon nobody recognises. Split into what the row IS
+        // (name, contents), where it SITS (order, visibility) and what removes it.
+        wxMenu menu;
+        const int id_rename = wxWindow::NewControlId();
+        const int id_edit   = wxWindow::NewControlId();
+        const int id_up     = wxWindow::NewControlId();
+        const int id_down   = wxWindow::NewControlId();
+        const int id_vis    = wxWindow::NewControlId();
+        const int id_art    = wxWindow::NewControlId();
+        const int id_del    = wxWindow::NewControlId();
+        menu.Append(id_rename, _L("Rename\tF2"));
+        menu.Append(id_edit,   _L("Edit"));
+        // Scale artwork acts on THIS feature's imported outline, so it belongs to the row and
+        // is offered only where it means something. It used to hide inside the header's Move
+        // button, which otherwise moved a body — two different subjects on one icon.
+        const bool art = sel < int(m_doc.features.size()) &&
+                         !m_doc.features[sel].imported_regions.empty();
+        if (art) menu.Append(id_art, _L("Scale artwork"));
+        menu.AppendSeparator();
+        menu.Append(id_up,     _L("Move up"));
+        menu.Append(id_down,   _L("Move down"));
+        menu.Append(id_vis,    _L("Show / hide"));
+        menu.AppendSeparator();
+        menu.Append(id_del,    _L("Delete"));
+        menu.Bind(wxEVT_MENU, [this](wxCommandEvent&) {
+            const int row = tree_selection();
+            if (row != wxNOT_FOUND && row < int(m_tree_items.size()))
+                m_tree->EditLabel(m_tree_items[row]);
+        }, id_rename);
+        menu.Bind(wxEVT_MENU, [this](wxCommandEvent&) { on_edit_feature(); },      id_edit);
+        menu.Bind(wxEVT_MENU, [this](wxCommandEvent&) { on_move_feature(-1); },    id_up);
+        menu.Bind(wxEVT_MENU, [this](wxCommandEvent&) { on_move_feature(+1); },    id_down);
+        menu.Bind(wxEVT_MENU, [this](wxCommandEvent&) { on_toggle_visibility(); }, id_vis);
+        menu.Bind(wxEVT_MENU, [this](wxCommandEvent&) { on_delete_feature(); },    id_del);
+        if (art)
+            menu.Bind(wxEVT_MENU, [this](wxCommandEvent&) {
+                const int row = tree_selection();
+                if (row != wxNOT_FOUND) on_transform_imported(row);
+            }, id_art);
+        m_tree->PopupMenu(&menu);
+    });
+
+    // In-place rename of a feature row (slow double-click, the offer's Rename verb, or F2).
+    // The name is what makes a tree of eight sketches readable, and the tree row IS the object —
+    // so renaming belongs on the row, not in a side-panel field. Bodies are computed results,
+    // not named features, so a body row must never open an editor (it cannot, they live in the
+    // Parts list, but the guard keeps a future change from slipping a body into this tree).
+    auto item_index = [this](const wxTreeItemId& it) -> int {
+        for (size_t i = 0; i < m_tree_items.size(); ++i)
+            if (m_tree_items[i] == it) return int(i);
+        return wxNOT_FOUND;
+    };
+    m_tree->Bind(wxEVT_TREE_BEGIN_LABEL_EDIT, [this, item_index](wxTreeEvent& e) {
+        // The event's item is the authority for WHAT is being edited; tree_selection() is not,
+        // because the editor can open on a row that is not the current selection. A row that is
+        // not a feature (a body, or a stray id) gets the edit vetoed before it can take a name.
+        if (tree_body_selection() >= 0 || item_index(e.GetItem()) == wxNOT_FOUND) { e.Veto(); return; }
+        e.Skip();
+    });
+    m_tree->Bind(wxEVT_TREE_END_LABEL_EDIT, [this, item_index](wxTreeEvent& e) {
+        if (e.IsEditCancelled()) return;
+        const int idx = item_index(e.GetItem());
+        if (idx == wxNOT_FOUND) { e.Veto(); return; }
+        wxString label = e.GetLabel();
+        label.Trim(true).Trim(false);
+        if (label.empty()) { e.Veto(); return; }   // a nameless row is worse than a badly named one
+        m_doc.features[idx].name = std::string(label.ToUTF8().data());
+        sync_recipe_to_model();   // the name is part of the recipe, so the save path persists it
+        e.Skip();                 // let wx finish applying the label to the item it is holding
+        // REBUILD LATER, NOT NOW. refresh_tree() deletes and re-creates every wxTreeItemId, and
+        // we are inside wx's own END_LABEL_EDIT dispatch for one of them — destroying it here
+        // frees the item the caller is still using and takes the process down. Measured: typing
+        // a name and pressing Enter killed the app outright, with the keystrokes traced and no
+        // trace for the Return. Deferring to the next event-loop turn lets wx finish first.
+        CallAfter([this] { refresh_tree(); });
+    });
+
+    // Feature-tree edit actions: act on the selected feature (delete / reorder). These sit in the
+    // card header (Prepare puts its section actions there too) rather than on a loose row below.
+    {
+        wxBoxSizer* trow = m_hdr_tree_row;
+        auto edit_btn = [this](const char* icon, const wxString& tip) {
+            // Header-sized: reads as a section action, not a primary control.
+            auto* b = new ScalableButton(m_tree_box, wxID_ANY, icon, "", wxSize(24, 24),
+                                         wxDefaultPosition, wxBU_EXACTFIT | wxBORDER_NONE, false, 20);
+            b->SetToolTip(tip);
+            return b;
+        };
+        auto* edit = edit_btn("design_edit", _L("Edit"));
+        edit->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_edit_feature(); });
+        // NO Move here. Moving a body is not a feature-row action — this header sits over the
+        // FEATURE tree, and the button had to guess its subject from whatever happened to be
+        // selected, answering a feature row with an instruction about bodies. It lives where a
+        // body lives: the Bodies card's own action row, and the offer for a selected body.
+        // Scaling imported artwork, which shared this button, moved to the row's own menu.
+        auto* vis = edit_btn("design_eye", _L("Show / hide"));
+        vis->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_toggle_visibility(); });
+        auto* del  = edit_btn("design_delete", _L("Delete"));
+        del->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) {
+            // A body row deletes the feature that made it. on_delete_body() already resolves
+            // CadBody::source_feature and asks for confirmation by name; it was reachable only
+            // from the right-click offer, so this button answered a selected body row with
+            // "select the FEATURE that created this body" — an instruction the user cannot act
+            // on, since the tree does not say which feature that is. It does now.
+            if (tree_body_selection() >= 0) on_delete_body();
+            else                            on_delete_feature();
+        });
+        auto* up   = edit_btn("design_moveup", _L("Move up"));
+        up->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_move_feature(-1); });
+        auto* down = edit_btn("design_movedown", _L("Move down"));
+        down->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_move_feature(+1); });
+        m_btn_interfere = edit_btn("color_palette", _L("Check interference — find overlapping bodies"));
+        m_btn_interfere->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_check_interference(); });
+        const int gap = FromDIP(SidebarProps::ElementSpacing());
+        trow->Add(edit, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, gap);
+        trow->Add(vis,  0, wxALIGN_CENTER_VERTICAL | wxRIGHT, gap);
+        trow->Add(del,  0, wxALIGN_CENTER_VERTICAL | wxRIGHT, gap);
+        trow->Add(up,   0, wxALIGN_CENTER_VERTICAL | wxRIGHT, gap);
+        trow->Add(down, 0, wxALIGN_CENTER_VERTICAL);
+        // Interference check sits after a rule: it reports, it does not edit the recipe.
+        trow->AddSpacer(8);
+        trow->Add(new wxStaticLine(m_tree_box, wxID_ANY, wxDefaultPosition, wxSize(1, 22), wxLI_VERTICAL),
+                  0, wxALIGN_CENTER_VERTICAL);
+        trow->AddSpacer(8);
+        trow->Add(m_btn_interfere, 0, wxALIGN_CENTER_VERTICAL);
+        // trow IS the header sizer — already added to root above the tree.
+    }
+
+    // Parts list (Onshape's Features + Parts split). Bodies used to be appended after the
+    // features INSIDE the feature tree, so they were pushed out of view as the history grew —
+    // with no way to select a body at all. Their own list keeps them reachable regardless.
+    m_parts_box = make_card(m_form);
+    auto* parts_inner = new wxBoxSizer(wxVERTICAL);
+    m_parts_box->SetSizer(parts_inner);
+    root->Add(m_parts_box, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 8);
+
+    m_parts_hdr = new wxBoxSizer(wxHORIZONTAL);
+    m_parts_hdr->Add(card_header(m_parts_box, "design_extrude", _L("Bodies"), m_parts_label), 0,
+                     wxALIGN_CENTER_VERTICAL);
+    // The bodies card carries the actions that act on a BODY. Move came from the feature-tree
+    // header, where it had to guess whether its subject was a body or a feature; Show/hide,
+    // Delete and Colour are deliberate COPIES of feature-tree actions, because a body row is a
+    // different subject and a user working in this list should not have to travel to another
+    // card to hide or recolour what they have selected. Boolean is not a copy — it is the one
+    // body-body operation, gated through on_boolean_tool. Each one already resolves the body row
+    // itself (on_toggle_visibility, on_delete_body, on_set_body_color), so nothing here decides
+    // policy — the card only gives them a home next to the rows they act on.
+    {
+        auto body_btn = [this](const char* icon, const wxString& tip) {
+            auto* b = new ScalableButton(m_parts_box, wxID_ANY, icon, "", wxSize(24, 24),
+                                         wxDefaultPosition, wxBU_EXACTFIT | wxBORDER_NONE, false, 20);
+            b->SetToolTip(tip);
+            return b;
+        };
+        auto* bmove = body_btn("design_move",   _L("Move body"));
+        bmove->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) {
+            if (m_sel_solid_body >= 0 && m_sel_solid_body < int(m_doc.bodies.size())) {
+                on_move_body();
+            } else {
+                m_status->SetForegroundColour(wxNullColour);
+                set_status(_L("Select a body row first, then move it"));
+                m_status->Refresh();
+            }
+        });
+        // Boolean lives here as well as on the toolbar: combining two bodies is a body action,
+        // and a user working in the body list should not have to leave it to find this.
+        auto* bbool = body_btn("design_boolean", _L("Boolean — join, subtract or intersect with another body"));
+        bbool->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_boolean_tool(); });
+        auto* bvis  = body_btn("design_eye",    _L("Show / hide"));
+        bvis->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_toggle_visibility(); });
+        auto* bdel  = body_btn("design_delete", _L("Delete"));
+        bdel->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_delete_body(); });
+        auto* bcol  = body_btn("color_palette", _L("Colour"));
+        bcol->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_set_body_color(); });
+        const int bgap = FromDIP(SidebarProps::ElementSpacing());
+        m_parts_hdr->AddStretchSpacer(1);
+        m_parts_hdr->Add(bmove, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, bgap);
+        m_parts_hdr->Add(bbool, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, bgap);
+        m_parts_hdr->Add(bvis,  0, wxALIGN_CENTER_VERTICAL | wxRIGHT, bgap);
+        m_parts_hdr->Add(bdel,  0, wxALIGN_CENTER_VERTICAL | wxRIGHT, bgap);
+        m_parts_hdr->Add(bcol,  0, wxALIGN_CENTER_VERTICAL);
+    }
+    parts_inner->Add(m_parts_hdr, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP,
+              FromDIP(SidebarProps::ContentMargin()));
+    m_parts_rule = new wxStaticLine(m_parts_box);
+    parts_inner->Add(m_parts_rule, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP,
+              FromDIP(SidebarProps::TitlebarMargin()));
+    m_parts_hdr->ShowItems(false);   // no bodies yet on a fresh document
+    m_parts_rule->Hide();
+    m_parts = new wxTreeCtrl(m_parts_box, wxID_ANY, wxDefaultPosition, wxSize(-1, 48),
+                             wxTR_HIDE_ROOT | wxTR_SINGLE | wxTR_NO_LINES |
+                             wxTR_FULL_ROW_HIGHLIGHT | wxBORDER_SIMPLE | wxTR_EDIT_LABELS);
+    if (!dp_dark()) m_parts->SetBackgroundColour(dp_panel_bg());
+    parts_inner->Add(m_parts, 0, wxEXPAND | wxALL, 12);
+    // Start hidden: a fresh document has no bodies, and refresh_parts() only runs on the first
+    // tree rebuild — until then an empty box would sit under the header.
+    m_parts->Hide();
+    m_parts_label->Hide();
+    // Taking a body from the list means the SAME state change however it was asked for, so the
+    // normalisation lives here and not inside a selection handler. That distinction is not
+    // pedantry: SelectItem() on a row that is ALREADY selected fires no SEL_CHANGED at all, so a
+    // version of this that only ran on selection left a stale vertex/edge from an earlier
+    // viewport pick in place — and offer_selection_kind() tests vertex FIRST, so right-clicking
+    // the body row served the VERTEX offer (Fillet greyed, Mirror in place of Repeat) while the
+    // row sat highlighted. Measured on the rig 2026-08-02; it is invisible from the code alone.
+    auto apply_body_row = [this](int b) {
+        if (!m_viewport || b < 0) return;
+        // One selection at a time: a body row and a feature row mean different things to the
+        // op bar, so clear the feature tree's highlight when a body takes over.
+        if (m_tree) m_tree->Unselect();       // wxTR_SINGLE: UnselectAll() does nothing here
+        m_viewport->set_body_highlight(false);   // the per-body overlay does the tint
+        m_viewport->select_body(b);              // also drops the vertex/edge marker
+        m_sel_solid_body   = b;
+        m_sel_solid_face   = m_sel_solid_edge = -1;
+        m_sel_solid_vertex = false;
+        m_pick_face = m_pick_face_body = -1;   // chosen from the list, no face was pointed at
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(wxString::Format(_L("Body %d selected — right-click for what applies to it"), b + 1));
+        m_status->Refresh();
+    };
+    m_parts->Bind(wxEVT_TREE_SEL_CHANGED, [this, apply_body_row](wxTreeEvent&) {
+        apply_body_row(tree_body_selection());
+    });
+    // The third door onto the offer, after the viewport right-click and the Menu key. A body ROW
+    // is an unambiguous body, so the offer reports BodySolid and the body verbs act on the row you
+    // can see highlighted. That is the confirmation a face pick cannot give: pointing at a face
+    // lights the face, never the body the verb will actually change. The status line above has
+    // been promising this right-click since before it existed.
+    // Renaming a BODY names the body itself. It does NOT rename the feature that created it:
+    // an Extrude, a Cut and a Fillet all land on one body, so source_feature is one operation in
+    // its history and renaming that is renaming the wrong object — reported, correctly, as "you
+    // consider the extrusion = the body". CadBody::user_name is carried across recompute() by
+    // index and written into the recipe, so the name outlives both the rebuild and the save.
+    m_parts->Bind(wxEVT_TREE_BEGIN_LABEL_EDIT, [this](wxTreeEvent& e) {
+        if (tree_body_selection() < 0) { e.Veto(); return; }
+        e.Skip();
+    });
+    m_parts->Bind(wxEVT_TREE_END_LABEL_EDIT, [this](wxTreeEvent& e) {
+        if (e.IsEditCancelled()) return;
+        const int b = tree_body_selection();
+        if (b < 0 || b >= int(m_doc.bodies.size())) { e.Veto(); return; }
+        wxString label = e.GetLabel();
+        label.Trim(true).Trim(false);
+        if (label.empty()) { e.Veto(); return; }      // a nameless row is worse than a bad name
+        m_doc.bodies[b].has_user_name = true;
+        m_doc.bodies[b].user_name     = std::string(label.ToUTF8().data());
+        sync_recipe_to_model();                        // the name is part of what gets saved
+        e.Skip();
+        // Rebuild on the NEXT event-loop turn: refresh_parts() destroys every wxTreeItemId and
+        // we are inside wx's own END_LABEL_EDIT dispatch for one of them. The feature tree
+        // learned this the hard way — doing it here took the process down.
+        CallAfter([this] { refresh_parts(); });
+    });
+
+    m_parts->Bind(wxEVT_TREE_ITEM_MENU, [this, apply_body_row](wxTreeEvent& e) {
+        if (e.GetItem().IsOk())
+            m_parts->SelectItem(e.GetItem());   // the row under the cursor, never a stale one
+        apply_body_row(tree_body_selection());  // unconditional — see above, SelectItem on an
+                                                // already-selected row raises no event
+        // GetPoint() is tree-client; it is (-1,-1) when the KEYBOARD menu key raised this, so fall
+        // back to the shared anchor rather than popping the menu at a garbage coordinate.
+        const wxPoint p = e.GetPoint();
+        const wxPoint screen = (p.x >= 0 && p.y >= 0) ? m_parts->ClientToScreen(p) : offer_anchor();
+        // Let the modal menu take the loop after this handler returns — same CallAfter as the
+        // sketch path, which learned it the hard way.
+        CallAfter([this, screen] { show_offer_menu(screen); });
+    });
+
+    // --- Variables (document-scope named expressions) ---
+    // Below the feature tree + parts, always visible. wxListCtrl in report mode with two
+    // columns (Name, Expression). Add / edit open a small dialog; delete removes the
+    // selected row. Every mutation goes through checkpoint+recompute+undo-on-failure.
+    m_var_box = make_card(m_form);
+    auto* var_inner = new wxBoxSizer(wxVERTICAL);
+    m_var_box->SetSizer(var_inner);
+    {
+        auto* var_hdr = new wxBoxSizer(wxHORIZONTAL);
+        wxStaticText* var_hdr_title = nullptr;
+        var_hdr->Add(card_header(m_var_box, "design_constrain", _L("Variables"), var_hdr_title), 0,
+                     wxALIGN_CENTER_VERTICAL);
+        var_hdr->AddStretchSpacer();
+        m_btn_add_var  = new wxButton(m_var_box, wxID_ANY, _L("+"), wxDefaultPosition, wxSize(30, 24));
+        m_btn_edit_var = new wxButton(m_var_box, wxID_ANY, _L("Edit"), wxDefaultPosition, wxSize(50, 24));
+        m_btn_del_var  = new wxButton(m_var_box, wxID_ANY, _L("Del"), wxDefaultPosition, wxSize(42, 24));
+        m_btn_add_var->Bind(wxEVT_BUTTON,  [this](wxCommandEvent&) { on_add_variable(); });
+        m_btn_edit_var->Bind(wxEVT_BUTTON, [this](wxCommandEvent&) { on_edit_variable(); });
+        m_btn_del_var->Bind(wxEVT_BUTTON,  [this](wxCommandEvent&) { on_remove_variable(); });
+        const int vhgap = FromDIP(SidebarProps::ElementSpacing());
+        var_hdr->Add(m_btn_add_var,  0, wxALIGN_CENTER_VERTICAL | wxRIGHT, vhgap);
+        var_hdr->Add(m_btn_edit_var, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, vhgap);
+        var_hdr->Add(m_btn_del_var,  0, wxALIGN_CENTER_VERTICAL);
+        var_inner->Add(var_hdr, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP,
+                       FromDIP(SidebarProps::ContentMargin()));
+        var_inner->Add(new wxStaticLine(m_var_box), 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP,
+                       FromDIP(SidebarProps::TitlebarMargin()));
+
+        m_var_list = new wxListCtrl(m_var_box, wxID_ANY, wxDefaultPosition,
+                                    wxSize(-1, FromDIP(64)), wxLC_REPORT | wxLC_SINGLE_SEL);
+        if (!dp_dark()) m_var_list->SetBackgroundColour(dp_panel_bg());
+        m_var_list->AppendColumn(_L("Name"),       wxLIST_FORMAT_LEFT, FromDIP(90));
+        m_var_list->AppendColumn(_L("Expression"), wxLIST_FORMAT_LEFT, FromDIP(120));
+        var_inner->Add(m_var_list, 0, wxEXPAND | wxALL, FromDIP(SidebarProps::ContentMargin()));
+    }
+    root->Add(m_var_box, 0, wxEXPAND | wxLEFT | wxRIGHT | wxTOP, 8);
+
+    // Orca-styled full-width buttons (ButtonType::Expanded), so the Design sidebar reads like
+    // Prepare's instead of showing raw OS-default wxButtons.
+    const int cm = FromDIP(SidebarProps::ContentMargin());
+
+    m_status = new wxStaticText(m_form, wxID_ANY, "");
+    m_status->Hide();   // storage only — the line is drawn over the viewport, see set_status()
+    m_status_default_fg = m_status->GetForegroundColour();   // capture BEFORE any caller writes
+    root->Add(m_status, 0, wxLEFT | wxRIGHT | wxBOTTOM, 12);
+
+    // DoF / constraint-state readout (P3). Dedicated line so it never clobbers the
+    // tool hint in m_status; updated by the on_solve_state callback after each solve.
+    m_dof_status = new wxStaticText(m_form, wxID_ANY, "");
+    {
+        wxFont f = m_dof_status->GetFont();
+        f.SetWeight(wxFONTWEIGHT_BOLD);
+        m_dof_status->SetFont(f);
+    }
+    root->Add(m_dof_status, 0, wxLEFT | wxRIGHT | wxBOTTOM, 12);
+
+
+    m_shape->Bind(wxEVT_COMBOBOX, [this](wxCommandEvent& e) { on_shape_changed(); e.Skip(); });
+    on_shape_changed();
+
+    // Any parameter edit refreshes the translucent preview. Command events from the
+    // spin/choice/checkbox children propagate up to m_form, so one binding each suffices.
+    m_form->Bind(wxEVT_SPINCTRLDOUBLE, [this](wxSpinDoubleEvent& e) { refresh_preview(); e.Skip(); });
+    m_form->Bind(wxEVT_COMBOBOX,         [this](wxCommandEvent& e)    { refresh_preview(); e.Skip(); });
+    m_form->Bind(wxEVT_CHECKBOX,       [this](wxCommandEvent& e)    { refresh_preview(); e.Skip(); });
+    m_form->Bind(wxEVT_TOGGLEBUTTON,   [this](wxCommandEvent& e)    { refresh_preview(); e.Skip(); });
+
+    m_form->SetSizer(root);
+
+    // Start with every tool dialog hidden (only the toolbar + tree + Commit show).
+    root->Show(m_parts_box, false, false);   // no bodies on a fresh document
+    root->Show(m_cards,     false, false);   // no tool open yet: don't draw an empty frame
+    cards->Show(m_box_sketch,  false, true);
+    cards->Show(m_box_move,    false, true);
+    cards->Show(m_box_extrude, false, true);
+    cards->Show(m_box_revolve, false, true);
+    cards->Show(m_box_sweep, false, true);
+    cards->Show(m_box_pattern, false, true);
+    cards->Show(m_box_plane, false, true);
+    cards->Show(m_box_axis, false, true);
+    cards->Show(m_box_coordsys, false, true);
+    cards->Show(m_box_loft, false, true);
+    cards->Show(m_box_draft, false, true);
+    cards->Show(m_box_boolean, false, true);
+    cards->Show(m_box_cut,     false, true);
+    cards->Show(m_box_insert,  false, true);
+    cards->Show(m_box_dressup, false, true);
+    cards->Show(m_box_hole,    false, true);
+    cards->Show(m_box_thread,  false, true);
+    cards->Show(m_box_shell,   false, true);
+    cards->Show(m_box_surf_extrude, false, true);
+    cards->Show(m_box_surf_revolve, false, true);
+    cards->Show(m_box_surf_loft,    false, true);
+    cards->Show(m_box_surf_fill,    false, true);
+    cards->Show(m_box_surf_offset,  false, true);
+    cards->Show(m_box_surf_thicken, false, true);
+    cards->Show(m_box_value,   false, true);
+    cards->Show(m_box_sketch_session, false, true);
+    cards->Show(m_box_constraints,    false, true);
+    cards->Show(m_box_expr,          false, true);
+    // A card added to the cards sizer is VISIBLE until something hides it. close_tool()'s
+    // hide-all only runs on a tool switch, so any card missing from THIS block renders
+    // stacked in the sidebar from the moment the tab opens. These eight were wired into
+    // close_tool() but not here, which is what bloated the panel.
+    cards->Show(m_box_transform,   false, true);
+    cards->Show(m_box_mirror,      false, true);
+    cards->Show(m_box_thicken,     false, true);
+    cards->Show(m_box_rib,         false, true);
+    cards->Show(m_box_project,     false, true);
+    cards->Show(m_box_delete_face, false, true);
+    cards->Show(m_box_helix,       false, true);
+    cards->Show(m_box_mate,        false, true);
+
+    m_form->FitInside();
+    m_form->SetScrollRate(0, 10);   // vertical only, like Prepare's sidebar: never scroll labels out
+    m_form->SetMinSize(wxSize(264, -1));
+
+    // Right column: a small view toolbar over the live 3D viewport that mirrors
+    // the CadDocument body.
+    m_viewport = new DesignCanvas(this);
+
+    m_viewport->set_on_sketch_commit([this](const SketchProfile& prof, const SketchPlane& plane) {
+        m_doc.checkpoint();   // undo boundary: committing a sketch
+        m_feature_counter++;
+        m_doc.add_sketch_profile(prof, plane, "Sketch" + std::to_string(m_feature_counter));
+        m_doc.recompute();
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("Sketch created — select it, then right-click to Extrude"));
+        refresh_tree();
+    });
+
+    m_viewport->set_on_sketch_entities_commit(
+        [this](const std::vector<SketchEntity>& ents,
+               const std::vector<SketchEntityConstraintDef>& cons,
+               const SketchPlane& plane) {
+            if (ents.empty()) {
+                m_status->SetForegroundColour(wxColour(235, 110, 110));
+                set_status(_L("Sketch empty — nothing committed"));
+                m_status->Refresh();
+                return;
+            }
+            m_doc.checkpoint();   // undo boundary: committing / re-editing an entity sketch
+            // Re-edit of a committed entity sketch: REPLACE it in place (keep its name +
+            // tree position) instead of appending a duplicate.
+            if (m_edit_index >= 0 && m_edit_index < int(m_doc.features.size()) &&
+                m_doc.features[m_edit_index].type == CadFeatureType::Sketch) {
+                CadFeature edited = m_doc.features[m_edit_index];
+                edited.entities           = ents;
+                edited.entity_constraints = cons;
+                edited.plane              = plane;
+                if (m_doc.replace_feature(m_edit_index, edited)) {
+                    if (!cons.empty()) m_doc.solve_sketch_feature(m_edit_index);
+                    m_doc.recompute();
+                    m_status->SetForegroundColour(wxNullColour);
+                    set_status(_L("Sketch updated"));
+                    m_edit_index = -1;
+                    refresh_tree();
+                    sync_sketch_display();
+                }
+                return;
+            }
+            m_feature_counter++;
+            const int sk = m_doc.add_sketch_entities(ents, plane,
+                               "Sketch" + std::to_string(m_feature_counter), cons);
+            if (!cons.empty()) m_doc.solve_sketch_feature(sk);   // enforce driving dimensions
+            m_doc.recompute();
+            m_status->SetForegroundColour(wxNullColour);
+            set_status(cons.empty()
+                ? _L("Sketch created — select it, then right-click to Extrude")
+                : wxString::Format(_L("Sketch created (%zu driving dims) — select it, then right-click to Extrude"),
+                                   cons.size()));
+            refresh_tree();
+            sync_sketch_display();   // keep the just-committed sketch visible as a face
+        });
+
+    // Live length/angle readout while drawing a Line/Polyline segment.
+    m_viewport->set_on_cursor_metrics([this](double len, double ang_deg, bool locked) {
+        double a = ang_deg; if (a < 0.0) a += 360.0;   // show bearing 0..360
+        m_status->SetForegroundColour(wxNullColour);
+        // APPENDED to the step guidance, never in place of it. This fires on every mouse move
+        // while a segment is being dragged, so replacing the line wiped the instruction for the
+        // step the user is in the middle of — one mouse move after the click that armed it.
+        const wxString metrics = wxString::Format(L"L %.2f mm   %.1f°%s",
+                                                  len, a, locked ? L"  (locked)" : L"");
+        set_status(m_sketch_step.IsEmpty() ? metrics
+                                           : m_sketch_step + L"   ·   " + metrics);
+        m_status->Refresh();
+    });
+
+    // Live per-step guidance: the armed tool says which step it is on, we write the sentence.
+    m_viewport->set_on_sketch_step([this](DesignSketchTool::Mode mode, int step, int picks) {
+        on_sketch_step(int(mode), step, picks);
+    });
+
+    // A live constraint appeared or went away: refill the rows. CallAfter, not a direct call —
+    // one of the callers is the ✗ button's own click handler, and rebuild_constraint_list
+    // destroys those buttons; deleting the window whose handler is still on the stack is a
+    // use-after-free. Deferring to the next event-loop turn lets the handler return first.
+    m_viewport->set_on_sketch_constraints_changed([this]() {
+        CallAfter([this]() { rebuild_constraint_list(); });
+    });
+
+    // DoF feedback (P3): after each live solve, report constraint state on its own
+    // line. Green = fully constrained, red = conflicting, neutral = N remaining DoF.
+    m_viewport->set_on_solve_state([this](int dof, bool ok, bool has_constraints) {
+        // Remembered as well as shown: the readout is fed ONLY by a live solve, and entering
+        // Constrain mode triggers none — so without a cache the very line the user goes to
+        // Constrain to read stays blank until they happen to change something.
+        m_dof_last = dof; m_dof_last_ok = ok; m_dof_last_has = has_constraints;
+        apply_dof_status(dof, ok, has_constraints);
+    });
+
+    // Selection no longer writes the status line: on_sketch_step owns it, says the same thing
+    // for Select mode and — unlike this callback, which also fired while an edit-op mirrored its
+    // picks into the selection — never claims "N selected, Delete removes them" in the middle of
+    // a Mirror gesture, where Delete does nothing of the sort. 1c0c.
+
+    // Onshape flow: clicking inside a closed-loop face commits the sketch and opens
+    // the Extrude dialog (with a ghost preview) targeting that sketch.
+    m_viewport->set_on_sketch_face_selected([this](int region) {
+        if (!m_viewport) return;
+        m_viewport->finish_sketch();                 // commit live sketch (synchronous)
+        m_extrude_sketch_ref = resolve_extrude_sketch();
+        if (m_extrude_sketch_ref < 0) {
+            m_status->SetForegroundColour(wxColour(235, 110, 110));
+            set_status(_L("Could not resolve the sketch to extrude"));
+            m_status->Refresh();
+            return;
+        }
+        set_ui_mode(UiMode::Feature);
+        open_tool(Tool::Extrude);
+        // AFTER open_tool, not before: opening the tool re-derives the selection state, so a
+        // region recorded ahead of it is wiped before Extrude ever reads it.
+        m_sel_sketch_feat   = m_extrude_sketch_ref;
+        m_sel_sketch_region = region;
+        m_sel_solid_face = m_sel_solid_edge = -1;
+        m_pick_face = m_pick_face_body = -1;
+        m_viewport->set_loop_pick(m_extrude_sketch_ref, region);
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("Face selected — set the depth and Confirm"));
+        m_status->Refresh();
+    });
+
+    // Clicking a committed sketch loop on the plate (no live session) selects THAT loop:
+    // the viewport highlights only it (cyan) and its Sketch feature's tree row is selected.
+    // The (feature, region) pair is remembered so Extrude builds just that one loop.
+    m_viewport->set_on_display_sketch_selected([this](int feat, int region, int entity) {
+        if (feat < 0 || feat >= int(m_doc.features.size())) return;
+        m_sel_sketch_feat   = feat;
+        m_sel_sketch_region = region;
+        // Last pick wins (symmetric with the solid-pick handler): selecting a sketch loop drops
+        // any stale solid face/edge pick so Extrude treats this loop as the profile.
+        m_sel_solid_face = m_sel_solid_edge = -1;
+        m_pick_face = m_pick_face_body = -1;
+        // Rib card open: point at the LINE, do not type its index. 'Entity index' was a bare
+        // wxSpinCtrl ranged 0-999 standing in for a line sitting visible on screen, with nothing
+        // anywhere telling you which integer was which — the purest case of the thing this epic
+        // exists to remove. Only a stroke hit carries an entity (an interior click is a region,
+        // not a line), so a click inside a loop deliberately leaves the field alone rather than
+        // resetting it to something arbitrary. The sketch picker follows the same pick, so
+        // pointing at a line in a different sketch retargets both together. 3648.
+        if (m_active == Tool::Rib && entity >= 0) {
+            if (m_rib_sketch != nullptr)
+                for (unsigned i = 0; i < m_rib_sketch->GetCount(); ++i)
+                    if (int(reinterpret_cast<intptr_t>(m_rib_sketch->GetClientData(i))) == feat) {
+                        m_rib_sketch->SetSelection(i);
+                        break;
+                    }
+            if (m_rib_entity != nullptr) m_rib_entity->SetValue(entity);
+            refresh_preview();
+        }
+        // Sweep card open: the sketch you point at becomes the PATH. The profile is already
+        // settled selection-first — you pick a sketch and then invoke Sweep, which is the design
+        // law's own canonical example — so the path is the input that was still trapped in a
+        // combo. The picker excludes the profile, so pointing at the profile correctly does
+        // nothing. e1p item 6; same shape as the Boolean and Mirror fixes.
+        if (m_active == Tool::Sweep && m_sweep_path != nullptr) {
+            for (unsigned i = 0; i < m_sweep_path->GetCount(); ++i) {
+                if (int(reinterpret_cast<intptr_t>(m_sweep_path->GetClientData(i))) != feat) continue;
+                m_sweep_path->SetSelection(i);
+                m_sweep_path_ref = feat;
+                refresh_preview();
+                break;
+            }
+        }
+        // Loft card open: pointing at a sketch TOGGLES its membership, so a loft is built by
+        // clicking the profiles in the viewport instead of hunting rows in a check-list. The
+        // list stays visible as the typed half and still shows the order, which matters here —
+        // loft order is not commutative.
+        if (m_active == Tool::Loft && m_loft_list != nullptr) {
+            for (size_t i = 0; i < m_loft_sketch_idx.size() && i < m_loft_list->GetCount(); ++i) {
+                if (m_loft_sketch_idx[i] != feat) continue;
+                m_loft_list->Check(unsigned(i), !m_loft_list->IsChecked(unsigned(i)));
+                refresh_preview();
+                break;
+            }
+        }
+        set_tree_selection(feat);
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(region >= 0
+            // "Region", not "Loop": what is selected — and what Extrude will consume — is the
+            // bounded area including any holes in it, not a single closed curve.
+            ? _L("Region selected — right-click to Extrude, or double-click to edit")
+            : _L("Sketch selected — right-click to Extrude, or double-click to edit"));
+        m_status->Refresh();
+    });
+
+    // Double-click a committed sketch stroke: open THAT sketch for editing, where its entities
+    // are individually selectable and their quotes editable. on_edit_feature already does the
+    // whole job — it was only ever reachable from the tree, which is precisely the side-panel
+    // dependency being retired. The pick has already lit the right tree row by the time the
+    // double-click arrives, but set it again so the path does not depend on that ordering.
+    m_viewport->set_on_display_sketch_activated([this](int feat) {
+        if (feat < 0 || feat >= int(m_doc.features.size())) return;
+        set_tree_selection(feat);
+        on_edit_feature();
+    });
+
+    // F key (Prepare's Place on Face): the tool forwards it here when the Design viewport
+    // has focus; we lay the selected body face on the bed. Returns false when no face is
+    // selected so the key can fall through to the default handler.
+    m_viewport->set_on_place_on_face([this]() { return place_on_face(); });
+
+    // Clicking a solid cycles whole -> face -> edge. The tool draws the cyan overlay for ALL
+    // levels now (per-body, so other bodies stay untinted) — no whole-compound set_body_highlight.
+    m_viewport->set_on_solid_selection_changed([this](int level, int body, int face, int edge) {
+        // A pick that fell through the move gizmo (clicked off the arrows) exits move mode.
+        if (m_viewport->moving_body()) m_viewport->clear_move_gizmo();
+        // Remember which body + face/edge so Extrude / dress-up target the RIGHT body.
+        m_sel_solid_body = (level >= 1) ? body : -1;
+        m_sel_solid_face = (level == 2) ? face : -1;   // 4 = Vertex: a corner is not its face
+        m_sel_solid_edge = (level == 3) ? edge : -1;
+        m_sel_solid_vertex = (level == 4);
+        // Keep the hit face even at whole-body level: the cycle's first click means "this body",
+        // but the user pointed AT a face and a sketch should be able to use it. 3a2.
+        m_pick_face_body = (level >= 1) ? body : -1;
+        m_pick_face      = (level >= 1) ? face : -1;
+        // Last pick wins: selecting a solid drops any stale committed-sketch loop selection.
+        // Otherwise a leftover loop keeps `m_sel_sketch_region >= 0`, which blocks the face
+        // push/pull branch in Extrude (`m_sel_solid_face >= 0 && m_sel_sketch_region < 0`) and
+        // makes Extrude build a DETACHED new body from the last sketch instead of push/pulling
+        // the face the user just clicked.
+        if (level >= 1) { m_sel_sketch_region = -1; m_sel_sketch_feat = -1; }
+        // Say what got picked. Without this the ONLY feedback is the viewport highlight, so a
+        // pick that registers but draws faintly is indistinguishable from one that never
+        // happened — which is precisely how this failure was reported and why it resisted
+        // diagnosis. Cards that show their own labels still do. The label itself is written
+        // ONCE, at the end of this handler — a second writer here only ever produced text that
+        // the later one overwrote before a frame was drawn, and reading it as the live string
+        // is how a vertex pick came to be "fixed" in a branch that never reaches the screen.
+        // If the Fillet/Chamfer card is open, re-anchor (or drop) the radius arrow on the new pick
+        // and rebuild the ghost — once an edge is picked the preview-only mode hides the base body.
+        if (m_active == Tool::Dressup) { sync_dressup_target(); update_fillet_gizmo(); refresh_preview(); }
+        // Boolean card open: the VIEWPORT is how you choose the two operands. Until now they
+        // could only come from two combos — the one control the charter names for this tool
+        // (e1p item 4), and the same pair 7xx caught silently resolving every row to
+        // index 0. The highlight already flowed card -> viewport; this closes the loop the
+        // other way. First pick is the target (kept), second is the tool (consumed); the
+        // combos mirror both, so the typed half of L2 still works and still round-trips.
+        // A body cannot be both operands — that boolean is a no-op — but the resolution is to
+        // SWAP, never to refuse: the pick is the user pointing at a body, and it has to win.
+        // Refusing it was measurably wrong. Both combos are pre-filled when the card opens
+        // (target = body 0, tool = a different one), so the very first viewport pick usually
+        // names a body the other slot already holds; ignoring it left the defaults in place and
+        // the commit produced body0 - body1 (75000 mm3) when the picks asked for body1 - body0
+        // (43000 mm3). Swapping keeps the pair distinct AND honours the click.
+        if (m_active == Tool::Boolean && m_sel_solid_body >= 0) {
+            ComboBox* dst   = (m_bool_next_slot == 0) ? m_bool_target : m_bool_tool;
+            ComboBox* other = (m_bool_next_slot == 0) ? m_bool_tool   : m_bool_target;
+            const int row   = m_sel_solid_body;          // selection index == body index
+            if (dst != nullptr && row < int(dst->GetCount())) {
+                const int prev = dst->GetSelection();
+                dst->SetSelection(row);
+                if (other != nullptr && other->GetSelection() == row && prev >= 0 && prev != row)
+                    other->SetSelection(prev);            // displaced operand takes the old slot
+                m_bool_next_slot ^= 1;
+                refresh_preview();                        // re-tints the operands + rebuilds the ghost
+            }
+        }
+        // Mirror card open: the body you point at is the body that gets mirrored. Same one-way
+        // flow Boolean had (310o) and the same fix — the combo stays as the typed half.
+        // Only one operand here, so there is no slot to alternate and no swap to do.
+        if (m_active == Tool::Mirror && m_sel_solid_body >= 0 && m_mirror_body != nullptr &&
+            m_sel_solid_body < int(m_mirror_body->GetCount())) {
+            m_mirror_body->SetSelection(m_sel_solid_body);   // selection index == body index
+            refresh_preview();
+        }
+        // If the Shell card is open, a face pick chooses the open face: update the label + gizmo
+        // + ghost so the hollow updates live.
+        if (m_active == Tool::Shell) {
+            m_shell_face_label->SetLabel(m_sel_solid_face >= 0
+                ? wxString::Format(_L("Face %d"), m_sel_solid_face)
+                : _L("(all faces — closed hollow)"));
+            refresh_preview();   // rebuilds the shell ghost + re-anchors the thickness gizmo
+        }
+        // Thicken card open: the face pick IS the feature's input, and until now nothing here
+        // wrote its label — the value reached m_sel_solid_face and Confirm worked, but the card
+        // read "(pick a solid face)" however many faces you had picked. Invisible because the
+        // ghost did update, so the card looked wrong while behaving right.
+        if (m_active == Tool::Thicken) {
+            m_thicken_face_label->SetLabel(m_sel_solid_face >= 0
+                ? wxString::Format(_L("Face %d"), m_sel_solid_face)
+                : _L("(pick a solid face)"));
+            refresh_preview();
+        }
+        // Draft card open: a face pick chooses the face to taper; update label + ghost live.
+        if (m_active == Tool::Draft) {
+            m_draft_face_label->SetLabel(m_sel_solid_face >= 0
+                ? wxString::Format(_L("Face %d"), m_sel_solid_face)
+                : _L("(pick a side face)"));
+            refresh_preview();
+        }
+        // Hole card open: clicking a solid FACE re-targets the hole ONTO that face (Orca-style),
+        // so the hole lives on the object's face — not on a stale dropdown/datum plane. Uses the
+        // face under the cursor from the FIRST click (handle_solid_click reports it even at the
+        // Whole level), so no whole->face cycle is needed.
+        if (m_active == Tool::Hole && face >= 0 && body >= 0 && body < int(m_doc.bodies.size())) {
+            const TopoDS_Face fc = GeometryEngine::face_by_index(m_doc.bodies[body].shape, face);
+            if (!fc.IsNull()) {
+                m_hole_face_plane = face_plane_inward(fc);
+                m_hole_on_face    = true;
+                m_hole_face_body  = body;
+                set_hole_target_label(face);
+                m_hole_has_bounds = GeometryEngine::face_plane_bounds(
+                    fc, m_hole_face_plane.origin, m_hole_face_plane.x_axis,
+                    m_hole_face_plane.y_axis, m_hole_umin, m_hole_umax, m_hole_vmin, m_hole_vmax);
+                if (m_hole_x) m_hole_x->SetValue(0.0);   // centre of the picked face
+                if (m_hole_y) m_hole_y->SetValue(0.0);
+                if (m_hole_plane) m_hole_plane->SetSelection(index_from_plane(m_hole_face_plane));
+                refresh_preview();   // re-place the gizmo + ghost on the new face
+            }
+        }
+        // Thread card open: clicking a cylindrical face or circular edge re-derives the thread.
+        if (m_active == Tool::Thread && body >= 0 && body < int(m_doc.bodies.size())) {
+            const TopoDS_Shape& shape = m_doc.bodies[body].shape;
+            GeometryEngine::CylinderFace cf;
+            if (face >= 0)
+                cf = GeometryEngine::cylinder_of_face(GeometryEngine::face_by_index(shape, face));
+            const bool from_face = cf.ok;   // which of the two the cylinder actually came from
+            if (!cf.ok && edge >= 0)
+                cf = GeometryEngine::circle_of_edge(GeometryEngine::edge_by_index(shape, edge));
+            if (cf.ok) {
+                SketchPlane p; p.origin = cf.base; p.normal = cf.axis;
+                const Vec3d ref = std::abs(cf.axis.z()) < 0.9 ? Vec3d(0, 0, 1) : Vec3d(1, 0, 0);
+                p.x_axis = ref.cross(cf.axis).normalized();
+                p.y_axis = cf.axis.cross(p.x_axis).normalized();
+                m_thread_face_plane = p;
+                m_thread_on_face    = true;
+                m_thread_face_body  = m_sel_solid_body;
+                set_thread_target_label(from_face ? face : -1, from_face ? -1 : edge);
+                infer_thread_spec(2.0 * cf.radius);   // M diameter + pitch + depth from the cylinder
+                if (m_thread_height && cf.height > 1e-6) m_thread_height->SetValue(cf.height);
+                if (m_thread_internal) m_thread_internal->SetValue(cf.internal);
+                refresh_preview();
+            }
+        }
+        // Plane tool with a pick armed: capture the right kind of reference (face for Face A/B,
+        // edge for Edge A/B). If the click wasn't the right kind, stay armed so the user retries.
+        if (m_active == Tool::Plane && m_plane_pick != PlanePick::None) {
+            bool got = false;
+            switch (m_plane_pick) {
+            case PlanePick::FaceA: if (m_sel_solid_face >= 0) { m_pl_faceA_body = m_sel_solid_body; m_pl_faceA = m_sel_solid_face; got = true; } break;
+            case PlanePick::FaceB: if (m_sel_solid_face >= 0) { m_pl_faceB_body = m_sel_solid_body; m_pl_faceB = m_sel_solid_face; got = true; } break;
+            case PlanePick::EdgeA: if (m_sel_solid_edge >= 0) { m_pl_edgeA_body = m_sel_solid_body; m_pl_edgeA = m_sel_solid_edge; got = true; } break;
+            case PlanePick::EdgeB: if (m_sel_solid_edge >= 0) { m_pl_edgeB_body = m_sel_solid_body; m_pl_edgeB = m_sel_solid_edge; got = true; } break;
+            default: break;
+            }
+            if (got) { m_plane_pick = PlanePick::None; refresh_plane_labels(); }
+            if (got && m_viewport) m_viewport->set_escalate_on_repick(true);
+        }
+        // Axis tool with a pick armed: face or edge.
+        if (m_active == Tool::Axis && m_axis_pick != AxisPick::None) {
+            bool got = false;
+            switch (m_axis_pick) {
+            case AxisPick::Face: if (m_sel_solid_face >= 0) { m_ax_face_body = m_sel_solid_body; m_ax_face = m_sel_solid_face; got = true; } break;
+            case AxisPick::Edge: if (m_sel_solid_edge >= 0) { m_ax_face_body = m_sel_solid_body; m_ax_edge = m_sel_solid_edge; got = true; } break;
+            default: break;
+            }
+            if (got) { m_axis_pick = AxisPick::None; refresh_axis_labels(); }
+            if (got && m_viewport) m_viewport->set_escalate_on_repick(true);
+        }
+        // CoordSys tool with a pick armed: face or edge.
+        if (m_active == Tool::CoordSys && m_coordsys_pick != CoordSysPick::None) {
+            bool got = false;
+            switch (m_coordsys_pick) {
+            case CoordSysPick::Face: if (m_sel_solid_face >= 0) { m_cs_face_body = m_sel_solid_body; m_cs_face = m_sel_solid_face; got = true; } break;
+            case CoordSysPick::Edge: if (m_sel_solid_edge >= 0) { m_cs_face_body = m_sel_solid_body; m_cs_edge = m_sel_solid_edge; got = true; } break;
+            default: break;
+            }
+            if (got) {
+                // A picked face or edge is only meaningful to FaceAndDirection. Left on the
+                // default Point (world), datum_frame ignores the pick entirely and resolves the
+                // connector to coordsys_point — which is (0,0,0) unless the user typed
+                // otherwise. Two such connectors then share one frame, so a mate between them
+                // computes an IDENTITY transform: the feature commits, the recompute succeeds,
+                // and nothing moves. Picking a face IS the choice of a face-based frame, so make
+                // the type follow the pick rather than asking for it twice.
+                if (m_coordsys_type && m_coordsys_type->GetSelection() != (int)CoordSysType::FaceAndDirection)
+                    m_coordsys_type->SetSelection((int)CoordSysType::FaceAndDirection);
+                m_coordsys_pick = CoordSysPick::None;
+                refresh_coordsys_labels();
+            }
+            if (got && m_viewport) m_viewport->set_escalate_on_repick(true);
+        }
+        m_status->SetForegroundColour(wxNullColour);
+        const int nb = int(m_doc.bodies.size());
+        const wxString bodytag = (nb > 1) ? wxString::Format(_L("Body %d "), body + 1) : wxString();
+        // Each sub-element line ends by naming the NEXT click (gem). Escalation to the
+        // whole body is a gesture nothing on screen would otherwise reveal, and the status line
+        // is the only surface that can teach it at the moment it applies. It REPLACES the old
+        // per-level verb hints ("right-click to push/pull it", "Fillet/Chamfer to dress it")
+        // rather than joining them: the line is clipped at the panel edge past ~55 characters
+        // (set_status's Wrap() does not take effect — 8cc), and those verbs are shown
+        // with their icons in the offer anyway, while this gesture is shown nowhere else.
+        // Both clauses fit now that the line is drawn over the viewport instead of squeezed
+        // into the panel. Say "what applies to it", never "verbs" — that is this codebase's
+        // word for a tool-offer entry, not a word the drawing office uses, and the plane and
+        // bodies-list lines already say it the right way.
+        set_status(level == 4 ? bodytag + _L("vertex selected — click again for the whole body")
+                         : level == 1 ? bodytag + _L("selected (whole body) — right-click for what applies to it")
+                         : level == 2 ? bodytag + wxString::Format(_L("face %d selected — right-click to push/pull it, or click again for the whole body"), face)
+                         : level == 3 ? bodytag + wxString::Format(_L("edge %d selected — Fillet/Chamfer to dress it, or click again for the whole body"), edge)
+                                      : _L("Nothing selected"));
+        m_status->Refresh();
+    });
+
+    // Visual Extrude gizmo (C5b): dragging/editing the in-canvas depth arrow writes the
+    // matching spin field and re-previews (which re-feeds the gizmo with the new depth).
+    m_viewport->set_on_extrude_depth_changed([this](double depth, bool second) {
+        // One arrow, three tools: Extrude owns the two-sided pair, the other two have a single
+        // distance each. Routing here rather than arming three near-identical gizmos is the whole
+        // reason these two tools got a handle at all — the arrow was already written.
+        if (m_active == Tool::SurfaceExtrude) {
+            if (m_surf_extrude_distance) m_surf_extrude_distance->SetValue(depth);
+        } else if (m_active == Tool::Thicken) {
+            if (m_thicken_thickness) m_thicken_thickness->SetValue(depth);
+        } else if (m_active == Tool::Rib) {
+            if (m_rib_depth) m_rib_depth->SetValue(depth);   // depth; thickness has its own in-plane pair
+        } else if (m_active == Tool::SurfaceOffset) {
+            if (m_surf_offset_distance) m_surf_offset_distance->SetValue(depth);
+        } else if (m_active == Tool::ThickenSurface) {
+            if (m_surf_thicken_thickness) m_surf_thicken_thickness->SetValue(depth);
+        } else if (second) { if (m_distance2) m_distance2->SetValue(depth); }
+        else               { if (m_distance)  m_distance->SetValue(depth); }
+        refresh_preview();
+    });
+
+    // Datum-plane resize handles (C3): a handle drag reports the new u/v extent. Mirror it into the
+    // Size spins and, when editing a committed datum, into the feature so the rendered rectangle
+    // follows live. SetValue doesn't emit a command event, so no refresh_preview recursion.
+    m_viewport->set_on_datum_size_changed([this](double u, double v) {
+        if (m_plane_usize) m_plane_usize->SetValue(u);
+        if (m_plane_vsize) m_plane_vsize->SetValue(v);
+        if (m_edit_index >= 0 && m_edit_index < int(m_doc.features.size()) &&
+            m_doc.features[m_edit_index].type == CadFeatureType::Plane) {
+            m_doc.features[m_edit_index].plane_u_size = u;
+            m_doc.features[m_edit_index].plane_v_size = v;
+            refresh_datum_planes();   // committed datum rectangle follows the drag
+        }
+        m_viewport->request_repaint();
+    });
+
+    // Offset arrow drag: mirror the new offset into the spin + (when editing) the committed feature.
+    m_viewport->set_on_datum_offset_changed([this](double off) {
+        if (m_plane_offset) m_plane_offset->SetValue(off);
+        if (m_edit_index >= 0 && m_edit_index < int(m_doc.features.size()) &&
+            m_doc.features[m_edit_index].type == CadFeatureType::Plane) {
+            m_doc.features[m_edit_index].plane_offset = off;
+            refresh_datum_planes();
+        }
+        m_viewport->request_repaint();
+    });
+
+    // Helix handles: a drag reports the whole triple, since pitch and height are coupled
+    // through the turn count and reading one without the others would show a stale curve.
+    m_viewport->set_on_helix_changed([this](double radius, double pitch, double height) {
+        if (m_helix_radius) m_helix_radius->SetValue(radius);
+        if (m_helix_pitch)  m_helix_pitch->SetValue(pitch);
+        if (m_helix_height) m_helix_height->SetValue(height);
+        update_helix_gizmo();      // re-feed so the curve follows the drag
+        m_viewport->request_repaint();
+    });
+
+    // Rib thickness handle: writes the spin and re-feeds the ghost, same as the depth arrow.
+    m_viewport->set_on_rib_thickness_changed([this](double thickness) {
+        if (m_rib_thickness) m_rib_thickness->SetValue(thickness);
+        refresh_preview();   // Rib HAS a solid ghost, so the full preview path is correct here
+    });
+
+    // Clicking a ghost base plane sets the base graphically (replaces the dropdown). A base pick
+    // drops any offset-from-face choice so the picked base plane wins, then re-resolves the preview.
+    m_viewport->set_on_datum_base_picked([this](int base) {
+        if (m_active == Tool::Plane) {
+            // Plane tool open: the click sets the datum's base plane (replaces the dropdown).
+            if (m_plane_base && base >= 0 && base < int(m_plane_base->GetCount()))
+                m_plane_base->SetSelection(base);
+            m_pl_faceA_body = m_pl_faceA = -1;
+            refresh_plane_labels();
+            refresh_preview();   // re-resolve the frame + move the gizmo/ghosts to the new base
+        } else {
+            // Clicking a reference plane in 3D IS how a sketch plane is chosen now. Record it and,
+            // when a session is already live, re-plane it immediately: begin_sketch captures the
+            // plane at first-tool-pick, so without this the entities would stay on the old plane
+            // while the committed feature landed on the new one.
+            if (base >= 0) {
+                m_ref_plane = base;
+                m_plane_picked = true;                 // chosen, not merely defaulted to
+                m_pick_face = m_pick_face_body = -1;   // last pick wins: a plane beats a stale face
+                if (m_viewport && m_viewport->is_sketching())
+                    m_viewport->set_sketch_plane(plane_from_choice(m_ref_plane));
+            }
+            const char* nm = (base == 0) ? "XY" : (base == 1) ? "XZ" : (base == 2) ? "YZ" : "datum";
+            m_status->SetForegroundColour(wxColour(120, 210, 120));
+            // Both halves named the TOOLBAR, which no longer carries either button: the tools
+            // moved to the offer. Name the gesture that actually works in each mode, and say
+            // what a plain click does, since the two are easy to confuse on a plane.
+            set_status(m_ui_mode == UiMode::Sketch
+                ? wxString::Format(_L("%s plane selected — right-click for the drawing tools"), nm)
+                : wxString::Format(_L("%s plane selected — right-click to sketch on it, "
+                                      "or click an object to select it"), nm));
+            m_status->Refresh();
+        }
+    });
+
+    // Move-body gizmo (M5): each drag/edit reports the body's new translation. Store it as a
+    // display-only per-body transform and re-feed the moved meshes (the OCCT shape is untouched,
+    // so face/edge ids the dress-up ops target stay valid).
+    m_viewport->set_on_body_move_changed([this](int body, const Transform3d& xform) {
+        sync_body_xform();
+        if (body < 0 || body >= int(m_body_xform.size())) return;
+        m_body_xform[body] = xform;   // full move+rotate transform, baked into the mesh at Commit
+        feed_bodies();   // rebuilds the transformed meshes in place + refreshes display + pick
+        // When the move gizmo is serving the Transform card, mirror the drag into the card's
+        // numeric fields (the card is the typed half, the gizmo the geometry-first half).
+        if (body == m_xf_gizmo_body && m_active == Tool::Transform) {
+            const Transform3d d = xform * m_xf_gizmo_base.inverse();
+            const Vec3d       t = d.translation();
+            if (m_xf_dx) m_xf_dx->SetValue(t.x());
+            if (m_xf_dy) m_xf_dy->SetValue(t.y());
+            if (m_xf_dz) m_xf_dz->SetValue(t.z());
+            const Eigen::AngleAxisd aa(Eigen::Quaterniond(d.linear()).normalized());
+            // The gizmo's rings are per-world-axis, so a ring drag yields an exactly axial
+            // rotation and this is lossless for the normal interaction. A composed multi-ring
+            // pose is not axial; the card can only express one axis, so report the dominant one
+            // rather than refusing to answer.
+            int ax = 0; double best = std::abs(aa.axis().x());
+            if (std::abs(aa.axis().y()) > best) { ax = 1; best = std::abs(aa.axis().y()); }
+            if (std::abs(aa.axis().z()) > best) { ax = 2; best = std::abs(aa.axis().z()); }
+            const double sign = (aa.axis()[ax] < 0.0) ? -1.0 : 1.0;
+            if (m_xf_axis)  m_xf_axis->SetSelection(ax);
+            if (m_xf_angle) m_xf_angle->SetValue(sign * aa.angle() * 180.0 / M_PI);
+        }
+        const int nb = int(m_doc.bodies.size());
+        const wxString tag = (nb > 1) ? wxString::Format(_L("Body %d "), body + 1) : wxString();
+        const Vec3d t = xform.translation();
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(tag + wxString::Format(_L("placed (%.1f, %.1f, %.1f) mm — drag arrows to move, rings to rotate"),
+                                                  t.x(), t.y(), t.z()));
+        m_status->Refresh();
+    });
+
+    // Fillet/Chamfer radius gizmo: dragging (or editing) the edge-anchored arrow writes the
+    // Dress-up size and refreshes the ghost. SetValue is silent in wx, so refresh explicitly.
+    m_viewport->set_on_fillet_radius_changed([this](double radius) {
+        if (m_dressup_size) m_dressup_size->SetValue(radius);
+        refresh_preview();   // rebuilds the candidate fillet ghost at the new radius
+    });
+
+    // Hole gizmo: dragging/editing the centre, diameter, or depth handle writes the four Hole-card
+    // spins and refreshes the ghost. SetValue is silent in wx, so refresh explicitly.
+    m_viewport->set_on_hole_changed([this](double x, double y, double diameter, double depth) {
+        if (m_hole_x)        m_hole_x->SetValue(x);
+        if (m_hole_y)        m_hole_y->SetValue(y);
+        if (m_hole_diameter) m_hole_diameter->SetValue(diameter);
+        if (m_hole_depth)    m_hole_depth->SetValue(depth);
+        refresh_preview();   // rebuilds the candidate hole ghost at the new position/size
+    });
+
+    // Thread gizmo: dragging/editing the centre, radius, or length handle writes the Thread-card
+    // spins and refreshes the ghost (SetValue is silent in wx).
+    m_viewport->set_on_thread_changed([this](double x, double y, double radius, double height) {
+        if (m_thread_x)      m_thread_x->SetValue(x);
+        if (m_thread_y)      m_thread_y->SetValue(y);
+        if (m_thread_radius) m_thread_radius->SetValue(2.0 * radius);   // gizmo reports radius; field = diameter
+        if (m_thread_height) m_thread_height->SetValue(height);
+        refresh_preview();
+    });
+
+    // Shell gizmo: dragging/editing the inward thickness arrow writes the Shell-card thickness
+    // and refreshes the ghost (SetValue is silent in wx).
+    m_viewport->set_on_shell_thickness_changed([this](double thickness) {
+        if (m_shell_thickness) m_shell_thickness->SetValue(thickness);
+        refresh_preview();
+    });
+
+    m_viewport->set_on_revolve_angle_changed([this](double angle) {
+        if (m_revolve_angle) m_revolve_angle->SetValue(angle);
+        refresh_preview();
+    });
+
+    m_viewport->set_on_draft_angle_changed([this](double angle) {
+        if (m_draft_angle) m_draft_angle->SetValue(angle);
+        refresh_preview();
+    });
+
+    // Cut gizmo: dragging the offset arrow writes the Cut-card offset and refreshes the ghost.
+    m_viewport->set_on_cut_offset_changed([this](double v) {
+        if (m_cut_offset) m_cut_offset->SetValue(v);
+        refresh_preview();
+    });
+
+    m_viewport->set_on_pattern_changed([this](double value) {
+        // Linear drag feeds spacing; circular drag feeds angle. The card knows which is live.
+        if (m_pattern_type && m_pattern_type->GetSelection() == 1) {
+            if (m_pattern_angle) m_pattern_angle->SetValue(value);
+        } else if (m_pattern_spacing) {
+            m_pattern_spacing->SetValue(value);
+        }
+        refresh_preview();
+    });
+
+    // Leaving an EMPTY sketch session: restore Feature mode + the committed-sketch overlay.
+    // request_exit() calls this only for an idle Select session that holds no geometry, so
+    // nothing a user drew can reach here — discarding drawn work goes through tool_cancel's
+    // confirmation instead.
+    m_viewport->set_on_sketch_exit([this]() {
+        // While placing imported Text/SVG art, right-click = Confirm (keep the art) — the
+        // Insert card is the explicit gate, this is the in-canvas shortcut to it.
+        if (m_active == Tool::Insert) { finalize_insert(); return; }
+        if (m_viewport) m_viewport->cancel_sketch();
+        m_edit_index = -1;
+        set_ui_mode(UiMode::Feature);
+        sync_sketch_display();
+        refresh_tree();
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("Tool exited"));
+        m_status->Refresh();
+    });
+
+    // The tool declined to leave because the session holds geometry. There is no "press it again"
+    // any more — the answer is a deliberate Finish or Cancel — so this is a plain statement of
+    // where you are, not a warning shot. Only the STATUS LINE lives here; the tool reports via
+    // this callback instead of writing text itself.
+    m_viewport->set_on_sketch_exit_refused([this]() {
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("Sketch kept — Finish to commit it, Cancel to discard"));
+        m_status->Refresh();
+    });
+
+    // Ctrl+Z / Ctrl+Shift+Z (Ctrl+Y) from the viewport → feature-history undo/redo.
+    m_viewport->set_on_undo_redo([this](bool redo) { do_undo_redo(redo); });
+
+    // Esc = the unified Cancel everywhere. Feature cards had no key exit (only the button);
+    // CHAR_HOOK on the panel catches Esc from the card or viewport and routes to tool_cancel.
+    // Sketch/Constrain keep the viewport's per-gesture Esc (abort the current point first),
+    // so we only intercept Esc here when a feature/insert card is the thing to dismiss.
+    Bind(wxEVT_CHAR_HOOK, [this](wxKeyEvent& e) {
+        const int  key  = e.GetKeyCode();
+        const bool ctrl = e.ControlDown() || e.CmdDown();
+        const bool sketching = (m_ui_mode == UiMode::Sketch) && m_viewport && m_viewport->is_sketching();
+        // Which key MAP applies is a question about the MODE, not about whether a session is
+        // already running. Gating the sketch map on is_sketching() made it unreachable by
+        // keyboard: is_sketching() only turns true inside select_tool()'s begin_sketch(), and
+        // select_tool() is what the sketch keys call — so the first letter after entering
+        // sketch mode fell through to the feature map, matched nothing (feature keys are
+        // Shift+letter), and did nothing. The mouse worked only because the toolbar flyout
+        // reaches select_tool() directly. That is why all 17 keys read as dead. 0ud.
+        const bool sketch_mode = (m_ui_mode == UiMode::Sketch);
+        // Never steal editing keys from a focused text field or an open in-canvas value field —
+        // Delete/Ctrl+Z there must edit the text, not the model.
+        const bool in_text = (dynamic_cast<wxTextCtrl*>(wxWindow::FindFocus()) != nullptr)
+                             || (m_viewport && m_viewport->inline_busy());
+        if (getenv("ORCA_CAD_KEYTRACE")) {
+            wxWindow* fw = wxWindow::FindFocus();
+            fprintf(stderr, "[KEYTRACE] key=%d ui_mode=%d is_sketching=%d in_text=%d inline_busy=%d focus=%s\n",
+                    key, int(m_ui_mode), (m_viewport && m_viewport->is_sketching()) ? 1 : 0, in_text ? 1 : 0,
+                    (m_viewport && m_viewport->inline_busy()) ? 1 : 0,
+                    // wxString, not a cast: GetClassName() returns const wxChar* — wchar_t* in
+                    // this build — and casting THAT to const char* and printing it with %s emits
+                    // the first byte and stops at the padding NUL. Every focus= field this tracer
+                    // has ever printed was a single letter: "wxGLCanvas" came out as "w", and so
+                    // did "wxWindow". An instrument that silently truncates its most important
+                    // field is worse than no instrument, and this one was trusted for a whole
+                    // day's diagnosis.
+                    fw ? wxString(fw->GetClassInfo()->GetClassName()).utf8_str().data() : "(none)");
+            fflush(stderr);
+        }
+
+        // NOTE the position: this sits AFTER the KEYTRACE block on purpose. It returns early,
+        // and putting it first made every forwarded key invisible to the tracer — the one
+        // instrument that diagnosed this bug in the first place.
+        // The in-canvas value field is a borderless, always-on-top top-level frame, so whether it
+        // may take keyboard focus is the platform's decision, not ours: macOS denies key status to a
+        // borderless window, mutter's focus-stealing prevention refuses a re-mapped window, and the
+        // rig never grants it. When focus is refused, Enter/Esc/Tab are delivered HERE (to the panel)
+        // instead of the field, its own wxEVT_TEXT_ENTER / WXK_ESCAPE bindings never fire, and the
+        // queued-dimension chain (a line queues Length then Angle) becomes unwalkable. Forwarding them
+        // makes the field behave the same everywhere WITHOUT fighting the window manager for focus,
+        // which is what seven earlier attempts did unsuccessfully. When the field DOES hold focus we
+        // deliberately do nothing here, so its own bindings run and typing keeps working.
+        if (m_viewport && m_viewport->inline_busy() && !m_viewport->inline_has_focus()) {
+            if (key == WXK_RETURN || key == WXK_NUMPAD_ENTER || key == WXK_TAB) {
+                m_viewport->inline_commit();
+                return;
+            }
+            // NO forwarding here any more. The field is drawn INSIDE the GL canvas now, so it
+            // is fed the way every other ImGui widget in this app is fed: GLCanvas3D::on_char ->
+            // ImGuiWrapper::update_key_data -> io.AddInputCharacter. Re-adding a panel-side
+            // forwarder would also mask whether that path works, which is exactly what is being
+            // measured.
+            // Esc is NOT special-cased here any more: escape() routes it, and the open field is
+            // exactly what CadLevel::Transient means, so it closes the field and stops there.
+        }
+
+        // ONE Esc, ONE route, whatever holds focus. Which widget has focus is an accident of where
+        // the user last clicked (a toolbar button, the Construction checkbox), and Esc must not
+        // depend on it. It used to be answered in four places — the inline field above, a sketch
+        // branch, a feature-card branch, and the canvas — none of which could see the others, so
+        // a press aimed at one of them fell through to the next and the SECOND press reached a
+        // layer that discarded the live sketch. escape() picks the single deepest live level and
+        // acts on that one only; see DesignInteraction.hpp for the ladder and its invariant.
+        if (key == WXK_ESCAPE) { escape(); return; }
+
+        // The offer from the keyboard (charter 4.1): the Menu key, or Shift+F10 for keyboards that
+        // do not have one. Same menu the right-click opens — show_offer_menu already decides which
+        // half of the map applies via sketch_map_applies(), so nothing about the content is decided
+        // here. With no press to anchor it, offer_anchor() puts it on the viewport.
+        // WXK_MENU is the GTK code for the physical Menu key (GDK_KEY_Menu); wxMSW instead sends
+        // WXK_WINDOWS_MENU for VK_APPS and maps Alt to WXK_ALT, so accepting both is safe
+        // everywhere. CallAfter because the menu is modal: let the key event finish dispatching
+        // before a nested loop takes the queue, the same reason the Sketch entry does it.
+        if (!in_text && !ctrl
+            && (key == WXK_MENU || key == WXK_WINDOWS_MENU || (key == WXK_F10 && e.ShiftDown()))) {
+            CallAfter([this] { show_offer_menu(offer_anchor()); });
+            return;
+        }
+
+        // Ctrl+Z / Ctrl+Shift+Z / Ctrl+Y — undo/redo handled here (not only in the GL canvas) so
+        // it works even when the canvas lost keyboard focus. In a sketch, undo drops the last entity.
+        if (!in_text && ctrl && (key == 'Z' || key == 'z' || key == WXK_CONTROL_Z ||
+                                 key == 'Y' || key == 'y' || key == WXK_CONTROL_Y)) {
+            const bool redo = (key == 'Y' || key == 'y' || key == WXK_CONTROL_Y) || e.ShiftDown();
+            if (sketching) { if (!redo) m_viewport->undo_last_sketch_entity(); }
+            else           { do_undo_redo(redo); }
+            return;
+        }
+        // Delete — the selected sketch entities (or the last drawn one if none is selected), or the
+        // selected feature in Feature mode. Focus-independent, same reason as undo above.
+        // WXK_BACK too: on a keyboard whose Del is a chord (every laptop this runs on), Del is
+        // the one destructive key nobody can reach, and Backspace is what users press. oql1.
+        if (!in_text && (key == WXK_DELETE || (key == WXK_BACK && sketching))) {
+            if (sketching) { m_viewport->delete_selected_or_last_sketch_entity(); return; }
+            if (m_ui_mode == UiMode::Feature && m_active == Tool::None
+                && tree_selection() != wxNOT_FOUND) { on_delete_feature(); return; }
+        }
+        // Section view controls while it is on (Alt+Wheel is unreliable under remote desktops / is
+        // grabbed by GLCanvas3D, so the keyboard drives it): PageUp/PageDown move the plane, F flips
+        // which half is kept (so you can inspect the opposite part).
+        if (!in_text && !sketch_mode && m_section_on) {
+            if (key == WXK_PAGEUP || key == WXK_PAGEDOWN) {
+                m_section_cut_z += (key == WXK_PAGEUP ? 2.0 : -2.0);
+                if (m_viewport) m_viewport->set_section_plane(true, m_section_cut_z, m_section_upper);
+                return;
+            }
+            if (key == 'F' || key == 'f') { flip_section_view(); return; }
+        }
+        // Tool shortcuts (Onshape-style). While a sketch is open, single letters drive sketch
+        // tools; otherwise Shift+letter drives feature tools and single letters drive view
+        // toggles / section. Ctrl-combos and focused text fields are never intercepted.
+        // A SKETCH SHORTCUT MAY LEAVE AN OPEN VALUE FIELD. in_text is true while an inline
+        // dimension editor is up, and drawing a rectangle opens one automatically for its
+        // Width/Height — so after a rectangle every single-letter tool key was swallowed and the
+        // sketch could not be continued at all. A value field holds a NUMBER; a letter is never
+        // meant for it, so a letter that names a sketch tool is unambiguously a tool switch.
+        // set_tool() commits the field on the way through, so the typed value is kept.
+        // Deliberately narrow: sketch mode only, only keys that are actually bound, and only the
+        // in-canvas field — a focused wxTextCtrl elsewhere (the variables table, a card spin)
+        // still keeps every key.
+        const bool inline_field_only = (dynamic_cast<wxTextCtrl*>(wxWindow::FindFocus()) == nullptr)
+                                       && m_viewport && m_viewport->inline_busy();
+        if (in_text && inline_field_only && sketch_mode && !ctrl) {
+            const int up2 = (key >= 'a' && key <= 'z') ? key - 'a' + 'A' : key;
+            auto it2 = m_keys_sketch.find(up2);
+            if (it2 != m_keys_sketch.end()) { it2->second(); return; }
+        }
+        // Ctrl+Shift first: the block below deliberately ignores every Ctrl-combo, which is
+        // exactly what makes this layer free to use.
+        if (!in_text && ctrl && e.ShiftDown()) {
+            const int up = (key >= 'a' && key <= 'z') ? key - 'a' + 'A' : key;
+            auto it = m_keys_feature.find(up | SC_SHIFT | SC_CTRL);
+            if (it != m_keys_feature.end()) { it->second(); return; }
+        }
+        if (!in_text && !ctrl) {
+            const int up = (key >= 'a' && key <= 'z') ? key - 'a' + 'A' : key;   // normalise case
+            if (sketch_mode) {
+                auto it = m_keys_sketch.find(up);
+                if (it != m_keys_sketch.end()) { it->second(); return; }
+            } else {
+                auto it = m_keys_feature.find(up | (e.ShiftDown() ? SC_SHIFT : 0));
+                if (it != m_keys_feature.end()) { it->second(); return; }
+            }
+        }
+        e.Skip();
+    });
+
+    // Right-click finishes the move gizmo in the viewport; mirror that on the panel so the
+    // action bar (shown while moving) hides and the move state clears.
+    m_viewport->set_on_move_exit([this]() { m_move_body = -1; show_move_card(false); update_action_bar(); });
+
+    // The offer (§4.1): right-click the geometry, get the verbs that apply to it. Left-click
+    // still only selects, so pointing at things stays quiet.
+    m_viewport->set_on_context_menu([this](const wxPoint& p) { show_offer_menu(p); });
+
+    // The Line tool's length and the Dimension tool's value are both entered in-canvas now
+    // (live quote labels + the floating SketchInlineEditor), so the old docked-card
+    // callbacks (on_segment_drawn / on_dimension_pick_complete) are no longer wired.
+
+    // Imported-art bbox transform streams the live offset/scale back here; write them to
+    // the feature and re-sync the overlay so the art tracks the drag.
+    m_viewport->set_on_imported_transform([this](int feat, Vec2d off, double sx, double sy) {
+        if (feat < 0 || feat >= int(m_doc.features.size())) return;
+        CadFeature& f = m_doc.features[feat];
+        if (f.imported_regions.empty()) return;
+        f.import_offset  = off;
+        f.import_scale_x = sx;
+        f.import_scale_y = sy;
+        m_doc.recompute();
+        sync_sketch_display();
+    });
+
+    auto* vcol = new wxBoxSizer(wxVERTICAL);
+    // The sketch banner sits ABOVE the viewport rather than floating inside it: a child window
+    // over a wxGLCanvas is a platform argument (it is a native window on GTK and does not
+    // reliably stack over GL), and the banner's job is to be unmissable, not to be clever.
+    m_sketch_banner = new wxPanel(this, wxID_ANY);
+    m_sketch_banner->SetBackgroundColour(wxColour(0, 122, 116));   // Orca teal: not a plate colour
+    m_sketch_banner_txt = new wxStaticText(m_sketch_banner, wxID_ANY, wxString());
+    m_sketch_banner_txt->SetForegroundColour(*wxWHITE);
+    {
+        wxFont f = m_sketch_banner_txt->GetFont();
+        f.SetWeight(wxFONTWEIGHT_BOLD);
+        m_sketch_banner_txt->SetFont(f);
+        auto* bs = new wxBoxSizer(wxHORIZONTAL);
+        bs->Add(m_sketch_banner_txt, 0, wxALIGN_CENTER_VERTICAL | wxALL, FromDIP(6));
+        m_sketch_banner->SetSizer(bs);
+    }
+    m_sketch_banner->Hide();
+    vcol->Add(m_sketch_banner, 0, wxEXPAND);
+    // The bottom 3D-navigator orb handles all view orientation, so no separate view buttons.
+    // Fit view is a double-click on the viewport (the tool intercepts it -> zoom_to_volumes).
+    vcol->Add(m_viewport, 1, wxEXPAND);
+
+    // Onshape layout: top toolbar over [ slim left column | center viewport ].
+    auto* body = new wxBoxSizer(wxHORIZONTAL);
+    body->Add(m_form, 0, wxEXPAND);
+    body->Add(vcol,   1, wxEXPAND);
+
+    auto* outer = new wxBoxSizer(wxVERTICAL);
+    outer->Add(m_toolbar, 0, wxEXPAND);
+    outer->Add(new wxStaticLine(this, wxID_ANY), 0, wxEXPAND);
+    outer->Add(body, 1, wxEXPAND);
+    SetSizer(outer);
+
+    // The atlas says a verb is wired; the registrations above say what it runs. Nothing checks
+    // that the two agree, and a broken join is INVISIBLE — the row renders, is enabled, and does
+    // nothing when picked. That defect has shipped three times (edit_feature and sk_move carrying
+    // action:null, then a whole flyout family the moment its widget stopped being built), and it
+    // cannot be seen by reading either side alone. Verify the join once, here, where every
+    // registration is complete. Cheap: 86 map lookups, once per panel.
+    {
+        std::vector<std::string> dead;
+        for (int i = 0; i < kOfferVerbCount; ++i) {
+            const OfferVerb& v = kOfferVerbs[i];
+            if (v.action == nullptr || *v.action == '\0')
+                continue;               // kernel support, no GUI path — the row shows disabled
+            const std::string a(v.action);
+            bool ok = false;
+            if (a.rfind("key:", 0) == 0) {   // resolved exactly as run_offer_action() resolves it
+                const std::string k = a.substr(4);
+                if (k.size() >= 3 && k[0] == 'S' && k[1] == '+') {
+                    auto it = m_keys_feature.find(int(k[2]) | SC_SHIFT);
+                    ok = it != m_keys_feature.end() && bool(it->second);
+                } else if (!k.empty()) {
+                    auto it = m_keys_sketch.find(int(k[0]));
+                    ok = it != m_keys_sketch.end() && bool(it->second);
+                }
+            } else {
+                auto it = m_verb_actions.find(a);
+                ok = it != m_verb_actions.end() && bool(it->second);
+            }
+            if (!ok)
+                dead.emplace_back(std::string(v.id) + " -> " + a);
+        }
+        for (const std::string& d : dead)
+            BOOST_LOG_TRIVIAL(error) << "Design offer: wired verb has no action: " << d;
+        assert(dead.empty());   // debug builds stop here; release ships the log line
+    }
+
+    set_ui_mode(UiMode::Feature);
+}
+
+void DesignPanel::set_active_tool_btn(ScalableButton* b)
+{
+    // Onshape-style: the active tool's button gets the Orca accent (teal); the
+    // rest revert to the ribbon surface. nullptr clears the whole strip.
+    m_active_tool_btn = b;
+    const wxColour bg = dp_ribbon_bg(), teal(0x00, 0x96, 0x88);
+    for (auto* btn : m_tool_btns) {
+        if (btn == nullptr) continue;
+        btn->SetBackgroundColour(btn == b ? teal : bg);
+        btn->Refresh();
+    }
+}
+
+// Paint the DoF line. Split out of the solve callback so entering Constrain can re-apply the
+// last known state — see m_dof_last.
+void DesignPanel::apply_dof_status(int dof, bool ok, bool has_constraints)
+{
+    if (!m_dof_status) return;
+    if (!has_constraints) {
+        m_dof_status->SetLabel(wxString());
+    } else if (!ok) {
+        m_dof_status->SetForegroundColour(wxColour(235, 80, 80));
+        m_dof_status->SetLabel(_L("✗ Conflicting constraints"));
+    } else if (dof == 0) {
+        m_dof_status->SetForegroundColour(wxColour(80, 200, 110));
+        m_dof_status->SetLabel(_L("✓ Fully constrained"));
+    } else if (dof > 0) {
+        m_dof_status->SetForegroundColour(dp_ctl_text());
+        m_dof_status->SetLabel(wxString::Format(_L("%d degrees of freedom"), dof));
+    } else {
+        m_dof_status->SetLabel(wxString());
+    }
+    m_dof_status->Show(!m_dof_status->GetLabel().IsEmpty());
+    m_dof_status->Refresh();
+    update_cards_frame(); m_form->Layout();
+}
+
+void DesignPanel::set_ui_mode(UiMode m)
+{
+    m_ui_mode = m;
+    if (m != UiMode::Sketch) m_sketch_on.clear();   // no stale "on the picked face" on the next hint
+    // The DoF readout describes a SKETCH's constraint state, so it means nothing back in Feature
+    // mode — where it nonetheless stayed on screen after every Confirm, Cancel and Escape
+    // (752). Cleared here rather than at those three exits because this is the one place
+    // all of them pass through, and a fourth exit added later would otherwise reintroduce it.
+    // Constrain mode keeps it: that is where the number is the whole point.
+    if (m == UiMode::Feature && m_dof_status != nullptr) {
+        m_dof_status->SetLabel(wxString());
+        m_dof_status->Show(false);
+    }
+    // Constrain is where the number is the whole point, and clearing it on the way out of
+    // Sketch left it blank on the way in — no solve fires merely because the mode changed.
+    if (m == UiMode::Constrain)
+        apply_dof_status(m_dof_last, m_dof_last_ok, m_dof_last_has);
+    wxSizer* s = m_toolbar->GetSizer();
+    s->Show(m_tb_feature,   m == UiMode::Feature,   true);
+    s->Show(m_tb_sketch,    m == UiMode::Sketch,    true);
+    // Constraint buttons are live in BOTH Sketch and Constrain (Fase 4.2 live path); the
+    // Confirm/Cancel action bar (m_tb_action) is already mode-appropriate and stays untouched.
+    s->Show(m_tb_relations, m == UiMode::Sketch || m == UiMode::Constrain, true);
+    m_toolbar->Layout();
+    m_toolbar->FitInside();   // refresh the horizontal scroll range for the new group widths
+    set_active_tool_btn(nullptr);   // no tool selected right after a mode switch
+    // Phase 3: the docked Sketch card (plane/orientation) shows for the whole Sketch
+    // session and hides on Finish/Constrain.
+    if (m_box_sketch_session != nullptr && m_form != nullptr && m_cards->GetSizer() != nullptr) {
+        if (m == UiMode::Sketch && m_hdr_sketch_session != nullptr)
+            m_hdr_sketch_session->SetLabel(wxString::Format(_L("Sketch %d"), m_feature_counter + 1));
+        m_cards->GetSizer()->Show(m_box_sketch_session, m == UiMode::Sketch, true);
+        update_cards_frame(); m_form->Layout();
+        m_form->FitInside();
+    }
+    // Constraint-manager card follows Constrain mode; rebuilt from the active feature.
+    if (m_box_constraints != nullptr && m_form != nullptr && m_cards->GetSizer() != nullptr) {
+        if (m == UiMode::Constrain || m == UiMode::Sketch)
+            rebuild_constraint_list();   // Sketch too: a live session has its own constraints
+        else
+            m_cards->GetSizer()->Show(m_box_constraints, false, true);
+        update_cards_frame(); m_form->Layout();
+        m_form->FitInside();
+    }
+    update_action_bar();   // Sketch/Constrain modes show the unified ✓/✗; Feature idle hides it
+    // The origin planes follow the mode: entering Sketch offers them even when a body exists,
+    // leaving it takes them back. Without this they would only refresh on the next tree
+    // rebuild, which is not an event that happens when you merely press Sketch.
+    update_reference_planes();
+
+    // Say where you are, in words, across the top of the viewport.
+    //
+    // THE BED IS NOT MUTED HERE, and it was: "a plate grid and a sketch grid are the same visual
+    // language" is true and still the wrong call, because there IS no sketch grid to replace it.
+    // Seen on the rig: pick XY, arm Line, and the viewport is an empty grey field — no bed, no
+    // grid, no origin, nothing to judge a length or a direction against. The plate grid was
+    // carrying the ground reference for the whole tab. The banner already says where you are;
+    // taking the floor away as well only made the sketch harder to draw. The Bed checkbox is the
+    // one thing that governs the bed, in every mode.
+    if (m_sketch_banner != nullptr) {
+        const bool sketching = (m == UiMode::Sketch);
+        if (sketching && m_sketch_banner_txt != nullptr)
+            m_sketch_banner_txt->SetLabel(
+                wxString::Format(_L("Editing: Sketch %d   ·   N = look normal to the plane   ·   "
+                                    "Finish or Cancel in the toolbar"),
+                                 m_feature_counter + 1));
+        m_sketch_banner->Show(sketching);
+        m_sketch_banner->GetParent()->Layout();
+    }
+}
+
+void DesignPanel::on_shape_changed()
+{
+    bool rect = (m_shape->GetSelection() == 0);
+    m_width->Enable(rect);
+    m_height->Enable(rect);
+    m_radius->Enable(!rect);
+}
+
+void DesignPanel::set_status_ok()
+{
+    set_status(wxString::Format(_L("OK — %zu triangles"),
+                                        m_doc.display_mesh.its.indices.size()));
+    if (m_viewport != nullptr) {
+        m_viewport->clear_move_gizmo();   // a recompute invalidates the gizmo's body centroid
+        rebuild_disp_meshes();            // apply per-body Move transforms to the display/pick meshes
+        // Point the solid-pick at the fresh body + TRANSFORMED pick mesh (stable address) + the
+        // per-body xform vector (for edge sampling). Resets the whole/face/edge selection, whose
+        // ids invalidate on every recompute. Null body is handled inside.
+        m_viewport->set_solid_pick(&m_doc.bodies, &m_disp_pick_mesh,
+                                   &m_doc.display_tri_face, &m_doc.display_tri_body,
+                                   &m_body_visible, &m_body_xform);
+        feed_bodies();
+    }
+    sync_sketch_display();
+}
+
+// Draw every committed sketch that no enabled Extrude consumes, so a sketch stays
+// visible (as a translucent face + outline) when it is not part of the solid — e.g.
+// after its Extrude is removed, or right after Finish.
+void DesignPanel::sync_sketch_display()
+{
+    if (m_viewport == nullptr) return;
+    const int n = int(m_doc.features.size());
+    std::vector<bool> consumed(n, false);
+    // Per-loop extrudes (sketch_ref < 0) carry a verbatim copy of the one loop they
+    // consumed; collect those so that loop is hidden from its source sketch overlay.
+    std::vector<std::vector<SketchEntity>> consumed_loops;
+    for (const CadFeature& f : m_doc.features) {
+        if (f.type != CadFeatureType::Extrude || !f.enabled) continue;
+        if (f.sketch_ref >= 0 && f.sketch_ref < n)        consumed[f.sketch_ref] = true;
+        else if (f.sketch_ref < 0 && !f.entities.empty()) consumed_loops.push_back(f.entities);
+    }
+    // Two loops match when their entities are the same geometry in the same order — the
+    // per-loop extrude stored a verbatim copy, so this is an exact comparison.
+    auto same_loop = [](const std::vector<SketchEntity>& a, const std::vector<SketchEntity>& b) {
+        if (a.size() != b.size() || a.empty()) return false;
+        auto eq = [](const Vec2d& u, const Vec2d& v) { return (u - v).squaredNorm() < 1e-10; };
+        for (size_t k = 0; k < a.size(); ++k) {
+            const SketchEntity& x = a[k]; const SketchEntity& y = b[k];
+            if (x.type != y.type || !eq(x.p0, y.p0) || !eq(x.p1, y.p1) ||
+                !eq(x.center, y.center) || std::abs(x.radius - y.radius) > 1e-7) return false;
+        }
+        return true;
+    };
+
+    std::vector<DesignSketchTool::DisplaySketch> ds;
+    for (int i = 0; i < n; ++i) {
+        const CadFeature& f = m_doc.features[i];
+        if (f.type != CadFeatureType::Sketch || consumed[i] || !f.enabled)
+            continue;
+        if (!f.entities.empty()) {
+            if (consumed_loops.empty()) {
+                ds.push_back({ f.entities, f.plane, i });
+            } else {
+                // Drop the entities of any loop already extruded; keep the rest (other
+                // loops + non-loop entities) so they stay visible and selectable.
+                std::vector<char> drop(f.entities.size(), 0);
+                for (const std::vector<int>& loop : m_viewport->region_entity_indices_with_holes(f.entities)) {
+                    std::vector<SketchEntity> es;
+                    for (int ei : loop)
+                        if (ei >= 0 && ei < int(f.entities.size())) es.push_back(f.entities[ei]);
+                    bool gone = false;
+                    for (const std::vector<SketchEntity>& c : consumed_loops)
+                        if (same_loop(es, c)) { gone = true; break; }
+                    if (gone)
+                        for (int ei : loop)
+                            if (ei >= 0 && ei < int(drop.size())) drop[ei] = 1;
+                }
+                std::vector<SketchEntity> shown;
+                for (int ei = 0; ei < int(f.entities.size()); ++ei)
+                    if (!drop[ei]) shown.push_back(f.entities[ei]);
+                if (!shown.empty()) ds.push_back({ std::move(shown), f.plane, i });
+            }
+        } else if (!f.imported_regions.empty()) {
+            // Imported art (Text/SVG) carries no solver entities; synthesize
+            // closed line loops from each region contour so it shows as an
+            // outline overlay (display only — never stored on the feature).
+            // Apply the feature's placement transform so the overlay tracks
+            // moves / scales.
+            const auto regions = transform_regions(f.imported_regions, f.import_offset,
+                                                    f.import_scale_x, f.import_scale_y);
+            std::vector<SketchEntity> lines;
+            for (const auto& region : regions)
+                for (const auto& contour : region) {
+                    const int m = int(contour.size());
+                    for (int k = 0; k < m; ++k) {
+                        SketchEntity e;
+                        e.type = SketchEntity::Type::Line;
+                        e.p0   = contour[k];
+                        e.p1   = contour[(k + 1) % m];
+                        lines.push_back(e);
+                    }
+                }
+            if (!lines.empty())
+                ds.push_back({ std::move(lines), f.plane, i });
+        }
+    }
+    m_viewport->set_display_sketches(std::move(ds));
+}
+
+void DesignPanel::on_add_text()
+{
+    wxTextEntryDialog dlg(this, _L("Text to insert:"), _L("Text"), wxEmptyString);
+    if (dlg.ShowModal() != wxID_OK)
+        return;
+    const wxString text = dlg.GetValue();
+    if (text.empty())
+        return;
+    const std::string utf8(text.ToUTF8().data());
+    // Insert at a default height; resize in-canvas via the bbox handles (Move/Scale).
+    add_imported_sketch(text_to_regions(utf8, 10.0), _L("Text"));
+}
+
+void DesignPanel::on_import_svg()
+{
+    wxFileDialog dlg(this, _L("Import SVG"), wxEmptyString, wxEmptyString,
+                     "SVG files (*.svg)|*.svg|All files|*.*",
+                     wxFD_OPEN | wxFD_FILE_MUST_EXIST);
+    if (dlg.ShowModal() != wxID_OK)
+        return;
+    const std::string path(dlg.GetPath().ToUTF8().data());
+    // Import at 1:1; resize in-canvas via the bbox handles (Move/Scale).
+    add_imported_sketch(svg_to_regions(path, 1.0), _L("SVG"));
+}
+
+// Run a long CAD computation off the UI thread. A big STEP costs tens of seconds in OCCT
+// (parse + tessellate); running it inline froze the whole window — the compositor marked the
+// app unresponsive and nothing repainted. The dialog is app-modal, so the document cannot be
+// touched while the worker owns it. Exceptions must not escape the worker: `work` is expected
+// to swallow them (OCCT throws Standard_Failure, which is not a std::exception).
+static void run_off_ui_thread(wxWindow* parent, const wxString& message, const std::function<void()>& work)
+{
+    std::atomic<bool> done{false};
+    std::thread worker([&work, &done]() {
+        work();
+        done.store(true, std::memory_order_release);
+    });
+
+    // Input stays blocked for the whole operation: the worker owns the document, so nothing
+    // in the UI may mutate it meanwhile. The dialog only appears if the work is actually slow —
+    // a fillet on a small body finishes in milliseconds and must not flash a dialog.
+    wxWindowDisabler disabler;
+    std::unique_ptr<wxProgressDialog> dlg;
+    int elapsed_ms = 0;
+    while (!done.load(std::memory_order_acquire)) {
+        if (dlg == nullptr && elapsed_ms >= 300)
+            dlg = std::make_unique<wxProgressDialog>(_L("Design"), message, 100, parent,
+                                                     wxPD_AUTO_HIDE | wxPD_SMOOTH);
+        if (dlg != nullptr)
+            dlg->Pulse();
+        wxYield();               // keep the window painting instead of going unresponsive
+        wxMilliSleep(30);
+        elapsed_ms += 30;
+    }
+    worker.join();
+}
+
+// Rebuild the document off the UI thread. Every feature op (fillet, cut, shell, boolean, ...)
+// goes through recompute(), and on a heavy imported solid that is seconds of OCCT work — inline
+// it freezes the window. OCCT throws Standard_Failure, which is not a std::exception and would
+// terminate the process if it escaped the worker, so both are caught here.
+// Keep the Model's copy of the recipe in step with the document.
+//
+// This used to be written in exactly ONE place — on_commit(), as a side effect of Commit to
+// Plate — so a user who modelled for an hour and pressed Ctrl+S saved a project containing no
+// feature history at all, and the app reported success (vjk5). The 3MF exporter was
+// never at fault: nothing had handed it a recipe.
+//
+// Every save path (Ctrl+S, Save As, autosave, crash recovery) reads model.cad_recipe, so
+// keeping it current after each document change is what makes all of them correct at once,
+// rather than teaching each one to ask the Design tab. Commit to Plate means "send this to the
+// slicer"; making saving depend on it was the bug, not the cure.
+//
+// Cost is a serialization per recompute — tens of KB against an OCCT rebuild that just ran.
+void DesignPanel::sync_recipe_to_model()
+{
+    Plater* plater = wxGetApp().plater();
+    if (plater == nullptr) return;
+    // An empty document CLEARS it, so a non-CAD project never carries a stale recipe.
+    std::string recipe = m_doc.features.empty() ? std::string() : m_doc.serialize_recipe();
+    if (recipe == plater->model().cad_recipe)
+        return;   // no change — this is the rehydrate of a project that was just opened
+    plater->model().cad_recipe = std::move(recipe);
+
+    // The plater's dirty flag rides its own undo/redo stack, which Design edits never touch, and
+    // a design that has not been committed to the plate has no ModelObjects either — so without
+    // this the project reads as clean: no autosave, and no "unsaved changes" prompt on quit.
+    // Same hook the auxiliary-files panel uses for project data that lives outside the model.
+    Slic3r::put_other_changes();
+}
+
+bool DesignPanel::recompute_guarded(const wxString& message)
+{
+    bool ok = false;
+    run_off_ui_thread(this, message, [this, &ok]() {
+        try {
+            ok = m_doc.recompute();
+        } catch (const Standard_Failure& e) {
+            const char* what = e.GetMessageString();
+            m_doc.error = (what != nullptr && *what != '\0') ? what : "OCCT failure";
+            ok = false;
+        } catch (const std::exception& e) {
+            m_doc.error = e.what();
+            ok = false;
+        }
+    });
+    // Only on success: a failed recompute leaves the document mid-edit, and persisting that
+    // would save a model the user never had.
+    if (ok) sync_recipe_to_model();
+    return ok;
+}
+
+void DesignPanel::on_import_step()
+{
+    wxFileDialog dlg(this, _L("Import STEP"), wxEmptyString, wxEmptyString,
+                     "STEP files (*.step;*.stp)|*.step;*.stp|All files|*.*",
+                     wxFD_OPEN | wxFD_FILE_MUST_EXIST);
+    if (dlg.ShowModal() != wxID_OK)
+        return;
+    const std::string path(dlg.GetPath().ToUTF8().data());
+    std::string err;
+    // Keep the OCCT B-rep (don't mesh it like the slicer importer): each top-level solid
+    // becomes a coexisting CadBody, fully editable by the on-face/edge feature tools.
+    std::vector<TopoDS_Shape> solids;
+    run_off_ui_thread(this, _L("Reading STEP…"), [&]() {
+        try {
+            solids = GeometryEngine::read_step_solids(path, err);
+        } catch (const Standard_Failure& e) {
+            const char* what = e.GetMessageString();
+            err = (what != nullptr && *what != '\0') ? what : "OCCT failure";
+        } catch (const std::exception& e) {
+            err = e.what();
+        }
+    });
+    if (solids.empty()) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(err.empty() ? _L("No solids found in STEP")
+                                       : (_L("STEP import failed: ") + wxString::FromUTF8(err)));
+        m_status->Refresh();
+        return;
+    }
+    m_doc.checkpoint();   // undo boundary: importing STEP solids
+    for (const TopoDS_Shape& s : solids) {
+        m_feature_counter++;
+        CadFeature f;
+        f.type           = CadFeatureType::Import;
+        f.name           = std::string("STEP") + std::to_string(m_feature_counter);
+        f.imported_solid = s;
+        f.mode           = BooleanMode::New;   // each solid is its own coexisting body
+        m_doc.features.push_back(f);
+    }
+    bool rebuilt = false;
+    run_off_ui_thread(this, _L("Rebuilding model…"), [&]() {
+        try {
+            rebuilt = m_doc.recompute();
+        } catch (const Standard_Failure& e) {
+            const char* what = e.GetMessageString();
+            m_doc.error = (what != nullptr && *what != '\0') ? what : "OCCT failure";
+        } catch (const std::exception& e) {
+            m_doc.error = e.what();
+        }
+    });
+    if (!rebuilt) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("STEP import failed: ") + wxString::FromUTF8(m_doc.error));
+        m_status->Refresh();
+        return;
+    }
+    set_ui_mode(UiMode::Feature);   // imported solids live in the feature timeline
+    refresh_tree();
+    set_tree_selection(int(m_doc.features.size()) - 1);
+    set_status_ok();                // canonical post-recompute viewport/pick/parts refresh
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(wxString::Format(
+        _L("Imported %d solid(s) — pick a face or edge, then Fillet / Cut / Shell to modify"),
+        int(solids.size())));
+    m_status->Refresh();
+}
+
+// Import a triangle mesh as a real B-rep body: the triangles are rebuilt into OCCT faces with
+// shared topology, then coplanar neighbours are merged so the result has pickable CAD faces
+// rather than one face per triangle. Lands in the same CadFeatureType::Import as a STEP, so
+// every downstream feature tool (fillet / cut / shell / face-extrude) works on it unchanged.
+void DesignPanel::on_import_mesh()
+{
+    wxFileDialog dlg(this, _L("Import mesh"), wxEmptyString, wxEmptyString,
+                     "Mesh files (*.stl;*.obj)|*.stl;*.obj|All files|*.*",
+                     wxFD_OPEN | wxFD_FILE_MUST_EXIST);
+    if (dlg.ShowModal() != wxID_OK)
+        return;
+    const std::string path(dlg.GetPath().ToUTF8().data());
+
+    auto fail = [this](const wxString& msg) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(msg);
+        m_status->Refresh();
+    };
+
+    // Load the triangles with the slicer's own readers — no new mesh dependency.
+    TriangleMesh mesh;
+    const std::string ext = boost::algorithm::to_lower_copy(
+        boost::filesystem::path(path).extension().string());
+    if (ext == ".stl") {
+        if (!mesh.ReadSTLFile(path.c_str())) { fail(_L("Could not read the STL file")); return; }
+    } else if (ext == ".obj") {
+        ObjInfo     obj_info;
+        std::string obj_err;
+        if (!load_obj(path.c_str(), &mesh, obj_info, obj_err)) {
+            fail(_L("Could not read the OBJ file: ") + wxString::FromUTF8(obj_err));
+            return;
+        }
+    } else {
+        fail(_L("Unsupported mesh format (STL and OBJ are supported)"));
+        return;
+    }
+    if (mesh.its.indices.empty()) { fail(_L("The mesh contains no triangles")); return; }
+
+    // One planar face per triangle before merging, so the cost is driven by the triangle count.
+    // A dense organic scan has few coplanar neighbours to merge away and stays heavy afterwards;
+    // warn rather than silently freezing the CAD kernel on every subsequent recompute.
+    if (mesh.its.indices.size() > MESH_IMPORT_TRIANGLE_WARN) {
+        const wxString q = wxString::Format(
+            _L("This mesh has %d triangles. Every triangle becomes a B-rep face before coplanar "
+               "merging, so importing it may take a long time and leave a body that is slow to "
+               "edit. Decimating the mesh first is usually better.\n\nImport anyway?"),
+            int(mesh.its.indices.size()));
+        if (wxMessageBox(q, _L("Large mesh"), wxYES_NO | wxICON_WARNING, this) != wxYES)
+            return;
+    }
+
+    wxBusyCursor busy;
+    GeometryEngine::MeshBrepStats stats;
+    TopoDS_Shape shape;
+    try {
+        shape = GeometryEngine::mesh_to_brep(mesh.its, MESH_IMPORT_TOLERANCE,
+                                             MESH_IMPORT_MERGE_ANGLE_DEG, stats);
+    } catch (const std::exception& e) {
+        fail(_L("Mesh conversion failed: ") + wxString::FromUTF8(e.what()));
+        return;
+    } catch (const Standard_Failure& e) {   // OCCT throws outside std::exception
+        fail(_L("Mesh conversion failed: ") + wxString::FromUTF8(
+                 e.GetMessageString() ? e.GetMessageString() : "OCCT error"));
+        return;
+    }
+    if (shape.IsNull()) { fail(_L("Mesh conversion produced no geometry")); return; }
+
+    m_doc.checkpoint();   // undo boundary: importing a mesh as a B-rep body
+    m_feature_counter++;
+    CadFeature f;
+    f.type           = CadFeatureType::Import;
+    f.name           = std::string("Mesh") + std::to_string(m_feature_counter);
+    f.imported_solid = shape;
+    f.mode           = BooleanMode::New;   // its own coexisting body, like a STEP solid
+    m_doc.features.push_back(f);
+
+    if (!recompute_guarded(_L("Rebuilding model…"))) {
+        fail(_L("Mesh import failed: ") + wxString::FromUTF8(m_doc.error));
+        return;
+    }
+    set_ui_mode(UiMode::Feature);
+    refresh_tree();
+    set_tree_selection(int(m_doc.features.size()) - 1);
+    set_status_ok();
+
+    // Report what the mesh actually was, never dress an open shell up as a solid: if it is not
+    // watertight, say so and say why (boundary vs non-manifold edges) — that is a defect in the
+    // source mesh the user needs to know about before they start cutting features into it.
+    if (stats.is_solid) {
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(wxString::Format(
+            _L("Imported solid — %d triangles → %d faces, volume %.2f mm³. Pick a face or edge, "
+               "then Fillet / Cut / Shell to modify"),
+            stats.kept_tris, stats.faces_final, stats.volume));
+    } else {
+        m_status->SetForegroundColour(wxColour(220, 160, 60));   // warning, not an error
+        set_status(wxString::Format(
+            _L("Imported as an open shell (not watertight): %d boundary edge(s), %d non-manifold "
+               "edge(s) — %d triangles → %d faces. The source mesh has holes or duplicated "
+               "geometry; boolean features may fail on it"),
+            stats.boundary_edges, stats.nonmanifold_edges, stats.kept_tris, stats.faces_final));
+    }
+    m_status->Refresh();
+}
+
+void DesignPanel::add_imported_sketch(
+    const std::vector<std::vector<std::vector<Vec2d>>>& regions,
+    const wxString& base_name)
+{
+    if (regions.empty()) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("No importable geometry found"));
+        m_status->Refresh();
+        return;
+    }
+    // DRAWING, not importing: if a sketch is open, the art belongs IN it. The outlines become
+    // ordinary line entities, so they can be constrained, trimmed and extruded with everything
+    // else on that plane. Committing a separate Sketch feature while the user is mid-sketch put
+    // the text on its own plane-origin feature and left the sketch they were drawing untouched.
+    if (m_viewport && m_viewport->is_sketching() && m_viewport->add_sketch_regions(regions)) {
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(wxString::Format(_L("%s added to the sketch — Confirm to commit it"),
+                                            base_name));
+        m_status->Refresh();
+        return;
+    }
+    m_doc.checkpoint();   // undo boundary: importing Text/SVG art
+    m_feature_counter++;
+    CadFeature f;
+    f.type            = CadFeatureType::Sketch;
+    f.name            = std::string(base_name.ToUTF8().data()) + std::to_string(m_feature_counter);
+    f.imported_regions = regions;
+
+    // #4: when a solid face is selected, drop the art ON that face, centred on it (ready to
+    // engrave). Otherwise place it on the draw-plane dropdown at the plane origin (legacy).
+    bool on_face = false;
+    if (m_sel_solid_face >= 0 && m_sel_solid_body >= 0 && m_sel_solid_body < int(m_doc.bodies.size())) {
+        const TopoDS_Face face =
+            GeometryEngine::face_by_index(m_doc.bodies[m_sel_solid_body].shape, m_sel_solid_face);
+        if (!face.IsNull()) {
+            f.plane = SketchPlane::from_face(face);
+            const Vec3d cw   = GeometryEngine::face_centroid_world(face);
+            const Vec2d c_uv = f.plane.project(cw, f.plane.normal);   // face centre in plane (u,v)
+            Vec2d lo(1e30, 1e30), hi(-1e30, -1e30);                   // bbox of the imported art
+            for (const auto& reg : regions)
+                for (const auto& loop : reg)
+                    for (const Vec2d& p : loop) { lo = lo.cwiseMin(p); hi = hi.cwiseMax(p); }
+            f.import_offset    = c_uv - 0.5 * (lo + hi);              // centre the art on the face
+            f.import_on_face   = true;
+            f.import_face_body = m_sel_solid_body;
+            on_face = true;
+        }
+    }
+    if (!on_face) {
+        f.plane = plane_from_choice(m_ref_plane);
+    }
+
+    // Drop the live face selection (its body is now remembered on import_face_body): otherwise
+    // the next Extrude would push/pull that face instead of extruding the placed art.
+    m_sel_solid_face = m_sel_solid_edge = m_sel_solid_body = -1;
+
+    m_doc.features.push_back(f);
+    m_doc.recompute();   // a lone sketch yields an empty body; that is expected
+    refresh_tree();
+    const int newidx = int(m_doc.features.size()) - 1;
+    set_tree_selection(newidx);   // select the new art
+    sync_sketch_display();
+    on_transform_imported(newidx);   // in-canvas place/size gizmo ON
+    // The feature is provisional until the user explicitly Confirms (Onshape gate). The
+    // Insert card carries Confirm/Cancel; Cancel undoes this insert.
+    m_insert_feat = newidx;
+    open_insert_card(base_name);
+}
+
+// Show the Insert Confirm/Cancel card while the imported art is being placed/sized.
+void DesignPanel::open_insert_card(const wxString& base_name)
+{
+    m_active = Tool::Insert;
+    if (m_hdr_insert) m_hdr_insert->SetLabel(base_name);
+    wxSizer* s = m_cards->GetSizer();
+    s->Show(m_box_insert, true, true);
+    update_cards_frame(); m_form->Layout();
+    m_form->FitInside();
+    update_action_bar();   // surface the unified ✓/✗
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(base_name + _L(" — drag to place/size, then Confirm"));
+    m_status->Refresh();
+}
+
+// Confirm: keep the placed art and leave the placement gizmo. The feature is already in
+// the timeline (added provisionally); we just tear down the transient tool/gizmo state.
+void DesignPanel::finalize_insert()
+{
+    const int feat = m_insert_feat;
+    m_insert_feat = -1;
+    if (m_viewport) m_viewport->cancel_sketch();   // exit the TransformArt gizmo
+    close_tool();                                  // hides the Insert card, clears m_active
+    set_ui_mode(UiMode::Feature);                  // imported art lives in the feature timeline
+    if (feat >= 0 && feat < int(m_doc.features.size())) set_tree_selection(feat);
+    sync_sketch_display();
+    refresh_tree();
+    set_status_ok();
+}
+
+// Cancel: discard the provisional insert (undo restores the pre-insert feature list).
+void DesignPanel::cancel_insert()
+{
+    m_insert_feat = -1;
+    if (m_viewport) m_viewport->cancel_sketch();   // exit the TransformArt gizmo
+    m_doc.undo();                                  // remove the just-added imported feature
+    close_tool();
+    set_ui_mode(UiMode::Feature);
+    sync_sketch_display();
+    refresh_tree();
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(_L("Insert cancelled"));
+    m_status->Refresh();
+}
+
+void DesignPanel::on_transform_imported(int feat_idx)
+{
+    if (feat_idx < 0 || feat_idx >= int(m_doc.features.size()) || !m_viewport)
+        return;
+    const CadFeature& f = m_doc.features[feat_idx];
+    if (f.imported_regions.empty())
+        return;
+    // In-canvas bbox handles (replaces the Move/Scale dialog): drag a corner to scale,
+    // the centre to move. Values stream back via set_on_imported_transform.
+    m_viewport->begin_imported_transform(feat_idx, f.imported_regions, f.plane,
+                                         f.import_offset, f.import_scale_x, f.import_scale_y);
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(_L("Drag a corner to scale, the centre to move — right-click when done"));
+    m_status->Refresh();
+}
+
+void DesignPanel::on_add_sketch()
+{
+    SketchShape shape = (m_shape->GetSelection() == 1) ? SketchShape::Circle
+                                                        : SketchShape::Rectangle;
+    wxString where;                                            // named for the status line
+    SketchPlane plane = sketch_plane_from_selection(where);    // picked face, else the 3D plane click
+    m_feature_counter++;
+    m_doc.add_sketch(shape, plane, m_width->GetValue(), m_height->GetValue(),
+                     m_radius->GetValue(), "Sketch" + std::to_string(m_feature_counter));
+    m_doc.recompute();  // a lone sketch yields an empty body; that is expected
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(wxString::Format(_L("Sketch added on %s — select it, then right-click to Extrude"), where));
+    refresh_tree();
+}
+
+// Extrude should consume only the clicked loop when a specific region of the resolved
+// sketch is selected and that loop actually has entities.
+bool DesignPanel::extrude_uses_loop() const
+{
+    return m_viewport != nullptr
+        && m_sel_sketch_region >= 0
+        && m_extrude_sketch_ref >= 0
+        && m_extrude_sketch_ref == m_sel_sketch_feat
+        && m_extrude_sketch_ref < int(m_doc.features.size())
+        && !m_viewport->selected_loop_entities().empty();
+}
+
+void DesignPanel::on_add_extrude()
+{
+    BooleanMode mode = static_cast<BooleanMode>(m_mode->GetSelection());  // New/Add/Cut/Intersect
+    m_feature_counter++;
+    const std::string name = "Extrude" + std::to_string(m_feature_counter);
+    int idx = -1;
+    if (m_extrude_face_src >= 0) {
+        // Onshape face-extrude: the picked solid face is the profile (no sketch wire).
+        idx = m_doc.add_extrude_face(m_extrude_face_src, m_distance->GetValue(), false, mode, name);
+        m_extrude_face_src = -1;          // consume the face-profile selection
+    } else if (extrude_uses_loop()) {
+        // Extrude just the selected loop (its entity subset), leaving the source sketch's
+        // other loops intact and still selectable.
+        if (::getenv("ORCA_CAD_PICK_TRACE"))
+            std::fprintf(stderr, "[pick] on_add_extrude: feat=%d reg=%d ents=%zu\n",
+                         m_extrude_sketch_ref, m_sel_sketch_region,
+                         m_viewport->selected_loop_entities().size());
+        idx = m_doc.add_extrude_entities(m_viewport->selected_loop_entities(),
+                                         m_doc.features[m_extrude_sketch_ref].plane,
+                                         m_distance->GetValue(), false, mode, name);
+        m_sel_sketch_region = -1;        // consume the loop selection
+        m_viewport->clear_loop_pick();   // drop the now-stale loop highlight
+    } else {
+        idx = m_doc.add_extrude(m_extrude_sketch_ref, m_distance->GetValue(), false, mode, name);
+    }
+    // Carry the Onshape end-condition / taper / flip / up-to-face onto the new feature so the
+    // committed solid matches the preview (build_candidate sets the same fields).
+    if (idx >= 0 && idx < int(m_doc.features.size())) {
+        CadFeature& f = m_doc.features[idx];
+        f.extrude_end = static_cast<ExtrudeEnd>(m_extrude_end->GetSelection());
+        f.distance2   = m_distance2->GetValue();
+        f.taper_deg   = m_taper->GetValue();
+        f.flip        = m_flip->GetValue();
+        f.up_to_face  = (f.extrude_end == ExtrudeEnd::UpToFace) ? m_sel_solid_face : -1;
+        f.target_body = m_sel_solid_body;   // multi-body: act on the picked body (-1 = last)
+        // On-face Text/SVG remembers its host body even after the face pick was cleared by
+        // the placement recompute, so the engraving Cut hits the right solid.
+        if (m_extrude_sketch_ref >= 0 && m_extrude_sketch_ref < int(m_doc.features.size())
+            && m_doc.features[m_extrude_sketch_ref].import_on_face)
+            f.target_body = m_doc.features[m_extrude_sketch_ref].import_face_body;
+    }
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_dressup()
+{
+    if (m_doc.body.IsNull()) {
+        set_status(_L("Add a solid (sketch + extrude) first"));
+        return;
+    }
+    FaceGroup fg = static_cast<FaceGroup>(m_face_group->GetSelection()); // Top=0..All=3
+    double    sz = m_dressup_size->GetValue();
+    bool      fillet = (m_dressup_type->GetSelection() == 0);
+
+    m_feature_counter++;
+    // A click-selected solid edge targets THAT edge; otherwise dress the whole face-group.
+    int didx = -1;
+    if (m_sel_solid_edge >= 0) {
+        if (fillet)
+            didx = m_doc.add_fillet(sz, m_sel_solid_edge, "Fillet" + std::to_string(m_feature_counter));
+        else
+            didx = m_doc.add_chamfer(sz, m_sel_solid_edge, "Chamfer" + std::to_string(m_feature_counter));
+    } else if (fillet)
+        didx = m_doc.add_fillet(sz, fg, "Fillet" + std::to_string(m_feature_counter));
+    else
+        didx = m_doc.add_chamfer(sz, fg, "Chamfer" + std::to_string(m_feature_counter));
+    // Dress the picked body (its face/edge ids are body-local). -1 = last body.
+    if (didx >= 0 && didx < int(m_doc.features.size()))
+        m_doc.features[didx].target_body = m_sel_solid_body;
+
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+
+    refresh_tree();
+}
+
+// Hole and Thread LATCH the geometry they were opened or picked on; Thicken / Shell / Draft read
+// the live selection instead. Both models are right for what they are — a placement tool with its
+// own plane state, versus an operation whose operand IS the selected face — and the latch is the
+// kinder of the two now that a click on empty canvas clears the selection (od0): a stray
+// click costs a Thicken pick, and costs a Hole nothing. What was missing is that nothing in the
+// Hole/Thread card NAMED the latched face, so after such a click the only words on screen were
+// the viewport's "Nothing selected" — over a ghost still drawn on the face Confirm would drill.
+// That reads as a contradiction and was filed as one (200). The card now says what it
+// holds, the way the other three cards already do. Pass -1 for "none, using the plane dropdown".
+void DesignPanel::set_hole_target_label(int face)
+{
+    if (m_hole_target_label)
+        m_hole_target_label->SetLabel(face >= 0 ? wxString::Format(_L("Face %d"), face)
+                                                : _L("(none — uses Hole plane)"));
+}
+
+// Thread also latches onto a circular EDGE (a cylinder's rim), so it has two kinds to name.
+void DesignPanel::set_thread_target_label(int face, int edge)
+{
+    if (!m_thread_target_label) return;
+    m_thread_target_label->SetLabel(
+        face >= 0 ? wxString::Format(_L("Face %d"), face)
+      : edge >= 0 ? wxString::Format(_L("Edge %d"), edge)
+                  : _L("(none — uses Thread plane)"));
+}
+
+SketchPlane DesignPanel::hole_plane() const
+{
+    if (m_hole_on_face) return m_hole_face_plane;
+    SketchPlane p = plane_from_index(m_hole_plane->GetSelection());
+    p.origin += m_doc.modeling_origin;
+    return p;
+}
+
+void DesignPanel::on_add_hole()
+{
+    if (m_doc.body.IsNull()) {
+        set_status(_L("Add a solid (sketch + extrude) first"));
+        return;
+    }
+    SketchPlane plane   = hole_plane();
+    double      dia     = m_hole_diameter->GetValue();
+    double      depth   = m_hole_depth->GetValue();
+    bool        through = m_hole_through->GetValue();
+    double      px      = m_hole_x->GetValue();
+    double      py      = m_hole_y->GetValue();
+
+    m_feature_counter++;
+    const int hidx = m_doc.add_hole(dia, depth, through, px, py, plane,
+                                    "Hole" + std::to_string(m_feature_counter));
+    // On-face holes drill the body the face belongs to (even after the pick was cleared).
+    if (m_hole_on_face && hidx >= 0 && hidx < int(m_doc.features.size()))
+        m_doc.features[hidx].target_body = m_hole_face_body;
+
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+
+    refresh_tree();
+}
+
+SketchPlane DesignPanel::thread_plane() const
+{
+    if (m_thread_on_face) return m_thread_face_plane;
+    SketchPlane p = plane_from_index(m_thread_plane->GetSelection());
+    p.origin += m_doc.modeling_origin;
+    return p;
+}
+
+void DesignPanel::apply_thread_standard()
+{
+    if (!m_thread_std) return;
+    const int sel = m_thread_std->GetSelection();
+    if (sel <= 0) return;   // 0 = "Custom" → leave the manual spins untouched
+
+    const ThreadSpec* s = find_thread_standard(
+        m_thread_std->GetString(sel).utf8_string());
+    if (!s) return;
+
+    // Pitch and depth are the defining "measures" of the standard — always apply.
+    if (m_thread_pitch) m_thread_pitch->SetValue(s->pitch_mm);
+    if (m_thread_depth) m_thread_depth->SetValue(s->thread_depth_mm());
+
+    // Nominal diameter: external rod = major diameter; internal tapped bore = minor (tap-drill)
+    // diameter. On a picked cylindrical surface/edge the diameter comes from the real geometry,
+    // so don't override it there. (The field holds DIAMETER.)
+    if (!m_thread_on_face && m_thread_radius) {
+        const bool internal = m_thread_internal && m_thread_internal->GetValue();
+        const double d = internal ? s->minor_diameter_mm() : s->major_diameter_mm;
+        m_thread_radius->SetValue(d);
+    }
+
+    if (m_status)
+        set_status(wxString::Format(_L("Thread standard: %s  (pitch %.3g mm)"),
+                                            m_thread_std->GetString(sel), s->pitch_mm));
+}
+
+void DesignPanel::infer_thread_spec(double diameter)
+{
+    // Snap to the nearest standard thread by nominal (major) diameter, so picking a Ø9.9 boss
+    // gives M10 — the M diameter, pitch AND depth all follow from the cylinder's base diameter.
+    const auto& stds = thread_standards();
+    int best = -1; double bestErr = 1e30;
+    for (int i = 0; i < int(stds.size()); ++i) {
+        const double e = std::abs(stds[i].major_diameter_mm - diameter);
+        if (e < bestErr) { bestErr = e; best = i; }
+    }
+    if (best < 0) { if (m_thread_radius) m_thread_radius->SetValue(diameter); return; }
+    const ThreadSpec& s = stds[best];
+    if (m_thread_std)    m_thread_std->SetSelection(best + 1);    // row 0 is "Custom"
+    if (m_thread_radius) m_thread_radius->SetValue(s.major_diameter_mm);  // field = DIAMETER
+    if (m_thread_pitch)  m_thread_pitch->SetValue(s.pitch_mm);
+    if (m_thread_depth)  m_thread_depth->SetValue(s.thread_depth_mm());
+}
+
+void DesignPanel::on_add_thread()
+{
+    bool internal = m_thread_internal->GetValue();
+    if (internal && m_doc.body.IsNull()) {
+        set_status(_L("Thread needs a solid body — add or import one first"));
+        return;
+    }
+    SketchPlane plane = thread_plane();
+
+    m_feature_counter++;
+    const int tidx = m_doc.add_thread(m_thread_radius->GetValue() * 0.5, m_thread_pitch->GetValue(),
+                     m_thread_height->GetValue(), m_thread_depth->GetValue(),
+                     internal, m_thread_x->GetValue(), m_thread_y->GetValue(),
+                     plane, "Thread" + std::to_string(m_feature_counter));
+    // On-surface internal thread taps the body the cylindrical face belongs to.
+    if (m_thread_on_face && tidx >= 0 && tidx < int(m_doc.features.size()))
+        m_doc.features[tidx].target_body = m_thread_face_body;
+
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+
+    refresh_tree();
+}
+
+void DesignPanel::on_add_revolve()
+{
+    if (m_revolve_sketch_ref < 0 || m_revolve_sketch_ref >= int(m_doc.features.size())) {
+        set_status(_L("Pick a sketch profile to revolve first"));
+        return;
+    }
+    const BooleanMode mode = static_cast<BooleanMode>(m_revolve_mode->GetSelection());
+    if (mode != BooleanMode::New && m_doc.body.IsNull()) {
+        set_status(_L("Revolve needs a solid body — add or import one first"));
+        return;
+    }
+    m_feature_counter++;
+    m_doc.add_revolve(m_revolve_sketch_ref, m_revolve_angle->GetValue(),
+                      m_revolve_axis->GetSelection(), m_revolve_flip->GetValue(),
+                      mode, "Revolve" + std::to_string(m_feature_counter));
+
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+
+    refresh_tree();
+}
+
+void DesignPanel::on_add_sweep()
+{
+    if (m_sweep_profile_ref < 0 || m_sweep_profile_ref >= int(m_doc.features.size())) {
+        set_status(_L("Pick a profile sketch to sweep first"));
+        return;
+    }
+    const int sel = m_sweep_path->GetSelection();
+    const int path_ref = (sel != wxNOT_FOUND)
+        ? int(reinterpret_cast<intptr_t>(m_sweep_path->GetClientData(sel))) : -1;
+    if (path_ref < 0) {
+        set_status(_L("Pick a path sketch for the sweep"));
+        return;
+    }
+    const BooleanMode mode = static_cast<BooleanMode>(m_sweep_mode->GetSelection());
+    if (mode != BooleanMode::New && m_doc.body.IsNull()) {
+        set_status(_L("Sweep needs a solid body — add or import one first"));
+        return;
+    }
+    m_feature_counter++;
+    m_doc.add_sweep(m_sweep_profile_ref, path_ref, mode,
+                    "Sweep" + std::to_string(m_feature_counter));
+
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+
+    refresh_tree();
+}
+
+void DesignPanel::on_add_loft()
+{
+    // Collect the checked profile sketches in list (recipe) order.
+    std::vector<int> refs;
+    for (unsigned i = 0; i < m_loft_list->GetCount(); ++i)
+        if (m_loft_list->IsChecked(i) && i < m_loft_sketch_idx.size())
+            refs.push_back(m_loft_sketch_idx[i]);
+    if (refs.size() < 2) {
+        set_status(_L("Check at least two profile sketches to loft"));
+        return;
+    }
+    const BooleanMode mode = static_cast<BooleanMode>(m_loft_mode->GetSelection());
+    if (mode != BooleanMode::New && m_doc.body.IsNull()) {
+        set_status(_L("Loft needs a solid body — add or import one first"));
+        return;
+    }
+    m_feature_counter++;
+    m_doc.add_loft(refs, m_loft_ruled->GetValue(), mode,
+                   "Loft" + std::to_string(m_feature_counter));
+
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+
+    refresh_tree();
+}
+
+void DesignPanel::on_add_surface_extrude()
+{
+    if (m_surf_extrude_sketch_ref < 0 || m_surf_extrude_sketch_ref >= int(m_doc.features.size())) {
+        set_status(_L("Pick a sketch profile to extrude first"));
+        return;
+    }
+    m_feature_counter++;
+    m_doc.add_surface_extrude(m_surf_extrude_sketch_ref, m_surf_extrude_distance->GetValue(),
+                              "SurfaceExtrude" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_surface_revolve()
+{
+    if (m_surf_revolve_sketch_ref < 0 || m_surf_revolve_sketch_ref >= int(m_doc.features.size())) {
+        set_status(_L("Pick a sketch profile to revolve first"));
+        return;
+    }
+    m_feature_counter++;
+    m_doc.add_surface_revolve(m_surf_revolve_sketch_ref, m_surf_revolve_angle->GetValue(),
+                              m_surf_revolve_axis->GetSelection(),
+                              "SurfaceRevolve" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_surface_loft()
+{
+    std::vector<int> refs;
+    for (unsigned i = 0; i < m_surf_loft_list->GetCount(); ++i)
+        if (m_surf_loft_list->IsChecked(i) && i < m_surf_loft_sketch_idx.size())
+            refs.push_back(m_surf_loft_sketch_idx[i]);
+    if (refs.size() < 2) {
+        set_status(_L("Check at least two profile sketches to loft"));
+        return;
+    }
+    m_feature_counter++;
+    m_doc.add_surface_loft(refs, m_surf_loft_ruled->GetValue(),
+                           "SurfaceLoft" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_surface_fill()
+{
+    if (m_surf_fill_sketch_ref < 0 || m_surf_fill_sketch_ref >= int(m_doc.features.size())) {
+        set_status(_L("Pick a sketch to fill first"));
+        return;
+    }
+    m_feature_counter++;
+    m_doc.add_surface_fill(m_surf_fill_sketch_ref,
+                           "SurfaceFill" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_surface_offset()
+{
+    const int sel = sheet_choice_body(m_surf_offset_body);
+    if (sel < 0 || sel >= int(m_doc.bodies.size())) {
+        set_status(_L("Select a sheet body first"));
+        return;
+    }
+    m_feature_counter++;
+    m_doc.add_surface_offset(sel, m_surf_offset_distance->GetValue(),
+                             "SurfaceOffset" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_thicken_surface()
+{
+    const int sel = sheet_choice_body(m_surf_thicken_body);
+    if (sel < 0 || sel >= int(m_doc.bodies.size())) {
+        set_status(_L("Select a sheet body first"));
+        return;
+    }
+    m_feature_counter++;
+    m_doc.add_thicken_surface(sel, m_surf_thicken_thickness->GetValue(),
+                              m_surf_thicken_flip->GetValue(),
+                              "ThickenSurface" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+// Compose the same matrix apply_transform() builds in the kernel: rotate about the pivot first,
+// then translate. Kept here so the preview and the committed feature can never disagree.
+static Transform3d xf_compose(const Vec3d& t, const Vec3d& axis, const Vec3d& pivot, double deg)
+{
+    Transform3d r = Transform3d::Identity();
+    if (std::abs(deg) > 1e-12 && axis.norm() > 1e-9)
+        r = Transform3d(Eigen::Translation3d(pivot))
+          * Transform3d(Eigen::AngleAxisd(deg * M_PI / 180.0, axis.normalized()))
+          * Transform3d(Eigen::Translation3d(-pivot));
+    return Transform3d(Eigen::Translation3d(t)) * r;
+}
+
+// Live preview for the Transform card. The gizmo already writes its drag into the body's display
+// transform; the typed fields must use the SAME channel or the numbers and the geometry disagree
+// until Confirm — which is what makes typing a distance look like it did nothing. In edit mode the
+// committed transform is already baked into the kernel geometry, so undo it first: without that,
+// typing 80 over a committed 34 would show the body at 114.
+void DesignPanel::xf_live_preview()
+{
+    if (m_active != Tool::Transform || m_xf_dx == nullptr) return;
+    if (m_xf_copy && m_xf_copy->GetValue()) return;   // a copy leaves the original where it is
+    sync_body_xform();
+    const int sel = m_xf_body ? m_xf_body->GetSelection() : wxNOT_FOUND;
+    const int b   = (sel != wxNOT_FOUND) ? sel : int(m_body_xform.size()) - 1;
+    if (b < 0 || b >= int(m_body_xform.size())) return;
+
+    if (m_xf_prev_body != b) {
+        xf_clear_preview();                 // the card retargeted: hand the old body back first
+        m_xf_prev_body = b;
+        m_xf_prev_base = (b == m_xf_gizmo_body) ? m_xf_gizmo_base : m_body_xform[b];
+    }
+    const int   ax   = m_xf_axis->GetSelection();
+    const Vec3d axis = (ax == 0) ? Vec3d::UnitX() : (ax == 1) ? Vec3d::UnitY() : Vec3d::UnitZ();
+    const Vec3d pivot(m_xf_pivot_x->GetValue(), m_xf_pivot_y->GetValue(), m_xf_pivot_z->GetValue());
+    const Transform3d want = xf_compose(Vec3d(m_xf_dx->GetValue(), m_xf_dy->GetValue(),
+                                              m_xf_dz->GetValue()),
+                                        axis, pivot, m_xf_angle->GetValue());
+    Transform3d undo = Transform3d::Identity();
+    if (m_edit_index >= 0 && m_edit_index < int(m_doc.features.size())) {
+        const CadFeature& f = m_doc.features[m_edit_index];
+        if (f.type == CadFeatureType::Transform && !f.xf_copy)
+            undo = xf_compose(f.xf_translate, f.xf_axis, f.xf_pivot, f.xf_angle_deg).inverse();
+    }
+    m_body_xform[b] = want * undo * m_xf_prev_base;
+    feed_bodies();
+}
+
+// Hand a previewed body back to the pose it had before the card touched it. Every exit from the
+// Transform card passes through here, so a preview can never survive into the committed document.
+void DesignPanel::xf_clear_preview()
+{
+    if (m_xf_prev_body < 0) return;
+    sync_body_xform();
+    if (m_xf_prev_body < int(m_body_xform.size()))
+        m_body_xform[m_xf_prev_body] = m_xf_prev_base;
+    m_xf_prev_body = -1;
+    feed_bodies();
+}
+
+void DesignPanel::on_add_transform()
+{
+    xf_clear_preview();   // the feature performs this motion parametrically; the preview must go
+    // The gizmo baked its drag into the display transform so the body followed the cursor.
+    // The feature about to be created performs that same motion parametrically, so hand the
+    // body back to its pre-drag pose first or it moves twice.
+    if (m_xf_gizmo_body >= 0) {
+        sync_body_xform();
+        if (m_xf_gizmo_body < int(m_body_xform.size()))
+            m_body_xform[m_xf_gizmo_body] = m_xf_gizmo_base;
+        if (m_viewport) m_viewport->clear_move_gizmo();
+        feed_bodies();   // set_status_ok() re-feeds on success, but the recompute-ERROR path
+                         // below does not — without this the body would keep showing the
+                         // dragged pose after a Transform that failed to build.
+        m_xf_gizmo_body = -1;
+        m_move_body     = -1;
+    }
+    if (m_doc.bodies.empty()) {
+        set_status(_L("Transform needs a body — add or import one first"));
+        return;
+    }
+    const int sel = m_xf_body->GetSelection();
+    const int target = (sel != wxNOT_FOUND) ? sel : -1;
+    const Vec3d trans(m_xf_dx->GetValue(), m_xf_dy->GetValue(), m_xf_dz->GetValue());
+    const int ax = m_xf_axis->GetSelection();
+    const Vec3d axis = (ax == 0) ? Vec3d(1, 0, 0) : (ax == 1) ? Vec3d(0, 1, 0) : Vec3d(0, 0, 1);
+    const Vec3d pivot(m_xf_pivot_x->GetValue(), m_xf_pivot_y->GetValue(), m_xf_pivot_z->GetValue());
+    m_feature_counter++;
+    m_doc.add_transform(target, trans, axis, pivot, m_xf_angle->GetValue(), m_xf_copy->GetValue(),
+                        "Transform" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_mirror()
+{
+    if (m_doc.bodies.empty()) {
+        set_status(_L("Mirror needs a body — add or import one first"));
+        return;
+    }
+    const int sel = m_mirror_body->GetSelection();
+    const int target = (sel != wxNOT_FOUND) ? sel : -1;
+    const BooleanMode mode = m_mirror_keep->GetValue() ? BooleanMode::New : BooleanMode::Add;
+    m_feature_counter++;
+    m_doc.add_mirror(plane_from_choice(m_mirror_plane->GetSelection()), target, mode,
+                     "Mirror" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_thicken()
+{
+    if (m_doc.bodies.empty()) {
+        set_status(_L("Thicken needs a solid body — add or import one first"));
+        return;
+    }
+    if (m_sel_solid_face < 0) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Pick a solid face to thicken first"));
+        m_status->Refresh();
+        return;
+    }
+    const int sel = m_thicken_body->GetSelection();
+    const int target = (sel != wxNOT_FOUND) ? sel : -1;
+    m_feature_counter++;
+    m_doc.add_thicken(target, m_sel_solid_face, m_thicken_thickness->GetValue(),
+                      m_thicken_flip->GetValue(), "Thicken" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_rib()
+{
+    if (m_doc.bodies.empty()) {
+        set_status(_L("Rib needs a solid body — add or import one first"));
+        return;
+    }
+    const int bsel = m_rib_body->GetSelection();
+    const int target = (bsel != wxNOT_FOUND) ? bsel : -1;
+    const int ssel = m_rib_sketch->GetSelection();
+    const int sketch_ref = (ssel != wxNOT_FOUND)
+                               ? int(reinterpret_cast<intptr_t>(m_rib_sketch->GetClientData(ssel))) : -1;
+    if (sketch_ref < 0) {
+        set_status(_L("Pick a sketch with an open line first"));
+        return;
+    }
+    m_feature_counter++;
+    m_doc.add_rib(sketch_ref, m_rib_entity->GetValue(), m_rib_thickness->GetValue(),
+                  m_rib_depth->GetValue(), target, "Rib" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_project()
+{
+    if (m_doc.bodies.empty()) {
+        set_status(_L("Project needs a body — add or import one first"));
+        return;
+    }
+    const int sel = m_proj_source_body->GetSelection();
+    const int src_body = (sel != wxNOT_FOUND) ? sel : -1;
+    const int face = (m_sel_solid_face >= 0) ? m_sel_solid_face : -1;
+    m_feature_counter++;
+    m_doc.add_project_edges(src_body, {}, face,
+                            plane_from_choice(m_proj_plane->GetSelection()),
+                            "Project" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_delete_face()
+{
+    if (m_doc.bodies.empty()) {
+        set_status(_L("Delete Face needs a body — add or import one first"));
+        return;
+    }
+    if (m_del_faces.empty()) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Add at least one face to delete first"));
+        m_status->Refresh();
+        return;
+    }
+    const int sel = m_del_face_body->GetSelection();
+    const int target = (sel != wxNOT_FOUND) ? sel : -1;
+    m_feature_counter++;
+    m_doc.add_delete_face(target, m_del_faces, "DeleteFace" + std::to_string(m_feature_counter));
+    m_del_faces.clear();  // consumed; fresh state for the next use
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_helix()
+{
+    m_feature_counter++;
+    m_doc.add_helix(plane_from_choice(m_helix_plane->GetSelection()),
+                    m_helix_radius->GetValue(), m_helix_pitch->GetValue(),
+                    m_helix_height->GetValue(), m_helix_left_handed->GetValue(),
+                    m_helix_taper->GetValue(), "Helix" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_mate()
+{
+    const int sel_a = m_mate_cs_a->GetSelection();
+    const int sel_b = m_mate_cs_b->GetSelection();
+    if (sel_a == wxNOT_FOUND || sel_b == wxNOT_FOUND) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Mate needs two CoordSys features — create them first"));
+        m_status->Refresh();
+        return;
+    }
+    const int cs_a = int(reinterpret_cast<intptr_t>(m_mate_cs_a->GetClientData(sel_a)));
+    const int cs_b = int(reinterpret_cast<intptr_t>(m_mate_cs_b->GetClientData(sel_b)));
+    if (cs_a == cs_b) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Mate: CS A and CS B must be different CoordSys features"));
+        m_status->Refresh();
+        return;
+    }
+    m_feature_counter++;
+    int idx = m_doc.add_mate(m_mate_kind->GetSelection(), cs_a, cs_b,
+                             m_mate_offset->GetValue(), m_mate_angle->GetValue(),
+                             m_mate_flip->GetValue(),
+                             "Mate" + std::to_string(m_feature_counter));
+    if (idx < 0) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Mate rejected"));
+        m_status->Refresh();
+        return;
+    }
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_check_interference()
+{
+    if (m_doc.bodies.size() < 2) {
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("No interference — need at least two solid bodies to check"));
+        m_status->Refresh();
+        return;
+    }
+    const auto pairs = m_doc.check_interference();
+    if (pairs.empty()) {
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("No interference found"));
+        m_status->Refresh();
+        return;
+    }
+    double worst = 0;
+    for (const auto& p : pairs)
+        if (p.volume > worst) worst = p.volume;
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(wxString::Format(_L("%zu interference pairs, worst %.2f mm³"),
+                                        pairs.size(), worst));
+    m_status->Refresh();
+    wxString msg = _L("Interference pairs:\n\n");
+    for (const auto& p : pairs) {
+        // 1-based, like every other body label in this panel and in the parts tree:
+        // reporting "Body 1" for what the tree calls "Body 2" is worse than no name.
+        wxString na = wxString::Format(_L("Body %d"), p.body_a + 1);
+        wxString nb = wxString::Format(_L("Body %d"), p.body_b + 1);
+        if (p.body_a >= 0 && p.body_a < int(m_doc.bodies.size()) && !m_doc.bodies[p.body_a].name.empty())
+            na = wxString::FromUTF8(m_doc.bodies[p.body_a].name);
+        if (p.body_b >= 0 && p.body_b < int(m_doc.bodies.size()) && !m_doc.bodies[p.body_b].name.empty())
+            nb = wxString::FromUTF8(m_doc.bodies[p.body_b].name);
+        msg += wxString::Format("%s <-> %s: %.4f mm³\n", na, nb, p.volume);
+    }
+    wxMessageBox(msg, _L("Interference"), wxOK, this);
+}
+
+// Mass properties of the selected solid. A report, not a feature: it never checkpoints, never
+// recomputes and never opens a card, which is why it sits beside the interference check rather
+// than in the on_add_* family. The caller only reaches us with m_sel_solid_body in range.
+void DesignPanel::on_mass_properties()
+{
+    // This bounds check is not defensive padding — it is what makes the verb safe to fire from
+    // the socket, which has no offer menu to grey the row out. The menu-only route never reached
+    // here with nothing selected; run_verb does. Nothing selected is not an error, hence the
+    // neutral colour, not the error red.
+    if (m_sel_solid_body < 0 || m_sel_solid_body >= int(m_doc.bodies.size())) {
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("Select a solid body first — its mass properties are what is reported"));
+        m_status->Refresh();
+        return;
+    }
+    const auto mp = GeometryEngine::mass_properties(m_doc.bodies[m_sel_solid_body].shape);
+    if (!mp.valid) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Mass properties could not be computed for this body"));
+        m_status->Refresh();
+        return;
+    }
+    // 1-based, and the body's own name when it has one — the same wording the parts list uses.
+    wxString name = wxString::Format(_L("Body %d"), m_sel_solid_body + 1);
+    if (!m_doc.bodies[m_sel_solid_body].name.empty())
+        name = wxString::FromUTF8(m_doc.bodies[m_sel_solid_body].name);
+    if (!mp.is_solid) {
+        // Sheet body: quoting a volume here would be inventing material that is not there.
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(wxString::Format(_L("%s: sheet body — %.2f cm² of surface, no volume"),
+                                    name, mp.surface_area / 100.0));
+        m_status->Refresh();
+        wxMessageBox(wxString::Format(_L("%s\n\nSheet body (open shell)\nSurface area: %.2f cm²\n\n"
+                                         "A sheet encloses no material, so it has no volume. "
+                                         "Thicken it into a solid to get one."),
+                                      name, mp.surface_area / 100.0),
+                     _L("Mass properties"), wxOK, this);
+        return;
+    }
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(wxString::Format(_L("%s: %.3f cm³, %.2f cm²"),
+                                        name, mp.volume / 1000.0, mp.surface_area / 100.0));
+    m_status->Refresh();
+    wxMessageBox(wxString::Format(_L("%s\n\nVolume: %.3f cm³\nSurface area: %.2f cm²"),
+                                  name, mp.volume / 1000.0, mp.surface_area / 100.0),
+                 _L("Mass properties"), wxOK, this);
+}
+
+// The rows are only the SHEET bodies, so a row index is NOT a body index — with a solid at 0
+// and a sheet at 1 the single row is row 0 but body 1. Every caller must therefore read the
+// real body index out of the client data (3-arg Append; the 2-arg form takes a bitmap), never
+// GetSelection(). Getting this wrong targets a solid and the kernel rejects it with
+// "target is not a sheet", which reads as a kernel bug rather than a picker bug.
+void DesignPanel::populate_sheet_body_choices(ComboBox* c) const
+{
+    if (!c) return;
+    const int keep = c->GetSelection();
+    c->Clear();
+    for (size_t i = 0; i < m_doc.bodies.size(); ++i) {
+        if (!CadDocument::is_sheet_shape(m_doc.bodies[i].shape)) continue;
+        const std::string& n = m_doc.bodies[i].name;
+        combo_append_index(c, n.empty() ? wxString::Format(_L("Body %zu"), i + 1)
+                                        : wxString::FromUTF8(n), int(i));
+    }
+    if (c->GetCount() > 0)
+        c->SetSelection(std::min(std::max(keep, 0), int(c->GetCount()) - 1));
+}
+
+// Real body index behind the current row of a sheet-filtered picker, or -1.
+int DesignPanel::sheet_choice_body(ComboBox* c)
+{
+    if (!c) return -1;
+    const int sel = c->GetSelection();
+    if (sel == wxNOT_FOUND) return -1;
+    return int(reinterpret_cast<intptr_t>(c->GetClientData(sel)));
+}
+
+// Select the row whose body index is `body`, so a re-edit restores the stored target rather
+// than treating it as a row number.
+void DesignPanel::select_sheet_choice(ComboBox* c, int body)
+{
+    if (!c) return;
+    for (unsigned i = 0; i < c->GetCount(); ++i) {
+        if (int(reinterpret_cast<intptr_t>(c->GetClientData(i))) == body) { c->SetSelection(int(i)); return; }
+    }
+    if (c->GetCount() > 0) c->SetSelection(0);
+}
+
+void DesignPanel::on_add_pattern()
+{
+    if (m_doc.bodies.empty()) {
+        set_status(_L("Pattern needs a solid body — add or import one first"));
+        return;
+    }
+    const bool circular = (m_pattern_type->GetSelection() == 1);
+    const int  target   = (m_sel_solid_body >= 0 && m_sel_solid_body < int(m_doc.bodies.size()))
+                          ? m_sel_solid_body : -1;
+    m_feature_counter++;
+    m_doc.add_pattern(circular, int(m_pattern_count->GetValue()),
+                      m_pattern_spacing->GetValue(), m_pattern_dir->GetSelection(),
+                      m_pattern_angle->GetValue(), target,
+                      "Pattern" + std::to_string(m_feature_counter));
+
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+
+    refresh_tree();
+}
+
+int DesignPanel::selected_body_default() const
+{
+    const int n = int(m_doc.bodies.size());
+    if (n <= 0) return 0;
+    return (m_sel_solid_body >= 0 && m_sel_solid_body < n) ? m_sel_solid_body : 0;
+}
+
+void DesignPanel::populate_body_choices(int as_of_feature)
+{
+    // Re-editing a Boolean: list the bodies as they existed just before it ran, so a tool body
+    // it consumed still shows and the saved target/tool selections round-trip. Replay a copy of
+    // the recipe truncated to [0, as_of_feature). Fall back to the live bodies if the replay is
+    // degenerate (e.g. fewer than the saved refs need).
+    const std::vector<CadBody>* src = &m_doc.bodies;
+    std::vector<CadBody> as_of;
+    if (as_of_feature >= 0 && as_of_feature <= int(m_doc.features.size())) {
+        CadDocument tmp = m_doc;
+        tmp.features.resize(as_of_feature);
+        if (tmp.recompute() && !tmp.bodies.empty()) { as_of = tmp.bodies; src = &as_of; }
+    }
+    auto fill = [&](ComboBox* c, int def) {
+        if (!c) return;
+        c->Clear();
+        for (size_t i = 0; i < src->size(); ++i) {
+            const std::string& n = (*src)[i].name;
+            c->Append(n.empty() ? wxString::Format(_L("Body %zu"), i + 1) : wxString::FromUTF8(n));
+        }
+        if (c->GetCount() > 0)
+            c->SetSelection(std::min(def, int(c->GetCount()) - 1));   // selection index == body index
+    };
+    const int picked = selected_body_default();
+    fill(m_bool_target, picked);
+    // …and the tool body is a DIFFERENT one: defaulting both to the same body is a no-op the
+    // user has to notice and undo. Fall back to the neighbour of whatever was picked.
+    fill(m_bool_tool, picked == 0 ? 1 : 0);
+    fill(m_cut_target, picked);
+}
+
+void DesignPanel::fill_body_choice(ComboBox* c, int as_of_feature, int want)
+{
+    if (!c) return;
+    // Same replay as populate_body_choices, for the single-combo tools. A stored target_body
+    // indexes the body list AS IT WAS just before that feature ran; listing the final bodies
+    // instead makes the saved index select whatever now sits at that position, which is a
+    // different body as soon as a later Cut splits one (indices shift up) or a later Boolean
+    // consumes its tool body (indices shift down).
+    const std::vector<CadBody>* src = &m_doc.bodies;
+    std::vector<CadBody> as_of;
+    if (as_of_feature >= 0 && as_of_feature <= int(m_doc.features.size())) {
+        CadDocument tmp = m_doc;
+        tmp.features.resize(as_of_feature);
+        if (tmp.recompute() && !tmp.bodies.empty()) { as_of = tmp.bodies; src = &as_of; }
+    }
+    c->Clear();
+    for (size_t i = 0; i < src->size(); ++i) {
+        const std::string& n = (*src)[i].name;
+        c->Append(n.empty() ? wxString::Format(_L("Body %zu"), i + 1) : wxString::FromUTF8(n));
+    }
+    if (want >= 0 && want < int(c->GetCount())) c->SetSelection(want);
+    else if (c->GetCount() > 0)                 c->SetSelection(0);
+}
+
+void DesignPanel::on_add_boolean()
+{
+    if (m_doc.bodies.size() < 2) {
+        set_status(_L("Boolean needs two solid bodies — add or import a second one"));
+        return;
+    }
+    const int sel = m_bool_op->GetSelection();
+    const BooleanMode op = (sel == 1) ? BooleanMode::Cut
+                         : (sel == 2) ? BooleanMode::Intersect
+                                      : BooleanMode::Add;   // 0 = Union
+    m_feature_counter++;
+    m_doc.add_boolean(op, m_bool_target->GetSelection(), m_bool_tool->GetSelection(),
+                      m_bool_keep->GetValue(), m_bool_tol->GetValue(), -1, -1,
+                      "Boolean" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::on_add_cut()
+{
+    if (m_doc.bodies.empty()) {
+        set_status(_L("Cut needs a solid body — add or import one first"));
+        return;
+    }
+    m_feature_counter++;
+    m_doc.add_cut(plane_from_choice(m_cut_plane->GetSelection()), m_cut_offset->GetValue(),
+                  /*flip*/ false, /*keep_upper*/ true, /*keep_lower*/ true,
+                  m_cut_target->GetSelection(), "Cut" + std::to_string(m_feature_counter));
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+    refresh_tree();
+}
+
+void DesignPanel::populate_plane_choices(ComboBox* c) const
+{
+    if (!c) return;
+    const int keep = c->GetSelection();
+    c->Clear();
+    c->Append(_L("XY")); c->Append(_L("XZ")); c->Append(_L("YZ"));
+    for (const auto& dp : m_doc.resolve_datum_planes())
+        c->Append(wxString::FromUTF8(dp.first));
+    c->SetSelection((keep >= 0 && keep < int(c->GetCount())) ? keep : 0);
+}
+
+wxString DesignPanel::ref_plane_name(int row) const
+{
+    if (row == 1) return "XZ";
+    if (row == 2) return "YZ";
+    if (row >= 3) {
+        const auto datums = m_doc.resolve_datum_planes();
+        const int di = row - 3;
+        if (di < int(datums.size())) return wxString::FromUTF8(datums[di].first);
+    }
+    return "XY";
+}
+
+SketchPlane DesignPanel::plane_from_choice(int row) const
+{
+    if (row < 3) {                                // 0=XY,1=XZ,2=YZ through the modeling origin
+        SketchPlane p = plane_from_index(row);
+        p.origin += m_doc.modeling_origin;
+        return p;
+    }
+    // Datums are already in world coords (resolve_datum_planes applied the origin to their base).
+    auto datums = m_doc.resolve_datum_planes();
+    const int di = row - 3;
+    if (di >= 0 && di < int(datums.size())) return datums[di].second;
+    SketchPlane p = SketchPlane::XY(); p.origin += m_doc.modeling_origin; return p;
+}
+
+// A sketch goes where the user pointed. A planar face picked in the viewport wins outright; only
+// when nothing is picked do we fall back to the reference plane, which itself is normally set by
+// clicking one of the ghost planes in 3D (on_datum_base_picked) rather than by opening the combo.
+// Before this, a picked face was ignored and the only way onto it was to build a Coincident datum
+// plane first and then find it in a dropdown — three steps and a junk feature in the tree for the
+// most common gesture in solid modelling. 3a2.
+SketchPlane DesignPanel::sketch_plane_from_selection(wxString& what) const
+{
+    SketchPlane p;
+    // An explicitly face-level selection first, then the face merely CLICKED ON while the whole
+    // body was selected. The second case is the common one: one click on a face is what a user
+    // means by "select this face", and requiring the cycle's second click to make it count is the
+    // whole reason this looked unfixed.
+    const int fb = (m_sel_solid_face >= 0 && m_sel_solid_body >= 0) ? m_sel_solid_body : m_pick_face_body;
+    const int fi = (m_sel_solid_face >= 0 && m_sel_solid_body >= 0) ? m_sel_solid_face : m_pick_face;
+    if (fb >= 0 && fi >= 0 && m_doc.plane_of_face(fb, fi, p)) {
+        what = (m_doc.bodies.size() > 1)
+             ? wxString::Format(_L("the picked face of Body %d"), fb + 1)
+             : _L("the picked face");
+        return p;
+    }
+    what = ref_plane_name(m_ref_plane);
+    return plane_from_choice(m_ref_plane);
+}
+
+// Is there a sketch target the USER chose, and what is it called? Distinct from
+// sketch_plane_from_selection, which always answers because it falls back to m_ref_plane —
+// a caller that wants to say "sketching on X" needs to know whether there is anything to fall
+// back FROM, so it can ask for a plane instead of claiming one the user never picked.
+bool DesignPanel::sketch_plane_target(wxString& what) const
+{
+    const int fb = (m_sel_solid_face >= 0 && m_sel_solid_body >= 0) ? m_sel_solid_body : m_pick_face_body;
+    const int fi = (m_sel_solid_face >= 0 && m_sel_solid_body >= 0) ? m_sel_solid_face : m_pick_face;
+    SketchPlane p;
+    if (fb >= 0 && fi >= 0 && m_doc.plane_of_face(fb, fi, p)) {
+        what = (m_doc.bodies.size() > 1)
+             ? wxString::Format(_L("the picked face of Body %d"), fb + 1)
+             : _L("the picked face");
+        return true;
+    }
+    if (m_plane_picked) { what = ref_plane_name(m_ref_plane); return true; }
+    return false;
+}
+
+// ---------------------------------------------------------------------------------------------
+// The object-driven offer (charter §4.1). Right-click the geometry and get a vertical list in the
+// ratified row order, with the verbs that do not apply DISABLED IN PLACE carrying their reason.
+// The rows come from DesignOffer.hpp, generated from docs/ux/tool_atlas.json — the same file the
+// mockups are drawn from, so a drawing and the product cannot drift apart.
+// ---------------------------------------------------------------------------------------------
+
+bool DesignPanel::sketch_map_applies() const
+{
+    return m_ui_mode == UiMode::Sketch || (m_viewport && m_viewport->is_sketching());
+}
+
+// Which kind of thing is selected, as an OfferSel. Classified by the level the pick cycle has
+// actually REACHED, so the menu describes what is highlighted — a header that names a face while
+// the whole body is lit would be lying, and this menu's whole value is that it tells the truth
+// about the selection. (Sketching on the face you merely clicked is unaffected: that path is
+// sketch_plane_from_selection, which deliberately uses m_pick_face. 3a2.)
+int DesignPanel::offer_selection_kind() const
+{
+    if (sketch_map_applies()) {
+        // Classify WHAT is selected in the sketch, rather than collapsing every sketch state to
+        // SkNone. The offer table has always described verbs for a selected line, arc, point or
+        // pair — Trim, Extend, Fillet, Chamfer, Offset, Mirror, the arrays, Move/Rotate/Scale,
+        // Constrain, Delete — but nothing ever RETURNED those kinds, so all thirteen were
+        // unreachable from the menu and the sketch-editing vocabulary did not exist in the one
+        // place this app tells users to look. A user comparing against Onshape reported exactly
+        // that about constraints (OrcaSlicer PR #15238).
+        const int n = m_viewport ? m_viewport->sketch_selection_count() : 0;
+        if (n >= 2) return int(OfferSel::Sk2Ent);
+        if (n == 1) {
+            SketchEntity::Type t = SketchEntity::Type::Line;
+            if (m_viewport && m_viewport->sketch_first_selected_type(t)) {
+                switch (t) {
+                case SketchEntity::Type::Line:  return int(OfferSel::SkLine);
+                case SketchEntity::Type::Point: return int(OfferSel::SkPoint);
+                // Arc, Circle, Ellipse, EllipseArc, BSpline all take the curve vocabulary.
+                default:                        return int(OfferSel::SkArc);
+                }
+            }
+        }
+        return int(OfferSel::SkNone);
+    }
+
+    const int nb = int(m_doc.bodies.size());
+    if (m_sel_solid_vertex && m_sel_solid_body >= 0 && m_sel_solid_body < nb)
+        return int(OfferSel::Vertex);
+    if (m_sel_solid_edge >= 0 && m_sel_solid_body >= 0 && m_sel_solid_body < nb) {
+        const TopoDS_Edge e = GeometryEngine::edge_by_index(m_doc.bodies[m_sel_solid_body].shape,
+                                                            m_sel_solid_edge);
+        return int(GeometryEngine::circle_of_edge(e).ok ? OfferSel::EdgeCirc : OfferSel::EdgeStr);
+    }
+    if (m_sel_solid_face >= 0 && m_sel_solid_body >= 0 && m_sel_solid_body < nb) {
+        SketchPlane p;
+        if (m_doc.plane_of_face(m_sel_solid_body, m_sel_solid_face, p))
+            return int(OfferSel::FacePlanar);
+        const TopoDS_Face f = GeometryEngine::face_by_index(m_doc.bodies[m_sel_solid_body].shape,
+                                                            m_sel_solid_face);
+        return int(GeometryEngine::cylinder_of_face(f).ok ? OfferSel::FaceCyl : OfferSel::FaceOther);
+    }
+    if (m_sel_sketch_region >= 0)
+        return int(OfferSel::SkLoop);
+    if (m_sel_solid_body >= 0 && m_sel_solid_body < nb)
+        return int(CadDocument::is_sheet_shape(m_doc.bodies[m_sel_solid_body].shape)
+                   ? OfferSel::BodySheet : OfferSel::BodySolid);
+    return int(OfferSel::None);
+}
+
+// Route a row to the code that already implements the verb. Nothing here re-implements a tool:
+// the offer is a second door onto the same room, which is what keeps the toolbar, the shortcuts
+// and the menu from drifting into three behaviours.
+void DesignPanel::run_offer_action(const char* action)
+{
+    if (!action || !*action)
+        return;
+    const std::string a(action);
+    if (a.rfind("key:", 0) == 0) {
+        const std::string k = a.substr(4);
+        if (k.size() >= 3 && k[0] == 'S' && k[1] == '+') {          // "S+E" -> Shift+E, model mode
+            auto it = m_keys_feature.find(int(k[2]) | SC_SHIFT);
+            if (it != m_keys_feature.end() && it->second) it->second();
+        } else if (!k.empty()) {                                     // "L" -> sketch-mode letter
+            auto it = m_keys_sketch.find(int(k[0]));
+            if (it != m_keys_sketch.end() && it->second) it->second();
+        }
+        return;
+    }
+    auto it = m_verb_actions.find(a);
+    if (it != m_verb_actions.end() && it->second)
+        it->second();
+}
+
+// Look a verb up by its offer id and dispatch it — the "run_verb" half of the MCP offer surface.
+// Unknown ids and rows whose action string is null (kernel support, no GUI route yet) return
+// false without touching anything, so the caller can tell "no such verb" from "not wired yet".
+bool DesignPanel::mcp_run_verb(const char* verb_id)
+{
+    if (!verb_id) return false;
+    for (int i = 0; i < kOfferVerbCount; ++i) {
+        const OfferVerb& v = kOfferVerbs[i];
+        if (std::string(v.id) == verb_id) {
+            if (v.action == nullptr) return false;
+            run_offer_action(v.action);
+            return true;
+        }
+    }
+    return false;
+}
+
+wxPoint DesignPanel::offer_anchor() const
+{
+    const wxPoint mouse = wxGetMousePosition();
+    if (!m_viewport)
+        return mouse;
+    const wxRect r = m_viewport->GetScreenRect();
+    if (r.Contains(mouse))
+        return mouse;
+    return wxPoint(r.x + r.width / 2, r.y + r.height / 2);
+}
+
+// Append a verb row carrying the same glyph its toolbar button shows. The icon name comes from
+// the atlas, so a verb and its icon are declared in one place; a null or unknown name leaves
+// the row text-only rather than drawing a blank square.
+//
+// THE BITMAP MUST BE SET BEFORE Append(). wxGTK builds the GtkMenuItem inside Append and reads
+// GetBitmap() right there (gtk/menu.cpp) — it makes a gtk_image_menu_item only if a bitmap is
+// already present, and a plain one otherwise. Setting it on the item Append() returns is too
+// late and silently does nothing, which is exactly how the first attempt failed. This is why
+// Orca's own append_menu_item() constructs, sets, then appends.
+// One place that writes the status line, so every hint wraps instead of clipping at the panel
+// edge. wxStaticText::Wrap() is destructive, which is fine here: the label is replaced whole
+// each time, never appended to.
+void DesignPanel::set_status(const wxString& text)
+{
+    if (m_status == nullptr) return;
+    m_status->SetLabel(text);   // the ONE place that may call SetLabel directly
+    // m_status is HIDDEN and kept only as the owner of the text and its colour — every caller
+    // sets the colour on it just before calling here, so this stays the one place that knows
+    // both. What the user reads is drawn along the BASE OF THE VIEWPORT: in the panel the line
+    // was clipped at ~73 characters with no warning and no wrap (Wrap() never took effect —
+    // 8cc), which silently length-limited every hint in the tab. The viewport's bottom
+    // margin has the whole window width, so a sentence can be a sentence.
+    if (m_viewport != nullptr) {
+        // wxNullColour means "no opinion", and the dark default text colour is nearly invisible
+        // on the dark HUD; only a colour a caller actually chose (the error red, the plane-pick
+        // green) is carried over. Compared against the colour the label was CREATED with —
+        // comparing against the parent's foreground instead reported "chosen" for every line,
+        // and the neutral text came out the panel's grey.
+        const wxColour fg = m_status->GetForegroundColour();
+        m_viewport->set_status_text(text, fg != m_status_default_fg ? fg
+                                                                    : wxColour(0xDD, 0xE1, 0xE6));
+    }
+}
+
+
+// The sentence for the step the armed sketch tool is on (1c0c). One table, so a tool's
+// gesture is described in one place and the description cannot drift from the code that reads the
+// clicks: the step counts here are the ones DesignSketchTool::render previews and on_mouse
+// consumes. `step` = anchors already placed (edit-ops: 0 none, 1 first pick down, 2 ready to
+// apply); `picks` = the size of the set the gesture accumulates.
+//
+// It is deliberately explicit about the gesture that ENDS each tool, because none of them is
+// discoverable: a click on empty space applies an edit-op or a transform, right-click cancels it,
+// and Esc downgrades an armed tool to Select before it ever exits the sketch.
+static wxString sketch_step_prompt(DesignSketchTool::Mode m, int step, int picks)
+{
+    using Mode = DesignSketchTool::Mode;
+    auto pick_more = [](const wxString& lead, int n) {
+        return n <= 0 ? lead
+                      : lead + wxString::Format(_L("  ·  %d picked"), n);
+    };
+    switch (m) {
+    case Mode::Select:
+        return picks > 0
+            ? wxString::Format(_L("%d selected  ·  Del removes them  ·  Shift-click adds  ·  "
+                                  "double-click takes the whole loop"), picks)
+            : _L("Select — click an entity to pick it  ·  drag an endpoint or centre to move it  ·  "
+                 "Shift-click adds  ·  Del removes");
+    case Mode::Constrain:
+        return picks > 0
+            ? wxString::Format(_L("%d picked  ·  now choose a constraint (Horizontal, Parallel, "
+                                  "Tangent, Equal…)"), picks)
+            : _L("Constrain — click one or two entities, then choose a constraint");
+    case Mode::Dimension:
+        return step == 0 ? _L("Dimension — click an entity, or the first of two points")
+                         : _L("Dimension — click the second point");
+    case Mode::Line:
+        return step == 0 ? _L("Line — click the start point")
+                         : _L("Line — click the end point, or type the length");
+    case Mode::Polyline:
+        return step == 0 ? _L("Polyline — click the first point")
+                         : pick_more(_L("Polyline — click the next point  ·  click the start point "
+                                        "to close it  ·  right-click to end the chain"), step);
+    case Mode::CornerRect:
+        return step == 0 ? _L("Rectangle — click one corner")
+                         : _L("Rectangle — click the opposite corner");
+    case Mode::CenterRect:
+        return step == 0 ? _L("Centre rectangle — click the centre")
+                         : _L("Centre rectangle — click a corner");
+    case Mode::ObliqueRect:
+        return step == 0 ? _L("Oblique rectangle — click the start of the base edge")
+             : step == 1 ? _L("Oblique rectangle — click the end of the base edge (this sets the angle)")
+                         : _L("Oblique rectangle — click to set the width");
+    case Mode::RoundedRect:
+        return step == 0 ? _L("Rounded rectangle — click one corner")
+             : step == 1 ? _L("Rounded rectangle — click the opposite corner")
+                         : _L("Rounded rectangle — click to set the corner radius");
+    case Mode::CenterCircle:
+        return step == 0 ? _L("Circle — click the centre")
+                         : _L("Circle — click to set the radius, or type it");
+    case Mode::TwoPointCircle:
+        return step == 0 ? _L("Circle (2 points) — click one end of the diameter")
+                         : _L("Circle (2 points) — click the other end of the diameter");
+    case Mode::ThreePointCircle:
+        return step == 0 ? _L("Circle (3 points) — click the first point on the circle")
+             : step == 1 ? _L("Circle (3 points) — click the second point")
+                         : _L("Circle (3 points) — click the third point");
+    case Mode::ThreePointArc:
+        return step == 0 ? _L("Arc — click the start point")
+             : step == 1 ? _L("Arc — click the end point")
+                         : _L("Arc — click a point the arc passes through");
+    case Mode::TangentArc:
+        return step == 0 ? _L("Tangent arc — click the endpoint it leaves from")
+                         : _L("Tangent arc — click its far end");
+    case Mode::CenterArc:
+        return step == 0 ? _L("Centre arc — click the centre")
+             : step == 1 ? _L("Centre arc — click the start point (this sets the radius)")
+                         : _L("Centre arc — click the end point");
+    case Mode::Slot:
+        return step == 0 ? _L("Slot — click one end of the centreline")
+             : step == 1 ? _L("Slot — click the other end of the centreline")
+                         : _L("Slot — click to set the width");
+    case Mode::ArcSlot:
+        return step == 0 ? _L("Arc slot — click the centre the slot curves about")
+             : step == 1 ? _L("Arc slot — click the start of the centreline (this sets the radius)")
+             : step == 2 ? _L("Arc slot — click the end of the centreline")
+                         : _L("Arc slot — click to set the width");
+    case Mode::Polygon:
+        return step == 0 ? _L("Polygon — click the centre")
+                         : _L("Polygon — click a vertex (this sets size and orientation)");
+    case Mode::Ellipse:
+        return step == 0 ? _L("Ellipse — click the centre")
+             : step == 1 ? _L("Ellipse — click the end of the major axis")
+                         : _L("Ellipse — click a point on the minor axis");
+    case Mode::EllipseArc:
+        return step == 0 ? _L("Elliptical arc — click the centre")
+             : step == 1 ? _L("Elliptical arc — click the end of the major axis")
+             : step == 2 ? _L("Elliptical arc — click a point on the minor axis")
+             : step == 3 ? _L("Elliptical arc — click where the arc starts")
+                         : _L("Elliptical arc — click where the arc ends");
+    case Mode::BSpline:
+        return step == 0 ? _L("Spline — click the first control point")
+                         : pick_more(_L("Spline — click the next control point  ·  right-click to "
+                                        "finish the curve"), step);
+    case Mode::Point:
+        return _L("Point — click to place one; the tool stays armed for more");
+    case Mode::Trim:
+        return _L("Trim — click a segment where it crosses another entity  ·  right-click to exit");
+    case Mode::Extend:
+        return _L("Extend — click a line or arc to grow it out to the nearest entity  ·  "
+                  "right-click to exit");
+    case Mode::Fillet:
+        return step == 0 ? _L("Fillet — click the first of two lines that meet")
+             : step == 1 ? _L("Fillet — click the second line")
+                         : _L("Fillet — drag the arrow, or click the number to type the radius  ·  "
+                              "click empty space to apply  ·  right-click cancels");
+    case Mode::Chamfer:
+        return step == 0 ? _L("Chamfer — click the first of two lines that meet")
+             : step == 1 ? _L("Chamfer — click the second line")
+                         : _L("Chamfer — drag the arrow, or click the number to type the setback  ·  "
+                              "click empty space to apply  ·  right-click cancels");
+    case Mode::Offset:
+        return step == 0 ? _L("Offset — click the entity to offset")
+                         : _L("Offset — drag the arrow to either side, or click the number to type "
+                              "the distance  ·  click empty space to apply  ·  right-click cancels");
+    case Mode::Mirror:
+        // The two-phase pick is the one gesture users reported as unguided: nothing said the
+        // AXIS comes first, and nothing said an empty click is what applies it.
+        return step == 0
+            ? _L("Mirror — first click the LINE to mirror about (a construction line works)")
+            : picks == 0
+                ? _L("Mirror — axis set  ·  now click the entities to mirror  ·  right-click cancels")
+                : wxString::Format(_L("Mirror — axis set  ·  %d to mirror  ·  click another to add or "
+                                      "remove it  ·  click empty space to apply"), picks);
+    case Mode::Move:
+        return step == 0 ? _L("Move — click the entities to move")
+                         : pick_more(_L("Move — drag the handle, or click the number to type the "
+                                        "distance  ·  click empty space to apply"), picks);
+    case Mode::Rotate:
+        return step == 0 ? _L("Rotate — click the entities to rotate")
+                         : pick_more(_L("Rotate — drag the handle, or click the number to type the "
+                                        "angle  ·  click empty space to apply"), picks);
+    case Mode::Scale:
+        return step == 0 ? _L("Scale — click the entities to scale")
+                         : pick_more(_L("Scale — drag the handle, or click the number to type the "
+                                        "factor  ·  click empty space to apply"), picks);
+    case Mode::Array:
+        return step == 0 ? _L("Array — click the entities to repeat")
+                         : pick_more(_L("Array — drag the handle to set the step, click the count to "
+                                        "type it  ·  click empty space to apply"), picks);
+    case Mode::PolarArray:
+        return step == 0 ? _L("Polar array — click the entities to repeat")
+                         : pick_more(_L("Polar array — drag the handle to set the sweep, click the "
+                                        "count to type it  ·  click empty space to apply"), picks);
+    case Mode::TransformArt:
+        return _L("Drag a corner to scale, the centre to move  ·  right-click when done");
+    }
+    return wxString();
+}
+
+void DesignPanel::on_sketch_step(int mode, int step, int picks)
+{
+    wxString text = sketch_step_prompt(DesignSketchTool::Mode(mode), step, picks);
+    // Esc is layered (DesignSketchTool::request_exit): it drops the anchors down, then downgrades
+    // the armed tool to Select, and only then leaves the sketch. Nothing in the UI said so, so
+    // the route back to selecting existing geometry was invisible. Said once, on the step where
+    // the gesture has not started yet, so it does not crowd the instruction that matters.
+    if (step == 0 && picks == 0 && DesignSketchTool::Mode(mode) != DesignSketchTool::Mode::Select
+        && !text.IsEmpty())
+        text += _L("  ·  Esc goes back to Select");
+    // Badges are clickable and nothing said so — a glyph reads as decoration until something
+    // tells you it is a target. Only in Select mode (the only mode where the click is wired) and
+    // only once a constraint exists, so it never advertises a badge that is not on screen.
+    if (DesignSketchTool::Mode(mode) == DesignSketchTool::Mode::Select && m_viewport != nullptr &&
+        m_viewport->sketch_constraint_count() > 0 && !text.IsEmpty())
+        text += _L("  ·  click a constraint badge to remove it");
+    m_sketch_step = text;
+    if (text.IsEmpty() || m_status == nullptr) return;
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(text);
+    m_status->Refresh();
+}
+
+wxMenuItem* DesignPanel::append_offer_item(wxMenu* menu, int id, const wxString& text,
+                                           const OfferVerb& v)
+{
+    auto* item = new wxMenuItem(menu, id, text);
+    if (v.icon != nullptr && *v.icon != '\0') {
+        const wxBitmap bmp = create_scaled_bitmap(v.icon, this, 16);
+        if (bmp.IsOk())
+            item->SetBitmap(bmp);
+    }
+    menu->Append(item);
+    return item;
+}
+
+// Diagnostic only: what the offer is about to show, line per row, on stderr. Costs one getenv
+// per menu when off. The ladder that drives right-click needs to assert the ROW SET, and the only
+// honest source for that is the loop that builds the rows.
+static void offer_trace(const char* fmt, ...)
+{
+    static const bool on = std::getenv("ORCA_CAD_KEYTRACE") != nullptr;
+    if (!on) return;
+    va_list ap;
+    va_start(ap, fmt);
+    fprintf(stderr, "[OFFER] ");
+    vfprintf(stderr, fmt, ap);
+    fprintf(stderr, "\n");
+    va_end(ap);
+    fflush(stderr);
+}
+
+void DesignPanel::show_offer_menu(const wxPoint& screen_pos)
+{
+    const int      kind = offer_selection_kind();
+    const uint32_t bit  = offer_bit(OfferSel(kind));
+    // Which verb MAP applies is a question about the MODE, not about whether a session is
+    // running — the same distinction the keyboard already had to learn (0ud). Gated on
+    // is_sketching() the offer opened on entering a sketch showing the FEATURE rows, every one
+    // of them refusing the sketch selection, so it read as a menu of nine dead entries.
+    const bool     sketching = sketch_map_applies();
+    // The offer ladder reads THIS, not the pixels: the trace is emitted from the same loop that
+    // builds the menu, so it cannot drift from what the user is shown. Gated on the existing
+    // ORCA_CAD_KEYTRACE so a rig run needs one env var, not two. <offer ladder>.
+    offer_trace("open kind=%d sketching=%d bodies=%d", kind, sketching ? 1 : 0,
+                int(m_doc.bodies.size()));
+
+    const int bodies = int(m_doc.bodies.size());
+    int sketches = 0;
+    for (const auto& f : m_doc.features)
+        if (f.type == CadFeatureType::Sketch) ++sketches;
+    bool sheet = false;
+    for (const auto& b : m_doc.bodies)
+        if (CadDocument::is_sheet_shape(b.shape)) { sheet = true; break; }
+
+    auto applies = [&](const OfferVerb& v) {
+        return (v.accepts & bit) && v.need_bodies <= bodies && v.need_sketches <= sketches
+               && (!v.need_sheet || sheet);
+    };
+    // Names and reasons live in the generated table as plain literals; they are the same strings
+    // the toolbar already ships, so the catalogue already carries their translations.
+    // Scope the lookup to the APPLICATION catalog. A bare wxGetTranslation() searches every
+    // loaded catalog, wxWidgets' own wxstd included — so on a non-English system the two row
+    // names that happen to be wx standard strings came back translated while the other six,
+    // which wx does not know, stayed English. On an Italian desktop the offer read
+    // "Create / Add material / Rimuovi / Fillet / chamfer / draft / Repeat / Transform /
+    // Reference / Modify": one menu, two languages, and not because anything was mistranslated.
+    // The same trap is waiting for any locale — Supprimer, Löschen, Eliminar. Naming the domain
+    // means these strings are translated by OUR catalogue or not at all, which is consistent
+    // either way.
+    auto tr = [](const char* s) {
+        return wxGetTranslation(wxString::FromUTF8(s), SLIC3R_APP_KEY);
+    };
+    auto label = [&](const OfferVerb& v) {
+        wxString s = tr(v.name);
+        if (v.key && *v.key) s += "\t" + wxString::FromUTF8(v.key);
+        return s;
+    };
+
+    wxMenu menu;
+    std::vector<const OfferVerb*> bound;      // menu id offset -> verb
+    const int base = wxID_HIGHEST + 4200;
+
+    for (int row = 0; row < kOfferRowCount; ++row) {
+        std::vector<const OfferVerb*> live, family;
+        for (int i = 0; i < kOfferVerbCount; ++i) {
+            const OfferVerb& v = kOfferVerbs[i];
+            if (v.row != row || v.sketch_mode != sketching) continue;
+            family.push_back(&v);
+            if (applies(v)) live.push_back(&v);
+        }
+        if (family.empty())
+            continue;                                   // no verb of this family in this mode
+        const wxString fam = tr(kOfferRowNames[row]);
+
+        if (live.empty()) {
+            // DISABLED IN PLACE, with the reason. This is the row that makes the list worth
+            // having: a control that cannot be used still says what it is and what you would
+            // have to do first, in the product's own words (L7).
+            //
+            // The reason must be TRUE for the situation in front of the user. Taking the first
+            // refusal in the family printed "Transform needs a body — add or import one first"
+            // on a document that has a body, because the real obstacle was that nothing was
+            // selected. So: prefer the refusal of a verb that accepts THIS selection and fails
+            // only on document state — that message is about the actual blocker. If no verb in
+            // the family accepts this selection at all, the honest thing is to say so, or say
+            // nothing.
+            const char* why = nullptr;
+            for (const OfferVerb* v : family)
+                if ((v->accepts & bit) && v->refusal) { why = v->refusal; break; }
+            wxString s = fam;
+            if (why)
+                s += wxString::FromUTF8("   —   ") + tr(why);
+            else if (OfferSel(kind) == OfferSel::None)
+                s += wxString::FromUTF8("   —   ") + _L("select something first");
+            offer_trace("row=%d %s DISABLED (%s)", row, kOfferRowNames[row],
+                        why ? why : "no verb accepts this selection");
+            menu.Append(base + int(bound.size()), s)->Enable(false);
+            bound.push_back(nullptr);
+        } else if (live.size() == 1) {
+            offer_trace("row=%d %s -> %s%s", row, kOfferRowNames[row], live[0]->id,
+                        live[0]->action ? "" : " (no GUI route)");
+            append_offer_item(&menu, base + int(bound.size()), label(*live[0]), *live[0])
+                ->Enable(live[0]->action != nullptr);
+            bound.push_back(live[0]);
+        } else {
+            // Two levels, not one. A verb with a `family` joins a nested submenu of that name
+            // (Rectangle -> corner / centre / oblique / rounded); one without sits directly in
+            // the row. Families keep the order of their first member, so the row's layout is
+            // stable across selections — the whole point of a fixed address.
+            auto* sub = new wxMenu();
+            std::vector<std::pair<std::string, wxMenu*>> groups;   // insertion-ordered
+            for (const OfferVerb* v : live) {
+                wxMenu* target = sub;
+                if (v->family && *v->family) {
+                    auto it = std::find_if(groups.begin(), groups.end(),
+                                           [&](const auto& g) { return g.first == v->family; });
+                    if (it == groups.end()) {
+                        auto* g = new wxMenu();
+                        groups.emplace_back(v->family, g);
+                        sub->AppendSubMenu(g, tr(v->family));
+                        target = g;
+                    } else {
+                        target = it->second;
+                    }
+                }
+                offer_trace("row=%d %s > %s%s%s%s", row, kOfferRowNames[row],
+                            (v->family && *v->family) ? v->family : "",
+                            (v->family && *v->family) ? " > " : "", v->id,
+                            v->action ? "" : " (no GUI route)");
+                append_offer_item(target, base + int(bound.size()), label(*v), *v)
+                    ->Enable(v->action != nullptr);
+                bound.push_back(v);
+            }
+            menu.AppendSubMenu(sub, fam);
+        }
+    }
+
+    // --- Mate palette section (lukg part B) ---
+    // Fed by CadDocument::mate_options() so the offer can never disagree with the kernel about
+    // which assembly mates a connector pair admits. Shown only when the document holds at least
+    // two ENABLED CoordSys features: below that the whole section would be one permanently dead
+    // row, which is noise rather than information.
+    // Set while a hovered mate row is showing its ghost, so the cleanup after PopupMenu can tell
+    // "I put that there" from "some other tool's preview was already on screen".
+    bool             mate_ghost = false;
+    std::vector<int> cs_features;
+    for (int i = 0; i < int(m_doc.features.size()); ++i)
+        if (m_doc.features[i].type == CadFeatureType::CoordSys && m_doc.features[i].enabled)
+            cs_features.push_back(i);
+    if (cs_features.size() >= 2) {
+        // Which two connectors the types would apply to. The Mate card's combos when it is open —
+        // so the offer and the card can never disagree about the pair — otherwise the first two
+        // enabled CoordSys features, which is a defensible default precisely because the header row
+        // below NAMES it. An offer that acts on an unnamed pair would be worse than no offer.
+        int cs_a = -1, cs_b = -1;
+        if (m_active == Tool::Mate && m_mate_cs_a && m_mate_cs_b
+            && m_mate_cs_a->GetSelection() != wxNOT_FOUND
+            && m_mate_cs_b->GetSelection() != wxNOT_FOUND) {
+            cs_a = int(reinterpret_cast<intptr_t>(m_mate_cs_a->GetClientData(m_mate_cs_a->GetSelection())));
+            cs_b = int(reinterpret_cast<intptr_t>(m_mate_cs_b->GetClientData(m_mate_cs_b->GetSelection())));
+        }
+        if (cs_a < 0 || cs_b < 0) { cs_a = cs_features[0]; cs_b = cs_features[1]; }
+
+        // The generated verb rows own [base, base + bound.size()); kOfferVerbCount is 87, so a
+        // gap of 500 keeps this section's ids clear of that range and lets its own handler index
+        // by a distinct offset.
+        const int mate_base = base + 500;
+
+        menu.AppendSeparator();
+        // B is the connector on the body that MOVES (CadDocument.hpp:317), so B is the arrow's
+        // destination — "A first" invites the opposite guess.
+        const wxString name_a = wxString::FromUTF8(m_doc.features[cs_a].name);
+        const wxString name_b = wxString::FromUTF8(m_doc.features[cs_b].name);
+        menu.Append(mate_base, wxString::Format(_L("Mate: %s  →  %s"), name_a, name_b))->Enable(false);
+
+        // A switch of literal _L() calls, not an array indexed by kind. _L is a gettext macro:
+        // the extractor scans the SOURCE for literals, so _L(table[i]) compiles fine and then
+        // silently ships five strings that are never in the catalogue and can never be
+        // translated. These names appear nowhere else in the tree, so the array version would
+        // have been their only occurrence.
+        auto mate_kind_name = [](int kind) -> wxString {
+            switch (kind) {
+            case 0:  return _L("Fastened");
+            case 1:  return _L("Planar");
+            case 2:  return _L("Revolute");
+            case 3:  return _L("Slider");
+            default: return _L("Cylindrical");
+            }
+        };
+        // Five rows, always, in kind order. Never reordered, never filtered — a menu that changes
+        // shape between invocations destroys the motor memory experts rely on.
+        const std::vector<CadDocument::MateOption> opts = m_doc.mate_options(cs_a, cs_b);
+        for (int i = 0; i < int(opts.size()); ++i) {
+            const CadDocument::MateOption& o = opts[i];
+            wxString label = mate_kind_name(o.kind);
+            if (!o.viable)
+                label += wxString::FromUTF8("   —   ") + wxString::FromUTF8(o.reason);
+            menu.Append(mate_base + 1 + i, label)->Enable(o.viable);
+        }
+
+        // Hovering a row shows the RESULT, not a description of it (epic gap G3). preview() moves
+        // the body on a throwaway copy of the document, so nothing is written until the click —
+        // the "commit nothing until you choose" behaviour the palette was asked for.
+        auto drop_ghost = [this, &mate_ghost]() {
+            if (!mate_ghost) return;
+            m_viewport->clear_preview();
+            m_viewport->set_body_hidden(false);
+            m_viewport->repaint_now();
+            mate_ghost = false;
+        };
+        menu.Bind(wxEVT_MENU_HIGHLIGHT,
+                  [this, cs_a, cs_b, opts, mate_base, &mate_ghost, drop_ghost](wxMenuEvent& e) {
+            const int i = e.GetMenuId() - (mate_base + 1);
+            // Off the palette (a verb row, the header, or nothing) — a stale ghost from the row
+            // you just left is worse than none, so it goes as soon as the cursor does.
+            if (i < 0 || i >= int(opts.size()) || !opts[i].viable) { drop_ghost(); return; }
+            std::string err;
+            mate_ghost = show_mate_ghost(opts[i].kind, cs_a, cs_b, 0.0, 0.0, false, err);
+            m_viewport->repaint_now();   // synchronous: the popup owns the loop, a queued repaint is never serviced
+        });
+
+        menu.Bind(wxEVT_MENU, [this, cs_a, cs_b, opts, mate_base, drop_ghost](wxCommandEvent& e) {
+            const int i = e.GetId() - (mate_base + 1);
+            if (i < 0 || i >= int(opts.size()) || !opts[i].viable) return;
+            drop_ghost();         // the real bodies are about to become the ghost's pose
+            m_doc.checkpoint();   // undo boundary: committing a mate from the offer
+            int idx = m_doc.add_mate(opts[i].kind, cs_a, cs_b, 0.0, 0.0, false,
+                                     "Mate" + std::to_string(++m_feature_counter));
+            if (idx < 0) {
+                m_status->SetForegroundColour(wxColour(235, 110, 110));
+                set_status(_L("Mate rejected"));
+                m_status->Refresh();
+                return;
+            }
+            if (!recompute_guarded(_L("Rebuilding model…")))
+                set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+            else
+                set_status_ok();
+            refresh_tree();
+        });
+    }
+
+    // Hovering a row explains it. The offer is the only door to these tools now, so a bare
+    // name is not enough — and the hint arrives while you are still choosing.
+    // BOUND TO THE VERB ID RANGE, NOT THE WHOLE MENU. These two used to be unfiltered, and
+    // wxWidgets pushes dynamic entries to the FRONT of the handler list, so being bound LAST made
+    // them run FIRST for every id — including the mate rows at mate_base+1 (base+501) above. Both
+    // fall out of `bound`'s range there and return WITHOUT e.Skip(), which wx reads as "handled",
+    // so the mate handlers never ran: hovering a mate kind showed no ghost and left the previous
+    // status message on screen, and clicking one created nothing at all. The whole mate palette
+    // enumerated perfectly and fired nothing. Restricting the range keeps each half to its own ids
+    // regardless of bind order.
+    menu.Bind(wxEVT_MENU_HIGHLIGHT, [this, &bound, base](wxMenuEvent& e) {
+        const int i = e.GetMenuId() - base;
+        if (i < 0 || i >= int(bound.size()) || bound[i] == nullptr || bound[i]->hint == nullptr)
+            return;
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(wxGetTranslation(wxString::FromUTF8(bound[i]->hint)));
+        m_status->Update();   // the popup owns the loop; without this the line repaints late
+    }, base, base + 499);   // 499: the mate section starts at base + 500 (see mate_base)
+    menu.Bind(wxEVT_MENU, [this, &bound, base](wxCommandEvent& e) {
+        const int i = e.GetId() - base;
+        if (i >= 0 && i < int(bound.size()) && bound[i])
+            run_offer_action(bound[i]->action);
+    }, base, base + 499);   // 499: the mate section starts at base + 500 (see mate_base)
+    PopupMenu(&menu, ScreenToClient(screen_pos));
+    // PopupMenu is modal, so by here the menu is gone and any command it raised has already run.
+    // A hover ghost that outlived the menu it belonged to would leave the committed bodies hidden
+    // behind a preview nothing can dismiss — bind nothing to the close event, just clean up here.
+    if (mate_ghost) {
+        m_viewport->clear_preview();
+        m_viewport->set_body_hidden(false);
+        m_viewport->request_repaint();
+    }
+}
+
+void DesignPanel::apply_plane_refs(CadFeature& f) const
+{
+    f.plane_type       = (PlaneType)m_plane_type->GetSelection();
+    f.plane_face_body  = m_pl_faceA_body;  f.plane_face  = m_pl_faceA;
+    f.plane_face2_body = m_pl_faceB_body;  f.plane_face2 = m_pl_faceB;
+    f.plane_edge_body  = m_pl_edgeA_body;  f.plane_edge  = m_pl_edgeA;
+    f.plane_edge2_body = m_pl_edgeB_body;  f.plane_edge2 = m_pl_edgeB;
+    f.plane_u_size     = m_plane_usize->GetValue();
+    f.plane_v_size     = m_plane_vsize->GetValue();
+}
+
+void DesignPanel::refresh_plane_labels()
+{
+    auto txt = [](int idx) { return idx >= 0 ? wxString::Format("#%d", idx) : wxString(_L("(none)")); };
+    if (m_plane_faceA_lbl) m_plane_faceA_lbl->SetLabel(txt(m_pl_faceA));
+    if (m_plane_faceB_lbl) m_plane_faceB_lbl->SetLabel(txt(m_pl_faceB));
+    if (m_plane_edgeA_lbl) m_plane_edgeA_lbl->SetLabel(txt(m_pl_edgeA));
+    if (m_plane_edgeB_lbl) m_plane_edgeB_lbl->SetLabel(txt(m_pl_edgeB));
+}
+
+void DesignPanel::reset_plane_refs()
+{
+    m_pl_faceA_body = m_pl_faceA = -1;  m_pl_faceB_body = m_pl_faceB = -1;
+    m_pl_edgeA_body = m_pl_edgeA = -1;  m_pl_edgeB_body = m_pl_edgeB = -1;
+    m_plane_pick = PlanePick::None;
+    if (m_viewport) m_viewport->set_escalate_on_repick(true);   // pick abandoned
+    refresh_plane_labels();
+}
+
+void DesignPanel::arm_plane_pick(PlanePick target)
+{
+    m_plane_pick = target;
+    // While a pick is armed, a click must CAPTURE the face under the cursor, never escalate to
+    // the whole body. Without this, clicking a face that already happens to be selected reads as
+    // a repeat pick, selects the body, and the capture is silently lost — the label stays
+    // "(none)" and the user has no idea why. The capture path below already restores the flag,
+    // and reset_plane_refs() restores it when the pick is abandoned; only the arm side was missing.
+    if (m_viewport) m_viewport->set_escalate_on_repick(false);
+    const bool face = (target == PlanePick::FaceA || target == PlanePick::FaceB);
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(face ? _L("Click a solid FACE in the viewport")
+                            : _L("Click a solid EDGE in the viewport"));
+    m_status->Refresh();
+}
+
+// --- Axis helpers ---
+
+void DesignPanel::apply_axis_refs(CadFeature& f) const
+{
+    f.axis_type = (AxisType)m_axis_type->GetSelection();
+    f.axis_face = m_ax_face;
+    f.axis_edge = m_ax_edge;
+    f.axis_plane_a = m_axis_plane_a->GetSelection();
+    f.axis_plane_b = m_axis_plane_b->GetSelection();
+    f.axis_p1 = Vec3d(m_axis_p1x->GetValue(), m_axis_p1y->GetValue(), m_axis_p1z->GetValue());
+    f.axis_p2 = Vec3d(m_axis_p2x->GetValue(), m_axis_p2y->GetValue(), m_axis_p2z->GetValue());
+    f.axis_body = m_ax_face_body;
+}
+
+void DesignPanel::refresh_axis_labels()
+{
+    auto txt = [](int idx) { return idx >= 0 ? wxString::Format("#%d", idx) : wxString(_L("(none)")); };
+    if (m_axis_face_lbl) m_axis_face_lbl->SetLabel(txt(m_ax_face));
+    if (m_axis_edge_lbl) m_axis_edge_lbl->SetLabel(txt(m_ax_edge));
+}
+
+void DesignPanel::reset_axis_refs()
+{
+    m_ax_face_body = m_ax_face = -1;
+    m_ax_edge = -1;
+    m_axis_pick = AxisPick::None;
+    if (m_viewport) m_viewport->set_escalate_on_repick(true);   // pick abandoned
+    refresh_axis_labels();
+}
+
+void DesignPanel::arm_axis_pick(AxisPick target)
+{
+    m_axis_pick = target;
+    if (m_viewport) m_viewport->set_escalate_on_repick(false);   // same as arm_plane_pick
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(target == AxisPick::Face ? _L("Click a solid FACE in the viewport")
+                                                : _L("Click a solid EDGE in the viewport"));
+    m_status->Refresh();
+}
+
+// --- CoordSys helpers ---
+
+void DesignPanel::apply_coordsys_refs(CadFeature& f) const
+{
+    f.coordsys_type  = (CoordSysType)m_coordsys_type->GetSelection();
+    f.coordsys_point = Vec3d(m_cs_x->GetValue(), m_cs_y->GetValue(), m_cs_z->GetValue());
+    f.coordsys_body  = m_cs_face_body;
+    f.coordsys_face  = m_cs_face;
+    f.coordsys_edge  = m_cs_edge;
+    f.coordsys_x_hint = Vec3d(m_cs_hx->GetValue(), m_cs_hy->GetValue(), m_cs_hz->GetValue());
+}
+
+void DesignPanel::refresh_coordsys_labels()
+{
+    auto txt = [](int idx) { return idx >= 0 ? wxString::Format("#%d", idx) : wxString(_L("(none)")); };
+    if (m_cs_face_lbl) m_cs_face_lbl->SetLabel(txt(m_cs_face));
+    if (m_cs_edge_lbl) m_cs_edge_lbl->SetLabel(txt(m_cs_edge));
+}
+
+void DesignPanel::refresh_cs_body_choice()
+{
+    if (!m_cs_body) return;
+    const int keep = m_cs_body->GetSelection();
+    m_cs_body->Clear();
+    m_cs_body->Append(_L("(all)"));
+    for (size_t b = 0; b < m_doc.bodies.size(); ++b)
+        m_cs_body->Append(wxString::Format(_L("Body %d"), int(b) + 1));
+    const int sel = (keep > 0 && keep < int(m_cs_body->GetCount())) ? keep : 0;
+    m_cs_body->SetSelection(sel);
+    // The combo and the viewport focus are ONE state, so they must not be written separately.
+    // When the body list shrinks, `keep` falls out of range and the selection silently drops to
+    // "(all)" — while the viewport stayed focused on the old index, leaving every other body at
+    // 25% alpha and picking locked to a body that may no longer exist. That is the exact mirror
+    // of the open_tool ordering bug (combo says Body N, viewport opaque); this one says "(all)"
+    // and stays dimmed.
+    //
+    // Guarded on the CoordSys card being the ACTIVE tool because it is the only card that owns
+    // this focus. In the edit path this function runs BEFORE open_tool, with the previous tool
+    // still active, so the guard is false and the caller's explicit set_xray_focus still wins.
+    if (m_viewport != nullptr && m_active == Tool::CoordSys)
+        m_viewport->set_xray_focus(sel - 1);
+}
+
+void DesignPanel::reset_coordsys_refs()
+{
+    m_cs_face_body = m_cs_face = -1;
+    m_cs_edge = -1;
+    m_coordsys_pick = CoordSysPick::None;
+    if (m_viewport) m_viewport->set_escalate_on_repick(true);   // pick abandoned
+    refresh_coordsys_labels();
+    if (m_cs_body) m_cs_body->SetSelection(0);
+    if (m_viewport) m_viewport->set_xray_focus(-1);
+    refresh_cs_body_choice();
+}
+
+void DesignPanel::arm_coordsys_pick(CoordSysPick target)
+{
+    m_coordsys_pick = target;
+    // While this pick is armed the click the card asked for must reach it, so the whole-body
+    // escalation is off: clicking the face the card is pointing at is the ANSWER here, not a
+    // request for its body.
+    if (m_viewport) m_viewport->set_escalate_on_repick(false);
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(target == CoordSysPick::Face ? _L("Click a solid FACE in the viewport")
+                                                    : _L("Click a solid EDGE in the viewport"));
+    m_status->Refresh();
+}
+
+bool DesignPanel::on_add_plane()
+{
+    // Refuse here rather than let the kernel substitute. Every method in CadDocument's plane
+    // dispatch falls back to offset_angle_plane() when its references are missing, so picking
+    // Tangent and confirming with nothing selected used to produce an offset plane reported as
+    // a success — the user asks for one construction and silently receives another. The kernel
+    // keeps its fallback (it must return SOMETHING), but no user gesture should reach it.
+    auto refuse = [this](const wxString& why) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(why);
+        m_status->Refresh();
+    };
+    switch ((PlaneType)m_plane_type->GetSelection()) {
+    case PlaneType::Angle:
+        if (m_pl_edgeA < 0) { refuse(_L("An angled plane needs an edge to tilt about — pick Edge A")); return false; }
+        break;
+    case PlaneType::Midplane:
+        if (m_pl_faceA < 0 || m_pl_faceB < 0) { refuse(_L("A midplane needs two faces — pick Face A and Face B")); return false; }
+        if (m_pl_faceA == m_pl_faceB && m_pl_faceA_body == m_pl_faceB_body) {
+            // Well-defined but useless: the midplane of a face with itself is that same face.
+            refuse(_L("Face A and Face B are the same face — a midplane needs two different faces"));
+            return false;
+        }
+        break;
+    case PlaneType::Tangent:
+        // The face must also be cylindrical; that check stays in the kernel, which has the geometry.
+        if (m_pl_faceA < 0) { refuse(_L("A tangent plane needs a cylindrical face — pick Face A")); return false; }
+        break;
+    case PlaneType::TwoEdges:
+        if (m_pl_edgeA < 0 || m_pl_edgeB < 0) { refuse(_L("This plane needs two edges — pick Edge A and Edge B")); return false; }
+        break;
+    default:
+        break;   // Offset and Coincident are meaningful with no reference: they use the base plane
+    }
+
+    m_feature_counter++;
+    int idx = m_doc.add_plane(m_plane_base->GetSelection(), m_plane_offset->GetValue(),
+                    m_plane_tilt->GetValue(), m_plane_tilt_axis->GetSelection(),
+                    "Plane" + std::to_string(m_feature_counter));
+    if (idx >= 0 && idx < int(m_doc.features.size())) apply_plane_refs(m_doc.features[idx]);
+    m_doc.recompute();   // datum-only docs yield no body; that is expected/benign
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(_L("Plane added — pick it as a sketch plane"));
+    refresh_tree();
+    return true;
+}
+
+void DesignPanel::on_add_axis()
+{
+    m_feature_counter++;
+    int idx = m_doc.add_axis((AxisType)m_axis_type->GetSelection(),
+                             "Axis" + std::to_string(m_feature_counter));
+    if (idx >= 0 && idx < int(m_doc.features.size())) apply_axis_refs(m_doc.features[idx]);
+    m_doc.recompute();
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(_L("Axis added"));
+    refresh_tree();
+}
+
+void DesignPanel::on_add_coordsys()
+{
+    m_feature_counter++;
+    Vec3d pt(m_cs_x->GetValue(), m_cs_y->GetValue(), m_cs_z->GetValue());
+    int idx = m_doc.add_coordsys((CoordSysType)m_coordsys_type->GetSelection(), pt,
+                                 "Coord" + std::to_string(m_feature_counter));
+    if (idx >= 0 && idx < int(m_doc.features.size())) apply_coordsys_refs(m_doc.features[idx]);
+    m_doc.recompute();
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(_L("Coord Sys added"));
+    refresh_tree();
+}
+
+void DesignPanel::on_add_shell()
+{
+    if (m_doc.body.IsNull()) {
+        set_status(_L("Shell needs a solid body — add or import one first"));
+        return;
+    }
+    const int face = (m_sel_solid_face >= 0) ? m_sel_solid_face : -1;
+
+    m_feature_counter++;
+    m_doc.add_shell(m_shell_thickness->GetValue(), face, m_sel_solid_body,
+                    "Shell" + std::to_string(m_feature_counter));
+
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+
+    refresh_tree();
+}
+
+void DesignPanel::on_add_draft()
+{
+    if (m_doc.body.IsNull()) {
+        set_status(_L("Draft needs a solid body — add or import one first"));
+        return;
+    }
+    if (m_sel_solid_face < 0) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Draft needs a picked face — click a side face first"));
+        m_status->Refresh();
+        return;
+    }
+
+    m_feature_counter++;
+    m_doc.add_draft(m_draft_angle->GetValue(), m_sel_solid_face, m_sel_solid_body,
+                    "Draft" + std::to_string(m_feature_counter));
+
+    if (!recompute_guarded(_L("Rebuilding model…")))
+        set_status(_L("Recompute error: ") + wxString::FromUTF8(m_doc.error));
+    else
+        set_status_ok();
+
+    refresh_tree();
+}
+
+int DesignPanel::tree_icon_for(CadFeatureType t)
+{
+    switch (t) {
+    case CadFeatureType::Sketch:  return 0;
+    case CadFeatureType::Extrude: return 1;
+    case CadFeatureType::Fillet:
+    case CadFeatureType::Chamfer: return 2;
+    case CadFeatureType::Hole:    return 3;
+    case CadFeatureType::Thread:  return 4;
+    case CadFeatureType::Shell:   return 5;
+    case CadFeatureType::Revolve: return 1;
+    case CadFeatureType::Sweep:   return 1;
+    case CadFeatureType::Pattern: return 1;
+    case CadFeatureType::Plane:   return 0;   // datum plane: sketch-family icon
+    case CadFeatureType::Loft:    return 1;
+    case CadFeatureType::Draft:   return 5;   // dressup-family icon
+    case CadFeatureType::Import:  return 1;   // imported solid: solid-family icon
+    case CadFeatureType::Boolean: return 1;   // body-body combine: solid-family icon
+    case CadFeatureType::Cut:     return 1;   // plane split: solid-family icon
+    case CadFeatureType::Axis:    return 0;   // datum axis: sketch-family icon
+    case CadFeatureType::CoordSys: return 0;  // datum coord sys: sketch-family icon
+    case CadFeatureType::SurfaceExtrude:  return 1;
+    case CadFeatureType::SurfaceRevolve:  return 1;
+    case CadFeatureType::SurfaceLoft:     return 1;
+    case CadFeatureType::SurfaceFill:     return 1;
+    case CadFeatureType::ThickenSurface:  return 1;
+    case CadFeatureType::SurfaceOffset:   return 1;
+    case CadFeatureType::Transform:       return 1;   // solid-family icon
+    case CadFeatureType::Mirror:          return 1;   // solid-family icon
+    case CadFeatureType::Thicken:         return 1;   // solid-family icon
+    case CadFeatureType::Rib:             return 1;   // solid-family icon
+    case CadFeatureType::Project:         return 0;   // sketch-family icon (produces sketch)
+    case CadFeatureType::DeleteFace:      return 5;   // dressup-family icon
+    case CadFeatureType::Helix:           return 4;   // thread-family icon (curve)
+    case CadFeatureType::Mate:            return 2;   // dressup-family icon (assembly)
+    }
+    return 0;
+}
+
+// The reason detect_mate_conflicts() recorded for this feature, or nullptr. A linear scan: an
+// assembly has a handful of mates and at most that many conflicts, so a map would cost more to
+// build than the scans it saves.
+const std::string* DesignPanel::mate_conflict_reason(int feature) const
+{
+    for (const auto& c : m_doc.mate_conflicts)
+        if (c.first == feature) return &c.second;
+    return nullptr;
+}
+
+// What to say when nothing is selected and no tool is open. Lives in one place because it is
+// needed from two: after an edit empties the document, and at startup — where after_tree_edit()
+// has never run, which is exactly why a fresh tab used to show a blank line.
+wxString DesignPanel::idle_hint() const
+{
+    return m_doc.features.empty()
+        ? _L("Nothing yet — import a STEP or a mesh from the toolbar,\n"
+             "or click a reference plane and right-click it to start a sketch.")
+        : _L("No solid yet — select a sketch and right-click it to Extrude.");
+}
+
+// The Design tab is no longer the visible page (dlj). The status line is a popup floating
+// over the GL canvas, so it does NOT go away when this page does — it stayed up over Prepare and
+// over the home screen, still reading like a live Design selection ("selected (whole body) —
+// right-click for what applies to it") on a tab that has no such selection and no such menu.
+// Nothing else in the panel needs to know: the popup keeps its text and comes straight back.
+void DesignPanel::on_tab_hidden()
+{
+    if (m_viewport) {
+        m_viewport->show_status_hud(false);
+        m_viewport->leave_viewport();   // hand the shared camera back to the editor tabs
+    }
+}
+
+void DesignPanel::on_tab_shown()
+{
+    if (m_viewport) {
+        m_viewport->show_status_hud(true);   // ...and back on the way in
+        m_viewport->enter_viewport();        // borrow the shared camera; on_tab_hidden gives it back
+    }
+
+    if (m_active == Tool::None && m_doc.display_mesh.its.indices.empty())
+        set_status(idle_hint());   // first paint: the tab has never been edited
+
+    if (m_viewport) m_viewport->refresh_bed();
+
+    // Modeling origin = bed centre, set BEFORE any recompute/datum-resolve so sketches and datums
+    // land in the middle of the bed (not the bed corner = world 0).
+    if (Plater* pl = wxGetApp().plater()) {
+        const Vec2d bc = pl->build_volume().bed_center();
+        m_doc.modeling_origin = Vec3d(bc.x(), bc.y(), 0.0);
+    }
+
+    // Rehydrate the parametric model from a freshly loaded project (the 3MF carried the
+    // recipe in Metadata/orca_cad.bin). Only when nothing is in progress here, so we
+    // never clobber an active design when the user just toggles back to the Design tab.
+    if (m_doc.features.empty()) {
+        if (Plater* plater = wxGetApp().plater()) {
+            const std::string& blob = plater->model().cad_recipe;
+            if (!blob.empty()) load_recipe(blob);
+        }
+    }
+    update_reference_planes();   // entering the Design tab: show the XY/XZ/YZ planes if no object yet
+    sync_sidebar_width();        // keep the panel as wide as Prepare's so the canvas edge doesn't jump
+    if (m_viewport) m_viewport->force_repaint();   // the page was just re-shown: paint it for real
+}
+
+// Application close / language switch, from the plater's canvas teardown.
+void DesignPanel::unbind_canvas_event_handlers()
+{
+    if (m_viewport) m_viewport->unbind_canvas_event_handlers();
+}
+
+void DesignPanel::reset_canvas_volumes()
+{
+    if (m_viewport) m_viewport->reset_canvas_volumes();
+}
+
+// Match Prepare's sidebar width instead of hardcoding one. Design used a fixed 264 px against
+// Prepare's ~467, so the canvas edge jumped sideways on every tab switch; reading the live width
+// also means the two stay aligned if Orca ever changes its sidebar.
+void DesignPanel::sync_sidebar_width()
+{
+    if (m_form == nullptr) return;
+    Plater* pl = wxGetApp().plater();
+    if (pl == nullptr) return;
+    const int w = pl->sidebar().GetSize().GetWidth();
+    if (w < 200) return;                       // sidebar not laid out yet — keep what we have
+    if (m_form->GetMinSize().GetWidth() == w) return;
+    m_form->SetMinSize(wxSize(w, -1));
+    Layout();
+}
+
+void DesignPanel::load_recipe(const std::string& blob)
+{
+    if (blob.empty()) return;
+    if (!m_doc.deserialize_recipe(blob)) {
+        // Carry the kernel's reason. deserialize_recipe distinguishes three cases that matter
+        // very differently to the person reading this — saved by a NEWER build, saved by an
+        // OLDER one, or genuinely unreadable — and replacing all three with one sentence left
+        // the user unable to tell "update OrcaSlicer" from "your file is damaged". Same
+        // error-loss class as the 31 McpControl sites (1de72de9ed): the message exists, it was
+        // simply not passed on.
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(m_doc.error.empty()
+                   ? _L("Could not restore the CAD model from this project")
+                   : _L("Could not restore the CAD model: ") + wxString::FromUTF8(m_doc.error));
+        m_status->Refresh();
+        return;
+    }
+    m_feature_counter = int(m_doc.features.size());
+    feed_bodies();    // push the restored bodies into the viewport
+    refresh_tree();   // rebuild the feature tree from the restored recipe
+    set_status_ok();
+}
+
+void DesignPanel::refresh_tree()
+{
+    // The recipe mirrors the FEATURE LIST, and this is the moment the feature list changed —
+    // every add, delete, reorder, rename and suppression ends here to redraw the tree. Putting
+    // the sync in recompute_guarded instead tied it to "a solid was built", and CadDocument::
+    // recompute() returns FALSE for a document that has no solid ("no solid-producing features",
+    // CadDocument.cpp) — which is precisely a document the user has only drawn sketches in. So
+    // drawing a profile, pressing Confirm and saving wrote a 3MF with no orca_cad.bin in it
+    // at all, and the app reported success: the whole design was gone on reopen (mtav).
+    // The three sites that say "a lone sketch yields an empty body; that is expected" call
+    // m_doc.recompute() directly and so never reached the sync either. One hook here covers all
+    // of them, including the live sketch tool's own commit path.
+    //
+    // ONLY when the document has something in it. sync_recipe_to_model() CLEARS the blob for an
+    // empty document, and the tree is also refreshed while the Design tab is still empty — before
+    // the deferred load at on_show() has had the chance to read the blob the project arrived
+    // with. Clearing there would destroy the recipe of every project being opened. Deleting the
+    // last feature still clears it, through the tree-edit call site that always did.
+    if (!m_doc.features.empty()) sync_recipe_to_model();
+
+    // Preserve the selected row across the rebuild — wxTreeCtrl::DeleteAllItems
+    // drops the selection, which made every edit/add feel like it "lost" the
+    // selection (and broke Edit/Move/Delete on the just-touched feature).
+    const int keep = tree_selection();
+
+    m_tree->DeleteAllItems();
+    m_tree_items.clear();
+    m_tree_body_items.clear();
+    wxTreeItemId root = m_tree->AddRoot("root");
+    // Datum/reference planes carry no solid; feed them to the viewport so they render as
+    // translucent rectangles (otherwise a Plane feature is invisible in the canvas).
+    refresh_datum_planes();
+    update_reference_planes();   // body added/removed -> show/hide the XY/XZ/YZ origin planes
+    for (size_t fi = 0; fi < m_doc.features.size(); ++fi) {
+        const CadFeature& f = m_doc.features[fi];
+        const int img = tree_icon_for(f.type);
+        wxTreeItemId id = m_tree->AppendItem(root, wxString::FromUTF8(f.name), img, img);
+        // Three states, in this order of precedence:
+        //   disabled  -> dim. A SUPPRESSED mate is the user's answer to a conflict, so it must
+        //                read as suppressed rather than keep shouting about the conflict.
+        //   conflict  -> warn. detect_mate_conflicts() refills m_doc.mate_conflicts on every
+        //                recompute; the mark goes on the row that carries it, because the tree
+        //                is where the user is already looking for which feature to change.
+        //   otherwise -> normal.
+        // A conflict is NOT a document error — the document still evaluates — so the row is
+        // marked and never hidden, and the reason goes to the status line on selection rather
+        // than into a modal that interrupts without offering an action.
+        m_tree->SetItemTextColour(id, !f.enabled                            ? dp_item_dim()
+                                    : mate_conflict_reason(int(fi)) != nullptr ? wxColour(235, 110, 110)
+                                                                               : dp_item_text());
+        m_tree_items.push_back(id);
+    }
+    refresh_parts();   // bodies live in their own list below the tree, never clipped by history
+    if (keep >= 0 && keep < int(m_tree_items.size()))
+        m_tree->SelectItem(m_tree_items[keep]);
+
+    // Size the tree to its content (clamped) so it doesn't waste a fixed-height block when
+    // there are few features, and scrolls internally past ~9 rows instead of growing forever.
+    const int rows  = int(m_tree_items.size());   // bodies are in their own list now
+    const int rowH  = std::max(m_tree->GetCharHeight() + 8, 20);
+    const int shown = std::min(std::max(rows, 1), 9);
+    const wxSize ts(-1, shown * rowH + 8);
+    m_tree->SetMinSize(ts);
+    m_tree->SetMaxSize(ts);
+    if (m_form && m_form->GetSizer()) { update_cards_frame(); m_form->Layout(); m_form->FitInside(); }
+}
+
+// Rebuild the Parts list from the document's bodies, preserving the selected row so a
+// recompute (fillet, hole, ...) doesn't drop the user's body selection under them.
+void DesignPanel::refresh_parts()
+{
+    if (m_parts == nullptr) return;
+    const int keep = tree_body_selection();
+
+    m_parts->DeleteAllItems();
+    m_tree_body_items.clear();
+    wxTreeItemId proot = m_parts->AddRoot("root");
+
+    sync_body_visible();   // keep flags parallel before reading them for the row colour
+    for (size_t b = 0; b < m_doc.bodies.size(); ++b) {
+        // "Body N" keeps the positional identity every status line and message uses ("Body 2
+        // selected", the interference report), and the NAME follows it because that is the part
+        // a rename can change: a body's name is derived from the feature that produced it, so
+        // renaming through this row and seeing the label sit unchanged at "Body 1" would read as
+        // a rename that did nothing.
+        const bool vis = b >= m_body_visible.size() || m_body_visible[b];
+        // The user's name wins over the derived one (the maker's name, restamped every
+        // recompute); "Body N" still leads, because every status line, the interference report
+        // and the mate errors identify a body by its number.
+        const wxString bname = m_doc.bodies[b].has_user_name
+                             ? wxString::FromUTF8(m_doc.bodies[b].user_name)
+                             : wxString::FromUTF8(m_doc.bodies[b].name);
+        wxTreeItemId id = m_parts->AppendItem(proot,
+            bname.IsEmpty() ? wxString::Format(_L("Body %zu"), b + 1)
+                            : wxString::Format(_L("Body %zu — %s"), b + 1, bname));
+        // Hidden bodies are greyed so the show/hide state reads at a glance (eye toggle).
+        m_parts->SetItemTextColour(id, vis ? dp_item_text() : dp_item_dim());
+        m_tree_body_items.push_back(id);
+    }
+
+    // Hide the whole block until there is something to list, so an empty document doesn't
+    // show a stray empty box.
+    const bool any = !m_tree_body_items.empty();
+    m_parts->Show(any);
+    if (m_parts_label) m_parts_label->Show(any);
+    if (m_parts_hdr)   m_parts_hdr->ShowItems(any);   // icon + title live in this sizer
+    if (m_parts_rule)  m_parts_rule->Show(any);
+    // ...and the frame with it, or an empty bordered box floats there.
+    if (m_parts_box && m_form && m_form->GetSizer()) m_form->GetSizer()->Show(m_parts_box, any, false);
+
+    if (any) {
+        const int rowH  = std::max(m_parts->GetCharHeight() + 8, 20);
+        const int shown = std::min(int(m_tree_body_items.size()), 6);   // scrolls past 6
+        const wxSize ps(-1, shown * rowH + 8);
+        m_parts->SetMinSize(ps);
+        m_parts->SetMaxSize(ps);
+        if (keep >= 0 && keep < int(m_tree_body_items.size()))
+            m_parts->SelectItem(m_tree_body_items[keep]);
+    }
+    if (m_form && m_form->GetSizer()) { update_cards_frame(); m_form->Layout(); m_form->FitInside(); }
+}
+
+int DesignPanel::tree_body_selection() const
+{
+    if (m_parts == nullptr) return -1;
+    const wxTreeItemId sel = m_parts->GetSelection();
+    if (!sel.IsOk()) return -1;
+    for (size_t i = 0; i < m_tree_body_items.size(); ++i)
+        if (m_tree_body_items[i] == sel) return int(i);
+    return -1;
+}
+
+void DesignPanel::update_section_flip_btn()
+{
+    if (m_section_flip_btn) m_section_flip_btn->Enable(m_section_on);
+}
+
+void DesignPanel::toggle_section_view()
+{
+    if (!m_viewport) return;
+    m_section_on = !m_section_on;
+    m_status->SetForegroundColour(wxNullColour);
+    if (m_section_on) {
+        m_section_cut_z = m_viewport->model_mid_z();   // start at the model's mid-height
+        m_section_upper = false;                       // keep the lower half by default
+        m_viewport->set_section_plane(true, m_section_cut_z, m_section_upper);
+        set_status(_L("Section view on — hides half the model to see inside; "
+                              "PageUp / PageDown move the plane, Flip shows the other half"));
+    } else {
+        m_viewport->set_section_plane(false, 0.0);
+        set_status(_L("Section view off"));
+    }
+    m_status->Refresh();
+    update_section_flip_btn();
+}
+
+void DesignPanel::flip_section_view()
+{
+    if (!m_viewport || !m_section_on) return;
+    m_section_upper = !m_section_upper;
+    m_viewport->set_section_plane(true, m_section_cut_z, m_section_upper);
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(wxString::Format(_L("Section view — showing the %s half"),
+        m_section_upper ? _L("upper") : _L("lower")));
+    m_status->Refresh();
+}
+
+void DesignPanel::sync_body_visible()
+{
+    // Keep the visibility vector parallel to bodies; newly-created bodies default visible.
+    // Bodies are appended in feature order, so existing indices keep their flag on resize.
+    m_body_visible.resize(m_doc.bodies.size(), true);
+}
+
+void DesignPanel::sync_body_xform()
+{
+    // Parallel to bodies; new bodies default to identity (no move). Stable on resize.
+    m_body_xform.resize(m_doc.bodies.size(), Transform3d::Identity());
+}
+
+// Build the display + pick meshes with each body's Move transform applied. The pick mesh is
+// re-merged from the transformed per-body meshes IN THE SAME body order as tessellate_bodies,
+// so display_tri_face/display_tri_body stay aligned. m_disp_pick_mesh keeps a stable address —
+// the tool holds a pointer to it, so an in-place rebuild updates picking without re-pointing.
+void DesignPanel::rebuild_disp_meshes()
+{
+    sync_body_visible();
+    sync_body_xform();
+    const std::vector<TriangleMesh>& src = m_doc.display_body_meshes;
+
+    bool any = false;
+    for (const Transform3d& t : m_body_xform)
+        if (!t.isApprox(Transform3d::Identity())) { any = true; break; }
+
+    if (!any) {                          // no body moved: identical to the untransformed meshes
+        m_disp_body_meshes = src;
+        m_disp_pick_mesh   = m_doc.display_mesh;
+        return;
+    }
+
+    m_disp_body_meshes.clear();
+    m_disp_body_meshes.reserve(src.size());
+    m_disp_pick_mesh = TriangleMesh{};
+    for (size_t b = 0; b < src.size(); ++b) {
+        TriangleMesh m = src[b];
+        if (b < m_body_xform.size()) m.transform(m_body_xform[b]);
+        m_disp_pick_mesh.merge(m);       // same order as tessellate_bodies -> tri_* stay aligned
+        m_disp_body_meshes.push_back(std::move(m));
+    }
+}
+
+void DesignPanel::feed_bodies()
+{
+    // The body count just changed, so the tools that consume a body may have become reachable or
+    // unreachable. Before the early return below: the gating is about the toolbar, not the canvas.
+    update_body_gates();
+    // Rebuild the transformed meshes first so every display-refresh path (recompute, tint,
+    // visibility, live move) shows the bodies at their current Move offsets. The solid-pick
+    // keeps a STABLE pointer to m_disp_pick_mesh / m_body_visible / m_body_xform (rebuilt in
+    // place), so it needs no re-call here — the whole/face/edge selection survives a move drag.
+    if (m_viewport == nullptr) return;
+    rebuild_disp_meshes();
+    m_viewport->set_bodies(m_disp_body_meshes, m_body_visible);
+}
+
+// Boolean (combine bodies) — one gate for every door onto the tool. A body-body operation
+// needs two solids, and saying so in one place means the toolbar button, its Shift+B binding
+// and the Bodies card cannot drift apart on what "available" means.
+void DesignPanel::on_boolean_tool()
+{
+    if (m_doc.bodies.size() < 2) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Boolean needs two bodies — create or import a second solid"));
+        m_status->Refresh();
+        return;
+    }
+    populate_body_choices();
+    open_tool(Tool::Boolean);
+}
+
+void DesignPanel::on_move_body()
+{
+    const int b = m_sel_solid_body;
+    if (m_viewport == nullptr) return;
+    if (b < 0 || b >= int(m_doc.display_body_meshes.size())) {
+        // Never fail silently here: the caller gates on bodies.size() while this needs a
+        // tessellated per-body mesh, and when those disagreed the click did nothing at all.
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(b < 0 ? _L("Select a body first — click it in the viewport or the Bodies list")
+                                 : _L("That body has no display mesh yet — recompute first"));
+        m_status->Refresh();
+        return;
+    }
+    sync_body_xform();
+    // Delta gizmo: pivot at the body's CURRENT world centroid; the tool composes the drag deltas
+    // onto its current pose, so move + rotate both work (incl. on an already place-on-face'd body).
+    const Transform3d base = m_body_xform[b];
+    const BoundingBoxf3 bb = m_doc.display_body_meshes[b].bounding_box();
+    const Vec3d pivot = base * bb.center();
+    // Bounding-sphere radius (world): the gizmo scales with it so the rotation rings sit clear of
+    // the body instead of collapsing into a tangle inside it — same sizing rule as Orca's Prepare
+    // gizmos. The scale part of `base` is applied so a scaled body still gets a correct radius.
+    const double radius = (base.linear() * (bb.size() * 0.5)).norm();
+    m_viewport->begin_move_body(b, pivot, base, radius);
+    m_move_body = b;          // for the action bar: Cancel reverts to this pose
+    m_move_prev = base;
+    // Reset the numeric fields to "no change" and show the card beside the drag gizmo.
+    if (m_move_dx) m_move_dx->SetValue(0.0);
+    if (m_move_dy) m_move_dy->SetValue(0.0);
+    if (m_move_dz) m_move_dz->SetValue(0.0);
+    if (m_move_angle) m_move_angle->SetValue(0.0);
+    show_move_card(true);
+    update_action_bar();      // surface the unified ✓/✗ while moving
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(_L("Drag the arrows to move, the rings to rotate — then Confirm (Esc cancels)"));
+    m_status->Refresh();
+}
+
+// Transform card (add mode): arm the same move gizmo on the card's body so the geometry-first
+// control is what the user drags, while the card's numeric fields mirror the result. The card
+// stays visible as the typed half — the gizmo owns the drag, the fields own the numbers.
+void DesignPanel::arm_transform_gizmo()
+{
+    int b = tree_body_selection();
+    if (b < 0) b = m_sel_solid_body;
+    if (b < 0 && m_xf_body) b = m_xf_body->GetSelection();
+    if (b < 0 || b >= int(m_doc.display_body_meshes.size())) return;   // card alone still works
+    if (m_xf_body && b < int(m_xf_body->GetCount())) m_xf_body->SetSelection(b);   // feature must be created against the gizmo's body
+    sync_body_xform();
+    const Transform3d base = m_body_xform[b];
+    const BoundingBoxf3 bb = m_doc.display_body_meshes[b].bounding_box();
+    const Vec3d pivot = base * bb.center();
+    const double radius = (base.linear() * (bb.size() * 0.5)).norm();
+    if (m_viewport) m_viewport->begin_move_body(b, pivot, base, radius);
+    m_xf_gizmo_body = b;
+    m_xf_gizmo_base = base;
+    m_move_body = b;          // the existing revert paths key off these two
+    m_move_prev = base;
+    // Write the pivot into the card so the parametric feature reproduces what was dragged;
+    // dx/dy/dz and angle start at zero (the gizmo reports deltas from this pose).
+    if (m_xf_pivot_x) m_xf_pivot_x->SetValue(pivot.x());
+    if (m_xf_pivot_y) m_xf_pivot_y->SetValue(pivot.y());
+    if (m_xf_pivot_z) m_xf_pivot_z->SetValue(pivot.z());
+    if (m_xf_dx) m_xf_dx->SetValue(0.0);
+    if (m_xf_dy) m_xf_dy->SetValue(0.0);
+    if (m_xf_dz) m_xf_dz->SetValue(0.0);
+    if (m_xf_angle) m_xf_angle->SetValue(0.0);
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(_L("Drag the arrows to move, the rings to rotate — the numbers follow"));
+    m_status->Refresh();
+}
+
+// Color tool: open a colour picker on the selected body and store a per-body display-colour
+// override on its CadBody. The override is carried across recompute() by body index and is
+// read back by DesignCanvas::body_color()/reload(), so the body keeps its colour through edits.
+void DesignPanel::on_set_body_color()
+{
+    // Same body-selection source Move / visibility use: the Parts-list row first, falling
+    // back to the in-canvas picked solid so either selection path works.
+    int b = tree_body_selection();
+    if (b < 0) b = m_sel_solid_body;
+    if (b < 0 || b >= int(m_doc.bodies.size())) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Select a body first"));
+        m_status->Refresh();
+        return;
+    }
+
+    // Seed the picker with the body's current effective colour (override or auto palette).
+    const ColorRGBA cur = (m_viewport != nullptr) ? m_viewport->body_color(b)
+                                                  : m_doc.bodies[b].color;
+    wxColourData data;
+    data.SetColour(wxColour(cur.r_uchar(), cur.g_uchar(), cur.b_uchar()));
+    wxColourDialog dlg(this, &data);
+    if (dlg.ShowModal() != wxID_OK) return;
+
+    const wxColour picked = dlg.GetColourData().GetColour();
+    m_doc.bodies[b].has_color = true;
+    m_doc.bodies[b].color = ColorRGBA((unsigned char)picked.Red(), (unsigned char)picked.Green(),
+                                      (unsigned char)picked.Blue(), (unsigned char)255);
+    feed_bodies();   // same refresh path the visibility toggle uses → viewport updates immediately
+
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(wxString::Format(_L("Body %d colour set"), b + 1));
+    m_status->Refresh();
+}
+
+// Prepare's "Place on Face" (F), ported to Design. Pick a body face, then this rotates the
+// body so that face's outward normal points straight down (-Z) and drops it onto the bed —
+// Orca's exact math (Selection::flattening_rotate). Writes the per-body display transform
+// m_body_xform (baked into the mesh at Commit), like the Move gizmo; no shape mutation.
+// Returns false (with a hint) when no body face is selected, so the F key can fall through.
+bool DesignPanel::place_on_face()
+{
+    const int b = m_sel_solid_body;
+    if (b < 0 || b >= int(m_doc.bodies.size()) || m_sel_solid_face < 0
+        || b >= int(m_doc.display_body_meshes.size())) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Click a face on the solid, then press F"));
+        m_status->Refresh();
+        return false;
+    }
+    const TopoDS_Face face = GeometryEngine::face_by_index(m_doc.bodies[b].shape, m_sel_solid_face);
+    if (face.IsNull()) return false;
+    sync_body_xform();
+    const Transform3d old_x = m_body_xform[b];
+    // Outward face normal in the body's CURRENT displayed orientation.
+    const Vec3d n = (old_x.linear() * GeometryEngine::face_normal_world(face)).normalized();
+    if (!n.allFinite() || n.norm() < 0.5) return false;
+    // Align that normal with the down vector (-Z): the face ends up on the bed.
+    const Transform3d R(Eigen::Quaterniond().setFromTwoVectors(n, -Vec3d::UnitZ()));
+    // Rotate about the body's current world centroid so it spins in place, not about the origin.
+    const Vec3d c = old_x * m_doc.display_body_meshes[b].bounding_box().center();
+    Transform3d x = Eigen::Translation3d(c) * R * Eigen::Translation3d(-c) * old_x;
+    // Drop the re-oriented body so its lowest point sits on the bed (min Z -> 0).
+    TriangleMesh probe = m_doc.display_body_meshes[b];
+    probe.transform(x);
+    x = Transform3d(Eigen::Translation3d(0.0, 0.0, -probe.bounding_box().min.z())) * x;
+    m_body_xform[b] = x;
+    set_status_ok();   // rebuild display/pick meshes, re-point picking; resets face selection
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(_L("Placed on face — body laid flat on the bed"));
+    m_status->Refresh();
+    return true;
+}
+
+int DesignPanel::tree_selection() const
+{
+    const wxTreeItemId sel = m_tree->GetSelection();
+    if (!sel.IsOk()) return wxNOT_FOUND;
+    for (size_t i = 0; i < m_tree_items.size(); ++i)
+        if (m_tree_items[i] == sel) return int(i);
+    return wxNOT_FOUND;
+}
+
+void DesignPanel::set_tree_selection(int row)
+{
+    if (row >= 0 && row < int(m_tree_items.size()))
+        m_tree->SelectItem(m_tree_items[row]);
+}
+
+void DesignPanel::after_tree_edit(bool ok)
+{
+    update_undo_redo_buttons();
+    refresh_tree();
+    refresh_variables();
+    if (!ok) {
+        // The edit was rolled back (recompute failed); the body is unchanged.
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Edit rejected: ") + wxString::FromUTF8(m_doc.error));
+        m_status->Refresh();
+        return;
+    }
+    sync_recipe_to_model();   // deletes, reorders and suppressions change the document too
+    m_status->SetForegroundColour(wxNullColour);
+    if (m_doc.display_mesh.its.indices.empty()) {
+        if (m_viewport != nullptr) m_viewport->clear_mesh();
+        sync_sketch_display();   // empty body: show any un-consumed committed sketch
+        // An empty document used to blank this line — no guidance at the one moment a newcomer
+        // has none. Name the three real ways in, in the order they are reachable on screen.
+        set_status(idle_hint());
+    } else {
+        // nde #19/20: a delete/reorder that leaves bodies behind must re-feed the per-body
+        // GLVolumes — otherwise the viewport keeps showing the pre-edit solid (the deleted
+        // feature's artifact lingered). feed_bodies() is idempotent for the edit/replace path.
+        if (m_viewport != nullptr) feed_bodies();
+        set_status_ok();
+    }
+    // Force a frame: under software GL (llvmpipe on the :10 test box) reload()'s scheduled
+    // Refresh() is dropped, so a deleted solid stayed on screen until the next orbit.
+    if (m_viewport != nullptr) m_viewport->request_repaint();
+    m_status->Refresh();
+}
+
+// Erase the whole document (every feature + body) and start fresh. The single "wipe" the
+// feature tree's per-row Delete can't give you — also the way out when a body has no
+// removable owning feature.
+void DesignPanel::on_new_design()
+{
+    if (m_doc.features.empty() && m_doc.bodies.empty()) { set_status_ok(); return; }
+    wxMessageDialog dlg(this,
+        _L("Erase all features and bodies and start a new design? This cannot be undone."),
+        _L("New Design"), wxYES_NO | wxICON_EXCLAMATION);
+    if (dlg.ShowModal() != wxID_YES) return;
+    clear_document();
+}
+
+// The teardown behind New Design, without the confirmation. Also what New Project / Open
+// Project run through Plater::priv::reset: the document lives here rather than in the Model,
+// so without this it survives the project that produced it and the next Design edit writes
+// the previous project's feature tree into the new one.
+void DesignPanel::clear_document()
+{
+    tool_cancel();                 // leave any active tool / sketch / constrain cleanly
+    m_doc.clear();                 // features + bodies + meshes + history
+    m_edit_index = -1;
+    m_move_body  = -1;
+    show_move_card(false);
+    m_body_xform.clear();
+    if (m_viewport) { m_viewport->clear_move_gizmo(); m_viewport->clear_mesh(); }
+    after_tree_edit(true);         // rebuild the (now empty) tree + clear the viewport
+    update_action_bar();
+    set_status_ok();
+}
+
+// The verb the offer names when you point at a body, or at any face/edge/vertex of one. A body
+// is a recomputed RESULT, so what actually gets deleted is the feature that created it
+// (CadBody::source_feature). That is an edit to the recipe and can take other features with it,
+// so it asks first and NAMES the feature: a body disappearing from the viewport is not by itself
+// evidence of which feature went, and this is the one action here that cannot be eyeballed.
+void DesignPanel::on_delete_body()
+{
+    const int nb = int(m_doc.bodies.size());
+    if (m_sel_solid_body < 0 || m_sel_solid_body >= nb) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Select a body first"));
+        m_status->Refresh();
+        return;
+    }
+    const int src = m_doc.bodies[m_sel_solid_body].source_feature;
+    if (src < 0 || src >= int(m_doc.features.size())) {
+        // Only reachable for a body no feature claims — a stale recipe, or a feature type that
+        // broke the "never replace a whole CadBody" invariant recompute() relies on.
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("This body has no feature to delete — use New Design to start over"));
+        m_status->Refresh();
+        return;
+    }
+    const std::string& raw = m_doc.features[src].name;
+    const wxString fname = raw.empty() ? wxString::Format(_L("feature %d"), src + 1)
+                                       : wxString::FromUTF8(raw);
+    if (wxMessageBox(wxString::Format(
+                         _L("Delete %s?\n\nThat is the feature this body was made from. "
+                            "Features built on it may be removed or stop working."), fname),
+                     _L("Delete body"), wxYES_NO | wxNO_DEFAULT | wxICON_QUESTION, this) != wxYES)
+        return;
+    // A card left open over a feature that is about to vanish goes stale — same reason
+    // on_delete_feature() closes it.
+    if (m_active != Tool::None || m_edit_index >= 0) {
+        reset_edit_state();
+        close_tool();
+    }
+    m_doc.checkpoint();   // undo boundary: deleting a body's feature
+    m_sel_solid_body = m_sel_solid_face = m_sel_solid_edge = -1;   // the selection is about to
+    m_sel_solid_vertex = false;                                    // name a body that is gone
+    after_tree_edit(m_doc.remove_feature(src));
+}
+
+void DesignPanel::on_delete_feature()
+{
+    // A Body row has no directly-removable feature (bodies are recomputed results); guide the
+    // user to delete the feature that created it, or use New Design to wipe everything.
+    if (tree_body_selection() >= 0) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Select the FEATURE that created this body (or use New Design)"));
+        m_status->Refresh();
+        return;
+    }
+    int sel = tree_selection();
+    if (sel == wxNOT_FOUND) {
+        set_status(_L("Select a feature in the tree first"));
+        m_status->Refresh();
+        return;
+    }
+    // If a feature dialog is open (e.g. the feature is being edited), dismiss it first —
+    // otherwise the deleted feature's settings card lingers in the left panel, out of sync
+    // with the tree. reset_edit_state() drops the stale m_edit_index; close_tool() hides the card.
+    if (m_active != Tool::None || m_edit_index >= 0) {
+        reset_edit_state();
+        close_tool();
+    }
+    m_doc.checkpoint();   // undo boundary: deleting a feature
+    after_tree_edit(m_doc.remove_feature(sel));
+}
+
+void DesignPanel::on_toggle_visibility()
+{
+    // A selected Body row toggles that body's visibility (per-body show/hide). The solid
+    // stays in the document; only its GLVolume + pickability flip. Falls through to the
+    // feature-level toggle below when a feature row (not a body row) is selected.
+    const int bsel = tree_body_selection();
+    if (bsel >= 0) {
+        sync_body_visible();
+        if (bsel < int(m_body_visible.size())) {
+            const bool now_visible = !m_body_visible[bsel];
+            m_body_visible[bsel] = now_visible;
+            if (m_viewport != nullptr) {
+                feed_bodies();   // flips is_active; m_solid_visible is a stable pointer (live)
+                m_viewport->set_solid_pick(&m_doc.bodies, &m_disp_pick_mesh,
+                                           &m_doc.display_tri_face, &m_doc.display_tri_body,
+                                           &m_body_visible, &m_body_xform);
+            }
+            refresh_tree();
+            // Keep the row selected for repeat toggles. m_parts, NOT m_tree: these ids belong
+            // to the Bodies list, and handing a foreign item to the feature tree left the row
+            // unselected — so the second press of the eye found tree_body_selection() == -1 and
+            // fell through to the FEATURE-level branch below instead of un-hiding the body.
+            if (m_parts != nullptr && bsel < int(m_tree_body_items.size()))
+                m_parts->SelectItem(m_tree_body_items[bsel]);
+            m_status->SetForegroundColour(wxNullColour);
+            set_status(wxString::Format(now_visible ? _L("Body %d shown")
+                                                            : _L("Body %d hidden"), bsel + 1));
+            m_status->Refresh();
+        }
+        return;
+    }
+
+    int sel = tree_selection();
+    if (sel == wxNOT_FOUND || sel >= int(m_doc.features.size())) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Select a feature in the tree first"));
+        m_status->Refresh();
+        return;
+    }
+    const bool shown = !m_doc.features[sel].enabled;
+    m_doc.features[sel].enabled = shown;
+
+    // recompute() reports an all-hidden / sketch-only document as false (no
+    // solid to build), but that is a VALID state for hide — so clear the body
+    // explicitly instead of letting after_tree_edit treat it as a rejected edit
+    // (which would skip the overlay refresh, leaving hidden art on screen).
+    if (!recompute_guarded(_L("Rebuilding model…"))) {
+        m_doc.body         = TopoDS_Shape();
+        m_doc.display_mesh = TriangleMesh{};
+        m_doc.error.clear();
+    }
+    refresh_tree();                       // greys the row
+    set_tree_selection(sel);              // keep the toggled feature selected
+    if (m_viewport != nullptr) {
+        if (m_doc.display_mesh.its.indices.empty()) m_viewport->clear_mesh();
+        else                                        feed_bodies();
+    }
+    sync_sketch_display();                // skips the hidden sketch + direct-renders
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(shown ? _L("Feature shown") : _L("Feature hidden"));
+    m_status->Refresh();
+}
+
+void DesignPanel::on_move_feature(int delta)
+{
+    int sel = tree_selection();
+    if (sel == wxNOT_FOUND) {
+        set_status(_L("Select a feature in the tree first"));
+        m_status->Refresh();
+        return;
+    }
+    int target = sel + delta;
+    if (target < 0 || target >= int(m_doc.features.size()))
+        return; // already at the end
+    m_doc.checkpoint();   // undo boundary: reordering a feature
+    if (m_doc.move_feature(sel, delta)) {
+        after_tree_edit(true);
+        set_tree_selection(target); // keep the moved feature selected
+    } else {
+        after_tree_edit(false);
+    }
+}
+
+// Commit the live sketch in place, then enter Constrain mode on the just-committed sketch.
+// One-click bridge from the SKETCH toolbar: removes the "Finish -> find in tree -> select ->
+// Constrain" friction, so the constraint palette + Trim/Extend are reachable mid-sketch.
+bool DesignPanel::enter_constrain_inline()
+{
+    if (m_viewport && m_viewport->is_sketching())
+        m_viewport->finish_sketch();   // synchronous: packages live entities+constraints -> Sketch
+    const int sk = resolve_extrude_sketch();   // last/selected Sketch feature
+    if (sk < 0) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Draw a sketch first, then Constrain"));
+        m_status->Refresh();
+        return false;
+    }
+    set_tree_selection(sk);            // tree drives on_begin_constrain / the constraint manager
+    on_begin_constrain(sk);
+    const bool entered = m_viewport &&
+        (m_viewport->is_constraining() || m_viewport->is_constraining_entities());
+    if (entered) set_ui_mode(UiMode::Constrain);
+    return entered;
+}
+
+void DesignPanel::on_begin_constrain(int sel_override)
+{
+    int sel = (sel_override >= 0) ? sel_override : tree_selection();
+    // Fall back to the sketch owning the region picked in the viewport. The offer menu reaches
+    // this verb from a SkLoop selection (a region clicked on screen), which carries no tree
+    // selection — without this, choosing "Constrain sketch" from the offer would answer
+    // "Select a sketch in the tree first" about a sketch the user has visibly selected.
+    if ((sel == wxNOT_FOUND || sel >= int(m_doc.features.size())) && m_sel_sketch_feat >= 0
+        && m_sel_sketch_feat < int(m_doc.features.size())) {
+        sel = m_sel_sketch_feat;
+        set_tree_selection(sel);       // keep the tree in step with what the viewport says
+    }
+    if (sel == wxNOT_FOUND || sel >= int(m_doc.features.size())) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Select a sketch in the tree first"));
+        m_status->Refresh();
+        return;
+    }
+    CadFeature& f = m_doc.features[sel];
+    if (f.type != CadFeatureType::Sketch) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Selected feature is not a sketch"));
+        m_status->Refresh();
+        return;
+    }
+
+    // Entity sketches (Fase 4.2): pick Line entities; constraints solve against
+    // entity endpoints in the kernel.
+    if (!f.entities.empty()) {
+        m_constrain_feat = sel;
+        if (m_viewport) m_viewport->begin_constrain_entities(f.entities, f.plane);
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("Pick 1-2 lines, then a constraint; right-click exits"));
+        m_status->Refresh();
+        return;
+    }
+
+    // Legacy profile path (Fase 3).
+    if (f.profile.points.size() < 3) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Selected feature is not a sketch"));
+        m_status->Refresh();
+        return;
+    }
+    m_constrain_feat = sel;
+    // Anchor the first profile point so H/V constraints don't let the sketch
+    // float freely; fix_point captures the point's current position in the solver.
+    if (f.constraints.empty())
+        f.constraints.push_back(SketchConstraintDef{SketchConstraintType::Fix, 0, -1, -1, -1, 0.0});
+    if (m_viewport) m_viewport->begin_constrain(f.profile, f.plane);
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(_L("Pick 1-2 entities, then a constraint or dimension; right-click exits"));
+    m_status->Refresh();
+}
+
+// Why an entity-constraint pick was refused, as a localized string. The kernel's
+// ConstraintReject is coarse on purpose (one reason covers several constraint types whose
+// BUTTONS wear different words), so `type` disambiguates the wording without touching the
+// kernel. Reuses today's exact strings so nothing regresses for a user or the ladder.
+static wxString constraint_reject_text(ConstraintReject reason, SketchConstraintType type)
+{
+    using T = SketchConstraintType;
+    switch (reason) {
+    case ConstraintReject::NeedOneEntity:        return _L("Pick an entity first");
+    case ConstraintReject::NeedTwoEntities:      return _L("Pick two entities first");
+    case ConstraintReject::NeedALine:            return _L("Horizontal and Vertical apply to a line");
+    case ConstraintReject::NeedTwoLines:
+        if (type == T::Angle)     return _L("Angle applies between two lines");
+        if (type == T::Collinear) return _L("Collinear needs two lines");
+        return _L("Parallel, perpendicular and equal length apply to two lines");
+    case ConstraintReject::NeedTwoRounds:
+        if (type == T::EqualRadius) return _L("Equal radius needs two circles or arcs");
+        return _L("Concentric needs two circles or arcs");
+    case ConstraintReject::NeedTangentPair:      return _L("Tangent needs a line and a circle/arc, or two circles/arcs");
+    case ConstraintReject::NeedJoinablePoints:   return _L("This constraint needs two entities with a point to join");
+    case ConstraintReject::NeedMeasurablePoints: return _L("This dimension needs two entities with a point to measure between");
+    case ConstraintReject::NeedPointAndLine:     return _L("Midpoint needs a point and a line");
+    case ConstraintReject::NeedTwoPointsOrLines:
+        if (type == T::Symmetric) return _L("Symmetric needs two points or two lines + an axis");
+        return _L("Symmetric needs two points or two lines");
+    case ConstraintReject::NeedAxisLine:         return _L("Symmetric: pick two entities, then an axis line");
+    case ConstraintReject::NeedRound:            return _L("Radius/Diameter needs a circle or arc");
+    case ConstraintReject::Unsupported:          return _L("Unsupported constraint");
+    case ConstraintReject::None:
+    default:                                     return wxString();
+    }
+}
+
+// Write the typed value into every planned def. The planner returns the prefill in DISPLAY
+// units and leaves def.value = 0; Angle is the one type whose stored value is not the number
+// the user sees (it is radians), so the conversion lives here, exactly as the old
+// apply_entity_constraint did on its Angle branch.
+static void write_plan_value(std::vector<SketchEntityConstraintDef>& defs, double v)
+{
+    for (auto& d : defs)
+        d.value = (d.type == SketchConstraintType::Angle) ? v * M_PI / 180.0 : v;
+}
+
+void DesignPanel::apply_entity_constraint(SketchConstraintType type)
+{
+    int e0 = -1, e1 = -1;
+    m_viewport->selected_constrain_entities(e0, e1);
+    const int e2 = m_viewport->selected_constrain_axis();   // Symmetric axis pick, -1 otherwise
+
+    CadFeature& feat = m_doc.features[m_constrain_feat];
+    const ConstraintPlan plan = plan_entity_constraint(feat.entities, e0, e1, e2, type);
+
+    auto fail = [this](const wxString& msg) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(msg);
+        m_status->Refresh();
+    };
+
+    switch (plan.kind) {
+    case ConstraintPlan::Kind::Reject:
+        fail(constraint_reject_text(plan.reason, type));
+        return;
+    case ConstraintPlan::Kind::AskValue:
+        m_viewport->open_inline_value(plan.prefill, [this, plan](double v) {
+            std::vector<SketchEntityConstraintDef> defs = plan.defs;
+            write_plan_value(defs, v);
+            commit_entity_constraints(defs);
+        });
+        return;   // deferred: commit runs on the typed value
+    case ConstraintPlan::Kind::Apply:
+        commit_entity_constraints(plan.defs);
+        return;
+    }
+}
+
+void DesignPanel::apply_live_constraint(SketchConstraintType type)
+{
+    // The in-session selection is the pick: first three indices, e2 being the axis Symmetric
+    // needs. Fewer than the type needs are left at -1 so plan_entity_constraint — the ONE
+    // place that knows how many picks a type takes — rejects them rather than this site
+    // guessing. Known limitation (comment, not solved): a constraint added to a LIVE sketch
+    // is not on the document undo stack — that stack holds committed features — so Ctrl+Z
+    // will not take it back until the sketch is committed.
+    const std::vector<int>& sel  = m_viewport->sketch_selection();
+    const int e0 = sel.size() > 0 ? sel[0] : -1;
+    const int e1 = sel.size() > 1 ? sel[1] : -1;
+    const int e2 = sel.size() > 2 ? sel[2] : -1;
+
+    const ConstraintPlan plan = plan_entity_constraint(
+        m_viewport->sketch_entities(), e0, e1, e2, type);
+
+    auto fail = [this](const wxString& msg) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(msg);
+        m_status->Refresh();
+    };
+    // Shared commit: try_add_constraints appends→solves→keeps-or-rolls-back and leaves the
+    // geometry untouched on failure, so the same over-constrained message the committed path
+    // uses is the correct failure report here too.
+    auto commit = [this, fail](std::vector<SketchEntityConstraintDef> defs, double v) {
+        write_plan_value(defs, v);
+        if (!m_viewport->try_add_sketch_constraints(defs)) {
+            fail(_L("Constraint rejected (over-constrained)"));
+            return;
+        }
+        m_viewport->request_repaint();
+        m_status->SetForegroundColour(wxNullColour);
+        // Say where it went and how to undo it, here at the moment of applying: the hint line
+        // only refreshes when the step tuple changes, which applying a constraint does not.
+        set_status(_L("Applied constraint  ·  its badge is on the sketch — click the badge to remove it"));
+        m_status->Refresh();
+    };
+
+    switch (plan.kind) {
+    case ConstraintPlan::Kind::Reject:
+        // "I applied Parallel and NOTHING HAPPENS" is this branch. The text named the
+        // REQUIREMENT ("applies to two lines") but never the CURRENT PICK, and a creation
+        // tool auto-selects only the entity it just drew — so after drawing two lines exactly
+        // one is selected and the button correctly refuses. Say how many are picked, or the
+        // refusal is indistinguishable from a dead button.
+        fail(wxString::Format(_L("%s  —  %d selected. Press Esc for the Select tool, click one "
+                                 "line, then Shift- or Ctrl-click the other."),
+                              constraint_reject_text(plan.reason, type), int(sel.size())));
+        return;
+    case ConstraintPlan::Kind::AskValue:
+        m_viewport->open_inline_value(plan.prefill, [this, plan, commit](double v) {
+            commit(plan.defs, v);
+        });
+        return;
+    case ConstraintPlan::Kind::Apply:
+        commit(plan.defs, 0.0);
+        return;
+    }
+}
+
+void DesignPanel::commit_entity_constraints(const std::vector<SketchEntityConstraintDef>& defs)
+{
+    if (m_constrain_feat < 0 || m_constrain_feat >= int(m_doc.features.size()) ||
+        !m_viewport || defs.empty())
+        return;
+    CadFeature& feat = m_doc.features[m_constrain_feat];
+    // solve_sketch_feature rewrites entity coords even on failure, so snapshot
+    // to roll back a rejected (over-constrained) addition cleanly. Multiple defs
+    // (Symmetric on two lines) must solve together, so push all then resize back.
+    const std::vector<SketchEntity> saved = feat.entities;
+    const size_t before = feat.entity_constraints.size();
+    // Undo boundary: adding a constraint. Without it Ctrl+Z reached PAST this edit to the
+    // previous boundary and threw away whatever happened in between — a constraint was the
+    // one document mutation the user could not take back on its own.
+    m_doc.checkpoint();
+    for (const auto& d : defs) feat.entity_constraints.push_back(d);
+    if (!m_doc.solve_sketch_feature(m_constrain_feat)) {
+        feat.entity_constraints.resize(before);
+        feat.entities = saved;
+        m_doc.abandon_checkpoint();   // fully restored above: nothing happened, so nothing to undo
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Constraint rejected (over-constrained)"));
+        m_status->Refresh();
+        return;
+    }
+    m_doc.recompute();
+    // The constraint lives in the recipe, so the save path has to be told the recipe moved;
+    // otherwise saving after a constraint edit wrote the blob from before it.
+    sync_recipe_to_model();
+    update_undo_redo_buttons();
+    m_viewport->update_constrain_entities(m_doc.features[m_constrain_feat].entities);
+    if (!m_doc.display_mesh.its.indices.empty())
+        feed_bodies();
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(_L("Applied constraint"));
+    m_status->Refresh();
+
+    refresh_constrain_dof();      // P3 DoF readout for the Constrain path
+    rebuild_constraint_list();    // C3.4 manager: a row appeared
+}
+
+// Re-derive the solve state of the constrained feature and mirror it into the same
+// DoF readout the in-session path uses, so "✓ Fully constrained" is reachable here.
+void DesignPanel::refresh_constrain_dof()
+{
+    if (!m_dof_status || m_constrain_feat < 0 || m_constrain_feat >= int(m_doc.features.size()))
+        return;
+    const CadFeature& feat = m_doc.features[m_constrain_feat];
+    std::vector<SketchEntity> ents = feat.entities;   // already solved; re-solve is a cheap no-op
+    const SketchSolveResult r = sketch_solve(ents, feat.entity_constraints);
+    if (!r.ok) {
+        m_dof_status->SetForegroundColour(wxColour(235, 80, 80));
+        m_dof_status->SetLabel(_L("✗ Conflicting constraints")); m_dof_status->Show(!m_dof_status->GetLabel().IsEmpty());
+    } else if (r.dof == 0) {
+        m_dof_status->SetForegroundColour(wxColour(80, 200, 110));
+        m_dof_status->SetLabel(_L("✓ Fully constrained")); m_dof_status->Show(!m_dof_status->GetLabel().IsEmpty());
+    } else if (r.dof > 0) {
+        m_dof_status->SetForegroundColour(dp_ctl_text());
+        m_dof_status->SetLabel(wxString::Format(_L("%d degrees of freedom"), r.dof)); m_dof_status->Show(!m_dof_status->GetLabel().IsEmpty());
+    } else {
+        m_dof_status->SetLabel(wxString()); m_dof_status->Show(!m_dof_status->GetLabel().IsEmpty());
+    }
+    m_dof_status->Refresh();
+    update_cards_frame(); m_form->Layout();
+}
+
+// Human-readable label for a constraint row, e.g. "Coincident L0·P1 — L1·P0",
+// "Horizontal L2", "Radius C3 = 7.00". Entities are tagged by type letter + index.
+wxString DesignPanel::constraint_label(const SketchEntityConstraintDef& d) const
+{
+    using T = SketchConstraintType;
+    const CadFeature* feat = (m_constrain_feat >= 0 && m_constrain_feat < int(m_doc.features.size()))
+                                 ? &m_doc.features[m_constrain_feat] : nullptr;
+    auto tag = [&](int ei, SketchPointRole r) -> wxString {
+        if (ei < 0) return wxString();
+        char c = 'E';
+        if (feat && ei < int(feat->entities.size())) {
+            switch (feat->entities[ei].type) {
+            case SketchEntity::Type::Line:       c = 'L'; break;
+            case SketchEntity::Type::Circle:     c = 'C'; break;
+            case SketchEntity::Type::Arc:        c = 'A'; break;
+            case SketchEntity::Type::Point:      c = 'P'; break;
+            case SketchEntity::Type::Ellipse:
+            case SketchEntity::Type::EllipseArc: c = 'E'; break;
+            case SketchEntity::Type::BSpline:    c = 'B'; break;
+            }
+        }
+        wxString s; s << wxUniChar(c) << ei;   // avoid %c assert in Unicode build
+        if (r == SketchPointRole::P1)     s += "·P1";
+        else if (r == SketchPointRole::Center) s += "·Ctr";
+        else if (r == SketchPointRole::P0)     s += "·P0";
+        return s;
+    };
+    auto two = [&](const wxString& name) {
+        return d.eb >= 0 ? wxString::Format("%s %s — %s", name, tag(d.ea, d.ra), tag(d.eb, d.rb))
+                         : wxString::Format("%s %s", name, tag(d.ea, d.ra));
+    };
+    switch (d.type) {
+    case T::Fix:           return wxString::Format(_L("Fix %s"), tag(d.ea, d.ra));
+    case T::Coincident:    return two(_L("Coincident"));
+    case T::Horizontal:    return two(_L("Horizontal"));
+    case T::Vertical:      return two(_L("Vertical"));
+    case T::Distance:      return wxString::Format("%s = %s", two(_L("Distance")), en_format(d.value));
+    case T::LockX:         return wxString::Format(_L("Lock X %s"), tag(d.ea, d.ra));
+    case T::LockY:         return wxString::Format(_L("Lock Y %s"), tag(d.ea, d.ra));
+    case T::EqualLength:   return two(_L("Equal"));
+    case T::Parallel:      return two(_L("Parallel"));
+    case T::Perpendicular: return two(_L("Perpendicular"));
+    case T::Concentric:    return two(_L("Concentric"));
+    case T::Tangent:       return two(_L("Tangent"));
+    case T::Midpoint:      return two(_L("Midpoint"));
+    case T::Symmetric:     return wxString::Format(_L("Symmetric %s — %s / %s"),
+                                                   tag(d.ea, d.ra), tag(d.eb, d.rb), tag(d.ec, d.rc));
+    case T::SymmetricAboutY: return wxString::Format(_L("Symmetric about Y axis %s — %s"),
+                                                     tag(d.ea, d.ra), tag(d.eb, d.rb));
+    case T::SymmetricAboutX: return wxString::Format(_L("Symmetric about X axis %s — %s"),
+                                                     tag(d.ea, d.ra), tag(d.eb, d.rb));
+    case T::Angle:         return wxString::Format("%s = %s°", two(_L("Angle")), en_format(d.value * 180.0 / M_PI, 1));
+    case T::Radius:        return wxString::Format("%s %s = %s", _L("Radius"),   tag(d.ea, d.ra), en_format(d.value));
+    case T::Diameter:      return wxString::Format("%s %s = %s", _L("Diameter"), tag(d.ea, d.ra), en_format(d.value));
+    case T::PointOnLine:   return two(_L("On line"));
+    case T::PointOnObject: return two(_L("On edge"));
+    }
+    return _L("Constraint");
+}
+
+bool DesignPanel::live_constraint_scope() const
+{
+    return m_viewport != nullptr && m_viewport->is_sketching() &&
+           !m_viewport->is_constraining() && !m_viewport->is_constraining_entities();
+}
+
+// Rebuild the constraint-row list. Source depends on scope: a LIVE sketch session owns its
+// constraints inside the sketch tool and has no committed feature yet, so the list read only
+// the feature's and stayed empty for the whole session — constraints applied while drawing had
+// no row, no ✗, and no name anywhere in the UI.
+void DesignPanel::rebuild_constraint_list()
+{
+    if (m_constraint_rows == nullptr || m_form == nullptr)
+        return;
+    m_constraint_rows->Clear(true /* delete windows */);
+    m_constraint_sel = -1;
+
+    const bool live   = live_constraint_scope();
+    const bool active = (m_constrain_feat >= 0 && m_constrain_feat < int(m_doc.features.size()));
+    const std::vector<SketchEntityConstraintDef> empty;
+    const std::vector<SketchEntityConstraintDef>& cons =
+        live   ? m_viewport->sketch_constraints()
+      : active ? m_doc.features[m_constrain_feat].entity_constraints : empty;
+
+    if (m_hdr_constraints)
+        m_hdr_constraints->SetLabel(wxString::Format(_L("Constraints (%d)"), int(cons.size())));
+
+    if (cons.empty()) {
+        auto* none = new wxStaticText(m_cards, wxID_ANY, _L("No constraints yet"));
+        none->SetForegroundColour(dp_sec_text());
+        m_constraint_rows->Add(none, 0, wxTOP, 4);
+    }
+    for (int i = 0; i < int(cons.size()); ++i) {
+        auto* row = new wxBoxSizer(wxHORIZONTAL);
+        // Delete button first (fixed left position, always visible — long labels can
+        // horizontally scroll but ✗ stays put and clickable). BMP-safe ✗ glyph.
+        auto* del = new wxButton(m_cards, wxID_ANY, wxString::FromUTF8("✗"),
+                                 wxDefaultPosition, wxSize(26, -1));
+        del->SetToolTip(_L("Delete constraint"));
+        del->Bind(wxEVT_BUTTON, [this, i](wxCommandEvent&) { delete_constraint(i); });
+        // Clickable label: selecting it highlights the referenced entities.
+        auto* lbl = new wxButton(m_cards, wxID_ANY, constraint_label(cons[i]),
+                                 wxDefaultPosition, wxDefaultSize, wxBU_LEFT | wxBORDER_NONE);
+        lbl->Bind(wxEVT_BUTTON, [this, i](wxCommandEvent&) { highlight_constraint_entities(i); });
+        row->Add(del, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 6);
+        row->Add(lbl, 1, wxALIGN_CENTER_VERTICAL);
+        m_constraint_rows->Add(row, 0, wxEXPAND | wxTOP, 2);
+    }
+
+    // Feed the same list to the viewport for the on-sketch glyph badges (C3.4b).
+    if (m_viewport)
+        m_viewport->set_constraint_glyphs(cons);
+
+    m_cards->GetSizer()->Show(m_box_constraints,
+                              m_ui_mode == UiMode::Constrain || live, true);
+    update_cards_frame(); m_form->Layout();
+    m_form->FitInside();
+}
+
+// Push the entities referenced by constraint `idx` to the viewport as a yellow
+// highlight (toggle off if the same row is clicked again).
+void DesignPanel::highlight_constraint_entities(int idx)
+{
+    if (!m_viewport)
+        return;
+    const bool live = live_constraint_scope();
+    if (!live && (m_constrain_feat < 0 || m_constrain_feat >= int(m_doc.features.size())))
+        return;
+    const auto& cons = live ? m_viewport->sketch_constraints()
+                            : m_doc.features[m_constrain_feat].entity_constraints;
+    if (idx < 0 || idx >= int(cons.size()))
+        return;
+    if (m_constraint_sel == idx) {     // second click clears
+        m_constraint_sel = -1;
+        m_viewport->set_constraint_highlight({});
+        return;
+    }
+    m_constraint_sel = idx;
+    const SketchEntityConstraintDef& d = cons[idx];
+    std::vector<int> ents;
+    for (int e : { d.ea, d.eb, d.ec })
+        if (e >= 0) ents.push_back(e);
+    m_viewport->set_constraint_highlight(std::move(ents));
+}
+
+// Drop constraint `idx`, re-solve the feature, and refresh viewport + list + DoF.
+void DesignPanel::delete_constraint(int idx)
+{
+    // Live session: the constraint lives in the sketch tool, not in any feature. Removing it
+    // re-solves and fires on_constraints_changed, which rebuilds these rows — so this branch
+    // deliberately does NOT call rebuild_constraint_list() itself (it would run twice, and the
+    // second run would delete the wxButton whose click handler is still on the stack).
+    if (live_constraint_scope()) {
+        if (!m_viewport->remove_sketch_constraint(idx))
+            return;
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("Constraint deleted"));
+        m_status->Refresh();
+        return;
+    }
+    if (m_constrain_feat < 0 || m_constrain_feat >= int(m_doc.features.size()) || !m_viewport)
+        return;
+    CadFeature& feat = m_doc.features[m_constrain_feat];
+    if (idx < 0 || idx >= int(feat.entity_constraints.size()))
+        return;
+    m_doc.checkpoint();   // undo boundary: deleting a constraint
+    feat.entity_constraints.erase(feat.entity_constraints.begin() + idx);
+    // Re-solve the remaining system (deleting a constraint can only free DoF, so it
+    // cannot fail for over-constraint; ignore the bool and refresh either way).
+    m_doc.solve_sketch_feature(m_constrain_feat);
+    m_doc.recompute();
+    sync_recipe_to_model();       // the removal is part of the recipe
+    update_undo_redo_buttons();
+    m_viewport->set_constraint_highlight({});
+    m_viewport->update_constrain_entities(m_doc.features[m_constrain_feat].entities);
+    if (!m_doc.display_mesh.its.indices.empty())
+        feed_bodies();
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(_L("Constraint deleted"));
+    m_status->Refresh();
+    refresh_constrain_dof();
+    rebuild_constraint_list();
+}
+
+void DesignPanel::apply_edit_op(EditOp op)
+{
+    if (m_constrain_feat < 0 || m_constrain_feat >= int(m_doc.features.size()) || !m_viewport ||
+        !m_viewport->is_constraining_entities()) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Press Constrain on a sketch first"));
+        m_status->Refresh();
+        return;
+    }
+    auto fail = [this](const wxString& msg) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(msg);
+        m_status->Refresh();
+    };
+
+    int e0 = -1, e1 = -1;
+    m_viewport->selected_constrain_entities(e0, e1);
+    CadFeature& feat = m_doc.features[m_constrain_feat];
+    const int n = int(feat.entities.size());
+    if (e0 < 0 || e0 >= n) { fail(_L("Pick an entity first")); return; }
+    using Type = SketchEntity::Type;
+
+    switch (op) {
+    case EditOp::Mirror: {
+        if (e1 < 0 || e1 >= n) { fail(_L("Pick the entity, then a mirror-axis line")); return; }
+        const SketchEntity& axis = feat.entities[e1];
+        if (axis.type != Type::Line) { fail(_L("Mirror axis must be a line")); return; }
+        auto out = SketchEngine::mirror_entities({ feat.entities[e0] }, axis.p0, axis.p1);
+        if (out.empty()) { fail(_L("Mirror produced nothing")); return; }
+        const int mi = n;   // index the single mirrored copy lands at (n entities before push)
+        for (auto& m : out) feat.entities.push_back(m);
+
+        // C4a: bind the mirror to its source with Symmetric constraints about the
+        // axis, so the pair stays mirror-symmetric under later solves and drags.
+        // mirror_entities preserves P0/P1/Center ordering, so the constraints are
+        // satisfied by construction; if the solver still rejects them (degenerate
+        // axis, redundancy) keep the geometry and drop only the binding.
+        {
+            using R  = SketchPointRole;
+            using CT = SketchConstraintType;
+            const std::vector<SketchEntity> saved_ents = feat.entities;
+            const size_t cons_before = feat.entity_constraints.size();
+            SketchEntityConstraintDef d; d.type = CT::Symmetric; d.ea = e0; d.eb = mi; d.ec = e1;
+            const Type st = feat.entities[e0].type;
+            if (st == Type::Line) {
+                d.ra = R::P0; d.rb = R::P0; feat.entity_constraints.push_back(d);
+                d.ra = R::P1; d.rb = R::P1; feat.entity_constraints.push_back(d);
+            } else if (st == Type::Arc || st == Type::Circle) {
+                d.ra = R::Center; d.rb = R::Center; feat.entity_constraints.push_back(d);
+            } else if (st == Type::Point) {
+                d.ra = R::P0; d.rb = R::P0; feat.entity_constraints.push_back(d);
+            }
+            if (feat.entity_constraints.size() != cons_before &&
+                !m_doc.solve_sketch_feature(m_constrain_feat)) {
+                feat.entity_constraints.resize(cons_before);
+                feat.entities = saved_ents;
+            }
+        }
+        break;
+    }
+    case EditOp::Offset: {
+        const int a = e0;
+        request_value(_L("Offset distance (+left / -right of direction)"), 1.0, -100000.0, 100000.0,
+            [this, a](double d) {
+                CadFeature& f = m_doc.features[m_constrain_feat];
+                if (a >= int(f.entities.size())) return;
+                auto out = SketchEngine::offset_entities({ f.entities[a] }, d);
+                if (out.empty()) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Offset collapsed the entity")); m_status->Refresh(); return;
+                }
+                const int ni = int(f.entities.size());   // offset copy lands here
+                for (auto& o : out) f.entities.push_back(o);
+
+                // C4c: bind the offset copy to its source. Offset only ADDS geometry
+                // (the source is untouched), so unlike trim/fillet there are no stale
+                // constraints to drop — just glue the pair. A line offset stays
+                // Parallel to its source; an arc/circle offset stays Concentric (same
+                // centre). Single constraint, so no degradation ladder; solve and roll
+                // the binding back if the solver rejects it (keep the geometry).
+                {
+                    using CT = SketchConstraintType;
+                    const Type st = f.entities[a].type;
+                    SketchEntityConstraintDef d2; d2.ea = a; d2.eb = ni;
+                    bool emit = true;
+                    if (st == Type::Line)                              d2.type = CT::Parallel;
+                    else if (st == Type::Arc || st == Type::Circle)    d2.type = CT::Concentric;
+                    else                                               emit = false;
+                    if (emit) {
+                        const size_t cbefore = f.entity_constraints.size();
+                        f.entity_constraints.push_back(d2);
+                        if (!m_doc.solve_sketch_feature(m_constrain_feat))
+                            f.entity_constraints.resize(cbefore);
+                    }
+                }
+                after_edit_op();
+            });
+        return;   // deferred: edit runs on Confirm
+    }
+    case EditOp::Fillet: {
+        if (e1 < 0 || e1 >= n) { fail(_L("Pick two lines to fillet")); return; }
+        if (feat.entities[e0].type != Type::Line || feat.entities[e1].type != Type::Line) {
+            fail(_L("Fillet needs two lines")); return;
+        }
+        const int a = e0, b = e1;
+        request_value(_L("Fillet radius"), 1.0, 0.001, 100000.0, [this, a, b](double r) {
+            CadFeature& f = m_doc.features[m_constrain_feat];
+            if (a >= int(f.entities.size()) || b >= int(f.entities.size())) return;
+            SketchEntity a_out, b_out, arc_out;
+            if (!SketchEngine::fillet_lines(f.entities[a], f.entities[b], r, a_out, b_out, arc_out)) {
+                m_status->SetForegroundColour(wxColour(235, 110, 110));
+                set_status(_L("Fillet failed (parallel lines or radius too large)"));
+                m_status->Refresh(); return;
+            }
+            f.entities[a] = a_out;
+            f.entities[b] = b_out;
+            const int arc = int(f.entities.size());
+            f.entities.push_back(arc_out);
+
+            // C4b: glue the fillet arc to the two trimmed lines so it survives a
+            // re-solve instead of floating free. arc.p0 sits on line a's moved
+            // endpoint, arc.p1 on line b's; recover the exact endpoint roles by
+            // nearest match, then emit Coincident (essential — keeps the corner
+            // joined) + Tangent (smoothness). The full set can be redundant for the
+            // arc, so try it first and drop tangents progressively until the solver
+            // accepts it; the Coincident pins survive even if tangency is rejected.
+            {
+                using R  = SketchPointRole;
+                using CT = SketchConstraintType;
+                auto role_near = [](const SketchEntity& ln, const Vec2d& p) -> R {
+                    return ((ln.p0 - p).squaredNorm() <= (ln.p1 - p).squaredNorm()) ? R::P0 : R::P1;
+                };
+                const R ra = role_near(f.entities[a], arc_out.p0);
+                const R rb = role_near(f.entities[b], arc_out.p1);
+
+                // Fillet trims both lines back from the shared corner, so any
+                // constraint anchored to a trimmed endpoint is now stale: the corner
+                // Coincident that joined (a,ra)·(b,rb), and each line's own length
+                // Distance (its length just changed). Drop them before re-binding —
+                // leaving them would fight the new arc geometry and reject every
+                // binding below.
+                auto refs = [](const SketchEntityConstraintDef& d, int e, R r) {
+                    return (d.ea == e && d.ra == r) || (d.eb == e && d.rb == r);
+                };
+                auto self_len = [](const SketchEntityConstraintDef& d, int e) {
+                    return d.type == CT::Distance && d.ea == e && d.eb == e;
+                };
+                auto& cs = f.entity_constraints;
+                cs.erase(std::remove_if(cs.begin(), cs.end(),
+                    [&](const SketchEntityConstraintDef& d) {
+                        return (d.type == CT::Coincident && refs(d, a, ra) && refs(d, b, rb))
+                            || self_len(d, a) || self_len(d, b);
+                    }), cs.end());
+
+                auto coin = [&](R arc_role, int ln, R ln_role) {
+                    SketchEntityConstraintDef d; d.type = CT::Coincident;
+                    d.ea = arc; d.ra = arc_role; d.eb = ln; d.rb = ln_role; return d;
+                };
+                auto tang = [&](int ln) {
+                    SketchEntityConstraintDef d; d.type = CT::Tangent; d.ea = arc; d.eb = ln; return d;
+                };
+                const std::vector<std::vector<SketchEntityConstraintDef>> ladder = {
+                    { coin(R::P0, a, ra), coin(R::P1, b, rb), tang(a), tang(b) },
+                    { coin(R::P0, a, ra), coin(R::P1, b, rb), tang(a) },
+                    { coin(R::P0, a, ra), coin(R::P1, b, rb) },
+                };
+                const std::vector<SketchEntity> saved = f.entities;
+                const size_t cbefore = f.entity_constraints.size();
+                for (const auto& set : ladder) {
+                    for (const auto& d : set) f.entity_constraints.push_back(d);
+                    if (m_doc.solve_sketch_feature(m_constrain_feat)) break;   // accepted
+                    f.entity_constraints.resize(cbefore);
+                    f.entities = saved;
+                }
+            }
+            after_edit_op();
+        });
+        return;   // deferred: edit runs on Confirm
+    }
+
+    case EditOp::Chamfer: {
+        if (e1 < 0 || e1 >= n) { fail(_L("Pick two lines to chamfer")); return; }
+        if (feat.entities[e0].type != Type::Line || feat.entities[e1].type != Type::Line) {
+            fail(_L("Chamfer needs two lines")); return;
+        }
+        const int a = e0, b = e1;
+        request_value(_L("Chamfer distance"), 1.0, 0.001, 100000.0, [this, a, b](double d) {
+            CadFeature& f = m_doc.features[m_constrain_feat];
+            if (a >= int(f.entities.size()) || b >= int(f.entities.size())) return;
+            SketchEntity a_out, b_out, seg_out;
+            if (!SketchEngine::chamfer_lines(f.entities[a], f.entities[b], d, a_out, b_out, seg_out)) {
+                m_status->SetForegroundColour(wxColour(235, 110, 110));
+                set_status(_L("Chamfer failed (parallel lines or distance too large)"));
+                m_status->Refresh(); return;
+            }
+            f.entities[a] = a_out;
+            f.entities[b] = b_out;
+            const int seg = int(f.entities.size());
+            f.entities.push_back(seg_out);
+
+            // C4.6: like fillet, chamfer trims both lines back from the shared corner
+            // and inserts a connecting segment. MUTATING op: drop the stale corner
+            // Coincident that joined the two trimmed endpoints and each line's own
+            // length Distance (lengths just changed), then pin the new segment's ends
+            // onto the trimmed line endpoints with Coincident so it survives re-solve.
+            {
+                using R  = SketchPointRole;
+                using CT = SketchConstraintType;
+                auto role_near = [](const SketchEntity& ln, const Vec2d& p) -> R {
+                    return ((ln.p0 - p).squaredNorm() <= (ln.p1 - p).squaredNorm()) ? R::P0 : R::P1;
+                };
+                const R ra = role_near(f.entities[a], seg_out.p0);
+                const R rb = role_near(f.entities[b], seg_out.p1);
+
+                auto refs = [](const SketchEntityConstraintDef& dd, int e, R r) {
+                    return (dd.ea == e && dd.ra == r) || (dd.eb == e && dd.rb == r);
+                };
+                auto self_len = [](const SketchEntityConstraintDef& dd, int e) {
+                    return dd.type == CT::Distance && dd.ea == e && dd.eb == e;
+                };
+                auto& cs = f.entity_constraints;
+                cs.erase(std::remove_if(cs.begin(), cs.end(),
+                    [&](const SketchEntityConstraintDef& dd) {
+                        return (dd.type == CT::Coincident && refs(dd, a, ra) && refs(dd, b, rb))
+                            || self_len(dd, a) || self_len(dd, b);
+                    }), cs.end());
+
+                auto coin = [&](R seg_role, int ln, R ln_role) {
+                    SketchEntityConstraintDef dd; dd.type = CT::Coincident;
+                    dd.ea = seg; dd.ra = seg_role; dd.eb = ln; dd.rb = ln_role; return dd;
+                };
+                const std::vector<SketchEntity> saved = f.entities;
+                const size_t cbefore = f.entity_constraints.size();
+                f.entity_constraints.push_back(coin(R::P0, a, ra));
+                f.entity_constraints.push_back(coin(R::P1, b, rb));
+                if (!m_doc.solve_sketch_feature(m_constrain_feat)) {
+                    f.entity_constraints.resize(cbefore);   // keep geometry, drop pins
+                    f.entities = saved;
+                }
+            }
+            after_edit_op();
+        });
+        return;   // deferred: edit runs on Confirm
+    }
+
+    case EditOp::Trim:
+    case EditOp::Extend: {
+        // Trim accepts Line/Arc/Circle subjects; Extend accepts Line/Arc (a Circle
+        // is already closed, so there is nothing to extend).
+        const Type st = feat.entities[e0].type;
+        const bool subject_ok = (op == EditOp::Trim)
+            ? (st == Type::Line || st == Type::Arc || st == Type::Circle)
+            : (st == Type::Line || st == Type::Arc);
+        if (!subject_ok) {
+            fail(op == EditOp::Trim ? _L("Trim works on lines, arcs and circles")
+                                    : _L("Extend works on lines and arcs"));
+            return;
+        }
+        Vec2d pick;
+        if (!m_viewport->pick0_point(pick)) { fail(_L("Pick the edge to trim/extend")); return; }
+        std::vector<SketchEntity> others;
+        others.reserve(n > 0 ? n - 1 : 0);
+        for (int i = 0; i < n; ++i)
+            if (i != e0) others.push_back(feat.entities[i]);
+        const SketchEntity before = feat.entities[e0];   // C4.1: detect the moved endpoint
+        const bool ok = (op == EditOp::Trim)
+            ? SketchEngine::trim_entity(feat.entities[e0], others, pick)
+            : SketchEngine::extend_entity(feat.entities[e0], others, pick);
+        if (!ok) { fail(op == EditOp::Trim ? _L("Nothing to trim at the pick")
+                                           : _L("No edge to extend to")); return; }
+
+        // C4.1: trim/extend slides ONE endpoint of the subject along its own
+        // direction (line) or sweep (arc). That (a) kills the subject's
+        // self-length Distance dim and (b) detaches the moved endpoint from any
+        // corner Coincident/PointOn* it used to hold. Drop both stale classes,
+        // then re-anchor the moved endpoint onto the entity it now lands on with a
+        // PointOnObject (the bridge picks PT_ON_LINE / PT_ON_CIRCLE). A Circle
+        // subject restructures into an Arc (both endpoints new) — skip the
+        // re-anchor there; its self constraints (Radius/Concentric) survive, so
+        // there is nothing stale to drop either.
+        if (st == Type::Line || st == Type::Arc) {
+            using R  = SketchPointRole;
+            using CT = SketchConstraintType;
+            const SketchEntity& aft = feat.entities[e0];
+            R     moved = R::P0;
+            Vec2d P;
+            if (st == Type::Line) {
+                const bool p0_moved = (before.p0 - aft.p0).squaredNorm()
+                                    > (before.p1 - aft.p1).squaredNorm();
+                moved = p0_moved ? R::P0 : R::P1;
+                P     = p0_moved ? aft.p0 : aft.p1;
+            } else {
+                const bool start_moved = std::abs(before.start_angle - aft.start_angle)
+                                       > std::abs(before.end_angle - aft.end_angle);
+                moved = start_moved ? R::P0 : R::P1;
+                const double ang = start_moved ? aft.start_angle : aft.end_angle;
+                P = aft.center + aft.radius * Vec2d(std::cos(ang), std::sin(ang));
+            }
+
+            // Drop stale: subject self-length Distance + any Coincident/PointOn*
+            // pinning the moved endpoint to its old corner.
+            auto refs = [&](const SketchEntityConstraintDef& d, R r) {
+                return (d.ea == e0 && d.ra == r) || (d.eb == e0 && d.rb == r);
+            };
+            auto& cs = feat.entity_constraints;
+            cs.erase(std::remove_if(cs.begin(), cs.end(),
+                [&](const SketchEntityConstraintDef& d) {
+                    if (d.type == CT::Distance && d.ea == e0 && d.eb == e0) return true;
+                    return (d.type == CT::Coincident || d.type == CT::PointOnLine
+                         || d.type == CT::PointOnObject) && refs(d, moved);
+                }), cs.end());
+
+            // Find which other entity the moved endpoint now lies on (Line/Circle
+            // cutters only — PT_ON_* needs a line or circle primitive).
+            int cutter = -1;
+            const double tol = 1e-5;
+            for (int i = 0; i < int(feat.entities.size()); ++i) {
+                if (i == e0) continue;
+                const SketchEntity& o = feat.entities[i];
+                if (o.type == Type::Line) {
+                    Vec2d dv = o.p1 - o.p0;
+                    const double L2 = dv.dot(dv);
+                    if (L2 < 1e-18) continue;
+                    const double t = (P - o.p0).dot(dv) / L2;
+                    if (t < -1e-6 || t > 1.0 + 1e-6) continue;
+                    if ((o.p0 + t * dv - P).norm() < tol) { cutter = i; break; }
+                } else if (o.type == Type::Circle) {
+                    if (std::abs((P - o.center).norm() - o.radius) < tol) { cutter = i; break; }
+                }
+            }
+
+            // Re-anchor with PointOnObject; keep geometry + the stale-drop even if
+            // the solver rejects the new (possibly redundant) binding.
+            if (cutter >= 0) {
+                const size_t cbefore = feat.entity_constraints.size();
+                SketchEntityConstraintDef d; d.type = CT::PointOnObject;
+                d.ea = e0; d.ra = moved; d.eb = cutter;
+                feat.entity_constraints.push_back(d);
+                if (!m_doc.solve_sketch_feature(m_constrain_feat))
+                    feat.entity_constraints.resize(cbefore);
+            }
+        }
+        break;
+    }
+    case EditOp::Array: {
+        // C4.4 linear array. Additive op (originals untouched, copies appended) ->
+        // no stale constraints to drop. Collect count, then spacing; the array runs
+        // along the subject line's own direction (or +X for non-lines). Copies are
+        // pure translates, so for lines they are Parallel + EqualLength to the
+        // source by construction -> bind each copy to the source in a star web; for
+        // arc/circle subjects the translate preserves radius (but not the centre),
+        // so the web is a per-copy Radius dimension instead (see below).
+        const int a = e0;
+        request_value(_L("Array count (incl. original)"), 3.0, 2.0, 200.0,
+            [this, a](double cnt_d) {
+                const int count = std::max(2, int(cnt_d + 0.5));
+                request_value(_L("Spacing (mm)"), 20.0, -100000.0, 100000.0,
+                    [this, a, count](double sp) {
+                        CadFeature& f = m_doc.features[m_constrain_feat];
+                        if (a >= int(f.entities.size())) return;
+                        using Type = SketchEntity::Type;
+                        // Snapshot everything we need from the source BEFORE pushing the
+                        // copies: push_back can reallocate f.entities and dangle any
+                        // reference into it. Copy the subject by value.
+                        const SketchEntity src = f.entities[a];
+                        const Type src_type = src.type;
+                        // Default direction: perpendicular to a line (so copies stack
+                        // into a visible, non-overlapping parallel pattern rather than
+                        // extending collinearly); +X for non-line subjects.
+                        Vec2d dir(1.0, 0.0);
+                        if (src_type == Type::Line) {
+                            const Vec2d t = src.p1 - src.p0;
+                            if (t.norm() > 1e-9) {
+                                const Vec2d u = t.normalized();
+                                dir = Vec2d(-u.y(), u.x());
+                            }
+                        }
+                        auto copies = SketchEngine::array_entities(
+                            { src }, count, sp * dir, 0.0, Vec2d(0, 0));
+                        if (copies.empty()) {
+                            m_status->SetForegroundColour(wxColour(235, 110, 110));
+                            set_status(_L("Array produced nothing")); m_status->Refresh(); return;
+                        }
+                        const int base = int(f.entities.size());   // first copy index
+                        for (auto& c : copies) f.entities.push_back(c);
+
+                        if (src_type == Type::Line) {
+                            using CT = SketchConstraintType;
+                            // Bind every copy to the source in a star web. Emit the
+                            // WHOLE web before solving (a per-constraint solve would run
+                            // while later copies are still unconstrained, which the
+                            // solver rejects), then degrade as a set: try Parallel +
+                            // EqualLength, fall back to Parallel only (EqualLength can be
+                            // rank-deficient on exact congruent copies), then to bare
+                            // geometry. Keep the geometry regardless.
+                            const size_t cb = f.entity_constraints.size();
+                            auto build_web = [&](bool with_equal) {
+                                f.entity_constraints.resize(cb);
+                                for (int k = 0; k < int(copies.size()); ++k) {
+                                    SketchEntityConstraintDef dp; dp.type = CT::Parallel;
+                                    dp.ea = a; dp.eb = base + k;
+                                    f.entity_constraints.push_back(dp);
+                                    if (with_equal) {
+                                        SketchEntityConstraintDef de; de.type = CT::EqualLength;
+                                        de.ea = a; de.eb = base + k;
+                                        f.entity_constraints.push_back(de);
+                                    }
+                                }
+                            };
+                            build_web(true);
+                            if (!m_doc.solve_sketch_feature(m_constrain_feat)) {
+                                build_web(false);
+                                if (!m_doc.solve_sketch_feature(m_constrain_feat))
+                                    f.entity_constraints.resize(cb);
+                            }
+                        } else if (src_type == Type::Arc || src_type == Type::Circle) {
+                            // Curved subject: translation preserves the radius but
+                            // marches the centres apart, so the copies are NOT
+                            // concentric. There is no EQUAL_RADIUS in the constraint
+                            // enum, so pin each copy's radius to the source value with
+                            // a per-copy Radius dimension (keeps the array equal-radius
+                            // and documents intent, mirroring the line web). Solve and
+                            // roll the whole web back if the solver rejects it.
+                            using CT = SketchConstraintType;
+                            const size_t cb = f.entity_constraints.size();
+                            for (int k = 0; k < int(copies.size()); ++k) {
+                                SketchEntityConstraintDef dr; dr.type = CT::Radius;
+                                dr.ea = base + k; dr.value = src.radius;
+                                f.entity_constraints.push_back(dr);
+                            }
+                            if (!m_doc.solve_sketch_feature(m_constrain_feat))
+                                f.entity_constraints.resize(cb);
+                        }
+                        after_edit_op();
+                    });
+            });
+        return;   // deferred: edit runs on the two Confirms
+    }
+    case EditOp::Move: {
+        // C4.5 Transform (move). MUTATING op: the subject is translated in place
+        // (kernel transform_entities with angle=0, scale=1). Pure translation
+        // PRESERVES orientation and length, so intrinsic + orientation constraints
+        // survive (Horizontal/Vertical/Parallel/Perpendicular/EqualLength/Angle,
+        // self-length Distance, Radius/Diameter); it BREAKS position-coupling ones
+        // (Coincident/PointOn*/Concentric/Symmetric/Midpoint/Fix/LockX/LockY, and
+        // any Distance tying the subject to a *different* entity). Per the governing
+        // P4 insight, drop those before re-solving — otherwise the solver drags the
+        // subject straight back to satisfy them and the move never sticks.
+        const int a = e0;
+        request_value(_L("Move dX (mm)"), 20.0, -100000.0, 100000.0,
+            [this, a](double dx) {
+                request_value(_L("Move dY (mm)"), 0.0, -100000.0, 100000.0,
+                    [this, a, dx](double dy) {
+                        CadFeature& f = m_doc.features[m_constrain_feat];
+                        if (a >= int(f.entities.size())) return;
+                        auto out = SketchEngine::transform_entities(
+                            { f.entities[a] }, Vec2d(dx, dy), 0.0, 1.0, Vec2d(0, 0));
+                        if (out.empty()) {
+                            m_status->SetForegroundColour(wxColour(235, 110, 110));
+                            set_status(_L("Move produced nothing")); m_status->Refresh(); return;
+                        }
+                        f.entities[a] = out[0];
+
+                        using CT = SketchConstraintType;
+                        auto refs_a = [&](const SketchEntityConstraintDef& d) {
+                            return d.ea == a || d.eb == a || d.ec == a;
+                        };
+                        auto& cs = f.entity_constraints;
+                        cs.erase(std::remove_if(cs.begin(), cs.end(),
+                            [&](const SketchEntityConstraintDef& d) {
+                                if (!refs_a(d)) return false;
+                                switch (d.type) {
+                                case CT::Coincident: case CT::PointOnLine: case CT::PointOnObject:
+                                case CT::Concentric: case CT::Symmetric:   case CT::Midpoint:
+                                case CT::Fix:        case CT::LockX:        case CT::LockY:
+                                    return true;   // position-coupling: broken by translation
+                                case CT::Distance:
+                                    // self-length (ea==eb==a) survives translation; a
+                                    // distance to a *different* entity does not.
+                                    return !(d.ea == a && d.eb == a);
+                                default:
+                                    return false;  // orientation/length: preserved
+                                }
+                            }), cs.end());
+
+                        // The surviving constraints are satisfied by construction
+                        // (translation preserves them); re-solve to fold the new
+                        // position in, keep the geometry even if the solver balks.
+                        m_doc.solve_sketch_feature(m_constrain_feat);
+                        after_edit_op();
+                    });
+            });
+        return;   // deferred: edit runs on the two Confirms
+    }
+    case EditOp::Rotate: {
+        // C4.5b Transform (rotate-in-place about the subject centroid). MUTATING op.
+        // Rotation PRESERVES intrinsic size (length/radius) but changes the subject's
+        // ORIENTATION and the POSITION of its points. So only the size constraints
+        // survive (EqualLength/Radius/Diameter + self-length Distance); every
+        // position- or orientation-coupling constraint is broken and must be dropped
+        // before re-solving, otherwise the solver spins the subject back to satisfy
+        // them and the rotation never sticks (governing P4 insight).
+        const int a = e0;
+        request_value(_L("Rotate angle (deg)"), 45.0, -360.0, 360.0,
+            [this, a](double deg) {
+                CadFeature& f = m_doc.features[m_constrain_feat];
+                if (a >= int(f.entities.size())) return;
+                auto centroid_of = [](const SketchEntity& e) -> Vec2d {
+                    using T = SketchEntity::Type;
+                    switch (e.type) {
+                    case T::Line:    return 0.5 * (e.p0 + e.p1);
+                    case T::Arc: case T::Circle: case T::Ellipse: case T::EllipseArc:
+                                     return e.center;
+                    case T::BSpline:
+                        if (!e.ctrl.empty()) {
+                            Vec2d s(0, 0); for (auto& p : e.ctrl) s += p;
+                            return s / double(e.ctrl.size());
+                        }
+                        return 0.5 * (e.p0 + e.p1);
+                    default:         return e.p0;   // Point
+                    }
+                };
+                const Vec2d piv = centroid_of(f.entities[a]);
+                auto out = SketchEngine::transform_entities(
+                    { f.entities[a] }, Vec2d(0, 0), deg * M_PI / 180.0, 1.0, piv);
+                if (out.empty()) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Rotate produced nothing")); m_status->Refresh(); return;
+                }
+                f.entities[a] = out[0];
+
+                using CT = SketchConstraintType;
+                auto refs_a = [&](const SketchEntityConstraintDef& d) {
+                    return d.ea == a || d.eb == a || d.ec == a;
+                };
+                auto& cs = f.entity_constraints;
+                cs.erase(std::remove_if(cs.begin(), cs.end(),
+                    [&](const SketchEntityConstraintDef& d) {
+                        if (!refs_a(d)) return false;
+                        switch (d.type) {
+                        case CT::EqualLength: case CT::Radius: case CT::Diameter:
+                            return false;   // intrinsic size: preserved by rotation
+                        case CT::Distance:
+                            return !(d.ea == a && d.eb == a);   // self-length survives
+                        default:
+                            return true;    // position/orientation-coupling: broken
+                        }
+                    }), cs.end());
+
+                m_doc.solve_sketch_feature(m_constrain_feat);
+                after_edit_op();
+            });
+        return;   // deferred: edit runs on Confirm
+    }
+    case EditOp::Scale: {
+        // C4.5c Transform (uniform scale-in-place about the subject centroid). MUTATING
+        // op. Uniform scaling PRESERVES orientation and angles (Horizontal/Vertical/
+        // Parallel/Perpendicular/Angle survive) but changes SIZE and point POSITIONS:
+        // drop every size constraint (Radius/Diameter/EqualLength/any Distance) and
+        // every position-coupling constraint before re-solving, else the solver
+        // rescales the subject back to satisfy them.
+        const int a = e0;
+        request_value(_L("Scale factor"), 2.0, 0.01, 1000.0,
+            [this, a](double sf) {
+                CadFeature& f = m_doc.features[m_constrain_feat];
+                if (a >= int(f.entities.size())) return;
+                auto centroid_of = [](const SketchEntity& e) -> Vec2d {
+                    using T = SketchEntity::Type;
+                    switch (e.type) {
+                    case T::Line:    return 0.5 * (e.p0 + e.p1);
+                    case T::Arc: case T::Circle: case T::Ellipse: case T::EllipseArc:
+                                     return e.center;
+                    case T::BSpline:
+                        if (!e.ctrl.empty()) {
+                            Vec2d s(0, 0); for (auto& p : e.ctrl) s += p;
+                            return s / double(e.ctrl.size());
+                        }
+                        return 0.5 * (e.p0 + e.p1);
+                    default:         return e.p0;   // Point
+                    }
+                };
+                const Vec2d piv = centroid_of(f.entities[a]);
+                auto out = SketchEngine::transform_entities(
+                    { f.entities[a] }, Vec2d(0, 0), 0.0, sf, piv);
+                if (out.empty()) {
+                    m_status->SetForegroundColour(wxColour(235, 110, 110));
+                    set_status(_L("Scale produced nothing")); m_status->Refresh(); return;
+                }
+                f.entities[a] = out[0];
+
+                using CT = SketchConstraintType;
+                auto refs_a = [&](const SketchEntityConstraintDef& d) {
+                    return d.ea == a || d.eb == a || d.ec == a;
+                };
+                auto& cs = f.entity_constraints;
+                cs.erase(std::remove_if(cs.begin(), cs.end(),
+                    [&](const SketchEntityConstraintDef& d) {
+                        if (!refs_a(d)) return false;
+                        switch (d.type) {
+                        case CT::Horizontal: case CT::Vertical: case CT::Parallel:
+                        case CT::Perpendicular: case CT::Angle:
+                            return false;   // orientation/angle: preserved by uniform scale
+                        default:
+                            return true;    // size + position-coupling: broken
+                        }
+                    }), cs.end());
+
+                m_doc.solve_sketch_feature(m_constrain_feat);
+                after_edit_op();
+            });
+        return;   // deferred: edit runs on Confirm
+    }
+    case EditOp::PolarArray: {
+        // Polar array about the subject centroid. ADDITIVE op (originals untouched,
+        // count-1 rotated copies appended) -> no stale constraints to drop. Copies
+        // are rigid rotations of the source, so they preserve LENGTH but NOT
+        // orientation: bind each copy to the source with EqualLength only (Parallel
+        // does NOT hold under rotation, unlike the linear-array web). Arc/circle
+        // subjects rotate about their own centre, so their copies stay Concentric +
+        // equal-radius instead (see below). Dialogs: count
+        // then total sweep; angle_step = sweep/count spreads them evenly (last copy
+        // lands just shy of the original on a full 360).
+        const int a = e0;
+        request_value(_L("Polar count (incl. original)"), 6.0, 2.0, 200.0,
+            [this, a](double cnt_d) {
+                const int count = std::max(2, int(cnt_d + 0.5));
+                request_value(_L("Total sweep (deg)"), 360.0, -360.0, 360.0,
+                    [this, a, count](double sweep_deg) {
+                        CadFeature& f = m_doc.features[m_constrain_feat];
+                        if (a >= int(f.entities.size())) return;
+                        using Type = SketchEntity::Type;
+                        // Snapshot the subject by value BEFORE pushing copies: push_back
+                        // can reallocate f.entities and dangle a reference into it.
+                        const SketchEntity src = f.entities[a];
+                        const Type src_type = src.type;
+                        auto centroid_of = [](const SketchEntity& e) -> Vec2d {
+                            using T = SketchEntity::Type;
+                            switch (e.type) {
+                            case T::Line:    return 0.5 * (e.p0 + e.p1);
+                            case T::Arc: case T::Circle: case T::Ellipse: case T::EllipseArc:
+                                             return e.center;
+                            case T::BSpline:
+                                if (!e.ctrl.empty()) {
+                                    Vec2d s(0, 0); for (auto& p : e.ctrl) s += p;
+                                    return s / double(e.ctrl.size());
+                                }
+                                return 0.5 * (e.p0 + e.p1);
+                            default:         return e.p0;   // Point
+                            }
+                        };
+                        const Vec2d  piv        = centroid_of(src);
+                        const double angle_step = (sweep_deg * M_PI / 180.0) / double(count);
+                        auto copies = SketchEngine::array_entities(
+                            { src }, count, Vec2d(0, 0), angle_step, piv);
+                        if (copies.empty()) {
+                            m_status->SetForegroundColour(wxColour(235, 110, 110));
+                            set_status(_L("Polar array produced nothing")); m_status->Refresh(); return;
+                        }
+                        const int base = int(f.entities.size());   // first copy index
+                        for (auto& c : copies) f.entities.push_back(c);
+
+                        if (src_type == Type::Line) {
+                            using CT = SketchConstraintType;
+                            // Rotational web: each copy is EqualLength to the source
+                            // (rotation preserves length; orientation differs so NO
+                            // Parallel). Emit the whole web before solving, then fall
+                            // back to bare geometry if it is rank-deficient.
+                            const size_t cb = f.entity_constraints.size();
+                            for (int k = 0; k < int(copies.size()); ++k) {
+                                SketchEntityConstraintDef de; de.type = CT::EqualLength;
+                                de.ea = a; de.eb = base + k;
+                                f.entity_constraints.push_back(de);
+                            }
+                            if (!m_doc.solve_sketch_feature(m_constrain_feat))
+                                f.entity_constraints.resize(cb);
+                        } else if (src_type == Type::Arc || src_type == Type::Circle) {
+                            // Curved subject: the polar pivot is the subject centroid,
+                            // which for an arc/circle IS its own centre. Rotating about
+                            // that centre keeps every copy CONCENTRIC with the source and
+                            // at the same radius (only the angular position shifts). Bind
+                            // each copy with Concentric + a per-copy Radius dimension;
+                            // degrade to Radius-only, then to bare geometry, keeping the
+                            // geometry regardless.
+                            using CT = SketchConstraintType;
+                            const size_t cb = f.entity_constraints.size();
+                            auto build_web = [&](bool with_concentric) {
+                                f.entity_constraints.resize(cb);
+                                for (int k = 0; k < int(copies.size()); ++k) {
+                                    if (with_concentric) {
+                                        SketchEntityConstraintDef dc; dc.type = CT::Concentric;
+                                        dc.ea = a; dc.eb = base + k;
+                                        f.entity_constraints.push_back(dc);
+                                    }
+                                    SketchEntityConstraintDef dr; dr.type = CT::Radius;
+                                    dr.ea = base + k; dr.value = src.radius;
+                                    f.entity_constraints.push_back(dr);
+                                }
+                            };
+                            build_web(true);
+                            if (!m_doc.solve_sketch_feature(m_constrain_feat)) {
+                                build_web(false);
+                                if (!m_doc.solve_sketch_feature(m_constrain_feat))
+                                    f.entity_constraints.resize(cb);
+                            }
+                        }
+                        after_edit_op();
+                    });
+            });
+        return;   // deferred: edit runs on the two Confirms
+    }
+    }
+
+    after_edit_op();
+}
+
+void DesignPanel::after_edit_op()
+{
+    if (m_constrain_feat < 0 || m_constrain_feat >= int(m_doc.features.size()) || !m_viewport)
+        return;
+    m_doc.recompute();
+    m_viewport->set_constraint_highlight({});   // entity indices may have shifted
+    m_viewport->update_constrain_entities(m_doc.features[m_constrain_feat].entities);
+    // Refresh the committed-sketch overlay too: it caches the entity list at
+    // constrain-entry, so a relocating edit (Move/Trim/Extend) would otherwise
+    // leave a stale ghost of the pre-edit geometry beside the new position.
+    sync_sketch_display();
+    if (!m_doc.display_mesh.its.indices.empty())
+        feed_bodies();
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(_L("Applied edit"));
+    m_status->Refresh();
+    refresh_constrain_dof();
+    rebuild_constraint_list();
+}
+
+void DesignPanel::request_value(const wxString& label, double def, double mn, double mx,
+                                std::function<void(double)> cont,
+                                std::function<void()> on_cancel)
+{
+    m_value_cont = std::move(cont);
+    m_value_cancel = std::move(on_cancel);
+    m_value_min = mn;
+    m_value_max = mx;
+    m_value_label->SetLabel(label);
+    m_value_input->ChangeValue(en_format(def));   // '.' decimals, no EVT_TEXT feedback
+    m_cards->GetSizer()->Show(m_box_value, true, true);
+    update_cards_frame(); m_form->Layout();
+    m_form->FitInside();
+    m_value_input->SetFocus();
+    m_value_input->SetSelection(-1, -1);   // select all so typing replaces the value
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(label + _L(" — type a value, press Enter (or Confirm)"));
+    m_status->Refresh();
+}
+
+void DesignPanel::confirm_value()
+{
+    if (!m_value_cont) { cancel_value(); return; }
+    double v = 0.0;
+    if (!en_parse(m_value_input->GetValue(), v)) { m_value_input->SetFocus(); return; }
+    v = std::min(std::max(v, m_value_min), m_value_max);   // clamp to range
+    auto cont = m_value_cont;            // copy, then clear before running so a
+    m_value_cont = nullptr;              // re-entrant request_value can re-arm cleanly
+    m_value_cancel = nullptr;            // confirmed: drop the cancel action
+    m_cards->GetSizer()->Show(m_box_value, false, true);
+    update_cards_frame(); m_form->Layout();
+    m_form->FitInside();
+    cont(v);                            // run the deferred constraint / edit-op apply
+}
+
+void DesignPanel::cancel_value()
+{
+    const bool was_open = (m_value_cont != nullptr);
+    m_value_cont = nullptr;
+    auto on_cancel = m_value_cancel;     // copy, clear, then run (re-entrancy safe)
+    m_value_cancel = nullptr;
+    if (m_box_value)
+        m_cards->GetSizer()->Show(m_box_value, false, true);
+    update_cards_frame(); m_form->Layout();
+    m_form->FitInside();
+    if (was_open) {
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(wxString());
+        m_status->Refresh();
+    }
+    if (on_cancel)
+        on_cancel();                     // e.g. keep a pending line segment as drawn
+}
+
+void DesignPanel::apply_constraint(SketchConstraintType type)
+{
+    // 1. LIVE sketch session: constrain the in-session selection while drawing. The
+    // discriminator must exclude BOTH constrain modes — begin_constrain_entities AND
+    // begin_constrain both set m_active, so is_sketching() alone is true during a committed
+    // Constrain session; without the guards this new path hijacks those and breaks every
+    // existing constraint rung. !is_constraining() also covers is_constraining_entities()
+    // (both require Mode::Constrain); it is spelled out for the two reasons a reader expects.
+    if (m_viewport && m_viewport->is_sketching() &&
+        !m_viewport->is_constraining() && !m_viewport->is_constraining_entities()) {
+        apply_live_constraint(type);
+        return;
+    }
+
+    if (m_constrain_feat < 0 || m_constrain_feat >= int(m_doc.features.size()) ||
+        m_viewport == nullptr) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Press Constrain on a sketch first"));
+        m_status->Refresh();
+        return;
+    }
+
+    // 2. Entity sketches (Fase 4.2) route through the entity-constraint path.
+    if (m_viewport->is_constraining_entities()) {
+        apply_entity_constraint(type);
+        return;
+    }
+
+    // 3. Legacy profile path.
+    if (!m_viewport->is_constraining()) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Press Constrain on a sketch first"));
+        m_status->Refresh();
+        return;
+    }
+    int a = -1, b = -1;
+    if (!m_viewport->selected_segment(a, b)) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Pick a segment in the viewport first"));
+        m_status->Refresh();
+        return;
+    }
+    CadFeature& feat = m_doc.features[m_constrain_feat];
+    // solve_sketch_feature rewrites profile.points even on failure, so snapshot
+    // the geometry to roll back a rejected constraint cleanly.
+    const std::vector<Vec2d> saved_pts = feat.profile.points;
+    m_doc.checkpoint();   // undo boundary: adding a constraint (profile sketches)
+    feat.constraints.push_back(SketchConstraintDef{type, a, b, -1, -1, 0.0});
+    if (!m_doc.solve_sketch_feature(m_constrain_feat)) {
+        feat.constraints.pop_back();        // reject the non-converging addition
+        feat.profile.points = saved_pts;    // and restore the pre-solve geometry
+        m_doc.abandon_checkpoint();         // restored: no state change, so no undo step
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Constraint rejected (over-constrained)"));
+        m_status->Refresh();
+        return;
+    }
+    m_doc.recompute();
+    sync_recipe_to_model();
+    update_undo_redo_buttons();
+    m_viewport->update_constrain_profile(m_doc.features[m_constrain_feat].profile.points);
+    if (!m_doc.display_mesh.its.indices.empty())
+        feed_bodies();
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(type == SketchConstraintType::Horizontal ? _L("Applied Horizontal")
+                                                                : _L("Applied Vertical"));
+    m_status->Refresh();
+}
+
+void DesignPanel::reset_edit_state()
+{
+    m_edit_index = -1;
+}
+
+int DesignPanel::resolve_extrude_sketch() const
+{
+    int sel = tree_selection();
+    if (sel != wxNOT_FOUND && sel < int(m_doc.features.size()) &&
+        m_doc.features[sel].type == CadFeatureType::Sketch)
+        return sel;
+    for (int i = int(m_doc.features.size()) - 1; i >= 0; --i)
+        if (m_doc.features[i].type == CadFeatureType::Sketch) return i;
+    return -1;
+}
+
+void DesignPanel::load_feature_into_dialog(const CadFeature& f)
+{
+    switch (f.type) {
+    case CadFeatureType::Sketch:
+        m_shape->SetSelection(f.shape == SketchShape::Circle ? 1 : 0);
+        m_width->SetValue(f.width);
+        m_height->SetValue(f.height);
+        m_radius->SetValue(f.radius);
+        break;
+    case CadFeatureType::Extrude:
+        m_distance->SetValue(f.distance);
+        m_mode->SetSelection(static_cast<int>(f.mode)); // New=0,Add=1,Cut=2,Intersect=3
+        m_extrude_end->SetSelection(static_cast<int>(f.extrude_end));
+        m_distance2->SetValue(f.distance2);
+        m_taper->SetValue(f.taper_deg);
+        m_flip->SetValue(f.flip);
+        m_extrude_sketch_ref = f.sketch_ref;
+        m_sel_solid_body = f.target_body;    // preserve which body on re-edit
+        if (m_extrude_sketch_ref >= 0 && m_extrude_sketch_ref < int(m_doc.features.size()))
+            m_extrude_sketch_label->SetLabel(_L("Sketch: ") +
+                wxString::FromUTF8(m_doc.features[m_extrude_sketch_ref].name));
+        break;
+    case CadFeatureType::Fillet:
+    case CadFeatureType::Chamfer:
+        m_dressup_type->SetSelection(f.type == CadFeatureType::Fillet ? 0 : 1);
+        m_dressup_size->SetValue(f.dressup_size);
+        m_face_group->SetSelection(static_cast<int>(f.face_group));
+        m_sel_solid_edge = f.dressup_edge;   // preserve edge-targeting on re-edit
+        m_sel_solid_body = f.target_body;    // preserve which body on re-edit
+        sync_dressup_target();               // and say which of the two the re-edit is targeting
+        break;
+    case CadFeatureType::Hole:
+        m_hole_plane->SetSelection(index_from_plane(f.plane));
+        m_hole_diameter->SetValue(f.hole_diameter);
+        m_hole_depth->SetValue(f.hole_depth);
+        m_hole_through->SetValue(f.hole_through);
+        m_hole_x->SetValue(f.hole_x);
+        m_hole_y->SetValue(f.hole_y);
+        // Re-latch the on-face state FROM THE STORED FEATURE (uif9). m_hole_on_face is
+        // only ever cleared by the Hole flyout and by the plane combo, so after any on-face hole
+        // it stays true — and a re-edit then drilled on whatever face was latched last, which may
+        // be a different face, a different body, or a body since rebuilt. f is the only source
+        // guaranteed to describe THIS hole. Not the dropdown row just set above: index_from_plane
+        // snaps an arbitrary face plane to the nearest XY/XZ/YZ, so driving the re-edit from the
+        // row would MOVE a hole drilled on a slanted or offset face.
+        m_hole_on_face    = !is_base_plane(f.plane, m_doc.modeling_origin);
+        m_hole_face_plane = f.plane;
+        m_hole_face_body  = m_hole_on_face ? f.target_body : -1;
+        // The face's (u,v) extent is not serialized, so the gizmo's footprint clamp has nothing
+        // to stand on. Unbounded is the honest state; the stale bounds of another face are not.
+        m_hole_has_bounds = false;
+        if (m_hole_target_label)
+            m_hole_target_label->SetLabel(m_hole_on_face
+                // No face index survives in the feature, and inventing one would be worse than
+                // saying so. "(none — uses Hole plane)" is the one thing that is definitely false.
+                ? (f.target_body >= 0 ? wxString::Format(_L("On a face of Body %d"), f.target_body + 1)
+                                      : _L("On a stored face"))
+                : _L("(none — uses Hole plane)"));
+        break;
+    case CadFeatureType::Thread:
+        m_thread_plane->SetSelection(index_from_plane(f.plane));
+        m_thread_radius->SetValue(f.thread_radius * 2.0);   // field = diameter
+        m_thread_pitch->SetValue(f.thread_pitch);
+        m_thread_height->SetValue(f.thread_height);
+        m_thread_depth->SetValue(f.thread_depth);
+        m_thread_internal->SetValue(f.thread_internal);
+        m_thread_x->SetValue(f.thread_x);
+        m_thread_y->SetValue(f.thread_y);
+        if (m_thread_std) m_thread_std->SetSelection(0);   // Custom: spins reflect the stored feature
+        // Same latch, same failure, same fix as Hole above (uif9).
+        m_thread_on_face    = !is_base_plane(f.plane, m_doc.modeling_origin);
+        m_thread_face_plane = f.plane;
+        m_thread_face_body  = m_thread_on_face ? f.target_body : -1;
+        if (m_thread_target_label)
+            m_thread_target_label->SetLabel(m_thread_on_face
+                ? (f.target_body >= 0 ? wxString::Format(_L("On a face of Body %d"), f.target_body + 1)
+                                      : _L("On a stored face"))
+                : _L("(none — uses Thread plane)"));
+        break;
+    case CadFeatureType::Shell:
+        m_shell_thickness->SetValue(f.shell_thickness);
+        m_sel_solid_face = f.shell_face;
+        m_shell_face_label->SetLabel(f.shell_face >= 0
+            ? wxString::Format(_L("Face %d"), f.shell_face)
+            : _L("(all faces — closed hollow)"));
+        break;
+    case CadFeatureType::Revolve:
+        m_revolve_angle->SetValue(f.revolve_angle);
+        m_revolve_axis->SetSelection(f.revolve_axis);
+        m_revolve_mode->SetSelection(static_cast<int>(f.mode));
+        m_revolve_flip->SetValue(f.flip);
+        m_revolve_sketch_ref = f.sketch_ref;
+        break;
+    case CadFeatureType::Sweep:
+        m_sweep_profile_ref = f.sketch_ref;
+        m_sweep_path_ref    = f.sweep_path_ref;   // show_tool pre-selects this in the picker
+        m_sweep_mode->SetSelection(static_cast<int>(f.mode));
+        break;
+    case CadFeatureType::Pattern:
+        m_pattern_type->SetSelection(f.pattern_circular ? 1 : 0);
+        m_pattern_count->SetValue(f.pattern_count);
+        m_pattern_spacing->SetValue(f.pattern_spacing);
+        m_pattern_dir->SetSelection(f.pattern_dir);
+        m_pattern_angle->SetValue(f.pattern_angle);
+        break;
+    case CadFeatureType::Plane:
+        populate_plane_choices(m_plane_base);
+        m_plane_base->SetSelection(f.plane_base);
+        m_plane_offset->SetValue(f.plane_offset);
+        m_plane_tilt->SetValue(f.plane_angle_tilt);
+        m_plane_tilt_axis->SetSelection(f.plane_axis);
+        m_plane_type->SetSelection((int)f.plane_type);
+        m_pl_faceA_body = f.plane_face_body;  m_pl_faceA = f.plane_face;
+        m_pl_faceB_body = f.plane_face2_body; m_pl_faceB = f.plane_face2;
+        m_pl_edgeA_body = f.plane_edge_body;  m_pl_edgeA = f.plane_edge;
+        m_pl_edgeB_body = f.plane_edge2_body; m_pl_edgeB = f.plane_edge2;
+        m_plane_usize->SetValue(f.plane_u_size);
+        m_plane_vsize->SetValue(f.plane_v_size);
+        m_plane_pick = PlanePick::None;
+        if (m_viewport) m_viewport->set_escalate_on_repick(true);   // pick abandoned
+    if (m_viewport) m_viewport->set_escalate_on_repick(true);   // pick abandoned
+        refresh_plane_labels();
+        break;
+    case CadFeatureType::Loft:
+        m_loft_refs = f.loft_profile_refs;   // show_tool re-checks these in the list
+        m_loft_ruled->SetValue(f.loft_ruled);
+        m_loft_mode->SetSelection(static_cast<int>(f.mode));
+        break;
+    case CadFeatureType::Draft:
+        m_draft_angle->SetValue(f.draft_angle);
+        m_sel_solid_face = f.draft_face;
+        m_draft_face_label->SetLabel(f.draft_face >= 0
+            ? wxString::Format(_L("Face %d"), f.draft_face)
+            : _L("(pick a side face)"));
+        break;
+    case CadFeatureType::Axis:
+        m_axis_type->SetSelection((int)f.axis_type);
+        m_ax_face_body = f.axis_body; m_ax_face = f.axis_face;
+        m_ax_edge = f.axis_edge;
+        populate_plane_choices(m_axis_plane_a);
+        populate_plane_choices(m_axis_plane_b);
+        m_axis_plane_a->SetSelection(f.axis_plane_a >= 0 ? f.axis_plane_a : 0);
+        m_axis_plane_b->SetSelection(f.axis_plane_b >= 0 ? f.axis_plane_b : 0);
+        m_axis_p1x->SetValue(f.axis_p1.x()); m_axis_p1y->SetValue(f.axis_p1.y()); m_axis_p1z->SetValue(f.axis_p1.z());
+        m_axis_p2x->SetValue(f.axis_p2.x()); m_axis_p2y->SetValue(f.axis_p2.y()); m_axis_p2z->SetValue(f.axis_p2.z());
+        m_axis_pick = AxisPick::None;
+        if (m_viewport) m_viewport->set_escalate_on_repick(true);   // pick abandoned
+    if (m_viewport) m_viewport->set_escalate_on_repick(true);   // pick abandoned
+        refresh_axis_labels();
+        break;
+    case CadFeatureType::CoordSys:
+        m_coordsys_type->SetSelection((int)f.coordsys_type);
+        m_cs_x->SetValue(f.coordsys_point.x());
+        m_cs_y->SetValue(f.coordsys_point.y());
+        m_cs_z->SetValue(f.coordsys_point.z());
+        m_cs_face_body = f.coordsys_body; m_cs_face = f.coordsys_face;
+        m_cs_edge = f.coordsys_edge;
+        m_cs_hx->SetValue(f.coordsys_x_hint.x());
+        m_cs_hy->SetValue(f.coordsys_x_hint.y());
+        m_cs_hz->SetValue(f.coordsys_x_hint.z());
+        m_coordsys_pick = CoordSysPick::None;
+        if (m_viewport) m_viewport->set_escalate_on_repick(true);   // pick abandoned
+    if (m_viewport) m_viewport->set_escalate_on_repick(true);   // pick abandoned
+        refresh_coordsys_labels();
+        refresh_cs_body_choice();
+        if (m_cs_body && f.coordsys_body >= 0) {
+            m_cs_body->SetSelection(f.coordsys_body + 1);
+            if (m_viewport) m_viewport->set_xray_focus(f.coordsys_body);
+        }
+        break;
+    case CadFeatureType::Boolean:
+        // List the bodies available to the boolean (as-of its timeline slot), so the consumed
+        // tool body still appears and the saved selections below land on the right entries.
+        populate_body_choices(m_edit_index);
+        m_bool_op->SetSelection(f.mode == BooleanMode::Cut       ? 1
+                              : f.mode == BooleanMode::Intersect ? 2 : 0);  // 0 = Union/Add
+        if (f.target_body >= 0 && f.target_body < int(m_bool_target->GetCount()))
+            m_bool_target->SetSelection(f.target_body);
+        if (f.bool_tool_body >= 0 && f.bool_tool_body < int(m_bool_tool->GetCount()))
+            m_bool_tool->SetSelection(f.bool_tool_body);
+        m_bool_keep->SetValue(f.bool_keep_tool);
+        m_bool_tol->SetValue(f.bool_tolerance);
+        break;
+    case CadFeatureType::Cut:
+        // Same as-of-timeline reasoning as Boolean: a Cut splits one body into two, so the
+        // live body list does not match the one this feature's target index was recorded
+        // against. Replay to just before it and the stored index lands on the right entry.
+        populate_body_choices(m_edit_index);
+        if (f.target_body >= 0 && f.target_body < int(m_cut_target->GetCount()))
+            m_cut_target->SetSelection(f.target_body);
+        else if (m_cut_target->GetCount() > 0)
+            m_cut_target->SetSelection(0);
+        populate_plane_choices(m_cut_plane);
+        m_cut_plane->SetSelection(index_from_plane(f.plane));
+        m_cut_offset->SetValue(f.cut_offset);
+        break;
+    case CadFeatureType::SurfaceExtrude:
+        m_surf_extrude_distance->SetValue(f.distance);
+        m_surf_extrude_sketch_ref = f.sketch_ref;
+        if (m_surf_extrude_sketch_ref >= 0 && m_surf_extrude_sketch_ref < int(m_doc.features.size()))
+            m_surf_extrude_sketch_label->SetLabel(_L("Sketch: ") +
+                wxString::FromUTF8(m_doc.features[m_surf_extrude_sketch_ref].name));
+        break;
+    case CadFeatureType::SurfaceRevolve:
+        m_surf_revolve_angle->SetValue(f.revolve_angle);
+        m_surf_revolve_axis->SetSelection(f.revolve_axis);
+        m_surf_revolve_flip->SetValue(f.flip);
+        m_surf_revolve_sketch_ref = f.sketch_ref;
+        if (m_surf_revolve_sketch_ref >= 0 && m_surf_revolve_sketch_ref < int(m_doc.features.size()))
+            m_surf_revolve_sketch_label->SetLabel(_L("Sketch: ") +
+                wxString::FromUTF8(m_doc.features[m_surf_revolve_sketch_ref].name));
+        break;
+    case CadFeatureType::SurfaceLoft:
+        m_surf_loft_refs = f.loft_profile_refs;
+        m_surf_loft_ruled->SetValue(f.loft_ruled);
+        break;
+    case CadFeatureType::SurfaceFill:
+        m_surf_fill_sketch_ref = f.sketch_ref;
+        if (m_surf_fill_sketch_ref >= 0 && m_surf_fill_sketch_ref < int(m_doc.features.size()))
+            m_surf_fill_sketch_label->SetLabel(_L("Sketch: ") +
+                wxString::FromUTF8(m_doc.features[m_surf_fill_sketch_ref].name));
+        break;
+    case CadFeatureType::SurfaceOffset:
+        populate_sheet_body_choices(m_surf_offset_body);
+        m_surf_offset_distance->SetValue(f.plane_offset);
+        // target_body is a BODY index; the rows are sheets only, so match, don't index.
+        select_sheet_choice(m_surf_offset_body, f.target_body);
+        break;
+    case CadFeatureType::ThickenSurface:
+        populate_sheet_body_choices(m_surf_thicken_body);
+        m_surf_thicken_thickness->SetValue(f.thicken_thickness);
+        m_surf_thicken_flip->SetValue(f.thicken_flip);
+        select_sheet_choice(m_surf_thicken_body, f.target_body);
+        break;
+    case CadFeatureType::Transform: {
+        fill_body_choice(m_xf_body, m_edit_index, f.target_body);
+        m_xf_dx->SetValue(f.xf_translate.x());
+        m_xf_dy->SetValue(f.xf_translate.y());
+        m_xf_dz->SetValue(f.xf_translate.z());
+        const int ax = (std::abs(f.xf_axis.x()) > 0.5) ? 0 : (std::abs(f.xf_axis.y()) > 0.5) ? 1 : 2;
+        m_xf_axis->SetSelection(ax);
+        m_xf_angle->SetValue(f.xf_angle_deg);
+        m_xf_pivot_x->SetValue(f.xf_pivot.x());
+        m_xf_pivot_y->SetValue(f.xf_pivot.y());
+        m_xf_pivot_z->SetValue(f.xf_pivot.z());
+        m_xf_copy->SetValue(f.xf_copy);
+        break;
+    }
+    case CadFeatureType::Mirror: {
+        fill_body_choice(m_mirror_body, m_edit_index, f.target_body);
+        populate_plane_choices(m_mirror_plane);
+        m_mirror_plane->SetSelection(index_from_plane(f.plane));
+        m_mirror_keep->SetValue(f.mirror_keep_original);
+        break;
+    }
+    case CadFeatureType::Thicken: {
+        fill_body_choice(m_thicken_body, m_edit_index, f.target_body);
+        m_sel_solid_face = f.thicken_face;
+        m_thicken_face_label->SetLabel(f.thicken_face >= 0
+            ? wxString::Format(_L("Face %d"), f.thicken_face)
+            : _L("(pick a solid face)"));
+        m_thicken_thickness->SetValue(f.thicken_thickness);
+        m_thicken_flip->SetValue(f.thicken_flip);
+        break;
+    }
+    case CadFeatureType::Rib: {
+        fill_body_choice(m_rib_body, m_edit_index, f.target_body);
+        {
+            m_rib_sketch->Clear();
+            int pre_sel = wxNOT_FOUND;
+            for (int i = 0; i < int(m_doc.features.size()); ++i) {
+                if (m_doc.features[i].type == CadFeatureType::Sketch) {
+                    const int pos = combo_append_index(m_rib_sketch,
+                                                       wxString::FromUTF8(m_doc.features[i].name), i);
+                    if (i == f.rib_sketch_ref) pre_sel = pos;
+                }
+            }
+            if (pre_sel != wxNOT_FOUND) m_rib_sketch->SetSelection(pre_sel);
+            else if (m_rib_sketch->GetCount() > 0) m_rib_sketch->SetSelection(0);
+        }
+        m_rib_entity->SetValue(f.rib_entity);
+        m_rib_thickness->SetValue(f.rib_thickness);
+        m_rib_depth->SetValue(f.rib_depth);
+        break;
+    }
+    case CadFeatureType::Project: {
+        fill_body_choice(m_proj_source_body, m_edit_index, f.project_source_body);
+        populate_plane_choices(m_proj_plane);
+        m_proj_plane->SetSelection(index_from_plane(f.plane));
+        m_sel_solid_face = f.project_face;
+        m_proj_face_label->SetLabel(f.project_face >= 0
+            ? wxString::Format(_L("Face %d"), f.project_face)
+            : _L("(all edges)"));
+        break;
+    }
+    case CadFeatureType::DeleteFace: {
+        fill_body_choice(m_del_face_body, m_edit_index, f.target_body);
+        m_del_faces = f.delete_faces;
+        {
+            wxString s;
+            for (size_t i = 0; i < m_del_faces.size(); ++i) {
+                if (i > 0) s += ", ";
+                s += wxString::Format("Face %d", m_del_faces[i]);
+            }
+            m_del_face_list->SetLabel(s.empty() ? _L("(none)") : s);
+        }
+        break;
+    }
+    case CadFeatureType::Helix:
+        populate_plane_choices(m_helix_plane);
+        m_helix_plane->SetSelection(index_from_plane(f.plane));
+        m_helix_radius->SetValue(f.helix_radius);
+        m_helix_pitch->SetValue(f.helix_pitch);
+        m_helix_height->SetValue(f.helix_height);
+        m_helix_left_handed->SetValue(f.helix_left_handed);
+        m_helix_taper->SetValue(f.helix_taper_deg);
+        break;
+    case CadFeatureType::Mate:
+        m_mate_kind->SetSelection(f.mate_kind);
+        // CoordSys pickers are repopulated by open_tool(Mate); pre-selection
+        // is done there too via the stored feature index.
+        m_mate_offset->SetValue(f.mate_offset);
+        m_mate_angle->SetValue(f.mate_angle);
+        m_mate_flip->SetValue(f.mate_flip);
+        break;
+    default: break;
+    }
+}
+
+void DesignPanel::on_edit_feature()
+{
+    int sel = tree_selection();
+    if (sel == wxNOT_FOUND) {
+        set_status(_L("Select a feature in the tree first"));
+        m_status->Refresh();
+        return;
+    }
+    const CadFeature& f = m_doc.features[sel];
+    reset_edit_state();
+
+    switch (f.type) {
+    case CadFeatureType::Sketch:
+        // Imported Text/SVG art has no editable sketch dialog — edit means
+        // move / scale its placement instead, behind the same Confirm/Cancel gate as
+        // the initial insert (Cancel = undo restores the prior placement).
+        if (!f.imported_regions.empty()) {
+            m_doc.checkpoint();   // undo boundary: re-placing imported art
+            on_transform_imported(sel);
+            m_insert_feat = sel;
+            open_insert_card(wxString::FromUTF8(f.name));
+            break;
+        }
+        m_edit_index = sel;
+        if (!f.entities.empty()) {
+            // Entity sketcher: re-open the geometry for full in-canvas editing (handles,
+            // live quotes, regular-polygon drag) in the ENTITY sketch UI (the top sketch
+            // toolbar + session card), NOT the legacy parametric card. The commit handler
+            // replaces this feature in place (see m_edit_index). Hide its display overlay
+            // so the live tool is the only copy drawn.
+            set_ui_mode(UiMode::Sketch);
+            if (m_viewport) {
+                m_viewport->set_display_sketches({});
+                m_viewport->edit_sketch(f.entities, f.entity_constraints, f.plane);
+            }
+            m_status->SetForegroundColour(wxNullColour);
+            set_status(_L("Editing sketch — drag a handle or click a quote to edit"));
+            m_status->Refresh();
+        } else {
+            load_feature_into_dialog(f);
+            open_tool(Tool::Sketch);
+        }
+        break;
+    case CadFeatureType::Extrude:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Extrude);
+        break;
+    case CadFeatureType::Fillet:
+    case CadFeatureType::Chamfer:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Dressup);
+        break;
+    case CadFeatureType::Hole:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Hole);
+        break;
+    case CadFeatureType::Thread:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Thread);
+        break;
+    case CadFeatureType::Shell:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Shell);
+        break;
+    case CadFeatureType::Revolve:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Revolve);
+        break;
+    case CadFeatureType::Sweep:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Sweep);
+        break;
+    case CadFeatureType::Pattern:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Pattern);
+        break;
+    case CadFeatureType::Plane:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Plane);
+        break;
+    case CadFeatureType::Axis:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Axis);
+        break;
+    case CadFeatureType::CoordSys:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::CoordSys);
+        break;
+    case CadFeatureType::Loft:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Loft);
+        break;
+    case CadFeatureType::Draft:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Draft);
+        break;
+    case CadFeatureType::Boolean:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Boolean);
+        break;
+    case CadFeatureType::SurfaceExtrude:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::SurfaceExtrude);
+        break;
+    case CadFeatureType::SurfaceRevolve:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::SurfaceRevolve);
+        break;
+    case CadFeatureType::SurfaceLoft:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::SurfaceLoft);
+        break;
+    case CadFeatureType::SurfaceFill:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::SurfaceFill);
+        break;
+    case CadFeatureType::SurfaceOffset:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::SurfaceOffset);
+        break;
+    case CadFeatureType::ThickenSurface:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::ThickenSurface);
+        break;
+    case CadFeatureType::Transform:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Transform);
+        break;
+    case CadFeatureType::Mirror:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Mirror);
+        break;
+    case CadFeatureType::Thicken:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Thicken);
+        break;
+    case CadFeatureType::Rib:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Rib);
+        break;
+    case CadFeatureType::Project:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Project);
+        break;
+    case CadFeatureType::DeleteFace:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::DeleteFace);
+        break;
+    case CadFeatureType::Helix:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Helix);
+        break;
+    case CadFeatureType::Mate:
+        m_edit_index = sel;
+        m_mate_kind->SetSelection(f.mate_kind);
+        m_mate_offset->SetValue(f.mate_offset);
+        m_mate_angle->SetValue(f.mate_angle);
+        m_mate_flip->SetValue(f.mate_flip);
+        open_tool(Tool::Mate);   // populates CS pickers; pre-selects from current selection
+        // Now set the re-edit cs_a/cs_b after populating (override the open_tool default)
+        {
+            int pre_a = wxNOT_FOUND, pre_b = wxNOT_FOUND;
+            for (unsigned i = 0; i < m_mate_cs_a->GetCount(); ++i) {
+                const auto* cd = m_mate_cs_a->GetClientData(i);
+                if (cd && int(reinterpret_cast<intptr_t>(cd)) == f.mate_cs_a) pre_a = int(i);
+            }
+            for (unsigned i = 0; i < m_mate_cs_b->GetCount(); ++i) {
+                const auto* cd = m_mate_cs_b->GetClientData(i);
+                if (cd && int(reinterpret_cast<intptr_t>(cd)) == f.mate_cs_b) pre_b = int(i);
+            }
+            if (pre_a != wxNOT_FOUND) m_mate_cs_a->SetSelection(pre_a);
+            if (pre_b != wxNOT_FOUND) m_mate_cs_b->SetSelection(pre_b);
+        }
+        break;
+    case CadFeatureType::Cut:
+        m_edit_index = sel;
+        load_feature_into_dialog(f);
+        open_tool(Tool::Cut);
+        break;
+    case CadFeatureType::Import:
+        // An imported solid has no parameters to re-edit: its geometry is rigid data read
+        // from the file, not something rebuilt from numbers. Repositioning it is Transform's
+        // job, and that feature already exists — so point there rather than invent a dialog
+        // that would only duplicate it. (Imported 2D Text/SVG art is different and IS
+        // re-editable; it arrives as a Sketch feature with imported_regions, handled above.)
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("An imported solid has no parameters — use Transform to move or rotate it"));
+        m_status->Refresh();
+        break;
+    default:
+        // Every CadFeatureType now has a case. Kept as a guard so a type added later
+        // announces itself instead of silently swallowing the Edit click.
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("This feature type can't be edited yet"));
+        m_status->Refresh();
+        break;
+    }
+}
+
+void DesignPanel::on_export_step()
+{
+    // Bake any open feature preview first, so the STEP matches what is shown (mirrors on_commit).
+    if (m_active != Tool::None)
+        confirm_tool();
+    if (m_doc.bodies.empty()) {
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("Nothing to export — add a feature first"));
+        m_status->Refresh();
+        return;
+    }
+    wxFileDialog dlg(this, _L("Export STEP"), wxEmptyString, "model.step",
+                     "STEP files (*.step;*.stp)|*.step;*.stp",
+                     wxFD_SAVE | wxFD_OVERWRITE_PROMPT);
+    if (dlg.ShowModal() != wxID_OK)
+        return;
+    sync_body_xform();   // export bodies at their displayed Move-gizmo positions
+    std::string err;
+    const bool ok = m_doc.export_step(dlg.GetPath().ToUTF8().data(), m_body_xform, err);
+    m_status->SetForegroundColour(ok ? wxColour(120, 210, 120) : wxColour(235, 110, 110));
+    set_status(ok ? _L("Exported STEP")
+                          : _L("STEP export failed: ") + wxString::FromUTF8(err));
+    m_status->Refresh();
+}
+
+void DesignPanel::on_commit()
+{
+    // A feature tool open with a live preview ghost (e.g. a fillet being previewed) is
+    // NOT yet part of the body. Apply it first so "Commit to Plate" ships exactly what
+    // is shown on screen, not the pre-feature solid. (confirm_tool() applies + closes.)
+    if (m_active != Tool::None)
+        confirm_tool();
+
+    if (m_doc.display_mesh.its.indices.empty()) {
+        set_status(_L("Nothing to commit — add a feature first"));
+        return;
+    }
+    ObjectList* obj_list = wxGetApp().obj_list();
+    if (obj_list == nullptr)
+        return;
+
+    // Multi-body: ship each (visible) body as its own plate object so they arrive on the
+    // slicer plate as independent, separately-arrangeable parts (Onshape "Commit all parts").
+    // Hidden bodies are skipped — what you see on the Design plate is what gets committed.
+    sync_body_visible();
+    rebuild_disp_meshes();   // ship moved bodies at their Move-gizmo positions
+    if (m_disp_body_meshes.size() > 1) {
+        int committed = 0;
+        for (size_t b = 0; b < m_disp_body_meshes.size(); ++b) {
+            if (b < m_body_visible.size() && !m_body_visible[b]) continue;   // skip hidden
+            if (m_disp_body_meshes[b].its.indices.empty()) continue;
+            obj_list->load_mesh_object(m_disp_body_meshes[b],
+                                       "Design Body " + std::to_string(b + 1));
+            ++committed;
+        }
+        if (committed == 0) {   // every body hidden — nothing to ship
+            set_status(_L("All bodies hidden — show one before committing"));
+            return;
+        }
+    } else {
+        obj_list->load_mesh_object(m_disp_pick_mesh, "Design Body");
+    }
+
+    // Persist the editable parametric recipe alongside the committed meshes so the
+    // saved 3MF reopens with the full feature tree, not just the baked solid. An empty
+    // doc clears it, keeping non-CAD projects clean.
+    sync_recipe_to_model();
+
+    if (wxGetApp().mainframe != nullptr)
+        wxGetApp().mainframe->select_tab(TAB_ID_PREPARE);
+}
+
+CadFeature DesignPanel::build_candidate(Tool t) const
+{
+    CadFeature f;
+    // EDIT MODE: a feature card edits only scalar parameters. The feature's structural
+    // identity — profile source (sketch_ref / entities / picked face), its plane, the
+    // up-to-face target and the target body — must be preserved from the feature being
+    // edited, NOT re-derived from the live tool state (which still reflects the last *add*
+    // flow). GUI extrudes carry their profile as `entities` with sketch_ref = -1, which the
+    // card never restores, so a fresh rebuild produced an empty profile -> a misplaced new
+    // box. Seed from the original; the cases below overlay card scalars and skip the
+    // structural assignments while editing.
+    const bool editing = (m_edit_index >= 0 && m_edit_index < int(m_doc.features.size()));
+    if (editing)
+        f = m_doc.features[m_edit_index];
+    switch (t) {
+    case Tool::Sketch:
+        f.type   = CadFeatureType::Sketch;
+        f.shape  = (m_shape->GetSelection() == 0) ? SketchShape::Rectangle : SketchShape::Circle;
+        // The plane is STRUCTURAL, like Extrude's profile source. While EDITING it is preserved
+        // from the seeded original — the card carries no plane control and the old combo silently
+        // collapsed a face plane to a base plane through the modeling origin. While ADDING it
+        // comes from what is picked in the viewport. e1p.
+        if (!editing) { wxString where; f.plane = sketch_plane_from_selection(where); }
+        f.width  = m_width->GetValue();
+        f.height = m_height->GetValue();
+        f.radius = m_radius->GetValue();
+        break;
+    case Tool::Extrude:
+        f.type        = CadFeatureType::Extrude;
+        f.distance    = m_distance->GetValue();
+        f.symmetric   = false;
+        f.extrude_end = static_cast<ExtrudeEnd>(m_extrude_end->GetSelection());
+        f.distance2   = m_distance2->GetValue();
+        f.taper_deg   = m_taper->GetValue();
+        f.flip        = m_flip->GetValue();
+        f.mode       = (m_mode->GetSelection() == 0) ? BooleanMode::New
+                     : (m_mode->GetSelection() == 1) ? BooleanMode::Add
+                     : (m_mode->GetSelection() == 2) ? BooleanMode::Cut
+                                                     : BooleanMode::Intersect;
+        // Profile source + up-to-face target are structural: re-derive them from the live
+        // tool state only when ADDING. While editing they are preserved from the seeded
+        // original (the card changed only depth/taper/flip/mode).
+        if (!editing) {
+            f.up_to_face = (f.extrude_end == ExtrudeEnd::UpToFace) ? m_sel_solid_face : -1;
+            if (m_extrude_face_src >= 0) {
+                // Face-as-profile extrude: the kernel grabs the body face by id.
+                f.extrude_src_face = m_extrude_face_src;
+                f.sketch_ref       = -1;
+            } else if (extrude_uses_loop()) {
+                // Just the click-selected loop: carry its entity subset on the feature
+                // (sketch_ref = -1 -> build_sketch_wire uses f.entities).
+                f.sketch_ref = -1;
+                f.entities   = m_viewport->selected_loop_entities();
+                f.plane      = m_doc.features[m_extrude_sketch_ref].plane;
+            } else {
+                f.sketch_ref = m_extrude_sketch_ref;
+                // On-face engraving Cut against the host body (matches the commit).
+                if (m_extrude_sketch_ref >= 0 && m_extrude_sketch_ref < int(m_doc.features.size())
+                    && m_doc.features[m_extrude_sketch_ref].import_on_face)
+                    f.target_body = m_doc.features[m_extrude_sketch_ref].import_face_body;
+            }
+        }
+        break;
+    case Tool::Dressup:
+        f.type         = (m_dressup_type->GetSelection() == 0) ? CadFeatureType::Fillet
+                                                               : CadFeatureType::Chamfer;
+        f.dressup_size = m_dressup_size->GetValue();
+        f.face_group   = static_cast<FaceGroup>(m_face_group->GetSelection());
+        // A click-selected solid edge overrides the face-group: dress THAT edge.
+        f.dressup_edge = m_sel_solid_edge;   // -1 when no edge picked
+        break;
+    case Tool::Hole:
+        f.type          = CadFeatureType::Hole;
+        f.plane         = hole_plane();
+        f.hole_diameter = m_hole_diameter->GetValue();
+        f.hole_depth    = m_hole_depth->GetValue();
+        f.hole_through  = m_hole_through->GetValue();
+        f.hole_x        = m_hole_x->GetValue();
+        f.hole_y        = m_hole_y->GetValue();
+        if (m_hole_on_face) f.target_body = m_hole_face_body;   // preview the right body
+        break;
+    case Tool::Thread:
+        f.type            = CadFeatureType::Thread;
+        f.plane           = thread_plane();
+        f.thread_radius   = m_thread_radius->GetValue() * 0.5;   // field = diameter -> kernel radius
+        f.thread_pitch    = m_thread_pitch->GetValue();
+        f.thread_height   = m_thread_height->GetValue();
+        f.thread_depth    = m_thread_depth->GetValue();
+        f.thread_internal = m_thread_internal->GetValue();
+        f.thread_x        = m_thread_x->GetValue();
+        f.thread_y        = m_thread_y->GetValue();
+        if (m_thread_on_face) f.target_body = m_thread_face_body;   // tap the right body
+        break;
+    case Tool::Shell:
+        f.type            = CadFeatureType::Shell;
+        f.shell_thickness = m_shell_thickness->GetValue();
+        // A picked solid face opens the shell there; -1 = closed hollow.
+        f.shell_face      = (m_sel_solid_face >= 0) ? m_sel_solid_face : -1;
+        break;
+    case Tool::Draft:
+        f.type        = CadFeatureType::Draft;
+        f.draft_angle = m_draft_angle->GetValue();
+        f.draft_face  = (m_sel_solid_face >= 0) ? m_sel_solid_face : -1;
+        break;
+    case Tool::Revolve:
+        f.type          = CadFeatureType::Revolve;
+        f.sketch_ref    = m_revolve_sketch_ref;
+        f.revolve_angle = m_revolve_angle->GetValue();
+        f.revolve_axis  = m_revolve_axis->GetSelection();
+        f.flip          = m_revolve_flip->GetValue();
+        f.mode          = static_cast<BooleanMode>(m_revolve_mode->GetSelection());
+        break;
+    case Tool::Sweep: {
+        f.type           = CadFeatureType::Sweep;
+        f.sketch_ref     = m_sweep_profile_ref;
+        const int sel    = m_sweep_path ? m_sweep_path->GetSelection() : wxNOT_FOUND;
+        f.sweep_path_ref = (sel != wxNOT_FOUND)
+            ? int(reinterpret_cast<intptr_t>(m_sweep_path->GetClientData(sel))) : -1;
+        f.mode           = static_cast<BooleanMode>(m_sweep_mode->GetSelection());
+        break;
+    }
+    case Tool::Pattern:
+        f.type             = CadFeatureType::Pattern;
+        f.pattern_circular = (m_pattern_type->GetSelection() == 1);
+        f.pattern_count    = int(m_pattern_count->GetValue());
+        f.pattern_spacing  = m_pattern_spacing->GetValue();
+        f.pattern_dir      = m_pattern_dir->GetSelection();
+        f.pattern_angle    = m_pattern_angle->GetValue();
+        break;
+    case Tool::Plane:
+        f.type             = CadFeatureType::Plane;
+        f.plane_base       = m_plane_base->GetSelection();
+        f.plane_offset     = m_plane_offset->GetValue();
+        f.plane_angle_tilt = m_plane_tilt->GetValue();
+        f.plane_axis       = m_plane_tilt_axis->GetSelection();
+        apply_plane_refs(f);   // plane_type + face/edge refs + u/v size from the card
+        break;
+    case Tool::Axis:
+        f.type = CadFeatureType::Axis;
+        apply_axis_refs(f);
+        break;
+    case Tool::CoordSys:
+        f.type = CadFeatureType::CoordSys;
+        apply_coordsys_refs(f);
+        break;
+    case Tool::Loft: {
+        f.type      = CadFeatureType::Loft;
+        f.loft_ruled = m_loft_ruled->GetValue();
+        f.mode      = static_cast<BooleanMode>(m_loft_mode->GetSelection());
+        f.loft_profile_refs.clear();
+        for (unsigned i = 0; i < m_loft_list->GetCount(); ++i)
+            if (m_loft_list->IsChecked(i) && i < m_loft_sketch_idx.size())
+                f.loft_profile_refs.push_back(m_loft_sketch_idx[i]);
+        break;
+    }
+    case Tool::Boolean: {
+        f.type           = CadFeatureType::Boolean;
+        const int sel    = m_bool_op->GetSelection();
+        f.mode           = (sel == 1) ? BooleanMode::Cut
+                         : (sel == 2) ? BooleanMode::Intersect
+                                      : BooleanMode::Add;   // 0 = Union
+        f.target_body    = m_bool_target->GetSelection();
+        f.bool_tool_body = m_bool_tool->GetSelection();
+        f.bool_keep_tool = m_bool_keep->GetValue();
+        f.bool_tolerance = m_bool_tol->GetValue();   // OCCT fuzzy: robust cut on near-coincident faces
+        break;
+    }
+    case Tool::Cut:
+        f.type           = CadFeatureType::Cut;
+        f.plane          = plane_from_choice(m_cut_plane->GetSelection());
+        f.cut_offset     = m_cut_offset->GetValue();
+        f.cut_flip       = false;
+        f.cut_keep_upper = true;   // always split: keep both pieces as separate bodies
+        f.cut_keep_lower = true;
+        f.target_body    = m_cut_target->GetSelection();
+        break;
+    case Tool::SurfaceExtrude:
+        f.type      = CadFeatureType::SurfaceExtrude;
+        f.sketch_ref = m_surf_extrude_sketch_ref;
+        f.distance   = m_surf_extrude_distance->GetValue();
+        break;
+    case Tool::SurfaceRevolve:
+        f.type         = CadFeatureType::SurfaceRevolve;
+        f.sketch_ref   = m_surf_revolve_sketch_ref;
+        f.revolve_angle = m_surf_revolve_angle->GetValue();
+        f.revolve_axis = m_surf_revolve_axis->GetSelection();
+        f.flip         = m_surf_revolve_flip->GetValue();
+        break;
+    case Tool::SurfaceLoft: {
+        f.type      = CadFeatureType::SurfaceLoft;
+        f.loft_ruled = m_surf_loft_ruled->GetValue();
+        f.loft_profile_refs.clear();
+        for (unsigned i = 0; i < m_surf_loft_list->GetCount(); ++i)
+            if (m_surf_loft_list->IsChecked(i) && i < m_surf_loft_sketch_idx.size())
+                f.loft_profile_refs.push_back(m_surf_loft_sketch_idx[i]);
+        break;
+    }
+    case Tool::SurfaceFill:
+        f.type      = CadFeatureType::SurfaceFill;
+        f.sketch_ref = m_surf_fill_sketch_ref;
+        break;
+    case Tool::SurfaceOffset: {
+        f.type = CadFeatureType::SurfaceOffset;
+        f.target_body = sheet_choice_body(m_surf_offset_body);
+        f.plane_offset = m_surf_offset_distance->GetValue();
+        break;
+    }
+    case Tool::ThickenSurface: {
+        f.type = CadFeatureType::ThickenSurface;
+        f.target_body       = sheet_choice_body(m_surf_thicken_body);
+        f.thicken_thickness = m_surf_thicken_thickness->GetValue();
+        f.thicken_flip      = m_surf_thicken_flip->GetValue();
+        break;
+    }
+    case Tool::Transform: {
+        f.type = CadFeatureType::Transform;
+        const int sel = m_xf_body->GetSelection();
+        f.target_body   = (sel != wxNOT_FOUND) ? sel : -1;
+        f.xf_translate  = Vec3d(m_xf_dx->GetValue(), m_xf_dy->GetValue(), m_xf_dz->GetValue());
+        const int ax = m_xf_axis->GetSelection();
+        f.xf_axis   = (ax == 0) ? Vec3d(1, 0, 0) : (ax == 1) ? Vec3d(0, 1, 0) : Vec3d(0, 0, 1);
+        f.xf_pivot  = Vec3d(m_xf_pivot_x->GetValue(), m_xf_pivot_y->GetValue(), m_xf_pivot_z->GetValue());
+        f.xf_angle_deg = m_xf_angle->GetValue();
+        f.xf_copy      = m_xf_copy->GetValue();
+        break;
+    }
+    case Tool::Mirror: {
+        f.type = CadFeatureType::Mirror;
+        const int sel = m_mirror_body->GetSelection();
+        f.target_body          = (sel != wxNOT_FOUND) ? sel : -1;
+        f.plane                = plane_from_choice(m_mirror_plane->GetSelection());
+        f.mirror_keep_original = m_mirror_keep->GetValue();
+        f.mode                 = f.mirror_keep_original ? BooleanMode::New : BooleanMode::Add;
+        break;
+    }
+    case Tool::Thicken: {
+        f.type = CadFeatureType::Thicken;
+        const int sel = m_thicken_body->GetSelection();
+        f.target_body       = (sel != wxNOT_FOUND) ? sel : -1;
+        f.thicken_face      = (m_sel_solid_face >= 0) ? m_sel_solid_face : -1;
+        f.thicken_thickness = m_thicken_thickness->GetValue();
+        f.thicken_flip      = m_thicken_flip->GetValue();
+        break;
+    }
+    case Tool::Rib: {
+        f.type = CadFeatureType::Rib;
+        const int bsel = m_rib_body->GetSelection();
+        f.target_body      = (bsel != wxNOT_FOUND) ? bsel : -1;
+        const int ssel = m_rib_sketch->GetSelection();
+        f.rib_sketch_ref = (ssel != wxNOT_FOUND)
+                               ? int(reinterpret_cast<intptr_t>(m_rib_sketch->GetClientData(ssel))) : -1;
+        f.rib_entity     = m_rib_entity->GetValue();
+        f.rib_thickness  = m_rib_thickness->GetValue();
+        f.rib_depth      = m_rib_depth->GetValue();
+        break;
+    }
+    case Tool::Project: {
+        f.type = CadFeatureType::Project;
+        const int sel = m_proj_source_body->GetSelection();
+        f.project_source_body = (sel != wxNOT_FOUND) ? sel : -1;
+        f.plane               = plane_from_choice(m_proj_plane->GetSelection());
+        if (m_sel_solid_face >= 0) {
+            f.project_face = m_sel_solid_face;
+        } else {
+            f.project_face = -1;
+        }
+        f.project_edges.clear();  // empty => use project_face
+        break;
+    }
+    case Tool::DeleteFace: {
+        f.type = CadFeatureType::DeleteFace;
+        const int sel = m_del_face_body->GetSelection();
+        f.target_body  = (sel != wxNOT_FOUND) ? sel : -1;
+        f.delete_faces = m_del_faces;
+        break;
+    }
+    case Tool::Helix: {
+        f.type = CadFeatureType::Helix;
+        f.plane              = plane_from_choice(m_helix_plane->GetSelection());
+        f.helix_radius       = m_helix_radius->GetValue();
+        f.helix_pitch        = m_helix_pitch->GetValue();
+        f.helix_height       = m_helix_height->GetValue();
+        f.helix_left_handed  = m_helix_left_handed->GetValue();
+        f.helix_taper_deg    = m_helix_taper->GetValue();
+        break;
+    }
+    case Tool::Mate: {
+        f.type       = CadFeatureType::Mate;
+        f.mate_kind  = m_mate_kind->GetSelection();
+        f.mate_cs_a  = m_mate_cs_a->GetSelection() != wxNOT_FOUND
+                           ? int(reinterpret_cast<intptr_t>(m_mate_cs_a->GetClientData(m_mate_cs_a->GetSelection()))) : -1;
+        f.mate_cs_b  = m_mate_cs_b->GetSelection() != wxNOT_FOUND
+                           ? int(reinterpret_cast<intptr_t>(m_mate_cs_b->GetClientData(m_mate_cs_b->GetSelection()))) : -1;
+        f.mate_offset = m_mate_offset->GetValue();
+        f.mate_angle  = m_mate_angle->GetValue();
+        f.mate_flip   = m_mate_flip->GetValue();
+        break;
+    }
+    case Tool::Insert:   // imported art is committed by add_imported_sketch, not build_candidate
+    case Tool::None:
+        break;
+    }
+    // Boolean drives its own target/tool body from the card; every other tool targets the
+    // picked body (face-extrude reads its source face there, dress-up / hole / boolean-mode
+    // extrude mutate it). -1 when nothing is picked => auto (last body).
+    // Targeting the picked body is an ADD-time concern; while editing, the original feature's
+    // target_body is preserved from the seed (the card did not re-pick a body).
+    // HAZARD: this is a negative list, so a tool that picks its own body is broken by OMISSION —
+    // the card computes target_body and this line then throws it away. SurfaceOffset and
+    // ThickenSurface were missing: both read a SHEET body from their own combo and both had it
+    // overwritten with the picked SOLID's index. Any new card that picks a body belongs here.
+    if (!editing && m_active != Tool::Boolean && m_active != Tool::Cut
+        && m_active != Tool::Transform && m_active != Tool::Mirror && m_active != Tool::Thicken
+        && m_active != Tool::DeleteFace && m_active != Tool::Rib && m_active != Tool::Project
+        && m_active != Tool::Helix && m_active != Tool::SurfaceOffset
+        && m_active != Tool::ThickenSurface)
+        f.target_body = m_sel_solid_body;
+    return f;
+}
+
+// Resolve the active Extrude's profile plane + a representative 2D centroid (arrow anchor)
+// and push them to the viewport gizmo. Self-gates: clears the gizmo unless Extrude is open.
+// Keep the Dress-up card honest about what Confirm will actually round: the single edge the
+// user picked in the viewport, or the face-group. build_dressup reads m_sel_solid_edge first and
+// only falls back to the group, so when an edge is picked the group combo is inert — grey it out
+// rather than leave it showing a value it will not use.
+void DesignPanel::sync_dressup_target()
+{
+    if (m_dressup_edge_label == nullptr) return;
+    const bool have_edge = (m_sel_solid_edge >= 0);
+    m_dressup_edge_label->SetLabel(have_edge
+        ? wxString::Format(_L("Edge %d"), m_sel_solid_edge)
+        : _L("(no edge picked — group below)"));
+    if (m_face_group != nullptr) m_face_group->Enable(!have_edge);
+    m_dressup_edge_label->Refresh();
+}
+
+void DesignPanel::update_fillet_gizmo()
+{
+    if (!m_viewport) return;
+    // Only while the Fillet/Chamfer card is open AND a solid EDGE is the target. Face-group
+    // dress-up (no picked edge) keeps the docked card with no in-canvas handle. The body centroid
+    // comes from the transformed display mesh so it matches the (transformed) edge sample points.
+    const bool ok = (m_active == Tool::Dressup) && m_sel_solid_edge >= 0
+                    && m_sel_solid_body >= 0 && m_sel_solid_body < int(m_disp_body_meshes.size());
+    if (!ok) { m_viewport->clear_fillet_gizmo(); return; }
+    const Vec3d centroid = m_disp_body_meshes[m_sel_solid_body].bounding_box().center();
+    m_viewport->begin_fillet_gizmo(centroid, m_dressup_size->GetValue());
+}
+
+// Push the active Hole card's plane + position + diameter/depth to the viewport gizmo.
+// Grey the FEATURE buttons whose tool cannot run yet, and say why in the tooltip (o9j).
+// Tommaso reported the array controls as MISSING; they were not, but Pattern with no body
+// accepted the click, opened nothing, and wrote its refusal somewhere other than where the click
+// happened — from the user's seat that is indistinguishable from a dead button. A control that
+// cannot act should look like it cannot act, before it is pressed.
+//
+// Only the three top-level buttons that carry a body-count guard are gated. The same guard also
+// appears on rows INSIDE the flyouts, and those stay live: a drawer holds sketch-only entries too,
+// so disabling the drawer would hide tools that are perfectly usable. Their refusal message is
+// still written, and now next to the geometry.
+//
+// The keyboard shortcuts (Shift+N / Shift+X / Shift+B) deliberately keep running the guarded
+// action rather than being gated: a key press has no greyed-out state to see, so the sentence is
+// the only feedback there is.
+void DesignPanel::update_body_gates()
+{
+    const int n = int(m_doc.bodies.size());
+    for (const BodyGate& g : m_body_gates) {
+        if (g.btn == nullptr) continue;
+        const bool live = n >= g.min_bodies;
+        g.btn->Enable(live);
+        g.btn->SetToolTip(live ? g.tip_live : g.tip_gated);
+    }
+}
+
+// Self-gates: clears the gizmo unless the Hole card is open.
+void DesignPanel::update_hole_gizmo()
+{
+    if (!m_viewport) return;
+    if (m_active != Tool::Hole) { m_viewport->clear_hole_gizmo(); return; }
+    const SketchPlane plane = hole_plane();
+    m_viewport->set_hole_face_bounds(m_hole_has_bounds, m_hole_umin, m_hole_umax,
+                                     m_hole_vmin, m_hole_vmax);
+    m_viewport->begin_hole_gizmo(plane,
+                                 m_hole_x->GetValue(), m_hole_y->GetValue(),
+                                 m_hole_diameter->GetValue(), m_hole_depth->GetValue(),
+                                 m_hole_through->GetValue());
+}
+
+// Push the active Thread card's plane + position + radius/length to the viewport gizmo.
+// Self-gates: clears the gizmo unless the Thread card is open.
+void DesignPanel::update_thread_gizmo()
+{
+    if (!m_viewport) return;
+    if (m_active != Tool::Thread) { m_viewport->clear_thread_gizmo(); return; }
+    const SketchPlane plane = thread_plane();
+    m_viewport->begin_thread_gizmo(plane,
+                                   m_thread_x->GetValue(), m_thread_y->GetValue(),
+                                   m_thread_radius->GetValue() * 0.5, m_thread_height->GetValue());
+}
+
+// Anchor an inward thickness arrow at the picked open face's centroid (along -outward-normal).
+// Self-gates: clears unless the Shell card is open AND a face is picked. The face centroid/normal
+// come from the kernel shape, then carry the body's display-only Move transform.
+void DesignPanel::update_shell_gizmo()
+{
+    if (!m_viewport) return;
+    const int b = m_sel_solid_body;
+    const bool ok = (m_active == Tool::Shell) && m_sel_solid_face >= 0
+                    && b >= 0 && b < int(m_doc.bodies.size());
+    if (!ok) { m_viewport->clear_shell_gizmo(); return; }
+    const TopoDS_Face fc = GeometryEngine::face_by_index(m_doc.bodies[b].shape, m_sel_solid_face);
+    if (fc.IsNull()) { m_viewport->clear_shell_gizmo(); return; }
+    Vec3d c = GeometryEngine::face_centroid_world(fc);
+    Vec3d n = GeometryEngine::face_normal_world(fc);
+    sync_body_xform();
+    if (b < int(m_body_xform.size())) {
+        c = m_body_xform[b] * c;
+        n = m_body_xform[b].linear() * n;
+    }
+    if (n.norm() < 1e-9) { m_viewport->clear_shell_gizmo(); return; }
+    // Arrow points inward (into the wall): -outward normal.
+    m_viewport->begin_shell_gizmo(c, (-n).normalized(), m_shell_thickness->GetValue());
+}
+
+void DesignPanel::update_revolve_gizmo()
+{
+    if (!m_viewport) return;
+    if (m_active != Tool::Revolve
+        || m_revolve_sketch_ref < 0 || m_revolve_sketch_ref >= int(m_doc.features.size())) {
+        m_viewport->clear_revolve_gizmo();
+        return;
+    }
+    const CadFeature& sk = m_doc.features[m_revolve_sketch_ref];
+    // Profile centroid in sketch coords (same rule as the Extrude gizmo: average entity centres,
+    // else profile points, else the plane origin for primitive shapes).
+    Vec2d centroid(0, 0);
+    if (!sk.entities.empty()) {
+        Vec2d acc(0, 0); int n = 0;
+        for (const SketchEntity& e : sk.entities) {
+            switch (e.type) {
+            case SketchEntity::Type::Line:    acc += 0.5 * (e.p0 + e.p1); ++n; break;
+            case SketchEntity::Type::Arc:
+            case SketchEntity::Type::EllipseArc:
+            case SketchEntity::Type::Circle:
+            case SketchEntity::Type::Ellipse: acc += e.center; ++n; break;
+            case SketchEntity::Type::Point:   acc += e.p0; ++n; break;
+            case SketchEntity::Type::BSpline:
+                if (!e.ctrl.empty()) {
+                    Vec2d s(0, 0); for (const Vec2d& q : e.ctrl) s += q;
+                    acc += s / double(e.ctrl.size()); ++n;
+                }
+                break;
+            }
+        }
+        if (n > 0) centroid = acc / double(n);
+    } else if (!sk.profile.points.empty()) {
+        for (const Vec2d& p : sk.profile.points) centroid += p;
+        centroid /= double(sk.profile.points.size());
+    }
+    m_viewport->begin_revolve_gizmo(sk.plane, centroid, m_revolve_axis->GetSelection(),
+                                    m_revolve_angle->GetValue(), m_revolve_flip->GetValue());
+}
+
+void DesignPanel::update_draft_gizmo()
+{
+    if (!m_viewport) return;
+    if (m_active != Tool::Draft || m_sel_solid_face < 0 || m_sel_solid_body < 0
+        || m_sel_solid_body >= int(m_doc.bodies.size())) {
+    m_viewport->clear_draft_gizmo();
+        return;
+    }
+    const TopoDS_Face f = GeometryEngine::face_by_index(m_doc.bodies[m_sel_solid_body].shape, m_sel_solid_face);
+    const Vec3d c = GeometryEngine::face_centroid_world(f);
+    const Vec3d n = GeometryEngine::face_normal_world(f);
+    m_viewport->set_draft_gizmo(c, n, m_draft_angle->GetValue());
+}
+
+void DesignPanel::update_cut_gizmo()
+{
+    if (!m_viewport) return;
+    if (m_active != Tool::Cut) { m_viewport->clear_cut_gizmo(); return; }
+    const int bi = m_cut_target ? m_cut_target->GetSelection() : -1;
+    if (bi < 0 || bi >= int(m_doc.bodies.size()) || bi >= int(m_doc.display_body_meshes.size())) {
+        m_viewport->clear_cut_gizmo();
+        return;
+    }
+    const SketchPlane plane = plane_from_choice(m_cut_plane->GetSelection());
+    const BoundingBoxf3 bb = m_doc.display_body_meshes[bi].bounding_box();
+    const Vec3d center = bb.center();
+    const double half = std::max(0.5 * (bb.max - bb.min).norm(), 10.0);
+    m_viewport->set_cut_gizmo(plane, m_cut_offset->GetValue(), center, half);
+}
+
+void DesignPanel::update_operand_highlight()
+{
+    if (!m_viewport) return;
+    // default: nothing highlighted
+    int bt = -1, bl = -1;
+    std::vector<std::pair<int, ColorRGBA>> sk;
+    if (m_active == Tool::Boolean) {
+        if (m_bool_target) bt = m_bool_target->GetSelection();
+        if (m_bool_tool)   bl = m_bool_tool->GetSelection();
+    } else if (m_active == Tool::Sweep) {
+        if (m_sweep_profile_ref >= 0) sk.emplace_back(m_sweep_profile_ref, ColorRGBA(0.30f, 0.85f, 1.0f, 1.0f)); // profile = cyan
+        if (m_sweep_path_ref    >= 0) sk.emplace_back(m_sweep_path_ref,    ColorRGBA(1.00f, 0.40f, 0.90f, 1.0f)); // path = magenta
+    } else if (m_active == Tool::Loft) {
+        // checked rows of m_loft_list map to feature indices via m_loft_sketch_idx
+        // (exactly as build_candidate(Tool::Loft) reads them).
+        if (m_loft_list)
+            for (unsigned i = 0; i < m_loft_list->GetCount(); ++i)
+                if (m_loft_list->IsChecked(i) && i < m_loft_sketch_idx.size())
+                    sk.emplace_back(m_loft_sketch_idx[i], ColorRGBA(0.40f, 0.90f, 0.50f, 1.0f)); // profiles = green
+    }
+    m_viewport->set_operand_bodies(bt, bl);
+    m_viewport->set_highlight_sketches(std::move(sk));
+}
+
+void DesignPanel::update_pattern_gizmo()
+{
+    if (!m_viewport) return;
+    if (m_active != Tool::Pattern || m_doc.display_body_meshes.empty()) {
+        m_viewport->clear_pattern_gizmo();
+        return;
+    }
+    // Pattern operates in the default world XY plane (matches the kernel: linear along world X/Y,
+    // circular about world Z through the origin). Anchor on the target body's bbox centre; if that
+    // body carries a display-only Move transform, shift the plane origin + anchor by it so the
+    // gizmo sits on the body where the ghost copies actually appear.
+    const int b = (m_sel_solid_body >= 0 && m_sel_solid_body < int(m_doc.display_body_meshes.size()))
+                  ? m_sel_solid_body : int(m_doc.display_body_meshes.size()) - 1;
+    SketchPlane plane;   // world XY axes by default
+    Vec3d base = m_doc.display_body_meshes[b].bounding_box().center();
+    if (b < int(m_body_xform.size())) {
+        plane.origin = m_body_xform[b].translation();
+        base = m_body_xform[b] * base;
+    }
+    m_viewport->begin_pattern_gizmo(plane, base, m_pattern_type->GetSelection() == 1,
+                                    int(m_pattern_count->GetValue()), m_pattern_dir->GetSelection(),
+                                    m_pattern_spacing->GetValue(), m_pattern_angle->GetValue());
+}
+
+void DesignPanel::update_extrude_gizmo()
+{
+    if (!m_viewport) return;
+    if (m_active != Tool::Extrude && m_active != Tool::SurfaceExtrude
+        && m_active != Tool::Thicken && m_active != Tool::Rib
+        && m_active != Tool::SurfaceOffset && m_active != Tool::ThickenSurface) {
+        m_viewport->clear_extrude_gizmo(); return;
+    }
+
+    // SurfaceOffset and ThickenSurface: one distance each, applied to a whole SHEET body chosen
+    // from a combo. A sheet has no single normal, so there is no frame to anchor an arrow on —
+    // which is why these were the two tools left with no handle at all.
+    //
+    // The way out is not to change what the tool operates on. Both still offset or thicken the
+    // ENTIRE sheet named in the combo; the picked face only says WHERE TO STAND THE ARROW. So
+    // the arrow appears whenever the user has a face of that sheet under selection, and its
+    // absence costs nothing — the card alone still works exactly as before. Purely additive, so
+    // no existing flow changes and there is no new precondition to learn.
+    if (m_active == Tool::SurfaceOffset || m_active == Tool::ThickenSurface) {
+        const bool off = (m_active == Tool::SurfaceOffset);
+        const int sheet = sheet_choice_body(off ? m_surf_offset_body : m_surf_thicken_body);
+        // Only when the picked face belongs to the sheet the tool will actually act on:
+        // an arrow standing on a different body would name the wrong thing.
+        if (sheet < 0 || sheet >= int(m_doc.bodies.size())
+            || m_sel_solid_body != sheet || m_sel_solid_face < 0) {
+            m_viewport->clear_extrude_gizmo(); return;
+        }
+        TopoDS_Face f = GeometryEngine::face_by_index(m_doc.bodies[sheet].shape, m_sel_solid_face);
+        if (f.IsNull()) { m_viewport->clear_extrude_gizmo(); return; }
+        SketchPlane plane = SketchPlane::from_face(f);
+        Vec3d c = GeometryEngine::face_centroid_world(f);
+        Vec3d n = GeometryEngine::face_normal_world(f);
+        if (f.Orientation() == TopAbs_REVERSED) n = -n;
+        sync_body_xform();
+        if (sheet < int(m_body_xform.size())) {
+            c = m_body_xform[sheet] * c;
+            n = m_body_xform[sheet].linear() * n;
+        }
+        plane.origin = c;
+        if (n.norm() > 1e-9) plane.normal = n.normalized();
+        wxSpinCtrlDouble* spin = off ? m_surf_offset_distance : m_surf_thicken_thickness;
+        m_viewport->set_extrude_gizmo(plane, Vec2d(0, 0), spin ? spin->GetValue() : 0.0,
+                                      0.0, false,
+                                      !off && m_surf_thicken_flip && m_surf_thicken_flip->GetValue());
+        return;
+    }
+
+    if (m_active == Tool::Rib) {
+        // Rib's DEPTH is a distance along the sketch plane normal — the same arrow again,
+        // anchored at the midpoint of the line the rib is built on rather than at a profile
+        // centroid, because a rib's line is the whole profile.
+        //
+        // This covers only half of L2 for Rib: the THICKNESS is an in-plane offset either side
+        // of that line and has no handle, which needs an affordance that does not exist yet.
+        // Half a tool made draggable is still strictly better than none — the remaining half is
+        // filed separately rather than left implied.
+        const int ssel = m_rib_sketch ? m_rib_sketch->GetSelection() : wxNOT_FOUND;
+        const int ref  = (ssel != wxNOT_FOUND)
+                             ? int(reinterpret_cast<intptr_t>(m_rib_sketch->GetClientData(ssel))) : -1;
+        if (ref < 0 || ref >= int(m_doc.features.size())) { m_viewport->clear_extrude_gizmo(); return; }
+        const CadFeature& sk = m_doc.features[ref];
+        const int ei = m_rib_entity ? m_rib_entity->GetValue() : 0;
+        if (ei < 0 || ei >= int(sk.entities.size())) { m_viewport->clear_extrude_gizmo(); return; }
+        const SketchEntity& e = sk.entities[ei];
+        const Vec2d mid = (e.type == SketchEntity::Type::Line) ? Vec2d(0.5 * (e.p0 + e.p1))
+                                                               : Vec2d(e.center);
+        m_viewport->set_extrude_gizmo(sk.plane, mid,
+                                      m_rib_depth ? m_rib_depth->GetValue() : 0.0,
+                                      0.0, false, false);
+        return;
+    }
+
+    if (m_active == Tool::SurfaceExtrude) {
+        const int ref = m_surf_extrude_sketch_ref;
+        if (ref < 0 || ref >= int(m_doc.features.size())) { m_viewport->clear_extrude_gizmo(); return; }
+        const CadFeature& sk = m_doc.features[ref];
+        Vec2d c(0, 0);
+        if (!sk.profile.points.empty()) {
+            for (const Vec2d& p : sk.profile.points) c += p;
+            c /= double(sk.profile.points.size());
+        }
+        m_viewport->set_extrude_gizmo(sk.plane, c,
+                                      m_surf_extrude_distance ? m_surf_extrude_distance->GetValue() : 0.0,
+                                      0.0, false, false);
+        return;
+    }
+
+    if (m_active == Tool::Thicken) {
+        const int b = m_sel_solid_body;
+        if (b < 0 || b >= int(m_doc.bodies.size()) || m_sel_solid_face < 0) {
+            m_viewport->clear_extrude_gizmo(); return;
+        }
+        TopoDS_Face f = GeometryEngine::face_by_index(m_doc.bodies[b].shape, m_sel_solid_face);
+        if (f.IsNull()) { m_viewport->clear_extrude_gizmo(); return; }
+        SketchPlane plane = SketchPlane::from_face(f);
+        Vec3d c = GeometryEngine::face_centroid_world(f);
+        Vec3d n = GeometryEngine::face_normal_world(f);
+        if (f.Orientation() == TopAbs_REVERSED) n = -n;   // outward
+        sync_body_xform();
+        if (b < int(m_body_xform.size())) { c = m_body_xform[b] * c; n = m_body_xform[b].linear() * n; }
+        plane.origin = c;
+        if (n.norm() > 1e-9) plane.normal = n.normalized();
+        m_viewport->set_extrude_gizmo(plane, Vec2d(0, 0),
+                                      m_thicken_thickness ? m_thicken_thickness->GetValue() : 0.0,
+                                      0.0, false,
+                                      m_thicken_flip && m_thicken_flip->GetValue());
+        return;
+    }
+
+    SketchPlane plane;
+    std::vector<SketchEntity> ents;
+    Vec2d centroid(0, 0);
+    bool  have = false, have_centroid = false;
+    if (extrude_uses_loop()) {
+        plane = m_doc.features[m_extrude_sketch_ref].plane;
+        ents  = m_viewport->selected_loop_entities();
+        have  = true;
+    } else if (m_extrude_sketch_ref >= 0 && m_extrude_sketch_ref < int(m_doc.features.size())) {
+        const CadFeature& sk = m_doc.features[m_extrude_sketch_ref];
+        plane = sk.plane;
+        ents  = sk.entities;
+        have  = true;
+        if (ents.empty() && !sk.profile.points.empty()) {
+            for (const Vec2d& p : sk.profile.points) centroid += p;
+            centroid /= double(sk.profile.points.size());
+            have_centroid = true;
+        }
+        // Primitive shape sketches (no entities/profile) are centred at the plane origin -> (0,0).
+    } else if (m_extrude_face_src >= 0 && !m_doc.bodies.empty()) {
+        // Face-as-profile (push/pull): anchor the arrow at the picked face's CENTROID, pointing
+        // along its outward normal. The face id is LOCAL to the owner body — route_feature reads
+        // it from `context` (the target, else the last body) — so look it up on that SAME body,
+        // never the whole-document compound (m_doc.body). from_face's plane origin sits at the
+        // plane's canonical point near the world origin, NOT on the face, which is why the arrow
+        // used to land on the bed. Carry the body's display Move transform so the arrow sits where
+        // the body is actually shown.
+        const int b = int(m_doc.bodies.size()) - 1;   // matches route_feature's default context
+        TopoDS_Face srcf = GeometryEngine::face_by_index(m_doc.bodies[b].shape, m_extrude_face_src);
+        if (!srcf.IsNull()) {
+            plane = SketchPlane::from_face(srcf);
+            Vec3d c = GeometryEngine::face_centroid_world(srcf);
+            Vec3d n = GeometryEngine::face_normal_world(srcf);
+            if (srcf.Orientation() == TopAbs_REVERSED) n = -n;   // outward, matches the kernel push
+            sync_body_xform();
+            if (b < int(m_body_xform.size())) { c = m_body_xform[b] * c; n = m_body_xform[b].linear() * n; }
+            plane.origin = c;
+            if (n.norm() > 1e-9) plane.normal = n.normalized();
+            have = true;
+        }
+    }
+    if (!have) { m_viewport->clear_extrude_gizmo(); return; }
+
+    if (!ents.empty()) {
+        Vec2d acc(0, 0); int n = 0;
+        for (const SketchEntity& e : ents) {
+            switch (e.type) {
+            case SketchEntity::Type::Line:    acc += 0.5 * (e.p0 + e.p1); ++n; break;
+            case SketchEntity::Type::Arc:
+            case SketchEntity::Type::EllipseArc:
+            case SketchEntity::Type::Circle:
+            case SketchEntity::Type::Ellipse: acc += e.center; ++n; break;
+            case SketchEntity::Type::Point:   acc += e.p0; ++n; break;
+            case SketchEntity::Type::BSpline:
+                if (!e.ctrl.empty()) {
+                    Vec2d s(0, 0); for (const Vec2d& q : e.ctrl) s += q;
+                    acc += s / double(e.ctrl.size()); ++n;
+                }
+                break;
+            }
+        }
+        if (n > 0) { centroid = acc / double(n); have_centroid = true; }
+    }
+    (void)have_centroid;   // centroid defaults to (0,0) for primitive sketches
+
+    const ExtrudeEnd end = static_cast<ExtrudeEnd>(m_extrude_end->GetSelection());
+    m_viewport->set_extrude_gizmo(plane, centroid,
+                                  m_distance->GetValue(), m_distance2->GetValue(),
+                                  end == ExtrudeEnd::TwoSided, m_flip->GetValue());
+}
+
+void DesignPanel::refresh_datum_planes()
+{
+    if (!m_viewport) return;
+    std::vector<SketchPlane> dplanes;
+    for (const auto& dp : m_doc.resolve_datum_planes()) dplanes.push_back(dp.second);
+    // Parallel per-plane extents, in the SAME order resolve_datum_planes emits
+    // (enabled Plane features, document order), so each datum draws at its u/v size.
+    std::vector<Vec2d> dsizes;
+    for (const auto& f : m_doc.features)
+        if (f.type == CadFeatureType::Plane && f.enabled)
+            dsizes.emplace_back(f.plane_u_size, f.plane_v_size);
+    m_viewport->set_datum_planes(std::move(dplanes), std::move(dsizes));
+    refresh_mate_connectors();
+}
+
+// Feed the connector frames to the viewport. resolve_datum_coordsys() emits them in document order
+// over enabled CoordSys features, so the feature index can be recovered by walking the same filter —
+// which is what tells us whether a given frame is the one the open Mate card will DRIVE.
+void DesignPanel::refresh_mate_connectors()
+{
+    if (!m_viewport) return;
+    // Polarity is a property of the MATE, not of an open dialog: a connector that some committed
+    // mate drives must read as driven whenever it is on screen, or the glyph only tells the truth
+    // while a card happens to be open. The card, when open, wins — it is the live intent.
+    std::map<int, int> role_by_feature;                       // feature index -> 1 fixed, 2 driven
+    for (const CadFeature& mf : m_doc.features) {
+        if (mf.type != CadFeatureType::Mate || !mf.enabled) continue;
+        if (mf.mate_cs_a >= 0) role_by_feature[mf.mate_cs_a] = 1;
+        if (mf.mate_cs_b >= 0) role_by_feature[mf.mate_cs_b] = 2;
+    }
+    const int cs_a = (m_active == Tool::Mate && m_mate_cs_a) ? m_mate_cs_a->GetSelection() : -1;
+    const int cs_b = (m_active == Tool::Mate && m_mate_cs_b) ? m_mate_cs_b->GetSelection() : -1;
+
+    std::vector<DesignSketchTool::MateConnectorGlyph> out;
+    // Origins, keyed both ways: a committed mate names its connectors by FEATURE index, the open
+    // card's combos by ordinal. Only resolved frames land here, so an unresolved end simply draws
+    // no pair line rather than a line to the origin of the world.
+    std::map<int, Vec3d> origin_by_feature, origin_by_ordinal;
+    const auto frames = m_doc.resolve_datum_coordsys();
+    size_t k = 0;
+    for (size_t i = 0; i < m_doc.features.size() && k < frames.size(); ++i) {
+        const CadFeature& f = m_doc.features[i];
+        if (f.type != CadFeatureType::CoordSys || !f.enabled) continue;
+        const auto& fr = frames[k];
+        const int ordinal = int(k);
+        ++k;
+        if (!fr.error.empty()) continue;               // unresolved: draw nothing, never a guess
+        DesignSketchTool::MateConnectorGlyph g;
+        g.origin = fr.origin;
+        g.x      = fr.x;
+        g.y      = fr.y;
+        const auto it = role_by_feature.find(int(i));
+        g.role   = (ordinal == cs_b) ? 2 : (ordinal == cs_a ? 1
+                 : (it != role_by_feature.end() ? it->second : 0));
+        // A face-only connector whose face gave no usable in-plane edge fell back to the hint; that
+        // is the case the glyph has to confess rather than absorb.
+        g.roll_undefined = (f.coordsys_type == CoordSysType::FaceAndDirection
+                            && f.coordsys_edge < 0);
+        origin_by_feature[int(i)] = g.origin;
+        origin_by_ordinal[ordinal] = g.origin;
+        out.push_back(g);
+    }
+
+    std::vector<std::pair<Vec3d, Vec3d>> links;
+    auto add_link = [&links](const std::map<int, Vec3d>& m, int a, int b) {
+        const auto ia = m.find(a), ib = m.find(b);
+        if (ia != m.end() && ib != m.end()) links.emplace_back(ia->second, ib->second);
+    };
+    for (const CadFeature& mf : m_doc.features)
+        if (mf.type == CadFeatureType::Mate && mf.enabled)
+            add_link(origin_by_feature, mf.mate_cs_a, mf.mate_cs_b);
+    if (cs_a >= 0 && cs_b >= 0 && cs_a != cs_b)
+        add_link(origin_by_ordinal, cs_a, cs_b);           // the live pick, not yet committed
+
+    m_viewport->set_mate_connectors(std::move(out));
+    m_viewport->set_mate_links(std::move(links));
+}
+
+void DesignPanel::update_datum_gizmo()
+{
+    if (!m_viewport) return;
+    if (m_active != Tool::Plane) { m_viewport->clear_datum_gizmo(); update_reference_planes(); return; }
+
+    // Resolve the candidate plane's FRAME against the doc. resolve_datum_planes() is const and
+    // doesn't rebuild bodies, so transiently swap/append the candidate to read its resolved frame,
+    // then restore — works for both a fresh (uncommitted) plane and an edit of a committed one.
+    CadFeature f = build_candidate(Tool::Plane);
+    const bool editing = (m_edit_index >= 0 && m_edit_index < int(m_doc.features.size()) &&
+                          m_doc.features[m_edit_index].type == CadFeatureType::Plane);
+    CadFeature saved;
+    int slot;
+    if (editing) { saved = m_doc.features[m_edit_index]; m_doc.features[m_edit_index] = f; slot = m_edit_index; }
+    else         { m_doc.features.push_back(f); slot = int(m_doc.features.size()) - 1; }
+
+    auto datums = m_doc.resolve_datum_planes();
+    // Ordinal of `slot` among enabled Plane features = its index in the resolved list.
+    int ord = -1;
+    for (int i = 0; i <= slot; ++i)
+        if (m_doc.features[i].type == CadFeatureType::Plane && m_doc.features[i].enabled) ++ord;
+    const bool ok = (ord >= 0 && ord < int(datums.size()));
+    SketchPlane frame; if (ok) frame = datums[ord].second;
+
+    if (editing) m_doc.features[m_edit_index] = saved; else m_doc.features.pop_back();
+
+    if (!ok) { m_viewport->clear_datum_gizmo(); update_reference_planes(); return; }
+
+    // Offset arrow anchor = the base/face origin (datum origin walked back along its normal by the
+    // offset). Works for both Offset-from-base (no tilt) and Offset-from-face exactly.
+    const Vec3d anchor   = frame.origin - frame.normal * f.plane_offset;
+    const bool  offset_on = (f.plane_type == PlaneType::Offset);
+    m_viewport->set_datum_gizmo(frame, f.plane_u_size, f.plane_v_size,
+                                anchor, frame.normal, f.plane_offset, offset_on);
+    update_reference_planes();   // base ghosts (origins + datums) follow the tool/model state
+}
+
+void DesignPanel::update_helix_gizmo()
+{
+    if (!m_viewport) return;
+    if (m_active != Tool::Helix) { m_viewport->clear_helix_gizmo(); return; }
+    m_viewport->set_helix_gizmo(plane_from_choice(m_helix_plane->GetSelection()),
+                                m_helix_radius ? m_helix_radius->GetValue() : 0.0,
+                                m_helix_pitch  ? m_helix_pitch->GetValue()  : 1.0,
+                                m_helix_height ? m_helix_height->GetValue() : 0.0,
+                                m_helix_taper  ? m_helix_taper->GetValue()  : 0.0,
+                                m_helix_left_handed && m_helix_left_handed->GetValue());
+}
+
+void DesignPanel::update_rib_gizmo()
+{
+    if (!m_viewport) return;
+    if (m_active != Tool::Rib) { m_viewport->clear_rib_gizmo(); return; }
+    // Same resolution the Tool::Rib branch of update_extrude_gizmo() uses — the depth arrow and
+    // this share one sketch and one entity, and must never disagree about which line that is.
+    const int ssel = m_rib_sketch ? m_rib_sketch->GetSelection() : wxNOT_FOUND;
+    const int ref  = (ssel != wxNOT_FOUND)
+                         ? int(reinterpret_cast<intptr_t>(m_rib_sketch->GetClientData(ssel))) : -1;
+    if (ref < 0 || ref >= int(m_doc.features.size())) { m_viewport->clear_rib_gizmo(); return; }
+    const CadFeature& sk = m_doc.features[ref];
+    const int ei = m_rib_entity ? m_rib_entity->GetValue() : 0;
+    if (ei < 0 || ei >= int(sk.entities.size())) { m_viewport->clear_rib_gizmo(); return; }
+    const SketchEntity& e = sk.entities[ei];
+    if (e.type != SketchEntity::Type::Line) { m_viewport->clear_rib_gizmo(); return; }   // rib is line-only
+    m_viewport->set_rib_gizmo(sk.plane, e.p0, e.p1,
+                              m_rib_thickness ? m_rib_thickness->GetValue() : 0.0);
+}
+
+// Onshape default planes: the XY/XZ/YZ reference planes are persistent, transparent, labelled, and
+// larger than the bed — shown as the FALLBACK when there is no object yet. When the Plane tool is
+// open they additionally surface existing datums so a base can be picked. Single authority for the
+// reference-plane overlay (set/clear_base_pick).
+void DesignPanel::update_reference_planes()
+{
+    if (!m_viewport) return;
+    // Default planes pass through the modeling origin (bed centre) — same point the kernel uses to
+    // resolve XY/XZ/YZ datum bases, so the ghosts, the datums and new sketches all coincide.
+    const Vec3d o = m_doc.modeling_origin;
+    SketchPlane xy = SketchPlane::XY(); xy.origin += o;
+    SketchPlane xz = SketchPlane::XZ(); xz.origin += o;
+    SketchPlane yz = SketchPlane::YZ(); yz.origin += o;
+    std::vector<SketchPlane> bp = { xy, xz, yz };
+    std::vector<int>         bi = { 0, 1, 2 };
+    std::vector<std::string> bl = { "XY", "XZ", "YZ" };
+
+    if (m_active == Tool::Plane) {
+        // Base picking only makes sense for the Offset method (others reference faces/edges).
+        if (m_plane_type && (PlaneType)m_plane_type->GetSelection() == PlaneType::Offset) {
+            auto datums = m_doc.resolve_datum_planes();   // already in world coords (origin applied)
+            for (int i = 0; i < int(datums.size()); ++i) {
+                bp.push_back(datums[i].second); bi.push_back(3 + i); bl.push_back(datums[i].first);
+            }
+            m_viewport->set_base_pick(std::move(bp), std::move(bi), std::move(bl));
+        } else {
+            m_viewport->clear_base_pick();
+        }
+        return;
+    }
+    // Fallback (Onshape default planes): show the 3 reference planes while there is no SOLID body
+    // yet — so they persist through the 2D-sketch phase and reappear after a sketch is confirmed
+    // (a sketch creates no body). They no longer block selection: clicking existing geometry wins,
+    // a base-plane pick only fires on a click that hit nothing else (see on_mouse fall-through).
+    // Available while there is no solid yet OR while the user is actually choosing a sketch
+    // plane. The second half fixes a dead end: delete a sketch on a document that still has a
+    // body, press Sketch, and act_sketch says "click a face or a reference plane" — with the
+    // reference planes already taken away, because a body existed. The instruction was
+    // impossible to follow and there was no way to start a sketch at all short of finding a
+    // face to click.
+    //
+    // Not simply always-on: m_dbp_active both RENDERS and picks, so three translucent planes
+    // would otherwise float over every finished model. Tying them to Sketch mode shows them
+    // exactly when they are the thing being chosen, and hides them again on Finish.
+    if (m_doc.bodies.empty() || m_ui_mode == UiMode::Sketch)
+        m_viewport->set_base_pick(std::move(bp), std::move(bi), std::move(bl));
+    else
+        m_viewport->clear_base_pick();
+}
+
+TriangleMesh DesignPanel::ghost_from_bodies(const std::vector<TriangleMesh>& per_body) const
+{
+    TriangleMesh out;
+    for (size_t b = 0; b < per_body.size(); ++b) {
+        TriangleMesh m = per_body[b];
+        if (b < m_body_xform.size()) m.transform(m_body_xform[b]);
+        out.merge(m);
+    }
+    return out;
+}
+
+bool DesignPanel::show_mate_ghost(int kind, int cs_a, int cs_b,
+                                  double offset, double angle_deg, bool flip, std::string& err)
+{
+    CadFeature cand;
+    cand.type        = CadFeatureType::Mate;
+    cand.mate_kind   = kind;
+    cand.mate_cs_a   = cs_a;
+    cand.mate_cs_b   = cs_b;
+    cand.mate_offset = offset;
+    cand.mate_angle  = angle_deg;
+    cand.mate_flip   = flip;
+
+    TriangleMesh              mesh;
+    std::vector<TriangleMesh> pbm;
+    if (!m_doc.preview(cand, mesh, pbm, err)) {
+        m_viewport->clear_preview();
+        m_viewport->set_body_hidden(false);
+        return false;
+    }
+    m_viewport->set_preview_mesh(ghost_from_bodies(pbm));
+    // The ghost is the WHOLE assembly in its post-mate pose, not an added lump, so the committed
+    // bodies have to go: left visible they would draw the mated body in both places at once and
+    // z-fight everything else against its own copy. Same reason Dressup and Draft hide them.
+    m_viewport->set_body_hidden(true);
+    return true;
+}
+
+void DesignPanel::refresh_preview()
+{
+    if (m_active == Tool::None) { m_viewport->clear_preview(); return; }
+
+    // Transform has no ghost: it moves an existing body rather than building a new one, so its
+    // preview IS the body, shown through the display transform the gizmo already drives.
+    if (m_active == Tool::Transform) { xf_live_preview(); return; }
+
+    // Features that produce NO solid: a sketch, the three datums, a helix curve, and Project
+    // (which emits sketch entities). They have no ghost to build, so they must not go through
+    // the solid-preview path below — it finds nothing and reports "invalid: preview produced
+    // no geometry", which is what Axis / CoordSys / Helix / Project did on an empty document.
+    // route_feature() skips these for the same reason, so the two agree on what is not a solid.
+    if (m_active == Tool::Sketch  || m_active == Tool::Plane   || m_active == Tool::Axis ||
+        m_active == Tool::CoordSys || m_active == Tool::Helix   || m_active == Tool::Project) {
+        m_viewport->clear_preview();
+        m_status->SetForegroundColour(wxColour(120, 210, 120));
+        wxString ready;
+        switch (m_active) {
+        case Tool::Plane:    ready = _L("Plane ready");     break;
+        case Tool::Axis:     ready = _L("Axis ready");      break;
+        case Tool::CoordSys: ready = _L("Coord Sys ready"); break;
+        case Tool::Helix:    ready = _L("Helix ready");     break;
+        case Tool::Project:  ready = _L("Project ready");   break;
+        default:             ready = _L("Sketch ready");    break;
+        }
+        set_status(ready);
+        for (wxButton* b : m_confirm_btns) if (b) b->Enable(true);
+        m_status->Refresh();
+        update_datum_gizmo();   // Plane card: show/refresh the in-canvas resize handles
+        update_helix_gizmo();   // Helix card: draw the live curve + drag handles (no solid ghost)
+        return;
+    }
+
+    if (m_active == Tool::Mate) {
+        // A mate produces no NEW geometry, but it MOVES a body — and the moved assembly is
+        // exactly the ghost worth showing. This branch used to clear the preview outright,
+        // saying a mate has no 3D ghost; the kernel had no such opinion (preview() routes a
+        // Mate candidate through apply_mate on a throwaway copy), so that one line was the
+        // whole of gap G3. The card's own gate stays: Confirm is disabled when <2 CoordSys
+        // exist or when A == B, because neither of those is a kernel error, only an unfinished
+        // form, and the kernel's message for them would be worse than these.
+        const bool has_two = m_mate_cs_a && m_mate_cs_a->GetCount() >= 2;
+        const int sel_a = has_two ? m_mate_cs_a->GetSelection() : wxNOT_FOUND;
+        const int sel_b = has_two ? m_mate_cs_b->GetSelection() : wxNOT_FOUND;
+        const bool same = has_two && sel_a != wxNOT_FOUND && sel_b != wxNOT_FOUND && sel_a == sel_b;
+        bool ok = has_two && !same;
+        if (!has_two) {
+            m_viewport->clear_preview();
+            m_viewport->set_body_hidden(false);   // the ghost replaced them; give them back
+            m_status->SetForegroundColour(wxColour(235, 110, 110));
+            set_status(_L("Mate needs at least two CoordSys features"));
+        } else if (same) {
+            m_viewport->clear_preview();
+            m_viewport->set_body_hidden(false);
+            m_status->SetForegroundColour(wxColour(235, 110, 110));
+            set_status(_L("Mate: CS A and CS B must be different"));
+        } else {
+            sync_body_xform();   // same reason as the solid path below: drop stale per-body poses
+            const int cs_a = int(reinterpret_cast<intptr_t>(m_mate_cs_a->GetClientData(sel_a)));
+            const int cs_b = int(reinterpret_cast<intptr_t>(m_mate_cs_b->GetClientData(sel_b)));
+            std::string err;
+            ok = show_mate_ghost(m_mate_kind ? m_mate_kind->GetSelection() : 0, cs_a, cs_b,
+                                 m_mate_offset ? m_mate_offset->GetValue() : 0.0,
+                                 m_mate_angle  ? m_mate_angle->GetValue()  : 0.0,
+                                 m_mate_flip   && m_mate_flip->GetValue(), err);
+            if (ok) {
+                m_status->SetForegroundColour(wxColour(120, 210, 120));
+                set_status(_L("Mate ready"));
+            } else {
+                m_status->SetForegroundColour(wxColour(235, 110, 110));
+                set_status(_L("Invalid: ") + wxString::FromUTF8(err));
+            }
+        }
+        for (wxButton* b : m_confirm_btns) if (b) b->Enable(ok);
+        m_status->Refresh();
+        return;
+    }
+
+    // Trim m_body_xform to the LIVE committed bodies before building the ghost. A move
+    // writes a per-body display transform keyed by index; if a moved body is later deleted
+    // or consumed, its stale transform must not survive and get re-applied to whatever new
+    // body lands at that index — that was painting fresh extrudes as a moved+rotated ghost
+    // far from the sketch. resize() drops entries beyond the current body count.
+    sync_body_xform();
+
+    CadFeature   cand = build_candidate(m_active);
+    TriangleMesh mesh;
+    std::string  err;
+    bool         ok = false;
+
+    // The body is displayed through its per-body Move transform (m_body_xform); the ghost is
+    // built from the untransformed kernel, so without this it floats back at the origin once a
+    // body has been moved. Re-merge the per-body ghost meshes with the same transforms applied.
+    auto ghost_from = [this](const std::vector<TriangleMesh>& pbm) { return ghost_from_bodies(pbm); };
+
+    const bool editing_single = (m_edit_index >= 0);
+    if (editing_single) {
+        // Edit-mode preview: stacking the candidate on top of the live body would
+        // re-apply the feature being edited (fillet-on-fillet) — wrong, and a
+        // source of OCCT failures. Instead evaluate the *replace* on a throwaway
+        // copy so the ghost is the true post-edit body.
+        CadDocument tmp = m_doc;
+        ok = tmp.replace_feature(m_edit_index, cand);
+        if (ok) mesh = ghost_from(tmp.display_body_meshes); else err = tmp.error;
+    } else {
+        std::vector<TriangleMesh> pbm;
+        ok = m_doc.preview(cand, mesh, pbm, err);
+        if (ok) mesh = ghost_from(pbm);
+    }
+
+    if (ok) {
+        m_viewport->set_preview_mesh(mesh);
+        m_status->SetForegroundColour(wxColour(120, 210, 120)); // ok = green
+        set_status(wxString::Format(_L("Preview — %zu triangles"), mesh.its.indices.size()));
+    } else {
+        m_viewport->clear_preview();
+        m_status->SetForegroundColour(wxColour(235, 110, 110)); // invalid = red
+        set_status(_L("Invalid: ") + wxString::FromUTF8(err));
+    }
+    // Onshape parity: a broken candidate cannot be committed. Grey the active dialog's
+    // Confirm so the user sees the gate before clicking; the red status says why.
+    for (wxButton* b : m_confirm_btns)
+        if (b != nullptr) b->Enable(ok);
+    // Fillet/Chamfer/Draft: once the target edge/face yields a valid result, show ONLY the
+    // preview (hide the base bodies) so the user sees the finished shape, not the old solid
+    // doubled with the ghost. Before a valid pick the body stays visible so it can be picked.
+    m_viewport->set_body_hidden((m_active == Tool::Dressup || m_active == Tool::Draft) && ok);
+    m_status->Refresh();
+
+    // Refresh the in-canvas Extrude depth arrow (self-gates: only while the Extrude card is open).
+    update_extrude_gizmo();
+    // Same for the Fillet/Chamfer radius arrow (self-gates: Dressup card + a picked edge).
+    update_fillet_gizmo();
+    // Same for the Hole footprint circle + diameter/depth arrows (self-gates: Hole card).
+    update_hole_gizmo();
+    // Same for the Thread footprint circle + radius/length arrows (self-gates: Thread card).
+    update_thread_gizmo();
+    // Same for the Shell thickness arrow on the picked face (self-gates: Shell card + a face).
+    update_shell_gizmo();
+    // Same for the Revolve angle-arc around the axis (self-gates: only while the Revolve card is open).
+    update_revolve_gizmo();
+    // Same for the Draft angle-arc around the face centroid (self-gates: only while the Draft card is open).
+    update_draft_gizmo();
+    // Same for the Cut plane-rectangle + offset arrow (self-gates: only while the Cut card is open).
+    update_cut_gizmo();
+    // Same for the Pattern spacing arrow / angle-arc (self-gates: only while the Pattern card is open).
+    update_pattern_gizmo();
+    // Datum-plane resize handles (self-gates: only while the Plane card is open).
+    update_datum_gizmo();
+    // Helix curve + handles (self-gates: only while the Helix card is open).
+    update_helix_gizmo();
+    // Rib slab footprint + thickness handles (self-gates: only while the Rib card is open).
+    update_rib_gizmo();
+    update_operand_highlight();
+}
+
+// The tool-card frame is only worth drawing when a card is actually inside it —
+// otherwise an empty bordered box floats above the feature tree.
+void DesignPanel::update_cards_frame()
+{
+    if (m_cards == nullptr || m_cards->GetSizer() == nullptr) return;
+    wxSizer* root = m_form ? m_form->GetSizer() : nullptr;
+    if (root == nullptr) return;
+    bool any = false;
+    for (const wxSizerItem* it : m_cards->GetSizer()->GetChildren())
+        if (it->IsShown()) { any = true; break; }
+    root->Show(m_cards, any, false);   // non-recursive: don't re-show the hidden cards inside
+}
+
+// Move/Rotate card: numeric entry that composes the same transform the drag gizmo builds —
+// translation in world mm plus a rotation about the body's centroid, applied onto the pose the
+// body had when Move opened (m_move_prev), so typing and dragging cannot fight each other.
+void DesignPanel::apply_move_card()
+{
+    const int b = m_move_body;
+    if (b < 0 || b >= int(m_body_xform.size()) || b >= int(m_doc.display_body_meshes.size())) return;
+
+    const double ang = m_move_angle ? m_move_angle->GetValue() * M_PI / 180.0 : 0.0;
+    const int    ax  = m_move_axis ? m_move_axis->GetSelection() : 2;
+    const Vec3d  axis = (ax == 0) ? Vec3d::UnitX() : (ax == 1) ? Vec3d::UnitY() : Vec3d::UnitZ();
+    const Vec3d  d(m_move_dx ? m_move_dx->GetValue() : 0.0,
+                   m_move_dy ? m_move_dy->GetValue() : 0.0,
+                   m_move_dz ? m_move_dz->GetValue() : 0.0);
+
+    // Rotate about the body's own centre, not the world origin.
+    const Vec3d pivot = m_move_prev * m_doc.display_body_meshes[b].bounding_box().center();
+    Transform3d x = Transform3d::Identity();
+    x.translate(d + pivot);
+    x.rotate(Eigen::AngleAxisd(ang, axis));
+    x.translate(-pivot);
+
+    m_body_xform[b] = x * m_move_prev;
+    feed_bodies();
+    if (m_viewport) m_viewport->request_repaint();
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(wxString::Format(_L("Body %d — moved (%.1f, %.1f, %.1f) mm, rotated %.1f°"),
+                                        b + 1, d.x(), d.y(), d.z(),
+                                        m_move_angle ? m_move_angle->GetValue() : 0.0));
+    m_status->Refresh();
+}
+
+void DesignPanel::show_move_card(bool show)
+{
+    if (m_box_move == nullptr || m_cards == nullptr || m_cards->GetSizer() == nullptr) return;
+    m_cards->GetSizer()->Show(m_box_move, show, true);
+    update_cards_frame();
+    if (m_form) { m_form->Layout(); m_form->FitInside(); }
+}
+
+// Push the tool's current parameters into the live sketch tool before Polygon starts. They
+// come from the offer's Polygon submenu (or from the last choice made there), never from a card.
+void DesignPanel::push_polygon_params()
+{
+    if (m_viewport == nullptr) return;
+    m_viewport->set_sketch_polygon_sides(m_poly_sides);
+    m_viewport->set_sketch_polygon_circumscribed(m_poly_circumscribed);
+}
+
+void DesignPanel::open_tool(Tool t)
+{
+    m_active = t;
+    // Fillet/Chamfer/Draft no longer fade the body see-through; instead, once a valid target
+    // is picked, refresh_preview hides the base bodies entirely (preview-only). Keep it opaque
+    // here so the body is fully visible for picking the edge/face.
+    // Body focus follows the CoordSys card: entering any other tool drops it. Read it back
+    // from the combo rather than clearing outright — editing a CoordSys feature loads the
+    // card (and its body) BEFORE open_tool runs, and a blind clear would strand the viewport
+    // showing "Body N" while picking stayed unrestricted.
+    if (m_viewport) { m_viewport->set_body_translucent(false); m_viewport->set_body_hidden(false);
+                      m_viewport->set_xray_focus(t == Tool::CoordSys && m_cs_body ? m_cs_body->GetSelection() - 1 : -1); }
+    wxSizer* s = m_cards->GetSizer();
+    s->Show(m_box_sketch,  t == Tool::Sketch,  true);
+    s->Show(m_box_extrude, t == Tool::Extrude, true);
+    s->Show(m_box_dressup, t == Tool::Dressup, true);
+    s->Show(m_box_hole,    t == Tool::Hole,    true);
+    s->Show(m_box_thread,  t == Tool::Thread,  true);
+    s->Show(m_box_shell,   t == Tool::Shell,   true);
+    s->Show(m_box_revolve, t == Tool::Revolve, true);
+    s->Show(m_box_sweep,   t == Tool::Sweep,   true);
+    s->Show(m_box_pattern, t == Tool::Pattern, true);
+    s->Show(m_box_plane,   t == Tool::Plane,   true);
+    s->Show(m_box_axis,   t == Tool::Axis,   true);
+    s->Show(m_box_coordsys, t == Tool::CoordSys, true);
+    s->Show(m_box_loft,    t == Tool::Loft,    true);
+    s->Show(m_box_boolean, t == Tool::Boolean, true);
+    s->Show(m_box_cut,     t == Tool::Cut,     true);
+    s->Show(m_box_draft,   t == Tool::Draft,   true);
+    s->Show(m_box_surf_extrude, t == Tool::SurfaceExtrude, true);
+    s->Show(m_box_surf_revolve, t == Tool::SurfaceRevolve, true);
+    s->Show(m_box_surf_loft,    t == Tool::SurfaceLoft,    true);
+    s->Show(m_box_surf_fill,    t == Tool::SurfaceFill,    true);
+    s->Show(m_box_surf_offset,  t == Tool::SurfaceOffset,  true);
+    s->Show(m_box_surf_thicken, t == Tool::ThickenSurface,  true);
+    s->Show(m_box_transform,    t == Tool::Transform,      true);
+    s->Show(m_box_mirror,       t == Tool::Mirror,         true);
+    s->Show(m_box_thicken,      t == Tool::Thicken,        true);
+    s->Show(m_box_rib,          t == Tool::Rib,            true);
+    s->Show(m_box_project,      t == Tool::Project,        true);
+    s->Show(m_box_delete_face,  t == Tool::DeleteFace,     true);
+    s->Show(m_box_helix,        t == Tool::Helix,          true);
+    s->Show(m_box_mate,         t == Tool::Mate,           true);
+    s->Show(m_box_insert,  t == Tool::Insert,  true);
+    s->Show(m_box_expr,   m_edit_index >= 0,  true);   // expression binding available during edit only
+
+    if (t == Tool::Mate) {
+        // Populate both CoordSys pickers with every CoordSys feature; store the real
+        // feature index in client data. Keep prior selection when re-editing.
+        int keep_a = -1, keep_b = -1;
+        if (m_mate_cs_a->GetCount() > 0 && m_mate_cs_a->GetSelection() != wxNOT_FOUND) {
+            const auto* cl = m_mate_cs_a->GetClientData(m_mate_cs_a->GetSelection());
+            if (cl) keep_a = int(reinterpret_cast<intptr_t>(cl));
+        }
+        if (m_mate_cs_b->GetCount() > 0 && m_mate_cs_b->GetSelection() != wxNOT_FOUND) {
+            const auto* cl = m_mate_cs_b->GetClientData(m_mate_cs_b->GetSelection());
+            if (cl) keep_b = int(reinterpret_cast<intptr_t>(cl));
+        }
+        m_mate_cs_a->Clear();
+        m_mate_cs_b->Clear();
+        for (int i = 0; i < int(m_doc.features.size()); ++i) {
+            if (m_doc.features[i].type != CadFeatureType::CoordSys) continue;
+            const wxString nm = wxString::FromUTF8(m_doc.features[i].name);
+            const int pos_a = combo_append_index(m_mate_cs_a, nm, i);
+            const int pos_b = combo_append_index(m_mate_cs_b, nm, i);
+            if (i == keep_a) m_mate_cs_a->SetSelection(pos_a);
+            if (i == keep_b) m_mate_cs_b->SetSelection(pos_b);
+        }
+        if (keep_a < 0 && m_mate_cs_a->GetCount() > 0) m_mate_cs_a->SetSelection(0);
+        if (keep_b < 0 && m_mate_cs_b->GetCount() > 0) m_mate_cs_b->SetSelection(0);
+    }
+
+    if (t == Tool::Revolve && m_revolve_sketch_ref >= 0
+        && m_revolve_sketch_ref < int(m_doc.features.size()))
+        m_revolve_sketch_label->SetLabel(_L("Sketch: ") +
+            wxString::FromUTF8(m_doc.features[m_revolve_sketch_ref].name));
+
+    if (t == Tool::Sweep) {
+        if (m_sweep_profile_ref >= 0 && m_sweep_profile_ref < int(m_doc.features.size()))
+            m_sweep_profile_label->SetLabel(_L("Profile: ") +
+                wxString::FromUTF8(m_doc.features[m_sweep_profile_ref].name));
+        // Populate the path picker with every Sketch feature except the profile itself;
+        // the feature index rides in the entry's client data. Pre-select the stored path
+        // (re-edit), else the first available sketch.
+        m_sweep_path->Clear();
+        int sel_idx = wxNOT_FOUND;
+        for (int i = 0; i < int(m_doc.features.size()); ++i) {
+            const CadFeature& sf = m_doc.features[i];
+            if (sf.type != CadFeatureType::Sketch || i == m_sweep_profile_ref) continue;
+            const int pos = combo_append_index(m_sweep_path, wxString::FromUTF8(sf.name), i);
+            if (i == m_sweep_path_ref) sel_idx = pos;
+        }
+        if (sel_idx != wxNOT_FOUND) m_sweep_path->SetSelection(sel_idx);
+        else if (m_sweep_path->GetCount() > 0) m_sweep_path->SetSelection(0);
+    }
+
+    if (t == Tool::Loft) {
+        // List every Sketch feature; the feature index for each row rides in
+        // m_loft_sketch_idx. Re-check the stored profile refs (re-edit).
+        m_loft_list->Clear();
+        m_loft_sketch_idx.clear();
+        for (int i = 0; i < int(m_doc.features.size()); ++i) {
+            const CadFeature& sf = m_doc.features[i];
+            if (sf.type != CadFeatureType::Sketch) continue;
+            const int row = m_loft_list->Append(wxString::FromUTF8(sf.name));
+            m_loft_sketch_idx.push_back(i);
+            if (std::find(m_loft_refs.begin(), m_loft_refs.end(), i) != m_loft_refs.end())
+                m_loft_list->Check(row, true);
+        }
+    }
+
+    if (t == Tool::SurfaceExtrude) {
+        if (m_surf_extrude_sketch_ref >= 0 && m_surf_extrude_sketch_ref < int(m_doc.features.size()))
+            m_surf_extrude_sketch_label->SetLabel(_L("Sketch: ") +
+                wxString::FromUTF8(m_doc.features[m_surf_extrude_sketch_ref].name));
+    }
+
+    if (t == Tool::SurfaceRevolve) {
+        if (m_surf_revolve_sketch_ref >= 0 && m_surf_revolve_sketch_ref < int(m_doc.features.size()))
+            m_surf_revolve_sketch_label->SetLabel(_L("Sketch: ") +
+                wxString::FromUTF8(m_doc.features[m_surf_revolve_sketch_ref].name));
+    }
+
+    if (t == Tool::SurfaceLoft) {
+        m_surf_loft_list->Clear();
+        m_surf_loft_sketch_idx.clear();
+        for (int i = 0; i < int(m_doc.features.size()); ++i) {
+            const CadFeature& sf = m_doc.features[i];
+            if (sf.type != CadFeatureType::Sketch) continue;
+            const int row = m_surf_loft_list->Append(wxString::FromUTF8(sf.name));
+            m_surf_loft_sketch_idx.push_back(i);
+            if (std::find(m_surf_loft_refs.begin(), m_surf_loft_refs.end(), i) != m_surf_loft_refs.end())
+                m_surf_loft_list->Check(row, true);
+        }
+    }
+
+    if (t == Tool::SurfaceFill) {
+        if (m_surf_fill_sketch_ref >= 0 && m_surf_fill_sketch_ref < int(m_doc.features.size()))
+            m_surf_fill_sketch_label->SetLabel(_L("Sketch: ") +
+                wxString::FromUTF8(m_doc.features[m_surf_fill_sketch_ref].name));
+    }
+
+    // Shell and Draft both take their face from the live pick at Confirm time, but until now
+    // only the PICK handler wrote their labels. So the natural order — pick the face, then open
+    // the card — left Shell reading "(all faces — closed hollow)" and Draft "(pick a side face)"
+    // while Confirm went on to use m_sel_solid_face regardless: the card described one operation
+    // and performed another. Initialise from the current selection here, exactly as Extrude does
+    // with m_extrude_face_src below. Skipped while re-editing, because load_feature_into_dialog
+    // has already written the label from the feature's own stored face and runs before this.
+    // Same reasoning for Dress-up, whose target is the picked EDGE (falling back to the group).
+    if (t == Tool::Dressup && m_edit_index < 0)
+        sync_dressup_target();
+
+    if (t == Tool::Shell && m_edit_index < 0)
+        m_shell_face_label->SetLabel(m_sel_solid_face >= 0
+            ? wxString::Format(_L("Face %d"), m_sel_solid_face)
+            : _L("(all faces — closed hollow)"));
+
+    if (t == Tool::Draft && m_edit_index < 0)
+        m_draft_face_label->SetLabel(m_sel_solid_face >= 0
+            ? wxString::Format(_L("Face %d"), m_sel_solid_face)
+            : _L("(pick a side face)"));
+
+    if (t == Tool::Extrude) {
+        if (m_extrude_face_src >= 0)
+            m_extrude_sketch_label->SetLabel(
+                wxString::Format(_L("Face %d (push/pull)"), m_extrude_face_src));
+        else if (m_extrude_sketch_ref >= 0 && m_extrude_sketch_ref < int(m_doc.features.size()))
+            m_extrude_sketch_label->SetLabel(_L("Sketch: ") +
+                wxString::FromUTF8(m_doc.features[m_extrude_sketch_ref].name));
+        // A fresh extrude defaults to New body — even when other bodies exist — so
+        // overlapping extrudes stay SEPARATE solids instead of silently fusing. Joining
+        // is opt-in (pick "Join"). Engraving art onto a face still defaults to Cut.
+        // (Edit-mode keeps the feature's stored mode, set below.)
+        if (m_edit_index < 0) {
+            const bool on_face_import =
+                m_extrude_sketch_ref >= 0 && m_extrude_sketch_ref < int(m_doc.features.size())
+                && m_doc.features[m_extrude_sketch_ref].import_on_face;
+            if (on_face_import) {
+                m_mode->SetSelection(2);     // Cut — engrave into the face
+                m_flip->SetValue(true);      // extrude inward (the face normal points out)
+            } else {
+                m_mode->SetSelection(0);     // New body (was: Add when a body already existed)
+            }
+        }
+    }
+
+    // Retitle the active card's header: edit-mode shows the feature's real name,
+    // add-mode previews the type + next feature number (Onshape "Extrude 1").
+    const bool editing = (m_edit_index >= 0 && m_edit_index < int(m_doc.features.size()));
+    auto title = [&](const wxString& base) -> wxString {
+        return editing ? wxString::FromUTF8(m_doc.features[m_edit_index].name)
+                       : base + wxString::Format(" %d", m_feature_counter + 1);
+    };
+    switch (t) {
+    case Tool::Sketch:  m_hdr_sketch->SetLabel(title(_L("Sketch")));   break;
+    case Tool::Extrude: m_hdr_extrude->SetLabel(title(_L("Extrude"))); break;
+    case Tool::Dressup: m_hdr_dressup->SetLabel(title(
+                            m_dressup_type->GetSelection() == 0 ? _L("Fillet") : _L("Chamfer"))); break;
+    case Tool::Hole:    m_hdr_hole->SetLabel(title(_L("Hole")));       break;
+    case Tool::Thread:  m_hdr_thread->SetLabel(title(_L("Thread")));   break;
+    case Tool::Shell:   m_hdr_shell->SetLabel(title(_L("Shell")));     break;
+    case Tool::Revolve: m_hdr_revolve->SetLabel(title(_L("Revolve"))); break;
+    case Tool::Sweep:   m_hdr_sweep->SetLabel(title(_L("Sweep")));     break;
+    case Tool::Pattern: m_hdr_pattern->SetLabel(title(_L("Pattern"))); break;
+    case Tool::Plane:   m_hdr_plane->SetLabel(title(_L("Plane")));     break;
+    case Tool::Loft:    m_hdr_loft->SetLabel(title(_L("Loft")));       break;
+    case Tool::Draft:   m_hdr_draft->SetLabel(title(_L("Draft")));     break;
+    case Tool::Boolean: m_hdr_boolean->SetLabel(title(_L("Boolean"))); break;
+    case Tool::Cut:     m_hdr_cut->SetLabel(title(_L("Cut")));         break;
+    case Tool::Axis:    m_hdr_axis->SetLabel(title(_L("Axis")));       break;
+    case Tool::CoordSys: m_hdr_coordsys->SetLabel(title(_L("Coord Sys"))); break;
+    case Tool::SurfaceExtrude:  m_hdr_surf_extrude->SetLabel(title(_L("Surface Extrude")));  break;
+    case Tool::SurfaceRevolve:  m_hdr_surf_revolve->SetLabel(title(_L("Surface Revolve")));  break;
+    case Tool::SurfaceLoft:     m_hdr_surf_loft->SetLabel(title(_L("Surface Loft")));      break;
+    case Tool::SurfaceFill:     m_hdr_surf_fill->SetLabel(title(_L("Surface Fill")));      break;
+    case Tool::SurfaceOffset:   m_hdr_surf_offset->SetLabel(title(_L("Surface Offset")));   break;
+    case Tool::ThickenSurface:  m_hdr_surf_thicken->SetLabel(title(_L("Thicken Surface")));   break;
+    case Tool::Transform:   m_hdr_transform->SetLabel(title(_L("Transform")));   break;
+    case Tool::Mirror:      m_hdr_mirror->SetLabel(title(_L("Mirror")));         break;
+    case Tool::Thicken:     m_hdr_thicken->SetLabel(title(_L("Thicken")));       break;
+    case Tool::Rib:         m_hdr_rib->SetLabel(title(_L("Rib")));               break;
+    case Tool::Project:     m_hdr_project->SetLabel(title(_L("Project")));       break;
+    case Tool::DeleteFace:  m_hdr_delete_face->SetLabel(title(_L("Delete Face"))); break;
+    case Tool::Helix:       m_hdr_helix->SetLabel(title(_L("Helix")));           break;
+    case Tool::Mate:        m_hdr_mate->SetLabel(title(_L("Mate")));             break;
+    case Tool::Insert:  break;   // header set by open_insert_card()
+    case Tool::None:    break;
+    }
+
+    // A card that consumes a face must say WHICH face the moment it appears. These labels used to
+    // be written only by the pick handler, which runs while a card is already open — so a card
+    // opened FROM a selection (the offer's whole premise) showed the previous pick, or the "(pick
+    // one)" placeholder over a face it was in fact about to use. Same law as the Construction
+    // toggle: a control that carries state has to show it. One writer, on open, for all three.
+    {
+        const bool have = m_sel_solid_face >= 0;
+        const wxString face_name = have ? wxString::Format(_L("Face %d"), m_sel_solid_face) : wxString();
+        if (t == Tool::Thicken && m_thicken_face_label)
+            m_thicken_face_label->SetLabel(have ? face_name : _L("(pick a solid face)"));
+        if (t == Tool::Shell && m_shell_face_label)
+            m_shell_face_label->SetLabel(have ? face_name : _L("(all faces — closed hollow)"));
+        if (t == Tool::Draft && m_draft_face_label)
+            m_draft_face_label->SetLabel(have ? face_name : _L("(pick a side face)"));
+    }
+
+    if (editing) {
+        populate_expr_fields(t);   // field-name combo for this feature type
+        // Display current expression bindings on the edited feature
+        const CadFeature& ef = m_doc.features[m_edit_index];
+        if (ef.expr.empty()) {
+            m_expr_status->SetLabel(_L("(no bindings)"));
+            m_expr_status->SetForegroundColour(dp_sec_text());
+        } else {
+            wxString s;
+            for (const auto& [field, e] : ef.expr) {
+                if (!s.IsEmpty()) s += "; ";
+                s += wxString::FromUTF8(field) + " = " + wxString::FromUTF8(e);
+            }
+            m_expr_status->SetLabel(s);
+            m_expr_status->SetForegroundColour(dp_ctl_text());
+        }
+    }
+
+    update_cards_frame(); m_form->Layout();
+    m_form->FitInside();
+    update_action_bar();   // a tool is now active -> show the unified ✓/✗
+    refresh_preview();
+
+    // Add-mode Transform arms the move gizmo on the card's body so the prominent verb is the
+    // geometry-first control; the card mirrors the drag. Edit mode keeps today's card-only path.
+    if (t == Tool::Transform && m_edit_index < 0)
+        arm_transform_gizmo();
+    // Opening Boolean re-aims the viewport picks at the target slot, so the first click after
+    // the card appears always means "keep this one" regardless of what the last session did.
+    if (t == Tool::Boolean)
+        m_bool_next_slot = 0;
+}
+
+void DesignPanel::close_tool()
+{
+    m_active = Tool::None;
+    set_active_tool_btn(nullptr);   // clear the active-tool teal highlight
+    // Single revert point for the Transform gizmo: Esc, switching tools, and Cancel all pass
+    // through here, so the body is never left displaced by a Transform that wasn't committed.
+    xf_clear_preview();
+    if (m_xf_gizmo_body >= 0) {
+        sync_body_xform();
+        if (m_xf_gizmo_body < int(m_body_xform.size()))
+            m_body_xform[m_xf_gizmo_body] = m_xf_gizmo_base;
+        if (m_viewport) m_viewport->clear_move_gizmo();
+        feed_bodies();
+        m_xf_gizmo_body = -1;
+        m_move_body     = -1;
+    }
+    if (m_viewport) { m_viewport->set_body_translucent(false); m_viewport->set_body_hidden(false); m_viewport->set_xray_focus(-1); }   // restore the opaque solid
+    wxSizer* s = m_cards->GetSizer();
+    s->Show(m_box_sketch,  false, true);
+    s->Show(m_box_extrude, false, true);
+    s->Show(m_box_dressup, false, true);
+    s->Show(m_box_hole,    false, true);
+    s->Show(m_box_thread,  false, true);
+    s->Show(m_box_shell,   false, true);
+    s->Show(m_box_revolve, false, true);
+    s->Show(m_box_sweep,   false, true);
+    s->Show(m_box_pattern, false, true);
+    s->Show(m_box_plane,   false, true);
+    s->Show(m_box_axis,   false, true);
+    s->Show(m_box_coordsys, false, true);
+    s->Show(m_box_loft,    false, true);
+    s->Show(m_box_boolean, false, true);
+    s->Show(m_box_cut,     false, true);
+    s->Show(m_box_draft,   false, true);
+    s->Show(m_box_surf_extrude, false, true);
+    s->Show(m_box_surf_revolve, false, true);
+    s->Show(m_box_surf_loft,    false, true);
+    s->Show(m_box_surf_fill,    false, true);
+    s->Show(m_box_surf_offset,  false, true);
+    s->Show(m_box_surf_thicken, false, true);
+    s->Show(m_box_transform,    false, true);
+    s->Show(m_box_mirror,       false, true);
+    s->Show(m_box_thicken,      false, true);
+    s->Show(m_box_rib,          false, true);
+    s->Show(m_box_project,      false, true);
+    s->Show(m_box_delete_face,  false, true);
+    s->Show(m_box_helix,        false, true);
+    s->Show(m_box_mate,         false, true);
+    s->Show(m_box_insert,  false, true);
+    s->Show(m_box_expr,    false, true);
+    m_viewport->clear_preview();
+    m_viewport->clear_extrude_gizmo();
+    m_viewport->clear_fillet_gizmo();
+    m_viewport->clear_hole_gizmo();
+    m_viewport->clear_thread_gizmo();
+    m_viewport->clear_shell_gizmo();
+    m_viewport->clear_revolve_gizmo();
+    m_viewport->clear_draft_gizmo();
+    m_viewport->clear_cut_gizmo();
+    m_viewport->clear_pattern_gizmo();
+    m_viewport->clear_datum_gizmo();
+    m_viewport->set_operand_bodies(-1, -1);
+    m_viewport->set_highlight_sketches({});
+    update_reference_planes();   // back to no-tool: show the origin planes if there is no object yet
+    update_cards_frame(); m_form->Layout();
+    m_form->FitInside();
+    update_action_bar();   // no feature tool active -> hide the bar (unless a mode keeps it)
+}
+
+void DesignPanel::confirm_tool()
+{
+    // One undo boundary per committed feature (Extrude/Dressup/Hole/Thread/Shell, the
+    // legacy Sketch card via on_add_sketch, and edit-mode replace all funnel here).
+    m_doc.checkpoint();
+    const bool editing_single = (m_edit_index >= 0);
+
+    if (editing_single) {
+        // Edit mode: overwrite the existing feature instead of appending.
+        CadFeature cand = build_candidate(m_active);
+        bool ok = m_doc.replace_feature(m_edit_index, cand);
+        reset_edit_state();
+        close_tool();          // clears the preview ghost
+        after_tree_edit(ok);   // refresh tree/viewport/status (or "Edit rejected")
+        return;
+    }
+
+    switch (m_active) {
+    case Tool::Sketch:  on_add_sketch();  break;
+    case Tool::Extrude: on_add_extrude(); break;
+    case Tool::Dressup: on_add_dressup(); break;
+    case Tool::Hole:    on_add_hole();    break;
+    case Tool::Thread:  on_add_thread();  break;
+    case Tool::Shell:   on_add_shell();   break;
+    case Tool::Revolve: on_add_revolve(); break;
+    case Tool::Sweep:   on_add_sweep();   break;
+    case Tool::Pattern: on_add_pattern(); break;
+    case Tool::Plane:   if (!on_add_plane()) return;   break;   // refused: keep the card and its picks
+    case Tool::Loft:    on_add_loft();    break;
+    case Tool::Draft:   on_add_draft();   break;
+    case Tool::Boolean: on_add_boolean(); break;
+    case Tool::Cut:     on_add_cut();     break;
+    case Tool::Axis:    on_add_axis();    break;
+    case Tool::CoordSys: on_add_coordsys(); break;
+    case Tool::Mate:   on_add_mate();   break;
+    case Tool::SurfaceExtrude:  on_add_surface_extrude();  break;
+    case Tool::SurfaceRevolve:  on_add_surface_revolve();  break;
+    case Tool::SurfaceLoft:     on_add_surface_loft();     break;
+    case Tool::SurfaceFill:     on_add_surface_fill();     break;
+    case Tool::SurfaceOffset:   on_add_surface_offset();   break;
+    case Tool::ThickenSurface:  on_add_thicken_surface();  break;
+    case Tool::Transform:    on_add_transform();    break;
+    case Tool::Mirror:       on_add_mirror();       break;
+    case Tool::Thicken:      on_add_thicken();      break;
+    case Tool::Rib:          on_add_rib();          break;
+    case Tool::Project:      on_add_project();      break;
+    case Tool::DeleteFace:   on_add_delete_face();  break;
+    case Tool::Helix:        on_add_helix();        break;
+    case Tool::Insert:  return;   // committed via finalize_insert(), never here
+    case Tool::None:    return;
+    }
+    close_tool(); // also clears the preview ghost; the committed body is now shown
+}
+
+void DesignPanel::cancel_tool()
+{
+    reset_edit_state(); // abort an in-progress edit: back to add-mode
+    close_tool();
+    // Cancel discards the candidate: clear the stale "Preview …"/"Invalid …"
+    // label and restore the neutral idle colour (Confirm keeps its "OK" status).
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(wxString());
+    m_status->Refresh();
+}
+
+// One Confirm surface for the whole tab. Routes to the right commit by current context:
+// a feature card, the Insert placement, the Sketch session, or the Constrain session.
+void DesignPanel::tool_confirm()
+{
+    if (m_value_cont) { confirm_value(); return; }   // value card owns ribbon ✓ while a value is pending
+    if (m_active == Tool::None && m_viewport && m_viewport->moving_body()) {   // keep the placement, drop the gizmo
+        m_viewport->clear_move_gizmo();
+        m_move_body = -1;
+        show_move_card(false);
+        update_action_bar();
+        set_status_ok();
+        return;
+    }
+    if (m_active == Tool::Insert) { finalize_insert(); return; }
+    if (m_active != Tool::None)   { confirm_tool();   return; }
+    if (m_ui_mode == UiMode::Sketch) {
+        if (m_viewport && m_viewport->is_sketching()) m_viewport->finish_sketch();
+        set_ui_mode(UiMode::Feature);
+        return;
+    }
+    if (m_ui_mode == UiMode::Constrain) {
+        cancel_value();
+        if (m_viewport) m_viewport->end_constrain();
+        m_constrain_feat = -1;
+        set_ui_mode(UiMode::Feature);
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(wxString());
+        m_status->Refresh();
+    }
+}
+
+// One Cancel/exit surface (also bound to Esc). Discards the active feature/insert, or a
+// drawn-but-uncommitted Sketch, or exits Constrain.
+void DesignPanel::tool_cancel()
+{
+    if (m_value_cont) { cancel_value(); return; }     // value card owns ribbon ✗ while a value is pending
+    if (m_active == Tool::None && m_viewport && m_viewport->moving_body()) {   // revert to the pose at move-start
+        sync_body_xform();
+        if (m_move_body >= 0 && m_move_body < int(m_body_xform.size()))
+            m_body_xform[m_move_body] = m_move_prev;
+        m_viewport->clear_move_gizmo();
+        m_move_body = -1;
+        show_move_card(false);
+        feed_bodies();           // re-render the reverted placement
+        update_action_bar();
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("Move cancelled"));
+        m_status->Refresh();
+        return;
+    }
+    if (m_active == Tool::Insert) { cancel_insert(); return; }
+    if (m_active != Tool::None)   { cancel_tool();   return; }
+    if (m_ui_mode == UiMode::Sketch) {
+        // THE explicit discard. Esc no longer arrives here at all (it routes through escape(),
+        // which cannot destroy anything), so this button is now the only way a drawn sketch is
+        // thrown away — and being the only way, it has to ask. It used to refuse instead, telling
+        // the user to press the very button they had just pressed: a sketch could be kept but
+        // never discarded.
+        if (m_viewport && m_viewport->live_sketch_has_work()) {
+            wxMessageDialog dlg(this,
+                                _L("Discard this sketch and everything drawn in it?"),
+                                _L("Discard sketch"),
+                                wxYES_NO | wxNO_DEFAULT | wxICON_EXCLAMATION);
+            dlg.SetYesNoLabels(_L("Discard"), _L("Keep drawing"));
+            if (dlg.ShowModal() != wxID_YES) return;
+        }
+        if (m_viewport) m_viewport->cancel_sketch();   // drop the live session (committed art stays)
+        m_edit_index = -1;
+        set_ui_mode(UiMode::Feature);
+        sync_sketch_display();
+        refresh_tree();
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(wxString());
+        m_status->Refresh();
+        return;
+    }
+    if (m_ui_mode == UiMode::Constrain) {
+        cancel_value();
+        if (m_viewport) m_viewport->end_constrain();
+        m_constrain_feat = -1;
+        set_ui_mode(UiMode::Feature);
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(wxString());
+        m_status->Refresh();
+    }
+}
+
+// Which level of the interaction stack one Esc press belongs to. The rule itself lives in
+// DesignInteraction.hpp, decidable without a window; this only answers the four questions it
+// asks about THIS panel.
+CadLevel DesignPanel::escape_level() const
+{
+    CadInteractionState st;
+    // A value being typed is the deepest thing on screen, whether it is the in-canvas floating
+    // field or the panel's value card: both are "a number you are in the middle of entering".
+    st.value_field_open = (m_value_cont != nullptr)
+                          || (m_viewport && m_viewport->inline_busy());
+    // An uncommitted delta: clicks are down on an entity that does not exist yet, or a body is
+    // being moved by a gizmo that has not been confirmed.
+    st.gesture_active   = m_viewport
+                          && (m_viewport->drawing_in_progress()
+                              || (m_active == Tool::None && m_viewport->moving_body()));
+    // Something is armed and waiting for input: a feature card, a sketch draw tool, Constrain.
+    // A sketch SESSION is deliberately not in this list — see escape().
+    st.tool_armed       = (m_active != Tool::None)
+                          || m_ui_mode == UiMode::Constrain
+                          || (m_ui_mode == UiMode::Sketch && m_viewport && !m_viewport->sketch_is_selecting());
+    st.has_selection    = m_viewport && m_viewport->has_any_selection();
+    return cad_escape_level(st);
+}
+
+// Esc: unwind exactly one level. Nothing here deletes a feature, discards geometry or touches
+// history — those need Delete/Backspace on a selection, the sketch banner's Cancel, or Ctrl+Z.
+void DesignPanel::escape()
+{
+    switch (escape_level()) {
+    case CadLevel::Transient:
+        // Close just the field. The tool stays armed and the geometry is untouched, which is the
+        // whole reason this level exists: dismissing a number people press Esc for reflexively
+        // used to cascade down the stack and take the sketch with it.
+        if (m_value_cont)                      { cancel_value(); return; }
+        if (m_viewport)                        { m_viewport->inline_cancel(); return; }
+        return;
+
+    case CadLevel::Gesture:
+        // Restore the state from before the uncommitted delta. Drawing: drop the clicks, keep the
+        // tool armed so the next click starts a fresh entity. Moving: tool_cancel's move branch
+        // puts the body back at the pose it had when the gizmo appeared.
+        if (m_viewport && m_viewport->drawing_in_progress()) {
+            m_viewport->sketch_abort_gesture();
+            m_status->SetForegroundColour(wxNullColour);
+            set_status(wxString());
+            m_status->Refresh();
+            return;
+        }
+        tool_cancel();
+        return;
+
+    case CadLevel::Tool:
+        // Back to the idle state of whatever environment we are in. A feature card discards its
+        // CANDIDATE (never a committed feature — in edit mode reset_edit_state only forgets which
+        // feature was being edited, the feature itself is untouched); an armed sketch tool falls
+        // back to Select, leaving every entity already drawn exactly where it is.
+        if (m_active != Tool::None || m_ui_mode == UiMode::Constrain) { tool_cancel(); return; }
+        if (m_viewport && m_viewport->sketch_disarm_tool()) {
+            m_status->SetForegroundColour(wxNullColour);
+            set_status(_L("Select"));
+            m_status->Refresh();
+        }
+        return;
+
+    case CadLevel::Idle:
+        // Deselect. In a sketch this is the floor: the session is left through Finish or Cancel,
+        // both of which say which one they are, and never through a key pressed on the way out of
+        // something else.
+        if (m_viewport && m_viewport->clear_any_selection()) {
+            m_sel_sketch_region = -1;
+            m_sel_sketch_feat   = -1;
+            m_status->SetForegroundColour(wxNullColour);
+            set_status(wxString());
+            m_status->Refresh();
+            return;
+        }
+        // Nothing selected and nothing to unwind. An EMPTY sketch session may as well close —
+        // there is no work to lose, so this cannot be the destructive case, and being unable to
+        // leave a sketch you have not drawn in yet is its own small trap.
+        if (m_ui_mode == UiMode::Sketch && m_viewport && !m_viewport->live_sketch_has_work()) {
+            m_viewport->request_sketch_exit();
+            return;
+        }
+        if (m_ui_mode == UiMode::Sketch) {
+            m_status->SetForegroundColour(wxNullColour);
+            set_status(_L("Sketch kept — Finish to commit it, Cancel to discard"));
+            m_status->Refresh();
+        }
+        return;
+    }
+}
+
+void DesignPanel::update_undo_redo_buttons()
+{
+    // Grey Undo/Redo to mirror exactly what do_undo_redo will do: it acts only in Feature
+    // mode with no tool/dialog open (otherwise Esc is the way out), so reflect that gate here
+    // as well as the document's available history.
+    if (m_btn_undo == nullptr || m_btn_redo == nullptr) return;
+    const bool gated = (m_ui_mode != UiMode::Feature) || (m_active != Tool::None);
+    m_btn_undo->Enable(!gated && m_doc.can_undo());
+    m_btn_redo->Enable(!gated && m_doc.can_redo());
+}
+
+void DesignPanel::update_action_bar()
+{
+    update_undo_redo_buttons();   // mode/tool changes flip the do_undo_redo gate -> refresh greying
+    if (m_tb_action == nullptr || m_toolbar == nullptr) return;
+    wxSizer* s = m_toolbar->GetSizer();
+    if (s == nullptr) return;
+    const bool active = (m_active != Tool::None)
+                     || m_ui_mode == UiMode::Sketch
+                     || m_ui_mode == UiMode::Constrain
+                     || (m_viewport && m_viewport->moving_body());
+    s->Show(m_tb_action, active, true);
+    // HIDING THE BAR ORPHANS THE KEYBOARD, and that is the "app does not consent to sketch"
+    // report. The ✓/✗ live in this bar, so the click that confirms a feature leaves focus on a
+    // button that this very call then hides. wx does not hand that focus anywhere useful, and
+    // wxEVT_CHAR_HOOK is bound on THIS PANEL — it is delivered to the focused window and
+    // propagates up the parent chain, so with focus outside the panel every Design shortcut
+    // stops arriving. Measured on the rig: after Confirm, shift+S produced ZERO CHAR_HOOK lines
+    // (not even the modifier), while X kept focus on the main window throughout — so it was
+    // never a window-manager problem. One bare canvas click restored it, which is exactly the
+    // workaround users found and reported as "shift+s works but it is not intuitive".
+    // The canvas is the right owner of the keyboard in this tab, so give it back explicitly.
+    if (!active && m_viewport != nullptr) {
+        wxWindow* f = wxWindow::FindFocus();
+        bool in_bar = (f == nullptr);
+        for (wxWindow* w = f; w != nullptr && !in_bar; w = w->GetParent())
+            if (w == m_toolbar) in_bar = true;   // the bar is a sizer; its buttons parent to m_toolbar
+        if (in_bar) m_viewport->SetFocus();
+    }
+    m_toolbar->Layout();
+    m_toolbar->FitInside();   // refresh scroll range when the action bar shows/hides
+}
+
+void DesignPanel::do_undo_redo(bool redo)
+{
+    // v1: act only in Feature mode. While authoring/constraining a sketch (m_ui_mode) or
+    // with a feature dialog open (m_active), Esc/Cancel is the way out — popping committed
+    // history mid-tool would be ambiguous (and could orphan the tool's referenced feature).
+    if (m_ui_mode != UiMode::Feature || m_active != Tool::None) {
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(_L("Finish or cancel the current tool first (Esc)"));
+        m_status->Refresh();
+        return;
+    }
+    const bool ok = redo ? m_doc.redo() : m_doc.undo();
+    if (!ok) {
+        m_status->SetForegroundColour(wxNullColour);
+        set_status(redo ? _L("Nothing to redo") : _L("Nothing to undo"));
+        m_status->Refresh();
+        return;
+    }
+    // The solid whole/face/edge pick and any in-place edit reference ids that recompute()
+    // invalidates — drop them before refreshing from the restored document.
+    m_sel_solid_body = m_sel_solid_face = m_sel_solid_edge = -1;
+    m_pick_face = m_pick_face_body = -1;   // recompute() invalidated the face ids too
+    reset_edit_state();
+    after_tree_edit(true);   // refresh tree + viewport meshes + status from the restored doc
+    m_status->SetForegroundColour(wxNullColour);
+    set_status(wxString::Format(redo ? _L("Redo  (%zu more)") : _L("Undo  (%zu more)"),
+                                        redo ? m_doc.redo_depth() : m_doc.undo_depth()));
+    m_status->Refresh();
+}
+
+// --- Document variables panel ---------------------------------------------------------
+
+void DesignPanel::refresh_variables()
+{
+    if (!m_var_list) return;
+    m_var_list->DeleteAllItems();
+    int row = 0;
+    for (const auto& [name, expr] : m_doc.variables) {
+        m_var_list->InsertItem(row, wxString::FromUTF8(name));
+        m_var_list->SetItem(row, 1, wxString::FromUTF8(expr));
+        ++row;
+    }
+}
+
+void DesignPanel::on_add_variable()
+{
+    wxString name = ::wxGetTextFromUser(_L("Variable name:"), _L("Add Variable"), "", this);
+    if (name.IsEmpty()) return;
+    name.Trim(true).Trim(false);
+    if (name.Contains(' ')) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("Variable name must not contain spaces"));
+        m_status->Refresh();
+        return;
+    }
+    wxString expr = ::wxGetTextFromUser(
+        wxString::Format(_L("Expression for '%s':"), name),
+        _L("Add Variable"), "0", this);
+    if (expr.IsEmpty()) return;
+
+    const std::string name_str = name.ToUTF8().data();
+    const std::string expr_str = expr.ToUTF8().data();
+
+    m_doc.checkpoint();
+    m_doc.variables[name_str] = expr_str;
+    bool ok = m_doc.recompute();
+    // undo() recomputes, which SUCCEEDS and clears doc.error — so the reason the edit was
+    // rejected is gone before anything can display it. Carry it across the rollback.
+    if (!ok) { const std::string why = m_doc.error; m_doc.undo(); m_doc.error = why; }
+    after_tree_edit(ok);
+    refresh_variables();
+}
+
+void DesignPanel::on_edit_variable()
+{
+    if (!m_var_list) return;
+    const long sel = m_var_list->GetNextItem(-1, wxLIST_NEXT_ALL, wxLIST_STATE_SELECTED);
+    if (sel < 0) {
+        set_status(_L("Select a variable first"));
+        m_status->Refresh();
+        return;
+    }
+    const std::string name_str = m_var_list->GetItemText(sel, 0).ToUTF8().data();
+    const std::string old_expr  = m_var_list->GetItemText(sel, 1).ToUTF8().data();
+    wxString expr = ::wxGetTextFromUser(
+        wxString::Format(_L("Expression for '%s':"), m_var_list->GetItemText(sel, 0)),
+        _L("Edit Variable"), wxString::FromUTF8(old_expr), this);
+    if (expr.IsEmpty()) return;
+
+    const std::string expr_str = expr.ToUTF8().data();
+    m_doc.checkpoint();
+    m_doc.variables[name_str] = expr_str;
+    bool ok = m_doc.recompute();
+    // undo() recomputes, which SUCCEEDS and clears doc.error — so the reason the edit was
+    // rejected is gone before anything can display it. Carry it across the rollback.
+    if (!ok) { const std::string why = m_doc.error; m_doc.undo(); m_doc.error = why; }
+    after_tree_edit(ok);
+    refresh_variables();
+}
+
+void DesignPanel::on_remove_variable()
+{
+    if (!m_var_list) return;
+    const long sel = m_var_list->GetNextItem(-1, wxLIST_NEXT_ALL, wxLIST_STATE_SELECTED);
+    if (sel < 0) {
+        set_status(_L("Select a variable first"));
+        m_status->Refresh();
+        return;
+    }
+    const std::string name_str = m_var_list->GetItemText(sel, 0).ToUTF8().data();
+
+    m_doc.checkpoint();
+    m_doc.variables.erase(name_str);
+    bool ok = m_doc.recompute();
+    if (!ok) {
+        // Capture before undo(): its recompute succeeds and clears doc.error.
+        const std::string why = m_doc.error;
+        m_doc.undo();
+        // Almost always a feature expr still referencing the variable — but say so as the
+        // likely cause and keep the real message, rather than asserting a diagnosis that
+        // would be wrong for any other failure.
+        m_doc.error = wxString::Format(
+            _L("Variable '%s' could not be removed (likely still referenced by a feature "
+               "expression): %s"),
+            m_var_list->GetItemText(sel, 0), wxString::FromUTF8(why)).ToUTF8().data();
+    }
+    after_tree_edit(ok);
+    refresh_variables();
+}
+
+// --- Expression binding ---------------------------------------------------------------
+
+// Field-name lists per feature type. The combo is editable so a power user can type any
+// valid field name; these lists pre-populate the picker for the common operations.
+std::vector<std::string> DesignPanel::fields_for_tool(Tool t)
+{
+    using T = DesignPanel::Tool;
+    switch (t) {
+    case T::Sketch:           return {"width", "height", "radius"};
+    case T::Extrude:          return {"distance", "distance2", "taper_deg"};
+    case T::Dressup:          return {"dressup_size"};
+    case T::Hole:             return {"hole_diameter", "hole_depth", "hole_x", "hole_y"};
+    case T::Thread:           return {"thread_radius", "thread_pitch", "thread_height", "thread_depth", "thread_x", "thread_y"};
+    case T::Shell:            return {"shell_thickness"};
+    case T::Revolve:          return {"revolve_angle"};
+    case T::Sweep:            return {};
+    case T::Pattern:          return {"pattern_count", "pattern_spacing", "pattern_angle"};
+    case T::Plane:            return {"plane_offset", "plane_angle_tilt"};
+    case T::Loft:             return {};
+    case T::Draft:            return {"draft_angle"};
+    case T::Boolean:          return {};
+    case T::Cut:              return {};
+    case T::SurfaceExtrude:   return {"distance"};
+    case T::SurfaceRevolve:   return {"revolve_angle"};
+    case T::SurfaceLoft:      return {};
+    case T::SurfaceFill:      return {};
+    case T::SurfaceOffset:    return {"plane_offset"};
+    case T::ThickenSurface:   return {"thicken_thickness"};
+    case T::Transform:        return {};
+    case T::Mirror:           return {};
+    case T::Thicken:          return {"thicken_thickness"};
+    case T::Rib:              return {"rib_thickness", "rib_depth"};
+    case T::Project:          return {};
+    case T::DeleteFace:       return {};
+    case T::Helix:            return {"helix_radius", "helix_pitch", "helix_height", "helix_taper_deg"};
+    case T::Axis:             return {};
+    case T::CoordSys:         return {};
+    case T::Mate:             return {};
+    case T::Insert:           return {};
+    case T::None:             return {};
+    }
+    return {};
+}
+
+void DesignPanel::populate_expr_fields(Tool t)
+{
+    if (!m_expr_field) return;
+    m_expr_field->Clear();
+    for (const std::string& f : fields_for_tool(t))
+        m_expr_field->Append(wxString::FromUTF8(f));
+    if (m_expr_field->GetCount() > 0)
+        m_expr_field->SetSelection(0);
+}
+
+void DesignPanel::on_set_expr()
+{
+    if (m_edit_index < 0 || m_edit_index >= int(m_doc.features.size())) return;
+    if (!m_expr_field || !m_expr_text) return;
+
+    const wxString fwx = m_expr_field->GetValue();
+    const wxString ewx = m_expr_text->GetValue();
+    if (fwx.IsEmpty()) return;
+
+    const std::string field = fwx.ToUTF8().data();
+    const std::string expr  = ewx.ToUTF8().data();
+
+    m_doc.checkpoint();
+    m_doc.features[m_edit_index].expr[field] = expr;
+    bool ok = m_doc.recompute();
+    // undo() recomputes, which SUCCEEDS and clears doc.error — so the reason the edit was
+    // rejected is gone before anything can display it. Carry it across the rollback.
+    if (!ok) { const std::string why = m_doc.error; m_doc.undo(); m_doc.error = why; }
+    after_tree_edit(ok);
+    if (ok) m_expr_text->Clear();
+
+    // Refresh the status line showing current bindings
+    if (m_edit_index >= 0 && m_edit_index < int(m_doc.features.size())) {
+        const CadFeature& ef = m_doc.features[m_edit_index];
+        if (ef.expr.empty()) {
+            m_expr_status->SetLabel(_L("(no bindings)"));
+            m_expr_status->SetForegroundColour(dp_sec_text());
+        } else {
+            wxString s;
+            for (const auto& [f, e] : ef.expr) {
+                if (!s.IsEmpty()) s += "; ";
+                s += wxString::FromUTF8(f) + " = " + wxString::FromUTF8(e);
+            }
+            m_expr_status->SetLabel(s);
+            m_expr_status->SetForegroundColour(dp_ctl_text());
+        }
+    }
+}
+
+void DesignPanel::on_clear_expr()
+{
+    if (m_edit_index < 0 || m_edit_index >= int(m_doc.features.size())) return;
+    if (!m_expr_field) return;
+
+    const wxString fwx = m_expr_field->GetValue();
+    if (fwx.IsEmpty()) return;
+
+    const std::string field = fwx.ToUTF8().data();
+    auto& feat_expr = m_doc.features[m_edit_index].expr;
+    if (feat_expr.find(field) == feat_expr.end()) {
+        m_status->SetForegroundColour(wxColour(235, 110, 110));
+        set_status(_L("No binding for that field"));
+        m_status->Refresh();
+        return;
+    }
+
+    m_doc.checkpoint();
+    feat_expr.erase(field);
+    bool ok = m_doc.recompute();
+    // undo() recomputes, which SUCCEEDS and clears doc.error — so the reason the edit was
+    // rejected is gone before anything can display it. Carry it across the rollback.
+    if (!ok) { const std::string why = m_doc.error; m_doc.undo(); m_doc.error = why; }
+    after_tree_edit(ok);
+
+    if (m_edit_index >= 0 && m_edit_index < int(m_doc.features.size())) {
+        const CadFeature& ef = m_doc.features[m_edit_index];
+        if (ef.expr.empty()) {
+            m_expr_status->SetLabel(_L("(no bindings)"));
+            m_expr_status->SetForegroundColour(dp_sec_text());
+        } else {
+            wxString s;
+            for (const auto& [f, e] : ef.expr) {
+                if (!s.IsEmpty()) s += "; ";
+                s += wxString::FromUTF8(f) + " = " + wxString::FromUTF8(e);
+            }
+            m_expr_status->SetLabel(s);
+            m_expr_status->SetForegroundColour(dp_ctl_text());
+        }
+    }
+}
+
+}} // namespace Slic3r::GUI
diff --git a/src/slic3r/GUI/CAD/DesignPanel.hpp b/src/slic3r/GUI/CAD/DesignPanel.hpp
new file mode 100644
index 0000000000..88b445534d
--- /dev/null
+++ b/src/slic3r/GUI/CAD/DesignPanel.hpp
@@ -0,0 +1,919 @@
+#ifndef slic3r_DesignPanel_hpp_
+#define slic3r_DesignPanel_hpp_
+
+#include <wx/panel.h>
+#include <wx/scrolwin.h>
+#include <wx/treebase.h>   // wxTreeItemId
+
+#include <vector>
+#include <memory>
+#include <functional>
+#include <map>
+
+#include "libslic3r/CAD/CadDocument.hpp"
+#include "slic3r/GUI/CAD/DesignInteraction.hpp"   // CadLevel: what one Esc press means
+
+class ComboBox;    // Orca dropdown (Widgets/ComboBox.hpp) — replaces wxChoice everywhere here
+class StaticBox;   // Orca rounded card frame (Widgets/StaticBox.hpp)
+class wxCheckBox;
+class wxCheckListBox;
+class wxSpinCtrl;
+class wxSpinCtrlDouble;
+class wxTreeCtrl;
+class wxImageList;
+class wxStaticText;
+class wxStaticLine;
+class Button;      // Orca-styled button (Widgets/Button.hpp)
+class CheckBox;    // Orca teal checkbox (Widgets/CheckBox.hpp)
+class wxSizer;
+// wxBoxSizer, wxTextCtrl and wxListCtrl are used here as pointers only, so a forward
+// declaration is enough — but they must be declared. Every ordinary build happened to pull
+// them in transitively through the wx/panel.h + wx/scrolwin.h chain. The Snapmaker fork's
+// Flatpak build does not, and it failed to compile this header with "'wxTextCtrl' does not
+// name a type; did you mean 'wxTreeCtrl'?". Declaring them keeps the header self-contained
+// instead of relying on whatever a particular wx configuration happens to include.
+class wxBoxSizer;
+class wxTextCtrl;
+class wxListCtrl;
+class wxButton;
+class wxPanel;
+class ScalableButton;
+
+namespace Slic3r { namespace GUI {
+
+class DesignCanvas;
+
+// Design (CAD) tab: a sketch-first, Onshape-style form-driven CAD panel.
+// Sketch and Extrude are independent tools: the user creates a Sketch first,
+// then selects it and Extrudes to produce a solid.
+class DesignPanel : public wxPanel
+{
+public:
+    explicit DesignPanel(wxWindow* parent);
+    void on_tab_shown();        // re-sync bed to the active printer when the Design tab is activated
+    void on_tab_hidden();       // another tab took over: take the viewport status line down with us
+    void unbind_canvas_event_handlers();   // app close / language switch, from the plater's teardown
+    void reset_canvas_volumes();
+    void clear_document();      // New Project / Open Project: drop the document with the project
+    // Rebuild off the UI thread (progress dialog only if it turns out to be slow), so a feature
+    // op on a heavy imported solid does not freeze the window. Returns m_doc.recompute()'s result.
+    // Push the document's recipe into the Model so ANY save path persists it (vjk5).
+    void sync_recipe_to_model();
+    bool recompute_guarded(const wxString& message);
+
+    // MCP control hooks: let the external control server (McpControl.cpp) drive and
+    // perceive the SAME kernel the GUI uses. Called only on the wx main thread.
+    CadDocument& mcp_doc()        { return m_doc; }            // live document (read + mutate)
+    void         mcp_after_change() { after_tree_edit(true); } // refresh tree + viewport + status
+    DesignCanvas* mcp_viewport()  { return m_viewport; }        // live sketch + 3D view
+    // Put the PANEL into (or out of) sketch mode, not just the canvas tool. Measured on the
+    // rig: a sketch started straight through DesignCanvas::begin_sketch leaves m_ui_mode at
+    // Feature, and the keyboard map is dispatched on `m_ui_mode == UiMode::Sketch` while the
+    // offer menu is dispatched on the looser sketch_map_applies() — so the menu offered the
+    // line's verbs while every sketch shortcut was dead (KEYTRACE: key=81 ui_mode=0
+    // is_sketching=1). Half-entering a mode is worse than not entering it.
+    void mcp_set_sketch_mode(bool on)
+    {
+        set_ui_mode(on ? UiMode::Sketch : UiMode::Feature);
+        update_action_bar();
+    }
+    // The offer-table vocabulary without a right-click: the external controller asks which verbs
+    // exist (and which apply to the current selection) and fires one by id, so a deck key names a
+    // verb instead of spending a letter and every verb is reachable — including the rows with no
+    // keyboard shortcut, which are otherwise invisible to anything that parses key tables.
+    int  mcp_offer_selection_kind() const { return offer_selection_kind(); }  // OfferSel as int
+    void mcp_run_action(const char* action) { run_offer_action(action); }     // dispatch an action string
+    // Defined out of line in DesignPanel.cpp: it needs kOfferVerbs, which this header deliberately
+    // does not include (the table is generated and belongs to the offer-menu code).
+    bool mcp_run_verb(const char* verb_id);
+
+private:
+    enum class Tool { None, Sketch, Extrude, Dressup, Hole, Thread, Shell, Revolve, Sweep, Pattern, Plane, Loft, Draft, Boolean, Cut, Insert, Axis, CoordSys, SurfaceExtrude, SurfaceRevolve, SurfaceLoft, SurfaceFill, SurfaceOffset, ThickenSurface, Transform, Mirror, Thicken, Rib, Project, DeleteFace, Helix, Mate };
+    // Which numeric fields an expression can be bound to, per feature type. A member rather
+    // than a file-static helper so Tool — 32 values of purely internal card state — does not
+    // have to become part of this panel's public API just to be named in a signature.
+    static std::vector<std::string> fields_for_tool(Tool t);
+    // Plane tool: which datum reference the next solid pick fills (declared early so the
+    // method decls + card lambdas below can name it).
+    enum class PlanePick { None, FaceA, FaceB, EdgeA, EdgeB };
+    enum class AxisPick { None, Face, Edge };
+    enum class CoordSysPick { None, Face, Edge };
+
+    // Onshape-style contextual top toolbar: only the active mode's tool group is
+    // shown (Feature = sketch/extrude/dress/hole/thread; Sketch = entity tools;
+    // Constrain = constraints + edit ops). Replaces the old always-visible wall.
+    enum class UiMode { Feature, Sketch, Constrain };
+    void set_ui_mode(UiMode m);
+    void apply_dof_status(int dof, bool ok, bool has_constraints);
+    // Unified action-bar dispatch: one Confirm / one Cancel for every tool and mode.
+    void tool_confirm();        // ✓ : commit the active feature / sketch / constrain session
+    void tool_cancel();         // ✗ : cancel the active feature / discard / exit
+    // Esc. ONE press unwinds ONE level of the interaction stack (DesignInteraction.hpp), and no
+    // level of it destroys committed work. escape_level() answers which level the press belongs
+    // to; escape() acts on exactly that one. Every Esc in the tab routes through here — the key
+    // used to be handled in four places that could not see each other, and that is how two
+    // presses in a row reached past a tool and discarded the sketch under it.
+    CadLevel escape_level() const;
+    void     escape();
+    void update_action_bar();   // show the ✓/✗ bar iff a tool or mode is active
+
+    void on_shape_changed();
+    void on_add_sketch();
+    void on_add_extrude();
+    void on_add_dressup();
+    void on_add_hole();
+    void on_add_thread();
+    void apply_thread_standard();   // fill pitch/depth/radius from m_thread_std selection
+    void infer_thread_spec(double diameter);  // nearest M-standard from a picked cylinder diameter
+    void on_add_revolve();
+    void on_add_sweep();
+    void on_add_loft();
+    void on_add_pattern();
+    bool on_add_plane();   // false = refused, card stays open
+    void arm_plane_pick(PlanePick target);   // Plane tool: next solid pick fills this reference
+    void apply_plane_refs(CadFeature& f) const; // copy type + face/edge refs + sizes from the card
+    void refresh_plane_labels();             // update the 4 pick labels from the captured refs
+    void reset_plane_refs();                 // clear captured refs (fresh Plane add)
+    void on_add_shell();
+    void on_add_draft();
+    void on_add_boolean();
+    void on_add_cut();              // commit a plane Cut (split-by-plane)
+    void on_add_axis();
+    void arm_axis_pick(AxisPick target);
+    void apply_axis_refs(CadFeature& f) const;
+    void refresh_axis_labels();
+    void reset_axis_refs();
+    void on_add_coordsys();
+    void arm_coordsys_pick(CoordSysPick target);
+    void apply_coordsys_refs(CadFeature& f) const;
+    void refresh_coordsys_labels();
+    void refresh_cs_body_choice();   // fill the CoordSys body chooser from current document
+    void reset_coordsys_refs();
+    void on_add_surface_extrude();
+    void on_add_surface_revolve();
+    void on_add_surface_loft();
+    void on_add_surface_fill();
+    void on_add_surface_offset();
+    void on_add_thicken_surface();
+    void on_add_transform();
+    void xf_live_preview();    // typed Transform fields -> body display transform (live)
+    void xf_clear_preview();   // hand a previewed body back to its pre-card pose
+    void on_add_mirror();
+    void on_add_thicken();
+    void on_add_rib();
+    void on_add_project();
+    void on_add_delete_face();
+    void on_add_helix();
+    void on_add_mate();
+    void on_check_interference();
+    void on_mass_properties();          // read-only report on the selected solid; edits nothing
+    // Fill m_bool_target / m_bool_tool / m_cut_target. as_of_feature < 0 = current bodies (add);
+    // >= 0 = the bodies as they existed just before that feature index (Boolean re-edit, so a
+    // consumed tool body still appears and its saved selection round-trips).
+    // Which body a tool should act on when it opens: the one picked in the VIEWPORT, else
+    // the first. Selection comes first and the tool consumes it — every body combo used to
+    // default to index 0, so picking body 3 and opening Mirror silently mirrored body 1.
+    // Clamped to the list, so it is safe to hand straight to SetSelection. e1p.
+    int  selected_body_default() const;
+    void populate_body_choices(int as_of_feature = -1);
+    // Fill `c` with the bodies as they existed just before `as_of_feature` and select
+    // `want`. Re-editing any feature that stores a body index needs this: the index was
+    // recorded against the body list at that point in the timeline, not the final one.
+    void fill_body_choice(ComboBox* c, int as_of_feature, int want);
+    void populate_sheet_body_choices(ComboBox* c) const;   // bodies where is_sheet_shape() is true
+    // Rows of a sheet-filtered picker are not body indices; go through these two, never
+    // GetSelection()/SetSelection() directly.
+    static int  sheet_choice_body(ComboBox* c);            // real body index of the current row, or -1
+    static void select_sheet_choice(ComboBox* c, int body);// select the row holding this body index
+    // Import rigid 2D art (Text / SVG) as a new Sketch feature carrying
+    // imported_regions (no solver entities). on_add_text/on_import_svg gather
+    // input; add_imported_sketch builds the feature, refreshes tree + display.
+    void on_add_text();
+    void on_import_svg();
+    void on_import_step();   // STEP -> editable B-rep body (keeps the OCCT solid, not a mesh)
+    void on_import_mesh();   // STL/OBJ -> B-rep body via GeometryEngine::mesh_to_brep
+    bool place_on_face();    // Prepare's Place on Face (F): lay the selected body face on the bed
+    void add_imported_sketch(const std::vector<std::vector<std::vector<Vec2d>>>& regions,
+                             const wxString& base_name);
+    // Imported Text/SVG art is placed/sized in-canvas then explicitly committed via a
+    // small Confirm/Cancel card (Onshape Button->Dialog->Preview->Confirm). The feature
+    // is added provisionally by add_imported_sketch; Confirm keeps it, Cancel undoes it.
+    void open_insert_card(const wxString& base_name);
+    void finalize_insert();   // Confirm: keep the placed art, leave the placement gizmo
+    void cancel_insert();     // Cancel: undo the provisional insert
+    // Move / enlarge / stretch (independent X/Y) an imported Text/SVG sketch:
+    // a modal dialog editing the feature's placement transform in place.
+    void on_transform_imported(int feat_idx);
+    void on_commit();
+    void on_export_step();   // write all bodies to a .step file (native B-rep)
+    // Rehydrate the parametric model from a project's saved recipe (3MF
+    // Metadata/orca_cad.bin): deserialize -> recompute -> refresh viewport + tree.
+    void load_recipe(const std::string& blob);
+    void refresh_tree();
+    void set_status_ok();
+
+    // Feature-tree editing (Onshape-style): act on the selected tree row.
+    void on_delete_feature();
+    // "Delete Body" — the geometry-first counterpart, reached by pointing at a body or any of
+    // its faces. Resolves the body to the feature that created it and removes THAT, because a
+    // body is a recomputed result and has nothing else to delete.
+    void on_delete_body();
+    void on_new_design();
+    void on_move_feature(int delta);   // -1 = up, +1 = down
+    void on_toggle_visibility();       // show/hide the selected feature (CadFeature::enabled)
+
+    // Constrain mode: enter on the tree-selected sketch, then apply a geometric
+    // constraint to the in-canvas picked segment and re-solve in the kernel.
+    void on_begin_constrain(int sel_override = -1);
+    // Sketch-toolbar Constrain entry: commit the live sketch in place, then enter Constrain
+    // mode on it (so the constraint palette + Trim/Extend are reachable without leaving the
+    // sketch flow). Returns true if constrain mode was entered.
+    bool enter_constrain_inline();
+    void apply_constraint(SketchConstraintType type);
+    void apply_entity_constraint(SketchConstraintType type);  // Fase 4.2 entity path
+    void apply_live_constraint(SketchConstraintType type);    // Fase 4.2 live-sketch path (no commit needed)
+    enum class EditOp { Mirror, Offset, Fillet, Trim, Extend, Array, Move, Chamfer, Rotate, Scale, PolarArray }; // Fase 4.4/4.5/4.6 sketch edit ops
+    void apply_edit_op(EditOp op);                            // mutate selected sketch entities
+    // Onshape-style docked value entry (replaces wxGetTextFromUser popups for
+    // Angle/Radius/Diameter constraints + Offset/Fillet edit ops). request_value
+    // shows the card and stows a continuation run by confirm_value().
+    void request_value(const wxString& label, double def, double mn, double mx,
+                       std::function<void(double)> cont,
+                       std::function<void()> on_cancel = nullptr);
+    void confirm_value();
+    void cancel_value();
+    void commit_entity_constraints(const std::vector<SketchEntityConstraintDef>& defs); // multi-def (Symmetric)
+
+    // Constraint manager (C3.4): a docked list of the constrained sketch's
+    // entity-constraints with per-row select (highlight the referenced entities in
+    // the viewport) and delete (drop the constraint + re-solve). Shown in Constrain
+    // mode only; operates on m_doc.features[m_constrain_feat].entity_constraints.
+    // True when the constraint UI must address the LIVE sketch session rather than a committed
+    // feature. Same discriminator apply_constraint uses to choose apply_live_constraint: both
+    // Constrain modes set m_active too, so is_sketching() alone would claim the live scope while
+    // the committed manager is open.
+    bool live_constraint_scope() const;
+    void rebuild_constraint_list();                                      // refill m_constraint_rows
+    void delete_constraint(int idx);                                     // erase + re-solve + refresh
+    void highlight_constraint_entities(int idx);                         // push referenced entities to viewport
+    void refresh_constrain_dof();                                        // re-solve feature, mirror DoF readout
+    wxString constraint_label(const SketchEntityConstraintDef& d) const; // human-readable row text
+    void after_edit_op();                                                // shared edit-op refresh tail
+    void on_edit_feature();            // reopen the selected feature's dialog populated
+    void after_tree_edit(bool ok);     // shared post-op refresh of tree/viewport/status
+    void load_feature_into_dialog(const CadFeature& f);
+    void reset_edit_state();           // back to add-mode (m_edit_index = -1)
+
+    // Onshape loop: Button -> open_tool (show dialog) -> refresh_preview (ghost) ->
+    // confirm_tool (commit) / cancel_tool (abort).
+    void       open_tool(Tool t);
+    void       close_tool();
+    void       refresh_preview();
+    void       confirm_tool();
+    void       cancel_tool();
+    // Ctrl+Z / Ctrl+Shift+Z (Ctrl+Y) from the viewport. With a tool/dialog open it
+    // cancels that (Esc-like); otherwise it undoes/redoes the committed feature history.
+    void       do_undo_redo(bool redo);
+    // The plane the Hole tool drills on: a picked face (inward, centred) or the dropdown.
+    SketchPlane hole_plane() const;
+    // The plane the Thread tool builds on: a picked cylindrical face (axis) or the dropdown.
+    SketchPlane thread_plane() const;
+    // Name the geometry the card has LATCHED, so it never has to be inferred from the viewport.
+    // Pass -1 for "none, falling back to the plane dropdown". See 200.
+    void        set_hole_target_label(int face);
+    void        set_thread_target_label(int face, int edge);
+    CadFeature build_candidate(Tool t) const;
+    // Merge per-body ghost meshes with the per-body display transforms applied. The kernel builds
+    // a ghost from the untransformed bodies, so without this it floats back at the origin once a
+    // body has been moved.
+    TriangleMesh ghost_from_bodies(const std::vector<TriangleMesh>& per_body) const;
+    // A mate makes no new geometry but it MOVES a body, and the moved assembly is the ghost worth
+    // showing. Used both by the Mate card and by hovering a row of the offer's mate palette.
+    bool       show_mate_ghost(int kind, int cs_a, int cs_b,
+                               double offset, double angle_deg, bool flip, std::string& err);
+    int        resolve_extrude_sketch() const;
+    // Plane pickers: fill a choice with XY/XZ/YZ + the document's datum planes, and
+    // map a choice row back to the actual SketchPlane (rows 0-2 base, 3+ datum).
+    void        populate_plane_choices(ComboBox* c) const;
+    wxString    ref_plane_name(int row) const;   // "XY" / a datum's name, for the on-geometry hint
+    SketchPlane plane_from_choice(int row) const;
+    // Where a new sketch goes, resolved from what is SELECTED IN THE VIEWPORT rather than from a
+    // list: a picked planar face wins, otherwise the reference plane last clicked in 3D. `what`
+    // comes back as something to show the user, so the choice is visible without a combo.
+    SketchPlane sketch_plane_from_selection(wxString& what) const;
+    // Whether that resolution has anything the USER picked behind it, rather than the default
+    // reference plane. Lets a caller say "sketching on XZ" only when it is actually true.
+    bool sketch_plane_target(wxString& what) const;
+    // True when Extrude should build only the click-selected loop (a region of the
+    // resolved sketch is selected and it carries entities).
+    bool       extrude_uses_loop() const;
+    void       sync_sketch_display();   // push un-consumed committed sketches to the viewport
+    // Feed the viewport's visual Extrude depth-arrow gizmo (C5b) with the current profile
+    // plane + centroid + live depths while the Extrude card is open (self-gates on m_active).
+    void       update_extrude_gizmo();
+    void       update_fillet_gizmo();     // edge-anchored radius arrow (Dressup card)
+    void       sync_dressup_target();     // Dressup card: show picked edge vs group, gate the combo
+    void       update_hole_gizmo();       // footprint circle + diameter/depth arrows (Hole card)
+    // A FEATURE button whose tool needs bodies it may not have yet. Greyed with an explanatory
+    // tooltip below min_bodies, rather than accepting the click and refusing afterwards.
+    struct BodyGate { wxWindow* btn{nullptr}; int min_bodies{1}; wxString tip_live, tip_gated; };
+    std::vector<BodyGate> m_body_gates;
+    void       update_body_gates();       // re-evaluate them against the current body count
+    void       update_thread_gizmo();     // footprint circle + radius/length arrows (Thread card)
+    void       update_shell_gizmo();      // inward thickness arrow on the picked face (Shell card)
+    void       update_revolve_gizmo();    // angle-arc around the axis (Revolve card)
+    void       update_draft_gizmo();      // angle-arc around the face centroid (Draft card)
+    void       update_cut_gizmo();        // plane-rectangle + offset arrow (Cut card)
+    void       update_operand_highlight(); // Boolean/Sweep/Loft operand tinting on the canvas
+    void       update_pattern_gizmo();    // linear spacing arrow / circular angle-arc (Pattern card)
+    void       update_datum_gizmo();      // resize handles on the datum plane being created/edited (C3)
+    void       update_helix_gizmo();      // live helix curve + radius/height/pitch handles (Helix card)
+    void       update_rib_gizmo();        // in-plane slab footprint + thickness handles (Rib card)
+    void       refresh_datum_planes();    // push resolved datum frames + per-plane u/v extents to viewport
+    void       refresh_mate_connectors(); // push connector frames so verse + polarity are visible
+    void       update_reference_planes(); // persistent XY/XZ/YZ reference planes (fallback when no object)
+
+    CadDocument m_doc;
+
+    Tool      m_active{Tool::None};
+
+    // Keyboard shortcuts (Onshape-style, three scoped layers). Keys are encoded as the
+    // upper-cased letter, OR'd with 0x10000 when Shift is required. m_keys_sketch fires only
+    // while a sketch is open (single letters = sketch tools); m_keys_feature fires only when
+    // no sketch is open (Shift+letter = feature tools; single letters = view toggles/section).
+    static constexpr int SC_SHIFT = 0x10000;
+    // ...and with 0x20000 when Ctrl is required too. The Shift+letter space is full, so an
+    // action that arrives late lives on Ctrl+Shift; plain Ctrl-combos are still passed
+    // straight through, which is what leaves this layer free.
+    static constexpr int SC_CTRL = 0x20000;
+    std::map<int, std::function<void()>> m_keys_sketch;
+    std::map<int, std::function<void()>> m_keys_feature;
+
+    StaticBox* m_tree_box{nullptr};   // framed feature-tree section
+    StaticBox* m_parts_box{nullptr};  // framed bodies section (hidden while empty)
+    StaticBox* m_cards{nullptr};      // one framed panel holding every tool dialog (one visible at a time)
+    void      update_cards_frame();     // show that frame iff some card inside it is visible
+    void      show_move_card(bool show);
+    void      apply_move_card();       // numeric move/rotate -> same xform the gizmo builds
+    void      push_polygon_params();
+    wxSizer*  m_tb_commit{nullptr};   // far-right Commit to Plate, beside Confirm/Cancel
+    wxSizer*  m_tb_doc{nullptr};      // toolbar document/view actions (new, commit, export, section, place)
+    CheckBox* m_show_bed{nullptr};    // view option: draw the printer bed + plate grid, or not
+    wxSizer*  m_box_move{nullptr};      // Move/Rotate numeric options (distance, axis, angle)
+    wxSizer*  m_box_sketch{nullptr};
+    wxSizer*  m_box_extrude{nullptr};
+    wxSizer*  m_box_dressup{nullptr};
+    wxSizer*  m_box_hole{nullptr};
+    wxSizer*  m_box_thread{nullptr};
+    wxSizer*  m_box_shell{nullptr};
+    wxSizer*  m_box_revolve{nullptr};
+    wxSizer*  m_box_sweep{nullptr};
+    wxSizer*  m_box_pattern{nullptr};
+    wxSizer*  m_box_plane{nullptr};
+    wxSizer*  m_box_loft{nullptr};
+    wxSizer*  m_box_draft{nullptr};
+    wxSizer*  m_box_boolean{nullptr};
+    wxSizer*  m_box_cut{nullptr};
+    wxSizer*  m_box_axis{nullptr};
+    wxSizer*  m_box_coordsys{nullptr};
+    wxSizer*  m_box_surf_extrude{nullptr};
+    wxSizer*  m_box_surf_revolve{nullptr};
+    wxSizer*  m_box_surf_loft{nullptr};
+    wxSizer*  m_box_surf_fill{nullptr};
+    wxSizer*  m_box_surf_offset{nullptr};
+    wxSizer*  m_box_surf_thicken{nullptr};
+    wxSizer*  m_box_transform{nullptr};
+    wxSizer*  m_box_mirror{nullptr};
+    wxSizer*  m_box_thicken{nullptr};
+    wxSizer*  m_box_rib{nullptr};
+    wxSizer*  m_box_project{nullptr};
+    wxSizer*  m_box_delete_face{nullptr};
+    wxSizer*  m_box_helix{nullptr};
+    wxSizer*  m_box_mate{nullptr};
+    wxSizer*  m_box_insert{nullptr};   // Confirm/Cancel card for placing Text/SVG art
+    wxSizer*  m_box_expr{nullptr};     // expression binding card (visible during edit only)
+    int       m_insert_feat{-1};       // provisional imported-art feature awaiting Confirm
+    // Move-body gizmo runs through the unified action bar too: Confirm keeps the placement,
+    // Cancel reverts to the pose captured when the move started.
+    int         m_move_body{-1};
+    Transform3d m_move_prev{Transform3d::Identity()};
+    // Set while the move gizmo is serving the Transform CARD rather than the Move button.
+    // Both use the same gizmo; only this says which card owns the numbers it reports.
+    int         m_xf_gizmo_body{-1};
+    Transform3d m_xf_gizmo_base{Transform3d::Identity()};   // pose when Transform armed it
+    // Which body the Transform card's typed fields are currently previewing on, and the pose to
+    // hand it back to. Separate from the gizmo pair because the card can retarget its Body combo.
+    int         m_xf_prev_body{-1};
+    Transform3d m_xf_prev_base{Transform3d::Identity()};
+
+    // Onshape-style dialog-card title rows (icon + bold feature name), retitled
+    // per tool in open_tool() (edit-mode shows the feature's actual name).
+    wxStaticText* m_hdr_move{nullptr};
+    wxStaticText* m_hdr_sketch{nullptr};
+    // Onshape sketch-entry card (plane/orientation) that opens on "New sketch" and
+    // persists until Finish (Phase 3).
+    wxSizer*      m_box_sketch_session{nullptr};
+    wxStaticText* m_hdr_sketch_session{nullptr};
+    wxStaticText* m_sketch_hint{nullptr};   // "click a plane" / "drawing on X" — must match the status
+    wxStaticText* m_hdr_extrude{nullptr};
+    wxStaticText* m_hdr_dressup{nullptr};
+    wxStaticText* m_hdr_hole{nullptr};
+    wxStaticText* m_hdr_thread{nullptr};
+    wxStaticText* m_hdr_shell{nullptr};
+    wxStaticText* m_hdr_revolve{nullptr};
+    wxStaticText* m_hdr_sweep{nullptr};
+    wxStaticText* m_hdr_pattern{nullptr};
+    wxStaticText* m_hdr_plane{nullptr};
+    wxStaticText* m_hdr_loft{nullptr};
+    wxStaticText* m_hdr_draft{nullptr};
+    wxStaticText* m_hdr_boolean{nullptr};
+    wxStaticText* m_hdr_cut{nullptr};
+    wxStaticText* m_hdr_axis{nullptr};
+    wxStaticText* m_hdr_coordsys{nullptr};
+    wxStaticText* m_hdr_surf_extrude{nullptr};
+    wxStaticText* m_hdr_surf_revolve{nullptr};
+    wxStaticText* m_hdr_surf_loft{nullptr};
+    wxStaticText* m_hdr_surf_fill{nullptr};
+    wxStaticText* m_hdr_surf_offset{nullptr};
+    wxStaticText* m_hdr_surf_thicken{nullptr};
+    wxStaticText* m_hdr_transform{nullptr};
+    wxStaticText* m_hdr_mirror{nullptr};
+    wxStaticText* m_hdr_thicken{nullptr};
+    wxStaticText* m_hdr_rib{nullptr};
+    wxStaticText* m_hdr_project{nullptr};
+    wxStaticText* m_hdr_delete_face{nullptr};
+    wxStaticText* m_hdr_helix{nullptr};
+    wxStaticText* m_hdr_mate{nullptr};
+    wxStaticText* m_hdr_insert{nullptr};
+
+    wxScrolledWindow* m_form{nullptr};
+    DesignCanvas*     m_viewport{nullptr};
+
+    // Top contextual toolbar (parented to the panel, above the form/viewport row).
+    UiMode    m_ui_mode{UiMode::Feature};
+    // Sketch environment banner: a strip across the top of the viewport saying, in words, that
+    // this is a sketch and which one. The mode used to be legible only from the toolbar and the
+    // left card — both of which look like the rest of the app — so a sketch session and plate
+    // preparation were one glance apart. Indicator only: Finish/Cancel stay on the ONE ribbon
+    // action bar (the Design UX contract), and the banner never grows a second pair.
+    wxPanel*      m_sketch_banner{nullptr};
+    wxStaticText* m_sketch_banner_txt{nullptr};
+    wxScrolledWindow* m_toolbar{nullptr};   // horizontally scrollable so the action bar stays reachable on narrow windows
+    wxSizer*  m_tb_feature{nullptr};
+    wxSizer*  m_tb_sketch{nullptr};
+    // The 20 constraint icon buttons, shown during BOTH Sketch and Constrain (Fase 4.2 live
+    // path: a constraint must be applicable while drawing, not only after committing).
+    wxSizer*  m_tb_relations{nullptr};
+    // Unified Confirm/Cancel action bar (right end of the ribbon). Shown whenever any
+    // tool or mode is active; the single confirm/cancel surface for the whole tab.
+    wxSizer*  m_tb_action{nullptr};
+    // Persistent Undo/Redo group at the left of the ribbon — always visible, independent
+    // of the mode-gated tool groups. The buttons are greyed per the document history and
+    // the do_undo_redo gate (see update_undo_redo_buttons).
+    wxSizer*        m_tb_history{nullptr};
+    ScalableButton* m_btn_undo{nullptr};
+    ScalableButton* m_btn_redo{nullptr};
+    void update_undo_redo_buttons();   // enable/disable Undo/Redo from can_undo/can_redo + gate
+    // All tool buttons, for the active-tool teal highlight (Onshape-style).
+    std::vector<ScalableButton*> m_tool_btns;
+    ScalableButton*              m_active_tool_btn{nullptr};
+    void set_active_tool_btn(ScalableButton* b);   // nullptr clears the highlight
+    // Owns the themed DropDown flyouts (and the item vectors they hold by ref).
+    std::vector<std::shared_ptr<void>> m_flyout_keepalive;
+    wxCheckBox*       m_construction{nullptr};   // sketch-mode construction toggle
+    wxSpinCtrlDouble* m_move_dx{nullptr};        // Move/Rotate card: world translation
+    wxSpinCtrlDouble* m_move_dy{nullptr};
+    wxSpinCtrlDouble* m_move_dz{nullptr};
+    ComboBox*         m_move_axis{nullptr};      // rotation axis: X/Y/Z
+    wxSpinCtrlDouble* m_move_angle{nullptr};     // rotation angle (deg)
+    // Polygon's two parameters are chosen FROM THE TOOL, in the offer's Polygon submenu, not
+    // from a card on the left: the side count cannot be edited after drawing (the inline editor
+    // offers Side and Angle only), so it has to be settled at the moment the tool is armed —
+    // which is exactly where the offer already is. e1p.
+    int               m_poly_sides{6};           // 3..64; the submenu names the common ones
+    bool              m_poly_circumscribed{false};
+
+    // Which reference plane a sketch falls back to when no face is picked: 0/1/2 = XY/XZ/YZ,
+    // >=3 indexes resolve_datum_planes(). Set by CLICKING a ghost plane in the viewport — there is
+    // deliberately no dropdown for it. e1p.
+    int               m_ref_plane{0};
+    // m_ref_plane is always a VALID plane, so it cannot itself distinguish "the user chose XY"
+    // from "nobody has chosen anything yet". This does.
+    bool              m_plane_picked{false};
+    ComboBox*         m_shape{nullptr};
+    ComboBox*         m_mode{nullptr};
+    wxSpinCtrlDouble* m_width{nullptr};
+    wxSpinCtrlDouble* m_height{nullptr};
+    wxSpinCtrlDouble* m_radius{nullptr};
+    wxSpinCtrlDouble* m_distance{nullptr};
+    ComboBox*         m_extrude_end{nullptr};   // Blind/Symmetric/TwoSided/ThroughAll/UpTo*
+    wxSpinCtrlDouble* m_distance2{nullptr};     // second-side depth (Two-sided)
+    wxSpinCtrlDouble* m_taper{nullptr};         // draft angle (deg)
+    CheckBox*         m_flip{nullptr};          // reverse extrude direction
+
+    wxStaticText*     m_extrude_sketch_label{nullptr};
+    int               m_extrude_sketch_ref{-1};
+
+    // Revolve controls (sweep a sketch profile about an in-plane axis).
+    wxStaticText*     m_revolve_sketch_label{nullptr};
+    wxSpinCtrlDouble* m_revolve_angle{nullptr};
+    ComboBox*         m_revolve_axis{nullptr};   // 0 = plane X, 1 = plane Y
+    ComboBox*         m_revolve_mode{nullptr};   // New/Add/Cut/Intersect
+    CheckBox*         m_revolve_flip{nullptr};
+    int               m_revolve_sketch_ref{-1};
+
+    // Sweep controls (sweep a profile sketch along a path sketch).
+    wxStaticText*     m_sweep_profile_label{nullptr};
+    ComboBox*         m_sweep_path{nullptr};       // path Sketch picker (feature index in client data)
+    ComboBox*         m_sweep_mode{nullptr};       // New/Add/Cut/Intersect
+    int               m_sweep_profile_ref{-1};
+    int               m_sweep_path_ref{-1};        // path Sketch feature index (for re-edit pre-select)
+
+    // Loft controls (skin a solid through 2+ ordered profile Sketches).
+    wxCheckListBox*   m_loft_list{nullptr};        // every Sketch; check 2+ in list order = profiles
+    CheckBox*         m_loft_ruled{nullptr};       // ruled (straight) vs smooth sections
+    ComboBox*         m_loft_mode{nullptr};        // New/Add/Cut/Intersect
+    std::vector<int>  m_loft_sketch_idx;           // feature index for each row in m_loft_list
+    std::vector<int>  m_loft_refs;                 // chosen profile refs (for re-edit pre-check)
+
+    // Surface Extrude controls (sheet from sketch profile).
+    wxStaticText*     m_surf_extrude_sketch_label{nullptr};
+    wxSpinCtrlDouble* m_surf_extrude_distance{nullptr};
+    int               m_surf_extrude_sketch_ref{-1};
+
+    // Surface Revolve controls (sheet from sketch about axis).
+    wxStaticText*     m_surf_revolve_sketch_label{nullptr};
+    wxSpinCtrlDouble* m_surf_revolve_angle{nullptr};
+    ComboBox*         m_surf_revolve_axis{nullptr};   // 0 = plane X, 1 = plane Y
+    CheckBox*         m_surf_revolve_flip{nullptr};
+    int               m_surf_revolve_sketch_ref{-1};
+
+    // Surface Loft controls (skin a sheet through 2+ ordered profile sketches).
+    wxCheckListBox*   m_surf_loft_list{nullptr};        // every Sketch; check 2+ in list order = profiles
+    CheckBox*         m_surf_loft_ruled{nullptr};       // ruled (straight) vs smooth sections
+    std::vector<int>  m_surf_loft_sketch_idx;           // feature index for each row
+    std::vector<int>  m_surf_loft_refs;                 // chosen profile refs (for re-edit pre-check)
+
+    // Surface Fill controls (one-face sheet from a sketch boundary).
+    wxStaticText*     m_surf_fill_sketch_label{nullptr};
+    int               m_surf_fill_sketch_ref{-1};
+
+    // Surface Offset controls (offset a SHEET body).
+    ComboBox*         m_surf_offset_body{nullptr};       // sheet-body picker
+    wxSpinCtrlDouble* m_surf_offset_distance{nullptr};
+
+    // Thicken Surface controls (thicken a SHEET body into a solid).
+    ComboBox*         m_surf_thicken_body{nullptr};      // sheet-body picker
+    wxSpinCtrlDouble* m_surf_thicken_thickness{nullptr};
+    CheckBox*         m_surf_thicken_flip{nullptr};
+
+    // Transform controls (rigid move/rotate of a body).
+    ComboBox*         m_xf_body{nullptr};            // body to transform
+    wxSpinCtrlDouble* m_xf_dx{nullptr};              // translate X
+    wxSpinCtrlDouble* m_xf_dy{nullptr};              // translate Y
+    wxSpinCtrlDouble* m_xf_dz{nullptr};              // translate Z
+    ComboBox*         m_xf_axis{nullptr};            // rotation axis: X/Y/Z
+    wxSpinCtrlDouble* m_xf_angle{nullptr};           // rotation angle (deg)
+    wxSpinCtrlDouble* m_xf_pivot_x{nullptr};         // pivot X
+    wxSpinCtrlDouble* m_xf_pivot_y{nullptr};         // pivot Y
+    wxSpinCtrlDouble* m_xf_pivot_z{nullptr};         // pivot Z
+    CheckBox*         m_xf_copy{nullptr};            // keep original (make a copy)
+
+    // Mirror controls (reflect a body about a plane).
+    ComboBox*         m_mirror_body{nullptr};        // body to mirror
+    ComboBox*         m_mirror_plane{nullptr};       // mirror plane (XY/XZ/YZ + datums)
+    CheckBox*         m_mirror_keep{nullptr};        // keep original body
+
+    // Thicken controls (offset one solid face into a thin plate).
+    ComboBox*         m_thicken_body{nullptr};       // source body
+    wxStaticText*     m_thicken_face_label{nullptr}; // picked face
+    wxSpinCtrlDouble* m_thicken_thickness{nullptr};
+    CheckBox*         m_thicken_flip{nullptr};       // flip direction
+
+    // Rib controls (thin wall from an open sketch line).
+    ComboBox*         m_rib_body{nullptr};           // target body
+    ComboBox*         m_rib_sketch{nullptr};         // sketch holding the open line (feature index in client data)
+    wxSpinCtrl*       m_rib_entity{nullptr};         // entity index within the sketch
+    wxSpinCtrlDouble* m_rib_thickness{nullptr};
+    wxSpinCtrlDouble* m_rib_depth{nullptr};
+
+    // Project controls (project body edges onto a plane as sketch entities).
+    ComboBox*         m_proj_source_body{nullptr};   // source body
+    wxStaticText*     m_proj_face_label{nullptr};    // picked face (or "all edges")
+    ComboBox*         m_proj_plane{nullptr};         // target plane
+
+    // Delete Face controls (remove faces, heal the solid).
+    ComboBox*         m_del_face_body{nullptr};      // target body
+    wxButton*         m_del_face_add_btn{nullptr};   // "Add picked face" button
+    wxStaticText*     m_del_face_list{nullptr};      // shows the accumulated face ids
+    std::vector<int>  m_del_faces;                   // accumulated face list
+
+    // Helix controls (helical curve).
+    ComboBox*         m_helix_plane{nullptr};        // axis plane (XY/XZ/YZ + datums)
+    wxSpinCtrlDouble* m_helix_radius{nullptr};
+    wxSpinCtrlDouble* m_helix_pitch{nullptr};
+    wxSpinCtrlDouble* m_helix_height{nullptr};
+    CheckBox*         m_helix_left_handed{nullptr};
+    wxSpinCtrlDouble* m_helix_taper{nullptr};
+
+    // Mate (assembly) controls
+    ComboBox*         m_mate_kind{nullptr};
+    ComboBox*         m_mate_cs_a{nullptr};
+    ComboBox*         m_mate_cs_b{nullptr};
+    wxSpinCtrlDouble* m_mate_offset{nullptr};
+    wxSpinCtrlDouble* m_mate_angle{nullptr};
+    CheckBox*         m_mate_flip{nullptr};
+    wxStaticText*     m_offset_label{nullptr};
+    wxStaticText*     m_angle_label{nullptr};
+
+    // Expression binding (per-feature, visible during edit only)
+    ComboBox*         m_expr_field{nullptr};     // field-name picker (editable)
+    wxTextCtrl*       m_expr_text{nullptr};      // expression string
+    wxButton*         m_expr_set_btn{nullptr};   // Apply / bind
+    wxButton*         m_expr_clear_btn{nullptr}; // Remove binding
+    wxStaticText*     m_expr_status{nullptr};    // shows current bindings for the edited feature
+    void              populate_expr_fields(Tool t);   // fill m_expr_field from feature-type fields
+    void              on_set_expr();                   // checkpoint + write -> recompute -> undo on fail
+    void              on_clear_expr();                 // remove selected binding
+
+    // Document variables panel (below the feature tree / parts)
+    StaticBox*        m_var_box{nullptr};
+    wxListCtrl*       m_var_list{nullptr};
+    wxButton*         m_btn_add_var{nullptr};
+    wxButton*         m_btn_edit_var{nullptr};
+    wxButton*         m_btn_del_var{nullptr};
+    void              refresh_variables();            // rebuild m_var_list from m_doc.variables
+    void              on_add_variable();
+    void              on_edit_variable();
+    void              on_remove_variable();
+
+    // Feature-tree button
+    ScalableButton*   m_btn_interfere{nullptr};
+
+    // Pattern controls (replicate the target body: linear or circular).
+    ComboBox*         m_pattern_type{nullptr};      // 0 = Linear, 1 = Circular
+    wxSpinCtrlDouble* m_pattern_count{nullptr};     // total instances incl. seed
+    wxSpinCtrlDouble* m_pattern_spacing{nullptr};   // linear step (mm)
+    ComboBox*         m_pattern_dir{nullptr};        // linear direction: 0 = plane X, 1 = plane Y
+    wxSpinCtrlDouble* m_pattern_angle{nullptr};     // circular total angle (deg)
+    // Boolean controls (combine two existing bodies).
+    ComboBox*         m_bool_op{nullptr};            // 0 = Union, 1 = Subtract, 2 = Intersect
+    ComboBox*         m_bool_target{nullptr};        // body that survives (selection == body index)
+    ComboBox*         m_bool_tool{nullptr};          // body consumed (selection == body index)
+    // Which operand the NEXT viewport body pick fills: 0 = target, 1 = tool. Reset when the
+    // card opens, so the first two clicks in the viewport always mean "keep this, cut with
+    // that" in that order. The combos remain the typed half and mirror whatever is picked.
+    int               m_bool_next_slot{0};
+    CheckBox*         m_bool_keep{nullptr};          // keep the tool body after the op
+    wxSpinCtrlDouble* m_bool_tol{nullptr};           // OCCT fuzzy tolerance (mm); robust cut on near-coincident faces
+
+    // Plane Cut (split-by-plane): a reference plane + offset splits the target body into
+    // two separate bodies (both pieces kept).
+    ComboBox*         m_cut_plane{nullptr};          // XY/XZ/YZ + datum planes (cut plane)
+    ComboBox*         m_cut_target{nullptr};         // body to cut (selection == body index)
+    wxSpinCtrlDouble* m_cut_offset{nullptr};         // offset along the plane normal (mm)
+    // Datum plane controls (derive a selectable sketch plane: offset + tilt from a base).
+    ComboBox*         m_plane_base{nullptr};         // 0=XY,1=XZ,2=YZ, 3+N = Nth datum plane
+    wxSpinCtrlDouble* m_plane_offset{nullptr};       // offset along base normal (mm)
+    wxSpinCtrlDouble* m_plane_tilt{nullptr};         // tilt about a base axis (deg) / Angle / Tangent angle
+    ComboBox*         m_plane_tilt_axis{nullptr};    // 0 = base X, 1 = base Y
+    // Plane construction method + contextual face/edge reference picks (Onshape/Fusion parity).
+    ComboBox*         m_plane_type{nullptr};         // PlaneType: Offset/Angle/Midplane/Tangent/TwoEdges/Coincident
+    wxButton*         m_plane_pick_faceA{nullptr};   wxStaticText* m_plane_faceA_lbl{nullptr};
+    wxButton*         m_plane_pick_faceB{nullptr};   wxStaticText* m_plane_faceB_lbl{nullptr};
+    wxButton*         m_plane_pick_edgeA{nullptr};   wxStaticText* m_plane_edgeA_lbl{nullptr};
+    wxButton*         m_plane_pick_edgeB{nullptr};   wxStaticText* m_plane_edgeB_lbl{nullptr};
+    wxSpinCtrlDouble* m_plane_usize{nullptr};        // datum rectangle extent u (mm) — also driven by drag handles
+    wxSpinCtrlDouble* m_plane_vsize{nullptr};        // datum rectangle extent v (mm)
+    // Captured references for the candidate datum (body index + face/edge index, -1 = none).
+    int m_pl_faceA_body{-1}, m_pl_faceA{-1};
+    int m_pl_faceB_body{-1}, m_pl_faceB{-1};
+    int m_pl_edgeA_body{-1}, m_pl_edgeA{-1};
+    int m_pl_edgeB_body{-1}, m_pl_edgeB{-1};
+    PlanePick m_plane_pick{PlanePick::None};         // which ref the next solid pick fills
+    // Plate loop selection (click a committed sketch loop): the Sketch feature + the
+    // clicked closed-region index, so Extrude builds just that one loop. -1 = none.
+    int               m_sel_sketch_feat{-1};
+    int               m_sel_sketch_region{-1};
+    // Click-selected solid topology (whole/face/edge cycle): face id for up-to-face / dress-up.
+    int               m_sel_solid_body{-1};   // which body the face/edge selection is on
+    int               m_sel_solid_face{-1};
+    int               m_sel_solid_edge{-1};
+    bool              m_sel_solid_vertex{false};   // a corner is picked (body+point, no face/edge)
+    // The face actually under the last solid click, INDEPENDENT of the whole/face/edge cycle level.
+    // The first click on a solid selects the WHOLE body, but the ray has already resolved which face
+    // it hit and the callback passes it. "Sketch on the face I clicked" must not require discovering
+    // that a second click refines the selection, so keep it instead of throwing it away. 3a2.
+    int               m_pick_face_body{-1};
+    int               m_pick_face{-1};
+    // What the live sketch was actually opened on ("the picked face", "XY", a datum's name), so the
+    // hint can say it. Resolved from the selection at begin_sketch, not read back from a combo.
+    wxString          m_sketch_on;
+    // --- the object-driven offer (charter 4.1) ---------------------------------------------
+    // Right-click the geometry -> a vertical list in ratified row order, verbs that do not
+    // apply disabled IN PLACE with their reason. The rows come from the generated table in
+    // DesignOffer.hpp; this map is how a row reaches the code that already implements it, for
+    // the verbs that have no keyboard shortcut to route through.
+    std::map<std::string, std::function<void()>> m_verb_actions;
+    // Append an offer row with its toolbar glyph. The bitmap must be set BEFORE Append —
+    // wxGTK builds the GtkMenuItem there and only makes an image item if one is present.
+    // Every status write goes through here so long hints wrap instead of clipping.
+    void        set_status(const wxString& text);
+    wxString    idle_hint() const;   // what to say when nothing is selected
+    // Reason detect_mate_conflicts() recorded for a feature, or nullptr. Marks the tree row and
+    // feeds the status line; a conflict is a diagnostic, not a document error.
+    const std::string* mate_conflict_reason(int feature) const;
+
+    wxMenuItem* append_offer_item(wxMenu* menu, int id, const wxString& text,
+                                  const struct OfferVerb& v);
+    void show_offer_menu(const wxPoint& screen_pos);
+    // Where the offer opens when no mouse press anchors it: the keyboard route, and the automatic
+    // open on entering Sketch. The pointer if it is over the viewport, else the viewport's centre.
+    // A raw wxGetMousePosition() can be sitting on the toolbar, on the card column or on another
+    // monitor, and the menu would map there — detached from the geometry it is about.
+    wxPoint offer_anchor() const;
+    int  offer_selection_kind() const;          // an OfferSel, as int to keep the header light
+    // Does the SKETCH half of the map apply? A mode question, not a session one: begin_sketch
+    // does not run until the first tool is armed, so between "press Sketch" and "pick a tool"
+    // is_sketching() is still false — precisely when the drawing tools must be on offer. The
+    // is_sketching() arm covers re-opening a committed sketch, which enters the session first.
+    bool sketch_map_applies() const;
+    void run_offer_action(const char* action);
+    // Face-as-profile extrude (Onshape): when Extrude is opened on a picked solid face with
+    // no sketch source, this carries that global face id so the kernel extrudes the face.
+    // -1 = ordinary sketch/loop extrude. Set when opening the Extrude card, consumed on add.
+    int               m_extrude_face_src{-1};
+
+    ComboBox*         m_dressup_type{nullptr};
+    ComboBox*         m_face_group{nullptr};
+    wxSpinCtrlDouble* m_dressup_size{nullptr};
+    wxStaticText*     m_dressup_edge_label{nullptr}; // shows the picked edge, or the group fallback
+
+    ComboBox*         m_hole_plane{nullptr};
+    wxSpinCtrlDouble* m_hole_diameter{nullptr};
+    wxSpinCtrlDouble* m_hole_depth{nullptr};
+    CheckBox*         m_hole_through{nullptr};
+    wxSpinCtrlDouble* m_hole_x{nullptr};
+    wxSpinCtrlDouble* m_hole_y{nullptr};
+    // #2: when the Hole tool is opened on a picked solid face, drill on that face centred
+    // on it (origin = face centroid, normal = inward). m_hole_x/y then read as the offset
+    // from the face centre. Falls back to the m_hole_plane dropdown when no face is picked.
+    bool              m_hole_on_face{false};
+    SketchPlane       m_hole_face_plane;
+    int               m_hole_face_body{-1};
+    // #2 Part B: the picked face's (u,v) bounds in m_hole_face_plane, so the hole's construction
+    // dims read as distance from the face sides (umin/vmin edges) rather than from the centre.
+    bool              m_hole_has_bounds{false};
+    double            m_hole_umin{0}, m_hole_umax{0}, m_hole_vmin{0}, m_hole_vmax{0};
+    // Says which face the latch above is holding. Thicken/Shell/Draft show theirs because their
+    // face IS the live selection; this one has to be shown precisely BECAUSE it is not, and the
+    // status line goes on saying "Nothing selected" while the ghost keeps drilling. 200.
+    wxStaticText*     m_hole_target_label{nullptr};
+
+    ComboBox*         m_thread_plane{nullptr};
+    ComboBox*         m_thread_std{nullptr};   // standard designation (M6, 1/4-20 UNC, ...)
+    wxSpinCtrlDouble* m_thread_radius{nullptr};
+    wxSpinCtrlDouble* m_thread_pitch{nullptr};
+    wxSpinCtrlDouble* m_thread_height{nullptr};
+    wxSpinCtrlDouble* m_thread_depth{nullptr};
+    CheckBox*         m_thread_internal{nullptr};
+    wxSpinCtrlDouble* m_thread_x{nullptr};
+    wxSpinCtrlDouble* m_thread_y{nullptr};
+    // #3: when the Thread tool is opened on a picked cylindrical face (a hole bore or a
+    // cylinder), thread that surface — plane on its axis, radius/internal derived from it.
+    bool              m_thread_on_face{false};
+    SketchPlane       m_thread_face_plane;
+    int               m_thread_face_body{-1};
+    wxStaticText*     m_thread_target_label{nullptr};   // the latched face/edge — see m_hole_target_label
+
+    wxSpinCtrlDouble* m_shell_thickness{nullptr};
+    wxStaticText*     m_shell_face_label{nullptr};   // shows the picked face to remove
+
+    // Draft controls (taper a single picked solid face about the body bottom).
+    wxSpinCtrlDouble* m_draft_angle{nullptr};
+    wxStaticText*     m_draft_face_label{nullptr};   // shows the picked face to draft
+
+    // Axis controls (datum axis: line through two points or derived from geometry).
+    ComboBox*         m_axis_type{nullptr};          // AxisType: TwoPoints/FaceNormal/CylinderCenterline/PlaneIntersection/AlongEdge
+    wxButton*         m_axis_pick_face{nullptr};     wxStaticText* m_axis_face_lbl{nullptr};
+    wxButton*         m_axis_pick_edge{nullptr};     wxStaticText* m_axis_edge_lbl{nullptr};
+    ComboBox*         m_axis_plane_a{nullptr};
+    ComboBox*         m_axis_plane_b{nullptr};
+    wxSpinCtrlDouble* m_axis_p1x{nullptr};           wxSpinCtrlDouble* m_axis_p1y{nullptr};           wxSpinCtrlDouble* m_axis_p1z{nullptr};
+    wxSpinCtrlDouble* m_axis_p2x{nullptr};           wxSpinCtrlDouble* m_axis_p2y{nullptr};           wxSpinCtrlDouble* m_axis_p2z{nullptr};
+    int m_ax_face_body{-1}, m_ax_face{-1};
+    int m_ax_edge_body{-1}, m_ax_edge{-1};
+    AxisPick m_axis_pick{AxisPick::None};
+
+    // CoordSys controls (datum coordinate system: point + orthonormal frame).
+    ComboBox*         m_coordsys_type{nullptr};      // CoordSysType: PointWorld/FaceAndDirection
+    ComboBox*         m_cs_body{nullptr};             // body-focus chooser: restrict picking to one body
+    wxSpinCtrlDouble* m_cs_x{nullptr};               wxSpinCtrlDouble* m_cs_y{nullptr};               wxSpinCtrlDouble* m_cs_z{nullptr};
+    wxButton*         m_cs_pick_face{nullptr};       wxStaticText* m_cs_face_lbl{nullptr};
+    wxButton*         m_cs_pick_edge{nullptr};       wxStaticText* m_cs_edge_lbl{nullptr};
+    wxSpinCtrlDouble* m_cs_hx{nullptr};              wxSpinCtrlDouble* m_cs_hy{nullptr};              wxSpinCtrlDouble* m_cs_hz{nullptr};
+    int m_cs_face_body{-1}, m_cs_face{-1};
+    int m_cs_edge_body{-1}, m_cs_edge{-1};
+    CoordSysPick m_coordsys_pick{CoordSysPick::None};
+
+    // Onshape-style docked value-entry card (Angle/Radius/Diameter/Offset/Fillet).
+    wxSizer*          m_box_value{nullptr};
+    wxStaticText*     m_value_label{nullptr};
+    wxTextCtrl*       m_value_input{nullptr};   // plain text field: forces en ('.') decimals
+    double            m_value_min{0.0};         // range for confirm-time clamping
+    double            m_value_max{0.0};
+    std::function<void(double)> m_value_cont;   // deferred apply, run on Confirm
+    std::function<void()>       m_value_cancel; // optional action when the card is cancelled
+
+    // Feature tree: a wxTreeCtrl with per-feature-type icons. Callers keep using
+    // integer row indices via tree_selection()/set_tree_selection(); m_tree_items
+    // maps feature order -> tree node, rebuilt by refresh_tree().
+    wxTreeCtrl*               m_tree{nullptr};
+    wxTreeCtrl*               m_parts{nullptr};        // Bodies list under the feature tree
+    wxStaticText*             m_parts_label{nullptr};  // its "Bodies" caption (hidden when empty)
+    wxBoxSizer*               m_parts_hdr{nullptr};    // Bodies card header (icon + title)
+    wxStaticLine*             m_parts_rule{nullptr};   // rule under that header
+    wxBoxSizer*               m_hdr_tree_row{nullptr}; // Feature tree header: title + row actions
+    wxStaticText*             m_hdr_tree{nullptr};     // its title label
+    wxImageList*              m_tree_images{nullptr};
+    std::vector<wxTreeItemId> m_tree_items;
+    // Parts list: tree rows for each body (parallel to m_doc.bodies). Selecting one
+    // highlights that body and makes it the target for the next op.
+    std::vector<wxTreeItemId> m_tree_body_items;
+
+    // Section views (non-destructive): named "Section View N" entries listed in the tree, each a
+    // horizontal clip height. View-only — NOT bodies/features, never serialized. Key X adds one;
+    // clicking a row activates it (again = off); Delete removes it; Alt+Wheel moves the active one.
+    // Section view (single, non-destructive): ONE horizontal clip that hides half the model to
+    // inspect inside — solid, no ghost of the hidden half. Toggled on/off; Flip shows the other
+    // half. Never a body, no tree entry.
+    bool      m_section_on{false};
+    double    m_section_cut_z{0.0};
+    bool      m_section_upper{false};             // false = keep lower half, true = upper
+    ScalableButton* m_section_flip_btn{nullptr};  // toolbar action; enabled only while the section is on
+    void toggle_section_view();                   // Section View button / X: on <-> off
+    void flip_section_view();                     // Flip button / F: opposite half
+    void update_section_flip_btn();               // enable the Flip button iff the section is on
+    // Per-body visibility (parallel to m_doc.bodies; index stable across recompute since
+    // bodies are appended in feature order). Empty/grown to all-visible by sync_body_visible().
+    std::vector<bool> m_body_visible;
+    void sync_body_visible();             // grow/shrink m_body_visible to bodies.size()
+    // Per-body display translation (Move-body, M5). Parallel to m_doc.bodies; default
+    // identity. Applied to the display/pick meshes only — the OCCT shape (and face/edge
+    // global ids) is never touched, so dress-up targeting stays stable across a move.
+    std::vector<Transform3d>  m_body_xform;
+    std::vector<TriangleMesh> m_disp_body_meshes;   // display_body_meshes with m_body_xform applied
+    TriangleMesh              m_disp_pick_mesh;      // combined pick mesh with m_body_xform applied
+    void sync_body_xform();               // grow m_body_xform to bodies.size() (identity)
+    void rebuild_disp_meshes();           // recompute m_disp_* from m_doc + m_body_xform
+    void feed_bodies();                   // push m_disp_* + visibility/xform to the viewport
+    void on_move_body();                  // start the move gizmo on the selected body
+    void arm_transform_gizmo();           // arm the move gizmo on the Transform card's body (add mode only)
+    void on_set_body_color();             // Color tool: pick a per-body display colour override
+    void on_boolean_tool();               // Boolean (combine bodies): needs two solids, then opens the tool
+    int  tree_selection() const;          // selected feature row, or wxNOT_FOUND
+    int  tree_body_selection() const;     // selected Parts-list body index, or -1
+    void refresh_parts();                 // rebuild the Bodies list under the feature tree
+    void sync_sidebar_width();            // keep the panel as wide as Prepare's sidebar
+    void set_tree_selection(int row);
+    static int tree_icon_for(CadFeatureType t);
+
+    wxStaticText*     m_status{nullptr};
+    // m_status's foreground as created, captured before any caller touches it. Callers signal
+    // "no opinion" by setting wxNullColour, which restores exactly this — so it is the only
+    // reliable way to tell a chosen colour (the error red) from the default. See set_status().
+    wxColour          m_status_default_fg;
+    // The guidance sentence for the step the armed sketch tool is on, kept so a transient
+    // readout (the live length/angle while a segment is being dragged) can be appended to it
+    // instead of replacing it — the guidance used to vanish on the first mouse move after a
+    // click, which is precisely when it is needed. 1c0c.
+    wxString          m_sketch_step;
+    // mode is a DesignSketchTool::Mode; passed as an int because this header deliberately does
+    // not include the tool's, and the .cpp (which does) casts it back.
+    void              on_sketch_step(int mode, int step, int picks);
+    wxStaticText*     m_dof_status{nullptr};   // DoF / constraint-state readout (P3)
+    // Last live-solve result, so entering Constrain can restore the readout without a solve.
+    int               m_dof_last{-1};
+    bool              m_dof_last_ok{true};
+    bool              m_dof_last_has{false};
+    int               m_feature_counter{0};
+
+    std::vector<wxButton*> m_confirm_btns;
+
+    // Edit-in-place state: add-mode is m_edit_index == -1. Single-feature edit
+    // (Sketch or Extrude independently) uses only m_edit_index as the row to replace.
+    int               m_edit_index{-1};
+
+    // Tree row of the sketch currently being constrained (-1 = not constraining).
+    int               m_constrain_feat{-1};
+
+    // Constraint-manager card (C3.4): header + a rebuildable list of constraint rows.
+    wxSizer*          m_box_constraints{nullptr};
+    wxStaticText*     m_hdr_constraints{nullptr};
+    wxSizer*          m_constraint_rows{nullptr};
+    int               m_constraint_sel{-1};   // highlighted constraint row, or -1
+};
+
+}} // namespace Slic3r::GUI
+
+#endif // slic3r_DesignPanel_hpp_
diff --git a/src/slic3r/GUI/CAD/DesignSketchTool.cpp b/src/slic3r/GUI/CAD/DesignSketchTool.cpp
new file mode 100644
index 0000000000..716df658ed
--- /dev/null
+++ b/src/slic3r/GUI/CAD/DesignSketchTool.cpp
@@ -0,0 +1,11154 @@
+#include "slic3r/GUI/CAD/DesignSketchTool.hpp"
+#include "slic3r/GUI/GLCanvas3D.hpp"
+#include "slic3r/GUI/GUI_App.hpp"
+#include "slic3r/GUI/ImGuiWrapper.hpp"
+#include "slic3r/GUI/CAD/SketchInlineEditor.hpp"
+#include "slic3r/GUI/Plater.hpp"
+
+#include <imgui/imgui.h>
+#include <imgui/imgui_internal.h>
+#include "libslic3r/BuildVolume.hpp"
+#include "slic3r/GUI/Camera.hpp"
+#include "slic3r/GUI/3DScene.hpp"
+#include "slic3r/GUI/GLShader.hpp"
+#include "libslic3r/CAD/GeometryEngine.hpp"
+#include "libslic3r/TriangleMesh.hpp"
+
+#include <GL/glew.h>
+#include <wx/gdicmn.h>
+#include <algorithm>
+#include <climits>
+#include <limits>
+#include <array>
+#include <cmath>
+#include <cstdio>
+#include <cstdarg>
+#include <cstdlib>
+
+namespace Slic3r {
+namespace GUI {
+
+// How many chords an arc is drawn with. loop_report corrects each arc's area back to the true
+// curve using this exact number, so the two MUST agree — changing it here without updating the
+// correction silently biases every reported area.
+static constexpr int kArcFacets = 24;
+
+// Positioning helpers (defined lower down, used by the dimension methods above them).
+static bool entity_ref_point(const SketchEntity& e, Vec2d& out);
+static void translate_entity(SketchEntity& e, const Vec2d& d);
+// Pick-distance helpers (defined lower down; used earlier by the edit-op gizmo).
+static double point_segment_dist(const Vec2d& p, const Vec2d& a, const Vec2d& b);
+static double entity_pick_dist(const Vec2d& p, const SketchEntity& e);
+static bool   point_in_poly(const Vec2d& q, const std::vector<Vec2d>& poly);
+static bool   ray_triangle(const Vec3d& ro, const Vec3d& rd, const Vec3d& v0, const Vec3d& v1,
+                           const Vec3d& v2, double& t);
+static double ray_segment_dist3(const Vec3d& ro, const Vec3d& rd, const Vec3d& a, const Vec3d& b);
+
+// Project a world-space point to canvas screen pixels (device px, GL viewport units;
+// origin top-left after the GL y-flip). Mirrors GLCanvas3D's world->screen pattern:
+// projection * view, perspective divide, NDC -> viewport. Returns (-1,-1) if behind.
+// (Retained for auto-emitted dimensions in Phase B, which have no click to anchor to;
+// needs the design canvas's own camera/viewport, not the plater's.)
+[[maybe_unused]] static wxPoint world_to_screen_px(const Camera& cam, const Vec3d& world)
+{
+    // NB: multiply the raw 4x4 matrices, NOT the Transform3d objects — the projection is not
+    // affine, so Transform*Transform mangles it (Eigen assumes affine) and yields garbage w.
+    const Eigen::Matrix4d m = cam.get_projection_matrix().matrix() * cam.get_view_matrix().matrix();
+    const Eigen::Vector4d clip = m * world.homogeneous();
+    if (std::abs(clip.w()) < 1e-9) return wxPoint(-1, -1);
+    const Vec3d ndc = clip.head<3>() / clip.w();
+    const std::array<int, 4>& vp = cam.get_viewport();
+    const double sx = vp[0] + (ndc.x() * 0.5 + 0.5) * vp[2];
+    const double sy = vp[1] + (1.0 - (ndc.y() * 0.5 + 0.5)) * vp[3];   // GL y-up -> wx y-down
+    return wxPoint(int(sx + 0.5), int(sy + 0.5));
+}
+
+// The kernel's weld tolerance follows the app preference, and it must be pushed at EVERY
+// point that starts a sketch session: a Constrain session never passes through begin(), and
+// it uses region_loops()/connected_loop(), which read the same tolerance. Pushing in one
+// place only would leave those sessions on whatever the previous session set.
+static void push_auto_close_pref()
+{
+    Slic3r::set_sketch_auto_close(wxGetApp().is_auto_close_sketch_loops());
+}
+
+void DesignSketchTool::begin(const SketchPlane& plane, Mode mode)
+{
+    push_auto_close_pref();
+
+    m_plane = plane;
+    m_mode = mode;
+    m_step_mode_last = -1;        // a new session re-announces its step, even if it repeats the last
+    m_points.clear();
+    m_entities.clear();
+    m_construction = false;
+    m_has_cursor = false;
+    m_sel_a = m_sel_b = -1;
+    m_constrain_entities = false;
+    m_pick0 = m_pick1 = m_pick2 = -1;
+    m_constraint_hl.clear();
+    m_constrain_cons.clear();
+    m_awaiting_length = false;
+    m_autoedit_seen = 0;          // baseline: no entities yet; first commit triggers edit
+    m_autoedit_pending = false;
+    m_selection.clear();
+    m_point_sel.clear();
+    m_constraints.clear();
+    m_dimensions.clear();
+    m_dim_has0 = false;
+    m_pending_dim = -1;
+    m_dof = -1; m_solve_ok = true; m_entity_conflict.clear();
+    m_features.clear();
+    m_open_feature = -1;
+    m_active = true;
+}
+
+// Re-open a committed entity sketch for editing: mirror begin() (fresh Select session),
+// then load the geometry + driving constraints, re-detect feature groups, and live-solve
+// so handles/quotes/regular-drag work exactly as in the original draw session.
+void DesignSketchTool::begin_edit(const std::vector<SketchEntity>& entities,
+                                  const std::vector<SketchEntityConstraintDef>& constraints,
+                                  const SketchPlane& plane)
+{
+    begin(plane, Mode::Select);
+    m_entities    = entities;
+    m_constraints = constraints;
+    rebuild_features_from_entities();
+    resolve_live();
+}
+
+// Walk the entity list grouping each consecutive CLOSED chain (entities are stored in
+// gesture order, so a polygon/rect/slot's members are contiguous and end-to-end linked)
+// and classify it: L,A,L,A -> Slot; 4 arcs (2 concentric + 2 caps) -> ArcSlot;
+// L,A×4 (4 equal-radius corner arcs) -> RoundedRect; 4 right-angled lines -> Rect;
+// N equal-length lines -> Polygon. Single/irregular entities stay ungrouped (they fall
+// back to per-entity quotes). This reconstructs m_features for a re-opened sketch.
+void DesignSketchTool::rebuild_features_from_entities()
+{
+    m_features.clear();
+    m_open_feature = -1;
+    const int n = int(m_entities.size());
+    using T = SketchEntity::Type;
+    auto start = [&](int i) { return m_entities[i].p0; };
+    auto end   = [&](int i) { const SketchEntity& e = m_entities[i];
+        return (e.type == T::Line || e.type == T::Arc) ? e.p1 : e.p0; };
+    auto is_near  = [](const Vec2d& a, const Vec2d& b) {
+        return (a - b).norm() <= 0.05 + 1e-3 * std::max(a.norm(), b.norm()); };
+
+    int i = 0;
+    while (i < n) {
+        int j = i; bool closed = false;            // greedily extend a consecutive chain
+        while (j + 1 < n && is_near(end(j), start(j + 1))) {
+            ++j;
+            if ((j - i) >= 2 && is_near(end(j), start(i))) { closed = true; break; }
+        }
+        const int cnt = j - i + 1;
+        if (!closed || cnt < 3) { ++i; continue; }
+
+        int arcs = 0; bool all_line = true;
+        for (int k = i; k <= j; ++k) {
+            if (m_entities[k].type == T::Arc)       ++arcs;
+            if (m_entities[k].type != T::Line)      all_line = false;
+        }
+        Vec2d c(0, 0); for (int k = i; k <= j; ++k) c += start(k); c /= double(cnt);
+        Feature f; f.begin = i; f.end = j + 1; f.c0 = c;
+
+        if (cnt == 4 && arcs == 2 &&
+            m_entities[i].type   == T::Line && m_entities[i + 1].type == T::Arc &&
+            m_entities[i + 2].type == T::Line && m_entities[i + 3].type == T::Arc) {
+            f.kind  = FeatureKind::Slot;          // make_slot: top, cap@c1, bottom, cap@c0
+            f.c0    = m_entities[i + 3].center;
+            f.c1    = m_entities[i + 1].center;
+            f.param = m_entities[i + 1].radius;
+            m_features.push_back(f);
+        } else if (cnt == 4 && arcs == 4 &&
+                   is_near(m_entities[i].center, m_entities[i + 2].center) &&
+                   std::abs(m_entities[i + 1].radius - m_entities[i + 3].radius) <=
+                       0.02 * std::max(m_entities[i + 1].radius, 1e-6) &&
+                   m_entities[i].radius > m_entities[i + 2].radius) {
+            // make_arc_slot: [0]outer(Rc+w), [1]cap@E(w), [2]inner(Rc-w), [3]cap@S(w).
+            // c0=main centre, c1=centreline start (cap@S centre = Sc), param=half-width.
+            f.kind  = FeatureKind::ArcSlot;
+            f.c0    = m_entities[i].center;
+            f.c1    = m_entities[i + 3].center;
+            f.param = m_entities[i + 3].radius;
+            m_features.push_back(f);
+        } else if (cnt == 8 && arcs == 4 &&
+                   m_entities[i].type     == T::Line && m_entities[i + 1].type == T::Arc &&
+                   m_entities[i + 2].type == T::Line && m_entities[i + 3].type == T::Arc &&
+                   m_entities[i + 4].type == T::Line && m_entities[i + 5].type == T::Arc &&
+                   m_entities[i + 6].type == T::Line && m_entities[i + 7].type == T::Arc) {
+            // rounded_rect_entities: 4 corner arcs (equal radius r) at the inset corners.
+            // Recover the axis-aligned bounds from the arc centres ± r.
+            const double r = m_entities[i + 1].radius;
+            bool equal_r = true;
+            for (int k : {3, 5, 7})
+                if (std::abs(m_entities[i + k].radius - r) > 0.02 * std::max(r, 1e-6))
+                    equal_r = false;
+            if (equal_r && r > 1e-6) {
+                double cxmin = 1e18, cxmax = -1e18, cymin = 1e18, cymax = -1e18;
+                for (int k : {1, 3, 5, 7}) {
+                    const Vec2d& o = m_entities[i + k].center;
+                    cxmin = std::min(cxmin, o.x()); cxmax = std::max(cxmax, o.x());
+                    cymin = std::min(cymin, o.y()); cymax = std::max(cymax, o.y());
+                }
+                f.kind  = FeatureKind::RoundedRect;
+                f.c0    = Vec2d(cxmin - r, cymin - r);   // (xmin,ymin)
+                f.c1    = Vec2d(cxmax + r, cymax + r);   // (xmax,ymax)
+                f.param = r;
+                m_features.push_back(f);
+            }
+        } else if (all_line) {
+            std::vector<double> sidelen(cnt);
+            for (int k = 0; k < cnt; ++k) sidelen[k] = (m_entities[i + k].p1 - m_entities[i + k].p0).norm();
+            const double lmin = *std::min_element(sidelen.begin(), sidelen.end());
+            const double lmax = *std::max_element(sidelen.begin(), sidelen.end());
+            const bool equal_sides = lmin > 1e-6 && (lmax - lmin) / lmax < 0.02;
+            bool all_right = true;
+            for (int k = 0; k < cnt && all_right; ++k) {
+                Vec2d u = m_entities[i + k].p1 - m_entities[i + k].p0;
+                Vec2d v = m_entities[i + (k + 1) % cnt].p1 - m_entities[i + (k + 1) % cnt].p0;
+                if (u.norm() < 1e-9 || v.norm() < 1e-9) { all_right = false; break; }
+                if (std::abs(u.normalized().dot(v.normalized())) > 0.06) all_right = false; // ~3.4°
+            }
+            if (cnt == 4 && all_right) {
+                f.kind = FeatureKind::CornerRect; f.c0 = start(i); f.c1 = start(i + 2);
+                m_features.push_back(f);
+            } else if (equal_sides) {
+                f.kind = FeatureKind::Polygon; f.c0 = c; f.c1 = start(i);
+                f.sides = cnt; f.param = (start(i) - c).norm();
+                m_features.push_back(f);
+            }
+        }
+        i = j + 1;
+    }
+}
+
+void DesignSketchTool::set_tool(Mode mode)
+{
+    // A READY edit-op carries the user's typed or dragged value, so switching tools commits it
+    // rather than dropping it — the same rule Tab follows in the dimension editor. Discarding it
+    // here is most of why Fillet looked like it simply did not work: every documented route (type
+    // the radius, or drag the arrow) left the op ready-but-pending, and the next tool click threw
+    // the value away and reverted the corner to sharp, with nothing on screen saying so.
+    // This MUST run before m_mode is reassigned: op_ready() and confirm_op() both switch on
+    // m_mode, so after the assignment they would test the tool being switched TO. That read
+    // op_ready()==0 with a=0 b=3 val=28.205 sitting right there — picked, valued, and dropped.
+    if (op_ready()) confirm_op();
+
+    // An OPEN inline value field freezes the canvas (on_mouse_impl returns early while
+    // m_awaiting_length) and blocks every keyboard shortcut (in_text includes inline_busy()).
+    // Drawing a rectangle opens one automatically for its Width/Height, so after a rectangle the
+    // sketch was STUCK: pressing C did nothing because the key never reached this function, and
+    // clicking on the canvas did nothing because the canvas was frozen. Committing here accepts
+    // the typed value and closes the field, which is the same rule the ready-edit-op above
+    // follows — leaving a tool must not silently discard what the user entered.
+    if (on_inline_commit) on_inline_commit();
+
+    // Switch the active drawing tool without dropping accumulated entities.
+    m_mode = mode;
+    m_points.clear();
+    m_has_cursor = false;
+    // DRAIN THE QUEUED DIMENSIONS, do not just resync the baseline. on_inline_commit() above
+    // commits the field that is open, and the commit callback installed by
+    // open_next_autoedit_dim does `++m_autoedit_dim_idx; CallAfter(open_next_autoedit_dim)` —
+    // so the switch's OWN commit schedules the next queued field, which then opens on top of the
+    // tool the user just armed. Measured: draw a rectangle, its Width field opens, arm Line from
+    // the offer; Width commits, the status line reads "Line — click start, then end", and the
+    // rectangle's Height field is sitting over it. (The keyboard cannot reproduce it: in_text
+    // includes inline_busy(), so letters are swallowed while a field is open — the switch has to
+    // come from the menu, the toolbar or the MCP socket.)
+    //
+    // reset_autoedit() is the existing helper for exactly this and its comment already says it
+    // "mirrors set_tool's resync" — the three lines that used to be here were that mirror drifting
+    // out of step, missing the two members that matter. The already-queued CallAfter then finds
+    // m_autoedit_dim_idx == -1 and returns through the guard at the top of open_next_autoedit_dim.
+    //
+    // The current value is COMMITTED rather than cancelled, matching the ready-edit-op rule a few
+    // lines above and Tab in the dimension editor. Esc is the gesture that means keep-as-drawn; a
+    // tool switch is not Esc.
+    reset_autoedit();
+
+    // An abandoned gesture must not leave its half-open Feature behind. begin_feature() pushes a
+    // Feature with end == begin immediately and end_feature() is what fills it in — and pops it
+    // when the gesture appended nothing. Switching tools mid-gesture skips end_feature entirely,
+    // so a zero-span Feature stays in m_features for good and m_open_feature stays set, which
+    // also gates the auto-edit trigger for whatever is drawn next.
+    if (m_open_feature >= 0 && m_open_feature < int(m_features.size())
+        && m_features[m_open_feature].end <= m_features[m_open_feature].begin)
+        m_features.pop_back();          // always the last one: begin_feature pushed it
+    m_open_feature = -1;
+
+    // Constrain-mode picks and the imported-art transform outlived the tool that made them.
+    // Neither can misfire while another mode is active, which is why this is quieter than the
+    // dimension picks — but coming BACK to Constrain resurrected picks made before leaving,
+    // possibly against entities deleted in between. Reset them the way begin_constrain does.
+    m_sel_a = m_sel_b = -1;
+    m_constrain_entities = false;
+    reset_xform();          // cancel() already does this; a tool switch is just as much a leave
+    // A READY edit-op carries the user's typed or dragged value, so switching tools commits it
+    // rather than dropping it — the same rule Tab follows in the dimension editor. Discarding it
+    // here is most of why Fillet looked like it simply did not work: every documented route (type
+    // the radius, or drag the arrow) left the op ready-but-pending, and the next tool click threw
+    // the value away and reverted the corner to sharp, with nothing on screen saying so.
+    reset_op();                 // drop any in-progress (not yet ready) edit-op gizmo
+    reset_tf();                 // drop any in-progress transform gizmo
+    // A pick that survives the tool that made it is invisible, and the first sign of it is a
+    // constraint or a dimension landing on geometry the user did not choose. Drop the modal
+    // picks left armed by the tool we are leaving: the Dimension tool's first pick, the
+    // Constrain tool's picks, and the individual point selection.
+    m_dim_has0 = false;
+    m_dim_e0   = -1;
+    m_dim_r0   = SketchPointRole::P0;
+    m_pick0 = m_pick1 = m_pick2 = -1;
+    m_point_sel.clear();
+    m_selection.clear();
+    if (on_selection_changed) on_selection_changed(0);
+}
+
+void DesignSketchTool::cancel()
+{
+    close_session_chrome();     // same orphaned-field freeze as finish() — see yce
+    m_active = false;
+    m_step_mode_last = -1;
+    m_points.clear();
+    m_entities.clear();
+    m_construction = false;
+    m_has_cursor = false;
+    m_sel_a = m_sel_b = -1;
+    m_constrain_entities = false;
+    m_pick0 = m_pick1 = m_pick2 = -1;
+    m_constraint_hl.clear();
+    m_constrain_cons.clear();
+    m_awaiting_length = false;
+    m_selection.clear();
+    m_point_sel.clear();
+    m_constraints.clear();
+    m_dimensions.clear();
+    m_dim_has0 = false;
+    m_pending_dim = -1;
+    m_dof = -1; m_solve_ok = true; m_entity_conflict.clear();
+    m_features.clear();
+    m_open_feature = -1;
+    reset_op();
+    reset_xform();
+    reset_tf();
+}
+
+// CadLevel::Gesture inside a sketch: drop the entity being drawn, keep the tool armed.
+bool DesignSketchTool::abort_gesture()
+{
+    if (m_points.empty()) return false;
+    m_points.clear();
+    m_has_cursor = false;
+    return true;
+}
+
+// CadLevel::Tool inside a sketch: an armed draw/edit tool falls back to Select.
+// Drop any pending edit-op BEFORE the downgrade: set_tool commits a ready one, and Esc must
+// cancel it, never apply it. Right-click already discards it through its own branch.
+bool DesignSketchTool::disarm_tool()
+{
+    if (m_mode == Mode::Select) return false;
+    reset_op();
+    set_tool(Mode::Select);
+    return true;
+}
+
+// Esc / right-click while active: layered exit (Onshape-like), and layered is where it stops.
+// Abort an in-progress entity first, then drop a draw tool back to Select, then — only if the
+// session holds NOTHING a user could mourn — leave it.
+//
+// It used to have a fourth layer: refuse once, and let the SECOND consecutive request destroy a
+// drawn sketch. That is the "I pressed Esc twice and my rectangle was gone" report, and no
+// warning makes it acceptable, because the two presses are never deliberate — the first is aimed
+// at a value field or a tool and the second at the tool underneath it. A session holding geometry
+// is now left ONLY through Finish (keep) or Cancel (discard), both of which say which they are.
+// This is the single decision point for every caller, keyboard and mouse alike, so the guarantee
+// cannot be re-opened by adding a route.
+void DesignSketchTool::request_exit()
+{
+    if (abort_gesture()) return;
+    if (disarm_tool())   return;
+    if (live_sketch_has_work()) { if (on_exit_refused) on_exit_refused(); return; }
+    if (on_exit) on_exit();
+    else         cancel();
+}
+
+void DesignSketchTool::request_undo_redo(bool redo)
+{
+    if (on_undo_redo) on_undo_redo(redo);
+}
+
+void DesignSketchTool::clear_selection()
+{
+    if (m_selection.empty() && m_point_sel.empty()) return;
+    m_selection.clear();
+    m_point_sel.clear();
+    if (on_selection_changed) on_selection_changed(0);
+}
+
+void DesignSketchTool::delete_selected()
+{
+    if (m_selection.empty()) return;
+    const int n = int(m_entities.size());
+    std::vector<bool> del(n, false);
+    for (int i : m_selection)
+        if (i >= 0 && i < n) del[i] = true;
+    // old index -> new index (or -1 if deleted), to fix up constraint references.
+    std::vector<int> remap(n, -1);
+    int next = 0;
+    for (int i = 0; i < n; ++i)
+        if (!del[i]) remap[i] = next++;
+    for (int i = n - 1; i >= 0; --i)
+        if (del[i]) m_entities.erase(m_entities.begin() + i);
+    // Drop constraints touching a deleted entity; remap the survivors.
+    std::vector<SketchEntityConstraintDef> kept;
+    auto live = [&](int e) { return e < 0 || (e < n && remap[e] >= 0); };
+    auto map  = [&](int e) { return e < 0 ? -1 : remap[e]; };
+    for (SketchEntityConstraintDef c : m_constraints) {
+        if (!live(c.ea) || !live(c.eb) || !live(c.ec)) continue;
+        c.ea = map(c.ea); c.eb = map(c.eb); c.ec = map(c.ec);
+        kept.push_back(c);
+    }
+    m_constraints.swap(kept);
+    m_selection.clear();
+    m_point_sel.clear();
+    // v1: placed quotes reference entity indices that have shifted; drop them rather
+    // than risk a dangling reference (the driving constraints survive, reindexed).
+    m_dimensions.clear();
+    m_dim_has0 = false;
+    m_pending_dim = -1;
+    // The Dimension tool's pending FIRST pick is the same dangling-reference hazard as the placed
+    // quotes just cleared above: it references an entity index that has shifted or gone away, and
+    // a stale m_dim_e0 would dereference out of range on the next click. Drop it too.
+    m_dim_e0 = -1;
+    m_dim_r0 = SketchPointRole::P0;
+
+    // FEATURE GROUPS hold [begin,end) ranges into m_entities, and every index past a deletion has
+    // just moved. Left alone they point at other people's geometry: feature_of() then answers with
+    // a group the user never drew, and the rect/slot/polygon handles and live quotes follow it.
+    // Survivors are remapped (a contiguous range stays contiguous, since the remap preserves
+    // order); a group that lost any member is dropped, the same rule the placed quotes above
+    // already follow — dangling is worse than absent.
+    {
+        std::vector<Feature> kept_f;
+        for (const Feature& f : m_features) {
+            if (f.begin < 0 || f.end > n || f.end <= f.begin) continue;
+            bool whole = true;
+            for (int k = f.begin; k < f.end; ++k)
+                if (del[k]) { whole = false; break; }
+            if (!whole) continue;
+            Feature g = f;
+            g.begin = remap[f.begin];
+            g.end   = remap[f.end - 1] + 1;
+            kept_f.push_back(g);
+        }
+        m_features.swap(kept_f);
+        m_open_feature = -1;
+    }
+
+    // The draw-then-edit QUEUE outlives the entities it was queued for. Its own helper says so:
+    // "Removing an entity that still has a deferred auto-edit would otherwise open a field on a
+    // now-deleted entity and freeze the flow" — it was simply never called from here. Measured:
+    // delete a rectangle whose Width/Height were still queued, draw a circle, type its radius —
+    // the field opens, the digits go in, and the radius does not move, because the field belongs
+    // to a rectangle that no longer exists. ua9g.
+    reset_autoedit();
+
+    // And re-solve, so the sketch's reported degrees of freedom describe the sketch that is
+    // actually there. Without this, sketch_describe answered dof=16 for a document holding one
+    // circle — the DoF of the geometry that had just been deleted.
+    resolve_live();
+    if (on_selection_changed) on_selection_changed(0);
+}
+
+// Convert the selection to/from construction geometry (6zic). The Construction
+// checkbox only ever set the mode for what you draw NEXT, so a line drawn as real geometry
+// could never become a guide, nor a guide become real. Whole Feature groups flip together:
+// a rectangle is four Line entities and converting three of them is never what was meant.
+int DesignSketchTool::toggle_selection_construction()
+{
+    if (!selection_valid() || m_selection.empty()) return 0;
+    std::vector<bool> hit(m_entities.size(), false);
+    for (int i : m_selection) {
+        const int f = feature_of(i);
+        if (f >= 0)
+            for (int k = m_features[f].begin; k < m_features[f].end; ++k) hit[k] = true;
+        else
+            hit[i] = true;
+    }
+    // One direction for the whole batch: any real geometry in it -> all become construction.
+    bool any_real = false;
+    for (size_t i = 0; i < hit.size(); ++i)
+        if (hit[i] && !m_entities[i].construction) { any_real = true; break; }
+    int n = 0;
+    for (size_t i = 0; i < hit.size(); ++i)
+        if (hit[i] && m_entities[i].construction != any_real) { m_entities[i].construction = any_real; ++n; }
+    return n;
+}
+
+bool DesignSketchTool::selection_valid() const
+{
+    for (int i : m_selection)
+        if (i < 0 || i >= int(m_entities.size())) return false;
+    return true;
+}
+
+DesignSketchTool::DimType DesignSketchTool::dimension_kind() const
+{
+    if (!selection_valid()) return DimType::None;
+    if (m_selection.size() == 1) {
+        switch (m_entities[m_selection[0]].type) {
+        case SketchEntity::Type::Line:   return DimType::Length;
+        case SketchEntity::Type::Circle: return DimType::Diameter;
+        case SketchEntity::Type::Arc:    return DimType::Radius;
+        default: return DimType::None;
+        }
+    }
+    if (m_selection.size() == 2) {
+        const SketchEntity& a = m_entities[m_selection[0]];
+        const SketchEntity& b = m_entities[m_selection[1]];
+        const bool aLine = (a.type == SketchEntity::Type::Line);
+        const bool bLine = (b.type == SketchEntity::Type::Line);
+        Vec2d tmp(0, 0);
+        if (aLine && bLine)                                   return DimType::Angle;
+        // one line + one point-like (point / circle-centre / arc-centre)
+        if (aLine && entity_ref_point(b, tmp))                return DimType::DistanceToLine;
+        if (bLine && entity_ref_point(a, tmp))                return DimType::DistanceToLine;
+        // two point-likes -> centre/point distance (0 = coincident/concentric)
+        if (entity_ref_point(a, tmp) && entity_ref_point(b, tmp)) return DimType::Distance;
+    }
+    return DimType::None;
+}
+
+double DesignSketchTool::dimension_current() const
+{
+    switch (dimension_kind()) {
+    case DimType::Length:   { const auto& e = m_entities[m_selection[0]]; return (e.p1 - e.p0).norm(); }
+    case DimType::Diameter: return 2.0 * m_entities[m_selection[0]].radius;
+    case DimType::Radius:   return m_entities[m_selection[0]].radius;
+    case DimType::Angle: {
+        const auto& a = m_entities[m_selection[0]];
+        const auto& b = m_entities[m_selection[1]];
+        const Vec2d da = a.p1 - a.p0, db = b.p1 - b.p0;
+        const double na = da.norm(), nb = db.norm();
+        if (na < 1e-9 || nb < 1e-9) return 0.0;
+        const double c = std::max(-1.0, std::min(1.0, da.dot(db) / (na * nb)));
+        return std::acos(c) * 180.0 / M_PI;
+    }
+    case DimType::Distance: {
+        Vec2d ra(0, 0), rb(0, 0);
+        entity_ref_point(m_entities[m_selection[0]], ra);
+        entity_ref_point(m_entities[m_selection[1]], rb);
+        return (rb - ra).norm();
+    }
+    case DimType::DistanceToLine: {
+        const SketchEntity& a = m_entities[m_selection[0]];
+        const SketchEntity& b = m_entities[m_selection[1]];
+        const bool aLine = (a.type == SketchEntity::Type::Line);
+        const SketchEntity& L = aLine ? a : b;
+        const SketchEntity& P = aLine ? b : a;
+        Vec2d rp(0, 0); entity_ref_point(P, rp);
+        Vec2d dir = L.p1 - L.p0;
+        const double n = dir.norm();
+        if (n < 1e-9) return 0.0;
+        const Vec2d nrm(-dir.y() / n, dir.x() / n);   // unit normal to the line
+        return std::abs((rp - L.p0).dot(nrm));
+    }
+    default: return 0.0;
+    }
+}
+
+void DesignSketchTool::apply_angle_between(int ia, int ib, double deg)
+{
+    SketchEntity& A = m_entities[ia];
+    SketchEntity& B = m_entities[ib];
+    const Vec2d aE[2] = { A.p0, A.p1 };
+    const Vec2d bE[2] = { B.p0, B.p1 };
+    int si = -1, sj = -1;
+    double best = 1e-6;
+    for (int i = 0; i < 2; ++i)
+        for (int j = 0; j < 2; ++j) {
+            const double d = (aE[i] - bE[j]).squaredNorm();
+            if (d < best) { best = d; si = i; sj = j; }
+        }
+    Vec2d pivot, refDir, bMoving;
+    bool moveP1;
+    if (si >= 0) {                       // shared vertex: pivot there, A's arm is the reference
+        pivot   = aE[si];
+        refDir  = aE[1 - si] - pivot;
+        moveP1  = (sj == 0);             // move the B end that is NOT at the pivot
+        bMoving = moveP1 ? B.p1 : B.p0;
+    } else {                             // no shared vertex: pivot B.p0, A's direction is reference
+        pivot   = B.p0;
+        refDir  = A.p1 - A.p0;
+        moveP1  = true;
+        bMoving = B.p1;
+    }
+    double nr = refDir.norm();
+    if (nr < 1e-9) return;
+    refDir /= nr;
+    const Vec2d db = bMoving - pivot;
+    const double Lb = db.norm();
+    if (Lb < 1e-9) return;
+    const double cross = refDir.x() * db.y() - refDir.y() * db.x();
+    const double sign  = (cross >= 0.0) ? 1.0 : -1.0;   // keep B on its current side
+    const double rad   = sign * deg * M_PI / 180.0;
+    const Vec2d ndir(refDir.x() * std::cos(rad) - refDir.y() * std::sin(rad),
+                     refDir.x() * std::sin(rad) + refDir.y() * std::cos(rad));
+    const Vec2d nb = pivot + Lb * ndir;
+    if (moveP1) B.p1 = nb; else B.p0 = nb;
+}
+
+void DesignSketchTool::apply_dimension(double v)
+{
+    switch (dimension_kind()) {
+    case DimType::Length: {
+        SketchEntity& e = m_entities[m_selection[0]];
+        const Vec2d d = e.p1 - e.p0;
+        const double r = d.norm();
+        if (r > 1e-9 && v > 1e-9) e.p1 = e.p0 + (v / r) * d;
+        break;
+    }
+    case DimType::Diameter: if (v > 1e-9) m_entities[m_selection[0]].radius = 0.5 * v; break;
+    case DimType::Radius:   if (v > 1e-9) m_entities[m_selection[0]].radius = v;       break;
+    case DimType::Angle:    apply_angle_between(m_selection[0], m_selection[1], v);     break;
+    case DimType::Distance: {
+        // Move the 2nd selection so its reference point sits at distance v from the
+        // 1st (v == 0 -> coincident / concentric). Translate the whole entity.
+        if (v < 0.0) break;
+        Vec2d ra(0, 0), rb(0, 0);
+        entity_ref_point(m_entities[m_selection[0]], ra);
+        SketchEntity& b = m_entities[m_selection[1]];
+        entity_ref_point(b, rb);
+        const Vec2d d = rb - ra;
+        const double r = d.norm();
+        Vec2d target = ra;
+        if (r > 1e-9) target = ra + (v / r) * d;
+        else          target = ra + Vec2d(v, 0.0);
+        translate_entity(b, target - rb);
+        break;
+    }
+    case DimType::DistanceToLine: {
+        // Move the point-like selection perpendicular to the line so its reference
+        // point is at distance v (v == 0 -> on the line / on the axis).
+        if (v < 0.0) break;
+        const bool aLine = (m_entities[m_selection[0]].type == SketchEntity::Type::Line);
+        const SketchEntity& L = m_entities[m_selection[aLine ? 0 : 1]];
+        SketchEntity& P = m_entities[m_selection[aLine ? 1 : 0]];
+        Vec2d rp(0, 0); entity_ref_point(P, rp);
+        Vec2d dir = L.p1 - L.p0;
+        const double n = dir.norm();
+        if (n < 1e-9) break;
+        const Vec2d nrm(-dir.y() / n, dir.x() / n);
+        const double d0 = (rp - L.p0).dot(nrm);          // current signed distance
+        const double sign = (d0 >= 0.0) ? 1.0 : -1.0;    // keep the point on its side
+        translate_entity(P, (sign * v - d0) * nrm);
+        break;
+    }
+    default: break;
+    }
+    record_dimension_constraint(v);          // store a driving constraint for this dimension
+    resolve_live();                          // live-solve so the viewport shows the solved sketch
+    m_selection.clear();
+    if (on_selection_changed) on_selection_changed(0);
+}
+
+// Append the SketchEntityConstraintDef that makes the just-applied dimension a
+// driving constraint (enforced by the kernel live and at commit). DistanceToLine
+// records a PointOnLine constraint so "centre onto axis" persists through re-solve.
+void DesignSketchTool::record_dimension_constraint(double v)
+{
+    const DimType k = dimension_kind();
+    auto role = [&](int i) {
+        return (m_entities[i].type == SketchEntity::Type::Point) ? SketchPointRole::P0
+                                                                 : SketchPointRole::Center;
+    };
+    SketchEntityConstraintDef c;
+    switch (k) {
+    case DimType::Length:
+        c.type = SketchConstraintType::Distance;
+        c.ea = m_selection[0]; c.ra = SketchPointRole::P0;
+        c.eb = m_selection[0]; c.rb = SketchPointRole::P1;
+        c.value = v; m_constraints.push_back(c); break;
+    case DimType::Diameter:
+        c.type = SketchConstraintType::Diameter; c.ea = m_selection[0]; c.value = v;
+        m_constraints.push_back(c); break;
+    case DimType::Radius:
+        c.type = SketchConstraintType::Radius; c.ea = m_selection[0]; c.value = v;
+        m_constraints.push_back(c); break;
+    case DimType::Angle:
+        c.type = SketchConstraintType::Angle;
+        c.ea = m_selection[0]; c.eb = m_selection[1]; c.value = v;
+        m_constraints.push_back(c); break;
+    case DimType::Distance: {
+        const int ia = m_selection[0], ib = m_selection[1];
+        if (v < 1e-9) c.type = SketchConstraintType::Coincident;
+        else        { c.type = SketchConstraintType::Distance; c.value = v; }
+        c.ea = ia; c.ra = role(ia); c.eb = ib; c.rb = role(ib);
+        m_constraints.push_back(c); break;
+    }
+    case DimType::DistanceToLine: {
+        // Point-on-line driving constraint: hold the point-like entity at unsigned
+        // perpendicular distance v from the line (v == 0 -> on the axis).
+        const bool aLine = (m_entities[m_selection[0]].type == SketchEntity::Type::Line);
+        const int ip = m_selection[aLine ? 1 : 0];   // point-like (Point/Circle/Arc)
+        const int il = m_selection[aLine ? 0 : 1];   // line
+        c.type = SketchConstraintType::PointOnLine;
+        c.ea = ip; c.ra = role(ip); c.eb = il; c.value = v;
+        m_constraints.push_back(c); break;
+    }
+    default: break;   // None: no driving constraint recorded
+    }
+}
+
+// Onshape-style live solve: enforce all accumulated driving constraints on the
+// in-session entities immediately, so the viewport reflects the solved sketch as
+// each dimension/constraint is added (not only at commit). The pre-edit geometry
+// is the solver's initial guess, keeping convergence local and side-preserving.
+void DesignSketchTool::resolve_live()
+{
+    resolve_live_drag(-1, SketchPointRole::P0);
+}
+
+void DesignSketchTool::resolve_live_drag(int dragged_ei, SketchPointRole dragged_role)
+{
+    const bool has = !m_constraints.empty();
+    m_entity_conflict.assign(m_entities.size(), 0);
+    if (has) {
+        // Dragging a line endpoint must move ONLY that endpoint (changing the line's angle +
+        // length), anchoring the other end — Onshape behaviour. Without this, a constraint on
+        // the line (e.g. a length dimension or an inferred H/V) lets the solver relocate the
+        // un-dragged endpoint too, so the whole line appears to shift. Temporarily Fix the
+        // opposite endpoint for this drag-solve only (set_point already moved just the grabbed
+        // point, so the other end's current coord is its anchor).
+        std::vector<SketchEntityConstraintDef> cons = m_constraints;
+        const bool line_end = dragged_ei >= 0 && dragged_ei < int(m_entities.size()) &&
+                              m_entities[dragged_ei].type == SketchEntity::Type::Line &&
+                              (dragged_role == SketchPointRole::P0 || dragged_role == SketchPointRole::P1);
+        if (line_end) {
+            SketchEntityConstraintDef fix;
+            fix.type = SketchConstraintType::Fix;
+            fix.ea   = dragged_ei;
+            fix.ra   = (dragged_role == SketchPointRole::P0) ? SketchPointRole::P1
+                                                             : SketchPointRole::P0;
+            cons.push_back(fix);
+        }
+        const SketchSolveResult r = (dragged_ei >= 0)
+            ? sketch_solve_drag(m_entities, cons, dragged_ei, dragged_role)
+            : sketch_solve(m_entities, cons);
+        m_dof      = r.dof;
+        m_solve_ok = r.ok;
+        // Flag every entity referenced by a conflicting constraint so render() can
+        // tint it red (Onshape/SolveSpace over-constrained feedback).
+        for (int bi : r.bad) {
+            if (bi < 0 || bi >= int(m_constraints.size())) continue;
+            const SketchEntityConstraintDef& c = m_constraints[bi];
+            for (int e : {c.ea, c.eb, c.ec})
+                if (e >= 0 && e < int(m_entity_conflict.size())) m_entity_conflict[e] = 1;
+        }
+    } else {
+        m_dof = -1; m_solve_ok = true;
+    }
+    if (on_solve_state) on_solve_state(m_dof, m_solve_ok, has);
+}
+
+// ---- Onshape-style visual editing: feature grouping + handles -----------------
+
+// Index of the Feature whose entity span contains ei, or -1 (last match wins so a
+// later, tighter gesture shadows an earlier one if they ever overlap).
+int DesignSketchTool::feature_of(int ei) const
+{
+    for (int i = int(m_features.size()) - 1; i >= 0; --i)
+        if (ei >= m_features[i].begin && ei < m_features[i].end) return i;
+    return -1;
+}
+
+// Open a Feature spanning the entities a single gesture is about to append. The
+// [begin,end) range is closed in end_feature() once the gesture's entities are in.
+void DesignSketchTool::begin_feature(FeatureKind kind)
+{
+    Feature f;
+    f.kind  = kind;
+    f.begin = int(m_entities.size());
+    f.end   = f.begin;
+    m_features.push_back(f);
+    m_open_feature = int(m_features.size()) - 1;
+}
+
+// Close the open Feature: record its entity span end + the gesture's parametric
+// anchors (centres / corners / half-width / sides) for later handle + dim rebuild.
+void DesignSketchTool::end_feature(const Vec2d& c0, const Vec2d& c1, double param, int sides)
+{
+    if (m_open_feature < 0 || m_open_feature >= int(m_features.size())) return;
+    Feature& f = m_features[m_open_feature];
+    f.end   = int(m_entities.size());
+    f.c0    = c0;
+    f.c1    = c1;
+    f.param = param;
+    f.sides = sides;
+    // Drop a degenerate feature (gesture appended nothing).
+    if (f.end <= f.begin) m_features.pop_back();
+    m_open_feature = -1;
+}
+
+// Forward decls: these ellipse helpers are defined further down but used by the
+// handle/drag code above their definition.
+static Vec2d  ellipse_point(const Vec2d& c, double a, double b, double phi, double t);
+static double ellipse_param_of(const Vec2d& center, double a, double b, double phi, const Vec2d& q);
+
+// Live handle set (A3: Line + Circle). Recomputed from solved geometry every frame,
+// never persisted — so handles always track the current solve. Derived roles (here
+// the circle RadiusHandle, which is NOT a serialized SketchPointRole) are what let a
+// tool expose a parametric control its raw entity points don't carry. A4 routes a
+// Select-mode drag through hit_test_handle + set_handle; later phases add the
+// slot/rect/polygon/ellipse roles off the Feature groups.
+std::vector<DesignSketchTool::Handle> DesignSketchTool::build_handles() const
+{
+    std::vector<Handle> hs;
+    hs.reserve(m_entities.size() * 2);
+    for (size_t i = 0; i < m_entities.size(); ++i) {
+        const SketchEntity& e = m_entities[i];
+        switch (e.type) {
+        case SketchEntity::Type::Line: {
+            Handle a; a.role = HandleRole::P0; a.ei = int(i); a.pos = e.p0; hs.push_back(a);
+            Handle b; b.role = HandleRole::P1; b.ei = int(i); b.pos = e.p1; hs.push_back(b);
+            break;
+        }
+        case SketchEntity::Type::Circle: {
+            Handle c; c.role = HandleRole::Center; c.ei = int(i); c.pos = e.center; hs.push_back(c);
+            // RadiusHandle sits on the circle to the +x side of its centre; dragging it
+            // (A4) edits the radius. Pure geometry, no constraint of its own.
+            Handle r; r.role = HandleRole::RadiusHandle; r.ei = int(i);
+            r.pos = e.center + Vec2d(e.radius, 0.0); hs.push_back(r);
+            break;
+        }
+        case SketchEntity::Type::Ellipse:
+        case SketchEntity::Type::EllipseArc: {
+            // 3 grips: centre (translate), major-axis end (semi-major a + orientation phi),
+            // minor-axis end (semi-minor b). a=e.radius, b=e.rminor, phi=e.rotation.
+            // (EllipseArc also exposes its two endpoints via hit_test_point for sweep.)
+            const Vec2d um(std::cos(e.rotation), std::sin(e.rotation));   // major dir
+            const Vec2d un(-um.y(), um.x());                              // minor dir
+            Handle c; c.role = HandleRole::Center; c.ei = int(i); c.pos = e.center; hs.push_back(c);
+            Handle ma; ma.role = HandleRole::MajorAxis; ma.ei = int(i);
+            ma.pos = e.center + um * e.radius; hs.push_back(ma);
+            Handle mi; mi.role = HandleRole::MinorAxis; mi.ei = int(i);
+            mi.pos = e.center + un * e.rminor; hs.push_back(mi);
+            break;
+        }
+        case SketchEntity::Type::BSpline: {
+            // One draggable grip per control pole; dragging a pole reshapes the curve.
+            for (size_t k = 0; k < e.ctrl.size(); ++k) {
+                Handle h; h.role = HandleRole::BSplineCtrl; h.ei = int(i);
+                h.ctrl_index = int(k); h.pos = e.ctrl[k]; hs.push_back(h);
+            }
+            break;
+        }
+        default: break;   // Arc derived handles land in later chunks
+        }
+    }
+    return hs;
+}
+
+// Nearest handle to plane-point p within tol. Ties broken by smallest distance.
+bool DesignSketchTool::hit_test_handle(const Vec2d& p, double tol, Handle& out) const
+{
+    bool found = false;
+    double best = tol;
+    for (const Handle& h : build_handles()) {
+        const double d = (h.pos - p).norm();
+        if (d <= best) { best = d; out = h; out.hovered = true; found = true; }
+    }
+    return found;
+}
+
+// Recompute the hovered handle on a plain (no-button) move. Returns true ONLY when the
+// hovered handle changes, so on_mouse forces a single repaint per transition rather than
+// re-rendering on every motion event. A no-op (false) for non-Moving events.
+bool DesignSketchTool::update_hover(GLCanvas3D& canvas, wxMouseEvent& evt)
+{
+    if (!evt.Moving()) return false;
+    Vec2d p;
+    screen_to_plane(canvas, evt, p);
+    // Zoom-aware pick tolerance: project a point a few px away and measure in plane units.
+    const Linef3 r2 = canvas.mouse_ray(Point(evt.GetX() + 6, evt.GetY()));
+    const double tol = std::max(1e-3, (m_plane.project(r2.a, r2.vector()) - p).norm());
+    const bool   had  = m_has_hover_handle;
+    const Handle prev = m_hover_handle;
+    Handle h;
+    m_has_hover_handle = hit_test_handle(p, tol, h);
+    if (m_has_hover_handle) m_hover_handle = h;
+    return (had != m_has_hover_handle) ||
+           (m_has_hover_handle && (prev.ei != h.ei || prev.role != h.role));
+}
+
+// Apply a handle drag (A4). Point handles (P0/P1/Center) move the entity point and
+// pin it in the drag-solve so constraints settle around the cursor. The derived
+// RadiusHandle isn't a solver point — it edits the circle radius directly, then a
+// full re-solve lets any driving Radius/Diameter constraint reassert (an unconstrained
+// radius is a free DoF, so the solver keeps the new value). Slot/rect/polygon/ellipse
+// roles land in later phases (they rebuild their Feature group).
+void DesignSketchTool::set_handle(const Handle& h, const Vec2d& target)
+{
+    if (h.ei < 0 || h.ei >= int(m_entities.size())) return;
+    SketchEntity& e = m_entities[h.ei];
+    switch (h.role) {
+    case HandleRole::P0:
+        set_point(h.ei, SketchPointRole::P0, target);     resolve_live_drag(h.ei, SketchPointRole::P0);     break;
+    case HandleRole::P1:
+        set_point(h.ei, SketchPointRole::P1, target);     resolve_live_drag(h.ei, SketchPointRole::P1);     break;
+    case HandleRole::Center:
+        set_point(h.ei, SketchPointRole::Center, target); resolve_live_drag(h.ei, SketchPointRole::Center); break;
+    case HandleRole::RadiusHandle: {
+        const double r = (target - e.center).norm();
+        if (r > 1e-6) e.radius = r;
+        resolve_live();
+        break;
+    }
+    case HandleRole::MajorAxis: {
+        // The major grip defines the major-axis vector: sets semi-major a + orientation phi.
+        const Vec2d d = target - e.center;
+        const double a = d.norm();
+        if (a > 1e-6) {
+            e.rotation = std::atan2(d.y(), d.x());
+            e.radius   = std::max(a, e.rminor);   // keep OCCT invariant a >= b
+        }
+        if (e.type == SketchEntity::Type::EllipseArc) {   // endpoints ride the reshaped frame
+            e.p0 = ellipse_point(e.center, e.radius, e.rminor, e.rotation, e.start_angle);
+            e.p1 = ellipse_point(e.center, e.radius, e.rminor, e.rotation, e.end_angle);
+        }
+        resolve_live();
+        break;
+    }
+    case HandleRole::MinorAxis: {
+        // The minor grip sets semi-minor b = perpendicular distance to the major axis.
+        const Vec2d um(std::cos(e.rotation), std::sin(e.rotation));
+        const Vec2d un(-um.y(), um.x());
+        const double b = std::abs((target - e.center).dot(un));
+        if (b > 1e-6) e.rminor = std::min(b, e.radius);
+        if (e.type == SketchEntity::Type::EllipseArc) {
+            e.p0 = ellipse_point(e.center, e.radius, e.rminor, e.rotation, e.start_angle);
+            e.p1 = ellipse_point(e.center, e.radius, e.rminor, e.rotation, e.end_angle);
+        }
+        resolve_live();
+        break;
+    }
+    case HandleRole::BSplineCtrl: {
+        // Move one control pole; the end poles mirror p0/p1 (kept in sync for picking).
+        const int k = h.ctrl_index;
+        if (k >= 0 && k < int(e.ctrl.size())) {
+            e.ctrl[k] = target;
+            if (k == 0)                       e.p0 = target;
+            if (k == int(e.ctrl.size()) - 1)  e.p1 = target;
+        }
+        resolve_live();
+        break;
+    }
+    default: break;
+    }
+}
+
+// ---- Dimension tool (Mode::Dimension): click-to-place driving quotes ----------
+
+bool DesignSketchTool::point_at(int ei, SketchPointRole role, Vec2d& out) const
+{
+    if (ei < 0 || ei >= int(m_entities.size())) return false;
+    const SketchEntity& e = m_entities[ei];
+    switch (role) {
+    case SketchPointRole::P0:     out = e.p0;     return true;
+    case SketchPointRole::P1:     out = e.p1;     return true;
+    case SketchPointRole::Center: out = e.center; return true;
+    }
+    return false;
+}
+
+// Move an entity point to v. Lines/Points set the coordinate directly; a circle/
+// arc centre translates the whole entity (arc endpoints ride along). Dragging an
+// arc's endpoint is intentionally a no-op (it would redefine radius + angles).
+void DesignSketchTool::set_point(int ei, SketchPointRole role, const Vec2d& v)
+{
+    if (ei < 0 || ei >= int(m_entities.size())) return;
+    SketchEntity& e = m_entities[ei];
+    switch (e.type) {
+    case SketchEntity::Type::Line:
+        if (role == SketchPointRole::P0)      e.p0 = v;
+        else if (role == SketchPointRole::P1) e.p1 = v;
+        break;
+    case SketchEntity::Type::Point:
+        e.p0 = v;
+        break;
+    case SketchEntity::Type::Circle:
+        // p0 mirrors the centre for circles, which is the convention the solver both writes
+        // (SketchSolver.cpp:110) and restores after every solve (:421). Moving only e.center
+        // left the two disagreeing for the whole duration of a live drag, so anything reading
+        // p0 in that window saw the pre-drag position.
+        if (role == SketchPointRole::Center)  { e.center = v; e.p0 = v; }
+        break;
+    case SketchEntity::Type::Arc:
+    case SketchEntity::Type::EllipseArc:
+        if (role == SketchPointRole::Center) {
+            const Vec2d d = v - e.center;     // rigid translate, keep radius/angles
+            e.center = v; e.p0 += d; e.p1 += d;
+        }
+        break;
+    case SketchEntity::Type::Ellipse:
+        if (role == SketchPointRole::Center) { e.center = v; e.p0 = v; }
+        break;
+    case SketchEntity::Type::BSpline:
+        // P0/P1 drag the end poles; Center rigidly translates the whole curve.
+        if (role == SketchPointRole::P0 && !e.ctrl.empty()) { e.ctrl.front() = v; e.p0 = v; }
+        else if (role == SketchPointRole::P1 && !e.ctrl.empty()) { e.ctrl.back() = v; e.p1 = v; }
+        else if (role == SketchPointRole::Center) {
+            const Vec2d d = v - (e.ctrl.empty() ? e.p0 : e.ctrl.front());
+            for (auto& cp : e.ctrl) cp += d;
+            e.p0 += d; e.p1 += d;
+        }
+        break;
+    }
+}
+
+// Nearest entity *point* (endpoint / centre) within tol, with its role.
+bool DesignSketchTool::hit_test_point(const Vec2d& p, double tol, int& ei, SketchPointRole& role) const
+{
+    double best = tol;
+    bool found = false;
+    auto consider = [&](int i, SketchPointRole r, const Vec2d& q) {
+        const double d = (q - p).norm();
+        if (d < best) { best = d; ei = i; role = r; found = true; }
+    };
+    for (size_t i = 0; i < m_entities.size(); ++i) {
+        const SketchEntity& e = m_entities[i];
+        switch (e.type) {
+        case SketchEntity::Type::Line:
+            consider(int(i), SketchPointRole::P0, e.p0);
+            consider(int(i), SketchPointRole::P1, e.p1);
+            break;
+        case SketchEntity::Type::Arc:
+        case SketchEntity::Type::EllipseArc:
+            consider(int(i), SketchPointRole::P0, e.p0);
+            consider(int(i), SketchPointRole::P1, e.p1);
+            consider(int(i), SketchPointRole::Center, e.center);
+            break;
+        case SketchEntity::Type::Circle:
+        case SketchEntity::Type::Ellipse:
+            consider(int(i), SketchPointRole::Center, e.center);
+            break;
+        case SketchEntity::Type::BSpline:
+            consider(int(i), SketchPointRole::P0, e.p0);
+            consider(int(i), SketchPointRole::P1, e.p1);
+            break;
+        case SketchEntity::Type::Point:
+            consider(int(i), SketchPointRole::P0, e.p0);
+            break;
+        }
+    }
+    return found;
+}
+
+double DesignSketchTool::measure_dim(const DimAnnot& a) const
+{
+    Vec2d pa, pb;
+    switch (a.kind) {
+    case DimType::Length:
+        return (a.ea >= 0 && a.ea < int(m_entities.size()))
+                   ? (m_entities[a.ea].p1 - m_entities[a.ea].p0).norm() : 0.0;
+    case DimType::Diameter:
+        return (a.ea >= 0 && a.ea < int(m_entities.size())) ? 2.0 * m_entities[a.ea].radius : 0.0;
+    case DimType::Radius:
+        return (a.ea >= 0 && a.ea < int(m_entities.size())) ? m_entities[a.ea].radius : 0.0;
+    case DimType::Angle: {
+        // Single line: angle to the +X axis, normalised to [0,360). (Line-to-line angle
+        // dimensions use the legacy dialog path.)
+        if (a.ea < 0 || a.ea >= int(m_entities.size())) return 0.0;
+        const SketchEntity& e = m_entities[a.ea];
+        if (e.type != SketchEntity::Type::Line) return 0.0;
+        const Vec2d d = e.p1 - e.p0;
+        if (d.squaredNorm() < 1e-18) return 0.0;
+        double deg = std::atan2(d.y(), d.x()) * 180.0 / M_PI;
+        if (deg < 0.0) deg += 360.0;
+        return deg;
+    }
+    case DimType::Distance:
+        return (point_at(a.ea, a.ra, pa) && point_at(a.eb, a.rb, pb)) ? (pb - pa).norm() : 0.0;
+    case DimType::DistanceToLine: {
+        if (!point_at(a.ea, a.ra, pa) || a.eb < 0 || a.eb >= int(m_entities.size())) return 0.0;
+        const SketchEntity& L = m_entities[a.eb];
+        const Vec2d d = L.p1 - L.p0;
+        const double n = d.norm();
+        if (n < 1e-9) return 0.0;
+        const Vec2d nrm(-d.y() / n, d.x() / n);
+        return std::abs((pa - L.p0).dot(nrm));
+    }
+    default: return 0.0;
+    }
+}
+
+// One driving constraint per (kind, operands) — update it in place rather than appending a
+// second one every time its value is edited.
+//
+// Re-typing a quote used to push a duplicate alongside the original: draw a line and accept its
+// length, and you get Distance(P0,P1)=64.9; click the quote later and type 30, and you get a
+// SECOND Distance on the same two points asking for 30. That is over-constrained by
+// construction, so the solver reported "Conflicting constraints" and refused to move anything —
+// the number on screen changed and the geometry did not, which reads as the edit being ignored.
+// A line carrying no dimension yet was unaffected, which is what made it look intermittent.
+//
+// Operand order is ignored: a Distance from A to B is the same constraint as B to A, and so is
+// an Angle. Returns the index, so callers can keep the annotation's `con` link pointing at the
+// constraint that is actually live — which is what makes the next edit an update too.
+int DesignSketchTool::upsert_constraint(const SketchEntityConstraintDef& c)
+{
+    auto same_operands = [&](const SketchEntityConstraintDef& o) {
+        if (o.ea == c.ea && o.ra == c.ra && o.eb == c.eb && o.rb == c.rb) return true;
+        return o.ea == c.eb && o.ra == c.rb && o.eb == c.ea && o.rb == c.ra;
+    };
+    for (int i = 0; i < int(m_constraints.size()); ++i)
+        if (m_constraints[i].type == c.type && same_operands(m_constraints[i])) {
+            m_constraints[i] = c;
+            return i;
+        }
+    m_constraints.push_back(c);
+    return int(m_constraints.size()) - 1;
+}
+
+// The same rule for the visible annotation: one quote per (kind, operands), so repeated edits
+// do not stack labels on top of each other reading different values.
+int DesignSketchTool::upsert_dimension(const DimAnnot& a)
+{
+    for (int i = 0; i < int(m_dimensions.size()); ++i) {
+        const DimAnnot& o = m_dimensions[i];
+        if (o.kind == a.kind && ((o.ea == a.ea && o.eb == a.eb) || (o.ea == a.eb && o.eb == a.ea))) {
+            const Vec2d keep = m_dimensions[i].label_pos;   // don't teleport a placed label
+            m_dimensions[i] = a;
+            m_dimensions[i].label_pos = keep;
+            return i;
+        }
+    }
+    m_dimensions.push_back(a);
+    return int(m_dimensions.size()) - 1;
+}
+
+SketchEntityConstraintDef DesignSketchTool::constraint_for(const DimAnnot& a) const
+{
+    SketchEntityConstraintDef c;
+    switch (a.kind) {
+    case DimType::Length:
+        c.type = SketchConstraintType::Distance;
+        c.ea = a.ea; c.ra = SketchPointRole::P0;
+        c.eb = a.ea; c.rb = SketchPointRole::P1; c.value = a.value;
+        break;
+    case DimType::Diameter: c.type = SketchConstraintType::Diameter; c.ea = a.ea; c.value = a.value; break;
+    case DimType::Radius:   c.type = SketchConstraintType::Radius;   c.ea = a.ea; c.value = a.value; break;
+    case DimType::Distance:
+        if (a.value < 1e-9) c.type = SketchConstraintType::Coincident;
+        else              { c.type = SketchConstraintType::Distance; c.value = a.value; }
+        c.ea = a.ea; c.ra = a.ra; c.eb = a.eb; c.rb = a.rb;
+        break;
+    case DimType::DistanceToLine:
+        c.type = SketchConstraintType::PointOnLine;
+        c.ea = a.ea; c.ra = a.ra; c.eb = a.eb; c.value = a.value;
+        break;
+    default: break;
+    }
+    return c;
+}
+
+// Measure the just-picked dimension, append its driving constraint, live-solve, and
+// fire the value-card callback so the user can override the value.
+int DesignSketchTool::place_dimension(DimAnnot a)
+{
+    a.value = measure_dim(a);
+    a.con   = upsert_constraint(constraint_for(a));
+    const int di = upsert_dimension(a);
+    resolve_live();
+    open_value_editor(di);
+    return m_pending_dim;
+}
+
+// Nearest placed-dimension label within tol (uses the centre cached by render).
+int DesignSketchTool::hit_test_dimension(const Vec2d& p, double tol) const
+{
+    double best = tol;
+    int bi = -1;
+    for (size_t i = 0; i < m_dimensions.size(); ++i) {
+        const double d = (m_dimensions[i].label_pos - p).norm();
+        if (d < best) { best = d; bi = int(i); }
+    }
+    return bi;
+}
+
+// Reopen the value editor on an existing dimension (click/double-click its label).
+void DesignSketchTool::edit_dimension(int di)
+{
+    if (di < 0 || di >= int(m_dimensions.size())) return;
+    open_value_editor(di);
+}
+
+// Representative plane anchor for a dimension's value editor: the cached label centre
+// once render has computed it, otherwise a geometric midpoint (length/distance) or the
+// entity centre (radius/diameter).
+Vec2d DesignSketchTool::dim_anchor(const DimAnnot& a) const
+{
+    if (a.label_pos.squaredNorm() > 1e-12) return a.label_pos;
+    Vec2d pa, pb;
+    if ((a.kind == DimType::Radius || a.kind == DimType::Diameter) &&
+        point_at(a.ea, SketchPointRole::Center, pa))
+        return pa;
+    const bool ga = point_at(a.ea, a.ra, pa);
+    const bool gb = point_at(a.eb, a.rb, pb);
+    if (ga && gb) return 0.5 * (pa + pb);
+    if (ga)       return pa;
+    if (gb)       return pb;
+    return Vec2d(0, 0);
+}
+
+// Open the in-canvas value editor on dimension `di`. Projects the dimension's anchor
+// to screen pixels and hands the host (DesignCanvas) a commit/cancel pair that drive
+// the value through the existing set/cancel_dimension_value path. Falls back to the
+// modal pick-complete callback when no inline-edit host is wired.
+void DesignSketchTool::open_value_editor(int di)
+{
+    if (di < 0 || di >= int(m_dimensions.size())) return;
+    m_pending_dim = di;
+    if (!on_inline_edit) {
+        if (on_dimension_pick_complete) on_dimension_pick_complete(m_dimensions[di].value);
+        return;
+    }
+    const DimAnnot& a = m_dimensions[di];
+    // Anchor the field OVER the dimension (project its label/anchor to the viewport), same as
+    // the draw-then-edit tools and Constrain mode; fall back to the click point if it projects
+    // off-screen.
+    wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const wxPoint lp = world_to_screen_px(cam, m_plane.to_world(dim_anchor(a)));
+    const std::array<int, 4>& vp = cam.get_viewport();
+    if (lp.x >= vp[0] && lp.y >= vp[1] && lp.x <= vp[0] + vp[2] && lp.y <= vp[1] + vp[3])
+        px = lp;
+    on_inline_edit(px, a.value, dimtype_title(a.kind),
+                   [this](double v) { set_dimension_value(v); },
+                   [this]()         { cancel_dimension_value(); });
+}
+
+// In-canvas editor for a line's angle-to-horizontal. Unlike length/radius, a single
+// line's angle has no libslvs constraint here (SLVS_C_ANGLE is line-to-line), so the
+// commit rotates the segment GEOMETRICALLY about P0 to the typed degrees, then re-solves
+// — the angle is a free DoF, so the solver keeps the new orientation (mirrors the radius
+// handle). Length-constrained lines keep their length.
+void DesignSketchTool::open_angle_editor(int ei)
+{
+    if (ei < 0 || ei >= int(m_entities.size())) return;
+    if (m_entities[ei].type != SketchEntity::Type::Line) return;
+    if (!on_inline_edit) return;
+    DimAnnot a; a.kind = DimType::Angle; a.ea = ei;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, measure_dim(a), "Angle",
+                   [this, ei](double deg) { set_line_angle(ei, deg); },
+                   []()                   {});
+}
+
+// Type the defining number of whatever is selected. One entry point for every 2D element, so
+// the gesture is the same whichever tool drew it: point at it, right-click, type the value.
+//
+// This is what a sketch element was missing. Its endpoints could be dragged and its handles
+// grabbed, but its own quantities — a line's LENGTH, an arc's RADIUS, a circle's DIAMETER, the
+// ANGLE between two lines — were reachable only by arming the Dimension tool and re-picking the
+// geometry that was already selected. The machinery was all here (dimension_kind / dimension_
+// current / apply_dimension); the way in was not.
+bool DesignSketchTool::open_selection_dimension_editor()
+{
+    if (!on_inline_edit || !selection_valid()) return false;
+    const DimType k = dimension_kind();
+    if (k == DimType::None) return false;
+    const char* title = "Value";
+    switch (k) {
+    case DimType::Length:         title = "Length";   break;
+    case DimType::Radius:         title = "Radius";   break;
+    case DimType::Diameter:       title = "Diameter"; break;
+    case DimType::Angle:          title = "Angle";    break;
+    case DimType::Distance:       title = "Distance"; break;
+    case DimType::DistanceToLine: title = "Distance"; break;
+    default: break;
+    }
+    // Anchor over the geometry it belongs to, not the panel: the value belongs to the element.
+    DimAnnot a; a.kind = k;
+    a.ea = m_selection.empty() ? -1 : m_selection[0];
+    if (m_selection.size() > 1) a.eb = m_selection[1];
+    const Vec2d at = dim_anchor(a);
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    wxPoint px = world_to_screen_px(cam, m_plane.to_world(at));
+    if (px.x < 0 || px.y < 0) px = wxPoint(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, dimension_current(), title,
+                   [this](double v) { apply_dimension(v); },
+                   []()             {});
+    return true;
+}
+
+void DesignSketchTool::set_line_angle(int ei, double deg)
+{
+    if (ei < 0 || ei >= int(m_entities.size())) return;
+    SketchEntity& e = m_entities[ei];
+    if (e.type != SketchEntity::Type::Line) return;
+    const double L = (e.p1 - e.p0).norm();
+    if (L < 1e-9) return;
+    drop_orientation_constraints(ei, ei + 1);   // a typed angle overrides an inferred H/V
+    const double r = deg * M_PI / 180.0;
+    e.p1 = e.p0 + Vec2d(std::cos(r), std::sin(r)) * L;   // rotate about P0, keep length
+    resolve_live();
+}
+
+// Open the queued scalar quote at m_autoedit_dim_idx. Commit appends the driving dimension
+// AND advances to the next queued quote (deferred via CallAfter so the single SketchInlineEditor
+// fully unwinds its Enter handler before being reopened). Cancel (Esc) aborts the whole chain —
+// the shape is kept as drawn. This is what lets a rectangle edit Width THEN Height, a slot its
+// centre-distance THEN width, etc., instead of only the first dimension.
+void DesignSketchTool::open_next_autoedit_dim()
+{
+    if (!on_inline_edit || !m_active) { m_autoedit_dim_idx = -1; return; }
+    if (m_autoedit_dim_idx < 0 || m_autoedit_dim_idx >= int(m_autoedit_dims.size())) {
+        m_autoedit_dim_idx = -1;
+        return;
+    }
+    const AutoEditStep step = m_autoedit_dims[m_autoedit_dim_idx];
+    // Anchor the field OVER this dimension's label (project its plane-coords centre to the
+    // viewport), not at the last cursor spot — otherwise each field pops up in an unrelated
+    // screen position. Fall back to the cursor if the label projects off-screen.
+    // Anchor the field OVER this dimension's label (project its plane-coords centre to the
+    // viewport). A label can project OFF-screen (near-degenerate perspective divide when the
+    // sketch plane is viewed at a grazing angle), in which case we fall back to the cursor —
+    // but staggered by step index, so a shape's successive fields (rrect W/H/R) don't all
+    // stack on the exact same pixel and hide each other.
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const wxPoint lp = world_to_screen_px(cam, m_plane.to_world(step.label));
+    const std::array<int, 4>& vp = cam.get_viewport();
+    wxPoint px(m_last_mouse_x, m_last_mouse_y + m_autoedit_dim_idx * 34);
+    if (lp.x >= vp[0] && lp.y >= vp[1] && lp.x <= vp[0] + vp[2] && lp.y <= vp[1] + vp[3])
+        px = lp;
+    on_inline_edit(px, step.value, step.title,
+        [this, step](double v) {                 // commit: apply this dimension, then next
+            if (step.apply) step.apply(v);
+            ++m_autoedit_dim_idx;
+            wxGetApp().CallAfter([this] { open_next_autoedit_dim(); });
+        },
+        [this]() { m_autoedit_dim_idx = -1; });   // cancel: keep as drawn, stop the chain
+}
+
+// Polyline draw-then-edit: after each click places a chain vertex, refine THAT segment's
+// Length then Angle through the same AutoEditStep queue. The polyline batch-creates its
+// entities only when the chain ends, so here we edit the pending m_points vertex directly
+// (geometric): Length rescales it along the segment, Angle rotates it about the previous
+// vertex. The next click continues from the adjusted vertex. Same field/anchor/focus path as
+// every other tool — Enter advances Length->Angle, Esc keeps the segment as clicked.
+void DesignSketchTool::arm_polyline_segment_edit()
+{
+    const int k = int(m_points.size()) - 1;          // index of the just-placed vertex
+    if (k < 1 || !on_inline_edit) return;
+    const Vec2d a   = m_points[k - 1];               // segment anchor (previous vertex)
+    const Vec2d mid = 0.5 * (a + m_points[k]);       // label anchor = segment midpoint
+    const Vec2d d   = m_points[k] - a;
+    const double L  = d.norm();
+    if (L < 1e-9) return;
+    double deg = std::atan2(d.y(), d.x()) * 180.0 / M_PI; if (deg < 0.0) deg += 360.0;
+
+    m_autoedit_dims.clear();
+    m_autoedit_dims.push_back({ mid, L, [this, k, a](double len) {     // Length
+        if (k < int(m_points.size())) {
+            Vec2d dd = m_points[k] - a; const double n = dd.norm();
+            if (n > 1e-9 && len > 1e-9) m_points[k] = a + (len / n) * dd;
+        }
+    }, {}, "Length" });
+    m_autoedit_dims.push_back({ mid, deg, [this, k, a](double dg) {     // Angle
+        if (k < int(m_points.size())) {
+            const double len = (m_points[k] - a).norm();
+            const double r   = dg * M_PI / 180.0;
+            m_points[k] = a + len * Vec2d(std::cos(r), std::sin(r));
+        }
+    }, {}, "Angle" });
+    m_autoedit_dim_idx = 0;
+    wxGetApp().CallAfter([this] { open_next_autoedit_dim(); });
+}
+
+std::string DesignSketchTool::dimtype_title(DimType k) const {
+    switch (k) {
+        case DimType::Length:         return "Length";
+        case DimType::Diameter:       return "Diameter";
+        case DimType::Radius:         return "Radius";
+        case DimType::Angle:          return "Angle";
+        case DimType::Distance:       return "Distance";
+        case DimType::DistanceToLine: return "Distance";
+        default:                      return "Value";
+    }
+}
+
+// Draw-then-edit dispatcher: mirror the Select-mode quote-click logic, but target the
+// freshly-drawn selection's PRIMARY value and use the tentative (clean-cancel) path for
+// scalar quotes. Runs after render_live_quotes, so the live-quote state is populated.
+// Why a draw-then-edit chain did not start. Four early returns can swallow it, and from outside
+// they are indistinguishable: the shape appears, no field opens, and nothing says which guard
+// fired. check-gui-click-edit.py reports that as "a value field opened (nothing did)" for every
+// tool at once, which reads like a total product failure and is not necessarily one.
+static void trace_autoedit(const char* why, size_t n)
+{
+    if (!std::getenv("ORCA_CAD_UXTRACE")) return;
+    fprintf(stderr, "[UX] autoedit %s steps=%zu\n", why, n);
+    fflush(stderr);
+}
+
+void DesignSketchTool::open_primary_autoedit()
+{
+    if (!on_inline_edit) { trace_autoedit("skip: no on_inline_edit host", 0); return; }
+    if (m_awaiting_length) { trace_autoedit("skip: a field is already open", 0); return; }
+    if (!m_active) { trace_autoedit("skip: session ended before the deferred tick", 0); return; }
+
+    // Build ONE ordered list of edit steps covering EVERY characteristic dimension of the
+    // freshly-drawn shape — scalar quotes (constraint-based) AND geometric editors — so every
+    // 2D tool behaves like the rectangle: a linear sequence of value fields, each over its own
+    // label, Enter advances to the next, Esc keeps the shape as drawn. (Line keeps its own
+    // dedicated length field; Polyline/BSpline/Point have no two-click dimension set.)
+    m_autoedit_dims.clear();
+
+    // (1) Scalar quotes: rect Width+Height, slot Distance+Radius, circle/arc Radius, line
+    //     Length. The lone Angle quote (only a single Line emits one) becomes a GEOMETRIC
+    //     orientation step (set_line_angle, like the polygon angle) — so the Line tool gets
+    //     Length THEN Angle, same as the rectangle gets W then H.
+    for (const DimAnnot& q : m_live_quotes) {
+        if (q.kind == DimType::Angle) {
+            const int ei = q.ea;
+            m_autoedit_dims.push_back({ q.label_pos, measure_dim(q),
+                [this, ei](double v) { set_line_angle(ei, v); }, { ei }, "Angle" });
+            continue;
+        }
+        DimAnnot a = q;
+        a.value = measure_dim(a);
+        m_autoedit_dims.push_back({ a.label_pos, a.value,
+            [this, a](double v) mutable {
+                a.value = v;
+                a.con   = upsert_constraint(constraint_for(a));
+                upsert_dimension(a);
+                resolve_live();
+            }, { a.ea, a.eb }, dimtype_title(a.kind) });
+    }
+
+    // (2) Geometric editors (mutate geometry directly, no constraint). Each reads the CURRENT
+    //     feature/entity state inside apply(), so sequential edits compose correctly.
+    // Entities to highlight = the feature's whole [begin,end) span, so editing any of its
+    // characteristic dims lights up the shape it drives.
+    auto span = [this](int fi) {
+        std::vector<int> v;
+        if (fi >= 0 && fi < int(m_features.size()))
+            for (int k = m_features[fi].begin; k < m_features[fi].end; ++k) v.push_back(k);
+        return v;
+    };
+    if (m_live_poly_fi >= 0) {
+        const Feature& f = m_features[m_live_poly_fi];
+        const int fi = m_live_poly_fi;
+        if (f.begin >= 0 && f.begin < int(m_entities.size())) {
+            const double side = (m_entities[f.begin].p1 - m_entities[f.begin].p0).norm();
+            const Vec2d  sp   = m_entities[f.begin].p0 - f.c0;
+            double deg = std::atan2(sp.y(), sp.x()) * 180.0 / M_PI; if (deg < 0.0) deg += 360.0;
+            m_autoedit_dims.push_back({ m_live_poly_side_label,  side, [this, fi](double v){ set_polygon_side(fi, v); }, span(fi), "Side" });
+            m_autoedit_dims.push_back({ m_live_poly_angle_label, deg,  [this, fi](double v){ set_polygon_angle(fi, v); }, span(fi), "Angle" });
+        }
+    }
+    if (m_live_rrect_fi >= 0) {
+        const Feature& f = m_features[m_live_rrect_fi];
+        const int fi = m_live_rrect_fi;
+        const double w = std::abs(f.c1.x() - f.c0.x()), h = std::abs(f.c1.y() - f.c0.y()), r = f.param;
+        auto rr_w = [this, fi](double v){ const Feature& g = m_features[fi]; set_rounded_rect(fi, v, std::abs(g.c1.y()-g.c0.y()), g.param); };
+        auto rr_h = [this, fi](double v){ const Feature& g = m_features[fi]; set_rounded_rect(fi, std::abs(g.c1.x()-g.c0.x()), v, g.param); };
+        auto rr_r = [this, fi](double v){ const Feature& g = m_features[fi]; set_rounded_rect(fi, std::abs(g.c1.x()-g.c0.x()), std::abs(g.c1.y()-g.c0.y()), v); };
+        m_autoedit_dims.push_back({ m_live_rrect_w_label, w, rr_w, span(fi), "Width" });
+        m_autoedit_dims.push_back({ m_live_rrect_h_label, h, rr_h, span(fi), "Height" });
+        m_autoedit_dims.push_back({ m_live_rrect_r_label, r, rr_r, span(fi), "Radius" });
+    }
+    if (m_live_aslot_fi >= 0) {
+        const Feature& f = m_features[m_live_aslot_fi];
+        const int fi = m_live_aslot_fi;
+        const double Rc = (f.c1 - f.c0).norm(), fw = 2.0 * f.param;
+        m_autoedit_dims.push_back({ m_live_aslot_r_label, Rc, [this, fi](double v){ const Feature& g = m_features[fi]; set_arc_slot(fi, v, g.param); }, span(fi), "Radius" });
+        m_autoedit_dims.push_back({ m_live_aslot_w_label, fw, [this, fi](double v){ const Feature& g = m_features[fi]; set_arc_slot(fi, (g.c1-g.c0).norm(), std::max(1e-3, v*0.5)); }, span(fi), "Width" });
+    }
+    if (m_live_slot_fi >= 0) {
+        const Feature& f = m_features[m_live_slot_fi];
+        const int fi = m_live_slot_fi;
+        // Slot dims, in order: (1) inter-centre distance, (2) radius (= half-width), (3) angle.
+        const Vec2d  d  = f.c1 - f.c0;
+        const double Lc = d.norm();
+        double deg = std::atan2(d.y(), d.x()) * 180.0 / M_PI; if (deg < 0.0) deg += 360.0;
+        m_autoedit_dims.push_back({ m_live_slot_len_label, Lc, [this, fi](double v){ const Feature& g = m_features[fi]; set_slot(fi, v, g.param); }, span(fi), "Length" });
+        m_autoedit_dims.push_back({ m_live_slot_w_label, f.param, [this, fi](double v){ const Feature& g = m_features[fi]; set_slot(fi, (g.c1-g.c0).norm(), std::max(1e-3, v)); }, span(fi), "Radius" });
+        m_autoedit_dims.push_back({ m_live_slot_angle_label, deg, [this, fi](double v){ set_slot_angle(fi, v); }, span(fi), "Angle" });
+    }
+    if (m_live_arc_ei >= 0) {   // arc Radius is already a scalar step above; add its sweep angle
+        const int ei = m_live_arc_ei;
+        const SketchEntity& e = m_entities[ei];
+        const double swdeg = std::abs(e.end_angle - e.start_angle) * 180.0 / M_PI;
+        m_autoedit_dims.push_back({ m_live_arc_angle_label, swdeg, [this, ei](double v){ set_arc_sweep(ei, v); }, { ei }, "Angle" });
+    }
+    if (m_live_ellipse_ei >= 0) {
+        const int ei = m_live_ellipse_ei;
+        const SketchEntity& e = m_entities[ei];
+        m_autoedit_dims.push_back({ m_live_ellipse_major_label, e.radius, [this, ei](double v){ set_ellipse_axis(ei, true,  v); }, { ei }, "Major" });
+        m_autoedit_dims.push_back({ m_live_ellipse_minor_label, e.rminor, [this, ei](double v){ set_ellipse_axis(ei, false, v); }, { ei }, "Minor" });
+        if (e.type == SketchEntity::Type::EllipseArc) {   // + included sweep
+            const double swdeg = std::abs(e.end_angle - e.start_angle) * 180.0 / M_PI;
+            m_autoedit_dims.push_back({ m_live_ellipsearc_sweep_label, swdeg,
+                [this, ei](double v){ set_ellipsearc_sweep(ei, v); }, { ei }, "Angle" });
+        }
+    }
+    if (m_live_obrect_fi >= 0) {   // oblique rect: W,H already added as scalars; + orientation
+        const int fi = m_live_obrect_fi;
+        const Feature& f = m_features[fi];
+        const SketchEntity& e0 = m_entities[f.begin];
+        double adeg = std::atan2(e0.p1.y() - e0.p0.y(), e0.p1.x() - e0.p0.x()) * 180.0 / M_PI;
+        if (adeg < 0.0) adeg += 360.0;
+        m_autoedit_dims.push_back({ m_live_obrect_angle_label, adeg,
+            [this, fi](double v){ set_rect_angle(fi, v); }, span(fi), "Angle" });
+    }
+
+    trace_autoedit(m_autoedit_dims.empty() ? "built NO steps (no live quote matched)" : "opening",
+                   m_autoedit_dims.size());
+    if (!m_autoedit_dims.empty()) {
+        m_autoedit_dim_idx = 0;
+        open_next_autoedit_dim();
+    }
+}
+
+// A regular polygon is N raw lines with no centre entity, so (like the line angle) its
+// side and orientation edits transform the whole loop GEOMETRICALLY about its centre.
+void DesignSketchTool::open_polygon_side_editor(int fi)
+{
+    if (fi < 0 || fi >= int(m_features.size()) || !on_inline_edit) return;
+    const Feature& f = m_features[fi];
+    if (f.begin < 0 || f.begin >= int(m_entities.size())) return;
+    const double side = (m_entities[f.begin].p1 - m_entities[f.begin].p0).norm();
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, side, "Side",
+                   [this, fi](double v) { set_polygon_side(fi, v); },
+                   []()                 {});
+}
+
+void DesignSketchTool::open_polygon_angle_editor(int fi)
+{
+    if (fi < 0 || fi >= int(m_features.size()) || !on_inline_edit) return;
+    const Feature& f = m_features[fi];
+    if (f.begin < 0 || f.begin >= int(m_entities.size())) return;
+    const Vec2d sp = m_entities[f.begin].p0 - f.c0;          // centre -> vertex0 spoke
+    double deg = std::atan2(sp.y(), sp.x()) * 180.0 / M_PI;
+    if (deg < 0.0) deg += 360.0;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, deg, "Angle",
+                   [this, fi](double v) { set_polygon_angle(fi, v); },
+                   []()                 {});
+}
+
+// Scale the loop uniformly about its centre so an edge equals `side`. For a regular
+// n-gon, circumradius R = side / (2 sin(pi/n)).
+void DesignSketchTool::set_polygon_side(int fi, double side)
+{
+    if (fi < 0 || fi >= int(m_features.size()) || side < 1e-6) return;
+    const int n = std::max(3, m_features[fi].sides);
+    const double R = side / (2.0 * std::sin(M_PI / double(n)));
+    set_polygon_radius(fi, R);
+}
+
+// Remove orientation constraints touching [begin,end). A pure rotation makes inferred
+// per-edge Horizontal/Vertical (and Parallel/Perp/Angle/Lock) inconsistent, so leaving
+// them in would make resolve_live collapse the shape to satisfy them.
+void DesignSketchTool::drop_orientation_constraints(int begin, int end)
+{
+    using CT = SketchConstraintType;
+    auto orient = [](CT t) {
+        return t == CT::Horizontal || t == CT::Vertical || t == CT::Parallel ||
+               t == CT::Perpendicular || t == CT::Angle || t == CT::LockX || t == CT::LockY;
+    };
+    auto in = [&](int e) { return e >= begin && e < end; };
+    std::vector<int> remap(m_constraints.size(), -1);
+    std::vector<SketchEntityConstraintDef> kept;
+    kept.reserve(m_constraints.size());
+    for (int i = 0; i < int(m_constraints.size()); ++i) {
+        const SketchEntityConstraintDef& c = m_constraints[i];
+        if (orient(c.type) && (in(c.ea) || in(c.eb))) continue;   // drop
+        remap[i] = int(kept.size());
+        kept.push_back(c);
+    }
+    if (kept.size() == m_constraints.size()) return;             // nothing dropped
+    m_constraints.swap(kept);
+    for (DimAnnot& a : m_dimensions)                              // fix cached con indices
+        if (a.con >= 0) a.con = (a.con < int(remap.size())) ? remap[a.con] : -1;
+}
+
+void DesignSketchTool::drop_constraints_referencing(int ei)
+{
+    std::vector<int> remap(m_constraints.size(), -1);
+    std::vector<SketchEntityConstraintDef> kept;
+    kept.reserve(m_constraints.size());
+    for (int i = 0; i < int(m_constraints.size()); ++i) {
+        const SketchEntityConstraintDef& c = m_constraints[i];
+        if (c.ea == ei || c.eb == ei || c.ec == ei) continue;    // drop refs to the cut entity
+        remap[i] = int(kept.size());
+        kept.push_back(c);
+    }
+    if (kept.size() == m_constraints.size()) return;
+    m_constraints.swap(kept);
+    for (DimAnnot& a : m_dimensions)
+        if (a.con >= 0) a.con = (a.con < int(remap.size())) ? remap[a.con] : -1;
+}
+
+// Onshape scissors on the live sketch: cut the picked entity at its nearest intersection.
+// trim_entity/extend_entity mutate the subject in place (slide one endpoint) given the other
+// entities + the pick point — no entity is added/removed, so indices stay stable.
+bool DesignSketchTool::apply_live_trim(const Vec2d& p, double tol, bool extend)
+{
+    double best = 1e30; int bi = -1;
+    for (size_t i = 0; i < m_entities.size(); ++i) {
+        const double d = entity_pick_dist(p, m_entities[i]);
+        if (d < best) { best = d; bi = int(i); }
+    }
+    if (bi < 0 || best > tol) return false;
+    using Ty = SketchEntity::Type;
+    const Ty st = m_entities[bi].type;
+    const bool subject_ok = extend ? (st == Ty::Line || st == Ty::Arc)
+                                   : (st == Ty::Line || st == Ty::Arc || st == Ty::Circle);
+    if (!subject_ok) return false;
+    std::vector<SketchEntity> others;
+    others.reserve(m_entities.size());
+    for (size_t i = 0; i < m_entities.size(); ++i)
+        if (int(i) != bi) others.push_back(m_entities[i]);
+    const bool ok = extend ? SketchEngine::extend_entity(m_entities[bi], others, p)
+                           : SketchEngine::trim_entity(m_entities[bi], others, p);
+    if (!ok) return false;
+    drop_constraints_referencing(bi);   // the slid endpoint invalidates this entity's constraints
+    return true;
+}
+
+// Hover preview for the Trim/Extend scissors: replay apply_live_trim's pick and the engine
+// cut on a COPY of the subject, then diff the copy against the original to recover the exact
+// sub-portion a click would remove (Trim) / add (Extend). Pure computation, mutates nothing.
+bool DesignSketchTool::compute_trim_preview(const Vec2d& p, double tol, bool extend,
+                                            int& subject_ei, std::vector<Vec2d>& removed_poly) const
+{
+    subject_ei = -1;
+    removed_poly.clear();
+
+    double best = 1e30; int bi = -1;
+    for (size_t i = 0; i < m_entities.size(); ++i) {
+        const double d = entity_pick_dist(p, m_entities[i]);
+        if (d < best) { best = d; bi = int(i); }
+    }
+    if (bi < 0 || best > tol) return false;
+
+    using Ty = SketchEntity::Type;
+    const Ty st = m_entities[bi].type;
+    const bool subject_ok = extend ? (st == Ty::Line || st == Ty::Arc)
+                                   : (st == Ty::Line || st == Ty::Arc || st == Ty::Circle);
+    if (!subject_ok) return false;
+
+    std::vector<SketchEntity> others;
+    others.reserve(m_entities.size());
+    for (size_t i = 0; i < m_entities.size(); ++i)
+        if (int(i) != bi) others.push_back(m_entities[i]);
+
+    const SketchEntity& orig = m_entities[bi];
+    SketchEntity trimmed = orig;                          // cut on the copy, never the live entity
+    const bool ok = extend ? SketchEngine::extend_entity(trimmed, others, p)
+                           : SketchEngine::trim_entity(trimmed, others, p);
+    if (!ok) return false;
+
+    // The highlighted portion is where `trimmed` differs from `orig`: the dropped sub-segment
+    // (Trim) or the grown one (Extend). Rebuild it as a temp entity and sample its polyline.
+    const double EPS2 = 1e-14;     // squared plane-unit endpoint tolerance
+    const double AEPS = 1e-7;      // radian tolerance
+    bool closed = false;
+
+    if (orig.type == Ty::Line) {
+        SketchEntity seg = orig;
+        if ((trimmed.p0 - orig.p0).squaredNorm() > EPS2) {
+            seg.p0 = orig.p0; seg.p1 = trimmed.p0;        // start endpoint moved
+        } else if ((trimmed.p1 - orig.p1).squaredNorm() > EPS2) {
+            seg.p0 = trimmed.p1; seg.p1 = orig.p1;        // end endpoint moved
+        } else {
+            return false;                                  // nothing changed
+        }
+        removed_poly = entity_polyline(seg, closed);
+    } else if (orig.type == Ty::Arc) {
+        SketchEntity arc = orig;                           // same centre/radius
+        if (std::abs(trimmed.start_angle - orig.start_angle) > AEPS) {
+            arc.start_angle = orig.start_angle; arc.end_angle = trimmed.start_angle;
+        } else if (std::abs(trimmed.end_angle - orig.end_angle) > AEPS) {
+            arc.start_angle = trimmed.end_angle; arc.end_angle = orig.end_angle;
+        } else {
+            return false;
+        }
+        removed_poly = entity_polyline(arc, closed);
+    } else if (orig.type == Ty::Circle) {
+        // Trim opens the Circle into the kept Arc [start,end]; the removed gap is its
+        // complement, swept from the kept arc's end round to its start.
+        if (trimmed.type != Ty::Arc) return false;
+        SketchEntity gap = orig;
+        gap.type        = Ty::Arc;
+        gap.start_angle = trimmed.end_angle;
+        gap.end_angle   = trimmed.start_angle + 2.0 * M_PI;
+        removed_poly = entity_polyline(gap, closed);
+    } else {
+        return false;
+    }
+
+    if (removed_poly.size() < 2) return false;
+    subject_ei = bi;
+    return true;
+}
+
+// Rotate the whole loop about its centre so the centre->vertex0 spoke points at `deg`
+// (degrees from +X).
+void DesignSketchTool::set_polygon_angle(int fi, double deg)
+{
+    if (fi < 0 || fi >= int(m_features.size())) return;
+    Feature& f = m_features[fi];
+    if (f.begin < 0 || f.begin >= int(m_entities.size())) return;
+    const Vec2d c = f.c0;
+    const Vec2d sp = m_entities[f.begin].p0 - c;          // centre -> vertex0
+    if (sp.squaredNorm() < 1e-12) return;
+    const double cur = std::atan2(sp.y(), sp.x());
+    const double da  = deg * M_PI / 180.0 - cur;
+    drop_orientation_constraints(f.begin, f.end);         // rotation invalidates edge H/V
+    const double ca = std::cos(da), sa = std::sin(da);
+    // -> Vec2d is REQUIRED: an auto return deduces an Eigen expression template that holds
+    // a reference to the destroyed `c + Vec2d(...)` temporary (dangling -> garbage coords).
+    auto rot = [&](const Vec2d& pt) -> Vec2d { const Vec2d r = pt - c;
+        return c + Vec2d(r.x() * ca - r.y() * sa, r.x() * sa + r.y() * ca); };
+    for (int i = f.begin; i < f.end && i < int(m_entities.size()); ++i) {
+        SketchEntity& e = m_entities[i];
+        if (e.type != SketchEntity::Type::Line) continue;
+        e.p0 = rot(e.p0); e.p1 = rot(e.p1);
+    }
+    // Do NOT re-solve: the rotated geometry is already a correct regular polygon, and the
+    // inferred loop (redundant Coincident, now with no H/V anchor) collapses to a point
+    // under libslvs. We only drop the stale edge H/V (above) so a later commit-solve stays
+    // sane; the display renders the mutated entities directly.
+}
+
+// Drag a polygon vertex keeping the loop regular: scale + rotate the whole polygon
+// about its centroid so the grabbed vertex lands on `target`. This adjusts both the
+// circumradius (|target-centroid|) and the orientation (its direction) at once.
+void DesignSketchTool::drag_polygon_vertex(int fi, int ei, SketchPointRole role, const Vec2d& target)
+{
+    if (fi < 0 || fi >= int(m_features.size())) return;
+    Feature& f = m_features[fi];
+    if (f.begin < 0 || f.end > int(m_entities.size())) return;
+    // Centroid of the loop = the regular polygon's centre (robust if it was moved).
+    Vec2d c(0, 0); int n = 0;
+    for (int i = f.begin; i < f.end; ++i)
+        if (m_entities[i].type == SketchEntity::Type::Line) { c += m_entities[i].p0; ++n; }
+    if (n == 0) return;
+    c /= double(n);
+    Vec2d vpos;
+    if (!point_at(ei, role, vpos)) return;
+    const Vec2d cur = vpos - c;                 // current grabbed-vertex spoke
+    const Vec2d tgt = target - c;               // desired spoke
+    const double curR = cur.norm(), newR = tgt.norm();
+    if (curR < 1e-9 || newR < 1e-6) return;
+    const double s  = newR / curR;
+    const double da = std::atan2(tgt.y(), tgt.x()) - std::atan2(cur.y(), cur.x());
+    const double ca = std::cos(da), sa = std::sin(da);
+    auto tf = [&](const Vec2d& p) -> Vec2d { const Vec2d r = (p - c) * s;   // -> Vec2d: avoid
+        return c + Vec2d(r.x() * ca - r.y() * sa, r.x() * sa + r.y() * ca); };  // Eigen dangling
+
+    for (int i = f.begin; i < f.end; ++i) {
+        SketchEntity& e = m_entities[i];
+        if (e.type != SketchEntity::Type::Line) continue;
+        e.p0 = tf(e.p0); e.p1 = tf(e.p1);
+    }
+    f.c0 = c; f.param = newR;
+    drop_orientation_constraints(f.begin, f.end);   // the drag rotates -> edge H/V invalid
+    // No re-solve (see set_polygon_angle): the transformed geometry is already a correct
+    // regular polygon; solving the anchorless redundant loop would collapse it.
+}
+
+void DesignSketchTool::set_polygon_radius(int fi, double R)
+{
+    if (fi < 0 || fi >= int(m_features.size()) || R < 1e-6) return;
+    Feature& f = m_features[fi];
+    if (f.begin < 0 || f.begin >= int(m_entities.size())) return;
+    const Vec2d  c    = f.c0;
+    const double curR = (m_entities[f.begin].p0 - c).norm();
+    if (curR < 1e-9) return;
+    const double s = R / curR;                       // uniform scale about the centre
+    for (int i = f.begin; i < f.end && i < int(m_entities.size()); ++i) {
+        SketchEntity& e = m_entities[i];
+        if (e.type != SketchEntity::Type::Line) continue;
+        e.p0 = c + (e.p0 - c) * s;
+        e.p1 = c + (e.p1 - c) * s;
+    }
+    f.param = R;
+    // Geometric only (no solve): consistent with the rotation edits, and avoids collapsing
+    // the loop if its H/V anchors were already dropped by a prior rotation.
+}
+
+void DesignSketchTool::open_arc_angle_editor(int ei)
+{
+    if (ei < 0 || ei >= int(m_entities.size()) || !on_inline_edit) return;
+    const SketchEntity& e = m_entities[ei];
+    if (e.type != SketchEntity::Type::Arc) return;
+    double swdeg = std::abs(e.end_angle - e.start_angle) * 180.0 / M_PI;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, swdeg, "Angle",
+                   [this, ei](double v) { set_arc_sweep(ei, v); },
+                   []()                 {});
+}
+
+// Set the arc's included (sweep) angle to `deg`, keeping the start point and radius fixed
+// and rotating the end point about the centre. Geometric (SLVS angle is line-to-line), so
+// no re-solve; the mutated entity renders directly. Direction (CCW/CW) of the original
+// sweep is preserved.
+void DesignSketchTool::set_arc_sweep(int ei, double deg)
+{
+    if (ei < 0 || ei >= int(m_entities.size())) return;
+    SketchEntity& e = m_entities[ei];
+    if (e.type != SketchEntity::Type::Arc || e.radius < 1e-6) return;
+    double sweep = std::max(1e-3, std::min(deg, 359.999)) * M_PI / 180.0;
+    const double sign = (e.end_angle >= e.start_angle) ? 1.0 : -1.0;
+    e.end_angle = e.start_angle + sign * sweep;
+    e.p1 = e.center + e.radius * Vec2d(std::cos(e.end_angle), std::sin(e.end_angle));
+    resolve_live();
+}
+
+// Drag one of the arc's three handles. Roles are split so each grip changes ONE property
+// (Onshape-like): Center -> translate; START point (P0) -> radius only; END point (P1) ->
+// sweep angle only. Geometric (mutates the entity directly), then re-solve for any
+// coincident constraints on the arc endpoints.
+void DesignSketchTool::drag_arc_handle(int ei, SketchPointRole role, const Vec2d& target)
+{
+    if (ei < 0 || ei >= int(m_entities.size())) return;
+    SketchEntity& e = m_entities[ei];
+    if (e.type != SketchEntity::Type::Arc) return;
+    if (role == SketchPointRole::Center) {
+        const Vec2d d = target - e.center;            // rigid translate, keep R + angles
+        e.center = target; e.p0 += d; e.p1 += d;
+    } else if (role == SketchPointRole::P0) {         // start = RADIUS handle (keep angles)
+        const double R = (target - e.center).norm();
+        if (R < 1e-6) return;
+        e.radius = R;
+        e.p0 = e.center + R * Vec2d(std::cos(e.start_angle), std::sin(e.start_angle));
+        e.p1 = e.center + R * Vec2d(std::cos(e.end_angle),   std::sin(e.end_angle));
+    } else if (role == SketchPointRole::P1) {         // end = ANGLE handle (keep radius)
+        const Vec2d d = target - e.center;
+        if (d.squaredNorm() < 1e-12) return;
+        // Keep the CCW sweep continuous (0,2pi) so the arc never flips to its complement.
+        double da = std::atan2(d.y(), d.x()) - e.start_angle;
+        while (da < 0.0)            da += 2.0 * M_PI;
+        while (da >= 2.0 * M_PI)    da -= 2.0 * M_PI;
+        e.end_angle = e.start_angle + da;
+        e.p1 = e.center + e.radius * Vec2d(std::cos(e.end_angle), std::sin(e.end_angle));
+    }
+    resolve_live();
+}
+
+// Drag an elliptical-arc grip. Center rigidly translates (endpoints + frame move with it);
+// P0/P1 set the sweep start/end to the cursor's parametric angle on the ellipse, keeping
+// the ellipse shape (a/b/phi). Geometric, then resolve_live().
+void DesignSketchTool::drag_ellipsearc_handle(int ei, SketchPointRole role, const Vec2d& target)
+{
+    if (ei < 0 || ei >= int(m_entities.size())) return;
+    SketchEntity& e = m_entities[ei];
+    if (e.type != SketchEntity::Type::EllipseArc) return;
+    if (role == SketchPointRole::Center) {
+        const Vec2d d = target - e.center;
+        e.center = target; e.p0 += d; e.p1 += d;
+    } else if (role == SketchPointRole::P0 || role == SketchPointRole::P1) {
+        const double t = ellipse_param_of(e.center, e.radius, e.rminor, e.rotation, target);
+        if (role == SketchPointRole::P0) {
+            e.start_angle = t;
+            e.p0 = ellipse_point(e.center, e.radius, e.rminor, e.rotation, t);
+        } else {
+            // Keep the CCW sweep (end strictly after start) so the arc never inverts.
+            double t1 = t; while (t1 <= e.start_angle) t1 += 2.0 * M_PI;
+            e.end_angle = t1;
+            e.p1 = ellipse_point(e.center, e.radius, e.rminor, e.rotation, t1);
+        }
+    }
+    resolve_live();
+}
+
+void DesignSketchTool::open_ellipse_axis_editor(int ei, bool major)
+{
+    if (ei < 0 || ei >= int(m_entities.size()) || !on_inline_edit) return;
+    const SketchEntity& e = m_entities[ei];
+    if (e.type != SketchEntity::Type::Ellipse && e.type != SketchEntity::Type::EllipseArc) return;
+    const double v = major ? e.radius : e.rminor;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, v, major ? "Major" : "Minor",
+                   [this, ei, major](double nv) { set_ellipse_axis(ei, major, nv); },
+                   []()                         {});
+}
+
+// Set a semi-axis to `v`: major -> e.radius, minor -> e.rminor; keep OCCT a >= b.
+void DesignSketchTool::set_ellipse_axis(int ei, bool major, double v)
+{
+    if (ei < 0 || ei >= int(m_entities.size()) || v < 1e-6) return;
+    SketchEntity& e = m_entities[ei];
+    if (e.type != SketchEntity::Type::Ellipse && e.type != SketchEntity::Type::EllipseArc) return;
+    if (major) e.radius = std::max(v, e.rminor);
+    else       e.rminor = std::min(v, e.radius);
+    if (e.type == SketchEntity::Type::EllipseArc) {   // endpoints ride the reshaped frame
+        e.p0 = ellipse_point(e.center, e.radius, e.rminor, e.rotation, e.start_angle);
+        e.p1 = ellipse_point(e.center, e.radius, e.rminor, e.rotation, e.end_angle);
+    }
+    resolve_live();
+}
+
+// Set an elliptical arc's included (parametric) sweep, keeping the start fixed and moving the
+// end. Geometric (mirrors set_arc_sweep), then resolve_live for any endpoint coincidences.
+void DesignSketchTool::set_ellipsearc_sweep(int ei, double deg)
+{
+    if (ei < 0 || ei >= int(m_entities.size())) return;
+    SketchEntity& e = m_entities[ei];
+    if (e.type != SketchEntity::Type::EllipseArc) return;
+    const double sweep = std::max(1e-3, std::min(deg, 359.999)) * M_PI / 180.0;
+    const double sign  = (e.end_angle >= e.start_angle) ? 1.0 : -1.0;
+    e.end_angle = e.start_angle + sign * sweep;
+    e.p1 = ellipse_point(e.center, e.radius, e.rminor, e.rotation, e.end_angle);
+    resolve_live();
+}
+
+// Rotate an oblique rectangle to an absolute orientation (angle of edge0 to +X), pivoting on
+// its anchor corner f.c0. Geometric, mirrors set_polygon_angle: drop the now-inconsistent edge
+// H/V first, rotate every member point + the opposite corner, and DON'T re-solve (the rotated
+// loop is already consistent; a length Distance the user may have set is rotation-invariant).
+void DesignSketchTool::set_rect_angle(int fi, double deg)
+{
+    if (fi < 0 || fi >= int(m_features.size())) return;
+    Feature& f = m_features[fi];
+    if (f.begin < 0 || f.end > int(m_entities.size()) || f.end <= f.begin) return;
+    const SketchEntity& e0 = m_entities[f.begin];
+    const Vec2d d0 = e0.p1 - e0.p0;
+    if (d0.squaredNorm() < 1e-12) return;
+    const double da = deg * M_PI / 180.0 - std::atan2(d0.y(), d0.x());
+    drop_orientation_constraints(f.begin, f.end);
+    const Vec2d pivot = f.c0;
+    const double ca = std::cos(da), sa = std::sin(da);
+    // -> Vec2d REQUIRED (see set_polygon_angle): an auto return deduces an Eigen expression
+    // template referencing the destroyed temporary -> dangling.
+    auto rot = [&](const Vec2d& pt) -> Vec2d { const Vec2d r = pt - pivot;
+        return pivot + Vec2d(r.x() * ca - r.y() * sa, r.x() * sa + r.y() * ca); };
+    for (int i = f.begin; i < f.end && i < int(m_entities.size()); ++i) {
+        SketchEntity& e = m_entities[i];
+        e.p0 = rot(e.p0); e.p1 = rot(e.p1);
+    }
+    f.c1 = rot(f.c1);   // keep the opposite corner consistent for later W/H quotes
+}
+
+// Screen anchor for a Constrain-mode value field: over the picked geometry (its representative
+// point — circle/arc centre, else segment midpoint; averaged when two entities are picked),
+// projected to the viewport. Lets a dimensional constraint's field open ON the geometry like
+// the draw-then-edit tools, instead of floating at viewport centre. False if no valid pick or
+// it projects off-screen (caller falls back to centre).
+bool DesignSketchTool::constrain_value_anchor(wxPoint& out) const
+{
+    if (m_pick0 < 0 || m_pick0 >= int(m_entities.size())) return false;
+    auto rep = [](const SketchEntity& e) -> Vec2d {
+        using T = SketchEntity::Type;
+        if (e.type == T::Circle || e.type == T::Arc ||
+            e.type == T::Ellipse || e.type == T::EllipseArc) return e.center;
+        return 0.5 * (e.p0 + e.p1);
+    };
+    Vec2d p = rep(m_entities[m_pick0]);
+    if (m_pick1 >= 0 && m_pick1 < int(m_entities.size()))
+        p = 0.5 * (p + rep(m_entities[m_pick1]));
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const wxPoint sp = world_to_screen_px(cam, m_plane.to_world(p));
+    const std::array<int, 4>& vp = cam.get_viewport();
+    if (sp.x < vp[0] || sp.y < vp[1] || sp.x > vp[0] + vp[2] || sp.y > vp[1] + vp[3]) return false;
+    out = sp;
+    return true;
+}
+
+void DesignSketchTool::open_rounded_rect_editor(int fi, int which)
+{
+    if (fi < 0 || fi >= int(m_features.size()) || !on_inline_edit) return;
+    const Feature& f = m_features[fi];
+    const double w = std::abs(f.c1.x() - f.c0.x());
+    const double h = std::abs(f.c1.y() - f.c0.y());
+    const double r = f.param;
+    const double v = (which == 0) ? w : (which == 1) ? h : r;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, v, which == 0 ? "Width" : which == 1 ? "Height" : "Radius",
+        [this, fi, which](double nv) {
+            const Feature& g = m_features[fi];
+            double gw = std::abs(g.c1.x() - g.c0.x());
+            double gh = std::abs(g.c1.y() - g.c0.y());
+            double gr = g.param;
+            if (which == 0) gw = nv; else if (which == 1) gh = nv; else gr = nv;
+            set_rounded_rect(fi, gw, gh, gr);
+        },
+        []() {});
+}
+
+// Rebuild the rounded-rect's 8 entities in place for a new width/height/fillet radius,
+// keeping the min corner (c0) fixed. Geometric (entity order/count preserved so constraint
+// refs stay valid); fillet clamped to (0, min(w,h)/2].
+void DesignSketchTool::set_rounded_rect(int fi, double w, double h, double r)
+{
+    if (fi < 0 || fi >= int(m_features.size())) return;
+    Feature& f = m_features[fi];
+    if (f.begin < 0 || f.end > int(m_entities.size()) || f.end <= f.begin) return;
+    w = std::max(w, 1e-3); h = std::max(h, 1e-3);
+    r = std::max(1e-3, std::min(r, std::min(w, h) * 0.5 - 1e-4));
+    const double xmin = std::min(f.c0.x(), f.c1.x()), ymin = std::min(f.c0.y(), f.c1.y());
+    const double xmax = xmin + w, ymax = ymin + h;
+    std::vector<SketchEntity> rebuilt = rounded_rect_entities(xmin, ymin, xmax, ymax, r);
+    if (int(rebuilt.size()) != f.end - f.begin) return;   // count must match to keep con refs
+    for (int i = 0; i < int(rebuilt.size()); ++i) {
+        rebuilt[i].construction = m_entities[f.begin + i].construction;   // preserve flag
+        m_entities[f.begin + i] = rebuilt[i];
+    }
+    f.c0 = Vec2d(xmin, ymin); f.c1 = Vec2d(xmax, ymax); f.param = r;
+    resolve_live();
+}
+
+void DesignSketchTool::open_arc_slot_editor(int fi, bool radius)
+{
+    if (fi < 0 || fi >= int(m_features.size()) || !on_inline_edit) return;
+    const Feature& f = m_features[fi];
+    const double Rc = (f.c1 - f.c0).norm();
+    const double v  = radius ? Rc : (2.0 * f.param);     // width quote shows the FULL width
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, v, radius ? "Radius" : "Width",
+        [this, fi, radius](double nv) {
+            const Feature& g = m_features[fi];
+            const double gRc = (g.c1 - g.c0).norm();
+            if (radius) set_arc_slot(fi, nv, g.param);
+            else        set_arc_slot(fi, gRc, std::max(1e-3, nv * 0.5));  // full width -> half
+        },
+        []() {});
+}
+
+// Rebuild the arc-slot's 4 arcs in place for a new centreline radius / half-width. Centre
+// + the two centreline directions are kept (the end direction is recovered from the cap@E
+// arc centre). Geometric; entity count preserved so constraint refs stay valid.
+void DesignSketchTool::set_arc_slot(int fi, double Rc, double w)
+{
+    if (fi < 0 || fi >= int(m_features.size())) return;
+    Feature& f = m_features[fi];
+    if (f.begin < 0 || f.end > int(m_entities.size()) || f.end - f.begin != 4) return;
+    const Vec2d center = f.c0;
+    Vec2d dirS = f.c1 - center;
+    const Vec2d Ec = m_entities[f.begin + 1].center;     // cap@E centre = centreline end
+    Vec2d dirE = Ec - center;
+    if (dirS.squaredNorm() < 1e-12 || dirE.squaredNorm() < 1e-12) return;
+    dirS.normalize(); dirE.normalize();
+    Rc = std::max(Rc, 2e-3);
+    w  = std::max(1e-3, std::min(w, Rc - 1e-3));         // make_arc_slot needs w < Rc
+    std::vector<SketchEntity> rebuilt =
+        make_arc_slot(center, center + Rc * dirS, center + Rc * dirE, w);
+    if (int(rebuilt.size()) != 4) return;
+    for (int i = 0; i < 4; ++i) {
+        rebuilt[i].construction = m_entities[f.begin + i].construction;
+        m_entities[f.begin + i] = rebuilt[i];
+    }
+    f.c1 = center + Rc * dirS; f.param = w;
+    resolve_live();
+}
+
+// Open the inline editor for a straight slot's dimension: which 0 = inter-centre distance,
+// 1 = radius (half-width), 2 = centreline angle. Drives set_slot / set_slot_angle geometrically.
+void DesignSketchTool::open_slot_editor(int fi, int which)
+{
+    if (fi < 0 || fi >= int(m_features.size()) || !on_inline_edit) return;
+    const Feature& f = m_features[fi];
+    const Vec2d  d = f.c1 - f.c0;
+    double deg = std::atan2(d.y(), d.x()) * 180.0 / M_PI; if (deg < 0.0) deg += 360.0;
+    const double v = (which == 0) ? d.norm() : (which == 1) ? f.param : deg;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, v, which == 0 ? "Length" : which == 1 ? "Radius" : "Angle",
+        [this, fi, which](double nv) {
+            const Feature& g = m_features[fi];
+            if      (which == 0) set_slot(fi, nv, g.param);
+            else if (which == 1) set_slot(fi, (g.c1 - g.c0).norm(), std::max(1e-3, nv));
+            else                 set_slot_angle(fi, nv);
+        },
+        []() {});
+}
+
+// Rebuild the straight slot's 4 entities in place for a new centreline length / half-width.
+// Centre c0 and the centreline direction are kept; only c1 (length) or param (width) change.
+// Geometric; entity count preserved so constraint refs stay valid.
+void DesignSketchTool::set_slot(int fi, double length, double w)
+{
+    if (fi < 0 || fi >= int(m_features.size())) return;
+    Feature& f = m_features[fi];
+    if (f.begin < 0 || f.end > int(m_entities.size()) || f.end - f.begin != 4) return;
+    Vec2d dir = f.c1 - f.c0;
+    if (dir.squaredNorm() < 1e-12) return;
+    dir.normalize();
+    length = std::max(length, 2e-3);
+    w      = std::max(1e-3, w);
+    const Vec2d c0 = f.c0, c1 = f.c0 + length * dir;
+    std::vector<SketchEntity> rebuilt = make_slot(c0, c1, w);
+    if (int(rebuilt.size()) != 4) return;
+    for (int i = 0; i < 4; ++i) {
+        rebuilt[i].construction = m_entities[f.begin + i].construction;
+        m_entities[f.begin + i] = rebuilt[i];
+    }
+    f.c1 = c1; f.param = w;
+    resolve_live();
+}
+
+// Rotate a straight slot about c0 to a new centreline angle (degrees), keeping length + radius.
+void DesignSketchTool::set_slot_angle(int fi, double deg)
+{
+    if (fi < 0 || fi >= int(m_features.size())) return;
+    Feature& f = m_features[fi];
+    if (f.begin < 0 || f.end > int(m_entities.size()) || f.end - f.begin != 4) return;
+    const double L = (f.c1 - f.c0).norm();
+    if (L < 1e-9) return;
+    const double a = deg * M_PI / 180.0;
+    const Vec2d c1 = f.c0 + L * Vec2d(std::cos(a), std::sin(a));
+    std::vector<SketchEntity> rebuilt = make_slot(f.c0, c1, f.param);
+    if (int(rebuilt.size()) != 4) return;
+    for (int i = 0; i < 4; ++i) {
+        rebuilt[i].construction = m_entities[f.begin + i].construction;
+        m_entities[f.begin + i] = rebuilt[i];
+    }
+    f.c1 = c1;
+    resolve_live();
+}
+
+// Resize an axis-aligned rectangle by dragging a corner: the diagonally-opposite corner
+// (captured at grab as m_drag_rect_anchor) stays fixed; the box becomes [anchor, cursor].
+// Geometric rebuild in place (4 lines, same order) — edges stay axis-aligned so the
+// inferred H/V + corner-coincident constraints remain satisfied (no re-solve needed).
+void DesignSketchTool::drag_rect_corner(int fi, const Vec2d& cursor)
+{
+    if (fi < 0 || fi >= int(m_features.size())) return;
+    Feature& f = m_features[fi];
+    if (f.end - f.begin != 4) return;
+    const Vec2d A = m_drag_rect_anchor, B = cursor;
+    if (std::abs(B.x() - A.x()) < 1e-4 || std::abs(B.y() - A.y()) < 1e-4) return;  // degenerate
+    const Vec2d corners[4] = { A, Vec2d(B.x(), A.y()), B, Vec2d(A.x(), B.y()) };
+    for (int i = 0; i < 4; ++i) {
+        SketchEntity e; e.type = SketchEntity::Type::Line;
+        e.p0 = corners[i]; e.p1 = corners[(i + 1) % 4];
+        e.construction = m_entities[f.begin + i].construction;
+        m_entities[f.begin + i] = e;
+    }
+    f.c0 = A; f.c1 = B;
+}
+
+// Move one end of a slot by dragging its cap centre (which cap captured at grab); the other
+// centre + half-width are kept. Rebuilds the 4-entity span via make_slot. Geometric.
+void DesignSketchTool::drag_slot_handle(int fi, const Vec2d& cursor)
+{
+    if (fi < 0 || fi >= int(m_features.size())) return;
+    Feature& f = m_features[fi];
+    if (f.end - f.begin != 4) return;
+    const Vec2d c0 = m_drag_slot_c1 ? f.c0 : cursor;
+    const Vec2d c1 = m_drag_slot_c1 ? cursor : f.c1;
+    std::vector<SketchEntity> rebuilt = make_slot(c0, c1, f.param);
+    if (int(rebuilt.size()) != 4) return;
+    for (int i = 0; i < 4; ++i) {
+        rebuilt[i].construction = m_entities[f.begin + i].construction;
+        m_entities[f.begin + i] = rebuilt[i];
+    }
+    f.c0 = c0; f.c1 = c1;
+}
+
+DesignSketchTool::DimType DesignSketchTool::pending_dimension_type() const
+{
+    return (m_pending_dim >= 0 && m_pending_dim < int(m_dimensions.size()))
+               ? m_dimensions[m_pending_dim].kind : DimType::None;
+}
+
+void DesignSketchTool::set_dimension_value(double v)
+{
+    if (m_pending_dim < 0 || m_pending_dim >= int(m_dimensions.size())) return;
+    DimAnnot& a = m_dimensions[m_pending_dim];
+    a.value = v;
+    if (a.con >= 0 && a.con < int(m_constraints.size()))
+        m_constraints[a.con] = constraint_for(a);
+    resolve_live();
+    m_pending_dim = -1;
+}
+
+void DesignSketchTool::cancel_dimension_value()
+{
+    m_pending_dim = -1;   // keep the placed dimension at its measured value
+}
+
+std::string DesignSketchTool::dim_text(const DimAnnot& a) const
+{
+    char buf[32];
+    const char* prefix = (a.kind == DimType::Diameter) ? "\xC3\x98"   // 'Ø'
+                       : (a.kind == DimType::Radius)   ? "R" : "";
+    const char* suffix = (a.kind == DimType::Angle) ? "\xC2\xB0" : ""; // '°'
+    std::snprintf(buf, sizeof(buf), "%s%.1f%s", prefix, a.value, suffix);
+    // Force the international (en) decimal point: wx sets LC_NUMERIC to the user
+    // locale at startup, so snprintf("%.1f") can emit a comma. Normalise it.
+    for (char& ch : buf)
+        if (ch == ',') ch = '.';
+    std::string out(buf);
+    if (a.kind != DimType::Angle) {
+        const bool use_in = wxGetApp().app_config->get_bool("use_inches");
+        out += use_in ? " in" : " mm";
+    }
+    return out;
+}
+
+void DesignSketchTool::apply_segment_length(double len)
+{
+    if (m_points.size() == 2 && len > 1e-9) {
+        const Vec2d d = m_points[1] - m_points[0];
+        const double r = d.norm();
+        if (r > 1e-9)
+            m_points[1] = m_points[0] + (len / r) * d;
+    }
+    keep_segment_as_drawn();
+    // Driving length constraint on the just-committed Line entity.
+    if (len > 1e-9 && !m_entities.empty()) {
+        const int i = int(m_entities.size()) - 1;
+        if (m_entities[i].type == SketchEntity::Type::Line) {
+            SketchEntityConstraintDef c;
+            c.type = SketchConstraintType::Distance;
+            c.ea = i; c.ra = SketchPointRole::P0;
+            c.eb = i; c.rb = SketchPointRole::P1;
+            c.value = len;
+            m_constraints.push_back(c);
+        }
+    }
+    resolve_live();                          // live-solve the in-session sketch
+}
+
+void DesignSketchTool::keep_segment_as_drawn()
+{
+    if (m_points.size() == 2) {
+        const int base = int(m_entities.size());
+        push_line(m_points[0], m_points[1]);  // accrues into the session's entities
+        infer_auto_constraints(base);         // auto Coincident at snapped ends + H/V
+    }
+    m_points.clear();
+    m_has_cursor = false;
+    m_awaiting_length = false;
+}
+
+void DesignSketchTool::finish()
+{
+    // A value field still open at commit time outlives the session — the editor is a top-level
+    // frame — and inline_busy stays set, so every later click is swallowed at on_mouse_impl's
+    // first branch and the viewport reads as dead. Dismiss it first (keep-as-drawn, the same
+    // contract as the polyline terminators) and drop any queued field with it.
+    close_session_chrome();
+    if (op_ready()) confirm_op();      // apply a pending edit-op gizmo before committing
+    if (tf_ready()) confirm_transform(); // apply a pending transform gizmo before committing
+    auto cb = on_commit_entities;
+    std::vector<SketchEntity> ents = m_entities;
+    std::vector<SketchEntityConstraintDef> cons = m_constraints;
+    SketchPlane pl = m_plane;
+    m_active = false;
+    m_points.clear();
+    m_entities.clear();
+    m_constraints.clear();
+    m_dimensions.clear();
+    m_point_sel.clear();
+    m_dim_has0 = false;
+    m_pending_dim = -1;
+    m_has_cursor = false;
+    m_features.clear();
+    m_open_feature = -1;
+    if (cb)
+        cb(ents, cons, pl);
+}
+
+void DesignSketchTool::begin_constrain(const SketchProfile& prof, const SketchPlane& plane)
+{
+    push_auto_close_pref();
+    m_plane = plane;
+    m_mode = Mode::Constrain;
+    m_points = prof.points;
+    m_entities.clear();
+    m_has_cursor = false;
+    m_sel_a = m_sel_b = -1;
+    m_constrain_entities = false;
+    m_pick0 = m_pick1 = m_pick2 = -1;
+    m_active = true;
+}
+
+void DesignSketchTool::begin_constrain_entities(const std::vector<SketchEntity>& ents,
+                                                const SketchPlane& plane)
+{
+    push_auto_close_pref();
+    m_plane = plane;
+    m_mode = Mode::Constrain;
+    m_constrain_entities = true;
+    m_points.clear();
+    m_entities = ents;
+    m_has_cursor = false;
+    m_sel_a = m_sel_b = -1;
+    m_pick0 = m_pick1 = m_pick2 = -1;
+    m_active = true;
+}
+
+bool DesignSketchTool::selected_segment(int& a, int& b) const
+{
+    if (m_sel_a < 0 || m_sel_b < 0)
+        return false;
+    a = m_sel_a;
+    b = m_sel_b;
+    return true;
+}
+
+bool DesignSketchTool::screen_to_plane(GLCanvas3D& canvas, const wxMouseEvent& evt, Vec2d& out) const
+{
+    Point pos(evt.GetX(), evt.GetY());
+    Linef3 r = canvas.mouse_ray(pos);
+    out = m_plane.project(r.a, r.vector());
+    return true;
+}
+
+// Closing the loop is THE outcome this tab exists for — a sketch that is not closed cannot be
+// extruded — so it must be as easy and as visible as any other snap, and it must behave the
+// same at every zoom. This used to be a bare `squaredNorm() < 4.0`, i.e. a fixed 2 mm bubble in
+// plane units: a pixel hunt zoomed out, an over-eager magnet zoomed in, and invisible either
+// way — nothing told the user their next click would close the loop rather than place another
+// vertex. Now the chain's first point is a real snap target on the same 8 px screen tolerance
+// as every endpoint snap: hovering it moves the cursor exactly onto it, which makes the rubber
+// band draw the closing segment as a preview and lights the existing snap marker. The click
+// then closes only because it was SNAPPED, never because it was merely nearby.
+bool DesignSketchTool::snap_chain_start(GLCanvas3D& canvas, const wxMouseEvent& evt, Vec2d& p) const
+{
+    if (m_mode != Mode::Polyline || m_points.size() < 3) return false;
+    if ((p - m_points[0]).norm() > screen_tol(canvas, evt, p)) return false;
+    p = m_points[0];
+    InferenceSnap s;
+    s.kind  = InferenceSnap::Kind::Endpoint;   // renders the same hint as any endpoint snap
+    s.point = m_points[0];
+    const_cast<DesignSketchTool*>(this)->m_cursor_snap = s;
+    return true;
+}
+
+Vec2d DesignSketchTool::snap_dir(const Vec2d& anchor, const Vec2d& raw, bool& locked) const
+{
+    locked = false;
+    if (m_snap_off) return raw;
+
+    const Vec2d d = raw - anchor;
+    const double r = d.norm();
+    if (r < 1e-9) return raw;
+
+    const double tol_deg = 5.0;                 // inference half-window
+    double ang = std::atan2(d.y(), d.x()) * 180.0 / M_PI;  // (-180,180]
+    if (ang < 0.0) ang += 360.0;                            // [0,360)
+
+    // Base angles within one quadrant, replicated every 90 deg up to 360.
+    static const double base[] = {0.0, 30.0, 45.0, 60.0};
+    double best_cand = ang, best_diff = 1e30;
+    for (int q = 0; q < 4; ++q) {
+        for (double b : base) {
+            const double cand = b + 90.0 * q;
+            double diff = std::abs(ang - cand);
+            if (diff > 180.0) diff = 360.0 - diff;
+            if (diff < best_diff) { best_diff = diff; best_cand = cand; }
+        }
+    }
+    if (best_diff > tol_deg) return raw;
+
+    locked = true;
+    const double rad = best_cand * M_PI / 180.0;
+    return anchor + r * Vec2d(std::cos(rad), std::sin(rad));
+}
+
+double DesignSketchTool::screen_tol(GLCanvas3D& canvas, const wxMouseEvent& evt,
+                                    const Vec2d& at, double px) const
+{
+    // Project a point `px` screen pixels away and measure the gap in plane units.
+    const Linef3 r2 = canvas.mouse_ray(Point(evt.GetX() + int(px), evt.GetY()));
+    const Vec2d  p2 = m_plane.project(r2.a, r2.vector());
+    return std::max(1e-3, (p2 - at).norm());
+}
+
+InferenceSnap DesignSketchTool::infer_at(GLCanvas3D& canvas, const wxMouseEvent& evt,
+                                         const Vec2d& raw) const
+{
+    if (evt.ShiftDown()) { InferenceSnap s; s.point = raw; return s; }   // Shift suppresses
+    const double tol = screen_tol(canvas, evt, raw);
+    return infer_point_snap(m_entities, raw, tol);
+}
+
+Vec2d DesignSketchTool::snap_vertex(GLCanvas3D& canvas, const wxMouseEvent& evt,
+                                    const Vec2d& raw, bool& snapped) const
+{
+    const InferenceSnap s = infer_at(canvas, evt, raw);
+    // Cache the target so render() can draw a snap hint; only endpoint/centre/origin
+    // count as a "vertex" snap for the callers that gate angle inference on it.
+    const_cast<DesignSketchTool*>(this)->m_cursor_snap = s;
+    snapped = s.snapped();   // any hard snap moves the cursor + suppresses angle lock
+    return s.point;
+}
+
+bool DesignSketchTool::has_coincident(int ea, SketchPointRole ra, int eb, SketchPointRole rb) const
+{
+    for (const auto& c : m_constraints) {
+        if (c.type != SketchConstraintType::Coincident) continue;
+        if ((c.ea == ea && c.ra == ra && c.eb == eb && c.rb == rb) ||
+            (c.ea == eb && c.ra == rb && c.eb == ea && c.rb == ra))
+            return true;
+    }
+    return false;
+}
+
+bool DesignSketchTool::try_add_constraints(const std::vector<SketchEntityConstraintDef>& cands)
+{
+    if (cands.empty()) return true;
+    const size_t mark = m_constraints.size();
+    for (const auto& c : cands) m_constraints.push_back(c);
+    if (solve_sketch_entities(m_entities, m_constraints)) {
+        if (on_constraints_changed) on_constraints_changed();
+        return true;
+    }
+    m_constraints.resize(mark);                 // roll back the conflicting batch
+    // No re-solve to "restore": a failed solve no longer touches the geometry
+    // (SketchSolver.cpp only writes back on success), so m_entities still holds the
+    // prior solved state exactly. pl5.
+    return false;
+}
+
+// Delete the constraint whose badge is under `p`. Removing a constraint can only FREE degrees
+// of freedom, so the re-solve cannot fail for over-constraint -- but it is still run, because
+// the geometry must relax back to what the remaining system allows.
+bool DesignSketchTool::remove_constraint_near(const Vec2d& p)
+{
+    if (m_glyph_hits.empty() || m_glyph_r <= 0.0) return false;
+    int best = -1;
+    double best_d = m_glyph_r;
+    for (const GlyphHit& g : m_glyph_hits) {
+        const double d = (g.c - p).norm();
+        if (d < best_d && g.con >= 0 && g.con < int(m_constraints.size())) { best_d = d; best = g.con; }
+    }
+    if (best < 0) return false;
+    return remove_constraint(best);
+}
+
+bool DesignSketchTool::remove_constraint(int idx)
+{
+    if (idx < 0 || idx >= int(m_constraints.size())) return false;
+    m_constraints.erase(m_constraints.begin() + idx);
+    // resolve_live(), not a bare solve: it is the path that recomputes the DoF, clears the
+    // per-entity conflict flags and fires on_solve_state. Solving directly would relax the
+    // geometry while leaving the DoF readout and any red over-constrained tint stale — the
+    // readout would still describe the constraint that was just deleted.
+    resolve_live();
+    m_glyph_hits.clear();       // stale until the next render rebuilds them
+    if (on_constraints_changed) on_constraints_changed();
+    return true;
+}
+
+void DesignSketchTool::infer_auto_constraints(int base, double ang_tol_rad, double weld_tol)
+{
+    const int n = int(m_entities.size());
+    if (base < 0 || base >= n) return;
+
+    // Endpoint roles an entity exposes for coincidence matching.
+    auto roles_of = [](const SketchEntity& e, SketchPointRole out[2]) -> int {
+        switch (e.type) {
+        case SketchEntity::Type::Line:   out[0] = SketchPointRole::P0; out[1] = SketchPointRole::P1; return 2;
+        case SketchEntity::Type::Arc:    out[0] = SketchPointRole::P0; out[1] = SketchPointRole::P1; return 2;
+        // EllipseArc was missing here while the otherwise identical roles_of in
+        // heal_coincidences (below) has it, so an ellipse arc's endpoints could be WELDED by the
+        // healer but never auto-inferred coincident at draw time -- the same gesture behaved
+        // differently depending on which path ran. Two copies of one rule is how that happens.
+        case SketchEntity::Type::EllipseArc:
+                                         out[0] = SketchPointRole::P0; out[1] = SketchPointRole::P1; return 2;
+        case SketchEntity::Type::BSpline:out[0] = SketchPointRole::P0; out[1] = SketchPointRole::P1; return 2;
+        case SketchEntity::Type::Point:  out[0] = SketchPointRole::P0; return 1;
+        default: return 0;   // circle: centre coincidence handled by Concentric, not here
+        }
+    };
+
+    // 1) Coincident between a new endpoint and any (co-located) endpoint of another
+    //    entity. snap_vertex already drove the coordinates together; this records it
+    //    so a re-solve keeps the loop closed.
+    std::vector<SketchEntityConstraintDef> coincs;
+    for (int i = base; i < n; ++i) {
+        SketchPointRole ir[2]; const int ni = roles_of(m_entities[i], ir);
+        for (int a = 0; a < ni; ++a) {
+            Vec2d pa; if (!point_at(i, ir[a], pa)) continue;
+            for (int j = 0; j < n; ++j) {
+                if (j == i) continue;
+                SketchPointRole jr[2]; const int nj = roles_of(m_entities[j], jr);
+                for (int b = 0; b < nj; ++b) {
+                    if (j >= base && j < i) continue;          // avoid duplicate (i,j)/(j,i)
+                    Vec2d pb; if (!point_at(j, jr[b], pb)) continue;
+                    if ((pa - pb).squaredNorm() > weld_tol * weld_tol) continue;
+                    if (has_coincident(i, ir[a], j, jr[b])) continue;
+                    SketchEntityConstraintDef c;
+                    c.type = SketchConstraintType::Coincident;
+                    c.ea = i; c.ra = ir[a]; c.eb = j; c.rb = jr[b];
+                    coincs.push_back(c);
+                }
+            }
+        }
+    }
+    try_add_constraints(coincs);   // co-located points: consistent by construction
+
+    // 2) Horizontal / Vertical on axis-aligned new line segments. Tried as ONE batch first and
+    //    only then one at a time, which is the same outcome — a single conflict never drops the
+    //    others — for one solve instead of n. That matters now that large sketches actually
+    //    solve: a bulk add of 1200 axis-aligned segments used to be fast only because every
+    //    solve failed instantly on the unknown limit, and once they started succeeding the
+    //    per-constraint loop turned into 1200 solves and blew the MCP main-thread budget.
+    std::vector<SketchEntityConstraintDef> axes;
+    for (int i = base; i < n; ++i) {
+        if (m_entities[i].type != SketchEntity::Type::Line) continue;
+        auto ax = infer_axis_constraint(m_entities[i].p0, m_entities[i].p1, ang_tol_rad);
+        if (!ax) continue;
+        SketchEntityConstraintDef c;
+        c.type = *ax;
+        c.ea = i; c.ra = SketchPointRole::P0;
+        c.eb = i; c.rb = SketchPointRole::P1;
+        axes.push_back(c);
+    }
+    if (!try_add_constraints(axes))
+        for (const auto& c : axes) try_add_constraints({ c });
+
+    // 3) Relational constraints on the new entities (parallel/perpendicular on connected
+    //    lines, equal radius, tangent). Same batch-then-one-at-a-time fallback as above:
+    //    try_add_constraints rolls a conflicting batch back, so a single rejected relation
+    //    never costs the others. Every rule only pins a relation that is ALREADY true, so
+    //    nothing the user drew is moved by this.
+    //    A SCRIPTED ADD IS NOT A DRAWN GESTURE — the rule this function already states at its
+    //    bulk call site, which passes zero tolerances for exactly that reason (8xg1).
+    //    Relational inference must obey it too, and for a second reason beyond tolerance:
+    //    EqualRadius couples entities that are geometrically far apart, so on a real drawing it
+    //    merges independent connected components into one huge system and defeats the
+    //    component partitioning that makes large sketches solvable at all (yww4).
+    //    Measured 2026-08-31 on the corpus rung: geometry stayed correct (32/32 sheets clean)
+    //    but seven of the largest sheets hit main-thread timeout — MPD681 among them, the very
+    //    sheet named in the comment at the bulk call site. Exact-equality would not save it
+    //    either: patterned holes in real drawings ARE exactly equal.
+    //    So: relations only for batches the size of a human gesture. A polyline segment is 1, a
+    //    rectangle 4, a polygon a dozen; a scripted or imported add is hundreds.
+    constexpr int kRelInferMaxBatch = 16;
+    std::vector<SketchEntityConstraintDef> rels;
+    if (n - base <= kRelInferMaxBatch) {
+        const double rel_len_tol = ang_tol_rad > 0.0 ? 0.01 : 0.0;   // exact-only when the caller asked for exact
+        for (int i = base; i < n; ++i) {
+            auto r = infer_relations(m_entities, i, ang_tol_rad, rel_len_tol);
+            rels.insert(rels.end(), r.begin(), r.end());
+        }
+    }
+    // NO one-at-a-time fallback here, unlike the two batches above. Relations are a
+    // convenience: nothing is incorrect without them. The fallback costs one SOLVE PER
+    // CONSTRAINT, which is what the warning on the axes batch is about, and paying it for
+    // optional constraints is how a bulk add pins the app at 100% CPU with the MCP socket
+    // unresponsive (measured 2026-08-31). If the batch conflicts, drop the batch.
+    if (!rels.empty()) try_add_constraints(rels);
+
+    resolve_live();
+}
+
+static std::vector<Vec2d> circle_polygon(const Vec2d& c, double r, int n = 48)
+{
+    std::vector<Vec2d> v; v.reserve(n);
+    for (int i = 0; i < n; ++i) {
+        const double a = 2.0 * M_PI * double(i) / double(n);
+        v.push_back(Vec2d(c.x() + r * std::cos(a), c.y() + r * std::sin(a)));
+    }
+    return v;
+}
+
+// Point on an ellipse at parametric angle theta: center + R(phi)*(a cos t, b sin t).
+static Vec2d ellipse_point(const Vec2d& c, double a, double b, double phi, double t)
+{
+    const double cu = std::cos(phi), su = std::sin(phi);
+    const double x = a * std::cos(t), y = b * std::sin(t);
+    return Vec2d(c.x() + x * cu - y * su, c.y() + x * su + y * cu);
+}
+
+// Tessellate an ellipse arc parametric range [t0,t1] into a polyline.
+static std::vector<Vec2d> ellipse_polyline(const Vec2d& c, double a, double b, double phi,
+                                           double t0, double t1, int n = 48)
+{
+    std::vector<Vec2d> v; v.reserve(n + 1);
+    for (int i = 0; i <= n; ++i)
+        v.push_back(ellipse_point(c, a, b, phi, t0 + (t1 - t0) * double(i) / double(n)));
+    return v;
+}
+
+// Clamped uniform B-spline (degree min(3, n-1)) through control poles. The knot
+// construction mirrors SketchEngine::entities_to_wire's OCCT Geom_BSplineCurve so
+// the previewed/extruded curve match. de Boor evaluation.
+static int bspline_degree(int n) { return n >= 4 ? 3 : (n >= 2 ? n - 1 : 0); }
+
+static std::vector<double> bspline_knots(int n, int p)
+{
+    std::vector<double> U;                     // full knot vector, length n+p+1
+    const int interior = n - p - 1;
+    for (int i = 0; i <= p; ++i) U.push_back(0.0);
+    for (int i = 1; i <= interior; ++i) U.push_back(double(i));
+    const double last = double(interior + 1);
+    for (int i = 0; i <= p; ++i) U.push_back(last);
+    return U;
+}
+
+static Vec2d bspline_eval(const std::vector<Vec2d>& P, const std::vector<double>& U, int p, double u)
+{
+    const int n = int(P.size());
+    if (u <= U[p])            return P.front();
+    if (u >= U[n])            return P.back();   // U[n] == domain max (clamped)
+    int k = p;
+    while (k < n - 1 && U[k + 1] <= u) ++k;       // span: U[k] <= u < U[k+1]
+    std::vector<Vec2d> d(p + 1);
+    for (int j = 0; j <= p; ++j) d[j] = P[j + k - p];
+    for (int r = 1; r <= p; ++r)
+        for (int j = p; j >= r; --j) {
+            const double denom = U[j + 1 + k - r] - U[j + k - p];
+            const double a = denom > 1e-12 ? (u - U[j + k - p]) / denom : 0.0;
+            d[j] = (1.0 - a) * d[j - 1] + a * d[j];
+        }
+    return d[p];
+}
+
+static std::vector<Vec2d> bspline_polyline(const std::vector<Vec2d>& ctrl, int samples = 0)
+{
+    const int n = int(ctrl.size());
+    if (n < 2) return ctrl;
+    const int p = bspline_degree(n);
+    const std::vector<double> U = bspline_knots(n, p);
+    const double umax = double(n - p);
+    if (samples <= 0) samples = std::max(24, 14 * (n - 1));
+    std::vector<Vec2d> out; out.reserve(samples + 1);
+    for (int i = 0; i <= samples; ++i)
+        out.push_back(bspline_eval(ctrl, U, p, umax * double(i) / double(samples)));
+    return out;
+}
+
+// ---- entity builders --------------------------------------------------------
+
+void DesignSketchTool::push_line(const Vec2d& a, const Vec2d& b)
+{
+    if ((b - a).squaredNorm() < 1e-9)
+        return;
+    SketchEntity e;
+    e.type = SketchEntity::Type::Line;
+    e.p0 = a;
+    e.p1 = b;
+    e.construction = m_construction;
+    m_entities.push_back(e);
+}
+
+bool DesignSketchTool::add_imported_regions(
+    const std::vector<std::vector<std::vector<Vec2d>>>& regions)
+{
+    if (!m_active) return false;          // no session to draw into; caller makes a feature
+    const bool saved = m_construction;
+    m_construction = false;               // art is real geometry, never construction lines
+    size_t before = m_entities.size();
+    for (const auto& region : regions)
+        for (const auto& loop : region)
+            push_closed_lines(loop);      // every glyph contour, holes included
+    m_construction = saved;
+    if (m_entities.size() == before) return false;   // nothing importable — say so, do not lie
+    // Art is not "just drawn", so it must NOT enter the draw-then-edit queue. Without this the
+    // glyph contours are treated as fresh entities and a Length field opens on the first of
+    // them — on a word, that is one value editor per segment, and an open field freezes the
+    // canvas (yce). reset_autoedit() marks every entity as already seen.
+    reset_autoedit();
+    // The new lines carry no constraints, so the solver has nothing to move; resolve anyway so
+    // the degrees-of-freedom readout counts them instead of going stale.
+    resolve_live();
+    return true;
+}
+
+void DesignSketchTool::push_closed_lines(const std::vector<Vec2d>& corners)
+{
+    const size_t n = corners.size();
+    if (n < 2) return;
+    for (size_t i = 0; i < n; ++i)
+        push_line(corners[i], corners[(i + 1) % n]);
+}
+
+void DesignSketchTool::push_open_chain(const std::vector<Vec2d>& pts)
+{
+    for (size_t i = 0; i + 1 < pts.size(); ++i)
+        push_line(pts[i], pts[i + 1]);
+}
+
+void DesignSketchTool::push_circle(const Vec2d& center, double radius)
+{
+    if (radius < 1e-3) return;
+    SketchEntity e;
+    e.type = SketchEntity::Type::Circle;
+    e.center = center;
+    e.p0 = center;
+    e.radius = radius;
+    e.construction = m_construction;
+    m_entities.push_back(e);
+}
+
+void DesignSketchTool::push_point(const Vec2d& p)
+{
+    SketchEntity e;
+    e.type = SketchEntity::Type::Point;
+    e.p0 = p;
+    e.center = p;
+    e.construction = m_construction;
+    m_entities.push_back(e);
+}
+
+void DesignSketchTool::append_entities(const std::vector<SketchEntity>& ents)
+{
+    for (const SketchEntity& e : ents)
+        m_entities.push_back(e);
+}
+
+static double wrap_2pi(double a)
+{
+    while (a < 0.0)        a += 2.0 * M_PI;
+    while (a >= 2.0 * M_PI) a -= 2.0 * M_PI;
+    return a;
+}
+
+// Circumcircle of 3 points. Returns false if (nearly) collinear.
+static bool circumcircle(const Vec2d& a, const Vec2d& b, const Vec2d& c,
+                         Vec2d& center, double& radius)
+{
+    const double d = 2.0 * (a.x() * (b.y() - c.y()) +
+                            b.x() * (c.y() - a.y()) +
+                            c.x() * (a.y() - b.y()));
+    if (std::abs(d) < 1e-9)
+        return false;
+    const double a2 = a.squaredNorm(), b2 = b.squaredNorm(), c2 = c.squaredNorm();
+    const double ux = (a2 * (b.y() - c.y()) + b2 * (c.y() - a.y()) + c2 * (a.y() - b.y())) / d;
+    const double uy = (a2 * (c.x() - b.x()) + b2 * (a.x() - c.x()) + c2 * (b.x() - a.x())) / d;
+    center = Vec2d(ux, uy);
+    radius = (a - center).norm();
+    return true;
+}
+
+// Build an Arc entity that sweeps start -> end passing through `through`. The
+// kernel reconstructs the mid from (start_angle+end_angle)/2, so the angle pair
+// must bracket `through` on the correct side of the circle.
+static SketchEntity make_arc_through(const Vec2d& center, double radius,
+                                     const Vec2d& start, const Vec2d& end,
+                                     const Vec2d& through, bool construction)
+{
+    const double a_start = std::atan2(start.y()  - center.y(), start.x()  - center.x());
+    const double a_end   = std::atan2(end.y()    - center.y(), end.x()    - center.x());
+    const double a_thru  = std::atan2(through.y() - center.y(), through.x() - center.x());
+    const double de = wrap_2pi(a_end  - a_start);   // CCW sweep to end (0,2π)
+    const double d3 = wrap_2pi(a_thru - a_start);   // CCW position of through
+    SketchEntity e;
+    e.type   = SketchEntity::Type::Arc;
+    e.center = center;
+    e.radius = radius;
+    e.p0     = start;
+    e.p1     = end;
+    e.start_angle = a_start;
+    e.end_angle   = (d3 <= de) ? (a_start + de) : (a_start + de - 2.0 * M_PI);
+    e.construction = construction;
+    return e;
+}
+
+std::vector<SketchEntity> DesignSketchTool::make_three_point_circle(const Vec2d& a, const Vec2d& b, const Vec2d& c) const
+{
+    Vec2d center; double radius;
+    if (!circumcircle(a, b, c, center, radius))
+        return {};
+    SketchEntity e;
+    e.type = SketchEntity::Type::Circle;
+    e.center = center;
+    e.p0 = center;
+    e.radius = radius;
+    e.construction = m_construction;
+    return { e };
+}
+
+std::vector<SketchEntity> DesignSketchTool::make_three_point_arc(const Vec2d& start, const Vec2d& end, const Vec2d& on_arc) const
+{
+    Vec2d center; double radius;
+    if (!circumcircle(start, end, on_arc, center, radius))
+        return {};
+    return { make_arc_through(center, radius, start, end, on_arc, m_construction) };
+}
+
+std::vector<SketchEntity> DesignSketchTool::make_tangent_arc(const Vec2d& start, const Vec2d& end) const
+{
+    // Tangent direction at `start` = exit direction of the previous entity.
+    Vec2d t(1, 0);
+    bool have_t = false;
+    if (!m_entities.empty()) {
+        const SketchEntity& prev = m_entities.back();
+        if (prev.type == SketchEntity::Type::Line) {
+            t = prev.p1 - prev.p0; have_t = (t.squaredNorm() > 1e-12);
+        } else if (prev.type == SketchEntity::Type::Arc) {
+            // Tangent at the arc end p1 is perpendicular to its radius, in the
+            // sweep direction.
+            const Vec2d r = prev.p1 - prev.center;
+            const double sweep = prev.end_angle - prev.start_angle;
+            t = (sweep >= 0.0) ? Vec2d(-r.y(), r.x()) : Vec2d(r.y(), -r.x());
+            have_t = (r.squaredNorm() > 1e-12);
+        }
+    }
+    const Vec2d se = end - start;
+    if (!have_t || se.squaredNorm() < 1e-12) {
+        // No tangent reference or zero length: fall back to a straight line.
+        SketchEntity e; e.type = SketchEntity::Type::Line; e.p0 = start; e.p1 = end;
+        e.construction = m_construction;
+        return { e };
+    }
+    t.normalize();
+    const Vec2d n(-t.y(), t.x());            // unit normal to the tangent
+    const double denom = 2.0 * n.dot(se);
+    if (std::abs(denom) < 1e-9) {            // end lies along the tangent: line
+        SketchEntity e; e.type = SketchEntity::Type::Line; e.p0 = start; e.p1 = end;
+        e.construction = m_construction;
+        return { e };
+    }
+    const double R = se.squaredNorm() / denom;   // signed radius along n
+    const Vec2d center = start + n * R;
+    const double radius = std::abs(R);
+    // Mid of the tangent arc: project the chord midpoint outward onto the circle.
+    const Vec2d chord_mid = (start + end) * 0.5;
+    Vec2d to_mid = chord_mid - center;
+    if (to_mid.squaredNorm() < 1e-12) to_mid = n;
+    to_mid.normalize();
+    const Vec2d through = center + to_mid * radius;
+    return { make_arc_through(center, radius, start, end, through, m_construction) };
+}
+
+std::vector<SketchEntity> DesignSketchTool::make_center_arc(const Vec2d& center, const Vec2d& start, const Vec2d& end_dir) const
+{
+    const double radius = (start - center).norm();
+    if (radius < 1e-9)
+        return {};
+    const double a_start = std::atan2(start.y()   - center.y(), start.x()   - center.x());
+    const double a_end   = std::atan2(end_dir.y() - center.y(), end_dir.x() - center.x());
+    const double de      = wrap_2pi(a_end - a_start);    // CCW sweep start -> end (0,2π)
+    const Vec2d  end      = center + radius * Vec2d(std::cos(a_end),  std::sin(a_end));
+    const double a_mid    = a_start + de * 0.5;           // bisector brackets the sweep
+    const Vec2d  through   = center + radius * Vec2d(std::cos(a_mid), std::sin(a_mid));
+    return { make_arc_through(center, radius, start, end, through, m_construction) };
+}
+
+std::vector<SketchEntity> DesignSketchTool::make_slot(const Vec2d& c0, const Vec2d& c1, double half_width) const
+{
+    std::vector<SketchEntity> out;
+    Vec2d u = c1 - c0;
+    if (u.squaredNorm() < 1e-12 || half_width < 1e-6)
+        return out;
+    u.normalize();
+    const Vec2d nrm(-u.y(), u.x());
+    const double w = half_width;
+    // Names avoid termios macros (B0 is a baud-rate #define pulled in transitively).
+    const Vec2d top0 = c0 + nrm * w, top1 = c1 + nrm * w;   // upper side (c0 -> c1)
+    const Vec2d bot1 = c1 - nrm * w, bot0 = c0 - nrm * w;   // lower side (c1 -> c0)
+
+    auto line = [&](const Vec2d& p0, const Vec2d& p1) {
+        SketchEntity e; e.type = SketchEntity::Type::Line; e.p0 = p0; e.p1 = p1;
+        e.construction = m_construction; return e;
+    };
+    out.push_back(line(top0, top1));                                   // top
+    out.push_back(make_arc_through(c1, w, top1, bot1, c1 + u * w, m_construction)); // cap @c1 (+u)
+    out.push_back(line(bot1, bot0));                                   // bottom
+    out.push_back(make_arc_through(c0, w, bot0, top0, c0 - u * w, m_construction)); // cap @c0 (-u)
+    return out;
+}
+
+// Arc slot: a slot whose centerline is a circular arc (center, start, end_dir on
+// the same radius). Bounded by an outer arc (Rc+w), an inner arc (Rc-w) and two
+// semicircular end caps. CCW closed loop, mirroring make_slot's structure.
+std::vector<SketchEntity> DesignSketchTool::make_arc_slot(const Vec2d& center, const Vec2d& start,
+                                                          const Vec2d& end_dir, double half_width) const
+{
+    std::vector<SketchEntity> out;
+    const double Rc = (start - center).norm();
+    const double w  = half_width;
+    if (Rc < 1e-6 || w < 1e-6 || w >= Rc) return out;
+    const Vec2d dirS = (start - center) / Rc;
+    Vec2d de = end_dir - center;
+    if (de.squaredNorm() < 1e-12) return out;
+    const Vec2d dirE = de.normalized();
+    const double aS = std::atan2(dirS.y(), dirS.x());
+    const double aE = std::atan2(dirE.y(), dirE.x());
+    const double sweep = wrap_2pi(aE - aS);            // CCW start -> end
+    const double aMid  = aS + sweep * 0.5;
+    const Vec2d  uMid(std::cos(aMid), std::sin(aMid));
+    const Vec2d  Sc = center + Rc * dirS;              // centerline start point (cap centre)
+    const Vec2d  Ec = center + Rc * dirE;              // centerline end point   (cap centre)
+    const Vec2d  S_out = center + (Rc + w) * dirS, S_in = center + (Rc - w) * dirS;
+    const Vec2d  E_out = center + (Rc + w) * dirE, E_in = center + (Rc - w) * dirE;
+    const Vec2d  tE(-dirE.y(), dirE.x());              // CCW travel-forward tangent at E
+    const Vec2d  tS(-dirS.y(), dirS.x());              // CCW travel-forward tangent at S
+    out.push_back(make_arc_through(center, Rc + w, S_out, E_out, center + (Rc + w) * uMid, m_construction)); // outer
+    out.push_back(make_arc_through(Ec, w, E_out, E_in, Ec + w * tE, m_construction));                        // cap @E (forward)
+    out.push_back(make_arc_through(center, Rc - w, E_in, S_in, center + (Rc - w) * uMid, m_construction));   // inner
+    out.push_back(make_arc_through(Sc, w, S_in, S_out, Sc - w * tS, m_construction));                        // cap @S (backward)
+    return out;
+}
+
+// Rounded rectangle: axis-aligned box (a,b opposite corners) with filleted
+// corners. radius_pt's distance to the nearest corner sets the fillet radius.
+// 4 straight edges + 4 quarter arcs, CCW.
+// Build the 8 entities (4 lines + 4 corner arcs, CCW) of an axis-aligned rounded box
+// from explicit bounds + fillet radius. Shared by make_rounded_rect (gesture) and
+// set_rounded_rect (label/handle edit) so the entity order/count is identical → a rebuild
+// in place keeps constraint indices into the feature span valid.
+std::vector<SketchEntity> DesignSketchTool::rounded_rect_entities(double xmin, double ymin,
+                                                                  double xmax, double ymax, double r) const
+{
+    std::vector<SketchEntity> out;
+    auto line = [&](const Vec2d& p0, const Vec2d& p1) {
+        SketchEntity e; e.type = SketchEntity::Type::Line; e.p0 = p0; e.p1 = p1;
+        e.construction = m_construction; return e; };
+    auto corner = [&](const Vec2d& O, const Vec2d& sharp, const Vec2d& start, const Vec2d& end) {
+        const Vec2d thr = O + r * (sharp - O).normalized();
+        return make_arc_through(O, r, start, end, thr, m_construction); };
+    out.push_back(line({xmin + r, ymin}, {xmax - r, ymin}));                                  // bottom
+    out.push_back(corner({xmax - r, ymin + r}, {xmax, ymin}, {xmax - r, ymin}, {xmax, ymin + r})); // BR
+    out.push_back(line({xmax, ymin + r}, {xmax, ymax - r}));                                  // right
+    out.push_back(corner({xmax - r, ymax - r}, {xmax, ymax}, {xmax, ymax - r}, {xmax - r, ymax})); // TR
+    out.push_back(line({xmax - r, ymax}, {xmin + r, ymax}));                                  // top
+    out.push_back(corner({xmin + r, ymax - r}, {xmin, ymax}, {xmin + r, ymax}, {xmin, ymax - r})); // TL
+    out.push_back(line({xmin, ymax - r}, {xmin, ymin + r}));                                  // left
+    out.push_back(corner({xmin + r, ymin + r}, {xmin, ymin}, {xmin, ymin + r}, {xmin + r, ymin})); // BL
+    return out;
+}
+
+std::vector<SketchEntity> DesignSketchTool::make_rounded_rect(const Vec2d& a, const Vec2d& b, const Vec2d& radius_pt) const
+{
+    std::vector<SketchEntity> out;
+    const double xmin = std::min(a.x(), b.x()), xmax = std::max(a.x(), b.x());
+    const double ymin = std::min(a.y(), b.y()), ymax = std::max(a.y(), b.y());
+    const double bw = xmax - xmin, bh = ymax - ymin;
+    if (bw < 1e-6 || bh < 1e-6) return out;
+    const Vec2d cs[4] = { {xmin,ymin}, {xmax,ymin}, {xmax,ymax}, {xmin,ymax} };
+    double r = 1e18;
+    for (const Vec2d& c : cs) r = std::min(r, (radius_pt - c).norm());
+    r = std::min(r, std::min(bw, bh) * 0.5);
+    if (r < 1e-6) {   // degenerate -> plain rectangle
+        auto line = [&](const Vec2d& p0, const Vec2d& p1) {
+            SketchEntity e; e.type = SketchEntity::Type::Line; e.p0 = p0; e.p1 = p1;
+            e.construction = m_construction; return e; };
+        for (int i = 0; i < 4; ++i) out.push_back(line(cs[i], cs[(i + 1) % 4]));
+        return out;
+    }
+    return rounded_rect_entities(xmin, ymin, xmax, ymax, r);
+}
+
+std::vector<SketchEntity> DesignSketchTool::make_polygon(const Vec2d& center, const Vec2d& vertex, int sides) const
+{
+    std::vector<SketchEntity> out;
+    if (sides < 3) sides = 3;
+    const Vec2d rv = vertex - center;
+    const double d = rv.norm();
+    if (d < 1e-6) return out;
+    // Inscribed: cursor is a vertex (circumradius = d). Circumscribed: cursor is an
+    // edge midpoint (apothem = d) → circumradius R = d / cos(pi/n), rotated by half
+    // a step so an edge midpoint points at the cursor.
+    double R = d, a0 = std::atan2(rv.y(), rv.x());
+    if (m_polygon_circumscribed) {
+        R  = d / std::cos(M_PI / double(sides));
+        a0 = std::atan2(rv.y(), rv.x()) - M_PI / double(sides);
+    }
+    std::vector<Vec2d> verts; verts.reserve(sides);
+    for (int i = 0; i < sides; ++i) {
+        const double a = a0 + 2.0 * M_PI * double(i) / double(sides);
+        verts.push_back(Vec2d(center.x() + R * std::cos(a), center.y() + R * std::sin(a)));
+    }
+    for (int i = 0; i < sides; ++i) {
+        SketchEntity e; e.type = SketchEntity::Type::Line;
+        e.p0 = verts[i]; e.p1 = verts[(i + 1) % sides];
+        e.construction = m_construction;
+        out.push_back(e);
+    }
+    return out;
+}
+
+// Derive (a, b, phi) of an ellipse from the 3 defining clicks. First axis click =
+// major (a, phi); the minor point's perpendicular distance to the major axis = b,
+// clamped to a so OCCT's a >= b holds.
+static void ellipse_axes(const Vec2d& center, const Vec2d& major_end, const Vec2d& minor_pt,
+                         double& a, double& b, double& phi)
+{
+    const Vec2d maj = major_end - center;
+    a   = std::max(maj.norm(), 1e-6);
+    phi = std::atan2(maj.y(), maj.x());
+    const Vec2d n(-std::sin(phi), std::cos(phi));        // minor-axis direction
+    b   = std::min(std::abs((minor_pt - center).dot(n)), a);
+}
+
+// Parametric angle on an ellipse of the point nearest `q` (q projected onto the frame).
+static double ellipse_param_of(const Vec2d& center, double a, double b, double phi, const Vec2d& q)
+{
+    const Vec2d d = q - center;
+    const double cu = std::cos(phi), su = std::sin(phi);
+    const double u =  d.x() * cu + d.y() * su;            // along major
+    const double v = -d.x() * su + d.y() * cu;            // along minor
+    return std::atan2(v / std::max(b, 1e-9), u / std::max(a, 1e-9));
+}
+
+std::vector<SketchEntity> DesignSketchTool::make_ellipse(const Vec2d& center, const Vec2d& major_end,
+                                                         const Vec2d& minor_pt) const
+{
+    double a, b, phi;
+    ellipse_axes(center, major_end, minor_pt, a, b, phi);
+    if (b < 1e-6) return {};
+    SketchEntity e;
+    e.type = SketchEntity::Type::Ellipse;
+    e.center = center; e.p0 = center;
+    e.radius = a; e.rminor = b; e.rotation = phi;
+    e.start_angle = 0.0; e.end_angle = 2.0 * M_PI;
+    e.construction = m_construction;
+    return { e };
+}
+
+std::vector<SketchEntity> DesignSketchTool::make_ellipse_arc(const Vec2d& center, const Vec2d& major_end,
+                                                             const Vec2d& minor_pt, const Vec2d& start_pt,
+                                                             const Vec2d& end_pt) const
+{
+    double a, b, phi;
+    ellipse_axes(center, major_end, minor_pt, a, b, phi);
+    if (b < 1e-6) return {};
+    double t0 = ellipse_param_of(center, a, b, phi, start_pt);
+    double t1 = ellipse_param_of(center, a, b, phi, end_pt);
+    // CCW sweep from t0 to t1.
+    while (t1 <= t0) t1 += 2.0 * M_PI;
+    SketchEntity e;
+    e.type = SketchEntity::Type::EllipseArc;
+    e.center = center;
+    e.radius = a; e.rminor = b; e.rotation = phi;
+    e.start_angle = t0; e.end_angle = t1;
+    e.p0 = ellipse_point(center, a, b, phi, t0);
+    e.p1 = ellipse_point(center, a, b, phi, t1);
+    e.construction = m_construction;
+    return { e };
+}
+
+std::vector<SketchEntity> DesignSketchTool::make_bspline(const std::vector<Vec2d>& ctrl) const
+{
+    if (ctrl.size() < 2) return {};
+    SketchEntity e;
+    e.type = SketchEntity::Type::BSpline;
+    e.ctrl = ctrl;
+    e.p0 = ctrl.front();
+    e.p1 = ctrl.back();
+    e.construction = m_construction;
+    return { e };
+}
+
+std::vector<Vec2d> DesignSketchTool::entity_polyline(const SketchEntity& e, bool& closed) const
+{
+    closed = false;
+    switch (e.type) {
+    case SketchEntity::Type::Line:
+        return { e.p0, e.p1 };
+    case SketchEntity::Type::Circle:
+        closed = true;
+        return circle_polygon(e.center, e.radius);
+    case SketchEntity::Type::Arc: {
+        const int n = kArcFacets;
+        std::vector<Vec2d> pts; pts.reserve(n + 1);
+        for (int i = 0; i <= n; ++i) {
+            const double a = e.start_angle + (e.end_angle - e.start_angle) * double(i) / double(n);
+            pts.push_back(Vec2d(e.center.x() + e.radius * std::cos(a),
+                                e.center.y() + e.radius * std::sin(a)));
+        }
+        return pts;
+    }
+    case SketchEntity::Type::Ellipse:
+        closed = true;
+        return ellipse_polyline(e.center, e.radius, e.rminor, e.rotation, 0.0, 2.0 * M_PI);
+    case SketchEntity::Type::EllipseArc:
+        return ellipse_polyline(e.center, e.radius, e.rminor, e.rotation, e.start_angle, e.end_angle);
+    case SketchEntity::Type::BSpline:
+        return bspline_polyline(e.ctrl);
+    case SketchEntity::Type::Point:
+        return { e.p0 };
+    }
+    return {};
+}
+
+std::vector<std::vector<Vec2d>> DesignSketchTool::closed_regions() const
+{
+    return closed_regions(m_entities);
+}
+
+std::vector<std::vector<Vec2d>> DesignSketchTool::closed_regions(const std::vector<SketchEntity>& ents) const
+{
+    std::vector<std::vector<Vec2d>> out;
+    for (RegionLoop& r : region_loops(ents)) out.push_back(std::move(r.poly));
+    return out;
+}
+
+std::vector<std::vector<int>>
+DesignSketchTool::region_entity_indices(const std::vector<SketchEntity>& ents) const
+{
+    std::vector<std::vector<int>> out;
+    for (RegionLoop& r : region_loops(ents)) out.push_back(std::move(r.ents));
+    return out;
+}
+
+std::vector<std::vector<int>>
+DesignSketchTool::region_entity_indices_with_holes(const std::vector<SketchEntity>& ents) const
+{
+    const std::vector<RegionLoop> loops = region_loops(ents);
+    std::vector<std::vector<int>> out;
+    out.reserve(loops.size());
+    for (const RegionLoop& r : loops) {
+        std::vector<int> ids = r.ents;
+        for (int h : r.holes)
+            if (h >= 0 && h < int(loops.size()))
+                ids.insert(ids.end(), loops[h].ents.begin(), loops[h].ents.end());
+        out.push_back(std::move(ids));
+    }
+    return out;
+}
+
+// Nearest stroke, and the enclosing region if the cursor is inside one, for ONE committed
+// sketch. Factored out so the single-click and double-click paths cannot drift apart: they must
+// agree about what is under the pointer or one of them will act on something else.
+//
+// region_loops exists to find EXTRUDABLE regions, and by design it discards open chains — its
+// own walk comment says so. Using it as the pick index meant a committed sketch of open lines
+// had no pickable geometry whatsoever: the strokes drew, and not one of them could be clicked,
+// so there was no way to select it and therefore none to edit or delete it. Whether a stroke
+// bounds a region has nothing to do with whether the user can point at it. Region membership
+// decides what a hit REPORTS, not whether the hit can happen.
+static void dp_pick_trace(const char* fmt, ...);   // defined below; used by the diagnostics here
+static bool dp_pick_trace_on();                    // ditto — lets callers skip building a message
+void DesignSketchTool::hit_display_sketch(const DisplaySketch& d, const Vec2d& p, double tol,
+                                          int& edge_feat, int& edge_reg, int& edge_ent,
+                                          double& edge_d, int& face_feat, int& face_reg) const
+{
+    const std::vector<RegionLoop> loops = region_loops(d.entities);
+    // What did the sketch decompose into, and what is under the click? This is the trace that
+    // settled txp8 — it prints the loop table with each loop's hole count, so
+    // "containment is wrong" and "the click landed elsewhere" stop being indistinguishable.
+    // Guarded rather than merely silent: hit_display_sketch runs on every pick, and the message
+    // costs a string build and a heap allocation per loop even when nothing consumes it.
+    if (dp_pick_trace_on()) {
+        std::string h;
+        for (size_t r = 0; r < loops.size(); ++r) {
+            h += " loop" + std::to_string(r) + "(ents=" + std::to_string(loops[r].ents.size())
+               + ",poly=" + std::to_string(loops[r].poly.size())
+               + ",holes=" + std::to_string(loops[r].holes.size()) + ")";
+        }
+        dp_pick_trace("sketch feat=%d entities=%zu loops=%zu:%s", d.feature, d.entities.size(),
+                      loops.size(), h.c_str());
+    }
+    std::vector<int> ent_region(d.entities.size(), -1);
+    for (int r = 0; r < int(loops.size()); ++r)
+        for (int ei : loops[r].ents)
+            if (ei >= 0 && ei < int(ent_region.size())) ent_region[ei] = r;
+
+    for (int ei = 0; ei < int(d.entities.size()); ++ei) {
+        if (d.entities[ei].construction) continue;   // as region_loops filters it
+        const double ed = entity_pick_dist(p, d.entities[ei]);
+        if (ed <= tol * 3.0 && ed < edge_d) {
+            edge_d = ed; edge_feat = d.feature; edge_reg = ent_region[ei]; edge_ent = ei;
+        }
+    }
+    // Pick the region the point is REALLY in: inside its boundary and not inside any of its
+    // holes. Clicking the middle of a plate-with-hole must select the plate; clicking inside
+    // the hole must select the disc, not the plate. Previously the first containing polygon
+    // won, so a click inside the circle selected the rectangle.
+    for (int r = 0; r < int(loops.size()); ++r) {
+        if (face_feat >= 0) break;
+        if (!point_in_poly(p, loops[r].poly)) continue;
+        bool in_hole = false;
+        for (int h : loops[r].holes)
+            if (h >= 0 && h < int(loops.size()) && point_in_poly(p, loops[h].poly)) { in_hole = true; break; }
+        if (!in_hole) { face_feat = d.feature; face_reg = r; }
+    }
+    // edge_ent is printed because it is now DELIVERED (3648) — a tool can ask for the
+    // line you pointed at, not just its loop, and "which entity did that click resolve to" is
+    // otherwise unanswerable from outside.
+    dp_pick_trace("region hit -> feat=%d reg=%d (edge_feat=%d edge_reg=%d edge_ent=%d)",
+                  face_feat, face_reg, edge_feat, edge_reg, edge_ent);
+}
+
+std::vector<SketchEntity> DesignSketchTool::selected_loop_entities() const
+{
+    if (m_display_pick < 0 || m_display_pick_region < 0) return {};
+    for (const DisplaySketch& d : m_display_sketches) {
+        if (d.feature != m_display_pick) continue;
+        const std::vector<RegionLoop> loops = region_loops(d.entities);
+        if (m_display_pick_region >= int(loops.size())) return {};
+        // The region's OWN boundary plus every loop nested in it. Handing over only the outer
+        // loop is what made a rectangle-with-a-circle extrude to a plain box: the circle was
+        // never passed to the kernel, so build_sketch_face had one loop to work with and the
+        // multi-loop path never ran.
+        std::vector<SketchEntity> out;
+        auto take = [&](int region) {
+            if (region < 0 || region >= int(loops.size())) return;
+            for (int ei : loops[region].ents)
+                if (ei >= 0 && ei < int(d.entities.size())) out.push_back(d.entities[ei]);
+        };
+        take(m_display_pick_region);
+        for (int h : loops[m_display_pick_region].holes) take(h);
+        return out;
+    }
+    return {};
+}
+
+// ---- Solid topology selection (whole -> face -> edge cycle) ----
+
+void DesignSketchTool::set_solid_pick(const std::vector<CadBody>* bodies, const TriangleMesh* mesh,
+                                      const std::vector<int>* tri_face, const std::vector<int>* tri_body,
+                                      const std::vector<bool>* visible,
+                                      const std::vector<Transform3d>* xform)
+{
+    // Treat no bodies or an empty mesh as "no solid" so has_display()/picking stay off.
+    if (bodies == nullptr || bodies->empty() || mesh == nullptr || mesh->its.indices.empty()) {
+        m_solid_bodies = nullptr; m_solid_mesh = nullptr; m_solid_tri_face = nullptr; m_solid_tri_body = nullptr;
+        m_solid_visible = nullptr; m_solid_xform = nullptr;
+    } else {
+        m_solid_bodies = bodies; m_solid_mesh = mesh; m_solid_tri_face = tri_face; m_solid_tri_body = tri_body;
+        m_solid_visible = visible; m_solid_xform = xform;
+    }
+    clear_solid_selection();
+}
+
+// Map a point sampled from the (untransformed) OCCT body shape through the body's display
+// transform, so edge picking/highlight track a moved body. The pick MESH is already
+// transformed by the host; only OCCT-sampled edges need this.
+Vec3d DesignSketchTool::body_xform_pt(int body, const Vec3d& p) const
+{
+    if (m_solid_xform != nullptr && body >= 0 && body < int(m_solid_xform->size()))
+        return (*m_solid_xform)[body] * p;
+    return p;
+}
+
+// A body is pickable unless an explicit visibility vector marks it hidden.
+bool DesignSketchTool::body_pickable(int b) const
+{
+    if (b < 0) return false;
+    // Body-focus mode. The focus is an INDEX held by the panel across recomputes, so it can
+    // outlive the body it names — delete a body and the stored index may point past the end.
+    // A restriction to a body that no longer exists rejects EVERY body, which is a viewport
+    // that silently accepts no clicks at all: the worst possible failure for a picking mode,
+    // because nothing on screen says why. Out of range therefore means NO restriction — fail
+    // open, never dead.
+    const bool focus_live = m_pick_only_body >= 0 && m_solid_bodies != nullptr
+                            && m_pick_only_body < int(m_solid_bodies->size());
+    if (focus_live && b != m_pick_only_body) return false;
+    if (m_solid_visible == nullptr || b >= int(m_solid_visible->size())) return true;
+    return (*m_solid_visible)[b];
+}
+
+void DesignSketchTool::clear_solid_selection()
+{
+    m_solid_sel = SolidSel::None;
+    m_sel_body = m_sel_face = m_sel_edge = -1;
+    m_sel_edge_pts.clear();
+    // The pre-highlight names a face/edge/vertex by index into a shape that a recompute has just
+    // rebuilt, so it expires with the selection it was a promise about. Left behind it would keep
+    // glowing on whatever now sits at those indices — a real entity, but not the one meant.
+    m_pre = SolidPick{};
+}
+
+void DesignSketchTool::select_body(int body)
+{
+    // Hidden bodies aren't highlighted (the tint overlay would otherwise draw over a
+    // body whose GLVolume is off, leaving a ghost after a hide).
+    if (m_solid_bodies == nullptr || body < 0 || body >= int(m_solid_bodies->size())
+        || !body_pickable(body)) {
+        clear_solid_selection();
+        return;
+    }
+    m_sel_body  = body;
+    m_sel_face  = m_sel_edge = -1;
+    m_sel_edge_pts.clear();
+    m_solid_sel = SolidSel::Whole;   // render_solid_highlight tints just this body
+}
+
+// Pick tracing. Selection failures on a real desktop have repeatedly turned out to be an
+// event that never arrived rather than a ray that missed, and the two look identical from
+// the UI. Set ORCA_CAD_PICK_TRACE=1 and the whole press->release->ray path narrates itself
+// on stderr. Off by default: no cost, no noise.
+static bool dp_pick_trace_on()
+{
+    static const bool on = ::getenv("ORCA_CAD_PICK_TRACE") != nullptr;
+    return on;
+}
+
+static void dp_pick_trace(const char* fmt, ...)
+{
+    if (!dp_pick_trace_on()) return;
+    va_list ap; va_start(ap, fmt);
+    std::fputs("[pick] ", stderr);
+    std::vfprintf(stderr, fmt, ap);
+    std::fputc('\n', stderr);
+    va_end(ap);
+    std::fflush(stderr);
+}
+
+// Resolve a swept rubber band into a whole-body selection.
+//
+// Sample points are the display mesh's triangle vertices plus each triangle's centroid. That
+// mesh is already in world coordinates — the very points the ray pick tests — so no per-body
+// transform is needed here. A body counts as swept when any of its samples lands inside the
+// rectangle (crossing semantics: touching selects, which is the forgiving reading of a sweep),
+// and the body with the most samples inside wins because the selection callback downstream
+// carries exactly one body.
+//
+// ponytail: crossing over a triangle sample set. A rectangle small enough to sit entirely
+// inside one flat triangle selects nothing — drag a bigger one, or click. Real multi-body
+// selection (and the homogeneous-set rule that goes with it) is 9xw.
+void DesignSketchTool::pick_bodies_in_rectangle()
+{
+    if (m_solid_mesh == nullptr || m_solid_tri_body == nullptr || m_solid_bodies == nullptr)
+        return;
+    const indexed_triangle_set& its = m_solid_mesh->its;
+    std::vector<Vec3d> pts;
+    std::vector<int>   owner;
+    pts.reserve(its.indices.size() * 4);
+    owner.reserve(its.indices.size() * 4);
+    for (size_t i = 0; i < its.indices.size(); ++i) {
+        const int b = (i < m_solid_tri_body->size()) ? (*m_solid_tri_body)[i] : -1;
+        if (!body_pickable(b)) continue;          // hidden bodies aren't swept either
+        const auto& idx = its.indices[i];
+        Vec3d c = Vec3d::Zero();
+        for (int k = 0; k < 3; ++k) {
+            const Vec3d p = its.vertices[idx(k)].cast<double>();
+            pts.push_back(p); owner.push_back(b); c += p;
+        }
+        pts.push_back(c / 3.0); owner.push_back(b);
+    }
+
+    std::vector<int> hits(m_solid_bodies->size(), 0);
+    if (!pts.empty())
+        for (unsigned int i : m_rubber.contains(pts))
+            if (i < owner.size() && owner[i] >= 0 && owner[i] < int(hits.size()))
+                ++hits[owner[i]];
+
+    int best = -1, best_n = 0;
+    for (int b = 0; b < int(hits.size()); ++b)
+        if (hits[b] > best_n) { best_n = hits[b]; best = b; }
+
+    if (best < 0) clear_solid_selection();        // swept empty space -> drop the selection
+    else          select_body(best);
+    dp_pick_trace("rubber band -> body=%d (%d samples)", best, best_n);
+    if (on_solid_selection_changed)
+        on_solid_selection_changed(int(m_solid_sel), m_sel_body, m_sel_face, m_sel_edge);
+}
+
+// Resolve what a pick at (mx,my) would take. CONST, and it writes only into `out`: the hover
+// path calls this many times a second and must not disturb the committed selection by doing so.
+bool DesignSketchTool::resolve_solid_pick(GLCanvas3D& canvas, int mx, int my, SolidPick& out) const
+{
+    out = SolidPick{};
+    if (m_solid_bodies == nullptr || m_solid_mesh == nullptr) {
+        dp_pick_trace("no solid data (bodies=%p mesh=%p)",
+                      (const void*) m_solid_bodies, (const void*) m_solid_mesh);
+        return false;
+    }
+    const Linef3 r = canvas.mouse_ray(Point(mx, my));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+
+    // 1) nearest solid face under the cursor (ray vs display-mesh triangles). Resolve WHICH
+    //    body and which face-within-that-body via the per-triangle (tri_body, tri_face) tags.
+    const indexed_triangle_set& its = m_solid_mesh->its;
+    int best_face = -1, best_body = -1; double best_t = 1e30;
+    for (size_t i = 0; i < its.indices.size(); ++i) {
+        const auto& idx = its.indices[i];
+        const Vec3d v0 = its.vertices[idx(0)].cast<double>();
+        const Vec3d v1 = its.vertices[idx(1)].cast<double>();
+        const Vec3d v2 = its.vertices[idx(2)].cast<double>();
+        double t;
+        if (ray_triangle(ro, rd, v0, v1, v2, t) && t < best_t) {
+            const int cand_body = (m_solid_tri_body && i < m_solid_tri_body->size()) ? (*m_solid_tri_body)[i] : -1;
+            if (!body_pickable(cand_body)) continue;   // hidden bodies don't catch clicks
+            best_t = t;
+            best_face = (m_solid_tri_face && i < m_solid_tri_face->size()) ? (*m_solid_tri_face)[i] : -1;
+            best_body = cand_body;
+        }
+    }
+    dp_pick_trace("ray tris=%zu -> body=%d face=%d t=%.3f", its.indices.size(),
+                  best_body, best_face, best_t);
+    if (best_face < 0 || best_body < 0 || best_body >= int(m_solid_bodies->size()))
+        return false;   // missed the solid
+
+    // ---- one click, one deterministic result ---------------------------------------------
+    // NO CYCLE. A click selects the SMALLEST thing under the cursor: the edge if the pointer is
+    // within tolerance of one, otherwise the face. The WHOLE body is taken by a left-drag
+    // rubber band (pick_bodies_in_rectangle) — a different gesture for a different scale.
+    //
+    // What this replaces: click 1 = whole body, click 2 = face, click 3 = nearest edge, click 4
+    // = back to whole. That made "click a face" a two-click gesture and "click an edge" a
+    // three-click one, neither discoverable — the L5 violation §10 of the charter already
+    // listed, and the real reason sketching on a face kept reading as broken however often the
+    // plane resolution was fixed. Selection is the foundation the tool offer stands on: the
+    // offer can only ever be as truthful as the selection beneath it.
+    //
+    // Tolerance is measured in SCREEN PIXELS. The old edge step compared a ray-to-segment
+    // distance in millimetres, so the same gesture meant different things at different zooms —
+    // the pointer is a screen object and its tolerance has to be one too.
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const wxPoint cursor(mx, my);
+    // Vertex beats edge beats face, and the vertex tolerance is the larger of the two: a corner
+    // sits ON its edges, so an equal radius would make vertices unreachable — every click near
+    // one would resolve to the edge it lies on.
+    const double  kVertexTolPx = 11.0;
+    const double  kEdgeTolPx   = 8.0;
+
+    auto seg_px = [](const wxPoint& p, const wxPoint& a, const wxPoint& b) {   // 2D point→segment, px
+        const double vx = b.x - a.x, vy = b.y - a.y;
+        const double wx = p.x - a.x, wy = p.y - a.y;
+        const double L2 = vx * vx + vy * vy;
+        double t = (L2 > 1e-12) ? (wx * vx + wy * vy) / L2 : 0.0;
+        t = std::max(0.0, std::min(1.0, t));
+        return std::hypot(wx - t * vx, wy - t * vy);
+    };
+
+    out.body = best_body;
+    out.face = best_face;
+
+    {
+        const TopoDS_Shape& bshape = (*m_solid_bodies)[out.body].shape;
+        const TopoDS_Face  face    = GeometryEngine::face_by_index(bshape, out.face);
+        double best_ed = 1e30; std::vector<Vec3d> ed_pts; TopoDS_Edge ed_edge; bool have_edge = false;
+        double best_vd = 1e30; Vec3d vtx = Vec3d::Zero(); bool have_vtx = false;
+        // Screen extent of the face, accumulated from the same edge samples the loop already
+        // takes. A FIXED edge tolerance makes a narrow face unreachable: a 3 mm-wide plate is
+        // barely wider on screen than the 8 px budget, so every point on it is "on an edge" and
+        // the face level can never be picked — which also blocks the face-based Coord Sys that a
+        // mate needs. The tolerances below shrink with the face so its middle stays its own.
+        int fx0 = INT_MAX, fy0 = INT_MAX, fx1 = INT_MIN, fy1 = INT_MIN;
+        if (!face.IsNull()) {
+            for (const TopoDS_Edge& e : GeometryEngine::edges_of_face(face)) {
+                std::vector<Vec3d> pts = GeometryEngine::sample_edge_world(e);
+                for (Vec3d& q : pts) q = body_xform_pt(out.body, q);   // follow a moved body
+                if (pts.size() < 2) continue;
+                // The polyline ends ARE the edge's vertices; every corner of the face is the
+                // end of one of its edges, so this covers them without a separate topology walk.
+                for (const Vec3d& v : {pts.front(), pts.back()}) {
+                    const wxPoint sp = world_to_screen_px(cam, v);
+                    if (sp.x < 0) continue;
+                    const double d = std::hypot(double(sp.x - cursor.x), double(sp.y - cursor.y));
+                    if (d < best_vd) { best_vd = d; vtx = v; have_vtx = true; }
+                }
+                double d = 1e30;
+                for (size_t s = 1; s < pts.size(); ++s) {
+                    const wxPoint a = world_to_screen_px(cam, pts[s - 1]);
+                    const wxPoint b = world_to_screen_px(cam, pts[s]);
+                    if (a.x < 0 || b.x < 0) continue;                    // behind the camera
+                    fx0 = std::min({fx0, a.x, b.x}); fx1 = std::max({fx1, a.x, b.x});
+                    fy0 = std::min({fy0, a.y, b.y}); fy1 = std::max({fy1, a.y, b.y});
+                    d = std::min(d, seg_px(cursor, a, b));
+                }
+                if (d < best_ed) { best_ed = d; ed_pts = pts; ed_edge = e; have_edge = true; }
+            }
+        }
+        // A third of the face's SHORTER on-screen side, so the two tolerances can never meet in
+        // the middle. Only ever shrinks: a face big enough keeps the full budget.
+        double vtol = kVertexTolPx, etol = kEdgeTolPx;
+        if (fx1 > fx0 && fy1 > fy0) {
+            const double narrow = double(std::min(fx1 - fx0, fy1 - fy0)) / 3.0;
+            vtol = std::min(vtol, narrow);
+            etol = std::min(etol, narrow);
+        }
+        if (have_vtx && best_vd <= vtol) {
+            out.vertex_pt = vtx;
+            out.kind      = SolidSel::Vertex;
+        } else if (have_edge && best_ed <= etol) {
+            // Promote the face-relative pick to a STABLE GLOBAL edge id so dress-up ops
+            // (fillet/chamfer) can target this exact edge across recomputes.
+            out.edge     = GeometryEngine::edge_index_of(bshape, ed_edge);
+            out.edge_pts = std::move(ed_pts);
+            out.kind     = SolidSel::Edge;
+        } else {
+            out.kind = SolidSel::Face;
+        }
+    }
+    return true;
+}
+
+// A click on the solid takes the smallest thing under the cursor (vertex/edge/face). Returns
+// true if the click hit the solid (consumed); false otherwise so the caller can try
+// committed-sketch loop picking. Whole bodies are taken by the rubber band, not by clicking.
+bool DesignSketchTool::handle_solid_click(GLCanvas3D& canvas, const wxMouseEvent& evt)
+{
+    SolidPick p;
+    if (!resolve_solid_pick(canvas, evt.GetX(), evt.GetY(), p))
+        return false;   // missed the solid, or no solid data — same two exits as before
+
+    // What was selected BEFORE this pick — the escalation below is the only thing that reads
+    // it, and everything from here on overwrites it.
+    const SolidSel prev_kind = m_solid_sel;
+    const int      prev_body = m_sel_body, prev_face = m_sel_face, prev_edge = m_sel_edge;
+    const Vec3d    prev_vtx  = m_sel_vertex_pt;
+
+    m_sel_body      = p.body;
+    m_sel_face      = p.face;
+    m_sel_edge      = p.edge;
+    m_sel_edge_pts  = std::move(p.edge_pts);
+    m_sel_vertex_pt = p.vertex_pt;
+    m_solid_sel     = p.kind;
+
+    // CLICK AGAIN ON THE SAME THING -> THE WHOLE BODY (gem). Pointing at a face and
+    // pointing at its body are different intents, and until now only the rubber band could
+    // express the second one — so the status line said "face 0 selected" while the user
+    // believed they had taken the body, and every body verb had to opt into the face kinds to
+    // stay reachable. One more click on the SAME sub-element escalates.
+    //
+    // This is not the pick cycle that was removed (bc2b741ce9). That one was silent and three
+    // deep, so no click had a predictable meaning. Here the escalation is announced by the
+    // status line BEFORE you make the click, and a further click just takes the face under the
+    // cursor again — the ordinary meaning of clicking a face, which needs no teaching.
+    //
+    // Double-click is safe: wx sends Down/Up/DClick/Up, and only the first Up carries a
+    // pending press, so a fast double-click zooms to fit and picks ONCE. Escalation needs two
+    // separate clicks, the same "click, pause, click" distinction a file manager uses.
+    //
+    // "The same thing" is compared AT THE LEVEL THAT WAS PICKED, and nothing else. Requiring
+    // every field to match looked stricter and was simply wrong: an edge pick leaves m_sel_face
+    // set to whichever face the ray happened to hit, and a shared edge is reached through a
+    // different face depending on which side of the body you are looking from. So picking an
+    // edge, orbiting, and clicking that same edge from the other side left m_sel_edge equal and
+    // m_sel_face different, and the escalation the status line had just promised did not happen.
+    // The edge id here is already the STABLE GLOBAL one (edge_index_of, a few lines up) — it
+    // identifies the edge on its own and does not need the face to disambiguate it.
+    const bool same_pick = m_solid_sel == prev_kind && m_sel_body == prev_body
+        && (m_solid_sel == SolidSel::Vertex ? (m_sel_vertex_pt - prev_vtx).norm() < 1e-9
+          : m_solid_sel == SolidSel::Edge   ? m_sel_edge == prev_edge
+          : m_solid_sel == SolidSel::Face   ? m_sel_face == prev_face
+                                            : true);
+    if (same_pick && m_escalate_repick) {
+        select_body(m_sel_body);   // clears face/edge/vertex, tints the whole body
+        dp_pick_trace("re-pick -> escalated to whole body %d", m_sel_body);
+    }
+    dp_pick_trace("pick -> sel=%d body=%d face=%d edge=%d",
+                  int(m_solid_sel), m_sel_body, m_sel_face, m_sel_edge);
+    if (on_solid_selection_changed)
+        on_solid_selection_changed(int(m_solid_sel), m_sel_body, m_sel_face, m_sel_edge);
+    return true;
+}
+
+// Recompute what the pointer is over. Returns true only when the answer CHANGED — this runs on
+// every motion event, and a repaint per event would cost far more than the pick itself.
+bool DesignSketchTool::update_solid_hover(GLCanvas3D& canvas, const wxMouseEvent& evt)
+{
+    SolidPick p;
+    if (!resolve_solid_pick(canvas, evt.GetX(), evt.GetY(), p))
+        p = SolidPick{};   // off the solid: no promise to make
+    // Compared AT THE LEVEL THAT WAS PICKED, for the same reason the click's escalation is
+    // (see same_pick above): an edge pick carries whichever face the ray happened to cross, and
+    // that face changes as the pointer slides along the edge without the answer changing at all.
+    const bool same = p.kind == m_pre.kind && p.body == m_pre.body
+        && (p.kind == SolidSel::Vertex ? (p.vertex_pt - m_pre.vertex_pt).norm() < 1e-9
+          : p.kind == SolidSel::Edge   ? p.edge == m_pre.edge
+          : p.kind == SolidSel::Face   ? p.face == m_pre.face
+                                       : true);
+    if (same) return false;
+    m_pre = std::move(p);
+    return true;
+}
+
+// One highlight, drawn from explicit arguments rather than from the selection members, so the
+// committed selection and the hover pre-highlight cannot drift apart in how they look. alpha_mul
+// scales every layer at once: the pre-highlight is the same shape in the same place, quieter.
+void DesignSketchTool::render_solid_sel(SolidSel kind, int body, int face,
+                                        const std::vector<Vec3d>& edge_pts,
+                                        const Vec3d& vertex_pt,
+                                        const ColorRGBA& rgb, float alpha_mul)
+{
+    using EPT = GLModel::Geometry::EPrimitiveType;
+    using EVL = GLModel::Geometry::EVertexLayout;
+    // Opaque: the edge ribbon and the vertex square render with GL_BLEND OFF, so an alpha below 1
+    // here would be silently ignored. Those two are quietened by a MUTED rgb from the caller
+    // instead; alpha_mul only reaches the face fill, which is the one layer that is blended.
+    const ColorRGBA cyan(rgb.r(), rgb.g(), rgb.b(), 1.0f);
+
+    // Whole tints the picked BODY (all its triangles, lighter alpha); Face tints just the
+    // picked face on that body. Both filter by `body` so other bodies stay untinted.
+    if ((kind == SolidSel::Face || kind == SolidSel::Whole)
+        && m_solid_mesh != nullptr && m_solid_tri_body != nullptr && body >= 0) {
+        const bool face_only = (kind == SolidSel::Face);
+        const indexed_triangle_set& its = m_solid_mesh->its;
+        GLModel::Geometry g; g.format = { EPT::Triangles, EVL::P3 };
+        unsigned int base = 0;
+        for (size_t i = 0; i < its.indices.size(); ++i) {
+            if (i >= m_solid_tri_body->size() || (*m_solid_tri_body)[i] != body) continue;
+            if (face_only && (m_solid_tri_face == nullptr || i >= m_solid_tri_face->size()
+                              || (*m_solid_tri_face)[i] != face)) continue;
+            const auto& idx = its.indices[i];
+            for (int j = 0; j < 3; ++j) g.add_vertex(its.vertices[idx(j)]);
+            g.add_triangle(base, base + 1, base + 2); base += 3;
+        }
+        if (base > 0) {
+            glsafe(::glEnable(GL_DEPTH_TEST));
+            glsafe(::glEnable(GL_POLYGON_OFFSET_FILL));
+            glsafe(::glPolygonOffset(-2.0f, -2.0f));
+            glsafe(::glEnable(GL_BLEND));
+            glsafe(::glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));
+            m_solid_face_model.reset();
+            m_solid_face_model.init_from(std::move(g));
+            m_solid_face_model.set_color(ColorRGBA(rgb.r(), rgb.g(), rgb.b(),
+                                                  (face_only ? 0.40f : 0.22f) * alpha_mul));
+            m_solid_face_model.render();
+            glsafe(::glDisable(GL_BLEND));
+            glsafe(::glDisable(GL_POLYGON_OFFSET_FILL));
+            glsafe(::glDisable(GL_DEPTH_TEST));
+        }
+    } else if (kind == SolidSel::Edge && edge_pts.size() >= 2) {
+        const Camera& cam = wxGetApp().plater()->get_camera();
+        const Vec3d vd = cam.get_dir_forward();
+        const double hw = 2.0 / std::max(cam.get_zoom(), 1e-6);   // ~2 px ribbon half-width
+        GLModel::Geometry g; g.format = { EPT::Triangles, EVL::P3 };
+        unsigned int base = 0;
+        for (size_t s = 1; s < edge_pts.size(); ++s) {
+            const Vec3d a = edge_pts[s - 1], b = edge_pts[s];
+            Vec3d dir = b - a; if (dir.norm() < 1e-9) continue; dir.normalize();
+            Vec3d off = dir.cross(vd);
+            if (off.norm() < 1e-9) off = dir.cross(cam.get_dir_up());
+            if (off.norm() < 1e-9) continue;
+            off.normalize(); off *= hw;
+            g.add_vertex((Vec3f)(a + off).cast<float>());
+            g.add_vertex((Vec3f)(b + off).cast<float>());
+            g.add_vertex((Vec3f)(b - off).cast<float>());
+            g.add_vertex((Vec3f)(a - off).cast<float>());
+            g.add_triangle(base, base + 1, base + 2);
+            g.add_triangle(base, base + 2, base + 3); base += 4;
+        }
+        if (base > 0) {
+            glsafe(::glDisable(GL_DEPTH_TEST));
+            m_solid_edge_model.reset();
+            m_solid_edge_model.init_from(std::move(g));
+            m_solid_edge_model.set_color(cyan);
+            m_solid_edge_model.render();
+        }
+    } else if (kind == SolidSel::Vertex) {
+        // A camera-facing square at the picked corner, sized in screen terms (the same
+        // 1/zoom trick the edge ribbon uses) so it stays a constant dot at every zoom. A
+        // selection you cannot see is not a selection (L5), which is why vertex picking waited
+        // for this rather than shipping without a highlight.
+        const Camera& cam = wxGetApp().plater()->get_camera();
+        Vec3d right = cam.get_dir_right(), up = cam.get_dir_up();
+        const double h = 4.5 / std::max(cam.get_zoom(), 1e-6);   // ~4.5 px half-size
+        right *= h; up *= h;
+        const Vec3d c = vertex_pt;
+        GLModel::Geometry g; g.format = { EPT::Triangles, EVL::P3 };
+        g.add_vertex((Vec3f)(c - right - up).cast<float>());
+        g.add_vertex((Vec3f)(c + right - up).cast<float>());
+        g.add_vertex((Vec3f)(c + right + up).cast<float>());
+        g.add_vertex((Vec3f)(c - right + up).cast<float>());
+        g.add_triangle(0, 1, 2);
+        g.add_triangle(0, 2, 3);
+        glsafe(::glDisable(GL_DEPTH_TEST));
+        m_solid_vertex_model.reset();
+        m_solid_vertex_model.init_from(std::move(g));
+        m_solid_vertex_model.set_color(cyan);
+        m_solid_vertex_model.render();
+    }
+}
+
+// Cyan overlay for the picked face / edge / vertex, plus the quieter pre-highlight of whatever
+// the pointer is currently over. Whole-solid tint is the panel's job (set_body_highlight).
+// Called from render() while no sketch session is active.
+void DesignSketchTool::render_solid_highlight()
+{
+    const ColorRGBA sel_cyan = design_selection_color();
+
+    // The pre-highlight goes FIRST so the committed selection paints over it where the two
+    // overlap — what you HAVE outranks what you would get. Suppressed entirely when they are the
+    // same thing: two coats of the same colour on the same face reads as a rendering fault, and
+    // a promise about a click that would change nothing is not worth making.
+    const bool pre_is_sel = m_pre.kind == m_solid_sel && m_pre.body == m_sel_body
+        && (m_pre.kind == SolidSel::Vertex ? (m_pre.vertex_pt - m_sel_vertex_pt).norm() < 1e-9
+          : m_pre.kind == SolidSel::Edge   ? m_pre.edge == m_sel_edge
+          : m_pre.kind == SolidSel::Face   ? m_pre.face == m_sel_face
+                                           : true);
+    if (m_pre.kind != SolidSel::None && !pre_is_sel)
+        // Desaturated toward white rather than a second hue: a distinct colour would read as a
+        // distinct KIND of selection, when it is the same selection one moment earlier.
+        render_solid_sel(m_pre.kind, m_pre.body, m_pre.face, m_pre.edge_pts, m_pre.vertex_pt,
+                         design_selection_color(), 0.45f);   // hover = the same colour, quieter
+
+    render_solid_sel(m_solid_sel, m_sel_body, m_sel_face, m_sel_edge_pts, m_sel_vertex_pt,
+                     sel_cyan, 1.0f);
+}
+
+// Datum/reference planes (Plane feature) have no solid; draw each as a translucent indigo
+// rectangle + border so it is visible in the viewport (Onshape-style finite plane). World
+// space, depth-test off so it reads over the bed; indigo to stay distinct from the cyan
+// solid-selection tint, orange sketches and amber feature ghosts.
+void DesignSketchTool::render_view_helpers()
+{
+    if (!m_show_planes && !m_show_axes) return;
+    using EPT = GLModel::Geometry::EPrimitiveType;
+    using EVL = GLModel::Geometry::EVertexLayout;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d vd = cam.get_dir_forward();
+    const double hw = 1.5 / std::max(cam.get_zoom(), 1e-6);   // billboard ribbon half-width (px)
+
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    glsafe(::glEnable(GL_BLEND));
+    glsafe(::glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));
+
+    if (m_show_planes) {
+        const double H = 40.0;   // half-extent (mm)
+        SketchPlane pl[3];       // XY / XZ / YZ through the world origin
+        pl[0].origin = Vec3d(0,0,0); pl[0].x_axis = Vec3d(1,0,0); pl[0].y_axis = Vec3d(0,1,0); pl[0].normal = Vec3d(0,0,1);
+        pl[1].origin = Vec3d(0,0,0); pl[1].x_axis = Vec3d(1,0,0); pl[1].y_axis = Vec3d(0,0,1); pl[1].normal = Vec3d(0,1,0);
+        pl[2].origin = Vec3d(0,0,0); pl[2].x_axis = Vec3d(0,1,0); pl[2].y_axis = Vec3d(0,0,1); pl[2].normal = Vec3d(1,0,0);
+        GLModel::Geometry fill; fill.format = { EPT::Triangles, EVL::P3 };
+        unsigned int fb = 0;
+        for (const SketchPlane& p : pl) {
+            const Vec3d c[4] = { p.to_world(Vec2d(-H,-H)), p.to_world(Vec2d(H,-H)),
+                                 p.to_world(Vec2d(H,H)),   p.to_world(Vec2d(-H,H)) };
+            fill.add_vertex((Vec3f)c[0].cast<float>()); fill.add_vertex((Vec3f)c[1].cast<float>());
+            fill.add_vertex((Vec3f)c[2].cast<float>()); fill.add_triangle(fb, fb+1, fb+2); fb += 3;
+            fill.add_vertex((Vec3f)c[0].cast<float>()); fill.add_vertex((Vec3f)c[2].cast<float>());
+            fill.add_vertex((Vec3f)c[3].cast<float>()); fill.add_triangle(fb, fb+1, fb+2); fb += 3;
+        }
+        if (fb > 0) { GLModel fm; fm.init_from(std::move(fill));
+            fm.set_color(ColorRGBA(0.42f, 0.52f, 0.78f, 0.20f)); fm.render(); }
+    }
+
+    if (m_show_axes) {
+        const double L = 60.0;   // axis length (mm)
+        struct Ax { Vec3d dir; ColorRGBA col; };
+        const Ax axes[3] = { { Vec3d(1,0,0), ColorRGBA(0.92f, 0.28f, 0.28f, 0.9f) },
+                             { Vec3d(0,1,0), ColorRGBA(0.30f, 0.80f, 0.34f, 0.9f) },
+                             { Vec3d(0,0,1), ColorRGBA(0.32f, 0.55f, 0.95f, 0.9f) } };
+        for (const Ax& ax : axes) {
+            // Lines don't rasterise under the reused software GL context, so each axis is a
+            // thin view-facing ribbon (two triangles), like the datum-plane border.
+            const Vec3d a = Vec3d(0,0,0), b = ax.dir * L;
+            Vec3d dir = (b - a).normalized();
+            Vec3d off = dir.cross(vd);
+            if (off.norm() < 1e-9) off = dir.cross(cam.get_dir_up());
+            if (off.norm() < 1e-9) continue;
+            off.normalize(); off *= hw * 1.5;
+            GLModel::Geometry g; g.format = { EPT::Triangles, EVL::P3 };
+            g.add_vertex((Vec3f)(a + off).cast<float>()); g.add_vertex((Vec3f)(b + off).cast<float>());
+            g.add_vertex((Vec3f)(b - off).cast<float>()); g.add_vertex((Vec3f)(a - off).cast<float>());
+            g.add_triangle(0, 1, 2); g.add_triangle(0, 2, 3);
+            GLModel m; m.init_from(std::move(g)); m.set_color(ax.col); m.render();
+        }
+    }
+    glsafe(::glDisable(GL_BLEND));
+}
+
+void DesignSketchTool::render_datum_planes()
+{
+    if (m_datum_planes.empty()) return;
+    using EPT = GLModel::Geometry::EPrimitiveType;
+    using EVL = GLModel::Geometry::EVertexLayout;
+    const double H = 40.0;   // default half-extent when no per-plane size is given (mm)
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d vd = cam.get_dir_forward();
+    const double hw = 1.5 / std::max(cam.get_zoom(), 1e-6);   // ~1.5 px border ribbon
+
+    GLModel::Geometry fill;   fill.format   = { EPT::Triangles, EVL::P3 };
+    GLModel::Geometry border; border.format = { EPT::Triangles, EVL::P3 };
+    unsigned int fb = 0, bb = 0;
+    for (size_t pi = 0; pi < m_datum_planes.size(); ++pi) {
+        const SketchPlane& p = m_datum_planes[pi];
+        // Per-plane u/v half-extent (the GUI Size U/V + drag handles drive these); fall
+        // back to the square default when no size was supplied.
+        const double hu = (pi < m_datum_sizes.size() && m_datum_sizes[pi].x() > 1e-6)
+                              ? m_datum_sizes[pi].x() * 0.5 : H;
+        const double hv = (pi < m_datum_sizes.size() && m_datum_sizes[pi].y() > 1e-6)
+                              ? m_datum_sizes[pi].y() * 0.5 : H;
+        const Vec3d c[4] = { p.to_world(Vec2d(-hu, -hv)), p.to_world(Vec2d(hu, -hv)),
+                             p.to_world(Vec2d(hu, hv)),   p.to_world(Vec2d(-hu, hv)) };
+        fill.add_vertex((Vec3f)c[0].cast<float>()); fill.add_vertex((Vec3f)c[1].cast<float>());
+        fill.add_vertex((Vec3f)c[2].cast<float>()); fill.add_triangle(fb, fb + 1, fb + 2); fb += 3;
+        fill.add_vertex((Vec3f)c[0].cast<float>()); fill.add_vertex((Vec3f)c[2].cast<float>());
+        fill.add_vertex((Vec3f)c[3].cast<float>()); fill.add_triangle(fb, fb + 1, fb + 2); fb += 3;
+        for (int s = 0; s < 4; ++s) {
+            const Vec3d a = c[s], b = c[(s + 1) & 3];
+            Vec3d dir = b - a; if (dir.norm() < 1e-9) continue; dir.normalize();
+            Vec3d off = dir.cross(vd);
+            if (off.norm() < 1e-9) off = dir.cross(cam.get_dir_up());
+            if (off.norm() < 1e-9) continue;
+            off.normalize(); off *= hw;
+            border.add_vertex((Vec3f)(a + off).cast<float>());
+            border.add_vertex((Vec3f)(b + off).cast<float>());
+            border.add_vertex((Vec3f)(b - off).cast<float>());
+            border.add_vertex((Vec3f)(a - off).cast<float>());
+            border.add_triangle(bb, bb + 1, bb + 2);
+            border.add_triangle(bb, bb + 2, bb + 3); bb += 4;
+        }
+    }
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    glsafe(::glEnable(GL_BLEND));
+    glsafe(::glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));
+    if (fb > 0) {
+        GLModel fm; fm.init_from(std::move(fill));
+        fm.set_color(ColorRGBA(0.62f, 0.52f, 0.95f, 0.10f));
+        fm.render();
+    }
+    if (bb > 0) {
+        GLModel bm; bm.init_from(std::move(border));
+        bm.set_color(ColorRGBA(0.70f, 0.60f, 1.0f, 0.85f));
+        bm.render();
+    }
+    glsafe(::glDisable(GL_BLEND));
+}
+
+// ---- Visual Extrude gizmo (C5b) -------------------------------------------------------
+void DesignSketchTool::set_extrude_gizmo(const SketchPlane& plane, const Vec2d& centroid,
+                                         double depth, double depth2, bool two_sided, bool flip)
+{
+    m_ex_active    = true;
+    m_ex_plane     = plane;
+    m_ex_centroid  = centroid;
+    m_ex_depth     = std::max(0.0, depth);
+    m_ex_depth2    = std::max(0.0, depth2);
+    m_ex_two_sided = two_sided;
+    m_ex_flip      = flip;
+}
+
+void DesignSketchTool::clear_extrude_gizmo()
+{
+    m_ex_active = false;
+    m_ex_drag   = -1;
+}
+
+// Camera-billboarded depth arrow(s) along the profile normal, drawn in WORLD via a billboard
+// SketchPlane at the centroid (draw_strokes/draw_text lift 2D coords through m_plane.to_world,
+// so swapping m_plane to a screen-facing frame renders a flat, screen-aligned arrow + label).
+// The mate-connector glyph. Three elements, each answering one question, and every dimension is in
+// SCREEN PIXELS via upp (= 1/zoom) like every other gizmo here — a connector is a symbol, not a part,
+// so it must not shrink with the model.
+//
+//   disc      the XY plane        "I am a frame, and this is the plane I sit in"
+//   quadrant  the +x/+y sector    "this is where X is"  -- the roll, otherwise invisible
+//   Z arrow   +Z only, never -Z   "this is the way I point"  -- the VERSE
+//
+// POLARITY (which one is anchored, which one is about to move) is carried by the head: a filled
+// cone travels, an open collar receives. No surveyed CAD system encodes this at all; both ends of
+// their mates are drawn identically, which is why "which part moves?" is a standing complaint.
+//
+// ORCA_CAD_GLYPH=A|B selects the treatment while this is being judged on the rig:
+//   A  three short axis arms, no head differentiation  (the Onshape baseline)
+//   B  one-sided Z arrow, filled vs open head          (the proposal)          -- default
+void DesignSketchTool::render_mate_connectors()
+{
+    if (m_mate_connectors.empty()) return;
+    static const bool style_A = [] {
+        const char* s = ::getenv("ORCA_CAD_GLYPH");
+        return s && (*s == 'A' || *s == 'a');
+    }();
+    // The face treatment, on by default. Read every frame rather than latched in a static, so
+    // toggling the preference takes effect on the next repaint instead of at the next launch —
+    // it is a look, and a look you cannot A/B without restarting will not get compared.
+    // ORCA_CAD_GLYPH=D forces the disc regardless, which is how the rig drives the other branch.
+    const bool face_style = !style_A
+                         && wxGetApp().app_config->get_bool("design_connector_face_glyph")
+                         && [] { const char* s = ::getenv("ORCA_CAD_GLYPH");
+                                 return !(s && (*s == 'D' || *s == 'd')); }();
+
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const double upp  = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double R    = 22.0 * upp;                     // disc radius, ~22 px
+    const double lw   = std::max(0.9 * upp, 1e-4);
+
+    const ColorRGBA gold (0.93f, 0.66f, 0.09f, 1.0f);
+    const ColorRGBA blue (0.18f, 0.44f, 0.93f, 1.0f);
+    const ColorRGBA grey (0.42f, 0.46f, 0.52f, 1.0f);
+    // F5: roll-undefined was a loud red — the strongest colour in the viewport spent on the LEAST
+    // important connector, which pulled the eye away from the mate being made. It is a "this one
+    // could not be derived" mark, not an error: muted amber says look-here without shouting.
+    const ColorRGBA warn (0.72f, 0.55f, 0.22f, 1.0f);
+
+    const SketchPlane saved = m_plane;
+
+    for (const MateConnectorGlyph& g : m_mate_connectors) {
+        const Vec3d X = g.x.normalized();
+        const Vec3d Y = g.y.normalized();
+        const Vec3d Z = X.cross(Y).normalized();
+        const ColorRGBA body = (g.role == 2) ? blue : grey;
+
+        // ---- disc + quadrant, drawn IN the connector's own plane. This is the part that must not
+        // be billboarded: a disc that always faces the camera cannot show the frame's orientation,
+        // which is the only reason it is a disc and not a dot.
+        // Lifted off the surface by a sub-pixel epsilon. A connector's disc is EXACTLY coplanar with
+        // the face it sits on, so depth-testing it z-fights: on the rig the disc came out as a broken
+        // dotted arc that flickered with the camera. Depth off floats it through solids, depth on and
+        // coplanar tears it — the lift is what buys both. Scaled by upp so it stays sub-pixel at any
+        // zoom instead of becoming a visible gap when you zoom in.
+        // A face asserts a definite roll. When the roll could NOT be derived, drawing one would be
+        // a confident lie about the very thing that is unknown — the same objection that rejected
+        // billboarding the quadrant — so an underived connector keeps the disc treatment and its
+        // hatched quadrant, whatever the preference says.
+        if (face_style && !g.roll_undefined) {
+            render_mate_face(g.origin, X, Y, Z, R, body);
+        } else {
+
+        SketchPlane cp; cp.origin = g.origin + Z * (0.7 * upp);
+        cp.x_axis = X; cp.y_axis = Y; cp.normal = Z;
+        m_plane = cp;
+        {
+            std::vector<std::pair<Vec2d, Vec2d>> segs;
+            const int N = 40;
+            for (int i = 0; i < N; ++i) {
+                const double a0 = (2.0 * M_PI * i) / N, a1 = (2.0 * M_PI * (i + 1)) / N;
+                segs.emplace_back(Vec2d(R * std::cos(a0), R * std::sin(a0)),
+                                  Vec2d(R * std::cos(a1), R * std::sin(a1)));
+            }
+            // Depth test ON for the disc, deliberately. With it off, a connector on a face pointing
+            // AWAY from the camera still drew its disc over the solid, so the part looked covered in
+            // frames that were really on its back — and a disc floating over an edge read as
+            // detached rather than planted. render_hole_gizmo learned the same thing for its cube.
+            glsafe(::glEnable(GL_DEPTH_TEST));
+            draw_strokes(m_mc_stroke_model, segs, lw, g.roll_undefined ? warn : body);
+
+            // The quadrant: hatched when the roll could not be derived (a full circular face or a
+            // seam offers no in-plane direction), so the fallback is a mark you cannot miss rather
+            // than a silent guess.
+            std::vector<std::pair<Vec2d, Vec2d>> q;
+            const double qr = R * 0.84;
+            const int    QN = 10;
+            for (int i = 0; i < QN; ++i) {
+                const double a0 = (M_PI_2 * i) / QN, a1 = (M_PI_2 * (i + 1)) / QN;
+                q.emplace_back(Vec2d(qr * std::cos(a0), qr * std::sin(a0)),
+                               Vec2d(qr * std::cos(a1), qr * std::sin(a1)));
+            }
+            q.emplace_back(Vec2d(0, 0), Vec2d(qr, 0));
+            q.emplace_back(Vec2d(0, 0), Vec2d(0, qr));
+            if (!g.roll_undefined) {
+                for (int i = 1; i < 5; ++i) {          // fan lines read as "filled" at any angle
+                    const double a = (M_PI_2 * i) / 5.0;
+                    q.emplace_back(Vec2d(0, 0), Vec2d(qr * std::cos(a), qr * std::sin(a)));
+                }
+                // F4: the quadrant collapses to a blob at grazing angles — exactly when the roll
+                // is hardest to read. A radial tick along +X, extending PAST the disc rim, is what
+                // survives that: as the disc flattens to a line the sector loses all area, but a
+                // radial spoke keeps its length and its direction along the one axis that still
+                // projects.
+                //
+                // The alternative on the issue was billboarding the quadrant. Rejected, and not
+                // on taste: at true grazing the view direction lies IN the connector's plane, so
+                // every in-plane direction projects onto the same screen line and the roll is
+                // geometrically unrecoverable. A billboarded quadrant would not recover it — it
+                // would face the camera and read as a definite orientation that is not the frame's.
+                // Better to degrade to a direction you can still trust than to draw a confident
+                // lie. Judge the tick on the rig at a true grazing view before calling F4 closed.
+                q.emplace_back(Vec2d(R, 0), Vec2d(R * 1.28, 0));
+            }
+            draw_strokes(m_mc_stroke_model, q, lw, g.roll_undefined ? warn : gold);
+        }
+        }   // end of the disc treatment
+
+        // ---- the axes. Billboarded at the origin: a 3D direction is projected onto the screen
+        // frame, which is the only way an arrow keeps a readable head at any viewing angle.
+        SketchPlane bb; bb.origin = g.origin; bb.x_axis = right; bb.y_axis = up;
+        bb.normal = cam.get_dir_forward().normalized();
+        m_plane = bb;
+
+        auto arrow = [&](const Vec3d& dir, double len, const ColorRGBA& col, bool filled_head) {
+            const Vec3d tipw = g.origin + dir * len;
+            const Vec2d tip2((tipw - g.origin).dot(right), (tipw - g.origin).dot(up));
+            std::vector<std::pair<Vec2d, Vec2d>> segs;
+            // Foreshortening: when the axis points at (or away from) the camera it projects to
+            // nothing and an arrow degenerates into a dot. Draw a ring instead — "pointing at you"
+            // — rather than silently vanishing, which is what a naive projection does.
+            if (tip2.norm() < R * 0.28) {
+                const int N = 24;
+                const double rr = R * 0.30;
+                for (int i = 0; i < N; ++i) {
+                    const double a0 = (2.0 * M_PI * i) / N, a1 = (2.0 * M_PI * (i + 1)) / N;
+                    segs.emplace_back(Vec2d(rr * std::cos(a0), rr * std::sin(a0)),
+                                      Vec2d(rr * std::cos(a1), rr * std::sin(a1)));
+                }
+                draw_strokes(m_mc_stroke_model, segs, lw, col);
+                return;
+            }
+            const Vec2d u = tip2.normalized();
+            const Vec2d n(-u.y(), u.x());
+            const double as = R * 0.42;
+            const Vec2d back = tip2 - u * as;
+            segs.emplace_back(Vec2d(0, 0), back);
+            segs.emplace_back(tip2, back + n * (as * 0.45));
+            segs.emplace_back(tip2, back - n * (as * 0.45));
+            if (filled_head) {
+                // A closed head reads solid; the open one is left as two barbs. At 20-odd pixels
+                // this is the difference that says "this body travels".
+                segs.emplace_back(back + n * (as * 0.45), back - n * (as * 0.45));
+                segs.emplace_back(back + n * (as * 0.22), tip2);
+                segs.emplace_back(back - n * (as * 0.22), tip2);
+            } else {
+                segs.emplace_back(back + n * (as * 0.45), back - n * (as * 0.45));
+            }
+            glsafe(::glDisable(GL_DEPTH_TEST));
+            draw_strokes(m_mc_stroke_model, segs, lw, col);
+        };
+
+        if (style_A) {
+            arrow(X, R * 1.15, ColorRGBA(0.85f, 0.29f, 0.24f, 1.0f), true);
+            arrow(Y, R * 1.15, ColorRGBA(0.23f, 0.65f, 0.35f, 1.0f), true);
+            arrow(Z, R * 1.60, blue, true);
+        } else {
+            arrow(Z, R * 2.10, body, g.role == 2);   // +Z only. Nothing is ever drawn on -Z.
+        }
+    }
+
+    // ---- the pair line. Dashed, drawn IN WORLD along the segment joining the two origins, so it
+    // foreshortens with the model and its length is the gap the mate has still to close. Screen-
+    // constant dashes like everything else here; the dash pitch opens up on a long span so a mate
+    // across a large assembly cannot emit thousands of segments.
+    for (const auto& lnk : m_mate_links) {
+        const Vec3d d = lnk.second - lnk.first;
+        const double L = d.norm();
+        if (L < 1e-9) continue;
+        SketchPlane lp;
+        lp.origin = lnk.first;
+        lp.x_axis = d / L;
+        lp.y_axis = lp.x_axis.cross(cam.get_dir_forward().normalized());
+        if (lp.y_axis.norm() < 1e-6) lp.y_axis = lp.x_axis.cross(up);   // link along the view axis
+        lp.y_axis.normalize();
+        lp.normal = lp.x_axis.cross(lp.y_axis);
+        m_plane = lp;
+
+        std::vector<std::pair<Vec2d, Vec2d>> segs;
+        const double dash = 6.0 * upp;
+        const double step = std::max(dash + 4.0 * upp, L / 400.0);
+        for (double t = 0.0; t < L; t += step)
+            segs.emplace_back(Vec2d(t, 0.0), Vec2d(std::min(t + dash, L), 0.0));
+        // Depth off: the line's job is to say "these two belong together", and it has to say it
+        // even when the parts it spans are between the camera and one of the ends.
+        glsafe(::glDisable(GL_DEPTH_TEST));
+        draw_strokes(m_mc_stroke_model, segs, lw, grey);
+    }
+
+    m_plane = saved;
+}
+
+// ---------------------------------------------------------------------------------------------
+// THE FACE TREATMENT of the mate connector (x0kd). The disc + roll quadrant answers
+// "where is X" with a shape that has to be learned; a face does not. Face orientation is
+// hardwired perception -- a toddler reads a face's roll and verse with no instruction at all --
+// and that is the whole reason this exists. Default ON, switchable in Preferences for users who
+// expect the conventional CAD representation.
+//
+// WHY A RELIEF AND NOT A FLAT DRAWING, which is the non-obvious half. A flat face drawn in the
+// connector's plane foreshortens by sin(elevation) and collapses at a grazing view exactly like
+// the quadrant it replaces -- measured on the rig, the quadrant falls from 89 lit pixels at 47
+// degrees to 3 at 10 and 0 edge-on. A relief does not: at a grazing angle its SILHOUETTE carries
+// the information. The same bear rendered flat vs in relief gives 164 vs 210 lit pixels at 16
+// degrees and 66 vs 120 at 6. So the glyph is a small shaded solid, not an outline.
+//
+// The geometry is EMITTED from the real part by doc/design/mate-connectors/emit_glyph_table.py,
+// not hand-drawn, so the glyph and the printed connector cannot drift apart. Two vertices stand
+// above the 3 mm plate in the actual B-rep, which is why the snout here is a tent with one crest
+// edge and four flanks drafted at 20 degrees rather than anything more elaborate.
+//
+// The cheek dot is the handedness mark. Without it the glyph differs from its own mirror by only
+// 5-9 % of its lit pixels, which is not enough to read; the dot roughly doubles that and, unlike
+// making the eyes uneven, identifies the side from that cheek alone instead of by comparison.
+// Emitted by doc/design/mate-connectors/emit_glyph_table.py from bear.step — do not hand-edit.
+// Normalised to the part's bounding span and centred: the renderer scales by one radius.
+static const Vec2d kBearOutline[] = {        // 12 verts, RDP eps 0.030, CCW
+    {+0.3842, +0.3294}, {+0.3156, +0.4002}, {+0.2424, +0.3294},
+    {-0.2524, +0.3294}, {-0.3377, +0.3877}, {-0.3693, +0.3298},
+    {-0.3256, +0.2631}, {-0.4893, -0.3337}, {-0.3960, -0.4002},
+    {+0.4151, -0.4002}, {+0.5000, -0.3154}, {+0.3156, +0.2631},
+};
+static const Vec2d kBearChin[] = {            // the CHIN BAR, flat. The muzzle is relief — see kBearCrest.
+    {-0.2682, -0.3578}, {+0.2628, -0.3578}, {+0.2237, -0.1786},
+};
+// {cx, cy, r}: two eyes, then the cheek dot that carries handedness (wi3z).
+static const Vec3d kBearMarks[] = {
+    {-0.1997, +0.1760, +0.0590},
+    {+0.1947, +0.1760, +0.0590},
+    {+0.2797, +0.0760, +0.0380},
+};
+// THE MUZZLE, lifted off the mesh: a tapered wedge, base quad + crest edge, 6 facets.
+// This is the only feature standing along +Z and the only one still legible edge-on.
+static const double kBearPlateZ = +0.0360;
+static const Vec2d kBearSnoutBase[] = {   // CCW from the nose end
+    {-0.0727, -0.2417},
+    {+0.0630, -0.2417},
+    {+0.0259, +0.1939},
+    {-0.0356, +0.1939},
+};
+static const Vec3d kBearCrest[] = {       // nose (tall) -> tail (short)
+    {-0.0048, -0.1793, +0.2073},
+    {-0.0048, +0.1605, +0.1279},
+};
+
+void DesignSketchTool::render_mate_face(const Vec3d& origin, const Vec3d& X, const Vec3d& Y,
+                                        const Vec3d& Z, double R, const ColorRGBA& body)
+{
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const Vec3d fwd   = cam.get_dir_forward().normalized();
+    const double S    = 2.0 * R;              // the table spans 1.0, the disc spans 2R
+
+    // Light fixed in CAMERA space, so orbiting the model does not swing the shading around and
+    // turn a stable symbol into a flickering one.
+    const Vec3d light = (-0.35 * right + 0.55 * up - 0.76 * fwd).normalized();
+
+    auto to_world = [&](const Vec3d& p) {
+        return origin + X * (p.x() * S) + Y * (p.y() * S) + Z * (p.z() * S);
+    };
+
+    struct Facet { std::vector<Vec3d> w; ColorRGBA c; double depth; };
+    std::vector<Facet> facets;
+    auto emit = [&](std::vector<Vec3d> pts, const ColorRGBA& base, bool shade) {
+        if (pts.size() < 3) return;
+        Facet f; f.w.reserve(pts.size());
+        for (const Vec3d& p : pts) f.w.push_back(to_world(p));
+        const Vec3d n0 = (f.w[1] - f.w[0]).cross(f.w[2] - f.w[0]);
+        Vec3d n = Z;
+        if (n0.norm() > 1e-12) n = n0.normalized();
+        if (n.dot(fwd) > 0.0) n = -n;                       // always take the camera-facing side
+        double k = 1.0;
+        if (shade) {
+            // Ambient floor so a facet turned away still reads as part of the same object rather
+            // than as a hole punched in it.
+            k = 0.42 + 0.58 * std::max(0.0, n.dot(light));
+        }
+        f.c = ColorRGBA(float(base.r() * k), float(base.g() * k), float(base.b() * k), base.a());
+        double d = 0.0;
+        for (const Vec3d& p : f.w) d += p.dot(fwd);
+        f.depth = d / double(f.w.size());
+        facets.push_back(std::move(f));
+    };
+
+    const int NO = int(sizeof(kBearOutline) / sizeof(kBearOutline[0]));
+    const double zp = kBearPlateZ;
+
+    // The plate: sides first so the silhouette exists at a grazing view, then the top.
+    for (int i = 0; i < NO; ++i) {
+        const Vec2d& a = kBearOutline[i];
+        const Vec2d& b = kBearOutline[(i + 1) % NO];
+        emit({ Vec3d(a.x(), a.y(), 0.0), Vec3d(b.x(), b.y(), 0.0),
+               Vec3d(b.x(), b.y(), zp),  Vec3d(a.x(), a.y(), zp) }, body, true);
+    }
+    {
+        std::vector<Vec3d> top;
+        top.reserve(NO);
+        for (int i = 0; i < NO; ++i) top.emplace_back(kBearOutline[i].x(), kBearOutline[i].y(), zp);
+        emit(std::move(top), body, true);
+    }
+
+    // The marks, a hair above the plate so they cannot z-fight it: two eyes then the cheek dot.
+    const ColorRGBA mark(body.r() * 0.30f, body.g() * 0.30f, body.b() * 0.30f, 1.0f);
+    const double zm = zp + 0.004;
+    for (const Vec3d& m : kBearMarks) {
+        std::vector<Vec3d> disc;
+        const int N = 12;
+        for (int i = 0; i < N; ++i) {
+            const double a = (2.0 * M_PI * i) / N;
+            disc.emplace_back(m.x() + m.z() * std::cos(a), m.y() + m.z() * std::sin(a), zm);
+        }
+        emit(std::move(disc), mark, false);
+    }
+    {
+        std::vector<Vec3d> chin;
+        for (const Vec2d& p : kBearChin) chin.emplace_back(p.x(), p.y(), zm);
+        emit(std::move(chin), mark, false);
+    }
+
+    // THE MUZZLE, and the two decisions that make it legible rather than merely present.
+    //
+    // It is the one feature standing along +Z, so it says which way the connector points, and it
+    // is all that survives edge-on where a drawing in the plane has nothing left. Its geometry is
+    // the part's own ridge: crest 29.0 mm, 6.58 mm drop, 13.1 deg, against the 28.3 / 6.61 / 13.1
+    // the review measured on the B-rep. Base taken from the mesh, NOT recomputed from
+    // height*tan(draft) -- that produced a needle, because the real base overhangs the crest at
+    // both ends and it is the overhang that makes this a wedge rather than a blade.
+    //
+    // BUT FIDELITY ALONE FAILS. Scaled honestly the ridge is 11.3 mm on an 83.3 mm face, 13.6 %
+    // of the width, and at 22-48 px that reads as a scratch -- Tommaso looked at the faithful
+    // version and could not find the muzzle at all, which is the only test that counts. A glyph
+    // is a symbol, not a scale model, so it gets two deliberate exaggerations:
+    //
+    //   COLOUR does the work. In the body tone the muzzle is a grey sliver whichever way it is
+    //   lit; in the accent it is the first thing the eye lands on at every elevation, and at 6
+    //   degrees it is the ONLY structured thing above the flat line. Measured share of lit
+    //   pixels at 90/16/6 deg: body 14.8/11.3/17.5 %, accent 18.3/19.2/23.9 %.
+    //   WIDTH 1.8x on top of that: 23.5/25.2/31.2 %, and it stops reading as a needle.
+    //
+    // The accent is the same gold the disc treatment spends on its roll quadrant, which is
+    // consistent -- it is this tab's "here is the direction that matters" colour. Polarity is
+    // still carried by the Z arrow's head, so nothing collides.
+    {
+        const ColorRGBA gold(0.93f, 0.66f, 0.09f, 1.0f);
+        const double widen = 1.8;
+        const Vec3d& A = kBearCrest[0];
+        const Vec3d& B = kBearCrest[1];
+        auto base = [&](int i) {
+            return Vec3d(kBearSnoutBase[i].x() * widen, kBearSnoutBase[i].y(), zp);
+        };
+        const Vec3d nl = base(0), nr = base(1), tr = base(2), tl = base(3);
+        emit({ nl, tl, B, A }, gold, true);          // left flank
+        emit({ nr, A, B, tr }, gold, true);          // right flank
+        emit({ nl, A, nr }, gold, true);             // nose cap, sloped by the base overhang
+        emit({ tr, B, tl }, gold, true);             // tail cap
+    }
+
+    // Painter's algorithm: depth testing is off for this overlay, so draw order IS the depth.
+    std::sort(facets.begin(), facets.end(),
+              [](const Facet& a, const Facet& b) { return a.depth > b.depth; });
+
+    // draw_fill works in m_plane, so project into a screen-aligned frame at the connector origin
+    // and hand it flat polygons. The relief survives because the PROJECTION is 3D, not the plane.
+    const SketchPlane saved = m_plane;
+    SketchPlane bb; bb.origin = origin; bb.x_axis = right; bb.y_axis = up; bb.normal = fwd;
+    m_plane = bb;
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    for (const Facet& f : facets) {
+        std::vector<Vec2d> poly;
+        poly.reserve(f.w.size());
+        for (const Vec3d& p : f.w) poly.emplace_back((p - origin).dot(right), (p - origin).dot(up));
+        draw_fill(m_mc_fill_model, poly, f.c);
+    }
+    m_plane = saved;
+}
+
+void DesignSketchTool::render_extrude_gizmo()
+{
+    if (!m_ex_active) return;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const Vec3d fwd   = cam.get_dir_forward().normalized();
+    const Vec3d base  = m_ex_plane.to_world(m_ex_centroid);
+    const Vec3d ndir  = (m_ex_flip ? -1.0 : 1.0) * m_ex_plane.normal.normalized();
+    const double upp  = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double th   = std::max(15.0 * upp, 1e-4);
+
+    // Express everything in the billboard frame (origin=base) so it always faces the camera.
+    const SketchPlane saved = m_plane;
+    SketchPlane bb; bb.origin = base; bb.x_axis = right; bb.y_axis = up; bb.normal = fwd;
+    m_plane = bb;
+    const ColorRGBA arrowc(1.0f, 0.62f, 0.16f, 1.0f);   // CAD amber
+
+    auto draw_arrow = [&](double depth, bool flip_side) {
+        if (depth <= 1e-6) return;
+        const Vec3d dirw = (flip_side ? -1.0 : 1.0) * ndir;      // world arrow direction
+        const Vec3d tipw = base + dirw * depth;
+        const Vec2d tip2((tipw - base).dot(right), (tipw - base).dot(up));
+        if (tip2.norm() < 1e-6) return;                          // axis ~ parallel to view: no arrow
+        const Vec2d u = tip2.normalized();
+        const Vec2d nrm(-u.y(), u.x());
+        std::vector<std::pair<Vec2d, Vec2d>> segs;
+        segs.emplace_back(Vec2d(0, 0), tip2);
+        const double as = std::max(tip2.norm() * 0.18, th * 0.9);   // arrowhead size
+        const Vec2d back = tip2 - u * as;
+        segs.emplace_back(tip2, back + nrm * (as * 0.5));
+        segs.emplace_back(tip2, back - nrm * (as * 0.5));
+        draw_strokes(m_ex_arrow_model, segs, std::max(0.7 * upp, 1e-4), arrowc);
+        DimAnnot a; a.kind = DimType::Distance; a.value = depth;
+        draw_text(m_line_model, dim_text(a), tip2 + u * (th * 1.4), th, arrowc);
+    };
+
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    draw_arrow(m_ex_depth, false);
+    if (m_ex_two_sided) draw_arrow(m_ex_depth2, true);
+    m_plane = saved;
+}
+
+// Ray vs the arrow segment(s) in world space; `which` = 0 primary, 1 second side.
+bool DesignSketchTool::hit_test_extrude_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const
+{
+    if (!m_ex_active) return false;
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double tol = 7.0 / std::max(cam.get_zoom(), 1e-6);    // ~7 px in world units
+    const Vec3d ndir = (m_ex_flip ? -1.0 : 1.0) * m_ex_plane.normal.normalized();
+    const Vec3d base = m_ex_plane.to_world(m_ex_centroid);
+    double dA = 1e30, dB = 1e30;
+    if (m_ex_depth  > 1e-6) dA = ray_segment_dist3(ro, rd, base, base + ndir * m_ex_depth);
+    if (m_ex_two_sided && m_ex_depth2 > 1e-6)
+        dB = ray_segment_dist3(ro, rd, base, base - ndir * m_ex_depth2);
+    if (dA <= tol && dA <= dB) { which = 0; return true; }
+    if (dB <= tol)             { which = 1; return true; }
+    return false;
+}
+
+// Drag the arrow handle: closest point on the world arrow axis to the mouse ray (skew-line
+// closest-point), projected onto the axis direction -> signed depth (clamped positive).
+void DesignSketchTool::drag_extrude_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt, int which)
+{
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Vec3d nd = (m_ex_flip ? -1.0 : 1.0) * m_ex_plane.normal.normalized();
+    const Vec3d e  = (which == 1 ? -1.0 : 1.0) * nd;            // axis dir for this arrow
+    const Vec3d base = m_ex_plane.to_world(m_ex_centroid);
+    const Vec3d w0 = base - ro;
+    const double a = e.dot(e), b = e.dot(rd), c = rd.dot(rd), dd = e.dot(w0), ee = rd.dot(w0);
+    const double denom = a * c - b * b;
+    if (std::abs(denom) < 1e-7) return;                        // camera ∥ axis: leave depth as-is
+    const double depth = std::max(0.01, (b * ee - c * dd) / denom);
+    if (which == 1) m_ex_depth2 = depth; else m_ex_depth = depth;
+    if (on_extrude_depth_changed) on_extrude_depth_changed(depth, which == 1);
+}
+
+void DesignSketchTool::open_extrude_editor(int which)
+{
+    if (!on_inline_edit) return;
+    const double cur = (which == 1) ? m_ex_depth2 : m_ex_depth;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, cur, "",
+        [this, which](double v) {
+            const double d = std::max(0.01, v);
+            if (which == 1) m_ex_depth2 = d; else m_ex_depth = d;
+            if (on_extrude_depth_changed) on_extrude_depth_changed(d, which == 1);
+        },
+        []() {});
+}
+
+// ---- Datum-plane resize gizmo (C3) ----------------------------------------------------
+void DesignSketchTool::set_datum_gizmo(const SketchPlane& plane, double usize, double vsize,
+                                       const Vec3d& base_origin, const Vec3d& base_normal,
+                                       double offset, bool offset_on)
+{
+    m_dz_active = true;
+    m_dz_plane  = plane;
+    m_dz_usize  = std::max(1.0, usize);
+    m_dz_vsize  = std::max(1.0, vsize);
+    m_dz_anchor = base_origin;
+    m_dz_normal = base_normal.normalized();
+    m_dz_offset = offset;
+    m_dz_offset_on = offset_on;
+}
+
+void DesignSketchTool::clear_datum_gizmo()
+{
+    m_dz_active = false;
+    m_dz_drag   = -1;
+}
+
+// Draw the datum rectangle outline + 4 camera-billboarded edge-midpoint handles. Self-contained
+// so it shows even for an uncommitted (not-yet-Confirmed) datum that render_datum_planes can't draw.
+void DesignSketchTool::render_datum_gizmo()
+{
+    if (!m_dz_active) return;
+    using EPT = GLModel::Geometry::EPrimitiveType;
+    using EVL = GLModel::Geometry::EVertexLayout;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const Vec3d vd    = cam.get_dir_forward();
+    const double upp  = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double hs   = 6.0 * upp;                       // handle half-size (~6 px)
+    const double hw   = 1.5 * upp;                       // outline ribbon half-width
+    const double hu   = m_dz_usize * 0.5, hv = m_dz_vsize * 0.5;
+    const SketchPlane& p = m_dz_plane;
+
+    // Rectangle outline (4 thin camera-facing ribbons).
+    const Vec3d c[4] = { p.to_world(Vec2d(-hu, -hv)), p.to_world(Vec2d(hu, -hv)),
+                         p.to_world(Vec2d(hu, hv)),   p.to_world(Vec2d(-hu, hv)) };
+    GLModel::Geometry border; border.format = { EPT::Triangles, EVL::P3 };
+    unsigned int bb = 0;
+    for (int s = 0; s < 4; ++s) {
+        const Vec3d a = c[s], b = c[(s + 1) & 3];
+        Vec3d dir = b - a; if (dir.norm() < 1e-9) continue; dir.normalize();
+        Vec3d off = dir.cross(vd);
+        if (off.norm() < 1e-9) off = dir.cross(up);
+        if (off.norm() < 1e-9) continue;
+        off.normalize(); off *= hw;
+        border.add_vertex((Vec3f)(a + off).cast<float>()); border.add_vertex((Vec3f)(b + off).cast<float>());
+        border.add_vertex((Vec3f)(b - off).cast<float>()); border.add_vertex((Vec3f)(a - off).cast<float>());
+        border.add_triangle(bb, bb + 1, bb + 2); border.add_triangle(bb, bb + 2, bb + 3); bb += 4;
+    }
+
+    // 4 edge-midpoint handle squares.
+    const Vec2d hpos[4] = { Vec2d(hu, 0), Vec2d(-hu, 0), Vec2d(0, hv), Vec2d(0, -hv) };
+    GLModel::Geometry handles; handles.format = { EPT::Triangles, EVL::P3 };
+    unsigned int hb = 0;
+    for (int i = 0; i < 4; ++i) {
+        const Vec3d ctr = p.to_world(hpos[i]);
+        const Vec3d q0 = ctr - right * hs - up * hs, q1 = ctr + right * hs - up * hs,
+                    q2 = ctr + right * hs + up * hs, q3 = ctr - right * hs + up * hs;
+        handles.add_vertex((Vec3f)q0.cast<float>()); handles.add_vertex((Vec3f)q1.cast<float>());
+        handles.add_vertex((Vec3f)q2.cast<float>()); handles.add_vertex((Vec3f)q3.cast<float>());
+        handles.add_triangle(hb, hb + 1, hb + 2); handles.add_triangle(hb, hb + 2, hb + 3); hb += 4;
+    }
+
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    if (bb > 0) {
+        GLModel m; m.init_from(std::move(border));
+        m.set_color(ColorRGBA(1.0f, 0.62f, 0.16f, 0.9f));   // CAD amber
+        m.render();
+    }
+    if (hb > 0) {
+        GLModel m; m.init_from(std::move(handles));
+        m.set_color(ColorRGBA(1.0f, 0.72f, 0.28f, 1.0f));
+        m.render();
+    }
+
+    // Offset arrow: a camera-facing ribbon from the base origin along the base normal to the
+    // datum origin, with a grabbable square at the tip. Drag the tip to set the offset distance.
+    if (m_dz_offset_on) {
+        const Vec3d tip = m_dz_anchor + m_dz_normal * m_dz_offset;
+        Vec3d off = m_dz_normal.cross(vd);
+        if (off.norm() < 1e-9) off = m_dz_normal.cross(up);
+        GLModel::Geometry shaft; shaft.format = { EPT::Triangles, EVL::P3 };
+        if (off.norm() > 1e-9 && (tip - m_dz_anchor).norm() > 1e-9) {
+            off.normalize(); off *= hw;
+            shaft.add_vertex((Vec3f)(m_dz_anchor + off).cast<float>());
+            shaft.add_vertex((Vec3f)(tip + off).cast<float>());
+            shaft.add_vertex((Vec3f)(tip - off).cast<float>());
+            shaft.add_vertex((Vec3f)(m_dz_anchor - off).cast<float>());
+            shaft.add_triangle(0, 1, 2); shaft.add_triangle(0, 2, 3);
+            GLModel sm; sm.init_from(std::move(shaft));
+            sm.set_color(ColorRGBA(0.30f, 0.78f, 1.0f, 0.95f));   // cyan offset axis
+            sm.render();
+        }
+        GLModel::Geometry tipsq; tipsq.format = { EPT::Triangles, EVL::P3 };
+        const Vec3d t0 = tip - right * hs - up * hs, t1 = tip + right * hs - up * hs,
+                    t2 = tip + right * hs + up * hs, t3 = tip - right * hs + up * hs;
+        tipsq.add_vertex((Vec3f)t0.cast<float>()); tipsq.add_vertex((Vec3f)t1.cast<float>());
+        tipsq.add_vertex((Vec3f)t2.cast<float>()); tipsq.add_vertex((Vec3f)t3.cast<float>());
+        tipsq.add_triangle(0, 1, 2); tipsq.add_triangle(0, 2, 3);
+        GLModel tm; tm.init_from(std::move(tipsq));
+        tm.set_color(ColorRGBA(0.45f, 0.86f, 1.0f, 1.0f));
+        tm.render();
+    }
+}
+
+bool DesignSketchTool::hit_test_datum_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const
+{
+    if (!m_dz_active) return false;
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double tol = 9.0 / std::max(cam.get_zoom(), 1e-6);   // ~9 px in world units
+    const double hu = m_dz_usize * 0.5, hv = m_dz_vsize * 0.5;
+    const Vec2d hpos[4] = { Vec2d(hu, 0), Vec2d(-hu, 0), Vec2d(0, hv), Vec2d(0, -hv) };
+    double best = tol; which = -1;
+    for (int i = 0; i < 4; ++i) {
+        const Vec3d pt = m_dz_plane.to_world(hpos[i]);
+        const Vec3d w  = pt - ro;
+        const double t = w.dot(rd) / std::max(rd.dot(rd), 1e-12);
+        const double d = (w - rd * t).norm();
+        if (d < best) { best = d; which = i; }
+    }
+    if (m_dz_offset_on) {                                       // offset arrow tip = handle 4
+        const Vec3d pt = m_dz_anchor + m_dz_normal * m_dz_offset;
+        const Vec3d w  = pt - ro;
+        const double t = w.dot(rd) / std::max(rd.dot(rd), 1e-12);
+        const double d = (w - rd * t).norm();
+        if (d < best) { best = d; which = 4; }
+    }
+    return which >= 0;
+}
+
+// Drag a handle: closest point of the mouse ray to the plane axis (u or v) through the origin,
+// |param| -> new half-extent, doubled to the full size.
+void DesignSketchTool::drag_datum_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int which)
+{
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    if (which == 4) {                                          // offset arrow: drag along base normal
+        const Vec3d e = m_dz_normal;                           // signed offset, may go negative
+        const Vec3d w0 = m_dz_anchor - ro;
+        const double a = e.dot(e), b = e.dot(rd), c = rd.dot(rd), dd = e.dot(w0), ee = rd.dot(w0);
+        const double denom = a * c - b * b;
+        if (std::abs(denom) < 1e-7) return;                    // camera ∥ normal: leave offset as-is
+        m_dz_offset = (b * ee - c * dd) / denom;               // signed distance along the normal
+        m_dz_plane.origin = m_dz_anchor + m_dz_normal * m_dz_offset;   // rectangle follows live
+        if (on_datum_offset_changed) on_datum_offset_changed(m_dz_offset);
+        return;
+    }
+    const bool  uaxis = (which == 0 || which == 1);
+    const Vec3d e   = (uaxis ? m_dz_plane.x_axis : m_dz_plane.y_axis).normalized();
+    const Vec3d base = m_dz_plane.origin;
+    const Vec3d w0 = base - ro;
+    const double a = e.dot(e), b = e.dot(rd), c = rd.dot(rd), dd = e.dot(w0), ee = rd.dot(w0);
+    const double denom = a * c - b * b;
+    if (std::abs(denom) < 1e-7) return;                        // camera ∥ axis: leave size as-is
+    const double s    = (b * ee - c * dd) / denom;             // signed coord along e of closest pt
+    const double size = std::max(2.0, 2.0 * std::abs(s));
+    if (uaxis) m_dz_usize = size; else m_dz_vsize = size;
+    if (on_datum_size_changed) on_datum_size_changed(m_dz_usize, m_dz_vsize);
+}
+
+// ---- Helix gizmo (plane-anchored curve + 3 drag handles) --------------------------------
+void DesignSketchTool::set_helix_gizmo(const SketchPlane& plane, double radius, double pitch,
+                                       double height, double taper, bool left_handed)
+{
+    m_hx_active = true;
+    m_hx_plane  = plane;
+    m_hx_radius = radius;
+    m_hx_pitch  = pitch;
+    m_hx_height = height;
+    m_hx_taper  = taper;
+    m_hx_left   = left_handed;
+}
+
+void DesignSketchTool::clear_helix_gizmo()
+{
+    m_hx_active = false;
+    m_hx_drag   = -1;
+}
+
+// Curve point at parameter t (t in turns): angle 2*pi*t, negated when left-handed, rising one
+// pitch per turn along the plane normal.
+//
+// Taper is an ANGLE IN DEGREES and must be read the way the kernel reads it. CadDocument's
+// helix_spine() builds a Geom_ConicalSurface of half-angle taper and computes the top radius as
+// R + H*tan(taper), so the radius grows with the HEIGHT RISEN, not as a fraction of R consumed
+// over the turn count. Getting that wrong draws a preview that collapses to a point for any
+// non-zero taper while the committed feature is fine — a preview that lies is worse than none.
+Vec3d DesignSketchTool::helix_point(double t) const
+{
+    const Vec3d O = m_hx_plane.origin;
+    const Vec3d n = m_hx_plane.normal.normalized();
+    const Vec3d u = m_hx_plane.x_axis.normalized();
+    const Vec3d v = m_hx_plane.y_axis.normalized();
+    const double a = (m_hx_left ? -1.0 : 1.0) * 2.0 * M_PI * t;
+    const double z = m_hx_pitch * t;                      // height risen at this parameter
+    double rt = m_hx_radius + z * std::tan(m_hx_taper * M_PI / 180.0);
+    // The kernel REFUSES a taper that drives the radius negative before the full height; the
+    // preview shows it collapsing instead, so the user can see which value did it.
+    if (rt < 0.0) rt = 0.0;
+    return O + u * (rt * std::cos(a)) + v * (rt * std::sin(a)) + n * z;
+}
+
+// Draw the live helix as a connected camera-facing ribbon, a dim axis line, and three square
+// handles (radius on the base circle, height on the axis top, pitch at the end of the first turn).
+void DesignSketchTool::render_helix_gizmo()
+{
+    if (!m_hx_active) return;
+    using EPT = GLModel::Geometry::EPrimitiveType;
+    using EVL = GLModel::Geometry::EVertexLayout;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const Vec3d vd    = cam.get_dir_forward();
+    const double upp  = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double hs   = 6.0 * upp;                       // handle half-size (~6 px)
+    const double hw   = 1.5 * upp;                       // ribbon half-width
+    const Vec3d O     = m_hx_plane.origin;
+    const Vec3d n     = m_hx_plane.normal.normalized();
+    const double turns = m_hx_pitch > 1e-9 ? m_hx_height / m_hx_pitch : 0.0;
+
+    // Curve ribbon: connected thin camera-facing quads over t in [0, turns].
+    const int segs = std::min(2048, std::max(48, int(turns * 32.0)));
+    GLModel::Geometry curve; curve.format = { EPT::Triangles, EVL::P3 };
+    unsigned int cb = 0;
+    auto add_seg = [&](const Vec3d& a, const Vec3d& b) {
+        Vec3d dir = b - a; if (dir.norm() < 1e-9) return; dir.normalize();
+        Vec3d off = dir.cross(vd);
+        if (off.norm() < 1e-9) off = dir.cross(up);
+        if (off.norm() < 1e-9) return;
+        off.normalize(); off *= hw;
+        curve.add_vertex((Vec3f)(a + off).cast<float>()); curve.add_vertex((Vec3f)(b + off).cast<float>());
+        curve.add_vertex((Vec3f)(b - off).cast<float>()); curve.add_vertex((Vec3f)(a - off).cast<float>());
+        curve.add_triangle(cb, cb + 1, cb + 2); curve.add_triangle(cb, cb + 2, cb + 3); cb += 4;
+    };
+    for (int i = 0; i < segs; ++i)
+        add_seg(helix_point(turns * i / segs), helix_point(turns * (i + 1) / segs));
+
+    // Axis: a dim line from the plane origin to the top of the helix.
+    const Vec3d top = O + n * m_hx_height;
+    GLModel::Geometry axis; axis.format = { EPT::Triangles, EVL::P3 };
+    {
+        Vec3d dir = top - O;
+        if (dir.norm() > 1e-9) {
+            dir.normalize();
+            Vec3d off = dir.cross(vd);
+            if (off.norm() < 1e-9) off = dir.cross(up);
+            if (off.norm() > 1e-9) {
+                off.normalize(); off *= hw * 0.6;
+                axis.add_vertex((Vec3f)(O + off).cast<float>()); axis.add_vertex((Vec3f)(top + off).cast<float>());
+                axis.add_vertex((Vec3f)(top - off).cast<float>()); axis.add_vertex((Vec3f)(O - off).cast<float>());
+                axis.add_triangle(0, 1, 2); axis.add_triangle(0, 2, 3);
+            }
+        }
+    }
+
+    // Three handles: 0=radius (t=0), 1=height (axis top), 2=pitch (end of first turn, or the
+    // whole curve if shorter than one turn so the handle never floats off a missing curve).
+    const Vec3d hpts[3] = { helix_point(0.0), top,
+                            helix_point(m_hx_height < m_hx_pitch ? turns : 1.0) };
+    const ColorRGBA hcol[3] = { ColorRGBA(1.0f, 0.72f, 0.28f, 1.0f),   // radius — amber
+                                ColorRGBA(0.45f, 0.86f, 1.0f, 1.0f),   // height — cyan
+                                ColorRGBA(0.30f, 0.80f, 0.34f, 1.0f) }; // pitch — green
+    const ColorRGBA hot(1.0f, 0.85f, 0.2f, 1.0f);
+
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    if (cb > 0) {
+        GLModel m; m.init_from(std::move(curve));
+        m.set_color(ColorRGBA(1.0f, 0.62f, 0.16f, 0.9f));   // CAD amber helix curve
+        m.render();
+    }
+    if (!axis.vertices.empty()) {
+        GLModel m; m.init_from(std::move(axis));
+        m.set_color(ColorRGBA(0.42f, 0.46f, 0.52f, 0.55f));   // dim grey axis
+        m.render();
+    }
+    for (int i = 0; i < 3; ++i) {
+        const Vec3d ctr = hpts[i];
+        const Vec3d q0 = ctr - right * hs - up * hs, q1 = ctr + right * hs - up * hs,
+                    q2 = ctr + right * hs + up * hs, q3 = ctr - right * hs + up * hs;
+        GLModel::Geometry sq; sq.format = { EPT::Triangles, EVL::P3 };
+        sq.add_vertex((Vec3f)q0.cast<float>()); sq.add_vertex((Vec3f)q1.cast<float>());
+        sq.add_vertex((Vec3f)q2.cast<float>()); sq.add_vertex((Vec3f)q3.cast<float>());
+        sq.add_triangle(0, 1, 2); sq.add_triangle(0, 2, 3);
+        GLModel m; m.init_from(std::move(sq));
+        m.set_color(m_hx_drag == i ? hot : hcol[i]);
+        m.render();
+    }
+}
+
+bool DesignSketchTool::hit_test_helix_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const
+{
+    if (!m_hx_active) return false;
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double tol = 9.0 / std::max(cam.get_zoom(), 1e-6);   // ~9 px in world units
+    const Vec3d O = m_hx_plane.origin;
+    const Vec3d n = m_hx_plane.normal.normalized();
+    const double turns = m_hx_pitch > 1e-9 ? m_hx_height / m_hx_pitch : 0.0;
+    const Vec3d hpts[3] = { helix_point(0.0), O + n * m_hx_height,
+                            helix_point(m_hx_height < m_hx_pitch ? turns : 1.0) };
+    double best = tol; which = -1;
+    for (int i = 0; i < 3; ++i) {
+        const Vec3d w  = hpts[i] - ro;
+        const double t = w.dot(rd) / std::max(rd.dot(rd), 1e-12);
+        const double d = (w - rd * t).norm();
+        if (d < best) { best = d; which = i; }
+    }
+    return which >= 0;
+}
+
+// Drag a handle: radius = cursor's in-plane distance from the origin, height/pitch = the signed
+// distance of the cursor's closest axis point. All fire the full (radius, pitch, height) triple.
+void DesignSketchTool::drag_helix_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int which)
+{
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const SketchPlane& p = m_hx_plane;
+    const Vec3d O = p.origin, n = p.normal.normalized();
+
+    if (which == 0) {                                          // radius: in-plane distance from O
+        const Vec2d lp = p.project(ro, rd);
+        m_hx_radius = std::max(0.01, lp.norm());
+    } else {                                                   // height/pitch: signed distance along n
+        const Vec3d e   = n;
+        const Vec3d w0  = O - ro;
+        const double a  = e.dot(e), b = e.dot(rd), c = rd.dot(rd), dd = e.dot(w0), ee = rd.dot(w0);
+        const double denom = a * c - b * b;
+        if (std::abs(denom) < 1e-7) return;                    // camera ∥ axis: leave value as-is
+        const double s = (b * ee - c * dd) / denom;            // signed distance along the axis
+        if (which == 1) m_hx_height = std::max(0.0, s);
+        else            m_hx_pitch  = std::max(0.01, s);       // zero/negative pitch divides by zero
+    }
+    if (on_helix_changed) on_helix_changed(m_hx_radius, m_hx_pitch, m_hx_height);
+}
+
+// ---- Rib thickness gizmo (in-plane slab footprint + 2 symmetric handles) -----------------
+void DesignSketchTool::set_rib_gizmo(const SketchPlane& plane, const Vec2d& p0, const Vec2d& p1,
+                                     double thickness)
+{
+    m_rb_active    = true;
+    m_rb_plane     = plane;
+    m_rb_p0        = p0;
+    m_rb_p1        = p1;
+    m_rb_thickness = thickness;
+}
+
+void DesignSketchTool::clear_rib_gizmo()
+{
+    m_rb_active = false;
+    m_rb_drag   = -1;
+}
+
+// Resolve the rib line's in-plane frame: unit direction d, perpendicular perp, midpoint, and
+// half-thickness. A degenerate line (zero length) has no direction to grow a slab perpendicular
+// to — return false so the caller draws nothing and never divides by zero.
+static bool rib_frame(const Vec2d& p0, const Vec2d& p1, double thickness,
+                      Vec2d& d, Vec2d& perp, Vec2d& mid, double& half)
+{
+    const Vec2d seg = p1 - p0;
+    const double len = seg.norm();
+    if (len < 1e-9) return false;
+    d    = seg / len;
+    perp = Vec2d(-d.y(), d.x());
+    mid  = 0.5 * (p0 + p1);
+    half = thickness * 0.5;
+    return true;
+}
+
+// Draw the rib slab's actual footprint (the rectangle p0±perp·half, p1±perp·half) as a thin
+// closed ribbon plus two square handles at mid ± perp·half. Both handles sit at half-thickness,
+// so a drag on either expresses the full thickness symmetrically.
+void DesignSketchTool::render_rib_gizmo()
+{
+    if (!m_rb_active) return;
+    Vec2d d, perp, mid; double half;
+    if (!rib_frame(m_rb_p0, m_rb_p1, m_rb_thickness, d, perp, mid, half)) return;
+    using EPT = GLModel::Geometry::EPrimitiveType;
+    using EVL = GLModel::Geometry::EVertexLayout;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const Vec3d vd    = cam.get_dir_forward();
+    const double upp  = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double hs   = 6.0 * upp;                       // handle half-size (~6 px)
+    const double hw   = 1.5 * upp;                       // ribbon half-width
+
+    // Slab footprint outline (4 thin camera-facing ribbons).
+    const Vec3d c[4] = { m_rb_plane.to_world(m_rb_p0 + perp * half),
+                         m_rb_plane.to_world(m_rb_p1 + perp * half),
+                         m_rb_plane.to_world(m_rb_p1 - perp * half),
+                         m_rb_plane.to_world(m_rb_p0 - perp * half) };
+    GLModel::Geometry border; border.format = { EPT::Triangles, EVL::P3 };
+    unsigned int bb = 0;
+    for (int s = 0; s < 4; ++s) {
+        const Vec3d a = c[s], b = c[(s + 1) & 3];
+        Vec3d dir = b - a; if (dir.norm() < 1e-9) continue; dir.normalize();
+        Vec3d off = dir.cross(vd);
+        if (off.norm() < 1e-9) off = dir.cross(up);
+        if (off.norm() < 1e-9) continue;
+        off.normalize(); off *= hw;
+        border.add_vertex((Vec3f)(a + off).cast<float>()); border.add_vertex((Vec3f)(b + off).cast<float>());
+        border.add_vertex((Vec3f)(b - off).cast<float>()); border.add_vertex((Vec3f)(a - off).cast<float>());
+        border.add_triangle(bb, bb + 1, bb + 2); border.add_triangle(bb, bb + 2, bb + 3); bb += 4;
+    }
+
+    // Two handles: 0 = +perp side, 1 = -perp side (both at half-thickness).
+    const Vec3d hpts[2] = { m_rb_plane.to_world(mid + perp * half),
+                            m_rb_plane.to_world(mid - perp * half) };
+    const ColorRGBA hot(1.0f, 0.85f, 0.2f, 1.0f);
+
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    if (bb > 0) {
+        GLModel m; m.init_from(std::move(border));
+        m.set_color(ColorRGBA(1.0f, 0.62f, 0.16f, 0.9f));   // CAD amber slab footprint
+        m.render();
+    }
+    for (int i = 0; i < 2; ++i) {
+        const Vec3d ctr = hpts[i];
+        const Vec3d q0 = ctr - right * hs - up * hs, q1 = ctr + right * hs - up * hs,
+                    q2 = ctr + right * hs + up * hs, q3 = ctr - right * hs + up * hs;
+        GLModel::Geometry sq; sq.format = { EPT::Triangles, EVL::P3 };
+        sq.add_vertex((Vec3f)q0.cast<float>()); sq.add_vertex((Vec3f)q1.cast<float>());
+        sq.add_vertex((Vec3f)q2.cast<float>()); sq.add_vertex((Vec3f)q3.cast<float>());
+        sq.add_triangle(0, 1, 2); sq.add_triangle(0, 2, 3);
+        GLModel m; m.init_from(std::move(sq));
+        m.set_color(m_rb_drag == i ? hot : ColorRGBA(0.30f, 0.80f, 0.34f, 1.0f));   // green
+        m.render();
+    }
+}
+
+bool DesignSketchTool::hit_test_rib_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const
+{
+    if (!m_rb_active) return false;
+    Vec2d d, perp, mid; double half;
+    if (!rib_frame(m_rb_p0, m_rb_p1, m_rb_thickness, d, perp, mid, half)) return false;
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double tol = 9.0 / std::max(cam.get_zoom(), 1e-6);   // ~9 px in world units
+    const Vec3d hpts[2] = { m_rb_plane.to_world(mid + perp * half),
+                            m_rb_plane.to_world(mid - perp * half) };
+    double best = tol; which = -1;
+    for (int i = 0; i < 2; ++i) {
+        const Vec3d w  = hpts[i] - ro;
+        const double t = w.dot(rd) / std::max(rd.dot(rd), 1e-12);
+        const double dd = (w - rd * t).norm();
+        if (dd < best) { best = dd; which = i; }
+    }
+    return which >= 0;
+}
+
+// Drag a handle: project the cursor ray onto the rib plane (the same call the helix radius drag
+// uses), take the perpendicular distance from the rib LINE to that point, and set the thickness
+// to twice that distance — the slab is centred on the line and the handle sits at half-thickness.
+void DesignSketchTool::drag_rib_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int which)
+{
+    (void)which;   // both handles behave identically: a drag on either sets the full thickness
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    Vec2d d, perp, mid; double half;
+    if (!rib_frame(m_rb_p0, m_rb_p1, m_rb_thickness, d, perp, mid, half)) return;
+    const Vec2d lp = m_rb_plane.project(ro, rd);
+    const Vec2d w  = lp - m_rb_p0;
+    const double dist = std::abs(w.x() * d.y() - w.y() * d.x());   // |cross(w, d)| = perp distance
+    m_rb_thickness = std::max(0.01, 2.0 * dist);                   // ×2: centred slab, handle at half
+    if (on_rib_thickness_changed) on_rib_thickness_changed(m_rb_thickness);
+}
+
+// ---- Reference/base planes (Onshape-style default planes) -----------------------------
+void DesignSketchTool::set_base_pick(std::vector<SketchPlane> planes, std::vector<int> bases,
+                                     std::vector<std::string> labels)
+{
+    m_dbp_active = !planes.empty();
+    m_dbp_planes = std::move(planes);
+    m_dbp_base   = std::move(bases);
+    m_dbp_labels = std::move(labels);
+    if (m_dbp_hover >= int(m_dbp_planes.size())) m_dbp_hover = -1;
+}
+
+void DesignSketchTool::clear_base_pick()
+{
+    m_dbp_active = false;
+    m_dbp_planes.clear();
+    m_dbp_base.clear();
+    m_dbp_labels.clear();
+    m_dbp_hover = -1;
+}
+
+// Reference planes sit INSIDE the bed. They used to be 0.6 * the bed's larger side, i.e. a square
+// 1.2x the plate, and three of them are drawn with depth testing off — so they painted over the
+// plate grid from edge to edge and the bed simply was not readable any more. "The planes hide the
+// bed", reported exactly that way. Small enough to leave the grid legible around them is also the
+// Onshape look this was reaching for: a modest square at the origin, not a tablecloth.
+double DesignSketchTool::dbp_half_extent() const
+{
+    double half = 75.0;
+    if (auto* pl = wxGetApp().plater()) {
+        const BoundingBoxf bb = pl->build_volume().bounding_volume2d();
+        const double w = bb.max.x() - bb.min.x(), d = bb.max.y() - bb.min.y();
+        if (w > 1.0 && d > 1.0) half = 0.3 * std::max(w, d);
+    }
+    return half;
+}
+
+// Draw the reference planes as large translucent labelled squares; the hovered one brightens.
+void DesignSketchTool::render_base_pick()
+{
+    if (!m_dbp_active || m_dbp_planes.empty()) return;
+    using EPT = GLModel::Geometry::EPrimitiveType;
+    using EVL = GLModel::Geometry::EVertexLayout;
+    const double H = dbp_half_extent();
+    // Onshape-ish per-plane tints: XY blue, XZ green, YZ red (keyed by base index 0/1/2; datums grey).
+    auto tint = [](int base, bool hot) -> ColorRGBA {
+        float a = hot ? 0.10f : 0.047f;   // base planes kept faint (reduced ~2/3 from 0.30/0.14)
+        if (base == 0) return ColorRGBA(0.30f, 0.55f, 0.95f, a);
+        if (base == 1) return ColorRGBA(0.35f, 0.80f, 0.45f, a);
+        if (base == 2) return ColorRGBA(0.92f, 0.42f, 0.42f, a);
+        return ColorRGBA(0.70f, 0.72f, 0.78f, a);
+    };
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    glsafe(::glDisable(GL_CULL_FACE));
+    glsafe(::glEnable(GL_BLEND));                                // alpha is ignored without this
+    glsafe(::glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));
+    const SketchPlane saved_plane = m_plane;
+    for (size_t i = 0; i < m_dbp_planes.size(); ++i) {
+        const SketchPlane& p = m_dbp_planes[i];
+        const Vec3d q0 = p.to_world(Vec2d(-H, -H)), q1 = p.to_world(Vec2d(H, -H)),
+                    q2 = p.to_world(Vec2d(H, H)),   q3 = p.to_world(Vec2d(-H, H));
+        GLModel::Geometry quad; quad.format = { EPT::Triangles, EVL::P3 };
+        quad.add_vertex((Vec3f)q0.cast<float>()); quad.add_vertex((Vec3f)q1.cast<float>());
+        quad.add_vertex((Vec3f)q2.cast<float>()); quad.add_vertex((Vec3f)q3.cast<float>());
+        quad.add_triangle(0, 1, 2); quad.add_triangle(0, 2, 3);
+        GLModel m; m.init_from(std::move(quad));
+        const bool hot = (int(i) == m_dbp_hover);
+        const int  base = (i < m_dbp_base.size()) ? m_dbp_base[i] : -1;
+        m.set_color(tint(base, hot));
+        m.render();
+
+        // Label near the top-left corner, drawn in the plane (draw_text lifts through m_plane).
+        if (i < m_dbp_labels.size() && !m_dbp_labels[i].empty()) {
+            m_plane = p;
+            const double th = H * 0.10;
+            const ColorRGBA lc = tint(base, true); ColorRGBA lcs(lc.r(), lc.g(), lc.b(), 1.0f);
+            draw_text(m_line_model, m_dbp_labels[i], Vec2d(-H + th * 2.0, H - th * 1.6), th, lcs);
+        }
+    }
+    m_plane = saved_plane;   // draw_text renders each label immediately (draw_strokes self-renders)
+    glsafe(::glDisable(GL_BLEND));
+}
+
+// Ray-pick the reference planes: intersect the mouse ray with each plane, keep hits inside the
+// square, return the index of the nearest by |t|. -1 on miss.
+int DesignSketchTool::hit_test_base_pick(GLCanvas3D& canvas, const wxMouseEvent& evt) const
+{
+    if (!m_dbp_active) return -1;
+    const double H = dbp_half_extent();
+
+    // THE LABEL WINS, and it has to. Each plane's name is a screen-space chip centred on its
+    // own in-plane anchor, and it is the one part of a base plane a user aims at deliberately —
+    // the quads are near-transparent and overlap everywhere. Ray-casting the quads alone made
+    // the labels pure decoration: on a fresh document at 1920x1060, clicking "XY" reported
+    // "XZ plane selected", because the XZ quad happens to sit in front at that pixel. Nothing
+    // about the click was ambiguous to the user; they clicked the word XY.
+    // Anchor and text height must track render_base_pick's, which is where they are drawn.
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double  th  = H * 0.10;
+    const Vec2d   anchor(-H + th * 2.0, H - th * 1.6);
+    int lbest = -1; double lbest_d = 1e30;
+    for (size_t i = 0; i < m_dbp_planes.size(); ++i) {
+        if (i >= m_dbp_labels.size() || m_dbp_labels[i].empty()) continue;
+        const wxPoint sp = world_to_screen_px(cam, m_dbp_planes[i].to_world(anchor));
+        if (sp.x < 0 && sp.y < 0) continue;                    // behind the camera
+        const double dx = std::abs(double(evt.GetX() - sp.x));
+        const double dy = std::abs(double(evt.GetY() - sp.y));
+        // Chip half-extents in px, scaled like the label itself. Generous rather than tight:
+        // missing the text and silently selecting a different plane is the failure being fixed.
+        const double hw = (9.0 + 5.0 * double(m_dbp_labels[i].size())) * double(m_render_scale);
+        const double hh = 11.0 * double(m_render_scale);
+        if (dx > hw || dy > hh) continue;
+        const double d = dx * dx + dy * dy;                    // nearest label if chips overlap
+        if (d < lbest_d) { lbest_d = d; lbest = int(i); }
+    }
+    if (lbest >= 0) return lbest;
+
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    int best = -1; double best_t = 1e30;
+    for (size_t i = 0; i < m_dbp_planes.size(); ++i) {
+        const SketchPlane& p = m_dbp_planes[i];
+        const double dn = rd.dot(p.normal);
+        if (std::abs(dn) < 1e-9) continue;                      // ray parallel to plane
+        const double t = (p.origin - ro).dot(p.normal) / dn;
+        if (t < 0) continue;                                    // behind the camera
+        const Vec3d hit = ro + rd * t;
+        const Vec3d d = hit - p.origin;
+        if (std::abs(d.dot(p.x_axis)) > H || std::abs(d.dot(p.y_axis)) > H) continue;
+        if (t < best_t) { best_t = t; best = int(i); }
+    }
+    return best;
+}
+
+// ---- Move-body gizmo (M5) -------------------------------------------------------------
+void DesignSketchTool::set_move_gizmo(int body, const Vec3d& pivot, const Transform3d& base_xform,
+                                      double body_radius)
+{
+    m_mv_active     = true;
+    m_mv_body       = body;
+    m_mv_base       = pivot;          // body's world centroid at Move-open = rotation pivot
+    m_mv_base_xform = base_xform;     // pose the deltas compose onto
+    m_mv_offset     = Vec3d::Zero();
+    m_mv_rot        = Eigen::Matrix3d::Identity();
+    m_mv_drag       = -1;
+    m_mv_radius     = std::max(body_radius, 0.0);
+}
+
+// Gizmo arm length in world mm. Orca's Prepare gizmos size themselves from the selection's
+// bounding sphere (GLGizmoRotate3D: m_radius = Offset + sphere radius) so the handles always sit
+// clear of the object; a fixed screen-size arm instead collapsed into a tangle buried inside a
+// large solid, which is why the rotation rings read as "missing". Same idea here, with a
+// screen-space floor so the gizmo stays grabbable on a tiny body or when zoomed far out.
+double DesignSketchTool::move_gizmo_arm(const Camera& cam) const
+{
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double screen_min = 70.0 * upp;              // never smaller than the old fixed size
+    return std::max(screen_min, m_mv_radius * 1.25);   // 25% clear of the body surface
+}
+
+void DesignSketchTool::clear_move_gizmo()
+{
+    m_mv_active = false;
+    m_mv_drag   = -1;
+    m_mv_body   = -1;
+    m_mv_offset = Vec3d::Zero();
+    m_mv_rot    = Eigen::Matrix3d::Identity();
+}
+
+// Final body transform = translate(delta) then rotate(delta, about pivot) on the open pose.
+Transform3d DesignSketchTool::compose_move_xform() const
+{
+    const Vec3d p = m_mv_base;
+    Transform3d R = Transform3d::Identity();
+    R.linear() = m_mv_rot;
+    const Transform3d rot_about_pivot =
+        Transform3d(Eigen::Translation3d(p)) * R * Transform3d(Eigen::Translation3d(-p));
+    return Transform3d(Eigen::Translation3d(m_mv_offset)) * rot_about_pivot * m_mv_base_xform;
+}
+
+// World axis `e` of ring `axis` plus an in-plane orthonormal basis (u,v).
+void DesignSketchTool::ring_basis(int axis, Vec3d& e, Vec3d& u, Vec3d& v) const
+{
+    switch (axis) {
+    case 0: e = Vec3d::UnitX(); u = Vec3d::UnitY(); v = Vec3d::UnitZ(); break;
+    case 1: e = Vec3d::UnitY(); u = Vec3d::UnitZ(); v = Vec3d::UnitX(); break;
+    default:e = Vec3d::UnitZ(); u = Vec3d::UnitX(); v = Vec3d::UnitY(); break;
+    }
+}
+
+// Three world-axis arrows (X red / Y green / Z blue) from the body centroid + current
+// offset, billboarded into a screen-facing frame like the extrude depth arrow.
+void DesignSketchTool::render_move_gizmo()
+{
+    if (!m_mv_active) return;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const Vec3d fwd   = cam.get_dir_forward().normalized();
+    const Vec3d anchor = m_mv_base + m_mv_offset;
+    const double upp  = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double th   = std::max(15.0 * upp, 1e-4);
+    const double L    = move_gizmo_arm(cam);        // scales with the body (see move_gizmo_arm)
+
+    const SketchPlane saved = m_plane;
+    SketchPlane bb; bb.origin = anchor; bb.x_axis = right; bb.y_axis = up; bb.normal = fwd;
+    m_plane = bb;
+
+    const Vec3d axes[3]   = { Vec3d::UnitX(), Vec3d::UnitY(), Vec3d::UnitZ() };
+    const ColorRGBA cols[3] = { ColorRGBA(0.92f, 0.28f, 0.28f, 1.0f),   // X red
+                                ColorRGBA(0.30f, 0.80f, 0.34f, 1.0f),   // Y green
+                                ColorRGBA(0.32f, 0.55f, 0.95f, 1.0f) }; // Z blue
+
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    for (int a = 0; a < 3; ++a) {
+        const Vec3d tipw = anchor + axes[a] * L;
+        const Vec2d tip2((tipw - anchor).dot(right), (tipw - anchor).dot(up));
+        if (tip2.norm() < 1e-6) continue;           // axis ~parallel to view: skip
+        const Vec2d u = tip2.normalized();
+        const Vec2d nrm(-u.y(), u.x());
+        std::vector<std::pair<Vec2d, Vec2d>> segs;
+        segs.emplace_back(Vec2d(0, 0), tip2);
+        const double as = std::max(tip2.norm() * 0.20, th * 0.9);
+        const Vec2d back = tip2 - u * as;
+        segs.emplace_back(tip2, back + nrm * (as * 0.5));
+        segs.emplace_back(tip2, back - nrm * (as * 0.5));
+        draw_strokes(m_mv_arrow_model, segs, std::max(0.7 * upp, 1e-4), cols[a]);
+        const double off = m_mv_offset[a];
+        if (std::abs(off) > 1e-4) {
+            DimAnnot da; da.kind = DimType::Distance; da.value = std::abs(off);
+            draw_text(m_line_model, dim_text(da), tip2 + u * (th * 1.4), th, cols[a]);
+        }
+    }
+    m_plane = saved;
+
+    // Three world-axis rotation rings (X/Y/Z), each a circle in the plane perpendicular to
+    // its axis through the gizmo anchor — drag a ring to rotate the body about that axis.
+    const double R = 0.83 * move_gizmo_arm(cam);   // rings just inside the arrow tips
+    for (int a = 0; a < 3; ++a) {
+        Vec3d e, u, v; ring_basis(a, e, u, v);
+        SketchPlane rp; rp.origin = anchor; rp.x_axis = u; rp.y_axis = v; rp.normal = e;
+        m_plane = rp;
+        std::vector<std::pair<Vec2d, Vec2d>> segs;
+        const int N = 48;
+        Vec2d prev(R, 0.0);
+        for (int i = 1; i <= N; ++i) {
+            const double t = 2.0 * M_PI * double(i) / double(N);
+            const Vec2d cur(R * std::cos(t), R * std::sin(t));
+            segs.emplace_back(prev, cur); prev = cur;
+        }
+        draw_strokes(m_mv_arrow_model, segs, std::max(0.55 * upp, 1e-4), cols[a]);
+    }
+    m_plane = saved;
+}
+
+// Ray vs each world-axis arrow segment; nearest within ~7 px wins.
+bool DesignSketchTool::hit_test_move_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt, int& axis) const
+{
+    if (!m_mv_active) return false;
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double L   = move_gizmo_arm(cam);         // must match render_move_gizmo
+    const Vec3d anchor = m_mv_base + m_mv_offset;
+    const Vec3d axes[3] = { Vec3d::UnitX(), Vec3d::UnitY(), Vec3d::UnitZ() };
+    int best = -1; double bestd = 7.0 * upp;        // ~7 px tolerance
+    for (int a = 0; a < 3; ++a) {
+        const double d = ray_segment_dist3(ro, rd, anchor, anchor + axes[a] * L);
+        if (d <= bestd) { bestd = d; best = a; }
+    }
+    if (best < 0) return false;
+    axis = best; return true;
+}
+
+// Skew-line closest point of the mouse ray to the axis line through the ORIGINAL centroid
+// -> signed offset along that axis (no clamp; a body can move either way).
+void DesignSketchTool::drag_move_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt, int axis)
+{
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Vec3d axes[3] = { Vec3d::UnitX(), Vec3d::UnitY(), Vec3d::UnitZ() };
+    const Vec3d e = axes[axis];
+    const Vec3d w0 = m_mv_base - ro;
+    const double a = e.dot(e), b = e.dot(rd), c = rd.dot(rd), dd = e.dot(w0), ee = rd.dot(w0);
+    const double denom = a * c - b * b;
+    if (std::abs(denom) < 1e-7) return;             // camera ∥ axis: leave offset as-is
+    m_mv_offset[axis] = (b * ee - c * dd) / denom;
+    if (on_body_move_changed) on_body_move_changed(m_mv_body, compose_move_xform());
+}
+
+void DesignSketchTool::open_move_editor(int axis)
+{
+    if (!on_inline_edit) return;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, m_mv_offset[axis], "",
+        [this, axis](double v) {
+            m_mv_offset[axis] = v;
+            if (on_body_move_changed) on_body_move_changed(m_mv_body, compose_move_xform());
+        },
+        []() {});
+}
+
+// Ray vs each rotation ring (sampled polyline); nearest within ~7 px wins -> axis 0/1/2.
+bool DesignSketchTool::hit_test_move_arc(GLCanvas3D& canvas, const wxMouseEvent& evt, int& axis) const
+{
+    if (!m_mv_active) return false;
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double R = 0.83 * move_gizmo_arm(cam);   // rings just inside the arrow tips
+    const Vec3d anchor = m_mv_base + m_mv_offset;
+    int best = -1; double bestd = 7.0 * upp;
+    const int N = 48;
+    for (int a = 0; a < 3; ++a) {
+        Vec3d e, u, v; ring_basis(a, e, u, v);
+        Vec3d prev = anchor + R * u;
+        for (int i = 1; i <= N; ++i) {
+            const double t = 2.0 * M_PI * double(i) / double(N);
+            const Vec3d cur = anchor + R * (std::cos(t) * u + std::sin(t) * v);
+            const double d = ray_segment_dist3(ro, rd, prev, cur);
+            if (d <= bestd) { bestd = d; best = a; }
+            prev = cur;
+        }
+    }
+    if (best < 0) return false;
+    axis = best; return true;
+}
+
+// Intersect the mouse ray with ring `axis`'s plane through the anchor -> in-plane angle.
+bool DesignSketchTool::arc_mouse_angle(GLCanvas3D& canvas, const wxMouseEvent& evt, int axis, double& ang) const
+{
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    Vec3d e, u, v; ring_basis(axis, e, u, v);
+    const Vec3d p = m_mv_base + m_mv_offset;
+    const double denom = rd.dot(e);
+    if (std::abs(denom) < 1e-9) return false;          // ray ∥ ring plane
+    const Vec3d hit = ro + ((p - ro).dot(e) / denom) * rd;
+    const Vec3d d = hit - p;
+    ang = std::atan2(d.dot(v), d.dot(u));
+    return true;
+}
+
+// Drag a ring -> rotate the body about that world axis by (mouse angle - grab angle).
+void DesignSketchTool::drag_move_arc(GLCanvas3D& canvas, const wxMouseEvent& evt, int axis)
+{
+    double ang;
+    if (!arc_mouse_angle(canvas, evt, axis, ang)) return;
+    Vec3d e, u, v; ring_basis(axis, e, u, v);
+    const double delta = ang - m_mv_arc_a0;
+    m_mv_rot = Eigen::AngleAxisd(delta, e).toRotationMatrix() * m_mv_rot_start;
+    if (on_body_move_changed) on_body_move_changed(m_mv_body, compose_move_xform());
+}
+
+// ---- Fillet/Chamfer radius gizmo ------------------------------------------------------
+// Anchor a single radius arrow at the picked edge midpoint (m_sel_edge_pts is already in world
+// space, body-transformed), perpendicular to the edge and pointing away from the body centroid —
+// the natural outward direction a fillet/chamfer grows.
+bool DesignSketchTool::set_fillet_gizmo(const Vec3d& body_centroid, double radius)
+{
+    if (m_sel_edge_pts.size() < 2) { m_fl_active = false; return false; }
+    const size_t n = m_sel_edge_pts.size();
+    // True geometric midpoint along the edge: a straight edge often samples to just its two
+    // endpoints, so the middle INDEX would land on an end. Walk the polyline to its half-length.
+    double total = 0.0;
+    for (size_t i = 1; i < n; ++i) total += (m_sel_edge_pts[i] - m_sel_edge_pts[i - 1]).norm();
+    m_fl_anchor = m_sel_edge_pts[0];
+    Vec3d t = m_sel_edge_pts[n - 1] - m_sel_edge_pts[0];
+    const double half = 0.5 * total;
+    double acc = 0.0;
+    for (size_t i = 1; i < n; ++i) {
+        const Vec3d seg = m_sel_edge_pts[i] - m_sel_edge_pts[i - 1];
+        const double L = seg.norm();
+        if (acc + L >= half && L > 1e-12) {
+            m_fl_anchor = m_sel_edge_pts[i - 1] + seg * ((half - acc) / L);
+            t = seg;
+            break;
+        }
+        acc += L;
+    }
+    if (t.norm() < 1e-9) return false;
+    t.normalize();
+    Vec3d r = m_fl_anchor - body_centroid;           // radial offset from the body centre
+    r -= r.dot(t) * t;                               // strip the along-edge component
+    if (r.norm() < 1e-6) {                           // edge passes through the centroid
+        r = t.cross(Vec3d::UnitZ());
+        if (r.norm() < 1e-6) r = t.cross(Vec3d::UnitX());
+    }
+    m_fl_dir    = r.normalized();
+    m_fl_radius = std::max(0.01, radius);
+    if (!m_fl_active) m_fl_drag = false;   // re-anchored every preview: preserve an in-progress drag
+    m_fl_active = true;
+    return true;
+}
+
+void DesignSketchTool::clear_fillet_gizmo()
+{
+    m_fl_active = false;
+    m_fl_drag   = false;
+}
+
+// Single billboarded radius arrow from the edge midpoint along m_fl_dir; length = radius (world),
+// floored to a grabbable screen size. Label shows the true radius (R-prefixed).
+void DesignSketchTool::render_fillet_gizmo()
+{
+    if (!m_fl_active) return;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const double upp  = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double th   = std::max(15.0 * upp, 1e-4);
+    const double L    = std::max(m_fl_radius, 40.0 * upp);   // WYSIWYG, floored to a comfortable handle
+    const Vec3d tipw  = m_fl_anchor + m_fl_dir * L;
+
+    const SketchPlane saved = m_plane;
+    SketchPlane bb; bb.origin = m_fl_anchor; bb.x_axis = right; bb.y_axis = up; bb.normal = cam.get_dir_forward().normalized();
+    m_plane = bb;
+    const ColorRGBA arrowc(1.0f, 0.62f, 0.16f, 1.0f);       // CAD amber
+
+    const Vec2d tip2((tipw - m_fl_anchor).dot(right), (tipw - m_fl_anchor).dot(up));
+    if (tip2.norm() > 1e-6) {
+        const Vec2d u = tip2.normalized();
+        const Vec2d nrm(-u.y(), u.x());
+        std::vector<std::pair<Vec2d, Vec2d>> segs;
+        segs.emplace_back(Vec2d(0, 0), tip2);
+        const double as = std::max(tip2.norm() * 0.20, th * 0.9);
+        const Vec2d back = tip2 - u * as;
+        segs.emplace_back(tip2, back + nrm * (as * 0.5));
+        segs.emplace_back(tip2, back - nrm * (as * 0.5));
+        glsafe(::glDisable(GL_DEPTH_TEST));
+        draw_strokes(m_fl_arrow_model, segs, std::max(0.7 * upp, 1e-4), arrowc);
+        DimAnnot da; da.kind = DimType::Radius; da.value = m_fl_radius;
+        draw_text(m_line_model, dim_text(da), tip2 + u * (th * 1.4), th, arrowc);
+    }
+    m_plane = saved;
+}
+
+// Ray vs the radius arrow segment; ~12 px tolerance over the (floored) handle length.
+bool DesignSketchTool::hit_test_fillet_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt) const
+{
+    if (!m_fl_active) return false;
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double L   = std::max(m_fl_radius, 40.0 * upp);
+    return ray_segment_dist3(ro, rd, m_fl_anchor, m_fl_anchor + m_fl_dir * L) <= 12.0 * upp;
+}
+
+// Skew-line closest point of the mouse ray to the radius axis -> signed distance along m_fl_dir
+// from the anchor. NaN when the camera is ~parallel to the axis (no meaningful projection).
+double DesignSketchTool::fillet_axis_proj(GLCanvas3D& canvas, const wxMouseEvent& evt) const
+{
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Vec3d e = m_fl_dir;
+    const Vec3d w0 = m_fl_anchor - ro;
+    const double a = e.dot(e), b = e.dot(rd), c = rd.dot(rd), dd = e.dot(w0), ee = rd.dot(w0);
+    const double denom = a * c - b * b;
+    if (std::abs(denom) < 1e-7) return std::nan("");
+    return (b * ee - c * dd) / denom;
+}
+
+// Record the grab reference so the drag is RELATIVE (grab anywhere on the handle without the
+// radius snapping to the grab point — important since the handle is floored to a min size).
+void DesignSketchTool::start_fillet_drag(GLCanvas3D& canvas, const wxMouseEvent& evt)
+{
+    m_fl_drag        = true;
+    m_fl_press_x     = evt.GetX();
+    m_fl_press_y     = evt.GetY();
+    m_fl_grab_radius = m_fl_radius;
+    const double p   = fillet_axis_proj(canvas, evt);
+    m_fl_grab_proj   = std::isnan(p) ? 0.0 : p;
+}
+
+void DesignSketchTool::drag_fillet_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt)
+{
+    const double proj = fillet_axis_proj(canvas, evt);
+    if (std::isnan(proj)) return;                   // camera ∥ axis: leave radius as-is
+    m_fl_radius = std::max(0.01, m_fl_grab_radius + (proj - m_fl_grab_proj));
+    if (on_fillet_radius_changed) on_fillet_radius_changed(m_fl_radius);
+}
+
+void DesignSketchTool::open_fillet_editor()
+{
+    if (!on_inline_edit) return;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, m_fl_radius, "",
+        [this](double v) {
+            m_fl_radius = std::max(0.01, v);
+            if (on_fillet_radius_changed) on_fillet_radius_changed(m_fl_radius);
+        },
+        []() {});
+}
+
+// ---- Hole gizmo -----------------------------------------------------------------------------
+// Positioned circular cut: footprint circle on the plane + a radial diameter arrow (plane u-axis)
+// + a normal-axis depth arrow (drawn only when !through, matching the kernel's blind cut) + a
+// draggable centre marker. The panel re-pushes this every preview, so (like the fillet gizmo) we
+// must NOT reset an in-progress drag when already active.
+void DesignSketchTool::set_hole_gizmo(const SketchPlane& plane, double x, double y,
+                                      double diameter, double depth, bool through)
+{
+    m_hl_plane    = plane;
+    m_hl_x        = x;
+    m_hl_y        = y;
+    m_hl_diameter = std::max(0.01, diameter);
+    m_hl_depth    = std::max(0.01, depth);
+    m_hl_through  = through;
+    if (!m_hl_active) m_hl_drag = -1;   // re-pushed every preview: preserve an in-progress drag
+    m_hl_active   = true;
+}
+
+void DesignSketchTool::clear_hole_gizmo()
+{
+    m_hl_active = false;
+    m_hl_drag   = -1;
+}
+
+void DesignSketchTool::set_hole_face_bounds(bool has, double umin, double umax, double vmin, double vmax)
+{
+    m_hl_has_bounds = has;
+    m_hl_umin = umin; m_hl_umax = umax; m_hl_vmin = vmin; m_hl_vmax = vmax;
+}
+
+void DesignSketchTool::render_hole_gizmo()
+{
+    if (!m_hl_active) return;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const double upp  = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double th   = std::max(15.0 * upp, 1e-4);
+
+    const Vec3d centre = m_hl_plane.to_world(Vec2d(m_hl_x, m_hl_y));
+    const Vec3d nrm    = m_hl_plane.normal.normalized();
+    const Vec3d ddir   = m_hl_plane.x_axis.normalized();     // diameter arrow runs along plane u
+    const double r     = std::max(0.01, m_hl_diameter * 0.5);
+
+    const SketchPlane saved = m_plane;
+
+    // (1) Footprint circle drawn ON the plane (lifts plane u/v -> world through to_world).
+    {
+        m_plane = m_hl_plane;
+        std::vector<std::pair<Vec2d, Vec2d>> segs;
+        const int N = 48;
+        for (int i = 0; i < N; ++i) {
+            const double a0 = (2.0 * M_PI * i) / N, a1 = (2.0 * M_PI * (i + 1)) / N;
+            segs.emplace_back(Vec2d(m_hl_x + r * std::cos(a0), m_hl_y + r * std::sin(a0)),
+                              Vec2d(m_hl_x + r * std::cos(a1), m_hl_y + r * std::sin(a1)));
+        }
+        glsafe(::glDisable(GL_DEPTH_TEST));
+        draw_strokes(m_hl_stroke_model, segs, std::max(0.6 * upp, 1e-4), ColorRGBA(1.0f, 0.62f, 0.16f, 1.0f));
+        m_plane = saved;
+    }
+
+    // (2) Billboarded handles (centre marker + diameter arrow + depth arrow), screen-facing frame
+    // at the centre so draw_strokes/draw_text read on top regardless of orientation.
+    SketchPlane bb; bb.origin = centre; bb.x_axis = right; bb.y_axis = up; bb.normal = cam.get_dir_forward().normalized();
+    m_plane = bb;
+    const ColorRGBA amber(1.0f, 0.62f, 0.16f, 1.0f);
+    const ColorRGBA blue (0.30f, 0.55f, 1.0f, 1.0f);
+
+    auto arrow_to = [&](const Vec3d& tipw, const ColorRGBA& col, const DimAnnot& da) {
+        const Vec2d tip2((tipw - centre).dot(right), (tipw - centre).dot(up));
+        if (tip2.norm() <= 1e-6) return;
+        const Vec2d u = tip2.normalized();
+        const Vec2d nrm2(-u.y(), u.x());
+        std::vector<std::pair<Vec2d, Vec2d>> segs;
+        segs.emplace_back(Vec2d(0, 0), tip2);
+        const double as = std::max(tip2.norm() * 0.20, th * 0.9);
+        const Vec2d back = tip2 - u * as;
+        segs.emplace_back(tip2, back + nrm2 * (as * 0.5));
+        segs.emplace_back(tip2, back - nrm2 * (as * 0.5));
+        glsafe(::glDisable(GL_DEPTH_TEST));
+        draw_strokes(m_hl_stroke_model, segs, std::max(0.7 * upp, 1e-4), col);
+        draw_text(m_line_model, dim_text(da), tip2 + u * (th * 1.4), th, col);
+    };
+
+    // Diameter arrow: WYSIWYG radius, floored to a grabbable handle; label shows Ø (full diameter).
+    {
+        const double L = std::max(r, 40.0 * upp);
+        DimAnnot da; da.kind = DimType::Diameter; da.value = m_hl_diameter;
+        arrow_to(centre + ddir * L, amber, da);
+    }
+    // Depth arrow along +normal (blind cut). Through cuts ignore depth, so skip the arrow then.
+    if (!m_hl_through) {
+        const double L = std::max(m_hl_depth, 40.0 * upp);
+        DimAnnot da; da.kind = DimType::Distance; da.value = m_hl_depth;
+        arrow_to(centre + nrm * L, blue, da);
+    }
+
+    m_plane = saved;
+
+    // Move handle: a small 3D CUBE at the hole centre (Orca text/SVG-on-face feel) — grab and drag
+    // it to slide the hole across the face. Built from the plane axes so it sits flat on the face.
+    {
+        using EPT = GLModel::Geometry::EPrimitiveType;
+        using EVL = GLModel::Geometry::EVertexLayout;
+        const double hs = 9.0 * upp;   // cube half-size (~9 px); hit-test uses the same below
+        const Vec3d U = ddir * hs, V = m_hl_plane.y_axis.normalized() * hs, Nn = nrm * hs;
+        // Cube centred EXACTLY on the surface point (= the hole). Depth-test ON occludes the inner
+        // half inside the solid, so the visible half-cube reads as planted at the hole — no depth-off
+        // float that looked offset from the on-surface footprint. Hit-test targets the same `centre`.
+        Vec3d c8[8];
+        for (int i = 0; i < 8; ++i)
+            c8[i] = centre + ((i & 1) ? U : -U) + ((i & 2) ? V : -V) + ((i & 4) ? Nn : -Nn);
+        // 6 faces (CCW), each as 2 triangles, lightly shaded so the box reads as a cube.
+        const int faces[6][4] = { {0,1,3,2},{4,6,7,5},{0,4,5,1},{2,3,7,6},{0,2,6,4},{1,5,7,3} };
+        const float shade[6]  = { 0.78f, 1.0f, 0.86f, 0.92f, 0.70f, 0.96f };
+        glsafe(::glEnable(GL_DEPTH_TEST));
+        glsafe(::glDisable(GL_CULL_FACE));
+        for (int f = 0; f < 6; ++f) {
+            GLModel::Geometry g; g.format = { EPT::Triangles, EVL::P3 };
+            for (int k = 0; k < 4; ++k) g.add_vertex((Vec3f)c8[faces[f][k]].cast<float>());
+            g.add_triangle(0, 1, 2); g.add_triangle(0, 2, 3);
+            GLModel m; m.init_from(std::move(g));
+            m.set_color(ColorRGBA(1.0f * shade[f], 0.62f * shade[f], 0.16f * shade[f], 1.0f));
+            m.render();
+        }
+    }
+}
+
+// Best-matching hole handle under the cursor: centre (0) / diameter (1) / depth (2), or -1.
+// Tested by ray-to-segment distance in world; ~12 px tolerance. Centre wins at the shared base.
+int DesignSketchTool::hit_test_hole_handle(GLCanvas3D& canvas, const wxMouseEvent& evt) const
+{
+    if (!m_hl_active) return -1;
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+
+    const Vec3d centre = m_hl_plane.to_world(Vec2d(m_hl_x, m_hl_y));
+    const Vec3d nrm    = m_hl_plane.normal.normalized();
+    const Vec3d ddir   = m_hl_plane.x_axis.normalized();
+    const double rad   = std::max(m_hl_diameter * 0.5, 40.0 * upp);
+    const double depL  = std::max(m_hl_depth, 40.0 * upp);
+    const double tol   = 12.0 * upp;
+
+    // Centre wins at the shared base: the move cube straddles the centre, so a grab within the cube
+    // half-size is a reposition. The arrows are only grabbable along the shaft extending outward,
+    // which also keeps an edge-on arrow (e.g. depth in top view) from stealing the reposition grab.
+    if (ray_segment_dist3(ro, rd, centre, centre) <= 9.0 * upp) return 0;   // cube half-size
+
+    int best = -1; double bestd = tol;
+    const double dD = ray_segment_dist3(ro, rd, centre, centre + ddir * rad);
+    if (dD < bestd) { bestd = dD; best = 1; }
+    if (!m_hl_through) {
+        const double dZ = ray_segment_dist3(ro, rd, centre, centre + nrm * depL);
+        if (dZ < bestd) { bestd = dZ; best = 2; }
+    }
+    return best;
+}
+
+// Skew-line closest point of the mouse ray to an axis (anchor + t*dir) -> signed distance along
+// dir. NaN when the camera is ~parallel to the axis (no meaningful projection).
+double DesignSketchTool::hole_axis_proj(GLCanvas3D& canvas, const wxMouseEvent& evt,
+                                        const Vec3d& anchor, const Vec3d& dir) const
+{
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Vec3d e = dir;
+    const Vec3d w0 = anchor - ro;
+    const double a = e.dot(e), b = e.dot(rd), c = rd.dot(rd), dd = e.dot(w0), ee = rd.dot(w0);
+    const double denom = a * c - b * b;
+    // Relative near-parallel guard: when the camera ray is ~along the axis (e.g. the depth axis in
+    // top view) denom collapses; a tiny absolute floor lets a huge, unstable projection through.
+    if (std::abs(denom) < 1e-4 * std::max(a * c, 1e-12)) return std::nan("");
+    return (b * ee - c * dd) / denom;
+}
+
+void DesignSketchTool::start_hole_drag(GLCanvas3D& canvas, const wxMouseEvent& evt, int which)
+{
+    m_hl_drag    = which;
+    m_hl_press_x = evt.GetX();
+    m_hl_press_y = evt.GetY();
+    const Vec3d centre = m_hl_plane.to_world(Vec2d(m_hl_x, m_hl_y));
+    if (which == 0) {
+        const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+        m_hl_grab_uv = m_hl_plane.project(r.a, r.b - r.a);
+        m_hl_grab_x  = m_hl_x;
+        m_hl_grab_y  = m_hl_y;
+    } else if (which == 1 || which == 2) {
+        const Vec3d dir = (which == 1) ? m_hl_plane.x_axis.normalized() : m_hl_plane.normal.normalized();
+        const double p  = hole_axis_proj(canvas, evt, centre, dir);
+        m_hl_grab_proj  = std::isnan(p) ? 0.0 : p;
+        m_hl_grab_val   = (which == 1) ? m_hl_diameter * 0.5 : m_hl_depth;
+    }
+    // which == 3/4 (X/Y dim labels) are edit-only: a stationary click opens the inline editor.
+}
+
+void DesignSketchTool::drag_hole_handle(GLCanvas3D& canvas, const wxMouseEvent& evt)
+{
+    if (m_hl_drag >= 3) return;                    // X/Y dim labels are click-to-edit, not drag
+    if (m_hl_drag == 0) {                          // reposition centre on the plane
+        const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+        const Vec2d uv = m_hl_plane.project(r.a, r.b - r.a);
+        m_hl_x = m_hl_grab_x + (uv.x() - m_hl_grab_uv.x());
+        m_hl_y = m_hl_grab_y + (uv.y() - m_hl_grab_uv.y());
+    } else {                                       // diameter (1) or depth (2): relative axis drag
+        const Vec3d centre = m_hl_plane.to_world(Vec2d(m_hl_x, m_hl_y));
+        const Vec3d dir = (m_hl_drag == 1) ? m_hl_plane.x_axis.normalized() : m_hl_plane.normal.normalized();
+        const double proj = hole_axis_proj(canvas, evt, centre, dir);
+        if (std::isnan(proj)) return;              // camera ∥ axis: leave value as-is
+        const double v = std::max(0.01, m_hl_grab_val + (proj - m_hl_grab_proj));
+        if (m_hl_drag == 1) m_hl_diameter = 2.0 * v;
+        else                m_hl_depth    = v;
+    }
+    if (on_hole_changed) on_hole_changed(m_hl_x, m_hl_y, m_hl_diameter, m_hl_depth);
+}
+
+void DesignSketchTool::open_hole_editor(int which)
+{
+    if (!on_inline_edit) return;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    if (which == 1) {
+        on_inline_edit(px, m_hl_diameter, "",
+            [this](double v) {
+                m_hl_diameter = std::max(0.01, v);
+                if (on_hole_changed) on_hole_changed(m_hl_x, m_hl_y, m_hl_diameter, m_hl_depth);
+            },
+            []() {});
+    } else if (which == 2) {
+        on_inline_edit(px, m_hl_depth, "",
+            [this](double v) {
+                m_hl_depth = std::max(0.01, v);
+                if (on_hole_changed) on_hole_changed(m_hl_x, m_hl_y, m_hl_diameter, m_hl_depth);
+            },
+            []() {});
+    } else if (which == 3) {                       // #2 Part B: edit the distance from the u-side
+        const double ru = m_hl_has_bounds ? m_hl_umin : 0.0;
+        on_inline_edit(px, m_hl_x - ru, "",
+            [this, ru](double v) {
+                m_hl_x = ru + v;
+                if (on_hole_changed) on_hole_changed(m_hl_x, m_hl_y, m_hl_diameter, m_hl_depth);
+            },
+            []() {});
+    } else if (which == 4) {                       // edit the distance from the v-side
+        const double rv = m_hl_has_bounds ? m_hl_vmin : 0.0;
+        on_inline_edit(px, m_hl_y - rv, "",
+            [this, rv](double v) {
+                m_hl_y = rv + v;
+                if (on_hole_changed) on_hole_changed(m_hl_x, m_hl_y, m_hl_diameter, m_hl_depth);
+            },
+            []() {});
+    }
+    // which == 0 (centre): no scalar to edit inline — it's a drag-only reposition handle.
+}
+
+// ---- Thread gizmo ---------------------------------------------------------------------------
+// Mirrors the hole gizmo: footprint circle on the plane at the nominal radius + a radial radius
+// arrow (R label) + a normal-axis length arrow (always shown) + a draggable centre marker.
+// Reuses hole_axis_proj() for the relative axis drags.
+void DesignSketchTool::set_thread_gizmo(const SketchPlane& plane, double x, double y,
+                                        double radius, double height)
+{
+    m_th_plane  = plane;
+    m_th_x      = x;
+    m_th_y      = y;
+    m_th_radius = std::max(0.01, radius);
+    m_th_height = std::max(0.01, height);
+    if (!m_th_active) m_th_drag = -1;   // re-pushed every preview: preserve an in-progress drag
+    m_th_active = true;
+}
+
+void DesignSketchTool::clear_thread_gizmo()
+{
+    m_th_active = false;
+    m_th_drag   = -1;
+}
+
+void DesignSketchTool::render_thread_gizmo()
+{
+    if (!m_th_active) return;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const double upp  = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double th   = std::max(15.0 * upp, 1e-4);
+
+    const Vec3d centre = m_th_plane.to_world(Vec2d(m_th_x, m_th_y));
+    const Vec3d nrm    = m_th_plane.normal.normalized();
+    const Vec3d ddir   = m_th_plane.x_axis.normalized();     // radius arrow runs along plane u
+    const double r     = std::max(0.01, m_th_radius);
+
+    const SketchPlane saved = m_plane;
+
+    // (1) Footprint circle on the plane at the nominal radius.
+    {
+        m_plane = m_th_plane;
+        std::vector<std::pair<Vec2d, Vec2d>> segs;
+        const int N = 48;
+        for (int i = 0; i < N; ++i) {
+            const double a0 = (2.0 * M_PI * i) / N, a1 = (2.0 * M_PI * (i + 1)) / N;
+            segs.emplace_back(Vec2d(m_th_x + r * std::cos(a0), m_th_y + r * std::sin(a0)),
+                              Vec2d(m_th_x + r * std::cos(a1), m_th_y + r * std::sin(a1)));
+        }
+        glsafe(::glDisable(GL_DEPTH_TEST));
+        draw_strokes(m_th_stroke_model, segs, std::max(0.6 * upp, 1e-4), ColorRGBA(0.55f, 0.80f, 0.30f, 1.0f));
+        m_plane = saved;
+    }
+
+    // (2) Billboarded handles.
+    SketchPlane bb; bb.origin = centre; bb.x_axis = right; bb.y_axis = up; bb.normal = cam.get_dir_forward().normalized();
+    m_plane = bb;
+    const ColorRGBA green(0.55f, 0.80f, 0.30f, 1.0f);
+    const ColorRGBA blue (0.30f, 0.55f, 1.0f, 1.0f);
+
+    auto arrow_to = [&](const Vec3d& tipw, const ColorRGBA& col, const DimAnnot& da) {
+        const Vec2d tip2((tipw - centre).dot(right), (tipw - centre).dot(up));
+        if (tip2.norm() <= 1e-6) return;
+        const Vec2d u = tip2.normalized();
+        const Vec2d nrm2(-u.y(), u.x());
+        std::vector<std::pair<Vec2d, Vec2d>> segs;
+        segs.emplace_back(Vec2d(0, 0), tip2);
+        const double as = std::max(tip2.norm() * 0.20, th * 0.9);
+        const Vec2d back = tip2 - u * as;
+        segs.emplace_back(tip2, back + nrm2 * (as * 0.5));
+        segs.emplace_back(tip2, back - nrm2 * (as * 0.5));
+        glsafe(::glDisable(GL_DEPTH_TEST));
+        draw_strokes(m_th_stroke_model, segs, std::max(0.7 * upp, 1e-4), col);
+        draw_text(m_line_model, dim_text(da), tip2 + u * (th * 1.4), th, col);
+    };
+
+    {   // Radius arrow (R label), floored to a grabbable handle.
+        const double L = std::max(r, 40.0 * upp);
+        DimAnnot da; da.kind = DimType::Radius; da.value = m_th_radius;
+        arrow_to(centre + ddir * L, green, da);
+    }
+    {   // Length arrow along +normal.
+        const double L = std::max(m_th_height, 40.0 * upp);
+        DimAnnot da; da.kind = DimType::Distance; da.value = m_th_height;
+        arrow_to(centre + nrm * L, blue, da);
+    }
+    {   // Centre marker.
+        const double s = 7.0 * upp;
+        std::vector<std::pair<Vec2d, Vec2d>> segs;
+        segs.emplace_back(Vec2d(-s, -s), Vec2d(s, -s));
+        segs.emplace_back(Vec2d( s, -s), Vec2d(s,  s));
+        segs.emplace_back(Vec2d( s,  s), Vec2d(-s, s));
+        segs.emplace_back(Vec2d(-s,  s), Vec2d(-s, -s));
+        glsafe(::glDisable(GL_DEPTH_TEST));
+        draw_strokes(m_th_stroke_model, segs, std::max(0.7 * upp, 1e-4), green);
+    }
+
+    m_plane = saved;
+}
+
+int DesignSketchTool::hit_test_thread_handle(GLCanvas3D& canvas, const wxMouseEvent& evt) const
+{
+    if (!m_th_active) return -1;
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+
+    const Vec3d centre = m_th_plane.to_world(Vec2d(m_th_x, m_th_y));
+    const Vec3d nrm    = m_th_plane.normal.normalized();
+    const Vec3d ddir   = m_th_plane.x_axis.normalized();
+    const double rad   = std::max(m_th_radius, 40.0 * upp);
+    const double hL    = std::max(m_th_height, 40.0 * upp);
+    const double tol   = 12.0 * upp;
+
+    if (ray_segment_dist3(ro, rd, centre, centre) <= tol) return 0;   // centre wins at the base
+    int best = -1; double bestd = tol;
+    const double dR = ray_segment_dist3(ro, rd, centre, centre + ddir * rad);
+    if (dR < bestd) { bestd = dR; best = 1; }
+    const double dH = ray_segment_dist3(ro, rd, centre, centre + nrm * hL);
+    if (dH < bestd) { bestd = dH; best = 2; }
+    return best;
+}
+
+void DesignSketchTool::start_thread_drag(GLCanvas3D& canvas, const wxMouseEvent& evt, int which)
+{
+    m_th_drag    = which;
+    m_th_press_x = evt.GetX();
+    m_th_press_y = evt.GetY();
+    const Vec3d centre = m_th_plane.to_world(Vec2d(m_th_x, m_th_y));
+    if (which == 0) {
+        const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+        m_th_grab_uv = m_th_plane.project(r.a, r.b - r.a);
+        m_th_grab_x  = m_th_x;
+        m_th_grab_y  = m_th_y;
+    } else {
+        const Vec3d dir = (which == 1) ? m_th_plane.x_axis.normalized() : m_th_plane.normal.normalized();
+        const double p  = hole_axis_proj(canvas, evt, centre, dir);
+        m_th_grab_proj  = std::isnan(p) ? 0.0 : p;
+        m_th_grab_val   = (which == 1) ? m_th_radius : m_th_height;
+    }
+}
+
+void DesignSketchTool::drag_thread_handle(GLCanvas3D& canvas, const wxMouseEvent& evt)
+{
+    if (m_th_drag == 0) {
+        const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+        const Vec2d uv = m_th_plane.project(r.a, r.b - r.a);
+        m_th_x = m_th_grab_x + (uv.x() - m_th_grab_uv.x());
+        m_th_y = m_th_grab_y + (uv.y() - m_th_grab_uv.y());
+    } else {
+        const Vec3d centre = m_th_plane.to_world(Vec2d(m_th_x, m_th_y));
+        const Vec3d dir = (m_th_drag == 1) ? m_th_plane.x_axis.normalized() : m_th_plane.normal.normalized();
+        const double proj = hole_axis_proj(canvas, evt, centre, dir);
+        if (std::isnan(proj)) return;
+        const double v = std::max(0.01, m_th_grab_val + (proj - m_th_grab_proj));
+        if (m_th_drag == 1) m_th_radius = v;
+        else                m_th_height = v;
+    }
+    if (on_thread_changed) on_thread_changed(m_th_x, m_th_y, m_th_radius, m_th_height);
+}
+
+void DesignSketchTool::open_thread_editor(int which)
+{
+    if (!on_inline_edit) return;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    if (which == 1) {
+        on_inline_edit(px, m_th_radius, "",
+            [this](double v) {
+                m_th_radius = std::max(0.01, v);
+                if (on_thread_changed) on_thread_changed(m_th_x, m_th_y, m_th_radius, m_th_height);
+            },
+            []() {});
+    } else if (which == 2) {
+        on_inline_edit(px, m_th_height, "",
+            [this](double v) {
+                m_th_height = std::max(0.01, v);
+                if (on_thread_changed) on_thread_changed(m_th_x, m_th_y, m_th_radius, m_th_height);
+            },
+            []() {});
+    }
+}
+
+// ---- Shell gizmo ----------------------------------------------------------------------------
+// A single inward thickness arrow at the picked open-face centroid (mirrors the fillet radius
+// arrow). RELATIVE drag (like fillet), reusing hole_axis_proj for the projection.
+void DesignSketchTool::set_shell_gizmo(const Vec3d& face_centroid, const Vec3d& inward_dir,
+                                       double thickness)
+{
+    m_sh_anchor    = face_centroid;
+    if (inward_dir.norm() > 1e-9) m_sh_dir = inward_dir.normalized();
+    m_sh_thickness = std::max(0.01, thickness);
+    if (!m_sh_active) m_sh_drag = false;   // re-pushed every preview: preserve an in-progress drag
+    m_sh_active = true;
+}
+
+void DesignSketchTool::clear_shell_gizmo()
+{
+    m_sh_active = false;
+    m_sh_drag   = false;
+}
+
+void DesignSketchTool::render_shell_gizmo()
+{
+    if (!m_sh_active) return;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const double upp  = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double th   = std::max(15.0 * upp, 1e-4);
+    const double L    = std::max(m_sh_thickness, 40.0 * upp);   // WYSIWYG, floored to a handle
+    const Vec3d tipw  = m_sh_anchor + m_sh_dir * L;
+
+    const SketchPlane saved = m_plane;
+    SketchPlane bb; bb.origin = m_sh_anchor; bb.x_axis = right; bb.y_axis = up; bb.normal = cam.get_dir_forward().normalized();
+    m_plane = bb;
+    const ColorRGBA teal(0.20f, 0.80f, 0.75f, 1.0f);
+
+    const Vec2d tip2((tipw - m_sh_anchor).dot(right), (tipw - m_sh_anchor).dot(up));
+    if (tip2.norm() > 1e-6) {
+        const Vec2d u = tip2.normalized();
+        const Vec2d nrm(-u.y(), u.x());
+        std::vector<std::pair<Vec2d, Vec2d>> segs;
+        segs.emplace_back(Vec2d(0, 0), tip2);
+        const double as = std::max(tip2.norm() * 0.20, th * 0.9);
+        const Vec2d back = tip2 - u * as;
+        segs.emplace_back(tip2, back + nrm * (as * 0.5));
+        segs.emplace_back(tip2, back - nrm * (as * 0.5));
+        glsafe(::glDisable(GL_DEPTH_TEST));
+        draw_strokes(m_sh_stroke_model, segs, std::max(0.7 * upp, 1e-4), teal);
+        DimAnnot da; da.kind = DimType::Distance; da.value = m_sh_thickness;
+        draw_text(m_line_model, dim_text(da), tip2 + u * (th * 1.4), th, teal);
+    }
+    m_plane = saved;
+}
+
+bool DesignSketchTool::hit_test_shell_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt) const
+{
+    if (!m_sh_active) return false;
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double L   = std::max(m_sh_thickness, 40.0 * upp);
+    return ray_segment_dist3(ro, rd, m_sh_anchor, m_sh_anchor + m_sh_dir * L) <= 12.0 * upp;
+}
+
+void DesignSketchTool::start_shell_drag(GLCanvas3D& canvas, const wxMouseEvent& evt)
+{
+    m_sh_drag      = true;
+    m_sh_press_x   = evt.GetX();
+    m_sh_press_y   = evt.GetY();
+    m_sh_grab_val  = m_sh_thickness;
+    const double p = hole_axis_proj(canvas, evt, m_sh_anchor, m_sh_dir);
+    m_sh_grab_proj = std::isnan(p) ? 0.0 : p;
+}
+
+void DesignSketchTool::drag_shell_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt)
+{
+    const double proj = hole_axis_proj(canvas, evt, m_sh_anchor, m_sh_dir);
+    if (std::isnan(proj)) return;
+    m_sh_thickness = std::max(0.01, m_sh_grab_val + (proj - m_sh_grab_proj));
+    if (on_shell_thickness_changed) on_shell_thickness_changed(m_sh_thickness);
+}
+
+void DesignSketchTool::open_shell_editor()
+{
+    if (!on_inline_edit) return;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, m_sh_thickness, "",
+        [this](double v) {
+            m_sh_thickness = std::max(0.01, v);
+            if (on_shell_thickness_changed) on_shell_thickness_changed(m_sh_thickness);
+        },
+        []() {});
+}
+
+// ---- Revolve angle-arc gizmo ----------------------------------------------------------------
+// Arc in the revolve plane (perpendicular to the axis) at the profile's radius. The arc center is
+// the projection of the profile centroid onto the axis, so the arc rides at the profile's height.
+// The yaxis sense follows m_rv_flip, matching the kernel's negative-angle reversed sweep.
+static Vec3d rv_yaxis(const Vec3d& axis, const Vec3d& ref, bool flip)
+{
+    Vec3d y = axis.cross(ref);
+    if (y.norm() < 1e-9) return ref;            // degenerate; never used (ref ⟂ axis by construction)
+    y.normalize();
+    return flip ? -y : y;
+}
+
+// Arc in the draft plane (perpendicular to the world +Z axis through the face centroid).
+// The arc sweeps from angle 0 to m_dr_angle, representing the taper amount.
+static Vec3d dr_yaxis(const Vec3d& axis, const Vec3d& ref)
+{
+    Vec3d y = axis.cross(ref);
+    if (y.norm() < 1e-9) return ref;
+    y.normalize();
+    return y;
+}
+
+void DesignSketchTool::set_draft_gizmo(const Vec3d& face_centroid, const Vec3d& face_normal, double angle)
+{
+    m_dr_center = face_centroid;
+    m_dr_angle  = std::min(89.0, std::max(-89.0, angle));
+    m_dr_axis   = Vec3d::UnitZ();                    // pull direction is world +Z
+    Vec3d ref = face_normal - face_normal.dot(m_dr_axis) * m_dr_axis;  // horizontal component
+    if (ref.norm() < 1e-6) ref = Vec3d::UnitX();     // fallback: face normal is parallel to Z
+    m_dr_ref    = ref / ref.norm();
+    m_dr_radius = 12.0;                              // fixed world-size manipulator
+    if (!m_dr_active) m_dr_drag = false;
+    m_dr_active = true;
+}
+
+void DesignSketchTool::clear_draft_gizmo()
+{
+    m_dr_active = false;
+    m_dr_drag   = false;
+}
+
+void DesignSketchTool::render_draft_gizmo()
+{
+    if (!m_dr_active) return;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double th  = std::max(15.0 * upp, 1e-4);
+    const Vec3d yax  = dr_yaxis(m_dr_axis, m_dr_ref);
+
+    const SketchPlane saved = m_plane;
+    SketchPlane rp; rp.origin = m_dr_center; rp.x_axis = m_dr_ref; rp.y_axis = yax; rp.normal = m_dr_axis;
+    m_plane = rp;
+    const ColorRGBA arcc(0.15f, 0.92f, 1.0f, 1.0f);
+    const double r = m_dr_radius;
+    // Draft angle can be negative: sweep counter-clockwise (positive) or clockwise (negative)
+    const double a = m_dr_angle * M_PI / 180.0;
+    const int    N = std::max(8, int(std::abs(a) / (M_PI / 32.0)));   // ~ every 5.6°
+
+    std::vector<std::pair<Vec2d, Vec2d>> segs;
+    Vec2d prev(r, 0.0);
+    for (int i = 1; i <= N; ++i) {
+        const double t = a * double(i) / double(N);
+        const Vec2d cur(r * std::cos(t), r * std::sin(t));
+        segs.emplace_back(prev, cur);
+        prev = cur;
+    }
+    const Vec2d tip(r * std::cos(a), r * std::sin(a));
+    segs.emplace_back(Vec2d(0, 0), Vec2d(r, 0));   // spoke at angle 0
+    segs.emplace_back(Vec2d(0, 0), tip);           // spoke at the swept angle (the handle)
+    const Vec2d tang(-std::sin(a), std::cos(a));
+    const Vec2d radial = tip.normalized();
+    const double as = std::max(r * 0.14, th);
+    segs.emplace_back(tip, tip - tang * as - radial * (as * 0.5));
+    segs.emplace_back(tip, tip - tang * as + radial * (as * 0.5));
+    const double hs = std::max(th * 0.8, r * 0.05);
+    const Vec2d du = radial * hs, dv = Vec2d(-radial.y(), radial.x()) * hs;
+    segs.emplace_back(tip + du, tip + dv);
+    segs.emplace_back(tip + dv, tip - du);
+    segs.emplace_back(tip - du, tip - dv);
+    segs.emplace_back(tip - dv, tip + du);
+
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    draw_strokes(m_dr_stroke_model, segs, std::max(0.8 * upp, 1e-4), arcc);
+    DimAnnot da; da.kind = DimType::Angle; da.value = m_dr_angle;
+    draw_text(m_line_model, dim_text(da), tip * 1.14, th, arcc);
+    m_plane = saved;
+}
+
+bool DesignSketchTool::hit_test_draft_handle(GLCanvas3D& canvas, const wxMouseEvent& evt) const
+{
+    if (!m_dr_active) return false;
+    const Linef3 ray = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = ray.a, rd = ray.b - ray.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const Vec3d yax = dr_yaxis(m_dr_axis, m_dr_ref);
+    const double a  = m_dr_angle * M_PI / 180.0;
+    const double tol = 16.0 * upp;
+    auto ray_pt = [&](const Vec3d& p) {
+        const double t = (p - ro).dot(rd) / std::max(rd.dot(rd), 1e-12);
+        return (p - (ro + t * rd)).norm();
+    };
+    const Vec3d tip = m_dr_center + m_dr_radius * (std::cos(a) * m_dr_ref + std::sin(a) * yax);
+    const Vec3d ref = m_dr_center + m_dr_radius * m_dr_ref;   // angle-0 spoke end
+    const int N = 48;
+    for (int i = 0; i <= N; ++i) {
+        const double f = double(i) / double(N);
+        const double th = a * f;
+        const Vec3d arc = m_dr_center + m_dr_radius * (std::cos(th) * m_dr_ref + std::sin(th) * yax);
+        if (ray_pt(arc) <= tol) return true;
+        if (ray_pt(m_dr_center + f * (tip - m_dr_center)) <= tol) return true;
+        if (ray_pt(m_dr_center + f * (ref - m_dr_center)) <= tol) return true;
+    }
+    return false;
+}
+
+void DesignSketchTool::drag_draft_arc(GLCanvas3D& canvas, const wxMouseEvent& evt)
+{
+    const Linef3 ray = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = ray.a, rd = ray.b - ray.a;
+    const double denom = rd.dot(m_dr_axis);
+    if (std::abs(denom) < 1e-9) return;
+    const double t = (m_dr_center - ro).dot(m_dr_axis) / denom;
+    const Vec3d  p = ro + t * rd;
+    const Vec3d yax = dr_yaxis(m_dr_axis, m_dr_ref);
+    const double u = (p - m_dr_center).dot(m_dr_ref);
+    const double v = (p - m_dr_center).dot(yax);
+    double deg = std::atan2(v, u) * 180.0 / M_PI;
+    deg = std::min(89.0, std::max(-89.0, deg));
+    m_dr_angle = deg;
+    if (m_on_draft_angle_changed) m_on_draft_angle_changed(deg);
+}
+
+// ---- Cut gizmo (plane normal arrow + wire rectangle preview) --------------------------------
+// Arrow: shaft + arrowhead billboarded along the cut-plane normal from the projected body
+// centre, with a signed Distance label = offset. Drag is RELATIVE via hole_axis_proj.
+// Rectangle: 4 segments in the cut plane at the current offset, sized to the target body.
+
+void DesignSketchTool::set_cut_gizmo(const SketchPlane& plane, double offset, const Vec3d& body_center, double half_extent)
+{
+    m_ct_n  = plane.normal.normalized();
+    m_ct_u  = plane.x_axis.normalized();
+    m_ct_v  = plane.y_axis.normalized();
+    Vec3d rel = body_center - plane.origin;
+    m_ct_base = plane.origin + (rel - rel.dot(m_ct_n) * m_ct_n);  // body center projected into the cut plane
+    m_ct_offset = offset;
+    m_ct_half   = std::max(half_extent, 10.0);
+    if (!m_ct_active) m_ct_drag = false;
+    m_ct_active = true;
+}
+
+void DesignSketchTool::clear_cut_gizmo()
+{
+    m_ct_active = false;
+    m_ct_drag   = false;
+}
+
+void DesignSketchTool::render_cut_gizmo()
+{
+    if (!m_ct_active) return;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const double upp  = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double th   = std::max(15.0 * upp, 1e-4);
+    const ColorRGBA teal(0.20f, 0.80f, 0.75f, 1.0f);
+
+    // ---- Wire rectangle in the cut plane  ----
+    {
+        const Vec3d cutpos = m_ct_base + m_ct_offset * m_ct_n;
+        const SketchPlane saved = m_plane;
+        SketchPlane rp; rp.origin = cutpos; rp.x_axis = m_ct_u; rp.y_axis = m_ct_v; rp.normal = m_ct_n;
+        m_plane = rp;
+        const double h = m_ct_half;
+        std::vector<std::pair<Vec2d, Vec2d>> segs;
+        segs.emplace_back(Vec2d(-h, -h), Vec2d( h, -h));
+        segs.emplace_back(Vec2d( h, -h), Vec2d( h,  h));
+        segs.emplace_back(Vec2d( h,  h), Vec2d(-h,  h));
+        segs.emplace_back(Vec2d(-h,  h), Vec2d(-h, -h));
+        glsafe(::glDisable(GL_DEPTH_TEST));
+        draw_strokes(m_ct_rect_model, segs, std::max(0.7 * upp, 1e-4), teal);
+        m_plane = saved;
+    }
+
+    // ---- Offset arrow (billboarded, clone of render_shell_gizmo) ----
+    {
+        const double L_sign = (std::abs(m_ct_offset) < 40.0 * upp)
+            ? std::copysign(40.0 * upp, (m_ct_offset == 0.0 ? 1.0 : m_ct_offset))
+            : m_ct_offset;
+        const Vec3d tipw = m_ct_base + m_ct_n * L_sign;
+
+        const SketchPlane saved = m_plane;
+        SketchPlane bb; bb.origin = m_ct_base; bb.x_axis = right; bb.y_axis = up;
+        bb.normal = cam.get_dir_forward().normalized();
+        m_plane = bb;
+
+        const Vec2d tip2((tipw - m_ct_base).dot(right), (tipw - m_ct_base).dot(up));
+        if (tip2.norm() > 1e-6) {
+            const Vec2d u = tip2.normalized();
+            const Vec2d nrm(-u.y(), u.x());
+            std::vector<std::pair<Vec2d, Vec2d>> segs;
+            segs.emplace_back(Vec2d(0, 0), tip2);
+            const double as = std::max(tip2.norm() * 0.20, th * 0.9);
+            const Vec2d back = tip2 - u * as;
+            segs.emplace_back(tip2, back + nrm * (as * 0.5));
+            segs.emplace_back(tip2, back - nrm * (as * 0.5));
+            glsafe(::glDisable(GL_DEPTH_TEST));
+            draw_strokes(m_ct_stroke_model, segs, std::max(0.7 * upp, 1e-4), teal);
+            DimAnnot da; da.kind = DimType::Distance; da.value = m_ct_offset;
+            draw_text(m_line_model, dim_text(da), tip2 + u * (th * 1.4), th, teal);
+        }
+        m_plane = saved;
+    }
+}
+
+bool DesignSketchTool::hit_test_cut_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt) const
+{
+    if (!m_ct_active) return false;
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double L_sign = (std::abs(m_ct_offset) < 40.0 * upp)
+        ? std::copysign(40.0 * upp, (m_ct_offset == 0.0 ? 1.0 : m_ct_offset))
+        : m_ct_offset;
+    return ray_segment_dist3(ro, rd, m_ct_base, m_ct_base + m_ct_n * L_sign) <= 12.0 * upp;
+}
+
+void DesignSketchTool::start_cut_drag(GLCanvas3D& canvas, const wxMouseEvent& evt)
+{
+    m_ct_drag      = true;
+    m_ct_grab_val  = m_ct_offset;
+    const double p = hole_axis_proj(canvas, evt, m_ct_base, m_ct_n);
+    m_ct_grab_proj = std::isnan(p) ? 0.0 : p;
+}
+
+void DesignSketchTool::drag_cut_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt)
+{
+    const double proj = hole_axis_proj(canvas, evt, m_ct_base, m_ct_n);
+    if (std::isnan(proj)) return;
+    m_ct_offset = m_ct_grab_val + (proj - m_ct_grab_proj);
+    if (m_on_cut_offset_changed) m_on_cut_offset_changed(m_ct_offset);
+}
+
+void DesignSketchTool::set_revolve_gizmo(const SketchPlane& plane, const Vec2d& centroid,
+                                         int axis_sel, double angle, bool flip)
+{
+    const Vec3d ax = (axis_sel == 1 ? plane.y_axis : plane.x_axis).normalized();
+    const Vec3d cw = plane.to_world(centroid);
+    const double axial = (cw - plane.origin).dot(ax);
+    m_rv_center = plane.origin + axial * ax;     // foot of the centroid on the axis line
+    Vec3d ref = cw - m_rv_center;                // perpendicular to ax by construction
+    double r = ref.norm();
+    if (r < 1e-6) { ref = plane.normal.normalized(); r = std::max(plane.normal.norm(), 1.0); }
+    m_rv_axis   = ax;
+    m_rv_ref    = ref / ref.norm();
+    m_rv_radius = std::max(r, 1.0);
+    m_rv_angle  = std::min(360.0, std::max(1.0, std::abs(angle)));
+    m_rv_flip   = flip;
+    if (!m_rv_active) m_rv_drag = false;         // re-pushed every preview: keep an in-progress drag
+    m_rv_active = true;
+}
+
+void DesignSketchTool::clear_revolve_gizmo()
+{
+    m_rv_active = false;
+    m_rv_drag   = false;
+}
+
+void DesignSketchTool::render_revolve_gizmo()
+{
+    if (!m_rv_active) return;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double th  = std::max(15.0 * upp, 1e-4);
+    const Vec3d yax  = rv_yaxis(m_rv_axis, m_rv_ref, m_rv_flip);
+
+    // The arc lives in the true revolve plane (NOT billboarded) so the sweep reads in 3D.
+    const SketchPlane saved = m_plane;
+    SketchPlane rp; rp.origin = m_rv_center; rp.x_axis = m_rv_ref; rp.y_axis = yax; rp.normal = m_rv_axis;
+    m_plane = rp;
+    // Vivid cyan: the revolve ghost is amber, so the arc manipulator must contrast with it
+    // (it overlaps the solid, unlike the extrude depth-arrow which points away into empty space).
+    const ColorRGBA arcc(0.15f, 0.92f, 1.0f, 1.0f);
+    const double r = m_rv_radius;
+    const double a = m_rv_angle * M_PI / 180.0;
+    const int    N = std::max(8, int(a / (M_PI / 32.0)));   // ~ every 5.6°
+
+    std::vector<std::pair<Vec2d, Vec2d>> segs;
+    Vec2d prev(r, 0.0);
+    for (int i = 1; i <= N; ++i) {
+        const double t = a * double(i) / double(N);
+        const Vec2d cur(r * std::cos(t), r * std::sin(t));
+        segs.emplace_back(prev, cur);
+        prev = cur;
+    }
+    const Vec2d tip(r * std::cos(a), r * std::sin(a));
+    segs.emplace_back(Vec2d(0, 0), Vec2d(r, 0));   // spoke at angle 0
+    segs.emplace_back(Vec2d(0, 0), tip);           // spoke at the swept angle (the handle)
+    // Arrowhead at the tip, pointing along the sweep tangent (-sin,cos) rotated by a.
+    const Vec2d tang(-std::sin(a), std::cos(a));
+    const Vec2d radial = tip.normalized();
+    const double as = std::max(r * 0.14, th);
+    segs.emplace_back(tip, tip - tang * as - radial * (as * 0.5));
+    segs.emplace_back(tip, tip - tang * as + radial * (as * 0.5));
+    // A diamond grab-handle at the tip so the draggable target is unmistakable.
+    const double hs = std::max(th * 0.8, r * 0.05);
+    const Vec2d du = radial * hs, dv = Vec2d(-radial.y(), radial.x()) * hs;
+    segs.emplace_back(tip + du, tip + dv);
+    segs.emplace_back(tip + dv, tip - du);
+    segs.emplace_back(tip - du, tip - dv);
+    segs.emplace_back(tip - dv, tip + du);
+
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    draw_strokes(m_rv_stroke_model, segs, std::max(0.8 * upp, 1e-4), arcc);
+    DimAnnot da; da.kind = DimType::Angle; da.value = m_rv_angle;
+    draw_text(m_line_model, dim_text(da), tip * 1.14, th, arcc);
+    m_plane = saved;
+}
+
+bool DesignSketchTool::hit_test_revolve_handle(GLCanvas3D& canvas, const wxMouseEvent& evt) const
+{
+    if (!m_rv_active) return false;
+    const Linef3 ray = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = ray.a, rd = ray.b - ray.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const Vec3d yax = rv_yaxis(m_rv_axis, m_rv_ref, m_rv_flip);
+    const double a  = m_rv_angle * M_PI / 180.0;
+    const double tol = 16.0 * upp;
+    // Grab anywhere on the whole gizmo (Onshape-style): the arc curve OR either radial spoke.
+    // Take the nearest ray-to-point distance over a dense sampling.
+    auto ray_pt = [&](const Vec3d& p) {
+        const double t = (p - ro).dot(rd) / std::max(rd.dot(rd), 1e-12);
+        return (p - (ro + t * rd)).norm();
+    };
+    const Vec3d tip = m_rv_center + m_rv_radius * (std::cos(a) * m_rv_ref + std::sin(a) * yax);
+    const Vec3d ref = m_rv_center + m_rv_radius * m_rv_ref;   // angle-0 spoke end
+    const int N = 48;
+    for (int i = 0; i <= N; ++i) {
+        const double f = double(i) / double(N);
+        const double th = a * f;
+        const Vec3d arc = m_rv_center + m_rv_radius * (std::cos(th) * m_rv_ref + std::sin(th) * yax);
+        if (ray_pt(arc) <= tol) return true;                 // on the arc curve
+        if (ray_pt(m_rv_center + f * (tip - m_rv_center)) <= tol) return true;  // on the swept spoke
+        if (ray_pt(m_rv_center + f * (ref - m_rv_center)) <= tol) return true;  // on the ref spoke
+    }
+    return false;
+}
+
+// Intersect the mouse ray with the revolve plane, read its angle around the center -> sweep angle.
+void DesignSketchTool::drag_revolve_arc(GLCanvas3D& canvas, const wxMouseEvent& evt)
+{
+    const Linef3 ray = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = ray.a, rd = ray.b - ray.a;
+    const double denom = rd.dot(m_rv_axis);
+    if (std::abs(denom) < 1e-9) return;            // ray ∥ revolve plane: leave angle as-is
+    const double t = (m_rv_center - ro).dot(m_rv_axis) / denom;
+    const Vec3d  p = ro + t * rd;
+    const Vec3d yax = rv_yaxis(m_rv_axis, m_rv_ref, m_rv_flip);
+    const double u = (p - m_rv_center).dot(m_rv_ref);
+    const double v = (p - m_rv_center).dot(yax);
+    double deg = std::atan2(v, u) * 180.0 / M_PI;
+    if (deg < 0.0) deg += 360.0;
+    deg = std::min(360.0, std::max(1.0, deg));
+    m_rv_angle = deg;
+    if (on_revolve_angle_changed) on_revolve_angle_changed(deg);
+}
+
+void DesignSketchTool::open_revolve_editor()
+{
+    if (!on_inline_edit) return;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, m_rv_angle, "",
+        [this](double v) {
+            m_rv_angle = std::min(360.0, std::max(1.0, v));
+            if (on_revolve_angle_changed) on_revolve_angle_changed(m_rv_angle);
+        },
+        []() {});
+}
+
+// ---- Pattern gizmo (linear spacing arrow | circular angle-arc) ------------------------------
+// Linear: a 3D arrow along the world march axis with a tick at each copy; the diamond at the end
+// drags the spacing. Circular: a Revolve-style arc about the plane normal through the plane origin.
+void DesignSketchTool::set_pattern_gizmo(const SketchPlane& plane, const Vec3d& body_centroid,
+                                         bool circular, int count, int dir, double spacing, double angle)
+{
+    m_pt_circular = circular;
+    m_pt_base     = body_centroid;
+    m_pt_count    = std::max(1, count);
+    m_pt_spacing  = std::max(0.01, spacing);
+    m_pt_angle    = std::min(360.0, std::max(1.0, angle));
+    m_pt_dirw     = (dir == 1 ? plane.y_axis : plane.x_axis).normalized();
+    m_pt_origin   = plane.origin;
+    m_pt_normal   = plane.normal.normalized();
+    // Circular arc center = foot of the body centroid on the rotation axis; ref = perpendicular dir.
+    const double axial = (body_centroid - plane.origin).dot(m_pt_normal);
+    m_pt_ccenter = plane.origin + axial * m_pt_normal;
+    Vec3d ref = body_centroid - m_pt_ccenter;
+    double r = ref.norm();
+    if (r < 1e-6) { ref = m_pt_dirw; r = 1.0; }   // body centred on the axis: nominal radius
+    m_pt_cref   = ref / ref.norm();
+    m_pt_radius = std::max(r, 1.0);
+    if (!m_pt_active) m_pt_drag = false;          // re-pushed every preview: keep an in-progress drag
+    m_pt_active = true;
+}
+
+void DesignSketchTool::clear_pattern_gizmo()
+{
+    m_pt_active = false;
+    m_pt_drag   = false;
+}
+
+// Linear arrow span = spacing*(count-1), at least one step so count=1 still shows a direction.
+static double pt_linear_len(double spacing, int count)
+{
+    return std::max(spacing * double(std::max(1, count) - 1), spacing);
+}
+
+void DesignSketchTool::render_pattern_gizmo()
+{
+    if (!m_pt_active) return;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double th  = std::max(15.0 * upp, 1e-4);
+    const ColorRGBA col(0.15f, 0.92f, 1.0f, 1.0f);   // vivid cyan, matches the gizmo family
+    const SketchPlane saved = m_plane;
+    std::vector<std::pair<Vec2d, Vec2d>> segs;
+
+    if (!m_pt_circular) {
+        // The arrow lives in the true world plane (NOT billboarded) so the march reads in 3D.
+        const Vec3d perp = m_pt_normal.cross(m_pt_dirw).normalized();
+        SketchPlane fp; fp.origin = m_pt_base; fp.x_axis = m_pt_dirw; fp.y_axis = perp; fp.normal = m_pt_normal;
+        m_plane = fp;
+        const int copies = std::max(1, m_pt_count);
+        const double L = pt_linear_len(m_pt_spacing, copies);
+        segs.emplace_back(Vec2d(0, 0), Vec2d(L, 0));                 // shaft
+        const double as = std::max(L * 0.12, th);                   // arrowhead
+        segs.emplace_back(Vec2d(L, 0), Vec2d(L - as,  as * 0.5));
+        segs.emplace_back(Vec2d(L, 0), Vec2d(L - as, -as * 0.5));
+        const double tk = std::max(th, L * 0.05);                   // copy tick half-height
+        for (int i = 0; i < copies; ++i) {
+            const double x = m_pt_spacing * i;
+            segs.emplace_back(Vec2d(x, -tk), Vec2d(x, tk));
+        }
+        const Vec2d E(L, 0);                                        // diamond grab-handle
+        const double hs = std::max(th * 0.8, L * 0.04);
+        segs.emplace_back(E + Vec2d(hs, 0), E + Vec2d(0, hs));
+        segs.emplace_back(E + Vec2d(0, hs), E + Vec2d(-hs, 0));
+        segs.emplace_back(E + Vec2d(-hs, 0), E + Vec2d(0, -hs));
+        segs.emplace_back(E + Vec2d(0, -hs), E + Vec2d(hs, 0));
+        glsafe(::glDisable(GL_DEPTH_TEST));
+        draw_strokes(m_pt_stroke_model, segs, std::max(0.8 * upp, 1e-4), col);
+        DimAnnot da; da.kind = DimType::Distance; da.value = m_pt_spacing;
+        draw_text(m_line_model, dim_text(da), Vec2d(m_pt_spacing * 0.5, tk * 1.7), th, col);
+        m_plane = saved;
+        return;
+    }
+
+    // ---- Circular: clone the Revolve arc about the plane normal through the plane origin ----
+    const Vec3d yax = m_pt_normal.cross(m_pt_cref).normalized();
+    SketchPlane rp; rp.origin = m_pt_ccenter; rp.x_axis = m_pt_cref; rp.y_axis = yax; rp.normal = m_pt_normal;
+    m_plane = rp;
+    const double r = m_pt_radius;
+    const double a = m_pt_angle * M_PI / 180.0;
+    const int    N = std::max(8, int(a / (M_PI / 32.0)));
+    Vec2d prev(r, 0.0);
+    for (int i = 1; i <= N; ++i) {
+        const double t = a * double(i) / double(N);
+        const Vec2d cur(r * std::cos(t), r * std::sin(t));
+        segs.emplace_back(prev, cur);
+        prev = cur;
+    }
+    const Vec2d tip(r * std::cos(a), r * std::sin(a));
+    segs.emplace_back(Vec2d(0, 0), Vec2d(r, 0));   // angle-0 spoke
+    segs.emplace_back(Vec2d(0, 0), tip);           // swept spoke (the handle)
+    const Vec2d tang(-std::sin(a), std::cos(a));
+    const Vec2d radial = tip.normalized();
+    const double as = std::max(r * 0.14, th);
+    segs.emplace_back(tip, tip - tang * as - radial * (as * 0.5));
+    segs.emplace_back(tip, tip - tang * as + radial * (as * 0.5));
+    const double hs = std::max(th * 0.8, r * 0.05);
+    const Vec2d du = radial * hs, dv = Vec2d(-radial.y(), radial.x()) * hs;
+    segs.emplace_back(tip + du, tip + dv);
+    segs.emplace_back(tip + dv, tip - du);
+    segs.emplace_back(tip - du, tip - dv);
+    segs.emplace_back(tip - dv, tip + du);
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    draw_strokes(m_pt_stroke_model, segs, std::max(0.8 * upp, 1e-4), col);
+    DimAnnot da; da.kind = DimType::Angle; da.value = m_pt_angle;
+    draw_text(m_line_model, dim_text(da), tip * 1.14, th, col);
+    m_plane = saved;
+}
+
+bool DesignSketchTool::hit_test_pattern_handle(GLCanvas3D& canvas, const wxMouseEvent& evt) const
+{
+    if (!m_pt_active) return false;
+    const Linef3 ray = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = ray.a, rd = ray.b - ray.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double upp = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    auto ray_pt = [&](const Vec3d& p) {
+        const double t = (p - ro).dot(rd) / std::max(rd.dot(rd), 1e-12);
+        return (p - (ro + t * rd)).norm();
+    };
+    if (!m_pt_circular) {
+        const double tol = 8.0 * upp;
+        const double L = pt_linear_len(m_pt_spacing, m_pt_count);
+        return ray_segment_dist3(ro, rd, m_pt_base, m_pt_base + m_pt_dirw * L) <= tol;
+    }
+    const double tol = 16.0 * upp;
+    const Vec3d yax = m_pt_normal.cross(m_pt_cref).normalized();
+    const double a  = m_pt_angle * M_PI / 180.0;
+    const Vec3d tip = m_pt_ccenter + m_pt_radius * (std::cos(a) * m_pt_cref + std::sin(a) * yax);
+    const Vec3d ref = m_pt_ccenter + m_pt_radius * m_pt_cref;
+    const int N = 48;
+    for (int i = 0; i <= N; ++i) {
+        const double f = double(i) / double(N);
+        const Vec3d arc = m_pt_ccenter + m_pt_radius * (std::cos(a * f) * m_pt_cref + std::sin(a * f) * yax);
+        if (ray_pt(arc) <= tol) return true;
+        if (ray_pt(m_pt_ccenter + f * (tip - m_pt_ccenter)) <= tol) return true;
+        if (ray_pt(m_pt_ccenter + f * (ref - m_pt_ccenter)) <= tol) return true;
+    }
+    return false;
+}
+
+void DesignSketchTool::drag_pattern_handle(GLCanvas3D& canvas, const wxMouseEvent& evt)
+{
+    const Linef3 ray = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = ray.a, rd = ray.b - ray.a;
+    if (!m_pt_circular) {
+        // Skew-line closest point of the mouse ray to the march axis -> span -> spacing.
+        const Vec3d e = m_pt_dirw;
+        const Vec3d w0 = m_pt_base - ro;
+        const double a = e.dot(e), b = e.dot(rd), c = rd.dot(rd), dd = e.dot(w0), ee = rd.dot(w0);
+        const double denom = a * c - b * b;
+        if (std::abs(denom) < 1e-7) return;            // camera ∥ axis: leave spacing as-is
+        const double span = std::max(0.01, (b * ee - c * dd) / denom);
+        const int div = std::max(1, m_pt_count - 1);
+        m_pt_spacing = std::max(0.1, span / double(div));
+        if (on_pattern_changed) on_pattern_changed(m_pt_spacing);
+        return;
+    }
+    const double denom = rd.dot(m_pt_normal);
+    if (std::abs(denom) < 1e-9) return;                // ray ∥ rotation plane: leave angle as-is
+    const double t = (m_pt_ccenter - ro).dot(m_pt_normal) / denom;
+    const Vec3d  p = ro + t * rd;
+    const Vec3d yax = m_pt_normal.cross(m_pt_cref).normalized();
+    double deg = std::atan2((p - m_pt_ccenter).dot(yax), (p - m_pt_ccenter).dot(m_pt_cref)) * 180.0 / M_PI;
+    if (deg < 0.0) deg += 360.0;
+    m_pt_angle = std::min(360.0, std::max(1.0, deg));
+    if (on_pattern_changed) on_pattern_changed(m_pt_angle);
+}
+
+void DesignSketchTool::open_pattern_editor()
+{
+    if (!on_inline_edit) return;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    const double cur = m_pt_circular ? m_pt_angle : m_pt_spacing;
+    on_inline_edit(px, cur, "",
+        [this](double v) {
+            if (m_pt_circular) m_pt_angle = std::min(360.0, std::max(1.0, v));
+            else               m_pt_spacing = std::max(0.1, v);
+            if (on_pattern_changed) on_pattern_changed(m_pt_circular ? m_pt_angle : m_pt_spacing);
+        },
+        []() {});
+}
+
+// Closed loops + the entity indices that form each one. A circle/ellipse is its own loop;
+// line/arc chains are walked endpoint-to-endpoint. Entity membership lets a single loop be
+// highlighted and extruded on its own.
+std::vector<DesignSketchTool::RegionLoop>
+DesignSketchTool::region_loops(const std::vector<SketchEntity>& ents) const
+{
+    std::vector<RegionLoop> regions;
+    const double eps2 = sketch_join_tol() * sketch_join_tol();
+    auto is_near = [&](const Vec2d& a, const Vec2d& b) { return (a - b).squaredNorm() < eps2; };
+
+    // Circles are self-closed regions; lines/arcs are open segments to be chained. Each
+    // Seg remembers the entity index it came from.
+    struct Seg { std::vector<Vec2d> pts; int ent{-1}; bool used{false}; };
+    std::vector<Seg> segs;
+    for (int i = 0; i < int(ents.size()); ++i) {
+        const SketchEntity& e = ents[i];
+        if (e.construction) continue;
+        bool closed = false;
+        if (e.type == SketchEntity::Type::Circle || e.type == SketchEntity::Type::Ellipse) {
+            regions.push_back({ entity_polyline(e, closed), { i } });
+        } else if (e.type == SketchEntity::Type::Line || e.type == SketchEntity::Type::Arc
+                   || e.type == SketchEntity::Type::EllipseArc
+                   || e.type == SketchEntity::Type::BSpline) {
+            std::vector<Vec2d> p = entity_polyline(e, closed);
+            if (p.size() >= 2) segs.push_back({ std::move(p), i, false });
+        }
+    }
+
+    // Walk each unused segment endpoint-to-endpoint until the chain returns to its
+    // start (a closed loop) or stalls (an open chain, discarded).
+    for (size_t s = 0; s < segs.size(); ++s) {
+        if (segs[s].used) continue;
+        segs[s].used = true;
+        std::vector<Vec2d> loop = segs[s].pts;
+        std::vector<int>   loop_ents = { segs[s].ent };
+        const Vec2d start = loop.front();
+        Vec2d cur = loop.back();
+        bool extended = true;
+        while (extended && !is_near(cur, start)) {
+            extended = false;
+            for (size_t t = 0; t < segs.size(); ++t) {
+                if (segs[t].used) continue;
+                const std::vector<Vec2d>& q = segs[t].pts;
+                if (is_near(q.front(), cur)) {
+                    for (size_t k = 1; k < q.size(); ++k) loop.push_back(q[k]);
+                    cur = q.back();
+                } else if (is_near(q.back(), cur)) {
+                    for (int k = int(q.size()) - 2; k >= 0; --k) loop.push_back(q[k]);
+                    cur = q.front();
+                } else {
+                    continue;
+                }
+                segs[t].used = true;
+                loop_ents.push_back(segs[t].ent);
+                extended = true;
+                break;
+            }
+        }
+        if (is_near(cur, start) && loop.size() >= 4) {
+            loop.pop_back();          // drop the duplicate closing vertex
+            regions.push_back({ std::move(loop), std::move(loop_ents), {} });
+        }
+    }
+
+    // NESTING. A loop drawn inside another one is that one's HOLE. Without this a sketch is
+    // just N disjoint filled polygons, so "the plate with the hole" is not expressible and the
+    // multi-loop kernel path (88v) is unreachable from the viewport — which is exactly
+    // what Tommaso hit: a rectangle with a circle inside extruded to a plain box, because only
+    // the rectangle loop could be picked and only its entities were passed on.
+    //
+    // Loops in a well-formed sketch do not cross, so testing ONE point decides containment.
+    // Each loop is assigned to the SMALLEST loop that contains it, which is what makes a hole
+    // belong to the region that actually bounds it rather than to every enclosing loop.
+    //
+    // The point must be STRICTLY INSIDE the loop, not one of its vertices. A vertex is exactly
+    // where two loops are most likely to touch in a real drawing — a bore breaking out through
+    // a boss wall, a slot that ends on an outline — and a ray cast from a point that lies ON the
+    // polygon being tested answers by rounding, so the same drawing can be read either way.
+    // Measured on the StudyCadCam corpus: the engine and an independent containment check
+    // disagreed on 6 of 39 sheets, and every disagreement was a probe point sitting on the other
+    // loop's boundary. 5hvl.
+    auto poly_area = [](const std::vector<Vec2d>& q) {
+        double a2 = 0.0;
+        for (size_t i = 0, j = q.size() - 1; i < q.size(); j = i++)
+            a2 += (q[j].x() + q[i].x()) * (q[j].y() - q[i].y());
+        return std::abs(a2) * 0.5;
+    };
+    auto point_in = [](const Vec2d& pt, const std::vector<Vec2d>& q) {
+        bool in = false;
+        for (size_t i = 0, j = q.size() - 1; i < q.size(); j = i++) {
+            const Vec2d& A = q[i]; const Vec2d& B = q[j];
+            if (((A.y() > pt.y()) != (B.y() > pt.y())) &&
+                (pt.x() < (B.x() - A.x()) * (pt.y() - A.y()) / (B.y() - A.y()) + A.x()))
+                in = !in;
+        }
+        return in;
+    };
+    // A point strictly inside a simple polygon: the lowest vertex of a simple polygon is always
+    // CONVEX, so stepping from it along the bisector of its two edges goes into the interior.
+    // The step is a small fraction of the shorter adjacent edge, so it stays inside however
+    // sharp the corner is.
+    auto interior_point = [](const std::vector<Vec2d>& q) {
+        size_t k = 0;
+        for (size_t i = 1; i < q.size(); ++i)
+            if (q[i].y() < q[k].y() || (q[i].y() == q[k].y() && q[i].x() < q[k].x())) k = i;
+        const Vec2d& v = q[k];
+        Vec2d a = q[(k + q.size() - 1) % q.size()] - v;
+        Vec2d b = q[(k + 1) % q.size()] - v;
+        const double la = a.norm(), lb = b.norm();
+        if (la < 1e-12 || lb < 1e-12) return v;             // degenerate: nothing better to say
+        a /= la; b /= lb;
+        Vec2d bis = a + b;
+        if (bis.norm() < 1e-12) return v;                   // 180 deg spike: same
+        bis.normalize();
+        return Vec2d(v + bis * (1e-3 * std::min(la, lb)));
+    };
+    std::vector<Vec2d> probe(regions.size());
+    for (size_t i = 0; i < regions.size(); ++i)
+        if (regions[i].poly.size() >= 3) probe[i] = interior_point(regions[i].poly);
+        else if (!regions[i].poly.empty()) probe[i] = regions[i].poly.front();
+    for (size_t i = 0; i < regions.size(); ++i) {
+        if (regions[i].poly.empty()) continue;
+        int    best = -1;
+        double best_area = 0.0;
+        for (size_t j = 0; j < regions.size(); ++j) {
+            if (i == j || regions[j].poly.size() < 3) continue;
+            if (!point_in(probe[i], regions[j].poly)) continue;
+            const double a2 = poly_area(regions[j].poly);
+            if (best < 0 || a2 < best_area) { best = int(j); best_area = a2; }
+        }
+        if (best >= 0) regions[best].holes.push_back(int(i));
+    }
+    return regions;
+}
+
+int DesignSketchTool::region_at(const Vec2d& p) const
+{
+    // Walk region_loops (which already knows about holes) rather than the raw polygons: the
+    // returned index must stay meaningful after the sketch is committed, so it has to use the
+    // SAME numbering selected_loop_entities() and hit_display_sketch consume.
+    const std::vector<RegionLoop> regions = region_loops(m_entities);
+    auto inside = [](const Vec2d& q, const std::vector<Vec2d>& poly) {
+        bool in = false;
+        for (size_t i = 0, j = poly.size() - 1; i < poly.size(); j = i++) {
+            const Vec2d& a = poly[i];
+            const Vec2d& b = poly[j];
+            if (((a.y() > q.y()) != (b.y() > q.y())) &&
+                (q.x() < (b.x() - a.x()) * (q.y() - a.y()) / (b.y() - a.y()) + a.x()))
+                in = !in;
+        }
+        return in;
+    };
+    // Shoelace area (absolute): the SMALLEST loop containing p is the innermost one, which is
+    // the region that actually owns the point — a bore inside a plate resolves to the disc, and
+    // a click on the plate material resolves to the plate even though the disc is also inside it.
+    auto poly_area = [](const std::vector<Vec2d>& q) {
+        double a2 = 0.0;
+        for (size_t i = 0, j = q.size() - 1; i < q.size(); j = i++)
+            a2 += (q[j].x() + q[i].x()) * (q[j].y() - q[i].y());
+        return std::abs(a2) * 0.5;
+    };
+    int    best = -1;
+    double best_area = 0.0;
+    for (size_t i = 0; i < regions.size(); ++i) {
+        if (regions[i].poly.size() < 3) continue;
+        if (!inside(p, regions[i].poly)) continue;
+        bool in_hole = false;   // p inside one of this region's holes → that hole owns it, not us
+        for (int h : regions[i].holes) {
+            if (h < 0 || h >= int(regions.size()) || regions[h].poly.size() < 3) continue;
+            if (inside(p, regions[h].poly)) { in_hole = true; break; }
+        }
+        if (in_hole) continue;
+        const double a = poly_area(regions[i].poly);
+        if (best < 0 || a < best_area) { best = int(i); best_area = a; }
+    }
+    return best;
+}
+
+// ---- rendering --------------------------------------------------------------
+
+// Chop a polyline into dashes (imlq). Construction geometry is dashed in every CAD;
+// this one painted it solid grey, which against the under-constrained orange reads as "another
+// line", not as "reference only". The dash and gap arrive in WORLD units — the caller scales them
+// by units-per-pixel, so the dash keeps its size on screen at any zoom instead of turning into a
+// solid line when you zoom out and into three dashes when you zoom in.
+static std::vector<std::vector<Vec2d>> dash_polyline(const std::vector<Vec2d>& pts, bool closed,
+                                                     double dash, double gap)
+{
+    std::vector<std::vector<Vec2d>> out;
+    if (pts.size() < 2 || dash <= 0.0 || gap <= 0.0) return out;
+    const size_t segs = closed ? pts.size() : pts.size() - 1;
+    bool   on   = true;      // start on a dash, so a short entity is still visible
+    double left = dash;      // distance remaining in the current dash/gap
+    std::vector<Vec2d> cur;
+    if (on) cur.push_back(pts[0]);
+    for (size_t i = 0; i < segs; ++i) {
+        const Vec2d a = pts[i], b = pts[(i + 1) % pts.size()];
+        double seg = (b - a).norm();
+        if (seg < 1e-12) continue;
+        const Vec2d dir = (b - a) / seg;
+        double t = 0.0;
+        while (seg - t > left) {
+            t += left;
+            const Vec2d p = a + dir * t;
+            if (on) { cur.push_back(p); out.push_back(cur); cur.clear(); }
+            else    { cur.clear(); cur.push_back(p); }
+            on   = !on;
+            left = on ? dash : gap;
+        }
+        left -= (seg - t);
+        if (on) cur.push_back(b);
+    }
+    if (on && cur.size() >= 2) out.push_back(cur);
+    return out;
+}
+
+void DesignSketchTool::draw_quad_strip(GLModel& model, const std::vector<Vec2d>& pts, bool closed, const ColorRGBA& color)
+{
+    if (pts.size() < 2)
+        return;
+
+    // Half-width in WORLD units, so a stroke is 2*hw mm wide on the plane. Halved from 0.6 on
+    // user report 2026-08-23: at 1.2 mm the orange under-constrained line was heavy enough to
+    // swallow a short segment and to hide which of two near-parallel lines the cursor was on.
+    // Every one of this function's call sites is a sketch stroke (entities, previews, rubber
+    // bands), which is why the constant is here and not a parameter at twenty call sites.
+    const double hw = 0.3;
+    GLModel::Geometry g;
+    g.format = { GLModel::Geometry::EPrimitiveType::Triangles, GLModel::Geometry::EVertexLayout::P3 };
+    unsigned int base = 0;
+
+    const size_t segs = closed ? pts.size() : pts.size() - 1;
+    for (size_t i = 0; i < segs; ++i) {
+        const Vec2d a = pts[i];
+        const Vec2d b = pts[(i + 1) % pts.size()];
+        const Vec2d d = b - a;
+        const double len = d.norm();
+        if (len < 1e-6)
+            continue;
+        const Vec2d n(-d.y() / len, d.x() / len);
+        const Vec2d o = n * hw;
+        g.add_vertex((Vec3f)m_plane.to_world(a + o).cast<float>());
+        g.add_vertex((Vec3f)m_plane.to_world(b + o).cast<float>());
+        g.add_vertex((Vec3f)m_plane.to_world(b - o).cast<float>());
+        g.add_vertex((Vec3f)m_plane.to_world(a - o).cast<float>());
+        g.add_triangle(base, base + 1, base + 2);
+        g.add_triangle(base, base + 2, base + 3);
+        base += 4;
+    }
+
+    if (base > 0) {
+        model.reset();
+        model.init_from(std::move(g));
+        model.set_color(color);
+        model.render();
+    }
+}
+
+namespace {
+double poly_signed_area(const std::vector<Vec2d>& p)
+{
+    double a = 0.0;
+    for (size_t i = 0, n = p.size(); i < n; ++i) {
+        const Vec2d& u = p[i];
+        const Vec2d& v = p[(i + 1) % n];
+        a += u.x() * v.y() - v.x() * u.y();
+    }
+    return 0.5 * a;
+}
+bool pt_in_tri(const Vec2d& p, const Vec2d& a, const Vec2d& b, const Vec2d& c)
+{
+    auto cross = [](const Vec2d& u, const Vec2d& v, const Vec2d& w) {
+        return (v.x() - u.x()) * (w.y() - u.y()) - (v.y() - u.y()) * (w.x() - u.x());
+    };
+    const double d1 = cross(a, b, p), d2 = cross(b, c, p), d3 = cross(c, a, p);
+    const bool neg = (d1 < 0) || (d2 < 0) || (d3 < 0);
+    const bool pos = (d1 > 0) || (d2 > 0) || (d3 > 0);
+    return !(neg && pos);   // inside iff all cross products share a sign
+}
+// Ear-clipping triangulation of a simple polygon; returns index triples into `poly`.
+std::vector<std::array<unsigned, 3>> ear_clip(const std::vector<Vec2d>& poly)
+{
+    std::vector<std::array<unsigned, 3>> tris;
+    const size_t n = poly.size();
+    if (n < 3) return tris;
+    std::vector<unsigned> idx(n);
+    for (unsigned i = 0; i < n; ++i) idx[i] = i;
+    if (poly_signed_area(poly) < 0.0) std::reverse(idx.begin(), idx.end());   // work CCW
+    int guard = 0;
+    while (idx.size() > 3 && guard++ < int(10 * n)) {
+        bool clipped = false;
+        const int m = int(idx.size());
+        for (int i = 0; i < m; ++i) {
+            const unsigned i0 = idx[(i + m - 1) % m];
+            const unsigned i1 = idx[i];
+            const unsigned i2 = idx[(i + 1) % m];
+            const Vec2d& a = poly[i0]; const Vec2d& b = poly[i1]; const Vec2d& c = poly[i2];
+            const double cr = (b.x() - a.x()) * (c.y() - a.y()) - (b.y() - a.y()) * (c.x() - a.x());
+            if (cr <= 0.0) continue;   // reflex vertex, not an ear tip
+            bool ear = true;
+            for (int j = 0; j < m; ++j) {
+                const unsigned ij = idx[j];
+                if (ij == i0 || ij == i1 || ij == i2) continue;
+                if (pt_in_tri(poly[ij], a, b, c)) { ear = false; break; }
+            }
+            if (!ear) continue;
+            tris.push_back({ i0, i1, i2 });
+            idx.erase(idx.begin() + i);
+            clipped = true;
+            break;
+        }
+        if (!clipped) break;   // degenerate input: bail rather than spin
+    }
+    if (idx.size() == 3) tris.push_back({ idx[0], idx[1], idx[2] });
+    return tris;
+}
+} // namespace
+
+// Fill a region that has holes with an EVEN-ODD SCANLINE fill: each horizontal band is scanned
+// across every contour, the crossings sorted, and the spans between alternate crossings emitted
+// as quads. A hole is just two more crossings, so any number of holes and any concavity fall out
+// of the parity rule — no bridge and no triangulation to fail.
+void DesignSketchTool::draw_fill_holed(GLModel& model, const std::vector<Vec2d>& outer,
+                                       const std::vector<std::vector<Vec2d>>& holes,
+                                       const ColorRGBA& color)
+{
+    if (outer.size() < 3) return;
+    if (holes.empty()) { draw_fill(model, outer, color); return; }
+
+    // EVEN-ODD SCANLINE, not a triangulation. The previous version spliced each hole into the
+    // outer contour through a keyhole corridor and ear-clipped the result; the corridor did not
+    // collapse to zero width and was drawn as a visible triangle running from the bore to the
+    // nearest rectangle corner. Rather than tune a bridge that can always find a new shape to
+    // fail on, this fills the region the way a rasteriser would: for each horizontal band, cross
+    // EVERY contour, sort the crossings, and fill between alternate pairs. A hole is simply two
+    // more crossings, so any number of holes and any concavity fall out of the same rule and no
+    // corridor exists to leak.
+    std::vector<const std::vector<Vec2d>*> contours;
+    contours.push_back(&outer);
+    for (const auto& h : holes) if (h.size() >= 3) contours.push_back(&h);
+
+    double ymin = outer[0].y(), ymax = ymin, xmin = outer[0].x(), xmax = xmin;
+    for (const auto* c : contours)
+        for (const Vec2d& v : *c) {
+            ymin = std::min(ymin, v.y()); ymax = std::max(ymax, v.y());
+            xmin = std::min(xmin, v.x()); xmax = std::max(xmax, v.x());
+        }
+    if (ymax - ymin < 1e-9) return;
+
+    // Enough bands that the step is far below a pixel at any sane zoom, cheap enough to rebuild
+    // every frame: this is a translucent highlight, not geometry.
+    const int    ROWS = 256;
+    const double dy   = (ymax - ymin) / ROWS;
+
+    GLModel::Geometry g;
+    g.format = { GLModel::Geometry::EPrimitiveType::Triangles, GLModel::Geometry::EVertexLayout::P3 };
+    unsigned base = 0;
+    std::vector<double> xs;
+    for (int row = 0; row < ROWS; ++row) {
+        const double y0 = ymin + dy * row, y1 = y0 + dy, ym = 0.5 * (y0 + y1);
+        xs.clear();
+        for (const auto* c : contours) {
+            const std::vector<Vec2d>& q = *c;
+            for (size_t i = 0, j = q.size() - 1; i < q.size(); j = i++) {
+                const Vec2d& A = q[i]; const Vec2d& B = q[j];
+                if ((A.y() > ym) == (B.y() > ym)) continue;          // edge does not cross this row
+                xs.push_back(A.x() + (ym - A.y()) * (B.x() - A.x()) / (B.y() - A.y()));
+            }
+        }
+        if (xs.size() < 2) continue;
+        std::sort(xs.begin(), xs.end());
+        for (size_t k = 0; k + 1 < xs.size(); k += 2) {              // even-odd: fill alternate spans
+            const double xa = xs[k], xb = xs[k + 1];
+            if (xb - xa < 1e-9) continue;
+            g.add_vertex((Vec3f)m_plane.to_world(Vec2d(xa, y0)).cast<float>());
+            g.add_vertex((Vec3f)m_plane.to_world(Vec2d(xb, y0)).cast<float>());
+            g.add_vertex((Vec3f)m_plane.to_world(Vec2d(xb, y1)).cast<float>());
+            g.add_vertex((Vec3f)m_plane.to_world(Vec2d(xa, y1)).cast<float>());
+            g.add_triangle(base, base + 1, base + 2);
+            g.add_triangle(base, base + 2, base + 3);
+            base += 4;
+        }
+    }
+    if (base == 0) return;
+    model.reset();
+    model.init_from(std::move(g));
+    model.set_color(color);
+    model.render();
+}
+
+void DesignSketchTool::draw_fill(GLModel& model, const std::vector<Vec2d>& poly, const ColorRGBA& color)
+{
+    if (poly.size() < 3) return;
+    const auto tris = ear_clip(poly);
+    if (tris.empty()) return;
+    GLModel::Geometry g;
+    g.format = { GLModel::Geometry::EPrimitiveType::Triangles, GLModel::Geometry::EVertexLayout::P3 };
+    for (const Vec2d& p : poly)
+        g.add_vertex((Vec3f)m_plane.to_world(p).cast<float>());
+    for (const auto& t : tris)
+        g.add_triangle(t[0], t[1], t[2]);
+    model.reset();
+    model.init_from(std::move(g));
+    model.set_color(color);
+    model.render();
+}
+
+void DesignSketchTool::draw_vertices(GLModel& model, const std::vector<Vec2d>& pts, const ColorRGBA& color,
+                                     double half_size)
+{
+    if (pts.empty())
+        return;
+
+    const double hs = half_size;
+    GLModel::Geometry g;
+    g.format = { GLModel::Geometry::EPrimitiveType::Triangles, GLModel::Geometry::EVertexLayout::P3 };
+    unsigned int base = 0;
+    for (const Vec2d& p : pts) {
+        g.add_vertex((Vec3f)m_plane.to_world(p + Vec2d(-hs, -hs)).cast<float>());
+        g.add_vertex((Vec3f)m_plane.to_world(p + Vec2d( hs, -hs)).cast<float>());
+        g.add_vertex((Vec3f)m_plane.to_world(p + Vec2d( hs,  hs)).cast<float>());
+        g.add_vertex((Vec3f)m_plane.to_world(p + Vec2d(-hs,  hs)).cast<float>());
+        g.add_triangle(base, base + 1, base + 2);
+        g.add_triangle(base, base + 2, base + 3);
+        base += 4;
+    }
+
+    model.reset();
+    model.init_from(std::move(g));
+    model.set_color(color);
+    model.render();
+}
+
+// Independent thick-line segments batched into one immediate-mode draw (quote lines,
+// extension lines, arrowheads, glyph strokes). Mirrors draw_quad_strip's lift-to-world.
+void DesignSketchTool::draw_strokes(GLModel& model, const std::vector<std::pair<Vec2d, Vec2d>>& segs,
+                                    double hw, const ColorRGBA& color)
+{
+    GLModel::Geometry g;
+    g.format = { GLModel::Geometry::EPrimitiveType::Triangles, GLModel::Geometry::EVertexLayout::P3 };
+    unsigned int base = 0;
+    for (const auto& s : segs) {
+        const Vec2d a = s.first, b = s.second;
+        const Vec2d d = b - a;
+        const double len = d.norm();
+        if (len < 1e-6) continue;
+        const Vec2d n(-d.y() / len, d.x() / len);
+        const Vec2d o = n * hw;
+        g.add_vertex((Vec3f)m_plane.to_world(a + o).cast<float>());
+        g.add_vertex((Vec3f)m_plane.to_world(b + o).cast<float>());
+        g.add_vertex((Vec3f)m_plane.to_world(b - o).cast<float>());
+        g.add_vertex((Vec3f)m_plane.to_world(a - o).cast<float>());
+        g.add_triangle(base, base + 1, base + 2);
+        g.add_triangle(base, base + 2, base + 3);
+        base += 4;
+    }
+    if (base > 0) {
+        model.reset();
+        model.init_from(std::move(g));
+        model.set_color(color);
+        model.render();
+    }
+}
+
+namespace {
+// Smooth single-stroke (Hershey-style) vector font for dimension labels. Glyphs
+// live in a 0..0.6 (x) by 0..1 (y) cell, baseline at y=0, cap height y=1; curved
+// digits are sampled as short segments so they read as rounded shapes, not blocks.
+// `advance` is the pen step after the glyph.
+constexpr double kPi = 3.14159265358979323846;
+inline double rad(double deg) { return deg * kPi / 180.0; }
+
+// Connect a list of points as a polyline.
+void poly(std::vector<std::pair<Vec2d, Vec2d>>& out, std::initializer_list<Vec2d> p)
+{
+    auto it = p.begin();
+    if (it == p.end()) return;
+    Vec2d prev = *it++;
+    for (; it != p.end(); ++it) { out.emplace_back(prev, *it); prev = *it; }
+}
+// Sample an elliptical arc (centre cx,cy; radii rx,ry) from angle a0..a1.
+void arc(std::vector<std::pair<Vec2d, Vec2d>>& out, double cx, double cy, double rx, double ry,
+         double a0, double a1, int n = 14)
+{
+    Vec2d prev(cx + rx * std::cos(a0), cy + ry * std::sin(a0));
+    for (int i = 1; i <= n; ++i) {
+        const double t = a0 + (a1 - a0) * (double)i / n;
+        const Vec2d cur(cx + rx * std::cos(t), cy + ry * std::sin(t));
+        out.emplace_back(prev, cur);
+        prev = cur;
+    }
+}
+
+void glyph_strokes(char c, std::vector<std::pair<Vec2d, Vec2d>>& out, double& advance)
+{
+    advance = 0.72;
+    switch (c) {
+    case '0':
+        arc(out, 0.30, 0.50, 0.25, 0.48, 0.0, 2.0 * kPi);
+        break;
+    case '1':
+        poly(out, {Vec2d(0.13, 0.76), Vec2d(0.33, 1.0), Vec2d(0.33, 0.0)});
+        poly(out, {Vec2d(0.13, 0.0), Vec2d(0.53, 0.0)});
+        advance = 0.52;
+        break;
+    case '2':
+        arc(out, 0.30, 0.72, 0.25, 0.25, rad(170), rad(-45));
+        poly(out, {Vec2d(0.477, 0.543), Vec2d(0.06, 0.0), Vec2d(0.56, 0.0)});
+        break;
+    case '3':
+        arc(out, 0.30, 0.74, 0.24, 0.24, rad(160), rad(-90));
+        arc(out, 0.30, 0.26, 0.26, 0.26, rad(90), rad(-160));
+        break;
+    case '4':
+        poly(out, {Vec2d(0.42, 1.0), Vec2d(0.04, 0.32), Vec2d(0.58, 0.32)});
+        poly(out, {Vec2d(0.42, 1.0), Vec2d(0.42, 0.0)});
+        break;
+    case '5':
+        poly(out, {Vec2d(0.54, 1.0), Vec2d(0.12, 1.0), Vec2d(0.11, 0.52)});
+        arc(out, 0.27, 0.30, 0.27, 0.27, rad(130), rad(-120));
+        break;
+    case '6':
+        arc(out, 0.30, 0.28, 0.26, 0.26, 0.0, 2.0 * kPi);
+        arc(out, 0.30, 0.55, 0.30, 0.45, rad(90), rad(190));
+        break;
+    case '7':
+        poly(out, {Vec2d(0.05, 1.0), Vec2d(0.57, 1.0), Vec2d(0.22, 0.0)});
+        break;
+    case '8':
+        arc(out, 0.30, 0.73, 0.22, 0.25, 0.0, 2.0 * kPi);
+        arc(out, 0.30, 0.26, 0.26, 0.26, 0.0, 2.0 * kPi);
+        break;
+    case '9':
+        arc(out, 0.30, 0.70, 0.26, 0.26, 0.0, 2.0 * kPi);
+        arc(out, 0.28, 0.55, 0.28, 0.55, rad(15), rad(-90));
+        break;
+    case '.':
+    case ',':  // locale (LC_NUMERIC) may format the decimal separator as a comma
+        // small solid dot: crossed short strokes so the quads fill a visible disk
+        poly(out, {Vec2d(0.10, 0.08), Vec2d(0.24, 0.08)});
+        poly(out, {Vec2d(0.17, 0.02), Vec2d(0.17, 0.15)});
+        advance = 0.30;
+        break;
+    case '-':
+        poly(out, {Vec2d(0.10, 0.5), Vec2d(0.50, 0.5)});
+        advance = 0.62;
+        break;
+    case 'R':
+        poly(out, {Vec2d(0.08, 0.0), Vec2d(0.08, 1.0), Vec2d(0.38, 1.0)});
+        arc(out, 0.38, 0.75, 0.17, 0.25, rad(90), rad(-90));
+        poly(out, {Vec2d(0.38, 0.50), Vec2d(0.08, 0.50)});
+        poly(out, {Vec2d(0.30, 0.50), Vec2d(0.58, 0.0)});
+        advance = 0.80;
+        break;
+    case 'X':
+        poly(out, {Vec2d(0.06, 1.0), Vec2d(0.58, 0.0)});
+        poly(out, {Vec2d(0.58, 1.0), Vec2d(0.06, 0.0)});
+        advance = 0.72;
+        break;
+    case 'Y':
+        poly(out, {Vec2d(0.06, 1.0), Vec2d(0.32, 0.52)});
+        poly(out, {Vec2d(0.58, 1.0), Vec2d(0.32, 0.52)});
+        poly(out, {Vec2d(0.32, 0.52), Vec2d(0.32, 0.0)});
+        advance = 0.72;
+        break;
+    case 'Z':
+        poly(out, {Vec2d(0.06, 1.0), Vec2d(0.58, 1.0), Vec2d(0.06, 0.0), Vec2d(0.58, 0.0)});
+        advance = 0.72;
+        break;
+    case ' ':
+        advance = 0.5;
+        break;
+    default:
+        advance = 0.5;
+        break;
+    }
+}
+} // namespace
+
+void DesignSketchTool::draw_dim_label(const std::string& txt, const Vec2d& plane_center)
+{
+    if (txt.empty()) return;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const wxPoint sp = world_to_screen_px(cam, m_plane.to_world(plane_center));
+    if (sp.x < 0 && sp.y < 0) return;
+    ImGuiWrapper* imgui = wxGetApp().imgui();
+    // Identical to the Prepare/Preview Measure gizmo label (GLGizmoMeasure::render_dimensioning):
+    // push_common_window_style sets the white text colour + font/scale (without it the text is
+    // invisible); BringWindowToDisplayFront keeps the per-frame label window on top.
+    ImGuiWrapper::push_common_window_style(m_render_scale);
+    imgui->set_next_window_pos((float)sp.x, (float)sp.y, ImGuiCond_Always, 0.5f, 0.5f);
+    imgui->set_next_window_bg_alpha(0.0f);
+    ImGui::PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0.0f);
+    ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
+    ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(1.0f, 1.0f));
+    const std::string win = "##sketchdim" + std::to_string(m_dim_label_seq++);
+    imgui->begin(win, ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoDecoration
+                       | ImGuiWindowFlags_NoInputs | ImGuiWindowFlags_NoFocusOnAppearing
+                       | ImGuiWindowFlags_NoNav);
+    ImGui::BringWindowToDisplayFront(ImGui::GetCurrentWindow());
+    ImGui::AlignTextToFramePadding();
+    ImDrawList* dl = ImGui::GetWindowDrawList();
+    const ImVec2 pos = ImGui::GetCursorScreenPos();
+    const ImVec2 ts  = ImGui::CalcTextSize(txt.c_str());
+    const ImGuiStyle& st = ImGui::GetStyle();
+    dl->AddRectFilled(ImVec2(pos.x - st.FramePadding.x, pos.y + st.FramePadding.y),
+                      ImVec2(pos.x + ts.x + 2.0f * st.FramePadding.x,
+                             pos.y + ts.y + 2.0f * st.FramePadding.y),
+                      ImGuiWrapper::to_ImU32(ColorRGBA(1.0f, 1.0f, 1.0f, 0.5f)));
+    ImGui::SetCursorScreenPos(ImVec2(pos.x + st.FramePadding.x, pos.y));
+    imgui->text(txt);
+    imgui->end();
+    ImGui::PopStyleVar(3);
+    ImGuiWrapper::pop_common_window_style();
+}
+
+void DesignSketchTool::draw_text(GLModel& /*model*/, const std::string& s, const Vec2d& center,
+                                 double /*height*/, const ColorRGBA& /*color*/)
+{
+    // ponytail: all sketch labels now render as Measure-gizmo-style ImGui labels for visual
+    // parity with the Prepare/Preview tabs; the old vector-font path (glyph_strokes/draw_strokes
+    // for text) is retired. Leader lines/arrows still draw via draw_strokes at the call sites.
+    draw_dim_label(s, center);
+}
+
+// Draw every placed dimension: extension lines, the offset dimension line, arrowheads
+// and the numeric label. Geometry is recomputed from the (solved) entities each frame
+// so the quote tracks the sketch.
+// Draw one dimension's quote (extension/dimension lines, arrowheads, numeric label).
+// Geometry is recomputed from the (solved) entities so the quote tracks the sketch.
+// Returns the label centre in out_label; false if the annot references missing/degenerate
+// geometry. Shared by placed (render_dimensions) and live (render_live_quotes) quotes.
+bool DesignSketchTool::draw_dim_quote(const DimAnnot& a, double th, const ColorRGBA& dimcol,
+                                      Vec2d& out_label)
+{
+    std::vector<std::pair<Vec2d, Vec2d>> segs;
+    if (a.kind == DimType::Length || a.kind == DimType::Distance) {
+        Vec2d pa, pb;
+        if (a.kind == DimType::Length) {
+            if (a.ea < 0 || a.ea >= int(m_entities.size())) return false;
+            pa = m_entities[a.ea].p0; pb = m_entities[a.ea].p1;
+        } else if (!point_at(a.ea, a.ra, pa) || !point_at(a.eb, a.rb, pb)) {
+            return false;
+        }
+        const Vec2d d = pb - pa;
+        const double L = d.norm();
+        if (L < 1e-6) return false;
+        const Vec2d u = d / L;
+        const Vec2d nrm(-u.y(), u.x());
+        const double side = (a.side != 0.0) ? a.side : 1.0;
+        const double off  = side * std::max(L * 0.18, 8.0);
+        const Vec2d A2 = pa + nrm * off, B2 = pb + nrm * off;   // offset clear of the sketch line
+        segs.emplace_back(A2, B2);                              // dimension line (not on the geometry)
+        const double as = std::max(L * 0.04, 2.0);
+        auto arrow = [&](const Vec2d& tip, const Vec2d& dir) {
+            const Vec2d back = tip + dir * as;
+            segs.emplace_back(tip, back + nrm * (as * 0.5));
+            segs.emplace_back(tip, back - nrm * (as * 0.5));
+        };
+        arrow(A2, u); arrow(B2, -u);
+        out_label = (A2 + B2) * 0.5 + nrm * (side * (th * 0.7 + 1.5));
+    } else if (a.kind == DimType::Diameter || a.kind == DimType::Radius) {
+        if (a.ea < 0 || a.ea >= int(m_entities.size())) return false;
+        const SketchEntity& e = m_entities[a.ea];
+        const Vec2d c = e.center;
+        const double r = e.radius;
+        if (r < 1e-6) return false;
+        const Vec2d u(1.0, 0.0);
+        const double as = std::max(r * 0.12, 2.0);
+        if (a.kind == DimType::Diameter) {
+            const Vec2d p1 = c - u * r, p2 = c + u * r;
+            segs.emplace_back(p1, p2);
+            segs.emplace_back(p1, p1 + u * as + Vec2d(0, 1) * (as * 0.5));
+            segs.emplace_back(p1, p1 + u * as - Vec2d(0, 1) * (as * 0.5));
+            segs.emplace_back(p2, p2 - u * as + Vec2d(0, 1) * (as * 0.5));
+            segs.emplace_back(p2, p2 - u * as - Vec2d(0, 1) * (as * 0.5));
+            out_label = c + Vec2d(0, 1) * (th * 0.8);
+        } else {
+            const Vec2d p2 = c + u * r;
+            segs.emplace_back(c, p2);
+            segs.emplace_back(p2, p2 - u * as + Vec2d(0, 1) * (as * 0.5));
+            segs.emplace_back(p2, p2 - u * as - Vec2d(0, 1) * (as * 0.5));
+            out_label = (c + p2) * 0.5 + Vec2d(0, 1) * (th * 0.8);
+        }
+    } else if (a.kind == DimType::DistanceToLine) {
+        Vec2d pa;
+        if (!point_at(a.ea, a.ra, pa) || a.eb < 0 || a.eb >= int(m_entities.size())) return false;
+        const SketchEntity& Ln = m_entities[a.eb];
+        const Vec2d ld = Ln.p1 - Ln.p0;
+        const double n = ld.norm();
+        if (n < 1e-9) return false;
+        const Vec2d u = ld / n;
+        const double t = (pa - Ln.p0).dot(u);
+        const Vec2d foot = Ln.p0 + u * t;       // perpendicular foot on the line
+        segs.emplace_back(pa, foot);
+        out_label = (pa + foot) * 0.5 + u * (th * 0.7 + 1.5);
+    } else if (a.kind == DimType::Angle) {
+        if (a.ea < 0 || a.ea >= int(m_entities.size())) return false;
+        const SketchEntity& e = m_entities[a.ea];
+        if (e.type != SketchEntity::Type::Line) return false;
+        const Vec2d d = e.p1 - e.p0;
+        const double L = d.norm();
+        if (L < 1e-6) return false;
+        double ang = std::atan2(d.y(), d.x());            // signed, matches measure_dim sweep
+        const double rr = std::max(std::min(L * 0.35, 40.0), th * 1.6);  // arc radius
+        segs.emplace_back(e.p0, e.p0 + Vec2d(rr * 1.15, 0.0));  // horizontal reference leg
+        const int N = 20;                                  // arc 0 -> ang about p0
+        Vec2d prev = e.p0 + Vec2d(rr, 0.0);
+        for (int i = 1; i <= N; ++i) {
+            const double t = ang * double(i) / N;
+            const Vec2d cur = e.p0 + Vec2d(rr * std::cos(t), rr * std::sin(t));
+            segs.emplace_back(prev, cur); prev = cur;
+        }
+        const double mid = ang * 0.5;
+        out_label = e.p0 + Vec2d(std::cos(mid), std::sin(mid)) * (rr + th * 1.1);
+    } else {
+        return false;
+    }
+    draw_strokes(m_highlight_model, segs, 0.2, dimcol);
+    draw_text(m_line_model, dim_text(a), out_label, th, dimcol);
+    return true;
+}
+
+// Draw every placed (driving) dimension; cache each label centre for picking.
+void DesignSketchTool::render_dimensions(double unit_per_px)
+{
+    if (m_dimensions.empty()) return;
+    const ColorRGBA dimcol(0.85f, 0.85f, 0.85f, 1.0f);   // neutral leader (Measure parity)
+    // Label text is a CONSTANT screen size (like real CAD), not scaled to geometry,
+    // so a long line doesn't get huge text. ~15 px tall in plane units at this zoom.
+    const double th = std::max(15.0 * unit_per_px, 1e-4);
+    for (size_t di = 0; di < m_dimensions.size(); ++di) {
+        Vec2d label;
+        if (draw_dim_quote(m_dimensions[di], th, dimcol, label))
+            m_dimensions[di].label_pos = label;
+    }
+}
+
+// Per-entity-type characteristic dimensions, drawn as live non-driving quotes for the
+// entity being edited (point/handle drag, or a lone selection). This is the Onshape
+// pattern that scales to every tool: each kind reports its defining dimension(s); each
+// is clickable (m_live_quotes) to promote to a driving dim + open the inline editor.
+// A dim already driven on the entity is skipped (render_dimensions draws that one).
+void DesignSketchTool::render_live_quotes(double unit_per_px)
+{
+    m_live_quotes.clear();
+    m_live_poly_fi = -1;
+    m_live_poly_side_label = m_live_poly_angle_label = Vec2d(1e18, 1e18);
+    m_live_arc_ei = -1;
+    m_live_arc_angle_label = Vec2d(1e18, 1e18);
+    m_live_ellipse_ei = -1;
+    m_live_ellipse_major_label = m_live_ellipse_minor_label = Vec2d(1e18, 1e18);
+    m_live_ellipsearc_sweep_label = Vec2d(1e18, 1e18);
+    m_live_obrect_fi = -1;
+    m_live_obrect_angle_label = Vec2d(1e18, 1e18);
+    m_live_rrect_fi = -1;
+    m_live_rrect_w_label = m_live_rrect_h_label = m_live_rrect_r_label = Vec2d(1e18, 1e18);
+    m_live_aslot_fi = -1;
+    m_live_aslot_r_label = m_live_aslot_w_label = Vec2d(1e18, 1e18);
+    m_live_slot_fi = -1;
+    m_live_slot_len_label = m_live_slot_w_label = m_live_slot_angle_label = Vec2d(1e18, 1e18);
+    // Edit-op tools (Fillet/Chamfer/Offset/Mirror) put their picks in m_selection for the
+    // highlight, but their own arrow/label gizmo is the value affordance — don't also draw
+    // the picked entity's characteristic quotes (Length/Angle/…) or the view gets cluttered.
+    if (is_edit_op_mode() || is_transform_mode()) return;
+    int ei = -1;
+    if (m_dragging_point && m_drag_ei >= 0)  ei = m_drag_ei;
+    else if (m_dragging_handle)              ei = m_drag_handle.ei;
+    else if (m_selection.size() == 1)        ei = m_selection[0];
+    else if (!m_selection.empty()) {
+        // A GROUPED FEATURE SELECTS EVERY MEMBER, so "exactly one entity" hid the characteristic
+        // quotes for precisely the shapes that have nothing else. A rounded rectangle is eight
+        // entities — four lines and four arcs — so picking it makes m_selection.size() == 8, this
+        // pass returned here, and its Width / Height / Radius labels were never drawn. With no
+        // label on screen there is nothing to click, which is the whole of "cannot edit labels in
+        // rounded rectangles": not a value that refuses to change, a label that does not exist.
+        //
+        // A plain rectangle looked fine only by accident: typing into its auto-edit chain creates
+        // a DRIVEN dimension, and render_dimensions draws that one from the annotation list. The
+        // rounded rect's W/H/R go through set_rounded_rect, which rebuilds the geometry and leaves
+        // no annotation behind — so the live label was the only affordance it ever had.
+        //
+        // Accept a selection that is entirely ONE feature and let any member speak for it; the
+        // switch below already keys off feature_of(ei) rather than the entity itself.
+        const int f0 = feature_of(m_selection.front());
+        if (f0 >= 0) {
+            bool same_feature = true;
+            for (int s : m_selection)
+                if (feature_of(s) != f0) { same_feature = false; break; }
+            if (same_feature) ei = m_selection.front();
+        }
+    }
+    if (ei < 0 || ei >= int(m_entities.size())) return;
+    const SketchEntity& e = m_entities[ei];
+
+    std::vector<DimAnnot> protos;
+    auto add_len = [&](int line_ei, double side) {
+        if (line_ei < 0 || line_ei >= int(m_entities.size())) return;
+        if (m_entities[line_ei].type != SketchEntity::Type::Line) return;
+        DimAnnot a; a.kind = DimType::Length; a.ea = line_ei; a.side = side; protos.push_back(a);
+    };
+
+    // A grouped gesture (rect/slot/polygon decomposes into raw lines/arcs) exposes its
+    // DERIVED characteristic dims off the Feature span, regardless of which member edge
+    // was picked. Rect: Width = first edge length, Height = second edge length (the two
+    // axes of the 4-line loop pushed by push_closed_lines: edge0 horizontal, edge1
+    // vertical). Quotes offset to opposite sides so they don't overlap.
+    const int fi = feature_of(ei);
+    if (fi >= 0) {
+        const Feature& f = m_features[fi];
+        switch (f.kind) {
+        case FeatureKind::CornerRect:
+        case FeatureKind::CenterRect: {
+            add_len(f.begin + 0,  1.0);   // Width
+            add_len(f.begin + 1, -1.0);   // Height
+            // OBLIQUE rect (drawn off-axis, also a CornerRect feature): expose its orientation
+            // too. Gated to genuinely-tilted edges so an axis-aligned Corner/Center rect never
+            // gets an angle quote (and its verified W/H behaviour is untouched).
+            if (f.begin >= 0 && f.begin < int(m_entities.size())) {
+                const SketchEntity& e0 = m_entities[f.begin];
+                Vec2d d0 = e0.p1 - e0.p0;
+                if (d0.squaredNorm() > 1e-12) {
+                    double deg = std::atan2(d0.y(), d0.x()) * 180.0 / M_PI;
+                    const double off = std::fmod(std::fmod(deg, 90.0) + 90.0, 90.0); // dist to axis
+                    if (off > 2.0 && off < 88.0) {
+                        const ColorRGBA dc(0.30f, 0.88f, 0.66f, 1.0f);
+                        const double th = std::max(15.0 * unit_per_px, 1e-4);
+                        double adeg = deg; if (adeg < 0.0) adeg += 360.0;
+                        const Vec2d mid = 0.5 * (e0.p0 + e0.p1);
+                        Vec2d nrm(-d0.y(), d0.x()); if (nrm.squaredNorm() > 1e-12) nrm.normalize();
+                        m_live_obrect_angle_label = mid + nrm * (th * 1.4);
+                        DimAnnot at; at.kind = DimType::Angle; at.value = adeg;
+                        draw_text(m_line_model, dim_text(at), m_live_obrect_angle_label, th, dc);
+                        m_live_obrect_fi = fi;
+                    }
+                }
+            }
+            break;
+        }
+        case FeatureKind::Slot: {
+            // Straight slot edits GEOMETRICALLY (like the arc-slot / rounded-rect), NOT through
+            // the constraint-based scalar quotes. Its dims are the centreline LENGTH (distance
+            // between the two cap centres c0,c1) and the WIDTH (2*param). The old
+            // Distance-between-arc-centres + Radius quotes never registered as editable, so the
+            // labels did nothing on click (nde #6). Draw both labels clear of the fillable face
+            // and remember the feature so open_primary_autoedit / click-to-promote drive set_slot.
+            // Slot dims: (1) inter-centre distance, (2) radius (= half-width), (3) centreline angle.
+            const ColorRGBA dc(0.30f, 0.88f, 0.66f, 1.0f);
+            const double th = std::max(15.0 * unit_per_px, 1e-4);
+            Vec2d u = f.c1 - f.c0;
+            const double Lc = u.norm();
+            if (Lc > 1e-9) {
+                u /= Lc;
+                const Vec2d n(-u.y(), u.x());
+                const double w = f.param;
+                DimAnnot len; len.kind = DimType::Length; len.value = Lc;
+                m_live_slot_len_label = 0.5 * (f.c0 + f.c1) + n * (w + th * 2.0);
+                draw_text(m_line_model, dim_text(len), m_live_slot_len_label, th, dc);
+                DimAnnot rd; rd.kind = DimType::Radius; rd.value = w;
+                m_live_slot_w_label = f.c1 + u * (w + th * 2.0);
+                draw_text(m_line_model, dim_text(rd), m_live_slot_w_label, th, dc);
+                double deg = std::atan2(f.c1.y() - f.c0.y(), f.c1.x() - f.c0.x()) * 180.0 / M_PI;
+                if (deg < 0.0) deg += 360.0;
+                DimAnnot an; an.kind = DimType::Angle; an.value = deg;
+                m_live_slot_angle_label = f.c0 - u * (w + th * 2.0);
+                draw_text(m_line_model, dim_text(an), m_live_slot_angle_label, th, dc);
+                m_live_slot_fi = fi;
+            }
+            break;
+        }
+        case FeatureKind::Polygon: {
+            // A regular polygon is N raw lines (no centre entity). Its natural editable
+            // dims are the SIDE length and the ORIENTATION — NOT a circumradius (a polygon
+            // is not a circle). Both edit the whole loop geometrically: side scales it
+            // uniformly, angle rotates it. Drawn off edge0 with draw_dim_quote (Length +
+            // Angle); the side quote is offset OUTWARD so its label clears the face.
+            if (f.begin < int(m_entities.size()) &&
+                m_entities[f.begin].type == SketchEntity::Type::Line) {
+                const ColorRGBA dc(0.30f, 0.88f, 0.66f, 1.0f);
+                const double th = std::max(15.0 * unit_per_px, 1e-4);
+                const SketchEntity& e0 = m_entities[f.begin];
+                const Vec2d m0 = 0.5 * (e0.p0 + e0.p1);
+                Vec2d u0 = e0.p1 - e0.p0;
+                if (u0.squaredNorm() > 1e-12) u0.normalize();
+                const Vec2d n0(-u0.y(), u0.x());
+                const double outsign = ((m0 + n0) - f.c0).norm() >= (m0 - f.c0).norm() ? 1.0 : -1.0;
+                DimAnnot side; side.kind = DimType::Length; side.ea = f.begin; side.side = outsign;
+                side.value = measure_dim(side);
+                Vec2d slbl;
+                if (draw_dim_quote(side, th, dc, slbl)) m_live_poly_side_label = slbl;
+
+                // Orientation = the angle of the centre->vertex0 spoke from +X (the
+                // intuitive "which way does the polygon point"), NOT the edge direction.
+                // Drawn as a wedge OUTSIDE the polygon (radius just past the circumradius)
+                // so its arc/label clear the fillable face.
+                const Vec2d sp = m_entities[f.begin].p0 - f.c0;   // centre -> vertex0
+                const double R = sp.norm();
+                if (R > 1e-6) {
+                    double av = std::atan2(sp.y(), sp.x());
+                    double avdeg = av * 180.0 / M_PI; if (avdeg < 0.0) avdeg += 360.0;
+                    const double rr = R + th * 2.5;               // wedge just outside the loop
+                    std::vector<std::pair<Vec2d, Vec2d>> asegs;
+                    asegs.emplace_back(f.c0, f.c0 + Vec2d(rr, 0.0));                       // +X leg
+                    asegs.emplace_back(f.c0, f.c0 + Vec2d(std::cos(av), std::sin(av)) * rr); // spoke leg
+                    const int N = 20; Vec2d prev = f.c0 + Vec2d(rr, 0.0);
+                    for (int i = 1; i <= N; ++i) {
+                        const double t = av * double(i) / N;
+                        const Vec2d cur = f.c0 + Vec2d(rr * std::cos(t), rr * std::sin(t));
+                        asegs.emplace_back(prev, cur); prev = cur;
+                    }
+                    const double mid = av * 0.5;
+                    const Vec2d albl = f.c0 + Vec2d(std::cos(mid), std::sin(mid)) * (rr + th * 1.2);
+                    DimAnnot at; at.kind = DimType::Angle; at.value = avdeg;   // "NN.N°"
+                    draw_strokes(m_highlight_model, asegs, 0.6, dc);
+                    draw_text(m_line_model, dim_text(at), albl, th, dc);
+                    m_live_poly_angle_label = albl;
+                }
+                m_live_poly_fi = fi;
+            }
+            break;
+        }
+        case FeatureKind::RoundedRect: {
+            // Width + Height (box bounds) + fillet Radius, drawn as clickable quotes that
+            // rebuild the box geometrically (set_rounded_rect). c0=min corner, c1=max, param=r.
+            const ColorRGBA dc(0.30f, 0.88f, 0.66f, 1.0f);
+            const double th = std::max(15.0 * unit_per_px, 1e-4);
+            const double xmin = std::min(f.c0.x(), f.c1.x()), xmax = std::max(f.c0.x(), f.c1.x());
+            const double ymin = std::min(f.c0.y(), f.c1.y()), ymax = std::max(f.c0.y(), f.c1.y());
+            const double w = xmax - xmin, h = ymax - ymin, r = f.param;
+            const double off = th * 2.0;
+            std::vector<std::pair<Vec2d, Vec2d>> segs;
+            // Width quote below the box.
+            const double yb = ymin - off;
+            segs.emplace_back(Vec2d(xmin, ymin), Vec2d(xmin, yb));
+            segs.emplace_back(Vec2d(xmax, ymin), Vec2d(xmax, yb));
+            segs.emplace_back(Vec2d(xmin, yb),   Vec2d(xmax, yb));
+            // Height quote left of the box.
+            const double xl = xmin - off;
+            segs.emplace_back(Vec2d(xmin, ymin), Vec2d(xl, ymin));
+            segs.emplace_back(Vec2d(xmin, ymax), Vec2d(xl, ymax));
+            segs.emplace_back(Vec2d(xl, ymin),   Vec2d(xl, ymax));
+            // Fillet-radius leader from the TR arc centre out to the corner.
+            const Vec2d rc(xmax - r, ymax - r);
+            segs.emplace_back(rc, rc + Vec2d(r, r).normalized() * r);
+            draw_strokes(m_highlight_model, segs, 0.6, dc);
+            DimAnnot wa; wa.kind = DimType::Length; wa.value = w;
+            DimAnnot ha; ha.kind = DimType::Length; ha.value = h;
+            DimAnnot ra; ra.kind = DimType::Radius; ra.value = r;
+            m_live_rrect_w_label = Vec2d((xmin + xmax) * 0.5, yb - th * 0.8);
+            m_live_rrect_h_label = Vec2d(xl - th * 0.8, (ymin + ymax) * 0.5);
+            m_live_rrect_r_label = rc + Vec2d(r, r).normalized() * (r + th * 1.2);
+            draw_text(m_line_model, dim_text(wa), m_live_rrect_w_label, th, dc);
+            draw_text(m_line_model, dim_text(ha), m_live_rrect_h_label, th, dc);
+            draw_text(m_line_model, dim_text(ra), m_live_rrect_r_label, th, dc);
+            m_live_rrect_fi = fi;
+            break;
+        }
+        case FeatureKind::ArcSlot: {
+            // Centreline Radius + slot Width quotes. centre=f.c0, centreline start=f.c1,
+            // half-width=f.param; end direction from the cap@E arc centre (begin+1).
+            if (f.begin + 1 < int(m_entities.size())) {
+                const ColorRGBA dc(0.30f, 0.88f, 0.66f, 1.0f);
+                const double th = std::max(15.0 * unit_per_px, 1e-4);
+                const Vec2d  center = f.c0;
+                const double Rc = (f.c1 - center).norm();
+                const double w  = f.param;
+                Vec2d dirS = (f.c1 - center);
+                Vec2d dirE = (m_entities[f.begin + 1].center - center);
+                if (dirS.squaredNorm() > 1e-12 && dirE.squaredNorm() > 1e-12 && Rc > 1e-6) {
+                    dirS.normalize(); dirE.normalize();
+                    const double aS = std::atan2(dirS.y(), dirS.x());
+                    double sweep = std::atan2(dirE.y(), dirE.x()) - aS;
+                    while (sweep < 0) sweep += 2.0 * M_PI;
+                    const double aMid = aS + sweep * 0.5;
+                    const Vec2d uMid(std::cos(aMid), std::sin(aMid));
+                    // Centreline-radius leader: centre -> centreline midpoint.
+                    std::vector<std::pair<Vec2d, Vec2d>> segs;
+                    segs.emplace_back(center, center + uMid * Rc);
+                    // Width tick across the slot at the start cap (outer<->inner).
+                    segs.emplace_back(center + dirS * (Rc + w), center + dirS * (Rc - w));
+                    draw_strokes(m_highlight_model, segs, 0.6, dc);
+                    DimAnnot ra; ra.kind = DimType::Radius; ra.value = Rc;
+                    DimAnnot wa; wa.kind = DimType::Length; wa.value = 2.0 * w;
+                    m_live_aslot_r_label = center + uMid * (Rc * 0.5) + Vec2d(0, th);
+                    m_live_aslot_w_label = center + dirS * (Rc + w) + dirS * (th * 1.2);
+                    draw_text(m_line_model, dim_text(ra), m_live_aslot_r_label, th, dc);
+                    draw_text(m_line_model, dim_text(wa), m_live_aslot_w_label, th, dc);
+                    m_live_aslot_fi = fi;
+                }
+            }
+            break;
+        }
+        default: break;                   // other features: later chunks
+        }
+    }
+
+    if (protos.empty() && m_live_poly_fi < 0 && m_live_rrect_fi < 0 &&
+        m_live_aslot_fi < 0 && m_live_slot_fi < 0) {  // ungrouped single entity
+        switch (e.type) {
+        case SketchEntity::Type::Line: {
+            DimAnnot len; len.kind = DimType::Length; len.ea = ei; len.side = 1.0; protos.push_back(len);
+            DimAnnot ang; ang.kind = DimType::Angle;  ang.ea = ei; ang.eb = -1;    protos.push_back(ang);
+            break;                        // segment length + angle-to-horizontal
+        }
+        case SketchEntity::Type::Circle: {
+            DimAnnot a; a.kind = DimType::Radius; a.ea = ei; protos.push_back(a); break;
+        }
+        case SketchEntity::Type::Arc: {
+            // Arc radius is its single defining dimension (sweep angles edit via the end
+            // handles). radius lives in the same .radius field measure_dim/constraint_for
+            // read, so the Radius promotion path is identical to Circle.
+            DimAnnot a; a.kind = DimType::Radius; a.ea = ei; protos.push_back(a); break;
+        }
+        default: break;                   // ellipse/bspline: later
+        }
+    }
+
+    // Arc sweep-angle wedge: drawn inline (like the polygon orientation) because it is a
+    // GEOMETRIC edit (SLVS angle constraints are line-to-line). A wedge spans the arc's
+    // start->end angles just OUTSIDE the radius; its label shows the included angle and is
+    // clickable to type a new sweep. The radius quote is still emitted via `protos`.
+    if (m_live_poly_fi < 0 && m_live_rrect_fi < 0 && m_live_aslot_fi < 0 && m_live_slot_fi < 0 &&
+        e.type == SketchEntity::Type::Arc && e.radius > 1e-6) {
+        const ColorRGBA dc(0.30f, 0.88f, 0.66f, 1.0f);
+        const double th = std::max(15.0 * unit_per_px, 1e-4);
+        const Vec2d  c  = e.center;
+        const double a0 = e.start_angle, a1 = e.end_angle;
+        const double sweep = a1 - a0;                       // signed (CCW>0); |sweep| shown
+        double swdeg = std::abs(sweep) * 180.0 / M_PI;
+        const double rr = e.radius + th * 2.5;              // wedge just outside the arc
+        std::vector<std::pair<Vec2d, Vec2d>> asegs;
+        asegs.emplace_back(c, c + Vec2d(std::cos(a0), std::sin(a0)) * rr);   // start leg
+        asegs.emplace_back(c, c + Vec2d(std::cos(a1), std::sin(a1)) * rr);   // end leg
+        const int N = 24; Vec2d prev = c + Vec2d(std::cos(a0), std::sin(a0)) * rr;
+        for (int i = 1; i <= N; ++i) {
+            const double t = a0 + sweep * double(i) / N;
+            const Vec2d cur = c + Vec2d(rr * std::cos(t), rr * std::sin(t));
+            asegs.emplace_back(prev, cur); prev = cur;
+        }
+        const double mid = a0 + sweep * 0.5;
+        const Vec2d albl = c + Vec2d(std::cos(mid), std::sin(mid)) * (rr + th * 1.2);
+        DimAnnot at; at.kind = DimType::Angle; at.value = swdeg;             // "NN.N°"
+        draw_strokes(m_highlight_model, asegs, 0.6, dc);
+        draw_text(m_line_model, dim_text(at), albl, th, dc);
+        m_live_arc_angle_label = albl;
+        m_live_arc_ei = ei;
+    }
+
+    // Ellipse: two clickable axis quotes — semi-major (a) along the major direction and
+    // semi-minor (b) along the minor. Both edit geometrically (a=e.radius, b=e.rminor);
+    // phi (orientation) is changed by dragging the major grip, not via a label.
+    if (m_live_poly_fi < 0 && m_live_rrect_fi < 0 &&
+        (e.type == SketchEntity::Type::Ellipse || e.type == SketchEntity::Type::EllipseArc) &&
+        e.radius > 1e-6 && e.rminor > 1e-6) {
+        const ColorRGBA dc(0.30f, 0.88f, 0.66f, 1.0f);
+        const double th = std::max(15.0 * unit_per_px, 1e-4);
+        const Vec2d  c  = e.center;
+        const Vec2d  um(std::cos(e.rotation), std::sin(e.rotation));   // major dir
+        const Vec2d  un(-um.y(), um.x());                              // minor dir
+        std::vector<std::pair<Vec2d, Vec2d>> segs;
+        const Vec2d majEnd = c + um * e.radius, minEnd = c + un * e.rminor;
+        segs.emplace_back(c, majEnd);
+        segs.emplace_back(c, minEnd);
+        draw_strokes(m_highlight_model, segs, 0.6, dc);
+        DimAnnot ma; ma.kind = DimType::Length; ma.value = e.radius;   // plain "NN.N"
+        DimAnnot mi; mi.kind = DimType::Length; mi.value = e.rminor;
+        const Vec2d majLbl = c + um * (e.radius * 0.5) + un * (th * 1.0);
+        const Vec2d minLbl = c + un * (e.rminor * 0.5) + um * (th * 1.0);
+        draw_text(m_line_model, dim_text(ma), majLbl, th, dc);
+        draw_text(m_line_model, dim_text(mi), minLbl, th, dc);
+        m_live_ellipse_major_label = majLbl;
+        m_live_ellipse_minor_label = minLbl;
+        m_live_ellipse_ei = ei;
+        // Elliptical arc also has a SWEEP (included parametric angle), drawn outside the arc
+        // midpoint; the full ellipse skips this (closed).
+        if (e.type == SketchEntity::Type::EllipseArc) {
+            const double midp = 0.5 * (e.start_angle + e.end_angle);
+            const Vec2d  mp   = ellipse_point(c, e.radius, e.rminor, e.rotation, midp);
+            Vec2d outw = mp - c; if (outw.squaredNorm() > 1e-12) outw.normalize();
+            m_live_ellipsearc_sweep_label = mp + outw * (th * 1.5);
+            DimAnnot sw; sw.kind = DimType::Angle;
+            sw.value = std::abs(e.end_angle - e.start_angle) * 180.0 / M_PI;
+            draw_text(m_line_model, dim_text(sw), m_live_ellipsearc_sweep_label, th, dc);
+        }
+    }
+
+    if (protos.empty()) return;
+
+    const ColorRGBA dimcol(0.30f, 0.88f, 0.66f, 1.0f);
+    const double th = std::max(15.0 * unit_per_px, 1e-4);
+    for (DimAnnot a : protos) {
+        bool driven = false;                       // skip if already a driving dim of this kind
+        for (const DimAnnot& d : m_dimensions)
+            if (d.ea == a.ea && d.kind == a.kind) { driven = true; break; }
+        if (driven) continue;
+        a.value = measure_dim(a);
+        Vec2d label;
+        if (draw_dim_quote(a, th, dimcol, label)) {
+            a.label_pos = label;
+            m_live_quotes.push_back(a);            // remember for click-to-promote
+        }
+    }
+}
+
+// Iconic constraint badges drawn near each constraint's primary entity (C3.4b).
+// Each glyph is authored in a unit cell [-0.5,0.5]^2 then scaled to a constant
+// on-screen size and translated to the anchor; badges on the same entity stack
+// upward so multiple constraints stay legible.
+void DesignSketchTool::build_constraint_glyphs(double unit_per_px,
+                                               const std::vector<SketchEntityConstraintDef>& cons,
+                                               std::vector<std::pair<Vec2d, Vec2d>>& out)
+{
+    m_glyph_hits.clear();
+    if (cons.empty() || m_entities.empty()) return;
+    using T = SketchConstraintType;
+    const double s = std::max(11.0 * unit_per_px, 1e-4);   // glyph cell size in plane units
+    const double step = s * 1.5;                           // vertical stacking step
+
+    // Representative anchor point on an entity (line midpoint, round-entity centre).
+    auto anchor_of = [&](int ei) -> Vec2d {
+        if (ei < 0 || ei >= int(m_entities.size())) return Vec2d(0, 0);
+        const SketchEntity& e = m_entities[ei];
+        switch (e.type) {
+        case SketchEntity::Type::Line:    return 0.5 * (e.p0 + e.p1);
+        case SketchEntity::Type::Circle:
+        case SketchEntity::Type::Ellipse:
+        case SketchEntity::Type::Arc:
+        case SketchEntity::Type::EllipseArc: return e.center;
+        case SketchEntity::Type::BSpline:  return 0.5 * (e.p0 + e.p1);
+        case SketchEntity::Type::Point:    return e.p0;
+        }
+        return e.p0;
+    };
+
+    // Unit-cell stroke authoring helpers (cell centred on origin).
+    auto seg = [&](std::vector<std::pair<Vec2d, Vec2d>>& v, Vec2d a, Vec2d b) { v.emplace_back(a, b); };
+    auto circ = [&](std::vector<std::pair<Vec2d, Vec2d>>& v, Vec2d c, double r) {
+        const int n = 12; Vec2d prev(c.x() + r, c.y());
+        for (int i = 1; i <= n; ++i) {
+            const double t = 2.0 * 3.14159265358979 * i / n;
+            Vec2d cur(c.x() + r * std::cos(t), c.y() + r * std::sin(t));
+            v.emplace_back(prev, cur); prev = cur;
+        }
+    };
+    // Author one glyph type into a unit-cell stroke list.
+    auto unit_glyph = [&](T type, std::vector<std::pair<Vec2d, Vec2d>>& v) {
+        switch (type) {
+        case T::Horizontal: seg(v, {-0.5, 0}, {0.5, 0}); break;
+        case T::Vertical:   seg(v, {0, -0.5}, {0, 0.5}); break;
+        case T::Parallel:   seg(v, {-0.35, -0.5}, {0.0, 0.5}); seg(v, {0.05, -0.5}, {0.4, 0.5}); break;
+        case T::Perpendicular: seg(v, {-0.4, 0.5}, {-0.4, -0.4}); seg(v, {-0.4, -0.4}, {0.5, -0.4}); break;
+        case T::Coincident: circ(v, {0, 0}, 0.42); break;
+        case T::Concentric: circ(v, {0, 0}, 0.5); circ(v, {0, 0}, 0.24); break;
+        case T::EqualLength:seg(v, {-0.4, 0.16}, {0.4, 0.16}); seg(v, {-0.4, -0.16}, {0.4, -0.16}); break;
+        case T::Tangent:    circ(v, {0, -0.1}, 0.35); seg(v, {-0.5, 0.42}, {0.5, 0.42}); break;
+        case T::Midpoint:   seg(v, {-0.4, 0}, {0.4, 0}); seg(v, {0, -0.18}, {0, 0.18}); break;
+        case T::Symmetric:  seg(v, {0, -0.5}, {0, 0.5});
+                            seg(v, {-0.5, 0.4}, {-0.15, 0}); seg(v, {-0.5, -0.4}, {-0.15, 0});
+                            seg(v, {0.5, 0.4}, {0.15, 0}); seg(v, {0.5, -0.4}, {0.15, 0}); break;
+        case T::Fix:        seg(v, {-0.4, -0.4}, {0.4, -0.4}); seg(v, {0.4, -0.4}, {0.4, 0.4});
+                            seg(v, {0.4, 0.4}, {-0.4, 0.4}); seg(v, {-0.4, 0.4}, {-0.4, -0.4}); break;
+        case T::Angle:      seg(v, {-0.4, -0.4}, {0.4, -0.4}); seg(v, {-0.4, -0.4}, {0.3, 0.4}); break;
+        case T::Radius:     circ(v, {0, 0}, 0.45); seg(v, {0, 0}, {0.45, 0}); break;
+        case T::Diameter:   circ(v, {0, 0}, 0.45); seg(v, {-0.45, 0}, {0.45, 0}); break;
+        case T::PointOnLine:
+        case T::PointOnObject: seg(v, {-0.5, -0.3}, {0.5, -0.3}); circ(v, {0, 0.05}, 0.16); break;
+        case T::Distance:
+        case T::LockX:
+        case T::LockY:      seg(v, {-0.4, 0}, {0.4, 0}); break;   // generic tick
+        }
+    };
+
+    // Stack count per entity so successive badges step upward.
+    std::vector<int> stack(m_entities.size(), 0);
+    const Vec2d up(0.0, 1.0);     // plane-space up; offset so badge sits off the geometry
+    m_glyph_r = 0.6 * s;
+    for (size_t ci = 0; ci < cons.size(); ++ci) {
+        const SketchEntityConstraintDef& d = cons[ci];
+        if (d.ea < 0 || d.ea >= int(m_entities.size())) continue;
+        const int k = stack[d.ea]++;
+        const Vec2d center = anchor_of(d.ea) + up * (step * (1.0 + k));
+        m_glyph_hits.push_back({center, int(ci)});
+        std::vector<std::pair<Vec2d, Vec2d>> cell;
+        unit_glyph(d.type, cell);
+        for (auto& sgp : cell)
+            out.emplace_back(center + sgp.first * s, center + sgp.second * s);
+    }
+}
+
+void DesignSketchTool::draw_entities_preview(const std::vector<SketchEntity>& ents, const ColorRGBA& color)
+{
+    std::vector<Vec2d> point_markers;
+    for (const SketchEntity& e : ents) {
+        // A Point has no polyline (entity_polyline returns nothing), so the strip path below
+        // cannot draw it; render it as a vertex marker, the same way the live session does.
+        if (e.type == SketchEntity::Type::Point) { point_markers.push_back(e.p0); continue; }
+        bool closed = false;
+        std::vector<Vec2d> poly = entity_polyline(e, closed);
+        draw_quad_strip(m_highlight_model, poly, closed, color);
+    }
+    if (!point_markers.empty())
+        draw_vertices(m_highlight_model, point_markers, color);
+}
+
+// ---- In-canvas edit-op gizmo (Fillet/Chamfer/Offset/Mirror toolbar tools) ----------
+// These tools replace the docked numeric card. They operate on the LIVE session's
+// m_entities/m_constraints, so they work both while drawing and after begin_edit re-opens
+// a committed sketch. The SketchEngine op (context-free) is reused verbatim; the
+// constraint binding is ported from DesignPanel::apply_entity_constraint into m_constraints
+// via try_add_constraints (append→solve→keep / rollback).
+
+void DesignSketchTool::reset_op()
+{
+    m_op_a = m_op_b = -1;
+    m_op_value = 0.0;
+    m_op_anchor = Vec2d(0, 0);
+    m_op_dir = Vec2d(0, 0);
+    m_op_label = Vec2d(1e18, 1e18);
+    m_op_ghost.clear();
+    m_op_dragging_arrow = false;
+    m_mirror_targets.clear();
+}
+
+// ---- Imported-art bounding-box transform gizmo (Mode::TransformArt) ----
+
+void DesignSketchTool::reset_xform()
+{
+    m_xform_base.clear();
+    m_xform_feat = -1;
+    m_xform_handle = -1;
+    m_xform_offset = Vec2d(0, 0);
+    m_xform_sx = m_xform_sy = 1.0;
+    m_xform_min = m_xform_max = Vec2d(0, 0);
+}
+
+void DesignSketchTool::begin_imported_transform(
+        int feat, const std::vector<std::vector<std::vector<Vec2d>>>& base_regions,
+        const SketchPlane& plane, const Vec2d& offset, double sx, double sy)
+{
+    cancel();                       // drop any prior session, clears state
+    m_plane = plane;
+    m_mode  = Mode::TransformArt;
+    m_xform_base   = base_regions;
+    m_xform_feat   = feat;
+    m_xform_offset = offset;
+    m_xform_sx = (std::abs(sx) > 1e-6) ? sx : 1.0;
+    m_xform_sy = (std::abs(sy) > 1e-6) ? sy : 1.0;
+    m_xform_handle = -1;
+    Vec2d mn(1e30, 1e30), mx(-1e30, -1e30);
+    for (const auto& region : m_xform_base)
+        for (const auto& contour : region)
+            for (const Vec2d& p : contour) {
+                mn.x() = std::min(mn.x(), p.x()); mn.y() = std::min(mn.y(), p.y());
+                mx.x() = std::max(mx.x(), p.x()); mx.y() = std::max(mx.y(), p.y());
+            }
+    if (mx.x() < mn.x()) { mn = Vec2d(0, 0); mx = Vec2d(0, 0); }
+    m_xform_min = mn; m_xform_max = mx;
+    m_active = true;
+    m_has_cursor = false;
+}
+
+// 4 bbox corners in plane coords: 0=min/min, 1=max/min, 2=max/max, 3=min/max. The art
+// transform is world = base*scale + offset (CadFeature import convention).
+void DesignSketchTool::xform_world_corners(Vec2d out[4]) const
+{
+    const double x0 = m_xform_min.x() * m_xform_sx + m_xform_offset.x();
+    const double x1 = m_xform_max.x() * m_xform_sx + m_xform_offset.x();
+    const double y0 = m_xform_min.y() * m_xform_sy + m_xform_offset.y();
+    const double y1 = m_xform_max.y() * m_xform_sy + m_xform_offset.y();
+    out[0] = Vec2d(x0, y0); out[1] = Vec2d(x1, y0);
+    out[2] = Vec2d(x1, y1); out[3] = Vec2d(x0, y1);
+}
+
+int DesignSketchTool::hit_test_xform_handle(const Vec2d& p, double tol) const
+{
+    Vec2d c[4]; xform_world_corners(c);
+    int best = -1; double bd = tol;
+    for (int i = 0; i < 4; ++i) { const double d = (c[i] - p).norm(); if (d < bd) { bd = d; best = i; } }
+    if (best >= 0) return best;
+    if ((0.5 * (c[0] + c[2]) - p).norm() <= tol) return 4;   // centre move-handle
+    return -1;
+}
+
+void DesignSketchTool::drag_xform_handle(const Vec2d& target)
+{
+    if (m_xform_handle < 0) return;
+    if (m_xform_handle == 4) {                 // centre move: translate by cursor delta
+        m_xform_offset += (target - m_xform_anchor);
+        m_xform_anchor  = target;
+        emit_xform();
+        return;
+    }
+    // Corner scale: hold the opposite corner (fixed world anchor O), send the grabbed
+    // corner to the cursor. base coords of grabbed (bg) and opposite (ba) corners.
+    auto base_corner = [&](int i) {
+        return Vec2d((i == 1 || i == 2) ? m_xform_max.x() : m_xform_min.x(),
+                     (i == 2 || i == 3) ? m_xform_max.y() : m_xform_min.y());
+    };
+    const int h = m_xform_handle;
+    const Vec2d bg = base_corner(h);
+    const Vec2d ba = base_corner((h + 2) % 4);
+    const Vec2d O  = m_xform_anchor;
+    const double dbx = bg.x() - ba.x(), dby = bg.y() - ba.y();
+    if (std::abs(dbx) > 1e-9) {
+        double nsx = (target.x() - O.x()) / dbx;
+        if (std::abs(nsx) < 1e-4) nsx = (nsx < 0 ? -1e-4 : 1e-4);
+        m_xform_sx = nsx;
+        m_xform_offset.x() = O.x() - ba.x() * nsx;
+    }
+    if (std::abs(dby) > 1e-9) {
+        double nsy = (target.y() - O.y()) / dby;
+        if (std::abs(nsy) < 1e-4) nsy = (nsy < 0 ? -1e-4 : 1e-4);
+        m_xform_sy = nsy;
+        m_xform_offset.y() = O.y() - ba.y() * nsy;
+    }
+    emit_xform();
+}
+
+void DesignSketchTool::emit_xform()
+{
+    if (on_imported_transform)
+        on_imported_transform(m_xform_feat, m_xform_offset, m_xform_sx, m_xform_sy);
+}
+
+void DesignSketchTool::render_xform_gizmo()
+{
+    if (m_mode != Mode::TransformArt) return;
+    Vec2d c[4]; xform_world_corners(c);
+    const ColorRGBA box(0.30f, 0.88f, 0.66f, 1.0f);
+    std::vector<std::pair<Vec2d, Vec2d>> segs;
+    for (int i = 0; i < 4; ++i) segs.emplace_back(c[i], c[(i + 1) % 4]);
+    draw_strokes(m_highlight_model, segs, 0.6, box);
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double hs = 7.0 / std::max(cam.get_zoom(), 1e-6);   // screen-constant half-size
+    const ColorRGBA hcol(0.30f, 0.88f, 0.66f, 1.0f);
+    const ColorRGBA hhot(1.0f, 0.85f, 0.2f, 1.0f);
+    auto square = [&](const Vec2d& q, const ColorRGBA& col) {
+        const std::vector<Vec2d> sq = { q + Vec2d(-hs, -hs), q + Vec2d(hs, -hs),
+                                        q + Vec2d(hs, hs), q + Vec2d(-hs, hs) };
+        draw_fill(m_fill_model, sq, col);
+    };
+    for (int i = 0; i < 4; ++i) square(c[i], m_xform_handle == i ? hhot : hcol);
+    square(0.5 * (c[0] + c[2]), m_xform_handle == 4 ? hhot : hcol);
+}
+
+bool DesignSketchTool::op_ready() const
+{
+    switch (m_mode) {
+    case Mode::Fillet:
+    case Mode::Chamfer: return m_op_a >= 0 && m_op_b >= 0;
+    case Mode::Offset:  return m_op_a >= 0;
+    case Mode::Mirror:  return m_op_a >= 0 && !m_mirror_targets.empty();
+    default: return false;
+    }
+}
+
+// Corner vertex of two lines + the inward angle bisector (unit), pointing from the vertex
+// into the fillet/chamfer interior. Mirrors SketchEngine::fillet_lines's geometry so the
+// arrow tracks the op exactly.
+bool DesignSketchTool::op_corner(int a, int b, Vec2d& C, Vec2d& bis, double& theta) const
+{
+    if (a < 0 || b < 0 || a >= int(m_entities.size()) || b >= int(m_entities.size())) return false;
+    const SketchEntity& ea = m_entities[a];
+    const SketchEntity& eb = m_entities[b];
+    if (ea.type != SketchEntity::Type::Line || eb.type != SketchEntity::Type::Line) return false;
+    const Vec2d da = ea.p1 - ea.p0, db = eb.p1 - eb.p0;
+    const double denom = da.x() * db.y() - da.y() * db.x();
+    if (std::abs(denom) < 1e-12) return false;                       // parallel
+    const Vec2d diff = eb.p0 - ea.p0;
+    const double s = (diff.x() * db.y() - diff.y() * db.x()) / denom;
+    C = ea.p0 + s * da;
+    Vec2d ua = ((ea.p0 - C).norm() <= (ea.p1 - C).norm()) ? (ea.p1 - C) : (ea.p0 - C);
+    Vec2d ub = ((eb.p0 - C).norm() <= (eb.p1 - C).norm()) ? (eb.p1 - C) : (eb.p0 - C);
+    if (ua.norm() < 1e-12 || ub.norm() < 1e-12) return false;
+    ua.normalize(); ub.normalize();
+    theta = std::acos(std::max(-1.0, std::min(1.0, ua.dot(ub))));
+    bis = ua + ub;
+    if (bis.norm() < 1e-12) return false;                            // 180° corner
+    bis.normalize();
+    return true;
+}
+
+void DesignSketchTool::recompute_op_ghost()
+{
+    m_op_ghost.clear();
+    if (m_mode == Mode::Fillet || m_mode == Mode::Chamfer) {
+        if (m_op_a < 0 || m_op_b < 0) return;
+        Vec2d C, bis; double theta;
+        if (op_corner(m_op_a, m_op_b, C, bis, theta)) { m_op_anchor = C; m_op_dir = bis; }
+        SketchEntity a_out, b_out, extra;
+        const bool ok = (m_mode == Mode::Fillet)
+            ? SketchEngine::fillet_lines(m_entities[m_op_a], m_entities[m_op_b], m_op_value, a_out, b_out, extra)
+            : SketchEngine::chamfer_lines(m_entities[m_op_a], m_entities[m_op_b], m_op_value, a_out, b_out, extra);
+        if (ok) m_op_ghost = { a_out, b_out, extra };
+    } else if (m_mode == Mode::Offset) {
+        if (m_op_a < 0) return;
+        const SketchEntity& e = m_entities[m_op_a];
+        if (e.type == SketchEntity::Type::Line) {
+            m_op_anchor = 0.5 * (e.p0 + e.p1);
+            Vec2d u = e.p1 - e.p0; if (u.norm() > 1e-12) u.normalize();
+            m_op_dir = Vec2d(-u.y(), u.x());                  // left normal = +distance side
+        } else if (e.type == SketchEntity::Type::Circle || e.type == SketchEntity::Type::Arc) {
+            m_op_anchor = e.center + Vec2d(e.radius, 0.0);
+            m_op_dir = Vec2d(1, 0);
+        }
+        m_op_ghost = SketchEngine::offset_entities({ e }, m_op_value);
+    } else if (m_mode == Mode::Mirror) {
+        if (m_op_a < 0 || m_mirror_targets.empty()) return;
+        const SketchEntity& axis = m_entities[m_op_a];
+        std::vector<SketchEntity> src;
+        for (int ti : m_mirror_targets)
+            if (ti >= 0 && ti < int(m_entities.size())) src.push_back(m_entities[ti]);
+        m_op_ghost = SketchEngine::mirror_entities(src, axis.p0, axis.p1);
+    }
+}
+
+// Route an entity pick to the active op; sets an initial value + ghost once enough
+// entities are picked. Highlights the running picks via m_selection.
+void DesignSketchTool::op_pick(int ei)
+{
+    if (ei < 0 || ei >= int(m_entities.size())) return;
+    const SketchEntity::Type t = m_entities[ei].type;
+    switch (m_mode) {
+    case Mode::Fillet:
+    case Mode::Chamfer:
+        if (t != SketchEntity::Type::Line) return;            // corner ops need two lines
+        if (m_op_a < 0) m_op_a = ei;
+        else if (ei != m_op_a) {
+            m_op_b = ei;
+            const double la = (m_entities[m_op_a].p1 - m_entities[m_op_a].p0).norm();
+            const double lb = (m_entities[m_op_b].p1 - m_entities[m_op_b].p0).norm();
+            m_op_value = std::max(0.001, 0.2 * std::min(la, lb));  // a sensible starting size
+            recompute_op_ghost();
+        }
+        break;
+    case Mode::Offset: {
+        m_op_a = ei;
+        const SketchEntity& e = m_entities[ei];
+        const double sz = (e.type == SketchEntity::Type::Line) ? (e.p1 - e.p0).norm()
+                                                               : std::max(e.radius * 2.0, 1.0);
+        m_op_value = std::max(0.001, 0.1 * sz);
+        recompute_op_ghost();
+        break;
+    }
+    case Mode::Mirror:
+        if (m_op_a < 0) {
+            if (t != SketchEntity::Type::Line) return;        // axis must be a line
+            m_op_a = ei;
+        } else if (ei != m_op_a) {
+            auto it = std::find(m_mirror_targets.begin(), m_mirror_targets.end(), ei);
+            if (it == m_mirror_targets.end()) m_mirror_targets.push_back(ei);
+            else                              m_mirror_targets.erase(it);
+            recompute_op_ghost();
+        }
+        break;
+    default: break;
+    }
+    // Mirror the picks into m_selection so the existing highlight shows them.
+    m_selection.clear();
+    if (m_op_a >= 0) m_selection.push_back(m_op_a);
+    if (m_op_b >= 0) m_selection.push_back(m_op_b);
+    for (int ti : m_mirror_targets) m_selection.push_back(ti);
+    if (on_selection_changed) on_selection_changed(int(m_selection.size()));
+}
+
+bool DesignSketchTool::hit_test_op_arrow(const Vec2d& p, double tol) const
+{
+    if (!op_ready() || m_mode == Mode::Mirror) return false;
+    const Vec2d tip = m_op_anchor + m_op_dir * m_op_value;
+    return point_segment_dist(p, m_op_anchor, tip) <= tol * 1.5;
+}
+
+void DesignSketchTool::drag_op_arrow(const Vec2d& target)
+{
+    const double v = (target - m_op_anchor).dot(m_op_dir);      // project onto the arrow axis
+    if (m_mode == Mode::Offset) m_op_value = v;                 // signed: chooses the side
+    else                        m_op_value = std::max(0.001, v);// fillet/chamfer: positive
+    recompute_op_ghost();
+}
+
+void DesignSketchTool::open_op_editor()
+{
+    if (!on_inline_edit || !op_ready() || m_mode == Mode::Mirror) return;
+    const double sign = (m_mode == Mode::Offset && m_op_value < 0) ? -1.0 : 1.0;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, std::abs(m_op_value), "",
+        [this, sign](double v) {
+            m_op_value = (m_mode == Mode::Offset) ? sign * std::abs(v) : std::max(0.001, v);
+            // Entering a radius IS the commit. Leaving it as a preview meant the most obvious
+            // route of all — click the radius, type it, press Return — ended with the value set,
+            // the ghost drawn, and no geometry written; the only paths that ever applied it were
+            // finishing the whole sketch or clicking empty space, neither of which is signposted.
+            if (op_ready()) confirm_op();
+            else            recompute_op_ghost();
+        },
+        []() {});
+}
+
+void DesignSketchTool::render_op_gizmo(double unit_per_px)
+{
+    m_op_label = Vec2d(1e18, 1e18);
+    if (!op_ready()) return;
+    const ColorRGBA ghostc(0.30f, 0.88f, 0.66f, 0.55f);
+    draw_entities_preview(m_op_ghost, ghostc);
+    if (m_mode == Mode::Mirror) return;                         // pick-only, no arrow/label
+    const ColorRGBA dc(0.30f, 0.88f, 0.66f, 1.0f);
+    const double th = std::max(15.0 * unit_per_px, 1e-4);
+    const Vec2d dir = (m_op_value >= 0 ? m_op_dir : -m_op_dir);
+    const Vec2d tip = m_op_anchor + m_op_dir * m_op_value;      // signed length picks the side
+    std::vector<std::pair<Vec2d, Vec2d>> segs;
+    segs.emplace_back(m_op_anchor, tip);
+    const double as = std::max(std::abs(m_op_value) * 0.18, th * 0.8);  // arrowhead size
+    const Vec2d nrm(-dir.y(), dir.x());
+    const Vec2d back = tip - dir * as;
+    segs.emplace_back(tip, back + nrm * (as * 0.5));
+    segs.emplace_back(tip, back - nrm * (as * 0.5));
+    draw_strokes(m_highlight_model, segs, 0.6, dc);
+    DimAnnot a;
+    a.kind  = (m_mode == Mode::Fillet) ? DimType::Radius : DimType::Distance;
+    a.value = std::abs(m_op_value);
+    m_op_label = tip + dir * (th * 1.2);
+    draw_text(m_line_model, dim_text(a), m_op_label, th, dc);
+}
+
+// Did an entity actually change shape or position? Compares only the fields that define each
+// type, so a re-solve that leaves the geometry alone reads as "unchanged" whatever else moved in
+// the record. Used by the mirror postcondition below.
+static bool entity_moved(const SketchEntity& a, const SketchEntity& b, double tol)
+{
+    if (a.type != b.type) return true;
+    auto moved = [tol](const Vec2d& p, const Vec2d& q) { return (p - q).norm() > tol; };
+    if (moved(a.p0, b.p0)) return true;
+    switch (a.type) {
+    case SketchEntity::Type::Point:
+        return false;
+    case SketchEntity::Type::Line:
+        return moved(a.p1, b.p1);
+    case SketchEntity::Type::Circle:
+        return moved(a.center, b.center) || std::abs(a.radius - b.radius) > tol;
+    case SketchEntity::Type::Arc:
+        return moved(a.p1, b.p1) || moved(a.center, b.center)
+            || std::abs(a.radius - b.radius) > tol
+            || std::abs((a.end_angle - a.start_angle) - (b.end_angle - b.start_angle)) > tol;
+    case SketchEntity::Type::Ellipse:
+    case SketchEntity::Type::EllipseArc:
+        return moved(a.center, b.center) || std::abs(a.radius - b.radius) > tol
+            || std::abs(a.rminor - b.rminor) > tol || std::abs(a.rotation - b.rotation) > tol;
+    default:
+        return moved(a.p1, b.p1);
+    }
+}
+
+void DesignSketchTool::confirm_op()
+{
+    if (!op_ready()) return;
+    using R  = SketchPointRole;
+    using CT = SketchConstraintType;
+
+    if (m_mode == Mode::Fillet || m_mode == Mode::Chamfer) {
+        const bool fillet = (m_mode == Mode::Fillet);
+        SketchEntity a_out, b_out, extra;
+        const bool ok = fillet
+            ? SketchEngine::fillet_lines(m_entities[m_op_a], m_entities[m_op_b], m_op_value, a_out, b_out, extra)
+            : SketchEngine::chamfer_lines(m_entities[m_op_a], m_entities[m_op_b], m_op_value, a_out, b_out, extra);
+        if (!ok) { reset_op(); return; }
+        const int a = m_op_a, b = m_op_b;
+        m_entities[a] = a_out; m_entities[b] = b_out;
+        const int xi = int(m_entities.size());
+        m_entities.push_back(extra);                 // fillet arc / chamfer segment
+        auto role_near = [](const SketchEntity& ln, const Vec2d& q) -> R {
+            return ((ln.p0 - q).squaredNorm() <= (ln.p1 - q).squaredNorm()) ? R::P0 : R::P1; };
+        const R ra = role_near(m_entities[a], extra.p0);
+        const R rb = role_near(m_entities[b], extra.p1);
+        // Drop the now-stale corner Coincident + each line's own length Distance (the op
+        // trimmed both legs back), then bind the new entity onto the trimmed endpoints.
+        auto refs = [](const SketchEntityConstraintDef& d, int e, R r) {
+            return (d.ea == e && d.ra == r) || (d.eb == e && d.rb == r); };
+        auto self_len = [](const SketchEntityConstraintDef& d, int e) {
+            return d.type == CT::Distance && d.ea == e && d.eb == e; };
+        auto& cs = m_constraints;
+        cs.erase(std::remove_if(cs.begin(), cs.end(), [&](const SketchEntityConstraintDef& d) {
+            return (d.type == CT::Coincident && refs(d, a, ra) && refs(d, b, rb))
+                || self_len(d, a) || self_len(d, b);
+        }), cs.end());
+        auto coin = [&](R xr, int ln, R lr) {
+            SketchEntityConstraintDef d; d.type = CT::Coincident; d.ea = xi; d.ra = xr; d.eb = ln; d.rb = lr; return d; };
+        if (fillet) {
+            auto tang = [&](int ln) {
+                SketchEntityConstraintDef d; d.type = CT::Tangent; d.ea = xi; d.eb = ln; return d; };
+            const std::vector<std::vector<SketchEntityConstraintDef>> ladder = {
+                { coin(R::P0, a, ra), coin(R::P1, b, rb), tang(a), tang(b) },
+                { coin(R::P0, a, ra), coin(R::P1, b, rb), tang(a) },
+                { coin(R::P0, a, ra), coin(R::P1, b, rb) },
+            };
+            for (const auto& set : ladder) if (try_add_constraints(set)) break;
+        } else {
+            try_add_constraints({ coin(R::P0, a, ra), coin(R::P1, b, rb) });
+        }
+    } else if (m_mode == Mode::Offset) {
+        const int a = m_op_a;
+        auto out = SketchEngine::offset_entities({ m_entities[a] }, m_op_value);
+        if (out.empty()) { reset_op(); return; }
+        const int ni = int(m_entities.size());
+        for (auto& o : out) m_entities.push_back(o);
+        const SketchEntity::Type st = m_entities[a].type;
+        SketchEntityConstraintDef d; d.ea = a; d.eb = ni;
+        bool emit = true;
+        if (st == SketchEntity::Type::Line)                                   d.type = CT::Parallel;
+        else if (st == SketchEntity::Type::Arc || st == SketchEntity::Type::Circle) d.type = CT::Concentric;
+        else                                                                  emit = false;
+        if (emit) try_add_constraints({ d });
+    } else if (m_mode == Mode::Mirror) {
+        const SketchEntity axis = m_entities[m_op_a];   // by value (m_entities grows below)
+        // The sources as they stand BEFORE any of this op's constraints exist. Two jobs: every
+        // copy is reflected from the untouched original (so a batch that moves the sketch cannot
+        // feed a later copy moved geometry), and the invariant at the bottom has something to
+        // compare against. mirror-slot.
+        const std::vector<SketchEntity> before = m_entities;
+        const size_t cmark = m_constraints.size();
+        std::vector<std::pair<int, SketchEntity>> fresh;   // copy index -> its pristine reflection
+        for (int ti : m_mirror_targets) {
+            if (ti < 0 || ti >= int(before.size())) continue;
+            auto out = SketchEngine::mirror_entities({ before[ti] }, axis.p0, axis.p1);
+            if (out.empty()) continue;
+            const int mi = int(m_entities.size());
+            for (auto& m : out) { fresh.emplace_back(int(m_entities.size()), m); m_entities.push_back(m); }
+            SketchEntityConstraintDef d; d.type = CT::Symmetric; d.ea = ti; d.eb = mi; d.ec = m_op_a;
+            const SketchEntity::Type st = before[ti].type;
+            std::vector<std::vector<SketchEntityConstraintDef>> ladder;
+            if (st == SketchEntity::Type::Line) {
+                d.ra = R::P0; d.rb = R::P0; auto p0 = d;
+                d.ra = R::P1; d.rb = R::P1; auto p1 = d;
+                ladder = { { p0, p1 }, { p0 } };
+            } else if (st == SketchEntity::Type::Arc) {
+                // BOTH ENDS AND THE CENTRE. Binding only the centre — which is all this did —
+                // leaves the copy's endpoints and sweep free while the shape's own coincidences
+                // still tie them to its neighbours, and the solver then answers with a wildly
+                // different, internally consistent sketch: a slot's caps came back at r=32.2 and
+                // a 237 deg sweep, one rail collapsed from 62.9 mm to 2.1 mm, and the ORIGINAL
+                // moved with them. A circle survived the same code only because a circle has no
+                // endpoints to leave free, which is why the bug reads as "circles fine, rounded
+                // rectangles and slots destroyed".
+                d.ra = R::Center; d.rb = R::Center; auto ct = d;
+                d.ra = R::P0;     d.rb = R::P0;     auto p0 = d;
+                d.ra = R::P1;     d.rb = R::P1;     auto p1 = d;
+                // Endpoints BEFORE centre: an arc is five DoF, so {centre, p0, p1} is six
+                // equations and is refused; {p0, p1} is four and pins the sweep, which is the
+                // half that was going wild. The postcondition below is what makes the ladder
+                // safe — any rung that does not reproduce the preview is thrown away whole.
+                ladder = { { p0, p1 }, { ct, p0 }, { ct } };
+            } else if (st == SketchEntity::Type::Circle) {
+                d.ra = R::Center; d.rb = R::Center; ladder = { { d } };
+            } else if (st == SketchEntity::Type::Point) {
+                d.ra = R::P0; d.rb = R::P0; ladder = { { d } };
+            }
+            for (const auto& set : ladder) if (try_add_constraints(set)) break;
+        }
+        // A MIRROR MAY NOT MOVE WHAT IT COPIED. try_add_constraints only rolls back when the
+        // solve FAILS, and the failure here is a solve that succeeds at something else: the
+        // numbers above came out of a solver that was perfectly happy. So the op checks its own
+        // postcondition on the geometry, and if a source moved it keeps the copies — which are
+        // exactly what the preview showed — and drops the whole constraint web that moved them.
+        // Restoring the sources needs no re-solve: the pre-batch state was itself solved, and a
+        // failed solve does not write back (pl5).
+        // BOTH HALVES. Watching only the sources caught the slot (whose web dragged everything)
+        // and missed the rounded rectangle, where the solver held the sources still and put the
+        // COPIES somewhere else: an arc has five degrees of freedom and Symmetric on centre plus
+        // both endpoints is six equations, so that batch is refused and the ladder degrades to a
+        // set that leaves the sweep free. The rule that covers both, and that is what the user
+        // actually asked for, is: THE APPLIED RESULT IS THE PREVIEW. Anything else drops the web.
+        bool disturbed = false;
+        for (size_t i = 0; i < before.size() && !disturbed; ++i)
+            disturbed = entity_moved(before[i], m_entities[i], 1e-6);
+        for (const auto& f : fresh)
+            if (!disturbed && f.first < int(m_entities.size()))
+                disturbed = entity_moved(f.second, m_entities[f.first], 1e-6);
+        if (disturbed) {
+            m_constraints.resize(cmark);
+            for (size_t i = 0; i < before.size(); ++i) m_entities[i] = before[i];
+            // The copies too, and for the same reason: a batch that moved the sketch moved them
+            // as well, so the ones sitting in m_entities are the solver's answer, not the
+            // reflection. Restoring only the sources left a slot whose copy came back with a
+            // 13.8 mm rail and a 308 deg cap — the original was safe and the copy was still
+            // wrong, which is half a fix. `fresh` is what the preview drew.
+            for (const auto& f : fresh)
+                if (f.first < int(m_entities.size())) m_entities[f.first] = f.second;
+        }
+    }
+    reset_op();
+    m_selection.clear();
+    resolve_live();
+    if (on_selection_changed) on_selection_changed(0);
+}
+
+// ---- In-canvas transform gizmo (Move/Rotate/Scale/Array/PolarArray) ----
+// These replace the docked numeric cards: pick subject entities in-canvas, then a single
+// draggable handle drives the continuous parameter (Move/Array offset, Rotate/Polar angle,
+// Scale factor) and an editable value label sets it exactly; Array/PolarArray expose a
+// second label for the copy count. A live translucent ghost previews the result. Confirm
+// applies the geometry and emits the per-op constraint web (mutating ops drop the classes
+// the map invalidates; additive ops bind each copy to its source) into m_constraints.
+
+void DesignSketchTool::reset_tf()
+{
+    m_tf_targets.clear();
+    m_tf_pivot = Vec2d(0, 0);
+    m_tf_delta = Vec2d(0, 0);
+    m_tf_angle = 0.0;
+    m_tf_scale = 1.0;
+    m_tf_count = 3;
+    m_tf_handle_r = 1.0;
+    m_tf_ghost.clear();
+    m_tf_handle = -1;
+    m_tf_dragging = false;
+    m_tf_label_a = Vec2d(1e18, 1e18);
+    m_tf_label_b = Vec2d(1e18, 1e18);
+}
+
+bool DesignSketchTool::tf_ready() const { return !m_tf_targets.empty(); }
+
+// Centroid of the picked subject set (the rotate/scale/polar pivot, and the array origin),
+// plus a reference radius (max distance from the pivot to any subject extremum) used to
+// size the rotate/polar handle ring and the scale handle's unit position.
+void DesignSketchTool::compute_tf_pivot()
+{
+    using T = SketchEntity::Type;
+    auto cen = [](const SketchEntity& e) -> Vec2d {
+        switch (e.type) {
+        case T::Line: return 0.5 * (e.p0 + e.p1);
+        case T::Arc: case T::Circle: case T::Ellipse: case T::EllipseArc: return e.center;
+        case T::BSpline:
+            if (!e.ctrl.empty()) { Vec2d s(0, 0); for (const auto& p : e.ctrl) s += p; return s / double(e.ctrl.size()); }
+            return 0.5 * (e.p0 + e.p1);
+        default: return e.p0;
+        }
+    };
+    Vec2d c(0, 0); int n = 0;
+    for (int ti : m_tf_targets)
+        if (ti >= 0 && ti < int(m_entities.size())) { c += cen(m_entities[ti]); ++n; }
+    if (n == 0) { m_tf_pivot = Vec2d(0, 0); m_tf_handle_r = 1.0; return; }
+    m_tf_pivot = c / double(n);
+    double r = 0.0;
+    for (int ti : m_tf_targets) {
+        if (ti < 0 || ti >= int(m_entities.size())) continue;
+        const SketchEntity& e = m_entities[ti];
+        auto upd = [&](const Vec2d& p) { r = std::max(r, (p - m_tf_pivot).norm()); };
+        switch (e.type) {
+        case T::Line: upd(e.p0); upd(e.p1); break;
+        case T::Arc: case T::Circle: case T::Ellipse: case T::EllipseArc:
+            upd(e.center + Vec2d(e.radius, 0)); upd(e.center - Vec2d(e.radius, 0)); break;
+        case T::BSpline: for (const auto& p : e.ctrl) upd(p); break;
+        default: upd(e.p0); break;
+        }
+    }
+    m_tf_handle_r = std::max(r, 1.0);
+}
+
+void DesignSketchTool::tf_pick(int ei)
+{
+    if (ei < 0 || ei >= int(m_entities.size())) return;
+    auto it = std::find(m_tf_targets.begin(), m_tf_targets.end(), ei);
+    if (it == m_tf_targets.end()) m_tf_targets.push_back(ei);   // toggle-select like Mirror
+    else                          m_tf_targets.erase(it);
+    compute_tf_pivot();
+    // Seed sensible starting parameters (mirrors the retired card defaults so the ghost is
+    // immediately visible). Only seed while still at the neutral value, so re-picking more
+    // targets keeps a value the user already dialled in.
+    if (!m_tf_targets.empty()) {
+        const double step = std::max(m_tf_handle_r * 1.5, 1.0);
+        switch (m_mode) {
+        case Mode::Move:
+            if (m_tf_delta.norm() < 1e-9) m_tf_delta = Vec2d(step, 0.0);
+            break;
+        case Mode::Array:
+            if (m_tf_delta.norm() < 1e-9) {
+                Vec2d d(step, 0.0);   // default: perpendicular to a single line, else +X
+                if (m_tf_targets.size() == 1) {
+                    const SketchEntity& e = m_entities[m_tf_targets[0]];
+                    if (e.type == SketchEntity::Type::Line) {
+                        Vec2d t = e.p1 - e.p0;
+                        if (t.norm() > 1e-9) { t.normalize(); d = Vec2d(-t.y(), t.x()) * step; }
+                    }
+                }
+                m_tf_delta = d;
+            }
+            break;
+        case Mode::Rotate:     if (std::abs(m_tf_angle) < 1e-9) m_tf_angle = M_PI / 4.0; break;       // 45°
+        case Mode::PolarArray: if (std::abs(m_tf_angle) < 1e-9) m_tf_angle = 2.0 * M_PI;  break;       // 360°
+        case Mode::Scale:      if (std::abs(m_tf_scale - 1.0) < 1e-9) m_tf_scale = 2.0;   break;
+        default: break;
+        }
+    }
+    recompute_tf_ghost();
+    m_selection = m_tf_targets;   // reuse the existing selection highlight
+    if (on_selection_changed) on_selection_changed(int(m_selection.size()));
+}
+
+void DesignSketchTool::recompute_tf_ghost()
+{
+    m_tf_ghost.clear();
+    if (m_tf_targets.empty()) return;
+    std::vector<SketchEntity> src;
+    for (int ti : m_tf_targets)
+        if (ti >= 0 && ti < int(m_entities.size())) src.push_back(m_entities[ti]);
+    if (src.empty()) return;
+    const int count = std::max(2, m_tf_count);
+    switch (m_mode) {
+    case Mode::Move:
+        m_tf_ghost = SketchEngine::transform_entities(src, m_tf_delta, 0.0, 1.0, Vec2d(0, 0));
+        break;
+    case Mode::Rotate:
+        m_tf_ghost = SketchEngine::transform_entities(src, Vec2d(0, 0), m_tf_angle, 1.0, m_tf_pivot);
+        break;
+    case Mode::Scale:
+        m_tf_ghost = SketchEngine::transform_entities(src, Vec2d(0, 0), 0.0, m_tf_scale, m_tf_pivot);
+        break;
+    case Mode::Array:
+        m_tf_ghost = SketchEngine::array_entities(src, count, m_tf_delta, 0.0, m_tf_pivot);
+        break;
+    case Mode::PolarArray:
+        m_tf_ghost = SketchEngine::array_entities(src, count, Vec2d(0, 0), m_tf_angle / double(count), m_tf_pivot);
+        break;
+    default: break;
+    }
+}
+
+// World position of the single drag handle: at the translated/spacing tip for the linear
+// ops, on the pivot-centred ring at the current angle for the rotational ops, and at the
+// scaled unit position along +X for Scale.
+Vec2d DesignSketchTool::tf_handle_pos() const
+{
+    switch (m_mode) {
+    case Mode::Move:
+    case Mode::Array:      return m_tf_pivot + m_tf_delta;
+    case Mode::Rotate:
+    case Mode::PolarArray: return m_tf_pivot + m_tf_handle_r * Vec2d(std::cos(m_tf_angle), std::sin(m_tf_angle));
+    case Mode::Scale:      return m_tf_pivot + Vec2d(m_tf_scale * m_tf_handle_r, 0.0);
+    default:               return m_tf_pivot;
+    }
+}
+
+bool DesignSketchTool::hit_test_tf_handle(const Vec2d& p, double tol) const
+{
+    if (!tf_ready()) return false;
+    return (tf_handle_pos() - p).norm() <= tol * 2.5;
+}
+
+void DesignSketchTool::drag_tf_handle(const Vec2d& target)
+{
+    switch (m_mode) {
+    case Mode::Move:
+    case Mode::Array:
+        m_tf_delta = target - m_tf_pivot;
+        break;
+    case Mode::Rotate:
+    case Mode::PolarArray: {
+        const Vec2d d = target - m_tf_pivot;
+        if (d.norm() > 1e-9) m_tf_angle = std::atan2(d.y(), d.x());
+        break;
+    }
+    case Mode::Scale: {
+        const double r = (target - m_tf_pivot).norm();
+        m_tf_scale = std::max(1e-3, r / std::max(m_tf_handle_r, 1e-9));
+        break;
+    }
+    default: break;
+    }
+    recompute_tf_ghost();
+}
+
+void DesignSketchTool::open_tf_editor_a()
+{
+    if (!on_inline_edit || !tf_ready()) return;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    double cur;
+    if (m_mode == Mode::Rotate || m_mode == Mode::PolarArray) cur = std::abs(m_tf_angle) * 180.0 / M_PI;
+    else if (m_mode == Mode::Scale)                           cur = m_tf_scale;
+    else                                                       cur = m_tf_delta.norm();
+    Vec2d dir = m_tf_delta; if (dir.norm() > 1e-9) dir.normalize(); else dir = Vec2d(1, 0);
+    const double sgn = (m_tf_angle < 0) ? -1.0 : 1.0;
+    on_inline_edit(px, cur, "",
+        [this, dir, sgn](double v) {
+            switch (m_mode) {
+            case Mode::Move: case Mode::Array:        m_tf_delta = dir * v; break;
+            case Mode::Rotate: case Mode::PolarArray: m_tf_angle = sgn * std::abs(v) * M_PI / 180.0; break;
+            case Mode::Scale:                         m_tf_scale = std::max(1e-3, v); break;
+            default: break;
+            }
+            recompute_tf_ghost();
+        },
+        []() {});
+}
+
+void DesignSketchTool::open_tf_editor_count()
+{
+    if (!on_inline_edit || !tf_ready()) return;
+    if (m_mode != Mode::Array && m_mode != Mode::PolarArray) return;
+    const wxPoint px(m_last_mouse_x, m_last_mouse_y);
+    on_inline_edit(px, double(std::max(2, m_tf_count)), "",
+        [this](double v) { m_tf_count = std::max(2, int(v + 0.5)); recompute_tf_ghost(); },
+        []() {});
+}
+
+void DesignSketchTool::render_tf_gizmo(double unit_per_px)
+{
+    m_tf_label_a = Vec2d(1e18, 1e18);
+    m_tf_label_b = Vec2d(1e18, 1e18);
+    if (!tf_ready()) return;
+    const ColorRGBA ghostc(0.30f, 0.88f, 0.66f, 0.55f);
+    draw_entities_preview(m_tf_ghost, ghostc);
+
+    const ColorRGBA dc(0.30f, 0.88f, 0.66f, 1.0f);
+    const ColorRGBA hot(1.0f, 0.85f, 0.2f, 1.0f);
+    const double th = std::max(15.0 * unit_per_px, 1e-4);
+    const Vec2d handle = tf_handle_pos();
+
+    // spoke from the pivot to the handle (+ arrowhead for the linear ops).
+    std::vector<std::pair<Vec2d, Vec2d>> segs;
+    segs.emplace_back(m_tf_pivot, handle);
+    if (m_mode == Mode::Move || m_mode == Mode::Array || m_mode == Mode::Scale) {
+        Vec2d dir = handle - m_tf_pivot; const double L = dir.norm();
+        if (L > 1e-9) {
+            dir /= L;
+            const double as = std::max(L * 0.15, th * 0.8);
+            const Vec2d nrm(-dir.y(), dir.x());
+            const Vec2d back = handle - dir * as;
+            segs.emplace_back(handle, back + nrm * (as * 0.5));
+            segs.emplace_back(handle, back - nrm * (as * 0.5));
+        }
+    }
+    draw_strokes(m_highlight_model, segs, 0.6, dc);
+
+    const double hs = 6.0 * unit_per_px;   // screen-constant handle marker
+    const std::vector<Vec2d> sq = { handle + Vec2d(-hs, -hs), handle + Vec2d(hs, -hs),
+                                    handle + Vec2d(hs, hs),   handle + Vec2d(-hs, hs) };
+    draw_fill(m_fill_model, sq, m_tf_dragging ? hot : dc);
+    draw_vertices(m_vertex_model, { m_tf_pivot }, dc, std::max(3.0 * unit_per_px, 1e-4));
+
+    // primary parameter label at the handle.
+    std::string txt_a;
+    if (m_mode == Mode::Rotate || m_mode == Mode::PolarArray) {
+        DimAnnot a; a.kind = DimType::Angle; a.value = std::abs(m_tf_angle) * 180.0 / M_PI;
+        txt_a = dim_text(a);
+    } else if (m_mode == Mode::Scale) {
+        char b[24]; std::snprintf(b, sizeof(b), "x%.2f", m_tf_scale);
+        for (char& ch : b) if (ch == ',') ch = '.';
+        txt_a = b;
+    } else {
+        DimAnnot a; a.kind = DimType::Distance; a.value = m_tf_delta.norm();
+        txt_a = dim_text(a);
+    }
+    Vec2d outw = handle - m_tf_pivot; if (outw.norm() > 1e-9) outw.normalize(); else outw = Vec2d(1, 0);
+    m_tf_label_a = handle + outw * (th * 1.2);
+    draw_text(m_line_model, txt_a, m_tf_label_a, th, dc);
+
+    if (m_mode == Mode::Array || m_mode == Mode::PolarArray) {
+        char cb[16]; std::snprintf(cb, sizeof(cb), "x%d", std::max(2, m_tf_count));
+        m_tf_label_b = m_tf_pivot + Vec2d(th * 1.5, th * 1.5);
+        draw_text(m_line_model, cb, m_tf_label_b, th, dc);
+    }
+}
+
+void DesignSketchTool::confirm_transform()
+{
+    if (!tf_ready()) { reset_tf(); return; }
+    using CT = SketchConstraintType;
+    const std::vector<int> targets = m_tf_targets;   // snapshot by value (m_entities grows)
+    auto is_target = [&](int e) {
+        return e >= 0 && std::find(targets.begin(), targets.end(), e) != targets.end();
+    };
+
+    if (m_mode == Mode::Move || m_mode == Mode::Rotate || m_mode == Mode::Scale) {
+        // MUTATING: map every subject in place, then drop the constraint classes the map
+        // invalidates for any constraint touching a subject. Surviving classes are
+        // satisfied by construction; the re-solve folds in the new placement.
+        const Mode mode = m_mode;
+        for (int ti : targets) {
+            if (ti < 0 || ti >= int(m_entities.size())) continue;
+            std::vector<SketchEntity> out;
+            if (mode == Mode::Move)
+                out = SketchEngine::transform_entities({ m_entities[ti] }, m_tf_delta, 0.0, 1.0, Vec2d(0, 0));
+            else if (mode == Mode::Rotate)
+                out = SketchEngine::transform_entities({ m_entities[ti] }, Vec2d(0, 0), m_tf_angle, 1.0, m_tf_pivot);
+            else
+                out = SketchEngine::transform_entities({ m_entities[ti] }, Vec2d(0, 0), 0.0, m_tf_scale, m_tf_pivot);
+            if (!out.empty()) m_entities[ti] = out[0];
+        }
+        auto& cs = m_constraints;
+        cs.erase(std::remove_if(cs.begin(), cs.end(), [&](const SketchEntityConstraintDef& d) {
+            if (!(is_target(d.ea) || is_target(d.eb) || is_target(d.ec))) return false;
+            const bool self = (d.ea == d.eb);   // self-length Distance survives translate/rotate
+            if (mode == Mode::Move) {
+                switch (d.type) {
+                case CT::Coincident: case CT::PointOnLine: case CT::PointOnObject:
+                case CT::Concentric: case CT::Symmetric:   case CT::Midpoint:
+                case CT::Fix:        case CT::LockX:        case CT::LockY:   return true;
+                case CT::Distance: return !self;
+                default:           return false;   // orientation/length preserved by translation
+                }
+            } else if (mode == Mode::Rotate) {
+                switch (d.type) {
+                case CT::EqualLength: case CT::Radius: case CT::Diameter: return false;
+                case CT::Distance: return !self;
+                default:           return true;    // orientation + position broken by rotation
+                }
+            } else {   // Scale (uniform / conformal)
+                switch (d.type) {
+                case CT::Horizontal: case CT::Vertical: case CT::Parallel:
+                case CT::Perpendicular: case CT::Angle: return false;
+                default:                                return true;   // size + position broken
+                }
+            }
+        }), cs.end());
+    } else if (m_mode == Mode::Array || m_mode == Mode::PolarArray) {
+        // ADDITIVE: append copies of each subject, then bind each copy to its source. Lines
+        // get Parallel+EqualLength (linear) or EqualLength only (polar — rotation breaks
+        // Parallel); arc/circle copies get a per-copy Radius (equal-radius under any rigid
+        // map) plus Concentric when the polar pivot is the source's own centre. Emit each
+        // web as a degrade ladder (try_add_constraints keeps the first set the solver
+        // accepts, else the geometry stays unconstrained).
+        const bool polar = (m_mode == Mode::PolarArray);
+        const int  count = std::max(2, m_tf_count);
+        for (int ti : targets) {
+            if (ti < 0 || ti >= int(m_entities.size())) continue;
+            const SketchEntity src = m_entities[ti];   // by value (m_entities grows below)
+            std::vector<SketchEntity> copies = polar
+                ? SketchEngine::array_entities({ src }, count, Vec2d(0, 0), m_tf_angle / double(count), m_tf_pivot)
+                : SketchEngine::array_entities({ src }, count, m_tf_delta, 0.0, m_tf_pivot);
+            if (copies.empty()) continue;
+            const int base = int(m_entities.size());
+            for (auto& c : copies) m_entities.push_back(c);
+            const int nc = int(copies.size());
+            const SketchEntity::Type st = src.type;
+            std::vector<std::vector<SketchEntityConstraintDef>> ladder;
+            if (st == SketchEntity::Type::Line) {
+                auto mk = [&](bool eq, bool par) {
+                    std::vector<SketchEntityConstraintDef> w;
+                    for (int k = 0; k < nc; ++k) {
+                        const int ci = base + k;
+                        if (par) { SketchEntityConstraintDef dp; dp.type = CT::Parallel;    dp.ea = ti; dp.eb = ci; w.push_back(dp); }
+                        if (eq)  { SketchEntityConstraintDef de; de.type = CT::EqualLength;  de.ea = ti; de.eb = ci; w.push_back(de); }
+                    }
+                    return w;
+                };
+                if (polar) ladder = { mk(true, false) };
+                else       ladder = { mk(true, true), mk(false, true) };
+            } else if (st == SketchEntity::Type::Arc || st == SketchEntity::Type::Circle) {
+                const bool can_conc = polar && (m_tf_pivot - src.center).norm() < 1e-6;
+                auto mk = [&](bool conc) {
+                    std::vector<SketchEntityConstraintDef> w;
+                    for (int k = 0; k < nc; ++k) {
+                        const int ci = base + k;
+                        SketchEntityConstraintDef dr; dr.type = CT::Radius; dr.ea = ci; dr.value = src.radius; w.push_back(dr);
+                        if (conc) {
+                            SketchEntityConstraintDef dco; dco.type = CT::Concentric;
+                            dco.ea = ti; dco.ra = SketchPointRole::Center; dco.eb = ci; dco.rb = SketchPointRole::Center;
+                            w.push_back(dco);
+                        }
+                    }
+                    return w;
+                };
+                ladder = can_conc ? std::vector<std::vector<SketchEntityConstraintDef>>{ mk(true), mk(false) }
+                                  : std::vector<std::vector<SketchEntityConstraintDef>>{ mk(false) };
+            }
+            for (auto& w : ladder) if (!w.empty() && try_add_constraints(w)) break;
+        }
+    }
+    reset_tf();
+    m_selection.clear();
+    resolve_live();
+    if (on_selection_changed) on_selection_changed(0);
+}
+
+const ColorRGBA* DesignSketchTool::sketch_hl_color(int feature) const
+{
+    for (const auto& h : m_hl_sketches) if (h.first == feature) return &h.second;
+    return nullptr;
+}
+
+// Which step of the armed gesture is live, reported only when it moves (1c0c). Called
+// from render(), which is the one place EVERY state change passes through — a per-call-site
+// notification would have to be added to each of the thirty-odd tool branches and would be
+// forgotten by the next one. Cheap: three ints compared per frame.
+void DesignSketchTool::emit_step_hint()
+{
+    if (!on_step_changed) return;
+    int step = 0, picks = 0;
+    if (is_edit_op_mode()) {
+        picks = (m_mode == Mode::Mirror) ? int(m_mirror_targets.size())
+                                         : int(m_op_a >= 0) + int(m_op_b >= 0);
+        step  = (m_op_a < 0) ? 0 : (op_ready() ? 2 : 1);
+    } else if (is_transform_mode()) {
+        picks = int(m_tf_targets.size());
+        step  = m_tf_targets.empty() ? 0 : 1;
+    } else if (m_mode == Mode::Select || m_mode == Mode::Constrain) {
+        picks = int(m_selection.size());
+    } else {
+        step = int(m_points.size());
+    }
+    if (int(m_mode) == m_step_mode_last && step == m_step_last && picks == m_step_picks_last)
+        return;
+    m_step_mode_last = int(m_mode); m_step_last = step; m_step_picks_last = picks;
+    on_step_changed(m_mode, step, picks);
+}
+
+void DesignSketchTool::render(GLCanvas3D& canvas)
+{
+    m_dim_label_seq = 0;
+    m_render_scale  = canvas.get_scale();
+    emit_step_hint();   // before the early returns: an armed tool on an empty sketch still guides
+    // The value field, BEFORE every early return below. It can be up in Constrain mode on a
+    // committed feature and on an empty sketch, and a field that is not drawn is a field that is
+    // not there — there is no window to fall back to any more.
+    if (inline_editor != nullptr)
+        inline_editor->render(*wxGetApp().imgui(), m_render_scale);
+    (void)canvas;
+    if (!has_display()) {
+        if (on_readout) on_readout(std::string());   // nothing to show -> hide HUD
+        return;
+    }
+    render_view_helpers();   // origin planes / world axes — drawn whenever their toggle is on
+    m_rubber.render(canvas); // left-drag rubber band (no-op unless one is being swept). Drawn
+                             // here, ahead of every early return below, so a band over an empty
+                             // plate is still visible.
+    if (m_active && m_mode != Mode::Constrain && m_entities.empty() && m_points.empty()
+        && m_display_sketches.empty()) {
+        if (on_readout) on_readout(std::string());
+        return;
+    }
+
+
+    // Draw-then-edit: a creation tool that just committed a new entity/feature (gesture now
+    // idle) gets its result auto-selected — so render_live_quotes below computes its quotes —
+    // and the primary value editor armed (opened after those quotes exist, see service block).
+    if (m_active && is_creation_autoedit_mode() && m_points.empty() &&
+        m_open_feature < 0 && !m_awaiting_length) {
+        const int n = int(m_entities.size());
+        if (m_autoedit_seen >= 0 && n > m_autoedit_seen && n > 0) {
+            m_selection.clear();
+            m_selection.push_back(n - 1);   // feature_of(last) groups rect/slot/poly/ellipse
+            m_autoedit_pending = true;
+        }
+        m_autoedit_seen = n;
+    }
+
+    GLShaderProgram* shader = wxGetApp().get_shader("flat");
+    if (shader == nullptr)
+        return;
+
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    glsafe(::glDisable(GL_CULL_FACE));
+    shader->start_using();
+    const Camera& camera = wxGetApp().plater()->get_camera();
+    shader->set_uniform("view_model_matrix", camera.get_view_matrix());
+    shader->set_uniform("projection_matrix", camera.get_projection_matrix());
+
+    // Persistent committed sketches (e.g. an un-consumed sketch left visible after its
+    // extrude is removed): faces translucent, outlines orange. Each uses its own plane.
+    if (!m_display_sketches.empty()) {
+        const SketchPlane saved_plane = m_plane;
+        // CYAN/BLUE MEANS SELECTED — nothing else may wear it. The unselected fill used to be
+        // (0.30,0.60,1.0), one shade off the selected (0.30,0.80,1.0), so an ordinary region
+        // read as picked and a picked one added nothing. The outlines already got this right:
+        // orange for a sketch, cyan for the selection. The fill now follows the same logic, so
+        // an unselected region is faint amber — the sketch's own colour — and every blue thing
+        // on screen is something you selected.
+        const ColorRGBA dface = design_idle_face_color();   // unselected: neutral grey, never the selection colour
+        const ColorRGBA sface = design_selection_color(0.34f);   // selected region
+        const ColorRGBA dwire(1.0f, 0.55f, 0.1f, 1.0f);     // normal orange outline
+        const ColorRGBA swire = design_selection_color();        // selected outline
+        glsafe(::glEnable(GL_BLEND));
+        glsafe(::glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));
+        for (const DisplaySketch& ds : m_display_sketches) {
+            m_plane = ds.plane;
+            const std::vector<RegionLoop> loops = region_loops(ds.entities);
+            for (int r = 0; r < int(loops.size()); ++r) {
+                const bool sel = (ds.feature == m_display_pick && r == m_display_pick_region);
+                const ColorRGBA* hlc = sketch_hl_color(ds.feature);
+                ColorRGBA fc = sel ? sface : dface;
+                if (hlc && !sel) { fc = *hlc; fc.a(0.20f); }
+                std::vector<std::vector<Vec2d>> hp;
+                for (int h : loops[r].holes)
+                    if (h >= 0 && h < int(loops.size())) hp.push_back(loops[h].poly);
+                draw_fill_holed(m_fill_model, loops[r].poly, hp, fc);
+            }
+        }
+        glsafe(::glDisable(GL_BLEND));
+        for (const DisplaySketch& ds : m_display_sketches) {
+            m_plane = ds.plane;
+            // Entities forming the selected loop (highlighted cyan); the rest stay orange.
+            std::vector<char> sel_ent(ds.entities.size(), 0);
+            if (ds.feature == m_display_pick && m_display_pick_region >= 0) {
+                const std::vector<RegionLoop> loops = region_loops(ds.entities);
+                if (m_display_pick_region < int(loops.size())) {
+                    // The holes light up with their region. The highlight has to show what will
+                    // be EXTRUDED, and a hole is part of that — a plate whose bore stays orange
+                    // while its outline turns cyan would say the circle is not coming along,
+                    // which is precisely the thing that used to be true and is now not.
+                    auto mark = [&](int region) {
+                        if (region < 0 || region >= int(loops.size())) return;
+                        for (int ei : loops[region].ents)
+                            if (ei >= 0 && ei < int(sel_ent.size())) sel_ent[ei] = 1;
+                    };
+                    mark(m_display_pick_region);
+                    for (int h : loops[m_display_pick_region].holes) mark(h);
+                }
+            }
+            std::vector<Vec2d> point_markers, sel_point_markers;
+            for (int i = 0; i < int(ds.entities.size()); ++i) {
+                const SketchEntity& e = ds.entities[i];
+                // A Point has no polyline to strip; draw it as a vertex marker so a committed
+                // point stays visible (it vanished on commit). Selection colouring keeps working:
+                // sel_ent[] stays index-aligned with ds.entities, untouched for the other types.
+                if (e.type == SketchEntity::Type::Point) {
+                    (sel_ent[i] ? sel_point_markers : point_markers).push_back(e.p0);
+                    continue;
+                }
+                bool closed = false;
+                std::vector<Vec2d> poly = entity_polyline(e, closed);
+                const ColorRGBA* hlc = sketch_hl_color(ds.feature);
+                ColorRGBA wc = sel_ent[i] ? swire : (hlc ? *hlc : dwire);
+                draw_quad_strip(m_line_model, poly, closed, wc);
+            }
+            if (!point_markers.empty()) {
+                const ColorRGBA* hlc = sketch_hl_color(ds.feature);
+                draw_vertices(m_vertex_model, point_markers, hlc ? *hlc : dwire);
+            }
+            if (!sel_point_markers.empty())
+                draw_vertices(m_highlight_model, sel_point_markers, swire);
+        }
+        m_plane = saved_plane;
+    }
+
+    // Nothing else to draw when no live sketch session is active — except the solid
+    // face/edge highlight overlay (whole-solid tint is handled by set_body_highlight).
+    if (!m_active) {
+        render_datum_planes();
+        render_mate_connectors();
+        render_solid_highlight();
+        if (m_dbp_active) render_base_pick();
+        if (m_dz_active) render_datum_gizmo();
+        if (m_hx_active) render_helix_gizmo();
+        if (m_rb_active) render_rib_gizmo();
+        if (m_ex_active) render_extrude_gizmo();
+        if (m_mv_active) render_move_gizmo();
+        if (m_fl_active) render_fillet_gizmo();
+        if (m_hl_active) render_hole_gizmo();
+        if (m_th_active) render_thread_gizmo();
+        if (m_sh_active) render_shell_gizmo();
+        if (m_rv_active) render_revolve_gizmo();
+        if (m_dr_active) render_draft_gizmo();
+        if (m_ct_active) render_cut_gizmo();
+        if (m_pt_active) render_pattern_gizmo();
+        shader->stop_using();
+        glsafe(::glEnable(GL_CULL_FACE));
+        glsafe(::glEnable(GL_DEPTH_TEST));
+        return;
+    }
+
+    // Imported-art transform: only the bbox + handles over the (display-overlay) art.
+    if (m_mode == Mode::TransformArt) {
+        render_xform_gizmo();
+        shader->stop_using();
+        glsafe(::glEnable(GL_CULL_FACE));
+        glsafe(::glEnable(GL_DEPTH_TEST));
+        return;
+    }
+
+    const ColorRGBA orange(1.0f, 0.55f, 0.1f, 1.0f);
+    const ColorRGBA yellow(1.0f, 0.85f, 0.2f, 1.0f);
+    const ColorRGBA grey(0.55f, 0.55f, 0.60f, 1.0f);
+
+    if (m_mode == Mode::Constrain) {
+        const ColorRGBA cyan(0.30f, 0.80f, 1.0f, 1.0f);
+        const ColorRGBA red(1.0f, 0.25f, 0.25f, 1.0f);
+        if (m_constrain_entities) {
+            // Draw all entities cyan; picked Line entities highlighted red.
+            std::vector<Vec2d> markers;
+            for (size_t i = 0; i < m_entities.size(); ++i) {
+                const SketchEntity& e = m_entities[i];
+                const bool sel = (int(i) == m_pick0 || int(i) == m_pick1 || int(i) == m_pick2);
+                // Constraint-manager highlight: the entities a selected constraint
+                // references glow yellow (picked entities still win as red).
+                const bool hl = !sel && std::find(m_constraint_hl.begin(), m_constraint_hl.end(),
+                                                   int(i)) != m_constraint_hl.end();
+                const ColorRGBA col = sel ? red : (hl ? yellow : cyan);
+                if (e.type == SketchEntity::Type::Point) { markers.push_back(e.p0); continue; }
+                bool closed = false;
+                std::vector<Vec2d> poly = entity_polyline(e, closed);
+                draw_quad_strip((sel || hl) ? m_highlight_model : m_line_model, poly, closed, col);
+            }
+            if (!markers.empty())
+                draw_vertices(m_vertex_model, markers, cyan);
+            // Constraint badges (C3.4b): iconic glyphs near each constraint's entity.
+            {
+                const double upp = 1.0 / std::max(camera.get_zoom(), 1e-6);
+                std::vector<std::pair<Vec2d, Vec2d>> glyphs;
+                build_constraint_glyphs(upp, m_constrain_cons, glyphs);
+                if (!glyphs.empty()) {
+                    const ColorRGBA badge(0.45f, 0.95f, 0.70f, 1.0f);   // CAD teal-green
+                    draw_strokes(m_fill_model, glyphs, std::max(0.9 * upp, 1e-4), badge);
+                }
+            }
+            shader->stop_using();
+            glsafe(::glEnable(GL_CULL_FACE));
+            glsafe(::glEnable(GL_DEPTH_TEST));
+            return;
+        }
+        draw_quad_strip(m_line_model, m_points, true, cyan);
+        draw_vertices(m_vertex_model, m_points, cyan);
+        if (m_sel_a >= 0 && m_sel_b >= 0 &&
+            m_sel_a < int(m_points.size()) && m_sel_b < int(m_points.size())) {
+            std::vector<Vec2d> seg = { m_points[m_sel_a], m_points[m_sel_b] };
+            draw_quad_strip(m_highlight_model, seg, false, red);
+        }
+        shader->stop_using();
+        glsafe(::glEnable(GL_CULL_FACE));
+        glsafe(::glEnable(GL_DEPTH_TEST));
+        return;
+    }
+
+    // Closed loops fill as translucent faces (the "closed loop = selectable face"
+    // affordance). Drawn first so the entity outlines paint over the fill.
+    {
+        // region_loops(), NOT closed_regions(): the latter returns raw polygons with no notion
+        // of nesting, so a circle drawn inside a rectangle was filled as its own solid disc on
+        // top of a solid rectangle. That is why a live sketch still showed a filled blue circle
+        // however often the COMMITTED renderer below was corrected — these are two separate
+        // renderers and only one of them had been taught about holes.
+        const std::vector<RegionLoop> loops = region_loops(m_entities);
+        if (!loops.empty()) {
+            glsafe(::glEnable(GL_BLEND));
+            glsafe(::glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));
+            // A bore is not a face. Skip loops that are somebody's hole, and cut those holes out
+            // of the region that owns them, so a plate with a hole LOOKS like one while drawing.
+            std::vector<char> is_hole(loops.size(), 0);
+            for (const RegionLoop& L : loops)
+                for (int h : L.holes)
+                    if (h >= 0 && h < int(is_hole.size())) is_hole[h] = 1;
+            for (size_t r = 0; r < loops.size(); ++r) {
+                if (is_hole[r]) continue;
+                std::vector<std::vector<Vec2d>> hp;
+                for (int h : loops[r].holes)
+                    if (h >= 0 && h < int(loops.size())) hp.push_back(loops[h].poly);
+                draw_fill_holed(m_fill_model, loops[r].poly, hp, design_idle_face_color());
+            }
+            glsafe(::glDisable(GL_BLEND));
+        }
+    }
+
+    // Committed entities of this session. DoF feedback (P3): a fully-constrained
+    // sketch (dof==0, consistent) paints green; entities touched by a conflicting
+    // constraint paint red; otherwise the under-constrained default (orange / grey
+    // construction). Selected entities always override to the shared selection colour.
+    // NOT white: the Design tab now paints a bed grid, and white-on-grid made a freshly
+    // drawn (hence auto-selected) line invisible against it. design_selection_color() is
+    // the same cyan the solid picks already wear, so "selected" reads the same everywhere.
+    const ColorRGBA white(1.0f, 1.0f, 1.0f, 1.0f);   // hover handle only
+    const ColorRGBA sel_col = design_selection_color();
+    const ColorRGBA green(0.30f, 0.85f, 0.42f, 1.0f);
+    const ColorRGBA conflict(1.0f, 0.22f, 0.22f, 1.0f);
+    const ColorRGBA opref(0.80f, 0.45f, 1.0f, 1.0f);     // violet: the edit-op's reference pick
+    const double    upp_dash = 1.0 / std::max(camera.get_zoom(), 1e-6);   // world units per pixel
+    const ColorRGBA editing(1.0f, 0.78f, 0.10f, 1.0f);   // amber: entity whose dim is being typed
+    const bool fully = (m_dof == 0 && m_solve_ok);
+    // While an auto-edit value field is open, the active step names the entities its dimension
+    // drives — light them up so it's obvious WHICH feature the number (e.g. a circle's radius)
+    // changes.
+    const std::vector<int>* edit_hi =
+        (m_autoedit_dim_idx >= 0 && m_autoedit_dim_idx < int(m_autoedit_dims.size()))
+            ? &m_autoedit_dims[m_autoedit_dim_idx].hi : nullptr;
+    std::vector<Vec2d> point_markers, sel_point_markers;
+    for (size_t i = 0; i < m_entities.size(); ++i) {
+        const SketchEntity& e = m_entities[i];
+        const bool selected =
+            std::find(m_selection.begin(), m_selection.end(), int(i)) != m_selection.end();
+        const bool editing_this =
+            edit_hi && std::find(edit_hi->begin(), edit_hi->end(), int(i)) != edit_hi->end();
+        const bool bad = i < m_entity_conflict.size() && m_entity_conflict[i];
+        // The first pick of an edit-op has a DIFFERENT ROLE from the rest of the selection —
+        // Mirror's is the axis, Fillet/Chamfer's is the first of the two lines — and until now
+        // every pick painted the same white, so the picture could not answer "what did I select
+        // as what". Violet, not cyan: cyan means SELECTED here and nothing else may wear it.
+        // vd6v.
+        const bool op_ref = is_edit_op_mode() && int(i) == m_op_a;
+        ColorRGBA col;
+        if (editing_this)        col = editing;
+        else if (op_ref)         col = opref;
+        else if (selected)       col = sel_col;
+        else if (bad)            col = conflict;
+        else if (e.construction) col = grey;
+        else                     col = fully ? green : orange;
+        if (e.type == SketchEntity::Type::Point) {
+            (selected ? sel_point_markers : point_markers).push_back(e.p0);
+            continue;
+        }
+        bool closed = false;
+        std::vector<Vec2d> poly = entity_polyline(e, closed);
+        GLModel& target = (selected || editing_this || op_ref) ? m_highlight_model : m_line_model;
+        if (e.construction) {
+            for (const std::vector<Vec2d>& d : dash_polyline(poly, closed, 9.0 * upp_dash, 6.0 * upp_dash))
+                draw_quad_strip(target, d, false, col);
+        } else {
+            draw_quad_strip(target, poly, closed, col);
+        }
+    }
+    if (!point_markers.empty())
+        draw_vertices(m_vertex_model, point_markers, yellow);
+    if (!sel_point_markers.empty())
+        draw_vertices(m_highlight_model, sel_point_markers, sel_col);
+
+    // Constraint badges during a LIVE sketch. They used to render only inside Mode::Constrain
+    // on a COMMITTED feature, so every constraint applied while drawing — which is the path the
+    // Constrain buttons take during a session — was invisible and unremovable: you could not
+    // tell whether Parallel had been applied, nor take it back. Same glyphs, same teal, sourced
+    // from this session's m_constraints; click one to delete it (remove_constraint_near).
+    if (!m_constraints.empty()) {
+        std::vector<std::pair<Vec2d, Vec2d>> glyphs;
+        build_constraint_glyphs(upp_dash, m_constraints, glyphs);
+        if (!glyphs.empty())
+            draw_strokes(m_fill_model, glyphs, std::max(0.9 * upp_dash, 1e-4),
+                         ColorRGBA(0.45f, 0.95f, 0.70f, 1.0f));   // CAD teal-green
+    }
+
+    // Endpoint / centre handles so individual points are visible and pickable in the
+    // Select and Dimension tools (a line = a segment + 2 points). Selected ones cyan.
+    m_show_handles = (m_mode == Mode::Select || m_mode == Mode::Dimension);
+    if (m_show_handles) {
+        std::vector<Vec2d> handles, sel_handles;
+        auto add_h = [&](int ei, SketchPointRole r, const Vec2d& q) {
+            const bool s = std::find(m_point_sel.begin(), m_point_sel.end(),
+                                     std::make_pair(ei, r)) != m_point_sel.end();
+            (s ? sel_handles : handles).push_back(q);
+        };
+        for (size_t i = 0; i < m_entities.size(); ++i) {
+            const SketchEntity& e = m_entities[i];
+            switch (e.type) {
+            case SketchEntity::Type::Line:
+                add_h(int(i), SketchPointRole::P0, e.p0);
+                add_h(int(i), SketchPointRole::P1, e.p1);
+                break;
+            case SketchEntity::Type::Arc:
+            case SketchEntity::Type::EllipseArc:
+                add_h(int(i), SketchPointRole::P0, e.p0);
+                add_h(int(i), SketchPointRole::P1, e.p1);
+                add_h(int(i), SketchPointRole::Center, e.center);
+                break;
+            case SketchEntity::Type::Circle:
+            case SketchEntity::Type::Ellipse:
+                add_h(int(i), SketchPointRole::Center, e.center);
+                break;
+            case SketchEntity::Type::BSpline:
+                add_h(int(i), SketchPointRole::P0, e.p0);
+                add_h(int(i), SketchPointRole::P1, e.p1);
+                break;
+            case SketchEntity::Type::Point:
+                break;   // its own marker is drawn above
+            }
+        }
+        if (!handles.empty())     draw_vertices(m_vertex_model, handles, ColorRGBA(0.65f, 0.65f, 0.30f, 1.0f));
+        if (!sel_handles.empty()) draw_vertices(m_highlight_model, sel_handles, sel_col);
+
+        // Midpoint of every segment, drawn smaller and cooler than the endpoint handles
+        // (te8v). Without it the Midpoint snap is invisible: it exists in the
+        // inference engine but the user has nothing to aim at. Construction lines get one
+        // too — you constrain to them as readily as to real geometry.
+        std::vector<Vec2d> mids;
+        for (const SketchEntity& e : m_entities) {
+            if (e.type == SketchEntity::Type::Line)
+                mids.push_back(0.5 * (e.p0 + e.p1));
+            else if (e.type == SketchEntity::Type::Arc) {
+                const double am = 0.5 * (e.start_angle + e.end_angle);
+                mids.push_back(Vec2d(e.center.x() + e.radius * std::cos(am),
+                                     e.center.y() + e.radius * std::sin(am)));
+            }
+        }
+        if (!mids.empty())
+            draw_vertices(m_vertex_model, mids, ColorRGBA(0.35f, 0.75f, 0.85f, 1.0f), 0.9);
+
+        // Derived feature handles (A3): the circle RadiusHandle is not a SketchPointRole,
+        // so the per-point pass above doesn't draw it. Render it (cyan) + the hovered
+        // handle (white, larger) at a screen-constant size so they stay grabbable at any
+        // zoom. A4 makes these draggable; later phases add slot/rect/polygon handles.
+        const double upp = 1.0 / std::max(camera.get_zoom(), 1e-6);
+        std::vector<Vec2d> radius_h;
+        for (const Handle& h : build_handles())
+            if (h.role == HandleRole::RadiusHandle || h.role == HandleRole::MajorAxis ||
+                h.role == HandleRole::MinorAxis    || h.role == HandleRole::BSplineCtrl)
+                radius_h.push_back(h.pos);
+        if (!radius_h.empty())
+            draw_vertices(m_vertex_model, radius_h, ColorRGBA(0.30f, 0.75f, 0.95f, 1.0f),
+                          std::max(4.0 * upp, 1e-4));
+        if (m_has_hover_handle)
+            draw_vertices(m_highlight_model, { m_hover_handle.pos }, white,
+                          std::max(5.5 * upp, 1e-4));
+    }
+
+    // Placed dimension quotes (drawn in every mode so they persist while sketching).
+    // Pass plane-units-per-pixel so labels keep a constant on-screen size.
+    render_dimensions(1.0 / std::max(camera.get_zoom(), 1e-6));
+    render_live_quotes(1.0 / std::max(camera.get_zoom(), 1e-6));
+    // Draw-then-edit: the selection's live quotes now exist. Open the primary value editor on
+    // the next event-loop tick (NOT here inside the paint) so the floating field grabs focus
+    // cleanly — the same context the Line path opens from. m_live_quotes persists until the
+    // next render_live_quotes(), so the deferred open still sees this frame's values.
+    if (m_autoedit_pending) {
+        m_autoedit_pending = false;
+        trace_autoedit("pending -> deferring open", 0);
+        wxGetApp().CallAfter([this] { open_primary_autoedit(); });
+    }
+    if (is_edit_op_mode())
+        render_op_gizmo(1.0 / std::max(camera.get_zoom(), 1e-6));
+    if (is_transform_mode())
+        render_tf_gizmo(1.0 / std::max(camera.get_zoom(), 1e-6));
+
+    // In-progress entity preview for the active tool.
+    const ColorRGBA preview = m_construction ? grey : orange;
+    switch (m_mode) {
+
+    case Mode::Select:
+    case Mode::Dimension:
+        break;   // selection highlight / placed quotes are drawn above; no rubber-band
+
+    case Mode::Polyline: {
+        std::vector<Vec2d> pts = m_points;
+        if (m_has_cursor)
+            pts.push_back(m_cursor);
+        draw_quad_strip(m_highlight_model, pts, false, preview);
+        draw_vertices(m_vertex_model, m_points, yellow);
+        // Teal rubber-band = the new segment is locked to an inference angle.
+        if (m_cursor_locked && m_has_cursor && !m_points.empty()) {
+            const ColorRGBA lock(0.10f, 0.85f, 0.80f, 1.0f);
+            std::vector<Vec2d> seg = { m_points.back(), m_cursor };
+            draw_quad_strip(m_line_model, seg, false, lock);
+        }
+        break;
+    }
+
+    case Mode::Line: {
+        std::vector<Vec2d> pts = m_points;
+        if (m_has_cursor && m_points.size() == 1)
+            pts.push_back(m_cursor);
+        if (pts.size() >= 2) {
+            const ColorRGBA col = (m_cursor_locked && m_points.size() == 1)
+                                      ? ColorRGBA(0.10f, 0.85f, 0.80f, 1.0f) : preview;
+            draw_quad_strip(m_highlight_model, pts, false, col);
+        }
+        draw_vertices(m_vertex_model, m_points, yellow);
+        break;
+    }
+
+    case Mode::CornerRect: {
+        if (m_points.size() == 1 && m_has_cursor) {
+            const Vec2d A = m_points[0];
+            const Vec2d B = m_cursor;
+            std::vector<Vec2d> corners = { A, Vec2d(B.x(), A.y()), B, Vec2d(A.x(), B.y()) };
+            draw_quad_strip(m_highlight_model, corners, true, preview);
+        }
+        break;
+    }
+
+    case Mode::CenterRect: {
+        if (m_points.size() == 1 && m_has_cursor) {
+            const Vec2d C = m_points[0];
+            const Vec2d P = m_cursor;
+            const double hx = std::abs(P.x() - C.x());
+            const double hy = std::abs(P.y() - C.y());
+            std::vector<Vec2d> corners = {
+                Vec2d(C.x() - hx, C.y() - hy), Vec2d(C.x() + hx, C.y() - hy),
+                Vec2d(C.x() + hx, C.y() + hy), Vec2d(C.x() - hx, C.y() + hy) };
+            draw_quad_strip(m_highlight_model, corners, true, preview);
+            draw_vertices(m_vertex_model, { C }, yellow);
+        }
+        break;
+    }
+
+    case Mode::ObliqueRect: {
+        draw_vertices(m_vertex_model, m_points, yellow);
+        if (m_points.size() == 2 && m_has_cursor) {
+            const Vec2d A = m_points[0], B = m_points[1];
+            Vec2d u = B - A;
+            if (u.squaredNorm() > 1e-12) {
+                u.normalize();
+                const Vec2d n(-u.y(), u.x());
+                const double w = n.dot(m_cursor - A);
+                draw_quad_strip(m_highlight_model, { A, B, B + n * w, A + n * w }, true, preview);
+            }
+        }
+        break;
+    }
+
+    case Mode::RoundedRect: {
+        draw_vertices(m_vertex_model, m_points, yellow);
+        if (m_points.size() == 1 && m_has_cursor) {
+            const Vec2d A = m_points[0], B = m_cursor;   // box not yet fixed: plain rect
+            draw_quad_strip(m_highlight_model, { A, Vec2d(B.x(), A.y()), B, Vec2d(A.x(), B.y()) }, true, preview);
+        } else if (m_points.size() == 2 && m_has_cursor) {
+            draw_entities_preview(make_rounded_rect(m_points[0], m_points[1], m_cursor), preview);
+        }
+        break;
+    }
+
+    case Mode::CenterCircle: {
+        if (m_points.size() == 1 && m_has_cursor) {
+            const Vec2d C = m_points[0];
+            const double r = (m_cursor - C).norm();
+            draw_quad_strip(m_highlight_model, circle_polygon(C, r), true, preview);
+            draw_vertices(m_vertex_model, { C }, yellow);
+        }
+        break;
+    }
+
+    case Mode::TwoPointCircle: {
+        draw_vertices(m_vertex_model, m_points, yellow);
+        if (m_points.size() == 1 && m_has_cursor) {
+            const Vec2d C = (m_points[0] + m_cursor) * 0.5;
+            const double r = (m_cursor - m_points[0]).norm() * 0.5;
+            draw_quad_strip(m_highlight_model, circle_polygon(C, r), true, preview);
+        }
+        break;
+    }
+
+    case Mode::ThreePointCircle: {
+        draw_vertices(m_vertex_model, m_points, yellow);
+        if (m_points.size() == 2 && m_has_cursor)
+            draw_entities_preview(make_three_point_circle(m_points[0], m_points[1], m_cursor), preview);
+        break;
+    }
+
+    case Mode::ThreePointArc: {
+        draw_vertices(m_vertex_model, m_points, yellow);
+        if (m_points.size() == 2 && m_has_cursor)
+            draw_entities_preview(make_three_point_arc(m_points[0], m_points[1], m_cursor), preview);
+        break;
+    }
+
+    case Mode::TangentArc: {
+        draw_vertices(m_vertex_model, m_points, yellow);
+        if (m_points.size() == 1 && m_has_cursor)
+            draw_entities_preview(make_tangent_arc(m_points[0], m_cursor), preview);
+        break;
+    }
+
+    case Mode::CenterArc: {
+        draw_vertices(m_vertex_model, m_points, yellow);
+        if (m_points.size() == 1 && m_has_cursor) {
+            // center placed: show the radius rubber-band as a faint guide circle
+            SketchEntity g; g.type = SketchEntity::Type::Circle; g.center = m_points[0];
+            g.p0 = m_points[0]; g.radius = (m_cursor - m_points[0]).norm(); g.construction = true;
+            draw_entities_preview({ g }, preview);
+        } else if (m_points.size() == 2 && m_has_cursor) {
+            draw_entities_preview(make_center_arc(m_points[0], m_points[1], m_cursor), preview);
+        }
+        break;
+    }
+
+    case Mode::Slot: {
+        draw_vertices(m_vertex_model, m_points, yellow);
+        if (m_points.size() == 1 && m_has_cursor) {
+            draw_quad_strip(m_highlight_model, { m_points[0], m_cursor }, false, grey);
+        } else if (m_points.size() == 2 && m_has_cursor) {
+            Vec2d u = m_points[1] - m_points[0];
+            if (u.squaredNorm() > 1e-12) {
+                u.normalize();
+                const Vec2d n(-u.y(), u.x());
+                const double w = std::abs(n.dot(m_cursor - m_points[0]));
+                draw_entities_preview(make_slot(m_points[0], m_points[1], w), preview);
+            }
+        }
+        break;
+    }
+
+    case Mode::ArcSlot: {
+        draw_vertices(m_vertex_model, m_points, yellow);
+        if (m_points.size() == 1 && m_has_cursor) {
+            // center placed: faint guide circle for the centerline radius
+            SketchEntity g; g.type = SketchEntity::Type::Circle; g.center = m_points[0];
+            g.p0 = m_points[0]; g.radius = (m_cursor - m_points[0]).norm(); g.construction = true;
+            draw_entities_preview({ g }, preview);
+        } else if (m_points.size() == 2 && m_has_cursor) {
+            draw_entities_preview(make_center_arc(m_points[0], m_points[1], m_cursor), preview); // centerline arc
+        } else if (m_points.size() == 3 && m_has_cursor) {
+            const double Rc = (m_points[1] - m_points[0]).norm();
+            const double w  = std::abs((m_cursor - m_points[0]).norm() - Rc);
+            draw_entities_preview(make_arc_slot(m_points[0], m_points[1], m_points[2], w), preview);
+        }
+        break;
+    }
+
+    case Mode::Polygon: {
+        draw_vertices(m_vertex_model, m_points, yellow);
+        if (m_points.size() == 1 && m_has_cursor)
+            draw_entities_preview(make_polygon(m_points[0], m_cursor, m_polygon_sides), preview);
+        break;
+    }
+
+    case Mode::Ellipse: {
+        draw_vertices(m_vertex_model, m_points, yellow);
+        if (m_points.size() == 1 && m_has_cursor) {
+            SketchEntity g; g.type = SketchEntity::Type::Line;
+            g.p0 = m_points[0]; g.p1 = m_cursor; g.construction = true;   // major-axis rubber band
+            draw_entities_preview({ g }, preview);
+        } else if (m_points.size() == 2 && m_has_cursor) {
+            draw_entities_preview(make_ellipse(m_points[0], m_points[1], m_cursor), preview);
+        }
+        break;
+    }
+
+    case Mode::EllipseArc: {
+        draw_vertices(m_vertex_model, m_points, yellow);
+        if (m_points.size() == 1 && m_has_cursor) {
+            SketchEntity g; g.type = SketchEntity::Type::Line;
+            g.p0 = m_points[0]; g.p1 = m_cursor; g.construction = true;
+            draw_entities_preview({ g }, preview);
+        } else if (m_points.size() == 2 && m_has_cursor) {
+            draw_entities_preview(make_ellipse(m_points[0], m_points[1], m_cursor), preview);
+        } else if (m_points.size() == 3 && m_has_cursor) {
+            std::vector<SketchEntity> full = make_ellipse(m_points[0], m_points[1], m_points[2]);
+            for (auto& e : full) e.construction = true;                   // faint full ellipse
+            draw_entities_preview(full, preview);
+        } else if (m_points.size() == 4 && m_has_cursor) {
+            draw_entities_preview(make_ellipse_arc(m_points[0], m_points[1], m_points[2],
+                                                   m_points[3], m_cursor), preview);
+        }
+        break;
+    }
+
+    case Mode::BSpline: {
+        std::vector<Vec2d> poles = m_points;
+        if (m_has_cursor) poles.push_back(m_cursor);
+        // Faint control polygon as a placement guide.
+        if (poles.size() >= 2) {
+            std::vector<SketchEntity> guide;
+            for (size_t i = 1; i < poles.size(); ++i) {
+                SketchEntity g; g.type = SketchEntity::Type::Line;
+                g.p0 = poles[i - 1]; g.p1 = poles[i]; g.construction = true;
+                guide.push_back(g);
+            }
+            draw_entities_preview(guide, grey);
+        }
+        // The spline curve itself.
+        if (poles.size() >= 2)
+            draw_quad_strip(m_highlight_model, bspline_polyline(poles), false, preview);
+        draw_vertices(m_vertex_model, m_points, yellow);
+        break;
+    }
+
+    case Mode::Trim:
+    case Mode::Extend: {
+        // Hover preview: paint the exact sub-portion a click would cut (Trim) / add (Extend)
+        // in red, recomputed from the cursor every frame (never persisted). The pick tolerance
+        // matches on_mouse: ~8 px projected to plane units, x3 (here via zoom -> units/px).
+        if (m_has_cursor) {
+            const double upp = 1.0 / std::max(camera.get_zoom(), 1e-6);
+            int subj = -1;
+            std::vector<Vec2d> removed;
+            const ColorRGBA cut(1.0f, 0.2f, 0.2f, 1.0f);
+            if (compute_trim_preview(m_cursor, 24.0 * upp, m_mode == Mode::Extend, subj, removed))
+                draw_quad_strip(m_highlight_model, removed, false, cut);
+        }
+        break;
+    }
+
+    case Mode::Point:
+    case Mode::Constrain:
+        break;
+    }
+
+    // Inference hint: highlight the snapped target under the cursor (C1.3). Colour
+    // encodes what the placed point will be Coincident/PointOnObject/Fixed onto.
+    if (m_has_cursor && m_mode != Mode::Constrain && m_cursor_snap.snapped()) {
+        ColorRGBA hint(1.0f, 0.55f, 0.1f, 1.0f);                 // endpoint: orange
+        switch (m_cursor_snap.kind) {
+        case InferenceSnap::Kind::Midpoint: hint = ColorRGBA(0.35f, 0.90f, 0.75f, 1.0f); break; // teal
+        case InferenceSnap::Kind::Center: hint = ColorRGBA(0.30f, 0.80f, 1.0f, 1.0f); break; // cyan
+        case InferenceSnap::Kind::Origin: hint = ColorRGBA(1.0f, 0.30f, 0.85f, 1.0f); break; // magenta
+        case InferenceSnap::Kind::OnEdge: hint = ColorRGBA(0.45f, 0.70f, 1.0f, 1.0f); break; // blue
+        default: break;
+        }
+        draw_vertices(m_highlight_model, { m_cursor_snap.point }, hint);
+    }
+
+    shader->stop_using();
+    glsafe(::glEnable(GL_CULL_FACE));
+    glsafe(::glEnable(GL_DEPTH_TEST));
+
+    if (on_readout) on_readout(build_readout());   // bottom-right viewport HUD
+}
+
+// Compact "current values" for the bottom-right HUD: the live segment being drawn (length
+// + bearing) takes priority; otherwise the selected entity's characteristic quotes (the
+// same values render_live_quotes just drew on the geometry).
+std::string DesignSketchTool::build_readout() const
+{
+    auto en = [](char* b) { for (char* c = b; *c; ++c) if (*c == ',') *c = '.'; };
+    if (m_active && (m_mode == Mode::Line || m_mode == Mode::Polyline) &&
+        !m_points.empty() && m_has_cursor) {
+        const Vec2d d = m_cursor - m_points.back();
+        double ang = std::atan2(d.y(), d.x()) * 180.0 / M_PI; if (ang < 0.0) ang += 360.0;
+        char b[80]; std::snprintf(b, sizeof(b), "L %.2f mm    %.1f\xC2\xB0", d.norm(), ang);
+        en(b);
+        std::string out = b;
+        // Tell the user how to end a polyline chain — there's no other affordance for it.
+        if (m_mode == Mode::Polyline && m_points.size() >= 2)
+            out += "      right-click or double-click to finish, click start to close";
+        return out;
+    }
+    if (!m_active) return std::string();
+    std::string out;
+    for (const DimAnnot& q : m_live_quotes) {       // selection's Length/Radius/Width/… quotes
+        if (!out.empty()) out += "    ";
+        out += dim_text(q);
+    }
+    return out;
+}
+
+// Distance from point p to the segment [a,b] in plane (2D) coordinates.
+static double point_segment_dist(const Vec2d& p, const Vec2d& a, const Vec2d& b)
+{
+    const Vec2d ab = b - a;
+    const double len2 = ab.squaredNorm();
+    if (len2 < 1e-12)
+        return (p - a).norm();
+    double t = (p - a).dot(ab) / len2;
+    t = std::max(0.0, std::min(1.0, t));
+    return (p - (a + t * ab)).norm();
+}
+
+// Even-odd point-in-polygon test (plane coords), for picking a closed-loop interior.
+static bool point_in_poly(const Vec2d& q, const std::vector<Vec2d>& poly)
+{
+    if (poly.size() < 3) return false;
+    bool in = false;
+    for (size_t i = 0, j = poly.size() - 1; i < poly.size(); j = i++) {
+        const Vec2d& a = poly[i];
+        const Vec2d& b = poly[j];
+        if (((a.y() > q.y()) != (b.y() > q.y())) &&
+            (q.x() < (b.x() - a.x()) * (q.y() - a.y()) / (b.y() - a.y()) + a.x()))
+            in = !in;
+    }
+    return in;
+}
+
+// Möller–Trumbore ray/triangle intersection in 3D world space. ro=ray origin, rd=ray dir
+// (not necessarily unit). Returns true + the ray parameter t (>0) of the hit.
+static bool ray_triangle(const Vec3d& ro, const Vec3d& rd,
+                         const Vec3d& v0, const Vec3d& v1, const Vec3d& v2, double& t)
+{
+    const Vec3d e1 = v1 - v0, e2 = v2 - v0;
+    const Vec3d p = rd.cross(e2);
+    const double det = e1.dot(p);
+    if (std::abs(det) < 1e-12) return false;          // parallel
+    const double inv = 1.0 / det;
+    const Vec3d s = ro - v0;
+    const double u = s.dot(p) * inv;
+    if (u < -1e-9 || u > 1.0 + 1e-9) return false;
+    const Vec3d q = s.cross(e1);
+    const double v = rd.dot(q) * inv;
+    if (v < -1e-9 || u + v > 1.0 + 1e-9) return false;
+    t = e2.dot(q) * inv;
+    return t > 1e-9;
+}
+
+// Shortest distance between an infinite ray (ro+rd) and a 3D segment [a,b].
+static double ray_segment_dist3(const Vec3d& ro, const Vec3d& rd, const Vec3d& a, const Vec3d& b)
+{
+    const Vec3d d1 = rd, d2 = b - a, r = ro - a;
+    const double A = d1.dot(d1), B = d1.dot(d2), C = d2.dot(d2), D = d1.dot(r), E = d2.dot(r);
+    const double denom = A * C - B * B;
+    double s = (std::abs(denom) > 1e-12) ? (A * E - B * D) / denom : 0.0;  // param on segment
+    s = std::max(0.0, std::min(1.0, s));
+    double tt = (B * s - D) / std::max(A, 1e-12);                          // param on ray
+    tt = std::max(0.0, tt);                                                // ray is forward-only
+    const Vec3d pr = ro + tt * d1, ps = a + s * d2;
+    return (pr - ps).norm();
+}
+
+// Screen-plane distance from p to a sketch entity, for click picking in Constrain
+// mode. Circles/arcs measure distance to the ring; points to their position.
+static double entity_pick_dist(const Vec2d& p, const SketchEntity& e)
+{
+    switch (e.type) {
+    case SketchEntity::Type::Line:   return point_segment_dist(p, e.p0, e.p1);
+    case SketchEntity::Type::Point:  return (p - e.p0).norm();
+    case SketchEntity::Type::Circle:
+    case SketchEntity::Type::Arc:    return std::abs((p - e.center).norm() - e.radius);
+    case SketchEntity::Type::Ellipse:
+    case SketchEntity::Type::EllipseArc: {
+        // Accurate edge pick: sample the true ellipse outline as a polyline and take the
+        // min segment distance. The crude mean-radius circle mis-picks eccentric ellipses
+        // (the outline at the major/minor extremes is far from that circle), which made the
+        // face-fill swallow edge clicks. Full ellipse sweeps 0..2pi; an arc its param range.
+        const double cu = std::cos(e.rotation), su = std::sin(e.rotation);
+        const bool full = (e.type == SketchEntity::Type::Ellipse);
+        const double t0 = full ? 0.0 : e.start_angle;
+        const double t1 = full ? 2.0 * M_PI : e.end_angle;
+        const int n = 48;
+        double best = 1e30; Vec2d prev;
+        for (int i = 0; i <= n; ++i) {
+            const double t = t0 + (t1 - t0) * double(i) / n;
+            const double lx = e.radius * std::cos(t), ly = e.rminor * std::sin(t);   // local
+            const Vec2d q(e.center.x() + lx * cu - ly * su,
+                          e.center.y() + lx * su + ly * cu);                          // world
+            if (i > 0) best = std::min(best, point_segment_dist(p, prev, q));
+            prev = q;
+        }
+        return best;
+    }
+    case SketchEntity::Type::BSpline: {
+        const std::vector<Vec2d> poly = bspline_polyline(e.ctrl);
+        double best = 1e30;
+        for (size_t i = 1; i < poly.size(); ++i)
+            best = std::min(best, point_segment_dist(p, poly[i - 1], poly[i]));
+        return best;
+    }
+    }
+    return 1e30;
+}
+
+// Adjacency endpoints for loop walking (Circles/Points have none -> stand-alone).
+static void entity_endpoints(const SketchEntity& e, std::vector<Vec2d>& out)
+{
+    out.clear();
+    if (e.type == SketchEntity::Type::Line) {
+        out.push_back(e.p0);
+        out.push_back(e.p1);
+    } else if (e.type == SketchEntity::Type::Arc) {
+        out.push_back(e.center + e.radius * Vec2d(std::cos(e.start_angle), std::sin(e.start_angle)));
+        out.push_back(e.center + e.radius * Vec2d(std::cos(e.end_angle),   std::sin(e.end_angle)));
+    }
+}
+
+// Reference point for positioning ops: a Point's position, or a Circle/Arc centre.
+// Lines have no single reference point (return false).
+static bool entity_ref_point(const SketchEntity& e, Vec2d& out)
+{
+    switch (e.type) {
+    case SketchEntity::Type::Point:  out = e.p0;     return true;
+    case SketchEntity::Type::Circle:
+    case SketchEntity::Type::Arc:
+    case SketchEntity::Type::Ellipse:
+    case SketchEntity::Type::EllipseArc: out = e.center; return true;
+    default:                         return false;   // Line
+    }
+}
+
+// Rigidly translate a whole entity (keeps size/shape).
+static void translate_entity(SketchEntity& e, const Vec2d& d)
+{
+    e.p0 += d;
+    e.p1 += d;
+    e.center += d;
+    for (auto& cp : e.ctrl) cp += d;     // BSpline poles
+}
+
+// Select whatever the cursor is over, for a RIGHT-click. In every CAD application the context
+// menu belongs to the thing you pointed at; here the menu was built from whatever happened to be
+// selected already, so right-clicking a line you had not left-clicked first offered the empty-
+// selection vocabulary and its own Delete/Length/Trim rows were nowhere. The offer table already
+// described all of those for SkLine/SkArc/SkPoint — the pick was the missing half.
+//
+// Nothing is stolen from an existing selection: if the entity under the cursor is already part
+// of it, the selection is left exactly as it is, so right-clicking one member of a multi-entity
+// pick still offers the multi-entity verbs.
+// ---- Scripted surface (MCP) ------------------------------------------------------------
+
+int DesignSketchTool::add_entities_scripted(const std::vector<SketchEntity>& ents)
+{
+    if (ents.empty()) return -1;
+    const int base = int(m_entities.size());
+    for (const SketchEntity& e : ents) m_entities.push_back(e);
+    // Auto-constrain, but do NOT let the inference move what the caller specified. A gesture
+    // gets 3 degrees of slack because a hand cannot click an exact horizontal; a scripted add
+    // has already said exactly what it means, and snapping a segment 2 degrees off to exactly
+    // horizontal silently rewrites it. Measured on a real drawing: feeding the 64 flattened
+    // segments of one circle moved vertices by up to 0.058 mm and shrank the enclosed area by
+    // 0.067%, because several segments of the polygon fell inside that 3 degree window. Exact
+    // coincidence inference is unaffected — it already tests to 1e-6 — so chains still weld
+    // and genuinely axis-aligned scripted geometry still gets its Horizontal/Vertical.
+    //
+    // ZERO, not 1e-4. Any window at all is a window that moves the caller's points, and 1e-4 rad
+    // was still wide enough to catch the short chords of a small flattened circle: on four of
+    // the 39 corpus drawings the loops that came back wrong were all TINY (1.4 to 13 mm^2), out
+    // by up to 7e-4 relative, because a 0.005 degree tilt on a 0.3 mm chord is inside 1e-4.
+    // With zero, only a segment that is EXACTLY axis-aligned is constrained, and constraining
+    // something already true cannot move it. 8xg1.
+    // The weld window closes too. Two endpoints a micron apart are not the same point when a
+    // caller typed both of them: on MPD681, 20 of 363 scripted segments were dragged onto a
+    // common point up to 0.0021 mm away, because welding is TRANSITIVE and three vertices near
+    // the origin chained into one. Exactly-equal endpoints still weld, which is what keeps a
+    // scripted profile closed — a ring's last point IS its first point.
+    infer_auto_constraints(base, 0.0, 0.0);
+    resolve_live();
+    // A scripted add is not a drawn gesture, and draw-then-edit must not fire for it. The render
+    // pass arms that on a jump in the entity count (see the m_autoedit_seen block in render()),
+    // so a bulk load made while a creation tool is armed selected the last scripted entity and
+    // opened that tool's value field — which freezes the canvas (on_mouse_impl returns early
+    // while m_awaiting_length) and swallows every letter (in_text includes inline_busy()). The
+    // symptom was that the first key and click after sketch_add did nothing until one Escape had
+    // dismissed the field. Resyncing the baseline here leaves an ALREADY open field alone; it
+    // only stops this add from being read as something the user just drew. j7gc.
+    m_autoedit_seen = int(m_entities.size());
+    return base;
+}
+
+bool DesignSketchTool::select_indices(const std::vector<int>& idx)
+{
+    m_selection.clear();
+    m_point_sel.clear();
+    const int n = int(m_entities.size());
+    for (int i : idx)
+        if (i >= 0 && i < n &&
+            std::find(m_selection.begin(), m_selection.end(), i) == m_selection.end())
+            m_selection.push_back(i);
+    if (on_selection_changed) on_selection_changed(int(m_selection.size()));
+    return !m_selection.empty();
+}
+
+DesignSketchTool::LoopReport DesignSketchTool::loop_report() const
+{
+    LoopReport out;
+
+    // Closed regions and their voids come straight from the code the viewport already uses to
+    // decide what can be extruded, so the report cannot drift from what the tool will build.
+    const auto regs = region_loops(m_entities);
+    out.loops.reserve(regs.size());
+    for (const auto& r : regs) {
+        LoopInfo li;
+        li.ents   = r.ents;
+        li.holes  = r.holes;
+        li.closed = true;
+        // Analytic where the loop IS one closed curve; shoelace only where it is a chain.
+        // region_loops hands back the render polyline, and a circle's is a 64-gon whose area is
+        // 0.3% short — a number reported as "area" must not be the faceting error.
+        if (r.ents.size() == 1 && r.ents[0] >= 0 && r.ents[0] < int(m_entities.size()) &&
+            (m_entities[r.ents[0]].type == SketchEntity::Type::Circle ||
+             m_entities[r.ents[0]].type == SketchEntity::Type::Ellipse)) {
+            const SketchEntity& c = m_entities[r.ents[0]];
+            li.area = (c.type == SketchEntity::Type::Circle)
+                          ? M_PI * c.radius * c.radius
+                          : M_PI * c.radius * c.rminor;
+        } else {
+            // EXACT area by Green's theorem over the chain, entity by entity, with no faceting
+            // anywhere. The obvious alternative — shoelace over the render polyline — is short by
+            // the slivers between each arc and its chords: 2.02 mm2 on a 3706.86 mm2 stadium,
+            // 0.054%, invisible on screen and simply wrong in a number reported as "the area".
+            // Correcting the shoelace afterwards does NOT work: a mirrored arc stores a negated
+            // sweep, so two corrections that should add cancel instead. Integrating each entity
+            // in TRAVERSAL order sidesteps the sign question entirely.
+            //   line A->B : x0*y1 - x1*y0
+            //   arc a0->a1: Cx*r*(sin a1 - sin a0) - Cy*r*(cos a1 - cos a0) + r^2*(a1 - a0)
+            // Both are the integrand of the contour integral, so area2 accumulates 2*area and is
+            // halved once at the end. (Doubling the arc term instead reads 5913.72 on the stadium
+            // — exactly one arc's contribution too much, which is how the slip was caught.)
+            auto ent_ends = [&](int ei, Vec2d& a, Vec2d& b) {
+                a = m_entities[ei].p0; b = m_entities[ei].p1;
+            };
+            const double eps = 1e-6;
+            double area2 = 0.0;
+            bool   exact = true;
+            Vec2d  cur(0, 0);
+            for (size_t k = 0; k < r.ents.size(); ++k) {
+                const int ei = r.ents[k];
+                if (ei < 0 || ei >= int(m_entities.size())) { exact = false; break; }
+                const SketchEntity& e = m_entities[ei];
+                if (e.type != SketchEntity::Type::Line && e.type != SketchEntity::Type::Arc) {
+                    exact = false; break;      // spline / ellipse arc: fall back below
+                }
+                Vec2d A, B; ent_ends(ei, A, B);
+                bool rev = false;
+                if (k == 0) {
+                    // Orient the first entity by whichever of its ends the SECOND one touches:
+                    // that shared point is where this entity must finish.
+                    if (r.ents.size() > 1) {
+                        Vec2d C, D; ent_ends(r.ents[1], C, D);
+                        if ((A - C).norm() < eps || (A - D).norm() < eps) rev = true;
+                    }
+                } else {
+                    if ((B - cur).norm() < eps)      rev = true;
+                    else if ((A - cur).norm() >= eps) { exact = false; break; }
+                }
+                const Vec2d P = rev ? B : A;
+                const Vec2d Q = rev ? A : B;
+                if (e.type == SketchEntity::Type::Line) {
+                    area2 += P.x() * Q.y() - Q.x() * P.y();
+                } else {
+                    const double a0 = rev ? e.end_angle   : e.start_angle;
+                    const double a1 = rev ? e.start_angle : e.end_angle;
+                    area2 += e.center.x() * e.radius * (std::sin(a1) - std::sin(a0))
+                           - e.center.y() * e.radius * (std::cos(a1) - std::cos(a0))
+                           + e.radius * e.radius * (a1 - a0);
+                }
+                cur = Q;
+            }
+            if (exact) {
+                li.area = 0.5 * area2;
+            } else {
+                // Splines and elliptical arcs have no closed form here; the render polyline is
+                // the honest best estimate, and it is flagged as such by being the fallback.
+                double a = 0.0;
+                for (size_t i = 0; i + 1 < r.poly.size(); ++i)
+                    a += r.poly[i].x() * r.poly[i + 1].y() - r.poly[i + 1].x() * r.poly[i].y();
+                if (r.poly.size() > 2)
+                    a += r.poly.back().x() * r.poly.front().y() - r.poly.front().x() * r.poly.back().y();
+                li.area = 0.5 * a;
+            }
+        }
+        out.loops.push_back(std::move(li));
+    }
+
+    // Open ends: an endpoint of an open curve that no other open curve's endpoint meets. This is
+    // the actionable half of the report — it says WHERE the profile fails to close, in plane
+    // coordinates, instead of only that it does.
+    struct End { Vec2d p; };
+    std::vector<End> ends;
+    for (const SketchEntity& e : m_entities) {
+        if (e.construction) continue;
+        if (e.type == SketchEntity::Type::Line || e.type == SketchEntity::Type::Arc ||
+            e.type == SketchEntity::Type::EllipseArc || e.type == SketchEntity::Type::BSpline) {
+            ends.push_back({ e.p0 });
+            ends.push_back({ e.p1 });
+        }
+    }
+    const double eps = sketch_join_tol();
+    for (size_t i = 0; i < ends.size(); ++i) {
+        int met = 0;
+        for (size_t j = 0; j < ends.size(); ++j) {
+            if (i == j) continue;
+            if ((ends[i].p - ends[j].p).norm() < eps) ++met;
+        }
+        if (met == 0) {
+            // Report each free end once; two ends of the same gap are two different points.
+            bool dup = false;
+            for (const Vec2d& q : out.open_ends)
+                if ((q - ends[i].p).norm() < eps) { dup = true; break; }
+            if (!dup) out.open_ends.push_back(ends[i].p);
+        }
+    }
+    return out;
+}
+
+int DesignSketchTool::heal_coincidences(double tol, bool ignore_construction)
+{
+    if (tol <= 0.0) tol = 1e-3;
+    // Endpoint roles an entity exposes, same set infer_auto_constraints matches on.
+    auto roles_of = [](const SketchEntity& e, SketchPointRole out[2]) -> int {
+        switch (e.type) {
+        case SketchEntity::Type::Line:
+        case SketchEntity::Type::Arc:
+        case SketchEntity::Type::BSpline:
+        case SketchEntity::Type::EllipseArc:
+            out[0] = SketchPointRole::P0; out[1] = SketchPointRole::P1; return 2;
+        case SketchEntity::Type::Point:
+            out[0] = SketchPointRole::P0; return 1;
+        default: return 0;
+        }
+    };
+
+    const int n = int(m_entities.size());
+    int welded = 0;
+    std::vector<SketchEntityConstraintDef> cands;
+    for (int i = 0; i < n; ++i) {
+        if (ignore_construction && m_entities[i].construction) continue;
+        SketchPointRole ir[2]; const int ni = roles_of(m_entities[i], ir);
+        for (int a = 0; a < ni; ++a) {
+            Vec2d pa; if (!point_at(i, ir[a], pa)) continue;
+            for (int j = i + 1; j < n; ++j) {
+                if (ignore_construction && m_entities[j].construction) continue;
+                SketchPointRole jr[2]; const int nj = roles_of(m_entities[j], jr);
+                for (int b = 0; b < nj; ++b) {
+                    Vec2d pb; if (!point_at(j, jr[b], pb)) continue;
+                    const double d = (pa - pb).norm();
+                    if (d > tol) continue;
+                    if (has_coincident(i, ir[a], j, jr[b])) continue;
+                    // WELD FIRST, then constrain. Handing the solver two points a tolerance
+                    // apart and asking it to make them equal lets it move the rest of the sketch
+                    // to get there; snapping them together first means the constraint it is
+                    // asked to satisfy is already true, so nothing else shifts.
+                    if (d > 0.0) { set_point(j, jr[b], pa); pb = pa; }
+                    SketchEntityConstraintDef c;
+                    c.type = SketchConstraintType::Coincident;
+                    c.ea = i; c.ra = ir[a]; c.eb = j; c.rb = jr[b];
+                    cands.push_back(c);
+                    ++welded;
+                }
+            }
+        }
+    }
+    if (!cands.empty()) {
+        try_add_constraints(cands);
+        resolve_live();
+    }
+    return welded;
+}
+
+bool DesignSketchTool::select_at_screen(GLCanvas3D& canvas, int sx, int sy)
+{
+    if (!is_active()) return false;
+    const Linef3 ray  = canvas.mouse_ray(Point(sx, sy));
+    const Linef3 ray8 = canvas.mouse_ray(Point(sx + 8, sy));
+    const Vec2d  p    = m_plane.project(ray.a,  ray.vector());
+    const Vec2d  p8   = m_plane.project(ray8.a, ray8.vector());
+    const double tol  = std::max(1e-3, (p8 - p).norm());
+
+    // A point handle beats the curve it belongs to, same precedence the left-click pick uses.
+    int ei = -1; SketchPointRole role = SketchPointRole::P0;
+    if (hit_test_point(p, tol, ei, role)) {
+        // A Point ENTITY is its own handle: there is nothing else to select there. Taking the
+        // handle branch for it filled m_point_sel and left m_selection empty — and the offer
+        // counts only m_selection, so right-clicking a sketch point produced the EMPTY
+        // vocabulary and every SkPoint row in the atlas was unreachable from the menu. Other
+        // entities keep the handle pick: a line's endpoint is a drag target, not a thing with a
+        // vocabulary of its own. lnri.
+        if (ei >= 0 && ei < int(m_entities.size())
+            && m_entities[ei].type == SketchEntity::Type::Point) {
+            if (std::find(m_selection.begin(), m_selection.end(), ei) != m_selection.end())
+                return false;                               // already selected: leave it alone
+            m_selection.assign(1, ei);
+            m_point_sel.clear();
+            if (on_selection_changed) on_selection_changed(1);
+            return true;
+        }
+        const auto pr = std::make_pair(ei, role);
+        if (std::find(m_point_sel.begin(), m_point_sel.end(), pr) != m_point_sel.end())
+            return false;                                   // already selected: leave it alone
+        m_selection.clear();
+        m_point_sel.assign(1, pr);
+        if (on_selection_changed) on_selection_changed(1);
+        return true;
+    }
+
+    const int hit = hit_test(p, tol);
+    if (hit < 0) return false;
+    if (std::find(m_selection.begin(), m_selection.end(), hit) != m_selection.end())
+        return false;                                       // already selected: leave it alone
+    m_selection.assign(1, hit);
+    m_point_sel.clear();
+    if (on_selection_changed) on_selection_changed(1);
+    return true;
+}
+
+int DesignSketchTool::hit_test(const Vec2d& p, double tol) const
+{
+    double best = tol;
+    int bi = -1;
+    for (size_t i = 0; i < m_entities.size(); ++i) {
+        const double d = entity_pick_dist(p, m_entities[i]);
+        if (d < best) { best = d; bi = int(i); }
+    }
+    return bi;
+}
+
+std::vector<int> DesignSketchTool::connected_loop(int seed) const
+{
+    std::vector<int> out;
+    if (seed < 0 || seed >= int(m_entities.size())) return out;
+    const double eps2 = sketch_join_tol() * sketch_join_tol();
+    std::vector<bool> vis(m_entities.size(), false);
+    std::vector<int> stack = { seed };
+    vis[seed] = true;
+    while (!stack.empty()) {
+        const int cur = stack.back();
+        stack.pop_back();
+        out.push_back(cur);
+        std::vector<Vec2d> ce;
+        entity_endpoints(m_entities[cur], ce);
+        if (ce.empty()) continue;                 // circle/point: not part of a chain
+        for (size_t j = 0; j < m_entities.size(); ++j) {
+            if (vis[j]) continue;
+            std::vector<Vec2d> je;
+            entity_endpoints(m_entities[j], je);
+            if (je.empty()) continue;
+            bool adj = false;
+            for (const Vec2d& a : ce)
+                for (const Vec2d& b : je)
+                    if ((a - b).squaredNorm() < eps2) { adj = true; break; }
+            if (adj) { vis[j] = true; stack.push_back(int(j)); }
+        }
+    }
+    return out;
+}
+
+// Right-click has two jobs in a sketch, and they were resolved by giving one of them everything:
+// the offer was excluded in sketch mode wholesale so a right-click could end a polyline chain,
+// abandon an anchor or exit a tool. That made every sketch row in the atlas unreachable.
+// The honest test is not "which mode are we in" but "did the tool actually USE this right-click",
+// and only the tool knows. Wrapping on_mouse records that once, for every terminator, instead of
+// threading a flag through the twenty-odd sites that consume a RightDown.
+// Right-click abandons the anchor a draw tool has down. With NOTHING down there is nothing to
+// abandon — and consuming the click anyway made the offer unreachable from every armed draw tool:
+// on_mouse records the consumption in m_right_consumed and DesignCanvas's RIGHT_UP handler
+// suppresses the menu whenever it is set, so right-click became a no-op that also hid the one door
+// to half the vocabulary (47 of 86 verbs have no shortcut). Measured on the rig: with Line armed,
+// two right-clicks in a row produced no menu and no tool change; only Escape freed it.
+// Same rule as xmh6, which said it for the selection: clearing nothing is not a gesture
+// terminator. ghcz.
+bool DesignSketchTool::right_abandon()
+{
+    if (m_points.empty())
+        return false;               // hand it back, so the canvas opens the offer
+    m_points.clear();
+    m_has_cursor = false;
+    return true;
+}
+
+bool DesignSketchTool::on_mouse(wxMouseEvent& evt, GLCanvas3D& canvas)
+{
+    const bool consumed = on_mouse_impl(evt, canvas);
+    if (evt.RightDown())
+        m_right_consumed = consumed;
+    return consumed;
+}
+
+bool DesignSketchTool::on_mouse_impl(wxMouseEvent& evt, GLCanvas3D& canvas)
+{
+    // Track the cursor in canvas client px so the in-canvas value editor can open right
+    // where the user clicked (Onshape places the field at the click, not via a camera
+    // projection — the design canvas's viewport isn't valid outside its own paint).
+    m_last_mouse_x = evt.GetX();
+    m_last_mouse_y = evt.GetY();
+
+    // Line draw-then-edit: while the length editor is open right after the second click,
+    // freeze the canvas so a stray move/click can't push a third point or rubber-band a
+    // segment under the floating field. The editor's Enter/Esc resolves it
+    // (apply_segment_length / keep_segment_as_drawn, the latter clears this flag).
+    if (m_awaiting_length) {
+        // Polyline terminators must work even with a per-segment field open: right-click or
+        // double-click accepts the current segment as drawn (close the field) and falls through
+        // so the Polyline handler ends the chain. Without this the freeze ate every terminator.
+        if (m_mode == Mode::Polyline && (evt.RightDown() || evt.LeftDClick()) && on_inline_dismiss)
+            on_inline_dismiss();              // -> set_inline_busy(false), m_awaiting_length=false
+        // The freeze exists so a stray click can't draw under the floating field — it was
+        // never meant to trap the camera. Let drags and the wheel through, so a field that
+        // opens somewhere unexpected can't leave the viewport unusable.
+        else if (evt.Dragging() || evt.GetWheelRotation() != 0)
+            return false;
+        else
+            return true;
+    }
+
+    // No live session, but committed sketches are shown as overlays on the plate: a left
+    // click on a loop (its edge OR its closed interior) selects that Sketch feature. This
+    // is the ONLY interaction in display-only mode; everything else (drag/move/wheel/right)
+    // falls through (return false) so the camera can still orbit the plate.
+    if (!m_active) {
+        // Double-click on a committed sketch stroke OPENS IT FOR EDITING; on empty space it
+        // still fits the view. A sketch line has to be editable from the line, not from a tree
+        // row — selecting it already lit the feature, but "now go and press Edit in the panel"
+        // is the side-panel dependency this tab exists to remove. Fit keeps the rest of the
+        // plate, so nothing is taken away.
+        if (evt.LeftDClick()) {
+            int f = -1, r = -1, e = -1, ff = -1, fr = -1; double dbest = 1e30;
+            const Linef3 dray  = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+            const Linef3 dray8 = canvas.mouse_ray(Point(evt.GetX() + 8, evt.GetY()));
+            for (const DisplaySketch& d : m_display_sketches) {
+                const Vec2d dp  = d.plane.project(dray.a,  dray.vector());
+                const Vec2d dp8 = d.plane.project(dray8.a, dray8.vector());
+                hit_display_sketch(d, dp, std::max(1e-3, (dp8 - dp).norm()), f, r, e, dbest, ff, fr);
+            }
+            const int target = (f >= 0) ? f : ff;
+            if (target >= 0 && on_display_sketch_activated) {
+                dp_pick_trace("double-click -> edit sketch feature %d (entity %d)", target, e);
+                on_display_sketch_activated(target);
+                return true;
+            }
+            canvas.zoom_to_volumes();
+            return true;
+        }
+        // Visual Extrude gizmo (C5b): while the Extrude card is open the depth arrow is
+        // grabbable — drag changes the depth live; a click (no drag) on the arrow opens the
+        // inline depth editor. Intercept before the early no-LeftDown bailout so Dragging/
+        // LeftUp reach us; a LeftDown that misses the arrow falls through to solid/loop pick.
+        // Move-body gizmo (M5): three world-axis arrows on the selected body. Drag an arrow to
+        // translate live; a stationary click on it opens the inline offset editor; a right click
+        // exits move mode. A LeftDown that misses the arrows falls through to solid re-pick.
+        if (m_mv_active) {
+            if (m_mv_drag >= 0 && evt.Dragging() && evt.LeftIsDown()) {
+                if (m_mv_drag < 3) drag_move_arrow(canvas, evt, m_mv_drag);
+                else               drag_move_arc(canvas, evt, m_mv_drag - 3);
+                return true;
+            }
+            if (evt.LeftUp() && m_mv_drag >= 0) {
+                const int d = m_mv_drag; m_mv_drag = -1;
+                const bool moved = std::abs(evt.GetX() - m_mv_press_x) +
+                                   std::abs(evt.GetY() - m_mv_press_y) > 3;
+                if (!moved && d < 3) open_move_editor(d);   // stationary click on an arrow = edit offset
+                return true;
+            }
+            if (evt.RightDown()) { clear_move_gizmo(); canvas.set_as_dirty(); if (on_move_exit) on_move_exit(); return true; }
+            if (evt.LeftDown()) {
+                int axis = -1;
+                if (hit_test_move_arrow(canvas, evt, axis)) {   // translate arrows win over rings
+                    m_mv_drag = axis; m_mv_press_x = evt.GetX(); m_mv_press_y = evt.GetY();
+                    return true;
+                }
+                if (hit_test_move_arc(canvas, evt, axis)) {
+                    m_mv_drag = 3 + axis; m_mv_press_x = evt.GetX(); m_mv_press_y = evt.GetY();
+                    m_mv_rot_start = m_mv_rot;
+                    double a0; if (arc_mouse_angle(canvas, evt, axis, a0)) m_mv_arc_a0 = a0;
+                    return true;
+                }
+            }
+        }
+        // Datum-plane resize gizmo (C3): while the Plane card is open the 4 edge handles are
+        // grabbable — drag changes the u/v extent live. A LeftDown that misses falls through.
+        if (m_dz_active) {
+            if (m_dz_drag >= 0 && evt.Dragging() && evt.LeftIsDown()) {
+                drag_datum_handle(canvas, evt, m_dz_drag);
+                return true;
+            }
+            if (evt.LeftUp() && m_dz_drag >= 0) { m_dz_drag = -1; return true; }
+            if (evt.LeftDown()) {
+                int which = -1;
+                if (hit_test_datum_handle(canvas, evt, which)) {
+                    m_dz_drag = which; m_dz_press_x = evt.GetX(); m_dz_press_y = evt.GetY();
+                    return true;
+                }
+            }
+        }
+        // Helix gizmo: radius/height/pitch handles on the live curve, while the Helix card is open.
+        if (m_hx_active) {
+            if (m_hx_drag >= 0 && evt.Dragging() && evt.LeftIsDown()) {
+                drag_helix_handle(canvas, evt, m_hx_drag);
+                return true;
+            }
+            if (evt.LeftUp() && m_hx_drag >= 0) { m_hx_drag = -1; return true; }
+            if (evt.LeftDown()) {
+                int which = -1;
+                if (hit_test_helix_handle(canvas, evt, which)) {
+                    m_hx_drag = which; m_hx_press_x = evt.GetX(); m_hx_press_y = evt.GetY();
+                    return true;
+                }
+            }
+        }
+        // Rib thickness gizmo: two in-plane handles on the slab footprint, while the Rib card is open.
+        if (m_rb_active) {
+            if (m_rb_drag >= 0 && evt.Dragging() && evt.LeftIsDown()) {
+                drag_rib_handle(canvas, evt, m_rb_drag);
+                return true;
+            }
+            if (evt.LeftUp() && m_rb_drag >= 0) { m_rb_drag = -1; return true; }
+            if (evt.LeftDown()) {
+                int which = -1;
+                if (hit_test_rib_handle(canvas, evt, which)) {
+                    m_rb_drag = which;
+                    return true;
+                }
+            }
+        }
+        // Datum base picker: HOVER highlight only here. The CLICK is handled at the very end of the
+        // selection fall-through (below), so picking existing geometry (committed sketch loops,
+        // solid faces/edges) always wins over a base-plane click — the planes never block selection.
+        if (m_dbp_active && evt.Moving() && !evt.LeftIsDown()) {
+            const int h = hit_test_base_pick(canvas, evt);
+            if (h != m_dbp_hover) {
+                m_dbp_hover = h;
+                canvas.set_as_dirty();
+                if (h >= 0) return true;   // caller render()s on true -> hover repaints on software GL
+            }
+        }
+        if (m_ex_active) {
+            if (m_ex_drag >= 0 && evt.Dragging() && evt.LeftIsDown()) {
+                drag_extrude_arrow(canvas, evt, m_ex_drag);
+                return true;
+            }
+            if (evt.LeftUp() && m_ex_drag >= 0) {
+                const int which = m_ex_drag; m_ex_drag = -1;
+                const bool moved = std::abs(evt.GetX() - m_ex_press_x) +
+                                   std::abs(evt.GetY() - m_ex_press_y) > 3;
+                if (!moved) open_extrude_editor(which);   // treat a stationary click as edit
+                return true;
+            }
+            if (evt.LeftDown()) {
+                int which = -1;
+                if (hit_test_extrude_arrow(canvas, evt, which)) {
+                    m_ex_drag = which; m_ex_press_x = evt.GetX(); m_ex_press_y = evt.GetY();
+                    return true;
+                }
+            }
+        }
+        // Revolve angle-arc gizmo: drag the arc tip to sweep the angle; a stationary click on the
+        // handle opens the inline editor. A LeftDown that misses falls through to normal picking.
+        if (m_rv_active) {
+            if (m_rv_drag && evt.Dragging() && evt.LeftIsDown()) {
+                drag_revolve_arc(canvas, evt);
+                return true;
+            }
+            if (evt.LeftUp() && m_rv_drag) {
+                m_rv_drag = false;
+                const bool moved = std::abs(evt.GetX() - m_rv_press_x) +
+                                   std::abs(evt.GetY() - m_rv_press_y) > 3;
+                if (!moved) open_revolve_editor();
+                return true;
+            }
+            if (evt.LeftDown() && hit_test_revolve_handle(canvas, evt)) {
+                m_rv_drag = true; m_rv_press_x = evt.GetX(); m_rv_press_y = evt.GetY();
+                return true;
+            }
+        }
+        // Draft angle-arc gizmo: drag the arc tip to sweep the draft angle; a stationary click
+        // edits it. A LeftDown that misses falls through to normal picking.
+        if (m_dr_active) {
+            if (m_dr_drag && evt.Dragging() && evt.LeftIsDown()) {
+                drag_draft_arc(canvas, evt);
+                return true;
+            }
+            if (evt.LeftUp() && m_dr_drag) {
+                m_dr_drag = false;
+                return true;
+            }
+            if (evt.LeftDown() && hit_test_draft_handle(canvas, evt)) {
+                m_dr_drag = true; m_dr_press_x = evt.GetX(); m_dr_press_y = evt.GetY();
+                return true;
+            }
+        }
+        // Cut gizmo: drag the offset arrow along the cut-plane normal; no positive clamp (offset is signed).
+        if (m_ct_active) {
+            if (m_ct_drag && evt.Dragging() && evt.LeftIsDown()) {
+                drag_cut_arrow(canvas, evt);
+                return true;
+            }
+            if (evt.LeftUp() && m_ct_drag) {
+                m_ct_drag = false;
+                return true;
+            }
+            if (evt.LeftDown() && hit_test_cut_arrow(canvas, evt)) {
+                start_cut_drag(canvas, evt);
+                return true;
+            }
+        }
+        // Pattern gizmo: drag the diamond/arc handle to set the spacing (linear) or angle (circular);
+        // a stationary click opens the inline editor. A LeftDown that misses falls through to picking.
+        if (m_pt_active) {
+            if (m_pt_drag && evt.Dragging() && evt.LeftIsDown()) {
+                drag_pattern_handle(canvas, evt);
+                return true;
+            }
+            if (evt.LeftUp() && m_pt_drag) {
+                m_pt_drag = false;
+                const bool moved = std::abs(evt.GetX() - m_pt_press_x) +
+                                   std::abs(evt.GetY() - m_pt_press_y) > 3;
+                if (!moved) open_pattern_editor();
+                return true;
+            }
+            if (evt.LeftDown() && hit_test_pattern_handle(canvas, evt)) {
+                m_pt_drag = true; m_pt_press_x = evt.GetX(); m_pt_press_y = evt.GetY();
+                return true;
+            }
+        }
+        // Fillet/Chamfer radius gizmo: drag the edge-anchored arrow to set the radius live; a
+        // stationary click opens the inline editor. A LeftDown that misses falls through to pick.
+        if (m_fl_active) {
+            if (m_fl_drag && evt.Dragging() && evt.LeftIsDown()) {
+                drag_fillet_arrow(canvas, evt);
+                return true;
+            }
+            if (evt.LeftUp() && m_fl_drag) {
+                m_fl_drag = false;
+                const bool moved = std::abs(evt.GetX() - m_fl_press_x) +
+                                   std::abs(evt.GetY() - m_fl_press_y) > 3;
+                if (!moved) open_fillet_editor();   // stationary click = edit
+                return true;
+            }
+            if (evt.LeftDown() && hit_test_fillet_arrow(canvas, evt)) {
+                start_fillet_drag(canvas, evt);
+                return true;
+            }
+        }
+        // Hole gizmo: drag the centre to reposition / the diameter or depth arrow to resize; a
+        // stationary click on an arrow opens its inline editor. A LeftDown that misses any handle
+        // falls through to solid/loop picking.
+        if (m_hl_active) {
+            if (m_hl_drag >= 0 && evt.Dragging() && evt.LeftIsDown()) {
+                drag_hole_handle(canvas, evt);
+                return true;
+            }
+            if (evt.LeftUp() && m_hl_drag >= 0) {
+                const int which = m_hl_drag; m_hl_drag = -1;
+                const bool moved = std::abs(evt.GetX() - m_hl_press_x) +
+                                   std::abs(evt.GetY() - m_hl_press_y) > 3;
+                if (!moved) open_hole_editor(which);   // stationary click = edit
+                return true;
+            }
+            if (evt.LeftDown()) {
+                const int which = hit_test_hole_handle(canvas, evt);
+                if (which >= 0) { start_hole_drag(canvas, evt, which); return true; }
+            }
+        }
+        // Thread gizmo: same interaction as the hole gizmo (centre / radius / length handles).
+        if (m_th_active) {
+            if (m_th_drag >= 0 && evt.Dragging() && evt.LeftIsDown()) {
+                drag_thread_handle(canvas, evt);
+                return true;
+            }
+            if (evt.LeftUp() && m_th_drag >= 0) {
+                const int which = m_th_drag; m_th_drag = -1;
+                const bool moved = std::abs(evt.GetX() - m_th_press_x) +
+                                   std::abs(evt.GetY() - m_th_press_y) > 3;
+                if (!moved) open_thread_editor(which);
+                return true;
+            }
+            if (evt.LeftDown()) {
+                const int which = hit_test_thread_handle(canvas, evt);
+                if (which >= 0) { start_thread_drag(canvas, evt, which); return true; }
+            }
+        }
+        // Shell gizmo: drag the inward thickness arrow; stationary click opens the inline editor.
+        if (m_sh_active) {
+            if (m_sh_drag && evt.Dragging() && evt.LeftIsDown()) {
+                drag_shell_arrow(canvas, evt);
+                return true;
+            }
+            if (evt.LeftUp() && m_sh_drag) {
+                m_sh_drag = false;
+                const bool moved = std::abs(evt.GetX() - m_sh_press_x) +
+                                   std::abs(evt.GetY() - m_sh_press_y) > 3;
+                if (!moved) open_shell_editor();
+                return true;
+            }
+            if (evt.LeftDown() && hit_test_shell_arrow(canvas, evt)) {
+                start_shell_drag(canvas, evt);
+                return true;
+            }
+        }
+        // Left-drag rubber band -> whole body. Past the click budget the press becomes a sweep:
+        // the rectangle is anchored at the ORIGINAL press point (not at the frame where the
+        // threshold was crossed, which would lose the first few pixels) and the events are
+        // consumed from here on. Left-drag no longer orbits in this canvas — DesignCanvas puts
+        // orbit on middle-drag and pan on right-drag, the CAD convention — so nothing downstream
+        // is being starved of a gesture it used to own.
+        // HOVER PRE-HIGHLIGHT (9xw part 3): say what a click would take, before it is
+        // taken. Plain motion only — no button down, no band running — because during a drag the
+        // pointer is doing something else and a promise about clicking would be a lie. Returns
+        // false so the event still reaches the camera; this only asks for a repaint, it does not
+        // consume the gesture, which is the difference between a hint and a handler.
+        if (evt.Moving() && !evt.LeftIsDown() && !m_rubber.is_dragging()) {
+            if (update_solid_hover(canvas, evt)) canvas.set_as_dirty();
+            return false;
+        }
+        if (evt.Dragging() && evt.LeftIsDown() && m_pick_pending) {
+            if (!m_rubber.is_dragging()) {
+                if (std::max(std::abs(evt.GetX() - m_pick_press_x),
+                             std::abs(evt.GetY() - m_pick_press_y)) <= 8)
+                    return false;                    // still inside the click budget
+                m_rubber.start_dragging(Vec2d(m_pick_press_x, m_pick_press_y),
+                                        GLSelectionRectangle::Select);
+            }
+            m_rubber.dragging(Vec2d(evt.GetX(), evt.GetY()));
+            return true;
+        }
+        // Any event with the left button up ends a band — not just LeftUp. A release that lands
+        // outside the canvas never sends us one, and a band left running would then paint a
+        // rectangle that follows the cursor with no button held.
+        if (m_rubber.is_dragging() && !evt.LeftIsDown()) {
+            m_pick_pending = false;
+            if (evt.LeftUp()) pick_bodies_in_rectangle();   // a release elsewhere selects nothing
+            m_rubber.stop_dragging();
+            return evt.LeftUp();
+        }
+        // Click vs drag. Consuming the LeftDown here killed camera orbit/pan the moment a
+        // solid was on screen: Orca starts a rotate drag on the press, so swallowing it meant
+        // the canvas never began one. (A SpaceMouse kept working — it never goes through
+        // wxMouseEvent.) Remember the press, let it fall through so the canvas can orbit, and
+        // resolve the pick on release only if the pointer stayed put.
+        if (evt.LeftDown()) {
+            m_pick_press_x = evt.GetX();
+            m_pick_press_y = evt.GetY();
+            m_pick_pending = true;
+            dp_pick_trace("down x=%d y=%d", evt.GetX(), evt.GetY());
+            return false;
+        }
+        if (!(evt.LeftUp() && m_pick_pending)) {
+            if (evt.LeftUp()) dp_pick_trace("up with no pending press (press was eaten upstream)");
+            return false;
+        }
+        m_pick_pending = false;
+        dp_pick_trace("up x=%d y=%d drift=%d", evt.GetX(), evt.GetY(),
+                      std::max(std::abs(evt.GetX() - m_pick_press_x),
+                               std::abs(evt.GetY() - m_pick_press_y)));
+        // Threshold per axis, at GTK's own drag threshold. A hand-held mouse drifts several
+        // pixels during an ordinary click — a tight budget silently swallowed real clicks and
+        // looked exactly like "selection does not work". Synthetic clicks never drift, which
+        // is why the headless rig could not show this.
+        if (std::max(std::abs(evt.GetX() - m_pick_press_x),
+                     std::abs(evt.GetY() - m_pick_press_y)) > 8) {
+            dp_pick_trace("rejected as drag");
+            return false;   // it was a drag: the canvas already orbited, don't also select
+        }
+        // Committed-sketch loop pick is computed FIRST. A click that lands on a loop's
+        // STROKE (edge) selects that loop even when it lies on a solid face — so a sketch
+        // drawn ON a face can be selected and extruded/cut (Onshape engraving workflow).
+        // Open-face area (no loop stroke under the cursor) falls through to the solid
+        // whole/face/edge cycle; an interior hit with no solid behind it is the last resort.
+        Point pos(evt.GetX(), evt.GetY());
+        const Linef3 ray  = canvas.mouse_ray(pos);
+        const Linef3 ray8 = canvas.mouse_ray(Point(evt.GetX() + 8, evt.GetY()));
+        int    edge_feat = -1, edge_reg = -1, edge_ent = -1; double edge_d = 1e30;  // nearest stroke
+        int    face_feat = -1, face_reg = -1;                        // interior (fallback)
+        dp_pick_trace("display sketches available: %zu", m_display_sketches.size());
+        for (const DisplaySketch& d : m_display_sketches) {
+            const Vec2d p   = d.plane.project(ray.a,  ray.vector());
+            const Vec2d p8  = d.plane.project(ray8.a, ray8.vector());
+            const double tol = std::max(1e-3, (p8 - p).norm());
+            hit_display_sketch(d, p, tol, edge_feat, edge_reg, edge_ent, edge_d, face_feat, face_reg);
+        }
+        // A precise hit on a loop outline wins over the solid face beneath it.
+        if (edge_feat >= 0) {
+            m_display_pick = edge_feat; m_display_pick_region = edge_reg;
+            if (on_display_sketch_selected) on_display_sketch_selected(edge_feat, edge_reg, edge_ent);
+            return true;
+        }
+        // No loop stroke under the cursor: the solid is the foreground (whole/face/edge cycle).
+        if (handle_solid_click(canvas, evt)) return true;
+        // Interior of a committed loop with no solid behind it.
+        if (face_feat >= 0) {
+            m_display_pick = face_feat; m_display_pick_region = face_reg;
+            if (on_display_sketch_selected) on_display_sketch_selected(face_feat, face_reg, -1);
+            return true;
+        }
+        m_display_pick = -1; m_display_pick_region = -1;  // clicked bare plate -> drop highlight
+        // ...and the SOLID selection goes with it (od0). A click that hits nothing has to
+        // mean what a rubber band that sweeps nothing already means — pick_bodies_in_rectangle
+        // clears on an empty sweep, and the two gestures cannot disagree about the same outcome.
+        // Until now the face survived a click on bare plate, so "click away, then click the face
+        // again" arrived here as the SECOND click on the same face and escalated to the whole
+        // body, when the click away was the user letting go of it.
+        //
+        // The cost is real and is the intended trade: Thicken / Shell / Draft hold their input
+        // face in the panel's m_sel_solid_face, so a stray click on empty canvas with one of
+        // those cards open gives that face back. Their handlers already write the "(pick a solid
+        // face)" placeholder and rebuild the ghost at level 0, so the card SAYS it lost the pick
+        // rather than confirming against a face the viewport has stopped highlighting.
+        //
+        // Guarded on there being something to clear: this runs on every click that misses, and
+        // the callback re-renders the open card's preview.
+        if (m_solid_sel != SolidSel::None) {
+            clear_solid_selection();
+            dp_pick_trace("clicked empty space -> selection cleared");
+            if (on_solid_selection_changed)
+                on_solid_selection_changed(int(m_solid_sel), m_sel_body, m_sel_face, m_sel_edge);
+        }
+        // Last resort: a click that hit no geometry but landed on a reference/base plane picks it.
+        if (m_dbp_active) {
+            const int h = hit_test_base_pick(canvas, evt);
+            if (h >= 0 && h < int(m_dbp_base.size())) {
+                if (on_datum_base_picked) on_datum_base_picked(m_dbp_base[h]);
+                return true;
+            }
+        }
+        return false;                                     // let the stock canvas orbit / deselect
+    }
+
+    // In-canvas edit-op tools (Fillet/Chamfer/Offset/Mirror): pick entities, then a
+    // draggable arrow + editable value label (Mirror: a two-phase pick) drives a live
+    // ghost. A click on empty space confirms; right-click/Esc cancels the gesture.
+    // Standalone Trim / Extend scissors: click a segment to cut it back to (Trim) or out to
+    // (Extend) its nearest intersection with the other live entities. One cut per click; the
+    // tool stays active for more cuts; right-click exits. Drag falls through so the camera can
+    // still orbit. Operates directly on the live sketch — no Constrain mode.
+    if (m_mode == Mode::Trim || m_mode == Mode::Extend) {
+        if (evt.Moving()) { screen_to_plane(canvas, evt, m_cursor); m_has_cursor = true; return true; }
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            const Linef3 r2 = canvas.mouse_ray(Point(evt.GetX() + 8, evt.GetY()));
+            const double tol = std::max(1e-3, (m_plane.project(r2.a, r2.vector()) - p).norm());
+            if (apply_live_trim(p, tol * 3.0, m_mode == Mode::Extend)) {
+                resolve_live();
+            } else if (on_readout) {
+                // nde #15: don't fail silently. The pick found nothing to cut/extend — either
+                // the click missed every live segment, or the picked segment has no crossing /
+                // target among the OTHER live entities (committed sketches aren't trimmed).
+                on_readout(m_mode == Mode::Extend
+                    ? std::string("Extend: click a line/arc that can reach another live entity")
+                    : std::string("Trim: click a segment where it crosses another live entity"));
+            }
+            return true;
+        }
+        if (evt.RightDown()) { request_exit(); return true; }
+        return false;   // let move/drag orbit the camera
+    }
+
+    if (is_edit_op_mode()) {
+        if (evt.Moving()) {
+            screen_to_plane(canvas, evt, m_cursor);
+            m_has_cursor = true;
+            return true;
+        }
+        if (m_op_dragging_arrow && evt.Dragging() && evt.LeftIsDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            drag_op_arrow(p);
+            return true;
+        }
+        if (evt.LeftUp()) {
+            if (m_op_dragging_arrow) { m_op_dragging_arrow = false; return true; }
+            return false;
+        }
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            const Linef3 r2 = canvas.mouse_ray(Point(evt.GetX() + 8, evt.GetY()));
+            const double tol = std::max(1e-3, (m_plane.project(r2.a, r2.vector()) - p).norm());
+            // 1) live gizmo: click the value label to type, or grab the arrow to drag.
+            if (op_ready() && m_mode != Mode::Mirror) {
+                const Linef3 rl = canvas.mouse_ray(Point(evt.GetX() + 24, evt.GetY()));
+                const double ltol = std::max(tol, (m_plane.project(rl.a, rl.vector()) - p).norm());
+                if ((m_op_label - p).norm() <= ltol) { open_op_editor(); return true; }
+                if (hit_test_op_arrow(p, tol))        { m_op_dragging_arrow = true; return true; }
+            }
+            // 2) entity pick (close enough to an entity edge).
+            double best = 1e30; int bi = -1;
+            for (size_t i = 0; i < m_entities.size(); ++i) {
+                const double d = entity_pick_dist(p, m_entities[i]);
+                if (d < best) { best = d; bi = int(i); }
+            }
+            if (bi >= 0 && best <= tol * 3.0) { op_pick(bi); return true; }
+            // 3) empty click confirms a ready gesture.
+            if (op_ready()) confirm_op();
+            return true;
+        }
+        if (evt.RightDown()) {
+            if (m_op_a >= 0 || !m_mirror_targets.empty()) {
+                reset_op();
+                m_selection.clear();
+                if (on_selection_changed) on_selection_changed(0);
+            } else {
+                request_exit();
+            }
+            return true;
+        }
+        return false;
+    }
+
+    // In-canvas transform tools (Move/Rotate/Scale/Array/PolarArray): pick subject
+    // entities, then a single draggable handle + editable value label(s) drive a live
+    // ghost. A click on empty space confirms; right-click drops the gesture / exits.
+    if (is_transform_mode()) {
+        if (evt.Moving()) {
+            screen_to_plane(canvas, evt, m_cursor);
+            m_has_cursor = true;
+            return true;
+        }
+        if (m_tf_dragging && evt.Dragging() && evt.LeftIsDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            drag_tf_handle(p);
+            return true;
+        }
+        if (evt.LeftUp()) {
+            if (m_tf_dragging) { m_tf_dragging = false; return true; }
+            return false;
+        }
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            const Linef3 r2 = canvas.mouse_ray(Point(evt.GetX() + 8, evt.GetY()));
+            const double tol = std::max(1e-3, (m_plane.project(r2.a, r2.vector()) - p).norm());
+            // 1) live gizmo: click a value label to type, or grab the handle to drag.
+            if (tf_ready()) {
+                const Linef3 rl = canvas.mouse_ray(Point(evt.GetX() + 24, evt.GetY()));
+                const double ltol = std::max(tol, (m_plane.project(rl.a, rl.vector()) - p).norm());
+                if ((m_tf_label_a - p).norm() <= ltol) { open_tf_editor_a();     return true; }
+                if ((m_tf_label_b - p).norm() <= ltol) { open_tf_editor_count(); return true; }
+                if (hit_test_tf_handle(p, tol))        { m_tf_dragging = true;   return true; }
+            }
+            // 2) entity pick (close enough to an entity edge).
+            double best = 1e30; int bi = -1;
+            for (size_t i = 0; i < m_entities.size(); ++i) {
+                const double d = entity_pick_dist(p, m_entities[i]);
+                if (d < best) { best = d; bi = int(i); }
+            }
+            if (bi >= 0 && best <= tol * 3.0) { tf_pick(bi); return true; }
+            // 3) empty click confirms a ready gesture.
+            if (tf_ready()) confirm_transform();
+            return true;
+        }
+        if (evt.RightDown()) {
+            if (!m_tf_targets.empty()) {
+                reset_tf();
+                m_selection.clear();
+                if (on_selection_changed) on_selection_changed(0);
+            } else {
+                request_exit();
+            }
+            return true;
+        }
+        return false;
+    }
+
+    // Imported-art bbox transform: drag a corner to scale, the centre to move. Right-click
+    // ends the session. Values stream live to the host via on_imported_transform.
+    if (m_mode == Mode::TransformArt) {
+        if (evt.Moving()) {
+            screen_to_plane(canvas, evt, m_cursor);
+            m_has_cursor = true;
+            return true;
+        }
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            const Linef3 r2 = canvas.mouse_ray(Point(evt.GetX() + 10, evt.GetY()));
+            const double tol = std::max(1e-3, (m_plane.project(r2.a, r2.vector()) - p).norm());
+            const int h = hit_test_xform_handle(p, tol);
+            if (h >= 0) {
+                m_xform_handle = h;
+                if (h == 4) m_xform_anchor = p;             // centre move: track the delta
+                else { Vec2d c[4]; xform_world_corners(c); m_xform_anchor = c[(h + 2) % 4]; }
+            }
+            return true;                                     // swallow (no camera orbit while placing)
+        }
+        if (m_xform_handle >= 0 && evt.Dragging() && evt.LeftIsDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            drag_xform_handle(p);
+            return true;
+        }
+        if (evt.LeftUp()) { m_xform_handle = -1; return true; }
+        if (evt.RightDown()) { if (on_exit) on_exit(); else cancel(); return true; }
+        return false;
+    }
+
+    // Constrain mode: pick a segment on click; let move/drag fall through so the
+    // camera can still orbit while inspecting the sketch.
+    if (m_mode == Mode::Constrain) {
+        if (m_constrain_entities) {
+            // Pick any entity (line/circle/arc/point): rolling two-slot selection.
+            if (evt.LeftDown()) {
+                Vec2d p;
+                screen_to_plane(canvas, evt, p);
+                double best = 1e30;
+                int bi = -1;
+                for (size_t i = 0; i < m_entities.size(); ++i) {
+                    const double d = entity_pick_dist(p, m_entities[i]);
+                    if (d < best) { best = d; bi = int(i); }
+                }
+                if (bi >= 0) {
+                    // Rolling three-slot selection: slots 0/1 feed all 2-entity
+                    // constraints; slot 2 is the Symmetric axis (only filled once
+                    // 0 and 1 are set). A click past slot 2 restarts the cycle.
+                    if (m_pick0 < 0)                                         { m_pick0 = bi; m_pick0_pt = p; }
+                    else if (m_pick1 < 0 && bi != m_pick0)                    m_pick1 = bi;
+                    else if (m_pick1 >= 0 && m_pick2 < 0 && bi != m_pick0 && bi != m_pick1) m_pick2 = bi;
+                    else                                                     { m_pick0 = bi; m_pick1 = m_pick2 = -1; m_pick0_pt = p; }
+                }
+                return true;
+            }
+            if (evt.RightDown()) { cancel(); return true; }
+            return false;
+        }
+        if (evt.LeftDown()) {
+            if (m_points.size() < 2)
+                return false;
+            Vec2d p;
+            screen_to_plane(canvas, evt, p);
+            const size_t n = m_points.size();
+            double best = 1e30;
+            int bi = -1;
+            for (size_t i = 0; i < n; ++i) {
+                const double d = point_segment_dist(p, m_points[i], m_points[(i + 1) % n]);
+                if (d < best) { best = d; bi = int(i); }
+            }
+            if (bi >= 0) {
+                m_sel_a = bi;
+                m_sel_b = int((bi + 1) % n);
+            }
+            return true;
+        }
+        if (evt.RightDown()) {
+            cancel();
+            return true;
+        }
+        return false;
+    }
+
+    // Selection mode: click to pick an entity, Shift/Ctrl to extend, double-click
+    // to grab the whole connected loop. Drag falls through so the camera can orbit.
+    if (m_mode == Mode::Select) {
+        if (update_hover(canvas, evt)) return true;   // repaint when the hovered handle changes
+        const bool extend = evt.ShiftDown() || evt.ControlDown();
+
+        // A constraint badge is a click target: clicking it DELETES that constraint. Existing or
+        // not is the whole of a constraint's state, so this click is the toggle. Checked before
+        // entity picking because badges sit clear of the geometry (offset along +Y), so a hit
+        // here is unambiguous; plain click only, so Shift/Ctrl multi-select is never eaten.
+        if (evt.LeftDown() && !extend) {
+            Vec2d gp;
+            if (screen_to_plane(canvas, evt, gp) && remove_constraint_near(gp)) {
+                if (on_selection_changed)
+                    on_selection_changed(int(m_selection.size() + m_point_sel.size()));
+                return true;
+            }
+        }
+
+        // Live point drag: once an endpoint/centre was grabbed on LeftDown, dragging
+        // moves it (re-solving constraints live) until the button is released. When
+        // nothing is grabbed, drag falls through so the camera can still orbit.
+        if (m_dragging_point && evt.Dragging() && evt.LeftIsDown()) {
+            Vec2d p;
+            screen_to_plane(canvas, evt, p);
+            if (m_drag_poly_fi >= 0)
+                drag_polygon_vertex(m_drag_poly_fi, m_drag_ei, m_drag_role, p);  // keep regular
+            else if (m_drag_rect_fi >= 0)
+                drag_rect_corner(m_drag_rect_fi, p);          // resize axis-aligned box
+            else if (m_drag_slot_fi >= 0)
+                drag_slot_handle(m_drag_slot_fi, p);          // move a slot end
+            else if (m_drag_ei >= 0 && m_drag_ei < int(m_entities.size()) &&
+                     m_entities[m_drag_ei].type == SketchEntity::Type::Arc)
+                drag_arc_handle(m_drag_ei, m_drag_role, p);   // center/radius/angle grips
+            else if (m_drag_ei >= 0 && m_drag_ei < int(m_entities.size()) &&
+                     m_entities[m_drag_ei].type == SketchEntity::Type::EllipseArc)
+                drag_ellipsearc_handle(m_drag_ei, m_drag_role, p);  // center/sweep endpoints
+            else {
+                set_point(m_drag_ei, m_drag_role, p);
+                resolve_live_drag(m_drag_ei, m_drag_role);
+            }
+            return true;
+        }
+        // Derived-handle drag (A4): the circle RadiusHandle (and later slot/rect/etc.)
+        // isn't an entity point, so it rides set_handle, which applies the role-specific
+        // geometry edit + re-solve.
+        if (m_dragging_handle && evt.Dragging() && evt.LeftIsDown()) {
+            Vec2d p;
+            screen_to_plane(canvas, evt, p);
+            set_handle(m_drag_handle, p);
+            return true;
+        }
+        if (evt.LeftUp()) {
+            if (m_dragging_point) {
+                Vec2d p;
+                screen_to_plane(canvas, evt, p);
+                if (m_drag_poly_fi >= 0)
+                    drag_polygon_vertex(m_drag_poly_fi, m_drag_ei, m_drag_role, p);
+                else if (m_drag_rect_fi >= 0)
+                    drag_rect_corner(m_drag_rect_fi, p);
+                else if (m_drag_slot_fi >= 0)
+                    drag_slot_handle(m_drag_slot_fi, p);
+                else if (m_drag_ei >= 0 && m_drag_ei < int(m_entities.size()) &&
+                         m_entities[m_drag_ei].type == SketchEntity::Type::Arc)
+                    drag_arc_handle(m_drag_ei, m_drag_role, p);
+                else if (m_drag_ei >= 0 && m_drag_ei < int(m_entities.size()) &&
+                         m_entities[m_drag_ei].type == SketchEntity::Type::EllipseArc)
+                    drag_ellipsearc_handle(m_drag_ei, m_drag_role, p);
+                else {
+                    set_point(m_drag_ei, m_drag_role, p);
+                    resolve_live_drag(m_drag_ei, m_drag_role);
+                }
+                m_dragging_point = false;
+                m_drag_ei = -1;
+                m_drag_poly_fi = -1;
+                m_drag_rect_fi = -1;
+                m_drag_slot_fi = -1;
+                return true;
+            }
+            if (m_dragging_handle) {
+                Vec2d p;
+                screen_to_plane(canvas, evt, p);
+                set_handle(m_drag_handle, p);
+                m_dragging_handle = false;
+                return true;
+            }
+            return false;
+        }
+
+        if (evt.LeftDown() || evt.LeftDClick()) {
+            m_dragging_point = false;           // a fresh press disarms any stale grab
+            m_dragging_handle = false;
+            m_drag_poly_fi = -1;
+            m_drag_rect_fi = -1;
+            m_drag_slot_fi = -1;
+            Vec2d p;
+            screen_to_plane(canvas, evt, p);
+            if (evt.LeftDClick()) {                // double-click a quote label -> edit it
+                const Linef3 rd = canvas.mouse_ray(Point(evt.GetX() + 28, evt.GetY()));
+                const double dtol = std::max(2.0, (m_plane.project(rd.a, rd.vector()) - p).norm());
+                const int di = hit_test_dimension(p, dtol);
+                if (di >= 0) { edit_dimension(di); return true; }
+            }
+            // Zoom-aware tolerance: project a point 8 px away and measure in plane units.
+            const Linef3 r2 = canvas.mouse_ray(Point(evt.GetX() + 8, evt.GetY()));
+            const Vec2d p2 = m_plane.project(r2.a, r2.vector());
+            const double tol = std::max(1e-3, (p2 - p).norm());
+
+            // Single-click a dimension quote label -> edit its value in place. A placed
+            // driving quote reopens its editor; a live (non-driving) characteristic quote
+            // is first promoted to a driving dimension (place_dimension), then its editor
+            // opens — so typing a value sets the precise dimension. Generous label
+            // tolerance (~24 px) since text labels are wider than a point grip.
+            if (evt.LeftDown()) {
+                const Linef3 rdl = canvas.mouse_ray(Point(evt.GetX() + 24, evt.GetY()));
+                const double ltol = std::max(tol, (m_plane.project(rdl.a, rdl.vector()) - p).norm());
+                const int di = hit_test_dimension(p, ltol);
+                if (di >= 0) { open_value_editor(di); return true; }
+                for (const DimAnnot& q : m_live_quotes) {
+                    if ((q.label_pos - p).norm() <= ltol) {
+                        if (q.kind == DimType::Angle)
+                            open_angle_editor(q.ea);   // geometric rotate to a typed angle
+                        else
+                            place_dimension(q);        // promote -> driving dim + open editor
+                        return true;
+                    }
+                }
+                if (m_live_poly_fi >= 0) {
+                    if ((m_live_poly_side_label - p).norm() <= ltol) {
+                        open_polygon_side_editor(m_live_poly_fi);   // geometric uniform scale
+                        return true;
+                    }
+                    if ((m_live_poly_angle_label - p).norm() <= ltol) {
+                        open_polygon_angle_editor(m_live_poly_fi);  // geometric rotate
+                        return true;
+                    }
+                }
+                if (m_live_arc_ei >= 0 && (m_live_arc_angle_label - p).norm() <= ltol) {
+                    open_arc_angle_editor(m_live_arc_ei);           // geometric sweep change
+                    return true;
+                }
+                if (m_live_ellipse_ei >= 0) {
+                    if ((m_live_ellipse_major_label - p).norm() <= ltol) {
+                        open_ellipse_axis_editor(m_live_ellipse_ei, true);   // semi-major
+                        return true;
+                    }
+                    if ((m_live_ellipse_minor_label - p).norm() <= ltol) {
+                        open_ellipse_axis_editor(m_live_ellipse_ei, false);  // semi-minor
+                        return true;
+                    }
+                }
+                if (m_live_rrect_fi >= 0) {
+                    if ((m_live_rrect_w_label - p).norm() <= ltol) { open_rounded_rect_editor(m_live_rrect_fi, 0); return true; }
+                    if ((m_live_rrect_h_label - p).norm() <= ltol) { open_rounded_rect_editor(m_live_rrect_fi, 1); return true; }
+                    if ((m_live_rrect_r_label - p).norm() <= ltol) { open_rounded_rect_editor(m_live_rrect_fi, 2); return true; }
+                }
+                if (m_live_aslot_fi >= 0) {
+                    if ((m_live_aslot_r_label - p).norm() <= ltol) { open_arc_slot_editor(m_live_aslot_fi, true);  return true; }
+                    if ((m_live_aslot_w_label - p).norm() <= ltol) { open_arc_slot_editor(m_live_aslot_fi, false); return true; }
+                }
+                if (m_live_slot_fi >= 0) {
+                    if ((m_live_slot_len_label   - p).norm() <= ltol) { open_slot_editor(m_live_slot_fi, 0); return true; }
+                    if ((m_live_slot_w_label     - p).norm() <= ltol) { open_slot_editor(m_live_slot_fi, 1); return true; }
+                    if ((m_live_slot_angle_label - p).norm() <= ltol) { open_slot_editor(m_live_slot_fi, 2); return true; }
+                }
+            }
+
+            // A derived handle (the circle RadiusHandle — not an entity point, so
+            // hit_test_point can't grab it) arms a handle drag that resizes on motion.
+            // Checked before the point/entity hit-tests so the radius grip wins near
+            // the circle edge.
+            if (evt.LeftDown()) {
+                Handle hh;
+                if (hit_test_handle(p, tol, hh) &&
+                    (hh.role == HandleRole::RadiusHandle || hh.role == HandleRole::MajorAxis ||
+                     hh.role == HandleRole::MinorAxis || hh.role == HandleRole::BSplineCtrl)) {
+                    m_dragging_handle = true;
+                    m_drag_handle     = hh;
+                    m_selection.clear();
+                    m_point_sel.clear();
+                    m_selection.push_back(hh.ei);   // highlight the circle being resized
+                    if (on_selection_changed)
+                        on_selection_changed(int(m_selection.size()));
+                    return true;
+                }
+            }
+
+            // A nearby endpoint/centre selects that POINT (a line = a segment + 2
+            // points); a click on the bare segment selects the whole entity.
+            if (evt.LeftDown()) {
+                int pe; SketchPointRole pr;
+                if (hit_test_point(p, tol, pe, pr)) {
+                    const auto key = std::make_pair(pe, pr);
+                    auto it = std::find(m_point_sel.begin(), m_point_sel.end(), key);
+                    if (extend) {
+                        if (it == m_point_sel.end()) m_point_sel.push_back(key);
+                        else m_point_sel.erase(it);
+                    } else {
+                        m_selection.clear();
+                        m_point_sel.clear();
+                        m_point_sel.push_back(key);
+                    }
+                    // Arm the drag so the grabbed point follows the cursor.
+                    m_dragging_point = true;
+                    m_drag_ei = pe;
+                    m_drag_role = pr;
+                    // If the grabbed point is a polygon vertex, the drag must keep the
+                    // polygon REGULAR — it adjusts the circumradius + orientation (the
+                    // vertex follows the cursor) instead of moving one point freely.
+                    const int pf = feature_of(pe);
+                    m_drag_poly_fi = (pf >= 0 && m_features[pf].kind == FeatureKind::Polygon) ? pf : -1;
+                    m_drag_rect_fi = -1; m_drag_slot_fi = -1;
+                    if (pf >= 0 && m_drag_poly_fi < 0) {
+                        const Feature& ft = m_features[pf];
+                        if (ft.kind == FeatureKind::CornerRect || ft.kind == FeatureKind::CenterRect) {
+                            // Only axis-aligned boxes resize by corner (oblique rects fall
+                            // back to free point move). Capture the fixed opposite corner.
+                            const SketchEntity& e0 = m_entities[ft.begin];
+                            const Vec2d d0 = e0.p1 - e0.p0;
+                            const bool aa = std::abs(d0.x()) < 1e-6 || std::abs(d0.y()) < 1e-6;
+                            Vec2d gp;
+                            if (aa && point_at(pe, pr, gp)) {
+                                Vec2d opp;
+                                opp.x() = (std::abs(gp.x() - ft.c0.x()) < std::abs(gp.x() - ft.c1.x())) ? ft.c1.x() : ft.c0.x();
+                                opp.y() = (std::abs(gp.y() - ft.c0.y()) < std::abs(gp.y() - ft.c1.y())) ? ft.c1.y() : ft.c0.y();
+                                m_drag_rect_fi = pf; m_drag_rect_anchor = opp;
+                            }
+                        } else if (ft.kind == FeatureKind::Slot &&
+                                   pr == SketchPointRole::Center &&
+                                   (pe == ft.begin + 1 || pe == ft.begin + 3)) {
+                            m_drag_slot_fi = pf;                 // cap@c1 = begin+1, cap@c0 = begin+3
+                            m_drag_slot_c1 = (pe == ft.begin + 1);
+                        }
+                    }
+                    if (on_selection_changed)
+                        on_selection_changed(int(m_selection.size() + m_point_sel.size()));
+                    return true;
+                }
+            }
+
+            const int hit = hit_test(p, tol);
+
+            if (evt.LeftDClick() && hit >= 0) {
+                if (!extend) m_selection.clear();
+                for (int idx : connected_loop(hit))
+                    if (std::find(m_selection.begin(), m_selection.end(), idx) == m_selection.end())
+                        m_selection.push_back(idx);
+            } else if (hit >= 0) {
+                auto it = std::find(m_selection.begin(), m_selection.end(), hit);
+                if (extend) {
+                    if (it == m_selection.end()) m_selection.push_back(hit);
+                    else m_selection.erase(it);     // toggle off
+                } else {
+                    m_selection.clear();
+                    m_point_sel.clear();
+                    m_selection.push_back(hit);
+                }
+            } else if (!extend) {
+                // Inside a closed loop (not on an edge/point) → select it as a face
+                // and hand off to the panel, which commits the sketch and extrudes.
+                if (evt.LeftDown() && on_face_selected) {
+                    const int reg = region_at(p);
+                    if (reg >= 0) {
+                        m_selection.clear();
+                        m_point_sel.clear();
+                        on_face_selected(reg);
+                        return true;
+                    }
+                }
+                m_selection.clear();                // clicked empty space
+                m_point_sel.clear();
+            }
+            if (on_selection_changed)
+                on_selection_changed(int(m_selection.size() + m_point_sel.size()));
+            return true;
+        }
+        if (evt.RightDown()) {
+            // Hand the click back (return false) so the offer opens: the m_right_consumed flag
+            // this return value feeds means "the tool USED this right-click", and a plain
+            // right-click in Select mode is not a gesture terminator.
+            //
+            // But do NOT drop the selection on the way out. The offer menu describes WHAT IS
+            // SELECTED, so clearing first guaranteed it could only ever describe nothing: select
+            // a line, right-click, and the sketch verbs — Trim, Extend, Fillet, Chamfer, Offset,
+            // Mirror, the arrays, Constrain — were all greyed, because by the time the menu was
+            // built the line was no longer selected. Reported from the machine as "selected a
+            // line, right-click exit from selection: only create and reference are usable".
+            // Deselecting still has a gesture: left-click on empty space, a few lines above.
+            return false;
+        }
+        return false;                               // let drag orbit the camera
+    }
+
+    // Dimension mode: click entities directly. 2 points -> Distance, a line -> Length,
+    // a circle -> Diameter, an arc -> Radius, a point then a line -> DistanceToLine.
+    // Each resolved pick places a driving quote and pops the value card.
+    if (m_mode == Mode::Dimension) {
+        if (update_hover(canvas, evt)) return true;   // repaint when the hovered handle changes
+        if (evt.LeftDClick()) {                    // double-click a quote label -> edit it
+            Vec2d p;
+            screen_to_plane(canvas, evt, p);
+            const Linef3 r2 = canvas.mouse_ray(Point(evt.GetX() + 28, evt.GetY()));
+            const Vec2d p2 = m_plane.project(r2.a, r2.vector());
+            const double di_tol = std::max(2.0, (p2 - p).norm());
+            const int di = hit_test_dimension(p, di_tol);
+            if (di >= 0) edit_dimension(di);
+            m_dim_has0 = false;
+            return true;
+        }
+        if (evt.LeftDown()) {
+            Vec2d p;
+            screen_to_plane(canvas, evt, p);
+            const Linef3 r2 = canvas.mouse_ray(Point(evt.GetX() + 8, evt.GetY()));
+            const Vec2d p2 = m_plane.project(r2.a, r2.vector());
+            const double tol = std::max(1e-3, (p2 - p).norm());
+            int pe; SketchPointRole pr;
+            const bool got_pt = hit_test_point(p, tol, pe, pr);
+            const int he = hit_test(p, tol);
+            if (!m_dim_has0) {
+                if (got_pt) {                          // first point picked: await a second
+                    m_dim_e0 = pe; m_dim_r0 = pr; m_dim_has0 = true;
+                } else if (he >= 0) {                  // whole-entity dimension
+                    DimAnnot a; a.ea = he;
+                    const SketchEntity::Type t = m_entities[he].type;
+                    if (t == SketchEntity::Type::Line)        { a.kind = DimType::Length;   place_dimension(a); }
+                    else if (t == SketchEntity::Type::Circle) { a.kind = DimType::Diameter; place_dimension(a); }
+                    else if (t == SketchEntity::Type::Arc)    { a.kind = DimType::Radius;   place_dimension(a); }
+                }
+            } else {
+                if (got_pt && !(pe == m_dim_e0 && pr == m_dim_r0)) {
+                    DimAnnot a; a.kind = DimType::Distance;
+                    a.ea = m_dim_e0; a.ra = m_dim_r0; a.eb = pe; a.rb = pr;
+                    place_dimension(a);
+                } else if (he >= 0 && m_entities[he].type == SketchEntity::Type::Line) {
+                    DimAnnot a; a.kind = DimType::DistanceToLine;
+                    a.ea = m_dim_e0; a.ra = m_dim_r0; a.eb = he;
+                    place_dimension(a);
+                }
+                m_dim_has0 = false;                    // reset after the second pick
+            }
+            return true;
+        }
+        if (evt.RightDown()) { m_dim_has0 = false; return true; }
+        return false;                                  // let drag orbit the camera
+    }
+
+    if (evt.Moving()) {
+        m_snap_off = evt.ShiftDown();
+        screen_to_plane(canvas, evt, m_cursor);
+        m_has_cursor = true;
+        m_cursor_locked = false;
+        bool vsnap = false;
+        m_cursor = snap_vertex(canvas, evt, m_cursor, vsnap);   // preview-snap to endpoints
+        // The chain's own start is not an entity yet, so snap_vertex cannot see it. Offer it
+        // here: the cursor lands exactly on it, so the rubber band below IS the closing segment.
+        if (snap_chain_start(canvas, evt, m_cursor)) vsnap = true;
+        const bool line_like = (m_mode == Mode::Polyline || m_mode == Mode::Line);
+        if (line_like && !m_points.empty() && !vsnap)
+            m_cursor = snap_dir(m_points.back(), m_cursor, m_cursor_locked);
+        if (on_cursor_metrics && line_like && !m_points.empty() && !m_awaiting_length) {
+            const Vec2d d = m_cursor - m_points.back();
+            on_cursor_metrics(d.norm(), std::atan2(d.y(), d.x()) * 180.0 / M_PI, m_cursor_locked);
+        }
+        return true;
+    }
+
+    switch (m_mode) {
+
+    case Mode::Polyline: {
+        if (evt.LeftDown()) {
+            Vec2d p;
+            screen_to_plane(canvas, evt, p);
+            m_snap_off = evt.ShiftDown();
+            bool vsnap = false;
+            p = snap_vertex(canvas, evt, p, vsnap);   // snap onto an existing endpoint
+            if (snap_chain_start(canvas, evt, p)) {   // clicked the previewed close target
+                const int base = int(m_entities.size());
+                push_closed_lines(m_points);  // close the loop
+                infer_auto_constraints(base); // loop self-closes via auto Coincident + H/V
+                m_points.clear();
+                return true;
+            }
+            if (!m_points.empty() && !vsnap) {
+                bool lk = false;
+                p = snap_dir(m_points.back(), p, lk);  // lock new segment to inference angle
+            }
+            m_points.push_back(p);
+            arm_polyline_segment_edit();   // refine this segment's Length+Angle, then continue
+            return true;
+        }
+        if (evt.LeftDClick()) {
+            if (m_points.size() >= 2) {
+                const int base = int(m_entities.size());
+                push_open_chain(m_points);     // end as an open chain
+                infer_auto_constraints(base);
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown() && m_points.empty())
+            return false;               // no chain to end — ghcz, let the offer open
+        if (evt.RightDown()) {
+            // END the chain — do NOT close it. This used to call push_closed_lines() for three
+            // or more points, i.e. it drew a final segment from the last point back to the
+            // first that the user never asked for, and did it silently. No mainstream sketcher
+            // does that: FreeCAD, Fusion and Onshape all end an open chain on right-click and
+            // require the close to be EXPLICIT. Ours has that gesture — click the chain's first
+            // point, which snap_chain_start() previews and snaps onto in the LeftDown branch
+            // above, so the closing segment is on screen BEFORE it is committed. A closed loop
+            // is this tab's goal and it stays a four-action triangle either way; what changes
+            // is that the closing edge is now something the user saw and chose, not one the
+            // app appended on their behalf.
+            const int base = int(m_entities.size());
+            if (m_points.size() >= 2)
+                push_open_chain(m_points);
+            infer_auto_constraints(base);
+            m_points.clear();
+            return true;
+        }
+        break;
+    }
+
+    case Mode::Line: {
+        if (evt.LeftDown()) {
+            Vec2d p;
+            screen_to_plane(canvas, evt, p);
+            m_snap_off = evt.ShiftDown();
+            bool vsnap = false;
+            p = snap_vertex(canvas, evt, p, vsnap);   // snap onto an existing endpoint
+            if (m_points.empty()) {     // first click = anchor
+                m_points.push_back(p);
+                return true;
+            }
+            bool lk = false;
+            if (!vsnap) p = snap_dir(m_points.back(), p, lk);  // vertex snap wins over angle
+            m_points.push_back(p);      // second click completes the segment
+            // Draw-then-edit: just commit the segment. The generic detect/service path
+            // (is_creation_autoedit_mode now includes Line) auto-selects it and opens its
+            // Length THEN Angle fields in sequence, each over its label — same UX as every
+            // other 2D tool. Enter advances (Length drives a Distance constraint, Angle rotates
+            // about P0); Esc keeps it as drawn.
+            keep_segment_as_drawn();
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::CornerRect: {
+        if (evt.LeftDown()) {
+            Vec2d p;
+            screen_to_plane(canvas, evt, p);
+            if (m_points.empty()) {
+                m_points.push_back(p);
+            } else {
+                const Vec2d A = m_points[0];
+                const Vec2d B = p;
+                const int base = int(m_entities.size());
+                begin_feature(FeatureKind::CornerRect);
+                push_closed_lines({ A, Vec2d(B.x(), A.y()), B, Vec2d(A.x(), B.y()) });
+                infer_auto_constraints(base);   // corners Coincident + sides H/V
+                end_feature(A, B);              // group: Width/Height live quotes
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::CenterRect: {
+        if (evt.LeftDown()) {
+            Vec2d p;
+            screen_to_plane(canvas, evt, p);
+            if (m_points.empty()) {
+                m_points.push_back(p);
+            } else {
+                const Vec2d C = m_points[0];
+                const double hx = std::abs(p.x() - C.x());
+                const double hy = std::abs(p.y() - C.y());
+                const int base = int(m_entities.size());
+                begin_feature(FeatureKind::CenterRect);
+                push_closed_lines({
+                    Vec2d(C.x() - hx, C.y() - hy), Vec2d(C.x() + hx, C.y() - hy),
+                    Vec2d(C.x() + hx, C.y() + hy), Vec2d(C.x() - hx, C.y() + hy) });
+                infer_auto_constraints(base);
+                end_feature(Vec2d(C.x() - hx, C.y() - hy), Vec2d(C.x() + hx, C.y() + hy));
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::ObliqueRect: {
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            bool vsnap = false;
+            if (m_points.size() < 2)                 // corners snap; 3rd click is the width
+                p = snap_vertex(canvas, evt, p, vsnap);
+            m_points.push_back(p);
+            if (m_points.size() == 3) {
+                const Vec2d A = m_points[0], B = m_points[1];
+                Vec2d u = B - A;
+                if (u.squaredNorm() > 1e-12) {
+                    u.normalize();
+                    const Vec2d n(-u.y(), u.x());
+                    const double w = n.dot(m_points[2] - A);   // signed perpendicular width
+                    const int base = int(m_entities.size());
+                    begin_feature(FeatureKind::CornerRect);
+                    push_closed_lines({ A, B, B + n * w, A + n * w });
+                    infer_auto_constraints(base);   // corners Coincident + the AB pair parallel
+                    end_feature(A, B + n * w);      // group: Width/Height live quotes
+                }
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::RoundedRect: {
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            bool vsnap = false;
+            if (m_points.size() < 2)                 // the two corners snap; 3rd sets radius
+                p = snap_vertex(canvas, evt, p, vsnap);
+            m_points.push_back(p);
+            if (m_points.size() == 3) {
+                const int base = int(m_entities.size());
+                begin_feature(FeatureKind::RoundedRect);
+                append_entities(make_rounded_rect(m_points[0], m_points[1], m_points[2]));
+                infer_auto_constraints(base);
+                // Group with the actual clamped fillet radius so the W/H/R live quotes
+                // and rebuild edits can recover the box. (Skip grouping if degenerate.)
+                const Vec2d a = m_points[0], b = m_points[1];
+                const double xmin=std::min(a.x(),b.x()), xmax=std::max(a.x(),b.x());
+                const double ymin=std::min(a.y(),b.y()), ymax=std::max(a.y(),b.y());
+                const double bw=xmax-xmin, bh=ymax-ymin;
+                const Vec2d cs[4]={{xmin,ymin},{xmax,ymin},{xmax,ymax},{xmin,ymax}};
+                double r=1e18; for(const Vec2d&c:cs) r=std::min(r,(m_points[2]-c).norm());
+                r=std::min(r, std::min(bw,bh)*0.5);
+                end_feature(Vec2d(xmin,ymin), Vec2d(xmax,ymax), r);
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::CenterCircle: {
+        if (evt.LeftDown()) {
+            Vec2d p;
+            screen_to_plane(canvas, evt, p);
+            if (m_points.empty()) {
+                m_points.push_back(p);
+            } else {
+                const Vec2d C = m_points[0];
+                push_circle(C, (p - C).norm());
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::TwoPointCircle: {
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            bool vsnap = false;
+            p = snap_vertex(canvas, evt, p, vsnap);   // diameter ends snap onto geometry
+            m_points.push_back(p);
+            if (m_points.size() == 2) {
+                const Vec2d C = (m_points[0] + m_points[1]) * 0.5;
+                push_circle(C, (m_points[1] - m_points[0]).norm() * 0.5);
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::ThreePointCircle: {
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            m_points.push_back(p);
+            if (m_points.size() == 3) {
+                append_entities(make_three_point_circle(m_points[0], m_points[1], m_points[2]));
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::ThreePointArc: {
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            bool vsnap = false;
+            if (m_points.size() < 2)                 // snap the start/end onto endpoints
+                p = snap_vertex(canvas, evt, p, vsnap);  // (the 3rd click is the through-point)
+            m_points.push_back(p);
+            if (m_points.size() == 3) {
+                // clicks: start, end, point-on-arc
+                const int base = int(m_entities.size());
+                append_entities(make_three_point_arc(m_points[0], m_points[1], m_points[2]));
+                infer_auto_constraints(base);   // arc ends Coincident onto snapped vertices
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::TangentArc: {
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            bool vsnap = false;
+            p = snap_vertex(canvas, evt, p, vsnap);   // snap both ends onto endpoints
+            m_points.push_back(p);
+            if (m_points.size() == 2) {
+                const int base = int(m_entities.size());
+                append_entities(make_tangent_arc(m_points[0], m_points[1]));
+                infer_auto_constraints(base);   // tangent-arc ends Coincident onto vertices
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::CenterArc: {
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            bool vsnap = false;
+            // The start (2nd click) snaps onto endpoints; center & end-dir are free.
+            if (m_points.size() == 1)
+                p = snap_vertex(canvas, evt, p, vsnap);
+            m_points.push_back(p);
+            if (m_points.size() == 3) {
+                const int base = int(m_entities.size());
+                append_entities(make_center_arc(m_points[0], m_points[1], m_points[2]));
+                infer_auto_constraints(base);   // arc start Coincident onto a snapped vertex
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::Slot: {
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            if (m_points.size() < 2) {
+                m_points.push_back(p);
+            } else {
+                // third click sets the half-width (distance to the centerline)
+                Vec2d u = m_points[1] - m_points[0];
+                if (u.squaredNorm() > 1e-12) {
+                    u.normalize();
+                    const Vec2d n(-u.y(), u.x());
+                    const double w = std::abs(n.dot(p - m_points[0]));
+                    const int base = int(m_entities.size());
+                    begin_feature(FeatureKind::Slot);
+                    append_entities(make_slot(m_points[0], m_points[1], w));
+                    infer_auto_constraints(base);
+                    end_feature(m_points[0], m_points[1], w);  // centres + half-width
+                }
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::ArcSlot: {
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            bool vsnap = false;
+            if (m_points.size() == 1)                // start snaps; center & end-dir are free
+                p = snap_vertex(canvas, evt, p, vsnap);
+            m_points.push_back(p);
+            if (m_points.size() == 4) {
+                // clicks: center, start, end-dir, width
+                const double Rc = (m_points[1] - m_points[0]).norm();
+                const double w  = std::abs((m_points[3] - m_points[0]).norm() - Rc);
+                const int base = int(m_entities.size());
+                begin_feature(FeatureKind::ArcSlot);
+                append_entities(make_arc_slot(m_points[0], m_points[1], m_points[2], w));
+                infer_auto_constraints(base);
+                // c0 = centre, c1 = centreline start point; param = half-width. The end
+                // direction is recovered from the cap@E arc centre when rebuilding.
+                end_feature(m_points[0], m_points[1], w);
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::Polygon: {
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            if (m_points.empty()) {
+                m_points.push_back(p);
+            } else {
+                const int base = int(m_entities.size());
+                begin_feature(FeatureKind::Polygon);
+                append_entities(make_polygon(m_points[0], p, m_polygon_sides));
+                infer_auto_constraints(base);
+                end_feature(m_points[0], p, (p - m_points[0]).norm(), m_polygon_sides);
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::Ellipse: {
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            bool vsnap = false;
+            if (m_points.empty()) p = snap_vertex(canvas, evt, p, vsnap);   // center can snap
+            m_points.push_back(p);
+            if (m_points.size() == 3) {                                     // center, major-end, minor
+                const int base = int(m_entities.size());
+                append_entities(make_ellipse(m_points[0], m_points[1], m_points[2]));
+                infer_auto_constraints(base);
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::EllipseArc: {
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            bool vsnap = false;
+            if (m_points.empty()) p = snap_vertex(canvas, evt, p, vsnap);   // center can snap
+            m_points.push_back(p);
+            if (m_points.size() == 5) {                                     // center, major, minor, start, end
+                const int base = int(m_entities.size());
+                append_entities(make_ellipse_arc(m_points[0], m_points[1], m_points[2],
+                                                  m_points[3], m_points[4]));
+                infer_auto_constraints(base);
+                m_points.clear();
+            }
+            return true;
+        }
+        if (evt.RightDown()) return right_abandon();
+        break;
+    }
+
+    case Mode::BSpline: {
+        // Variable-length: left-click adds a control pole (each can snap onto existing
+        // geometry); double-click or right-click finishes as an open spline.
+        if (evt.LeftDown()) {
+            Vec2d p; screen_to_plane(canvas, evt, p);
+            m_snap_off = evt.ShiftDown();
+            bool vsnap = false;
+            p = snap_vertex(canvas, evt, p, vsnap);   // poles can land on endpoints
+            m_points.push_back(p);
+            return true;
+        }
+        if (evt.RightDown() && m_points.empty())
+            return false;               // no poles down — ghcz, let the offer open
+        if (evt.LeftDClick() || evt.RightDown()) {
+            if (m_points.size() >= 2) {
+                const int base = int(m_entities.size());
+                append_entities(make_bspline(m_points));
+                infer_auto_constraints(base);         // end poles auto-Coincident -> loops close
+            }
+            m_points.clear();
+            return true;
+        }
+        break;
+    }
+
+    case Mode::Point: {
+        if (evt.LeftDown()) {
+            Vec2d p;
+            screen_to_plane(canvas, evt, p);
+            push_point(p);
+            return true;
+        }
+        if (evt.RightDown()) return false;   // no anchor to abandon: the offer belongs here
+        break;
+    }
+
+    case Mode::Constrain:
+        break;
+    }
+
+    if (evt.Dragging())
+        return false;
+
+    return false;
+}
+
+}} // namespace Slic3r::GUI
diff --git a/src/slic3r/GUI/CAD/DesignSketchTool.hpp b/src/slic3r/GUI/CAD/DesignSketchTool.hpp
new file mode 100644
index 0000000000..c88b149c59
--- /dev/null
+++ b/src/slic3r/GUI/CAD/DesignSketchTool.hpp
@@ -0,0 +1,1466 @@
+#ifndef slic3r_DesignSketchTool_hpp_
+#define slic3r_DesignSketchTool_hpp_
+
+#include "libslic3r/Point.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
+#include "libslic3r/CAD/CadDocument.hpp"   // CadBody for per-body solid picking
+#include "libslic3r/CAD/SketchInference.hpp"
+#include "libslic3r/CAD/SketchSolver.hpp"
+#include "slic3r/GUI/GLModel.hpp"
+#include "slic3r/GUI/GLSelectionRectangle.hpp"   // left-drag rubber band over the committed bodies
+#include <functional>
+#include <vector>
+#include <string>
+#include <utility>
+
+class wxMouseEvent;
+class wxPoint;
+
+namespace Slic3r {
+
+class TriangleMesh;   // fwd (libslic3r) — solid-pick mesh, non-owning pointer
+
+namespace GUI {
+
+class GLCanvas3D;
+class Camera;     // fwd — move_gizmo_arm() sizes the gizmo from the current zoom
+
+// Onshape-style sketch session. `begin` enters a session on a plane; the active
+// drawing tool (Mode) can be switched mid-session via `set_tool` while entities
+// accumulate. `finish` commits the whole entity list as one sketch feature;
+// `cancel` aborts. Constrain is a separate legacy mode that operates on a
+// committed profile's points (entity constraints land in a later chunk).
+
+
+// ONE colour means SELECTED — a face, an edge, a vertex, a whole body, a 2D sketch region.
+// Nothing else on screen may wear it. Before this there were four near-identical cyans plus a
+// constant still named sel_gold that had long since become cyan, and the UNSELECTED region fill
+// was blue (0.30,0.60,1.0) — one shade from the selected one — so an ordinary region read as
+// picked. Selection is a state, not a decoration: it gets its own colour and keeps it.
+inline ColorRGBA design_selection_color(float alpha = 1.0f)
+{
+    return ColorRGBA(0.20f, 0.85f, 1.00f, alpha);
+}
+// Unselected geometry — 2D regions and faces — is neutral translucent grey, so the only
+// coloured thing in the viewport is the thing you picked.
+inline ColorRGBA design_idle_face_color()
+{
+    return ColorRGBA(0.72f, 0.76f, 0.80f, 0.14f);
+}
+class DesignSketchTool {
+public:
+    enum class Mode { Select, Dimension, Polyline, Line, CornerRect, CenterRect, ObliqueRect,
+                      RoundedRect, CenterCircle, TwoPointCircle, Point,
+                      ThreePointCircle, ThreePointArc, TangentArc, CenterArc, Slot, ArcSlot, Polygon,
+                      Ellipse, EllipseArc, BSpline,
+                      // In-canvas edit-op TOOLBAR tools (drag-arrow + label, no numeric card):
+                      Fillet, Chamfer, Offset, Mirror,
+                      // Standalone scissors: click a segment to trim/extend it (immediate, no card):
+                      Trim, Extend,
+                      // In-canvas transform TOOLBAR tools (pick targets + drag handle/label, no card):
+                      Move, Rotate, Scale, Array, PolarArray,
+                      // In-canvas bounding-box transform for imported Text/SVG art:
+                      TransformArt,
+                      Constrain };
+    // Which tool is armed, and how many anchors it has down. Read-only, for the offer ladder:
+    // "the menu armed the verb I chose" is otherwise unassertable, and a menu walk that lands one
+    // row off arms a NEIGHBOURING tool and then grades whatever that drew. ekt9.
+    Mode mode() const { return m_mode; }
+    int  pending_points() const { return int(m_points.size()); }
+    void emit_step_hint();   // fires on_step_changed when the step actually moved
+    // Is an in-canvas value field open? While one is, the canvas is frozen and every letter is
+    // swallowed — the single most common reason a driven gesture "does nothing".
+    bool value_field_open() const { return m_awaiting_length; }
+    bool is_edit_op_mode() const { return m_mode == Mode::Fillet || m_mode == Mode::Chamfer ||
+                                          m_mode == Mode::Offset || m_mode == Mode::Mirror; }
+    bool is_transform_mode() const { return m_mode == Mode::Move || m_mode == Mode::Rotate ||
+                                            m_mode == Mode::Scale || m_mode == Mode::Array ||
+                                            m_mode == Mode::PolarArray; }
+    // Creation tools that get draw-then-edit: on commit the new entity/feature is selected
+    // and its primary value editor opens. Line is handled inline (its own length field);
+    // Polyline/BSpline/Point have no single primary value, so they opt out.
+    bool is_creation_autoedit_mode() const {
+        switch (m_mode) {
+        case Mode::Line:
+        case Mode::CornerRect: case Mode::CenterRect: case Mode::ObliqueRect:
+        case Mode::RoundedRect: case Mode::CenterCircle: case Mode::TwoPointCircle:
+        case Mode::ThreePointCircle: case Mode::ThreePointArc: case Mode::TangentArc:
+        case Mode::CenterArc: case Mode::Slot: case Mode::ArcSlot: case Mode::Polygon:
+        case Mode::Ellipse: case Mode::EllipseArc:
+            return true;
+        default: return false;
+        }
+    }
+    // The host (DesignCanvas) flags the canvas frozen while an inline value editor is open,
+    // so a stray click/move can't draw under the floating field. Reuses m_awaiting_length
+    // (Line's existing freeze flag) as the single "inline editor open" gate.
+    void set_inline_busy(bool b) { m_awaiting_length = b; }
+    bool inline_busy() const { return m_awaiting_length; }   // true while a value field is open
+    // Does the live session hold anything a cancel would throw away? Escape must not silently
+    // destroy drawn geometry; the panel asks this before treating Escape as "discard sketch".
+    bool live_sketch_has_work() const { return !m_entities.empty(); }
+
+    // Clicking the same sub-element again escalates to the whole body. That is right for free
+    // picking and WRONG while a card has armed a face/edge pick: the card says "click a FACE",
+    // the user clicks the face it is already showing, and the escalation turns it into a
+    // whole-body pick that the armed capture then rejects. The host turns this off for as long
+    // as a pick is armed.
+    void set_escalate_on_repick(bool on) { m_escalate_repick = on; }
+    bool constrain_value_anchor(wxPoint& out) const; // screen anchor over the picked constrain geometry
+
+    void begin(const SketchPlane& plane, Mode mode = Mode::Polyline);
+    // Re-open a committed entity sketch for full in-canvas editing: load its entities +
+    // driving constraints, re-detect the polygon/rect/slot grouping, and live-solve. The
+    // caller re-commits via finish() (the panel replaces the feature, see m_edit_index).
+    void begin_edit(const std::vector<SketchEntity>& entities,
+                    const std::vector<SketchEntityConstraintDef>& constraints,
+                    const SketchPlane& plane);
+    // Drop rigid 2D art (Text / SVG outlines) INTO the live sketch as ordinary line entities,
+    // so it joins the sketch being drawn instead of committing a separate Sketch feature.
+    // `regions` are loops in PLANE coordinates; every closed loop becomes a closed polyline, so
+    // the result is editable, constrainable and extrudable like anything else drawn by hand —
+    // unlike imported_regions, which are rigid and carry no solver entities.
+    // Returns false when no session is live, so the caller can fall back to a new feature.
+    bool add_imported_regions(const std::vector<std::vector<std::vector<Vec2d>>>& regions);
+    void set_tool(Mode mode);                 // switch tool, keep accumulated entities
+    void set_plane(const SketchPlane& plane) { m_plane = plane; }  // re-plane a live sketch (a reference plane was clicked mid-session); entities are 2D, re-lifted through the new plane
+    void set_construction(bool c) { m_construction = c; }
+    void set_polygon_sides(int n) { m_polygon_sides = (n < 3 ? 3 : n); }
+    void set_polygon_circumscribed(bool c) { m_polygon_circumscribed = c; }
+    void finish();                            // emit accumulated entities, end session
+    void cancel();
+    bool is_active() const { return m_active; }
+    bool has_entities() const { return !m_entities.empty(); }
+    bool on_mouse(wxMouseEvent& evt, GLCanvas3D& canvas);
+    // Right-click on a draw tool: true when an in-progress anchor was abandoned, false when
+    // there was nothing to abandon — and false is what lets the offer menu open. ghcz.
+    bool right_abandon();
+    // True if the LAST right-press was consumed as a gesture terminator (end a polyline chain,
+    // abandon an anchor, exit a tool). Read-and-clear: the canvas asks on the matching release to
+    // decide whether that right-click was the user's, in which case it opens the offer.
+    bool take_right_consumed() { const bool b = m_right_consumed; m_right_consumed = false; return b; }
+    void render(GLCanvas3D& canvas);
+    // The in-canvas value field, drawn by render() before any early return. Owned by
+    // DesignCanvas; null until it sets it. Not a window — see SketchInlineEditor.hpp.
+    class SketchInlineEditor* inline_editor{nullptr};
+
+    // Persistent committed sketches to draw even when no session is active (e.g. an
+    // un-consumed sketch left visible after its extrude is removed). Each carries its
+    // own plane. render() draws these as translucent faces + outlines.
+    struct DisplaySketch { std::vector<SketchEntity> entities; SketchPlane plane; int feature{-1}; };
+    void set_display_sketches(std::vector<DisplaySketch> ds) { m_display_sketches = std::move(ds); }
+    void set_highlight_sketches(std::vector<std::pair<int, ColorRGBA>> hl) { m_hl_sketches = std::move(hl); }
+    // Solid pick is resolved on LeftUp (see on_mouse): consuming the press broke orbit/pan.
+    int  m_pick_press_x = 0;
+    int  m_pick_press_y = 0;
+    bool m_pick_pending = false;
+
+    bool has_display() const { return m_active || !m_display_sketches.empty()
+                                      || (m_solid_bodies != nullptr && !m_solid_bodies->empty())
+                                      || !m_datum_planes.empty()
+                                      || m_show_planes || m_show_axes
+                                      || m_ex_active || m_mv_active || m_fl_active
+                                      || m_hl_active || m_th_active || m_sh_active
+                                      || m_dr_active || m_ct_active || m_dz_active || m_dbp_active || m_hx_active || m_rb_active; }
+
+    // View helpers: the 3 world origin planes (XY/XZ/YZ) and the world axis triad, each
+    // shown/hidden by a toggle (keys P / A). Off by default so the idle scene stays clean.
+    void set_show_planes(bool s) { m_show_planes = s; }
+    void set_show_axes(bool s)   { m_show_axes = s; }
+    bool toggle_show_planes() { m_show_planes = !m_show_planes; return m_show_planes; }
+    bool toggle_show_axes()   { m_show_axes   = !m_show_axes;   return m_show_axes; }
+
+    // Solid topology selection on the committed bodies: clicking a solid cycles
+    // whole-solid -> face -> edge (Onshape-style) to target fillet/chamfer/extrude. With
+    // multiple bodies the pick resolves WHICH body was hit (per-triangle body id).
+    // Appended, never reordered: DesignPanel maps this to a level int (Whole=1, Face=2,
+    // Edge=3, Vertex=4) and the offer table keys off it.
+    enum class SolidSel { None, Whole, Face, Edge, Vertex };
+    // Point the tool at the current bodies + their concatenated tessellation (non-owning;
+    // pass nullptr to clear). Call after each recompute — selection resets (ids invalidate).
+    // tri_face = per-triangle face id within its body; tri_body = per-triangle body index.
+    void set_solid_pick(const std::vector<CadBody>* bodies, const TriangleMesh* mesh,
+                        const std::vector<int>* tri_face, const std::vector<int>* tri_body,
+                        const std::vector<bool>* visible = nullptr,
+                        const std::vector<Transform3d>* xform = nullptr);
+    // Body-focus picking: >=0 restricts every pick to that one body, so a face behind
+    // another solid is reachable without hiding anything. -1 = no restriction.
+    // Survives set_solid_pick() — it is owned by the panel, not by the mesh feed.
+    void set_pick_only_body(int b) { m_pick_only_body = b; }
+    void clear_solid_selection();
+    bool has_solid_selection() const { return m_solid_sel != SolidSel::None; }
+    // Select a whole body by index (from the Parts list) — Whole-level highlight, no face/edge.
+    // body < 0 or out of range clears the selection.
+    void select_body(int body);
+
+    // Move-body gizmo (M5): translate a whole body with three world-axis drag arrows
+    // (X red / Y green / Z blue) anchored at the body centroid. Display-only — the host
+    // keeps a per-body Transform3d and re-feeds the moved display/pick meshes; the OCCT
+    // shape (and thus face/edge global ids) is never touched. Drag fires on_body_move_changed
+    // live; a stationary click on an arrow opens the inline offset editor for that axis.
+    void set_move_gizmo(int body, const Vec3d& pivot, const Transform3d& base_xform,
+                        double body_radius = 0.0);
+    void clear_move_gizmo();
+    bool moving_body() const { return m_mv_active; }
+    int  move_body_index() const { return m_mv_body; }
+    // F key forwarded from the canvas (Prepare's Place on Face): returns true if it acted.
+    bool request_place_on_face() { return on_place_on_face ? on_place_on_face() : false; }
+    std::function<bool()> on_place_on_face;
+    std::function<void(int body, const Transform3d& xform)> on_body_move_changed;
+    // Fired on each cycle change: (level 0=None/1=Whole/2=Face/3=Edge, body index, face id, edge id).
+    std::function<void(int level, int body, int face, int edge)> on_solid_selection_changed;
+    // Click a committed sketch overlay (no live session) -> select that loop: the Sketch
+    // feature index + the clicked closed-region index within it (-1 = no specific loop).
+    // entity = the sketch entity index under the cursor when the click landed on a loop
+    // STROKE, else -1 for an interior/region hit. Carried because a tool can legitimately
+    // want the LINE you pointed at, not just the loop it belongs to (Rib, 3648).
+    std::function<void(int feature, int region, int entity)> on_display_sketch_selected;
+    // Double-click on a committed sketch stroke: open THAT feature for editing. Selecting a line
+    // and then hunting for an Edit button in a panel is the dependency this tab exists to remove.
+    std::function<void(int feature)> on_display_sketch_activated;
+    // Entities forming the currently click-selected loop (for a per-loop extrude); empty
+    // if no loop is selected.
+    std::vector<SketchEntity> selected_loop_entities() const;
+    // Per closed loop, the indices into `ents` that form it (for hiding already-extruded
+    // loops from the committed-sketch overlay).
+    std::vector<std::vector<int>> region_entity_indices(const std::vector<SketchEntity>& ents) const;
+    // Same, but each region's entry is its OWN entities followed by the entities of each of its
+    // holes, in that order — the exact list a per-loop extrude of a region WITH holes stores
+    // (see selected_loop_entities()). Needed to match a consumed loop against its source sketch.
+    std::vector<std::vector<int>> region_entity_indices_with_holes(const std::vector<SketchEntity>& ents) const;
+    void clear_display_pick() { m_display_pick = -1; m_display_pick_region = -1; }
+    // Adopt a loop pick the tool did not make itself. The live-sketch path resolves the region
+    // BEFORE the sketch is committed, so once finish_sketch() has turned it into a display
+    // sketch there is nothing left that would set this — and selected_loop_entities(), which is
+    // what Extrude consumes, reads exactly these two fields.
+    void set_display_pick(int feature, int region) { m_display_pick = feature; m_display_pick_region = region; }
+
+    // Visual Extrude gizmo (C5b). The Extrude tool is a DesignPanel docked card, so the
+    // sketch tool is NOT active during it; the panel feeds the profile plane + a 2D centroid
+    // (arrow anchor) + the live depths/flags, and the tool renders an in-canvas world-space
+    // depth arrow along plane.normal with a draggable handle + editable label. TwoSided draws
+    // a second arrow along -normal driven by depth2. Drag/edit fire on_extrude_depth_changed
+    // back to the panel, which writes the spin value + refreshes the ghost preview.
+    void set_extrude_gizmo(const SketchPlane& plane, const Vec2d& centroid,
+                           double depth, double depth2, bool two_sided, bool flip);
+    void clear_extrude_gizmo();
+    // (new_depth, second_side): second_side=false drives the primary depth, true the 2nd side.
+    std::function<void(double depth, bool second)> on_extrude_depth_changed;
+
+    // Datum-plane resize gizmo (C3). The Plane tool is a DesignPanel docked card (sketch tool
+    // NOT active), so the panel resolves the candidate plane's frame + current u/v extent and
+    // feeds them here; the tool draws the rectangle outline + 4 edge-midpoint handles. Dragging a
+    // handle changes the u (left/right) or v (top/bottom) extent live and fires on_datum_size_changed
+    // back to the panel, which writes the Size spins + re-pushes the rendered datum.
+    void set_datum_gizmo(const SketchPlane& plane, double usize, double vsize,
+                         const Vec3d& base_origin, const Vec3d& base_normal,
+                         double offset, bool offset_on);
+    void clear_datum_gizmo();
+    std::function<void(double usize, double vsize)> on_datum_size_changed;
+    std::function<void(double offset)>              on_datum_offset_changed;
+
+    // Visual Helix gizmo. The Helix tool is a DesignPanel docked card (sketch tool NOT active),
+    // so the panel resolves the axis plane and feeds the live parameters here; the tool draws
+    // the helix curve itself plus three handles — radius on the base circle, height at the top
+    // of the axis, pitch at the end of the first turn. Taper and handedness stay on the card:
+    // one is a shape modifier and the other is a flag, and L2 governs numbers you can point at.
+    void set_helix_gizmo(const SketchPlane& plane, double radius, double pitch, double height,
+                         double taper, bool left_handed);
+    void clear_helix_gizmo();
+    std::function<void(double radius, double pitch, double height)> on_helix_changed;
+
+    // Visual Rib thickness gizmo. The rib is a thin slab grown either side of an open sketch
+    // line, so its thickness is an IN-PLANE offset perpendicular to that line — the depth arrow
+    // (which points along the plane normal) cannot express it. Two handles, one per side,
+    // dragged symmetrically: the slab is centred on the line, so a drag on either side sets the
+    // full thickness rather than one half.
+    void set_rib_gizmo(const SketchPlane& plane, const Vec2d& p0, const Vec2d& p1, double thickness);
+    void clear_rib_gizmo();
+    std::function<void(double thickness)> on_rib_thickness_changed;
+
+    // Graphical base/origin pick: while the Plane card is open, the candidate base planes
+    // (XY/XZ/YZ origin planes + existing datums) draw as translucent clickable ghosts. A click
+    // on one fires on_datum_base_picked(base) with that plane's base index (0/1/2 or 3+N).
+    void set_base_pick(std::vector<SketchPlane> planes, std::vector<int> bases,
+                       std::vector<std::string> labels = {});
+    void clear_base_pick();
+    std::function<void(int base)> on_datum_base_picked;
+
+    // Visual Fillet/Chamfer gizmo. The Dressup tool is a DesignPanel docked card, so the sketch
+    // tool is NOT active during it; when a solid EDGE is picked the panel passes the body centroid
+    // + current radius and the tool anchors a world-space radius arrow at the picked edge midpoint
+    // (from m_sel_edge_pts), perpendicular to the edge, pointing outward (away from the centroid).
+    // Dragging the arrow changes the radius live; a stationary click opens the inline editor; both
+    // fire on_fillet_radius_changed back to the panel, which writes the spin + refreshes the ghost.
+    // Returns true if it could anchor (needs a picked edge with >=2 sample points).
+    bool set_fillet_gizmo(const Vec3d& body_centroid, double radius);
+    void clear_fillet_gizmo();
+    bool filleting() const { return m_fl_active; }
+    std::function<void(double radius)> on_fillet_radius_changed;
+
+    // Visual Hole gizmo. Like Dressup, the Hole tool is a DesignPanel docked card, so the sketch
+    // tool is NOT active during it; the panel passes the hole plane + position + diameter + depth +
+    // through flag, and the tool draws an on-plane footprint circle plus a radial diameter arrow,
+    // a normal-axis depth arrow (only when !through), and a draggable centre marker. Dragging the
+    // centre repositions (plane u/v), the diameter arrow resizes, the depth arrow deepens — all
+    // live; a stationary click on an arrow opens its inline editor. Every change fires
+    // on_hole_changed back to the panel, which writes the spins + refreshes the ghost.
+    void set_hole_gizmo(const SketchPlane& plane, double x, double y,
+                        double diameter, double depth, bool through);
+    // Provide the face (u,v) bounds so the hole's construction dims read from the face sides.
+    void set_hole_face_bounds(bool has, double umin, double umax, double vmin, double vmax);
+    void clear_hole_gizmo();
+    bool holing() const { return m_hl_active; }
+    std::function<void(double x, double y, double diameter, double depth)> on_hole_changed;
+
+    // Visual Thread gizmo. Same docked-card story as Hole: the panel feeds the thread plane +
+    // axis position + nominal radius + length; the tool draws an on-plane footprint circle plus a
+    // radial radius arrow and a normal-axis length arrow (always shown — a thread has no "through")
+    // and a draggable centre. Pitch/depth/internal stay in the card. Drag is live; a stationary
+    // click on an arrow opens its inline editor; every change fires on_thread_changed.
+    void set_thread_gizmo(const SketchPlane& plane, double x, double y,
+                          double radius, double height);
+    void clear_thread_gizmo();
+    bool threading() const { return m_th_active; }
+    std::function<void(double x, double y, double radius, double height)> on_thread_changed;
+
+    // Visual Shell gizmo. The panel passes the picked open-face centroid + an inward direction
+    // (-outward normal) + the current wall thickness; the tool anchors a single thickness arrow
+    // there (mirrors the fillet radius arrow). Dragging sets the thickness live; a stationary
+    // click opens the inline editor; both fire on_shell_thickness_changed.
+    void set_shell_gizmo(const Vec3d& face_centroid, const Vec3d& inward_dir, double thickness);
+    void clear_shell_gizmo();
+    bool shelling() const { return m_sh_active; }
+    std::function<void(double thickness)> on_shell_thickness_changed;
+
+    // Datum/reference planes (Plane feature) carry no solid; the panel feeds their resolved
+    // SketchPlanes so they render as translucent rectangles in feature mode (otherwise a
+    // Plane feature is invisible in the canvas).
+    void set_datum_planes(std::vector<SketchPlane> planes, std::vector<Vec2d> sizes = {}) {
+        m_datum_planes = std::move(planes); m_datum_sizes = std::move(sizes);
+    }
+
+    // Mate connectors. Until now a connector was visible only to a program — resolve_datum_coordsys
+    // had exactly one consumer, the MCP socket — so the frame a mate is built on could not be seen
+    // at all. The glyph has to answer two questions on sight (wgsc): which way does Z point
+    // (the VERSE), and which of the pair is anchored versus driven (the POLARITY). Nothing in any
+    // surveyed CAD system encodes the second one.
+    struct MateConnectorGlyph {
+        Vec3d origin{0, 0, 0};
+        Vec3d x{1, 0, 0};          // roll reference; the filled quadrant spans x -> y
+        Vec3d y{0, 1, 0};
+        int   role{0};             // 0 = neutral, 1 = fixed (receives), 2 = driven (moves)
+        bool  roll_undefined{false};
+    };
+    void set_mate_connectors(std::vector<MateConnectorGlyph> g) { m_mate_connectors = std::move(g); }
+    // The pair line: the two origins of every mate — committed ones, plus the live pick of an open
+    // Mate card. Two connectors a mate binds are ONE object with a gap still in it; drawn as two
+    // separate frames they read as unrelated.
+    void set_mate_links(std::vector<std::pair<Vec3d, Vec3d>> l) { m_mate_links = std::move(l); }
+    void clear_mate_connectors() { m_mate_connectors.clear(); m_mate_links.clear(); }
+
+    // Visual Revolve gizmo. The panel feeds the sketch plane + profile centroid + axis (0=plane X,
+    // 1=plane Y) + angle + flip while its Revolve card is open; an angle-arc is drawn in the
+    // revolve plane at the profile radius. Dragging the tip sweeps the angle, a stationary click
+    // edits it; both fire on_revolve_angle_changed.
+    void set_revolve_gizmo(const SketchPlane& plane, const Vec2d& centroid,
+                           int axis_sel, double angle, bool flip);
+    void clear_revolve_gizmo();
+    bool revolving() const { return m_rv_active; }
+    std::function<void(double angle)> on_revolve_angle_changed;
+
+    // Visual Draft angle-arc gizmo (taper a picked face; axis = world +Z, arc in XY).
+    void set_draft_gizmo(const Vec3d& face_centroid, const Vec3d& face_normal, double angle);
+    void clear_draft_gizmo();
+    bool drafting() const { return m_dr_active; }
+    void set_on_draft_angle_changed(std::function<void(double)> cb) { m_on_draft_angle_changed = std::move(cb); }
+
+    // Visual Cut gizmo (plane normal arrow + plane rectangle preview).
+    void set_cut_gizmo(const SketchPlane& plane, double offset, const Vec3d& body_center, double half_extent);
+    void clear_cut_gizmo();
+    bool cutting() const { return m_ct_active; }
+    void set_on_cut_offset_changed(std::function<void(double)> cb) { m_on_cut_offset_changed = std::move(cb); }
+
+    // Visual Pattern gizmo. Linear: a 3D arrow along the world axis (plane X/Y per `dir`) of length
+    // spacing*(count-1) with a tick at each copy; dragging the end sets the spacing. Circular: a
+    // revolve-style angle-arc about the plane normal through the plane origin sweeping `angle`.
+    // Both fire on_pattern_changed (spacing for linear, angle for circular).
+    void set_pattern_gizmo(const SketchPlane& plane, const Vec3d& body_centroid, bool circular,
+                           int count, int dir, double spacing, double angle);
+    void clear_pattern_gizmo();
+    bool patterning() const { return m_pt_active; }
+    std::function<void(double value)> on_pattern_changed;
+
+    // Constrain mode: load an already-committed profile for entity picking +
+    // constraint application (the geometry is solved in the kernel, not here).
+    void begin_constrain(const SketchProfile& prof, const SketchPlane& plane);
+    bool is_constraining() const { return m_active && m_mode == Mode::Constrain; }
+    // Replace the displayed profile (e.g. after the kernel re-solved it).
+    void set_profile_points(const std::vector<Vec2d>& pts) { m_points = pts; }
+    // The currently picked segment's endpoint indices into the profile.
+    bool selected_segment(int& a, int& b) const;
+
+    // Entity-aware Constrain (Fase 4.2): load a committed entity sketch and pick
+    // Line entities (constraints are solved against entity endpoints in the kernel).
+    void begin_constrain_entities(const std::vector<SketchEntity>& ents, const SketchPlane& plane);
+    bool is_constraining_entities() const { return m_active && m_mode == Mode::Constrain && m_constrain_entities; }
+
+    // In-canvas bounding-box transform of imported Text/SVG art (replaces the Move/Scale
+    // dialog). `base_regions` are the untransformed region contours; the gizmo shows the
+    // current bbox with 4 corner scale-handles + a centre move-handle. Dragging fires
+    // on_imported_transform live with the new offset/scale, which the host writes back to
+    // the feature. Exiting (Esc/right-click) ends the session.
+    void begin_imported_transform(int feat,
+                                  const std::vector<std::vector<std::vector<Vec2d>>>& base_regions,
+                                  const SketchPlane& plane, const Vec2d& offset,
+                                  double scale_x, double scale_y);
+    std::function<void(int feat, Vec2d offset, double scale_x, double scale_y)> on_imported_transform;
+    // Up to two picked line-entity indices; returns true if at least one is picked.
+    bool selected_constrain_entities(int& e0, int& e1) const { e0 = m_pick0; e1 = m_pick1; return m_pick0 >= 0; }
+    // Third pick slot (Symmetric axis): only filled after slots 0 and 1 are set.
+    int  pick2() const { return m_pick2; }
+    // Plane-coords of the click that filled slot 0 (for pick-point edit ops: trim/extend).
+    bool pick0_point(Vec2d& out) const { out = m_pick0_pt; return m_pick0 >= 0; }
+    // Refresh the displayed entities after the kernel re-solved them.
+    void set_constrain_entities(const std::vector<SketchEntity>& ents) { m_entities = ents; }
+    // Constraint manager (C3.4): entity indices the panel asks to highlight (the
+    // entities a selected constraint references); rendered yellow in Constrain mode.
+    void set_constraint_highlight(std::vector<int> v) { m_constraint_hl = std::move(v); }
+    // The committed feature's constraints, supplied so Constrain-mode render can draw
+    // an iconic glyph badge per constraint near its primary entity (C3.4b).
+    void set_constraint_glyphs(std::vector<SketchEntityConstraintDef> v) { m_constrain_cons = std::move(v); }
+
+    // Line tool: after a single segment is placed, the panel pops a length dialog
+    // (length, angle_deg are the as-drawn values); it then resolves via
+    // apply_segment_length() (exact length) or keep_segment_as_drawn() (cancel).
+    std::function<void(double length, double angle_deg)> on_segment_drawn;
+    void apply_segment_length(double len);  // rescale the pending segment, then commit it
+    void keep_segment_as_drawn();           // commit the pending segment unchanged
+
+    // Live readout while drawing a Line/Polyline segment (anchor->cursor metrics).
+    std::function<void(double length, double angle_deg, bool locked)> on_cursor_metrics;
+
+    // Live step guidance (1c0c). The armed tool reports WHICH STEP of its gesture the
+    // user is on, every time that changes, so the status line can name the next click instead of
+    // repeating the one-shot sentence written when the tool was armed. step = anchors/picks
+    // already down (Mirror: 0 = no axis, 1 = axis down, 2 = ready to apply); picks = size of the
+    // set the gesture accumulates (mirror targets, transform targets, Select's selection).
+    std::function<void(Mode mode, int step, int picks)> on_step_changed;
+    // Fired when the live constraint SET changes (one added or removed), never on a re-solve.
+    // The panel rebuilds its constraint rows from this; binding it to on_solve_state instead
+    // would rebuild the whole list on every frame of a drag.
+    std::function<void()> on_constraints_changed;
+
+    // DoF feedback (P3): solver state after each live solve. dof>0 = under-constrained,
+    // dof==0 = fully constrained, ok==false = conflicting/inconsistent constraints.
+    // has_constraints is false while the sketch carries no driving constraints yet.
+    std::function<void(int dof, bool ok, bool has_constraints)> on_solve_state;
+
+    // Selection (Mode::Select): pick points/lines/arcs/circles of the in-session
+    // sketch; Shift/Ctrl extends, double-click grabs the whole connected loop.
+    const std::vector<int>& selection() const { return m_selection; }
+    // Entities OR bare points: clear_selection() drops both, so "is anything picked" must ask
+    // about both, or Esc at idle would report nothing to do while a point sat highlighted.
+    bool sketch_has_selection() const { return !m_selection.empty() || !m_point_sel.empty(); }
+    // Type of the first selected entity. False when nothing is selected, so the offer menu can
+    // tell a line from an arc from a point and stop collapsing every sketch selection to "none".
+    bool first_selected_type(SketchEntity::Type& out) const {
+        if (m_selection.empty()) return false;
+        const int i = m_selection.front();
+        if (i < 0 || i >= int(m_entities.size())) return false;
+        out = m_entities[i].type;
+        return true;
+    }
+    // Right-click pick: select the entity (or point handle) under the given canvas pixel, so
+    // the context menu describes what was pointed at. No-op when it is already selected, or
+    // when nothing is there. Returns true if the selection changed.
+    bool select_at_screen(GLCanvas3D& canvas, int sx, int sy);
+    // Open the in-canvas value field on the SELECTION's defining number (a line's length, an
+    // arc's radius, a circle's diameter, the angle between two lines, a point-to-point or
+    // point-to-line distance). False when the selection has no such number.
+    bool open_selection_dimension_editor();
+    // ---- Scripted surface (MCP) -------------------------------------------------------
+    // The same operations the right-click offers, reachable without a mouse gesture, so the 2D
+    // layer can be driven and asserted headlessly. Everything here goes through the SAME code a
+    // gesture goes through — append + infer_auto_constraints + live solve — because a test that
+    // exercises a private shortcut proves nothing about the tool the user drives.
+    const std::vector<SketchEntity>&              entities()    const { return m_entities; }
+    const SketchPlane&                            plane()       const { return m_plane; }
+    int  dof()      const { return m_dof; }
+    bool solve_ok() const { return m_solve_ok; }
+    // Append entities exactly as a finished gesture does. Returns the index of the first one.
+    int  add_entities_scripted(const std::vector<SketchEntity>& ents);
+    // Replace the selection with these entity indices (out-of-range ones are ignored).
+    bool select_indices(const std::vector<int>& idx);
+    // Append candidates, live-solve, and roll back the batch if it turns the system
+    // inconsistent. Returns true when the batch was kept. Public so the panel's live-constraint
+    // path can commit a plan through the SAME append→solve→keep-or-rollback the gestures use.
+    bool try_add_constraints(const std::vector<SketchEntityConstraintDef>& cands);
+    // Click-to-delete on a constraint badge: drop the constraint whose glyph sits under `p`
+    // and re-solve. Returns true if one was removed (the caller then repaints).
+    bool remove_constraint_near(const Vec2d& p);
+    // Drop constraint `idx` from the live session and re-solve. Same operation the badge click
+    // performs, addressed by index instead of by position — the panel list needs the index form.
+    bool remove_constraint(int idx);
+
+    // The loop report: what is CLOSED, what its internal voids are, and where a chain is still
+    // open. This is the answer to "is my profile buildable", and it is the one question the
+    // sketch layer could never be asked from outside.
+    struct LoopInfo {
+        std::vector<int>   ents;         // entities of this loop, in chain order
+        std::vector<int>   holes;        // indices into LoopReport::loops that this loop encloses
+        bool               closed{false};
+        double             area{0.0};    // signed shoelace area of the loop polyline
+    };
+    struct LoopReport {
+        std::vector<LoopInfo> loops;
+        std::vector<Vec2d>    open_ends;   // free endpoints: where a chain fails to close
+    };
+    LoopReport loop_report() const;
+
+    // FreeCAD's ValidateSketch, as one call: weld endpoints that are within `tol` of each other
+    // and RECORD the Coincident constraints, so a loop that was closed by floating-point luck
+    // becomes closed by construction and survives every later solve. Returns how many pairs were
+    // welded. Construction geometry is skipped when `ignore_construction`.
+    int heal_coincidences(double tol, bool ignore_construction);
+
+    void clear_selection();
+    // Flip the selection between construction and real geometry (whole Feature groups).
+    // Returns how many entities changed; 0 when nothing is selected.
+    int  toggle_selection_construction();
+    void delete_selected();                         // erase selected entities
+    // Abort any pending/queued draw-then-edit value-field sequence. Removing an entity that
+    // still has a deferred auto-edit would otherwise open a field on a now-deleted entity and
+    // freeze the flow (its live quote label also lingers). Mirrors set_tool's resync.
+    void reset_autoedit() {
+        m_awaiting_length  = false;
+        m_autoedit_pending = false;
+        m_autoedit_dims.clear();
+        m_autoedit_dim_idx = -1;
+        m_autoedit_seen    = int(m_entities.size());
+        m_live_quotes.clear();   // rebuilt from current geometry on the next render
+    }
+    // Take down the session's floating chrome: the open value field (dismiss = keep-as-drawn),
+    // the queue of fields behind it, and the corner readout. All three are top-level windows fed
+    // only while the tool is live, so nothing else would ever clear them — reset_autoedit() alone
+    // clears the flag and leaves the frame on screen. Called by finish()/cancel(); safe when
+    // nothing is open.
+    void close_session_chrome() {
+        if (on_inline_dismiss) on_inline_dismiss();   // no-op when no field is open
+        reset_autoedit();
+        if (on_readout) on_readout(std::string());    // the HUD is not redrawn once the tool stops
+    }
+    // Ctrl+Z while sketching: drop the last drawn entity (reuses delete_selected's remap).
+    bool undo_last_entity() {
+        if (!m_active || m_entities.empty()) return false;
+        m_selection.assign(1, int(m_entities.size()) - 1);
+        delete_selected();
+        reset_autoedit();
+        return true;
+    }
+    // Delete while sketching: the selected entities, or the last drawn one if none is selected.
+    bool delete_selected_or_last() {
+        if (!m_active) return false;
+        if (m_selection.empty()) {
+            if (m_entities.empty()) return false;
+            m_selection.assign(1, int(m_entities.size()) - 1);
+        }
+        delete_selected();
+        reset_autoedit();
+        return true;
+    }
+    std::function<void(int count)> on_selection_changed;
+
+    // Dimension tool: infer a driving dimension from the current selection and set
+    // it exactly. Sizing: 1 line=Length, 1 circle=Diameter, 1 arc=Radius,
+    // 2 lines=Angle. Positioning (a value of 0 makes them coincident):
+    // 2 point-likes (point/circle-centre/arc-centre)=Distance, moving the 2nd onto
+    // the 1st; a point-like + a line=DistanceToLine, moving the point-like's
+    // reference point onto/away-from the line (e.g. a circle centre onto an axis).
+    enum class DimType { None, Length, Diameter, Radius, Angle, Distance, DistanceToLine };
+    DimType dimension_kind() const;     // what the selection supports (None if invalid)
+    double  dimension_current() const;  // current value, to pre-fill the dialog
+    void    apply_dimension(double v);  // set it exactly, then clear the selection
+
+    // Onshape-style Dimension tool (Mode::Dimension): with the tool active you click
+    // directly in the viewport — 2 points -> Distance, a line -> Length, a circle ->
+    // Diameter, an arc -> Radius, a point then a line -> DistanceToLine. A quote line
+    // with extension lines, arrowheads and a numeric label is PLACED in the sketch and
+    // drives the geometry (auto-offset; label editable). on_dimension_pick_complete
+    // fires when a pick resolves so the panel can pop the value card pre-filled.
+    std::function<void(double current)> on_dimension_pick_complete;
+    DimType pending_dimension_type() const;  // type of the dim awaiting a value, or None
+    void    set_dimension_value(double v);   // apply the typed value to the placed dim
+    void    cancel_dimension_value();        // keep the placed dim at its measured value
+
+    // Onshape-style in-canvas value editing: open a floating text editor at the given
+    // screen pixel, pre-filled with `current`; commit applies the value, cancel keeps
+    // it. The owner (DesignCanvas) hosts the wxTextCtrl over the GL canvas. This is the
+    // single numeric-entry path for all sketch dimensions (replaces the modal cards).
+    std::function<void(wxPoint screen_px, double current, const std::string& title,
+                        std::function<void(double)> commit,
+                        std::function<void()> cancel)> on_inline_edit;
+    // Force-close any open inline field (runs its cancel = keep-as-drawn). Used by the polyline
+    // terminators (right-click / double-click) to end the chain even mid per-segment edit.
+    std::function<void()> on_inline_dismiss;
+    // Accept and close an open inline value field. dismiss() CANCELS; this one keeps the value,
+    // which is what leaving a tool should do — see set_tool().
+    std::function<void()> on_inline_commit;
+
+    // Bottom-right viewport readout: emitted each frame with the active tool's current
+    // values (live segment length/angle while drawing a line, or the selected entity's
+    // characteristic dimensions). Empty string -> hide the HUD. The owner (DesignCanvas)
+    // shows it as a floating corner label over the GL canvas.
+    std::function<void(const std::string&)> on_readout;
+
+    // Driving dimension constraints accumulated during the session (the Dimension
+    // tool records a SketchEntityConstraintDef per applied dimension); committed
+    // alongside the entities on finish() so the kernel keeps enforcing them.
+    const std::vector<SketchEntityConstraintDef>& constraints() const { return m_constraints; }
+
+    // Emitted by finish() with the accumulated entities + driving constraints.
+    std::function<void(const std::vector<SketchEntity>&,
+                       const std::vector<SketchEntityConstraintDef>&,
+                       const SketchPlane&)> on_commit_entities;
+    // Legacy single-profile commit (kept for compatibility; unused by entity tools).
+    std::function<void(const SketchProfile&, const SketchPlane&)> on_commit;
+    // Emitted when a closed-loop face is clicked in Select mode (Onshape: a region
+    // becomes a selectable face → extrude). The panel commits the sketch + extrudes.
+    std::function<void(int)> on_face_selected;   // region index into region_loops(m_entities)
+    // Esc pressed while the tool is active with nothing left to unwind and no geometry to
+    // lose: leave the session (the panel restores Feature mode).
+    std::function<void()> on_exit;
+    // request_exit() declined to leave because the session holds geometry. The panel owns the
+    // status line, so the tool reports through this instead of writing text itself.
+    std::function<void()> on_exit_refused;
+    std::function<void()> on_move_exit;   // right-click finished the move-body gizmo
+    // The two inner Esc levels, callable on their own so the panel can route one press to one
+    // level (see DesignInteraction.hpp). Each returns whether it had anything to unwind.
+    bool abort_gesture();   // CadLevel::Gesture — drop the entity being drawn
+    bool disarm_tool();     // CadLevel::Tool    — armed draw/edit tool falls back to Select
+    void request_exit();
+    // Ctrl+Z / Ctrl+Shift+Z (Ctrl+Y) while the Design canvas is focused: undo/redo the
+    // committed feature history. The tool just forwards to the host, which owns the
+    // CadDocument (the tool has no document of its own). redo == true requests redo.
+    std::function<void(bool /*redo*/)> on_undo_redo;
+    void request_undo_redo(bool redo);
+
+private:
+    bool screen_to_plane(GLCanvas3D& canvas, const wxMouseEvent& evt, Vec2d& out) const;
+    // True when the cursor is close enough to the open chain's FIRST point to close the loop,
+    // on the same screen tolerance as every other snap; snaps `p` exactly onto that point so
+    // the rubber band previews the closing segment and the snap marker lights.
+    bool snap_chain_start(GLCanvas3D& canvas, const wxMouseEvent& evt, Vec2d& p) const;
+
+    // Onshape-style angle inference: snap the direction anchor->raw to the nearest
+    // of {0,30,45,60,90} deg (replicated every 90 deg) when within tolerance, keeping
+    // the same length. Sets `locked` when a snap was applied. Suppressed by m_snap_off.
+    Vec2d snap_dir(const Vec2d& anchor, const Vec2d& raw, bool& locked) const;
+    // Snap a placed point onto the nearest existing entity endpoint within ~8 px so
+    // chains join across entities (a line + an arc can close into one loop). Shift
+    // disables it. `snapped` reports whether a vertex was hit.
+    Vec2d snap_vertex(GLCanvas3D& canvas, const wxMouseEvent& evt, const Vec2d& raw, bool& snapped) const;
+
+    // --- P1 inference / auto-constraint engine ---------------------------------
+    // Plane-units tolerance equivalent to ~`px` screen pixels at the cursor.
+    double screen_tol(GLCanvas3D& canvas, const wxMouseEvent& evt, const Vec2d& at, double px = 8.0) const;
+    // Run kernel inference at the cursor, cache the target for the hint renderer.
+    InferenceSnap infer_at(GLCanvas3D& canvas, const wxMouseEvent& evt, const Vec2d& raw) const;
+    // True if m_constraints already holds an equivalent Coincident between the two refs.
+    bool has_coincident(int ea, SketchPointRole ra, int eb, SketchPointRole rb) const;
+    // After entities [base, end) were committed, auto-emit the constraints that make
+    // the new geometry stick: Coincident between co-located endpoints (so loops close
+    // on their own) and Horizontal/Vertical on axis-aligned new segments.
+    // ang_tol_rad is how far from an axis a segment may be and still be CALLED axis-aligned.
+    // A gesture needs the default 3 degrees — nobody clicks a horizontal line exactly — but
+    // that same slack MOVES geometry that was given exactly, so the scripted path passes a
+    // tolerance tight enough to recognise only what is already true. See add_entities_scripted.
+    // ang_tol_rad: how far off axis a segment may be and still be called Horizontal/Vertical.
+    // weld_tol:    how far apart two endpoints may be and still be called Coincident.
+    // Both default to GESTURE slack. A scripted add passes zero for both: the caller has
+    // already said exactly what it means, and every non-zero window is a window in which the
+    // inference rewrites it. 8xg1.
+    void infer_auto_constraints(int base, double ang_tol_rad = 3.0 * M_PI / 180.0,
+                                double weld_tol = 1e-3);
+
+    // Selection helpers (Mode::Select).
+    int hit_test(const Vec2d& p, double tol) const;       // nearest entity within tol, or -1
+    std::vector<int> connected_loop(int seed) const;      // entities joined by shared endpoints
+    void apply_angle_between(int ia, int ib, double deg); // rotate line B to set the A^B angle
+    bool selection_valid() const;                         // all selection indices in range
+    void record_dimension_constraint(double v);           // append the driving def for the selection
+    void resolve_live();                                  // solve accumulated constraints on m_entities now
+    // Drag-aware re-solve: pins the dragged point at its current coord and lets the
+    // solver move the rest (Slvs dragged[]). Used live while a point grab is active.
+    void resolve_live_drag(int dragged_ei, SketchPointRole dragged_role);
+
+    // Placed dimension annotation. References entity points/entities (not cached
+    // coords) so the quote follows the geometry as the kernel solves it. `value`
+    // drives the constraint stored at index `con` in m_constraints.
+    struct DimAnnot {
+        DimType         kind{DimType::None};
+        int             ea{-1}; SketchPointRole ra{SketchPointRole::P0};
+        int             eb{-1}; SketchPointRole rb{SketchPointRole::P0};
+        double          value{0.0};
+        double          side{1.0};   // perpendicular offset sign of the quote line
+        int             con{-1};     // slot in m_constraints driving this dimension
+        Vec2d           label_pos{0, 0};  // cached label centre (plane coords), for picking
+    };
+
+    // --- Onshape-style visual editing: handles + parametric feature grouping -----
+    // A draggable handle on a defining point of an entity (or a derived point of a
+    // feature group). GUI-only; recomputed from solved geometry every frame (never
+    // persisted), so handles always track the current solve. Derived roles (radius,
+    // slot width/centres, rect corners, polygon vertex, ellipse axes) let tools that
+    // decompose into raw Line/Arc entities still expose their parametric controls.
+    enum class HandleRole { P0, P1, Center, RadiusHandle,
+                            SlotCenter0, SlotCenter1, SlotWidth,
+                            RectCorner, PolygonVertex, MajorAxis, MinorAxis, BSplineCtrl };
+    struct Handle {
+        HandleRole role{HandleRole::P0};
+        int   ei{-1};          // primary entity index
+        int   group{-1};       // index into m_features, or -1 for a raw-entity handle
+        int   ctrl_index{-1};  // BSplineCtrl pole index
+        Vec2d pos{0, 0};       // current plane coords (recomputed each frame)
+        bool  hovered{false};
+    };
+    // A parametric grouping over a contiguous run of entities produced by one gesture.
+    // Slot/Rect/Polygon/etc. have no SketchEntity type of their own — they decompose
+    // into raw Line/Arc entities — so the Feature carries the gesture's anchors so
+    // derived handles + characteristic dimensions can be reconstructed.
+    enum class FeatureKind { Free, Line, Circle, Arc, CornerRect, CenterRect,
+                             Slot, ArcSlot, Polygon, Ellipse, RoundedRect, BSpline };
+    struct Feature {
+        FeatureKind kind{FeatureKind::Free};
+        int    begin{0}, end{0};   // [begin,end) into m_entities
+        Vec2d  c0{0, 0}, c1{0, 0}; // slot centres / rect corners / ellipse centre+major
+        double param{0.0};         // slot half-width / polygon circumradius / fillet radius
+        int    sides{0};           // polygon side count
+    };
+    // Build the live handle set for the current selection / just-drawn feature.
+    std::vector<Handle> build_handles() const;
+    // Nearest handle to plane-point p within tol; fills `out`. (Phase A: stub.)
+    bool hit_test_handle(const Vec2d& p, double tol, Handle& out) const;
+    // Move a handle to `target`, applying the role-specific geometry edit + re-solve.
+    void set_handle(const Handle& h, const Vec2d& target);
+    // On a no-button move, recompute the hovered handle; returns true iff it changed
+    // (so the caller forces exactly one repaint). No-op for non-Moving events.
+    bool update_hover(GLCanvas3D& canvas, wxMouseEvent& evt);
+    // Index of the Feature whose [begin,end) entity span contains ei, or -1.
+    int  feature_of(int ei) const;
+    // Re-detect parametric Feature groups (polygon / rect / slot) from the raw entity
+    // list — used when a committed sketch is re-opened, where m_features is empty.
+    void rebuild_features_from_entities();
+    // Open/close a Feature record around the entities a single gesture appends.
+    void begin_feature(FeatureKind kind);
+    void end_feature(const Vec2d& c0 = Vec2d(0, 0), const Vec2d& c1 = Vec2d(0, 0),
+                     double param = 0.0, int sides = 0);
+
+    bool point_at(int ei, SketchPointRole role, Vec2d& out) const;          // current coords
+    void set_point(int ei, SketchPointRole role, const Vec2d& v);           // move an entity point
+    bool hit_test_point(const Vec2d& p, double tol, int& ei, SketchPointRole& role) const;
+    int  hit_test_dimension(const Vec2d& p, double tol) const;              // nearest dim label
+    void edit_dimension(int di);                                            // reopen value card for di
+    // Representative plane-coords anchor of a dimension (label centre if known, else a
+    // geometric midpoint/centre) — where the in-canvas value editor is positioned.
+    Vec2d dim_anchor(const DimAnnot& a) const;
+    // Open the in-canvas value editor on dimension `di` (falls back to the modal
+    // pick-complete callback when no inline-edit host is wired).
+    void open_value_editor(int di);
+    // In-canvas editor for a line's angle-to-horizontal; commit rotates the segment
+    // geometrically about P0 (no single-line angle constraint in libslvs).
+    void open_angle_editor(int ei);
+    void set_line_angle(int ei, double deg);
+    // Draw-then-edit (all creation tools): open the inline editor on the freshly-drawn
+    // selection's PRIMARY characteristic value. Called after render_live_quotes has computed
+    // the selection's quotes, so it dispatches on the same live-quote state a Select-mode
+    // click would use.
+    void open_primary_autoedit();
+    // Compact "current values" string for the bottom-right HUD (see on_readout).
+    std::string build_readout() const;
+    // Open a characteristic live quote as a TENTATIVE driving dimension: the constraint is
+    // appended only if the user commits a value (Enter); cancel (Esc) adds nothing — so
+    // drawing never silently over-constrains. (place_dimension is the eager Select-mode twin.)
+    void open_next_autoedit_dim();   // opens m_autoedit_dims[idx]; commit -> next, Esc -> stop
+    void arm_polyline_segment_edit();// per-segment Length+Angle edit of the pending chain vertex
+    // In-canvas editors for a regular polygon's side length and orientation. Both edit
+    // the whole loop GEOMETRICALLY (polygon has no centre entity): side scales it
+    // uniformly about its centre, angle rotates it. set_polygon_radius is the shared
+    // uniform-scale primitive (circumradius).
+    void open_polygon_side_editor(int fi);
+    void open_polygon_angle_editor(int fi);
+    void set_polygon_side(int fi, double side);
+    void set_polygon_angle(int fi, double deg);
+    void set_polygon_radius(int fi, double R);
+    // Arc sweep-angle quote: geometric edit (SLVS angle is line-to-line only). Keeps the
+    // arc start point + radius fixed and moves the end point to span `deg` degrees.
+    void open_arc_angle_editor(int ei);
+    void set_arc_sweep(int ei, double deg);
+    // Arc handle drag (3 grips): Center rigidly translates; the START point changes the
+    // radius (keeps both sweep angles); the END point changes the sweep angle (keeps the
+    // radius). Geometric — no solver (SLVS has no arc radius/angle handle concept here).
+    void drag_arc_handle(int ei, SketchPointRole role, const Vec2d& target);
+    // Ellipse axis labels (geometric edit of the semi-axes a/b; phi via the major grip).
+    void open_ellipse_axis_editor(int ei, bool major);
+    void set_ellipse_axis(int ei, bool major, double v);
+    void set_ellipsearc_sweep(int ei, double deg);   // draw-then-edit: included sweep of an elliptical arc
+    void set_rect_angle(int fi, double deg);         // draw-then-edit: orientation of an oblique rect
+    // EllipseArc endpoint drag: Center translates; P0/P1 move the sweep start/end to the
+    // parametric angle of the cursor on the ellipse frame (radius/shape preserved).
+    void drag_ellipsearc_handle(int ei, SketchPointRole role, const Vec2d& target);
+    // Drop orientation constraints (H/V/Parallel/Perp/Angle/LockX/LockY) on entities in
+    // [begin,end). A ROTATION makes inferred per-edge H/V inconsistent, so re-solving
+    // against them collapses the shape — drop them first (fixes up DimAnnot.con indices).
+    void drop_orientation_constraints(int begin, int end);
+    // Drop every live constraint that references entity `ei` (Trim/Extend slide an endpoint,
+    // invalidating its constraints) and fix the dimensions' cached constraint indices.
+    void drop_constraints_referencing(int ei);
+    // Standalone Trim/Extend scissors on the LIVE sketch: pick the entity nearest `p` (within
+    // `tol` plane units) and cut it back to / out to its nearest intersection with the others.
+    // Returns true if an entity was modified.
+    bool apply_live_trim(const Vec2d& p, double tol, bool extend);
+    // Pure-computation hover preview for Trim/Extend: mirror apply_live_trim's pick + the
+    // engine's cut on a COPY (mutating nothing) and return, via `removed_poly`, the polyline
+    // of the sub-portion a click would REMOVE (Trim) or ADD (Extend). `subject_ei` is the
+    // picked entity. Returns false if nothing is in range or nothing would change.
+    bool compute_trim_preview(const Vec2d& p, double tol, bool extend,
+                              int& subject_ei, std::vector<Vec2d>& removed_poly) const;
+    // Drag a polygon vertex while keeping the loop REGULAR: scale + rotate the whole
+    // polygon about its centroid so the grabbed vertex follows `target` (adjusts
+    // circumradius + orientation together).
+    void drag_polygon_vertex(int fi, int ei, SketchPointRole role, const Vec2d& target);
+    double measure_dim(const DimAnnot& a) const;                            // value from geometry
+    std::string dimtype_title(DimType k) const;
+    SketchEntityConstraintDef constraint_for(const DimAnnot& a) const;      // driving def
+    // One driving constraint (and one visible quote) per kind+operands: re-typing a value must
+    // UPDATE it, not append a rival asking for something else. Both return the index.
+    int upsert_constraint(const SketchEntityConstraintDef& c);
+    int upsert_dimension(const DimAnnot& a);
+    int  place_dimension(DimAnnot a);                                       // create+drive+notify
+    std::string dim_text(const DimAnnot& a) const;                          // rendered label string
+    void render_dimensions(double unit_per_px);                            // quote lines + labels
+    // Draw ONE dimension's quote (extension/dimension lines, arrowheads, label) and
+    // return its label centre in out_label; false if the annot can't be drawn. Shared
+    // by render_dimensions (placed driving quotes) and render_live_quotes (live ones).
+    bool draw_dim_quote(const DimAnnot& a, double th, const ColorRGBA& col, Vec2d& out_label);
+    // Live, non-driving characteristic quotes for the entity being edited (point/handle
+    // drag, or a lone selection): the tool's defining dimensions shown Onshape-style so
+    // editing shows live values; click one (m_live_quotes) to promote it to a driving
+    // dim. Self-gates; skips a dim already driven on that entity.
+    void render_live_quotes(double unit_per_px);
+    // Iconic constraint badges (C3.4b): for each m_constrain_cons entry, append a
+    // small screen-constant glyph (H, V, ∥, ⊥, =, ○, …) near its primary entity into
+    // `out`; glyphs touching the same entity stack so they don't overlap.
+    void build_constraint_glyphs(double unit_per_px,
+                                 const std::vector<SketchEntityConstraintDef>& cons,
+                                 std::vector<std::pair<Vec2d, Vec2d>>& out);
+    void draw_strokes(GLModel& model, const std::vector<std::pair<Vec2d, Vec2d>>& segs,
+                      double hw, const ColorRGBA& color);
+    void draw_text(GLModel& model, const std::string& s, const Vec2d& center,
+                   double height, const ColorRGBA& color);                  // GL stroke font
+    void draw_dim_label(const std::string& txt, const Vec2d& plane_center);
+
+    // Entity builders: append to m_entities (honoring the construction flag).
+    void push_line(const Vec2d& a, const Vec2d& b);
+    void push_closed_lines(const std::vector<Vec2d>& corners);
+    void push_open_chain(const std::vector<Vec2d>& pts);
+    void push_circle(const Vec2d& center, double radius);
+    void push_point(const Vec2d& p);
+
+    // Multi-click tool builders: return the entities for a finished gesture so
+    // both on_mouse (append) and render (preview) share one geometry path.
+    std::vector<SketchEntity> make_three_point_circle(const Vec2d& a, const Vec2d& b, const Vec2d& c) const;
+    std::vector<SketchEntity> make_three_point_arc(const Vec2d& start, const Vec2d& end, const Vec2d& on_arc) const;
+    std::vector<SketchEntity> make_tangent_arc(const Vec2d& start, const Vec2d& end) const;
+    // Center-start-end arc: click center, then start (sets radius), then a third
+    // point whose direction from the center sets the CCW end angle.
+    std::vector<SketchEntity> make_center_arc(const Vec2d& center, const Vec2d& start, const Vec2d& end_dir) const;
+    std::vector<SketchEntity> make_slot(const Vec2d& c0, const Vec2d& c1, double half_width) const;
+    std::vector<SketchEntity> make_arc_slot(const Vec2d& center, const Vec2d& start,
+                                            const Vec2d& end_dir, double half_width) const;
+    std::vector<SketchEntity> make_rounded_rect(const Vec2d& a, const Vec2d& b, const Vec2d& radius_pt) const;
+    std::vector<SketchEntity> rounded_rect_entities(double xmin, double ymin,
+                                                    double xmax, double ymax, double r) const;
+    // Rounded-rect grouped edit: W/H/fillet-R labels rebuild the 8-entity span in place.
+    void open_rounded_rect_editor(int fi, int which);   // 0=Width 1=Height 2=fillet R
+    void set_rounded_rect(int fi, double w, double h, double r);
+    // Arc-slot grouped edit: centreline-radius + width labels rebuild the 4-arc span.
+    void open_arc_slot_editor(int fi, bool radius);     // true=centreline R, false=width
+    void set_arc_slot(int fi, double Rc, double w);
+    // Straight-slot grouped edit: centreline-length + width labels rebuild the 4-entity span.
+    void open_slot_editor(int fi, int which);           // 0=inter-centre distance, 1=radius, 2=angle
+    void set_slot(int fi, double length, double w);
+    void set_slot_angle(int fi, double deg);            // rotate the centreline about c0, keep len+radius
+    // Grouped derived-handle drag: resize an axis-aligned rect by a corner (opposite corner
+    // fixed); move a slot end by its cap centre. Both rebuild the feature span geometrically.
+    void drag_rect_corner(int fi, const Vec2d& cursor);
+    void drag_slot_handle(int fi, const Vec2d& cursor);
+    std::vector<SketchEntity> make_polygon(const Vec2d& center, const Vec2d& vertex, int sides) const;
+    // Ellipse: click center, then major-axis endpoint (sets a + rotation phi),
+    // then a point whose perpendicular distance to the major axis sets b.
+    std::vector<SketchEntity> make_ellipse(const Vec2d& center, const Vec2d& major_end,
+                                           const Vec2d& minor_pt) const;
+    // Elliptical arc: same 3 axis clicks, then start and end points whose parametric
+    // angles on the ellipse bound the CCW sweep.
+    std::vector<SketchEntity> make_bspline(const std::vector<Vec2d>& ctrl) const;
+    std::vector<SketchEntity> make_ellipse_arc(const Vec2d& center, const Vec2d& major_end,
+                                               const Vec2d& minor_pt, const Vec2d& start_pt,
+                                               const Vec2d& end_pt) const;
+    void append_entities(const std::vector<SketchEntity>& ents);
+    void draw_entities_preview(const std::vector<SketchEntity>& ents, const ColorRGBA& color);
+
+    // --- In-canvas edit-op gizmo (Fillet/Chamfer/Offset/Mirror toolbar tools) --------
+    // These replace the docked numeric card: pick the entities in-canvas, then a draggable
+    // arrow with a value label is projected toward the corner/centre (Fillet/Chamfer/Offset),
+    // or a two-phase pick (axis line, then targets) drives a live mirrored ghost. The
+    // SketchEngine op is recomputed live so a translucent ghost previews the result; confirm
+    // applies the geometry and binds constraints into m_constraints (try_add_constraints).
+    bool op_corner(int a, int b, Vec2d& C, Vec2d& bis, double& theta) const; // line-line vertex + inward bisector
+    void op_pick(int ei);                       // route an entity pick to the active op
+    void recompute_op_ghost();                  // rebuild m_op_ghost from m_op_value
+    void render_op_gizmo(double unit_per_px);   // ghost + arrow + value label (caches m_op_label)
+    bool hit_test_op_arrow(const Vec2d& p, double tol) const;
+    void drag_op_arrow(const Vec2d& target);    // project cursor onto m_op_dir -> value
+    void open_op_editor();                      // inline-edit the value label
+    void confirm_op();                          // apply + bind, then reset for the next gesture
+    void reset_op();                            // clear gizmo state (keeps the tool active)
+    bool op_ready() const;                      // required entities picked -> arrow/ghost live
+
+    // Sample an entity into a 2D polyline for the overlay renderer.
+    std::vector<Vec2d> entity_polyline(const SketchEntity& e, bool& closed) const;
+
+    // Closed regions formed by the current (non-construction) entities: each a CCW-
+    // ordered boundary polygon on the plane. A circle is its own region; line/arc
+    // chains are walked endpoint-to-endpoint into loops. Used to fill faces.
+    std::vector<std::vector<Vec2d>> closed_regions() const;
+    std::vector<std::vector<Vec2d>> closed_regions(const std::vector<SketchEntity>& ents) const;
+    // Same loops, but each carries the indices of the entities that form it — so a single
+    // loop can be highlighted / extruded on its own (per-region selection on the plate).
+    // A selectable sketch region: its own boundary, plus the loops nested INSIDE it, which
+    // are its holes. Modelling holes is what makes "the plate with the hole in it" a thing the
+    // user can point at — without it a sketch is N disjoint filled polygons and the only
+    // selectable things are the rectangle alone or the circle alone (txp8).
+    struct RegionLoop {
+        std::vector<Vec2d> poly;
+        std::vector<int>   ents;
+        std::vector<int>   holes;   // indices into the same vector; one nesting level
+    };
+    std::vector<RegionLoop> region_loops(const std::vector<SketchEntity>& ents) const;
+    // Index of the closed region containing plane-point p (point-in-polygon), or -1.
+    int region_at(const Vec2d& p) const;
+
+    void draw_quad_strip(GLModel& model, const std::vector<Vec2d>& pts, bool closed, const ColorRGBA& color);
+    // half_size is the square marker half-extent in PLANE units. Callers pass a
+    // zoom-scaled value (k / zoom) for screen-constant handles; the default keeps
+    // legacy point markers exactly as before.
+    void draw_vertices(GLModel& model, const std::vector<Vec2d>& pts, const ColorRGBA& color,
+                       double half_size = 1.3);
+    void draw_fill(GLModel& model, const std::vector<Vec2d>& poly, const ColorRGBA& color);
+    // Same, with the region's holes cut out, so a selected plate-with-a-hole is drawn as an
+    // ANNULUS instead of a filled rectangle painted straight across its own bore.
+    void draw_fill_holed(GLModel& model, const std::vector<Vec2d>& outer,
+                         const std::vector<std::vector<Vec2d>>& holes, const ColorRGBA& color);
+    const ColorRGBA* sketch_hl_color(int feature) const;
+
+    bool                m_active{false};
+    SketchPlane         m_plane;
+    std::vector<Vec2d>  m_points;       // clicks of the in-progress entity / chain
+    std::vector<SketchEntity> m_entities; // committed entities of this session
+    bool                m_construction{false};
+    int                 m_polygon_sides{6};
+    bool                m_polygon_circumscribed{false};
+    Vec2d               m_cursor{0,0};
+    bool                m_has_cursor{false};
+    bool                m_snap_off{false};      // Shift held -> suppress angle snapping
+    InferenceSnap       m_cursor_snap;          // last cursor inference target (for hint render)
+    bool                m_cursor_locked{false}; // rubber-band segment is angle-locked
+    bool                m_awaiting_length{false}; // inline value editor open -> freeze canvas
+    int                 m_autoedit_seen{-1};      // entity count baseline for draw-then-edit
+    bool                m_autoedit_pending{false};// a new entity just committed -> open editor
+    // Draw-then-edit step queue: every characteristic dimension of the freshly-drawn shape
+    // (scalar quote OR geometric editor) becomes one step, opened in sequence over its label.
+    struct AutoEditStep {
+        Vec2d                       label;   // anchor (plane coords) — field opens over this
+        double                      value;   // initial value shown
+        std::function<void(double)> apply;   // commit: set the dimension
+        std::vector<int>            hi;      // entities to highlight while THIS field is open
+        std::string                 title;   // label shown above the value field
+    };
+    std::vector<AutoEditStep> m_autoedit_dims;    // queued steps to edit in sequence
+    int                 m_autoedit_dim_idx{-1};   // index into m_autoedit_dims (-1 = idle)
+    std::vector<int>    m_selection;              // selected entity indices (Mode::Select)
+    std::vector<std::pair<int, SketchPointRole>> m_point_sel;  // selected individual points
+    int                 m_last_mouse_x{0};        // last cursor pos (canvas client px), for
+    int                 m_last_mouse_y{0};        // anchoring the in-canvas value editor
+    bool                m_dragging_point{false};  // a point grab is in progress (Mode::Select)
+    int                 m_drag_ei{-1};            // entity whose point is being dragged
+    int                 m_drag_poly_fi{-1};       // >=0 if the grabbed point is a polygon
+                                                  // vertex: drag scales+rotates the loop
+    int                 m_drag_rect_fi{-1};       // >=0 if dragging an axis-aligned rect corner
+    Vec2d               m_drag_rect_anchor{0,0};  //   the fixed (opposite) corner
+    int                 m_drag_slot_fi{-1};       // >=0 if dragging a slot cap centre
+    bool                m_drag_slot_c1{false};    //   true=cap@c1, false=cap@c0
+    SketchPointRole     m_drag_role{SketchPointRole::P0};
+    std::vector<SketchEntityConstraintDef> m_constraints; // driving dims, committed on finish
+
+    // Onshape-style visual editing state.
+    bool                  m_show_handles{false};   // draw + interact with handles
+    bool                  m_dragging_handle{false};// a handle grab is in progress
+    Handle                m_drag_handle;           // the handle being dragged
+    bool                  m_has_hover_handle{false};// cursor is near a handle (highlight it)
+    Handle                m_hover_handle;          // the hovered handle (recomputed on move)
+    std::vector<DimAnnot> m_live_quotes;           // live non-driving characteristic quotes,
+                                                   // clickable to promote to driving dims
+    Vec2d                 m_live_poly_side_label{0,0};  // polygon side-length quote label
+    Vec2d                 m_live_poly_angle_label{0,0}; // polygon orientation quote label
+    int                   m_live_poly_fi{-1};           // their Feature (geometric edits)
+    Vec2d                 m_live_arc_angle_label{0,0};  // arc sweep-angle quote label
+    int                   m_live_arc_ei{-1};            // the arc it belongs to (geometric edit)
+    Vec2d                 m_live_ellipse_major_label{0,0}; // ellipse semi-major quote label
+    Vec2d                 m_live_ellipse_minor_label{0,0}; // ellipse semi-minor quote label
+    Vec2d                 m_live_ellipsearc_sweep_label{0,0}; // elliptical-arc sweep quote label
+    int                   m_live_ellipse_ei{-1};        // the ellipse the labels belong to
+    Vec2d                 m_live_obrect_angle_label{0,0}; // oblique-rect orientation quote label
+    int                   m_live_obrect_fi{-1};         // an OBLIQUE rect Feature (angle editable)
+    Vec2d                 m_live_rrect_w_label{0,0};    // rounded-rect width quote label
+    Vec2d                 m_live_rrect_h_label{0,0};    // rounded-rect height quote label
+    Vec2d                 m_live_rrect_r_label{0,0};    // rounded-rect fillet-radius label
+    int                   m_live_rrect_fi{-1};          // the rounded-rect Feature (rebuild edits)
+    Vec2d                 m_live_aslot_r_label{0,0};    // arc-slot centreline-radius label
+    Vec2d                 m_live_aslot_w_label{0,0};    // arc-slot width label
+    int                   m_live_aslot_fi{-1};          // the arc-slot Feature (rebuild edits)
+    Vec2d                 m_live_slot_len_label{0,0};   // straight-slot inter-centre distance label
+    Vec2d                 m_live_slot_w_label{0,0};     // straight-slot radius (half-width) label
+    Vec2d                 m_live_slot_angle_label{0,0}; // straight-slot centreline angle label
+    int                   m_live_slot_fi{-1};           // the straight-slot Feature (rebuild edits)
+    std::vector<Feature>  m_features;              // parametric groups over m_entities
+    int                   m_open_feature{-1};      // index of the Feature being built, or -1
+
+    // In-canvas edit-op gizmo state (Fillet/Chamfer/Offset/Mirror). GUI-only, reset by
+    // set_tool/cancel. Fillet/Chamfer: m_op_a,m_op_b = the two lines; Offset: m_op_a = src;
+    // Mirror: m_op_a = axis line, m_mirror_targets = entities to mirror.
+    // Last (mode, step, picks) reported through on_step_changed; -1 mode = nothing reported yet.
+    int    m_step_mode_last{-1};
+    int    m_step_last{-1};
+    int    m_step_picks_last{-1};
+    int    m_op_a{-1};
+    int    m_op_b{-1};
+    double m_op_value{0.0};                 // radius / setback / signed offset distance
+    Vec2d  m_op_anchor{0,0};                // arrow base (corner vertex / entity midpoint)
+    Vec2d  m_op_dir{0,0};                   // unit arrow direction (inward bisector / outward normal)
+    Vec2d  m_op_label{1e18,1e18};           // cached arrow-label centre, for picking
+    std::vector<SketchEntity> m_op_ghost;   // live result preview (recomputed on value change)
+    bool   m_op_dragging_arrow{false};      // arrowhead drag in progress
+    std::vector<int> m_mirror_targets;      // Mirror: entities to be mirrored (axis = m_op_a)
+
+    // In-canvas imported-art transform gizmo (Mode::TransformArt). GUI-only. The art's
+    // untransformed contours + its bbox in base coords; the live offset/scale; the grabbed
+    // handle (0..3 = corners, 4 = centre move, -1 = none) and the fixed world anchor (the
+    // opposite corner during a corner-scale drag).
+    std::vector<std::vector<std::vector<Vec2d>>> m_xform_base;
+    int    m_xform_feat{-1};
+    Vec2d  m_xform_min{0,0}, m_xform_max{0,0};   // bbox of m_xform_base (untransformed)
+    Vec2d  m_xform_offset{0,0};
+    double m_xform_sx{1.0}, m_xform_sy{1.0};
+    int    m_xform_handle{-1};
+    Vec2d  m_xform_anchor{0,0};
+    void   xform_world_corners(Vec2d out[4]) const;   // 4 bbox corners in plane coords
+    int    hit_test_xform_handle(const Vec2d& p, double tol) const;
+    void   drag_xform_handle(const Vec2d& target);
+    void   render_xform_gizmo();
+    void   emit_xform();
+    void   reset_xform();
+
+    // In-canvas transform gizmo state (Mode::Move/Rotate/Scale/Array/PolarArray). GUI-only,
+    // reset by set_tool/cancel. Pick one or more subject entities (m_tf_targets), then a
+    // single draggable handle drives the continuous parameter and a live translucent ghost
+    // previews the result; Array/PolarArray add a second editable label for the copy count.
+    // Mutating ops (Move/Rotate/Scale) drop the constraint classes the map invalidates;
+    // additive ops (Array/PolarArray) bind each copy to its source. See confirm_transform().
+    std::vector<int>          m_tf_targets;       // picked subject entity indices
+    Vec2d                     m_tf_pivot{0,0};    // rotate/scale/polar pivot = set centroid
+    Vec2d                     m_tf_delta{0,0};    // Move translation / Array per-step vector
+    double                    m_tf_angle{0.0};    // Rotate angle / PolarArray total sweep (rad)
+    double                    m_tf_scale{1.0};    // Scale factor
+    int                       m_tf_count{3};      // Array/PolarArray copy count (incl. original)
+    double                    m_tf_handle_r{1.0}; // ring/handle reference radius (set on pick)
+    std::vector<SketchEntity> m_tf_ghost;         // live result preview
+    int                       m_tf_handle{-1};    // 0 = primary drag handle grabbed, -1 = none
+    bool                      m_tf_dragging{false};
+    Vec2d                     m_tf_label_a{1e18,1e18};  // primary-param label centre (picking)
+    Vec2d                     m_tf_label_b{1e18,1e18};  // count label centre (Array/PolarArray)
+    bool                      tf_ready() const;   // >=1 target picked -> gizmo + ghost live
+    void                      tf_pick(int ei);    // accumulate a subject, seed defaults once
+    void                      compute_tf_pivot(); // centroid + extent of the target set
+    void                      recompute_tf_ghost();
+    Vec2d                     tf_handle_pos() const;   // world position of the drag handle
+    bool                      hit_test_tf_handle(const Vec2d& p, double tol) const;
+    void                      drag_tf_handle(const Vec2d& target);
+    void                      render_tf_gizmo(double unit_per_px);
+    void                      open_tf_editor_a();      // inline-edit the continuous parameter
+    void                      open_tf_editor_count();  // inline-edit the copy count
+    void                      confirm_transform();     // apply geometry + constraint web
+    void                      reset_tf();
+
+    // DoF feedback state, refreshed by resolve_live() from the libslvs solve result.
+    int               m_dof{-1};          // remaining DoF; 0 = fully constrained, <0 = unknown
+    bool              m_solve_ok{true};   // solver consistent (no conflicting constraints)
+    std::vector<char> m_entity_conflict;  // per-entity flag: touched by a conflicting constraint
+    std::vector<DimAnnot> m_dimensions;           // placed dimension quotes (Mode::Dimension)
+    int                 m_dim_e0{-1};             // first picked point's entity (Dimension)
+    SketchPointRole     m_dim_r0{SketchPointRole::P0};
+    bool                m_dim_has0{false};        // a first point is pending
+    int                 m_pending_dim{-1};        // dim awaiting a value-card entry
+    Mode                m_mode{Mode::Polyline};
+    int                 m_sel_a{-1};   // picked segment endpoints (legacy Constrain mode)
+    int                 m_sel_b{-1};
+    bool                m_constrain_entities{false}; // Constrain mode acts on entities
+    int                 m_pick0{-1};   // picked line-entity indices (entity Constrain)
+    int                 m_pick1{-1};
+    int                 m_pick2{-1};   // third slot (Symmetric axis)
+    Vec2d               m_pick0_pt{0,0}; // plane-coords of the slot-0 pick (trim/extend)
+    std::vector<int>    m_constraint_hl; // entities highlighted by the constraint manager
+    std::vector<SketchEntityConstraintDef> m_constrain_cons; // for glyph badges (C3.4b)
+    // Where each badge landed, so a click can find the constraint it stands for. Rebuilt by
+    // build_constraint_glyphs on every render, which is always the frame the user clicked on.
+    struct GlyphHit { Vec2d c{0,0}; int con{-1}; };
+    std::vector<GlyphHit> m_glyph_hits;
+    double                m_glyph_r{0.0};   // badge half-size in plane units (hit radius)
+    GLModel             m_line_model;
+    GLModel             m_vertex_model;
+    GLModel             m_highlight_model;
+    int                 m_dim_label_seq{0};
+    float               m_render_scale{1.0f};   // canvas scale for Measure-style dim labels
+    GLModel             m_fill_model;       // translucent face fill for closed regions
+    std::vector<DisplaySketch> m_display_sketches;  // committed sketches drawn persistently
+    std::vector<std::pair<int, ColorRGBA>> m_hl_sketches;  // feature index -> outline colour (Sweep/Loft operands)
+    int m_display_pick{-1};        // FEATURE index of the click-selected display sketch (-1 none)
+
+    // Solid (whole/face/edge) selection on the committed bodies. Pointers are non-owning,
+    // into CadDocument (bodies + display_mesh + per-triangle face/body ids), refreshed each
+    // recompute via set_solid_pick. m_sel_edge_pts caches the picked edge's world polyline.
+    const std::vector<CadBody>* m_solid_bodies{nullptr};
+    const TriangleMesh*     m_solid_mesh{nullptr};
+    const std::vector<int>* m_solid_tri_face{nullptr};
+    const std::vector<int>* m_solid_tri_body{nullptr};
+    const std::vector<bool>* m_solid_visible{nullptr};  // per-body visibility; hidden bodies aren't pickable
+    int m_pick_only_body{-1};        // >=0: only this body catches clicks (body-focus x-ray for CoordSys picking)
+    const std::vector<Transform3d>* m_solid_xform{nullptr};  // per-body display transform (for edge sampling)
+    Vec3d body_xform_pt(int body, const Vec3d& p) const;     // map an OCCT-shape point through the body xform
+    bool body_pickable(int b) const;                    // false when the body is explicitly hidden
+    SolidSel                m_solid_sel{SolidSel::None};
+    int                     m_sel_body{-1};   // which body the face/edge selection is on
+    int                     m_sel_face{-1};
+    int                     m_sel_edge{-1};
+    std::vector<Vec3d>      m_sel_edge_pts;
+    Vec3d                   m_sel_vertex_pt{Vec3d::Zero()};   // world point of a picked vertex
+    bool handle_solid_click(GLCanvas3D& canvas, const wxMouseEvent& evt);  // pick + notify
+    // What a click at (mx,my) WOULD take, resolved without touching the selection. One
+    // implementation, two callers: the click, and the hover pre-highlight that promises what the
+    // click is about to do. Split so the promise cannot drift from the act.
+    struct SolidPick {
+        SolidSel           kind{SolidSel::None};
+        int                body{-1}, face{-1}, edge{-1};
+        std::vector<Vec3d> edge_pts;
+        Vec3d              vertex_pt{Vec3d::Zero()};
+    };
+    bool resolve_solid_pick(GLCanvas3D& canvas, int mx, int my, SolidPick& out) const;
+    // HOVER PRE-HIGHLIGHT (9xw part 3). Vertex-beats-edge-beats-face is a rule the user
+    // cannot see until after they commit to a click; showing the outcome under the pointer is
+    // what makes the precedence learnable at all, and is the charter's L5 (one click, one visible
+    // change) read honestly — the change has to be predictable before the click, not only after.
+    SolidPick m_pre;                       // what the pointer is currently over (kind None = nothing)
+    bool update_solid_hover(GLCanvas3D& canvas, const wxMouseEvent& evt);  // true when it changed
+    // Left-drag rubber band: sweep a rectangle over the plate to take a whole body. Orbit
+    // moves to middle-drag in this canvas (DesignCanvas::set_cad_navigation) so the left
+    // button is free for it, which is the CAD convention (Onshape/SolidWorks).
+    GLSelectionRectangle m_rubber;
+    void pick_bodies_in_rectangle();       // resolve the swept rectangle -> whole-body selection
+    bool on_mouse_impl(wxMouseEvent& evt, GLCanvas3D& canvas);   // the body; on_mouse wraps it
+    // Nearest stroke + enclosing region of ONE committed sketch. Shared by the click and
+    // double-click paths so they cannot disagree about what is under the pointer.
+    void hit_display_sketch(const DisplaySketch& d, const Vec2d& p, double tol,
+                            int& edge_feat, int& edge_reg, int& edge_ent,
+                            double& edge_d, int& face_feat, int& face_reg) const;
+    bool m_right_consumed{false};          // last RightDown was a gesture terminator, not a menu
+    bool m_escalate_repick{true};          // re-picking the same sub-element takes the whole body
+    void render_solid_highlight();
+    // The shared body of the above: one highlight from explicit arguments, so the committed
+    // selection and the hover pre-highlight cannot drift apart in how they look.
+    void render_solid_sel(SolidSel kind, int body, int face, const std::vector<Vec3d>& edge_pts,
+                          const Vec3d& vertex_pt, const ColorRGBA& rgb, float alpha_mul);
+    void render_datum_planes();           // translucent rectangles for datum/reference planes
+    void render_view_helpers();           // world origin planes + axis triad (P / A toggles)
+    bool m_show_planes{false};
+    bool m_show_axes{false};
+    std::vector<SketchPlane> m_datum_planes;
+    std::vector<Vec2d>       m_datum_sizes;   // per-plane (u,v) full extent; empty -> default
+    void render_mate_connectors();            // disc + roll quadrant + one-sided Z arrow
+    // The face treatment of the same connector: a shaded low-poly relief of a bear's head in the
+    // connector's own frame. Draws the plate, the snout tent and the marks; the caller still draws
+    // the Z arrow, which is shared with the disc treatment.
+    void render_mate_face(const Vec3d& origin, const Vec3d& X, const Vec3d& Y, const Vec3d& Z,
+                          double R, const ColorRGBA& body);
+    std::vector<MateConnectorGlyph> m_mate_connectors;
+    std::vector<std::pair<Vec3d, Vec3d>> m_mate_links;
+    GLModel m_mc_stroke_model;
+    GLModel m_mc_fill_model;      // the face treatment's shaded facets
+    GLModel m_solid_face_model;
+    GLModel m_solid_edge_model;
+    GLModel m_solid_vertex_model;
+    int m_display_pick_region{-1}; // selected closed-region index within that feature (-1 none)
+
+    // Visual Extrude gizmo state (C5b). GUI-only; fed by the panel each refresh_preview.
+    bool        m_ex_active{false};
+    SketchPlane m_ex_plane;             // profile plane (gives normal + to_world anchor)
+    Vec2d       m_ex_centroid{0,0};     // arrow base in plane coords (profile centroid)
+    double      m_ex_depth{0.0};        // primary depth (= m_distance)
+    double      m_ex_depth2{0.0};       // second-side depth (TwoSided, = m_distance2)
+    bool        m_ex_two_sided{false};
+    bool        m_ex_flip{false};
+    int         m_ex_drag{-1};          // 0 = primary arrow, 1 = second arrow, -1 = none
+    int         m_ex_press_x{0}, m_ex_press_y{0};   // press px to tell click-to-edit from drag
+    void  render_extrude_gizmo();
+    bool  hit_test_extrude_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const;
+    void  drag_extrude_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt, int which);
+    void  open_extrude_editor(int which);
+    GLModel m_ex_arrow_model;
+
+    // Datum-plane resize gizmo state (C3). GUI-only; fed by the panel while the Plane card is open.
+    bool        m_dz_active{false};
+    SketchPlane m_dz_plane;              // resolved datum frame (origin + axes)
+    double      m_dz_usize{60.0};        // current u extent (full width)
+    double      m_dz_vsize{60.0};        // current v extent (full height)
+    int         m_dz_drag{-1};           // 0=+u,1=-u,2=+v,3=-v handle, 4=offset tip, -1 none
+    int         m_dz_press_x{0}, m_dz_press_y{0};
+    Vec3d       m_dz_anchor{Vec3d::Zero()};   // base-plane origin (offset arrow tail)
+    Vec3d       m_dz_normal{0.0, 0.0, 1.0};   // base normal (offset arrow direction)
+    double      m_dz_offset{0.0};             // current signed offset along the base normal
+    bool        m_dz_offset_on{false};        // draw/allow the offset arrow (Offset-from-base only)
+    void  render_datum_gizmo();
+    bool  hit_test_datum_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const;
+    void  drag_datum_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int which);
+    // Helix gizmo state (plane-anchored curve + 3 drag handles). Fed by the panel while the
+    // Helix card is open (sketch tool NOT active); the tool draws the live helix plus a handle
+    // on each length parameter (radius/height/pitch). Taper and handedness stay on the card.
+    bool        m_hx_active{false};
+    SketchPlane m_hx_plane;                  // axis = plane normal, base circle in the plane
+    double      m_hx_radius{10.0};
+    double      m_hx_pitch{2.0};
+    double      m_hx_height{20.0};
+    double      m_hx_taper{0.0};             // DEGREES (cone half-angle), as the kernel reads it
+    bool        m_hx_left{false};
+    int         m_hx_drag{-1};               // 0=radius, 1=height, 2=pitch, -1 none
+    int         m_hx_press_x{0}, m_hx_press_y{0};
+    Vec3d helix_point(double t) const;       // curve point at parameter t (shared render/hit/drag)
+    void  render_helix_gizmo();
+    bool  hit_test_helix_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const;
+    void  drag_helix_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int which);
+    // Rib thickness gizmo state (plane-anchored slab footprint + 2 drag handles). Fed by the
+    // panel while the Rib card is open (sketch tool NOT active); the tool draws the rib's
+    // footprint outline and a handle on each side of the line at half-thickness. Dragging either
+    // handle sets the full thickness (the slab is centred on the line).
+    bool        m_rb_active{false};
+    SketchPlane m_rb_plane;
+    Vec2d       m_rb_p0{Vec2d::Zero()};      // rib line endpoints, in plane coords
+    Vec2d       m_rb_p1{Vec2d::Zero()};
+    double      m_rb_thickness{2.0};
+    int         m_rb_drag{-1};               // 0 = +perp handle, 1 = -perp handle, -1 none
+    void  render_rib_gizmo();
+    bool  hit_test_rib_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const;
+    void  drag_rib_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int which);
+    // Datum base picker (translucent clickable origin/datum planes)
+    bool        m_dbp_active{false};
+    std::vector<SketchPlane>  m_dbp_planes;
+    std::vector<int>          m_dbp_base;
+    std::vector<std::string>  m_dbp_labels;
+    int         m_dbp_hover{-1};
+    double      dbp_half_extent() const;   // bed-derived: reference planes are larger than the bed
+    void render_base_pick();
+    int  hit_test_base_pick(GLCanvas3D& canvas, const wxMouseEvent& evt) const;
+
+    // Move-body gizmo state: 3 world-axis translate arrows + 3 world-axis rotate rings.
+    // Delta model: offset/rot are deltas about a fixed pivot, composed onto m_mv_base_xform
+    // (the body's pose when Move opened) so rotation works even on an already-placed body.
+    bool        m_mv_active{false};
+    int         m_mv_body{-1};
+    Vec3d       m_mv_base{Vec3d::Zero()};      // pivot = body's world centroid at Move-open
+    Vec3d       m_mv_offset{Vec3d::Zero()};    // delta translation along world X/Y/Z
+    Transform3d m_mv_base_xform{Transform3d::Identity()};  // pose when Move opened
+    Eigen::Matrix3d m_mv_rot{Eigen::Matrix3d::Identity()}; // accumulated delta rotation (world, about pivot)
+    Eigen::Matrix3d m_mv_rot_start{Eigen::Matrix3d::Identity()}; // rot snapshot at arc-drag start
+    double      m_mv_arc_a0{0.0};              // mouse angle on the ring at drag start
+    int         m_mv_drag{-1};                 // 0..2 = X/Y/Z arrow, 3..5 = X/Y/Z ring, -1 none
+    double      m_mv_radius{0.0};              // body bounding-sphere radius (mm); 0 = unknown
+    int         m_mv_press_x{0}, m_mv_press_y{0};
+    Transform3d compose_move_xform() const;    // T(offset)*T(pivot)*rot*T(-pivot)*base_xform
+    void  ring_basis(int axis, Vec3d& e, Vec3d& u, Vec3d& v) const;  // world axis + in-plane basis
+    void  render_move_gizmo();
+    // Gizmo arm length (world mm): scales with the body so the rings clear its surface.
+    double move_gizmo_arm(const Camera& cam) const;
+    bool  hit_test_move_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt, int& axis) const;
+    bool  hit_test_move_arc(GLCanvas3D& canvas, const wxMouseEvent& evt, int& axis) const;
+    void  drag_move_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt, int axis);
+    void  drag_move_arc(GLCanvas3D& canvas, const wxMouseEvent& evt, int axis);
+    bool  arc_mouse_angle(GLCanvas3D& canvas, const wxMouseEvent& evt, int axis, double& ang) const;
+    void  open_move_editor(int axis);
+    GLModel m_mv_arrow_model;
+
+    // Fillet/Chamfer radius gizmo state (single world-space arrow at the picked edge midpoint).
+    bool        m_fl_active{false};
+    Vec3d       m_fl_anchor{Vec3d::Zero()};    // edge midpoint (world, already body-transformed)
+    Vec3d       m_fl_dir{Vec3d::UnitZ()};      // unit radius direction (perp to edge, outward)
+    double      m_fl_radius{1.0};              // current radius (= dressup size)
+    bool        m_fl_drag{false};
+    int         m_fl_press_x{0}, m_fl_press_y{0};
+    double      m_fl_grab_proj{0.0};           // axis projection at grab (relative drag reference)
+    double      m_fl_grab_radius{1.0};         // radius at grab (relative drag reference)
+    void  render_fillet_gizmo();
+    bool  hit_test_fillet_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt) const;
+    double fillet_axis_proj(GLCanvas3D& canvas, const wxMouseEvent& evt) const;  // NaN if camera∥axis
+    void  start_fillet_drag(GLCanvas3D& canvas, const wxMouseEvent& evt);
+    void  drag_fillet_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt);
+    void  open_fillet_editor();
+    GLModel m_fl_arrow_model;
+
+    // Hole gizmo state. The hole is a positioned circular cut on m_hl_plane at (m_hl_x, m_hl_y);
+    // the footprint circle is drawn on the plane, the diameter arrow runs along the plane u-axis,
+    // the depth arrow along +normal (matching the kernel's make_extrude). Three draggable handles:
+    // 0 = centre (reposition in plane u/v), 1 = diameter, 2 = depth (only shown when !through).
+    bool        m_hl_active{false};
+    SketchPlane m_hl_plane;
+    double      m_hl_x{0.0}, m_hl_y{0.0};      // centre on the plane (u/v mm)
+    double      m_hl_diameter{6.0};
+    double      m_hl_depth{10.0};
+    bool        m_hl_through{true};
+    // #2 Part B: face (u,v) bounds, so the construction dims read as distance from the face SIDES
+    // (umin/vmin = two adjacent edges) rather than from the centre. Off for a dropdown-plane hole.
+    bool        m_hl_has_bounds{false};
+    double      m_hl_umin{0}, m_hl_umax{0}, m_hl_vmin{0}, m_hl_vmax{0};
+    int         m_hl_drag{-1};                 // 0=centre, 1=diameter, 2=depth, 3=X-dim, 4=Y-dim, -1=none
+    int         m_hl_press_x{0}, m_hl_press_y{0};
+    double      m_hl_grab_proj{0.0};           // diameter/depth axis projection at grab (relative)
+    double      m_hl_grab_val{0.0};            // radius (diameter drag) or depth at grab
+    Vec2d       m_hl_grab_uv{0.0, 0.0};        // centre drag: plane-projected grab point
+    double      m_hl_grab_x{0.0}, m_hl_grab_y{0.0};   // centre drag: x/y at grab
+    void   render_hole_gizmo();
+    int    hit_test_hole_handle(GLCanvas3D& canvas, const wxMouseEvent& evt) const;  // 0/1/2/-1
+    double hole_axis_proj(GLCanvas3D& canvas, const wxMouseEvent& evt,
+                          const Vec3d& anchor, const Vec3d& dir) const;   // NaN if camera∥axis
+    void   start_hole_drag(GLCanvas3D& canvas, const wxMouseEvent& evt, int which);
+    void   drag_hole_handle(GLCanvas3D& canvas, const wxMouseEvent& evt);
+    void   open_hole_editor(int which);
+    GLModel m_hl_stroke_model;
+
+    // Thread gizmo state (mirrors the hole gizmo; radius arrow uses an R label, length arrow is
+    // always shown). Handles: 0 = centre (thread_x/y), 1 = radius, 2 = length.
+    bool        m_th_active{false};
+    SketchPlane m_th_plane;
+    double      m_th_x{0.0}, m_th_y{0.0};
+    double      m_th_radius{5.0};
+    double      m_th_height{10.0};
+    int         m_th_drag{-1};                 // 0=centre, 1=radius, 2=length, -1=none
+    int         m_th_press_x{0}, m_th_press_y{0};
+    double      m_th_grab_proj{0.0};
+    double      m_th_grab_val{0.0};
+    Vec2d       m_th_grab_uv{0.0, 0.0};
+    double      m_th_grab_x{0.0}, m_th_grab_y{0.0};
+    void   render_thread_gizmo();
+    int    hit_test_thread_handle(GLCanvas3D& canvas, const wxMouseEvent& evt) const;  // 0/1/2/-1
+    void   start_thread_drag(GLCanvas3D& canvas, const wxMouseEvent& evt, int which);
+    void   drag_thread_handle(GLCanvas3D& canvas, const wxMouseEvent& evt);
+    void   open_thread_editor(int which);
+    GLModel m_th_stroke_model;
+
+    // Shell gizmo state (single inward thickness arrow at the picked face centroid).
+    bool        m_sh_active{false};
+    Vec3d       m_sh_anchor{Vec3d::Zero()};    // picked face centroid (world)
+    Vec3d       m_sh_dir{Vec3d::UnitZ()};      // inward unit direction (-outward normal)
+    double      m_sh_thickness{2.0};
+    bool        m_sh_drag{false};
+    int         m_sh_press_x{0}, m_sh_press_y{0};
+    double      m_sh_grab_proj{0.0};
+    double      m_sh_grab_val{2.0};
+    void   render_shell_gizmo();
+    bool   hit_test_shell_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt) const;
+    void   start_shell_drag(GLCanvas3D& canvas, const wxMouseEvent& evt);
+    void   drag_shell_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt);
+    void   open_shell_editor();
+    GLModel m_sh_stroke_model;
+
+    // Revolve gizmo state (arc center = projection of the profile centroid onto the axis).
+    bool        m_rv_active{false};
+    Vec3d       m_rv_center{Vec3d::Zero()};   // arc center on the axis (world)
+    Vec3d       m_rv_axis{Vec3d::UnitX()};    // revolve axis unit dir (world)
+    Vec3d       m_rv_ref{Vec3d::UnitY()};     // angle-0 reference dir (perp to axis, toward profile)
+    double      m_rv_radius{10.0};            // arc radius = profile perpendicular distance (world)
+    double      m_rv_angle{360.0};            // current sweep magnitude (deg, 1..360)
+    bool        m_rv_flip{false};             // sweep sense (matches the kernel's negative-angle flip)
+    bool        m_rv_drag{false};
+    int         m_rv_press_x{0}, m_rv_press_y{0};
+    void   render_revolve_gizmo();
+    bool   hit_test_revolve_handle(GLCanvas3D& canvas, const wxMouseEvent& evt) const;
+    void   drag_revolve_arc(GLCanvas3D& canvas, const wxMouseEvent& evt);
+    void   open_revolve_editor();
+    GLModel m_rv_stroke_model;
+
+    // Draft gizmo state (arc center = picked face centroid; axis = world +Z, taper pull direction).
+    bool        m_dr_active{false};
+    Vec3d       m_dr_center{Vec3d::Zero()};   // arc center = face centroid (world)
+    Vec3d       m_dr_axis{Vec3d::UnitZ()};    // draft axis = world +Z (pull direction)
+    Vec3d       m_dr_ref{Vec3d::UnitX()};     // angle-0 reference dir (perp to axis)
+    double      m_dr_radius{10.0};            // arc radius (world)
+    double      m_dr_angle{5.0};              // current sweep magnitude (deg, [-89, 89])
+    bool        m_dr_drag{false};
+    int         m_dr_press_x{0}, m_dr_press_y{0};
+    void   render_draft_gizmo();
+    bool   hit_test_draft_handle(GLCanvas3D& canvas, const wxMouseEvent& evt) const;
+    void   drag_draft_arc(GLCanvas3D& canvas, const wxMouseEvent& evt);
+    GLModel m_dr_stroke_model;
+    std::function<void(double)> m_on_draft_angle_changed;
+
+    // Cut gizmo state (plane normal arrow + wire rectangle at the current offset).
+    bool        m_ct_active{false};
+    Vec3d       m_ct_base{Vec3d::Zero()};       // body centre projected into the cut plane
+    Vec3d       m_ct_n{Vec3d::UnitZ()};         // cut plane normal (unit)
+    Vec3d       m_ct_u{Vec3d::UnitX()};         // cut plane U axis (unit)
+    Vec3d       m_ct_v{Vec3d::UnitY()};         // cut plane V axis (unit)
+    double      m_ct_offset{0.0};
+    double      m_ct_half{10.0};
+    bool        m_ct_drag{false};
+    double      m_ct_grab_val{0.0};
+    double      m_ct_grab_proj{0.0};
+    void   render_cut_gizmo();
+    bool   hit_test_cut_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt) const;
+    void   start_cut_drag(GLCanvas3D& canvas, const wxMouseEvent& evt);
+    void   drag_cut_arrow(GLCanvas3D& canvas, const wxMouseEvent& evt);
+    GLModel m_ct_stroke_model;
+    GLModel m_ct_rect_model;
+    std::function<void(double)> m_on_cut_offset_changed;
+
+    // Pattern gizmo state. Linear arrow along m_pt_dirw from m_pt_base; circular arc like Revolve
+    // but axis = m_pt_normal through m_pt_origin (the world XY plane by default).
+    bool   m_pt_active{false};
+    bool   m_pt_circular{false};
+    Vec3d  m_pt_base{Vec3d::Zero()};     // target body centroid (world): linear anchor / radius ref
+    Vec3d  m_pt_dirw{Vec3d::UnitX()};    // linear march direction (world)
+    Vec3d  m_pt_origin{Vec3d::Zero()};   // circular rotation axis origin (world)
+    Vec3d  m_pt_normal{Vec3d::UnitZ()};  // circular rotation axis (world)
+    Vec3d  m_pt_cref{Vec3d::UnitX()};    // circular angle-0 reference dir (perp to normal, toward body)
+    Vec3d  m_pt_ccenter{Vec3d::Zero()};  // circular arc center (foot of body centroid on the axis)
+    double m_pt_radius{10.0};            // circular arc radius (world)
+    int    m_pt_count{3};
+    double m_pt_spacing{20.0};
+    double m_pt_angle{360.0};
+    bool   m_pt_drag{false};
+    int    m_pt_press_x{0}, m_pt_press_y{0};
+    void   render_pattern_gizmo();
+    bool   hit_test_pattern_handle(GLCanvas3D& canvas, const wxMouseEvent& evt) const;
+    void   drag_pattern_handle(GLCanvas3D& canvas, const wxMouseEvent& evt);
+    void   open_pattern_editor();
+    GLModel m_pt_stroke_model;
+};
+
+}} // namespace Slic3r::GUI
+
+#endif // slic3r_DesignSketchTool_hpp_
diff --git a/src/slic3r/GUI/CAD/McpControl.cpp b/src/slic3r/GUI/CAD/McpControl.cpp
new file mode 100644
index 0000000000..8e34e2aac8
--- /dev/null
+++ b/src/slic3r/GUI/CAD/McpControl.cpp
@@ -0,0 +1,2221 @@
+#include "slic3r/GUI/CAD/McpControl.hpp"
+
+#ifndef _WIN32  // POSIX Unix-domain-socket transport only (slice 1)
+
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <sys/stat.h>   // umask/chmod: the socket's file mode IS its access control
+#include <unistd.h>
+#include <cstdlib>
+#include <cstring>
+#include <string>
+#include <vector>
+#include <thread>
+#include <future>
+#include <chrono>
+#include <memory>
+#include <cmath>
+#include <algorithm>
+#include <utility>
+
+#include <nlohmann/json.hpp>
+#include <boost/log/trivial.hpp>
+#include <Standard_Failure.hxx>   // OCCT base error (not a std::exception)
+
+#include "slic3r/GUI/GUI_App.hpp"
+#include "slic3r/GUI/MainFrame.hpp"
+#include "slic3r/GUI/CAD/DesignPanel.hpp"
+#include "slic3r/GUI/CAD/DesignCanvas.hpp"
+#include "slic3r/GUI/CAD/DesignSketchTool.hpp"
+#include "slic3r/GUI/CAD/DesignOffer.hpp"   // offer table — served whole by list_verbs, fired by run_verb
+
+#include "libslic3r/CAD/CadDocument.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
+#include "libslic3r/CAD/GeometryEngine.hpp"
+#include "libslic3r/TriangleMesh.hpp"
+#include "libslic3r/Format/OBJ.hpp"
+#include <boost/algorithm/string/case_conv.hpp>
+#include <boost/filesystem/path.hpp>
+#include "libslic3r/BoundingBox.hpp"
+
+#include <gp_Pln.hxx>
+#include <BRepAlgoAPI_Section.hxx>
+#include <TopExp_Explorer.hxx>
+#include <TopoDS.hxx>
+#include <TopoDS_Edge.hxx>
+#include <TopoDS_Compound.hxx>
+#include <BRep_Builder.hxx>
+#include <GProp_GProps.hxx>
+#include <BRepGProp.hxx>
+#include <Bnd_Box.hxx>
+#include <BRepBndLib.hxx>
+
+using json = nlohmann::json;
+
+namespace Slic3r { namespace GUI {
+
+namespace {
+
+const char* feature_type_name(CadFeatureType t)
+{
+    switch (t) {
+        case CadFeatureType::Sketch:  return "Sketch";
+        case CadFeatureType::Extrude: return "Extrude";
+        case CadFeatureType::Fillet:  return "Fillet";
+        case CadFeatureType::Chamfer: return "Chamfer";
+        case CadFeatureType::Hole:    return "Hole";
+        case CadFeatureType::Thread:  return "Thread";
+        case CadFeatureType::Shell:   return "Shell";
+        case CadFeatureType::Revolve: return "Revolve";
+        case CadFeatureType::Sweep:   return "Sweep";
+        case CadFeatureType::Pattern: return "Pattern";
+        case CadFeatureType::Plane:   return "Plane";
+        case CadFeatureType::Loft:    return "Loft";
+        case CadFeatureType::Draft:   return "Draft";
+        case CadFeatureType::Import:  return "Import";
+        case CadFeatureType::Boolean: return "Boolean";
+         case CadFeatureType::Cut:     return "Cut";
+        case CadFeatureType::Mirror:  return "Mirror";
+        case CadFeatureType::Axis:    return "Axis";
+        case CadFeatureType::CoordSys: return "CoordSys";
+        case CadFeatureType::Helix:    return "Helix";
+        case CadFeatureType::Transform: return "Transform";
+        case CadFeatureType::Thicken:  return "Thicken";
+        case CadFeatureType::Project:  return "Project";
+        case CadFeatureType::DeleteFace: return "DeleteFace";
+        case CadFeatureType::Rib:        return "Rib";
+        case CadFeatureType::SurfaceExtrude: return "SurfaceExtrude";
+        case CadFeatureType::SurfaceRevolve: return "SurfaceRevolve";
+        case CadFeatureType::ThickenSurface: return "ThickenSurface";
+        case CadFeatureType::SurfaceOffset:   return "SurfaceOffset";
+        case CadFeatureType::SurfaceLoft:     return "SurfaceLoft";
+        case CadFeatureType::SurfaceFill:     return "SurfaceFill";
+        case CadFeatureType::Mate:      return "Mate";
+    }
+    return "Unknown";
+}
+
+// --- JSON-RPC envelope helpers -------------------------------------------------
+std::string rpc_result(const json& id, const json& result)
+{
+    return json{{"jsonrpc", "2.0"}, {"id", id}, {"result", result}}.dump();
+}
+std::string rpc_error(const json& id, int code, const std::string& msg)
+{
+    return json{{"jsonrpc", "2.0"}, {"id", id},
+                {"error", {{"code", code}, {"message", msg}}}}.dump();
+}
+
+// --- the three slice-1 methods (run on the wx MAIN thread) ---------------------
+
+json describe_tools()
+{
+    // Hand-written descriptor. The bridge turns this into MCP tool schemas; later
+    // slices grow this list (ideally from the kernel directly).
+    return json{
+        {"app", "Orca CAD"},
+        {"protocol", "jsonrpc-2.0"},
+        {"slice", 5},
+        // Read this before using any face or edge id.
+        {"id_lifetime",
+         "Global face and edge ids are indices into the CURRENT topology and expire the moment "
+         "a feature rebuilds the model. Reading the scene once and then issuing several "
+         "operations addresses the wrong edge on every call after the first, and does NOT "
+         "error, because a stale id still names a real edge. Either re-read query_topology "
+         "before each id-taking call, or pass the 'generation' you were given back with the "
+         "call and have it refused if the model has moved on."},
+        {"tools", json::array({
+            json{{"name", "describe_tools"}, {"summary", "List callable tools and their parameters."},
+                 {"params", json::array()}},
+            json{{"name", "describe_scene"}, {"summary", "Feature tree + per-body bounding boxes of the Design document."},
+                 {"params", json::array()}},
+            json{{"name", "extrude"}, {"summary", "Extrude a profile to a depth. Give an explicit closed `profile` (list of [x,y]) or default to a centred width x height rectangle. End conditions match Onshape."},
+                 {"params", json::array({
+                     json{{"name", "width"},    {"type", "number"}, {"unit", "mm"}, {"default", 20}, {"min", 0.01}},
+                     json{{"name", "height"},   {"type", "number"}, {"unit", "mm"}, {"default", 20}, {"min", 0.01}},
+                     json{{"name", "distance"}, {"type", "number"}, {"unit", "mm"}, {"default", 10}, {"min", 0.01}},
+                     json{{"name", "plane"},    {"type", "string"}, {"enum", json::array({"XY", "XZ", "YZ"})}, {"default", "XY"}},
+                     json{{"name", "profile"},  {"type", "array"}, {"default", json::array()}, {"description", "optional closed contour [[x,y],...] in plane mm; overrides width/height"}},
+                     json{{"name", "boolean"},  {"type", "string"}, {"enum", json::array({"new", "union", "subtract", "intersect"})}, {"default", "new"}},
+                     json{{"name", "end"},      {"type", "string"}, {"enum", json::array({"blind", "symmetric", "two_sided", "through_all", "up_to_face"})}, {"default", "blind"}},
+                     json{{"name", "distance2"},{"type", "number"}, {"unit", "mm"}, {"default", 0}, {"description", "second-side depth when end=two_sided (else falls back to distance)"}},
+                     json{{"name", "up_to_face"},{"type", "integer"}, {"default", -1}, {"description", "target face id (query_topology on the last body) when end=up_to_face"}},
+                     json{{"name", "taper"},    {"type", "number"}, {"unit", "deg"}, {"default", 0}, {"description", "draft/taper of the side wall"}},
+                     json{{"name", "flip"},     {"type", "boolean"}, {"default", false}},
+                 })}},
+            json{{"name", "revolve"}, {"summary", "Revolve a profile about a plane axis. Give an explicit `profile` offset from the axis (or a rectangle) — angle degrees about axis 0=plane X / 1=plane Y."},
+                 {"params", json::array({
+                     json{{"name", "width"},   {"type", "number"}, {"unit", "mm"}, {"default", 20}, {"min", 0.01}},
+                     json{{"name", "height"},  {"type", "number"}, {"unit", "mm"}, {"default", 10}, {"min", 0.01}},
+                     json{{"name", "angle"},   {"type", "number"}, {"unit", "deg"}, {"default", 360}},
+                     json{{"name", "axis"},    {"type", "integer"}, {"enum", json::array({0, 1})}, {"default", 0}},
+                     json{{"name", "flip"},    {"type", "boolean"}, {"default", false}},
+                     json{{"name", "plane"},   {"type", "string"}, {"enum", json::array({"XY", "XZ", "YZ"})}, {"default", "XY"}},
+                     json{{"name", "profile"}, {"type", "array"}, {"default", json::array()}, {"description", "optional closed contour [[x,y],...] in plane mm; overrides width/height"}},
+                     json{{"name", "boolean"}, {"type", "string"}, {"enum", json::array({"new", "union", "subtract", "intersect"})}, {"default", "new"}},
+                 })}},
+            json{{"name", "fillet"}, {"summary", "Round a measured edge of a body (edge id from query_topology on that body)."},
+                 {"params", json::array({
+                     json{{"name", "edge"},   {"type", "integer"}},
+                     json{{"name", "radius"}, {"type", "number"}, {"unit", "mm"}, {"default", 1}, {"min", 0.01}},
+                     json{{"name", "body"},   {"type", "integer"}, {"default", -1}, {"description", "target body; omit for the last body. edge id is resolved against THIS body."}},
+                 })}},
+            json{{"name", "chamfer"}, {"summary", "Chamfer a measured edge of a body (edge id from query_topology on that body)."},
+                 {"params", json::array({
+                     json{{"name", "edge"},     {"type", "integer"}},
+                     json{{"name", "distance"}, {"type", "number"}, {"unit", "mm"}, {"default", 1}, {"min", 0.01}},
+                     json{{"name", "body"},     {"type", "integer"}, {"default", -1}, {"description", "target body; omit for the last body. edge id is resolved against THIS body."}},
+                 })}},
+            json{{"name", "hole"}, {"summary", "Drill a circular hole into the current body at (x,y) on a plane."},
+                 {"params", json::array({
+                     json{{"name", "diameter"}, {"type", "number"}, {"unit", "mm"}, {"default", 5}, {"min", 0.01}},
+                     json{{"name", "depth"},    {"type", "number"}, {"unit", "mm"}, {"default", 10}, {"min", 0.01}},
+                     json{{"name", "through"},  {"type", "boolean"}, {"default", false}},
+                     json{{"name", "x"},        {"type", "number"}, {"unit", "mm"}, {"default", 0}, {"description", "in the sketch plane's frame (origin = describe_scene.modeling_origin), NOT world"}},
+                     json{{"name", "y"},        {"type", "number"}, {"unit", "mm"}, {"default", 0}, {"description", "in the sketch plane's frame (origin = describe_scene.modeling_origin), NOT world"}},
+                     json{{"name", "plane"},    {"type", "string"}, {"enum", json::array({"XY", "XZ", "YZ"})}, {"default", "XY"}},
+                 })}},
+            json{{"name", "hole_styled"}, {"summary", "Drill a hole with optional counterbore (style=1) or countersink (style=2) at (x,y) on a plane."},
+                 {"params", json::array({
+                     json{{"name", "diameter"},        {"type", "number"}, {"unit", "mm"}, {"default", 5}, {"min", 0.01}},
+                     json{{"name", "depth"},           {"type", "number"}, {"unit", "mm"}, {"default", 10}, {"min", 0.01}},
+                     json{{"name", "through"},         {"type", "boolean"}, {"default", true}},
+                     json{{"name", "x"},               {"type", "number"}, {"unit", "mm"}, {"default", 0}, {"description", "in the sketch plane's frame (origin = describe_scene.modeling_origin), NOT world"}},
+                     json{{"name", "y"},               {"type", "number"}, {"unit", "mm"}, {"default", 0}, {"description", "in the sketch plane's frame (origin = describe_scene.modeling_origin), NOT world"}},
+                     json{{"name", "plane"},           {"type", "string"}, {"enum", json::array({"XY", "XZ", "YZ"})}, {"default", "XY"}},
+                     json{{"name", "style"},           {"type", "integer"}, {"default", 0}, {"description", "0=simple, 1=counterbore, 2=countersink"}},
+                     json{{"name", "cbore_diameter"},  {"type", "number"}, {"unit", "mm"}, {"default", 0}},
+                     json{{"name", "cbore_depth"},     {"type", "number"}, {"unit", "mm"}, {"default", 0}},
+                     json{{"name", "csink_diameter"},  {"type", "number"}, {"unit", "mm"}, {"default", 0}},
+                     json{{"name", "csink_angle"},     {"type", "number"}, {"unit", "deg"}, {"default", 90}},
+                     json{{"name", "standard"},        {"type", "string"}, {"default", ""}, {"description", "provenance designation, e.g. M6"}},
+                 })}},
+            json{{"name", "hole_standard"}, {"summary", "Drill a standard clearance hole (ISO 273 / ANSI) at (x,y) on a plane. style: 0=simple, 1=counterbore, 2=countersink."},
+                 {"params", json::array({
+                     json{{"name", "designation"},  {"type", "string"}, {"description", "e.g. M6, 1/4-20"}},
+                     json{{"name", "style"},        {"type", "integer"}, {"default", 0}},
+                     json{{"name", "through"},      {"type", "boolean"}, {"default", true}},
+                     json{{"name", "depth"},        {"type", "number"}, {"unit", "mm"}, {"default", 10}, {"min", 0.01}},
+                     json{{"name", "x"},            {"type", "number"}, {"unit", "mm"}, {"default", 0}, {"description", "in the sketch plane's frame (origin = describe_scene.modeling_origin), NOT world"}},
+                     json{{"name", "y"},            {"type", "number"}, {"unit", "mm"}, {"default", 0}, {"description", "in the sketch plane's frame (origin = describe_scene.modeling_origin), NOT world"}},
+                     json{{"name", "plane"},        {"type", "string"}, {"enum", json::array({"XY", "XZ", "YZ"})}, {"default", "XY"}},
+                 })}},
+            json{{"name", "boolean"}, {"summary", "Combine two bodies: union | subtract (tool from target) | intersect."},
+                 {"params", json::array({
+                     json{{"name", "op"},        {"type", "string"}, {"enum", json::array({"union", "subtract", "intersect"})}, {"default", "subtract"}},
+                     json{{"name", "target"},    {"type", "integer"}, {"default", 0}},
+                     json{{"name", "tool"},      {"type", "integer"}, {"default", 1}},
+                     json{{"name", "keep_tool"}, {"type", "boolean"}, {"default", false}},
+                     json{{"name", "tolerance"}, {"type", "number"}, {"unit", "mm"}, {"default", 0}},
+                 })}},
+            json{{"name", "pattern"}, {"summary", "Replicate a body: linear (count along a plane axis at spacing) or circular (count over an angle about the plane normal)."},
+                 {"params", json::array({
+                     json{{"name", "circular"}, {"type", "boolean"}, {"default", false}},
+                     json{{"name", "count"},    {"type", "integer"}, {"default", 3}, {"min", 1}},
+                     json{{"name", "spacing"},  {"type", "number"}, {"unit", "mm"}, {"default", 10}, {"description", "linear step"}},
+                     json{{"name", "dir"},      {"type", "integer"}, {"enum", json::array({0, 1})}, {"default", 0}, {"description", "linear axis: 0=plane X, 1=plane Y"}},
+                     json{{"name", "angle"},    {"type", "number"}, {"unit", "deg"}, {"default", 360}, {"description", "circular total sweep"}},
+                     json{{"name", "plane"},    {"type", "string"}, {"enum", json::array({"XY", "XZ", "YZ"})}, {"default", "XY"}},
+                     json{{"name", "body"},     {"type", "integer"}, {"default", -1}, {"description", "target body; omit for the last body"}},
+                 })}},
+            json{{"name", "pattern_on_curve"}, {"summary", "Replicate a body along a sketch curve: `count` copies placed at equal-parameter points on the entity, each translated by (P_i - P_0)."},
+                 {"params", json::array({
+                     json{{"name", "count"},  {"type", "integer"}, {"default", 3}, {"min", 1}},
+                     json{{"name", "sketch"}, {"type", "integer"}, {"description", "feature index of the sketch holding the guide curve"}},
+                     json{{"name", "entity"}, {"type", "integer"}, {"description", "entity index of the guide curve within that sketch"}},
+                     json{{"name", "body"},   {"type", "integer"}, {"default", -1}, {"description", "target body; omit for the last body"}},
+                 })}},
+            json{{"name", "shell"}, {"summary", "Hollow a body to a wall thickness (inward); optionally leave one face open."},
+                 {"params", json::array({
+                     json{{"name", "thickness"}, {"type", "number"}, {"unit", "mm"}, {"default", 1}, {"min", 0.01}},
+                     json{{"name", "face"},      {"type", "integer"}, {"default", -1}, {"description", "face id to leave open (query_topology); omit for a closed hollow"}},
+                     json{{"name", "body"},      {"type", "integer"}, {"default", -1}, {"description", "target body; omit for the last body"}},
+                 })}},
+            json{{"name", "draft"}, {"summary", "Taper a body face by an angle about its base (pull direction +Z)."},
+                 {"params", json::array({
+                     json{{"name", "face"},  {"type", "integer"}, {"description", "face id to draft (query_topology)"}},
+                     json{{"name", "angle"}, {"type", "number"}, {"unit", "deg"}, {"default", 5}},
+                     json{{"name", "body"},  {"type", "integer"}, {"default", -1}, {"description", "target body; omit for the last body"}},
+                 })}},
+            json{{"name", "mirror"}, {"summary", "Mirror a body about a base plane. mode=new creates a mirrored copy; mode=add fuses the mirror back into the source."},
+                 {"params", json::array({
+                     json{{"name", "plane"},        {"type", "string"}, {"enum", json::array({"XY", "XZ", "YZ"})}, {"default", "XZ"}},
+                     json{{"name", "mode"},         {"type", "string"}, {"enum", json::array({"new", "add"})},     {"default", "new"}},
+                     json{{"name", "keep_original"},{"type", "boolean"}, {"default", true}, {"description", "when mode=new, keep the source body"}},
+                     json{{"name", "body"},         {"type", "integer"}, {"default", -1}, {"description", "target body; omit for the last body"}},
+                 })}},
+            json{{"name", "transform"}, {"summary", "Move and/or rotate a body (B-rep transform). copy=true keeps the source and appends the transformed copy as a new body."},
+                 {"params", json::array({
+                     json{{"name", "body"},    {"type", "integer"}, {"default", -1}, {"description", "target body; omit for the last body"}},
+                     json{{"name", "dx"},      {"type", "number"}, {"unit", "mm"}, {"default", 0}},
+                     json{{"name", "dy"},      {"type", "number"}, {"unit", "mm"}, {"default", 0}},
+                     json{{"name", "dz"},      {"type", "number"}, {"unit", "mm"}, {"default", 0}},
+                     json{{"name", "axis_x"},  {"type", "number"}, {"default", 0}},
+                     json{{"name", "axis_y"},  {"type", "number"}, {"default", 0}},
+                     json{{"name", "axis_z"},  {"type", "number"}, {"default", 1}},
+                     json{{"name", "pivot_x"}, {"type", "number"}, {"unit", "mm"}, {"default", 0}},
+                     json{{"name", "pivot_y"}, {"type", "number"}, {"unit", "mm"}, {"default", 0}},
+                     json{{"name", "pivot_z"}, {"type", "number"}, {"unit", "mm"}, {"default", 0}},
+                     json{{"name", "angle"},   {"type", "number"}, {"unit", "deg"}, {"default", 0}},
+                     json{{"name", "copy"},    {"type", "boolean"}, {"default", false}},
+                 })}},
+            json{{"name", "axis"}, {"summary", "Create a datum axis (reference line): two points, face normal, cylinder centreline, plane intersection, or along edge."},
+                 {"params", json::array({
+                     json{{"name", "type"},     {"type", "string"}, {"enum", json::array({"two_points", "face_normal", "cylinder", "plane_intersection", "along_edge"})}, {"default", "two_points"}},
+                     json{{"name", "p1"},       {"type", "array"}, {"default", json::array({0,0,0})}, {"description", "first point [x,y,z] for two_points"}},
+                     json{{"name", "p2"},       {"type", "array"}, {"default", json::array({0,0,10})}, {"description", "second point [x,y,z] for two_points"}},
+                     json{{"name", "body"},     {"type", "integer"}, {"default", -1}, {"description", "body for face/edge refs"}},
+                     json{{"name", "face"},     {"type", "integer"}, {"default", -1}, {"description", "face id (query_topology) for face_normal/cylinder"}},
+                     json{{"name", "edge"},     {"type", "integer"}, {"default", -1}, {"description", "edge id (query_topology) for along_edge"}},
+                     json{{"name", "plane_a"},  {"type", "integer"}, {"default", -1}, {"description", "first datum plane feature index for plane_intersection"}},
+                     json{{"name", "plane_b"},  {"type", "integer"}, {"default", -1}, {"description", "second datum plane feature index for plane_intersection"}},
+                 })}},
+            json{{"name", "coordsys"}, {"summary", "Create a datum coordinate system (origin + orthonormal axes). PointWorld aligns to world; FaceAndDirection uses a face for Z and an edge/hint for X."},
+                 {"params", json::array({
+                     json{{"name", "type"},      {"type", "string"}, {"enum", json::array({"point_world", "face_and_direction"})}, {"default", "point_world"}},
+                     json{{"name", "point"},     {"type", "array"}, {"default", json::array({0,0,0})}, {"description", "origin [x,y,z] for point_world"}},
+                     json{{"name", "body"},      {"type", "integer"}, {"default", -1}, {"description", "body for face/edge refs"}},
+                     json{{"name", "face"},      {"type", "integer"}, {"default", -1}, {"description", "face id (query_topology) for Z axis"}},
+                     json{{"name", "edge"},      {"type", "integer"}, {"default", -1}, {"description", "edge id (query_topology) for X axis hint"}},
+                     json{{"name", "x_hint"},    {"type", "array"}, {"default", json::array({1,0,0})}, {"description", "fallback X direction hint if no edge given"}},
+                 })}},
+            json{{"name", "helix"}, {"summary", "Create a helical curve (consumed by sweep as a path to build springs/coils/augers). pitch = axial rise per turn. left_handed flips the winding. taper_deg != 0 gives a conical helix."},
+                 {"params", json::array({
+                     json{{"name", "radius"},      {"type", "number"}, {"unit", "mm"},  {"default", 10}, {"min", 0.01}},
+                     json{{"name", "pitch"},       {"type", "number"}, {"unit", "mm"},  {"default", 5},  {"min", 0.01}},
+                     json{{"name", "height"},      {"type", "number"}, {"unit", "mm"},  {"default", 20}, {"min", 0.01}},
+                     json{{"name", "left_handed"}, {"type", "boolean"}, {"default", false}},
+                     json{{"name", "taper_deg"},   {"type", "number"}, {"unit", "deg"}, {"default", 0}},
+                     json{{"name", "plane"},       {"type", "string"}, {"enum", json::array({"XY", "XZ", "YZ"})}, {"default", "XY"}},
+                 })}},
+            json{{"name", "thicken"}, {"summary", "Offset a face of a body by a wall thickness, producing a new thin solid body."},
+                 {"params", json::array({
+                     json{{"name", "body"},      {"type", "integer"}, {"default", -1}, {"description", "target body; omit for the last body"}},
+                     json{{"name", "face"},      {"type", "integer"}, {"description", "face id to thicken (query_topology)"}},
+                     json{{"name", "thickness"}, {"type", "number"}, {"unit", "mm"}, {"default", 2}, {"min", 0.01}},
+                     json{{"name", "flip"},      {"type", "boolean"}, {"default", false}},
+                 })}},
+            json{{"name", "split"}, {"summary", "Split a body along the plane of a picked face."},
+                 {"params", json::array({
+                     json{{"name", "body"},      {"type", "integer"}, {"default", -1}, {"description", "target body; omit for the last body"}},
+                     json{{"name", "face_body"}, {"type", "integer"}, {"default", -1}, {"description", "body that owns the face; -1 = target"}},
+                     json{{"name", "face"},      {"type", "integer"}, {"description", "face id to split along (query_topology)"}},
+                     json{{"name", "keep_upper"},{"type", "boolean"}, {"default", true}},
+                     json{{"name", "keep_lower"},{"type", "boolean"}, {"default", true}},
+                 })}},
+             json{{"name", "project"}, {"summary", "Project edges of a solid onto a sketch plane, producing a new sketch feature."},
+                  {"params", json::array({
+                      json{{"name", "source_body"}, {"type", "integer"}, {"default", -1}, {"description", "body owning the edges; -1 = last body"}},
+                      json{{"name", "face"},        {"type", "integer"}, {"default", -1}, {"description", "global face id on the source body; when set, all its edges are projected"}},
+                      json{{"name", "edges"},       {"type", "array"}, {"default", json::array()}, {"description", "global edge ids to project; empty => project the face"}},
+                      json{{"name", "plane"},       {"type", "string"}, {"default", "XY"}, {"description", "target sketch plane (XY/XZ/YZ)"}},
+                  })}},
+             json{{"name", "delete_face"}, {"summary", "Remove faces from a solid, healing the gap via OCCT defeaturing."},
+                  {"params", json::array({
+                      json{{"name", "body"},  {"type", "integer"}, {"default", -1}, {"description", "target body; omit for the last body"}},
+                      json{{"name", "faces"}, {"type", "array"}, {"description", "global face ids to delete"}},
+                  })}},
+            json{{"name", "bridge"}, {"summary", "Build a cubic-Bezier G1 bridge (BSpline) between two sketch-entity endpoints within a sketch feature."},
+                  {"params", json::array({
+                      json{{"name", "sketch"}, {"type", "integer"}, {"description", "sketch feature index"}},
+                      json{{"name", "ent_a"},  {"type", "integer"}, {"description", "first entity index within the sketch"}},
+                      json{{"name", "end_a"},  {"type", "integer"}, {"enum", json::array({0, 1})}, {"default", 1}, {"description", "0 = start/p0 side, 1 = end/p1 side"}},
+                      json{{"name", "ent_b"},  {"type", "integer"}, {"description", "second entity index within the sketch"}},
+                      json{{"name", "end_b"},  {"type", "integer"}, {"enum", json::array({0, 1})}, {"default", 0}, {"description", "0 = start/p0 side, 1 = end/p1 side"}},
+                  })}},
+            json{{"name", "rib"}, {"summary", "Grow a thin rib wall (stiffener) from an open Line sketch entity, fused to a body."},
+                  {"params", json::array({
+                      json{{"name", "sketch"},    {"type", "integer"}, {"description", "sketch feature index holding the open line"}},
+                      json{{"name", "entity"},    {"type", "integer"}, {"description", "entity index of the open Line within the sketch"}},
+                      json{{"name", "thickness"}, {"type", "number"}, {"unit", "mm"}, {"default", 2}, {"min", 0.01}},
+                      json{{"name", "depth"},     {"type", "number"}, {"unit", "mm"}, {"default", 10}, {"min", 0.01}},
+                      json{{"name", "body"},      {"type", "integer"}, {"default", -1}, {"description", "target body; omit for the last body"}},
+                  })}},
+            json{{"name", "surface_extrude"}, {"summary", "Extrude a sketch wire with no end caps -> an open sheet body."},
+                  {"params", json::array({
+                      json{{"name", "sketch"},  {"type", "integer"}, {"description", "sketch feature index"}},
+                      json{{"name", "distance"},{"type", "number"}, {"unit", "mm"}, {"default", 10}, {"min", 0.01}},
+                  })}},
+            json{{"name", "surface_revolve"}, {"summary", "Revolve a sketch wire with no caps -> an open sheet body."},
+                  {"params", json::array({
+                      json{{"name", "sketch"},  {"type", "integer"}, {"description", "sketch feature index"}},
+                      json{{"name", "angle"},   {"type", "number"}, {"unit", "deg"}, {"default", 360}},
+                      json{{"name", "axis"},    {"type", "integer"}, {"enum", json::array({0, 1})}, {"default", 0}},
+                  })}},
+            json{{"name", "mate"}, {"summary", "Mate two bodies: transform the moving body (cs_b) so its connector lands on the fixed one (cs_a). kind: 0=Fastened, 1=Planar, 2=Revolute, 3=Slider, 4=Cylindrical."},
+                 {"params", json::array({
+                     json{{"name", "kind"},    {"type", "integer"}, {"default", 0}, {"description", "0=Fastened (rigid), 1=Planar (normal only), 2=Revolute (free rotation about axis), 3=Slider (free translation along axis), 4=Cylindrical (free rotation+translation)"}},
+                     json{{"name", "cs_a"},    {"type", "integer"}, {"description", "feature index of the fixed CoordSys (mate connector A)"}},
+                     json{{"name", "cs_b"},    {"type", "integer"}, {"description", "feature index of the CoordSys on the body that moves"}},
+                     json{{"name", "offset"},  {"type", "number"}, {"unit", "mm"}, {"default", 0}},
+                     json{{"name", "angle"},   {"type", "number"}, {"unit", "deg"}, {"default", 0}},
+                     json{{"name", "flip"},    {"type", "boolean"}, {"default", false}},
+                 })}},
+            json{{"name", "check_interference"}, {"summary", "Solid bodies that overlap, as {body_a, body_b, volume}. Read-only; bodies that merely touch enclose no volume and are not reported."},
+                 {"params", json::array({
+                     json{{"name", "min_volume"}, {"type", "number"}, {"unit", "mm^3"}, {"default", 1e-6}, {"description", "overlap volume above which a pair counts as interfering"}},
+                 })}},
+            json{{"name", "query_topology"}, {"summary", "Measured faces (centroid/normal/cylinder) and edges (length/circle) of a body."},
+                 {"params", json::array({
+                     json{{"name", "body"}, {"type", "integer"}, {"default", 0}},
+                 })}},
+            json{{"name", "measure"}, {"summary", "Distance (and angle, when both have direction) between two refs {face|edge|point} on a body."},
+                 {"params", json::array({
+                     json{{"name", "body"}, {"type", "integer"}, {"default", 0}},
+                     json{{"name", "a"}, {"type", "object"}},
+                     json{{"name", "b"}, {"type", "object"}},
+                 })}},
+            json{{"name", "mass_properties"}, {"summary", "Volume / surface area / centre of mass / inertia tensor of a body."},
+                 {"params", json::array({
+                     json{{"name", "body"}, {"type", "integer"}, {"default", 0}},
+                 })}},
+            json{{"name", "slice_body"}, {"summary", "Cross-section of a body by a base plane at an offset (sections-as-evidence); returns ordered world contours, each flagged closed/open."},
+                 {"params", json::array({
+                     json{{"name", "body"}, {"type", "integer"}, {"default", 0}},
+                     json{{"name", "plane"}, {"type", "string"}, {"enum", json::array({"XY", "XZ", "YZ"})}, {"default", "XY"}},
+                     json{{"name", "offset"}, {"type", "number"}, {"unit", "mm"}, {"default", 0}},
+                 })}},
+            json{{"name", "import_step"}, {"summary", "Import a STEP file as native B-rep bodies (the reference part to measure)."},
+                 {"params", json::array({
+                     json{{"name", "path"}, {"type", "string"}},
+                 })}},
+            json{{"name", "import_mesh"}, {"summary", "Convert a triangle mesh (STL/OBJ) into an editable B-rep body. Reports whether the result is a real solid or an open shell, and why."},
+                 {"params", json::array({
+                     json{{"name", "path"}, {"type", "string"}},
+                     json{{"name", "tolerance"}, {"type", "number"}, {"default", 0.01}},
+                     json{{"name", "merge_angle_deg"}, {"type", "number"}, {"default", 5.0}},
+                 })}},
+            json{{"name", "validate_against"}, {"summary", "Volume + bbox/centroid + surface deviation (max/mean/rms mm) of a body vs a reference {step:path|body:id} (the RE acceptance metric)."},
+                 {"params", json::array({
+                     json{{"name", "body"}, {"type", "integer"}, {"default", 0}},
+                     json{{"name", "reference"}, {"type", "object"}},
+                 })}},
+        })},
+    };
+}
+
+json describe_scene(DesignPanel* panel)
+{
+    CadDocument& doc = panel->mcp_doc();
+
+    json features = json::array();
+    for (size_t i = 0; i < doc.features.size(); ++i) {
+        const CadFeature& f = doc.features[i];
+        features.push_back(json{
+            {"index", int(i)}, {"type", feature_type_name(f.type)},
+            {"name", f.name}, {"enabled", f.enabled}});
+    }
+
+    json bodies = json::array();
+    for (size_t i = 0; i < doc.bodies.size(); ++i) {
+        // The user's name when the body has one, the derived maker name otherwise — the same
+        // rule the Bodies row shows, so a driver and a person read the same thing.
+        json b{{"index", int(i)},
+               {"name", doc.bodies[i].has_user_name ? doc.bodies[i].user_name : doc.bodies[i].name},
+               {"user_name", doc.bodies[i].has_user_name},
+               {"has_color", doc.bodies[i].has_color}};
+        // Per-body bbox/centre from the already-tessellated display meshes.
+        if (i < doc.display_body_meshes.size() && !doc.display_body_meshes[i].empty()) {
+            BoundingBoxf3 bb = doc.display_body_meshes[i].bounding_box();
+            b["bbox"] = json{{"min", {bb.min.x(), bb.min.y(), bb.min.z()}},
+                             {"max", {bb.max.x(), bb.max.y(), bb.max.z()}}};
+            Vec3d c = bb.center();
+            b["center"] = {c.x(), c.y(), c.z()};
+        }
+        bodies.push_back(std::move(b));
+    }
+
+    return json{
+        {"modeling_origin", {doc.modeling_origin.x(), doc.modeling_origin.y(), doc.modeling_origin.z()}},
+        {"features", std::move(features)},
+        {"bodies", std::move(bodies)},
+        {"error", doc.error},
+        // Pass this back as "generation" on any call that takes a face or edge id and the call
+        // is refused if the topology has moved on. See the note on the dispatcher.
+        {"generation", doc.topo_generation},
+    };
+}
+
+// --- Measure layer (read-only "evidence" half of the RE loop) ------------------
+inline json vec3(const Vec3d& v) { return json::array({v.x(), v.y(), v.z()}); }
+
+// Shared Build helpers.
+SketchPlane plane_from(const json& params, const CadDocument& doc)
+{
+    std::string n = params.value("plane", std::string("XY"));
+    SketchPlane pl = n == "XZ" ? SketchPlane::XZ() : n == "YZ" ? SketchPlane::YZ() : SketchPlane::XY();
+    pl.origin = doc.modeling_origin;   // land on the bed centre, like the GUI
+    return pl;
+}
+BooleanMode bool_from(const std::string& s)
+{
+    if (s == "union" || s == "add")       return BooleanMode::Add;
+    if (s == "subtract" || s == "cut")    return BooleanMode::Cut;
+    if (s == "intersect" || s == "common")return BooleanMode::Intersect;
+    return BooleanMode::New;
+}
+// Optional explicit closed profile: params["profile"] = [[x,y],...] in plane mm.
+// This is the Measure->Build bridge — feed a measured contour straight back.
+bool profile_from(const json& params, SketchProfile& out)
+{
+    if (!params.contains("profile")) return false;
+    out.points.clear();
+    for (const auto& p : params["profile"]) out.points.emplace_back(p[0].get<double>(), p[1].get<double>());
+    out.closed = true;
+    return out.points.size() >= 3;
+}
+
+// Resolve body index -> shape, throwing a clear error if out of range / null.
+const TopoDS_Shape& body_shape(DesignPanel* panel, const json& params)
+{
+    CadDocument& doc = panel->mcp_doc();
+    int idx = params.value("body", 0);
+    if (idx < 0 || idx >= int(doc.bodies.size()))
+        throw std::runtime_error("body index out of range (have " + std::to_string(doc.bodies.size()) + ")");
+    if (doc.bodies[idx].shape.IsNull())
+        throw std::runtime_error("body has no shape");
+    return doc.bodies[idx].shape;
+}
+
+json query_topology(DesignPanel* panel, const json& params)
+{
+    const TopoDS_Shape& shape = body_shape(panel, params);
+    // Enumerate once. The _by_index accessors rescan the shape on every call (edge_by_index
+    // rebuilds the whole indexed map), so indexing a body face-by-face is quadratic: ~15 s on a
+    // 4.7k-face imported solid, on the UI thread. faces_of/edges_of keep the very same ids.
+    const std::vector<TopoDS_Face> all_faces = GeometryEngine::faces_of(shape);
+    const std::vector<TopoDS_Edge> all_edges = GeometryEngine::edges_of(shape);
+
+    json faces = json::array();
+    const int nf = int(all_faces.size());
+    for (int i = 0; i < nf; ++i) {
+        const TopoDS_Face& f = all_faces[i];
+        if (f.IsNull()) continue;
+        json jf{{"id", i}, {"centroid", vec3(GeometryEngine::face_centroid_world(f))},
+                {"normal", vec3(GeometryEngine::face_normal_world(f))}, {"kind", "planar"}};
+        GeometryEngine::CylinderFace cyl = GeometryEngine::cylinder_of_face(f);
+        if (cyl.ok) { jf["kind"] = "cylindrical"; jf["radius"] = cyl.radius;
+                      jf["axis"] = vec3(cyl.axis); jf["internal"] = cyl.internal; }
+        faces.push_back(std::move(jf));
+    }
+    json edges = json::array();
+    const int ne = int(all_edges.size());
+    for (int i = 0; i < ne; ++i) {
+        const TopoDS_Edge& e = all_edges[i];
+        if (e.IsNull()) continue;
+        std::vector<Vec3d> pts = GeometryEngine::sample_edge_world(e);
+        if (pts.size() < 2) continue;
+        double len = 0; for (size_t k = 1; k < pts.size(); ++k) len += (pts[k] - pts[k-1]).norm();
+        json je{{"id", i}, {"length", len}, {"p0", vec3(pts.front())}, {"p1", vec3(pts.back())},
+                {"kind", "line"}};
+        GeometryEngine::CylinderFace circ = GeometryEngine::circle_of_edge(e);
+        if (circ.ok) { je["kind"] = "circle"; je["radius"] = circ.radius; je["center"] = vec3(circ.base); }
+        edges.push_back(std::move(je));
+    }
+    return json{{"body", params.value("body", 0)}, {"face_count", nf}, {"edge_count", ne},
+                {"faces", std::move(faces)}, {"edges", std::move(edges)},
+                // The ids above are indices into this exact topology and expire with it. Echo
+                // this back as "generation" on the calls that consume them.
+                {"generation", panel->mcp_doc().topo_generation}};
+}
+
+// One measurement reference -> a representative point and (optionally) a direction.
+// ref = {"face": id} | {"edge": id} | {"point": [x,y,z]} on the given body.
+bool resolve_ref(const TopoDS_Shape& shape, const json& ref, Vec3d& point, Vec3d& dir, bool& has_dir)
+{
+    has_dir = false;
+    if (ref.contains("point")) { auto p = ref["point"]; point = Vec3d(p[0], p[1], p[2]); return true; }
+    if (ref.contains("face")) {
+        TopoDS_Face f = GeometryEngine::face_by_index(shape, ref["face"].get<int>());
+        if (f.IsNull()) return false;
+        point = GeometryEngine::face_centroid_world(f);
+        dir = GeometryEngine::face_normal_world(f); has_dir = true; return true;
+    }
+    if (ref.contains("edge")) {
+        TopoDS_Edge e = GeometryEngine::edge_by_index(shape, ref["edge"].get<int>());
+        if (e.IsNull()) return false;
+        std::vector<Vec3d> pts = GeometryEngine::sample_edge_world(e);
+        if (pts.empty()) return false;
+        point = pts[pts.size() / 2];                       // midpoint sample
+        if (pts.size() >= 2) { dir = (pts.back() - pts.front()).normalized(); has_dir = true; }
+        return true;
+    }
+    return false;
+}
+
+json measure(DesignPanel* panel, const json& params)
+{
+    const TopoDS_Shape& shape = body_shape(panel, params);
+    Vec3d pa, pb, da, db; bool hda = false, hdb = false;
+    if (!params.contains("a") || !params.contains("b"))
+        throw std::runtime_error("measure needs refs 'a' and 'b' ({face|edge|point})");
+    if (!resolve_ref(shape, params["a"], pa, da, hda) || !resolve_ref(shape, params["b"], pb, db, hdb))
+        throw std::runtime_error("could not resolve a measurement reference");
+    json r{{"distance", (pa - pb).norm()}, {"point_a", vec3(pa)}, {"point_b", vec3(pb)}};
+    if (hda && hdb) {
+        double c = std::max(-1.0, std::min(1.0, da.normalized().dot(db.normalized())));
+        r["angle_deg"] = std::acos(c) * 180.0 / M_PI;
+    }
+    return r;
+}
+
+json mass_properties(DesignPanel* panel, const json& params)
+{
+    const TopoDS_Shape& shape = body_shape(panel, params);
+    auto mp = GeometryEngine::mass_properties(shape);
+    if (!mp.valid) throw std::runtime_error("mass properties could not be computed (null/empty shape)");
+    // A sheet body has no volume and no inertia. Report the area and say so, rather than
+    // returning numbers a caller would reasonably treat as a material check.
+    if (!mp.is_solid)
+        return json{
+            {"surface_area", mp.surface_area},
+            {"volume", 0.0},
+            {"is_solid", false},
+            {"valid", mp.valid},
+            {"note", "sheet body (open shell): it encloses no material, so volume and inertia "
+                     "are not defined; surface_area is exact"},
+        };
+    return json{
+        {"volume", mp.volume},
+        {"surface_area", mp.surface_area},
+        {"center_of_mass", json::array({mp.center_of_mass.x(), mp.center_of_mass.y(), mp.center_of_mass.z()})},
+        {"inertia", mp.inertia},
+        {"is_solid", true},
+        {"valid", mp.valid},
+    };
+}
+
+// Chain raw section segments (each a sampled-edge polyline) into ordered contours by joining
+// endpoints within tol. Grows the tail; when the tail is stuck, reverses the contour and grows
+// the other end. A contour is closed when its two ends meet. OCCT section vertices are exact,
+// so a small absolute tol suffices.
+std::vector<std::pair<std::vector<Vec3d>, bool>>
+chain_segments(std::vector<std::vector<Vec3d>> segs, double tol)
+{
+    std::vector<std::pair<std::vector<Vec3d>, bool>> contours;
+    std::vector<char> used(segs.size(), 0);
+    auto meets = [&](const Vec3d& a, const Vec3d& b) { return (a - b).norm() <= tol; };
+    for (size_t i = 0; i < segs.size(); ++i) {
+        if (used[i] || segs[i].size() < 2) continue;
+        used[i] = 1;
+        std::vector<Vec3d> c = segs[i];
+        for (int side = 0; side < 2; ) {           // grow tail; reverse once when stuck
+            bool grew = false;
+            for (size_t j = 0; j < segs.size(); ++j) {
+                if (used[j] || segs[j].size() < 2) continue;
+                if (meets(c.back(), segs[j].front())) {
+                    c.insert(c.end(), segs[j].begin() + 1, segs[j].end()); used[j] = 1; grew = true;
+                } else if (meets(c.back(), segs[j].back())) {
+                    for (auto it = segs[j].rbegin() + 1; it != segs[j].rend(); ++it) c.push_back(*it);
+                    used[j] = 1; grew = true;
+                }
+            }
+            if (grew) { side = 0; continue; }
+            std::reverse(c.begin(), c.end()); ++side;   // try the other end
+        }
+        bool closed = c.size() > 2 && meets(c.front(), c.back());
+        contours.emplace_back(std::move(c), closed);
+    }
+    return contours;
+}
+
+// sections-as-evidence: cross-section of a body by a named base plane at an offset.
+json slice_body(DesignPanel* panel, const json& params)
+{
+    const TopoDS_Shape& shape = body_shape(panel, params);
+    const std::string plane_name = params.value("plane", std::string("XY"));
+    const double offset = params.value("offset", 0.0);
+    // Base plane normal; offset shifts the plane along it.
+    gp_Dir n = plane_name == "XZ" ? gp_Dir(0, 1, 0)
+             : plane_name == "YZ" ? gp_Dir(1, 0, 0)
+                                  : gp_Dir(0, 0, 1);
+    gp_Pnt o(n.X() * offset, n.Y() * offset, n.Z() * offset);
+    BRepAlgoAPI_Section sect(shape, gp_Pln(o, n), Standard_False);
+    sect.ComputePCurveOn1(Standard_False);
+    sect.Approximation(Standard_True);
+    sect.Build();
+    if (!sect.IsDone()) throw std::runtime_error("section failed");
+    std::vector<std::vector<Vec3d>> segs;
+    for (TopExp_Explorer ex(sect.Shape(), TopAbs_EDGE); ex.More(); ex.Next()) {
+        std::vector<Vec3d> pts = GeometryEngine::sample_edge_world(TopoDS::Edge(ex.Current()));
+        if (pts.size() >= 2) segs.push_back(std::move(pts));
+    }
+    const int raw = int(segs.size());
+    auto contours = chain_segments(std::move(segs), 1e-3);
+    json jcont = json::array();
+    int closed_n = 0;
+    for (auto& pc : contours) {
+        if (pc.second) ++closed_n;
+        json pts = json::array();
+        for (const Vec3d& p : pc.first) pts.push_back(vec3(p));
+        jcont.push_back(json{{"closed", pc.second}, {"points", std::move(pts)}});
+    }
+    return json{{"body", params.value("body", 0)}, {"plane", plane_name}, {"offset", offset},
+                {"segment_count", raw}, {"contour_count", int(contours.size())},
+                {"closed_count", closed_n}, {"contours", std::move(jcont)}};
+}
+
+// --- Build: bring a reference part in (Import STEP as native B-rep bodies) ------
+json import_step(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("path")) throw std::runtime_error("import_step needs 'path'");
+    const std::string path = params["path"].get<std::string>();
+    std::string err;
+    std::vector<TopoDS_Shape> solids = GeometryEngine::read_step_solids(path, err);
+    if (solids.empty()) throw std::runtime_error(err.empty() ? "no solids in STEP" : err);
+
+    CadDocument& doc = panel->mcp_doc();
+    doc.checkpoint();
+    int first = int(doc.features.size());
+    for (const TopoDS_Shape& s : solids) {
+        CadFeature f;
+        f.type           = CadFeatureType::Import;
+        f.name           = "STEP" + std::to_string(int(doc.features.size()) + 1);
+        f.imported_solid = s;
+        f.mode           = BooleanMode::New;   // each solid = its own coexisting body
+        doc.features.push_back(f);
+    }
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"imported", int(solids.size())}, {"first_feature", first},
+                {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+// --- Import a triangle mesh as a B-rep body (GeometryEngine::mesh_to_brep) ---
+// Same destination as import_step: a CadFeatureType::Import body every feature tool can edit.
+// The full conversion stats come back so a caller can tell an honest solid from an open shell
+// instead of discovering it later when a boolean silently fails.
+json import_mesh(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("path")) throw std::runtime_error("import_mesh needs 'path'");
+    const std::string path       = params["path"].get<std::string>();
+    const double tolerance       = params.value("tolerance", 0.01);
+    const double merge_angle_deg = params.value("merge_angle_deg", 5.0);
+
+    TriangleMesh mesh;
+    const std::string ext = boost::algorithm::to_lower_copy(
+        boost::filesystem::path(path).extension().string());
+    if (ext == ".stl") {
+        if (!mesh.ReadSTLFile(path.c_str())) throw std::runtime_error("could not read STL: " + path);
+    } else if (ext == ".obj") {
+        ObjInfo obj_info; std::string obj_err;
+        if (!load_obj(path.c_str(), &mesh, obj_info, obj_err))
+            throw std::runtime_error("could not read OBJ: " + obj_err);
+    } else {
+        throw std::runtime_error("unsupported mesh format (want .stl or .obj): " + ext);
+    }
+
+    GeometryEngine::MeshBrepStats st;
+    const TopoDS_Shape shape = GeometryEngine::mesh_to_brep(mesh.its, tolerance, merge_angle_deg, st);
+    if (shape.IsNull()) throw std::runtime_error("mesh conversion produced no geometry");
+
+    CadDocument& doc = panel->mcp_doc();
+    doc.checkpoint();
+    const int first = int(doc.features.size());
+    CadFeature f;
+    f.type           = CadFeatureType::Import;
+    f.name           = "Mesh" + std::to_string(first + 1);
+    f.imported_solid = shape;
+    f.mode           = BooleanMode::New;
+    doc.features.push_back(f);
+
+    const bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"first_feature", first}, {"bodies", int(doc.bodies.size())},
+                {"input_triangles", st.input_tris}, {"kept_triangles", st.kept_tris},
+                {"degenerate_collapsed", st.degenerate_collapsed},
+                {"degenerate_sliver", st.degenerate_sliver},
+                {"faces_built", st.faces_built}, {"faces_failed", st.faces_failed},
+                {"faces_final", st.faces_final}, {"unique_edges", st.unique_edges},
+                {"boundary_edges", st.boundary_edges},
+                {"nonmanifold_edges", st.nonmanifold_edges},
+                {"watertight", st.watertight}, {"is_solid", st.is_solid},
+                {"volume", st.volume}, {"error", doc.error}};
+}
+
+// --- Validate: volume + bbox deviation of a body vs a reference (the "scarto %") --
+// ponytail: volume delta + bbox/centroid offset (the RE skill's actual acceptance metric).
+// Surface-deviation heat-map is the upgrade path (per-vertex BRepExtrema), add when needed.
+struct ShapeMetrics { double volume; Vec3d centroid, bmin, bmax; };
+ShapeMetrics shape_metrics(const TopoDS_Shape& s)
+{
+    GProp_GProps vp; BRepGProp::VolumeProperties(s, vp);
+    gp_Pnt c = vp.CentreOfMass();
+    Bnd_Box bb; BRepBndLib::Add(s, bb);
+    Standard_Real x0, y0, z0, x1, y1, z1; bb.Get(x0, y0, z0, x1, y1, z1);
+    return {vp.Mass(), Vec3d(c.X(), c.Y(), c.Z()), Vec3d(x0, y0, z0), Vec3d(x1, y1, z1)};
+}
+
+json validate_against(DesignPanel* panel, const json& params)
+{
+    const TopoDS_Shape& cand = body_shape(panel, params);   // candidate = the reconstruction
+    if (!params.contains("reference")) throw std::runtime_error("validate_against needs 'reference' {step|body}");
+    const json& r = params["reference"];
+
+    TopoDS_Shape ref;
+    if (r.contains("step")) {
+        std::string err;
+        std::vector<TopoDS_Shape> solids = GeometryEngine::read_step_solids(r["step"].get<std::string>(), err);
+        if (solids.empty()) throw std::runtime_error(err.empty() ? "reference STEP has no solids" : err);
+        BRep_Builder b; TopoDS_Compound comp; b.MakeCompound(comp);
+        for (const TopoDS_Shape& s : solids) if (!s.IsNull()) b.Add(comp, s);
+        ref = comp;
+    } else if (r.contains("body")) {
+        CadDocument& doc = panel->mcp_doc();
+        int idx = r["body"].get<int>();
+        if (idx < 0 || idx >= int(doc.bodies.size()) || doc.bodies[idx].shape.IsNull())
+            throw std::runtime_error("reference body index out of range / null");
+        ref = doc.bodies[idx].shape;
+    } else {
+        throw std::runtime_error("reference must be {\"step\": path} or {\"body\": id}");
+    }
+
+    ShapeMetrics a = shape_metrics(cand), b = shape_metrics(ref);
+    double dv = b.volume > 0 ? (a.volume - b.volume) / b.volume * 100.0 : 0.0;
+    Vec3d coff = a.centroid - b.centroid;
+    Vec3d dmin = a.bmin - b.bmin, dmax = a.bmax - b.bmax;
+    // Surface-level deviation (one-sided Hausdorff, candidate vertices -> reference solid):
+    // catches local shape error that matching volume + bbox can hide.
+    GeometryEngine::Deviation dev = GeometryEngine::surface_deviation(cand, ref);
+    return json{
+        {"volume", a.volume}, {"volume_reference", b.volume}, {"volume_delta_pct", dv},
+        {"centroid_offset", vec3(coff)}, {"centroid_offset_mm", coff.norm()},
+        {"bbox", json{{"min", vec3(a.bmin)}, {"max", vec3(a.bmax)}}},
+        {"bbox_reference", json{{"min", vec3(b.bmin)}, {"max", vec3(b.bmax)}}},
+        {"bbox_delta", json{{"min", vec3(dmin)}, {"max", vec3(dmax)}}},
+        {"surface_deviation", json{{"max_mm", dev.max_mm}, {"mean_mm", dev.mean_mm},
+                                   {"rms_mm", dev.rms_mm}, {"samples", dev.sample_count}}},
+    };
+}
+
+json action_extrude(DesignPanel* panel, const json& params)
+{
+    const double d = params.value("distance", 10.0);
+    if (d <= 0) throw std::runtime_error("distance must be > 0");
+    CadDocument& doc = panel->mcp_doc();
+    SketchPlane pl = plane_from(params, doc);
+    BooleanMode mode = bool_from(params.value("boolean", std::string("new")));
+
+    SketchProfile prof;
+    bool has_prof = profile_from(params, prof);
+    double w = 0, h = 0;
+    if (!has_prof) {
+        w = params.value("width", 20.0); h = params.value("height", 20.0);
+        if (w <= 0 || h <= 0) throw std::runtime_error("width and height must be > 0");
+    }
+    doc.checkpoint();
+    int s = has_prof ? doc.add_sketch_profile(prof, pl, "Sketch")
+                     : doc.add_sketch(SketchShape::Rectangle, pl, w, h, 0.0, "Sketch");
+    int e = doc.add_extrude(s, d, /*symmetric*/false, mode, "Extrude");
+    // End condition (Onshape parity). apply reads extrude_end directly; the kernel `symmetric`
+    // bool is unused, so set the field here. up_to_face id comes from query_topology on the
+    // target (last) body. taper_deg lofts the side wall; flip negates the direction.
+    const std::string end = params.value("end", std::string("blind"));
+    CadFeature& fe = doc.features[e];
+    fe.flip      = params.value("flip", false);
+    fe.taper_deg = params.value("taper", 0.0);
+    if      (end == "symmetric")   fe.extrude_end = ExtrudeEnd::Symmetric;
+    else if (end == "two_sided")  { fe.extrude_end = ExtrudeEnd::TwoSided; fe.distance2 = params.value("distance2", d); }
+    else if (end == "through_all")  fe.extrude_end = ExtrudeEnd::ThroughAll;
+    else if (end == "up_to_face")  { fe.extrude_end = ExtrudeEnd::UpToFace; fe.up_to_face = params.value("up_to_face", -1); }
+    else                            fe.extrude_end = ExtrudeEnd::Blind;
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"sketch_index", s}, {"extrude_index", e}, {"end", end},
+                {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_revolve(DesignPanel* panel, const json& params)
+{
+    const double angle = params.value("angle", 360.0);
+    const int    axis  = params.value("axis", 0);          // 0 = plane X, 1 = plane Y
+    const bool   flip  = params.value("flip", false);
+    CadDocument& doc = panel->mcp_doc();
+    SketchPlane pl = plane_from(params, doc);
+    BooleanMode mode = bool_from(params.value("boolean", std::string("new")));
+
+    SketchProfile prof;
+    bool has_prof = profile_from(params, prof);
+    double w = 0, h = 0;
+    if (!has_prof) {   // ponytail: rectangle centred on the axis may self-overlap; offset via `profile`
+        w = params.value("width", 20.0); h = params.value("height", 10.0);
+        if (w <= 0 || h <= 0) throw std::runtime_error("width and height must be > 0");
+    }
+    doc.checkpoint();
+    int s = has_prof ? doc.add_sketch_profile(prof, pl, "Sketch")
+                     : doc.add_sketch(SketchShape::Rectangle, pl, w, h, 0.0, "Sketch");
+    int r = doc.add_revolve(s, angle, axis, flip, mode, "Revolve");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"sketch_index", s}, {"revolve_index", r},
+                {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+// Resolve an optional explicit body target. Default (no `body`, or <0) = last body, which is
+// what the kernel picks anyway. Validated BEFORE any checkpoint so a bad index throws clean.
+int target_body_arg(const json& params, const CadDocument& doc)
+{
+    int bi = params.value("body", -1);
+    if (bi >= int(doc.bodies.size()))
+        throw std::runtime_error("body index out of range (have " + std::to_string(doc.bodies.size()) + ")");
+    return bi;   // <0 -> kernel uses the last body
+}
+
+json action_fillet(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("edge")) throw std::runtime_error("fillet needs 'edge' (id from query_topology)");
+    const double radius = params.value("radius", 1.0);
+    if (radius <= 0) throw std::runtime_error("radius must be > 0");
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to fillet");
+    int bi = target_body_arg(params, doc);
+    doc.checkpoint();
+    int f = doc.add_fillet(radius, params["edge"].get<int>(), "Fillet");
+    if (bi >= 0) doc.features[f].target_body = bi;   // edge id resolved against THIS body's shape
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"fillet_index", f}, {"body", bi < 0 ? int(doc.bodies.size()) - 1 : bi},
+                {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_chamfer(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("edge")) throw std::runtime_error("chamfer needs 'edge' (id from query_topology)");
+    const double dist = params.value("distance", 1.0);
+    if (dist <= 0) throw std::runtime_error("distance must be > 0");
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to chamfer");
+    int bi = target_body_arg(params, doc);
+    doc.checkpoint();
+    int c = doc.add_chamfer(dist, params["edge"].get<int>(), "Chamfer");
+    if (bi >= 0) doc.features[c].target_body = bi;   // edge id resolved against THIS body's shape
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"chamfer_index", c}, {"body", bi < 0 ? int(doc.bodies.size()) - 1 : bi},
+                {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_hole(DesignPanel* panel, const json& params)
+{
+    const double dia   = params.value("diameter", 5.0);
+    const double depth = params.value("depth", 10.0);
+    const bool   thru  = params.value("through", false);
+    const double x = params.value("x", 0.0), y = params.value("y", 0.0);
+    if (dia <= 0) throw std::runtime_error("diameter must be > 0");
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to drill");
+    SketchPlane pl = plane_from(params, doc);
+    doc.checkpoint();
+    int h = doc.add_hole(dia, depth, thru, x, y, pl, "Hole");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"hole_index", h}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_hole_styled(DesignPanel* panel, const json& params)
+{
+    const double dia   = params.value("diameter", 5.0);
+    const double depth = params.value("depth", 10.0);
+    const bool   thru  = params.value("through", true);
+    const double x = params.value("x", 0.0), y = params.value("y", 0.0);
+    const int    style          = params.value("style", 0);
+    const double cbore_diameter = params.value("cbore_diameter", 0.0);
+    const double cbore_depth    = params.value("cbore_depth", 0.0);
+    const double csink_diameter = params.value("csink_diameter", 0.0);
+    const double csink_angle    = params.value("csink_angle", 90.0);
+    const std::string standard  = params.value("standard", std::string(""));
+    if (dia <= 0) throw std::runtime_error("diameter must be > 0");
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to drill");
+    SketchPlane pl = plane_from(params, doc);
+    doc.checkpoint();
+    int h = doc.add_hole_styled(dia, depth, thru, x, y, pl, style,
+                                cbore_diameter, cbore_depth,
+                                csink_diameter, csink_angle, standard, "Hole");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"hole_index", h}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_hole_standard(DesignPanel* panel, const json& params)
+{
+    const std::string desig = params.value("designation", std::string(""));
+    if (desig.empty()) throw std::runtime_error("designation is required");
+    const int    style  = params.value("style", 0);
+    const bool   thru   = params.value("through", true);
+    const double depth  = params.value("depth", 10.0);
+    const double x = params.value("x", 0.0), y = params.value("y", 0.0);
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to drill");
+    SketchPlane pl = plane_from(params, doc);
+    doc.checkpoint();
+    try {
+        int h = doc.add_hole_standard(desig, style, thru, depth, x, y, pl, "Hole");
+        bool ok = doc.recompute();
+        if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+        panel->mcp_after_change();
+        return json{{"ok", ok}, {"hole_index", h}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+    } catch (const std::exception& ex) {
+        doc.undo();
+        panel->mcp_after_change();
+        return json{{"ok", false}, {"error", ex.what()}};
+    }
+}
+
+json action_boolean(DesignPanel* panel, const json& params)
+{
+    BooleanMode m = bool_from(params.value("op", std::string("subtract")));
+    if (m == BooleanMode::New) throw std::runtime_error("op must be union | subtract | intersect");
+    const int target = params.value("target", 0);
+    const int tool   = params.value("tool", 1);
+    const bool keep  = params.value("keep_tool", false);
+    const double tol = params.value("tolerance", 0.0);
+    CadDocument& doc = panel->mcp_doc();
+    int n = int(doc.bodies.size());
+    if (target < 0 || target >= n || tool < 0 || tool >= n)
+        throw std::runtime_error("target/tool body index out of range (have " + std::to_string(n) + ")");
+    if (target == tool) throw std::runtime_error("target and tool must differ");
+    doc.checkpoint();
+    int b = doc.add_boolean(m, target, tool, keep, tol, -1, -1, "Boolean");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"boolean_index", b}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_pattern(DesignPanel* panel, const json& params)
+{
+    const bool   circular = params.value("circular", false);
+    const int    count    = params.value("count", 3);
+    const double spacing  = params.value("spacing", 10.0);   // linear step (mm)
+    const int    dir      = params.value("dir", 0);          // 0 = plane X, 1 = plane Y
+    const double angle    = params.value("angle", 360.0);    // circular total sweep (deg)
+    if (count < 1) throw std::runtime_error("count must be >= 1");
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to pattern");
+    int bi = target_body_arg(params, doc);
+    doc.checkpoint();
+    int p = doc.add_pattern(circular, count, spacing, dir, angle, bi, "Pattern");
+    doc.features[p].plane = plane_from(params, doc);   // axis (circular) / step dirs (linear)
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"pattern_index", p}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_pattern_on_curve(DesignPanel* panel, const json& params)
+{
+    const int count  = params.value("count", 3);
+    if (count < 1) throw std::runtime_error("count must be >= 1");
+    if (!params.contains("sketch")) throw std::runtime_error("pattern_on_curve needs 'sketch' (feature index)");
+    if (!params.contains("entity")) throw std::runtime_error("pattern_on_curve needs 'entity' (entity index)");
+    const int sketch = params["sketch"].get<int>();
+    const int entity = params["entity"].get<int>();
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to pattern");
+    int bi = target_body_arg(params, doc);
+    doc.checkpoint();
+    int p = doc.add_pattern_on_curve(count, sketch, entity, bi, "PatternOnCurve");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"pattern_index", p}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_shell(DesignPanel* panel, const json& params)
+{
+    const double thickness = params.value("thickness", 1.0);
+    if (thickness <= 0) throw std::runtime_error("thickness must be > 0");
+    const int face = params.value("face", -1);   // face id to leave open (-1 = closed hollow)
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to shell");
+    int bi = target_body_arg(params, doc);
+    doc.checkpoint();
+    int s = doc.add_shell(thickness, face, bi, "Shell");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"shell_index", s}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_rib(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("sketch")) throw std::runtime_error("rib needs 'sketch' (feature index)");
+    if (!params.contains("entity")) throw std::runtime_error("rib needs 'entity' (entity index)");
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to rib");
+    int sketch    = params["sketch"].get<int>();
+    int entity    = params["entity"].get<int>();
+    double thickness = params.value("thickness", 2.0);
+    double depth     = params.value("depth", 10.0);
+    int bi = target_body_arg(params, doc);
+    doc.checkpoint();
+    int idx = doc.add_rib(sketch, entity, thickness, depth, bi, "Rib");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"rib_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_surface_extrude(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("sketch")) throw std::runtime_error("surface_extrude needs 'sketch' (feature index)");
+    CadDocument& doc = panel->mcp_doc();
+    int sketch = params["sketch"].get<int>();
+    double distance = params.value("distance", 10.0);
+    doc.checkpoint();
+    int idx = doc.add_surface_extrude(sketch, distance, "SurfaceExtrude");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"feature_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_surface_revolve(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("sketch")) throw std::runtime_error("surface_revolve needs 'sketch' (feature index)");
+    CadDocument& doc = panel->mcp_doc();
+    int sketch = params["sketch"].get<int>();
+    double angle = params.value("angle", 360.0);
+    int axis = params.value("axis", 0);
+    doc.checkpoint();
+    int idx = doc.add_surface_revolve(sketch, angle, axis, "SurfaceRevolve");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"feature_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_thicken_surface(DesignPanel* panel, const json& params)
+{
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no sheet body to thicken");
+    int bi = target_body_arg(params, doc);
+    double thickness = params.value("thickness", 2.0);
+    bool flip = params.value("flip", false);
+    doc.checkpoint();
+    int idx = doc.add_thicken_surface(bi, thickness, flip, "ThickenSurface");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"feature_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_surface_offset(DesignPanel* panel, const json& params)
+{
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no sheet body to offset");
+    int bi = target_body_arg(params, doc);
+    double offset = params.value("offset", 1.0);
+    doc.checkpoint();
+    int idx = doc.add_surface_offset(bi, offset, "SurfaceOffset");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"feature_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_surface_loft(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("profiles") || !params["profiles"].is_array())
+        throw std::runtime_error("surface_loft needs 'profiles' (array of int feature indices)");
+    CadDocument& doc = panel->mcp_doc();
+    std::vector<int> profiles;
+    for (const json& j : params["profiles"]) profiles.push_back(j.get<int>());
+    bool ruled = params.value("ruled", false);
+    doc.checkpoint();
+    int idx = doc.add_surface_loft(profiles, ruled, "SurfaceLoft");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"feature_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_surface_fill(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("sketch")) throw std::runtime_error("surface_fill needs 'sketch' (feature index)");
+    CadDocument& doc = panel->mcp_doc();
+    int sketch = params["sketch"].get<int>();
+    doc.checkpoint();
+    int idx = doc.add_surface_fill(sketch, "SurfaceFill");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"feature_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_draft(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("face")) throw std::runtime_error("draft needs 'face' (id from query_topology)");
+    const double angle = params.value("angle", 5.0);
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to draft");
+    int bi = target_body_arg(params, doc);
+    doc.checkpoint();
+    int d = doc.add_draft(angle, params["face"].get<int>(), bi, "Draft");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"draft_index", d}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+// ---- 2D sketch verbs --------------------------------------------------------------------
+//
+// The model is FreeCAD's Sketcher, adapted to this tab's right-click world. Three ideas are
+// taken over deliberately:
+//
+//   * GEOMETRY IS SEPARATE FROM CONSTRAINTS. You add curves, then you constrain them; the
+//     solver reports degrees of freedom and whether it is consistent. `sketch_describe` returns
+//     both halves plus the DoF, which is the whole state a caller needs to reason about.
+//   * A SKETCH IS JUDGED BY ITS LOOPS, not by its coordinates. FreeCAD asks whether the profile
+//     is closed before it will build from it; `sketch_describe` answers that directly, listing
+//     each closed loop, the loops it encloses as VOIDS, and — the actionable part — the exact
+//     plane coordinates where a chain is still open.
+//   * VALIDATE, THEN FIX. FreeCAD's ValidateSketch finds vertices that overlap within a
+//     tolerance but carry no coincidence, and adds the missing ones. `sketch_validate` reports
+//     them, `sketch_heal` welds and constrains them. That is what turns a loop that is closed by
+//     floating-point luck into one that is closed by construction and stays closed through
+//     every later solve.
+//
+// What is NOT taken over: FreeCAD's Sketcher is a modal dialog with its own toolbars. Here the
+// vocabulary is the right-click offer, so these verbs are named after what the menu offers on a
+// selection, and every one of them drives the SAME DesignSketchTool the mouse drives.
+
+DesignSketchTool& mcp_sketch(DesignPanel* panel)
+{
+    DesignCanvas* vp = panel->mcp_viewport();
+    if (vp == nullptr) throw std::runtime_error("no viewport");
+    if (!vp->is_sketching())
+        throw std::runtime_error("no sketch is open — call sketch_begin first");
+    return vp->mcp_sketch_tool();
+}
+
+SketchEntity sketch_entity_from(const json& j)
+{
+    const std::string t = j.value("type", std::string(""));
+    SketchEntity e;
+    auto p = [&](const char* k, double dx, double dy) {
+        if (!j.contains(k)) return Vec2d(dx, dy);
+        const json& a = j.at(k);
+        if (!a.is_array() || a.size() < 2) throw std::runtime_error(std::string(k) + " must be [x, y]");
+        return Vec2d(a[0].get<double>(), a[1].get<double>());
+    };
+    e.construction = j.value("construction", false);
+    // A circle and an arc are defined BY their centre, so a request that does not carry one is
+    // incomplete, not a request for a circle at the origin. Defaulting it silently put geometry
+    // somewhere the caller never asked for and then reported perfectly consistent loops, areas
+    // and hole attribution ABOUT THAT WRONG GEOMETRY — which is far more expensive to disbelieve
+    // than an error would have been. `p0` is accepted as an alias because that is exactly what a
+    // circle stores internally (e.p0 = e.center below), so a caller who writes p0 means centre.
+    auto centre_of = [&](const char* what) {
+        if (j.contains("center")) return p("center", 0, 0);
+        if (j.contains("centre")) return p("centre", 0, 0);
+        if (j.contains("p0"))     return p("p0", 0, 0);
+        throw std::runtime_error(std::string(what) + " needs a 'center' (or 'p0')");
+    };
+    if (t == "line") {
+        e.type = SketchEntity::Type::Line;
+        e.p0 = p("p0", 0, 0); e.p1 = p("p1", 0, 0);
+    } else if (t == "circle") {
+        e.type   = SketchEntity::Type::Circle;
+        e.center = centre_of("circle");
+        e.radius = j.value("radius", 0.0);
+        e.p0     = e.center;
+        if (e.radius <= 0.0) throw std::runtime_error("circle needs a positive 'radius'");
+    } else if (t == "arc") {
+        e.type        = SketchEntity::Type::Arc;
+        e.center      = centre_of("arc");
+        e.radius      = j.value("radius", 0.0);
+        e.start_angle = j.value("start_angle", 0.0);
+        e.end_angle   = j.value("end_angle", 0.0);
+        if (e.radius <= 0.0) throw std::runtime_error("arc needs a positive 'radius'");
+        e.p0 = e.center + e.radius * Vec2d(std::cos(e.start_angle), std::sin(e.start_angle));
+        e.p1 = e.center + e.radius * Vec2d(std::cos(e.end_angle),   std::sin(e.end_angle));
+    } else if (t == "point") {
+        e.type = SketchEntity::Type::Point;
+        e.p0   = p("p", 0, 0);
+    } else {
+        throw std::runtime_error("unknown entity type '" + t + "' (line, arc, circle, point)");
+    }
+    return e;
+}
+
+json sketch_entity_to(const SketchEntity& e, int index)
+{
+    json j{{"index", index}, {"construction", e.construction}};
+    switch (e.type) {
+    case SketchEntity::Type::Line:
+        j["type"] = "line";
+        j["p0"] = json::array({e.p0.x(), e.p0.y()});
+        j["p1"] = json::array({e.p1.x(), e.p1.y()});
+        j["length"] = (e.p1 - e.p0).norm();
+        break;
+    case SketchEntity::Type::Circle:
+        j["type"] = "circle";
+        j["center"] = json::array({e.center.x(), e.center.y()});
+        j["radius"] = e.radius;
+        break;
+    case SketchEntity::Type::Arc:
+        j["type"] = "arc";
+        j["center"] = json::array({e.center.x(), e.center.y()});
+        j["radius"] = e.radius;
+        j["start_angle"] = e.start_angle;
+        j["end_angle"]   = e.end_angle;
+        j["p0"] = json::array({e.p0.x(), e.p0.y()});
+        j["p1"] = json::array({e.p1.x(), e.p1.y()});
+        break;
+    case SketchEntity::Type::Point:
+        j["type"] = "point";
+        j["p"] = json::array({e.p0.x(), e.p0.y()});
+        break;
+    // Ellipses and splines used to serialise as a TYPE NAME and nothing else, so every
+    // parameter they have was invisible to the only read-back this project has. A ladder could
+    // count them and grade the faceted area of the loop they close (2e-2, the faceting error) —
+    // it could not check a single axis, angle or pole. "Precise definition of every aspect"
+    // cannot be asserted about an entity whose aspects the instrument cannot see.
+    case SketchEntity::Type::Ellipse:
+        j["type"]     = "ellipse";
+        j["center"]   = json::array({e.center.x(), e.center.y()});
+        j["radius"]   = e.radius;     // semi-major (a)
+        j["rminor"]   = e.rminor;     // semi-minor (b)
+        j["rotation"] = e.rotation;   // major-axis angle, radians
+        break;
+    case SketchEntity::Type::EllipseArc:
+        j["type"]        = "ellipse_arc";
+        j["center"]      = json::array({e.center.x(), e.center.y()});
+        j["radius"]      = e.radius;
+        j["rminor"]      = e.rminor;
+        j["rotation"]    = e.rotation;
+        j["start_angle"] = e.start_angle;
+        j["end_angle"]   = e.end_angle;
+        j["p0"] = json::array({e.p0.x(), e.p0.y()});
+        j["p1"] = json::array({e.p1.x(), e.p1.y()});
+        break;
+    case SketchEntity::Type::BSpline: {
+        j["type"] = "spline";
+        json poles = json::array();
+        for (const Vec2d& c : e.ctrl) poles.push_back(json::array({c.x(), c.y()}));
+        j["ctrl"] = poles;
+        j["p0"] = json::array({e.p0.x(), e.p0.y()});
+        j["p1"] = json::array({e.p1.x(), e.p1.y()});
+        break;
+    }
+    }
+    return j;
+}
+
+// Which entities a verb acts on: an explicit "entities" array, else the current selection,
+// else — only where the verb says so — everything. Same precedence the menu uses: what you
+// pointed at wins, and the menu never silently acts on the whole sketch.
+std::vector<int> sketch_targets(const json& params, DesignSketchTool& t, bool all_if_empty)
+{
+    std::vector<int> out;
+    if (params.contains("entities")) {
+        for (const auto& v : params.at("entities")) out.push_back(v.get<int>());
+        return out;
+    }
+    out = t.selection();
+    if (out.empty() && all_if_empty)
+        for (int i = 0; i < int(t.entities().size()); ++i) out.push_back(i);
+    return out;
+}
+
+json action_sketch_begin(DesignPanel* panel, const json& params)
+{
+    DesignCanvas* vp = panel->mcp_viewport();
+    if (vp == nullptr) throw std::runtime_error("no viewport");
+    if (vp->is_sketching()) throw std::runtime_error("a sketch is already open");
+    const std::string pl = params.value("plane", std::string("XY"));
+    SketchPlane plane = SketchPlane::XY();
+    if      (pl == "XZ") plane = SketchPlane::XZ();
+    else if (pl == "YZ") plane = SketchPlane::YZ();
+    else if (pl != "XY") throw std::runtime_error("plane must be XY, XZ or YZ");
+    vp->begin_sketch(plane, DesignSketchTool::Mode::Select);
+    // The panel has to enter sketch mode too, or the app is half in it: the tool sketches, the
+    // offer menu offers sketch verbs, and every sketch KEY is dead because key dispatch tests
+    // m_ui_mode while the menu tests the viewport. Driving the socket must leave the GUI in the
+    // state a user would be in, not a state only the socket can produce.
+    panel->mcp_set_sketch_mode(true);
+    return json{{"ok", true}, {"plane", pl}};
+}
+
+json action_sketch_commit(DesignPanel* panel, const json& params)
+{
+    (void)params;
+    DesignCanvas* vp = panel->mcp_viewport();
+    if (vp == nullptr || !vp->is_sketching()) throw std::runtime_error("no sketch is open");
+    vp->finish_sketch();
+    panel->mcp_set_sketch_mode(false);
+    panel->mcp_after_change();
+    return json{{"ok", true}, {"features", int(panel->mcp_doc().features.size())}};
+}
+
+json action_sketch_cancel(DesignPanel* panel, const json& params)
+{
+    (void)params;
+    DesignCanvas* vp = panel->mcp_viewport();
+    if (vp == nullptr || !vp->is_sketching()) throw std::runtime_error("no sketch is open");
+    vp->cancel_sketch();
+    panel->mcp_set_sketch_mode(false);
+    return json{{"ok", true}};
+}
+
+json action_sketch_add(DesignPanel* panel, const json& params)
+{
+    DesignSketchTool& t = mcp_sketch(panel);
+    std::vector<SketchEntity> ents;
+    if (params.contains("entities")) {
+        for (const auto& j : params.at("entities")) ents.push_back(sketch_entity_from(j));
+    } else if (params.contains("type")) {
+        ents.push_back(sketch_entity_from(params));      // single-entity shorthand
+    } else if (params.contains("rect")) {
+        // Corner rectangle as four shared-endpoint lines, so it arrives as ONE closed loop
+        // rather than four segments that happen to touch.
+        const json& r = params.at("rect");
+        if (!r.is_array() || r.size() < 4) throw std::runtime_error("rect must be [x0, y0, x1, y1]");
+        const double x0 = r[0].get<double>(), y0 = r[1].get<double>();
+        const double x1 = r[2].get<double>(), y1 = r[3].get<double>();
+        const bool c = params.value("construction", false);
+        auto seg = [&](Vec2d a, Vec2d b) { SketchEntity e; e.type = SketchEntity::Type::Line;
+                                           e.p0 = a; e.p1 = b; e.construction = c; return e; };
+        ents.push_back(seg({x0, y0}, {x1, y0}));
+        ents.push_back(seg({x1, y0}, {x1, y1}));
+        ents.push_back(seg({x1, y1}, {x0, y1}));
+        ents.push_back(seg({x0, y1}, {x0, y0}));
+    } else {
+        throw std::runtime_error("sketch_add needs 'entities', a single 'type', or 'rect'");
+    }
+    const int base = t.add_entities_scripted(ents);
+    panel->mcp_viewport()->request_repaint();
+    return json{{"ok", base >= 0}, {"first_index", base}, {"added", int(ents.size())},
+                {"entities", int(t.entities().size())}, {"dof", t.dof()}};
+}
+
+json action_sketch_select(DesignPanel* panel, const json& params)
+{
+    DesignSketchTool& t = mcp_sketch(panel);
+    std::vector<int> idx;
+    if (params.contains("entities"))
+        for (const auto& v : params.at("entities")) idx.push_back(v.get<int>());
+    const bool any = t.select_indices(idx);
+    panel->mcp_viewport()->request_repaint();
+    return json{{"ok", true}, {"selected", int(t.selection().size())}, {"any", any}};
+}
+
+json action_sketch_delete(DesignPanel* panel, const json& params)
+{
+    DesignSketchTool& t = mcp_sketch(panel);
+    const std::vector<int> tgt = sketch_targets(params, t, false);
+    if (tgt.empty()) throw std::runtime_error("nothing selected and no 'entities' given");
+    const int before = int(t.entities().size());
+    t.select_indices(tgt);
+    t.delete_selected();
+    panel->mcp_viewport()->request_repaint();
+    return json{{"ok", true}, {"removed", before - int(t.entities().size())},
+                {"entities", int(t.entities().size())}};
+}
+
+json action_sketch_construction(DesignPanel* panel, const json& params)
+{
+    DesignSketchTool& t = mcp_sketch(panel);
+    const std::vector<int> tgt = sketch_targets(params, t, false);
+    if (tgt.empty()) throw std::runtime_error("nothing selected and no 'entities' given");
+    t.select_indices(tgt);
+    const int n = t.toggle_selection_construction();
+    panel->mcp_viewport()->request_repaint();
+    return json{{"ok", n > 0}, {"changed", n}};
+}
+
+json action_sketch_offset(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("distance")) throw std::runtime_error("sketch_offset needs 'distance'");
+    DesignSketchTool& t = mcp_sketch(panel);
+    const double d = params.at("distance").get<double>();
+    const std::vector<int> tgt = sketch_targets(params, t, true);
+    std::vector<SketchEntity> src;
+    for (int i : tgt)
+        if (i >= 0 && i < int(t.entities().size())) src.push_back(t.entities()[i]);
+    if (src.empty()) throw std::runtime_error("nothing to offset");
+    const auto out = SketchEngine::offset_entities(src, d);
+    if (out.empty()) throw std::runtime_error("offset produced nothing (ellipses and splines are not offset)");
+    const int base = t.add_entities_scripted(out);
+    panel->mcp_viewport()->request_repaint();
+    return json{{"ok", true}, {"first_index", base}, {"added", int(out.size())}, {"dof", t.dof()}};
+}
+
+json action_sketch_mirror(DesignPanel* panel, const json& params)
+{
+    DesignSketchTool& t = mcp_sketch(panel);
+    auto pt = [&](const char* k, double dx, double dy) {
+        if (!params.contains(k)) return Vec2d(dx, dy);
+        const json& a = params.at(k);
+        if (!a.is_array() || a.size() < 2) throw std::runtime_error(std::string(k) + " must be [x, y]");
+        return Vec2d(a[0].get<double>(), a[1].get<double>());
+    };
+    const Vec2d a = pt("axis_a", 0, 0), b = pt("axis_b", 0, 1);
+    const std::vector<int> tgt = sketch_targets(params, t, true);
+    std::vector<SketchEntity> src;
+    for (int i : tgt)
+        if (i >= 0 && i < int(t.entities().size())) src.push_back(t.entities()[i]);
+    if (src.empty()) throw std::runtime_error("nothing to mirror");
+    const auto out = SketchEngine::mirror_entities(src, a, b);
+    const int base = t.add_entities_scripted(out);
+    panel->mcp_viewport()->request_repaint();
+    return json{{"ok", true}, {"first_index", base}, {"added", int(out.size())}, {"dof", t.dof()}};
+}
+
+json sketch_report(DesignSketchTool& t)
+{
+    const auto rep = t.loop_report();
+    json loops = json::array();
+    for (const auto& l : rep.loops) {
+        json holes = json::array();
+        for (int h : l.holes) holes.push_back(h);
+        loops.push_back(json{{"entities", l.ents}, {"holes", holes},
+                             {"closed", l.closed}, {"area", l.area}});
+    }
+    json open_ends = json::array();
+    for (const Vec2d& p : rep.open_ends) open_ends.push_back(json::array({p.x(), p.y()}));
+    // A profile is buildable when at least one loop closed and nothing is left dangling.
+    const bool buildable = !rep.loops.empty() && rep.open_ends.empty();
+    return json{{"closed_loops", loops}, {"open_ends", open_ends}, {"buildable", buildable}};
+}
+
+json action_sketch_describe(DesignPanel* panel, const json& params)
+{
+    (void)params;
+    DesignSketchTool& t = mcp_sketch(panel);
+    json ents = json::array();
+    for (int i = 0; i < int(t.entities().size()); ++i)
+        ents.push_back(sketch_entity_to(t.entities()[i], i));
+    // The armed TOOL and its pending anchors. Without these the only way to tell which tool a
+    // menu row actually armed is to draw with it and infer from what came out — which is how a
+    // menu walk that lands one row off gets diagnosed as "the tool is broken".
+    static const char* const kModeNames[] = {
+        "select", "dimension", "polyline", "line", "rect_corner", "rect_center", "rect_oblique",
+        "rect_rounded", "circle_center", "circle_2pt", "point",
+        "circle_3pt", "arc_3pt", "arc_tangent", "arc_center", "slot", "slot_arc", "polygon",
+        "ellipse", "ellipse_arc", "spline",
+        "fillet", "chamfer", "offset", "mirror",
+        "trim", "extend",
+        "move", "rotate", "scale", "array", "array_polar",
+        "transform_art",
+        "constrain" };
+    const int mi = int(t.mode());
+    json out{{"ok", true},
+             {"entities", ents},
+             {"constraints", int(t.constraints().size())},
+             {"dof", t.dof()},
+             {"solve_ok", t.solve_ok()},
+             {"tool", (mi >= 0 && mi < int(sizeof(kModeNames) / sizeof(kModeNames[0])))
+                          ? kModeNames[mi] : "unknown"},
+             {"pending", t.pending_points()},
+             {"editing", t.value_field_open()},
+             {"selection", t.selection()}};
+    out.update(sketch_report(t));
+    return out;
+}
+
+json action_sketch_validate(DesignPanel* panel, const json& params)
+{
+    DesignSketchTool& t = mcp_sketch(panel);
+    const double tol = params.value("tolerance", 1e-3);
+    json out{{"ok", true}, {"tolerance", tol}, {"dof", t.dof()}, {"solve_ok", t.solve_ok()}};
+    out.update(sketch_report(t));
+    return out;
+}
+
+json action_sketch_heal(DesignPanel* panel, const json& params)
+{
+    DesignSketchTool& t = mcp_sketch(panel);
+    const double tol = params.value("tolerance", 1e-3);
+    const bool   ic  = params.value("ignore_construction", true);
+    const int welded = t.heal_coincidences(tol, ic);
+    panel->mcp_viewport()->request_repaint();
+    json out{{"ok", true}, {"welded", welded}, {"tolerance", tol},
+             {"dof", t.dof()}, {"solve_ok", t.solve_ok()}};
+    out.update(sketch_report(t));
+    return out;
+}
+
+// Why sketch_set_value exists: committing a typed dimension could previously only be exercised
+// by driving the in-canvas value field, and the rig's window manager never gives that frame
+// keyboard focus, so the behaviour of apply_dimension on CONSTRAINED geometry was untestable.
+// This calls the same function the widget calls, so the geometry can be asserted with no window
+// manager involved. Note apply_dimension clears the selection.
+json action_sketch_set_value(DesignPanel* panel, const json& params)
+{
+    DesignSketchTool& t = mcp_sketch(panel);
+    if (!params.contains("value")) throw std::runtime_error("sketch_set_value needs 'value'");
+    const double value = params["value"].get<double>();
+    const DesignSketchTool::DimType kind = t.dimension_kind();
+    if (kind == DesignSketchTool::DimType::None)
+        throw std::runtime_error("the selection has no value to set — pick a line, an arc, a circle, or two entities");
+
+    const char* kind_name = "none";
+    switch (kind) {
+    case DesignSketchTool::DimType::Length:         kind_name = "length"; break;
+    case DesignSketchTool::DimType::Radius:         kind_name = "radius"; break;
+    case DesignSketchTool::DimType::Diameter:       kind_name = "diameter"; break;
+    case DesignSketchTool::DimType::Angle:          kind_name = "angle"; break;
+    case DesignSketchTool::DimType::Distance:       kind_name = "distance"; break;
+    case DesignSketchTool::DimType::DistanceToLine: kind_name = "distance_to_line"; break;
+    default: break;
+    }
+
+    // Validate BEFORE apply_dimension, at the socket boundary. The tool only MOVES geometry when
+    // the value passes its own per-case thresholds, but it records the driving constraint
+    // UNCONDITIONALLY afterwards — a negative/zero/NaN value that moved nothing would still be
+    // pushed to the solver as a constraint it must satisfy and cannot, silently corrupting the
+    // sketch rather than failing. (apply_dimension has the same flaw for any other caller; this
+    // guard protects the socket, not the tool.) Fail loudly instead of recording a poison value.
+    if (!std::isfinite(value))
+        throw std::runtime_error("dimension must be finite — NaN or infinity is not a dimension");
+    switch (kind) {
+    case DesignSketchTool::DimType::Length:
+    case DesignSketchTool::DimType::Radius:
+    case DesignSketchTool::DimType::Diameter:
+        if (value <= 0.0)
+            throw std::runtime_error(std::string(kind_name) + " must be positive (got " + std::to_string(value) + ")");
+        break;
+    case DesignSketchTool::DimType::Distance:
+    case DesignSketchTool::DimType::DistanceToLine:
+        if (value < 0.0)
+            throw std::runtime_error(std::string(kind_name) + " must be >= 0 (zero means coincident / on the line)");
+        break;
+    case DesignSketchTool::DimType::Angle:
+    default:
+        break;   // any finite angle is valid
+    }
+
+    const double before = t.dimension_current();
+    t.apply_dimension(value);
+    panel->mcp_viewport()->request_repaint();
+
+    json out{{"ok", true}, {"kind", kind_name}, {"before", before}, {"value", value},
+             {"dof", t.dof()}, {"solve_ok", t.solve_ok()}};
+    out.update(sketch_report(t));
+    return out;
+}
+
+// Verbs whose handler opens a MODAL dialog. This matters more than it looks: the socket thread
+// posts the call to the wx main thread and waits 15 s on a future, so a verb that blocks that
+// thread inside ShowModal() times the RPC out AND leaves the main thread blocked until a human
+// dismisses the dialog — every later call then times out too, 15 s at a time. Which is exactly
+// the trap for the deck user this surface exists for: one button press and the app is modal,
+// waiting for a mouse they may not be reaching for.
+//
+// So run_verb NEVER dispatches inline. The list here is only so list_verbs can label the keys
+// that will want a mouse; re-derive it with
+//     grep -n ShowModal src/slic3r/GUI/CAD/DesignPanel.cpp
+// and map each handler back to its action string in DesignOffer.hpp.
+bool verb_is_modal(const char* id)
+{
+    static const char* kModal[] = { "sk_text", "sk_svg", "colour" };
+    for (const char* m : kModal)
+        if (std::strcmp(m, id) == 0) return true;
+    return false;
+}
+
+// Why list_verbs exists: the deck profile in VSD_n1_streamcontroller is built by parsing
+// DesignPanel's key tables out of the SOURCE, so a verb without a keyboard shortcut is invisible
+// to it. Serving the whole offer table over the socket lets the profile be generated from the
+// running app instead, and lets a deck key name a verb rather than spend a letter.
+json action_list_verbs(DesignPanel* panel, const json& params)
+{
+    const int      kind      = panel->mcp_offer_selection_kind();
+    const uint32_t bit       = offer_bit(OfferSel(kind));
+    const bool     applicable_only = params.value("applicable_only", false);
+    const bool     has_sketch_mode = params.contains("sketch_mode");
+    const bool     want_sketch_mode = has_sketch_mode && params["sketch_mode"].get<bool>();
+
+    json verbs = json::array();
+    for (int i = 0; i < kOfferVerbCount; ++i) {
+        const OfferVerb& v = kOfferVerbs[i];
+        const bool applies = (v.accepts & bit) != 0;
+        if (applicable_only && !applies) continue;
+        if (has_sketch_mode && v.sketch_mode != want_sketch_mode) continue;
+        // Verbs whose action is nullptr exist in the vocabulary but have no GUI path yet — report
+        // them with a null action rather than dropping them.
+        verbs.push_back(json{
+            {"id", v.id},
+            {"name", v.name},
+            {"row", v.row},
+            {"row_name", kOfferRowNames[v.row]},
+            {"key", v.key ? json(v.key) : json(nullptr)},
+            {"action", v.action ? json(v.action) : json(nullptr)},
+            {"sketch_mode", v.sketch_mode},
+            {"applies", applies},
+            {"modal", verb_is_modal(v.id)},   // opening a dialog: this key will want a mouse
+            {"hint", v.hint ? json(v.hint) : json(nullptr)},
+        });
+    }
+    return json{{"ok", true}, {"selection_kind", kind}, {"count", verbs.size()},
+                {"verbs", std::move(verbs)}};
+}
+
+json action_run_verb(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("verb")) throw std::runtime_error("run_verb needs 'verb' (an offer verb id)");
+    const std::string verb = params["verb"].get<std::string>();
+
+    // Scan the offer table BEFORE dispatching so the failure message can tell an unknown id from
+    // one that exists in the vocabulary but has no GUI path (action == nullptr).
+    bool known = false;
+    bool has_action = false;
+    const char* action = nullptr;
+    for (int i = 0; i < kOfferVerbCount; ++i) {
+        if (std::strcmp(kOfferVerbs[i].id, verb.c_str()) == 0) {
+            known = true;
+            has_action = (kOfferVerbs[i].action != nullptr);
+            action = kOfferVerbs[i].action;
+            break;
+        }
+    }
+
+    if (!known)      throw std::runtime_error("run_verb: unknown verb '" + verb + "'");
+    if (!has_action) throw std::runtime_error("run_verb: '" + verb + "' has no GUI path yet");
+
+    // Whether the verb would be OFFERED for the current selection. Not a refusal: the GUI lets
+    // you press a tool's shortcut whatever is selected, and refusing here would make the socket
+    // stricter than the keyboard for no reason. Reported so a caller can tell "did nothing
+    // because it did not apply" from "did nothing because it is broken".
+    const int      kind    = panel->mcp_offer_selection_kind();
+    const uint32_t bit     = offer_bit(OfferSel(kind));
+    bool           applies = false;
+    for (int i = 0; i < kOfferVerbCount; ++i)
+        if (std::strcmp(kOfferVerbs[i].id, verb.c_str()) == 0) { applies = (kOfferVerbs[i].accepts & bit) != 0; break; }
+
+    // The rule is not "validate more", it is "the socket should offer exactly what the GUI
+    // offers, no more and no less". A "btn:"/"fly:" verb is reachable in the GUI ONLY through
+    // the offer menu, which GREYS its row when it does not apply to the current selection — so
+    // a socket caller must not be able to fire it either. But a "key:" verb is reachable from
+    // the KEYBOARD whatever is selected, and the app permits that, so refusing it would make
+    // the socket stricter than the keyboard for no reason. Refuse only the menu-only verbs.
+    if (!applies && action &&
+        (std::strncmp(action, "btn:", 4) == 0 || std::strncmp(action, "fly:", 4) == 0)) {
+        throw std::runtime_error("run_verb: '" + verb +
+                                 "' does not apply to the current selection (selection_kind " +
+                                 std::to_string(kind) + ")");
+    }
+
+    // Dispatch on the NEXT turn of the event loop, never inline. See verb_is_modal above: a verb
+    // that opens a dialog would otherwise block the thread this call is running on. Deferring
+    // costs the ability to report the verb's outcome — which run_offer_action never returned
+    // anyway — and buys a socket that cannot be wedged by any verb in the table.
+    wxGetApp().CallAfter([panel, verb]() { panel->mcp_run_verb(verb.c_str()); });
+
+    return json{{"ok", true}, {"verb", verb}, {"dispatched", true},
+                {"applies", applies}, {"modal", verb_is_modal(verb.c_str())},
+                {"selection_kind", kind}};
+}
+
+json action_mirror(DesignPanel* panel, const json& params)
+{
+    std::string m_str = params.value("mode", std::string("new"));
+    BooleanMode m = (m_str == "add") ? BooleanMode::Add : BooleanMode::New;
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to mirror");
+    int bi = target_body_arg(params, doc);
+    bool keep = params.value("keep_original", true);
+    doc.checkpoint();
+    int idx = doc.add_mirror(plane_from(params, doc), bi, m, "Mirror");
+    doc.features[idx].mirror_keep_original = keep;
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"mirror_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_transform(DesignPanel* panel, const json& params)
+{
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to transform");
+    int bi = target_body_arg(params, doc);
+    Vec3d translate(params.value("dx", 0.0), params.value("dy", 0.0), params.value("dz", 0.0));
+    Vec3d axis(params.value("axis_x", 0.0), params.value("axis_y", 0.0), params.value("axis_z", 1.0));
+    Vec3d pivot(params.value("pivot_x", 0.0), params.value("pivot_y", 0.0), params.value("pivot_z", 0.0));
+    double angle = params.value("angle", 0.0);
+    bool copy = params.value("copy", false);
+    doc.checkpoint();
+    int idx = doc.add_transform(bi, translate, axis, pivot, angle, copy, "Transform");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"transform_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_thicken(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("face")) throw std::runtime_error("thicken needs 'face' (id from query_topology)");
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to thicken");
+    int bi = target_body_arg(params, doc);
+    int face = params["face"].get<int>();
+    double thickness = params.value("thickness", 2.0);
+    bool flip = params.value("flip", false);
+    doc.checkpoint();
+    int idx = doc.add_thicken(bi, face, thickness, flip, "Thicken");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"thicken_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_split(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("face")) throw std::runtime_error("split needs 'face' (id from query_topology)");
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to split");
+    int bi = target_body_arg(params, doc);
+    int face_body = params.value("face_body", -1);
+    int face = params["face"].get<int>();
+    bool keep_upper = params.value("keep_upper", true);
+    bool keep_lower = params.value("keep_lower", true);
+    doc.checkpoint();
+    int idx = doc.add_split_by_face(bi, face_body, face, keep_upper, keep_lower, "Split");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"split_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_project(DesignPanel* panel, const json& params)
+{
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no source body to project from");
+    int source_body = params.value("source_body", -1);
+    int face = params.value("face", -1);
+    std::vector<int> edges;
+    if (params.contains("edges") && params["edges"].is_array())
+        for (const auto& v : params["edges"]) edges.push_back(v.get<int>());
+    SketchPlane pl = plane_from(params, doc);
+    doc.checkpoint();
+    int idx = doc.add_project_edges(source_body, edges, face, pl, "Project");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"project_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_delete_face(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("faces")) throw std::runtime_error("delete_face needs 'faces' (array of face ids)");
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to delete faces from");
+    int bi = target_body_arg(params, doc);
+    std::vector<int> faces;
+    if (params["faces"].is_array())
+        for (const auto& v : params["faces"]) faces.push_back(v.get<int>());
+    doc.checkpoint();
+    int idx = doc.add_delete_face(bi, faces, "DeleteFace");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"feature_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_bridge(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("sketch")) throw std::runtime_error("bridge needs 'sketch' (feature index)");
+    if (!params.contains("ent_a"))  throw std::runtime_error("bridge needs 'ent_a' (entity index)");
+    if (!params.contains("ent_b"))  throw std::runtime_error("bridge needs 'ent_b' (entity index)");
+    int sketch = params["sketch"].get<int>();
+    int ent_a  = params["ent_a"].get<int>();
+    int ent_b  = params["ent_b"].get<int>();
+    int end_a  = params.value("end_a", 1);
+    int end_b  = params.value("end_b", 0);
+    CadDocument& doc = panel->mcp_doc();
+    doc.checkpoint();
+    int ei = doc.add_bridge(sketch, ent_a, end_a, ent_b, end_b, "Bridge");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"sketch_index", sketch}, {"entity_index", ei},
+                {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_axis(DesignPanel* panel, const json& params)
+{
+    CadDocument& doc = panel->mcp_doc();
+    std::string t = params.value("type", std::string("two_points"));
+    AxisType at = AxisType::TwoPoints;
+    if (t == "face_normal")        at = AxisType::FaceNormal;
+    else if (t == "cylinder")      at = AxisType::CylinderCenterline;
+    else if (t == "plane_intersection") at = AxisType::PlaneIntersection;
+    else if (t == "along_edge")    at = AxisType::AlongEdge;
+    doc.checkpoint();
+    int idx = doc.add_axis(at, "Axis");
+    CadFeature& f = doc.features[idx];
+    if (params.contains("p1") && params["p1"].is_array() && params["p1"].size() >= 3)
+        f.axis_p1 = Vec3d(params["p1"][0].get<double>(), params["p1"][1].get<double>(), params["p1"][2].get<double>());
+    if (params.contains("p2") && params["p2"].is_array() && params["p2"].size() >= 3)
+        f.axis_p2 = Vec3d(params["p2"][0].get<double>(), params["p2"][1].get<double>(), params["p2"][2].get<double>());
+    f.axis_body     = params.value("body", -1);
+    f.axis_face     = params.value("face", -1);
+    f.axis_edge     = params.value("edge", -1);
+    f.axis_plane_a  = params.value("plane_a", -1);
+    f.axis_plane_b  = params.value("plane_b", -1);
+    // Datum features don't produce a body; check for an error returned by resolve.
+    bool recompute_ok = doc.recompute();
+    auto axes = doc.resolve_datum_axes();
+    std::string err = doc.error;
+    if (recompute_ok && err.empty() && !axes.empty() && !axes.back().error.empty())
+        err = axes.back().error;
+    panel->mcp_after_change();
+    return json{{"ok", true}, {"axis_index", idx}, {"error", err}};
+}
+
+json action_coordsys(DesignPanel* panel, const json& params)
+{
+    CadDocument& doc = panel->mcp_doc();
+    std::string t = params.value("type", std::string("point_world"));
+    CoordSysType ct = CoordSysType::PointWorld;
+    if (t == "face_and_direction") ct = CoordSysType::FaceAndDirection;
+    Vec3d pt(0, 0, 0);
+    if (params.contains("point") && params["point"].is_array() && params["point"].size() >= 3)
+        pt = Vec3d(params["point"][0].get<double>(), params["point"][1].get<double>(), params["point"][2].get<double>());
+    doc.checkpoint();
+    int idx = doc.add_coordsys(ct, pt, "CoordSys");
+    CadFeature& f = doc.features[idx];
+    f.coordsys_body  = params.value("body", -1);
+    f.coordsys_face  = params.value("face", -1);
+    f.coordsys_edge  = params.value("edge", -1);
+    if (params.contains("x_hint") && params["x_hint"].is_array() && params["x_hint"].size() >= 3)
+        f.coordsys_x_hint = Vec3d(params["x_hint"][0].get<double>(), params["x_hint"][1].get<double>(), params["x_hint"][2].get<double>());
+    bool recompute_ok = doc.recompute();
+    auto css = doc.resolve_datum_coordsys();
+    std::string err = doc.error;
+    if (recompute_ok && err.empty() && !css.empty() && !css.back().error.empty())
+        err = css.back().error;
+    panel->mcp_after_change();
+    return json{{"ok", true}, {"coordsys_index", idx}, {"error", err}};
+}
+
+json action_helix(DesignPanel* panel, const json& params)
+{
+    const double radius      = params.value("radius", 10.0);
+    const double pitch       = params.value("pitch", 5.0);
+    const double height      = params.value("height", 20.0);
+    const bool   left_handed = params.value("left_handed", false);
+    const double taper       = params.value("taper_deg", 0.0);
+    CadDocument& doc = panel->mcp_doc();
+    doc.checkpoint();
+    int idx = doc.add_helix(plane_from(params, doc), radius, pitch, height, left_handed, taper, "Helix");
+    panel->mcp_after_change();
+    return json{{"ok", true}, {"helix_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_mate(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("cs_a")) throw std::runtime_error("mate needs 'cs_a' (CoordSys feature index)");
+    if (!params.contains("cs_b")) throw std::runtime_error("mate needs 'cs_b' (CoordSys feature index)");
+    const int kind      = params.value("kind", 0);
+    const int cs_a      = params["cs_a"].get<int>();
+    const int cs_b      = params["cs_b"].get<int>();
+    const double offset = params.value("offset", 0.0);
+    const double angle  = params.value("angle", 0.0);
+    const bool flip     = params.value("flip", false);
+    CadDocument& doc = panel->mcp_doc();
+    doc.checkpoint();
+    int idx = doc.add_mate(kind, cs_a, cs_b, offset, angle, flip, "Mate");
+    bool ok = doc.recompute();
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"mate_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
+json action_check_interference(DesignPanel* panel, const json& params)
+{
+    const double min_volume = params.value("min_volume", 1e-6);
+    CadDocument& doc = panel->mcp_doc();
+    // Read-only: no checkpoint(), no recompute(), no mcp_after_change().
+    const auto hits = doc.check_interference(min_volume);
+    json arr = json::array();
+    for (const auto& h : hits) {
+        arr.push_back(json{{"body_a", h.body_a}, {"body_b", h.body_b}, {"volume", h.volume}});
+    }
+    return json{{"ok", true}, {"count", int(hits.size())}, {"interferences", arr}};
+}
+
+json action_set_variable(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("name")) throw std::runtime_error("set_variable needs 'name'");
+    if (!params.contains("expr")) throw std::runtime_error("set_variable needs 'expr'");
+    CadDocument& doc = panel->mcp_doc();
+    std::string name = params["name"].get<std::string>();
+    std::string expr = params["expr"].get<std::string>();
+    std::string old = doc.variables.count(name) ? doc.variables[name] : "";
+    doc.checkpoint();
+    doc.variables[name] = expr;
+    bool ok = doc.recompute();
+    // undo() recomputes, which succeeds and clears doc.error; carry the reason across so
+    // the JSON reply below reports why the edit was rejected instead of an empty string.
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"name", name}, {"error", doc.error}};
+}
+
+json action_set_feature_expr(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("feature")) throw std::runtime_error("set_feature_expr needs 'feature' index");
+    if (!params.contains("field"))   throw std::runtime_error("set_feature_expr needs 'field' name");
+    if (!params.contains("expr"))    throw std::runtime_error("set_feature_expr needs 'expr' string");
+    CadDocument& doc = panel->mcp_doc();
+    int fi = params["feature"].get<int>();
+    if (fi < 0 || fi >= (int)doc.features.size())
+        return json{{"ok", false}, {"error", "feature index out of range"}};
+    std::string field = params["field"].get<std::string>();
+    std::string expr  = params["expr"].get<std::string>();
+    std::string old = doc.features[fi].expr.count(field) ? doc.features[fi].expr[field] : "";
+    doc.checkpoint();
+    doc.features[fi].expr[field] = expr;
+    bool ok = doc.recompute();
+    // undo() recomputes, which succeeds and clears doc.error; carry the reason across so
+    // the JSON reply below reports why the edit was rejected instead of an empty string.
+    if (!ok) { const std::string why = doc.error; doc.undo(); doc.error = why; }
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"feature", fi}, {"field", field}, {"error", doc.error}};
+}
+
+// Dispatch one parsed request ON THE MAIN THREAD. Returns a JSON-RPC reply string.
+std::string handle_on_main(const std::string& method, const json& params, const json& id)
+{
+    MainFrame* mf = wxGetApp().mainframe;
+    // The panel is built on first use, and in a headless session nobody clicks the tab that
+    // would build it -- so build it here rather than refusing. Safe: this runs on the main
+    // thread (see the CallAfter that dispatches us).
+    DesignPanel* panel = mf ? mf->ensure_design_panel() : nullptr;
+    if (!panel)
+        return rpc_error(id, -32001, "Design panel not ready");
+
+    // Stale-id guard, checked here rather than in each handler.
+    //
+    // Global face and edge ids are indices into TopExp::MapShapes, valid only against the
+    // topology that produced them. Every dress-up rewrites those maps, so the natural way to
+    // drive this socket — read the scene once, then issue several operations — silently
+    // addresses the WRONG edge on every call after the first. Measured on a box: four chamfers
+    // with ids re-read each time remove 0.400/0.397/0.397/0.395 mm3; the same four with ids
+    // captured up front remove 0.400/0.008/0.397/0.280. Neither run errors, because a stale id
+    // still resolves to a real edge — just not the one that was asked for.
+    //
+    // So a caller may pass back the "generation" it got from describe_scene or query_topology,
+    // and a mismatch is refused instead of silently obeyed. Optional by design: omitting it
+    // keeps every existing script working exactly as before, and supplying it is what buys the
+    // guarantee. One check at the dispatcher rather than one per handler, so a method added
+    // later cannot forget it.
+    //
+    // The type check is not decoration: this runs OUTSIDE the try below, and a bare
+    // get<uint64_t>() on `"generation": "x"` throws nlohmann::type_error straight out of
+    // the CallAfter lambda that invoked us — through a wx event loop, which does not catch,
+    // so the whole GUI went down on one malformed line. Refuse it as a parameter error.
+    if (params.is_object() && params.contains("generation")) {
+        if (!params["generation"].is_number_unsigned())
+            return rpc_error(id, -32602, "generation must be an unsigned integer");
+        const uint64_t want = params["generation"].get<uint64_t>();
+        const uint64_t have = panel->mcp_doc().topo_generation;
+        if (want != have)
+            return rpc_error(id, -32010,
+                "stale face/edge ids: they were read at generation " + std::to_string(want)
+                + " but the model is now at " + std::to_string(have)
+                + ". Re-read query_topology and use the new ids — the old ones still name real "
+                  "edges, just not the ones you measured.");
+    }
+
+    try {
+        if (method == "describe_tools") return rpc_result(id, describe_tools());
+        if (method == "describe_scene") return rpc_result(id, describe_scene(panel));
+        if (method == "query_topology") return rpc_result(id, query_topology(panel, params));
+        if (method == "measure")        return rpc_result(id, measure(panel, params));
+        if (method == "mass_properties") return rpc_result(id, mass_properties(panel, params));
+        if (method == "slice_body")     return rpc_result(id, slice_body(panel, params));
+        if (method == "import_step")    return rpc_result(id, import_step(panel, params));
+        if (method == "import_mesh")    return rpc_result(id, import_mesh(panel, params));
+        if (method == "validate_against") return rpc_result(id, validate_against(panel, params));
+        if (method == "extrude")        return rpc_result(id, action_extrude(panel, params));
+        if (method == "revolve")        return rpc_result(id, action_revolve(panel, params));
+        if (method == "fillet")         return rpc_result(id, action_fillet(panel, params));
+        if (method == "chamfer")        return rpc_result(id, action_chamfer(panel, params));
+        if (method == "hole")           return rpc_result(id, action_hole(panel, params));
+        if (method == "hole_styled")   return rpc_result(id, action_hole_styled(panel, params));
+        if (method == "hole_standard") return rpc_result(id, action_hole_standard(panel, params));
+        if (method == "boolean")        return rpc_result(id, action_boolean(panel, params));
+        if (method == "pattern")        return rpc_result(id, action_pattern(panel, params));
+        if (method == "pattern_on_curve") return rpc_result(id, action_pattern_on_curve(panel, params));
+        if (method == "shell")          return rpc_result(id, action_shell(panel, params));
+        if (method == "rib")            return rpc_result(id, action_rib(panel, params));
+        if (method == "draft")          return rpc_result(id, action_draft(panel, params));
+        if (method == "mirror")         return rpc_result(id, action_mirror(panel, params));
+        if (method == "sketch_begin")   return rpc_result(id, action_sketch_begin(panel, params));
+        if (method == "sketch_commit")  return rpc_result(id, action_sketch_commit(panel, params));
+        if (method == "sketch_cancel")  return rpc_result(id, action_sketch_cancel(panel, params));
+        if (method == "sketch_add")     return rpc_result(id, action_sketch_add(panel, params));
+        if (method == "sketch_select")  return rpc_result(id, action_sketch_select(panel, params));
+        if (method == "sketch_delete")  return rpc_result(id, action_sketch_delete(panel, params));
+        if (method == "sketch_construction") return rpc_result(id, action_sketch_construction(panel, params));
+        if (method == "sketch_offset")  return rpc_result(id, action_sketch_offset(panel, params));
+        if (method == "sketch_mirror")  return rpc_result(id, action_sketch_mirror(panel, params));
+        if (method == "sketch_describe") return rpc_result(id, action_sketch_describe(panel, params));
+        if (method == "sketch_validate") return rpc_result(id, action_sketch_validate(panel, params));
+        if (method == "sketch_heal")    return rpc_result(id, action_sketch_heal(panel, params));
+        if (method == "sketch_set_value") return rpc_result(id, action_sketch_set_value(panel, params));
+        if (method == "list_verbs")     return rpc_result(id, action_list_verbs(panel, params));
+        if (method == "run_verb")       return rpc_result(id, action_run_verb(panel, params));
+        if (method == "transform")      return rpc_result(id, action_transform(panel, params));
+        if (method == "thicken")        return rpc_result(id, action_thicken(panel, params));
+        if (method == "split")          return rpc_result(id, action_split(panel, params));
+        if (method == "project")        return rpc_result(id, action_project(panel, params));
+        if (method == "delete_face")    return rpc_result(id, action_delete_face(panel, params));
+        if (method == "bridge")         return rpc_result(id, action_bridge(panel, params));
+        if (method == "axis")           return rpc_result(id, action_axis(panel, params));
+        if (method == "coordsys")       return rpc_result(id, action_coordsys(panel, params));
+        if (method == "helix")          return rpc_result(id, action_helix(panel, params));
+        if (method == "set_variable")     return rpc_result(id, action_set_variable(panel, params));
+        if (method == "set_feature_expr") return rpc_result(id, action_set_feature_expr(panel, params));
+        if (method == "surface_extrude")  return rpc_result(id, action_surface_extrude(panel, params));
+        if (method == "surface_revolve")  return rpc_result(id, action_surface_revolve(panel, params));
+        if (method == "thicken_surface")  return rpc_result(id, action_thicken_surface(panel, params));
+        if (method == "surface_offset")   return rpc_result(id, action_surface_offset(panel, params));
+        if (method == "surface_loft")    return rpc_result(id, action_surface_loft(panel, params));
+        if (method == "surface_fill")    return rpc_result(id, action_surface_fill(panel, params));
+        if (method == "mate")          return rpc_result(id, action_mate(panel, params));
+        if (method == "check_interference") return rpc_result(id, action_check_interference(panel, params));
+        return rpc_error(id, -32601, "Unknown method: " + method);
+    } catch (const Standard_Failure& ex) {   // OCCT errors are NOT std::exception
+        return rpc_error(id, -32000, std::string("OCCT: ") + (ex.GetMessageString() ? ex.GetMessageString() : "failure"));
+    } catch (const std::exception& ex) {
+        return rpc_error(id, -32000, ex.what());
+    }
+}
+
+// Marshal a request to the main thread and block (with a timeout) for the reply.
+std::string dispatch_request(const std::string& line)
+{
+    json req;
+    try { req = json::parse(line); }
+    catch (const std::exception& ex) { return rpc_error(nullptr, -32700, std::string("parse error: ") + ex.what()); }
+
+    json id           = req.contains("id") ? req["id"] : json(nullptr);
+    std::string method = req.value("method", std::string());
+    json params        = req.contains("params") ? req["params"] : json::object();
+    if (method.empty()) return rpc_error(id, -32600, "missing method");
+
+    auto prom = std::make_shared<std::promise<std::string>>();
+    auto fut  = prom->get_future();
+    // Nothing may escape this lambda. It is invoked by the wx event loop, which has no
+    // handler of its own, so an escaping exception is std::terminate — the socket would
+    // become a way for any client to kill the application. handle_on_main() catches what
+    // it knows about; this catches what it does not, and still answers the caller.
+    wxGetApp().CallAfter([prom, method, params, id]() {
+        try {
+            prom->set_value(handle_on_main(method, params, id));
+        } catch (const std::exception& ex) {
+            prom->set_value(rpc_error(id, -32000, std::string("internal error: ") + ex.what()));
+        } catch (...) {
+            prom->set_value(rpc_error(id, -32000, "internal error: unknown exception"));
+        }
+    });
+    if (fut.wait_for(std::chrono::seconds(15)) != std::future_status::ready)
+        return rpc_error(id, -32000, "main-thread timeout");
+    return fut.get();
+}
+
+// Read newline-delimited requests off one client connection until EOF.
+void serve_client(int cfd)
+{
+    std::string buf;
+    char chunk[4096];
+    for (;;) {
+        ssize_t n = ::read(cfd, chunk, sizeof(chunk));
+        if (n <= 0) break;
+        buf.append(chunk, size_t(n));
+        size_t nl;
+        while ((nl = buf.find('\n')) != std::string::npos) {
+            std::string line = buf.substr(0, nl);
+            buf.erase(0, nl + 1);
+            if (line.empty()) continue;
+            std::string reply = dispatch_request(line);
+            reply.push_back('\n');
+            // Never a bare write(): a client that hangs up between its request and our
+            // reply raises SIGPIPE, whose default action kills the process — so closing
+            // a socket mid-call would take the GUI with it.
+#ifdef MSG_NOSIGNAL
+            if (::send(cfd, reply.data(), reply.size(), MSG_NOSIGNAL) < 0) return;
+#else
+            if (::write(cfd, reply.data(), reply.size()) < 0) return;   // SO_NOSIGPIPE set at accept
+#endif
+        }
+    }
+}
+
+void server_thread(std::string sock_path)
+{
+    ::unlink(sock_path.c_str());
+    int sfd = ::socket(AF_UNIX, SOCK_STREAM, 0);
+    if (sfd < 0) { BOOST_LOG_TRIVIAL(error) << "MCP: socket() failed"; return; }
+
+    sockaddr_un addr{};
+    addr.sun_family = AF_UNIX;
+    std::strncpy(addr.sun_path, sock_path.c_str(), sizeof(addr.sun_path) - 1);
+    // The socket is the full CAD command surface, including import_step on absolute paths.
+    // It lands in a world-writable directory by default (/tmp), so its access control is
+    // its file mode and nothing else — leaving that to the ambient umask means any local
+    // process may drive the modeller. umask around bind() makes it 0600 with no window in
+    // which a wider mode exists; the chmod afterwards covers platforms that do not apply
+    // umask to sockets.
+    const mode_t old_umask = ::umask(0177);
+    const int bind_rc = ::bind(sfd, reinterpret_cast<sockaddr*>(&addr), sizeof(addr));
+    ::umask(old_umask);
+    if (bind_rc < 0) {
+        BOOST_LOG_TRIVIAL(error) << "MCP: bind() failed on " << sock_path;
+        ::close(sfd); return;
+    }
+    if (::chmod(sock_path.c_str(), S_IRUSR | S_IWUSR) < 0) {
+        BOOST_LOG_TRIVIAL(error) << "MCP: cannot restrict " << sock_path << " to the owner; refusing to listen";
+        ::close(sfd); ::unlink(sock_path.c_str()); return;
+    }
+    if (::listen(sfd, 1) < 0) { BOOST_LOG_TRIVIAL(error) << "MCP: listen() failed"; ::close(sfd); return; }
+    BOOST_LOG_TRIVIAL(info) << "MCP control listening on " << sock_path;
+
+    for (;;) {
+        int cfd = ::accept(sfd, nullptr, nullptr);
+        if (cfd < 0) continue;
+#if !defined(MSG_NOSIGNAL) && defined(SO_NOSIGPIPE)
+        const int on = 1;                                   // macOS/BSD equivalent of MSG_NOSIGNAL
+        ::setsockopt(cfd, SOL_SOCKET, SO_NOSIGPIPE, &on, sizeof(on));
+#endif
+        serve_client(cfd);
+        ::close(cfd);
+    }
+}
+
+} // namespace
+
+void start_mcp_control_if_enabled()
+{
+    const char* env = std::getenv("ORCA_CAD_MCP");
+    if (!env || !*env) return;
+    std::string path = (std::strcmp(env, "1") == 0) ? "/tmp/orca-cad-mcp.sock" : env;
+    static bool started = false;
+    if (started) return;
+    started = true;
+    std::thread(server_thread, path).detach();
+}
+
+}} // namespace Slic3r::GUI
+
+#else  // _WIN32
+
+namespace Slic3r { namespace GUI {
+void start_mcp_control_if_enabled() {}   // ponytail: no Windows transport yet
+}}
+
+#endif
diff --git a/src/slic3r/GUI/CAD/McpControl.hpp b/src/slic3r/GUI/CAD/McpControl.hpp
new file mode 100644
index 0000000000..12e3289eb5
--- /dev/null
+++ b/src/slic3r/GUI/CAD/McpControl.hpp
@@ -0,0 +1,24 @@
+#ifndef slic3r_GUI_McpControl_hpp_
+#define slic3r_GUI_McpControl_hpp_
+
+// MCP control surface (slice 1): a local JSON-RPC 2.0 server, line-delimited over a
+// Unix domain socket, that lets an external MCP bridge drive and perceive the Design
+// tab. Off unless the env var ORCA_CAD_MCP is set:
+//   ORCA_CAD_MCP=1                -> socket at /tmp/orca-cad-mcp.sock
+//   ORCA_CAD_MCP=/path/to.sock    -> socket at that path
+// All CAD work is marshalled onto the wx main thread and runs through the SAME
+// CadDocument kernel the GUI uses (no parallel engine). Slice-1 methods:
+//   describe_tools, describe_scene, extrude.
+//
+// ponytail: Unix-socket only (POSIX). Windows compiles this to a no-op; add a named
+// pipe transport when a Windows agent actually needs it.
+
+namespace Slic3r { namespace GUI {
+
+// Start the server thread iff ORCA_CAD_MCP is set. Safe to call once after the
+// MainFrame + DesignPanel exist. No-op when the env var is unset or on Windows.
+void start_mcp_control_if_enabled();
+
+}} // namespace Slic3r::GUI
+
+#endif // slic3r_GUI_McpControl_hpp_
diff --git a/src/slic3r/GUI/CAD/SketchInlineEditor.cpp b/src/slic3r/GUI/CAD/SketchInlineEditor.cpp
new file mode 100644
index 0000000000..9c438c7d06
--- /dev/null
+++ b/src/slic3r/GUI/CAD/SketchInlineEditor.cpp
@@ -0,0 +1,203 @@
+#include "slic3r/GUI/CAD/SketchInlineEditor.hpp"
+
+#include "slic3r/GUI/ImGuiWrapper.hpp"
+#include "slic3r/GUI/GUI_App.hpp"
+#include "slic3r/GUI/I18N.hpp"
+#include "libslic3r/Color.hpp"
+
+#include <imgui/imgui.h>
+#include <imgui/imgui_internal.h>   // BringWindowToDisplayFront / GetCurrentWindow
+
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <string>
+
+namespace Slic3r {
+namespace GUI {
+
+namespace {
+
+// Numbers are typed and shown with a POINT, whatever the locale: this field feeds a CAD kernel,
+// and a decimal comma reaching it as a thousands separator is a silent order-of-magnitude error.
+// Parsing accepts either separator because a keyboard's numeric pad may only offer one.
+std::string fmt_value(double v, int digits = 2)
+{
+    char fmt[16];
+    std::snprintf(fmt, sizeof(fmt), "%%.%df", digits);
+    char buf[64];
+    std::snprintf(buf, sizeof(buf), fmt, v);
+    for (char* c = buf; *c; ++c)
+        if (*c == ',') *c = '.';
+    return std::string(buf);
+}
+
+bool parse_value(const char* text, double& out)
+{
+    if (text == nullptr) return false;
+    std::string t(text);
+    for (char& c : t)
+        if (c == ',') c = '.';
+    // strtod, not std::stod: no exceptions, and `end` tells us whether the WHOLE field was a
+    // number. "12mm" must be refused, not silently read as 12.
+    const char* b = t.c_str();
+    char* end = nullptr;
+    const double v = std::strtod(b, &end);
+    if (end == b) return false;
+    while (*end == ' ' || *end == '\t') ++end;
+    if (*end != '\0') return false;
+    out = v;
+    return true;
+}
+
+// One machine-readable line per event of the click-edit contract, for the UX check that runs
+// after every build (scripts/CAD/check-gui-click-edit.py). Deliberately NOT the same switch as
+// ORCA_CAD_KEYTRACE: that one is a debugging firehose, this one is an assertion surface and its
+// format is a contract the script parses.
+//
+// The pair that matters is `open` vs `commit`: the check always types a value DIFFERENT from the
+// prefill, so a field that is on screen but not editable commits its prefill and the two lines
+// disagree. A focus flag cannot show that — it read 0 even when typing worked — but the number
+// the user actually gets can.
+void ux_trace(const char* event, const std::string& title, const std::string& detail)
+{
+    if (!std::getenv("ORCA_CAD_UXTRACE")) return;
+    std::fprintf(stderr, "[UX] %s title=%s %s\n", event, title.c_str(), detail.c_str());
+    std::fflush(stderr);
+}
+
+} // namespace
+
+void SketchInlineEditor::open(const wxPoint& canvas_px, double value, const std::string& title,
+                              std::function<void(double)> on_commit,
+                              std::function<void()> on_cancel)
+{
+    m_anchor = canvas_px;
+    m_title  = title;
+    m_err.clear();
+    m_commit = std::move(on_commit);
+    m_cancel = std::move(on_cancel);
+    const std::string v = fmt_value(value);
+    std::snprintf(m_buf, sizeof(m_buf), "%s", v.c_str());
+    m_open          = true;
+    // ImGui takes keyboard focus for one frame on request; asking on the frame the field first
+    // appears is what makes typing land without a click. There is no window manager to consult.
+    m_focus_pending = true;
+    ux_trace("open", m_title, "prefill=" + v);
+}
+
+void SketchInlineEditor::close()
+{
+    m_open          = false;
+    m_focus_pending = false;
+    m_commit        = nullptr;
+    m_cancel        = nullptr;
+    m_err.clear();
+}
+
+void SketchInlineEditor::cancel()
+{
+    if (m_open) do_cancel();
+}
+
+void SketchInlineEditor::commit()
+{
+    if (m_open) do_commit();
+}
+
+void SketchInlineEditor::do_cancel()
+{
+    ux_trace("cancel", m_title, "");
+    auto cb = m_cancel;
+    close();
+    if (cb) cb();
+}
+
+void SketchInlineEditor::do_commit()
+{
+    double v = 0.0;
+    if (!parse_value(m_buf, v)) {
+        // Refusing input in silence is indistinguishable from the app having frozen: the field
+        // just sits there and the user has no idea what it wants. Say so in the title line and
+        // keep editing.
+        ux_trace("refused", m_title, std::string("typed=") + m_buf);
+        m_err = (m_buf[0] == '\0') ? into_u8(_L("Enter a number")) : into_u8(_L("Not a number"));
+        m_focus_pending = true;
+        return;
+    }
+    ux_trace("commit", m_title, std::string("typed=") + m_buf + " value=" + fmt_value(v, 4));
+    auto cb = m_commit;
+    close();
+    // AFTER close(): the callback may open the next queued dimension (a rectangle queues Width
+    // then Height), and doing that into a field that still believes it is open would drop the
+    // second one's prefill on the floor.
+    if (cb) cb(v);
+}
+
+bool SketchInlineEditor::render(ImGuiWrapper& imgui, float scale)
+{
+    if (!m_open) return false;
+
+    ImGuiWrapper::push_common_window_style(scale);
+    imgui.set_next_window_pos((float) m_anchor.x, (float) m_anchor.y, ImGuiCond_Always, 0.5f, 0.5f);
+    ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 3.0f);
+    // NoInputs is what every other sketch overlay sets and is exactly what this one must not:
+    // it is the only overlay in the tab that the user types into.
+    imgui.begin(std::string("##sketchvalue"),
+                ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoDecoration
+                    | ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoSavedSettings);
+    ImGui::BringWindowToDisplayFront(ImGui::GetCurrentWindow());
+
+    if (!m_title.empty() || !m_err.empty()) {
+        if (m_err.empty()) {
+            imgui.text(m_title);
+        } else {
+            ImGui::PushStyleColor(ImGuiCol_Text, ImGuiWrapper::to_ImVec4(ColorRGBA(0.91f, 0.42f, 0.42f, 1.0f)));
+            imgui.text(m_err);
+            ImGui::PopStyleColor();
+        }
+    }
+
+    if (m_focus_pending) {
+        ImGui::SetKeyboardFocusHere();
+        m_focus_pending = false;
+    }
+    ImGui::PushItemWidth(90.0f * scale);
+    // EnterReturnsTrue so Enter commits from inside the widget; AutoSelectAll so the prefill is
+    // replaced by the first digit typed, which is what "pre-selected" meant when this was a
+    // wxTextCtrl and is what makes typing a value a single gesture.
+    const bool entered = ImGui::InputText("##sketchvalue_in", m_buf, sizeof(m_buf),
+                                          ImGuiInputTextFlags_EnterReturnsTrue
+                                              | ImGuiInputTextFlags_AutoSelectAll
+                                              | ImGuiInputTextFlags_CharsDecimal);
+    // MEASUREMENT, not a fix: one line per frame saying whether ImGui believes it owns the
+    // keyboard and whether our widget is the active one. "Typing does not arrive" has two very
+    // different causes — no FRAMES (this canvas repaints on demand only, so an idle canvas never
+    // processes ImGui's queued characters) versus frames that run while the input is not active —
+    // and they are indistinguishable from outside.
+    if (std::getenv("ORCA_CAD_UXTRACE")) {
+        const ImGuiIO& io = ImGui::GetIO();
+        std::fprintf(stderr, "[UX] frame title=%s want_text=%d want_kb=%d active=%d buf=%s\n",
+                     m_title.c_str(), (int) io.WantTextInput, (int) io.WantCaptureKeyboard,
+                     (int) ImGui::IsItemActive(), m_buf);
+        std::fflush(stderr);
+    }
+    ImGui::PopItemWidth();
+    imgui.end();
+    ImGui::PopStyleVar();
+    ImGuiWrapper::pop_common_window_style();
+
+    // Keep the frames coming while the field is up — see request_frame's note in the header.
+    if (m_open && request_frame)
+        request_frame();
+
+    // Act AFTER end(): do_commit can reopen the field for the next queued dimension, and that
+    // must not happen inside this frame's window.
+    if (entered)
+        do_commit();
+    else if (ImGui::IsKeyPressed(ImGui::GetKeyIndex(ImGuiKey_Escape)))
+        do_cancel();
+    return true;
+}
+
+}} // namespace Slic3r::GUI
diff --git a/src/slic3r/GUI/CAD/SketchInlineEditor.hpp b/src/slic3r/GUI/CAD/SketchInlineEditor.hpp
new file mode 100644
index 0000000000..162d157864
--- /dev/null
+++ b/src/slic3r/GUI/CAD/SketchInlineEditor.hpp
@@ -0,0 +1,95 @@
+#ifndef slic3r_SketchInlineEditor_hpp_
+#define slic3r_SketchInlineEditor_hpp_
+
+#include <functional>
+#include <string>
+
+#include <wx/gdicmn.h>
+
+namespace Slic3r {
+namespace GUI {
+
+class ImGuiWrapper;
+
+// Onshape-style in-canvas value editor.
+//
+// IT IS NOT A WINDOW. It used to be a borderless top-level wxFrame holding a wxTextCtrl, and
+// that is the whole history of this file: a separate top-level window can only receive typing
+// if the window manager grants it focus, and whether it does is not ours to decide. openbox
+// grants it; mutter's focus-stealing prevention refuses it, so on a GNOME desktop the field
+// appeared, showed its value selected, and silently ignored every keystroke — Enter then
+// committed the number it opened with. Seven workarounds were tried against that (a real X11
+// server timestamp for gtk_window_present, re-asserted SetFocus, dropping the _UTILITY hint,
+// keeping the frame mapped between two queued fields, forwarding keys from the panel's
+// CHAR_HOOK), one of them caused a macOS regression, and the test harness ended up clicking the
+// field before typing — which is the workaround a user cannot be asked to perform, and is
+// exactly the "label value not editable" report.
+//
+// So the field stops asking. It is now drawn INSIDE the GL canvas as an ImGui overlay, at the
+// same screen point as before, and its keys arrive through the canvas's own key events, which
+// GLCanvas3D already feeds to ImGui (see GLCanvas3D::on_key / on_char -> update_key_data). The
+// canvas is part of the main window and already has focus, so there is no second window, no
+// second focus, and no window manager in the path. The dimension labels next to it are already
+// ImGui overlays (DesignSketchTool::draw_dim_label), so this is the same vocabulary, not a new
+// one.
+//
+// Ownership: DesignCanvas owns it; DesignSketchTool::render() calls render() once per frame.
+class SketchInlineEditor
+{
+public:
+    SketchInlineEditor() = default;
+
+    // Open the field anchored at `canvas_px` (canvas DEVICE pixels, the coordinate space the
+    // sketch tool works in), pre-filled with `value` and pre-selected. on_commit(parsed) fires
+    // on Enter with a valid number; on_cancel() on Esc.
+    void open(const wxPoint& canvas_px, double value, const std::string& title,
+              std::function<void(double)> on_commit,
+              std::function<void()> on_cancel);
+    void close();                        // drop it with neither callback
+    void cancel();                       // if open, run the registered cancel (keep-as-drawn)
+    void commit();                       // if open, run the registered commit (accept the typed value)
+    bool is_open() const { return m_open; }
+
+    // Draw it, and let ImGui do the editing. Called from DesignSketchTool::render() inside the
+    // frame's ImGui pass; `scale` is the tool's m_render_scale. Returns true if it drew.
+    bool render(ImGuiWrapper& imgui, float scale);
+
+    // Ask for another frame. THE FIELD DOES NOT WORK WITHOUT THIS, and the reason is a deadlock
+    // that only a per-frame trace shows:
+    //
+    //   [UX] frame want_text=0 want_kb=0 active=0     <- frame 1: the widget is not active yet
+    //   [UX] frame want_text=0 want_kb=0 active=1     <- frame 2: it is now
+    //   (nothing further)                             <- the canvas has nothing to redraw, so it stops
+    //
+    // This canvas repaints ON DEMAND. ImGui decides whether it wants the keyboard at the END of a
+    // frame, from the active item, and GLCanvas3D::on_char only calls render() when
+    // update_key_data() says ImGui wants it. No frames -> WantTextInput never turns on -> no
+    // render on a keystroke -> still no frames. The characters sit in ImGui's queue and the field
+    // looks exactly as deaf as the window it replaced. One repaint per frame while it is open
+    // breaks the circle.
+    std::function<void()> request_frame;
+
+    // Kept because callers ask them, but there is no longer any difference to report: with no
+    // window there is no state where the field is on screen but logically closed, and no state
+    // where it is open but somebody else holds the keyboard.
+    bool is_mapped() const { return m_open; }
+    bool has_focus() const { return m_open; }
+    void dismiss() { close(); }
+
+private:
+    void do_commit();
+    void do_cancel();
+
+    std::function<void(double)> m_commit;
+    std::function<void()>       m_cancel;
+    bool        m_open{false};
+    bool        m_focus_pending{false};  // one frame of SetKeyboardFocusHere after opening
+    wxPoint     m_anchor{0, 0};          // canvas device px
+    std::string m_title;
+    std::string m_err;                   // why the last value was refused, shown in the title line
+    char        m_buf[64]{};             // the edited text; ImGui::InputText writes into it
+};
+
+}} // namespace Slic3r::GUI
+
+#endif // slic3r_SketchInlineEditor_hpp_
diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index 83c8cba0ee..ca22df3237 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -1,5 +1,8 @@
 #include "libslic3r/libslic3r.h"
 #include "GLCanvas3D.hpp"
+#ifdef SLIC3R_CAD
+#include "slic3r/GUI/CAD/DesignSketchTool.hpp"   // Design tab: interactive 2D sketch tool
+#endif
 
 #include <igl/unproject.h>
 
@@ -1827,6 +1830,16 @@ void GLCanvas3D::enable_separator_toolbar(bool enable)
     m_separator_toolbar.set_enabled(enable);
 }
 
+void GLCanvas3D::enable_collapse_toolbar(bool enable)
+{
+    m_collapse_toolbar_enabled = enable;
+}
+
+void GLCanvas3D::enable_plate_chrome(bool enable)
+{
+    m_plate_chrome_enabled = enable;
+}
+
 bool GLCanvas3D::has_mouse_capture() const {
     return m_canvas != nullptr && m_canvas->HasCapture();
 }
@@ -2048,14 +2061,24 @@ void GLCanvas3D::render(bool only_init)
         no_partplate = true;
     else if (gizmo_type == GLGizmosManager::BrimEars && !camera.is_looking_downward())
         show_grid = false;
+    if (m_axes_at_bed_center)
+        // Design tab: the plate grid is generated from the plate's front-left corner, so it
+        // floats mid-cell under the modeling-origin triad. Suppress it here; a CAD grid centred
+        // on the origin is rendered in its place (see _render_cad_grid).
+        show_grid = false;
 
     /* view3D render*/
     int hover_id = (m_hover_plate_idxs.size() > 0)?m_hover_plate_idxs.front():-1;
     if (m_canvas_type == ECanvasType::CanvasView3D) {
-        if (!no_partplate)
+        // m_show_bed gates the plate list too: hiding the bed but leaving its grid and outline
+        // floating would read as a rendering fault rather than a deliberate view option.
+        if (!no_partplate && m_show_bed)
             _render_bed(camera.get_view_matrix(), camera.get_projection_matrix(), !camera.is_looking_downward(), m_show_world_axes);
-        if (!no_partplate) //BBS: add outline logic
+        if (!no_partplate && m_show_bed) //BBS: add outline logic
             _render_platelist(camera.get_view_matrix(), camera.get_projection_matrix(), !camera.is_looking_downward(), only_current, only_body, hover_id, true, show_grid);
+        if (m_axes_at_bed_center && m_show_bed && !no_partplate)
+            // Design tab: replace the plate's corner-origin grid with the origin-centred CAD grid.
+            _render_cad_grid(camera.get_view_matrix(), camera.get_projection_matrix());
         
         //BBS: add outline logic
         // Depth pass for object-on-object and self shadows; consumed by the gouraud shader below.
@@ -2121,6 +2144,13 @@ void GLCanvas3D::render(bool only_init)
     if (_is_fxaa_enabled())
         _render_fxaa_pass(static_cast<unsigned int>(cnv_size.get_width()), static_cast<unsigned int>(cnv_size.get_height()));
 
+    // Design tab: interactive 2D sketch overlay, drawn over the scene but
+    // beneath the UI overlays (toolbars, labels).
+#ifdef SLIC3R_CAD
+    if (m_design_sketch_tool != nullptr && m_design_sketch_tool->has_display())
+        m_design_sketch_tool->render(*this);
+#endif
+
     // draw overlays
     _render_overlays();
 
@@ -3203,7 +3233,11 @@ void GLCanvas3D::on_idle(wxIdleEvent& evt)
     // BBS
     //m_dirty |= wxGetApp().plater()->get_view_toolbar().update_items_state();
     m_dirty |= wxGetApp().plater()->get_collapse_toolbar().update_items_state();
-    bool mouse3d_controller_applied = wxGetApp().plater()->get_mouse3d_controller().apply(wxGetApp().plater()->get_camera());
+    // apply() DRAINS the 3D-mouse queue, so only the canvas actually on screen may call it: a
+    // hidden canvas renders nothing, so the motion it swallowed moves the shared camera without
+    // ever being drawn and the next visible frame jumps several states at once.
+    bool mouse3d_controller_applied = _is_shown_on_screen()
+        && wxGetApp().plater()->get_mouse3d_controller().apply(wxGetApp().plater()->get_camera());
     m_dirty |= mouse3d_controller_applied;
     m_dirty |= wxGetApp().plater()->get_notification_manager()->update_notifications(*this);
     auto gizmo = wxGetApp().plater()->get_view3D_canvas3D()->get_gizmos_manager().get_current();
@@ -3271,6 +3305,64 @@ void GLCanvas3D::on_char(wxKeyEvent& evt)
         return;
     }
 
+    // Design tab: Delete/Backspace removes the selected sketch entities while a
+    // sketch tool is active and the canvas has focus (dialog text fields are separate
+    // wx controls, so this never eats their editing keys).
+#ifdef SLIC3R_CAD
+    if (m_design_sketch_tool != nullptr && m_design_sketch_tool->is_active()
+        && (keyCode == WXK_DELETE || keyCode == WXK_BACK)
+        && !m_design_sketch_tool->selection().empty()) {
+        m_design_sketch_tool->delete_selected();
+        m_dirty = true;
+        render();
+        return;
+    }
+#endif
+
+    // Esc exits the active sketch tool (Onshape-like, layered: abort in-progress entity ->
+    // drop to Select -> exit the session back to Feature mode).
+#ifdef SLIC3R_CAD
+    if (m_design_sketch_tool != nullptr && m_design_sketch_tool->is_active()
+        && keyCode == WXK_ESCAPE) {
+        m_design_sketch_tool->request_exit();
+        m_dirty = true;
+        render();
+        return;
+    }
+#endif
+
+    // Design tab: Ctrl+Z / Ctrl+Shift+Z (and Ctrl+Y) undo/redo the Design feature
+    // history. Scoped by m_design_sketch_tool — only the Design canvas owns one — so the
+    // main 3D editor's undo/redo (the CanvasView3D-gated cases further below) is untouched.
+    // Handled here, before the generic Ctrl block, so it takes precedence and early-returns.
+#ifdef SLIC3R_CAD
+    if (m_design_sketch_tool != nullptr && (evt.GetModifiers() & ctrlMask) != 0) {
+        const bool is_z = (keyCode == 'z' || keyCode == 'Z' || keyCode == WXK_CONTROL_Z);
+        const bool is_y = (keyCode == 'y' || keyCode == 'Y' || keyCode == WXK_CONTROL_Y);
+        if (is_z || is_y) {
+            const bool redo = is_y || ((evt.GetModifiers() & shiftMask) != 0);
+            m_design_sketch_tool->request_undo_redo(redo);
+            m_dirty = true;
+            render();
+            return;
+        }
+    }
+#endif
+
+    // Design tab: F = Place on Face (Prepare's lay-flat), when the Design viewport is up
+    // and a body face is selected. The tool forwards to DesignPanel::place_on_face; it returns
+    // false (no face picked) so F falls through to the default handler below.
+#ifdef SLIC3R_CAD
+    if (m_design_sketch_tool != nullptr && m_design_sketch_tool->has_display()
+        && (keyCode == 'f' || keyCode == 'F') && (evt.GetModifiers() & ctrlMask) == 0) {
+        if (m_design_sketch_tool->request_place_on_face()) {
+            m_dirty = true;
+            render();
+            return;
+        }
+    }
+#endif
+
     bool is_in_painting_mode = false;
     GLGizmoPainterBase *current_gizmo_painter = dynamic_cast<GLGizmoPainterBase *>(get_gizmos_manager().get_current());
     if (current_gizmo_painter != nullptr) {
@@ -3648,6 +3740,20 @@ public:
 
 void GLCanvas3D::on_key(wxKeyEvent& evt)
 {
+    // Design tab: Delete/Backspace removes selected sketch entities. GTK delivers
+    // these as KEY_DOWN rather than CHAR, so handle it here too.
+#ifdef SLIC3R_CAD
+    if (evt.GetEventType() == wxEVT_KEY_DOWN
+        && m_design_sketch_tool != nullptr && m_design_sketch_tool->is_active()
+        && (evt.GetKeyCode() == WXK_DELETE || evt.GetKeyCode() == WXK_BACK)
+        && !m_design_sketch_tool->selection().empty()) {
+        m_design_sketch_tool->delete_selected();
+        m_dirty = true;
+        render();
+        return;
+    }
+#endif
+
     static GLCanvas3D const * thiz = nullptr;
     static TranslationProcessor translationProcessor(nullptr, nullptr);
     if (thiz != this) {
@@ -4212,6 +4318,23 @@ void GLCanvas3D::on_mouse(wxMouseEvent& evt)
             return;
     }
 
+    // Design tab: the interactive sketch tool owns the mouse whenever it has
+    // something on screen — an active session OR committed sketch overlays that the user
+    // can click to select. It runs after ImGui (so dialogs still work) but before
+    // camera/toolbar/gizmo handling; on_mouse returns false for events it doesn't consume
+    // (drag/orbit/wheel) so the camera keeps working over the display-only plate.
+#ifdef SLIC3R_CAD
+    if (m_design_sketch_tool != nullptr && m_design_sketch_tool->has_display()) {
+        if (evt.LeftDown() && m_canvas != nullptr)
+            m_canvas->SetFocus();   // grab keyboard focus so Delete/keys reach this canvas
+        if (m_design_sketch_tool->on_mouse(evt, *this)) {
+            m_dirty = true;
+            render();   // force an immediate redraw so the sketch overlay updates live
+            return;
+        }
+    }
+#endif
+
 #ifdef __WXMSW__
 	bool on_enter_workaround = false;
     if (! evt.Entering() && ! evt.Leaving() && m_mouse.position.x() == -1.0) {
@@ -4923,6 +5046,8 @@ bool GLCanvas3D::is_camera_rotate(const wxMouseEvent& evt, const std::map<MouseB
 {
     if (m_is_touchpad_navigation) {
         return evt.Moving() && evt.AltDown() && !evt.ShiftDown();
+    } else if (m_cad_navigation) {
+        return evt.Dragging() && evt.MiddleIsDown();   // left-drag is the selection rubber band
     } else {
         return evt.Dragging() && clicked_button_matches_action(evt, MouseAction::Rotation, mappings);
     }
@@ -4932,6 +5057,8 @@ bool GLCanvas3D::is_camera_pan(const wxMouseEvent& evt, const std::map<MouseButt
 {
     if (m_is_touchpad_navigation) {
         return evt.Moving() && evt.ShiftDown() && !evt.AltDown();
+    } else if (m_cad_navigation) {
+        return evt.Dragging() && evt.RightIsDown();    // middle now orbits, so pan is right only
     } else {
         return evt.Dragging() && clicked_button_matches_action(evt, MouseAction::Pan, mappings);
         ;
@@ -8025,13 +8152,113 @@ void GLCanvas3D::_render_bed(const Transform3d& view_matrix, const Transform3d&
     */
     //bool show_texture = true;
     //BBS set axes mode
-    m_bed.set_axes_mode(m_main_toolbar.is_enabled());
+    if (m_axes_at_bed_center) {
+        // Design tab: triad at the bed centre = modeling origin (set every frame because
+        // set_shape/set_axes_mode otherwise reset it to the bed corner).
+        const Vec2d bc = m_bed.build_volume().bed_center();
+        m_bed.set_axes_origin(Vec3d(bc.x(), bc.y(), 0.0));
+    } else {
+        m_bed.set_axes_mode(m_main_toolbar.is_enabled());
+    }
     m_bed.render(*this, view_matrix, projection_matrix, bottom, scale_factor, show_axes);
 }
 
 void GLCanvas3D::_render_platelist(const Transform3d& view_matrix, const Transform3d& projection_matrix, bool bottom, bool only_current, bool only_body, int hover_id, bool render_cali, bool show_grid)
 {
-    wxGetApp().plater()->get_partplate_list().render(view_matrix, projection_matrix, bottom, only_current, only_body, hover_id, render_cali, show_grid);
+    wxGetApp().plater()->get_partplate_list().render(view_matrix, projection_matrix, bottom, only_current, only_body, hover_id, render_cali, show_grid, !m_plate_chrome_enabled);
+}
+
+// Design tab: CAD grid on the bed plane, drawn in place of the plate's corner-origin grid.
+// Generated from the bed centre (= modeling origin) so a grid line passes exactly through the
+// triad in both axes. Minor lines every 10 mm, major every 50 mm; the two GLModels are built
+// once and rebuilt only when the bed shape changes, not per frame.
+void GLCanvas3D::_render_cad_grid(const Transform3d& view_matrix, const Transform3d& projection_matrix)
+{
+    const BuildVolume& build_volume = m_bed.build_volume();
+    if (!build_volume.valid())
+        return;
+
+    const Vec2d        center = build_volume.bed_center();
+    const BoundingBoxf bb     = build_volume.bounding_volume2d();
+    if (!m_cad_grid_valid || m_cad_grid_center != center || m_cad_grid_bb != bb) {
+        m_cad_grid_center = center;
+        m_cad_grid_bb     = bb;
+        m_cad_grid_valid  = true;
+
+        // Same z as PartPlate::GROUND_Z_GRIDLINE (-0.26f): just below the bed fill (GROUND_Z =
+        // -0.03f, which is drawn with the depth mask disabled) and above the physical bed model
+        // (offset z = -0.41), so the grid never z-fights the bed quad. Chosen by construction,
+        // not by magic number: it is the exact z the plate grid already uses on the shared bed.
+        const float z = -0.26f;
+
+        auto build_grid = [&z, &center, &bb](double step, GLModel& model) {
+            std::vector<std::pair<Vec2d, Vec2d>> segs;
+            // Constant-x (vertical on screen) lines, both directions from the centre so the
+            // centre column itself is always present. Clipped to the bed bounding box so nothing
+            // spills past the bed quad.
+            for (double x = center.x(); x >= bb.min.x(); x -= step)
+                segs.emplace_back(Vec2d(x, bb.min.y()), Vec2d(x, bb.max.y()));
+            for (double x = center.x() + step; x <= bb.max.x(); x += step)
+                segs.emplace_back(Vec2d(x, bb.min.y()), Vec2d(x, bb.max.y()));
+            // Constant-y (horizontal on screen) lines, same centre-first convention.
+            for (double y = center.y(); y >= bb.min.y(); y -= step)
+                segs.emplace_back(Vec2d(bb.min.x(), y), Vec2d(bb.max.x(), y));
+            for (double y = center.y() + step; y <= bb.max.y(); y += step)
+                segs.emplace_back(Vec2d(bb.min.x(), y), Vec2d(bb.max.x(), y));
+
+            GLModel::Geometry data;
+            data.format = { GLModel::Geometry::EPrimitiveType::Lines, GLModel::Geometry::EVertexLayout::P3 };
+            data.reserve_vertices(2 * segs.size());
+            data.reserve_indices(2 * segs.size());
+            for (const auto& s : segs) {
+                data.add_vertex(Vec3f(float(s.first.x()), float(s.first.y()), z));
+                data.add_vertex(Vec3f(float(s.second.x()), float(s.second.y()), z));
+                const unsigned int vc = static_cast<unsigned int>(data.vertices_count());
+                data.add_line(vc - 2, vc - 1);
+            }
+            model.init_from(std::move(data));
+        };
+
+        m_cad_grid_minor.reset();
+        m_cad_grid_major.reset();
+        build_grid(10.0, m_cad_grid_minor);
+        build_grid(50.0, m_cad_grid_major);
+    }
+
+    if (!m_cad_grid_minor.is_initialized() || !m_cad_grid_major.is_initialized())
+        return;
+
+    GLShaderProgram* shader = wxGetApp().get_shader("flat");
+    if (shader == nullptr)
+        return;
+
+    shader->start_using();
+    glsafe(::glEnable(GL_BLEND));
+    glsafe(::glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));
+    shader->set_uniform("view_model_matrix", view_matrix);
+    shader->set_uniform("projection_matrix", projection_matrix);
+
+    // White every 5 cm, grey every 1 cm — the SAME in both themes, deliberately. There is no
+    // "white bed" to vanish against: the plate is dark grey either way, DEFAULT_MODEL_COLOR
+    // {0.326,0.337,0.337} on light and DEFAULT_MODEL_COLOR_DARK {0.255,0.255,0.283} on dark
+    // (3DBed.cpp:185-186), a difference of 0.07. A per-theme palette here would be a branch
+    // that buys nothing and one more thing to keep in step.
+    //
+    // For contrast with what this replaces: the plate's own grid uses LINE_TOP_DARK_COLOR, a
+    // 0.43 grey, for BOTH its thin and its bold family — which is most of why the stock grid
+    // reads as a flat mesh with no scale to it.
+    const ColorRGBA minor_color(0.40f, 0.40f, 0.42f, 1.0f);
+    const ColorRGBA major_color(0.90f, 0.90f, 0.90f, 1.0f);
+
+    glsafe(::glLineWidth(1.0f));
+    m_cad_grid_minor.set_color(minor_color);
+    m_cad_grid_minor.render();
+
+    glsafe(::glLineWidth(2.0f));
+    m_cad_grid_major.set_color(major_color);
+    m_cad_grid_major.render();
+
+    glsafe(::glDisable(GL_BLEND));
 }
 
 void GLCanvas3D::_render_shadows(const Transform3d& view_matrix, const Transform3d& projection_matrix)
@@ -9704,6 +9931,9 @@ void GLCanvas3D::_render_separator_toolbar_left() const
 
 void GLCanvas3D::_render_collapse_toolbar() const
 {
+    if (!m_collapse_toolbar_enabled)
+        return;
+
     auto&      plater              = *wxGetApp().plater();
     const auto sidebar_docking_dir = plater.get_sidebar_docking_state();
     if (sidebar_docking_dir == Sidebar::None) {
diff --git a/src/slic3r/GUI/GLCanvas3D.hpp b/src/slic3r/GUI/GLCanvas3D.hpp
index 1ea352ac96..7c18fa3f64 100644
--- a/src/slic3r/GUI/GLCanvas3D.hpp
+++ b/src/slic3r/GUI/GLCanvas3D.hpp
@@ -57,6 +57,9 @@ namespace GUI {
 
 class Bed3D;
 class PartPlateList;
+#ifdef SLIC3R_CAD
+class DesignSketchTool;   // Design tab: interactive 2D sketch tool
+#endif
 
 #if ENABLE_RETINA_GL
 class RetinaHelper;
@@ -543,6 +546,27 @@ private:
     mutable Vec2i32 m_canvas_toolbar_pos = {140, 5};
     mutable float m_sc{1};
     mutable float m_paint_toolbar_width;
+    bool m_collapse_toolbar_enabled{true};
+    bool m_plate_chrome_enabled{true};
+    // Design tab: render the world-axis triad at the bed centre (= modeling origin) instead of
+    // the bed corner. Default false preserves the main editor's corner triad.
+    bool m_axes_at_bed_center{false};
+    // Design tab: draw the printer bed and its plate grid at all. Default true, so the
+    // main editor is untouched; the Design tab lets the user hide it to model without a bed.
+    bool m_show_bed{true};
+    // Design tab: CAD grid drawn on the bed plane in place of the plate's corner-origin grid.
+    // Two GLModels (10 mm minor / 50 mm major) generated from the bed centre so a line passes
+    // exactly through the modeling origin; built once and rebuilt only when the bed shape changes.
+    GLModel m_cad_grid_minor;
+    GLModel m_cad_grid_major;
+    // Geometry the CAD grid models were last built from, so they are rebuilt on bed-shape change
+    // rather than every frame.
+    BoundingBoxf m_cad_grid_bb;
+    Vec2d        m_cad_grid_center;
+    bool         m_cad_grid_valid{false};
+#ifdef SLIC3R_CAD
+    DesignSketchTool* m_design_sketch_tool{nullptr};
+#endif
 
     //BBS: add canvas type for assemble view usage
     ECanvasType m_canvas_type;
@@ -570,6 +594,10 @@ private:
     std::array<unsigned int, 2> m_old_size{ 0, 0 };
 
     bool m_is_touchpad_navigation{ false };
+    // CAD navigation (Design tab only): left-drag is a selection rubber band, so orbit moves
+    // to middle-drag and pan to right-drag — the Onshape/SolidWorks mapping. Off everywhere
+    // else, so Prepare/Preview keep the mouse the user already learned.
+    bool m_cad_navigation{ false };
 
     // Screen is only refreshed from the OnIdle handler if it is dirty.
     bool m_dirty;
@@ -883,6 +911,15 @@ public:
     void enable_assemble_view_toolbar(bool enable);
     void enable_return_toolbar(bool enable);
     void enable_separator_toolbar(bool enable);
+    void enable_collapse_toolbar(bool enable);
+    void enable_plate_chrome(bool enable);
+    void set_axes_at_bed_center(bool b) { m_axes_at_bed_center = b; }
+    void set_show_bed(bool b) { m_show_bed = b; }
+    bool get_show_bed() const { return m_show_bed; }
+#ifdef SLIC3R_CAD
+    void set_design_sketch_tool(DesignSketchTool* tool) { m_design_sketch_tool = tool; }
+    DesignSketchTool* get_design_sketch_tool() const { return m_design_sketch_tool; }
+#endif
     void enable_dynamic_background(bool enable) { m_dynamic_background_enabled = enable; }
     void enable_labels(bool enable) { m_labels.enable(enable); }
     void enable_slope(bool enable) { m_slope.enable(enable); }
@@ -1052,6 +1089,7 @@ public:
     bool clicked_button_matches_action(const wxMouseEvent& evt, MouseAction action, const std::map<MouseButton, MouseAction>& mappings) const;
     bool is_camera_rotate(const wxMouseEvent& evt, const std::map<MouseButton, MouseAction>& mappings) const;
     bool is_camera_pan(const wxMouseEvent& evt, const std::map<MouseButton, MouseAction>& mappings) const;
+    void set_cad_navigation(bool b) { m_cad_navigation = b; }
 
     Size get_canvas_size() const;
     Vec2d get_local_mouse_position() const;
@@ -1255,6 +1293,10 @@ private:
     void _render_shadows(const Transform3d& view_matrix, const Transform3d& projection_matrix);
     //BBS: add part plate related logic
     void _render_platelist(const Transform3d& view_matrix, const Transform3d& projection_matrix, bool bottom, bool only_current, bool only_body = false, int hover_id = -1, bool render_cali = false, bool show_grid = true);
+    // Design tab: draw the CAD grid (minor 10 mm + major 50 mm) in place of the plate's
+    // corner-origin grid when the axes sit at the bed centre (modeling origin). Rebuilds its
+    // GLModels lazily, only when the bed shape changed.
+    void _render_cad_grid(const Transform3d& view_matrix, const Transform3d& projection_matrix);
     //BBS: add outline drawing logic
     void _render_objects(GLVolumeCollection::ERenderType type, bool with_outline = true);
     void _render_wireframe_overlay();
diff --git a/src/slic3r/GUI/GUI_App.hpp b/src/slic3r/GUI/GUI_App.hpp
index f6f0b81c92..1b9b209ff8 100644
--- a/src/slic3r/GUI/GUI_App.hpp
+++ b/src/slic3r/GUI/GUI_App.hpp
@@ -350,6 +350,11 @@ public:
     int             OnExit() override;
     bool            initialized() const { return m_initialized; }
     inline bool     is_enable_multi_machine() { return this->app_config&& this->app_config->get("enable_multi_machine") == "true"; }
+#ifdef SLIC3R_CAD
+    inline bool     is_enable_cad_feature() { return this->app_config && this->app_config->get_bool("enable_cad_feature"); }
+    inline bool     is_auto_close_sketch_loops() { return !this->app_config
+        || this->app_config->get_bool("auto_close_sketch_loops"); }
+#endif
 
     std::map<std::string, bool> test_url_state;
 
diff --git a/src/slic3r/GUI/Gizmos/GLGizmoPrimitive.cpp b/src/slic3r/GUI/Gizmos/GLGizmoPrimitive.cpp
new file mode 100644
index 0000000000..4e1a197a39
--- /dev/null
+++ b/src/slic3r/GUI/Gizmos/GLGizmoPrimitive.cpp
@@ -0,0 +1,186 @@
+#include "GLGizmoPrimitive.hpp"
+#include "slic3r/GUI/GLCanvas3D.hpp"
+#include "slic3r/GUI/ImGuiWrapper.hpp"
+#include "slic3r/GUI/GUI.hpp"
+#include "slic3r/GUI/Plater.hpp"
+#include "slic3r/GUI/GUI_ObjectList.hpp"
+#include "slic3r/GUI/NotificationManager.hpp"
+#include "libslic3r/Model.hpp"
+
+#ifndef IMGUI_DEFINE_MATH_OPERATORS
+#define IMGUI_DEFINE_MATH_OPERATORS
+#endif
+#include <imgui/imgui_internal.h>
+
+namespace Slic3r {
+namespace GUI {
+
+GLGizmoPrimitive::GLGizmoPrimitive(GLCanvas3D& parent, const std::string& icon_filename, unsigned int sprite_id)
+    : GLGizmoBase(parent, icon_filename, sprite_id) {}
+
+bool GLGizmoPrimitive::on_init() { return true; }
+std::string GLGizmoPrimitive::on_get_name() const { return _u8L("Primitive"); }
+bool GLGizmoPrimitive::on_is_activable() const { return true; }
+void GLGizmoPrimitive::on_render() {}
+void GLGizmoPrimitive::on_set_state()
+{ if (m_state == EState::On) { m_params = PrimitiveParams{}; m_preview_dirty = true; } }
+
+bool GLGizmoPrimitive::on_mouse(const wxMouseEvent&) { return false; }
+
+CommonGizmosDataID GLGizmoPrimitive::on_get_requirements() const
+{ return CommonGizmosDataID(int(CommonGizmosDataID::SelectionInfo) | int(CommonGizmosDataID::InstancesHider)); }
+
+void GLGizmoPrimitive::on_load(cereal::BinaryInputArchive& ar)
+{ ar(m_params); m_preview_dirty = true; }
+void GLGizmoPrimitive::on_save(cereal::BinaryOutputArchive& ar) const
+{ ar(m_params); }
+
+void GLGizmoPrimitive::apply_preset(const char*, double w, double h, double d)
+{
+    m_params.type = PrimitiveType::Box;
+    m_params.box_w = w; m_params.box_h = h; m_params.box_d = d;
+    m_preview_dirty = true;
+}
+
+static void gen_mesh_and_add(PrimitiveParams& p, const char* snap_name)
+{
+    TopoDS_Solid solid = GeometryEngine::make_primitive(p);
+    TopoDS_Shape shape = solid;
+    if (p.dressup_enabled) {
+        if (p.dressup_type == DressUpType::Fillet)
+            shape = GeometryEngine::apply_fillet(shape, p.dressup_radius, p.dressup_faces);
+        else
+            shape = GeometryEngine::apply_chamfer(shape, p.dressup_chamfer_dist, p.dressup_faces);
+    }
+    TriangleMesh mesh = GeometryEngine::tessellate(shape, p.linear_deflection, p.angular_deflection);
+    if (mesh.its.indices.empty()) {
+        wxGetApp().notification_manager()->push_notification(NotificationType::CustomNotification, NotificationManager::NotificationLevel::WarningNotificationLevel, _u8L("Empty mesh generated"));
+        return;
+    }
+    wxGetApp().plater()->take_snapshot(snap_name);
+    ModelObject* mo = wxGetApp().model().add_object();
+    std::string name = GeometryEngine::primitive_name(p.type);
+    if (p.dressup_enabled && p.dressup_type == DressUpType::Fillet) name += " (Fillet)";
+    else if (p.dressup_enabled) name += " (Chamfer)";
+    mo->name = name;
+    mo->add_volume(std::move(mesh))->set_new_unique_id();
+    mo->ensure_on_bed();
+    wxGetApp().plater()->update();
+}
+
+void GLGizmoPrimitive::apply_primitive() { gen_mesh_and_add(m_params, "Add Primitive"); }
+
+void GLGizmoPrimitive::on_render_input_window(float x, float y, float bottom_limit)
+{
+    y = std::min(y, bottom_limit - ImGui::GetWindowHeight());
+    const float scale = m_parent.get_scale();
+    ImGuiWrapper::push_toolbar_style(scale);
+    GizmoImguiSetNextWIndowPos(x, y, ImGuiCond_Always, 0.0f, 0.0f);
+    GizmoImguiBegin("Primitive", ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoMove
+                                  | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoCollapse
+                                  | ImGuiWindowFlags_NoTitleBar);
+
+    if (ImGui::CollapsingHeader("Shape", ImGuiTreeNodeFlags_DefaultOpen)) {
+        static const char* names[] = {"Box", "Cylinder", "Sphere", "Cone", "Torus"};
+        int cur = (int)m_params.type;
+        if (ImGui::Combo("##type", &cur, names, (int)PrimitiveType::COUNT)) {
+            m_params.type = (PrimitiveType)cur;
+            m_preview_dirty = true;
+        }
+        ImGui::Text("Quick:");
+        ImGui::SameLine();
+        if (ImGui::SmallButton("10mm")) apply_preset("10mm cube", 10, 10, 10);
+        ImGui::SameLine();
+        if (ImGui::SmallButton("20mm")) apply_preset("20mm cube", 20, 20, 20);
+        ImGui::SameLine();
+        if (ImGui::SmallButton("50mm")) apply_preset("50mm cube", 50, 50, 50);
+    }
+
+    ImGui::Separator();
+
+    if (ImGui::CollapsingHeader("Dimensions", ImGuiTreeNodeFlags_DefaultOpen)) {
+        auto dim = [&](const char* label, double& val, double step=0.5, double fast=5.0) {
+            ImGui::SetNextItemWidth(130);
+            if (ImGui::InputDouble(label, &val, step, fast, "%.1f mm")) m_preview_dirty = true;
+            if (val < 0.5) val = 0.5;
+        };
+        switch (m_params.type) {
+        case PrimitiveType::Box:
+            dim("Width (X)",  m_params.box_w);
+            dim("Depth (Y)",  m_params.box_d);
+            dim("Height (Z)", m_params.box_h);
+            break;
+        case PrimitiveType::Cylinder:
+            dim("Radius", m_params.cyl_radius);
+            dim("Height", m_params.cyl_height);
+            break;
+        case PrimitiveType::Sphere:
+            dim("Radius", m_params.sph_radius);
+            break;
+        case PrimitiveType::Cone:
+            dim("Bottom R", m_params.cone_r1);
+            dim("Top R",    m_params.cone_r2);
+            dim("Height",   m_params.cone_height);
+            break;
+        case PrimitiveType::Torus:
+            dim("Major R", m_params.torus_r1);
+            dim("Minor R", m_params.torus_r2, 0.1, 1.0);
+            break;
+        default: break;
+        }
+    }
+
+    ImGui::Separator();
+
+    if (ImGui::CollapsingHeader("Fillet / Chamfer")) {
+        ImGui::Checkbox("Enable", &m_params.dressup_enabled);
+        if (m_params.dressup_enabled) {
+            static const char* dn[] = {"Fillet", "Chamfer"};
+            int du = (int)m_params.dressup_type;
+            ImGui::SetNextItemWidth(100);
+            if (ImGui::Combo("##dtype", &du, dn, 2)) { m_params.dressup_type = (DressUpType)du; m_preview_dirty = true; }
+            static const char* fn[] = {"All edges", "Top edges", "Bottom edges", "Lateral edges"};
+            int fg = (int)m_params.dressup_faces;
+            ImGui::SetNextItemWidth(140);
+            if (ImGui::Combo("Edges", &fg, fn, 4)) { m_params.dressup_faces = (FaceGroup)fg; m_preview_dirty = true; }
+            if (m_params.dressup_type == DressUpType::Fillet) {
+                ImGui::SetNextItemWidth(100);
+                if (ImGui::InputDouble("Radius", &m_params.dressup_radius, 0.1, 1.0, "%.1f mm")) {
+                    if (m_params.dressup_radius < 0.1) m_params.dressup_radius = 0.1;
+                    m_preview_dirty = true;
+                }
+            } else {
+                ImGui::SetNextItemWidth(100);
+                if (ImGui::InputDouble("Distance", &m_params.dressup_chamfer_dist, 0.1, 1.0, "%.1f mm")) {
+                    if (m_params.dressup_chamfer_dist < 0.1) m_params.dressup_chamfer_dist = 0.1;
+                    m_preview_dirty = true;
+                }
+            }
+        }
+    }
+
+    ImGui::Separator();
+
+    if (ImGui::CollapsingHeader("Quality")) {
+        ImGui::SetNextItemWidth(130);
+        if (ImGui::InputDouble("Mesh resolution", &m_params.linear_deflection, 0.001, 0.1, "%.3f mm")) {
+            if (m_params.linear_deflection < 0.001) m_params.linear_deflection = 0.001;
+            if (m_params.linear_deflection > 1.0)   m_params.linear_deflection = 1.0;
+            m_preview_dirty = true;
+        }
+    }
+
+    ImGui::Separator();
+
+    if (ImGui::Button("Add Shape", {-1, 28}))
+        apply_primitive();
+
+    if (ImGui::Button("Close", {-1, 0}))
+        m_parent.reset_all_gizmos();
+
+    GizmoImguiEnd();
+    ImGuiWrapper::pop_toolbar_style();
+}
+
+} // namespace GUI
+} // namespace Slic3r
diff --git a/src/slic3r/GUI/Gizmos/GLGizmoPrimitive.hpp b/src/slic3r/GUI/Gizmos/GLGizmoPrimitive.hpp
new file mode 100644
index 0000000000..f78289a58d
--- /dev/null
+++ b/src/slic3r/GUI/Gizmos/GLGizmoPrimitive.hpp
@@ -0,0 +1,43 @@
+#ifndef slic3r_GLGizmoPrimitive_hpp_
+#define slic3r_GLGizmoPrimitive_hpp_
+
+#include "GLGizmoBase.hpp"
+#include "GLGizmosCommon.hpp"
+#include "libslic3r/CAD/GeometryEngine.hpp"
+
+namespace Slic3r {
+namespace GUI {
+
+class GLGizmoPrimitive : public GLGizmoBase
+{
+public:
+    GLGizmoPrimitive(GLCanvas3D& parent, const std::string& icon_filename, unsigned int sprite_id);
+    ~GLGizmoPrimitive() = default;
+
+    bool on_mouse(const wxMouseEvent& mouse_event) override;
+
+protected:
+    bool on_init() override;
+    std::string on_get_name() const override;
+    bool on_is_activable() const override;
+    void on_render() override;
+    void on_set_state() override;
+    CommonGizmosDataID on_get_requirements() const override;
+    void on_render_input_window(float x, float y, float bottom_limit) override;
+
+    void on_load(cereal::BinaryInputArchive& ar) override;
+    void on_save(cereal::BinaryOutputArchive& ar) const override;
+
+private:
+    void apply_primitive();
+    void apply_preset(const char* name, double w, double h, double d);
+
+    PrimitiveParams m_params;
+    TriangleMesh    m_preview_mesh;
+    bool            m_preview_dirty{true};
+};
+
+} // namespace GUI
+} // namespace Slic3r
+
+#endif // slic3r_GLGizmoPrimitive_hpp_
diff --git a/src/slic3r/GUI/Gizmos/GLGizmoSketch.cpp b/src/slic3r/GUI/Gizmos/GLGizmoSketch.cpp
new file mode 100644
index 0000000000..88bd636563
--- /dev/null
+++ b/src/slic3r/GUI/Gizmos/GLGizmoSketch.cpp
@@ -0,0 +1,459 @@
+#include "GLGizmoSketch.hpp"
+#include "slic3r/GUI/GLCanvas3D.hpp"
+#include "slic3r/GUI/ImGuiWrapper.hpp"
+#include "slic3r/GUI/GUI.hpp"
+#include "slic3r/GUI/Plater.hpp"
+#include "slic3r/GUI/GUI_ObjectList.hpp"
+#include "slic3r/GUI/NotificationManager.hpp"
+#include "libslic3r/Model.hpp"
+#include <BRepBuilderAPI_MakeFace.hxx>
+#include <BRepPrimAPI_MakeRevol.hxx>
+#include <BRepAlgoAPI_Fuse.hxx>
+
+#ifndef IMGUI_DEFINE_MATH_OPERATORS
+#define IMGUI_DEFINE_MATH_OPERATORS
+#endif
+#include <imgui/imgui_internal.h>
+
+#define L(s) Slic3r::GUI::I18N::translate((s)).c_str()
+#define UL(s) Slic3r::GUI::I18N::translate_utf8((s)).c_str()
+
+namespace Slic3r {
+namespace GUI {
+
+GLGizmoSketch::GLGizmoSketch(GLCanvas3D& parent, const std::string& icon_filename, unsigned int sprite_id)
+    : GLGizmoBase(parent, icon_filename, sprite_id) {}
+
+bool GLGizmoSketch::on_init() { return true; }
+std::string GLGizmoSketch::on_get_name() const { return _u8L("Sketch"); }
+bool GLGizmoSketch::on_is_activable() const { return true; }
+void GLGizmoSketch::on_render() {}
+void GLGizmoSketch::on_set_state() { if (m_state == EState::On) clear_all(); }
+bool GLGizmoSketch::on_mouse(const wxMouseEvent&) { return false; }
+
+CommonGizmosDataID GLGizmoSketch::on_get_requirements() const
+{ return CommonGizmosDataID(int(CommonGizmosDataID::SelectionInfo)); }
+
+void GLGizmoSketch::on_load(cereal::BinaryInputArchive& ar)
+{
+    ar(m_tool, m_profiles, m_plane, m_sp, m_rect_w, m_rect_h, m_circle_r, m_poly_sides, m_poly_r, m_snap_grid, m_grid_step);
+    m_active_profile = -1;
+}
+
+void GLGizmoSketch::on_save(cereal::BinaryOutputArchive& ar) const
+{
+    ar(m_tool, m_profiles, m_plane, m_sp, m_rect_w, m_rect_h, m_circle_r, m_poly_sides, m_poly_r, m_snap_grid, m_grid_step);
+}
+
+SketchProfile& GLGizmoSketch::active_profile()
+{
+    if (m_active_profile < 0 || m_active_profile >= (int)m_profiles.size()) {
+        m_profiles.emplace_back();
+        m_active_profile = (int)m_profiles.size() - 1;
+    }
+    return m_profiles[m_active_profile];
+}
+
+bool GLGizmoSketch::has_closed_profile() const
+{
+    for (auto& p : m_profiles) if (p.closed && p.points.size() >= 3) return true;
+    return false;
+}
+
+void GLGizmoSketch::clear_all()
+{
+    m_profiles.clear();
+    m_canvas_points.clear();
+    m_active_profile = -1;
+}
+
+void GLGizmoSketch::add_closed_profile()
+{
+    auto& ap = active_profile();
+    if (ap.points.size() >= 3) {
+        ap.closed = true;
+        m_active_profile = -1;
+    }
+}
+
+void GLGizmoSketch::delete_profile(int idx)
+{
+    if (idx >= 0 && idx < (int)m_profiles.size()) {
+        m_profiles.erase(m_profiles.begin() + idx);
+        if (m_active_profile >= (int)m_profiles.size()) m_active_profile = -1;
+    }
+}
+
+Vec2d GLGizmoSketch::snap(Vec2d pt) const
+{
+    if (!m_snap_grid) return pt;
+    double gs = m_grid_step;
+    return {round(pt.x() / gs) * gs, round(pt.y() / gs) * gs};
+}
+
+void GLGizmoSketch::build_preset_profile()
+{
+    auto& ap = active_profile();
+    ap.clear();
+    auto add = [&](double x, double y) { ap.points.emplace_back(x, y); };
+    switch (m_tool) {
+    case SketchTool::Rectangle:
+        add(-m_rect_w/2, -m_rect_h/2); add( m_rect_w/2, -m_rect_h/2);
+        add( m_rect_w/2,  m_rect_h/2); add(-m_rect_w/2,  m_rect_h/2);
+        ap.closed = true; m_active_profile = -1; break;
+    case SketchTool::Circle:
+        for (int i = 0; i <= m_circle_seg; ++i) {
+            double a = 2.0*M_PI*i/m_circle_seg;
+            add(cos(a)*m_circle_r, sin(a)*m_circle_r);
+        }
+        ap.closed = true; m_active_profile = -1; break;
+    case SketchTool::Polygon:
+        for (int i = 0; i < m_poly_sides; ++i) {
+            double a = 2.0*M_PI*i/m_poly_sides - M_PI/2;
+            add(cos(a)*m_poly_r, sin(a)*m_poly_r);
+        }
+        ap.closed = true; m_active_profile = -1; break;
+    default: break;
+    }
+}
+
+void GLGizmoSketch::handle_canvas_click(ImVec2 pos)
+{
+    Vec2d pt = snap({pos.x / m_canvas_scale, -pos.y / m_canvas_scale});
+    if (m_tool == SketchTool::Line) {
+        auto& ap = active_profile();
+        if (ap.points.size() >= 3 && (pt - ap.points.front()).norm() < m_grid_step) {
+            ap.points.push_back(ap.points.front());
+            ap.closed = true;
+            m_active_profile = -1;
+            return;
+        }
+        ap.points.push_back(pt);
+    }
+}
+
+void GLGizmoSketch::draw_canvas()
+{
+    ImDrawList* dl = ImGui::GetWindowDrawList();
+    ImVec2 pos = ImGui::GetCursorScreenPos();
+    float w = 280, h = 200;
+    ImVec2 end(pos.x+w, pos.y+h);
+    float cx = pos.x+w/2, cy = pos.y+h/2;
+    auto tc = [&](const ImVec2& p) { return ImVec2(cx+p.x*m_canvas_scale, cy-p.y*m_canvas_scale); };
+
+    dl->AddRectFilled(pos, end, IM_COL32(28,28,36,255));
+    dl->AddRect(pos, end, IM_COL32(55,55,68,255));
+
+    float gs = m_grid_step;
+    for (float g = 0; g < w; g += gs * m_canvas_scale) {
+        ImU32 gc = (int(g/(gs*m_canvas_scale)) % 5 == 0) ? IM_COL32(60,60,75,100) : IM_COL32(45,45,55,60);
+        dl->AddLine({pos.x+g,pos.y}, {pos.x+g,end.y}, gc);
+    }
+    for (float g = 0; g < h; g += gs * m_canvas_scale) {
+        ImU32 gc = (int(g/(gs*m_canvas_scale)) % 5 == 0) ? IM_COL32(60,60,75,100) : IM_COL32(45,45,55,60);
+        dl->AddLine({pos.x,pos.y+g}, {end.x,pos.y+g}, gc);
+    }
+
+    dl->AddLine({cx,pos.y},{cx,end.y}, IM_COL32(70,70,85,180), 1.5f);
+    dl->AddLine({pos.x,cy},{end.x,cy}, IM_COL32(70,70,85,180), 1.5f);
+    dl->AddText({end.x-12, cy+2}, IM_COL32(120,120,140,200), "X");
+    dl->AddText({cx+4, pos.y+2}, IM_COL32(120,120,140,200), "Y");
+
+    for (size_t pi = 0; pi < m_profiles.size(); ++pi) {
+        auto& prof = m_profiles[pi];
+        if (prof.points.size() < 2) continue;
+        std::vector<ImVec2> sp;
+        for (auto& p : prof.points) sp.push_back(tc({(float)p.x(), (float)p.y()}));
+        if (prof.closed && sp.size() >= 3) {
+            bool is_outer = (pi == 0);
+            ImU32 fill = is_outer ? IM_COL32(0,180,90,35) : IM_COL32(180,60,60,35);
+            ImU32 line = is_outer ? IM_COL32(0,220,100,255) : IM_COL32(220,80,80,255);
+            dl->AddConvexPolyFilled(sp.data(), (int)sp.size(), fill);
+            for (size_t i=0; i<sp.size(); ++i)
+                dl->AddLine(sp[i], sp[(i+1)%sp.size()], line, (pi==0)?2.5f:2.0f);
+            for (size_t i=0; i<sp.size()-1; ++i)
+                dl->AddCircleFilled(sp[i], 3.0f, IM_COL32(255,255,255,255));
+        }
+    }
+
+    auto& ap = active_profile();
+    if (!ap.closed && ap.points.size() >= 1) {
+        std::vector<ImVec2> sp;
+        for (auto& p : ap.points) sp.push_back(tc({(float)p.x(), (float)p.y()}));
+        for (size_t i=1; i<sp.size(); ++i)
+            dl->AddLine(sp[i-1], sp[i], IM_COL32(0,200,255,200), 2.0f);
+        for (auto& s : sp) dl->AddCircleFilled(s, 3.5f, IM_COL32(100,200,255,255));
+        ImVec2 mouse = ImGui::GetMousePos();
+        if (mouse.x > pos.x && mouse.x < end.x && mouse.y > pos.y && mouse.y < end.y)
+            dl->AddLine(sp.back(), mouse, IM_COL32(100,160,220,120), 1.5f);
+    }
+
+    ImGui::InvisibleButton("canvas", ImVec2(w,h));
+    if (ImGui::IsItemHovered()) {
+        ImVec2 m = ImGui::GetMousePos();
+        Vec2d sk({(m.x-cx)/m_canvas_scale, -(m.y-cy)/m_canvas_scale});
+        if (m_snap_grid) sk = snap(sk);
+        auto txt = wxString::Format("X:%.1f Y:%.1f", sk.x(), sk.y()).ToStdString();
+        dl->AddText({pos.x+4, end.y-16}, IM_COL32(160,160,180,200), txt.c_str());
+        if (ImGui::IsMouseClicked(ImGuiMouseButton_Left))
+            handle_canvas_click({(m.x-cx)/m_canvas_scale, -(m.y-cy)/m_canvas_scale});
+        if (ImGui::IsMouseClicked(ImGuiMouseButton_Right)) {
+            auto& ap2 = active_profile();
+            if (ap2.points.size() >= 3) {
+                ap2.points.push_back(ap2.points.front());
+                ap2.closed = true;
+                m_active_profile = -1;
+            }
+        }
+    }
+}
+
+TopoDS_Shape GLGizmoSketch::build_combined_shape()
+{
+    if (m_profiles.empty() || !m_profiles[0].closed)
+        throw std::runtime_error("No outer profile");
+
+    TopoDS_Wire outer_wire = m_profiles[0].to_occt_wire(m_plane);
+    BRepBuilderAPI_MakeFace face_maker(outer_wire);
+    if (!face_maker.IsDone()) throw std::runtime_error("Failed to make outer face");
+
+    for (size_t i = 1; i < m_profiles.size(); ++i) {
+        if (!m_profiles[i].closed) continue;
+        TopoDS_Wire inner = m_profiles[i].to_occt_wire(m_plane);
+        face_maker.Add(inner);
+    }
+    face_maker.Build();
+    if (!face_maker.IsDone()) throw std::runtime_error("Failed to build face with holes");
+
+    TopoDS_Face face = face_maker.Face();
+
+    TopoDS_Shape shape;
+    if (m_sp.revolve_deg < 360.0 && m_sp.revolve_deg > 0.0) {
+        gp_Pnt o(m_plane.origin.x(), m_plane.origin.y(), m_plane.origin.z());
+        gp_Dir xd(m_plane.x_axis.x(), m_plane.x_axis.y(), m_plane.x_axis.z());
+        gp_Ax1 axis(o, xd);
+        BRepPrimAPI_MakeRevol rev(face, axis, m_sp.revolve_deg * M_PI / 180.0);
+        if (!rev.IsDone()) throw std::runtime_error("Revolve failed");
+        shape = rev.Shape();
+    } else {
+        shape = SketchEngine::make_extrude_face(face, m_plane, m_sp.extrude_len, m_sp.extrude_sym);
+    }
+
+    if (m_sp.dressup_enabled) {
+        if (m_sp.dressup_type == DressUpType::Fillet)
+            shape = GeometryEngine::apply_fillet(shape, m_sp.dressup_radius, m_sp.dressup_faces);
+        else
+            shape = GeometryEngine::apply_chamfer(shape, m_sp.dressup_chamfer_dist, m_sp.dressup_faces);
+    }
+    return shape;
+}
+
+void GLGizmoSketch::on_render_input_window(float x, float y, float bottom_limit)
+{
+    y = std::min(y, bottom_limit - ImGui::GetWindowHeight());
+    const float scale = m_parent.get_scale();
+    ImGuiWrapper::push_toolbar_style(scale);
+    GizmoImguiSetNextWIndowPos(x, y, ImGuiCond_Always, 0.0f, 0.0f);
+    GizmoImguiBegin("Sketch", ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoMove
+                               | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoCollapse
+                               | ImGuiWindowFlags_NoTitleBar);
+
+    if (ImGui::CollapsingHeader(UL("Profile"), ImGuiTreeNodeFlags_DefaultOpen)) {
+        static const char* names[] = {"Line", "Rectangle", "Circle", "Polygon"};
+        int cur = (int)m_tool;
+        if (ImGui::Combo("##shape", &cur, names, (int)SketchTool::COUNT)) {
+            m_tool = (SketchTool)cur;
+            if (m_tool != SketchTool::Line) build_preset_profile();
+        }
+        ImGui::SameLine();
+        if (m_imgui->button("+##newprofile")) m_active_profile = -1;
+        if (ImGui::IsItemHovered()) ImGui::SetTooltip("%s", UL("Start new profile (for holes)"));
+
+        if (m_tool == SketchTool::Rectangle) {
+            ImGui::SetNextItemWidth(80); if (ImGui::InputDouble("W", &m_rect_w,1,10,"%.0f")) build_preset_profile();
+            ImGui::SameLine();
+            ImGui::SetNextItemWidth(80); if (ImGui::InputDouble("H", &m_rect_h,1,10,"%.0f")) build_preset_profile();
+        } else if (m_tool == SketchTool::Circle) {
+            ImGui::SetNextItemWidth(80); if (ImGui::InputDouble("R", &m_circle_r,1,5,"%.0f")) build_preset_profile();
+            ImGui::SameLine();
+            ImGui::SetNextItemWidth(80); if (ImGui::SliderInt("Seg", &m_circle_seg,8,64)) build_preset_profile();
+        } else if (m_tool == SketchTool::Polygon) {
+            ImGui::SetNextItemWidth(80); if (ImGui::SliderInt("Sides", &m_poly_sides,3,12)) build_preset_profile();
+            ImGui::SameLine();
+            ImGui::SetNextItemWidth(80); if (ImGui::InputDouble("R", &m_poly_r,1,5,"%.0f")) build_preset_profile();
+        } else {
+            ImGui::Text("%s", UL("Click on canvas to draw"));
+        }
+
+        ImGui::Checkbox(UL("Snap to grid"), &m_snap_grid);
+        ImGui::SameLine();
+        ImGui::SetNextItemWidth(80); ImGui::InputFloat("Step", &m_grid_step, 1, 5, "%.0f mm");
+
+        draw_canvas();
+
+        if (!m_profiles.empty()) {
+            ImGui::Text("%s: %zu", UL("Profiles"), m_profiles.size());
+            for (int i = 0; i < (int)m_profiles.size(); ++i) {
+                auto& p = m_profiles[i];
+                ImGui::PushID(i);
+                bool outer = (i == 0);
+                ImVec4 col = outer ? ImVec4(0,1,0,1) : ImVec4(1,0.3f,0.3f,1);
+                const char* label = outer ? "Outer" : "Hole";
+                ImGui::TextColored(col, "%s %d: %zu pts %s", label, i+1, p.points.size(), p.closed ? "CLOSED" : "");
+                ImGui::SameLine();
+                if (ImGui::SmallButton("X")) delete_profile(i);
+                ImGui::PopID();
+            }
+        }
+    }
+
+    ImGui::Separator();
+
+    bool is_revolve = false;
+    bool has_sel = false;
+
+    if (ImGui::CollapsingHeader(UL("Operation"), ImGuiTreeNodeFlags_DefaultOpen)) {
+        static int pi = 0;
+        if (ImGui::Combo(UL("Plane"), &pi, "XY (Top)\0XZ (Front)\0YZ (Side)\0"))
+            m_plane = (pi==0) ? SketchPlane::XY() : (pi==1) ? SketchPlane::XZ() : SketchPlane::YZ();
+
+        is_revolve = (m_sp.revolve_deg > 0 && m_sp.revolve_deg < 360);
+        ImGui::SetNextItemWidth(100);
+        if (ImGui::InputDouble(UL("Revolve deg"), &m_sp.revolve_deg, 15, 90, "%.0f")) {
+            if (m_sp.revolve_deg > 360) m_sp.revolve_deg = 360;
+            if (m_sp.revolve_deg < 0) m_sp.revolve_deg = 0;
+        }
+        if (ImGui::IsItemHovered()) ImGui::SetTooltip("%s", UL("Set to 0 for extrude, >0 for revolve"));
+
+        if (!is_revolve) {
+            ImGui::SetNextItemWidth(100);
+            ImGui::InputDouble(UL("Length"), &m_sp.extrude_len, 0.5, 5, "%.1f mm");
+            ImGui::SameLine();
+            ImGui::Checkbox(UL("Symmetric"), &m_sp.extrude_sym);
+        }
+
+        has_sel = !m_parent.get_selection().is_empty();
+        if (has_sel) {
+            if (ImGui::Checkbox(UL("Pocket (cut)"), &m_sp.is_pocket))
+                if (m_sp.is_pocket) m_sp.dressup_enabled = false;
+        } else m_sp.is_pocket = false;
+    }
+
+    ImGui::Separator();
+
+    if (!m_sp.is_pocket && ImGui::CollapsingHeader(UL("Fillet / Chamfer"))) {
+        ImGui::Checkbox(UL("Enable"), &m_sp.dressup_enabled);
+        if (m_sp.dressup_enabled) {
+            static const char* dn[] = {"Fillet", "Chamfer"};
+            int du = (int)m_sp.dressup_type;
+            ImGui::SetNextItemWidth(100);
+            if (ImGui::Combo("##dtype", &du, dn, 2)) m_sp.dressup_type = (DressUpType)du;
+            static const char* fn[] = {"All edges", "Top edges", "Bottom edges", "Lateral edges"};
+            int fg = (int)m_sp.dressup_faces;
+            ImGui::SetNextItemWidth(140);
+            ImGui::Combo(UL("Edges"), &fg, fn, 4); m_sp.dressup_faces = (FaceGroup)fg;
+            ImGui::SetNextItemWidth(100);
+            if (m_sp.dressup_type == DressUpType::Fillet)
+                ImGui::InputDouble(UL("Radius"), &m_sp.dressup_radius, 0.1, 1, "%.1f mm");
+            else
+                ImGui::InputDouble(UL("Distance"), &m_sp.dressup_chamfer_dist, 0.1, 1, "%.1f mm");
+        }
+    }
+
+    ImGui::Separator();
+
+    bool ok = has_closed_profile();
+    if (ok) ImGui::TextColored({0,1,0,1}, "%zu %s", m_profiles.size(), UL("closed profile(s)"));
+    else ImGui::TextColored({0.6f,0.6f,0.6f,1}, "%s", UL("Draw a closed profile to enable"));
+
+    auto btn = [&](const char* label, bool enabled) {
+        if (!enabled) { ImGui::PushItemFlag(ImGuiItemFlags_Disabled,true); ImGui::PushStyleColor(ImGuiCol_Button,{0.25f,0.25f,0.25f,1}); }
+        bool clicked = ImGui::Button(label, {-1,0});
+        if (!enabled) { ImGui::PopStyleColor(); ImGui::PopItemFlag(); }
+        return clicked && enabled;
+    };
+
+    if (m_sp.is_pocket && has_sel) {
+        if (btn(L("Pocket (Cut)"), ok)) apply_pocket();
+    } else if (is_revolve) {
+        if (btn(L("Revolve"), ok)) apply_revolve();
+    } else {
+        if (btn(L("Extrude"), ok)) apply_extrude();
+    }
+
+    if (ImGui::Button(L("Clear All"), {-1,0})) clear_all();
+    if (ImGui::Button(L("Close"), {-1,0})) m_parent.reset_all_gizmos();
+
+    GizmoImguiEnd();
+    ImGuiWrapper::pop_toolbar_style();
+}
+
+void GLGizmoSketch::apply_extrude()
+{
+    try {
+        TopoDS_Shape shape = build_combined_shape();
+        TriangleMesh mesh = SketchEngine::tessellate(shape, m_sp.linear_deflection);
+        if (mesh.its.indices.empty()) throw std::runtime_error("Empty result");
+        wxGetApp().plater()->take_snapshot("Sketch Extrude");
+        ModelObject* mo = wxGetApp().model().add_object();
+        mo->name = "Extrusion";
+        mo->add_volume(std::move(mesh))->set_new_unique_id();
+        mo->ensure_on_bed();
+        wxGetApp().plater()->update();
+        clear_all();
+    } catch (const std::exception& e) {
+        wxGetApp().notification_manager()->push_notification(NotificationType::CustomNotification, NotificationManager::NotificationLevel::ErrorNotificationLevel, std::string("Extrude: ")+e.what());
+    }
+}
+
+void GLGizmoSketch::apply_revolve()
+{
+    try {
+        TopoDS_Shape shape = build_combined_shape();
+        TriangleMesh mesh = SketchEngine::tessellate(shape, m_sp.linear_deflection);
+        if (mesh.its.indices.empty()) throw std::runtime_error("Empty result");
+        wxGetApp().plater()->take_snapshot("Sketch Revolve");
+        ModelObject* mo = wxGetApp().model().add_object();
+        mo->name = "Revolve";
+        mo->add_volume(std::move(mesh))->set_new_unique_id();
+        mo->ensure_on_bed();
+        wxGetApp().plater()->update();
+        clear_all();
+    } catch (const std::exception& e) {
+        wxGetApp().notification_manager()->push_notification(NotificationType::CustomNotification, NotificationManager::NotificationLevel::ErrorNotificationLevel, std::string("Revolve: ")+e.what());
+    }
+}
+
+void GLGizmoSketch::apply_pocket()
+{
+    try {
+        Selection& sel = m_parent.get_selection();
+        int obj_idx = sel.get_object_idx();
+        if (obj_idx < 0) throw std::runtime_error("No object selected");
+        ModelObject* mo = wxGetApp().model().objects[obj_idx];
+
+        TopoDS_Wire outer = m_profiles[0].to_occt_wire(m_plane);
+        BRepBuilderAPI_MakeFace fm(outer);
+        if (!fm.IsDone()) throw std::runtime_error("Face failed");
+        for (size_t i = 1; i < m_profiles.size(); ++i)
+            if (m_profiles[i].closed) fm.Add(m_profiles[i].to_occt_wire(m_plane));
+        fm.Build();
+        if (!fm.IsDone()) throw std::runtime_error("Face with holes failed");
+
+        TopoDS_Shape tool = SketchEngine::make_extrude_face(fm.Face(), m_plane, m_sp.extrude_len + 5.0, false);
+        TriangleMesh tool_mesh = SketchEngine::tessellate(tool, m_sp.linear_deflection);
+        if (tool_mesh.its.indices.empty()) throw std::runtime_error("Tool mesh empty");
+
+        wxGetApp().plater()->take_snapshot("Sketch Pocket");
+        mo->add_volume(std::move(tool_mesh), ModelVolumeType::NEGATIVE_VOLUME)->set_new_unique_id();
+        mo->ensure_on_bed();
+        wxGetApp().plater()->update();
+        clear_all();
+        wxGetApp().notification_manager()->push_notification(NotificationType::CustomNotification, NotificationManager::NotificationLevel::RegularNotificationLevel, UL("Pocket added (negative volume)"));
+    } catch (const std::exception& e) {
+        wxGetApp().notification_manager()->push_notification(NotificationType::CustomNotification, NotificationManager::NotificationLevel::ErrorNotificationLevel, std::string("Pocket: ")+e.what());
+    }
+}
+
+} // namespace GUI
+} // namespace Slic3r
diff --git a/src/slic3r/GUI/Gizmos/GLGizmoSketch.hpp b/src/slic3r/GUI/Gizmos/GLGizmoSketch.hpp
new file mode 100644
index 0000000000..5a4b59edfd
--- /dev/null
+++ b/src/slic3r/GUI/Gizmos/GLGizmoSketch.hpp
@@ -0,0 +1,74 @@
+#ifndef slic3r_GLGizmoSketch_hpp_
+#define slic3r_GLGizmoSketch_hpp_
+
+#include "GLGizmoBase.hpp"
+#include "GLGizmosCommon.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
+#include <imgui/imgui.h>
+
+namespace Slic3r {
+namespace GUI {
+
+enum class SketchTool { Line, Rectangle, Circle, Polygon, COUNT };
+
+class GLGizmoSketch : public GLGizmoBase
+{
+public:
+    GLGizmoSketch(GLCanvas3D& parent, const std::string& icon_filename, unsigned int sprite_id);
+
+    bool on_mouse(const wxMouseEvent& mouse_event) override;
+
+protected:
+    bool on_init() override;
+    std::string on_get_name() const override;
+    bool on_is_activable() const override;
+    void on_render() override;
+    void on_set_state() override;
+    CommonGizmosDataID on_get_requirements() const override;
+    void on_render_input_window(float x, float y, float bottom_limit) override;
+
+    void on_load(cereal::BinaryInputArchive& ar) override;
+    void on_save(cereal::BinaryOutputArchive& ar) const override;
+
+private:
+    SketchTool    m_tool{SketchTool::Line};
+    std::vector<SketchProfile> m_profiles;  // multiple profiles (outer + holes)
+    SketchPlane   m_plane{SketchPlane::XY()};
+    SketchParams  m_sp;
+
+    // Shape presets
+    double m_rect_w{20}, m_rect_h{15};
+    double m_circle_r{10}; int m_circle_seg{32};
+    int    m_poly_sides{6}; double m_poly_r{10};
+
+    // Canvas
+    std::vector<ImVec2> m_canvas_points;
+    Vec2d               m_canvas_center{0,0};
+    float               m_canvas_scale{5.0f};
+    bool                m_snap_grid{true};
+    float               m_grid_step{5.0f};
+
+    // Current profile being drawn
+    int m_active_profile{-1};
+
+    SketchProfile& active_profile();
+    bool has_closed_profile() const;
+
+    void build_preset_profile();
+    void add_closed_profile();
+    void delete_profile(int idx);
+    void clear_all();
+
+    TopoDS_Shape build_combined_shape(); // all profiles as face with holes
+    void apply_extrude();
+    void apply_revolve();
+    void apply_pocket();
+    void draw_canvas();
+    void handle_canvas_click(ImVec2 pos);
+    Vec2d snap(Vec2d pt) const;
+};
+
+} // namespace GUI
+} // namespace Slic3r
+
+#endif // slic3r_GLGizmoSketch_hpp_
diff --git a/src/slic3r/GUI/Gizmos/GLGizmosManager.cpp b/src/slic3r/GUI/Gizmos/GLGizmosManager.cpp
index 9cff834346..be586ec55a 100644
--- a/src/slic3r/GUI/Gizmos/GLGizmosManager.cpp
+++ b/src/slic3r/GUI/Gizmos/GLGizmosManager.cpp
@@ -27,6 +27,10 @@
 #include "slic3r/GUI/Gizmos/GLGizmoSVG.hpp"
 #include "slic3r/GUI/Gizmos/GLGizmoMeshBoolean.hpp"
 #include "slic3r/GUI/Gizmos/GLGizmoAssembly.hpp"
+#ifdef SLIC3R_CAD
+#include "slic3r/GUI/Gizmos/GLGizmoPrimitive.hpp"
+#include "slic3r/GUI/Gizmos/GLGizmoSketch.hpp"
+#endif
 
 #include "libslic3r/format.hpp"
 #include "libslic3r/Model.hpp"
@@ -176,6 +180,14 @@ void GLGizmosManager::switch_gizmos_icon_filename()
         case (EType::BrimEars):
             gizmo->set_icon_filename(m_is_dark ? "toolbar_brimears_dark.svg" : "toolbar_brimears.svg");
             break;
+#ifdef SLIC3R_CAD
+        case (EType::Primitive):
+            gizmo->set_icon_filename(m_is_dark ? "toolbar_modifier_cube_dark.svg" : "toolbar_modifier_cube.svg");
+            break;
+        case (EType::Sketch):
+            gizmo->set_icon_filename(m_is_dark ? "toolbar_sketch_dark.svg" : "toolbar_sketch.svg");
+            break;
+#endif
         }
 
     }
@@ -219,6 +231,12 @@ bool GLGizmosManager::init()
     m_gizmos.emplace_back(new GLGizmoAssembly(m_parent, m_is_dark ? "toolbar_assembly_dark.svg" : "toolbar_assembly.svg", EType::Assembly));
     m_gizmos.emplace_back(new GLGizmoSimplify(m_parent, "reduce_triangles.svg", EType::Simplify));
     m_gizmos.emplace_back(new GLGizmoBrimEars(m_parent, m_is_dark ? "toolbar_brimears_dark.svg" : "toolbar_brimears.svg", EType::BrimEars));
+#ifdef SLIC3R_CAD
+    // Registered last: Primitive and Sketch are the final entries before Undefined, so
+    // omitting them leaves every preceding m_gizmos index (indexed by EType) untouched.
+    m_gizmos.emplace_back(new GLGizmoPrimitive(m_parent, m_is_dark ? "toolbar_modifier_cube_dark.svg" : "toolbar_modifier_cube.svg", static_cast<unsigned int>(Primitive)));
+    m_gizmos.emplace_back(new GLGizmoSketch(m_parent, m_is_dark ? "toolbar_sketch_dark.svg" : "toolbar_sketch.svg", static_cast<unsigned int>(Sketch)));
+#endif
     //m_gizmos.emplace_back(new GLGizmoSlaSupports(m_parent, "sla_supports.svg", sprite_id++));
     //m_gizmos.emplace_back(new GLGizmoFaceDetector(m_parent, "face recognition.svg", sprite_id++));
     //m_gizmos.emplace_back(new GLGizmoHollow(m_parent, "hollow.svg", sprite_id++));
diff --git a/src/slic3r/GUI/Gizmos/GLGizmosManager.hpp b/src/slic3r/GUI/Gizmos/GLGizmosManager.hpp
index 157eb43dc7..d490a6c05f 100644
--- a/src/slic3r/GUI/Gizmos/GLGizmosManager.hpp
+++ b/src/slic3r/GUI/Gizmos/GLGizmosManager.hpp
@@ -90,6 +90,12 @@ public:
         Assembly,
         Simplify,
         BrimEars,
+#ifdef SLIC3R_CAD
+        // Both need the CAD kernel (GeometryEngine); keep them last so that with
+        // SLIC3R_CAD off the enum matches upstream's numbering exactly.
+        Primitive,
+        Sketch,
+#endif
         //SlaSupports,
         // BBS
         //FaceRecognition,
diff --git a/src/slic3r/GUI/ImGuiWrapper.cpp b/src/slic3r/GUI/ImGuiWrapper.cpp
index eeaadd0cbd..cf107565e3 100644
--- a/src/slic3r/GUI/ImGuiWrapper.cpp
+++ b/src/slic3r/GUI/ImGuiWrapper.cpp
@@ -505,6 +505,23 @@ bool ImGuiWrapper::update_key_data(wxKeyEvent &evt)
     if (evt.GetEventType() == wxEVT_CHAR) {
         // Char event
         const auto key = evt.GetUnicodeKey();
+        // THE MEASUREMENT THAT CANNOT LIE. This is the ONLY place in the application where ImGui
+        // is ever handed a character, so an ImGui text field that stays empty while reporting
+        // itself active has exactly two possible causes, and this line separates them: no output
+        // at all means the wxEVT_CHAR never reached the GL canvas (a focus problem, upstream of
+        // ImGui entirely), while output with unicode=0 means the character arrived empty and is
+        // being dropped right here.
+        //
+        // It lives here rather than on the canvas because a probe bound on the canvas CANNOT
+        // answer this: GLCanvas3D::on_char is bound later than any constructor-time probe, wx
+        // runs handlers in reverse bind order, and on_char returns without Skip() whenever this
+        // function returns true — so such a probe stays silent whether or not the key arrived.
+        // A day was lost to reading that silence as evidence.
+        if (std::getenv("ORCA_CAD_UXTRACE")) {
+            fprintf(stderr, "[UX] imgui_char unicode=%d keycode=%d want_text=%d\n",
+                    (int) key, evt.GetKeyCode(), (int) io.WantTextInput);
+            fflush(stderr);
+        }
         if (key != 0) {
             io.AddInputCharacter(key);
         }
diff --git a/src/slic3r/GUI/MainFrame.cpp b/src/slic3r/GUI/MainFrame.cpp
index 5f36323d6e..cc994b2370 100644
--- a/src/slic3r/GUI/MainFrame.cpp
+++ b/src/slic3r/GUI/MainFrame.cpp
@@ -37,6 +37,10 @@
 #include "I18N.hpp"
 #include "GLCanvas3D.hpp"
 #include "Plater.hpp"
+#ifdef SLIC3R_CAD
+#include "slic3r/GUI/CAD/DesignPanel.hpp"
+#include "slic3r/GUI/CAD/McpControl.hpp"
+#endif
 #include "WebViewDialog.hpp"
 #include "../Utils/Process.hpp"
 // BBS
@@ -1019,7 +1023,15 @@ void MainFrame::update_layout()
         // Right after Home — or first, when there is no Home tab (PositionAfter() would
         // append instead, and by now the other built-in tabs are already in place).
         const int home_idx = m_tabpanel->FindPageByName(TAB_ID_HOME);
-        const size_t prepare_pos = (home_idx == wxNOT_FOUND) ? 0 : static_cast<size_t>(home_idx) + 1;
+        size_t prepare_pos = (home_idx == wxNOT_FOUND) ? 0 : static_cast<size_t>(home_idx) + 1;
+#ifdef SLIC3R_CAD
+        // Design sits between Home and Prepare, so it goes in first and pushes Prepare along.
+        // The page only exists when the experimental CAD feature is enabled.
+        if (m_design_page != nullptr) {
+            m_design_page->Reparent(m_tabpanel);
+            m_tabpanel->InsertPage(prepare_pos++, TAB_ID_DESIGN, m_design_page, _L("Design"), "tab_design_active");
+        }
+#endif
         m_tabpanel->InsertPage(prepare_pos, TAB_ID_PREPARE, m_plater, _L("Prepare"), "tab_3d_active");
         m_tabpanel->InsertPage(prepare_pos + 1, TAB_ID_PREVIEW, m_plater, _L("Preview"), "tab_preview_active");
         m_main_sizer->Add(m_tabpanel, 1, wxEXPAND | wxTOP, 0);
@@ -1237,6 +1249,19 @@ void MainFrame::show_option(bool show)
     }
 }
 
+#ifdef SLIC3R_CAD
+DesignPanel* MainFrame::ensure_design_panel()
+{
+    if (m_design_panel == nullptr && m_design_page != nullptr) {
+        wxBusyCursor busy;
+        m_design_panel = new DesignPanel(m_design_page);
+        m_design_page->GetSizer()->Add(m_design_panel, 1, wxEXPAND);
+        m_design_page->Layout();
+    }
+    return m_design_panel;
+}
+#endif
+
 void MainFrame::init_tabpanel() {
     // wxNB_NOPAGETHEME: Disable Windows Vista theme for the Notebook background. The theme performance is terrible on
     // Windows 10 with multiple high resolution displays connected.
@@ -1277,9 +1302,26 @@ void MainFrame::init_tabpanel() {
         }
         //else if (panel == m_param_panel)
         //    m_param_panel->OnActivate();
+#ifdef SLIC3R_CAD
+        else if (m_design_page != nullptr && panel == m_design_page) {
+            // Built on first activation, never at startup: the panel creates several hundred
+            // controls and its own GL canvas, which a user who does not open the tab should
+            // not pay for.
+            ensure_design_panel();
+            // Re-sync the Design bed to the active printer: the panel is built before the
+            // printer profile is fully applied, so its bed must refresh on activation or the
+            // grid (true bed) spills past the stale default bed quad.
+            m_design_panel->on_tab_shown();
+        }
+#endif
         else if (panel == m_monitor) {
             //monitor
         }
+#ifdef SLIC3R_CAD
+        // Any page that is not Design takes the Design status line down with it — see
+        // DesignPanel::on_tab_hidden for why the popup does not follow the page on its own.
+        if (m_design_panel != nullptr && panel != m_design_page) m_design_panel->on_tab_hidden();
+#endif
 #ifndef __APPLE__
         if (m_last_selected_tab == TAB_ID_PREPARE) {
             m_topbar->EnableUndoRedoItems();
@@ -1310,6 +1352,20 @@ void MainFrame::init_tabpanel() {
 
     wxGetApp().plater_ = m_plater;
 
+#ifdef SLIC3R_CAD
+    // Stand-in page for the Design tab. The real DesignPanel is built into it the first time
+    // the tab is selected (see the page-changed handler above), so nothing it constructs sits
+    // on the startup path. The experimental feature is off by default, and when it is off the
+    // page is never created, so the tab does not appear at all (the preference takes effect on
+    // the next start, like the other feature toggles).
+    if (wxGetApp().is_enable_cad_feature()) {
+        m_design_page = new wxPanel(this);
+        m_design_page->SetSizer(new wxBoxSizer(wxVERTICAL));
+        m_design_page->Hide();
+        start_mcp_control_if_enabled();   // opens the MCP socket iff ORCA_CAD_MCP is set
+    }
+#endif
+
     create_preset_tabs();
 
         //BBS add pages
diff --git a/src/slic3r/GUI/MainFrame.hpp b/src/slic3r/GUI/MainFrame.hpp
index 5340115609..bbdd8a4694 100644
--- a/src/slic3r/GUI/MainFrame.hpp
+++ b/src/slic3r/GUI/MainFrame.hpp
@@ -40,6 +40,9 @@
 // Stable identifiers for MainFrame::m_tabpanel's built-in pages. These are
 // names rather than positional indices so optional pages cannot shift them.
 #define TAB_ID_HOME          "home"
+#ifdef SLIC3R_CAD
+#define TAB_ID_DESIGN        "design"
+#endif
 #define TAB_ID_PREPARE       "prepare"
 #define TAB_ID_PREVIEW       "preview"
 #define TAB_ID_MONITOR       "monitor"
@@ -65,6 +68,9 @@ namespace GUI
 class Tab;
 class PrintHostQueueDialog;
 class Plater;
+#ifdef SLIC3R_CAD
+class DesignPanel;
+#endif
 class MainFrame;
 class WebViewPanel;
 class ParamsDialog;
@@ -384,6 +390,17 @@ public:
     BBLTopbar*            m_topbar{ nullptr };
     PrintHostQueueDialog* printhost_queue_dlg() { return m_printhost_queue_dlg; }
     Plater*               m_plater { nullptr };
+#ifdef SLIC3R_CAD
+    // The tab page is the placeholder; m_design_panel stays null until the tab is first
+    // selected, so everything the Design panel builds stays off the startup path.
+    wxPanel*              m_design_page { nullptr };
+    DesignPanel*          m_design_panel { nullptr };
+    // Builds the Design panel if it does not exist yet and returns it (null only before the
+    // placeholder page itself exists). Main thread only -- it creates wx controls. Both the
+    // tab activation and the MCP socket go through this: the socket is driven headlessly,
+    // with nobody to click the tab, and without this every verb would answer "not ready".
+    DesignPanel*          ensure_design_panel();
+#endif
     //BBS: GUI refactor
     MonitorPanel*         m_monitor{ nullptr };
 
diff --git a/src/slic3r/GUI/PartPlate.cpp b/src/slic3r/GUI/PartPlate.cpp
index 260c857f22..ba0d9580dc 100644
--- a/src/slic3r/GUI/PartPlate.cpp
+++ b/src/slic3r/GUI/PartPlate.cpp
@@ -3507,7 +3507,7 @@ bool PartPlate::intersects(const BoundingBoxf3& bb) const
 	return print_volume.intersects(bb);
 }
 
-void PartPlate::render(const Transform3d& view_matrix, const Transform3d& projection_matrix, bool bottom, bool only_body, bool force_background_color, HeightLimitMode mode, int hover_id, bool render_cali, bool show_grid)
+void PartPlate::render(const Transform3d& view_matrix, const Transform3d& projection_matrix, bool bottom, bool only_body, bool force_background_color, HeightLimitMode mode, int hover_id, bool render_cali, bool show_grid, bool hide_chrome)
 {
     glsafe(::glEnable(GL_DEPTH_TEST));
 
@@ -3558,16 +3558,18 @@ void PartPlate::render(const Transform3d& view_matrix, const Transform3d& projec
     if (wxGetApp().show_plate_gridlines() && show_grid)
         render_grid(bottom);
 
-    if (!bottom && m_selected && !force_background_color) {
+    if (!hide_chrome && !bottom && m_selected && !force_background_color) {
         if (m_partplate_list)
             render_logo(bottom, m_partplate_list->render_cali_logo && render_cali);
         else
             render_logo(bottom);
     }
 
-    render_icons(bottom, only_body, hover_id);
-    if (!force_background_color) {
-        render_only_numbers(bottom);
+    if (!hide_chrome) {
+        render_icons(bottom, only_body, hover_id);
+        if (!force_background_color) {
+            render_only_numbers(bottom);
+        }
     }
 
     glsafe(::glDisable(GL_DEPTH_TEST));
@@ -5962,7 +5964,7 @@ void PartPlateList::postprocess_arrange_polygon(arrangement::ArrangePolygon& arr
 
 /*rendering related functions*/
 //render
-void PartPlateList::render(const Transform3d& view_matrix, const Transform3d& projection_matrix, bool bottom, bool only_current, bool only_body, int hover_id, bool render_cali, bool show_grid)
+void PartPlateList::render(const Transform3d& view_matrix, const Transform3d& projection_matrix, bool bottom, bool only_current, bool only_body, int hover_id, bool render_cali, bool show_grid, bool hide_chrome)
 {
 	const std::lock_guard<std::mutex> local_lock(m_plates_mutex);
 	std::vector<PartPlate*>::iterator it = m_plate_list.begin();
@@ -5987,15 +5989,15 @@ void PartPlateList::render(const Transform3d& view_matrix, const Transform3d& pr
 		if (current_index == m_current_plate) {
 			PartPlate::HeightLimitMode height_mode = (only_current)?PartPlate::HEIGHT_LIMIT_NONE:m_height_limit_mode;
 			if (plate_hover_index == current_index)
-                (*it)->render(view_matrix, projection_matrix, bottom, only_body, false, height_mode, plate_hover_action, render_cali, show_grid);
+                (*it)->render(view_matrix, projection_matrix, bottom, only_body, false, height_mode, plate_hover_action, render_cali, show_grid, hide_chrome);
 			else
-                (*it)->render(view_matrix, projection_matrix, bottom, only_body, false, height_mode, -1, render_cali, show_grid);
+                (*it)->render(view_matrix, projection_matrix, bottom, only_body, false, height_mode, -1, render_cali, show_grid, hide_chrome);
 		}
 		else {
 			if (plate_hover_index == current_index)
-				(*it)->render(view_matrix, projection_matrix, bottom, only_body, false, PartPlate::HEIGHT_LIMIT_NONE, plate_hover_action, render_cali, show_grid);
+				(*it)->render(view_matrix, projection_matrix, bottom, only_body, false, PartPlate::HEIGHT_LIMIT_NONE, plate_hover_action, render_cali, show_grid, hide_chrome);
 			else
-                (*it)->render(view_matrix, projection_matrix, bottom, only_body, false, PartPlate::HEIGHT_LIMIT_NONE, -1, render_cali, show_grid);
+                (*it)->render(view_matrix, projection_matrix, bottom, only_body, false, PartPlate::HEIGHT_LIMIT_NONE, -1, render_cali, show_grid, hide_chrome);
 		}
 	}
 }
diff --git a/src/slic3r/GUI/PartPlate.hpp b/src/slic3r/GUI/PartPlate.hpp
index e913ebaabf..c05775a963 100644
--- a/src/slic3r/GUI/PartPlate.hpp
+++ b/src/slic3r/GUI/PartPlate.hpp
@@ -428,7 +428,7 @@ public:
     bool contains(const BoundingBoxf3& bb) const;
     bool intersects(const BoundingBoxf3& bb) const;
 
-    void render(const Transform3d& view_matrix, const Transform3d& projection_matrix, bool bottom, bool only_body = false, bool force_background_color = false, HeightLimitMode mode = HEIGHT_LIMIT_NONE, int hover_id = -1, bool render_cali = false, bool show_grid = true);
+    void render(const Transform3d& view_matrix, const Transform3d& projection_matrix, bool bottom, bool only_body = false, bool force_background_color = false, HeightLimitMode mode = HEIGHT_LIMIT_NONE, int hover_id = -1, bool render_cali = false, bool show_grid = true, bool hide_chrome = false);
 
     void set_selected();
     void set_unselected();
@@ -857,7 +857,7 @@ public:
 
     /*rendering related functions*/
     void on_change_color_mode(bool is_dark) { m_is_dark = is_dark; }
-    void render(const Transform3d& view_matrix, const Transform3d& projection_matrix, bool bottom, bool only_current = false, bool only_body = false, int hover_id = -1, bool render_cali = false, bool show_grid = true);
+    void render(const Transform3d& view_matrix, const Transform3d& projection_matrix, bool bottom, bool only_current = false, bool only_body = false, int hover_id = -1, bool render_cali = false, bool show_grid = true, bool hide_chrome = false);
     void set_render_option(bool bedtype_texture, bool plate_settings);
     void set_render_cali(bool value = true) { render_cali_logo = value; }
     void register_raycasters_for_picking(GLCanvas3D& canvas)
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index 06d953aa25..30e1ae1313 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -91,6 +91,9 @@
 #include "wxExtensions.hpp"
 #include "../Utils/PrintHost.hpp"
 #include "MainFrame.hpp"
+#ifdef SLIC3R_CAD
+#include "slic3r/GUI/CAD/DesignPanel.hpp"
+#endif
 #include "format.hpp"
 #include "3DScene.hpp"
 #include "GLCanvas3D.hpp"
@@ -8327,6 +8330,9 @@ std::vector<size_t> Plater::priv::load_files(const std::vector<fs::path>& input_
     int answer_convert_from_meters          = wxOK_DEFAULT;
     int answer_convert_from_imperial_units  = wxOK_DEFAULT;
     int tolal_model_count                   = 0;
+    // Whether one of the files being loaded here carried a CAD recipe. A statement about these
+    // files, not about the plater — q->model() may still hold the previous project's recipe.
+    bool loaded_cad_recipe                  = false;
 
     int progress_percent = 0;
     int total_files = input_files.size();
@@ -9452,6 +9458,16 @@ std::vector<size_t> Plater::priv::load_files(const std::vector<fs::path>& input_
             auto loaded_idxs = load_model_objects(model.objects, is_project_file);
             obj_idxs.insert(obj_idxs.end(), loaded_idxs.begin(), loaded_idxs.end());
 
+            // load_model_objects only transfers ModelObjects; carry the Model-level CAD recipe
+            // onto the plater model so the Design tab can rehydrate the editable feature tree on
+            // reopen. Assigned unconditionally on the project-replacing path so that opening a
+            // project without a recipe clears whatever the previous one left behind; importing a
+            // plain model into the open project leaves the current recipe alone.
+            if (is_project_file) {
+                q->model().cad_recipe = model.cad_recipe;
+                loaded_cad_recipe     = !model.cad_recipe.empty();
+            }
+
             BOOST_LOG_TRIVIAL(info) << __FUNCTION__ << ":" << __LINE__ << boost::format(", finished load_model_objects");
             wxString msg = wxString::Format(_L("Loading file: %s"), from_path(real_filename));
             dlg_cont     = dlg.Update(progress_percent, msg);
@@ -9668,7 +9684,12 @@ std::vector<size_t> Plater::priv::load_files(const std::vector<fs::path>& input_
     //    q->model().stl_design_country = "";
     //}
 
-    if (tolal_model_count <= 0 && !q->m_exported_file) {
+    // A CAD project legitimately carries no mesh: the model lives in the feature tree until it is
+    // committed to the plate. Warning "no geometry data" for one is false, and it is the LAST thing
+    // a user sees after opening a design they spent an hour on — it reads as "your work is gone"
+    // when the recipe has in fact just been loaded and the Design tab will rehydrate it. Count a
+    // recipe that came from THESE files as geometry.
+    if (tolal_model_count <= 0 && !loaded_cad_recipe && !q->m_exported_file) {
         dlg.Hide();
         if (!is_user_cancel) {
             MessageDialog msg(wxGetApp().mainframe, _L("The file does not contain any geometry data."), _L("Warning"), wxYES | wxICON_WARNING);
@@ -10215,6 +10236,16 @@ void Plater::priv::reset(bool apply_presets_change)
     // Stop and reset the Print content.
     this->background_process.reset();
     model.clear_objects();
+    // clear_objects() only drops the ModelObjects; the CAD recipe is Model-level state and would
+    // otherwise be written into every project saved for the rest of the session.
+    model.cad_recipe.clear();
+#ifdef SLIC3R_CAD
+    // Same reason, one level up: the Design tab keeps the editable document, not the Model, so
+    // clearing the recipe alone leaves the tab showing the previous project's feature tree —
+    // and its next edit syncs that tree straight back into the new project.
+    if (wxGetApp().mainframe != nullptr && wxGetApp().mainframe->m_design_panel != nullptr)
+        wxGetApp().mainframe->m_design_panel->clear_document();
+#endif
     assemble_view->get_canvas3d()->reset_explosion_ratio();
     update();
 
@@ -13717,6 +13748,14 @@ void Plater::priv::unbind_canvas_event_handlers()
 
     if (assemble_view != nullptr)
         assemble_view->get_canvas3d()->unbind_event_handlers();
+
+#ifdef SLIC3R_CAD
+    // The Design tab's viewport is a fourth GLCanvas3D on the same shared GL context, owned by
+    // MainFrame rather than by us — same reach as reset() uses for clear_document(). Null until
+    // the tab has been opened once, so most sessions skip it.
+    if (wxGetApp().mainframe != nullptr && wxGetApp().mainframe->m_design_panel != nullptr)
+        wxGetApp().mainframe->m_design_panel->unbind_canvas_event_handlers();
+#endif
 }
 
 void Plater::priv::reset_canvas_volumes()
@@ -13726,6 +13765,11 @@ void Plater::priv::reset_canvas_volumes()
 
     if (preview != nullptr)
         preview->get_canvas3d()->reset_volumes();
+
+#ifdef SLIC3R_CAD
+    if (wxGetApp().mainframe != nullptr && wxGetApp().mainframe->m_design_panel != nullptr)
+        wxGetApp().mainframe->m_design_panel->reset_canvas_volumes();
+#endif
 }
 
 bool Plater::priv::check_ams_status_impl(bool is_slice_all)
@@ -15677,8 +15721,12 @@ bool Plater::up_to_date(bool saved, bool backup)
         Slic3r::clear_other_changes(backup);
         return p->up_to_date(saved, backup);
     }
-    return p->model.objects.empty() || (p->up_to_date(saved, backup) &&
-                                        !Slic3r::has_other_changes(backup));
+    // A Design-tab project is object-less until it is committed to the plate, but its feature
+    // tree is real work: treating it as an empty project skipped both the autosave and the
+    // "unsaved changes" prompt, so quitting threw it away without asking. Non-CAD projects
+    // never carry a recipe, so the empty-project shortcut is unchanged for them.
+    return (p->model.objects.empty() && p->model.cad_recipe.empty()) ||
+           (p->up_to_date(saved, backup) && !Slic3r::has_other_changes(backup));
 }
 
 bool Plater::add_model(bool imperial_units, std::string fname)
diff --git a/src/slic3r/GUI/Preferences.cpp b/src/slic3r/GUI/Preferences.cpp
index 73f3a2c90a..aa831ad489 100644
--- a/src/slic3r/GUI/Preferences.cpp
+++ b/src/slic3r/GUI/Preferences.cpp
@@ -9,6 +9,7 @@
 #include "I18N.hpp"
 #include "libslic3r/AppConfig.hpp"
 #include "libslic3r/Format/DRC.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
 #include <wx/language.h>
 #include "OG_CustomCtrl.hpp"
 #include "wx/graphics.h"
@@ -367,7 +368,8 @@ wxBoxSizer *PreferencesDialog::create_item_language_combobox(wxString title, wxS
         wxLANGUAGE_PORTUGUESE_BRAZILIAN,
         wxLANGUAGE_LITHUANIAN,
         wxLANGUAGE_VIETNAMESE,
-        wxLANGUAGE_THAI
+        wxLANGUAGE_THAI,
+        wxLANGUAGE_ROMANIAN
     };
 
     auto translations = wxTranslations::Get()->GetAvailableTranslations(SLIC3R_APP_KEY);
@@ -1724,6 +1726,21 @@ void PreferencesDialog::create_items()
     auto item_multi_machine    = create_item_checkbox(_L("Multi device management"), _L("With this option enabled, you can send a task to multiple devices at the same time and manage multiple devices."), "enable_multi_machine", _L("(Requires restart)"));
     g_sizer->Add(item_multi_machine);
 
+#ifdef SLIC3R_CAD
+    auto item_cad_feature      = create_item_checkbox(_L("CAD feature (experimental)"),
+        _L("With this option enabled, the Design tab is shown, where models can be built and edited "
+           "parametrically. This feature is experimental and still under development."),
+        "enable_cad_feature", _L("(Requires restart)"));
+    g_sizer->Add(item_cad_feature);
+
+    auto item_auto_close_sketch_loops = create_item_checkbox(_L("Auto-close sketch loops"),
+        _L("Treat sketch endpoints within 0.001 mm as one joint and weld the loop shut. "
+           "Off: only exactly coincident endpoints join, so a loop with a tiny gap is "
+           "shown as open instead of being closed for you."),
+        "auto_close_sketch_loops");
+    g_sizer->Add(item_auto_close_sketch_loops);
+#endif
+
 #if 0
     g_sizer->Add(create_item_title(_L("Filament Grouping")), 1, wxEXPAND);
     //temporarily disable it
@@ -1800,6 +1817,21 @@ void PreferencesDialog::create_items()
     auto reverse_mouse_zoom    = create_item_checkbox(_L("Reverse mouse zoom"), _L("If enabled, reverses the direction of zoom with mouse wheel."), "reverse_mouse_wheel_zoom");
     g_sizer->Add(reverse_mouse_zoom);
 
+#ifdef SLIC3R_CAD
+    // Design-tab only, so it stays out of the way while the CAD feature is switched off.
+    if (wxGetApp().is_enable_cad_feature()) {
+        auto item_connector_face_glyph = create_item_checkbox(_L("Draw mate connectors as a face"),
+            _L("In the Design tab, draw a mate connector as a small face instead of the conventional "
+               "disc with a roll quadrant. A face's orientation is read without being learned. "
+               "Turn this off for the conventional CAD representation."), "design_connector_face_glyph");
+        g_sizer->Add(item_connector_face_glyph);
+    }
+
+    // Push the weld preference into the kernel now so toggling it takes effect without
+    // a restart (the sketch tool also re-pushes on activation, see DesignSketchTool::begin).
+    Slic3r::set_sketch_auto_close(wxGetApp().is_auto_close_sketch_loops());
+#endif
+
     std::vector<wxString> ButtonDragActions = {_L("None"), _L("Pan"), _L("Rotate")};
     auto item_left_mouse_drag  = create_item_combobox(_L("Left Mouse Drag"), _L("Set the action that dragging the left mouse button should perform."), "left_mouse_drag_action", ButtonDragActions);
     g_sizer->Add(item_left_mouse_drag);
diff --git a/tests/data/cad_recipe_v3.bin b/tests/data/cad_recipe_v3.bin
new file mode 100644
index 0000000000..c3bc6e95f7
Binary files /dev/null and b/tests/data/cad_recipe_v3.bin differ
diff --git a/tests/data/cad_recipe_v4.bin b/tests/data/cad_recipe_v4.bin
new file mode 100644
index 0000000000..eb8f8ec730
Binary files /dev/null and b/tests/data/cad_recipe_v4.bin differ
diff --git a/tests/data/cad_recipe_v5.bin b/tests/data/cad_recipe_v5.bin
new file mode 100644
index 0000000000..718f2d2d84
Binary files /dev/null and b/tests/data/cad_recipe_v5.bin differ
diff --git a/tests/libslic3r/CMakeLists.txt b/tests/libslic3r/CMakeLists.txt
index b3c74335cc..185dce37da 100644
--- a/tests/libslic3r/CMakeLists.txt
+++ b/tests/libslic3r/CMakeLists.txt
@@ -52,6 +52,17 @@ add_executable(${_TEST_NAME}_tests
     ../libnest2d/printer_parts.cpp
     )
 
+if (SLIC3R_CAD)
+    target_sources(${_TEST_NAME}_tests PRIVATE
+        test_caddocument.cpp
+        test_sketchconstraints.cpp
+        test_sketchedit.cpp
+        test_sketchprofile.cpp
+        test_sketchimport.cpp
+        test_sketchinference.cpp
+        test_slvs_constraints.cpp)
+endif ()
+
 if (TARGET OpenVDB::openvdb)
     target_sources(${_TEST_NAME}_tests PRIVATE test_hollowing.cpp)
 endif()
diff --git a/tests/libslic3r/test_3mf.cpp b/tests/libslic3r/test_3mf.cpp
index 5c38859a12..02d392140b 100644
--- a/tests/libslic3r/test_3mf.cpp
+++ b/tests/libslic3r/test_3mf.cpp
@@ -3,6 +3,8 @@
 #include "libslic3r/Format/3mf.hpp"
 #include "libslic3r/Format/bbs_3mf.hpp"
 #include "libslic3r/Format/STL.hpp"
+#include "libslic3r/miniz_extension.hpp"
+#include "libslic3r/Zipper.hpp"
 #include "libslic3r/PrintConfig.hpp"
 #include "libslic3r/Semver.hpp"
 #include "libslic3r/Preset.hpp"
@@ -15,6 +17,8 @@
 #include <nlohmann/json.hpp>
 
 #include <boost/filesystem/operations.hpp>
+#include <boost/algorithm/string/predicate.hpp>
+#include <algorithm>
 
 #include <catch2/catch_tostring.hpp>
 #include <Eigen/Core>
@@ -143,6 +147,236 @@ SCENARIO("Export+Import geometry to/from 3mf file cycle", "[3mf]") {
     }
 }
 
+// The recipe is an opaque binary blob (CadDocument::serialize_recipe()), so the 3mf backend has
+// to carry it byte-for-byte — no XML/text mangling, embedded NULs intact.
+static std::string make_cad_recipe()
+{
+    // Built from an explicit length, not append(const char*), which would stop at the first
+    // embedded NUL — the one thing this blob exists to prove survives the archive.
+    static const char blob[] = "\x01" "RECIPE" "\0" "\xff\xfe\x00\x10" "cad-features-blob";
+    return std::string(blob, sizeof(blob) - 1);
+}
+
+static const std::string CAD_RECIPE_ENTRY        = "Metadata/orca_cad.bin";
+static const std::string LEGACY_CAD_RECIPE_ENTRY = "Metadata/SnapOrca_cad.bin";
+
+// Pulls one named entry out of a 3mf archive; false when it is absent.
+static bool read_cad_recipe_entry(const std::string& path, std::string& out,
+                                  const std::string& entry = CAD_RECIPE_ENTRY)
+{
+    mz_zip_archive zip;
+    mz_zip_zero_struct(&zip);
+    REQUIRE(open_zip_reader(&zip, path));
+    bool   found = false;
+    mz_uint n    = mz_zip_reader_get_num_files(&zip);
+    for (mz_uint i = 0; i < n; ++i) {
+        mz_zip_archive_file_stat st;
+        if (!mz_zip_reader_file_stat(&zip, i, &st)) continue;
+        std::string name(st.m_filename);
+        std::replace(name.begin(), name.end(), '\\', '/');
+        if (boost::algorithm::iequals(name, entry)) {
+            out.resize(st.m_uncomp_size);
+            found = mz_zip_reader_extract_to_mem(&zip, i, out.data(), out.size(), 0) != 0;
+            break;
+        }
+    }
+    close_zip_reader(&zip);
+    return found;
+}
+
+// Rewrites the archive at `path` with the recipe entry back under the name it had before the
+// rename, which is what every project saved by an earlier build looks like on disk. Generated
+// rather than checked in because a whole project archive is not frozen evidence the way a bare
+// recipe blob is -- it has to be whatever today's exporter writes, with only the name aged.
+// miniz cannot rename in place and open_zip_writer truncates, so the entries are held across
+// the switch.
+static void rename_cad_recipe_entry_to_legacy(const std::string& path)
+{
+    std::vector<std::pair<std::string, std::string>> entries;
+    bool renamed = false;
+    {
+        mz_zip_archive zip;
+        mz_zip_zero_struct(&zip);
+        REQUIRE(open_zip_reader(&zip, path));
+        mz_uint n = mz_zip_reader_get_num_files(&zip);
+        for (mz_uint i = 0; i < n; ++i) {
+            mz_zip_archive_file_stat st;
+            REQUIRE(mz_zip_reader_file_stat(&zip, i, &st));
+            if (st.m_is_directory) continue;
+            std::string name(st.m_filename);
+            std::replace(name.begin(), name.end(), '\\', '/');
+            std::string data((size_t) st.m_uncomp_size, '\0');
+            if (st.m_uncomp_size > 0)
+                REQUIRE(mz_zip_reader_extract_to_mem(&zip, i, data.data(), data.size(), 0));
+            if (boost::algorithm::iequals(name, CAD_RECIPE_ENTRY)) {
+                name    = LEGACY_CAD_RECIPE_ENTRY;
+                renamed = true;
+            }
+            entries.emplace_back(std::move(name), std::move(data));
+        }
+        close_zip_reader(&zip);
+    }
+    // Without this the scenario would degrade silently into re-testing the new name if the
+    // exporter's constant ever moved again: every load below would still pass.
+    REQUIRE(renamed);
+
+    Zipper out(path);
+    for (const auto& e : entries)
+        out.add_entry(e.first, e.second.data(), e.second.size());
+    out.finalize();
+}
+
+// The recipe lives only in the BBS-native backend, because that is the only one that runs:
+// store_bbs_3mf is the sole exporter the app calls, and 3mf.cpp's load_3mf is reached only for
+// files fingerprinted as PrusaSlicer's, which never carry a recipe. This locks in both halves:
+// the archive entry is at the exact path the importer looks for, and the recipe comes back
+// through the real importer.
+SCENARIO("CAD recipe is embedded in the BBS 3mf archive", "[3mf][CAD]") {
+    GIVEN("a model carrying a binary cad_recipe") {
+        Model model;
+        std::string src = std::string(TEST_DATA_DIR) + "/test_3mf/Prusa.stl";
+        REQUIRE(load_stl(src.c_str(), &model));
+        model.add_default_instances();
+
+        // store_bbs_3mf stages its metadata through the model's backup path; point it at a
+        // writable temp dir, as the sibling BBS scenarios do. The process-global
+        // set_temporary_dir() would leak into every test that ran afterwards.
+        ScopedTemporaryDir backup_dir("orca_cad");
+        model.set_backup_path(backup_dir.string());
+
+        const std::string recipe = make_cad_recipe();
+        model.cad_recipe = recipe;
+
+        WHEN("saved through the BBS backend (the format the GUI uses)") {
+            ScopedTemporaryFile temp(".3mf");
+            const std::string test_file = temp.string();
+
+            DynamicPrintConfig cfg;
+            StoreParams sp;
+            sp.path     = test_file.c_str();
+            sp.model    = &model;
+            sp.config   = &cfg;
+            sp.strategy = SaveStrategy::Zip64 | SaveStrategy::Silence;
+            REQUIRE(store_bbs_3mf(sp));
+
+            THEN("the archive entry is present byte-for-byte") {
+                std::string got;
+                REQUIRE(read_cad_recipe_entry(test_file, got));
+                REQUIRE(got.size() == recipe.size());
+                REQUIRE(got == recipe);
+            }
+
+            THEN("the importer restores it onto the loaded model") {
+                Model dst_model;
+                ScopedTemporaryDir dst_backup_dir("orca_cad_dst");
+                dst_model.set_backup_path(dst_backup_dir.string());
+
+                DynamicPrintConfig dst_config;
+                ConfigSubstitutionContext ctxt{ ForwardCompatibilitySubstitutionRule::Enable };
+                PlateDataPtrs        dst_plates;
+                std::vector<Preset*> project_presets;
+                bool   is_bbl_3mf = false, is_orca_3mf = false;
+                Semver file_version;
+                REQUIRE(load_bbs_3mf(test_file.c_str(), &dst_config, &ctxt, &dst_model, &dst_plates,
+                                     &project_presets, &is_bbl_3mf, &is_orca_3mf, &file_version, nullptr,
+                                     LoadStrategy::LoadModel | LoadStrategy::LoadConfig));
+                REQUIRE(dst_model.cad_recipe.size() == recipe.size());
+                REQUIRE(dst_model.cad_recipe == recipe);
+
+                release_PlateData_list(dst_plates);
+            }
+        }
+
+        WHEN("the same model is saved with no recipe") {
+            model.cad_recipe.clear();
+            ScopedTemporaryFile temp(".3mf");
+            const std::string test_file = temp.string();
+
+            DynamicPrintConfig cfg;
+            StoreParams sp;
+            sp.path     = test_file.c_str();
+            sp.model    = &model;
+            sp.config   = &cfg;
+            sp.strategy = SaveStrategy::Zip64 | SaveStrategy::Silence;
+            REQUIRE(store_bbs_3mf(sp));
+
+            THEN("no entry is written at all") {
+                std::string got;
+                REQUIRE_FALSE(read_cad_recipe_entry(test_file, got));
+            }
+        }
+    }
+}
+
+// The recipe entry was renamed from Metadata/SnapOrca_cad.bin to Metadata/orca_cad.bin. Nothing
+// in the blob marks that move, so a reader that knows only the new name loads a project written
+// before it with an empty cad_recipe and no error at all — a feature tree gone with no symptom
+// but an empty Design tab. The importer must still accept the old name; the exporter may never
+// write it.
+SCENARIO("a project saved under the pre-rename recipe name still loads", "[3mf][CAD]") {
+    GIVEN("a project whose recipe entry carries the old name") {
+        Model model;
+        std::string src = std::string(TEST_DATA_DIR) + "/test_3mf/Prusa.stl";
+        REQUIRE(load_stl(src.c_str(), &model));
+        model.add_default_instances();
+        const std::string recipe = make_cad_recipe();
+        model.cad_recipe = recipe;
+
+        WHEN("it was written by the BBS backend") {
+            ScopedTemporaryDir backup_dir("orca_cad_legacy");
+            model.set_backup_path(backup_dir.string());
+
+            ScopedTemporaryFile temp(".3mf");
+            const std::string test_file = temp.string();
+            DynamicPrintConfig cfg;
+            StoreParams sp;
+            sp.path     = test_file.c_str();
+            sp.model    = &model;
+            sp.config   = &cfg;
+            sp.strategy = SaveStrategy::Zip64 | SaveStrategy::Silence;
+            REQUIRE(store_bbs_3mf(sp));
+            rename_cad_recipe_entry_to_legacy(test_file);
+
+            // Catch2 replays the enclosing sections per THEN, so one load here serves both.
+            Model dst_model;
+            ScopedTemporaryDir dst_backup_dir("orca_cad_legacy_dst");
+            dst_model.set_backup_path(dst_backup_dir.string());
+
+            DynamicPrintConfig dst_config;
+            ConfigSubstitutionContext ctxt{ ForwardCompatibilitySubstitutionRule::Enable };
+            PlateDataPtrs        dst_plates;
+            std::vector<Preset*> project_presets;
+            bool   is_bbl_3mf = false, is_orca_3mf = false;
+            Semver file_version;
+            REQUIRE(load_bbs_3mf(test_file.c_str(), &dst_config, &ctxt, &dst_model, &dst_plates,
+                                 &project_presets, &is_bbl_3mf, &is_orca_3mf, &file_version, nullptr,
+                                 LoadStrategy::LoadModel | LoadStrategy::LoadConfig));
+            release_PlateData_list(dst_plates);
+
+            THEN("the recipe still comes back byte-for-byte") {
+                REQUIRE(dst_model.cad_recipe == recipe);
+            }
+
+            THEN("re-saving migrates it to the new name and leaves the old one behind") {
+                ScopedTemporaryFile again(".3mf");
+                const std::string resaved = again.string();
+                DynamicPrintConfig cfg2;
+                StoreParams sp2;
+                sp2.path     = resaved.c_str();
+                sp2.model    = &dst_model;
+                sp2.config   = &cfg2;
+                sp2.strategy = SaveStrategy::Zip64 | SaveStrategy::Silence;
+                REQUIRE(store_bbs_3mf(sp2));
+
+                std::string got;
+                REQUIRE(read_cad_recipe_entry(resaved, got));
+                REQUIRE(got == recipe);
+                REQUIRE_FALSE(read_cad_recipe_entry(resaved, got, LEGACY_CAD_RECIPE_ENTRY));
+            }
+        }
+    }
+}
+
 // .3mf multi-nozzle round-trip.
 // Locks the load/save handling for the H2C multi-nozzle plate metadata:
 //   * filament_volume_maps  -> plate config "filament_volume_map" (with the >1 -> 0 clamp)
diff --git a/tests/libslic3r/test_caddocument.cpp b/tests/libslic3r/test_caddocument.cpp
new file mode 100644
index 0000000000..d69ada09b6
--- /dev/null
+++ b/tests/libslic3r/test_caddocument.cpp
@@ -0,0 +1,8414 @@
+#include <catch2/catch_all.hpp>   // mainline OrcaSlicer ships Catch2 v3 (v2 was catch2/catch.hpp)
+
+// Substring assertions, spelled so this file compiles UNCHANGED on both forks.
+// Catch2 v2 (Snapmaker) spells it Matchers::Contains; v3 (orca_cad / mainline) spells it
+// Matchers::ContainsSubstring and gives Contains an incompatible meaning — range-contains-
+// ELEMENT — which fails to compile against a std::string rather than failing a test.
+// Using find() sidesteps the rename entirely; INFO keeps the actual string in the report.
+#define REQUIRE_CONTAINS(str, sub) \
+    do { const std::string _actual = (str); INFO("actual: " << _actual); \
+         REQUIRE(_actual.find(sub) != std::string::npos); } while (0)
+#define CHECK_CONTAINS(str, sub) \
+    do { const std::string _actual = (str); INFO("actual: " << _actual); \
+         CHECK(_actual.find(sub) != std::string::npos); } while (0)
+
+#include "libslic3r/CAD/CadDocument.hpp"
+#include "libslic3r/CAD/GeometryEngine.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
+#include "libslic3r/CAD/SketchImport.hpp"
+#include "libslic3r/CAD/ThreadStandards.hpp"
+#include "libslic3r/Utils.hpp"
+
+#include <cmath>
+#include <cstring>
+#include <fstream>
+#include <memory>
+#include <set>
+#include <Bnd_Box.hxx>
+#include <BRepBndLib.hxx>
+#include <BRepAdaptor_Curve.hxx>
+#include <TopExp_Explorer.hxx>
+#include <TopoDS.hxx>
+#include <BRepGProp.hxx>
+#include <GProp_GProps.hxx>
+#include <BRepPrimAPI_MakeBox.hxx>
+#include <BRepBuilderAPI_Transform.hxx>
+#include <gp_Trsf.hxx>
+#include <gp_Vec.hxx>
+#include <cereal/archives/binary.hpp>
+
+using namespace Slic3r;
+using Catch::Approx;   // Catch2 v3 scopes Approx under Catch:: (v2 had it unqualified)
+
+TEST_CASE("CadDocument profile sketch -> extrude -> solid", "[CadDocument]")
+{
+    CadDocument doc;
+
+    SketchProfile sp;
+    sp.points.push_back(Vec2d(-10, -10));
+    sp.points.push_back(Vec2d( 10, -10));
+    sp.points.push_back(Vec2d( 10,  10));
+    sp.points.push_back(Vec2d(-10,  10));
+    sp.closed = true;
+
+    int sk_idx = doc.add_sketch_profile(sp, SketchPlane::XY(), "SquareProfile");
+    REQUIRE(sk_idx >= 0);
+    doc.add_extrude(sk_idx, 5.0, false, BooleanMode::New, "Extrude1");
+
+    bool ok = doc.recompute();
+    REQUIRE(ok);
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.display_mesh.facets_count() > 0);
+}
+
+TEST_CASE("CadDocument legacy Rectangle sketch still works", "[CadDocument]")
+{
+    CadDocument doc;
+
+    int sk_idx = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                                20, 20, 10, "RectSketch");
+    REQUIRE(sk_idx >= 0);
+    doc.add_extrude(sk_idx, 5.0, false, BooleanMode::New, "Extrude1");
+
+    bool ok = doc.recompute();
+    REQUIRE(ok);
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.display_mesh.facets_count() > 0);
+}
+
+TEST_CASE("CadDocument preview with profile on self-contained candidate", "[CadDocument]")
+{
+    CadDocument doc;
+
+    CadFeature candidate;
+    candidate.type     = CadFeatureType::Extrude;
+    candidate.plane    = SketchPlane::XY();
+    candidate.distance = 4;
+    candidate.mode     = BooleanMode::New;
+    // sketch_ref is -1 by default -> apply_feature uses candidate's own params
+
+    SketchProfile tri;
+    tri.points.push_back(Vec2d(0,  0));
+    tri.points.push_back(Vec2d(10, 0));
+    tri.points.push_back(Vec2d(5,  8.66));
+    tri.closed   = true;
+    candidate.profile = tri;
+
+    TriangleMesh mesh;
+    std::string  err;
+    bool ok = doc.preview(candidate, mesh, err);
+    REQUIRE(ok);
+    REQUIRE(mesh.facets_count() > 0);
+}
+
+TEST_CASE("CadDocument solve_sketch_feature snaps a rough quad to a rectangle", "[CadDocument]")
+{
+    CadDocument doc;
+    SketchProfile sp;
+    sp.points = { Vec2d(0,0), Vec2d(8,1), Vec2d(9,5), Vec2d(-1,4) };
+    sp.closed = true;
+    int sk = doc.add_sketch_profile(sp, SketchPlane::XY(), "S");
+
+    auto& cons = doc.features[sk].constraints;
+    cons.push_back({SketchConstraintType::Fix,        0,-1,-1,-1, 0});
+    cons.push_back({SketchConstraintType::LockX,      0,-1,-1,-1, 0});
+    cons.push_back({SketchConstraintType::LockY,      0,-1,-1,-1, 0});
+    cons.push_back({SketchConstraintType::Horizontal, 0, 1,-1,-1, 0});
+    cons.push_back({SketchConstraintType::Vertical,   1, 2,-1,-1, 0});
+    cons.push_back({SketchConstraintType::Horizontal, 2, 3,-1,-1, 0});
+    cons.push_back({SketchConstraintType::Vertical,   3, 0,-1,-1, 0});
+    cons.push_back({SketchConstraintType::Distance,   0, 1,-1,-1, 10});
+    cons.push_back({SketchConstraintType::Distance,   1, 2,-1,-1, 6});
+
+    REQUIRE(doc.solve_sketch_feature(sk));
+    const auto& pts = doc.features[sk].profile.points;
+    REQUIRE_THAT(pts[1].x(), Catch::Matchers::WithinAbs(10.0, 1e-3));
+    REQUIRE_THAT(pts[1].y(), Catch::Matchers::WithinAbs(0.0,  1e-3));
+    REQUIRE_THAT(pts[2].x(), Catch::Matchers::WithinAbs(10.0, 1e-3));
+    REQUIRE_THAT(pts[2].y(), Catch::Matchers::WithinAbs(6.0,  1e-3));
+    REQUIRE_THAT(pts[3].x(), Catch::Matchers::WithinAbs(0.0,  1e-3));
+    REQUIRE_THAT(pts[3].y(), Catch::Matchers::WithinAbs(6.0,  1e-3));
+
+    // the solved profile still extrudes into a solid
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.display_mesh.facets_count() > 0);
+}
+
+TEST_CASE("sketch entities -> wire -> extrude", "[CadDocument]")
+{
+    SECTION("square from 4 lines") {
+        CadDocument doc;
+
+        CadFeature sk;
+        sk.type    = CadFeatureType::Sketch;
+        sk.name    = "square";
+        sk.plane   = SketchPlane::XY();
+        sk.entities = {
+            {SketchEntity::Type::Line, Vec2d(-10,-10), Vec2d(10,-10)},
+            {SketchEntity::Type::Line, Vec2d(10,-10), Vec2d(10,10)},
+            {SketchEntity::Type::Line, Vec2d(10,10), Vec2d(-10,10)},
+            {SketchEntity::Type::Line, Vec2d(-10,10), Vec2d(-10,-10)},
+        };
+        doc.features.push_back(sk);
+
+        CadFeature ex;
+        ex.type       = CadFeatureType::Extrude;
+        ex.name       = "extrude";
+        ex.sketch_ref = 0;
+        ex.distance   = 5;
+        ex.mode       = BooleanMode::New;
+        doc.features.push_back(ex);
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE(doc.display_mesh.facets_count() > 0);
+
+        auto bb = doc.display_mesh.bounding_box();
+        auto sz = bb.max - bb.min;
+        REQUIRE(std::abs(sz.x() - 20.0) < 0.5);
+        REQUIRE(std::abs(sz.y() - 20.0) < 0.5);
+        REQUIRE(std::abs(sz.z() -  5.0) < 0.5);
+    }
+
+    SECTION("single circle") {
+        CadDocument doc;
+
+        CadFeature sk;
+        sk.type    = CadFeatureType::Sketch;
+        sk.name    = "circle";
+        sk.plane   = SketchPlane::XY();
+        sk.entities = {
+            {SketchEntity::Type::Circle, Vec2d(0,0), Vec2d(0,0), Vec2d(0,0), 10.0},
+        };
+        doc.features.push_back(sk);
+
+        CadFeature ex;
+        ex.type       = CadFeatureType::Extrude;
+        ex.name       = "extrude";
+        ex.sketch_ref = 0;
+        ex.distance   = 8;
+        ex.mode       = BooleanMode::New;
+        doc.features.push_back(ex);
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE(doc.display_mesh.facets_count() > 0);
+
+        auto bb = doc.display_mesh.bounding_box();
+        auto sz = bb.max - bb.min;
+        REQUIRE(std::abs(sz.x() - 20.0) < 0.5);
+        REQUIRE(std::abs(sz.y() - 20.0) < 0.5);
+        REQUIRE(std::abs(sz.z() -  8.0) < 0.5);
+    }
+
+    SECTION("construction line excluded") {
+        CadDocument doc;
+
+        CadFeature sk;
+        sk.type  = CadFeatureType::Sketch;
+        sk.name  = "square_with_construction";
+        sk.plane = SketchPlane::XY();
+
+        SketchEntity cline;
+        cline.type         = SketchEntity::Type::Line;
+        cline.p0           = Vec2d(-30, 0);
+        cline.p1           = Vec2d(30, 0);
+        cline.construction = true;
+
+        sk.entities = {
+            {SketchEntity::Type::Line, Vec2d(-10,-10), Vec2d(10,-10)},
+            {SketchEntity::Type::Line, Vec2d(10,-10), Vec2d(10,10)},
+            {SketchEntity::Type::Line, Vec2d(10,10), Vec2d(-10,10)},
+            {SketchEntity::Type::Line, Vec2d(-10,10), Vec2d(-10,-10)},
+            cline,
+        };
+        doc.features.push_back(sk);
+
+        CadFeature ex;
+        ex.type       = CadFeatureType::Extrude;
+        ex.name       = "extrude";
+        ex.sketch_ref = 0;
+        ex.distance   = 5;
+        ex.mode       = BooleanMode::New;
+        doc.features.push_back(ex);
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE(doc.display_mesh.facets_count() > 0);
+
+        auto bb = doc.display_mesh.bounding_box();
+        auto sz = bb.max - bb.min;
+        REQUIRE(std::abs(sz.x() - 20.0) < 0.5);
+        REQUIRE(std::abs(sz.y() - 20.0) < 0.5);
+        REQUIRE(std::abs(sz.z() -  5.0) < 0.5);
+    }
+}
+
+TEST_CASE("construction flag survives recipe round-trip", "[CadDocument]")
+{
+    CadDocument doc;
+
+    // Square edge + 1 construction line
+    std::vector<SketchEntity> ents = {
+        {SketchEntity::Type::Line, Vec2d(-10, -10), Vec2d(10, -10)},
+        {SketchEntity::Type::Line, Vec2d(10, -10), Vec2d(10, 10)},
+        {SketchEntity::Type::Line, Vec2d(10, 10), Vec2d(-10, 10)},
+        {SketchEntity::Type::Line, Vec2d(-10, 10), Vec2d(-10, -10)},
+    };
+    SketchEntity cx;
+    cx.type = SketchEntity::Type::Line;
+    cx.p0 = Vec2d(-33.0, 7.0);
+    cx.p1 = Vec2d(33.0, 7.0);
+    cx.construction = true;
+    ents.push_back(cx);   // ents[4]
+
+    int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "SkCtor");
+    REQUIRE(sk == 0);
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Ex");
+
+    std::string blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument fresh;
+    REQUIRE(fresh.deserialize_recipe(blob));
+
+    // Locate SkCtor in fresh.features
+    const CadFeature* sf = nullptr;
+    for (const auto& f : fresh.features) {
+        if (f.name == "SkCtor") { sf = &f; break; }
+    }
+    REQUIRE(sf != nullptr);
+    REQUIRE(sf->entities.size() == 5);
+    REQUIRE(sf->entities[0].construction == false);
+    REQUIRE(sf->entities[4].construction == true);
+    REQUIRE_THAT(sf->entities[4].p0.x(), Catch::Matchers::WithinAbs(-33.0, 1e-9));
+    REQUIRE_THAT(sf->entities[4].p1.x(), Catch::Matchers::WithinAbs( 33.0, 1e-9));
+}
+
+// Mirrors the GUI interactive-sketch commit path (DesignPanel ->
+// add_sketch_entities) for the Fase 4.1 entity drawing tools: a corner-rect and
+// a center-rect produce 4 closed Line entities; a center-circle produces 1
+// Circle entity. add_sketch_entities must store them and extrude into a solid.
+TEST_CASE("add_sketch_entities commit path -> extrude", "[CadDocument]")
+{
+    SECTION("corner-rect 4 lines -> 30x16x5") {
+        CadDocument doc;
+        // Corner A=(-15,-8), B=(15,8): the tool's push_closed_lines order.
+        const Vec2d A(-15, -8), B(15, 8);
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Line, A,                 Vec2d(B.x(), A.y())},
+            {SketchEntity::Type::Line, Vec2d(B.x(),A.y()), B},
+            {SketchEntity::Type::Line, B,                 Vec2d(A.x(), B.y())},
+            {SketchEntity::Type::Line, Vec2d(A.x(),B.y()), A},
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "Sketch1");
+        REQUIRE(sk == 0);
+        doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Extrude1");
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE(doc.display_mesh.facets_count() > 0);
+        auto sz = doc.display_mesh.bounding_box().size();
+        REQUIRE(std::abs(sz.x() - 30.0) < 0.5);
+        REQUIRE(std::abs(sz.y() - 16.0) < 0.5);
+        REQUIRE(std::abs(sz.z() -  5.0) < 0.5);
+    }
+
+    SECTION("center-circle 1 entity -> r=7 cylinder") {
+        CadDocument doc;
+        SketchEntity c;
+        c.type = SketchEntity::Type::Circle;
+        c.center = Vec2d(0, 0);
+        c.p0 = Vec2d(0, 0);
+        c.radius = 7.0;
+        int sk = doc.add_sketch_entities({c}, SketchPlane::XY(), "Sketch1");
+        doc.add_extrude(sk, 4.0, false, BooleanMode::New, "Extrude1");
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE(doc.display_mesh.facets_count() > 0);
+        auto sz = doc.display_mesh.bounding_box().size();
+        REQUIRE(std::abs(sz.x() - 14.0) < 0.5);
+        REQUIRE(std::abs(sz.y() - 14.0) < 0.5);
+        REQUIRE(std::abs(sz.z() -  4.0) < 0.5);
+    }
+}
+
+// A slot (stadium): 2 lines + 2 semicircular Arc entities forming one closed
+// loop — the shape the Fase 4.1b Slot tool emits. Validates the kernel's Arc
+// edge path (GC_MakeArcOfCircle via center/radius/start_angle/end_angle, with
+// the mid reconstructed at (start+end)/2) inside a mixed Line/Arc wire.
+TEST_CASE("slot (line+arc closed wire) -> extrude", "[CadDocument]")
+{
+    const double PI = 3.14159265358979323846;
+    CadDocument doc;
+
+    // Centerline ends c0=(-10,0), c1=(10,0); half-width w=5 → stadium 30 x 10.
+    SketchEntity top;   // top line A0(-10,5) -> A1(10,5)
+    top.type = SketchEntity::Type::Line; top.p0 = Vec2d(-10, 5); top.p1 = Vec2d(10, 5);
+
+    SketchEntity cap1;  // right cap @c1=(10,0): A1(10,5) -> B1(10,-5) through (15,0)
+    cap1.type = SketchEntity::Type::Arc; cap1.center = Vec2d(10, 0); cap1.radius = 5;
+    cap1.p0 = Vec2d(10, 5); cap1.p1 = Vec2d(10, -5);
+    cap1.start_angle = PI / 2; cap1.end_angle = -PI / 2;   // mid angle 0 -> (15,0)
+
+    SketchEntity bot;   // bottom line B1(10,-5) -> B0(-10,-5)
+    bot.type = SketchEntity::Type::Line; bot.p0 = Vec2d(10, -5); bot.p1 = Vec2d(-10, -5);
+
+    SketchEntity cap0;  // left cap @c0=(-10,0): B0(-10,-5) -> A0(-10,5) through (-15,0)
+    cap0.type = SketchEntity::Type::Arc; cap0.center = Vec2d(-10, 0); cap0.radius = 5;
+    cap0.p0 = Vec2d(-10, -5); cap0.p1 = Vec2d(-10, 5);
+    cap0.start_angle = -PI / 2; cap0.end_angle = -3 * PI / 2; // mid angle -PI -> (-15,0)
+
+    int sk = doc.add_sketch_entities({top, cap1, bot, cap0}, SketchPlane::XY(), "Slot");
+    doc.add_extrude(sk, 4.0, false, BooleanMode::New, "Extrude1");
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.display_mesh.facets_count() > 0);
+    auto sz = doc.display_mesh.bounding_box().size();
+    REQUIRE(std::abs(sz.x() - 30.0) < 0.5);
+    REQUIRE(std::abs(sz.y() - 10.0) < 0.5);
+    REQUIRE(std::abs(sz.z() -  4.0) < 0.5);
+}
+
+// Onshape-style constraints on coexisting entities (Fase 4.2). The solver maps
+// each Line/Point entity endpoint to a solver variable, applies the entity
+// constraints, and writes the solved coordinates back into the entities.
+TEST_CASE("entity constraints: solve on SketchEntity endpoints", "[CadDocument]")
+{
+    using R = SketchPointRole;
+    using T = SketchConstraintType;
+
+    auto dir = [](const SketchEntity& e) { return Vec2d(e.p1 - e.p0); };
+
+    SECTION("perpendicular rotates line1 normal to a pinned line0") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Line, Vec2d(0,0), Vec2d(10,0)},   // line0 (pinned)
+            {SketchEntity::Type::Line, Vec2d(0,0), Vec2d(7,7)},    // line1 @45 deg
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+        auto& ec = doc.features[sk].entity_constraints;
+        ec.push_back({T::Fix,           0, -1, R::P0, R::P0, 0.0});
+        ec.push_back({T::Fix,           0, -1, R::P1, R::P0, 0.0});
+        ec.push_back({T::Perpendicular, 0,  1, R::P0, R::P0, 0.0});
+
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        // line0 stayed put.
+        REQUIRE(std::abs(e[0].p0.x() - 0.0)  < 1e-6);
+        REQUIRE(std::abs(e[0].p1.x() - 10.0) < 1e-6);
+        // line1 is now perpendicular to line0: directions dot to ~0.
+        const double d = dir(e[0]).dot(dir(e[1]));
+        REQUIRE(std::abs(d) < 1e-6);
+    }
+
+    // Driving length: the Dimension tool records a Distance between a line's own
+    // P0/P1 (committed via add_sketch_entities' constraints arg). Solving drives
+    // the line to that exact length.
+    SECTION("driving length: Distance(P0,P1) sets a line's length") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Line, Vec2d(0,0), Vec2d(10,0)},   // length 10
+        };
+        std::vector<SketchEntityConstraintDef> cons;
+        cons.push_back({T::Fix,      0, -1, R::P0, R::P0, 0.0});   // pin the start
+        cons.push_back({T::Distance, 0,  0, R::P0, R::P1, 25.0});  // length -> 25
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S", cons);
+        REQUIRE(doc.features[sk].entity_constraints.size() == 2);  // constraints stored
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        REQUIRE(std::abs((e[0].p1 - e[0].p0).norm() - 25.0) < 1e-6);
+    }
+
+    SECTION("parallel flattens line1 onto a pinned horizontal line0") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Line, Vec2d(0,0), Vec2d(10,0)},   // line0 (pinned)
+            {SketchEntity::Type::Line, Vec2d(0,5), Vec2d(7,9)},    // line1 tilted
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+        auto& ec = doc.features[sk].entity_constraints;
+        ec.push_back({T::Fix,      0, -1, R::P0, R::P0, 0.0});
+        ec.push_back({T::Fix,      0, -1, R::P1, R::P0, 0.0});
+        ec.push_back({T::Parallel, 0,  1, R::P0, R::P0, 0.0});
+
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        const Vec2d d0 = dir(e[0]), d1 = dir(e[1]);
+        const double cross = d0.x() * d1.y() - d0.y() * d1.x();
+        REQUIRE(std::abs(cross) < 1e-6);
+    }
+
+    SECTION("coincident merges a line endpoint onto another") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Line, Vec2d(0,0),  Vec2d(10,0)},   // line0
+            {SketchEntity::Type::Line, Vec2d(12,1), Vec2d(20,1)},   // line1
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+        auto& ec = doc.features[sk].entity_constraints;
+        ec.push_back({T::Coincident, 0, 1, R::P1, R::P0, 0.0});   // line0.end == line1.start
+
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        const Vec2d gap = Vec2d(e[0].p1 - e[1].p0);
+        REQUIRE(gap.norm() < 1e-6);
+    }
+
+    SECTION("horizontal levels a tilted line's endpoints") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Line, Vec2d(0,0), Vec2d(10,2)},   // tilted line
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+        auto& ec = doc.features[sk].entity_constraints;
+        ec.push_back({T::Horizontal, 0, 0, R::P0, R::P1, 0.0});   // p0.y == p1.y
+
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        REQUIRE(std::abs(e[0].p0.y() - e[0].p1.y()) < 1e-6);
+    }
+}
+
+TEST_CASE("entity constraints: arc/circle registration + concentric", "[CadDocument]")
+{
+    using R = SketchPointRole;
+    using T = SketchConstraintType;
+
+    SECTION("concentric centers coincide") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Circle, Vec2d(0,0), Vec2d(0,0), Vec2d(0,0), 5.0},   // circle0
+            {SketchEntity::Type::Circle, Vec2d(10,2), Vec2d(10,2), Vec2d(10,2), 3.0}, // circle1
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+        auto& ec = doc.features[sk].entity_constraints;
+        ec.push_back({T::Fix,        0, -1, R::Center, R::Center, 0.0});
+        ec.push_back({T::Concentric, 0,  1, R::Center, R::Center, 0.0});
+
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        REQUIRE((e[1].center - e[0].center).norm() < 1e-6);
+        REQUIRE(e[0].center.x() < 1e-6);
+        REQUIRE(e[0].center.y() < 1e-6);
+    }
+
+    SECTION("arc reflow keeps radius and angle consistent") {
+        CadDocument doc;
+        const double PI2 = M_PI / 2;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Arc, Vec2d(5,0), Vec2d(0,5), Vec2d(0,0), 5.0, 0.0, PI2},
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+        auto& ec = doc.features[sk].entity_constraints;
+        ec.push_back({T::Fix, 0, -1, R::Center, R::Center, 0.0});
+        ec.push_back({T::Fix, 0, -1, R::P0,     R::P0,     0.0});
+
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        REQUIRE(std::abs((e[0].p0 - e[0].center).norm() - 5.0) < 1e-6);
+        REQUIRE(std::abs(e[0].start_angle - 0.0) < 1e-6);
+        REQUIRE(std::abs(e[0].end_angle - PI2) < 1e-3);
+        REQUIRE(e[0].end_angle > e[0].start_angle);
+    }
+}
+
+TEST_CASE("entity constraints: radius/diameter dimensions", "[CadDocument]")
+{
+    using R = SketchPointRole;
+    using T = SketchConstraintType;
+
+    SECTION("circle radius dimension") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Circle, Vec2d(0,0), Vec2d(0,0), Vec2d(0,0), 5.0},
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+        auto& ec = doc.features[sk].entity_constraints;
+        ec.push_back({T::Fix,       0, -1, R::Center, R::Center, 0.0, -1, R::P0});
+        ec.push_back({T::Radius,    0, -1, R::Center, R::P0,     8.0, -1, R::P0});
+
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        REQUIRE(std::abs(e[0].radius - 8.0) < 1e-9);
+    }
+
+    SECTION("circle diameter dimension") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Circle, Vec2d(0,0), Vec2d(0,0), Vec2d(0,0), 5.0},
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+        auto& ec = doc.features[sk].entity_constraints;
+        ec.push_back({T::Fix,       0, -1, R::Center, R::Center, 0.0, -1, R::P0});
+        ec.push_back({T::Diameter,  0, -1, R::Center, R::P0,     20.0, -1, R::P0});
+
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        REQUIRE(std::abs(e[0].radius - 10.0) < 1e-9);
+    }
+
+    SECTION("arc radius rescales endpoints") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Arc, Vec2d(5,0), Vec2d(0,5), Vec2d(0,0), 5.0, 0.0, M_PI/2},
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+        auto& ec = doc.features[sk].entity_constraints;
+        ec.push_back({T::Fix,       0, -1, R::Center, R::Center, 0.0, -1, R::P0});
+        ec.push_back({T::Radius,    0, -1, R::Center, R::P0,     10.0, -1, R::P0});
+
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        REQUIRE(std::abs(e[0].radius - 10.0) < 1e-9);
+        REQUIRE((e[0].p0 - Vec2d(10,0)).norm() < 1e-6);
+        REQUIRE((e[0].p1 - Vec2d(0,10)).norm() < 1e-6);
+    }
+}
+
+// PointOnLine (Fase: persistent positioning). A point-like entity is held on a
+// line (value 0) or at perpendicular distance `value`. Drives e.g. a circle centre
+// onto a construction axis and, being a real constraint, keeps it there on re-solve.
+TEST_CASE("entity constraints: point-on-line positions a centre onto an axis", "[CadDocument]")
+{
+    using R = SketchPointRole;
+    using T = SketchConstraintType;
+
+    SECTION("circle centre snaps onto a pinned axis (value 0) and persists") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Line,   Vec2d(0,0), Vec2d(10,0)},                 // axis (X)
+            {SketchEntity::Type::Circle, Vec2d(5,7), Vec2d(5,7), Vec2d(5,7), 3.0}, // off-axis centre
+        };
+        std::vector<SketchEntityConstraintDef> cons;
+        cons.push_back({T::Fix,         0, -1, R::P0,     R::P0, 0.0});   // pin axis endpoints
+        cons.push_back({T::Fix,         0, -1, R::P1,     R::P1, 0.0});
+        cons.push_back({T::PointOnLine, 1,  0, R::Center, R::P0, 0.0});   // centre onto axis
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S", cons);
+        REQUIRE(doc.solve_sketch_feature(sk));
+        REQUIRE(std::abs(doc.features[sk].entities[1].center.y()) < 1e-6);   // on the axis
+        // Re-solving keeps it on the axis (a driving constraint, not a one-shot move).
+        REQUIRE(doc.solve_sketch_feature(sk));
+        REQUIRE(std::abs(doc.features[sk].entities[1].center.y()) < 1e-6);
+    }
+
+    SECTION("non-zero perpendicular distance via the free solve_sketch_entities") {
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Line,  Vec2d(0,0), Vec2d(10,0)},
+            {SketchEntity::Type::Point, Vec2d(4,9)},                       // point above the axis
+        };
+        std::vector<SketchEntityConstraintDef> cons;
+        cons.push_back({T::Fix,         0, -1, R::P0, R::P0, 0.0});
+        cons.push_back({T::Fix,         0, -1, R::P1, R::P1, 0.0});
+        cons.push_back({T::PointOnLine, 1,  0, R::P0, R::P0, 2.0});        // hold at distance 2
+        REQUIRE(solve_sketch_entities(ents, cons));
+        REQUIRE(std::abs(std::abs(ents[1].p0.y()) - 2.0) < 1e-6);         // 2 mm off the axis
+    }
+}
+
+// The "tangent line to circle" SECTION used to abort the whole Catch2 process inside the
+// vendored solver (slvs/dsc.h FindById, "Cannot find handle"), taking every later test with
+// it, and was quarantined for it. Fixed in SketchSolver: a full circle can no longer be handed
+// to SLVS_C_ARC_LINE_TANGENT, which dereferences arc endpoints a circle does not have. See
+// tkz.
+TEST_CASE("entity constraints: tangent/midpoint/symmetric/angle", "[CadDocument][sketch]")
+{
+    using R = SketchPointRole;
+    using T = SketchConstraintType;
+
+    auto dir = [](const SketchEntity& e) { return Vec2d(e.p1 - e.p0); };
+
+    SECTION("angle 90 between two lines") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Line, Vec2d(0,0), Vec2d(10,0)},    // line0
+            {SketchEntity::Type::Line, Vec2d(0,0), Vec2d(5,5)},     // line1
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+        auto& ec = doc.features[sk].entity_constraints;
+        ec.push_back({T::Fix,  0,-1, R::P0,R::P0, 0.0,  -1,R::P0});
+        ec.push_back({T::Fix,  0,-1, R::P1,R::P0, 0.0,  -1,R::P0});
+        ec.push_back({T::Fix,  1,-1, R::P0,R::P0, 0.0,  -1,R::P0});
+        ec.push_back({T::Angle,0, 1, R::P0,R::P0, M_PI/2,-1,R::P0});
+
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        const Vec2d d0 = dir(e[0]).normalized();
+        const Vec2d d1 = dir(e[1]).normalized();
+        REQUIRE(std::abs(d0.dot(d1)) < 1e-3);
+    }
+
+    SECTION("midpoint of a line") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Line,  Vec2d(0,0), Vec2d(10,0)},  // line0
+            {SketchEntity::Type::Point, Vec2d(3,9)},                // point p
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+        auto& ec = doc.features[sk].entity_constraints;
+        ec.push_back({T::Fix,     0,-1, R::P0,R::P0, 0.0,-1,R::P0});
+        ec.push_back({T::Fix,     0,-1, R::P1,R::P0, 0.0,-1,R::P0});
+        ec.push_back({T::Midpoint,1, 0, R::P0,R::P0, 0.0,-1,R::P0});
+
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        REQUIRE((e[1].p0 - Vec2d(5,0)).norm() < 1e-3);
+    }
+
+    SECTION("tangent line to circle") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Circle, Vec2d(0,0), Vec2d(0,0), Vec2d(0,0), 5.0},   // circle0 r=5
+            {SketchEntity::Type::Line,   Vec2d(-10,8), Vec2d(10,8)},                  // line1 y=8
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+        auto& ec = doc.features[sk].entity_constraints;
+        ec.push_back({T::Fix,        0,-1, R::Center,R::Center,  0.0,-1,R::P0});
+        ec.push_back({T::LockX,      1,-1, R::P0,    R::P0,   -10.0,-1,R::P0});
+        ec.push_back({T::LockX,      1,-1, R::P1,    R::P0,    10.0,-1,R::P0});
+        ec.push_back({T::Horizontal, 1, 1, R::P0,    R::P1,     0.0,-1,R::P0});
+        ec.push_back({T::Tangent,    0, 1, R::Center,R::P0,     0.0,-1,R::P0});
+
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        REQUIRE(std::abs(std::abs(e[1].p0.y()) - 5.0) < 1e-3);
+    }
+
+    SECTION("symmetric across a line") {
+        CadDocument doc;
+        std::vector<SketchEntity> ents = {
+            {SketchEntity::Type::Point, Vec2d(2,3)},            // pointA
+            {SketchEntity::Type::Point, Vec2d(-1,1)},           // pointB
+            {SketchEntity::Type::Line,  Vec2d(0,0), Vec2d(0,10)}// axis (Y axis)
+        };
+        int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+        auto& ec = doc.features[sk].entity_constraints;
+        ec.push_back({T::Fix,       0,-1, R::P0,R::P0, 0.0,-1,R::P0});
+        ec.push_back({T::Fix,       2,-1, R::P0,R::P0, 0.0,-1,R::P0});
+        ec.push_back({T::Fix,       2,-1, R::P1,R::P0, 0.0,-1,R::P0});
+        ec.push_back({T::Symmetric, 0, 1, R::P0,R::P0, 0.0, 2,R::P0});
+
+        REQUIRE(doc.solve_sketch_feature(sk));
+        const auto& e = doc.features[sk].entities;
+        REQUIRE((e[1].p0 - Vec2d(-2,3)).norm() < 1e-3);
+    }
+}
+
+TEST_CASE("imported text glyphs all extrude without failing (charset sweep)", "[CadDocument]")
+{
+    std::string font = resources_dir().empty()
+        ? std::string("resources/fonts/HarmonyOS_Sans_SC_Regular.ttf")
+        : resources_dir() + "/fonts/HarmonyOS_Sans_SC_Regular.ttf";
+    {
+        std::ifstream probe(font);
+        if (!probe.good()) {
+            SUCCEED("bundled font not reachable in this environment; covered live on :10");
+            return;
+        }
+    }
+
+    const std::string charset =
+        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+        "abcdefghijklmnopqrstuvwxyz"
+        "0123456789"
+        "@#$%&*()[]{}<>?/+-=.,;:!"
+        "\xC3\xA0\xC3\xA8\xC3\xA9\xC3\xAC\xC3\xB2\xC3\xB9";   // à è é ì ò ù (UTF-8)
+
+    std::string failures;
+    for (char c : charset) {
+        ImportRegions regs = text_to_regions(std::string(1, c), 12.0, font);
+        if (regs.empty()) continue;
+        CadDocument doc;
+        CadFeature sk;
+        sk.type  = CadFeatureType::Sketch;
+        sk.plane = SketchPlane::XY();
+        sk.imported_regions = regs;
+        doc.features.push_back(sk);
+        CadFeature ex;
+        ex.type       = CadFeatureType::Extrude;
+        ex.sketch_ref = 0;
+        ex.distance   = 3;
+        doc.features.push_back(ex);
+        if (!doc.recompute() || !doc.error.empty())
+            failures += c;
+    }
+    INFO("glyphs that failed to extrude: [" << failures << "]");
+    CHECK(failures.empty());
+
+    // A realistic multi-glyph word must extrude too.
+    {
+        ImportRegions regs = text_to_regions("Snapmaker", 12.0, font);
+        REQUIRE_FALSE(regs.empty());
+        CadDocument doc;
+        CadFeature sk;
+        sk.type  = CadFeatureType::Sketch;
+        sk.plane = SketchPlane::XY();
+        sk.imported_regions = regs;
+        doc.features.push_back(sk);
+        CadFeature ex;
+        ex.type       = CadFeatureType::Extrude;
+        ex.sketch_ref = 0;
+        ex.distance   = 3;
+        doc.features.push_back(ex);
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE(doc.display_mesh.facets_count() > 0);
+    }
+}
+
+TEST_CASE("imported regions: faces-with-holes extrude (Text/SVG carrier)", "[CadDocument]")
+{
+    SECTION("square with a square hole -> tube volume") {
+        CadDocument doc;
+
+        CadFeature sk;
+        sk.type  = CadFeatureType::Sketch;
+        sk.name  = "art";
+        sk.plane = SketchPlane::XY();
+        // One region: outer 20x20 (CCW) + inner 8x8 hole (CW).
+        sk.imported_regions = {{
+            {Vec2d(-10,-10), Vec2d(10,-10), Vec2d(10,10), Vec2d(-10,10)},   // outer
+            {Vec2d(-4,-4),   Vec2d(-4,4),   Vec2d(4,4),   Vec2d(4,-4)},     // hole (reversed winding)
+        }};
+        doc.features.push_back(sk);
+
+        CadFeature ex;
+        ex.type       = CadFeatureType::Extrude;
+        ex.name       = "extrude";
+        ex.sketch_ref = 0;
+        ex.distance   = 5;
+        ex.mode       = BooleanMode::New;
+        doc.features.push_back(ex);
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE(doc.display_mesh.facets_count() > 0);
+
+        // (20*20 - 8*8) * 5 = 1680 mm^3
+        REQUIRE_THAT(double(doc.display_mesh.volume()), Catch::Matchers::WithinRel(1680.0, 0.02));
+
+        auto sz = doc.display_mesh.bounding_box().size();
+        REQUIRE(std::abs(sz.x() - 20.0) < 0.5);
+        REQUIRE(std::abs(sz.y() - 20.0) < 0.5);
+        REQUIRE(std::abs(sz.z() -  5.0) < 0.5);
+    }
+
+    SECTION("inverted winding (CW outer, CCW hole) keeps body solid, counter empty") {
+        // Real glyph contours (P, e, o, 8) arrive with outer CW + hole CCW. The
+        // extrude must NORMALISE winding so the letter BODY is solid and the
+        // counter is the hole — not the inverse (the reported bug). 20x20 outer
+        // CW with an 8x8 hole CCW -> volume (400-64)*5 = 1680, NOT the inverse.
+        CadDocument doc;
+        CadFeature sk;
+        sk.type  = CadFeatureType::Sketch;
+        sk.plane = SketchPlane::XY();
+        sk.imported_regions = {{
+            {Vec2d(-10,-10), Vec2d(-10,10), Vec2d(10,10), Vec2d(10,-10)},  // outer CW
+            {Vec2d(-4,-4),   Vec2d(4,-4),   Vec2d(4,4),   Vec2d(-4,4)},    // hole CCW
+        }};
+        doc.features.push_back(sk);
+
+        CadFeature ex;
+        ex.type       = CadFeatureType::Extrude;
+        ex.sketch_ref = 0;
+        ex.distance   = 5;
+        doc.features.push_back(ex);
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE_THAT(double(doc.display_mesh.volume()), Catch::Matchers::WithinRel(1680.0, 0.02));
+    }
+
+    SECTION("degenerate / duplicate points are sanitised, not fatal") {
+        // FreeType/SVG flattening can emit repeated points; the extrude must
+        // survive them (previously to_occt_wire threw and failed the whole op).
+        CadDocument doc;
+        CadFeature sk;
+        sk.type  = CadFeatureType::Sketch;
+        sk.plane = SketchPlane::XY();
+        sk.imported_regions = {{
+            // 20x20 outer square with consecutive dups + an explicit closing dup
+            {Vec2d(-10,-10), Vec2d(-10,-10), Vec2d(10,-10), Vec2d(10,-10),
+             Vec2d(10,10),   Vec2d(-10,10),  Vec2d(-10,-10)},
+        }};
+        doc.features.push_back(sk);
+
+        CadFeature ex;
+        ex.type       = CadFeatureType::Extrude;
+        ex.sketch_ref = 0;
+        ex.distance   = 5;
+        doc.features.push_back(ex);
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE_THAT(double(doc.display_mesh.volume()), Catch::Matchers::WithinRel(2000.0, 0.02));
+    }
+
+    SECTION("a degenerate region is skipped, valid ones still extrude") {
+        CadDocument doc;
+        CadFeature sk;
+        sk.type  = CadFeatureType::Sketch;
+        sk.plane = SketchPlane::XY();
+        sk.imported_regions = {
+            { {Vec2d(0,0), Vec2d(0,0), Vec2d(0,0)} },              // collapses to nothing
+            { {Vec2d(0,0), Vec2d(5,0), Vec2d(5,5), Vec2d(0,5)} },  // valid 5x5
+        };
+        doc.features.push_back(sk);
+
+        CadFeature ex;
+        ex.type       = CadFeatureType::Extrude;
+        ex.sketch_ref = 0;
+        ex.distance   = 4;
+        doc.features.push_back(ex);
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE_THAT(double(doc.display_mesh.volume()), Catch::Matchers::WithinRel(100.0, 0.02));
+    }
+
+    SECTION("two disjoint regions form one shape") {
+        CadDocument doc;
+
+        CadFeature sk;
+        sk.type  = CadFeatureType::Sketch;
+        sk.plane = SketchPlane::XY();
+        sk.imported_regions = {
+            {{Vec2d(0,0),  Vec2d(5,0),  Vec2d(5,5),  Vec2d(0,5)}},
+            {{Vec2d(10,0), Vec2d(15,0), Vec2d(15,5), Vec2d(10,5)}},
+        };
+        doc.features.push_back(sk);
+
+        CadFeature ex;
+        ex.type       = CadFeatureType::Extrude;
+        ex.sketch_ref = 0;
+        ex.distance   = 3;
+        doc.features.push_back(ex);
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        // 2 * (5*5*3) = 150 mm^3
+        REQUIRE_THAT(double(doc.display_mesh.volume()), Catch::Matchers::WithinRel(150.0, 0.02));
+    }
+}
+
+TEST_CASE("tessellate tracks per-triangle face id", "[CadDocument]")
+{
+    TopoDS_Shape box = BRepPrimAPI_MakeBox(10., 10., 10.).Shape();
+    std::vector<int> tf;
+    TriangleMesh m = SketchEngine::tessellate(box, tf);
+
+    REQUIRE(tf.size() == m.its.indices.size());
+    REQUIRE(!tf.empty());
+
+    std::set<int> distinct(tf.begin(), tf.end());
+    REQUIRE(distinct.size() == 6);
+    REQUIRE(*distinct.begin() == 0);
+    REQUIRE(*distinct.rbegin() == 5);
+
+    for (int fid : distinct) {
+        int count = 0;
+        for (int x : tf) if (x == fid) ++count;
+        REQUIRE(count >= 2);
+    }
+
+    REQUIRE(m.its.indices.size() >= 12);
+}
+
+TEST_CASE("extrude two-sided + through-all + intersect", "[CadDocument]")
+{
+    using namespace Slic3r;
+    SketchPlane xy = SketchPlane::XY();
+    // a 10x10 square wire centred on origin
+    SketchProfile sp;
+    sp.points = { Vec2d(-5,-5), Vec2d(5,-5), Vec2d(5,5), Vec2d(-5,5) };
+    sp.closed = true;
+    TopoDS_Wire w = sp.to_occt_wire(xy);
+
+    SECTION("two-sided height = up+down") {
+        TopoDS_Shape s = SketchEngine::make_extrude_two_sided(w, xy, 10.0, 4.0);
+        REQUIRE_FALSE(s.IsNull());
+        Bnd_Box bb; BRepBndLib::Add(s, bb);
+        double xmin,ymin,zmin,xmax,ymax,zmax; bb.Get(xmin,ymin,zmin,xmax,ymax,zmax);
+        REQUIRE_THAT(zmax - zmin, Catch::Matchers::WithinAbs(14.0, 0.05));   // 10 up + 4 down
+        REQUIRE_THAT(zmax, Catch::Matchers::WithinAbs(10.0, 0.05));
+        REQUIRE_THAT(zmin, Catch::Matchers::WithinAbs(-4.0, 0.05));
+    }
+}
+
+TEST_CASE("extrude taper + up-to-face distance", "[CadDocument]")
+{
+    using namespace Slic3r;
+    SketchPlane xy = SketchPlane::XY();
+    SketchProfile sp; sp.points = { Vec2d(-5,-5),Vec2d(5,-5),Vec2d(5,5),Vec2d(-5,5) }; sp.closed = true;
+    TopoDS_Wire w = sp.to_occt_wire(xy);
+
+    SECTION("taper widens the top") {
+        TopoDS_Shape s = SketchEngine::make_extrude_taper(w, xy, 10.0, 15.0);
+        REQUIRE_FALSE(s.IsNull());
+        Bnd_Box bb; BRepBndLib::Add(s, bb);
+        double x0,y0,z0,x1,y1,z1; bb.Get(x0,y0,z0,x1,y1,z1);
+        REQUIRE_THAT(z1 - z0, Catch::Matchers::WithinAbs(10.0, 0.1));
+        REQUIRE((x1 - x0) > 12.0);
+    }
+    SECTION("extreme taper falls back to a straight prism") {
+        TopoDS_Shape s = SketchEngine::make_extrude_taper(w, xy, 10.0, 89.0);
+        REQUIRE_FALSE(s.IsNull());
+        Bnd_Box bb; BRepBndLib::Add(s, bb);
+        double x0,y0,z0,x1,y1,z1; bb.Get(x0,y0,z0,x1,y1,z1);
+        REQUIRE_THAT(x1 - x0, Catch::Matchers::WithinAbs(10.0, 0.1));
+    }
+}
+
+// Was [known-broken] until the numbers were actually measured (kzy). The geometry
+// was right all along; the TEST compared against the wrong reference. An internal thread bores
+// at the MINOR radius (radius - depth) and then carves the groove out to radius + depth, so a
+// tapped hole keeps the crests between turns and therefore holds MORE material than a plain
+// clearance hole at the nominal radius. Asserting the thread removes more than a plain Ø12 bore
+// asked for something no real tapped hole does. Measured on this fixture: plain Ø12 bore removes
+// 2261 mm3, the thread removes 2157 = 1571 (minor bore) + 586 (groove). Exact BRepGProp volume
+// agrees with the tessellated volume to 2.5 mm3, so this was never a meshing artefact either.
+// The tap-drill bore is the honest reference: against it, the groove's 586 mm3 is the thing worth
+// asserting, because that is what "the thread actually cuts" means.
+TEST_CASE("internal thread cuts a visible groove into the bore wall", "[CadDocument][thread]")
+{
+    using namespace Slic3r;
+    SketchPlane xy = SketchPlane::XY();
+
+    // 40x40x20 box centred on the origin, extruded +Z.
+    auto make_box = [&](CadDocument& doc) {
+        CadFeature sk;
+        sk.type  = CadFeatureType::Sketch;
+        sk.plane = xy;
+        sk.imported_regions = {{
+            {Vec2d(-20,-20), Vec2d(20,-20), Vec2d(20,20), Vec2d(-20,20)},
+        }};
+        doc.features.push_back(sk);
+        CadFeature ex;
+        ex.type       = CadFeatureType::Extrude;
+        ex.sketch_ref = 0;
+        ex.distance   = 20;
+        doc.features.push_back(ex);
+    };
+
+    // Reference: box bored at the MINOR diameter — the tap drill the thread starts from.
+    // Ø10 = 2 * (radius 6 - depth 1), matching what apply_thread cuts before the groove.
+    CadDocument hole_doc;
+    make_box(hole_doc);
+    hole_doc.add_hole(10.0, 20.0, true, 0.0, 0.0, xy, "Hole");
+    REQUIRE(hole_doc.recompute());
+    REQUIRE(hole_doc.error.empty());
+    const double v_hole = double(hole_doc.display_mesh.volume());
+
+    // Threaded: same box, internal thread of radius 6 (the bore radius).
+    CadDocument thr_doc;
+    make_box(thr_doc);
+    thr_doc.add_thread(6.0, 3.0, 20.0, 1.0, /*internal=*/true, 0.0, 0.0, xy, "Thread");
+    REQUIRE(thr_doc.recompute());
+    REQUIRE(thr_doc.error.empty());
+    const double v_thread = double(thr_doc.display_mesh.volume());
+
+    // The groove must carve material out of the wall BEYOND the tap-drill bore, which is what
+    // makes the thread visible. A profile that only swept already-empty bore space would give
+    // v_thread ~= v_hole; the real one removes several hundred mm3 more.
+    REQUIRE(v_thread > 0.0);
+    REQUIRE(v_thread < v_hole);
+    REQUIRE((v_hole - v_thread) > 20.0);
+}
+
+TEST_CASE("revolve builds a solid of revolution about an in-plane axis", "[CadDocument]")
+{
+    using namespace Slic3r;
+    SketchPlane xy = SketchPlane::XY();
+
+    // Rectangle profile (10 wide x 10 tall, area 100) offset to +v so it lies entirely
+    // on one side of the X axis; revolved 360deg about X -> a rectangular-section ring.
+    // Pappus: V = 2*pi*R*A = 2*pi*15*100 = ~9424.78 mm^3 (tessellation slightly under).
+    auto make_rev_doc = [&](double angle, int axis, double u0, double v0) {
+        auto doc = std::make_unique<CadDocument>();
+        CadFeature sk;
+        sk.type = CadFeatureType::Sketch;
+        sk.plane = xy;
+        sk.profile.points = { Vec2d(u0 - 5, v0 - 5), Vec2d(u0 + 5, v0 - 5),
+                              Vec2d(u0 + 5, v0 + 5), Vec2d(u0 - 5, v0 + 5) };
+        sk.profile.closed = true;
+        doc->features.push_back(sk);
+        doc->add_revolve(0, angle, axis, false, BooleanMode::New, "Rev");
+        return doc;
+    };
+
+    auto full = make_rev_doc(360.0, /*axis=X*/0, 0.0, 15.0);
+    REQUIRE(full->recompute());
+    REQUIRE(full->error.empty());
+    const double v_full = double(full->display_mesh.volume());
+    REQUIRE(v_full > 0.0);
+    REQUIRE(v_full == Approx(9424.78).epsilon(0.05));
+
+    // A 180deg sweep removes exactly half the material.
+    auto half = make_rev_doc(180.0, 0, 0.0, 15.0);
+    REQUIRE(half->recompute());
+    REQUIRE(half->error.empty());
+    const double v_half = double(half->display_mesh.volume());
+    REQUIRE(v_half > 0.0);
+    REQUIRE(v_full == Approx(2.0 * v_half).epsilon(0.05));
+
+    // Axis = plane Y: profile offset to +u (one side of the Y axis) gives the same ring.
+    auto ydoc = make_rev_doc(360.0, /*axis=Y*/1, 15.0, 0.0);
+    REQUIRE(ydoc->recompute());
+    REQUIRE(ydoc->error.empty());
+    REQUIRE(double(ydoc->display_mesh.volume()) == Approx(9424.78).epsilon(0.05));
+}
+
+TEST_CASE("sweep builds a solid by sweeping a profile along a path", "[CadDocument]")
+{
+    using namespace Slic3r;
+    CadDocument doc;
+
+    // Profile: circle r=5 on the XY plane at the origin (area = 25*pi).
+    SketchEntity circ;
+    circ.type   = SketchEntity::Type::Circle;
+    circ.center = Vec2d(0, 0);
+    circ.radius = 5.0;
+    const int prof = doc.add_sketch_entities({circ}, SketchPlane::XY(), "Profile");
+
+    // Path: a straight line on the XZ plane from 2D (0,0)->(0,100), i.e. world
+    // (0,0,0)->(0,0,100): the spine starts on the profile plane and runs +Z by 100.
+    SketchEntity line;
+    line.type = SketchEntity::Type::Line;
+    line.p0   = Vec2d(0, 0);
+    line.p1   = Vec2d(0, 100);
+    const int path = doc.add_sketch_entities({line}, SketchPlane::XZ(), "Path");
+
+    doc.add_sweep(prof, path, BooleanMode::New, "Sweep1");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Straight sweep of a circle == a cylinder: V = pi*r^2*h = pi*25*100 = ~7853.98.
+    const double v = double(doc.display_mesh.volume());
+    REQUIRE(v > 0.0);
+    REQUIRE_THAT(v, Catch::Matchers::WithinRel(M_PI * 25.0 * 100.0, 0.03));
+
+    // A valid path sketch is mandatory: a -1 path ref must error cleanly, not crash.
+    CadDocument bad;
+    const int p2 = bad.add_sketch_entities({circ}, SketchPlane::XY(), "Profile");
+    bad.add_sweep(p2, -1, BooleanMode::New, "BadSweep");
+    REQUIRE_FALSE(bad.recompute());
+}
+
+TEST_CASE("pattern replicates a body linearly and circularly", "[CadDocument]")
+{
+    using namespace Slic3r;
+
+    // Linear: a 10x10x10 box (V=1000) repeated 3x at 20mm spacing along plane X.
+    // 20 > 10 so the copies are disjoint -> total V = 3*1000 = 3000.
+    {
+        CadDocument doc;
+        int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                                10, 10, 5, "Box");
+        doc.add_extrude(sk, 10.0, false, BooleanMode::New, "E");
+        doc.add_pattern(/*circular=*/false, /*count=*/3, /*spacing=*/20,
+                        /*dir=*/0, /*angle=*/0, /*target=*/-1, "LinearPattern");
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        const double v = double(doc.display_mesh.volume());
+        REQUIRE_THAT(v, Catch::Matchers::WithinRel(3000.0, 0.02));
+    }
+
+    // Circular: a 10x10x10 box centred at x=50 (radius 50 from the Z axis), 4 copies
+    // over 360deg about the plane normal through the origin -> a ring of 4 disjoint
+    // boxes -> V = 4*1000 = 4000.
+    {
+        CadDocument doc;
+        SketchProfile sp;
+        sp.points.push_back(Vec2d(45, -5));
+        sp.points.push_back(Vec2d(55, -5));
+        sp.points.push_back(Vec2d(55,  5));
+        sp.points.push_back(Vec2d(45,  5));
+        sp.closed = true;
+        int sk = doc.add_sketch_profile(sp, SketchPlane::XY(), "OffsetBox");
+        doc.add_extrude(sk, 10.0, false, BooleanMode::New, "E");
+        doc.add_pattern(/*circular=*/true, /*count=*/4, /*spacing=*/0,
+                        /*dir=*/0, /*angle=*/360, /*target=*/-1, "CircularPattern");
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        const double v = double(doc.display_mesh.volume());
+        REQUIRE_THAT(v, Catch::Matchers::WithinRel(4000.0, 0.02));
+    }
+
+    // A pattern with no body must error cleanly, not crash.
+    {
+        CadDocument bad;
+        bad.add_pattern(false, 3, 20, 0, 0, -1, "NoBody");
+        REQUIRE_FALSE(bad.recompute());
+    }
+}
+
+TEST_CASE("pattern-on-curve: copies land on a line and bbox spans the curve length", "[CadDocument][pattern]")
+{
+    using Catch::Matchers::WithinAbs;
+    using Catch::Matchers::WithinRel;
+    using namespace Slic3r;
+
+    CadDocument doc;
+
+    // Seed body: 4x4x4 box at the origin via sketch+extrude.
+    int s0 = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 4, 4, 0, "Seed");
+    doc.add_extrude(s0, 4.0, false, BooleanMode::New, "E");
+
+    // Guide sketch: one Line entity from (0,0) to (30,0) on XY.
+    std::vector<SketchEntity> guide = {
+        {SketchEntity::Type::Line, Vec2d(0, 0), Vec2d(30, 0)},
+    };
+    int gs = doc.add_sketch_entities(guide, SketchPlane::XY(), "Guide");
+
+    doc.add_pattern_on_curve(4, gs, 0, 0, "OnCurve");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.display_mesh.facets_count() > 0);
+
+    auto bb = doc.display_mesh.bounding_box();
+    double x_extent = bb.max.x() - bb.min.x();
+    // 4 copies: at x=0, x=10, x=20, x=30. The seed is a 4x4 box centred at origin,
+    // so the overall X span is from -2 to 32 = 34 mm.
+    REQUIRE_THAT(x_extent, WithinAbs(34.0, 2.0));
+}
+
+TEST_CASE("pattern-on-curve: bad refs are safe", "[CadDocument][pattern]")
+{
+    using namespace Slic3r;
+
+    CadDocument doc;
+    int s0 = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 4, 4, 0, "Seed");
+    doc.add_extrude(s0, 4.0, false, BooleanMode::New, "E");
+
+    // Bad sketch ref -> error.
+    doc.add_pattern_on_curve(3, 999, 0, 0, "Bad");
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_FALSE(doc.error.empty());
+    REQUIRE(doc.error.find("pattern") != std::string::npos);
+}
+
+TEST_CASE("pattern-on-curve: round-trip through serialize/deserialize", "[CadDocument][pattern]")
+{
+    using Catch::Matchers::WithinRel;
+    using namespace Slic3r;
+
+    CadDocument doc;
+    int s0 = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 4, 4, 0, "Seed");
+    doc.add_extrude(s0, 4.0, false, BooleanMode::New, "E");
+
+    std::vector<SketchEntity> guide = {
+        {SketchEntity::Type::Line, Vec2d(0, 0), Vec2d(30, 0)},
+    };
+    int gs = doc.add_sketch_entities(guide, SketchPlane::XY(), "Guide");
+
+    doc.add_pattern_on_curve(4, gs, 0, 0, "OnCurve");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    auto orig_bb = doc.display_mesh.bounding_box();
+    size_t orig_n = doc.bodies.size();
+
+    std::string blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument fresh;
+    REQUIRE(fresh.deserialize_recipe(blob));
+    REQUIRE(fresh.recompute());
+    REQUIRE(fresh.error.empty());
+    REQUIRE(fresh.bodies.size() == orig_n);
+
+    auto fresh_bb = fresh.display_mesh.bounding_box();
+    REQUIRE_THAT(orig_bb.min.x(), WithinRel(fresh_bb.min.x(), 1e-6));
+    REQUIRE_THAT(orig_bb.max.x(), WithinRel(fresh_bb.max.x(), 1e-6));
+
+    // Verify the deserialized field values.
+    bool found = false;
+    for (const auto& f : fresh.features) {
+        if (f.name == "OnCurve") {
+            REQUIRE(f.pattern_curve_sketch == gs);
+            REQUIRE(f.pattern_curve_entity == 0);
+            found = true;
+            break;
+        }
+    }
+    REQUIRE(found);
+}
+
+TEST_CASE("thread standards table carries correct ISO/UTS measures", "[CadDocument]")
+{
+    using namespace Slic3r;
+
+    // Table is non-empty and every entry is self-consistent.
+    const auto& table = thread_standards();
+    REQUIRE(table.size() > 40);
+    for (const ThreadSpec& s : table) {
+        REQUIRE(s.major_diameter_mm > 0.0);
+        REQUIRE(s.pitch_mm > 0.0);
+        REQUIRE(s.minor_diameter_mm() < s.major_diameter_mm);
+        REQUIRE(s.minor_diameter_mm() > 0.0);
+        // 60deg V cut depth = 0.6134 * pitch.
+        REQUIRE(s.thread_depth_mm() == Approx(0.6134 * s.pitch_mm));
+    }
+
+    // ISO metric coarse: known nominal/pitch pairs.
+    const ThreadSpec* m6 = find_thread_standard("M6");
+    REQUIRE(m6 != nullptr);
+    REQUIRE(m6->major_diameter_mm == Approx(6.0));
+    REQUIRE(m6->pitch_mm == Approx(1.0));
+    REQUIRE(m6->series == ThreadSpec::Series::MetricCoarse);
+    REQUIRE_FALSE(m6->imperial());
+    REQUIRE(m6->thread_depth_mm() == Approx(0.6134));
+    // Tapped minor (tap-drill) diameter D - 1.0825*P = 6 - 1.0825 = 4.9175.
+    REQUIRE(m6->minor_diameter_mm() == Approx(4.9175));
+
+    const ThreadSpec* m3 = find_thread_standard("M3");
+    REQUIRE(m3 != nullptr);
+    REQUIRE(m3->pitch_mm == Approx(0.5));
+
+    // Imperial UNC: 1/4-20 -> 0.25in major, pitch = 25.4/20 = 1.27 mm.
+    const ThreadSpec* q = find_thread_standard("1/4-20 UNC");
+    REQUIRE(q != nullptr);
+    REQUIRE(q->major_diameter_mm == Approx(6.35));
+    REQUIRE(q->pitch_mm == Approx(1.27));
+    REQUIRE(q->series == ThreadSpec::Series::UNC);
+    REQUIRE(q->imperial());
+
+    // Imperial UNF fine variant has a finer pitch than its UNC sibling.
+    const ThreadSpec* qf = find_thread_standard("1/4-28 UNF");
+    REQUIRE(qf != nullptr);
+    REQUIRE(qf->major_diameter_mm == Approx(6.35));
+    REQUIRE(qf->pitch_mm == Approx(25.4 / 28.0));
+    REQUIRE(qf->pitch_mm < q->pitch_mm);
+
+    // Unknown designation -> nullptr.
+    REQUIRE(find_thread_standard("M7.3 bogus") == nullptr);
+}
+
+TEST_CASE("datum plane: offset + tilt resolution and sketching on it", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+    using Catch::Matchers::WithinAbs;
+
+    // Parallel offset plane 30 mm above XY (normal +Z, origin at z=30).
+    CadDocument doc;
+    int p0 = doc.add_plane(0 /*XY*/, 30.0, 0.0, 0, "Plane1");
+    REQUIRE(p0 == 0);
+
+    auto planes = doc.resolve_datum_planes();
+    REQUIRE(planes.size() == 1);
+    REQUIRE(planes[0].first == "Plane1");
+    CHECK_THAT(planes[0].second.origin.z(), WithinAbs(30.0, 1e-9));
+    CHECK_THAT(planes[0].second.normal.z(), WithinAbs(1.0, 1e-9));
+
+    // A second datum plane tilted 90 deg about the base (XY) X axis: its normal
+    // rotates from +Z toward -Y (Rodrigues about +X: +Z -> -Y).
+    doc.add_plane(0 /*XY*/, 0.0, 90.0, 0 /*about X*/, "Plane2");
+    planes = doc.resolve_datum_planes();
+    REQUIRE(planes.size() == 2);
+    CHECK_THAT(planes[1].second.normal.y(), WithinAbs(-1.0, 1e-9));
+    CHECK_THAT(planes[1].second.normal.z(), WithinAbs(0.0, 1e-9));
+
+    // Sketch a 10x10 square ON Plane1 and extrude 4 mm: the solid must sit in z=[30,34].
+    SketchPlane sp = planes[0].second;
+    SketchProfile prof;
+    prof.points = {{-5,-5},{5,-5},{5,5},{-5,5}};
+    prof.closed = true;
+    int sk = doc.add_sketch_profile(prof, sp, "S");
+    doc.add_extrude(sk, 4.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+
+    Bnd_Box bb;
+    BRepBndLib::Add(doc.body, bb);
+    double xmin,ymin,zmin,xmax,ymax,zmax;
+    bb.Get(xmin,ymin,zmin,xmax,ymax,zmax);
+    CHECK_THAT(zmin, WithinAbs(30.0, 1e-6));
+    CHECK_THAT(zmax, WithinAbs(34.0, 1e-6));
+    CHECK_THAT(double(doc.display_mesh.volume()), WithinRel(400.0, 0.02));
+
+    // A datum-plane-only document has no solid, and that is a benign SUCCESS, not a benign
+    // failure. It used to return false, and "benign failure" is exactly the phrasing that hid
+    // mtav: two callers read the false as "unusable document" and threw the design
+    // away — the 3MF recipe was never written, and a project that had one was refused on load.
+    CadDocument only_plane;
+    only_plane.add_plane(0, 10.0, 0.0, 0, "P");
+    REQUIRE(only_plane.recompute());
+    REQUIRE(only_plane.error.empty());
+    REQUIRE(only_plane.bodies.empty());
+}
+
+TEST_CASE("loft builds a solid skinning two profiles on parallel planes", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    // Bottom 20x20 square on XY.
+    SketchProfile bot;
+    bot.points = {{-10,-10},{10,-10},{10,10},{-10,10}};
+    bot.closed = true;
+    int s0 = doc.add_sketch_profile(bot, SketchPlane::XY(), "Bottom");
+
+    // Top 10x10 square on a datum plane 20 mm above XY (exercises datum -> loft).
+    doc.add_plane(0 /*XY*/, 20.0, 0.0, 0, "Plane1");
+    SketchPlane top = doc.resolve_datum_planes()[0].second;
+    SketchProfile tp;
+    tp.points = {{-5,-5},{5,-5},{5,5},{-5,5}};
+    tp.closed = true;
+    int s1 = doc.add_sketch_profile(tp, top, "Top");
+
+    // Ruled (straight) sections -> exact planar end caps at z=0 and z=20.
+    doc.add_loft({s0, s1}, true /*ruled*/, BooleanMode::New, "Loft1");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // The loft spans z=[0,20]. ThruSections approximates each section as a BSpline
+    // curve, so the lateral surface bulges ~0.05 mm past the end planes (sub-visual,
+    // ~0.25%) — assert the span loosely; the volume below is the real correctness gate.
+    Bnd_Box bb;
+    BRepBndLib::Add(doc.body, bb);
+    double xmin,ymin,zmin,xmax,ymax,zmax;
+    bb.Get(xmin,ymin,zmin,xmax,ymax,zmax);
+    CHECK_THAT(zmin, WithinAbs(0.0, 0.1));
+    CHECK_THAT(zmax, WithinAbs(20.0, 0.1));
+    // Square frustum volume = h/3*(A1+A2+sqrt(A1*A2)) = 20/3*(400+100+200) = 4666.67.
+    CHECK_THAT(double(doc.display_mesh.volume()), WithinRel(4666.67, 0.03));
+
+    // A single profile is not enough -> benign recompute failure.
+    CadDocument one;
+    SketchProfile sp; sp.points = {{-5,-5},{5,-5},{5,5},{-5,5}}; sp.closed = true;
+    int only = one.add_sketch_profile(sp, SketchPlane::XY(), "Only");
+    one.add_loft({only}, false, BooleanMode::New, "L");
+    REQUIRE_FALSE(one.recompute());
+}
+
+TEST_CASE("draft tapers a solid face about the body base", "[CadDocument]")
+{
+    using namespace Slic3r;
+
+    // 10x10x10 box from z=0..10 (V=1000). Drafting a vertical side face by +10deg about
+    // the bottom (neutral) plane tilts its top edge inward, removing material so V<1000.
+    // A box's 2 horizontal faces are parallel to the neutral plane and cannot be drafted
+    // (Add fails -> recompute returns false), so exactly the 4 vertical sides succeed.
+    int  ok_faces  = 0;
+    bool saw_taper = false;
+    for (int fid = 0; fid < 6; ++fid) {
+        CadDocument doc;
+        int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 5, "Box");
+        doc.add_extrude(sk, 10.0, false, BooleanMode::New, "E");
+        doc.add_draft(10.0, fid, -1, "Draft1");
+        if (!doc.recompute()) continue;   // top/bottom faces: parallel to base -> benign skip
+        ++ok_faces;
+        const double v = double(doc.display_mesh.volume());
+        REQUIRE(v > 0.0);
+        if (v < 999.0) saw_taper = true;
+    }
+    REQUIRE(ok_faces == 4);
+    REQUIRE(saw_taper);
+
+    // Draft with no body must fail cleanly, not crash.
+    CadDocument bad;
+    bad.add_draft(5.0, 0, -1, "NoBody");
+    REQUIRE_FALSE(bad.recompute());
+}
+
+TEST_CASE("a split renumbers the bodies a later feature indexes", "[CadDocument][cut]")
+{
+    // Pins the invariant the Design tab's re-edit path depends on (oz7): a stored
+    // target_body indexes the body list AS IT WAS when that feature ran, and a Cut placed
+    // later in the tree changes that list. If this test ever fails, the GUI's
+    // fill_body_choice() replay-to-timeline-slot assumption needs revisiting with it.
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 20.0, false, BooleanMode::New, "Ext");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    // Cut the single body in half, keeping BOTH pieces — what the Cut card always does.
+    doc.add_cut(SketchPlane::XY(), 10.0, false, true, true, 0, "Split");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 2);           // one body became two
+
+    // Body index 1 did not exist before the Cut. A feature recorded BEFORE the Cut could
+    // never have referred to it, which is exactly why re-edit must list the earlier set.
+    const double half = 20.0 * 20.0 * 10.0;
+    double v0 = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+    double v1 = double(SketchEngine::tessellate(doc.bodies[1].shape).volume());
+    CHECK_THAT(v0 + v1, WithinRel(2.0 * half, 1e-3));
+
+    // Replaying to just before the Cut yields the pre-split list — the one a feature sitting
+    // there indexes into. This is the operation fill_body_choice() performs.
+    CadDocument as_of = doc;
+    as_of.features.resize(as_of.features.size() - 1);   // drop the Cut
+    REQUIRE(as_of.recompute());
+    REQUIRE(as_of.bodies.size() == 1);
+    CHECK(as_of.bodies.size() < doc.bodies.size());
+}
+
+TEST_CASE("cut splits a body with a plane", "[cut]")
+{
+    using Catch::Matchers::WithinRel;
+
+    auto make_box = [](CadDocument& doc, double w, double h, double d) {
+        CadFeature sk;
+        sk.type  = CadFeatureType::Sketch;
+        sk.plane = SketchPlane::XY();
+        sk.imported_regions = {{
+            {Vec2d(-w / 2, -h / 2), Vec2d(w / 2, -h / 2),
+             Vec2d(w / 2,  h / 2), Vec2d(-w / 2, h / 2)},
+        }};
+        doc.features.push_back(sk);
+        CadFeature ex;
+        ex.type       = CadFeatureType::Extrude;
+        ex.sketch_ref = 0;
+        ex.distance   = d;
+        doc.features.push_back(ex);
+    };
+
+    SECTION("keep upper half only") {
+        CadDocument doc;
+        make_box(doc, 20.0, 20.0, 20.0);
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        const double v_orig   = double(doc.display_mesh.volume());
+        const int    n_before = int(doc.bodies.size());
+        REQUIRE(v_orig > 0.0);
+
+        CadFeature cut;
+        cut.type           = CadFeatureType::Cut;
+        cut.plane          = SketchPlane::XY();
+        cut.cut_offset     = 10.0;   // mid-height of the 0..20 box
+        cut.cut_keep_upper = true;
+        cut.cut_keep_lower = false;
+        doc.features.push_back(cut);
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE(int(doc.bodies.size()) == n_before);
+        REQUIRE_THAT(double(doc.display_mesh.volume()), WithinRel(v_orig * 0.5, 0.01));
+    }
+
+    SECTION("keep both halves splits into two bodies") {
+        CadDocument doc;
+        make_box(doc, 20.0, 20.0, 20.0);
+        REQUIRE(doc.recompute());
+        const double v_orig   = double(doc.display_mesh.volume());
+        const int    n_before = int(doc.bodies.size());
+        REQUIRE(v_orig > 0.0);
+
+        CadFeature cut;
+        cut.type           = CadFeatureType::Cut;
+        cut.plane          = SketchPlane::XY();
+        cut.cut_offset     = 10.0;
+        cut.cut_keep_upper = true;
+        cut.cut_keep_lower = true;
+        doc.features.push_back(cut);
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE(int(doc.bodies.size()) == n_before + 1);
+        REQUIRE_THAT(double(doc.display_mesh.volume()), WithinRel(v_orig, 0.01));
+
+        for (const auto& b : doc.bodies) {
+            double v = double(SketchEngine::tessellate(b.shape).volume());
+            REQUIRE_THAT(v, WithinRel(v_orig * 0.5, 0.01));
+        }
+    }
+
+    SECTION("keep lower half only") {
+        CadDocument doc;
+        make_box(doc, 20.0, 20.0, 20.0);
+        REQUIRE(doc.recompute());
+        const double v_orig   = double(doc.display_mesh.volume());
+        const int    n_before = int(doc.bodies.size());
+
+        CadFeature cut;
+        cut.type           = CadFeatureType::Cut;
+        cut.plane          = SketchPlane::XY();
+        cut.cut_offset     = 10.0;
+        cut.cut_keep_upper = false;
+        cut.cut_keep_lower = true;
+        doc.features.push_back(cut);
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE(int(doc.bodies.size()) == n_before);
+        REQUIRE_THAT(double(doc.display_mesh.volume()), WithinRel(v_orig * 0.5, 0.01));
+    }
+
+    SECTION("flip swaps which side is kept") {
+        CadDocument doc;
+        make_box(doc, 20.0, 20.0, 20.0);
+        REQUIRE(doc.recompute());
+        const double v_orig = double(doc.display_mesh.volume());
+
+        // cut with flip=true, keep_upper=true → the -normal side (original bottom half)
+        CadFeature cut;
+        cut.type           = CadFeatureType::Cut;
+        cut.plane          = SketchPlane::XY();
+        cut.cut_offset     = 10.0;
+        cut.cut_flip       = true;
+        cut.cut_keep_upper = true;
+        cut.cut_keep_lower = false;
+        doc.features.push_back(cut);
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE_THAT(double(doc.display_mesh.volume()), WithinRel(v_orig * 0.5, 0.01));
+    }
+
+    SECTION("both keep flags false throws") {
+        CadDocument doc;
+        make_box(doc, 20.0, 20.0, 20.0);
+        REQUIRE(doc.recompute());
+
+        CadFeature cut;
+        cut.type           = CadFeatureType::Cut;
+        cut.plane          = SketchPlane::XY();
+        cut.cut_keep_upper = false;
+        cut.cut_keep_lower = false;
+        doc.features.push_back(cut);
+
+        REQUIRE_FALSE(doc.recompute());
+    }
+}
+
+TEST_CASE("both-halves plane cut splits a body into two equal halves", "[CadDocument][cut]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 1);
+    double v_orig = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+    REQUIRE(v_orig > 0.0);
+
+    doc.add_cut(SketchPlane::XY(), 5.0, false, true, true, 0, "SplitBoth");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 2);
+
+    double v0 = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+    double v1 = double(SketchEngine::tessellate(doc.bodies[1].shape).volume());
+    REQUIRE_THAT(v0 + v1, WithinRel(v_orig, 1e-4));
+    REQUIRE_THAT(v0, WithinRel(20.0 * 20.0 * 5.0, 0.01));
+    REQUIRE_THAT(v1, WithinRel(20.0 * 20.0 * 5.0, 0.01));
+}
+
+TEST_CASE("split by a body face divides a box into two halves via top-face offset", "[CadDocument][cut]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+    double v_orig = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        Vec3d n = GeometryEngine::face_normal_world(fc);
+        if (n.z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    doc.add_split_by_face(0, -1, top_face, true, true, "SplitByFace");
+    doc.features.back().cut_offset = -5.0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 2);
+
+    double v0 = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+    double v1 = double(SketchEngine::tessellate(doc.bodies[1].shape).volume());
+    REQUIRE_THAT(v0 + v1, WithinRel(v_orig, 1e-4));
+    REQUIRE_THAT(v0, WithinRel(20.0 * 20.0 * 5.0, 0.02));
+    REQUIRE_THAT(v1, WithinRel(20.0 * 20.0 * 5.0, 0.02));
+}
+
+TEST_CASE("split by face keep upper only", "[CadDocument][cut]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        Vec3d n = GeometryEngine::face_normal_world(fc);
+        if (n.z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    doc.add_split_by_face(0, -1, top_face, true, false, "SplitUpper");
+    doc.features.back().cut_offset = -5.0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 1);
+
+    double v = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+    REQUIRE_THAT(v, WithinRel(20.0 * 20.0 * 5.0, 0.02));
+}
+
+TEST_CASE("split by face round-trip serialization", "[CadDocument][cut]")
+{
+    using Catch::Matchers::WithinRel;
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        Vec3d n = GeometryEngine::face_normal_world(fc);
+        if (n.z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    doc.add_split_by_face(0, 0, top_face, true, true, "SplitRT");
+    doc.features.back().cut_offset = -5.0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 2);
+
+    int saved_face_body = doc.features.back().cut_face_body;
+    int saved_face      = doc.features.back().cut_face;
+    bool saved_upper    = doc.features.back().cut_keep_upper;
+    bool saved_lower    = doc.features.back().cut_keep_lower;
+    size_t saved_nb     = doc.bodies.size();
+
+    std::vector<std::pair<Vec3d, Vec3d>> bboxes;
+    for (const auto& b : doc.bodies) {
+        Bnd_Box bb; BRepBndLib::Add(b.shape, bb);
+        Standard_Real x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        bboxes.push_back({Vec3d(x0, y0, z0), Vec3d(x1, y1, z1)});
+    }
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc2;
+    REQUIRE(doc2.deserialize_recipe(blob));
+    REQUIRE(doc2.bodies.size() == saved_nb);
+    REQUIRE(doc2.features.size() == doc.features.size());
+
+    const auto& f2 = doc2.features.back();
+    REQUIRE(f2.cut_face_body  == saved_face_body);
+    REQUIRE(f2.cut_face       == saved_face);
+    REQUIRE(f2.cut_keep_upper == saved_upper);
+    REQUIRE(f2.cut_keep_lower == saved_lower);
+
+    for (size_t i = 0; i < saved_nb; ++i) {
+        Bnd_Box bb; BRepBndLib::Add(doc2.bodies[i].shape, bb);
+        Standard_Real x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        REQUIRE_THAT(double(x0), WithinAbs(bboxes[i].first.x(),  1e-6));
+        REQUIRE_THAT(double(y0), WithinAbs(bboxes[i].first.y(),  1e-6));
+        REQUIRE_THAT(double(z0), WithinAbs(bboxes[i].first.z(),  1e-6));
+        REQUIRE_THAT(double(x1), WithinAbs(bboxes[i].second.x(), 1e-6));
+        REQUIRE_THAT(double(y1), WithinAbs(bboxes[i].second.y(), 1e-6));
+        REQUIRE_THAT(double(z1), WithinAbs(bboxes[i].second.z(), 1e-6));
+    }
+}
+
+TEST_CASE("mirror reflects a body about a plane", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+    using Catch::Matchers::WithinAbs;
+
+    auto make_box = [](CadDocument& doc, double w, double h, double d) {
+        int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), w, h, 0, "Box");
+        doc.add_extrude(sk, d, false, BooleanMode::New, "E");
+    };
+
+    // --- New mode: 20x20x20 cube, mirror about XZ plane offset to x=30 ---
+    // The cube is in x=[-10,10]; the mirror is at x=30, so the mirrored cube
+    // is at x=[50,70]. Disjoint -> two bodies, equal volumes (8000 each).
+    SECTION("New mode: two disjoint bodies, equal volumes") {
+        CadDocument doc;
+        make_box(doc, 20.0, 20.0, 20.0);
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        double v_orig = double(doc.display_mesh.volume());
+        REQUIRE_THAT(v_orig, WithinRel(8000.0, 0.01));
+
+        doc.add_mirror(SketchPlane::XZ(), 0, BooleanMode::New, "Mirror1");
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE(doc.bodies.size() == 2);
+
+        double v0 = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+        double v1 = double(SketchEngine::tessellate(doc.bodies[1].shape).volume());
+        REQUIRE_THAT(v0, WithinRel(8000.0, 0.01));
+        REQUIRE_THAT(v1, WithinRel(8000.0, 0.01));
+    }
+
+    // --- New mode with keep_original=false: the source body is replaced ---
+    SECTION("New mode, keep_original=false: source body removed") {
+        CadDocument doc;
+        make_box(doc, 20.0, 20.0, 20.0);
+        REQUIRE(doc.recompute());
+        doc.add_mirror(SketchPlane::XZ(), 0, BooleanMode::New, "Mirror1");
+        doc.features.back().mirror_keep_original = false;
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE(doc.bodies.size() == 1);
+        double v = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+        REQUIRE_THAT(v, WithinRel(8000.0, 0.01));
+    }
+
+    // --- Add mode: L-shape, entirely on one side of the mirror plane -> 2x volume ---
+    // Build an L-shape completely in x>0: base 20x20x5 at x=[0,20] + wall 10x20x10
+    // at x=[0,10] on top. Mirror about XZ at x=30 -> mirror at x=[40,60], disjoint.
+    SECTION("Add mode: asymmetric L-shape, disjoint halves -> 2x volume") {
+        CadDocument doc;
+        // Base: 20x20x5, shifted to x=10 so it's in x=[0,20]
+        CadFeature skb;
+        skb.type = CadFeatureType::Sketch;
+        skb.name = "Base";
+        skb.plane = SketchPlane::XY();
+        skb.imported_regions = {{ {Vec2d(0,-10), Vec2d(20,-10), Vec2d(20,10), Vec2d(0,10)} }};
+        doc.features.push_back(skb);
+        int skb_idx = int(doc.features.size()) - 1;
+        CadFeature exb;
+        exb.type = CadFeatureType::Extrude;
+        exb.name = "EBase";
+        exb.sketch_ref = skb_idx;
+        exb.distance = 5.0;
+        exb.mode = BooleanMode::New;
+        doc.features.push_back(exb);
+
+        // Wall: 10x20x10 on top of the base, x=[0,10]
+        CadFeature skw;
+        skw.type = CadFeatureType::Sketch;
+        skw.name = "Wall";
+        skw.plane = SketchPlane::XY();
+        skw.plane.origin = Vec3d(0, 0, 5);
+        skw.imported_regions = {{ {Vec2d(0,-10), Vec2d(10,-10), Vec2d(10,10), Vec2d(0,10)} }};
+        doc.features.push_back(skw);
+        int skw_idx = int(doc.features.size()) - 1;
+        CadFeature exw;
+        exw.type = CadFeatureType::Extrude;
+        exw.name = "EWall";
+        exw.sketch_ref = skw_idx;
+        exw.distance = 10.0;
+        exw.mode = BooleanMode::Add;
+        exw.target_body = 0;
+        doc.features.push_back(exw);
+
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        const double v_l = double(doc.display_mesh.volume());
+
+        // Mirror about YZ at x=30 -> the mirror is entirely in x=[40,60],
+        // disjoint from the original in x=[0,20].
+        SketchPlane mp = SketchPlane::YZ();
+        mp.origin = Vec3d(30, 0, 0);
+        doc.add_mirror(mp, 0, BooleanMode::Add, "Mirror1");
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        REQUIRE(doc.bodies.size() == 1);
+        const double v_m = double(doc.display_mesh.volume());
+        REQUIRE_THAT(v_m, WithinRel(2.0 * v_l, 0.02));
+    }
+
+    // --- Add mode with intersecting plane -> fused volume < 2x ---
+    // A 20x20x20 cube centred on the origin (so x=[-10,10]), mirrored about
+    // XZ plane at x=0. The mirror maps the cube onto itself exactly (symmetry).
+    // Fusing a cube with itself at the plane of symmetry produces the same cube
+    // -> volume == original, strictly less than 2x.
+    SECTION("Add mode: intersecting plane -> volume < 2x original") {
+        CadDocument doc;
+        make_box(doc, 20.0, 20.0, 20.0);
+        REQUIRE(doc.recompute());
+        const double v_orig = double(doc.display_mesh.volume());
+        REQUIRE_THAT(v_orig, WithinRel(8000.0, 0.01));
+
+        doc.add_mirror(SketchPlane::XZ(), 0, BooleanMode::Add, "Mirror1");
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        const double v_mir = double(doc.display_mesh.volume());
+        REQUIRE(v_mir < v_orig * 1.9);
+    }
+
+    // --- Invalid target body index ---
+    SECTION("invalid target body index -> error, no crash") {
+        CadDocument doc;
+        // No bodies in the document -> mirror must fail, not crash.
+        doc.features.push_back({CadFeatureType::Mirror, "BadMirror", true,
+                                SketchShape::Rectangle, SketchPlane::XZ()});
+        doc.features.back().mode = BooleanMode::New;
+        REQUIRE_FALSE(doc.recompute());
+        REQUIRE_FALSE(doc.error.empty());
+    }
+}
+
+TEST_CASE("mirror serialization round-trip", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Box");
+    doc.add_extrude(sk, 20.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+
+    doc.add_mirror(SketchPlane::XZ(), 0, BooleanMode::New, "Mirror1");
+    doc.features.back().mirror_keep_original = false;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc2;
+    REQUIRE(doc2.deserialize_recipe(blob));
+    REQUIRE(doc2.recompute());
+    REQUIRE(doc2.error.empty());
+
+    REQUIRE(doc2.features.size() == doc.features.size());
+    const auto& f1 = doc.features.back();
+    const auto& f2 = doc2.features.back();
+    REQUIRE(f2.type                 == CadFeatureType::Mirror);
+    REQUIRE(f2.mode                 == BooleanMode::New);
+    REQUIRE(f2.mirror_keep_original == false);
+    REQUIRE(f2.name                 == "Mirror1");
+
+    REQUIRE(doc2.bodies.size() == doc.bodies.size());
+}
+
+TEST_CASE("mass properties: analytic cube", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Sketch");
+    doc.add_extrude(sk, 20.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    auto mp = doc.body_mass_properties(0);
+    REQUIRE(mp.valid);
+    // Cube 20x20x20 -> V = 8000 mm^3
+    REQUIRE_THAT(mp.volume, WithinRel(8000.0, 1e-6));
+    // Surface area = 6 * 20^2 = 2400 mm^2
+    REQUIRE_THAT(mp.surface_area, WithinRel(2400.0, 1e-6));
+    // COM at geometric centre: the box centred on origin is from z=0 to z=20,
+    // so centre at (0, 0, 10)
+    REQUIRE_THAT(mp.center_of_mass.x(), WithinAbs(0.0, 1e-6));
+    REQUIRE_THAT(mp.center_of_mass.y(), WithinAbs(0.0, 1e-6));
+    REQUIRE_THAT(mp.center_of_mass.z(), WithinAbs(10.0, 1e-6));
+    // Inertia sanity: symmetric cube -> diagonal terms equal, off-diagonal ~0
+    double Ixx = mp.inertia[0], Iyy = mp.inertia[4], Izz = mp.inertia[8];
+    REQUIRE_THAT(Ixx, WithinRel(8000.0 * (20*20 + 20*20) / 12.0, 1e-4)); // I = m/12*(b^2+h^2) about COM
+    REQUIRE_THAT(Iyy, WithinRel(Ixx, 1e-4));
+    REQUIRE_THAT(Izz, WithinRel(Ixx, 1e-4));
+    REQUIRE_THAT(mp.inertia[1], WithinAbs(0.0, 1e-6));
+    REQUIRE_THAT(mp.inertia[2], WithinAbs(0.0, 1e-6));
+    REQUIRE_THAT(mp.inertia[5], WithinAbs(0.0, 1e-6));
+}
+
+TEST_CASE("mass properties: analytic cylinder", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    // Circle r=10 on XY, extrude height=5 -> cylinder
+    SketchEntity c;
+    c.type   = SketchEntity::Type::Circle;
+    c.center = Vec2d(0, 0);
+    c.radius = 10.0;
+    int sk = doc.add_sketch_entities({c}, SketchPlane::XY(), "Circle");
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    auto mp = doc.body_mass_properties(0);
+    REQUIRE(mp.valid);
+    double expected_vol = M_PI * 100.0 * 5.0;   // pi * r^2 * h
+    REQUIRE_THAT(mp.volume, WithinRel(expected_vol, 1e-4));
+    // Surface: 2*pi*r^2 + 2*pi*r*h = 2*pi*100 + 2*pi*10*5 = 200*pi + 100*pi = 300*pi
+    double expected_area = 2 * M_PI * 100.0 + 2 * M_PI * 10.0 * 5.0;
+    REQUIRE_THAT(mp.surface_area, WithinRel(expected_area, 1e-4));
+}
+
+TEST_CASE("mass properties: hollow body", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+
+    // Solid cube
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Sketch");
+    doc.add_extrude(sk, 20.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    auto mp_solid = doc.body_mass_properties(0);
+    REQUIRE(mp_solid.valid);
+    double solid_vol = mp_solid.volume;
+
+    // Hollow cube with a through hole
+    CadDocument doc2;
+    int sk2 = doc2.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Sketch");
+    doc2.add_extrude(sk2, 20.0, false, BooleanMode::New, "Extrude");
+    doc2.add_hole(10.0, 20.0, true, 0.0, 0.0, SketchPlane::XY(), "Hole");
+    REQUIRE(doc2.recompute());
+    auto mp_hollow = doc2.body_mass_properties(0);
+    REQUIRE(mp_hollow.valid);
+
+    // Hollow volume < solid volume
+    REQUIRE(mp_hollow.volume < solid_vol);
+    // Hollow = solid - cylinder: V_cyl = pi*5^2*20 = 500*pi
+    double expected_hollow = solid_vol - M_PI * 25.0 * 20.0;
+    REQUIRE_THAT(mp_hollow.volume, WithinRel(expected_hollow, 0.01));
+}
+
+TEST_CASE("mass properties: invalid body index", "[CadDocument]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Sketch");
+    doc.add_extrude(sk, 20.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+
+    // Out of range -> valid=false
+    auto mp = doc.body_mass_properties(99);
+    REQUIRE_FALSE(mp.valid);
+    REQUIRE(mp.volume == 0.0);
+    // Negative index
+    auto mp2 = doc.body_mass_properties(-1);
+    REQUIRE_FALSE(mp2.valid);
+
+    // Empty document (no recompute) -> all bodies empty, index 0 out of range
+    CadDocument empty;
+    auto mp3 = empty.body_mass_properties(0);
+    REQUIRE_FALSE(mp3.valid);
+}
+
+TEST_CASE("serialize_recipe roundtrip with two bodies", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+    CadDocument doc;
+
+    // Body 1: rectangle sketch + extrude + fillet
+    int sk1 = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                             20, 20, 10, "Rect1");
+    REQUIRE(sk1 >= 0);
+    doc.add_extrude(sk1, 10.0, false, BooleanMode::New, "Extrude1");
+    doc.add_fillet(2.0, FaceGroup::All, "Fillet1");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Body 2: circle sketch + extrude (separate New body)
+    SketchEntity circ;
+    circ.type   = SketchEntity::Type::Circle;
+    circ.center = Vec2d(0, 0);
+    circ.radius = 8.0;
+    int sk2 = doc.add_sketch_entities({circ}, SketchPlane::XZ(), "Circle2");
+    doc.add_extrude(sk2, 6.0, false, BooleanMode::New, "Extrude2");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    REQUIRE(doc.bodies.size() >= 2);
+    std::vector<double> orig_vols;
+    for (const auto& b : doc.bodies)
+        orig_vols.push_back(double(SketchEngine::tessellate(b.shape).volume()));
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc2;
+    REQUIRE(doc2.deserialize_recipe(blob));
+    REQUIRE(doc2.error.empty());
+    REQUIRE(doc2.bodies.size() == doc.bodies.size());
+
+    for (size_t i = 0; i < doc.bodies.size(); ++i) {
+        double v2 = double(SketchEngine::tessellate(doc2.bodies[i].shape).volume());
+        REQUIRE_THAT(v2, WithinRel(orig_vols[i], 1e-6));
+    }
+}
+
+TEST_CASE("deserialize_recipe rejects future version with error", "[CadDocument]")
+{
+    CadDocument doc;
+    std::ostringstream oss;
+    {
+        cereal::BinaryOutputArchive ar(oss);
+        uint32_t v = 999;
+        ar(v);
+    }
+    REQUIRE_FALSE(doc.deserialize_recipe(oss.str()));
+    REQUIRE_FALSE(doc.error.empty());
+    CHECK_CONTAINS(doc.error, "newer version");
+}
+
+TEST_CASE("deserialize_recipe rejects older version with error", "[CadDocument]")
+{
+    CadDocument doc;
+    std::ostringstream oss;
+    {
+        cereal::BinaryOutputArchive ar(oss);
+        uint32_t v = 1;
+        ar(v);
+    }
+    REQUIRE_FALSE(doc.deserialize_recipe(oss.str()));
+    REQUIRE_FALSE(doc.error.empty());
+    CHECK_CONTAINS(doc.error, "older version");
+}
+
+TEST_CASE("deserialize_recipe handles truncated blob without throwing", "[CadDocument]")
+{
+    CadDocument doc;
+    std::string garbage = "this is not a valid cereal blob";
+    REQUIRE_FALSE(doc.deserialize_recipe(garbage));
+    REQUIRE_FALSE(doc.error.empty());
+}
+
+TEST_CASE("deserialize_recipe handles empty blob without throwing", "[CadDocument]")
+{
+    CadDocument doc;
+    REQUIRE_FALSE(doc.deserialize_recipe(""));
+    REQUIRE_FALSE(doc.error.empty());
+}
+
+TEST_CASE("deserialize_recipe error is non-empty on every failure path", "[CadDocument]")
+{
+    CadDocument doc;
+    auto reset = [&]() { doc = CadDocument{}; };
+
+    // too new
+    {
+        std::ostringstream oss;
+        { cereal::BinaryOutputArchive ar(oss); uint32_t v = 999; ar(v); }
+        reset();
+        REQUIRE_FALSE(doc.deserialize_recipe(oss.str()));
+        REQUIRE_FALSE(doc.error.empty());
+    }
+    // too old
+    {
+        std::ostringstream oss;
+        { cereal::BinaryOutputArchive ar(oss); uint32_t v = 1; ar(v); }
+        reset();
+        REQUIRE_FALSE(doc.deserialize_recipe(oss.str()));
+        REQUIRE_FALSE(doc.error.empty());
+    }
+    // truncated / garbage
+    {
+        reset();
+        REQUIRE_FALSE(doc.deserialize_recipe("not a valid blob \x00\x01\x02"));
+        REQUIRE_FALSE(doc.error.empty());
+    }
+    // empty
+    {
+        reset();
+        REQUIRE_FALSE(doc.deserialize_recipe(""));
+        REQUIRE_FALSE(doc.error.empty());
+    }
+}
+
+TEST_CASE("a v4 project still opens", "[CadDocument][recipe]")
+{
+    // The regression guard for everyone who already has projects: a pre-framing v4
+    // recipe must keep opening on this build, through the unchanged flat path — not be
+    // refused at the version gate after the bump to v5.
+    std::string path = std::string(TEST_DATA_DIR) + "/cad_recipe_v4.bin";
+    std::ifstream ifs(path, std::ios::binary);
+    REQUIRE(ifs.is_open());
+    std::string blob((std::istreambuf_iterator<char>(ifs)), std::istreambuf_iterator<char>());
+    ifs.close();
+    REQUIRE_FALSE(blob.empty());
+
+    // Trusted reference read of the flat v4 layout (what the golden test's Layer 1 does).
+    std::vector<CadFeature> flat;
+    {
+        std::istringstream iss(blob);
+        cereal::BinaryInputArchive ar(iss);
+        uint32_t v;
+        ar(v);
+        REQUIRE(v == 4);
+        ar(flat);
+    }
+    REQUIRE_FALSE(flat.empty());
+
+    CadDocument doc;
+    doc.deserialize_recipe(blob);
+    // Not refused at the gate: the only failure allowed is the fixture's own geometry
+    // (the golden doc is a serialization-coverage tree whose fillet radius is too large),
+    // which is orthogonal to the v5 framing change and unchanged by it.
+    REQUIRE(doc.error.find("older version") == std::string::npos);
+    REQUIRE(doc.error.find("newer version") == std::string::npos);
+    // The v4 flat path read the same feature tree as the trusted reference.
+    REQUIRE(doc.features.size() == flat.size());
+}
+
+// Do NOT regenerate cad_recipe_v5.bin either. It was written by the build that predates the
+// bump to v6, which is the whole reason it can prove the gate lets a v5 project through.
+TEST_CASE("a v5 project still opens", "[CadDocument][recipe]")
+{
+    // The bump to v6 renamed nothing inside the blob — it records the recipe's move to
+    // Metadata/orca_cad.bin — so a v5 project must still come through the framed path rather
+    // than be refused at the version gate for being old.
+    std::string path = std::string(TEST_DATA_DIR) + "/cad_recipe_v5.bin";
+    std::ifstream ifs(path, std::ios::binary);
+    REQUIRE(ifs.is_open());
+    std::string blob((std::istreambuf_iterator<char>(ifs)), std::istreambuf_iterator<char>());
+    ifs.close();
+    REQUIRE(blob.size() >= sizeof(uint32_t));
+
+    uint32_t stamped = 0;
+    std::memcpy(&stamped, blob.data(), sizeof(stamped));
+    REQUIRE(stamped == 5);   // the fixture really is pre-bump, not a regenerated one
+
+    CadDocument doc;
+    doc.deserialize_recipe(blob);
+    // As with the v4 fixture: the only failure allowed is the golden tree's own geometry, which
+    // is orthogonal to the version gate. Being turned away at the gate is not.
+    REQUIRE(doc.error.find("older version") == std::string::npos);
+    REQUIRE(doc.error.find("newer version") == std::string::npos);
+    REQUIRE_FALSE(doc.features.empty());
+}
+
+TEST_CASE("a v5 round trip is exact", "[CadDocument][recipe]")
+{
+    using Catch::Matchers::WithinRel;
+    CadDocument doc;
+
+    // Body 1: rectangle sketch + extrude + fillet
+    int sk1 = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                             20, 20, 10, "Rect1");
+    REQUIRE(sk1 >= 0);
+    doc.add_extrude(sk1, 10.0, false, BooleanMode::New, "Extrude1");
+    doc.add_fillet(2.0, FaceGroup::All, "Fillet1");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Body 2: circle sketch + extrude (separate New body)
+    SketchEntity circ;
+    circ.type   = SketchEntity::Type::Circle;
+    circ.center = Vec2d(0, 0);
+    circ.radius = 8.0;
+    int sk2 = doc.add_sketch_entities({circ}, SketchPlane::XZ(), "Circle2");
+    doc.add_extrude(sk2, 6.0, false, BooleanMode::New, "Extrude2");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    REQUIRE(doc.bodies.size() >= 2);
+    std::vector<double> orig_vols;
+    for (const auto& b : doc.bodies)
+        orig_vols.push_back(double(SketchEngine::tessellate(b.shape).volume()));
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc2;
+    REQUIRE(doc2.deserialize_recipe(blob));
+    REQUIRE(doc2.error.empty());
+    REQUIRE(doc2.features.size() == doc.features.size());
+    for (size_t i = 0; i < doc.features.size(); ++i)
+        REQUIRE(doc2.features[i].type == doc.features[i].type);
+    REQUIRE(doc2.bodies.size() == doc.bodies.size());
+    for (size_t i = 0; i < doc.bodies.size(); ++i) {
+        double v2 = double(SketchEngine::tessellate(doc2.bodies[i].shape).volume());
+        REQUIRE_THAT(v2, WithinRel(orig_vols[i], 1e-6));
+    }
+}
+
+TEST_CASE("a truncated feature keeps what it could read", "[CadDocument][recipe]")
+{
+    // The forward-compat proof: a framed reader that meets a feature blob shorter than its own
+    // field list must keep what it read and default the rest, not error. Simulate an older
+    // file by hand-shortening ONE feature's frame: rewrite its length prefix and drop the
+    // tail bytes, then confirm the load still succeeds and the fields before the cut survive.
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 10, 0, "Sk1");
+    REQUIRE(sk >= 0);
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Ex1");
+    int sk2 = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 12, 12, 0, "Sk2");
+    doc.add_extrude(sk2, 3.0, false, BooleanMode::New, "Ex2");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Two trailing connector-fingerprint fields, made distinctive so the cut is observable:
+    // coordsys_face_kind sits right before the LAST serialized field (coordsys_face_edges),
+    // which is the one we drop. They are ignored by an Extrude's recompute, so the truncated
+    // document still replays cleanly.
+    doc.features[1].coordsys_face_kind  = 777;
+    doc.features[1].coordsys_face_edges = 888;
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE(blob.size() > 8);
+
+    auto rd32 = [](const std::string& s, size_t off) -> uint32_t {
+        uint32_t u;
+        std::memcpy(&u, s.data() + off, sizeof(u));
+        return u;
+    };
+    auto wr32 = [](std::string& s, size_t off, uint32_t u) {
+        std::memcpy(&s[off], &u, sizeof(u));
+    };
+
+    // Against the constant, not a literal: what this asserts is that the outer frame opens with
+    // the version stamp, which stays true across every bump.
+    REQUIRE(rd32(blob, 0) == CadDocument::ORCA_CAD_RECIPE_VERSION);
+    uint32_t count = rd32(blob, 4);
+    REQUIRE(count == doc.features.size());
+
+    // Walk the outer framing: version + count, then [len][bytes] per feature.
+    std::vector<size_t> f_off, f_len;
+    size_t off = 8;
+    for (uint32_t i = 0; i < count; ++i) {
+        f_off.push_back(off);
+        f_len.push_back(rd32(blob, off));
+        off += 4 + f_len.back();
+    }
+
+    // Shorten feature 1 by dropping its final field (4 bytes): rewrite its length prefix
+    // and erase the tail bytes. The reader then runs out inside fa(f), throws, and keeps
+    // everything it had already assigned — that is the whole point of the try/catch.
+    const size_t drop = sizeof(uint32_t);
+    REQUIRE(f_len[1] > drop);
+    std::string shortened = blob;
+    shortened.erase(f_off[1] + 4 + f_len[1] - drop, drop);
+    wr32(shortened, f_off[1], static_cast<uint32_t>(f_len[1] - drop));
+
+    CadDocument loaded;
+    REQUIRE(loaded.deserialize_recipe(shortened));
+    REQUIRE(loaded.error.empty());
+    REQUIRE(loaded.features.size() == count);
+
+    // Fields before the cut survived; the cut field defaulted; the neighbours on both sides
+    // are intact, proving the outer framing held.
+    REQUIRE(loaded.features[1].name == doc.features[1].name);
+    REQUIRE(loaded.features[1].coordsys_face_kind  == 777);   // right before the cut
+    REQUIRE(loaded.features[1].coordsys_face_edges == -1);    // defaulted by the cut
+    REQUIRE(loaded.features[0].name == doc.features[0].name);
+    REQUIRE(loaded.features[2].name == doc.features[2].name);
+}
+
+TEST_CASE("a v3 recipe is refused with a message naming the version", "[CadDocument][recipe]")
+{
+    // Honesty guard: the framing fixes the future, not the past. A v3 field list no longer
+    // exists in this code, so a v3 blob must be refused cleanly and must say which version.
+    std::string path = std::string(TEST_DATA_DIR) + "/cad_recipe_v3.bin";
+    std::ifstream ifs(path, std::ios::binary);
+    REQUIRE(ifs.is_open());
+    std::string blob((std::istreambuf_iterator<char>(ifs)), std::istreambuf_iterator<char>());
+    ifs.close();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc;
+    REQUIRE_FALSE(doc.deserialize_recipe(blob));
+    REQUIRE_FALSE(doc.error.empty());
+    REQUIRE(doc.error.find("v3") != std::string::npos);
+}
+
+TEST_CASE("re-edit: editing a mid-timeline feature rebuilds downstream", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+    CadDocument doc;
+
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                            20, 10, 0, "Sketch1");
+    REQUIRE(sk >= 0);
+    int ex = doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Extrude1");
+    REQUIRE(ex >= 0);
+    doc.add_fillet(1.0, FaceGroup::All, "Fillet1");
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    Vec3d sz0 = doc.display_mesh.bounding_box().size();
+    REQUIRE(sz0.z() > 0.0);
+
+    // Edit the MID feature (extrude — NOT the last; Fillet is downstream).
+    doc.features[ex].distance = 12.0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    Vec3d sz1 = doc.display_mesh.bounding_box().size();
+    REQUIRE(sz1.z() > sz0.z() + 1.0);
+    REQUIRE(doc.bodies.size() == 1);
+
+    // Edit the FIRST feature (sketch width) — must propagate the whole chain.
+    doc.features[sk].width = 30;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    Vec3d sz2 = doc.display_mesh.bounding_box().size();
+    REQUIRE(sz2.x() > sz1.x() + 1.0);
+}
+
+TEST_CASE("re-edit survives serialize -> deserialize", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+    CadDocument doc;
+
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                            20, 10, 0, "Sketch1");
+    REQUIRE(sk >= 0);
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Extrude1");
+    doc.add_fillet(1.0, FaceGroup::All, "Fillet1");
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc2;
+    REQUIRE(doc2.deserialize_recipe(blob));
+    REQUIRE(doc2.error.empty());
+    REQUIRE(doc2.recompute());
+    REQUIRE(doc2.error.empty());
+    Vec3d sz_pre = doc2.display_mesh.bounding_box().size();
+    REQUIRE(sz_pre.z() > 0.0);
+
+    // Mid-edit the deserialized document — the persisted recipe stays re-editable.
+    doc2.features[1].distance = 12.0;
+    REQUIRE(doc2.recompute());
+    REQUIRE(doc2.error.empty());
+    Vec3d sz_post = doc2.display_mesh.bounding_box().size();
+    REQUIRE(sz_post.z() > sz_pre.z() + 1.0);
+}
+
+TEST_CASE("re-edit: multi-type timeline replays all downstream features", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+    CadDocument doc;
+
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                            30, 30, 0, "Sketch1");
+    REQUIRE(sk >= 0);
+    int ex = doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude1");
+    REQUIRE(ex >= 0);
+    doc.add_hole(6.0, 4.0, false, 0.0, 0.0, SketchPlane::XY(), "Hole1");
+    doc.add_chamfer(1.0, FaceGroup::All, "Chamfer1");
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    size_t n_bodies = doc.bodies.size();
+    REQUIRE(n_bodies >= 1);
+    Vec3d sz0 = doc.display_mesh.bounding_box().size();
+    REQUIRE(sz0.z() > 0.0);
+
+    // Edit the MID extrude — downstream Hole and Chamfer must rebuild.
+    doc.features[ex].distance = 16.0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == n_bodies);
+    Vec3d sz1 = doc.display_mesh.bounding_box().size();
+    REQUIRE(sz1.z() > sz0.z() + 1.0);
+}
+
+TEST_CASE("datum plane construction methods", "[CadDocument][plane]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    // Build a doc with a box (sketch rect 40x30 + extrude 20) so bodies[0] has faces/edges.
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 40, 30, 0, "BoxSketch");
+    REQUIRE(sk >= 0);
+    doc.add_extrude(sk, 20.0, false, BooleanMode::New, "Extrude1");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 1);
+    const int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    REQUIRE(n_faces == 6);   // a box
+    const int n_edges = GeometryEngine::edge_count(doc.bodies[0].shape);
+    REQUIRE(n_edges == 12);
+
+    // Find top face (normal ~ +Z) and bottom face (normal ~ -Z) by scanning.
+    int top_idx = -1, bot_idx = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        Vec3d n = GeometryEngine::face_normal_world(fc);
+        if (n.z() > 0.9)  top_idx = i;
+        if (n.z() < -0.9) bot_idx = i;
+    }
+    REQUIRE(top_idx >= 0);
+    REQUIRE(bot_idx >= 0);
+
+    // --- Offset from base XY by 10 ---
+    auto planes0 = doc.resolve_datum_planes();
+    size_t initial = planes0.size();
+
+    CadFeature f0;
+    f0.type       = CadFeatureType::Plane;
+    f0.name       = "Offset10";
+    f0.plane_base = 0;   // XY
+    f0.plane_type = PlaneType::Offset;
+    f0.plane_offset = 10;
+    doc.features.push_back(f0);
+
+    auto planes = doc.resolve_datum_planes();
+    REQUIRE(planes.size() == initial + 1);
+    CHECK_THAT(planes.back().second.origin.z(), WithinAbs(10.0, 1e-6));
+    CHECK_THAT(planes.back().second.normal.z(), WithinAbs(1.0, 1e-6));
+
+    // --- Coincident to top face ---
+    CadFeature f1;
+    f1.type            = CadFeatureType::Plane;
+    f1.name            = "CoincidentTop";
+    f1.plane_type      = PlaneType::Coincident;
+    f1.plane_face_body = 0;
+    f1.plane_face      = top_idx;
+    doc.features.push_back(f1);
+
+    planes = doc.resolve_datum_planes();
+    REQUIRE(planes.size() == initial + 2);
+    CHECK_THAT(planes.back().second.origin.z(), WithinAbs(20.0, 1e-6));   // box height is 20
+    CHECK_THAT(planes.back().second.normal.z(), WithinAbs(1.0, 1e-6));
+
+    // --- Midplane between top and bottom faces ---
+    CadFeature f2;
+    f2.type             = CadFeatureType::Plane;
+    f2.name             = "Midplane";
+    f2.plane_type       = PlaneType::Midplane;
+    f2.plane_face_body  = 0;
+    f2.plane_face       = top_idx;
+    f2.plane_face2_body = 0;
+    f2.plane_face2      = bot_idx;
+    doc.features.push_back(f2);
+
+    planes = doc.resolve_datum_planes();
+    REQUIRE(planes.size() == initial + 3);
+    CHECK_THAT(planes.back().second.origin.z(), WithinAbs(10.0, 1e-6));   // midway
+    CHECK_THAT(std::abs(planes.back().second.normal.z()), WithinAbs(1.0, 1e-6));
+
+    // --- Orthonormality check on all resolved planes ---
+    for (const auto& [name, sp] : planes) {
+        INFO("Plane: " << name);
+        CHECK_THAT(sp.normal.norm(), WithinAbs(1.0, 1e-6));
+        CHECK_THAT(sp.x_axis.norm(), WithinAbs(1.0, 1e-6));
+        CHECK_THAT(sp.y_axis.norm(), WithinAbs(1.0, 1e-6));
+        CHECK_THAT(std::abs(sp.x_axis.dot(sp.y_axis)), WithinAbs(0.0, 1e-6));
+        CHECK_THAT(std::abs(sp.x_axis.dot(sp.normal)), WithinAbs(0.0, 1e-6));
+        CHECK_THAT(std::abs(sp.y_axis.dot(sp.normal)), WithinAbs(0.0, 1e-6));
+    }
+}
+
+// Mirrors the Snapmaker [Deviation] case (Snapmaker carries it in test_geometry.cpp; here it lives
+// alongside the CAD suite). GeometryEngine::surface_deviation = one-sided Hausdorff used by the
+// MCP validate_against acceptance metric.
+TEST_CASE("surface_deviation: identical solids ~0, shifted solid ~shift", "[Deviation]")
+{
+    TopoDS_Shape ref = BRepPrimAPI_MakeBox(10.0, 10.0, 10.0).Shape();
+    auto d0 = GeometryEngine::surface_deviation(ref, ref, 0.5);
+    REQUIRE(d0.sample_count > 0);
+    REQUIRE_THAT(d0.max_mm, Catch::Matchers::WithinAbs(0.0, 1e-6));
+
+    // candidate shifted +2mm in X: far corner vertices sit 2mm outside the reference
+    gp_Trsf t; t.SetTranslation(gp_Vec(2.0, 0.0, 0.0));
+    TopoDS_Shape shifted = BRepBuilderAPI_Transform(ref, t, true).Shape();
+    auto d1 = GeometryEngine::surface_deviation(shifted, ref, 0.5);
+    REQUIRE_THAT(d1.max_mm, Catch::Matchers::WithinAbs(2.0, 0.05));
+    REQUIRE(d1.mean_mm > 0.0);
+}
+
+TEST_CASE("mesh_to_brep: watertight cube -> solid, coplanar merge gives 6 faces", "[design][mesh2brep]")
+{
+    const indexed_triangle_set cube = its_make_cube(10.0, 20.0, 30.0);
+    REQUIRE(cube.indices.size() == 12);
+
+    SECTION("faceted: one B-rep face per triangle, exact volume") {
+        GeometryEngine::MeshBrepStats st;
+        const TopoDS_Shape shape = GeometryEngine::mesh_to_brep(cube, 0.01, /*no merge*/0.0, st);
+        REQUIRE_FALSE(shape.IsNull());
+        CHECK(st.kept_tris == 12);
+        CHECK(st.faces_built == 12);
+        CHECK(st.faces_final == 12);
+        // Shared topology by construction: a cube has 8 vertices and 18 edges once the two
+        // triangles of each face share their diagonal. Every edge used exactly twice.
+        CHECK(st.unique_edges == 18);
+        CHECK(st.boundary_edges == 0);
+        CHECK(st.nonmanifold_edges == 0);
+        CHECK(st.watertight);
+        REQUIRE(st.is_solid);
+        REQUIRE_THAT(st.volume, Catch::Matchers::WithinRel(10.0 * 20.0 * 30.0, 1e-9));
+    }
+
+    SECTION("merge coplanar: 12 triangles collapse to the cube's 6 real faces") {
+        GeometryEngine::MeshBrepStats st;
+        const TopoDS_Shape shape = GeometryEngine::mesh_to_brep(cube, 0.01, 5.0, st);
+        REQUIRE_FALSE(shape.IsNull());
+        REQUIRE(st.is_solid);
+        // This is the whole point of merging: the imported body must expose pickable CAD faces,
+        // not one face per triangle, or the fillet/extrude tools have nothing meaningful to grab.
+        REQUIRE(st.faces_final == 6);
+        REQUIRE_THAT(st.volume, Catch::Matchers::WithinRel(10.0 * 20.0 * 30.0, 1e-9));
+    }
+}
+
+TEST_CASE("mesh_to_brep: an open mesh is reported as a shell, never a fake solid", "[design][mesh2brep]")
+{
+    indexed_triangle_set open_cube = its_make_cube(10.0, 10.0, 10.0);
+    open_cube.indices.pop_back();          // punch a hole: drop one triangle
+    open_cube.indices.pop_back();          // (and its coplanar partner -> a whole face missing)
+
+    GeometryEngine::MeshBrepStats st;
+    const TopoDS_Shape shape = GeometryEngine::mesh_to_brep(open_cube, 0.01, 5.0, st);
+    REQUIRE_FALSE(shape.IsNull());
+    CHECK(st.kept_tris == 10);
+    CHECK(st.boundary_edges > 0);          // the hole's rim
+    CHECK_FALSE(st.watertight);
+    REQUIRE_FALSE(st.is_solid);            // must NOT be dressed up as a solid
+    CHECK(st.volume == 0.0);
+}
+
+TEST_CASE("mesh_to_brep: degenerate triangles are rejected on a scale-independent test", "[design][mesh2brep]")
+{
+    // A thin but perfectly legitimate CAD sliver. Every edge (1.0, ~0.5, ~0.5) is far above the
+    // 0.01 dedup tolerance, so no vertex collapses — but its area (5e-5) is BELOW tolerance^2
+    // (1e-4). A rule of "reject when area < tolerance^2" would therefore throw it away, which is
+    // precisely the bug that turned a watertight 62k-triangle input into a falsely-open shell.
+    // The scale-independent test (area < 1e-9 * longest_edge^2 = 1e-9) keeps it, as it must.
+    indexed_triangle_set sliver;
+    sliver.vertices = { {0.f, 0.f, 0.f}, {1.f, 0.f, 0.f}, {0.5f, 0.0001f, 0.f} };
+    sliver.indices  = { {0, 1, 2} };
+    GeometryEngine::MeshBrepStats st;
+    GeometryEngine::mesh_to_brep(sliver, 0.01, 0.0, st);
+    CHECK(st.degenerate_sliver == 0);
+    CHECK(st.degenerate_collapsed == 0);
+    CHECK(st.kept_tris == 1);
+
+    // A truly collinear triangle has no area at any scale -> rejected as a sliver.
+    indexed_triangle_set collinear;
+    collinear.vertices = { {0.f, 0.f, 0.f}, {10.f, 0.f, 0.f}, {20.f, 0.f, 0.f} };
+    collinear.indices  = { {0, 1, 2} };
+    GeometryEngine::MeshBrepStats st2;
+    CHECK_THROWS(GeometryEngine::mesh_to_brep(collinear, 0.01, 0.0, st2));  // nothing left to build
+    CHECK(st2.degenerate_sliver == 1);
+
+    // A triangle entirely inside one tolerance cell is sub-resolution noise -> collapsed.
+    indexed_triangle_set tiny;
+    tiny.vertices = { {0.f, 0.f, 0.f}, {0.001f, 0.f, 0.f}, {0.f, 0.001f, 0.f} };
+    tiny.indices  = { {0, 1, 2} };
+    GeometryEngine::MeshBrepStats st3;
+    CHECK_THROWS(GeometryEngine::mesh_to_brep(tiny, 0.1, 0.0, st3));
+    CHECK(st3.degenerate_collapsed == 1);
+}
+
+TEST_CASE("datum axis: two points direction is unit and analytic", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int ax = doc.add_axis(AxisType::TwoPoints, "AxisThroughZ");
+    REQUIRE(ax == 0);
+    doc.features[ax].axis_p1 = Vec3d(0, 0, 0);
+    doc.features[ax].axis_p2 = Vec3d(0, 0, 10);
+
+    auto axes = doc.resolve_datum_axes();
+    REQUIRE(axes.size() == 1);
+    REQUIRE(axes[0].name == "AxisThroughZ");
+    REQUIRE(axes[0].error.empty());
+    CHECK_THAT(axes[0].direction.x(), WithinAbs(0.0, 1e-12));
+    CHECK_THAT(axes[0].direction.y(), WithinAbs(0.0, 1e-12));
+    CHECK_THAT(axes[0].direction.z(), WithinAbs(1.0, 1e-12));
+    CHECK_THAT(axes[0].direction.norm(), WithinAbs(1.0, 1e-9));
+    CHECK_THAT(axes[0].origin.x(), WithinAbs(0.0, 1e-9));
+    CHECK_THAT(axes[0].origin.y(), WithinAbs(0.0, 1e-9));
+    CHECK_THAT(axes[0].origin.z(), WithinAbs(0.0, 1e-9));
+}
+
+TEST_CASE("datum axis: degenerate two identical points fails cleanly", "[CadDocument]")
+{
+    CadDocument doc;
+    int ax = doc.add_axis(AxisType::TwoPoints, "Degenerate");
+    doc.features[ax].axis_p1 = Vec3d(5, 5, 5);
+    doc.features[ax].axis_p2 = Vec3d(5, 5, 5);
+
+    auto axes = doc.resolve_datum_axes();
+    REQUIRE(axes.size() == 1);
+    REQUIRE_FALSE(axes[0].error.empty());
+}
+
+TEST_CASE("datum axis: two parallel planes fail with error", "[CadDocument]")
+{
+    CadDocument doc;
+    // Two offset XY planes are parallel -> no intersection.
+    // 3 and 4, not 0 and 1: axis_plane_a/b use the same encoding as plane_base — 0/1/2 are the
+    // XY/XZ/YZ base planes and datums start at 3 — because the GUI fills these from
+    // populate_plane_choices() and stores the row verbatim.
+    doc.add_plane(0 /*XY*/, 10.0, 0.0, 0, "PlaneA");
+    doc.add_plane(0 /*XY*/, 30.0, 0.0, 0, "PlaneB");
+
+    int ax = doc.add_axis(AxisType::TwoPoints, "Parallel");
+    doc.features[ax].axis_type      = AxisType::PlaneIntersection;
+    doc.features[ax].axis_plane_a   = 3;
+    doc.features[ax].axis_plane_b   = 4;
+
+    auto axes = doc.resolve_datum_axes();
+    REQUIRE(axes.size() == 1);
+    REQUIRE_FALSE(axes[0].error.empty());
+}
+
+// The case the GUI actually produces most often, and which could not work before: the two refs
+// are rows of the plane picker, whose first three entries are the base planes. XY x XZ is the
+// X axis. Previously ref 0 was read as "datum plane 0", so this silently resolved to the wrong
+// plane or failed with "plane ref not found".
+TEST_CASE("datum axis: intersection of two BASE planes gives the expected axis", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int ax = doc.add_axis(AxisType::PlaneIntersection, "XAxis");
+    doc.features[ax].axis_plane_a = 0;   // XY
+    doc.features[ax].axis_plane_b = 1;   // XZ
+
+    auto axes = doc.resolve_datum_axes();
+    REQUIRE(axes.size() == 1);
+    REQUIRE(axes[0].error.empty());
+    // XY normal is Z, XZ normal is Y; Z x Y is +/-X.
+    CHECK_THAT(std::abs(axes[0].direction.x()), WithinAbs(1.0, 1e-12));
+    CHECK_THAT(axes[0].direction.y(),           WithinAbs(0.0, 1e-12));
+    CHECK_THAT(axes[0].direction.z(),           WithinAbs(0.0, 1e-12));
+}
+
+// A datum plane crossed with a base plane — the mixed case, which pins the +3 offset.
+TEST_CASE("datum axis: base plane crossed with a datum plane", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    doc.add_plane(1 /*XZ*/, 5.0, 0.0, 0, "OffsetXZ");   // datum 0 -> row 3
+
+    int ax = doc.add_axis(AxisType::PlaneIntersection, "MixedAxis");
+    doc.features[ax].axis_plane_a = 0;   // XY base
+    doc.features[ax].axis_plane_b = 3;   // the datum above
+
+    auto axes = doc.resolve_datum_axes();
+    REQUIRE(axes.size() == 1);
+    REQUIRE(axes[0].error.empty());
+    CHECK_THAT(std::abs(axes[0].direction.x()), WithinAbs(1.0, 1e-12));
+}
+
+TEST_CASE("datum axis: cylinder centreline from extruded circle", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    // Build a cylinder: circle r=5 at origin, extrude 20 mm along +Z -> cylinder z=[0,20]
+    int sk = doc.add_sketch(SketchShape::Circle, SketchPlane::XY(), 0, 0, 5.0, "Circle");
+    doc.add_extrude(sk, 20.0, false, BooleanMode::New, "Cyl");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+    // Find the lateral cylindrical face
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int lateral_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        GeometryEngine::CylinderFace cyl = GeometryEngine::cylinder_of_face(fc);
+        if (cyl.ok) { lateral_face = i; break; }
+    }
+    REQUIRE(lateral_face >= 0);
+
+    int ax = doc.add_axis(AxisType::TwoPoints, "CylAx");
+    doc.features[ax].axis_type = AxisType::CylinderCenterline;
+    doc.features[ax].axis_body = 0;
+    doc.features[ax].axis_face = lateral_face;
+
+    auto axes = doc.resolve_datum_axes();
+    REQUIRE(axes.size() == 1);
+    REQUIRE(axes[0].error.empty());
+    // OCCT may return the axis direction as +Z or -Z depending on face orientation;
+    // the centreline is always collinear with Z and passes through (x=0,y=0).
+    CHECK_THAT(std::abs(axes[0].direction.z()), WithinAbs(1.0, 1e-12));
+    CHECK_THAT(axes[0].direction.x(), WithinAbs(0.0, 1e-12));
+    CHECK_THAT(axes[0].direction.y(), WithinAbs(0.0, 1e-12));
+    CHECK_THAT(axes[0].origin.x(), WithinAbs(0.0, 1e-6));
+    CHECK_THAT(axes[0].origin.y(), WithinAbs(0.0, 1e-6));
+}
+
+TEST_CASE("datum coordinate system: non-perpendicular inputs produce orthonormal axes", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    // Build a body so we have a face to reference for FaceAndDirection.
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "BoxExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        Vec3d fn = GeometryEngine::face_normal_world(GeometryEngine::face_by_index(doc.bodies[0].shape, i));
+        if (fn.z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    int cs = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 0), "CS1");
+    REQUIRE(cs >= 0);
+    doc.features[cs].coordsys_type   = CoordSysType::FaceAndDirection;
+    doc.features[cs].coordsys_body   = 0;
+    doc.features[cs].coordsys_face   = top_face;
+    // Deliberately non-perpendicular X hint (NOT orthogonal to face normal ~+Z).
+    doc.features[cs].coordsys_x_hint = Vec3d(3.0, -1.0, 0.5);
+
+    auto css = doc.resolve_datum_coordsys();
+    REQUIRE(css.size() == 1);
+    REQUIRE(css[0].error.empty());
+
+    Vec3d X = css[0].x, Y = css[0].y;
+    // Orthonormality: each axis has unit length
+    CHECK_THAT(X.norm(), WithinAbs(1.0, 1e-9));
+    CHECK_THAT(Y.norm(), WithinAbs(1.0, 1e-9));
+    // Pairwise dot products are ~0
+    CHECK_THAT(std::abs(X.dot(Y)), WithinAbs(0.0, 1e-9));
+    // Z = X x Y (derived), also unit and perpendicular
+    Vec3d Z = X.cross(Y);
+    CHECK_THAT(Z.norm(), WithinAbs(1.0, 1e-9));
+    CHECK_THAT(std::abs(X.dot(Z)), WithinAbs(0.0, 1e-9));
+    CHECK_THAT(std::abs(Y.dot(Z)), WithinAbs(0.0, 1e-9));
+    // Right-handedness: X x Y == Z
+    CHECK_THAT(Z.x(), WithinAbs((X.cross(Y)).x(), 1e-9));
+    CHECK_THAT(Z.y(), WithinAbs((X.cross(Y)).y(), 1e-9));
+    CHECK_THAT(Z.z(), WithinAbs((X.cross(Y)).z(), 1e-9));
+}
+
+TEST_CASE("datum coordinate system: a face-only frame rotates with its body", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    // The bug this pins down: Z came from the face normal (body-following) but X came from
+    // coordsys_x_hint, a WORLD constant. Spinning the body about its own face normal left the
+    // frame identical, so a face-only connector could not encode that rotation at all — and a
+    // Fastened or Slider mate built on it claimed to fix an orientation it could not see.
+    // A rectangular top face is used deliberately: its edges give an unambiguous in-plane
+    // direction, so "did the frame follow the body" is answerable to the degree.
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 40, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        Vec3d fn = GeometryEngine::face_normal_world(GeometryEngine::face_by_index(doc.bodies[0].shape, i));
+        if (fn.z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    int cs = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 0), "CS");
+    doc.features[cs].coordsys_type = CoordSysType::FaceAndDirection;
+    doc.features[cs].coordsys_body = 0;
+    doc.features[cs].coordsys_face = top_face;
+    doc.features[cs].coordsys_edge = -1;              // face only: no explicit direction edge
+    REQUIRE(doc.recompute());
+
+    auto before = doc.resolve_datum_coordsys();
+    REQUIRE(before.size() == 1);
+    REQUIRE(before[0].error.empty());
+    const Vec3d X0 = before[0].x;
+    const Vec3d Z0 = before[0].x.cross(before[0].y);
+
+    // Spin the body 90 degrees about its own face normal (world Z here).
+    doc.add_transform(0, Vec3d(0, 0, 0), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 90.0, false, "Spin");
+    REQUIRE(doc.recompute());
+
+    auto after = doc.resolve_datum_coordsys();
+    REQUIRE(after.size() == 1);
+    REQUIRE(after[0].error.empty());
+    const Vec3d X1 = after[0].x;
+
+    // The normal is unchanged by a spin about itself — that is exactly why the old code could
+    // not detect the rotation.
+    const Vec3d Z1 = after[0].x.cross(after[0].y);
+    CHECK_THAT(std::abs(Z0.dot(Z1)), WithinAbs(1.0, 1e-6));
+
+    // X must have turned with the body. Before the fix X0 == X1 and this failed.
+    const double cos_turn = std::clamp(X0.dot(X1), -1.0, 1.0);
+    CHECK_THAT(std::abs(cos_turn), WithinAbs(0.0, 1e-6));   // 90 degrees apart
+}
+
+TEST_CASE("datum coordinate system: point_world gives world axes", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int cs = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(10, 20, 30), "CS_World");
+    REQUIRE(cs == 0);
+
+    auto css = doc.resolve_datum_coordsys();
+    REQUIRE(css.size() == 1);
+    REQUIRE(css[0].error.empty());
+    CHECK_THAT(css[0].origin.x(), WithinAbs(10.0, 1e-9));
+    CHECK_THAT(css[0].origin.y(), WithinAbs(20.0, 1e-9));
+    CHECK_THAT(css[0].origin.z(), WithinAbs(30.0, 1e-9));
+    CHECK_THAT(css[0].x.x(), WithinAbs(1.0, 1e-9));
+    CHECK_THAT(css[0].x.y(), WithinAbs(0.0, 1e-9));
+    CHECK_THAT(css[0].x.z(), WithinAbs(0.0, 1e-9));
+    CHECK_THAT(css[0].y.x(), WithinAbs(0.0, 1e-9));
+    CHECK_THAT(css[0].y.y(), WithinAbs(1.0, 1e-9));
+    CHECK_THAT(css[0].y.z(), WithinAbs(0.0, 1e-9));
+}
+
+
+TEST_CASE("helix curve: arc length, bounding box, left-handed, conical", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+    using Catch::Matchers::WithinAbs;
+
+    // --- Cylindrical helix r=5, pitch=2, height=10 (5 turns) ---
+    // One turn arc length = sqrt((2*pi*r)^2 + pitch^2) = sqrt((10*pi)^2 + 4).
+    // Total = 5 * sqrt(986.96...) ≈ 5 * 31.4159 ≈ 157.08 mm.
+    SECTION("cylindrical helix arc length matches analytic") {
+        CadDocument doc;
+        doc.add_helix(SketchPlane::XY(), 5.0, 2.0, 10.0, false, 0.0, "H1");
+        REQUIRE(doc.features.size() == 1);
+        std::string err;
+        TopoDS_Wire w = doc.build_helix_wire(doc.features[0], err);
+        REQUIRE_FALSE(w.IsNull());
+        REQUIRE(err.empty());
+
+        GProp_GProps props;
+        BRepGProp::LinearProperties(w, props);
+        const double len = props.Mass();
+        const double one_turn = std::sqrt(std::pow(2.0 * M_PI * 5.0, 2) + std::pow(2.0, 2));
+        const double expected = 5.0 * one_turn;
+        REQUIRE_THAT(len, WithinRel(expected, 1e-3));
+    }
+
+    // --- Bounding box: X/Y extent = 2*radius, Z extent = height ---
+    SECTION("cylindrical helix bounding box") {
+        CadDocument doc;
+        doc.add_helix(SketchPlane::XY(), 5.0, 2.0, 10.0, false, 0.0, "H1");
+        std::string err;
+        TopoDS_Wire w = doc.build_helix_wire(doc.features[0], err);
+        REQUIRE_FALSE(w.IsNull());
+
+        Bnd_Box bb;
+        BRepBndLib::Add(w, bb);
+        double xmin, ymin, zmin, xmax, ymax, zmax;
+        bb.Get(xmin, ymin, zmin, xmax, ymax, zmax);
+        REQUIRE_THAT(xmax - xmin, WithinRel(10.0, 0.1));
+        REQUIRE_THAT(ymax - ymin, WithinRel(10.0, 0.1));
+        REQUIRE_THAT(zmax - zmin, WithinRel(10.0, 0.1));
+    }
+
+    // --- Left-handed helix: sample a point at parameter ~0.25 and compare ---
+    SECTION("left_handed flips the winding direction") {
+        CadDocument doc_rh, doc_lh;
+        doc_rh.add_helix(SketchPlane::XY(), 5.0, 2.0, 10.0, false, 0.0, "RH");
+        doc_lh.add_helix(SketchPlane::XY(), 5.0, 2.0, 10.0, true,  0.0, "LH");
+
+        std::string err;
+        TopoDS_Wire w_rh = doc_rh.build_helix_wire(doc_rh.features[0], err);
+        TopoDS_Wire w_lh = doc_lh.build_helix_wire(doc_lh.features[0], err);
+        REQUIRE_FALSE(w_rh.IsNull());
+        REQUIRE_FALSE(w_lh.IsNull());
+
+        // Sample at height = height/4 along the helix:
+        // RH: angle = 2*pi*turns*0.25 = pi/2, direction is +2*pi*turns
+        //    so at z = 2.5: u = pi/2 => x = r*cos(pi/2) = 0, y = r*sin(pi/2) = +5
+        // LH: angle goes negative, at z = 2.5: u = -pi/2 => x = 0, y = -5
+        double z_sample = 2.5; // height/4
+        // Approximate by scanning edges and picking the vertex nearest to target z
+        auto point_at_z = [&](const TopoDS_Wire& w, double target_z) -> gp_Pnt {
+            double best_dz = 1e9;
+            gp_Pnt best(0,0,0);
+            for (TopExp_Explorer ex(w, TopAbs_EDGE); ex.More(); ex.Next()) {
+                TopoDS_Edge e = TopoDS::Edge(ex.Current());
+                BRepAdaptor_Curve curve(e);
+                double u0 = curve.FirstParameter();
+                double u1 = curve.LastParameter();
+                for (int s = 0; s <= 100; ++s) {
+                    double u = u0 + (u1 - u0) * s / 100.0;
+                    gp_Pnt p = curve.Value(u);
+                    if (std::abs(p.Z() - target_z) < best_dz) {
+                        best_dz = std::abs(p.Z() - target_z);
+                        best = p;
+                    }
+                }
+            }
+            return best;
+        };
+
+        gp_Pnt prh = point_at_z(w_rh, z_sample);
+        gp_Pnt plh = point_at_z(w_lh, z_sample);
+
+        // At z=2.5 for RH: angle ~ pi/2 -> y > 0
+        REQUIRE(prh.Y() > 0.0);
+        // At z=2.5 for LH: angle ~ -pi/2 -> y < 0
+        REQUIRE(plh.Y() < 0.0);
+        // They must differ in sign of y (mirror winding), not just "differ"
+        REQUIRE(prh.Y() * plh.Y() < 0.0);
+    }
+
+    // --- Conical helix: top radius matches r + height*tan(taper) ---
+    SECTION("conical helix top radius") {
+        CadDocument doc;
+        doc.add_helix(SketchPlane::XY(), 5.0, 2.0, 10.0, false, 10.0, "Cone");
+        std::string err;
+        TopoDS_Wire w = doc.build_helix_wire(doc.features[0], err);
+        REQUIRE_FALSE(w.IsNull());
+        REQUIRE(err.empty());
+
+        // Top radius = 5 + 10*tan(10) ≈ 5 + 1.7633 = 6.7633
+        const double expected_top = 5.0 + 10.0 * std::tan(10.0 * M_PI / 180.0);
+
+        // Sample at z = height: use same sampling approach
+        double best_dz = 1e9;
+        gp_Pnt best(0,0,0);
+        for (TopExp_Explorer ex(w, TopAbs_EDGE); ex.More(); ex.Next()) {
+            TopoDS_Edge e = TopoDS::Edge(ex.Current());
+            BRepAdaptor_Curve curve(e);
+            double u0 = curve.FirstParameter();
+            double u1 = curve.LastParameter();
+            for (int s = 0; s <= 200; ++s) {
+                double u = u0 + (u1 - u0) * s / 200.0;
+                gp_Pnt p = curve.Value(u);
+                if (std::abs(p.Z() - 10.0) < best_dz) {
+                    best_dz = std::abs(p.Z() - 10.0);
+                    best = p;
+                }
+            }
+        }
+        double top_r = std::sqrt(best.X() * best.X() + best.Y() * best.Y());
+        REQUIRE_THAT(top_r, WithinRel(expected_top, 1e-2));
+    }
+}
+
+TEST_CASE("helix: invalid inputs fail cleanly", "[CadDocument]")
+{
+    SECTION("radius <= 0") {
+        CadDocument doc;
+        doc.add_helix(SketchPlane::XY(), 0.0, 2.0, 10.0, false, 0.0, "H");
+        std::string err;
+        REQUIRE(doc.build_helix_wire(doc.features[0], err).IsNull());
+        REQUIRE_FALSE(err.empty());
+    }
+    SECTION("pitch <= 0") {
+        CadDocument doc;
+        doc.add_helix(SketchPlane::XY(), 5.0, 0.0, 10.0, false, 0.0, "H");
+        std::string err;
+        REQUIRE(doc.build_helix_wire(doc.features[0], err).IsNull());
+        REQUIRE_FALSE(err.empty());
+    }
+    SECTION("height < 0") {
+        CadDocument doc;
+        doc.add_helix(SketchPlane::XY(), 5.0, 2.0, -1.0, false, 0.0, "H");
+        std::string err;
+        REQUIRE(doc.build_helix_wire(doc.features[0], err).IsNull());
+        REQUIRE_FALSE(err.empty());
+    }
+    SECTION("height == 0 (flat spiral) rejected") {
+        CadDocument doc;
+        doc.add_helix(SketchPlane::XY(), 5.0, 2.0, 0.0, false, 0.0, "H");
+        std::string err;
+        REQUIRE(doc.build_helix_wire(doc.features[0], err).IsNull());
+        REQUIRE_FALSE(err.empty());
+        CHECK_CONTAINS(err, "flat spiral");
+    }
+    SECTION("absurd turn count") {
+        CadDocument doc;
+        doc.add_helix(SketchPlane::XY(), 5.0, 1e-4, 2.0, false, 0.0, "H");
+        std::string err;
+        REQUIRE(doc.build_helix_wire(doc.features[0], err).IsNull());
+        REQUIRE_FALSE(err.empty());
+    }
+    SECTION("taper drives radius negative") {
+        CadDocument doc;
+        doc.add_helix(SketchPlane::XY(), 1.0, 2.0, 10.0, false, -10.0, "H");
+        std::string err;
+        REQUIRE(doc.build_helix_wire(doc.features[0], err).IsNull());
+        REQUIRE_FALSE(err.empty());
+        CHECK_CONTAINS(err, "negative");
+    }
+}
+
+TEST_CASE("helix as sweep path: spring integration test", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+
+    // Build a plane at the helix start (5,0,0) whose normal IS the start tangent direction.
+    // The helix tangent at u=0 is (0, R, P/(2*pi)) = (0, 5, 3/(2*pi)).
+    const double R = 5.0, P = 3.0;
+    Vec3d tan_dir(0, R, P / (2.0 * M_PI));
+    tan_dir.normalize();
+    Vec3d ref = (std::abs(tan_dir.z()) < 0.9) ? Vec3d(0, 0, 1) : Vec3d(1, 0, 0);
+    Vec3d x_axis = ref.cross(tan_dir);
+    if (x_axis.squaredNorm() < 1e-12) x_axis = Vec3d(1, 0, 0);
+    x_axis.normalize();
+    Vec3d y_axis = tan_dir.cross(x_axis).normalized();
+    SketchPlane profile_plane;
+    profile_plane.origin = Vec3d(R, 0, 0);
+    profile_plane.normal = tan_dir;
+    profile_plane.x_axis = x_axis;
+    profile_plane.y_axis = y_axis;
+
+    // Profile: small circle r=1.5 centered at 2D (0,0) = world (5,0,0) = helix start
+    SketchEntity prof;
+    prof.type   = SketchEntity::Type::Circle;
+    prof.center = Vec2d(0, 0);
+    prof.radius = 1.5;
+    int prof_idx = doc.add_sketch_entities({prof}, profile_plane, "CircleProfile");
+
+    // Helix path: r=5, pitch=3, height=15 (5 turns) about Z axis from origin
+    int helix_idx = doc.add_helix(SketchPlane::XY(), R, P, 15.0, false, 0.0, "HelixPath");
+
+    int sweep_idx = doc.add_sweep(prof_idx, helix_idx, BooleanMode::New, "Spring");
+    REQUIRE(sweep_idx >= 0);
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.display_mesh.facets_count() > 0);
+
+    const double v = double(doc.display_mesh.volume());
+    REQUIRE(v > 0.0);
+
+    const double one_turn = std::sqrt(std::pow(2.0 * M_PI * R, 2) + std::pow(P, 2));
+    const double total_len = 5.0 * one_turn;
+    const double prof_area = M_PI * 1.5 * 1.5;
+    const double expected_v = prof_area * total_len;
+    REQUIRE_THAT(v, WithinRel(expected_v, 0.1));
+}
+
+TEST_CASE("helix serialization round-trip with distinctive values", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    doc.add_helix(SketchPlane::XZ(), 7.5, 3.25, 22.0, true, 5.0, "Helix_RT");
+    doc.features.back().helix_radius      = 7.5;
+    doc.features.back().helix_pitch       = 3.25;
+    doc.features.back().helix_height      = 22.0;
+    doc.features.back().helix_left_handed = true;
+    doc.features.back().helix_taper_deg   = 5.0;
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    // Deserialize through the real entry point — recompute fails because a lone
+    // helix doesn't produce a solid, but the serialized field values must survive.
+    CadDocument doc2;
+    doc2.deserialize_recipe(blob);
+    REQUIRE(doc2.features.size() == 1);
+
+    const auto& f = doc2.features[0];
+    REQUIRE(f.type == CadFeatureType::Helix);
+    REQUIRE(f.name == "Helix_RT");
+    REQUIRE_THAT(f.helix_radius,      WithinAbs(7.5, 1e-9));
+    REQUIRE_THAT(f.helix_pitch,       WithinAbs(3.25, 1e-9));
+    REQUIRE_THAT(f.helix_height,      WithinAbs(22.0, 1e-9));
+    REQUIRE(f.helix_left_handed == true);
+    REQUIRE_THAT(f.helix_taper_deg,   WithinAbs(5.0, 1e-9));
+}
+
+TEST_CASE("helix with sweep path from a non-sketch/non-helix feature errors", "[CadDocument]")
+{
+    // An Extrude feature used as sweep path must fail cleanly.
+    CadDocument doc;
+
+    // Profile: circle
+    SketchEntity prof;
+    prof.type   = SketchEntity::Type::Circle;
+    prof.center = Vec2d(0, 0);
+    prof.radius = 2.0;
+    int prof_idx = doc.add_sketch_entities({prof}, SketchPlane::XY(), "Profile");
+
+    // Path: an Extrude feature (not a Sketch or Helix)
+    CadFeature ex;
+    ex.type       = CadFeatureType::Extrude;
+    ex.name       = "NotAValidPath";
+    ex.sketch_ref = -1;
+    doc.features.push_back(ex);
+    int path_idx = int(doc.features.size()) - 1;
+
+    int sw = doc.add_sweep(prof_idx, path_idx, BooleanMode::New, "BadSweep");
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_FALSE(doc.error.empty());
+}
+
+TEST_CASE("transform translate shifts body bbox by the given vector", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "S");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Box");
+    REQUIRE(doc.recompute());
+
+    Bnd_Box bb0;
+    BRepBndLib::Add(doc.bodies[0].shape, bb0);
+    double xmin0, ymin0, zmin0, xmax0, ymax0, zmax0;
+    bb0.Get(xmin0, ymin0, zmin0, xmax0, ymax0, zmax0);
+    double vol0 = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+
+    doc.checkpoint();
+    doc.add_transform(0, Vec3d(5, 0, 0), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 0, false, "Move");
+    REQUIRE(doc.recompute());
+
+    REQUIRE(doc.bodies.size() == 1);
+    double vol1 = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+    REQUIRE_THAT(vol1, WithinRel(vol0, 1e-6));
+
+    Bnd_Box bb1;
+    BRepBndLib::Add(doc.bodies[0].shape, bb1);
+    double xmin1, ymin1, zmin1, xmax1, ymax1, zmax1;
+    bb1.Get(xmin1, ymin1, zmin1, xmax1, ymax1, zmax1);
+    REQUIRE_THAT(xmin1, WithinAbs(xmin0 + 5, 1e-6));
+    REQUIRE_THAT(xmax1, WithinAbs(xmax0 + 5, 1e-6));
+}
+
+TEST_CASE("transform rotate 90 about Z swaps XY bbox extents", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "S");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Box");
+    REQUIRE(doc.recompute());
+
+    Bnd_Box bb0;
+    BRepBndLib::Add(doc.bodies[0].shape, bb0);
+    double xmin0, ymin0, zmin0, xmax0, ymax0, zmax0;
+    bb0.Get(xmin0, ymin0, zmin0, xmax0, ymax0, zmax0);
+    double vol0 = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+    double dx0 = xmax0 - xmin0;
+    double dy0 = ymax0 - ymin0;
+
+    doc.checkpoint();
+    doc.add_transform(0, Vec3d(0, 0, 0), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 90, false, "Rot90");
+    REQUIRE(doc.recompute());
+
+    double vol1 = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+    REQUIRE_THAT(vol1, WithinRel(vol0, 1e-6));
+
+    Bnd_Box bb1;
+    BRepBndLib::Add(doc.bodies[0].shape, bb1);
+    double xmin1, ymin1, zmin1, xmax1, ymax1, zmax1;
+    bb1.Get(xmin1, ymin1, zmin1, xmax1, ymax1, zmax1);
+    double dx1 = xmax1 - xmin1;
+    double dy1 = ymax1 - ymin1;
+    REQUIRE_THAT(dx1, WithinAbs(dy0, 1e-6));
+    REQUIRE_THAT(dy1, WithinAbs(dx0, 1e-6));
+}
+
+TEST_CASE("transform copy keeps original and appends transformed body", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "S");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Box");
+    REQUIRE(doc.recompute());
+
+    Bnd_Box bb0;
+    BRepBndLib::Add(doc.bodies[0].shape, bb0);
+    double xmin0, ymin0, zmin0, xmax0, ymax0, zmax0;
+    bb0.Get(xmin0, ymin0, zmin0, xmax0, ymax0, zmax0);
+
+    doc.checkpoint();
+    doc.add_transform(0, Vec3d(5, 0, 0), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 0, true, "Copy");
+    REQUIRE(doc.recompute());
+
+    REQUIRE(doc.bodies.size() == 2);
+
+    Bnd_Box bb_orig;
+    BRepBndLib::Add(doc.bodies[0].shape, bb_orig);
+    double xo_min, yo_min, zo_min, xo_max, yo_max, zo_max;
+    bb_orig.Get(xo_min, yo_min, zo_min, xo_max, yo_max, zo_max);
+    REQUIRE_THAT(xo_min, WithinAbs(xmin0, 1e-6));
+    REQUIRE_THAT(xo_max, WithinAbs(xmax0, 1e-6));
+
+    Bnd_Box bb_copy;
+    BRepBndLib::Add(doc.bodies[1].shape, bb_copy);
+    double xc_min, yc_min, zc_min, xc_max, yc_max, zc_max;
+    bb_copy.Get(xc_min, yc_min, zc_min, xc_max, yc_max, zc_max);
+    REQUIRE_THAT(xc_min, WithinAbs(xmin0 + 5, 1e-6));
+    REQUIRE_THAT(xc_max, WithinAbs(xmax0 + 5, 1e-6));
+}
+
+TEST_CASE("transform degenerate axis errors", "[CadDocument]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "S");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Box");
+    REQUIRE(doc.recompute());
+
+    doc.checkpoint();
+    doc.add_transform(0, Vec3d(0, 0, 0), Vec3d(0, 0, 0), Vec3d(0, 0, 0), 45, false, "Bad");
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE(doc.error.find("axis") != std::string::npos);
+}
+
+TEST_CASE("transform moved body participates in later boolean at its new position", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    // Two boxes that do NOT overlap
+    int sk0 = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 5, "S0");
+    doc.add_extrude(sk0, 5.0, false, BooleanMode::New, "Box0");
+
+    int sk1 = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 5, "S1");
+    doc.add_extrude(sk1, 5.0, false, BooleanMode::New, "Box1");
+    doc.features.back().target_body = 0;
+    REQUIRE(doc.recompute());
+
+    double v0 = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+    double v1 = double(SketchEngine::tessellate(doc.bodies[1].shape).volume());
+    double sum = v0 + v1;
+
+    // Move body 1 so it overlaps body 0
+    doc.checkpoint();
+    doc.add_transform(1, Vec3d(5, 5, 0), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 0, false, "Move1");
+    REQUIRE(doc.recompute());
+
+    doc.add_boolean(BooleanMode::Add, 0, 1, false, 0.0, -1, -1, "Fuse");
+    REQUIRE(doc.recompute());
+
+    REQUIRE(doc.bodies.size() == 1);
+    double vf = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+    // Partial overlap: strictly more than one box (the move DID take effect) and strictly
+    // less than both (they still intersect). Without a real B-rep transform the two boxes
+    // stay coincident and vf would equal v0 -- that is what `vf > v0` catches.
+    REQUIRE(vf > v0 * 1.05);
+    REQUIRE(vf < sum);
+}
+
+TEST_CASE("transform round-trip preserves all xf_* fields", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "S");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Box");
+    doc.add_transform(0, Vec3d(3, 4, 5), Vec3d(0, 1, 0), Vec3d(1, 2, 3), 37, true, "RoundTrip");
+    REQUIRE(doc.recompute());
+    int nb = int(doc.bodies.size());
+    REQUIRE(nb >= 1);
+
+    // Capture bboxes before serialization
+    std::vector<std::pair<Vec3d, Vec3d>> bboxes_before;
+    for (int i = 0; i < nb; ++i) {
+        Bnd_Box bb;
+        BRepBndLib::Add(doc.bodies[i].shape, bb);
+        double x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        bboxes_before.push_back({Vec3d(x0, y0, z0), Vec3d(x1, y1, z1)});
+    }
+
+    auto blob = doc.serialize_recipe();
+
+    CadDocument doc2;
+    REQUIRE(doc2.deserialize_recipe(blob));
+    REQUIRE(doc2.bodies.size() == size_t(nb));
+
+    // Check the Transform feature fields
+    bool found = false;
+    for (const auto& f : doc2.features) {
+        if (f.type != CadFeatureType::Transform) continue;
+        REQUIRE_THAT(f.xf_translate.x(), WithinAbs(3, 1e-9));
+        REQUIRE_THAT(f.xf_translate.y(), WithinAbs(4, 1e-9));
+        REQUIRE_THAT(f.xf_translate.z(), WithinAbs(5, 1e-9));
+        REQUIRE_THAT(f.xf_axis.x(), WithinAbs(0, 1e-9));
+        REQUIRE_THAT(f.xf_axis.y(), WithinAbs(1, 1e-9));
+        REQUIRE_THAT(f.xf_axis.z(), WithinAbs(0, 1e-9));
+        REQUIRE_THAT(f.xf_pivot.x(), WithinAbs(1, 1e-9));
+        REQUIRE_THAT(f.xf_pivot.y(), WithinAbs(2, 1e-9));
+        REQUIRE_THAT(f.xf_pivot.z(), WithinAbs(3, 1e-9));
+        REQUIRE_THAT(f.xf_angle_deg, WithinAbs(37, 1e-9));
+        REQUIRE(f.xf_copy == true);
+        found = true;
+        break;
+    }
+    REQUIRE(found);
+
+    // Verify bboxes equal
+    for (int i = 0; i < nb; ++i) {
+        Bnd_Box bb;
+        BRepBndLib::Add(doc2.bodies[i].shape, bb);
+        double x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        REQUIRE_THAT(x0, WithinAbs(bboxes_before[i].first.x(), 1e-6));
+        REQUIRE_THAT(y0, WithinAbs(bboxes_before[i].first.y(), 1e-6));
+        REQUIRE_THAT(z0, WithinAbs(bboxes_before[i].first.z(), 1e-6));
+        REQUIRE_THAT(x1, WithinAbs(bboxes_before[i].second.x(), 1e-6));
+        REQUIRE_THAT(y1, WithinAbs(bboxes_before[i].second.y(), 1e-6));
+        REQUIRE_THAT(z1, WithinAbs(bboxes_before[i].second.z(), 1e-6));
+    }
+}
+
+// --- Thicken tests ---
+
+TEST_CASE("thicken a planar face to a plate", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxSketch");
+    REQUIRE(sk >= 0);
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude1");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        Vec3d n = GeometryEngine::face_normal_world(fc);
+        if (n.z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    doc.add_thicken(0, top_face, 3.0, false, "Plate");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 2);
+
+    double v = double(SketchEngine::tessellate(doc.bodies[1].shape).volume());
+    REQUIRE_THAT(v, WithinRel(20.0 * 20.0 * 3.0, 0.01));
+}
+
+TEST_CASE("thicken flip offsets against face normal", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxSketch");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude1");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        Vec3d n = GeometryEngine::face_normal_world(fc);
+        if (n.z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    // non-flipped: plate grows above the box (z > 10)
+    CadDocument doc2;
+    int sk2 = doc2.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxSketch2");
+    doc2.add_extrude(sk2, 10.0, false, BooleanMode::New, "Extrude2");
+    REQUIRE(doc2.recompute());
+    int nf2 = GeometryEngine::face_count(doc2.bodies[0].shape);
+    int tf2 = -1;
+    for (int i = 0; i < nf2; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc2.bodies[0].shape, i);
+        Vec3d n = GeometryEngine::face_normal_world(fc);
+        if (n.z() > 0.9) { tf2 = i; break; }
+    }
+    REQUIRE(tf2 >= 0);
+    doc2.add_thicken(0, tf2, 3.0, false, "PlateFwd");
+    REQUIRE(doc2.recompute());
+    Bnd_Box bb_fwd; BRepBndLib::Add(doc2.bodies[1].shape, bb_fwd);
+    Standard_Real x0, y0, z0, x1, y1, z1;
+    bb_fwd.Get(x0, y0, z0, x1, y1, z1);
+
+    // flipped: plate grows below the face plane (z < 10)
+    CadDocument doc3;
+    int sk3 = doc3.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxSketch3");
+    doc3.add_extrude(sk3, 10.0, false, BooleanMode::New, "Extrude3");
+    REQUIRE(doc3.recompute());
+    int nf3 = GeometryEngine::face_count(doc3.bodies[0].shape);
+    int tf3 = -1;
+    for (int i = 0; i < nf3; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc3.bodies[0].shape, i);
+        Vec3d n = GeometryEngine::face_normal_world(fc);
+        if (n.z() > 0.9) { tf3 = i; break; }
+    }
+    REQUIRE(tf3 >= 0);
+    doc3.add_thicken(0, tf3, 3.0, true, "PlateRev");
+    REQUIRE(doc3.recompute());
+    Bnd_Box bb_rev; BRepBndLib::Add(doc3.bodies[1].shape, bb_rev);
+    Standard_Real rx0, ry0, rz0, rx1, ry1, rz1;
+    bb_rev.Get(rx0, ry0, rz0, rx1, ry1, rz1);
+
+    // forward plate bbox z > 10 (source face at z=10, +3 offset = z in (10,13))
+    REQUIRE(z0 >= 9.9);
+    // reverse plate bbox z < 10 (source face at z=10, -3 offset = z in (7,10))
+    REQUIRE(rz1 <= 10.1);
+}
+
+TEST_CASE("thicken bad face index returns error", "[CadDocument]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Ext");
+    REQUIRE(doc.recompute());
+
+    doc.add_thicken(0, 9999, 3.0, false, "Bad");
+    bool ok = doc.recompute();
+    REQUIRE_FALSE(ok);
+    REQUIRE(doc.error.find("face") != std::string::npos);
+}
+
+TEST_CASE("thicken zero thickness returns error", "[CadDocument]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Ext");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        Vec3d n = GeometryEngine::face_normal_world(fc);
+        if (n.z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    doc.add_thicken(0, top_face, 0.0, false, "Zero");
+    bool ok = doc.recompute();
+    REQUIRE_FALSE(ok);
+    REQUIRE(doc.error.find("thickness") != std::string::npos);
+}
+
+TEST_CASE("thickened plate fuses with source", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Ext");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    double v_box = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        Vec3d n = GeometryEngine::face_normal_world(fc);
+        if (n.z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    doc.add_thicken(0, top_face, 3.0, false, "Plate");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 2);
+
+    doc.add_boolean(BooleanMode::Add, 0, 1, false, 0.0, -1, -1, "Fuse");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    double v_fused = double(SketchEngine::tessellate(doc.bodies[0].shape).volume());
+    REQUIRE(v_fused > v_box);
+}
+
+TEST_CASE("thicken round-trip serialization", "[CadDocument]")
+{
+    using Catch::Matchers::WithinAbs;
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Ext");
+    REQUIRE(doc.recompute());
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        Vec3d n = GeometryEngine::face_normal_world(fc);
+        if (n.z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+    doc.add_thicken(0, top_face, 3.0, false, "Plate");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 2);
+
+    // Remember field values
+    int tf  = doc.features.back().thicken_face;
+    double tt = doc.features.back().thicken_thickness;
+    bool tb   = doc.features.back().thicken_flip;
+    size_t nb = doc.bodies.size();
+
+    std::vector<std::pair<Vec3d, Vec3d>> bboxes;
+    for (const auto& b : doc.bodies) {
+        Bnd_Box bb; BRepBndLib::Add(b.shape, bb);
+        Standard_Real x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        bboxes.push_back({Vec3d(x0, y0, z0), Vec3d(x1, y1, z1)});
+    }
+
+    std::string blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc2;
+    REQUIRE(doc2.deserialize_recipe(blob));
+    REQUIRE(doc2.features.size() == doc.features.size());
+    REQUIRE(doc2.bodies.size() == nb);
+
+    const CadFeature& f2 = doc2.features.back();
+    REQUIRE(f2.thicken_face     == tf);
+    REQUIRE_THAT(f2.thicken_thickness, WithinAbs(tt, 1e-9));
+    REQUIRE(f2.thicken_flip     == tb);
+
+    for (size_t i = 0; i < nb; ++i) {
+        Bnd_Box bb; BRepBndLib::Add(doc2.bodies[i].shape, bb);
+        Standard_Real x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        REQUIRE_THAT(double(x0), WithinAbs(bboxes[i].first.x(),  1e-6));
+        REQUIRE_THAT(double(y0), WithinAbs(bboxes[i].first.y(),  1e-6));
+        REQUIRE_THAT(double(z0), WithinAbs(bboxes[i].first.z(),  1e-6));
+        REQUIRE_THAT(double(x1), WithinAbs(bboxes[i].second.x(), 1e-6));
+        REQUIRE_THAT(double(y1), WithinAbs(bboxes[i].second.y(), 1e-6));
+        REQUIRE_THAT(double(z1), WithinAbs(bboxes[i].second.z(), 1e-6));
+    }
+}
+
+// --- Project feature tests ---
+
+TEST_CASE("project a box top face to 4 lines, extrudable", "[CadDocument][project]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Ext");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        Vec3d n = GeometryEngine::face_normal_world(fc);
+        if (n.z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    int proj = doc.add_project_edges(0, {}, top_face, SketchPlane::XY(), "ProjTop");
+    REQUIRE(proj >= 0);
+    doc.add_extrude(proj, 5.0, false, BooleanMode::New, "FromProj");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    const auto& pf = doc.features[proj];
+    REQUIRE(pf.entities.size() == 4);
+    for (const auto& e : pf.entities)
+        REQUIRE(e.type == SketchEntity::Type::Line);
+
+    REQUIRE(doc.bodies.size() >= 2);
+    double v = double(SketchEngine::tessellate(doc.bodies.back().shape).volume());
+    REQUIRE_THAT(v, WithinRel(20.0 * 20.0 * 5.0, 1e-3));
+}
+
+TEST_CASE("project a cylinder top edge to 1 circle, extrudable", "[CadDocument][project]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    SketchEntity c;
+    c.type   = SketchEntity::Type::Circle;
+    c.center = Vec2d(0, 0);
+    c.radius = 6.0;
+    int sk = doc.add_sketch_entities({c}, SketchPlane::XY(), "Circ");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Cyl");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int n_edges = GeometryEngine::edge_count(doc.bodies[0].shape);
+    int top_edge = -1;
+    for (int i = 0; i < n_edges; ++i) {
+        TopoDS_Edge e = GeometryEngine::edge_by_index(doc.bodies[0].shape, i);
+        auto pts = GeometryEngine::sample_edge_world(e);
+        if (pts.empty()) continue;
+        Vec3d mid = Vec3d::Zero();
+        for (const auto& p : pts) mid += p;
+        mid /= double(pts.size());
+        if (mid.z() > 9.0) {
+            BRepAdaptor_Curve ac(e);
+            if (ac.GetType() == GeomAbs_Circle) { top_edge = i; break; }
+        }
+    }
+    REQUIRE(top_edge >= 0);
+
+    int proj = doc.add_project_edges(0, {top_edge}, -1, SketchPlane::XY(), "ProjCirc");
+    REQUIRE(proj >= 0);
+    doc.add_extrude(proj, 4.0, false, BooleanMode::New, "FromCirc");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    const auto& pf = doc.features[proj];
+    REQUIRE(pf.entities.size() == 1);
+    REQUIRE(pf.entities[0].type == SketchEntity::Type::Circle);
+    REQUIRE_THAT(pf.entities[0].radius, WithinRel(6.0, 1e-3));
+
+    REQUIRE(doc.bodies.size() >= 2);
+    double v = double(SketchEngine::tessellate(doc.bodies.back().shape).volume());
+    REQUIRE_THAT(v, WithinRel(M_PI * 36.0 * 4.0, 1e-2));
+}
+
+TEST_CASE("project with no face and no edge selection projects every edge", "[CadDocument][project]")
+{
+    // This is the state the Project card opens in — its label reads "(all edges)". Before the
+    // all-edges branch existed it threw "no edges or face selected", so the card's default
+    // could never be confirmed.
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Ext");
+    REQUIRE(doc.recompute());
+
+    int proj = doc.add_project_edges(0, {}, -1, SketchPlane::XY(), "ProjAll");
+    REQUIRE(proj >= 0);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // A box has 12 edges; the 4 running along Z collapse to points on XY and are dropped,
+    // leaving the 4 bottom and 4 top edges.
+    const auto& pf = doc.features[proj];
+    REQUIRE(pf.entities.size() == 8);
+    for (const auto& e : pf.entities) {
+        REQUIRE(e.type == SketchEntity::Type::Line);
+        REQUIRE((e.p1 - e.p0).norm() > 1e-6);
+    }
+}
+
+TEST_CASE("project bad face id returns error", "[CadDocument][project]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Ext");
+    REQUIRE(doc.recompute());
+
+    doc.add_project_edges(0, {}, 9999, SketchPlane::XY(), "Bad");
+    bool ok = doc.recompute();
+    REQUIRE_FALSE(ok);
+    bool has_project = doc.error.find("project") != std::string::npos
+                    || doc.error.find("face")     != std::string::npos;
+    REQUIRE(has_project);
+}
+
+TEST_CASE("project round-trip serialization", "[CadDocument][project]")
+{
+    using Catch::Matchers::WithinAbs;
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Ext");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        Vec3d n = GeometryEngine::face_normal_world(fc);
+        if (n.z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    doc.add_project_edges(0, {}, top_face, SketchPlane::XY(), "ProjTop");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int saved_src   = doc.features.back().project_source_body;
+    int saved_face  = doc.features.back().project_face;
+    auto saved_edges = doc.features.back().project_edges;
+    size_t saved_nb = doc.bodies.size();
+
+    std::vector<std::pair<Vec3d, Vec3d>> bboxes;
+    for (const auto& b : doc.bodies) {
+        Bnd_Box bb; BRepBndLib::Add(b.shape, bb);
+        Standard_Real x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        bboxes.push_back({Vec3d(x0, y0, z0), Vec3d(x1, y1, z1)});
+    }
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc2;
+    REQUIRE(doc2.deserialize_recipe(blob));
+    REQUIRE(doc2.bodies.size() == saved_nb);
+    REQUIRE(doc2.features.size() == doc.features.size());
+
+    const auto& f2 = doc2.features.back();
+    REQUIRE(f2.project_source_body == saved_src);
+    REQUIRE(f2.project_face  == saved_face);
+    REQUIRE(f2.project_edges == saved_edges);
+
+    for (size_t i = 0; i < saved_nb; ++i) {
+        Bnd_Box bb; BRepBndLib::Add(doc2.bodies[i].shape, bb);
+        Standard_Real x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        REQUIRE_THAT(double(x0), WithinAbs(bboxes[i].first.x(),  1e-6));
+        REQUIRE_THAT(double(y0), WithinAbs(bboxes[i].first.y(),  1e-6));
+        REQUIRE_THAT(double(z0), WithinAbs(bboxes[i].first.z(),  1e-6));
+        REQUIRE_THAT(double(x1), WithinAbs(bboxes[i].second.x(), 1e-6));
+        REQUIRE_THAT(double(y1), WithinAbs(bboxes[i].second.y(), 1e-6));
+        REQUIRE_THAT(double(z1), WithinAbs(bboxes[i].second.z(), 1e-6));
+    }
+}
+
+TEST_CASE("Use/Convert Entities: box top-face edges land as construction geometry", "[CadDocument][project]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Ext");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        if (GeometryEngine::face_normal_world(fc).z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    int target = doc.add_sketch_entities({}, SketchPlane::XY(), "Use");
+    REQUIRE(target >= 0);
+
+    int appended = doc.project_edges_into_sketch(target, 0, {}, top_face);
+    REQUIRE(appended == 4);
+
+    const auto& ents = doc.features[target].entities;
+    REQUIRE(ents.size() == 4);
+    for (const auto& e : ents) {
+        REQUIRE(e.type == SketchEntity::Type::Line);
+        REQUIRE(e.construction == true);
+    }
+}
+
+TEST_CASE("Use/Convert Entities: construction references never become solid", "[CadDocument][project]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Ext");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        if (GeometryEngine::face_normal_world(fc).z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    const size_t body_count_before = doc.bodies.size();
+    const double volume_before     = doc.body_mass_properties(0).volume;
+
+    int target   = doc.add_sketch_entities({}, SketchPlane::XY(), "Use");
+    int appended = doc.project_edges_into_sketch(target, 0, {}, top_face);
+    REQUIRE(appended == 4);
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == body_count_before);
+    REQUIRE_THAT(doc.body_mass_properties(0).volume, WithinRel(volume_before, 1e-9));
+}
+
+TEST_CASE("Use/Convert Entities: bad references return -1 and change nothing", "[CadDocument][project]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Ext");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int target = doc.add_sketch_entities({}, SketchPlane::XY(), "Use");
+    REQUIRE(target >= 0);
+
+    REQUIRE(doc.project_edges_into_sketch(-1, 0, {}, -1) == -1);
+    REQUIRE(doc.project_edges_into_sketch(999, 0, {}, -1) == -1);
+    REQUIRE(doc.project_edges_into_sketch(target, -1, {}, -1) == -1);
+    REQUIRE(doc.project_edges_into_sketch(target, 999, {}, -1) == -1);
+    REQUIRE(doc.features[target].entities.empty());
+}
+
+TEST_CASE("Use/Convert Entities: cylinder edge arrives as a Circle, not a polyline", "[CadDocument][project]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    SketchEntity c;
+    c.type   = SketchEntity::Type::Circle;
+    c.center = Vec2d(0, 0);
+    c.radius = 6.0;
+    int sk = doc.add_sketch_entities({c}, SketchPlane::XY(), "Circ");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Cyl");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int n_edges = GeometryEngine::edge_count(doc.bodies[0].shape);
+    int top_edge = -1;
+    for (int i = 0; i < n_edges; ++i) {
+        TopoDS_Edge e = GeometryEngine::edge_by_index(doc.bodies[0].shape, i);
+        auto pts = GeometryEngine::sample_edge_world(e);
+        if (pts.empty()) continue;
+        Vec3d mid = Vec3d::Zero();
+        for (const auto& p : pts) mid += p;
+        mid /= double(pts.size());
+        if (mid.z() > 9.0) {
+            BRepAdaptor_Curve ac(e);
+            if (ac.GetType() == GeomAbs_Circle) { top_edge = i; break; }
+        }
+    }
+    REQUIRE(top_edge >= 0);
+
+    int target   = doc.add_sketch_entities({}, SketchPlane::XY(), "Use");
+    int appended = doc.project_edges_into_sketch(target, 0, {top_edge}, -1);
+    REQUIRE(appended == 1);
+
+    const auto& ents = doc.features[target].entities;
+    REQUIRE(ents.size() == 1);
+    REQUIRE(ents[0].type == SketchEntity::Type::Circle);
+    REQUIRE(ents[0].construction == true);
+    REQUIRE_THAT(ents[0].radius, WithinRel(6.0, 1e-6));
+}
+
+TEST_CASE("Project feature still emits non-construction entities (regression guard)", "[CadDocument][project]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Ext");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int n_faces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int top_face = -1;
+    for (int i = 0; i < n_faces; ++i) {
+        TopoDS_Face fc = GeometryEngine::face_by_index(doc.bodies[0].shape, i);
+        if (GeometryEngine::face_normal_world(fc).z() > 0.9) { top_face = i; break; }
+    }
+    REQUIRE(top_face >= 0);
+
+    int proj = doc.add_project_edges(0, {}, top_face, SketchPlane::XY(), "ProjTop");
+    REQUIRE(proj >= 0);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    const auto& pf = doc.features[proj];
+    REQUIRE(pf.entities.size() == 4);
+    for (const auto& e : pf.entities)
+        REQUIRE(e.construction == false);
+}
+
+// --- Golden recipe fixture (v1 format tripwire) ---
+
+static CadDocument make_golden_doc_v1()
+{
+    CadDocument doc;
+
+    // ---- Body 0: base box with distinctive taper ----
+    int sk0 = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                             30, 20, 15, "Sketch_Base");
+    doc.add_extrude(sk0, 15.0, false, BooleanMode::New, "Extrude_Base");
+    int ex0 = int(doc.features.size()) - 1;
+    doc.features[ex0].taper_deg = 8.5;
+    doc.features[ex0].extrude_end = ExtrudeEnd::Blind;
+
+    // Dress-up: fillet lateral faces, chamfer top face — distinct non-default sizes
+    doc.add_fillet(3.5, FaceGroup::Lateral, "Fillet_Lat35");
+    doc.add_chamfer(2.0, FaceGroup::Top, "Chamfer_Top2");
+
+    // Hole: offset position, non-through
+    doc.add_hole(7.5, 11.0, false, 4.0, 3.0, SketchPlane::XY(), "Hole_Off75");
+
+    // Draft: angle 7.25 deg on face 3
+    doc.add_draft(7.25, 3, 0, "Draft_F3");
+
+    // Shell: thickness 1.375 mm, open face 1
+    doc.add_shell(1.375, 1, 0, "Shell_T1375");
+
+    // Thread: internal, radius 4, pitch 2.5, height 15, depth 1.25
+    doc.add_thread(4.0, 2.5, 15.0, 1.25, true, 0.0, 0.0, SketchPlane::XY(), "Thread_Int");
+
+    // Cut: plane XY, offset 10, flip, keep upper only
+    doc.add_cut(SketchPlane::XY(), 10.0, true, true, false, 0, "Cut_Flip");
+
+    // Pattern: linear 5 copies, spacing 13.5 mm along plane X
+    doc.add_pattern(false, 5, 13.5, 0, 360.0, 0, "Pattern_Lin5");
+
+    // ---- Datum plane ----
+    doc.add_plane(0, 25.0, 0.0, 0, "Plane_Datum25");
+
+    // ---- Revolve: self-contained body (sketch + revolve) ----
+    {
+        CadFeature sk;
+        sk.type = CadFeatureType::Sketch;
+        sk.name = "Sketch_Rev";
+        sk.plane = SketchPlane::XY();
+        sk.entities = {{SketchEntity::Type::Circle, Vec2d(12,0), Vec2d(12,0), Vec2d(12,0), 4.0}};
+        doc.features.push_back(sk);
+    }
+    int rev_sk = int(doc.features.size()) - 1;
+    doc.add_revolve(rev_sk, 217.0, 1, false, BooleanMode::New, "Revolve_Y217");
+
+    // ---- Sweep: self-contained body (profile + path sketches + sweep) ----
+    {
+        CadFeature sk;
+        sk.type = CadFeatureType::Sketch;
+        sk.name = "Sketch_SwProf";
+        sk.plane = SketchPlane::XY();
+        sk.entities = {{SketchEntity::Type::Circle, Vec2d(0,0), Vec2d(0,0), Vec2d(0,0), 3.0}};
+        doc.features.push_back(sk);
+    }
+    int sw_prof = int(doc.features.size()) - 1;
+    {
+        CadFeature sk;
+        sk.type = CadFeatureType::Sketch;
+        sk.name = "Sketch_SwPath";
+        sk.plane = SketchPlane::XZ();
+        sk.entities = {{SketchEntity::Type::Line, Vec2d(0,0), Vec2d(0,35)}};
+        doc.features.push_back(sk);
+    }
+    int sw_path = int(doc.features.size()) - 1;
+    doc.add_sweep(sw_prof, sw_path, BooleanMode::New, "Sweep_Z35");
+
+    // ---- Loft: self-contained body (two profiles + loft) ----
+    {
+        CadFeature sk;
+        sk.type = CadFeatureType::Sketch;
+        sk.name = "Sketch_LoftBot";
+        sk.plane = SketchPlane::XY();
+        sk.profile.points = {{-7,-7},{7,-7},{7,7},{-7,7}};
+        sk.profile.closed = true;
+        doc.features.push_back(sk);
+    }
+    int loft_bot = int(doc.features.size()) - 1;
+    {
+        CadFeature sk;
+        sk.type = CadFeatureType::Sketch;
+        sk.name = "Sketch_LoftTop";
+        sk.plane.origin = Vec3d(0, 0, 25);
+        sk.plane.normal = Vec3d(0, 0, 1);
+        sk.plane.x_axis = Vec3d(1, 0, 0);
+        sk.plane.y_axis = Vec3d(0, 1, 0);
+        sk.profile.points = {{-9,-9},{9,-9},{9,9},{-9,9}};
+        sk.profile.closed = true;
+        doc.features.push_back(sk);
+    }
+    int loft_top = int(doc.features.size()) - 1;
+    doc.add_loft({loft_bot, loft_top}, true, BooleanMode::New, "Loft_Ruled");
+
+    // ---- Boolean: distinctive tolerance and face-mate params ----
+    doc.add_boolean(BooleanMode::Cut, 0, 1, false, 0.01, 2, 3, "Boolean_Cut");
+
+    // ---- Extrude variant: symmetric + two-sided end ----
+    {
+        CadFeature sk;
+        sk.type = CadFeatureType::Sketch;
+        sk.name = "Sketch_Ex2";
+        sk.plane = SketchPlane::XZ();
+        sk.entities = {{SketchEntity::Type::Circle, Vec2d(0,0), Vec2d(0,0), Vec2d(0,0), 6.0}};
+        doc.features.push_back(sk);
+    }
+    int sk_ex2 = int(doc.features.size()) - 1;
+    {
+        CadFeature ex;
+        ex.type = CadFeatureType::Extrude;
+        ex.name = "Extrude_Sym";
+        ex.sketch_ref = sk_ex2;
+        ex.distance = 25.0;
+        ex.symmetric = true;
+        ex.mode = BooleanMode::New;
+        ex.extrude_end = ExtrudeEnd::Symmetric;
+        ex.distance2 = 12.5;
+        doc.features.push_back(ex);
+    }
+
+    // ---- Mirror: XZ plane, New mode, keep_original=false (distinctive non-defaults) ----
+    doc.add_mirror(SketchPlane::XZ(), 0, BooleanMode::New, "Mirror_XZ");
+    doc.features.back().mirror_keep_original = false;
+
+    // ---- Datum Axis: two-points with distinctive non-default coordinates ----
+    {
+        int ax = doc.add_axis(AxisType::TwoPoints, "Axis_TP");
+        doc.features[ax].axis_p1 = Vec3d(10, 20, 30);
+        doc.features[ax].axis_p2 = Vec3d(13, 24, 34);
+        doc.features[ax].axis_body = 1;
+        doc.features[ax].axis_face = 3;
+        doc.features[ax].axis_edge = 2;
+        doc.features[ax].axis_plane_a = 4;
+        doc.features[ax].axis_plane_b = 5;
+    }
+
+    // ---- Datum CoordSys: PointWorld with distinctive origin ----
+    {
+        int cs = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(7, 8, 9), "CS_PtWorld");
+        doc.features[cs].coordsys_body   = 2;
+        doc.features[cs].coordsys_face   = 1;
+        doc.features[cs].coordsys_edge   = 0;
+        doc.features[cs].coordsys_x_hint = Vec3d(0.5, 0.8, 0.3);
+    }
+
+    // ---- Helix: conical left-handed with distinctive non-default values ----
+    {
+        int hx = doc.add_helix(SketchPlane::XZ(), 11.5, 4.25, 18.0, true, 3.0, "Helix_CLH");
+        (void)hx;
+    }
+
+    // ---- Transform: rigid move/rotate with distinctive non-default values ----
+    doc.add_transform(0, Vec3d(3.5, 4.5, 5.5), Vec3d(0.0, 1.0, 0.0), Vec3d(1.5, 2.5, 3.5),
+                      37.0, true, "GoldenTransform");
+
+    doc.add_thicken(0, 0, 1.75, true, "GoldenThicken");
+
+    doc.add_split_by_face(0, 0, 2, true, false, "GoldenSplit");
+
+    doc.add_project_edges(0, {}, 0, SketchPlane::XY(), "GoldenProject");
+
+    // Construction-flag on-disk lock: a real edge + a construction edge with distinctive
+    // literals. Regen-golden does not recompute, so this only exercises serialization.
+    {
+        std::vector<SketchEntity> ge;
+        SketchEntity real0; real0.type = SketchEntity::Type::Line;
+        real0.p0 = Vec2d(-12.0, -12.0); real0.p1 = Vec2d(12.0, -12.0);
+        SketchEntity ctor; ctor.type = SketchEntity::Type::Line;
+        ctor.p0 = Vec2d(-40.0, 9.0); ctor.p1 = Vec2d(40.0, 9.0);
+        ctor.construction = true;
+        ge.push_back(real0);
+        ge.push_back(ctor);
+        doc.add_sketch_entities(ge, SketchPlane::XY(), "Sketch_Ctor");
+    }
+
+    // ---- Mate connectors: two CoordSys features with distinctive non-default values ----
+    int cs_idx_a = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(11, 12, 13), "CS_MateA");
+    doc.features[cs_idx_a].coordsys_body = 0;
+    doc.features[cs_idx_a].coordsys_x_hint = Vec3d(0.1, 0.2, 0.9);
+    int cs_idx_b = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(14, 15, 16), "CS_MateB");
+    doc.features[cs_idx_b].coordsys_body = 1;
+    doc.features[cs_idx_b].coordsys_x_hint = Vec3d(0.6, 0.7, 0.3);
+
+    // ---- Mate: Fastened with all six fields carrying distinctive non-defaults ----
+    doc.add_mate(1, cs_idx_a, cs_idx_b, 7.25, 33.0, true, "GoldenMate");
+
+    return doc;
+}
+
+TEST_CASE("regenerate golden recipe fixture", "[.regen]")
+{
+    CadDocument doc = make_golden_doc_v1();
+    // ponytail: serialize_recipe() only needs features, recompute is unnecessary
+    // for a fixture that exercises the serialization format.
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    // Version-free on purpose: this writes whatever today's format is, so a version bump does
+    // not have to remember to edit it. The version-stamped fixtures beside it are frozen
+    // evidence from older builds and are never regenerated.
+    std::string path = std::string(TEST_DATA_DIR) + "/cad_recipe_current.bin";
+    std::ofstream ofs(path, std::ios::binary);
+    REQUIRE(ofs.is_open());
+    ofs.write(blob.data(), static_cast<std::streamsize>(blob.size()));
+    ofs.close();
+    SUCCEED("Fixture written to " << path);
+}
+
+// The previous format's real blob, kept on disk deliberately. It is the only thing that can
+// prove the version gate does its job: a v3 recipe carries FEWER fields per feature than this
+// build reads, so without the bump to v4 it would have passed the gate and had two ints read
+// past the end of every connector — into the next feature's bytes. Silent corruption of a saved
+// project, which is far worse than a refusal. This asserts the refusal is clean and says why.
+//
+// Do NOT regenerate cad_recipe_v3.bin. Its value is entirely that it was written by an older
+// build; rewriting it with today's code destroys the only evidence this test rests on.
+TEST_CASE("a previous-format recipe is refused, not silently misread", "[CadDocument]")
+{
+    std::string path = std::string(TEST_DATA_DIR) + "/cad_recipe_v3.bin";
+    std::ifstream ifs(path, std::ios::binary);
+    REQUIRE(ifs.is_open());
+    std::string blob((std::istreambuf_iterator<char>(ifs)), std::istreambuf_iterator<char>());
+    ifs.close();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc;
+    REQUIRE_FALSE(doc.deserialize_recipe(blob));
+    REQUIRE_FALSE(doc.error.empty());
+    REQUIRE(doc.error.find("older version") != std::string::npos);
+    REQUIRE(doc.features.empty());   // nothing half-read was left behind
+}
+
+TEST_CASE("golden recipe v1 still deserialises", "[CadDocument]")
+{
+    using Catch::Matchers::WithinRel;
+    using Catch::Matchers::WithinAbs;
+
+    // Read the golden blob from disk
+    std::string path = std::string(TEST_DATA_DIR) + "/cad_recipe_v4.bin";
+    std::ifstream ifs(path, std::ios::binary);
+    REQUIRE(ifs.is_open());
+    std::string blob((std::istreambuf_iterator<char>(ifs)),
+                      std::istreambuf_iterator<char>());
+    ifs.close();
+    REQUIRE_FALSE(blob.empty());
+
+    // --- Layer 1: deserialize features WITHOUT recomputing, assert field values ---
+    std::vector<CadFeature> features;
+    {
+        std::istringstream iss(blob);
+        cereal::BinaryInputArchive ar(iss);
+        uint32_t v;
+        ar(v);
+        REQUIRE(v <= CadDocument::ORCA_CAD_RECIPE_VERSION);
+        ar(features);
+    }
+
+    CadDocument expected = make_golden_doc_v1();
+    // Scoped tightly: this advice is ONLY valid for a count mismatch. It must not be in
+    // scope for the field-value assertions below, where "regenerate the fixture" is the
+    // one thing you must never do -- regenerating after a reorder bakes the corrupted
+    // layout in as the new golden and permanently disarms this test.
+    {
+        INFO("Feature count changed - did you add/remove features in make_golden_doc_v1()?");
+        INFO("If so: run libslic3r_tests \"[.regen]\" and re-run this test.");
+        REQUIRE(features.size() == expected.features.size());
+    }
+
+    // A failure BELOW this point means the on-disk serialization format changed: some field
+    // in CadFeature::save/load was reordered, retyped, or removed. Fields may only ever be
+    // APPENDED at the end of both lists. Do NOT regenerate the fixture to make this pass --
+    // fix the field order instead. See scripts/CAD/run-kernel-tests.sh and the [.regen] case.
+
+    // Field-by-field assertions against expected values.
+    // Every field set to a distinctive non-default literal must be checked here.
+    // A field reorder in save()/load() that swaps fields of differing types
+    // will produce a wrong value at this position and FAIL the test.
+
+    for (size_t i = 0; i < features.size(); ++i) {
+        const auto& f = features[i];
+        const auto& e = expected.features[i];
+
+        INFO("Feature index " << i << " type " << int(f.type));
+
+        REQUIRE(f.type == e.type);
+        REQUIRE(f.name == e.name);
+        REQUIRE(f.enabled == e.enabled);
+
+        // Sketch params (all Sketch types)
+        if (f.type == CadFeatureType::Sketch) {
+            REQUIRE(f.shape == e.shape);
+            if (e.name == "Sketch_Base") {
+                REQUIRE(f.width  == 30);
+                REQUIRE(f.height == 20);
+                REQUIRE(f.radius == 15);
+            }
+            if (e.name == "Sketch_Rev" || e.name == "Sketch_SwProf" || e.name == "Sketch_Ex2" || e.name == "Sketch_SwPath") {
+                REQUIRE(f.entities.size() == e.entities.size());
+                if (!f.entities.empty()) {
+                    REQUIRE(f.entities[0].type == e.entities[0].type);
+                    REQUIRE_THAT(f.entities[0].p0.x(), WithinAbs(e.entities[0].p0.x(), 1e-9));
+                    REQUIRE_THAT(f.entities[0].p0.y(), WithinAbs(e.entities[0].p0.y(), 1e-9));
+                }
+            }
+            if (e.name == "Sketch_LoftBot" || e.name == "Sketch_LoftTop") {
+                REQUIRE(f.profile.points.size() == e.profile.points.size());
+                REQUIRE(f.profile.closed == e.profile.closed);
+            }
+            if (e.name == "Sketch_LoftTop") {
+                REQUIRE_THAT(f.plane.origin.z(), WithinAbs(25.0, 1e-9));
+            }
+            if (e.name == "Sketch_Ctor") {
+                REQUIRE(f.entities.size() == 2);
+                REQUIRE(f.entities[0].construction == false);
+                REQUIRE(f.entities[1].construction == true);
+                REQUIRE_THAT(f.entities[1].p0.x(), WithinAbs(-40.0, 1e-9));
+            }
+        }
+
+        // Extrude params
+        if (f.type == CadFeatureType::Extrude) {
+            REQUIRE(f.mode == e.mode);
+            if (e.name == "Extrude_Base") {
+                REQUIRE(f.distance   == 15.0);
+                REQUIRE(f.symmetric  == false);
+                REQUIRE(f.extrude_end == ExtrudeEnd::Blind);
+                REQUIRE_THAT(f.taper_deg, WithinAbs(8.5, 1e-9));
+            }
+            if (e.name == "Extrude_Sym") {
+                REQUIRE(f.distance    == 25.0);
+                REQUIRE(f.symmetric   == true);
+                REQUIRE(f.extrude_end == ExtrudeEnd::Symmetric);
+                REQUIRE_THAT(f.distance2, WithinAbs(12.5, 1e-9));
+            }
+        }
+
+        // Fillet
+        if (f.type == CadFeatureType::Fillet && e.name == "Fillet_Lat35") {
+            REQUIRE_THAT(f.dressup_size, WithinAbs(3.5, 1e-9));
+            REQUIRE(f.face_group == FaceGroup::Lateral);
+        }
+
+        // Chamfer
+        if (f.type == CadFeatureType::Chamfer && e.name == "Chamfer_Top2") {
+            REQUIRE_THAT(f.dressup_size, WithinAbs(2.0, 1e-9));
+            REQUIRE(f.face_group == FaceGroup::Top);
+        }
+
+        // Hole
+        if (f.type == CadFeatureType::Hole && e.name == "Hole_Off75") {
+            REQUIRE_THAT(f.hole_diameter, WithinAbs(7.5, 1e-9));
+            REQUIRE_THAT(f.hole_depth,    WithinAbs(11.0, 1e-9));
+            REQUIRE(f.hole_through == false);
+            REQUIRE_THAT(f.hole_x, WithinAbs(4.0, 1e-9));
+            REQUIRE_THAT(f.hole_y, WithinAbs(3.0, 1e-9));
+        }
+
+        // Draft
+        if (f.type == CadFeatureType::Draft && e.name == "Draft_F3") {
+            REQUIRE(f.draft_face == 3);
+            REQUIRE_THAT(f.draft_angle, WithinAbs(7.25, 1e-9));
+        }
+
+        // Shell
+        if (f.type == CadFeatureType::Shell && e.name == "Shell_T1375") {
+            REQUIRE_THAT(f.shell_thickness, WithinAbs(1.375, 1e-9));
+            REQUIRE(f.shell_face == 1);
+        }
+
+        // Thread
+        if (f.type == CadFeatureType::Thread && e.name == "Thread_Int") {
+            REQUIRE_THAT(f.thread_radius,   WithinAbs(4.0, 1e-9));
+            REQUIRE_THAT(f.thread_pitch,    WithinAbs(2.5, 1e-9));
+            REQUIRE_THAT(f.thread_height,   WithinAbs(15.0, 1e-9));
+            REQUIRE_THAT(f.thread_depth,    WithinAbs(1.25, 1e-9));
+            REQUIRE(f.thread_internal == true);
+            REQUIRE_THAT(f.thread_x, WithinAbs(0.0, 1e-9));
+            REQUIRE_THAT(f.thread_y, WithinAbs(0.0, 1e-9));
+        }
+
+        // Cut
+        if (f.type == CadFeatureType::Cut && e.name == "Cut_Flip") {
+            REQUIRE_THAT(f.cut_offset,     WithinAbs(10.0, 1e-9));
+            REQUIRE(f.cut_flip       == true);
+            REQUIRE(f.cut_keep_upper == true);
+            REQUIRE(f.cut_keep_lower == false);
+        }
+
+        // Pattern
+        if (f.type == CadFeatureType::Pattern && e.name == "Pattern_Lin5") {
+            REQUIRE(f.pattern_circular == false);
+            REQUIRE(f.pattern_count    == 5);
+            REQUIRE_THAT(f.pattern_spacing, WithinAbs(13.5, 1e-9));
+            REQUIRE(f.pattern_dir == 0);
+        }
+
+        // Datum Plane
+        if (f.type == CadFeatureType::Plane && e.name == "Plane_Datum25") {
+            REQUIRE(f.plane_base       == 0);
+            REQUIRE_THAT(f.plane_offset, WithinAbs(25.0, 1e-9));
+            REQUIRE_THAT(f.plane_angle_tilt, WithinAbs(0.0, 1e-9));
+            REQUIRE(f.plane_axis == 0);
+        }
+
+        // Revolve
+        if (f.type == CadFeatureType::Revolve && e.name == "Revolve_Y217") {
+            REQUIRE_THAT(f.revolve_angle, WithinAbs(217.0, 1e-9));
+            REQUIRE(f.revolve_axis == 1);
+        }
+
+        // Sweep
+        if (f.type == CadFeatureType::Sweep && e.name == "Sweep_Z35") {
+            REQUIRE(f.sweep_path_ref == e.sweep_path_ref);
+            REQUIRE(f.sweep_path_ref >= 0);
+        }
+
+        // Loft
+        if (f.type == CadFeatureType::Loft && e.name == "Loft_Ruled") {
+            REQUIRE(f.loft_ruled == true);
+            REQUIRE(f.loft_profile_refs.size() == 2);
+        }
+
+        // Boolean
+        if (f.type == CadFeatureType::Boolean && e.name == "Boolean_Cut") {
+            REQUIRE(f.mode          == BooleanMode::Cut);
+            REQUIRE(f.bool_tool_body == 1);
+            REQUIRE(f.bool_keep_tool == false);
+            REQUIRE_THAT(f.bool_tolerance,   WithinAbs(0.01, 1e-9));
+            REQUIRE(f.bool_target_face == 2);
+            REQUIRE(f.bool_tool_face   == 3);
+        }
+
+        // Mirror
+        if (f.type == CadFeatureType::Mirror && e.name == "Mirror_XZ") {
+            REQUIRE(f.mode                 == BooleanMode::New);
+            REQUIRE(f.mirror_keep_original == false);
+            REQUIRE(f.target_body          == 0);
+        }
+
+        // Datum Axis
+        if (f.type == CadFeatureType::Axis && e.name == "Axis_TP") {
+            REQUIRE(f.axis_type  == AxisType::TwoPoints);
+            REQUIRE_THAT(f.axis_p1.x(), WithinAbs(10.0, 1e-9));
+            REQUIRE_THAT(f.axis_p1.y(), WithinAbs(20.0, 1e-9));
+            REQUIRE_THAT(f.axis_p1.z(), WithinAbs(30.0, 1e-9));
+            REQUIRE_THAT(f.axis_p2.x(), WithinAbs(13.0, 1e-9));
+            REQUIRE_THAT(f.axis_p2.y(), WithinAbs(24.0, 1e-9));
+            REQUIRE_THAT(f.axis_p2.z(), WithinAbs(34.0, 1e-9));
+            REQUIRE(f.axis_body     == 1);
+            REQUIRE(f.axis_face     == 3);
+            REQUIRE(f.axis_edge     == 2);
+            REQUIRE(f.axis_plane_a  == 4);
+            REQUIRE(f.axis_plane_b  == 5);
+        }
+
+        // Datum CoordSys
+        if (f.type == CadFeatureType::CoordSys && e.name == "CS_PtWorld") {
+            REQUIRE(f.coordsys_type == CoordSysType::PointWorld);
+            REQUIRE_THAT(f.coordsys_point.x(), WithinAbs(7.0, 1e-9));
+            REQUIRE_THAT(f.coordsys_point.y(), WithinAbs(8.0, 1e-9));
+            REQUIRE_THAT(f.coordsys_point.z(), WithinAbs(9.0, 1e-9));
+            REQUIRE(f.coordsys_body == 2);
+            REQUIRE(f.coordsys_face == 1);
+            REQUIRE(f.coordsys_edge == 0);
+            REQUIRE_THAT(f.coordsys_x_hint.x(), WithinAbs(0.5, 1e-9));
+            REQUIRE_THAT(f.coordsys_x_hint.y(), WithinAbs(0.8, 1e-9));
+            REQUIRE_THAT(f.coordsys_x_hint.z(), WithinAbs(0.3, 1e-9));
+        }
+
+        // Helix
+        if (f.type == CadFeatureType::Helix && e.name == "Helix_CLH") {
+            REQUIRE_THAT(f.helix_radius,      WithinAbs(11.5, 1e-9));
+            REQUIRE_THAT(f.helix_pitch,       WithinAbs(4.25, 1e-9));
+            REQUIRE_THAT(f.helix_height,      WithinAbs(18.0, 1e-9));
+            REQUIRE(f.helix_left_handed == true);
+            REQUIRE_THAT(f.helix_taper_deg,   WithinAbs(3.0, 1e-9));
+        }
+
+        // Transform
+        if (f.type == CadFeatureType::Transform && e.name == "GoldenTransform") {
+            REQUIRE_THAT(f.xf_translate.x(), WithinAbs(3.5, 1e-9));
+            REQUIRE_THAT(f.xf_translate.y(), WithinAbs(4.5, 1e-9));
+            REQUIRE_THAT(f.xf_translate.z(), WithinAbs(5.5, 1e-9));
+            REQUIRE_THAT(f.xf_axis.x(),      WithinAbs(0.0, 1e-9));
+            REQUIRE_THAT(f.xf_axis.y(),      WithinAbs(1.0, 1e-9));
+            REQUIRE_THAT(f.xf_axis.z(),      WithinAbs(0.0, 1e-9));
+            REQUIRE_THAT(f.xf_pivot.x(),     WithinAbs(1.5, 1e-9));
+            REQUIRE_THAT(f.xf_pivot.y(),     WithinAbs(2.5, 1e-9));
+            REQUIRE_THAT(f.xf_pivot.z(),     WithinAbs(3.5, 1e-9));
+            REQUIRE_THAT(f.xf_angle_deg,     WithinAbs(37.0, 1e-9));
+            REQUIRE(f.xf_copy == true);
+        }
+
+        // Thicken
+        if (f.type == CadFeatureType::Thicken && e.name == "GoldenThicken") {
+            REQUIRE(f.thicken_face     == 0);
+            REQUIRE_THAT(f.thicken_thickness, WithinAbs(1.75, 1e-9));
+            REQUIRE(f.thicken_flip     == true);
+        }
+
+        // Cut-by-face: GoldenSplit uses cut_face_body/cut_face instead of plane
+        if (f.type == CadFeatureType::Cut && e.name == "GoldenSplit") {
+            REQUIRE(f.cut_face_body  == 0);
+            REQUIRE(f.cut_face       == 2);
+            REQUIRE(f.cut_keep_upper == true);
+            REQUIRE(f.cut_keep_lower == false);
+        }
+
+        // Project
+        if (f.type == CadFeatureType::Project && e.name == "GoldenProject") {
+            REQUIRE(f.project_source_body == 0);
+            REQUIRE(f.project_face  == 0);
+            REQUIRE(f.project_edges == e.project_edges);
+        }
+
+        // Mate
+        if (f.type == CadFeatureType::Mate && e.name == "GoldenMate") {
+            REQUIRE(f.mate_kind   == 1);
+            REQUIRE(f.mate_cs_a   == e.mate_cs_a);
+            REQUIRE(f.mate_cs_b   == e.mate_cs_b);
+            REQUIRE_THAT(f.mate_offset, WithinAbs(7.25, 1e-9));
+            REQUIRE_THAT(f.mate_angle,  WithinAbs(33.0, 1e-9));
+            REQUIRE(f.mate_flip   == true);
+        }
+    }
+
+    // --- Layer 2: geometry check (optional — only if the document recomputes) ---
+    // Build expected document and try to recompute it.
+    // ponytail: the field-value layer above is the real tripwire;
+    // this layer is a bonus sanity check on the full recompute path.
+    CadDocument exp_doc = make_golden_doc_v1();
+    bool exp_ok = exp_doc.recompute();
+    if (!exp_ok) {
+        INFO("Expected document from make_golden_doc_v1() could not recompute "
+             "(complex feature tree). Field-value checks above are sufficient.");
+    }
+
+    CadDocument doc;
+    bool ser_ok = doc.deserialize_recipe(blob);
+
+    if (exp_ok && ser_ok) {
+        REQUIRE(doc.error.empty());
+        REQUIRE(doc.bodies.size() == exp_doc.bodies.size());
+        for (size_t i = 0; i < doc.bodies.size(); ++i) {
+            double v = double(SketchEngine::tessellate(doc.bodies[i].shape).volume());
+            double ev = double(SketchEngine::tessellate(exp_doc.bodies[i].shape).volume());
+            REQUIRE_THAT(v, WithinRel(ev, 1e-6));
+        }
+    } else {
+        INFO("The golden recipe fixture was loaded and field-value checks passed.");
+        INFO("Recompute on the deserialized or expected document failed — this is");
+        INFO("expected for the extended golden fixture (many feature types coexist");
+        INFO("purely for serialization coverage). The field-value tripwire above is");
+        INFO("the primary format check.");
+    }
+}
+
+// --- Rib tests (M5b) ---
+
+TEST_CASE("rib adds material to a box", "[CadDocument][rib]")
+{
+    using Catch::Matchers::WithinRel;
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+
+    // Build a box: 40x40x10 extruded on XY -> z=[0,10]
+    int sk_box = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                                40, 40, 10, "Box");
+    doc.add_extrude(sk_box, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    double Vbox = double(doc.display_mesh.volume());
+    REQUIRE(Vbox > 0.0);
+
+    // Sketch a single open Line across the box footprint, on the same XY plane.
+    // Line from (5,20) to (35,20), centred in Y but off-centre in X.
+    std::vector<SketchEntity> ents = {
+        {SketchEntity::Type::Line, Vec2d(5, 20), Vec2d(35, 20)},
+    };
+    int sk_rib = doc.add_sketch_entities(ents, SketchPlane::XY(), "RibLine");
+    REQUIRE(sk_rib >= 0);
+
+    int fi = doc.add_rib(sk_rib, 0, 3.0, 12.0, 0, "Rib");
+    REQUIRE(fi >= 0);
+    REQUIRE(doc.features[fi].type == CadFeatureType::Rib);
+
+    bool ok = doc.recompute();
+    REQUIRE(ok);
+    REQUIRE(doc.error.empty());
+    // The rib fused extra material -> volume must be strictly larger.
+    double Vrib = double(doc.display_mesh.volume());
+    REQUIRE(Vrib > Vbox);
+
+    // A rib with a bad sketch ref must fail cleanly, not crash.
+    CadDocument bad;
+    bad.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    bad.add_extrude(0, 10.0, false, BooleanMode::New, "E");
+    REQUIRE(bad.recompute());
+    bad.add_rib(999, 0, 3.0, 10.0, 0, "BadRib");
+    REQUIRE_FALSE(bad.recompute());
+}
+
+TEST_CASE("rib accepts a Project feature as its sketch ref", "[CadDocument][rib]")
+{
+    // Project carries plane + Line entities, which is all a rib reads. Every other consumer
+    // (Extrude, SurfaceExtrude, SurfaceRevolve) already accepts it; Rib used to reject it,
+    // which made "project a body edge, then rib along it" unreachable.
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 40, 40, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    double Vbox = double(doc.display_mesh.volume());
+
+    // Project the whole body onto XY: the 4 top and 4 bottom edges survive as Lines.
+    int proj = doc.add_project_edges(0, {}, -1, SketchPlane::XY(), "Proj");
+    REQUIRE(proj >= 0);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.features[proj].entities.size() == 8);
+
+    int fi = doc.add_rib(proj, 0, 3.0, 12.0, 0, "RibFromProjection");
+    REQUIRE(fi >= 0);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(double(doc.display_mesh.volume()) > Vbox);
+}
+
+TEST_CASE("rib non-line entity rejected safely", "[CadDocument][rib]")
+{
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+
+    // Sketch with a Circle entity (not a Line)
+    std::vector<SketchEntity> ents = {
+        {SketchEntity::Type::Circle, Vec2d(0, 0), Vec2d(0, 0), Vec2d(0, 0), 5.0},
+    };
+    int sk2 = doc.add_sketch_entities(ents, SketchPlane::XY(), "CircleSketch");
+    doc.add_rib(sk2, 0, 2.0, 10.0, 0, "BadRib");
+
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_FALSE(doc.error.empty());
+    REQUIRE_CONTAINS(doc.error, "rib");
+}
+
+TEST_CASE("rib round-trip serialization", "[CadDocument][rib]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 40, 40, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+
+    std::vector<SketchEntity> ents = {
+        {SketchEntity::Type::Line, Vec2d(5, 20), Vec2d(35, 20)},
+    };
+    int sk2 = doc.add_sketch_entities(ents, SketchPlane::XY(), "RibLine");
+    doc.add_rib(sk2, 0, 3.0, 12.0, 0, "Rib");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    size_t nb = doc.bodies.size();
+    double Vdoc = double(doc.display_mesh.volume());
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument fresh;
+    REQUIRE(fresh.deserialize_recipe(blob));
+    REQUIRE(fresh.bodies.size() == nb);
+    double Vfresh = double(fresh.display_mesh.volume());
+    REQUIRE_THAT(Vfresh, WithinAbs(Vdoc, 1e-6));
+
+    // Find the rib feature and check its fields survived.
+    const CadFeature* rf = nullptr;
+    for (const auto& f : fresh.features) {
+        if (f.type == CadFeatureType::Rib) { rf = &f; break; }
+    }
+    REQUIRE(rf != nullptr);
+    REQUIRE_THAT(rf->rib_thickness, WithinAbs(3.0, 1e-9));
+    REQUIRE_THAT(rf->rib_depth,     WithinAbs(12.0, 1e-9));
+}
+
+// --- Bridge tests (M3c) ---
+
+TEST_CASE("bridge two collinear lines", "[CadDocument][bridge]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    std::vector<SketchEntity> ents = {
+        {SketchEntity::Type::Line, Vec2d(0,0), Vec2d(10,0)},
+        {SketchEntity::Type::Line, Vec2d(20,0), Vec2d(30,0)},
+    };
+    int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+    REQUIRE(sk == 0);
+
+    int bi = doc.add_bridge(0, 0, 1, 1, 0, "Bridge");
+    REQUIRE(bi == 2);
+
+    const auto& se = doc.features[0].entities;
+    REQUIRE(se.size() == 3);
+    REQUIRE(se[bi].type == SketchEntity::Type::BSpline);
+    REQUIRE(se[bi].ctrl.size() == 4);
+    REQUIRE_THAT(se[bi].ctrl.front().x(), WithinAbs(10.0, 1e-6));
+    REQUIRE_THAT(se[bi].ctrl.front().y(), WithinAbs(0.0, 1e-6));
+    REQUIRE_THAT(se[bi].ctrl.back().x(), WithinAbs(20.0, 1e-6));
+    REQUIRE_THAT(se[bi].ctrl.back().y(), WithinAbs(0.0, 1e-6));
+}
+
+TEST_CASE("bridge closes a C profile and extrudes", "[CadDocument][bridge]")
+{
+    using Catch::Matchers::WithinAbs;
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    // Right-side of a closed square: P0(10,-10), up to P1(10,10)
+    std::vector<SketchEntity> ents = {
+        // bottom edge: (-10,-10) to (10,-10)
+        {SketchEntity::Type::Line, Vec2d(-10,-10), Vec2d(10,-10)},
+        // left edge: (10,-10) to (10,10)
+        {SketchEntity::Type::Line, Vec2d(10,-10), Vec2d(10,10)},
+        // top edge: (10,10) to (-10,10)
+        {SketchEntity::Type::Line, Vec2d(10,10), Vec2d(-10,10)},
+    };
+    // Missing: left edge from (-10,10) to (-10,-10). Build it as a separate line
+    // entity so the bridge connects two existing lines.
+    int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "C");
+    REQUIRE(sk == 0);
+
+    // Add the closing line as entity 3: (-10,10) to (-10,-10)
+    CadFeature& f = doc.features[sk];
+    SketchEntity closing;
+    closing.type = SketchEntity::Type::Line;
+    closing.p0 = Vec2d(-10, 10);
+    closing.p1 = Vec2d(-10, -10);
+    // The C is entities 0,1,2 (bottom cap, right side, top cap).
+    // Entity 0 end=1 is (10,-10); entity 2 start=0 is (10,10). That's a U.
+    // But we need a closed square from C shape.
+    // Re-think: a C shape open on the left side.
+    // Entities: 0 = bottom edge (-10,-10)->(10,-10) [end=1 at (10,-10)]
+    //           1 = right edge (10,-10)->(10,10) [start=0 at (10,-10), end=1 at (10,10)]
+    //           2 = top edge (10,10)->(-10,10) [start=0 at (10,10), end=1 at (-10,10)]
+    // The C is open: entity 2's end is at (-10,10) and entity 0's start is at (-10,-10).
+    // Bridge: entity 2 end=1 (-10,10) -> entity 0 start=0 (-10,-10).
+    f.entities.push_back(closing);
+    REQUIRE(f.entities.size() == 4);
+
+    // Now bridge from top end (entity 2 end=1 = (-10,10)) to bottom start (entity 0 end=0 = (-10,-10))
+    int bi = doc.add_bridge(sk, 2/*top edge*/, 1/*end*/, 0/*bottom edge*/, 0/*start*/, "Bridge");
+    REQUIRE(bi == 4);
+    REQUIRE(f.entities.size() == 5);
+
+    // Now the entities should form a closed loop -> extrude
+    int ex = doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(ex >= 0);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.display_mesh.facets_count() > 0);
+    REQUIRE_THAT(double(doc.display_mesh.volume()), WithinRel(20.0 * 20.0 * 5.0, 1e-2));
+}
+
+TEST_CASE("bridge bad indices throw", "[CadDocument][bridge]")
+{
+    CadDocument doc;
+    std::vector<SketchEntity> ents = {
+        {SketchEntity::Type::Line, Vec2d(0,0), Vec2d(10,0)},
+        {SketchEntity::Type::Line, Vec2d(20,0), Vec2d(30,0)},
+    };
+    doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+
+    // out-of-range entity a
+    REQUIRE_THROWS(doc.add_bridge(0, 99, 1, 1, 0, "Bad"));
+    // out-of-range entity b
+    REQUIRE_THROWS(doc.add_bridge(0, 0, 1, 99, 0, "Bad"));
+    // out-of-range sketch_ref
+    REQUIRE_THROWS(doc.add_bridge(99, 0, 1, 1, 0, "Bad"));
+    // non-sketch feature as sketch_ref
+    doc.add_extrude(0, 5.0, false, BooleanMode::New, "Ex");
+    REQUIRE_THROWS(doc.add_bridge(1, 0, 1, 1, 0, "Bad"));
+}
+
+TEST_CASE("bridge round-trip serialization", "[CadDocument][bridge]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    // The two collinear stubs plus the bridge span (0,0)->(30,0); the remaining three lines
+    // return to the origin so the profile is genuinely CLOSED. It used to be just the two
+    // stubs and the bridge, an entirely open chain that "extruded" only because OCCT will
+    // make a face out of an open wire — the silently-wrong geometry this area exists to stop.
+    // This test is about the bridge's serialization round-trip, and deserialize_recipe
+    // recomputes, so the document has to be one that legitimately builds.
+    std::vector<SketchEntity> ents = {
+        {SketchEntity::Type::Line, Vec2d(0,0),   Vec2d(10,0)},
+        {SketchEntity::Type::Line, Vec2d(20,0),  Vec2d(30,0)},
+        {SketchEntity::Type::Line, Vec2d(30,0),  Vec2d(30,10)},
+        {SketchEntity::Type::Line, Vec2d(30,10), Vec2d(0,10)},
+        {SketchEntity::Type::Line, Vec2d(0,10),  Vec2d(0,0)},
+    };
+    int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "S");
+    REQUIRE(sk == 0);
+    int bi = doc.add_bridge(sk, 0, 1, 1, 0, "Bridge");
+    REQUIRE(bi == 5);
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc2;
+    REQUIRE(doc2.deserialize_recipe(blob));
+    REQUIRE(doc2.features.size() == 2);
+
+    const auto& br = doc2.features[0].entities[5];
+    REQUIRE(br.type == SketchEntity::Type::BSpline);
+    REQUIRE(br.ctrl.size() == 4);
+    REQUIRE_THAT(br.ctrl.front().x(), WithinAbs(10.0, 1e-9));
+    REQUIRE_THAT(br.ctrl.front().y(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(br.ctrl.back().x(), WithinAbs(20.0, 1e-9));
+    REQUIRE_THAT(br.ctrl.back().y(), WithinAbs(0.0, 1e-9));
+}
+
+TEST_CASE("delete_face removes a fillet face and restores volume", "[CadDocument][deleteface]")
+{
+    using Catch::Matchers::WithinRel;
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    REQUIRE(sk >= 0);
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    double Vbox = double(doc.display_mesh.volume());
+    REQUIRE(Vbox > 0.0);
+
+    doc.add_fillet(2.0, FaceGroup::All, "Fillet");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    double Vf = double(doc.display_mesh.volume());
+    REQUIRE(Vf < Vbox);
+
+    int nfaces = GeometryEngine::face_count(doc.bodies[0].shape);
+    doc.checkpoint();
+    bool found = false;
+    for (int fi = 0; fi < nfaces && !found; ++fi) {
+        int idx = doc.add_delete_face(0, {fi}, "Unfillet");
+        (void)idx;
+        if (doc.recompute() && doc.error.empty()) {
+            double Vr = double(doc.display_mesh.volume());
+            if (Vr > Vf) {
+                found = true;
+            }
+        }
+        if (!found) doc.undo();
+    }
+    REQUIRE(found);
+}
+
+TEST_CASE("delete_face with bad face index fails safely", "[CadDocument][deleteface]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    REQUIRE(sk >= 0);
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_delete_face(0, {9999}, "Bad");
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_CONTAINS(doc.error, "face");
+}
+
+TEST_CASE("delete_face round-trip serialization", "[CadDocument][deleteface]")
+{
+    using Catch::Matchers::WithinRel;
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    REQUIRE(sk >= 0);
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    doc.add_fillet(2.0, FaceGroup::All, "Fillet");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int nfaces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int fillet_face = -1;
+    for (int fi = 0; fi < nfaces; ++fi) {
+        doc.checkpoint();
+        doc.add_delete_face(0, {fi}, "Unfillet");
+        bool ok = doc.recompute();
+        if (ok && doc.error.empty()) {
+            fillet_face = fi;
+            break;
+        }
+        doc.undo();
+    }
+    REQUIRE(fillet_face >= 0);
+
+    std::vector<std::pair<Vec3d, Vec3d>> bboxes;
+    for (const auto& b : doc.bodies) {
+        Bnd_Box bb; BRepBndLib::Add(b.shape, bb);
+        Standard_Real x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        bboxes.push_back({Vec3d(x0, y0, z0), Vec3d(x1, y1, z1)});
+    }
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc2;
+    REQUIRE(doc2.deserialize_recipe(blob));
+    REQUIRE(doc2.error.empty());
+    REQUIRE(doc2.recompute());
+    REQUIRE(doc2.error.empty());
+    REQUIRE(doc2.bodies.size() == doc.bodies.size());
+
+    for (size_t i = 0; i < bboxes.size(); ++i) {
+        Bnd_Box bb; BRepBndLib::Add(doc2.bodies[i].shape, bb);
+        Standard_Real x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        REQUIRE_THAT(double(x0), WithinAbs(bboxes[i].first.x(),  1e-6));
+        REQUIRE_THAT(double(y0), WithinAbs(bboxes[i].first.y(),  1e-6));
+        REQUIRE_THAT(double(z0), WithinAbs(bboxes[i].first.z(),  1e-6));
+        REQUIRE_THAT(double(x1), WithinAbs(bboxes[i].second.x(), 1e-6));
+        REQUIRE_THAT(double(y1), WithinAbs(bboxes[i].second.y(), 1e-6));
+        REQUIRE_THAT(double(z1), WithinAbs(bboxes[i].second.z(), 1e-6));
+    }
+}
+
+TEST_CASE("hole: counterbore removes more material than a simple bore", "[CadDocument][hole]")
+{
+    using Catch::Matchers::WithinAbs;
+    auto make_box_hole = [](int style, double cbore_d, double cbore_depth,
+                             double csink_d, double csink_angle, const std::string& desig) {
+        CadDocument doc;
+        int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 30, 30, 0, "Box");
+        doc.add_extrude(sk, 15.0, false, BooleanMode::New, "Extrude");
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        double v_box = doc.body_mass_properties(0).volume;
+        if (style == 0)
+            doc.add_hole(6.0, 10.0, false, 0.0, 0.0, SketchPlane::XY(), "Hole");
+        else
+            doc.add_hole_styled(6.0, 10.0, false, 0.0, 0.0, SketchPlane::XY(), style,
+                                cbore_d, cbore_depth, csink_d, csink_angle, desig, "Hole");
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        double v = doc.body_mass_properties(0).volume;
+        REQUIRE(v < v_box);
+        return v;
+    };
+
+    double v_simple   = make_box_hole(0, 0, 0, 0, 0, "");
+    double v_cbore    = make_box_hole(1, 11.0, 6.0, 0, 0, "M6");
+    REQUIRE(v_cbore < v_simple);
+}
+
+TEST_CASE("hole: countersink removes more material than a simple bore", "[CadDocument][hole]")
+{
+    using Catch::Matchers::WithinAbs;
+    auto make_box = []() {
+        CadDocument doc;
+        int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 30, 30, 0, "Box");
+        doc.add_extrude(sk, 15.0, false, BooleanMode::New, "Extrude");
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        return doc;
+    };
+
+    CadDocument doc_simple = make_box();
+    doc_simple.add_hole(6.0, 10.0, false, 0.0, 0.0, SketchPlane::XY(), "Hole");
+    REQUIRE(doc_simple.recompute());
+    double v_simple = doc_simple.body_mass_properties(0).volume;
+    double v_box = 30.0 * 30.0 * 15.0;
+
+    CadDocument doc_csink = make_box();
+    doc_csink.add_hole_styled(6.0, 10.0, false, 0.0, 0.0, SketchPlane::XY(), 2,
+                              0.0, 0.0, 12.0, 90.0, "M6", "Hole");
+    REQUIRE(doc_csink.recompute());
+    double v_csink = doc_csink.body_mass_properties(0).volume;
+
+    REQUIRE(v_simple < v_box);
+    REQUIRE(v_csink < v_simple);
+}
+
+TEST_CASE("hole: standards table lookup", "[CadDocument][hole]")
+{
+    using Catch::Matchers::WithinAbs;
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 30, 30, 0, "Box");
+    doc.add_extrude(sk, 15.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+
+    int fi = doc.add_hole_standard("M6", 0, true, 10, 0, 0, SketchPlane::XY(), "H");
+    REQUIRE(fi >= 0);
+    REQUIRE_THAT(doc.features[fi].hole_diameter, WithinAbs(6.6, 1e-6));
+    REQUIRE(doc.features[fi].hole_standard == "M6");
+
+    REQUIRE_THROWS(doc.add_hole_standard("M999", 0, true, 10, 0, 0, SketchPlane::XY(), "H"));
+    try {
+        doc.add_hole_standard("M999", 0, true, 10, 0, 0, SketchPlane::XY(), "H");
+    } catch (const std::exception& ex) {
+        CHECK_CONTAINS(std::string(ex.what()), "standard");
+    }
+}
+
+TEST_CASE("hole: round-trip preserves styled counterbore hole", "[CadDocument][hole]")
+{
+    using Catch::Matchers::WithinAbs;
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 30, 30, 0, "Box");
+    doc.add_extrude(sk, 15.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_hole_styled(6.0, 10.0, false, 0.0, 0.0, SketchPlane::XY(), 1,
+                        11.0, 6.0, 0.0, 90.0, "M6", "Cbore");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    std::vector<std::pair<Vec3d, Vec3d>> bboxes;
+    for (const auto& b : doc.bodies) {
+        Bnd_Box bb; BRepBndLib::Add(b.shape, bb);
+        Standard_Real x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        bboxes.emplace_back(Vec3d(x0, y0, z0), Vec3d(x1, y1, z1));
+    }
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc2;
+    REQUIRE(doc2.deserialize_recipe(blob));
+    REQUIRE(doc2.error.empty());
+    REQUIRE(doc2.bodies.size() == doc.bodies.size());
+
+    for (size_t i = 0; i < bboxes.size(); ++i) {
+        Bnd_Box bb; BRepBndLib::Add(doc2.bodies[i].shape, bb);
+        Standard_Real x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        REQUIRE_THAT(double(x0), WithinAbs(bboxes[i].first.x(),  1e-6));
+        REQUIRE_THAT(double(y0), WithinAbs(bboxes[i].first.y(),  1e-6));
+        REQUIRE_THAT(double(z0), WithinAbs(bboxes[i].first.z(),  1e-6));
+        REQUIRE_THAT(double(x1), WithinAbs(bboxes[i].second.x(), 1e-6));
+        REQUIRE_THAT(double(y1), WithinAbs(bboxes[i].second.y(), 1e-6));
+        REQUIRE_THAT(double(z1), WithinAbs(bboxes[i].second.z(), 1e-6));
+    }
+
+    bool found = false;
+    for (const auto& f : doc2.features) {
+        if (f.type == CadFeatureType::Hole && f.name == "Cbore") {
+            REQUIRE(f.hole_style == 1);
+            REQUIRE_THAT(f.hole_cbore_diameter, WithinAbs(11.0, 1e-9));
+            found = true;
+        }
+    }
+    REQUIRE(found);
+}
+
+TEST_CASE("variables drive a box (parametric sketch + extrude)", "[CadDocument][variables]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                             20, 20, 10, "Sketch");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.features.size() >= 2);
+    int ex = sk + 1;
+
+    doc.variables = {{"w", "10"}, {"h", "w*2"}};
+    doc.features[sk].expr = {{"width", "w"}, {"height", "w"}};
+    doc.features[ex].expr = {{"distance", "h"}};
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE_FALSE(doc.body.IsNull());
+
+    Bnd_Box bb; BRepBndLib::Add(doc.body, bb);
+    double xlo, ylo, zlo, xhi, yhi, zhi;
+    bb.Get(xlo, ylo, zlo, xhi, yhi, zhi);
+    REQUIRE_THAT(xhi - xlo, WithinAbs(10.0, 1.0));
+    REQUIRE_THAT(yhi - ylo, WithinAbs(10.0, 1.0));
+    REQUIRE_THAT(zhi - zlo, WithinAbs(20.0, 2.0));
+}
+
+TEST_CASE("function + pi in expression binding", "[CadDocument][variables]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Circle, SketchPlane::XY(),
+                             20, 20, 10, "Sketch");
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.features.size() >= 2);
+
+    doc.variables = {{"r", "sqrt(16)+abs(-2)"}};
+    doc.features[sk].expr = {{"radius", "r"}};
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE_THAT(doc.features[sk].radius, WithinAbs(6.0, 1e-6));
+
+    doc.variables = {{"r", "max(3, pi)"}};
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE_THAT(doc.features[sk].radius, WithinAbs(M_PI, 1e-6));
+
+    doc.variables = {{"r", "5"}, {"d", "r*2"}};
+    doc.features[sk].expr = {{"radius", "d"}};
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE_THAT(doc.features[sk].radius, WithinAbs(10.0, 1e-6));
+}
+
+TEST_CASE("cycle detected fails recompute with error", "[CadDocument][variables]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                             20, 20, 10, "Sketch");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    doc.features[sk].expr = {{"width", "a"}};
+
+    doc.variables = {{"a", "b"}, {"b", "a"}};
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_CONTAINS(doc.error, "cycle");
+}
+
+TEST_CASE("unknown parameter fails recompute", "[CadDocument][variables]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                             20, 20, 10, "Sketch");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    doc.features[sk].expr = {{"nope", "1"}};
+
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_CONTAINS(doc.error, "unknown parameter");
+}
+
+TEST_CASE("unknown identifier fails recompute", "[CadDocument][variables]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                             20, 20, 10, "Sketch");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    doc.features[sk].expr = {{"width", "x"}};
+
+    doc.variables = {{"x", "y+1"}};
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_CONTAINS(doc.error, "unknown identifier");
+}
+
+// The checkpoint -> mutate -> recompute -> undo-on-failure pattern is what both the GUI and
+// McpControl use to keep a bad edit out of the document. It only works if the snapshot covers
+// `variables` as well as `features`: undo() used to restore features alone, so a bad variable
+// survived the rollback and every later recompute failed — the document was left unusable.
+TEST_CASE("undo rolls back a bad variable, not just features", "[CadDocument][variables]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Sketch");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    doc.features[sk].expr = {{"width", "w"}};
+    doc.variables = {{"w", "20"}};
+    REQUIRE(doc.recompute());
+
+    // Caller sets a variable to something unevaluable, exactly as action_set_variable does.
+    doc.checkpoint();
+    doc.variables["w"] = "nosuchvar + 1";
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE(doc.undo());
+
+    // The good value must be back...
+    REQUIRE(doc.variables.at("w") == "20");
+    // ...and, the part that actually bit, the document must still be usable.
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+}
+
+// A variable ADDED under a checkpoint must disappear entirely on undo, not linger with a
+// stale value: the pre-mutation snapshot simply did not contain the key.
+TEST_CASE("undo removes a variable that did not exist before the checkpoint", "[CadDocument][variables]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Sketch");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.variables.empty());
+
+    doc.checkpoint();
+    doc.variables["bogus"] = "1/0 +";     // syntactically broken
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE(doc.undo());
+
+    REQUIRE(doc.variables.count("bogus") == 0);
+    REQUIRE(doc.recompute());
+}
+
+TEST_CASE("parametric recipe round-trips through serialize/deserialize", "[CadDocument][variables]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(),
+                             20, 20, 10, "Sketch");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.features.size() >= 2);
+    int ex = sk + 1;
+
+    doc.variables = {{"w", "10"}, {"h", "w*2"}};
+    doc.features[sk].expr = {{"width", "w"}, {"height", "w"}};
+    doc.features[ex].expr = {{"distance", "h"}};
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    Bnd_Box bb_orig; BRepBndLib::Add(doc.body, bb_orig);
+    double ox0, oy0, oz0, ox1, oy1, oz1;
+    bb_orig.Get(ox0, oy0, oz0, ox1, oy1, oz1);
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc2;
+    REQUIRE(doc2.deserialize_recipe(blob));
+
+    REQUIRE(doc2.variables.size() == 2);
+    REQUIRE(doc2.variables["w"] == "10");
+    REQUIRE(doc2.variables["h"] == "w*2");
+
+    bool found_sk = false, found_ex = false;
+    for (const auto& f : doc2.features) {
+        if (f.name == "Sketch") {
+            REQUIRE(f.expr.size() == 2);
+            REQUIRE(f.expr.at("width") == "w");
+            REQUIRE(f.expr.at("height") == "w");
+            found_sk = true;
+        }
+        if (f.name == "Extrude") {
+            REQUIRE(f.expr.size() == 1);
+            REQUIRE(f.expr.at("distance") == "h");
+            found_ex = true;
+        }
+    }
+    REQUIRE(found_sk);
+    REQUIRE(found_ex);
+
+    REQUIRE(doc2.bodies.size() == doc.bodies.size());
+
+    Bnd_Box bb2; BRepBndLib::Add(doc2.body, bb2);
+    double nx0, ny0, nz0, nx1, ny1, nz1;
+    bb2.Get(nx0, ny0, nz0, nx1, ny1, nz1);
+    REQUIRE_THAT(nx0, WithinAbs(ox0, 1e-6));
+    REQUIRE_THAT(ny0, WithinAbs(oy0, 1e-6));
+    REQUIRE_THAT(nz0, WithinAbs(oz0, 1e-6));
+    REQUIRE_THAT(nx1, WithinAbs(ox1, 1e-6));
+    REQUIRE_THAT(ny1, WithinAbs(oy1, 1e-6));
+    REQUIRE_THAT(nz1, WithinAbs(oz1, 1e-6));
+}
+
+TEST_CASE("surface-extrude makes an open shell", "[CadDocument][surface]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Rect");
+    REQUIRE(sk >= 0);
+    int fi = doc.add_surface_extrude(sk, 12.0, "Skin");
+    REQUIRE(fi == 1);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 1);
+    REQUIRE(CadDocument::is_sheet_shape(doc.bodies.back().shape));
+
+    // A rectangle skin has 4 side faces (no end caps).
+    int face_count = 0, solid_count = 0;
+    for (TopExp_Explorer fe(doc.bodies.back().shape, TopAbs_FACE); fe.More(); fe.Next()) ++face_count;
+    for (TopExp_Explorer se(doc.bodies.back().shape, TopAbs_SOLID); se.More(); se.Next()) ++solid_count;
+    REQUIRE(face_count >= 1);
+    REQUIRE(solid_count == 0);
+    REQUIRE(doc.display_mesh.facets_count() > 0);
+}
+
+TEST_CASE("surface-revolve makes an open shell", "[CadDocument][surface]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    // A small rectangle offset from the axis: u=10..15, v=0..5.
+    SketchProfile sp;
+    sp.points = {{10,0},{15,0},{15,5},{10,5}};
+    sp.closed = true;
+    const int sk = doc.add_sketch_profile(sp, SketchPlane::XY(), "Profile");
+    REQUIRE(sk >= 0);
+    int fi = doc.add_surface_revolve(sk, 360, 0, "Rev");
+    REQUIRE(fi == 1);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 1);
+    REQUIRE(CadDocument::is_sheet_shape(doc.bodies.back().shape));
+
+    int solid_count = 0;
+    for (TopExp_Explorer se(doc.bodies.back().shape, TopAbs_SOLID); se.More(); se.Next()) ++solid_count;
+    REQUIRE(solid_count == 0);
+    REQUIRE(doc.display_mesh.facets_count() > 0);
+}
+
+TEST_CASE("surface-extrude bad ref safe", "[CadDocument][surface]")
+{
+    CadDocument doc;
+    int fi = doc.add_surface_extrude(999, 10, "Bad");
+    REQUIRE(fi == 0);
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_CONTAINS(doc.error, "surface-extrude");
+}
+
+TEST_CASE("surface round-trip serialize/deserialize", "[CadDocument][surface]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Rect");
+    doc.add_surface_extrude(sk, 12.0, "Skin");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(CadDocument::is_sheet_shape(doc.bodies.back().shape));
+
+    size_t orig_nb = doc.bodies.size();
+    Bnd_Box orig_bb;
+    BRepBndLib::Add(doc.bodies.back().shape, orig_bb);
+
+    std::string blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument fresh;
+    REQUIRE(fresh.deserialize_recipe(blob));
+    REQUIRE(fresh.error.empty());
+    REQUIRE(fresh.bodies.size() == orig_nb);
+    REQUIRE(CadDocument::is_sheet_shape(fresh.bodies.back().shape));
+
+    Bnd_Box fresh_bb;
+    BRepBndLib::Add(fresh.bodies.back().shape, fresh_bb);
+    Standard_Real ox0, oy0, oz0, ox1, oy1, oz1;
+    orig_bb.Get(ox0, oy0, oz0, ox1, oy1, oz1);
+    Standard_Real fx0, fy0, fz0, fx1, fy1, fz1;
+    fresh_bb.Get(fx0, fy0, fz0, fx1, fy1, fz1);
+    REQUIRE_THAT(double(fx0), WithinAbs(double(ox0), 1e-6));
+    REQUIRE_THAT(double(fy0), WithinAbs(double(oy0), 1e-6));
+    REQUIRE_THAT(double(fz0), WithinAbs(double(oz0), 1e-6));
+    REQUIRE_THAT(double(fx1), WithinAbs(double(ox1), 1e-6));
+    REQUIRE_THAT(double(fy1), WithinAbs(double(oy1), 1e-6));
+    REQUIRE_THAT(double(fz1), WithinAbs(double(oz1), 1e-6));
+}
+
+TEST_CASE("thicken-surface makes a solid from a sheet", "[CadDocument][surface]")
+{
+    using Catch::Matchers::WithinRel;
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Rect");
+    REQUIRE(sk >= 0);
+    int si = doc.add_surface_extrude(sk, 12.0, "Skin");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 1);
+    REQUIRE(CadDocument::is_sheet_shape(doc.bodies.back().shape));
+
+    Bnd_Box sheet_bb;
+    BRepBndLib::Add(doc.bodies.back().shape, sheet_bb);
+
+    int ti = doc.add_thicken_surface(0, 2.0, false, "Wall");
+    REQUIRE(ti == 2);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 2);
+
+    REQUIRE(!CadDocument::is_sheet_shape(doc.bodies.back().shape));
+    double vol = doc.body_mass_properties(1).volume;
+    REQUIRE(vol > 0);
+
+    Bnd_Box thick_bb;
+    BRepBndLib::Add(doc.bodies.back().shape, thick_bb);
+    Standard_Real sx0, sy0, sz0, sx1, sy1, sz1;
+    Standard_Real tx0, ty0, tz0, tx1, ty1, tz1;
+    sheet_bb.Get(sx0, sy0, sz0, sx1, sy1, sz1);
+    thick_bb.Get(tx0, ty0, tz0, tx1, ty1, tz1);
+    REQUIRE_THAT(double(tx0), WithinAbs(double(sx0), 2.1));
+    REQUIRE_THAT(double(tx1), WithinAbs(double(sx1), 2.1));
+}
+
+// Regression for lu27, with the rig's own numbers. A 60x60x40 four-walled open box
+// used to report volume 96000 and an inertia diagonal of [-4.2e7, -4.2e7, -6.9e7] — negative
+// principal moments, which no real body can have. VolumeProperties was being integrated over
+// an open shell as though it were closed, and std::abs() on the mass hid the only obvious tell.
+// The area was always right, so that stays reported and valid; the volume and inertia must not.
+TEST_CASE("mass properties of a sheet body report area only, never a volume",
+          "[CadDocument][surface]")
+{
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 60, 60, 0, "Rect");
+    REQUIRE(sk >= 0);
+    doc.add_surface_extrude(sk, 40.0, "Skin");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 1);
+
+    auto sheet = doc.body_mass_properties(0);
+    REQUIRE_FALSE(sheet.is_solid);
+    REQUIRE(sheet.valid);                       // the area IS trustworthy
+    REQUIRE_THAT(sheet.surface_area, WithinRel(9600.0, 1e-6));   // 4 walls x 60 x 40
+    REQUIRE(sheet.volume == 0.0);
+    for (double v : sheet.inertia)
+        REQUIRE(v == 0.0);
+
+    // The solid thickened from that same sheet is the contrast case: it does have a volume,
+    // and its principal moments are positive, as any real body's must be.
+    REQUIRE(doc.add_thicken_surface(0, 2.0, false, "Wall") >= 0);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 2);
+
+    auto solid = doc.body_mass_properties(1);
+    REQUIRE(solid.is_solid);
+    REQUIRE(solid.valid);
+    REQUIRE(solid.volume > 0.0);
+    REQUIRE(solid.inertia[0] > 0.0);
+    REQUIRE(solid.inertia[4] > 0.0);
+    REQUIRE(solid.inertia[8] > 0.0);
+}
+
+// wm4s. The wall of a thickened open box must contain the corner material. Thickening
+// each face along its own normal and sewing (MakeThickSolidBySimple) leaves the four vertical
+// corners empty and measured 29648.15 where the geometry requires 44000; the two controls below
+// were exact before and must stay exact, since they are what a corner-only fix must not disturb.
+TEST_CASE("thicken surface fills the corners of a closed-loop wall", "[CadDocument][surface]")
+{
+    using Catch::Matchers::WithinRel;
+
+    SECTION("open box: (60^2 - 50^2) * 40") {
+        CadDocument doc;
+        int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 60, 60, 0, "Rect");
+        REQUIRE(sk >= 0);
+        doc.add_surface_extrude(sk, 40.0, "Skin");          // 4 walls, no caps
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.body_mass_properties(0).surface_area == Approx(9600.0)); // the sheet is what we think
+
+        REQUIRE(doc.add_thicken_surface(0, 5.0, false, "Wall") >= 0);
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+
+        auto w = doc.body_mass_properties(1);
+        REQUIRE(w.is_solid);                                 // NOT a shell: the old ByJoin attempts
+        REQUIRE_THAT(w.volume, WithinRel(44000.0, 1e-6));    //   returned volume 0.0 / is_solid false
+        // The wall must sit ON the sheet, not around it: an inverted capped solid offsets the
+        // wrong way and lands at 70x70 with a volume larger than its own bounding box.
+        const auto bb = doc.display_body_meshes[1].bounding_box();
+        REQUIRE_THAT(bb.max.x() - bb.min.x(), WithinRel(60.0, 1e-3));
+        REQUIRE_THAT(bb.max.z() - bb.min.z(), WithinRel(40.0, 1e-3));
+    }
+
+    SECTION("control, flat sheet stays exact: 3600 * 5") {
+        CadDocument doc;
+        int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 60, 60, 0, "Rect");
+        REQUIRE(doc.add_surface_fill(sk, "Face") >= 0);      // one flat face, no rim to mitre
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.add_thicken_surface(0, 5.0, false, "Plate") >= 0);
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+
+        auto p = doc.body_mass_properties(1);
+        REQUIRE(p.is_solid);
+        REQUIRE_THAT(p.volume, WithinRel(18000.0, 1e-6));
+    }
+}
+
+TEST_CASE("surface-offset creates another sheet shifted outward", "[CadDocument][surface]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Rect");
+    REQUIRE(sk >= 0);
+    int si = doc.add_surface_extrude(sk, 12.0, "Skin");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    Bnd_Box src_bb;
+    BRepBndLib::Add(doc.bodies.back().shape, src_bb);
+
+    int oi = doc.add_surface_offset(0, 1.0, "Off");
+    REQUIRE(oi == 2);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 2);
+    REQUIRE(CadDocument::is_sheet_shape(doc.bodies.back().shape));
+
+    Bnd_Box off_bb;
+    BRepBndLib::Add(doc.bodies.back().shape, off_bb);
+    Standard_Real sx0, sy0, sz0, sx1, sy1, sz1;
+    Standard_Real ox0, oy0, oz0, ox1, oy1, oz1;
+    src_bb.Get(sx0, sy0, sz0, sx1, sy1, sz1);
+    off_bb.Get(ox0, oy0, oz0, ox1, oy1, oz1);
+    REQUIRE(std::abs(double(ox0) - double(sx0)) > 1e-3);
+    REQUIRE(std::abs(double(ox1) - double(sx1)) > 1e-3);
+    REQUIRE(std::abs(double(oy0) - double(sy0)) > 1e-3);
+    REQUIRE(std::abs(double(oy1) - double(sy1)) > 1e-3);
+}
+
+TEST_CASE("thicken-surface on non-sheet fails", "[CadDocument][surface]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Rect");
+    REQUIRE(sk >= 0);
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Solid");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE_FALSE(CadDocument::is_sheet_shape(doc.bodies.back().shape));
+
+    doc.add_thicken_surface(0, 2.0, false, "Bad");
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_CONTAINS(doc.error, "sheet");
+}
+
+TEST_CASE("thicken-surface round-trip serialize/deserialize", "[CadDocument][surface]")
+{
+    using Catch::Matchers::WithinAbs;
+    using Catch::Matchers::WithinRel;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Rect");
+    doc.add_surface_extrude(sk, 12.0, "Skin");
+    REQUIRE(doc.recompute());
+    doc.add_thicken_surface(0, 2.0, false, "Wall");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE_FALSE(CadDocument::is_sheet_shape(doc.bodies.back().shape));
+
+    size_t orig_nb = doc.bodies.size();
+    Bnd_Box orig_bb;
+    BRepBndLib::Add(doc.bodies.back().shape, orig_bb);
+
+    std::string blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument fresh;
+    REQUIRE(fresh.deserialize_recipe(blob));
+    REQUIRE(fresh.error.empty());
+    REQUIRE(fresh.bodies.size() == orig_nb);
+    REQUIRE_FALSE(CadDocument::is_sheet_shape(fresh.bodies.back().shape));
+
+    Bnd_Box fresh_bb;
+    BRepBndLib::Add(fresh.bodies.back().shape, fresh_bb);
+    Standard_Real ox0, oy0, oz0, ox1, oy1, oz1;
+    Standard_Real fx0, fy0, fz0, fx1, fy1, fz1;
+    orig_bb.Get(ox0, oy0, oz0, ox1, oy1, oz1);
+    fresh_bb.Get(fx0, fy0, fz0, fx1, fy1, fz1);
+    REQUIRE_THAT(double(fx0), WithinAbs(double(ox0), 1e-6));
+    REQUIRE_THAT(double(fy0), WithinAbs(double(oy0), 1e-6));
+    REQUIRE_THAT(double(fz0), WithinAbs(double(oz0), 1e-6));
+    REQUIRE_THAT(double(fx1), WithinAbs(double(ox1), 1e-6));
+    REQUIRE_THAT(double(fy1), WithinAbs(double(oy1), 1e-6));
+    REQUIRE_THAT(double(fz1), WithinAbs(double(oz1), 1e-6));
+}
+
+TEST_CASE("surface-loft makes an open shell", "[CadDocument][surface]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    SketchProfile bot;
+    bot.points = {{-10,-10},{10,-10},{10,10},{-10,10}};
+    bot.closed = true;
+    int s0 = doc.add_sketch_profile(bot, SketchPlane::XY(), "Bottom");
+
+    doc.add_plane(0 /*XY*/, 20.0, 0.0, 0, "Plane1");
+    SketchPlane top = doc.resolve_datum_planes()[0].second;
+    SketchProfile tp;
+    tp.points = {{-5,-5},{5,-5},{5,5},{-5,5}};
+    tp.closed = true;
+    int s1 = doc.add_sketch_profile(tp, top, "Top");
+
+    int fi = doc.add_surface_loft({s0, s1}, false, "Skin");
+    REQUIRE(fi >= 0);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 1);
+    REQUIRE(CadDocument::is_sheet_shape(doc.bodies.back().shape));
+
+    // Contrast with a solid loft on the same profiles.
+    CadDocument doc2;
+    SketchProfile bot2;
+    bot2.points = {{-10,-10},{10,-10},{10,10},{-10,10}};
+    bot2.closed = true;
+    int a0 = doc2.add_sketch_profile(bot2, SketchPlane::XY(), "Bottom");
+    doc2.add_plane(0 /*XY*/, 20.0, 0.0, 0, "Plane1");
+    SketchPlane top2 = doc2.resolve_datum_planes()[0].second;
+    SketchProfile tp2;
+    tp2.points = {{-5,-5},{5,-5},{5,5},{-5,5}};
+    tp2.closed = true;
+    int a1 = doc2.add_sketch_profile(tp2, top2, "Top");
+    doc2.add_loft({a0, a1}, false, BooleanMode::New, "SolidLoft");
+    REQUIRE(doc2.recompute());
+    REQUIRE(doc2.error.empty());
+    REQUIRE_FALSE(CadDocument::is_sheet_shape(doc2.bodies.back().shape));
+}
+
+TEST_CASE("surface-fill makes a one-face sheet", "[CadDocument][surface]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Rect");
+    REQUIRE(sk >= 0);
+    int fi = doc.add_surface_fill(sk, "Patch");
+    REQUIRE(fi == 1);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 1);
+    REQUIRE(CadDocument::is_sheet_shape(doc.bodies.back().shape));
+
+    int face_count = 0;
+    for (TopExp_Explorer fe(doc.bodies.back().shape, TopAbs_FACE); fe.More(); fe.Next()) ++face_count;
+    REQUIRE(face_count >= 1);
+}
+
+TEST_CASE("surface-loft / surface-fill bad refs safe", "[CadDocument][surface]")
+{
+    {
+        CadDocument doc;
+        doc.add_surface_loft({999}, false, "Bad");
+        REQUIRE_FALSE(doc.recompute());
+        REQUIRE_CONTAINS(doc.error, "surface-loft");
+    }
+    {
+        CadDocument doc;
+        doc.add_surface_fill(999, "Bad");
+        REQUIRE_FALSE(doc.recompute());
+        REQUIRE_CONTAINS(doc.error, "surface-fill");
+    }
+}
+
+TEST_CASE("surface-loft round-trip serialize/deserialize", "[CadDocument][surface]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    SketchProfile bot;
+    bot.points = {{-10,-10},{10,-10},{10,10},{-10,10}};
+    bot.closed = true;
+    int s0 = doc.add_sketch_profile(bot, SketchPlane::XY(), "Bottom");
+    doc.add_plane(0 /*XY*/, 20.0, 0.0, 0, "Plane1");
+    SketchPlane top = doc.resolve_datum_planes()[0].second;
+    SketchProfile tp;
+    tp.points = {{-5,-5},{5,-5},{5,5},{-5,5}};
+    tp.closed = true;
+    int s1 = doc.add_sketch_profile(tp, top, "Top");
+    doc.add_surface_loft({s0, s1}, false, "Skin");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(CadDocument::is_sheet_shape(doc.bodies.back().shape));
+
+    size_t orig_nb = doc.bodies.size();
+    Bnd_Box orig_bb;
+    BRepBndLib::Add(doc.bodies.back().shape, orig_bb);
+
+    std::string blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument fresh;
+    REQUIRE(fresh.deserialize_recipe(blob));
+    REQUIRE(fresh.error.empty());
+    REQUIRE(fresh.bodies.size() == orig_nb);
+    REQUIRE(CadDocument::is_sheet_shape(fresh.bodies.back().shape));
+
+    Bnd_Box fresh_bb;
+    BRepBndLib::Add(fresh.bodies.back().shape, fresh_bb);
+    Standard_Real ox0, oy0, oz0, ox1, oy1, oz1;
+    Standard_Real fx0, fy0, fz0, fx1, fy1, fz1;
+    orig_bb.Get(ox0, oy0, oz0, ox1, oy1, oz1);
+    fresh_bb.Get(fx0, fy0, fz0, fx1, fy1, fz1);
+    REQUIRE_THAT(double(fx0), WithinAbs(double(ox0), 1e-6));
+    REQUIRE_THAT(double(fy0), WithinAbs(double(oy0), 1e-6));
+    REQUIRE_THAT(double(fz0), WithinAbs(double(oz0), 1e-6));
+    REQUIRE_THAT(double(fx1), WithinAbs(double(ox1), 1e-6));
+    REQUIRE_THAT(double(fy1), WithinAbs(double(oy1), 1e-6));
+    REQUIRE_THAT(double(fz1), WithinAbs(double(oz1), 1e-6));
+}
+
+// --- Mate tests (M8a) ---
+
+TEST_CASE("fastened mate with zero offset/angle", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk_box = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk_box, 5.0, false, BooleanMode::New, "BoxExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk_cyl = doc.add_sketch(SketchShape::Circle, SketchPlane::XY(), 0, 0, 3, "Cyl");
+    doc.add_extrude(sk_cyl, 10.0, false, BooleanMode::New, "CylExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 2);
+
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 5), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int mi = doc.add_mate(0, cs_fixed, cs_moving, 0.0, 0.0, false, "Mate");
+    REQUIRE(mi >= 0);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    gp_Pnt com = props.CentreOfMass();
+    REQUIRE_THAT(double(com.X()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Y()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Z()), WithinAbs(5.0, 1e-4));
+}
+
+TEST_CASE("fastened mate with offset", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk2 = doc.add_sketch(SketchShape::Circle, SketchPlane::XY(), 0, 0, 3, "Cyl");
+    doc.add_extrude(sk2, 10.0, false, BooleanMode::New, "CylExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 5), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(0, cs_fixed, cs_moving, 7.0, 0.0, false, "Mate");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    gp_Pnt com = props.CentreOfMass();
+    REQUIRE_THAT(double(com.Z()), WithinAbs(12.0, 1e-4));
+}
+
+TEST_CASE("fastened mate with angle", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk2 = doc.add_sketch(SketchShape::Circle, SketchPlane::XY(), 0, 0, 3, "Cyl");
+    doc.add_extrude(sk2, 10.0, false, BooleanMode::New, "CylExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 5), "CS_Moving");
+    doc.features[cs_moving].coordsys_x_hint = Vec3d(1, 0, 0);
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(0, cs_fixed, cs_moving, 0.0, 90.0, false, "Mate");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    gp_Pnt com = props.CentreOfMass();
+    REQUIRE_THAT(double(com.X()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Y()), WithinAbs(5.0, 1e-4));
+}
+
+TEST_CASE("fastened mate with flip", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk2 = doc.add_sketch(SketchShape::Circle, SketchPlane::XY(), 0, 0, 3, "Cyl");
+    doc.add_extrude(sk2, 10.0, false, BooleanMode::New, "CylExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 5), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(0, cs_fixed, cs_moving, 0.0, 0.0, true, "Mate");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    gp_Pnt com = props.CentreOfMass();
+    REQUIRE_THAT(double(com.X()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Y()), WithinAbs(5.0, 1e-4));
+    // Flip opposes Z axes: for a symmetric cylinder this is invisible in centroid,
+    // but the mate executed cleanly and the body moved to the target connector.
+}
+
+TEST_CASE("planar mate: normal distance becomes mate_offset", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk2 = doc.add_sketch(SketchShape::Circle, SketchPlane::XY(), 0, 0, 3, "Cyl");
+    doc.add_extrude(sk2, 10.0, false, BooleanMode::New, "CylExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(20, 0, 0), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(1, cs_fixed, cs_moving, 3.0, 0.0, false, "MatePlanar");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    gp_Pnt com = props.CentreOfMass();
+    // Connector B was at z=0 (bottom of 10mm cylinder). After planar mate with
+    // offset=3 and A at z=5, the z-distance from A to B becomes 3 => B.z = 8.
+    // The cylinder centroid (was at z=5) moves to z=13.
+    REQUIRE_THAT(double(com.Z()), WithinAbs(13.0, 1e-4));
+}
+
+TEST_CASE("mate round-trip serialization", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_a = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_A");
+    doc.features[cs_a].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk2 = doc.add_sketch(SketchShape::Circle, SketchPlane::XY(), 0, 0, 3, "Cyl");
+    doc.add_extrude(sk2, 10.0, false, BooleanMode::New, "CylExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_b = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(20, 0, 5), "CS_B");
+    doc.features[cs_b].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(1, cs_a, cs_b, 7.25, 33.0, true, "Mate");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    size_t nb = doc.bodies.size();
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument fresh;
+    REQUIRE(fresh.deserialize_recipe(blob));
+    REQUIRE(fresh.bodies.size() == nb);
+
+    const CadFeature* mf = nullptr;
+    for (const auto& f : fresh.features) {
+        if (f.type == CadFeatureType::Mate) { mf = &f; break; }
+    }
+    REQUIRE(mf != nullptr);
+    REQUIRE(mf->mate_kind   == 1);
+    REQUIRE_THAT(mf->mate_offset, WithinAbs(7.25, 1e-9));
+    REQUIRE_THAT(mf->mate_angle,  WithinAbs(33.0, 1e-9));
+    REQUIRE(mf->mate_flip   == true);
+}
+
+TEST_CASE("version 2 blob is rejected", "[CadDocument][mate]")
+{
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    std::ostringstream oss;
+    {
+        cereal::BinaryOutputArchive ar(oss);
+        uint32_t fake_v = 2;
+        ar(fake_v);
+        ar(doc.features);
+        ar(doc.variables);
+    }
+    std::string blob = oss.str();
+
+    CadDocument fresh;
+    REQUIRE_FALSE(fresh.deserialize_recipe(blob));
+    REQUIRE_CONTAINS(fresh.error, "older version");
+}
+
+TEST_CASE("mate error: out of range connectors", "[CadDocument][mate]")
+{
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS");
+    doc.features[cs].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(0, 999, cs, 0, 0, false, "Bad");
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_CONTAINS(doc.error, "mate_cs_a out of range");
+    doc.features.pop_back(); doc.error.clear();
+
+    doc.add_mate(0, cs, 999, 0, 0, false, "Bad");
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_CONTAINS(doc.error, "mate_cs_b out of range");
+    doc.features.pop_back(); doc.error.clear();
+
+    doc.add_mate(0, sk, cs, 0, 0, false, "Bad");
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_CONTAINS(doc.error, "not a valid CoordSys");
+    doc.features.pop_back(); doc.error.clear();
+}
+
+// A mate stores its two connectors as FEATURE INDICES. remove_feature() erases a slot and remaps
+// every surviving sketch_ref through the deletion, but it did not remap mate_cs_a / mate_cs_b —
+// so deleting anything ahead of a connector slid both references down onto whatever features
+// happened to occupy those indices. The validation in recompute() only catches out-of-range and
+// non-CoordSys targets; when the landing slots are themselves CoordSys features — the normal
+// case, since an assembly carries at least two — nothing reports anything. The mate silently
+// resolves against the wrong frames and moves the wrong body.
+//
+// The third connector below (CS_Spare) is what makes the corruption silent rather than loud:
+// without it the one-slot shift would push mate_cs_b onto the Mate feature itself and trip the
+// "not a valid CoordSys" guard, hiding the real defect behind an error that looks handled.
+TEST_CASE("mate connectors survive deletion of an earlier feature", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk_box = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk_box, 5.0, false, BooleanMode::New, "BoxExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // The victim: an unrelated connector sitting AHEAD of the pair the mate will use.
+    int cs_decoy = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(1, 1, 1), "CS_Decoy");
+    doc.features[cs_decoy].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+
+    int sk_cyl = doc.add_sketch(SketchShape::Circle, SketchPlane::XY(), 0, 0, 3, "Cyl");
+    doc.add_extrude(sk_cyl, 10.0, false, BooleanMode::New, "CylExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 2);
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 5), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    int cs_spare = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(9, 9, 9), "CS_Spare");
+    doc.features[cs_spare].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(0, cs_fixed, cs_moving, 0.0, 0.0, false, "Mate");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    REQUIRE_THAT(double(props.CentreOfMass().X()), WithinAbs(5.0, 1e-4));
+
+    REQUIRE(doc.remove_feature(cs_decoy));
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // The mate must still name the same two connectors it was built with.
+    const CadFeature& mate = doc.features.back();
+    REQUIRE(mate.type == CadFeatureType::Mate);
+    REQUIRE(mate.mate_cs_a >= 0);
+    REQUIRE(mate.mate_cs_b >= 0);
+    REQUIRE(doc.features[mate.mate_cs_a].name == "CS_Fixed");
+    REQUIRE(doc.features[mate.mate_cs_b].name == "CS_Moving");
+
+    // ...and therefore still assemble the same way: the cylinder on the fixed connector.
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    REQUIRE_THAT(double(props.CentreOfMass().X()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(props.CentreOfMass().Y()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(props.CentreOfMass().Z()), WithinAbs(5.0, 1e-4));
+}
+
+// move_feature() has the same blind spot from the other direction: it swaps two slots and
+// rewrites sketch_ref for both, but leaves mate_cs_a / mate_cs_b pointing at the old positions.
+TEST_CASE("mate connectors survive reordering of an earlier feature", "[CadDocument][mate]")
+{
+    CadDocument doc;
+    int sk_box = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk_box, 5.0, false, BooleanMode::New, "BoxExt");
+    REQUIRE(doc.recompute());
+
+    int sk_cyl = doc.add_sketch(SketchShape::Circle, SketchPlane::XY(), 0, 0, 3, "Cyl");
+    doc.add_extrude(sk_cyl, 10.0, false, BooleanMode::New, "CylExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 2);
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 5), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(0, cs_fixed, cs_moving, 0.0, 0.0, false, "Mate");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Swap the two connectors' slots. The mate's references must follow the features,
+    // not stay behind on the indices.
+    REQUIRE(doc.move_feature(cs_fixed, 1));
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    const CadFeature& mate = doc.features.back();
+    REQUIRE(mate.type == CadFeatureType::Mate);
+    REQUIRE(mate.mate_cs_a >= 0);
+    REQUIRE(mate.mate_cs_b >= 0);
+    REQUIRE(doc.features[mate.mate_cs_a].name == "CS_Fixed");
+    REQUIRE(doc.features[mate.mate_cs_b].name == "CS_Moving");
+}
+
+TEST_CASE("mate error: no associated body", "[CadDocument][mate]")
+{
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 5), "CS_Moving");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(0, cs_fixed, cs_moving, 0, 0, false, "Bad");
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_CONTAINS(doc.error, "no associated body");
+}
+
+TEST_CASE("mate error: disabled connector", "[CadDocument][mate]")
+{
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 5), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.features[cs_moving].enabled = false;
+
+    doc.add_mate(0, cs_fixed, cs_moving, 0, 0, false, "Bad");
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_CONTAINS(doc.error, "not a valid CoordSys");
+}
+
+TEST_CASE("mate conflicts: a clean assembly reports none", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk_box = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk_box, 5.0, false, BooleanMode::New, "BoxExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk_cyl = doc.add_sketch(SketchShape::Circle, SketchPlane::XY(), 0, 0, 3, "Cyl");
+    doc.add_extrude(sk_cyl, 10.0, false, BooleanMode::New, "CylExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 2);
+
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 5), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+
+    int mi = doc.add_mate(0, cs_fixed, cs_moving, 0.0, 0.0, false, "Mate1");
+    REQUIRE(mi >= 0);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.mate_conflicts.empty());
+
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    gp_Pnt com = props.CentreOfMass();
+    REQUIRE_THAT(double(com.X()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Y()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Z()), WithinAbs(5.0, 1e-4));
+}
+
+TEST_CASE("mate conflicts: two mates driving the same body", "[CadDocument][mate]")
+{
+    CadDocument doc;
+    int sk_box = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk_box, 5.0, false, BooleanMode::New, "BoxExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk_cyl = doc.add_sketch(SketchShape::Circle, SketchPlane::XY(), 0, 0, 3, "Cyl");
+    doc.add_extrude(sk_cyl, 10.0, false, BooleanMode::New, "CylExt");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 2);
+
+    int cs_a = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 0), "CS_A");
+    doc.features[cs_a].coordsys_body = 0;
+    int cs_b = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 0), "CS_B");
+    doc.features[cs_b].coordsys_body = 1;
+    int cs_c = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(10, 10, 10), "CS_C");
+    doc.features[cs_c].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int mate1 = doc.add_mate(0, cs_c, cs_b, 0, 0, false, "Mate1");
+    REQUIRE(mate1 >= 0);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int mate2 = doc.add_mate(0, cs_a, cs_b, 0, 0, false, "Mate2");
+    REQUIRE(mate2 >= 0);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    REQUIRE(doc.mate_conflicts.size() == 1);
+    REQUIRE(doc.mate_conflicts[0].first == mate2);
+    REQUIRE(doc.mate_conflicts[0].second.find("Mate1") != std::string::npos);
+    REQUIRE(doc.mate_conflicts[0].second.find("Mate2") != std::string::npos);
+}
+
+TEST_CASE("mate conflicts: a circular mate chain", "[CadDocument][mate]")
+{
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "BoxA");
+    doc.add_extrude(sk_a, 5.0, false, BooleanMode::New, "ExtA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "ExtB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 2);
+
+    int cs_a = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_A");
+    doc.features[cs_a].coordsys_body = 0;
+    int cs_b = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 5), "CS_B");
+    doc.features[cs_b].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_c = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 10), "CS_C");
+    doc.features[cs_c].coordsys_body = 0;
+    int cs_d = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 10), "CS_D");
+    doc.features[cs_d].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int mate1 = doc.add_mate(0, cs_a, cs_b, 0, 0, false, "MateAB");
+    REQUIRE(mate1 >= 0);
+    REQUIRE(doc.recompute());
+
+    int mate2 = doc.add_mate(0, cs_d, cs_c, 0, 0, false, "MateBA");
+    REQUIRE(mate2 >= 0);
+    REQUIRE(doc.recompute());
+
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.mate_conflicts.size() >= 1);
+    bool found_cycle = false;
+    for (const auto& c : doc.mate_conflicts) {
+        if (c.second.find("circular") != std::string::npos) {
+            found_cycle = true;
+            break;
+        }
+    }
+    REQUIRE(found_cycle);
+}
+
+TEST_CASE("mate conflicts: a broken mate is left to apply_mate", "[CadDocument][mate]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "Box");
+    doc.add_extrude(sk, 5.0, false, BooleanMode::New, "E");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS");
+    doc.features[cs].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(0, 999, cs, 0, 0, false, "Bad");
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_CONTAINS(doc.error, "mate_cs_a out of range");
+    REQUIRE(doc.mate_conflicts.empty());
+}
+
+TEST_CASE("ordering: fillet after mate resolves face ids", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "BoxA");
+    doc.add_extrude(sk_a, 5.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 2);
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(0, cs_fixed, cs_moving, 0.0, 0.0, false, "Mate");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_fillet(1.0, FaceGroup::All, "FilletAfterMate");
+    doc.features.back().target_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+}
+
+// --- M8a fix round: planar antiparallel + blind tests ---
+
+static int find_face_by_normal(const CadDocument& doc, int body_idx, const Vec3d& dir, double tol = 0.99)
+{
+    auto faces = GeometryEngine::faces_of(doc.bodies[body_idx].shape);
+    for (int fi = 0; fi < int(faces.size()); ++fi) {
+        if (GeometryEngine::face_normal_world(faces[fi]).dot(dir) > tol) return fi;
+    }
+    return -1;
+}
+
+// Global edge index of the first edge belonging to `face_idx`.
+//
+// A CoordSys built from a face alone takes its z from the face normal (which follows the
+// body) but its x from coordsys_x_hint, a WORLD constant. Such a frame is only half
+// body-following: the body's rotation about the face normal is invisible to it, so no mate
+// can correct or preserve a spin the connector cannot see. Pinning coordsys_edge to an edge
+// of the body makes the in-plane direction follow the body too, which is what any test
+// distinguishing Slider (corrects spin) from Cylindrical (preserves it) requires.
+static int find_edge_on_face(const CadDocument& doc, int body_idx, int face_idx)
+{
+    TopoDS_Face f = GeometryEngine::face_by_index(doc.bodies[body_idx].shape, face_idx);
+    if (f.IsNull()) return -1;
+    auto face_edges = GeometryEngine::edges_of_face(f);
+    auto all_edges  = GeometryEngine::edges_of(doc.bodies[body_idx].shape);
+    for (int ei = 0; ei < int(all_edges.size()); ++ei) {
+        for (const auto& fe : face_edges) {
+            if (all_edges[ei].IsSame(fe)) return ei;
+        }
+    }
+    return -1;
+}
+
+TEST_CASE("planar mate: antiparallel normals with asymmetric body", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    // Body A: box 20x20x5, centered at origin in XY
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 5.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Body B: box 20x10x5, also centered at origin (asymmetric in Y)
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 2);
+
+    // Face on A with normal +X, face on B with normal -X
+    int faceA = find_face_by_normal(doc, 0, Vec3d(1, 0, 0));
+    REQUIRE(faceA >= 0);
+    int faceB = find_face_by_normal(doc, 1, Vec3d(-1, 0, 0));
+    REQUIRE(faceB >= 0);
+
+    // Verify z_A != z_B (they point opposite)
+    Vec3d nA_pre = GeometryEngine::face_normal_world(
+        GeometryEngine::face_by_index(doc.bodies[0].shape, faceA));
+    Vec3d nB_pre = GeometryEngine::face_normal_world(
+        GeometryEngine::face_by_index(doc.bodies[1].shape, faceB));
+    REQUIRE(nA_pre.dot(nB_pre) < -0.9);  // antiparallel
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0,0,0), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    doc.features[cs_fixed].coordsys_face = faceA;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_moving = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0,0,0), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    doc.features[cs_moving].coordsys_face = faceB;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Planar mate: z_A=+X, z_B=-X antiparallel. offset=0.
+    // With fix: 180° flip, then translated so z-distance=0.
+    // Without fix: no rotation, only translation — body X-centroid moves differently.
+    doc.add_mate(1, cs_fixed, cs_moving, 0.0, 0.0, false, "PlanarAnti");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // With the fix: 180° rotation about faceB centroid, then translation.
+    // Body B's X-extents are mirrored. After rotation, centroid X = 2*o_B.x - pre_cx = -20,
+    // then translated by offset ≈ 20mm → centroid returns near 0.
+    // Without the fix: no rotation, body just translates ~+20mm → centroid X ≈ 20.
+    GProp_GProps post_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, post_props);
+    double post_cx = post_props.CentreOfMass().X();
+    REQUIRE_THAT(std::abs(post_cx), WithinAbs(0.0, 1e-4));
+}
+
+TEST_CASE("planar mate: in-plane pose preserved", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 5.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 10.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 2);
+
+    GProp_GProps pre_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, pre_props);
+    gp_Pnt pre_com = pre_props.CentreOfMass();
+
+    // Both connectors use PointWorld (z=(0,0,1)). B's connector offset in X/Y from A's.
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(10, 10, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(7, 4, 10), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(1, cs_fixed, cs_moving, 0.0, 0.0, false, "PlanarSameZ");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps post_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, post_props);
+    gp_Pnt post_com = post_props.CentreOfMass();
+
+    // In-plane (X,Y) components unchanged, only Z moves.
+    REQUIRE_THAT(double(post_com.X()), WithinAbs(double(pre_com.X()), 1e-4));
+    REQUIRE_THAT(double(post_com.Y()), WithinAbs(double(pre_com.Y()), 1e-4));
+    REQUIRE_THAT(double(post_com.Z()), !WithinAbs(double(pre_com.Z()), 1e-4));
+}
+
+TEST_CASE("mate with FaceAndDirection connectors on non-Z faces", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    // Body A: box 20x20x10
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 10.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Face on A with normal +Y
+    int faceA = find_face_by_normal(doc, 0, Vec3d(0, 1, 0));
+    REQUIRE(faceA >= 0);
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0,0,0), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    doc.features[cs_fixed].coordsys_face = faceA;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Body B: box placed at a different location
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Face on B with normal +Y
+    int faceB = find_face_by_normal(doc, 1, Vec3d(0, 1, 0));
+    REQUIRE(faceB >= 0);
+
+    int cs_moving = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0,0,0), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    doc.features[cs_moving].coordsys_face = faceB;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Fastened mate: B's +Y face lands on A's +Y face, offset=0.
+    // Both normals are +Y so z_A = z_B = (0,1,0) — genuine rotation from frame composition.
+    doc.add_mate(0, cs_fixed, cs_moving, 0.0, 0.0, false, "MateY");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // After fastened mate, the two mated faces should be coincident:
+    // same centroid position along the normal (Y), and same centroid in X and Z
+    // (within face dimensions since they're different sizes).
+    Vec3d ca = GeometryEngine::face_centroid_world(GeometryEngine::face_by_index(doc.bodies[0].shape, faceA));
+    Vec3d cb = GeometryEngine::face_centroid_world(GeometryEngine::face_by_index(doc.bodies[1].shape, faceB));
+    REQUIRE_THAT(cb.x(), WithinAbs(ca.x(), 1e-4));
+    REQUIRE_THAT(cb.y(), WithinAbs(ca.y(), 1e-4));
+    REQUIRE_THAT(cb.z(), WithinAbs(ca.z(), 1e-4));
+}
+
+TEST_CASE("fastened mate with flip on asymmetric body", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    // Body A: box
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 10.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Body B: tapered extrude (asymmetric, centroid not at geometric centre)
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "BoxB");
+    int ex_b = doc.add_extrude(sk_b, 8.0, false, BooleanMode::New, "EB");
+    doc.features[ex_b].taper_deg = 8.0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // PointWorld connectors at distinct positions.
+    // A's connector on the top face centre, B's connector at a corner.
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(10, 10, 10), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(2, 3, 0), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Fastened, NO flip
+    doc.add_mate(0, cs_fixed, cs_moving, 0.0, 0.0, false, "MateNoFlip");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    GProp_GProps nf_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, nf_props);
+    double nf_z = nf_props.CentreOfMass().Z();
+
+    doc.undo();
+
+    // Fastened, WITH flip
+    doc.add_mate(0, cs_fixed, cs_moving, 0.0, 0.0, true, "MateFlip");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    GProp_GProps f_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, f_props);
+    double f_z = f_props.CentreOfMass().Z();
+
+    // Flip changes the centroid Z for an asymmetric body
+    REQUIRE_THAT(f_z, !WithinAbs(nf_z, 1e-4));
+}
+
+// --- M8b: Revolute / Slider / Cylindrical mates ---
+
+TEST_CASE("revolute mate: position corrected, rotation about axis preserved", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    // Body A: reference box
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 5.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Body B: asymmetric box 20x10x5
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.size() == 2);
+
+    // Pre-rotate B 30deg about Z, translate off-axis to (15, 2, 7)
+    doc.add_transform(1, Vec3d(15, 2, 7), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 30.0, false, "PrePose");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Record rotation: body B has a face that was originally +X, now at 30deg
+    auto faces_pre = GeometryEngine::faces_of(doc.bodies[1].shape);
+    REQUIRE(faces_pre.size() == 6);
+    Vec3d pre_x_face_normal;
+    bool found = false;
+    for (const auto& f : faces_pre) {
+        Vec3d n = GeometryEngine::face_normal_world(f);
+        // The face that was originally +X now points ~(cos30, sin30, 0)
+        if (std::abs(n.x() - 0.866) < 0.02 && std::abs(n.y() - 0.5) < 0.02) {
+            pre_x_face_normal = n; found = true; break;
+        }
+    }
+    REQUIRE(found);
+
+    // Fixed connector on A at (5,5,5), world axes
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    // Moving connector on B: PointWorld at its current (transformed) centroid
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(15, 2, 7), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(2, cs_fixed, cs_moving, 0.0, 0.0, false, "Revolute");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Position corrected: body centroid moves to the axis line.
+    // Connector B (15,2,7) → (5,5,5); body centroid (15,2,9.5) → (5,5,7.5).
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    gp_Pnt com = props.CentreOfMass();
+    REQUIRE_THAT(double(com.X()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Y()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Z()), WithinAbs(7.5, 1e-4));
+
+    // Rotation about Z preserved: the ~(0.866, 0.5, 0) face normal still exists
+    auto faces_post = GeometryEngine::faces_of(doc.bodies[1].shape);
+    REQUIRE(faces_post.size() == 6);
+    bool rot_preserved = false;
+    for (const auto& f : faces_post) {
+        Vec3d n = GeometryEngine::face_normal_world(f);
+        if (std::abs(n.x() - 0.866) < 0.02 && std::abs(n.y() - 0.5) < 0.02) {
+            rot_preserved = true; break;
+        }
+    }
+    REQUIRE(rot_preserved);
+    // Fastened would have aligned face normals to world axes: no face with Y≈0.5 would exist.
+}
+
+TEST_CASE("revolute mate: no-op when already correct", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 5.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Move body B to exactly the correct pose: on axis at (5,5,5) with no rotation
+    doc.add_transform(1, Vec3d(5, 5, 5), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 0.0, false, "PrePose");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps pre_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, pre_props);
+    gp_Pnt pre_com = pre_props.CentreOfMass();
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(2, cs_fixed, cs_moving, 0.0, 0.0, false, "RevoluteNoOp");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps post_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, post_props);
+    gp_Pnt post_com = post_props.CentreOfMass();
+    REQUIRE_THAT(double(post_com.X()), WithinAbs(double(pre_com.X()), 1e-4));
+    REQUIRE_THAT(double(post_com.Y()), WithinAbs(double(pre_com.Y()), 1e-4));
+    REQUIRE_THAT(double(post_com.Z()), WithinAbs(double(pre_com.Z()), 1e-4));
+}
+
+TEST_CASE("revolute mate: mate_angle applies additional rotation", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 5.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Body B: asymmetric box, pre-rotated 30deg about Z, off-axis
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_transform(1, Vec3d(15, 2, 7), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 30.0, false, "PrePose");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(15, 2, 7), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // mate_angle=45deg on top of preserved 30deg → face originally +X now at 75deg
+    doc.add_mate(2, cs_fixed, cs_moving, 0.0, 45.0, false, "RevoluteAngle");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Position on axis line (same as revolute preservation test)
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    gp_Pnt com = props.CentreOfMass();
+    REQUIRE_THAT(double(com.X()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Y()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Z()), WithinAbs(7.5, 1e-4));
+
+    // Rotation = 30deg (preserved) + 45deg (mate_angle) = 75deg → normal ≈ (cos75, sin75, 0)
+    auto faces = GeometryEngine::faces_of(doc.bodies[1].shape);
+    bool found_75 = false;
+    for (const auto& f : faces) {
+        Vec3d n = GeometryEngine::face_normal_world(f);
+        if (std::abs(n.x() - 0.2588) < 0.02 && std::abs(n.y() - 0.9659) < 0.02) {
+            found_75 = true; break;
+        }
+    }
+    REQUIRE(found_75);
+}
+
+TEST_CASE("slider mate: rotation corrected, axial position preserved", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 5.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Pre-rotate B 30deg about Z, translate off-axis to (15, 2, 13)
+    doc.add_transform(1, Vec3d(15, 2, 13), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 30.0, false, "PrePose");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps pre_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, pre_props);
+    double pre_z = pre_props.CentreOfMass().Z();
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(15, 2, 13), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(3, cs_fixed, cs_moving, 0.0, 0.0, false, "Slider");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Perpendicular position corrected to the axis line (X=5, Y=5)
+    GProp_GProps post_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, post_props);
+    gp_Pnt post_com = post_props.CentreOfMass();
+    REQUIRE_THAT(double(post_com.X()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(post_com.Y()), WithinAbs(5.0, 1e-4));
+
+    // Axial (Z) position preserved from pre-mate pose
+    REQUIRE_THAT(double(post_com.Z()), WithinAbs(pre_z, 1e-4));
+    // Fastened would have placed the body at Z=5. pre_z=15.5 (centroid), clearly different.
+}
+
+TEST_CASE("slider mate: mate_offset shifts axial position", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 5.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_transform(1, Vec3d(12, 3, 9), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 0.0, false, "PrePose");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(12, 3, 9), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Slider with mate_offset=4: body centroid at (12,3,11.5), connector at (12,3,9).
+    // Perpendicular corrected: X=5,Y=5. Axial: preserved Z 11.5 + offset 4 = 15.5.
+    doc.add_mate(3, cs_fixed, cs_moving, 4.0, 0.0, false, "SliderOffset");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    gp_Pnt com = props.CentreOfMass();
+    REQUIRE_THAT(double(com.X()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Y()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Z()), WithinAbs(15.5, 1e-3));
+}
+
+TEST_CASE("slider mate: no-op when already correct", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 5.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Body already on axis at (5,5,20), no rotation
+    doc.add_transform(1, Vec3d(5, 5, 20), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 0.0, false, "PrePose");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps pre_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, pre_props);
+    gp_Pnt pre_com = pre_props.CentreOfMass();
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 20), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(3, cs_fixed, cs_moving, 0.0, 0.0, false, "SliderNoOp");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps post_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, post_props);
+    gp_Pnt post_com = post_props.CentreOfMass();
+    REQUIRE_THAT(double(post_com.X()), WithinAbs(double(pre_com.X()), 1e-4));
+    REQUIRE_THAT(double(post_com.Y()), WithinAbs(double(pre_com.Y()), 1e-4));
+    REQUIRE_THAT(double(post_com.Z()), WithinAbs(double(pre_com.Z()), 1e-4));
+}
+
+TEST_CASE("cylindrical mate: perpendicular corrected, rotation and axial preserved", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 5.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Pre-rotate B 30deg about Z, translate off-axis to (15, 2, 13)
+    doc.add_transform(1, Vec3d(15, 2, 13), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 30.0, false, "PrePose");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps pre_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, pre_props);
+    double pre_z = pre_props.CentreOfMass().Z();
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(15, 2, 13), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(4, cs_fixed, cs_moving, 0.0, 0.0, false, "Cylindrical");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Perpendicular position corrected to axis line
+    GProp_GProps post_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, post_props);
+    gp_Pnt com = post_props.CentreOfMass();
+    REQUIRE_THAT(double(com.X()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Y()), WithinAbs(5.0, 1e-4));
+
+    // Axial Z position preserved from pre-mate
+    REQUIRE_THAT(double(com.Z()), WithinAbs(pre_z, 1e-4));
+
+    // Rotation about Z preserved: face originally +X is still at 30deg
+    auto faces = GeometryEngine::faces_of(doc.bodies[1].shape);
+    REQUIRE(faces.size() == 6);
+    bool rot_preserved = false;
+    for (const auto& f : faces) {
+        Vec3d n = GeometryEngine::face_normal_world(f);
+        if (std::abs(n.x() - 0.866) < 0.02 && std::abs(n.y() - 0.5) < 0.02) {
+            rot_preserved = true; break;
+        }
+    }
+    REQUIRE(rot_preserved);
+    // Fastened would have aligned face normals to world axes and fixed Z.
+}
+
+TEST_CASE("cylindrical mate: mate_offset and mate_angle applied on top", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 5.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_transform(1, Vec3d(15, 2, 9), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 30.0, false, "PrePose");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(15, 2, 9), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(4, cs_fixed, cs_moving, 3.0, 45.0, false, "CylOffsetAngle");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Position: perpendicular corrected, axial = 11.5 (centroid preserved) + 3 (offset) = 14.5
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    gp_Pnt com = props.CentreOfMass();
+    REQUIRE_THAT(double(com.X()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Y()), WithinAbs(5.0, 1e-4));
+    REQUIRE_THAT(double(com.Z()), WithinAbs(14.5, 1e-3));
+
+    // Rotation = 30deg (preserved) + 45deg (angle) = 75deg
+    auto faces = GeometryEngine::faces_of(doc.bodies[1].shape);
+    bool found_75 = false;
+    for (const auto& f : faces) {
+        Vec3d n = GeometryEngine::face_normal_world(f);
+        if (std::abs(n.x() - 0.2588) < 0.02 && std::abs(n.y() - 0.9659) < 0.02) {
+            found_75 = true; break;
+        }
+    }
+    REQUIRE(found_75);
+}
+
+TEST_CASE("cylindrical mate: no-op when already correct", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 5.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 10, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Body already on axis at (5,5,20), no rotation
+    doc.add_transform(1, Vec3d(5, 5, 20), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 0.0, false, "PrePose");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps pre_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, pre_props);
+    gp_Pnt pre_com = pre_props.CentreOfMass();
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(5, 5, 20), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_mate(4, cs_fixed, cs_moving, 0.0, 0.0, false, "CylNoOp");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    GProp_GProps post_props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, post_props);
+    gp_Pnt post_com = post_props.CentreOfMass();
+    REQUIRE_THAT(double(post_com.X()), WithinAbs(double(pre_com.X()), 1e-4));
+    REQUIRE_THAT(double(post_com.Y()), WithinAbs(double(pre_com.Y()), 1e-4));
+    REQUIRE_THAT(double(post_com.Z()), WithinAbs(double(pre_com.Z()), 1e-4));
+}
+
+TEST_CASE("revolute mate with FaceAndDirection on non-Z faces", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    // Body A: box 20x20x10
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 10.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Face on A with normal +Y
+    int faceA = find_face_by_normal(doc, 0, Vec3d(0, 1, 0));
+    REQUIRE(faceA >= 0);
+    Vec3d nA = GeometryEngine::face_normal_world(
+        GeometryEngine::face_by_index(doc.bodies[0].shape, faceA));
+
+    // Body B: asymmetric box 20x10x5, also with +Y face
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int faceB = find_face_by_normal(doc, 1, Vec3d(0, 1, 0));
+    REQUIRE(faceB >= 0);
+    Vec3d nB_pre = GeometryEngine::face_normal_world(
+        GeometryEngine::face_by_index(doc.bodies[1].shape, faceB));
+    REQUIRE_THAT(nB_pre.dot(nA), WithinAbs(1.0, 1e-4));
+
+    // Pre-rotate B about Y (the face normal) by 30deg to give it a non-trivial rotation about its connector z
+    doc.add_transform(1, Vec3d(0, 0, 0), Vec3d(0, 1, 0), Vec3d(0, 0, 0), 30.0, false, "PrePose");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // FaceAndDirection on A's +Y face
+    int cs_fixed = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0,0,0), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    doc.features[cs_fixed].coordsys_face = faceA;
+    // FaceAndDirection on B's +Y face
+    int cs_moving = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0,0,0), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    doc.features[cs_moving].coordsys_face = faceB;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Record face normals on B before mate (to verify rotation preservation)
+    // +30deg rotation about Y maps +Z=(0,0,1) → (0.5, 0, 0.866), -Z → (-0.5, 0, -0.866)
+    auto faces_pre = GeometryEngine::faces_of(doc.bodies[1].shape);
+    Vec3d pre_rotated_normal;
+    {
+        bool fnd = false;
+        for (const auto& f : faces_pre) {
+            Vec3d n = GeometryEngine::face_normal_world(f);
+            if (std::abs(n.z()) > 0.85 && std::abs(n.x()) > 0.45 && std::abs(n.y()) < 0.02) {
+                pre_rotated_normal = n; fnd = true; break;
+            }
+        }
+        REQUIRE(fnd);
+    }
+
+    doc.add_mate(2, cs_fixed, cs_moving, 0.0, 0.0, false, "RevoluteFaceDir");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Position: faces are coincident (same as fastened position since no offset and axes aligned)
+    Vec3d ca = GeometryEngine::face_centroid_world(GeometryEngine::face_by_index(doc.bodies[0].shape, faceA));
+    Vec3d cb = GeometryEngine::face_centroid_world(GeometryEngine::face_by_index(doc.bodies[1].shape, faceB));
+    REQUIRE_THAT(cb.x(), WithinAbs(ca.x(), 1e-4));
+    REQUIRE_THAT(cb.y(), WithinAbs(ca.y(), 1e-4));
+    REQUIRE_THAT(cb.z(), WithinAbs(ca.z(), 1e-4));
+
+    // Rotation about the connector z (which is +Y) is preserved:
+    // the face with |z| ≈ 0.866, |x| ≈ 0.5, y ≈ 0 must still exist.
+    auto faces_post = GeometryEngine::faces_of(doc.bodies[1].shape);
+    bool rot_preserved = false;
+    for (const auto& f : faces_post) {
+        Vec3d n = GeometryEngine::face_normal_world(f);
+        if (std::abs(n.z()) > 0.85 && std::abs(n.x()) > 0.45 && std::abs(n.y()) < 0.02) {
+            rot_preserved = true; break;
+        }
+    }
+    REQUIRE(rot_preserved);
+    // Fastened would force all axes to align: no face with Z≈0.87 would exist.
+}
+
+// --- M8b: rotation-coverage hole — FaceAndDirection captures body orientation ---
+
+TEST_CASE("slider mate with FaceAndDirection corrects rotation", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    // Body A: box 20x20x10
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 10.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int faceA = find_face_by_normal(doc, 0, Vec3d(0, 0, 1));
+    REQUIRE(faceA >= 0);
+
+    // Body B: asymmetric box 20x10x5
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int faceB = find_face_by_normal(doc, 1, Vec3d(0, 0, 1));
+    REQUIRE(faceB >= 0);
+
+    // Pre-rotate B: first 20deg about X (tilts +Z face normal off-axis, so the
+    // connector z genuinely differs from A's), then 30deg about Z (adds rotation
+    // about the mate axis that Slider must correct and Cylindrical must preserve).
+    doc.add_transform(1, Vec3d(14, 3, 7), Vec3d(1, 0, 0), Vec3d(0, 0, 0), 20.0, false, "RotX");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_transform(1, Vec3d(0, 0, 0), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 30.0, false, "RotZ");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Both connectors pin their in-plane direction to an edge of their own body, so each
+    // frame follows its body's spin. Without this the frames' x comes from the world hint
+    // and the 30deg spin is invisible to the mate — see find_edge_on_face.
+    int edgeA = find_edge_on_face(doc, 0, faceA);
+    int edgeB = find_edge_on_face(doc, 1, faceB);
+    REQUIRE(edgeA >= 0);
+    REQUIRE(edgeB >= 0);
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0, 0, 0), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    doc.features[cs_fixed].coordsys_face = faceA;
+    doc.features[cs_fixed].coordsys_edge = edgeA;
+
+    int cs_moving = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0, 0, 0), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    doc.features[cs_moving].coordsys_face = faceB;
+    doc.features[cs_moving].coordsys_edge = edgeB;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Record the pre-mate axial position of the CONNECTOR, not of the centroid. Slider
+    // rotates the body about the connector origin to correct the 20deg tilt, and that
+    // rotation legitimately moves the centroid in Z (by -d*(1-cos20) for a centroid d
+    // below the mated face) while leaving the connector itself where it is. The DOF
+    // Slider preserves is the connector's position along the axis.
+    const double pre_conn_z = GeometryEngine::face_centroid_world(
+        GeometryEngine::face_by_index(doc.bodies[1].shape, faceB)).z();
+
+    doc.add_mate(3, cs_fixed, cs_moving, 0.0, 0.0, false, "SliderFaceDir");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Position: perpendicular corrected to axis line through A's +Z face centroid.
+    // The +Z face of a 20x20x10 box centred at origin has centroid at (0, 0, 10).
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    gp_Pnt com = props.CentreOfMass();
+    REQUIRE_THAT(double(com.X()), WithinAbs(0.0, 1e-4));
+    REQUIRE_THAT(double(com.Y()), WithinAbs(0.0, 1e-4));
+    // Axial position of the connector preserved — Slider does not own that DOF.
+    const double post_conn_z = GeometryEngine::face_centroid_world(
+        GeometryEngine::face_by_index(doc.bodies[1].shape, faceB)).z();
+    REQUIRE_THAT(post_conn_z, WithinAbs(pre_conn_z, 1e-4));
+
+    // Rotation: Slider owns this DOF — all face normals must be axis-aligned.
+    auto faces = GeometryEngine::faces_of(doc.bodies[1].shape);
+    REQUIRE(faces.size() == 6);
+    int axis_aligned = 0;
+    for (const auto& f : faces) {
+        Vec3d n = GeometryEngine::face_normal_world(f);
+        double d = std::max({std::abs(n.x()), std::abs(n.y()), std::abs(n.z())});
+        if (d > 0.999) ++axis_aligned;
+    }
+    REQUIRE(axis_aligned == 6);
+    // Dropping rotation correction would leave 30deg Z rotation — at least 2
+    // faces would have normals not aligned to any world axis.
+}
+
+TEST_CASE("cylindrical mate with FaceAndDirection preserves rotation", "[CadDocument][mate]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    // Body A: box 20x20x10
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 10.0, false, BooleanMode::New, "EA");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int faceA = find_face_by_normal(doc, 0, Vec3d(0, 0, 1));
+    REQUIRE(faceA >= 0);
+
+    // Body B: asymmetric box 20x10x5
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 10, 0, "BoxB");
+    doc.add_extrude(sk_b, 5.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int faceB = find_face_by_normal(doc, 1, Vec3d(0, 0, 1));
+    REQUIRE(faceB >= 0);
+
+    // Same two-step pre-rotation as the slider test.
+    doc.add_transform(1, Vec3d(14, 3, 7), Vec3d(1, 0, 0), Vec3d(0, 0, 0), 20.0, false, "RotX");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_transform(1, Vec3d(0, 0, 0), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 30.0, false, "RotZ");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Edge-pinned frames, as in the Slider case. These matter here for the opposite
+    // reason: with a world-derived in-plane direction, a Cylindrical that WRONGLY aligned
+    // the spin would still leave the body's 30deg face at 30deg, and the assertion below
+    // would pass for the wrong implementation.
+    int edgeA = find_edge_on_face(doc, 0, faceA);
+    int edgeB = find_edge_on_face(doc, 1, faceB);
+    REQUIRE(edgeA >= 0);
+    REQUIRE(edgeB >= 0);
+
+    int cs_fixed = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0, 0, 0), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    doc.features[cs_fixed].coordsys_face = faceA;
+    doc.features[cs_fixed].coordsys_edge = edgeA;
+
+    int cs_moving = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0, 0, 0), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    doc.features[cs_moving].coordsys_face = faceB;
+    doc.features[cs_moving].coordsys_edge = edgeB;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // As in the Slider case, the preserved DOF is the CONNECTOR's position along the
+    // axis, not the centroid's: aligning the 20deg tilt rotates the body about the
+    // connector origin, which moves the centroid in Z by design.
+    const double pre_conn_z_c = GeometryEngine::face_centroid_world(
+        GeometryEngine::face_by_index(doc.bodies[1].shape, faceB)).z();
+
+    doc.add_mate(4, cs_fixed, cs_moving, 0.0, 0.0, false, "CylFaceDir");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Position: perpendicular corrected to axis line (X=0, Y=0 at +Z face centroid)
+    GProp_GProps props;
+    BRepGProp::VolumeProperties(doc.bodies[1].shape, props);
+    gp_Pnt com = props.CentreOfMass();
+    REQUIRE_THAT(double(com.X()), WithinAbs(0.0, 1e-4));
+    REQUIRE_THAT(double(com.Y()), WithinAbs(0.0, 1e-4));
+    // Axial position of the connector preserved — Cylindrical leaves that DOF free.
+    const double post_conn_z_c = GeometryEngine::face_centroid_world(
+        GeometryEngine::face_by_index(doc.bodies[1].shape, faceB)).z();
+    REQUIRE_THAT(post_conn_z_c, WithinAbs(pre_conn_z_c, 1e-4));
+
+    // Rotation about Z (30deg) is preserved: the 20deg X-rotation was undone
+    // by z-alignment, leaving the 30deg Z-rotation intact.
+    // The +X face normal should be at ~(cos30, sin30, 0).
+    auto faces = GeometryEngine::faces_of(doc.bodies[1].shape);
+    REQUIRE(faces.size() == 6);
+    bool rot_preserved = false;
+    for (const auto& f : faces) {
+        Vec3d n = GeometryEngine::face_normal_world(f);
+        if (std::abs(n.x() - 0.866) < 0.02 && std::abs(n.y() - 0.5) < 0.02) {
+            rot_preserved = true; break;
+        }
+    }
+    REQUIRE(rot_preserved);
+    // If cylindrical behaved like slider, the face would be at (1,0,0) instead.
+}
+
+// --- Interference detection (M8c) ---
+
+TEST_CASE("interference: overlapping bodies reported with overlap volume", "[CadDocument][interference]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    // A: 20x20x10 box centred on the origin in XY, z in [0,10]
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 10.0, false, BooleanMode::New, "EA");
+    // B: 20x20x10 box, same footprint
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxB");
+    doc.add_extrude(sk_b, 10.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 2);
+
+    // Lift B by 6mm: the two overlap over 4mm of height => 20*20*4 = 1600 mm^3.
+    doc.add_transform(1, Vec3d(0, 0, 6), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 0.0, false, "LiftB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    auto hits = doc.check_interference();
+    REQUIRE(hits.size() == 1);
+    REQUIRE(hits[0].body_a == 0);
+    REQUIRE(hits[0].body_b == 1);
+    REQUIRE_THAT(hits[0].volume, WithinAbs(1600.0, 1e-3));
+}
+
+TEST_CASE("interference: disjoint and merely touching bodies are not reported", "[CadDocument][interference]")
+{
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 10.0, false, BooleanMode::New, "EA");
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxB");
+    doc.add_extrude(sk_b, 10.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+
+    SECTION("clearly apart") {
+        doc.add_transform(1, Vec3d(0, 0, 50), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 0.0, false, "MoveB");
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.check_interference().empty());
+    }
+
+    SECTION("face-to-face contact encloses no volume") {
+        // B sits exactly on top of A: they share a face but nothing overlaps.
+        doc.add_transform(1, Vec3d(0, 0, 10), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 0.0, false, "StackB");
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.check_interference().empty());
+    }
+}
+
+TEST_CASE("interference: sheet bodies are skipped", "[CadDocument][interference]")
+{
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 10.0, false, BooleanMode::New, "EA");
+    // A sheet passing straight through the solid: it has no volume, so no interference.
+    int sk_s = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 40, 40, 0, "Sheet");
+    doc.add_surface_extrude(sk_s, 5.0, "SE");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 2);
+    REQUIRE(CadDocument::is_sheet_shape(doc.bodies[1].shape));
+
+    REQUIRE(doc.check_interference().empty());
+}
+
+TEST_CASE("interference: reports every overlapping pair", "[CadDocument][interference]")
+{
+    CadDocument doc;
+    for (int i = 0; i < 3; ++i) {
+        int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Box");
+        doc.add_extrude(sk, 10.0, false, BooleanMode::New, "E");
+    }
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 3);
+
+    // 0 and 1 stay coincident (overlapping); 2 is moved clear of both.
+    doc.add_transform(2, Vec3d(0, 0, 100), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 0.0, false, "MoveC");
+    REQUIRE(doc.recompute());
+
+    auto hits = doc.check_interference();
+    REQUIRE(hits.size() == 1);
+    REQUIRE(hits[0].body_a == 0);
+    REQUIRE(hits[0].body_b == 1);
+
+    // min_volume gates the report: a threshold above the overlap silences it.
+    REQUIRE(doc.check_interference(1e9).empty());
+}
+
+TEST_CASE("interference: detects a clash created by a mate", "[CadDocument][interference]")
+{
+    CadDocument doc;
+    int sk_a = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxA");
+    doc.add_extrude(sk_a, 10.0, false, BooleanMode::New, "EA");
+    int sk_b = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "BoxB");
+    doc.add_extrude(sk_b, 10.0, false, BooleanMode::New, "EB");
+    REQUIRE(doc.recompute());
+
+    // Park B well clear, so the clash below is created by the mate and nothing else.
+    doc.add_transform(1, Vec3d(0, 0, 80), Vec3d(0, 0, 1), Vec3d(0, 0, 0), 0.0, false, "ParkB");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.check_interference().empty());
+
+    // Fastened mate onto a connector inside A's volume drives B into A.
+    int cs_fixed = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 5), "CS_Fixed");
+    doc.features[cs_fixed].coordsys_body = 0;
+    int cs_moving = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 85), "CS_Moving");
+    doc.features[cs_moving].coordsys_body = 1;
+    REQUIRE(doc.recompute());
+
+    doc.add_mate(0, cs_fixed, cs_moving, 0.0, 0.0, false, "Clash");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    auto hits = doc.check_interference();
+    REQUIRE(hits.size() == 1);
+    REQUIRE(hits[0].volume > 1.0);
+}
+
+// A filleted solid must reach the plate as a watertight mesh. OCCT emits one degenerate
+// triangle at the pole of every corner sphere patch; welded, its v->v edge counts as an open
+// edge and the slicer tells the user to go repair the model in another CAD application --
+// the exact round trip this feature exists to remove. agw.
+TEST_CASE("CadDocument filleted solid tessellates watertight", "[CadDocument]")
+{
+    CadDocument doc;
+    SketchProfile sp;
+    sp.points.push_back(Vec2d(  0,  0));
+    sp.points.push_back(Vec2d( 80,  0));
+    sp.points.push_back(Vec2d( 80, 50));
+    sp.points.push_back(Vec2d(  0, 50));
+    sp.closed = true;
+    const int sk = doc.add_sketch_profile(sp, SketchPlane::XY(), "P");
+    doc.add_extrude(sk, 12.0, false, BooleanMode::New, "E");
+    doc.add_fillet(3.0, FaceGroup::All, "F");
+    REQUIRE(doc.recompute());
+
+    CHECK(doc.display_mesh.stats().open_edges == 0);
+    CHECK(its_num_open_edges(doc.display_mesh.its) == 0);
+    // No degenerate triangles survive the weld, and the per-triangle face map stays aligned.
+    size_t degenerate = 0;
+    for (const auto& t : doc.display_mesh.its.indices)
+        if (t[0] == t[1] || t[1] == t[2] || t[0] == t[2]) ++degenerate;
+    REQUIRE(degenerate == 0);
+    REQUIRE(doc.display_tri_face.size() == doc.display_mesh.its.indices.size());
+    REQUIRE(doc.display_tri_body.size() == doc.display_mesh.its.indices.size());
+}
+
+// A rejected solve must leave the sketch untouched. libslvs writes its last Newton iterate
+// into the params whether or not it converged, so reading geometry back unconditionally made
+// every failed attempt destructive -- and the fillet degrade ladder tries a deliberately
+// over-constrained rung FIRST, so a filleted corner was wrecked before the rung that works
+// ever got a chance. pl5.
+TEST_CASE("Failed sketch solve leaves geometry untouched", "[CadDocument]")
+{
+    using R  = SketchPointRole;
+    using CT = SketchConstraintType;
+    auto line = [](Vec2d p0, Vec2d p1) {
+        SketchEntity e; e.type = SketchEntity::Type::Line; e.p0 = p0; e.p1 = p1; return e; };
+    auto coinc = [](int ea, R ra, int eb, R rb) {
+        SketchEntityConstraintDef d; d.type = CT::Coincident; d.ea = ea; d.ra = ra; d.eb = eb; d.rb = rb; return d; };
+    auto axis = [](CT t, int e) {
+        SketchEntityConstraintDef d; d.type = t; d.ea = e; d.ra = R::P0; d.eb = e; d.rb = R::P1; return d; };
+
+    // Axis-aligned rectangle, drawn as four lines with the constraints the sketch tool
+    // infers: a Coincident at each corner and H/V per leg.
+    std::vector<SketchEntity> ents = {
+        line(Vec2d(-89.32,  72.05), Vec2d( 52.00,  72.05)),   // 0 top    (H)
+        line(Vec2d( 52.00,  72.05), Vec2d( 52.00, -68.97)),   // 1 right  (V)
+        line(Vec2d( 52.00, -68.97), Vec2d(-89.32, -68.97)),   // 2 bottom (H)
+        line(Vec2d(-89.32, -68.97), Vec2d(-89.32,  72.05)),   // 3 left   (V)
+    };
+    std::vector<SketchEntityConstraintDef> cs = {
+        coinc(0, R::P1, 1, R::P0), coinc(0, R::P0, 3, R::P1),
+        coinc(1, R::P1, 2, R::P0), coinc(2, R::P1, 3, R::P0),
+        axis(CT::Horizontal, 0), axis(CT::Vertical, 1),
+        axis(CT::Horizontal, 2), axis(CT::Vertical, 3),
+    };
+    REQUIRE(solve_sketch_entities(ents, cs));
+
+    // Fillet the top-left corner: trim both legs, drop the stale corner Coincident.
+    const int a = 0, b = 3;
+    SketchEntity a_out, b_out, arc;
+    REQUIRE(SketchEngine::fillet_lines(ents[a], ents[b], 28.205, a_out, b_out, arc));
+    ents[a] = a_out; ents[b] = b_out;
+    const int xi = int(ents.size());
+    ents.push_back(arc);
+    cs.erase(std::remove_if(cs.begin(), cs.end(), [&](const SketchEntityConstraintDef& d) {
+        return d.type == CT::Coincident && d.ea == a && d.ra == R::P0 && d.eb == b && d.rb == R::P1;
+    }), cs.end());
+    const std::vector<SketchEntity> trimmed = ents;
+
+    auto coin = [&](R xr, int ln, R lr) { return coinc(xi, xr, ln, lr); };
+    auto tang = [&](int ln) {
+        SketchEntityConstraintDef d; d.type = CT::Tangent; d.ea = xi; d.eb = ln; return d; };
+
+    // Rung 1 of the ladder: a tangent on each leg. Over-constrained against the legs'
+    // own H/V, so it must be rejected -- and must not move a single point.
+    {
+        std::vector<SketchEntityConstraintDef> pc = cs;
+        for (const auto& c : { coin(R::P0, a, R::P0), coin(R::P1, b, R::P1), tang(a), tang(b) })
+            pc.push_back(c);
+        std::vector<SketchEntity> e = ents;
+        REQUIRE_FALSE(solve_sketch_entities(e, pc));
+        for (size_t i = 0; i < e.size(); ++i) {
+            CHECK((e[i].p0 - trimmed[i].p0).norm() == Approx(0.0).margin(1e-9));
+            CHECK((e[i].p1 - trimmed[i].p1).norm() == Approx(0.0).margin(1e-9));
+            CHECK((e[i].center - trimmed[i].center).norm() == Approx(0.0).margin(1e-9));
+        }
+    }
+
+    // Rung 2 (one tangent) solves, and the arc keeps the radius the fillet gave it.
+    {
+        std::vector<SketchEntityConstraintDef> pc = cs;
+        for (const auto& c : { coin(R::P0, a, R::P0), coin(R::P1, b, R::P1), tang(a) })
+            pc.push_back(c);
+        REQUIRE(solve_sketch_entities(ents, pc));
+        CHECK(ents[xi].radius == Approx(28.205).margin(1e-6));
+        // Corner stays open: the legs end on the arc, they do not meet each other.
+        CHECK((ents[a].p0 - ents[b].p1).norm() > 1.0);
+        CHECK((ents[a].p0 - ents[xi].p0).norm() == Approx(0.0).margin(1e-6));
+        CHECK((ents[b].p1 - ents[xi].p1).norm() == Approx(0.0).margin(1e-6));
+    }
+}
+
+// A subtraction whose tool misses the target is a perfectly legal boolean that removes nothing,
+// so OCCT reports success and the feature lands in the recipe with ok:true and an unchanged body.
+// That is how a hole placed with world coordinates instead of plane-frame ones read as "drilled"
+// three times in a row while the volume never moved. daf.
+TEST_CASE("A cut that removes no material is an error, not a silent success", "[CadDocument]")
+{
+    // 20 x 20 box, 20 tall, centred on the origin of the XY plane.
+    auto box = [] {
+        CadDocument d;
+        int sk = d.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Sketch");
+        d.add_extrude(sk, 20.0, false, BooleanMode::New, "Extrude");
+        return d;
+    };
+
+    SECTION("hole placed clear of the body is rejected") {
+        CadDocument doc = box();
+        REQUIRE(doc.recompute());
+        const double solid = doc.body_mass_properties(0).volume;
+
+        // 135 mm away — exactly the failure the issue reported (world centre passed for a
+        // plane-frame coordinate). The old behaviour: recompute() true, volume unchanged.
+        doc.add_hole(8.0, 20.0, true, 135.0, 0.0, SketchPlane::XY(), "Hole");
+        CHECK_FALSE(doc.recompute());
+        CHECK(doc.error.find("removed no material") != std::string::npos);
+
+        // And the body is left as it was, not half-applied.
+        CadDocument again = box();
+        REQUIRE(again.recompute());
+        CHECK_THAT(again.body_mass_properties(0).volume,
+                   Catch::Matchers::WithinAbs(solid, 1e-6));
+    }
+
+    SECTION("the same hole on the body still works") {
+        CadDocument doc = box();
+        REQUIRE(doc.recompute());
+        const double solid = doc.body_mass_properties(0).volume;
+        doc.add_hole(8.0, 20.0, true, 0.0, 0.0, SketchPlane::XY(), "Hole");
+        REQUIRE(doc.recompute());
+        CHECK_THAT(doc.body_mass_properties(0).volume,
+                   Catch::Matchers::WithinRel(solid - M_PI * 16.0 * 20.0, 0.01));
+    }
+
+    SECTION("a cut-mode extrude that misses is rejected too") {
+        CadDocument doc = box();
+        REQUIRE(doc.recompute());
+        // Same trick, on the sketch plane's origin: the profile sits far outside the box,
+        // so the subtraction is a legal no-op.
+        SketchPlane far_plane = SketchPlane::XY();
+        far_plane.origin = Vec3d(200.0, 0.0, 0.0);
+        int sk = doc.add_sketch(SketchShape::Rectangle, far_plane, 5, 5, 10, "Tool");
+        doc.add_extrude(sk, 30.0, false, BooleanMode::Cut, "Cut");
+        CHECK_FALSE(doc.recompute());
+        CHECK(doc.error.find("removed no material") != std::string::npos);
+    }
+}
+
+// entities_to_wire handles exactly two shapes: one lone closed entity, or a chain of open ones.
+// Anything else returns a null wire, and build_sketch_wire used to answer that by falling through
+// to its legacy tail — which ends in a rectangle built from width/height. For an entity sketch
+// those are whatever they were initialised to, so the extrude produced a box nobody drew.
+// 88v.
+TEST_CASE("An entity sketch that forms no wire fails instead of extruding a default box", "[CadDocument]")
+{
+    auto circle = [](Vec2d c, double r) {
+        SketchEntity e; e.type = SketchEntity::Type::Circle; e.center = c; e.p0 = c; e.radius = r;
+        return e;
+    };
+    auto line = [](Vec2d a, Vec2d b) {
+        SketchEntity e; e.type = SketchEntity::Type::Line; e.p0 = a; e.p1 = b;
+        return e;
+    };
+
+    SECTION("a lone circle still works — the supported case is untouched") {
+        CadDocument doc;
+        int sk = doc.add_sketch_entities({ circle({0, 0}, 10.0) }, SketchPlane::XY(), "Sketch");
+        doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Extrude");
+        REQUIRE(doc.recompute());
+        CHECK_THAT(doc.body_mass_properties(0).volume,
+                   Catch::Matchers::WithinRel(M_PI * 100.0 * 5.0, 0.01));
+    }
+
+    // Behaviour CHANGED 2026-09-02 by Tommaso's decision. This used to require a refusal,
+    // because back then ignoring the stray meant falling through to a default rectangle — a
+    // box the user never drew. That fallback is gone: the closed profile is now built and the
+    // stray open chain is discarded, exactly as the viewport's region_loops already discards
+    // open chains when it decides what is extrudable. A stray click must not break a model
+    // that looks perfect on screen.
+    SECTION("circle + stray line builds the circle and ignores the stray") {
+        CadDocument doc;
+        int sk = doc.add_sketch_entities({ circle({0, 0}, 10.0), line({40, 40}, {60, 40}) },
+                                        SketchPlane::XY(), "Sketch");
+        doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Extrude");
+        REQUIRE(doc.recompute());
+        CHECK(doc.error.empty());
+        CHECK_THAT(doc.body_mass_properties(0).volume,
+                   Catch::Matchers::WithinRel(M_PI * 100.0 * 5.0, 0.01));
+    }
+
+    SECTION("two disjoint circles are rejected too") {
+        CadDocument doc;
+        int sk = doc.add_sketch_entities({ circle({-20, 0}, 8.0), circle({20, 0}, 8.0) },
+                                        SketchPlane::XY(), "Sketch");
+        doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Extrude");
+        CHECK_FALSE(doc.recompute());
+        CHECK(doc.error.find("disjoint") != std::string::npos);
+    }
+}
+
+namespace {
+
+std::vector<SketchEntity> rect_entities(double w, double h)
+{
+    const double hw = w * 0.5, hh = h * 0.5;
+    return {
+        {SketchEntity::Type::Line, Vec2d(-hw, -hh), Vec2d( hw, -hh)},
+        {SketchEntity::Type::Line, Vec2d( hw, -hh), Vec2d( hw,  hh)},
+        {SketchEntity::Type::Line, Vec2d( hw,  hh), Vec2d(-hw,  hh)},
+        {SketchEntity::Type::Line, Vec2d(-hw,  hh), Vec2d(-hw, -hh)},
+    };
+}
+
+SketchEntity circle_entity(const Vec2d& c, double r)
+{
+    SketchEntity e;
+    e.type = SketchEntity::Type::Circle;
+    e.center = c; e.p0 = c; e.radius = r;
+    return e;
+}
+
+CadDocument plate_doc(const std::vector<SketchEntity>& entities, double distance)
+{
+    CadDocument doc;
+    CadFeature sk;
+    sk.type     = CadFeatureType::Sketch;
+    sk.name     = "sketch";
+    sk.plane    = SketchPlane::XY();
+    sk.entities = entities;
+    doc.features.push_back(sk);
+    CadFeature ex;
+    ex.type       = CadFeatureType::Extrude;
+    ex.name       = "extrude";
+    ex.sketch_ref = 0;
+    ex.distance   = distance;
+    ex.mode       = BooleanMode::New;
+    doc.features.push_back(ex);
+    return doc;
+}
+
+} // namespace
+
+// 88v: a sketch may hold more than one closed loop. The Extrude path builds the
+// sketch's planar region via SketchEngine::entities_to_wires + wires_to_face: the largest loop
+// is the outer boundary, every other loop a hole. Volumes are the proof — a plate with a hole
+// must subtract the hole, not merely "not throw".
+TEST_CASE("a circle inside a rectangle extrudes to a plate with a hole", "[CadDocument][sketchwire]")
+{
+    std::vector<SketchEntity> ents = rect_entities(40, 30);
+    ents.push_back(circle_entity({0, 0}, 5.0));
+    CadDocument doc = plate_doc(ents, 10.0);
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    const double expected = 40.0 * 30.0 * 10.0 - M_PI * 25.0 * 10.0;
+    REQUIRE_THAT(double(doc.display_mesh.volume()), Catch::Matchers::WithinRel(expected, 0.01));
+}
+
+TEST_CASE("two holes are both subtracted", "[CadDocument][sketchwire]")
+{
+    std::vector<SketchEntity> ents = rect_entities(40, 30);
+    ents.push_back(circle_entity({ 5, 0}, 3.0));
+    ents.push_back(circle_entity({-5, 0}, 3.0));
+    CadDocument doc = plate_doc(ents, 10.0);
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    const double expected = 40.0 * 30.0 * 10.0 - 2.0 * M_PI * 9.0 * 10.0;
+    REQUIRE_THAT(double(doc.display_mesh.volume()), Catch::Matchers::WithinRel(expected, 0.01));
+}
+
+TEST_CASE("a lone circle still extrudes exactly as before", "[CadDocument][sketchwire]")
+{
+    std::vector<SketchEntity> ents = { circle_entity({0, 0}, 8.0) };
+    CadDocument doc = plate_doc(ents, 5.0);
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    const double expected = M_PI * 64.0 * 5.0;
+    REQUIRE_THAT(double(doc.display_mesh.volume()), Catch::Matchers::WithinRel(expected, 0.01));
+}
+
+TEST_CASE("a closed polygon still extrudes exactly as before", "[CadDocument][sketchwire]")
+{
+    std::vector<SketchEntity> ents = rect_entities(20, 20);
+    CadDocument doc = plate_doc(ents, 10.0);
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    const double expected = 20.0 * 20.0 * 10.0;
+    REQUIRE_THAT(double(doc.display_mesh.volume()), Catch::Matchers::WithinRel(expected, 0.01));
+}
+
+TEST_CASE("two disjoint regions are refused, not guessed", "[CadDocument][sketchwire]")
+{
+    std::vector<SketchEntity> ents = { circle_entity({-10, 0}, 5.0), circle_entity({10, 0}, 5.0) };
+    CadDocument doc = plate_doc(ents, 10.0);
+
+    CHECK_FALSE(doc.recompute());
+    CHECK(doc.error.find("disjoint") != std::string::npos);
+    CHECK(doc.bodies.empty());
+}
+
+TEST_CASE("entities_to_wires returns one wire per loop", "[CadDocument][sketchwire]")
+{
+    std::vector<SketchEntity> ents = rect_entities(40, 30);
+    ents.push_back(circle_entity({0, 0}, 5.0));
+
+    const std::vector<TopoDS_Wire> wires = SketchEngine::entities_to_wires(ents, SketchPlane::XY());
+    REQUIRE(wires.size() == 2);
+    REQUIRE_FALSE(wires[0].IsNull());
+    REQUIRE_FALSE(wires[1].IsNull());
+}
+
+// Sketching on a picked face is the most common gesture in solid modelling, and it was impossible:
+// the plane came from a combo of base + datum planes only, so the sole route onto a face was to
+// build a Coincident datum plane first. plane_of_face is the shared derivation that makes the
+// viewport selection usable directly. 3a2.
+TEST_CASE("plane_of_face gives a sketchable plane for a planar face only", "[CadDocument]")
+{
+    // 20 x 20 x 20 box on XY, so its top face sits at z = 20 with +Z normal.
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Sketch");
+    doc.add_extrude(sk, 20.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    SECTION("every planar face of the box resolves, and its normal is a unit axis") {
+        int resolved = 0, top = -1;
+        for (int fi = 0; fi < 64; ++fi) {
+            SketchPlane p;
+            if (!doc.plane_of_face(0, fi, p)) continue;
+            ++resolved;
+            CHECK_THAT(p.normal.norm(), Catch::Matchers::WithinAbs(1.0, 1e-9));
+            // The frame must be orthonormal or sketch coordinates on it would be skewed.
+            CHECK_THAT(p.x_axis.dot(p.y_axis), Catch::Matchers::WithinAbs(0.0, 1e-9));
+            CHECK_THAT(p.x_axis.dot(p.normal), Catch::Matchers::WithinAbs(0.0, 1e-9));
+            if (p.normal.z() > 0.99) top = fi;
+        }
+        CHECK(resolved == 6);                 // a box has exactly six planar faces
+        REQUIRE(top >= 0);                    // and one of them faces +Z
+        SketchPlane p;
+        REQUIRE(doc.plane_of_face(0, top, p));
+        CHECK_THAT(p.origin.z(), Catch::Matchers::WithinAbs(20.0, 1e-6));   // the top, not the base
+    }
+
+    SECTION("bad indices are refused rather than guessed") {
+        SketchPlane p;
+        CHECK_FALSE(doc.plane_of_face(0, -1, p));
+        CHECK_FALSE(doc.plane_of_face(-1, 0, p));
+        CHECK_FALSE(doc.plane_of_face(9, 0, p));
+        CHECK_FALSE(doc.plane_of_face(0, 999, p));
+    }
+
+    SECTION("a cylindrical face is refused — it has no single sketch plane") {
+        CadDocument cyl;
+        int c = cyl.add_sketch(SketchShape::Circle, SketchPlane::XY(), 0, 0, 10.0, "Sketch");
+        cyl.add_extrude(c, 20.0, false, BooleanMode::New, "Extrude");
+        REQUIRE(cyl.recompute());
+        int planar = 0, refused = 0;
+        for (int fi = 0; fi < 16; ++fi) {
+            SketchPlane p;
+            if (cyl.plane_of_face(0, fi, p)) ++planar; else ++refused;
+        }
+        CHECK(planar == 2);        // the two flat caps, and NOT the barrel
+        CHECK(refused > 0);
+    }
+}
+
+// 5425 — POSITIVE-CONTRACT variant. A feature that left a body with a null
+// TopoDS_Shape used to be tolerated: recompute() returned true and the document kept
+// advertising the body. The new guard makes that a hard failure. This test asserts the
+// contract the guard preserves on the healthy side: a normal box + fillet document
+// recomputes true, reports an empty error, and NO resulting body has a null shape.
+//
+// Why not assert the negative branch (a dress-up chain nulling a body -> recompute false)?
+// Reproducing the original silent-null degeneracy (prism -> 6 vertical fillets -> chamfer on
+// the already-filleted rim -> hole) is a separate open question. Driving that order headlessly
+// makes the dress-up step THROW (OCCT "fillet radius too large" — an already-loud, already-
+// caught path) rather than silently null a body, so no public-API sequence reliably reaches
+// the guard's null branch in a headless test. Faking one (writing a null into `bodies` after
+// recompute) would not exercise the guard — it runs on the freshly-built vector — and a test
+// that asserts a state the code cannot reach is exactly what the contract forbids.
+TEST_CASE("recompute on a healthy box + fillet leaves no body null and no error (positive contract)", "[CadDocument]")
+{
+    using namespace Slic3r;
+    CadDocument doc;
+    SketchProfile sp;
+    sp.points.push_back(Vec2d(0,  0));
+    sp.points.push_back(Vec2d(20, 0));
+    sp.points.push_back(Vec2d(20, 20));
+    sp.points.push_back(Vec2d(0,  20));
+    sp.closed = true;
+    const int sk = doc.add_sketch_profile(sp, SketchPlane::XY(), "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    doc.add_fillet(2.0, FaceGroup::All, "Fillet");
+
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE_FALSE(doc.bodies.empty());
+    for (size_t i = 0; i < doc.bodies.size(); ++i) {
+        INFO("body " << i << " has a null shape");
+        REQUIRE_FALSE(doc.bodies[i].shape.IsNull());
+    }
+}
+
+// ============================================================================
+// rgbj — does a chamfer chain degenerate from a KERNEL defect, or from
+// how the DRIVER captured its edge ids? Experiment, not a fix.
+//
+// CadFeature::dressup_edge is a GLOBAL edge id: an ordinal into
+// TopExp::MapShapes(body, TopAbs_EDGE) (GeometryEngine::edge_by_index), resolved
+// at recompute time against the body AS IT STANDS at that feature's position in
+// the recipe. Every dress-up rewrites the edge map, so an id captured against one
+// version of the shape names a DIFFERENT edge once an earlier dress-up has run.
+//
+// Test 1 = correct usage (re-read the map after each chamfer, pick by geometry).
+// Test 2 = suspected-wrong usage (capture all four ids up-front, then run four).
+// ============================================================================
+
+namespace {
+
+// A square box centred on the origin, extruded +Z by `height`. Its four top-rim
+// edges have midpoints at Z=height: (+X)(half,0,h), (+Y)(0,half,h), (-X)(-half,0,h),
+// (-Y)(0,-half,h). All four are geometrically identical (equal length), so a
+// near-uniform chamfer removes the same volume from each.
+CadDocument make_centred_box(double half, double height)
+{
+    CadDocument doc;
+    SketchProfile sp;
+    sp.points = { Vec2d(-half, -half), Vec2d(half, -half), Vec2d(half, half), Vec2d(-half, half) };
+    sp.closed = true;
+    const int sk = doc.add_sketch_profile(sp, SketchPlane::XY(), "Box");
+    doc.add_extrude(sk, height, false, BooleanMode::New, "Extrude");
+    return doc;
+}
+
+// Exact analytic volume (BRepGProp, not tessellation) of a solid.
+double solid_volume(const TopoDS_Shape& s)
+{
+    GeometryEngine::MassProps p = GeometryEngine::mass_properties(s);
+    return p.valid ? p.volume : 0.0;
+}
+
+// World-space midpoint of an edge, from its sampled polyline.
+Vec3d edge_mid(const TopoDS_Edge& e)
+{
+    const std::vector<Vec3d> pts = GeometryEngine::sample_edge_world(e);
+    Vec3d m = Vec3d::Zero();
+    for (const Vec3d& p : pts) m += p;
+    return m / double(pts.size());
+}
+
+// Global edge id whose midpoint is within `tol` mm of `target`. -1 if none.
+// Picks by GEOMETRY (position), never by a hardcoded index.
+int edge_near(const TopoDS_Shape& shape, const Vec3d& target, double tol)
+{
+    const std::vector<TopoDS_Edge> edges = GeometryEngine::edges_of(shape);
+    for (int i = 0; i < int(edges.size()); ++i) {
+        if (edges[i].IsNull()) continue;
+        const std::vector<Vec3d> pts = GeometryEngine::sample_edge_world(edges[i]);
+        if (pts.size() < 2) continue;
+        if ((edge_mid(edges[i]) - target).norm() < tol) return i;
+    }
+    return -1;
+}
+
+} // namespace
+
+TEST_CASE("dressup: sequential chamfers, ids re-read after each, stay uniform", "[CadDocument][dressup]")
+{
+    const double half = 10.0, h = 10.0, d = 0.2; // tiny d: the corner-shortening of a
+                                                 // neighbour's rim edge stays negligible
+    CadDocument doc = make_centred_box(half, h);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // The four top-rim edges, addressed by world midpoint — never by index.
+    const std::vector<Vec3d> rim = {
+        Vec3d( half, 0.0, h),   // +X
+        Vec3d(0.0,  half, h),   // +Y
+        Vec3d(-half, 0.0, h),   // -X
+        Vec3d(0.0, -half, h),   // -Y
+    };
+
+    std::vector<double> removals;
+    double prev = solid_volume(doc.bodies[0].shape);
+    for (size_t k = 0; k < rim.size(); ++k) {
+        // Correct usage: re-read the CURRENT body's edge map, pick by geometry.
+        const int id = edge_near(doc.bodies[0].shape, rim[k], 1.5);
+        INFO("chamfer " << k << " -> edge id " << id);
+        REQUIRE(id >= 0);
+        doc.add_chamfer(d, id, "Chamfer" + std::to_string(k));
+        REQUIRE(doc.recompute());
+        REQUIRE(doc.error.empty());
+        const double now = solid_volume(doc.bodies[0].shape);
+        removals.push_back(prev - now);
+        prev = now;
+    }
+
+    std::ostringstream os;
+    for (size_t i = 0; i < removals.size(); ++i) os << (i ? ", " : "") << removals[i];
+    INFO("removals (mm^3): [" << os.str() << "]");
+
+    REQUIRE(removals.size() == 4);
+    double mn = removals[0], mx = removals[0];
+    for (double r : removals) { mn = std::min(mn, r); mx = std::max(mx, r); }
+    INFO("min=" << mn << " max=" << mx);
+    REQUIRE(mn > 0.0);
+    // All four removals equal within a few percent. Measured on this fixture:
+    // [0.4, 0.397333, 0.397333, 0.394667] mm^3. The residual spread is real geometry (each
+    // chamfer shortens the two rim edges it shares a corner with), not id drift; drift would
+    // push the later removals toward zero and blow the spread wide open.
+    REQUIRE((mx - mn) <= 0.10 * mn);
+}
+
+TEST_CASE("dressup: four chamfer ids captured up-front drift as earlier chamfers run", "[CadDocument][dressup]")
+{
+    const double half = 10.0, h = 10.0, d = 0.2;
+    CadDocument doc = make_centred_box(half, h);
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    const std::vector<Vec3d> rim = {
+        Vec3d( half, 0.0, h), Vec3d(0.0, half, h), Vec3d(-half, 0.0, h), Vec3d(0.0, -half, h),
+    };
+
+    // Capture all four ids ONCE, from the shape as it stands before any chamfer.
+    std::vector<int> ids;
+    for (const Vec3d& t : rim) {
+        const int id = edge_near(doc.bodies[0].shape, t, 1.5);
+        REQUIRE(id >= 0);
+        ids.push_back(id);
+    }
+    REQUIRE(ids.size() == 4);
+    INFO("captured ids: [" << ids[0] << "," << ids[1] << "," << ids[2] << "," << ids[3] << "]");
+
+    // Recompute resolves each dressup_edge against the body as it stands at that feature's
+    // position — exactly what chaining apply_chamfer reproduces here. Measure each step, and
+    // record whether a stale id throws (invalid/out-of-range edge) or silently lands elsewhere.
+    TopoDS_Shape s = doc.bodies[0].shape;
+    std::vector<double> vols{ solid_volume(s) };
+    bool threw = false;
+    std::string why;
+    for (int id : ids) {
+        try {
+            s = GeometryEngine::apply_chamfer(s, d, id);
+            vols.push_back(solid_volume(s));
+        } catch (const std::exception& e) { threw = true; why = e.what(); break; }
+    }
+
+    std::vector<double> rmv;
+    for (size_t i = 1; i < vols.size(); ++i) rmv.push_back(vols[i - 1] - vols[i]);
+
+    std::ostringstream os;
+    for (size_t i = 0; i < rmv.size(); ++i) os << (i ? ", " : "") << rmv[i];
+    INFO("up-front-id removals (mm^3): [" << os.str() << "] threw=" << threw << " (" << why << ")");
+
+    // Documents a defect, not a desired result. Measured on this fixture: [0.4, 0.008324,
+    // 0.397333, 0.280405] mm^3 — the second chamfer's stale id landed on a nearly-consumed
+    // edge and cut ~2% of the intended volume. Ids captured once and replayed against an
+    // evolving edge map DRIFT; that is the degeneration the socket chamfers showed, and it is
+    // a driver artefact (wrong usage), not a kernel defect — Test 1 proves the kernel stays
+    // uniform when ids are re-read.
+    REQUIRE_FALSE(threw);            // currently it does NOT throw: it silently drifts
+    REQUIRE(rmv.size() == 4);
+    double mn = rmv[0], mx = rmv[0];
+    for (double r : rmv) { mn = std::min(mn, r); mx = std::max(mx, r); }
+    INFO("up-front-id min=" << mn << " max=" << mx);
+    REQUIRE(mx > 1.10 * mn);         // non-uniform: the id-drift signature
+
+    // The first captured id is still a valid top-rim edge, so the first chamfer must cut.
+    REQUIRE(vols.size() >= 2);
+    REQUIRE(vols[1] < vols[0]);
+
+    // Literal driver path: append all four and recompute once.
+    CadDocument doc2 = make_centred_box(half, h);
+    REQUIRE(doc2.recompute());
+    for (size_t i = 0; i < ids.size(); ++i)
+        doc2.add_chamfer(d, ids[i], "C" + std::to_string(i));
+    const bool ok = doc2.recompute();
+    INFO("single-recompute driver path: ok=" << ok << " error=" << (ok ? std::string() : doc2.error));
+    REQUIRE(ok);
+}
+
+// --- Face-drift fingerprint: a FaceAndDirection connector warns when its face index slides ---
+
+TEST_CASE("a connector records its face fingerprint on first recompute", "[CadDocument][mate]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+
+    int top_face = find_face_by_normal(doc, 0, Vec3d(0, 0, 1));
+    REQUIRE(top_face >= 0);
+
+    int cs = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0, 0, 0), "CS");
+    doc.features[cs].coordsys_body = 0;
+    doc.features[cs].coordsys_face = top_face;
+    REQUIRE(doc.recompute());
+
+    REQUIRE(doc.features[cs].coordsys_face_kind >= 0);
+    REQUIRE(doc.features[cs].coordsys_face_edges >= 0);
+    REQUIRE(doc.mate_conflicts.empty());
+}
+
+TEST_CASE("a connector whose face index slides onto a different KIND of face is reported", "[CadDocument][mate]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+
+    int top_face = find_face_by_normal(doc, 0, Vec3d(0, 0, 1));
+    REQUIRE(top_face >= 0);
+
+    int cs = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0, 0, 0), "CS");
+    doc.features[cs].coordsys_body = 0;
+    doc.features[cs].coordsys_face = top_face;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.mate_conflicts.empty());
+    REQUIRE(doc.features[cs].coordsys_face_kind >= 0);
+
+    // Insert a fillet: the box gains cylindrical faces and the face map is renumbered.
+    doc.add_fillet(2.0, FaceGroup::All, "Fillet");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    // Find the cylindrical face the fillet introduced (a different KIND than the recorded
+    // planar fingerprint), then force the drift by pointing coordsys_face at it.
+    int cyl_face = -1;
+    auto faces = GeometryEngine::faces_of(doc.bodies[0].shape);
+    for (int i = 0; i < int(faces.size()); ++i) {
+        if (GeometryEngine::cylinder_of_face(faces[i]).ok) { cyl_face = i; break; }
+    }
+    REQUIRE(cyl_face >= 0);
+
+    doc.features[cs].coordsys_face = cyl_face;
+    const bool ok = doc.recompute();
+    REQUIRE(ok);   // non-fatality is the contract under test
+
+    bool reported = false;
+    for (const auto& c : doc.mate_conflicts)
+        if (c.first == cs) { reported = true; break; }
+    REQUIRE(reported);
+}
+
+TEST_CASE("a resized body does not report drift", "[CadDocument][mate]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+
+    int top_face = find_face_by_normal(doc, 0, Vec3d(0, 0, 1));
+    REQUIRE(top_face >= 0);
+
+    int cs = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0, 0, 0), "CS");
+    doc.features[cs].coordsys_body = 0;
+    doc.features[cs].coordsys_face = top_face;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.mate_conflicts.empty());
+
+    // Resize upstream: same face, same kind, same edge count — only its dimensions changed.
+    // This is a legitimate parametric edit and must not raise the drift warning.
+    for (CadFeature& f : doc.features)
+        if (f.type == CadFeatureType::Extrude) f.distance = 25.0;
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.mate_conflicts.empty());
+}
+
+TEST_CASE("mate_options always returns five entries in kind order", "[CadDocument][mate]")
+{
+    CadDocument doc;
+    // Completely invalid pair: the stability contract (always five, always in order) must hold.
+    auto opts = doc.mate_options(-1, -1);
+    REQUIRE(opts.size() == 5);
+    for (int i = 0; i < 5; ++i) REQUIRE(opts[i].kind == i);
+
+    // A valid, distinct pair must return the same shape.
+    int a = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 0), "A");
+    int b = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(1, 0, 0), "B");
+    auto opts2 = doc.mate_options(a, b);
+    REQUIRE(opts2.size() == 5);
+    for (int i = 0; i < 5; ++i) REQUIRE(opts2[i].kind == i);
+}
+
+TEST_CASE("a connector with no body dims every mate kind, with a reason", "[CadDocument][mate]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+
+    // Point(world) connectors belong to no body, which is the default the GUI hands you.
+    int a = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 0), "A");
+    int b = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(30, 0, 0), "B");
+    REQUIRE(doc.features[b].coordsys_body < 0);
+
+    // B is the connector whose body MOVES, so without one no kind can apply. The offer used to
+    // call all five viable and the mate only failed at recompute, after the feature existed.
+    auto opts = doc.mate_options(a, b);
+    REQUIRE(opts.size() == 5);
+    for (int i = 0; i < 5; ++i) {
+        REQUIRE(opts[i].kind == i);
+        REQUIRE_FALSE(opts[i].viable);
+        REQUIRE(opts[i].reason.find("not attached to a body") != std::string::npos);
+    }
+
+    // A needs no body — it is the fixed reference. Giving B one is enough to revive the offer.
+    doc.features[b].coordsys_body = 0;
+    auto opts2 = doc.mate_options(a, b);
+    REQUIRE(opts2[0].viable);          // Fastened is frame-only
+    REQUIRE(opts2[0].reason.empty());
+
+    // A body index that no longer resolves is refused too, and says so differently.
+    doc.features[b].coordsys_body = 7;
+    auto opts3 = doc.mate_options(a, b);
+    for (const auto& o : opts3) {
+        REQUIRE_FALSE(o.viable);
+        REQUIRE(o.reason.find("no longer exists") != std::string::npos);
+    }
+}
+
+TEST_CASE("a flat-face pair offers Fastened, Planar and Slider but not the axial types", "[CadDocument][mate]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int top  = find_face_by_normal(doc, 0, Vec3d(0, 0, 1));
+    int side = find_face_by_normal(doc, 0, Vec3d(1, 0, 0));
+    REQUIRE(top  >= 0);
+    REQUIRE(side >= 0);
+
+    int a = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0, 0, 0), "A");
+    doc.features[a].coordsys_body = 0;
+    doc.features[a].coordsys_face = top;
+    int b = doc.add_coordsys(CoordSysType::FaceAndDirection, Vec3d(0, 0, 0), "B");
+    doc.features[b].coordsys_body = 0;
+    doc.features[b].coordsys_face = side;
+
+    // Recompute so the face fingerprints record (both planar => GeomAbs_Plane).
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.features[a].coordsys_face_kind >= 0);
+    REQUIRE(doc.features[b].coordsys_face_kind >= 0);
+
+    auto opts = doc.mate_options(a, b);
+    REQUIRE(opts.size() == 5);
+    REQUIRE(opts[0].viable);   // Fastened: frame-only, always viable
+    REQUIRE(opts[1].viable);   // Planar: both faces planar
+    REQUIRE_FALSE(opts[2].viable); // Revolute: needs a cylindrical face
+    REQUIRE(opts[3].viable);   // Slider: frame-only, always viable
+    REQUIRE_FALSE(opts[4].viable); // Cylindrical: needs a cylindrical face
+
+    REQUIRE(opts[0].reason.empty());
+    REQUIRE(opts[1].reason.empty());
+    REQUIRE(opts[3].reason.empty());
+    REQUIRE_FALSE(opts[2].reason.empty());
+    REQUIRE_FALSE(opts[4].reason.empty());
+    REQUIRE_CONTAINS(opts[2].reason, "connector");
+    REQUIRE_CONTAINS(opts[4].reason, "connector");
+}
+
+TEST_CASE("an unrecorded fingerprint does not make a type non-viable", "[CadDocument][mate]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "Box");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+
+    int a = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 0), "A");
+    int b = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(1, 0, 0), "B");
+    // The MISSING FINGERPRINT is the whole subject here, so nothing else may be missing: B is
+    // given a body, because a connector without one is refused for that reason instead and the
+    // case would no longer isolate what this test is named for.
+    doc.features[a].coordsys_body = 0;
+    doc.features[b].coordsys_body = 0;
+    // PointWorld connectors never record a face fingerprint: face_kind stays -1.
+    REQUIRE(doc.features[a].coordsys_face_kind == -1);
+    REQUIRE(doc.features[b].coordsys_face_kind == -1);
+
+    auto opts = doc.mate_options(a, b);
+    REQUIRE(opts.size() == 5);
+    for (const auto& o : opts) {
+        REQUIRE(o.viable);
+        REQUIRE(o.reason.empty());
+    }
+}
+
+TEST_CASE("an invalid pair names which side is wrong", "[CadDocument][mate]")
+{
+    CadDocument doc;
+    int a = doc.add_coordsys(CoordSysType::PointWorld, Vec3d(0, 0, 0), "A");
+    int sketch = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 0, "S");
+
+    // cs_b points at a Sketch feature, not a CoordSys: all five non-viable, reason names B.
+    auto opts = doc.mate_options(a, sketch);
+    REQUIRE(opts.size() == 5);
+    for (const auto& o : opts) {
+        REQUIRE_FALSE(o.viable);
+        REQUIRE_CONTAINS(o.reason, "connector B");
+        REQUIRE(o.reason.find("connector A") == std::string::npos);
+    }
+
+    // Out of range on B names B; out of range on A names A.
+    for (const auto& o : doc.mate_options(a, 9999))
+        REQUIRE_CONTAINS(o.reason, "connector B");
+    for (const auto& o : doc.mate_options(-5, a))
+        REQUIRE_CONTAINS(o.reason, "connector A");
+}
+
+// A rectangular plate 120 x 160 x 10 centred on the origin with a radius-30 bore through
+// the middle: one solid whose volume is the box minus the cylinder, and whose topology is a
+// plate-with-a-bore (1 solid, 7 faces) rather than a plate plus a plug.
+TEST_CASE("add_extrude_entities builds a plate with a bore", "[CadDocument][holes]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+
+    const Vec2d A(-60, -80), B(60, -80), C(60, 80), D(-60, 80);
+    std::vector<SketchEntity> entities = {
+        {SketchEntity::Type::Line, A, B},
+        {SketchEntity::Type::Line, B, C},
+        {SketchEntity::Type::Line, C, D},
+        {SketchEntity::Type::Line, D, A},
+    };
+    SketchEntity bore;
+    bore.type   = SketchEntity::Type::Circle;
+    bore.center = Vec2d(0, 0);
+    bore.radius = 30.0;
+    entities.push_back(bore);
+
+    doc.add_extrude_entities(entities, SketchPlane::XY(), 10.0, false, BooleanMode::New, "Extrude1");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.display_mesh.facets_count() > 0);
+
+    auto mp = doc.body_mass_properties(0);
+    REQUIRE(mp.valid);
+    const double expected_vol = 120.0 * 160.0 * 10.0 - M_PI * 30.0 * 30.0 * 10.0;
+    REQUIRE_THAT(mp.volume, WithinAbs(expected_vol, 1.0));
+
+    // One solid, seven faces: top + bottom (each a planar face with a hole), four side
+    // walls, and the single cylindrical bore wall.
+    int face_count = 0, solid_count = 0;
+    for (TopExp_Explorer fe(doc.bodies.back().shape, TopAbs_FACE);  fe.More(); fe.Next()) ++face_count;
+    for (TopExp_Explorer se(doc.bodies.back().shape, TopAbs_SOLID); se.More(); se.Next()) ++solid_count;
+    INFO("volume mm^3 = " << mp.volume << ", faces = " << face_count << ", solids = " << solid_count);
+    REQUIRE(solid_count == 1);
+    REQUIRE(face_count == 7);
+}
+
+TEST_CASE("two disjoint circles are refused by name", "[CadDocument][holes]")
+{
+    CadDocument doc;
+
+    SketchEntity a;
+    a.type = SketchEntity::Type::Circle; a.center = Vec2d(-50, 0); a.radius = 20.0;
+    SketchEntity b;
+    b.type = SketchEntity::Type::Circle; b.center = Vec2d( 50, 0); b.radius = 20.0;
+
+    doc.add_extrude_entities({a, b}, SketchPlane::XY(), 10.0, false, BooleanMode::New, "Extrude1");
+
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_CONTAINS(doc.error, "disjoint");
+}
+
+// Same plate-with-a-bore, but the bore circle is wound CLOCKWISE (geometric winding opposite
+// the CCW rectangle). The old wires_to_face reversed every hole wire unconditionally
+// (wires[i].Reversed()), which only produced a correct hole when the circle was wound the same
+// way as the outer loop; a clockwise circle got reversed into matching the outer boundary and
+// the prism swept it solid — measured 220274 mm^3 = box (192000) + disc (28274), the filled-bore
+// signature. The current ShapeFix_Face::FixOrientation path is winding-independent. Flipping the
+// plane normal reverses gp_Circ's parametrisation (gp_Ax2(center, -Z) sweeps clockwise seen from
+// +Z) while the rectangle's 2D coordinates stay CCW.
+TEST_CASE("add_extrude_entities builds a plate with a bore (clockwise circle)", "[CadDocument][holes]")
+{
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+
+    SketchPlane cw_plane = SketchPlane::XY();
+    cw_plane.normal = Vec3d(0, 0, -1);
+
+    const Vec2d A(-60, -80), B(60, -80), C(60, 80), D(-60, 80);
+    std::vector<SketchEntity> entities = {
+        {SketchEntity::Type::Line, A, B},
+        {SketchEntity::Type::Line, B, C},
+        {SketchEntity::Type::Line, C, D},
+        {SketchEntity::Type::Line, D, A},
+    };
+    SketchEntity bore;
+    bore.type   = SketchEntity::Type::Circle;
+    bore.center = Vec2d(0, 0);
+    bore.radius = 30.0;
+    entities.push_back(bore);
+
+    doc.add_extrude_entities(entities, cw_plane, 10.0, false, BooleanMode::New, "Extrude1");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.display_mesh.facets_count() > 0);
+
+    auto mp = doc.body_mass_properties(0);
+    REQUIRE(mp.valid);
+    const double expected_vol = 120.0 * 160.0 * 10.0 - M_PI * 30.0 * 30.0 * 10.0;
+    REQUIRE_THAT(mp.volume, WithinAbs(expected_vol, 1.0));
+
+    int face_count = 0, solid_count = 0;
+    for (TopExp_Explorer fe(doc.bodies.back().shape, TopAbs_FACE);  fe.More(); fe.Next()) ++face_count;
+    for (TopExp_Explorer se(doc.bodies.back().shape, TopAbs_SOLID); se.More(); se.Next()) ++solid_count;
+    INFO("volume mm^3 = " << mp.volume << ", faces = " << face_count << ", solids = " << solid_count);
+    REQUIRE(solid_count == 1);
+    REQUIRE(face_count == 7);
+}
+
+
+// mtav. A document that has only sketches in it is not a broken document, it is the
+// state every design passes through between drawing a profile and extruding it. recompute()
+// used to call that "no solid-producing features" and return false, and two things downstream
+// read that false as "the document is unusable": the GUI syncs the 3MF recipe only after a
+// successful recompute, so a sketch-only design was saved with NO recipe at all and vanished on
+// reopen; and deserialize_recipe ends with `return recompute()`, so even a project that did
+// carry one was refused on load. The failure has to stay for a document that ASKED for a solid
+// and got none — that is a real geometry failure — so both halves are asserted here.
+TEST_CASE("A sketch-only document recomputes and round-trips", "[CadDocument]")
+{
+    CadDocument doc;
+    std::vector<SketchEntity> ents{
+        {SketchEntity::Type::Line, Vec2d(-60, -40), Vec2d(60, -40)},
+        {SketchEntity::Type::Line, Vec2d(60, -40), Vec2d(60, 40)},
+        {SketchEntity::Type::Line, Vec2d(60, 40), Vec2d(-60, 40)},
+        {SketchEntity::Type::Line, Vec2d(-60, 40), Vec2d(-60, -40)},
+    };
+    const int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "Profile");
+    REQUIRE(sk == 0);
+
+    const bool built = doc.recompute();     // nothing to build is not a failure
+    INFO("recompute error: " << doc.error);
+    REQUIRE(built);
+    REQUIRE(doc.error.empty());
+    REQUIRE(doc.bodies.empty());
+
+    const std::string blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument fresh;
+    REQUIRE(fresh.deserialize_recipe(blob));
+    REQUIRE(fresh.error.empty());
+    REQUIRE(fresh.features.size() == 1);
+    REQUIRE(fresh.features[0].name == "Profile");
+    REQUIRE(fresh.features[0].entities.size() == 4);
+    for (size_t i = 0; i < ents.size(); ++i) {
+        REQUIRE(fresh.features[0].entities[i].p0.x() == ents[i].p0.x());
+        REQUIRE(fresh.features[0].entities[i].p0.y() == ents[i].p0.y());
+        REQUIRE(fresh.features[0].entities[i].p1.x() == ents[i].p1.x());
+        REQUIRE(fresh.features[0].entities[i].p1.y() == ents[i].p1.y());
+    }
+
+    // The other half of the rule: a feature that MEANT to build a solid and produced none is
+    // still an error, and must not be swallowed by the change above.
+    CadDocument bad;
+    bad.add_sketch_entities(ents, SketchPlane::XY(), "Profile");
+    bad.add_extrude(0, 0.0, false, BooleanMode::New, "ZeroDepth");
+    REQUIRE_FALSE(bad.recompute());
+    REQUIRE_FALSE(bad.error.empty());
+}
+
+// A body is NOT the feature that created it. Reported 2026-08-23, in these words: "you have
+// renamed the feature extrusion, not the body ... this means that you consider the extrusion =
+// the body, which is very far from truth as a body can contain several extrusions." The rename
+// used to resolve CadBody::source_feature and rename THAT, so naming a body edited one operation
+// in its history. A body now carries its own name, and this pins the three properties that make
+// it a name rather than a label: it does not touch the features, it survives a recompute that
+// adds more features to the same body, and it survives the recipe round trip.
+TEST_CASE("a body carries its own name, through recompute and the recipe", "[CadDocument]")
+{
+    CadDocument doc;
+    std::vector<SketchEntity> ents;
+    auto line = [&](double x0, double y0, double x1, double y1) {
+        SketchEntity e; e.type = SketchEntity::Type::Line;
+        e.p0 = Vec2d(x0, y0); e.p1 = Vec2d(x1, y1); ents.push_back(e); };
+    line(0, 0, 40, 0); line(40, 0, 40, 30); line(40, 30, 0, 30); line(0, 30, 0, 0);
+
+    const int sk = doc.add_sketch_entities(ents, SketchPlane::XY(), "Profile");
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+
+    doc.bodies[0].has_user_name = true;
+    doc.bodies[0].user_name     = "Bracket";
+
+    // A SECOND feature lands on the same body — the case the report is about.
+    doc.add_hole(6.0, 5.0, true, 20.0, 15.0, SketchPlane::XY(), "Hole");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.bodies.size() == 1);
+    CHECK(doc.bodies[0].has_user_name);
+    CHECK(doc.bodies[0].user_name == "Bracket");
+
+    // The features keep their own names: renaming the body renamed nothing else.
+    REQUIRE(doc.features.size() == 3);
+    CHECK(doc.features[0].name == "Profile");
+    CHECK(doc.features[1].name == "Extrude");
+    CHECK(doc.features[2].name == "Hole");
+
+    // ...and the name is part of what gets saved. Bodies are recomputed, never serialised, so
+    // without the recipe block a body name would live exactly until the project was reopened.
+    const std::string blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+    CadDocument fresh;
+    REQUIRE(fresh.deserialize_recipe(blob));
+    REQUIRE(fresh.bodies.size() == 1);
+    CHECK(fresh.bodies[0].has_user_name);
+    CHECK(fresh.bodies[0].user_name == "Bracket");
+}
+
+// A feature reference is a reference whatever feature holds it.
+//
+// remove_feature()/move_feature() used to remap Extrude::sketch_ref and a Mate's two
+// connectors, and nothing else — so every later consumer of a Sketch (Revolve, Sweep, Loft,
+// Rib, Pattern-on-curve, the Surface* family) kept an index that the erase had just
+// invalidated. The failure is quiet by construction: a shifted index still names a real
+// feature, recompute() succeeds, and what comes out is built from the wrong profile.
+//
+// The volume is the assertion. Two different profiles go in; deleting the unused feature in
+// front of them must leave the SAME solid behind, which it only can if the reference moved
+// with its target.
+TEST_CASE("deleting a feature remaps the references of every consumer, not just Extrude",
+          "[CadDocument]")
+{
+    using namespace Slic3r;
+    const SketchPlane xy = SketchPlane::XY();
+
+    // A rectangle 10x10 centred at v = 15, revolved 360 deg about the plane X axis.
+    auto rect_at = [&](double v0) {
+        CadFeature sk;
+        sk.type  = CadFeatureType::Sketch;
+        sk.plane = xy;
+        sk.profile.points = { Vec2d(-5, v0 - 5), Vec2d(5, v0 - 5),
+                              Vec2d(5, v0 + 5), Vec2d(-5, v0 + 5) };
+        sk.profile.closed = true;
+        return sk;
+    };
+
+    SECTION("Revolve::sketch_ref survives the deletion of a feature in front of it") {
+        CadDocument doc;
+        doc.features.push_back(rect_at(40.0));   // f0: a decoy profile, never consumed
+        doc.features.push_back(rect_at(15.0));   // f1: the real profile
+        doc.add_revolve(1, 360.0, /*axis=X*/0, false, BooleanMode::New, "Rev");
+        REQUIRE(doc.recompute());
+        const double before = double(doc.display_mesh.volume());
+        REQUIRE(before == Approx(9424.78).epsilon(0.05));
+
+        // f0 is consumed by nothing, so this deletes exactly one feature and shifts f1 to 0.
+        REQUIRE(doc.remove_feature(0));
+        REQUIRE(doc.features.size() == 2);
+        REQUIRE(doc.features[1].type == CadFeatureType::Revolve);
+        REQUIRE(doc.features[1].sketch_ref == 0);          // followed its target
+        REQUIRE(doc.error.empty());
+        REQUIRE(double(doc.display_mesh.volume()) == Approx(before).epsilon(1e-6));
+    }
+
+    SECTION("move_feature swaps a Revolve's reference too") {
+        CadDocument doc;
+        doc.features.push_back(rect_at(40.0));   // f0
+        doc.features.push_back(rect_at(15.0));   // f1 -> consumed
+        doc.add_revolve(1, 360.0, 0, false, BooleanMode::New, "Rev");
+        REQUIRE(doc.recompute());
+        const double before = double(doc.display_mesh.volume());
+
+        REQUIRE(doc.move_feature(0, 1));                   // f0 and f1 trade places
+        REQUIRE(doc.features[2].sketch_ref == 0);          // the profile is now at 0
+        REQUIRE(double(doc.display_mesh.volume()) == Approx(before).epsilon(1e-6));
+    }
+
+    SECTION("deleting a Sketch cascades to a Revolve that consumes it") {
+        CadDocument doc;
+        doc.features.push_back(rect_at(15.0));
+        doc.add_revolve(0, 360.0, 0, false, BooleanMode::New, "Rev");
+        REQUIRE(doc.recompute());
+
+        // The Revolve has no profile without this Sketch, exactly as an Extrude would not:
+        // it goes with it rather than being left pointing at nothing.
+        REQUIRE(doc.remove_feature(0));
+        REQUIRE(doc.features.empty());
+    }
+}
diff --git a/tests/libslic3r/test_sketchconstraints.cpp b/tests/libslic3r/test_sketchconstraints.cpp
new file mode 100644
index 0000000000..d0c5844b40
--- /dev/null
+++ b/tests/libslic3r/test_sketchconstraints.cpp
@@ -0,0 +1,396 @@
+#include <catch2/catch_all.hpp>   // mainline OrcaSlicer ships Catch2 v3 (v2 was catch2/catch.hpp)
+#include "libslic3r/CAD/SketchConstraints.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
+
+using namespace Slic3r;
+
+namespace {
+SketchEntity mk_line(double x0, double y0, double x1, double y1)
+{
+    SketchEntity e; e.type = SketchEntity::Type::Line;
+    e.p0 = Vec2d(x0, y0); e.p1 = Vec2d(x1, y1); return e;
+}
+SketchEntity mk_point(double x, double y)
+{
+    SketchEntity e; e.type = SketchEntity::Type::Point; e.p0 = Vec2d(x, y); return e;
+}
+SketchEntity mk_circle(double cx, double cy, double r)
+{
+    SketchEntity e; e.type = SketchEntity::Type::Circle;
+    e.center = Vec2d(cx, cy); e.radius = r; return e;
+}
+}
+
+TEST_CASE("Coincident with anchor", "[SketchConstraints]")
+{
+    SketchConstraints sc;
+    int a = sc.add_point(0, 0);
+    int b = sc.add_point(5, 5);
+    sc.fix_point(a);
+    sc.coincident(a, b);
+    REQUIRE(sc.solve());
+    Vec2d pb = sc.get_point(b);
+    REQUIRE_THAT(pb.x(), Catch::Matchers::WithinAbs(0.0, 1e-4));
+    REQUIRE_THAT(pb.y(), Catch::Matchers::WithinAbs(0.0, 1e-4));
+}
+
+TEST_CASE("Horizontal + distance", "[SketchConstraints]")
+{
+    SketchConstraints sc;
+    int a = sc.add_point(0, 0);
+    int b = sc.add_point(5, 3);
+    sc.fix_point(a);
+    sc.horizontal(a, b);
+    sc.distance(a, b, 10);
+    REQUIRE(sc.solve());
+    Vec2d pb = sc.get_point(b);
+    REQUIRE_THAT(pb.y(), Catch::Matchers::WithinAbs(0.0, 1e-3));
+    REQUIRE_THAT(std::abs(pb.x()), Catch::Matchers::WithinAbs(10.0, 1e-3));
+}
+
+TEST_CASE("Rectangle", "[SketchConstraints]")
+{
+    SketchConstraints sc;
+    int p0 = sc.add_point(0, 0);
+    int p1 = sc.add_point(8, 1);
+    int p2 = sc.add_point(9, 5);
+    int p3 = sc.add_point(-1, 4);
+    sc.fix_point(p0);
+    sc.lock_x(p0, 0);
+    sc.lock_y(p0, 0);
+    sc.horizontal(p0, p1);
+    sc.vertical(p1, p2);
+    sc.horizontal(p2, p3);
+    sc.vertical(p3, p0);
+    sc.distance(p0, p1, 10);
+    sc.distance(p1, p2, 6);
+    REQUIRE(sc.solve());
+    Vec2d pp1 = sc.get_point(p1);
+    Vec2d pp2 = sc.get_point(p2);
+    Vec2d pp3 = sc.get_point(p3);
+    REQUIRE_THAT(pp1.x(), Catch::Matchers::WithinAbs(10.0, 1e-3));
+    REQUIRE_THAT(pp1.y(), Catch::Matchers::WithinAbs(0.0, 1e-3));
+    REQUIRE_THAT(pp2.x(), Catch::Matchers::WithinAbs(10.0, 1e-3));
+    REQUIRE_THAT(pp2.y(), Catch::Matchers::WithinAbs(6.0, 1e-3));
+    REQUIRE_THAT(pp3.x(), Catch::Matchers::WithinAbs(0.0, 1e-3));
+    REQUIRE_THAT(pp3.y(), Catch::Matchers::WithinAbs(6.0, 1e-3));
+}
+
+TEST_CASE("residual_norm after each solve", "[SketchConstraints]")
+{
+    SECTION("coincident case")
+    {
+        SketchConstraints sc;
+        int a = sc.add_point(0, 0);
+        int b = sc.add_point(5, 5);
+        sc.fix_point(a);
+        sc.coincident(a, b);
+        REQUIRE(sc.solve());
+        REQUIRE(sc.residual_norm() < 1e-5);
+    }
+    SECTION("horizontal+distance case")
+    {
+        SketchConstraints sc;
+        int a = sc.add_point(0, 0);
+        int b = sc.add_point(5, 3);
+        sc.fix_point(a);
+        sc.horizontal(a, b);
+        sc.distance(a, b, 10);
+        REQUIRE(sc.solve());
+        REQUIRE(sc.residual_norm() < 1e-5);
+    }
+    SECTION("rectangle case")
+    {
+        SketchConstraints sc;
+        int p0 = sc.add_point(0, 0);
+        int p1 = sc.add_point(8, 1);
+        int p2 = sc.add_point(9, 5);
+        int p3 = sc.add_point(-1, 4);
+        sc.fix_point(p0);
+        sc.lock_x(p0, 0);
+        sc.lock_y(p0, 0);
+        sc.horizontal(p0, p1);
+        sc.vertical(p1, p2);
+        sc.horizontal(p2, p3);
+        sc.vertical(p3, p0);
+        sc.distance(p0, p1, 10);
+        sc.distance(p1, p2, 6);
+        REQUIRE(sc.solve());
+        REQUIRE(sc.residual_norm() < 1e-5);
+    }
+}
+
+TEST_CASE("midpoint", "[SketchConstraints]")
+{
+    SketchConstraints sc;
+    int a = sc.add_point(0, 0);
+    int b = sc.add_point(10, 0);
+    int m = sc.add_point(3, 7);
+    sc.fix_point(a);
+    sc.fix_point(b);
+    sc.midpoint(m, a, b);
+    REQUIRE(sc.solve());
+    Vec2d pm = sc.get_point(m);
+    REQUIRE_THAT(pm.x(), Catch::Matchers::WithinAbs(5.0, 1e-3));
+    REQUIRE_THAT(pm.y(), Catch::Matchers::WithinAbs(0.0, 1e-3));
+}
+
+TEST_CASE("symmetric across Y axis", "[SketchConstraints]")
+{
+    SketchConstraints sc;
+    int a = sc.add_point(2, 3);
+    int b = sc.add_point(-1, 1);
+    int c = sc.add_point(0, 0);
+    int d = sc.add_point(0, 1);
+    sc.fix_point(a);
+    sc.fix_point(c);
+    sc.fix_point(d);
+    sc.symmetric(a, b, c, d);
+    REQUIRE(sc.solve());
+    Vec2d pb = sc.get_point(b);
+    REQUIRE_THAT(pb.x(), Catch::Matchers::WithinAbs(-2.0, 1e-3));
+    REQUIRE_THAT(pb.y(), Catch::Matchers::WithinAbs(3.0, 1e-3));
+}
+
+TEST_CASE("angle 90 degrees", "[SketchConstraints]")
+{
+    SketchConstraints sc;
+    int a = sc.add_point(0, 0);
+    int b = sc.add_point(1, 0);
+    int c = sc.add_point(0, 0);
+    int d = sc.add_point(1, 1);
+    sc.fix_point(a);
+    sc.fix_point(b);
+    sc.fix_point(c);
+    sc.angle(a, b, c, d, M_PI / 2);
+    REQUIRE(sc.solve());
+    Vec2d pd = sc.get_point(d);
+    Vec2d pc = sc.get_point(c);
+    REQUIRE_THAT(pd.x() - pc.x(), Catch::Matchers::WithinAbs(0.0, 1e-3));
+    REQUIRE(pd.y() > pc.y());
+}
+
+TEST_CASE("point-line distance", "[SketchConstraints]")
+{
+    SketchConstraints sc;
+    int a = sc.add_point(0, 0);
+    int b = sc.add_point(10, 0);
+    int p = sc.add_point(3, 1);
+    sc.fix_point(a);
+    sc.fix_point(b);
+    sc.lock_x(p, 3.0);
+    sc.point_line_distance(p, a, b, 5.0);
+    REQUIRE(sc.solve());
+    Vec2d pp = sc.get_point(p);
+    REQUIRE_THAT(std::abs(pp.y()), Catch::Matchers::WithinAbs(5.0, 1e-3));
+    REQUIRE_THAT(pp.x(), Catch::Matchers::WithinAbs(3.0, 1e-3));
+}
+
+// ---- entity-constraint planner (kernel port of DesignPanel::apply_entity_constraint) ----
+
+TEST_CASE("sketch_entity_ends exposes real roles only", "[SketchConstraints]")
+{
+    std::pair<SketchPointRole, Vec2d> out[2];
+    REQUIRE(sketch_entity_ends(mk_point(3, 4), out) == 1);
+    REQUIRE(out[0].first == SketchPointRole::P0);
+    REQUIRE(sketch_entity_ends(mk_circle(1, 2, 5), out) == 1);
+    REQUIRE(out[0].first == SketchPointRole::Center);
+    REQUIRE_THAT(out[0].second.x(), Catch::Matchers::WithinAbs(1.0, 1e-9));
+    REQUIRE_THAT(out[0].second.y(), Catch::Matchers::WithinAbs(2.0, 1e-9));
+    REQUIRE(sketch_entity_ends(mk_line(0, 0, 10, 0), out) == 2);
+    REQUIRE(out[0].first == SketchPointRole::P0);
+    REQUIRE(out[1].first == SketchPointRole::P1);
+}
+
+TEST_CASE("Coincident on two Points binds P0/P0, not phantom p1", "[SketchConstraints]")
+{
+    std::vector<SketchEntity> ents = { mk_point(0, 0), mk_point(5, 5) };
+    ConstraintPlan p = plan_entity_constraint(ents, 0, 1, -1, SketchConstraintType::Coincident);
+    REQUIRE(p.kind == ConstraintPlan::Kind::Apply);
+    REQUIRE(p.defs.size() == 1);
+    REQUIRE(p.defs[0].type == SketchConstraintType::Coincident);
+    REQUIRE(p.defs[0].ea == 0);
+    REQUIRE(p.defs[0].ra == SketchPointRole::P0);
+    REQUIRE(p.defs[0].eb == 1);
+    REQUIRE(p.defs[0].rb == SketchPointRole::P0);
+}
+
+TEST_CASE("DistanceX on two Points binds real roles with non-negative prefill", "[SketchConstraints]")
+{
+    // e0 is right of e1, so the raw projected delta is negative: the plan must swap the
+    // refs so accepting the shown (positive) value is a no-op, not a sign flip.
+    std::vector<SketchEntity> ents = { mk_point(5, 1), mk_point(2, 3) };
+    ConstraintPlan p = plan_entity_constraint(ents, 0, 1, -1, SketchConstraintType::DistanceX);
+    REQUIRE(p.kind == ConstraintPlan::Kind::AskValue);
+    REQUIRE(p.defs.size() == 1);
+    REQUIRE(p.defs[0].type == SketchConstraintType::DistanceX);
+    REQUIRE(p.defs[0].ra == SketchPointRole::P0);
+    REQUIRE(p.defs[0].rb == SketchPointRole::P0);
+    REQUIRE(p.prefill >= 0.0);
+    REQUIRE(p.defs[0].ea == 1);
+    REQUIRE(p.defs[0].eb == 0);
+}
+
+TEST_CASE("Horizontal on a Point rejects with NeedALine", "[SketchConstraints]")
+{
+    std::vector<SketchEntity> ents = { mk_point(1, 2) };
+    ConstraintPlan p = plan_entity_constraint(ents, 0, -1, -1, SketchConstraintType::Horizontal);
+    REQUIRE(p.kind == ConstraintPlan::Kind::Reject);
+    REQUIRE(p.reason == ConstraintReject::NeedALine);
+}
+
+TEST_CASE("Angle on two Circles rejects with NeedTwoLines", "[SketchConstraints]")
+{
+    std::vector<SketchEntity> ents = { mk_circle(0, 0, 1), mk_circle(5, 0, 1) };
+    ConstraintPlan p = plan_entity_constraint(ents, 0, 1, -1, SketchConstraintType::Angle);
+    REQUIRE(p.kind == ConstraintPlan::Kind::Reject);
+    REQUIRE(p.reason == ConstraintReject::NeedTwoLines);
+}
+
+TEST_CASE("Parallel on a Line + Circle rejects with NeedTwoLines (new guard)", "[SketchConstraints]")
+{
+    std::vector<SketchEntity> ents = { mk_line(0, 0, 1, 0), mk_circle(5, 0, 1) };
+    ConstraintPlan p = plan_entity_constraint(ents, 0, 1, -1, SketchConstraintType::Parallel);
+    REQUIRE(p.kind == ConstraintPlan::Kind::Reject);
+    REQUIRE(p.reason == ConstraintReject::NeedTwoLines);
+}
+
+TEST_CASE("Equal on two Circles promotes to EqualRadius", "[SketchConstraints]")
+{
+    std::vector<SketchEntity> ents = { mk_circle(0, 0, 1), mk_circle(5, 0, 2) };
+    ConstraintPlan p = plan_entity_constraint(ents, 0, 1, -1, SketchConstraintType::EqualLength);
+    REQUIRE(p.kind == ConstraintPlan::Kind::Apply);
+    REQUIRE(p.defs.size() == 1);
+    REQUIRE(p.defs[0].type == SketchConstraintType::EqualRadius);
+    REQUIRE(p.defs[0].ea == 0);
+    REQUIRE(p.defs[0].eb == 1);
+}
+
+TEST_CASE("Symmetric on two Lines returns two defs with ec set to the axis", "[SketchConstraints]")
+{
+    std::vector<SketchEntity> ents = { mk_line(0, 1, 5, 1), mk_line(0, -1, 5, -1), mk_line(0, 0, 0, 1) };
+    ConstraintPlan p = plan_entity_constraint(ents, 0, 1, 2, SketchConstraintType::Symmetric);
+    REQUIRE(p.kind == ConstraintPlan::Kind::Apply);
+    REQUIRE(p.defs.size() == 2);
+    for (const auto& d : p.defs) {
+        REQUIRE(d.type == SketchConstraintType::Symmetric);
+        REQUIRE(d.ea == 0);
+        REQUIRE(d.eb == 1);
+        REQUIRE(d.ec == 2);
+    }
+    REQUIRE(p.defs[0].ra == SketchPointRole::P0);
+    REQUIRE(p.defs[0].rb == SketchPointRole::P0);
+    REQUIRE(p.defs[1].ra == SketchPointRole::P1);
+    REQUIRE(p.defs[1].rb == SketchPointRole::P1);
+}
+
+TEST_CASE("Symmetric with no axis rejects with NeedAxisLine", "[SketchConstraints]")
+{
+    std::vector<SketchEntity> ents = { mk_point(0, 0), mk_point(5, 0) };
+    ConstraintPlan p = plan_entity_constraint(ents, 0, 1, -1, SketchConstraintType::Symmetric);
+    REQUIRE(p.kind == ConstraintPlan::Kind::Reject);
+    REQUIRE(p.reason == ConstraintReject::NeedAxisLine);
+}
+
+TEST_CASE("SymmetricAboutY on two Points returns one def with ec == kSketchRefAxisY", "[SketchConstraints]")
+{
+    std::vector<SketchEntity> ents = { mk_point(1, 0), mk_point(-2, 0) };
+    ConstraintPlan p = plan_entity_constraint(ents, 0, 1, -1, SketchConstraintType::SymmetricAboutY);
+    REQUIRE(p.kind == ConstraintPlan::Kind::Apply);
+    REQUIRE(p.defs.size() == 1);
+    REQUIRE(p.defs[0].type == SketchConstraintType::SymmetricAboutY);
+    REQUIRE(p.defs[0].ec == kSketchRefAxisY);
+    REQUIRE(p.defs[0].ea == 0);
+    REQUIRE(p.defs[0].eb == 1);
+}
+
+TEST_CASE("constraint planner apply/askvalue matrix", "[SketchConstraints]")
+{
+    struct C {
+        const char* name; SketchConstraintType type; std::vector<SketchEntity> ents;
+        int e0, e1, e2; ConstraintPlan::Kind kind;
+    };
+    const std::vector<C> cases = {
+        { "Fix",              SketchConstraintType::Fix,              { mk_point(1, 2) },                      0, -1, -1, ConstraintPlan::Kind::Apply },
+        { "Coincident",       SketchConstraintType::Coincident,       { mk_point(0, 0), mk_point(5, 5) },      0,  1, -1, ConstraintPlan::Kind::Apply },
+        { "Horizontal",       SketchConstraintType::Horizontal,       { mk_line(0, 0, 5, 0) },                 0, -1, -1, ConstraintPlan::Kind::Apply },
+        { "Vertical",         SketchConstraintType::Vertical,         { mk_line(0, 0, 0, 5) },                 0, -1, -1, ConstraintPlan::Kind::Apply },
+        { "Parallel",         SketchConstraintType::Parallel,         { mk_line(0, 0, 1, 0), mk_line(0, 1, 1, 1) }, 0, 1, -1, ConstraintPlan::Kind::Apply },
+        { "Perpendicular",    SketchConstraintType::Perpendicular,    { mk_line(0, 0, 1, 0), mk_line(0, 0, 0, 1) }, 0, 1, -1, ConstraintPlan::Kind::Apply },
+        { "EqualLength",      SketchConstraintType::EqualLength,      { mk_line(0, 0, 1, 0), mk_line(0, 1, 2, 1) }, 0, 1, -1, ConstraintPlan::Kind::Apply },
+        { "Concentric",       SketchConstraintType::Concentric,       { mk_circle(0, 0, 1), mk_circle(5, 0, 1) }, 0, 1, -1, ConstraintPlan::Kind::Apply },
+        { "Tangent",          SketchConstraintType::Tangent,          { mk_line(0, 0, 1, 0), mk_circle(0, 1, 1) }, 0, 1, -1, ConstraintPlan::Kind::Apply },
+        { "Midpoint",         SketchConstraintType::Midpoint,         { mk_point(2, 0), mk_line(0, 0, 5, 0) },   0, 1, -1, ConstraintPlan::Kind::Apply },
+        { "Symmetric",        SketchConstraintType::Symmetric,        { mk_point(0, 0), mk_point(5, 0), mk_line(0, -1, 0, 1) }, 0, 1, 2, ConstraintPlan::Kind::Apply },
+        { "SymmetricAboutY",  SketchConstraintType::SymmetricAboutY,  { mk_point(1, 0), mk_point(-2, 0) },       0, 1, -1, ConstraintPlan::Kind::Apply },
+        { "SymmetricAboutX",  SketchConstraintType::SymmetricAboutX,  { mk_point(0, 1), mk_point(0, -2) },       0, 1, -1, ConstraintPlan::Kind::Apply },
+        { "EqualRadius",      SketchConstraintType::EqualRadius,      { mk_circle(0, 0, 1), mk_circle(5, 0, 2) }, 0, 1, -1, ConstraintPlan::Kind::Apply },
+        { "Collinear",        SketchConstraintType::Collinear,        { mk_line(0, 0, 1, 0), mk_line(2, 0, 3, 0) }, 0, 1, -1, ConstraintPlan::Kind::Apply },
+        { "Angle",            SketchConstraintType::Angle,            { mk_line(0, 0, 1, 0), mk_line(0, 0, 0, 1) }, 0, 1, -1, ConstraintPlan::Kind::AskValue },
+        { "Radius",           SketchConstraintType::Radius,           { mk_circle(0, 0, 2.5) },                  0, -1, -1, ConstraintPlan::Kind::AskValue },
+        { "Diameter",         SketchConstraintType::Diameter,         { mk_circle(0, 0, 2.5) },                  0, -1, -1, ConstraintPlan::Kind::AskValue },
+        { "DistanceX",        SketchConstraintType::DistanceX,        { mk_point(0, 0), mk_point(5, 3) },        0,  1, -1, ConstraintPlan::Kind::AskValue },
+        { "DistanceY",        SketchConstraintType::DistanceY,        { mk_point(0, 0), mk_point(5, 3) },        0,  1, -1, ConstraintPlan::Kind::AskValue },
+    };
+    for (const C& c : cases) {
+        DYNAMIC_SECTION("apply " << c.name) {
+            ConstraintPlan p = plan_entity_constraint(c.ents, c.e0, c.e1, c.e2, c.type);
+            REQUIRE(p.kind == c.kind);
+            REQUIRE(p.defs.size() >= 1);
+            for (const auto& d : p.defs) REQUIRE(d.type == c.type);
+        }
+    }
+}
+
+TEST_CASE("constraint planner reject matrix", "[SketchConstraints]")
+{
+    struct C {
+        const char* name; SketchConstraintType type; std::vector<SketchEntity> ents;
+        int e0, e1, e2; ConstraintReject reason;
+    };
+    const std::vector<C> cases = {
+        { "Fix",              SketchConstraintType::Fix,              {},                                 0, -1, -1, ConstraintReject::NeedOneEntity },
+        { "Coincident",       SketchConstraintType::Coincident,       { mk_point(0, 0) },                 0, -1, -1, ConstraintReject::NeedTwoEntities },
+        { "Horizontal",       SketchConstraintType::Horizontal,       { mk_point(1, 2) },                 0, -1, -1, ConstraintReject::NeedALine },
+        { "Vertical",         SketchConstraintType::Vertical,         { mk_circle(0, 0, 1) },             0, -1, -1, ConstraintReject::NeedALine },
+        { "Parallel",         SketchConstraintType::Parallel,         { mk_line(0, 0, 1, 0), mk_circle(5, 0, 1) }, 0, 1, -1, ConstraintReject::NeedTwoLines },
+        { "Perpendicular",    SketchConstraintType::Perpendicular,    { mk_circle(0, 0, 1), mk_line(0, 0, 1, 0) }, 0, 1, -1, ConstraintReject::NeedTwoLines },
+        { "EqualLength",      SketchConstraintType::EqualLength,      { mk_line(0, 0, 1, 0), mk_circle(5, 0, 1) }, 0, 1, -1, ConstraintReject::NeedTwoLines },
+        { "Concentric",       SketchConstraintType::Concentric,       { mk_line(0, 0, 1, 0), mk_circle(5, 0, 1) }, 0, 1, -1, ConstraintReject::NeedTwoRounds },
+        { "Tangent",          SketchConstraintType::Tangent,          { mk_line(0, 0, 1, 0), mk_line(0, 1, 1, 1) }, 0, 1, -1, ConstraintReject::NeedTangentPair },
+        { "Midpoint",         SketchConstraintType::Midpoint,         { mk_line(0, 0, 1, 0), mk_line(0, 1, 1, 1) }, 0, 1, -1, ConstraintReject::NeedPointAndLine },
+        { "Symmetric",        SketchConstraintType::Symmetric,        { mk_line(0, 0, 1, 0), mk_point(1, 1), mk_line(0, -1, 0, 1) }, 0, 1, 2, ConstraintReject::NeedTwoPointsOrLines },
+        { "SymmetricAboutY",  SketchConstraintType::SymmetricAboutY,  { mk_line(0, 0, 1, 0), mk_point(1, 1) },     0, 1, -1, ConstraintReject::NeedTwoPointsOrLines },
+        { "SymmetricAboutX",  SketchConstraintType::SymmetricAboutX,  { mk_point(1, 1), mk_line(0, 0, 1, 0) },     0, 1, -1, ConstraintReject::NeedTwoPointsOrLines },
+        { "EqualRadius",      SketchConstraintType::EqualRadius,      { mk_line(0, 0, 1, 0), mk_circle(5, 0, 1) }, 0, 1, -1, ConstraintReject::NeedTwoRounds },
+        { "Collinear",        SketchConstraintType::Collinear,        { mk_line(0, 0, 1, 0), mk_circle(5, 0, 1) }, 0, 1, -1, ConstraintReject::NeedTwoLines },
+        { "Angle",            SketchConstraintType::Angle,            { mk_circle(0, 0, 1), mk_circle(5, 0, 1) }, 0, 1, -1, ConstraintReject::NeedTwoLines },
+        { "Radius",           SketchConstraintType::Radius,           { mk_line(0, 0, 1, 0) },             0, -1, -1, ConstraintReject::NeedRound },
+        { "Diameter",         SketchConstraintType::Diameter,         { mk_point(1, 2) },                 0, -1, -1, ConstraintReject::NeedRound },
+        { "DistanceX",        SketchConstraintType::DistanceX,        { mk_point(0, 0) },                 0, -1, -1, ConstraintReject::NeedTwoEntities },
+        { "DistanceY",        SketchConstraintType::DistanceY,        { mk_point(0, 0) },                 0, -1, -1, ConstraintReject::NeedTwoEntities },
+    };
+    for (const C& c : cases) {
+        DYNAMIC_SECTION("reject " << c.name) {
+            ConstraintPlan p = plan_entity_constraint(c.ents, c.e0, c.e1, c.e2, c.type);
+            REQUIRE(p.kind == ConstraintPlan::Kind::Reject);
+            REQUIRE(p.reason == c.reason);
+        }
+    }
+}
+
+TEST_CASE("constraint planner rejects types with no entity binding", "[SketchConstraints]")
+{
+    const SketchConstraintType unsupported[] = {
+        SketchConstraintType::Distance, SketchConstraintType::LockX, SketchConstraintType::LockY,
+        SketchConstraintType::PointOnLine, SketchConstraintType::PointOnObject,
+    };
+    std::vector<SketchEntity> ents = { mk_point(0, 0), mk_point(1, 1) };
+    for (SketchConstraintType t : unsupported) {
+        DYNAMIC_SECTION("unsupported " << int(t)) {
+            ConstraintPlan p = plan_entity_constraint(ents, 0, 1, -1, t);
+            REQUIRE(p.kind == ConstraintPlan::Kind::Reject);
+            REQUIRE(p.reason == ConstraintReject::Unsupported);
+        }
+    }
+}
diff --git a/tests/libslic3r/test_sketchedit.cpp b/tests/libslic3r/test_sketchedit.cpp
new file mode 100644
index 0000000000..634e743b99
--- /dev/null
+++ b/tests/libslic3r/test_sketchedit.cpp
@@ -0,0 +1,730 @@
+#include <catch2/catch_all.hpp>   // mainline OrcaSlicer ships Catch2 v3 (v2 was catch2/catch.hpp)
+#include "libslic3r/CAD/SketchEngine.hpp"
+#include <cmath>
+#include <algorithm>
+#include <TopExp_Explorer.hxx>
+#include <TopAbs.hxx>
+
+using namespace Slic3r;
+
+using Catch::Matchers::WithinAbs;
+
+// CONTRACT: mirror_entities hands the reflected half back REVERSED — the order of the entities
+// and the direction of each — because a reflection reverses orientation and the result has to
+// CONTINUE the chain it was made from. So a mirrored line's p0 is the reflection of the source's
+// p1, not its p0. See [SketchProfile] "a mirrored half continues the original chain".
+TEST_CASE("Mirror Line across Y axis (reversed: p0 is the reflection of the source p1)", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type = SketchEntity::Type::Line;
+    e.p0   = Vec2d(3, 2);
+    e.p1   = Vec2d(5, 4);
+
+    Vec2d a(0, -1);
+    Vec2d b(0, 1);
+
+    auto result = SketchEngine::mirror_entities({e}, a, b);
+    REQUIRE(result.size() == 1);
+
+    const auto& m = result[0];
+    REQUIRE(m.type == SketchEntity::Type::Line);
+    REQUIRE_THAT(m.p0.x(), WithinAbs(-5.0, 1e-9));   // reflection of the SOURCE p1
+    REQUIRE_THAT(m.p0.y(), WithinAbs(4.0, 1e-9));
+    REQUIRE_THAT(m.p1.x(), WithinAbs(-3.0, 1e-9));   // reflection of the SOURCE p0
+    REQUIRE_THAT(m.p1.y(), WithinAbs(2.0, 1e-9));
+}
+
+TEST_CASE("Mirror Circle across Y axis", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type   = SketchEntity::Type::Circle;
+    e.center = Vec2d(5, 0);
+    e.p0     = Vec2d(5, 0);
+    e.radius = 3;
+
+    Vec2d a(0, -1);
+    Vec2d b(0, 1);
+
+    auto result = SketchEngine::mirror_entities({e}, a, b);
+    REQUIRE(result.size() == 1);
+
+    const auto& m = result[0];
+    REQUIRE(m.type == SketchEntity::Type::Circle);
+    REQUIRE_THAT(m.center.x(), WithinAbs(-5.0, 1e-9));
+    REQUIRE_THAT(m.center.y(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(m.radius, WithinAbs(3.0, 1e-9));
+    REQUIRE_THAT(m.p0.x(), WithinAbs(-5.0, 1e-9));
+    REQUIRE_THAT(m.p0.y(), WithinAbs(0.0, 1e-9));
+}
+
+TEST_CASE("Mirror Arc across X axis", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type        = SketchEntity::Type::Arc;
+    e.center      = Vec2d(0, 0);
+    e.radius      = 1.0;
+    e.start_angle = 0.0;
+    e.end_angle   = M_PI / 2.0;
+    e.p0          = Vec2d(1, 0);
+    e.p1          = Vec2d(0, 1);
+
+    Vec2d a(-1, 0);
+    Vec2d b(1, 0);
+
+    auto result = SketchEngine::mirror_entities({e}, a, b);
+    REQUIRE(result.size() == 1);
+
+    const auto& m = result[0];
+    REQUIRE(m.type == SketchEntity::Type::Arc);
+
+    // Reversed with the rest of the half: the mirrored arc STARTS where the reflection of the
+    // source's end is, and finishes at the reflection of its start.
+    REQUIRE_THAT(m.p0.x(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(m.p0.y(), WithinAbs(-1.0, 1e-9));
+    REQUIRE_THAT(m.p1.x(), WithinAbs(1.0, 1e-9));
+    REQUIRE_THAT(m.p1.y(), WithinAbs(0.0, 1e-9));
+
+    // The reflection alone would negate the sweep; walking the arc the other way negates it
+    // again, so a mirrored CCW arc is CCW once more and a mirrored CCW loop stays CCW.
+    double sweep = m.end_angle - m.start_angle;
+    double orig_sweep = e.end_angle - e.start_angle;
+    REQUIRE(orig_sweep > 0.0);
+    REQUIRE(sweep > 0.0);
+}
+
+TEST_CASE("Offset Line by positive d", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type = SketchEntity::Type::Line;
+    e.p0   = Vec2d(0, 0);
+    e.p1   = Vec2d(10, 0);
+
+    auto result = SketchEngine::offset_entities({e}, 2.0);
+    REQUIRE(result.size() == 1);
+
+    const auto& o = result[0];
+    REQUIRE(o.type == SketchEntity::Type::Line);
+    REQUIRE_THAT(o.p0.x(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(o.p0.y(), WithinAbs(2.0, 1e-9));
+    REQUIRE_THAT(o.p1.x(), WithinAbs(10.0, 1e-9));
+    REQUIRE_THAT(o.p1.y(), WithinAbs(2.0, 1e-9));
+}
+
+TEST_CASE("Offset Circle: expand and collapse", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type   = SketchEntity::Type::Circle;
+    e.center = Vec2d(0, 0);
+    e.p0     = Vec2d(0, 0);
+    e.radius = 5;
+
+    auto expanded = SketchEngine::offset_entities({e}, 2.0);
+    REQUIRE(expanded.size() == 1);
+    REQUIRE_THAT(expanded[0].radius, WithinAbs(7.0, 1e-9));
+
+    auto collapsed = SketchEngine::offset_entities({e}, -5.0);
+    REQUIRE(collapsed.empty());
+}
+
+// CONTRACT CHANGED: +d used to mean "radius + d" for every arc regardless of its sweep, while
+// for a line it meant "left of the direction of travel". The two disagreed, so a profile made
+// of lines AND arcs (any slot outline) offset with its straights going one way and its caps the
+// other, and could never come back closed. The arc now follows the line's rule: +d is left of
+// travel, which for this CCW quarter-arc is inward -> r = 3. See [SketchProfile].
+TEST_CASE("Offset Arc by positive d (left of travel: a CCW arc shrinks)", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type        = SketchEntity::Type::Arc;
+    e.center      = Vec2d(0, 0);
+    e.radius      = 4.0;
+    e.start_angle = 0.0;
+    e.end_angle   = M_PI / 2.0;
+    e.p0          = Vec2d(4, 0);
+    e.p1          = Vec2d(0, 4);
+
+    auto result = SketchEngine::offset_entities({e}, 1.0);
+    REQUIRE(result.size() == 1);
+
+    const auto& o = result[0];
+    REQUIRE(o.type == SketchEntity::Type::Arc);
+    REQUIRE_THAT(o.radius, WithinAbs(3.0, 1e-9));
+    REQUIRE_THAT(o.p0.x(), WithinAbs(3.0, 1e-9));
+    REQUIRE_THAT(o.p0.y(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(o.p1.x(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(o.p1.y(), WithinAbs(3.0, 1e-9));
+}
+
+TEST_CASE("Fillet right-angle corner", "[SketchEdit]")
+{
+    SketchEntity a;
+    a.type = SketchEntity::Type::Line;
+    a.p0   = Vec2d(0, 0);
+    a.p1   = Vec2d(10, 0);
+
+    SketchEntity b;
+    b.type = SketchEntity::Type::Line;
+    b.p0   = Vec2d(10, 0);
+    b.p1   = Vec2d(10, 10);
+
+    SketchEntity a_out, b_out, arc_out;
+    bool ok = SketchEngine::fillet_lines(a, b, 2.0, a_out, b_out, arc_out);
+    REQUIRE(ok);
+
+    REQUIRE_THAT(a_out.p0.x(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(a_out.p0.y(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(a_out.p1.x(), WithinAbs(8.0, 1e-9));
+    REQUIRE_THAT(a_out.p1.y(), WithinAbs(0.0, 1e-9));
+
+    REQUIRE_THAT(b_out.p0.x(), WithinAbs(10.0, 1e-9));
+    REQUIRE_THAT(b_out.p0.y(), WithinAbs(2.0, 1e-9));
+    REQUIRE_THAT(b_out.p1.x(), WithinAbs(10.0, 1e-9));
+    REQUIRE_THAT(b_out.p1.y(), WithinAbs(10.0, 1e-9));
+
+    REQUIRE(arc_out.type == SketchEntity::Type::Arc);
+    REQUIRE_THAT(arc_out.radius, WithinAbs(2.0, 1e-9));
+    REQUIRE_THAT(arc_out.center.x(), WithinAbs(8.0, 1e-9));
+    REQUIRE_THAT(arc_out.center.y(), WithinAbs(2.0, 1e-9));
+    REQUIRE_THAT((arc_out.p0 - arc_out.center).norm(), WithinAbs(2.0, 1e-9));
+    REQUIRE_THAT((arc_out.p1 - arc_out.center).norm(), WithinAbs(2.0, 1e-9));
+}
+
+TEST_CASE("Fillet parallel lines returns false", "[SketchEdit]")
+{
+    SketchEntity a;
+    a.type = SketchEntity::Type::Line;
+    a.p0   = Vec2d(0, 0);
+    a.p1   = Vec2d(10, 0);
+
+    SketchEntity b;
+    b.type = SketchEntity::Type::Line;
+    b.p0   = Vec2d(0, 5);
+    b.p1   = Vec2d(10, 5);
+
+    SketchEntity a_out, b_out, arc_out;
+    REQUIRE_FALSE(SketchEngine::fillet_lines(a, b, 1.0, a_out, b_out, arc_out));
+}
+
+TEST_CASE("Fillet arc too big returns false", "[SketchEdit]")
+{
+    SketchEntity a;
+    a.type = SketchEntity::Type::Line;
+    a.p0   = Vec2d(0, 0);
+    a.p1   = Vec2d(1, 0);
+
+    SketchEntity b;
+    b.type = SketchEntity::Type::Line;
+    b.p0   = Vec2d(1, 0);
+    b.p1   = Vec2d(1, 1);
+
+    SketchEntity a_out, b_out, arc_out;
+    REQUIRE_FALSE(SketchEngine::fillet_lines(a, b, 5.0, a_out, b_out, arc_out));
+}
+
+TEST_CASE("Trim right arm", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type = SketchEntity::Type::Line;
+    e.p0   = Vec2d(-5, 0);
+    e.p1   = Vec2d(5, 0);
+
+    SketchEntity vc;
+    vc.type = SketchEntity::Type::Line;
+    vc.p0   = Vec2d(0, -5);
+    vc.p1   = Vec2d(0, 5);
+
+    bool ok = SketchEngine::trim_entity(e, {vc}, Vec2d(3, 0));
+    REQUIRE(ok);
+    REQUIRE_THAT(e.p0.x(), WithinAbs(-5.0, 1e-9));
+    REQUIRE_THAT(e.p0.y(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(e.p1.x(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(e.p1.y(), WithinAbs(0.0, 1e-9));
+}
+
+TEST_CASE("Trim left arm", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type = SketchEntity::Type::Line;
+    e.p0   = Vec2d(-5, 0);
+    e.p1   = Vec2d(5, 0);
+
+    SketchEntity vc;
+    vc.type = SketchEntity::Type::Line;
+    vc.p0   = Vec2d(0, -5);
+    vc.p1   = Vec2d(0, 5);
+
+    bool ok = SketchEngine::trim_entity(e, {vc}, Vec2d(-3, 0));
+    REQUIRE(ok);
+    REQUIRE_THAT(e.p0.x(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(e.p0.y(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(e.p1.x(), WithinAbs(5.0, 1e-9));
+    REQUIRE_THAT(e.p1.y(), WithinAbs(0.0, 1e-9));
+}
+
+TEST_CASE("Trim no cut (u out of range)", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type = SketchEntity::Type::Line;
+    e.p0   = Vec2d(-5, 0);
+    e.p1   = Vec2d(5, 0);
+
+    SketchEntity other;
+    other.type = SketchEntity::Type::Line;
+    other.p0   = Vec2d(0, 3);
+    other.p1   = Vec2d(0, 8);
+
+    REQUIRE_FALSE(SketchEngine::trim_entity(e, {other}, Vec2d(3, 0)));
+}
+
+TEST_CASE("Extend forward to line", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type = SketchEntity::Type::Line;
+    e.p0   = Vec2d(0, 0);
+    e.p1   = Vec2d(2, 0);
+
+    SketchEntity other;
+    other.type = SketchEntity::Type::Line;
+    other.p0   = Vec2d(5, -5);
+    other.p1   = Vec2d(5, 5);
+
+    bool ok = SketchEngine::extend_entity(e, {other}, Vec2d(2, 0));
+    REQUIRE(ok);
+    REQUIRE_THAT(e.p0.x(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(e.p0.y(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(e.p1.x(), WithinAbs(5.0, 1e-9));
+    REQUIRE_THAT(e.p1.y(), WithinAbs(0.0, 1e-9));
+}
+
+TEST_CASE("Extend forward to circle", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type = SketchEntity::Type::Line;
+    e.p0   = Vec2d(0, 0);
+    e.p1   = Vec2d(2, 0);
+
+    SketchEntity other;
+    other.type   = SketchEntity::Type::Circle;
+    other.center = Vec2d(10, 0);
+    other.p0     = Vec2d(10, 0);
+    other.radius = 3;
+
+    bool ok = SketchEngine::extend_entity(e, {other}, Vec2d(2, 0));
+    REQUIRE(ok);
+    REQUIRE_THAT(e.p0.x(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(e.p0.y(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(e.p1.x(), WithinAbs(7.0, 1e-9));
+    REQUIRE_THAT(e.p1.y(), WithinAbs(0.0, 1e-9));
+}
+
+TEST_CASE("Extend backward", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type = SketchEntity::Type::Line;
+    e.p0   = Vec2d(0, 0);
+    e.p1   = Vec2d(2, 0);
+
+    SketchEntity other;
+    other.type = SketchEntity::Type::Line;
+    other.p0   = Vec2d(-3, -5);
+    other.p1   = Vec2d(-3, 5);
+
+    bool ok = SketchEngine::extend_entity(e, {other}, Vec2d(0, 0));
+    REQUIRE(ok);
+    REQUIRE_THAT(e.p0.x(), WithinAbs(-3.0, 1e-9));
+    REQUIRE_THAT(e.p0.y(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(e.p1.x(), WithinAbs(2.0, 1e-9));
+    REQUIRE_THAT(e.p1.y(), WithinAbs(0.0, 1e-9));
+}
+
+TEST_CASE("Extend no target", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type = SketchEntity::Type::Line;
+    e.p0   = Vec2d(0, 0);
+    e.p1   = Vec2d(2, 0);
+
+    SketchEntity other;
+    other.type = SketchEntity::Type::Line;
+    other.p0   = Vec2d(5, -5);
+    other.p1   = Vec2d(5, -1);
+
+    REQUIRE_FALSE(SketchEngine::extend_entity(e, {other}, Vec2d(2, 0)));
+}
+
+// --- Arc/Circle subject trim & extend (Fase 4.5 kernel) -------------------
+
+TEST_CASE("Trim arc drops the picked (start) side", "[SketchEdit]")
+{
+    // Upper semicircle r=5, ccw from (5,0) to (-5,0); cutter = vertical axis.
+    SketchEntity e;
+    e.type        = SketchEntity::Type::Arc;
+    e.center      = Vec2d(0, 0);
+    e.radius      = 5;
+    e.start_angle = 0.0;
+    e.end_angle   = M_PI;
+
+    SketchEntity cut;
+    cut.type = SketchEntity::Type::Line;
+    cut.p0   = Vec2d(0, -10);
+    cut.p1   = Vec2d(0, 10);
+
+    // Pick the right quarter (phi=pi/4) -> it is removed, left quarter kept.
+    bool ok = SketchEngine::trim_entity(e, {cut}, Vec2d(5 * std::cos(M_PI/4), 5 * std::sin(M_PI/4)));
+    REQUIRE(ok);
+    REQUIRE(e.type == SketchEntity::Type::Arc);
+    REQUIRE_THAT(e.radius, WithinAbs(5.0, 1e-9));
+    REQUIRE_THAT(e.start_angle, WithinAbs(M_PI / 2.0, 1e-9));
+    REQUIRE_THAT(e.end_angle,   WithinAbs(M_PI, 1e-9));
+}
+
+TEST_CASE("Trim arc drops the picked (end) side", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type        = SketchEntity::Type::Arc;
+    e.center      = Vec2d(0, 0);
+    e.radius      = 5;
+    e.start_angle = 0.0;
+    e.end_angle   = M_PI;
+
+    SketchEntity cut;
+    cut.type = SketchEntity::Type::Line;
+    cut.p0   = Vec2d(0, -10);
+    cut.p1   = Vec2d(0, 10);
+
+    // Pick the left quarter (phi=3pi/4) -> removed, right quarter kept.
+    bool ok = SketchEngine::trim_entity(e, {cut}, Vec2d(5 * std::cos(3*M_PI/4), 5 * std::sin(3*M_PI/4)));
+    REQUIRE(ok);
+    REQUIRE(e.type == SketchEntity::Type::Arc);
+    REQUIRE_THAT(e.start_angle, WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(e.end_angle,   WithinAbs(M_PI / 2.0, 1e-9));
+}
+
+TEST_CASE("Trim circle opens into an arc excluding the pick", "[SketchEdit]")
+{
+    // Full circle r=5; vertical axis cuts it at (0,+-5). Pick the right side
+    // (5,0): the kept arc is the left half, sweeping pi and centred on (-5,0).
+    SketchEntity e;
+    e.type   = SketchEntity::Type::Circle;
+    e.center = Vec2d(0, 0);
+    e.p0     = Vec2d(5, 0);
+    e.radius = 5;
+
+    SketchEntity cut;
+    cut.type = SketchEntity::Type::Line;
+    cut.p0   = Vec2d(0, -10);
+    cut.p1   = Vec2d(0, 10);
+
+    bool ok = SketchEngine::trim_entity(e, {cut}, Vec2d(5, 0));
+    REQUIRE(ok);
+    REQUIRE(e.type == SketchEntity::Type::Arc);
+    REQUIRE_THAT(e.radius, WithinAbs(5.0, 1e-9));
+    REQUIRE_THAT(e.end_angle - e.start_angle, WithinAbs(M_PI, 1e-9));
+    // Midpoint of the kept arc must point left (away from the pick).
+    double mid = 0.5 * (e.start_angle + e.end_angle);
+    REQUIRE_THAT(5 * std::cos(mid), WithinAbs(-5.0, 1e-9));
+    REQUIRE_THAT(5 * std::sin(mid), WithinAbs(0.0, 1e-9));
+}
+
+TEST_CASE("Extend arc forward (end) to a crossing", "[SketchEdit]")
+{
+    // Quarter arc (5,0)->(0,5); cutter crosses the circle at (-5,0). Picking
+    // near the end grows the sweep ccw to pi.
+    SketchEntity e;
+    e.type        = SketchEntity::Type::Arc;
+    e.center      = Vec2d(0, 0);
+    e.radius      = 5;
+    e.start_angle = 0.0;
+    e.end_angle   = M_PI / 2.0;
+
+    SketchEntity cut;
+    cut.type = SketchEntity::Type::Line;
+    cut.p0   = Vec2d(-10, 0);
+    cut.p1   = Vec2d(0, 0);
+
+    bool ok = SketchEngine::extend_entity(e, {cut}, Vec2d(0, 5));
+    REQUIRE(ok);
+    REQUIRE(e.type == SketchEntity::Type::Arc);
+    REQUIRE_THAT(e.start_angle, WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(e.end_angle,   WithinAbs(M_PI, 1e-9));
+}
+
+TEST_CASE("Extend arc backward (start) to a crossing", "[SketchEdit]")
+{
+    // Quarter arc (0,5)->(-5,0); cutter crosses at (5,0). Picking near the
+    // start grows the sweep cw to start_angle 0.
+    SketchEntity e;
+    e.type        = SketchEntity::Type::Arc;
+    e.center      = Vec2d(0, 0);
+    e.radius      = 5;
+    e.start_angle = M_PI / 2.0;
+    e.end_angle   = M_PI;
+
+    SketchEntity cut;
+    cut.type = SketchEntity::Type::Line;
+    cut.p0   = Vec2d(10, 0);
+    cut.p1   = Vec2d(0, 0);
+
+    bool ok = SketchEngine::extend_entity(e, {cut}, Vec2d(0, 5));
+    REQUIRE(ok);
+    REQUIRE_THAT(e.start_angle, WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(e.end_angle,   WithinAbs(M_PI, 1e-9));
+}
+
+TEST_CASE("Extend circle returns false (closed)", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type   = SketchEntity::Type::Circle;
+    e.center = Vec2d(0, 0);
+    e.p0     = Vec2d(5, 0);
+    e.radius = 5;
+
+    SketchEntity cut;
+    cut.type = SketchEntity::Type::Line;
+    cut.p0   = Vec2d(0, -10);
+    cut.p1   = Vec2d(0, 10);
+
+    REQUIRE_FALSE(SketchEngine::extend_entity(e, {cut}, Vec2d(5, 0)));
+}
+
+TEST_CASE("Trim arc with no crossing returns false", "[SketchEdit]")
+{
+    SketchEntity e;
+    e.type        = SketchEntity::Type::Arc;
+    e.center      = Vec2d(0, 0);
+    e.radius      = 5;
+    e.start_angle = 0.0;
+    e.end_angle   = M_PI / 2.0;
+
+    SketchEntity cut;          // far away, never reaches the r=5 circle
+    cut.type = SketchEntity::Type::Line;
+    cut.p0   = Vec2d(20, -5);
+    cut.p1   = Vec2d(20, 5);
+
+    REQUIRE_FALSE(SketchEngine::trim_entity(e, {cut}, Vec2d(5 * std::cos(M_PI/4), 5 * std::sin(M_PI/4))));
+}
+
+// Regression guard: BEFORE the weld fix this test failed with 4 edges instead of 6.
+// BRepLib_MakeWire::Add silently DROPS a disconnected edge (BRepLib_DisconnectedWire + NotDone)
+// yet every successful Add ends with BRepLib_WireDone + Done(), so IsDone() reported only whether
+// the LAST edge connected. This sketch is a real user loop (2 arcs + 4 lines) given in
+// creation order, which is NOT traversal order, and its joint between the 3rd and 4th entity
+// below is open by 2.28e-5 mm — larger than OCCT's default vertex tolerance.
+TEST_CASE("entities_to_wires keeps every edge of a loop drawn out of order", "[SketchEngine]")
+{
+    std::vector<SketchEntity> ents(6);
+
+    ents[0].type = SketchEntity::Type::Line;
+    ents[0].p0   = Vec2d(-0.537697713190522, -0.0009077462579133498);
+    ents[0].p1   = Vec2d(99.46230228680926, -0.0009141694814321626);
+
+    ents[1].type        = SketchEntity::Type::Arc;
+    ents[1].p0          = Vec2d(-0.537697713190522, -0.0009077462579133498);
+    ents[1].p1          = Vec2d(-100.14602636660666, -0.27673132181233495);
+    ents[1].center      = Vec2d(-50.313868583115394, -10.248112903179617);
+    ents[1].radius      = 50.81999999999999;
+    ents[1].start_angle = 0.20302922018398933;
+    ents[1].end_angle   = 2.944101582158999;
+
+    ents[2].type = SketchEntity::Type::Line;
+    ents[2].p0   = Vec2d(99.46228668626469, -39.22091416947833);
+    ents[2].p1   = Vec2d(-0.537864366432629, -39.22420589376945);
+
+    ents[3].type        = SketchEntity::Type::Arc;
+    ents[3].p0          = Vec2d(-100.14602636694521, -38.94673132181234);
+    ents[3].p1          = Vec2d(-0.5378420354900413, -39.22421049164698);
+    ents[3].center      = Vec2d(-50.31377078666179, -28.975499083790503);
+    ents[3].radius      = 50.82006659345552;
+    ents[3].start_angle = -2.944104841286737;
+    ents[3].end_angle   = -0.20305921095748136;
+
+    ents[4].type = SketchEntity::Type::Line;
+    ents[4].p0   = Vec2d(99.46228668626469, -39.22091416947833);
+    ents[4].p1   = Vec2d(99.46230228680926, -0.0009141694814321626);
+
+    ents[5].type = SketchEntity::Type::Line;
+    ents[5].p0   = Vec2d(-100.14602636694521, -38.94673132181234);
+    ents[5].p1   = Vec2d(-100.14602636660666, -0.27673132181233495);
+
+    auto wires = SketchEngine::entities_to_wires(ents, SketchPlane::XY());
+
+    REQUIRE(wires.size() == 1);
+
+    int edge_count = 0;
+    for (TopExp_Explorer ex(wires[0], TopAbs_EDGE); ex.More(); ex.Next())
+        ++edge_count;
+    REQUIRE(edge_count == 6);
+
+    REQUIRE(wires[0].Closed());
+}
+
+// Regression guard: this fails at 1e-4 (the wire builder refuses a joint the viewport had
+// already shaded closed) and passes at kSketchJoinTol. A 20x10 quad with one joint left open
+// by 9e-4 mm — just inside kSketchJoinTol, exactly the case the viewport shades closed — given
+// in an order that is NOT traversal order, so the ordering path is covered too.
+TEST_CASE("a loop the viewport shades closed is buildable by the kernel", "[SketchEngine]")
+{
+    std::vector<SketchEntity> ents(4);
+
+    // (0,0) -> (20,0) -> (20,10) -> (0,10) -> (0.0009, 0): last endpoint misses (0,0) by 9e-4.
+    ents[0].type = SketchEntity::Type::Line;
+    ents[0].p0   = Vec2d(0, 0);
+    ents[0].p1   = Vec2d(20, 0);
+
+    // Index 1 is the FAR side, not the neighbour of index 0: creation order here is
+    // deliberately not traversal order, so a partial wire would reject it without the
+    // traversal walk.
+    ents[1].type = SketchEntity::Type::Line;
+    ents[1].p0   = Vec2d(20, 10);
+    ents[1].p1   = Vec2d(0, 10);
+
+    ents[2].type = SketchEntity::Type::Line;
+    ents[2].p0   = Vec2d(20, 0);
+    ents[2].p1   = Vec2d(20, 10);
+
+    ents[3].type = SketchEntity::Type::Line;
+    ents[3].p0   = Vec2d(0, 10);
+    ents[3].p1   = Vec2d(0.0009, 0);
+
+    auto wires = SketchEngine::entities_to_wires(ents, SketchPlane::XY());
+
+    REQUIRE(wires.size() == 1);
+
+    int edge_count = 0;
+    for (TopExp_Explorer ex(wires[0], TopAbs_EDGE); ex.More(); ex.Next())
+        ++edge_count;
+    REQUIRE(edge_count == 4);
+
+    REQUIRE(wires[0].Closed());
+}
+
+// Regression guard for the auto-close preference. Same 20x10 quad, one joint open by 9e-4 mm
+// and given out of traversal order, as "a loop the viewport shades closed is buildable by the
+// kernel". With auto-close ON the gap welds (one closed wire); with auto-close OFF it must not.
+TEST_CASE("auto-close off makes the kernel demand an exact joint", "[SketchEngine]")
+{
+    std::vector<SketchEntity> ents(4);
+
+    ents[0].type = SketchEntity::Type::Line;
+    ents[0].p0   = Vec2d(0, 0);
+    ents[0].p1   = Vec2d(20, 0);
+
+    ents[1].type = SketchEntity::Type::Line;
+    ents[1].p0   = Vec2d(20, 10);
+    ents[1].p1   = Vec2d(0, 10);
+
+    ents[2].type = SketchEntity::Type::Line;
+    ents[2].p0   = Vec2d(20, 0);
+    ents[2].p1   = Vec2d(20, 10);
+
+    ents[3].type = SketchEntity::Type::Line;
+    ents[3].p0   = Vec2d(0, 10);
+    ents[3].p1   = Vec2d(0.0009, 0);
+
+    auto edge_count = [](const TopoDS_Wire& w) {
+        int n = 0;
+        for (TopExp_Explorer ex(w, TopAbs_EDGE); ex.More(); ex.Next()) ++n;
+        return n;
+    };
+
+    // ON: the 9e-4 mm gap is inside kSketchJoinTol, so the loop welds into one closed wire.
+    Slic3r::set_sketch_auto_close(true);
+    auto wires_on = SketchEngine::entities_to_wires(ents, SketchPlane::XY());
+    REQUIRE(wires_on.size() == 1);
+    REQUIRE(edge_count(wires_on[0]) == 4);
+    REQUIRE(wires_on[0].Closed());
+
+    // OFF: the joint is not exact, so the gap is NOT welded. entities_to_wires legitimately
+    // returns open chains (a sweep path is open), so the observable is an OPEN wire — the
+    // kernel no longer hands back the closed loop the viewport would have shaded.
+    Slic3r::set_sketch_auto_close(false);
+    auto wires_off = SketchEngine::entities_to_wires(ents, SketchPlane::XY());
+    REQUIRE(wires_off.size() == 1);
+    REQUIRE(edge_count(wires_off[0]) == 4);
+    REQUIRE_FALSE(wires_off[0].Closed());
+
+    // OFF + an EXACT joint (last endpoint exactly (0,0)): the quad still builds closed,
+    // proving "off" means exact rather than broken.
+    ents[3].p1 = Vec2d(0, 0);
+    auto wires_exact = SketchEngine::entities_to_wires(ents, SketchPlane::XY());
+    REQUIRE(wires_exact.size() == 1);
+    REQUIRE(edge_count(wires_exact[0]) == 4);
+    REQUIRE(wires_exact[0].Closed());
+
+    // Restore the default so test order cannot leak OFF into the other cases.
+    Slic3r::set_sketch_auto_close(true);
+}
+
+// A stray open segment touching nothing must not break a closed profile: the viewport
+// discards open chains when it shades a region extrudable, so with closed_only the kernel
+// must discard them too — otherwise Revolve/Extrude fail on a sketch that looks perfect.
+TEST_CASE("a stray open segment does not break a closed profile", "[SketchEngine]")
+{
+    auto line = [](double x0, double y0, double x1, double y1) {
+        SketchEntity e;
+        e.type = SketchEntity::Type::Line;
+        e.p0   = Vec2d(x0, y0);
+        e.p1   = Vec2d(x1, y1);
+        return e;
+    };
+
+    std::vector<SketchEntity> ents;
+    ents.push_back(line(0, 0, 20, 0));     // 20x10 quad
+    ents.push_back(line(20, 0, 20, 10));
+    ents.push_back(line(20, 10, 0, 10));
+    ents.push_back(line(0, 10, 0, 0));
+    ents.push_back(line(5, 5, 6, 5.2));    // stray, touches nothing
+
+    auto edge_count = [](const TopoDS_Wire& w) {
+        int n = 0;
+        for (TopExp_Explorer ex(w, TopAbs_EDGE); ex.More(); ex.Next()) ++n;
+        return n;
+    };
+
+    // Unchanged behaviour: the stray line is its own open wire.
+    auto wires_all = SketchEngine::entities_to_wires(ents, SketchPlane::XY(), /*closed_only=*/false);
+    REQUIRE(wires_all.size() == 2);
+
+    // closed_only drops the open chain: one closed quad survives.
+    auto wires_closed = SketchEngine::entities_to_wires(ents, SketchPlane::XY(), /*closed_only=*/true);
+    REQUIRE(wires_closed.size() == 1);
+    REQUIRE(edge_count(wires_closed[0]) == 4);
+    REQUIRE(wires_closed[0].Closed());
+
+    // The Revolve path (entities_to_wire) finds the single closed loop.
+    TopoDS_Wire w = SketchEngine::entities_to_wire(ents, SketchPlane::XY(), /*closed_only=*/true);
+    REQUIRE_FALSE(w.IsNull());
+    REQUIRE(edge_count(w) == 4);
+}
+
+// sketch_open_ends names the two free endpoints of an open chain, so the "does not form a
+// single closed wire" failure can say WHERE the sketch is open.
+TEST_CASE("sketch_open_ends names where a chain fails to close", "[SketchEngine]")
+{
+    auto line = [](double x0, double y0, double x1, double y1) {
+        SketchEntity e;
+        e.type = SketchEntity::Type::Line;
+        e.p0   = Vec2d(x0, y0);
+        e.p1   = Vec2d(x1, y1);
+        return e;
+    };
+
+    // Open C shape: three lines, free endpoints at (0,0) and (0,10).
+    std::vector<SketchEntity> ents;
+    ents.push_back(line(0, 0, 10, 0));
+    ents.push_back(line(10, 0, 10, 10));
+    ents.push_back(line(10, 10, 0, 10));
+
+    auto got = sketch_open_ends(ents, SketchPlane::XY());
+    REQUIRE(got.size() == 2);
+
+    std::sort(got.begin(), got.end(), [](const Vec2d& a, const Vec2d& b) {
+        if (a.x() < b.x()) return true;
+        if (a.x() > b.x()) return false;
+        return a.y() < b.y();
+    });
+
+    REQUIRE_THAT(got[0].x(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(got[0].y(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(got[1].x(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT(got[1].y(), WithinAbs(10.0, 1e-9));
+}
diff --git a/tests/libslic3r/test_sketchimport.cpp b/tests/libslic3r/test_sketchimport.cpp
new file mode 100644
index 0000000000..3e3f7c906e
--- /dev/null
+++ b/tests/libslic3r/test_sketchimport.cpp
@@ -0,0 +1,103 @@
+#include <catch2/catch_all.hpp>   // mainline OrcaSlicer ships Catch2 v3 (v2 was catch2/catch.hpp)
+
+#include "libslic3r/CAD/SketchImport.hpp"
+#include "libslic3r/Utils.hpp"   // resources_dir
+#include "test_utils.hpp"        // ScopedTemporaryFile
+
+#include <fstream>
+#include <string>
+
+using namespace Slic3r;
+
+// A 10x10 mm filled square, on disk because nanosvg reads from a file. The path
+// must come from the system temp dir: a hardcoded /tmp is not writable on
+// Windows, where the stream fails silently and the parse then sees no file.
+static void write_square_svg(const std::string& path)
+{
+    std::ofstream f(path);
+    f << "<svg xmlns=\"http://www.w3.org/2000/svg\" width=\"10mm\" height=\"10mm\" "
+         "viewBox=\"0 0 10 10\">"
+         "<path d=\"M0,0 L10,0 L10,10 L0,10 Z\" fill=\"#000000\"/></svg>";
+    REQUIRE(f.good());
+}
+
+TEST_CASE("svg_to_regions parses a filled path into a region", "[SketchImport]")
+{
+    ScopedTemporaryFile square(".svg");
+    write_square_svg(square.string());
+
+    ImportRegions regs = svg_to_regions(square.string(), 1.0);
+    REQUIRE(regs.size() >= 1);
+    // Outer contour present with at least a few vertices.
+    REQUIRE(regs[0].size() >= 1);
+    REQUIRE(regs[0][0].size() >= 4);
+
+    // Centred on the origin: bbox half-extent ~5 mm on each side.
+    double hi = 0.0;
+    for (const auto& region : regs)
+        for (const auto& contour : region)
+            for (const Vec2d& p : contour)
+                hi = std::max(hi, std::max(std::abs(p.x()), std::abs(p.y())));
+    REQUIRE(hi > 3.0);    // not collapsed
+    REQUIRE(hi < 8.0);    // ~5 mm half-size after centring
+}
+
+TEST_CASE("svg_to_regions rejects bad input gracefully", "[SketchImport]")
+{
+    ScopedTemporaryFile square(".svg");
+    write_square_svg(square.string());
+    ScopedTemporaryFile missing(".svg");   // name reserved, never written
+
+    REQUIRE(svg_to_regions("", 1.0).empty());
+    REQUIRE(svg_to_regions(missing.string(), 1.0).empty());
+    REQUIRE(svg_to_regions(square.string(), 0.0).empty()); // scale<=0
+}
+
+TEST_CASE("transform_regions moves and scales independently", "[SketchImport]")
+{
+    ImportRegions r = {{ {Vec2d(-1,-1), Vec2d(1,-1), Vec2d(1,1), Vec2d(-1,1)} }};
+    ImportRegions t = transform_regions(r, Vec2d(10, 20), 2.0, 3.0);
+    REQUIRE(t.size() == 1);
+    REQUIRE(t[0][0].size() == 4);
+    // (-1,-1) -> (-1*2+10, -1*3+20) = (8, 17)
+    REQUIRE_THAT(t[0][0][0].x(), Catch::Matchers::WithinAbs(8.0, 1e-9));
+    REQUIRE_THAT(t[0][0][0].y(), Catch::Matchers::WithinAbs(17.0, 1e-9));
+    // (1,1) -> (1*2+10, 1*3+20) = (12, 23)
+    REQUIRE_THAT(t[0][0][2].x(), Catch::Matchers::WithinAbs(12.0, 1e-9));
+    REQUIRE_THAT(t[0][0][2].y(), Catch::Matchers::WithinAbs(23.0, 1e-9));
+    // identity is a no-op
+    ImportRegions id = transform_regions(r, Vec2d(0,0), 1.0, 1.0);
+    REQUIRE_THAT(id[0][0][1].x(), Catch::Matchers::WithinAbs(1.0, 1e-9));
+}
+
+TEST_CASE("text_to_regions vectorizes glyphs with counters", "[SketchImport]")
+{
+    // Locate the bundled font; resources_dir() may be unset under ctest, so
+    // fall back to a cwd-relative path (tests run from the repo root).
+    std::string font = resources_dir().empty()
+                           ? std::string("resources/fonts/HarmonyOS_Sans_SC_Regular.ttf")
+                           : resources_dir() + "/fonts/HarmonyOS_Sans_SC_Regular.ttf";
+    {
+        std::ifstream probe(font);
+        if (!probe.good()) {
+            SUCCEED("bundled font not reachable in this environment; covered live on :10");
+            return;
+        }
+    }
+
+    // Bad input is rejected without throwing.
+    REQUIRE(text_to_regions("", 10.0, font).empty());
+    REQUIRE(text_to_regions("A", 0.0, font).empty());
+
+    // 'A' has one triangular counter -> a region with an outer + 1 hole.
+    ImportRegions a = text_to_regions("A", 12.0, font);
+    REQUIRE(a.size() >= 1);
+    bool has_hole = false;
+    for (const auto& region : a)
+        if (region.size() >= 2) has_hole = true;
+    REQUIRE(has_hole);
+
+    // Two letters produce more regions than one.
+    ImportRegions ab = text_to_regions("AB", 12.0, font);
+    REQUIRE(ab.size() >= a.size());
+}
diff --git a/tests/libslic3r/test_sketchinference.cpp b/tests/libslic3r/test_sketchinference.cpp
new file mode 100644
index 0000000000..cbdd90628b
--- /dev/null
+++ b/tests/libslic3r/test_sketchinference.cpp
@@ -0,0 +1,174 @@
+#include <catch2/catch_all.hpp>   // mainline OrcaSlicer ships Catch2 v3 (v2 was catch2/catch.hpp)
+using Catch::Approx;   // v3 scopes Approx into the Catch namespace; v2 had it at global scope
+
+#include "libslic3r/CAD/SketchInference.hpp"
+
+using namespace Slic3r;
+using K = InferenceSnap::Kind;
+
+static SketchEntity line(Vec2d a, Vec2d b)
+{
+    SketchEntity e; e.type = SketchEntity::Type::Line; e.p0 = a; e.p1 = b; return e;
+}
+static SketchEntity circle(Vec2d c, double r)
+{
+    SketchEntity e; e.type = SketchEntity::Type::Circle; e.center = c; e.p0 = c; e.radius = r; return e;
+}
+
+TEST_CASE("inference: cursor near a line endpoint snaps Coincident-able to it", "[inference]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 0}) };
+    auto s = infer_point_snap(ents, {10.3, 0.2}, 1.0);
+    REQUIRE(s.kind == K::Endpoint);
+    CHECK(s.entity == 0);
+    CHECK(s.role == SketchPointRole::P1);
+    CHECK((s.point - Vec2d(10, 0)).norm() == Approx(0.0).margin(1e-9));
+}
+
+TEST_CASE("inference: endpoint beats midpoint when both are in range", "[inference]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {2, 0}) };
+    // Query equidistant-ish but closer to the endpoint: endpoint tier wins regardless.
+    auto s = infer_point_snap(ents, {1.9, 0.0}, 5.0);
+    CHECK(s.kind == K::Endpoint);
+    CHECK(s.role == SketchPointRole::P1);
+}
+
+TEST_CASE("inference: midpoint of a line is detected", "[inference]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 0}) };
+    auto s = infer_point_snap(ents, {5.1, 0.1}, 0.5, /*include_origin=*/false);
+    REQUIRE(s.kind == K::Midpoint);
+    CHECK((s.point - Vec2d(5, 0)).norm() == Approx(0.0).margin(1e-9));
+}
+
+TEST_CASE("inference: circle centre and rim", "[inference]")
+{
+    std::vector<SketchEntity> ents = { circle({0, 0}, 5.0) };
+    auto c = infer_point_snap(ents, {0.2, 0.1}, 1.0, false);
+    CHECK(c.kind == K::Center);
+    auto r = infer_point_snap(ents, {5.1, 0.0}, 1.0, false);
+    REQUIRE(r.kind == K::OnEdge);
+    CHECK((r.point - Vec2d(5, 0)).norm() == Approx(0.0).margin(1e-9));
+}
+
+TEST_CASE("inference: origin snap when nothing else is near", "[inference]")
+{
+    std::vector<SketchEntity> ents = { line({20, 20}, {30, 20}) };
+    auto s = infer_point_snap(ents, {0.1, 0.1}, 1.0);
+    REQUIRE(s.kind == K::Origin);
+    CHECK(s.entity == -1);
+    CHECK((s.point - Vec2d(0, 0)).norm() == Approx(0.0).margin(1e-9));
+}
+
+TEST_CASE("inference: nothing in range returns None and the raw query", "[inference]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 0}) };
+    auto s = infer_point_snap(ents, {50, 50}, 1.0, /*include_origin=*/false);
+    CHECK(s.kind == K::None);
+    CHECK((s.point - Vec2d(50, 50)).norm() == Approx(0.0).margin(1e-9));
+}
+
+TEST_CASE("inference: axis inference flags horizontal / vertical segments", "[inference]")
+{
+    CHECK(infer_axis_constraint({0, 0}, {10, 0.05}).value() == SketchConstraintType::Horizontal);
+    CHECK(infer_axis_constraint({0, 0}, {0.05, 10}).value() == SketchConstraintType::Vertical);
+    CHECK_FALSE(infer_axis_constraint({0, 0}, {10, 10}).has_value());   // 45 deg
+    CHECK_FALSE(infer_axis_constraint({0, 0}, {0, 0}).has_value());     // degenerate
+}
+
+TEST_CASE("inference: perpendicular inferred for a connected square corner", "[inference]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 0}), line({10, 0}, {10, 7}) };
+    auto r = infer_relations(ents, 1);
+    REQUIRE(r.size() == 1);
+    CHECK(r[0].type == SketchConstraintType::Perpendicular);
+    CHECK(r[0].ea == 0);
+    CHECK(r[0].eb == 1);
+}
+
+TEST_CASE("inference: parallel inferred for connected collinear-ish lines", "[inference]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 0}), line({10, 0}, {21, 0.1}) };
+    auto r = infer_relations(ents, 1);
+    REQUIRE(r.size() == 1);
+    CHECK(r[0].type == SketchConstraintType::Parallel);
+    CHECK(r[0].ea == 0);
+    CHECK(r[0].eb == 1);
+}
+
+TEST_CASE("inference: two unconnected parallel lines infer nothing", "[inference]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 0}), line({0, 5}, {10, 5}) };
+    auto r = infer_relations(ents, 1);
+    CHECK(r.empty());
+}
+
+TEST_CASE("inference: a corner outside tolerance infers nothing", "[inference]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 0}), line({10, 0}, {15, 7}) };
+    auto r = infer_relations(ents, 1);
+    CHECK(r.empty());
+}
+
+TEST_CASE("inference: equal radius inferred for near-equal circles", "[inference]")
+{
+    auto r = infer_relations({ circle({0, 0}, 5.0), circle({30, 0}, 5.02) }, 1);
+    REQUIRE(r.size() == 1);
+    CHECK(r[0].type == SketchConstraintType::EqualRadius);
+    CHECK(r[0].ea == 0);
+    CHECK(r[0].eb == 1);
+
+    auto r2 = infer_relations({ circle({0, 0}, 5.0), circle({30, 0}, 6.0) }, 1);
+    CHECK(r2.empty());
+}
+
+TEST_CASE("inference: tangent inferred for a line meeting a circle tangentially", "[inference]")
+{
+    std::vector<SketchEntity> ents = { circle({0, 0}, 5.0), line({0, 5}, {10, 5}) };
+    auto r = infer_relations(ents, 1);
+    REQUIRE(r.size() == 1);
+    CHECK(r[0].type == SketchConstraintType::Tangent);
+    CHECK(r[0].ea == 0);
+    CHECK(r[0].eb == 1);
+
+    std::vector<SketchEntity> off = { circle({0, 0}, 5.0), line({0, 5}, {10, 9}) };
+    CHECK(infer_relations(off, 1).empty());
+}
+
+TEST_CASE("inference: nothing inferred against a higher index", "[inference]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 0}), line({10, 0}, {10, 7}) };
+    auto r = infer_relations(ents, 0);
+    CHECK(r.empty());
+}
+
+TEST_CASE("inference: degenerate entities are ignored", "[inference]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 0}), line({10, 0}, {10, 0}) };
+    auto r = infer_relations(ents, 1);
+    CHECK(r.empty());
+}
+
+// The cap that keeps infer_relations linear rather than quadratic. Without it a drawing with
+// many equal holes yields a constraint per PAIR: 200 equal circles produced ~20000 candidates,
+// the batch was rejected as over-constrained, and the caller's one-at-a-time fallback then ran
+// a solve per constraint -- which pinned the app at 95% of a core with the MCP socket
+// unresponsive, and is what the corpus rung caught.
+TEST_CASE("inference: at most one relation per rule per new entity", "[inference]")
+{
+    // 40 circles of the same radius; the 41st must not produce 40 EqualRadius constraints.
+    std::vector<SketchEntity> ents;
+    for (int i = 0; i < 41; ++i) {
+        SketchEntity c;
+        c.type = SketchEntity::Type::Circle;
+        c.center = Vec2d(i * 20.0, 0.0);
+        c.p0 = c.center;
+        c.radius = 5.0;
+        ents.push_back(c);
+    }
+    auto rels = infer_relations(ents, 40);
+    CHECK(rels.size() == 1);
+    CHECK(rels[0].type == SketchConstraintType::EqualRadius);
+    CHECK(rels[0].eb == 40);
+}
diff --git a/tests/libslic3r/test_sketchprofile.cpp b/tests/libslic3r/test_sketchprofile.cpp
new file mode 100644
index 0000000000..7f455eb936
--- /dev/null
+++ b/tests/libslic3r/test_sketchprofile.cpp
@@ -0,0 +1,209 @@
+// Closed-profile harness for the 2D sketch layer.
+//
+// The existing [SketchEdit] cases check one entity at a time — offset ONE line, mirror ONE
+// arc — and every one of them passes while the feature they belong to is unusable. What a
+// user actually does is combine 2D features into a CLOSED PROFILE and extrude it, and the
+// property that makes that work is topological, not per-entity: after the operation, do the
+// pieces still form a single closed loop?
+//
+// So these cases assert the loop, not the coordinates. That is the invariant every sketch
+// operation has to preserve and the only one that predicts whether the GUI can build a solid
+// out of the result.
+#include <catch2/catch_all.hpp>   // mainline OrcaSlicer ships Catch2 v3 (v2 was catch2/catch.hpp)
+#include "libslic3r/CAD/SketchEngine.hpp"
+#include <BRepGProp.hxx>
+#include <GProp_GProps.hxx>
+#include <cmath>
+
+using namespace Slic3r;
+using Catch::Matchers::WithinAbs;
+
+namespace {
+
+SketchPlane xy_plane() { return SketchPlane::XY(); }
+
+SketchEntity line(const Vec2d& a, const Vec2d& b)
+{
+    SketchEntity e;
+    e.type = SketchEntity::Type::Line;
+    e.p0 = a; e.p1 = b;
+    return e;
+}
+
+// A CCW rectangle as four Line entities sharing endpoints exactly.
+std::vector<SketchEntity> rect(double w, double h)
+{
+    return { line({0, 0}, {w, 0}), line({w, 0}, {w, h}),
+             line({w, h}, {0, h}), line({0, h}, {0, 0}) };
+}
+
+// How many of the wires the sketch resolves to are CLOSED.
+int closed_wires(const std::vector<SketchEntity>& ents)
+{
+    const auto ws = SketchEngine::entities_to_wires(ents, xy_plane());
+    int n = 0;
+    for (const auto& w : ws)
+        if (!w.IsNull() && w.Closed()) ++n;
+    return n;
+}
+
+// Enclosed area of the single closed loop the sketch resolves to. -1 when it is not one
+// closed loop — the failure the whole file exists to catch.
+double profile_area(const std::vector<SketchEntity>& ents)
+{
+    const auto ws = SketchEngine::entities_to_wires(ents, xy_plane());
+    if (ws.size() != 1 || ws[0].IsNull() || !ws[0].Closed()) return -1.0;
+    const TopoDS_Face f = SketchEngine::wires_to_face(ws, xy_plane());
+    GProp_GProps props;
+    BRepGProp::SurfaceProperties(f, props);
+    return props.Mass();
+}
+
+SketchEntity arc(const Vec2d& c, double r, double a0, double a1)
+{
+    SketchEntity e;
+    e.type        = SketchEntity::Type::Arc;
+    e.center      = c;
+    e.radius      = r;
+    e.start_angle = a0;
+    e.end_angle   = a1;
+    e.p0 = c + r * Vec2d(std::cos(a0), std::sin(a0));
+    e.p1 = c + r * Vec2d(std::cos(a1), std::sin(a1));
+    return e;
+}
+
+} // namespace
+
+TEST_CASE("profile baseline: a hand-built rectangle is one closed loop", "[SketchProfile]")
+{
+    REQUIRE(closed_wires(rect(40, 20)) == 1);
+}
+
+TEST_CASE("profile: mirroring a closed rectangle keeps it closed", "[SketchProfile]")
+{
+    const auto m = SketchEngine::mirror_entities(rect(40, 20), Vec2d(-10, 0), Vec2d(-10, 1));
+    REQUIRE(m.size() == 4);
+    REQUIRE(closed_wires(m) == 1);
+}
+
+TEST_CASE("profile: mirroring an open half-profile closes it against the axis", "[SketchProfile]")
+{
+    // Half a rectangle, open along x=0 — the classic "draw half, mirror it" gesture.
+    const std::vector<SketchEntity> half = {
+        line({0, 0}, {20, 0}), line({20, 0}, {20, 10}), line({20, 10}, {0, 10}) };
+    auto all = half;
+    for (const auto& e : SketchEngine::mirror_entities(half, Vec2d(0, 0), Vec2d(0, 1)))
+        all.push_back(e);
+    REQUIRE(all.size() == 6);
+    REQUIRE(closed_wires(all) == 1);
+}
+
+TEST_CASE("profile: offsetting a closed rectangle keeps it closed", "[SketchProfile]")
+{
+    const auto out = SketchEngine::offset_entities(rect(40, 20), 5.0);
+    REQUIRE(out.size() == 4);
+    REQUIRE(closed_wires(out) == 1);
+}
+
+TEST_CASE("profile: offset outward grows the enclosed area by the right amount", "[SketchProfile]")
+{
+    // A rectangle offset outward by d is (w+2d) x (h+2d) with the corners rounded at r=d,
+    // so its area is w*h + 2d(w+h) + pi*d^2 whichever way the corners are healed... except
+    // for a sharp-corner offset, which is exactly (w+2d)*(h+2d). Either healing is defensible;
+    // a set of four disconnected segments is not, and that is what this measures.
+    const double w = 40, h = 20, d = 5;
+    const auto out = SketchEngine::offset_entities(rect(w, h), d);
+    const auto ws  = SketchEngine::entities_to_wires(out, xy_plane());
+    REQUIRE(ws.size() == 1);
+    REQUIRE(ws[0].Closed());
+}
+
+TEST_CASE("profile: offset sign is left-of-travel, so +d shrinks a CCW rectangle", "[SketchProfile]")
+{
+    // The convention has to be pinned by a test, because it is the one thing a caller cannot
+    // read off the geometry: +d = left of the direction of travel = inward for a CCW loop.
+    // Miter join on a rectangle keeps the corners sharp, so the result is exact.
+    const double w = 40, h = 20, d = 5;
+    REQUIRE_THAT(profile_area(SketchEngine::offset_entities(rect(w, h), d)),
+                 WithinAbs((w - 2 * d) * (h - 2 * d), 1e-6));
+    REQUIRE_THAT(profile_area(SketchEngine::offset_entities(rect(w, h), -d)),
+                 WithinAbs((w + 2 * d) * (h + 2 * d), 1e-6));
+}
+
+TEST_CASE("profile: offsetting a stadium (two lines + two arcs) stays closed", "[SketchProfile]")
+{
+    // A slot outline: straight top and bottom joined by half-circle caps. This is the case the
+    // per-entity offset could never repair, because both seams are line-to-arc.
+    const double L = 30, r = 8, d = 3;
+    const std::vector<SketchEntity> slot = {
+        line({0, -r}, {L, -r}),
+        arc({L, 0}, r, -M_PI / 2, M_PI / 2),
+        line({L, r}, {0, r}),
+        arc({0, 0}, r, M_PI / 2, 3 * M_PI / 2),
+    };
+    REQUIRE(closed_wires(slot) == 1);
+    const auto out = SketchEngine::offset_entities(slot, -d);   // -d = outward for this CCW loop
+    REQUIRE(closed_wires(out) == 1);
+    // Offsetting a stadium outward by d gives the stadium with radius r+d: L*2(r+d) + pi(r+d)^2.
+    // Lines and caps must move the SAME way — that is the assertion this case exists for.
+    const double rr = r + d;
+    REQUIRE_THAT(profile_area(out), WithinAbs(L * 2 * rr + M_PI * rr * rr, 1e-6));
+}
+
+TEST_CASE("profile: an open chain offsets without being forced closed", "[SketchProfile]")
+{
+    // A sweep path is legitimately open; the repair must join its interior seams and leave
+    // the two free ends alone.
+    const std::vector<SketchEntity> open_chain = {
+        line({0, 0}, {20, 0}), line({20, 0}, {20, 10}) };
+    const auto out = SketchEngine::offset_entities(open_chain, 4.0);
+    REQUIRE(out.size() == 2);
+    REQUIRE(closed_wires(out) == 0);
+    // The interior seam is repaired: the two offset segments still meet.
+    REQUIRE_THAT((out[0].p1 - out[1].p0).norm(), WithinAbs(0.0, 1e-9));
+}
+
+TEST_CASE("profile: a mirrored half offsets as one loop, not two", "[SketchProfile]")
+{
+    // The classic "draw half, mirror it" gesture on a stadium. mirror_entities emits a half
+    // that travels the opposite way round, so the concatenation must still chain as ONE closed
+    // loop and its mirrored cap must offset outward like the original, not inward.
+    const double L = 30, R = 15, d = 4;
+    const std::vector<SketchEntity> half = {
+        line({0, -R}, {L, -R}),
+        arc({L, 0}, R, -M_PI / 2, M_PI / 2),
+        line({L, R}, {0, R}),
+    };
+    std::vector<SketchEntity> all = half;
+    for (const auto& e : SketchEngine::mirror_entities(half, Vec2d(0, 0), Vec2d(0, 1)))
+        all.push_back(e);
+    REQUIRE(closed_wires(all) == 1);
+
+    const auto out = SketchEngine::offset_entities(all, -d);   // -d = outward for this loop
+    REQUIRE(closed_wires(out) == 1);
+    for (const auto& o : out)
+        if (o.type == SketchEntity::Type::Arc)
+            REQUIRE_THAT(o.radius, WithinAbs(R + d, 1e-9));
+}
+
+TEST_CASE("profile: a mirrored half continues the original chain", "[SketchProfile]")
+{
+    // The point of emitting the reflected half reversed: appending it to the source must give a
+    // chain you can WALK, head-to-tail, with no consumer having to notice that half of it came
+    // from a mirror. The end of the last source entity must be the start of the first mirrored
+    // one, and the end of the last mirrored one must close back to the very first start.
+    const std::vector<SketchEntity> half = {
+        line({0, -15}, {50, -15}), line({50, -15}, {50, 15}), line({50, 15}, {0, 15}) };
+    const auto m = SketchEngine::mirror_entities(half, Vec2d(0, 0), Vec2d(0, 1));
+    REQUIRE(m.size() == 3);
+
+    REQUIRE_THAT((half.back().p1 - m.front().p0).norm(), WithinAbs(0.0, 1e-9));
+    REQUIRE_THAT((m.back().p1   - half.front().p0).norm(), WithinAbs(0.0, 1e-9));
+
+    for (size_t i = 0; i + 1 < m.size(); ++i)
+        REQUIRE_THAT((m[i].p1 - m[i + 1].p0).norm(), WithinAbs(0.0, 1e-9));
+
+    auto all = half;
+    for (const auto& e : m) all.push_back(e);
+    REQUIRE(closed_wires(all) == 1);
+}
diff --git a/tests/libslic3r/test_slvs_constraints.cpp b/tests/libslic3r/test_slvs_constraints.cpp
new file mode 100644
index 0000000000..6dfac07348
--- /dev/null
+++ b/tests/libslic3r/test_slvs_constraints.cpp
@@ -0,0 +1,401 @@
+#include <catch2/catch_all.hpp>   // mainline OrcaSlicer ships Catch2 v3 (v2 was catch2/catch.hpp)
+using Catch::Approx;   // v3 scopes Approx into the Catch namespace; v2 had it at global scope
+
+#include "libslic3r/CAD/SketchSolver.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
+
+using namespace Slic3r;
+using CT = SketchConstraintType;
+using R  = SketchPointRole;
+
+static SketchEntity line(Vec2d a, Vec2d b)
+{
+    SketchEntity e; e.type = SketchEntity::Type::Line; e.p0 = a; e.p1 = b; return e;
+}
+static SketchEntity circle(Vec2d c, double r)
+{
+    SketchEntity e; e.type = SketchEntity::Type::Circle; e.center = c; e.p0 = c; e.radius = r; return e;
+}
+static SketchEntityConstraintDef con(CT t, int ea, R ra, int eb, R rb, double v = 0.0)
+{
+    SketchEntityConstraintDef c; c.type = t; c.ea = ea; c.ra = ra; c.eb = eb; c.rb = rb; c.value = v; return c;
+}
+
+TEST_CASE("slvs: distance + horizontal + fix solves a line length", "[slvs]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {5, 1}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Fix,        0, R::P0, 0, R::P0),
+        con(CT::Horizontal, 0, R::P0, 0, R::P1),
+        con(CT::Distance,   0, R::P0, 0, R::P1, 10.0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK((ents[0].p1 - ents[0].p0).norm() == Approx(10.0).margin(1e-6));
+    CHECK(ents[0].p0.x() == Approx(0.0).margin(1e-6));
+    CHECK(ents[0].p0.y() == Approx(0.0).margin(1e-6));
+    CHECK(ents[0].p1.y() == Approx(0.0).margin(1e-6));   // horizontal
+}
+
+TEST_CASE("slvs: coincident joins two line endpoints (loop closes)", "[slvs]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 0}), line({10.3, 0.2}, {10, 10}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Coincident, 0, R::P1, 1, R::P0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK((ents[0].p1 - ents[1].p0).norm() == Approx(0.0).margin(1e-6));
+}
+
+TEST_CASE("slvs: parallel + perpendicular on lines", "[slvs]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 1}), line({0, 5}, {10, 5.5}), line({0, 0}, {0.5, 10}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Fix,           0, R::P0, 0, R::P0),
+        con(CT::Horizontal,    0, R::P0, 0, R::P1),
+        con(CT::Parallel,      0, R::P0, 1, R::P0),     // line1 parallel to line0
+        con(CT::Perpendicular, 0, R::P0, 2, R::P0),     // line2 perpendicular to line0
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(ents[1].p1.y() - ents[1].p0.y() == Approx(0.0).margin(1e-6));            // line1 horizontal
+    CHECK(ents[2].p1.x() - ents[2].p0.x() == Approx(0.0).margin(1e-6));            // line2 vertical
+}
+
+TEST_CASE("slvs: circle radius constraint", "[slvs]")
+{
+    std::vector<SketchEntity> ents = { circle({2, 2}, 3.0) };
+    std::vector<SketchEntityConstraintDef> cons = { con(CT::Radius, 0, R::P0, -1, R::P0, 7.0) };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(ents[0].radius == Approx(7.0).margin(1e-6));
+}
+
+TEST_CASE("slvs: degrees of freedom reported", "[slvs]")
+{
+    // One free line with only a Fix on the start: 4 DoF total minus 2 (fix) = 2 remaining.
+    std::vector<SketchEntity> ents = { line({0, 0}, {3, 4}) };
+    std::vector<SketchEntityConstraintDef> cons = { con(CT::Fix, 0, R::P0, 0, R::P0) };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(res.dof == 2);
+}
+
+TEST_CASE("slvs: drag pulls a point while constraints hold", "[slvs]")
+{
+    // A vertical line of fixed length 10, P0 pinned at the origin. Dragging P1 toward
+    // (10,0) must keep the length (Distance constraint) but rotate the line so the end
+    // follows the cursor into positive x — the dragged param wins the under-constrained DoF.
+    std::vector<SketchEntity> ents = { line({0, 0}, {0, 10}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Fix,      0, R::P0, 0, R::P0),
+        con(CT::Distance, 0, R::P0, 0, R::P1, 10.0),
+    };
+    ents[0].p1 = Vec2d(10, 0);   // user dropped the endpoint here
+    auto res = sketch_solve_drag(ents, cons, 0, R::P1);
+    REQUIRE(res.ok);
+    CHECK((ents[0].p1 - ents[0].p0).norm() == Approx(10.0).margin(1e-6));  // length held
+    CHECK(ents[0].p0.x() == Approx(0.0).margin(1e-6));                     // P0 still pinned
+    CHECK(ents[0].p0.y() == Approx(0.0).margin(1e-6));
+    CHECK(ents[0].p1.x() > 1.0);   // end followed the drag toward +x (not stuck vertical)
+}
+
+TEST_CASE("slvs: over-constrained / inconsistent is detected", "[slvs]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {5, 0}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Fix,      0, R::P0, 0, R::P0),
+        con(CT::Fix,      0, R::P1, 0, R::P1),
+        con(CT::Distance, 0, R::P0, 0, R::P1, 99.0),   // contradicts the pinned endpoints
+    };
+    auto res = sketch_solve(ents, cons);
+    CHECK_FALSE(res.ok);   // SLVS_RESULT_INCONSISTENT
+}
+
+// yww4. libslvs sizes its System with a compile-time `MAX_UNKNOWNS = 1024`, and the
+// solver is handed every entity in the sketch at 2 params per point — so a sketch of about 480
+// lines is the last one that fits and the next comes back TOO_MANY_UNKNOWNS. Because
+// try_add_constraints rolls a failed batch back, that turned into: every auto-inferred constraint
+// on a large sketch silently dropped, and from then on no dimension could ever be applied to it.
+// Constraints only couple entities that share a point, so the sketch is solved component by
+// component when the whole system does not fit.
+TEST_CASE("slvs: a sketch past the solver's unknown limit still solves", "[slvs]")
+{
+    // 300 disjoint squares: 1200 lines, 4800 unknowns whole, 8 per component.
+    const int N = 300;
+    std::vector<SketchEntity> ents;
+    std::vector<SketchEntityConstraintDef> cons;
+    for (int i = 0; i < N; ++i) {
+        const double x = (i % 30) * 10.0, y = (i / 30) * 10.0;
+        const int b = int(ents.size());
+        ents.push_back(line({x, y},         {x + 4.0, y}));
+        ents.push_back(line({x + 4.0, y},   {x + 4.0, y + 4.0}));
+        ents.push_back(line({x + 4.0, y + 4.0}, {x, y + 4.0}));
+        ents.push_back(line({x, y + 4.0},   {x, y}));
+        for (int k = 0; k < 4; ++k)
+            cons.push_back(con(CT::Coincident, b + k, R::P1, b + (k + 1) % 4, R::P0));
+    }
+    REQUIRE(ents.size() == size_t(4 * N));
+
+    std::vector<SketchEntity> before = ents;
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    for (size_t i = 0; i < ents.size(); ++i) {         // already satisfied: nothing may move
+        CHECK(ents[i].p0.x() == Approx(before[i].p0.x()).margin(1e-9));
+        CHECK(ents[i].p0.y() == Approx(before[i].p0.y()).margin(1e-9));
+        CHECK(ents[i].p1.x() == Approx(before[i].p1.x()).margin(1e-9));
+        CHECK(ents[i].p1.y() == Approx(before[i].p1.y()).margin(1e-9));
+    }
+
+    // And a dimension typed onto one of them lands exactly, which is what stopped working.
+    cons.push_back(con(CT::Distance, 0, R::P0, 0, R::P1, 7.0));
+    auto res2 = sketch_solve(ents, cons);
+    REQUIRE(res2.ok);
+    CHECK((ents[0].p1 - ents[0].p0).norm() == Approx(7.0).margin(1e-9));
+
+    // A conflict inside ONE component must still be caught, not swallowed by the split.
+    cons.push_back(con(CT::Distance, 0, R::P0, 0, R::P1, 99.0));
+    auto res3 = sketch_solve(ents, cons);
+    CHECK_FALSE(res3.ok);
+}
+
+TEST_CASE("slvs: equal radius drives two circles to one radius", "[slvs][CadDocument]")
+{
+    std::vector<SketchEntity> ents = { circle({0, 0}, 5.0), circle({10, 0}, 12.0) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::EqualRadius, 0, R::P0, 1, R::P0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(ents[0].radius == Approx(ents[1].radius).margin(1e-9));
+    CHECK(ents[0].radius > 1e-6);   // equal-at-zero would satisfy the line above trivially
+}
+
+TEST_CASE("slvs: equal radius plus a radius dimension pins both", "[slvs][CadDocument]")
+{
+    std::vector<SketchEntity> ents = { circle({0, 0}, 5.0), circle({10, 0}, 12.0) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::EqualRadius, 0, R::P0, 1, R::P0),
+        con(CT::Radius, 0, R::P0, -1, R::P0, 8.0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(ents[0].radius == Approx(8.0).margin(1e-9));
+    CHECK(ents[1].radius == Approx(8.0).margin(1e-9));
+}
+
+TEST_CASE("slvs: collinear makes two offset lines share one line", "[slvs][CadDocument]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 0}), line({0, 4}, {10, 4}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Collinear, 0, R::P0, 1, R::P0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    const Vec2d& a0 = ents[0].p0;
+    const Vec2d  ad = ents[0].p1 - ents[0].p0;
+    for (int k = 0; k <= 1; ++k) {
+        const Vec2d& pk = (k == 0) ? ents[1].p0 : ents[1].p1;
+        const double cross = ad.x() * (pk.y() - a0.y()) - ad.y() * (pk.x() - a0.x());
+        CHECK(cross == Approx(0.0).margin(1e-9));
+    }
+    // A line collapsed to a point is trivially collinear with anything, so the cross
+    // products above would pass on a degenerate solve. Both lines must survive intact.
+    CHECK(ad.norm() == Approx(10.0).margin(1e-9));
+    CHECK((ents[1].p1 - ents[1].p0).norm() == Approx(10.0).margin(1e-9));
+}
+
+TEST_CASE("slvs: collinear on already-collinear lines moves nothing", "[slvs][CadDocument]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 0}), line({20, 0}, {30, 0}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Collinear, 0, R::P0, 1, R::P0),
+    };
+    std::vector<SketchEntity> before = ents;
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    for (size_t i = 0; i < ents.size(); ++i) {         // already satisfied: nothing may move
+        CHECK(ents[i].p0.x() == Approx(before[i].p0.x()).margin(1e-9));
+        CHECK(ents[i].p0.y() == Approx(before[i].p0.y()).margin(1e-9));
+        CHECK(ents[i].p1.x() == Approx(before[i].p1.x()).margin(1e-9));
+        CHECK(ents[i].p1.y() == Approx(before[i].p1.y()).margin(1e-9));
+    }
+}
+
+TEST_CASE("slvs: distance-x drives the horizontal gap and leaves Y alone", "[slvs][CadDocument]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {3, 7}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Fix,       0, R::P0, 0, R::P0),
+        con(CT::DistanceX, 0, R::P0, 0, R::P1, 10.0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    // SIGNED, not abs. PROJ_PT_DISTANCE constrains (pB - pA).dot(unit(dir)), and a
+    // LINE_SEGMENT's direction is point[0] - point[1] (slvs entity.cpp), so the reference
+    // line is built head-first to mean +X. Assert on abs and a flipped reference passes
+    // while every dimension lands the point on the wrong side of its anchor.
+    CHECK(ents[0].p1.x() - ents[0].p0.x() == Approx(10.0).margin(1e-9));
+    CHECK(ents[0].p1.y() == Approx(7.0).margin(1e-9));   // Y must not be disturbed
+}
+
+TEST_CASE("slvs: distance-y drives the vertical gap and leaves X alone", "[slvs][CadDocument]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {3, 7}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Fix,       0, R::P0, 0, R::P0),
+        con(CT::DistanceY, 0, R::P0, 0, R::P1, 10.0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(ents[0].p1.y() - ents[0].p0.y() == Approx(10.0).margin(1e-9));   // signed: see above
+    CHECK(ents[0].p1.x() == Approx(3.0).margin(1e-9));   // X must not be disturbed
+}
+
+TEST_CASE("slvs: distance-x is not the straight-line distance", "[slvs][CadDocument]")
+{
+    // B is at straight-line distance 10 from A; DistanceX = 6 is already satisfied, so a
+    // correct projection leaves B untouched. This is the case that fails if the constraint
+    // were wired to SLVS_C_PT_PT_DISTANCE, which would drag B onto the radius-6 circle.
+    std::vector<SketchEntity> ents = { line({0, 0}, {6, 8}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Fix,       0, R::P0, 0, R::P0),
+        con(CT::DistanceX, 0, R::P0, 0, R::P1, 6.0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(ents[0].p1.x() == Approx(6.0).margin(1e-9));
+    CHECK(ents[0].p1.y() == Approx(8.0).margin(1e-9));
+}
+
+TEST_CASE("slvs: distance-x plus distance-y fully locates a point", "[slvs][CadDocument]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {1, 1}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Fix,       0, R::P0, 0, R::P0),
+        con(CT::DistanceX, 0, R::P0, 0, R::P1, 4.0),
+        con(CT::DistanceY, 0, R::P0, 0, R::P1, 3.0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(ents[0].p1.x() - ents[0].p0.x() == Approx(4.0).margin(1e-9));   // signed: see above
+    CHECK(ents[0].p1.y() - ents[0].p0.y() == Approx(3.0).margin(1e-9));
+}
+
+// The property the GUI's ref-ordering exists to preserve: DistanceX is SIGNED, so applying
+// the CURRENT projected delta as the target must not move anything. If the refs are ordered
+// so the shown value is positive while the actual signed delta is negative, accepting the
+// value a dimension opens with teleports the point to the other side of its anchor.
+TEST_CASE("slvs: applying a point's own distance-x is a no-op", "[slvs][CadDocument]")
+{
+    // p1 sits to the LEFT of p0, so the signed delta p1 - p0 is negative.
+    std::vector<SketchEntity> ents = { line({0, 0}, {-4, 7}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Fix,       0, R::P0, 0, R::P0),
+        con(CT::DistanceX, 0, R::P0, 0, R::P1, -4.0),   // the CURRENT signed delta
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(ents[0].p1.x() == Approx(-4.0).margin(1e-9));   // stayed left, did not flip to +4
+    CHECK(ents[0].p1.y() == Approx(7.0).margin(1e-9));
+}
+
+static SketchEntity point(Vec2d p)
+{
+    SketchEntity e; e.type = SketchEntity::Type::Point; e.p0 = p; return e;
+}
+
+TEST_CASE("slvs: coincident onto the origin sentinel pins a point", "[slvs][CadDocument]")
+{
+    std::vector<SketchEntity> ents = { point({5, 5}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Coincident, 0, R::P0, kSketchRefOrigin, R::P0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(ents[0].p0.x() == Approx(0.0).margin(1e-9));
+    CHECK(ents[0].p0.y() == Approx(0.0).margin(1e-9));
+}
+
+// NOTE on why these pin the free direction instead of asserting "the other coordinate is
+// left alone". sys.dragged[] is populated only while a drag is in progress, so a plain
+// sketch_solve of an UNDER-constrained system is free to move any parameter -- solvespace
+// runs a Newton iteration, it does not minimise movement. PointOnLine alone is one equation
+// in two unknowns, and the point measurably slides along the axis (from (7,4) to (4,0)).
+// That is legal, not a defect, so the well-posed test states both coordinates.
+TEST_CASE("slvs: point-on-line onto the X axis, located along it from the origin", "[slvs][CadDocument]")
+{
+    std::vector<SketchEntity> ents = { point({7, 4}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::PointOnLine, 0, R::P0, kSketchRefAxisX, R::P0),
+        con(CT::DistanceX,   kSketchRefOrigin, R::P0, 0, R::P0, 7.0),   // both sentinels at once
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(ents[0].p0.y() == Approx(0.0).margin(1e-9));   // driven onto the X axis
+    CHECK(ents[0].p0.x() == Approx(7.0).margin(1e-9));   // and located along it
+}
+
+TEST_CASE("slvs: point-on-line onto the Y axis, located along it from the origin", "[slvs][CadDocument]")
+{
+    std::vector<SketchEntity> ents = { point({4, 7}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::PointOnLine, 0, R::P0, kSketchRefAxisY, R::P0),
+        con(CT::DistanceY,   kSketchRefOrigin, R::P0, 0, R::P0, 7.0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(ents[0].p0.x() == Approx(0.0).margin(1e-9));   // driven onto the Y axis
+    CHECK(ents[0].p0.y() == Approx(7.0).margin(1e-9));   // and located along it
+}
+
+TEST_CASE("slvs: parallel to the X axis levels a line without collapsing it", "[slvs][CadDocument]")
+{
+    std::vector<SketchEntity> ents = { line({0, 0}, {10, 3}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Fix,      0, R::P0, 0, R::P0),
+        con(CT::Parallel, 0, R::P0, kSketchRefAxisX, R::P0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(ents[0].p1.y() == Approx(0.0).margin(1e-9));   // leveled onto y = 0
+    // A bare Parallel leaves length free; the solver preserves the endpoint's free
+    // x-coordinate, so the line lands at (10,0) — length 10, not the original sqrt(109).
+    // Assert that free coordinate rather than abs(): a flipped/collapsed line would not
+    // land exactly here.
+    CHECK(ents[0].p1.x() == Approx(10.0).margin(1e-9));
+    CHECK((ents[0].p1 - ents[0].p0).norm() == Approx(10.0).margin(1e-6));   // did not collapse
+}
+
+TEST_CASE("slvs: symmetric-about-Y mirrors two points across x = 0", "[slvs][CadDocument]")
+{
+    std::vector<SketchEntity> ents = { point({3, 5}), point({9, 5}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::SymmetricAboutY, 0, R::P0, 1, R::P0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(ents[0].p0.x() == Approx(-ents[1].p0.x()).margin(1e-9));   // mirror across x = 0
+    // Neither x may be 0: a both-collapsed-to-the-axis solution also satisfies the mirror
+    // trivially. Squared, not abs(), so a near-zero x still fails cleanly.
+    CHECK(ents[0].p0.x() * ents[0].p0.x() > 1e-12);
+    CHECK(ents[1].p0.x() * ents[1].p0.x() > 1e-12);
+    CHECK(ents[0].p0.y() == Approx(5.0).margin(1e-9));   // Y values untouched
+    CHECK(ents[1].p0.y() == Approx(5.0).margin(1e-9));
+}
+
+TEST_CASE("slvs: reference-based constraint adds no degrees of freedom", "[slvs][CadDocument]")
+{
+    // A free line with Fix on P0 and Parallel to the X axis: 4 DoF - 2 (fix) - 1 (angle)
+    // = 1 (length still free). If the G_FIXED reference entities leaked unknowns into the
+    // solved group, this figure would be wrong.
+    std::vector<SketchEntity> ents = { line({0, 0}, {3, 4}) };
+    std::vector<SketchEntityConstraintDef> cons = {
+        con(CT::Fix,      0, R::P0, 0, R::P0),
+        con(CT::Parallel, 0, R::P0, kSketchRefAxisX, R::P0),
+    };
+    auto res = sketch_solve(ents, cons);
+    REQUIRE(res.ok);
+    CHECK(res.dof == 1);
+}
diff --git a/tools/orca_cad_mcp_bridge.py b/tools/orca_cad_mcp_bridge.py
new file mode 100644
index 0000000000..d54320a9cb
--- /dev/null
+++ b/tools/orca_cad_mcp_bridge.py
@@ -0,0 +1,180 @@
+#!/usr/bin/env python3
+"""Zero-dependency stdio MCP server bridging to the Orca/Orca-CAD control socket.
+
+Speaks MCP (JSON-RPC 2.0 over newline-delimited stdio) to an MCP client (Claude Code),
+and forwards each tool call to the app's Unix-domain control socket (opened by the GUI
+when launched with ORCA_CAD_MCP set). The tool list is built *live* from the app's own
+`describe_tools` reply — introspection drives the schema, so new kernel methods surface
+without touching this file.
+
+Usage:  orca_cad_mcp_bridge.py [SOCKET_PATH]   (default /tmp/orca-cad-mcp.sock)
+The app must be running with ORCA_CAD_MCP set; if the socket is down, tools/list falls
+back to the slice-1 set and tool calls report the connection error (never crash).
+"""
+import sys, os, json, socket, itertools
+
+SOCK_PATH = sys.argv[1] if len(sys.argv) > 1 else "/tmp/orca-cad-mcp.sock"
+SERVER_INFO = {"name": "orca-cad", "version": "0.1"}
+_app_id = itertools.count(1)
+
+# --- app control-socket round-trip --------------------------------------------
+def app_call(method, params=None):
+    """One request to the app over the unix socket. Raises on transport failure."""
+    req = {"jsonrpc": "2.0", "id": next(_app_id), "method": method}
+    if params is not None:
+        req["params"] = params
+    s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    s.settimeout(20)
+    try:
+        s.connect(SOCK_PATH)
+        s.sendall((json.dumps(req) + "\n").encode())
+        buf = b""
+        while not buf.endswith(b"\n"):
+            chunk = s.recv(65536)
+            if not chunk:
+                break
+            buf += chunk
+    finally:
+        s.close()
+    return json.loads(buf.decode())
+
+# --- describe_tools -> MCP tool schemas ---------------------------------------
+_TYPE_MAP = {"number": "number", "integer": "integer", "string": "string",
+             "boolean": "boolean", "array": "array", "object": "object"}
+
+def _param_schema(p):
+    sch = {"type": _TYPE_MAP.get(p.get("type", "string"), "string")}
+    desc = p.get("description")
+    if "unit" in p:    desc = (desc + " " if desc else "") + f"in {p['unit']}"
+    if desc:           sch["description"] = desc
+    if "enum" in p:    sch["enum"] = p["enum"]
+    if "min" in p:     sch["minimum"] = p["min"]
+    if "max" in p:     sch["maximum"] = p["max"]
+    if "default" in p: sch["default"] = p["default"]
+    return sch
+
+# Fallback when the app socket is unreachable at list time (e.g. the GUI isn't up yet when the
+# MCP client lists tools at session start). The LIVE describe_tools reply is authoritative — this
+# mirrors its 16-method surface so the agent still sees the full toolset; params without a
+# `default` are surfaced as required. Keep in sync with McpControl.cpp describe_tools().
+def _p(name, typ="number", **kw): return dict(name=name, type=typ, **kw)
+_PLANE = _p("plane", "string", enum=["XY", "XZ", "YZ"], default="XY")
+_FALLBACK_TOOLS = {"tools": [
+    {"name": "describe_tools", "summary": "List callable tools and their parameters.", "params": []},
+    {"name": "describe_scene", "summary": "Feature tree + per-body bounding boxes.", "params": []},
+    {"name": "extrude", "summary": "Extrude a profile (or width x height rectangle) to a depth; Onshape end conditions.",
+     "params": [_p("width", default=20), _p("height", default=20), _p("distance", default=10), _PLANE,
+                _p("profile", "array", default=[], description="closed [[x,y],...] overrides width/height"),
+                _p("boolean", "string", enum=["new", "union", "subtract", "intersect"], default="new"),
+                _p("end", "string", enum=["blind", "symmetric", "two_sided", "through_all", "up_to_face"], default="blind"),
+                _p("distance2", default=0, description="second side when end=two_sided"),
+                _p("up_to_face", "integer", default=-1, description="target face id when end=up_to_face"),
+                _p("taper", default=0), _p("flip", "boolean", default=False)]},
+    {"name": "revolve", "summary": "Revolve a profile about a plane axis.",
+     "params": [_p("width", default=20), _p("height", default=10), _p("angle", default=360),
+                _p("axis", "integer", enum=[0, 1], default=0), _p("flip", "boolean", default=False), _PLANE,
+                _p("profile", "array", default=[], description="closed [[x,y],...] overrides width/height"),
+                _p("boolean", "string", enum=["new", "union", "subtract", "intersect"], default="new")]},
+    {"name": "fillet", "summary": "Round a measured edge of a body.",
+     "params": [_p("edge", "integer"), _p("radius", default=1),
+                _p("body", "integer", default=-1, description="target body; omit for last")]},
+    {"name": "chamfer", "summary": "Chamfer a measured edge of a body.",
+     "params": [_p("edge", "integer"), _p("distance", default=1),
+                _p("body", "integer", default=-1, description="target body; omit for last")]},
+    {"name": "hole", "summary": "Drill a circular hole at (x,y) on a plane.",
+     "params": [_p("diameter", default=5), _p("depth", default=10), _p("through", "boolean", default=False),
+                _p("x", default=0), _p("y", default=0), _PLANE]},
+    {"name": "boolean", "summary": "Combine two bodies: union | subtract | intersect.",
+     "params": [_p("op", "string", enum=["union", "subtract", "intersect"], default="subtract"),
+                _p("target", "integer", default=0), _p("tool", "integer", default=1),
+                _p("keep_tool", "boolean", default=False), _p("tolerance", default=0)]},
+    {"name": "pattern", "summary": "Replicate a body: linear or circular.",
+     "params": [_p("circular", "boolean", default=False), _p("count", "integer", default=3),
+                _p("spacing", default=10), _p("dir", "integer", enum=[0, 1], default=0),
+                _p("angle", default=360), _PLANE, _p("body", "integer", default=-1, description="target body; omit for last")]},
+    {"name": "shell", "summary": "Hollow a body to a wall thickness; optionally open one face.",
+     "params": [_p("thickness", default=1), _p("face", "integer", default=-1, description="face id to leave open; omit for closed"),
+                _p("body", "integer", default=-1, description="target body; omit for last")]},
+    {"name": "draft", "summary": "Taper a body face by an angle (pull +Z).",
+     "params": [_p("face", "integer"), _p("angle", default=5),
+                _p("body", "integer", default=-1, description="target body; omit for last")]},
+    {"name": "query_topology", "summary": "Measured faces and edges of a body.",
+     "params": [_p("body", "integer", default=0)]},
+    {"name": "measure", "summary": "Distance/angle between two refs {face|edge|point} on a body.",
+     "params": [_p("body", "integer", default=0), _p("a", "object"), _p("b", "object")]},
+    {"name": "slice_body", "summary": "Cross-section of a body; ordered closed/open contours.",
+     "params": [_p("body", "integer", default=0), _PLANE, _p("offset", default=0)]},
+    {"name": "import_step", "summary": "Import a STEP file as native B-rep bodies.",
+     "params": [_p("path", "string")]},
+    {"name": "validate_against", "summary": "Volume + bbox + surface deviation of a body vs a reference {step|body}.",
+     "params": [_p("body", "integer", default=0), _p("reference", "object")]},
+]}
+
+def list_tools():
+    try:
+        desc = app_call("describe_tools").get("result", {})
+        if "tools" not in desc:
+            desc = _FALLBACK_TOOLS
+    except Exception:
+        desc = _FALLBACK_TOOLS
+    out = []
+    for t in desc["tools"]:
+        params = t.get("params", [])
+        props = {p["name"]: _param_schema(p) for p in params}
+        required = [p["name"] for p in params if "default" not in p]
+        out.append({
+            "name": t["name"],
+            "description": t.get("summary", ""),
+            "inputSchema": {"type": "object", "properties": props, "required": required},
+        })
+    return out
+
+# --- MCP method handlers ------------------------------------------------------
+def handle(req):
+    m = req.get("method")
+    rid = req.get("id")
+    if m == "initialize":
+        ver = (req.get("params") or {}).get("protocolVersion", "2024-11-05")
+        return {"jsonrpc": "2.0", "id": rid, "result": {
+            "protocolVersion": ver,
+            "capabilities": {"tools": {"listChanged": False}},
+            "serverInfo": SERVER_INFO}}
+    if m == "ping":
+        return {"jsonrpc": "2.0", "id": rid, "result": {}}
+    if m == "tools/list":
+        return {"jsonrpc": "2.0", "id": rid, "result": {"tools": list_tools()}}
+    if m == "tools/call":
+        p = req.get("params") or {}
+        name = p.get("name")
+        args = p.get("arguments") or {}
+        try:
+            reply = app_call(name, args)
+        except Exception as e:
+            return {"jsonrpc": "2.0", "id": rid, "result": {
+                "content": [{"type": "text", "text": f"control socket unreachable ({SOCK_PATH}): {e}"}],
+                "isError": True}}
+        if "error" in reply:
+            return {"jsonrpc": "2.0", "id": rid, "result": {
+                "content": [{"type": "text", "text": json.dumps(reply["error"])}], "isError": True}}
+        return {"jsonrpc": "2.0", "id": rid, "result": {
+            "content": [{"type": "text", "text": json.dumps(reply.get("result"), indent=2)}]}}
+    if rid is not None:  # unknown *request*
+        return {"jsonrpc": "2.0", "id": rid, "error": {"code": -32601, "message": f"method not found: {m}"}}
+    return None  # notification (e.g. notifications/initialized) -> no reply
+
+def main():
+    for line in sys.stdin:
+        line = line.strip()
+        if not line:
+            continue
+        try:
+            req = json.loads(line)
+        except Exception:
+            continue
+        resp = handle(req)
+        if resp is not None:
+            sys.stdout.write(json.dumps(resp) + "\n")
+            sys.stdout.flush()
+
+if __name__ == "__main__":
+    main()