The constraint list follows you into a live sketch

The rows, their ✗ buttons and the click-to-highlight were all built against
m_doc.features[m_constrain_feat].entity_constraints — a COMMITTED feature. A live sketch
has no committed feature, so the card was hidden for the whole session and the list it
would have shown was empty by construction. Every constraint applied while drawing was
nameless: the badge said one existed, nothing said which.

rebuild_constraint_list now picks its source by scope. live_constraint_scope() is the same
discriminator apply_constraint already used to route to apply_live_constraint — both
Constrain modes set m_active, so is_sketching() alone would claim the live scope while the
committed manager is open. delete_constraint and highlight_constraint_entities branch on
it too, and the card shows in Sketch mode as well as Constrain.

Keeping the rows in step needed a signal that did not exist: on_solve_state fires on every
frame of a drag, so rebuilding from it would rebuild the list continuously. The tool now
fires on_constraints_changed only when the constraint SET changes — one added by
try_add_constraints, one removed by remove_constraint (the indexed form the badge click and
the ✗ row now share).

The rebuild is deferred through CallAfter. One of its 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.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011FbJKJAJxxkhDTs9XdZzKA

src/slic3r/GUI/CAD/DesignCanvas.cpp

@@ -1494,6 +1494,23 @@ 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);

src/slic3r/GUI/CAD/DesignCanvas.hpp

@@ -302,6 +302,9 @@ public:
     // 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).

src/slic3r/GUI/CAD/DesignPanel.cpp

@@ -3591,6 +3591,14 @@ DesignPanel::DesignPanel(wxWindow* parent)
         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) {
@@ -4448,8 +4456,8 @@ void DesignPanel::set_ui_mode(UiMode m)
     }
     // 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)
-            rebuild_constraint_list();
+        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();
@@ -8002,7 +8010,16 @@ wxString DesignPanel::constraint_label(const SketchEntityConstraintDef& d) const
     return _L("Constraint");
 }
 
-// Rebuild the constraint-row list from the constrained feature's entity_constraints.
+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)
@@ -8010,10 +8027,12 @@ void DesignPanel::rebuild_constraint_list()
     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 =
-        active ? m_doc.features[m_constrain_feat].entity_constraints : empty;
+        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())));
@@ -8044,7 +8063,8 @@ void DesignPanel::rebuild_constraint_list()
     if (m_viewport)
         m_viewport->set_constraint_glyphs(cons);
 
-    m_cards->GetSizer()->Show(m_box_constraints, m_ui_mode == UiMode::Constrain, true);
+    m_cards->GetSizer()->Show(m_box_constraints,
+                              m_ui_mode == UiMode::Constrain || live, true);
     update_cards_frame(); m_form->Layout();
     m_form->FitInside();
 }
@@ -8053,9 +8073,13 @@ void DesignPanel::rebuild_constraint_list()
 // highlight (toggle off if the same row is clicked again).
 void DesignPanel::highlight_constraint_entities(int idx)
 {
-    if (!m_viewport || m_constrain_feat < 0 || m_constrain_feat >= int(m_doc.features.size()))
+    if (!m_viewport)
         return;
-    const auto& cons = m_doc.features[m_constrain_feat].entity_constraints;
+    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
@@ -8074,6 +8098,18 @@ void DesignPanel::highlight_constraint_entities(int idx)
 // 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];

src/slic3r/GUI/CAD/DesignPanel.hpp

@@ -240,6 +240,11 @@ private:
     // 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

src/slic3r/GUI/CAD/DesignSketchTool.cpp

@@ -2359,8 +2359,10 @@ bool DesignSketchTool::try_add_constraints(const std::vector<SketchEntityConstra
     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 (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
@@ -2381,13 +2383,20 @@ bool DesignSketchTool::remove_constraint_near(const Vec2d& p)
         if (d < best_d && g.con >= 0 && g.con < int(m_constraints.size())) { best_d = d; best = g.con; }
     }
     if (best < 0) return false;
-    m_constraints.erase(m_constraints.begin() + best);
+    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;
 }
 

src/slic3r/GUI/CAD/DesignSketchTool.hpp

@@ -442,6 +442,10 @@ public:
     // 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.
@@ -488,6 +492,9 @@ public:
     // 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