diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 3cbdc25f5f..995c4bd74d 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -56,6 +56,40 @@ function(orcaslicer_discover_tests TARGET)
     catch_discover_tests(${TARGET} ADD_TAGS_AS_LABELS)
 endfunction()
 
+# Stages a private Python runtime beside TARGET's output and (on macOS) links
+# in the matching rpath, so an embedded pybind11 interpreter in TARGET can find
+# libpython/the stdlib at runtime without depending on the build machine's
+# Python install. Apply this to every test target that embeds an interpreter -
+# duplicating the WIN32/APPLE blocks by hand lets them drift out of sync.
+function(orcaslicer_stage_test_python_runtime TARGET)
+    if (WIN32)
+        add_custom_command(TARGET ${TARGET} POST_BUILD
+            COMMAND ${CMAKE_COMMAND} -E make_directory "$<TARGET_FILE_DIR:${TARGET}>/python"
+            COMMAND ${CMAKE_COMMAND} -E copy_directory "${CMAKE_PREFIX_PATH}/libpython" "$<TARGET_FILE_DIR:${TARGET}>/python"
+            COMMAND ${CMAKE_COMMAND} -E copy_if_different
+                "${CMAKE_PREFIX_PATH}/libpython/python${_bundled_python_abi}.dll"
+                "${CMAKE_PREFIX_PATH}/libpython/vcruntime140.dll"
+                "${CMAKE_PREFIX_PATH}/libpython/vcruntime140_1.dll"
+                "$<TARGET_FILE_DIR:${TARGET}>"
+            COMMENT "Copying Python runtime for ${TARGET}"
+            VERBATIM
+        )
+    elseif (APPLE)
+        target_link_options(${TARGET} PRIVATE
+            "LINKER:-rpath,@executable_path/python/lib")
+
+        add_custom_command(TARGET ${TARGET} POST_BUILD
+            COMMAND ${CMAKE_COMMAND} -E rm -rf
+                "$<TARGET_FILE_DIR:${TARGET}>/python"
+            COMMAND ${CMAKE_COMMAND} -E copy_directory
+                "${CMAKE_PREFIX_PATH}/libpython"
+                "$<TARGET_FILE_DIR:${TARGET}>/python"
+            COMMENT "Copying Python runtime for ${TARGET}"
+            VERBATIM
+        )
+    endif()
+endfunction()
+
 add_subdirectory(libnest2d)
 add_subdirectory(libslic3r)
 add_subdirectory(slic3rutils)
diff --git a/tests/slic3rutils/CMakeLists.txt b/tests/slic3rutils/CMakeLists.txt
index 16c19910ee..fb1fec2e73 100644
--- a/tests/slic3rutils/CMakeLists.txt
+++ b/tests/slic3rutils/CMakeLists.txt
@@ -31,32 +31,7 @@ set_property(TARGET ${_TEST_NAME}_tests PROPERTY FOLDER "tests")
 
 orcaslicer_copy_test_dlls()
 
-if (WIN32)
-    add_custom_command(TARGET ${_TEST_NAME}_tests POST_BUILD
-        COMMAND ${CMAKE_COMMAND} -E make_directory "$<TARGET_FILE_DIR:${_TEST_NAME}_tests>/python"
-        COMMAND ${CMAKE_COMMAND} -E copy_directory "${CMAKE_PREFIX_PATH}/libpython" "$<TARGET_FILE_DIR:${_TEST_NAME}_tests>/python"
-        COMMAND ${CMAKE_COMMAND} -E copy_if_different
-            "${CMAKE_PREFIX_PATH}/libpython/python${_bundled_python_abi}.dll"
-            "${CMAKE_PREFIX_PATH}/libpython/vcruntime140.dll"
-            "${CMAKE_PREFIX_PATH}/libpython/vcruntime140_1.dll"
-            "$<TARGET_FILE_DIR:${_TEST_NAME}_tests>"
-        COMMENT "Copying Python runtime for slic3rutils plugin host API tests"
-        VERBATIM
-    )
-elseif (APPLE)
-    target_link_options(${_TEST_NAME}_tests PRIVATE
-        "LINKER:-rpath,@executable_path/python/lib")
-
-    add_custom_command(TARGET ${_TEST_NAME}_tests POST_BUILD
-        COMMAND ${CMAKE_COMMAND} -E rm -rf
-            "$<TARGET_FILE_DIR:${_TEST_NAME}_tests>/python"
-        COMMAND ${CMAKE_COMMAND} -E copy_directory
-            "${CMAKE_PREFIX_PATH}/libpython"
-            "$<TARGET_FILE_DIR:${_TEST_NAME}_tests>/python"
-        COMMENT "Copying Python runtime for macOS plugin host API tests"
-        VERBATIM
-    )
-endif()
+orcaslicer_stage_test_python_runtime(${_TEST_NAME}_tests)
 
 orcaslicer_discover_tests(${_TEST_NAME}_tests)
 
@@ -71,10 +46,12 @@ endif ()
 target_link_libraries(printer_agent_plugin_tests test_common libslic3r_gui libslic3r pybind11::embed Catch2::Catch2)
 set_property(TARGET printer_agent_plugin_tests PROPERTY FOLDER "tests")
 
-# why: the existing target stages the complete bundled Python home under
-# python/, which is the layout PythonInterpreter discovers beside the test exe.
+# why: both targets' post-build steps stage/clear the same python/ directory
+# beside the shared test output dir; serialize them so the copies can't race.
 add_dependencies(printer_agent_plugin_tests ${_TEST_NAME}_tests)
 
 orcaslicer_copy_test_dlls()
 
+orcaslicer_stage_test_python_runtime(printer_agent_plugin_tests)
+
 orcaslicer_discover_tests(printer_agent_plugin_tests)
diff --git a/tests/slic3rutils/test_printer_agent.cpp b/tests/slic3rutils/test_printer_agent.cpp
index c97d70099c..7a2fb24e7b 100644
--- a/tests/slic3rutils/test_printer_agent.cpp
+++ b/tests/slic3rutils/test_printer_agent.cpp
@@ -5,6 +5,8 @@
 #include <slic3r/Utils/NetworkAgentFactory.hpp>
 #include <slic3r/plugin/PythonPluginBridge.hpp>
 
+#include "python_test_support.hpp"
+
 #include <pybind11/embed.h>
 #include <pybind11/pybind11.h>
 
@@ -209,29 +211,11 @@ TEST_CASE("unit: printer-agent registry register / lookup / duplicate-reject", "
 // every printer-agent plugin subclasses. If a binding is renamed or removed,
 // plugins fail at runtime even though C++ still compiles.
 // ===========================================================================
-namespace {
-
-void ensure_python_initialized()
-{
-    // why: the `orca` module is embedded in this binary, so a bare interpreter
-    // can import it without a bundled Python home. The app interpreter expects
-    // that deployed layout, which is not present beside this test binary.
-    if (!Py_IsInitialized()) {
-        static py::scoped_interpreter interpreter;
-        (void) interpreter;
-    }
-}
-
-py::module_ import_orca_module()
-{
-    ensure_python_initialized();
-    // Force PythonPluginBridge.cpp into the binary so the embedded
-    // PYBIND11_EMBEDDED_MODULE(orca, ...) registration (incl. printer_agent) exists.
-    (void) Slic3r::PythonPluginBridge::instance();
-    return py::module_::import("orca");
-}
-
-} // namespace
+// ensure_python_initialized()/import_orca_module() come from python_test_support.hpp:
+// a bare scoped_interpreter with no PyConfig.home falls back to the build-time
+// stdlib path, which doesn't exist beside this test binary, so Py_Initialize()
+// fails to load the codecs needed for the filesystem encoding. The shared helper
+// points PyConfig.home at the python/ runtime staged next to the test executable.
 
 TEST_CASE("integration: orca.printer_agent binding surface", "[integration][Python]")
 {