From 9dc50cef727713575972674dbd8a323e764c2d9f Mon Sep 17 00:00:00 2001
From: forbes <zoe.forbes@kindred-systems.com>
Date: Thu, 29 Jan 2026 23:54:10 -0600
Subject: [PATCH] Fix SIGSEGV in Assembly solver during document restore

AssemblyObject::onChanged() was calling updateSolveStatus() when the
Group property changed during document restore. This triggered the
solver (solve -> validateNewPlacements) while child objects were still
being deserialized, causing a segfault in validateNewPlacements() due
to accessing uninitialized data.

Add isRestoring() and isPerformingTransaction() guards matching the
pattern used by GroupExtension::onChanged() and other FreeCAD modules.
---
 src/Mod/Assembly/App/AssemblyObject.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/Mod/Assembly/App/AssemblyObject.cpp b/src/Mod/Assembly/App/AssemblyObject.cpp
index 859859cecf..4cd4c1fec6 100644
--- a/src/Mod/Assembly/App/AssemblyObject.cpp
+++ b/src/Mod/Assembly/App/AssemblyObject.cpp
@@ -139,7 +139,10 @@ App::DocumentObjectExecReturn* AssemblyObject::execute()
 
 void AssemblyObject::onChanged(const App::Property* prop)
 {
-    if (prop == &Group) {
+    if (prop == &Group
+        && !isRestoring()
+        && getDocument()
+        && !getDocument()->isPerformingTransaction()) {
         updateSolveStatus();
     }
     App::Part::onChanged(prop);