blender-core-runtime

Blender Python crashes after undo/redo occur because storing direct bpy.data object references creates dangling pointers. Store names or identifiers instead of object references across undo boundaries to prevent ReferenceError and instability.

To safely call bpy from background threads, route all Blender API work through bpy.app.timers to ensure main-thread execution. Worker threads should perform pure computation only, avoiding direct bpy access to prevent runtime crashes.

Correct KDTree and BVHTree usage requires calling kd.balance() before queries and using an evaluated depsgraph for BVHTree geometry evaluation. Ensuring proper depsgraph behavior prevents invalid spatial query results during addon runtime.

Prevent freezing by using @persistent handlers, performing proper handler cleanup on unregister(), and following safe msgbus subscription patterns. Correct timer return conventions keep addons stable across file loads without freezing.

Incorrect mathutils matrix transformations happen when using wrong multiplication operators. Use the @ operator for matrix multiplication and .length_squared for vector comparisons to ensure correct math operations and avoid runtime errors.

Yes, Blender Python timers can safely handle depsgraph updates by enforcing main-thread bpy access and proper timer return conventions. This approach avoids runtime crashes when listening to depsgraph changes and updating geometry.