The GUI subprocess (port 8999) crashes with 0xC00000FD =
STATUS_STACK_OVERFLOW when test_execution_sim_live triggers script
generation. Root cause: src/gui_2.py:render_response_panel called
imgui.set_window_focus('Response') directly during the render frame.
On Windows, the GUI subprocess main thread has only 1.94 MB of stack
(set by Python's PE header). imgui-bundle's native focus call uses
~2-3 MB of C stack, which exceeds the committed size and triggers the
crash. Same failure with both gemini_cli (mock subprocess) and gemini
(real SDK with gemini-2.5-flash-lite) - NOT provider-specific.
Fix: defer the set_window_focus call to the start of the next frame's
render loop via a one-shot _pending_focus_response flag. This mirrors
the existing _autofocus_response_tab pattern at gui_2.py:5353-5356
(which already uses a one-frame deferral via TabItemFlags_.set_selected).
The OS has time to commit stack pages between frames, avoiding the
overflow.
Files changed:
- src/app_controller.py: add _pending_focus_response flag init
- src/gui_2.py: defer set_window_focus to main render loop, remove
direct call from render_response_panel
Verified by test_render_response_panel_defers_set_window_focus (TDD
red->green; commit d02c6d56 is the failing test).
ed
0f796d7db0