Per user feedback this round:
1. T-shirt size removed from conductor/workflow.md (policy),
conductor/tracks.md (registry), and the prior
NEGATIVE_FLOWS_INVESTIGATION_20260617.md report.
2. Layout regenerated from _default_windows (17KB -> 3KB, 10 stale
windows -> 3). Layout fix did NOT fix the crash.
Three new diagnostic experiments (results appended to the report):
- diag_no_click.py: process survives 60s without clicks (render loop
is stable in isolation; crash is click-triggered).
- diag_thread.py: standalone ThreadPoolExecutor + adapter call works
fine in all 3 MOCK_MODE modes (subprocess spawn is not the issue).
- diag_realbig2_run.py: bumping threading.stack_size(8MB) does NOT
prevent the crash (io_pool worker is not where the stack is exhausted).
Refined hypothesis: the crash is in the MAIN THREAD's imgui-bundle
render loop (1.94 MB stack), running concurrently with the io_pool
worker's adapter call. The subprocess spawn + CreateProcessW causes
the kernel to allocate resources at the moment the main thread is
deep in imgui-bundle C++ frames, exhausting the main thread's small
guard page.
What's needed for definitive diagnosis: a Windows crash dump (procdump
-ma or cdb.exe) to see the actual C-side stack frame, OR a
SetUnhandledExceptionFilter in sitecustomize.py that logs the
crashing thread's TEB and call stack to stderr before the process dies.
Per user feedback:
1. Removed T-shirt size metric from the report. The T-shirt size
convention is defined in conductor/tracks.md (lines 47, 738, 748,
790) and conductor/workflow.md (lines 574, 576, 587, 656) - it was
added 2026-06-16 as part of the no-day-estimates rule.
2. Re-investigated the actual call stack depth. The Python call chain
at crash time is only 13 frames deep. This is NOT a Python
recursion bug.
3. Measured the main thread stack via kernel32.GetCurrentThreadStackLimits.
It is 1.94 MB on this Python 3.11.6 installation. The sitecustomize
sets threading.stack_size(8MB) for NEW threads, but the main
thread was already created with its PE-header-baked 1.94MB.
4. Bumped io_pool workers to 8MB via threading.stack_size(8MB) in
sitecustomize.py. Process STILL dies with 0xC00000FD. So the
stack overflow is NOT in the io_pool worker. It is in the main
thread, running the imgui-bundle render loop.
5. The main thread is 1.94MB. After ~50-60 render frames, imgui-bundle's
native C++ stack usage accumulates. The click on btn_gen_send
triggers the io_pool worker AND continues the render loop. The
next render frame's C++ stack usage overflows the main thread's
1.94MB guard page, killing the process.
The fix is NOT about the io_pool thread stack. It is about either:
(a) reducing imgui-bundle's per-frame C++ stack usage (e.g., fix the
stale manualslop_layout.ini that references 10 deleted window
names - WARNING shown in every log since 2026-06-10)
(b) bumping the main thread's stack at the OS level (editbin /STACK
on python.exe)
(c) running the render loop in a subprocess
Capture a WER crash dump to identify the exact C-side stack frame
that overflows. Add SetUnhandledExceptionFilter via sitecustomize.py
to log the crashing thread's TEB to stderr before the process dies.
ed