Ctrl+C in sloppy.py's terminal would hang the process when a worker of
the shared 4-thread I/O pool was mid-task in user code (e.g. a long-
running Gemini/Anthropic HTTP request). The hang chain:
1. SIGINT delivered to main thread
2. Python raises KeyboardInterrupt (default handler)
3. Exception propagates out of main()
4. Interpreter finalization begins
5. ThreadPoolExecutor.__del__ runs shutdown(wait=True)
6. shutdown(wait=True) joins all worker threads
7. The blocked worker never returns -> hang
An atexit-based fix (mirroring the conftest fix at 8957c9a5) was
attempted first: register pool.shutdown(wait=False) at pool creation.
Verified empirically that this DOES NOT WORK — atexit handlers do not
fire at all when a pool worker is blocked in user code. The hang still
occurs in ThreadPoolExecutor.__del__ -> shutdown(wait=True).
Production fix: a SIGINT handler installed by AppController.__init__
that drains the pool non-blockingly and calls os._exit(0), bypassing
the broken finalization chain. One wire covers all three modes
(GUI/headless/web) since they all create an AppController.
Files:
- src/app_controller.py: new module-level _install_sigint_exit_handler
helper called from __init__; one-line docstring at the function
level documents the rationale.
- tests/test_app_controller_sigint.py: new test file with 2 regression
tests (unit: handler is installed on main thread; subprocess: handler
exits within 2s when invoked with a blocked worker).
- tests/test_io_pool.py: module docstring updated to explain the
reverted atexit approach and point readers at the production fix.
Best-effort: signal.signal may fail on non-main threads (some conftest
warmup paths); failure is swallowed. The conftest's own atexit fix at
8957c9a5 covers the test fixture's normal-exit path.
