fix(cli): stop main() leaking SIGPIPE=SIG_DFL into the process (sy-6zq)#533
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…q, sy-1n1) main() installed SIGPIPE=SIG_DFL (so piped CLI output ends silently like a normal Unix tool) but never restored it. The disposition is process-global, and main() is imported and called directly by ~10 tests plus library callers — so SIG_DFL leaked into the pytest process. A later unrelated broken-pipe write during output capture or coverage teardown was then delivered as SIGPIPE, silently killing the runner with exit 141. Which CI matrix entry died was non-deterministic (depends on test ordering), which is why the flake appeared to wander across Python 3.11/3.12/3.14 and blocked the merge queue. Fix has two layers: - main() snapshots the prior SIGPIPE handler (signal.getsignal) and restores it in the finally block. CLI piping behavior during the run is unchanged; the global disposition simply no longer outlives the invocation. - conftest.py adds an autouse fixture that restores SIGPIPE around every test, making this class of leak structurally impossible regardless of which code paths a test exercises (mirrors the existing network-block fixture). isatty() gating was rejected: stdout is not a tty exactly when piped to head, which is the case the SIG_DFL restore exists to handle. Verified: full suite 3039 passed (no exit 141, 87% cov); broken-pipe + shim tests 14 passed; CLI piping stays silent and exits 0; ruff clean. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
main()installedSIGPIPE=SIG_DFL(so piped CLI output ends silently like a normal Unix tool) but never restored it. The SIGPIPE disposition is process-global, andmain()is imported and called directly by ~10 tests plus library callers — soSIG_DFLleaked into the pytest process. A later unrelated broken-pipe write during output capture or coverage teardown was then delivered as SIGPIPE, silently killing the CI runner with exit 141. Which matrix entry died was non-deterministic (depends on test ordering), which is why the flake wandered across Python 3.11/3.12/3.14 and intermittently blocked the merge queue.Changes
src/synth_panel/main.py:main()now snapshots the prior SIGPIPE handler viasignal.getsignal()and restores it in afinallyblock. CLI piping behavior during the run is unchanged; the global disposition simply no longer outlives the invocation.tests/conftest.py: adds an autouse fixture that restores SIGPIPE around every test, making this class of leak structurally impossible regardless of which code paths a test exercises (mirrors the existing network-block fixture).isatty()gating was rejected: stdout is not a tty exactly when piped tohead, which is the case theSIG_DFLrestore exists to handle.Test plan
tests/test_broken_pipe.py+ shim: 14 passed.synthpanel … | head) stays silent and exits 0.ruffclean.References