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* fix(gateway): bound lifespan shutdown hooks to prevent worker hang Gateway worker can hang indefinitely in `uvicorn --reload` mode with the listening socket still bound — all /api/* requests return 504, and SIGKILL is the only recovery. Root cause (py-spy dump from a reproduction showed 16+ stacked frames of signal_handler -> Event.set -> threading.Lock.__enter__ on the main thread): CPython's `threading.Event` uses `Condition(Lock())` where the inner Lock is non-reentrant. uvicorn's BaseReload signal handler calls `should_exit.set()` directly from signal context; if a second signal (SIGTERM/SIGHUP from the reload supervisor, or watchfiles-triggered reload) arrives while the first handler holds the Lock, the reentrant call deadlocks on itself. The reload supervisor keeps sending those signals only when the worker fails to exit promptly. DeerFlow's lifespan currently awaits `stop_channel_service()` with no timeout; if a channel's `stop()` stalls (e.g. Feishu/Slack WebSocket waiting for an ack), the worker can't exit, the supervisor keeps signaling, and the deadlock becomes reachable. This is a defense-in-depth fix — it does not repair the upstream uvicorn/CPython issue, but it ensures DeerFlow's lifespan exits within a bounded window so the supervisor has no reason to keep firing signals. No behavior change on the happy path. Wraps the shutdown hook in `asyncio.wait_for(timeout=5.0)` and logs a warning on timeout before proceeding to worker exit. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * Update backend/app/gateway/app.py Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * style: apply make format (ruff) to test assertions Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com> Co-authored-by: Willem Jiang <willem.jiang@gmail.com> Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>