Windows: daemon cannot start — `loop.add_signal_handler` raises NotImplementedError in setup_signal_handlers

[fvegiard]

Summary

setup_signal_handlers() calls loop.add_signal_handler(), which is not implemented on Windows event loops. run_daemon calls it unconditionally, so the daemon dies with NotImplementedError immediately after subsystem init.

Still present on main @ 45b0ea0: runner_maintenance.py#L730-L731.

Traceback

File "...\gobby\runner_lifecycle.py", line 114, in run_daemon
  setup_signal_handlers(
      lambda: setattr(runner, "_shutdown_requested", True),
      shutdown_intent_callback=lambda intent: setattr(runner, "_shutdown_intent", intent),
  )
File "...\gobby\runner_maintenance.py", line 717, in setup_signal_handlers
  loop.add_signal_handler(sig, _make_handler(sig))
File "...\Lib\asyncio\events.py", line 599, in add_signal_handler
  raise NotImplementedError
NotImplementedError

Logged as Fatal error by runner_lifecycle.run_daemon; gobby start reports Health check failed.

Reproduce

On Windows, with the fcntl import blocker patched (filed separately), run gobby start.

Root cause

asyncio.ProactorEventLoop / SelectorEventLoop on Windows do not implement add_signal_handler — it is documented as Unix-only. The loop over (SIGTERM, SIGINT) has no platform guard.

Suggested fix

Fall back to signal.signal and marshal into the loop, which gives the same graceful-shutdown behaviour on Windows:

     for sig in (signal.SIGTERM, signal.SIGINT):
-        loop.add_signal_handler(sig, _make_handler(sig))
+        handler = _make_handler(sig)
+        try:
+            loop.add_signal_handler(sig, handler)
+        except NotImplementedError:  # Windows: event loops lack signal handlers
+            signal.signal(sig, lambda _s, _f, _h=handler: loop.call_soon_threadsafe(_h))

With this applied the daemon starts and stays up on Windows.

Note

This is the second of two sequential Windows blockers; the first is the unguarded fcntl/termios import in agents/tmux/pty_bridge.py, filed as #26. Both are needed to reach a running daemon.

Environment

• gobby 0.4.6 (installed via uv tool install)
• Python 3.13 (CPython, windows-x86_64)
• Windows 11 Pro 10.0.26220

[joshwilhelmi]

Fixed on the 0.5.0 branch in 2e63ec8. setup_signal_handlers falls back to signal.signal when the event loop lacks add_signal_handler, and schedules each signal's handler on the loop thread. Details in #28.