Windows: daemon cannot start — unguarded `fcntl`/`termios` import in agents/tmux/pty_bridge.py

[fvegiard]

Summary

gobby/agents/tmux/pty_bridge.py imports fcntl and termios at module scope. Both are POSIX-only, so the daemon cannot start on Windows — the import chain runs during gobby start and dies before the runner comes up.

Still present on main @ 45b0ea0: pty_bridge.py#L11-L18.

Traceback

File "...\gobby\runner.py", line 219, in __init__
  from gobby.runner_init import (
File "...\gobby\runner_init\__init__.py", line 6, in <module>
  from gobby.runner_init.orchestration import init_orchestration
File "...\gobby\runner_init\orchestration.py", line 9, in <module>
  from gobby.agents.lifecycle_monitor import AgentLifecycleMonitor
File "...\gobby\agents\lifecycle_monitor.py", line 28, in <module>
  from gobby.agents.tmux.session_manager import TmuxSessionManager
File "...\gobby\agents\tmux\__init__.py", line 23, in <module>
  from gobby.agents.tmux.pty_bridge import TmuxPTYBridge
File "...\gobby\agents\tmux\pty_bridge.py", line 14, in <module>
  import fcntl
ModuleNotFoundError: No module named 'fcntl'

gobby start reports Health check failed and the daemon exits; the traceback lands in ~/.gobby/logs/gobby-error.log.

Reproduce

On Windows: uv tool install gobby then gobby start.

Root cause

gobby/agents/tmux/__init__.py unconditionally imports TmuxPTYBridge, and that module imports fcntl/termios at the top. Since lifecycle_monitor pulls in the tmux package during daemon init, there is no way to reach the runner on a platform without those modules.

Both are only used inside methods — fcntl.ioctl(..., termios.TIOCSWINSZ, ...) at lines 82 and 177 — so nothing at import time needs them.

Suggested fix

Guard the import; PTY bridging is inherently POSIX-only and can fail at call time instead of import time:

 import asyncio
-import fcntl
 import logging
 import os
 import struct
-import termios
 from dataclasses import dataclass, field
 from datetime import UTC, datetime
 
+try:  # POSIX-only: tmux PTY bridging is unavailable on Windows
+    import fcntl
+    import termios
+except ImportError:  # pragma: no cover - Windows
+    fcntl = None  # type: ignore[assignment]
+    termios = None  # type: ignore[assignment]
+
 from gobby.config.tmux import TmuxConfig

Ideally the two ioctl call sites would also raise a clear error when fcntl is None, rather than an AttributeError.

Note

Fixing this alone is not sufficient to start the daemon on Windows — the next blocker is loop.add_signal_handler raising NotImplementedError, filed separately.

Windows isn't listed as a supported platform in the README, but gobby/agents/tmux/wsl_compat.py (needs_wsl, convert_windows_path_to_wsl) suggests it's at least partly intended. Happy to open a PR if a Windows daemon is in scope.

Environment

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

[fvegiard]

The follow-on blocker referenced above is now filed as #27 (loop.add_signal_handler raising NotImplementedError). Both patches together are what got the daemon running on Windows 11 here.

[joshwilhelmi]

Fixed on the 0.5.0 branch in 2e63ec8. pty_bridge.py guards its fcntl/termios imports, and attach refuses clearly on Windows. Two other module-scope POSIX imports on the startup path were fixed in the same commit. Details in #28.