tmux session detection only works on the default socket — custom -L/-S sockets and TMUX_TMPDIR are not detected (diff viewer greyed out)

[bedfordsean]

(Filing here as moshi-hooks is archived and homebrew-moshi has issues disabled — happy to move this wherever you prefer.)

Environment: moshi-hook 0.2.63 (brew), macOS 15 (arm64), iOS app with Pro, mosh + SSH sessions.

Summary

Remote tmux session detection (moshi-hook context --ssh-connection/--mosh-port) only detects tmux when the server runs on the literal default socket /tmp/tmux-<uid>/default. Two common setups break it:

1. Custom socket (tmux -L name or tmux -S /path/sock)
2. TMUX_TMPDIR relocation (still default-socket semantics, different directory — a common macOS setup because /private/tmp gets periodically cleaned)

In both cases context falls back to the login shell:

$ moshi-hook context --mosh-port 60001   # session IS attached to tmux (custom socket)
{
  "kind": "shell",
  "cwd": "/Users/sean"
}

Consequence: the diff viewer button stays greyed out for any tmux user with a non-stock socket (cwd resolves to the login shell's ~, which isn't a git repo), while plain no-tmux shells work fine. Everything else (pairing, tmux picker, gateway) works with custom sockets, so the greyed diff button looks like a client bug rather than a socket-path issue — took a while to pin down.

Migrating our servers to the true default socket fixed detection completely, confirming by elimination.

Suggested fixes (any one would do)

• Resolve the socket from the attached tmux client process argv (-S/-L are visible under the session's process tree), or from $TMUX of any pane process
• Honor TMUX_TMPDIR when probing the default socket
• Or an env override on the daemon, e.g. MOSHI_TMUX_SOCKET, analogous to the existing MOSHI_HERDR_PATH

Related packaging note

The brew service plist ships no PATH in EnvironmentVariables, so the daemon runs with the bare system PATH — on a stock homebrew-tmux Mac the daemon itself can't find tmux for its gateway/capture spawns until the user hand-patches the plist (which brew services restart reverts). Consider baking a sane PATH into the formula's service block.

Happy to test builds — the app is excellent, this was the one rough edge.