Tmux CLI

tmux-cli

Instructions

• Use the tmux-cli command to communicate with other CLI Agents or Scripts in other tmux panes. Do tmux-cli --help to see how to use it!
  • This command depends on installing the claude-code-tools. If you get an error indicating that the command is not available, ask the user to install it using: uv tool install claude-code-tools.
  • When using tmux-cli to connect to remote machines you must run it outside the sandbox (the tmux socket is outside the sandbox's allowed paths, and the pane's ssh needs the environment's SSH auth). A sandboxed capture returns empty. Allow-list tmux-cli once to avoid repeated approval prompts.
• When you are finished with all tasks that you need tmux-cli for clean up the session.

Remote SSH hosts (default pattern)

When you need to run more than one command on a remote host over SSH, do NOT issue repeated one-off ssh host 'cmd' calls - each re-authenticates and needs its own approval. Open ONE persistent session and drive it. This is the default for any multi-command remote work.

1. Reuse an existing session rather than spawning a new one each task (windows accumulate otherwise): check tmux-cli status / tmux-cli list_panes, reuse its pane if healthy, and only tmux-cli launch "zsh" if none exists. Note the returned pane id.
2. Arm auto-cleanup on the pane BEFORE connecting, so nothing lingers if the task is abandoned:
   • Idle timeout: export TMOUT=1800 in the launched zsh (self-exits after 30 min idle at a prompt).
   • Hard cap watchdog (zsh): ( sleep 5400 && tmux kill-session -t remote-cli-session ) &! - kills the whole session after 90 min regardless of activity. tmux-cli's remote session is named remote-cli-session on the default socket, so raw tmux can target it. &! backgrounds and disowns so it survives the shell exiting.
3. Connect with keepalive so a dropped link tears itself down: ssh -o ServerAliveInterval=60 -o ServerAliveCountMax=3 -o StrictHostKeyChecking=no user@host.
4. After connecting, set the same idle timeout on the remote shell (busybox ash and bash both honour it): export TMOUT=1800.
5. Run work with send + wait_idle + capture. Only the pane's ssh uses the network / SSH auth; tmux-cli itself only talks to the local tmux socket.
6. Tear it down explicitly when done: tmux-cli cleanup kills the managed session; tmux-cli kill --pane=<id> kills a single pane. Do not leave idle sessions behind - the timeouts above are a backstop, not a substitute for cleanup.

Key Commands

Execute with Exit Code Detection

Use tmux-cli execute when you need to know if a shell command succeeded or failed:

tmux-cli execute "make test" --pane=2
# Returns JSON: {"output": "...", "exit_code": 0}

tmux-cli execute "npm install" --pane=ops:1.3 --timeout=60
# Returns exit_code=0 on success, non-zero on failure, -1 on timeout

This is useful for:

• Running builds and knowing if they passed
• Running tests and detecting pass/fail
• Multi-step automation that should abort on failure

Note: execute is for shell commands only, not for agent-to-agent chat.

Tips

• For communicating with another Claude Code instance, use send + wait_idle + capture instead.
• To wait for a condition, use Monitor with an until-loop (e.g. until <check>; do sleep 2; done), to wait for a command you started, use run_in_background: true.