tmux

name	tmux
description	Remote control tmux sessions for interactive CLIs (python, gdb, etc.) by sending keystrokes and scraping pane output.
license	Vibecoded
references	["https://github.com/mitsuhiko/agent-stuff/tree/main/skills/tmux"]

tmux Skill

Use tmux as a programmable terminal multiplexer for interactive work. Works on Linux and macOS with stock tmux; avoid custom config by using a private socket.

Quickstart (isolated socket)

SOCKET_DIR=${TMPDIR:-/tmp}/pi-tmux-sockets  # well-known dir for all agent sockets
mkdir -p "$SOCKET_DIR"
SOCKET="$SOCKET_DIR/pi.sock"                # keep agent sessions separate from personal tmux
SESSION=pi-python                           # slug-like names; avoid spaces
tmux -S "$SOCKET" new -d -s "$SESSION" -n shell
tmux -S "$SOCKET" send-keys -t "$SESSION":0.0 -- 'python3 -q' Enter
tmux -S "$SOCKET" capture-pane -p -J -t "$SESSION":0.0 -S -200  # watch output
tmux -S "$SOCKET" kill-session -t "$SESSION"                   # clean up

After starting a session ALWAYS tell the user how to monitor the session by giving them a command to copy paste:

To monitor this session yourself:
  tmux -S "$SOCKET" attach -t pi-lldb

Or to capture the output once:
  tmux -S "$SOCKET" capture-pane -p -J -t pi-lldb:0.0 -S -200

This must ALWAYS be printed right after a session was started and once again at the end of the tool loop. But the earlier you send it, the happier the user will be.

Socket convention

• Agents MUST place tmux sockets under PI_TMUX_SOCKET_DIR (defaults to ${TMPDIR:-/tmp}/pi-tmux-sockets) and use tmux -S "$SOCKET" so we can enumerate/clean them. Create the dir first: mkdir -p "$PI_TMUX_SOCKET_DIR".
• Default socket path to use unless you must isolate further: SOCKET="$PI_TMUX_SOCKET_DIR/pi.sock".

Running inside cmux (user's tmux session)

When running inside a cmux workspace, the user already has a tmux session (named cmux-{workspace_id}). $TMUX will be set.

For user-visible work (dev servers, test runners, build watchers), create windows/panes in the user's existing session:

tmux new-window -n "dev-server" -c "/path/to/project"
tmux send-keys -t "dev-server" 'npm run dev' Enter
tmux capture-pane -p -J -t "dev-server" -S -200

For isolated agent work (REPL exploration, experiments the user didn't ask to see), use the private socket as described below.

Rule: If the user asked you to run something, put it in their session. If you need to explore interactively as part of your own reasoning, use the private socket.

Targeting panes and naming

• Target format: {session}:{window}.{pane}, defaults to :0.0 if omitted. Keep names short (e.g., pi-py, pi-gdb).
• Use -S "$SOCKET" consistently to stay on the private socket path. If you need user config, drop -f /dev/null; otherwise -f /dev/null gives a clean config.
• Inspect: tmux -S "$SOCKET" list-sessions, tmux -S "$SOCKET" list-panes -a.

Finding sessions

• List sessions on your active socket with metadata: ./scripts/find-sessions.sh -S "$SOCKET"; add -q partial-name to filter.
• Scan all sockets under the shared directory: ./scripts/find-sessions.sh --all (uses PI_TMUX_SOCKET_DIR or ${TMPDIR:-/tmp}/pi-tmux-sockets).

Sending input safely

• Prefer literal sends to avoid shell splitting: tmux -L "$SOCKET" send-keys -t target -l -- "$cmd"
• When composing inline commands, use single quotes or ANSI C quoting to avoid expansion: tmux ... send-keys -t target -- $'python3 -m http.server 8000'.
• To send control keys: tmux ... send-keys -t target C-c, C-d, C-z, Escape, etc.

Watching output

• Capture recent history (joined lines to avoid wrapping artifacts): tmux -L "$SOCKET" capture-pane -p -J -t target -S -200.
• For continuous monitoring, poll with the helper script (below) instead of tmux wait-for (which does not watch pane output).
• You can also temporarily attach to observe: tmux -L "$SOCKET" attach -t "$SESSION"; detach with Ctrl+b d.
• When giving instructions to a user, explicitly print a copy/paste monitor command alongside the action don't assume they remembered the command.

Spawning Processes

Some special rules for processes:

• when asked to debug, use lldb by default
• when starting a python interactive shell, always set the PYTHON_BASIC_REPL=1 environment variable. This is very important as the non-basic console interferes with your send-keys.

Synchronizing / waiting for prompts

• Use timed polling to avoid races with interactive tools. Example: wait for a Python prompt before sending code:

  ./scripts/wait-for-text.sh -t "$SESSION":0.0 -p '^>>>' -T 15 -l 4000
  

• For long-running commands, poll for completion text ("Type quit to exit", "Program exited", etc.) before proceeding.

Interactive tool recipes

• Python REPL: tmux ... send-keys -- 'python3 -q' Enter; wait for ^>>>; send code with -l; interrupt with C-c. Always with PYTHON_BASIC_REPL.
• gdb: tmux ... send-keys -- 'gdb --quiet ./a.out' Enter; disable paging tmux ... send-keys -- 'set pagination off' Enter; break with C-c; issue bt, info locals, etc.; exit via quit then confirm y.
• Other TTY apps (ipdb, psql, mysql, node, bash): same pattern—start the program, poll for its prompt, then send literal text and Enter.

Cleanup

• Kill a session when done: tmux -S "$SOCKET" kill-session -t "$SESSION".
• Kill all sessions on a socket: tmux -S "$SOCKET" list-sessions -F '#{session_name}' | xargs -r -n1 tmux -S "$SOCKET" kill-session -t.
• Remove everything on the private socket: tmux -S "$SOCKET" kill-server.

Helper: wait-for-text.sh

./scripts/wait-for-text.sh polls a pane for a regex (or fixed string) with a timeout. Works on Linux/macOS with bash + tmux + grep.

./scripts/wait-for-text.sh -t session:0.0 -p 'pattern' [-F] [-T 20] [-i 0.5] [-l 2000]

• -t/--target pane target (required)
• -p/--pattern regex to match (required); add -F for fixed string
• -T timeout seconds (integer, default 15)
• -i poll interval seconds (default 0.5)
• -l history lines to search from the pane (integer, default 1000)
• Exits 0 on first match, 1 on timeout. On failure prints the last captured text to stderr to aid debugging.