dpaluy/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=${TMPDIR:-/tmp}/agent-tmux-sockets  # well-known dir for all agent sockets
mkdir -p "$SOCKET_DIR"
SOCKET="$SOCKET_DIR/agent.sock"                # keep agent sessions separate from your personal tmux
SESSION=app-name-command                       # slug-like names; avoid spaces
tmux -S "$SOCKET" new -d -s "$SESSION" -n shell
TARGET=$(tmux -S "$SOCKET" list-panes -t "$SESSION" -F '#S:#I.#P' | head -n1)
tmux -S "$SOCKET" send-keys -t "$TARGET" -- 'pnpm run dev' Enter
tmux -S "$SOCKET" capture-pane -p -J -t "$TARGET" -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 $SESSION

Or to capture the output once:
  TARGET=$(tmux -S "$SOCKET" list-panes -t $SESSION -F '#S:#I.#P' | head -n1)
  tmux -S "$SOCKET" capture-pane -p -J -t "$TARGET" -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 AGENT_TMUX_SOCKET_DIR (defaults to ${TMPDIR:-/tmp}/agent-tmux-sockets) and use tmux -S "$SOCKET" so we can enumerate/clean them. Create the dir first: mkdir -p "$AGENT_TMUX_SOCKET_DIR".
• Default socket path to use unless you must isolate further: SOCKET="$AGENT_TMUX_SOCKET_DIR/agent.sock".
• tmux reads the user's config when a server starts. If you connect to an already-running server on that socket, its existing options (like base-index/pane-base-index) stay in effect even if the user's config is different now.
• If you need deterministic fresh tmux state, use a unique socket path or kill the existing server on that socket first. Use -f /dev/null only when you explicitly want stock tmux behavior.

Targeting panes and naming

• Target format: {session}:{window}.{pane}. Examples like :0.0 and :1.1 are both valid depending on tmux server options.
• Never hardcode pane indices from an example. Always discover the real target after creating a session: TARGET=$(tmux -S "$SOCKET" list-panes -t "$SESSION" -F '#S:#I.#P' | head -n1).
• User tmux config can change numbering via base-index and pane-base-index, but only for freshly started servers. Reused sockets may still be using older/default numbering.
• Use -S "$SOCKET" consistently to stay on the private socket path.
• Inspect: tmux -S "$SOCKET" list-sessions, tmux -S "$SOCKET" list-panes -a, tmux -S "$SOCKET" show-options -g | rg '^base-index', tmux -S "$SOCKET" show-window-options -g | rg '^pane-base-index'.

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 AGENT_TMUX_SOCKET_DIR or ${TMPDIR:-/tmp}/agent-tmux-sockets).

Sending input safely

• Prefer literal sends to avoid shell splitting: tmux -S "$SOCKET" send-keys -t target -l -- "$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 -S "$SOCKET" capture-pane -p -J -t target -S -200.
• For continuous monitoring, poll with the helper script (below) instead of tmux wait-for (which does not watch pane output).
• You can also temporarily attach to observe: tmux -S "$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:

  TARGET=$(tmux -S "$SOCKET" list-panes -t "$SESSION" -F '#S:#I.#P' | head -n1)
  ./scripts/wait-for-text.sh -S "$SOCKET" -t "$TARGET" -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 [-L socket-name|-S socket-path] -t session:window.pane -p 'pattern' [-F] [-T 20] [-i 0.5] [-l 2000]

• -L/--socket tmux socket name passed to tmux -L
• -S/--socket-path tmux socket path passed to tmux -S
• -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.