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=${TMPDIR:-/tmp}/claude-tmux-sockets  # well-known dir for all agent sockets
mkdir -p "$SOCKET_DIR"
SOCKET="$SOCKET_DIR/claude.sock"                # keep agent sessions separate from your personal tmux
SESSION=claude-python                           # slug-like names; avoid spaces
tmux -S "$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 claude-lldb

Or to capture the output once:
  tmux -S "$SOCKET" capture-pane -p -J -t claude-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 CLAUDE_TMUX_SOCKET_DIR (defaults to ${TMPDIR:-/tmp}/claude-tmux-sockets) and use tmux -S "$SOCKET" so we can enumerate/clean them. Create the dir first: mkdir -p "$CLAUDE_TMUX_SOCKET_DIR".
• Default socket path to use unless you must isolate further: SOCKET="$CLAUDE_TMUX_SOCKET_DIR/claude.sock".

Targeting panes and naming

• Target format: {session}:{window}.{pane}, defaults to :0.0 if omitted. Keep names short (e.g., claude-py, claude-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.

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 "$SOCKET" capture-pane -p -J -t target -S -200.
• For continuous monitoring, poll instead of tmux wait-for (which does not watch pane output).
• You can also temporarily attach to observe: tmux -L "$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.

Spawning Processes

• When asked to debug, use lldb by default.
• When starting a python interactive shell, always set the PYTHON_BASIC_REPL=1 environment variable. The non-basic console interferes with send-keys.

Synchronizing / waiting for prompts

• Use timed polling to avoid races with interactive tools.
• For long-running commands, poll for completion text 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; 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.