tmux

name	tmux
description	Use when you need a persistent terminal environment for long-running processes, programs requiring a TTY, REPLs, debuggers, TUI apps, or concurrent terminals — while the agent continues executing other commands.

tmux (agent automation) skill

Purpose

You are not teaching the human tmux. You are using tmux yourself as a controllable terminal multiplexer to:

• run long-lived processes (servers, watchers, debuggers)
• interact with programs that need a TTY
• keep state across multiple commands (REPLs, shells)
• run multiple concurrent terminals (logs in one pane, debugger in another)

Prime directive (don't trash the user's tmux)

Use a dedicated session in the user's existing tmux server.

• Session name: ai-agent-sandbox
• Do NOT create a separate socket (-L) — work within the user's existing tmux server
• Only manipulate ai-agent-sandbox, never touch user's other sessions

Targets (tmux addressing)

Always use explicit targets.

• full target format: ai-agent-sandbox:<window>.<pane>
• examples: ai-agent-sandbox:main.1, ai-agent-sandbox:1.1

Check indexing first — don't assume 0 or 1:

tmux display-message -p "#{base-index}"

Standard workflow

1) Ensure session exists

tmux start-server
tmux has-session -t ai-agent-sandbox 2>/dev/null \
  || tmux new-session -d -s ai-agent-sandbox -n main

2) Create panes/windows as needed

tmux split-window -t ai-agent-sandbox:main -h
tmux select-layout -t ai-agent-sandbox:main even-horizontal

3) Send commands

tmux send-keys -t ai-agent-sandbox:main.1 "bash -lc 'rg -n \"TODO\" .'" C-m

• Prefer bash -lc '…' for a predictable shell environment
• Keep the tmux string simple; let bash -lc handle quoting complexity

4) Synchronize — never use sleep

Use tmux wait-for for deterministic completion:

TOKEN="AI_AGENT_DONE_$$"

# send command in pane, signal token on finish
tmux send-keys -t ai-agent-sandbox:main.1 \
  "bash -lc 'set -e; rg -n \"TODO\" .; tmux wait-for -S ${TOKEN}'" C-m

# block until done
tmux wait-for "${TOKEN}"

If the command might fail but you still need completion:

bash -lc 'set +e; <cmd>; echo EXIT:$?; tmux wait-for -S TOKEN'

5) Capture output

# last 200 lines
tmux capture-pane -p -t ai-agent-sandbox:main.1 -S -200

For full buffer, increase history first:

tmux set-option -t ai-agent-sandbox -g history-limit 20000

Common recipes

Long-lived server + health check

# start server in pane 1
tmux send-keys -t ai-agent-sandbox:main.1 "bash -lc 'bin/dev'" C-m

# check health in pane 2
tmux send-keys -t ai-agent-sandbox:main.2 "bash -lc 'sleep 1; curl -fsS localhost:3000/health'" C-m

Stream logs to disk:

LOG=/tmp/ai-agent-tmux-main1.log
: >"$LOG"
tmux pipe-pane -o -t ai-agent-sandbox:main.1 "cat >> '$LOG'"

Stop a stuck command

tmux send-keys -t ai-agent-sandbox:main.1 C-c

Interactive REPL / debugger

1. Start REPL in a pane
2. Send lines via send-keys
3. Capture output after each step
4. Synchronize with wait-for or detect prompts via captured output

Guardrails

• Never tmux kill-server — kill only your session
• Always use explicit -t <target>
• Never tmux attach unless the user asked for a live view
• Don't rely on user keybindings; use the tmux CLI only

Cleanup

tmux kill-session -t ai-agent-sandbox