Tmux

tmux Session Control

Control tmux sessions by sending keystrokes and reading output. Essential for managing Claude Code sessions.

When to Use

• Monitoring Claude/Codex sessions in tmux
• Sending input to interactive terminal applications
• Scraping output from long-running processes
• Navigating tmux panes/windows programmatically

For one-off commands, non-interactive scripts, or starting new processes, use exec directly.

Example Sessions

Common Commands

List Sessions

tmux list-sessions
tmux ls

Capture Output

# Last 20 lines of pane
tmux capture-pane -t shared -p | tail -20

# Entire scrollback
tmux capture-pane -t shared -p -S -

# Specific pane in window
tmux capture-pane -t shared:0.0 -p

Send Keys

# Send text (doesn't press Enter)
tmux send-keys -t shared "hello"

# Send text + Enter
tmux send-keys -t shared "y" Enter

# Send special keys
tmux send-keys -t shared Enter
tmux send-keys -t shared Escape
tmux send-keys -t shared C-c          # Ctrl+C
tmux send-keys -t shared C-d          # Ctrl+D (EOF)
tmux send-keys -t shared C-z          # Ctrl+Z (suspend)

Window/Pane Navigation

# Select window
tmux select-window -t shared:0

# Select pane
tmux select-pane -t shared:0.1

# List windows
tmux list-windows -t shared

Session Management

# Create new session
tmux new-session -d -s newsession

# Kill session
tmux kill-session -t sessionname

# Rename session
tmux rename-session -t old new

Sending Input Safely

For interactive TUIs (Claude Code, Codex, etc.), split text and Enter into separate sends to avoid paste/multiline edge cases:

tmux send-keys -t shared -l -- "Please apply the patch in src/foo.ts"
sleep 0.1
tmux send-keys -t shared Enter

Claude Code Session Patterns

Check if Session Needs Input

# Look for prompts
tmux capture-pane -t worker-3 -p | tail -10 | grep -E "❯|Yes.*No|proceed|permission"

Approve Claude Code Prompt

# Send 'y' and Enter
tmux send-keys -t worker-3 'y' Enter

# Or select numbered option
tmux send-keys -t worker-3 '2' Enter

Check All Sessions Status

for s in shared worker-2 worker-3 worker-4 worker-5 worker-6 worker-7 worker-8; do
  echo "=== $s ==="
  tmux capture-pane -t $s -p 2>/dev/null | tail -5
done

Send Task to Session

tmux send-keys -t worker-4 "Fix the bug in auth.js" Enter

Notes

• Use capture-pane -p to print to stdout (essential for scripting)
• -S - captures entire scrollback history
• Target format: session:window.pane (e.g., shared:0.0)
• Sessions persist across SSH disconnects