Smux

smux

Tmux pane control and cross-pane agent communication. Use tmux-bridge (the high-level CLI) for all cross-pane interactions. Fall back to raw tmux commands only when you need low-level control.

tmux-bridge — Cross-Pane Communication

A CLI that lets any AI agent interact with any other tmux pane. Works via plain bash. Every command is atomic: type types text (no Enter), keys sends special keys, read captures pane content.

DO NOT WAIT OR POLL

Other panes have agents that will reply to you via tmux-bridge. Their reply appears directly in YOUR pane as a [tmux-bridge from:...] message. Do not sleep, poll, read the target pane for a response, or loop. Type your message, press Enter, and move on.

The ONLY time you read a target pane is:

• Before interacting with it (enforced by the read guard)
• After typing to verify your text landed before pressing Enter
• When interacting with a non-agent pane (plain shell, running process)

Read Guard

The CLI enforces read-before-act. You cannot type or keys to a pane unless you have read it first.

1. tmux-bridge read <target> marks the pane as "read"
2. tmux-bridge type/keys <target> checks for that mark — errors if you haven't read
3. After a successful type/keys, the mark is cleared — you must read again before the next interaction

$ tmux-bridge type codex "hello"
error: must read the pane before interacting. Run: tmux-bridge read codex

Command Reference

Target Resolution

Targets can be:

• tmux native: session:window.pane (e.g. shared:0.1), pane ID (%3), or window index (0)
• label: Any string set via tmux-bridge name — resolved automatically

Read-Act-Read Cycle

Every interaction follows read → act → read. The CLI enforces this.

Sending a message to an agent:

tmux-bridge read codex 20                    # 1. READ — satisfy read guard
tmux-bridge message codex 'Please review src/auth.ts'
                                              # 2. MESSAGE — auto-prepends sender info, no Enter
tmux-bridge read codex 20                    # 3. READ — verify text landed
tmux-bridge keys codex Enter                 # 4. KEYS — submit
# STOP. Do NOT read codex for a reply. The agent replies into YOUR pane.

Approving a prompt (non-agent pane):

tmux-bridge read worker 10                   # 1. READ — see the prompt
tmux-bridge type worker "y"                  # 2. TYPE
tmux-bridge read worker 10                   # 3. READ — verify
tmux-bridge keys worker Enter                # 4. KEYS — submit
tmux-bridge read worker 20                   # 5. READ — see the result

Messaging Convention

The message command auto-prepends sender info and location:

[tmux-bridge from:claude pane:%4 at:3:0.0] Please review src/auth.ts

The receiver gets: who sent it (from), the exact pane to reply to (pane), and the session/window location (at). When you see this header, reply using tmux-bridge to the pane ID from the header.

Agent-to-Agent Workflow

# 1. Label yourself
tmux-bridge name "$(tmux-bridge id)" claude

# 2. Discover other panes
tmux-bridge list

# 3. Send a message (read-act-read)
tmux-bridge read codex 20
tmux-bridge message codex 'Please review the changes in src/auth.ts'
tmux-bridge read codex 20
tmux-bridge keys codex Enter

Example Conversation

Agent A (claude) sends:

tmux-bridge read codex 20
tmux-bridge message codex 'What is the test coverage for src/auth.ts?'
tmux-bridge read codex 20
tmux-bridge keys codex Enter

Agent B (codex) sees in their prompt:

[tmux-bridge from:claude pane:%4 at:3:0.0] What is the test coverage for src/auth.ts?

Agent B replies using the pane ID from the header:

tmux-bridge read %4 20
tmux-bridge message %4 '87% line coverage. Missing the OAuth refresh token path (lines 142-168).'
tmux-bridge read %4 20
tmux-bridge keys %4 Enter

Raw tmux Commands

Use these when you need direct tmux control beyond what tmux-bridge provides — session management, window navigation, creating panes, or low-level scripting.

Capture Output

tmux capture-pane -t shared -p | tail -20    # Last 20 lines
tmux capture-pane -t shared -p -S -          # Entire scrollback
tmux capture-pane -t shared:0.0 -p           # Specific pane

Send Keys

tmux send-keys -t shared -l -- "text here"   # Type text (literal mode)
tmux send-keys -t shared Enter               # Press Enter
tmux send-keys -t shared Escape              # Press Escape
tmux send-keys -t shared C-c                 # Ctrl+C
tmux send-keys -t shared C-d                 # Ctrl+D (EOF)

For interactive TUIs, split text and Enter into separate sends:

tmux send-keys -t shared -l -- "Please apply the patch"
sleep 0.1
tmux send-keys -t shared Enter

Panes and Windows

# Create panes (prefer over new windows)
tmux split-window -h -t SESSION              # Horizontal split
tmux split-window -v -t SESSION              # Vertical split
tmux select-layout -t SESSION tiled          # Re-balance

# Navigate
tmux select-window -t shared:0
tmux select-pane -t shared:0.1
tmux list-windows -t shared

Session Management

tmux list-sessions
tmux new-session -d -s newsession
tmux kill-session -t sessionname
tmux rename-session -t old new

Claude Code Patterns

# Check if session needs input
tmux capture-pane -t worker-3 -p | tail -10 | grep -E "❯|Yes.*No|proceed|permission"

# Approve a prompt
tmux send-keys -t worker-3 'y' Enter

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

Tips

• Read guard is enforced — you MUST read before every type/keys
• Every action clears the read mark — after type, read again before keys
• Never wait or poll — agent panes reply via tmux-bridge into YOUR pane
• Label panes early — easier than using %N IDs
• type uses literal mode — special characters are typed as-is
• read defaults to 50 lines — pass a higher number for more context
• Non-agent panes are the exception — you DO need to read them to see output
• Use capture-pane -p to print to stdout (essential for scripting)
• Target format: session:window.pane (e.g., shared:0.0)