pi-tmux

A pi coding agent extension that manages a tmux session per project (one per git root).

Fork of @romansix/pi-tmux with split pane support for iTerm2.

For the current working notes on iTerm2 tmux CC mode, pane swapping, and the non-CC session workaround, see docs/engineering/tmux-cc-pane-findings.md.

Install

pi install git:github.com/victor-software-house/pi-tmux

Or try without installing:

pi -e git:github.com/victor-software-house/pi-tmux

Features

tmux tool

Provides a tmux tool for the agent with these actions:

• run -- Run a command in a new tmux window. When the command finishes, the agent is automatically notified with the exit code and recent output, so it doesn't need to wait around.
• attach -- Open a terminal view attached to the session. Supports iTerm2, Terminal.app, kitty, ghostty, WezTerm, and tmux nesting. Use mode param to control layout: tab (default), split-vertical, or split-horizontal. Splits open inside the current iTerm2 pane.
• peek -- Capture recent output from tmux windows. Use window to target a specific window, or omit for all.
• list -- List all windows in the session.
• kill -- Kill the entire session.
• mute -- Suppress silence notifications for a window. Use when a command is expected to have long silence periods, not waiting for input.

Commands run in a wrapper script for exit-code tracking and silence detection.

Silence detection

When running commands that might prompt for input (installers, interactive tools, confirmations), the agent can set silenceTimeout to be notified when the command goes quiet.

Parameter	Description	Default
silenceTimeout	Initial seconds of silence before notifying. 0 or omitted to disable.	--
silenceBackoffFactor	Multiply the interval after each notification.	1.5
silenceBackoffCap	Max silence interval in seconds.	300 (5 min)

The notification includes a peek of the window output so the agent can decide whether to act or mute the window.

Commands

• /tmux -- Open a terminal tab attached to the project's tmux session
• /tmux split-vertical -- Open as a vertical split pane in the current iTerm2 session
• /tmux split-horizontal -- Open as a horizontal split pane
• /tmux:cat -- Select a tmux window and bring its output into the conversation
• /tmux:clear -- Kill idle tmux windows (shells with no running child processes)

Changes from upstream

• attach action supports mode parameter: tab (default), split-vertical, split-horizontal
• /tmux command accepts mode argument with autocomplete
• iTerm2 AppleScript uses split vertically / split horizontally on current session for split modes

Recommended tmux setup

Pi uses modified key sequences (Ctrl+Shift+P, Ctrl+Enter, etc.) that stock tmux cannot forward correctly. The recommended setup uses the jixiuf/tmux fork, which adds the Kitty keyboard protocol.

Install the tmux fork

# Build from source (macOS)
brew install libevent ncurses utf8proc autoconf automake pkg-config
git clone https://github.com/jixiuf/tmux.git /tmp/jixiuf-tmux
cd /tmp/jixiuf-tmux
sh autogen.sh
PKG_CONFIG_PATH="/opt/homebrew/opt/ncurses/lib/pkgconfig:/opt/homebrew/lib/pkgconfig" \
  LDFLAGS="-L/opt/homebrew/lib" \
  ./configure --prefix=/usr/local --enable-utf8proc
make -j$(sysctl -n hw.logicalcpu)
brew unlink tmux
sudo cp tmux /usr/local/bin/tmux

Verify: tmux -V should show next-3.7.

~/.tmux.conf

# Kitty keyboard protocol (jixiuf/tmux fork)
set -s kitty-keys on
set -as terminal-features '*:kitkeys'

# Extended keys fallback
set -g extended-keys on
set -g extended-keys-format csi-u
set -as terminal-features 'xterm*:extkeys'
set -as terminal-features 'tmux*:extkeys'

# Mouse
set -g mouse on

# Truecolor and undercurl
set -g default-terminal "tmux-256color"
set -as terminal-features ',xterm-256color:RGB'
set -as terminal-features ',xterm-256color:usstyle'

# Fast escape
set -g escape-time 10

# Focus events
set -g focus-events on

# Clipboard via OSC 52
set -g set-clipboard on

# Allow passthrough (shell integration, imgcat)
set -g allow-passthrough on

# Scrollback
set -g history-limit 50000

# Renumber windows on close
set -g renumber-windows on

iTerm2 settings

If using iTerm2 with tmux -CC integration:

1. Create a profile named tmux and configure it (colors, font, etc.)
2. Enable Settings > General > tmux > Use tmux profile rather than profile of connecting session

Why not stock tmux?

Stock tmux supports extended-keys with CSI-u encoding, but extended-keys always breaks Ctrl-C in regular shells. The on mode (apps opt-in) is safe but pi does not explicitly request extended keys, so modified keys are not forwarded.

The jixiuf fork adds kitty-keys, which handles the full Kitty keyboard protocol and correctly forwards Ctrl+Shift+P, Ctrl+Enter, and other modified keys without breaking Ctrl-C.

Credits

Original: @romansix/pi-tmux by indigoviolet. Inspired by normful/picadillo's run-in-tmux skill.

License

Apache 2.0