cmux - Terminal Multiplexer

Overview

cmux is a native macOS terminal application (Swift/AppKit) that provides terminal multiplexing with workspaces, panes, and splits. It uses Ghostty's rendering engine (libghostty) for GPU-accelerated terminal output. The CLI communicates with the running app via a Unix domain socket at /tmp/cmux.sock.

Think of cmux as "tmux reimagined as a native macOS app" -- it has workspaces (like tmux windows), panes (like tmux panes), and surfaces (individual terminal or browser instances within panes), all controllable via a rich CLI.

When to Load the Reference

This skill covers the mental model, common commands, gotchas, and erk integration. Load references/cmux-reference.md when you need:

• Browser automation syntax (40+ subcommands: navigation, forms, cookies, storage, console, waiting, dialogs, downloads, state)
• Window management (list-windows, new-window, focus-window, close-window, move-workspace-to-window)
• Surface management (move-surface, reorder-surface, drag-surface-to-split, surface-health)
• Panel/Tab commands (list-panels, focus-panel, tab-action, rename-tab)
• Sidebar metadata (clear-status, list-status, clear-progress, clear-log, list-log, sidebar-state)
• Full tmux compat (20+ commands: pipe-pane, wait-for, copy-mode, set-hook, bind-key, popup, etc.)
• Utility/diagnostic (ping, capabilities, claude-hook, set-app-focus)