cmux

cmux is a macOS terminal from Manaflow, written in Swift and AppKit, that embeds libghostty, Ghostty's terminal core, for GPU rendering. It is built for running many AI coding agents such as Claude Code and Codex in parallel. It adds a vertical-tab sidebar and a notification system on top of Ghostty-compatible terminals. It suits developers on macOS 14 or later who keep many agent sessions open and want to see which one is waiting for input.

Terminal appearance comes from Ghostty config. cmux reads ~/.config/ghostty/config and Ghostty's macOS location, then applies cmux-only overrides from ~/Library/Application Support/com.cmuxterm.app/config.ghostty. App behavior, the sidebar, workspace colors and keyboard shortcuts are set in the Settings window or in ~/.config/cmux/cmux.json, which has a published JSON schema and reloads on save. cmux controls some Ghostty settings itself: term is always xterm-256color, and window options handled by Ghostty.app's own code have no effect.

Each window holds workspaces, shown as vertical tabs that list the git branch, linked PR, working directory, listening ports and latest notification text. Workspaces split into panes, and each pane holds horizontal tabs. Notifications come from OSC 9, 99 and 777 sequences or the cmux notify command. A pane waiting for attention gets a blue ring, and Cmd+Shift+U jumps to the latest unread. A CLI and socket API create workspaces, split panes and send keystrokes. A built-in browser pane has a scriptable API ported from agent-browser, and cmux ssh opens workspaces on remote machines. Ligatures and the kitty graphics protocol work because they come from libghostty.

cmux runs only on macOS. An iOS app that attaches to the Mac's terminals is in TestFlight beta. Session restore brings back the layout, working directories and best-effort scrollback, but not running processes, unless you opt into tmux or zellij integration. The app is GPL-3.0-or-later, while the server components under web/ and some workers/ and services/ directories use the Business Source License 1.1. The project releases often, and its terminal core is a fork of Ghostty with local patches.