cmux is a free, open-source terminal for macOS, built on Ghostty. It is made for people who keep many terminals open at once, such as when running several AI coding agents. Vertical tabs show useful details in a sidebar, and panes light up when an agent needs your attention, so you do not have to hunt through tabs. It is a native Swift and AppKit app, not Electron.

Key Features

• Vertical Tabs: The sidebar shows each tab git branch, working directory, ports, and notification text.
• Notification Rings: Panes light up when an agent needs attention, so you can spot it right away.
• In-App Browser: Split a browser next to your terminal, with a scriptable API.
• Split Panes: Use horizontal and vertical splits inside each tab.
• Programmable: A CLI and socket API let you automate workspaces and scripts.
• GPU-Accelerated: It uses libghostty for smooth rendering.
• Ghostty Compatible: cmux reads your existing Ghostty config, so your themes, fonts, and colors carry over.
• Lightweight and Native: Built with Swift and AppKit, with no Electron.
• Keyboard Shortcuts: Extensive shortcuts cover workspaces, splits, the browser, and more.

Frequently Asked Questions (FAQ)

Is cmux free?

Yes. cmux is free and open source under the GPL-3.0-or-later license.

What macOS version does cmux need?

cmux needs macOS 14 or later.

How do I install cmux?

You can install it with Homebrew using the commands brew tap manaflow-ai/cmux and brew install --cask cmux, or download the DMG from the cmux website. The app updates itself after that.

Do I need Ghostty installed to use cmux?

No. cmux is its own app, built on Ghostty rendering technology. If you already use Ghostty, cmux reads your existing Ghostty config for themes, fonts, and colors.

What are the notification rings?

When an AI coding agent is waiting for you, its pane lights up and the notification text shows in the sidebar. cmux picks up standard terminal notification sequences and has a CLI command, cmux notify, that you can connect to agent hooks.

Does cmux restore my session after I quit?

cmux saves your session and restores your layout and terminal scrollback on a best-effort basis. It does not restore live process state, so programs like tmux or vim reopen as normal terminals.

What is the difference between cmux and Muxy?

Both are free, open-source Mac terminals built on libghostty. Muxy organizes terminals by project and adds built-in git tools and a file editor, while cmux focuses on vertical tabs, agent notifications, and an in-app browser.