cmux

What is cmux?

cmux is a native macOS terminal application developed by Manaflow, built on top of libghostty — the rendering engine behind Ghostty — rather than being a fork of it. It is purpose-built for developers running multiple AI coding agents simultaneously, such as Claude Code, Codex, Gemini CLI, Aider, and others. Written in Swift and AppKit, cmux is lightweight, GPU-accelerated, and requires no config files or prefix keys. It extends beyond a conventional terminal by offering a built-in browser, notification rings for agent attention, and a fully scriptable CLI and socket API. cmux is free and open source.

Key Features

• Vertical Tab Sidebar

  Each tab in the sidebar displays the current git branch, working directory, open ports, and notification text, giving developers a clear overview of all active sessions at a glance.

• Agent Notification Rings

  Visual notification rings alert developers when a coding agent is waiting for input, preventing idle agents from going unnoticed during multitasking.

• Split Panes

  Supports both horizontal and vertical splits within each tab, enabling side-by-side terminal sessions or a terminal paired with the built-in browser.

• In-App Browser

  An embedded browser can be displayed alongside the terminal with a scriptable API, eliminating the need to switch between apps when referencing documentation or previewing outputs.

• Scriptable CLI & Socket API

  Full automation support via a CLI and socket API — create workspaces, manage tabs, split panes, send keystrokes, and open URLs programmatically.

• Lightweight Native Performance

  Built with Swift and AppKit with GPU acceleration via libghostty, cmux avoids Electron overhead for a fast, resource-efficient experience.

Use Cases

• Multi-Agent Development : Developers running multiple AI coding agents (e.g., Claude Code, Codex, Aider) in parallel can monitor all sessions from a single window with clear visual cues for agent status.
• Terminal Automation & Scripting : DevOps engineers and power users can automate complex workflows by scripting workspace creation, pane management, and keystroke injection via the socket API.
• Documentation-Alongside-Coding : Developers can split the terminal and the built-in browser side by side, referencing API docs or web previews without leaving the coding environment.
• Multi-Project Workspace Management : Teams or individual developers managing several projects simultaneously benefit from tab-level context (branch, directory, ports) to stay oriented across all workspaces.

FAQs