cmux

cmux is an open-source, native macOS terminal built on Ghostty (libghostty) for the coding-agent era. Vertical tabs show git branch, ports, and notification text; panes light up with blue rings when an agent needs you. Split panes, an in-app browser, and a CLI/socket API make it a programmable home for Claude Code, Codex, OpenCode, and any other CLI agent. 25k+ GitHub stars, GPL-licensed.

Key Features

• Vertical tabs: Sidebar shows git branch, linked PR status, working directory, listening ports, and latest notification per workspace.
• Notification rings: Panes get a blue ring and tabs light up when coding agents need attention — via OSC 9/99/777 or the cmux notify CLI wired into agent hooks.
• In-app browser: Split a real browser alongside your terminal; navigate, click, type, and read DOM/console over the socket API.
• Split panes: Horizontal and vertical splits within each tab.
• Programmable: CLI and Unix socket API for workspaces, splits, keystrokes, screenshots, and browser automation.
• Native & fast: Swift + AppKit, GPU-accelerated via libghostty, no Electron. Reads your ~/.config/ghostty/config.

Use Cases

Who Should Use This Tool?

• Agent multitaskers: Developers juggling several coding agents who need to know instantly which one is waiting.
• macOS terminal fans: Ghostty users who want vertical tabs and agent awareness without switching terminals entirely.
• Agent-native workflows: People who want agents to drive their terminal and browser programmatically.

Problems It Solves

1. Which agent needs me?: Notification rings and unread badges replace pane-by-pane checking.
2. Terminal + browser juggling: Split a browser next to the terminal so agents can verify their own web changes.
3. Hidden agent subprocesses: When an agent spawns teammates, cmux turns them into native panes and splits instead of hidden processes.

Pricing

cmux is free and open source, GPL-licensed. The optional Founders Edition backs development and unlocks early access.

Advantages & Unique Selling Points

Compared to Competitors:

1. Terminal, not a wrapper: Unlike Herdr's runtime or manager apps, cmux is a terminal that works with any agent out of the box.
2. Agent-aware notifications: tmux keeps sessions alive but can't tell you which pane is blocked; cmux rings and badges do.
3. Built-in scriptable browser: No other macOS terminal embeds a programmable browser with DOM access.

What Makes It Stand Out:

• Built by Manaflow AI on Ghostty; endorsed by Mitchell Hashimoto, creator of Ghostty.
• Native Swift/AppKit: fast startup, low memory, no Electron.
• Claude Code teams and oh-my-opencode spawn as native panes and splits.

User Reviews

"Another day, another libghostty-based project, this time a macOS terminal with vertical tabs, better organization/notifications, embedded/scriptable browser specifically targeted towards people who use a ton of terminal-based agentic workflows." — Mitchell Hashimoto, creator of Ghostty

"cmux is great. Current split: Codex Mac app for knowledge work. cmux + Codex CLI for coding." — Peter Steinberger, OpenClaw creator

Getting Started

Quick Start Guide

1. Install: Download from cmux.com or brew install --cask cmux.
2. Open a workspace: cmux reads your Ghostty config for themes, fonts, and colors.
3. Launch agents: Run Claude Code, Codex, or any CLI agent; panes light up when they need you.
4. Automate: Use the CLI/socket API to create splits, drive the browser, and wire cmux notify into agent hooks.

Integration

• Agents: Claude Code, Codex, OpenCode, Gemini CLI, Kiro, Aider, Goose, Amp, Cline, Cursor Agent, and more.
• Claude Code Teams and oh-my-opencode multi-model orchestration spawn as native panes.
• Browser import from Chrome, Firefox, Arc, and 20+ browsers for authenticated sessions.
• SSH workspaces; attach to remote tmux sessions (beta).

Frequently Asked Questions

Is cmux open source?

Yes, free and GPL-licensed. The Founders Edition is an optional paid tier for early access to upcoming features.

How is it different from tmux?

tmux is a multiplexer that runs inside any terminal; cmux is a native macOS app with vertical tabs, notifications, and a built-in browser — no config files or prefix keys required.

Does it work with any agent?

Yes. cmux is a terminal, so any agent that runs in a terminal works out of the box.

Alternatives

If cmux isn't the right fit, consider these alternatives:

• Herdr: Terminal runtime that keeps agents alive in persistent, detachable sessions.
• Emdash: Worktree-based parallel agent environment with diff review.
• Superset: Desktop control plane for running an army of CLI agents.

Tips & Best Practices

1. Wire notifications into hooks: Connect cmux notify to Claude Code/OpenCode hooks so blocked agents always surface.
2. Use browser panes for self-verification: Let agents drive the in-app browser to check their own UI changes.
3. Keep one tab per task: Vertical tabs per WIP task keep agents, PRs, and resources organized.