cmux: A macOS Terminal Built for AI Coding Agents
manaflow-ai/cmuxcmux is a macOS terminal app, built on Ghostty, aimed at people running several AI coding agents in parallel. It adds vertical tabs, notification rings when an agent needs input, and a split in-app browser so you can watch agents work without hopping between windows.
Reach for cmux if you're on a Mac and routinely run several coding agents (Claude Code, Codex, opencode) at once and keep losing track of which one is waiting on you. Skip it if you're not on macOS, or if a single agent in your existing terminal already covers your workflow — this solves a multitasking problem, not a coding one.
The problem it solves
Running one AI coding agent in a terminal is fine. Running four is chaos: they finish or stall at different times, each buried in its own tab or window, and you don't notice an agent is blocked on a question until you go looking. Plain terminals give you no signal about which pane needs attention.
What is it?
cmux is an open-source macOS terminal built on Ghostty. Its focus is coordinating multiple AI coding agents: panes get a blue notification ring and tabs light up when an agent needs your attention, a notification panel collects everything pending, and a scriptable in-app browser (ported from vercel-labs' agent-browser) sits beside the terminal. It ships as a macOS app via a .dmg or Homebrew cask.
Why it's getting attention
Running a fleet of coding agents in parallel has become a real workflow, and the tooling around it is thin. cmux targets exactly that gap — the terminal as a place to supervise agents rather than just type commands. Its topic list leans into tmux-style multiplexing, parallel agents, and support for Claude Code, Codex, Gemini, opencode, and amp.
Key features
- ✓Notification rings: panes and tabs light up when a coding agent is waiting on you
- ✓A notification panel that gathers all pending alerts and jumps to the latest unread
- ✓Vertical tabs for organizing many concurrent agent sessions
- ✓A split in-app browser with a scriptable API, ported from vercel-labs/agent-browser
- ✓Built on Ghostty, with tmux-style multiplexing for parallel agents
- ✓Ships as a native macOS app via .dmg download or Homebrew cask
Best use cases
- •Supervising several AI coding agents running at the same time on macOS
- •Getting a clear signal about which agent pane is blocked and needs input
- •Keeping a browser open beside agents to check output or drive a scriptable page
- •Organizing long-running agent sessions into vertical tabs instead of scattered windows
How to install / try
cmux is macOS-only. Install with Homebrew: `brew install --cask cmux` (update later with `brew upgrade --cask cmux`), or download the macOS `.dmg` from the project's releases. On first launch macOS may ask you to confirm opening the app.
How to use
Open cmux like a normal terminal and start your coding agents in its panes and vertical tabs. When an agent needs attention, its pane gets a blue ring and the tab lights up; the notification panel lists everything pending so you can jump to the most recent unread. Split the in-app browser alongside the terminal when you want to watch or script a page.
Strengths
- ✓Solves a concrete multitasking pain: knowing which of many agents is waiting on you
- ✓Notification rings and panel are a genuinely useful signal, not decoration
- ✓Built on Ghostty, so you get a modern terminal underneath the agent tooling
- ✓Simple install as a native macOS app via Homebrew or a .dmg
Limitations & risks
- △macOS only — there's no Windows or Linux build, so it's a non-starter off a Mac
- △The GitHub metadata lists no license, so reuse and redistribution terms are unclear
- △It's a supervision layer, not an agent — you still bring and configure your own coding agents
- △The value mostly shows up when you run many agents at once; for a single agent it's overkill
Alternatives
Who should try it — and who should skip
macOS developers who run multiple AI coding agents in parallel and keep losing track of which one is blocked. If your day involves four agent sessions and a lot of context-switching, the notification model earns its place. If you're on Linux/Windows, or you run one agent at a time, it isn't for you.
Frequently asked questions
No. cmux is a native macOS app, distributed as a .dmg and a Homebrew cask. There's no Windows or Linux build.
No. It's a terminal for supervising coding agents like Claude Code, Codex, Gemini, and opencode. You still install and configure the agents yourself.
When a coding agent needs your attention, its pane gets a blue ring and its tab lights up, so you can see which of several running agents is waiting on input.
A browser you can split alongside the terminal, with a scriptable API ported from vercel-labs/agent-browser, so you can view or drive a page without leaving cmux.