cmux: A macOS Terminal Built for AI Coding Agents
/cmux
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 โ this solves a multitasking problem, not a coding one.
Four Coding Agents, No Idea Which One Is Stuck
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.
A Ghostty-Based Terminal Built to Supervise Agents
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.
Notification Rings and a Scriptable In-App Browser
- โNotification rings: panes and tabs light up when a coding agent is waiting on you
- โA notification panel that gathers all pending alerts and jumps to the latest unread
- โVertical tabs for organizing many concurrent agent sessions
- โA split in-app browser with a scriptable API, ported from vercel-labs/agent-browser
- โBuilt on Ghostty, with tmux-style multiplexing for parallel agents
- โShips as a native macOS app via .dmg download or Homebrew cask
Turning the Terminal Into an Agent Dashboard
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 โ 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.
Running Claude Code, Codex, and opencode in Parallel
- โขSupervising several AI coding agents running at the same time on macOS
- โขGetting a clear signal about which agent pane is blocked and needs input
- โขKeeping a browser open beside agents to check output or drive a scriptable page
- โขOrganizing long-running agent sessions into vertical tabs instead of scattered windows
Homebrew Cask or a Direct .dmg Download
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.
Watching for the Blue Ring That Needs You
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.
A Real Signal in a Sea of Agent Panes
- โSolves a concrete multitasking pain: knowing which of many agents is waiting on you
- โNotification rings and panel are a genuinely useful signal, not decoration
- โBuilt on Ghostty, so you get a modern terminal underneath the agent tooling
- โSimple install as a native macOS app via Homebrew or a .dmg
macOS-Only, and No License Listed
- โณmacOS only โ there's no Windows or Linux build, so it's a non-starter off a Mac
- โณThe GitHub metadata lists no license, so reuse and redistribution terms are unclear
- โณIt's a supervision layer, not an agent โ you still bring and configure your own coding agents
- โณThe value mostly shows up when you run many agents at once; for a single agent it's overkill
tmux, Ghostty, Zellij, Warp
Who Needs a Supervision Layer Like This
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.
cmux Questions, Answered
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.
Related repositories
Is cmux worth your time?
ChatGPT, Claude and Perplexity can all read this page. Ask one of them what it makes of cmux.