cmux

Features

• Browser import — Import cookies, history, and sessions from Chrome, Firefox, Arc, and 20+ browsers so browser panes start authenticated

• Custom commands — Define project-specific actions in cmux.json that launch from the command palette

• Programmable — CLI and socket API to create workspaces, split panes, send keystrokes, and automate the browser

• Native macOS app — Built with Swift and AppKit, not Electron. Fast startup, low memory.

• Ghostty compatible — Reads your existing ~/.config/ghostty/config for themes, fonts, and colors

• GPU-accelerated — Powered by libghostty for smooth rendering

• Keyboard shortcuts — Extensive shortcuts for workspaces, splits, browser, and more

• Open source — Free and GPL-licensed

Install

DMG (recommended)

Open the .dmg and drag cmux to your Applications folder. cmux auto-updates via Sparkle, so you only need to download once.

Homebrew

brew tap manaflow-ai/cmux
brew install --cask cmux

To update later:

brew upgrade --cask cmux

On first launch, macOS may ask you to confirm opening an app from an identified developer. Click Open to proceed.

Why cmux?

I run a lot of Claude Code and Codex sessions in parallel. I was using Ghostty with a bunch of split panes, and relying on native macOS notifications to know when an agent needed me. But Claude Code's notification body is always just "Claude is waiting for your input" with no context, and with enough tabs open I couldn't even read the titles anymore.

I tried a few coding orchestrators but most of them were Electron/Tauri apps and the performance bugged me. I also just prefer the terminal since GUI orchestrators lock you into their workflow. So I built cmux as a native macOS app in Swift/AppKit. It uses libghostty for terminal rendering and reads your existing Ghostty config for themes, fonts, and colors.

The main additions are the sidebar and notification system. The sidebar has vertical tabs that show git branch, linked PR status/number, working directory, listening ports, and the latest notification text for each workspace. The notification system picks up terminal sequences (OSC 9/99/777) and has a CLI (cmux notify) you can wire into agent hooks for Claude Code, OpenCode, etc. When an agent is waiting, its pane gets a blue ring and the tab lights up in the sidebar, so I can tell which one needs me across splits and tabs. Cmd+Shift+U jumps to the most recent unread.

The in-app browser has a scriptable API ported from agent-browser. Agents can snapshot the accessibility tree, get element refs, click, fill forms, and evaluate JS. You can split a browser pane next to your terminal and have Claude Code interact with your dev server directly.

Everything is scriptable through the CLI and socket API — create workspaces/tabs, split panes, send keystrokes, open URLs in the browser.

The Zen of cmux

cmux is not prescriptive about how developers hold their tools. It's a terminal and browser with a CLI, and the rest is up to you.

cmux is a primitive, not a solution. It gives you a terminal, a browser, notifications, workspaces, splits, tabs, and a CLI to control all of it. cmux doesn't force you into an opinionated way to use coding agents. What you build with the primitives is yours.

The best developers have always built their own tools. Nobody has figured out the best way to work with agents yet, and the teams building closed products definitely haven't either. The developers closest to their own codebases will figure it out first.

Give a million developers composable primitives and they'll collectively find the most efficient workflows faster than any product team could design top-down.

Documentation

For more info on how to configure cmux, head over to our docs.

Keyboard Shortcuts

Workspaces

Shortcut Action

⌘ N New workspace

⌘ 1–8 Jump to workspace 1–8

⌘ 9 Jump to last workspace

⌃ ⌘ ] Next workspace

⌃ ⌘ [ Previous workspace

⌘ ⇧ W Close workspace

⌘ ⇧ R Rename workspace

⌥ ⌘ E Edit workspace description

⌘ B Toggle sidebar

⌥ ⌘ B Toggle right sidebar

⌘ ⇧ E Toggle right sidebar focus

Surfaces

Shortcut Action

⌘ T New surface

⌘ ⇧ ] Next surface

⌘ ⇧ [ Previous surface

⌃ Tab Next surface

⌃ ⇧ Tab Previous surface

⌃ 1–8 Jump to surface 1–8

⌃ 9 Jump to last surface

⌘ W Close surface

Split Panes

Shortcut Action

⌘ D Split right

⌘ ⇧ D Split down

⌥ ⌘ ← → ↑ ↓ Focus pane directionally

⌘ ⇧ H Flash focused panel

Browser

Browser developer-tool shortcuts follow Safari defaults and are customizable in Settings → Keyboard Shortcuts. Command palette navigation shortcuts, including ⌃ P, are also customizable and can be cleared so the keypress reaches the active terminal.

Shortcut Action

⌘ ⇧ L Open browser in split

⌘ L Focus address bar

⌘ [ Back

⌘ ] Forward

⌘ R Reload page

⌥ ⌘ I Toggle Developer Tools (Safari default)

⌥ ⌘ C Show JavaScript Console (Safari default)

Notifications

Shortcut Action

⌘ I Show notifications panel

⌘ ⇧ U Jump to latest unread

⌥ ⌘ U Toggle current item unread state

⌃ ⌘ U Mark current item as oldest unread and jump to next latest unread

Find

Shortcut Action

⌘ F Find

⌘ ⇧ F Find in directory

⌘ G / ⌥ ⌘ G Find next / previous

⌥ ⌘ ⇧ F Hid