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.

Shell completion

The Homebrew cask installs completions for zsh, bash, and fish. Start a new shell after installing. If they don't load, make sure Homebrew's completion directories are wired into your shell (see Homebrew's shell completion docs).

If you installed cmux another way, add the matching line to your shell startup file, then start a new shell:

autoload -Uz compinit && compinit
eval "$(cmux completion zsh)"

eval "$(cmux completion bash)"

cmux completion fish | source

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.

To theme cmux (colors, fonts, transparency, sidebar, and more), see Customizing cmux's look.

For shell watcher churn and managed-Mac process audit volume, see the supported CMUX_NO_GIT_WATCH=1 mitigation and its Git/PR update trade-offs.

Keyboard Shortcuts

Workspaces

Shortcut	Action
⌘ N	New local workspace
⌘ Y	New Cloud workspace on the last usable Cloud context; opens New Cloud Machine when none is available
⌘ ⇧ Y	New Cloud machine
⌘ 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 J K L	Resize pane left/down/up/right
⌘ ⇧ 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
—	Mark all notifications read (unbound by default; configure in Settings or cmux.json)
—	Clear all notifications (unbound by default; configure in Settings or cmux.json)

Find

Shortcut	Action
⌘ F	Find
⌘ ⇧ F	Find in directory
⌘ G / ⌥ ⌘ G	Find next / previous
⌥ ⌘ ⇧ F	Hide find bar
⌘ E	Use selection for find

Terminal

Shortcut	Action
⌘ K	Clear scrollback
⌘ C	Copy (with selection)
⌘ V	Paste
⌘ + / ⌘ -	Increase / decrease font size
⌘ 0	Reset font size

Window

Shortcut	Action
⌘ ⇧ N	New window
⌘ ⇧ O	Reopen previous session
⌘ ,	Settings
⌘ ⇧ ,	Reload configuration
⌘ Q	Quit

Nightly Builds

Download cmux NIGHTLY (universal; updates then switch to your Mac's architecture automatically)

cmux NIGHTLY is a separate app with its own bundle ID, so it runs alongside the stable version. Built automatically from the latest main commit and auto-updates via its own Sparkle feed.

Report nightly bugs on GitHub Issues or in #nightly-bugs on Discord.

Session restore

Quitting cmux saves the current session. On relaunch, cmux restores app-owned state:

• Window/workspace/pane layout
• Working directories
• Terminal scrollback (best effort)
• Browser URL and navigation history

cmux does not checkpoint arbitrary live process state. Ordinary terminals, tmux, vim, shells, and unsupported terminal apps reopen as normal terminals. For live detach/reattach across cmux quit, crashes, and updates, opt in to the local tmux owner with cmux local-tmux; see docs/local-tmux.md for its lifecycle and machine-sleep limits. zellij users can use cmux local-zellij instead; see docs/local-zellij.md.

Supported agent sessions can resume when hooks have saved a native session ID. Install hooks after installing the agent CLI so its binary is on PATH:

cmux hooks setup
cmux hooks setup codex
cmux hooks setup --agent opencode

cmux hooks setup installs supported agents it can find and prints a summary for skipped agents. Supported resume integrations include Claude Code, Codex, Grok, OpenCode, Pi, Amp, Cursor CLI, Gemini, Rovo Dev, Copilot, CodeBuddy, Factory, and Qoder. Claude Code is handled by the cmux Claude wrapper when Claude integration is enabled in Settings.

Advanced users and integrations can attach a custom resume command to the current terminal surface. This is useful for tools with their own durable state, such as tmux sessions or custom agent CLIs:

cmux surface resume set --kind tmux --checkpoint work --shell "tmux attach -t work"
cmux surface resume show --json
cmux surface resume clear --checkpoint work

The binding stays attached to the cmux surface. Public CLI or socket-created bindings are stored for inspection and manual restore unless you approve a signed command prefix for automatic restore. Approved prefixes are also bound to the working directory and exact environment values, when present. Review or edit approvals in Settings > Terminal > Resume Commands. cmux only auto-runs resume bindings it marks trusted, such as live process-detected tmux bindings or user-approved prefixes. Sensitive environment keys such as tokens, passwords, secrets, and API keys are dropped before a resume binding is stored.

To keep restored agent terminals idle instead of automatically running their resume commands, turn off Settings > Terminal > Resume Agent Sessions on Reopen or set this in ~/.config/cmux/cmux.json:

{
  "terminal": {
    "autoResumeAgentSessions": false
  }
}

This only disables automatic agent resume commands. cmux still restores the saved layout, working directories, scrollback, and browser history.

If you need to reapply the last saved snapshot manually, use:

• File > Reopen Previous Session
• ⌘ ⇧ O
• cmux restore-session

Each cmux install (stable, nightly, rc, staging, and tagged debug builds) keeps its own saved session. To bring a session from one install into another, for example after trying nightly and switching back to stable, run this from the install you want to open it in:

cmux restore-session --from nightly          # or stable, rc, staging, debug:<tag>
cmux restore-session --export ~/session.json # write this install's saved session to a file
cmux restore-session --export ~/session.json --force # replace an existing export file
cmux restore-session --from ~/session.json   # reopen an exported file

The imported session opens as additional windows next to the ones you have, like cmux restore-session; the other install's saved file is only read. Agent resume carries over because hook session mappings in ~/.cmuxterm/ are shared by every install. Browser cookies and logins are per install and do not move.

--from <channel> restores another install's own session file with the same trust as your own session, including automatic agent resume. --from <path> treats the file as untrusted: layout, working directories, text scrollback, and http(s) browser tabs restore, but nothing in the file runs automatically. Built-in agents (Claude Code, Codex, Amp, and the rest) resume with the command cmux builds from the agent kind and session id, ignoring launch arguments stored in the file, and only when the working directory already exists on this Mac. Custom agent resume commands, resume bindings, and tmux start commands are kept for manual restore only (approved resume prefixes never apply to them): the CLI reports how many were held back, and in each terminal cmux surface resume show shows the command and cmux restore --surface runs it. Terminal control sequences in the scrollback (clipboard, notifications, links, titles), draft attachments, non-http(s) browser pages and profiles, SSH/cloud connections, and workspace environment variables from the file are dropped. A snapshot saved by a newer cmux (newer session format) is refused with an error; if a downgraded cmux finds one in its own session file, it keeps a copy next to it as session-<bundle id>.schema-v<N>.json.

Under the hood, cmux writes a versioned snapshot under ~/Library/Application Support/cmux/ and agent hooks write session mappings under ~/.cmuxterm/. On restore, cmux rebuilds the layout first, then runs the supported agent's native resume command when automatic agent resume is enabled.

Read the full guide at https://cmux.com/docs/session-restore.

FAQ

How does cmux relate to Ghostty?

cmux is not a fork of Ghostty. It uses libghostty as a library for terminal rendering, the same way apps use WebKit for web views. Ghostty is a standalone terminal; cmux is a different app built on top of its rendering engine.

What platforms does it support?

macOS only, for now. cmux is a native Swift + AppKit app.

Is there an iOS app?

Yes, in beta. Pair your iPhone with your Mac from the Mobile Connect window and attach to your terminals from your phone, with optional forwarding of terminal notifications. It ships on TestFlight as cmux BETA. Early access is included with cmux Pro. See the iOS docs.

What coding agents does cmux work with?

All of them. cmux is a terminal, so any agent that runs in a terminal works out of the box: Claude Code, Codex, OpenCode, Gemini CLI, Kiro, Aider, Goose, Amp, Cline, Cursor Agent, and anything else you can launch from the command line.

Can cmux orchestrate multiple agents and subagents?

Yes. When an agent spawns subagents or teammates, cmux turns them into native panes and splits instead of hidden background processes. It supports Claude Code teams and oh-my-opencode multi-model orchestration, so every agent in a run is visible and controllable.

Can I use cmux with remote machines?

Yes. Open workspaces over SSH and attach to remote tmux sessions, so agents can run on a remote host while you drive them from cmux. See SSH and remote.

How do notifications work?

When a process needs attention, cmux shows notification rings around panes, unread badges in the sidebar, a notification popover, and a macOS desktop notification. These fire automatically via standard terminal escape sequences (OSC 9/99/777), or you can trigger them with the cmux CLI and agent hooks. Any agent that supports hooks or OSC works, including Claude Code, Codex, OpenCode, and pi.

Is cmux programmable?

Yes. Every action is available through the cmux CLI and a Unix socket: create workspaces, open split panes, send input, read screen contents, take screenshots, and drive the in-app browser. See the CLI reference and browser automation docs.

What can the built-in browser do?

cmux can split a real browser pane next to your terminal, and it is fully programmable: navigate, snapshot the DOM, click, type, evaluate JavaScript, and read console and network activity over the same socket API. Agents use it to verify their own web changes without leaving cmux. See browser automation.

Does cmux have skills?

Yes. Skills are reusable workflows you can give any agent running in cmux, for things like CLI control, workspace automation, settings, and browser surfaces. Browse the open collection at cmux-skills, or read the skills docs.

Can I customize keyboard shortcuts?

Terminal keybindings are read from your Ghostty config file (~/.config/ghostty/config), including leader sequences and key tables. Ghostty tab actions target cmux workspaces; see the action mapping, precedence, and limitations. cmux-specific shortcuts (workspaces, splits, browser, notifications) can be customized in Settings. See the default shortcuts for a full list.

Can I customize cmux?

Yes. Terminal rendering uses your Ghostty config, so themes, fonts, colors, and cursor carry over directly. cmux's own settings in ~/.config/cmux/cmux.json control the sidebar, tab bar, split panes, and behavior, and every keyboard shortcut is editable. See configuration.

Are my sessions saved?

cmux restores windows, workspaces, panes, working directories, and best-effort scrollback when you relaunch. Supported agent integrations can resume from their saved session IDs. Those are reconstructed app state and resume commands; they do not keep arbitrary live processes running. Use cmux local-tmux for live local detach/reattach across cmux quit, crashes, and updates. A local tmux server cannot survive logout, restart, shutdown, or power loss; use cmux ssh-tmux, cmux mosh-tmux, or a persistent cloud VM when the owner must remain online while this Mac is offline. See session restore and docs/local-tmux.md.

How does it compare to tmux?

tmux is a terminal multiplexer that runs inside any terminal. cmux is a native macOS app with a GUI: vertical tabs, split panes, an embedded browser, and a socket API, all built in, no config files or prefix keys needed. That said, lots of people happily run cmux with SSH and tmux together, and cmux can attach to your remote tmux sessions natively (beta).

Is cmux free?

Yes, cmux is free to use. The source code is available on GitHub.

How can I support cmux?

cmux is free and open source, and always will be. If you want to back development and get early access to what's next, including cmux AI, the iOS app, and Cloud VMs, check out cmux Pro.

I have a feature request or found a bug?

We want to hear it. Open an issue or pull request on GitHub, or email us.

Star History

Contributing

New here? Start here is the short path from "I want to change something" to a merged pull request, including what you can fix without a Mac. Then the contributor guide and fast local checks.

Ways to get involved:

• Follow us on X for updates @manaflowai, @lawrencecchen, and @austinywang
• Join the conversation on Discord
• Create and participate in GitHub issues and discussions
• Let us know what you're building with cmux

Community

• Discord
• WhatsApp
• GitHub
• X / Twitter
• YouTube
• LinkedIn
• Reddit

cmux Pro

cmux is free, open source, and always will be. If you'd like to support development and get early access to what's coming next:

Get cmux Pro

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.

License

cmux is open source under GPL-3.0-or-later. The cmux server software (web/, the Cloudflare workers, and the relay services listed in LICENSE) uses the Business Source License 1.1 instead: you can read, modify, and run it for non-production use, and production use or self-hosting requires a commercial license.

If your organization cannot comply with GPL, commercial terms may be available for portions for which Manaflow controls the necessary rights. They do not relicense third-party material or outside contributions for which Manaflow lacks a separate grant. See LICENSE for the exact scope and contact [email protected] for details.