Muxy

A native macOS terminal workspace for running many coding agents in parallel — real Ghostty rendering, every session in one window, and a quiet signal the moment an agent needs you.

• It IS your Ghostty. Muxy embeds libghostty and loads your own ~/.config/ghostty/config — theme, font, opacity, padding, everything, 1:1. Light/dark follows the system.
• A session is what used to be a window. ⌘N opens one, you cd somewhere and start your agent; ⌘T opens a tab right there. The sidebar sorts sessions by repository and shows branch and PR on its own — nothing to configure.
• Agent-aware. A Claude Code hook reports working, done and needs you per tab. The session's tile changes, the Dock shows a count, and a banner (click → that session) appears when Muxy is in the background.
• PR status at a glance. The PR badge follows the CI checks and GitHub's merge state: blue while checks run, yellow when they failed and something in the session is working on it, red when they failed or the PR has conflicts, grey for drafts and PRs GitHub still holds back (review, out-of-date branch, required check missing), green only when it could be merged right now.
• Windows when you want them. Drag a session from the sidebar and drop it anywhere — it opens as its own window right there; drop it on another window's sidebar and it moves in. Running processes don't notice.
• English or German. English by default; switch in Settings (⌘,).
• Built to stay fast. Exactly one terminal surface per window is attached; background sessions keep their PTY but cost no rendering. No animations while idle.

Install

brew tap theitger/tap
brew trust theitger/tap        # Homebrew ≥ 6 requires tap trust
brew install --cask muxy
xattr -dr com.apple.quarantine /Applications/Muxy.app

The last line is needed because the app is ad-hoc signed (no Apple Developer certificate) — without it Gatekeeper blocks the first launch as "unverified developer".

Build from source

git clone https://github.com/theitger/muxy && cd muxy
./Scripts/make-app.sh   # fetches the pinned GhosttyKit binary, builds ~/Applications/Muxy.app

Requires macOS 14+, Xcode 15+ command line tools. If Ghostty.app is installed, its shell integration and terminfo are bundled into Muxy.

Setup

1. Agent status: ./Scripts/install-claude-hook.sh adds UserPromptSubmit/PreToolUse/Notification/Stop/StopFailure hooks to your Claude Code settings. They are a no-op outside Muxy and leave other hooks untouched; rerun it after updating Muxy.
2. muxy on your PATH (optional): ln -s "$PWD/Scripts/muxy" ~/.local/bin/muxy, then muxy . opens a session in the current directory. Folders dropped on the Dock icon do the same.

Keys

Key	Action
⌘N	new session (in home)
⇧⌘N	new window
⌘T	new tab in the current tab's directory
⌘W	close tab → the last tab closes the session → an empty window closes
⌘1…9 · ⌃Tab	switch tab
⌃1…9 · ⌘⌥↑/↓	switch session
⌘J	next session that wants you (any window)
⌘K	search sessions
⌘B	show/hide the sidebar (drag its edge to resize)

Closing a window ends its sessions (confirmed if something runs); ⌘Q confirms too. Muxy keeps running without windows — click the Dock icon.

Architecture notes

• SwiftUI + AppKit shell around libghostty (via libghostty-spm, vendored and pinned under Vendor/ with two small patches marked muxy patch; the ~50 MB GhosttyKit binary is fetched at build time, checksum-verified).
• Ghostty's exec backend spawns your login shell per tab — real PTY, real VT, no custom terminal code in this repo.
• The working directory (OSC 7) and command exit codes (OSC 133) come from the shell; repository, branch, PR and its checks are derived from them with git and gh (checks re-polled every minute).
• Chrome colors are parsed from your Ghostty theme files at launch and derived programmatically, so the UI always matches the terminal.

Credits & license

MIT © Tristan Heitger. Muxy stands on Ghostty by Mitchell Hashimoto (MIT) and libghostty-spm by @Lakr233 (MIT, license included under Vendor/). Not affiliated with the Ghostty project.