Muster is a free, open-source Mac menu bar app for users running several AI coding agents at once. When a Claude Code, Codex, or Cursor session needs your input, an alert appears at the top of the screen with keys to respond: ⌥↩ to allow, ⌥⌫ to deny, ⌥↓ to see why the agent is asking, and ⌥1 to ⌥9 to pick options. ⌥Tab lists all sessions, highlights the one waiting on you, and opens its window or terminal. It reads session files agents already write and responds through their hooks on 127.0.0.1, requiring no account and keeping data on your Mac. It's built with Native AppKit, is a 2 MB download, MIT licensed, and works on macOS 14 or later. View startup