What is Muster?
Muster is a free, open-source macOS menu bar app that tracks sessions in Claude Code, Codex, and Cursor and alerts you when an agent needs input. It lets users respond to supported Claude Code and Codex permission requests or questions from an on-screen alert, while Cursor prompts open in Cursor. A session switcher and search help developers who run several coding agents move among recent sessions without hunting through windows.
Muster Features:
Waiting Alerts: Muster shows an on-screen alert when an agent needs attention and keeps the request visible until you respond.
Request Details: Expand an alert to inspect an agent's reason, full command, edit file and size, or question options and notes.
Prompt Responses: Allow or deny supported Claude Code and Codex requests, answer Claude Code questions, or open a waiting Cursor chat.
Session Switching: Use the keyboard switcher to move through recent sessions, with the one waiting for you shown first.
Session Search: Search sessions from the last three hours and view token counts and estimated costs at API list prices.
Shortcut Controls: Change the switcher and search shortcuts, and see when another app is already using a chosen shortcut.
Muster Benefits:
Fewer Interruptions: Answer supported requests without leaving your current app, so routine agent approvals do not require a trip to another window.
Clearer Decisions: Review the command or question context before responding, helping you make an informed choice instead of approving blindly.
Easier Coordination: Keep several active coding sessions in view and identify which one needs you first, reducing the effort of tracking parallel work.
Cost Awareness: Compare session token use and estimated API-rate costs to spot which sessions are consuming more resources.
Private Local Use: Use the app without an account or app analytics, while local questions and answers communicate over localhost.
Use Cases:
Parallel Coding: Monitor Claude Code, Codex, and Cursor sessions while several agents work on different coding tasks.
Command Approval: Review a Claude Code or Codex request to run a command and respond from Muster rather than switching to its window.
Agent Questions: Choose an answer to a Claude Code multiple-choice question after expanding the alert to read its options and notes.
Session Recovery: Find a recent agent session by searching its list when you need to return to a task or locate its window.
Cursor Follow-Up: Notice that a Cursor chat is waiting, then jump to the chat in Cursor to respond there.