cmux — Open-Source Terminal Multiplexer for AI Coding Agents

Introduction

cmux is an open-source Ghostty-based terminal for macOS designed for developers who run multiple AI coding agents simultaneously. It provides vertical tabs, agent notifications, and workspace management so you can orchestrate parallel sessions without losing track of what each agent is doing.

What cmux Does

• Provides a Ghostty-powered terminal with vertical tab layout for agent sessions
• Delivers real-time notifications when agents finish tasks or need input
• Organizes workspaces so each project gets its own set of agent tabs
• Supports programmable session management for automated workflows
• Integrates with Claude Code, Codex, Gemini CLI, and other coding agents

Architecture Overview

cmux is built in Swift on top of the Ghostty terminal emulator. It wraps Ghostty's rendering engine and adds a workspace layer that tracks per-tab process state, surfaces completion events as native macOS notifications, and exposes a scripting interface for session orchestration.

Self-Hosting & Configuration

• Install via Homebrew on macOS: brew install --cask cmux
• Configure default shell and agent startup commands in preferences
• Set workspace layouts per project directory
• Customize notification rules for agent events
• Supports keyboard shortcuts for tab navigation and session control

Key Features

• Vertical tab layout keeps many agent sessions visible at once
• Native macOS notifications surface agent completion events
• Workspace grouping organizes tabs by project
• Programmable session management for automated agent orchestration
• Built on Ghostty for fast GPU-accelerated rendering

Comparison with Similar Tools

• tmux — powerful but text-only multiplexer without native GUI or notifications
• Zellij — modern terminal workspace but not agent-aware
• iTerm2 — feature-rich macOS terminal but no built-in agent workflow support
• Ghostty — the rendering engine cmux builds on, without the workspace layer
• Warp — AI-powered terminal focused on single-user workflows, not agent orchestration

FAQ

Q: Does cmux work on Linux or Windows? A: Currently macOS only, as it builds on Ghostty's macOS integration.

Q: Can I use cmux with any coding agent? A: Yes. Any CLI-based agent that runs in a terminal works inside cmux.

Q: Is cmux a fork of Ghostty? A: No. It uses Ghostty as a rendering dependency and adds workspace and notification layers on top.

Q: How does cmux differ from running multiple terminal tabs? A: cmux adds agent-aware notifications, programmable session control, and workspace grouping that standard tabs lack.

Sources

• https://github.com/manaflow-ai/cmux