Developer Lawrence Chen has built cmux, a native macOS terminal application designed to manage multiple AI coding agents like Claude Code and Codex. The tool addresses the challenge of tracking parallel agent sessions by adding vertical tabs, a notification system, and an in-app browser to the existing Ghostty terminal.

The application reads your existing Ghostty configuration for themes and colors while adding a sidebar that displays git branch, working directory, listening ports, and notification text for each workspace. When agents need input, their panes get blue rings and tabs light up in the sidebar, making it easy to identify which session requires attention across multiple splits.

Built with Swift and AppKit rather than Electron or Tauri, cmux offers better performance and integrates a scriptable browser API ported from agent-browser. This allows AI agents to interact directly with development servers through accessibility tree snapshots, element references, form filling, and JavaScript evaluation. The tool provides CLI and socket APIs for automation, enabling users to create workspaces, split panes, send keystrokes, and open URLs programmatically.