Show HN: Ghostty-based terminal with vertical tabs and notifications

A new terminal for AI coding agents

A developer has released cmux, a new macOS terminal application built for managing multiple AI coding agents like Claude Code. It's based on the Ghostty terminal and adds a notification system and vertical tabs to track active AI sessions.

The app is a native Swift and AppKit application, not built on Electron, and uses the GPU-accelerated libghostty for rendering. It reads a user's existing Ghostty configuration file for themes and settings.

Built to solve a notification problem

The developer, who runs many Claude Code sessions in parallel, created cmux to solve a workflow issue. They found that native macOS notifications from AI agents lacked context, and with many terminal tabs open, it was difficult to see which session needed attention.

"I tried a few coding orchestrators but most of them were Electron/Tauri apps and the performance bugged me," the developer wrote. "I also just prefer the terminal since GUI orchestrators lock you into their workflow."

Core features: sidebars and alerts

The main additions in cmux are a sidebar and an integrated notification system.

• Sidebar with Vertical Tabs: Shows the git branch, working directory, listening ports, and the latest notification text for each workspace.
• Agent Notification System: Detects when an AI agent is waiting. The corresponding terminal pane gets a blue ring and its tab lights up in the sidebar.
• Notification Panel: Users can press Cmd+Shift+U to jump to the most recent unread notification or open a panel to see all pending alerts.

The system works by picking up terminal sequences or through a CLI command (cmux notify) that can be wired into an AI agent's hooks.

An in-app, scriptable browser

cmux includes a built-in browser that can be split alongside a terminal pane. Its API is ported from the agent-browser project, allowing AI agents to interact with web pages directly.

Through this API, agents can:

• Snapshot a page's accessibility tree.
• Get references to elements.
• Click, fill forms, and evaluate JavaScript.

The entire application is scriptable via a CLI and a socket API, letting users automate workspace creation, pane splitting, keystrokes, and browser actions.

How to install cmux

The application is available for macOS. The recommended installation method is to download the DMG file and drag cmux into the Applications folder. The app auto-updates via Sparkle.

It can also be installed via Homebrew:

• First, tap the repository: brew tap manaflow-ai/cmux
• Then install the cask: brew install --cask cmux
• Update later with: brew upgrade --cask cmux

On first launch, macOS may require the user to confirm opening an app from an identified developer.

Keyboard shortcuts for navigation

The application supports numerous keyboard shortcuts for managing workspaces, panes, and the browser. Key shortcuts include:

• Workspaces: Cmd+N (new), Cmd+1-8 (jump to), Ctrl+Cmd+] (next).
• Surfaces/Tabs: Cmd+T (new), Ctrl+Tab (next).
• Split Panes: Cmd+D (split right), Option+Cmd+Arrow Keys (focus pane).
• Browser: Cmd+Shift+L (open in split), Cmd+L (focus address bar).
• Notifications: Cmd+I (show panel), Cmd+Shift+U (jump to latest unread).

License and availability

cmux is licensed under the GNU Affero General Public License v3.0 or later (AGPL-3.0-or-later). The project appears to be a personal tool released publicly to address a specific niche in the AI-assisted development workflow.