// the find
manaflow-ai/cmux
Ghostty-based macOS terminal with vertical tabs and notifications for AI coding agents
cmux is a native macOS terminal app built on libghostty (the Ghostty terminal engine) that adds a vertical tab sidebar, per-pane notification rings, and an embedded browser aimed at developers running multiple AI coding agent sessions in parallel. It's essentially Ghostty with a purpose-built UI layer for wrangling Claude Code, Codex, Gemini CLI, and similar tools across many concurrent sessions.
- Native Swift/AppKit with GPU-accelerated rendering via libghostty — not Electron. Startup time and memory usage are meaningfully better than the Tauri/Electron alternatives in this space.
- The notification system is genuinely useful: OSC 9/99/777 sequence detection plus a `cmux notify` CLI hook means agents can signal which specific pane needs attention, something vanilla macOS notifications can't do across many tabs.
- SSH workspace support routes browser panes through the remote network, so localhost URLs in the embedded browser just work against a remote dev server — that's a non-obvious integration detail that saves real friction.
- Well-structured codebase with discrete Swift packages (CMUXAgentLaunch, CMUXWorkstream, CMUXAgentVault, etc.), written review bot rules for actor isolation and concurrency, and a file-length budget TSV — signals the team is thinking about maintainability beyond just shipping features.
- macOS-only, no Linux or Windows support, and the dependency on libghostty (itself a relatively young library with its own stability caveats) means you're betting on two projects staying in sync.
- The source tree is present but building from source isn't documented — there's no Package.swift at the root, no build instructions in CONTRIBUTING.md, and the Xcode project isn't visible in the file tree. For a GPL-3.0 project, this is a real gap; you effectively have to take the DMG.
- The in-app browser uses WKWebView/WebKit under the hood (it's the only option on macOS without Chromium), which has persistent quirks around certain web APIs, CSP policies, and IndexedDB that will bite users whose dev servers rely on modern browser behavior.
- The Founder's Edition paywall (personal iMessage/WhatsApp with the founder, cloud VMs, iOS app) signals the long-term monetization plan lives outside the open-source repo. The features that make multi-agent workflows actually scalable — cloud VMs, sync — are the paid tier, so the free version has a ceiling.