Key takeaways
- 21,700+ GitHub stars as of June 2026 (up from ~5,200 in March) — native Swift/AppKit app built on libghostty for GPU-accelerated terminal rendering
- Notification rings and sidebar badges solve the 'which agent needs me?' problem across dozens of parallel sessions
- Agent-agnostic terminal — works with any CLI agent out of the box, no lock-in to specific workflows
- Backed by Manaflow (YC S24), which has pivoted to cmux as its flagship product with dual GPL/commercial licensing
FAQ
What is cmux?
cmux is a free, open-source native macOS terminal app built on libghostty that adds vertical tabs, notification rings, split panes, and a built-in browser — optimized for running parallel AI coding agents.
How much does cmux cost?
cmux is free and open source, dual-licensed under GPL-3.0-or-later with a commercial license available from Manaflow for organizations that can't comply with GPL.
Who competes with cmux?
Ghostty (standalone terminal without agent features), Supacode (also libghostty-based), and Agentastic (native Swift with code review). For orchestration, Tembo.
Does cmux manage git worktrees?
No. cmux is a terminal, not an orchestrator. It shows git branch and PR status in the sidebar but doesn't create or manage worktrees — pair it with dmux or manual worktree workflows.
What's the relationship between cmux and Ghostty?
cmux uses libghostty as a library for terminal rendering, similar to how apps use WebKit. It reads your existing Ghostty config for themes, fonts, and colors. Ghostty is a standalone terminal; cmux adds agent-focused features on top.
Executive Summary
cmux is a native macOS terminal app built on libghostty that solves a specific pain point: knowing which of your many parallel coding agents needs attention.[1] It adds vertical tabs with notification rings, a sidebar showing git branch and PR status, split panes, and a built-in scriptable browser — all in a Swift/AppKit app that reads your existing Ghostty config.
| Attribute | Value |
|---|---|
| Company | Manaflow, Inc. (YC S24) |
| Founded | 2024 (Manaflow); cmux launched February 2026 |
| Funding | Y Combinator pre-seed (S24); further funding not publicly disclosed[2] |
| Headquarters | San Francisco |
| GitHub Stars | ~21,800 (as of June 11, 2026)[1] |
Product Overview
cmux was born from the frustration of running many Claude Code and Codex sessions in Ghostty split panes, where native macOS notifications all say the same unhelpful "Claude is waiting for your input."[1] The creator wanted a terminal that could show which agent needs attention at a glance.
Unlike orchestrators that manage agent lifecycles, cmux is a terminal — it provides the environment where agents run, with better notification and organization primitives. Any CLI agent works out of the box.
Key Capabilities
| Capability | Description |
|---|---|
| Notification Rings | Blue ring around panes + sidebar badges when agents need attention |
| Vertical Tabs | Sidebar shows git branch, PR status, working directory, listening ports, latest notification |
| Split Panes | Horizontal and vertical splits within workspaces |
| Built-in Browser | Scriptable browser API (ported from Vercel's agent-browser) alongside terminal |
| Socket API | CLI and socket API for automation — create workspaces, split panes, send keystrokes |
| Teammate Mode | One command spawns Claude Code teammates as native splits with sidebar metadata and notifications (added spring 2026) |
| Ghostty Compatible | Reads existing ~/.config/ghostty/config for themes, fonts, colors |
| GPU Accelerated | Powered by libghostty for smooth rendering |
Product Surfaces
| Surface | Description | Availability |
|---|---|---|
| macOS App | Native Swift/AppKit desktop app | GA |
| CLI | cmux command for scripting and automation | GA |
Technical Architecture
cmux is a native Swift/AppKit application that embeds libghostty as a library for terminal rendering.[3] This is the same approach as using WebKit for web views — Ghostty provides the terminal engine, cmux adds the UI chrome and notification system.
Key Technical Details
| Aspect | Detail |
|---|---|
| Deployment | macOS app (.dmg or Homebrew) |
| Runtime | Native Swift/AppKit, GPU-accelerated via libghostty |
| Model(s) | None — agent-agnostic terminal |
| Integrations | Any CLI agent, Ghostty config, git, GitHub PRs |
| Open Source | Yes — dual-licensed GPL-3.0-or-later, commercial license available[4] |
Strengths
- Notification system is the killer feature — Blue rings on panes, sidebar badges, notification popover, and native macOS notifications triggered via terminal escape sequences (OSC 9/99/777) or CLI hooks[1]
- Native performance — Swift/AppKit with libghostty means fast startup, low memory, and GPU-accelerated rendering — no Electron tax
- Zero lock-in — It's a terminal; any agent that runs in a terminal works. No opinionated workflow imposed[3]
- Scriptable — Socket API and CLI for creating workspaces, splitting panes, sending keystrokes, and controlling the built-in browser — enables custom orchestration
- Strong community signal — 21,700+ GitHub stars and 1,600+ forks as of June 2026, a #2 Hacker News launch, Product Hunt launch, and active Discord[1][5]
- Rapid release cadence — Four releases in the first week of June 2026 alone (v0.64.11–v0.64.14), with the repo pushed to daily[6]
Cautions
- macOS only — No Windows, Linux, or web version; limits team adoption in mixed-OS environments
- Not an orchestrator — Doesn't manage git worktrees, agents, or tasks; you still need to set up and launch agents yourself
- GPL-3.0 dual licensing — Copyleft license is more restrictive than MIT; organizations that can't comply must buy a commercial license from Manaflow[4]
- Performance complaints under load — Some users report laggy scrolling and higher CPU usage than plain Ghostty, and the open issue count (2,600+) reflects the breakneck release pace[7][1]
- Young, fast-moving codebase — Launch-week users hit real bugs (tab focus, tab switching); quality is improving but expect rough edges[5]
- No worktree management — Shows git branch in sidebar but doesn't create/manage worktrees; pair with dmux or similar for isolation
What Developers Say
Community sentiment as of June 2026, from cmux's Hacker News launch and follow-on discussion:
- Praise: "Vertical tabs for a terminal emulator seems killer, I'll be trying this out for sure." — Hacker News[5]
- Praise: "Ghostty was already my fave terminal, so this is just taking it to the next level... I also hate Electron... Loving cmux so far!" — Product Hunt[8]
- Criticism: "Looks like this could be really cool, but it's a buggy mess. Can't switch top tabs, can't close tabs." — Hacker News (launch week; the maintainer shipped a fix)[5]
- Criticism: A May 2026 HN post asked "Why cmux is so lagging when scrolling, also it uses more CPU than Ghostty" — performance overhead versus plain Ghostty remains a recurring complaint[7]
The launch thread (198 points, 77 comments) skews positive, with the maintainer responding to nearly every piece of feedback and filing issues on the spot.[5]
Pricing & Licensing
| Tier | Price | Includes |
|---|---|---|
| Open Source | Free | Full functionality (GPL-3.0-or-later) |
| Commercial License | Contact Manaflow | For organizations that cannot comply with GPL |
Licensing model: Dual-licensed — GPL-3.0-or-later for open-source use, with a commercial license available from Manaflow (founders@manaflow.com) for organizations that can't comply with GPL.[4]
Hidden costs: None for cmux itself. Agent CLI subscriptions are separate.
Competitive Positioning
Direct Competitors
| Competitor | Differentiation |
|---|---|
| Ghostty | cmux adds notifications, vertical tabs, sidebar, browser — Ghostty is the raw terminal engine |
| Supacode | Also libghostty-based but adds worktree management — cmux is more terminal, less orchestrator |
| Agentastic | Native Swift with code review — cmux focuses on terminal primitives, not review workflows |
| Tembo | Full orchestration platform — cmux is the terminal layer, not the orchestration layer |
When to Choose cmux Over Alternatives
- Choose cmux when: You want a fast native terminal with notification awareness for parallel agents
- Choose Emdash when: You want GUI-based worktree management and issue tracker integration
- Choose dmux when: You want tmux-based worktree orchestration (pairs well with cmux's notification approach)
Ideal Customer Profile
Best fit:
- Developers running many parallel agent sessions who need notification management
- Ghostty users wanting agent-optimized features on top of their existing config
- Terminal-first developers who dislike Electron-based tools
Poor fit:
- Teams needing centralized orchestration, signed commits, or enterprise governance
- Developers wanting an all-in-one orchestrator that manages worktrees and agent lifecycles
- Mixed-OS teams (Windows/Linux users)
Viability Assessment
| Factor | Assessment |
|---|---|
| Financial Health | Moderate — Manaflow is YC S24-backed; revenue model is commercial licensing |
| Market Position | Strong in niche — the breakout terminal layer for agent workflows |
| Innovation Pace | Rapid — repo pushed to daily, multiple releases per week[6] |
| Community/Ecosystem | Strong — 21.8K stars (4x growth since March 2026), Product Hunt, Discord[1] |
| Long-term Outlook | Positive — clear niche, strong community, company now all-in on cmux |
cmux fills a specific gap: the terminal itself. While orchestrators manage what agents do, cmux manages where you see them. Notably, Manaflow has pivoted from its original YC S24 product (a spreadsheet for LLM agents) to position itself as "an open source applied AI lab" with cmux as its flagship — the company's bet is now cmux itself, monetized through dual licensing.[2][4]
Bottom Line
cmux is the best terminal app for developers running parallel coding agents on macOS, and its trajectory since launch confirms it — quadrupling from ~5,200 to ~21,800 GitHub stars between March and June 2026.[1] Its notification system — rings, badges, popover — solves the real problem of tracking which agent needs you across dozens of sessions. It deliberately stays out of orchestration, making it a composable building block rather than an opinionated platform.
Recommended for: macOS developers running parallel agent sessions who want native performance and notification awareness.
Not recommended for: Teams needing orchestration, worktree management, or cross-platform support — or anyone allergic to a fast-moving codebase with a large open-issue backlog.
Outlook: cmux is on track to become the default terminal for Mac developers using AI coding agents. Manaflow has gone all-in, repositioning the company around cmux with a dual GPL/commercial licensing model, and added features like one-command Claude Code teammate-mode splits. Watch the performance-versus-Ghostty complaints and whether commercial licensing gains enterprise traction.
Research by Ry Walker Research • methodology
Sources
- [1] cmux GitHub Repository
- [2] Manaflow on Y Combinator
- [3] cmux Website
- [4] cmux LICENSE (dual GPL-3.0/commercial)
- [5] Show HN: cmux — Ghostty-based terminal with vertical tabs and notifications
- [6] cmux Releases
- [7] HN: Why cmux is so lagging when scrolling, also it uses more CPU than Ghostty
- [8] cmux on Product Hunt
- [9] Manaflow Website
- [10] cmux Demo Video