YCombinator

Free

Open source applied AI lab building next-gen devtools

FreeFree tier

Type

Open Source

Company

Manaflow

Visit Website GitHub (40 stars)

About YCombinator

Manaflow is an open-source applied AI lab that builds next-generation developer tools. Their flagship product, cmux, is an open-source terminal built specifically for coding agents. cmux is based on Ghostty (Swift/AppKit) for macOS and offers features like vertical tabs, a built-in browser, notifications, workspaces, splits, and a CLI that allows AI agents to command the browser, create workspaces, and start other agents. It is designed as a composable primitive, not a prescriptive solution, giving developers full flexibility to build custom agent-driven workflows. cmux is free, open-source (AGPL), and has gained 3.5k GitHub stars in two weeks, trusted by builders from Nvidia, Google, and OpenAI. Manaflow was part of Y Combinator's Summer 2024 batch and is based in San Francisco.

Key Features

Open-source (AGPL) terminal built for coding agents

Based on Ghostty, native macOS (Swift/AppKit)

Vertical tabs for managing multiple agent sessions

Blue rings around panes that need attention

Built-in browser controllable via CLI

CLI allows agents to command browser, create workspaces, and start new agent terminals

Workspaces, splits, and tabs for flexible layout

Designed as composable primitives, not a prescriptive solution

Notifications for agent activity

Trusted by thousands of builders from Nvidia, Google, and OpenAI

Pros & Cons

Pros

Free and open-source (AGPL) with no lock-in
Composable primitives allow full flexibility for developers
Built specifically for modern AI agent workflows
Fast, native macOS terminal based on Ghostty
Strong early traction: 3.5k GitHub stars in two weeks, #2 on Hacker News
Batteries included: browser, notifications, tabs, splits

Cons

Currently only available for macOS
Early-stage project with rapid iteration; may have limited documentation or stability
Requires comfort with terminal-based workflows and possibly command-line agents
Not a full IDE replacement for all developers; designed for agent-heavy use cases

Best For

Managing fleets of coding agents (e.g., multiple Claude Code or Codex sessions)Building custom agent orchestrators and harnesses on top of cmuxExperimenting with AI-driven development workflowsReplacing traditional IDEs with agent-centric terminal environments

FAQ

What is cmux?

cmux is an open-source terminal built for coding agents, based on Ghostty. It includes vertical tabs, a built-in browser, notifications, and a CLI that allows AI agents to control the terminal, browser, and workspaces.

Is cmux free?

Yes, cmux is free and open-source under the AGPL license.

Who is using cmux?

cmux is used by thousands of builders from companies like Nvidia, Google, and OpenAI.

How does cmux handle coding agents?

cmux provides a CLI that agents can use to command the built-in browser, create new workspaces, and start other agents in new terminals, allowing agents to use cmux just like a human would.