cmux

What is cmux?

The cmux documentation describes a macOS terminal application built on the Ghostty terminal engine. Its primary design feature is a vertical tab layout, which stacks tabs along the side of the window rather than across the top. The tool also includes a notification system specifically intended for AI coding agents — the terminal can surface alerts when an agent task completes or requires input. The project is maintained on GitHub under manaflow-ai/cmux, where the repository shows 25,211 stars. Based on the repository description, cmux positions itself as a terminal front-end tailored to the workflow patterns of agent-assisted development, not as a general-purpose replacement for existing terminal emulators.

Who is cmux for?

The target audience, according to the project documentation and repository signals, is developers who run AI coding agents (such as Claude Code, Codex, or similar agentic tools) as part of their daily editing loop. The vertical tab design aims to keep multiple agent sessions visible side by side, while the notification layer attempts to solve the problem of an agent finishing work while the developer is in another window. The tool is macOS-only — the documentation makes no mention of Linux or Windows builds. It assumes the user already relies on Ghostty-compatible configuration and is comfortable with a terminal that departs from the traditional horizontal tab convention. Developers who rarely use AI agents or who prefer tmux, iTerm2, or Warp will find fewer reasons to switch.

How much does cmux cost?

The pricing page on the cmux website lists the tool as free with a starting price of $0/month. There is no mention of a paid tier, usage limits, or a subscription. The GitHub repository also carries no license or purchase requirements that would imply a commercial product. Given the project’s relative youth and single-platform scope, the free model appears to be a means of building an early user base rather than a freemium upsell. Whether this remains the case in future versions is not addressed in the available documentation.