What cmux Adds to the macOS Terminal Stack

cmux launched publicly in February 2026 as a Ghostty-based macOS terminal for coding agents. On paper, that sounds like one more terminal app in a market that already has Apple’s Terminal, iTerm2, Ghostty, tmux, and a growing number of tools built around AI coding.

The reason people care is simpler than the product pitch. Running one shell is easy. Running several coding sessions at once is harder. Once developers start using tools like Codex, Claude Code, OpenCode, Gemini CLI, or Aider in parallel, the real problem is keeping track of what needs attention and where.

What cmux is

Manaflow introduced cmux on February 12, 2026 as a native macOS terminal built on Ghostty. The company later posted it to Hacker News on February 19, 2026 and published a follow-up on February 21.

The basic product claim is clear enough from the official docs and README. cmux is a macOS terminal with vertical workspaces, split panes, a notification system built around agent hooks, a browser pane, and a CLI plus socket API for scripting.

That does not make it the first advanced terminal. It does make it a fairly direct answer to a newer problem: how to manage several coding sessions without losing track of which one matters right now.

Why cmux exists

The terminal problem has changed.

For years, terminal users mostly cared about speed, tabs, panes, themes, and shell integration. Those things still matter. But once a developer starts running several coding sessions at the same time, another issue shows up. Which session is waiting for input? Which workspace belongs to which branch? Which browser view belongs to which local server?

cmux is built around that problem. The app tries to keep tasks visible instead of treating every tab like a plain terminal box.

How it fits next to Terminal, iTerm2, and Ghostty

Apple’s Terminal is still the baseline. It gives users windows, tabs, window groups, and AppleScript automation. For plenty of people, that is enough.

iTerm2 went much further. It added split panes, shell integration, triggers, badges, notifications, and a large set of settings. Its current documentation even includes a built-in web browser and AI chat integration.

Ghostty changed the conversation in a different way. Instead of trying to win on feature count alone, it pushed hard on speed, native platform UI, GPU acceleration, and a reusable terminal engine through libghostty.

cmux sits on top of that history. It is not replacing the whole category. It is taking the terminal in a more task-oriented direction for people who run several coding sessions at once.

What cmux actually adds

The main change is not one feature. It is how the app organizes work.

cmux uses a vertical sidebar to show workspaces and tabs with details such as git branch, pull request status, working directory, listening ports, and the latest notification text. The goal is to make each workspace easier to scan.

Its notification system is just as important. According to the project docs, cmux can listen for terminal notification sequences such as OSC 9, 99, and 777, and it also provides a cmux notify command that can be wired into coding-agent hooks. That gives users more context than a generic system alert.

The browser pane matters for the same reason. Agents can inspect accessibility trees, click elements, fill forms, read console logs, and run JavaScript next to the terminal session they belong to. The point is not that browser automation is new. The point is that browser work and terminal work now live side by side inside the same task view.

What feels different about it

It would be wrong to say cmux invented split panes, metadata, notifications, or terminal automation. Older terminals already did a lot of that work.

What feels different is the default unit of work.

In Terminal, the unit is usually a shell window. In iTerm2, it becomes a richer session. In Ghostty, it becomes a faster and cleaner terminal view. In cmux, it becomes a workspace that may contain several panes, several coding sessions, and a browser that all belong to the same task.

That is a good fit for people who already work this way. It will matter less to people who only keep one shell open.

Who this is for

cmux is not automatically a better terminal for everyone.

If you mostly use one editor, one shell, and one coding tool at a time, Terminal, iTerm2, or Ghostty may already be enough. But if you are running several coding sessions at once, juggling branches, or moving constantly between terminal output and browser checks, then cmux’s design makes more sense.

That is the clearest way to read it. cmux is less a general terminal upgrade than a focused tool for a specific kind of multi-session development work.

Bottom line

cmux matters because it shows one way the terminal is changing under AI coding workloads.

The old questions were mostly about speed, panes, and customization. The newer question is how to keep several coding sessions visible and manageable without leaving the terminal. cmux is one answer to that question. It is not the only answer, but it is a useful sign of where this part of the tool market is going.