---
title: "What is Muse Code? Meta's terminal coding agent"
url: https://helicon.sh/glossary/muse-code
description: "Muse Code is Meta's AI coding agent, used through the muse command line tool on macOS, Linux and Windows. A plain definition, what it does, and how clients connect to it."
updated: 2026-09-19
site: Helicon
---

# What is Muse Code?

Muse Code is Meta's AI coding agent. You use it through the `muse` command line tool, which runs on macOS, Linux and Windows, and it works inside a project directory: reading files, editing them, running commands and asking for approval. Other applications can drive it over the Muse Code Session Protocol.

## What it does

- Works inside a working directory, with the files actually on disk.
- Reads, edits and creates files, and runs shell commands.
- Asks for approval before acting, according to the mode you set.
- Keeps a session per working directory, with a turn by turn history.
- Can fan work out to parallel subagents and run multi step workflows.

## How you pay for it

Muse Code is used through a subscription rather than per request API keys for most people. That is why a client that routes your work through its own API metering is a common complaint: the plan you already bought stops being the thing that pays.

## How other apps use it

Meta ships an MIT licensed SDK for the Muse Code Session Protocol, so a client can start `muse serve` and drive a session properly instead of scraping terminal output. Helicon is one such client. VS Code extensions and Agent Client Protocol bridges are others.

## Frequently asked questions

### Is Muse Code free?

It is used through a Meta subscription. Helicon, a client for it, is free and MIT licensed and adds no billing of its own.

### Does Muse Code run on Windows?

Yes, natively, and it also runs inside WSL2.

### Is Muse Code the same as the Muse assistant app?

No. Muse Code is the coding agent used through the muse CLI. The Muse assistant app for Mac is a different product.

## Related

- [the muse CLI](https://helicon.sh/glossary/muse-cli): The muse command line tool is how you run Muse Code. What it installs, what muse login does, and why a GUI still needs it present.
- [the Muse Code Session Protocol](https://helicon.sh/glossary/msp): MSP is the JSON-RPC protocol that applications use to drive a Muse Code session over stdio, instead of parsing terminal output. What it carries and why it matters.
- [Muse Code GUI](https://helicon.sh/muse-code-gui): Yes, Muse Code has graphical interfaces. A standalone desktop and web app, VS Code extensions, ACP editor bridges and other open-source wrappers, compared honestly.

---

Helicon is a free, MIT licensed, unofficial community client for Meta's Muse Code CLI. Not made, sponsored or endorsed by Meta. Source: https://helicon.sh/. Machine readable index: https://helicon.sh/llms.txt