```
 ⠀⠀⠀⠀⠀⠀⣠⣾⣿⣿⣿⠀⠀⠀⠀⠀⠀⠀⠀
 ⠀⠀⠀⠀⠀⢰⣿⡿⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
 ⠀⠀⠀⣠⣶⣿⣿⣷⣶⡶⣶⣶⣆⠀⠀⠀⣴⣶⣶⠆
 ⠀⠀⠀⠉⢹⣿⣿⠉⠉⠀⠘⢿⣿⣧⣀⣾⣿⡿⠃⠀             Tiny, open, embeddable, native coding agent.
 ⠀⠀⠀⠀⣼⣿⡏⠀⠀⠀⠀⠀⠻⣿⣿⣿⠟⠀⠀⠀
 ⠀⠀⠀⢀⣿⣿⠃⠀⠀⠀⠀⢠⣦⠘⢿⣿⣷⡀⠀⠀             curl -fsSL https://fx.sh/setup.sh | bash
 ⠀⠀⠀⣸⣿⡟⠀⠀⠀⠀⣰⣿⣿⠗⠀⠻⣿⣿⣄⠀
 ⠀⠀⠀⣿⣿⠇⠀⠀⠀⠾⠿⠿⠋⠀⠀⠀⠘⠿⠿⠦             ⚠ Status: Experimental. Use at your own risk.
  ⠀⣸⣿⡿⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
 ⣿⣿⣿⠟⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
```

fx is a coding agent CLI written in Zig: a small native binary that is open source (Apache-2.0), model-agnostic, and embeddable as a harness in larger systems. Its interface stays closer to a Unix shell than an IDE in the terminal.

## Highlights

- **Any model:** Vercel AI Gateway, ChatGPT or Grok subscriptions, or your own OpenAI-compatible endpoint such as Ollama or OpenRouter
- **Any interface:** interactive shell, one-shot `fx ask` for scripts, or embedded through libfx and ACP
- **Shell-like output:** inline rendering that preserves your terminal scrollback
- **Extensible:** skills, MCP servers, and subagents

<p>
  <a href="https://vercel.com/labs#labs-products"><img alt="Vercel Labs Product" src="https://img.shields.io/badge/LABS-PRODUCT-0a0a0a.svg?style=for-the-badge&amp;logo=Vercel&amp;labelColor=000000" height="28"></a>
  <a href="https://github.com/vercel-labs/fx/releases/latest"><img alt="fx CLI release" src="https://img.shields.io/github/v/release/vercel-labs/fx.svg?style=for-the-badge&amp;labelColor=000000&amp;label=release" height="28"></a>
  <a href="https://github.com/vercel-labs/fx/blob/main/LICENSE"><img alt="License: Apache-2.0" src="https://img.shields.io/github/license/vercel-labs/fx.svg?style=for-the-badge&amp;labelColor=000000" height="28"></a>
</p>

## Install

```bash
curl -fsSL https://fx.sh/setup.sh | bash
```

## Get started

Sign in with one of:

- `fx login`: Vercel AI Gateway
- `fx login codex`: ChatGPT subscription (OpenAI Codex OAuth)
- `fx login grok`: Grok subscription (xAI OAuth)
- `fx setup`: AI Gateway API key

Then start the interactive shell from a project:

```bash
cd your_project
fx
```

Or make a one-shot request:

```bash
fx ask "explain the changes in this repository"
```

Inside the shell, run `/help` to browse interactive commands.

## Documentation

Visit [fx.sh/docs](https://fx.sh/docs) for the full manual: sessions, models, custom model connections, permissions, configuration, skills, MCP, subagents, embedding, and the complete CLI and slash command references. Agents can read any page as Markdown by appending `.md` to its URL, or fetch [llms-full.txt](https://fx.sh/llms-full.txt) for everything in one file.

## Custom model connections

Add named connections for any OpenAI Chat Completions endpoint, including local servers such as Ollama and gateways such as OpenRouter, in `~/.fx/settings.json`, then select one for the profile or a single invocation:

```bash
fx provider local
FX_PROVIDER=openrouter FX_MODEL=openai/gpt-4.1 fx ask "review this change"
```

See [Custom model connections](https://fx.sh/docs/configure-fx/custom-model-connections) for connection JSON, model metadata, and behavior details.

## Themes

fx ships with `fx-dark` and `fx-light` and follows your terminal's light or dark mode. Pin a variant with `FX_THEME=light` or `FX_THEME=dark`, or drop a VS Code format theme at `~/.fx/themes/<name>.json` and select it with the `theme` setting or `FX_THEME=<name>` per launch. See [Configuration](https://fx.sh/docs/configure-fx/configuration) for all environment variables.

## Embed fx

fx builds as a native binary or WebAssembly. Applications embedding fx can provide network transport, session storage, configuration, permission handling, and terminal I/O.

| Surface | Use |
| --- | --- |
| `fx acp` | Connect the native agent to editors and other Agent Client Protocol clients. |
| `createFxAgent()` | Embed the agent core in a JavaScript host with `fx-core.wasm`. |
| `createFxTerminal()` | Embed the interactive terminal with `fx-term.wasm`. |

The SDK is published to npm as [libfx](https://www.npmjs.com/package/libfx). See the [WebAssembly SDK](sdk/README.md) and the runnable Node.js, browser, Next.js, and Nuxt [examples](examples/README.md). The WebAssembly SDK is experimental.

## Build from source

Building fx requires [Zig 0.16.0+](https://ziglang.org/download/):

```bash
git clone https://github.com/vercel-labs/fx.git
cd fx
zig build -Doptimize=ReleaseSafe
./zig-out/bin/fx
```

Run the test suite with `zig build test`. See [CONTRIBUTING.md](CONTRIBUTING.md) for development and contribution guidelines.

## Security

Report security vulnerabilities through the [contact page](https://fx.sh/contact) instead of a public issue.

## License

[Apache-2.0](LICENSE). Third-party licenses and attributions are listed in [THIRD_PARTY_NOTICES.md](THIRD_PARTY_NOTICES.md).

## Credits

Interface sounds by [cuelume](https://github.com/Danilaa1/cuelume).