vercel-labs/fx

What it solves

fx provides a lightweight, high-performance coding agent that avoids the bloat of heavy terminal-based IDEs. It solves the need for a minimal, embeddable agent harness that can be integrated into larger systems or used as a simple CLI tool for coding tasks.

How it works

Written in Zig, fx is a model-agnostic agent that operates directly on a project workspace. It can be run as a standalone CLI or embedded into other applications as a native binary or WebAssembly module. It supports the Agent Client Protocol (ACP) for editor connectivity and integrates with the Model Context Protocol (MCP) for external tools. It also allows for the creation of subagents and reusable instruction sets called "skills."

Who it’s for

It is designed for developers who want a fast, low-overhead coding assistant that feels like a Unix shell, as well as researchers and software architects looking to embed agentic capabilities into their own applications.

Highlights

• Extreme Minimalism: Distributed as a tiny 7.8 MiB binary.
• Flexible Deployment: Supports local or cloud inference and can be compiled to WebAssembly.
• Embeddable: Provides SDKs to embed the agent core or interactive terminal into JavaScript hosts.
• Extensible: Supports MCP for external tools, subagents for delegating work, and custom skills for reusable instructions.