AI product Open source

fx

fx is an open-source coding-agent harness and command-line interface written in Zig by Vercel Labs. It is designed as a compact Unix-like alternative to a terminal IDE, with interactive and one-shot requests for inspecting and modifying repository code, running shell commands, and saving or resuming sessions. The agent supports skills, MCP tools, plugins, subagents, permission rules, and headless requests, and can be embedded natively or through WebAssembly. It is model-agnostic, supports local and cloud inference, is distributed under the Apache-2.0 license, and is marked experimental by its repository.

View repository Visit site Mentioned in 3 videos ↓

What fx is used for

3 uses taken from transcripts — each links to the moment in the video.

  • A small native command-line coding agent for terminal use. It inspects and changes repository code, runs shell commands, saves sessions, and supports MCP, skills, plugins, subagents, and headless requests while remaining local.

  • A compact coding agent designed more like a Unix command than a terminal IDE. It supports interactive and one-shot requests, resumable sessions, embedded native or WebAssembly use, skills, MCP tools, subagents, and permission rules.

  • A tiny coding agent written in Zig that is designed to feel like a Unix command rather than an IDE in a terminal. It supports interactive sessions, one-shot JSON output, MCP tools, subagents, editor connections through ACP, and WebAssembly embedding.

Videos mentioning fx

3 in the library.