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fx

Vercel Labsmeasured

A whole coding agent in one Zig binary with no runtime to install, plus a WebAssembly build that drops the same core into a JavaScript host. Permissions are enforced inside the harness.

spec

Maker
Vercel Labs
Kind
other
Version
0.0.3 · checked 2026-08-20
License
Apache-2.0
npm
Not published to npm. The npm package named fx is an unrelated command-line JSON viewer.

getting it

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

how it is built

Language
Zig
Ships as
Single binary
What it can enforce
Gate in the harness
Out of the box
Gated by default
Extends via
Skills and MCP · Subagents
Embeds via
WASM and ACP
Runtime
Native
Licence
Apache-2.0

going deeper

This one is measured. Every concept in its docs is laid out as a place, sized by how much source sits behind it, with a real recorded turn you can step through.

open fx in the playground