Script Vercel's fx Agent: Headless Runs in CI

Vercel Labs open sourced fx on August 18, 2026, and it went straight to the front page of Hacker News. The pitch is unusual for a coding agent: a single native binary written in Zig, about 6.3 MiB on disk, roughly a 10 microsecond cold start, single-digit megabytes of memory at baseline, Apache-2.0, and model-agnostic. It is not trying to be an IDE inside your terminal. It behaves like a Unix program.

That last part is the interesting bit, and it is the part almost every write-up has skipped. Because fx starts instantly and speaks JSON, it is the first coding agent that is genuinely comfortable as a step inside a script rather than a thing you sit in front of. You can call it from a Makefile, a GitHub Actions job, a cron entry, or another agent's sandbox, and get back a parseable envelope instead of a wall of ANSI escape codes.