I built a pure-Rust headless browser for AI agents. No Chromium. No V8. (Open Source)

There have been many great headless browsers for AI agents, mostly written in Rust, though many still rely on Chromium or V8 internally. So I built h5i with Claude Code: a headless browser written entirely in Rust. It uses Rust engines for all of JavaScript execution, HTML, the DOM, CSS, layout, and rendering. h5i also owns the networking layer to policy-check and record all requests. I've used Claude to design the details of the API structure, handle the numerous corner cases that are inevitable in browsers, find and fix bugs, and set up benchmarks. In a simple benchmark on a documentation-style page, h5i was approximately 3× faster while using 86% less memory than Chromium. GitHub: github.com/h5i-dev/h5i (Apache-2.0)