本文重点介绍了“embedding-shapes”的一个项目。出于对 Cursor 的 FastRender 等高资源多智能体项目的质疑，该开发者仅用一个 AI 智能体和三天时间就开发出了一个功能完备的 Web 浏览器。由此产生的 20，000 行 Rust 代码在不依赖外部 Crate 的情况下实现了 HTML 和 CSS 渲染，仅依靠原生系统框架进行底层渲染。作者 Simon Willison 通过运行一个 1MB 的二进制文件验证了该项目，该文件成功渲染了他的博客，包括 SVG 和 CSS 渐变等复杂元素。这项实验表明，当一名优秀的人类开发者指导一个能力出色的单个 AI 智能体时，构建浏览器等复杂软件的门槛比以前想象的要低得多。
One Human + One Agent = One Browser From Scratch (via) embedding-shapes was so infuriated by the hype around Cursor's FastRender browser project - thousands of parallel agents producing ~1.6 million lines of Rust - that they were inspired to take a go at building a web browser using coding agents themselves.
The result is one-agent-one-browser and it's really impressive. Over three days they drove a single Codex CLI agent to build 20,000 lines of Rust that successfully renders HTML+CSS with no Rust crate dependencies at all - though it does (reasonably) use Windows, macOS and Linux system frameworks for image and text rendering.
I installed the 1MB macOS binary release and ran it against my blog:
chmod 755 ~/Downloads/one-agent-one-browser-macOS-ARM64
~/Downloads/one-agent-one-browser-macOS-ARM64 https://simonwillison.net/
Here's the result:
It even rendered my SVG feed subscription icon! A PNG image is missing from the page, which looks like an intermittent bug (there's code to render PNGs).
The code is pretty readable too - here's the flexbox implementation.
I had thought that "build a web browser" was the ideal prompt to really stretch the capabilities of coding agents - and that it would take sophisticated multi-agent harnesses (as seen in the Cursor project) and millions of lines of code to achieve.
Turns out one agent driven by a talented engineer, three days and 20,000 lines of Rust is enough to get a very solid basic renderer working!
I'm going to upgrade my prediction for 2029: I think we're going to get a production-grade web browser built by a small team using AI assistance by then.