Wilson Lin on FastRender: a browser built by parallel agents

Summary

Wilson Lin on FastRender: a browser built by thousands of parallel agents 23rd January 2026 Last week Cursor published Scaling long-running autonomous coding, an article describing their research efforts into coordinating large numbers of autonomous coding agents. One of the projects mentioned in the article was FastRender, a web browser they built from scratch using their agent swarms. I wanted to learn more so I asked Wilson Lin, the engineer behind FastRender, if we could record a conversation about the project. That 47 minute video is now available on YouTube. I’ve included some of the highlights below. See my previous post for my notes and screenshots from trying out FastRender myself. What FastRender can do right now We started the conversation with a demo of FastRender loading different pages (03:15). The JavaScript engine isn’t working yet so we instead loaded github.com/wilsonzlin/fastrender, Wikipedia and CNN—all of which were usable, if a little slow to display. JavaScript had been disabled by one of the agents, which decided to add a feature flag! 04:02 JavaScript is disabled right now. The agents made a decision as they were currently still implementing the engine and making progress towards other parts... they decided to turn it off or put it behind a feature flag, technically. From side-project to core research Wilson started what become FastRender as a personal side-project to explore the capabilities of the latest generation of frontier models—Claude Opus 4.5, GPT-5.1, and GPT-5.2. 00:56 FastRender was a personal project of mine from, I’d say, November. It was an experiment to see how well frontier models like Opus 4.5 and back then GPT-5.1 could do with much more complex, difficult tasks. A browser rendering engine was the ideal choice for this, because it’s both extremely ambitious and complex but also well specified. And you can visually see how well it’s working! 01:57 As that experiment progressed, I was seeing better and better results from si...