Cursor's latest "browser experiment" implied success without evidence

Summary

2026-01-16 Cursor's latest "browser experiment" implied success without evidence On January 14th 2026, Cursor published a blog post titled "Scaling long-running autonomous coding" (https://cursor.com/blog/scaling-agents) In the blog post, they talk about their experiments with running "coding agents autonomously for weeks" with the explicit goal of understand[ing] how far we can push the frontier of agentic coding for projects that typically take human teams months to complete They talk about some approaches they tried, why they think those failed, and how to address the difficulties. Finally they arrived at a point where something "solved most of our coordination problems and let us scale to very large projects without any single agent", which then led to this: To test this system, we pointed it at an ambitious goal: building a web browser from scratch. The agents ran for close to a week, writing over 1 million lines of code across 1,000 files. You can explore the source code on GitHub (https://github.com/wilsonzlin/fastrender) This is where things get a bit murky and unclear. They claim "Despite the codebase size, new agents can still understand it and make meaningful progress" and "Hundreds of workers run concurrently, pushing to the same branch with minimal conflicts", but they never actually say if this is successful or not, is it actually working? Can you run this browser yourself? We don't know and they never say explicitly. After this, they embed the following video: Video And below it, they say "While it might seem like a simple screenshot, building a browser from scratch is extremely difficult.". They never actually claim this browser is working and functional error: could not compile 'fastrender' (lib) due to 34 previous errors; 94 warnings emitted And if you try to compile it yourself, you'll see that it's very far away from being a functional browser at all, and seemingly, it never actually was able to build. Multiple recent GitHub Actions runs on main ...