The Specification Gap: Why Your AI Produces Impressive-Looking Output With Fundamental Problems + The Prompt Kit To Help You Fix It
Cursor ran a fleet of agents for close to a week in January 2026, and found GPT-5.2 best for extended autonomous work. When the experiment finished, the system had generated over a million lines of Rust code across a thousand files and built a browser rendering engine—HTML and CSS parsing, cascade, layout, text pipeline, paint, and JavaScript integration. The FastRender repo describes itself as “under heavy development,” and Simon Willison actually ran it and posted screenshots: it kind of works.