Cursor used agents to write a browser, proving AI can write shoddy code at scale

A week ago, Cursor CEO Michael Truell celebrated what sounded like a remarkable event.

"We built a browser with GPT-5.2 in Cursor," he said in a social media post. "It ran uninterrupted for one week."

This browser, he said, consisted of three million lines of code across thousands of files. "The rendering engine is from-scratch in Rust with HTML parsing, CSS cascade, layout, text shaping, paint, and a custom JS VM.”

An 88 percent job failure rate is indicative of a code base that doesn't work

"It *kind of* works! It still has issues and is of course very far from WebKit/Chromium parity, but we were astonished that simple websites render quickly and largely correctly," he added.

Some developers managed to compile the code after some bug fixes. Others reported success after revisions to the build instructions.

But by and large, developers aren’t convinced Cursor has ...