Cursor is better at marketing than coding

Cursor presented a project claiming a browser built with GPT-5.2 and extensive Rust rendering-engine work totaling 3M+ lines across thousands of files. Public messaging emphasized a working engine with HTML parsing, CSS cascade, layout, text shaping, paint, and a custom JS VM, with the caveat that "it kind of works." Examination of the engineer's FastRender blog and the repository shows a semi-functional demo, code that often fails to compile or run, and a marketing spin that overstates results. The week-long autonomous agent run used hundreds of agents and consumed an estimated 10–20 trillion tokens, implying multi-million-dollar model costs.

"I won't say they lied, but CEO Michael Truell certainly tweeted: "We built a browser with GPT-5.2 in Cursor." He followed up with: "It's 3M+ 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." That sounds impressive, doesn't it? He also added: "It *kind of* works," which is not the most ringing endorsement."

"If you actually looked at Cursor engineer Wilson Lin's blog post about FastRender, the AI-created web browser, you won't see much boasting about a working web browser. Instead, there's a video of a web browser sort of working, and a much less positive note that "building a browser from scratch is extremely difficult." The thing about making such a software announcement on GitHub is that while the headlines are proclaiming another AI victory, developers have this nasty trick. They actually git the code."

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