Building a C compiler is definitely hard for humans, but I don’t think it’s particularly strong evidence of "intelligence" from an LLM. It’s a very well understood, heavily documented problem with lots of existing implementations and explanations in the training data.

These kinds of tasks are relatively easy for LLMs, they’re operating in a solved design space and recombining known patterns. It looks impressive to us because writing a compiler from scratch is difficult and time consuming for a human, not because of the problem itself.

That doesn’t mean LLMs aren’t useful, even if progress plateaued tomorrow, they’d still be very valuable tools. But building yet another C compiler or browser isn’t that compelling as a benchmark. The industry keeps making claims about reasoning and general intelligence, but I’d expect to see systems producing genuinely new approaches or clearly better solutions, not just derivations of existing OSS.

Instead of copying a big project, I'd be more impressed if they could innovate in a small one.