I unleashed it on a compiler codebase that I've been developing for several months now using Claude Sonnet 4.5/6, Gemini 3.1 Pro, DeepSeek V4 Pro(recent), and a bit of Qwen3.6-27B. Right away Fable found several longstanding bugs in our compiler that we hadn't found before. It found that there was a critical part of our design that needed to be mostly redesigned/rewritten and gave a very well-reasoned rationale for doing so.

what sort of compiler?

A compiler that takes C code (a subset of C with some extensions) and compiles it to microcode for a type of microcoded, algorithmic state machine that we're developing.

it would be cool to have this task (or some variant) in a benchmark.

They should have made it three times bigger instead of two.

It's worse than gpt 5.5 xhigh

The jagged frontier strikes again.

I’d say it’s overall better, but not universally better.