Interesting.

I tried Fable vs Codex 5.5 xhigh on three different cases.

1. A resource leak with unknown cause. Both of them zoomed onto the same potential issue and proposed almost identical patches. Fable missed an edge case that Codex handled correctly.

2. Review of a SPICE model. Models had different comments, none substantial. Both missed important issues that were simulated inadequately. Clearly a valley where they are undertrained.

3. An open research problem in CS, presented as a codebase with documentation and performance metrics over datasets. Both were spinning wheels. Which can certainly mean the whole approach had run its course but older models were not able to identify the previous round of improvement either.

I liked the prose coming out of Fable more: it was almost like if Obama was giving tech speeches. By actual solution metrics however they both appear in the same place, naturally with the caveat that we didn't really have more time with Fable to compare further.