So far, Opus 5 feels like a strange but useful in-between of gpt-5.6-sol and Fable 5
It has a lot of Fable's taste, but also comes with gpt-5.6's thoroughness and, well, "autism" (it takes things super literally).
It writes code that is slightly worse to look at than Fable, but more likely to be correct. It regularly is catching things that Fable missed.
So far, feels like a good compromise compared to 5.6's messy code and Fable's habit of being too clever to be correct.
I think I'm gonna like this model a lot.