This just doesn't match my experience writing idiomatic C code for embedded real-time systems with ChatGPT-5.5 and -5.6. Are Opus and Fable really that different? I general I find that a fully correct implementation for some function may take an hour and be nearly one-shot, but going from there to code I'd be willing to actually commit is at least 4x the time commitment with regular back-and-forth -- so four hours of deep engagement for every one hour of one-shot. ChatGPT-5.6 Sol seems to be better that -5.5 at the one hour do-it portion, but worse at the four hour do-it-well portion.