I have never been a part of the group that believes in frontier labs downgrading models. But this theory seems plausible to me for the first time.

I guarantee they are at least tweaking quants, caching systems, and finding ways to move serving costs down. This definitely impacts the model’s intelligence at times. There are also a lot of model tweaks, RLHF rollouts etc. I don’t think it means they are doing anything malicious or deceptive. And if Opus 5.5 is literally smarter than Fable? Ehh, it is plausible :)