This account claims Sonnet and Opus 5.6 are in A/B testing now. There is nerfing when they release a new version, for reallocating resources.

https://x.com/tokengremlin/status/2119783808773841101

how reliable is this twitter account?

i've seen people on social media claiming all sorts of things about Fable 5.5, Opus 5.6 and Sol 6.2 and what-not for the past few weeks, but it just seems like engagement farming with no proof