The pricing is different than 5.1, the model is faster than 5.1. This all suggests that the architecture/size is not the same as Fable 5.1.

So, this is probably Fable 5.5; it's just named Fable 5.2.

Also, this is probably Model 3 from METR's report [^1]. They would name Model 4 Fable 5.5, once (and if) they decide to release it.

[^1]: https://metr.org/blog/2026-11-05-anthropic-ai-rd-acceleratio...