It was in the announcement, too. I’m 99% sure they edited it after they changed their mind, because I knew about it from reading that, and never opened the model card.
And to be clear, this isn't the safeguard where the model is explicitly downgraded to Opus, but rather where the Fable/Mythos model's "effectiveness" is transparently "limited" via "prompt modification, steering vectors, or parameter-efficient fine-tuning (PEFT)".
[0]: https://web.archive.org/web/20260609173222/https://www.anthr...
[1]: https://simonwillison.net/2026/Jun/10/if-claude-fable-stops-...