Claude Fable 5.1 - the strongest Claude, now cheaper on long sessions

Claude Fable 5.1 is now the default model on the Ultra tier, replacing Claude Fable 5. It is Anthropic's most capable model, tuned for the hardest reasoning and long agent sessions - and it comes with a real cost improvement: reading cached context is 4x cheaper than on Fable 5. In practice that is most of what a long coding session pays for, so the deeper into a project you are, the more you save.

Token prices are unchanged. Claude Fable 5 remains available in the model picker if you have it selected.