The announcement
Anthropic announced Claude Fable 5.1 and Mythos 5.1 on September 1. The announcement also discusses changes to pricing, privacy options, and safeguards. Those conditions need to be checked alongside capability claims.
What to take from it
A release can change both model behavior and the terms under which you use it. Check the actual product and access program that apply to you. Treat the provider’s evaluation results as evidence to examine, then test a representative task of your own.