Anthropic · Claude Fable 5.1

Claude Fable 5.1 and Mythos 5.1

Fable 5.1 reaches general availability on AWS, Google Cloud and Azure, with Anthropic citing 52.6% on Terminal-Bench-Science against Fable 5's 24.7%, 55.8% on Terminal-Bench 4.0, and parity with Fable 5 at lower effort settings. Pricing is $10 per million input and $50 per million output tokens with a 75% cache-read discount, roughly 25% cheaper overall for typical workloads. Mythos 5.1 is the same model with lower safeguards, released only to verified cybersecurity professionals and life scientists through trusted access programmes - the second profession-gated release this week.