Anthropic Releases Claude Fable 5.1 and Mythos 5.1 with 25% Price Cut and Enhanced Security

Anthropic has released its latest models for coding and knowledge work, Claude Fable 5.1 and Claude Mythos 5.1. While both models use the same base model, Mythos 5.1 includes specialized safety measures for cybersecurity and life sciences and is available only through trusted access programs. In contrast, Fable 5.1 is available to the general public.

Improved Pricing and Data Retention Policies

Reflecting customer feedback, the price of Fable 5.1 has been reduced by 25% compared to the previous Fable 5. Due to reduced cache read costs, advanced agent tasks can see cost savings of up to 45%. Additionally, the new Enterprise Frontier Safeguards (EFS) system has been introduced, allowing customers to maintain complete data privacy while preventing adversarial use. EFS stores data in customer-managed cloud infrastructure rather than Anthropic's, and will be rolled out gradually starting this fall.

Performance Enhancements and Strengthened Safeguards

Fable 5.1 sets new performance benchmarks in coding, knowledge work, and long-horizon problem-solving tasks. Notably, in tests by Millennium, Fable 5.1 identified the root cause of a rare crash in internal systems that had remained unresolved for years. In the cybersecurity domain, false positives have been reduced by 60%, allowing the discovery of software vulnerabilities while blocking exploit development. In the life sciences sector, Anthropic is collaborating with the US government to establish an access program for Mythos 5.1's advanced biological capabilities.