Claude Fable 5 and Claude Mythos 5 Released

Anthropic has released a new Mythos-class model, Claude Fable 5. This model shows top-tier performance across nearly all benchmarks, including software engineering, knowledge work, vision, and scientific research, with the performance gap over existing models growing especially wide on more complex tasks.

To prevent security risks, safeguards have been applied to Fable 5. Queries on sensitive topics such as cybersecurity are instead handled by the previous-generation model, Claude Opus 4.8. These safeguards were tuned to activate in less than 5% of sessions on average.

At the same time, Claude Mythos 5 was also unveiled for cybersecurity professionals and infrastructure providers. It shares the same base model as Fable 5 but has certain domain-specific safeguards removed, and is being deployed through Project Glasswing, a collaboration with the US government. Mythos 5 possesses the most powerful cybersecurity capabilities in the world.

Key features and pricing information are as follows:

• Software Engineering: In tests by Stripe, a large-scale codebase migration that would normally take months was completed in just a single day.
• Pricing: $10 per 1 million input tokens and $50 per 1 million output tokens, less than half the price of the previous Mythos Preview.
• Use Cases: Cyber defense, life sciences research (accelerating the development of new therapeutics), and more.