Claude Mythos 5.2

Claude Mythos 5.2 is a large language model from Anthropic, released on 9 November 2026 alongside Claude Fable 5.2. According to Anthropic, Fable and Mythos are the same underlying model. Fable ships with strong cybersecurity and biology safeguards so it can be offered to all users. Mythos is the version for organizations doing beneficial cybersecurity or biomedical research.

Access to Mythos is by application through Anthropic's expanded Life Sciences and Cyber Verification Programs. Anthropic reports improvements over earlier versions in coding, reasoning and vision, and output up to 30% faster than Fable/Mythos 5.1. Its published benchmark table lists Mythos 5.2 results for CyScenarioBench (76.3%), CVE Rediscovery (89.6%), de novo protein binder design (85.1) and Terminal-Bench-Science (75.3%, against 74.6% for Fable 5.2). Those scores come from Anthropic, not independent testing.

Pricing is listed as $8 per million input tokens and $40 per million output tokens. An optional fast mode generates tokens up to 2.5 times faster at $16 and $80 per million tokens. Anthropic recommends Claude Opus 5.5 as the default for most tasks and suggests Fable or Mythos for the most ambitious, open-ended technical work.