Claude Mythos 5.1

Changes from previous version

Upgrade from Claude Mythos 5 with stronger coding, scientific research, and cyber capabilities, plus access through CVP and LSVP rather than Project Glasswing alone. Cache reads drop to $0.25/M, matching Claude Fable 5.1.

Release Summary

Same underlying model as Claude Fable 5.1 with more permissive safeguards for vetted cybersecurity and life sciences work. Restricted to Anthropic's Cyber Verification Program and Life Sciences Verification Program (initially a set of US organizations). Scores 60.9% on Terminal-Bench 4.0 versus Fable 5.1's 55.8% with production safeguards. Also powers Claude Security. Same list API pricing as Fable 5.1: $10/M input, $50/M output, and $0.25/M cache reads. API ID claude-mythos-5-1.

Timeline

Other Claude Mythos versions