Anthropic Released Claude Fable 5, the First Model in Mythos Class

Anthropic announced Claude Fable 5, a Mythos-class model with state-of-the-art capabilities and built-in cybersecurity safeguards that route risky prompts to a less-capable model (Claude Opus 4.8) and notify users on fallback; a restricted Mythos 5 variant with safeguards lifted is being offered to vetted defenders via Project Glasswing. The release notes internal and external red-teaming results, a bug bounty, pricing, and a 30-day data retention policy for safety monitoring.