Anthropic’s new model is Mythos on a leash

Anthropic announced Claude Fable 5, a public-release variant of its withheld Mythos model that routes cybersecurity and biology queries to the less-capable Claude Opus 4.8 and implements new guardrails; the article outlines testing results, data-retention and access policies, and dual-use/jailbreak risks while noting Opus 4.8 can reproduce many vulnerabilities without safeguards but that Anthropic's protections significantly reduce that capability.