Summary
Anthropic made Claude Fable 5 generally available across its API and major cloud platforms while keeping Claude Mythos 5 limited to approved customers. The launch introduces Mythos-class capabilities with explicit retention, review, and safety constraints, including adaptive thinking behavior and no zero-data-retention option for covered models.
What changed
Claude Fable 5 became generally available, while Claude Mythos 5 remained limited availability for approved customers, with model-specific data retention and safety requirements.
Why it matters
Anthropic is creating a new access pattern for frontier models: broad availability for the safeguarded version, restricted access for the highest-risk variant, and explicit trust requirements around data retention and review. This makes model capability, safety posture, and enterprise data policy inseparable purchasing considerations.
Evidence excerpt
Anthropic's docs say Claude Fable 5 is generally available on the Claude API, AWS, Vertex AI, and Microsoft Foundry, while Claude Mythos 5 is limited availability; both carry 30-day data retention and are not available under zero data retention.