Claude Mythos 5.1
Anthropic · 2026-09-01
Claude Mythos 5.1 is Anthropic's September 2026 model offered through invitation-only trusted access programs. It shares Fable 5.1's underlying model with different cybersecurity and life-sciences safeguards. Adaptive thinking is always on with configurable effort; the published June 2026 knowledge cutoff has no day precision. Only results explicitly identified as Mythos 5.1 belong to this model.
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