Unverified50% confidenceReleaseExact time
Anthropic released two models on September 2nd, Fable 5.1 and Mythos 5.1, which share the same set of base model weights but differ in safety policies and access scope.
1
Sources
50%
Confidence
Medium-term (~90 days)
Relevance
9/12/2026
First Seen
Valid until: 12/11/2026
Sources
Related Entities
Related Claims
UnverifiedClaude Fable 5 and Claude Mythos 5 have officially launched as Anthropic's most advanced AI models to date.71% similarUnverifiedAnthropic's Fable 5 has the internal codename Mythos 5 and is its frontier research-grade model.69% similarUnverifiedA user reported that Claude Mythos 5 briefly appeared as a model option in Anthropic's API before being quickly pulled.68% similarUnverifiedAnthropic's next-generation frontier model Claude Fable 5.2 is reportedly ready and is regarded as a significant upgrade over Fable 5.1.67% similarUnverifiedClaude Fable 5.1 and Claude Mythos 5.1 are built on exactly the same underlying model with no difference in intelligence level; the only distinction lies in the safety protection level.67% similar
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