AnthropicLaunchAI ModelsSeptember 1, 2026

Anthropic launches Claude Fable 5.1 and Mythos 5.1

Claude Fable 5.1 and Mythos 5.1 are the same model with different safeguards; Fable 5.1 is generally available, Mythos 5.1 only via trusted access. Fable 5.1 costs ~25% less than Fable 5 for typical workloads, with up to ~45% savings on agentic work.

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