Anthropic released the same model twice with different guardrails.
Anthropic launched Claude Fable 5.1 and Claude Mythos 5.1 on 1 September. They are one model behind two safeguard layers, and only vetted cyber and biology teams get Mythos. Prices per token did not move, but cache reads fell 75 percent.
Why it mattersIf you build with Claude, repeated long-context work now costs about a quarter less. The split also shows labs handing out the same intelligence by who you are.
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