Anthropic Ships Claude Fable 5.1 and Mythos 5.1 With a 75% Cut to Cache Costs

Anthropic's new frontier pair targets long-running agents and coding, but the quietly bigger story is the pricing — a 75% reduction on cache reads that changes the economics of production agent workloads.

Anthropic introduced two new frontier models on Tuesday, Claude Fable 5.1 and Claude Mythos 5.1, which the company called "the world's most advanced models for coding and knowledge work". The launch announcement went viral within hours, but the headline capability claims are only half the story. The detail that builders latched onto was buried in the pricing table.

As @makaneko_AI flagged, the more consequential change may be that the same class of performance is now dramatically cheaper — with cache read pricing cut by 75%. For anyone running agents that repeatedly reference large, stable context windows, that is not a rounding error. It is the difference between a workflow that pencils out and one that doesn't.

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