Anthropic releases Claude Fable 5.1 and Mythos 5.1, cutting cache read prices by 75%

Anthropic launched Claude Fable 5.1 and Mythos 5.1, identical models differentiated only by safety layers, with cache-read costs reduced 75% to $0.25 per million tokens, lowering typical workloads by ~25% and agentic workloads up to 45%. Fable 5.1 achieved 52.6% on Terminal-Bench-Science 0.1 and 55.8% on Terminal-Bench 4.0, versus 24.7% for its predecessor, and its outputs embed an EU-mandated watermark detectable via a private-preview API for approved organizations.