Hacker News
Anthropic Ships Claude Fable 5.1 and a Gated Mythos 5.1 Twin, With Cache Reads Cut 75% to $0.25/Mtok
Fable 5.1 and Mythos 5.1 are the same underlying model at two safeguard levels: Fable is generally available, Mythos goes only to vetted cybersecurity and life-sciences organizations, currently US-only. Fable 5.1 scores 52.6% on Terminal-Bench-Science 0.1 (versus 24.7% for Fable 5 and 29.0% for Opus 5), 55.8% on Terminal-Bench 4.0, 60.9% on Humanity's Last Exam without tools, and 73.4% on CursorBench 3.2.0. Token pricing holds at $10/$50 per million in/out, but cache reads drop 75% to $0.25/Mtok, which Anthropic puts at ~25% cheaper for typical workloads and up to 45% for highly agentic runs.
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