Anthropic released Claude Fable 5.1, priced about 25% below Fable 5 for typical work

Anthropic released Fable 5.1 and Mythos 5.1 on September 1 — the same underlying model behind two different safeguard settings, with Fable generally available and Mythos limited to trusted-access programs. Cheaper cache reads put typical token-billed work about 25% below Fable 5, and agent-heavy runs up to roughly 45% lower. Anthropic also announced Enterprise Frontier Safeguards, which keeps monitoring data in the customer's own cloud account, with zero data retention offered to eligible customers until that ships later this fall.

What it means The change that shows up on a bill is the cache-read price, which is where long agentic runs spend; Devin's team said it is what finally made a Fable-class model economical for their code review.