Anthropic releases Claude Fable 5.1 and Mythos 5.1, cutting cache prices by 75%
The release introduces cheaper prompt caching, refined safeguards for cybersecurity, and a zero-data-retention option to deploy models on customer-controlled cloud servers.
- Anthropic launched Claude Fable 5.1 and Claude Mythos 5.1 on September 1, 2026, designed for advanced coding, knowledge work, and scientific research, according to The Verge and AWS.
- While standard pricing remains at $10 per million input and $50 per million output tokens, cache read prices are slashed 75% to $0.25 per million tokens, cutting costs for agentic tasks by up to 45%.
- A new partnership with AWS introduces Enterprise Frontier Safeguards (EFS), offering eligible customers zero data retention by keeping data within their controlled cloud infrastructure.
- Fable 5.1 is generally available, while Mythos 5.1 is restricted to vetted researchers, featuring relaxed safeguards that block 60% fewer cybersecurity requests and 85% fewer biology requests.