Anthropic · Claude · Mythos · Decrypt
Anthropic released Claude Fable 5.1 and Claude Mythos 5.1 on Tuesday
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The company claims new AI models are the world's “ most advanced for coding and knowledge work,” and it lands three months into a launch cycle that has already included an 18-day export-control shutdown, a mid-summer pricing fight over subscription access, and a July release of Claude Opus 5 that undercut Fable 5 on…
Key facts
- Claude Fable 5.1 is available now on the Claude API, Amazon Bedrock, Google Cloud, and Microsoft Foundry, under the model ID "claude-fable-5-1
- But Fable 5.1 still costs twice as much per token as Opus 5—$10 input and $50 output versus Opus 5's $5 and $25
- Anthropic released Claude Fable 5.1 and Claude Mythos 5.1 on Tuesday, its first update to the Mythos-class model line since Fable 5 launched on June 9
- Mythos 5.1 stays restricted to vetted cybersecurity and life-sciences professionals through Anthropic's Cyber Verification Program and Life Sciences Verification Program, the successor to the Project
Summary
Anthropic released Claude Fable 5.1 and Claude Mythos 5.1 on September 1, scoring 52.6% on Terminal-Bench-Science 0.1 against Fable 5's 24.7%, and 55.8% on Terminal-Bench 4.0 against 42.0%. Cache reads now cost 75% less, cutting typical workload costs by roughly 25% and highly agentic workloads by up to 45%, with base pricing unchanged at $10/$50 per million tokens. Fable 5.1 is not included in Pro plans or standard Team seats, which run it on usage credits; Max and premium Team or Enterprise seats get it included for up to 50% of weekly limits.