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Claude Mythos 5.1

Model ● Covered in 11 stories + Follow

Claude Mythos 5.1 is Anthropic’s AI model released as part of the Claude Fable/Mythos 5.1 updates, positioned for coding and knowledge work and offered under a “trusted organizations” or vetted access program with additional safeguard constraints. In recent coverage it has been used alongside Anthropic’s biology automation efforts, including a reported wet-lab setup where Claude-powered robots generated 12 candidate molecules with a 50% hit rate, and it is discussed in terms of pricing changes such as a 75% reduction in cache-read costs to $0.25 per million tokens while output token usage increased for some workloads.

Updated 12 October 2026

Specifications

No specifications recorded yet.

Latest developments

66% of billion-dollar companies leave critical bugs unpatched — the part the AI bug-hunting hype leaves out The New Stack · 5 days ago · 28
Anthropic opens AI-powered biology research lab SiliconANGLE · 1 month ago · 24
Claude Mythos 5.1 and Fable 5.1: Capabilities Zvi (Don't Worry About the Vase) · 1 month ago · 23 Deep Learning Weekly: Issue 471 Deep Learning Weekly · 1 month ago · 16 Fortune Tech: Anthropic Fable and Mythos 5.1, OpenAI Astra limits, AI token tax Fortune · 40
The Sequence Learning Loop - Issue 925: Learn About Fable and Mythos 5.1, GLM-5.3-Flash, and Qwen 3.8 TheSequence · 1 month ago · 49
[AINews] Claude Fable/Mythos 5.1: new SOTA model, 75% cache price cut but 70% more output tokens Latent Space · 1 month ago · 9
Fable 5.1: The New Best AI Model Is Once Again More Expensive Trending Topics · 1 month ago · 39

Timeline

Month Quarter Year

Q4 2026

Q3 2026

Anthropic opened an AI-powered wet biology research lab in the San Francisco Bay Area using robotic systems driven by Claude Deployment

Anthropic released the Claude Fable 5.1 and Claude Mythos 5.1 AI models with updated pricing and restricted availability for vetted organizations. Model release

Anthropic released Claude Fable 5.1 and Claude Mythos 5.1, including changes to agent API behavior and watermark-based text detection. Model release

Anthropic released updated Claude models Fable 5.1 and Mythos 5.1 with lower cache-read pricing and modified access and safeguards Model release

Anthropic launches Claude Fable 5.1 and Claude Mythos 5.1, including AWS Bedrock availability and agentic-work pricing changes. Product launch

Anthropic adjusted Claude Code usage limits effective September 14 and reported a reduction in Claude cache read costs Pricing change

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