Claude Mythos 5.1 Cybersecurity & Life Sciences Model
Released by Anthropic on 1 September 2026 alongside Claude Fable 5.1: the same underlying model at a different safeguard tier, with Mythos 5.1 limited to vetted cybersecurity and life-sciences users through trusted access
Model Overview
Specs, access and pricing details below
Features
- ✓ The same underlying model as Claude Fable 5.1 but with different safeguard levels; Mythos 5.1 is offered in limited form through Anthropic's Trusted Access programs
- ✓ Built for cyber defence and life sciences, allowing capabilities that would otherwise be blocked for specialist biological or cybersecurity research while reducing false positives on legitimate work
- ✓ Shares Fable 5.1's specs: a 1M-token context window, 128K output tokens and always-on adaptive thinking
- ✓ Usage-based pricing of $10 per million input tokens and $50 per million output tokens, with cache reads at $0.25 per million tokens, a 75% cut from Fable 5
- ✓ Powers Anthropic's Claude Security codebase scanner, which moved up to Mythos 5.1 in this release
How to Use
- Confirm you are a vetted cyber defender or life-sciences researcher
- Apply for access through Anthropic's Trusted Access / Glasswing programs
- Once approved, call Claude Mythos 5.1 in the Claude platform and the relevant security products
- Submit code-scanning or research tasks, review the results and keep the necessary audit records
FAQ
What is Claude Mythos 5.1?
Anthropic's frontier model released on 1 September 2026 alongside Claude Fable 5.1. Anthropic says the two are the same underlying model with different safeguard levels: Fable 5.1 is generally available, while Mythos 5.1 is provided to vetted cybersecurity and life-sciences users through trusted access programs.
Why isn't Mythos 5.1 public?
Because it can access capabilities that would be blocked under normal safeguards for specialist biological or cybersecurity research; Anthropic restricts it to vetted organisations and researchers to reduce false positives on legitimate research.
What are Mythos 5.1's specs?
It shares Fable 5.1's specification: a 1M-token context window, 128K output tokens and always-on adaptive thinking.
How much does Claude Mythos 5.1 cost?
The same as Fable 5.1: $10 per million input tokens and $50 per million output tokens, with cache reads at $0.25 per million tokens, a 75% reduction from Fable 5.
Who can apply for Mythos 5.1?
Access requires applying through the Trusted Access programs for cyber defenders or life scientists; once approved it can be used in the Claude platform and security products.
How is Mythos 5.1 related to Claude Security?
Directly: Anthropic's codebase scanner, Claude Security, was upgraded to run on Mythos 5.1 in this release.