By No Code MBA · Facts checked
- Provider
- Anthropic
- Announcement date
- Status at last check
- Limited access or preview
- Model family
- Claude Mythos
- Preceding model
- Claude Mythos 5
- Capabilities
- Text, Coding
What changed
Mythos 5.1 succeeds Mythos 5, itself an update to Mythos Preview, and Anthropic describes it as its most capable model class for cybersecurity and biology research, with gains in both areas. It is the same underlying model as the generally available Claude Fable 5.1, without Fable's safeguards that block exploit generation and route dual-use biology questions to other models. Anthropic says Mythos 5.1 benchmark results differ from Fable 5.1 only where those safeguards intervene. Claude Security now runs on it.
Access and availability
Restricted to vetted cyberdefenders and life scientists through Anthropic's Cyber Verification Program and Life Sciences Verification Program; builders without verification can use Claude Fable 5.1 instead.
Official access documentationPricing
Starts at $10 per million input tokens and $50 per million output tokens
Official pricingWhat you can build
Check eligibility and deployment conditions before planning an integration.
Read our Fable 5.1 vs Mythos 5.1 breakdownLimitations
Access requires verification, and Mythos 5.1 requires accepting 30-day data retention for safety monitoring by default. Anthropic did not publish numeric cyber or biology results specific to Mythos 5.1.