Anthropic Adds Cybersecurity Safeguards to Claude Fable 5 and Expands Mythos 5 Access
Summary
Anthropic says Claude Fable 5 falls back to Claude Opus 4.8 for cybersecurity and biology tasks. The company also reported red-team testing and is upgrading trusted Project Glasswing users to Mythos 5.
Key points
- Anthropic announced general availability of Claude Fable 5 through the Claude API.
- For cybersecurity and biology tasks, Fable 5 is designed to fall back to the less capable Claude Opus 4.8.
- Anthropic says at least 95% of sessions run on Fable 5 without triggering a fallback.
- The company reported internal classifier red-teaming and an external bug bounty spanning more than 1,000 hours, with no universal jailbreaks found.
- Anthropic is upgrading trusted users, including Project Glasswing cybersecurity partners, from Claude Mythos Preview to Mythos 5.
Article Details
- Event Type
- Anthropic announced the general availability of Claude Fable 5 with safeguards that restrict its use in high-risk domains, and upgraded trusted Project Glasswing users from Claude Mythos Preview to Claude Mythos 5.
- Impact
- Fable 5 is available immediately through the Claude API for developers. In cybersecurity and biology, it falls back to the less capable Claude Opus 4.8; Anthropic says at least 95% of sessions run without triggering a fallback. Anthropic reported that internal and external red-teaming found no universal jailbreaks or critical safeguard bypasses. Access to Mythos 5 will expand gradually through a trusted-access program.
Vendors
Products
Claude Fable 5Anthropic on Tuesday announced the general availability of Claude Fable 5, a powerful Mythos-class AI model engineered with new safeguards that specifically restrict its use in high-risk domains, including cybersecurity.Claude Mythos 5Anthropic also announced on Tuesday that trusted users, including its cybersecurity partners in Project Glasswing, are being upgraded from Claude Mythos Preview to Claude Mythos 5.Claude Mythos PreviewAnthropic also announced on Tuesday that trusted users, including its cybersecurity partners in Project Glasswing, are being upgraded from Claude Mythos Preview to Claude Mythos 5.Claude Opus 4.8In sensitive areas such as cybersecurity and biology, the model automatically falls back to the less capable Claude Opus 4.8 to prevent potential misuse.