Anthropic today launched two new AI models — Claude Fable 5 and Claude Mythos 5 — marking the company’s first broad release of the powerful “Mythos-class” AI capabilities it previously kept behind a restricted cybersecurity program.

The company says Fable 5, which is the version most users and developers will get, exceeds every Claude model it has previously made generally available, with stronger performance across software engineering, knowledge work, vision, scientific research and long-running tasks.

Claude Mythos 5 is a more restricted, upgraded version of the prior, similarly restricted Mythos model. As such, it has certain safeguards lifted for approved users, including Anthropic's cybersecurity partners in its Project Glasswing effort, and select biology researchers.

The key difference is that Fable 5 wraps the same underlying Mythos-class capability in new safeguards. Anthropic says requests involving certain high-risk areas — including cybersecurity, biology and chemistry, and model distillation — are automatically routed to Claude Opus 4.8 instead, with users notified when that happens.

The company says more than 95% of Fable sessions run entirely on Fable’s own responses, with no fallback, and that internal and external red-teaming efforts found no “universal jailbreaks” after more than 1,000 hours of testing.

Anthropic says Fable 5 is available to the general public today but that Mythos 5 will initially only be made available to users who already have access to the older Claude Mythos Preview.

Pricing, access and a tricky rollout

Anthropic is pricing both Fable 5 and Mythos 5 at $10 per million input tokens and $50 per million output tokens. The company says that is less than half the price of Claude Mythos Preview, but still ranks as the most expensive of major AI models available globally.

For developers, Fable 5 is available through the Claude API as claude-fable-5. Anthropic says Fable 5 is fully available today on the Claude API and on consumption-based Enterprise plans.

For subscription users, the rollout is more complicated. Anthropic says Fable 5 will be included on Pro, Max, Team and seat-based Enterprise plans at no extra cost from today through June 22.

On June 23, the company plans to remove Fable 5 from those plans, after which using it will require usage credits. Anthropic says it aims to restore Fable 5 as a stand...