Anthropic Launches Claude Fable 5, Its First Public Mythos-Class Model

Anthropic today announced the launch of Claude Fable 5, a Mythos-class model that it says is safe for general use.

According to Anthropic, Fable 5's capabilities exceed those of any model it has made generally available, and Fable has demonstrated "exceptional performance" for software engineering, knowledge work, vision, scientific research, and more. It outperforms Opus models on longer, more complex tasks. Fable 5 can work autonomously for longer than any prior Claude model.

Fable 5 is being released with conservative safeguards to prevent it from being misused in areas like cybersecurity. Questions about some topics will instead be answered by Opus 4.8, with safeguards expected to trigger in less than five percent of sessions on average. Most queries related to cybersecurity, chemistry, and biology will get responses from Opus 4.8 instead of Fable 5.

Anthropic is also releasing Claude Mythos 5 for a small group of cyberdefenders and infrastructure providers. It uses the same underlying model as Fable 5, but with some of the safeguards lifted. Mythos 5 is being deployed through Project Glasswing as an upgrade to the Claude Mythos Preview. Anthropic says Mythos 5 has the strongest cybersecurity capabilities of any model in the world, with access set to expand through a broader trusted access program.

Fable 5 and Mythos 5 are available at $10 per million input tokens and $50 per million output tokens, which is less than half the price of the Claude Mythos Preview. Mythos 5 is available to those who have access to the Mythos Preview, and that includes Apple. Apple is one of Anthropic's Project Glasswing partners.

Claude Fable 5 is included in Pro, Max, Team, and seat-based Enterprise plans from today until June 22. On June 23, the model will be removed from those plans and using it will require usage credits. When Fable 5 capacity is sufficient, Anthropic plans to re-add it to subscription plans.