Claude Mythos goes public in new Fable 5 model that’s ‘safe for general use’

Ben Schoon | Jun 9 2026 - 10:50 am PT

As AI models get more powerful, there’s also going to be a level of danger. Anthropic announced Mythos not long ago as a model that was too dangerous for public availability, but a new version of that, Claude Fable 5, is now available and, apparently, “safe for general use.”

In a post today, Anthropic explains that Claude Fable 5 is a “Mythos-class” model that’s available for public use and exceeds the capabilities of any other generally available AI model Anthropic has ever published.

Fable 5’s capabilities exceed those of any model we’ve ever made generally available. It is state-of-the-art on nearly all tested benchmarks of AI capability, showing exceptional performance in software engineering, knowledge work, vision, scientific research, and many other areas. The longer and more complex the task, the larger Fable 5’s lead over our other models.

The fear with Mythos was mainly around cybersecurity, as the model was quickly found to be able to find and use exploits in the digital world. With Fable, Anthropic says that safeguards are in place and that, if a topic comes up that Fable isn’t allowed to interact with, Claude Opus 4.8 will step into the conversation instead. Anthropic says it has tuned this “conservatively,” so it might trigger more often than you’d expect.

Meanwhile, Claude Mythos 5 will be available to “a small group of cyberdefenders and infrastructure providers” as the same model as Fable 5, but with “safeguards lifted in some areas.”

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Mythos 5 will initially be deployed through Project Glasswing, in collaboration with the US government, as an upgrade to Claude Mythos Preview. It has the strongest cybersecurity capabilities of any model in the world. Soon, we intend to expand access to Mythos 5 through a broader trusted access program.

Anthropic adds that the “capabilities of models like Fable 5 and Mythos 5 have the potential to do profound good for the world,” and shows some drastic gains in tasks like agentic coding, tool use, and cybersecurity compared to the Mythos Preview, Opus 4.8, GPT 5.5, and Gemini 3.1 Pro.

The release of Fable 5, though, will be a bit tricky.

Anthropic says that, as of today, Fable 5 is available to all Pro, Max, Team, and seat-based Enterprise plans, but only through June 23. At that point, Fable 5 will shift to a usage credit-based plan with the hope of restoring standard access “when sufficient capacity allows.”

From today through June 22, Fable 5 is included on Pro, Max, Team, and seat-based Enterprise plans at no extra cost.

On June 23, we’ll remove Fable 5 from those plans. Using it after that will require usage credits. If capacity allows, we’ll extend the included window.

After this point—when sufficient capacity allows us to do so—we aim to restore Fable 5 as a standard part of subscription plans. We intend to do this as quickly as we can.