In April, Anthropic unveiled its Claude Mythos AI model, which it said was too powerful to release publicly. Instead, the company has shared access with software vendors, including Apple, in an effort to use the model to improve cybersecurity.
Now, as promised, Anthropic has released what it calls a Mythos-class model that customers can actually use. The new model is called Claude Fable.
Claude Fable 5 and Claude Myths 5
Anthropic calls the Claude Fable 5 its first Mythos-class model that is publicly available to customers.
“The capabilities of Fable 5 exceed those of any model we have made available to the public,” the company says. “It is the latest in almost 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 greater the advantage of Fable 5 over our other models.”
Anthropic adds that its new Claude Fable 5 model comes with specific safeguards, given its capabilities:
Launching a model with this capability comes with risks. Without safeguards, Fable 5’s capabilities in areas like cybersecurity could be misused and cause serious harm. Therefore, we launched the model with safeguards that mean that queries on some topics will receive a response from our next most capable model, Claude Opus 4.8. To launch the model safely and quickly, we have adjusted these safeguards conservatively: they sometimes detect harmless requests, although they are triggered, on average, in less than 5% of sessions. With more capable models arriving in the coming months, we are working to improve our protections and reduce false positives as quickly as possible.
Beyond Claude Fable 5, Anthropic also details Claude Mythos 5, which is basically Fable 5 without many safeguards. Mythos 5 is only available to a “small group of cyber defenders and infrastructure providers,” according to Anthropic. This includes those with access to Claude Mythos Preview.
The company says that both Fable 5 and Mythos 5 cost less than half the price of Claude Mythos Preview: $10 per million tokens in and $50 per million tokens out.
The new, more expensive models perform favorably compared to the Claude Opus 4.8 and GPT-5.5, according to Anthropic’s results.
Anthropic says the two new models can “operate autonomously for longer than any previous Claude model.” This enhances Claude’s use around software engineering, knowledge work, vision, as well as memory and long-term context.
Claude Fable 5 reaches customers starting today. Anthropic says it expects demand for Fable 5 to be “very high and difficult to predict.” For that reason, subscription plans will be able to access Fable 5 in stages, according to Anthropic.
- From today until June 22, Fable 5 is included in seat-based Pro, Max, Team, and Enterprise plans at no additional cost.
- On June 23, we will remove Fable 5 from those plans. Using it after that will require usage credits. If capacity allows, we will expand the included window.
- After this point, when sufficient capacity allows, we aim to restore Fable 5 as a standard part of subscription plans. We intend to do this as quickly as we can.
You can learn much more about the new Claude Fable 5 model from Anthropic here.
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