GoKawiilBack in April, Anthropic unveiled its Claude Mythos AI model that it said was too powerful to publicly release. Instead, the company has shared access with software vendors, including Apple, in an effort to use the model for enhanced 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 Mythos 5
Anthropic calls Claude Fable 5 its first Mythos-class model that’s publicly available for customers.
“Fable 5’s capabilities exceed those of any model we’ve ever made generally available,” the company says. “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.”
Anthropic adds that its new Claude Fable 5 model comes with specific safeguards, given its capabilities:
Releasing a model this capable comes with risks. Without safeguards, Fable 5’s capabilities in areas like cybersecurity could be misused to cause serious damage. We’ve therefore launched the model with safeguards that mean queries on some topics will instead receive a response from our next-most-capable model, Claude Opus 4.8. To release the model both safely and quickly, we’ve tuned these safeguards conservatively—they’ll sometimes catch harmless requests, though they trigger, on average, in less than 5% of sessions. With more capable models arriving in the coming months, we’re working to improve our safeguards and reduce false positives as quickly as we can.
Beyond Claude Fable 5, Anthropic also details Claude Mythos 5, which is basically Fable 5 without a lot of the safeguards. Mythos 5 is only available to a “small group of cyberdefenders and infrastructure providers,” per Anthropic. This includes those with Claude Mythos Preview access.
The company says both Fable 5 and Mythos 5 cost less than half Claude Mythos Preview’s price at $10 per million input tokens and $50 per million output tokens.
The pricier new models perform favorably compared to Claude Opus 4.8 and GPT-5.5, according to Anthropic’s results.
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