Anthropic Releases Claude Fable 5, Offers Enhanced Mythos 5 to Cyber Defenders
June 11, 2026 — Anthropic has launched Claude Fable 5, a Mythos-class model made safe for general use. Fable 5’s capabilities exceed those of any model ever made generally available by Anthropic. 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 the company’s other models.
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. Anthropic has therefore launched the model with safeguards that mean queries on some topics will instead receive a response from the next-most-capable model, Claude Opus 4.8. To release the model both safely and quickly, Anthropic has 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, the company is working to improve its safeguards and reduce false positives as quickly as possible.
For a small group of cyberdefenders and infrastructure providers, Anthropic is also launching Claude Mythos 5. It’s the same underlying model as Fable 5, but with the safeguards lifted in some areas. 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, Anthropic intends to expand access to Mythos 5 through a broader trusted access program.
The capabilities of models like Fable 5 and Mythos 5 have the potential to do profound good for the world. The beginnings of this have been seen in Project Glasswing, where the models have helped cyber defenders secure critically important software. It’s also been seen in life sciences research, where the models are positing novel hypotheses and speeding up the development of new therapeutics.
Fable 5 and Mythos 5 are being offered at $10 per million input tokens and $50 per million output tokens—less than half the price of Claude Mythos Preview. Today’s joint launch is another step towards Anthropic’s goal of bringing advanced AI capabilities to as many users as possible, as quickly and as safely as possible.
Learn more about Fable 5 and Mythos 5 here.
Source: Anthropic
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