Anthropic on Tuesday announced the official launch of Claude Mythos 5, a restricted-access AI model the company says has unprecedented cybersecurity capabilities, alongside Claude Fable 5, a version designed for broader public use.
“In April, we began Project Glasswing, releasing the first Mythos-class model (Claude Mythos Preview) to only a limited group of cyber defenders and critical software infrastructure providers,” Anthropic wrote. “When we did so, we stated that we hoped to eventually release Mythos-level capabilities to all our users, so long as we had developed new safeguards that were strong enough to reliably prevent misuse.”
Introducing Claude Fable 5: a Mythos-class model that we’ve made safe for general use.
“In consultation with the U.S. government, we plan to steadily expand access to Claude Mythos 5, continuing our periodic addition of new partners, as well as pursuing a trusted access program that allows cybersecurity organizations to apply in a more systematic manner,” Anthropic wrote, adding that users of Mythos Preview can upgrade to Mythos 5.
Alongside Mythos 5, Anthropic released Claude Fable 5, a Mythos-class AI model that uses the same core design of Mythos 5 but with additional safeguards for the general public.
“Fable 5’s capabilities exceed those of any model we’ve ever made generally available,” Anthropic wrote. “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.”
According to Anthropic, Mythos 5 and Fable 5 achieved top scores on several software engineering, cybersecurity, biology, and reasoning benchmarks. The company reported a 78% score on ExploitBench, which measures vulnerability discovery and exploitation, and an 88% score on the Terminal-Bench coding benchmark. Anthropic said the results show the models can handle longer and more complex tasks than previous Claude systems.
“Releasing a model this capable comes with risks,” Anthropic wrote. “Without safeguards, Fable 5’s capabilities in areas like cybersecurity could be misused to cause serious damage.”
