Anthropic releases its first Mythos-class model to the public

Anthropic is making its first Mythos-tier model available to the general public. On Tuesday, the AI lab announced it was rolling out Fable 5—the first widespread release of an AI model from a significantly more powerful class of model—as a general release, and Claude Mythos 5 to vetted partners who already have access to the Claude Mythos Preview.It’s a considerable step for the lab, which initially deemed Mythos-class models too dangerous to release due to their increased ability to find cybersecurity weaknesses. It also comes just over a week after the company confidentially filed for IPO paperwork.Fortune first reported the existence of the new and more powerful model in March after a data leak revealed its existence. In April, Anthropic officially announced Mythos, calling it a “step change” in capabilities. It opted to tightly control its rollout through an initiative called Project Glasswing. The project was aimed at giving cybersecurity professionals access to the models’ cyber skills so they could strengthen their defenses against new threats posed by increasingly advanced AI models. Now, Anthropic says it is confident new guardrails are enough to ensure these dangerous skills don’t fall into the wrong hands. “The reason why we’re releasing Fable Five now is very much due to us feeling more confident with our safety guardrails in place,” Dianne Penn, Anthropic’s head of product management, research and labs, told Fortune. The company said that responses in specific high-risk areas, such as biology and cybersecurity, will be blocked and will, in most cases, be answered by Claude Opus 4.8, Anthropic’s less powerful model, released earlier this year. The fear is that giving users free access to Mythos-level intelligence could enable bad actors to carry out more advanced cyberattacks or develop bioweapons more easily. The company also said it had extensively red-teamed its classifiers (machine learning