Anthropic accidentally reveals ‘Claude Mythos’ model: The next frontier in AI power

Anthropic unwittingly revealed its upcoming “Claude Mythos” model due to a content management error on March 27, 2026. The leaked files reportedly include blog drafts and nearly 3,000 unpublished assets, revealing that Mythos outperforms Opus in cybersecurity, software programming, and academic reasoning. 

The model will initially be available to select clients for on-chain data protection and virtual asset defense with no public release planned in the near future. The leak underscores its edge in cyber capabilities, prompting a cautious rollout focused on defenders to bolster exciting systems.

Amid the growing buzz,the company has disclosed an upcoming invite-only retreat for CEO Dario Amodei will demo features to European executives, while navigating US military tensions over AI use.

Anthropic leak reveals “Claude Mythos”: A next-gen AI built for cybersecurity

Claude Mythos is a new model in development mode and being tested by Anthropic, positioned above the existing Opus series. Anthropic has confirmed that this model represents a leap in capability and is the most powerful system the company has built to date. According to leaked drafts, the model scores significantly higher than Claude Opus 4.6 in critical areas, including software programming and academic reasoning.

The model’s performance in cybersecurity is described as far surpassing all existing AI models, marking a major technical milestone for the industry. This information surfaced after unpublished drafts and assets were exposed due to a configuration error in Anthropic’s content management system. Because of its advanced capabilities and high operational costs, Anthropic reportedly plans to offer the model initially to a select group of early customers specifically on cybersecurity defense. The leak involved nearly 3,000 unpublished assets, including images, PDFs, and internal documents. Among the revelations were details regarding an upcoming closed-door summit in the UK for European corporate CEOs, which Anthropic CEO Dario Amodei is scheduled to attend. 

The security flaw was independently identified by Alexandre Pauwels and Roy Paz. Due to the model’s extreme power and high-operational cost, Anthropic will not release it to the general public in the short term. Instead, it will be offered only to a select group of early customers specifically for cybersecurity defense use cases.