Anthropic Accidentally Leaked Their Next Model. It's Called Mythos.

A CMS Misconfiguration Heard Around the Industry On March 26, 2026, someone at Anthropic left the door open. Not a backdoor in a model, not an API key in a public repo -- a content management system misconfiguration that exposed blog drafts and roughly 3,000 unpublished assets to the public internet. Among those files were references to something called Claude Mythos, and the AI development community has not stopped talking about it since. What makes this particularly striking is the timing. Just five days later, on March 31, Claude Code's source code leaked through a separate incident. Two major leaks in one week from a company that positions itself as the safety-first AI lab. The irony writes itself. What We Actually Know About Mythos Let's separate signal from noise. Anthropic confirmed they are "developing a general purpose model with meaningful advances in reasoning, coding, and cybersecurity." They also described it as "a step change and the most capable we've built to date." The