Discord-Linked Group Accessed Anthropic’s Claude Mythos AI in Vendor Breach

Anthropic is investigating a vendor breach after a Discord-linked group accessed its Claude Mythos AI model, with no evidence of impact on core systems.

Two weeks after Anthropic announced Claude Mythos Preview (aka Claude Mythos and Mythos AI) as part of its Project Glasswing initiative, the company is investigating unauthorized access to the model through a third-party vendor environment.

How the Breach Happened

Reportedly, a handful of users on a Discord channel gained access to Mythos. Their focus was on gathering intelligence about unreleased AI models and appears to have used a combination of tactics to access the system.

Bloomberg News reported on April 21, 2026, that the group made an “educated guess” about the model’s online location based on familiarity with Anthropic’s URL formatting conventions for other models.

The breach was facilitated, at least in part, by an individual currently employed at a third-party contractor working with ...