Anthropic halts access to Fable 5 and Mythos 5 following government directive

On June 13, 2026, the U.S. government ordered Anthropic to block access to its models, Fable 5 and Mythos 5, for all foreign nations due to national security concerns. This directive also applied to Anthropic employees. In compliance with the order, the company has ceased access to these models for all customers. Anthropic stated that the government did not provide specific details regarding the national security concerns, and any evidence of potential vulnerabilities was communicated verbally. The company characterized the discovered vulnerabilities as minor and noted that similar issues existed in other models.