Anthropic has suspended access to its latest Fable 5 and Mythos 5 artificial intelligence models for all foreign nationals after receiving a US government order citing national security concerns.

The San Francisco-based company said it was forced to “abruptly disable” access to ensure compliance with the directive, which also affects foreign nationals working at Anthropic. Older models, including Opus 4.8, remain available.

Mythos drew attention after Anthropic warned it could become a powerful tool for hackers capable of identifying vulnerabilities in computer networks. While the company initially shared the model with critical infrastructure operators to strengthen cyber defenses, some experts argued its capabilities could be used for both offensive and defensive purposes.