Anthropic has temporarily suspended access to the Fable 5 and Mythos 5 models for all customers following a request from the US government. The company said the directive, issued on the advice of national security agencies, requires foreign nationals to restrict their use of these models.
Anthropic said the order applies not only to users living outside the US, but also to foreign nationals within the country, as well as the company’s foreign employees. In order to comply with the request, the Fable 5 and Mythos 5 models have been disabled for all customers. Other Claude models will continue to operate as before.
The company said the government letter did not disclose specific security concerns. Anthropic believes that the decision may be due to the discovery of certain “jailbreak” methods in the Fable 5 model.
Anthropic also stressed that it does not agree with the decision. The company noted that before the Fable 5 was released, it had spent thousands of hours of security checks with the US government and independent organizations and created strong protection mechanisms for the model.
“We believe that the discovery of a potentially limited jailbreak method should not be a reason to recall a commercial model. We believe this is a misunderstanding and are working to restore access as soon as possible,” Anthropic said in a statement.
It should be noted that Anthropic introduced the Claude Fable 5 model in June 2026. At that time, the company introduced additional security measures to prevent abuse of the model, and announced that requests for some sensitive topics were redirected to the more secure Claude Opus 4.8 model. At the same time, a closed version of the Mythos 5 model was made available only to a limited number of cybersecurity professionals and infrastructure providers.
