Anthropic Suspends Fable 5 and Mythos 5 After U.S. Order

Anthropic disabled global access to its Fable 5 and Mythos 5 models after receiving a U.S. export-control directive at 5:21 p.m. ET on June 12. The directive, citing national security authorities, required suspension of access to those models by any foreign national, whether inside or outside the United States, including foreign-national Anthropic employees. To comply with the order, the company disabled the two models for all customers. Other Claude models remain available; new sessions will run a user’s selected default model or fall back to Opus 4.8.

An export-control directive restricts transfer of specified technologies to foreign nationals. The letter Anthropic received did not identify a specific national security concern. Federal officials provided a verbal demonstration of a narrow jailbreak technique, according to Anthropic, which reviewed the demonstration and described the bypass as minor. The company said the vulnerability appeared simple and that other publicly available models can expose similar weaknesses.

Anthropic said Fable 5 launched with stronger safeguards than prior models and was tested with U.S. and U.K. agencies and multiple third-party teams that red-teamed protections for thousands of hours. No tester has found a universal jailbreak capable of bypassing Fable 5 protections across a broad range of cyber capabilities, the company added. Anthropic described its safety approach as defense in depth, combining targeted safeguards, continuous monitoring and 30-day data retention for Mythos-class models.

The company disagrees that a narrow potential jailbreak justifies recalling a commercial model deployed to hundreds of millions of users and called the directive a likely misunderstanding. Anthropic said it is complying with the order, will provide more technical details within 24 hours and is working to restore access to Fable 5 and Mythos 5 as soon as possible.