Anthropic Suspends Fable 5 and Mythos 5 Access

The Government Directive

Anthropic has suspended all access to its Fable 5 and Mythos 5 models in response to a U.S. government export control directive. The order mandates that access be restricted for all foreign nationals, regardless of whether they are located inside or outside the United States. Due to the technical difficulty of verifying the nationality of every user, Anthropic opted to disable the models entirely for all customers to ensure compliance. The directive was issued without specific details regarding the national security risks, though Anthropic indicates the government is concerned about methods used to jailbreak the models.

Security and Jailbreak Concerns

Anthropic reports that the government's concerns appear to stem from a demonstration of a non-universal jailbreak technique that allows the model to identify software vulnerabilities. Anthropic argues that this capability is already widely available in other public models, such as GPT 5.5, and is commonly used by security defenders to audit codebases. The company maintains that its internal red-teaming efforts, which spanned thousands of hours, did not uncover a universal jailbreak method. Anthropic suggests that perfect jailbreak resistance is currently impossible for any model provider and that the government's intervention may set a precedent for future restrictions on both closed-source and open-weight models.