Anthropic must shut down its AI models Fable 5 and Mythos 5 for all customers worldwide. According to the company, the trigger is a US government export control directive received on June 12, 2026, which prohibits foreign nationals from accessing both models – including foreign Anthropic employees within the USA. All other Claude models are not affected by the order. The measure is part of an escalating dispute between Anthropic and parts of the US security bureaucracy that occurred previously.
As Anthropic explains in a statement, the authority did not provide specific technical details regarding the stated national security concerns. According to the company's understanding, the government assumes that a method exists to “jailbreak” Fable 5, i.e., to bypass its protective mechanisms. Anthropic describes the measure as a “misunderstanding” and is working on restoring access.
When starting Claude, Anthropic refers to the explanation why Fable 5 is currently deactivated for all customers.
Anthropic describes the criticized technique as a verbally transmitted, potentially non-universal jailbreak. At its core, it involves instructing the model to read a specific codebase and fix software errors. A demonstration of this technique was reviewed, revealing only a small number of already known, minor vulnerabilities that publicly available models could also detect – the company explicitly mentions OpenAI's GPT-5.5 in this context.
