In brief
The U.S. government ordered Anthropic to suspend access to its two most advanced AI models, Fable 5 and Mythos 5, citing a national security concern over a potential jailbreak vulnerability.
Anthropic complied but disputed the finding, arguing the vulnerability is simple and already replicable using other publicly available models like GPT-5.5.
The company warned the directive sets a dangerous precedent that, if applied industry-wide, could halt all new frontier AI model deployments.
The U.S. government issued an emergency export control directive on Friday ordering Anthropic to immediately suspend access to its two most powerful artificial intelligence models—Claude Fable 5 and Claude Mythos 5, both released just days earlier—for all foreign nationals, including the company's own employees, citing national security concerns.The directive bars any foreign national from accessing the models, whether inside or outside the United States. The sweeping scope of the order forced Anthropic to disable the models for its entire customer base to ensure compliance.The letter did not provide specific details of its national security concern, but the government believes it has become aware of a method of bypassing, or "jailbreaking," the publicly available Fable 5 model. Mythos 5, which has fewer guardrails and is particularly powerful at discovering cybersecurity exploits, was only available to select partners.Anthropic disputed the severity of the finding. The company said it reviewed a demonstration of the technique and concluded that the vulnerabilities identified appear relatively simple, and that other publicly available models are able to discover them as well without requiring any bypass.The company said the government has so far provided only verbal evidence of a potential narrow, non-universal jailbreak—essentially consisting of asking the model to read a specific codebase and fix any software flaws. Anthropic added that it validated that the level of capability on display is already widely available from competing models, including OpenAI's GPT-5.5.While complying with the directive, Anthropic said it believes the action sets a dangerous precedent. "If this standard was applied across the industry," the company wrote, "we believe it would essentially halt all new model deployments for all frontier model providers."Access to all other Anthropic models will not be affected. The company said it is working to restore access as soon as possible.
