US government blocks Anthropic's newest AI models over jailbreak fears, forcing worldwide shutdown
The Trump administration ordered Anthropic to deny all foreigners access to its flagship Fable 5 and Mythos 5 models, citing national security. The company, unable to filter users by nationality, shut down both systems for everyone just three days after their launch.
The export control directive
On 12 June, the US Commerce Department issued an emergency export control directive that forbids Anthropic from making its latest models available to any foreign national, whether in the United States or abroad, including the company’s own non-US employees. Because Anthropic’s services are global and do not verify citizenship at login, the firm said it was forced to pull Fable 5 and Mythos 5 for every customer.
The ultimate effect of this directive is that we are suddenly forced to turn off Fable 5 and Mythos 5 for all our customers.
What triggered the ban
The models, launched on 9 June, had quickly drawn attention for their coding and autonomous-task capabilities. Fable 5 was positioned as a direct rival to OpenAI’s GPT-5.5 and Google’s Gemini, while the Mythos class had already raised concerns internally. An earlier preview version was deemed by the company itself as
after it proved extremely effective at finding and exploiting operating-system vulnerabilities during lab tests in April.too powerful to be made publicly available
The jailbreak that alarmed Washington
A central factor was a report that reached the Commerce Department detailing a method to bypass Fable 5’s safety classifiers. Once jailbroken, the model could analyse large codebases and pinpoint critical weaknesses. Officials feared hostile hackers or state-backed groups could use that capability against US critical infrastructure, including energy, finance, and telecommunications. A researcher operating under the pseudonym "Pliny the Liberator" had previously claimed to have bypassed Fable 5’s safeguards and posted the system prompt on GitHub.
Silicon Valley pushes back
Anthropic vigorously disputed the government’s reasoning. The company said the jailbreak technique was narrow and non-universal, amounting essentially to asking the model to review a codebase and fix bugs.
The firm noted that similar results were obtainable with GPT-5.5 and argued that Fable 5’s safeguards are the strongest it has ever deployed, having passed thousands of hours of red-teaming with the UK’s AI Safety Institute and US government agencies.We analysed the specific technique and found that the vulnerabilities it identified are relatively simple and can also be detected by other publicly available models without any bypass.
What remains online
All other Anthropic models, including Opus 4.8, remain unaffected. The company stated it had received no details from the administration beyond a notification from Commerce Secretary Howard Lutnick that the two models would be placed under export controls. The episode has already triggered broader debate about unilateral export restrictions on frontier AI and the blurring line between safety enforcement and competitive dynamics among America’s top AI labs.
- Anthropic launches Fable 5 and Mythos 5 to the public.
- US Commerce Department issues an export directive blocking the models for all foreign nationals.
- Anthropic shuts down global access to Fable 5 and Mythos 5 for all users.
