US Government Forces Anthropic to Disable Powerful AI Models Over Security Breach

Sudden Shutdown Disrupts Hundreds of Millions

Anthropic disabled its two most powerful artificial intelligence models on Friday to comply with a United States government order blocking their use by any foreign national, forcing the company to "abruptly disable" access to the models for all customers . The company received the directive at 5:21pm Eastern Time on Friday , leaving users worldwide unable to access the cutting-edge Fable 5 and Mythos 5 models that had been released just days earlier.

The ban affects foreigners currently in the US – including those working at Anthropic itself . The government letter did not provide specific details of its national security concern , though officials told Anthropic they made the decision after learning of a technique to bypass Fable 5's safeguards .

Cybersecurity Capabilities Spark Government Concern

The artificial intelligence behind Anthropic's Mythos AI model is particularly adept at detecting software vulnerabilities, some of which have remained undiscovered for decades . These safeguards were designed to prevent users from accessing the powerful cybersecurity abilities of Mythos, the underlying AI model on which Fable 5 is built . The company claimed at launch that the model's capabilities "exceed those of any model we've ever made generally available" and was particularly effective at identifying software vulnerabilities .

A concern from the outset has been that such AI could become a dangerous cyberweapon in the wrong hands . The Fable 5 model, released just this week, is based on Mythos technology, but its cybersecurity and biotechnology capabilities are blocked, while Mythos 5 is the non-public full version, which should continue to be used only by government agencies and selected corporate partners .

Company Disputes Government Assessment

Anthropic said it believed the jailbreak the government was citing was a narrow one that would unlock Mythos's cybersecurity capabilities in only one specific instance and not a universal one that would defeat all of Fable 5's safeguards . No testers have yet been able to find a universal jailbreak—a jailbreak method that can very broadly bypass the model's safeguards, unblocking a wide range of cyber capabilities .

The company also said it believed the same jailbreak could be used to elicit similar capabilities from other publicly available models, including OpenAI's GPT-5.5, that are not subject to similar national security export controls . "We disagree that the finding of a narrow potential jailbreak should be cause for recalling a commercial model deployed to hundreds of millions of people," Anthropic wrote in its blog post .

Critics See Self-Inflicted Wounds

Others said that Anthropic was simply reaping what it had sown . When Anthropic first debuted its Mythos model, the company argued the model was too dangerous to release broadly . "If you describe your product as a munition in every press release, eventually a government takes you at your word," Peter Girnus, a cybersecurity researcher, said .

This unprecedented government intervention highlights the growing tension between AI innovation and national security concerns. As companies develop increasingly powerful models capable of sophisticated cyberattacks, the line between commercial AI tools and potential weapons becomes increasingly blurred. The shutdown serves as a stark reminder that even the most advanced AI capabilities remain subject to government oversight when security concerns arise.