Anthropic disables Fable and Mythos AI models after U.S. government bars it from giving foreigners access - Fortune

Anthropic was forced to disable all access to its newest AI models, Fable 5 and Mythos 5, late on Friday after the U.S. Commerce Department used national security export controls to bar the company from distributing the models to any foreign national.

The directive includes not just people located outside the U.S., but also any foreign national in the U.S., including Anthropic’s own non-citizen employees.

Given the scope of the directive, Anthropic argued it had no choice but to disable the models for all users. It clarified that access to its less powerful Claude models, including its latest Claude Opus 4.8 model, was not affected.

“We apologize for this disruption to our customers,” Anthropic wrote in a post on X. “We believe this is a misunderstanding and are working to restore access as soon as possible.”

Anthropic confidentially filed for a public listing earlier this month. A recent funding round valued the company at $965 billion. The government export control decision could make investors less enthusiastic about an Anthropic IPO, causing them to question whether it will be able to stay at the cutting-edge of AI model development if the government continues to single out its models for various restrictions.

Anthropic said in a blog post that it received the directive at 5:21 pm Eastern Time. It said the letter it received “did not provide specific details” of the government’s national security concern.

But the company also said that officials had told Anthropic that the government made the decision after learning of a technique to bypass Fable 5’s safeguards. 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.

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. It 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. “If this standard was applied across the industry, we believe it would essentially halt all new model deployments for all frontier model providers.

“As we have stated publicly, we believe the government should have the ability to block unsafe deployments, as part of a statutory process that is transparent, fair, clear, and grounded in technical facts. This action does not adhere to those principles,” Anthropic said.

AI industry insiders and policy experts reacted with disbelief to the unprecedented U.S. directive.

Some saw the move as a further attempt by the Trump administration to punish Anthropic. U.S. President Donald Trump in February ordered all federal agencies to stop using Anthropic’s models after the company refused to agree to the Pentagon’s preferred contract terms for AI vendors, which stipulated that any AI models it purchased could be used “for any lawful purpose.” Anthropic had been seeking exemptions from having its models used for autonomous weapons systems or mass domestic surveillance.

The Pentagon declared Anthropic a “supply chain risk” in early March, requiring the U.S. military to cease using its models and prohibiting defense contractors from using them for government contracts. Anthropic is challenging that designation in federal court.

Several key Trump technology policy advisors, most notably former AI and crypto czar David Sacks and Pentagon undersecretary of defense for research and engineering Emil Michael, have publicly attacked Anthropic and its executives. Sacks has accused Anthropic of being “woke” and “leftist” as well as engaging in “a sophisticated regulatory capture strategy based on fear-mongering.”

Dean Ball, an AI policy expert who briefly served in the Trump administration but is highly critical of its recent decisions around Anthropic, said on X that “I can’t tell if this is lawfare against Anthropic in particular or extreme national-security hawkery. Regardless, it is simply cartoonish.”