US Commerce Secretary Howard Lutnick warned Anthropic that it must obtain government permission before giving foreign nationals access to its most advanced AI models, according to a Bloomberg report citing a letter sent to CEO Dario Amodei.

The letter, dated Friday, ordered Anthropic not to provide its Fable 5 and Mythos 5 models to foreign nationals anywhere in the world without a license from the Commerce Department. 

Lutnick cited US export control laws covering civilian technology that could be used for intelligence purposes by an adversary’s military, though the letter did not explain why the restrictions were necessary.

The directive prompted Anthropic to disable access to both models late Friday. The company has since held talks with US officials, including meetings between technical staff and Commerce Department officials, as it seeks to resolve the issue.

Anthropic has said it believes the order was issued after the US government became aware of a possible jailbreak in Fable 5, a recently released version of Mythos that the company had restricted from performing cybersecurity tasks. The company called the move disproportionate and warned that applying the same standard across the industry could halt new frontier model deployments.

The order represents one of the most aggressive US government interventions yet into the operations of a frontier AI company. It comes weeks after Anthropic confidentially filed for an IPO, with its latest valuation reportedly above $900 billion.

The restrictions also raise broader questions for the AI industry. If advanced models can be pulled from global markets through export controls, AI labs may face new uncertainty around international revenue, enterprise contracts, and access for foreign employees or customers.

Lutnick said the license requirement would remain in effect until further notice. The Commerce Department declined to comment on the specifics of the letter, while Anthropic pointed to its public statement on the export controls.