Washington has ordered Anthropic – a leading entity in America’s AI sector – to block all foreign nationals from accessing its latest models, Fable 5 and Mythos 5, citing national security concerns, according to the Silicon Valley-based firm.

The unprecedented export-control measure – the first to target specific AI models – came just days after Anthropic released the models, underscoring Washington’s increasingly hands-on approach to regulating frontier artificial intelligence technologies.

According to Anthropic’s statement, issued on Friday night, the directive arrived at 5.21pm Eastern time and extends even to Anthropic’s own foreign-born employees.

“The net effect of this order is that we must abruptly disable Fable 5 and Mythos 5 for all our customers to ensure compliance. Access to all other Anthropic models will not be affected,” the company said.

Anthropic released Fable 5 and Mythos 5 on Tuesday, marketing them as its most powerful models to date. Both systems have similar underlying technical foundations, but only Fable 5 was released to the public with additional safety and security restrictions, while Mythos 5 was released only to trusted partners.

Anthropic previously warned that Fable 5 “could be misused to cause serious damage” without the safeguards it introduced, including restrictions on discussing sensitive cybersecurity, biology and chemistry topics.

The releases came two months after Anthropic first unveiled a preview version of the Mythos model to a small group of industry partners under an initiative called Project Glasswing, touting unprecedented cybersecurity capabilities.