Anthropic pulled access to its newly released AI models Mythos 5 and Fable 5 over the weekend after the US government imposed sweeping restrictions on who could use them.

The AI lab said in a statement that the federal government told it Friday afternoon that it had become aware of a way of "jailbreaking" Fable 5, bypassing limits that Anthropic had implemented to reduce the risk the model could be misused. When Anthropic first announced Mythos, it released the software only to a select group of government agencies and technology professionals because of its ability to uncover cybersecurity vulnerabilities. 

The government imposed what are known as export controls on the products, which Anthropic said means it had to suspend access to the two models by any foreign national, whether inside or outside of the US. The only way it could do so is by shutting the models down entirely, the company said.

Anthropic said late Friday that it disagreed that the jailbreak it was shown warranted such sweeping action, and that such a standard could "essentially halt" new frontier AI models if applied broadly.

"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," Anthropic said. "This action does not adhere to those principles."

Representatives for Anthropic and the US Department of Commerce did not immediately respond to requests for comment.

Anthropic has reportedly sent staff to Washington to negotiate with the Trump administration to sort out the issue. The Wall Street Journal reported that Anthropic leaders spent several hours on calls Saturday with Secretary of Commerce Howard Lutnick and National Cyber Director Sean Cairncross.

This isn't the AI developer's first conflict with Washington over AI models. The Department of Defense declared Anthropic a "supply chain risk" earlier this year after the company insisted on restrictions against the use of its Claude AI models for fully autonomous weapons or mass domestic surveillance. The Pentagon wanted the ability to use the models for "all lawful purposes."