Anthropic Has Disabled Access to Fable 5 and Mythos 5

Anthropic has disabled access to two of its most advanced artificial intelligence models after the U.S. government ordered the company to suspend use of the systems by foreign nationals, citing “national security authorities,” the AI firm says.

The order, received at 5:21 p.m. ET, required Anthropic to block access to its Fable 5 and Mythos 5 models “by any foreign national, whether inside or outside the United States, including foreign national Anthropic employees,” the company said.

Anthropic said it immediately disabled the models for all customers to ensure compliance with the directive, while adding that its other AI models would not be affected.

The move came days after Anthropic unveiled Fable 5 and Mythos 5, models the company described as among the most capable AI systems available across several industry benchmarks. Fable 5 represented Anthropic’s first release of an advanced model with safeguards designed to prevent responses in specific high-risk areas.

The models followed the release of Claude Mythos Preview, which drew attention from Wall Street and government officials in April for its advanced cybersecurity capabilities. Anthropic said it had not planned a broad public release of that model, instead limiting access to selected companies through a cybersecurity initiative known as Project Glasswing.

In a statement, Anthropic said the government did not provide specific details about the national security concerns behind the directive and apologized to customers affected by the sudden restriction.

“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.”

The directive marks the latest dispute between Anthropic and the U.S. government after tensions between the company and the Department of Defense escalated earlier this year.

Following failed negotiations, the Pentagon designated Anthropic a supply chain risk, a classification that means the company is considered a potential threat to U.S. national security. The designation has historically been associated with foreign adversaries and requires defense contractors to certify that they will not use Anthropic’s Claude models in military-related work.

Anthropic later sued the Trump administration seeking to overturn the designation, with the legal dispute still ongoing.

The confrontation highlights growing tensions between Washington and leading AI developers as governments seek greater control over the deployment of frontier AI systems, particularly those with advanced cybersecurity, intelligence and defense applications.

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