Anthropic blocks Fable 5 and Mythos 5 access to comply with US national security order

Anthropic on Friday disabled access to its Fable 5 and Mythos 5 artificial intelligence models following a directive from the US government citing national security authorities under export control law.

The company confirmed it received the order at 5:21 pm ET, instructing it to immediately suspend access to both models for "any foreign national, whether inside or outside the United States, including foreign national Anthropic employees." All other Anthropic models remain unaffected.

The models and their significance

The suspension came just days after Anthropic unveiled Fable 5 and Mythos 5, two models the company described as state-of-the-art across a range of industry benchmarks. Fable 5 was particularly notable as the first time Anthropic had made such an advanced model available to the public, enabled by new safeguards designed to block responses in specific high-risk areas.

Both models built on the earlier release of Claude Mythos Preview, which drew significant attention from Wall Street and government officials in April due to its advanced cybersecurity capabilities. Anthropic had previously opted not to make Mythos Preview generally available, instead limiting its rollout to a select group of companies through a cybersecurity initiative called Project Glasswing.

Government order and Anthropic's response

Anthropic confirmed that the US government did not provide specific details about the nature of its national security concern when issuing the order. The company apologised to customers for the disruption caused by the abrupt suspension and stated its position on government oversight of AI in a formal statement.

"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."

A deepening clash with Washington

Friday's announcement marks the latest in a series of escalating disputes between Anthropic and the US government. Earlier this year, negotiations between the company and the Department of Defense broke down publicly, after which the DOD declared Anthropic a supply chain risk — a designation that historically has been reserved for foreign adversaries.

The label requires defence contractors to certify that they will not use Anthropic's Claude models in any work carried out for the military. Anthropic subsequently filed a lawsuit against the Trump administration in an effort to overturn the blacklisting, and that litigation remains ongoing.