Anthropic Suspends Claude Fable 5 for Foreign Users After US Security Order but Court Allows Continued Government Use

Anthropic suspended new access to Claude Fable 5 and disabled the model for all customers after US authorities ordered it to bar foreign nationals from using the system. The company said the order forced it to disable both Fable 5 and Mythos 5 to maintain compliance.

It stated that national security officials had not identified specific concerns with the model but believed they had identified a method of bypassing or jailbreaking its safeguards.

Anthropic reviewed a demonstration of the technique and found it exposed a small number of previously known, minor vulnerabilities. The company added that other publicly available models could discover the same issues without requiring a bypass. Claude Fable 5 is a version of Anthropic's Claude Mythos line.

The company had described the model as "too powerful to release" before making it available and said its capabilities exceed those of any model it has previously offered to the public. Anthropic enabled pre-release access for a handful of organisations in April to test the system. The UK government's AI Security Institute found the model could exploit defences and systems 73 percent of the time.

Anthropic and the Trump administration are involved in a separate lawsuit over an earlier order directing government agencies to stop using the company's AI tools. US Defence Secretary Pete Hegseth labelled Anthropic a "supply chain risk," a designation historically applied to companies based in adversarial countries.

A US judge ruled the Pentagon directive could not be enforced, allowing government agencies and organisations working with the US military to continue using Anthropic's tools while the case proceeds.