U.S. government bars Anthropic from giving its newest AI models Fable 5 and Mythos 5 to foreign nationals, forcing the company to disable access for all users due to a discovered security vulnerability.

What happened: The U.S. Commerce Department issued an export control directive on Friday evening (5:21 pm Eastern Time) prohibiting Anthropic from distributing Fable 5 and Mythos 5 to any foreign national, including non-citizen employees in the U.S. Anthropic responded by disabling access to both models for all users to comply with the broad scope of the restriction. Access to its older Claude models, including Claude Opus 4.8, was not affected.

Why it matters: The government cited a technique that can bypass Fable 5's safeguards to access Mythos's cybersecurity capabilities as the reason. However, Anthropic argues the jailbreak is narrow and that the same technique could be used on other publicly available models like OpenAI's GPT-5.5, which are not subject to similar controls. The move comes after months of tension—the Trump administration ordered federal agencies to stop using Anthropic's models in February, and the Pentagon declared the company a "supply chain risk" in early March. Anthropic is currently preparing for a public listing and valued at $965 billion（約150兆円）, so the government's action may concern investors about the company's ability to operate freely.

What to watch: Anthropic has stated it believes the directive is a misunderstanding and is working to restore access as soon as possible. The company is also challenging the Pentagon's "supply chain risk" designation in federal court. Policy experts are divided—some view the move as targeted punishment, while others argue Anthropic invited the scrutiny by marketing Mythos as too dangerous to release broadly and highlighting Fable 5's safeguards in press releases.