Anthropic Fable 5 and Mythos 5 Access Blocked to All Users Following Government Directive

Anthropic has disabled its two most capable AI models, Fable 5 and Mythos 5, after the U.S. government issued an export control directive late on June 12 ordering the company to block access for any foreign national, whether inside or outside the United States, including Anthropic’s own foreign-national employees.

Because the company says it cannot reliably separate foreign users from the rest of its base in real time, the practical result is a worldwide shutoff of both models. All other Anthropic models remain online.

Anthropic Fable 5 and Mythos 5 access Blocked

The US government, citing national security authorities, delivered the directive to Anthropic at 5:21 PM ET on Friday, June 12, 2026. The order mandates that no foreign national, whether inside or outside the United States, including Anthropic’s own foreign national employees, be permitted access to the two models.

Because selectively enforcing nationality-based access controls at scale is operationally impractical, Anthropic extended the restriction to its entire global customer base to ensure full legal compliance. Access to all other Anthropic models remains unaffected.

The directive did not provide specific details about its national security concern, but Anthropic’s understanding is that the government believes it has identified a method to bypass or “jailbreaking” Fable 5.

The alleged jailbreak technique, as described to Anthropic, essentially involves instructing the model to read a specific codebase and identify software flaws. According to Anthropic, the government has so far only provided verbal evidence of a potential narrow, non-universal jailbreak.

Anthropic reviewed a demonstration of the specific technique and found that it surfaced only a small number of previously known, minor vulnerabilities. Critically, the company states that other publicly available models, including OpenAI’s GPT-5.5, can produce the same output without requiring any bypass.

Anthropic has publicly acknowledged that perfect jailbreak resistance is not achievable by any model provider today. In response, the company adopted a defense-in-depth strategy: engineering non-universal jailbreaks to be narrow in scope and universal jailbreaks to be prohibitively expensive to produce, combined with comprehensive monitoring to detect and shut down successful attacks rapidly.

As part of this strategy, Anthropic implemented a 30-day customer data retention policy for Mythos-class models to support ongoing jailbreak research and mitigation.

Anthropic has apologized to affected customers and stated it is working urgently to restore access, with a commitment to release further technical details within 24 hours of the directive.

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