US government orders suspension of Fable 5 and Mythos 5

On June 12, 2026, Anthropic received a government directive at 5:21 PM ET citing national security authorities. The order requires suspension of all access to Fable 5 and Mythos 5 by foreign nationals—both inside and outside the United States, including foreign national Anthropic employees. To ensure compliance, Anthropic has disabled both models for all customers worldwide.

The government's concern: The directive did not provide specific details about the national security concern. Anthropic's understanding is that the government believes a jailbreak method for Fable 5 has been discovered—specifically a technique involving asking the model to read a specific codebase and fix software flaws.

Anthropic's assessment: Anthropic reviewed the demonstration behind the directive and found that the capability shown is already widely available in other publicly deployed models, including OpenAI's GPT-5.5. The specific vulnerabilities identified are minor, previously known, and can be discovered without any bypass. Anthropic has not received evidence of a universal jailbreak—one that broadly bypasses Fable's safeguards across a wide range of capabilities.

How Fable 5's safeguards were designed: When Fable 5 launched, Anthropic worked with the US government, the UK AISI, and multiple third-party organizations to red-team safeguards for thousands of hours. Anthropic acknowledged from the outset that perfect jailbreak resistance is not possible for any model. Instead, Fable 5 uses a 'defense in depth' strategy: making jailbreaks either narrow or very expensive to produce, combined with thorough monitoring and a mandatory 30-day data retention policy to enable rapid detection and mitigation.

Anthropic's position: Anthropic is complying with the directive but strongly disagrees with the decision. The company states that applying this standard across the industry would essentially halt all new model deployments for all frontier providers. Anthropic believes the government should have the ability to block unsafe deployments—but through a transparent, fair, and technically grounded process, which this action does not follow.

Impact on users: Access to all other Claude models—Sonnet 4.6, Opus 4.6, Haiku 4.5, and all previous versions—remains fully unaffected. Anthropic apologizes for the disruption and is working to restore access to Fable 5 and Mythos 5 as quickly as possible. More technical details are expected within 24 hours.