On June 12, 2026, the US government issued an export control directive citing national security authorities that prohibits any foreign national—inside or outside the United States—from accessing Anthropic’s Fable 5 and Mythos 5 models. The measure explicitly covers foreign-national Anthropic employees as well. Anthropic says that to comply, it had to immediately disable access to Fable 5 and Mythos 5 for all customers.
When the directive arrived and what it said
Anthropic reports it received the directive at 5:21 p.m. (ET) on June 12, 2026. The government letter did not provide detailed public explanations of the national security concern. According to Anthropic, the government indicated it had become aware of a method for bypassing, or “jailbreaking,” Fable 5’s safeguards.
Anthropic’s review of the alleged jailbreak
Anthropic says it reviewed a demonstration of the described technique and found it identified a small number of previously known, relatively minor vulnerabilities. The company states these vulnerabilities appear simple and that other publicly available models can also discover them without requiring a bypass.
The company further reports that the government provided only verbal evidence of a potential narrow, non-universal jailbreak—essentially prompting the model to read a particular codebase and fix software flaws. Anthropic reviewed what it believes is the report underlying the government’s directive and validated that the capability displayed there is widely available from other models, including OpenAI’s GPT-5.5, and is used daily by defenders who secure systems.
Anthropic says it will share additional details over the next 24 hours.
Background: Anthropic’s safety posture for Fable
Anthropic describes extensive pre-launch testing of Fable: it worked with the US government, the United Kingdom’s AISI, multiple private third parties, and internal teams for thousands of hours of red-team testing. According to the company, these tests showed Fable’s safeguards to be substantially more effective than those in prior deployed models.
The company states that no testers have found a universal jailbreak—a broadly effective method that would comprehensively bypass the model’s safeguards. At the same time, Anthropic acknowledges that perfect jailbreak resistance likely does not exist today for any provider. The industry’s safeguards are vulnerable to non-universal jailbreaks, which can elicit some cyber-related information in specific circumstances, and universal jailbreaks may eventually be discovered.
Because perfect resistance appears unattainable today, Anthropic says it adopted a defense-in-depth strategy for Fable 5: make jailbreaks narrow (if non-universal) or expensive to produce (if universal), combine layered protections with thorough monitoring, and rapidly detect and shut down successful attacks. As part of that approach, Anthropic requires 30-day retention of customer data for Fable—an operational cost the company says it bears to research and mitigate jailbreaks.
Company position and practical consequences
Anthropic states it will comply with the government’s legal directive and remove access to Fable 5 and Mythos 5 for all users. However, the company disputes that finding a narrow potential jailbreak justifies recalling a commercial model deployed to hundreds of millions of people. Anthropic warns that applying such a standard industry-wide would effectively halt new model deployments by frontier providers.
Anthropic has previously argued that the government should have authority to block unsafe deployments, but that this should occur through a statutory process that is transparent, fair, clear, and grounded in technical facts. The company says the current action does not meet those principles.
Next steps and impact on customers
Anthropic apologized for the disruption to customers and said it believes the directive is a misunderstanding; the company is working to restore access as soon as possible. It also pledged to provide more information about the report that prompted the government action within the next 24 hours.
Anthropic added that access to all its other models will not be affected by this order; the restriction applies only to Fable 5 and Mythos 5 while the company complies with the directive.
Summary
On June 12, 2026, a US export-control directive required Anthropic to block foreign nationals from using Fable 5 and Mythos 5, prompting Anthropic to disable those models for all users to ensure compliance. Anthropic says the directive followed a government claim about a narrow jailbreak technique that the company views as insufficient grounds for such a broad takedown and says similar behavior is present in other publicly available models. The company is complying while contesting the measure’s scope and working to restore access.
