Anthropic has disabled access to Fable 5 and Mythos 5 after the US government issued an export control directive citing national security authorities.

The order requires Anthropic to suspend access to the two models for all foreign nationals, whether they are inside or outside the United States. The restriction also applies to foreign national employees working at Anthropic.

Anthropic said the order forced it to abruptly disable Fable 5 and Mythos 5 for all customers to ensure compliance. Access to all other Claude models remains unaffected.

The company apologised to customers for the disruption and said it believes the issue is a misunderstanding. Anthropic said it is working to restore access as soon as possible.

Anthropic said it received the directive from the government on June 12 at 5:21 pm ET.

According to the company, the government letter did not provide specific details of the national security concern.

Anthropic said its understanding is that the government believes it has become aware of a method to bypass, or jailbreak, Fable 5.

The company said it reviewed a demonstration of the technique being used to identify a small number of previously known and minor software vulnerabilities.

Anthropic said the vulnerabilities appeared relatively simple and could also be discovered by other publicly available models without using the bypass.https://twitter.com/AnthropicAI/status/2065597531644743999

Anthropic launched Claude Fable 5 on June 9 as a Mythos-class model made safe for general use.

The company described Fable 5 as its most capable model made generally available, with strong performance in software engineering, knowledge work, vision, scientific research, and long-running tasks.

Anthropic also launched Claude Mythos 5 for a smaller group of cyber defenders and infrastructure providers through Project Glasswing.

Mythos 5 is the same underlying model as Fable 5, but with some safeguards lifted in selected areas for trusted users.

The US government, citing national security authorities, has issued an export control directive to suspend all access to Fable 5 and Mythos 5 by any foreign national, whether inside or outside the United States, including foreign national Anthropic employees.

The net effect of…

— Anthropic (@AnthropicAI) June 13, 2026

Anthropic said Fable 5 includes strong safeguards to reduce the risk of misuse in areas such as cybersecurity.

The company said some users had complained that the safeguards were too broad.

Before launching Fable 5, Anthropic said it worked with the US government, the UK AI Security Institute, third-party organisations and internal teams to test the model’s safeguards for thousands of hours.

The company said no testers had found a universal jailbreak that could broadly bypass the model’s safeguards.

Anthropic also said it uses a defense-in-depth approach for Fable 5, aiming to make any jailbreak narrow or expensive to produce, while using monitoring to detect and stop successful attacks.

Reuters reported that senior Anthropic technical staff were scheduled to meet officials at the US Department of Commerce in Washington to discuss the dispute.

The report said Anthropic technical staff had met officials virtually every day since the government contacted the company.

Cybersecurity leaders have also pushed back against the restrictions. According to Axios, a group of security experts argued that limiting access to Anthropic’s most advanced models could hurt defenders more than attackers.

The group said similar capabilities exist in other leading AI models and that blocking Fable 5 could create market uncertainty without reducing the broader security risk.

Anthropic said it is complying with the legal directive and removing access to Fable 5 and Mythos 5 for all users.

However, the company disagreed that a narrow potential jailbreak should lead to the recall of a commercial model used by a large number of people.

Anthropic said applying the same standard across the AI industry could effectively halt new model deployments from frontier model providers.

The company said the government should be able to block unsafe deployments, but only through a transparent and fair process grounded in technical facts.

Anthropic said this action does not meet that standard.

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