Anthropic Suspends Fable 5 and Mythos 5 Following US Government National Security Directive

Anthropic has suspended access to its newly launched Fable 5 and Mythos 5 artificial intelligence models after receiving a directive from the U.S. government citing national security concerns.

Anthropic Disables AI Models After Government Order

The company said it received the directive at 5:21 p.m. ET on Friday. The order instructed Anthropic to immediately suspend access to Fable 5 and Mythos 5 for all foreign nationals, regardless of whether they were located inside or outside the United States. The restriction also applies to foreign-national employees working at Anthropic.

To ensure full compliance with the directive, Anthropic chose to disable access to both models for all users. The company clarified that its other AI systems, including Opus 4.8, remain available and are not affected by the order.

National Security Concerns Linked to Potential AI Jailbreak

According to Anthropic, government officials did not provide detailed information about the alleged security threat. However, the company believes authorities are concerned about a possible jailbreak technique that could bypass safety protections built into Fable 5.

Anthropic said the evidence presented so far points only to a limited or “non-universal” jailbreak. The reported method involves asking the model to analyze a specific software codebase and identify vulnerabilities or security flaws.

Anthropic Challenges the Decision

The company argued that a narrow jailbreak differs significantly from a universal jailbreak, which could broadly override a model’s safeguards across many use cases.

Anthropic stated that recalling a commercial AI model over a limited vulnerability sets a concerning precedent.

Company Seeks Restoration of Access

Fable 5 and Mythos 5 were launched only days before the suspension and were built on top of Mythos Preview, a powerful language model previously credited with identifying thousands of software vulnerabilities.

Anthropic said it believes the government directive may be based on a misunderstanding and is actively working with authorities to clarify the issue.