Anthropic closes Claude Fable 5 and Mythos 5

Anthropic temporarily interrupted access to Claude Fable 5 and Claude Mythos 5 for all users, following a US government directive to restrict access to foreigners. The company explained that the order requires them to completely disable both models.

Anthropic said that US national security authorities have not publicly identified any specific issues and claimed that the government is aware of a method to bypass or "jailbreak" Fable 5.

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According to Anthropic, the vulnerabilities are “relatively simple” and there are other publicly available models that have the same security holes without requiring a jailbreak.

“We looked at a demonstration of this particular technique used to identify a small number of previously known, minor vulnerabilities,” Anthropic explained. “These vulnerabilities all appear to be relatively simple, and we have found that other publicly available models also have them without requiring a workaround.”

Customers on Pro, Max, and Enterprise plans who accessed Fable 5 during the free preview period will no longer be able to use the model. The Mythos 5 Partner Access Program is also affected.

Anthropic has not given a timeline for when Fable 5 and Mythos 5 will be available again or what requirements must be met to lift the suspension. Other Claude models, including the Claude Opus 4.8, remain accessible.

The suspension comes amid an ongoing dispute between Anthropic and the Trump administration. President Donald Trump has publicly criticized the company and former U.S. Secretary of Defense Pete Hegseth has called Anthropic a “ supply chain risk .”

This designation, usually reserved for adversaries, marks the first time an American company has released a tool or service not secure enough for government use.

Anthropic sued the Pentagon over the designation, and a U.S. judge has ruled that the Pentagon's directive cannot be enforced while the lawsuit is pending. As a result, government agencies and organizations that work with the U.S. military can continue to use Anthropic's products temporarily.

Anthropic had stated that Fable 5 exceeds the capabilities of any model the company has released, with the Mythos architecture described as "too powerful to release" without meaningful safeguards.

Anthropic has not announced any modifications it plans to make to address the government's concerns.

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Although the press releases will range from very select to rare, I said I'd pass...because sometimes the editors hide.