Anthropic's Claude Fable 5 and Mythos 5 AI suspended over security fears

Anthropic suspends new AI tools over US government security concerns

Anthropic has suspended its powerful new AI model after US authorities raised security concerns just days following its public release.

In a statement published on its website, Anthropic said it was ordered to suspend foreign nationals from using Claude Fable 5, a program that the company self-described as "too powerful".

"The net effect of this order is that we must abruptly disable Fable 5 and Mythos 5 for all our customers to ensure compliance," the company wrote.

Anthropic and the Trump administration are involved in a separate ongoing lawsuit over an order to stop government agencies using the company's AI tools. The BBC has approached the US Department of Commerce for comment.

Claude Fable 5 is a version of Anthropic's Claude Mythos, an AI program rivalling competitors OpenAI's ChatGPT and Google's Gemini.

Anthropic said US national security authorities had not identified specific concerns.

"Our understanding is that the government believes it has become aware of a method of bypassing, or 'jailbreaking' Fable 5," the company said.

Jailbreaking is a process of getting past software restrictions designed to protect a cyber network, allowing hackers to access sensitive information or unblock features.

"We reviewed a demonstration of this specific technique being used to identify a small number of previously known, minor vulnerabilities," Anthropic said.

"These vulnerabilities all appear relatively simple, and we have found that other publicly-available models are able to discover them as well without requiring a bypass."

Ahead of the release of Claude Fable 5, the company touted various "safeguards" it had implemented to prevent cyber hacking.

Finance, technology and government leaders had expressed concerns about its public rollout, following a private release in April for previewing and testing vulnerabilities within its own system.

Anthropic said it enabled pre-release access for a handful of organisations because the tool was so intelligent that it could be dangerous because of its ability to exploit or hack computer systems.

The company self-proclaimed that it was "too powerful to release" before Claude Fable 5 was publicly released, which some critics questioned as inflated hype and marketing spin.

"Fable's capabilities exceed those of any model we've ever made generally available," the company said.

Anthropic has found itself in the crosshairs of the Trump administration recently.

Donald Trump has criticised the company publicly and then US Defence Secretary Pete Hegseth labelled it a "supply chain risk" – the first time a US company has ever publicly received such a designation.

The designation means a tool or service is not secure enough for government use, and is historically reserved for companies based in adversarial countries.

Anthropic is suing the Pentagon following the designation. A US judge has ruled the Pentagon's directive could not be enforced, meaning government agencies and organisations working with the US military can still use Anthropic while the lawsuit continues.