In accordance with a US national security order, Anthropic said on Friday that access to two potent AI models, Fable 5 and Mythos 5, had been suspended.
The firm announced in a blog post that, due to national security concerns, it had received a government decree prohibiting any foreign nationals—including Anthropic employees—from accessing Fable 5 and Mythos 5 just three days after the game's public launch.In order to ensure compliance, we must immediately disable Fable 5 and Mythos 5 for all of our customers, according to the order.The letter was received around 5:21 p.m. (2121 GMT), according to the firm.According to Axios, US Commerce Secretary Howard Lutnick wrote the letter.AFP's request was not immediately answered by US Commerce representatives.
The company said that the letter did not specify what the government was particularly concerned about. But according to the company's "understanding is that the government believes it has become aware of a method of bypassing, or 'jailbreaking'" the Fable 5 model, which could facilitate hacking.
Released on Tuesday, Fable 5 is a locked-down version of Mythos 5, a state-of-the-art AI model that Anthropic withheld from the public due to worries that it has previously unheard-of capabilities to detect software vulnerabilities, or gaps in code that hackers may exploit.

Only a few businesses have access to Mythos 5, the unconstrained model.
Anthropic claimed to have examined the "jailbreaking" technique at the heart of the rumours and the hacking prospects it revealed, but it doesn't think Fable 5 offers hackers any capabilities that aren't already accessible through other open models.
The company claimed that none of its security testers had discovered a "universal jailbreak," or a method to get around its defences against aiding hackers."We disagree that a commercial model that has been distributed to hundreds of millions of people should be recalled due to the discovery of a narrow potential jailbreak," the business stated.

"If this standard was applied across the industry, we believe it would essentially halt all new model deployments for all frontier model providers."
The Pentagon has terminated contracts with Anthropic due to the company's refusal to permit its technology to be utilised for autonomous weapons and mass monitoring, which has resulted in a legal standoff with the Trump administration.