U.S. Orders Anthropic to Disable Claude Fable 5, Mythos 5 Over Security Concerns

U.S. Orders Anthropic to Disable Claude Fable 5, Mythos 5 Over Security Concerns

Artificial Intelligence (AI) startup Anthropic’s two newest frontier models, Claude Fable 5 and Claude Mythos 5, were abruptly taken offline worldwide last week after the U.S. government issued an export‑control directive citing national security authorities.

Axios first reported that Commerce Secretary Howard Lutnick on Friday sent a letter to Anthropic CEO Dario Amodei stating Mythos 5 and Fable 5 models would be subject to export controls to any location outside of the U.S. and to all foreign persons within the country, including Anthropic employees.

To ensure compliance, Anthropic said in a statement that it disabled the two models for all customers. No other Anthropic models were affected.

“Our understanding is that the government believes it has become aware of a method of bypassing, or ‘jailbreaking’ Fable 5” to identify minor software vulnerabilities in the model, Anthropic said.

…Among other advanced skills, Fable 5 generated novel molecular biology hypotheses and conducted largely autonomous genomics research.

Mythos 5 enabled researchers to accelerate the drug discovery process by 10 times and matched or outperformed experienced scientists on certain protein design tasks, the company said.

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

In a nutshell, the U.S. government ordered Anthropic to cut off access to its newest Claude models under an export‑control directive that barred all “foreign nationals” from using them, citing national security concerns tied to a claimed jailbreak technique that could allegedly bypass safeguards and assist in discovering software vulnerabilities.

Legal Insurrection readers may recall that in March, I reported that hackers reportedly “jailbroke” Anthropic’s Claude chatbot and used it to help steal roughly 150 GB of sensitive data from multiple Mexican government entities, including tax and voter records.

This order forced Anthropic to disable the models globally rather than attempt real‑time nationality filtering.

Anthropic asserts that the demonstrated jailbreak threat was narrow, non‑universal, and exposed only minor, previously known vulnerabilities that other public models can also exploit.

The models built on the release of Claude Mythos Preview, which captivated Wall Street and government officials with its advanced cybersecurity capabilities in April. The company said it did not plan to make the model generally available, and it has limited the rollout to a select group of companies as part of a cybersecurity initiative called Project Glasswing.

In its statement on Friday, Anthropic said the government did not provide specific details about its national security concern. The company apologized to its customers for the disruption.

“As we have stated publicly, we believe the government should have the ability to block unsafe deployments, as part of a statutory process that is transparent, fair, clear, and grounded in technical facts,” Anthropic said. “This action does not adhere to those principles.”

A few cybersecurity “experts” and Anthropic employees believe the Trump administration is unfairly targeting the AI startup.

Some cybersecurity experts said the Trump administration was unfairly targeting Anthropic. By Tuesday afternoon, more than 150 of them had signed an open letter to Howard Lutnick, the commerce secretary, and Sean Cairncross, the national cyber director, calling for them to lift the restrictions on Anthropic’s models.

The list of signatories included cybersecurity luminaries credited with large contributions to internet security, as well as an A.I. expert at the chip giant Nvidia and a former top official at the National Security Agency who oversaw responsible A.I. use.

“Anthropic has built multiple protections into the Fable model to prevent its use for cyber offensive uses,” the letter said. “These protections were so aggressive as to be the source of humor in the cyber community on launch day.”

At Anthropic, some employees shared the letter with one another, seeing it as proof that they were being unfairly targeted. On company channels, workers also asked how their employer planned to move forward if the White House continued limiting their ability to release new A.I. models.

Ultimately, while Anthropic and its supporters argue the government’s response is disproportionate and risks stifling innovation, the episode underscores a broader reality: frontier AI systems with demonstrated cybersecurity applications are now firmly within the scope of national security scrutiny.

Given the prior incident in which a jailbroken Claude model was reportedly leveraged in a significant data breach involving Mexican government systems, policymakers appear inclined to act preemptively rather than reactively.

That precedent, whether fully representative or not, reinforces the rationale for a cautious approach, suggesting that even narrow vulnerabilities in highly capable models can have outsized real-world consequences when scaled or misused.

AI is a tool. All tools can be forged into weapons by those motivated to do so.

Donations tax deductible
to the full extent allowed by law.