US Orders Anthropic to Pull Its Most Advanced AI Models Over National Security Concerns

NEW YORK — Anthropic abruptly disabled worldwide access to its two newest and most capable artificial intelligence models, Fable 5 and Mythos 5, on Thursday after the US government invoked national security export controls to bar all foreign nationals from using them. The company disclosed the order in a public statement, saying it received the directive that afternoon and had no practical choice but to shut the systems off for every customer globally to ensure compliance. Anthropic stressed that it fundamentally disagrees with the government's characterization of the security risk involved and is working urgently to resolve the dispute — but that the legal directive left it no viable alternative to an immediate, blanket shutdown.

According to Anthropic, the directive — which multiple news organizations attributed to the Commerce Department, with Bloomberg citing a US official who confirmed the letter's existence — suspends access to Fable 5 and Mythos 5 by any foreign national, whether located inside or outside the United States. That scope extends even to the company's own non-citizen employees. Because there is no reliable mechanism to separate foreign nationals from US persons in real time across a user base numbering in the hundreds of millions, particularly on same-day notice, Anthropic concluded that a blanket global shutdown was the only way to achieve compliance within the required window. The company characterized the situation as unprecedented in the AI industry.

Anthropic's account frames the episode as a disagreement over technical facts. The company said its understanding is that the government acted after learning of a method to bypass, or jailbreak, Fable 5's safeguards. Anthropic said it reviewed a demonstration of the technique and found that it surfaced only a small number of previously known, minor vulnerabilities — ones that other publicly available models can also surface without any bypass. The company said that to date, the government had not provided a detailed written explanation of its specific security concern, making it difficult to evaluate or respond to the underlying worry directly.

In its original launch materials, Anthropic had described a defense-in-depth strategy for Fable 5, acknowledging that perfect resistance to jailbreaks is likely not currently possible for any provider. The company said its aim was to keep jailbreaks either narrow in scope or very expensive to produce, paired with monitoring systems designed to detect and shut down attacks quickly. The models occupy the top of Anthropic's lineup: Fable 5 marked the first time the company had released such an advanced system to the general public, while the Mythos line traces back to a Mythos Preview that attracted attention from Wall Street and government officials in April for its cybersecurity capabilities.

Anthropic said it is complying with the legal directive while openly disagreeing with it. The company argued that recalling a commercial model used by hundreds of millions of people over a narrow potential jailbreak sets a standard that, if applied across the industry, would essentially halt all new frontier model deployments. It pointed to its own previously stated policy position that the government should be able to block unsafe AI deployments — but only through a statutory process with clear standards and due process protections, not through ad hoc export control letters issued on same-day timelines. The company said it supports regulatory oversight of AI but believes the mechanism used here is the wrong one.

The timing adds a layer of complexity. The models had been made publicly available only days before the order arrived, and Fortune reported that Anthropic recently filed confidentially for a public listing following a valuation of approximately $61 billion. An abrupt government-ordered shutdown of flagship products is an unusual event for a company preparing to enter the public markets, and observers noted that the episode illustrates how thoroughly national security law has come to sit atop the AI industry — and how a legal regime built to govern the movement of physical goods across borders is being stretched to cover software accessed through a browser.

Stripped of the specifics, this is a story about who holds the off switch for frontier AI, and the answer, at least for now, is the state. Almost the entire factual record so far comes from Anthropic itself — an interested party — while the government has said little publicly and, by Anthropic's account, did not detail its concern in writing. Independent confirmation of the order's existence has come from officials cited by Bloomberg and other outlets, but the substance of the security worry remains opaque. Whether the shutdown proves to be a brief compliance episode that resolves quickly or the opening move in a broader regulatory confrontation over AI export controls is the question the industry is watching most closely.