Anthropic Blocks Yemen Accounts Over AI-Assisted Weapons Attempts

Anthropic has blocked a set of accounts in northern Yemen, territory held by the Iran-backed Houthi movement, after finding that users were trying to harness its Claude artificial intelligence model for advanced weapons work.

The company said the users did not manage to field an operational device, but they did carry out an unsuccessful test of a guided rocket. Anthropic learned of the failure because the same users returned to the Claude chatbot to ask why the test had gone wrong.

In a report released on Thursday, the company said it had identified a cell in northern Yemen running three separate weapons programmes. These included a multi-variant missile designed to glide at hypersonic speed and a warhead that uses mobile phone hardware to steer itself mid-course. According to Anthropic, the actors used Claude Code in place of human software engineers to write guidance, navigation and control software. Multi-variant missiles allow different warheads and guidance systems to be fitted to a single base design, a cheaper way to produce land, sea and air weapons.

Anthropic said it also found evidence that, before the accounts were banned, the users had built an offline simulation toolkit that does not rely on Claude or any other computing platform. The company said it shared its findings with private and public partners.

The report is the third Anthropic has published since March 2025 on global misuse of its AI platforms. It covers findings from December to August, spanning activity from state-sponsored groups spreading propaganda to unnamed actors researching how to make biological weapons more lethal.

Mountainous northern Yemen is controlled by the Houthis, suggesting the rebels are pursuing more sophisticated weapons even as they already deploy a range of drones, missiles and other munitions in their campaign to take more territory in Yemen and to damage Saudi Arabia's oil exports. Hazam al-Assad, a member of the Houthis' political bureau, rejected the suggestion that the group would rely on open sources to develop military capabilities, calling it unreasonable and illogical. He said the group's armed forces have modern, diverse and developed production capabilities accumulated during what he described as Saudi aggression on Yemen, referring to the kingdom's role in the country's 12-year civil war, and that all weapons are used for self-defence.

Weapons analyst Trevor Ball of Armament Research Services said that while the Houthis might be asking Claude about hypersonic missiles, they are far from having the production or technical capacity to build them, noting that U.S. hypersonic missiles are still in testing. He said the Houthis already possess Iranian-made anti-ship missiles able to adjust guidance mid-course, and are probably trying to develop their own capabilities to reduce reliance on Iranian shipments of weapons and components.

Iran has claimed to have hypersonic missiles and said it fired them at Israel last year. It denies arming the Houthis, which would violate a U.N. embargo, though Iranian weapons have been found on the battlefield and seized from shipments bound for Yemen.

The Houthis have launched waves of attacks on Saudi oil facilities and tankers in the Red Sea, threatening global trade as Iran continues to disrupt shipping in the Strait of Hormuz. Since Wednesday, the rebels have made rapid territorial gains in their war with Yemen's Saudi-backed government, seizing strategic ground along the Red Sea coast and in the Bab al-Mandeb Strait, a key alternative to the Strait of Hormuz.

Adam Baron, a Yemen-focused researcher at the New America think tank in Washington, said the Houthis have kept pace with technological development. He said there is a tendency to see them as barefoot tribal fighters, which he said is not true, pointing to their use of Claude, their manipulation of social media narratives and their ability to capitalise on the transfer of Iranian and wider axis expertise as evidence of deep institutional tech savvy.

The Houthis are known to have acquired and developed a sophisticated arsenal, including Iranian-made cruise and ballistic missiles with a range of more than 2,000 kilometres and unmanned submarines used in attacks.