Anthropic: Yemen Cell Used Claude to Build Missile Guidance Software

Anthropic published a threat-intelligence report on 10 September 2026 describing how a cell of threat actors based in northern Yemen used Claude Code to develop software for weapons systems. The company said it identified the activity during an internal investigation, banned the accounts involved and shared its findings with public- and private-sector partners.

Three weapons programmes

According to the report, the cell worked on three programmes at once: a guided rocket built around a commodity phone-class flight computer with final-phase homing guidance; a multi-stage ballistic missile with a stated range goal above 2,000 kilometres; and a multi-variant missile set described as “R2000” that included a hypersonic glide vehicle variant. With Claude Code the operators integrated an open-source autopilot with the phone-class flight computer, wrote control and position-estimation software, tuned control parameters, ran firmware builds and carried out flight simulations. Anthropic estimates that work of this kind would normally have required a team of engineers.

How the safeguards were evaded

Anthropic says its safeguards blocked many of the requests but not all of them. The operators hid their goals and the products the software was meant for, and split the work across multiple sessions so that no single session revealed their full intent. Several Claude instances ran in parallel with separate roles: one wrote code, another carried out research and a third reviewed the first one's output.

Failed test fire and wider findings

Anthropic says it has no evidence that the actors succeeded in fielding an operational device, but that they did test-fire a guided rocket. The field test appears to have failed, and within hours the operators returned to Claude to work out why. The Yemen case was one of six examples of conventional-weapons misuse in the report; the others involved actors in China and Russia and covered firearms, missiles, armed drones, bombs and munitions. Anthropic did not name the cell, though the details point to the Iran-backed Houthis, who control much of northern Yemen. Security researcher Bruce Schneier read the case as a systemic signal, warning that similar patterns are likely to spread to other actors and weapons types.