Anthropic’s September 2026 report describes an ambitious weapons development effort in northern Yemen where a group worked on three sophisticated missile projects simultaneously, including a guided rocket using phone-grade flight computers and an R2000 programme with a hypersonic glide vehicle variant.
Rather than hire software engineers, the actors used Claude Code to write guidance, navigation, and control software. Several Claude instances ran in parallel with assigned roles while humans acted as team leads. Activity occurred December 2025 through August 2026 using Claude Haiku, Sonnet, and Opus models.
The group test-fired a guided rocket that appears to have failed; actors returned to Claude within hours to diagnose the failure. Anthropic banned accounts and shared intelligence with government and industry partners. The group had already built an offline simulation toolkit independent of Claude or commercial tools like MATLAB.