Then I attacked it. On an agent that obeyed 43% of injection attacks, the rules cut successful attacks to 0 out of 60, across all five attack goals: stealing a secret, phoning home, poisoning files, planting a payment IBAN and moving customer data. They held on Claude Haiku 5.5 too, with zero false blocks, and on the AgentDojo benchmark they cut worst-case attack success from 98% to 3.1%.