My AI agents ran up $47.35 in charges overnight while I slept, and I thought I'd been hacked. It came from an instruction I'd written myself: repeat until the job is finished, with no number attached. Each of the three agents ran hundreds of turns. My OpenAI and Anthropic accounts got auto-recharged five times. An agent is really a loop of API calls. A loop costs little to write and plenty to leave uncapped. Every brief now opens with a BUDGET line. OpenAI spend is capped at $5 a script and…