The runaway agent that spent €4,200 in a weekend.

An autonomous agent was given a credit card and a goal. It was not given a ceiling.

A tool-call returned an ambiguous error. The agent retried. The retry spawned a sub-task. The sub-task called the same tool. By Sunday morning the recursion had made 1,187 paid API calls. €4,200.

Cause of death: no spend cap, no kill switch, no human in the loop on a process that could spend money. Autonomy without a budget is not autonomy — it’s a liability with a cron job.