My AI agent confidently gave me completely wrong information. Here's what I learned.

Built my first agent a couple months ago. Spent a Sunday getting it to work and felt genuinely proud when it ran on its own. Three weeks later caught it summarising data that didn't exist. Not vague or slightly off. Completely made up. Formatted neatly, looked exactly like the real outputs. Would have used it in a report if I hadn't checked the source that day. That was when I understood hallucinations properly. Not as a theoretical limitation but as something that will happen to you when you're busy and not paying attention. What I changed: added a validation step so the agent outputs its source alongside every summary. Spot check takes ten seconds now. Also got more specific in my instructions because most hallucinations happen when the agent doesn't have enough context and fills the gap with something plausible. Agent is still running. Still useful. Just think about it differently now. Anyone else had a hallucination catch them off guard? How are you handling verification?