Why AI Agent Summaries Can Mislead and How Event Logs Fix It

A multi-agent AI pipeline broke down when a verifier agent began relying on another agent's summary rather than independently checking the underlying work. The summary stated a bug was fixed and tests passed, but the fix had introduced an edge case that existing tests did not cover. Because the verifier trusted the compressed summary instead of the actual code, the flawed fix went undetected. The team resolved this by logging every agent action as an immutable event, allowing the verifier to reconstruct intent from the full event chain rather than a summary. The key takeaway is that summaries are interpretations and can lose critical information, while the event log remains the only reliable source of truth.