In our multi-agent collaboration system, every upstream artifact is verified by downstream agents. The event log looked perfect: every VERIFY was a pass. We ran the process three times and it converged cleanly.

Then we stitched the artifacts from six agents together and ran the game.

It crashed immediately. The log had no obvious anomalies.

TL;DR#

• The verification protocol checked interfaces and local logic, not data contracts across producers/consumers.
• The event model carried zero information about return shapes/types, so no amount of offline analysis could infer contract mismatches.
• Adding a small, explicit data contract table (declared by the task designer) and writing contract_check=pass|fail|not_checked into the event stream made this class of failures visible before freeze.