Part 4 ended with a question I couldn't answer: has anyone actually measured what gate decisions do on the reconstructed provenance vector versus the original? Not argued from first principles. Measured. Nobody in the comments had data. Neither did I. So I built the harness: provenance-compaction-lab . Four arms, one oracle Four provenance-tracking arms observe the same synthetic trajectory — same seed, same degradation events, same merges. They differ only in what happens...