Most "data lineage" you've seen answers a schema question: table B comes from table A , or column B.total comes from columns A.price and A.qty . That's genuinely useful, and tools like OpenLineage do it well. But notice what it doesn't tell you: it says which columns can influence an output. It never says which values actually did . That gap is the whole subject of this post. I built a small, self-contained reference pipeline that captures provenance at the row and field level ...