Metadata filtering

Similarity is not enough

Most real queries carry implicit constraints: this workspace, this product version, documents the user may actually see. Those belong in a metadata filter, not in the embedding.

Access control especially. Filtering by permission at query time is the only way to be sure a user never sees a passage from a document they cannot open — post-filtering the results is both slower and easier to get wrong.

Aggressive filters can leave nothing to retrieve. Detect the empty case and tell the user, rather than generating an answer from no context at all.