build_citation_graph now does:
SELECT c.citing_id, COALESCE(p.id, c.cited_id) AS cited_id
FROM citations c
LEFT JOIN papers p ON p.openalex_id = c.cited_id
Before: cited_id (OpenAlex IDs) never matched papers.id (DOIs) →
13 cross-citations between ingested papers were invisible in graph.
After: in-KB papers use their canonical DOI key; dangling references
keep their raw OpenAlex ID unchanged.
Test: test_cross_citation_uses_doi_when_in_kb (42 passed).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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