OpenAlex returns arXiv works under the arXiv DOI (10.48550/arXiv.<id>); _normalize_doi (DQ-5) left it as 10.48550/arxiv.<id>, but the corpus keys arXiv papers on the BARE id (2305.10988 / math/0603097). So re-ingesting an arXiv paper by its bare id missed INSERT ... ON CONFLICT (id) and tripped papers_openalex_id_key — the arXiv half of DQ-5, explicitly deferred there and surfaced again driving the R-C .tex re-ingest.
Add _canonical_id() (normalize DOI, then strip the 10.48550/arxiv. prefix) and use it in _map_paper. Regression tests (modern + legacy arXiv DOI, regular DOI unchanged, fetch_paper bare id). Confirmed live: re-ingesting 2305.10988 now UPDATEs in place. Full suite 370 passed; ruff + mypy clean.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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