Repeated knowledge-ingest of identical content (same sha256, new
asset_id -> new canonical object key) reuses the Document row but
appends a second ORIGINAL_PDF artifact, because ensure_artifact identity
is (document_id, storage_key). process_document_id then crashed with
MultipleResultsFound on scalar_one_or_none and Celery retried forever.
New latest_artifact helper picks the newest row deterministically
(created_at DESC, id DESC) — every duplicate references byte-identical
objects (sha256 verified at ingest), so the latest reference is always
safe.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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