- R-4: arxiv.fetch_source had a try/except httpx.RequestError that only re-raised — removed (no behaviour change, less noise). - R-5: semanticscholar URLs now quote(paper_id, safe=':') so a legacy-arXiv '/' (arXiv:math/0603097) doesn't corrupt the path and silently return no references. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>