Empirical finding 2026-05-01 on 'explain spin glass modeling, tensors?':
returned STRICT 1/1 with claim 'Spin glass modeling involves...
mathematical tools such as tensors' cited to a chunk from the
*Quantum chromodynamics* article. Token-coverage check inside the
chunk passed accidentally on shared physics vocabulary
(spin/model/etc.), but the article isn't about spin glasses — the
claim is a retrieval-driven hallucination.
Root retrieval cause: AND-mode FTS5 returned zero hits (Spin_glass
article has 0 occurrences of 'modeling' or 'tensors'); OR-mode
fallback ranked by raw BM25, so 'Glass' (glass*274) outranked
'Spin glass' (spin*29 + glass*15) despite Spin_glass matching 2
distinct query tokens vs Glass's 1. Verifier then accepted the
hallucinated claim because the cited QCD chunk has incidental
physics vocabulary overlap.
New ``diagnose_title_relevance(claim_text, cited_source_titles)``
sidecar: claim's content tokens (stemmed) must overlap the union
of cited source titles. Zero overlap → ``title_mismatch``. Catches
the spin-tensors case (claim about spin glass, cited title 'Quantum
chromodynamics' → zero stem overlap) without false-positives on
legitimate cross-document grounding (Lois_Lane article cited for a
Lois-Lane claim still has lois+lane overlap).
Sidecar-only for now — staying out of the binary verifier output
until bench evidence justifies hard-promotion. Not yet wired into
inspect_cache_key (per-claim citation source mapping isn't in
providence_cache yet) or the bench. Available as a utility for
operators auditing specific (claim, source_title) pairs.
5 new unit tests covering match/mismatch/no-titles/no-claim-tokens
and underscore-normalization for Wikipedia titles.
russell@unturf.com
26e3af9033