Fox 2026-04-29: 'who is supermans girlfriend?' returned 7-of-8 unrelated
`Girlfriends`-titled articles (TV show, movies, songs); only 1 actual
Superman-related doc made it. Two coupled defects:
1. Title-overlap accept fired on ANY single-token match. A 2-token
query was admitting docs that shared only ONE qtoken. `Girlfriends`
passed because its title matched "girlfriend" even though no
"superman" anywhere in the doc.
2. `_body_density_passes` required at least HALF the qtokens — too
lenient for the 2-token case (1 of 2 = 50% = pass).
3. Possessive plural mismatch: question_hash strips apostrophes so
"superman's" → "supermans", but the corpus has bare "Superman".
`body.count("supermans")` returns 0 even on the canonical doc.
Three coordinated fixes in `aborist/qa/query.py`:
- New `_stem_token_for_match(t)` helper: strips a trailing `s` for
tokens > 4 chars (so `supermans` → `superman`, `girlfriends` →
`girlfriend`). Conservative: skips short tokens & double-s endings
to avoid `class` / `boss` / `pass` corruption.
- `_body_density_passes` now uses `_body_count_with_stem` (literal-
first, stem-fallback) AND a tightened breadth threshold:
≤ 2 tokens require ALL of them
3+ tokens require N - 1 (allow one weak signal token to miss)
- `_filter_by_title_relevance` mirrors the same breadth threshold for
title-overlap. Synonym fallback (any-match against synonym_expand)
is preserved ONLY for 1-token queries — otherwise a stray synonym
hit (e.g. AMD synonym matching an Intel-only title) over-recalls.
End-to-end on the actual corpus (3.4M articles, 8 shards):
before: 'supermans girlfriend' → 7 unrelated `Girlfriends` titles, 1 Superman doc
after: Lois_Lane in top-K (the canonical answer), other Superman-related
docs alongside, Girlfriends-only-titled docs filtered out
Tests:
- test_query_filter_requires_breadth_for_multi_token_queries — synthetic
3-doc corpus pinning the new behavior (Lois Lane keeps; girlfriends-tv
& superman-music both drop).
- test_query_filter_one_token_query_still_synonym_expands — pin the
1-token loose path is preserved (no over-tightening).
349 passed, 1 skipped.
Burned the two stale UNGROUNDED girlfriend-query cache records so a
fresh `make query` exercises the new filter end-to-end.
russell@unturf.com
d6f98929d7