Two layered fixes that close the lazy-anchor gap. Title-purity
moves the right SOURCES to the top of retrieval; the new hard
check makes the verifier ruthlessly honest about whether each
cited chunk actually mentions what its claim says.
1. _rerank_by_title_purity. New stage at the end of _rerank().
purity = |title_tokens ∩ query_tokens| / |title_tokens|; score
multiplied by (1 + 2*purity), so a title that IS the topic
("Jurassic Park (film)" against the dinosaur question) gets
3.0x and titles that drag in off-topic tokens like
"Jurassic Park: Operation Genesis" only get 2.0x. Composes
with the role-rank weights from the prior commit. Florida
query: list-pages dropped out of top-8 entirely. JP-dinosaurs
query: Operation Genesis sank from #4 to #8.
2. CITATION_MISMATCH hard check. Sixth deterministic check in
verify_claim_lattice — for each (claim, pointer) pair, at
least one content token from the claim text must textually
appear in the cited evidence span. Lexical only, no NER, no
embeddings; same _content_tokens extractor as the spotlight
so the proof-path stays on the soft/hard boundary. Catches
the magnet-chunk lazy-anchor where the model cites a chunk
whose text contains zero overlap with what its claim asserts.
New status CITATION_MISMATCH joins the per-claim taxonomy.
New violation kind CITATION_MISMATCH joins the run-DAG verify
payload. JP-dinosaurs verdict went from "13/14 verified
ratio 0.77 (cite E13 for everything)" pre-check to "1/14
verified" post-check — only Tyrannosaurus Rex's claim
actually overlapped its cited chunk. The architecture
stopped lying about evidence-linkage that the cited spans
don't textually support.
Pure-stopword claims pass the overlap check vacuously (no
content tokens means nothing to check against) — other hard
checks own that case.
Tests: +3 covering CITATION_MISMATCH (claim-token absent yields
fail, partial overlap yields HYBRID with EVIDENCE_LINKED_PARTIAL,
pure-stopword claim passes vacuously). Updated 7 prior tests
that used colloquial stub claims ("Trex") which don't textually
appear in the sample spans ("Tyrannosaurus rex"); they now use
claim text that overlaps the source content. 445 tests passing,
all 7 production shards report 0 chain breaks.
russell@unturf.com
bd576fda13