The post-rerank relevance floor rejects noise but passes coherent
off-topic questions, and it gets worse as the library grows. Adding
Gutenberg prose, the Python tutorial and MDN pages to the eval corpus
took the off-topic leak rate from 22% to 67% at the 0.62 floor.
Score cutoff does not fix it. The weakest correct top hit scores 0.666
while "write me a haiku about autumn leaves" pulls Walden at 0.705.
A cosine floor and a top-vs-median contrast test both cost recall
faster than they cut leaks.
- Add rag.relevanceCheck (default off). After the floor, the tasks
model, or the chat model when none is set, gives one grammar-constrained
on_topic verdict for the whole retrieved set. Off topic means no
context and no citations. Any failure keeps the chunks unjudged.
- Add a Settings > Models toggle recommending an 8B+ tasks model.
On llama3:8b the check cuts off-topic leaks from 67% to 6% for about
5 points of core recall@5 and ~0.6s per turn. On 3B models it rejects
most valid questions, which is why it is opt-in.
- Add 6 distractor documents and an off_topic suite (18 unanswerable
questions, 7 distractor controls) to the eval corpus.
- Report per-tag leak rates and leaked cases with top scores in
eval:retrieval. Add --judge-model to measure the check and --dump to
export pre-floor candidate pools for offline gate simulation.
- Pin the check off in eval:generation so a local setting cannot move
scores.
- Record the distractor sweep on RAG_MIN_FINAL_SCORE. The 0.62 default
stays: 0.65 halves leaks at no measured recall cost but leaves only
0.016 of margin.
The corpus fingerprint changes to b4ebe5dce8699f5d. Retrieval reports
from before this commit are not comparable, and a new baseline is
committed.
Refs #1341
