test_hebbian_activation_boost failed intermittently. Root causes, all in the
query path:
- normalize_scores mapped a set of identical scores — including the
single-candidate case — to 0.0, so a lone perfect match contributed nothing
to the fused score. Identical positive scores now normalise to 1.0 (all
equally the best match); identical non-positive scores stay 0.0.
- merge_vector_keyword sorted a HashMap's entries by score alone and then
truncated, so which ties survived varied from run to run; hybrid_search had
the same problem in its final sort. Both now break ties by index.
- hybrid_search applied the Hebbian boost to every returned record, including
the zero-score filler that pads the list when fewer than k records match.
With random tie-breaking a filler record could collect as many boosts as the
real hit. Only records with a positive fused score are reinforced now.
Co-Authored-By: Claude Fable 5.1 <[email protected]>
