Add `do_query_expansion: false` to load without query expansion
Hello!
Heads up, this PR was AI-generated and human-reviewed.
Pull Request overview
- Add
"do_query_expansion": falsetoconfig_sentence_transformers.json, so the model loads without ColBERT-style[MASK]query expansion.
Details
When this model is loaded through PyLate or Sentence Transformers' MultiVectorEncoder, a ColBERT config with no explicit do_query_expansion flag defaults to query expansion being on. That pads every query out to query_length with [MASK] tokens. If the model was trained without query expansion, those never-trained expansion vectors dominate the MaxSim score for short queries and pull retrieval quality down.
Adding do_query_expansion: false restores the behavior the model was trained with. On the 13 NanoBEIR datasets (mean nDCG@10) this raises the mean score from 0.527 to 0.662.
The change is a single key in config_sentence_transformers.json, nothing else is touched. Happy to adjust the wording or approach if you had something else in mind.
- Tom Aarsen