loRA-adapter

The paper proposes query-aware routing for multilingual encoders, combining a query-only low-rank adapter (SampoTron) trained against frozen Nemotron-3-Embed-1B document embeddings with deterministic language routing. This yields a 20.9% relative nDCG@10 gain across six English, Finnish, and Swedish retrieval directions while preserving same-language performance and the existing document index.