GUIR at SemEval-2026 Task 8: Training-Free Multi-Query Fusion for Robust Conversational Retrieval

Pasha Abrishamchian, Ophir Frieder, Nazli Goharian


Abstract
We describe our SemEval-2026 Task 8 Subtask A system, which focuses on evaluating and improving the retrieval aspect of multi-turn Retrieval-Augmented Generation (RAG) conversations. We implement a training-free fusion approach that combines three distinct query representations to retrieve documents independently. The results from these three views are pooled and reranked using a MonoT5 cross-encoder. Our findings demonstrate that this fusion approach consistently outperforms single-strategy baselines, revealing that optimal retrieval strategies vary significantly at the query level, and establishing multi-query fusion as a baseline for multi-turn RAG systems.
Anthology ID:
2026.semeval-1.325
Volume:
Proceedings of the 20th International Workshop on Semantic Evaluation (2026)
Month:
July
Year:
2026
Address:
San Diego, California, USA
Editors:
Ekaterina Kochmar, Debanjan Ghosh, Kai North, Mamoru Komachi
Venues:
SemEval | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
2583–2591
Language:
URL:
https://preview.aclanthology.org/ingest-acl-workshops/2026.semeval-1.325/
DOI:
Bibkey:
Cite (ACL):
Pasha Abrishamchian, Ophir Frieder, and Nazli Goharian. 2026. GUIR at SemEval-2026 Task 8: Training-Free Multi-Query Fusion for Robust Conversational Retrieval. In Proceedings of the 20th International Workshop on Semantic Evaluation (2026), pages 2583–2591, San Diego, California, USA. Association for Computational Linguistics.
Cite (Informal):
GUIR at SemEval-2026 Task 8: Training-Free Multi-Query Fusion for Robust Conversational Retrieval (Abrishamchian et al., SemEval 2026)
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PDF:
https://preview.aclanthology.org/ingest-acl-workshops/2026.semeval-1.325.pdf