Vendi-RAG: Adaptively Trading-Off Diversity And Quality Significantly Improves Retrieval Augmented Generation With LLMs

Mohammad Reza Rezaei, Adji Bousso Dieng


Abstract
Retrieval-augmented generation (RAG) for multi-hop question answering is limited by retrieving semantically redundant documents, when reasoning instead needs diverse, complementary sources. We introduce Vendi-RAG, which treats set-level semantic diversity as a first-class retrieval objective. It combines an eigenvalue-based diversity score (the Vendi Score) with query relevance into a single Vendi Retrieval Score, embedded in an iterative loop that uses an LLM-based answer-quality signal to adaptively rebalance diversity and relevance. On HotpotQA, MuSiQue, and 2WikiMultiHopQA, Vendi-RAG improves accuracy by +2.4, +1.6, and +2.4 points over the strongest diversity-aware iterative baseline (Adaptive Retrieval + MMR). A fixed-s variant captures most of the gain at no extra inference cost, while the LLM-judge loop adds a smaller but significant gain on hard queries. Results hold across five instruction-tuned backbones and two dense retrievers, identifying set-level retrieval diversity as a primary, controllable axis for improving multi-hop RAG.
Anthology ID:
2026.findings-emnlp.1499
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
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SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
31909–31932
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URL:
https://aclanthology.org/2026.findings-emnlp.1499/
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Cite (ACL):
Mohammad Reza Rezaei and Adji Bousso Dieng. 2026. Vendi-RAG: Adaptively Trading-Off Diversity And Quality Significantly Improves Retrieval Augmented Generation With LLMs. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 31909–31932, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Vendi-RAG: Adaptively Trading-Off Diversity And Quality Significantly Improves Retrieval Augmented Generation With LLMs (Rezaei & Dieng, Findings 2026)
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https://aclanthology.org/2026.findings-emnlp.1499.pdf