@inproceedings{tan-etal-2026-pra,
    title = "{PRA}-{RAG}: Provably Robust Aggregation in Retrieval-Augmented Generation against Retrieval Corruption",
    author = "Tan, Xue  and
      Zheng, Yi  and
      Huo, Chang  and
      Zhang, Yunruo  and
      Liu, Yu  and
      Luan, Hao  and
      Yu, Zhuyang  and
      Dai, Jun  and
      Sun, Xiaoyan  and
      Chen, Ping",
    editor = "Liakata, Maria  and
      Moreira, Viviane P.  and
      Zhang, Jiajun  and
      Jurgens, David",
    booktitle = "Findings of the {A}ssociation for {C}omputational {L}inguistics: {ACL} 2026",
    month = jul,
    year = "2026",
    address = "San Diego, California, United States",
    publisher = "Association for Computational Linguistics",
    url = "https://preview.aclanthology.org/ingest-acl/2026.findings-acl.1794/",
    pages = "36002--36017",
    ISBN = "979-8-89176-395-1",
    abstract = "Retrieval-Augmented Generation (RAG) enhances Large Language Models (LLMs) by incorporating external knowledge, effectively mitigating their inherent knowledge limitations. However, RAG remains vulnerable to poisoning attacks that manipulate retrieved texts to mislead model outputs. Existing defense mechanisms often lack theoretical robustness guarantees and perform unreliably when the LLM has limited knowledge of the retrieved content. In this work, we propose PRA-RAG, a provably robust retrieval aggregation algorithm designed to defend against poisoning attacks on retrieved texts. PRA-RAG samples multiple combinations of retrieved texts and utilizes geometric structures in the embedding space to identify a robust subset, from which a stable aggregated representation is derived. We provide theoretical bounds on the maximum impact of poisoned retrieved content and establish a quantitative measure of RAG{'}s robustness. Experiments across multiple benchmarks and RAG architectures demonstrate that PRA-RAG reduces the attack success rate to as low as 1{\%} while maintaining an accuracy of 71{\%}, significantly outperforming representative state-of-the-art (SOTA) methods."
}