@inproceedings{son-etal-2026-rcem,
title = "{RCEM}: Robust Conversational Search {EM}bedder in Distributional Shift",
author = "Son, Kilho and
Hsu, Bo-June Paul and
Zhang, Cha and
Florencio, Dinei",
editor = "Atanasova, Pepa and
Haffari, Gholamreza and
Wang, Minghan",
booktitle = "Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.emnlp-industry.167/",
pages = "2830--2843",
ISBN = "979-8-89176-460-6",
abstract = "We propose RCEM, a Robust Conversational search EMbedder that augments text embedders with LLM query reformulation capabilities while approximately preserving their original generalization performance. Unlike prior conversational dense retrieval approaches that learn direct conversation-to-passage matching, RCEM aligns conversations, prepended by special token, to LLM-rewritten queries, while attempting to preserve the original embedding space. The approximately preserved embedding space automatically maps the rewritten queries to the relevant passages. As a result, RCEM (1) reduces overfitting by aligning conversations to shorter rewritten queries rather than full passages, (2) eliminates the need for conversation-to-passage relevance labels for training, and (3) approximately preserves the original embedding space, enabling conversational retrieval over indexes built by the base embedder without re-indexing. Extensive experiments show that RCEM consistently outperforms prior approaches, improving up to 30{\%} retrieval accuracy under distributional shift."
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<abstract>We propose RCEM, a Robust Conversational search EMbedder that augments text embedders with LLM query reformulation capabilities while approximately preserving their original generalization performance. Unlike prior conversational dense retrieval approaches that learn direct conversation-to-passage matching, RCEM aligns conversations, prepended by special token, to LLM-rewritten queries, while attempting to preserve the original embedding space. The approximately preserved embedding space automatically maps the rewritten queries to the relevant passages. As a result, RCEM (1) reduces overfitting by aligning conversations to shorter rewritten queries rather than full passages, (2) eliminates the need for conversation-to-passage relevance labels for training, and (3) approximately preserves the original embedding space, enabling conversational retrieval over indexes built by the base embedder without re-indexing. Extensive experiments show that RCEM consistently outperforms prior approaches, improving up to 30% retrieval accuracy under distributional shift.</abstract>
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%0 Conference Proceedings
%T RCEM: Robust Conversational Search EMbedder in Distributional Shift
%A Son, Kilho
%A Hsu, Bo-June Paul
%A Zhang, Cha
%A Florencio, Dinei
%Y Atanasova, Pepa
%Y Haffari, Gholamreza
%Y Wang, Minghan
%S Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-460-6
%F son-etal-2026-rcem
%X We propose RCEM, a Robust Conversational search EMbedder that augments text embedders with LLM query reformulation capabilities while approximately preserving their original generalization performance. Unlike prior conversational dense retrieval approaches that learn direct conversation-to-passage matching, RCEM aligns conversations, prepended by special token, to LLM-rewritten queries, while attempting to preserve the original embedding space. The approximately preserved embedding space automatically maps the rewritten queries to the relevant passages. As a result, RCEM (1) reduces overfitting by aligning conversations to shorter rewritten queries rather than full passages, (2) eliminates the need for conversation-to-passage relevance labels for training, and (3) approximately preserves the original embedding space, enabling conversational retrieval over indexes built by the base embedder without re-indexing. Extensive experiments show that RCEM consistently outperforms prior approaches, improving up to 30% retrieval accuracy under distributional shift.
%U https://aclanthology.org/2026.emnlp-industry.167/
%P 2830-2843
Markdown (Informal)
[RCEM: Robust Conversational Search EMbedder in Distributional Shift](https://aclanthology.org/2026.emnlp-industry.167/) (Son et al., EMNLP 2026)
ACL