Code-Switching Information Retrieval: Benchmarks, Analysis, and the Limits of Current Retrievers

Fuente: arXiv
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Main Authors: Zeng, Qingcheng, Lu, Yuheng, Zhou, Zeqi, Qi, Heli, Yu, Puxuan, Zhao, Fuheng, Yanaka, Hitomi, Xuan, Weihao, Yokoya, Naoto
Format: Preprint
Published: 2026
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author Zeng, Qingcheng
Lu, Yuheng
Zhou, Zeqi
Qi, Heli
Yu, Puxuan
Zhao, Fuheng
Yanaka, Hitomi
Xuan, Weihao
Yokoya, Naoto
author_facet Zeng, Qingcheng
Lu, Yuheng
Zhou, Zeqi
Qi, Heli
Yu, Puxuan
Zhao, Fuheng
Yanaka, Hitomi
Xuan, Weihao
Yokoya, Naoto
contents Code-switching is a pervasive linguistic phenomenon in global communication, yet modern information retrieval systems remain predominantly designed for, and evaluated within, monolingual contexts. To bridge this critical disconnect, we present a holistic study dedicated to code-switching IR. We introduce CSR-L (Code-Switching Retrieval benchmark-Lite), constructing a dataset via human annotation to capture the authentic naturalness of mixed-language queries. Our evaluation across statistical, dense, and late-interaction paradigms reveals that code-switching acts as a fundamental performance bottleneck, degrading the effectiveness of even robust multilingual models. We demonstrate that this failure stems from substantial divergence in the embedding space between pure and code-switched text. Scaling this investigation, we propose CS-MTEB, a comprehensive benchmark covering 11 diverse tasks, where we observe performance declines of up to 27%. Finally, we show that standard multilingual techniques like vocabulary expansion are insufficient to resolve these deficits completely. These findings underscore the fragility of current systems and establish code-switching as a crucial frontier for future IR optimization.
format Preprint
id arxiv_https___arxiv_org_abs_2604_17632
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Code-Switching Information Retrieval: Benchmarks, Analysis, and the Limits of Current Retrievers
Zeng, Qingcheng
Lu, Yuheng
Zhou, Zeqi
Qi, Heli
Yu, Puxuan
Zhao, Fuheng
Yanaka, Hitomi
Xuan, Weihao
Yokoya, Naoto
Information Retrieval
Code-switching is a pervasive linguistic phenomenon in global communication, yet modern information retrieval systems remain predominantly designed for, and evaluated within, monolingual contexts. To bridge this critical disconnect, we present a holistic study dedicated to code-switching IR. We introduce CSR-L (Code-Switching Retrieval benchmark-Lite), constructing a dataset via human annotation to capture the authentic naturalness of mixed-language queries. Our evaluation across statistical, dense, and late-interaction paradigms reveals that code-switching acts as a fundamental performance bottleneck, degrading the effectiveness of even robust multilingual models. We demonstrate that this failure stems from substantial divergence in the embedding space between pure and code-switched text. Scaling this investigation, we propose CS-MTEB, a comprehensive benchmark covering 11 diverse tasks, where we observe performance declines of up to 27%. Finally, we show that standard multilingual techniques like vocabulary expansion are insufficient to resolve these deficits completely. These findings underscore the fragility of current systems and establish code-switching as a crucial frontier for future IR optimization.
title Code-Switching Information Retrieval: Benchmarks, Analysis, and the Limits of Current Retrievers
topic Information Retrieval
url https://arxiv.org/abs/2604.17632