Shahrood University of Technology Journal of AI and Data Mining 2322-5211 Articles in Press 2026 07 18 Robust Multilingual RAG under Query Perturbations: An English-Persian Benchmark 3856 10.22044/jadm.2026.17608.2908 EN Niloofar Ranjbar Persian Gulf University Hamed Baghbani Jam Faculty of Engineering, Persian Gulf University, Bushehr, Iran Journal Article 2026 04 13 Retrieval-augmented generation (RAG) is commonly evaluated on clean inputs that underrepresent realistic multilingual variation. We present an English-Persian movie-domain robustness benchmark built from a corpus of 31,564 records, 120 clean queries, and 720 aligned perturbations. The benchmark covers six deterministic query types and 14 operational perturbation labels grouped into four families. We compare BM25, multilingual dense retrieval, character n-gram TF-IDF, and hybrid retrieval, and evaluate top-1 deterministic answer extraction against a field-specific top-5 RAG system using Qwen2-7B-Instruct. Hybrid retrieval achieves 81.50 MRR@10 on clean queries and 67.76 under perturbation; field-specific RAG reaches 84.17% and 72.08% accuracy, respectively. Clustered paired-bootstrap 95% confidence intervals exclude zero for all principal system differences. English-title noise is the most damaging family, whereas query-form and punctuation variation is comparatively well tolerated. A 43-case consistency audit verifies implementation of the rule-based failure categories, and full-output analysis shows that retrieval-coverage errors dominate the difficult English-title family. These results support component-level evaluation of multilingual RAG robustness.