Trust Before Fusion: QIMG-7 and Source-Aware Resolution for Polluted Multimodal RAG
On the map: Retrieval-augmented generation → Multimodal RAG
Abstract (arXiv)
Multimodal retrieval-augmented generation (RAG) is often evaluated with clean evidence, yet real retrieval can return topically relevant but unreliable content: false text and misleading images from corrupted metadata, entity swaps, typographic overlays, semantic edits, adversarial patches, blends, or style transfer. We introduce QIMG-7, a controlled benchmark for multimodal retrieval pollution in multi-sentence factual QA, spanning four datasets, seven image-attack families, and 16 paired clean/polluted regimes, for 1,760 evaluation rows per method. Across four generator/gate stacks, naive multimodal fusion is brittle: in the main gpt-4o-mini stack, Full-MM support drops from 0.908 with clean text to 0.490 with polluted text, often making Parametric fallback safer than retrieval. We propose source-aware trust resolution (SATR), a training-free approach that compares Parametric, Text-only, and Full-MM candidate answers and selects among candidate answers or falls back based on source reliability. The Field-Selector variant achieves the best balanced score, 0.816, improving over Full-MM by 11.7 points and over the Cascaded Router by 2.7 points. Ablations show that, in this text-first setting, explicit text-reliability modeling is the dominant driver of these gains. Overall, in text-first factual QA with multimodal retrieval conflict, our results support selective trust rather than unconditional fusion. Artifacts are available at https://github.com/SaadElDine/Trust_Before_Fusion.
Key facts. No citing papers in the map yet (data through 7 Oct 2026). Placed in Multimodal RAG, one of 15 directions in Retrieval-augmented generation. Builds on 15 of its 27 references that are in the map. First posted on arXiv 12 Jul 2026.
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15 of 27 references.
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- 2025RAG-Check: Evaluating Multimodal Retrieval Augmented Generation Performance7 Jan
- 2024VisRAG: Vision-based Retrieval-augmented Generation on Multi-modality Documents14 Oct
- 2024MRAG-Bench: Vision-Centric Evaluation for Retrieval-Augmented Multimodal Models10 Oct
Other references · 12
- 2020Retrieval-Augmented Generation for Knowledge-Intensive NLP Taskscited by 9,160
- 2023Self-RAG: Learning to Retrieve, Generate, and Critique through Self-Reflectioncited by 1,800
- 2023FActScore: Fine-grained Atomic Evaluation of Factual Precision in Long Form Text Generationcited by 1,259
- 2020Leveraging Passage Retrieval with Generative Models for Open Domain Question Answeringcited by 1,203
- 2023AlpacaFarm: A Simulation Framework for Methods that Learn from Human Feedbackcited by 738
- 2023Aligning Large Multimodal Models with Factually Augmented RLHFcited by 703
- 2024Adaptive-RAG: Learning to Adapt Retrieval-Augmented Large Language Models through Question Complexitycited by 437
- 2024Fine-grained Hallucination Detection and Editing for Language Modelscited by 146
- 2024Certifiably Robust RAG against Retrieval Corruptioncited by 144
- 2023On the Risk of Misinformation Pollution with Large Language Modelscited by 124
- 2024VERISCORE: Evaluating the factuality of verifiable claims in long-form text generationcited by 114
- 2025Worse than Zero-shot? A Fact-Checking Dataset for Evaluating the Robustness of RAG Against Misleading Retrievalscited by 27
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