Conflicting Needles in a Haystack: How LLMs behave when faced with contradictory information

Murathan Kurfali, Robert Östling


Abstract
Large Language Models (LLMs) have demonstrated an impressive ability to retrieve and summarize complex information, but their reliability in conflicting contexts remains poorly understood. We introduce an adversarial extension of the Needle-in-a-Haystack framework in which three mutually exclusive “needles” are embedded within long documents. By systematically manipulating factors such as position, repetition, layout, and domain relevance, we evaluate how LLMs handle contradictions. We find that models almost always fail to signal uncertainty and instead confidently select a single answer, exhibiting strong and consistent biases toward repetition, recency, and particular surface forms. We further analyze whether these patterns persist across model families and sizes, and we evaluate both probability-based and generation-based retrieval. Our framework highlights critical limitations in the robustness of current LLMs—including commercial systems—to contradiction. These limitations reveal potential shortcomings in RAG systems’ ability to handle noisy or manipulated inputs and exposes risks for deployment in high-stakes applications.
Anthology ID:
2025.emnlp-main.1742
Volume:
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
Month:
November
Year:
2025
Address:
Suzhou, China
Editors:
Christos Christodoulopoulos, Tanmoy Chakraborty, Carolyn Rose, Violet Peng
Venue:
EMNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
34349–34364
Language:
URL:
https://preview.aclanthology.org/author-page-yu-wang-polytechnic/2025.emnlp-main.1742/
DOI:
10.18653/v1/2025.emnlp-main.1742
Bibkey:
Cite (ACL):
Murathan Kurfali and Robert Östling. 2025. Conflicting Needles in a Haystack: How LLMs behave when faced with contradictory information. In Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing, pages 34349–34364, Suzhou, China. Association for Computational Linguistics.
Cite (Informal):
Conflicting Needles in a Haystack: How LLMs behave when faced with contradictory information (Kurfali & Östling, EMNLP 2025)
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https://preview.aclanthology.org/author-page-yu-wang-polytechnic/2025.emnlp-main.1742.pdf
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