DSC2025 -- ViHallu Challenge: Detecting Hallucination in Vietnamese LLMs

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Autori principali: Nguyen, Anh Thi-Hoang, Tran, Khanh Quoc, Van Huynh, Tin, Nguyen, Phuoc Tan-Hoang, Nguyen, Cam Tan, Van Nguyen, Kiet
Natura: Preprint
Pubblicazione: 2026
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author Nguyen, Anh Thi-Hoang
Tran, Khanh Quoc
Van Huynh, Tin
Nguyen, Phuoc Tan-Hoang
Nguyen, Cam Tan
Van Nguyen, Kiet
author_facet Nguyen, Anh Thi-Hoang
Tran, Khanh Quoc
Van Huynh, Tin
Nguyen, Phuoc Tan-Hoang
Nguyen, Cam Tan
Van Nguyen, Kiet
contents The reliability of large language models (LLMs) in production environments remains significantly constrained by their propensity to generate hallucinations -- fluent, plausible-sounding outputs that contradict or fabricate information. While hallucination detection has recently emerged as a priority in English-centric benchmarks, low-to-medium resource languages such as Vietnamese remain inadequately covered by standardized evaluation frameworks. This paper introduces the DSC2025 ViHallu Challenge, the first large-scale shared task for detecting hallucinations in Vietnamese LLMs. We present the ViHallu dataset, comprising 10,000 annotated triplets of (context, prompt, response) samples systematically partitioned into three hallucination categories: no hallucination, intrinsic, and extrinsic hallucinations. The dataset incorporates three prompt types -- factual, noisy, and adversarial -- to stress-test model robustness. A total of 111 teams participated, with the best-performing system achieving a macro-F1 score of 84.80\%, compared to a baseline encoder-only score of 32.83\%, demonstrating that instruction-tuned LLMs with structured prompting and ensemble strategies substantially outperform generic architectures. However, the gap to perfect performance indicates that hallucination detection remains a challenging problem, particularly for intrinsic (contradiction-based) hallucinations. This work establishes a rigorous benchmark and explores a diverse range of detection methodologies, providing a foundation for future research into the trustworthiness and reliability of Vietnamese language AI systems.
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institution arXiv
publishDate 2026
record_format arxiv
spellingShingle DSC2025 -- ViHallu Challenge: Detecting Hallucination in Vietnamese LLMs
Nguyen, Anh Thi-Hoang
Tran, Khanh Quoc
Van Huynh, Tin
Nguyen, Phuoc Tan-Hoang
Nguyen, Cam Tan
Van Nguyen, Kiet
Computation and Language
Artificial Intelligence
The reliability of large language models (LLMs) in production environments remains significantly constrained by their propensity to generate hallucinations -- fluent, plausible-sounding outputs that contradict or fabricate information. While hallucination detection has recently emerged as a priority in English-centric benchmarks, low-to-medium resource languages such as Vietnamese remain inadequately covered by standardized evaluation frameworks. This paper introduces the DSC2025 ViHallu Challenge, the first large-scale shared task for detecting hallucinations in Vietnamese LLMs. We present the ViHallu dataset, comprising 10,000 annotated triplets of (context, prompt, response) samples systematically partitioned into three hallucination categories: no hallucination, intrinsic, and extrinsic hallucinations. The dataset incorporates three prompt types -- factual, noisy, and adversarial -- to stress-test model robustness. A total of 111 teams participated, with the best-performing system achieving a macro-F1 score of 84.80\%, compared to a baseline encoder-only score of 32.83\%, demonstrating that instruction-tuned LLMs with structured prompting and ensemble strategies substantially outperform generic architectures. However, the gap to perfect performance indicates that hallucination detection remains a challenging problem, particularly for intrinsic (contradiction-based) hallucinations. This work establishes a rigorous benchmark and explores a diverse range of detection methodologies, providing a foundation for future research into the trustworthiness and reliability of Vietnamese language AI systems.
title DSC2025 -- ViHallu Challenge: Detecting Hallucination in Vietnamese LLMs
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2601.04711