FaithLens: Detecting and Explaining Faithfulness Hallucination

Fuente: arXiv
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Auteurs principaux: Si, Shuzheng, Wang, Qingyi, Zhao, Haozhe, Bai, Yuzhuo, Chen, Guanqiao, Luo, Kangyang, Chen, Gang, Qi, Fanchao, Zhang, Minjia, Chang, Baobao, Sun, Maosong
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Publié: 2025
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author Si, Shuzheng
Wang, Qingyi
Zhao, Haozhe
Bai, Yuzhuo
Chen, Guanqiao
Luo, Kangyang
Chen, Gang
Qi, Fanchao
Zhang, Minjia
Chang, Baobao
Sun, Maosong
author_facet Si, Shuzheng
Wang, Qingyi
Zhao, Haozhe
Bai, Yuzhuo
Chen, Guanqiao
Luo, Kangyang
Chen, Gang
Qi, Fanchao
Zhang, Minjia
Chang, Baobao
Sun, Maosong
contents Recognizing whether outputs from large language models (LLMs) contain faithfulness hallucination is crucial for real-world applications, e.g., retrieval-augmented generation and summarization. In this paper, we introduce FaithLens, a cost-efficient and effective faithfulness hallucination detection model that can jointly provide binary predictions and corresponding explanations to improve trustworthiness. To achieve this, we first synthesize training data with explanations via advanced LLMs and apply a well-defined data filtering strategy to ensure label correctness, explanation quality, and data diversity. Subsequently, we fine-tune the model on these well-curated training data as a cold start and further optimize it with rule-based reinforcement learning, using rewards for both prediction correctness and explanation quality. Results on 12 diverse tasks show that the 8B-parameter FaithLens outperforms advanced models such as GPT-5.2 and o3. Also, FaithLens can produce high-quality explanations, delivering a distinctive balance of trustworthiness, efficiency, and effectiveness.
format Preprint
id arxiv_https___arxiv_org_abs_2512_20182
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle FaithLens: Detecting and Explaining Faithfulness Hallucination
Si, Shuzheng
Wang, Qingyi
Zhao, Haozhe
Bai, Yuzhuo
Chen, Guanqiao
Luo, Kangyang
Chen, Gang
Qi, Fanchao
Zhang, Minjia
Chang, Baobao
Sun, Maosong
Computation and Language
Artificial Intelligence
Recognizing whether outputs from large language models (LLMs) contain faithfulness hallucination is crucial for real-world applications, e.g., retrieval-augmented generation and summarization. In this paper, we introduce FaithLens, a cost-efficient and effective faithfulness hallucination detection model that can jointly provide binary predictions and corresponding explanations to improve trustworthiness. To achieve this, we first synthesize training data with explanations via advanced LLMs and apply a well-defined data filtering strategy to ensure label correctness, explanation quality, and data diversity. Subsequently, we fine-tune the model on these well-curated training data as a cold start and further optimize it with rule-based reinforcement learning, using rewards for both prediction correctness and explanation quality. Results on 12 diverse tasks show that the 8B-parameter FaithLens outperforms advanced models such as GPT-5.2 and o3. Also, FaithLens can produce high-quality explanations, delivering a distinctive balance of trustworthiness, efficiency, and effectiveness.
title FaithLens: Detecting and Explaining Faithfulness Hallucination
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2512.20182