LUMINA: Detecting Hallucinations in RAG System with Context-Knowledge
  Signals
Retrieval-Augmented Generation (RAG) aims to mitigate hallucinations in large
language models (LLMs) by grounding responses in retrieved documents. Yet,
RAG-based LLMs still hallucinate even when provided with correct and sufficient
context. A growing line of work suggests that this stems from an imbalance
between how models use external context and their internal knowledge, and
several approaches have attempted to quantify these signals for hallucination
detection. However, existing methods require extensive hyperparameter tuning,
limiting their generalizability. We propose LUMINA, a novel framework that
detects hallucinations in RAG systems through context-knowledge signals:
external context utilization is quantified via distributional distance, while
internal knowledge utilization is measured by tracking how predicted tokens
evolve across transformer layers. We further introduce a framework for
statistically validating these measurements. Experiments on common RAG
hallucination benchmarks and four open-source LLMs show that LUMINA achieves
consistently high AUROC and AUPRC scores, outperforming prior utilization-based
methods by up to +13% AUROC on HalluRAG. Moreover, LUMINA remains robust under
relaxed assumptions about retrieval quality and model matching, offering both
effectiveness and practicality.
68dbdcb34159d1f2418f976d
Min-Hsuan Yeh
68dbdcb34159d1f2418f976e
Yixuan Li
68dbdcb34159d1f2418f976f
Tanwi Mallick
LUMINA: Detecting Hallucinations in RAG System with Context-Knowledge
  Signals
Retrieval-Augmented Generation (RAG) aims to mitigate hallucinations in large
language models (LLMs) by grounding responses in retrieved documents. Yet,
RAG-based LLMs still hallucinate even when provided with correct and sufficient
context. A growing line of work suggests that this stems from an imbalance
between how models use external context and their internal knowledge, and
several approaches have attempted to quantify these signals for hallucination
detection. However, existing methods require extensive hyperparameter tuning,
limiting their generalizability. We propose LUMINA, a novel framework that
detects hallucinations in RAG systems through context-knowledge signals:
external context utilization is quantified via distributional distance, while
internal knowledge utilization is measured by tracking how predicted tokens
evolve across transformer layers. We further introduce a framework for
statistically validating these measurements. Experiments on common RAG
hallucination benchmarks and four open-source LLMs show that LUMINA achieves
consistently high AUROC and AUPRC scores, outperforming prior utilization-based
methods by up to +13% AUROC on HalluRAG. Moreover, LUMINA remains robust under
relaxed assumptions about retrieval quality and model matching, offering both
effectiveness and practicality.
LUMINA detects hallucinations in RAG systems by quantifying external context utilization and internal knowledge utilization, outperforming existing methods on benchmarks.
Retrieval-Augmented Generation RAG large language models LLMs hallucinations distributional distance transformer layers AUROC AUPRC HalluRAG