Fine-Grained Uncertainty Quantification for Long-Form Language Model Outputs: A Comparative Study

Fuente: arXiv
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Autores principales: Bouchard, Dylan, Chauhan, Mohit Singh, Bajaj, Viren, Skarbrevik, David
Formato: Preprint
Publicado: 2026
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author Bouchard, Dylan
Chauhan, Mohit Singh
Bajaj, Viren
Skarbrevik, David
author_facet Bouchard, Dylan
Chauhan, Mohit Singh
Bajaj, Viren
Skarbrevik, David
contents Uncertainty quantification has emerged as an effective approach to closed-book hallucination detection for LLMs, but existing methods are largely designed for short-form outputs and do not generalize well to long-form generation. We introduce a taxonomy for fine-grained uncertainty quantification in long-form LLM outputs that distinguishes methods by design choices at three stages: response decomposition, unit-level scoring, and response-level aggregation. We formalize several families of consistency-based black-box scorers, providing generalizations and extensions of existing methods. In our experiments across multiple LLMs and datasets, we find 1) claim-response entailment consistently performs better or on par with more complex claim-level scorers, 2) claim-level scoring generally yields better results than sentence-level scoring, and 3) uncertainty-aware decoding is highly effective for improving the factuality of long-form outputs. Our framework clarifies relationships between prior methods, enables apples-to-apples comparisons, and provides practical guidance for selecting components for fine-grained UQ.
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institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Fine-Grained Uncertainty Quantification for Long-Form Language Model Outputs: A Comparative Study
Bouchard, Dylan
Chauhan, Mohit Singh
Bajaj, Viren
Skarbrevik, David
Computation and Language
Artificial Intelligence
Machine Learning
Uncertainty quantification has emerged as an effective approach to closed-book hallucination detection for LLMs, but existing methods are largely designed for short-form outputs and do not generalize well to long-form generation. We introduce a taxonomy for fine-grained uncertainty quantification in long-form LLM outputs that distinguishes methods by design choices at three stages: response decomposition, unit-level scoring, and response-level aggregation. We formalize several families of consistency-based black-box scorers, providing generalizations and extensions of existing methods. In our experiments across multiple LLMs and datasets, we find 1) claim-response entailment consistently performs better or on par with more complex claim-level scorers, 2) claim-level scoring generally yields better results than sentence-level scoring, and 3) uncertainty-aware decoding is highly effective for improving the factuality of long-form outputs. Our framework clarifies relationships between prior methods, enables apples-to-apples comparisons, and provides practical guidance for selecting components for fine-grained UQ.
title Fine-Grained Uncertainty Quantification for Long-Form Language Model Outputs: A Comparative Study
topic Computation and Language
Artificial Intelligence
Machine Learning
url https://arxiv.org/abs/2602.17431