SFAD: Speculative Factuality-Aware Decoding

Guanqiao Chen, Di Wang, Lijie Hu


Abstract
As one of the most critical challenges in large language models, contextual faithfulness directly determines their reliability in knowledge-intensive applications. This task is particularly challenging as it requires balancing factual consistency with generation efficiency. Contrastive decoding methods require dual forward passes (with and without context) to compare model outputs, doubling inference computational overhead, while post-training alignment demands extensive reinforcement learning with substantial computational overhead. To address this challenge, we present SFAD, a speculative decoding framework that enhances contextual faithfulness without inference degradation. We first construct ConFide, a preference dataset with fine-grained atomic perturbations, to train a context-faithful draft model via Direct Preference Optimization. During inference, Epistemic Friction detects potential hallucinations by quantifying distributional tension weighted by specialist certainty. When friction exceeds the threshold, Asymmetric Logit Steering refines the target distribution through residual-based logit injection; otherwise, standard speculation proceeds. Extensive experiments demonstrate that SFAD substantially improves faithfulness while achieving 2.48× speedup, offering a practical solution for efficient LLMs.
Anthology ID:
2026.findings-emnlp.1144
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
24221–24239
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1144/
DOI:
Bibkey:
Cite (ACL):
Guanqiao Chen, Di Wang, and Lijie Hu. 2026. SFAD: Speculative Factuality-Aware Decoding. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 24221–24239, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
SFAD: Speculative Factuality-Aware Decoding (Chen et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1144.pdf