Look Before You Leap: Factual Decoding with Internal Attribution Signals

Hayeong Ryu, JungMin Yun, Byeonggeuk Lim, Sunhee Jo, YoungBin Kim


Abstract
Hallucination remains a critical challenge in large language models (LLMs), where early factual errors compound through autoregressive generation in a snowballing effect that neither post-hoc correction nor weight-level intervention can effectively preempt. We propose DescaPE (DEcoding Signal Control Against Path Error-snowballing), a decoding framework that leverages internal model signals to suppress hallucination-prone trajectories at inference time. Through sliding-window MLP ablation, we identify a factual-salient layer span within LLMs whose derived signal is selectively elevated for factual tokens and exhibits anomalous spikes at hallucination-prone steps. We train a lightweight probe to approximate this signal from a single forward pass and integrate it into candidate scoring to penalize high-risk continuations while rewarding factually grounded ones. Experiments across five factuality benchmarks on three LLMs demonstrate that DescaPE achieves factuality improvements over decoding-time baselines in multiple settings, while incurring only 1.10x latency overhead in our efficiency evaluation. Our code is available at https://github.com/hayeonggg/DESCAPE.
Anthology ID:
2026.findings-emnlp.323
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:
6836–6857
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.323/
DOI:
Bibkey:
Cite (ACL):
Hayeong Ryu, JungMin Yun, Byeonggeuk Lim, Sunhee Jo, and YoungBin Kim. 2026. Look Before You Leap: Factual Decoding with Internal Attribution Signals. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 6836–6857, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Look Before You Leap: Factual Decoding with Internal Attribution Signals (Ryu et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.323.pdf