@inproceedings{wang-etal-2026-anti,
title = "Anti-Prior Reinforcement Learning for Context-Grounded Reasoning",
author = "Wang, Zheng and
LU, Zexin and
Hu, Xuming",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Findings of the {A}ssociation for {C}omputational {L}inguistics: {EMNLP} 2026",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.findings-emnlp.1892/",
pages = "40308--40327",
ISBN = "979-8-89176-462-0",
abstract = "Large language models are increasingly asked to treat the input context as the source of task-specific rules, procedures, and evidence. A difficult case arises when this context contradicts pretrained priors: models may mention the local rule but still execute familiar semantic, commonsense, positional, or operator shortcuts. We study this failure mode as \textit{prior-dominated reasoning}, where either the final answer or the intermediate trajectory follows a plausible prior-consistent path rather than the current context. We propose \textit{Anti-Prior Reinforcement Learning}, a post-training framework that constructs executable context-prior conflict tasks and trains with a gated verifier reward. The reward gives positive credit for answer correctness, context anchoring, and step-wise local rule use, while penalizing prior-consistent answers and reasoning steps. On Qwen3-8B, Anti-Prior RL improves controlled validation accuracy from 51.7{\%} to 74.5{\%} and controlled OOD accuracy from 46.4{\%} to 73.4{\%}, while reducing OOD prior-answer/prior-step hit rates from 15.9{\%}/40.2{\%} to 1.5{\%}/8.9{\%}. It also improves over SFT and LongRLVR on downstream CL-Bench, RULER-QA, and LongBench v2 across both Qwen3-8B and Qwen2.5-7B-1M, and outperforms outcome-only RL on Qwen3-8B. Together, these results provide complementary evidence that the learned behavior transfers beyond the constructed prior-conflict setting to broader context-learning and reasoning benchmarks."
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<abstract>Large language models are increasingly asked to treat the input context as the source of task-specific rules, procedures, and evidence. A difficult case arises when this context contradicts pretrained priors: models may mention the local rule but still execute familiar semantic, commonsense, positional, or operator shortcuts. We study this failure mode as prior-dominated reasoning, where either the final answer or the intermediate trajectory follows a plausible prior-consistent path rather than the current context. We propose Anti-Prior Reinforcement Learning, a post-training framework that constructs executable context-prior conflict tasks and trains with a gated verifier reward. The reward gives positive credit for answer correctness, context anchoring, and step-wise local rule use, while penalizing prior-consistent answers and reasoning steps. On Qwen3-8B, Anti-Prior RL improves controlled validation accuracy from 51.7% to 74.5% and controlled OOD accuracy from 46.4% to 73.4%, while reducing OOD prior-answer/prior-step hit rates from 15.9%/40.2% to 1.5%/8.9%. It also improves over SFT and LongRLVR on downstream CL-Bench, RULER-QA, and LongBench v2 across both Qwen3-8B and Qwen2.5-7B-1M, and outperforms outcome-only RL on Qwen3-8B. Together, these results provide complementary evidence that the learned behavior transfers beyond the constructed prior-conflict setting to broader context-learning and reasoning benchmarks.</abstract>
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%0 Conference Proceedings
%T Anti-Prior Reinforcement Learning for Context-Grounded Reasoning
%A Wang, Zheng
%A LU, Zexin
%A Hu, Xuming
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Findings of the Association for Computational Linguistics: EMNLP 2026
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-462-0
%F wang-etal-2026-anti
%X Large language models are increasingly asked to treat the input context as the source of task-specific rules, procedures, and evidence. A difficult case arises when this context contradicts pretrained priors: models may mention the local rule but still execute familiar semantic, commonsense, positional, or operator shortcuts. We study this failure mode as prior-dominated reasoning, where either the final answer or the intermediate trajectory follows a plausible prior-consistent path rather than the current context. We propose Anti-Prior Reinforcement Learning, a post-training framework that constructs executable context-prior conflict tasks and trains with a gated verifier reward. The reward gives positive credit for answer correctness, context anchoring, and step-wise local rule use, while penalizing prior-consistent answers and reasoning steps. On Qwen3-8B, Anti-Prior RL improves controlled validation accuracy from 51.7% to 74.5% and controlled OOD accuracy from 46.4% to 73.4%, while reducing OOD prior-answer/prior-step hit rates from 15.9%/40.2% to 1.5%/8.9%. It also improves over SFT and LongRLVR on downstream CL-Bench, RULER-QA, and LongBench v2 across both Qwen3-8B and Qwen2.5-7B-1M, and outperforms outcome-only RL on Qwen3-8B. Together, these results provide complementary evidence that the learned behavior transfers beyond the constructed prior-conflict setting to broader context-learning and reasoning benchmarks.
%U https://aclanthology.org/2026.findings-emnlp.1892/
%P 40308-40327
Markdown (Informal)
[Anti-Prior Reinforcement Learning for Context-Grounded Reasoning](https://aclanthology.org/2026.findings-emnlp.1892/) (Wang et al., Findings 2026)
ACL