Efficient Prior-Guided Reasoning for Robust Retrieval-Augmented Generation under Conflicts

Retrieval-Augmented Generation (RAG) has become a standard paradigm for grounding Large Language Models (LLMs) with external knowledge. However, RAG performance often degrades substantially when faced with noisy, outdated, or conflicting retrieved information. In this work, we empirically demonstrate that Prior-Guided Reasoning-a strategy that explicitly elicits the model's parametric knowledge as prior information to guide reasoning on retrieved documents-effectively mitigates the impact of external conflicts. Building on this, we propose BrPr (Bernoulligated reinforcement learning for Prior-Guided reasoning), a framework that achieves robust performance across varying degrees of external inconsistency. Furthermore, by employing a Bernoulli-gated dropout mechanism during training, BrPr distills the prior-driven reasoning capability into the model parameters, enabling efficient latent reasoning without explicit prior generation. The experimental results demonstrate that BrPr consistently exhibits superior robustness to external conflicts and noise.