WWW 2026 | 强化学习重塑GraphRAG，多跳推理F1提升83.81%

TL;DR - GraphRAG-R1 (Nankai, Beihang, HKUST-GZ, Huawei; WWW 2026 Oral) uses process-constrained reinforcement learning to teach an LLM when and how much to retrieve over a knowledge graph, reporting up to +83.81% F1 on multi-hop QA. It matters because it shifts GraphRAG from fixed retrieval heuristics to a learned, agentic retrieve-and-reason policy.

• Built on GRPO with "Rollout-with-Thinking": the model pauses generation via special tokens to call a graph retriever mid-chain, embedding hybrid graph-text results back into reasoning.
• Two reward functions counter reward hacking: PRA (Progressive Retrieval Attenuation) exponentially decays reward for repeated retrievals to prevent shallow search; CAF (Cost-Aware F1) scales F1 by a retrieval-count decay to penalize over-thinking. Ablations show removing either degrades retrieval depth or wastes compute.
• Three-stage curriculum (SFT cold start → PRA behavior shaping → CAF optimization) on Qwen2.5-7B; reported F1 gains: HotpotQA +38.08%, MuSiQue +62.43%, 2Wiki +83.81%, PopQA +19.96% zero-shot.
• Plug-and-play: trained once with HippoRAG2, transfers to KGP, ToG, LightRAG, G-Retriever with 20%+ average gains (up to 45.22%), at lower token cost; validated on Qwen2.5-7B-Instruct and LLaMA-3-8B.