arXiv — NLP / Computation & Language · · 3 min read

HARPO: Hallucination-Aware Reinforcement Learning for Faithful and Creative Language Generation

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Computer Science > Computation and Language

arXiv:2610.03063 (cs)
[Submitted on 2 Oct 2026]

Title:HARPO: Hallucination-Aware Reinforcement Learning for Faithful and Creative Language Generation

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Abstract:Large Language Models (LLMs) are prone to generating hallucinated content, which compromises their reliability in knowledge-intensive tasks. To address this challenge without sacrificing creativity, we propose HARPO, a reinforcement learning framework designed to jointly optimize faithfulness and creativity. HARPO incorporates a Hallucination-Aware Generative Reward Model (HA-GRM), trained via verifiable feedback, to assess both faithfulness and writing quality. A Selective Activation Mechanism (SAM) activates writing rewards only for outputs judged hallucination-free by HA-GRM, while a data curriculum progressively shifts training from creative writing to hallucination-centric tasks. On RAGTruth, our Qwen3-4B-based HA-GRM achieves a response-level F1 score of 78.08%, compared with 66.37% for the supervised fine-tuning baseline. Experiments on Qwen2.5 and Qwen3 models from 1.7B to 8B parameters show improvements in both faithful generation and writing quality. On Qwen3-4B, HARPO reduces the HA-GRM-judged hallucination rate on MultiHopRAG from 3.29% to 1.02%, while increasing the Arena-Hard-v2.0 creative-writing score from 16.95% to 27.54%.
Comments: 11 pages
Subjects: Computation and Language (cs.CL)
Cite as: arXiv:2610.03063 [cs.CL]
  (or arXiv:2610.03063v1 [cs.CL] for this version)
  https://doi.org/10.48550/arXiv.2610.03063
arXiv-issued DOI via DataCite (pending registration)

Submission history

From: Tiezheng Yu [view email]
[v1] Fri, 2 Oct 2026 09:46:40 UTC (1,283 KB)
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