ZipRL: Adaptive Multi-Turn Context Compression with Hindsight Response Replay

Zhexin Hu, Li Wang, Xiaohan Wang, Jiajun Chai, Xiaojun Guo, Wei Lin, Xin Zhou, Guojun Yin


Abstract
Adaptive context compression is vital for scaling Large Language Models (LLMs) to complex, multi-turn agent tasks. However, rule-based compression methods may discard task-critical nuances, while Reinforcement Learning (RL) approaches usually struggle to balance information retention and token efficiency under the sparse rewards inherent to long-horizon workflows. To bridge this gap, we propose ZipRL, a novel adaptive compression framework tailored for Reinforcement Learning from Verifiable Rewards (RLVR). ZipRL features a multi-granularity compression mechanism for active, non-uniform information reduction, coupled with Hindsight Response Replay (HRR)—a technique designed to densify training signals during RLVR optimization. Theoretically, we prove ZipRL’s superior task-relevant utility over uniform methods. Concretely, ZipRL utilizes coarse-to-fine prompts for macro-compression and incorporates HRR into GRPO via generalized advantage reshaping. Multiple models of varying versions and parameter scales validate the effectiveness of our approach. Benchmarks on five agent tasks show ZipRL outperforms state-of-the-art approaches by 27.9% and 34.7% across Qwen3-4B and Qwen3-8B models, while maintaining exceptional token efficiency and robustness under extreme 256-turn extrapolation stress tests. Our code is available at https://github.com/huzhexin/ZipRL.
Anthology ID:
2026.findings-emnlp.1614
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
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Pages:
34371–34391
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URL:
https://aclanthology.org/2026.findings-emnlp.1614/
DOI:
Bibkey:
Cite (ACL):
Zhexin Hu, Li Wang, Xiaohan Wang, Jiajun Chai, Xiaojun Guo, Wei Lin, Xin Zhou, and Guojun Yin. 2026. ZipRL: Adaptive Multi-Turn Context Compression with Hindsight Response Replay. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 34371–34391, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
ZipRL: Adaptive Multi-Turn Context Compression with Hindsight Response Replay (Hu et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1614.pdf