OffSeeker: Online Reinforcement Learning Is Not All You Need for Deep Research Agents

Yuhang Zhou, Kai Zheng, Qiguang Chen, Mengkang Hu, Qingfeng Sun, Can Xu, Jingjing Chen


Abstract
Deep research agents have shown remarkable potential in handling long-horizon tasks. However, state-of-the-art performance typically relies on online reinforcement learning (RL), which is financially expensive due to extensive API calls. While offline training offers a more efficient alternative, its progress is hindered by the scarcity of high-quality research trajectories. In this paper, we demonstrate that expensive online reinforcement learning is not all you need to build powerful research agents. To bridge this gap, we introduce a fully open-source suite designed for effective offline training. Our core contributions include DeepForge, a ready-to-use task synthesis framework that generates large-scale research queries without heavy preprocessing; and a curated collection of 66k QA pairs, 33k SFT trajectories, and 21k DPO pairs. Leveraging these resources, we train OffSeeker, a model developed entirely offline. Extensive evaluations across six benchmarks show that OffSeeker not only leads among similar-sized agents but also remains competitive with 30B-parameter systems trained via heavy online RL.
Anthology ID:
2026.emnlp-main.173
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
3966–3986
Language:
URL:
https://aclanthology.org/2026.emnlp-main.173/
DOI:
Bibkey:
Cite (ACL):
Yuhang Zhou, Kai Zheng, Qiguang Chen, Mengkang Hu, Qingfeng Sun, Can Xu, and Jingjing Chen. 2026. OffSeeker: Online Reinforcement Learning Is Not All You Need for Deep Research Agents. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 3966–3986, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
OffSeeker: Online Reinforcement Learning Is Not All You Need for Deep Research Agents (Zhou et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.173.pdf