Long Document Reconstruction Unlocks Scalable Long-Context RLVR

Yao Xiao, Lei Wang, Yue Deng, Guanzheng Chen, Ziqi Jin, Jung-jae Kim, Xiaoli Li, Roy Ka-Wei Lee, Lidong Bing


Abstract
Reinforcement Learning with Verifiable Rewards (RLVR) has become a prominent paradigm to enhance the capabilities (i.e. long-context) of Large Language Models (LLMs). However, it often relies on gold-standard answers or explicit evaluation rubrics provided by powerful teacher models or human experts, which are costly and time-consuming. In this work, we investigate unsupervised approaches to enhance the long-context capabilities of LLMs, eliminating the need for heavy human annotations or teacher models’ supervision. Specifically, we first replace a few paragraphs with special placeholders in a long document. LLMs are then trained through reinforcement learning to reconstruct the long document by correctly identifying and sequencing missing paragraphs from a set of candidate options. This training paradigm enables the model to capture global narrative coherence, significantly boosting long-context performance. We validate the effectiveness of our method on two widely used benchmarks, RULER and LongBench v2. While acquiring noticeable gains on RULER (nearly 10 points), it can also achieve a reasonable improvement on LongBench v2 without any manually curated long-context QA data. Furthermore, we conduct extensive ablation studies to analyze the impact of reward designs, data curation strategies, training schemes, and data scaling effects on model performance. We will release our code, data, and models.
Anthology ID:
2026.emnlp-main.135
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:
3122–3135
Language:
URL:
https://aclanthology.org/2026.emnlp-main.135/
DOI:
Bibkey:
Cite (ACL):
Yao Xiao, Lei Wang, Yue Deng, Guanzheng Chen, Ziqi Jin, Jung-jae Kim, Xiaoli Li, Roy Ka-Wei Lee, and Lidong Bing. 2026. Long Document Reconstruction Unlocks Scalable Long-Context RLVR. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 3122–3135, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Long Document Reconstruction Unlocks Scalable Long-Context RLVR (Xiao et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.135.pdf