CoDiQ: Test-Time Scaling for Controllable Difficult Question Generation

Zhongyuan Peng, Caijun Xu, Changyi Xiao, Shibo Hong, Ge Zhang, Wenhao Huang, Yixin Cao


Abstract
Large Reasoning Models (LRMs) benefit substantially from training on challenging competition-level questions. However, existing automated question synthesis methods lack precise difficulty control, incur high computational costs, and struggle to generate competition-level questions at scale. In this paper, we propose CoDiQ (Controllable Difficult Question Generation), a novel framework enabling fine-grained difficulty control via test-time scaling while ensuring question solvability. Specifically, first, we identify a test-time scaling tendency (extended reasoning token budget boosts difficulty but reduces solvability) and the intrinsic properties defining the upper bound of a model’s ability to generate valid, high-difficulty questions. Then, we develop CoDiQ-Generator from Qwen3-8B, which improves the upper bound of difficult question generation, making it particularly well-suited for challenging question construction. Building on the CoDiQ framework, we build CoDiQ-Corpus (44K competition-grade question sequences). Human evaluations show these questions are significantly more challenging than LiveCodeBench/AIME with over 82% solvability. Training LRMs on CoDiQ-Corpus substantially improves reasoning performance, verifying that scaling controlled-difficulty training questions enhances reasoning capabilities. We open-source CoDiQ-Corpus, CoDiQ-Generator, and implementations to support related research.
Anthology ID:
2026.emnlp-main.219
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:
5037–5072
Language:
URL:
https://aclanthology.org/2026.emnlp-main.219/
DOI:
Bibkey:
Cite (ACL):
Zhongyuan Peng, Caijun Xu, Changyi Xiao, Shibo Hong, Ge Zhang, Wenhao Huang, and Yixin Cao. 2026. CoDiQ: Test-Time Scaling for Controllable Difficult Question Generation. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 5037–5072, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
CoDiQ: Test-Time Scaling for Controllable Difficult Question Generation (Peng et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.219.pdf