Large Language Models

CoDiQ: Test-Time Scaling for Controllable Difficult Question Generation

ZZhongyuan PengCCaijun XuCChangyi XiaoSShibo HongEEli ZhangSStephen HuangYYixin Cao
Published
February 2, 2026
Authors
7
Word Count
10,825
Code
Includes code

Revolutionizing difficult question generation for LRMs.

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.

Key Takeaways

  • 1

    CoDiQ scales question difficulty at inference time.

  • 2

    Maintains high solvability while increasing question complexity.

  • 3

    Improves Large Reasoning Model performance on benchmarks.

Limitations

  • Currently limited to English math and code tasks.

  • Computationally intensive verification process.

Keywords

Large Reasoning Modelstest-time scalingcontrollable difficulty controlCoDiQ-GeneratorCoDiQ-Corpusquestion generationreasoning performancecompetition-level questions

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