GeoChallenge-90K: A Multi-Answer Multiple-Choice Benchmark for Diagram-Grounded Geometric Reasoning

Yushun Zhang, Weiping Fu, Zesheng Yang, Bo Zhao, Lingling Zhang, Jian Zhang, Yumeng Fu, Jiaxing Huang, Jun Liu


Abstract
Evaluating the symbolic reasoning of large language models (LLMs) calls for geometry benchmarks that require multi-step proofs grounded in both text and diagrams. However, existing benchmarks are often limited in scale and rarely provide visually grounded multiple-choice questions, limiting reliable evaluation of complex reasoning. We introduce GeoChallenge, a dataset of 90K automatically generated multiple-choice geometry proof problems, each requiring multi-step reasoning over aligned textual descriptions and diagrams. GeoChallenge provides fine-grained complexity ratings and formal language annotations to enable controlled evaluation. Experiments on multiple advanced LLMs show a clear performance gap between models and humans (the best-performing model, GPT-5-nano, achieves 75.89 exact match vs. 94.74 for humans). Further analysis also reveals three common failure patterns of LLMs: (1) exact match failures under the multiple-choice setting; (2) weak visual reliance; and (3) overextended reasoning without convergence.
Anthology ID:
2026.emnlp-main.2583
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
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Pages:
58710–58730
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URL:
https://aclanthology.org/2026.emnlp-main.2583/
DOI:
Bibkey:
Cite (ACL):
Yushun Zhang, Weiping Fu, Zesheng Yang, Bo Zhao, Lingling Zhang, Jian Zhang, Yumeng Fu, Jiaxing Huang, and Jun Liu. 2026. GeoChallenge-90K: A Multi-Answer Multiple-Choice Benchmark for Diagram-Grounded Geometric Reasoning. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 58710–58730, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
GeoChallenge-90K: A Multi-Answer Multiple-Choice Benchmark for Diagram-Grounded Geometric Reasoning (Zhang et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2583.pdf