Knowing What to Solve Before How: Preplan Empowered LLM Mathematical Reasoning

Shaojie Wang, Liang Zhang


Abstract
Current plan-based reasoning methods improve large language models (LLMs) by inserting a planning stage before execution, giving rise to the **question → plan → cot** paradigm. While effective, a closer examination reveals an inherent paradigm-level gap: both the planning and its execution stages decide *how to solve* a problem, while the prior question of *what to solve*; recognizing the problem type, the applicable tools, and the foreseeable pitfalls; remains entirely implicit. To bridge this gap, we propose **PPC** (**P**replan-**P**lan-**C**oT), a framework that introduces an explicit problem-understanding stage, the *preplan*, yielding a new **question → preplan → plan → cot** paradigm. Realizing this paradigm requires safeguarding the conceptual integrity of preplan at both ends. Specifically, we design a three-stage synthesis pipeline with a *spoiler-score detector* that filters out leakage and spoiler failures to build clean preplan supervision, and a composite GRPO reward enforces that the generated plan genuinely follows from the preplan. Experiments across four backbones and five mathematical reasoning benchmarks show that PPC achieves the best results on 39 of 40 metrics, improving *maj@16* and *pass@16* by +2.23 and +3.06 over the strongest baseline without introducing additional inference token overhead.
Anthology ID:
2026.findings-emnlp.171
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
3608–3623
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.171/
DOI:
Bibkey:
Cite (ACL):
Shaojie Wang and Liang Zhang. 2026. Knowing What to Solve Before How: Preplan Empowered LLM Mathematical Reasoning. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 3608–3623, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Knowing What to Solve Before How: Preplan Empowered LLM Mathematical Reasoning (Wang & Zhang, Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.171.pdf