When LLM Meets Tree Search: A Systematic View of Inference as Search in Large Language Models

Jiaqi Wei, Xiang Zhang, Yuejin Yang, Wenxuan Huang, Juntai Cao, Sheng Xu, Xiang Zhuang, Zhangyang Gao, Muhammad Abdul-Mageed, Laks V. S. Lakshmanan, Chenyu You, Wanli Ouyang, Siqi Sun


Abstract
As pretraining scaling laws approach saturation, Test-Time Scaling (TTS) has emerged as an important direction for improving reasoning by allocating inference-time compute to a fixed model prior. Viewed at a high level, TTS reframes inference as search over a space of partial reasoning states. While Chain-of-Thought (CoT) exposes intermediate steps, common instantiations rely on single-trajectory decoding, limiting recovery from early errors and exploration. This survey systematizes recent progress in tree-search-based reasoning, viewing inference as instance-specific optimization rather than decoding. We trace the evolution from uninformed search to Monte Carlo Tree Search (MCTS), highlighting how sampling-based control supports principled exploration–exploitation trade-offs. To unify a fragmented literature, we introduce a Unified Design Space spanning search topology, evaluation signals, and control dynamics, and advocate a standardized compute-reporting abstraction to make compute–accuracy trade-offs explicit and comparable.
Anthology ID:
2026.findings-emnlp.643
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
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SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
13488–13543
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URL:
https://aclanthology.org/2026.findings-emnlp.643/
DOI:
Bibkey:
Cite (ACL):
Jiaqi Wei, Xiang Zhang, Yuejin Yang, Wenxuan Huang, Juntai Cao, Sheng Xu, Xiang Zhuang, Zhangyang Gao, Muhammad Abdul-Mageed, Laks V. S. Lakshmanan, Chenyu You, Wanli Ouyang, and Siqi Sun. 2026. When LLM Meets Tree Search: A Systematic View of Inference as Search in Large Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 13488–13543, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
When LLM Meets Tree Search: A Systematic View of Inference as Search in Large Language Models (Wei et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.643.pdf