COLT: Lightweight Multi-LLM Collaboration through Shared MCTS Reasoning for Model Compilation

• URL: http://arxiv.org/abs/2602.01935v1
• Date: Mon, 02 Feb 2026 10:37:05 GMT
• Title: COLT: Lightweight Multi-LLM Collaboration through Shared MCTS Reasoning for Model Compilation
• Authors: Annabelle Sujun Tang, Christopher Priebe, Lianhui Qin, Hadi Esmaeilzadeh,
• Abstract summary: We propose a lightweight collaborative multi-LLM framework, dubbed COLT, for compiler optimization.<n>A key contribution is the use of a single shared MCTS tree as the collaboration substrate across LLMs.
• Score: 5.792898693767499
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Model serving costs dominate AI systems, making compiler optimization essential for scalable deployment. Recent works show that a large language model (LLM) can guide compiler search by reasoning over program structure and optimization history. However, using a single large model throughout the search is expensive, while smaller models are less reliable when used alone. Thus, this paper seeks to answer whether multi-LLM collaborative reasoning relying primarily on small LLMs can match or exceed the performance of a single large model. As such, we propose a lightweight collaborative multi-LLM framework, dubbed COLT, for compiler optimization that enables coordinated reasoning across multiple models within a single Monte Carlo tree search (MCTS) process. A key contribution is the use of a single shared MCTS tree as the collaboration substrate across LLMs, enabling the reuse of transformation prefixes and cross-model value propagation. Hence, we circumvent both heavy internal reasoning mechanisms and conventional agentic machinery that relies on external planners, multiple concurrent LLMs, databases, external memory/versioning of intermediate results, and controllers by simply endogenizing model selection within the lightweight MCTS optimization loop. Every iteration, the acting LLM proposes a joint action: (compiler transformation, model to be queried next). We also introduce a model-aware tree policy that biases search toward smaller models while preserving exploration, and a course-alteration mechanism that escalates to the largest model when the search exhibits persistent regressions attributable to smaller models.

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