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Bibliographic Details
Main Authors: Hu, Zhiyuan, Hu, Yunhai, Liu, Juncheng, Li, Shuyue Stella, Wang, Yucheng, Xu, Zhen, Ng, See-Kiong, Luu, Anh Tuan, Xu, Xinxing, Hooi, Bryan, Breazeal, Cynthia, Park, Hae Won
Format: Preprint
Published: 2026
Subjects:
Online Access:https://arxiv.org/abs/2601.09667
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Table of Contents:
  • Multi-agent systems have evolved into practical LLM-driven collaborators for many applications, gaining robustness from diversity and cross-checking. However, multi-agent RL (MARL) training is resource-intensive and unstable: co-adapting teammates induce non-stationarity, and rewards are often sparse and high-variance. Therefore, we introduce \textbf{Multi-Agent Test-Time Reinforcement Learning (MATTRL)}, a framework that injects structured textual experience into multi-agent deliberation at inference time. MATTRL forms a multi-expert team of specialists for multi-turn discussions, retrieves and integrates test-time experiences, and reaches consensus for final decision-making. We also study credit assignment for constructing a turn-level experience pool, then reinjecting it into the dialogue. Across challenging benchmarks in medicine, math, and education, MATTRL improves accuracy by an average of 3.67\% over a multi-agent baseline, and by 8.67\% over comparable single-agent baselines. Ablation studies examine different credit-assignment schemes and provide a detailed comparison of how they affect training outcomes. MATTRL offers a stable, effective and efficient path to distribution-shift-robust multi-agent reasoning without tuning.