AAMAS Conference 2026 Conference Paper
B3C: A Minimalist Approach to Offline Multi-Agent Reinforcement Learning
- Woojun Kim
- Katia P. Sycara
Overestimation arising from selecting unseen actions during policy evaluation is a major challenge in offline reinforcement learning (RL). A minimalist approach in the single-agent setting—adding behaviorcloning(BC)regularizationtoexistingonlineRLalgorithms— has been shown to be effective in terms of achieving competitive performance with minimal modification to online algorithms; however, thisapproachisunderstudiedinmulti-agentsettings. Inparticular, overestimation becomes worse in multi-agent settings due to the presence of multiple actions, resulting in the BC regularizationbased approach easily suffering from either over-regularization or critic divergence. To address this, we propose a simple yet effective method, BehaviorCloningregularizationwithCriticClipping(B3C), which clips the target critic value in policy evaluation based on the maximum return in the dataset and pushes the limit of the weight on the RL objective over BC regularization, thereby demonstrating superiorperformanceacrossbenchmarks. Additionally, weleverage existing value factorization techniques, particularly non-linear factorization, which is understudied in offline settings. Integrated with non-linear value factorization, B3C outperforms state-of-the-art algorithms on various offline multi-agent benchmarks.