Enhancing Value Decomposition With Target Transformation in Cooperative Multi-Agent Reinforcement Learning

The increasing need for cooperation among intelligent machines has heightened the importance of cooperative multi-agent reinforcement learning (MARL). However, a dominant class of cooperative MARL approaches relies on monotonic value decomposition, which enables scalable decentralized execution but restricts the representable class of joint action-values. However, existing remedies bias learning targets toward high-value samples, which can be fragile under stochastic returns because optimistic emphasis may amplify lucky but suboptimal trajectories. To solve this challenge, we propose Target Transformation, which maps non-monotonic and stochastic learning targets into a monotonic-representable surrogate while preserving the optimal joint action. Building on this idea, we develop Uncertainty-aware Target Transformation (UT2) with value-based and policy-based instantiations that combine an uncertainty estimator with a best-individual coordination envelope. Experiments on diverse cooperative MARL benchmarks show that UT2 improves both performance and stability over strong baselines, with larger gains as non-monotonicity and stochasticity increase.