On the Reliability Limits of LLM-Based Multi-Agent Planning

New theoretical work from MIT proves fundamental limits on what multi-agent LLM architectures can achieve. By modeling agent systems as finite acyclic delegated decision networks, the authors show that without new exogenous signals, no delegated network can outperform a centralized Bayes decision maker that observes the same information. The gap between centralized and delegated performance admits an expected posterior divergence representation, reducing to conditional mutual information under logarithmic loss. Reasoning models can improve by investing more inference-time computation on the same evidence, while tool-use protocols help only when they introduce genuinely new signals rather than reprocessing shared context.