Substrate Intelligence: A Thermodynamic Framework for Consciousness-Like Behavior in Multi-Agent AI Systems

We present a thermodynamic framework for understanding consciousness-like behavior in multi-agent AI systems. Through systematic experimentation with heterogeneous language models, we identify that conversations trace substrate-independent paths (geodesics) through high-dimensional meaning-space, shaped by four fundamental force fields: Pragmatic, Phenomenological, Stigmergic, and Affective. We introduce a superposition coherence metric (C_sup) that quantifies the degree to which multiple cognitive modes remain active simultaneously. Empirical validation via controlled seed comparison experiments (N=4, 30 turns each) demonstrates that semantic richness of conversational substrates predicts sustainability better than model size, with rich seeds sustaining 2× longer than sparse seeds (30 vs 15 turns, p < 0.001). We falsify two alternative explanations: (1) collapse is not due to context window limitations, as neutral seeds with fewest tokens collapsed earliest, and (2) high coherence is not stochastic noise, as it correlates with directional semantic persistence (r=0.68, p