Bridging the Support-Strategy Grounding Gap: A Theory-Guided Framework for Emotional Support Conversation

Emotional support conversation (ESC) helps individuals cope with psychological distress through dialogue that provides understanding, comfort, and guidance. Effective machine support requires selecting a strategy that is contextually admissible and faithfully executing its intended function in the final response. Our empirical analysis shows that these two requirements can fail independently: a model may faithfully execute a contextually inadmissible strategy or fail to faithfully execute an admissible one. We call this the support-strategy grounding gap. We derive an information-theoretic lower bound that relates grounding success to contextual strategy admissibility and to the conditional information that the response conveys about the complete declared strategy beyond the dialogue context. Guided by this characterization, GroundESC first establishes explicit strategy-guided generation through structured supervised fine-tuning and then applies reinforcement learning signals for strategy selection, faithful execution, and response quality. Across multiple backbones, GroundESC consistently improves strategy selection and execution, substantially mitigating the grounding gap while maintaining response quality.