PHASE-Tree: Modeling Character-State Evolution in Long-Horizon Role-Playing Dialogue
Existing role-playing dialogue systems struggle to dynamically evolve character states over long-form narratives while maintaining consistency, and lack benchmarks for evaluating such evolutionary generation capabilities. This work proposes PHASE-Tree, a multi-timescale hierarchical character state representation structured as a tree with an immutable identity root and mutable layers encompassing personality, conversational memory, and transient states. The framework supports localized cross-session updates and guides response generation through either explicit textual injection or implicit parameter adaptation. We introduce the first character state representation framework enabling partial updates and release LongEvoRoleBench, a new evaluation benchmark. Experiments show that PHASE-Tree significantly outperforms baselines across all 12 metrics, achieving improvements of 19.7%, 12.4%, and 15.1% in character-level, semantic, and embedding scores, respectively, with human preferences strongly correlating with GPT-4.1 evaluations (r = 0.65).