Youtu-GraphRAG: Vertically Unified Agents for Graph Retrieval-Augmented Complex Reasoning - Dong, Junnan; An, Siyu; Yu, Yifei; ZHANG, QIANWEN; Luo, Linhao; Huang, Xiao; yin, di; Wu, Yunsheng; Sun, Xing (International Conference on Learning Representations, 2026)