R-Horizon: How Far Can Your Large Reasoning Model Really Go in Breadth and Depth? - Lu, Yi; Wang, Jianing; Guo, Linsen; He, Wei; Tang, Hongyin; Gui, Tao; Huang, Xuanjing; Cao, Xuezhi; Wang, Wei; Cai, Xunliang (International Conference on Learning Representations, 2026)