A^2FM: An Adaptive Agent Foundation Model for Tool-Aware Hybrid Reasoning - Chen, Qianben; Cao, Jingyi; Zhang, Jiayu; Qin, Tianrui; LiXiaowan; Zhu; Shi, Dingfeng; Zhu, He; Liu, Minghao; Liang, Xiaobo; Zhang, Ge; Yang, Jian; et al. (International Conference on Learning Representations, 2026)