BFM-Zero: A Promptable Behavioral Foundation Model for Humanoid Control Using Unsupervised Reinforcement Learning - Li, Yitang; Luo, Zhengyi; Zhang, Tonghe; Dai, Cunxi; Kanervisto, Anssi; Tirinzoni, Andrea; Weng, Haoyang; Kitani, Kris; Guzek, Mateusz; Touati, Ahmed; Lazaric, Alessandro; Pirotta, Matteo; et al. (International Conference on Learning Representations, 2026)