Auditing Black-Box LLM APIs with a Rank-Based Uniformity Test - Zhu, Xiaoyuan; Ye, Yaowen; Qiu, Tianyi; Zhu, Hanlin; Tan, Sijun; Mannan, Ajraf; Michala, Jonathan; Popa, Raluca; Neiswanger, Willie (International Conference on Learning Representations, 2026)