Heterogeneous Swarms: Jointly Optimizing Model Roles and Weights for Multi-LLM Systems - Feng, Shangbin; Wang, Zifeng; Goyal, Palash; Wang, Yike; Shi, Weijia; Xia, Huang; Palangi, Hamid; Zettlemoyer, Luke; Tsvetkov, Yulia; Lee, Chen-Yu; Pfister, Tomas (Advances in Neural Information Processing Systems, 2025)