Liu, Y., Liu, X., Sun, Z., & Hu, W. (2026). Answering the Unanswerable Is to Err Knowingly: Analyzing and Mitigating Abstention Failures in Large Reasoning Models. Proceedings of the AAAI Conference on Artificial Intelligence, 40(38), 32231–32239. https://doi.org/10.1609/aaai.v40i38.40496