In recent years, the rapid advancement of large language models (LLMs) has enabled generated texts to closely mimic human writing, posing significant challenges to the detection of AI-generated content. Current mainstream zero-shot detection methods largely adopt a machine-centric perspective, relying on proxy models to compute token-level AI-likelihood scores and treating all tokens equally during overall detection. However, such approaches overlook the prediction discrepancies that arise when humans and large language models interpret the same text. We argue that tokens exhibiting greater divergence between human and machine predictions can provide stronger clues for determining the authorship of a text. To address this limitation, we propose HAPDA—a human-machine prediction discrepancy adapter for AI-generated text detection (AGTD). The framework consists of two core components: (1) a joint fine-tuning strategy for training paired human-preference and machine-preference models, and (2) a discrepancy-aware reweighting mechanism designed to calibrate token-level detection scores in downstream detectors. Extensive experiments demonstrate that HAPDA consistently and significantly enhances the detection performance of five representative baseline models under various evaluation scenarios.

Text generated by Large Language Models (LLMs) now rivals human writing, raising concerns about its misuse. However, mainstream AI-generated text detection (AGTD) methods primarily target document-level long texts and struggle to generalize effectively to sentence-level short texts. And current sentence-level AGTD (S-AGTD) research faces two significant limitations: (1) lack of a comprehensive evaluation on complex human-AI hybrid content, where human-written text (HWT) and AI-generated text (AGT) alternate irregularly, and (2) failure to incorporate contextual information, which serves as a crucial supplementary feature for identifying the origin of the detected sentence. Therefore, in our work, we propose AutoFill-Refine, a high-quality synthesis strategy for human-AI hybrid texts, and then construct a dedicated S-AGTD benchmark dataset. Besides, we introduce SenDetEX, a novel framework for sentence-level AI-generated text detection via style and context fusion. Extensive experiments demonstrate that SenDetEX significantly outperforms all baseline models in detection accuracy, while exhibiting remarkable transferability and robustness. Source code is available at https://github.com/TristoneJiang/SenDetEX.