The rise of generative AI has led to challenges in distinguishing AI-generated text from human-written content, raising concerns about misinformation and content authenticity. Detecting AI-generated text remains challenging, especially under various stylistic domains and paraphrased inputs. We introduce SGG-ATD, a novel detection framework that models structural and contextual relationships between LLM-predicted and original-input text. By masking parts of the input and reconstructing them using a language model, we capture implicit coherence patterns. These are encoded in a graph where cosine and contextual links between keywords guide classification via a Graph Convolutional Network (GCN). SGG-ATD achieves strong performance across diverse datasets and shows resilience to adversarial rephrasing and out-of-distribution inputs, outperforming competitive baselines.