A Graph Foundation Model for Unified Clustering

Graph clustering is a fundamental task for understanding graph-structured data without labels, yet classical end-to-end methods require retraining on each dataset, limiting their generalization ability. Although Graph Foundation Models (GFMs) enable transferable learning across diverse graph tasks, they are not directly applicable to graph clustering. This limitation stems from two key factors: the inability to learn mutually beneficial knowledge on both the node and graph levels, and the lack of a completely unsupervised clustering-oriented design. To bridge this gap, we propose a Graph Foundation Model for Unified Clustering (GFM-UC), which pre-trains on the source domain and only requires fine-tuning for fast clustering in the target domain. The entire learning process does not require any labels. Specifically, in the pre-training stage, we select learnable high-confidence unified subgraph prototypes from the source domain. And then we generalize them to train the clustering network collaboratively. In the fine-tuning stage, we align the target domain with the source domain in a distribution-aware manner to further refine the clustering head and obtain more well-separated cluster boundaries. Extensive experiments on five datasets demonstrate that our method significantly outperforms existing state-of-the-art approaches.