CALLIOPE: Private Insights into AI Use, without Embeddings

We propose _CALLIOPE_, a top-down framework for discovering topic hierarchies in large corpora of unstructured data (e.g., LLM conversations), while supporting differential privacy (DP). Unlike traditional and even recent LLM-augmented approaches that ultimately rely on clustering vector embeddings, our framework leverages LLM capabilities directly for the entire pipeline. Experiments demonstrate that this approach provides better utility over existing (embedding-based) methods in the DP setting, especially in the high privacy regime. We evaluate the quality of _CALLIOPE_ outputs using a variety of traditionally studied clustering metrics, as well as some novel utility metrics that we introduce.