CutMaster: Towards Agentic Hour-Scale Video Editing

Transforming an hour-scale source video into a short montage conditioned on background music, a user request, and a target duration requires balancing narrative alignment, emotional pacing, and visual quality. Existing agentic editing systems often organize decisions by processing stage or tool, leaving dependencies among these objectives implicit and resulting in suboptimal visual selection. We present **CutMaster**, an objective-factorized, stateful, and verification-driven agentic workflow built around a six-role team. A request-independent material analyst constructs reusable material memory, after which five request-conditioned roles coordinate their decisions through a shared editorial state. Music-aligned slots capture emotional pacing, story anchors provide narrative grounding, and a visually validated candidate space supports beam-search-based composition. Bounded replanning repairs intermediate states when earlier decisions become infeasible. We further introduce MontageX-Bench, a 40-task benchmark spanning four editing intents and three source domains. Compared with five recent state-of-the-art baselines, CutMaster achieves a Quality score of 81.40, outperforming the strongest baseline at 75.55, while providing the best overall balance across narrative, pacing, and visual-quality metrics.