GEAR: Generalized Alternating Regressor for Multi-Behavior Sequential Recommendation

Modern recommender systems face a critical challenge in modeling the intricate interplay between multi-behavior interactions of users (e.g., clicks, adds-to-cart and purchases) and temporal dynamics that drive evolving preferences. While existing multi-behavior sequential recommendation methods attempt to capture these signals, they often suffer from fragmented modeling, such as decoupling behaviors and items into separate sequences, neglecting time-aware transitions, or relying on computationally intensive architectures that hinder real-world scalability. To address these limitations, we propose GEneralized Alternating Regressor (GEAR), a novel framework that unifies behaviors, items, and temporal contexts into a single autoregressive sequence through an alternating architecture. At its core, GEAR represents user interactions as triplets and processes them through a modular transformer architecture. In this architecture, each triplet is alternately modeled at lower layers to disentangle fine-grained patterns, while upper layers jointly learn cross-signal dependencies. This design mimics the interlocking mechanism of gears, enabling the seamless transitions between multi-behavior dynamics and item transitions. Additionally, we incorporate a time-bias term to quantify the decay of behavioral influence across both short- and long-term horizons. Extensive experiments on real-world datasets validate the effectiveness, generalizability, and computational efficiency of the proposed framework.