LogMoE: Lightweight Expert Mixture for Cross-System Log Anomaly Detection

Robust anomaly detection in system logs plays a crucial role in maintaining stable and reliable software operations. However, existing methods often struggle to accommodate evolving log formats and distributional shifts across systems, as they heavily rely on large volumes of labeled data, log parsing, and predefined event templates. To address these challenges, we propose LogMoE, a scalable and parsing-free log anomaly detection framework. LogMoE utilizes labeled logs from multiple mature systems to train a set of lightweight expert models, which are integrated via a gating mechanism within a Mixture-of-Experts (MoE) architecture. This design enables LogMoE to generalize effectively to previously unseen target systems. By eliminating the need for log parsing, our approach remains robust against the heterogeneity of log formats and syntactic structures. We conduct extensive evaluations on eight log datasets under varying generalization scenarios: single-system, homogeneous-system, and heterogeneous-system. Experimental results demonstrate that LogMoE consistently achieves robust generalization, particularly under conditions with scarce labeled data in the target system. As such, LogMoE provides a scalable, parsing-free, and generalization-capable solution tailored for complex and continuously evolving software system environments, positioning it as a future-ready approach to log anomaly detection.