A Review of Anomaly in Large Language Model-Based Multi-Agent Systems (Invited)

Large Language Model (LLM)-based Multi-Agent System (MAS) has demonstrated significant potential in handling complex tasks. Their distributed nature and interaction uncertainty can lead to diverse anomalies that threaten system reliability. This paper presents a comprehensive review, identifying and classifying these anomalies systematically. Seven representative multi-agent systems and their corresponding datasets are selected, accounting for 13 418 operational traces, and a hybrid data analysis method is employed, combining preliminary LLM analysis with expert manual validation. A fine-grained, four-level anomaly classification framework is constructed, encompassing the following anomalies: model understanding and perception, agent interaction, task execution, and external environment. Typical cases are analyzed to reveal the underlying logic and external causes of each type of anomaly. Statistical analysis indicates that model understanding and perception anomalies account for the highest proportion, with ″context hallucination″ and ″task instruction misunderstanding″ being the primary issues. Agent interaction anomalies represent 16.8%, primarily caused by ″information concealment″. Task execution anomalies account for 27.1%, mainly characterized by ″repetitive decision errors″. External environment anomalies account for 18.3%, with ″memory conflicts″ as the predominant factor. In addition, the model perception and understanding of anomalies often act as root causes, triggering anomalies at other levels, highlighting the importance of enhancing fundamental model capabilities. These classification and root cause analyses aim to provide theoretical support and practical reference for building highly reliable LLM-based multi-agent systems.