From Flat Logs to Causal Graphs: Hierarchical Failure Attribution for LLM-based Multi-Agent Systems

TL;DR

This work proposes CHIEF, a novel framework that transforms chaotic trajectories into a structured hierarchical causal graph and implements counterfactual attribution via a progressive causal screening strategy to rigorously distinguish true root causes from propagated symptoms.

Abstract

LLM-powered Multi-Agent Systems (MAS) have demonstrated remarkable capabilities in complex domains but suffer from inherent fragility and opaque failure mechanisms. Existing failure attribution methods, whether relying on direct prompting, costly replays, or supervised fine-tuning, typically treat execution logs as flat sequences. This linear perspective fails to disentangle the intricate causal links inherent to MAS, leading to weak observability and ambiguous responsibility boundaries. To address these challenges, we propose CHIEF, a novel framework that transforms chaotic trajectories into a structured hierarchical causal graph. It then employs hierarchical oracle-guided backtracking to efficiently prune the search space via sybthesized virtual oracles. Finally, it implements counterfactual attribution via a progressive causal screening strategy to rigorously distinguish true root causes from propagated symptoms. Experiments on Who&When benchmark show that CHIEF outperforms eight strong and state-of-the-art baselines on both agent- and step-level accuracy. Ablation studies further confirm the critical role of each proposed module.

Figures (13)

• Figure 1: A failure log induced by an unsatisfied constraint. Although the Orchestrator marking constraints (red, Step 14), the Websurfer overlooks these constraints during execution (Step 16).
• Figure 2: The overview of CHIEF.
• Figure 3: Knowledge Base construction description and formatting.
• Figure 4: Retrieved exemplars injected into the prompt
• Figure 5: Prompt for RAG-based task decomposition.