ResearchResearch paperSafety & Alignment · Agents & Tool Use · Large Language Models1 source · Oct 20, 2026

A Mechanistic Study of Automated Failure Attribution in LLM-based Agentic Systems

Agentic systems have demonstrated strong capabilities on complex tasks by enabling multiple interacting large language model (LLM)-based agents to collaborate and execute subtasks in parallel.

Key points

  • However, this collaborative structure introduces new challenges for reliably evaluating and diagnosing system failures, particularly failure attribution: tracing a system's execution to identify the agent step responsible for an incorrect final outcome.
  • Using linear probes applied to internal activations, we uncover a significant knows-but-won't-say gap: models encode sufficient information to attribute a failure correctly but fail to explicitly output the responsible step.
  • Building on this finding, we propose grafting, a simple manual intervention that exploits knowledge already encoded in the model to improve AFA performance without requiring ground-truth labels at inference time.
  • Extensive evaluations across multiple LLMs and benchmark settings demonstrate that grafting consistently outperforms direct-prompting approaches, underscoring the potential of leveraging latent model knowledge for more reliable failure attribution.

Sources (1)

  • [1]A Mechanistic Study of Automated Failure Attribution in LLM-based Agentic Systems
    arXiv (AI, ML, NLP, CV, robotics, multi-agent) · Oct 20, 06:33 PM
    Agentic systems have demonstrated strong capabilities on complex tasks by enabling multiple interacting large language model (LLM)-based agents to collaborate and execute subtasks in parallel.
    However, this collaborative structure introduces new challenges for reliably evaluating and diagnosing system failures, particularly failure attribution: tracing a system's execution to identify the agent step responsible for an incorrect final outcome.

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