{"slug": "a-mechanistic-study-of-automated-failure-attribution-in-llm-based-agentic", "title": "A Mechanistic Study of Automated Failure Attribution in LLM-based Agentic Systems", "summary": "A new arXiv paper (2610.28811v1) reports that LLM judges used for automated failure attribution in multi-agent systems encode enough internal information to identify the failing step but fail to say it, a gap the authors call \"knows-but-won't-say.\" Using linear probes on internal activations, the authors identify this latent knowledge and propose \"grafting,\" a manual intervention that exploits it without ground-truth labels at inference time; they report grafting consistently outperforms direct prompting across multiple LLMs and benchmark settings. Code is available at github.com/wendyzheng22/mi4afa.", "body_md": "arXiv:2610.28811v1 Announce Type: new \nAbstract: 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. Because manually performing this task is time- and labor-intensive, recent work has turned to LLMs as judges to automate the process, referred to as automated failure attribution (AFA). These approaches assume that a sufficiently capable model can infer the failing step directly from an interaction transcript. In practice, however, direct prompting often performs poorly, which motivates follow-up work that explores various ways to improve AFA performance, including alternative prompting strategies and inference-time interventions. In this paper, we examine a more fundamental question: whether this weak behavioral performance reflects a genuine capability limitation. Using linear probes applied to internal activations, we uncover a significant \\emph{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 \\emph{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. Our code is available at https://github.com/wendyzheng22/mi4afa.", "url": "https://wpnews.pro/news/a-mechanistic-study-of-automated-failure-attribution-in-llm-based-agentic", "canonical_source": "https://arxiv.org/abs/2610.28811", "published_at": "2026-10-22 04:00:00+00:00", "updated_at": "2026-10-22 04:14:08.111000+00:00", "lang": "en", "topics": ["ai-agents", "large-language-models", "ai-research", "machine-learning"], "entities": ["arXiv", "wendyzheng22/mi4afa"], "also_reported_by": [], "alternates": {"html": "https://wpnews.pro/news/a-mechanistic-study-of-automated-failure-attribution-in-llm-based-agentic", "markdown": "https://wpnews.pro/news/a-mechanistic-study-of-automated-failure-attribution-in-llm-based-agentic.md", "text": "https://wpnews.pro/news/a-mechanistic-study-of-automated-failure-attribution-in-llm-based-agentic.txt", "jsonld": "https://wpnews.pro/news/a-mechanistic-study-of-automated-failure-attribution-in-llm-based-agentic.jsonld"}}