PrefixGuard: From LLM-Agent Traces to Online Failure-Warning Monitors
PrefixGuard introduces a novel framework for monitoring LLM-agent execution in real-time by detecting failures before they occur through prefix analysis rather than post-hoc outcome checks. The system combines offline trace induction with supervised learning to achieve strong performance across multiple benchmarks, outperforming both raw-text baselines and direct LLM judging approaches.