TraceProbe: An Execution-Based Benchmark for Diagnosing Safety Failures in LLM Agents

Yuxiang He, Jian Zhao, Yufei Liu, Yuchen Yuan, Xuelong Li


Abstract
Large language model (LLM) agents increasingly act through files, tools, memory, retrieved content, and other agents, which can trigger safety failures during execution. Existing benchmarks mostly focus on endpoint outcome evaluation or model-assisted moderation of pre-constructed trajectories, leaving limited evidence about where risks enter and how they propagate. To address this issue, we introduce TraceProbe, an execution-based benchmark for agent safety diagnosis. TraceProbe places agents in executable sandbox scenarios, scores endpoint and latent rule violations based on normalized traces and structured evidence, and replays recorded tool actions for step-level risk localization. Our benchmark contains 155 scenarios across three risk-source categories: non-adversarial failures, internal authority compromise, and external attacks. Across 12 contemporary LLMs, the mean attack success rate (ASR) is 0.347, indicating substantial residual risk, especially under internal authority compromise. Our analysis also demonstrates that endpoint-safe runs can contain unsafe intermediate actions, and the actual execution paths of agents may differ from the intended hazards of the testing scenarios. The TraceProbe benchmark and our findings support a more actionable form of agent safety evaluation: beyond assessing ASR or final outcomes, evaluators can also ask what went wrong, where it occurred, and where an intervention could be placed.
Anthology ID:
2026.emnlp-main.1233
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
28121–28140
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1233/
DOI:
Bibkey:
Cite (ACL):
Yuxiang He, Jian Zhao, Yufei Liu, Yuchen Yuan, and Xuelong Li. 2026. TraceProbe: An Execution-Based Benchmark for Diagnosing Safety Failures in LLM Agents. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 28121–28140, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
TraceProbe: An Execution-Based Benchmark for Diagnosing Safety Failures in LLM Agents (He et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1233.pdf