Code Agents Don’t Understand Root Cause:Evaluating Code Agents on Linux Kernel Fault Localization

Yuekeng Li, Ao Xu, Jie Shi, Sihang Jiang, Lipeng Ma, Bo Xu, Yanghua Xiao


Abstract
Code agents are increasingly used in debugging workflows, where fault localization (FL) is often evaluated as endpoint retrieval: whether a model names the faulty code location. This view is inadequate for Linux kernel debugging, where failure logs may expose downstream symptoms while the erroneous state is introduced earlier and propagates through various dependences. We introduce KernelPath, a 200-instance Linux 5.10 function-level FL benchmark that pairs each root cause function with a source-grounded state propagation path and a dependence layer. KernelPath evaluates both endpoint localization and ordered diagnostic process recovery. Experiments with SOTA agents show that agents often retrieve plausible candidates but remain unreliable at recovering the diagnostic process, with performance degrading sharply under complex dependence relations. Further diagnostic probes show that agents can use explicit state-transition evidence, yet fail to infer how functions affect the erroneous state, drifting toward neighboring objectives such as repair-site selection, or up stream suspicious function retrieval. These findings reveal an unstable task model for kernel FL in current code agents.
Anthology ID:
2026.emnlp-main.2201
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:
50033–50053
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2201/
DOI:
Bibkey:
Cite (ACL):
Yuekeng Li, Ao Xu, Jie Shi, Sihang Jiang, Lipeng Ma, Bo Xu, and Yanghua Xiao. 2026. Code Agents Don’t Understand Root Cause:Evaluating Code Agents on Linux Kernel Fault Localization. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 50033–50053, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Code Agents Don’t Understand Root Cause:Evaluating Code Agents on Linux Kernel Fault Localization (Li et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2201.pdf