RepairGate: RL-Trained Skill Repair and Abstention for Lifelong Agent Libraries

Xiaoyu Chen, Fengge Wu, Junsuo Zhao, Yun Fan


Abstract
LLM agents increasingly rely on externalized skill libraries, yet existing maintainers typically delegate skill editing to a prompted LLM, leaving the question of how to train a skill maintainer open. We present RepairGate, a 9B drop-in wrapper around the standard candidate patcher: a counterfactually-trained post-trial gate accepts, blocks, or overrides each candidate patch, with a structured repair protocol for field-level edits and overlap-aware regularization to control library growth. Across six base agents on SkillFlow, RepairGate delivers +7.73 pp over Vanilla and +9.13 pp over prompted +Iter, with the largest gains on the weakest base agents where prompted iteration regresses, at a standardized 0.033/trial local overhead on top of the shared candidate-patching pipeline. Code and data: https://github.com/xxy33/RepairGate
Anthology ID:
2026.findings-emnlp.648
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
13610–13630
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.648/
DOI:
10.18653/2026.findings-emnlp.648
Bibkey:
Cite (ACL):
Xiaoyu Chen, Fengge Wu, Junsuo Zhao, and Yun Fan. 2026. RepairGate: RL-Trained Skill Repair and Abstention for Lifelong Agent Libraries. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 13610–13630, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
RepairGate: RL-Trained Skill Repair and Abstention for Lifelong Agent Libraries (Chen et al., Findings 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.findings-emnlp.648.pdf