Historian: Reducing Manual Validation in APR Benchmarking via Evidence-Based Assessment

Abstract: Assessing the correctness of patches generated by Automated Program Repair (APR) is a major bottleneck. Manual validation is labor-intensive and limited: exact matching overlooks valid variants, while semantic inspection is subjective and hard to reproduce. Existing Automated Patch Correctness Assessment (APCA) often relies on opaque predictive models that treat each patch as novel, repeatedly re-assessing semantically redundant patches. Our analysis of a large corpus of tool-generated patches reveals a duality: about 39% of unique correct patches are syntactic clones, suggesting opportunities for automation, yet about 65% of bugs have multiple distinct correct fixes, making single-reference assessment insufficient. We present Historian, a framework that leverages LLMs to perform multi-reference comparisons against a knowledge base of historically validated patches, producing traceable, evidence-based verdicts while conservatively isolating novel cases as Unknown. In leave-one-tool-out evaluation, Historian achieves 95.0% coverage with 88.4% accuracy, reducing manual validation to 5% of patches. As an evidence-based pre-filter, enhancing the accuracy of standalone APCA tools by up to 21.8% and enabling a hybrid pipeline with 86.2% overall accuracy and 100% coverage. A longitudinal analysis of tool-generated patches (2020-2024) shows that redundancy in repair attempts is common, indicating that many patches repeatedly rediscover established ones and strengthening the sustainability of evidence-based APR assessment.