HAFixAgent: History-Aware Automated Program Repair Agent
Authors: name: Yu Shi, name: Hao Li, name: Bram Adams, name: Ahmed E. Hassan

Automated program repair (APR) has recently shifted toward large language
models and agent-based systems, yet most systems rely on local snapshot
context, overlooking repository history. Prior work shows that repository
history helps repair single-line bugs, since the last commit touching the buggy
line is often the bug-introducing one. In this paper, we investigate whether
repository history can also improve agentic APR systems at scale, especially
for complex multi-hunk bugs. We present HAFixAgent, a History-Aware Bug-Fixing
Agent that injects blame-derived repository heuristics into its repair loop. A
preliminary study of all 854 real-world bugs from Defects4J motivates our
design, showing that bug-relevant history is both widely available and highly
concentrated. Empirical comparison of HAFixAgent with two state-of-the-art
baselines shows: (1) Effectiveness: HAFixAgent significantly improves over the
agent-based baseline (by 212.3%) and the multi-hunk baseline (by 29.9%). (2)
Efficiency: history does not significantly increase agent steps and keeps token
costs comparable, with notably lower median costs for complex
multi-file-multi-hunk bugs. (3) Practicality: combining different historical
heuristics repairs more bugs, offering a clear cost-benefit trade-off.
HAFixAgent offers a practical recipe for history-aware agentic APR: ground the
agent in version control history, prioritize diff-based historical context, and
integrate complementary heuristics when needed.