Jia Liufu

Repository-level software engineering agents previously treated each attempt's pass or fail as a terminal reward, discarding the failed patch and verifier feedback. FC-SWE restores the repository to its original task state after a patch fails verification, uses the failed patch and verifier diagnostics as context for a recovery trajectory, keeps each trajectory's own verifier outcome, and compares only the initial and recovery trajectories actually executed for the same issue. On all 500 SWE-bench Verified tasks with the same Qwen3.5-4B policy, first-attempt resolution rises from GRPO's 38.9% to 41.7% and two-attempt cumulative resolution from 48.5% to 52.8%; trained with at most two attempts per chain, the same policy reaches 70.7% with eleven test-time attempts.

Repository-level software engineering agents previously treated each attempt's pass or fail as a terminal reward, discarding the failed patch and verifier feedback. FC-SWE restores the repository to its original task state after a patch fails verification, uses the failed patch and verifier diagnostics as context for a recovery trajectory, keeps each trajectory's own verifier outcome, and compares only the initial and recovery trajectories actually executed for the same issue. On all 500 SWE-bench Verified tasks with the same Qwen3.5-4B policy, first-attempt resolution rises from GRPO's 38.9% to 41.7% and two-attempt cumulative resolution from 48.5% to 52.8%; trained with at most two attempts per chain, the same policy reaches 70.7% with eleven test-time attempts.