SWE-ABS: Adversarial Benchmark Strengthening Exposes Inflated Success Rates on Test-based Benchmark

The SWE-Bench Verified leaderboard is approaching saturation, with the top system achieving 78.80%. However, we reveal that this performance is inflated: our re-evaluation demonstrates that one in five ``solved'' patches from the top-30 agents are semantically incorrect, passing only because weak test suites fail to expose their errors. We present SWE-ABS, an adversarial framework that strengthens test suites through a two-stage pipeline: (1) coverage-driven augmentation utilizing program slicing to target untested code regions, and (2) mutation-driven adversarial testing that synthesizes plausible-but-incorrect patches to expose semantic blind spots. On SWE-Bench Verified (500 instances), SWE-ABS strengthens 50.2% of instances (a $25.1\times$ improvement over prior work) and rejects 19.78% of previously passing patches. Consequently, the top agent's score decreases from 78.80% to 62.20%, causing significant leaderboard reshuffling (e.g., the top-ranked agent drops to 5th place).