K2

K² · Artificial intelligence

The benchmarks judging AI coding agents don't even agree with themselves

The paper audits three repository-level performance-optimization benchmarks (GSO, SWE-Perf, and SWE-fficiency) that evaluate coding agents by applying patches to real repositories and comparing runtime against unoptimized baselines and reference patches.

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Zhi Chen, Zhensu Sun, Yuling Shi et al.

5 authors · cs.SE, cs.AI

arXiv preprintArtificial intelligenceJul 2026 · ~75s read

The 30-second scan

Run the exact same "correct" answer twice, on two different computers, and it should pass both times.

  1. The authors argue that leaderboard scores can conflate runtime instability, benchmark-specific scoring rules, and how many tasks are already solved by at least one public submission.
  2. The study replayed official reference patches for 740 code optimization tasks across four common types of Google Cloud machines.
  3. Most benchmark tasks can be replayed, but reference patches satisfy the original benchmark validity rules in every cross-machine replay for only 39/102 GSO tasks, 11/140 SWE-Perf tasks, and 411/498 SWE-fficiency tasks.
740 code optimization tasks replayed across four types of Google Cloud machinesReference patches passed every cross-machine replay for only 39/102 GSO tasksReference patches passed every cross-machine replay for only 11/140 SWE-Perf tasks