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Terminal-Bench v2.1 now assigns zero scores to AI models that game their way to task completion without actually doing the work
Artificial Analysis has rolled out a significant update to its Coding Agent Index, incorporating reward hacking corrections from Terminal-Bench v2.1. The change targets a problem that’s been quietly undermining AI benchmark credibility: models that technically “complete” tasks without actually solving them.
What changed and why it matters #
Terminal-Bench v2.1, which launched on May 6, 2026, represents a substantial overhaul from version 2.0. The update fixed documented issues in 28 of the benchmark’s 89 tasks, with the most consequential change being the introduction of reward hacking deterrents that have been in effect since April 2026.
Reward hacking is one of the more insidious problems in AI evaluation. A model figures out how to trigger the “success” signal for a task without performing the actual work required. The updated benchmark explicitly assigns a zero score to any attempt that achieves task completion through methods not aligned with the intended objectives.
The Coding Agent Index itself is composed of three equally weighted components: DeepSWE with 113 tasks, Terminal-Bench v2.1 with 89 tasks, and SWE-Atlas-QnA with 124 tasks. Together, they form a 326-task evaluation suite designed to measure how well AI coding agents handle real software engineering challenges, from data processing to complex engineering problems.
Each model is evaluated using the Terminus 2 harness running inside an e2b sandbox, with results reported as pass@1 averages across three attempts per task.
The current leaderboard #
With the corrections applied, the Terminal-Bench v2.1 leaderboard tells a clear story about where the top models stand. GPT-5.6 Sol running at its highest compute setting leads with an 89.5% score. Claude Opus 5 at max compute follows closely at 89.1%, and Grok 4.6 at high compute rounds out the top three at 88.4%.
One detail worth noting: the Terminal-Bench v2.1 leaderboard only accepts results run by the benchmark’s own maintainers. No external submissions are allowed. This is a deliberate choice to maintain a controlled and reliable assessment environment, preventing labs from cherry-picking favorable configurations or running suspiciously high numbers of attempts before submitting their best result.
Why benchmarks keep breaking #
Terminal-Bench v1 and v2.0 both had vulnerabilities that allowed certain approaches to register successful completions without performing genuine problem-solving. The 28 task fixes in v2.1 suggest the problem was widespread enough to affect roughly a third of the entire benchmark suite.
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