Reproduce “StateM: Reaching 95.3% Raw Accuracy, or a \$15 Frontier Run, on Terminal-Bench 2.1 via Harness Scaling” on OpenResearch

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About this paper

Ziheng Qin, Yaxin Lu, Zhangyang Atlas Wang, Kai Wang

StateM introduces an agent-native control layer that significantly enhances the reliability of long-horizon CLI agents by managing execution states and procedural knowledge externally. The system achieved up to 95.28% raw accuracy on Terminal-Bench 2.1, an increase of 10.38 percentage points, and enabled a 1/11x reduction in total development and evaluation costs for comparable performance using a lower-cost model.

Key insights

  • Substantial performance gains in long-horizon agents can be achieved through "harness scaling"—improving the execution system—without modifying the underlying model weights.
  • An external, jointly editable control layer like StateM facilitates failure-driven optimization, allowing procedural knowledge to accumulate and persist, improving agent reliability over time.
  • The economic efficiency of agent deployment can be significantly improved, as lower-cost models can achieve high performance when paired with an effectively adapted harness.

Summary by alphaXiv.

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