Self‑Evolving Harness Engineering Propels GPT‑5.4 to a 7‑Point Gain, Securing a Global Top‑3 Spot

The paper introduces Agentic Harness Engineering (AHE), an observability‑driven framework that automatically evolves coding‑agent harnesses, boosting GPT‑5.4's pass@1 score on Terminal‑Bench 2 from 69.7% to 77.0% (+7.3 points), achieving a worldwide top‑three ranking and demonstrating strong cross‑task and cross‑model generalization.

Agentic Harness EngineeringCross-Model GeneralizationGPT-5.4

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Self‑Evolving Harness Engineering Propels GPT‑5.4 to a 7‑Point Gain, Securing a Global Top‑3 Spot

Machine Learning Algorithms & Natural Language Processing

May 1, 2026 · Artificial Intelligence

Agentic Harness Engineering Enables Agents to Self‑Evolve and Outperform Codex in 10 Rounds

The Agentic Harness Engineering (AHE) framework lets coding agents automatically read massive execution traces, identify failure patterns, and iteratively modify harness components—prompt, tools, middleware, and memory—achieving a pass@1 increase from 69.7% to 77.0% and surpassing human‑tuned Codex‑CLI after ten automated evolution rounds.

Agentic Harness EngineeringBenchmarkingObservability

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Agentic Harness Engineering Enables Agents to Self‑Evolve and Outperform Codex in 10 Rounds