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About this paper

Siqi Yang, Qianlan Yang, Yu-Xiong Wang, Saurabh Pujar, Martin Hirzel

A study systematically explores how self-evolving harnesses improve coding agents, revealing that gains primarily compensate for execution defects rather than extending core capabilities. The research found that while abstract disciplinary concepts are portable, 20-40% of evolved harness content is ecosystem-specific, impacting transferability across different programming languages and models.

Key insights

  • Self-evolving harnesses primarily compensate for "harness-recoverable execution defects" (e.g., editing test files, shipping non-compiling code) rather than extending the base model's fundamental capabilities.
  • Evolved harnesses encode abstract disciplinary concepts that are moderately shared across languages, but their concrete ecosystem-specific instantiations are largely disjoint, with 20-40% of content being ecosystem-specific.
  • Gains from self-evolution were minimal in "null regions" (Python across models, GPT-5-mini across languages) where base models already exhibited few harness-recoverable defects.

Summary by alphaXiv.

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