Google open-sources Harness² research on recursive agent harness improvement
Google researchers introduced and open-sourced Harness², a system that modifies agent harness code, system prompts, tools, and skills during execution. It combines task-level proposal, probing, and composition with a persistent library of improvement experience, supporting OpenCode and Codex. The reported WorkBuddy-Bench results show GLM-5 improving from 64.2 to 75.7 with OpenCode after a single improvement step, exceeding the unmodified Gemini 3.5 Flash score of 72.4.
Why it matters
The reported comparison shows how harness changes can alter model rankings on the same benchmark, making execution setup a consequential variable when assessing agent performance.




