Testing 7 models across Claude Code, Codex and Pi: native harness isn't always best
CShorten30 · x · 2026-09-17
An evaluation ran 7 models inside Claude Code, Codex and Pi, with three surprising findings:
- Harness choice has little effect on task success rate but can significantly affect cost.
- A simple harness can be competitive.
- The native harness isn't always the best.
With millions using coding agents, harness selection is an overlooked variable; the authors argue "harness-routing" deserves attention.
Related event: 7 Models × 3 Coding Harnesses: Harness Choice Drives Cost, Not Success(7 posts)→
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