7 Models, 3 Coding Harnesses: Native Harness Isn't Always Best and Costs Vary Widely
blaizedsouza · x · 2026-09-17
An evaluation of 7 models across Claude Code, Codex, and Pi harnesses surfaces 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, the impact of harness choice has remained unclear. LangChain founder Harrison Chase amplified the work, noting models may not actually benefit from a native harness—a useful signal for anyone picking an agent setup.
Related event: 7 Models × 3 Coding Harnesses: Harness Choice Drives Cost, Not Success(7 posts)→
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