Overview
The harness is more controllable than the model. A team cannot directly redesign the underlying model, but it can improve the codebase, instructions, tools, execution environment, and review process every day.
This makes harness work a durable source of advantage. Model improvements may raise the capability of every user at once. Harness improvements compound inside a particular workflow because they encode how that team plans, delegates, checks, and learns.
Harness-first thinking also reduces dependence on hype cycles. A newly released model may be better, but practical adoption still involves cost, latency, and availability. A team with a strong harness can evaluate the model as one replaceable component rather than reorganizing its entire practice around each release.