If acceptance is the constraint, the engineering lives in the harness around the model, not in the model itself. Models commoditise; a better model raises generation, not acceptance. The harness is where differentiation sits: small reviewable problem scopes, feedforward context that sets an agent up to be right first time, and feedback controls — compilers, linters, type checkers, tests, evals — wired in as deterministic gates.
It is an emerging idea we are developing rather than a settled standard. Buying a smarter model does not close the acceptance-gap; building a better harness does.