Greenfield is where AI looks the best in a sales call. A prompt becomes a working prototype in an afternoon. The slide deck writes itself. The hard parts — load testing, idempotent migrations, secrets management, the fourth alert at 3am — are invisible at the prototype stage, which is exactly where most projects sign off on AI as the delivery model.
What follows is predictable. UAT exposes the half of the requirements the agent never inferred. Security review exposes the half of the architecture nobody owned. The cutover slips. Engineers get pulled in to repair a system they didn't help design. The original timeline survives only as a footnote in the post-mortem.
The honest version of greenfield delivery uses AI heavily — and constrains it harder. PlanTrace makes every plan item answer to the PRD. ArchTrace makes every change answer to the architecture. Senior engineers own the parts AI shouldn't. The result is software that ships in weeks and runs on a Tuesday.