These three documents together drove the product, engineering, and design trifecta for PavingOS. The PRD defines the problem and the wedge. The engineering specs define how the system is built. The design contract defines how it has to feel and behave. Together they were the PRD, the engineering contract, and the agent prompt: one set of artifacts product, engineering, and AI coding agents could all execute against.
This was drafted in December 2025 and hasn't been changed since. Today I'd update the prompts, the information, and the requirements for each piece. I'm sharing the set as written, lightly cleaned only where needed for privacy.
The narrative case study of the build is First Contact. These pages are the underlying specs.
The three documents
Product Requirements (PRD) — The problem, ICP, jobs-to-be-done, and MVP wedge: estimating → job costing feedback loop for paving contractors.
Engineering Specs — System architecture, offline strategy, data model, APIs, security, and testing.
Design Contract — Experience laws and friction limits. How the product must feel and behave for field and office users, including AI coding agents.