The difference between spec-first and plan-to-implementation is the same difference between what to build and how to build. Initial analysis with AI and specs should focus on what to build, not how to build.
In the engineering world, two things are really close. That’s why product thinking is required in agentic software development. Although AI shrinks the thinking from design to implementation, the design step comes first. If an engineer sees the AI’s design thinking while reading the code, it’s already too expensive. It’s also cognitively demanding.
If two engineers have a whiteboard session on the design, the code review becomes really easy. That’s what we should focus on: make agreements and disagreements visible as early as possible to avoid costly mistakes. In a brownfield project, this can include refactoring parts of the project, whereas greenfield projects are easier to design on the whiteboard.
