"Greenfield" codebases don't really exist anymore. Let me explain: I get asked a lot: "do your skills work on greenfield codebases?" or "do they work on legacy codebases?" Greenfield vs Brownfield is a distinction that has never really felt real to me. - Greenfield: you are building new software from scratch - Brownfield: you are editing existing software The truth is that the green field that we imagine when we start out a new project is an illusion. We are not spitting out software into an empty void. There are existing systems to integrate with. User preferences to work around. The only difference between Greenfield and Brownfield is the state of your repo. In a Greenfield project you haven't set up coding conventions. There is no prior art to work from. You have an opportunity to set up your agent's experience in that repo from scratch. But since code is being produced faster than ever before, how long does that codebase stay green? Two days? A week at most? All the fields are brown, and being churned up faster than ever. Your default posture should be "this is a legacy codebase", even if it's a week old.