Clean architecture in Flutter is the single biggest reason the production apps I ship stay maintainable after a year of feature churn. Over 4+ years building iOS and Android apps, I've watched "just put the logic in the widget" turn setState spaghetti into a codebase nobody wants to touch. This guide walks through how I actually split a Flutter app into domain , data , and presentation layers with BLoC — using one concrete feature so you can copy the structure into your own project today. ...