flutter-widget-local-state-heuristics

To separate ephemeral Flutter widget state from persistent module state, use setState only for transient UI toggles and visuals, while wrapping module-scoped state in a controller to coordinate non-UI data across widgets.

You should avoid using setState in a Flutter StatefulWidget when managing persistent, shared, or domain-related state, as this state belongs in a ModuleScope controller rather than leaking into presentation widgets.

The best way to manage module-scoped state in Flutter without state leakage is implementing a Controller + StreamValue approach, establishing strict boundaries that keep domain state out of presentation widgets.

Flutter module controller state disappears during widget rebuilds when domain state is incorrectly stored in the local widget using setState instead of being owned and persisted by the module controller.

No, you do not need a controller for every Flutter StatefulWidget with local UI state; setState is appropriate and recommended for ephemeral UI-only toggles and transient visuals that do not require module-level persistence.