This comment is misleading. You're not preserving the state, but you're forcing the destruction of the widgets (and recreation) when the ValueKey changes.

Since we always have that information available, I'd make that parameter mandatory. It would help to avoid further surprises.

If I understand correctly the documentation it will not recreate the widget if what you mean by widget is the underlying element. If I had kept the keys in the CountdownBuilder I agree that the underlying element would have been recreated which is why I moved it in the AnalysisLayout. I believe that thanks to the local key, it will simply call update on the element to update the widget configuration.

Since we always have that information available, I'd make that parameter mandatory. It would help to avoid further surprises.

I didn't want to force this parameter as it is only useful when there is a board footer or header. Should I still make it mandatory and keep only the first line of the doc comment to not make it confusing ?

I got it. But there is no harm making it mandatory as we have the data ready and it's not used in a lot of places. Also it is future proof, in case we'll use stateful widgets in other screens than broadcast.

I made the pov parameter mandatory and added comments where we use a key to explain why it is needed