Best practices for multi-screen state sharing in Circuit?

[easyhooon]

Hi! I'm working on a multi-screen registration flow and wondering about the best approach for sharing state across screens in Circuit.

Use Case

Screen A (Personal Info) → Screen B (Address) → Screen C (Verification) → Screen D (Complete)

Challenge

In Compose Navigation + AAC ViewModel, I've been using SharedViewModel to share state across screens. This provides:

// https://youtu.be/h61Wqy3qcKg?si=OqctoATR5MGbypOW
@Composable
inline fun <reified T : ViewModel> NavBackStackEntry.sharedViewModel(
    navController: NavHostController,
): T {
    val navGraphRoute = destination.parent?.route ?: return hiltViewModel()
    val parentEntry = remember(this) {
        navController.getBackStackEntry(navGraphRoute)
    }
    return hiltViewModel(parentEntry)
}

State preservation when navigating back/forth

No need to pass complex data through navigation arguments
Automatic lifecycle management

Question

What's the recommended Circuit pattern for this? Options I'm considering:

1. Navigation arguments - Navigation arguments - Passing complex data around becomes messy, and Screen B loses its data when you navigate A → B → A (since B gets recreated)

2. Shared repository/service - I don't think this is suitable for this use case (repositories are more for caching/persistence)

3. Custom shared presenter - Is this possible/recommended? - This is my main question! Is it possible to create a presenter that persists across multiple screens?"

Since Circuit Presenters are tied to specific Screens(UI), how do you handle multi-screen flows that need shared state?

Any guidance appreciated! Thanks! ⚡️

[stagg]

Think our best example for a common presenter is the tacos sample, we also cover a this in a bit more detail in the composite presenter issue #1801 (comment). That approach mostly comes down to how coordinated or isolated the presentation needs to be, and how ephemeral the state is.

For the outlined case I can still see a shared data layer handling the common state. With the screens sharing an identifier/session key of some sort that is used to retrieve and edit the state. The data layer (or business logic) can handle cleanup, memory/disk persistence etc. Some possible state restoration and testing advantages with that too.