Cannot reassign worldTracking / planeDetection providers in my PlacementManager when switching environments

Environment

Xcode: 16.2

VisionOS SDK 2.4

Swift 6.1

Targets: Apple Vision Pro (immersive space)

Frameworks: ARKit, RealityKit, SwiftUI

What I’m Trying to Do

I have a view-model class PlacementManager that holds two AR providers:

private var worldTracking: WorldTrackingProvider
private var planeDetection: PlaneDetectionProvider

I want to dynamically replace these providers in a setEnvironment(_:) method (so I can save/clear a JSON scene and restart ARKit).

What’s Happening

If I declare them as :

private let worldTracking = WorldTrackingProvider()
private let planeDetection = PlaneDetectionProvider()

I get compile-errors when I later do:

self.worldTracking = newWorldTracking // Cannot assign to property: 'worldTracking' is a 'let' constant

If I change them to un-initialized vars:

private var worldTracking: WorldTrackingProvider
private var planeDetection: PlaneDetectionProvider

then in my init() I get:

self used in property access 'worldTracking' before all stored properties are initialized

Code snipet

@Observable
final class PlacementManager : ObservableObject {
    private var worldTracking: WorldTrackingProvider
    private var planeDetection: PlaneDetectionProvider
    // … other props …
  
    @MainActor
    init() {
        // error: self.worldTracking used before init…
        planeAnchorHandler = PlaneAnchorHandler(rootEntity: root)
        persistenceManager = PersistenceManager(
          worldTracking: worldTracking,
          rootEntity: root
        )
        // …
    }

    @MainActor
    func setEnvironment(env: Environnement) async {
        let newWorldTracking  = WorldTrackingProvider()
        let newPlaneDetection = PlaneDetectionProvider()
        try await appState!.arkitSession.run(
          [ newWorldTracking, newPlaneDetection ]
        )
        self.worldTracking  = newWorldTracking
        self.planeDetection = newPlaneDetection
        // …
    }
}

What I’ve Tried

Giving them default values at declaration (= WorldTrackingProvider())

Initializing them at the top of init() before any use

Passing the new providers into arkitSession.run(...)

My Question

What is the recommended Swift-style pattern to declare and reassign these ARKit provider properties so that:

They’re fully initialized before use in init(), and

I can swap them out later in setEnvironment(...) without compiler errors?

Any pointers (or links to forum threads / docs) would be greatly appreciated!