Posted this on StackOverflow as well.

I'm working on a SwiftUI app using SwiftData for state management. I've encountered an issue with view updates when mutating a model. Here's a minimal example to illustrate the problem:

import SwiftUI
import SwiftData

// MARK: - Models

@Model
class A {
  @Relationship var bs: [B] = [B]()

  init(bs: [B]) {
    self.bs = bs
  }
}

@Model
class B {
  @Relationship var cs: [C] = [C]()

  init(cs: [C]) {
    self.cs = cs
  }
}

@Model
class C {
  var done: Bool

  init(done: Bool) {
    self.done = done
  }
}

// MARK: - Views

struct CView: View {
  var c: C

  var body: some View {
    @Bindable var c = c
    HStack {
      Toggle(isOn: $c.done, label: {
        Text("Done")
      })
    }
  }
}

struct BView: View {
  var b: B

  var body: some View {
    List(b.cs) { c in
      CView(c: c)
    }
  }
}

struct AView: View {
  var a: A

  var body: some View {
    List(a.bs) { b in
      NavigationLink {
          BView(b: b)
      } label: {
        Text("B \(b.cs.allSatisfy({ $0.done }).description)")
      }
    }
  }
}

struct ContentView: View {
  @Query private var aList: [A]

  var body: some View {
    NavigationStack {
      List(aList) { a in
        NavigationLink {
          AView(a: a)
        } label: {
          Text("A \(a.bs.allSatisfy({ $0.cs.allSatisfy({ $0.done }) }).description)")
        }
      }
    }
  }
}

@main
struct Minimal: App {
  var body: some Scene {
    WindowGroup {
      ContentView()
    }
  }
}

#Preview {
  let config = ModelConfiguration(isStoredInMemoryOnly: true)
  let container = try! ModelContainer(for: A.self, configurations: config)

  var c = C(done: false)
  container.mainContext.insert(c)
  var b = B(cs: [c])
  container.mainContext.insert(b)
  var a = A(bs: [b])
  container.mainContext.insert(a)

  return ContentView()
    .modelContainer(container)
}

In this setup, I have a CView where I toggle the state of a model C. After toggling C and navigating back, the grandparent view AView does not reflect the updated state (it still shows false instead of true). However, if I navigate back to the root ContentView and then go to AView, the status is updated correctly.

Why doesn't AView update immediately after mutating C in CView, but updates correctly when navigating back to the root ContentView? I expected the grandparent view to reflect the changes immediately as per SwiftData's observation mechanism.

I also recorded a gif of the flow: imgur.com/a/d6SwJSD