SwiftUI view that pushes twice on iOS 18 b2

ContentView.swift

//
//  ContentView.swift
//  dev
//
//  Created by César Pinto Castillo on 2024-07-03.
//

import SwiftUI

struct ContentView: View {
    @State private var pathManager = PathManager()
    @State private var selectedTab: Tabs = .first

    var body: some View {
        TabView(selection: $selectedTab) {
            Tab("First", systemImage: "circle", value: .first) {
                NavigationStack(path: $pathManager.firstPath) {
                    NavigationLink(value: NavigationPath.third) {
                        Text("Open Third")
                    }
                    .navigationDestination()
                }
            }
            Tab("Second", systemImage: "square", value: .second) {
                NavigationStack(path: $pathManager.secondPath) {
                    NavigationLink(value: NavigationPath.fourth) {
                        Text("Open Fourth")
                    }
                    .navigationDestination()
                }
            }
        }
    }
}

enum Tabs {
    case first
    case second
}

enum NavigationPath {
    case third
    case fourth
}

extension View {
    func navigationDestination() -> some View {
        self.navigationDestination(for: NavigationPath.self) { path in
            switch path {
            case .fourth:
                Text("Fourth")
            case .third:
                Text("Third")
            }
        }
    }
}

@Observable
class PathManager {
    var firstPath: [NavigationPath] = []
    var secondPath: [NavigationPath] = []
}

#Preview {
    ContentView()
}

Check out my answer on Apple Dev Forums. It's a bug in iOS 18 and 18.0.1.