The Problem My team has recently discovered a problem in one of our macOS apps. It uses SwiftUI and Combine, as it still needs to support macOS 13. It uses a NavigationSplitView to display a sidebar-detail UI. On macOS 15, we started running into a bug: When selecting an item from the sidebar, the corresponding detail does not initially show up, and a detail page shows up only when selecting a second item from the sidebar. The following message would be printed into Xcode's console: Publishing changes from within view updates is not allowed, this will cause undefined behavior. This message would only get printed into the console, and would not be attached to any specific line. Oftentimes, selecting a subsequent item from the sidebar also either completely clears the detail page, doesn't do anything, and there was a crash reported as well. The app is compiled using Xcode 16.0. Architecture Overview The app uses NavigationSplitView with multiple different detail pages. .id is attached to the detail view in its corresponding NavigationLink, which used to properly show the corresponding detail page. The ID is stored in an observable AppState, which uses Combine's ObservableObject in the production app, and Observation's Observable in the minimal example. Example Code Minimal Reproductible Example You can see a minimal reproducible example here: https://github.com/buresdv/Navigation-Problems This example also features a debug field at the end of the sidebar, called "navigationSelection". When clicking one of the items, the ID gets correctly set, but the detail page does not update. Production App The production app is a bit more complex, but the core system is the same. For complete code, see: https://github.com/buresdv/Cork Some relevant lines include the navigation root, sidebar list, and the navigation links Notes We were able to reproduce these issues on multiple user systems This issue seems to have started occuring when we updated to macOS 15 At the same time, we updated the app to Strict Concurrency Checking and Swift 6, although we did not change anything in the navigation system