How to Protect Routes in Expo Router with Clerk

The guide provides a comprehensive walkthrough on how to secure routes in an Expo Router application using Clerk for authentication, focusing on both public and private routes, role-based access control, and feature-based authorization. It explains how to organize an app's route structure into (auth) and (app) groups, employing layout-level guards with Clerk's tokenCache and <ClerkProvider> to manage user authentication states. The document covers the use of Expo's Stack.Protected for declarative navigation, which simplifies the cleanup of navigation history when guards fail and offers an alternative method using useAuth() with <Redirect>. It also addresses common issues, such as the flash-of-wrong-screen problem during startup, by using SplashScreen.preventAutoHideAsync() and checking authentication states before rendering routes. The guide further details the implementation of sign-up and sign-in screens using Clerk's Core 3 API and highlights the importance of server-side validation for role-based access controls. Additionally, it explores the handling of deep links, ensuring users are redirected to the correct screens post-authentication, and advises on managing authentication state during app restarts with Clerk's tokenCache for persistence.