User becomes undefined after refresh, preventing data fetching

The issue you're experiencing with the user becoming undefined after a page refresh or navigation in your Next.js 15 project using AWS Amplify Gen 2 is likely related to session management and how the authentication state is being maintained across page loads.

To address this problem and ensure the user stays authenticated across page reloads, consider the following approaches:

1. Session Management: Make sure you're properly managing the user session. In Amplify Gen 2, you can use the fetchAuthSession API to retrieve and refresh the user's session. This API automatically refreshes the user's session when the authentication tokens have expired and a valid refresh token is present.

2. Server-Side Session Handling: For Next.js server-side rendering, you need to handle authentication differently. Amplify offers specialized data clients for Next.js server runtimes. Depending on your setup, you can use either:

   • generateServerClientUsingCookies(): This uses the Next.js cookies function and dynamically refetches cookies at runtime for each API request.
   • generateServerClientUsingReqRes(): This requires NextRequest and NextResponse to be provided to an runWithAmplifyServerContext function to prevent token contamination.

3. Middleware Authentication Check: Implement middleware in your Next.js app to check the auth session using the fetchAuthSession API. This can help protect routes and ensure the user is authenticated before accessing certain pages.

4. Client-Side Configuration: Ensure that you're calling Amplify.configure(outputs) in your client-side code, typically in a component that wraps your entire application. This configuration is crucial for maintaining the authentication state.

5. API Route for Current User: Consider implementing an API route that enables GET /apis/get-current-user. When you call fetch('/apis/get-current-user'), it should return a payload containing the user data for the current signed-in user. This can be used to retrieve user information after page reloads.

6. Use Amplify's SSR Utilities: Utilize Amplify's server-side rendering utilities, such as runWithAmplifyServerContextRunner, to properly handle Amplify APIs in a server-side context.

By implementing these strategies, you should be able to maintain the user's authenticated state across page reloads and navigation, ensuring that user-related data can be fetched consistently throughout your application.

Remember to test thoroughly in different scenarios, including page refreshes, navigation between routes, and after periods of inactivity to ensure robust session management.

Sources
Manage user sessions - AWS Amplify Gen 2 Documentation
Next.js server runtime - React - AWS Amplify Gen 2 Documentation
Server-Side Rendering - JavaScript - AWS Amplify Gen 2 Documentation