Page components from a Razor Class Library redirected to the NotFound page.

[wendellestradairely]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When navigating to routes provided by a Razor Class Library (RCL), the page initially loads correctly. However, after a few seconds, it automatically redirects to the NotFound page.

Details

Render mode: InteractiveAuto
Interactivity location: Global
Blazor type: Web App (Server + WebAssembly)

Issue scope: Only occurs for routes defined in a Razor Class Library. Routes in the main app work as expected.

Expected Behavior

The RCL route should remain stable and interactive without redirecting to the NotFound page.

Steps To Reproduce

1. Create a Razor Class Library (RCL) that defines one or more routable components (e.g., @page "/test").
2. Reference the RCL from the main Blazor Web App.
3. Configure the app to use InteractiveAuto render mode with Global interactivity.
4. Run the app and navigate to the RCL route (e.g., /test).

Observe that:

• The page loads correctly at first.
• After a few seconds, it redirects to the NotFound page automatically.

Exceptions (if any)

No response

.NET Version

.NET 10 rc1

Anything else?

No response

[MihuBot]

I'm a bot. Here is a possible related and/or duplicate issue (I may be wrong):

• New Blazor Web Application, navigate to the server project's component auto display "Not Found". #58480

[javiercn]

@wendellestradairely thanks for contacting us.

We have investigated the reported behavior, and we don't believe this is an issue in the framework but an issue in your app.

What we observed

When testing a Blazor Web App with InteractiveAuto render mode and Global interactivity, we found that routable components defined in a Razor Class Library (RCL) can fail to load properly, resulting in immediate 404 errors or redirects to the NotFound page. However, when the application is configured correctly according to the framework's requirements, the RCL routes work as expected.

Why this happens

Blazor Web Apps with InteractiveAuto render mode operate in a hybrid manner, using both static server-side rendering (SSR) initially and then transitioning to interactive Server or WebAssembly mode. This dual nature requires route discovery to be configured in two separate locations:

1. Server-side routing configuration - The MapRazorComponents call in Program.cs must include the RCL assembly via AddAdditionalAssemblies to enable static SSR to recognize routes from the library.

2. Client-side routing configuration - The <Router> component in Routes.razor must also specify the RCL assembly in its AdditionalAssemblies parameter to allow the interactive WebAssembly router to discover those routes.

If either configuration is missing, the routing system cannot properly locate the RCL components. When only the server-side configuration is present, the initial SSR may work but the interactive router fails to find the route after the WebAssembly runtime loads, causing the redirect to NotFound. When only the client-side configuration is present, the server returns a 404 before the interactive mode even activates.

Recommended approaches

To ensure RCL routes work correctly in a Blazor Web App with InteractiveAuto render mode, we recommend verifying both routing configurations are in place:

In your server project's Program.cs:

app.MapRazorComponents<App>()
    .AddInteractiveServerRenderMode()
    .AddInteractiveWebAssemblyRenderMode()
    .AddAdditionalAssemblies(typeof(RazorLibrary._Imports).Assembly);

In your client project's Routes.razor:

<Router AppAssembly="typeof(Program).Assembly" 
        AdditionalAssemblies="new[] { typeof(RazorLibrary._Imports).Assembly }"
        NotFoundPage="typeof(Pages.NotFound)">
    <Found>
        <RouteView RouteData="context" />
    </Found>
</Router>

Additionally, ensure that your client project has a direct project reference to the RCL, not just the server project, as the WebAssembly runtime needs access to the RCL's compiled assembly.

With these configurations in place, routes from the RCL should load correctly.

[facebundy]

@javiercn Thanks for the detailed explanation. I was actually trying to load the RCLs dynamically at runtime. That AdditionalAssemblies thing in the Routes.razor of the Client project is what I'm lacking. I did that config, and everything works perfectly fine now. Thank you so much!