Blazor full-stack: server-only pages prerender before they 404, creating a jarring FOUC

[gulbanana]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Visiting the /Error page from a link displays the page for a second while prerending and then falls back to a Not Found. Here's a demo:

firefox_hqeNJA4AqM.mp4

Expected Behavior

The page should be built in a way that will work on both client and server.

Steps To Reproduce

1. Create a new Blazor Web App project with interactivity type Auto and interactivity location Global.
2. If using RC2 instead of RTM, move the Error page from client to server as described here Creating a new Blazor Web App NET8 RC2 with WebAssembly Interactivity creates broken Error.razor page in Client project #51352 (comment)
3. Add an <a href="/Error"> to the home page.
4. Run the app and click on the link.

Exceptions (if any)

No response

.NET Version

8.0.100-rc.2.23502.2

Anything else?

No response

[javiercn]

@gulbanana thanks for contacting us.

The error page is only meant to be there for handling error scenarios in SSR. We don't expect it to be used as a page that gets linked to from other locations in the app.

The behavior is a bit odd, but it's the best we can do today, since the page lives on the server but doesn't live on the client.

If in .NET 9.0 we pursue a unified project experience; this problem will logically go away.

Thanks for contacting us.

We're moving this issue to the .NET 9 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.