blazor.web.js not found after migrating Blazor server app to .Net 10

[vsfeedback]

This issue has been moved from a ticket on Developer Community.

---

[severity:I'm unable to use this version] [regression] [worked-in:2022 preview]
I switched the target framework from .Net 9 to .Net 10 in a working project and the project failed to start getting a 404 error for _framework/blazor.web.js. No NuGet updates found.

Note: I did the port to .Net 10 in a new branch and switching back to the .Net 9 branch gets the project working again.

---

Original Comments

Feedback Bot on 10/8/2025, 03:34 AM:

We have directed your feedback to the appropriate engineering team for further evaluation. The team will review the feedback and notify you about the next steps.

[MihuBot]

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

• [dotnet-sdk-10.0.100-preview.1.25110.2] Some blazor apps get "Failed to load resource: the server responded with a status of 404" error after retagrt to .NET 10 #60366

[javiercn]

Thanks for contacting us.

Have you updated the TFM and triggered a build or did you try to run the original app against a newer runtime?

If you built the app after the TFM, are there any razor files within your main project? Does setting <RequiresAspNetWebAssets>true</RequiresAspNetWebAssets> fix the issue?

[dotnet-policy-service]

Hi @@vsfeedback. We have added the "Needs: Author Feedback" label to this issue, which indicates that we have an open question for you before we can take further action. This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.