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billbyrnes's avatar
billbyrnes
Copper Contributor
Oct 16, 2026

Blazor App No Longer Compiles

I just updated MS Visual Studio 2022 Community Edition to version 18.11.0. After the update, Blazor apps no longer compile in for the release version, they still work for the debug version of the project. This is true with existing projects and new Blazor App projects created with C#. I get this error message:

=====================

10/16/2026 4:16:12 AM

Project: BillByrnes.csproj

Recoverable

System.AggregateException: One or more errors occurred.

---> (Inner Exception #0) Microsoft.Assumes+InternalErrorException: No pending webSession for web server 1

at Microsoft.Assumes.Fail(String message)

at Microsoft.WebTools.ProjectSystem.HotReload.WebHotReloadAgent.StartSession(IWebServer webServer)

at Microsoft.WebTools.ProjectSystem.Debugger.BaseDebugTargetsProvider.<OnAfterLaunchAsync>d__84.MoveNext()

<--- (Inner Exception #0)

===================

Any help would be appreciated.

Thanks,

Bill Byrnes

email address removed for privacy reasons

visual studio

1 Reply

  • Jamony's avatar
    Jamony
    MCT
    Oct 16, 2026

    The stack trace is from Hot Reload session startup, so first separate a Release compilation failure from an IDE launch failure. From the project directory, run dotnet build --configuration Release and capture its output. If that succeeds, the compiler can build Release and the next investigation should focus on Visual Studio's launch tooling. Disable Hot Reload temporarily in its settings, or set hotReloadEnabled to false in the relevant launchSettings.json profile, then retry the same launch. Microsoft documents that profile setting; this is an isolation test, not a confirmed fix for your exception. If the command-line build fails too, investigate its first actual build error instead. Also copy the complete product and version information from Help, About, since the stated product name and version need clarification. Report the issue with your minimal new-project reproduction, target framework, SDK version and both test results.