An error dialog `The server process is no longer running` pop ups when running the 11.0 Blazor WebAssembly Standalone App

[jinzhao1127]

REGRESSION INFO Work well on 11.0 Preview 4 and previous 11.0 Preview 5

INSTALL STEPS

1. Clean Win11 x64 25h2 ENU
2. Install the latest VS 18.8 Insider 1
3. Install 11.0 Preview 5
4. Apply feed

Platform

• Windows
• macOS
• Linux

Repro Steps

1. File > New Project > Blazor WebAssembly Standalone App, click Next > select ".NET 11.0" > Set Authentication type to None >Create
2. Debug project with F5/Ctrl + F5

Note

1. This issue does not repro on Blazor Web Server/WebAssembly app.
2. This issue does not repro on dotnet run.
3. This issue does not repro on 10.0/9.0/8.0 project
4. The project template changed by [Blazor] Replace DevServer with BlazorGateway for standalone WASM apps #65982, not sue if related with this change.

Actual Result
When running Blazor WebAssembly Standalone App, vs pop up an error dialog The server process is no longer running.

Console Log

A fatal error was encountered. The library 'hostpolicy.dll' required to execute the application was not found in 'C:\Users\v-zhajin\source\repos\BlazorApp6\BlazorApp6\bin\Debug\net11.0\'.
Failed to run as a self-contained app.
  - The application was run as a self-contained app because 'C:\Users\v-zhajin\source\repos\BlazorApp6\BlazorApp6\bin\Debug\net11.0\BlazorApp6.runtimeconfig.json' did not specify a framework.
  - If this should be a framework-dependent app, specify the appropriate framework in 'C:\Users\v-zhajin\source\repos\BlazorApp6\BlazorApp6\bin\Debug\net11.0\BlazorApp6.runtimeconfig.json'

[github-actions]

Triage Summary

Area: area-blazor (Issue affects Blazor WebAssembly Standalone App template and project execution in Visual Studio)

Type: Bug - The application fails to start when launched from Visual Studio due to missing hostpolicy.dll and incorrect runtimeconfig.json configuration.

Regression Info

• Previously working version: .NET 11.0 Preview 4 and earlier
• Broken since: .NET 11.0 Preview 5
• The error indicates the runtime is treating the app as self-contained when it should be framework-dependent. The runtimeconfig.json file is not specifying the framework reference, causing the runtime to look for hostpolicy.dll in the app directory instead of using the shared framework.

Potential Duplicates

None found. This appears to be a new regression specific to the Blazor WebAssembly Standalone App template changes in .NET 11.0 Preview 5.

Notes

• The issue only reproduces when running from Visual Studio (F5/Ctrl+F5), not with dotnet run
• Only affects Blazor WebAssembly Standalone App template (not Blazor Web Server/WebAssembly hybrid apps)
• The reporter suspects this may be related to PR [Blazor] Replace DevServer with BlazorGateway for standalone WASM apps #65982, which replaced DevServer with BlazorGateway for standalone WASM apps and was merged into 11.0-preview4 milestone
• The error message suggests the runtimeconfig.json is missing the framework reference, causing the runtime to attempt self-contained deployment without the necessary files
• This appears to be a Visual Studio project system or MSBuild target issue specific to how the Blazor WebAssembly Standalone template is configured

Generated by Issue Triage Agent for dotnet/aspnetcore for issue #66836 · ● 493.1K · ◷

[jinzhao1127]

@javiercn could you look at this issue?

[javiercn]

This is caused by VS not running the target (the CLI does it?) @baronfel do you know if this is the case or is the AI gaslighting me?

[baronfel]

@javiercn what target are you thinking of here? I don't see any mention of a binlog or msbuild invocation in the user report or AI analysis, so I don't know how to begin helping.

[EmilyFeng97]

This issue also repro when running the Blazor WebAssembly Standalone App in VS Code.