Blazor Web App projects show Microsoft.AspNetCore.App.Internal.Assets in NuGet without explicit package reference

[marcominerva]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

After upgrading to Visual Studio 2026 v18.2.0 (and consequently .NET 10.0.2), both new and existing Blazor Web App projects show a NuGet package named Microsoft.AspNetCore.App.Internal.Assets:

This package appears in the NuGet package list even though there is no explicit package reference to it in the project’s .csproj file. It cannot be removed manually, but project builds and runs correctly.

Expected Behavior

Only explicitly referenced packages (or clearly documented implicit framework references) should appear in the NuGet package list.

.NET Version

10.0.102

[mikedepetris]

Thank you @marcominerva

[javiercn]

@marcominerva thanks for contacting us.

We switched the way blazor.web.js and blazor.server.js to avoid embedding them in the assembly as we used to. The SDK automatically adds the package implicitly in the same way we do for the webassembly runtime bits.

I'm not sure why it is showing up in the package references. @maraf do you have an idea of why this is the case and how to "hide it"?

[maraf]

It should be achieved by the IsImplicitlyDefined on PackageReference

https://github.com/dotnet/sdk/blob/main/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.FrameworkReferenceResolution.targets#L240-L242

I'll investigate why it doesn't apply for Microsoft.AspNetCore.App.Internal.Assets.

[tlevey01]

Hello, after upgrading from VS2022/.Net 8 to VS2026/.Net 10, my dependent project won't build because of error: ...MSB4018: System.ArgumentException: An item with the same key has already been added. (it also references blazor.web.js). I've removed all duplicate package references in the .csproj file, but I still see Microsoft.AspNetCore.App.Internal.Assets as a Top-Level Package for both projects. Is it causing this duplication error and if so, any ideas how to fix it? Thanks!

[maraf]

@tlevey01 Can you please extract a minimal reproduction repo? Alternative share a binlog from build dotnet build -bl. You can share it securely through https://developercommunity.visualstudio.com and add a link here.

[maraf]

"It is by design". Marking the package reference as "implicitly defined" removes it from Solution Explorer, but all of the implicitly defined packages (Microsoft.NET.ILLink.Tasks, Microsoft.NET.Sdk.WebAssembly.Pack and Microsoft.AspNetCore.App.Internal.Assets) are visible in Package Manager. It is the as with VS 2022 (first the first two packages mentioned)

[tlevey01]

@maraf, thanks for reaching out. Reproducing this issue is simple:

1. Create a new "Blazor Web App" (with or without authentication) using .Net 10 in Visual Studio 2026
2. Add another Blazor Web App to the solution

Both projects build and start fine, but

3. Add a Reference to the first project in the second project and the error above is generated and the second project won't build (the first one still builds)

In .Net 8 and 9, you get an error that the assets in the wwwroot folder are duplicated, but both projects build and run if you remove the duplicate files in one of the projects.

The problem file appears to be:

.nuget\packages\microsoft.aspnetcore.app.internal.assets\10.0.2_framework\blazor.web.js

[maraf]

Thank you for defaults.

I'm not sure if adding references between webapp projects is a supported scenario. What is your motivation to do so?

@javiercn Can you please provide clarity in this regard?

[tlevey01]

It's working fine in .Net 8 and 9 (however, you can no longer have duplicate files in the wwwroot folder). As for the reason, the apps primarily share services.