[WebToolsE2E][Hot Reload] Hot Reload fails after "Start new Instance" in Blazor WASM with ENC2018 and "Assembly updates cannot be applied while a debugger is attached"

REGRESSION INFO: In C# Dev Kit May Prerelease 9 (3.29.195) this issue will be encounter instead 3417

INSTALL STEPS

1. OS: window x64
2. Install SDK 10.0.400
3. Install VS Code Insider - 1.135.0
4. Install May Prerelease 10 C# DK : 3.31.199
5. Install May Prerelease 10 C#: 2.149.34

REPRO STEPS

1. Make sure enable "[Experimental] Enables C# Hot Reload while debugging"
2. Open VS Code > Create .NET Project > Blazor Web App ~ Auto ~ Per page/component
3. Build project successfully.
4. Right click the csproj >debug >Start new Instance
5. Components > Change code from Home.razor h1 to:
   <h1>Hello, worldssss!</h1>
6. Trigger hot reload

Note:

• Repro in Auto + Per/Page Component
• Repro in Auto + Global
• Repro WASM + Per/Page Component
• Repro in WASM + Global
• Repro in Blazor WebAssembly Standalone App
• Not repro in Server + Per/Page Component
• Not repro in Server + Global
• Rerunning the project will still not work and will encounter the same issue

ACTUAL
A pop up warning will show that Hot Reload applied changes requires a full restart

Logs:

2026-07-31 10:24:48.535 [error]  C:\Users\v-jbolocon\Downloads\BlazorApp13\BlazorApp13\BlazorApp13\obj\Debug\net10.0\Microsoft.CodeAnalysis.Razor.Compiler\Microsoft.NET.Sdk.Razor.SourceGenerators.RazorSourceGenerator\Components/Pages/Home_razor.g.cs (line 1): error ENC2018: Changes made in project 'BlazorApp13' require restarting the application: `

After clicking "Rebuild and apply Changes" there will be a warning and Hot Reload does not work

2026-07-31 10:26:15.490 [info]  Hot Reload: Rebuild in progress
2026-07-31 10:26:20.132 [info]  Hot Reload: Rebuild completed
2026-07-31 10:26:20.150 [info]  Code changes were successfully applied.
2026-07-31 10:26:20.202 [info]  No code changes were found.
2026-07-31 10:26:38.448 [error]  BlazorApp13 (net10.0):2: The runtime failed to applying the change: Assembly updates cannot be applied while a debugger is attached.
2026-07-31 10:26:38.449 [warning]  BlazorApp13 (net10.0):2: Further changes won't be applied to this process.
2026-07-31 10:26:38.450 [warning]  BlazorApp13 (net10.0):2: Further changes won't be applied to this process.
2026-07-31 10:26:38.467 [info]  Code changes were successfully applied.

EXPECTED
Triggering hot reload will apply changes successfully without errors

Reproduce the issue with the listed SDK, VS Code Insider, C# Dev Kit, and C# extension versions using a Blazor WebAssembly project, then inspect the csproj debug Start new Instance path and the Home.razor edit. Compare the successful Server cases with the WASM cases and use the ENC2018 and debugger-attached logs as the failure criteria; done means hot reload applies the edit without requiring a restart or producing errors.