Blazor wasm standalone hot reload not working

[monkeyK1n9]

Description

After upgrading to the latest VS insiders version, hot reload does not work in my Blazor wasm standalone under .net 10 rc.
I get this error in the browser console:
logging.ts:129 [MONO] * Assertion at /__w/1/s/src/runtime/src/mono/mono/component/hot_reload.c:1037, condition `<disabled>' not met

In the Hot reload output view in VS insiders, I see this:
ManagedError: Applying deltas through the debugger and System.Reflection.Metadata.MetadataUpdater.ApplyUpdate simultaneously is not supported.

Just to make sure if it was related to my project, I created a new project, and I saw the same issue.
Note that, Roslyn server as preview feature is on.

I created another .NET 9 blazor wasm standalone project in VS2022 and hot reload works fine and I later used again this same project in VS insiders and hot reload does not work.
My launch settings in all these cases are the same as the template default.

Lastly, I noticed that:

• When running dotnet watch in the terminal, hot reload works fine in either of these projects
• When launching the app in VS Insiders without debugging, hot reload works fine (to see if disabling the debugger as the error above said could help)

Reproduction Steps

Create a blazor wasm standalone project in VS Insider with .net 10 preview and start the app with debugging on either profile.
The same happens in VSCode.

Expected behavior

Hot reload should work. This is alone the case when using dotnet watch, or running the app without debugging.

Actual behavior

Hot reload not working

Regression?

On .NET 9, when creating the new project, hot reload works, but not on .NET 10 rc.

Known Workarounds

Using dotnet watch in VS Insiders or running the app without debugging.

Configuration

.NET 10 SDK 10.0.100-rc.1

Processor Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz 2.59 GHz
Installed RAM 24.0 GB
Architecture x64

Browser Chrome

Other information

No response

[MihuBot]

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

• Hot reload - EnC: we do not support patching of existing PARAM table cols. token=0x08000d0e #93149
• Could not load file or assembly 'em_10 (Blazor hot reload) #93239

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.

[maraf]

@tmat Can you please take a look?

[tmat]

If the project targets net10.0 this should be fixed by dotnet/project-system#9811.
If the project targets net9.0 it's fixed by dotnet/aspnetcore#63979, which requires the WASM package reference to be updated to the latest 9.0.x version.

[monkeyK1n9]

With the recent release of .NET 10 rc2, and Visual studio insiders 2026, the issue is fixed.

Thanks for the big effort from the team