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CoreCLR+WebAssembly doesn't work on macOS #131799
Description
Description
Attempts to use CoreCLR+WebAssembly with .NET 11 Preview 6 fails on macOS. It works on Linux and Windows.
Reproduction Steps
Create a blazorwasm project and set $(UseMonoRuntime)=false:
dotnet new blazorwasm -o blazorwasm-testapp
cd blazorwasm-testapp
cat <<'EOF' | git apply
diff --git a/blazorwasm-testapp.csproj b/blazorwasm-testapp.csproj
index 0c0a2f8..2a47a07 100644
--- a/blazorwasm-testapp.csproj
+++ b/blazorwasm-testapp.csproj
@@ -6,6 +6,7 @@
<ImplicitUsings>enable</ImplicitUsings>
<OverrideHtmlAssetPlaceholders>true</OverrideHtmlAssetPlaceholders>
<StaticWebAssetSpaFallbackEnabled>true</StaticWebAssetSpaFallbackEnabled>
+ <UseMonoRuntime>false</UseMonoRuntime>
</PropertyGroup>
<ItemGroup>
EOFThen build and/or run the project:
dotnet build
Expected behavior
It builds!
This succesfully happens on both Windows and Linux.
# Windows
> dotnet build
Restore complete (0.2s)
info NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
blazorwasm-testapp net11.0 browser-wasm succeeded (0.9s) → bin\Debug\net11.0\wwwroot
Build succeeded in 1.4s# Linux
$ dotnet build
Restore complete (0.3s)
info NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
blazorwasm-testapp net11.0 browser-wasm succeeded (1.9s) → bin/Debug/net11.0/wwwroot
Build succeeded in 2.4sActual behavior
It does not build on macOS:
% dotnet build
Restore complete (0.2s)
info NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
blazorwasm-testapp net11.0 browser-wasm failed with 1 error(s) (0.2s)
…/dotnet-sdk-11.0.100-preview.6.26359.118/packs/Microsoft.NET.Runtime.WebAssembly.Sdk/11.0.0-preview.6.26359.118/Sdk/WasmApp.Common.targets(408,5): error Could not find JsonFilePath=$HOME/.nuget/packages/microsoft.netcore.app.runtime.browser-wasm/11.0.0-preview.6.26359.118/runtimes/browser-wasm/native/src/wasm-props.json
Build failed with 1 error(s) in 0.6s
Regression?
No. CoreCLR+WebAssembly is new to .NET 11.
Known Workarounds
No response
Configuration
No response
Other information
No response
Activity
jonpryor commentedon Aug 4, 2026
WasmApp.Common.targets(408,5)is:runtime/src/mono/wasm/build/WasmApp.Common.targets
Line 408 in b492b5e
Furthermore, the
<ReadWasmProps/>task is not mentioned in the binlog from the Linux build, nor isWasmApp.Common.targets!dotnet-policy-service commentedon Aug 4, 2026
Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.
jonpryor commentedon Aug 4, 2026
After chatting with @pavelsavara on Discord, we have determined that .NET 11 Preview 7 fixes things on macOS.
.NET 11 Preview 7: https://ci.dot.net/public/Sdk/11.0.100-preview.7.26381.103/dotnet-sdk-11.0.100-preview.7.26381.103-osx-arm64.tar.gz
Linked from: https://github.com/dotnet/dotnet/blob/main/docs/builds-table.md
Requires adding a
nuget.configwith the For .NET 11 builds contents: