Basic.Reference.Assemblies / .NET 10 / Rider bug

Steps to Reproduce

1. JetBrains Rider (2025.3.0.1) (on macOS 26.0.1, untested on other operating systems)
2. .NET 10 SDK (10.0.100)
3. Package Locking Enabled (RestorePackagesWithLockFile)
4. Install Basic.Reference.Assemblies
5. dotnet restore --force-evaluate
6. dotnet build will work
7. Building in Rider will produce the following error:

Build with surface heuristics started at 20:03:33
Use build tool: /usr/local/share/dotnet/sdk/10.0.100/MSBuild.dll
CONSOLE: MSBuild version 18.0.2+b0f34d51f for .NET
CONSOLE: Build started 14/11/2025 20:03:33.
CONSOLE: Project "/var/folders/2z/xql84rkd37qfkqsb_1sxys440000gn/T/Luzoric.proj" on node 1 (default targets).
CONSOLE: ControllerTarget:
CONSOLE:   Run controller from /Users/steve/Applications/Rider.app/Contents/lib/ReSharperHost/JetBrains.Platform.MsBuildTask.v17.dll
0>------- Started building project: Dn10
0>Dn10.csproj: Error NU1101 : Unable to find package System.Collections.Immutable. No packages exist with this id in source(s): /usr/local/share/dotnet/library-packs, nuget.org
0>Dn10.csproj: Error NU1101 : Unable to find package System.Reflection.Metadata. No packages exist with this id in source(s): /usr/local/share/dotnet/library-packs, nuget.org
0>------- Finished building project: Dn10. Succeeded: False. Errors: 2. Warnings: 0
Build completed in 00:00:00.627