diff --git a/eng/pipelines/templates/stages/vmr-build.yml b/eng/pipelines/templates/stages/vmr-build.yml
index bdede627acf5..f5ba03ffc93b 100644
--- a/eng/pipelines/templates/stages/vmr-build.yml
+++ b/eng/pipelines/templates/stages/vmr-build.yml
@@ -379,7 +379,7 @@ stages:
         vmrBranch: ${{ variables.VmrBranch }}
         pool: ${{ parameters.pool_Windows }}
         targetOS: windows
-        targetArchitecture: x64
+        targetArchitecture: x86
         useDevVersions: true # Use dev versions for CI validation of the experience.
         runTests: false # Temporarily do not run tests. The nuget comparison fails for some non-obvious reason and needs further investigation. Mostly, I'm not sure why it ever passed. https://github.com/dotnet/sdk/issues/42920
 
diff --git a/src/SourceBuild/content/repo-projects/Directory.Build.props b/src/SourceBuild/content/repo-projects/Directory.Build.props
index 6d200e0e2799..8f134097e901 100644
--- a/src/SourceBuild/content/repo-projects/Directory.Build.props
+++ b/src/SourceBuild/content/repo-projects/Directory.Build.props
@@ -81,6 +81,9 @@
     <!-- Indicate that the build is being run from the orchestrator -->
     <BuildArgs>$(BuildArgs) /p:DotNetBuildOrchestrator=true</BuildArgs>
 
+    <!-- Pass down configuration properties -->
+    <BuildArgs>$(BuildArgs) /p:TargetRid=$(TargetRid)</BuildArgs>
+
     <!-- Pass through DotNetBuildPass for join point vertical support. -->
     <BuildArgs Condition="'$(DotNetBuildPass)' != '' and '$(DotNetBuildPass)' != '1'">$(BuildArgs) /p:DotNetBuildPass=$(DotNetBuildPass)</BuildArgs>
 
diff --git a/src/SourceBuild/content/repo-projects/Directory.Build.targets b/src/SourceBuild/content/repo-projects/Directory.Build.targets
index c554a1082169..c6e5077c20e6 100644
--- a/src/SourceBuild/content/repo-projects/Directory.Build.targets
+++ b/src/SourceBuild/content/repo-projects/Directory.Build.targets
@@ -37,8 +37,6 @@
   </PropertyGroup>
 
   <PropertyGroup>
-    <BuildCommand Condition="'$(BuildCommand)' == '' and '$(IsUtilityProject)' != 'true'">$(BuildScript) $(BuildActions) $(BuildArgs)</BuildCommand>
-
     <!-- MinimalConsoleLogOutput determines if the repository build should be logged to a separate file or directly to the console.
          Enable it by default as with prallel repository builds the log becomes non-readable. -->
     <RepoConsoleLogFile>$(ArtifactsLogRepoDir)$(RepositoryName).log</RepoConsoleLogFile>
@@ -449,6 +447,20 @@
     </ItemGroup>
   </Target>
 
+  <Target Name="SetBuildProperties"
+          DependsOnTargets="GetTransitiveRepositoryReferences">
+    <PropertyGroup>
+      <!-- Infer the projects runtime identifier as the vertical's RID when doing a vertical build
+           and filter down RID lists to the target RID in such a scenario. This is necessary when the host (SDK) rid
+           is different from the target rid, i.e. when building win-x86 with a win-x64 SDK but only when consuming
+           live runtime. Exclude from source-only builds which don't use the portable RID format which causes the
+           ProcessFrameworkReferences not be able to restore for the given RID.  -->
+      <BuildArgs Condition="'$(DotNetBuildSourceOnly)' != 'true' and '@(TransitiveRepositoryReference->AnyHaveMetadataValue('Identity', 'runtime'))' == 'true'">$(BuildArgs) /p:DotNetBuildTargetRidOnly=true</BuildArgs>
+
+      <BuildCommand Condition="'$(BuildCommand)' == '' and '$(IsUtilityProject)' != 'true'">$(BuildScript) $(BuildActions) $(BuildArgs)</BuildCommand>
+    </PropertyGroup>
+  </Target>
+
   <Target Name="RepoBuild"
           Inputs="$(MSBuildProjectFullPath)"
           Outputs="$(BaseIntermediateOutputPath)Build.complete"
@@ -460,7 +472,8 @@
                             UpdateEngCommonFiles;
                             CreateBuildInputProps;
                             DiscoverBuiltSdkOverrides;
-                            SetSourceBuiltSdkOverrides">
+                            SetSourceBuiltSdkOverrides;
+                            SetBuildProperties">
     <Message Importance="High" Text="[$([System.DateTime]::Now.ToString('HH:mm:ss.ff'))] Building $(RepositoryName)" />
     <Message Importance="High" Text="Running command:" />
     <Message Importance="High" Text="  $(BuildCommand)" />
@@ -734,6 +747,7 @@
   <Target Name="Build"
           DependsOnTargets="
     BuildRepoReferences;
+    SetBuildProperties;
     RepoBuild;
     LogRepoArtifacts;
     CopyInnerBuildRestoredPackages;
diff --git a/src/SourceBuild/content/repo-projects/razor.proj b/src/SourceBuild/content/repo-projects/razor.proj
index cdd00ec7c5b1..b587cd61786a 100644
--- a/src/SourceBuild/content/repo-projects/razor.proj
+++ b/src/SourceBuild/content/repo-projects/razor.proj
@@ -4,8 +4,6 @@
     <!-- The toolset compiler doesn't get killed with 'build-server shutdown'.
          Instead of disabling shared compilation, disable the toolset compiler package. -->
     <BuildArgs>$(BuildArgs) /p:UsingToolMicrosoftNetCompilers=false</BuildArgs>
-    <!-- Pass down the target RID so we can create the correct apphost for the language servers. -->
-    <BuildArgs>$(BuildArgs) /p:TargetRid=$(TargetRid)</BuildArgs>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/src/SourceBuild/content/repo-projects/roslyn.proj b/src/SourceBuild/content/repo-projects/roslyn.proj
index 36a0b85db7e3..809fee03b12b 100644
--- a/src/SourceBuild/content/repo-projects/roslyn.proj
+++ b/src/SourceBuild/content/repo-projects/roslyn.proj
@@ -12,6 +12,7 @@
     <!-- Use the repo root build script -->
     <BuildScript>$(ProjectDirectory)build$(ShellExtension)</BuildScript>
   </PropertyGroup>
+
   <PropertyGroup Condition="'$(BuildOS)' == 'windows' and '$(UseOfficialBuildVersioning)' != 'false'">
     <BuildArgs>$(BuildArgs) $(FlagParameterPrefix)officialBuildId $(OfficialBuildId)</BuildArgs>
     <BuildArgs>$(BuildArgs) $(FlagParameterPrefix)officialSkipTests true</BuildArgs>
@@ -19,8 +20,8 @@
     <BuildArgs>$(BuildArgs) $(FlagParameterPrefix)officialSourceBranchName placeholder</BuildArgs>
     <BuildArgs>$(BuildArgs) $(FlagParameterPrefix)officialVisualStudioDropAccessToken placeholder</BuildArgs>
   </PropertyGroup>
+
   <PropertyGroup>
-    <BuildArgs Condition="'$(DotNetBuildSourceOnly)' != 'true'">$(BuildArgs) /p:TargetRid=$(TargetRid)</BuildArgs>
     <BuildArgs>$(BuildArgs) /p:TreatWarningsAsErrors=false</BuildArgs>
     <BuildArgs>$(BuildArgs) /p:ApplyPartialNgenOptimization=false</BuildArgs>
     <BuildArgs>$(BuildArgs) /p:EnablePartialNgenOptimization=false</BuildArgs>
diff --git a/src/SourceBuild/content/repo-projects/runtime.proj b/src/SourceBuild/content/repo-projects/runtime.proj
index 5c187068e132..d1e2e17126ef 100644
--- a/src/SourceBuild/content/repo-projects/runtime.proj
+++ b/src/SourceBuild/content/repo-projects/runtime.proj
@@ -8,7 +8,6 @@
 
     <BuildArgs>$(BuildArgs) $(FlagParameterPrefix)arch $(TargetArchitecture)</BuildArgs>
     <BuildArgs>$(BuildArgs) $(FlagParameterPrefix)os $(TargetOS)</BuildArgs>
-    <BuildArgs>$(BuildArgs) /p:TargetRid=$(TargetRid)</BuildArgs>
     <BuildArgs Condition="'$(DotNetBuildRuntimeWasmEnableThreads)' == 'true'">$(BuildArgs) /p:DotNetBuildRuntimeWasmEnableThreads=true</BuildArgs>
     <BuildArgs Condition="'$(DotNetBuildRuntimeNativeAOTRuntimePack)' == 'true'">$(BuildArgs) /p:DotNetBuildRuntimeNativeAOTRuntimePack=true</BuildArgs>
     <BuildArgs Condition="'$(DotNetBuildMonoEnableLLVM)' != ''">$(BuildArgs) /p:DotNetBuildMonoEnableLLVM=$(DotNetBuildMonoEnableLLVM)</BuildArgs>
diff --git a/src/SourceBuild/content/repo-projects/sdk.proj b/src/SourceBuild/content/repo-projects/sdk.proj
index 7f34a2f370f9..f5f7cc67e817 100644
--- a/src/SourceBuild/content/repo-projects/sdk.proj
+++ b/src/SourceBuild/content/repo-projects/sdk.proj
@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.Build.NoTargets">
+<Project Sdk="Microsoft.Build.NoTargets">
 
   <PropertyGroup>
     <LogVerbosityOptOut>true</LogVerbosityOptOut>
@@ -6,7 +6,6 @@
     <BuildArgs Condition="'$(TargetOS)' == 'windows'">$(BuildArgs) -nativeToolsOnMachine</BuildArgs>
     <BuildArgs>$(BuildArgs) /p:PackageProjectUrl=https://github.com/dotnet/sdk</BuildArgs>
     <BuildArgs>$(BuildArgs) /p:PortableRid=$(PortableRid)</BuildArgs>
-    <BuildArgs>$(BuildArgs) /p:TargetRid=$(TargetRid)</BuildArgs>
 
     <BuildArgs>$(BuildArgs) $(FlagParameterPrefix)v $(LogVerbosity)</BuildArgs>
 
diff --git a/src/SourceBuild/patches/arcade/0001-set-rid-for-project-for-live-runtime.patch b/src/SourceBuild/patches/arcade/0001-set-rid-for-project-for-live-runtime.patch
new file mode 100644
index 000000000000..54d57dab139a
--- /dev/null
+++ b/src/SourceBuild/patches/arcade/0001-set-rid-for-project-for-live-runtime.patch
@@ -0,0 +1,150 @@
+From 0b326d7d0d266808c6109282c6417d26835ef648 Mon Sep 17 00:00:00 2001
+From: Jeremy Koritzinsky <jekoritz@microsoft.com>
+Date: Thu, 2 Jan 2025 12:19:02 -0800
+Subject: [PATCH] Infer the projects runtime identifier as the vertical's RID
+ when doing a vertical build and filter down RID lists to the target RID in
+ such a scenario.
+
+Backport: https://github.com/dotnet/arcade/pull/15371
+
+---
+ .../UnifiedBuild/Unified-Build-Controls.md    |  1 +
+ .../tools/BeforeNETSdkTargets.targets         |  4 +
+ ...ifierInference.BeforeNETSdkTargets.targets | 79 +++++++++++++++++++
+ .../tools/Settings.props                      |  1 +
+ .../SourceBuildArcadeBuild.targets            |  1 +
+ 5 files changed, 86 insertions(+)
+ create mode 100644 src/Microsoft.DotNet.Arcade.Sdk/tools/BeforeNETSdkTargets.targets
+ create mode 100644 src/Microsoft.DotNet.Arcade.Sdk/tools/RuntimeIdentifierInference.BeforeNETSdkTargets.targets
+
+diff --git a/Documentation/UnifiedBuild/Unified-Build-Controls.md b/Documentation/UnifiedBuild/Unified-Build-Controls.md
+index 809d94443..872e14167 100644
+--- a/Documentation/UnifiedBuild/Unified-Build-Controls.md
++++ b/Documentation/UnifiedBuild/Unified-Build-Controls.md
+@@ -135,6 +135,7 @@ These controls may be used for **infrastructure or product purposes**.
+ | -------- | -------- | -------- | -------- |
+ | DotNetBuildWithOnlineSources | "true", "false", "" | "false" by default when `SourceOnly` switch is active. | When "true", do not remove non-local input sources. Infrastructure switch only. This switch is only exposed at the orchestrator level.</br>This replaces the existing `DotNetBuildOffline` switch. |
+ | DotNetBuildSourceOnly | "true", "false", "" | "" | When "true", build only from source. Online sources may remain unless `DotNetBuildOffline` is set to true. This is both an infrastructure and a product switch.<br/>This is roughly equivalent to `DotNetBuildFromSource` in the current infrastructure, though other controls may be better suited. |
++| DotNetBuildTargetRidOnly | "true", "false", "" | "" | When not set, defaults to "true" if the repository build transitively depends on dotnet/runtime and `DotNetBuildOrchestrator` == "true"; otherwise "false". When "true", builds projects for the current `TargetRid` instead of using the current runtime identifier. |
+ 
+ ### Output Controls
+ 
+diff --git a/src/Microsoft.DotNet.Arcade.Sdk/tools/BeforeNETSdkTargets.targets b/src/Microsoft.DotNet.Arcade.Sdk/tools/BeforeNETSdkTargets.targets
+new file mode 100644
+index 000000000..84b2020b6
+--- /dev/null
++++ b/src/Microsoft.DotNet.Arcade.Sdk/tools/BeforeNETSdkTargets.targets
+@@ -0,0 +1,4 @@
++<!-- Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. -->
++<Project>
++  <Import Project="RuntimeIdentifierInference.BeforeNETSdkTargets.targets" />
++</Project>
+diff --git a/src/Microsoft.DotNet.Arcade.Sdk/tools/RuntimeIdentifierInference.BeforeNETSdkTargets.targets b/src/Microsoft.DotNet.Arcade.Sdk/tools/RuntimeIdentifierInference.BeforeNETSdkTargets.targets
+new file mode 100644
+index 000000000..9eba3fad9
+--- /dev/null
++++ b/src/Microsoft.DotNet.Arcade.Sdk/tools/RuntimeIdentifierInference.BeforeNETSdkTargets.targets
+@@ -0,0 +1,79 @@
++<!-- Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. -->
++<Project>
++  <PropertyGroup>
++    <_EnableArcadeRuntimeIdentifierInference Condition="'$(_EnableArcadeRuntimeIdentifierInference)' == ''">$(EnableArcadeRuntimeIdentifierInference)</_EnableArcadeRuntimeIdentifierInference>
++
++    <!-- If the user has specified a RID for their project, don't overwrite it. -->
++    <_EnableArcadeRuntimeIdentifierInference Condition="'$(_EnableArcadeRuntimeIdentifierInference)' == '' and '$(RuntimeIdentifier)' != ''">false</_EnableArcadeRuntimeIdentifierInference>
++
++    <!--
++      If the SDK will infer this project as "RID agnostic", don't infer RIDs.
++      This should generally match the logic for setting IsRidAgnostic in the SDK.
++    -->
++    <_RidAgnosticProject Condition="('$(OutputType)' == 'Library' or '$(IsTestProject)' == 'true') and '$(RuntimeIdentifiers)' == ''">true</_RidAgnosticProject>
++
++    <!-- If this project is RID-agnostic, don't infer RIDs. -->
++    <_EnableArcadeRuntimeIdentifierInference Condition="'$(_EnableArcadeRuntimeIdentifierInference)' == '' and ('$(IsRidAgnostic)' == 'true' or '$(_RidAgnosticProject)' == 'true')">false</_EnableArcadeRuntimeIdentifierInference>
++
++    <!--
++      We only need to infer if the project would use the RID
++    -->
++    <_BuildFlavorRequiredRid
++      Condition="
++        '$(SelfContained)' == 'true' or
++        ('$(_IsPublishing)' == 'true' and
++          (
++            '$(PublishReadyToRun)' == 'true' or
++            '$(PublishSingleFile)' == 'true' or
++            '$(PublishAot)' == 'true'
++          )
++        )">true</_BuildFlavorRequiredRid>
++    <_EnableArcadeRuntimeIdentifierInference Condition="'$(_EnableArcadeRuntimeIdentifierInference)' == '' and '$(_BuildFlavorRequiredRid)' != 'true'">false</_EnableArcadeRuntimeIdentifierInference>
++
++    <!--
++      When we're doing a build of a single vertical, we may not have a runtime or host available for any RID outside of our current target.
++      For many of our projects, we don't actually need to build any RID-specific assets, but the SDK may still try to pull down assets for other RIDs,
++      in particular for the RID matching the SDK's RID.
++      To avoid this, we'll default to setting the RID to the vertical's target RID.
++      To preserve expected behavior for projects that don't specify a RID in a non-vertical build, we won't append the RID to the output path if the user hasn't explicitly requested it.
++    -->
++    <_EnableArcadeRuntimeIdentifierInference Condition="'$(_EnableArcadeRuntimeIdentifierInference)' == '' and '$(DotNetBuildTargetRidOnly)' == 'true'">true</_EnableArcadeRuntimeIdentifierInference>
++
++    <_EnableArcadeRuntimeIdentifierFilters Condition="'$(EnableArcadeRuntimeIdentifierFilters)' != ''">$(EnableArcadeRuntimeIdentifierFilters)</_EnableArcadeRuntimeIdentifierFilters>
++
++    <!--
++      If we infer a RID for the project, default to filtering down the list of RIDs the project specifies and automatically excluding projects that don't build for this RID.
++    -->
++    <_EnableArcadeRuntimeIdentifierFilters Condition="'$(_EnableArcadeRuntimeIdentifierFilters)' == '' and '$(_EnableArcadeRuntimeIdentifierInference)' == 'true'">$(_EnableArcadeRuntimeIdentifierFilters)</_EnableArcadeRuntimeIdentifierFilters>
++  </PropertyGroup>
++
++  <PropertyGroup Condition="'$(_EnableArcadeRuntimeIdentifierInference)' == 'true'">
++    <!-- If we're inferring a RID, regular builds wouldn't have appended the RID to the output path. Default to not appending to the output path to preserve expected output locations. -->
++    <AppendRuntimeIdentifierToOutputPath Condition="'$(AppendRuntimeIdentifierToOutputPath)' == ''">false</AppendRuntimeIdentifierToOutputPath>
++    <RuntimeIdentifier>$(TargetRid)</RuntimeIdentifier>
++
++    <!-- If this project would have been inferred as "RID agnostic", preserve that as well. -->
++    <IsRidAgnostic Condition="'$(_RidAgnosticProject)' == 'true'">true</IsRidAgnostic>
++  </PropertyGroup>
++
++  <PropertyGroup Condition="'$(_EnableArcadeRuntimeIdentifierFilters)' == 'true' and '$(RuntimeIdentifiers)' != ''">
++    <!-- Prepend and append with semicolons to make the Contains call below simpler. -->
++    <_ExplicitlySpecifiedRuntimeIdentifiers>;$(RuntimeIdentifiers);</_ExplicitlySpecifiedRuntimeIdentifiers>
++
++    <!--
++      Sometimes we may need to filter the RuntimeIdentifiers list by a RID that is not TargetRid.
++      Determine which RID to filter on here.
++
++      We can't actually use the RID graph here as RID graph filtering is only possible in a task, and we need to do this during property evaluation.
++    -->
++    <_FilterRuntimeIdentifier>$(TargetRid)</_FilterRuntimeIdentifier>
++    <!-- If we're introducing a new runtime identifier with TargetRid, filter instead on BaseOS. -->
++    <_FilterRuntimeIdentifier Condition="'$(BaseOS)' != ''">$(BaseOS)</_FilterRuntimeIdentifier>
++
++    <!-- If a project builds for a set of RIDs specified in the project file and this vertical isn't in the list, suppress building this project. -->
++    <_SuppressAllTargets Condition="'$(DisableArcadeExcludeFromBuildSupport)' != 'true' and $(_ExplicitlySpecifiedRuntimeIdentifiers).Contains(';$(_FilterRuntimeIdentifier);')) == 'false'">true</_SuppressAllTargets>
++
++    <!-- The .NET SDK will try to restore for all specified RIDs. Change the list of RIDs to only our inferred RID to ensure that restore only restores assets that could be available. -->
++    <RuntimeIdentifiers>$(RuntimeIdentifier)</RuntimeIdentifiers>
++  </PropertyGroup>
++</Project>
+diff --git a/src/Microsoft.DotNet.Arcade.Sdk/tools/Settings.props b/src/Microsoft.DotNet.Arcade.Sdk/tools/Settings.props
+index b19ed1c3e..0b1d6c41d 100644
+--- a/src/Microsoft.DotNet.Arcade.Sdk/tools/Settings.props
++++ b/src/Microsoft.DotNet.Arcade.Sdk/tools/Settings.props
+@@ -6,6 +6,7 @@
+     <_ArcadeOverriddenCustomBeforeMicrosoftCommonCrossTargetingTargets>$(CustomBeforeMicrosoftCommonCrossTargetingTargets)</_ArcadeOverriddenCustomBeforeMicrosoftCommonCrossTargetingTargets>
+     <CustomBeforeMicrosoftCommonTargets>$(MSBuildThisFileDirectory)BeforeCommonTargets.targets</CustomBeforeMicrosoftCommonTargets>
+     <CustomBeforeMicrosoftCommonCrossTargetingTargets>$(MSBuildThisFileDirectory)BeforeCommonTargets.CrossTargeting.targets</CustomBeforeMicrosoftCommonCrossTargetingTargets>
++    <BeforeMicrosoftNETSdkTargets>$(BeforeMicrosoftNETSdkTargets);$(MSBuildThisFileDirectory)BeforeNETSdkTargets.targets</BeforeMicrosoftNETSdkTargets>
+     <!-- MSBuild has "global" variables (ie command-line or MSBuild task properties) override local declarations.  That's generally not the behavior that we want in Arcade.
+          We want to be able to have Arcade MSBuild a project / target with the property set as a default, but let the project override that value.  To work around MSBuild,
+          we pass in `_blah` and set it to a local property (`blah`) which is not global. -->
+diff --git a/src/Microsoft.DotNet.Arcade.Sdk/tools/SourceBuild/SourceBuildArcadeBuild.targets b/src/Microsoft.DotNet.Arcade.Sdk/tools/SourceBuild/SourceBuildArcadeBuild.targets
+index 76e314d1f..a94d4e5ac 100644
+--- a/src/Microsoft.DotNet.Arcade.Sdk/tools/SourceBuild/SourceBuildArcadeBuild.targets
++++ b/src/Microsoft.DotNet.Arcade.Sdk/tools/SourceBuild/SourceBuildArcadeBuild.targets
+@@ -55,6 +55,7 @@
+            - DotNetBuildSourceOnly - Build from source only. Pass through outer build value if present. -->
+       <InnerBuildArgs Condition="'$(DotNetBuildRepo)' == 'true'">$(InnerBuildArgs) /p:DotNetBuildInnerRepo=true</InnerBuildArgs>
+       <InnerBuildArgs Condition="'$(DotNetBuildSourceOnly)' != ''">$(InnerBuildArgs) /p:DotNetBuildSourceOnly=$(DotNetBuildSourceOnly)</InnerBuildArgs>
++      <InnerBuildArgs Condition="'$(DotNetBuildTargetRidOnly)' != ''">$(InnerBuildArgs) /p:DotNetBuildTargetRidOnly=$(DotNetBuildTargetRidOnly)</InnerBuildArgs>
+       <!-- Use a fresh clone of the repo so that source-build modifications are isolated. -->
+       <InnerBuildArgs>$(InnerBuildArgs) /p:RepoRoot="$(InnerSourceBuildRepoRoot)$(_DirSeparatorEscapedCharForExecArg)"</InnerBuildArgs>
+       <!-- Override the artifacts dir to cleanly separate the inner build from outer build. -->
diff --git a/src/SourceBuild/patches/roslyn/0001-Use-BaseOS-instead-of-TargetRid-when-its-available.patch b/src/SourceBuild/patches/roslyn/0001-Use-BaseOS-instead-of-TargetRid-when-its-available.patch
new file mode 100644
index 000000000000..cf2d19f1ce75
--- /dev/null
+++ b/src/SourceBuild/patches/roslyn/0001-Use-BaseOS-instead-of-TargetRid-when-its-available.patch
@@ -0,0 +1,34 @@
+From fe7b6d17a00a69b6bb8cb25d640af56f74a60032 Mon Sep 17 00:00:00 2001
+From: Jeremy Koritzinsky <jekoritz@microsoft.com>
+Date: Tue, 21 Jan 2025 11:31:58 -0800
+Subject: [PATCH] Use BaseOS instead of TargetRid when its available.
+
+In Source Build, BaseOS is the portable runtime identifier for TargetRid.
+
+Backport: https://github.com/dotnet/roslyn/pull/76838
+
+---
+ .../Microsoft.CodeAnalysis.LanguageServer.csproj           | 7 ++++---
+ 1 file changed, 4 insertions(+), 3 deletions(-)
+
+diff --git a/src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Microsoft.CodeAnalysis.LanguageServer.csproj b/src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Microsoft.CodeAnalysis.LanguageServer.csproj
+index 9b556fcdb8f..a76305b4a29 100644
+--- a/src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Microsoft.CodeAnalysis.LanguageServer.csproj
++++ b/src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Microsoft.CodeAnalysis.LanguageServer.csproj
+@@ -45,12 +45,13 @@
+     <PublishDir Condition="'$(RuntimeIdentifier)' == ''">$(ArtifactsDir)/LanguageServer/$(Configuration)/$(TargetFramework)/neutral</PublishDir>
+ 
+     <!-- List of runtime identifiers that we want to publish an executable for. -->
+-    <!-- When building a VMR vertical, we don't need to pack everything. Just pack the passed in TargetRid.
+-         TargetRid is provided to roslyn via the build arguments passed in the VMR orchestrator's repo project.
++    <!-- When building a VMR vertical, we don't need to pack everything. Just pack the passed in TargetRid or BaseOS.
++         TargetRid and BaseOS are provided to roslyn via the build arguments passed in the VMR orchestrator's repo project.
+          https://github.com/dotnet/dotnet/blob/main/repo-projects/roslyn.proj. For definitions of the TargetRid
+          and other common properties, see https://github.com/dotnet/arcade/blob/main/Documentation/UnifiedBuild/Unified-Build-Controls.md -->
+     <RuntimeIdentifiers Condition="'$(TargetRid)' != ''">$(TargetRid)</RuntimeIdentifiers>
+-    <RuntimeIdentifiers Condition="'$(TargetRid)' == ''">win-x64;win-arm64;linux-x64;linux-arm64;linux-musl-x64;linux-musl-arm64;osx-x64;osx-arm64</RuntimeIdentifiers>
++    <RuntimeIdentifiers Condition="'$(BaseOS)' != ''">$(BaseOS)</RuntimeIdentifiers>
++    <RuntimeIdentifiers Condition="'$(TargetRid)' == '' and '$(BaseOS)' == ''">win-x64;win-arm64;linux-x64;linux-arm64;linux-musl-x64;linux-musl-arm64;osx-x64;osx-arm64</RuntimeIdentifiers>
+     <!-- Publish ready to run executables when we're publishing platform specific executables. -->
+     <PublishReadyToRun Condition="'$(RuntimeIdentifier)' != '' AND '$(Configuration)' == 'Release' ">true</PublishReadyToRun>
+   </PropertyGroup>