diff --git a/eng/Version.Details.xml b/eng/Version.Details.xml
index 7ea417466f4..9937b0aea87 100644
--- a/eng/Version.Details.xml
+++ b/eng/Version.Details.xml
@@ -11,82 +11,82 @@
       <Sha>ad3c9aa85596f42c6a483233c50fab8cee8c412a</Sha>
       <SourceBuild RepoName="source-build-reference-packages" ManagedOnly="true" />
     </Dependency>
-    <Dependency Name="Microsoft.Net.Compilers.Toolset" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.Net.Compilers.Toolset" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CommonLanguageServerProtocol.Framework" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CommonLanguageServerProtocol.Framework" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.ExternalAccess.Razor" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.ExternalAccess.Razor" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.Common" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.Common" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.CSharp" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.CSharp" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.CSharp.EditorFeatures" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.CSharp.EditorFeatures" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.CSharp.Features" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.CSharp.Features" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.EditorFeatures" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.EditorFeatures" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.EditorFeatures.Common" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.EditorFeatures.Common" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.EditorFeatures.Text" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.EditorFeatures.Text" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.EditorFeatures.Wpf" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.EditorFeatures.Wpf" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.Remote.ServiceHub" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.Remote.ServiceHub" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.VisualBasic.Workspaces" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.VisualBasic.Workspaces" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.Workspaces.Common" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.Workspaces.Common" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.Workspaces.MSBuild" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.Workspaces.MSBuild" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.VisualStudio.LanguageServices" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.VisualStudio.LanguageServices" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.CodeAnalysis.Test.Utilities" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.CodeAnalysis.Test.Utilities" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
     </Dependency>
     <!-- Intermediate is necessary for source build. -->
-    <Dependency Name="Microsoft.SourceBuild.Intermediate.roslyn" Version="4.12.0-3.24454.5">
+    <Dependency Name="Microsoft.SourceBuild.Intermediate.roslyn" Version="4.12.0-3.24466.4">
       <Uri>https://github.com/dotnet/roslyn</Uri>
-      <Sha>9f86520c46f67d2a8a59af189f8fd87e35c574bb</Sha>
+      <Sha>7b7951aa13c50ad768538e58ed3805898b058928</Sha>
       <SourceBuild RepoName="roslyn" ManagedOnly="true" />
     </Dependency>
   </ProductDependencies>
diff --git a/eng/Versions.props b/eng/Versions.props
index 707ebbb49ad..a78ad1ba11c 100644
--- a/eng/Versions.props
+++ b/eng/Versions.props
@@ -53,25 +53,25 @@
     <MicrosoftSourceBuildIntermediatearcadePackageVersion>9.0.0-beta.24453.1</MicrosoftSourceBuildIntermediatearcadePackageVersion>
     <MicrosoftDotNetXliffTasksPackageVersion>1.0.0-beta.23475.1</MicrosoftDotNetXliffTasksPackageVersion>
     <MicrosoftSourceBuildIntermediatexlifftasksPackageVersion>1.0.0-beta.23475.1</MicrosoftSourceBuildIntermediatexlifftasksPackageVersion>
-    <MicrosoftNetCompilersToolsetPackageVersion>4.12.0-3.24454.5</MicrosoftNetCompilersToolsetPackageVersion>
-    <MicrosoftCommonLanguageServerProtocolFrameworkPackageVersion>4.12.0-3.24454.5</MicrosoftCommonLanguageServerProtocolFrameworkPackageVersion>
-    <MicrosoftCodeAnalysisExternalAccessRazorPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisExternalAccessRazorPackageVersion>
-    <MicrosoftCodeAnalysisCommonPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisCommonPackageVersion>
-    <MicrosoftCodeAnalysisCSharpPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisCSharpPackageVersion>
-    <MicrosoftCodeAnalysisCSharpEditorFeaturesPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisCSharpEditorFeaturesPackageVersion>
-    <MicrosoftCodeAnalysisCSharpFeaturesPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisCSharpFeaturesPackageVersion>
-    <MicrosoftCodeAnalysisCSharpWorkspacesPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisCSharpWorkspacesPackageVersion>
-    <MicrosoftCodeAnalysisEditorFeaturesPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisEditorFeaturesPackageVersion>
-    <MicrosoftCodeAnalysisEditorFeaturesCommonPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisEditorFeaturesCommonPackageVersion>
-    <MicrosoftCodeAnalysisEditorFeaturesTextPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisEditorFeaturesTextPackageVersion>
-    <MicrosoftCodeAnalysisEditorFeaturesWpfPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisEditorFeaturesWpfPackageVersion>
-    <MicrosoftCodeAnalysisRemoteServiceHubPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisRemoteServiceHubPackageVersion>
-    <MicrosoftCodeAnalysisTestUtilitiesPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisTestUtilitiesPackageVersion>
-    <MicrosoftCodeAnalysisVisualBasicWorkspacesPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisVisualBasicWorkspacesPackageVersion>
-    <MicrosoftCodeAnalysisWorkspacesCommonPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisWorkspacesCommonPackageVersion>
-    <MicrosoftCodeAnalysisWorkspacesMSBuildPackageVersion>4.12.0-3.24454.5</MicrosoftCodeAnalysisWorkspacesMSBuildPackageVersion>
-    <MicrosoftSourceBuildIntermediateroslynPackageVersion>4.12.0-3.24454.5</MicrosoftSourceBuildIntermediateroslynPackageVersion>
-    <MicrosoftVisualStudioLanguageServicesPackageVersion>4.12.0-3.24454.5</MicrosoftVisualStudioLanguageServicesPackageVersion>
+    <MicrosoftNetCompilersToolsetPackageVersion>4.12.0-3.24466.4</MicrosoftNetCompilersToolsetPackageVersion>
+    <MicrosoftCommonLanguageServerProtocolFrameworkPackageVersion>4.12.0-3.24466.4</MicrosoftCommonLanguageServerProtocolFrameworkPackageVersion>
+    <MicrosoftCodeAnalysisExternalAccessRazorPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisExternalAccessRazorPackageVersion>
+    <MicrosoftCodeAnalysisCommonPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisCommonPackageVersion>
+    <MicrosoftCodeAnalysisCSharpPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisCSharpPackageVersion>
+    <MicrosoftCodeAnalysisCSharpEditorFeaturesPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisCSharpEditorFeaturesPackageVersion>
+    <MicrosoftCodeAnalysisCSharpFeaturesPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisCSharpFeaturesPackageVersion>
+    <MicrosoftCodeAnalysisCSharpWorkspacesPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisCSharpWorkspacesPackageVersion>
+    <MicrosoftCodeAnalysisEditorFeaturesPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisEditorFeaturesPackageVersion>
+    <MicrosoftCodeAnalysisEditorFeaturesCommonPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisEditorFeaturesCommonPackageVersion>
+    <MicrosoftCodeAnalysisEditorFeaturesTextPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisEditorFeaturesTextPackageVersion>
+    <MicrosoftCodeAnalysisEditorFeaturesWpfPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisEditorFeaturesWpfPackageVersion>
+    <MicrosoftCodeAnalysisRemoteServiceHubPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisRemoteServiceHubPackageVersion>
+    <MicrosoftCodeAnalysisTestUtilitiesPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisTestUtilitiesPackageVersion>
+    <MicrosoftCodeAnalysisVisualBasicWorkspacesPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisVisualBasicWorkspacesPackageVersion>
+    <MicrosoftCodeAnalysisWorkspacesCommonPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisWorkspacesCommonPackageVersion>
+    <MicrosoftCodeAnalysisWorkspacesMSBuildPackageVersion>4.12.0-3.24466.4</MicrosoftCodeAnalysisWorkspacesMSBuildPackageVersion>
+    <MicrosoftSourceBuildIntermediateroslynPackageVersion>4.12.0-3.24466.4</MicrosoftSourceBuildIntermediateroslynPackageVersion>
+    <MicrosoftVisualStudioLanguageServicesPackageVersion>4.12.0-3.24466.4</MicrosoftVisualStudioLanguageServicesPackageVersion>
     <!--
       Exception - Microsoft.Extensions.ObjectPool and System.Collections.Immutable packages are not updated by automation,
       but are present in Version.Details.xml for source-build PVP flow. See the comment in Version.Details.xml for more information.
diff --git a/eng/targets/Services.props b/eng/targets/Services.props
index fc2acc27dfa..0501df0e116 100644
--- a/eng/targets/Services.props
+++ b/eng/targets/Services.props
@@ -32,5 +32,6 @@
     <ServiceHubService Include="Microsoft.VisualStudio.Razor.Formatting" ClassName="Microsoft.CodeAnalysis.Remote.Razor.RemoteFormattingService+Factory" />
     <ServiceHubService Include="Microsoft.VisualStudio.Razor.GoToImplementation" ClassName="Microsoft.CodeAnalysis.Remote.Razor.RemoteGoToImplementationService+Factory" />
     <ServiceHubService Include="Microsoft.VisualStudio.Razor.SpellCheck" ClassName="Microsoft.CodeAnalysis.Remote.Razor.RemoteSpellCheckService+Factory" />
+    <ServiceHubService Include="Microsoft.VisualStudio.Razor.Diagnostics" ClassName="Microsoft.CodeAnalysis.Remote.Razor.RemoteDiagnosticsService+Factory" />
   </ItemGroup>
 </Project>
diff --git a/src/Razor/benchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks/LanguageServer/RazorDiagnosticsBenchmark.cs b/src/Razor/benchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks/LanguageServer/RazorDiagnosticsBenchmark.cs
index 1733e5058fa..7071c1986f1 100644
--- a/src/Razor/benchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks/LanguageServer/RazorDiagnosticsBenchmark.cs
+++ b/src/Razor/benchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks/LanguageServer/RazorDiagnosticsBenchmark.cs
@@ -13,6 +13,7 @@
 using Microsoft.AspNetCore.Razor.LanguageServer.Diagnostics;
 using Microsoft.AspNetCore.Razor.LanguageServer.EndpointContracts;
 using Microsoft.AspNetCore.Razor.LanguageServer.Hosting;
+using Microsoft.CodeAnalysis.Razor.Diagnostics;
 using Microsoft.CodeAnalysis.Razor.DocumentMapping;
 using Microsoft.CodeAnalysis.Razor.Logging;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
diff --git a/src/Razor/benchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks.csproj b/src/Razor/benchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks.csproj
index 1010350dd29..d3179687681 100644
--- a/src/Razor/benchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks.csproj
+++ b/src/Razor/benchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks.csproj
@@ -43,6 +43,9 @@
     <Compile Include="..\..\test\Microsoft.AspNetCore.Razor.Test.Common.Tooling\Workspaces\TestWorkspaceServices.cs">
       <Link>TestServices\%(FileName)%(Extension)</Link>
     </Compile>
+    <Compile Include="..\..\test\Microsoft.AspNetCore.Razor.Test.Common.Tooling\Mef\ExportProviderExtensions.cs">
+      <Link>TestServices\%(FileName)%(Extension)</Link>
+    </Compile>
 
     <None Remove=".gitignore" />
     <None Remove="BenchmarkDotNet.Artifacts\**" />
diff --git a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/DocumentPullDiagnosticsEndpoint.cs b/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/DocumentPullDiagnosticsEndpoint.cs
index eba0c7da011..5e39d98c2f4 100644
--- a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/DocumentPullDiagnosticsEndpoint.cs
+++ b/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/DocumentPullDiagnosticsEndpoint.cs
@@ -10,6 +10,7 @@
 using Microsoft.AspNetCore.Razor.LanguageServer.Hosting;
 using Microsoft.AspNetCore.Razor.PooledObjects;
 using Microsoft.AspNetCore.Razor.Telemetry;
+using Microsoft.CodeAnalysis.Razor.Diagnostics;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
 using Microsoft.CodeAnalysis.Razor.Protocol;
 using Microsoft.CodeAnalysis.Razor.Protocol.Diagnostics;
@@ -72,7 +73,9 @@ public TextDocumentIdentifier GetTextDocumentIdentifier(VSInternalDocumentDiagno
             return null;
         }
 
-        var razorDiagnostics = await GetRazorDiagnosticsAsync(documentContext, cancellationToken).ConfigureAwait(false);
+        var documentSnapshot = documentContext.Snapshot;
+
+        var razorDiagnostics = await GetRazorDiagnosticsAsync(documentSnapshot).ConfigureAwait(false);
 
         var (csharpDiagnostics, htmlDiagnostics) = await GetHtmlCSharpDiagnosticsAsync(documentContext, correlationId, cancellationToken).ConfigureAwait(false);
 
@@ -96,7 +99,7 @@ public TextDocumentIdentifier GetTextDocumentIdentifier(VSInternalDocumentDiagno
             {
                 if (report.Diagnostics is not null)
                 {
-                    var mappedDiagnostics = await _translateDiagnosticsService.TranslateAsync(RazorLanguageKind.CSharp, report.Diagnostics, documentContext, cancellationToken).ConfigureAwait(false);
+                    var mappedDiagnostics = await _translateDiagnosticsService.TranslateAsync(RazorLanguageKind.CSharp, report.Diagnostics, documentSnapshot).ConfigureAwait(false);
                     report.Diagnostics = mappedDiagnostics;
                 }
 
@@ -110,7 +113,7 @@ public TextDocumentIdentifier GetTextDocumentIdentifier(VSInternalDocumentDiagno
             {
                 if (report.Diagnostics is not null)
                 {
-                    var mappedDiagnostics = await _translateDiagnosticsService.TranslateAsync(RazorLanguageKind.Html, report.Diagnostics, documentContext, cancellationToken).ConfigureAwait(false);
+                    var mappedDiagnostics = await _translateDiagnosticsService.TranslateAsync(RazorLanguageKind.Html, report.Diagnostics, documentSnapshot).ConfigureAwait(false);
                     report.Diagnostics = mappedDiagnostics;
                 }
 
@@ -121,10 +124,10 @@ public TextDocumentIdentifier GetTextDocumentIdentifier(VSInternalDocumentDiagno
         return allDiagnostics.ToArray();
     }
 
-    private static async Task<VSInternalDiagnosticReport[]?> GetRazorDiagnosticsAsync(DocumentContext documentContext, CancellationToken cancellationToken)
+    private static async Task<VSInternalDiagnosticReport[]?> GetRazorDiagnosticsAsync(IDocumentSnapshot documentSnapshot)
     {
-        var codeDocument = await documentContext.GetCodeDocumentAsync(cancellationToken).ConfigureAwait(false);
-        var sourceText = await documentContext.GetSourceTextAsync(cancellationToken).ConfigureAwait(false);
+        var codeDocument = await documentSnapshot.GetGeneratedOutputAsync().ConfigureAwait(false);
+        var sourceText = codeDocument.Source.Text;
         var csharpDocument = codeDocument.GetCSharpDocument();
         var diagnostics = csharpDocument.Diagnostics;
 
@@ -133,7 +136,7 @@ public TextDocumentIdentifier GetTextDocumentIdentifier(VSInternalDocumentDiagno
             return null;
         }
 
-        var convertedDiagnostics = RazorDiagnosticConverter.Convert(diagnostics, sourceText, documentContext.Snapshot);
+        var convertedDiagnostics = RazorDiagnosticConverter.Convert(diagnostics, sourceText, documentSnapshot);
 
         return
         [
diff --git a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/RazorDiagnosticsPublisher.cs b/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/RazorDiagnosticsPublisher.cs
index 1f3320294e5..204b03658af 100644
--- a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/RazorDiagnosticsPublisher.cs
+++ b/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/RazorDiagnosticsPublisher.cs
@@ -13,6 +13,7 @@
 using Microsoft.AspNetCore.Razor.PooledObjects;
 using Microsoft.AspNetCore.Razor.Utilities;
 using Microsoft.CodeAnalysis.Razor;
+using Microsoft.CodeAnalysis.Razor.Diagnostics;
 using Microsoft.CodeAnalysis.Razor.Logging;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
 using Microsoft.CodeAnalysis.Razor.Protocol;
@@ -187,7 +188,7 @@ .. csharpDiagnostics ?? []
                     if (_documentContextFactory.Value.TryCreate(delegatedParams.TextDocument.Uri, projectContext: null, out var documentContext))
                     {
                         return await _translateDiagnosticsService.Value
-                            .TranslateAsync(RazorLanguageKind.CSharp, fullDiagnostics.Items, documentContext, token)
+                            .TranslateAsync(RazorLanguageKind.CSharp, fullDiagnostics.Items, documentContext.Snapshot)
                             .ConfigureAwait(false);
                     }
                 }
diff --git a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Extensions/IServiceCollectionExtensions.cs b/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Extensions/IServiceCollectionExtensions.cs
index 8f12aff65d8..df9b7b61097 100644
--- a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Extensions/IServiceCollectionExtensions.cs
+++ b/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Extensions/IServiceCollectionExtensions.cs
@@ -22,6 +22,7 @@
 using Microsoft.AspNetCore.Razor.LanguageServer.Tooltip;
 using Microsoft.AspNetCore.Razor.ProjectEngineHost;
 using Microsoft.CodeAnalysis.Razor.Completion;
+using Microsoft.CodeAnalysis.Razor.Diagnostics;
 using Microsoft.CodeAnalysis.Razor.DocumentMapping;
 using Microsoft.CodeAnalysis.Razor.Formatting;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
diff --git a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/RazorLanguageServer.cs b/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/RazorLanguageServer.cs
index be86fe01409..70d4fcd1351 100644
--- a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/RazorLanguageServer.cs
+++ b/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/RazorLanguageServer.cs
@@ -131,7 +131,6 @@ protected override ILspServices ConstructLspServices()
 
         services.AddLifeCycleServices(this, _clientConnection, _lspServerActivationTracker);
 
-        services.AddDiagnosticServices();
         services.AddSemanticTokensServices(featureOptions);
         services.AddDocumentManagementServices(featureOptions);
         services.AddCompletionServices();
@@ -143,6 +142,9 @@ protected override ILspServices ConstructLspServices()
 
         if (!featureOptions.UseRazorCohostServer)
         {
+            // Diagnostics
+            services.AddDiagnosticServices();
+
             // Auto insert
             services.AddSingleton<IOnAutoInsertProvider, CloseTextTagOnAutoInsertProvider>();
             services.AddSingleton<IOnAutoInsertProvider, AutoClosingTagOnAutoInsertProvider>();
diff --git a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/CSSErrorCodes.cs b/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Diagnostics/CSSErrorCodes.cs
similarity index 89%
rename from src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/CSSErrorCodes.cs
rename to src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Diagnostics/CSSErrorCodes.cs
index bafb8675ab1..658f918272f 100644
--- a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/CSSErrorCodes.cs
+++ b/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Diagnostics/CSSErrorCodes.cs
@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the MIT license. See License.txt in the project root for license information.
 
-namespace Microsoft.AspNetCore.Razor.LanguageServer;
+namespace Microsoft.CodeAnalysis.Razor.Diagnostics;
 
 // Note: This type should be kept in sync with WTE's ErrorCodes.cs
 internal static class CSSErrorCodes
diff --git a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/HTMLErrorCodes.cs b/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Diagnostics/HTMLErrorCodes.cs
similarity index 97%
rename from src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/HTMLErrorCodes.cs
rename to src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Diagnostics/HTMLErrorCodes.cs
index 015feacef97..dc0042a9dd7 100644
--- a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/HTMLErrorCodes.cs
+++ b/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Diagnostics/HTMLErrorCodes.cs
@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the MIT license. See License.txt in the project root for license information.
 
-namespace Microsoft.AspNetCore.Razor.LanguageServer;
+namespace Microsoft.CodeAnalysis.Razor.Diagnostics;
 
 // Note: This type should be kept in sync with WTE's ErrorCodes.cs
 internal static class HtmlErrorCodes
diff --git a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/RazorDiagnosticConverter.cs b/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Diagnostics/RazorDiagnosticConverter.cs
similarity index 71%
rename from src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/RazorDiagnosticConverter.cs
rename to src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Diagnostics/RazorDiagnosticConverter.cs
index 1ee9556ff92..bbbacbee1d5 100644
--- a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/RazorDiagnosticConverter.cs
+++ b/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Diagnostics/RazorDiagnosticConverter.cs
@@ -2,15 +2,17 @@
 // Licensed under the MIT license. See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Globalization;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.VisualStudio.LanguageServer.Protocol;
-using Range = Microsoft.VisualStudio.LanguageServer.Protocol.Range;
+using LspDiagnostic = Microsoft.VisualStudio.LanguageServer.Protocol.Diagnostic;
+using LspDiagnosticSeverity = Microsoft.VisualStudio.LanguageServer.Protocol.DiagnosticSeverity;
+using LspRange = Microsoft.VisualStudio.LanguageServer.Protocol.Range;
 
-namespace Microsoft.AspNetCore.Razor.LanguageServer.Diagnostics;
+namespace Microsoft.CodeAnalysis.Razor.Diagnostics;
 
 internal static class RazorDiagnosticConverter
 {
@@ -46,9 +48,9 @@ public static VSDiagnosticProjectInformation[] GetProjectInformation(IDocumentSn
                 }];
     }
 
-    internal static Diagnostic[] Convert(IReadOnlyList<RazorDiagnostic> diagnostics, SourceText sourceText, IDocumentSnapshot documentSnapshot)
+    internal static LspDiagnostic[] Convert(ImmutableArray<RazorDiagnostic> diagnostics, SourceText sourceText, IDocumentSnapshot documentSnapshot)
     {
-        var convertedDiagnostics = new Diagnostic[diagnostics.Count];
+        var convertedDiagnostics = new LspDiagnostic[diagnostics.Length];
 
         var i = 0;
         foreach (var diagnostic in diagnostics)
@@ -60,18 +62,18 @@ internal static Diagnostic[] Convert(IReadOnlyList<RazorDiagnostic> diagnostics,
     }
 
     // Internal for testing
-    internal static DiagnosticSeverity ConvertSeverity(RazorDiagnosticSeverity severity)
+    internal static LspDiagnosticSeverity ConvertSeverity(RazorDiagnosticSeverity severity)
     {
         return severity switch
         {
-            RazorDiagnosticSeverity.Error => DiagnosticSeverity.Error,
-            RazorDiagnosticSeverity.Warning => DiagnosticSeverity.Warning,
-            _ => DiagnosticSeverity.Information,
+            RazorDiagnosticSeverity.Error => LspDiagnosticSeverity.Error,
+            RazorDiagnosticSeverity.Warning => LspDiagnosticSeverity.Warning,
+            _ => LspDiagnosticSeverity.Information,
         };
     }
 
     // Internal for testing
-    internal static Range? ConvertSpanToRange(SourceSpan sourceSpan, SourceText sourceText)
+    internal static LspRange? ConvertSpanToRange(SourceSpan sourceSpan, SourceText sourceText)
     {
         if (sourceSpan == SourceSpan.Undefined)
         {
diff --git a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/RazorTranslateDiagnosticsService.cs b/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Diagnostics/RazorTranslateDiagnosticsService.cs
similarity index 87%
rename from src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/RazorTranslateDiagnosticsService.cs
rename to src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Diagnostics/RazorTranslateDiagnosticsService.cs
index 11fc9b5f5aa..b662d2ca2b3 100644
--- a/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Diagnostics/RazorTranslateDiagnosticsService.cs
+++ b/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Diagnostics/RazorTranslateDiagnosticsService.cs
@@ -6,7 +6,6 @@
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
-using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Language.Syntax;
@@ -18,12 +17,14 @@
 using Microsoft.CodeAnalysis.Razor.Protocol;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.VisualStudio.LanguageServer.Protocol;
-using Diagnostic = Microsoft.VisualStudio.LanguageServer.Protocol.Diagnostic;
-using DiagnosticSeverity = Microsoft.VisualStudio.LanguageServer.Protocol.DiagnosticSeverity;
-using Range = Microsoft.VisualStudio.LanguageServer.Protocol.Range;
-using SyntaxNode = Microsoft.AspNetCore.Razor.Language.Syntax.SyntaxNode;
+using LspDiagnostic = Microsoft.VisualStudio.LanguageServer.Protocol.Diagnostic;
+using LspDiagnosticSeverity = Microsoft.VisualStudio.LanguageServer.Protocol.DiagnosticSeverity;
+using LspRange = Microsoft.VisualStudio.LanguageServer.Protocol.Range;
 
-namespace Microsoft.AspNetCore.Razor.LanguageServer.Diagnostics;
+namespace Microsoft.CodeAnalysis.Razor.Diagnostics;
+
+using RazorDiagnosticFactory = AspNetCore.Razor.Language.RazorDiagnosticFactory;
+using SyntaxNode = AspNetCore.Razor.Language.Syntax.SyntaxNode;
 
 /// <summary>
 /// Contains several methods for mapping and filtering Razor and C# diagnostics. It allows for
@@ -48,16 +49,14 @@ internal class RazorTranslateDiagnosticsService(IDocumentMappingService document
     /// </summary>
     /// <param name="diagnosticKind">The `RazorLanguageKind` of the `Diagnostic` objects included in `diagnostics`.</param>
     /// <param name="diagnostics">An array of `Diagnostic` objects to translate.</param>
-    /// <param name="documentContext">The `DocumentContext` for the code document associated with the diagnostics.</param>
-    /// <param name="cancellationToken">A `CancellationToken` to observe while waiting for the task to complete.</param>
+    /// <param name="documentSnapshot">The `DocumentContext` for the code document associated with the diagnostics.</param>
     /// <returns>An array of translated diagnostics</returns>
-    internal async Task<Diagnostic[]> TranslateAsync(
+    internal async Task<LspDiagnostic[]> TranslateAsync(
         RazorLanguageKind diagnosticKind,
-        Diagnostic[] diagnostics,
-        DocumentContext documentContext,
-        CancellationToken cancellationToken)
+        LspDiagnostic[] diagnostics,
+        IDocumentSnapshot documentSnapshot)
     {
-        var codeDocument = await documentContext.GetCodeDocumentAsync(cancellationToken).ConfigureAwait(false);
+        var codeDocument = await documentSnapshot.GetGeneratedOutputAsync().ConfigureAwait(false);
         if (codeDocument.IsUnsupported() != false)
         {
             _logger.LogInformation($"Unsupported code document.");
@@ -78,20 +77,20 @@ internal async Task<Diagnostic[]> TranslateAsync(
         var mappedDiagnostics = MapDiagnostics(
             diagnosticKind,
             filteredDiagnostics,
-            documentContext.Snapshot,
+            documentSnapshot,
             codeDocument);
 
         return mappedDiagnostics;
     }
 
-    private Diagnostic[] FilterCSharpDiagnostics(Diagnostic[] unmappedDiagnostics, RazorCodeDocument codeDocument)
+    private LspDiagnostic[] FilterCSharpDiagnostics(LspDiagnostic[] unmappedDiagnostics, RazorCodeDocument codeDocument)
     {
         return unmappedDiagnostics.Where(d =>
             !ShouldFilterCSharpDiagnosticBasedOnErrorCode(d, codeDocument)).ToArray();
     }
 
-    private static Diagnostic[] FilterHTMLDiagnostics(
-        Diagnostic[] unmappedDiagnostics,
+    private static LspDiagnostic[] FilterHTMLDiagnostics(
+        LspDiagnostic[] unmappedDiagnostics,
         RazorCodeDocument codeDocument)
     {
         var syntaxTree = codeDocument.GetSyntaxTree();
@@ -110,14 +109,14 @@ private static Diagnostic[] FilterHTMLDiagnostics(
         return filteredDiagnostics;
     }
 
-    private Diagnostic[] MapDiagnostics(
+    private LspDiagnostic[] MapDiagnostics(
         RazorLanguageKind languageKind,
-        Diagnostic[] diagnostics,
+        LspDiagnostic[] diagnostics,
         IDocumentSnapshot documentSnapshot,
         RazorCodeDocument codeDocument)
     {
         var projects = RazorDiagnosticConverter.GetProjectInformation(documentSnapshot);
-        using var mappedDiagnostics = new PooledArrayBuilder<Diagnostic>();
+        using var mappedDiagnostics = new PooledArrayBuilder<LspDiagnostic>();
 
         foreach (var diagnostic in diagnostics)
         {
@@ -146,7 +145,7 @@ private Diagnostic[] MapDiagnostics(
     }
 
     private static bool InCSharpLiteral(
-        Diagnostic d,
+        LspDiagnostic d,
         SourceText sourceText,
         RazorSyntaxTree syntaxTree)
     {
@@ -177,7 +176,7 @@ or SyntaxKind.CSharpStatementLiteral
                 or SyntaxKind.CSharpEphemeralTextLiteral;
     }
 
-    private static bool AppliesToTagHelperTagName(Diagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
+    private static bool AppliesToTagHelperTagName(LspDiagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
     {
         // Goal of this method is to filter diagnostics that touch TagHelper tag names. Reason being is TagHelpers can output anything. Meaning
         // If you have a TagHelper like:
@@ -214,7 +213,7 @@ private static bool AppliesToTagHelperTagName(Diagnostic diagnostic, SourceText
         return true;
     }
 
-    private static bool ShouldFilterHtmlDiagnosticBasedOnErrorCode(Diagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
+    private static bool ShouldFilterHtmlDiagnosticBasedOnErrorCode(LspDiagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
     {
         if (!diagnostic.Code.HasValue)
         {
@@ -235,7 +234,7 @@ private static bool ShouldFilterHtmlDiagnosticBasedOnErrorCode(Diagnostic diagno
             _ => false,
         };
 
-        static bool IsCSharpInStyleBlock(Diagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
+        static bool IsCSharpInStyleBlock(LspDiagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
         {
             // C# in a style block causes diagnostics because the HTML background document replaces C# with "~"
             var owner = syntaxTree.FindInnermostNode(sourceText, diagnostic.Range.Start);
@@ -253,7 +252,7 @@ static bool IsCSharpInStyleBlock(Diagnostic diagnostic, SourceText sourceText, R
 
         // Ideally this would be solved instead by not emitting the "!" at the HTML backing file,
         // but we don't currently have a system to accomplish that
-        static bool IsAnyFilteredTooFewElementsError(Diagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
+        static bool IsAnyFilteredTooFewElementsError(LspDiagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
         {
             var owner = syntaxTree.FindInnermostNode(sourceText, diagnostic.Range.Start);
             if (owner is null)
@@ -282,7 +281,7 @@ static bool IsAnyFilteredTooFewElementsError(Diagnostic diagnostic, SourceText s
 
         // Ideally this would be solved instead by not emitting the "!" at the HTML backing file,
         // but we don't currently have a system to accomplish that
-        static bool IsHtmlWithBangAndMatchingTags(Diagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
+        static bool IsHtmlWithBangAndMatchingTags(LspDiagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
         {
             var owner = syntaxTree.FindInnermostNode(sourceText, diagnostic.Range.Start);
             if (owner is null)
@@ -306,11 +305,11 @@ static bool IsHtmlWithBangAndMatchingTags(Diagnostic diagnostic, SourceText sour
             return haveBang && namesEquivalent;
         }
 
-        static bool IsAnyFilteredInvalidNestingError(Diagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
+        static bool IsAnyFilteredInvalidNestingError(LspDiagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
             => IsInvalidNestingWarningWithinComponent(diagnostic, sourceText, syntaxTree) ||
                IsInvalidNestingFromBody(diagnostic, sourceText, syntaxTree);
 
-        static bool IsInvalidNestingWarningWithinComponent(Diagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
+        static bool IsInvalidNestingWarningWithinComponent(LspDiagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
         {
             var owner = syntaxTree.FindInnermostNode(sourceText, diagnostic.Range.Start);
             if (owner is null)
@@ -325,7 +324,7 @@ static bool IsInvalidNestingWarningWithinComponent(Diagnostic diagnostic, Source
 
         // Ideally this would be solved instead by not emitting the "!" at the HTML backing file,
         // but we don't currently have a system to accomplish that
-        static bool IsInvalidNestingFromBody(Diagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
+        static bool IsInvalidNestingFromBody(LspDiagnostic diagnostic, SourceText sourceText, RazorSyntaxTree syntaxTree)
         {
             var owner = syntaxTree.FindInnermostNode(sourceText, diagnostic.Range.Start);
             if (owner is null)
@@ -350,7 +349,7 @@ static bool IsInvalidNestingFromBody(Diagnostic diagnostic, SourceText sourceTex
     }
 
     private static bool InAttributeContainingCSharp(
-        Diagnostic diagnostic,
+        LspDiagnostic diagnostic,
         SourceText sourceText,
         RazorSyntaxTree syntaxTree,
         Dictionary<TextSpan, bool> processedAttributes)
@@ -400,7 +399,7 @@ n is GenericBlockSyntax ||
         }
     }
 
-    private bool ShouldFilterCSharpDiagnosticBasedOnErrorCode(Diagnostic diagnostic, RazorCodeDocument codeDocument)
+    private bool ShouldFilterCSharpDiagnosticBasedOnErrorCode(LspDiagnostic diagnostic, RazorCodeDocument codeDocument)
     {
         if (diagnostic.Code is not { } code ||
             !code.TryGetSecond(out var str) ||
@@ -413,10 +412,10 @@ private bool ShouldFilterCSharpDiagnosticBasedOnErrorCode(Diagnostic diagnostic,
         {
             "CS1525" => ShouldIgnoreCS1525(diagnostic, codeDocument),
             _ => s_cSharpDiagnosticsToIgnore.Contains(str) &&
-                diagnostic.Severity != DiagnosticSeverity.Error
+                diagnostic.Severity != LspDiagnosticSeverity.Error
         };
 
-        bool ShouldIgnoreCS1525(Diagnostic diagnostic, RazorCodeDocument codeDocument)
+        bool ShouldIgnoreCS1525(LspDiagnostic diagnostic, RazorCodeDocument codeDocument)
         {
             if (CheckIfDocumentHasRazorDiagnostic(codeDocument, RazorDiagnosticFactory.TagHelper_EmptyBoundAttribute.Id) &&
                 TryGetOriginalDiagnosticRange(diagnostic, codeDocument, out var originalRange) &&
@@ -440,7 +439,7 @@ private static bool CheckIfDocumentHasRazorDiagnostic(RazorCodeDocument codeDocu
         return codeDocument.GetSyntaxTree().Diagnostics.Any(razorDiagnosticCode, static (d, code) => d.Id == code);
     }
 
-    private bool TryGetOriginalDiagnosticRange(Diagnostic diagnostic, RazorCodeDocument codeDocument, [NotNullWhen(true)] out Range? originalRange)
+    private bool TryGetOriginalDiagnosticRange(LspDiagnostic diagnostic, RazorCodeDocument codeDocument, [NotNullWhen(true)] out LspRange? originalRange)
     {
         if (IsRudeEditDiagnostic(diagnostic))
         {
@@ -460,7 +459,7 @@ private bool TryGetOriginalDiagnosticRange(Diagnostic diagnostic, RazorCodeDocum
         {
             // Couldn't remap the range correctly.
             // If this isn't an `Error` Severity Diagnostic we can discard it.
-            if (diagnostic.Severity != DiagnosticSeverity.Error)
+            if (diagnostic.Severity != LspDiagnosticSeverity.Error)
             {
                 return false;
             }
@@ -474,14 +473,14 @@ private bool TryGetOriginalDiagnosticRange(Diagnostic diagnostic, RazorCodeDocum
         return true;
     }
 
-    private static bool IsRudeEditDiagnostic(Diagnostic diagnostic)
+    private static bool IsRudeEditDiagnostic(LspDiagnostic diagnostic)
     {
         return diagnostic.Code.HasValue &&
             diagnostic.Code.Value.TryGetSecond(out var str) &&
             str.StartsWith("ENC");
     }
 
-    private bool TryRemapRudeEditRange(Range diagnosticRange, RazorCodeDocument codeDocument, [NotNullWhen(true)] out Range? remappedRange)
+    private bool TryRemapRudeEditRange(LspRange diagnosticRange, RazorCodeDocument codeDocument, [NotNullWhen(true)] out LspRange? remappedRange)
     {
         // This is a rude edit diagnostic that has already been mapped to the Razor document. The mapping isn't absolutely correct though,
         // it's based on the runtime code generation of the Razor document therefore we need to re-map the already mapped diagnostic in a
diff --git a/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Remote/IRemoteDiagnosticsService.cs b/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Remote/IRemoteDiagnosticsService.cs
new file mode 100644
index 00000000000..e8f841af660
--- /dev/null
+++ b/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Remote/IRemoteDiagnosticsService.cs
@@ -0,0 +1,20 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System.Collections.Immutable;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.ExternalAccess.Razor;
+using RoslynLspDiagnostic = Microsoft.VisualStudio.LanguageServer.Protocol.Diagnostic;
+
+namespace Microsoft.CodeAnalysis.Razor.Remote;
+
+internal interface IRemoteDiagnosticsService : IRemoteJsonService
+{
+    ValueTask<ImmutableArray<RoslynLspDiagnostic>> GetDiagnosticsAsync(
+        JsonSerializableRazorPinnedSolutionInfoWrapper solutionInfo,
+        JsonSerializableDocumentId documentId,
+        RoslynLspDiagnostic[] csharpDiagnostics,
+        RoslynLspDiagnostic[] htmlDiagnostics,
+        CancellationToken cancellationToken);
+}
diff --git a/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Remote/RazorServices.cs b/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Remote/RazorServices.cs
index 4ede4292572..2e4257cdb3c 100644
--- a/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Remote/RazorServices.cs
+++ b/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Remote/RazorServices.cs
@@ -35,6 +35,7 @@ internal static class RazorServices
             (typeof(IRemoteDocumentSymbolService), null),
             (typeof(IRemoteRenameService), null),
             (typeof(IRemoteGoToImplementationService), null),
+            (typeof(IRemoteDiagnosticsService), null),
         ];
 
     private const string ComponentName = "Razor";
diff --git a/src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/Diagnostics/RemoteDiagnosticsService.cs b/src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/Diagnostics/RemoteDiagnosticsService.cs
new file mode 100644
index 00000000000..4f110734989
--- /dev/null
+++ b/src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/Diagnostics/RemoteDiagnosticsService.cs
@@ -0,0 +1,56 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System.Collections.Immutable;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.CodeAnalysis.ExternalAccess.Razor;
+using Microsoft.CodeAnalysis.Razor.Diagnostics;
+using Microsoft.CodeAnalysis.Razor.Protocol;
+using Microsoft.CodeAnalysis.Razor.Remote;
+using Microsoft.CodeAnalysis.Remote.Razor.ProjectSystem;
+using LspDiagnostic = Microsoft.VisualStudio.LanguageServer.Protocol.Diagnostic;
+
+namespace Microsoft.CodeAnalysis.Remote.Razor;
+
+internal sealed class RemoteDiagnosticsService(in ServiceArgs args) : RazorDocumentServiceBase(in args), IRemoteDiagnosticsService
+{
+    internal sealed class Factory : FactoryBase<IRemoteDiagnosticsService>
+    {
+        protected override IRemoteDiagnosticsService CreateService(in ServiceArgs args)
+            => new RemoteDiagnosticsService(in args);
+    }
+
+    private readonly RazorTranslateDiagnosticsService _translateDiagnosticsService = args.ExportProvider.GetExportedValue<RazorTranslateDiagnosticsService>();
+
+    public ValueTask<ImmutableArray<LspDiagnostic>> GetDiagnosticsAsync(
+        JsonSerializableRazorPinnedSolutionInfoWrapper solutionInfo,
+        JsonSerializableDocumentId documentId,
+        LspDiagnostic[] csharpDiagnostics,
+        LspDiagnostic[] htmlDiagnostics,
+        CancellationToken cancellationToken)
+        => RunServiceAsync(
+            solutionInfo,
+            documentId,
+            context => GetDiagnosticsAsync(context, csharpDiagnostics, htmlDiagnostics, cancellationToken),
+            cancellationToken);
+
+    private async ValueTask<ImmutableArray<LspDiagnostic>> GetDiagnosticsAsync(
+        RemoteDocumentContext context,
+        LspDiagnostic[] csharpDiagnostics,
+        LspDiagnostic[] htmlDiagnostics,
+        CancellationToken cancellationToken)
+    {
+        // We've got C# and Html, lets get Razor diagnostics
+        var codeDocument = await context.GetCodeDocumentAsync(cancellationToken).ConfigureAwait(false);
+        // Yes, CSharpDocument.Documents are the Razor diagnostics. Don't ask.
+        var razorDiagnostics = codeDocument.GetCSharpDocument().Diagnostics;
+
+        return [
+            .. RazorDiagnosticConverter.Convert(razorDiagnostics, codeDocument.Source.Text, context.Snapshot),
+            .. await _translateDiagnosticsService.TranslateAsync(RazorLanguageKind.CSharp, csharpDiagnostics, context.Snapshot),
+            .. await _translateDiagnosticsService.TranslateAsync(RazorLanguageKind.Html, htmlDiagnostics, context.Snapshot)
+        ];
+    }
+}
diff --git a/src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/Diagnostics/RemoteRazorTranslateDiagnosticsService.cs b/src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/Diagnostics/RemoteRazorTranslateDiagnosticsService.cs
new file mode 100644
index 00000000000..78ae0833889
--- /dev/null
+++ b/src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/Diagnostics/RemoteRazorTranslateDiagnosticsService.cs
@@ -0,0 +1,17 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System.Composition;
+using Microsoft.CodeAnalysis.Razor.Diagnostics;
+using Microsoft.CodeAnalysis.Razor.DocumentMapping;
+using Microsoft.CodeAnalysis.Razor.Logging;
+
+namespace Microsoft.CodeAnalysis.Remote.Razor.Diagnostics;
+
+[Export(typeof(RazorTranslateDiagnosticsService)), Shared]
+[method: ImportingConstructor]
+internal sealed class RemoteRazorTranslateDiagnosticsService(
+    IDocumentMappingService documentMappingService,
+    ILoggerFactory loggerFactory) : RazorTranslateDiagnosticsService(documentMappingService, loggerFactory)
+{
+}
diff --git a/src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostDocumentPullDiagnosticsEndpoint.cs b/src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostDocumentPullDiagnosticsEndpoint.cs
new file mode 100644
index 00000000000..2959ef1a0b9
--- /dev/null
+++ b/src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostDocumentPullDiagnosticsEndpoint.cs
@@ -0,0 +1,204 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Composition;
+using System.Linq;
+using System.Text.Json;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor;
+using Microsoft.AspNetCore.Razor.PooledObjects;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.ExternalAccess.Razor;
+using Microsoft.CodeAnalysis.ExternalAccess.Razor.Cohost;
+using Microsoft.CodeAnalysis.Razor.Logging;
+using Microsoft.CodeAnalysis.Razor.ProjectSystem;
+using Microsoft.CodeAnalysis.Razor.Remote;
+using Microsoft.CodeAnalysis.Razor.Workspaces;
+using Microsoft.VisualStudio.LanguageServer.ContainedLanguage;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using ExternalHandlers = Microsoft.CodeAnalysis.ExternalAccess.Razor.Cohost.Handlers;
+using LspDiagnostic = Microsoft.VisualStudio.LanguageServer.Protocol.Diagnostic;
+
+namespace Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
+
+#pragma warning disable RS0030 // Do not use banned APIs
+[Shared]
+[CohostEndpoint(VSInternalMethods.DocumentPullDiagnosticName)]
+[Export(typeof(IDynamicRegistrationProvider))]
+[ExportCohostStatelessLspService(typeof(CohostDocumentPullDiagnosticsEndpoint))]
+[method: ImportingConstructor]
+#pragma warning restore RS0030 // Do not use banned APIs
+internal class CohostDocumentPullDiagnosticsEndpoint(
+    IRemoteServiceInvoker remoteServiceInvoker,
+    IHtmlDocumentSynchronizer htmlDocumentSynchronizer,
+    LSPRequestInvoker requestInvoker,
+    IFilePathService filePathService,
+    ILoggerFactory loggerFactory)
+    : AbstractRazorCohostDocumentRequestHandler<VSInternalDocumentDiagnosticsParams, VSInternalDiagnosticReport[]?>, IDynamicRegistrationProvider
+{
+    private readonly IRemoteServiceInvoker _remoteServiceInvoker = remoteServiceInvoker;
+    private readonly IHtmlDocumentSynchronizer _htmlDocumentSynchronizer = htmlDocumentSynchronizer;
+    private readonly LSPRequestInvoker _requestInvoker = requestInvoker;
+    private readonly IFilePathService _filePathService = filePathService;
+    private readonly ILogger _logger = loggerFactory.GetOrCreateLogger<CohostDocumentPullDiagnosticsEndpoint>();
+
+    protected override bool MutatesSolutionState => false;
+
+    protected override bool RequiresLSPSolution => true;
+
+    public Registration? GetRegistration(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    {
+        // TODO: if (clientCapabilities.TextDocument?.Diagnostic?.DynamicRegistration is true)
+        {
+            return new Registration()
+            {
+                Method = VSInternalMethods.DocumentPullDiagnosticName,
+                RegisterOptions = new VSInternalDiagnosticRegistrationOptions()
+                {
+                    DocumentSelector = filter,
+                    DiagnosticKinds = [VSInternalDiagnosticKind.Syntax]
+                }
+            };
+        }
+
+        // return null;
+    }
+
+    protected override RazorTextDocumentIdentifier? GetRazorTextDocumentIdentifier(VSInternalDocumentDiagnosticsParams request)
+        => request.TextDocument?.ToRazorTextDocumentIdentifier();
+
+    protected override Task<VSInternalDiagnosticReport[]?> HandleRequestAsync(VSInternalDocumentDiagnosticsParams request, RazorCohostRequestContext context, CancellationToken cancellationToken)
+        => HandleRequestAsync(context.TextDocument.AssumeNotNull(), cancellationToken);
+
+    private async Task<VSInternalDiagnosticReport[]?> HandleRequestAsync(TextDocument razorDocument, CancellationToken cancellationToken)
+    {
+        // Diagnostics is a little different, because Roslyn is not designed to run diagnostics in OOP. Their system will transition to OOP
+        // as it needs, but we have to start here in devenv. This is not as big a problem as it sounds, specifically for diagnostics, because
+        // we only need to tell Roslyn the document we need diagnostics for. If we had to map positions or ranges etc. it would be worse
+        // because we'd have to transition to our OOP to find out that info, then back here to get the diagnostics, then back to OOP to process.
+        _logger.LogDebug($"Getting diagnostics for {razorDocument.FilePath}");
+
+        var csharpTask = GetCSharpDiagnosticsAsync(razorDocument, cancellationToken);
+        var htmlTask = GetHtmlDiagnosticsAsync(razorDocument, cancellationToken);
+
+        try
+        {
+            await Task.WhenAll(htmlTask, csharpTask).ConfigureAwait(false);
+        }
+        catch (Exception e)
+        {
+            if (e is not OperationCanceledException)
+            {
+                _logger.LogError(e, $"Exception thrown in PullDiagnostic delegation");
+                throw;
+            }
+        }
+
+        var csharpDiagnostics = await csharpTask.ConfigureAwait(false);
+        var htmlDiagnostics = await htmlTask.ConfigureAwait(false);
+
+        _logger.LogDebug($"Calling OOP with the {csharpDiagnostics.Length} C# and {htmlDiagnostics.Length} Html diagnostics");
+        var diagnostics = await _remoteServiceInvoker.TryInvokeAsync<IRemoteDiagnosticsService, ImmutableArray<LspDiagnostic>>(
+            razorDocument.Project.Solution,
+            (service, solutionInfo, cancellationToken) => service.GetDiagnosticsAsync(solutionInfo, razorDocument.Id, csharpDiagnostics, htmlDiagnostics, cancellationToken),
+            cancellationToken).ConfigureAwait(false);
+
+        if (diagnostics.IsDefaultOrEmpty)
+        {
+            return null;
+        }
+
+        _logger.LogDebug($"Reporting {diagnostics.Length} diagnostics back to the client");
+        return
+        [
+            new()
+            {
+                Diagnostics = diagnostics.ToArray(),
+                ResultId = Guid.NewGuid().ToString()
+            }
+        ];
+    }
+
+    private async Task<LspDiagnostic[]> GetCSharpDiagnosticsAsync(TextDocument razorDocument, CancellationToken cancellationToken)
+    {
+        // TODO: This code will not work when the source generator is hooked up.
+        //       How do we get the source generated C# document without OOP? Can we reverse engineer a file path?
+        var projectKey = razorDocument.Project.ToProjectKey();
+        var csharpFilePath = _filePathService.GetRazorCSharpFilePath(projectKey, razorDocument.FilePath.AssumeNotNull());
+        // We put the project Id in the generated document path, so there can only be one document
+        if (razorDocument.Project.Solution.GetDocumentIdsWithFilePath(csharpFilePath) is not [{ } generatedDocumentId] ||
+            razorDocument.Project.GetDocument(generatedDocumentId) is not { } generatedDocument)
+        {
+            return [];
+        }
+
+        _logger.LogDebug($"Getting C# diagnostics for {generatedDocument.FilePath}");
+        var csharpDiagnostics = await ExternalHandlers.Diagnostics.GetDocumentDiagnosticsAsync(generatedDocument, supportsVisualStudioExtensions: true, cancellationToken).ConfigureAwait(false);
+
+        // This is, to say the least, not ideal. In future we're going to normalize on to Roslyn LSP types, and this can go.
+        var options = new JsonSerializerOptions();
+        foreach (var converter in RazorServiceDescriptorsWrapper.GetLspConverters())
+        {
+            options.Converters.Add(converter);
+        }
+
+        if (JsonSerializer.Deserialize<LspDiagnostic[]>(JsonSerializer.SerializeToDocument(csharpDiagnostics), options) is not { } convertedDiagnostics)
+        {
+            return [];
+        }
+
+        return convertedDiagnostics;
+    }
+
+    private async Task<LspDiagnostic[]> GetHtmlDiagnosticsAsync(TextDocument razorDocument, CancellationToken cancellationToken)
+    {
+        var htmlDocument = await _htmlDocumentSynchronizer.TryGetSynchronizedHtmlDocumentAsync(razorDocument, cancellationToken).ConfigureAwait(false);
+        if (htmlDocument is null)
+        {
+            return [];
+        }
+
+        var diagnosticsParams = new VSInternalDocumentDiagnosticsParams
+        {
+            TextDocument = new TextDocumentIdentifier { Uri = htmlDocument.Uri }
+        };
+
+        _logger.LogDebug($"Getting Html diagnostics for {htmlDocument.Uri}");
+
+        var result = await _requestInvoker.ReinvokeRequestOnServerAsync<VSInternalDocumentDiagnosticsParams, VSInternalDiagnosticReport[]?>(
+            htmlDocument.Buffer,
+            VSInternalMethods.DocumentPullDiagnosticName,
+            RazorLSPConstants.HtmlLanguageServerName,
+            diagnosticsParams,
+            cancellationToken).ConfigureAwait(false);
+
+        if (result?.Response is null)
+        {
+            return [];
+        }
+
+        using var allDiagnostics = new PooledArrayBuilder<LspDiagnostic>();
+        foreach (var report in result.Response)
+        {
+            if (report.Diagnostics is not null)
+            {
+                allDiagnostics.AddRange(report.Diagnostics);
+            }
+        }
+
+        return allDiagnostics.ToArray();
+    }
+
+    internal TestAccessor GetTestAccessor() => new(this);
+
+    internal readonly struct TestAccessor(CohostDocumentPullDiagnosticsEndpoint instance)
+    {
+        public Task<VSInternalDiagnosticReport[]?> HandleRequestAsync(TextDocument razorDocument, CancellationToken cancellationToken)
+            => instance.HandleRequestAsync(razorDocument, cancellationToken);
+    }
+}
+
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Completion/Delegation/DelegatedCompletionItemResolverTest.NetFx.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Completion/Delegation/DelegatedCompletionItemResolverTest.NetFx.cs
index 06fcc14d264..8aeefbf6e87 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Completion/Delegation/DelegatedCompletionItemResolverTest.NetFx.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Completion/Delegation/DelegatedCompletionItemResolverTest.NetFx.cs
@@ -12,7 +12,6 @@
 using Microsoft.AspNetCore.Razor.LanguageServer.Formatting;
 using Microsoft.AspNetCore.Razor.LanguageServer.Test;
 using Microsoft.AspNetCore.Razor.Test.Common.LanguageServer;
-using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.CodeAnalysis.Razor.Formatting;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
 using Microsoft.CodeAnalysis.Razor.Protocol;
@@ -26,7 +25,6 @@
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Completion.Delegation;
 
-[UseExportProvider]
 public class DelegatedCompletionItemResolverTest : LanguageServerTestBase
 {
     private readonly VSInternalClientCapabilities _clientCapabilities;
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Completion/Delegation/DelegatedCompletionListProviderTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Completion/Delegation/DelegatedCompletionListProviderTest.cs
index cc82c40eb4d..faf9392f1f1 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Completion/Delegation/DelegatedCompletionListProviderTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Completion/Delegation/DelegatedCompletionListProviderTest.cs
@@ -10,7 +10,6 @@
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.LanguageServer.Hosting;
 using Microsoft.AspNetCore.Razor.Test.Common.LanguageServer;
-using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
 using Microsoft.CodeAnalysis.Razor.Protocol;
 using Microsoft.CodeAnalysis.Testing;
@@ -21,7 +20,6 @@
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Completion.Delegation;
 
-[UseExportProvider]
 public class DelegatedCompletionListProviderTest : LanguageServerTestBase
 {
     private readonly TestDelegatedCompletionListProvider _provider;
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/CSharpDiagnosticsEndToEndTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/CSharpDiagnosticsEndToEndTest.cs
index 8122d21ac0e..6a650134e75 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/CSharpDiagnosticsEndToEndTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/CSharpDiagnosticsEndToEndTest.cs
@@ -9,6 +9,7 @@
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.LanguageServer.EndpointContracts;
+using Microsoft.CodeAnalysis.Razor.Diagnostics;
 using Microsoft.CodeAnalysis.Testing;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.VisualStudio.LanguageServer.Protocol;
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/DocumentPullDiagnosticsEndpointTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/DocumentPullDiagnosticsEndpointTest.cs
index ecbadccdd23..c930ee00dd7 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/DocumentPullDiagnosticsEndpointTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/DocumentPullDiagnosticsEndpointTest.cs
@@ -5,6 +5,7 @@
 using Microsoft.AspNetCore.Razor.LanguageServer.Hosting;
 using Microsoft.AspNetCore.Razor.Test.Common.LanguageServer;
 using Microsoft.AspNetCore.Razor.Test.Common.Workspaces;
+using Microsoft.CodeAnalysis.Razor.Diagnostics;
 using Microsoft.VisualStudio.LanguageServer.Protocol;
 using Moq;
 using Xunit;
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/RazorDiagnosticConverterTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/RazorDiagnosticConverterTest.cs
index 4e670005541..b62496963d5 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/RazorDiagnosticConverterTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/RazorDiagnosticConverterTest.cs
@@ -6,6 +6,7 @@
 using System.Globalization;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Test.Common.LanguageServer;
+using Microsoft.CodeAnalysis.Razor.Diagnostics;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.VisualStudio.LanguageServer.Protocol;
 using Xunit;
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/RazorDiagnosticsPublisherTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/RazorDiagnosticsPublisherTest.cs
index 869786c9280..c3f9cf2eb0a 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/RazorDiagnosticsPublisherTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/RazorDiagnosticsPublisherTest.cs
@@ -14,6 +14,7 @@
 using Microsoft.AspNetCore.Razor.Test.Common.ProjectSystem;
 using Microsoft.AspNetCore.Razor.Test.Common.Workspaces;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Razor.Diagnostics;
 using Microsoft.CodeAnalysis.Razor.DocumentMapping;
 using Microsoft.CodeAnalysis.Razor.Logging;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/DocumentHighlighting/DocumentHighlightEndpointTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/DocumentHighlighting/DocumentHighlightEndpointTest.cs
index 655f2796130..6510f2dd7ee 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/DocumentHighlighting/DocumentHighlightEndpointTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/DocumentHighlighting/DocumentHighlightEndpointTest.cs
@@ -11,7 +11,6 @@
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.LanguageServer.Hosting;
 using Microsoft.AspNetCore.Razor.Test.Common.LanguageServer;
-using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.CodeAnalysis.Razor.Protocol;
 using Microsoft.CodeAnalysis.Razor.Workspaces;
 using Microsoft.CodeAnalysis.Testing;
@@ -23,7 +22,6 @@
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.DocumentHighlighting;
 
-[UseExportProvider]
 public class DocumentHighlightEndpointTest(ITestOutputHelper testOutput) : LanguageServerTestBase(testOutput)
 {
     [Fact]
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CSharpStatementBlockOnTypeFormattingTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CSharpStatementBlockOnTypeFormattingTest.cs
index 9e769c37366..9354fecb02c 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CSharpStatementBlockOnTypeFormattingTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CSharpStatementBlockOnTypeFormattingTest.cs
@@ -4,12 +4,15 @@
 #nullable disable
 
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Razor.Formatting;
 using Xunit;
 using Xunit.Abstractions;
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Formatting;
 
-public class CSharpStatementBlockOnTypeFormattingTest(ITestOutputHelper testOutput) : FormattingTestBase(testOutput)
+[Collection(HtmlFormattingCollection.Name)]
+public class CSharpStatementBlockOnTypeFormattingTest(HtmlFormattingFixture fixture, ITestOutputHelper testOutput)
+    : FormattingTestBase(fixture.Service, testOutput)
 {
     [Fact]
     public async Task CloseCurly_IfBlock_SingleLineAsync()
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CodeActionFormattingTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CodeActionFormattingTest.cs
index c7067eae067..b5f33ec5aa6 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CodeActionFormattingTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CodeActionFormattingTest.cs
@@ -4,12 +4,15 @@
 #nullable disable
 
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Razor.Formatting;
 using Xunit;
 using Xunit.Abstractions;
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Formatting;
 
-public class CodeActionFormattingTest(ITestOutputHelper testOutput) : FormattingTestBase(testOutput)
+[Collection(HtmlFormattingCollection.Name)]
+public class CodeActionFormattingTest(HtmlFormattingFixture fixture, ITestOutputHelper testOutput)
+    : FormattingTestBase(fixture.Service, testOutput)
 {
     [Fact]
     public async Task AddDebuggerDisplay()
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CodeDirectiveFormattingTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CodeDirectiveFormattingTest.cs
index 24ca9cf007a..fbccac31ee2 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CodeDirectiveFormattingTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CodeDirectiveFormattingTest.cs
@@ -5,12 +5,15 @@
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Test.Common;
+using Microsoft.CodeAnalysis.Razor.Formatting;
 using Xunit;
 using Xunit.Abstractions;
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Formatting;
 
-public class CodeDirectiveFormattingTest(ITestOutputHelper testOutput) : FormattingTestBase(testOutput)
+[Collection(HtmlFormattingCollection.Name)]
+public class CodeDirectiveFormattingTest(HtmlFormattingFixture fixture, ITestOutputHelper testOutput)
+    : FormattingTestBase(fixture.Service, testOutput)
 {
     internal override bool UseTwoPhaseCompilation => true;
 
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CodeDirectiveOnTypeFormattingTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CodeDirectiveOnTypeFormattingTest.cs
index e879f2b59cd..37992612a07 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CodeDirectiveOnTypeFormattingTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/CodeDirectiveOnTypeFormattingTest.cs
@@ -5,12 +5,15 @@
 
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Test.Common;
+using Microsoft.CodeAnalysis.Razor.Formatting;
 using Xunit;
 using Xunit.Abstractions;
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Formatting;
 
-public class CodeDirectiveOnTypeFormattingTest(ITestOutputHelper testOutput) : FormattingTestBase(testOutput)
+[Collection(HtmlFormattingCollection.Name)]
+public class CodeDirectiveOnTypeFormattingTest(HtmlFormattingFixture fixture, ITestOutputHelper testOutput)
+    : FormattingTestBase(fixture.Service, testOutput)
 {
     [Fact]
     public async Task FormatsIfStatementInComponent()
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/FormattingLanguageServerClient.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/FormattingLanguageServerClient.cs
index f647e7d31d6..5779ad5aa30 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/FormattingLanguageServerClient.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/FormattingLanguageServerClient.cs
@@ -18,8 +18,9 @@
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Formatting;
 
-internal class FormattingLanguageServerClient(ILoggerFactory loggerFactory) : IClientConnection
+internal class FormattingLanguageServerClient(HtmlFormattingService htmlFormattingService, ILoggerFactory loggerFactory) : IClientConnection
 {
+    private readonly HtmlFormattingService _htmlFormattingService = htmlFormattingService;
     private readonly Dictionary<string, RazorCodeDocument> _documents = [];
     private readonly ILoggerFactory _loggerFactory = loggerFactory;
 
@@ -36,7 +37,7 @@ private async Task<RazorDocumentFormattingResponse> FormatAsync(DocumentOnTypeFo
     {
         var generatedHtml = GetGeneratedHtml(@params.TextDocument.Uri);
 
-        var edits =  await HtmlFormatting.GetOnTypeFormattingEditsAsync(_loggerFactory, @params.TextDocument.Uri, generatedHtml, @params.Position, @params.Options.InsertSpaces, @params.Options.TabSize);
+        var edits =  await _htmlFormattingService.GetOnTypeFormattingEditsAsync(_loggerFactory, @params.TextDocument.Uri, generatedHtml, @params.Position, @params.Options.InsertSpaces, @params.Options.TabSize);
 
         return new()
         {
@@ -48,7 +49,7 @@ private async Task<RazorDocumentFormattingResponse> FormatAsync(DocumentFormatti
     {
         var generatedHtml = GetGeneratedHtml(@params.TextDocument.Uri);
 
-        var edits = await HtmlFormatting.GetDocumentFormattingEditsAsync(_loggerFactory, @params.TextDocument.Uri, generatedHtml, @params.Options.InsertSpaces, @params.Options.TabSize);
+        var edits = await _htmlFormattingService.GetDocumentFormattingEditsAsync(_loggerFactory, @params.TextDocument.Uri, generatedHtml, @params.Options.InsertSpaces, @params.Options.TabSize);
 
         return new()
         {
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/FormattingTestBase.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/FormattingTestBase.cs
index 6c3b299990b..8e070db10f5 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/FormattingTestBase.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/FormattingTestBase.cs
@@ -34,10 +34,14 @@ namespace Microsoft.AspNetCore.Razor.LanguageServer.Formatting;
 
 public class FormattingTestBase : RazorToolingIntegrationTestBase
 {
-    public FormattingTestBase(ITestOutputHelper testOutput)
+    private readonly HtmlFormattingService _htmlFormattingService;
+
+    internal FormattingTestBase(HtmlFormattingService htmlFormattingService, ITestOutputHelper testOutput)
         : base(testOutput)
     {
         ITestOnlyLoggerExtensions.TestOnlyLoggingEnabled = true;
+
+        _htmlFormattingService = htmlFormattingService;
     }
 
     private protected async Task RunFormattingTestAsync(
@@ -94,7 +98,7 @@ private async Task RunFormattingTestInternalAsync(string input, string expected,
         var formattingService = await TestRazorFormattingService.CreateWithFullSupportAsync(LoggerFactory, codeDocument, razorLSPOptions);
         var documentContext = new DocumentContext(uri, documentSnapshot, projectContext: null);
 
-        var client = new FormattingLanguageServerClient(LoggerFactory);
+        var client = new FormattingLanguageServerClient(_htmlFormattingService, LoggerFactory);
         client.AddCodeDocument(codeDocument);
 
         var htmlFormatter = new HtmlFormatter(client);
@@ -159,7 +163,7 @@ private protected async Task RunOnTypeFormattingTestAsync(
         }
         else
         {
-            var client = new FormattingLanguageServerClient(LoggerFactory);
+            var client = new FormattingLanguageServerClient(_htmlFormattingService, LoggerFactory);
             client.AddCodeDocument(codeDocument);
 
             var htmlFormatter = new HtmlFormatter(client);
@@ -168,7 +172,7 @@ private protected async Task RunOnTypeFormattingTestAsync(
         }
 
         // Assert
-        var edited = razorSourceText.WithChanges( changes);
+        var edited = razorSourceText.WithChanges(changes);
         var actual = edited.ToString();
 
         AssertEx.EqualOrDiff(expected, actual);
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/HtmlFormattingCollection.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/HtmlFormattingCollection.cs
new file mode 100644
index 00000000000..c8eacf6f87d
--- /dev/null
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/HtmlFormattingCollection.cs
@@ -0,0 +1,13 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using Microsoft.CodeAnalysis.Razor.Formatting;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Razor.LanguageServer.Formatting;
+
+[CollectionDefinition(Name)]
+public class HtmlFormattingCollection : ICollectionFixture<HtmlFormattingFixture>
+{
+    public const string Name = nameof(HtmlFormattingCollection);
+}
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/HtmlFormattingTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/HtmlFormattingTest.cs
index 300f2fc42c1..593b32dd64e 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/HtmlFormattingTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/HtmlFormattingTest.cs
@@ -14,7 +14,9 @@
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Formatting;
 
-public class HtmlFormattingTest(ITestOutputHelper testOutput) : FormattingTestBase(testOutput)
+[Collection(HtmlFormattingCollection.Name)]
+public class HtmlFormattingTest(HtmlFormattingFixture fixture, ITestOutputHelper testOutput)
+    : FormattingTestBase(fixture.Service, testOutput)
 {
     internal override bool UseTwoPhaseCompilation => true;
 
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/RazorFormattingTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/RazorFormattingTest.cs
index 27bb6dc6e7c..6a3cd641b89 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/RazorFormattingTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Formatting_NetFx/RazorFormattingTest.cs
@@ -7,12 +7,14 @@
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.LanguageServer.Hosting;
 using Microsoft.AspNetCore.Razor.Test.Common;
+using Microsoft.CodeAnalysis.Razor.Formatting;
 using Xunit;
 using Xunit.Abstractions;
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Formatting;
 
-public class RazorFormattingTest(ITestOutputHelper testOutput) : FormattingTestBase(testOutput)
+[Collection(HtmlFormattingCollection.Name)]
+public class RazorFormattingTest(HtmlFormattingFixture fixture, ITestOutputHelper testOutput) : FormattingTestBase(fixture.Service, testOutput)
 {
     [Fact]
     public async Task Section_BraceOnNextLine()
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Hover/HoverServiceTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Hover/HoverServiceTest.cs
index 246335632f0..c884946e106 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Hover/HoverServiceTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Hover/HoverServiceTest.cs
@@ -13,7 +13,6 @@
 using Microsoft.AspNetCore.Razor.ProjectSystem;
 using Microsoft.AspNetCore.Razor.Test.Common;
 using Microsoft.AspNetCore.Razor.Test.Common.LanguageServer;
-using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.AspNetCore.Razor.Test.Common.ProjectSystem;
 using Microsoft.CodeAnalysis.Razor.DocumentMapping;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
@@ -29,7 +28,6 @@
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Test.Hover;
 
-[UseExportProvider]
 public class HoverServiceTest(ITestOutputHelper testOutput) : TagHelperServiceTestBase(testOutput)
 {
     private static VSInternalClientCapabilities CreateMarkDownCapabilities()
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/MapCode/MapCodeTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/MapCode/MapCodeTest.cs
index 31ea7e1b81e..0fa73622a5a 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/MapCode/MapCodeTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/MapCode/MapCodeTest.cs
@@ -10,7 +10,6 @@
 using Microsoft.AspNetCore.Razor.LanguageServer.MapCode;
 using Microsoft.AspNetCore.Razor.Telemetry;
 using Microsoft.AspNetCore.Razor.Test.Common.LanguageServer;
-using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
 using Microsoft.CodeAnalysis.Razor.Protocol;
 using Microsoft.CodeAnalysis.Testing;
@@ -22,7 +21,6 @@
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Test.MapCode;
 
-[UseExportProvider]
 public class MapCodeTest(ITestOutputHelper testOutput) : LanguageServerTestBase(testOutput)
 {
     private const string RazorFilePath = "C:/path/to/file.razor";
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Refactoring/RenameEndpointDelegationTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Refactoring/RenameEndpointDelegationTest.cs
index e96dbb8b141..0a06da92a94 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Refactoring/RenameEndpointDelegationTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Refactoring/RenameEndpointDelegationTest.cs
@@ -7,7 +7,6 @@
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Language;
-using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
 using Microsoft.CodeAnalysis.Razor.Rename;
 using Microsoft.CodeAnalysis.Razor.Workspaces;
@@ -19,7 +18,6 @@
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Refactoring;
 
-[UseExportProvider]
 public class RenameEndpointDelegationTest(ITestOutputHelper testOutput) : SingleServerDelegatingEndpointTestBase(testOutput)
 {
     [Fact]
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Refactoring/RenameEndpointTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Refactoring/RenameEndpointTest.cs
index 1ff45c926a5..2bb699fdf80 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Refactoring/RenameEndpointTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Refactoring/RenameEndpointTest.cs
@@ -17,7 +17,6 @@
 using Microsoft.AspNetCore.Razor.ProjectSystem;
 using Microsoft.AspNetCore.Razor.Test.Common;
 using Microsoft.AspNetCore.Razor.Test.Common.LanguageServer;
-using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Razor.DocumentMapping;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
@@ -33,7 +32,6 @@
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Refactoring;
 
-[UseExportProvider]
 public class RenameEndpointTest(ITestOutputHelper testOutput) : LanguageServerTestBase(testOutput)
 {
     private static readonly string s_project1BasePath = PathUtilities.CreateRootedPath("First");
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Semantic/SemanticTokensTest.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Semantic/SemanticTokensTest.cs
index 455da63ae60..3f0365de187 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Semantic/SemanticTokensTest.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Semantic/SemanticTokensTest.cs
@@ -19,7 +19,6 @@
 using Microsoft.AspNetCore.Razor.PooledObjects;
 using Microsoft.AspNetCore.Razor.Test.Common;
 using Microsoft.AspNetCore.Razor.Test.Common.LanguageServer;
-using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
 using Microsoft.CodeAnalysis.Razor.Protocol;
@@ -35,7 +34,6 @@
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer.Semantic;
 
-[UseExportProvider]
 public partial class SemanticTokensTest(ITestOutputHelper testOutput) : TagHelperServiceTestBase(testOutput)
 {
     private readonly Mock<IClientConnection> _clientConnection = new(MockBehavior.Strict);
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/SingleServerDelegatingEndpointTestBase.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/SingleServerDelegatingEndpointTestBase.cs
index 49c4fbb7423..c2c8405e394 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/SingleServerDelegatingEndpointTestBase.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/SingleServerDelegatingEndpointTestBase.cs
@@ -7,7 +7,6 @@
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Test.Common.LanguageServer;
-using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.AspNetCore.Razor.Test.Common.ProjectSystem;
 using Microsoft.CodeAnalysis.Razor.DocumentMapping;
 using Microsoft.CodeAnalysis.Razor.ProjectSystem;
@@ -19,7 +18,6 @@
 
 namespace Microsoft.AspNetCore.Razor.LanguageServer;
 
-[UseExportProvider]
 public abstract partial class SingleServerDelegatingEndpointTestBase(ITestOutputHelper testOutput) : LanguageServerTestBase(testOutput)
 {
     private protected IDocumentContextFactory? DocumentContextFactory { get; private set; }
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Formatting_NetFx/HtmlFormattingFixture.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Formatting_NetFx/HtmlFormattingFixture.cs
new file mode 100644
index 00000000000..13881a19c93
--- /dev/null
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Formatting_NetFx/HtmlFormattingFixture.cs
@@ -0,0 +1,18 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System;
+
+namespace Microsoft.CodeAnalysis.Razor.Formatting;
+
+public class HtmlFormattingFixture : IDisposable
+{
+    private readonly HtmlFormattingService _htmlFormattingService = new();
+
+    internal HtmlFormattingService Service => _htmlFormattingService;
+
+    public void Dispose()
+    {
+        _htmlFormattingService.Dispose();
+    }
+}
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Formatting_NetFx/HtmlFormatting.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Formatting_NetFx/HtmlFormattingService.cs
similarity index 78%
rename from src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Formatting_NetFx/HtmlFormatting.cs
rename to src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Formatting_NetFx/HtmlFormattingService.cs
index 1879dfadf1d..7c082b276cc 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Formatting_NetFx/HtmlFormatting.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Formatting_NetFx/HtmlFormattingService.cs
@@ -10,6 +10,7 @@
 using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.CodeAnalysis.Razor.Logging;
 using Microsoft.CodeAnalysis.Text;
+using Microsoft.VisualStudio.Composition;
 using Microsoft.VisualStudio.LanguageServer.Protocol;
 using Microsoft.VisualStudio.Text;
 using Microsoft.VisualStudio.Utilities;
@@ -17,9 +18,21 @@
 
 namespace Microsoft.CodeAnalysis.Razor.Formatting;
 
-internal static class HtmlFormatting
+internal sealed class HtmlFormattingService : IDisposable
 {
-    public static Task<TextEdit[]?> GetDocumentFormattingEditsAsync(ILoggerFactory loggerFactory, Uri uri, string generatedHtml, bool insertSpaces, int tabSize)
+    private ExportProvider? _exportProvider;
+
+    private ExportProvider ExportProvider => _exportProvider ?? (_exportProvider = TestComposition.Editor.ExportProviderFactory.CreateExportProvider());
+
+    public void Dispose()
+    {
+        if (_exportProvider is not null)
+        {
+            _exportProvider.Dispose();
+        }
+    }
+
+    public Task<TextEdit[]?> GetDocumentFormattingEditsAsync(ILoggerFactory loggerFactory, Uri uri, string generatedHtml, bool insertSpaces, int tabSize)
     {
         var request = $$"""
             {
@@ -37,7 +50,7 @@ internal static class HtmlFormatting
         return CallWebToolsApplyFormattedEditsHandlerAsync(loggerFactory, request, uri, generatedHtml);
     }
 
-    public static Task<TextEdit[]?> GetOnTypeFormattingEditsAsync(ILoggerFactory loggerFactory, Uri uri, string generatedHtml, Position position, bool insertSpaces, int tabSize)
+    public Task<TextEdit[]?> GetOnTypeFormattingEditsAsync(ILoggerFactory loggerFactory, Uri uri, string generatedHtml, Position position, bool insertSpaces, int tabSize)
     {
         var generatedHtmlSource = SourceText.From(generatedHtml, Encoding.UTF8);
         var absoluteIndex = generatedHtmlSource.GetRequiredAbsoluteIndex(position);
@@ -64,10 +77,9 @@ internal static class HtmlFormatting
         return CallWebToolsApplyFormattedEditsHandlerAsync(loggerFactory, request, uri, generatedHtml);
     }
 
-    private static async Task<TextEdit[]?> CallWebToolsApplyFormattedEditsHandlerAsync(ILoggerFactory loggerFactory, string serializedValue, Uri documentUri, string generatedHtml)
+    private async Task<TextEdit[]?> CallWebToolsApplyFormattedEditsHandlerAsync(ILoggerFactory loggerFactory, string serializedValue, Uri documentUri, string generatedHtml)
     {
-        var exportProvider = TestComposition.Editor.ExportProviderFactory.CreateExportProvider();
-        var contentTypeService = exportProvider.GetExportedValue<IContentTypeRegistryService>();
+        var contentTypeService = ExportProvider.GetExportedValue<IContentTypeRegistryService>();
 
         lock (contentTypeService)
         {
@@ -77,7 +89,7 @@ internal static class HtmlFormatting
             }
         }
 
-        var textBufferFactoryService = (ITextBufferFactoryService3)exportProvider.GetExportedValue<ITextBufferFactoryService>();
+        var textBufferFactoryService = (ITextBufferFactoryService3)ExportProvider.GetExportedValue<ITextBufferFactoryService>();
         var bufferManager = WebTools.BufferManager.New(contentTypeService, textBufferFactoryService, []);
         var logger = loggerFactory.GetOrCreateLogger("ApplyFormattedEditsHandler");
         var applyFormatEditsHandler = WebTools.ApplyFormatEditsHandler.New(textBufferFactoryService, bufferManager, logger);
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Language/IntegrationTests/RazorToolingIntegrationTestBase.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Language/IntegrationTests/RazorToolingIntegrationTestBase.cs
index 8d4d088e7d9..c7ad99dc1b7 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Language/IntegrationTests/RazorToolingIntegrationTestBase.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Language/IntegrationTests/RazorToolingIntegrationTestBase.cs
@@ -12,7 +12,6 @@
 using Microsoft.AspNetCore.Components;
 using Microsoft.AspNetCore.Razor.PooledObjects;
 using Microsoft.AspNetCore.Razor.Test.Common;
-using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.Razor;
@@ -22,7 +21,6 @@
 
 namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests;
 
-[UseExportProvider]
 public class RazorToolingIntegrationTestBase : ToolingTestBase
 {
     internal const string ArbitraryWindowsPath = "x:\\dir\\subdir\\Test";
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/LanguageServer/CSharpTestLspServer.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/LanguageServer/CSharpTestLspServer.cs
index 2b20c842cf4..f095947c978 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/LanguageServer/CSharpTestLspServer.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/LanguageServer/CSharpTestLspServer.cs
@@ -22,7 +22,7 @@ namespace Microsoft.AspNetCore.Razor.Test.Common.LanguageServer;
 public sealed class CSharpTestLspServer : IAsyncDisposable
 {
     private readonly AdhocWorkspace _testWorkspace;
-    private readonly IRazorLanguageServerTarget _languageServer;
+    private readonly ExportProvider _exportProvider;
 
     private readonly JsonRpc _clientRpc;
     private readonly JsonRpc _serverRpc;
@@ -41,6 +41,7 @@ private CSharpTestLspServer(
         CancellationToken cancellationToken)
     {
         _testWorkspace = testWorkspace;
+        _exportProvider = exportProvider;
         _cancellationToken = cancellationToken;
 
         var (clientStream, serverStream) = FullDuplexStream.CreatePair();
@@ -67,7 +68,7 @@ private CSharpTestLspServer(
 
         _clientRpc.StartListening();
 
-        _languageServer = CreateLanguageServer(_serverRpc, _serverMessageFormatter.JsonSerializerOptions, testWorkspace, languageServerFactory, exportProvider, serverCapabilities);
+        _ = CreateLanguageServer(_serverRpc, _serverMessageFormatter.JsonSerializerOptions, testWorkspace, languageServerFactory, exportProvider, serverCapabilities);
 
         static SystemTextJsonFormatter CreateSystemTextJsonMessageFormatter(AbstractRazorLanguageServerFactoryWrapper languageServerFactory)
         {
@@ -146,6 +147,7 @@ internal Task<ResponseType> ExecuteRequestAsync<RequestType, ResponseType>(
     public async ValueTask DisposeAsync()
     {
         _testWorkspace.Dispose();
+        _exportProvider.Dispose();
 
         _clientRpc.Dispose();
         _clientMessageFormatter.Dispose();
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/LanguageServer/CSharpTestLspServerHelpers.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/LanguageServer/CSharpTestLspServerHelpers.cs
index ecf351fe1e8..b91d512c39c 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/LanguageServer/CSharpTestLspServerHelpers.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/LanguageServer/CSharpTestLspServerHelpers.cs
@@ -6,7 +6,6 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
-using System.IO;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -14,9 +13,7 @@
 using Microsoft.AspNetCore.Razor.Test.Common.Workspaces;
 using Microsoft.AspNetCore.Razor.Threading;
 using Microsoft.CodeAnalysis;
-using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.ExternalAccess.Razor;
-using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.Razor;
 using Microsoft.CodeAnalysis.Testing;
 using Microsoft.CodeAnalysis.Text;
@@ -109,8 +106,7 @@ private static AdhocWorkspace CreateCSharpTestWorkspace(
         IRazorSpanMappingService razorSpanMappingService,
         bool multiTargetProject)
     {
-        var hostServices = MefHostServices.Create(exportProvider.AsCompositionContext());
-        var workspace = TestWorkspace.Create(hostServices);
+        var workspace = TestWorkspace.CreateWithDiagnosticAnalyzers(exportProvider);
 
         // Add project and solution to workspace
         var projectInfoNet60 = ProjectInfo.Create(
@@ -135,14 +131,10 @@ private static AdhocWorkspace CreateCSharpTestWorkspace(
             ? [projectInfoNet60, projectInfoNet80]
             : [projectInfoNet80];
 
-        var solutionInfo = SolutionInfo.Create(
-            id: SolutionId.CreateNewId("TestSolution"),
-            version: VersionStamp.Default,
-            projects: projectInfos);
-
-        workspace.AddSolution(solutionInfo);
-
-        AddAnalyzersToWorkspace(workspace, exportProvider);
+        foreach (var projectInfo in projectInfos)
+        {
+            workspace.AddProject(projectInfo);
+        }
 
         // Add document to workspace. We use an IVT method to create the DocumentInfo variable because there's
         // a special constructor in Roslyn that will help identify the document as belonging to Razor.
@@ -172,30 +164,6 @@ private static AdhocWorkspace CreateCSharpTestWorkspace(
         return workspace;
     }
 
-    private static void AddAnalyzersToWorkspace(Workspace workspace, ExportProvider exportProvider)
-    {
-        var analyzerLoader = RazorTestAnalyzerLoader.CreateAnalyzerAssemblyLoader();
-
-        var analyzerPaths = new DirectoryInfo(AppContext.BaseDirectory).GetFiles("*.dll")
-            .Where(f => f.Name.StartsWith("Microsoft.CodeAnalysis.", StringComparison.Ordinal) && !f.Name.Contains("LanguageServer") && !f.Name.Contains("Test.Utilities"))
-            .Select(f => f.FullName)
-            .ToImmutableArray();
-        var references = new List<AnalyzerFileReference>();
-        foreach (var analyzerPath in analyzerPaths)
-        {
-            if (File.Exists(analyzerPath))
-            {
-                references.Add(new AnalyzerFileReference(analyzerPath, analyzerLoader));
-            }
-        }
-
-        workspace.TryApplyChanges(workspace.CurrentSolution.WithAnalyzerReferences(references));
-
-        // Make sure Roslyn is producing diagnostics for our workspace
-        var razorTestAnalyzerLoader = exportProvider.GetExportedValue<RazorTestAnalyzerLoader>();
-        razorTestAnalyzerLoader.InitializeDiagnosticsServices(workspace);
-    }
-
     private record CSharpFile(Uri DocumentUri, SourceText CSharpSourceText);
 
     private class EmptyMappingService : IRazorSpanMappingService
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/ExportProviderCache.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/ExportProviderCache.cs
index 2b2a62815a7..e8937fd4a96 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/ExportProviderCache.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/ExportProviderCache.cs
@@ -2,14 +2,10 @@
 // Licensed under the MIT license. See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Concurrent;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Linq;
 using System.Reflection;
-using System.Threading;
 using System.Threading.Tasks;
-using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.VisualStudio.Composition;
 
 namespace Microsoft.AspNetCore.Razor.Test.Common.Mef;
@@ -18,60 +14,6 @@ public static class ExportProviderCache
 {
     private static readonly PartDiscovery s_partDiscovery = CreatePartDiscovery(Resolver.DefaultInstance);
 
-    private static readonly TestComposition s_defaultHostExportProviderComposition = TestComposition.Empty
-        .AddAssemblies(MefHostServices.DefaultAssemblies);
-    private static readonly ConcurrentDictionary<string, Scope> s_scopes = new();
-    private const string DefaultScope = "default";
-
-    private static readonly object s_lock = new();
-
-    internal static bool Enabled { get; private set; }
-
-    internal static ExportProvider[] ExportProvidersForCleanup
-    {
-        get
-        {
-            var scopes = s_scopes.Values.ToArray();
-            var defaultScope = scopes.Where(scope => scope.Name == DefaultScope);
-            var allButDefault = scopes.Where(scope => scope.Name != DefaultScope);
-
-            // Make sure to return the default scope as the last element
-            return allButDefault.Concat(defaultScope)
-                .Where(scope => scope._currentExportProvider is { })
-                .Select(scope => scope._currentExportProvider!)
-                .ToArray();
-        }
-    }
-
-    internal static void SetEnabled_OnlyUseExportProviderAttributeCanCall(bool value)
-    {
-        lock (s_lock)
-        {
-            Enabled = value;
-            if (!Enabled)
-            {
-                foreach (var scope in s_scopes.Values.ToArray())
-                {
-                    scope.Clear();
-                }
-            }
-        }
-    }
-
-    /// <summary>
-    /// Use to create <see cref="IExportProviderFactory"/> for default instances of <see cref="MefHostServices"/>.
-    /// </summary>
-    public static IExportProviderFactory GetOrCreateExportProviderFactory(IEnumerable<Assembly> assemblies)
-    {
-        if (assemblies is ImmutableArray<Assembly> assembliesArray &&
-            assembliesArray == MefHostServices.DefaultAssemblies)
-        {
-            return s_defaultHostExportProviderComposition.ExportProviderFactory;
-        }
-
-        return CreateExportProviderFactory(CreateAssemblyCatalog(assemblies), scopeName: DefaultScope);
-    }
-
     public static ComposableCatalog CreateAssemblyCatalog(IEnumerable<Assembly> assemblies, Resolver? resolver = null)
     {
         var discovery = resolver is null ? s_partDiscovery : CreatePartDiscovery(resolver);
@@ -125,151 +67,48 @@ bool IsExcludedPart(ComposablePartDefinition part)
         }
     }
 
-    public static IExportProviderFactory CreateExportProviderFactory(ComposableCatalog catalog, string? scopeName = null)
+    public static IExportProviderFactory CreateExportProviderFactory(ComposableCatalog catalog)
     {
-        var scope = s_scopes.GetOrAdd(scopeName ?? DefaultScope, scopeName => new Scope(scopeName));
         var configuration = CompositionConfiguration.Create(catalog.WithCompositionService());
+        ValidateConfiguration(configuration);
+
         var runtimeComposition = RuntimeComposition.CreateRuntimeComposition(configuration);
         var exportProviderFactory = runtimeComposition.CreateExportProviderFactory();
 
-        return new SingleExportProviderFactory(scope, catalog, configuration, exportProviderFactory);
+        return exportProviderFactory;
     }
 
-    private sealed class SingleExportProviderFactory : IExportProviderFactory
+    private static void ValidateConfiguration(CompositionConfiguration configuration)
     {
-        private readonly Scope _scope;
-        private readonly ComposableCatalog _catalog;
-        private readonly CompositionConfiguration _configuration;
-        private readonly IExportProviderFactory _exportProviderFactory;
-
-        public SingleExportProviderFactory(Scope scope, ComposableCatalog catalog, CompositionConfiguration configuration, IExportProviderFactory exportProviderFactory)
+        foreach (var errorCollection in configuration.CompositionErrors)
         {
-            _scope = scope;
-            _catalog = catalog;
-            _configuration = configuration;
-            _exportProviderFactory = exportProviderFactory;
-        }
-
-        private ExportProvider GetOrCreateExportProvider()
-        {
-            if (!Enabled)
-            {
-                // The [UseExportProvider] attribute on tests ensures that the pre- and post-conditions of methods
-                // in this type are met during test conditions.
-                throw new InvalidOperationException($"{nameof(ExportProviderCache)} may only be used from tests marked with {nameof(UseExportProviderAttribute)}");
-            }
-
-            var expectedCatalog = Interlocked.CompareExchange(ref _scope._expectedCatalog, _catalog, null) ?? _catalog;
-            RequireForSingleExportProvider(expectedCatalog == _catalog);
-
-            var expected = _scope._expectedProviderForCatalog;
-            if (expected is null)
+            foreach (var error in errorCollection)
             {
-                foreach (var errorCollection in _configuration.CompositionErrors)
+                foreach (var part in error.Parts)
                 {
-                    foreach (var error in errorCollection)
+                    foreach (var pair in part.SatisfyingExports)
                     {
-                        foreach (var part in error.Parts)
+                        var (importBinding, exportBindings) = (pair.Key, pair.Value);
+                        if (exportBindings.Count <= 1)
                         {
-                            foreach (var pair in part.SatisfyingExports)
-                            {
-                                var (importBinding, exportBindings) = (pair.Key, pair.Value);
-                                if (exportBindings.Count <= 1)
-                                {
-                                    // Ignore composition errors for missing parts
-                                    continue;
-                                }
+                            // Ignore composition errors for missing parts
+                            continue;
+                        }
 
-                                if (importBinding.ImportDefinition.Cardinality != ImportCardinality.ZeroOrMore)
-                                {
-                                    // This failure occurs when a binding fails because multiple exports were
-                                    // provided but only a single one (at most) is expected. This typically occurs
-                                    // when a test ExportProvider is created with a mock implementation without
-                                    // first removing a value provided by default.
-                                    throw new InvalidOperationException(
-                                        "Failed to construct the MEF catalog for testing. Multiple exports were found for a part for which only one export is expected:" + Environment.NewLine
-                                        + error.Message);
-                                }
-                            }
+                        if (importBinding.ImportDefinition.Cardinality != ImportCardinality.ZeroOrMore)
+                        {
+                            // This failure occurs when a binding fails because multiple exports were
+                            // provided but only a single one (at most) is expected. This typically occurs
+                            // when a test ExportProvider is created with a mock implementation without
+                            // first removing a value provided by default.
+                            throw new InvalidOperationException(
+                                "Failed to construct the MEF catalog for testing. Multiple exports were found for a part for which only one export is expected:" + Environment.NewLine
+                                + error.Message);
                         }
                     }
                 }
-
-                expected = _exportProviderFactory.CreateExportProvider();
-                expected = Interlocked.CompareExchange(ref _scope._expectedProviderForCatalog, expected, null) ?? expected;
-                Interlocked.CompareExchange(ref _scope._currentExportProvider, expected, null);
-            }
-
-            var exportProvider = _scope._currentExportProvider;
-            RequireForSingleExportProvider(exportProvider == expected);
-
-            return exportProvider!;
-        }
-
-        ExportProvider IExportProviderFactory.CreateExportProvider()
-        {
-            // Currently this implementation deviates from the typical behavior of IExportProviderFactory. For the
-            // duration of a single test, an instance of SingleExportProviderFactory will continue returning the
-            // same ExportProvider instance each time this method is called.
-            //
-            // It may be clearer to refactor the implementation to only allow one call to CreateExportProvider in
-            // the context of a single test. https://github.com/dotnet/roslyn/issues/25863
-            lock (s_lock)
-            {
-                return GetOrCreateExportProvider();
             }
         }
-
-        private void RequireForSingleExportProvider(bool condition)
-        {
-            if (!condition)
-            {
-                // The ExportProvider provides services that act as singleton instances in the context of an
-                // application (this include cases of multiple exports, where the 'singleton' is the list of all
-                // exports matching the contract). When reasoning about the behavior of test code, it is valuable to
-                // know service instances will be used in a consistent manner throughout the execution of a test,
-                // regardless of whether they are passed as arguments or obtained through requests to the
-                // ExportProvider.
-                //
-                // Restricting a test to a single ExportProvider guarantees that objects that *look* like singletons
-                // will *behave* like singletons for the duration of the test. Each test is expected to create and
-                // use its ExportProvider in a consistent manner.
-                //
-                // A test that validates remote services is allowed to create a couple of ExportProviders:
-                // one for local workspace and the other for the remote one.
-                //
-                // When this exception is thrown by a test, it typically means one of the following occurred:
-                //
-                // * A test failed to pass an ExportProvider via an optional argument to a method, resulting in the
-                //   method attempting to create a default ExportProvider which did not match the one assigned to
-                //   the test.
-                // * A test attempted to perform multiple test sequences in the context of a single test method,
-                //   rather than break up the test into distinct tests for each case.
-                // * A test referenced different predefined ExportProvider instances within the context of a test.
-                //   Each test is expected to use the same ExportProvider throughout the test.
-                throw new InvalidOperationException($"Only one {_scope.Name} {nameof(ExportProvider)} can be created in the context of a single test.");
-            }
-        }
-    }
-
-    private sealed class Scope
-    {
-        public readonly string Name;
-        public ExportProvider? _currentExportProvider;
-        public ComposableCatalog? _expectedCatalog;
-        public ExportProvider? _expectedProviderForCatalog;
-
-        public Scope(string name)
-        {
-            Name = name;
-        }
-
-        public void Clear()
-        {
-            _currentExportProvider = null;
-            _expectedCatalog = null;
-            _expectedProviderForCatalog = null;
-        }
     }
 
     private sealed class SimpleAssemblyLoader : IAssemblyLoader
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/ExportProviderExtensions.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/ExportProviderExtensions.cs
index 05540f3862b..18d5c5dd654 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/ExportProviderExtensions.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/ExportProviderExtensions.cs
@@ -3,12 +3,12 @@
 
 using System;
 using System.Collections.Generic;
-using System.Composition.Hosting.Core;
 using System.Composition;
+using System.Composition.Hosting.Core;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
-using Microsoft.VisualStudio.Composition;
 using System.Reflection;
+using Microsoft.VisualStudio.Composition;
 
 namespace Microsoft.AspNetCore.Razor.Test.Common.Mef;
 
@@ -31,43 +31,55 @@ public CompositionContextShim(ExportProvider exportProvider)
         public override bool TryGetExport(CompositionContract contract, [NotNullWhen(true)] out object? export)
         {
             var importMany = contract.MetadataConstraints.Contains(new KeyValuePair<string, object>("IsImportMany", true));
-            var (contractType, metadataType) = GetContractType(contract.ContractType, importMany);
+            var (contractType, metadataType, isLazy) = GetContractType(contract.ContractType, importMany);
 
-            if (metadataType != null)
+            var method = (metadataType, isLazy) switch
             {
-                var methodInfo = (from method in _exportProvider.GetType().GetTypeInfo().GetMethods()
-                                  where method.Name == nameof(ExportProvider.GetExports)
-                                  where method.IsGenericMethod && method.GetGenericArguments().Length == 2
-                                  where method.GetParameters().Length == 1 && method.GetParameters()[0].ParameterType == typeof(string)
-                                  select method).Single();
-                var parameterizedMethod = methodInfo.MakeGenericMethod(contractType, metadataType);
-                export = parameterizedMethod.Invoke(_exportProvider, new[] { contract.ContractName });
-                Assumes.NotNull(export);
+                (not null, true) => GetExportProviderGenericMethod(nameof(ExportProvider.GetExports), contractType, metadataType),
+                (null, true) => GetExportProviderGenericMethod(nameof(ExportProvider.GetExports), contractType),
+                (null, false) => GetExportProviderGenericMethod(nameof(ExportProvider.GetExportedValues), contractType),
+                _ => null
+            };
+
+            if (method is null)
+            {
+                export = null;
+                return false;
             }
-            else
+
+            export = method.Invoke(_exportProvider, [contract.ContractName]);
+            Assumes.NotNull(export);
+
+            return true;
+
+            static MethodInfo GetExportProviderGenericMethod(string methodName, params Type[] typeArguments)
             {
-                var methodInfo = (from method in _exportProvider.GetType().GetTypeInfo().GetMethods()
-                                  where method.Name == nameof(ExportProvider.GetExports)
-                                  where method.IsGenericMethod && method.GetGenericArguments().Length == 1
+                var methodInfo = (from method in typeof(ExportProvider).GetTypeInfo().GetMethods()
+                                  where method.Name == methodName
+                                  where method.IsGenericMethod && method.GetGenericArguments().Length == typeArguments.Length
                                   where method.GetParameters().Length == 1 && method.GetParameters()[0].ParameterType == typeof(string)
                                   select method).Single();
-                var parameterizedMethod = methodInfo.MakeGenericMethod(contractType);
-                export = parameterizedMethod.Invoke(_exportProvider, new[] { contract.ContractName });
-                Assumes.NotNull(export);
-            }
 
-            return true;
+                return methodInfo.MakeGenericMethod(typeArguments);
+            }
         }
 
-        private static (Type exportType, Type? metadataType) GetContractType(Type contractType, bool importMany)
+        private static (Type exportType, Type? metadataType, bool isLazy) GetContractType(Type contractType, bool importMany)
         {
-            if (importMany && contractType.IsConstructedGenericType)
+            if (importMany)
             {
-                if (contractType.GetGenericTypeDefinition() == typeof(IList<>)
-                    || contractType.GetGenericTypeDefinition() == typeof(ICollection<>)
-                    || contractType.GetGenericTypeDefinition() == typeof(IEnumerable<>))
+                if (contractType.IsConstructedGenericType)
+                {
+                    if (contractType.GetGenericTypeDefinition() == typeof(IList<>)
+                        || contractType.GetGenericTypeDefinition() == typeof(ICollection<>)
+                        || contractType.GetGenericTypeDefinition() == typeof(IEnumerable<>))
+                    {
+                        contractType = contractType.GenericTypeArguments[0];
+                    }
+                }
+                else if (contractType.IsArray)
                 {
-                    contractType = contractType.GenericTypeArguments[0];
+                    contractType = contractType.GetElementType().AssumeNotNull();
                 }
             }
 
@@ -75,11 +87,11 @@ private static (Type exportType, Type? metadataType) GetContractType(Type contra
             {
                 if (contractType.GetGenericTypeDefinition() == typeof(Lazy<>))
                 {
-                    return (contractType.GenericTypeArguments[0], null);
+                    return (contractType.GenericTypeArguments[0], null, true);
                 }
                 else if (contractType.GetGenericTypeDefinition() == typeof(Lazy<,>))
                 {
-                    return (contractType.GenericTypeArguments[0], contractType.GenericTypeArguments[1]);
+                    return (contractType.GenericTypeArguments[0], contractType.GenericTypeArguments[1], true);
                 }
                 else
                 {
@@ -87,7 +99,7 @@ private static (Type exportType, Type? metadataType) GetContractType(Type contra
                 }
             }
 
-            throw new NotSupportedException();
+            return (contractType, null, false);
         }
     }
 }
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/TestComposition.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/TestComposition.cs
index 4144af3544b..d73f291ca9c 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/TestComposition.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/TestComposition.cs
@@ -22,8 +22,7 @@ public sealed partial class TestComposition
     public static readonly TestComposition Empty = new(
         ImmutableHashSet<Assembly>.Empty,
         ImmutableHashSet<Type>.Empty,
-        ImmutableHashSet<Type>.Empty,
-        scope: null);
+        ImmutableHashSet<Type>.Empty);
 
     public static readonly TestComposition Roslyn = Empty
         .AddAssemblies(MefHostServices.DefaultAssemblies)
@@ -102,32 +101,17 @@ public override int GetHashCode()
     /// </summary>
     public readonly ImmutableHashSet<Type> Parts;
 
-    /// <summary>
-    /// The scope in which to create the export provider, or <see langword="null"/> to use the default scope.
-    /// </summary>
-    public readonly string? Scope;
-
     private readonly Lazy<IExportProviderFactory> _exportProviderFactory;
 
-    private TestComposition(ImmutableHashSet<Assembly> assemblies, ImmutableHashSet<Type> parts, ImmutableHashSet<Type> excludedPartTypes, string? scope)
+    private TestComposition(ImmutableHashSet<Assembly> assemblies, ImmutableHashSet<Type> parts, ImmutableHashSet<Type> excludedPartTypes)
     {
         Assemblies = assemblies;
         Parts = parts;
         ExcludedPartTypes = excludedPartTypes;
-        Scope = scope;
 
         _exportProviderFactory = new Lazy<IExportProviderFactory>(GetOrCreateFactory);
     }
 
-#if false
-/// <summary>
-/// Returns a new instance of <see cref="HostServices"/> for the composition. This will either be a MEF composition or VS MEF composition host,
-/// depending on what layer the composition is for. Editor Features and VS layers use VS MEF composition while anything else uses System.Composition.
-/// </summary>
-public HostServices GetHostServices()
-    => VisualStudioMefHostServices.Create(ExportProviderFactory.CreateExportProvider());
-#endif
-
     /// <summary>
     /// VS MEF <see cref="ExportProvider"/>.
     /// </summary>
@@ -145,7 +129,7 @@ private IExportProviderFactory GetOrCreateFactory()
             }
         }
 
-        var newFactory = ExportProviderCache.CreateExportProviderFactory(GetCatalog(), Scope);
+        var newFactory = ExportProviderCache.CreateExportProviderFactory(GetCatalog());
 
         lock (s_factoryCache)
         {
@@ -215,7 +199,7 @@ public TestComposition WithAssemblies(ImmutableHashSet<Assembly> assemblies)
         var testAssembly = assemblies.FirstOrDefault(IsTestAssembly);
         Verify.Operation(testAssembly is null, $"Test assemblies are not allowed in test composition: {testAssembly}. Specify explicit test parts instead.");
 
-        return new TestComposition(assemblies, Parts, ExcludedPartTypes, Scope);
+        return new TestComposition(assemblies, Parts, ExcludedPartTypes);
 
         static bool IsTestAssembly(Assembly assembly)
         {
@@ -230,13 +214,10 @@ static bool IsTestAssembly(Assembly assembly)
     }
 
     public TestComposition WithParts(ImmutableHashSet<Type> parts)
-        => parts == Parts ? this : new TestComposition(Assemblies, parts, ExcludedPartTypes, Scope);
+        => parts == Parts ? this : new TestComposition(Assemblies, parts, ExcludedPartTypes);
 
     public TestComposition WithExcludedPartTypes(ImmutableHashSet<Type> excludedPartTypes)
-        => excludedPartTypes == ExcludedPartTypes ? this : new TestComposition(Assemblies, Parts, excludedPartTypes, Scope);
-
-    public TestComposition WithScope(string? scope)
-        => scope == Scope ? this : new TestComposition(Assemblies, Parts, ExcludedPartTypes, scope);
+        => excludedPartTypes == ExcludedPartTypes ? this : new TestComposition(Assemblies, Parts, excludedPartTypes);
 
     /// <summary>
     /// Use for VS MEF composition troubleshooting.
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/UseExportProviderAttribute.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/UseExportProviderAttribute.cs
deleted file mode 100644
index 8f2d7ba28f3..00000000000
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Mef/UseExportProviderAttribute.cs
+++ /dev/null
@@ -1,232 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the MIT license. See License.txt in the project root for license information.
-
-using System;
-using System.Reflection;
-using Microsoft.CodeAnalysis.Host;
-using Microsoft.VisualStudio.Composition;
-using Xunit.Sdk;
-
-namespace Microsoft.AspNetCore.Razor.Test.Common.Mef;
-
-/// <summary>
-/// This attribute supports tests that need to use a MEF container (<see cref="ExportProvider"/>) directly or
-/// indirectly during the test sequence. It ensures production code uniformly handles the export provider created
-/// during a test, and cleans up the state before the test completes.
-/// </summary>
-/// <remarks>
-/// <para>This attribute serves several important functions for tests that use state variables which are otherwise
-/// shared at runtime:</para>
-/// <list type="bullet">
-/// <item>Ensures <see cref="HostServices"/> implementations all use the same <see cref="ExportProvider"/>, which is
-/// the one created by the test.</item>
-/// <item>Clears static cached values in production code holding instances of <see cref="HostServices"/>, or any
-/// object obtained from it or one of its related interfaces such as <see cref="HostLanguageServices"/>.</item>
-/// <item>Isolates tests by waiting for asynchronous operations to complete before a test is considered
-/// complete.</item>
-/// <item>When required, provides a separate <see cref="ExportProvider"/> for the <see cref="T:RemoteWorkspace"/>
-/// executing in the test process. If this provider is created during testing, it is cleaned up with the primary
-/// export provider during test teardown.</item>
-/// </list>
-/// </remarks>
-[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
-public class UseExportProviderAttribute : BeforeAfterTestAttribute
-{
-    /// <summary>
-    /// Asynchronous operations are expected to be cancelled at the end of the test that started them. Operations
-    /// cancelled by the test are cleaned up immediately. The remaining operations are given an opportunity to run
-    /// to completion. If this timeout is exceeded by the asynchronous operations running after a test completes,
-    /// the test is failed.
-    /// </summary>
-    private static readonly TimeSpan s_cleanupTimeout = TimeSpan.FromMinutes(1);
-
-#if false
-private MefHostServices? _hostServices;
-#endif
-
-    public override void Before(MethodInfo? methodUnderTest)
-    {
-#if false
-    MefHostServices.TestAccessor.HookServiceCreation(CreateMefHostServices);
-
-    // make sure we enable this for all unit tests
-    AsynchronousOperationListenerProvider.Enable(enable: true, diagnostics: true);
-#endif
-
-        ExportProviderCache.SetEnabled_OnlyUseExportProviderAttributeCanCall(true);
-    }
-
-    /// <summary>
-    /// To the extent reasonably possible, this method resets the state of the test environment to the same state as
-    /// it started, ensuring that tests running in sequence cannot influence the outcome of later tests.
-    /// </summary>
-    /// <remarks>
-    /// <para>The test cleanup runs in two primary steps:</para>
-    /// <list type="number">
-    /// <item>Waiting for asynchronous operations started by the test to complete.</item>
-    /// <item>Disposing of mutable resources created by the test.</item>
-    /// <item>Clearing static state variables related to the use of MEF during a test.</item>
-    /// </list>
-    /// </remarks>
-    public override void After(MethodInfo? methodUnderTest)
-    {
-        try
-        {
-            foreach (var exportProvider in ExportProviderCache.ExportProvidersForCleanup)
-            {
-                DisposeExportProvider(exportProvider);
-            }
-        }
-        finally
-        {
-#if false
-        // Replace hooks with ones that always throw exceptions. These hooks detect cases where code executing
-        // after the end of a test attempts to create an ExportProvider.
-        MefHostServices.TestAccessor.HookServiceCreation(DenyMefHostServicesCreationBetweenTests);
-#endif
-
-            // Reset static state variables.
-#if false
-        _hostServices = null;
-#endif
-            ExportProviderCache.SetEnabled_OnlyUseExportProviderAttributeCanCall(false);
-        }
-    }
-
-    private static void DisposeExportProvider(ExportProvider? exportProvider)
-    {
-        if (exportProvider is null)
-        {
-            return;
-        }
-
-        // Dispose of the export provider, including calling Dispose for any IDisposable services created during the test.
-        using var _ = exportProvider;
-
-#if false
-    if (exportProvider.GetExportedValues<IAsynchronousOperationListenerProvider>().SingleOrDefault() is { } listenerProvider)
-    {
-        if (exportProvider.GetExportedValues<IThreadingContext>().SingleOrDefault()?.HasMainThread ?? false)
-        {
-            // Immediately clear items from the foreground notification service for which cancellation is
-            // requested. This service maintains a queue separately from Tasks, and work items scheduled for
-            // execution after a delay are not immediately purged when cancellation is requested. This code
-            // instructs the service to walk the list of queued work items and immediately cancel and purge any
-            // which are already cancelled.
-            var foregroundNotificationService = exportProvider.GetExportedValues<IForegroundNotificationService>().SingleOrDefault() as ForegroundNotificationService;
-            foregroundNotificationService?.ReleaseCancelledItems();
-        }
-
-        // Verify the synchronization context was not used incorrectly
-        var testExportJoinableTaskContext = exportProvider.GetExportedValues<TestExportJoinableTaskContext>().SingleOrDefault();
-        var denyExecutionSynchronizationContext = testExportJoinableTaskContext?.SynchronizationContext as TestExportJoinableTaskContext.DenyExecutionSynchronizationContext;
-
-        // Join remaining operations with a timeout
-        using (var timeoutTokenSource = new CancellationTokenSource(s_cleanupTimeout))
-        {
-            if (denyExecutionSynchronizationContext is object)
-            {
-                // Immediately cancel the test if the synchronization context is improperly used
-                denyExecutionSynchronizationContext.InvalidSwitch += delegate { timeoutTokenSource.CancelAfter(0); };
-                denyExecutionSynchronizationContext.ThrowIfSwitchOccurred();
-            }
-
-            try
-            {
-                // This attribute cleans up the in-process and out-of-process export providers separately, so we
-                // don't need to provide a workspace when waiting for operations to complete.
-                var waiter = ((AsynchronousOperationListenerProvider)listenerProvider).WaitAllDispatcherOperationAndTasksAsync(workspace: null);
-                waiter.JoinUsingDispatcher(timeoutTokenSource.Token);
-            }
-            catch (OperationCanceledException ex) when (timeoutTokenSource.IsCancellationRequested)
-            {
-                // If the failure was caused by an invalid thread change, throw that exception
-                denyExecutionSynchronizationContext?.ThrowIfSwitchOccurred();
-
-                var messageBuilder = new StringBuilder("Failed to clean up listeners in a timely manner.");
-                foreach (var token in ((AsynchronousOperationListenerProvider)listenerProvider).GetTokens())
-                {
-                    messageBuilder.AppendLine().Append($"  {token}");
-                }
-
-                throw new TimeoutException(messageBuilder.ToString(), ex);
-            }
-        }
-
-        denyExecutionSynchronizationContext?.ThrowIfSwitchOccurred();
-
-        foreach (var testErrorHandler in exportProvider.GetExportedValues<ITestErrorHandler>())
-        {
-            var exceptions = testErrorHandler.Exceptions;
-            if (exceptions.Count > 0)
-            {
-                throw new AggregateException("Tests threw unexpected exceptions", exceptions);
-            }
-        }
-    }
-#endif
-    }
-
-#if false
-private MefHostServices CreateMefHostServices(IEnumerable<Assembly> assemblies)
-{
-    ExportProvider exportProvider;
-
-    if (assemblies is ImmutableArray<Assembly> array &&
-        array == MefHostServices.DefaultAssemblies &&
-        ExportProviderCache.LocalExportProviderForCleanup != null)
-    {
-        if (_hostServices != null)
-        {
-            return _hostServices;
-        }
-
-        exportProvider = ExportProviderCache.LocalExportProviderForCleanup;
-    }
-    else
-    {
-        exportProvider = ExportProviderCache.GetOrCreateExportProviderFactory(assemblies).CreateExportProvider();
-    }
-
-    Interlocked.CompareExchange(
-            ref _hostServices,
-            new ExportProviderMefHostServices(exportProvider),
-            null);
-
-    return _hostServices;
-}
-
-private static MefHostServices DenyMefHostServicesCreationBetweenTests(IEnumerable<Assembly> assemblies)
-{
-    // If you hit this, one of three situations occurred:
-    //
-    // 1. A test method that uses ExportProvider is not marked with UseExportProviderAttribute (can also be
-    //    applied to the containing type or a base type.
-    // 2. A test attempted to create an ExportProvider during the test cleanup operations after the
-    //    ExportProvider was already disposed.
-    // 3. A test attempted to use an ExportProvider in the constructor of the test, or during the initialization
-    //    of a field in the test class.
-    throw new InvalidOperationException("Cannot create host services after test tear down.");
-}
-
-private class ExportProviderMefHostServices : MefHostServices, IMefHostExportProvider
-{
-    private readonly VisualStudioMefHostServices _vsHostServices;
-
-    public ExportProviderMefHostServices(ExportProvider exportProvider)
-        : base(new ContainerConfiguration().CreateContainer())
-    {
-        _vsHostServices = VisualStudioMefHostServices.Create(exportProvider);
-    }
-
-    protected internal override HostWorkspaceServices CreateWorkspaceServices(Workspace workspace)
-        => _vsHostServices.CreateWorkspaceServices(workspace);
-
-    IEnumerable<Lazy<TExtension, TMetadata>> IMefHostExportProvider.GetExports<TExtension, TMetadata>()
-        => _vsHostServices.GetExports<TExtension, TMetadata>();
-
-    IEnumerable<Lazy<TExtension>> IMefHostExportProvider.GetExports<TExtension>()
-        => _vsHostServices.GetExports<TExtension>();
-}
-#endif
-}
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Microsoft.AspNetCore.Razor.Test.Common.Tooling.csproj b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Microsoft.AspNetCore.Razor.Test.Common.Tooling.csproj
index 89019499fa8..6683bf95cdb 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Microsoft.AspNetCore.Razor.Test.Common.Tooling.csproj
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Microsoft.AspNetCore.Razor.Test.Common.Tooling.csproj
@@ -89,10 +89,6 @@
     <InternalsVisibleTo Include="rzls" Key="$(RazorKey)" />
   </ItemGroup>
 
-  <ItemGroup>
-    <Folder Include="Resources\Benchmarking\" />
-  </ItemGroup>
-
   <Import Condition="'$(TargetFramework)' != '$(DefaultNetFxTargetFramework)'" Project="..\..\..\Shared\Microsoft.AspNetCore.Razor.Serialization.Json\Microsoft.AspNetCore.Razor.Serialization.Json.projitems" Label="Shared" />
 
 </Project>
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/TestCode.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/TestCode.cs
index 6930bda0d33..9374bd108ab 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/TestCode.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/TestCode.cs
@@ -47,6 +47,9 @@ public TextSpan Span
     public ImmutableArray<TextSpan> Spans
         => GetNamedSpans(string.Empty);
 
+    public ImmutableDictionary<string, ImmutableArray<TextSpan>> NamedSpans
+        => _nameToSpanMap;
+
     public ImmutableArray<TextSpan> GetNamedSpans(string name)
         => _nameToSpanMap[name];
 
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Workspaces/TestWorkspace.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Workspaces/TestWorkspace.cs
index cae18632e56..57042c42c99 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Workspaces/TestWorkspace.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common.Tooling/Workspaces/TestWorkspace.cs
@@ -2,8 +2,17 @@
 // Licensed under the MIT license. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.IO;
+using System.Linq;
+using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.ExternalAccess.Razor;
 using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.VisualStudio.Composition;
 
 namespace Microsoft.AspNetCore.Razor.Test.Common.Workspaces;
 
@@ -14,6 +23,17 @@ public static class TestWorkspace
     public static Workspace Create(Action<AdhocWorkspace>? configure = null)
         => Create(services: null, configure: configure);
 
+    public static AdhocWorkspace CreateWithDiagnosticAnalyzers(ExportProvider exportProvider)
+    {
+        var hostServices = MefHostServices.Create(exportProvider.AsCompositionContext());
+
+        var workspace = Create(hostServices);
+
+        AddAnalyzersToWorkspace(workspace, exportProvider);
+
+        return workspace;
+    }
+
     public static AdhocWorkspace Create(HostServices? services, Action<AdhocWorkspace>? configure = null)
     {
         lock (s_workspaceLock)
@@ -27,4 +47,24 @@ public static AdhocWorkspace Create(HostServices? services, Action<AdhocWorkspac
             return workspace;
         }
     }
+
+    private static void AddAnalyzersToWorkspace(Workspace workspace, ExportProvider exportProvider)
+    {
+        var analyzerLoader = RazorTestAnalyzerLoader.CreateAnalyzerAssemblyLoader();
+
+        var analyzerPaths = new DirectoryInfo(AppContext.BaseDirectory).GetFiles("*.dll")
+            .Where(f => f.Name.StartsWith("Microsoft.CodeAnalysis.", StringComparison.Ordinal) && !f.Name.Contains("LanguageServer") && !f.Name.Contains("Test.Utilities"))
+            .Select(f => f.FullName)
+            .ToImmutableArray();
+        var references = new List<AnalyzerFileReference>();
+        foreach (var analyzerPath in analyzerPaths)
+        {
+            if (File.Exists(analyzerPath))
+            {
+                references.Add(new AnalyzerFileReference(analyzerPath, analyzerLoader));
+            }
+        }
+
+        workspace.TryApplyChanges(workspace.CurrentSolution.WithAnalyzerReferences(references));
+    }
 }
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentFormattingEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentFormattingEndpointTest.cs
index 3c8f9b268b0..7370b711fc1 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentFormattingEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentFormattingEndpointTest.cs
@@ -5,7 +5,6 @@
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Test.Common;
-using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.ExternalAccess.Razor;
 using Microsoft.CodeAnalysis.Razor.Formatting;
@@ -19,8 +18,9 @@
 
 namespace Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
 
-[UseExportProvider]
-public class CohostDocumentFormattingEndpointTest(ITestOutputHelper testOutputHelper) : CohostEndpointTestBase(testOutputHelper)
+[Collection(HtmlFormattingCollection.Name)]
+public class CohostDocumentFormattingEndpointTest(HtmlFormattingFixture htmlFormattingFixture, ITestOutputHelper testOutputHelper)
+    : CohostEndpointTestBase(testOutputHelper)
 {
     // All of the formatting tests in the language server exercise the formatting engine and cover various edge cases
     // and provide regression prevention. The tests here are not exhaustive, but they validate the the cohost endpoints
@@ -108,7 +108,7 @@ private void M(string thisIsMyString)
 
     private async Task VerifyDocumentFormattingAsync(string input, string expected)
     {
-        var document = CreateProjectAndRazorDocument(input);
+        var document = await CreateProjectAndRazorDocumentAsync(input);
         var inputText = await document.GetTextAsync(DisposalToken);
 
         var htmlDocumentPublisher = new HtmlDocumentPublisher(RemoteServiceInvoker, StrictMock.Of<TrackingLSPDocumentManager>(), StrictMock.Of<JoinableTaskContext>(), LoggerFactory);
@@ -116,7 +116,7 @@ private async Task VerifyDocumentFormattingAsync(string input, string expected)
         Assert.NotNull(generatedHtml);
 
         var uri = new Uri(document.CreateUri(), $"{document.FilePath}{FeatureOptions.HtmlVirtualDocumentSuffix}");
-        var htmlEdits = await HtmlFormatting.GetDocumentFormattingEditsAsync(LoggerFactory, uri, generatedHtml, insertSpaces: true, tabSize: 4);
+        var htmlEdits = await htmlFormattingFixture.Service.GetDocumentFormattingEditsAsync(LoggerFactory, uri, generatedHtml, insertSpaces: true, tabSize: 4);
 
         var requestInvoker = new TestLSPRequestInvoker([(Methods.TextDocumentFormattingName, htmlEdits)]);
 
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentHighlightEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentHighlightEndpointTest.cs
index ce044474c00..65de7ed10a9 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentHighlightEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentHighlightEndpointTest.cs
@@ -147,7 +147,7 @@ @inject [|IDis$$posable|] Disposable
     private async Task VerifyDocumentHighlightsAsync(string input, DocumentHighlight[]? htmlResponse = null)
     {
         TestFileMarkupParser.GetPositionAndSpans(input, out var source, out int cursorPosition, out ImmutableArray<TextSpan> spans);
-        var document = CreateProjectAndRazorDocument(source);
+        var document = await CreateProjectAndRazorDocumentAsync(source);
         var inputText = await document.GetTextAsync(DisposalToken);
         var position = inputText.GetPosition(cursorPosition);
 
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentPullDiagnosticsTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentPullDiagnosticsTest.cs
new file mode 100644
index 00000000000..1bc8fd332cc
--- /dev/null
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentPullDiagnosticsTest.cs
@@ -0,0 +1,121 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor;
+using Microsoft.AspNetCore.Razor.Test.Common;
+using Microsoft.CodeAnalysis.Text;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using Roslyn.Test.Utilities;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
+
+public class CohostDocumentPullDiagnosticsTest(ITestOutputHelper testOutputHelper) : CohostEndpointTestBase(testOutputHelper)
+{
+    [Fact]
+    public Task CSharp()
+        => VerifyDiagnosticsAsync("""
+            <div></div>
+
+            @code
+            {
+                public void IJustMetYou()
+                {
+                    {|CS0103:CallMeMaybe|}();
+                }
+            }
+            """);
+
+    [Fact]
+    public Task Razor()
+        => VerifyDiagnosticsAsync("""
+            <div>
+
+            {|RZ10012:<NonExistentComponent />|}
+
+            </div>
+            """);
+
+    [Fact]
+    public Task Html()
+    {
+        TestCode input = """
+            <div>
+
+            {|HTM1337:<not_a_tag />|}
+
+            </div>
+            """;
+
+        return VerifyDiagnosticsAsync(input,
+            htmlResponse: [new VSInternalDiagnosticReport
+            {
+                Diagnostics =
+                [
+                    new Diagnostic
+                    {
+                        Code = "HTM1337",
+                        Range = SourceText.From(input.Text).GetRange(input.NamedSpans.First().Value.First())
+                    }
+                ]
+            }]);
+    }
+
+    [Fact]
+    public Task CombinedAndNestedDiagnostics()
+        => VerifyDiagnosticsAsync("""
+            @using System.Threading.Tasks;
+
+            <div>
+
+            {|RZ10012:<NonExistentComponent />|}
+
+            @code
+            {
+                public void IJustMetYou()
+                {
+                    {|CS0103:CallMeMaybe|}();
+                }
+            }
+
+            <div>
+                @{
+                    {|CS4033:await Task.{|CS1501:Delay|}()|};
+                }
+
+                {|RZ9980:<p>|}
+            </div>
+
+            </div>
+            """);
+
+    private async Task VerifyDiagnosticsAsync(TestCode input, VSInternalDiagnosticReport[]? htmlResponse = null)
+    {
+        var document = await CreateProjectAndRazorDocumentAsync(input.Text, createSeparateRemoteAndLocalWorkspaces: true);
+        var inputText = await document.GetTextAsync(DisposalToken);
+
+        var requestInvoker = new TestLSPRequestInvoker([(VSInternalMethods.DocumentPullDiagnosticName, htmlResponse)]);
+
+        var endpoint = new CohostDocumentPullDiagnosticsEndpoint(RemoteServiceInvoker, TestHtmlDocumentSynchronizer.Instance, requestInvoker, FilePathService, LoggerFactory);
+
+        var result = await endpoint.GetTestAccessor().HandleRequestAsync(document, DisposalToken);
+
+        var markers = result!.SelectMany(d => d.Diagnostics.AssumeNotNull()).SelectMany(d =>
+            new[] {
+                (index: inputText.GetTextSpan(d.Range).Start, text: $"{{|{d.Code!.Value.Second}:"),
+                (index: inputText.GetTextSpan(d.Range).End, text:"|}")
+            });
+
+        var testOutput = input.Text;
+        foreach (var (index, text) in markers.OrderByDescending(i => i.index))
+        {
+            testOutput = testOutput.Insert(index, text);
+        }
+
+        AssertEx.EqualOrDiff(input.OriginalInput, testOutput);
+    }
+}
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentSpellCheckEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentSpellCheckEndpointTest.cs
index 6711a4bdc2b..51c5d3d28a9 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentSpellCheckEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentSpellCheckEndpointTest.cs
@@ -57,7 +57,7 @@ Eat more chickin.
 
     private async Task VerifySemanticTokensAsync(TestCode input)
     {
-        var document = CreateProjectAndRazorDocument(input.Text);
+        var document = await CreateProjectAndRazorDocumentAsync(input.Text);
         var sourceText = await document.GetTextAsync(DisposalToken);
 
         var endpoint = new CohostDocumentSpellCheckEndpoint(RemoteServiceInvoker);
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentSymbolEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentSymbolEndpointTest.cs
index 0f008bc6ef2..2cc98c4c923 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentSymbolEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostDocumentSymbolEndpointTest.cs
@@ -69,7 +69,7 @@ public Task DocumentSymbols_CSharpMethods(bool hierarchical)
     private async Task VerifyDocumentSymbolsAsync(string input, bool hierarchical = false)
     {
         TestFileMarkupParser.GetSpans(input, out input, out ImmutableDictionary<string, ImmutableArray<TextSpan>> spansDict);
-        var document = CreateProjectAndRazorDocument(input);
+        var document = await CreateProjectAndRazorDocumentAsync(input);
 
         var endpoint = new CohostDocumentSymbolEndpoint(RemoteServiceInvoker);
 
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostEndpointTestBase.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostEndpointTestBase.cs
index 3573e1badf6..bec19c8cbab 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostEndpointTestBase.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostEndpointTestBase.cs
@@ -9,10 +9,13 @@
 using Microsoft.AspNetCore.Razor;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Test.Common;
+using Microsoft.AspNetCore.Razor.Test.Common.Mef;
+using Microsoft.AspNetCore.Razor.Test.Common.Workspaces;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Razor.Remote;
 using Microsoft.CodeAnalysis.Razor.Workspaces;
 using Microsoft.CodeAnalysis.Remote.Razor;
+using Microsoft.CodeAnalysis.Remote.Razor.ProjectSystem;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.VisualStudio.Composition;
 using Xunit.Abstractions;
@@ -68,7 +71,7 @@ private protected void UpdateClientInitializationOptions(Func<RemoteClientInitia
         FeatureOptions.SetOptions(_clientInitializationOptions);
     }
 
-    protected TextDocument CreateProjectAndRazorDocument(string contents, string? fileKind = null, (string fileName, string contents)[]? additionalFiles = null)
+    protected Task<TextDocument> CreateProjectAndRazorDocumentAsync(string contents, string? fileKind = null, (string fileName, string contents)[]? additionalFiles = null, bool createSeparateRemoteAndLocalWorkspaces = false)
     {
         // Using IsLegacy means null == component, so easier for test authors
         var isComponent = !FileKinds.IsLegacy(fileKind);
@@ -82,6 +85,56 @@ protected TextDocument CreateProjectAndRazorDocument(string contents, string? fi
         var projectId = ProjectId.CreateNewId(debugName: projectName);
         var documentId = DocumentId.CreateNewId(projectId, debugName: documentFilePath);
 
+        var remoteWorkspace = RemoteWorkspaceAccessor.GetWorkspace();
+        var remoteDocument = CreateProjectAndRazorDocument(remoteWorkspace, projectId, projectName, documentId, documentFilePath, contents, additionalFiles);
+
+        if (createSeparateRemoteAndLocalWorkspaces)
+        {
+            // Usually its fine to just use the remote workspace, but sometimes we need to also have things available in the
+            // "devenv" side of Roslyn, which is a different workspace with a different set of services. We don't have any
+            // actual solution syncing set up for testing, and don't really use a service broker, but since we also would
+            // expect to never make changes to a workspace, it should be fine to simply create duplicated solutions as part
+            // of test setup.
+            return CreateLocalProjectAndRazorDocumentAsync(remoteDocument.Project.Solution, projectId, projectName, documentId, documentFilePath, contents, additionalFiles);
+        }
+
+        // If we're just creating one workspace, then its the remote one and we just return the remote document
+        // and assume that the endpoint under test doesn't need to do anything on the devenv side. This makes it
+        // easier for tests to mutate solutions
+        return Task.FromResult(remoteDocument);
+    }
+
+    private async Task<TextDocument> CreateLocalProjectAndRazorDocumentAsync(Solution remoteSolution, ProjectId projectId, string projectName, DocumentId documentId, string documentFilePath, string contents, (string fileName, string contents)[]? additionalFiles)
+    {
+        var exportProvider = TestComposition.Roslyn.ExportProviderFactory.CreateExportProvider();
+        AddDisposable(exportProvider);
+        var workspace = TestWorkspace.CreateWithDiagnosticAnalyzers(exportProvider);
+        AddDisposable(workspace);
+
+        var razorDocument = CreateProjectAndRazorDocument(workspace, projectId, projectName, documentId, documentFilePath, contents, additionalFiles);
+
+        // Until the source generator is hooked up, the workspace representing "local" projects doesn't have anything
+        // to actually compile the Razor to C#, so we just do it now at creation
+        var solution = razorDocument.Project.Solution;
+        // We're cheating a bit here and using the remote export provider to get something to do the compilation
+        var factory = _exportProvider.AssumeNotNull().GetExportedValue<DocumentSnapshotFactory>();
+        var snapshot = factory.GetOrCreate(razorDocument);
+        // Compile the Razor file
+        var codeDocument = await snapshot.GetGeneratedOutputAsync(false);
+        // Update the generated doc contents
+        var generatedDocumentIds = solution.GetDocumentIdsWithFilePath(documentFilePath + CSharpVirtualDocumentSuffix);
+        solution = solution.WithDocumentText(generatedDocumentIds, codeDocument.GetCSharpSourceText());
+        razorDocument = solution.GetAdditionalDocument(documentId).AssumeNotNull();
+
+        // If we're creating remote and local workspaces, then we'll return the local document, and have to allow
+        // the remote service invoker to map from the local solution to the remote one.
+        RemoteServiceInvoker.MapSolutionIdToRemote(razorDocument.Project.Solution.Id, remoteSolution);
+
+        return razorDocument;
+    }
+
+    private static TextDocument CreateProjectAndRazorDocument(CodeAnalysis.Workspace workspace, ProjectId projectId, string projectName, DocumentId documentId, string documentFilePath, string contents, (string fileName, string contents)[]? additionalFiles)
+    {
         var projectInfo = ProjectInfo
             .Create(
                 projectId,
@@ -93,9 +146,6 @@ protected TextDocument CreateProjectAndRazorDocument(string contents, string? fi
             .WithDefaultNamespace(TestProjectData.SomeProject.RootNamespace)
             .WithMetadataReferences(AspNet80.ReferenceInfos.All.Select(r => r.Reference));
 
-        // Importantly, we use Roslyn's remote workspace here so that when our OOP services call into Roslyn, their code
-        // will be able to access their services.
-        var workspace = RemoteWorkspaceAccessor.GetWorkspace();
         var solution = workspace.CurrentSolution.AddProject(projectInfo);
 
         solution = solution
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostFoldingRangeEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostFoldingRangeEndpointTest.cs
index 08ad6977496..1bfb8b299cd 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostFoldingRangeEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostFoldingRangeEndpointTest.cs
@@ -7,7 +7,6 @@
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor;
 using Microsoft.AspNetCore.Razor.Language;
-using Microsoft.CodeAnalysis.Razor.Workspaces;
 using Microsoft.CodeAnalysis.Testing;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.VisualStudio.LanguageServer.Protocol;
@@ -218,7 +217,7 @@ public void M() {[|
     private async Task VerifyFoldingRangesAsync(string input, string? fileKind = null)
     {
         TestFileMarkupParser.GetSpans(input, out var source, out ImmutableDictionary<string, ImmutableArray<TextSpan>> spans);
-        var document = CreateProjectAndRazorDocument(source, fileKind);
+        var document = await CreateProjectAndRazorDocumentAsync(source, fileKind);
         var inputText = await document.GetTextAsync(DisposalToken);
 
         var htmlSpans = spans.GetValueOrDefault("html").NullToEmpty();
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostGoToDefinitionEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostGoToDefinitionEndpointTest.cs
index b97fe4ef07a..f5b8b6e77e3 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostGoToDefinitionEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostGoToDefinitionEndpointTest.cs
@@ -8,7 +8,6 @@
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Test.Common;
 using Microsoft.CodeAnalysis.ExternalAccess.Razor;
-using Microsoft.CodeAnalysis.Remote.Razor;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.VisualStudio.LanguageServer.Protocol;
 using Xunit;
@@ -313,7 +312,7 @@ public async Task Html()
             </script>
             """;
 
-        var document = CreateProjectAndRazorDocument(input.Text);
+        var document = await CreateProjectAndRazorDocumentAsync(input.Text);
         var inputText = await document.GetTextAsync(DisposalToken);
 
         var htmlResponse = new SumType<Location, Location[], DocumentLink[]>?(new Location[]
@@ -333,7 +332,7 @@ private static string FileName(string projectRelativeFileName)
 
     private async Task VerifyGoToDefinitionAsync(TestCode input, string? fileKind = null, SumType<Location, Location[], DocumentLink[]>? htmlResponse = null)
     {
-        var document = CreateProjectAndRazorDocument(input.Text, fileKind);
+        var document = await CreateProjectAndRazorDocumentAsync(input.Text, fileKind);
         var result = await GetGoToDefinitionResultAsync(document, input, htmlResponse);
 
         Assumes.NotNull(result);
@@ -349,11 +348,11 @@ private async Task VerifyGoToDefinitionAsync(TestCode input, string? fileKind =
         Assert.Equal(document.CreateUri(), location.Uri);
     }
 
-    private Task<SumType<RoslynLocation, RoslynLocation[], RoslynDocumentLink[]>?> GetGoToDefinitionResultAsync(
+    private async Task<SumType<RoslynLocation, RoslynLocation[], RoslynDocumentLink[]>?> GetGoToDefinitionResultAsync(
         TestCode input, string? fileKind = null, params (string fileName, string contents)[]? additionalFiles)
     {
-        var document = CreateProjectAndRazorDocument(input.Text, fileKind, additionalFiles);
-        return GetGoToDefinitionResultAsync(document, input, htmlResponse: null);
+        var document = await CreateProjectAndRazorDocumentAsync(input.Text, fileKind, additionalFiles);
+        return await GetGoToDefinitionResultAsync(document, input, htmlResponse: null);
     }
 
     private async Task<SumType<RoslynLocation, RoslynLocation[], RoslynDocumentLink[]>?> GetGoToDefinitionResultAsync(
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostGoToImplementationEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostGoToImplementationEndpointTest.cs
index 4ee5dab2c8d..b6c91a29bea 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostGoToImplementationEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostGoToImplementationEndpointTest.cs
@@ -100,7 +100,7 @@ public async Task Html()
             </script>
             """;
 
-        var document = CreateProjectAndRazorDocument(input.Text);
+        var document = await CreateProjectAndRazorDocumentAsync(input.Text);
         var inputText = await document.GetTextAsync(DisposalToken);
 
         var htmlResponse = new SumType<LspLocation[], VSInternalReferenceItem[]>?(new LspLocation[]
@@ -119,7 +119,7 @@ public async Task Html()
 
     private async Task VerifyCSharpGoToImplementationAsync(TestCode input)
     {
-        var document = CreateProjectAndRazorDocument(input.Text);
+        var document = await CreateProjectAndRazorDocumentAsync(input.Text);
 
         var requestInvoker = new TestLSPRequestInvoker();
 
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostInlayHintEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostInlayHintEndpointTest.cs
index f7a3df1d975..05c9b4486ec 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostInlayHintEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostInlayHintEndpointTest.cs
@@ -131,7 +131,7 @@ public Task InlayHints_ComponentAttributes()
     private async Task VerifyInlayHintsAsync(string input, Dictionary<string, string> toolTipMap, string output, bool displayAllOverride = false)
     {
         TestFileMarkupParser.GetSpans(input, out input, out ImmutableDictionary<string, ImmutableArray<TextSpan>> spansDict);
-        var document = CreateProjectAndRazorDocument(input);
+        var document = await CreateProjectAndRazorDocumentAsync(input);
         var inputText = await document.GetTextAsync(DisposalToken);
 
         var endpoint = new CohostInlayHintEndpoint(RemoteServiceInvoker);
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostLinkedEditingRangeEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostLinkedEditingRangeEndpointTest.cs
index 28c05827166..865f5101125 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostLinkedEditingRangeEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostLinkedEditingRangeEndpointTest.cs
@@ -159,7 +159,7 @@ The end.
     private async Task VerifyLinkedEditingRangeAsync(string input)
     {
         TestFileMarkupParser.GetPositionAndSpans(input, out input, out int cursorPosition, out ImmutableArray<TextSpan> spans);
-        var document = CreateProjectAndRazorDocument(input);
+        var document = await CreateProjectAndRazorDocumentAsync(input);
         var sourceText = await document.GetTextAsync(DisposalToken);
 
         var endpoint = new CohostLinkedEditingRangeEndpoint(RemoteServiceInvoker);
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostOnAutoInsertEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostOnAutoInsertEndpointTest.cs
index b7dbb70194a..74d5036d454 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostOnAutoInsertEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostOnAutoInsertEndpointTest.cs
@@ -196,7 +196,7 @@ private async Task VerifyOnAutoInsertAsync(
         bool formatOnType = true,
         bool autoClosingTags = true)
     {     
-        var document = CreateProjectAndRazorDocument(input.Text);
+        var document = await CreateProjectAndRazorDocumentAsync(input.Text);
         var sourceText = await document.GetTextAsync(DisposalToken);
 
         var clientSettingsManager = new ClientSettingsManager([], null, null);
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostOnTypeFormattingEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostOnTypeFormattingEndpointTest.cs
index 7a1e3d913f3..1919956dad4 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostOnTypeFormattingEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostOnTypeFormattingEndpointTest.cs
@@ -5,7 +5,6 @@
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Test.Common;
-using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.ExternalAccess.Razor;
 using Microsoft.CodeAnalysis.Razor.Formatting;
@@ -19,8 +18,9 @@
 
 namespace Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
 
-[UseExportProvider]
-public class CohostOnTypeFormattingEndpointTest(ITestOutputHelper testOutputHelper) : CohostEndpointTestBase(testOutputHelper)
+[Collection(HtmlFormattingCollection.Name)]
+public class CohostOnTypeFormattingEndpointTest(HtmlFormattingFixture htmlFormattingFixture, ITestOutputHelper testOutputHelper)
+    : CohostEndpointTestBase(testOutputHelper)
 {
     [Fact]
     public async Task InvalidTrigger()
@@ -103,7 +103,7 @@ await VerifyOnTypeFormattingAsync(
 
     private async Task VerifyOnTypeFormattingAsync(TestCode input, string expected, char triggerCharacter, bool html = false)
     {
-        var document = CreateProjectAndRazorDocument(input.Text);
+        var document = await CreateProjectAndRazorDocumentAsync(input.Text);
         var inputText = await document.GetTextAsync(DisposalToken);
         var position = inputText.GetPosition(input.Position);
 
@@ -115,7 +115,7 @@ private async Task VerifyOnTypeFormattingAsync(TestCode input, string expected,
             Assert.NotNull(generatedHtml);
 
             var uri = new Uri(document.CreateUri(), $"{document.FilePath}{FeatureOptions.HtmlVirtualDocumentSuffix}");
-            var htmlEdits = await HtmlFormatting.GetOnTypeFormattingEditsAsync(LoggerFactory, uri, generatedHtml, position, insertSpaces: true, tabSize: 4);
+            var htmlEdits = await htmlFormattingFixture.Service.GetOnTypeFormattingEditsAsync(LoggerFactory, uri, generatedHtml, position, insertSpaces: true, tabSize: 4);
 
             requestInvoker = new TestLSPRequestInvoker([(Methods.TextDocumentOnTypeFormattingName, htmlEdits)]);
         }
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostRangeFormattingEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostRangeFormattingEndpointTest.cs
index 32d03e28002..97b3db3fd79 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostRangeFormattingEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostRangeFormattingEndpointTest.cs
@@ -5,7 +5,6 @@
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Test.Common;
-using Microsoft.AspNetCore.Razor.Test.Common.Mef;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.ExternalAccess.Razor;
 using Microsoft.CodeAnalysis.Razor.Formatting;
@@ -19,8 +18,9 @@
 
 namespace Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
 
-[UseExportProvider]
-public class CohostRangeFormattingEndpointTest(ITestOutputHelper testOutputHelper) : CohostEndpointTestBase(testOutputHelper)
+[Collection(HtmlFormattingCollection.Name)]
+public class CohostRangeFormattingEndpointTest(HtmlFormattingFixture htmlFormattingFixture, ITestOutputHelper testOutputHelper)
+    : CohostEndpointTestBase(testOutputHelper)
 {
     [Fact]
     public Task RangeFormatting()
@@ -102,7 +102,7 @@ private void M(string thisIsMyString)
 
     private async Task VerifyRangeFormattingAsync(TestCode input, string expected)
     {
-        var document = CreateProjectAndRazorDocument(input.Text);
+        var document = await CreateProjectAndRazorDocumentAsync(input.Text);
         var inputText = await document.GetTextAsync(DisposalToken);
 
         var htmlDocumentPublisher = new HtmlDocumentPublisher(RemoteServiceInvoker, StrictMock.Of<TrackingLSPDocumentManager>(), StrictMock.Of<JoinableTaskContext>(), LoggerFactory);
@@ -110,7 +110,7 @@ private async Task VerifyRangeFormattingAsync(TestCode input, string expected)
         Assert.NotNull(generatedHtml);
 
         var uri = new Uri(document.CreateUri(), $"{document.FilePath}{FeatureOptions.HtmlVirtualDocumentSuffix}");
-        var htmlEdits = await HtmlFormatting.GetDocumentFormattingEditsAsync(LoggerFactory, uri, generatedHtml, insertSpaces: true, tabSize: 4);
+        var htmlEdits = await htmlFormattingFixture.Service.GetDocumentFormattingEditsAsync(LoggerFactory, uri, generatedHtml, insertSpaces: true, tabSize: 4);
 
         var requestInvoker = new TestLSPRequestInvoker([(Methods.TextDocumentFormattingName, htmlEdits)]);
 
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostRenameEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostRenameEndpointTest.cs
index 9328744f2ae..6e1af1d4f06 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostRenameEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostRenameEndpointTest.cs
@@ -198,7 +198,7 @@ public class Component : Microsoft.AspNetCore.Components.ComponentBase
     private async Task VerifyRenamesAsync(string input, string newName, string expected, string? fileKind = null, (string fileName, string contents)[]? additionalFiles = null, (string oldName, string newName)[]? renames = null)
     {
         TestFileMarkupParser.GetPosition(input, out var source, out var cursorPosition);
-        var document = CreateProjectAndRazorDocument(source, fileKind, additionalFiles);
+        var document = await CreateProjectAndRazorDocumentAsync(source, fileKind, additionalFiles);
         var inputText = await document.GetTextAsync(DisposalToken);
         var position = inputText.GetPosition(cursorPosition);
 
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostSemanticTokensRangeEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostSemanticTokensRangeEndpointTest.cs
index 42b792b7ad5..7f841c9b12d 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostSemanticTokensRangeEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostSemanticTokensRangeEndpointTest.cs
@@ -90,7 +90,7 @@ @section MySection {
 
     private async Task VerifySemanticTokensAsync(string input, bool colorBackground, bool precise, string? fileKind = null, [CallerMemberName] string? testName = null)
     {
-        var document = CreateProjectAndRazorDocument(input, fileKind);
+        var document = await CreateProjectAndRazorDocumentAsync(input, fileKind);
         var sourceText = await document.GetTextAsync(DisposalToken);
 
         var legend = TestRazorSemanticTokensLegendService.Instance;
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostSignatureHelpEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostSignatureHelpEndpointTest.cs
index 7c599b0a3ed..8facef4127a 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostSignatureHelpEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostSignatureHelpEndpointTest.cs
@@ -91,7 +91,7 @@ void Act()
     private async Task VerifySignatureHelpAsync(string input, string expected, bool autoListParams = true, SignatureHelpTriggerKind? triggerKind = null)
     {
         TestFileMarkupParser.GetPosition(input, out input, out var cursorPosition);
-        var document = CreateProjectAndRazorDocument(input);
+        var document = await CreateProjectAndRazorDocumentAsync(input);
         var sourceText = await document.GetTextAsync(DisposalToken);
 
         var clientSettingsManager = new ClientSettingsManager([], null, null);
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostTextPresentationEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostTextPresentationEndpointTest.cs
index f946a642581..f2a4acc5b67 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostTextPresentationEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostTextPresentationEndpointTest.cs
@@ -55,7 +55,7 @@ private static string File(string projectRelativeFileName)
     private async Task VerifyUriPresentationAsync(string input, string text, string? expected, WorkspaceEdit? htmlResponse = null)
     {
         TestFileMarkupParser.GetSpan(input, out input, out var span);
-        var document = CreateProjectAndRazorDocument(input);
+        var document = await CreateProjectAndRazorDocumentAsync(input);
         var sourceText = await document.GetTextAsync(DisposalToken);
 
         var requestInvoker = new TestLSPRequestInvoker([(VSInternalMethods.TextDocumentTextPresentationName, htmlResponse)]);
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostUriPresentationEndpointTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostUriPresentationEndpointTest.cs
index d1f965f0b76..68b3be9565a 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostUriPresentationEndpointTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostUriPresentationEndpointTest.cs
@@ -286,7 +286,7 @@ private static string File(string projectRelativeFileName)
     private async Task VerifyUriPresentationAsync(string input, Uri[] uris, string? expected, WorkspaceEdit? htmlResponse = null, (string fileName, string contents)[]? additionalFiles = null)
     {
         TestFileMarkupParser.GetSpan(input, out input, out var span);
-        var document = CreateProjectAndRazorDocument(input, additionalFiles: additionalFiles);
+        var document = await CreateProjectAndRazorDocumentAsync(input, additionalFiles: additionalFiles);
         var sourceText = await document.GetTextAsync(DisposalToken);
 
         var requestInvoker = new TestLSPRequestInvoker([(VSInternalMethods.TextDocumentUriPresentationName, htmlResponse)]);
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/HtmlFormattingCollection.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/HtmlFormattingCollection.cs
new file mode 100644
index 00000000000..0380b2d5675
--- /dev/null
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/HtmlFormattingCollection.cs
@@ -0,0 +1,13 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using Microsoft.CodeAnalysis.Razor.Formatting;
+using Xunit;
+
+namespace Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
+
+[CollectionDefinition(Name)]
+public class HtmlFormattingCollection : ICollectionFixture<HtmlFormattingFixture>
+{
+    public const string Name = nameof(HtmlFormattingCollection);
+}
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/RazorComponentDefinitionServiceTest.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/RazorComponentDefinitionServiceTest.cs
index 041b95c6eee..c7b1fd79b4c 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/RazorComponentDefinitionServiceTest.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/RazorComponentDefinitionServiceTest.cs
@@ -76,7 +76,7 @@ await VerifyDefinitionAsync(input, surveyPrompt, (FileName("SurveyPrompt.razor")
 
     private async Task VerifyDefinitionAsync(TestCode input, TestCode expectedDocument, params (string fileName, string contents)[]? additionalFiles)
     {
-        var document = CreateProjectAndRazorDocument(input.Text, FileKinds.Component, additionalFiles);
+        var document = await CreateProjectAndRazorDocumentAsync(input.Text, FileKinds.Component, additionalFiles);
 
         var service = OOPExportProvider.GetExportedValue<IRazorComponentDefinitionService>();
         var documentSnapshotFactory = OOPExportProvider.GetExportedValue<DocumentSnapshotFactory>();
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/TestBrokeredServiceInterceptor.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/TestBrokeredServiceInterceptor.cs
index 7d0da662311..fffa4b394c6 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/TestBrokeredServiceInterceptor.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/TestBrokeredServiceInterceptor.cs
@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
@@ -14,6 +15,7 @@ namespace Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
 internal sealed class TestBrokeredServiceInterceptor : IRazorBrokeredServiceInterceptor
 {
     private readonly TestSolutionStore _solutionStore = new();
+    private readonly Dictionary<SolutionId, Solution> _localToRemoteSolutionMap = [];
 
     public Task<RazorPinnedSolutionInfoWrapper> GetSolutionInfoAsync(Solution solution, CancellationToken cancellationToken)
         => _solutionStore.AddAsync(solution, cancellationToken);
@@ -32,6 +34,18 @@ public ValueTask<T> RunServiceAsync<T>(
 
         Assert.NotNull(solution);
 
+        // Rather than actually syncing assets, we just let the test author directly map from a local solution
+        // to a remote solution;
+        if (_localToRemoteSolutionMap.TryGetValue(solution.Id, out var remoteSolution))
+        {
+            solution = remoteSolution;
+        }
+
         return implementation(solution);
     }
+
+    internal void MapSolutionIdToRemote(SolutionId localSolutionId, Solution remoteSolution)
+    {
+        _localToRemoteSolutionMap.Add(localSolutionId, remoteSolution);
+    }
 }
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/TestRemoteServiceInvoker.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/TestRemoteServiceInvoker.cs
index 9e5c8651aac..581d08f35a4 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/TestRemoteServiceInvoker.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/TestRemoteServiceInvoker.cs
@@ -57,6 +57,11 @@ private async Task<TService> GetOrCreateServiceAsync<TService>()
         return await invocation(service, solutionInfo, cancellationToken);
     }
 
+    public void MapSolutionIdToRemote(SolutionId localSolutionId, Solution remoteSolution)
+    {
+        _serviceInterceptor.MapSolutionIdToRemote(localSolutionId, remoteSolution);
+    }
+
     public void Dispose()
     {
         _reentrantSemaphore.Dispose();
diff --git a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/LanguageClient/TestLSPRequestInvoker.cs b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/LanguageClient/TestLSPRequestInvoker.cs
index 3bbf1c56ee0..c4d01769a9f 100644
--- a/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/LanguageClient/TestLSPRequestInvoker.cs
+++ b/src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/LanguageClient/TestLSPRequestInvoker.cs
@@ -111,7 +111,8 @@ public async override Task<ReinvocationResponse<TOut>> ReinvokeRequestOnServerAs
             return new ReinvocationResponse<TOut>(languageClientName: RazorLSPConstants.RazorCSharpLanguageServerName, result);
         }
 
-        if (_htmlResponses.TryGetValue(method, out var response))
+        if (_htmlResponses is not null &&
+            _htmlResponses.TryGetValue(method, out var response))
         {
             return new ReinvocationResponse<TOut>(languageClientName: "html", (TOut)response);
         }