diff --git a/src/Compiler/Microsoft.AspNetCore.Razor.Language/src/DefaultRazorTagHelperContextDiscoveryPhase.cs b/src/Compiler/Microsoft.AspNetCore.Razor.Language/src/DefaultRazorTagHelperContextDiscoveryPhase.cs
index 370d39e130b..21fbe74bc71 100644
--- a/src/Compiler/Microsoft.AspNetCore.Razor.Language/src/DefaultRazorTagHelperContextDiscoveryPhase.cs
+++ b/src/Compiler/Microsoft.AspNetCore.Razor.Language/src/DefaultRazorTagHelperContextDiscoveryPhase.cs
@@ -17,7 +17,7 @@ internal sealed class DefaultRazorTagHelperContextDiscoveryPhase : RazorEnginePh
 {
     protected override void ExecuteCore(RazorCodeDocument codeDocument)
     {
-        var syntaxTree = codeDocument.GetSyntaxTree();
+        var syntaxTree = codeDocument.GetPreTagHelperSyntaxTree() ?? codeDocument.GetSyntaxTree();
         ThrowForMissingDocumentDependency(syntaxTree);
 
         var descriptors = codeDocument.GetTagHelpers();
@@ -69,7 +69,6 @@ protected override void ExecuteCore(RazorCodeDocument codeDocument)
 
         var context = TagHelperDocumentContext.Create(tagHelperPrefix, descriptors);
         codeDocument.SetTagHelperContext(context);
-        codeDocument.SetPreTagHelperSyntaxTree(syntaxTree);
     }
 
     private static bool MatchesDirective(TagHelperDescriptor descriptor, string typePattern, string assemblyName)
diff --git a/src/Compiler/Microsoft.AspNetCore.Razor.Language/src/DefaultRazorTagHelperRewritePhase.cs b/src/Compiler/Microsoft.AspNetCore.Razor.Language/src/DefaultRazorTagHelperRewritePhase.cs
index 402020d1afc..cb8632d70b0 100644
--- a/src/Compiler/Microsoft.AspNetCore.Razor.Language/src/DefaultRazorTagHelperRewritePhase.cs
+++ b/src/Compiler/Microsoft.AspNetCore.Razor.Language/src/DefaultRazorTagHelperRewritePhase.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 #nullable enable
 
+using System.Collections.Generic;
 using Microsoft.AspNetCore.Razor.Language.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Language;
@@ -9,17 +10,19 @@ internal sealed class DefaultRazorTagHelperRewritePhase : RazorEnginePhaseBase
 {
     protected override void ExecuteCore(RazorCodeDocument codeDocument)
     {
-        var syntaxTree = codeDocument.GetPreTagHelperSyntaxTree();
+        var syntaxTree = codeDocument.GetPreTagHelperSyntaxTree() ?? codeDocument.GetSyntaxTree();
+        ThrowForMissingDocumentDependency(syntaxTree);
+
         var context = codeDocument.GetTagHelperContext();
-        if (syntaxTree is null || context.TagHelpers.Count == 0)
+        if (context?.TagHelpers.Count > 0)
         {
-            // No descriptors, no-op.
-            return;
+            var rewrittenSyntaxTree = TagHelperParseTreeRewriter.Rewrite(syntaxTree, context.Prefix, context.TagHelpers, out var usedHelpers);
+            codeDocument.SetSyntaxTree(rewrittenSyntaxTree);
+            codeDocument.SetReferencedTagHelpers(usedHelpers);
+        }
+        else
+        {
+            codeDocument.SetReferencedTagHelpers(new HashSet<TagHelperDescriptor>());
         }
-
-        var rewrittenSyntaxTree = TagHelperParseTreeRewriter.Rewrite(syntaxTree, context.Prefix, context.TagHelpers, out var usedHelpers);
-
-        codeDocument.SetReferencedTagHelpers(usedHelpers);
-        codeDocument.SetSyntaxTree(rewrittenSyntaxTree);
     }
 }
diff --git a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/Microsoft.NET.Sdk.Razor.SourceGenerators.csproj b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/Microsoft.NET.Sdk.Razor.SourceGenerators.csproj
index 682739d6978..b5a9a50af34 100644
--- a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/Microsoft.NET.Sdk.Razor.SourceGenerators.csproj
+++ b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/Microsoft.NET.Sdk.Razor.SourceGenerators.csproj
@@ -19,6 +19,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <ProjectReference Include="..\..\Shared\Microsoft.AspNetCore.Razor.Utilities.Shared\Microsoft.AspNetCore.Razor.Utilities.Shared.csproj" />
     <ProjectReference Include="..\Microsoft.AspNetCore.Mvc.Razor.Extensions\src\Microsoft.AspNetCore.Mvc.Razor.Extensions.csproj" />
     <ProjectReference Include="..\Microsoft.AspNetCore.Razor.Language\src\Microsoft.AspNetCore.Razor.Language.csproj" />
     <ProjectReference Include="..\Microsoft.CodeAnalysis.Razor\src\Microsoft.CodeAnalysis.Razor.csproj" />
diff --git a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/RazorSourceGenerator.Helpers.cs b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/RazorSourceGenerator.Helpers.cs
index d7cb91e4910..7dfece6c432 100644
--- a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/RazorSourceGenerator.Helpers.cs
+++ b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/RazorSourceGenerator.Helpers.cs
@@ -83,8 +83,7 @@ private static RazorProjectEngine GetDiscoveryProjectEngine(
             return discoveryProjectEngine;
         }
 
-        private static RazorProjectEngine GetGenerationProjectEngine(
-            IReadOnlyList<TagHelperDescriptor> tagHelpers,
+        private static SourceGeneratorProjectEngine GetGenerationProjectEngine(
             SourceGeneratorProjectItem item,
             IEnumerable<SourceGeneratorProjectItem> imports,
             RazorSourceGenerationOptions razorSourceGeneratorOptions)
@@ -96,7 +95,7 @@ private static RazorProjectEngine GetGenerationProjectEngine(
                 fileSystem.Add(import);
             }
 
-            var projectEngine = RazorProjectEngine.Create(razorSourceGeneratorOptions.Configuration, fileSystem, b =>
+            var projectEngine = (DefaultRazorProjectEngine)RazorProjectEngine.Create(razorSourceGeneratorOptions.Configuration, fileSystem, b =>
             {
                 b.Features.Add(new DefaultTypeNameFeature());
                 b.SetRootNamespace(razorSourceGeneratorOptions.RootNamespace);
@@ -107,16 +106,13 @@ private static RazorProjectEngine GetGenerationProjectEngine(
                     options.SupportLocalizedComponentNames = razorSourceGeneratorOptions.SupportLocalizedComponentNames;
                 }));
 
-                b.Features.Add(new StaticTagHelperFeature { TagHelpers = tagHelpers });
-                b.Features.Add(new DefaultTagHelperDescriptorProvider());
-
                 CompilerFeatures.Register(b);
                 RazorExtensions.Register(b);
 
                 b.SetCSharpLanguageVersion(razorSourceGeneratorOptions.CSharpLanguageVersion);
             });
 
-            return projectEngine;
+            return new SourceGeneratorProjectEngine(projectEngine);
         }
     }
 }
diff --git a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/RazorSourceGenerator.cs b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/RazorSourceGenerator.cs
index 4fd80d7e3b6..b813fdba645 100644
--- a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/RazorSourceGenerator.cs
+++ b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/RazorSourceGenerator.cs
@@ -2,13 +2,15 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.AspNetCore.Razor.PooledObjects;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
 
 namespace Microsoft.NET.Sdk.Razor.SourceGenerators
 {
@@ -66,11 +68,12 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
             var generatedDeclarationCode = componentFiles
                 .Combine(importFiles.Collect())
                 .Combine(razorSourceGeneratorOptions)
+                .WithLambdaComparer((old, @new) => (old.Right.Equals(@new.Right) && old.Left.Left.Equals(@new.Left.Left) && old.Left.Right.SequenceEqual(@new.Left.Right)), (a) => a.GetHashCode())
                 .Select(static (pair, _) =>
                 {
 
                     var ((sourceItem, importFiles), razorSourceGeneratorOptions) = pair;
-                    RazorSourceGeneratorEventSource.Log.GenerateDeclarationCodeStart(sourceItem.FilePath);
+                    RazorSourceGeneratorEventSource.Log.GenerateDeclarationCodeStart(sourceItem.RelativePhysicalPath);
 
                     var projectEngine = GetDeclarationProjectEngine(sourceItem, importFiles, razorSourceGeneratorOptions);
 
@@ -78,57 +81,69 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
 
                     var result = codeGen.GetCSharpDocument().GeneratedCode;
 
-                    RazorSourceGeneratorEventSource.Log.GenerateDeclarationCodeStop(sourceItem.FilePath);
+                    RazorSourceGeneratorEventSource.Log.GenerateDeclarationCodeStop(sourceItem.RelativePhysicalPath);
 
-                    return result;
+                    return (result, sourceItem.RelativePhysicalPath);
                 });
 
             var generatedDeclarationSyntaxTrees = generatedDeclarationCode
                 .Combine(parseOptions)
-                .Select(static (pair, _) =>
+                .Select(static (pair, ct) =>
                 {
-                    var (generatedDeclarationCode, parseOptions) = pair;
-                    return CSharpSyntaxTree.ParseText(generatedDeclarationCode, (CSharpParseOptions)parseOptions);
+                    var ((generatedDeclarationCode, filePath), parseOptions) = pair;
+                    return CSharpSyntaxTree.ParseText(generatedDeclarationCode, (CSharpParseOptions)parseOptions, filePath, cancellationToken: ct);
                 });
 
-            var tagHelpersFromCompilation = compilation
-                .Combine(generatedDeclarationSyntaxTrees.Collect())
+            var tagHelpersFromComponents = generatedDeclarationSyntaxTrees
+                .Combine(compilation)
                 .Combine(razorSourceGeneratorOptions)
-                .Select(static (pair, _) =>
+                .SelectMany(static (pair, ct) =>
                 {
-                    RazorSourceGeneratorEventSource.Log.DiscoverTagHelpersFromCompilationStart();
 
-                    var ((compilation, generatedDeclarationSyntaxTrees), razorSourceGeneratorOptions) = pair;
+                    var ((generatedDeclarationSyntaxTree, compilation), razorSourceGeneratorOptions) = pair;
+                    RazorSourceGeneratorEventSource.Log.DiscoverTagHelpersFromComponentStart(generatedDeclarationSyntaxTree.FilePath);
 
                     var tagHelperFeature = new StaticCompilationTagHelperFeature();
                     var discoveryProjectEngine = GetDiscoveryProjectEngine(compilation.References.ToImmutableArray(), tagHelperFeature);
 
-                    var compilationWithDeclarations = compilation.AddSyntaxTrees(generatedDeclarationSyntaxTrees);
+                    var compilationWithDeclarations = compilation.AddSyntaxTrees(generatedDeclarationSyntaxTree);
+
+                    // try and find the specific root class this component is declaring, falling back to the assembly if for any reason the code is not in the shape we expect
+                    ISymbol targetSymbol = compilationWithDeclarations.Assembly;
+                    var root = generatedDeclarationSyntaxTree.GetRoot(ct);
+                    if (root is CompilationUnitSyntax { Members: [NamespaceDeclarationSyntax { Members: [ClassDeclarationSyntax classSyntax, ..] }, ..] })
+                    {
+                        var declaredClass = compilationWithDeclarations.GetSemanticModel(generatedDeclarationSyntaxTree).GetDeclaredSymbol(classSyntax, ct);
+                        Debug.Assert(declaredClass is null || declaredClass is { AllInterfaces: [{ Name: "IComponent" }, ..] });
+                        targetSymbol = declaredClass ?? targetSymbol;
+                    }
 
                     tagHelperFeature.Compilation = compilationWithDeclarations;
-                    tagHelperFeature.TargetSymbol = compilationWithDeclarations.Assembly;
+                    tagHelperFeature.TargetSymbol = targetSymbol;
 
-                    var result = (IList<TagHelperDescriptor>)tagHelperFeature.GetDescriptors();
-                    RazorSourceGeneratorEventSource.Log.DiscoverTagHelpersFromCompilationStop();
+                    var result = tagHelperFeature.GetDescriptors();
+                    RazorSourceGeneratorEventSource.Log.DiscoverTagHelpersFromComponentStop(generatedDeclarationSyntaxTree.FilePath);
                     return result;
-                })
-                .WithLambdaComparer(static (a, b) =>
+                });
+
+            var tagHelpersFromCompilation = compilation
+                .Combine(razorSourceGeneratorOptions)
+                .Select(static (pair, _) =>
                 {
-                    if (a.Count != b.Count)
-                    {
-                        return false;
-                    }
+                    RazorSourceGeneratorEventSource.Log.DiscoverTagHelpersFromCompilationStart();
 
-                    for (var i = 0; i < a.Count; i++)
-                    {
-                        if (!a[i].Equals(b[i]))
-                        {
-                            return false;
-                        }
-                    }
+                    var (compilation, razorSourceGeneratorOptions) = pair;
+
+                    var tagHelperFeature = new StaticCompilationTagHelperFeature();
+                    var discoveryProjectEngine = GetDiscoveryProjectEngine(compilation.References.ToImmutableArray(), tagHelperFeature);
 
-                    return true;
-                }, getHashCode: static a => a.Count);
+                    tagHelperFeature.Compilation = compilation;
+                    tagHelperFeature.TargetSymbol = compilation.Assembly;
+
+                    var result = tagHelperFeature.GetDescriptors();
+                    RazorSourceGeneratorEventSource.Log.DiscoverTagHelpersFromCompilationStop();
+                    return result;
+                });
 
             var tagHelpersFromReferences = compilation
                 .Combine(razorSourceGeneratorOptions)
@@ -171,7 +186,7 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
                     var tagHelperFeature = new StaticCompilationTagHelperFeature();
                     var discoveryProjectEngine = GetDiscoveryProjectEngine(compilation.References.ToImmutableArray(), tagHelperFeature);
 
-                    List<TagHelperDescriptor> descriptors = new();
+                    using var pool = ArrayBuilderPool<TagHelperDescriptor>.GetPooledObject(out var descriptors);
                     tagHelperFeature.Compilation = compilation;
                     foreach (var reference in compilation.References)
                     {
@@ -183,47 +198,84 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
                     }
 
                     RazorSourceGeneratorEventSource.Log.DiscoverTagHelpersFromReferencesStop();
-                    return (ICollection<TagHelperDescriptor>)descriptors;
+                    return descriptors.ToImmutable();
                 });
 
-            var allTagHelpers = tagHelpersFromCompilation
+            var allTagHelpers = tagHelpersFromComponents.Collect()
+                .Combine(tagHelpersFromCompilation)
                 .Combine(tagHelpersFromReferences)
                 .Select(static (pair, _) =>
                 {
-                    var (tagHelpersFromCompilation, tagHelpersFromReferences) = pair;
-                    var count = tagHelpersFromCompilation.Count + tagHelpersFromReferences.Count;
+                    var ((tagHelpersFromComponents, tagHelpersFromCompilation), tagHelpersFromReferences) = pair;
+                    var count = tagHelpersFromCompilation.Length + tagHelpersFromReferences.Length + tagHelpersFromComponents.Length;
                     if (count == 0)
                     {
-                        return Array.Empty<TagHelperDescriptor>();
+                        return ImmutableArray<TagHelperDescriptor>.Empty;
                     }
 
-                    var allTagHelpers = new TagHelperDescriptor[count];
-                    tagHelpersFromCompilation.CopyTo(allTagHelpers, 0);
-                    tagHelpersFromReferences.CopyTo(allTagHelpers, tagHelpersFromCompilation.Count);
+                    using var pool = ArrayBuilderPool<TagHelperDescriptor>.GetPooledObject(out var allTagHelpers);
+					allTagHelpers.AddRange(tagHelpersFromCompilation);
+                    allTagHelpers.AddRange(tagHelpersFromReferences);
+                    allTagHelpers.AddRange(tagHelpersFromComponents);
 
-                    return allTagHelpers;
+                    return allTagHelpers.ToImmutable();
                 });
 
             var generatedOutput = sourceItems
                 .Combine(importFiles.Collect())
-                .Combine(allTagHelpers)
+                .WithLambdaComparer((old, @new) => old.Left.Equals(@new.Left) && old.Right.SequenceEqual(@new.Right), (a) => a.GetHashCode())
                 .Combine(razorSourceGeneratorOptions)
                 .Select(static (pair, _) =>
                 {
-                    var (((sourceItem, imports), allTagHelpers), razorSourceGeneratorOptions) = pair;
+                    var ((sourceItem, imports), razorSourceGeneratorOptions) = pair;
+
+                    RazorSourceGeneratorEventSource.Log.ParseRazorDocumentStart(sourceItem.RelativePhysicalPath);
+
+                    var projectEngine = GetGenerationProjectEngine(sourceItem, imports, razorSourceGeneratorOptions);
+
+                    var document = projectEngine.ProcessInitialParse(sourceItem);
+
+                    RazorSourceGeneratorEventSource.Log.ParseRazorDocumentStop(sourceItem.RelativePhysicalPath);
+                    return (projectEngine, sourceItem.RelativePhysicalPath, document);
+                })
+
+                // Add the tag helpers in, but ignore if they've changed or not, only reprocessing the actual document changed
+                .Combine(allTagHelpers)
+                .WithLambdaComparer((old, @new) => old.Left.Equals(@new.Left), (item) => item.GetHashCode())
+                .Select((pair, _) =>
+                {
+                    var ((projectEngine, filePath, codeDocument), allTagHelpers) = pair;
+                    RazorSourceGeneratorEventSource.Log.RewriteTagHelpersStart(filePath);
 
-                    RazorSourceGeneratorEventSource.Log.RazorCodeGenerateStart(sourceItem.FilePath);
+                    codeDocument = projectEngine.ProcessTagHelpers(codeDocument, allTagHelpers, checkForIdempotency: false);
 
-                    // Add a generated suffix so tools, such as coverlet, consider the file to be generated
-                    var hintName = GetIdentifierFromPath(sourceItem.RelativePhysicalPath) + ".g.cs";
+                    RazorSourceGeneratorEventSource.Log.RewriteTagHelpersStop(filePath);
+                    return (projectEngine, filePath, codeDocument);
+                })
+
+                // next we do a second parse, along with the helpers, but check for idempotency. If the tag helpers used on the previous parse match, the compiler can skip re-computing them
+                .Combine(allTagHelpers)
+                .Select((pair, _) =>
+                {
 
-                    var projectEngine = GetGenerationProjectEngine(allTagHelpers, sourceItem, imports, razorSourceGeneratorOptions);
+                    var ((projectEngine, filePath, document), allTagHelpers) = pair;
+                    RazorSourceGeneratorEventSource.Log.CheckAndRewriteTagHelpersStart(filePath);
 
-                    var codeDocument = projectEngine.Process(sourceItem);
-                    var csharpDocument = codeDocument.GetCSharpDocument();
+                    document = projectEngine.ProcessTagHelpers(document, allTagHelpers, checkForIdempotency: true);
 
-                    RazorSourceGeneratorEventSource.Log.RazorCodeGenerateStop(sourceItem.FilePath);
-                    return (hintName, csharpDocument);
+                    RazorSourceGeneratorEventSource.Log.CheckAndRewriteTagHelpersStop(filePath);
+                    return (projectEngine, filePath, document);
+                })
+
+                .Select((pair, _) =>
+                {
+                    var (projectEngine, filePath, document) = pair;
+                    RazorSourceGeneratorEventSource.Log.RazorCodeGenerateStart(filePath);
+                    document = projectEngine.ProcessRemaining(document);
+                    var csharpDocument = document.CodeDocument.GetCSharpDocument();
+
+                    RazorSourceGeneratorEventSource.Log.RazorCodeGenerateStop(filePath);
+                    return (filePath, csharpDocument);
                 })
                 .WithLambdaComparer(static (a, b) =>
                 {
@@ -238,7 +290,11 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
 
             context.RegisterSourceOutput(generatedOutput, static (context, pair) =>
             {
-                var (hintName, csharpDocument) = pair;
+                var (filePath, csharpDocument) = pair;
+
+                // Add a generated suffix so tools, such as coverlet, consider the file to be generated
+                var hintName = GetIdentifierFromPath(filePath) + ".g.cs";
+
                 RazorSourceGeneratorEventSource.Log.AddSyntaxTrees(hintName);
                 for (var i = 0; i < csharpDocument.Diagnostics.Count; i++)
                 {
diff --git a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/RazorSourceGeneratorEventSource.cs b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/RazorSourceGeneratorEventSource.cs
index 758d0069b8b..b94646cc81a 100644
--- a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/RazorSourceGeneratorEventSource.cs
+++ b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/RazorSourceGeneratorEventSource.cs
@@ -59,5 +59,37 @@ private RazorSourceGeneratorEventSource() { }
         private const int GenerateDeclarationSyntaxTreeStopId = 14;
         [Event(GenerateDeclarationSyntaxTreeStopId, Level = EventLevel.Informational)]
         public void GenerateDeclarationSyntaxTreeStop() => WriteEvent(GenerateDeclarationSyntaxTreeStopId);
+
+        private const int DiscoverTagHelpersFromComponentStartId = 15;
+        [Event(DiscoverTagHelpersFromComponentStartId, Level = EventLevel.Informational)]
+        public void DiscoverTagHelpersFromComponentStart(string filePath) => WriteEvent(DiscoverTagHelpersFromComponentStartId, filePath);
+
+        private const int DiscoverTagHelpersFromComponentStopId = 16;
+        [Event(DiscoverTagHelpersFromComponentStopId, Level = EventLevel.Informational)]
+        public void DiscoverTagHelpersFromComponentStop(string filePath) => WriteEvent(DiscoverTagHelpersFromComponentStopId, filePath);
+
+        private const int ParseRazorDocumentStartId = 17;
+        [Event(ParseRazorDocumentStartId, Level = EventLevel.Informational)]
+        public void ParseRazorDocumentStart(string file) => WriteEvent(ParseRazorDocumentStartId, file);
+
+        private const int ParseRazorDocumentStopId = 18;
+        [Event(ParseRazorDocumentStopId, Level = EventLevel.Informational)]
+        public void ParseRazorDocumentStop(string file) => WriteEvent(ParseRazorDocumentStopId, file);
+
+        private const int RewriteTagHelpersStartId = 19;
+        [Event(RewriteTagHelpersStartId, Level = EventLevel.Informational)]
+        public void RewriteTagHelpersStart(string file) => WriteEvent(RewriteTagHelpersStartId, file);
+
+        private const int RewriteTagHelpersStopId = 20;
+        [Event(RewriteTagHelpersStopId, Level = EventLevel.Informational)]
+        public void RewriteTagHelpersStop(string file) => WriteEvent(RewriteTagHelpersStopId, file);
+
+        private const int CheckAndRewriteTagHelpersStartId = 21;
+        [Event(CheckAndRewriteTagHelpersStartId, Level = EventLevel.Informational)]
+        public void CheckAndRewriteTagHelpersStart(string file) => WriteEvent(CheckAndRewriteTagHelpersStartId, file);
+
+        private const int CheckAndRewriteTagHelpersStopId = 22;
+        [Event(CheckAndRewriteTagHelpersStopId, Level = EventLevel.Informational)]
+        public void CheckAndRewriteTagHelpersStop(string file) => WriteEvent(CheckAndRewriteTagHelpersStopId, file);
     }
 }
diff --git a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/SourceGeneratorProjectEngine.cs b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/SourceGeneratorProjectEngine.cs
new file mode 100644
index 00000000000..4acb91159b3
--- /dev/null
+++ b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/SourceGeneratorProjectEngine.cs
@@ -0,0 +1,115 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#nullable enable
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using Microsoft.AspNetCore.Razor.Language;
+
+namespace Microsoft.NET.Sdk.Razor.SourceGenerators;
+
+internal class SourceGeneratorProjectEngine : DefaultRazorProjectEngine
+{
+    private readonly int discoveryPhaseIndex = -1;
+
+    private readonly int rewritePhaseIndex = -1;
+
+    public SourceGeneratorProjectEngine(DefaultRazorProjectEngine projectEngine)
+        : base(projectEngine.Configuration, projectEngine.Engine, projectEngine.FileSystem, projectEngine.ProjectFeatures)
+    {
+        for (int i = 0; i < Engine.Phases.Count; i++)
+        {
+            if (Engine.Phases[i] is DefaultRazorTagHelperContextDiscoveryPhase)
+            {
+                discoveryPhaseIndex = i;
+            }
+            else if (Engine.Phases[i] is DefaultRazorTagHelperRewritePhase)
+            {
+                rewritePhaseIndex = i;
+            }
+            else if (discoveryPhaseIndex >= 0 && rewritePhaseIndex >= 0)
+            {
+                break;
+            }
+        }
+        Debug.Assert(discoveryPhaseIndex >= 0);
+        Debug.Assert(rewritePhaseIndex >= 0);
+    }
+
+    public SourceGeneratorRazorCodeDocument ProcessInitialParse(RazorProjectItem projectItem)
+    {
+        var codeDocument = CreateCodeDocumentCore(projectItem);
+        ProcessPartial(codeDocument, 0, discoveryPhaseIndex);
+
+        // record the syntax tree, before the tag helper re-writing occurs
+        codeDocument.SetPreTagHelperSyntaxTree(codeDocument.GetSyntaxTree());
+        return new SourceGeneratorRazorCodeDocument(codeDocument);
+    }
+
+    public SourceGeneratorRazorCodeDocument ProcessTagHelpers(SourceGeneratorRazorCodeDocument sgDocument, IReadOnlyList<TagHelperDescriptor> tagHelpers, bool checkForIdempotency)
+    {
+        Debug.Assert(sgDocument.CodeDocument.GetPreTagHelperSyntaxTree() is not null);
+
+        int startIndex = discoveryPhaseIndex;
+        var codeDocument = sgDocument.CodeDocument;
+        var previousTagHelpers = codeDocument.GetTagHelpers();
+        if (checkForIdempotency && previousTagHelpers is not null)
+        {
+            // compare the tag helpers with the ones the document last used
+            if (Enumerable.SequenceEqual(tagHelpers, previousTagHelpers))
+            {
+                // tag helpers are the same, nothing to do!
+                return sgDocument;
+            }
+            else
+            {
+                // tag helpers have changed, figure out if we need to re-write
+                var oldContextHelpers = codeDocument.GetTagHelperContext().TagHelpers;
+
+                // re-run the scope check to figure out which tag helpers this document can see
+                codeDocument.SetTagHelpers(tagHelpers);
+                Engine.Phases[discoveryPhaseIndex].Execute(codeDocument);
+
+                // Check if any new tag helpers were added or ones we previously used were removed
+                var newContextHelpers = codeDocument.GetTagHelperContext().TagHelpers;
+                var added = newContextHelpers.Except(oldContextHelpers);
+                var referencedByRemoved = codeDocument.GetReferencedTagHelpers().Except(newContextHelpers);
+                if (!added.Any() && !referencedByRemoved.Any())
+                {
+                    //  Either nothing new, or any that got removed weren't used by this document anyway
+                    return sgDocument;
+                }
+
+                // We need to re-write the document, but can skip the scoping as we just performed it
+                startIndex = rewritePhaseIndex;
+            }
+        }
+        else
+        {
+            codeDocument.SetTagHelpers(tagHelpers);
+        }
+
+        ProcessPartial(codeDocument, startIndex, rewritePhaseIndex + 1);
+        return new SourceGeneratorRazorCodeDocument(codeDocument);
+    }
+
+    public SourceGeneratorRazorCodeDocument ProcessRemaining(SourceGeneratorRazorCodeDocument sgDocument)
+    {
+        var codeDocument = sgDocument.CodeDocument;
+        Debug.Assert(codeDocument.GetReferencedTagHelpers() is not null);
+
+        ProcessPartial(sgDocument.CodeDocument, rewritePhaseIndex, Engine.Phases.Count);
+        return new SourceGeneratorRazorCodeDocument(codeDocument);
+    }
+
+    private void ProcessPartial(RazorCodeDocument codeDocument, int startIndex, int endIndex)
+    {
+        Debug.Assert(startIndex >= 0 && startIndex <= endIndex && endIndex <= Engine.Phases.Count);
+        for (var i = startIndex; i < endIndex; i++)
+        {
+            Engine.Phases[i].Execute(codeDocument);
+        }
+    }
+}
diff --git a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/SourceGeneratorRazorCodeDocument.cs b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/SourceGeneratorRazorCodeDocument.cs
new file mode 100644
index 00000000000..707e4345e63
--- /dev/null
+++ b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/SourceGeneratorRazorCodeDocument.cs
@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#nullable enable
+
+using Microsoft.AspNetCore.Razor.Language;
+
+namespace Microsoft.NET.Sdk.Razor.SourceGenerators;
+
+/// <summary>
+/// A wrapper for <see cref="RazorCodeDocument"/>
+/// </summary>
+/// <remarks>
+/// The razor compiler modifies the <see cref="RazorCodeDocument"/> in place during the various phases,
+/// meaning object identity is maintained even when the contents have changed.
+/// 
+/// We need to be able to identify from the source generator if a given code document was modified or 
+/// returned unchanged. Rather than implementing deep equality on the <see cref="RazorCodeDocument"/> 
+/// which can get expensive when the <see cref="ItemCollection"/> is large, we instead use a wrapper class.
+/// If the underlying document is unchanged we return the original wrapper class. If the underlying 
+/// document is changed, we return a new instance of the wrapper.
+/// </remarks>
+internal class SourceGeneratorRazorCodeDocument
+{
+    public RazorCodeDocument CodeDocument { get; }
+
+    public SourceGeneratorRazorCodeDocument(RazorCodeDocument razorCodeDocument)
+    {
+        this.CodeDocument = razorCodeDocument;
+    }
+}
diff --git a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/StaticCompilationTagHelperFeature.cs b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/StaticCompilationTagHelperFeature.cs
index 15d54b36587..4828c20dd5d 100644
--- a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/StaticCompilationTagHelperFeature.cs
+++ b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/StaticCompilationTagHelperFeature.cs
@@ -2,8 +2,10 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Linq;
 using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.AspNetCore.Razor.PooledObjects;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Razor;
 
@@ -11,18 +13,16 @@ namespace Microsoft.NET.Sdk.Razor.SourceGenerators
 {
     internal sealed class StaticCompilationTagHelperFeature : RazorEngineFeatureBase, ITagHelperFeature
     {
-        private static readonly List<TagHelperDescriptor> EmptyList = new();
-        
         private ITagHelperDescriptorProvider[]? _providers;
 
-        public List<TagHelperDescriptor> GetDescriptors()
+        public ImmutableArray<TagHelperDescriptor> GetDescriptors()
         {
             if (Compilation is null)
             {
-                return EmptyList;
+                return ImmutableArray<TagHelperDescriptor>.Empty;
             }
 
-            var results = new List<TagHelperDescriptor>();
+            using var pool = ArrayBuilderPool<TagHelperDescriptor>.GetPooledObject(out var results);
             var context = TagHelperDescriptorProviderContext.Create(results);
             context.SetCompilation(Compilation);
             if (TargetSymbol is not null)
@@ -35,7 +35,7 @@ public List<TagHelperDescriptor> GetDescriptors()
                 _providers[i].Execute(context);
             }
 
-            return results;
+            return results.ToImmutable();
         }
 
         IReadOnlyList<TagHelperDescriptor> ITagHelperFeature.GetDescriptors() => GetDescriptors();
diff --git a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/StaticTagHelperFeature.cs b/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/StaticTagHelperFeature.cs
deleted file mode 100644
index 89207e40b8a..00000000000
--- a/src/Compiler/Microsoft.NET.Sdk.Razor.SourceGenerators/StaticTagHelperFeature.cs
+++ /dev/null
@@ -1,25 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System.Collections.Generic;
-using Microsoft.AspNetCore.Razor.Language;
-
-namespace Microsoft.NET.Sdk.Razor.SourceGenerators
-{
-    internal sealed class StaticTagHelperFeature : RazorEngineFeatureBase, ITagHelperFeature
-    {
-        public IReadOnlyList<TagHelperDescriptor> TagHelpers { get; set; }
-
-        public IReadOnlyList<TagHelperDescriptor> GetDescriptors() => TagHelpers;
-
-        public StaticTagHelperFeature()
-        {
-            TagHelpers = new List<TagHelperDescriptor>();
-        }
-
-        public StaticTagHelperFeature(IEnumerable<TagHelperDescriptor> tagHelpers)
-        {
-            TagHelpers = new List<TagHelperDescriptor>(tagHelpers);
-        }
-    }
-}
diff --git a/src/Compiler/test/Microsoft.NET.Sdk.Razor.SourceGenerators.Tests/RazorSourceGeneratorTests.cs b/src/Compiler/test/Microsoft.NET.Sdk.Razor.SourceGenerators.Tests/RazorSourceGeneratorTests.cs
index 6d93d01cec3..caf1a74d5ea 100644
--- a/src/Compiler/test/Microsoft.NET.Sdk.Razor.SourceGenerators.Tests/RazorSourceGeneratorTests.cs
+++ b/src/Compiler/test/Microsoft.NET.Sdk.Razor.SourceGenerators.Tests/RazorSourceGeneratorTests.cs
@@ -7,7 +7,6 @@
 using System.IO;
 using System.Linq;
 using System.Text;
-using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Test.Common;
 using Microsoft.CodeAnalysis;
@@ -61,21 +60,6 @@ protected override void BuildRenderTree(global::Microsoft.AspNetCore.Components.
             Assert.Single(result.GeneratedSources);
         }
 
-        internal class InMemoryAdditionalText : AdditionalText
-        {
-            private readonly SourceText _content;
-
-            public InMemoryAdditionalText(string path, string content)
-            {
-                Path = path;
-                _content = SourceText.From(content, Encoding.UTF8);
-            }
-
-            public override string Path { get; }
-
-            public override SourceText GetText(CancellationToken cancellationToken = default) => _content;
-        }
-
         [Fact]
         public async Task SourceGeneratorEvents_RazorFiles_Works()
         {
@@ -143,74 +127,41 @@ protected override void BuildRenderTree(global::Microsoft.AspNetCore.Components.
 
             Assert.Collection(eventListener.Events,
                 e => Assert.Equal("ComputeRazorSourceGeneratorOptions", e.EventName),
-                e =>
-                {
-                    Assert.Equal("GenerateDeclarationCodeStart", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Pages/Index.razor", file);
-                },
-                e =>
-                {
-                    Assert.Equal("GenerateDeclarationCodeStop", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Pages/Index.razor", file);
-                },
-                e =>
-                {
-                    Assert.Equal("GenerateDeclarationCodeStart", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Pages/Counter.razor", file);
-                },
-                e =>
-                {
-                    Assert.Equal("GenerateDeclarationCodeStop", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Pages/Counter.razor", file);
-                },
+                e => e.AssertSingleItem("ParseRazorDocumentStart", "Pages/Index.razor"),
+                e => e.AssertSingleItem("ParseRazorDocumentStop", "Pages/Index.razor"),
+                e => e.AssertSingleItem("ParseRazorDocumentStart", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("ParseRazorDocumentStop", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("GenerateDeclarationCodeStart", "Pages/Index.razor"),
+                e => e.AssertSingleItem("GenerateDeclarationCodeStop", "Pages/Index.razor"),
+                e => e.AssertSingleItem("GenerateDeclarationCodeStart", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("GenerateDeclarationCodeStop", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStart", "Pages/Index.razor"),
+                e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStop", "Pages/Index.razor"),
+                e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStart", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStop", "Pages/Counter.razor"),
                 e => Assert.Equal("DiscoverTagHelpersFromCompilationStart", e.EventName),
                 e => Assert.Equal("DiscoverTagHelpersFromCompilationStop", e.EventName),
                 e => Assert.Equal("DiscoverTagHelpersFromReferencesStart", e.EventName),
                 e => Assert.Equal("DiscoverTagHelpersFromReferencesStop", e.EventName),
-                e =>
-                {
-                    Assert.Equal("RazorCodeGenerateStart", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Pages/Index.razor", file);
-                },
-                e =>
-                {
-                    Assert.Equal("RazorCodeGenerateStop", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Pages/Index.razor", file);
-                },
-                e =>
-                {
-                    Assert.Equal("RazorCodeGenerateStart", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Pages/Counter.razor", file);
-                },
-                e =>
-                {
-                    Assert.Equal("RazorCodeGenerateStop", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Pages/Counter.razor", file);
-                },
-                e =>
-                {
-                    Assert.Equal("AddSyntaxTrees", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("Pages_Index_razor.g.cs", file);
-                },
-                e =>
-                {
-                    Assert.Equal("AddSyntaxTrees", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("Pages_Counter_razor.g.cs", file);
-                });
+                e => e.AssertSingleItem("RewriteTagHelpersStart", "Pages/Index.razor"),
+                e => e.AssertSingleItem("RewriteTagHelpersStop", "Pages/Index.razor"),
+                e => e.AssertSingleItem("RewriteTagHelpersStart", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("RewriteTagHelpersStop", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("CheckAndRewriteTagHelpersStart", "Pages/Index.razor"),
+                e => e.AssertSingleItem("CheckAndRewriteTagHelpersStop", "Pages/Index.razor"),
+                e => e.AssertSingleItem("CheckAndRewriteTagHelpersStart", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("CheckAndRewriteTagHelpersStop", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("RazorCodeGenerateStart", "Pages/Index.razor"),
+                e => e.AssertSingleItem("RazorCodeGenerateStop", "Pages/Index.razor"),
+                e => e.AssertSingleItem("RazorCodeGenerateStart", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("RazorCodeGenerateStop", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("AddSyntaxTrees", "Pages_Index_razor.g.cs"),
+                e => e.AssertSingleItem("AddSyntaxTrees", "Pages_Counter_razor.g.cs")
+            );
         }
 
         [Fact]
-        public async Task IncrementalCompilation_DoesNotReexecuteSteps_WhenRazorFilesAreUnchanged()
+        public async Task IncrementalCompilation_DoesNotReExecuteSteps_WhenRazorFilesAreUnchanged()
         {
             // Arrange
             using var eventListener = new RazorEventListener();
@@ -392,36 +343,18 @@ protected override void BuildRenderTree(global::Microsoft.AspNetCore.Components.
             Assert.Equal(2, result.GeneratedSources.Length);
 
             Assert.Collection(eventListener.Events,
-               e =>
-               {
-                   Assert.Equal("GenerateDeclarationCodeStart", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("GenerateDeclarationCodeStop", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStart", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStop", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("AddSyntaxTrees", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("Pages_Counter_razor.g.cs", file);
-               });
+               e => e.AssertSingleItem("ParseRazorDocumentStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("ParseRazorDocumentStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("GenerateDeclarationCodeStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("GenerateDeclarationCodeStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("RewriteTagHelpersStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("RewriteTagHelpersStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("RazorCodeGenerateStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("RazorCodeGenerateStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("AddSyntaxTrees", "Pages_Counter_razor.g.cs")
+            );
         }
 
         [Fact]
@@ -514,8 +447,13 @@ public class Person
             Assert.Equal(2, result.GeneratedSources.Length);
 
             Assert.Collection(eventListener.Events,
-               e => Assert.Equal("DiscoverTagHelpersFromCompilationStart", e.EventName),
-               e => Assert.Equal("DiscoverTagHelpersFromCompilationStop", e.EventName));
+                e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStart", "Pages/Index.razor"),
+                e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStop", "Pages/Index.razor"),
+                e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStart", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStop", "Pages/Counter.razor"),
+                e => Assert.Equal("DiscoverTagHelpersFromCompilationStart", e.EventName),
+                e => Assert.Equal("DiscoverTagHelpersFromCompilationStop", e.EventName)
+               );
         }
 
         [Fact]
@@ -613,6 +551,8 @@ public class Person
 }", Encoding.UTF8)).Project;
             compilation = await project.GetCompilationAsync();
 
+            eventListener.Events.Clear();
+
             result = RunGenerator(compilation!, ref driver, expectedDiagnostics)
                         .VerifyOutputsMatch(result);
 
@@ -620,8 +560,13 @@ public class Person
             Assert.Equal(2, result.GeneratedSources.Length);
 
             Assert.Collection(eventListener.Events,
+               e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStart", "Pages/Index.razor"),
+               e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStop", "Pages/Index.razor"),
+               e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStop", "Pages/Counter.razor"),
                e => Assert.Equal("DiscoverTagHelpersFromCompilationStart", e.EventName),
-               e => Assert.Equal("DiscoverTagHelpersFromCompilationStop", e.EventName));
+               e => Assert.Equal("DiscoverTagHelpersFromCompilationStop", e.EventName)
+           );
         }
 
         [Fact]
@@ -766,38 +711,20 @@ protected override void BuildRenderTree(global::Microsoft.AspNetCore.Components.
             Assert.Equal(2, result.GeneratedSources.Length);
 
             Assert.Collection(eventListener.Events,
-               e =>
-               {
-                   Assert.Equal("GenerateDeclarationCodeStart", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("GenerateDeclarationCodeStop", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e => Assert.Equal("DiscoverTagHelpersFromCompilationStart", e.EventName),
-               e => Assert.Equal("DiscoverTagHelpersFromCompilationStop", e.EventName),
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStart", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStop", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("AddSyntaxTrees", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("Pages_Counter_razor.g.cs", file);
-               });
+               e => e.AssertSingleItem("ParseRazorDocumentStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("ParseRazorDocumentStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("GenerateDeclarationCodeStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("GenerateDeclarationCodeStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("RewriteTagHelpersStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("RewriteTagHelpersStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("RazorCodeGenerateStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("RazorCodeGenerateStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("AddSyntaxTrees", "Pages_Counter_razor.g.cs")
+            );
         }
 
         [Fact]
@@ -946,50 +873,24 @@ protected override void BuildRenderTree(global::Microsoft.AspNetCore.Components.
             Assert.Equal(2, result.GeneratedSources.Length);
 
             Assert.Collection(eventListener.Events,
-               e =>
-               {
-                   Assert.Equal("GenerateDeclarationCodeStart", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("GenerateDeclarationCodeStop", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e => Assert.Equal("DiscoverTagHelpersFromCompilationStart", e.EventName),
-               e => Assert.Equal("DiscoverTagHelpersFromCompilationStop", e.EventName),
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStart", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Index.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStop", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Index.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStart", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStop", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("AddSyntaxTrees", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("Pages_Counter_razor.g.cs", file);
-               });
+                e => e.AssertSingleItem("ParseRazorDocumentStart", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("ParseRazorDocumentStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("GenerateDeclarationCodeStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("GenerateDeclarationCodeStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStop", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("RewriteTagHelpersStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("RewriteTagHelpersStop", "Pages/Counter.razor"),
+                e => e.AssertSingleItem("CheckAndRewriteTagHelpersStart", "Pages/Index.razor"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStop", "Pages/Index.razor"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("RazorCodeGenerateStart", "Pages/Index.razor"),
+               e => e.AssertSingleItem("RazorCodeGenerateStop", "Pages/Index.razor"),
+               e => e.AssertSingleItem("RazorCodeGenerateStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("RazorCodeGenerateStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("AddSyntaxTrees", "Pages_Counter_razor.g.cs")
+            );
         }
 
         [Fact]
@@ -1120,40 +1021,24 @@ protected override void BuildRenderTree(global::Microsoft.AspNetCore.Components.
             Assert.Equal(2, result.GeneratedSources.Length);
 
             Assert.Collection(eventListener.Events,
+               e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStart", "Pages/Index.razor"),
+               e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStop", "Pages/Index.razor"),
+               e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("DiscoverTagHelpersFromComponentStop", "Pages/Counter.razor"),
                e => Assert.Equal("DiscoverTagHelpersFromCompilationStart", e.EventName),
                e => Assert.Equal("DiscoverTagHelpersFromCompilationStop", e.EventName),
                e => Assert.Equal("DiscoverTagHelpersFromReferencesStart", e.EventName),
                e => Assert.Equal("DiscoverTagHelpersFromReferencesStop", e.EventName),
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStart", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Index.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStop", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Index.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStart", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStop", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Counter.razor", file);
-               },
-               e =>
-               {
-                   Assert.Equal("AddSyntaxTrees", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("Pages_Index_razor.g.cs", file);
-               });
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStart", "Pages/Index.razor"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStop", "Pages/Index.razor"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("RazorCodeGenerateStart", "Pages/Index.razor"),
+               e => e.AssertSingleItem("RazorCodeGenerateStop", "Pages/Index.razor"),
+               e => e.AssertSingleItem("RazorCodeGenerateStart", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("RazorCodeGenerateStop", "Pages/Counter.razor"),
+               e => e.AssertSingleItem("AddSyntaxTrees", "Pages_Index_razor.g.cs")
+            );
 
             // Verify caching
             eventListener.Events.Clear();
@@ -1305,46 +1190,29 @@ internal sealed class Views_Shared__Layout : global::Microsoft.AspNetCore.Mvc.Ra
 
             Assert.Collection(eventListener.Events,
                 e => Assert.Equal("ComputeRazorSourceGeneratorOptions", e.EventName),
+                e => e.AssertSingleItem("ParseRazorDocumentStart", "Pages/Index.cshtml"),
+                e => e.AssertSingleItem("ParseRazorDocumentStop", "Pages/Index.cshtml"),
+                e => e.AssertSingleItem("ParseRazorDocumentStart", "Views/Shared/_Layout.cshtml"),
+                e => e.AssertSingleItem("ParseRazorDocumentStop", "Views/Shared/_Layout.cshtml"),
                 e => Assert.Equal("DiscoverTagHelpersFromCompilationStart", e.EventName),
                 e => Assert.Equal("DiscoverTagHelpersFromCompilationStop", e.EventName),
                 e => Assert.Equal("DiscoverTagHelpersFromReferencesStart", e.EventName),
                 e => Assert.Equal("DiscoverTagHelpersFromReferencesStop", e.EventName),
-                e =>
-                {
-                    Assert.Equal("RazorCodeGenerateStart", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Pages/Index.cshtml", file);
-                },
-                e =>
-                {
-                    Assert.Equal("RazorCodeGenerateStop", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Pages/Index.cshtml", file);
-                },
-                e =>
-                {
-                    Assert.Equal("RazorCodeGenerateStart", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Views/Shared/_Layout.cshtml", file);
-                },
-                e =>
-                {
-                    Assert.Equal("RazorCodeGenerateStop", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Views/Shared/_Layout.cshtml", file);
-                },
-                e =>
-                {
-                    Assert.Equal("AddSyntaxTrees", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("Pages_Index_cshtml.g.cs", file);
-                },
-                e =>
-                {
-                    Assert.Equal("AddSyntaxTrees", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("Views_Shared__Layout_cshtml.g.cs", file);
-                });
+                e => e.AssertSingleItem("RewriteTagHelpersStart", "Pages/Index.cshtml"),
+                e => e.AssertSingleItem("RewriteTagHelpersStop", "Pages/Index.cshtml"),
+                e => e.AssertSingleItem("RewriteTagHelpersStart", "Views/Shared/_Layout.cshtml"),
+                e => e.AssertSingleItem("RewriteTagHelpersStop", "Views/Shared/_Layout.cshtml"),
+                e => e.AssertSingleItem("CheckAndRewriteTagHelpersStart", "Pages/Index.cshtml"),
+                e => e.AssertSingleItem("CheckAndRewriteTagHelpersStop", "Pages/Index.cshtml"),
+                e => e.AssertSingleItem("CheckAndRewriteTagHelpersStart", "Views/Shared/_Layout.cshtml"),
+                e => e.AssertSingleItem("CheckAndRewriteTagHelpersStop", "Views/Shared/_Layout.cshtml"),
+                e => e.AssertSingleItem("RazorCodeGenerateStart", "Pages/Index.cshtml"),
+                e => e.AssertSingleItem("RazorCodeGenerateStop", "Pages/Index.cshtml"),
+                e => e.AssertSingleItem("RazorCodeGenerateStart", "Views/Shared/_Layout.cshtml"),
+                e => e.AssertSingleItem("RazorCodeGenerateStop", "Views/Shared/_Layout.cshtml"),
+                e => e.AssertSingleItem("AddSyntaxTrees", "Pages_Index_cshtml.g.cs"),
+                e => e.AssertSingleItem("AddSyntaxTrees", "Views_Shared__Layout_cshtml.g.cs")
+            );
         }
 
         [Fact]
@@ -1536,24 +1404,16 @@ internal sealed class Views_Shared__Layout : global::Microsoft.AspNetCore.Mvc.Ra
             Assert.Equal(2, result.GeneratedSources.Length);
 
             Assert.Collection(eventListener.Events,
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStart", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Views/Shared/_Layout.cshtml", file);
-               },
-                e =>
-                {
-                    Assert.Equal("RazorCodeGenerateStop", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Views/Shared/_Layout.cshtml", file);
-                },
-                e =>
-                {
-                    Assert.Equal("AddSyntaxTrees", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("Views_Shared__Layout_cshtml.g.cs", file);
-                });
+               e => e.AssertSingleItem("ParseRazorDocumentStart", "Views/Shared/_Layout.cshtml"),
+               e => e.AssertSingleItem("ParseRazorDocumentStop", "Views/Shared/_Layout.cshtml"),
+               e => e.AssertSingleItem("RewriteTagHelpersStart", "Views/Shared/_Layout.cshtml"),
+               e => e.AssertSingleItem("RewriteTagHelpersStop", "Views/Shared/_Layout.cshtml"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStart", "Views/Shared/_Layout.cshtml"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStop", "Views/Shared/_Layout.cshtml"),
+               e => e.AssertSingleItem("RazorCodeGenerateStart", "Views/Shared/_Layout.cshtml"),
+               e => e.AssertSingleItem("RazorCodeGenerateStop", "Views/Shared/_Layout.cshtml"),
+               e => e.AssertSingleItem("AddSyntaxTrees", "Views_Shared__Layout_cshtml.g.cs")
+            );
         }
 
         [Fact]
@@ -1712,8 +1572,8 @@ public class Person
 
             Assert.Collection(eventListener.Events,
                e => Assert.Equal("DiscoverTagHelpersFromCompilationStart", e.EventName),
-               e => Assert.Equal("DiscoverTagHelpersFromCompilationStop", e.EventName));
-
+               e => Assert.Equal("DiscoverTagHelpersFromCompilationStop", e.EventName)
+               );
         }
 
         [Fact]
@@ -1863,7 +1723,92 @@ public override void Process(TagHelperContext context, TagHelperOutput output)
 }", Encoding.UTF8)).Project;
             compilation = await project.GetCompilationAsync();
 
-            result = RunGenerator(compilation!, ref driver);
+            result = RunGenerator(compilation!, ref driver)
+                  .VerifyOutputsMatch(result, (0, @"
+#pragma checksum ""Pages/Index.cshtml"" ""{ff1816ec-aa5e-4d10-87f7-6f4963833460}"" ""5d59ecd7b7cf7355d7f60234988be34b81a8b614""
+// <auto-generated/>
+#pragma warning disable 1591
+[assembly: global::Microsoft.AspNetCore.Razor.Hosting.RazorCompiledItemAttribute(typeof(AspNetCoreGeneratedDocument.Pages_Index), @""mvc.1.0.view"", @""/Pages/Index.cshtml"")]
+namespace AspNetCoreGeneratedDocument
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Mvc;
+    using Microsoft.AspNetCore.Mvc.Rendering;
+    using Microsoft.AspNetCore.Mvc.ViewFeatures;
+    [global::Microsoft.AspNetCore.Razor.Hosting.RazorCompiledItemMetadataAttribute(""Identifier"", ""/Pages/Index.cshtml"")]
+    [global::System.Runtime.CompilerServices.CreateNewOnMetadataUpdateAttribute]
+    #nullable restore
+    internal sealed class Pages_Index : global::Microsoft.AspNetCore.Mvc.Razor.RazorPage<dynamic>
+    #nullable disable
+    {
+        #line hidden
+        #pragma warning disable 0649
+        private global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperExecutionContext __tagHelperExecutionContext;
+        #pragma warning restore 0649
+        private global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner __tagHelperRunner = new global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner();
+        #pragma warning disable 0169
+        private string __tagHelperStringValueBuffer;
+        #pragma warning restore 0169
+        private global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager __backed__tagHelperScopeManager = null;
+        private global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager __tagHelperScopeManager
+        {
+            get
+            {
+                if (__backed__tagHelperScopeManager == null)
+                {
+                    __backed__tagHelperScopeManager = new global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager(StartTagHelperWritingScope, EndTagHelperWritingScope);
+                }
+                return __backed__tagHelperScopeManager;
+            }
+        }
+        private global::MyApp.HeaderTagHelper __MyApp_HeaderTagHelper;
+        #pragma warning disable 1998
+        public async override global::System.Threading.Tasks.Task ExecuteAsync()
+        {
+            WriteLiteral(""\r\n"");
+            __tagHelperExecutionContext = __tagHelperScopeManager.Begin(""h2"", global::Microsoft.AspNetCore.Razor.TagHelpers.TagMode.StartTagAndEndTag, ""5d59ecd7b7cf7355d7f60234988be34b81a8b6142529"", async() => {
+                WriteLiteral(""Hello world"");
+            }
+            );
+            __MyApp_HeaderTagHelper = CreateTagHelper<global::MyApp.HeaderTagHelper>();
+            __tagHelperExecutionContext.Add(__MyApp_HeaderTagHelper);
+            await __tagHelperRunner.RunAsync(__tagHelperExecutionContext);
+            if (!__tagHelperExecutionContext.Output.IsContentModified)
+            {
+                await __tagHelperExecutionContext.SetOutputContentAsync();
+            }
+            Write(__tagHelperExecutionContext.Output);
+            __tagHelperExecutionContext = __tagHelperScopeManager.End();
+        }
+        #pragma warning restore 1998
+        #nullable restore
+        [global::Microsoft.AspNetCore.Mvc.Razor.Internal.RazorInjectAttribute]
+        public global::Microsoft.AspNetCore.Mvc.ViewFeatures.IModelExpressionProvider ModelExpressionProvider { get; private set; } = default!;
+        #nullable disable
+        #nullable restore
+        [global::Microsoft.AspNetCore.Mvc.Razor.Internal.RazorInjectAttribute]
+        public global::Microsoft.AspNetCore.Mvc.IUrlHelper Url { get; private set; } = default!;
+        #nullable disable
+        #nullable restore
+        [global::Microsoft.AspNetCore.Mvc.Razor.Internal.RazorInjectAttribute]
+        public global::Microsoft.AspNetCore.Mvc.IViewComponentHelper Component { get; private set; } = default!;
+        #nullable disable
+        #nullable restore
+        [global::Microsoft.AspNetCore.Mvc.Razor.Internal.RazorInjectAttribute]
+        public global::Microsoft.AspNetCore.Mvc.Rendering.IJsonHelper Json { get; private set; } = default!;
+        #nullable disable
+        #nullable restore
+        [global::Microsoft.AspNetCore.Mvc.Razor.Internal.RazorInjectAttribute]
+        public global::Microsoft.AspNetCore.Mvc.Rendering.IHtmlHelper<dynamic> Html { get; private set; } = default!;
+        #nullable disable
+    }
+}
+#pragma warning restore 1591
+"));
 
             Assert.Empty(result.Diagnostics);
             Assert.Equal(2, result.GeneratedSources.Length);
@@ -1871,36 +1816,14 @@ public override void Process(TagHelperContext context, TagHelperOutput output)
             Assert.Collection(eventListener.Events,
                e => Assert.Equal("DiscoverTagHelpersFromCompilationStart", e.EventName),
                e => Assert.Equal("DiscoverTagHelpersFromCompilationStop", e.EventName),
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStart", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Pages/Index.cshtml", file);
-               },
-                e =>
-                {
-                    Assert.Equal("RazorCodeGenerateStop", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Pages/Index.cshtml", file);
-                },
-               e =>
-               {
-                   Assert.Equal("RazorCodeGenerateStart", e.EventName);
-                   var file = Assert.Single(e.Payload);
-                   Assert.Equal("/Views/Shared/_Layout.cshtml", file);
-               },
-                e =>
-                {
-                    Assert.Equal("RazorCodeGenerateStop", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("/Views/Shared/_Layout.cshtml", file);
-                },
-                e =>
-                {
-                    Assert.Equal("AddSyntaxTrees", e.EventName);
-                    var file = Assert.Single(e.Payload);
-                    Assert.Equal("Pages_Index_cshtml.g.cs", file);
-                });
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStart", "Pages/Index.cshtml"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStop", "Pages/Index.cshtml"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStart", "Views/Shared/_Layout.cshtml"),
+               e => e.AssertSingleItem("CheckAndRewriteTagHelpersStop", "Views/Shared/_Layout.cshtml"),
+               e => e.AssertSingleItem("RazorCodeGenerateStart", "Pages/Index.cshtml"),
+               e => e.AssertSingleItem("RazorCodeGenerateStop", "Pages/Index.cshtml"),
+               e => e.AssertSingleItem("AddSyntaxTrees", "Pages_Index_cshtml.g.cs")
+           );
         }
 
         [Fact]
@@ -2567,5 +2490,60 @@ public async Task SourceGenerator_EmptyTargetPath(string targetPath)
 
             Assert.Empty(result.GeneratedSources);
         }
+
+        [Fact]
+        public async Task SourceGenerator_Class_Inside_CodeBlock()
+        {
+            var project = CreateTestProject(new()
+            {
+                ["Component.Razor"] =
+"""
+<h1>Hello world</h1>
+
+@code
+{
+    public class X {}
+}
+"""});
+
+            var compilation = await project.GetCompilationAsync();
+            var driver = await GetDriverAsync(project);
+
+            var result = RunGenerator(compilation!, ref driver).VerifyPageOutput(
+@"#pragma checksum ""Component.Razor"" ""{ff1816ec-aa5e-4d10-87f7-6f4963833460}"" ""20b14071a74e1fd554d7b3dff6ff41722270ebee""
+// <auto-generated/>
+#pragma warning disable 1591
+namespace MyApp
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+    public partial class Component : global::Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(global::Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder __builder)
+        {
+            __builder.AddMarkupContent(0, ""<h1>Hello world</h1>"");
+        }
+        #pragma warning restore 1998
+#nullable restore
+#line 4 ""Component.Razor""
+ 
+    public class X {}
+
+#line default
+#line hidden
+#nullable disable
+    }
+}
+#pragma warning restore 1591
+");
+
+            Assert.Empty(result.Diagnostics);
+            Assert.Single(result.GeneratedSources);
+        }
     }
 }
diff --git a/src/Compiler/test/Microsoft.NET.Sdk.Razor.SourceGenerators.Tests/RazorSourceGeneratorTestsBase.cs b/src/Compiler/test/Microsoft.NET.Sdk.Razor.SourceGenerators.Tests/RazorSourceGeneratorTestsBase.cs
index 9b00b6fab90..5c6945c03d6 100644
--- a/src/Compiler/test/Microsoft.NET.Sdk.Razor.SourceGenerators.Tests/RazorSourceGeneratorTestsBase.cs
+++ b/src/Compiler/test/Microsoft.NET.Sdk.Razor.SourceGenerators.Tests/RazorSourceGeneratorTestsBase.cs
@@ -349,4 +349,11 @@ private static string TrimChecksum(string text)
         Assert.StartsWith("#pragma", trimmed);
         return trimmed.Substring(trimmed.IndexOf('\n') + 1);
     }
+
+    public static void AssertSingleItem(this RazorEventListener.RazorEvent e, string expectedEventName, string expectedFileName)
+    {
+        Assert.Equal(expectedEventName, e.EventName);
+        var file = Assert.Single(e.Payload);
+        Assert.Equal(expectedFileName, file);
+    }
 }