diff --git a/src/Microsoft.VisualStudio.ProjectSystem.Managed/Microsoft.VisualStudio.ProjectSystem.Managed.csproj b/src/Microsoft.VisualStudio.ProjectSystem.Managed/Microsoft.VisualStudio.ProjectSystem.Managed.csproj
index 9fa046c5ac5..756260c60ee 100644
--- a/src/Microsoft.VisualStudio.ProjectSystem.Managed/Microsoft.VisualStudio.ProjectSystem.Managed.csproj
+++ b/src/Microsoft.VisualStudio.ProjectSystem.Managed/Microsoft.VisualStudio.ProjectSystem.Managed.csproj
@@ -43,6 +43,9 @@
     <Compile Update="ProjectSystem\Rules\ResolvedAnalyzerReference.xaml.cs">
       <DependentUpon>ResolvedAnalyzerReference.xaml</DependentUpon>
     </Compile>
+    <Compile Update="ProjectSystem\Rules\ResolvedCompilationReference.cs">
+      <DependentUpon>ResolvedCompilationReference.xaml</DependentUpon>
+    </Compile>
     <Compile Update="ProjectSystem\Rules\ResolvedPackageReference.cs">
       <DependentUpon>ResolvedPackageReference.xaml</DependentUpon>
     </Compile>
@@ -91,6 +94,9 @@
     <Compile Update="ProjectSystem\Rules\UpToDateCheckOutput.cs">
       <DependentUpon>UpToDateCheckOutput.xaml</DependentUpon>
     </Compile>
+    <Compile Update="ProjectSystem\Rules\CopyUpToDateMarker.cs">
+      <DependentUpon>CopyUpToDateMarker.xaml</DependentUpon>
+    </Compile>
     <Compile Update="ProjectSystem\Rules\Folder.cs">
       <DependentUpon>Folder.xaml</DependentUpon>
     </Compile>
@@ -168,6 +174,10 @@
       <Generator>MSBuild:GenerateRuleSourceFromXaml</Generator>
       <SubType>Designer</SubType>
     </XamlPropertyRule>
+    <XamlPropertyRule Include="ProjectSystem\Rules\CopyUpToDateMarker.xaml">
+      <Generator>MSBuild:GenerateRuleSourceFromXaml</Generator>
+      <SubType>Designer</SubType>
+    </XamlPropertyRule>
     <XamlPropertyRule Include="ProjectSystem\Rules\Folder.xaml">
       <Generator>MSBuild:GenerateRuleSourceFromXaml</Generator>
       <SubType>Designer</SubType>
@@ -280,6 +290,10 @@
       <Generator>MSBuild:GenerateRuleSourceFromXaml</Generator>
       <SubType>Designer</SubType>
     </XamlPropertyRule>
+    <XamlPropertyRule Include="ProjectSystem\Rules\ResolvedCompilationReference.xaml">
+      <Generator>MSBuild:GenerateRuleSourceFromXaml</Generator>
+      <SubType>Designer</SubType>
+    </XamlPropertyRule>
     <XamlPropertyRule Include="ProjectSystem\Rules\ProjectDebugger.xaml">
       <Generator>MSBuild:GenerateRuleSourceFromXaml</Generator>
       <SubType>Designer</SubType>
diff --git a/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/BuildUpToDateCheck.cs b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/BuildUpToDateCheck.cs
index de76b2f7a3f..e689d1d8627 100644
--- a/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/BuildUpToDateCheck.cs
+++ b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/BuildUpToDateCheck.cs
@@ -48,6 +48,7 @@ private void Log(LogLevel level, string message, params object[] values)
         private const string ResolvedPath = "ResolvedPath";
         private const string CopyToOutputDirectory = "CopyToOutputDirectory";
         private const string Never = "Never";
+        private const string OriginalPath = "OriginalPath";
 
         private static HashSet<string> KnownOutputGroups = new HashSet<string>
         {
@@ -60,13 +61,17 @@ private void Log(LogLevel level, string message, params object[] values)
 
         private static ImmutableHashSet<string> ReferenceSchemas => ImmutableHashSet<string>.Empty
             .Add(ResolvedAnalyzerReference.SchemaName)
-            .Add(ResolvedAssemblyReference.SchemaName)
-            .Add(ResolvedCOMReference.SchemaName)
-            .Add(ResolvedProjectReference.SchemaName);
+            .Add(ResolvedCompilationReference.SchemaName);
+
+        private static ImmutableHashSet<string> UpToDateSchemas => ImmutableHashSet<string>.Empty
+            .Add(CopyUpToDateMarker.SchemaName)
+            .Add(UpToDateCheckInput.SchemaName)
+            .Add(UpToDateCheckOutput.SchemaName);
 
         private static ImmutableHashSet<string> ProjectPropertiesSchemas => ImmutableHashSet<string>.Empty
             .Add(ConfigurationGeneral.SchemaName)
-            .Union(ReferenceSchemas);
+            .Union(ReferenceSchemas)
+            .Union(UpToDateSchemas);
 
         private readonly IProjectSystemOptions _projectSystemOptions;
         private readonly ConfiguredProject _configuredProject;
@@ -79,11 +84,15 @@ private void Log(LogLevel level, string message, params object[] values)
         private bool _isDisabled = true;
         private bool _itemsChangedSinceLastCheck = true;
         private string _msBuildProjectFullPath;
+        private string _markerFile;
         private HashSet<string> _imports = new HashSet<string>();
         private HashSet<string> _itemTypes = new HashSet<string>();
         private Dictionary<string, HashSet<string>> _items = new Dictionary<string, HashSet<string>>();
-        private Dictionary<string, HashSet<string>> _references = new Dictionary<string, HashSet<string>>();
+        private HashSet<string> _customInputs = new HashSet<string>();
         private HashSet<string> _customOutputs = new HashSet<string>();
+        private HashSet<string> _analyzerReferences = new HashSet<string>();
+        private HashSet<string> _compilationReferences = new HashSet<string>();
+        private HashSet<string> _copyReferenceInputs = new HashSet<string>();
         private Dictionary<string, HashSet<string>> _outputGroups = new Dictionary<string, HashSet<string>>();
 
         [ImportingConstructor]
@@ -117,14 +126,50 @@ private void OnProjectChanged(IProjectSubscriptionUpdate e)
             _isDisabled = disableFastUpToDateCheckString != null && string.Equals(disableFastUpToDateCheckString, TrueValue, StringComparison.OrdinalIgnoreCase);
 
             _msBuildProjectFullPath = e.CurrentState.GetPropertyOrDefault(ConfigurationGeneral.SchemaName, ConfigurationGeneral.MSBuildProjectFullPathProperty, _msBuildProjectFullPath);
-            foreach (var referenceSchema in ReferenceSchemas)
+
+            if (e.ProjectChanges.TryGetValue(ResolvedAnalyzerReference.SchemaName, out var changes) &&
+                changes.Difference.AnyChanges)
             {
-                if (e.ProjectChanges.TryGetValue(referenceSchema, out var changes) &&
-                    changes.Difference.AnyChanges)
+                _analyzerReferences = new HashSet<string>(changes.After.Items.Select(item => item.Value[ResolvedPath]));
+            }
+
+            if (e.ProjectChanges.TryGetValue(ResolvedCompilationReference.SchemaName, out changes) &&
+                changes.Difference.AnyChanges)
+            {
+                _compilationReferences.Clear();
+                _copyReferenceInputs.Clear();
+
+                foreach (var item in changes.After.Items)
                 {
-                    _references[referenceSchema] = new HashSet<string>(changes.After.Items.Select(item => item.Value[ResolvedPath]));
+                    _compilationReferences.Add(item.Value[ResolvedPath]);
+                    if (!string.IsNullOrWhiteSpace(item.Value[CopyUpToDateMarker.SchemaName]))
+                    {
+                        _copyReferenceInputs.Add(item.Value[CopyUpToDateMarker.SchemaName]);
+                    }
+                    if (!string.IsNullOrWhiteSpace(item.Value[OriginalPath]))
+                    {
+                        _copyReferenceInputs.Add(item.Value[OriginalPath]);
+                    }
                 }
             }
+
+            if (e.ProjectChanges.TryGetValue(UpToDateCheckInput.SchemaName, out var inputs) &&
+                inputs.Difference.AnyChanges)
+            {
+                _customInputs = new HashSet<string>(inputs.After.Items.Select(item => item.Value[FullPath]));
+            }
+
+            if (e.ProjectChanges.TryGetValue(UpToDateCheckOutput.SchemaName, out var outputs) &&
+                outputs.Difference.AnyChanges)
+            {
+                _customOutputs = new HashSet<string>(outputs.After.Items.Select(item => item.Value[FullPath]));
+            }
+
+            if (e.ProjectChanges.TryGetValue(CopyUpToDateMarker.SchemaName, out var upToDateMarkers) &&
+                upToDateMarkers.Difference.AnyChanges)
+            {
+                _markerFile = upToDateMarkers.After.Items.Count == 1 ? upToDateMarkers.After.Items.Single().Value[FullPath] : null;
+            }
         }
 
         private void OnProjectImportsChanged(IProjectImportTreeSnapshot e)
@@ -161,12 +206,6 @@ private void OnSourceItemChanged(IProjectSubscriptionUpdate e, IProjectItemSchem
                 _items[itemType.Key] = new HashSet<string>(items);
                 _itemsChangedSinceLastCheck = true;
             }
-
-            if (e.ProjectChanges.TryGetValue(UpToDateCheckOutput.SchemaName, out var outputs) &&
-                outputs.Difference.AnyChanges)
-            {
-                _customOutputs = new HashSet<string>(outputs.After.Items.Select(item => item.Value[FullPath]));
-            }
         }
 
         private void OnOutputGroupChanged(IImmutableDictionary<string, IOutputGroup> e)
@@ -289,10 +328,9 @@ private HashSet<string> CollectInputs(Logger logger)
                 AddInputs(logger, inputs, pair.Value, pair.Key);
             }
 
-            foreach (var pair in _references)
-            {
-                AddInputs(logger, inputs, pair.Value, pair.Key);
-            }
+            AddInputs(logger, inputs, _analyzerReferences, ResolvedAnalyzerReference.SchemaName);
+            AddInputs(logger, inputs, _compilationReferences, ResolvedCompilationReference.SchemaName);
+            AddInputs(logger, inputs, _customInputs, UpToDateCheckInput.SchemaName);
 
             return inputs;
         }
@@ -306,12 +344,12 @@ private HashSet<string> CollectOutputs(Logger logger)
                 AddOutputs(logger, outputs, pair.Value, pair.Key);
             }
 
-            AddOutputs(logger, outputs, _customOutputs, "UpToDateCheckOutput");
+            AddOutputs(logger, outputs, _customOutputs, UpToDateCheckOutput.SchemaName);
 
             return outputs;
         }
 
-        private (DateTime? time, string path) GetLatestInput(HashSet<string> inputs, IDictionary<string, DateTime> timestampCache)
+        private (DateTime? time, string path) GetLatestInput(HashSet<string> inputs, IDictionary<string, DateTime> timestampCache, bool ignoreMissing = false)
         {
             DateTime? latest = DateTime.MinValue;
             string latestPath = null;
@@ -319,7 +357,7 @@ private HashSet<string> CollectOutputs(Logger logger)
             foreach (var input in inputs)
             {
                 var time = GetTimestamp(input, timestampCache);
-                if (latest != null && (time == null || time > latest))
+                if (latest != null && (time == null && !ignoreMissing || time > latest))
                 {
                     latest = time;
                     latestPath = input;
@@ -347,6 +385,50 @@ private HashSet<string> CollectOutputs(Logger logger)
             return (earliest, earliestPath);
         }
 
+        // Reference assembly copy markers are strange. The property is always going to be present on 
+        // references to SDK-based projects, regardless of whether or not those referenced projects 
+        // will actually produce a marker. And an item always will be present in an SDK-based project, 
+        // regardless of whether or not the project produces a marker. So, basically, we only check 
+        // here if the project actually produced a marker and we only check it against references that
+        // actually produced a marker.
+        private bool CheckMarkers(Logger logger, IDictionary<string, DateTime> timestampCache)
+        {
+            if (string.IsNullOrWhiteSpace(_markerFile) || !_copyReferenceInputs.Any())
+            {
+                return true;
+            }
+
+            foreach (var referenceMarkerFile in _copyReferenceInputs)
+            {
+                logger.Verbose("Found possible input marker '{0}'.", referenceMarkerFile);
+            }
+
+            logger.Verbose("Found possible output marker '{0}'.", _markerFile);
+
+            var latestInputMarker = GetLatestInput(_copyReferenceInputs, timestampCache, true);
+            var outputMarkerTime = GetTimestamp(_markerFile, timestampCache);
+
+            if (latestInputMarker.path != null)
+            {
+                logger.Info("Latest write timestamp on input marker is {0} on '{1}'.", latestInputMarker.time.Value, latestInputMarker.path);
+            }
+            else
+            {
+                logger.Info("No input markers exist, skipping marker check.");
+            }
+
+            if (outputMarkerTime != null)
+            {
+                logger.Info("Write timestamp on output marker is {0} on '{1}'.", outputMarkerTime, _markerFile);
+            }
+            else
+            {
+                logger.Info("Output marker '{0}' does not exist, skipping marker check.", _markerFile);
+            }
+
+            return latestInputMarker.path == null || outputMarkerTime == null || outputMarkerTime > latestInputMarker.time;
+        }
+
         public async Task<bool> IsUpToDateAsync(BuildAction buildAction, TextWriter logWriter, CancellationToken cancellationToken = default(CancellationToken))
         {
             cancellationToken.ThrowIfCancellationRequested();
@@ -368,7 +450,7 @@ private HashSet<string> CollectOutputs(Logger logger)
             
             if (latestInput.time != null)
             {
-                logger.Info("Lastest write timestamp on input is {0} on '{1}'.", latestInput.time.Value, latestInput.path);
+                logger.Info("Latest write timestamp on input is {0} on '{1}'.", latestInput.time.Value, latestInput.path);
             }
             else
             {
@@ -385,7 +467,13 @@ private HashSet<string> CollectOutputs(Logger logger)
             }
 
             // We are up to date if the earliest output write happened after the latest input write
-            var isUpToDate = latestInput.time != null && earliestOutput.time != null && earliestOutput.time > latestInput.time;
+            var markersUpToDate = CheckMarkers(logger, timestampCache);
+            var isUpToDate = 
+                latestInput.time != null 
+                && earliestOutput.time != null 
+                && earliestOutput.time > latestInput.time 
+                && markersUpToDate;
+
             logger.Info("Project is{0} up to date.", (!isUpToDate ? " not" : ""));
 
             return isUpToDate;
diff --git a/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/CopyUpToDateMarker.cs b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/CopyUpToDateMarker.cs
new file mode 100644
index 00000000000..d5deeec97e8
--- /dev/null
+++ b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/CopyUpToDateMarker.cs
@@ -0,0 +1,12 @@
+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+using System.Diagnostics.CodeAnalysis;
+
+namespace Microsoft.VisualStudio.ProjectSystem
+{
+    [ExcludeFromCodeCoverage]
+    [SuppressMessage("Style", "IDE0016:Use 'throw' expression")]
+    partial class CopyUpToDateMarker
+    {
+    }
+}
diff --git a/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/CopyUpToDateMarker.xaml b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/CopyUpToDateMarker.xaml
new file mode 100644
index 00000000000..7666a2d590c
--- /dev/null
+++ b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/CopyUpToDateMarker.xaml
@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.-->
+<Rule
+    Name="CopyUpToDateMarker"
+    DisplayName="Up-to-date check marker for reference assemblies"
+    PageTemplate="generic"
+    Description="File Properties"
+    xmlns="http://schemas.microsoft.com/build/2009/properties">
+    <Rule.DataSource>
+        <DataSource Persistence="ProjectFile" HasConfigurationCondition="False" ItemType="CopyUpToDateMarker" SourceOfDefaultValue="AfterContext" />
+    </Rule.DataSource>
+    <Rule.Categories>
+        <Category Name="Advanced" DisplayName="Advanced" />
+        <Category Name="Misc" DisplayName="Misc" />
+    </Rule.Categories>
+
+    <StringProperty
+      Name="FullPath"
+      DisplayName="Full Path"
+      ReadOnly="true"
+      Category="Misc"
+      Description="Location of the file.">
+        <StringProperty.DataSource>
+            <DataSource Persistence="Intrinsic" ItemType="CopyUpToDateMarker" PersistedName="FullPath" SourceOfDefaultValue="AfterContext" />
+        </StringProperty.DataSource>
+    </StringProperty>
+
+    <BoolProperty Name="Visible" Default="false" Visible="false" />
+</Rule>
diff --git a/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/ProjectItemsSchema.xaml b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/ProjectItemsSchema.xaml
index 1c4600a8474..778f5f27eea 100644
--- a/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/ProjectItemsSchema.xaml
+++ b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/ProjectItemsSchema.xaml
@@ -58,23 +58,9 @@
       <NameValuePair Name="DefaultMetadata_Generator" Value="ResXFileCodeGenerator" />
     </ContentType>
 
-    <ContentType
-      Name="UpToDateCheckInput"
-      DisplayName="Up-to-date check input"
-      ItemType="UpToDateCheckInput">
-    </ContentType>
-
-    <ContentType
-      Name="UpToDateCheckOutput"
-      DisplayName="Up-to-date check output"
-      ItemType="UpToDateCheckOutput">
-    </ContentType>
-
     <ItemType Name="None" DisplayName="None"/>
     <ItemType Name="Content" DisplayName="Content" />
     <ItemType Name="EmbeddedResource" DisplayName="Embedded resource"/>
-    <ItemType Name="UpToDateCheckInput" DisplayName="Up-to-date check input"/>
-    <ItemType Name="UpToDateCheckOutput" DisplayName="Up-to-date check output" UpToDateCheckInput="False"/>
 
     <FileExtension Name=".asax" ContentType="Asax" />
     <FileExtension Name=".asmx" ContentType="HTML" />
diff --git a/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/ResolvedCompilationReference.cs b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/ResolvedCompilationReference.cs
new file mode 100644
index 00000000000..485904ab74e
--- /dev/null
+++ b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/ResolvedCompilationReference.cs
@@ -0,0 +1,12 @@
+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+using System.Diagnostics.CodeAnalysis;
+
+namespace Microsoft.VisualStudio.ProjectSystem
+{
+    [ExcludeFromCodeCoverage]
+    [SuppressMessage("Style", "IDE0016:Use 'throw' expression")]
+    partial class ResolvedCompilationReference
+    {
+    }
+}
diff --git a/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/ResolvedCompilationReference.xaml b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/ResolvedCompilationReference.xaml
new file mode 100644
index 00000000000..a01b05d683b
--- /dev/null
+++ b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Rules/ResolvedCompilationReference.xaml
@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information. -->
+<Rule
+    Name="ResolvedCompilationReference"
+    DisplayName="Resolved Compilation Reference"
+    PageTemplate="generic"
+    Description="Resolved Compilation Reference Properties"
+    xmlns="http://schemas.microsoft.com/build/2009/properties">
+    <Rule.DataSource>
+        <DataSource Persistence="ResolvedReference" ItemType="ReferencePathWithRefAssemblies" HasConfigurationCondition="False" SourceOfDefaultValue="AfterContext"
+                    SourceType="TargetResults" MSBuildTarget="CollectResolvedCompilationReferencesDesignTime"/>
+    </Rule.DataSource>
+
+    <StringProperty Name="ResolvedPath" ReadOnly="True" DisplayName="Path" Description="Location of the referenced assembly.">
+        <StringProperty.DataSource>
+            <DataSource PersistedName="Identity" SourceOfDefaultValue="AfterContext" />
+        </StringProperty.DataSource>
+    </StringProperty>
+    
+    <StringProperty Name="OriginalPath" ReadOnly="True" Visible="False"/>
+    <StringProperty Name="CopyUpToDateMarker" ReadOnly="True" Visible="False"/>
+</Rule>
diff --git a/src/Targets/Microsoft.Managed.DesignTime.targets b/src/Targets/Microsoft.Managed.DesignTime.targets
index 874431234d7..6c825e74dde 100644
--- a/src/Targets/Microsoft.Managed.DesignTime.targets
+++ b/src/Targets/Microsoft.Managed.DesignTime.targets
@@ -135,6 +135,10 @@
       <Context>File</Context>
     </PropertyPageSchema>
 
+    <PropertyPageSchema Include="$(ManagedXamlResourcesDirectory)CopyUpToDateMarker.xaml">
+      <Context>File</Context>
+    </PropertyPageSchema>
+
     <PropertyPageSchema Include="$(ManagedXamlResourcesDirectory)SpecialFolder.xaml">
       <Context>File;ProjectSubscriptionService</Context>
     </PropertyPageSchema>
@@ -240,6 +244,10 @@
     <PropertyPageSchema Include="$(ManagedXamlResourcesDirectory)ResolvedAnalyzerReference.xaml">
       <Context>ProjectSubscriptionService;BrowseObject</Context>
     </PropertyPageSchema>
+
+    <PropertyPageSchema Include="$(ManagedXamlResourcesDirectory)ResolvedCompilationReference.xaml">
+      <Context>ProjectSubscriptionService</Context>
+    </PropertyPageSchema>
   </ItemGroup>
 
   <!-- Targets -->
@@ -266,5 +274,8 @@
 
   <!-- This target collects all Analyzers in the project. -->
   <Target Name="CollectAnalyzersDesignTime" DependsOnTargets="CompileDesignTime" Returns="@(Analyzer)" />
+  
+  <!-- This target collects all the resolved references that are used to actually compile. -->
+  <Target Name="CollectResolvedCompilationReferencesDesignTime" DependsOnTargets="CompileDesignTime" Returns="@(ReferencePathWithRefAssemblies)" />
 
 </Project>
\ No newline at end of file