diff --git a/build.proj b/build.proj
index 2edac3d8e1..56f2c5599d 100644
--- a/build.proj
+++ b/build.proj
@@ -17,6 +17,7 @@
     <MakeDir Directories="$(SourceBuiltPackagesPath)" />
     <MakeDir Directories="$(SourceBuiltAssetsDir)" />
     <MakeDir Directories="$(LocalBlobStorageRoot)" />
+    <MakeDir Directories="$(MSBuildDebugPathTargetDir)" />
   </Target>
 
   <Target Name="InitBuild">
diff --git a/dir.props b/dir.props
index 9f6f8e636e..d6d09c3b9e 100644
--- a/dir.props
+++ b/dir.props
@@ -62,12 +62,14 @@
     <RestoreSourcePropsPath>$(IntermediatePath)RestoreSources.props</RestoreSourcePropsPath>
     <PackageVersionPropsPath>$(IntermediatePath)PackageVersions.props</PackageVersionPropsPath>
     <LoggingDir>$(BaseOutputPath)logs/</LoggingDir>
+    <MSBuildDebugPathTargetDir>$(BaseOutputPath)msbuild-debug/</MSBuildDebugPathTargetDir>
     <!-- Dir where git info is generated during online builds. -->
     <GitInfoOutputDir>$(BaseOutputPath)git-info/</GitInfoOutputDir>
     <!-- Dir where git info is placed inside the tarball. -->
     <GitInfoOfflineDir>$(ProjectDir)git-info/</GitInfoOfflineDir>
     <PackageReportDir>$(BaseOutputPath)prebuilt-report/</PackageReportDir>
     <PackageReportDataFile>$(PackageReportDir)prebuilt-usage.xml</PackageReportDataFile>
+    <ProjectAssetsJsonArchiveFile>$(PackageReportDir)all-project-assets-json-files.zip</ProjectAssetsJsonArchiveFile>
     <ProdConManifestFile>$(PackageReportDir)prodcon-build.xml</ProdConManifestFile>
     <PoisonedReportFile>$(PackageReportDir)poisoned.txt</PoisonedReportFile>
     <ConflictingPackageReportDir>$(BaseOutputPath)conflict-report/</ConflictingPackageReportDir>
diff --git a/netci.groovy b/netci.groovy
index e7af288a82..3e6736debb 100644
--- a/netci.groovy
+++ b/netci.groovy
@@ -13,7 +13,9 @@ def addArchival(def job) {
   // Grab these logs from all of those locations.
   [ "", "source-build/", "tarball-output/"].each { logRoot ->
     archivalSettings.addFiles("${logRoot}bin/logs/*")
-    archivalSettings.addFiles("${logRoot}bin/prebuilt-report/*")
+    archivalSettings.addFiles("${logRoot}bin/prebuilt-report/**/*")
+    archivalSettings.addFiles("${logRoot}bin/conflict-report/**/*")
+    archivalSettings.addFiles("${logRoot}bin/msbuild-debug/**/*")
     archivalSettings.addFiles("${logRoot}src/**/*.binlog")
     archivalSettings.addFiles("${logRoot}src/**/*.log")
     archivalSettings.addFiles("${logRoot}init-tools.log")
@@ -58,11 +60,11 @@ def addBuildStepsAndSetMachineAffinity(def job, String os, String configuration)
     steps {
       if (os == "Windows_NT") {
         batchFile("git submodule update --init --recursive");
-        batchFile(".\\build.cmd /p:Configuration=${configuration} ${loggingOptions}")
+        batchFile(".\\build.cmd /p:Configuration=${configuration} /p:FailOnPrebuiltBaselineError=true ${loggingOptions}")
       }
       else {
         shell("git submodule update --init --recursive");
-        shell("./build.sh /p:Configuration=${configuration} ${loggingOptions}");
+        shell("./build.sh /p:Configuration=${configuration} /p:FailOnPrebuiltBaselineError=true ${loggingOptions}");
         smokeTestExcludes = "";
         if (os == "Fedora24" || os == "OSX10.12") {
           // Dev certs doesn't seem to work in these platforms. https://github.com/dotnet/source-build/issues/560
@@ -132,7 +134,7 @@ def addPushJob(String project, String branch, String os, String configuration)
             shell("cd ./source-build;./build.sh /p:ArchiveDownloadedPackages=true /p:Configuration=${configuration} ${loggingOptions}");
             shell("cd ./source-build;./build-source-tarball.sh ../tarball-output --skip-build");
 
-            shell("cd ./tarball-output;./build.sh /p:Configuration=${configuration} ${loggingOptions}")
+            shell("cd ./tarball-output;./build.sh /p:Configuration=${configuration} /p:FailOnPrebuiltBaselineError=true ${loggingOptions}")
             shell("cd ./tarball-output;./smoke-test.sh --minimal --configuration ${configuration}")
         }
       }
@@ -178,13 +180,13 @@ def addPushJob(String project, String branch, String os, String configuration)
         steps{
             shell("cd ./source-build;git submodule update --init --recursive");
             // First build the product itself
-            shell("docker run -u=\"\$(id -u):\$(id -g)\" -t --sig-proxy=true -e HOME=/opt/code/home -v \$(pwd)/source-build:/opt/code --rm -w /opt/code ${imageName} /opt/code/build.sh /p:ArchiveDownloadedPackages=true /p:Configuration=${configuration} /p:ContinueOnPrebuiltBaselineError=true ${loggingOptions}");
+            shell("docker run -u=\"\$(id -u):\$(id -g)\" -t --sig-proxy=true -e HOME=/opt/code/home -v \$(pwd)/source-build:/opt/code --rm -w /opt/code ${imageName} /opt/code/build.sh /p:ArchiveDownloadedPackages=true /p:Configuration=${configuration} ${loggingOptions}");
             // Have to make this directory before volume-sharing it unlike non-docker build - existing directory is really only a warning in build-source-tarball.sh
             shell("mkdir tarball-output");
             // now build the tarball
             shell("docker run -u=\"\$(id -u):\$(id -g)\" -t --sig-proxy=true -e HOME=/opt/code/home --network none -v \$(pwd)/source-build:/opt/code -v \$(pwd)/tarball-output:/opt/tarball --rm -w /opt/code ${imageName} /opt/code/build-source-tarball.sh /opt/tarball --skip-build");
             // now build from the tarball offline and without access to the regular non-tarball build
-            shell("docker run -u=\"\$(id -u):\$(id -g)\" -t --sig-proxy=true -e HOME=/opt/tarball/home --network none -v \$(pwd)/tarball-output:/opt/tarball --rm -w /opt/tarball ${imageName} /opt/tarball/build.sh /p:Configuration=${configuration} ${loggingOptions}");
+            shell("docker run -u=\"\$(id -u):\$(id -g)\" -t --sig-proxy=true -e HOME=/opt/tarball/home --network none -v \$(pwd)/tarball-output:/opt/tarball --rm -w /opt/tarball ${imageName} /opt/tarball/build.sh /p:Configuration=${configuration} /p:FailOnPrebuiltBaselineError=true ${loggingOptions}");
             // finally, run a smoke-test on the result
             shell("docker run -u=\"\$(id -u):\$(id -g)\" -t --sig-proxy=true -e HOME=/opt/tarball/home -v \$(pwd)/tarball-output:/opt/tarball --rm -w /opt/tarball ${imageName} /opt/tarball/smoke-test.sh --minimal --configuration ${configuration}");
         }
diff --git a/repos/dir.props b/repos/dir.props
index bea8d507cd..e5b99b25d1 100644
--- a/repos/dir.props
+++ b/repos/dir.props
@@ -56,6 +56,9 @@
     <EnvironmentVariables Include="PB_IsStable=$(UseStableVersions)" Condition="'$(UseStableVersions)' != ''" />
     <EnvironmentVariables Include="PackageVersionStamp=$(VersionStamp)" Condition="'$(VersionStamp)' != ''" />
 
+    <!-- If MSBuild exits early, make sure debug output like 'MSBuild_*.failure.txt' ends up in a place we can see it. -->
+    <EnvironmentVariables Include="MSBUILDDEBUGPATH=$(MSBuildDebugPathTargetDir)" />
+
     <!-- Turn off node reuse for source build because repos use conflicting versions 
          of compilers which cause assembly load errors.  
          See https://github.com/dotnet/source-build/issues/541 -->
diff --git a/repos/dir.targets b/repos/dir.targets
index 04cd9f7237..d3386477d8 100644
--- a/repos/dir.targets
+++ b/repos/dir.targets
@@ -192,11 +192,13 @@
     <PropertyGroup>
       <_ReportDir>$(ConflictingPackageReportDir)before-$(RepositoryName)/</_ReportDir>
       <_ReportDataFile>$(_ReportDir)usage.xml</_ReportDataFile>
+      <_ProjectAssetsJsonArchiveFile>$(_ReportDir)all-project-assets-json-files.zip</_ProjectAssetsJsonArchiveFile>
     </PropertyGroup>
 
     <WritePackageUsageData NuGetPackageInfos="@(ConflictingPackageInfos)"
                            RootDir="$(ProjectDir)"
-                           DataFile="$(_ReportDataFile)" />
+                           DataFile="$(_ReportDataFile)"
+                           ProjectAssetsJsonArchiveFile="$(_ProjectAssetsJsonArchiveFile)" />
 
     <WriteUsageReports DataFile="$(_ReportDataFile)"
                        OutputDirectory="$(_ReportDir)" />
@@ -385,7 +387,8 @@
       TargetRid="$(TargetRid)"
       ProjectDirectories="@(ProjectDirectories)"
       RootDir="$(ProjectDir)"
-      DataFile="$(PackageReportDataFile)" />
+      DataFile="$(PackageReportDataFile)"
+      ProjectAssetsJsonArchiveFile="$(ProjectAssetsJsonArchiveFile)" />
   </Target>
 
   <Target Name="GetAllProjectDirectories">
@@ -407,7 +410,12 @@
       <BaselineDataFile Condition="'$(OfflineBuild)' == 'true'">$(BaselineDataFile)offline.xml</BaselineDataFile>
       <BaselineDataFile Condition="'$(OfflineBuild)' != 'true'">$(BaselineDataFile)online.xml</BaselineDataFile>
 
-      <ContinueOnPrebuiltBaselineError Condition="'$(ContinueOnPrebuiltBaselineError)' == ''">false</ContinueOnPrebuiltBaselineError>
+      <FailOnPrebuiltBaselineError Condition="'$(FailOnPrebuiltBaselineError)' == ''">false</FailOnPrebuiltBaselineError>
+    </PropertyGroup>
+
+    <PropertyGroup Condition="'$(ContinueOnPrebuiltBaselineError)' == ''">
+      <ContinueOnPrebuiltBaselineError>false</ContinueOnPrebuiltBaselineError>
+      <ContinueOnPrebuiltBaselineError Condition="'$(FailOnPrebuiltBaselineError)' != 'true'">true</ContinueOnPrebuiltBaselineError>
     </PropertyGroup>
 
     <ValidateUsageAgainstBaseline
diff --git a/tools-local/tasks/Microsoft.DotNet.SourceBuild.Tasks/UsageReport/WritePackageUsageData.cs b/tools-local/tasks/Microsoft.DotNet.SourceBuild.Tasks/UsageReport/WritePackageUsageData.cs
index 60bc3a0001..72f82cf35b 100644
--- a/tools-local/tasks/Microsoft.DotNet.SourceBuild.Tasks/UsageReport/WritePackageUsageData.cs
+++ b/tools-local/tasks/Microsoft.DotNet.SourceBuild.Tasks/UsageReport/WritePackageUsageData.cs
@@ -11,6 +11,7 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.IO;
+using System.IO.Compression;
 using System.Linq;
 using System.Threading.Tasks;
 using Task = Microsoft.Build.Utilities.Task;
@@ -68,6 +69,12 @@ public class WritePackageUsageData : Task
         [Required]
         public string DataFile { get; set; }
 
+        /// <summary>
+        /// If passed, the path of the archive file to generate that includes a copy of all
+        /// project.asset.json files found.
+        /// </summary>
+        public string ProjectAssetsJsonArchiveFile { get; set; }
+
         public override bool Execute()
         {
             DateTime startTime = DateTime.Now;
@@ -124,6 +131,35 @@ public override bool Execute()
                 "project.assets.json",
                 SearchOption.AllDirectories);
 
+            if (!string.IsNullOrEmpty(ProjectAssetsJsonArchiveFile))
+            {
+                Log.LogMessage(MessageImportance.Low, "Archiving project.assets.json files...");
+
+                Directory.CreateDirectory(Path.GetDirectoryName(ProjectAssetsJsonArchiveFile));
+
+                using (var projectAssetArchive = new ZipArchive(
+                    File.Open(
+                        ProjectAssetsJsonArchiveFile,
+                        FileMode.Create,
+                        FileAccess.ReadWrite),
+                    ZipArchiveMode.Create))
+                {
+                    // Only one entry can be open at a time, so don't do this during the Parallel
+                    // ForEach later.
+                    foreach (var file in assetFiles)
+                    {
+                        string relativePath = file.Substring(RootDir.Length);
+                        using (var stream = File.OpenRead(file))
+                        using (Stream entryWriter = projectAssetArchive
+                            .CreateEntry(relativePath, CompressionLevel.Optimal)
+                            .Open())
+                        {
+                            stream.CopyTo(entryWriter);
+                        }
+                    }
+                }
+            }
+
             Log.LogMessage(MessageImportance.Low, "Reading usage info...");
 
             var usages = new ConcurrentBag<Usage>();