diff --git a/src/Tools/PrepareTests/TestDiscovery.cs b/src/Tools/PrepareTests/TestDiscovery.cs
index 78fe54d00d64a..1205d91f318fd 100644
--- a/src/Tools/PrepareTests/TestDiscovery.cs
+++ b/src/Tools/PrepareTests/TestDiscovery.cs
@@ -10,6 +10,7 @@
 using System.IO.Pipes;
 using System.Threading.Tasks;
 using System.Threading;
+using System.Text;
 
 namespace PrepareTests;
 internal class TestDiscovery
@@ -85,14 +86,22 @@ static bool RunWorker(string dotnetPath, string pathToWorker, string pathToAssem
             pipeClient.StartInfo.FileName = pathToWorker;
         }
 
+        var errorOutput = new StringBuilder();
+
         using (var pipeServer = new AnonymousPipeServerStream(PipeDirection.Out, HandleInheritability.Inheritable))
         {
             // Pass the client process a handle to the server.
             arguments.Add(pipeServer.GetClientHandleAsString());
             pipeClient.StartInfo.Arguments = string.Join(" ", arguments);
             pipeClient.StartInfo.UseShellExecute = false;
+
+            // Errors will be logged to stderr, redirect to us so we can capture it.
+            pipeClient.StartInfo.RedirectStandardError = true;
+            pipeClient.ErrorDataReceived += PipeClient_ErrorDataReceived;
             pipeClient.Start();
 
+            pipeClient.BeginErrorReadLine();
+
             pipeServer.DisposeLocalCopyOfClientHandle();
 
             try
@@ -120,10 +129,15 @@ static bool RunWorker(string dotnetPath, string pathToWorker, string pathToAssem
 
         if (!success)
         {
-            Console.WriteLine($"Failed to discover tests in {pathToAssembly}");
+            Console.WriteLine($"Failed to discover tests in {pathToAssembly}:{Environment.NewLine}{errorOutput}");
         }
 
         return success;
+
+        void PipeClient_ErrorDataReceived(object sender, DataReceivedEventArgs e)
+        {
+            errorOutput.AppendLine(e.Data);
+        }
     }
 
     private static List<string> GetAssemblies(string binDirectory, bool isUnix)
diff --git a/src/Tools/TestDiscoveryWorker/Program.cs b/src/Tools/TestDiscoveryWorker/Program.cs
index 9c5c12375d84e..882ab62b3db1c 100644
--- a/src/Tools/TestDiscoveryWorker/Program.cs
+++ b/src/Tools/TestDiscoveryWorker/Program.cs
@@ -24,76 +24,85 @@
     return ExitFailure;
 }
 
-using var pipeClient = new AnonymousPipeClientStream(PipeDirection.In, args[0]);
-using var sr = new StreamReader(pipeClient);
-string? output;
-
-// Wait for 'sync message' from the server.
-do
+try
 {
-    output = await sr.ReadLineAsync().ConfigureAwait(false);
-}
-while (!(output?.StartsWith("ASSEMBLY", StringComparison.OrdinalIgnoreCase) == true));
+    using var pipeClient = new AnonymousPipeClientStream(PipeDirection.In, args[0]);
+    using var sr = new StreamReader(pipeClient);
+    string? output;
 
-if ((output = await sr.ReadLineAsync().ConfigureAwait(false)) is not null)
-{
-    var assemblyFileName = output;
+    // Wait for 'sync message' from the server.
+    do
+    {
+        output = await sr.ReadLineAsync().ConfigureAwait(false);
+    }
+    while (!(output?.StartsWith("ASSEMBLY", StringComparison.OrdinalIgnoreCase) == true));
 
-#if NET6_0_OR_GREATER   
-    var resolver = new System.Runtime.Loader.AssemblyDependencyResolver(assemblyFileName);
-    System.Runtime.Loader.AssemblyLoadContext.Default.Resolving += (context, assemblyName) =>
+    if ((output = await sr.ReadLineAsync().ConfigureAwait(false)) is not null)
     {
-        var assemblyPath = resolver.ResolveAssemblyToPath(assemblyName);
-        if (assemblyPath is not null)
+        var assemblyFileName = output;
+
+#if NET6_0_OR_GREATER
+        var resolver = new System.Runtime.Loader.AssemblyDependencyResolver(assemblyFileName);
+        System.Runtime.Loader.AssemblyLoadContext.Default.Resolving += (context, assemblyName) =>
         {
-            return context.LoadFromAssemblyPath(assemblyPath);
-        }
+            var assemblyPath = resolver.ResolveAssemblyToPath(assemblyName);
+            if (assemblyPath is not null)
+            {
+                return context.LoadFromAssemblyPath(assemblyPath);
+            }
 
-        return null;
-    };
+            return null;
+        };
 #endif
 
-    string testDescriptor = Path.GetFileName(assemblyFileName);
+        string testDescriptor = Path.GetFileName(assemblyFileName);
 #if NET
-    testDescriptor += " (.NET Core)";
+        testDescriptor += " (.NET Core)";
 #else
     testDescriptor += " (.NET Framework)";
 #endif
 
-    await Console.Out.WriteLineAsync($"Discovering tests in {testDescriptor}...").ConfigureAwait(false);
+        await Console.Out.WriteLineAsync($"Discovering tests in {testDescriptor}...").ConfigureAwait(false);
 
-    using var xunit = new XunitFrontController(AppDomainSupport.IfAvailable, assemblyFileName, shadowCopy: false);
-    var configuration = ConfigReader.Load(assemblyFileName);
-    var sink = new Sink();
-    xunit.Find(includeSourceInformation: false,
-               messageSink: sink,
-               discoveryOptions: TestFrameworkOptions.ForDiscovery(configuration));
+        using var xunit = new XunitFrontController(AppDomainSupport.IfAvailable, assemblyFileName, shadowCopy: false);
+        var configuration = ConfigReader.Load(assemblyFileName);
+        var sink = new Sink();
+        xunit.Find(includeSourceInformation: false,
+                   messageSink: sink,
+                   discoveryOptions: TestFrameworkOptions.ForDiscovery(configuration));
 
-    var testsToWrite = new HashSet<string>();
-    await foreach (var fullyQualifiedName in sink.GetTestCaseNamesAsync())
-    {
-        testsToWrite.Add(fullyQualifiedName);
-    }
+        var testsToWrite = new HashSet<string>();
+        await foreach (var fullyQualifiedName in sink.GetTestCaseNamesAsync())
+        {
+            testsToWrite.Add(fullyQualifiedName);
+        }
 
-    if (sink.AnyWriteFailures)
-    {
-        await Console.Error.WriteLineAsync($"Channel failed to write for '{assemblyFileName}'").ConfigureAwait(false);
-        return ExitFailure;
-    }
+        if (sink.AnyWriteFailures)
+        {
+            await Console.Error.WriteLineAsync($"Channel failed to write for '{assemblyFileName}'").ConfigureAwait(false);
+            return ExitFailure;
+        }
 
 #if NET6_0_OR_GREATER
-    await Console.Out.WriteLineAsync($"Discovered {testsToWrite.Count} tests in {testDescriptor}").ConfigureAwait(false);
+        await Console.Out.WriteLineAsync($"Discovered {testsToWrite.Count} tests in {testDescriptor}").ConfigureAwait(false);
 #else
-    await Console.Out.WriteLineAsync($"Discovered {testsToWrite.Count} tests in {testDescriptor}").ConfigureAwait(false);
+        await Console.Out.WriteLineAsync($"Discovered {testsToWrite.Count} tests in {testDescriptor}").ConfigureAwait(false);
 #endif
 
-    var directory = Path.GetDirectoryName(assemblyFileName);
-    using var fileStream = File.Create(Path.Combine(directory!, "testlist.json"));
-    await JsonSerializer.SerializeAsync(fileStream, testsToWrite).ConfigureAwait(false);
-    return ExitSuccess;
-}
+        var directory = Path.GetDirectoryName(assemblyFileName);
+        using var fileStream = File.Create(Path.Combine(directory!, "testlist.json"));
+        await JsonSerializer.SerializeAsync(fileStream, testsToWrite).ConfigureAwait(false);
+        return ExitSuccess;
+    }
 
-return ExitFailure;
+    return ExitFailure;
+}
+catch (Exception ex)
+{
+    // Write the exception details to stderr so the host process can pick it up.
+    await Console.Error.WriteLineAsync(ex.ToString()).ConfigureAwait(false);
+    return 1;
+}
 
 file class Sink : IMessageSink
 {
diff --git a/src/Workspaces/Core/MSBuild.BuildHost/Microsoft.CodeAnalysis.Workspaces.MSBuild.BuildHost.csproj b/src/Workspaces/Core/MSBuild.BuildHost/Microsoft.CodeAnalysis.Workspaces.MSBuild.BuildHost.csproj
index 1d4bf4f98739d..1ce8835d46e43 100644
--- a/src/Workspaces/Core/MSBuild.BuildHost/Microsoft.CodeAnalysis.Workspaces.MSBuild.BuildHost.csproj
+++ b/src/Workspaces/Core/MSBuild.BuildHost/Microsoft.CodeAnalysis.Workspaces.MSBuild.BuildHost.csproj
@@ -30,7 +30,9 @@
     <PackageReference Include="Microsoft.Build.Tasks.Core" VersionOverride="17.3.2" ExcludeAssets="Runtime" PrivateAssets="All" />
     <PackageReference Include="Microsoft.Build.Locator" PrivateAssets="All" />
     <PackageReference Include="System.CommandLine" />
+    <PackageReference Include="System.Collections.Immutable" />
     <PackageReference Include="Newtonsoft.Json" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Condition="'$(TargetFrameworkIdentifier)' != '.NETCoreApp'" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="..\..\..\Compilers\Core\Portable\InternalUtilities\*.cs" Link="InternalUtilities\%(FileName).cs" />