diff --git a/src/Tasks.UnitTests/SGen_Tests.cs b/src/Tasks.UnitTests/SGen_Tests.cs
index 2755cc179aa..6c0cf499b1d 100644
--- a/src/Tasks.UnitTests/SGen_Tests.cs
+++ b/src/Tasks.UnitTests/SGen_Tests.cs
@@ -2,11 +2,15 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
+using Microsoft.Build.Framework;
 using Microsoft.Build.Tasks;
+using Microsoft.Build.Utilities;
 using Shouldly;
 using Xunit;
+using Xunit.Abstractions;
 
 #nullable disable
 
@@ -14,13 +18,19 @@ namespace Microsoft.Build.UnitTests
 {
     public class SGen_Tests
     {
+        private readonly ITestOutputHelper _output;
+
+        public SGen_Tests(ITestOutputHelper output)
+        {
+            _output = output;
+        }
+
 #if RUNTIME_TYPE_NETCORE
         [Fact]
         public void TaskFailsOnCore()
         {
-            using (TestEnvironment testenv = TestEnvironment.Create())
-            {
-                MockLogger logger = ObjectModelHelpers.BuildProjectExpectFailure(@$"
+            using TestEnvironment testenv = TestEnvironment.Create(_output);
+            MockLogger logger = ObjectModelHelpers.BuildProjectExpectFailure(@$"
 <Project>
     <Target Name=""MyTarget"">
         <SGen
@@ -40,9 +50,8 @@ public void TaskFailsOnCore()
         />
     </Target>
 </Project>");
-                logger.ErrorCount.ShouldBe(1);
-                logger.Errors.First().Code.ShouldBe("MSB3474");
-            }
+            logger.ErrorCount.ShouldBe(1);
+            logger.Errors.First().Code.ShouldBe("MSB3474");
         }
 #else
         internal sealed class SGenExtension : SGen
@@ -273,6 +282,94 @@ public void TestReferencesCommandLine()
 
             Assert.Equal(targetCommandLine, commandLine);
         }
+
+        /// <summary>
+        /// Verifies that GenerateFullPathToTool resolves SdkToolsPath relative to the
+        /// TaskEnvironment's project directory and returns an absolute path, validating
+        /// the TaskEnvironment.GetAbsolutePath() integration.
+        /// </summary>
+        [Fact]
+        public void GenerateFullPathToTool_ResolvesRelativeSdkToolsPathViaTaskEnvironment()
+        {
+            using TestEnvironment env = TestEnvironment.Create(_output);
+            string projectDir = env.CreateFolder().Path;
+            string sdkSubDir = "sdk";
+            string sdkFullDir = Path.Combine(projectDir, sdkSubDir);
+            Directory.CreateDirectory(sdkFullDir);
+            string fakeTool = Path.Combine(sdkFullDir, "sgen.exe");
+            File.WriteAllBytes(fakeTool, []);
+
+            using var driver = new MultiThreadedTaskEnvironmentDriver(projectDir);
+            var taskEnv = new TaskEnvironment(driver);
+
+            TestableSGen t = new TestableSGen();
+            t.TaskEnvironment = taskEnv;
+            t.BuildEngine = new MockEngine(_output);
+            t.SdkToolsPath = sdkSubDir; // relative path — must resolve via TaskEnvironment
+
+            string result = t.CallGenerateFullPathToTool();
+
+            result.ShouldNotBeNull("GenerateFullPathToTool should find the tool via SdkToolsPath");
+            result.ShouldBe(fakeTool);
+        }
+
+        /// <summary>
+        /// Verifies that in GetProcessStartInfo
+        /// working directory comes from the TaskEnvironment.
+        /// </summary>
+        [Fact]
+        public void GetProcessStartInfo_UsesTaskEnvironmentWorkingDirectory()
+        {
+            using TestEnvironment env = TestEnvironment.Create(_output);
+            string expectedWorkingDir = env.DefaultTestDirectory.Path;
+            using var driver = new MultiThreadedTaskEnvironmentDriver(expectedWorkingDir);
+            var taskEnv = new TaskEnvironment(driver);
+
+            TestableSGen t = new TestableSGen();
+            t.TaskEnvironment = taskEnv;
+            t.BuildEngine = new MockEngine(_output);
+
+            ProcessStartInfo startInfo = t.CallGetProcessStartInfo(Path.Combine(expectedWorkingDir, "sgen.exe"), "/nologo", null);
+
+            startInfo.WorkingDirectory.ShouldBe(expectedWorkingDir);
+        }
+
+        /// <summary>
+        /// Verifies that BuildAssemblyPath uses TaskEnvironment.GetAbsolutePath
+        /// instead of Path.GetFullPath, by providing a relative path that resolves
+        /// correctly against the TaskEnvironment's project directory.
+        /// </summary>
+        [Fact]
+        public void BuildAssemblyPath_UsesTaskEnvironmentGetAbsolutePath()
+        {
+            using TestEnvironment env = TestEnvironment.Create(_output);
+            string projectDir = env.CreateFolder().Path;
+            string subDir = "output";
+            Directory.CreateDirectory(Path.Combine(projectDir, subDir));
+
+            using var driver = new MultiThreadedTaskEnvironmentDriver(projectDir);
+            var taskEnv = new TaskEnvironment(driver);
+
+            TestableSGen t = new TestableSGen();
+            t.TaskEnvironment = taskEnv;
+            t.BuildEngine = new MockEngine(_output);
+            t.BuildAssemblyPath = subDir; // relative path
+
+            string result = t.BuildAssemblyPath;
+
+            result.ShouldBe(Path.Combine(projectDir, subDir));
+        }
+
+        /// <summary>
+        /// Subclass that exposes protected methods for testing without reflection.
+        /// </summary>
+        private sealed class TestableSGen : SGen
+        {
+            public string CallGenerateFullPathToTool() => GenerateFullPathToTool();
+
+            public ProcessStartInfo CallGetProcessStartInfo(string pathToTool, string commandLineCommands, string responseFileSwitch)
+                => GetProcessStartInfo(pathToTool, commandLineCommands, responseFileSwitch);
+        }
 #endif
     }
 }
diff --git a/src/Tasks/SGen.cs b/src/Tasks/SGen.cs
index 7be17cf5dc2..427d034d1ab 100644
--- a/src/Tasks/SGen.cs
+++ b/src/Tasks/SGen.cs
@@ -68,6 +68,7 @@ internal interface ISGenTaskContract
     }
 
 #if RUNTIME_TYPE_NETCORE
+    [MSBuildMultiThreadableTask]
     public class SGen : ToolTaskExtension, ISGenTaskContract
     {
 #pragma warning disable format // region formatting is different in net7.0 and net472, and cannot be fixed for both
@@ -138,6 +139,7 @@ public override bool Execute()
     /// <summary>
     /// Genererates a serialization assembly containing XML serializers for the input assembly.
     /// </summary>
+    [MSBuildMultiThreadableTask]
     public class SGen : ToolTaskExtension, ISGenTaskContract
     {
         private string _buildAssemblyPath;
@@ -170,7 +172,7 @@ public string BuildAssemblyPath
                 string thisPath;
                 try
                 {
-                    thisPath = Path.GetFullPath(_buildAssemblyPath);
+                    thisPath = TaskEnvironment.GetAbsolutePath(_buildAssemblyPath).GetCanonicalForm().Value;
                 }
                 catch (Exception e) when (ExceptionHandling.IsIoRelatedException(e))
                 {
@@ -255,16 +257,9 @@ public string SerializationAssemblyName
             }
         }
 
-        private string SerializationAssemblyPath
-        {
-            get
-            {
-                Debug.Assert(BuildAssemblyPath.Length > 0, "Build assembly path is blank");
-                return Path.Combine(BuildAssemblyPath, SerializationAssemblyName);
-            }
-        }
+        private AbsolutePath SerializationAssemblyPath => new AbsolutePath(Path.Combine(BuildAssemblyPath, SerializationAssemblyName));
 
-        private string AssemblyFullPath => Path.Combine(BuildAssemblyPath, BuildAssemblyName);
+        private AbsolutePath AssemblyFullPath => new AbsolutePath(Path.Combine(BuildAssemblyPath, BuildAssemblyName));
 
         public string SdkToolsPath
         {
@@ -307,17 +302,21 @@ protected override string GenerateFullPathToTool()
 
             // If COMPLUS_InstallRoot\COMPLUS_Version are set (the dogfood world), we want to find it there, instead of
             // the SDK, which may or may not be installed. The following will look there.
-            if (!String.IsNullOrEmpty(Environment.GetEnvironmentVariable("COMPLUS_InstallRoot")) || !String.IsNullOrEmpty(Environment.GetEnvironmentVariable("COMPLUS_Version")))
+            if (!String.IsNullOrEmpty(TaskEnvironment.GetEnvironmentVariable("COMPLUS_InstallRoot")) || !String.IsNullOrEmpty(TaskEnvironment.GetEnvironmentVariable("COMPLUS_Version")))
             {
                 pathToTool = ToolLocationHelper.GetPathToDotNetFrameworkFile(ToolExe, TargetDotNetFrameworkVersion.Latest);
             }
 
-            if (String.IsNullOrEmpty(pathToTool) || !FileSystems.Default.FileExists(pathToTool))
+            if (String.IsNullOrEmpty(pathToTool) || !FileSystems.Default.FileExists(TaskEnvironment.GetAbsolutePath(pathToTool)))
             {
-                pathToTool = SdkToolsPathUtility.GeneratePathToTool(SdkToolsPathUtility.FileInfoExists, ProcessorArchitecture.CurrentProcessArchitecture, SdkToolsPath, ToolExe, Log, true);
+                pathToTool = SdkToolsPathUtility.GeneratePathToTool(
+                    f => !string.IsNullOrEmpty(f)
+                    ? SdkToolsPathUtility.FileInfoExists(TaskEnvironment.GetAbsolutePath(f))
+                    : SdkToolsPathUtility.FileInfoExists(f),
+                    ProcessorArchitecture.CurrentProcessArchitecture, SdkToolsPath, ToolExe, Log, true);
             }
 
-            return pathToTool;
+            return string.IsNullOrEmpty(pathToTool) ? pathToTool : TaskEnvironment.GetAbsolutePath(pathToTool).Value;
         }
 
         /// <summary>
@@ -330,7 +329,7 @@ protected override bool ValidateParameters()
             {
                 foreach (string reference in References)
                 {
-                    if (!FileSystems.Default.FileExists(reference))
+                    if (string.IsNullOrEmpty(reference) || !FileSystems.Default.FileExists(TaskEnvironment.GetAbsolutePath(reference)))
                     {
                         Log.LogErrorWithCodeFromResources("SGen.ResourceNotFound", reference);
                         return false;
@@ -365,11 +364,11 @@ protected override string GenerateCommandLineCommands()
                 {
                     Debug.Assert(ShouldGenerateSerializer, "GenerateCommandLineCommands() should not be called if ShouldGenerateSerializer is true and SerializationAssembly is null.");
 
-                    SerializationAssembly = [new TaskItem(SerializationAssemblyPath)];
+                    SerializationAssembly = [new TaskItem(SerializationAssemblyPath.OriginalValue)];
                 }
 
                 // Add the assembly switch
-                commandLineBuilder.AppendSwitchIfNotNull("/assembly:", AssemblyFullPath);
+                commandLineBuilder.AppendSwitchIfNotNull("/assembly:", AssemblyFullPath.Value);
 
                 commandLineBuilder.AppendWhenTrue("/proxytypes", Bag, "UseProxyTypes");
 
@@ -441,11 +440,11 @@ protected override string GenerateCommandLineCommands()
                 // leave the earlier produced assembly around to be propagated by later processes.
                 catch (UnauthorizedAccessException e)
                 {
-                    Log.LogErrorWithCodeFromResources("SGen.CouldNotDeleteSerializer", SerializationAssemblyPath, e.Message);
+                    Log.LogErrorWithCodeFromResources("SGen.CouldNotDeleteSerializer", SerializationAssemblyPath.OriginalValue, e.Message);
                 }
                 catch (IOException e)
                 {
-                    Log.LogErrorWithCodeFromResources("SGen.CouldNotDeleteSerializer", SerializationAssemblyPath, e.Message);
+                    Log.LogErrorWithCodeFromResources("SGen.CouldNotDeleteSerializer", SerializationAssemblyPath.OriginalValue, e.Message);
                 }
                 // The DirectoryNotFoundException is safely ignorable since that means that there is no
                 // existing serialization assembly.  This would be extremely unlikely anyway because we