diff --git a/src/Tasks.UnitTests/GetAssemblyIdentity_Tests.cs b/src/Tasks.UnitTests/GetAssemblyIdentity_Tests.cs
new file mode 100644
index 00000000000..c7c879c2006
--- /dev/null
+++ b/src/Tasks.UnitTests/GetAssemblyIdentity_Tests.cs
@@ -0,0 +1,194 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.IO;
+using System.Reflection;
+using Microsoft.Build.Framework;
+using Microsoft.Build.Tasks;
+using Microsoft.Build.Utilities;
+using Shouldly;
+using Xunit;
+
+#nullable disable
+
+namespace Microsoft.Build.UnitTests
+{
+    public sealed class GetAssemblyIdentity_Tests
+    {
+        private readonly ITestOutputHelper _output;
+
+        public GetAssemblyIdentity_Tests(ITestOutputHelper output)
+        {
+            _output = output;
+        }
+
+        private GetAssemblyIdentity CreateTaskUnderTest(MockEngine engine = null)
+        {
+            return new GetAssemblyIdentity
+            {
+                BuildEngine = engine ?? new MockEngine(_output),
+            };
+        }
+
+        [Fact]
+        public void AbsolutePathToExistingAssembly_ProducesCorrectIdentity()
+        {
+            // Use this test assembly as the input — it's guaranteed to exist.
+            // Use the compile-time assembly name as the baseline rather than
+            // AssemblyName.GetAssemblyName(path), to avoid asserting against the same
+            // reflection API the production code uses internally.
+            string assemblyPath = typeof(GetAssemblyIdentity_Tests).Assembly.Location;
+            AssemblyName expectedName = typeof(GetAssemblyIdentity_Tests).Assembly.GetName();
+
+            GetAssemblyIdentity task = CreateTaskUnderTest();
+            task.AssemblyFiles = [new TaskItem(assemblyPath)];
+
+            task.Execute().ShouldBeTrue();
+
+            task.Assemblies.Length.ShouldBe(1);
+            task.Assemblies[0].ItemSpec.ShouldBe(expectedName.FullName);
+            task.Assemblies[0].GetMetadata("Name").ShouldBe(expectedName.Name);
+            task.Assemblies[0].GetMetadata("Version").ShouldBe(expectedName.Version.ToString());
+        }
+
+        [Fact]
+        public void NonExistentFile_LogsErrorAndReturnsFalse()
+        {
+            var engine = new MockEngine(_output);
+            GetAssemblyIdentity task = CreateTaskUnderTest(engine);
+            task.AssemblyFiles = [new TaskItem("does-not-exist.dll")];
+
+            task.Execute().ShouldBeFalse();
+
+            AssertCouldNotGetAssemblyName(engine);
+            engine.Log.ShouldContain("does-not-exist.dll");
+        }
+
+        [Fact]
+        public void NonAssemblyFile_LogsErrorAndReturnsFalse()
+        {
+            using TestEnvironment env = TestEnvironment.Create(_output);
+            TransientTestFile textFile = env.CreateFile("notanassembly.txt", "This is not an assembly.");
+
+            var engine = new MockEngine(_output);
+            GetAssemblyIdentity task = CreateTaskUnderTest(engine);
+            task.AssemblyFiles = [new TaskItem(textFile.Path)];
+
+            task.Execute().ShouldBeFalse();
+
+            AssertCouldNotGetAssemblyName(engine);
+        }
+
+        [Fact]
+        public void MixedBatch_GoodAndBadItems()
+        {
+            using TestEnvironment env = TestEnvironment.Create(_output);
+            TransientTestFile textFile = env.CreateFile("bad.txt", "not an assembly");
+
+            string goodAssemblyPath = typeof(GetAssemblyIdentity_Tests).Assembly.Location;
+            AssemblyName expectedName = typeof(GetAssemblyIdentity_Tests).Assembly.GetName();
+
+            var engine = new MockEngine(_output);
+            GetAssemblyIdentity task = CreateTaskUnderTest(engine);
+            task.AssemblyFiles =
+            [
+                new TaskItem(goodAssemblyPath),
+                new TaskItem(textFile.Path),
+            ];
+
+            // Execute returns false because one item failed.
+            task.Execute().ShouldBeFalse();
+
+            // The good item should still appear in the output.
+            task.Assemblies.Length.ShouldBe(1);
+            task.Assemblies[0].ItemSpec.ShouldBe(expectedName.FullName);
+
+            // The bad item should have produced an error.
+            engine.Errors.ShouldBe(1);
+        }
+
+        [Fact]
+        public void EmptyItemSpec_LogsErrorAndReturnsFalse()
+        {
+            var engine = new MockEngine(_output);
+            GetAssemblyIdentity task = CreateTaskUnderTest(engine);
+            task.AssemblyFiles = [new TaskItem("")];
+
+            task.Execute().ShouldBeFalse();
+
+            AssertCouldNotGetAssemblyName(engine);
+        }
+
+        [Fact]
+        public void NullItemSpec_LogsErrorAndReturnsFalse()
+        {
+            var engine = new MockEngine(_output);
+            GetAssemblyIdentity task = CreateTaskUnderTest(engine);
+            Assert.Throws<ArgumentNullException>(() => task.AssemblyFiles = [new TaskItem((ITaskItem)null)]);
+        }
+
+        [Fact]
+        public void RelativePath_ResolvesAgainstProjectDirectory()
+        {
+            using TestEnvironment env = TestEnvironment.Create(_output);
+            TransientTestFolder projectDir = env.CreateFolder();
+
+            string sourceAssembly = typeof(GetAssemblyIdentity_Tests).Assembly.Location;
+            AssemblyName expectedName = typeof(GetAssemblyIdentity_Tests).Assembly.GetName();
+
+            string relativeFileName = "TestAssembly.dll";
+            File.Copy(sourceAssembly, Path.Combine(projectDir.Path, relativeFileName));
+
+            var engine = new MockEngine(_output);
+            GetAssemblyIdentity task = CreateTaskUnderTest(engine);
+            task.TaskEnvironment = TaskEnvironment.CreateWithProjectDirectoryAndEnvironment(projectDir.Path);
+            task.AssemblyFiles = [new TaskItem(relativeFileName)];
+
+            task.Execute().ShouldBeTrue();
+
+            task.Assemblies.Length.ShouldBe(1);
+            task.Assemblies[0].ItemSpec.ShouldBe(expectedName.FullName);
+        }
+
+        [Fact]
+        public void OutputItem_DoesNotContainAbsolutizedPaths()
+        {
+            string assemblyPath = typeof(GetAssemblyIdentity_Tests).Assembly.Location;
+            AssemblyName expectedName = typeof(GetAssemblyIdentity_Tests).Assembly.GetName();
+
+            GetAssemblyIdentity task = CreateTaskUnderTest();
+            task.AssemblyFiles = [new TaskItem(assemblyPath)];
+
+            task.Execute().ShouldBeTrue();
+
+            task.Assemblies.Length.ShouldBe(1);
+
+            // ItemSpec should be the assembly identity string, not a path.
+            task.Assemblies[0].ItemSpec.ShouldBe(expectedName.FullName);
+        }
+
+        [Fact]
+        public void OutputItem_CopiesInputMetadataVerbatim()
+        {
+            string assemblyPath = typeof(GetAssemblyIdentity_Tests).Assembly.Location;
+
+            var inputItem = new TaskItem(assemblyPath);
+            inputItem.SetMetadata("CustomMeta", "CustomValue");
+
+            GetAssemblyIdentity task = CreateTaskUnderTest();
+            task.AssemblyFiles = [inputItem];
+
+            task.Execute().ShouldBeTrue();
+
+            task.Assemblies.ShouldHaveSingleItem()
+                .GetMetadata("CustomMeta").ShouldBe("CustomValue");
+        }
+
+        private void AssertCouldNotGetAssemblyName(MockEngine engine)
+        {
+            engine.Errors.ShouldBe(1);
+            engine.Log.ShouldContain("MSB3441");
+        }
+    }
+}
diff --git a/src/Tasks/GetAssemblyIdentity.cs b/src/Tasks/GetAssemblyIdentity.cs
index 375e0d2d430..ab7fbed39fd 100644
--- a/src/Tasks/GetAssemblyIdentity.cs
+++ b/src/Tasks/GetAssemblyIdentity.cs
@@ -23,8 +23,12 @@ namespace Microsoft.Build.Tasks
     ///  Input:  Assembly Include="foo.exe"
     ///  Output: Identity Include="Foo, Version=1.0.0.0", Name="Foo, Version="1.0.0.0"
     /// </comment>
-    public class GetAssemblyIdentity : TaskExtension
+    [MSBuildMultiThreadableTask]
+    public class GetAssemblyIdentity : TaskExtension, IMultiThreadableTask
     {
+        /// <inheritdoc />
+        public TaskEnvironment TaskEnvironment { get; set; } = TaskEnvironment.Fallback;
+
         private ITaskItem[] _assemblyFiles;
 
         [Required]
@@ -65,10 +69,14 @@ public override bool Execute()
             var list = new List<ITaskItem>();
             foreach (ITaskItem item in AssemblyFiles)
             {
+                string assemblyPath = !string.IsNullOrEmpty(item.ItemSpec)
+                    ? TaskEnvironment.GetAbsolutePath(item.ItemSpec)
+                    : item.ItemSpec;
+
                 AssemblyName an;
                 try
                 {
-                    an = AssemblyName.GetAssemblyName(item.ItemSpec);
+                    an = AssemblyName.GetAssemblyName(assemblyPath);
                 }
                 catch (BadImageFormatException e)
                 {
@@ -100,6 +108,7 @@ public override bool Execute()
                 item.CopyMetadataTo(newItem);
                 list.Add(newItem);
             }
+
             Assemblies = list.ToArray();
             return !Log.HasLoggedErrors;
         }