diff --git a/src/Adapter/MSTestAdapter.PlatformServices/Discovery/AssemblyEnumerator.cs b/src/Adapter/MSTestAdapter.PlatformServices/Discovery/AssemblyEnumerator.cs
index 89bf1c82ed..efdb766f24 100644
--- a/src/Adapter/MSTestAdapter.PlatformServices/Discovery/AssemblyEnumerator.cs
+++ b/src/Adapter/MSTestAdapter.PlatformServices/Discovery/AssemblyEnumerator.cs
@@ -289,12 +289,14 @@ private static bool TryUnfoldITestDataSource(ITestDataSource dataSource, UnitTes
 
         var discoveredTests = new List<UnitTestElement>();
         bool dataSourceHasData = false;
+        // PERF: Hoist outside the loop — MethodInfo.GetParameters() returns a fresh array copy on each
+        // call (CLR safety guarantee), so calling it per row allocates N identical arrays for N data rows.
+        ParameterInfo[] parameters = methodInfo.GetParameters();
 
         foreach (object?[] dataOrTestDataRow in dataEnumerable)
         {
             dataSourceHasData = true;
             object?[] d = dataOrTestDataRow;
-            ParameterInfo[] parameters = methodInfo.GetParameters();
 
             // The effective ignore message for this row is the row-level ignore message (from
             // TestDataRow<T>), falling back to the whole-source ignore message. It must be
diff --git a/src/Adapter/MSTestAdapter.PlatformServices/Execution/TestMethodInfo.cs b/src/Adapter/MSTestAdapter.PlatformServices/Execution/TestMethodInfo.cs
index 165a49355d..df0879e8cb 100644
--- a/src/Adapter/MSTestAdapter.PlatformServices/Execution/TestMethodInfo.cs
+++ b/src/Adapter/MSTestAdapter.PlatformServices/Execution/TestMethodInfo.cs
@@ -60,7 +60,17 @@ internal ITestContext TestContext
     /// <summary>
     /// Gets the parameter types of the test method.
     /// </summary>
-    public ParameterInfo[] ParameterTypes => MethodInfo.GetParameters();
+    /// <remarks>
+    /// Lazy-cached: <c>MethodInfo.GetParameters()</c> returns a fresh array copy on every call
+    /// (CLR safety guarantee), so caching avoids N redundant copies for data-driven tests with N rows.
+    /// This cached array is shared across internal call sites and MUST NOT be mutated. The explicit
+    /// <see cref="ITestMethod.ParameterTypes"/> implementation hands external consumers a fresh copy to
+    /// preserve the previous "fresh array per call" behavior and protect the cache from mutation.
+    /// </remarks>
+    public ParameterInfo[] ParameterTypes => field ??= MethodInfo.GetParameters();
+
+    /// <inheritdoc />
+    ParameterInfo[] ITestMethod.ParameterTypes => (ParameterInfo[])ParameterTypes.Clone();
 
     /// <summary>
     /// Gets the return type of the test method.