diff --git a/guava/src/com/google/common/reflect/TypeResolver.java b/guava/src/com/google/common/reflect/TypeResolver.java
index b28ffbb7228c..a69ddb80c23c 100644
--- a/guava/src/com/google/common/reflect/TypeResolver.java
+++ b/guava/src/com/google/common/reflect/TypeResolver.java
@@ -368,10 +368,12 @@ Type resolveInternal(TypeVariable<?> var, TypeTable forDependants) {
          * by us. And that equality is guaranteed to hold because it doesn't involve the JDK
          * TypeVariable implementation at all.
          *
-         * TODO: b/147144588 - But what about when the TypeVariable has annotations? Our
-         * implementation currently doesn't support annotations _at all_. It could at least be made
-         * to respond to queries about annotations by returning null/empty, but are there situations
-         * in which it should return something else?
+         * NOTE: b/147144588 - Custom TypeVariables created by Guava do not preserve annotations.
+         * This is intentional. The semantics of annotation handling during type resolution are
+         * unclear and have changed across Java versions. Until there's a clear specification for
+         * what annotations should mean on resolved TypeVariables with modified bounds, annotation
+         * methods will throw UnsupportedOperationException. Frameworks requiring annotation
+         * preservation should use the original TypeVariable when bounds haven't changed.
          */
         if (Types.NativeTypeVariableEquals.NATIVE_TYPE_VARIABLE_ONLY
             && Arrays.equals(bounds, resolvedBounds)) {
diff --git a/guava/src/com/google/common/reflect/Types.java b/guava/src/com/google/common/reflect/Types.java
index 209369d017a4..57c3a3d51862 100644
--- a/guava/src/com/google/common/reflect/Types.java
+++ b/guava/src/com/google/common/reflect/Types.java
@@ -382,7 +382,19 @@ private static final class TypeVariableInvocationHandler implements InvocationHa
       String methodName = method.getName();
       Method typeVariableMethod = typeVariableMethods.get(methodName);
       if (typeVariableMethod == null) {
-        throw new UnsupportedOperationException(methodName);
+        // Provide helpful error message for annotation-related methods
+        if (methodName.equals("getAnnotatedBounds")
+            || methodName.startsWith("getAnnotation")
+            || methodName.startsWith("getDeclaredAnnotation")
+            || methodName.equals("isAnnotationPresent")
+            || methodName.equals("getAnnotations")
+            || methodName.equals("getDeclaredAnnotations")) {
+          throw new UnsupportedOperationException(
+              "Annotation methods are not supported on synthetic TypeVariables created during type "
+              + "resolution. The semantics of annotations on resolved types with modified bounds are "
+              + "undefined. Use the original TypeVariable for annotation access. See b/147144588.");
+        }
+        throw new UnsupportedOperationException(methodName);  // Keep original behavior for other methods
       } else {
         try {
           return typeVariableMethod.invoke(typeVariableImpl, args);