fix: validate A2A version and extensions on all gRPC handler methods

transport/grpc/src/main/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandler.java

@@ -199,8 +199,6 @@ public void sendMessage(org.a2aproject.sdk.grpc.SendMessageRequest request,
                            StreamObserver<org.a2aproject.sdk.grpc.SendMessageResponse> responseObserver) {
         try {
             ServerCallContext context = createCallContext(responseObserver);
-            A2AVersionValidator.validateProtocolVersion(getAgentCardInternal(), context);
-            A2AExtensions.validateRequiredExtensions(getAgentCardInternal(), context);
             MessageSendParams params = FromProto.messageSendParams(request);
             EventKind taskOrMessage = getRequestHandler().onMessageSend(params, context);
             org.a2aproject.sdk.grpc.SendMessageResponse response = ToProto.taskOrMessage(taskOrMessage);
@@ -396,8 +394,6 @@ public void sendStreamingMessage(org.a2aproject.sdk.grpc.SendMessageRequest requ
         try {
             ServerCallContext context = createCallContext(responseObserver);
             installForkedContextWrapper(context);
-            A2AVersionValidator.validateProtocolVersion(getAgentCardInternal(), context);
-            A2AExtensions.validateRequiredExtensions(getAgentCardInternal(), context);
             MessageSendParams params = FromProto.messageSendParams(request);
             Flow.Publisher<StreamingEventKind> publisher = getRequestHandler().onMessageSendStream(params, context);
             convertToStreamResponse(publisher, responseObserver, context);
@@ -570,6 +566,7 @@ public void getExtendedAgentCard(org.a2aproject.sdk.grpc.GetExtendedAgentCardReq
                 handleError(responseObserver, new UnsupportedOperationError());
                 return;
             }
+            ServerCallContext context = createCallContext(responseObserver);
             AgentCard extendedAgentCard = getExtendedAgentCard();
             if (extendedAgentCard != null) {
                 responseObserver.onNext(ToProto.agentCard(extendedAgentCard));
@@ -645,6 +642,7 @@ public void deleteTaskPushNotificationConfig(org.a2aproject.sdk.grpc.DeleteTaskP
      */
     private <V> ServerCallContext createCallContext(StreamObserver<V> responseObserver) {
         CallContextFactory factory = getCallContextFactory();
+        ServerCallContext context;
         if (factory == null) {
             // Default implementation when no custom CallContextFactory is provided
             // This handles both CDI injection scenarios and test scenarios where callContextFactory is null
@@ -701,12 +699,16 @@ private <V> ServerCallContext createCallContext(StreamObserver<V> responseObserv
                 requestedExtensions = A2AExtensions.getRequestedExtensions(List.of(extensionsHeader));
             }
 
-            return new ServerCallContext(user, state, requestedExtensions, requestedVersion);
+            context = new ServerCallContext(user, state, requestedExtensions, requestedVersion);
         } else {
             // TODO: CallContextFactory interface expects ServerCall + Metadata, but we only have StreamObserver
             // This is another manifestation of the architectural limitation mentioned above
-            return factory.create(responseObserver); // Fall back to basic create() method for now
+            context = factory.create(responseObserver); // Fall back to basic create() method for now
         }
+
+        A2AVersionValidator.validateProtocolVersion(getAgentCardInternal(), context);
+        A2AExtensions.validateRequiredExtensions(getAgentCardInternal(), context);
+        return context;
     }
 
     /**

transport/grpc/src/test/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandlerTest.java

@@ -1073,6 +1073,52 @@ public <V> ServerCallContext create(StreamObserver<V> streamObserver) {
         assertGrpcError(streamRecorder, Status.Code.UNIMPLEMENTED);
     }
 
+    @Test
+    public void testVersionNotSupportedErrorOnGetTask() throws Exception {
+        // Regression test: getTask previously skipped A2A protocol version
+        // and extension validation, unlike sendMessage/sendStreamingMessage.
+        AgentCard agentCard = AgentCard.builder()
+                .name("test-card")
+                .description("Test card with version 1.0")
+                .supportedInterfaces(Collections.singletonList(new AgentInterface("GRPC", "http://localhost:9999")))
+                .version("1.0.0")
+                .capabilities(AgentCapabilities.builder()
+                        .streaming(true)
+                        .pushNotifications(false)
+                        .build())
+                .defaultInputModes(List.of("text"))
+                .defaultOutputModes(List.of("text"))
+                .skills(List.of())
+                .build();
+
+        // Create handler that provides incompatible version 2.0 in the context
+        GrpcHandler handler = new TestGrpcHandler(agentCard, requestHandler, internalExecutor) {
+            @Override
+            protected CallContextFactory getCallContextFactory() {
+                return new CallContextFactory() {
+                    @Override
+                    public <V> ServerCallContext create(StreamObserver<V> streamObserver) {
+                        return new ServerCallContext(
+                                UnauthenticatedUser.INSTANCE,
+                                Map.of("grpc_response_observer", streamObserver),
+                                new HashSet<>(),
+                                "2.0" // Incompatible version
+                        );
+                    }
+                };
+            }
+        };
+
+        GetTaskRequest request = GetTaskRequest.newBuilder()
+                .setId(AbstractA2ARequestHandlerTest.MINIMAL_TASK.id())
+                .build();
+        StreamRecorder<Task> streamRecorder = StreamRecorder.create();
+        handler.getTask(request, streamRecorder);
+        streamRecorder.awaitCompletion(5, TimeUnit.SECONDS);
+
+        assertGrpcError(streamRecorder, Status.Code.UNIMPLEMENTED);
+    }
+
     @Test
     public void testCompatibleVersionSuccess() throws Exception {
         // Create AgentCard with protocol version 1.0