From 643f1f803e992892b1bac89c8ccfb9481e563141 Mon Sep 17 00:00:00 2001
From: meraklbz <lbz2770828522@gmail.com>
Date: Mon, 10 Aug 2026 20:08:51 +0800
Subject: [PATCH 1/2] fix: return UnsupportedOperationError (-32004) when
 streaming is not supported

---
 .../a2aproject/sdk/transport/grpc/handler/GrpcHandler.java  | 6 +++---
 .../sdk/transport/grpc/handler/GrpcHandlerTest.java         | 4 ++--
 .../sdk/transport/jsonrpc/handler/JSONRPCHandler.java       | 5 ++---
 .../sdk/transport/jsonrpc/handler/JSONRPCHandlerTest.java   | 5 ++---
 .../a2aproject/sdk/transport/rest/handler/RestHandler.java  | 4 ++--
 .../sdk/transport/rest/handler/RestHandlerTest.java         | 2 +-
 6 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/transport/grpc/src/main/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandler.java b/transport/grpc/src/main/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandler.java
index 70185f32d..127f41662 100644
--- a/transport/grpc/src/main/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandler.java
+++ b/transport/grpc/src/main/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandler.java
@@ -375,7 +375,7 @@ public void listTaskPushNotificationConfigs(org.a2aproject.sdk.grpc.ListTaskPush
      *
      * <p><b>Error Handling:</b>
      * <ul>
-     *   <li>Streaming not enabled → {@link org.a2aproject.sdk.spec.InvalidRequestError}</li>
+     *   <li>Streaming not enabled → {@link org.a2aproject.sdk.spec.UnsupportedOperationError}</li>
      *   <li>Other {@link A2AError} → mapped to appropriate gRPC status code</li>
      *   <li>{@link SecurityException} → {@code UNAUTHENTICATED} or {@code PERMISSION_DENIED}</li>
      *   <li>{@link Throwable} → {@code INTERNAL} error</li>
@@ -388,7 +388,7 @@ public void listTaskPushNotificationConfigs(org.a2aproject.sdk.grpc.ListTaskPush
     public void sendStreamingMessage(org.a2aproject.sdk.grpc.SendMessageRequest request,
                                      StreamObserver<org.a2aproject.sdk.grpc.StreamResponse> responseObserver) {
         if (!getAgentCardInternal().capabilities().streaming()) {
-            handleError(responseObserver, new InvalidRequestError());
+            handleError(responseObserver, new UnsupportedOperationError());
             return;
         }
 
@@ -413,7 +413,7 @@ public void sendStreamingMessage(org.a2aproject.sdk.grpc.SendMessageRequest requ
     public void subscribeToTask(org.a2aproject.sdk.grpc.SubscribeToTaskRequest request,
                                  StreamObserver<org.a2aproject.sdk.grpc.StreamResponse> responseObserver) {
         if (!getAgentCardInternal().capabilities().streaming()) {
-            handleError(responseObserver, new InvalidRequestError());
+            handleError(responseObserver, new UnsupportedOperationError());
             return;
         }
 
diff --git a/transport/grpc/src/test/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandlerTest.java b/transport/grpc/src/test/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandlerTest.java
index 66c620164..98a563187 100644
--- a/transport/grpc/src/test/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandlerTest.java
+++ b/transport/grpc/src/test/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandlerTest.java
@@ -625,7 +625,7 @@ public void testStreamingNotSupportedError() throws Exception {
         AgentCard card = AbstractA2ARequestHandlerTest.createAgentCard(false, true);
         GrpcHandler handler = new TestGrpcHandler(card, requestHandler, internalExecutor);
         StreamRecorder<StreamResponse> streamRecorder = sendStreamingMessageRequest(handler);
-        assertGrpcError(streamRecorder, Status.Code.INVALID_ARGUMENT);
+        assertGrpcError(streamRecorder, Status.Code.UNIMPLEMENTED);
     }
 
     @Test
@@ -639,7 +639,7 @@ public void testStreamingNotSupportedErrorOnSubscribeToTask() throws Exception {
         StreamRecorder<StreamResponse> streamRecorder = StreamRecorder.create();
         handler.subscribeToTask(request, streamRecorder);
         streamRecorder.awaitCompletion(5, TimeUnit.SECONDS);
-        assertGrpcError(streamRecorder, Status.Code.INVALID_ARGUMENT);
+        assertGrpcError(streamRecorder, Status.Code.UNIMPLEMENTED);
     }
 
     @Test
diff --git a/transport/jsonrpc/src/main/java/org/a2aproject/sdk/transport/jsonrpc/handler/JSONRPCHandler.java b/transport/jsonrpc/src/main/java/org/a2aproject/sdk/transport/jsonrpc/handler/JSONRPCHandler.java
index e6ad92568..ec9fd3b85 100644
--- a/transport/jsonrpc/src/main/java/org/a2aproject/sdk/transport/jsonrpc/handler/JSONRPCHandler.java
+++ b/transport/jsonrpc/src/main/java/org/a2aproject/sdk/transport/jsonrpc/handler/JSONRPCHandler.java
@@ -46,7 +46,6 @@
 import org.a2aproject.sdk.spec.ExtendedAgentCardNotConfiguredError;
 import org.a2aproject.sdk.spec.EventKind;
 import org.a2aproject.sdk.spec.InternalError;
-import org.a2aproject.sdk.spec.InvalidRequestError;
 import org.a2aproject.sdk.spec.UnsupportedOperationError;
 import org.a2aproject.sdk.spec.ListTaskPushNotificationConfigsResult;
 import org.a2aproject.sdk.spec.PushNotificationNotSupportedError;
@@ -283,7 +282,7 @@ public Flow.Publisher<SendStreamingMessageResponse> onMessageSendStream(
             return ZeroPublisher.fromItems(
                     new SendStreamingMessageResponse(
                             request.getId(),
-                            new InvalidRequestError("Streaming is not supported by the agent")));
+                            new UnsupportedOperationError(null, "Streaming is not supported by the agent", null)));
         }
 
         try {
@@ -380,7 +379,7 @@ public Flow.Publisher<SendStreamingMessageResponse> onSubscribeToTask(
             return ZeroPublisher.fromItems(
                     new SendStreamingMessageResponse(
                             request.getId(),
-                            new InvalidRequestError("Streaming is not supported by the agent")));
+                            new UnsupportedOperationError(null, "Streaming is not supported by the agent", null)));
         }
         requestHandler.authorizeTaskAccess(request.getParams().id(), context, TaskOperation.SUBSCRIBE_TO_TASK);
         try {
diff --git a/transport/jsonrpc/src/test/java/org/a2aproject/sdk/transport/jsonrpc/handler/JSONRPCHandlerTest.java b/transport/jsonrpc/src/test/java/org/a2aproject/sdk/transport/jsonrpc/handler/JSONRPCHandlerTest.java
index 431c089ae..6cd6deb99 100644
--- a/transport/jsonrpc/src/test/java/org/a2aproject/sdk/transport/jsonrpc/handler/JSONRPCHandlerTest.java
+++ b/transport/jsonrpc/src/test/java/org/a2aproject/sdk/transport/jsonrpc/handler/JSONRPCHandlerTest.java
@@ -61,7 +61,6 @@
 import org.a2aproject.sdk.spec.ExtensionSupportRequiredError;
 import org.a2aproject.sdk.spec.GetTaskPushNotificationConfigParams;
 import org.a2aproject.sdk.spec.InternalError;
-import org.a2aproject.sdk.spec.InvalidRequestError;
 import org.a2aproject.sdk.spec.ListTaskPushNotificationConfigsParams;
 import org.a2aproject.sdk.spec.ListTasksParams;
 import org.a2aproject.sdk.spec.Message;
@@ -1047,7 +1046,7 @@ public void onComplete() {
         });
 
         assertEquals(1, results.size());
-        if (results.get(0).getError() != null && results.get(0).getError() instanceof InvalidRequestError ire) {
+        if (results.get(0).getError() != null && results.get(0).getError() instanceof UnsupportedOperationError ire) {
             assertEquals("Streaming is not supported by the agent", ire.getMessage());
         } else {
             fail("Expected a response containing an error");
@@ -1094,7 +1093,7 @@ public void onComplete() {
         });
 
         assertEquals(1, results.size());
-        if (results.get(0).getError() != null && results.get(0).getError() instanceof InvalidRequestError ire) {
+        if (results.get(0).getError() != null && results.get(0).getError() instanceof UnsupportedOperationError ire) {
             assertEquals("Streaming is not supported by the agent", ire.getMessage());
         } else {
             fail("Expected a response containing an error");
diff --git a/transport/rest/src/main/java/org/a2aproject/sdk/transport/rest/handler/RestHandler.java b/transport/rest/src/main/java/org/a2aproject/sdk/transport/rest/handler/RestHandler.java
index 131d5b9b7..f4f59dc58 100644
--- a/transport/rest/src/main/java/org/a2aproject/sdk/transport/rest/handler/RestHandler.java
+++ b/transport/rest/src/main/java/org/a2aproject/sdk/transport/rest/handler/RestHandler.java
@@ -293,7 +293,7 @@ public HTTPRestResponse sendMessage(ServerCallContext context, String tenant, St
     public HTTPRestResponse sendStreamingMessage(ServerCallContext context, String tenant, String body) {
         try {
             if (!agentCard.capabilities().streaming()) {
-                return createErrorResponse(new InvalidRequestError("Streaming is not supported by the agent"));
+                return createErrorResponse(new UnsupportedOperationError(null, "Streaming is not supported by the agent", null));
             }
             A2AVersionValidator.validateProtocolVersion(agentCard, context);
             A2AExtensions.validateRequiredExtensions(agentCard, context);
@@ -425,7 +425,7 @@ public HTTPRestResponse createTaskPushNotificationConfiguration(ServerCallContex
     public HTTPRestResponse subscribeToTask(ServerCallContext context, String tenant, String taskId) {
         try {
             if (!agentCard.capabilities().streaming()) {
-                return createErrorResponse(new InvalidRequestError("Streaming is not supported by the agent"));
+                return createErrorResponse(new UnsupportedOperationError(null, "Streaming is not supported by the agent", null));
             }
             TaskIdParams params = TaskIdParams.builder().id(taskId).tenant(tenant).build();
             try {
diff --git a/transport/rest/src/test/java/org/a2aproject/sdk/transport/rest/handler/RestHandlerTest.java b/transport/rest/src/test/java/org/a2aproject/sdk/transport/rest/handler/RestHandlerTest.java
index 8be11c609..890b59e53 100644
--- a/transport/rest/src/test/java/org/a2aproject/sdk/transport/rest/handler/RestHandlerTest.java
+++ b/transport/rest/src/test/java/org/a2aproject/sdk/transport/rest/handler/RestHandlerTest.java
@@ -362,7 +362,7 @@ public void testSendStreamingMessageNotSupported() {
         RestHandler.HTTPRestResponse response = handler.sendStreamingMessage(callContext, "", requestBody);
 
         assertProblemDetail(response, 400,
-                "INVALID_REQUEST",
+                "UNSUPPORTED_OPERATION",
                 "Streaming is not supported by the agent");
     }
 

From c0fea53ea9b42deb09f0eef8950f9898dc6a5173 Mon Sep 17 00:00:00 2001
From: meraklbz <lbz2770828522@gmail.com>
Date: Tue, 11 Aug 2026 21:20:35 +0800
Subject: [PATCH 2/2] fix: align gRPC streaming-unsupported error message with
 other transports

The JSON-RPC and REST transports report
'Streaming is not supported by the agent' when the agent card does not
advertise streaming; the gRPC transport used the bare default message.
Use the same message in sendStreamingMessage and subscribeToTask.
---
 .../a2aproject/sdk/transport/grpc/handler/GrpcHandler.java  | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/transport/grpc/src/main/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandler.java b/transport/grpc/src/main/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandler.java
index 127f41662..c6a309be4 100644
--- a/transport/grpc/src/main/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandler.java
+++ b/transport/grpc/src/main/java/org/a2aproject/sdk/transport/grpc/handler/GrpcHandler.java
@@ -388,7 +388,8 @@ public void listTaskPushNotificationConfigs(org.a2aproject.sdk.grpc.ListTaskPush
     public void sendStreamingMessage(org.a2aproject.sdk.grpc.SendMessageRequest request,
                                      StreamObserver<org.a2aproject.sdk.grpc.StreamResponse> responseObserver) {
         if (!getAgentCardInternal().capabilities().streaming()) {
-            handleError(responseObserver, new UnsupportedOperationError());
+            handleError(responseObserver,
+                    new UnsupportedOperationError(null, "Streaming is not supported by the agent", null));
             return;
         }
 
@@ -413,7 +414,8 @@ public void sendStreamingMessage(org.a2aproject.sdk.grpc.SendMessageRequest requ
     public void subscribeToTask(org.a2aproject.sdk.grpc.SubscribeToTaskRequest request,
                                  StreamObserver<org.a2aproject.sdk.grpc.StreamResponse> responseObserver) {
         if (!getAgentCardInternal().capabilities().streaming()) {
-            handleError(responseObserver, new UnsupportedOperationError());
+            handleError(responseObserver,
+                    new UnsupportedOperationError(null, "Streaming is not supported by the agent", null));
             return;
         }