fix: Add A2ATransport.http_json to the default supported transports list

remote_a2a_agent is only including A2ATransport.jsonrpc on the default supported list, but it should also include http_json since it is a common transport (default used by agent engine)

Co-authored-by: Kathy Wu <wukathy@google.com>
PiperOrigin-RevId: 895444831
Change-Id: Ieb510bf549a251e30389a7b76754aacb940963f6

Author: wukath

src/google/adk/agents/remote_a2a_agent.py

@@ -233,7 +233,7 @@ async def _ensure_httpx_client(self) -> httpx.AsyncClient:
           httpx_client=self._httpx_client,
           streaming=False,
           polling=False,
-          supported_transports=[A2ATransport.jsonrpc],
+          supported_transports=[A2ATransport.jsonrpc, A2ATransport.http_json],
       )
       self._a2a_client_factory = A2AClientFactory(config=client_config)
     return self._httpx_client

tests/unittests/agents/test_remote_a2a_agent.py

@@ -35,6 +35,7 @@
 from a2a.types import TaskStatus as A2ATaskStatus
 from a2a.types import TaskStatusUpdateEvent
 from a2a.types import TextPart
+from a2a.types import TransportProtocol as A2ATransport
 from google.adk.a2a.agent import ParametersConfig
 from google.adk.a2a.agent import RequestInterceptor
 from google.adk.a2a.agent.config import A2aRemoteAgentConfig
@@ -198,6 +199,10 @@ async def test_ensure_httpx_client_creates_new_client(self):
     assert client is not None
     assert agent._httpx_client == client
     assert agent._httpx_client_needs_cleanup is True
+    assert agent._a2a_client_factory._config.supported_transports == [
+        A2ATransport.jsonrpc,
+        A2ATransport.http_json,
+    ]
 
   @pytest.mark.asyncio
   async def test_ensure_httpx_client_reuses_existing_client(self):