fix(a2a): advertise streaming on agent_registry agent cards

src/google/adk/integrations/agent_registry/agent_registry.py

@@ -51,6 +51,7 @@
 
 # pylint: disable=g-import-not-at-top
 try:
+  from a2a.types import AgentCapabilities
   from a2a.types import AgentSkill
   from google.adk.a2a import _compat
   from google.adk.agents.remote_a2a_agent import RemoteA2aAgent
@@ -666,6 +667,8 @@ def get_remote_a2a_agent(
       )
 
     binding = protocol_binding or _compat.TP_HTTP_JSON
+    # Registry metadata has no capability details. Pass streaming explicitly so
+    # constructed cards do not advertise streaming:false.
     agent_card = _compat.build_agent_card(
         name=name,
         description=description,
@@ -674,6 +677,7 @@ def get_remote_a2a_agent(
         protocol_binding=getattr(binding, "value", binding),
         protocol_version=protocol_version,
         skills=skills,
+        capabilities=AgentCapabilities(streaming=True),
         default_input_modes=["text"],
         default_output_modes=["text"],
     )

tests/unittests/integrations/agent_registry/test_agent_registry.py

@@ -615,6 +615,29 @@ def test_get_remote_a2a_agent_defaults(self, registry):
         agent._agent_card, "1.0" if _compat.IS_A2A_V1 else "0.3.0"
     )
 
+  def test_get_remote_a2a_agent_advertises_streaming(self, registry):
+    """Constructed registry cards advertise streaming when no card is supplied."""
+    mock_response = MagicMock()
+    mock_response.json.return_value = {
+        "displayName": "TestAgent",
+        "description": "Test Desc",
+        "version": "1.0",
+        "protocols": [{
+            "type": _ProtocolType.A2A_AGENT,
+            "interfaces": [{
+                "url": "https://my-agent.com",
+            }],
+        }],
+    }
+    mock_response.raise_for_status = MagicMock()
+    registry._session.get.return_value = mock_response
+
+    registry._credentials.token = "token"
+    registry._credentials.refresh = MagicMock()
+
+    agent = registry.get_remote_a2a_agent("test-agent")
+    assert agent._agent_card.capabilities.streaming is True
+
   def test_get_remote_a2a_agent_with_card(self, registry):
     mock_response = MagicMock()
     mock_response.json.return_value = {