fix: Add push notification config store to agent_to_a2a

This change allows users to provide a custom PushNotificationConfigStore when converting an ADK agent to an A2A Starlette application. If no custom store is provided, an InMemoryPushNotificationConfigStore is used by default, thios now lets A2A push notification configuration RPCs

Close #4126

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 874118109

src/google/adk/a2a/utils/agent_to_a2a.py

@@ -20,7 +20,9 @@ from typing import Union
 
 from a2a.server.apps import A2AStarletteApplication
 from a2a.server.request_handlers import DefaultRequestHandler
+from a2a.server.tasks import InMemoryPushNotificationConfigStore
 from a2a.server.tasks import InMemoryTaskStore
+from a2a.server.tasks import PushNotificationConfigStore
 from a2a.types import AgentCard
 from starlette.applications import Starlette
 
@@ -78,6 +80,7 @@ def to_a2a(
     port: int = 8000,
     protocol: str = "http",
     agent_card: Optional[Union[AgentCard, str]] = None,
+    push_config_store: Optional[PushNotificationConfigStore] = None,
     runner: Optional[Runner] = None,
 ) -> Starlette:
   """Convert an ADK agent to a A2A Starlette application.
@@ -90,6 +93,9 @@ def to_a2a(
       agent_card: Optional pre-built AgentCard object or path to agent card
                   JSON. If not provided, will be built automatically from the
                   agent.
+      push_config_store: Optional A2A push notification config store. If not
+        provided, an in-memory store will be created so push-notification
+        config RPC methods are supported.
       runner: Optional pre-built Runner object. If not provided, a default
               runner will be created using in-memory services.
 
@@ -127,8 +133,13 @@ def to_a2a(
       runner=runner or create_runner,
   )
 
+  if push_config_store is None:
+    push_config_store = InMemoryPushNotificationConfigStore()
+
   request_handler = DefaultRequestHandler(
-      agent_executor=agent_executor, task_store=task_store
+      agent_executor=agent_executor,
+      task_store=task_store,
+      push_config_store=push_config_store,
   )
 
   # Use provided agent card or build one from the agent

src/google/adk/cli/fast_api.py

@@ -525,6 +525,7 @@ def get_fast_api_app(
   if a2a:
     from a2a.server.apps import A2AStarletteApplication
     from a2a.server.request_handlers import DefaultRequestHandler
+    from a2a.server.tasks import InMemoryPushNotificationConfigStore
     from a2a.server.tasks import InMemoryTaskStore
     from a2a.types import AgentCard
     from a2a.utils.constants import AGENT_CARD_WELL_KNOWN_PATH
@@ -563,8 +564,12 @@ def get_fast_api_app(
               runner=create_a2a_runner_loader(app_name),
           )
 
+          push_config_store = InMemoryPushNotificationConfigStore()
+
           request_handler = DefaultRequestHandler(
-              agent_executor=agent_executor, task_store=a2a_task_store
+              agent_executor=agent_executor,
+              task_store=a2a_task_store,
+              push_config_store=push_config_store,
           )
 
           with (p / "agent.json").open("r", encoding="utf-8") as f: