feat: support a2a routes in api server app

agentkit/apps/agent_server_app/agent_server_app.py

@@ -12,15 +12,17 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import json
+import logging
+from contextlib import asynccontextmanager
 from typing import override
 
 import uvicorn
-import json
-from fastapi import Request
-from fastapi import HTTPException
+from fastapi import FastAPI, HTTPException, Request
 from fastapi.responses import StreamingResponse
-from opentelemetry import trace
+from google.adk.a2a.utils.agent_to_a2a import to_a2a
 from google.adk.agents.base_agent import BaseAgent
+from google.adk.agents.run_config import RunConfig, StreamingMode
 from google.adk.artifacts.in_memory_artifact_service import (
     InMemoryArtifactService,
 )
@@ -35,15 +37,20 @@
 from google.adk.evaluation.local_eval_sets_manager import LocalEvalSetsManager
 from google.adk.memory.in_memory_memory_service import InMemoryMemoryService
 from google.adk.sessions.base_session_service import BaseSessionService
-from google.adk.agents.run_config import RunConfig, StreamingMode
 from google.adk.utils.context_utils import Aclosing
 from google.genai import types
+from opentelemetry import trace
 from veadk import Agent
 from veadk.memory.short_term_memory import ShortTermMemory
+from veadk.runner import Runner
 
-from agentkit.apps.base_app import BaseAgentkitApp
+from agentkit.apps.agent_server_app.middleware import (
+    AgentkitTelemetryHTTPMiddleware,
+)
 from agentkit.apps.agent_server_app.telemetry import telemetry
-from agentkit.apps.agent_server_app.middleware import AgentkitTelemetryHTTPMiddleware
+from agentkit.apps.base_app import BaseAgentkitApp
+
+logger = logging.getLogger(__name__)
 
 
 class AgentKitAgentLoader(BaseAgentLoader):
@@ -63,7 +70,9 @@ def list_agents(self) -> list[str]:
 
 class AgentkitAgentServerApp(BaseAgentkitApp):
     def __init__(
-        self, agent: BaseAgent, short_term_memory: BaseSessionService | ShortTermMemory
+        self,
+        agent: BaseAgent,
+        short_term_memory: BaseSessionService | ShortTermMemory,
     ) -> None:
         super().__init__()
 
@@ -88,7 +97,22 @@ def __init__(
             agents_dir=".",
         )
 
-        self.app = self.server.get_fast_api_app()
+        runner = Runner(agent=agent)
+        _a2a_server_app = to_a2a(agent=agent, runner=runner)
+
+        @asynccontextmanager
+        async def lifespan(app: FastAPI):
+            # trigger A2A server app startup
+            logger.info(
+                "Triggering A2A server app startup within API server..."
+            )
+            for handler in _a2a_server_app.router.on_startup:
+                await handler()
+            yield
+
+        self.app = self.server.get_fast_api_app(lifespan=lifespan)
+
+        self.app.mount("/", _a2a_server_app)
 
         # Attach ASGI middleware for unified telemetry across all routes
         self.app.add_middleware(AgentkitTelemetryHTTPMiddleware)
@@ -100,14 +124,18 @@ async def _invoke_compat(request: Request):
             # Extract headers (fallback keys supported)
             headers = request.headers
             user_id = (
-                headers.get("user_id") or headers.get("x-user-id") or "agentkit_user"
+                headers.get("user_id")
+                or headers.get("x-user-id")
+                or "agentkit_user"
             )
             session_id = headers.get("session_id") or ""
 
             # Determine app_name from loader
             app_names = self.server.agent_loader.list_agents()
             if not app_names:
-                raise HTTPException(status_code=404, detail="No agents configured")
+                raise HTTPException(
+                    status_code=404, detail="No agents configured"
+                )
             app_name = app_names[0]
 
             # Parse payload and convert to ADK Content
@@ -156,7 +184,9 @@ async def event_generator():
                             user_id=user_id,
                             session_id=session_id,
                             new_message=content,
-                            run_config=RunConfig(streaming_mode=StreamingMode.SSE),
+                            run_config=RunConfig(
+                                streaming_mode=StreamingMode.SSE
+                            ),
                         )
                     ) as agen:
                         async for event in agen:
@@ -171,7 +201,9 @@ async def event_generator():
                     pass
                 except Exception as e:
                     yield f'data: {{"error": "{str(e)}"}}\n\n'
-                    telemetry.trace_agent_server_finish(func_result="", exception=e)
+                    telemetry.trace_agent_server_finish(
+                        func_result="", exception=e
+                    )
 
             return StreamingResponse(
                 event_generator(),