diff --git a/src/a2a/server/apps/jsonrpc/fastapi_app.py b/src/a2a/server/apps/jsonrpc/fastapi_app.py
index 20acfc575..0ec9d1ab2 100644
--- a/src/a2a/server/apps/jsonrpc/fastapi_app.py
+++ b/src/a2a/server/apps/jsonrpc/fastapi_app.py
@@ -1,5 +1,3 @@
-import importlib.resources
-import json
 import logging
 
 from collections.abc import Awaitable, Callable
@@ -36,43 +34,6 @@
 logger = logging.getLogger(__name__)
 
 
-class A2AFastAPI(FastAPI):
-    """A FastAPI application that adds A2A-specific OpenAPI components."""
-
-    _a2a_components_added: bool = False
-
-    def openapi(self) -> dict[str, Any]:
-        """Generates the OpenAPI schema for the application."""
-        if self.openapi_schema:
-            return self.openapi_schema
-
-        # Try to use the a2a.json schema generated from the proto file
-        # if available, instead of generating one from the python types.
-        try:
-            from a2a import types  # noqa: PLC0415
-
-            schema_file = importlib.resources.files(types).joinpath('a2a.json')
-            if schema_file.is_file():
-                self.openapi_schema = json.loads(
-                    schema_file.read_text(encoding='utf-8')
-                )
-                if self.openapi_schema:
-                    return self.openapi_schema
-        except Exception:  # noqa: BLE001
-            logger.warning(
-                "Could not load 'a2a.json' from 'a2a.types'. Falling back to auto-generation."
-            )
-
-        openapi_schema = super().openapi()
-        if not self._a2a_components_added:
-            # A2ARequest is now a Union type of proto messages, so we can't use
-            # model_json_schema. Instead, we just mark it as added without
-            # adding the schema since proto types don't have Pydantic schemas.
-            # The OpenAPI schema will still be functional for the endpoints.
-            self._a2a_components_added = True
-        return openapi_schema
-
-
 class A2AFastAPIApplication(JSONRPCApplication):
     """A FastAPI application implementing the A2A protocol server endpoints.
 
@@ -180,7 +141,7 @@ def build(
         Returns:
             A configured FastAPI application instance.
         """
-        app = A2AFastAPI(**kwargs)
+        app = FastAPI(**kwargs)
 
         self.add_routes_to_app(app, agent_card_url, rpc_url)
 
diff --git a/src/a2a/server/apps/rest/fastapi_app.py b/src/a2a/server/apps/rest/fastapi_app.py
index ea9a501b9..aac13b382 100644
--- a/src/a2a/server/apps/rest/fastapi_app.py
+++ b/src/a2a/server/apps/rest/fastapi_app.py
@@ -1,3 +1,5 @@
+import importlib.resources
+import json
 import logging
 
 from collections.abc import Awaitable, Callable
@@ -56,6 +58,45 @@
 }
 
 
+class A2AFastAPI(FastAPI):
+    """A FastAPI application that adds A2A-specific OpenAPI components."""
+
+    _a2a_components_added: bool = False
+    rpc_url: str = ''
+
+    def openapi(self) -> dict[str, Any]:
+        """Generates the OpenAPI schema for the application."""
+        if self.openapi_schema:
+            return self.openapi_schema
+
+        # Try to use the a2a.json schema generated from the proto file
+        # if available, instead of generating one from the python types.
+        try:
+            from a2a import types  # noqa: PLC0415
+
+            schema_file = importlib.resources.files(types).joinpath('a2a.json')
+            if schema_file.is_file():
+                self.openapi_schema = json.loads(
+                    schema_file.read_text(encoding='utf-8')
+                )
+                if self.rpc_url and self.openapi_schema:
+                    paths = self.openapi_schema.get('paths', {})
+                    self.openapi_schema['paths'] = {
+                        f'{self.rpc_url}{k}': v for k, v in paths.items()
+                    }
+                if self.openapi_schema:
+                    return self.openapi_schema
+        except Exception:  # noqa: BLE001
+            logger.warning(
+                "Could not load 'a2a.json' from 'a2a.types'. Falling back to auto-generation."
+            )
+
+        openapi_schema = super().openapi()
+        if not self._a2a_components_added:
+            self._a2a_components_added = True
+        return openapi_schema
+
+
 class A2ARESTFastAPIApplication:
     """A FastAPI application implementing the A2A protocol server REST endpoints.
 
@@ -140,7 +181,8 @@ def build(
         Returns:
             A configured FastAPI application instance.
         """
-        app = FastAPI(**kwargs)
+        app = A2AFastAPI(**kwargs)
+        app.rpc_url = rpc_url
 
         @app.exception_handler(StarletteHTTPException)
         async def http_exception_handler(
diff --git a/tck/sut_agent.py b/tck/sut_agent.py
index 7196b828b..5af6309db 100644
--- a/tck/sut_agent.py
+++ b/tck/sut_agent.py
@@ -8,6 +8,7 @@
 import grpc.aio
 import uvicorn
 
+from fastapi import FastAPI
 from starlette.applications import Starlette
 
 import a2a.compat.v0_3.a2a_v0_3_pb2_grpc as a2a_v0_3_grpc
@@ -19,6 +20,7 @@
 from a2a.server.apps import (
     A2ARESTFastAPIApplication,
     A2AStarletteApplication,
+    A2AFastAPIApplication,
 )
 from a2a.server.events.event_queue import EventQueue
 from a2a.server.request_handlers.default_request_handler import (
@@ -196,22 +198,24 @@ def serve(task_store: TaskStore) -> None:
         task_store=task_store,
     )
 
-    main_app = Starlette()
+    main_app = FastAPI()
 
     # JSONRPC
-    jsonrpc_server = A2AStarletteApplication(
+    jsonrpc_server = A2AFastAPIApplication(
         agent_card=agent_card,
         http_handler=request_handler,
     )
-    jsonrpc_server.add_routes_to_app(main_app, rpc_url=JSONRPC_URL)
+    json_rpc_app = jsonrpc_server.build(rpc_url=JSONRPC_URL)
 
     # REST
     rest_server = A2ARESTFastAPIApplication(
         agent_card=agent_card,
         http_handler=request_handler,
     )
-    rest_app = rest_server.build(rpc_url=REST_URL)
-    main_app.mount('', rest_app)
+    rest_app = rest_server.build()
+
+    main_app.mount(REST_URL,rest_app)
+    main_app.mount('',json_rpc_app)
 
     config = uvicorn.Config(
         main_app, host='127.0.0.1', port=http_port, log_level='info'