diff --git a/src/a2a/server/request_handlers/default_request_handler.py b/src/a2a/server/request_handlers/default_request_handler.py
index 63d0fdc74..c777e34cc 100644
--- a/src/a2a/server/request_handlers/default_request_handler.py
+++ b/src/a2a/server/request_handlers/default_request_handler.py
@@ -555,11 +555,15 @@ async def on_subscribe_to_task(
 
         if task.status.state in TERMINAL_TASK_STATES:
             raise ServerError(
-                error=InvalidParamsError(
+                error=UnsupportedOperationError(
                     message=f'Task {task.id} is in terminal state: {task.status.state}'
                 )
             )
 
+        # The operation MUST return a Task object as the first event in the stream
+        # https://a2a-protocol.org/latest/specification/#316-subscribe-to-task
+        yield task
+
         task_manager = TaskManager(
             task_id=task.id,
             context_id=task.context_id,
diff --git a/tests/server/request_handlers/test_default_request_handler.py b/tests/server/request_handlers/test_default_request_handler.py
index 9a00ba6c6..350d595a4 100644
--- a/tests/server/request_handlers/test_default_request_handler.py
+++ b/tests/server/request_handlers/test_default_request_handler.py
@@ -1499,7 +1499,10 @@ async def exec_side_effect(_request, queue: EventQueue):
     # Allow producer to emit the next event
     allow_second_event.set()
 
-    received = await resub_gen.__anext__()
+    first_subscribe_event = await anext(resub_gen)
+    assert first_subscribe_event == task_for_resub
+
+    received = await anext(resub_gen)
     assert received == second_event
 
     # Finish producer to allow cleanup paths to complete
@@ -2706,7 +2709,7 @@ async def test_on_subscribe_to_task_in_terminal_state(terminal_state):
         async for _ in request_handler.on_subscribe_to_task(params, context):
             pass  # pragma: no cover
 
-    assert isinstance(exc_info.value.error, InvalidParamsError)
+    assert isinstance(exc_info.value.error, UnsupportedOperationError)
     assert exc_info.value.error.message
     assert (
         f'Task {task_id} is in terminal state: {terminal_state}'
diff --git a/tests/server/request_handlers/test_jsonrpc_handler.py b/tests/server/request_handlers/test_jsonrpc_handler.py
index fca1175af..a9e940a03 100644
--- a/tests/server/request_handlers/test_jsonrpc_handler.py
+++ b/tests/server/request_handlers/test_jsonrpc_handler.py
@@ -703,7 +703,9 @@ async def streaming_coro():
             collected_events: list[Any] = []
             async for event in response:
                 collected_events.append(event)
-            assert len(collected_events) == len(events)
+            assert (
+                len(collected_events) == len(events) + 1
+            )  # First event is task itself
             assert mock_task.history is not None and len(mock_task.history) == 0
 
     async def test_on_subscribe_no_existing_task_error(self) -> None: