fix(realtime): unblock fixed speech after tool calls

backend/services/pipecat/realtime_tools.py

@@ -46,13 +46,20 @@ RealtimeToolDispatcher = Callable[
     [str, dict[str, Any], str], Awaitable[RealtimeToolResult]
 ]
 SendProviderEvent = Callable[[dict[str, Any]], Awaitable[None]]
+WaitForResponseBoundary = Callable[[], Awaitable[Any]]
 
 
 class RealtimeToolSession:
     """Serialize provider calls and answer every call id at most once."""
 
-    def __init__(self, send_event: SendProviderEvent) -> None:
+    def __init__(
+        self,
+        send_event: SendProviderEvent,
+        *,
+        wait_for_response_boundary: WaitForResponseBoundary | None = None,
+    ) -> None:
         self._send_event = send_event
+        self._wait_for_response_boundary = wait_for_response_boundary
         self._dispatcher: RealtimeToolDispatcher | None = None
         self._handled_call_ids: set[str] = set()
         self._lock = asyncio.Lock()
@@ -105,6 +112,12 @@ class RealtimeToolSession:
                     },
                 }
             )
+            # Function-call argument events arrive before the provider's
+            # response.done boundary. Starting another response sooner is
+            # rejected by both supported realtime providers. The provider
+            # receive loop stays free while this background task waits.
+            if self._wait_for_response_boundary is not None:
+                await self._wait_for_response_boundary()
             if result.after_output is not None:
                 await result.after_output()
             if result.continue_response: