Change apply_update / _update_settings return type from set[str] to dict[str, Any]. The dict maps each changed field name to its pre-update value, enabling services to do granular diffing of complex settings objects. Existing call-site patterns ("field" in changed, if changed, iteration) work unchanged; set-difference sites use changed.keys() - {...}.

src/pipecat/services/openai/stt.py

@@ -17,7 +17,7 @@ Provides two STT services:
 import base64
 import json
 from dataclasses import dataclass, field
-from typing import AsyncGenerator, Literal, Optional, Union
+from typing import Any, AsyncGenerator, Literal, Optional, Union
 
 from loguru import logger
 
@@ -268,7 +268,7 @@ class OpenAIRealtimeSTTService(WebsocketSTTService):
         """
         return True
 
-    async def _update_settings(self, update: STTSettings) -> set[str]:
+    async def _update_settings(self, update: STTSettings) -> dict[str, Any]:
         """Apply a settings update and send session update if needed.
 
         Keeps ``_language_code`` and ``_prompt`` in sync with settings
@@ -278,7 +278,7 @@ class OpenAIRealtimeSTTService(WebsocketSTTService):
             update: A :class:`STTSettings` (or ``OpenAIRealtimeSTTSettings``) delta.
 
         Returns:
-            Set of field names whose values actually changed.
+            Dict mapping changed field names to their previous values.
         """
         changed = await super()._update_settings(update)