fix(gemini-realtime): drop the native-audio speechConfig strip on Google AI Studio too

Live probes against every gemini_native_audio model on both providers show
setup accepts a valid prebuilt voice and 1007s only unknown voice names, so
the strip predicate rested on a false premise and silently discarded the
client's voice on AI Studio native-audio sessions

litellm/llms/gemini/realtime/transformation.py

@@ -115,13 +115,6 @@ class GeminiRealtimeConfig(BaseRealtimeConfig):
         """Google AI Studio Gemini 3.5+ accepts ``id`` on functionResponses; Vertex AI rejects it."""
         return True
 
-    def _strip_native_audio_speech_config(self) -> bool:
-        """Google AI Studio native-audio Live was never verified to accept ``speechConfig`` on setup.
-
-        Vertex AI accepts it and reads the requested voice.
-        """
-        return True
-
     @staticmethod
     def _usage_detail_alias(details: Any, defaults: dict[str, int]) -> dict[str, Any]:
         if not isinstance(details, dict):
@@ -390,10 +383,6 @@ class GeminiRealtimeConfig(BaseRealtimeConfig):
         entry: Final = GeminiRealtimeConfig._model_cost_entry(model)
         return bool(entry.get("gemini_native_audio") or entry.get("gemini_audio_only_live"))
 
-    @staticmethod
-    def _is_native_audio_model(model: str) -> bool:
-        return bool(GeminiRealtimeConfig._model_cost_entry(model).get("gemini_native_audio"))
-
     @staticmethod
     def _coerce_response_modalities(model: str, modalities: list[Any]) -> list[str]:
         """Map unsupported TEXT responseModalities to AUDIO for audio-only Live models."""
@@ -407,8 +396,8 @@ class GeminiRealtimeConfig(BaseRealtimeConfig):
         without_text: Final = [modality for modality in normalized if modality != "TEXT"]
         return without_text if without_text else ["AUDIO"]
 
-    def _finalize_gemini_live_setup(self, model: str, setup: dict[str, Any]) -> dict[str, Any]:
-        """Drop fields Gemini Live native-audio rejects on ``setup``."""
+    @staticmethod
+    def _finalize_gemini_live_setup(model: str, setup: dict[str, Any]) -> dict[str, Any]:
         generation_config: Final = setup.get("generationConfig")
         if isinstance(generation_config, dict):
             modalities: Final = generation_config.get("responseModalities")
@@ -416,8 +405,6 @@ class GeminiRealtimeConfig(BaseRealtimeConfig):
                 generation_config["responseModalities"] = GeminiRealtimeConfig._coerce_response_modalities(
                     model, modalities
                 )
-            if self._strip_native_audio_speech_config() and GeminiRealtimeConfig._is_native_audio_model(model):
-                generation_config.pop("speechConfig", None)
         return setup
 
     def _handle_session_update(

litellm/llms/vertex_ai/realtime/transformation.py

@@ -35,9 +35,6 @@ class VertexAIRealtimeConfig(GeminiRealtimeConfig):
     def _include_function_response_id(self) -> bool:
         return False
 
-    def _strip_native_audio_speech_config(self) -> bool:
-        return False
-
     # ------------------------------------------------------------------
     # URL
     # ------------------------------------------------------------------

tests/test_litellm/llms/gemini/realtime/test_gemini_realtime_transformation.py

@@ -1298,8 +1298,7 @@ def test_gemini_realtime_pipecat_ga_session_voice_and_tools(patch_gemini_audio_c
     assert len(messages) == 1
     setup = json.loads(messages[0])["setup"]
     assert setup["generationConfig"]["responseModalities"] == ["AUDIO"]
-    # Native-audio Live rejects speechConfig on setup (see _finalize_gemini_live_setup).
-    assert "speechConfig" not in setup.get("generationConfig", {})
+    assert setup["generationConfig"]["speechConfig"]["voiceConfig"]["prebuiltVoiceConfig"]["voiceName"] == "Kore"
     assert setup["tools"][0]["function_declarations"][0]["name"] == "terminate_call"
     assert setup["realtimeInputConfig"]["automaticActivityDetection"]["disabled"] is False
 
@@ -1843,20 +1842,6 @@ def test_is_audio_only_live_model_uses_cost_map(model, expected, patch_gemini_au
     assert GeminiRealtimeConfig._is_audio_only_live_model(model) == expected
 
 
-@pytest.mark.parametrize(
-    "model,expected",
-    [
-        ("gemini-2.5-flash-native-audio-latest", True),
-        ("gemini/gemini-2.5-flash-native-audio-latest", True),
-        ("gemini-3.1-flash-live-preview", False),
-        ("gemini/gemini-3.1-flash-live-preview", False),
-        ("gemini-2.0-flash", False),
-    ],
-)
-def test_is_native_audio_model_uses_cost_map(model, expected, patch_gemini_audio_cost_map_entries):
-    assert GeminiRealtimeConfig._is_native_audio_model(model) == expected
-
-
 def test_is_setup_message_and_is_content_message():
     config = GeminiRealtimeConfig()
     assert config.is_setup_message({"setup": {}}) is True

tests/test_litellm/llms/vertex_ai/realtime/test_vertex_ai_realtime_transformation.py

@@ -491,8 +491,8 @@ def test_vertex_native_audio_keeps_requested_voice(patch_native_audio_cost_map_e
     assert generation_config["responseModalities"] == ["AUDIO"]
 
 
-def test_google_ai_studio_native_audio_still_strips_voice(patch_native_audio_cost_map_entry):
-    """Google AI Studio's own native-audio Live is untouched: only Vertex was verified to accept speechConfig."""
+def test_google_ai_studio_native_audio_keeps_requested_voice(patch_native_audio_cost_map_entry):
+    """Regression: AI Studio native-audio Live accepts speechConfig too, so the voice survives on both providers."""
     from litellm.llms.gemini.realtime.transformation import GeminiRealtimeConfig
 
     messages = GeminiRealtimeConfig().transform_realtime_request(
@@ -510,7 +510,7 @@ def test_google_ai_studio_native_audio_still_strips_voice(patch_native_audio_cos
     )
 
     generation_config = json.loads(messages[0])["setup"]["generationConfig"]
-    assert "speechConfig" not in generation_config
+    assert generation_config["speechConfig"]["voiceConfig"]["prebuiltVoiceConfig"]["voiceName"] == "Aoede"
 
 
 def test_vertex_native_audio_drops_openai_stock_voice(patch_native_audio_cost_map_entry):