fix(speech): use the deployment's api_base and timeout for Gemini and Vertex AI TTS

Backport of #50803 to lts/1.108.x.
Cherry-picked from 86cd49d476 (litellm_speech_bridge_api_base).

litellm/endpoints/speech/speech_to_completion_bridge/handler.py

@@ -7,6 +7,8 @@ from typing import TYPE_CHECKING, Final
 from typing_extensions import TypedDict
 
 if TYPE_CHECKING:
+    import httpx
+
     from litellm import LiteLLMLoggingObj
     from litellm.types.llms.openai import HttpxBinaryResponseContent
 
@@ -85,6 +87,8 @@ class SpeechToCompletionBridgeHandler:
         headers: dict,
         logging_obj: "LiteLLMLoggingObj",
         custom_llm_provider: str,
+        api_base: str | None,
+        timeout: "float | httpx.Timeout | None",
     ) -> "HttpxBinaryResponseContent":
         received_args: Final = locals()
         from litellm import completion
@@ -104,7 +108,7 @@ class SpeechToCompletionBridgeHandler:
             model=model,
             input=input,
             optional_params=optional_params,
-            litellm_params=litellm_params,
+            litellm_params={**litellm_params, "api_base": api_base, "timeout": timeout},
             headers=headers,
             litellm_logging_obj=logging_obj,
             custom_llm_provider=custom_llm_provider,

litellm/main.py

@@ -8751,6 +8751,8 @@ def speech(
                 headers=headers or {},
                 logging_obj=logging_obj,
                 custom_llm_provider=custom_llm_provider,
+                api_base=api_base,
+                timeout=timeout,
             )
 
         # Vertex AI Text-to-Speech (Google Cloud TTS)
@@ -8802,6 +8804,8 @@ def speech(
             headers=headers or {},
             logging_obj=logging_obj,
             custom_llm_provider=custom_llm_provider,
+            api_base=api_base,
+            timeout=timeout,
         )
     elif custom_llm_provider == "runwayml":
         from litellm.llms.runwayml.text_to_speech.transformation import (

tests/unit/llms/vertex_ai/text_to_speech/test_transformation.py

@@ -1098,3 +1098,49 @@ def test_lyria_malformed_item_position_does_not_change_the_mapped_error(payload:
             custom_llm_provider="vertex_ai",
             original_exception=exc_info.value,
         )
+
+
+_PCM_AUDIO: Final = b"\x00\x00\x01\x00" * 2400
+_GENERATE_CONTENT_RESPONSE: Final = {
+    "candidates": [
+        {
+            "content": {
+                "role": "model",
+                "parts": [
+                    {
+                        "inlineData": {
+                            "mimeType": "audio/L16;codec=pcm;rate=24000",
+                            "data": base64.b64encode(_PCM_AUDIO).decode(),
+                        }
+                    }
+                ],
+            },
+            "finishReason": "STOP",
+        }
+    ],
+    "usageMetadata": {"promptTokenCount": 5, "candidatesTokenCount": 10, "totalTokenCount": 15},
+}
+
+
+@pytest.mark.parametrize("custom_llm_provider", ("vertex_ai", "vertex_ai_beta"))
+@pytest.mark.asyncio
+async def test_aspeech_vertex_ai_gemini_tts_routes_to_configured_api_base(
+    respx_mock: respx.MockRouter, google_token_endpoint: responses.RequestsMock, custom_llm_provider: str
+) -> None:
+    gateway_route: Final = respx_mock.post(
+        "https://vertex.gateway.internal/v1/projects/test-project/locations/global"
+        "/publishers/google/models/gemini-3.8-flash-tts:generateContent"
+    ).mock(return_value=httpx.Response(200, json=_GENERATE_CONTENT_RESPONSE))
+
+    response: Final = await litellm.aspeech(
+        model=f"{custom_llm_provider}/gemini-3.8-flash-tts",
+        input="Say hello",
+        voice="Kore",
+        vertex_credentials=_AUTHORIZED_USER,
+        vertex_location="global",
+        api_base="https://vertex.gateway.internal",
+    )
+
+    assert gateway_route.call_count == 1
+    assert gateway_route.calls.last.request.headers["authorization"] == "Bearer minted-google-token"
+    assert _PCM_AUDIO in response.content

tests/unit/test_main.py

@@ -4777,6 +4777,67 @@ def test_speech_mistral_routes_to_configured_api_base(respx_mock: respx.MockRout
     assert response.content == audio_bytes
 
 
+GEMINI_TTS_MODEL: Final = "gemini-3.8-flash-tts"
+GEMINI_GATEWAY_BASE: Final = "https://gemini.gateway.internal/v1beta"
+GEMINI_DEFAULT_GENERATE_CONTENT_URL: Final = (
+    rf"https://generativelanguage\.googleapis\.com/[^/]+/models/{GEMINI_TTS_MODEL}:generateContent"
+)
+
+
+@pytest.mark.parametrize("endpoint_param", ["api_base", "base_url"])
+@pytest.mark.parametrize("sync_mode", [True, False])
+async def test_speech_gemini_tts_routes_to_configured_api_base(
+    respx_mock: respx.MockRouter, monkeypatch: pytest.MonkeyPatch, endpoint_param: str, sync_mode: bool
+):
+    monkeypatch.setattr(litellm, "disable_aiohttp_transport", True)
+    gateway_route: Final = respx_mock.post(f"{GEMINI_GATEWAY_BASE}/models/{GEMINI_TTS_MODEL}:generateContent").mock(
+        return_value=httpx.Response(200, json=_gemini_tts_generate_content_response())
+    )
+    speech_kwargs: Final = {
+        "model": f"gemini/{GEMINI_TTS_MODEL}",
+        "input": "hello from litellm",
+        "voice": "Kore",
+        "api_key": "fake-gemini-key",
+        endpoint_param: GEMINI_GATEWAY_BASE,
+    }
+
+    response: Final = litellm.speech(**speech_kwargs) if sync_mode else await litellm.aspeech(**speech_kwargs)
+
+    assert gateway_route.call_count == 1
+    assert gateway_route.calls.last.request.headers["x-goog-api-key"] == "fake-gemini-key"
+    assert b"pcm-audio-bytes" in response.content
+
+
+def test_speech_gemini_tts_applies_the_caller_timeout(respx_mock: respx.MockRouter):
+    route: Final = respx_mock.post(url__regex=GEMINI_DEFAULT_GENERATE_CONTENT_URL).mock(
+        return_value=httpx.Response(200, json=_gemini_tts_generate_content_response())
+    )
+
+    litellm.speech(
+        model=f"gemini/{GEMINI_TTS_MODEL}", input="hello", voice="Kore", api_key="fake-gemini-key", timeout=7.5
+    )
+
+    assert route.calls.last.request.extensions["timeout"] == httpx.Timeout(7.5).as_dict()
+
+
+def test_speech_gemini_tts_without_a_timeout_waits_as_long_as_the_same_chat_completion(respx_mock: respx.MockRouter):
+    route: Final = respx_mock.post(url__regex=GEMINI_DEFAULT_GENERATE_CONTENT_URL).mock(
+        return_value=httpx.Response(200, json=_gemini_tts_generate_content_response())
+    )
+
+    litellm.speech(model=f"gemini/{GEMINI_TTS_MODEL}", input="hello", voice="Kore", api_key="fake-gemini-key")
+    litellm.completion(
+        model=f"gemini/{GEMINI_TTS_MODEL}",
+        messages=[{"role": "user", "content": "hello"}],
+        modalities=["audio"],
+        audio={"voice": "Kore", "format": "pcm16"},
+        api_key="fake-gemini-key",
+    )
+
+    speech_call, chat_call = route.calls
+    assert speech_call.request.extensions["timeout"] == chat_call.request.extensions["timeout"]
+
+
 FOUNDRY_HOST: Final = "https://my-project.services.ai.azure.com"