fix: add language field to CartesiaTTSConfiguration and pass to Cartesia TTS service (#442)

* fix: add language field to CartesiaTTSConfiguration and pass to TTS service

Closes #432

* chore: regenerate OpenAPI spec to fix drift-check

The openapi.json snapshot had drifted from the FastAPI app definition
because main gained new organization endpoints (billing, credits,
context) after this branch was created. Regenerate it with
'python -m scripts.dump_docs_openapi' to bring it back in sync.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* chore: clarify Cartesia language schema

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Abhishek Kumar <abhishek@a6k.me>

api/services/configuration/registry.py

@@ -978,6 +978,11 @@ class CartesiaTTSConfiguration(BaseTTSConfiguration):
         le=2.0,
         description="Volume multiplier for generated speech.",
     )
+    language: str = Field(
+        default="en",
+        description="Cartesia language code for TTS synthesis (e.g. 'en', 'tr', 'fr', 'de').",
+        json_schema_extra={"allow_custom_input": True},
+    )
 
 
 @register_tts

api/services/pipecat/service_factory.py

@@ -452,11 +452,13 @@ def create_tts_service(
         generation_config = (
             GenerationConfig(**gen_config_kwargs) if gen_config_kwargs else None
         )
+        language = getattr(user_config.tts, "language", None) or "en"
         return CartesiaTTSService(
             api_key=user_config.tts.api_key,
             settings=CartesiaTTSSettings(
                 voice=user_config.tts.voice,
                 model=user_config.tts.model,
+                language=language,
                 **(
                     {"generation_config": generation_config}
                     if generation_config

api/tests/test_cartesia_tts_service_factory.py

@@ -43,3 +43,35 @@ def test_create_cartesia_tts_service_passes_selected_model():
     assert kwargs["api_key"] == "test-key"
     assert kwargs["settings"].model == "sonic-3.5"
     assert kwargs["settings"].voice == "test-voice-id"
+
+
+def test_cartesia_tts_configuration_default_language_is_english():
+    config = CartesiaTTSConfiguration(api_key="test-key")
+
+    assert config.language == "en"
+
+
+def test_create_cartesia_tts_service_passes_language_to_settings():
+    user_config = SimpleNamespace(
+        tts=SimpleNamespace(
+            provider=ServiceProviders.CARTESIA.value,
+            api_key="test-key",
+            model="sonic-3.5",
+            voice="test-voice-id",
+            speed=1.0,
+            volume=1.0,
+            language="tr",
+        )
+    )
+    audio_config = SimpleNamespace(
+        transport_out_sample_rate=24000,
+        transport_in_sample_rate=16000,
+    )
+
+    with patch(
+        "api.services.pipecat.service_factory.CartesiaTTSService"
+    ) as mock_service:
+        create_tts_service(user_config, audio_config)
+
+    kwargs = mock_service.call_args.kwargs
+    assert kwargs["settings"].language == "tr"