diff --git a/src/pipecat/services/anthropic/llm.py b/src/pipecat/services/anthropic/llm.py
index 67777e049..c0c4ca664 100644
--- a/src/pipecat/services/anthropic/llm.py
+++ b/src/pipecat/services/anthropic/llm.py
@@ -249,43 +249,57 @@ class AnthropicLLMService(LLMService):
             system_instruction: Optional system instruction to use as the system prompt.
             **kwargs: Additional arguments passed to parent LLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "AnthropicLLMSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "AnthropicLLMSettings")
-
-        _params = params or AnthropicLLMService.InputParams()
-
-        # Handle existing enable_prompt_caching_beta deprecation
-        enable_prompt_caching = _params.enable_prompt_caching
-        if _params.enable_prompt_caching_beta is not None:
-            import warnings
-
-            with warnings.catch_warnings():
-                warnings.simplefilter("always")
-                warnings.warn(
-                    "enable_prompt_caching_beta is deprecated. Use enable_prompt_caching instead.",
-                    DeprecationWarning,
-                    stacklevel=2,
-                )
-            if enable_prompt_caching is None:
-                enable_prompt_caching = _params.enable_prompt_caching_beta
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = AnthropicLLMSettings(
-            model=model or "claude-sonnet-4-6",
-            max_tokens=_params.max_tokens,
-            enable_prompt_caching=enable_prompt_caching or False,
-            temperature=_params.temperature,
-            top_k=_params.top_k,
-            top_p=_params.top_p,
+            model="claude-sonnet-4-6",
+            max_tokens=4096,
+            enable_prompt_caching=False,
+            temperature=NOT_GIVEN,
+            top_k=NOT_GIVEN,
+            top_p=NOT_GIVEN,
             frequency_penalty=None,
             presence_penalty=None,
             seed=None,
             filter_incomplete_user_turns=False,
             user_turn_completion_config=None,
-            thinking=_params.thinking,
-            extra=_params.extra if isinstance(_params.extra, dict) else {},
+            thinking=NOT_GIVEN,
+            extra={},
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", AnthropicLLMSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", AnthropicLLMSettings)
+            if not settings:
+                default_settings.max_tokens = params.max_tokens
+                default_settings.temperature = params.temperature
+                default_settings.top_k = params.top_k
+                default_settings.top_p = params.top_p
+                default_settings.thinking = params.thinking
+                if isinstance(params.extra, dict):
+                    default_settings.extra = params.extra
+                # Handle enable_prompt_caching / enable_prompt_caching_beta
+                enable_prompt_caching = params.enable_prompt_caching
+                if params.enable_prompt_caching_beta is not None:
+                    import warnings
+
+                    with warnings.catch_warnings():
+                        warnings.simplefilter("always")
+                        warnings.warn(
+                            "enable_prompt_caching_beta is deprecated. "
+                            "Use enable_prompt_caching instead.",
+                            DeprecationWarning,
+                            stacklevel=2,
+                        )
+                    if enable_prompt_caching is None:
+                        enable_prompt_caching = params.enable_prompt_caching_beta
+                default_settings.enable_prompt_caching = enable_prompt_caching or False
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/assemblyai/stt.py b/src/pipecat/services/assemblyai/stt.py
index 85d4029b7..e140f7543 100644
--- a/src/pipecat/services/assemblyai/stt.py
+++ b/src/pipecat/services/assemblyai/stt.py
@@ -32,7 +32,7 @@ from pipecat.frames.frames import (
     VADUserStoppedSpeakingFrame,
 )
 from pipecat.processors.frame_processor import FrameDirection
-from pipecat.services.settings import NOT_GIVEN, STTSettings, _NotGiven
+from pipecat.services.settings import NOT_GIVEN, STTSettings, _NotGiven, _warn_deprecated_param
 from pipecat.services.stt_latency import ASSEMBLYAI_TTFS_P99
 from pipecat.services.stt_service import WebsocketSTTService
 from pipecat.transcriptions.language import Language
@@ -108,9 +108,9 @@ class AssemblyAISTTService(WebsocketSTTService):
         self,
         *,
         api_key: str,
-        language: Language = Language.EN,  # AssemblyAI only supports English
+        language: Optional[Language] = None,
         api_endpoint_base_url: str = "wss://streaming.assemblyai.com/v3/ws",
-        connection_params: AssemblyAIConnectionParams = AssemblyAIConnectionParams(),
+        connection_params: Optional[AssemblyAIConnectionParams] = None,
         vad_force_turn_endpoint: bool = True,
         should_interrupt: bool = True,
         speaker_format: Optional[str] = None,
@@ -151,20 +151,23 @@ class AssemblyAISTTService(WebsocketSTTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to parent STTService class.
         """
+        # Resolve connection_params early — needed for validation and turn mode config
+        _connection_params = connection_params or AssemblyAIConnectionParams()
+
         # AssemblyAI turn detection mode (vad_force_turn_endpoint=False) requires the
         # SpeechStarted event for reliable barge-in. Only u3-rt-pro supports
         # this. Other models must use Pipecat turn detection.
-        is_u3_pro = connection_params.speech_model == "u3-rt-pro"
+        is_u3_pro = _connection_params.speech_model == "u3-rt-pro"
         if not vad_force_turn_endpoint and not is_u3_pro:
             raise ValueError(
                 f"AssemblyAI turn detection mode (vad_force_turn_endpoint=False) requires "
                 f"u3-rt-pro for SpeechStarted support. Either set "
-                f"vad_force_turn_endpoint=True for {connection_params.speech_model}, "
+                f"vad_force_turn_endpoint=True for {_connection_params.speech_model}, "
                 f"or use speech_model='u3-rt-pro'."
             )
 
         # Validate that prompt and keyterms_prompt are not both set
-        if connection_params.prompt is not None and connection_params.keyterms_prompt is not None:
+        if _connection_params.prompt is not None and _connection_params.keyterms_prompt is not None:
             raise ValueError(
                 "The prompt and keyterms_prompt parameters cannot be used in the same request. "
                 "Please choose either one or the other based on your use case. When you use "
@@ -174,7 +177,7 @@ class AssemblyAISTTService(WebsocketSTTService):
             )
 
         # Warn if user sets a custom prompt (recommend testing without one first)
-        if connection_params.prompt is not None:
+        if _connection_params.prompt is not None:
             logger.warning(
                 "Custom prompt detected. Prompting is a beta feature. We recommend testing "
                 "with no prompt first, as this will use our optimized default prompt for "
@@ -186,18 +189,32 @@ class AssemblyAISTTService(WebsocketSTTService):
         # When vad_force_turn_endpoint is enabled, configure connection params
         # for Pipecat turn detection mode (fast finals for smart turn analyzer)
         if vad_force_turn_endpoint:
-            connection_params = self._configure_pipecat_turn_mode(connection_params, is_u3_pro)
+            _connection_params = self._configure_pipecat_turn_mode(_connection_params, is_u3_pro)
 
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = AssemblyAISTTSettings(
             model=None,
-            language=language,
-            connection_params=connection_params,
+            language=Language.EN,
+            connection_params=AssemblyAIConnectionParams(),
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if language is not None:
+            _warn_deprecated_param("language", AssemblyAISTTSettings, "language")
+            default_settings.language = language
+
+        # 3. Apply connection_params overrides — only if settings not provided
+        if connection_params is not None:
+            _warn_deprecated_param("connection_params", AssemblyAISTTSettings)
+            if not settings:
+                default_settings.connection_params = _connection_params
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
         super().__init__(
-            sample_rate=connection_params.sample_rate,
+            sample_rate=_connection_params.sample_rate,
             ttfs_p99_latency=ttfs_p99_latency,
             settings=default_settings,
             **kwargs,
diff --git a/src/pipecat/services/asyncai/tts.py b/src/pipecat/services/asyncai/tts.py
index b7ddec2e1..ef5c95bfe 100644
--- a/src/pipecat/services/asyncai/tts.py
+++ b/src/pipecat/services/asyncai/tts.py
@@ -10,7 +10,7 @@ import asyncio
 import base64
 import json
 from dataclasses import dataclass, field
-from typing import Any, AsyncGenerator, Mapping, Optional
+from typing import Any, AsyncGenerator, Mapping, Optional, Self
 
 import aiohttp
 from loguru import logger
@@ -88,7 +88,7 @@ class AsyncAITTSSettings(TTSSettings):
     output_sample_rate: int | _NotGiven = field(default_factory=lambda: NOT_GIVEN)
 
     @classmethod
-    def from_mapping(cls, settings: Mapping[str, Any]) -> "AsyncAITTSSettings":
+    def from_mapping(cls, settings: Mapping[str, Any]) -> Self:
         """Construct settings from a plain dict, destructuring legacy nested ``output_format``."""
         flat = dict(settings)
         nested = flat.pop("output_format", None)
@@ -171,25 +171,33 @@ class AsyncAITTSService(AudioContextTTSService):
             text_aggregation_mode: How to aggregate text before synthesis.
             **kwargs: Additional arguments passed to the parent service.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "AsyncAITTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "AsyncAITTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "AsyncAITTSSettings")
-
-        _params = params or AsyncAITTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = AsyncAITTSSettings(
-            model=model or "async_flash_v1.0",
-            voice=voice_id,
+            model="async_flash_v1.0",
+            voice=None,
+            language=None,
             output_container=container,
             output_encoding=encoding,
             output_sample_rate=0,
-            language=self.language_to_service_language(_params.language)
-            if _params.language
-            else None,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", AsyncAITTSSettings, "voice")
+            default_settings.voice = voice_id
+        if model is not None:
+            _warn_deprecated_param("model", AsyncAITTSSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", AsyncAITTSSettings)
+            if not settings:
+                default_settings.language = (
+                    self.language_to_service_language(params.language) if params.language else None
+                )
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -554,25 +562,33 @@ class AsyncAIHttpTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to the parent TTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "AsyncAITTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "AsyncAITTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "AsyncAITTSSettings")
-
-        _params = params or AsyncAIHttpTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = AsyncAITTSSettings(
-            model=model or "async_flash_v1.0",
-            voice=voice_id,
+            model="async_flash_v1.0",
+            voice=None,
+            language=None,
             output_container=container,
             output_encoding=encoding,
             output_sample_rate=0,
-            language=self.language_to_service_language(_params.language)
-            if _params.language
-            else None,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", AsyncAITTSSettings, "voice")
+            default_settings.voice = voice_id
+        if model is not None:
+            _warn_deprecated_param("model", AsyncAITTSSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", AsyncAITTSSettings)
+            if not settings:
+                default_settings.language = (
+                    self.language_to_service_language(params.language) if params.language else None
+                )
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/aws/llm.py b/src/pipecat/services/aws/llm.py
index e244a78ac..205d02f1f 100644
--- a/src/pipecat/services/aws/llm.py
+++ b/src/pipecat/services/aws/llm.py
@@ -816,37 +816,53 @@ class AWSBedrockLLMService(LLMService):
             system_instruction: Optional system instruction to use as the system prompt.
             **kwargs: Additional arguments passed to parent LLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "AWSBedrockLLMSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "AWSBedrockLLMSettings")
-
-        _params = params or AWSBedrockLLMService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = AWSBedrockLLMSettings(
-            model=model or "us.amazon.nova-lite-v1:0",
-            max_tokens=_params.max_tokens,
-            temperature=_params.temperature,
-            top_p=_params.top_p,
+            model="us.amazon.nova-lite-v1:0",
+            max_tokens=None,
+            temperature=None,
+            top_p=None,
             top_k=None,
             frequency_penalty=None,
             presence_penalty=None,
             seed=None,
             filter_incomplete_user_turns=False,
             user_turn_completion_config=None,
-            latency=_params.latency,
-            additional_model_request_fields=_params.additional_model_request_fields
-            if isinstance(_params.additional_model_request_fields, dict)
-            else {},
+            latency=None,
+            additional_model_request_fields={},
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", AWSBedrockLLMSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", AWSBedrockLLMSettings)
+            if not settings:
+                default_settings.max_tokens = params.max_tokens
+                default_settings.temperature = params.temperature
+                default_settings.top_p = params.top_p
+                default_settings.latency = params.latency
+                if isinstance(params.additional_model_request_fields, dict):
+                    default_settings.additional_model_request_fields = (
+                        params.additional_model_request_fields
+                    )
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
         super().__init__(settings=default_settings, **kwargs)
 
-        self._stop_sequences = (
-            stop_sequences if stop_sequences is not None else (_params.stop_sequences or [])
-        )
+        # Handle stop_sequences (not a settings field)
+        if stop_sequences is not None:
+            self._stop_sequences = stop_sequences
+        elif params is not None:
+            self._stop_sequences = params.stop_sequences or []
+        else:
+            self._stop_sequences = []
 
         # Initialize the AWS Bedrock client
         if not client_config:
diff --git a/src/pipecat/services/aws/nova_sonic/llm.py b/src/pipecat/services/aws/nova_sonic/llm.py
index 887c3f46c..7fec1c73c 100644
--- a/src/pipecat/services/aws/nova_sonic/llm.py
+++ b/src/pipecat/services/aws/nova_sonic/llm.py
@@ -270,30 +270,40 @@ class AWSNovaSonicLLMService(LLMService):
 
             **kwargs: Additional arguments passed to the parent LLMService.
         """
-        # Check for deprecated parameter usage
-        if model != "amazon.nova-2-sonic-v1:0":
-            _warn_deprecated_param("model", "AWSNovaSonicLLMSettings", "model")
-        if voice_id != "matthew":
-            _warn_deprecated_param("voice_id", "AWSNovaSonicLLMSettings", "voice_id")
-        if params is not None:
-            _warn_deprecated_param("params", "AWSNovaSonicLLMSettings")
-
-        _params = params or Params()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = AWSNovaSonicLLMSettings(
-            model=model,
-            voice_id=voice_id,
-            temperature=_params.temperature,
-            max_tokens=_params.max_tokens,
-            top_p=_params.top_p,
+            model="amazon.nova-2-sonic-v1:0",
+            voice_id="matthew",
+            temperature=0.7,
+            max_tokens=1024,
+            top_p=0.9,
             top_k=None,
             frequency_penalty=None,
             presence_penalty=None,
             seed=None,
             filter_incomplete_user_turns=False,
             user_turn_completion_config=None,
-            endpointing_sensitivity=_params.endpointing_sensitivity,
+            endpointing_sensitivity=None,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model != "amazon.nova-2-sonic-v1:0":
+            _warn_deprecated_param("model", AWSNovaSonicLLMSettings, "model")
+            default_settings.model = model
+        if voice_id != "matthew":
+            _warn_deprecated_param("voice_id", AWSNovaSonicLLMSettings, "voice_id")
+            default_settings.voice_id = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", AWSNovaSonicLLMSettings)
+            if not settings:
+                default_settings.temperature = params.temperature
+                default_settings.max_tokens = params.max_tokens
+                default_settings.top_p = params.top_p
+                default_settings.endpointing_sensitivity = params.endpointing_sensitivity
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -308,12 +318,13 @@ class AWSNovaSonicLLMService(LLMService):
         self._client: Optional[BedrockRuntimeClient] = None
 
         # Audio I/O config (hardware settings, not runtime-tunable)
-        self._input_sample_rate = _params.input_sample_rate
-        self._input_sample_size = _params.input_sample_size
-        self._input_channel_count = _params.input_channel_count
-        self._output_sample_rate = _params.output_sample_rate
-        self._output_sample_size = _params.output_sample_size
-        self._output_channel_count = _params.output_channel_count
+        _audio_params = params or Params()
+        self._input_sample_rate = _audio_params.input_sample_rate
+        self._input_sample_size = _audio_params.input_sample_size
+        self._input_channel_count = _audio_params.input_channel_count
+        self._output_sample_rate = _audio_params.output_sample_rate
+        self._output_sample_size = _audio_params.output_sample_size
+        self._output_channel_count = _audio_params.output_channel_count
         self._system_instruction = system_instruction
         self._tools = tools
 
diff --git a/src/pipecat/services/aws/stt.py b/src/pipecat/services/aws/stt.py
index 061b17889..950624fbf 100644
--- a/src/pipecat/services/aws/stt.py
+++ b/src/pipecat/services/aws/stt.py
@@ -110,22 +110,27 @@ class AWSTranscribeSTTService(WebsocketSTTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to parent STTService class.
         """
-        if sample_rate is not None:
-            _warn_deprecated_param("sample_rate", "AWSTranscribeSTTSettings", "sample_rate")
-        if language is not None:
-            _warn_deprecated_param("language", "AWSTranscribeSTTSettings", "language")
-
-        _sample_rate = sample_rate or 16000
-        _language = language or Language.EN
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = AWSTranscribeSTTSettings(
-            language=self.language_to_service_language(_language) or "en-US",
-            sample_rate=_sample_rate,
+            language=self.language_to_service_language(Language.EN) or "en-US",
+            sample_rate=16000,
             media_encoding="linear16",
             number_of_channels=1,
             show_speaker_label=False,
             enable_channel_identification=False,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if sample_rate is not None:
+            _warn_deprecated_param("sample_rate", AWSTranscribeSTTSettings, "sample_rate")
+            default_settings.sample_rate = sample_rate
+        if language is not None:
+            _warn_deprecated_param("language", AWSTranscribeSTTSettings, "language")
+            default_settings.language = self.language_to_service_language(language) or "en-US"
+
+        # 3. No params to apply
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -136,9 +141,9 @@ class AWSTranscribeSTTService(WebsocketSTTService):
         )
 
         # Validate sample rate - AWS Transcribe only supports 8000 Hz or 16000 Hz
-        if _sample_rate not in [8000, 16000]:
+        if default_settings.sample_rate not in [8000, 16000]:
             logger.warning(
-                f"AWS Transcribe only supports 8000 Hz or 16000 Hz sample rates. Converting from {_sample_rate} Hz to 16000 Hz."
+                f"AWS Transcribe only supports 8000 Hz or 16000 Hz sample rates. Converting from {default_settings.sample_rate} Hz to 16000 Hz."
             )
             self._settings.sample_rate = 16000
 
diff --git a/src/pipecat/services/aws/tts.py b/src/pipecat/services/aws/tts.py
index 83ef4125c..f248db27a 100644
--- a/src/pipecat/services/aws/tts.py
+++ b/src/pipecat/services/aws/tts.py
@@ -209,25 +209,39 @@ class AWSPollyTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent TTSService class.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "AWSPollyTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "AWSPollyTTSSettings")
-
-        _params = params or AWSPollyTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = AWSPollyTTSSettings(
             model=None,
-            voice=voice_id or "Joanna",
-            engine=_params.engine,
-            language=self.language_to_service_language(_params.language)
-            if _params.language
-            else "en-US",
-            pitch=_params.pitch,
-            rate=_params.rate,
-            volume=_params.volume,
-            lexicon_names=_params.lexicon_names,
+            voice="Joanna",
+            language="en-US",
+            engine=None,
+            pitch=None,
+            rate=None,
+            volume=None,
+            lexicon_names=None,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", AWSPollyTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", AWSPollyTTSSettings)
+            if not settings:
+                default_settings.engine = params.engine
+                default_settings.language = (
+                    self.language_to_service_language(params.language)
+                    if params.language
+                    else "en-US"
+                )
+                default_settings.pitch = params.pitch
+                default_settings.rate = params.rate
+                default_settings.volume = params.volume
+                default_settings.lexicon_names = params.lexicon_names
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/azure/image.py b/src/pipecat/services/azure/image.py
index 9f5d48c33..ca58644f2 100644
--- a/src/pipecat/services/azure/image.py
+++ b/src/pipecat/services/azure/image.py
@@ -68,7 +68,7 @@ class AzureImageGenServiceREST(ImageGenService):
                 parameters, ``settings`` values take precedence.
         """
         if model is not None:
-            _warn_deprecated_param("model", "AzureImageGenSettings", "model")
+            _warn_deprecated_param("model", AzureImageGenSettings, "model")
 
         default_settings = AzureImageGenSettings(model=model)
         if settings is not None:
diff --git a/src/pipecat/services/azure/llm.py b/src/pipecat/services/azure/llm.py
index 3c28e190e..734a0bacf 100644
--- a/src/pipecat/services/azure/llm.py
+++ b/src/pipecat/services/azure/llm.py
@@ -48,10 +48,15 @@ class AzureLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="gpt-4o")
 
-        default_settings = OpenAILLMSettings(model=model or "gpt-4o")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/azure/stt.py b/src/pipecat/services/azure/stt.py
index 02a7ca8ed..66f871ad3 100644
--- a/src/pipecat/services/azure/stt.py
+++ b/src/pipecat/services/azure/stt.py
@@ -107,15 +107,22 @@ class AzureSTTService(STTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to parent STTService.
         """
-        if language != Language.EN_US:
-            _warn_deprecated_param("language", "AzureSTTSettings", "language")
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = AzureSTTSettings(
             model=None,
             region=region,
-            language=language_to_azure_language(language) if language else None,
+            language=language_to_azure_language(Language.EN_US),
             sample_rate=sample_rate,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if language is not None and language != Language.EN_US:
+            _warn_deprecated_param("language", AzureSTTSettings, "language")
+            default_settings.language = language_to_azure_language(language)
+
+        # 3. No params to apply
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/azure/tts.py b/src/pipecat/services/azure/tts.py
index 7e5791f03..3a67cb2ff 100644
--- a/src/pipecat/services/azure/tts.py
+++ b/src/pipecat/services/azure/tts.py
@@ -290,27 +290,43 @@ class AzureTTSService(TTSService, AzureBaseTTSService):
             text_aggregation_mode: How to aggregate text before synthesis.
             **kwargs: Additional arguments passed to parent WordTTSService.
         """
-        if voice is not None:
-            _warn_deprecated_param("voice", "AzureTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "AzureTTSSettings")
-
-        _params = params or AzureBaseTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = AzureTTSSettings(
             model=None,
-            emphasis=_params.emphasis,
-            language=self.language_to_service_language(_params.language)
-            if _params.language
-            else "en-US",
-            pitch=_params.pitch,
-            rate=_params.rate,
-            role=_params.role,
-            style=_params.style,
-            style_degree=_params.style_degree,
-            voice=voice or "en-US-SaraNeural",
-            volume=_params.volume,
+            voice="en-US-SaraNeural",
+            language="en-US",
+            emphasis=None,
+            pitch=None,
+            rate=None,
+            role=None,
+            style=None,
+            style_degree=None,
+            volume=None,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice is not None:
+            _warn_deprecated_param("voice", AzureTTSSettings, "voice")
+            default_settings.voice = voice
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", AzureTTSSettings)
+            if not settings:
+                default_settings.emphasis = params.emphasis
+                default_settings.language = (
+                    self.language_to_service_language(params.language)
+                    if params.language
+                    else "en-US"
+                )
+                default_settings.pitch = params.pitch
+                default_settings.rate = params.rate
+                default_settings.role = params.role
+                default_settings.style = params.style
+                default_settings.style_degree = params.style_degree
+                default_settings.volume = params.volume
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -779,27 +795,43 @@ class AzureHttpTTSService(TTSService, AzureBaseTTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent TTSService.
         """
-        if voice is not None:
-            _warn_deprecated_param("voice", "AzureTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "AzureTTSSettings")
-
-        _params = params or AzureBaseTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = AzureTTSSettings(
             model=None,
-            emphasis=_params.emphasis,
-            language=self.language_to_service_language(_params.language)
-            if _params.language
-            else "en-US",
-            pitch=_params.pitch,
-            rate=_params.rate,
-            role=_params.role,
-            style=_params.style,
-            style_degree=_params.style_degree,
-            voice=voice or "en-US-SaraNeural",
-            volume=_params.volume,
+            voice="en-US-SaraNeural",
+            language="en-US",
+            emphasis=None,
+            pitch=None,
+            rate=None,
+            role=None,
+            style=None,
+            style_degree=None,
+            volume=None,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice is not None:
+            _warn_deprecated_param("voice", AzureTTSSettings, "voice")
+            default_settings.voice = voice
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", AzureTTSSettings)
+            if not settings:
+                default_settings.emphasis = params.emphasis
+                default_settings.language = (
+                    self.language_to_service_language(params.language)
+                    if params.language
+                    else "en-US"
+                )
+                default_settings.pitch = params.pitch
+                default_settings.rate = params.rate
+                default_settings.role = params.role
+                default_settings.style = params.style
+                default_settings.style_degree = params.style_degree
+                default_settings.volume = params.volume
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/camb/tts.py b/src/pipecat/services/camb/tts.py
index de8b16ab8..9a1b753a6 100644
--- a/src/pipecat/services/camb/tts.py
+++ b/src/pipecat/services/camb/tts.py
@@ -230,34 +230,45 @@ class CambTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent TTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "CambTTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "CambTTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "CambTTSSettings")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = CambTTSSettings(
+            model="mars-flash",
+            voice=147320,
+            language="en-us",
+            user_instructions=None,
+        )
 
-        _params = params or CambTTSService.InputParams()
-        _model = model or "mars-flash"
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", CambTTSSettings, "model")
+            default_settings.model = model
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", CambTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", CambTTSSettings)
+            if not settings:
+                if params.language is not None:
+                    default_settings.language = (
+                        self.language_to_service_language(params.language) or "en-us"
+                    )
+                if params.user_instructions is not None:
+                    default_settings.user_instructions = params.user_instructions
+
+        # 4. Apply settings delta (canonical API, always wins)
+        if settings is not None:
+            default_settings.apply_update(settings)
 
         # Warn if sample rate doesn't match model's supported rate
+        _model = default_settings.model
         if sample_rate and sample_rate != MODEL_SAMPLE_RATES.get(_model):
             logger.warning(
                 f"Camb.ai's {_model} model only supports {MODEL_SAMPLE_RATES.get(_model)}Hz "
                 f"sample rate. Current rate of {sample_rate}Hz may cause issues."
             )
 
-        default_settings = CambTTSSettings(
-            model=_model,
-            voice=voice_id or 147320,
-            language=(
-                self.language_to_service_language(_params.language) if _params.language else "en-us"
-            ),
-            user_instructions=_params.user_instructions,
-        )
-        if settings is not None:
-            default_settings.apply_update(settings)
-
         super().__init__(
             sample_rate=sample_rate,
             settings=default_settings,
diff --git a/src/pipecat/services/cartesia/stt.py b/src/pipecat/services/cartesia/stt.py
index 530f6a4d1..aa66b102e 100644
--- a/src/pipecat/services/cartesia/stt.py
+++ b/src/pipecat/services/cartesia/stt.py
@@ -28,7 +28,7 @@ from pipecat.frames.frames import (
     VADUserStoppedSpeakingFrame,
 )
 from pipecat.processors.frame_processor import FrameDirection
-from pipecat.services.settings import NOT_GIVEN, STTSettings, _NotGiven
+from pipecat.services.settings import NOT_GIVEN, STTSettings, _NotGiven, _warn_deprecated_param
 from pipecat.services.stt_latency import CARTESIA_TTFS_P99
 from pipecat.services.stt_service import WebsocketSTTService
 from pipecat.transcriptions.language import Language
@@ -177,26 +177,34 @@ class CartesiaSTTService(WebsocketSTTService):
         """
         sample_rate = sample_rate or (live_options.sample_rate if live_options else None)
 
-        default_options = CartesiaLiveOptions(
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = CartesiaSTTSettings(
             model="ink-whisper",
             language=Language.EN.value,
             encoding="pcm_s16le",
-            sample_rate=sample_rate,
         )
 
-        merged_options = default_options.to_dict()
-        if live_options:
-            merged_options.update(live_options.to_dict())
-            # Filter out "None" string values
-            merged_options = {
-                k: v for k, v in merged_options.items() if not isinstance(v, str) or v != "None"
-            }
+        # 2. (no deprecated direct args for this service)
 
-        default_settings = CartesiaSTTSettings(
-            model=merged_options["model"],
-            language=merged_options.get("language"),
-            encoding=merged_options.get("encoding", "pcm_s16le"),
-        )
+        # 3. Apply live_options overrides — only if settings not provided
+        if live_options is not None:
+            _warn_deprecated_param("live_options", CartesiaSTTSettings)
+            if not settings:
+                lo_dict = live_options.to_dict()
+                # Filter out "None" string values
+                lo_dict = {
+                    k: v
+                    for k, v in lo_dict.items()
+                    if (not isinstance(v, str) or v != "None") and k != "sample_rate"
+                }
+                if "model" in lo_dict:
+                    default_settings.model = lo_dict["model"]
+                if "language" in lo_dict:
+                    default_settings.language = lo_dict["language"]
+                if "encoding" in lo_dict:
+                    default_settings.encoding = lo_dict["encoding"]
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/cartesia/tts.py b/src/pipecat/services/cartesia/tts.py
index 82f3b7d73..6930026f3 100644
--- a/src/pipecat/services/cartesia/tts.py
+++ b/src/pipecat/services/cartesia/tts.py
@@ -11,7 +11,7 @@ import json
 import warnings
 from dataclasses import dataclass, field
 from enum import Enum
-from typing import Any, AsyncGenerator, List, Literal, Mapping, Optional
+from typing import Any, AsyncGenerator, List, Literal, Mapping, Optional, Self
 
 from loguru import logger
 from pydantic import BaseModel, Field
@@ -216,7 +216,7 @@ class CartesiaTTSSettings(TTSSettings):
     pronunciation_dict_id: str | _NotGiven = field(default_factory=lambda: NOT_GIVEN)
 
     @classmethod
-    def from_mapping(cls, settings: Mapping[str, Any]) -> "CartesiaTTSSettings":
+    def from_mapping(cls, settings: Mapping[str, Any]) -> Self:
         """Construct settings from a plain dict, destructuring legacy nested ``output_format``."""
         flat = dict(settings)
         nested = flat.pop("output_format", None)
@@ -316,13 +316,6 @@ class CartesiaTTSService(AudioContextTTSService):
 
             **kwargs: Additional arguments passed to the parent service.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "CartesiaTTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "CartesiaTTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "CartesiaTTSSettings")
-
         # By default, we aggregate sentences before sending to TTS. This adds
         # ~200-300ms of latency per sentence (waiting for the sentence-ending
         # punctuation token from the LLM). Setting
@@ -336,22 +329,39 @@ class CartesiaTTSService(AudioContextTTSService):
         # if we're interrupted. Cartesia gives us word-by-word timestamps. We
         # can use those to generate text frames ourselves aligned with the
         # playout timing of the audio!
-        _params = params or CartesiaTTSService.InputParams()
 
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = CartesiaTTSSettings(
-            model=model or "sonic-3",
-            voice=voice_id,
+            model="sonic-3",
             output_container=container,
             output_encoding=encoding,
             output_sample_rate=0,
-            language=(
-                self.language_to_service_language(_params.language) if _params.language else None
-            ),
-            speed=_params.speed,
-            emotion=_params.emotion,
-            generation_config=_params.generation_config,
-            pronunciation_dict_id=_params.pronunciation_dict_id,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", CartesiaTTSSettings, "voice")
+            default_settings.voice = voice_id
+        if model is not None:
+            _warn_deprecated_param("model", CartesiaTTSSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", CartesiaTTSSettings)
+            if not settings:
+                if params.language is not None:
+                    default_settings.language = self.language_to_service_language(params.language)
+                if params.speed is not None:
+                    default_settings.speed = params.speed
+                if params.emotion is not None:
+                    default_settings.emotion = params.emotion
+                if params.generation_config is not None:
+                    default_settings.generation_config = params.generation_config
+                if params.pronunciation_dict_id is not None:
+                    default_settings.pronunciation_dict_id = params.pronunciation_dict_id
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -782,29 +792,38 @@ class CartesiaHttpTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to the parent TTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "CartesiaTTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "CartesiaTTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "CartesiaTTSSettings")
-
-        _params = params or CartesiaHttpTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = CartesiaTTSSettings(
-            model=model or "sonic-3",
-            voice=voice_id,
+            model="sonic-3",
             output_container=container,
             output_encoding=encoding,
             output_sample_rate=0,
-            language=(
-                self.language_to_service_language(_params.language) if _params.language else None
-            ),
-            speed=_params.speed,
-            emotion=_params.emotion,
-            generation_config=_params.generation_config,
-            pronunciation_dict_id=_params.pronunciation_dict_id,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", CartesiaTTSSettings, "voice")
+            default_settings.voice = voice_id
+        if model is not None:
+            _warn_deprecated_param("model", CartesiaTTSSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", CartesiaTTSSettings)
+            if not settings:
+                if params.language is not None:
+                    default_settings.language = self.language_to_service_language(params.language)
+                if params.speed is not None:
+                    default_settings.speed = params.speed
+                if params.emotion is not None:
+                    default_settings.emotion = params.emotion
+                if params.generation_config is not None:
+                    default_settings.generation_config = params.generation_config
+                if params.pronunciation_dict_id is not None:
+                    default_settings.pronunciation_dict_id = params.pronunciation_dict_id
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/cerebras/llm.py b/src/pipecat/services/cerebras/llm.py
index 053594083..98fbfe0e3 100644
--- a/src/pipecat/services/cerebras/llm.py
+++ b/src/pipecat/services/cerebras/llm.py
@@ -46,10 +46,15 @@ class CerebrasLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="gpt-oss-120b")
 
-        default_settings = OpenAILLMSettings(model=model or "gpt-oss-120b")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/deepgram/flux/stt.py b/src/pipecat/services/deepgram/flux/stt.py
index 04c2f1da3..8ddd2ef0d 100644
--- a/src/pipecat/services/deepgram/flux/stt.py
+++ b/src/pipecat/services/deepgram/flux/stt.py
@@ -206,10 +206,6 @@ class DeepgramFluxSTTService(WebsocketSTTService):
                     ),
                 )
         """
-        if model is not None:
-            _warn_deprecated_param("model", "DeepgramFluxSTTSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "DeepgramFluxSTTSettings")
         # Note: For DeepgramFluxSTTService, differently from other processes, we need to create
         # the _receive_task inside _connect_websocket, because the websocket should only be
         # considered connected and ready to send audio once we receive from Flux the message
@@ -220,20 +216,39 @@ class DeepgramFluxSTTService(WebsocketSTTService):
         # was never destroyed.
         # So we can keep it here as false, because inside the method send_with_retry, it will
         # already try to reconnect if needed.
-        _params = params or DeepgramFluxSTTService.InputParams()
 
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = DeepgramFluxSTTSettings(
-            model=model or "flux-general-en",
+            model="flux-general-en",
             language=Language.EN,
             encoding=flux_encoding,
-            eager_eot_threshold=_params.eager_eot_threshold,
-            eot_threshold=_params.eot_threshold,
-            eot_timeout_ms=_params.eot_timeout_ms,
-            keyterm=_params.keyterm or [],
-            mip_opt_out=_params.mip_opt_out,
-            tag=_params.tag or [],
-            min_confidence=_params.min_confidence,
+            eager_eot_threshold=None,
+            eot_threshold=None,
+            eot_timeout_ms=None,
+            keyterm=[],
+            mip_opt_out=None,
+            tag=[],
+            min_confidence=None,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", DeepgramFluxSTTSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", DeepgramFluxSTTSettings)
+            if not settings:
+                default_settings.eager_eot_threshold = params.eager_eot_threshold
+                default_settings.eot_threshold = params.eot_threshold
+                default_settings.eot_timeout_ms = params.eot_timeout_ms
+                default_settings.keyterm = params.keyterm or []
+                default_settings.mip_opt_out = params.mip_opt_out
+                default_settings.tag = params.tag or []
+                default_settings.min_confidence = params.min_confidence
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/deepgram/sagemaker/stt.py b/src/pipecat/services/deepgram/sagemaker/stt.py
index 6d813157d..d7a867e38 100644
--- a/src/pipecat/services/deepgram/sagemaker/stt.py
+++ b/src/pipecat/services/deepgram/sagemaker/stt.py
@@ -14,7 +14,7 @@ languages, and various Deepgram features.
 
 import asyncio
 import json
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 from typing import Any, AsyncGenerator, Optional
 
 from loguru import logger
@@ -32,8 +32,7 @@ from pipecat.frames.frames import (
 )
 from pipecat.processors.frame_processor import FrameDirection
 from pipecat.services.aws.sagemaker.bidi_client import SageMakerBidiClient
-from pipecat.services.deepgram.stt import DeepgramSTTSettings
-from pipecat.services.settings import STTSettings
+from pipecat.services.settings import NOT_GIVEN, STTSettings, _NotGiven, _warn_deprecated_param
 from pipecat.services.stt_latency import DEEPGRAM_SAGEMAKER_TTFS_P99
 from pipecat.services.stt_service import STTService
 from pipecat.transcriptions.language import Language
@@ -51,13 +50,14 @@ except ModuleNotFoundError as e:
 
 
 @dataclass
-class DeepgramSageMakerSTTSettings(_DeepgramSTTSettingsBase):
+class DeepgramSageMakerSTTSettings(STTSettings):
     """Settings for the Deepgram SageMaker STT service.
 
-    See ``_DeepgramSTTSettingsBase`` for full documentation.
+    Parameters:
+        live_options: Deepgram LiveOptions for the SageMaker connection.
     """
 
-    pass
+    live_options: Any | _NotGiven = field(default_factory=lambda: NOT_GIVEN)
 
 
 class DeepgramSageMakerSTTService(STTService):
@@ -130,13 +130,29 @@ class DeepgramSageMakerSTTService(STTService):
             punctuate=True,
         )
 
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = DeepgramSageMakerSTTSettings(
-            model=default_options.model,
-            language=default_options.language,
+            model="nova-3",
+            language=Language.EN,
             live_options=default_options,
         )
-        if live_options:
-            default_settings._merge_live_options_delta(live_options)
+
+        # 2. (no deprecated direct args like model= for this service)
+
+        # 3. Apply live_options overrides — only if settings not provided
+        if live_options is not None:
+            _warn_deprecated_param("live_options", DeepgramSageMakerSTTSettings)
+            if not settings:
+                # Merge user live_options onto defaults
+                merged_dict = {**default_options.to_dict(), **live_options.to_dict()}
+                merged_live_options = LiveOptions(**merged_dict)
+                default_settings.live_options = merged_live_options
+                if hasattr(live_options, "model") and live_options.model is not None:
+                    default_settings.model = live_options.model
+                if hasattr(live_options, "language") and live_options.language is not None:
+                    default_settings.language = live_options.language
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/deepgram/sagemaker/tts.py b/src/pipecat/services/deepgram/sagemaker/tts.py
index 8d03f6eac..62cd25188 100644
--- a/src/pipecat/services/deepgram/sagemaker/tts.py
+++ b/src/pipecat/services/deepgram/sagemaker/tts.py
@@ -102,7 +102,7 @@ class DeepgramSageMakerTTSService(TTSService):
             **kwargs: Additional arguments passed to the parent TTSService.
         """
         if voice is not None:
-            _warn_deprecated_param("voice", "DeepgramSageMakerTTSSettings", "voice")
+            _warn_deprecated_param("voice", DeepgramSageMakerTTSSettings, "voice")
 
         voice = voice or "aura-2-helena-en"
 
diff --git a/src/pipecat/services/deepgram/stt.py b/src/pipecat/services/deepgram/stt.py
index fe3add7cf..f311567aa 100644
--- a/src/pipecat/services/deepgram/stt.py
+++ b/src/pipecat/services/deepgram/stt.py
@@ -25,7 +25,14 @@ from pipecat.frames.frames import (
     VADUserStoppedSpeakingFrame,
 )
 from pipecat.processors.frame_processor import FrameDirection
-from pipecat.services.settings import _S, NOT_GIVEN, STTSettings, _NotGiven, is_given
+from pipecat.services.settings import (
+    _S,
+    NOT_GIVEN,
+    STTSettings,
+    _NotGiven,
+    _warn_deprecated_param,
+    is_given,
+)
 from pipecat.services.stt_latency import DEEPGRAM_TTFS_P99
 from pipecat.services.stt_service import STTService
 from pipecat.transcriptions.language import Language
@@ -303,6 +310,7 @@ class DeepgramSTTService(STTService):
                 )
             base_url = url
 
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = DeepgramSTTSettings(
             model="nova-3-general",
             language=Language.EN,
@@ -317,13 +325,19 @@ class DeepgramSTTService(STTService):
             endpointing=None,
         )
 
-        if live_options:
-            lo_dict = live_options.to_dict()
-            delta = DeepgramSTTSettings.from_mapping(
-                {k: v for k, v in lo_dict.items() if k != "sample_rate"}
-            )
-            default_settings.apply_update(delta)
+        # 2. (no deprecated direct args like model= for this service)
 
+        # 3. Apply live_options overrides — only if settings not provided
+        if live_options is not None:
+            _warn_deprecated_param("live_options", DeepgramSTTSettings)
+            if not settings:
+                lo_dict = live_options.to_dict()
+                delta = DeepgramSTTSettings.from_mapping(
+                    {k: v for k, v in lo_dict.items() if k != "sample_rate"}
+                )
+                default_settings.apply_update(delta)
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/deepgram/tts.py b/src/pipecat/services/deepgram/tts.py
index 7c391490d..98a615f9b 100644
--- a/src/pipecat/services/deepgram/tts.py
+++ b/src/pipecat/services/deepgram/tts.py
@@ -98,20 +98,26 @@ class DeepgramTTSService(WebsocketTTSService):
         Raises:
             ValueError: If encoding is not in SUPPORTED_ENCODINGS.
         """
-        if voice is not None:
-            _warn_deprecated_param("voice", "DeepgramTTSSettings", "voice")
-
         if encoding.lower() not in self.SUPPORTED_ENCODINGS:
             raise ValueError(
                 f"Unsupported encoding '{encoding}'. Must be one of {', '.join(self.SUPPORTED_ENCODINGS)} for WebSocket TTS."
             )
 
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = DeepgramTTSSettings(
-            model=voice or "aura-2-helena-en",
-            voice=voice or "aura-2-helena-en",
+            model="aura-2-helena-en",
+            voice="aura-2-helena-en",
             language=None,
             encoding=encoding,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice is not None:
+            _warn_deprecated_param("voice", DeepgramTTSSettings, "voice")
+            default_settings.model = voice
+            default_settings.voice = voice
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -414,15 +420,21 @@ class DeepgramHttpTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent TTSService class.
         """
-        if voice is not None:
-            _warn_deprecated_param("voice", "DeepgramTTSSettings", "voice")
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = DeepgramTTSSettings(
-            model=voice or "aura-2-helena-en",
-            voice=voice or "aura-2-helena-en",
+            model="aura-2-helena-en",
+            voice="aura-2-helena-en",
             language=None,
             encoding=encoding,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice is not None:
+            _warn_deprecated_param("voice", DeepgramTTSSettings, "voice")
+            default_settings.model = voice
+            default_settings.voice = voice
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/deepseek/llm.py b/src/pipecat/services/deepseek/llm.py
index 8cc9ac56e..c383f5609 100644
--- a/src/pipecat/services/deepseek/llm.py
+++ b/src/pipecat/services/deepseek/llm.py
@@ -46,10 +46,15 @@ class DeepSeekLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="deepseek-chat")
 
-        default_settings = OpenAILLMSettings(model=model or "deepseek-chat")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/elevenlabs/stt.py b/src/pipecat/services/elevenlabs/stt.py
index 1eebcffde..d93f95332 100644
--- a/src/pipecat/services/elevenlabs/stt.py
+++ b/src/pipecat/services/elevenlabs/stt.py
@@ -275,20 +275,29 @@ class ElevenLabsSTTService(SegmentedSTTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to SegmentedSTTService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "ElevenLabsSTTSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "ElevenLabsSTTSettings")
-
-        _params = params or ElevenLabsSTTService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = ElevenLabsSTTSettings(
-            model=model or "scribe_v2",
-            language=self.language_to_service_language(_params.language)
-            if _params.language
-            else "eng",
-            tag_audio_events=_params.tag_audio_events,
+            model="scribe_v2",
+            language="eng",
+            tag_audio_events=True,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", ElevenLabsSTTSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", ElevenLabsSTTSettings)
+            if not settings:
+                if params.language is not None:
+                    default_settings.language = (
+                        self.language_to_service_language(params.language) or "eng"
+                    )
+                default_settings.tag_audio_events = params.tag_audio_events
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -515,25 +524,40 @@ class ElevenLabsRealtimeSTTService(WebsocketSTTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to WebsocketSTTService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "ElevenLabsRealtimeSTTSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "ElevenLabsRealtimeSTTSettings")
-
-        _params = params or ElevenLabsRealtimeSTTService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = ElevenLabsRealtimeSTTSettings(
-            model=model or "scribe_v2_realtime",
-            language=_params.language_code,
-            commit_strategy=_params.commit_strategy,
-            vad_silence_threshold_secs=_params.vad_silence_threshold_secs,
-            vad_threshold=_params.vad_threshold,
-            min_speech_duration_ms=_params.min_speech_duration_ms,
-            min_silence_duration_ms=_params.min_silence_duration_ms,
-            include_timestamps=_params.include_timestamps,
-            enable_logging=_params.enable_logging,
-            include_language_detection=_params.include_language_detection,
+            model="scribe_v2_realtime",
+            language=None,
+            commit_strategy=CommitStrategy.MANUAL,
+            vad_silence_threshold_secs=None,
+            vad_threshold=None,
+            min_speech_duration_ms=None,
+            min_silence_duration_ms=None,
+            include_timestamps=False,
+            enable_logging=False,
+            include_language_detection=False,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", ElevenLabsRealtimeSTTSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", ElevenLabsRealtimeSTTSettings)
+            if not settings:
+                default_settings.language = params.language_code
+                default_settings.commit_strategy = params.commit_strategy
+                default_settings.vad_silence_threshold_secs = params.vad_silence_threshold_secs
+                default_settings.vad_threshold = params.vad_threshold
+                default_settings.min_speech_duration_ms = params.min_speech_duration_ms
+                default_settings.min_silence_duration_ms = params.min_silence_duration_ms
+                default_settings.include_timestamps = params.include_timestamps
+                default_settings.enable_logging = params.enable_logging
+                default_settings.include_language_detection = params.include_language_detection
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/elevenlabs/tts.py b/src/pipecat/services/elevenlabs/tts.py
index 15c2dbb2e..3cec12431 100644
--- a/src/pipecat/services/elevenlabs/tts.py
+++ b/src/pipecat/services/elevenlabs/tts.py
@@ -408,13 +408,6 @@ class ElevenLabsTTSService(AudioContextTTSService):
 
             **kwargs: Additional arguments passed to the parent service.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "ElevenLabsTTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "ElevenLabsTTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "ElevenLabsTTSSettings")
-
         # By default, we aggregate sentences before sending to TTS. This adds
         # ~200-300ms of latency per sentence (waiting for the sentence-ending
         # punctuation token from the LLM). Setting
@@ -431,24 +424,49 @@ class ElevenLabsTTSService(AudioContextTTSService):
         # Finally, ElevenLabs doesn't provide information on when the bot stops
         # speaking for a while, so we want the parent class to send TTSStopFrame
         # after a short period not receiving any audio.
-        _params = params or ElevenLabsTTSService.InputParams()
 
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = ElevenLabsTTSSettings(
-            model=model or "eleven_turbo_v2_5",
-            voice=voice_id,
-            language=(
-                self.language_to_service_language(_params.language) if _params.language else None
-            ),
-            stability=_params.stability,
-            similarity_boost=_params.similarity_boost,
-            style=_params.style,
-            use_speaker_boost=_params.use_speaker_boost,
-            speed=_params.speed,
-            auto_mode=str(_params.auto_mode).lower(),
-            enable_ssml_parsing=_params.enable_ssml_parsing,
-            enable_logging=_params.enable_logging,
-            apply_text_normalization=_params.apply_text_normalization,
+            model="eleven_turbo_v2_5",
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", ElevenLabsTTSSettings, "voice")
+            default_settings.voice = voice_id
+        if model is not None:
+            _warn_deprecated_param("model", ElevenLabsTTSSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        _pronunciation_dictionary_locators = pronunciation_dictionary_locators
+        if params is not None:
+            _warn_deprecated_param("params", ElevenLabsTTSSettings)
+            if not settings:
+                if params.language is not None:
+                    default_settings.language = self.language_to_service_language(params.language)
+                if params.stability is not None:
+                    default_settings.stability = params.stability
+                if params.similarity_boost is not None:
+                    default_settings.similarity_boost = params.similarity_boost
+                if params.style is not None:
+                    default_settings.style = params.style
+                if params.use_speaker_boost is not None:
+                    default_settings.use_speaker_boost = params.use_speaker_boost
+                if params.speed is not None:
+                    default_settings.speed = params.speed
+                if params.auto_mode is not None:
+                    default_settings.auto_mode = str(params.auto_mode).lower()
+                if params.enable_ssml_parsing is not None:
+                    default_settings.enable_ssml_parsing = params.enable_ssml_parsing
+                if params.enable_logging is not None:
+                    default_settings.enable_logging = params.enable_logging
+                if params.apply_text_normalization is not None:
+                    default_settings.apply_text_normalization = params.apply_text_normalization
+                if _pronunciation_dictionary_locators is None:
+                    _pronunciation_dictionary_locators = params.pronunciation_dictionary_locators
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -469,11 +487,7 @@ class ElevenLabsTTSService(AudioContextTTSService):
 
         self._output_format = ""  # initialized in start()
         self._voice_settings = self._set_voice_settings()
-        self._pronunciation_dictionary_locators = (
-            pronunciation_dictionary_locators
-            if pronunciation_dictionary_locators is not None
-            else _params.pronunciation_dictionary_locators
-        )
+        self._pronunciation_dictionary_locators = _pronunciation_dictionary_locators
 
         self._cumulative_time = 0
         # Track partial words that span across alignment chunks
@@ -982,29 +996,44 @@ class ElevenLabsHttpTTSService(TTSService):
 
             **kwargs: Additional arguments passed to the parent service.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "ElevenLabsHttpTTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "ElevenLabsHttpTTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "ElevenLabsHttpTTSSettings")
-
-        _params = params or ElevenLabsHttpTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = ElevenLabsHttpTTSSettings(
-            model=model or "eleven_turbo_v2_5",
-            voice=voice_id,
-            language=(
-                self.language_to_service_language(_params.language) if _params.language else None
-            ),
-            optimize_streaming_latency=_params.optimize_streaming_latency,
-            stability=_params.stability,
-            similarity_boost=_params.similarity_boost,
-            style=_params.style,
-            use_speaker_boost=_params.use_speaker_boost,
-            speed=_params.speed,
-            apply_text_normalization=_params.apply_text_normalization,
+            model="eleven_turbo_v2_5",
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", ElevenLabsHttpTTSSettings, "voice")
+            default_settings.voice = voice_id
+        if model is not None:
+            _warn_deprecated_param("model", ElevenLabsHttpTTSSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        _pronunciation_dictionary_locators = pronunciation_dictionary_locators
+        if params is not None:
+            _warn_deprecated_param("params", ElevenLabsHttpTTSSettings)
+            if not settings:
+                if params.language is not None:
+                    default_settings.language = self.language_to_service_language(params.language)
+                if params.optimize_streaming_latency is not None:
+                    default_settings.optimize_streaming_latency = params.optimize_streaming_latency
+                if params.stability is not None:
+                    default_settings.stability = params.stability
+                if params.similarity_boost is not None:
+                    default_settings.similarity_boost = params.similarity_boost
+                if params.style is not None:
+                    default_settings.style = params.style
+                if params.use_speaker_boost is not None:
+                    default_settings.use_speaker_boost = params.use_speaker_boost
+                if params.speed is not None:
+                    default_settings.speed = params.speed
+                if params.apply_text_normalization is not None:
+                    default_settings.apply_text_normalization = params.apply_text_normalization
+                if _pronunciation_dictionary_locators is None:
+                    _pronunciation_dictionary_locators = params.pronunciation_dictionary_locators
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -1025,11 +1054,7 @@ class ElevenLabsHttpTTSService(TTSService):
 
         self._output_format = ""  # initialized in start()
         self._voice_settings = self._set_voice_settings()
-        self._pronunciation_dictionary_locators = (
-            pronunciation_dictionary_locators
-            if pronunciation_dictionary_locators is not None
-            else _params.pronunciation_dictionary_locators
-        )
+        self._pronunciation_dictionary_locators = _pronunciation_dictionary_locators
 
         # Track cumulative time to properly sequence word timestamps across utterances
         self._cumulative_time = 0
diff --git a/src/pipecat/services/fal/image.py b/src/pipecat/services/fal/image.py
index d172f77dd..5d061619c 100644
--- a/src/pipecat/services/fal/image.py
+++ b/src/pipecat/services/fal/image.py
@@ -95,10 +95,15 @@ class FalImageGenService(ImageGenService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent ImageGenService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "FalImageGenSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = FalImageGenSettings(model="fal-ai/fast-sdxl")
 
-        default_settings = FalImageGenSettings(model=model or "fal-ai/fast-sdxl")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", FalImageGenSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/fal/stt.py b/src/pipecat/services/fal/stt.py
index 1a8a7076c..b5561d964 100644
--- a/src/pipecat/services/fal/stt.py
+++ b/src/pipecat/services/fal/stt.py
@@ -217,20 +217,29 @@ class FalSTTService(SegmentedSTTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to SegmentedSTTService.
         """
-        if params is not None:
-            _warn_deprecated_param("params", "FalSTTSettings")
-
-        _params = params or FalSTTService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = FalSTTSettings(
             model=None,
-            language=self.language_to_service_language(_params.language)
-            if _params.language
-            else "en",
-            task=_params.task,
-            chunk_level=_params.chunk_level,
-            version=_params.version,
+            language=language_to_fal_language(Language.EN) or "en",
+            task="transcribe",
+            chunk_level="segment",
+            version="3",
         )
+
+        # 2. (no deprecated direct args for this service)
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", FalSTTSettings)
+            if not settings:
+                default_settings.language = (
+                    language_to_fal_language(params.language) if params.language else "en"
+                )
+                default_settings.task = params.task
+                default_settings.chunk_level = params.chunk_level
+                default_settings.version = params.version
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/fireworks/llm.py b/src/pipecat/services/fireworks/llm.py
index 33d7d22e2..cb5a0cf39 100644
--- a/src/pipecat/services/fireworks/llm.py
+++ b/src/pipecat/services/fireworks/llm.py
@@ -46,12 +46,15 @@ class FireworksLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="accounts/fireworks/models/firefunction-v2")
 
-        default_settings = OpenAILLMSettings(
-            model=model or "accounts/fireworks/models/firefunction-v2"
-        )
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/fish/tts.py b/src/pipecat/services/fish/tts.py
index 431b51729..3d4412186 100644
--- a/src/pipecat/services/fish/tts.py
+++ b/src/pipecat/services/fish/tts.py
@@ -12,7 +12,7 @@ for streaming text-to-speech synthesis with customizable voice parameters.
 
 import uuid
 from dataclasses import dataclass, field
-from typing import Any, AsyncGenerator, ClassVar, Dict, Literal, Mapping, Optional
+from typing import Any, AsyncGenerator, ClassVar, Dict, Literal, Mapping, Optional, Self
 
 from loguru import logger
 from pydantic import BaseModel
@@ -72,7 +72,7 @@ class FishAudioTTSSettings(TTSSettings):
     _aliases: ClassVar[Dict[str, str]] = {"voice_id": "voice", "sample_rate": "fish_sample_rate"}
 
     @classmethod
-    def from_mapping(cls, settings: Mapping[str, Any]) -> "FishAudioTTSSettings":
+    def from_mapping(cls, settings: Mapping[str, Any]) -> Self:
         """Construct settings from a plain dict, destructuring legacy nested ``prosody``."""
         flat = dict(settings)
         nested = flat.pop("prosody", None)
@@ -156,15 +156,6 @@ class FishAudioTTSService(InterruptibleTTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to the parent service.
         """
-        if reference_id is not None:
-            _warn_deprecated_param("reference_id", "FishAudioTTSSettings", "voice")
-        if model_id is not None:
-            _warn_deprecated_param("model_id", "FishAudioTTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "FishAudioTTSSettings")
-
-        _params = params or FishAudioTTSService.InputParams()
-
         # Validation for model and reference_id parameters
         if model and reference_id:
             raise ValueError(
@@ -184,17 +175,42 @@ class FishAudioTTSService(InterruptibleTTSService):
                 )
             reference_id = model
 
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = FishAudioTTSSettings(
-            model=model_id or "s1",
-            voice=reference_id,
+            model="s1",
+            voice=None,
             fish_sample_rate=0,
-            latency=_params.latency,
+            latency="normal",
             format=output_format,
-            normalize=_params.normalize,
-            prosody_speed=_params.prosody_speed,
-            prosody_volume=_params.prosody_volume,
-            reference_id=reference_id,
+            normalize=True,
+            prosody_speed=1.0,
+            prosody_volume=0,
+            reference_id=None,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if reference_id is not None:
+            _warn_deprecated_param("reference_id", FishAudioTTSSettings, "voice")
+            default_settings.voice = reference_id
+            default_settings.reference_id = reference_id
+        if model_id is not None:
+            _warn_deprecated_param("model_id", FishAudioTTSSettings, "model")
+            default_settings.model = model_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", FishAudioTTSSettings)
+            if not settings:
+                if params.latency is not None:
+                    default_settings.latency = params.latency
+                if params.normalize is not None:
+                    default_settings.normalize = params.normalize
+                if params.prosody_speed is not None:
+                    default_settings.prosody_speed = params.prosody_speed
+                if params.prosody_volume is not None:
+                    default_settings.prosody_volume = params.prosody_volume
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/gladia/stt.py b/src/pipecat/services/gladia/stt.py
index e1e0d9276..a12829b0d 100644
--- a/src/pipecat/services/gladia/stt.py
+++ b/src/pipecat/services/gladia/stt.py
@@ -289,23 +289,6 @@ class GladiaSTTService(WebsocketSTTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to the STTService parent class.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "GladiaSTTSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "GladiaSTTSettings")
-
-        params = params or GladiaInputParams()
-
-        if params.language is not None:
-            with warnings.catch_warnings():
-                warnings.simplefilter("always")
-                warnings.warn(
-                    "The 'language' parameter is deprecated and will be removed in a future version. "
-                    "Use 'language_config' instead.",
-                    DeprecationWarning,
-                    stacklevel=2,
-                )
-
         if confidence:
             with warnings.catch_warnings():
                 warnings.simplefilter("always")
@@ -316,28 +299,64 @@ class GladiaSTTService(WebsocketSTTService):
                     stacklevel=2,
                 )
 
-        # Resolve deprecated language → language_config at init time
-        language_config = params.language_config
-        if not language_config and params.language:
-            language_code = self.language_to_service_language(params.language)
-            if language_code:
-                language_config = LanguageConfig(languages=[language_code], code_switching=False)
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = GladiaSTTSettings(
-            model=model or "solaria-1",
+            model="solaria-1",
             language=None,
-            encoding=params.encoding,
-            bit_depth=params.bit_depth,
-            channels=params.channels,
-            custom_metadata=params.custom_metadata,
-            endpointing=params.endpointing,
-            maximum_duration_without_endpointing=params.maximum_duration_without_endpointing,
-            language_config=language_config,
-            pre_processing=params.pre_processing,
-            realtime_processing=params.realtime_processing,
-            messages_config=params.messages_config,
-            enable_vad=params.enable_vad,
+            encoding="wav/pcm",
+            bit_depth=16,
+            channels=1,
+            custom_metadata=None,
+            endpointing=None,
+            maximum_duration_without_endpointing=5,
+            language_config=None,
+            pre_processing=None,
+            realtime_processing=None,
+            messages_config=None,
+            enable_vad=False,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", GladiaSTTSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", GladiaSTTSettings)
+            if params.language is not None:
+                with warnings.catch_warnings():
+                    warnings.simplefilter("always")
+                    warnings.warn(
+                        "The 'language' parameter is deprecated and will be removed in a future "
+                        "version. Use 'language_config' instead.",
+                        DeprecationWarning,
+                        stacklevel=2,
+                    )
+            if not settings:
+                default_settings.encoding = params.encoding
+                default_settings.bit_depth = params.bit_depth
+                default_settings.channels = params.channels
+                default_settings.custom_metadata = params.custom_metadata
+                default_settings.endpointing = params.endpointing
+                default_settings.maximum_duration_without_endpointing = (
+                    params.maximum_duration_without_endpointing
+                )
+                default_settings.pre_processing = params.pre_processing
+                default_settings.realtime_processing = params.realtime_processing
+                default_settings.messages_config = params.messages_config
+                default_settings.enable_vad = params.enable_vad
+                # Resolve deprecated language → language_config at init time
+                language_config = params.language_config
+                if not language_config and params.language:
+                    language_code = self.language_to_service_language(params.language)
+                    if language_code:
+                        language_config = LanguageConfig(
+                            languages=[language_code], code_switching=False
+                        )
+                default_settings.language_config = language_config
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/google/gemini_live/llm.py b/src/pipecat/services/google/gemini_live/llm.py
index 518684dfb..6e7a8f8a1 100644
--- a/src/pipecat/services/google/gemini_live/llm.py
+++ b/src/pipecat/services/google/gemini_live/llm.py
@@ -708,36 +708,63 @@ class GeminiLiveLLMService(LLMService):
                     DeprecationWarning,
                     stacklevel=2,
                 )
-        if model is not None:
-            _warn_deprecated_param("model", "GeminiLiveLLMSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "GeminiLiveLLMSettings")
-
-        _params = params or InputParams()
 
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = GeminiLiveLLMSettings(
-            model=model or "models/gemini-2.5-flash-native-audio-preview-12-2025",
-            frequency_penalty=_params.frequency_penalty,
-            max_tokens=_params.max_tokens,
-            presence_penalty=_params.presence_penalty,
-            temperature=_params.temperature,
-            top_k=_params.top_k,
-            top_p=_params.top_p,
+            model="models/gemini-2.5-flash-native-audio-preview-12-2025",
+            frequency_penalty=None,
+            max_tokens=4096,
+            presence_penalty=None,
+            temperature=None,
+            top_k=None,
+            top_p=None,
             seed=None,
             filter_incomplete_user_turns=False,
             user_turn_completion_config=None,
-            modalities=_params.modalities,
-            language=language_to_gemini_language(_params.language) if _params.language else "en-US",
-            media_resolution=_params.media_resolution,
-            vad=_params.vad,
-            context_window_compression=_params.context_window_compression.model_dump()
-            if _params.context_window_compression
-            else {},
-            thinking=_params.thinking or {},
-            enable_affective_dialog=_params.enable_affective_dialog or False,
-            proactivity=_params.proactivity or {},
-            extra=_params.extra if isinstance(_params.extra, dict) else {},
+            modalities=GeminiModalities.AUDIO,
+            language="en-US",
+            media_resolution=GeminiMediaResolution.UNSPECIFIED,
+            vad=None,
+            context_window_compression={},
+            thinking={},
+            enable_affective_dialog=False,
+            proactivity={},
+            extra={},
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", GeminiLiveLLMSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", GeminiLiveLLMSettings)
+            if not settings:
+                default_settings.frequency_penalty = params.frequency_penalty
+                default_settings.max_tokens = params.max_tokens
+                default_settings.presence_penalty = params.presence_penalty
+                default_settings.temperature = params.temperature
+                default_settings.top_k = params.top_k
+                default_settings.top_p = params.top_p
+                default_settings.modalities = params.modalities
+                default_settings.language = (
+                    language_to_gemini_language(params.language) if params.language else "en-US"
+                )
+                default_settings.media_resolution = params.media_resolution
+                default_settings.vad = params.vad
+                default_settings.context_window_compression = (
+                    params.context_window_compression.model_dump()
+                    if params.context_window_compression
+                    else {}
+                )
+                default_settings.thinking = params.thinking or {}
+                default_settings.enable_affective_dialog = params.enable_affective_dialog or False
+                default_settings.proactivity = params.proactivity or {}
+                if isinstance(params.extra, dict):
+                    default_settings.extra = params.extra
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -750,7 +777,7 @@ class GeminiLiveLLMService(LLMService):
         self._last_sent_time = 0
         self._base_url = base_url
         self._voice_id = voice_id
-        self._language_code = _params.language
+        self._language_code = params.language if params is not None else Language.EN_US
 
         self._system_instruction_from_init = system_instruction
         self._tools_from_init = tools
diff --git a/src/pipecat/services/google/gemini_live/llm_vertex.py b/src/pipecat/services/google/gemini_live/llm_vertex.py
index eadcb66d1..5d63251d9 100644
--- a/src/pipecat/services/google/gemini_live/llm_vertex.py
+++ b/src/pipecat/services/google/gemini_live/llm_vertex.py
@@ -20,6 +20,8 @@ from pipecat.adapters.schemas.tools_schema import ToolsSchema
 from pipecat.services.google.gemini_live.llm import (
     GeminiLiveLLMService,
     GeminiLiveLLMSettings,
+    GeminiMediaResolution,
+    GeminiModalities,
     HttpOptions,
     InputParams,
     language_to_gemini_language,
@@ -109,11 +111,6 @@ class GeminiLiveVertexLLMService(GeminiLiveLLMService):
                 "Invalid parameter 'api_key'. Use 'credentials' or 'credentials_path' for Vertex AI authentication."
             )
 
-        if model is not None:
-            _warn_deprecated_param("model", "GeminiLiveLLMSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "GeminiLiveLLMSettings")
-
         # These need to be set before calling super().__init__() because
         # super().__init__() invokes create_client(), which needs these.
         self._credentials = self._get_credentials(credentials, credentials_path)
@@ -123,31 +120,63 @@ class GeminiLiveVertexLLMService(GeminiLiveLLMService):
         # Build default_settings from deprecated args, then apply settings delta.
         # We pass settings= to super() instead of model=/params= to avoid
         # double deprecation warnings from the parent.
-        _params = params or InputParams()
 
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = GeminiLiveLLMSettings(
-            model=model or "google/gemini-live-2.5-flash-native-audio",
-            frequency_penalty=_params.frequency_penalty,
-            max_tokens=_params.max_tokens,
-            presence_penalty=_params.presence_penalty,
-            temperature=_params.temperature,
-            top_k=_params.top_k,
-            top_p=_params.top_p,
+            model="google/gemini-live-2.5-flash-native-audio",
+            frequency_penalty=None,
+            max_tokens=4096,
+            presence_penalty=None,
+            temperature=None,
+            top_k=None,
+            top_p=None,
             seed=None,
             filter_incomplete_user_turns=False,
             user_turn_completion_config=None,
-            modalities=_params.modalities,
-            language=language_to_gemini_language(_params.language) if _params.language else "en-US",
-            media_resolution=_params.media_resolution,
-            vad=_params.vad,
-            context_window_compression=_params.context_window_compression.model_dump()
-            if _params.context_window_compression
-            else {},
-            thinking=_params.thinking or {},
-            enable_affective_dialog=_params.enable_affective_dialog or False,
-            proactivity=_params.proactivity or {},
-            extra=_params.extra if isinstance(_params.extra, dict) else {},
+            modalities=GeminiModalities.AUDIO,
+            language="en-US",
+            media_resolution=GeminiMediaResolution.UNSPECIFIED,
+            vad=None,
+            context_window_compression={},
+            thinking={},
+            enable_affective_dialog=False,
+            proactivity={},
+            extra={},
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", GeminiLiveLLMSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", GeminiLiveLLMSettings)
+            if not settings:
+                default_settings.frequency_penalty = params.frequency_penalty
+                default_settings.max_tokens = params.max_tokens
+                default_settings.presence_penalty = params.presence_penalty
+                default_settings.temperature = params.temperature
+                default_settings.top_k = params.top_k
+                default_settings.top_p = params.top_p
+                default_settings.modalities = params.modalities
+                default_settings.language = (
+                    language_to_gemini_language(params.language) if params.language else "en-US"
+                )
+                default_settings.media_resolution = params.media_resolution
+                default_settings.vad = params.vad
+                default_settings.context_window_compression = (
+                    params.context_window_compression.model_dump()
+                    if params.context_window_compression
+                    else {}
+                )
+                default_settings.thinking = params.thinking or {}
+                default_settings.enable_affective_dialog = params.enable_affective_dialog or False
+                default_settings.proactivity = params.proactivity or {}
+                if isinstance(params.extra, dict):
+                    default_settings.extra = params.extra
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/google/image.py b/src/pipecat/services/google/image.py
index ce29c0276..09ec61554 100644
--- a/src/pipecat/services/google/image.py
+++ b/src/pipecat/services/google/image.py
@@ -90,17 +90,21 @@ class GoogleImageGenService(ImageGenService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to the parent ImageGenService.
         """
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = GoogleImageGenSettings(model="imagen-3.0-generate-002")
+
+        # 3. Apply params overrides — only if settings not provided
         if params is not None:
-            _warn_deprecated_param("params", "GoogleImageGenSettings")
+            _warn_deprecated_param("params", GoogleImageGenSettings)
+            if not settings:
+                default_settings.model = params.model
 
-        params = params or GoogleImageGenService.InputParams()
-
-        default_settings = GoogleImageGenSettings(model=params.model)
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
         super().__init__(settings=default_settings, **kwargs)
-        self._params = params
+        self._params = params or GoogleImageGenService.InputParams()
 
         # Add client header
         http_options = update_google_client_http_options(http_options)
diff --git a/src/pipecat/services/google/llm.py b/src/pipecat/services/google/llm.py
index 5d5a87188..49e6d2366 100644
--- a/src/pipecat/services/google/llm.py
+++ b/src/pipecat/services/google/llm.py
@@ -814,27 +814,40 @@ class GoogleLLMService(LLMService):
             http_options: HTTP options for the client.
             **kwargs: Additional arguments passed to parent class.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "GoogleLLMSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "GoogleLLMSettings")
-
-        _params = params or GoogleLLMService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = GoogleLLMSettings(
-            model=model or "gemini-2.5-flash",
-            max_tokens=_params.max_tokens,
-            temperature=_params.temperature,
-            top_k=_params.top_k,
-            top_p=_params.top_p,
+            model="gemini-2.5-flash",
+            max_tokens=4096,
+            temperature=None,
+            top_k=None,
+            top_p=None,
             frequency_penalty=None,
             presence_penalty=None,
             seed=None,
             filter_incomplete_user_turns=False,
             user_turn_completion_config=None,
-            thinking=_params.thinking,
-            extra=_params.extra if isinstance(_params.extra, dict) else {},
+            thinking=None,
+            extra={},
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", GoogleLLMSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", GoogleLLMSettings)
+            if not settings:
+                default_settings.max_tokens = params.max_tokens
+                default_settings.temperature = params.temperature
+                default_settings.top_k = params.top_k
+                default_settings.top_p = params.top_p
+                default_settings.thinking = params.thinking
+                if isinstance(params.extra, dict):
+                    default_settings.extra = params.extra
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/google/llm_openai.py b/src/pipecat/services/google/llm_openai.py
index aa8794469..4705e8f68 100644
--- a/src/pipecat/services/google/llm_openai.py
+++ b/src/pipecat/services/google/llm_openai.py
@@ -84,10 +84,15 @@ class GoogleLLMOpenAIBetaService(OpenAILLMService):
                 stacklevel=2,
             )
 
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="gemini-2.0-flash")
 
-        default_settings = OpenAILLMSettings(model=model or "gemini-2.0-flash")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/google/llm_vertex.py b/src/pipecat/services/google/llm_vertex.py
index 9258a4d67..b1a9de584 100644
--- a/src/pipecat/services/google/llm_vertex.py
+++ b/src/pipecat/services/google/llm_vertex.py
@@ -148,15 +148,9 @@ class GoogleVertexLLMService(GoogleLLMService):
                 "Invalid parameter 'api_key'. Use 'credentials' or 'credentials_path' for Vertex AI authentication."
             )
 
-        if model is not None:
-            _warn_deprecated_param("model", "GoogleLLMSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "GoogleLLMSettings")
-
-        # Handle deprecated InputParams fields
+        # Handle deprecated InputParams fields (location/project_id extraction
+        # must happen before validation, regardless of settings)
         if params and isinstance(params, GoogleVertexLLMService.InputParams):
-            # Extract location and project_id from params if not provided
-            # directly, for backward compatibility
             if project_id is None:
                 project_id = params.project_id
             if location is None:
@@ -188,22 +182,40 @@ class GoogleVertexLLMService(GoogleLLMService):
         self._project_id = project_id
         self._location = location
 
-        # Build default_settings from deprecated args
-        _params = params or GoogleLLMService.InputParams()
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = GoogleLLMSettings(
-            model=model or "gemini-2.5-flash",
-            max_tokens=_params.max_tokens,
-            temperature=_params.temperature,
-            top_k=_params.top_k,
-            top_p=_params.top_p,
+            model="gemini-2.5-flash",
+            max_tokens=4096,
+            temperature=None,
+            top_k=None,
+            top_p=None,
             frequency_penalty=None,
             presence_penalty=None,
             seed=None,
             filter_incomplete_user_turns=False,
             user_turn_completion_config=None,
-            thinking=_params.thinking,
-            extra=_params.extra if isinstance(_params.extra, dict) else {},
+            thinking=None,
+            extra={},
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", GoogleLLMSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", GoogleLLMSettings)
+            if not settings:
+                default_settings.max_tokens = params.max_tokens
+                default_settings.temperature = params.temperature
+                default_settings.top_k = params.top_k
+                default_settings.top_p = params.top_p
+                default_settings.thinking = params.thinking
+                if isinstance(params.extra, dict):
+                    default_settings.extra = params.extra
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/google/stt.py b/src/pipecat/services/google/stt.py
index 23a586b96..5415a5403 100644
--- a/src/pipecat/services/google/stt.py
+++ b/src/pipecat/services/google/stt.py
@@ -509,26 +509,44 @@ class GoogleSTTService(STTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to STTService.
         """
-        if params is not None:
-            _warn_deprecated_param("params", "GoogleSTTSettings")
-
-        _params = params or GoogleSTTService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = GoogleSTTSettings(
             language=None,
-            languages=list(_params.language_list),
+            languages=[Language.EN_US],
             language_codes=None,
-            model=_params.model,
-            use_separate_recognition_per_channel=_params.use_separate_recognition_per_channel,
-            enable_automatic_punctuation=_params.enable_automatic_punctuation,
-            enable_spoken_punctuation=_params.enable_spoken_punctuation,
-            enable_spoken_emojis=_params.enable_spoken_emojis,
-            profanity_filter=_params.profanity_filter,
-            enable_word_time_offsets=_params.enable_word_time_offsets,
-            enable_word_confidence=_params.enable_word_confidence,
-            enable_interim_results=_params.enable_interim_results,
-            enable_voice_activity_events=_params.enable_voice_activity_events,
+            model="latest_long",
+            use_separate_recognition_per_channel=False,
+            enable_automatic_punctuation=True,
+            enable_spoken_punctuation=False,
+            enable_spoken_emojis=False,
+            profanity_filter=False,
+            enable_word_time_offsets=False,
+            enable_word_confidence=False,
+            enable_interim_results=True,
+            enable_voice_activity_events=False,
         )
+
+        # 2. No direct init arg overrides
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", GoogleSTTSettings)
+            if not settings:
+                default_settings.languages = list(params.language_list)
+                default_settings.model = params.model
+                default_settings.use_separate_recognition_per_channel = (
+                    params.use_separate_recognition_per_channel
+                )
+                default_settings.enable_automatic_punctuation = params.enable_automatic_punctuation
+                default_settings.enable_spoken_punctuation = params.enable_spoken_punctuation
+                default_settings.enable_spoken_emojis = params.enable_spoken_emojis
+                default_settings.profanity_filter = params.profanity_filter
+                default_settings.enable_word_time_offsets = params.enable_word_time_offsets
+                default_settings.enable_word_confidence = params.enable_word_confidence
+                default_settings.enable_interim_results = params.enable_interim_results
+                default_settings.enable_voice_activity_events = params.enable_voice_activity_events
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/google/tts.py b/src/pipecat/services/google/tts.py
index 78719f8fa..6b17caed5 100644
--- a/src/pipecat/services/google/tts.py
+++ b/src/pipecat/services/google/tts.py
@@ -622,27 +622,40 @@ class GoogleHttpTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent TTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "GoogleHttpTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "GoogleHttpTTSSettings")
-
-        _params = params or GoogleHttpTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = GoogleHttpTTSSettings(
             model=None,
-            pitch=_params.pitch,
-            rate=_params.rate,
-            speaking_rate=_params.speaking_rate,
-            volume=_params.volume,
-            emphasis=_params.emphasis,
-            language=self.language_to_service_language(_params.language)
-            if _params.language
-            else "en-US",
-            gender=_params.gender,
-            google_style=_params.google_style,
-            voice=voice_id or "en-US-Chirp3-HD-Charon",
+            voice="en-US-Chirp3-HD-Charon",
+            language="en-US",
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", GoogleHttpTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", GoogleHttpTTSSettings)
+            if not settings:
+                if params.pitch is not None:
+                    default_settings.pitch = params.pitch
+                if params.rate is not None:
+                    default_settings.rate = params.rate
+                if params.speaking_rate is not None:
+                    default_settings.speaking_rate = params.speaking_rate
+                if params.volume is not None:
+                    default_settings.volume = params.volume
+                if params.emphasis is not None:
+                    default_settings.emphasis = params.emphasis
+                if params.language is not None:
+                    default_settings.language = self.language_to_service_language(params.language)
+                if params.gender is not None:
+                    default_settings.gender = params.gender
+                if params.google_style is not None:
+                    default_settings.google_style = params.google_style
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -1062,21 +1075,28 @@ class GoogleTTSService(GoogleBaseTTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent TTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "GoogleStreamTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "GoogleStreamTTSSettings")
-
-        _params = params or GoogleTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = GoogleStreamTTSSettings(
             model=None,
-            language=self.language_to_service_language(_params.language)
-            if _params.language
-            else "en-US",
-            speaking_rate=_params.speaking_rate,
-            voice=voice_id or "en-US-Chirp3-HD-Charon",
+            voice="en-US-Chirp3-HD-Charon",
+            language="en-US",
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", GoogleStreamTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", GoogleStreamTTSSettings)
+            if not settings:
+                if params.language is not None:
+                    default_settings.language = self.language_to_service_language(params.language)
+                if params.speaking_rate is not None:
+                    default_settings.speaking_rate = params.speaking_rate
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -1292,34 +1312,47 @@ class GeminiTTSService(GoogleBaseTTSService):
                 DeprecationWarning,
                 stacklevel=2,
             )
-        if model is not None:
-            _warn_deprecated_param("model", "GeminiTTSSettings", "model")
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "GeminiTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "GeminiTTSSettings")
 
         if sample_rate and sample_rate != self.GOOGLE_SAMPLE_RATE:
             logger.warning(
                 f"Google TTS only supports {self.GOOGLE_SAMPLE_RATE}Hz sample rate. "
                 f"Current rate of {sample_rate}Hz may cause issues."
             )
-        _params = params or GeminiTTSService.InputParams()
-
-        voice_id = voice_id or "Kore"
-        if voice_id not in self.AVAILABLE_VOICES:
-            logger.warning(f"Voice '{voice_id}' not in known voices list. Using anyway.")
 
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = GeminiTTSSettings(
-            model=model or "gemini-2.5-flash-tts",
-            language=self.language_to_service_language(_params.language)
-            if _params.language
-            else "en-US",
-            prompt=_params.prompt,
-            multi_speaker=_params.multi_speaker,
-            speaker_configs=_params.speaker_configs,
-            voice=voice_id,
+            model="gemini-2.5-flash-tts",
+            voice="Kore",
+            language="en-US",
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", GeminiTTSSettings, "model")
+            default_settings.model = model
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", GeminiTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        if default_settings.voice not in self.AVAILABLE_VOICES:
+            logger.warning(
+                f"Voice '{default_settings.voice}' not in known voices list. Using anyway."
+            )
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", GeminiTTSSettings)
+            if not settings:
+                if params.language is not None:
+                    default_settings.language = self.language_to_service_language(params.language)
+                if params.prompt is not None:
+                    default_settings.prompt = params.prompt
+                if params.multi_speaker is not None:
+                    default_settings.multi_speaker = params.multi_speaker
+                if params.speaker_configs is not None:
+                    default_settings.speaker_configs = params.speaker_configs
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/gradium/stt.py b/src/pipecat/services/gradium/stt.py
index 5974133c0..51ac8a7cd 100644
--- a/src/pipecat/services/gradium/stt.py
+++ b/src/pipecat/services/gradium/stt.py
@@ -148,16 +148,23 @@ class GradiumSTTService(WebsocketSTTService):
                 stacklevel=2,
             )
 
-        if params is not None:
-            _warn_deprecated_param("params", "GradiumSTTSettings")
-
-        _params = params or GradiumSTTService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = GradiumSTTSettings(
             model=None,
-            language=_params.language,
-            delay_in_frames=_params.delay_in_frames or None,
+            language=None,
+            delay_in_frames=None,
         )
+
+        # 2. (no deprecated direct args for this service)
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", GradiumSTTSettings)
+            if not settings:
+                default_settings.language = params.language
+                default_settings.delay_in_frames = params.delay_in_frames
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/gradium/tts.py b/src/pipecat/services/gradium/tts.py
index 6f076f933..b3b9b50ca 100644
--- a/src/pipecat/services/gradium/tts.py
+++ b/src/pipecat/services/gradium/tts.py
@@ -103,19 +103,28 @@ class GradiumTTSService(AudioContextTTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent class.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "GradiumTTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "GradiumTTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "GradiumTTSSettings")
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = GradiumTTSSettings(
-            model=model or "default",
-            voice=voice_id or "YTpq7expH9539ERJ",
+            model="default",
+            voice="YTpq7expH9539ERJ",
             language=None,
             output_format="pcm",
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", GradiumTTSSettings, "model")
+            default_settings.model = model
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", GradiumTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", GradiumTTSSettings)
+            # Note: params.temp has no corresponding settings field
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/grok/llm.py b/src/pipecat/services/grok/llm.py
index 2e6a93c4e..f552f059a 100644
--- a/src/pipecat/services/grok/llm.py
+++ b/src/pipecat/services/grok/llm.py
@@ -102,10 +102,15 @@ class GrokLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="grok-3-beta")
 
-        default_settings = OpenAILLMSettings(model=model or "grok-3-beta")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/grok/realtime/llm.py b/src/pipecat/services/grok/realtime/llm.py
index 87f5eaaaa..2f2df1b45 100644
--- a/src/pipecat/services/grok/realtime/llm.py
+++ b/src/pipecat/services/grok/realtime/llm.py
@@ -153,11 +153,7 @@ class GrokRealtimeLLMService(LLMService):
             start_audio_paused: Whether to start with audio input paused. Defaults to False.
             **kwargs: Additional arguments passed to parent LLMService.
         """
-        if session_properties is not None:
-            _warn_deprecated_param(
-                "session_properties", "GrokRealtimeLLMSettings", "session_properties"
-            )
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = GrokRealtimeLLMSettings(
             model=None,
             temperature=None,
@@ -169,8 +165,17 @@ class GrokRealtimeLLMService(LLMService):
             seed=None,
             filter_incomplete_user_turns=False,
             user_turn_completion_config=None,
-            session_properties=session_properties or events.SessionProperties(),
+            session_properties=events.SessionProperties(),
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if session_properties is not None:
+            _warn_deprecated_param(
+                "session_properties", GrokRealtimeLLMSettings, "session_properties"
+            )
+            default_settings.session_properties = session_properties
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/groq/llm.py b/src/pipecat/services/groq/llm.py
index 0ea3b3f50..f88d5a877 100644
--- a/src/pipecat/services/groq/llm.py
+++ b/src/pipecat/services/groq/llm.py
@@ -45,10 +45,15 @@ class GroqLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="llama-3.3-70b-versatile")
 
-        default_settings = OpenAILLMSettings(model=model or "llama-3.3-70b-versatile")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/groq/stt.py b/src/pipecat/services/groq/stt.py
index e6ea42fd8..ac6a4325c 100644
--- a/src/pipecat/services/groq/stt.py
+++ b/src/pipecat/services/groq/stt.py
@@ -69,27 +69,30 @@ class GroqSTTService(BaseWhisperSTTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to BaseWhisperSTTService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "BaseWhisperSTTSettings", "model")
-        if language is not None:
-            _warn_deprecated_param("language", "BaseWhisperSTTSettings", "language")
-        if prompt is not None:
-            _warn_deprecated_param("prompt", "BaseWhisperSTTSettings", "prompt")
-        if temperature is not None:
-            _warn_deprecated_param("temperature", "BaseWhisperSTTSettings", "temperature")
-
-        model = model or "whisper-large-v3-turbo"
-        language = language or Language.EN
-
-        # Build settings from deprecated params and pass via settings=
-        # to avoid double deprecation warnings in BaseWhisperSTTService.
+        # --- 1. Hardcoded defaults ---
         default_settings = BaseWhisperSTTSettings(
-            model=model,
-            language=self.language_to_service_language(language),
+            model="whisper-large-v3-turbo",
+            language=self.language_to_service_language(Language.EN),
             base_url=base_url,
-            prompt=prompt,
-            temperature=temperature,
         )
+
+        # --- 2. Deprecated direct-arg overrides ---
+        if model is not None:
+            _warn_deprecated_param("model", BaseWhisperSTTSettings, "model")
+            default_settings.model = model
+        if language is not None:
+            _warn_deprecated_param("language", BaseWhisperSTTSettings, "language")
+            default_settings.language = self.language_to_service_language(language)
+        if prompt is not None:
+            _warn_deprecated_param("prompt", BaseWhisperSTTSettings, "prompt")
+            default_settings.prompt = prompt
+        if temperature is not None:
+            _warn_deprecated_param("temperature", BaseWhisperSTTSettings, "temperature")
+            default_settings.temperature = temperature
+
+        # --- 3. (no params object for this service) ---
+
+        # --- 4. Settings delta (canonical API, always wins) ---
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/groq/tts.py b/src/pipecat/services/groq/tts.py
index d16964d8c..b1c546713 100644
--- a/src/pipecat/services/groq/tts.py
+++ b/src/pipecat/services/groq/tts.py
@@ -114,26 +114,35 @@ class GroqTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent TTSService class.
         """
-        if model_name is not None:
-            _warn_deprecated_param("model_name", "GroqTTSSettings", "model")
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "GroqTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "GroqTTSSettings")
-
         if sample_rate != self.GROQ_SAMPLE_RATE:
             logger.warning(f"Groq TTS only supports {self.GROQ_SAMPLE_RATE}Hz sample rate. ")
 
-        _params = params or GroqTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = GroqTTSSettings(
-            model=model_name or "canopylabs/orpheus-v1-english",
-            voice=voice_id or "autumn",
-            language=str(_params.language) if _params.language else "en",
+            model="canopylabs/orpheus-v1-english",
+            voice="autumn",
+            language="en",
             output_format=output_format,
-            speed=_params.speed,
+            speed=1.0,
             groq_sample_rate=sample_rate,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model_name is not None:
+            _warn_deprecated_param("model_name", GroqTTSSettings, "model")
+            default_settings.model = model_name
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", GroqTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", GroqTTSSettings)
+            if not settings:
+                default_settings.language = str(params.language) if params.language else "en"
+                default_settings.speed = params.speed
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/hume/tts.py b/src/pipecat/services/hume/tts.py
index 5b7300816..7b0ecd0c8 100644
--- a/src/pipecat/services/hume/tts.py
+++ b/src/pipecat/services/hume/tts.py
@@ -126,11 +126,6 @@ class HumeTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to the parent class.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "HumeTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "HumeTTSSettings")
-
         api_key = api_key or os.getenv("HUME_API_KEY")
         if not api_key:
             raise ValueError("HumeTTSService requires an API key (env HUME_API_KEY or api_key=)")
@@ -140,16 +135,30 @@ class HumeTTSService(TTSService):
                 f"Hume TTS streams at {HUME_SAMPLE_RATE} Hz; configured sample_rate={sample_rate}"
             )
 
-        _params = params or HumeTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = HumeTTSSettings(
             model=None,
-            voice=voice_id,
+            voice=None,
             language=None,  # Not applicable here
-            description=_params.description,
-            speed=_params.speed,
-            trailing_silence=_params.trailing_silence,
+            description=None,
+            speed=None,
+            trailing_silence=None,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", HumeTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", HumeTTSSettings)
+            if not settings:
+                default_settings.description = params.description
+                default_settings.speed = params.speed
+                default_settings.trailing_silence = params.trailing_silence
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/inworld/tts.py b/src/pipecat/services/inworld/tts.py
index f1797ad55..688ba542a 100644
--- a/src/pipecat/services/inworld/tts.py
+++ b/src/pipecat/services/inworld/tts.py
@@ -18,7 +18,18 @@ import base64
 import json
 import uuid
 from dataclasses import dataclass, field
-from typing import Any, AsyncGenerator, ClassVar, Dict, List, Literal, Mapping, Optional, Tuple
+from typing import (
+    Any,
+    AsyncGenerator,
+    ClassVar,
+    Dict,
+    List,
+    Literal,
+    Mapping,
+    Optional,
+    Self,
+    Tuple,
+)
 
 import aiohttp
 import websockets
@@ -91,7 +102,7 @@ class InworldTTSSettings(TTSSettings):
     }
 
     @classmethod
-    def from_mapping(cls, settings: Mapping[str, Any]) -> "InworldTTSSettings":
+    def from_mapping(cls, settings: Mapping[str, Any]) -> Self:
         """Construct settings from a plain dict, destructuring legacy nested ``audioConfig``."""
         flat = dict(settings)
         nested = flat.pop("audioConfig", None)
@@ -168,27 +179,42 @@ class InworldHttpTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to the parent class.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "InworldTTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "InworldTTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "InworldTTSSettings")
-
-        _params = params or InworldHttpTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = InworldTTSSettings(
-            model=model or "inworld-tts-1.5-max",
-            voice=voice_id or "Ashley",
+            model="inworld-tts-1.5-max",
+            voice="Ashley",
             language=None,
             audio_encoding=encoding,
             audio_sample_rate=0,
-            speaking_rate=_params.speaking_rate,
-            temperature=_params.temperature,
-            timestamp_transport_strategy=_params.timestamp_transport_strategy,
+            speaking_rate=None,
+            temperature=None,
+            timestamp_transport_strategy="ASYNC",
             auto_mode=None,  # Not applicable for HTTP TTS
             apply_text_normalization=None,  # Not applicable for HTTP TTS
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", InworldTTSSettings, "voice")
+            default_settings.voice = voice_id
+        if model is not None:
+            _warn_deprecated_param("model", InworldTTSSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", InworldTTSSettings)
+            if not settings:
+                if params.speaking_rate is not None:
+                    default_settings.speaking_rate = params.speaking_rate
+                if params.temperature is not None:
+                    default_settings.temperature = params.temperature
+                if params.timestamp_transport_strategy is not None:
+                    default_settings.timestamp_transport_strategy = (
+                        params.timestamp_transport_strategy
+                    )
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -580,27 +606,50 @@ class InworldTTSService(AudioContextTTSService):
             append_trailing_space: Whether to append a trailing space to text before sending to TTS.
             **kwargs: Additional arguments passed to the parent class.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "InworldTTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "InworldTTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "InworldTTSSettings")
-
-        _params = params or InworldTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = InworldTTSSettings(
-            model=model or "inworld-tts-1.5-max",
-            voice=voice_id or "Ashley",
+            model="inworld-tts-1.5-max",
+            voice="Ashley",
             language=None,
             audio_encoding=encoding,
             audio_sample_rate=0,
-            speaking_rate=_params.speaking_rate,
-            temperature=_params.temperature,
-            apply_text_normalization=_params.apply_text_normalization,
-            timestamp_transport_strategy=_params.timestamp_transport_strategy,
-            auto_mode=_params.auto_mode if _params.auto_mode is not None else aggregate_sentences,
+            speaking_rate=None,
+            temperature=None,
+            apply_text_normalization=None,
+            timestamp_transport_strategy="ASYNC",
+            auto_mode=True if aggregate_sentences is None else aggregate_sentences,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", InworldTTSSettings, "voice")
+            default_settings.voice = voice_id
+        if model is not None:
+            _warn_deprecated_param("model", InworldTTSSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        _buffer_max_delay_ms = None
+        _buffer_char_threshold = None
+        if params is not None:
+            _warn_deprecated_param("params", InworldTTSSettings)
+            if not settings:
+                if params.speaking_rate is not None:
+                    default_settings.speaking_rate = params.speaking_rate
+                if params.temperature is not None:
+                    default_settings.temperature = params.temperature
+                if params.apply_text_normalization is not None:
+                    default_settings.apply_text_normalization = params.apply_text_normalization
+                if params.timestamp_transport_strategy is not None:
+                    default_settings.timestamp_transport_strategy = (
+                        params.timestamp_transport_strategy
+                    )
+                if params.auto_mode is not None:
+                    default_settings.auto_mode = params.auto_mode
+            _buffer_max_delay_ms = params.max_buffer_delay_ms
+            _buffer_char_threshold = params.buffer_char_threshold
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -622,8 +671,8 @@ class InworldTTSService(AudioContextTTSService):
         self._timestamp_type = "WORD"
 
         self._buffer_settings = {
-            "maxBufferDelayMs": _params.max_buffer_delay_ms,
-            "bufferCharThreshold": _params.buffer_char_threshold,
+            "maxBufferDelayMs": _buffer_max_delay_ms,
+            "bufferCharThreshold": _buffer_char_threshold,
         }
 
         self._receive_task = None
diff --git a/src/pipecat/services/kokoro/tts.py b/src/pipecat/services/kokoro/tts.py
index 8bab78f93..7e53060da 100644
--- a/src/pipecat/services/kokoro/tts.py
+++ b/src/pipecat/services/kokoro/tts.py
@@ -151,19 +151,28 @@ class KokoroTTSService(TTSService):
             **kwargs: Additional arguments passed to parent `TTSService`.
 
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "KokoroTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "KokoroTTSSettings")
-
-        _params = params or KokoroTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = KokoroTTSSettings(
             model=None,
-            voice=voice_id,
-            language=language_to_kokoro_language(_params.language),
-            lang_code=language_to_kokoro_language(_params.language),
+            voice=None,
+            language=language_to_kokoro_language(Language.EN),
+            lang_code=language_to_kokoro_language(Language.EN),
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", KokoroTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", KokoroTTSSettings)
+            if not settings:
+                lang_code = language_to_kokoro_language(params.language)
+                default_settings.language = lang_code
+                default_settings.lang_code = lang_code
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -172,14 +181,14 @@ class KokoroTTSService(TTSService):
             **kwargs,
         )
 
-        self._lang_code = language_to_kokoro_language(_params.language)
+        self._lang_code = default_settings.lang_code
 
-        model = Path(model_path) if model_path else KOKORO_CACHE_DIR / "kokoro-v1.0.onnx"
+        model_file = Path(model_path) if model_path else KOKORO_CACHE_DIR / "kokoro-v1.0.onnx"
         voices = Path(voices_path) if voices_path else KOKORO_CACHE_DIR / "voices-v1.0.bin"
 
-        _ensure_model_files(model, voices)
+        _ensure_model_files(model_file, voices)
 
-        self._kokoro = Kokoro(str(model), str(voices))
+        self._kokoro = Kokoro(str(model_file), str(voices))
 
         self._resampler = create_stream_resampler()
 
diff --git a/src/pipecat/services/lmnt/tts.py b/src/pipecat/services/lmnt/tts.py
index a8ccec358..c69eadfef 100644
--- a/src/pipecat/services/lmnt/tts.py
+++ b/src/pipecat/services/lmnt/tts.py
@@ -125,17 +125,25 @@ class LmntTTSService(InterruptibleTTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent InterruptibleTTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "LmntTTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "LmntTTSSettings", "model")
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = LmntTTSSettings(
-            model=model or "blizzard",
-            voice=voice_id,
+            model="blizzard",
+            voice=None,
             language=self.language_to_service_language(language),
             format="raw",
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", LmntTTSSettings, "voice")
+            default_settings.voice = voice_id
+        if model is not None:
+            _warn_deprecated_param("model", LmntTTSSettings, "model")
+            default_settings.model = model
+
+        # 3. No params for this service
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/minimax/tts.py b/src/pipecat/services/minimax/tts.py
index 9e520f763..2d9f49636 100644
--- a/src/pipecat/services/minimax/tts.py
+++ b/src/pipecat/services/minimax/tts.py
@@ -12,7 +12,7 @@ for streaming text-to-speech synthesis.
 
 import json
 from dataclasses import dataclass, field
-from typing import Any, AsyncGenerator, ClassVar, Dict, Mapping, Optional
+from typing import Any, AsyncGenerator, ClassVar, Dict, Mapping, Optional, Self
 
 import aiohttp
 from loguru import logger
@@ -123,7 +123,7 @@ class MiniMaxTTSSettings(TTSSettings):
     _aliases: ClassVar[Dict[str, str]] = {"voice_id": "voice"}
 
     @classmethod
-    def from_mapping(cls, settings: Mapping[str, Any]) -> "MiniMaxTTSSettings":
+    def from_mapping(cls, settings: Mapping[str, Any]) -> Self:
         """Construct settings from a plain dict, destructuring legacy nested dicts.
 
         Handles ``voice_setting`` (with ``vol`` → ``volume`` rename) and
@@ -245,74 +245,82 @@ class MiniMaxHttpTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent TTSService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "MiniMaxTTSSettings", "model")
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "MiniMaxTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "MiniMaxTTSSettings")
-
-        _params = params or MiniMaxHttpTTSService.InputParams()
-
-        # Resolve language boost
-        language_boost = None
-        if _params.language:
-            service_lang = self.language_to_service_language(_params.language)
-            if service_lang:
-                language_boost = service_lang
-
-        # Resolve emotion
-        emotion = None
-        if _params.emotion:
-            supported_emotions = [
-                "happy",
-                "sad",
-                "angry",
-                "fearful",
-                "disgusted",
-                "surprised",
-                "neutral",
-                "fluent",
-            ]
-            if _params.emotion in supported_emotions:
-                emotion = _params.emotion
-            else:
-                logger.warning(
-                    f"Unsupported emotion: {_params.emotion}. Supported emotions: {supported_emotions}"
-                )
-
-        # Resolve text_normalization
-        text_normalization = None
-        if _params.english_normalization is not None:
-            import warnings
-
-            with warnings.catch_warnings():
-                warnings.simplefilter("always")
-                warnings.warn(
-                    "Parameter `english_normalization` is deprecated and will be removed in a future version. Use `text_normalization` instead.",
-                    DeprecationWarning,
-                )
-            text_normalization = _params.english_normalization
-        if _params.text_normalization is not None:
-            text_normalization = _params.text_normalization
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = MiniMaxTTSSettings(
-            model=model or "speech-02-turbo",
-            voice=voice_id or "Calm_Woman",
+            model="speech-02-turbo",
+            voice="Calm_Woman",
             language=None,
             stream=True,
-            speed=_params.speed,
-            volume=_params.volume,
-            pitch=_params.pitch,
-            language_boost=language_boost,
-            emotion=emotion,
-            text_normalization=text_normalization,
-            latex_read=_params.latex_read,
+            speed=1.0,
+            volume=1.0,
+            pitch=0,
+            language_boost=None,
+            emotion=None,
+            text_normalization=None,
+            latex_read=None,
             audio_bitrate=128000,
             audio_format="pcm",
             audio_channel=1,
             audio_sample_rate=0,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", MiniMaxTTSSettings, "model")
+            default_settings.model = model
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", MiniMaxTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", MiniMaxTTSSettings)
+            if not settings:
+                default_settings.speed = params.speed
+                default_settings.volume = params.volume
+                default_settings.pitch = params.pitch
+                default_settings.latex_read = params.latex_read
+
+                # Resolve language boost
+                if params.language:
+                    service_lang = self.language_to_service_language(params.language)
+                    if service_lang:
+                        default_settings.language_boost = service_lang
+
+                # Resolve emotion
+                if params.emotion:
+                    supported_emotions = [
+                        "happy",
+                        "sad",
+                        "angry",
+                        "fearful",
+                        "disgusted",
+                        "surprised",
+                        "neutral",
+                        "fluent",
+                    ]
+                    if params.emotion in supported_emotions:
+                        default_settings.emotion = params.emotion
+                    else:
+                        logger.warning(
+                            f"Unsupported emotion: {params.emotion}. Supported emotions: {supported_emotions}"
+                        )
+
+                # Resolve text_normalization
+                if params.english_normalization is not None:
+                    import warnings
+
+                    with warnings.catch_warnings():
+                        warnings.simplefilter("always")
+                        warnings.warn(
+                            "Parameter `english_normalization` is deprecated and will be removed in a future version. Use `text_normalization` instead.",
+                            DeprecationWarning,
+                        )
+                    default_settings.text_normalization = params.english_normalization
+                if params.text_normalization is not None:
+                    default_settings.text_normalization = params.text_normalization
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/mistral/llm.py b/src/pipecat/services/mistral/llm.py
index da1f612c9..ca72cde37 100644
--- a/src/pipecat/services/mistral/llm.py
+++ b/src/pipecat/services/mistral/llm.py
@@ -48,10 +48,15 @@ class MistralLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="mistral-small-latest")
 
-        default_settings = OpenAILLMSettings(model=model or "mistral-small-latest")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/moondream/vision.py b/src/pipecat/services/moondream/vision.py
index b80928a43..3f0701c80 100644
--- a/src/pipecat/services/moondream/vision.py
+++ b/src/pipecat/services/moondream/vision.py
@@ -102,10 +102,15 @@ class MoondreamService(VisionService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to the parent VisionService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "MoondreamSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = MoondreamSettings(model="vikhyatk/moondream2")
 
-        default_settings = MoondreamSettings(model=model or "vikhyatk/moondream2")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", MoondreamSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/neuphonic/tts.py b/src/pipecat/services/neuphonic/tts.py
index e1efee96b..ae85c3ab5 100644
--- a/src/pipecat/services/neuphonic/tts.py
+++ b/src/pipecat/services/neuphonic/tts.py
@@ -154,21 +154,31 @@ class NeuphonicTTSService(InterruptibleTTSService):
             text_aggregation_mode: How to aggregate text before synthesis.
             **kwargs: Additional arguments passed to parent InterruptibleTTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "NeuphonicTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "NeuphonicTTSSettings")
-
-        _params = params or NeuphonicTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = NeuphonicTTSSettings(
             model=None,
-            language=self.language_to_service_language(_params.language),
-            speed=_params.speed,
+            voice=None,
+            language=self.language_to_service_language(Language.EN),
+            speed=1.0,
             encoding=encoding,
             sampling_rate=sample_rate,
-            voice=voice_id,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", NeuphonicTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", NeuphonicTTSSettings)
+            if not settings:
+                if params.language is not None:
+                    default_settings.language = self.language_to_service_language(params.language)
+                if params.speed is not None:
+                    default_settings.speed = params.speed
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -487,21 +497,33 @@ class NeuphonicHttpTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent TTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "NeuphonicTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "NeuphonicTTSSettings")
-
-        _params = params or NeuphonicHttpTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = NeuphonicTTSSettings(
             model=None,
-            voice=voice_id,
-            language=self.language_to_service_language(_params.language) or "en",
-            speed=_params.speed,
+            voice=None,
+            language=self.language_to_service_language(Language.EN) or "en",
+            speed=1.0,
             encoding=encoding,
             sampling_rate=sample_rate,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", NeuphonicTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", NeuphonicTTSSettings)
+            if not settings:
+                if params.language is not None:
+                    default_settings.language = (
+                        self.language_to_service_language(params.language) or "en"
+                    )
+                if params.speed is not None:
+                    default_settings.speed = params.speed
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/nvidia/llm.py b/src/pipecat/services/nvidia/llm.py
index 1667457b9..f09db54fa 100644
--- a/src/pipecat/services/nvidia/llm.py
+++ b/src/pipecat/services/nvidia/llm.py
@@ -52,12 +52,15 @@ class NvidiaLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="nvidia/llama-3.1-nemotron-70b-instruct")
 
-        default_settings = OpenAILLMSettings(
-            model=model or "nvidia/llama-3.1-nemotron-70b-instruct"
-        )
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/nvidia/stt.py b/src/pipecat/services/nvidia/stt.py
index 63e901005..3ceaf45fa 100644
--- a/src/pipecat/services/nvidia/stt.py
+++ b/src/pipecat/services/nvidia/stt.py
@@ -174,15 +174,21 @@ class NvidiaSTTService(STTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to STTService.
         """
-        if params is not None:
-            _warn_deprecated_param("params", "NvidiaSTTSettings")
-
-        _params = params or NvidiaSTTService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = NvidiaSTTSettings(
             model=model_function_map.get("model_name"),
-            language=_params.language,
+            language=Language.EN_US,
         )
+
+        # 2. (no deprecated direct args for this service)
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", NvidiaSTTSettings)
+            if not settings:
+                default_settings.language = params.language
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -492,21 +498,33 @@ class NvidiaSegmentedSTTService(SegmentedSTTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to SegmentedSTTService
         """
-        if params is not None:
-            _warn_deprecated_param("params", "NvidiaSegmentedSTTSettings")
-
-        _params = params or NvidiaSegmentedSTTService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = NvidiaSegmentedSTTSettings(
             model=model_function_map.get("model_name"),
-            language=self.language_to_service_language(_params.language or Language.EN_US)
-            or "en-US",
-            profanity_filter=_params.profanity_filter,
-            automatic_punctuation=_params.automatic_punctuation,
-            verbatim_transcripts=_params.verbatim_transcripts,
-            boosted_lm_words=_params.boosted_lm_words,
-            boosted_lm_score=_params.boosted_lm_score,
+            language=language_to_nvidia_riva_language(Language.EN_US) or "en-US",
+            profanity_filter=False,
+            automatic_punctuation=True,
+            verbatim_transcripts=False,
+            boosted_lm_words=None,
+            boosted_lm_score=4.0,
         )
+
+        # 2. (no deprecated direct args for this service)
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", NvidiaSegmentedSTTSettings)
+            if not settings:
+                default_settings.language = (
+                    language_to_nvidia_riva_language(params.language or Language.EN_US) or "en-US"
+                )
+                default_settings.profanity_filter = params.profanity_filter
+                default_settings.automatic_punctuation = params.automatic_punctuation
+                default_settings.verbatim_transcripts = params.verbatim_transcripts
+                default_settings.boosted_lm_words = params.boosted_lm_words
+                default_settings.boosted_lm_score = params.boosted_lm_score
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/nvidia/tts.py b/src/pipecat/services/nvidia/tts.py
index 75caa27e4..be0b90071 100644
--- a/src/pipecat/services/nvidia/tts.py
+++ b/src/pipecat/services/nvidia/tts.py
@@ -117,19 +117,29 @@ class NvidiaTTSService(TTSService):
             use_ssl: Whether to use SSL for the NVIDIA Riva server. Defaults to True.
             **kwargs: Additional arguments passed to parent TTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "NvidiaTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "NvidiaTTSSettings")
-
-        _params = params or NvidiaTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = NvidiaTTSSettings(
             model=model_function_map.get("model_name"),
-            voice=voice_id or "Magpie-Multilingual.EN-US.Aria",
-            language=_params.language,
-            quality=_params.quality,
+            voice="Magpie-Multilingual.EN-US.Aria",
+            language=Language.EN_US,
+            quality=20,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", NvidiaTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", NvidiaTTSSettings)
+            if not settings:
+                if params.language is not None:
+                    default_settings.language = params.language
+                if params.quality is not None:
+                    default_settings.quality = params.quality
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/ollama/llm.py b/src/pipecat/services/ollama/llm.py
index 8fc94985d..2a4a3e78f 100644
--- a/src/pipecat/services/ollama/llm.py
+++ b/src/pipecat/services/ollama/llm.py
@@ -44,10 +44,15 @@ class OLLamaLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="llama2")
 
-        default_settings = OpenAILLMSettings(model=model or "llama2")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/openai/base_llm.py b/src/pipecat/services/openai/base_llm.py
index 912b3f0b1..e3c3676c3 100644
--- a/src/pipecat/services/openai/base_llm.py
+++ b/src/pipecat/services/openai/base_llm.py
@@ -150,24 +150,41 @@ class BaseOpenAILLMService(LLMService):
             system_instruction: Optional system instruction to prepend to messages.
             **kwargs: Additional arguments passed to the parent LLMService.
         """
-        _params = params or BaseOpenAILLMService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = OpenAILLMSettings(
-            model=model or "gpt-4o",
-            frequency_penalty=_params.frequency_penalty,
-            presence_penalty=_params.presence_penalty,
-            seed=_params.seed,
-            temperature=_params.temperature,
-            top_p=_params.top_p,
+            model="gpt-4o",
+            frequency_penalty=NOT_GIVEN,
+            presence_penalty=NOT_GIVEN,
+            seed=NOT_GIVEN,
+            temperature=NOT_GIVEN,
+            top_p=NOT_GIVEN,
             top_k=None,
-            max_tokens=_params.max_tokens,
-            max_completion_tokens=_params.max_completion_tokens,
-            service_tier=_params.service_tier,
+            max_tokens=NOT_GIVEN,
+            max_completion_tokens=NOT_GIVEN,
+            service_tier=NOT_GIVEN,
             filter_incomplete_user_turns=False,
             user_turn_completion_config=None,
-            extra=_params.extra if isinstance(_params.extra, dict) else {},
+            extra={},
         )
 
+        # 2. Apply direct init arg overrides (no warnings in base class)
+        if model is not None:
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None and not settings:
+            default_settings.frequency_penalty = params.frequency_penalty
+            default_settings.presence_penalty = params.presence_penalty
+            default_settings.seed = params.seed
+            default_settings.temperature = params.temperature
+            default_settings.top_p = params.top_p
+            default_settings.max_tokens = params.max_tokens
+            default_settings.max_completion_tokens = params.max_completion_tokens
+            default_settings.service_tier = params.service_tier
+            if isinstance(params.extra, dict):
+                default_settings.extra = params.extra
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/openai/image.py b/src/pipecat/services/openai/image.py
index a145df6e5..fd9bd0ba8 100644
--- a/src/pipecat/services/openai/image.py
+++ b/src/pipecat/services/openai/image.py
@@ -70,10 +70,15 @@ class OpenAIImageGenService(ImageGenService):
             settings: Runtime-updatable settings. When provided alongside deprecated
                 parameters, ``settings`` values take precedence.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAIImageGenSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAIImageGenSettings(model="dall-e-3")
 
-        default_settings = OpenAIImageGenSettings(model=model or "dall-e-3")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAIImageGenSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/openai/llm.py b/src/pipecat/services/openai/llm.py
index a8ab760c4..56515ce89 100644
--- a/src/pipecat/services/openai/llm.py
+++ b/src/pipecat/services/openai/llm.py
@@ -10,6 +10,8 @@ import json
 from dataclasses import dataclass
 from typing import Any, Optional
 
+from openai import NOT_GIVEN
+
 from pipecat.frames.frames import (
     FunctionCallCancelFrame,
     FunctionCallInProgressFrame,
@@ -95,27 +97,44 @@ class OpenAILLMService(BaseOpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to the parent BaseOpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "OpenAILLMSettings")
-
-        _params = params or BaseOpenAILLMService.InputParams()
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = OpenAILLMSettings(
-            model=model or "gpt-4.1",
-            frequency_penalty=_params.frequency_penalty,
-            presence_penalty=_params.presence_penalty,
-            seed=_params.seed,
-            temperature=_params.temperature,
-            top_p=_params.top_p,
+            model="gpt-4.1",
+            frequency_penalty=NOT_GIVEN,
+            presence_penalty=NOT_GIVEN,
+            seed=NOT_GIVEN,
+            temperature=NOT_GIVEN,
+            top_p=NOT_GIVEN,
             top_k=None,
-            max_tokens=_params.max_tokens,
-            max_completion_tokens=_params.max_completion_tokens,
-            service_tier=_params.service_tier,
+            max_tokens=NOT_GIVEN,
+            max_completion_tokens=NOT_GIVEN,
+            service_tier=NOT_GIVEN,
             filter_incomplete_user_turns=False,
             user_turn_completion_config=None,
-            extra=_params.extra if isinstance(_params.extra, dict) else {},
+            extra={},
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", OpenAILLMSettings)
+            if not settings:
+                default_settings.frequency_penalty = params.frequency_penalty
+                default_settings.presence_penalty = params.presence_penalty
+                default_settings.seed = params.seed
+                default_settings.temperature = params.temperature
+                default_settings.top_p = params.top_p
+                default_settings.max_tokens = params.max_tokens
+                default_settings.max_completion_tokens = params.max_completion_tokens
+                default_settings.service_tier = params.service_tier
+                if isinstance(params.extra, dict):
+                    default_settings.extra = params.extra
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/openai/realtime/llm.py b/src/pipecat/services/openai/realtime/llm.py
index d6e7a71bd..1230ed2db 100644
--- a/src/pipecat/services/openai/realtime/llm.py
+++ b/src/pipecat/services/openai/realtime/llm.py
@@ -168,12 +168,6 @@ class OpenAIRealtimeLLMService(LLMService):
 
             **kwargs: Additional arguments passed to parent LLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAIRealtimeLLMSettings", "model")
-        if session_properties is not None:
-            _warn_deprecated_param(
-                "session_properties", "OpenAIRealtimeLLMSettings", "session_properties"
-            )
         if send_transcription_frames is not None:
             import warnings
 
@@ -186,8 +180,9 @@ class OpenAIRealtimeLLMService(LLMService):
                     stacklevel=2,
                 )
 
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = OpenAIRealtimeLLMSettings(
-            model=model or "gpt-realtime-1.5",
+            model="gpt-realtime-1.5",
             temperature=None,
             max_tokens=None,
             top_p=None,
@@ -197,8 +192,20 @@ class OpenAIRealtimeLLMService(LLMService):
             seed=None,
             filter_incomplete_user_turns=False,
             user_turn_completion_config=None,
-            session_properties=session_properties or events.SessionProperties(),
+            session_properties=events.SessionProperties(),
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAIRealtimeLLMSettings, "model")
+            default_settings.model = model
+        if session_properties is not None:
+            _warn_deprecated_param(
+                "session_properties", OpenAIRealtimeLLMSettings, "session_properties"
+            )
+            default_settings.session_properties = session_properties
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/openai/stt.py b/src/pipecat/services/openai/stt.py
index 5c31d3f02..ea2814619 100644
--- a/src/pipecat/services/openai/stt.py
+++ b/src/pipecat/services/openai/stt.py
@@ -94,23 +94,35 @@ class OpenAISTTService(BaseWhisperSTTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to BaseWhisperSTTService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "BaseWhisperSTTSettings", "model")
-
-        super().__init__(
-            model=model or "gpt-4o-transcribe",
-            api_key=api_key,
+        # --- 1. Hardcoded defaults ---
+        _language = language or Language.EN
+        default_settings = BaseWhisperSTTSettings(
+            model="gpt-4o-transcribe",
+            language=self.language_to_service_language(_language),
             base_url=base_url,
-            language=language,
             prompt=prompt,
             temperature=temperature,
+        )
+
+        # --- 2. Deprecated direct-arg overrides ---
+        if model is not None:
+            _warn_deprecated_param("model", BaseWhisperSTTSettings, "model")
+            default_settings.model = model
+
+        # --- 3. (no params object for this service) ---
+
+        # --- 4. Settings delta (canonical API, always wins) ---
+        if settings is not None:
+            default_settings.apply_update(settings)
+
+        super().__init__(
+            api_key=api_key,
+            base_url=base_url,
+            settings=default_settings,
             ttfs_p99_latency=ttfs_p99_latency,
             **kwargs,
         )
 
-        if settings is not None:
-            self._settings.apply_update(settings)
-
     async def _transcribe(self, audio: bytes) -> Transcription:
         assert self._language is not None  # Assigned in the BaseWhisperSTTService class
 
@@ -242,14 +254,21 @@ class OpenAIRealtimeSTTService(WebsocketSTTService):
                 "Install it with: pip install pipecat-ai[openai]"
             )
 
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAIRealtimeSTTSettings", "model")
-
+        # --- 1. Hardcoded defaults ---
         default_settings = OpenAIRealtimeSTTSettings(
-            model=model or "gpt-4o-transcribe",
+            model="gpt-4o-transcribe",
             language=language,
             prompt=prompt,
         )
+
+        # --- 2. Deprecated direct-arg overrides ---
+        if model is not None:
+            _warn_deprecated_param("model", OpenAIRealtimeSTTSettings, "model")
+            default_settings.model = model
+
+        # --- 3. (no params object for this service) ---
+
+        # --- 4. Settings delta (canonical API, always wins) ---
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -262,7 +281,7 @@ class OpenAIRealtimeSTTService(WebsocketSTTService):
         self._api_key = api_key
         self._base_url = base_url
 
-        self._prompt = prompt
+        self._prompt = self._settings.prompt
         self._turn_detection = turn_detection
         self._noise_reduction = noise_reduction
         self._should_interrupt = should_interrupt
diff --git a/src/pipecat/services/openai/tts.py b/src/pipecat/services/openai/tts.py
index 42c963808..a119c3d14 100644
--- a/src/pipecat/services/openai/tts.py
+++ b/src/pipecat/services/openai/tts.py
@@ -150,34 +150,43 @@ class OpenAITTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to TTSService.
         """
-        if voice is not None:
-            _warn_deprecated_param("voice", "OpenAITTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAITTSSettings", "model")
-        if instructions is not None:
-            _warn_deprecated_param("instructions", "OpenAITTSSettings", "instructions")
-        if speed is not None:
-            _warn_deprecated_param("speed", "OpenAITTSSettings", "speed")
-        if params is not None:
-            _warn_deprecated_param("params", "OpenAITTSSettings")
-
         if sample_rate and sample_rate != self.OPENAI_SAMPLE_RATE:
             logger.warning(
                 f"OpenAI TTS only supports {self.OPENAI_SAMPLE_RATE}Hz sample rate. "
                 f"Current rate of {sample_rate}Hz may cause issues."
             )
 
-        _params = params or OpenAITTSService.InputParams()
-        _instructions = instructions if instructions is not None else _params.instructions
-        _speed = speed if speed is not None else _params.speed
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = OpenAITTSSettings(
-            model=model or "gpt-4o-mini-tts",
-            voice=voice or "alloy",
+            model="gpt-4o-mini-tts",
+            voice="alloy",
             language=None,
-            instructions=_instructions,
-            speed=_speed,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice is not None:
+            _warn_deprecated_param("voice", OpenAITTSSettings, "voice")
+            default_settings.voice = voice
+        if model is not None:
+            _warn_deprecated_param("model", OpenAITTSSettings, "model")
+            default_settings.model = model
+        if instructions is not None:
+            _warn_deprecated_param("instructions", OpenAITTSSettings, "instructions")
+            default_settings.instructions = instructions
+        if speed is not None:
+            _warn_deprecated_param("speed", OpenAITTSSettings, "speed")
+            default_settings.speed = speed
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", OpenAITTSSettings)
+            if not settings:
+                if params.instructions is not None:
+                    default_settings.instructions = params.instructions
+                if params.speed is not None:
+                    default_settings.speed = params.speed
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/openai_realtime_beta/openai.py b/src/pipecat/services/openai_realtime_beta/openai.py
index cb660ce72..11b60c3b9 100644
--- a/src/pipecat/services/openai_realtime_beta/openai.py
+++ b/src/pipecat/services/openai_realtime_beta/openai.py
@@ -167,15 +167,9 @@ class OpenAIRealtimeBetaLLMService(LLMService):
                 stacklevel=2,
             )
 
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAIRealtimeBetaLLMSettings", "model")
-        if session_properties is not None:
-            _warn_deprecated_param(
-                "session_properties", "OpenAIRealtimeBetaLLMSettings", "session_properties"
-            )
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = OpenAIRealtimeBetaLLMSettings(
-            model=model or "gpt-4o-realtime-preview-2025-06-03",
+            model="gpt-4o-realtime-preview-2025-06-03",
             temperature=None,
             max_tokens=None,
             top_p=None,
@@ -185,8 +179,20 @@ class OpenAIRealtimeBetaLLMService(LLMService):
             seed=None,
             filter_incomplete_user_turns=False,
             user_turn_completion_config=None,
-            session_properties=session_properties or events.SessionProperties(),
+            session_properties=events.SessionProperties(),
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAIRealtimeBetaLLMSettings, "model")
+            default_settings.model = model
+        if session_properties is not None:
+            _warn_deprecated_param(
+                "session_properties", OpenAIRealtimeBetaLLMSettings, "session_properties"
+            )
+            default_settings.session_properties = session_properties
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/openpipe/llm.py b/src/pipecat/services/openpipe/llm.py
index 7fb4ebd2d..9724c0a3f 100644
--- a/src/pipecat/services/openpipe/llm.py
+++ b/src/pipecat/services/openpipe/llm.py
@@ -64,10 +64,15 @@ class OpenPipeLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="gpt-4.1")
 
-        default_settings = OpenAILLMSettings(model=model or "gpt-4.1")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/openrouter/llm.py b/src/pipecat/services/openrouter/llm.py
index ea307aaee..42f01c77d 100644
--- a/src/pipecat/services/openrouter/llm.py
+++ b/src/pipecat/services/openrouter/llm.py
@@ -50,10 +50,15 @@ class OpenRouterLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="openai/gpt-4o-2024-11-20")
 
-        default_settings = OpenAILLMSettings(model=model or "openai/gpt-4o-2024-11-20")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/perplexity/llm.py b/src/pipecat/services/perplexity/llm.py
index 1fbf763f3..2d350b736 100644
--- a/src/pipecat/services/perplexity/llm.py
+++ b/src/pipecat/services/perplexity/llm.py
@@ -53,10 +53,15 @@ class PerplexityLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="sonar")
 
-        default_settings = OpenAILLMSettings(model=model or "sonar")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/piper/tts.py b/src/pipecat/services/piper/tts.py
index 73c555c9d..fd6b0bf16 100644
--- a/src/pipecat/services/piper/tts.py
+++ b/src/pipecat/services/piper/tts.py
@@ -76,10 +76,17 @@ class PiperTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to the parent `TTSService`.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "PiperTTSSettings", "voice")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = PiperTTSSettings(model=None, voice=None, language=None)
 
-        default_settings = PiperTTSSettings(model=None, voice=voice_id, language=None)
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", PiperTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. No params for this service
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -92,15 +99,15 @@ class PiperTTSService(TTSService):
 
         _voice = self._settings.voice
         model_file = f"{_voice}.onnx"
-        model_path = Path(download_dir) / model_file
+        model_path_resolved = Path(download_dir) / model_file
 
-        if not model_path.exists():
+        if not model_path_resolved.exists():
             logger.debug(f"Downloading Piper '{_voice}' model")
             download_voice(_voice, download_dir, force_redownload=force_redownload)
 
-        logger.debug(f"Loading Piper '{_voice}' model from {model_path}")
+        logger.debug(f"Loading Piper '{_voice}' model from {model_path_resolved}")
 
-        self._voice = PiperVoice.load(model_path, use_cuda=use_cuda)
+        self._voice = PiperVoice.load(model_path_resolved, use_cuda=use_cuda)
 
         logger.debug(f"Loaded Piper '{_voice}' model")
 
@@ -222,10 +229,17 @@ class PiperHttpTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to the parent TTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "PiperHttpTTSSettings", "voice")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = PiperHttpTTSSettings(model=None, voice=None, language=None)
 
-        default_settings = PiperHttpTTSSettings(model=None, voice=voice_id, language=None)
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", PiperHttpTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. No params for this service
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/qwen/llm.py b/src/pipecat/services/qwen/llm.py
index db407f880..92d24fa76 100644
--- a/src/pipecat/services/qwen/llm.py
+++ b/src/pipecat/services/qwen/llm.py
@@ -45,10 +45,15 @@ class QwenLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="qwen-plus")
 
-        default_settings = OpenAILLMSettings(model=model or "qwen-plus")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/resembleai/tts.py b/src/pipecat/services/resembleai/tts.py
index ade4361e0..28ec8a522 100644
--- a/src/pipecat/services/resembleai/tts.py
+++ b/src/pipecat/services/resembleai/tts.py
@@ -95,17 +95,30 @@ class ResembleAITTSService(AudioContextTTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to the parent service.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "ResembleAITTSSettings", "voice")
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = ResembleAITTSSettings(
             model=None,
-            voice=voice_id,
+            voice=None,
             language=None,
-            precision=precision,
-            output_format=output_format,
-            resemble_sample_rate=sample_rate,
+            precision="PCM_16",
+            output_format="wav",
+            resemble_sample_rate=22050,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", ResembleAITTSSettings, "voice")
+            default_settings.voice = voice_id
+        if precision is not None:
+            default_settings.precision = precision
+        if output_format is not None:
+            default_settings.output_format = output_format
+        if sample_rate is not None:
+            default_settings.resemble_sample_rate = sample_rate
+
+        # 3. No params for this service
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/rime/tts.py b/src/pipecat/services/rime/tts.py
index c607a2e06..1de4087de 100644
--- a/src/pipecat/services/rime/tts.py
+++ b/src/pipecat/services/rime/tts.py
@@ -226,38 +226,57 @@ class RimeTTSService(AudioContextTTSService):
 
             **kwargs: Additional arguments passed to parent class.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "RimeTTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "RimeTTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "RimeTTSSettings")
-
-        # Initialize with parent class settings for proper frame handling
-        _params = params or RimeTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = RimeTTSSettings(
-            model=model or "arcana",
-            voice=voice_id,
+            model="arcana",
+            voice=None,
             audioFormat="pcm",
             samplingRate=0,  # updated in start()
-            language=self.language_to_service_language(_params.language)
-            if _params.language
-            else None,
-            segment=_params.segment,
-            inlineSpeedAlpha=None,  # Not applicable here
-            speedAlpha=_params.speed_alpha,
+            language=None,
+            segment=None,
+            inlineSpeedAlpha=None,
+            speedAlpha=None,
             # Arcana params
-            repetition_penalty=_params.repetition_penalty,
-            temperature=_params.temperature,
-            top_p=_params.top_p,
+            repetition_penalty=None,
+            temperature=None,
+            top_p=None,
             # Mistv2 params
-            reduceLatency=_params.reduce_latency,
-            pauseBetweenBrackets=_params.pause_between_brackets,
-            phonemizeBetweenBrackets=_params.phonemize_between_brackets,
-            noTextNormalization=_params.no_text_normalization,
-            saveOovs=_params.save_oovs,
+            reduceLatency=None,
+            pauseBetweenBrackets=None,
+            phonemizeBetweenBrackets=None,
+            noTextNormalization=None,
+            saveOovs=None,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", RimeTTSSettings, "voice")
+            default_settings.voice = voice_id
+        if model is not None:
+            _warn_deprecated_param("model", RimeTTSSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", RimeTTSSettings)
+            if not settings:
+                default_settings.language = (
+                    self.language_to_service_language(params.language) if params.language else None
+                )
+                default_settings.segment = params.segment
+                default_settings.speedAlpha = params.speed_alpha
+                # Arcana params
+                default_settings.repetition_penalty = params.repetition_penalty
+                default_settings.temperature = params.temperature
+                default_settings.top_p = params.top_p
+                # Mistv2 params
+                default_settings.reduceLatency = params.reduce_latency
+                default_settings.pauseBetweenBrackets = params.pause_between_brackets
+                default_settings.phonemizeBetweenBrackets = params.phonemize_between_brackets
+                default_settings.noTextNormalization = params.no_text_normalization
+                default_settings.saveOovs = params.save_oovs
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -713,35 +732,50 @@ class RimeHttpTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent TTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "RimeTTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "RimeTTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "RimeTTSSettings")
-
-        _params = params or RimeHttpTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = RimeTTSSettings(
-            model=model or "mistv2",
-            language=self.language_to_service_language(_params.language)
-            if _params.language
-            else "eng",
+            model="mistv2",
+            voice=None,
+            language="eng",
             audioFormat="pcm",
             samplingRate=0,
             segment=None,
-            speedAlpha=_params.speed_alpha,
-            reduceLatency=_params.reduce_latency,
-            pauseBetweenBrackets=_params.pause_between_brackets,
-            phonemizeBetweenBrackets=_params.phonemize_between_brackets,
+            speedAlpha=None,
+            reduceLatency=None,
+            pauseBetweenBrackets=None,
+            phonemizeBetweenBrackets=None,
             noTextNormalization=None,
             saveOovs=None,
-            inlineSpeedAlpha=_params.inline_speed_alpha if _params.inline_speed_alpha else None,
+            inlineSpeedAlpha=None,
             repetition_penalty=None,
             temperature=None,
             top_p=None,
-            voice=voice_id,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", RimeTTSSettings, "voice")
+            default_settings.voice = voice_id
+        if model is not None:
+            _warn_deprecated_param("model", RimeTTSSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", RimeTTSSettings)
+            if not settings:
+                default_settings.language = (
+                    self.language_to_service_language(params.language) if params.language else "eng"
+                )
+                default_settings.speedAlpha = params.speed_alpha
+                default_settings.reduceLatency = params.reduce_latency
+                default_settings.pauseBetweenBrackets = params.pause_between_brackets
+                default_settings.phonemizeBetweenBrackets = params.phonemize_between_brackets
+                default_settings.inlineSpeedAlpha = (
+                    params.inline_speed_alpha if params.inline_speed_alpha else None
+                )
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -936,28 +970,40 @@ class RimeNonJsonTTSService(InterruptibleTTSService):
             text_aggregation_mode: How to aggregate text before synthesis.
             **kwargs: Additional arguments passed to parent class.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "RimeNonJsonTTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "RimeNonJsonTTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "RimeNonJsonTTSSettings")
-
-        _params = params or RimeNonJsonTTSService.InputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = RimeNonJsonTTSSettings(
-            voice=voice_id,
-            model=model or "arcana",
+            voice=None,
+            model="arcana",
             audioFormat=audio_format,
             samplingRate=sample_rate,
-            language=self.language_to_service_language(_params.language)
-            if _params.language
-            else None,
-            segment=_params.segment,
-            repetition_penalty=_params.repetition_penalty,
-            temperature=_params.temperature,
-            top_p=_params.top_p,
+            language=None,
+            segment=None,
+            repetition_penalty=None,
+            temperature=None,
+            top_p=None,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", RimeNonJsonTTSSettings, "voice")
+            default_settings.voice = voice_id
+        if model is not None:
+            _warn_deprecated_param("model", RimeNonJsonTTSSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", RimeNonJsonTTSSettings)
+            if not settings:
+                default_settings.language = (
+                    self.language_to_service_language(params.language) if params.language else None
+                )
+                default_settings.segment = params.segment
+                default_settings.repetition_penalty = params.repetition_penalty
+                default_settings.temperature = params.temperature
+                default_settings.top_p = params.top_p
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -974,8 +1020,8 @@ class RimeNonJsonTTSService(InterruptibleTTSService):
         self._api_key = api_key
         self._url = url
         # Add any extra parameters for future compatibility
-        if _params.extra:
-            self._settings.extra.update(_params.extra)
+        if params and params.extra:
+            self._settings.extra.update(params.extra)
 
         self._receive_task = None
         self._context_id: Optional[str] = None
diff --git a/src/pipecat/services/sambanova/llm.py b/src/pipecat/services/sambanova/llm.py
index 5114297a8..f9b7b1380 100644
--- a/src/pipecat/services/sambanova/llm.py
+++ b/src/pipecat/services/sambanova/llm.py
@@ -57,10 +57,15 @@ class SambaNovaLLMService(OpenAILLMService):  # type: ignore
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="Llama-4-Maverick-17B-128E-Instruct")
 
-        default_settings = OpenAILLMSettings(model=model or "Llama-4-Maverick-17B-128E-Instruct")
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/sambanova/stt.py b/src/pipecat/services/sambanova/stt.py
index 4ca156b88..0c2d77e36 100644
--- a/src/pipecat/services/sambanova/stt.py
+++ b/src/pipecat/services/sambanova/stt.py
@@ -71,27 +71,30 @@ class SambaNovaSTTService(BaseWhisperSTTService):  # type: ignore
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to `pipecat.services.whisper.base_stt.BaseWhisperSTTService`.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "BaseWhisperSTTSettings", "model")
-        if language is not None:
-            _warn_deprecated_param("language", "BaseWhisperSTTSettings", "language")
-        if prompt is not None:
-            _warn_deprecated_param("prompt", "BaseWhisperSTTSettings", "prompt")
-        if temperature is not None:
-            _warn_deprecated_param("temperature", "BaseWhisperSTTSettings", "temperature")
-
-        model = model or "Whisper-Large-v3"
-        language = language or Language.EN
-
-        # Build settings from deprecated params and pass via settings=
-        # to avoid double deprecation warnings in BaseWhisperSTTService.
+        # --- 1. Hardcoded defaults ---
         default_settings = BaseWhisperSTTSettings(
-            model=model,
-            language=self.language_to_service_language(language),
+            model="Whisper-Large-v3",
+            language=self.language_to_service_language(Language.EN),
             base_url=base_url,
-            prompt=prompt,
-            temperature=temperature,
         )
+
+        # --- 2. Deprecated direct-arg overrides ---
+        if model is not None:
+            _warn_deprecated_param("model", BaseWhisperSTTSettings, "model")
+            default_settings.model = model
+        if language is not None:
+            _warn_deprecated_param("language", BaseWhisperSTTSettings, "language")
+            default_settings.language = self.language_to_service_language(language)
+        if prompt is not None:
+            _warn_deprecated_param("prompt", BaseWhisperSTTSettings, "prompt")
+            default_settings.prompt = prompt
+        if temperature is not None:
+            _warn_deprecated_param("temperature", BaseWhisperSTTSettings, "temperature")
+            default_settings.temperature = temperature
+
+        # --- 3. (no params object for this service) ---
+
+        # --- 4. Settings delta (canonical API, always wins) ---
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/sarvam/stt.py b/src/pipecat/services/sarvam/stt.py
index 97c8d1ccc..fd9a55f14 100644
--- a/src/pipecat/services/sarvam/stt.py
+++ b/src/pipecat/services/sarvam/stt.py
@@ -238,44 +238,56 @@ class SarvamSTTService(STTService):
             keepalive_interval: Seconds between idle checks when keepalive is enabled.
             **kwargs: Additional arguments passed to the parent STTService.
         """
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = SarvamSTTSettings(
+            model="saarika:v2.5",
+            language=None,
+            prompt=None,
+            mode=None,
+            vad_signals=None,
+            high_vad_sensitivity=None,
+        )
+
+        # 2. Apply direct init arg overrides (deprecated)
         if model is not None:
-            _warn_deprecated_param("model", "SarvamSTTSettings", "model")
+            _warn_deprecated_param("model", SarvamSTTSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
         if params is not None:
-            _warn_deprecated_param("params", "SarvamSTTSettings")
+            _warn_deprecated_param("params", SarvamSTTSettings)
+            if not settings:
+                default_settings.language = params.language
+                default_settings.prompt = params.prompt
+                default_settings.mode = params.mode
+                default_settings.vad_signals = params.vad_signals
+                default_settings.high_vad_sensitivity = params.high_vad_sensitivity
 
-        model = model or "saarika:v2.5"
-        _params = params or SarvamSTTService.InputParams()
+        # 4. Apply settings delta (canonical API, always wins)
+        if settings is not None:
+            default_settings.apply_update(settings)
 
-        # Get model configuration (validates model exists)
-        if model not in MODEL_CONFIGS:
+        # Resolve model config and validate (after all overrides)
+        resolved_model = default_settings.model
+        if resolved_model not in MODEL_CONFIGS:
             allowed = ", ".join(sorted(MODEL_CONFIGS.keys()))
-            raise ValueError(f"Unsupported model '{model}'. Allowed values: {allowed}.")
+            raise ValueError(f"Unsupported model '{resolved_model}'. Allowed values: {allowed}.")
 
-        self._config = MODEL_CONFIGS[model]
+        self._config = MODEL_CONFIGS[resolved_model]
 
         # Validate parameters against model capabilities
-        if _params.prompt is not None and not self._config.supports_prompt:
-            raise ValueError(f"Model '{model}' does not support prompt parameter.")
-        if _params.mode is not None and not self._config.supports_mode:
-            raise ValueError(f"Model '{model}' does not support mode parameter.")
-        if _params.language is not None and not self._config.supports_language:
+        if default_settings.prompt is not None and not self._config.supports_prompt:
+            raise ValueError(f"Model '{resolved_model}' does not support prompt parameter.")
+        if default_settings.mode is not None and not self._config.supports_mode:
+            raise ValueError(f"Model '{resolved_model}' does not support mode parameter.")
+        if default_settings.language is not None and not self._config.supports_language:
             raise ValueError(
-                f"Model '{model}' does not support language parameter (auto-detects language)."
+                f"Model '{resolved_model}' does not support language parameter (auto-detects language)."
             )
 
         # Resolve mode default from model config
-        mode = _params.mode if _params.mode is not None else self._config.default_mode
-
-        default_settings = SarvamSTTSettings(
-            model=model,
-            language=_params.language,
-            prompt=_params.prompt,
-            mode=mode,
-            vad_signals=_params.vad_signals,
-            high_vad_sensitivity=_params.high_vad_sensitivity,
-        )
-        if settings is not None:
-            default_settings.apply_update(settings)
+        if default_settings.mode is None:
+            default_settings.mode = self._config.default_mode
 
         super().__init__(
             sample_rate=sample_rate,
@@ -301,7 +313,7 @@ class SarvamSTTService(STTService):
         self._socket_client = None
         self._receive_task = None
 
-        if _params.vad_signals:
+        if default_settings.vad_signals:
             self._register_event_handler("on_speech_started")
             self._register_event_handler("on_speech_stopped")
             self._register_event_handler("on_utterance_end")
diff --git a/src/pipecat/services/sarvam/tts.py b/src/pipecat/services/sarvam/tts.py
index 14386d743..8c76e0ec9 100644
--- a/src/pipecat/services/sarvam/tts.py
+++ b/src/pipecat/services/sarvam/tts.py
@@ -467,55 +467,89 @@ class SarvamHttpTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent TTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "SarvamHttpTTSSettings", "voice")
-        if model is not None:
-            _warn_deprecated_param("model", "SarvamHttpTTSSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "SarvamHttpTTSSettings")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = SarvamHttpTTSSettings(
+            model="bulbul:v2",
+            voice="anushka",
+            language="en-IN",
+            enable_preprocessing=False,
+            pace=1.0,
+            pitch=None,
+            loudness=None,
+            temperature=None,
+        )
 
-        model = model or "bulbul:v2"
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", SarvamHttpTTSSettings, "model")
+            default_settings.model = model
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", SarvamHttpTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", SarvamHttpTTSSettings)
+            if not settings:
+                if params.language is not None:
+                    default_settings.language = (
+                        self.language_to_service_language(params.language) or "en-IN"
+                    )
+                if params.enable_preprocessing is not None:
+                    default_settings.enable_preprocessing = params.enable_preprocessing
+                if params.pace is not None:
+                    default_settings.pace = params.pace
+                if params.pitch is not None:
+                    default_settings.pitch = params.pitch
+                if params.loudness is not None:
+                    default_settings.loudness = params.loudness
+                if params.temperature is not None:
+                    default_settings.temperature = params.temperature
+
+        # 4. Apply settings delta (canonical API, always wins)
+        if settings is not None:
+            default_settings.apply_update(settings)
 
         # Get model configuration (validates model exists)
-        if model not in TTS_MODEL_CONFIGS:
+        resolved_model = default_settings.model
+        if resolved_model not in TTS_MODEL_CONFIGS:
             allowed = ", ".join(sorted(TTS_MODEL_CONFIGS.keys()))
-            raise ValueError(f"Unsupported model '{model}'. Allowed values: {allowed}.")
+            raise ValueError(f"Unsupported model '{resolved_model}'. Allowed values: {allowed}.")
 
-        self._config = TTS_MODEL_CONFIGS[model]
+        self._config = TTS_MODEL_CONFIGS[resolved_model]
 
         # Set default sample rate based on model if not specified
         if sample_rate is None:
             sample_rate = self._config.default_sample_rate
 
-        _params = params or SarvamHttpTTSService.InputParams()
-
-        # Set default voice based on model if not specified
-        if voice_id is None:
-            voice_id = self._config.default_speaker
+        # Set default voice based on model if not specified via any mechanism
+        if voice_id is None and (settings is None or settings.voice is NOT_GIVEN):
+            default_settings.voice = self._config.default_speaker
 
         # Validate and clamp pace to model's valid range
-        pace = _params.pace
+        pace = default_settings.pace
         pace_min, pace_max = self._config.pace_range
         if pace is not None and (pace < pace_min or pace > pace_max):
             logger.warning(f"Pace {pace} is outside model range ({pace_min}-{pace_max}). Clamping.")
-            pace = max(pace_min, min(pace_max, pace))
+            default_settings.pace = max(pace_min, min(pace_max, pace))
 
-        default_settings = SarvamHttpTTSSettings(
-            language=(
-                self.language_to_service_language(_params.language) if _params.language else "en-IN"
-            ),
-            enable_preprocessing=(
-                True if self._config.preprocessing_always_enabled else _params.enable_preprocessing
-            ),
-            pace=pace,
-            pitch=None,
-            loudness=None,
-            temperature=None,
-            model=model,
-            voice=voice_id,
-        )
-        if settings is not None:
-            default_settings.apply_update(settings)
+        # Force preprocessing for models that require it
+        if self._config.preprocessing_always_enabled:
+            default_settings.enable_preprocessing = True
+
+        # Warn about unsupported model-specific parameters
+        if not self._config.supports_pitch and default_settings.pitch not in (None, 0.0):
+            logger.warning(f"pitch parameter is ignored for {resolved_model}")
+            default_settings.pitch = None
+        if not self._config.supports_loudness and default_settings.loudness not in (None, 1.0):
+            logger.warning(f"loudness parameter is ignored for {resolved_model}")
+            default_settings.loudness = None
+        if not self._config.supports_temperature and default_settings.temperature not in (
+            None,
+            0.6,
+        ):
+            logger.warning(f"temperature parameter is ignored for {resolved_model}")
+            default_settings.temperature = None
 
         super().__init__(
             sample_rate=sample_rate,
@@ -527,22 +561,6 @@ class SarvamHttpTTSService(TTSService):
         self._base_url = base_url
         self._session = aiohttp_session
 
-        # Add parameters based on model support
-        if self._config.supports_pitch:
-            self._settings.pitch = _params.pitch
-        elif _params.pitch != 0.0:
-            logger.warning(f"pitch parameter is ignored for {model}")
-
-        if self._config.supports_loudness:
-            self._settings.loudness = _params.loudness
-        elif _params.loudness != 1.0:
-            logger.warning(f"loudness parameter is ignored for {model}")
-
-        if self._config.supports_temperature:
-            self._settings.temperature = _params.temperature
-        elif _params.temperature != 0.6:
-            logger.warning(f"temperature parameter is ignored for {model}")
-
     def can_generate_metrics(self) -> bool:
         """Check if this service can generate processing metrics.
 
@@ -858,62 +876,105 @@ class SarvamTTSService(InterruptibleTTSService):
 
         See https://docs.sarvam.ai/api-reference-docs/text-to-speech/stream
         """
-        if model is not None:
-            _warn_deprecated_param("model", "SarvamTTSSettings", "model")
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "SarvamTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "SarvamTTSSettings")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = SarvamTTSSettings(
+            model="bulbul:v2",
+            voice="anushka",
+            language="en-IN",
+            speech_sample_rate="22050",
+            enable_preprocessing=False,
+            min_buffer_size=50,
+            max_chunk_length=150,
+            output_audio_codec="linear16",
+            output_audio_bitrate="128k",
+            pace=1.0,
+            pitch=None,
+            loudness=None,
+            temperature=None,
+        )
 
-        model = model or "bulbul:v2"
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", SarvamTTSSettings, "model")
+            default_settings.model = model
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", SarvamTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", SarvamTTSSettings)
+            if not settings:
+                if params.language is not None:
+                    default_settings.language = (
+                        self.language_to_service_language(params.language) or "en-IN"
+                    )
+                if params.enable_preprocessing is not None:
+                    default_settings.enable_preprocessing = params.enable_preprocessing
+                if params.min_buffer_size is not None:
+                    default_settings.min_buffer_size = params.min_buffer_size
+                if params.max_chunk_length is not None:
+                    default_settings.max_chunk_length = params.max_chunk_length
+                if params.output_audio_codec is not None:
+                    default_settings.output_audio_codec = params.output_audio_codec
+                if params.output_audio_bitrate is not None:
+                    default_settings.output_audio_bitrate = params.output_audio_bitrate
+                if params.pace is not None:
+                    default_settings.pace = params.pace
+                if params.pitch is not None:
+                    default_settings.pitch = params.pitch
+                if params.loudness is not None:
+                    default_settings.loudness = params.loudness
+                if params.temperature is not None:
+                    default_settings.temperature = params.temperature
+
+        # 4. Apply settings delta (canonical API, always wins)
+        if settings is not None:
+            default_settings.apply_update(settings)
 
         # Get model configuration (validates model exists)
-        if model not in TTS_MODEL_CONFIGS:
+        resolved_model = default_settings.model
+        if resolved_model not in TTS_MODEL_CONFIGS:
             allowed = ", ".join(sorted(TTS_MODEL_CONFIGS.keys()))
-            raise ValueError(f"Unsupported model '{model}'. Allowed values: {allowed}.")
+            raise ValueError(f"Unsupported model '{resolved_model}'. Allowed values: {allowed}.")
 
-        self._config = TTS_MODEL_CONFIGS[model]
+        self._config = TTS_MODEL_CONFIGS[resolved_model]
 
         # Set default sample rate based on model if not specified
         if sample_rate is None:
             sample_rate = self._config.default_sample_rate
+            default_settings.speech_sample_rate = str(sample_rate)
 
-        # Set default voice based on model if not specified
-        if voice_id is None:
-            voice_id = self._config.default_speaker
-
-        _params = params or SarvamTTSService.InputParams()
+        # Set default voice based on model if not specified via any mechanism
+        if voice_id is None and (settings is None or settings.voice is NOT_GIVEN):
+            default_settings.voice = self._config.default_speaker
 
         # Validate and clamp pace to model's valid range
-        pace = _params.pace
+        pace = default_settings.pace
         pace_min, pace_max = self._config.pace_range
         if pace is not None and (pace < pace_min or pace > pace_max):
             logger.warning(f"Pace {pace} is outside model range ({pace_min}-{pace_max}). Clamping.")
-            pace = max(pace_min, min(pace_max, pace))
+            default_settings.pace = max(pace_min, min(pace_max, pace))
 
-        default_settings = SarvamTTSSettings(
-            language=(
-                self.language_to_service_language(_params.language) if _params.language else "en-IN"
-            ),
-            speech_sample_rate=str(sample_rate),
-            enable_preprocessing=(
-                True if self._config.preprocessing_always_enabled else _params.enable_preprocessing
-            ),
-            min_buffer_size=_params.min_buffer_size,
-            max_chunk_length=_params.max_chunk_length,
-            output_audio_codec=_params.output_audio_codec,
-            output_audio_bitrate=_params.output_audio_bitrate,
-            pace=pace,
-            pitch=None,
-            loudness=None,
-            temperature=None,
-            model=model,
-            voice=voice_id,
-        )
-        if settings is not None:
-            default_settings.apply_update(settings)
+        # Force preprocessing for models that require it
+        if self._config.preprocessing_always_enabled:
+            default_settings.enable_preprocessing = True
 
-        # Initialize parent class first
+        # Warn about unsupported model-specific parameters
+        if not self._config.supports_pitch and default_settings.pitch not in (None, 0.0):
+            logger.warning(f"pitch parameter is ignored for {resolved_model}")
+            default_settings.pitch = None
+        if not self._config.supports_loudness and default_settings.loudness not in (None, 1.0):
+            logger.warning(f"loudness parameter is ignored for {resolved_model}")
+            default_settings.loudness = None
+        if not self._config.supports_temperature and default_settings.temperature not in (
+            None,
+            0.6,
+        ):
+            logger.warning(f"temperature parameter is ignored for {resolved_model}")
+            default_settings.temperature = None
+
+        # Initialize parent class
         super().__init__(
             aggregate_sentences=aggregate_sentences,
             text_aggregation_mode=text_aggregation_mode,
@@ -926,25 +987,9 @@ class SarvamTTSService(InterruptibleTTSService):
         )
 
         # WebSocket endpoint URL with model query parameter
-        self._websocket_url = f"{url}?model={model}"
+        self._websocket_url = f"{url}?model={resolved_model}"
         self._api_key = api_key
 
-        # Add parameters based on model support
-        if self._config.supports_pitch:
-            self._settings.pitch = _params.pitch
-        elif _params.pitch != 0.0:
-            logger.warning(f"pitch parameter is ignored for {model}")
-
-        if self._config.supports_loudness:
-            self._settings.loudness = _params.loudness
-        elif _params.loudness != 1.0:
-            logger.warning(f"loudness parameter is ignored for {model}")
-
-        if self._config.supports_temperature:
-            self._settings.temperature = _params.temperature
-        elif _params.temperature != 0.6:
-            logger.warning(f"temperature parameter is ignored for {model}")
-
         self._receive_task = None
         self._keepalive_task = None
         self._context_id: Optional[str] = None
diff --git a/src/pipecat/services/settings.py b/src/pipecat/services/settings.py
index 546104b9a..d9ec5bc7b 100644
--- a/src/pipecat/services/settings.py
+++ b/src/pipecat/services/settings.py
@@ -56,7 +56,7 @@ if TYPE_CHECKING:
 
 def _warn_deprecated_param(
     param_name: str,
-    settings_class_name: str,
+    settings_class: type,
     settings_field: str | None = None,
     stacklevel: int = 3,
 ):
@@ -64,12 +64,13 @@ def _warn_deprecated_param(
 
     Args:
         param_name: Name of the deprecated parameter.
-        settings_class_name: Name of the settings class to use instead.
+        settings_class: The settings class to use instead.
         settings_field: Specific field on the settings class, if different
             from *param_name*.
         stacklevel: Stack depth for the warning.  Default ``3`` targets
             the caller's caller (i.e. user code that instantiated the service).
     """
+    settings_class_name = settings_class.__name__
     if settings_field:
         msg = (
             f"The `{param_name}` parameter is deprecated. "
diff --git a/src/pipecat/services/soniox/stt.py b/src/pipecat/services/soniox/stt.py
index c9b3fb7c9..b37a76b0f 100644
--- a/src/pipecat/services/soniox/stt.py
+++ b/src/pipecat/services/soniox/stt.py
@@ -218,25 +218,42 @@ class SonioxSTTService(WebsocketSTTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to the STTService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "SonioxSTTSettings", "model")
-        if params is not None:
-            _warn_deprecated_param("params", "SonioxSTTSettings")
-
-        _params = params or SonioxInputParams()
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = SonioxSTTSettings(
-            model=model or _params.model,
+            model="stt-rt-v4",
             language=None,
-            audio_format=_params.audio_format,
-            num_channels=_params.num_channels,
-            language_hints=_params.language_hints,
-            language_hints_strict=_params.language_hints_strict,
-            context=_params.context,
-            enable_speaker_diarization=_params.enable_speaker_diarization,
-            enable_language_identification=_params.enable_language_identification,
-            client_reference_id=_params.client_reference_id,
+            audio_format="pcm_s16le",
+            num_channels=1,
+            language_hints=None,
+            language_hints_strict=None,
+            context=None,
+            enable_speaker_diarization=False,
+            enable_language_identification=False,
+            client_reference_id=None,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", SonioxSTTSettings, "model")
+            default_settings.model = model
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", SonioxSTTSettings)
+            if not settings:
+                default_settings.model = params.model
+                default_settings.audio_format = params.audio_format
+                default_settings.num_channels = params.num_channels
+                default_settings.language_hints = params.language_hints
+                default_settings.language_hints_strict = params.language_hints_strict
+                default_settings.context = params.context
+                default_settings.enable_speaker_diarization = params.enable_speaker_diarization
+                default_settings.enable_language_identification = (
+                    params.enable_language_identification
+                )
+                default_settings.client_reference_id = params.client_reference_id
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/speechmatics/stt.py b/src/pipecat/services/speechmatics/stt.py
index 2d3e90896..620646d31 100644
--- a/src/pipecat/services/speechmatics/stt.py
+++ b/src/pipecat/services/speechmatics/stt.py
@@ -417,57 +417,86 @@ class SpeechmaticsSTTService(STTService):
         if not self._base_url:
             raise ValueError("Missing Speechmatics base URL")
 
-        if params is not None:
-            _warn_deprecated_param("params", "SpeechmaticsSTTSettings")
-
-        # Default params
-        params = params or SpeechmaticsSTTService.InputParams()
         self._should_interrupt = should_interrupt
 
-        # Deprecation check
-        self._check_deprecated_args(kwargs, params)
+        # Deprecation check (mutates params in-place for legacy kwargs migration)
+        _params = params or SpeechmaticsSTTService.InputParams()
+        self._check_deprecated_args(kwargs, _params)
 
-        # Output formatting defaults
-        speaker_active_format = params.speaker_active_format
-        if speaker_active_format is None:
-            speaker_active_format = (
-                "@{speaker_id}: {text}" if params.enable_diarization else "{text}"
-            )
-        speaker_passive_format = params.speaker_passive_format or speaker_active_format
-
-        # Settings — seeded from InputParams
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = SpeechmaticsSTTSettings(
             model=None,  # Will be resolved from operating_point after config is built
-            language=params.language,
-            domain=params.domain,
-            turn_detection_mode=params.turn_detection_mode,
-            speaker_active_format=speaker_active_format,
-            speaker_passive_format=speaker_passive_format,
-            focus_speakers=params.focus_speakers,
-            ignore_speakers=params.ignore_speakers,
-            focus_mode=params.focus_mode,
-            known_speakers=params.known_speakers,
-            additional_vocab=params.additional_vocab,
-            audio_encoding=params.audio_encoding,
-            operating_point=params.operating_point,
-            max_delay=params.max_delay,
-            end_of_utterance_silence_trigger=params.end_of_utterance_silence_trigger,
-            end_of_utterance_max_delay=params.end_of_utterance_max_delay,
-            punctuation_overrides=params.punctuation_overrides,
-            include_partials=params.include_partials,
-            split_sentences=params.split_sentences,
-            enable_diarization=params.enable_diarization,
-            speaker_sensitivity=params.speaker_sensitivity,
-            max_speakers=params.max_speakers,
-            prefer_current_speaker=params.prefer_current_speaker,
-            extra_params=params.extra_params,
+            language=Language.EN,
+            domain=None,
+            turn_detection_mode=TurnDetectionMode.EXTERNAL,
+            speaker_active_format="{text}",
+            speaker_passive_format="{text}",
+            focus_speakers=[],
+            ignore_speakers=[],
+            focus_mode=SpeakerFocusMode.RETAIN,
+            known_speakers=[],
+            additional_vocab=[],
+            audio_encoding=AudioEncoding.PCM_S16LE,
+            operating_point=None,
+            max_delay=None,
+            end_of_utterance_silence_trigger=None,
+            end_of_utterance_max_delay=None,
+            punctuation_overrides=None,
+            include_partials=None,
+            split_sentences=None,
+            enable_diarization=None,
+            speaker_sensitivity=None,
+            max_speakers=None,
+            prefer_current_speaker=None,
+            extra_params=None,
         )
 
+        # 2. No direct init arg overrides
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", SpeechmaticsSTTSettings)
+            if not settings:
+                default_settings.language = _params.language
+                default_settings.domain = _params.domain
+                default_settings.turn_detection_mode = _params.turn_detection_mode
+                # Output formatting defaults
+                speaker_active_format = _params.speaker_active_format
+                if speaker_active_format is None:
+                    speaker_active_format = (
+                        "@{speaker_id}: {text}" if _params.enable_diarization else "{text}"
+                    )
+                default_settings.speaker_active_format = speaker_active_format
+                default_settings.speaker_passive_format = (
+                    _params.speaker_passive_format or speaker_active_format
+                )
+                default_settings.focus_speakers = _params.focus_speakers
+                default_settings.ignore_speakers = _params.ignore_speakers
+                default_settings.focus_mode = _params.focus_mode
+                default_settings.known_speakers = _params.known_speakers
+                default_settings.additional_vocab = _params.additional_vocab
+                default_settings.audio_encoding = _params.audio_encoding
+                default_settings.operating_point = _params.operating_point
+                default_settings.max_delay = _params.max_delay
+                default_settings.end_of_utterance_silence_trigger = (
+                    _params.end_of_utterance_silence_trigger
+                )
+                default_settings.end_of_utterance_max_delay = _params.end_of_utterance_max_delay
+                default_settings.punctuation_overrides = _params.punctuation_overrides
+                default_settings.include_partials = _params.include_partials
+                default_settings.split_sentences = _params.split_sentences
+                default_settings.enable_diarization = _params.enable_diarization
+                default_settings.speaker_sensitivity = _params.speaker_sensitivity
+                default_settings.max_speakers = _params.max_speakers
+                default_settings.prefer_current_speaker = _params.prefer_current_speaker
+                default_settings.extra_params = _params.extra_params
+
         # Build SDK config from settings, then resolve model from operating_point
         self._client: VoiceAgentClient | None = None
         self._config: VoiceAgentConfig = self._build_config(default_settings)
         default_settings.model = self._config.operating_point.value
 
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -496,7 +525,7 @@ class SpeechmaticsSTTService(STTService):
         self._bot_speaking: bool = False
 
         # Event handlers
-        if params.enable_diarization:
+        if default_settings.enable_diarization:
             self._register_event_handler("on_speakers_result")
 
     # ============================================================================
diff --git a/src/pipecat/services/speechmatics/tts.py b/src/pipecat/services/speechmatics/tts.py
index 8ce6ae2ef..dff3e5f0f 100644
--- a/src/pipecat/services/speechmatics/tts.py
+++ b/src/pipecat/services/speechmatics/tts.py
@@ -104,24 +104,32 @@ class SpeechmaticsTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to TTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "SpeechmaticsTTSSettings", "voice")
-        if params is not None:
-            _warn_deprecated_param("params", "SpeechmaticsTTSSettings")
-
         if sample_rate and sample_rate != self.SPEECHMATICS_SAMPLE_RATE:
             logger.warning(
                 f"Speechmatics TTS only supports {self.SPEECHMATICS_SAMPLE_RATE}Hz sample rate. "
                 f"Current rate of {sample_rate}Hz may cause issues."
             )
-        _params = params or SpeechmaticsTTSService.InputParams()
 
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = SpeechmaticsTTSSettings(
             model=None,
-            voice=voice_id or "sarah",
+            voice="sarah",
             language=None,
-            max_retries=_params.max_retries,
+            max_retries=5,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", SpeechmaticsTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 3. Apply params overrides — only if settings not provided
+        if params is not None:
+            _warn_deprecated_param("params", SpeechmaticsTTSSettings)
+            if not settings:
+                default_settings.max_retries = params.max_retries
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/together/llm.py b/src/pipecat/services/together/llm.py
index 48e15ae5c..0fd8b637b 100644
--- a/src/pipecat/services/together/llm.py
+++ b/src/pipecat/services/together/llm.py
@@ -45,12 +45,15 @@ class TogetherLLMService(OpenAILLMService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional keyword arguments passed to OpenAILLMService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "OpenAILLMSettings", "model")
+        # 1. Initialize default_settings with hardcoded defaults
+        default_settings = OpenAILLMSettings(model="meta-llama/Meta-Llama-3.1-8B-Instruct-Turbo")
 
-        default_settings = OpenAILLMSettings(
-            model=model or "meta-llama/Meta-Llama-3.1-8B-Instruct-Turbo"
-        )
+        # 2. Apply direct init arg overrides (deprecated)
+        if model is not None:
+            _warn_deprecated_param("model", OpenAILLMSettings, "model")
+            default_settings.model = model
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/ultravox/llm.py b/src/pipecat/services/ultravox/llm.py
index 933930152..094d22827 100644
--- a/src/pipecat/services/ultravox/llm.py
+++ b/src/pipecat/services/ultravox/llm.py
@@ -186,6 +186,7 @@ class UltravoxRealtimeLLMService(LLMService):
                 May only be set with OneShotInputParams.
             **kwargs: Additional arguments passed to parent LLMService.
         """
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = UltravoxRealtimeLLMSettings(
             model=None,
             temperature=None,
@@ -199,6 +200,10 @@ class UltravoxRealtimeLLMService(LLMService):
             user_turn_completion_config=None,
             output_medium=None,
         )
+
+        # (No step 2/3 — params is required and not deprecated)
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/whisper/base_stt.py b/src/pipecat/services/whisper/base_stt.py
index a4eee299b..91bc54633 100644
--- a/src/pipecat/services/whisper/base_stt.py
+++ b/src/pipecat/services/whisper/base_stt.py
@@ -174,24 +174,30 @@ class BaseWhisperSTTService(SegmentedSTTService):
                 Override for your deployment. See https://github.com/pipecat-ai/stt-benchmark
             **kwargs: Additional arguments passed to SegmentedSTTService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "BaseWhisperSTTSettings", "model")
-        if language is not None:
-            _warn_deprecated_param("language", "BaseWhisperSTTSettings", "language")
-        if prompt is not None:
-            _warn_deprecated_param("prompt", "BaseWhisperSTTSettings", "prompt")
-        if temperature is not None:
-            _warn_deprecated_param("temperature", "BaseWhisperSTTSettings", "temperature")
-
-        _language = language or Language.EN
-
+        # --- 1. Hardcoded defaults ---
         default_settings = BaseWhisperSTTSettings(
-            model=model,
-            language=self.language_to_service_language(_language),
+            model=None,
+            language=None,
             base_url=base_url,
-            prompt=prompt,
-            temperature=temperature,
         )
+
+        # --- 2. Deprecated direct-arg overrides ---
+        if model is not None:
+            _warn_deprecated_param("model", BaseWhisperSTTSettings, "model")
+            default_settings.model = model
+        if language is not None:
+            _warn_deprecated_param("language", BaseWhisperSTTSettings, "language")
+            default_settings.language = self.language_to_service_language(language)
+        if prompt is not None:
+            _warn_deprecated_param("prompt", BaseWhisperSTTSettings, "prompt")
+            default_settings.prompt = prompt
+        if temperature is not None:
+            _warn_deprecated_param("temperature", BaseWhisperSTTSettings, "temperature")
+            default_settings.temperature = temperature
+
+        # --- 3. (no params object for this service) ---
+
+        # --- 4. Settings delta (canonical API, always wins) ---
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -202,10 +208,8 @@ class BaseWhisperSTTService(SegmentedSTTService):
         )
         self._client = self._create_client(api_key, base_url)
         self._language = self._settings.language
-        self._prompt = self._settings.prompt if self._settings.prompt else prompt
-        self._temperature = (
-            self._settings.temperature if self._settings.temperature else temperature
-        )
+        self._prompt = self._settings.prompt
+        self._temperature = self._settings.temperature
         self._include_prob_metrics = include_prob_metrics
 
     def _create_client(self, api_key: Optional[str], base_url: Optional[str]):
diff --git a/src/pipecat/services/whisper/stt.py b/src/pipecat/services/whisper/stt.py
index 38fd287fa..17fe24c2d 100644
--- a/src/pipecat/services/whisper/stt.py
+++ b/src/pipecat/services/whisper/stt.py
@@ -256,30 +256,35 @@ class WhisperSTTService(SegmentedSTTService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to SegmentedSTTService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "WhisperSTTSettings", "model")
-        if device is not None:
-            _warn_deprecated_param("device", "WhisperSTTSettings", "device")
-        if compute_type is not None:
-            _warn_deprecated_param("compute_type", "WhisperSTTSettings", "compute_type")
-        if no_speech_prob is not None:
-            _warn_deprecated_param("no_speech_prob", "WhisperSTTSettings", "no_speech_prob")
-        if language is not None:
-            _warn_deprecated_param("language", "WhisperSTTSettings", "language")
-
-        _model = model if model is not None else Model.DISTIL_MEDIUM_EN
-        _device = device or "auto"
-        _compute_type = compute_type or "default"
-        _no_speech_prob = no_speech_prob if no_speech_prob is not None else 0.4
-        _language = language or Language.EN
-
+        # --- 1. Hardcoded defaults ---
         default_settings = WhisperSTTSettings(
-            model=_model if isinstance(_model, str) else _model.value,
-            language=_language,
-            device=_device,
-            compute_type=_compute_type,
-            no_speech_prob=_no_speech_prob,
+            model=Model.DISTIL_MEDIUM_EN.value,
+            language=Language.EN,
+            device="auto",
+            compute_type="default",
+            no_speech_prob=0.4,
         )
+
+        # --- 2. Deprecated direct-arg overrides ---
+        if model is not None:
+            _warn_deprecated_param("model", WhisperSTTSettings, "model")
+            default_settings.model = model if isinstance(model, str) else model.value
+        if device is not None:
+            _warn_deprecated_param("device", WhisperSTTSettings, "device")
+            default_settings.device = device
+        if compute_type is not None:
+            _warn_deprecated_param("compute_type", WhisperSTTSettings, "compute_type")
+            default_settings.compute_type = compute_type
+        if no_speech_prob is not None:
+            _warn_deprecated_param("no_speech_prob", WhisperSTTSettings, "no_speech_prob")
+            default_settings.no_speech_prob = no_speech_prob
+        if language is not None:
+            _warn_deprecated_param("language", WhisperSTTSettings, "language")
+            default_settings.language = language
+
+        # --- 3. (no params object for this service) ---
+
+        # --- 4. Settings delta (canonical API, always wins) ---
         if settings is not None:
             default_settings.apply_update(settings)
 
@@ -430,27 +435,32 @@ class WhisperSTTServiceMLX(WhisperSTTService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to SegmentedSTTService.
         """
-        if model is not None:
-            _warn_deprecated_param("model", "WhisperMLXSTTSettings", "model")
-        if no_speech_prob is not None:
-            _warn_deprecated_param("no_speech_prob", "WhisperMLXSTTSettings", "no_speech_prob")
-        if language is not None:
-            _warn_deprecated_param("language", "WhisperMLXSTTSettings", "language")
-        if temperature is not None:
-            _warn_deprecated_param("temperature", "WhisperMLXSTTSettings", "temperature")
-
-        _model = model if model is not None else MLXModel.TINY
-        _no_speech_prob = no_speech_prob if no_speech_prob is not None else 0.6
-        _language = language or Language.EN
-        _temperature = temperature if temperature is not None else 0.0
-
+        # --- 1. Hardcoded defaults ---
         default_settings = WhisperMLXSTTSettings(
-            model=_model if isinstance(_model, str) else _model.value,
-            language=_language,
-            no_speech_prob=_no_speech_prob,
-            temperature=_temperature,
+            model=MLXModel.TINY.value,
+            language=Language.EN,
+            no_speech_prob=0.6,
+            temperature=0.0,
             engine="mlx",
         )
+
+        # --- 2. Deprecated direct-arg overrides ---
+        if model is not None:
+            _warn_deprecated_param("model", WhisperMLXSTTSettings, "model")
+            default_settings.model = model if isinstance(model, str) else model.value
+        if no_speech_prob is not None:
+            _warn_deprecated_param("no_speech_prob", WhisperMLXSTTSettings, "no_speech_prob")
+            default_settings.no_speech_prob = no_speech_prob
+        if language is not None:
+            _warn_deprecated_param("language", WhisperMLXSTTSettings, "language")
+            default_settings.language = language
+        if temperature is not None:
+            _warn_deprecated_param("temperature", WhisperMLXSTTSettings, "temperature")
+            default_settings.temperature = temperature
+
+        # --- 3. (no params object for this service) ---
+
+        # --- 4. Settings delta (canonical API, always wins) ---
         if settings is not None:
             default_settings.apply_update(settings)
 
diff --git a/src/pipecat/services/xtts/tts.py b/src/pipecat/services/xtts/tts.py
index 88137172f..c5bfe629e 100644
--- a/src/pipecat/services/xtts/tts.py
+++ b/src/pipecat/services/xtts/tts.py
@@ -118,15 +118,20 @@ class XTTSService(TTSService):
                 parameters, ``settings`` values take precedence.
             **kwargs: Additional arguments passed to parent TTSService.
         """
-        if voice_id is not None:
-            _warn_deprecated_param("voice_id", "XTTSTTSSettings", "voice")
-
+        # 1. Initialize default_settings with hardcoded defaults
         default_settings = XTTSTTSSettings(
             model=None,
-            voice=voice_id,
+            voice=None,
             language=self.language_to_service_language(language),
             base_url=base_url,
         )
+
+        # 2. Apply direct init arg overrides (deprecated)
+        if voice_id is not None:
+            _warn_deprecated_param("voice_id", XTTSTTSSettings, "voice")
+            default_settings.voice = voice_id
+
+        # 4. Apply settings delta (canonical API, always wins)
         if settings is not None:
             default_settings.apply_update(settings)