fix: warn when unsupported parameters are silently ignored

src/celeste/__init__.py

@@ -29,6 +29,7 @@
     StreamNotExhaustedError,
     UnsupportedCapabilityError,
     UnsupportedParameterError,
+    UnsupportedParameterWarning,
     UnsupportedProviderError,
     ValidationError,
 )
@@ -272,6 +273,7 @@ def create_client(
     "StrictRefResolvingJsonSchemaGenerator",
     "UnsupportedCapabilityError",
     "UnsupportedParameterError",
+    "UnsupportedParameterWarning",
     "UnsupportedProviderError",
     "Usage",
     "UsageField",

src/celeste/client.py

@@ -1,5 +1,6 @@
 """Base client for modality-specific AI operations."""
 
+import warnings
 from abc import ABC, abstractmethod
 from collections.abc import AsyncIterator
 from json import JSONDecodeError
@@ -10,7 +11,7 @@
 
 from celeste.auth import Authentication
 from celeste.core import Modality, Provider
-from celeste.exceptions import StreamingNotSupportedError
+from celeste.exceptions import StreamingNotSupportedError, UnsupportedParameterWarning
 from celeste.http import HTTPClient, get_http_client
 from celeste.io import Chunk as ChunkBase
 from celeste.io import FinishReason, Input, Output, Usage
@@ -408,9 +409,18 @@ def _build_request(
         request = self._init_request(inputs)
 
         for mapper in self.parameter_mappers():
-            value = parameters.get(mapper.name)
+            value = parameters.pop(mapper.name, None)
             request = mapper.map(request, value, self.model)
 
+        for name, value in parameters.items():
+            if value is not None:
+                warnings.warn(
+                    f"Parameter '{name}' is not supported by model "
+                    f"'{self.model.id}' and will be ignored.",
+                    UnsupportedParameterWarning,
+                    stacklevel=4,
+                )
+
         if extra_body:
             self._deep_merge(request, extra_body)
 

src/celeste/exceptions.py

@@ -245,6 +245,10 @@ def __init__(self, parameter: str, model_id: str) -> None:
         )
 
 
+class UnsupportedParameterWarning(UserWarning):
+    """Emitted when a parameter is not supported by a provider and will be ignored."""
+
+
 __all__ = [
     "ClientNotFoundError",
     "ConstraintViolationError",
@@ -259,5 +263,6 @@ def __init__(self, parameter: str, model_id: str) -> None:
     "StreamingNotSupportedError",
     "UnsupportedCapabilityError",
     "UnsupportedParameterError",
+    "UnsupportedParameterWarning",
     "UnsupportedProviderError",
 ]

tests/unit_tests/test_client.py

@@ -11,7 +11,7 @@
 from celeste.auth import APIKey
 from celeste.client import ModalityClient
 from celeste.core import Modality, Provider
-from celeste.exceptions import StreamingNotSupportedError
+from celeste.exceptions import StreamingNotSupportedError, UnsupportedParameterWarning
 from celeste.io import Chunk, Input, Output, Usage
 from celeste.models import Model, Operation
 from celeste.parameters import ParameterMapper, Parameters
@@ -222,6 +222,71 @@ def parameter_mappers(cls) -> list[ParameterMapper[str]]:
         assert request["first_param"] == "first"
         assert request["second_param"] == "second"
 
+    def test_build_request_warns_on_unsupported_parameter(
+        self, text_model: Model, api_key: str
+    ) -> None:
+        """_build_request emits UnsupportedParameterWarning for unmapped parameters."""
+
+        class ClientWithOneMapper(ConcreteModalityClient):
+            @classmethod
+            def parameter_mappers(cls) -> list[ParameterMapper[str]]:
+                return [_create_test_mapper(ParamEnum.FIRST_PARAM)]
+
+        client = ClientWithOneMapper(
+            modality=Modality.TEXT,
+            model=text_model,
+            provider=text_model.provider,
+            auth=APIKey(secret=SecretStr(api_key)),
+        )
+
+        inputs = _TestInput(prompt="test")
+
+        with pytest.warns(UnsupportedParameterWarning, match="second_param.*gpt-4"):
+            client._build_request(inputs, first_param="ok", second_param="unsupported")
+
+    def test_build_request_no_warning_for_supported_parameters(
+        self, text_model: Model, api_key: str
+    ) -> None:
+        """_build_request does not warn when all parameters have mappers."""
+        import warnings
+
+        class ClientWithMapper(ConcreteModalityClient):
+            @classmethod
+            def parameter_mappers(cls) -> list[ParameterMapper[str]]:
+                return [_create_test_mapper(ParamEnum.TEST_PARAM)]
+
+        client = ClientWithMapper(
+            modality=Modality.TEXT,
+            model=text_model,
+            provider=text_model.provider,
+            auth=APIKey(secret=SecretStr(api_key)),
+        )
+
+        inputs = _TestInput(prompt="test")
+
+        with warnings.catch_warnings():
+            warnings.simplefilter("error", UnsupportedParameterWarning)
+            client._build_request(inputs, test_param="supported")
+
+    def test_build_request_no_warning_for_none_unsupported_parameter(
+        self, text_model: Model, api_key: str
+    ) -> None:
+        """_build_request does not warn when unsupported parameter value is None."""
+        import warnings
+
+        client = ConcreteModalityClient(
+            modality=Modality.TEXT,
+            model=text_model,
+            provider=text_model.provider,
+            auth=APIKey(secret=SecretStr(api_key)),
+        )
+
+        inputs = _TestInput(prompt="test")
+
+        with warnings.catch_warnings():
+            warnings.simplefilter("error", UnsupportedParameterWarning)
+            client._build_request(inputs, test_param=None)
+
     @pytest.mark.parametrize(
         "param_value,expected_output",
         [