From a03378f6d18a09f68322f2b1b123195ec8965a1a Mon Sep 17 00:00:00 2001 From: mateo-berri <277851410+mateo-berri@users.noreply.github.com> Date: Mon, 31 Aug 2026 21:14:54 -0700 Subject: [PATCH 1/2] fix(openai): forward reasoning_effort for unknown model aliases instead of failing closed --- .../llms/openai/chat/gpt_transformation.py | 4 ++ .../chat/test_openai_gpt_transformation.py | 41 +++++++++++++++++++ 2 files changed, 45 insertions(+) diff --git a/litellm/llms/openai/chat/gpt_transformation.py b/litellm/llms/openai/chat/gpt_transformation.py index 5894658e5d2..255ee3159c3 100644 --- a/litellm/llms/openai/chat/gpt_transformation.py +++ b/litellm/llms/openai/chat/gpt_transformation.py @@ -178,6 +178,10 @@ class OpenAIGPTConfig(BaseLLMModelInfo, BaseConfig): model_specific_params.append( "user" ) # user is not a param supported by all openai-compatible endpoints - e.g. azure ai + else: + model_specific_params.append( + "reasoning_effort" + ) # unknown model: likely a proxy alias for a reasoning-capable model, so forward and let the server decide return base_params + model_specific_params def _map_openai_params( diff --git a/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py b/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py index 3f346b5e8e7..1ee53a90d7d 100644 --- a/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py +++ b/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py @@ -145,6 +145,47 @@ class TestGetOptionalParamsIntegration: assert regular_params.get("user") == "my-end-user" assert responses_params.get("user") == "my-end-user" + def test_reasoning_effort_supported_for_unknown_model_alias(self): + """An openai/-routed model litellm doesn't recognize is likely a proxy alias: + reasoning_effort must be forwarded so the server decides support.""" + supported_params = OpenAIGPTConfig().get_supported_openai_params( + "my-claude-alias" + ) + assert "reasoning_effort" in supported_params + + def test_reasoning_effort_not_supported_for_known_non_reasoning_models(self): + """Known OpenAI models keep failing closed client-side.""" + config = OpenAIGPTConfig() + assert "reasoning_effort" not in config.get_supported_openai_params("gpt-4o") + assert "reasoning_effort" not in config.get_supported_openai_params( + "responses/gpt-4.1-mini" + ) + + def test_reasoning_effort_forwarded_in_optional_params_for_unknown_model_alias( + self, + ): + """Regression test for reasoning_effort raising UnsupportedParamsError + client-side for openai/-prefixed proxy aliases before any HTTP request.""" + from litellm.utils import get_optional_params + + optional_params = get_optional_params( + model="my-claude-alias", + custom_llm_provider="openai", + reasoning_effort="low", + ) + assert optional_params.get("reasoning_effort") == "low" + + def test_reasoning_effort_still_rejected_for_known_non_reasoning_model(self): + """A real OpenAI model that doesn't reason still rejects the param client-side.""" + from litellm.utils import get_optional_params + + with pytest.raises(litellm.utils.UnsupportedParamsError): + get_optional_params( + model="gpt-4o", + custom_llm_provider="openai", + reasoning_effort="low", + ) + class TestOpenAIChatCompletionStreamingHandler: """Tests for OpenAIChatCompletionStreamingHandler.chunk_parser()""" From 0a9676bd4f7af7880a49aafe665b3951343e1cd9 Mon Sep 17 00:00:00 2001 From: mateo-berri <277851410+mateo-berri@users.noreply.github.com> Date: Mon, 31 Aug 2026 21:42:31 -0700 Subject: [PATCH 2/2] fix(openai): scope unknown-model reasoning_effort forwarding to the plain openai provider --- .../llms/openai/chat/gpt_transformation.py | 26 ++++++++++++------- litellm/llms/openai/openai.py | 10 +++++-- litellm/utils.py | 7 +++++ .../chat/test_openai_gpt_transformation.py | 26 +++++++++++++++++-- 4 files changed, 56 insertions(+), 13 deletions(-) diff --git a/litellm/llms/openai/chat/gpt_transformation.py b/litellm/llms/openai/chat/gpt_transformation.py index 255ee3159c3..d4747b2fb06 100644 --- a/litellm/llms/openai/chat/gpt_transformation.py +++ b/litellm/llms/openai/chat/gpt_transformation.py @@ -170,20 +170,20 @@ class OpenAIGPTConfig(BaseLLMModelInfo, BaseConfig): if model != "gpt-3.5-turbo-16k" and model != "gpt-4": # gpt-4 does not support 'response_format' model_specific_params.append("response_format") - # Normalize model name for responses API (e.g., "responses/gpt-4.1" -> "gpt-4.1") - model_for_check: Final = model.split("responses/", 1)[1] if "responses/" in model else model - if ( - model_for_check in litellm.open_ai_chat_completion_models - ) or model_for_check in litellm.open_ai_text_completion_models: + if OpenAIGPTConfig.is_openai_catalog_model(model): model_specific_params.append( "user" ) # user is not a param supported by all openai-compatible endpoints - e.g. azure ai - else: - model_specific_params.append( - "reasoning_effort" - ) # unknown model: likely a proxy alias for a reasoning-capable model, so forward and let the server decide return base_params + model_specific_params + @staticmethod + def is_openai_catalog_model(model: str) -> bool: + model_for_check: Final = model.split("responses/", 1)[1] if "responses/" in model else model + return ( + model_for_check in litellm.open_ai_chat_completion_models + or model_for_check in litellm.open_ai_text_completion_models + ) + def _map_openai_params( self, non_default_params: dict, @@ -759,6 +759,14 @@ class OpenAIGPTConfig(BaseLLMModelInfo, BaseConfig): ) +class OpenAIUnknownModelConfig(OpenAIGPTConfig): + """A model the openai provider does not recognize is typically a LiteLLM proxy alias, so + forward reasoning_effort and let the server decide whether it is supported.""" + + def get_supported_openai_params(self, model: str) -> list: # mutable-ok: inherited contract + return super().get_supported_openai_params(model) + ["reasoning_effort"] # mutable-ok: inherited contract + + class OpenAIChatCompletionStreamingHandler(BaseModelResponseIterator): def _map_reasoning_to_reasoning_content(self, choices: list) -> list: """ diff --git a/litellm/llms/openai/openai.py b/litellm/llms/openai/openai.py index 16fa0017b23..56495f0097d 100644 --- a/litellm/llms/openai/openai.py +++ b/litellm/llms/openai/openai.py @@ -43,6 +43,7 @@ from litellm.utils import ( from ...types.llms.openai import * from ..base import BaseLLM from .chat.gpt_5_transformation import OpenAIGPT5Config +from .chat.gpt_transformation import OpenAIGPTConfig, OpenAIUnknownModelConfig from .chat.o_series_transformation import OpenAIOSeriesConfig from .common_utils import ( BaseOpenAILLM, @@ -189,7 +190,12 @@ class OpenAIConfig(BaseConfig): elif litellm.openAIGPTAudioConfig.is_model_gpt_audio_model(model=model): return litellm.openAIGPTAudioConfig.get_supported_openai_params(model=model) else: - return litellm.openAIGPTConfig.get_supported_openai_params(model=model) + return self._gpt_config_for_model(model).get_supported_openai_params(model=model) + + def _gpt_config_for_model(self, model: str) -> OpenAIGPTConfig: + if type(self) is OpenAIConfig and not OpenAIGPTConfig.is_openai_catalog_model(model): + return OpenAIUnknownModelConfig() + return litellm.openAIGPTConfig def _map_openai_params(self, non_default_params: dict, optional_params: dict, model: str) -> dict: supported_openai_params: Final = self.get_supported_openai_params(model) @@ -231,7 +237,7 @@ class OpenAIConfig(BaseConfig): drop_params=drop_params, ) - return litellm.openAIGPTConfig.map_openai_params( + return self._gpt_config_for_model(model).map_openai_params( non_default_params=non_default_params, optional_params=optional_params, model=model, diff --git a/litellm/utils.py b/litellm/utils.py index f5adca8f272..15c1b0e9c0f 100644 --- a/litellm/utils.py +++ b/litellm/utils.py @@ -8278,10 +8278,17 @@ class ProviderConfigManager: """ # Handle OpenAI special cases (O-series and GPT-5 models) if provider == LlmProviders.OPENAI: + from litellm.llms.openai.chat.gpt_transformation import ( + OpenAIGPTConfig, + OpenAIUnknownModelConfig, + ) + if litellm.openaiOSeriesConfig.is_model_o_series_model(model=model): return litellm.openaiOSeriesConfig if litellm.OpenAIGPT5Config.is_model_gpt_5_model(model=model): return litellm.OpenAIGPT5Config() + if not OpenAIGPTConfig.is_openai_catalog_model(model): + return OpenAIUnknownModelConfig() # Handle Azure before the generic map so base_model can be threaded through if provider == LlmProviders.AZURE: diff --git a/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py b/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py index 1ee53a90d7d..3ef5e39fc5f 100644 --- a/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py +++ b/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py @@ -148,19 +148,41 @@ class TestGetOptionalParamsIntegration: def test_reasoning_effort_supported_for_unknown_model_alias(self): """An openai/-routed model litellm doesn't recognize is likely a proxy alias: reasoning_effort must be forwarded so the server decides support.""" - supported_params = OpenAIGPTConfig().get_supported_openai_params( + from litellm.llms.openai.openai import OpenAIConfig + + supported_params = OpenAIConfig().get_supported_openai_params( "my-claude-alias" ) assert "reasoning_effort" in supported_params def test_reasoning_effort_not_supported_for_known_non_reasoning_models(self): """Known OpenAI models keep failing closed client-side.""" - config = OpenAIGPTConfig() + from litellm.llms.openai.openai import OpenAIConfig + + config = OpenAIConfig() assert "reasoning_effort" not in config.get_supported_openai_params("gpt-4o") assert "reasoning_effort" not in config.get_supported_openai_params( "responses/gpt-4.1-mini" ) + def test_reasoning_effort_not_inherited_by_openai_compatible_subclasses(self): + """Providers subclassing either openai config keep their own reasoning_effort gating + for their models, which are all unknown to the openai catalog.""" + from litellm.llms.openai.openai import OpenAIConfig + + class InheritingDispatcherConfig(OpenAIConfig): + pass + + class InheritingGPTConfig(OpenAIGPTConfig): + pass + + assert "reasoning_effort" not in InheritingDispatcherConfig().get_supported_openai_params( + "some-unknown-model" + ) + assert "reasoning_effort" not in InheritingGPTConfig().get_supported_openai_params( + "some-unknown-model" + ) + def test_reasoning_effort_forwarded_in_optional_params_for_unknown_model_alias( self, ):