From 855f56fa946674c3a25ee873fca6a09d4783edcd Mon Sep 17 00:00:00 2001 From: mateo-berri <277851410+mateo-berri@users.noreply.github.com> Date: Sat, 29 Aug 2026 16:25:28 -0700 Subject: [PATCH] fix(openai): flatten top-level tool schema combinators on chat completions --- .../llms/openai/chat/gpt_transformation.py | 82 ++++++++++-- .../chat/test_openai_gpt_transformation.py | 118 ++++++++++++++++++ 2 files changed, 190 insertions(+), 10 deletions(-) diff --git a/litellm/llms/openai/chat/gpt_transformation.py b/litellm/llms/openai/chat/gpt_transformation.py index 5894658e5d2..89062f60fc7 100644 --- a/litellm/llms/openai/chat/gpt_transformation.py +++ b/litellm/llms/openai/chat/gpt_transformation.py @@ -4,7 +4,8 @@ Support for gpt model family import json import os -from collections.abc import AsyncIterator, Coroutine, Iterator +from collections.abc import AsyncIterator, Coroutine, Iterator, Mapping +from types import MappingProxyType from typing import TYPE_CHECKING, Any, Final, Literal, Optional, cast, overload from urllib.parse import urlparse @@ -19,6 +20,7 @@ from litellm.litellm_core_utils.llm_response_utils.convert_dict_to_response impo ) from litellm.litellm_core_utils.prompt_templates.common_utils import ( drop_tool_reference_parts_from_tool_messages, + flatten_top_level_schema_combinators, get_tool_call_names, hoist_images_from_tool_messages, ) @@ -65,6 +67,22 @@ else: LiteLLMLoggingObj = Any +_NO_TOOLS_UPDATE: Final[Mapping[str, object]] = MappingProxyType({}) + + +def _tool_with_flattened_parameters(tool: Mapping[str, object]) -> Mapping[str, object]: + function: Final = tool.get("function") + if not isinstance(function, dict): + return tool + parameters: Final = function.get("parameters") + if not isinstance(parameters, dict): + return tool + flattened: Final = flatten_top_level_schema_combinators(parameters) + if flattened is parameters: + return tool + return {**tool, "function": {**function, "parameters": flattened}} # mutable-ok: request tools are JSON dicts + + class OpenAIGPTConfig(BaseLLMModelInfo, BaseConfig): """ Reference: https://platform.openai.com/docs/api-reference/chat/create @@ -393,6 +411,26 @@ class OpenAIGPTConfig(BaseLLMModelInfo, BaseConfig): ) return messages, tools + def _targets_openai_hosted_endpoint( + self, + custom_llm_provider: str | None, + api_base: str | None, + ) -> bool: + """ + True only for the generic `openai` provider actually pointed at + api.openai.com (no custom api_base, or an openai.com host): the one + backend enforcing OpenAI-only request strictness. + """ + if custom_llm_provider != "openai": + return False + resolved_api_base = api_base or litellm.api_base or os.getenv("OPENAI_BASE_URL") or os.getenv("OPENAI_API_BASE") + if not resolved_api_base: + return True + hostname: Final = urlparse(resolved_api_base).hostname + if hostname is None: + return True + return hostname == "openai.com" or hostname.endswith(".openai.com") + def _should_preserve_cache_control_for_endpoint( self, custom_llm_provider: str | None, @@ -404,15 +442,37 @@ class OpenAIGPTConfig(BaseLLMModelInfo, BaseConfig): api_base. Those can understand cache_control, so it must survive there. Real OpenAI cannot, so it is still stripped for an openai.com host. """ - if custom_llm_provider != "openai": - return False - resolved_api_base = api_base or litellm.api_base or os.getenv("OPENAI_BASE_URL") or os.getenv("OPENAI_API_BASE") - if not resolved_api_base: - return False - hostname: Final = urlparse(resolved_api_base).hostname - if hostname is None: - return False - return hostname != "openai.com" and not hostname.endswith(".openai.com") + return custom_llm_provider == "openai" and not self._targets_openai_hosted_endpoint( + custom_llm_provider, api_base + ) + + def _flattened_tools_update_for_openai( + self, + optional_params: Mapping[str, object], + litellm_params: Mapping[str, object], + ) -> Mapping[str, object]: + """ + OpenAI's chat completions validator rejects tool `parameters` carrying + 'oneOf'/'anyOf'/'allOf'/'enum'/'const'/'not' at the top level for every + model family (unlike the Responses API, where GPT-5+ accepts them), so + tool schemas bound for api.openai.com get their top-level combinators + flattened; OpenAI-compatible backends on a custom api_base accept the + caller's schema as-is and keep it. + """ + tools: Final = optional_params.get("tools") + if not isinstance(tools, list): + return _NO_TOOLS_UPDATE + provider: Final = litellm_params.get("custom_llm_provider") + raw_api_base: Final = litellm_params.get("api_base") + if not self._targets_openai_hosted_endpoint( + provider if isinstance(provider, str) else None, + raw_api_base if isinstance(raw_api_base, str) else None, + ): + return _NO_TOOLS_UPDATE + flattened: Final = [ # mutable-ok: request tools are a JSON list + _tool_with_flattened_parameters(tool) if isinstance(tool, dict) else tool for tool in tools + ] + return MappingProxyType({"tools": flattened}) def transform_request( self, @@ -444,6 +504,7 @@ class OpenAIGPTConfig(BaseLLMModelInfo, BaseConfig): "model": model, "messages": messages, **optional_params, + **self._flattened_tools_update_for_openai(optional_params, litellm_params), } async def async_transform_request( @@ -473,6 +534,7 @@ class OpenAIGPTConfig(BaseLLMModelInfo, BaseConfig): "model": model, "messages": transformed_messages, **optional_params, + **self._flattened_tools_update_for_openai(optional_params, litellm_params), } else: ## allow for any object specific behaviour to be handled 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..e65ef239068 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 @@ -975,3 +975,121 @@ class TestOpenAIPromptCacheBreakpointChatPath: assert request["messages"][1]["content"] == [{"type": "text", "text": "hi", "prompt_cache_breakpoint": self.EXPLICIT}] assert request["extra_body"] == {"prompt_cache_options": self.EXPLICIT} assert "prompt_cache_options" not in request + + +class TestToolSchemaCombinatorFlatteningForOpenAI: + """ + Regression tests for LIT-6488: OpenAI's chat completions validator rejects + tool parameters carrying a top-level anyOf/oneOf/allOf for every model + family (GPT-5 included, unlike the Responses API), so requests bound for + api.openai.com get those combinators flattened into one object schema, + while OpenAI-compatible backends on a custom api_base and other providers + keep the caller's schema untouched. + """ + + def setup_method(self): + self.config = OpenAIGPTConfig() + + @pytest.fixture(autouse=True) + def _clean_openai_base_env(self, monkeypatch): + monkeypatch.delenv("OPENAI_BASE_URL", raising=False) + monkeypatch.delenv("OPENAI_API_BASE", raising=False) + monkeypatch.setattr(litellm, "api_base", None, raising=False) + + @staticmethod + def _anyof_tool(): + return { + "type": "function", + "function": { + "name": "automation_update", + "description": "Update an automation", + "parameters": { + "type": "object", + "anyOf": [ + { + "properties": {"id": {"type": "string"}, "enabled": {"type": "boolean"}}, + "required": ["id", "enabled"], + }, + { + "properties": {"id": {"type": "string"}, "schedule": {"type": "string"}}, + "required": ["id", "schedule"], + }, + ], + "properties": {"id": {"type": "string"}}, + "required": ["id"], + }, + }, + } + + def _transform(self, config, model, litellm_params, tools): + return config.transform_request( + model=model, + messages=[{"role": "user", "content": "hi"}], + optional_params={"tools": tools}, + litellm_params=litellm_params, + headers={}, + ) + + def test_flattens_top_level_anyof_for_hosted_openai(self): + request = self._transform( + self.config, "gpt-4o", {"custom_llm_provider": "openai", "api_base": None}, [self._anyof_tool()] + ) + parameters = request["tools"][0]["function"]["parameters"] + assert "anyOf" not in parameters + assert parameters["type"] == "object" + assert set(parameters["properties"]) == {"id", "enabled", "schedule"} + assert parameters["required"] == ["id"] + assert request["tools"][0]["function"]["name"] == "automation_update" + + def test_gpt5_family_flattens_on_chat_completions(self): + request = self._transform( + OpenAIGPT5Config(), "gpt-5.6", {"custom_llm_provider": "openai", "api_base": None}, [self._anyof_tool()] + ) + assert "anyOf" not in request["tools"][0]["function"]["parameters"] + + def test_custom_api_base_keeps_union(self): + tool = self._anyof_tool() + request = self._transform( + self.config, + "gpt-4o", + {"custom_llm_provider": "openai", "api_base": "http://localhost:8000/v1"}, + [tool], + ) + assert request["tools"][0]["function"]["parameters"] == self._anyof_tool()["function"]["parameters"] + + def test_non_openai_provider_keeps_union(self): + request = self._transform( + self.config, "some-oss-model", {"custom_llm_provider": "groq", "api_base": None}, [self._anyof_tool()] + ) + assert request["tools"][0]["function"]["parameters"] == self._anyof_tool()["function"]["parameters"] + + def test_caller_tool_dict_is_not_mutated(self): + tool = self._anyof_tool() + self._transform(self.config, "gpt-4o", {"custom_llm_provider": "openai", "api_base": None}, [tool]) + assert tool == self._anyof_tool() + + def test_clean_object_schema_passes_through_as_same_object(self): + tool = { + "type": "function", + "function": { + "name": "lookup", + "parameters": {"type": "object", "properties": {"id": {"type": "string"}}, "required": ["id"]}, + }, + } + request = self._transform( + self.config, "gpt-4o", {"custom_llm_provider": "openai", "api_base": None}, [tool] + ) + assert request["tools"][0] is tool + + @pytest.mark.asyncio + async def test_async_transform_request_flattens_for_hosted_openai(self): + request = await self.config.async_transform_request( + model="gpt-4o", + messages=[{"role": "user", "content": "hi"}], + optional_params={"tools": [self._anyof_tool()]}, + litellm_params={"custom_llm_provider": "openai", "api_base": None}, + headers={}, + ) + parameters = request["tools"][0]["function"]["parameters"] + assert "anyOf" not in parameters + assert set(parameters["properties"]) == {"id", "enabled", "schedule"}