openai[patch]: support Responses streaming in AzureChatOpenAI (#31641)

Resolves https://github.com/langchain-ai/langchain/issues/31303,
https://github.com/langchain-ai/langchain/issues/31624

libs/partners/openai/langchain_openai/chat_models/azure.py

@@ -4,14 +4,14 @@ from __future__ import annotations
 
 import logging
 import os
-from collections.abc import Awaitable
+from collections.abc import AsyncIterator, Awaitable, Iterator
 from typing import Any, Callable, Optional, TypedDict, TypeVar, Union
 
 import openai
 from langchain_core.language_models import LanguageModelInput
 from langchain_core.language_models.chat_models import LangSmithParams
 from langchain_core.messages import BaseMessage
-from langchain_core.outputs import ChatResult
+from langchain_core.outputs import ChatGenerationChunk, ChatResult
 from langchain_core.runnables import Runnable
 from langchain_core.utils import from_env, secret_from_env
 from langchain_core.utils.pydantic import is_basemodel_subclass
@@ -736,6 +736,24 @@ class AzureChatOpenAI(BaseChatOpenAI):
 
         return chat_result
 
+    def _stream(self, *args: Any, **kwargs: Any) -> Iterator[ChatGenerationChunk]:
+        """Route to Chat Completions or Responses API."""
+        if self._use_responses_api({**kwargs, **self.model_kwargs}):
+            return super()._stream_responses(*args, **kwargs)
+        else:
+            return super()._stream(*args, **kwargs)
+
+    async def _astream(
+        self, *args: Any, **kwargs: Any
+    ) -> AsyncIterator[ChatGenerationChunk]:
+        """Route to Chat Completions or Responses API."""
+        if self._use_responses_api({**kwargs, **self.model_kwargs}):
+            async for chunk in super()._astream_responses(*args, **kwargs):
+                yield chunk
+        else:
+            async for chunk in super()._astream(*args, **kwargs):
+                yield chunk
+
     def with_structured_output(
         self,
         schema: Optional[_DictOrPydanticClass] = None,