AsyncStream missing aclose() causes AttributeError in streaming structured output

[landim]

Bug Report

Summary

AsyncStream exposes close() but not aclose(), causing AttributeError when callers use the standard Python async cleanup convention.

Reproduction

from openai._streaming import AsyncStream

stream = AsyncStream(...)
await stream.aclose()
# AttributeError: 'AsyncStream' object has no attribute 'aclose'. Did you mean: 'close'?

The error surfaces in production when using client.beta.chat.completions.stream() (or any path through AsyncChatCompletionStream) with instrumentation libraries (e.g. Langfuse) that wrap the raw stream. The call chain is:

1. AsyncChatCompletionStreamManager.__aexit__ (line 290) calls self.__stream.close()
2. AsyncChatCompletionStream.close() (line 215) calls self._response.aclose()
3. self._response = raw_stream.response — when instrumentation wraps AsyncStream, .response resolves to the AsyncStream itself rather than the underlying httpx.Response
4. AsyncStream has close() but not aclose() → AttributeError

Full traceback

File ".../openai/lib/streaming/chat/_completions.py", line 290, in __aexit__
    await self.__stream.close()
  File ".../openai/lib/streaming/chat/_completions.py", line 215, in close
    await self._response.aclose()
AttributeError: 'AsyncStream' object has no attribute 'aclose'. Did you mean: 'close'?

Environment

• openai SDK version: 2.9.0
• Python 3.12
• Instrumentation: Langfuse 3.11.2+ (wraps OpenAI streaming responses)
• Framework: LangChain + langchain-openai (uses with_structured_output() with streaming)

Expected behavior

AsyncStream should expose aclose() as a standard async cleanup method, matching the convention used by httpx.Response, asyncio.StreamWriter, and Python async generators.

Notes

• The sync Stream class is not affected since its callers use close().
• aclose() is the standard Python async cleanup convention — async generators, asyncio.StreamWriter, httpx.AsyncByteStream, etc. all expose it.
• This is also referenced in langfuse/langfuse#5685 as the root cause.