openai: read stream_options (#21548)

OpenAI recently added a `stream_options` parameter to its chat
completions API (see [release
notes](https://platform.openai.com/docs/changelog/added-chat-completions-stream-usage)).
When this parameter is set to `{"usage": True}`, an extra "empty"
message is added to the end of a stream containing token usage. Here we
propagate token usage to `AIMessage.usage_metadata`.

We enable this feature by default. Streams would now include an extra
chunk at the end, **after** the chunk with
`response_metadata={'finish_reason': 'stop'}`.

New behavior:
```
[AIMessageChunk(content='', id='run-4b20dbe0-3817-4f62-b89d-03ef76f25bde'),
 AIMessageChunk(content='Hello', id='run-4b20dbe0-3817-4f62-b89d-03ef76f25bde'),
 AIMessageChunk(content='!', id='run-4b20dbe0-3817-4f62-b89d-03ef76f25bde'),
 AIMessageChunk(content='', response_metadata={'finish_reason': 'stop'}, id='run-4b20dbe0-3817-4f62-b89d-03ef76f25bde'),
 AIMessageChunk(content='', id='run-4b20dbe0-3817-4f62-b89d-03ef76f25bde', usage_metadata={'input_tokens': 8, 'output_tokens': 9, 'total_tokens': 17})]
```

Old behavior (accessible by passing `stream_options={"include_usage":
False}` into (a)stream:
```
[AIMessageChunk(content='', id='run-1312b971-c5ea-4d92-9015-e6604535f339'),
 AIMessageChunk(content='Hello', id='run-1312b971-c5ea-4d92-9015-e6604535f339'),
 AIMessageChunk(content='!', id='run-1312b971-c5ea-4d92-9015-e6604535f339'),
 AIMessageChunk(content='', response_metadata={'finish_reason': 'stop'}, id='run-1312b971-c5ea-4d92-9015-e6604535f339')]
```

From what I can tell this is not yet implemented in Azure, so we enable
only for ChatOpenAI.

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

@@ -58,6 +58,7 @@ from langchain_core.messages import (
     ToolMessage,
     ToolMessageChunk,
 )
+from langchain_core.messages.ai import UsageMetadata
 from langchain_core.output_parsers import (
     JsonOutputParser,
     PydanticOutputParser,
@@ -483,7 +484,20 @@ class BaseChatOpenAI(BaseChatModel):
                 if not isinstance(chunk, dict):
                     chunk = chunk.model_dump()
                 if len(chunk["choices"]) == 0:
+                    if token_usage := chunk.get("usage"):
+                        usage_metadata = UsageMetadata(
+                            input_tokens=token_usage.get("prompt_tokens", 0),
+                            output_tokens=token_usage.get("completion_tokens", 0),
+                            total_tokens=token_usage.get("total_tokens", 0),
+                        )
+                        chunk = ChatGenerationChunk(
+                            message=default_chunk_class(
+                                content="", usage_metadata=usage_metadata
+                            )
+                        )
+                    else:
                         continue
+                else:
                     choice = chunk["choices"][0]
                     if choice["delta"] is None:
                         continue
@@ -589,7 +603,20 @@ class BaseChatOpenAI(BaseChatModel):
                 if not isinstance(chunk, dict):
                     chunk = chunk.model_dump()
                 if len(chunk["choices"]) == 0:
+                    if token_usage := chunk.get("usage"):
+                        usage_metadata = UsageMetadata(
+                            input_tokens=token_usage.get("prompt_tokens", 0),
+                            output_tokens=token_usage.get("completion_tokens", 0),
+                            total_tokens=token_usage.get("total_tokens", 0),
+                        )
+                        chunk = ChatGenerationChunk(
+                            message=default_chunk_class(
+                                content="", usage_metadata=usage_metadata
+                            )
+                        )
+                    else:
                         continue
+                else:
                     choice = chunk["choices"][0]
                     if choice["delta"] is None:
                         continue
@@ -1135,6 +1162,29 @@ class ChatOpenAI(BaseChatOpenAI):
         """Return whether this model can be serialized by Langchain."""
         return True
 
+    def _stream(self, *args: Any, **kwargs: Any) -> Iterator[ChatGenerationChunk]:
+        """Set default stream_options."""
+        default_stream_options = {"include_usage": True}
+        stream_options = kwargs.get("stream_options", {})
+        merged_stream_options = {**default_stream_options, **stream_options}
+        kwargs["stream_options"] = merged_stream_options
+
+        return super()._stream(*args, **kwargs)
+
+    async def _astream(
+        self,
+        *args: Any,
+        **kwargs: Any,
+    ) -> AsyncIterator[ChatGenerationChunk]:
+        """Set default stream_options."""
+        default_stream_options = {"include_usage": True}
+        stream_options = kwargs.get("stream_options", {})
+        merged_stream_options = {**default_stream_options, **stream_options}
+        kwargs["stream_options"] = merged_stream_options
+
+        async for chunk in super()._astream(*args, **kwargs):
+            yield chunk
+
 
 def _is_pydantic_class(obj: Any) -> bool:
     return isinstance(obj, type) and issubclass(obj, BaseModel)

libs/partners/openai/poetry.lock

@@ -1268,4 +1268,4 @@ watchmedo = ["PyYAML (>=3.10)"]
 [metadata]
 lock-version = "2.0"
 python-versions = ">=3.8.1,<4.0"
-content-hash = "0d142c2f1c4d08dbdcbd15b8005ffa606d4d36781c52e9411993cabd41de261b"
+content-hash = "62f0a24221c64dc8035ccf7cca3f8ac2eaf47d653a441645c8021120833ecb52"

libs/partners/openai/pyproject.toml

@@ -13,7 +13,7 @@ license = "MIT"
 [tool.poetry.dependencies]
 python = ">=3.8.1,<4.0"
 langchain-core = {version =">=0.2.2rc1,<0.3", allow-prereleases=true}
-openai = "^1.24.0"
+openai = "^1.26.0"
 tiktoken = ">=0.7,<1"
 
 [tool.poetry.group.test]

libs/partners/openai/tests/integration_tests/chat_models/test_base.py

@@ -346,9 +346,34 @@ def test_stream() -> None:
     llm = ChatOpenAI()
 
     full: Optional[BaseMessageChunk] = None
+    chunks_with_token_counts = 0
     for chunk in llm.stream("I'm Pickle Rick"):
         assert isinstance(chunk.content, str)
         full = chunk if full is None else full + chunk
+        assert isinstance(chunk, AIMessageChunk)
+        if chunk.usage_metadata is not None:
+            chunks_with_token_counts += 1
+    if chunks_with_token_counts != 1:
+        raise AssertionError(
+            "Expected exactly one chunk with token counts. "
+            "AIMessageChunk aggregation adds counts. Check that "
+            "this is behaving properly."
+        )
+
+    # check token usage is populated
+    assert isinstance(full, AIMessageChunk)
+    assert full.usage_metadata is not None
+    assert full.usage_metadata["input_tokens"] > 0
+    assert full.usage_metadata["output_tokens"] > 0
+    assert full.usage_metadata["total_tokens"] > 0
+
+    # check not populated
+    aggregate: Optional[BaseMessageChunk] = None
+    for chunk in llm.stream("Hello", stream_options={"include_usage": False}):
+        assert isinstance(chunk.content, str)
+        aggregate = chunk if aggregate is None else aggregate + chunk
+    assert isinstance(aggregate, AIMessageChunk)
+    assert aggregate.usage_metadata is None
 
 
 async def test_astream() -> None:
@@ -356,9 +381,34 @@ async def test_astream() -> None:
     llm = ChatOpenAI()
 
     full: Optional[BaseMessageChunk] = None
+    chunks_with_token_counts = 0
     async for chunk in llm.astream("I'm Pickle Rick"):
         assert isinstance(chunk.content, str)
         full = chunk if full is None else full + chunk
+        assert isinstance(chunk, AIMessageChunk)
+        if chunk.usage_metadata is not None:
+            chunks_with_token_counts += 1
+    if chunks_with_token_counts != 1:
+        raise AssertionError(
+            "Expected exactly one chunk with token counts. "
+            "AIMessageChunk aggregation adds counts. Check that "
+            "this is behaving properly."
+        )
+
+    # check token usage is populated
+    assert isinstance(full, AIMessageChunk)
+    assert full.usage_metadata is not None
+    assert full.usage_metadata["input_tokens"] > 0
+    assert full.usage_metadata["output_tokens"] > 0
+    assert full.usage_metadata["total_tokens"] > 0
+
+    # check not populated
+    aggregate: Optional[BaseMessageChunk] = None
+    async for chunk in llm.astream("Hello", stream_options={"include_usage": False}):
+        assert isinstance(chunk.content, str)
+        aggregate = chunk if aggregate is None else aggregate + chunk
+    assert isinstance(aggregate, AIMessageChunk)
+    assert aggregate.usage_metadata is None
 
 
 async def test_abatch() -> None: