feat(openai): enable stream_usage when using default base URL and client (#33205)

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

@@ -615,6 +615,25 @@ class AzureChatOpenAI(BaseChatOpenAI):
             or os.getenv("OPENAI_ORG_ID")
             or os.getenv("OPENAI_ORGANIZATION")
         )
+
+        # Enable stream_usage by default if using default base URL and client
+        if all(
+            getattr(self, key, None) is None
+            for key in (
+                "stream_usage",
+                "openai_proxy",
+                "openai_api_base",
+                "base_url",
+                "client",
+                "root_client",
+                "async_client",
+                "root_async_client",
+                "http_client",
+                "http_async_client",
+            )
+        ):
+            self.stream_usage = True
+
         # For backwards compatibility. Before openai v1, no distinction was made
         # between azure_endpoint and base_url (openai_api_base).
         openai_api_base = self.openai_api_base

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

@@ -99,7 +99,13 @@ from langchain_core.utils.pydantic import (
     is_basemodel_subclass,
 )
 from langchain_core.utils.utils import _build_model_kwargs, from_env, secret_from_env
-from pydantic import BaseModel, ConfigDict, Field, SecretStr, model_validator
+from pydantic import (
+    BaseModel,
+    ConfigDict,
+    Field,
+    SecretStr,
+    model_validator,
+)
 from pydantic.v1 import BaseModel as BaseModelV1
 from typing_extensions import Self
 
@@ -478,11 +484,18 @@ class BaseChatOpenAI(BaseChatModel):
     )
     """Timeout for requests to OpenAI completion API. Can be float, ``httpx.Timeout`` or
         None."""
-    stream_usage: bool = False
-    """Whether to include usage metadata in streaming output. If True, an additional
+    stream_usage: Optional[bool] = None
+    """Whether to include usage metadata in streaming output. If enabled, an additional
     message chunk will be generated during the stream including usage metadata.
 
+    This parameter is enabled unless ``openai_api_base`` is set or the model is
+    initialized with a custom client, as many chat completions APIs do not support
+    streaming token usage.
+
     !!! version-added "Added in version 0.3.9"
+
+    !!! warning "Behavior changed in 0.3.35"
+        Enabled for default base URL and client.
     """
     max_retries: Optional[int] = None
     """Maximum number of retries to make when generating."""
@@ -761,6 +774,25 @@ class BaseChatOpenAI(BaseChatModel):
             or os.getenv("OPENAI_ORGANIZATION")
         )
         self.openai_api_base = self.openai_api_base or os.getenv("OPENAI_API_BASE")
+
+        # Enable stream_usage by default if using default base URL and client
+        if all(
+            getattr(self, key, None) is None
+            for key in (
+                "stream_usage",
+                "openai_proxy",
+                "openai_api_base",
+                "base_url",
+                "client",
+                "root_client",
+                "async_client",
+                "root_async_client",
+                "http_client",
+                "http_async_client",
+            )
+        ):
+            self.stream_usage = True
+
         client_params: dict = {
             "api_key": (
                 self.openai_api_key.get_secret_value() if self.openai_api_key else None
@@ -1073,7 +1105,7 @@ class BaseChatOpenAI(BaseChatModel):
         for source in stream_usage_sources:
             if isinstance(source, bool):
                 return source
-        return self.stream_usage
+        return self.stream_usage or False
 
     def _stream(
         self,