fix(core): override streaming callback if streaming attribute is set (#33351)

Author: ccurme

libs/core/langchain_core/language_models/chat_models.py

@@ -470,8 +470,10 @@ def _should_stream(
         if "stream" in kwargs:
             return kwargs["stream"]
 
-        if getattr(self, "streaming", False):
-            return True
+        if "streaming" in self.model_fields_set:
+            streaming_value = getattr(self, "streaming", None)
+            if isinstance(streaming_value, bool):
+                return streaming_value
 
         # Check if any streaming callback handlers have been passed in.
         handlers = run_manager.handlers if run_manager else []

libs/core/tests/unit_tests/language_models/chat_models/test_base.py

@@ -364,6 +364,8 @@ def _llm_type(self) -> str:
 
 
 class StreamingModel(NoStreamingModel):
+    streaming: bool = False
+
     @override
     def _stream(
         self,
@@ -427,6 +429,13 @@ async def test_disable_streaming_async(
     ).content == expected
 
 
+async def test_streaming_attribute_overrides_streaming_callback() -> None:
+    model = StreamingModel(streaming=False)
+    assert (
+        await model.ainvoke([], config={"callbacks": [_AstreamEventsCallbackHandler()]})
+    ).content == "invoke"
+
+
 @pytest.mark.parametrize("disable_streaming", [True, False, "tool_calling"])
 def test_disable_streaming_no_streaming_model(
     *,