openai: disable streaming for o1 by default (#29147)

Currently 400s
https://community.openai.com/t/streaming-support-for-o1-o1-2024-12-17-resulting-in-400-unsupported-value/1085043

o1-mini and o1-preview stream fine

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

@@ -562,6 +562,15 @@ class BaseChatOpenAI(BaseChatModel):
             values["temperature"] = 1
         return values
 
+    @model_validator(mode="before")
+    @classmethod
+    def validate_disable_streaming(cls, values: Dict[str, Any]) -> Any:
+        """Disable streaming if n > 1."""
+        model = values.get("model_name") or values.get("model") or ""
+        if model == "o1" and values.get("disable_streaming") is None:
+            values["disable_streaming"] = True
+        return values
+
     @model_validator(mode="after")
     def validate_environment(self) -> Self:
         """Validate that api key and python package exists in environment."""