Forgot to notate validator as a classmethod.

vllm/entrypoints/openai/protocol.py

@@ -241,6 +241,7 @@ def logit_bias_logits_processor(
         )
 
     @model_validator(mode='before')
+    @classmethod
     def validate_stream_options(cls, values):
         if values.get('stream_options') is not None and not values.get('stream'):
             raise ValueError("stream_options can only be set if stream is true")