OpenAI's "Dev Day Holiday Edition—12 Days of OpenAI: Day 9" YouTube video announces several new features and improvements to their API. Key updates include the general availability of the powerful O1 model with enhanced capabilities like function calling, structured outputs, and vision input. The real-time API receives a significant upgrade with WebRTC support, simplifying real-time voice application development and reducing costs. Finally, a new preference fine-tuning method is introduced, enabling developers to better align models with their specific user preferences. New SDKs for Go and Java are also released.