GPT-5.5 Instant Update

Updated GPT-5.5 Instant in ChatGPT and the API to improve response style and quality with easier reading, more natural conversation, and better pacing. Canvas is no longer available in GPT-5.5 Instant or GPT-5.5 Thinking; writing and coding functionality is now supported directly in chat through writing blocks and code blocks. Paid users can continue using canvas for a limited time through legacy models.