OpenAI updated GPT-5.5 Instant for more natural responses and is phasing out older models o3 and GPT-4.5.

Source Brief

OpenAI updated GPT-5.5 Instant for more natural responses and is phasing out older models o3 and GPT-4.5. The Canvas feature is removed; writing and coding tasks now happen directly in chat. A minor but noticeable improvement for everyday users.