OpenAI: GPT-5.1 has started to be fully rolled out to all ChatGPT users this week

According to OpenAI's announcement, GPT-5.1 has begun a full rollout to all Chat GPT users this week. This version shows significant improvements in following custom instructions, reasoning accuracy, and conversational naturalness. GPT-5.1 supports adaptive reasoning, intelligently extending thinking time for complex questions, resulting in clearer responses with fewer technical terms. GPT-5 users can continue to use it for three months, and the Pro version will be updated to GPT-5.1 Pro.