OpenAI has rolled out ChatGPT 5.1, enhancing its AI language model with significant upgrades in conversational quality and user customization. This version introduces two operating modes: GPT-5.1 Instant and GPT-5.1 Thinking. Instant mode prioritizes warmth and playfulness in responses, making it suitable for casual interactions and quick tasks like summarizing content. In contrast, Thinking mode focuses on deeper reasoning, adjusting response time based on question complexity. Simpler queries receive quicker answers, while complex ones benefit from more thorough responses. A notable feature in ChatGPT 5.1 is the expanded tone and style options. Users can now choose from styles like Professional, Candid, and Quirky, alongside existing presets. This flexibility allows for responses that align closely with individual or brand voices. The AI can even suggest tone adjustments if it senses a shift in user preference, making customization smoother. Changes take effect immediately in ongoing conversations, enhancing the overall user experience. For brands and developers, these upgrades mean more adaptable virtual assistants that can align with brand image through precise tone tuning. The new model is optimized for faster responses and reduced token usage, ultimately lowering API costs. OpenAI plans to provide both operating modes through its API while allowing the previous GPT-5 versions to remain available for a transition period. Technical improvements also include better context retention for longer conversations, which is essential for applications like customer support and onboarding. Users can adjust response speed with a thinking time toggle, depending on their subscription level.