OpenAI has launched GPT-5.1 today, an updated version of its flagship model introduced in August, describing it as a smarter, more engaging upgrade to ChatGPT. The new release includes two distinct models: GPT-5.1 Instant and GPT-5.1 Thinking. According to OpenAI, the Instant version is “warmer, more intelligent, and better at following your instructions” than its predecessor, while the Thinking variant is faster on simple tasks, easier to understand, and more persistent when handling complex queries. In most cases, the system will automatically match user requests to the most suitable model. The new models are beginning to roll out to ChatGPT users this week, with the previous GPT-5 models remaining accessible for three months via a legacy models dropdown before being phased out entirely. As part of the update, OpenAI is expanding its personality presets, now offering eight conversational styles: Default, Professional, Friendly, Candid, Quirky, Efficient, Nerdy, and Cynical. The company also announced a new experiment allowing users to fine-tune ChatGPT’s tone directly through settings—some users will start testing this feature this week. Fidji Simo, OpenAI’s CEO of Applications, emphasized the shift away from a one-size-fits-all approach in a Wednesday Substack post, noting, “With more than 800 million people using ChatGPT, we’re well past the point of one-size-fits-all.” The initial launch of GPT-5 in August was met with mixed reactions. Despite high expectations set by CEO Sam Altman, many users were underwhelmed by the incremental improvements and criticized OpenAI for making GPT-5 the default model without offering a clear upgrade path. The backlash was significant enough that OpenAI quickly restored GPT-4o as a user option just one day after the GPT-5 launch. The underwhelming reception has also affected OpenAI’s strategic partner, Microsoft, which has increasingly turned to rival models from Anthropic. Anthropic’s models now power key features in Microsoft’s AI ecosystem, including Copilot Researcher, GitHub Copilot, Copilot Studio, and a new Office Agent capable of generating Word and PowerPoint documents directly from the Copilot chat interface. GPT-5.1’s release comes just weeks after OpenAI introduced ChatGPT Atlas, its AI-powered web browser. The tool features an “agent mode” currently available only to ChatGPT Plus and Pro subscribers, enabling the AI to take actions in the browser on behalf of users—similar to the company’s Operator tool.