OpenAI has launched GPT-5.1, enhancing its API platform for developers. This new model offers a balance of intelligence and speed, particularly for coding and agentic tasks. One major improvement is its adaptive reasoning, where GPT-5.1 adjusts its thinking time based on task complexity. This results in faster responses for simpler tasks—like generating an npm command—taking about 2 seconds instead of 10. The model introduces a "no reasoning" mode that allows for quicker responses where deep thinking isn't necessary, which can boost performance for latency-sensitive applications. Extended prompt caching is another key feature, allowing prompts to remain active for up to 24 hours. This change significantly reduces response times and costs for follow-up requests, making it easier to manage long-running interactions like coding sessions or multi-turn chats. Developers can implement this by adding a specific parameter in their API calls. Pricing for cached tokens remains 90% cheaper than uncached tokens, enhancing cost-efficiency for users. GPT-5.1 also improves coding capabilities. It shows a more intuitive coding personality and better communication during task sequences. Testing by companies like Balyasny Asset Management and Pace indicates that GPT-5.1 outperforms previous models, running 2-3 times faster while using half as many tokens for complex tasks. Early feedback from coding firms highlights its efficiency in reasoning and accuracy during multi-file projects, leading to smoother pull requests and quicker iterations.