A useful but little-known Claude API feature 🏎 Is your chat UI making users wait? When latency matters most, Fast Mode is the answer. Claude's Fast Mode prioritizes response speed over depth. For interactive UIs, real-time processing, and anything where speed is the UX, it noticeably cuts time-to-first-token without completely sacrificing quality. 📌 Title: Fast Mode (Beta Research Preview) 🔗 URL: 🧩 Overview Standard Claude responses are quality-first, with deep reasoning and thorough answers. But for chat completions, interactive UI elements, and real-time tool calls, speed directly impacts user experience. Fast Mode is designed for those cases, prioritizing response speed. Answers are less elaborate, but perceived responsiveness improves dramatically. 🛠 How to use it Enable the fast mode parameter in your API request. Your existing prompts and tool configurations work as-is. Combine with streaming and time-to-first-token drops further, giving users the feeling of instant responsiveness. 🏗 Building it into production ・Chat UIs: speed up the initial response to user messages. Use a two-stage pattern where you respond fast first, then add details if needed. ・IDE code completion: real-time suggestions while typing need to be fast above all else. Fast Mode minimizes completion lag. ・Agent intermediate steps: use high quality for final outputs but Fast Mode for tool selection and routing decisions in between. Mixing modes per step cuts total processing time. ・Mobile apps: on flaky connections, smaller and faster responses provide a better UX. Fast Mode naturally keeps responses compact. 💡 Use cases 💬 Real-time chat and conversational AI ⌨️ Code completion and input assistance 🔀 Agent routing and intermediate decisions 📱 Low-latency mobile responses ⚠️ Watch out This is a beta research preview, so the API surface may change. It's not suited for complex reasoning or long-form generation. The key is clearly separating "speed-critical paths" from "quality-critical paths" and applying Fast Mode only where it fits. ✨ Latency hits UX directly. Try switching your chat UI's initial response to Fast Mode and feel the difference in responsiveness. #Claude# #LLM#