Anthropic product designer Nate Parrott created Claude Design as a side project after the release of Opus 4.5 in November 2025. Parrott was the only designer on the Claude Code VS Code project, supported by two engineers. After Opus 4.5 was released, the two engineers suddenly began delivering at a frantic pace, producing far more than before, while Parrott remained at his usual speed and fell behind. To catch up, he spent his free time building a small tool, which became Claude Design. It was used by over one million people in its first week online. Parrott noted that AI first accelerated engineering, making design the slowest link. The turning point was November 24, 2025, the day Opus 4.5 was released. Parrott’s initial approach treated design as a textual task, but results were not ideal. Over the next month, he treated it as a side project and discovered that Claude is especially skilled at writing HTML, which he realized is a rich interactive visual medium.