pen.dev

pen.dev (formerly pencil.dev) is a design editor where AI agents work on a canvas with you. You can design websites, apps and slides, import .fig files or web pages, and export HTML with CSS or Tailwind. Designs are saved as .pen files, an open JSON format you can keep in your git repository next to the code.

It runs as a desktop app for Apple silicon and Intel Macs, in the browser at app.pen.dev, as a VS Code and Cursor extension, and as a CLI. Claude Code, Codex and other agents can drive it through its local MCP server.

The free plan includes the full local editor and 5 days a month of designing with an agent. Pro is $16 per user a month billed annually and Ultra $48. You can use hosted models (MiniMax, GLM, Qwen, DeepSeek) or connect your own ChatGPT or Claude subscription or API key, so prompts go to the provider you choose.