A design canvas that coding agents draw on
Pencil now goes by pen.dev. The old pencil.dev domain redirects there, and the extension and the docs use the new name. It is a vector design editor where AI agents work directly on the canvas and a person tidies up by hand afterwards. It runs as a desktop app on macOS, Windows or Linux, as a VS Code and Cursor extension, or from a CLI. Designs are .pen files, plain JSON kept in the repo next to the code they describe, so the agent writing a component can open the mockup it started from.
JSON design files, MCP clients and a headless CLI
- A
.penfile is JSON (comments allowed) described by a TypeScript schema printed in the docs, which tell you to let Git commits hold its history. - Claude Code, Codex, Cursor and other MCP clients attach locally to the running app: stdio to the MCP server, then a Unix socket on macOS and Linux or a named pipe on Windows.
- From a mockup, the agent writes React, Vue or Svelte code; pointed at an existing
src/components/Button.tsx, it redraws that component on the canvas. The built-in exporter only does HTML with CSS or Tailwind. - The CLI (
@pen.dev/cli, Node.js 22.19 or later) runs the editor with no UI. It hands the agent a prompt, exports PNG, JPEG, WEBP or PDF, and runs in CI with aPEN_CLI_KEY. - Figma comes in as a whole file or as pasted layers, minus images. The desktop app also turns a page from its built-in browser,
localhostincluded, into editable layers, without the page's JavaScript. - Models connect through an existing ChatGPT or Claude subscription, or an API key.
Metered agent days, a closed EULA and a schema that may break
The software is proprietary and most of it needs an account. The EULA, effective October 15, 2026, grants a limited, non-exclusive, non-transferable licence and forbids copying, modifying, redistributing or decompiling the software. The CLI requires a login for agent runs, exports and interactive mode. A share link uploads the document with every file it uses, and anyone holding the link can view and download them. For an open source route, Penpot is MPL-2.0, can be self-hosted and has an MCP server of its own.
The free plan stops at five agent days a month. Free is aimed at exploration and personal work: five days a month of designing with an agent, one agent at a time, 25 image or SVG generations. A day counts as soon as an agent draws, Claude Code over MCP included, even on the user's own subscription. Pro costs $20 per user per month, or $16 billed annually, with daily agent use and up to three parallel agents; Ultra costs $60, or $48 billed annually, with six agents and team-wide credits.
The .pen schema is open but not frozen. The homepage calls the schema "fully opened", yet the format docs, now at schema version 2.21, reserve the right to make breaking changes. When it opens an older file, pen.dev converts it and saves in the new format, so the docs advise keeping the original before switching app versions. For Git conflicts, they say to redo the change inside pen.dev rather than merge the JSON by hand.
Version 0.6.78 shipped on October 22, 2026. That is the latest extension release on Open VSX, not flagged as a pre-release; 0.6.68 came out on August 25. The site makes no mention of a beta or early access. The publisher is High Agency, Inc., based in California.