Pencil rebrands to pen.dev, lets 6 AI agents design together

Six AI agents, one canvas, zero human hands on the mouse. That is the pitch behind pen.dev, the newly rebranded design tool formerly known as Pencil, which now lets multiple AI agents collaborate simultaneously on the same interface design inside a developer's own IDE.

The rebrand, completed in 2026, comes as the product claims to have crossed 100,000 users within eight weeks of launch, according to CEO Tom Krcha. That growth trajectory has drawn attention less for the user count itself than for what those users are doing: handing over visual design work to AI agents that can read, write, and iterate on a shared canvas without a designer manually placing every element.

Design files as code

pen.dev's core technical bet is that design should live where code already lives. Its files use a .pen format built on JSON, stored directly in the project repository and tracked with Git like any other source file. That structure is what makes multi-agent collaboration technically feasible: agents connect through the Model Context Protocol (MCP) with full read and write access to the canvas, meaning any MCP-compatible AI assistant can open, modify, and hand off design work.

The tool runs inside popular coding environments, including Cursor, Claude Code, VS Code, Windsurf, and Google Antigravity, alongside a standalone desktop app for macOS, Windows (with ARM64 support still pending), and Linux. Among supported models, Claude 4.6 is currently described as producing the strongest results for pen.dev's design workflows.

Bridging designers and engineers

pen.dev also targets teams migrating from traditional design tools. It supports importing full Figma files or individual layers via copy-and-paste, and ships with built-in icon sets from Material Symbols, Lucide, Feather, and Phosphor. Finished designs export directly to HTML, CSS, or React code.

The "swarm mode" feature, which allows up to six agents to design in parallel on one visual canvas, is the clearest signal of where the product is headed: treating interface design less as a solitary creative task and more as an orchestration problem for AI agents.

On pricing, pen.dev is currently free to use, with the vendor stating that paid tiers may be introduced later. No timeline or pricing structure has been disclosed, so teams adopting it now are effectively building on a tool whose long-term cost model remains undefined.