Installation

pen.dev is available as a desktop app, an IDE extension, and a command-line tool.

Desktop app

Download the desktop app from the pen.dev downloads page .

macOS

1. Download the macOS package for your Mac
2. Open the downloaded DMG
3. Move pen.dev to Applications
4. Launch pen.dev

Windows

1. Download the Windows installer
2. Run the installer
3. Launch pen.dev

Linux

Download the AppImage or tarball for your system from the pen.dev downloads page .

For an x64 AppImage:

chmod +x Pen-linux-x86_64.AppImage
./Pen-linux-x86_64.AppImage

For an ARM64 AppImage:

chmod +x Pen-linux-arm64.AppImage
./Pen-linux-arm64.AppImage

For an x64 tarball:

tar -xzf Pen-linux-x64.tar.gz

For an ARM64 tarball:

tar -xzf Pen-linux-arm64.tar.gz

Check the version or update

Open the pen.dev menu on macOS, or Help on Windows or Linux. Select About Pen to check the installed version or Check for Updates… to look for an update.

IDE extension

VS Code and Cursor

1. Open the Extensions view in VS Code or Cursor
2. Search for pen.dev
3. Select Install
4. Create or open a file whose name ends in .pen

CLI

The CLI requires Node.js 22.19 or later.

npm install -g @pen.dev/cli

Confirm the command is available:

pen version

To update, run npm install -g @pen.dev/cli again.

See the CLI reference before running an agent or editing a document headlessly.

Connect an AI client with MCP

MCP lets an external AI client work with the .pen document open in the desktop app or IDE extension. pen.dev sets up supported MCP integrations when it starts.

Open Settings (⚙️) → MCP to see the integrations supported by your installed version. Desktop integrations include Claude Code CLI, Codex CLI, Gemini CLI, Antigravity 2.0, OpenCode CLI, Kiro CLI and Claude Desktop. The ChatGPT desktop app and Codex IDE extension  use the same MCP configuration as Codex CLI.

Claude Code

Install Claude Code using the official installation instructions . If you use npm, run:

npm install -g @anthropic-ai/claude-code

Then:

1. Open a .pen document in pen.dev
2. Enable Claude Code CLI in Settings (⚙️) → MCP
3. Start or restart Claude Code
4. Use /mcp in Claude Code to confirm that pencil is connected

ChatGPT and Codex

pen.dev configures the Codex MCP entry used by ChatGPT desktop, Codex CLI and the Codex IDE extension on the same computer.

1. Open a .pen document in pen.dev
2. Enable Codex CLI in Settings (⚙️) → MCP
3. Start or restart ChatGPT or Codex
4. Confirm that pencil appears in the client’s MCP server list

To try your connected agent, follow Create your first design.

Troubleshooting

A .pen file opens as text in the IDE

1. Confirm the pen.dev extension is installed and enabled
2. Run pen.dev: Toggle Design Mode from the Command Palette

The pen command is not found

1. Confirm Node.js is version 22.19 or later
2. Re-run npm install -g @pen.dev/cli
3. Run pen version

For other symptoms, use Troubleshooting.