Marmo UI vs pen.dev
Marmo UI
marmoui.compen.dev
pen.devSide by side
| Figure | Marmo UI | pen.dev |
|---|---|---|
| Price from | $9.99/mo | $16/mo |
| Free plan | Yes | Yes |
| Free trial | Yes | — |
| Open source | — | — |
| Web | Yes | Yes |
| Windows | — | Yes |
| macOS | — | Yes |
| Linux | — | Yes |
| API | — | Yes |
| Plans published | 2 | 4 |
| Spec score · AI UI Design Generators | 7.8 (#16) | 8.9 (#3) |
| Data handling | The pricing FAQ says generated code does not phone home. | Text AI requests using a user's own provider credentials go directly from the device to that provider, while hosted-model requests pass through High Agency infrastructure in real time. |
| Integrations | The install guide documents connections for Claude Code, Codex, Cursor, Gemini CLI, Windsurf, and other MCP clients. | Official documentation lists MCP integrations including Claude Code, Codex, Gemini CLI, Antigravity, OpenCode, Kiro, and Claude Desktop. |
| Product | Marmo is an open-source React design system paired with a hosted MCP server that gives AI agents live component APIs, composition patterns, and generation rules. | pen.dev describes itself as an agentic canvas for building software and a vector design tool integrated with development environments. |
Plans
In their own words
Marmo UI
Marmo UI pairs an open-source React design system with a hosted MCP server to help AI agents compose dashboards and apps using named @marmoui/ui components. The server provides live component APIs, composition patterns and generation rules; generated files pass through a review step that checks imports, props and compositions. The library includes more than 50 production-ready components and comes with Storybook and a Figma library. Developers install the React package with npm. The free plan includes documentation, the design tools and MIT-licensed core components, and allows unlimited projects, commercial use and no rate limits. Pro adds generation guided by a DESIGN.md file with brand details, plus composition patterns, Pro blocks, a hosted design-system site and priority support. It costs $9.99 per month, and a 14-day trial is listed. Integration instructions cover Claude Code, Codex, Cursor, Gemini CLI, Windsurf and other MCP clients. Generated code belongs to the user, uses the user’s own LLM tokens and stays in the user’s repository; it does not phone home.
pen.dev
pen.dev is a canvas for building software and a vector design tool integrated with development environments. Its editor works with components, variables, themes, scripts and shaders, and can import Figma files and HTML. It can export to HTML, CSS and Tailwind, as well as PNG, JPEG, WEBP and PDF. Users can work with its integrated agent or connect external agents through MCP; the available plans specify how many agents can run in parallel. Documented integrations include Claude Code, Codex, Gemini CLI, Antigravity, OpenCode, Kiro and Claude Desktop. Integrated provider options include OpenAI, Anthropic, Google Gemini, Cursor, GitHub Copilot, xAI, OpenRouter and other API-key providers. Its.pen design file is open JSON with an open schema. Tools include a Chrome extension for importing webpages, IDE extensions and an npm-installed CLI requiring Node.js 22.19 or later. The pricing page says pen.dev stays free until plans launch. The Free plan is free; Pro is $16 a month; Ultra is $48 a month.