pen.dev

Overview

pen.dev combines vector design with software building in a canvas that can work alongside AI agents. It is best suited to designers and developers who want editable interface work, code exports and agent workflows together. Its broad toolset is appealing, though sustained generation and parallel agent use may call for a paid per-user plan.

Key features

The editor supports components, variables, themes, scripts and shaders, which gives reusable design work more room than a static mockup. Figma and HTML import, plus sketch or image input, help users start from existing material or a visual reference. Exports include PNG, JPEG, WEBP and PDF, alongside HTML, CSS and Tailwind for code-oriented handoff.

The .pen format is an open JSON file with a fully open schema, a practical choice for teams that want design data they can inspect. Users can work with the integrated agent or connect external agents through MCP. 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. The breadth is useful for workflows already using these tools; the number of agents that can run at once depends on the plan.

A Chrome extension imports webpages, and IDE extensions are available for Cursor, VS Code, Antigravity and Windsurf. The CLI installs through npm and requires Node.js 22.19 or later, so command-line use has a specific runtime prerequisite. For text-based AI requests made with a user's own provider credentials, the privacy policy says data goes directly from the device to that provider. Account data, cloud files and shared content receive encryption in transit and at rest and access controls. Requests to pen.dev's own models and image or SVG services pass through its servers in real time and are not stored, logged or cached there.

Pricing

Plans are coming soon, and pen.dev remains free until they launch. The published tiers indicate how capacity is expected to differ, but the free plan is the only current option during this period.

• Free: free. It includes 5 Agent days/month, 25 image and SVG generations/month and one agent at a time. This suits occasional use, but the generation and agent-day caps may constrain regular production work.
• Pro: $16 a month, billed $16 / user / month. It raises usage to unlimited Agent days, 350 image and SVG generations/month and up to 3 agents in parallel. It is the more suitable tier for an individual or team member who needs frequent agent access and moderate generation volume.
• Ultra: $48 a month, billed $48 / user / month. It includes unlimited Agent days, 750 image and SVG generations/month and up to 6 parallel agents. The higher quota is aimed at users whose work benefits from several simultaneous agents; the per-user price makes seat count relevant.
• Enterprise: custom pricing, with unlimited usage and custom usage, pricing and support for procurement and onboarding. Enterprise customers are directed to contact the company about their requirements.

There is no free trial. Until the plans launch, the service stays free; after launch, the free tier's monthly generation and agent-day limits are the main trade-off for avoiding a subscription.

Platforms

pen.dev supports web, macOS, Windows and Linux, with API and extension availability. Its Chrome extension handles webpage imports, while IDE extensions connect the workflow to supported editors.

Who it's for

pen.dev is a strong fit for people who move between vector interface design and development, especially those who want to use MCP-connected agents or export HTML, CSS or Tailwind. The open file format also suits teams that value inspectable design data. It is less compelling for high-volume work that must stay free, given the monthly caps, or for users who do not need its design and agent workflows together.

Pros and cons

• Pro: Design features, sketch and image input, and visual and code exports cover several stages of interface work in one tool.
• Pro: An open .pen JSON schema and broad documented agent connections give technical teams flexibility in how they work with designs.
• Con: The free tier limits Agent days to five monthly, image and SVG generations to 25, and concurrent agents to one.
• Con: Pro and Ultra pricing is per user, so the published monthly amount scales with the number of seats.
• Con: The CLI requires Node.js 22.19 or later, which adds a prerequisite for command-line workflows.

Alternatives

For a prototype-focused option with a post-trial free tier, UXPin offers two prototypes and 50 AI credits after its 14-day trial. Paper is an alternative with a free plan that includes unlimited viewers and editors and 100 weekly MCP tool calls. Starry may suit users who want a free download without a subscription and are willing to provide their own API key for AI chat. Coherent is a free, open-source option with unlimited projects and a bring-your-own-LLM-key model.

Figma Make is an option for users who want Figma's AI design workflow, with a Professional Full seat at $16 a month and 3,000 AI credits monthly. For a free site-building starting point, Relume provides one project and one page on its forever-free plan. UX Pilot is worth considering when the first design free or enterprise API and access controls are priorities. Visily offers a free Starter tier with 300 AI credits per month for users seeking a credit-based AI design option.

Browse AI UI Design Generators or AI Wireframe Generators to compare more tools in these categories.

Verdict

Choose pen.dev if your work spans vector interface design, software development and AI agents, and you value open design files and code exports. Its range of inputs, outputs and integrations is the main draw. Look elsewhere if you need dependable high-volume generation without a per-user subscription: the free tier is capped, and the higher published quotas come with monthly fees.