Is Vellum an alternative to pen.dev and Paper?

Vellum is an open-source design canvas for you and your coding agents, with files in your repository. It competes with pen.dev and Paper on the same job: describe a screen, watch an agent draw it, steer it, then take the code. The three differ in what they put on disk, whether an account is required, how agent edits are permitted and what they cost.

Paper's canvas is HTML and CSS. Why is Vellum's file a vector document?

Because the design of record should not change when the code does. Vellum stores layers, components and variables as a vector document, then exports HTML with CSS or Tailwind, PNG, JPEG, WEBP, SVG and PDF, and design tokens as CSS variables, a Tailwind v4 theme or Design Tokens JSON.

Does Vellum work with the agents I already use?

Yes. The vellum command is an MCP server, so Claude Code, Codex, Cursor, Gemini CLI, Windsurf, Copilot CLI, Zed and other MCP clients can design on the canvas. A built-in agent runs on your own provider key.

Can my team collaborate in Vellum?

Not in the editors yet. The room service is built; the editors are not attached to it. Share links open read-only snapshots, and the design file itself reviews in Git. Paper is ahead here today.

What does Vellum cost?

Free during the beta — no card and no charge now. After the beta, a one-time purchase — not a subscription. Date to be announced. The purchase covers the app. Agents run on your own subscription or provider key.

Alternatives / Paper

A paper.design alternative for design that stays in your repo

Paper is a connected canvas for teams shipping with agents, where the canvas is real HTML and CSS and agents join over MCP. Its wager is that the canvas should speak the language of the web, so a frame is HTML and CSS and an agent reads and writes the same thing a browser does.

Vellum makes a different wager. A design is a vector document, not a rendered page: plain JSON in your repository, with a canvas, a format specification and an agent path that you can review and undo.

This page compares the two on the decisions that outlast a release: the file, the licence, agent permissions, accounts and price.

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What Paper does well

A canvas built on web standards, so a design and its code share one language and HTML and CSS come out the other side.
Agents join over MCP, with token, style and component sync between the codebase and the canvas.
Content and data connections: real copy, real records and a browser app for teams.
Multiplayer is core, and the free plan includes unlimited editors and viewers.

What changes with Vellum

The design of record is a vector document, not a page

Frames, paths, auto-layout, components and variables are stored as a vector document, and the code is an export with options rather than the storage format. That keeps a design stable when the codebase changes, and lets every layer keep a name, a role and a component link.

The canvas is open source

The document model, layout engine, renderers, daemon, command line and MCP server are in the repository under Apache-2.0. There is no hosted service between you and your files.

The file is deterministic JSON in your repo

A Vellum document is one .vellum file with a published specification. The same document serializes to the same bytes, so designs diff in a pull request, review as images in Git, and merge with the branch.

Agent access is scoped and attributable

Every agent write goes through one guard. You can watch a turn, stop it, undo the turn or a single change, and lease a frame so two agents cannot edit it at once. Provider keys stay in the system keychain, and local work needs no account.

One price instead of a per-editor plan

Free during the beta — no card and no charge now. After the beta, a one-time purchase — not a subscription. Date to be announced. Agents run on your own subscription or provider key.

Vellum, pen.dev and Paper side by side

How the three canvases differ. Vendor facts were read from their public documentation and pricing pages on 5 November 2026.
What to compare	Vellum	pen.dev	Paper
Design file	One .vellum file of plain JSON in your repository.	.pen files kept on your computer beside your code.	A canvas of real HTML and CSS, synced with your codebase.
Source and licence	Open source, Apache-2.0: canvas, daemon, CLI and MCP server.	A vendor application; see pen.dev for its terms.	A vendor application; see Paper for its terms.
Account	Not needed for local design, export, the command line or MCP.	Sign in to the app. The free plan includes 5 days a month designing with an agent.	An account in the browser app. The free plan includes unlimited editors.
Agents	Any MCP client or the built-in agent. Writes go through one permissioned path, with per-turn history and undo.	On-canvas models, hosted or with your own key, and MCP for external clients.	IDE and command-line agents over MCP, with in-app agent setup.
Team collaboration	Not in the editors yet.	Share links, comments, versions and team workspaces.	A multiplayer canvas; editors are free on the free plan.
Price	Free during the beta. Then USD 59.99 once, not a subscription.	Free tier. Pro is USD 16 per user a month; Ultra is USD 48; enterprise on request.	Free plan. Pro is USD 16 per editor a month billed yearly, USD 20 monthly; organizations on request.
Platforms	Desktop app, VS Code extension, command line and MCP server.	Desktop app, IDE extension and command line.	Desktop app and the browser.

Where Paper is ahead

Multiplayer is shipped there; in Vellum the room service is built but the editors are not attached to it yet.
Data connections, live content and the browser app are further along.
HTML and CSS as the canvas format is a coherent bet for teams that want the design and the page to be the same artefact.

Choose Vellum when

The design has to live in the repository and diff in a pull request.
You want an open-source canvas with no account for local work.
You want agent edits that can be reviewed, stopped and undone change by change.
A one-time price matters more than a per-editor plan.

Choose Paper when

The canvas should be HTML and CSS, and a frame should be a page.
Your team works in the browser and multiplayer is a requirement today.
You want design data connected to live content and records.

paper.design alternative: questions

Is Vellum an alternative to pen.dev and Paper?: Vellum is an open-source design canvas for you and your coding agents, with files in your repository. It competes with pen.dev and Paper on the same job: describe a screen, watch an agent draw it, steer it, then take the code. The three differ in what they put on disk, whether an account is required, how agent edits are permitted and what they cost.
Paper's canvas is HTML and CSS. Why is Vellum's file a vector document?: Because the design of record should not change when the code does. Vellum stores layers, components and variables as a vector document, then exports HTML with CSS or Tailwind, PNG, JPEG, WEBP, SVG and PDF, and design tokens as CSS variables, a Tailwind v4 theme or Design Tokens JSON.
Does Vellum work with the agents I already use?: Yes. The vellum command is an MCP server, so Claude Code, Codex, Cursor, Gemini CLI, Windsurf, Copilot CLI, Zed and other MCP clients can design on the canvas. A built-in agent runs on your own provider key.
Can my team collaborate in Vellum?: Not in the editors yet. The room service is built; the editors are not attached to it. Share links open read-only snapshots, and the design file itself reviews in Git. Paper is ahead here today.
What does Vellum cost?: Free during the beta — no card and no charge now. After the beta, a one-time purchase — not a subscription. Date to be announced. The purchase covers the app. Agents run on your own subscription or provider key.

Where these facts come from

Vellum statements are checked against its own documentation. Facts about Paper come from paper.design, its documentation and its pricing page, read on 5 November 2026. Vendors change their plans; check theirs before you decide.

This page is written by the Vellum project. It says where Paper is ahead, and it links to the vendor for anything it does not state.

Bring your next screen into the repository.

Open a file, describe the screen, and watch an agent draw it beside your code.

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