Google Stitch's DESIGN.md, explained
Stitch is Google Labs' AI design tool, and design.md is its memory: a plain markdown file that stores your palette, fonts, and styling rules so every screen the AI generates matches the last one. Google has since released DESIGN.md as an open spec — which turned a Stitch feature into a format the whole AI-tools ecosystem can read.
What design.md does inside Stitch
Stitch generates UI designs from prompts. Without a persistent design system, every generation is a fresh roll of the dice: the third screen drifts from the first, the palette wobbles, the type scale wanders. Stitch's answer is design.md — a file that records the design system once, which the tool then reads before generating anything new.
Because the file persists across sessions, consistency stops depending on how well you re-describe your style each time. The system of record is the file, not the prompt history. Change the file, and every subsequent generation follows.
Why Google open-sourced the format
In 2026 Google Labs released DESIGN.md as an open spec: a published format for describing a visual identity to coding agents, with the spec and tooling available publicly rather than locked inside Stitch. The stated idea is a persistent, structured understanding of a design system that any agent can share.
The move makes sense from both directions. For users, a design system encoded once should not be hostage to one tool — the same file should work in whatever AI ships next quarter. For the format, openness is what turns a feature into a standard: the more tools read DESIGN.md, the more valuable every DESIGN.md becomes.
The practical consequence: the format's structure — machine-readable design tokens up top, human-readable rationale below, in one markdown file — is now public convention, and an ecosystem of readers, writers, and libraries has grown around it.
Using the same file beyond Stitch
Because the file is plain markdown, nothing about it is Stitch-specific. Coding agents like Claude Code, Cursor, and Codex read a DESIGN.md from your project root the same way they read a README — and apply it when they generate UI. Chat assistants can take the file pasted into a conversation. Agent pipelines can fetch it programmatically.
The workflow is the same everywhere: the file states the design system; the agent reads it before building; the output matches the spec instead of the model's average taste. Which tool renders the screens is an implementation detail — the design system lives in the file.
That portability is the real payoff of the open spec. Encode a style once and it follows you across tools, instead of being re-prompted from scratch in each one.
Where Curio fits: the library layer
Stitch and the open spec answer the format question: how should a design system be written down for a machine? They deliberately do not answer the content question: where do the styles themselves come from? Out of the box, a DESIGN.md is an empty vessel — you still have to fill it with a design system you own or can articulate.
That is the layer Curio occupies. It is a curated library of real design styles — movements, brands, cultural traditions — each researched and encoded as a complete, ready-to-use DESIGN.md-style spec. You browse a style; your AI applies it over MCP, a share link, or a download. The format tells the machine how to read a design system. A library gives you design systems worth reading.
FAQ
Do I need a design.md to use Stitch?
Stitch generates designs either way, but without the file every generation starts from scratch stylistically. The design.md is what makes results consistent across screens and sessions — it is the difference between a tool that draws and a tool that follows your design system.
Does a DESIGN.md written for Stitch work in other tools?
Yes — that is the point of the open spec. The file is plain markdown with structured tokens, so any agent that can read text can follow it: Claude Code, Cursor, Codex, chat assistants, or your own pipeline. No exporter, no conversion step.
Is Curio a competitor to Stitch?
No — they sit on different layers and combine naturally. Stitch (and the open spec) define how a design system is written for machines; Curio is a library of ready-made design systems in that same convention. Use Stitch or any agent as the tool, and Curio as the place the style comes from.
Where do I find the open DESIGN.md spec?
Google Labs publishes the spec and companion tooling publicly — search for the google-labs-code design.md repository on GitHub, or Google's announcement of the open-source release. The format itself is simple enough that reading one well-formed file teaches you most of it.