Google Labs open-sourced the draft specification for DESIGN.md, a single-file format that gives AI coding agents consistent design rules, on April 21, 2026. The move opens up a mechanism previously used inside the company's AI UI generation tool Google Stitch so it can be used with any AI agent. The spec and drafts are published in the official repository and on Google's blog .
April 21, 2026 · Google Labs
DESIGN.md: A README for How AI Should Design
Google Labs open-sourced the draft spec for a single-file format that hands AI coding agents consistent, machine-readable design rules — a mechanism once locked inside its Stitch tool, now open to any agent under Apache-2.0.
96,000+
GitHub stars for a community collection of brand design files, in a short period
461+
DESIGN.md files hosted in a browsable public library
~9
Body sections: theme, palette, typography, components, layout & more
Inside one file
YAML FRONT MATTER
Machine-readable tokens
Colors (hex) · font sizes · spacing · corner radius · elevation · component styling
MARKDOWN BODY
Human-readable rationale
Visual theme · color palette · typography · component styling · layout principles
Placed at the project root — a "design-side README" paired with AGENTS.md, readable directly by Claude Code, Cursor, and Stitch.
Why it exists
From re-prompting every time → to one persistent source of truth
Generic "AI slop"
Tailwind-look UIs, inconsistent color & spacing
→
Plain-text tokens + rules
Agent reads it directly, no re-specifying
→
On-brand, consistent UI
Portable across any AI agent
The praise
Brand consistency improves significantly
Fewer CSS tweaks and design revisions
Simpler prompts, less generic UI
Apple's file → iOS-style HTML+Tailwind home screen
The caution
Tokens alone aren't enough — prose quality matters
Poor files automate inconsistent design
State, accessibility & performance stay weak for AI
30 days: colors matched, but application judgment fell short
A measured verdict: useful as a supporting tool aiming to become an industry standard — but expectations may be running hotter than the alpha-stage reality warrants.
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