Brand Kit is now the Brand section of Design System. Existing Brand Kits became the Brand section of a private Design System with the same name; their share links keep working and /brand-kits opens Design System.
A Design System documents foundations (color, typography, spacing, sizing, radius, border, shadow, layout, breakpoint, motion and icon tokens), components with variants, states, properties and the source file to reuse, patterns, page archetypes, content rules, accessibility rules and assistant rules. Sections can be renamed, reordered, hidden and shared separately. A shared system is private, unlisted or public and shows approved items only.
To start from an existing application, copy the prompt, run it with a coding assistant in the repository, and upload or paste the file it writes. The review page counts what the file contains; inferred items wait in Needs review and inconsistencies list each value found. Export gives DESIGN_SYSTEM.md at Compact, Standard or Complete detail, design-system.json, tokens.json, tokens.css and a ZIP. Design System is marked Coming soon; editing, shared pages and downloads require a Magpie admin account during this preview.