devup-ui — routing-first zero-runtime CSS-in-JS adoption

Keyword: devup-ui · @devup-ui/react · zero runtime · build-time CSS extraction · devup.json

Devup UI processes all styles at build time with a Rust-powered preprocessor. There is no runtime style engine: pick the matching bundler plugin first, then write styles; the plugin is what makes everything else work.

Devup UI removes the developer-experience vs. performance trade-off of traditional CSS-in-JS by extracting styles at compile time:

Zero Runtime — no JavaScript executes for styling at runtime
Zero Config / Zero FOUC — no client Provider, no style flash
Complete syntax coverage — variables, conditionals, responsive arrays, pseudo selectors
Familiar API — styled() compatible with styled-components / Emotion patterns
Smallest bundle — base-37 class names (a, b, … aa, ab); dynamic values become CSS variables
RSC support — works inside React Server Components

When to use this skill

The user wants to add Devup UI to a project and needs the right bundler plugin wired in
The user is choosing between Next.js / Vite / Rsbuild / Webpack / Bun integration
The user wants to write styles with Box/css props or the styled() API and isn't sure how the shorthand props (bg, px, responsive arrays, _hover) map
The user wants type-safe theming with devup.json (colors, typography, dynamic theme switching via CSS variables)
The user wants to migrate from styled-components / Emotion / Tailwind / Panda / vanilla-extract to a zero-runtime setup
The user keeps reaching for a runtime CSS-in-JS Provider and needs to know it is unnecessary (and harmful to RSC) with Devup UI

Route out when the real need is broader than styling mechanics: token/visual-language governance → design-system; reusable-component API/anatomy → design-system; layout/breakpoint strategy → responsive-design; accessibility → web-accessibility; bundle/RSC/rerender performance beyond styling → react-best-practices.

Instructions

Step 1 — Capture one intake packet before editing config

Collect, in one pass:

Bundler — Next.js, Vite, Rsbuild, Webpack, or Bun (this decides the plugin package)
React mode — App Router / RSC vs. client-only (RSC needs no Provider; do not add one)
Theming — does the project need devup.json tokens and dynamic (e.g. dark) themes?
Origin — greenfield, or migrating from styled-components / Emotion / Tailwind / Panda / vanilla-extract?
Package manager — npm / pnpm / yarn / bun

Step 2 — Install the core package and the matching bundler plugin

npm install @devup-ui/react
# then exactly ONE bundler plugin:
npm install @devup-ui/next-plugin     # Next.js
npm install @devup-ui/vite-plugin     # Vite
npm install @devup-ui/rsbuild-plugin  # Rsbuild
npm install @devup-ui/webpack-plugin  # Webpack
npm install @devup-ui/bun-plugin      # Bun

Or use the helper, which also installs the skill as a plugin and can scaffold the chosen bundler in a target project:

bash scripts/install.sh                                   # install the skill only
BUNDLER=next PROJECT=/path/to/app bash scripts/install.sh # + npm packages for Next.js
BUNDLER=vite PKG_MANAGER=pnpm PROJECT=. bash scripts/install.sh
GLOBAL=1 bash scripts/install.sh                          # install the skill globally

Step 3 — Wire the build-time plugin (the load-bearing step)

// next.config.js  (Next.js)
import { DevupUI } from '@devup-ui/next-plugin'
export default DevupUI({})

// vite.config.ts  (Vite)
import { DevupUI } from '@devup-ui/vite-plugin'
import react from '@vitejs/plugin-react'
import { defineConfig } from 'vite'
export default defineConfig({ plugins: [react(), DevupUI()] })

Rsbuild uses DevupUIRsbuildPlugin(), Webpack uses new DevupUIWebpackPlugin(), Bun imports @devup-ui/bun-plugin. Full snippets: references/installation-and-plugins.md.

Step 4 — Write styles

import { Box, css, styled } from '@devup-ui/react'

// Prop-based styling with shorthands and responsive arrays
const view = (
  <Box bg="white" p={4} borderRadius="8px" _hover={{ bg: 'gray.100' }}>
    <Box fontSize={[14, 16, 20]} color="primary">Responsive text</Box>
  </Box>
)

// styled-components / Emotion compatible API
const Card = styled('div', {
  bg: 'white',
  p: 4,            // 4 * 4 = 16px spacing scale
  borderRadius: '8px',
  boxShadow: '0 4px 6px rgba(0,0,0,0.1)',
  _hover: { boxShadow: '0 10px 15px rgba(0,0,0,0.1)' },
})

Numeric spacing props multiply by 4px. Array values are breakpoint-responsive. _hover, _focus, etc. are pseudo selectors. Dynamic values compile to CSS variables (no runtime style recompute). Details: references/styling-api.md.

Step 5 — Theme with `devup.json` (only if needed)

{
  "theme": {
    "colors": {
      "default": { "primary": "#0070f3", "text": "#000" },
      "dark":    { "primary": "#3291ff", "text": "#fff" }
    },
    "typography": {
      "heading": { "fontFamily": "Pretendard", "fontSize": "24px", "fontWeight": 700, "lineHeight": 1.3 }
    }
  }
}

Theme tokens are type-safe and theme switching is zero-cost (CSS variables). RSC works without a Provider — do not add a client Provider for theming. Migration recipes and route-outs: references/theming-and-migration.md.

Route-outs (do not over-promise styling)

Token governance, naming, visual-language direction → design-system
Reusable-component API / slot anatomy / controlled ownership → design-system
Page-shell / breakpoint / reflow strategy → responsive-design
Accessibility semantics, focus, labels, reflow → web-accessibility
Waterfalls, bundle size, RSC boundaries, rerender churn → react-best-practices

Install as a plugin

npx skills add https://github.com/akillness/jeo-skills --skill devup-ui

devup-ui