## Summary
Completes the migration of the frontend styling system from **Emotion**
(`@emotion/styled`, `@emotion/react`) to **Linaria** (`@linaria/react`,
`@linaria/core`), a zero-runtime CSS-in-JS library where styles are
extracted at build time.
This is the final step of the migration — all ~494 files across
`twenty-front`, `twenty-ui`, `twenty-website`, and `twenty-sdk` are now
fully converted.
## Changes
### Styling Migration (across ~480 component files)
- Replaced all `@emotion/styled` imports with `@linaria/react`
- Converted runtime theme access patterns (`({ theme }) => theme.x.y`)
to build-time `themeCssVariables` CSS custom properties
- Replaced `useTheme()` hook (from Emotion) with
`useContext(ThemeContext)` where runtime theme values are still needed
(e.g., passing colors to non-CSS props like icon components)
- Removed `@emotion/react` `css` helper usages in favor of Linaria
template literals
### Dependency & Configuration Changes
- **Removed**: `@emotion/react`, `@emotion/styled` from root
`package.json`
- **Added**: `@wyw-in-js/babel-preset`, `next-with-linaria` (for
twenty-website SSR support)
- Updated Nx generator defaults from `@emotion/styled` to
`@linaria/react` in `nx.json`
- Simplified `vite.config.ts` (removed Emotion-specific configuration)
- Updated `twenty-website/next.config.js` to use `next-with-linaria` for
SSR Linaria support
### Storybook & Testing
- Removed `ThemeProvider` from Emotion in Storybook previews
(`twenty-front`, `twenty-sdk`)
- Now relies solely on `ThemeContextProvider` for theme injection
### Documentation
- Removed the temporary `docs/emotion-to-linaria-migration-plan.md`
(migration complete)
- Updated `CLAUDE.md` and `README.md` to reflect Linaria as the styling
stack
- Updated frontend style guide docs across all locales
## How it works
Linaria extracts styles at build time via the `@wyw-in-js/vite` plugin.
All expressions in `styled` template literals must be **statically
evaluable** — no runtime theme objects or closures over component state.
- **Static styles** use `themeCssVariables` which map to CSS custom
properties (`var(--theme-color-x)`)
- **Runtime theme access** (for non-CSS use cases like icon `color`
props) uses `useContext(ThemeContext)` instead of Emotion's `useTheme()`
## Migrate twenty-ui from Emotion to Linaria
Completes the migration of all `twenty-ui` components from Emotion
(runtime CSS-in-JS) to Linaria (zero-runtime, CSS extracted at build
time).
- Replaced `@emotion/styled` with `@linaria/react` across ~170 files
- Removed all Emotion dependencies from `twenty-ui`
- Introduced a CSS custom properties-based theme system:
`themeCssVariables` where every leaf is a `var(--t-xxx)` reference,
injected onto `document.documentElement` by
`ThemeCssVariableInjectorEffect`
- No more `theme` prop threading — styled components reference
`themeCssVariables.x.y` directly at build time
- Updated `twenty-front` consumers to remove `theme={theme}` prop
passing
**Before / After:**
```tsx
// Emotion
color: ${({ theme }) => theme.font.color.primary};
padding: ${({ theme }) => theme.spacing(4)};
// Linaria
color: ${themeCssVariables.font.color.primary};
padding: ${themeCssVariables.spacing[4]};
```
### Theme architecture
Two build-time utilities produce the theme system:
- **`buildThemeReferencingRootCssVariables`** — walks the theme object
and builds a nested mirror where every leaf is a `var(--t-xxx)` string
(evaluated at build time by wyw-in-js)
- **`prepareThemeForRootCssVariableInjection`** — walks the runtime
theme and collects flat `[--css-variable-name, value]` pairs, injected
onto `document.documentElement` by `ThemeCssVariableInjectorEffect`
Both share naming conventions (`camelToKebab`, `SPACING_VALUES`,
`formatSpacingKey`) and are unit tested.
### Spacing cleanup
Spacing scale now uses integers 0–32 (generated via loop), with `0.5`
and `1.5` as the only fractional exceptions. All other fractional
spacing usages (`0.25`, `0.75`, `1.25`, `2.5`, `3.5`) were replaced with
literal pixel values across ~20 twenty-front files.
### Framer Motion integration
Linaria doesn't support `styled(motion.div)` — wrapping a motion element
with `styled()` causes the component body to be stripped at build time.
Instead, we define the styled component first, then wrap it with
`motion.create()`:
```tsx
const StyledBarBase = styled.div`
background-color: ${themeCssVariables.font.color.primary};
height: 100%;
`;
const StyledBar = motion.create(StyledBarBase);
```
### Block interpolations
Linaria doesn't support interpolations that return multiple CSS
declarations (Linaria wraps the entire block in a single `var()`,
producing invalid CSS). These were split into individual property
interpolations:
```tsx
// Emotion — single interpolation returning multiple declarations
border-left: ${({ divider, theme }) => {
const border = `1px solid ${theme.border.color.light}`;
return divider ? `border-${divider}: ${border}` : '';
}}
// Linaria — one interpolation per property
border-left: ${({ divider }) =>
divider === 'left' ? `1px solid ${themeCssVariables.border.color.light}` : 'none'};
border-right: ${({ divider }) =>
divider === 'right' ? `1px solid ${themeCssVariables.border.color.light}` : 'none'};
```
### Dynamic styles via CSS variables
When a component needs to compute styles from multiple props with
complex branching logic (e.g. `Button` combining `variant`, `accent`,
`inverted`, `disabled`, `focus`, `position`), Linaria's prop
interpolations become unwieldy. In those cases we use a
`computeDynamicStyles` function that returns a `CSSProperties` object
injected via `style={}`, referenced from the static CSS with `var()`:
```tsx
const StyledButton = styled.button`
background: var(--btn-bg);
border-color: var(--btn-border-color);
&:hover { background: var(--btn-hover-bg); }
`;
const dynamicStyles = useMemo(() => {
const s = computeButtonDynamicStyles(variant, accent, ...);
return { '--btn-bg': s.background, '--btn-hover-bg': s.hoverBackground } as CSSProperties;
}, [variant, accent, ...]);
return <StyledButton style={dynamicStyles} />;
```
### CSS var + unit concatenation
CSS custom properties can't be concatenated with unit suffixes directly
(`var(--x)px` is invalid). Values that need units use `calc()`:
```tsx
// Broken
transition: background ${themeCssVariables.animation.duration.instant}s ease;
// Fixed
transition: background calc(${themeCssVariables.animation.duration.instant} * 1s) ease;
```
Upgraded from 8.6.15 to 9.1.17 in two steps:
- 8.6.15 -> 9.0.0
- 9.0.0 -> 9.1.17
I had to disable `storybook-addon-cookie` since it is not supported for
Storybook 9. However, I do intend to upgrade to Storybook 10 when this
is merged, so we can replace the aforementioned add-on with this fork
specifically created to support Storybook 10 and above:
https://www.npmjs.com/package/@storybook-community/storybook-addon-cookie.
Additionally, once we upgrade to Version 10 successfully, I will start
looking into integrating the official Vitest add-on.
Charles Bochet
