---

name: frontend-style-guide description: Apply the Lightdash frontend style guide when working on React components, migrating Mantine v6 to v8, or styling frontend code. Use when editing TSX files, fixing styling issues, or when user mentions Mantine, styling, or CSS modules. allowed-tools: Read, Edit, Write, Glob, Grep

Lightdash Frontend Style Guide

Apply these rules when working on any frontend component in packages/frontend/.

Mantine 8 Migration

CRITICAL: We are migrating from Mantine 6 to 8. Always upgrade v6 components when you encounter them.

Component Checklist

When creating/updating components:

• Use @mantine-8/core imports
• No style or styles or sx props
• Check Mantine docs/types for available component props
• Use inline-style component props for styling when available (and follow <=3 props rule)
• Use CSS modules when component props aren't available or when more than 3 inline-style props are needed
• Theme values ('md', 'lg', 'xl', or 'ldGray.1', 'ldGray.2', 'ldDark.1', 'ldDark.2', etc) instead of magic numbers

Quick Migration Guide

Copy// ❌ Mantine 6
import { Button, Group } from '@mantine/core';

<Group spacing="xs" noWrap>
    <Button sx={{ mt: 20 }}>Click</Button>
</Group>;

// ✅ Mantine 8
import { Button, Group } from '@mantine-8/core';

<Group gap="xs" wrap="nowrap">
    <Button mt={20}>Click</Button>
</Group>;

Key Prop Changes

• spacing → gap
• noWrap → wrap="nowrap"
• sx → Component props (e.g., mt, w, c) or CSS modules
• leftIcon → leftSection
• rightIcon → rightSection

Styling Best Practices

Core Principle: Theme First

The goal is to use theme defaults whenever possible. Style overrides should be the exception, not the rule.

Styling Hierarchy

1. Best: No custom styles (use theme defaults)
2. Theme extension: For repeated patterns, add to mantine8Theme.ts
3. Component props: Simple overrides (1-3 props like mt="xl" w={240})
4. CSS modules: Complex styling or more than 3 props

NEVER Use

• styles prop (always use CSS modules instead)
• sx prop (it's a v6 prop)
• style prop (inline styles)

Theme Extensions (For Repeated Patterns)

If you find yourself applying the same style override multiple times, add it to the theme in mantine8Theme.ts:

Copy// In src/mantine8Theme.ts - inside the components object
components: {
    Button: Button.extend({
        styles: {
            root: {
                minWidth: '120px',
                fontWeight: 600,
            }
        }
    }),
}

Context-Specific Overrides

Inline-style Component Props (1-3 simple props)

Copy// ✅ Good
<Button mt="xl" w={240} c="blue.6">Submit</Button>

// ❌ Bad - Too many props, use CSS modules instead
<Button mt={20} mb={20} ml={10} mr={10} w={240} c="blue.6" bg="white">Submit</Button>

Common inline-style props:

• Layout: mt, mb, ml, mr, m, p, pt, pb, pl, pr
• Sizing: w, h, maw, mah, miw, mih
• Colors: c (color), bg (background)
• Font: ff, fs, fw
• Text: ta, lh

CSS Modules (complex styles or >3 props)

Create a .module.css file in the same folder as the component:

Copy/* Component.module.css */
.customCard {
    transition: transform 0.2s ease;
    cursor: pointer;
}

.customCard:hover {
    transform: translateY(-2px);
    box-shadow: var(--mantine-shadow-lg);
}

Copyimport styles from './Component.module.css';

<Card className={styles.customCard}>{/* content */}</Card>;

Do NOT include .css.d.ts files - Vite handles this automatically.

Color Guidelines

Prefer default component colors - Mantine handles theme switching automatically.

When you need custom colors, use our custom scales for dark mode compatibility:

Copy// ❌ Bad - Standard Mantine colors (poor dark mode support)
<Text c="gray.6">Secondary text</Text>

// ✅ Good - ldGray for borders and neutral elements
<Text c="ldGray.6">Secondary text</Text>

// ✅ Good - ldDark for elements that appear dark in light mode
<Button bg="ldDark.8" c="ldDark.0">Dark button</Button>

// ✅ Good - Foreground/background variables
<Text c="foreground">Primary text</Text>
<Box bg="background">Main background</Box>

Custom Color Scales

Dark Mode in CSS Modules

Use @mixin dark for theme-specific overrides:

Copy.clickableRow {
    &:hover {
        background-color: var(--mantine-color-ldGray-0);

        @mixin dark {
            background-color: var(--mantine-color-ldDark-5);
        }
    }
}

Alternative: use CSS light-dark() function for single-line theme switching:

Copy.clickableRow:hover {
    background-color: light-dark(var(--mantine-color-ldGray-0), var(--mantine-color-ldDark-5));
}

Always Use Theme Tokens

Copy// ❌ Bad - Magic numbers
<Box p={16} mt={24}>

// ✅ Good - Theme tokens
<Box p="md" mt="lg">

Remove Dead Styles

Before moving styles to CSS modules, check if they're actually needed:

Copy// ❌ Unnecessary - display: block has no effect on flex children
<Flex justify="flex-end">
    <Button style={{display: 'block'}}>Submit</Button>
</Flex>

// ✅ Better - Remove the style entirely
<Flex justify="flex-end">
    <Button>Submit</Button>
</Flex>

Theme-Aware Component Logic

For JavaScript logic that needs to know the current theme:

Copyimport { useMantineColorScheme } from '@mantine/core';

const MyComponent = () => {
    const { colorScheme } = useMantineColorScheme();
    const iconColor = colorScheme === 'dark' ? 'blue.4' : 'blue.6';
    // ...
};

Reusable Components

Modals

• Always use MantineModal from components/common/MantineModal - never use Mantine's Modal directly
• See stories/Modal.stories.tsx for usage examples
• For forms inside modals: use id on the form and form="form-id" on the submit button
• For alerts inside modals: use Callout with variants danger, warning, info

Callouts

• Use Callout from components/common/Callout
• Variants: danger, warning, info

Mantine Documentation

List of all components and links to their documentation in LLM-friendly format: https://mantine.dev/llms.txt