UI Stack \- Framework: Next.js (App Router + Pages Router) \- Styling: Tailwind CSS via @dust-tt/sparkle preset \- Component library: Sparkle (internal, open source) \- Dark mode: class-based (darkMode: "class"), every token has a -night variant

Typography \- Sans font: Geist (variable font) \- Mono font: Geist Mono \- Scale: xs 12px → 9xl 80px, with negative letter-spacing at larger sizes \- Font weights: copy 400 · label 500 · heading-sm–3xl 550 · heading-4xl+ 450 \- Three type styles: copy-, label-, heading- (+ heading-mono-)

Color Philosophy \- Fully custom palette: gray, stone, blue, green, rose, golden, violet, red, orange, lime, emerald, pink \- Every shade has a mirrored -night sibling (light ↔ dark inversion) \- Semantic aliases: foreground, background, primary, highlight (blue), warning (rose), success (green), info (golden), border, muted, faint, hover, separator, ring \- Brand tokens: hunter-green, electric-blue, red-rose, orange-golden mapped to palette

Spacing & Layout \- Default Tailwind spacing scale \- Sidebar spacing: 0.75rem \- Conversation max-width: 48rem \- Breakpoints: xxs 384px · xs 512px · sm 640px · md 768px · lg 1024px · xl 1280px · 2xl 1536px \- Size scale additions: 100→400px, 125→500px, 150→600px

Border Radius \- Tailwind defaults + 4xl: 2rem

Shadows \- Box shadows use gray-950 base with low opacity \- Scale: sm, DEFAULT, md, lg, xl, 2xl

Transitions \- Named durations: enter 200ms · exit 160ms · modal-enter 300ms · modal-exit 240ms \- Rich easing library: out-quad, out-expo, emphasized (cubic-bezier(0.23,1,0.32,1)), enter, move

:root { / TYPOGRAPHY / --font-family-base: 'Geist', sans-serif; --font-family-mono: 'Geist Mono', monospace; --font-weight-copy: 400; --font-weight-label: 500; --font-weight-heading: 550; --font-weight-heading-large: 450;

/ FONT SIZES / --text-xs: 12px; --leading-xs: 16px; --tracking-xs: normal; --text-sm: 14px; --leading-sm: 20px; --tracking-sm: -0.28px; --text-base: 16px; --leading-base: 24px; --tracking-base: -0.32px; --text-lg: 18px; --leading-lg: 26px; --tracking-lg: -0.36px; --text-xl: 20px; --leading-xl: 28px; --tracking-xl: -0.4px; --text-2xl: 24px; --leading-2xl: 30px; --tracking-2xl: -0.96px; --text-3xl: 32px; --leading-3xl: 36px; --tracking-3xl: -1.28px; --text-4xl: 40px; --leading-4xl: 42px; --tracking-4xl: -2.4px; --text-5xl: 48px; --leading-5xl: 52px; --tracking-5xl: -2.88px;

/ SPACING / --space-xs: 0.25rem; / 4px / --space-sm: 0.5rem; / 8px / --space-md: 1rem; / 16px / --space-lg: 1.5rem; / 24px / --space-xl: 2rem; / 32px / --space-2xl: 3rem; / 48px / --space-sidebar: 0.75rem;

/ COLORS — Light mode / --color-background: #ffffff; --color-app-background: #FBFAF9; --color-foreground: #111418; --color-foreground-muted: #596170; --color-foreground-faint: #969CA5;

/ Primary (gray scale) / --color-primary: #2A3241; --color-primary-light: #596170; --color-primary-dark: #111418; --color-primary-muted: #7B818D;

/ Highlight (blue) / --color-highlight: #1C91FF; --color-highlight-light: #4BABFF; --color-highlight-dark: #137FE3;

/ Warning (rose) / --color-warning: #E14322; --color-warning-light: #ED756C; --color-warning-dark: #C93913;

/ Success (green) / --color-success: #6AA668; --color-success-light: #91C174; --color-success-dark: #418B5C;

/ Info (golden) / --color-info: #FFAA0D; --color-info-light: #FFBE2C; --color-info-dark: #FE9C1A;

/ Brand / --color-brand: #418B5C; --color-brand-electric-blue: #1C91FF; --color-brand-red-rose: #E14322; --color-brand-golden: #FE9C1A;

/ Borders & UI chrome / --color-border: #EEEEEF; --color-border-dark: #DFE0E2; --color-border-focus: #4BABFF; --color-separator: #EEEEEF; --color-hover: #EEEEEF; --color-muted-background: #F7F7F7; --color-ring: #9FDBFF;

/ BORDER RADIUS / --radius-sm: 0.125rem; / 2px / --radius-md: 0.375rem; / 6px / --radius-lg: 0.5rem; / 8px / --radius-xl: 0.75rem; / 12px / --radius-2xl: 1rem; / 16px / --radius-3xl: 1.5rem; / 24px / --radius-4xl: 2rem; / 32px / --radius-full: 9999px;

/ SHADOWS / --shadow-sm: 0 1px 2px rgba(17,20,24,0.05); --shadow-md: 0 2px 6px rgba(17,20,24,0.10); --shadow-lg: 0 4px 12px rgba(17,20,24,0.12); --shadow-xl: 0 10px 20px rgba(17,20,24,0.12); --shadow-2xl: 0 25px 50px rgba(17,20,24,0.12);

/ TRANSITIONS / --transition-default: all 200ms cubic-bezier(0.215, 0.61, 0.355, 1); --transition-enter: 200ms cubic-bezier(0.215, 0.61, 0.355, 1); --transition-exit: 160ms cubic-bezier(0.25, 0.46, 0.45, 0.94); --transition-modal-enter: 300ms cubic-bezier(0.23, 1, 0.32, 1); --transition-modal-exit: 240ms cubic-bezier(0.455, 0.03, 0.515, 0.955); --transition-emphasized: cubic-bezier(0.23, 1, 0.32, 1);

/ LAYOUT / --max-w-conversation: 48rem; --panel-height: var(--panel-height); }

/ Dark mode overrides / .dark { --color-background: #111418; --color-app-background: #1C222D; --color-foreground: #D3D5D9; --color-foreground-muted: #969CA5; --color-foreground-faint: #596170; --color-primary: #D3D5D9; --color-primary-light: #B2B6BD; --color-primary-dark: #EEEEEF; --color-border: #2A3241; --color-border-dark: #364153; --color-border-focus: #137FE3; --color-hover: #2A3241; --color-muted-background: #111418; --color-ring: #364153; }

Dust / Sparkle — Design Tokens Reference

Color Tokens

Token	Light	Dark (night)	Usage
background	#ffffff	#111418	Page background
app-background	#FBFAF9	#1C222D	App shell background
foreground	#111418	#D3D5D9	Primary text
muted.foreground	#596170	#969CA5	Secondary text
faint	#969CA5	#596170	Placeholder / disabled text
primary	#2A3241	#D3D5D9	Default UI color
primary.dark	#111418	#EEEEEF	Emphasis
highlight	#1C91FF	#1C91FF	Interactive / links
highlight.dark	#137FE3	#4BABFF	Hover state
warning	#E14322	#E14322	Errors / destructive
success	#6AA668	#6AA668	Positive states
info	#FFAA0D	#FFAA0D	Informational / golden
brand	#418B5C	#418B5C	Brand hunter-green
border	#EEEEEF	#2A3241	Default border
border.dark	#DFE0E2	#364153	Prominent border
border.focus	#4BABFF	#137FE3	Focus ring color
hover	#EEEEEF	#2A3241	Hover background
separator	#EEEEEF	#2A3241	Dividers
ring	#9FDBFF	#364153	Focus ring
sidebar.primary	#292524	#D6D3D1	Sidebar text

Palette Reference

Name	50	200	500	800	950
gray	#F7F7F7	#D3D5D9	#7B818D	#2A3241	#111418
stone	#FBFAF9	#E7E5E4	#79716B	#292524	#0C0A09
blue	#E9F7FF	#9FDBFF	#1C91FF	#085092	#041728
green	#FEFFF0	#E2F78C	#6AA668	#105B2B	#04140A
rose	#FFF1F7	#FFC3DF	#E14322	#8C230D	#220A04
golden	#FFFAE0	#FFE262	#FFAA0D	#AF5511	#331606
violet	#F5F3FF	#DDD6FE	#8B5CF6	#5B21B6	#2E1065

Typography Tokens

Class	Size	Line Height	Letter Spacing	Weight
copy-xs	12px	16px	normal	400
copy-sm	14px	20px	-0.28px	400
copy-base	16px	24px	-0.32px	400
copy-lg	18px	26px	-0.36px	400
label-xs	12px	16px	normal	500
label-sm	14px	20px	-0.28px	500
label-base	16px	24px	-0.32px	500
heading-sm	14px	20px	-0.28px	550
heading-base	16px	24px	-0.32px	550
heading-xl	20px	28px	-0.4px	550
heading-3xl	32px	36px	-1.28px	550
heading-4xl	40px	42px	-2.4px	450
heading-6xl	56px	60px	-3.36px	450
heading-mono-2xl	24px	30px	-0.96px	400 mono

Spacing Tokens

Token	Value	px equiv
space-1	0.25rem	4px
space-2	0.5rem	8px
space-3	0.75rem	12px
space-4	1rem	16px
space-6	1.5rem	24px
space-8	2rem	32px
space-12	3rem	48px
space-16	4rem	64px
sidebar-side-spacing	0.75rem	12px

Border Radius

Token	Value
rounded-sm	2px
rounded	4px
rounded-md	6px
rounded-lg	8px
rounded-xl	12px
rounded-2xl	16px
rounded-3xl	24px
rounded-4xl	32px
rounded-full	9999px

Shadows

Token	Value
shadow-sm	0 1px 2px gray-950/5%
shadow	0 2px 6px gray-950/10%
shadow-md	0 4px 12px gray-950/12%
shadow-lg	0 10px 20px gray-950/12%
shadow-xl	0 20px 25px gray-950/12%
shadow-2xl	0 25px 50px gray-950/12%

Breakpoints

Name	Width
xxs	384px
xs	512px
sm	640px
md	768px
lg	1024px
xl	1280px
2xl	1536px

Implementation Notes — Dust Design System

Source \- Repository: [github.com/dust-tt/dust](http://github.com/dust-tt/dust) (fully open source, MIT) \- Design system package: /sparkle — published as @dust-tt/sparkle on npm \- Data provenance: Extracted directly from sparkle/tailwind-preset.js and front/tailwind.config.js — these are the ground-truth token files, not approximations

UI Framework \- Next.js (both App Router and Pages Router in use across the monorepo) \- Tailwind CSS via a custom preset (@dust-tt/sparkle/tailwind-preset) \- Component system: Sparkle (internal design system, open source) \- Tailwind plugins in use: @tailwindcss/forms, @tailwindcss/container-queries, tailwind-scrollbar-hide, tailwindcss-animate

Theme / Dark Mode \- Dark mode via darkMode: "class" — a .dark class on or a parent element \- Every semantic color token has a paired -night value baked into the Tailwind config \- The color inversion strategy is explicit: light shade 100 ↔ dark shade 900, etc. \- No CSS custom property swap at runtime — Tailwind generates both light and dark utility classes statically

Notable Patterns \- Typography classes are Tailwind components (addComponents), not utilities — e.g. .heading-3xl, .copy-base, .label-sm \- Custom easing curves named out-expo, emphasized, enter, move — richer than standard Tailwind \- Negative letter-spacing scales with size: all headings above sm use negative tracking for a premium editorial feel \- Geist font family (Vercel's open source font) used for both sans and mono \- Golden color replaces amber/yellow — a warm amber with custom 12-stop scale (50–950) \- Sidebar uses stone palette (warm gray) rather than cool gray, for visual differentiation \- Conversation max-width is hardcoded at 48rem — a key layout constraint for the chat UI \- Animation conventions: spring-like cubic-bezier (0.34, 1.56, 0.64, 1) for entry animations, standard ease-out for exits \- Container queries are used (@tailwindcss/container-queries) with named sizes from xxs: 24rem to xl: 80rem