UI Conventions (apps/web)

i18n — every user-facing string, both locales

• Framework: next-intl, locales zh (default) and en. Message files: apps/web/messages/{zh,en}.json — a key added to one file MUST be added to the other in the same commit.
• Components use useTranslations('namespace'). Never hardcode user-facing strings — including chart tooltips, title attributes, and aria-labels (historically the most-missed spots).
• Utility functions that produce display text (formatDuration style) must not embed English words; return structured data and translate in the component.

Dark mode — check on every visual change

This is the project's highest-frequency rework source. Rules:

1. Never a lone light class. Every bg-*-50/100, text-*-500/600, border-*-200 needs a dark: counterpart. Grep your diff for bg-white|bg-.*-50|text-gray- before committing.
2. Prefer theme tokens over palette classes where one exists: bg-background, bg-popover, text-muted-foreground, border-border (defined in app/globals.css for both themes).
3. Inline SVG / chart colors can't use Tailwind — define both palettes and switch on resolvedTheme:

const { resolvedTheme } = useTheme(); // next-themes
const palette = resolvedTheme === "dark" ? DARK_COLORS : LIGHT_COLORS;

Precedents: components/features/countries/world-traffic-map.tsx (MAP_THEME), components/features/rules/rule-chain-flow.tsx. Recharts axis ticks should use fill: "currentColor" or CSS variables, not hex grays.

4. Badge/status color sets: copy an existing complete set (e.g. the health badge classes in app/[locale]/dashboard/components/header/index.tsx) rather than writing light-only classes.

Three states, always

Every data view needs loading (skeleton), empty, and error states. Error must be visible and actionable (retry button) — return null on error is a known anti-pattern here (see the chain-flow retry card in rule-chain-flow.tsx for the reference implementation). Route-level failures are caught by app/[locale]/error.tsx / app/global-error.tsx; heavy visualizations should still fail locally, not blank the page.

Data layer

• Server state via React Query; query keys are centralized in lib/stats-query-keys.ts — never inline ad-hoc keys.
• The stats WebSocket (lib/websocket.ts) tags pushes with backendId and the hook drops mismatched messages — preserve this when touching the message path (prevents cross-backend cache bleed on backend switch).
• Custom memo comparators must compare every prop the component renders from (a missed prop froze the Active Policy whitelist once — include new props in the comparator when you add them).

Components

• shadcn/ui (new-york) + Tailwind v4 + lucide-react. Base primitives in components/ui/ — reuse before creating; use the Radix Dialog for modals (no hand-rolled fixed overlays — they lose Esc/focus-trap behavior).
• Aesthetic bar: modern SaaS quality; avoid flat "admin panel" layouts. Search and other high-frequency entries should be prominent (icon inside input, clear affordances).