# Dark Mode Theming Stinger > Audits and implements dark mode for React/Next.js: CSS tokens, next-themes wiring, FOWT prevention, SSR hydration, Tailwind v4 config, multi-brand theming. Use for dark mode setup or flashing bugs. - Skill: `legioncodeinc/dark-mode-theming-stinger` (Agent Skill, multi-file: 25 files) - Install (CLI): `npx skillmds@latest add legioncodeinc/dark-mode-theming-stinger` - Raw SKILL.md: https://api.skillmd.com/api/skills/legioncodeinc/dark-mode-theming-stinger/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Web & Frontend - License: MIT - Author: legioncodeinc (https://skillmd.com/u/legioncodeinc) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/legioncodeinc/dark-mode-theming-stinger --- # Dark Mode Theming Stinger The dark-mode theming surface is one of the most deceptively complex areas of a modern React/Next.js stack. Getting it right requires aligning four systems: CSS token architecture, a theme provider library, SSR hydration semantics, and (in multi-brand apps) a runtime CSS variable override layer. Getting any one of them wrong produces visible flashes, hydration warnings, inaccessible OS-native controls, or cross-tenant token leakage. This Stinger encodes the 2026 consensus patterns for all of these. Read `SKILL.md` for the overview and task routing; follow the specific guide for deep implementation. --- ## When to use this skill Load this skill when `dark-mode-theming-worker-bee` is invoked, or the user says: - "Set up dark mode" - "next-themes keeps flashing" - "Dark mode on SSR" - "Multi-brand theming" - "CSS variable token layer" - "Tailwind v4 dark mode" - "prefers-color-scheme in Next.js" - "White-label theme runtime swap" This skill covers the full dark-mode theming surface for React/Next.js applications: CSS variable token architecture (semantic vs. primitive), `next-themes` wiring (ThemeProvider, storageKey, enableSystem), FOWT (flash-of-wrong-theme) prevention via a blocking inline script, SSR hydration safety (suppressHydrationWarning, typeof window guards, mounted guard pattern), Tailwind v4 dark-mode configuration (@custom-variant, selector strategy), and multi-brand/white-label runtime theme swapping via CSS variable overrides. Do NOT use for palette creation or source-of-truth token file authorship (`design-system-worker-bee`), per-component visual deltas (`ux-ui-svelte-worker-bee`), or persisted-preference schema design (`db-worker-bee`). See the scope boundary table below for the full routing map. --- ## Task routing | Task | Guide | |------|-------| | Understand principles and token contract | `guides/00-principles.md` | | Build the `:root` / `.dark` CSS variable layer | `guides/01-css-token-architecture.md` | | Wire `next-themes` ThemeProvider | `guides/02-next-themes-wiring.md` | | Eliminate flash-of-wrong-theme | `guides/03-fowt-prevention.md` | | Fix SSR hydration warnings / mounted guard | `guides/04-ssr-hydration-safety.md` | | Configure Tailwind v4 dark mode | `guides/05-tailwind-v4-dark-mode.md` | | Implement multi-brand / white-label theming | `guides/06-multi-brand-runtime-swap.md` | | Happy-path example (App Router + next-themes + Tailwind v4) | `examples/happy-path-app-router.md` | | Edge-case example (cookie-based SSR match) | `examples/edge-case-cookie-ssr.md` | | Token layer skeleton template | `templates/tokens.css.template.md` | | Audit report template | `templates/audit-report.template.md` | --- ## The six non-negotiables These are the directives from the Command Brief, repeated here as the guardrails for every implementation: 1. **Never emit raw hex in component code.** All color references go through `var(--token-name)`. See `guides/00-principles.md`. 2. **Always inject the FOWT-prevention script before first paint.** See `guides/03-fowt-prevention.md`. 3. **Distinguish `prefers-color-scheme` (system preference) from persisted preference (localStorage / cookie).** System preference is the fallback, not the override. See `guides/02-next-themes-wiring.md`. 4. **Flag `typeof window` guards in every SSR-executed code path that reads theme state.** See `guides/04-ssr-hydration-safety.md`. 5. **Scope multi-brand overrides to CSS variables, not JS state.** CSS variable overrides are zero-JS and zero-rerender. See `guides/06-multi-brand-runtime-swap.md`. 6. **Separate semantic tokens from primitive tokens.** `--color-primary` must point to a semantic alias, not a raw hex value. See `guides/01-css-token-architecture.md`. --- ## Scope boundary | In scope | Out of scope: route to | |----------|------------------------| | CSS variable token layer (`:root`, `.dark`, per-brand blocks) | Palette creation, token source-of-truth file: `design-system-worker-bee` | | `next-themes` wiring (ThemeProvider, props, storageKey) | Per-component visual deltas (which token for which role): `ux-ui-svelte-worker-bee` | | FOWT prevention (inline script, script placement) | Persisted-preference DB schema (`user_preferences.theme`): `db-worker-bee` | | SSR hydration safety (`suppressHydrationWarning`, guards) | CSS variable injection input validation: `security-worker-bee` | | Tailwind v4 dark mode (`@custom-variant`) | Tailwind config beyond `darkMode`: `ux-ui-svelte-worker-bee` | | Multi-brand CSS variable overrides | Auth-gated per-user theme (server-side preference + RBAC): `auth-worker-bee` + `db-worker-bee` | --- ## Quick-start checklist For a standard Next.js 15 App Router + `next-themes` + Tailwind v4 stack: - [ ] Token layer: `:root` semantic tokens + `.dark` overrides in `globals.css` - [ ] `color-scheme` CSS property set on `:root` and `.dark` - [ ] `meta[name="color-scheme"]` in `layout.tsx` - [ ] `ThemeProvider` in a `"use client"` providers component - [ ] `suppressHydrationWarning` on `` - [ ] `disableTransitionOnChange` enabled on `ThemeProvider` - [ ] Tailwind: `@custom-variant dark (&:where(.dark, .dark *))` in `globals.css` - [ ] No raw hex values in any component `.tsx` file --- *Research trail: `research/research-summary.md` | Command Brief: `ai-tools/command-briefs/dark-mode-theming-worker-bee-command-brief.md`*