bvandeusen
1dcce4e304
Web SPA dark/light/system theme. Token strategy: dual :root + [data-theme="light"] blocks in tokens.generated.css; Tailwind unchanged. Light palette is parchment/aged-paper. Adds non-flipping --fs-on-action for action button labels. FOUC prevented via inline app.html head script.
245 lines
10 KiB
Markdown
245 lines
10 KiB
Markdown
# M7 #362 — Web SPA Theme Toggle (Dark / Light / System)
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**Status:** Design
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**Milestone:** M7 (v1.0 web-first sweep)
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**Issue:** Fable #362
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**Scope:** Web SPA only. Flutter mobile mirror is out of scope (separate task in Tier 1 catch-up).
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## Goal
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Let a user choose Dark, Light, or follow-system theme for the Minstrel web SPA. Persist the choice across sessions. Apply it before first paint to avoid FOUC.
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## Out of scope
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- Per-page or per-section theme overrides.
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- Multi-color brand palettes beyond the dark + light pair.
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- Time-of-day automatic switching independent of the OS preference.
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- Cross-tab live sync (settings change in tab A doesn't propagate to tab B). Documented as a known limitation.
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- Flutter client mirror.
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- Animated transitions between modes (instant flip).
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## Architecture
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### Token strategy
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Existing system: design tokens defined in `web/src/lib/styles/tokens.json`, generated to `web/src/lib/styles/tokens.generated.css` by `web/scripts/tokens-to-css.js`, and consumed by Tailwind via `var(--fs-*)` references in `web/tailwind.config.js`.
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Theme is implemented by emitting **two blocks** of custom-property values in the generated CSS:
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```css
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:root {
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/* Dark palette (default) + flat tokens used in both modes */
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--fs-obsidian: #0E1013;
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...
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--fs-moss: #5A7563;
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--fs-on-action: #E8E2D2;
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}
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[data-theme="light"] {
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/* Light overrides only — flat tokens are NOT repeated */
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--fs-obsidian: #F8F5EE;
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--fs-iron: #ECE6D5;
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...
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}
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```
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Tailwind config is **not** changed. The `var(--fs-*)` indirection means every utility class (`bg-fs-iron`, `text-fs-parchment`, etc.) automatically swaps when the `[data-theme="light"]` selector matches.
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The active theme is selected by setting `data-theme="light"` (or absent / `"dark"`) on `<html>`.
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### tokens.json schema change
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Current shape (flat):
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```json
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{
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"colors": {
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"obsidian": "#0E1013",
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"iron": "#14171A",
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...
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}
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}
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```
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New shape:
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```json
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{
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"colors": {
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"dark": {
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"obsidian": "#0E1013",
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"iron": "#14171A",
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"slate": "#1C1F23",
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"pewter": "#2C313A",
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"parchment": "#E8E2D2",
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"vellum": "#C9C2AE",
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"ash": "#8A8474"
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},
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"light": {
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"obsidian": "#F8F5EE",
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"iron": "#ECE6D5",
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"slate": "#DCD3BD",
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"pewter": "#B8AE94",
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"parchment": "#14171A",
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"vellum": "#2C313A",
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"ash": "#5C6068"
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},
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"flat": {
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"moss": "#5A7563",
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"bronze": "#8C6A3F",
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"oxblood": "#7A2E2E",
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"warning": "#C99A4A",
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"error": "#A04848",
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"info": "#5A7A8A",
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"accent": "#4A6B5C",
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"on-action": "#E8E2D2"
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}
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}
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}
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```
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`flat` tokens are emitted once in `:root` only. They do not flip.
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### Generator change
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`web/scripts/tokens-to-css.js` is updated to:
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1. Walk `colors.dark` + `colors.flat`, emit a `:root { ... }` block with `--fs-<name>: <value>;` lines.
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2. Walk `colors.light`, emit a `[data-theme="light"] { ... }` block.
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3. Preserve existing non-color sections of `tokens.json` (typography, spacing, etc.) — those continue to emit into `:root` only.
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### `--fs-on-action` token
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A new flat token, value `#E8E2D2` (frozen at the dark-mode parchment value). Used as the label color on action buttons whose backgrounds (`--fs-moss`, `--fs-bronze`, `--fs-oxblood`) do not flip. Without this, action button text would invert in light mode and lose contrast against the mid-tone earth backgrounds.
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Tailwind utility: `text-fs-on-action`.
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### Theme store
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New file: `web/src/lib/stores/theme.svelte.ts`.
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Exports a small rune-state module:
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```ts
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type ThemePreference = 'dark' | 'light' | 'system';
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type ResolvedTheme = 'dark' | 'light';
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export const theme: { value: ThemePreference }; // user preference
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export const resolvedTheme: { value: ResolvedTheme }; // what's actually applied
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export function setTheme(pref: ThemePreference): void;
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```
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Implementation:
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- On module load, read `localStorage['minstrel:theme']` (default: `'system'`).
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- If `'system'`, resolve via `matchMedia('(prefers-color-scheme: light)')` and subscribe to `change` events to keep `resolvedTheme` in sync.
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- `setTheme(pref)` writes localStorage, updates `theme.value`, recomputes `resolvedTheme.value`, and sets `document.documentElement.dataset.theme = resolvedTheme.value`.
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### FOUC prevention
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`web/src/app.html` gains an inline script in `<head>`, **before** any CSS link:
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```html
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<script>
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(function () {
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try {
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var t = localStorage.getItem('minstrel:theme') || 'system';
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var resolved = t === 'system'
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? (matchMedia('(prefers-color-scheme: light)').matches ? 'light' : 'dark')
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: t;
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document.documentElement.setAttribute('data-theme', resolved);
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} catch (e) { /* localStorage unavailable — accept default dark */ }
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})();
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</script>
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```
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This runs synchronously before paint, so the correct theme is applied on first render. SSR/prerender paths see no theme attribute server-side; the script applies it client-side before paint.
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### Settings UI
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`web/src/routes/settings/+page.svelte` gains an "Appearance" card at the top:
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```
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┌─ Appearance ─────────────────────┐
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│ Theme: │
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│ ( ) Dark (•) Light ( ) System │
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│ │
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│ System follows your device's │
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│ light/dark preference. │
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└──────────────────────────────────┘
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```
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Implemented as three radio inputs (or a segmented control component if one already exists in the project — implementer to check). Selection writes through `setTheme()`.
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## Light palette spec
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Full token map with values:
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| Token | Dark (current) | Light (new) | Role |
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|---|---|---|---|
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| `--fs-obsidian` | `#0E1013` | `#F8F5EE` | page bg |
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| `--fs-iron` | `#14171A` | `#ECE6D5` | card/surface bg |
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| `--fs-slate` | `#1C1F23` | `#DCD3BD` | hover surface |
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| `--fs-pewter` | `#2C313A` | `#B8AE94` | borders |
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| `--fs-parchment` | `#E8E2D2` | `#14171A` | primary text |
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| `--fs-vellum` | `#C9C2AE` | `#2C313A` | secondary text |
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| `--fs-ash` | `#8A8474` | `#5C6068` | muted text |
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| `--fs-moss` | `#5A7563` | *(unchanged)* | secondary action bg |
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| `--fs-bronze` | `#8C6A3F` | *(unchanged)* | warning action bg |
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| `--fs-oxblood` | `#7A2E2E` | *(unchanged)* | destructive action bg |
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| `--fs-warning` | `#C99A4A` | *(unchanged)* | semantic marker |
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| `--fs-error` | `#A04848` | *(unchanged)* | semantic marker |
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| `--fs-info` | `#5A7A8A` | *(unchanged)* | semantic marker |
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| `--fs-accent` | `#4A6B5C` | *(unchanged)* | brand accent |
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| `--fs-on-action` | `#E8E2D2` | *(unchanged)* | action button label |
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Design rationale: light palette is "parchment / aged paper" — warm cream surfaces, dark text. Reads as an old book opened on a daylit desk; aligns with the FabledSword mythic register and preserves the bookish tone in light mode. Action and semantic colors are mid-tone earth/jewel hues that read on both light and dark backgrounds.
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## Files touched
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**Modify:**
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1. `web/src/lib/styles/tokens.json` — restructure `colors` into `dark`/`light`/`flat` sub-maps; add `on-action` to `flat`.
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2. `web/scripts/tokens-to-css.js` — emit dual `:root` + `[data-theme="light"]` blocks for colors; preserve other token sections in `:root`.
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3. `web/src/app.html` — add inline FOUC script in `<head>`.
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4. `web/src/routes/settings/+page.svelte` — add Appearance card with 3-way theme selector.
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5. Action button label class audit — find every site using `text-fs-parchment` on a `bg-fs-moss` / `bg-fs-bronze` / `bg-fs-oxblood` button and replace with `text-fs-on-action`. Expected count: 5–10 sites.
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**Create:**
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6. `web/src/lib/stores/theme.svelte.ts` — theme preference + resolved-theme rune store with matchMedia listener and localStorage persistence.
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**Generated (do not hand-edit):**
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7. `web/src/lib/styles/tokens.generated.css` — regenerated by `npm run tokens` (or whatever script invokes `tokens-to-css.js`).
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## Edge cases
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1. **Action button text contrast** — addressed by `--fs-on-action` non-flipping token. Audit during implementation.
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2. **Cover-art images** — external content, doesn't theme. Eyeball the missing-cover placeholder/glyph fallback in light mode.
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3. **Focus rings** — grep for `ring-offset-fs-*`; if any uses a flipping token, switch to a non-flipping equivalent or `ring-offset-background`.
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4. **Cross-tab sync** — out of scope. Theme change in tab A doesn't update tab B until reload. Documented limitation.
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5. **SSR** — server doesn't know preference; inline head script applies it client-side before paint.
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6. **Error pages** — SvelteKit `+error.svelte` and framework error fallback inherit `data-theme` attribute. No special handling.
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7. **localStorage unavailable** — try/catch around localStorage read; falls back to default `system`.
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## Testing
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Per project memory rule (no in-task tests; CI verifies), implementation tasks do not run tests. Plan does include the following test files for CI to execute:
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- **Token generator unit test** (`web/scripts/tokens-to-css.test.js`) — feed sample tokens.json with `dark`/`light`/`flat`, assert emitted CSS contains `:root` block with dark + flat values, and `[data-theme="light"]` block with light values only.
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- **Theme store test** (`web/src/lib/stores/theme.svelte.test.ts`) — mock `matchMedia` and `localStorage`. Verify (a) default is `system` resolving via matchMedia, (b) `setTheme('light')` persists + updates resolved, (c) matchMedia `change` event updates resolvedTheme when in `system` mode.
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- **Settings Appearance card test** (`web/src/routes/settings/Appearance.test.ts`) — render, click each segment, assert localStorage write + `data-theme` attribute on `<html>`.
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**Manual verification checklist** (pre-merge eyeball pass): home, library, search, playlists list, playlist detail, queue, history, settings, admin (users / library / quarantine / lidarr) — all in both modes.
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## Implementation order (informs plan)
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1. Restructure `tokens.json` (no behavior change yet — generator still emits one block).
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2. Update generator to emit dual blocks.
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3. Regenerate `tokens.generated.css`. Verify no visual regression in dark mode.
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4. Add `--fs-on-action` flat token. Audit + swap action button label classes.
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5. Create `theme.svelte.ts` store.
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6. Add FOUC script to `app.html`.
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7. Add Appearance card to Settings page, wire to store.
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8. Manual eyeball pass in both modes; fix any contrast/border surprises.
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