@@ -4,7 +4,7 @@ Design rationale and non-obvious conventions. See [CLAUDE.md](../CLAUDE.md) for
 
 ## Docs
 
-- [Presentation Themes](./themes.md): Minecraft activation and assets, CS:GO and GTA styling, icon-only theme picker, dark-chart/export integration, and presentation-only API exclusion.
+- [Presentation Themes](./themes.md): Minecraft activation and assets, CS:GO, GTA and Halo styling, Halo theme music, icon-only theme picker, dark-chart/export integration, and presentation-only API exclusion.
 - [Playable Minecraft](./minecraft-game.md): the opt-in game launched from the Minecraft theme, controls, saves, lifecycle and verification.
 
 - [Dashboard Read-only Views](./dashboard-readonly-views.md): API/filter inventory, source audit and verification scope
 
@@ -40,8 +40,8 @@ contrast branch.
 ## CS:GO implementation
 
 `src/lib/themes.ts` centralizes picker order
-(`light, dark, minecraft, csgo, gta, kart, doom`), dark-background classification, and the
-chart-palette alias used by CS:GO and GTA. CS:GO retains the
+(`light, dark, minecraft, csgo, gta, kart, doom, halo`), dark-background classification, and the
+chart-palette alias used by CS:GO, GTA, Mario Kart, DOOM and Halo. CS:GO retains the
 existing sans-serif font for chart legibility and preserves the dark theme's
 vendor, high-contrast, and overlay palettes. It does not recolor hardware
 series into team colors.
@@ -87,6 +87,35 @@ and the separately reported permission are recorded in
 `packages/app/public/decorative/gta/README.md`. These assets are not covered
 by the repository's code license.
 
+## Halo implementation
+
+Halo follows the GTA pattern: it is dark-classified everywhere (`isDarkTheme`),
+aliases onto the dark chart seed (`chartPaletteTheme`), and keeps the dark
+vendor, high-contrast, and overlay palettes. The picker shows it with a shield
+icon after DOOM. There is no playable game.
+
+The chrome follows the Halo Infinite menus: deep navy near-opaque panels over
+the Zeta Halo press-kit artwork, Forerunner-cyan accents and selected-tab
+underlines, Industry (Halo Infinite's UI face) for the header, tabs and
+headings, and DM Sans body copy. `HaloThemeBanner` pairs the Master Chief
+"Ring Vista" artwork with the official Halo logo and a live-text "InferenceX"
+wordmark. `HaloDecorations` follows the root class and the embed attribute and
+mounts local responsive WebP images (`aria-hidden`, `pointer-events: none`)
+only while Halo is active.
+
+`HaloMusic` loops the Halo: Combat Evolved title theme from a local MP3 while
+the theme is mounted. Music is on by default; if the browser blocks autoplay,
+playback starts on the next pointer or key press. The header `HaloToggles`
+button (behind the Halo-gated `HaloTogglesLazy` wrapper, also in the mobile
+menu) stores `halo-music` in `localStorage`. Leaving the theme unmounts the
+player and stops playback; embeds never mount it.
+
+Fonts load from the lazy theme CSS only. Provenance and the maintainer-reported
+Bungie/Microsoft permission are recorded in
+`packages/app/src/app/fonts/HALO-FONTS.md` and
+`packages/app/public/decorative/halo/README.md`. These assets are not covered
+by the repository's code license.
+
 ## Playable Minecraft
 
 The Minecraft banner launches an optional, full [playable Minecraft](./minecraft-game.md)
@@ -156,7 +185,7 @@ and Firefox CI matrix. It covers:
   loaded JS/CSS fingerprints for the optional engines and Minecraft game,
   font registration, and absence of optional theme/game DOM.
 - English/Chinese embeds with each optional theme saved, before and after
-  hydration. Saved music/sound opt-ins must not activate outside Minecraft.
+  hydration. Saved Minecraft and Halo music/sound opt-ins must not activate outside their themes.
 - Raw-HTML metadata and headings for normal and Googlebot requests, preload
   hints, and unchanged SEO metadata when selecting and leaving optional themes.
 
@@ -165,6 +194,17 @@ establish zero shared theme-selector overhead, guarantee search rankings, or
 replace production Core Web Vitals measurements. The shared pre-paint colors
 remain intentional to avoid a flash when an opted-in theme is restored.
 
+The isolation suites derive optional themes from `APP_THEMES`, so registering
+a new theme adds its embed and activation/teardown cases automatically.
+Halo is also included in the inactive-path asset and saved-preference guards.
+Keep artwork, font declarations, layout CSS and music behind the selection
+boundary. Do not add theme asset preload hints to shared layouts.
+The default-page checks seed saved music/sound opt-ins for every guarded theme;
+these preferences must not start media on light/dark pages or embeds.
+Crawler and theme-switch comparisons also cover robots, Open Graph and Twitter
+metadata. Run these tests on the implementation's final commit before merge;
+passing an earlier commit does not verify later changes.
+
 - Direct selection of every theme from the picker, keyboard navigation,
   persistence after reload, and cleanup on exit.
 - No CS:GO image requests on a cold light/dark landing; images load only
 
@@ -10,6 +10,7 @@ const ICONS: Record<string, string> = {
   gta: 'lucide-car',
   kart: 'lucide-flag',
   doom: 'lucide-skull',
+  halo: 'lucide-shield',
 };
 
 function pick(theme: string) {
@@ -52,7 +53,7 @@ describe('ModeToggle', () => {
   });
 
   it('selects any theme directly and closes the menu', () => {
-    for (const theme of ['kart', 'doom', 'gta', 'minecraft', 'dark', 'csgo', 'light']) {
+    for (const theme of ['kart', 'doom', 'halo', 'gta', 'minecraft', 'dark', 'csgo', 'light']) {
       pick(theme);
       cy.get('html').should('have.class', theme);
       cy.get('[data-testid="theme-menu"]').should('not.exist');
 
@@ -1,29 +1,47 @@
+import { APP_THEMES } from '../../src/lib/themes';
+
+const optionalThemes = APP_THEMES.filter((theme) => !['light', 'dark', 'system'].includes(theme));
 const featureCode =
-  /THREE\.WebGLRenderer|WebGLRenderer:|LOS SANTOS 3D|minecraft-click\.mp3|ender-dragon\.mp3|Loading Luigi Circuit|inferencex-minecraft-worlds|mc-panorama-cube|\.mc-hotbar-wrap|\.csgo-scene|\.gta-scene|\.mc-dragon-flyacross|\.kart-scene|\.doom-scene|font-family:\s*["']?(?:Monocraft|Pricedown|ChaletComprime)/i;
-const featureAsset =
-  /\/decorative\/(?:minecraft|csgo|gta|kart|doom)\/|minecraft-click\.mp3|Monocraft-|Pricedown|ChaletComprime|youtube(?:-nocookie)?\.com|ytimg\.com/i;
+  /THREE\.WebGLRenderer|WebGLRenderer:|LOS SANTOS 3D|minecraft-click\.mp3|ender-dragon\.mp3|Loading Luigi Circuit|inferencex-minecraft-worlds|mc-panorama-cube|\.mc-hotbar-wrap|\.csgo-scene|\.gta-scene|\.mc-dragon-flyacross|\.kart-scene|\.doom-scene|\.halo-scene|halo-theme\.css|font-family:\s*["']?(?:Monocraft|Pricedown|ChaletComprime|Industry|Halo)/i;
+const featureAsset = new RegExp(
+  `/decorative/(?:${optionalThemes.join('|')})/|minecraft-click\\.mp3|Monocraft-|Pricedown|ChaletComprime|Industry-|halo[^/]*\\.(?:woff2?|ttf|otf|mp3|ogg|wav)|youtube(?:-nocookie)?\\.com|ytimg\\.com`,
+  'i',
+);
 const featureElements =
   '[data-testid="minecraft-game"], [data-testid="minecraft-play-banner"], [data-testid="kart-game"], [data-testid$="-theme-banner"], .mc-dragon-flyacross';
 const isFeatureAsset = (url: string) => featureAsset.test(decodeURIComponent(url));
 
+function saveMediaOptIns(win: Window, enabled: boolean) {
+  for (const theme of optionalThemes) {
+    win.localStorage.setItem(`${theme}-music`, String(enabled));
+    win.localStorage.setItem(`${theme}-sound`, String(enabled));
+  }
+}
+
 function expectNoOptionalResources(requests: string[]) {
   cy.window().then((win) => {
     // Request interception catches in-flight requests too; resource timing only lists completed ones.
     expect(requests.filter(isFeatureAsset), 'optional requests started').to.deep.equal([]);
     const resources = win.performance.getEntriesByType('resource');
     expect(resources.filter((entry) => isFeatureAsset(entry.name))).to.have.length(0);
     expect(
-      [...win.document.fonts].filter((font) => /monocraft|pricedown|chalet/i.test(font.family)),
+      [...win.document.fonts].filter((font) =>
+        /monocraft|pricedown|chalet|industry|halo/i.test(font.family),
+      ),
     ).to.have.length(0);
     for (const resource of resources.filter((entry) => /\.(?:js|css)(?:\?|$)/.test(entry.name)))
       cy.request(resource.name).its('body').should('not.match', featureCode);
   });
   cy.get(featureElements).should('not.exist');
+  cy.get('audio, video, iframe[src*="youtube"]').should('not.exist');
 }
 const seo = (doc: Document) => [
   doc.title,
   doc.querySelector('meta[name="description"]')?.getAttribute('content'),
   doc.querySelector('link[rel="canonical"]')?.getAttribute('href'),
+  ...[
+    ...doc.querySelectorAll('meta[name="robots"], meta[property^="og:"], meta[name^="twitter:"]'),
+  ].map((node) => node.outerHTML),
   ...[...doc.querySelectorAll('link[hreflang], script[type="application/ld+json"]')].map(
     (node) => node.outerHTML,
   ),
@@ -50,8 +68,7 @@ describe('optional themes stay off the default page', () => {
           if (theme === 'default') win.localStorage.removeItem('theme');
           else win.localStorage.setItem('theme', theme);
           // Stored opt-ins must not start media outside the selected theme.
-          win.localStorage.setItem('minecraft-music', 'true');
-          win.localStorage.setItem('minecraft-sound', 'true');
+          saveMediaOptIns(win, true);
         },
       });
       if (theme === 'light' || theme === 'dark') cy.get('html').should('have.class', theme);
@@ -71,7 +88,7 @@ describe('optional themes stay off the default page', () => {
     });
   }
 
-  for (const theme of ['minecraft', 'csgo', 'gta', 'kart', 'doom']) {
+  for (const theme of optionalThemes) {
     for (const prefix of ['', '/zh']) {
       it(`${prefix || 'English'} embed ignores saved ${theme} before and after hydration`, () => {
         const requests: string[] = [];
@@ -81,8 +98,7 @@ describe('optional themes stay off the default page', () => {
         cy.visit(`${prefix}/embed/model/deepseek-v4?theme=light`, {
           onBeforeLoad(win) {
             win.localStorage.setItem('theme', theme);
-            win.localStorage.setItem('minecraft-music', 'true');
-            win.localStorage.setItem('minecraft-sound', 'true');
+            saveMediaOptIns(win, true);
           },
         });
         cy.get('html').should('have.class', 'light').and('have.attr', 'data-inferencex-embed');
@@ -115,11 +131,7 @@ describe('optional themes stay off the default page', () => {
             (link) => isFeatureAsset(link.getAttribute('href') ?? ''),
           ),
         ).to.have.length(0);
-        expect(
-          doc.querySelector(
-            '[data-testid="kart-game"], [data-testid="gta-theme-banner"], [data-testid="csgo-theme-banner"], [data-testid="doom-theme-banner"]',
-          ),
-        ).to.equal(null);
+        expect(doc.querySelector(featureElements)).to.equal(null);
         // Metadata and indexable headings are in raw HTML, without running JavaScript.
         cy.request(route).then((normal) => {
           const normalDoc = new DOMParser().parseFromString(normal.body, 'text/html');
@@ -134,8 +146,7 @@ describe('optional themes stay off the default page', () => {
     cy.visit('/about', {
       onBeforeLoad(win) {
         win.localStorage.setItem('theme', 'light');
-        win.localStorage.setItem('minecraft-music', 'false');
-        win.localStorage.setItem('minecraft-sound', 'false');
+        saveMediaOptIns(win, false);
       },
     });
     // The server-rendered trigger is visible before its click handler hydrates.
@@ -144,7 +155,7 @@ describe('optional themes stay off the default page', () => {
       .and('contain', 'currently');
     cy.document().then((doc) => {
       const baseline = seo(doc);
-      for (const theme of ['csgo', 'gta', 'minecraft', 'kart', 'doom']) {
+      for (const theme of optionalThemes) {
         cy.get('[data-testid="theme-toggle"]').click();
         cy.get(`[data-testid="theme-option-${theme}"]`).click();
         if (theme === 'minecraft') cy.get('canvas').should('exist');
 
@@ -0,0 +1,31 @@
+# Halo assets
+
+These are Microsoft / Bungie / 343 Industries (Halo Studios) assets, not assets
+covered by this repository's code license. On 2026-10-07 the requesting
+maintainer reported permission from Bungie and Microsoft to use Halo assets,
+fonts and theme music in InferenceX. That is a maintainer-reported permission,
+not an independently reviewed license or a claim of endorsement by Microsoft,
+Bungie or Halo Studios.
+
+All files were downloaded on 2026-10-07. Images are official Halo Infinite
+press-kit releases, fetched from Halopedia's press-kit mirror.
+
+## Artwork
+
+| File                                        | Source                                                                                                                  | Source SHA-256                                                     | Transformation                                                                    |
+| ------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------ | --------------------------------------------------------------------------------- |
+| `zeta-halo.webp`, `zeta-halo-mobile.webp`   | [HINF PK ZetaHalo.png](https://www.halopedia.org/File:HINF_PK_ZetaHalo.png) (1920 × 1080)                               | `e8613afe5a2ca6802924439133b575ffd4b9afda7e27f61779bf1eed335ce2ee` | Bottom 105 px (press watermarks) cropped; WebP q78; 720 × 641 centered phone crop |
+| `ring-vista.webp`, `ring-vista-mobile.webp` | [Halo Infinite E319 A Ring Vista.jpg](https://www.halopedia.org/File:Halo_Infinite_E319_A_Ring_Vista.jpg) (7680 × 4320) | `61cbc5b3cc97cfa4484930c7716aba52f64f24970106ca05ad332e6df2001fc0` | Left 6% and bottom 10% (watermark) cropped; resized to 1600 / 800 px wide WebP    |
+| `halo-logo.webp`                            | [Halo logo (2012-present).png](<https://www.halopedia.org/File:Halo_logo_(2012-present).png>) (3178 × 619)              | `9fa435d9f7fff3b2f0d7b702538940f04ecfd1e8284816ead0ae72d9fd2cb533` | Trimmed to its alpha bounds; resized to 720 px wide WebP with alpha               |
+
+## Music
+
+| File             | Source                                                                                                                                                                                   | Source SHA-256                                                     | Transformation                                                              |
+| ---------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------ | --------------------------------------------------------------------------- |
+| `halo-theme.mp3` | "Halo Original Title" from the KHInsider [Halo: Combat Evolved gamerip](https://downloads.khinsider.com/game-soundtracks/album/halo-combat-evolved-gamerip-soundtrack-xbox-gamerip-2001) | `99e0945068506013472b676e8ae2ea68c69fca816e7c0bd65d27e595597f0393` | Re-encoded with `ffmpeg` to 44.1 kHz stereo 128 kbps MP3, metadata stripped |
+
+Composed by Martin O'Donnell and Michael Salvatori for Bungie. The track loops
+while the Halo theme is selected; the header music toggle (`halo-music` in
+`localStorage`) mutes it. See `components/halo/halo-music.tsx`.
+
+Fonts are documented in `src/app/fonts/HALO-FONTS.md`.