diff --git a/ui/desktop/src/components/GooseSidebar/ThemeSelector.tsx b/ui/desktop/src/components/GooseSidebar/ThemeSelector.tsx
index ae6f5e342..b336a2fac 100644
--- a/ui/desktop/src/components/GooseSidebar/ThemeSelector.tsx
+++ b/ui/desktop/src/components/GooseSidebar/ThemeSelector.tsx
@@ -1,5 +1,5 @@
 import React from 'react';
-import { Moon, Sliders, Sun } from 'lucide-react';
+import { Moon, Sliders, Sparkles, Sun } from 'lucide-react';
 import { Button } from '../ui/button';
 import { useTheme } from '../../contexts/ThemeContext';
 import { defineMessages, useIntl } from '../../i18n';
@@ -17,6 +17,10 @@ const i18n = defineMessages({
     id: 'themeSelector.dark',
     defaultMessage: 'Dark',
   },
+  aura: {
+    id: 'themeSelector.aura',
+    defaultMessage: 'Aura',
+  },
   system: {
     id: 'themeSelector.system',
     defaultMessage: 'System',
@@ -41,7 +45,7 @@ const ThemeSelector: React.FC<ThemeSelectorProps> = ({
     <div className={`${!horizontal ? 'px-1 py-2 space-y-2' : ''} ${className}`}>
       {!hideTitle && <div className="text-xs text-text-primary px-3">{intl.formatMessage(i18n.theme)}</div>}
       <div
-        className={`${horizontal ? 'flex' : 'grid grid-cols-3'} gap-1 ${!horizontal ? 'px-3' : ''}`}
+        className={`${horizontal ? 'flex' : 'grid grid-cols-4'} gap-1 ${!horizontal ? 'px-3' : ''}`}
       >
         <Button
           data-testid="light-mode-button"
@@ -73,6 +77,21 @@ const ThemeSelector: React.FC<ThemeSelectorProps> = ({
           <span>{intl.formatMessage(i18n.dark)}</span>
         </Button>
 
+        <Button
+          data-testid="aura-mode-button"
+          onClick={() => setUserThemePreference('aura')}
+          className={`flex items-center justify-center gap-1 p-2 rounded-md border transition-colors text-xs ${
+            userThemePreference === 'aura'
+              ? 'bg-background-inverse text-text-inverse border-text-inverse hover:!bg-background-inverse hover:!text-text-inverse'
+              : 'border-border-primary hover:!bg-background-secondary text-text-secondary hover:text-text-primary'
+          }`}
+          variant="ghost"
+          size="sm"
+        >
+          <Sparkles className="h-3 w-3" />
+          <span>{intl.formatMessage(i18n.aura)}</span>
+        </Button>
+
         <Button
           data-testid="system-mode-button"
           onClick={() => setUserThemePreference('system')}
diff --git a/ui/desktop/src/contexts/ThemeContext.tsx b/ui/desktop/src/contexts/ThemeContext.tsx
index 16c97e7bd..3140b0dbb 100644
--- a/ui/desktop/src/contexts/ThemeContext.tsx
+++ b/ui/desktop/src/contexts/ThemeContext.tsx
@@ -1,13 +1,15 @@
-import React, { createContext, useContext, useEffect, useState, useCallback } from 'react';
-import { applyThemeTokens, buildMcpHostStyles } from '../theme/theme-tokens';
+import React, { createContext, useContext, useEffect, useState, useCallback, useMemo } from 'react';
+import { applyThemeTokens, buildMcpHostStyles, themes } from '../theme/theme-tokens';
+import type { ThemeId, ThemeVariant } from '../theme/theme-tokens';
 import type { McpUiHostStyles } from '@modelcontextprotocol/ext-apps/app-bridge';
 
-type ThemePreference = 'light' | 'dark' | 'system';
-type ResolvedTheme = 'light' | 'dark';
+type ThemePreference = 'light' | 'dark' | 'aura' | 'system';
+type ResolvedTheme = ThemeVariant;
 
 interface ThemeContextValue {
   userThemePreference: ThemePreference;
   setUserThemePreference: (pref: ThemePreference) => void;
+  resolvedThemeId: ThemeId;
   resolvedTheme: ResolvedTheme;
   mcpHostStyles: McpUiHostStyles;
 }
@@ -18,7 +20,9 @@ function getSystemTheme(): ResolvedTheme {
   return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
 }
 
-function resolveTheme(preference: ThemePreference): ResolvedTheme {
+// Resolve a user preference to a concrete theme id. 'system' picks the light or
+// dark built-in from the OS; named themes (light/dark/aura) map to themselves.
+function resolveThemeId(preference: ThemePreference): ThemeId {
   if (preference === 'system') {
     return getSystemTheme();
   }
@@ -32,9 +36,6 @@ function applyThemeToDocument(theme: ResolvedTheme): void {
   document.documentElement.style.colorScheme = theme;
 }
 
-// Built once — light-dark() values are theme-independent
-const mcpHostStyles = buildMcpHostStyles();
-
 interface ThemeProviderProps {
   children: React.ReactNode;
 }
@@ -42,7 +43,9 @@ interface ThemeProviderProps {
 export function ThemeProvider({ children }: ThemeProviderProps) {
   // Start with light theme to avoid flash, will update once settings load
   const [userThemePreference, setUserThemePreferenceState] = useState<ThemePreference>('light');
-  const [resolvedTheme, setResolvedTheme] = useState<ResolvedTheme>('light');
+  const [resolvedThemeId, setResolvedThemeId] = useState<ThemeId>('light');
+  const resolvedTheme = themes[resolvedThemeId].variant;
+  const mcpHostStyles = useMemo(() => buildMcpHostStyles(resolvedThemeId), [resolvedThemeId]);
 
   useEffect(() => {
     async function loadThemeFromSettings() {
@@ -52,15 +55,10 @@ export function ThemeProvider({ children }: ThemeProviderProps) {
           window.electron.getSetting('theme'),
         ]);
 
-        let preference: ThemePreference;
-        if (useSystemTheme) {
-          preference = 'system';
-        } else {
-          preference = savedTheme;
-        }
+        const preference: ThemePreference = useSystemTheme ? 'system' : savedTheme;
 
         setUserThemePreferenceState(preference);
-        setResolvedTheme(resolveTheme(preference));
+        setResolvedThemeId(resolveThemeId(preference));
       } catch (error) {
         console.warn('[ThemeContext] Failed to load theme settings:', error);
       }
@@ -72,8 +70,8 @@ export function ThemeProvider({ children }: ThemeProviderProps) {
   const setUserThemePreference = useCallback(async (preference: ThemePreference) => {
     setUserThemePreferenceState(preference);
 
-    const resolved = resolveTheme(preference);
-    setResolvedTheme(resolved);
+    const resolvedId = resolveThemeId(preference);
+    setResolvedThemeId(resolvedId);
 
     // Save to settings
     try {
@@ -89,9 +87,9 @@ export function ThemeProvider({ children }: ThemeProviderProps) {
 
     // Broadcast to other windows via Electron
     window.electron?.broadcastThemeChange({
-      mode: resolved,
+      mode: themes[resolvedId].variant,
       useSystemTheme: preference === 'system',
-      theme: resolved,
+      theme: resolvedId,
     });
   }, []);
 
@@ -102,7 +100,7 @@ export function ThemeProvider({ children }: ThemeProviderProps) {
     const mediaQuery = window.matchMedia('(prefers-color-scheme: dark)');
 
     const handleChange = () => {
-      setResolvedTheme(getSystemTheme());
+      setResolvedThemeId(getSystemTheme());
     };
 
     mediaQuery.addEventListener('change', handleChange);
@@ -114,15 +112,13 @@ export function ThemeProvider({ children }: ThemeProviderProps) {
     if (!window.electron) return;
 
     const handleThemeChanged = (_event: unknown, ...args: unknown[]) => {
-      const themeData = args[0] as { useSystemTheme: boolean; theme: string };
+      const themeData = args[0] as { useSystemTheme: boolean; theme: ThemeId };
       const newPreference: ThemePreference = themeData.useSystemTheme
         ? 'system'
-        : themeData.theme === 'dark'
-          ? 'dark'
-          : 'light';
+        : themeData.theme;
 
       setUserThemePreferenceState(newPreference);
-      setResolvedTheme(resolveTheme(newPreference));
+      setResolvedThemeId(resolveThemeId(newPreference));
 
       // Save to settings (don't await, fire and forget)
       if (newPreference === 'system') {
@@ -139,15 +135,17 @@ export function ThemeProvider({ children }: ThemeProviderProps) {
     };
   }, []);
 
-  // Apply theme class and CSS tokens whenever resolvedTheme changes
+  // Apply theme class and CSS tokens whenever the resolved theme changes
   useEffect(() => {
-    applyThemeToDocument(resolvedTheme);
-    applyThemeTokens(resolvedTheme);
-  }, [resolvedTheme]);
+    applyThemeToDocument(themes[resolvedThemeId].variant);
+    applyThemeTokens(resolvedThemeId);
+    document.documentElement.dataset.theme = resolvedThemeId;
+  }, [resolvedThemeId]);
 
   const value: ThemeContextValue = {
     userThemePreference,
     setUserThemePreference,
+    resolvedThemeId,
     resolvedTheme,
     mcpHostStyles,
   };
diff --git a/ui/desktop/src/i18n/messages/de.json b/ui/desktop/src/i18n/messages/de.json
index b4ed93b84..8bb591d93 100644
--- a/ui/desktop/src/i18n/messages/de.json
+++ b/ui/desktop/src/i18n/messages/de.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "Telemetrie-Einstellungen konnten nicht aktualisiert werden."
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "Dunkel"
   },
diff --git a/ui/desktop/src/i18n/messages/en.json b/ui/desktop/src/i18n/messages/en.json
index 0c2ddf79a..d2812a895 100644
--- a/ui/desktop/src/i18n/messages/en.json
+++ b/ui/desktop/src/i18n/messages/en.json
@@ -4469,6 +4469,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "Failed to update telemetry settings."
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "Dark"
   },
diff --git a/ui/desktop/src/i18n/messages/es.json b/ui/desktop/src/i18n/messages/es.json
index 7b274e551..ebf27411a 100644
--- a/ui/desktop/src/i18n/messages/es.json
+++ b/ui/desktop/src/i18n/messages/es.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "No se pudieron actualizar los ajustes de telemetría."
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "Oscuro"
   },
diff --git a/ui/desktop/src/i18n/messages/fr.json b/ui/desktop/src/i18n/messages/fr.json
index e65755c88..887690a6f 100644
--- a/ui/desktop/src/i18n/messages/fr.json
+++ b/ui/desktop/src/i18n/messages/fr.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "Échec de la mise à jour des paramètres de télémétrie."
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "Sombre"
   },
diff --git a/ui/desktop/src/i18n/messages/hi.json b/ui/desktop/src/i18n/messages/hi.json
index 674606433..45fc60cb7 100644
--- a/ui/desktop/src/i18n/messages/hi.json
+++ b/ui/desktop/src/i18n/messages/hi.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "टेलीमेट्री सेटिंग अपडेट करने में विफल."
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "अंधेरा"
   },
diff --git a/ui/desktop/src/i18n/messages/id.json b/ui/desktop/src/i18n/messages/id.json
index c0dba490b..30841c2c2 100644
--- a/ui/desktop/src/i18n/messages/id.json
+++ b/ui/desktop/src/i18n/messages/id.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "Gagal memperbarui pengaturan telemetri."
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "Gelap"
   },
diff --git a/ui/desktop/src/i18n/messages/it.json b/ui/desktop/src/i18n/messages/it.json
index b0d25fef3..01f052f28 100644
--- a/ui/desktop/src/i18n/messages/it.json
+++ b/ui/desktop/src/i18n/messages/it.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "Impossibile aggiornare le impostazioni di telemetria."
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "Scuro"
   },
diff --git a/ui/desktop/src/i18n/messages/ja.json b/ui/desktop/src/i18n/messages/ja.json
index a0973b0bb..be6ffeaa1 100644
--- a/ui/desktop/src/i18n/messages/ja.json
+++ b/ui/desktop/src/i18n/messages/ja.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "テレメトリ設定を更新できませんでした。"
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "ダーク"
   },
diff --git a/ui/desktop/src/i18n/messages/ko.json b/ui/desktop/src/i18n/messages/ko.json
index 53a07e342..bee5f69d9 100644
--- a/ui/desktop/src/i18n/messages/ko.json
+++ b/ui/desktop/src/i18n/messages/ko.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "원격 분석 설정을 업데이트하지 못했습니다."
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "다크"
   },
diff --git a/ui/desktop/src/i18n/messages/ms.json b/ui/desktop/src/i18n/messages/ms.json
index e2ed52864..8581c644e 100644
--- a/ui/desktop/src/i18n/messages/ms.json
+++ b/ui/desktop/src/i18n/messages/ms.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "Gagal mengemas kini tetapan telemetri."
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "Gelap"
   },
diff --git a/ui/desktop/src/i18n/messages/pt.json b/ui/desktop/src/i18n/messages/pt.json
index f772f54a2..0e885c3b1 100644
--- a/ui/desktop/src/i18n/messages/pt.json
+++ b/ui/desktop/src/i18n/messages/pt.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "Falha ao atualizar as definições de telemetria."
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "Escuro"
   },
diff --git a/ui/desktop/src/i18n/messages/ru.json b/ui/desktop/src/i18n/messages/ru.json
index 48080862b..9fd0d7a43 100644
--- a/ui/desktop/src/i18n/messages/ru.json
+++ b/ui/desktop/src/i18n/messages/ru.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "Не удалось обновить настройки телеметрии."
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "Темная"
   },
diff --git a/ui/desktop/src/i18n/messages/tr.json b/ui/desktop/src/i18n/messages/tr.json
index 0aaa9f832..9887e3e2b 100644
--- a/ui/desktop/src/i18n/messages/tr.json
+++ b/ui/desktop/src/i18n/messages/tr.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "Telemetri ayarları güncellenemedi."
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "Karanlık"
   },
diff --git a/ui/desktop/src/i18n/messages/vi.json b/ui/desktop/src/i18n/messages/vi.json
index bc7fb1445..3ab62edab 100644
--- a/ui/desktop/src/i18n/messages/vi.json
+++ b/ui/desktop/src/i18n/messages/vi.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "Không thể cập nhật cài đặt đo từ xa."
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "Tối"
   },
diff --git a/ui/desktop/src/i18n/messages/zh-CN.json b/ui/desktop/src/i18n/messages/zh-CN.json
index 28cceb80c..9ae95cb87 100644
--- a/ui/desktop/src/i18n/messages/zh-CN.json
+++ b/ui/desktop/src/i18n/messages/zh-CN.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "更新遥测设置失败。"
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "深色"
   },
diff --git a/ui/desktop/src/i18n/messages/zh-TW.json b/ui/desktop/src/i18n/messages/zh-TW.json
index 62b8a9c6f..6a4583fa1 100644
--- a/ui/desktop/src/i18n/messages/zh-TW.json
+++ b/ui/desktop/src/i18n/messages/zh-TW.json
@@ -4439,6 +4439,9 @@
   "telemetrySettings.updateError": {
     "defaultMessage": "無法更新遙測設定。"
   },
+  "themeSelector.aura": {
+    "defaultMessage": "Aura"
+  },
   "themeSelector.dark": {
     "defaultMessage": "深色"
   },
diff --git a/ui/desktop/src/styles/main.css b/ui/desktop/src/styles/main.css
index b1406695b..0e478cb59 100644
--- a/ui/desktop/src/styles/main.css
+++ b/ui/desktop/src/styles/main.css
@@ -979,3 +979,13 @@ pre:has(> code.bg-inline-code) {
 .mcp-app-container.mcp-enter-inline {
   animation: mcp-enter-inline 180ms cubic-bezier(0.2, 0, 0, 1) both;
 }
+
+/* ═══════════════════════════════════════════════════════════
+   AURA THEME — component overrides
+   User message bubbles use the inverted bg-text-primary surface,
+   which turns light in Aura. Restore Aura's dark chat bubble.
+   ═══════════════════════════════════════════════════════════ */
+[data-theme='aura'] .user-message-bubble {
+  background-color: #393647;
+  color: #edecee;
+}
diff --git a/ui/desktop/src/theme/theme-tokens.ts b/ui/desktop/src/theme/theme-tokens.ts
index fa1d2d5d6..f0fc0bf65 100644
--- a/ui/desktop/src/theme/theme-tokens.ts
+++ b/ui/desktop/src/theme/theme-tokens.ts
@@ -200,11 +200,96 @@ const darkColorTokens: ColorTokens = {
   '--shadow-lg': '0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -4px rgba(0, 0, 0, 0.2)',
 };
 
+// ---------------------------------------------------------------------------
+// Aura theme — colors & shadows (dark variant)
+// Ported from OpenChamber's Aura preset: purple-black surfaces, purple accent,
+// mint/peach/cyan/coral status colors, monospace typography.
+// ---------------------------------------------------------------------------
+const auraColorTokens: ColorTokens = {
+  // Backgrounds
+  '--color-background-primary': '#15141b',
+  '--color-background-secondary': '#1a1921',
+  '--color-background-tertiary': '#201e2b',
+  '--color-background-inverse': '#a277ff',
+  '--color-background-ghost': 'transparent',
+  '--color-background-info': '#82e2ff',
+  '--color-background-danger': '#ff6767',
+  '--color-background-success': '#61ffca',
+  '--color-background-warning': '#ffca85',
+  '--color-background-disabled': '#25232f',
+
+  // Text
+  '--color-text-primary': '#edecee',
+  '--color-text-secondary': '#8a8282',
+  '--color-text-tertiary': '#6d6d6d',
+  '--color-text-inverse': '#15141b',
+  '--color-text-ghost': '#8a8282',
+  '--color-text-info': '#82e2ff',
+  '--color-text-danger': '#ff6767',
+  '--color-text-success': '#61ffca',
+  '--color-text-warning': '#ffca85',
+  '--color-text-disabled': '#525b68',
+
+  // Borders
+  '--color-border-primary': '#2d2b38',
+  '--color-border-secondary': '#47415a',
+  '--color-border-tertiary': '#4e496c',
+  '--color-border-inverse': '#edecee',
+  '--color-border-ghost': 'transparent',
+  '--color-border-info': '#82e2ff',
+  '--color-border-danger': '#ff6767',
+  '--color-border-success': '#61ffca',
+  '--color-border-warning': '#ffca85',
+  '--color-border-disabled': '#2d2b38',
+
+  // Rings
+  '--color-ring-primary': '#47415a',
+  '--color-ring-secondary': '#2d2b38',
+  '--color-ring-inverse': '#15141b',
+  '--color-ring-info': '#82e2ff',
+  '--color-ring-danger': '#ff6767',
+  '--color-ring-success': '#61ffca',
+  '--color-ring-warning': '#ffca85',
+
+  // Shadows (dark)
+  '--shadow-hairline': '0 0 0 1px rgba(0, 0, 0, 0.2)',
+  '--shadow-sm': '0 1px 2px 0 rgba(0, 0, 0, 0.2)',
+  '--shadow-md': '0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -2px rgba(0, 0, 0, 0.2)',
+  '--shadow-lg': '0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -4px rgba(0, 0, 0, 0.2)',
+};
+
+// Aura is monospace-first — override the shared sans family.
+const auraFontTokens: Partial<Pick<ThemeTokens, BaseTokenKey>> = {
+  '--font-sans': 'ui-monospace, "SFMono-Regular", "Menlo", "Cascadia Mono", "Segoe UI Mono", monospace',
+  '--font-mono': 'ui-monospace, "SFMono-Regular", "Menlo", "Cascadia Mono", "Segoe UI Mono", monospace',
+};
+
 // ---------------------------------------------------------------------------
 // Merged token maps — used by applyThemeTokens() and buildMcpHostStyles()
 // ---------------------------------------------------------------------------
 export const lightTokens: ThemeTokens = { ...baseTokens, ...lightColorTokens };
 export const darkTokens: ThemeTokens = { ...baseTokens, ...darkColorTokens };
+export const auraTokens: ThemeTokens = { ...baseTokens, ...auraFontTokens, ...auraColorTokens };
+
+// ---------------------------------------------------------------------------
+// Theme registry — the set of selectable named themes.
+// `variant` drives the .dark/.light class and colorScheme for anything outside
+// the token system; `tokens` is the map applied to :root. Adding a future theme
+// is a single entry here plus its token map above.
+// ---------------------------------------------------------------------------
+export type ThemeId = 'light' | 'dark' | 'aura';
+export type ThemeVariant = 'light' | 'dark';
+
+interface ThemeDefinition {
+  variant: ThemeVariant;
+  tokens: ThemeTokens;
+}
+
+export const themes: Record<ThemeId, ThemeDefinition> = {
+  light: { variant: 'light', tokens: lightTokens },
+  dark: { variant: 'dark', tokens: darkTokens },
+  aura: { variant: 'dark', tokens: auraTokens },
+};
 
 // ---------------------------------------------------------------------------
 // Helpers
@@ -244,43 +329,51 @@ const HOST_FONT_CSS = `
 
 /**
  * Build the McpUiHostStyles object for MCP apps.
- * Color keys use light-dark() so a single payload works for both themes.
- * Non-color keys (fonts, radii, shadows) use plain values from baseTokens
- * (or light as the default when values differ, e.g. shadows).
+ *
+ * For the built-in light/dark pair, color keys use light-dark() so a single
+ * payload resolves correctly against the guest's color-scheme. Custom themes
+ * (e.g. aura) share a variant with dark but carry their own palette and fonts,
+ * so light-dark() can't express them — emit that theme's concrete token values
+ * instead. Non-color keys always use the theme's own values so overrides like
+ * Aura's monospace font family reach the guest.
  * css.fonts provides @font-face rules so sandboxed apps can load host fonts.
  */
-export function buildMcpHostStyles(): McpUiHostStyles {
+export function buildMcpHostStyles(themeId: ThemeId = 'light'): McpUiHostStyles {
+  const tokens = (themes[themeId] ?? themes.light).tokens;
+  const isBuiltinVariant = themeId === 'light' || themeId === 'dark';
   const variables: McpUiStyles = {} as McpUiStyles;
   for (const key of Object.keys(lightTokens) as McpUiStyleVariableKey[]) {
-    const light = lightTokens[key];
-    const dark = darkTokens[key];
-    if (key.startsWith('--color-')) {
-      variables[key] = `light-dark(${light}, ${dark})`;
+    if (key.startsWith('--color-') && isBuiltinVariant) {
+      variables[key] = `light-dark(${lightTokens[key]}, ${darkTokens[key]})`;
     } else {
-      variables[key] = light;
+      variables[key] = tokens[key];
     }
   }
   return { variables, css: { fonts: HOST_FONT_CSS } };
 }
 
 /**
- * Resolve the current theme from localStorage / system preference.
+ * Resolve the current theme id from localStorage / system preference.
+ * Best-effort pre-paint resolution; the authoritative preference lives in the
+ * Electron settings store and is applied by ThemeContext once loaded.
  */
-export function getResolvedTheme(): 'light' | 'dark' {
+export function getResolvedTheme(): ThemeId {
   const useSystem = localStorage.getItem('use_system_theme') !== 'false';
   if (useSystem) {
     return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
   }
-  return localStorage.getItem('theme') === 'dark' ? 'dark' : 'light';
+  const stored = localStorage.getItem('theme');
+  if (stored === 'aura') return 'aura';
+  return stored === 'dark' ? 'dark' : 'light';
 }
 
 /**
- * Apply theme tokens to the document root as CSS custom properties.
+ * Apply a theme's tokens to the document root as CSS custom properties.
  * When called without an argument, resolves the theme from localStorage.
  */
-export function applyThemeTokens(theme?: 'light' | 'dark'): void {
+export function applyThemeTokens(theme?: ThemeId): void {
   const resolved = theme ?? getResolvedTheme();
-  const tokens = resolved === 'dark' ? darkTokens : lightTokens;
+  const { tokens } = themes[resolved] ?? themes.light;
   const root = document.documentElement;
   for (const [key, value] of Object.entries(tokens)) {
     root.style.setProperty(key, value);
diff --git a/ui/desktop/src/utils/settings.ts b/ui/desktop/src/utils/settings.ts
index ec69d46b0..f693cd97c 100644
--- a/ui/desktop/src/utils/settings.ts
+++ b/ui/desktop/src/utils/settings.ts
@@ -48,7 +48,7 @@ export interface Settings {
   keyboardShortcuts: KeyboardShortcuts;
 
   // UI preferences (migrated from localStorage)
-  theme: 'dark' | 'light';
+  theme: 'dark' | 'light' | 'aura';
   useSystemTheme: boolean;
   language: LanguageSetting;
   responseStyle: string;