diff --git a/lib/__tests__/builtin-themes.test.ts b/lib/__tests__/builtin-themes.test.ts
index 937e5c1e..04c616a8 100644
--- a/lib/__tests__/builtin-themes.test.ts
+++ b/lib/__tests__/builtin-themes.test.ts
@@ -2,8 +2,8 @@ import { describe, it, expect } from 'vitest';
 import { BUILTIN_THEMES } from '../builtin-themes';
 
 describe('BUILTIN_THEMES', () => {
-  it('contains exactly 5 themes', () => {
-    expect(BUILTIN_THEMES).toHaveLength(5);
+  it('contains exactly 6 themes', () => {
+    expect(BUILTIN_THEMES).toHaveLength(6);
   });
 
   it('all themes have required fields', () => {
@@ -44,6 +44,7 @@ describe('BUILTIN_THEMES', () => {
     expect(names).toContain('Catppuccin');
     expect(names).toContain('Solarized');
     expect(names).toContain('Roundcube Elastic');
+    expect(names).toContain('Aurora Glass');
   });
 
   it('theme IDs are unique', () => {
diff --git a/lib/builtin-themes.ts b/lib/builtin-themes.ts
index 16093461..0fc940fd 100644
--- a/lib/builtin-themes.ts
+++ b/lib/builtin-themes.ts
@@ -635,6 +635,245 @@ body[data-theme-skin="builtin-roundcube-elastic"] .bg-secondary.border-r .border
   border-left-width: 3px !important;
 }`;
 
+// "Aurora Glass" - an ultra-modern glassmorphism skin. Vibrant indigo→cyan
+// accents float over a fixed gradient-mesh canvas; every structural surface
+// (nav rail, folder sidebar, cards, popovers, menus, dialogs, toolbars) is a
+// translucent frosted pane with heavy backdrop-blur + saturation, hairline
+// luminous borders and soft glow on the primary action.
+//
+// The colour tokens stay near-solid for legible text contrast; the frosted
+// translucency + blur all live in the skin, where a single selector can pair
+// an rgba background with the matching backdrop-filter.
+const auroraCSS = `
+:root {
+  --color-border: rgba(13, 18, 45, 0.10);
+  --color-input: rgba(13, 18, 45, 0.12);
+  --color-ring: #6d5cff;
+  --color-background: #eef1fb;
+  --color-foreground: #14162e;
+  --color-primary: #6d5cff;
+  --color-primary-foreground: #ffffff;
+  --color-secondary: #e3e7f7;
+  --color-secondary-foreground: #14162e;
+  --color-muted: #e7eaf6;
+  --color-muted-foreground: #5b6080;
+  --color-accent: #e0e7ff;
+  --color-accent-foreground: #4338ca;
+  --color-destructive: #f43f5e;
+  --color-destructive-foreground: #ffffff;
+  --color-popover: #ffffff;
+  --color-popover-foreground: #14162e;
+  --color-sidebar: #eef1fb;
+  --color-sidebar-foreground: #14162e;
+  --color-sidebar-border: rgba(13, 18, 45, 0.08);
+  --color-sidebar-accent: rgba(109, 92, 255, 0.10);
+  --color-sidebar-accent-foreground: #4338ca;
+  --color-card: #ffffff;
+  --color-card-foreground: #14162e;
+  --color-success: #10b981;
+  --color-success-foreground: #ffffff;
+  --color-warning: #f59e0b;
+  --color-warning-foreground: #14162e;
+  --color-info: #06b6d4;
+  --color-info-foreground: #ffffff;
+  --color-selection: rgba(109, 92, 255, 0.14);
+  --color-selection-foreground: #4338ca;
+  --color-unread: #6d5cff;
+  --color-chart-1: #6d5cff;
+  --color-chart-2: #06b6d4;
+  --color-chart-3: #ec4899;
+  --color-chart-4: #f59e0b;
+  --color-chart-5: #10b981;
+}
+.dark {
+  --color-border: rgba(255, 255, 255, 0.08);
+  --color-input: rgba(255, 255, 255, 0.10);
+  --color-ring: #8b7bff;
+  --color-background: #06070f;
+  --color-foreground: #eef0ff;
+  --color-primary: #8b7bff;
+  --color-primary-foreground: #ffffff;
+  --color-secondary: rgba(255, 255, 255, 0.06);
+  --color-secondary-foreground: #eef0ff;
+  --color-muted: rgba(255, 255, 255, 0.05);
+  --color-muted-foreground: #9aa0c4;
+  --color-accent: rgba(139, 123, 255, 0.16);
+  --color-accent-foreground: #c4bbff;
+  --color-destructive: #fb7185;
+  --color-destructive-foreground: #1a0b10;
+  --color-popover: #12132a;
+  --color-popover-foreground: #eef0ff;
+  --color-sidebar: #08091a;
+  --color-sidebar-foreground: #eef0ff;
+  --color-sidebar-border: rgba(255, 255, 255, 0.07);
+  --color-sidebar-accent: rgba(139, 123, 255, 0.18);
+  --color-sidebar-accent-foreground: #c4bbff;
+  --color-card: rgba(255, 255, 255, 0.04);
+  --color-card-foreground: #eef0ff;
+  --color-success: #34d399;
+  --color-success-foreground: #052e1f;
+  --color-warning: #fbbf24;
+  --color-warning-foreground: #1a1405;
+  --color-info: #22d3ee;
+  --color-info-foreground: #04222a;
+  --color-selection: rgba(139, 123, 255, 0.22);
+  --color-selection-foreground: #c4bbff;
+  --color-unread: #8b7bff;
+  --color-chart-1: #8b7bff;
+  --color-chart-2: #22d3ee;
+  --color-chart-3: #f472b6;
+  --color-chart-4: #fbbf24;
+  --color-chart-5: #34d399;
+}`;
+
+// Glassmorphism skin: the frosted translucency, backdrop-blur, gradient-mesh
+// canvas, luminous borders and glow that the colour tokens alone can't carry.
+// Scoped under the skin body attribute so it detaches cleanly on switch-off.
+const auroraSkin = `
+body[data-theme-skin="builtin-aurora-glass"] {
+  font-family: "Inter", "SF Pro Display", "Segoe UI", system-ui, -apple-system, sans-serif;
+  letter-spacing: -0.01em;
+}
+
+/* ── Gradient-mesh canvas ──────────────────────────────────────── */
+/* A multi-stop radial mesh painted onto the app-shell root (the unique
+   .bg-background.overflow-hidden container) so the frosted panes have
+   something luminous to blur. Painting it directly on the shell - rather than
+   a fixed body::before with z-indexed children - avoids creating stacking
+   contexts on portaled popups/dialogs (Radix portals render as direct <body>
+   children), which would otherwise break their layering. */
+body[data-theme-skin="builtin-aurora-glass"] .bg-background.overflow-hidden {
+  background-color: var(--color-background);
+  background-image:
+    radial-gradient(60rem 60rem at 12% -10%, rgba(109, 92, 255, 0.22), transparent 60%),
+    radial-gradient(50rem 50rem at 105% 5%, rgba(6, 182, 212, 0.18), transparent 55%),
+    radial-gradient(55rem 55rem at 80% 110%, rgba(236, 72, 153, 0.16), transparent 60%),
+    radial-gradient(45rem 45rem at -5% 95%, rgba(16, 185, 129, 0.12), transparent 55%);
+}
+.dark body[data-theme-skin="builtin-aurora-glass"] .bg-background.overflow-hidden {
+  background-image:
+    radial-gradient(60rem 60rem at 12% -10%, rgba(109, 92, 255, 0.16), transparent 58%),
+    radial-gradient(50rem 50rem at 105% 5%, rgba(6, 182, 212, 0.11), transparent 52%),
+    radial-gradient(55rem 55rem at 80% 110%, rgba(236, 72, 153, 0.10), transparent 58%),
+    radial-gradient(45rem 45rem at -5% 95%, rgba(16, 185, 129, 0.07), transparent 52%);
+}
+
+/* ── Pill-soft radii everywhere ───────────────────────────────── */
+body[data-theme-skin="builtin-aurora-glass"] .rounded-md,
+body[data-theme-skin="builtin-aurora-glass"] .rounded-lg {
+  border-radius: 0.85rem !important;
+}
+body[data-theme-skin="builtin-aurora-glass"] .rounded-xl,
+body[data-theme-skin="builtin-aurora-glass"] .rounded-2xl {
+  border-radius: 1.25rem !important;
+}
+
+/* ── Frosted panes: the shared glass recipe ───────────────────── */
+/* Nav rail, folder sidebar, content backing, cards, popovers, dialogs and
+   menus all share one frosted treatment - translucent fill + heavy backdrop
+   blur + saturation so the mesh and neighbours bleed through softly. */
+body[data-theme-skin="builtin-aurora-glass"] .w-14.bg-secondary,
+body[data-theme-skin="builtin-aurora-glass"] .bg-secondary.border-r {
+  background-color: rgba(255, 255, 255, 0.55) !important;
+  backdrop-filter: blur(26px) saturate(180%);
+  -webkit-backdrop-filter: blur(26px) saturate(180%);
+  border-color: rgba(13, 18, 45, 0.08) !important;
+}
+.dark body[data-theme-skin="builtin-aurora-glass"] .w-14.bg-secondary,
+.dark body[data-theme-skin="builtin-aurora-glass"] .bg-secondary.border-r {
+  background-color: rgba(8, 9, 22, 0.82) !important;
+  border-color: rgba(255, 255, 255, 0.07) !important;
+}
+
+/* The "no conversation selected" empty pane sits inside an opaque
+   bg-background column, so it can't inherit the shell mesh - paint the same
+   gradient mesh directly onto it so the placeholder reads as glass too. */
+body[data-theme-skin="builtin-aurora-glass"] .bg-gradient-to-br.from-muted\\/30.to-muted\\/50 {
+  background-color: var(--color-background) !important;
+  background-image:
+    radial-gradient(50rem 50rem at 15% 0%, rgba(109, 92, 255, 0.22), transparent 60%),
+    radial-gradient(45rem 45rem at 100% 10%, rgba(6, 182, 212, 0.18), transparent 55%),
+    radial-gradient(50rem 50rem at 85% 105%, rgba(236, 72, 153, 0.16), transparent 60%) !important;
+}
+.dark body[data-theme-skin="builtin-aurora-glass"] .bg-gradient-to-br.from-muted\\/30.to-muted\\/50 {
+  background-image:
+    radial-gradient(50rem 50rem at 15% 0%, rgba(109, 92, 255, 0.18), transparent 58%),
+    radial-gradient(45rem 45rem at 100% 10%, rgba(6, 182, 212, 0.12), transparent 52%),
+    radial-gradient(50rem 50rem at 85% 105%, rgba(236, 72, 153, 0.11), transparent 58%) !important;
+}
+/* The reading-pane message backing goes clear glass so the frosted panes and
+   gradient bleed through softly. */
+body[data-theme-skin="builtin-aurora-glass"] .bg-muted\\/30 {
+  background: transparent !important;
+}
+
+/* Cards, popovers and dialogs: brighter frosted glass with a luminous edge. */
+body[data-theme-skin="builtin-aurora-glass"] .bg-card,
+body[data-theme-skin="builtin-aurora-glass"] .bg-popover,
+body[data-theme-skin="builtin-aurora-glass"] [role="menu"],
+body[data-theme-skin="builtin-aurora-glass"] [role="dialog"],
+body[data-theme-skin="builtin-aurora-glass"] [role="listbox"] {
+  background-color: rgba(255, 255, 255, 0.72) !important;
+  backdrop-filter: blur(28px) saturate(190%);
+  -webkit-backdrop-filter: blur(28px) saturate(190%);
+  border: 1px solid rgba(255, 255, 255, 0.6) !important;
+  box-shadow: 0 12px 40px -12px rgba(20, 22, 46, 0.28), inset 0 1px 0 rgba(255, 255, 255, 0.7) !important;
+}
+.dark body[data-theme-skin="builtin-aurora-glass"] .bg-card,
+.dark body[data-theme-skin="builtin-aurora-glass"] .bg-popover,
+.dark body[data-theme-skin="builtin-aurora-glass"] [role="menu"],
+.dark body[data-theme-skin="builtin-aurora-glass"] [role="dialog"],
+.dark body[data-theme-skin="builtin-aurora-glass"] [role="listbox"] {
+  background-color: rgba(16, 17, 38, 0.86) !important;
+  border: 1px solid rgba(255, 255, 255, 0.10) !important;
+  box-shadow: 0 16px 48px -12px rgba(0, 0, 0, 0.6), inset 0 1px 0 rgba(255, 255, 255, 0.08) !important;
+}
+
+/* ── Primary action: gradient fill + glow ─────────────────────── */
+body[data-theme-skin="builtin-aurora-glass"] .bg-primary.text-primary-foreground {
+  background-image: linear-gradient(135deg, #7c5cff 0%, #6d5cff 45%, #4f9bff 100%) !important;
+  border: none !important;
+  color: #ffffff !important;
+  box-shadow: 0 6px 20px -4px rgba(109, 92, 255, 0.55), inset 0 1px 0 rgba(255, 255, 255, 0.35) !important;
+  transition: box-shadow 160ms ease, filter 160ms ease;
+}
+body[data-theme-skin="builtin-aurora-glass"] .bg-primary.text-primary-foreground:hover {
+  filter: brightness(1.08);
+  box-shadow: 0 10px 30px -4px rgba(109, 92, 255, 0.7), inset 0 1px 0 rgba(255, 255, 255, 0.4) !important;
+}
+.dark body[data-theme-skin="builtin-aurora-glass"] .bg-primary.text-primary-foreground {
+  background-image: linear-gradient(135deg, #8b7bff 0%, #6d5cff 50%, #22d3ee 130%) !important;
+  box-shadow: 0 6px 24px -4px rgba(139, 123, 255, 0.6), inset 0 1px 0 rgba(255, 255, 255, 0.2) !important;
+}
+
+/* ── Selected folder / row: soft tinted glass + accent bar ────── */
+body[data-theme-skin="builtin-aurora-glass"] .bg-secondary.border-r .border-l-2.border-primary {
+  border-left-width: 3px !important;
+}
+
+/* ── On/off switch: gradient when active ──────────────────────── */
+body[data-theme-skin="builtin-aurora-glass"] [role="switch"][aria-checked="true"] {
+  background-image: linear-gradient(135deg, #7c5cff, #4f9bff) !important;
+  border-color: transparent !important;
+  box-shadow: 0 2px 10px -1px rgba(109, 92, 255, 0.6) !important;
+}
+.dark body[data-theme-skin="builtin-aurora-glass"] [role="switch"][aria-checked="true"] {
+  background-image: linear-gradient(135deg, #8b7bff, #22d3ee) !important;
+}
+
+/* ── Menu hover: tinted accent slab (keeps glass legible) ─────── */
+body[data-theme-skin="builtin-aurora-glass"] [role="menu"] [role="menuitem"]:hover,
+body[data-theme-skin="builtin-aurora-glass"] [role="menu"] [role="menuitem"]:focus,
+body[data-theme-skin="builtin-aurora-glass"] [role="menu"] [role="menuitem"]:focus-visible {
+  background-color: rgba(109, 92, 255, 0.14) !important;
+  color: var(--color-foreground) !important;
+}
+.dark body[data-theme-skin="builtin-aurora-glass"] [role="menu"] [role="menuitem"]:hover,
+.dark body[data-theme-skin="builtin-aurora-glass"] [role="menu"] [role="menuitem"]:focus,
+.dark body[data-theme-skin="builtin-aurora-glass"] [role="menu"] [role="menuitem"]:focus-visible {
+  background-color: rgba(139, 123, 255, 0.22) !important;
+}`;
+
 export const BUILTIN_THEMES: InstalledTheme[] = [
   {
     id: 'builtin-qui',
@@ -693,4 +932,17 @@ export const BUILTIN_THEMES: InstalledTheme[] = [
     enabled: true,
     builtIn: true,
   },
+  {
+    id: 'builtin-aurora-glass',
+    name: 'Aurora Glass',
+    version: '1.0.0',
+    author: 'Built-in',
+    description: 'Ultra-modern glassmorphism - frosted blurred panes floating over a vibrant indigo→cyan gradient mesh, with glowing gradient actions',
+    css: auroraCSS,
+    skin: auroraSkin,
+    variants: ['light', 'dark'],
+    typography: { fontSans: '"Inter", "SF Pro Display", "Segoe UI", system-ui, sans-serif' },
+    enabled: true,
+    builtIn: true,
+  },
 ];
diff --git a/stores/theme-store.ts b/stores/theme-store.ts
index a737dc89..1313ca60 100644
--- a/stores/theme-store.ts
+++ b/stores/theme-store.ts
@@ -451,11 +451,25 @@ export const useThemeStore = create<ThemeState>()(
       onRehydrateStorage: () => {
         return (state) => {
           if (state) {
-            // Ensure built-in themes are always present after rehydration
+            // Ensure built-in themes are always present after rehydration.
+            // Drop persisted themes that were flagged builtIn but no longer
+            // exist in BUILTIN_THEMES (e.g. a built-in removed from source) so
+            // stale built-ins don't survive as phantom "user" themes.
             const builtInIds = new Set(BUILTIN_THEMES.map(t => t.id));
-            const userThemes = state.installedThemes.filter(t => !builtInIds.has(t.id));
+            const userThemes = state.installedThemes.filter(
+              t => !builtInIds.has(t.id) && !t.builtIn
+            );
             state.installedThemes = [...BUILTIN_THEMES, ...userThemes];
 
+            // If the active theme pointed at a now-removed built-in, fall back
+            // to the default so the UI doesn't reference a missing theme.
+            if (
+              state.activeThemeId &&
+              !state.installedThemes.some(t => t.id === state.activeThemeId)
+            ) {
+              state.activeThemeId = null;
+            }
+
             // Re-apply theme immediately after rehydration
             const resolvedTheme = state.theme === 'system' ? getSystemTheme() : state.theme;
             applyTheme(resolvedTheme);