diff --git a/packages/core/src/theme/themeRegistry.ts b/packages/core/src/theme/themeRegistry.ts
new file mode 100644
index 000000000..95ac04d15
--- /dev/null
+++ b/packages/core/src/theme/themeRegistry.ts
@@ -0,0 +1,66 @@
+export interface ColorPalette {
+  primary: string;
+  secondary: string;
+  background: string;
+  text: string;
+  border?: string;
+  accent?: string;
+}
+
+export interface ThemeDefinition {
+  name: string;
+  palette: ColorPalette;
+}
+
+/**
+ * ThemeRegistryManager - Extensible Color Palette & Dynamic Theme Registry Subsystem (#3334).
+ */
+export class ThemeRegistryManager {
+  private themes: Map<string, ThemeDefinition> = new Map();
+  private activeThemeName: string = 'default';
+
+  constructor() {
+    this.registerTheme({
+      name: 'default',
+      palette: {
+        primary: '#3b82f6',
+        secondary: '#64748b',
+        background: '#0f172a',
+        text: '#f8fafc',
+        border: '#334155',
+        accent: '#eab308',
+      },
+    });
+  }
+
+  registerTheme(theme: ThemeDefinition): void {
+    if (!theme || !theme.name) return;
+    this.themes.set(theme.name, theme);
+  }
+
+  setActiveTheme(name: string): boolean {
+    if (this.themes.has(name)) {
+      this.activeThemeName = name;
+      return true;
+    }
+    return false;
+  }
+
+  getActiveTheme(): ThemeDefinition {
+    return this.themes.get(this.activeThemeName) || Array.from(this.themes.values())[0];
+  }
+
+  extendPalette(themeName: string, customPalette: Partial<ColorPalette>): void {
+    const existing = this.themes.get(themeName);
+    if (existing) {
+      existing.palette = {
+        ...existing.palette,
+        ...customPalette,
+      };
+    }
+  }
+
+  listThemes(): string[] {
+    return Array.from(this.themes.keys());
+  }
+}
diff --git a/packages/core/test/themeRegistry.test.ts b/packages/core/test/themeRegistry.test.ts
new file mode 100644
index 000000000..daab9ff80
--- /dev/null
+++ b/packages/core/test/themeRegistry.test.ts
@@ -0,0 +1,38 @@
+import { describe, it, expect, beforeEach } from 'bun:test';
+import { ThemeRegistryManager } from '../src/theme/themeRegistry';
+
+describe('ThemeRegistryManager Unit Tests', () => {
+  let registry: ThemeRegistryManager;
+
+  beforeEach(() => {
+    registry = new ThemeRegistryManager();
+  });
+
+  it('should initialize with default theme', () => {
+    const active = registry.getActiveTheme();
+    expect(active.name).toBe('default');
+    expect(active.palette.primary).toBe('#3b82f6');
+  });
+
+  it('should register and switch to custom themes dynamically', () => {
+    registry.registerTheme({
+      name: 'dracula',
+      palette: {
+        primary: '#bd93f9',
+        secondary: '#6272a4',
+        background: '#282a36',
+        text: '#f8f8f2',
+      },
+    });
+
+    expect(registry.listThemes()).toContain('dracula');
+    const switched = registry.setActiveTheme('dracula');
+    expect(switched).toBe(true);
+    expect(registry.getActiveTheme().palette.primary).toBe('#bd93f9');
+  });
+
+  it('should allow extending existing palette colors', () => {
+    registry.extendPalette('default', { primary: '#ff0000' });
+    expect(registry.getActiveTheme().palette.primary).toBe('#ff0000');
+  });
+});