diff --git a/app/customize/components/ControlsPanel.massive-scaling.test.tsx b/app/customize/components/ControlsPanel.massive-scaling.test.tsx
new file mode 100644
index 000000000..1c8eeeb05
--- /dev/null
+++ b/app/customize/components/ControlsPanel.massive-scaling.test.tsx
@@ -0,0 +1,168 @@
+import { fireEvent, render, screen, act } from '@testing-library/react';
+import { describe, expect, it, vi } from 'vitest';
+import { ControlsPanel } from './ControlsPanel';
+import type { BadgeSize, Font, Scale } from '../types';
+
+vi.mock('@/context/TranslationContext', () => ({
+  useTranslation: () => ({ t: (key: string) => key }),
+}));
+
+const createProps = () => ({
+  username: 'octocat',
+  theme: 'dark',
+  bgHex: '',
+  bgType: 'solid' as 'solid' | 'linear' | 'radial',
+  bgStart: '',
+  bgEnd: '',
+  bgAngle: 90,
+  accentHex: '',
+  textHex: '',
+  scale: 'linear' as Scale,
+  speed: 'normal',
+  font: 'inter' as Font,
+  year: '',
+  radius: 12,
+  size: 'md' as BadgeSize,
+  onUsernameChange: vi.fn(),
+  onThemeChange: vi.fn(),
+  onBgHexChange: vi.fn(),
+  onBgTypeChange: vi.fn(),
+  onBgStartChange: vi.fn(),
+  onBgEndChange: vi.fn(),
+  onBgAngleChange: vi.fn(),
+  onAccentHexChange: vi.fn(),
+  onTextHexChange: vi.fn(),
+  onScaleChange: vi.fn(),
+  onSpeedChange: vi.fn(),
+  onFontChange: vi.fn(),
+  onYearChange: vi.fn(),
+  onSizeChange: vi.fn(),
+  onClearOverrides: vi.fn(),
+  onRadiusChange: vi.fn(),
+});
+
+describe('ControlsPanel - Massive Scaling', () => {
+  it('handles username input with massive character strings without breaking or crashing', () => {
+    const props = createProps();
+    const massiveUsername = 'a'.repeat(20000);
+    props.username = massiveUsername;
+
+    render(<ControlsPanel {...props} />);
+
+    const usernameInput = screen.getByPlaceholderText(
+      'customize.controls.username_placeholder'
+    ) as HTMLInputElement;
+    expect(usernameInput).toBeInTheDocument();
+    expect(usernameInput.value).toBe(massiveUsername);
+
+    const evenLargerUsername = 'b'.repeat(40000);
+    fireEvent.change(usernameInput, { target: { value: evenLargerUsername } });
+    expect(props.onUsernameChange).toHaveBeenCalledWith(evenLargerUsername);
+  });
+
+  it('handles extreme high bounds for border radius without crashing by clamping values to HTML range bounds', () => {
+    const props = createProps();
+    props.radius = 1000000; // Above default max (50)
+
+    const { rerender } = render(<ControlsPanel {...props} />);
+
+    const slider = screen.getByRole('slider') as HTMLInputElement;
+    expect(slider).toBeInTheDocument();
+    // JSDOM range input automatically clamps the value to max attribute (50)
+    expect(Number(slider.value)).toBe(50);
+
+    props.radius = -500000; // Below default min (0)
+    rerender(<ControlsPanel {...props} />);
+    // JSDOM range input clamps value to min attribute (0)
+    expect(Number(slider.value)).toBe(0);
+
+    // Verify callback triggers correctly on user slider interaction
+    fireEvent.change(slider, { target: { value: '25' } });
+    expect(props.onRadiusChange).toHaveBeenCalledWith(25);
+  });
+
+  it('handles extreme temporal scaling by mocking system date to a far future year', () => {
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date(3000, 0, 1));
+
+    const props = createProps();
+    const { container } = render(<ControlsPanel {...props} />);
+
+    const yearSelect = container.querySelector('#year-select') as HTMLSelectElement;
+    expect(yearSelect).toBeInTheDocument();
+
+    const options = yearSelect.querySelectorAll('option');
+    // currentYear = 3000. options are: yearOption = currentYear - i - 1 for i in 0 .. currentYear - 2019 - 1 (inclusive)
+    // Plus the option value="" for "currentYear (current)"
+    // So total options is: (3000 - 2019) + 1 = 982
+    expect(options.length).toBe(982);
+
+    vi.useRealTimers();
+  });
+
+  it('handles custom HEX input controls under extreme/boundary color values without crashing', () => {
+    const props = createProps();
+    props.bgType = 'linear';
+    props.bgStart = 'invalid-hex-start-long-string-🚀';
+    props.bgEnd = '1234567890abcdef!@#';
+    props.accentHex = 'emoji🌟';
+    props.textHex = '123';
+
+    const { container, rerender } = render(<ControlsPanel {...props} />);
+
+    const bgStartInput = container.querySelector('#bg-start-hex-input') as HTMLInputElement;
+    expect(bgStartInput).toBeInTheDocument();
+    expect(bgStartInput.value).toBe('invalid-hex-start-long-string-🚀');
+
+    const bgEndInput = container.querySelector('#bg-end-hex-input') as HTMLInputElement;
+    expect(bgEndInput).toBeInTheDocument();
+    expect(bgEndInput.value).toBe('1234567890abcdef!@#');
+
+    const accentInput = container.querySelector('#accent-hex-input') as HTMLInputElement;
+    const textInput = container.querySelector('#text-hex-input') as HTMLInputElement;
+    expect(accentInput.value).toBe('emoji🌟');
+    expect(textInput.value).toBe('123');
+
+    // Accent picker fallback test due to invalid hex value. The input ID is `${id}-picker` where id is 'accent-hex-input'
+    const accentPicker = container.querySelector('#accent-hex-input-picker') as HTMLInputElement;
+    expect(accentPicker).toBeInTheDocument();
+    expect(accentPicker.value).toBe('#000000');
+
+    // Fire changes with extreme inputs
+    fireEvent.change(accentInput, {
+      target: { value: 'invalid_hex_value_with_long_length_and_symbols_$' },
+    });
+    expect(props.onAccentHexChange).toHaveBeenCalledWith(
+      'invalid_hex_value_with_long_length_and_symbols_$'
+    );
+
+    props.bgType = 'radial';
+    rerender(<ControlsPanel {...props} />);
+    expect(container.querySelector('#bg-start-hex-input')).toBeInTheDocument();
+
+    props.bgType = 'solid';
+    rerender(<ControlsPanel {...props} />);
+    expect(container.querySelector('#bg-hex-input')).toBeInTheDocument();
+    expect(container.querySelector('#bg-start-hex-input')).toBeNull();
+  });
+
+  it('renders and processes rapid updates efficiently under load', () => {
+    const props = createProps();
+    const { rerender } = render(<ControlsPanel {...props} />);
+
+    const start = performance.now();
+
+    act(() => {
+      for (let i = 0; i < 30; i++) {
+        const scaleVal = i % 2 === 0 ? 'linear' : 'log';
+        const radiusVal = i % 50;
+        rerender(
+          <ControlsPanel {...props} scale={scaleVal} radius={radiusVal} username={`user-${i}`} />
+        );
+      }
+    });
+
+    const duration = performance.now() - start;
+    expect(duration).toBeLessThan(2000);
+  });
+});