fix: reset child column scroll position when switching parent option

src/OptionList/Column.tsx

@@ -104,6 +104,23 @@ export default function Column<OptionType extends DefaultOptionType = DefaultOpt
     [options, checkedSet, fieldNames, halfCheckedSet, loadingKeys, prevValuePath],
   );
 
+  const prevOptionsRef = React.useRef(options);
+
+  // Reset scroll when the column content is swapped but no option is active,
+  // e.g. the child column after switching to another parent option. The `ul`
+  // element is reused in this case and would keep its previous scroll offset.
+  React.useEffect(() => {
+    if (prevOptionsRef.current === options) {
+      return;
+    }
+    prevOptionsRef.current = options;
+
+    const menuElement = menuRef.current;
+    if (menuElement && !menuElement.querySelector(`.${menuItemPrefixCls}-active`)) {
+      menuElement.scrollTo?.(0, 0);
+    }
+  }, [options, menuItemPrefixCls]);
+
   React.useEffect(() => {
     if (menuRef.current) {
       const selector = `.${menuItemPrefixCls}-active`;

tests/scroll.spec.tsx

@@ -0,0 +1,79 @@
+import React from 'react';
+import { render } from '@testing-library/react';
+import Cascader from '../src';
+import { clickOption, expectOpen } from './util';
+
+describe('Cascader.Scroll', () => {
+  const options = ['aa', 'bb'].map(prefix => ({
+    value: prefix,
+    label: prefix,
+    children: Array.from({ length: 30 }, (_, i) => ({
+      value: `${prefix}-${i}`,
+      label: `${prefix}-${i}`,
+    })),
+  }));
+
+  const renderCascader = () =>
+    render(
+      <Cascader options={options} open>
+        <input readOnly />
+      </Cascader>,
+    );
+
+  const mockScrollTo = (menu: HTMLElement) => {
+    const calls: Array<[number, number]> = [];
+    menu.scrollTo = ((left: number, top: number) => {
+      calls.push([left, top]);
+    }) as HTMLElement['scrollTo'];
+    return calls;
+  };
+
+  beforeEach(() => {
+    jest.useFakeTimers();
+  });
+
+  afterEach(() => {
+    jest.useRealTimers();
+  });
+
+  it('reset child column scroll when switching parent', () => {
+    const { container } = renderCascader();
+
+    expectOpen(container);
+
+    // Expand the first parent to show the child column
+    clickOption(container, 0, 0);
+    let menus = container.querySelectorAll('.rc-cascader-menu');
+    expect(menus).toHaveLength(2);
+
+    const calls = mockScrollTo(menus[1] as HTMLElement);
+
+    // Switch to the second parent: the child column shows a fresh list
+    clickOption(container, 0, 1);
+
+    menus = container.querySelectorAll('.rc-cascader-menu');
+    expect(menus).toHaveLength(2);
+    expect(calls).toContainEqual([0, 0]);
+  });
+
+  it('keep child column scroll when options are unchanged', () => {
+    const { container, rerender } = renderCascader();
+
+    expectOpen(container);
+
+    clickOption(container, 0, 0);
+    const menus = container.querySelectorAll('.rc-cascader-menu');
+    expect(menus).toHaveLength(2);
+
+    const calls = mockScrollTo(menus[1] as HTMLElement);
+
+    // Re-render with the same parent column content: scroll must not be touched
+    rerender(
+      <Cascader options={options} open>
+        <input readOnly />
+      </Cascader>,
+    );
+
+    expect(calls).toHaveLength(0);
+  });
+});