import Box from '@mui/material/Box'; import Stack from '@mui/material/Stack'; import { createTheme, ThemeProvider } from '@mui/material/styles'; // Retain type safety. declare module '@mui/system' { interface Shape { sm: number; md: number; lg: number; } } const theme = createTheme({ unstable_sxConfig: { // You can now use the borderRadius key in sx // by providing direct values from the palette borderRadius: { themeKey: 'shape', }, }, shape: { sm: 4, md: 8, lg: 12, }, }); export default function ChangeTheBehaviorSxProp() { return ( ); }