react-query/integrations/svelte-vite/src/App.svelte

<script>
  import { QueryClientProvider, QueryClient } from '@tanstack/svelte-query'
  import { SvelteQueryDevtools } from '@tanstack/svelte-query-devtools'
  import Simple from './Simple.svelte'

  const queryClient = new QueryClient()
</script>

<QueryClientProvider client={queryClient}>
  <Simple />
  <SvelteQueryDevtools />
</QueryClientProvider>