I have the same problem in my next.js(app) project. When I put cursor in import { | } from 'react-hook-form' I see "function useForm<TFieldValues extends RHF.FieldValues = RHF.FieldValues, TContext = any, TTransformedValues extends RHF.FieldValues | undefined = undefined>(props?: RHF.UseFormProps<TFieldValues, TContext>): RHF.UseFormReturn<TFieldValues, TContext, TTransformedValues> import useForm Custom hook to manage the entire form." But the hook does not imported and console.log('useForm:', useForm); show: " Server useForm: undefined" and I got runtime error: "[ Server ] Error: (0 , react_hook_form__WEBPACK_IMPORTED_MODULE_2__.useForm) is not a function". That means that useForm does not imported.