Zustand (^3.7.0) persist middleware with deferred hydration.

deferredPersist.ts

import { persist, PersistOptions } from 'zustand/middleware';
import { GetState, SetState, StoreApi } from 'zustand/vanilla';

type DeferredPersistOptions<S extends object> = PersistOptions<S, Partial<S>> & {
    hydrateOnResolve?: Promise<void>;
};

const DEFAULT_GET_STORAGE = () => localStorage;

export default function deferredPersist<
    S extends object,
    CustomSetState extends SetState<S> = SetState<S>,
    CustomGetState extends GetState<S> = GetState<S>,
    CustomStoreApi extends StoreApi<S> = StoreApi<S>,
>(
    config: (set: CustomSetState, get: CustomGetState, api: CustomStoreApi) => S,
    deferredOptions: DeferredPersistOptions<S>,
) {
    const hydrateOnResolve = deferredOptions.hydrateOnResolve || Promise.resolve();
    const getStorage = deferredOptions.getStorage || DEFAULT_GET_STORAGE;

    const options: PersistOptions<S> = {
        ...deferredOptions,
        getStorage: () => ({
            setItem: async (...args) => hydrateOnResolve.then(() => getStorage().setItem(...args)),
            getItem: async (...args) => hydrateOnResolve.then(() => getStorage().getItem(...args)),
            removeItem: async (...args) => hydrateOnResolve.then(() => getStorage().removeItem?.(...args)),
        }),
    };

    return persist<S, CustomSetState, CustomGetState, CustomStoreApi>(config, options);
}

Impementation for ^4.1.5