Can you please make a sandbox ideally with unstorage only? 🙏🏼

Yes, sorry thought it was clear enough. Here is a repro: https://stackblitz.com/edit/stackblitz-starters-rrstqp?file=index.js

Would be great to add a starter to readme for quickly spinning one up.

useStorage('namespace').clear() also not working with namespace

I think I found the bug, the cause of the issue is the function prefixStorage.

export function prefixStorage<T extends StorageValue>(
  storage: Storage<T>,
  base: string
): Storage<T> {
  base = normalizeBaseKey(base);
  if (!base) {
    return storage;
  }
  const nsStorage: Storage = { ...storage };
  for (const property of storageKeyProperties) {
    // @ts-ignore
    nsStorage[property] = (key = "", ...args) =>
      // @ts-ignore
      storage[property](base + key, ...args);
  }
  nsStorage.getKeys = (key = "", ...arguments_) =>
    storage
      .getKeys(base + key, ...arguments_)
      // Remove Prefix
      .then((keys) => keys.map((key) => key.slice(base.length)));

  return nsStorage;
}

In this code it tries to iterate through the storageKeyProperties to splice the base for each key, but in fact the storageKeyProperties does not contain the getItems and setItems strings, and this splice step is not implemented in runBatch. This means that when traversing the asyncCall in getItems, the key in the argument does not actually contain a namespace.

Additionally, since the traversal code here can't handle more complex cases, the function getKeys is also handled separately, which may be another reason why the issue arose.
#336

All in all, I'm trying to deal with the current issue and will bring up a pr when I'm done.

(The above is from a translation tool, please understand that it may be misleading)

Same issue here.
prefix storage clear doesn't work
Also clear with base doesn't work for in-memory storage