Adding document reference to user in Sanity client create and patch

Looking at your code, the issue is that when you use .set() with a reference field, you need to provide a proper reference object structure, not just the ID as a string. Here's how to fix it:

const addRefToUser = async (res) => {
  await getClient(false)
    .patch("user.cf26c3dd-7c63-4fcc-b936-6069b05213a7")
    .set({ 
      calculator: {
        _type: 'reference',
        _ref: res._id
      }
    })
    .commit()
    .then((res) => console.log(res));
};

The key change is structuring the reference as an object with _type: 'reference' and _ref: res._id instead of just passing res._id directly. This is the proper structure for strong references in Sanity.

However, if your schema defines calculator as an array of references (which is common), you'll want to use the append operation instead:

const addRefToUser = async (res) => {
  await getClient(false)
    .patch("user.cf26c3dd-7c63-4fcc-b936-6069b05213a7")
    .setIfMissing({ calculator: [] })
    .append('calculator', [{
      _type: 'reference',
      _ref: res._id,
      _key: res._id // good practice for array items
    }])
    .commit()
    .then((res) => console.log(res));
};

The patches documentation explains how different operations work. The setIfMissing ensures the array exists before appending, and append adds the new reference to the array.

Also, a small optimization - you can simplify your _addCalc_ function since .then() already returns the result:

const _addCalc_ = async () => {
  const res = await getClient(false).create({
    ...calcDetails,
    _type: "calculator",
  });
  return addRefToUser(res);
};

This approach is cleaner and handles the async flow more naturally than mixing await with .then().