Promises

const numberPromise = z.promise(z.number());

"Parsing" works a little differently with promise schemas. Validation happens in two parts:

Zod synchronously checks that the input is an instance of Promise (i.e. an object with .then and .catch methods.).
Zod uses .then to attach an additional validation step onto the existing Promise. You'll have to use .catch on the returned Promise to handle validation failures.

numberPromise.parse("tuna");
// ZodError: Non-Promise type: string
 
numberPromise.parse(Promise.resolve("tuna"));
// => Promise<number>
 
const test = async () => {
  await numberPromise.parse(Promise.resolve("tuna"));
  // ZodError: Non-number type: string
 
  await numberPromise.parse(Promise.resolve(3.14));
  // => 3.14
};