sendou.ink/app/modules/auth/user.ts

import { useMatches } from "@remix-run/react";
import invariant from "tiny-invariant";
import type { RootLoaderData } from "~/root";

export function useUser() {
  const [root] = useMatches();
  invariant(root);

  return (root.data as RootLoaderData | undefined)?.user;
}