private fields broken in specific case

Link to the code that reproduces this issue

https://codesandbox.io/p/devbox/cool-yalow-zzkp58

To Reproduce

Click preview
Wait for it to hydrate
It throws an error: "attempted to get private field on non-instance"

Current vs. Expected behavior

Here is the same code running in react without Next.js:
https://codesandbox.io/p/sandbox/tslrlg
The getter does not throw and returns the value of the private field.

In the broken Next.js version, it renders fine on the server side, but when it rehydrates it throws.
The bug only happens if all of these are true:

• using Next.js
• a function is imported from another file
• that looks like this: () => new class ClassName {/* class body */}
• the returned instance is passed through useMemo or useRef

The following function formats do not trigger the error:

• () => { return new class ClassName {/* class body */} }
• () => new ClassName()
• () => instance
• exporting the class constructor

"use client";
import { useRef } from "react";
import { construct } from "./construct";

export default function Home() {
  const a = construct()
  const ref = useRef(a);
  const b = ref.current;

  return b.test;      // throws client-side
}

export const construct = () => new class {
  #test = 99
  get test() { return this.#test }
}

Provide environment information

It's running on CodeSandbox

Which area(s) are affected? (Select all that apply)

Runtime

Which stage(s) are affected? (Select all that apply)

next dev (local)

Start with the CodeSandbox reproducer, comparing the Next.js and React-only examples, then trace the Home component’s useRef path and imported construct function during client hydration. Done means the Next.js example hydrates without the private-field error and b.test returns 99; no repository file or test is named in the report.