signIn function not redirecting to custom signIn page

[iltan987]

Environment

OS: Windows 10 Version 22H2 (OS Build 19045.5487)
Node.js: v23.6.0
npm: 11.1.0

next: 15.1.7
react: 19.0.0
next-auth: 5.0.0-beta.25

Reproduction URL

https://github.com/iltan987/custom_page_issue

Describe the issue

As I understood, signIn function with no parameters, should redirect to signIn page. If the signIn page is customized in auth.ts, signIn function should redirect to new one but it doesn't, yet it redirects to '/api/auth/signin' page.
If you refresh the wrongly redirected one, you get the correct URL but needs a refresh.
Also, redirected page has the content of correct one.
So, just the URL is wrong. Page is correct.
You can use https://custompageissue.vercel.app to check

src/auth.ts:

import NextAuth from "next-auth";
import Google from "next-auth/providers/google";

export const { handlers, auth, signIn, signOut } = NextAuth({
  providers: [Google],
  pages: {
    signIn: "/login",
  },
});

src/app/middleware.ts:

export { auth as middleware } from "@/auth";

src/app/api/auth/[...nextauth]/route.ts:

import { handlers } from "@/auth";
export const { GET, POST } = handlers;

src/app/login/page.tsx

const Login = () => {
  return (
    <div>
      <h1>Login</h1>
    </div>
  );
};
export default Login;

How to reproduce

Configure custom signIn page.
Call signIn function with no parameter from anywhere in your page.
It will be redirected to /api/auth/signin page instead of customized one.

Expected behavior

After configuring custom signIn page and calling signIn function, it should redirect to the one in customized signIn (e.g. /login) instead of /api/auth/signin