getting TypeError: Failed to fetch

Environment

 System:
    OS: macOS 15.1.1
    CPU: (8) arm64 Apple M1
    Memory: 664.33 MB / 8.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.12.0 - ~/.nvm/versions/node/v22.12.0/bin/node
    npm: 10.9.0 - ~/.nvm/versions/node/v22.12.0/bin/npm
    pnpm: 9.15.0 - /opt/homebrew/bin/pnpm
    bun: 1.1.4 - ~/.bun/bin/bun
    Watchman: 2024.11.25.00 - /opt/homebrew/bin/watchman
  Browsers:
    Brave Browser: 134.1.76.82
    Chrome: 134.0.6998.166
    Safari: 18.1.1
  npmPackages:
    @auth/prisma-adapter: ^2.8.0 => 2.8.0 
    next: 15.2.3 => 15.2.3 
    next-auth: ^5.0.0-beta.25 => 5.0.0-beta.25 
    react: ^19.0.0 => 19.0.0 

Reproduction URL

https://github.com/ar-chit/twitter-clone

Describe the issue

While trying to log in using the Credentials provider, It throws TypeError: Failed to fetch in browser's console.

https://github.com/user-attachments/assets/2ecc4b6c-a46a-44b0-98c2-b46db4a162b6

Browser's console (development):

Browser's console (production):

Terminal:

Network Tab:

How to reproduce

1. clone this repo: https://github.com/ar-chit/twitter-clone.git
2. install dependencies: npm i
3. start the project: npm run dev
4. open the localhost link and try to login, you'll see the issue.

.env:
DATABASE_URL=postgres-url
AUTH_SECRET="izlp6unU+8O2DqrzSCJAeN1Ae/VAbvpADw7hDHTYD2U="

Alternatively, you can see the issue on https://twitter-clone-brown-delta.vercel.app

Expected behavior

The user shall log in successfully if the credentials entered are correct.

Start with the linked twitter-clone reproduction and follow the documented npm i and npm run dev steps, then inspect the Credentials-provider login flow alongside the browser console, terminal, and Network tab output. Done means valid credentials complete login successfully in the local reproduction and deployed reproduction.