Stale Fallback

localhost:3000 hardcoded in production code

warningAI Qualitystale-fallback

Why this matters

AI tools hardcode localhost URLs during development. In production, these either fail (the port isn't open) or leak information about your development setup.

✗ Bad

const API_URL = "http://localhost:3000/api";

export async function fetchUser(id: string) {
  const res = await fetch(
    `http://localhost:3000/api/users/${id}`
  );
  return res.json();
}

✓ Good

const API_URL = process.env.NEXT_PUBLIC_API_URL
  ?? "http://localhost:3000/api";

export async function fetchUser(id: string) {
  const res = await fetch(`${API_URL}/users/${id}`);
  return res.json();
}

How to fix

Replace hardcoded localhost URLs with environment variables. Use NEXT_PUBLIC_API_URL or similar, with localhost as a development-only fallback.

All rules