Auto-skip default sign-in page when only one provider is configured

[gaescadev]

Goals

1. When only one OAuth provider is configured, automatically redirect users straight into that provider’s universal-login flow instead of rendering the default “pick a provider” page.
2. Eliminate boilerplate of custom pages.signIn overrides, client- or server-side redirects, and extra API routes just to skip an unused UI.
3. Improve DX for common single-provider use cases (e.g. Auth0, Google-only apps) by providing an opt-in flag or built-in behavior.

Non-Goals

1. Removing the ability to render a custom sign-in page when multiple providers are configured.
2. Changing the existing default behavior when zero or more than one provider is present.
3. Introducing any breaking changes to the OAuth handshake or callback flows.

Background

Out of the box, Auth.js (v5) always renders a “pick-a-provider” page at /api/auth/signin, even if you’ve only configured a single OAuth provider. In practice, nearly every single-provider integration ends up with one of these workarounds:
• Pointing pages.signIn at the provider-specific endpoint (e.g. /api/auth/signin/auth0), which in turn requires custom API-route glue to avoid infinite GET/POST loops.
• Writing a client- or server-side redirect component at /signin to call signIn("auth0") or redirect("/api/auth/signin/auth0").
• Adding Next.js redirects/rewrites in next.config.js.

All of these solve the problem, but they’re boilerplate. A simple opt-in flag or built-in “if providers.length === 1 then redirect” behavior would streamline single-provider setups and reduce confusion for new users.

Proposal

import NextAuth from "next-auth"
import Auth0 from "next-auth/providers/auth0"

export default NextAuth({
  providers: [
    Auth0({ /* … */ })
  ],
  // New flag:
  autoRedirectOnSingleProvider: true,
})