SvelteKit adapter-auto "Could not detect a supported production environment" in CI

SvelteKit's adapter-auto inspects environment variables to pick a host adapter (Vercel, Netlify, Cloudflare). On a plain CI runner those variables are absent, so it cannot choose an adapter and the build fails.

What this error means

svelte-kit build / vite build fails with "Could not detect a supported production environment. See https://svelte.dev/docs/kit/adapters to learn how to configure your app to run on the platform of your choice".

sveltekit

> Using @sveltejs/adapter-auto
Error: Could not detect a supported production environment. See
https://svelte.dev/docs/kit/adapters to learn how to configure your app to run on
the platform of your choice

Common causes

adapter-auto cannot identify a generic runner

GitHub Actions and most CI runners are not one of the hosts adapter-auto detects, so it has nothing to map to.

Building for a static or self-hosted target

When the deploy target is static files or a Node server, adapter-auto is the wrong default and must be replaced.

How to fix it

Install and configure an explicit adapter

Pick the adapter for your real target (static, node, or a host).
Install it and set it in svelte.config.js.
Commit both so CI uses the explicit adapter.

Terminal

npm i -D @sveltejs/adapter-node

Reference the adapter in config

Replace adapter-auto with the explicit adapter for your deploy.

svelte.config.js

import adapter from '@sveltejs/adapter-node';
export default {
  kit: { adapter: adapter() }
};

How to prevent it

Use an explicit adapter that matches your deploy target.
Reserve adapter-auto for the hosts it actually supports.
Commit the adapter dependency and config together.