sveltejs/kit · warning

Could not detect a supported production environment. See htt

Error message

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 choosing

What it means

adapter-auto's `adapt` step could not identify the hosting platform from environment variables and no suitable adapter is installed. The build succeeds, but no server output suited to production is produced, and this warning explains how to pick an adapter.

Source

Thrown at packages/adapter-auto/index.js:147

	return {
		...adapter,
		adapt: (builder) => {
			builder.log.info(`Detected environment: ${match.name}. Using ${match.module}`);
			return adapter.adapt(builder);
		}
	};
}

/** @type {typeof import('./index.js').default} */
export default () => ({
	name: '@sveltejs/adapter-auto',
	adapt: async (builder) => {
		const adapter = await get_adapter();

		if (adapter) return adapter.adapt(builder);

		builder.log.warn(
			'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 choosing'
		);
	},
	supports: {
		read: () => {
			supports_error(
				'The read function imported from $app/server only works in certain environments'
			);
		},
		instrumentation: () => {
			supports_error('`instrumentation.server.js` only works in certain environments');
		}
	}
});

/**
 * @param {string} message
 * @returns {never}

View on GitHub (pinned to 03f1687fe6)

Solutions

1. Install and configure the adapter for your target, e.g. `@sveltejs/adapter-node` for self-hosting
2. Keep adapter-auto only if you deploy exclusively to a detected platform
3. Check CI env vars — the platform's variables must be present for auto-detection

Example fix

// svelte.config.js before
import adapter from '@sveltejs/adapter-auto';
// after
import adapter from '@sveltejs/adapter-node';

// fail fast if relying on auto-detection without platform env vars
const detected = ['VERCEL', 'NETLIFY', 'CLOUDFLARE', 'FLY_APP_NAME'].some((v) => process.env[v]);
if (!detected) console.warn('adapter-auto will not detect a platform; configure an explicit adapter');

When it happens

Trigger: Running a production build on a machine/CI with none of the detected platform env vars (VERCEL, NETLIFY, CLOUDFULARE, etc.) and no explicit adapter in svelte.config.js; `get_adapter()` resolves to undefined.

Common situations: Building a Docker image or self-hosted server while still using adapter-auto; deploying to a platform adapter-auto doesn't recognize; local builds meant to test production output.

Related errors

• ${message}. Since you're using @sveltejs/adapter-auto, Svelt
• Cloudflare Pages' _routes.json should be configured from the
• If you plan to continue deploying to ${match.name}, conside
• Could not resolve peer dependency "${name}" relative to your
• Could not find valid "${subpackage}" export in ${name}/packa

AI-assisted analysis of sveltejs/kit@03f1687fe6 (2026-09-02). Data as JSON: /api/errors/9f0a4c9516f978e5. Report an issue: GitHub.