Reading `config.kit` inside adapters is deprecated — it…

Error message

Reading `config.kit` inside adapters is deprecated — it should access configuration on the `config` object directly. You may need to update your adapter

What it means

In older SvelteKit versions, adapters read `config.kit` to access kit configuration. Now the config object passed to adapters already contains the resolved kit fields merged at the top level, so `config.kit` is a shim that returns the whole config (not the kit section) and warns once per adapt() run that reading `config.kit` inside adapters is deprecated and the adapter should be updated.

Solutions

Update the adapter package to its latest version compatible with current SvelteKit.
If it's your own adapter, replace every `config.kit.x` access with `config.x` (fields are hoisted to the top level).
Check adapter issues/changelog for deprecation notes and migrate accordingly.

Example fix

// before (adapter code)
const outDir = config.kit.outDir;
// after
const outDir = config.outDir;

Defensive patterns

Strategy: validation

Validate before calling

// Adapter-side guard
if ('kit' in config) {
  console.warn('Adapter reads config.kit; update to read config.* directly');
}
const outDir = config.outDir ?? '.svelte-kit/output';

Prevention

Pin and regularly update community adapters
Grep custom adapters for `config.kit` during SvelteKit upgrades
Read the SvelteKit adapter API changelog when bumping major versions

When it happens

Trigger: Running adapt() with a third-party or outdated adapter whose code accesses `config.kit.*` instead of `config.*`, triggering the lazy getter installed by create_builder in the kit config wrapper.

Common situations: Using an old community adapter pinned to a pre-1.0 SvelteKit; a custom in-house adapter written against legacy `config.kit` paths; failing to upgrade an adapter after a SvelteKit version bump.

Related errors

AI-assisted analysis of sveltejs/kit@03f1687fe6 (2026-09-02). Data as JSON: /api/errors/676aa537a6fa51ff. Report an issue: GitHub.

Appendix: source

Thrown at packages/kit/src/core/adapt/index.js:40

	app_manifest,
	log,
	remotes,
	vite_config,
	explicit_env_config
) {
	const { name, adapt } = config.adapter;

	console.log(styleText(['bold', 'cyan'], `\n> Using ${name}`));

	let warned = false;

	const builder = create_builder({
		config: {
			...config,
			get kit() {
				if (!warned) {
					warned = true;
					log.warn(
						`Reading \`config.kit\` inside adapters is deprecated — it should access configuration on the \`config\` object directly. You may need to update your adapter`
					);
				}

				return config;
			}
		},
		build_data,
		server_metadata,
		route_data: build_data.manifest_data.routes.filter((route) => route.page || route.endpoint),
		prerendered,
		prerender_map,
		app_manifest,
		log,
		remotes,
		vite_config,
		explicit_env_config
	});

View on GitHub (pinned to 03f1687fe6)