sveltejs/kit · error · Error

The `router.resolution` option cannot be 'server' if `output

Error message

The `router.resolution` option cannot be 'server' if `output.bundleStrategy` is 'inline' or 'single'

What it means

Server-side route resolution requires the client bundle to load per-route modules on demand, so it only works with `output.bundleStrategy: 'split'`. validate_config throws when `router.resolution` is 'server' but the bundle strategy is 'inline' or 'single', since those strategies produce a bundle that cannot perform server-driven resolution.

Source

Thrown at packages/kit/src/core/config/index.js:197

		const files = validated.files;

		files.hooks.client ??= path.join(files.src, 'hooks.client');
		files.hooks.server ??= path.join(files.src, 'hooks.server');
		files.hooks.universal ??= path.join(files.src, 'hooks');
		files.params ??= path.join(files.src, 'params');
		files.routes ??= path.join(files.src, 'routes');
		files.serviceWorker ??= path.join(files.src, 'service-worker');
		files.appTemplate ??= path.join(files.src, 'app.html');
		files.errorTemplate ??= path.join(files.src, 'error.html');

		if (validated.router.resolution === 'server') {
			if (validated.router.type === 'hash') {
				throw new Error(
					"The `router.resolution` option cannot be 'server' if `router.type` is 'hash'"
				);
			}
			if (validated.output.bundleStrategy !== 'split') {
				throw new Error(
					"The `router.resolution` option cannot be 'server' if `output.bundleStrategy` is 'inline' or 'single'"
				);
			}
		}

		if (typeof config.adapter?.vite === 'function') {
			validated.adapter.vite = config.adapter.vite({
				config: validated
			});
		}

		return validated;
	} catch (e) {
		const error = /** @type {Error} */ (e);

		// Print a nicer version of the error to the console
		console.log(styleText(['bold', 'red'], `\n${error.message}\n`));

View on GitHub (pinned to 03f1687fe6)

Solutions

1. Set `kit.output.bundleStrategy: 'split'` in svelte.config.js.
2. Or set `kit.router.resolution: 'client'` to keep the inline/single bundle strategy.
3. If you need a single-file bundle, reconsider whether server resolution is actually required for your deployment target.

Example fix

// before
kit: { router: { resolution: 'server' }, output: { bundleStrategy: 'single' } }
// after
kit: { router: { resolution: 'server' }, output: { bundleStrategy: 'split' } }

const { router = {}, output = {} } = config.kit ?? {};
if (router.resolution === 'server' && output.bundleStrategy !== 'split') {
  throw new Error("router.resolution 'server' requires output.bundleStrategy 'split'");
}

try {
  await viteBuild();
} catch (e) {
  if (e.message.includes("cannot be 'server' if `output.bundleStrategy`")) {
    console.error("Set kit.output.bundleStrategy to 'split' or use client resolution");
  }
  throw e;
}

When it happens

Trigger: validate_config finds `validated.kit.router.resolution === 'server'` and `validated.kit.output.bundleStrategy` is 'inline' or 'single' (anything other than 'split').

Common situations: Users adopt bundleStrategy 'inline'/'single' (often for simple static deployments) while router.resolution was switched to 'server' for SEO or nested-layout resolution; config defaults from an older project template clashing with newly added options.

Related errors

• The `router.resolution` option cannot be 'server' if `router
• The _headers file should be placed in the project root rathe
• The _redirects file should be placed in the project root rat
• routes.include must contain 100 or fewer routes
• The _headers file should be placed in the project root rathe

AI-assisted analysis of sveltejs/kit@03f1687fe6 (2026-09-02). Data as JSON: /api/errors/b9ea6570465c0539. Report an issue: GitHub.