withastro/astro · error · Error

Integration "${maybeConflictingIntegration}" conflicts with

Error message

Integration "${maybeConflictingIntegration}" conflicts with "${settings.adapter.name}". You can only configure one deployment integration.

What it means

`validateSetAdapter` enforces that only one deployment adapter may be registered. If `settings.adapter` is already set and a new integration tries to set a differently-named adapter, Astro throws a plain `Error` naming both. This prevents two deployment integrations (e.g., Node + Vercel) from fighting over output configuration.

Source

Thrown at packages/astro/src/core/dev/adapter-validation.ts:28

	if (hasWarnedMissingAdapter) return;
	if (settings.buildOutput === 'server' && !settings.config.adapter) {
		logger.warn(
			'config',
			'This project contains server-rendered routes, but no adapter is installed. This is fine for development, but an adapter will be required to build your site for production.',
		);
		hasWarnedMissingAdapter = true;
	}
}

export function validateSetAdapter(
	logger: AstroLogger,
	settings: AstroSettings,
	adapter: AstroAdapter,
	maybeConflictingIntegration: string,
	command?: 'dev' | 'build' | string,
) {
	if (settings.adapter && settings.adapter.name !== adapter.name) {
		throw new Error(
			`Integration "${maybeConflictingIntegration}" conflicts with "${settings.adapter.name}". You can only configure one deployment integration.`,
		);
	}

	if (settings.buildOutput === 'server' && adapter.adapterFeatures?.buildOutput === 'static') {
		// If the adapter is not compatible with the build output, throw an error
		if (command === 'build') {
			const adapterRecommendation = getAdapterStaticRecommendation(adapter.name);

			throw new AstroError({
				...AstroErrorData.AdapterSupportOutputMismatch,
				message: AstroErrorData.AdapterSupportOutputMismatch.message(adapter.name),
				hint: adapterRecommendation ? adapterRecommendation : undefined,
			});
		} else if (command === 'dev') {
			logger.warn(
				null,
				`The adapter ${adapter.name} does not support emitting a server output, but the project contain server-rendered pages. Your project will not build correctly.`,

View on GitHub (pinned to d081033d5f)

Solutions

1. Keep only one deployment integration in `astro.config.integrations`.
2. If switching adapters, fully remove the previous adapter integration and its import.
3. For multi-target builds, use separate config files / env-driven single adapter selection rather than registering both.

Example fix

// before — astro.config.mjs
import node from '@astrojs/node';
import vercel from '@astrojs/vercel/serverless';
export default defineConfig({
  adapter: node({ mode: 'standalone' }),
  integrations: [vercel()],
});

// after
import vercel from '@astrojs/vercel/serverless';
export default defineConfig({
  adapter: vercel(),
});

const adapters = integrations.filter(i => i && i.name && /adapter|node|vercel|netlify|cloudflare/.test(i.name)); if (adapters.length > 1) throw new Error('Multiple adapters detected');

When it happens

Trigger: Adding two deployment integrations to `astro.config` (e.g., `@astrojs/node` and `@astrojs/vercel`) so that the second integration's `updateConfig({ adapter })` triggers `validateSetAdapter` with a name differing from the first.

Common situations: Switching adapters and forgetting to remove the old integration; a starter template that bundled an adapter being combined with a user-added one; monorepo shared config accidentally merging two adapter integrations.

Related errors

• AdapterSupportOutputMismatch
• CacheQueryConfigConflict
• ClientAddressNotAvailable
• Action not found: ${path}
• CannotOptimizeSvg

AI-assisted analysis of withastro/astro@d081033d5f (2026-08-12). Data as JSON: /api/errors/6493868aeedfc80a. Report an issue: GitHub.