This warning occurs when Vite encounters a race condition during dependency pre-bundling, causing source map files to be temporarily unavailable. While it appears in DevTools, it typically does not affect application functionality.
This error appears in the browser console when Vite is unable to load source map files for dynamically imported chunks, particularly those loaded via React.lazy() and Suspense. The root cause is a timing issue during Vite's dependency pre-bundling process. When Vite starts the development server, it pre-bundles dependencies to optimize performance. During this process, Vite cleans the cache folder and then runs esbuild asynchronously. This creates a window where the cache folder may be empty while esbuild hasn't finished generating the new files. If a browser request for a source map file occurs during this window, the file won't be found, triggering the warning. This is particularly common with React Suspense because lazy-loaded components generate separate chunks that each have their own source maps. The asynchronous nature of both Suspense loading and Vite's pre-bundling can cause these warnings to appear during initial development server startup or when dependencies change.
First, confirm that your application is working correctly despite the warning. Open your browser console and check:
Failed to load source map from suspense chunkIf your React application renders properly and all features work, this is a development-only warning that doesn't affect functionality. Source maps are only used by DevTools for debugging - they don't impact production builds or runtime behavior.
Stop your development server and clear the Vite cache to force a fresh pre-bundling process:
# Stop the dev server (Ctrl+C)
# Remove Vite cache
rm -rf node_modules/.vite
# Restart development server
npm run dev
# or
yarn devThis ensures all dependencies are pre-bundled fresh and source maps are generated in the correct order. Wait for pre-bundling to complete before making any browser requests.
Adjust your Vite configuration to control source map generation during development:
// vite.config.ts
import { defineConfig } from 'vite';
import react from '@vitejs/plugin-react';
export default defineConfig({
plugins: [react()],
build: {
sourcemap: true
},
css: {
devSourcemap: true
},
// Optimize dependency pre-bundling
optimizeDeps: {
include: ['react', 'react-dom']
}
});The optimizeDeps.include option ensures critical dependencies are pre-bundled immediately, reducing race conditions.
If the warnings are distracting during development, you can temporarily disable source map loading in Chrome DevTools:
1. Open Chrome DevTools (F12)
2. Click the three dots menu (⋮) in the top-right
3. Select Settings
4. Under Sources, uncheck "Enable JavaScript source maps"
Note: This only hides the warning - it doesn't fix the underlying issue. You'll lose source map debugging capabilities while this is disabled.
If you're using multiple Vite plugins, their order can affect source map generation. Try reordering plugins in your vite.config.ts:
// vite.config.ts
import { defineConfig } from 'vite';
import react from '@vitejs/plugin-react';
import svgr from 'vite-plugin-svgr';
export default defineConfig({
plugins: [
// Place React plugin first
react(),
// Other plugins after
svgr()
]
});Some plugins modify source map generation, so placing the React plugin first ensures it has priority.
Wrap your Suspense boundaries with error boundaries to handle loading failures gracefully:
import { Suspense, lazy } from 'react';
import { ErrorBoundary } from 'react-error-boundary';
const LazyComponent = lazy(() => import('./components/MyComponent'));
function App() {
return (
<ErrorBoundary fallback={<div>Failed to load component</div>}>
<Suspense fallback={<div>Loading...</div>}>
<LazyComponent />
</Suspense>
</ErrorBoundary>
);
}This ensures your app handles chunk loading failures properly, even if source maps are unavailable.
Why this happens with React Suspense specifically:
React.lazy() creates code-split chunks that are loaded on demand. Each chunk has its own source map file. When you use Suspense with multiple lazy-loaded components, Vite generates multiple chunk files (e.g., MyComponent-abc123.js and MyComponent-abc123.js.map). The browser requests these in parallel, which increases the likelihood of hitting the pre-bundling race condition.
Production considerations:
This warning only appears in development mode. Production builds generate source maps differently:
// vite.config.ts
export default defineConfig({
build: {
sourcemap: process.env.NODE_ENV === 'development'
}
});You can conditionally disable source maps in production to prevent exposing your source code, or use a service like Sentry to securely upload source maps for error tracking without exposing them publicly.
Long-term fix:
The Vite team is aware of this race condition (GitHub issue #6508). Future versions may implement better synchronization between cache clearing and pre-bundling. Until then, the warning is cosmetic and doesn't impact development workflow.
Network considerations:
If you're experiencing this on slow connections, the pre-bundling process may take longer, increasing the race condition window. Using optimizeDeps.include to pre-bundle critical dependencies can reduce this issue.
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