How to fix Failed to load source map from suspense chunk in React

ReactBEGINNERLOWUpdated Dec 11, 2025· 148 views

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.

Quick fix

Fixes Failed to load source map from suspense chunk

Failed to load source map from suspense chunk
  1. Verify the warning is non-critical
  2. Clear Vite cache and restart dev server
  3. Configure source map settings in vite.config.ts
  4. Disable source maps in DevTools (temporary workaround)
react — error
Failed to load source map from suspense chunk
Failed to load source map from suspense chunk

What this error means

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.

Typical symptoms

  • Warning appears in browser DevTools console during development
  • Message references source map files in .vite cache folder
  • Warning typically appears on initial page load or hot reload
  • Application continues to function normally despite the warning
  • Error may reference React.lazy() loaded component chunks
  • Warning disappears after full page reload

Common causes

  1. Race condition between Vite dependency pre-bundling and browser requests
  2. Vite cache folder being cleared while esbuild is still running
  3. Browser requesting source maps before pre-bundling completes
  4. Missing source map files from third-party dependencies
  5. Plugin order issues in vite.config.ts affecting source map generation
  6. Stale HTTP requests paused on async file reads during cache refresh

How to fix "Failed to load source map from suspense chunk"

1Verify the warning is non-critical

First, confirm that your application is working correctly despite the warning. Open your browser console and check:

bash
Failed to load source map from suspense chunk

If 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.

2Clear Vite cache and restart dev server

Stop your development server and clear the Vite cache to force a fresh pre-bundling process:

bash
# Stop the dev server (Ctrl+C)

# Remove Vite cache
rm -rf node_modules/.vite

# Restart development server
npm run dev
# or
yarn dev

This 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.

3Configure source map settings in vite.config.ts

Adjust your Vite configuration to control source map generation during development:

typescript
// 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.

4Disable source maps in DevTools (temporary workaround)

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.

5Check plugin order in configuration

If you're using multiple Vite plugins, their order can affect source map generation. Try reordering plugins in your vite.config.ts:

typescript
// 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.

6Add error boundary for lazy-loaded components

Wrap your Suspense boundaries with error boundaries to handle loading failures gracefully:

typescript
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.

Advanced notes

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:

typescript
// 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.

Frequently asked questions

What does "Failed to load source map from suspense chunk" mean?
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.
How do I fix "Failed to load source map from suspense chunk"?
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.
What causes "Failed to load source map from suspense chunk"?
Race condition between Vite dependency pre-bundling and browser requests Vite cache folder being cleared while esbuild is still running Browser requesting source maps before pre-bundling completes
Is the "Failed to load source map from suspense chunk" error serious?
It is a low-severity error — more of a blocker than a risk. The steps above resolve it.

Official resources & further reading