Client-side errors are reported to monitoring

A server-side Sentry initialization without a client-side counterpart means rendering crashes, JavaScript exceptions, and failed client-side fetches are never reported. CWE-778 (Insufficient Logging) applies to both server and browser contexts — client errors that go unreported are failures with no observable signal. ISO 25010 reliability.fault-tolerance requires fault detection across all execution environments. In practice, many production JavaScript errors — component hydration mismatches, failed dynamic imports, browser-specific rendering bugs — occur exclusively in the browser and are invisible to server-side monitoring alone.

Add sentry.client.config.ts for Next.js to initialize the browser SDK, and forward errors caught by error boundaries to the monitoring service.

// sentry.client.config.ts
import * as Sentry from '@sentry/nextjs'
Sentry.init({
  dsn: process.env.NEXT_PUBLIC_SENTRY_DSN,
  tracesSampleRate: 0.1,
})

In your error boundary:

<ErrorBoundary
  onError={(error, info) => Sentry.captureException(error, { extra: info })}
  fallbackRender={({ resetErrorBoundary }) => (
    <div>Something went wrong. <button onClick={resetErrorBoundary}>Try again</button></div>
  )}
>
  <App />
</ErrorBoundary>

Verify by triggering a deliberate client-side throw in development and confirming it appears in your Sentry issues list.