Error Monitoring in Next.js 15 with Sentry What I Actually Track

error.tsx` catches a failure and shows the user something reasonable. It does not tell you the failure happened at all unless you are actively watching. For a while my "monitoring" was a client messaging me that something was broken, which is not monitoring, it is finding out from the worst possible source. Here is the Sentry setup I actually use now, tuned to catch what matters without burying it in noise. 1. The Setup bash npx @sentry/wizard@latest -i nextjs The wizard generates the config files and wraps next.config.ts automatically. Worth reviewing what it creates rather than trusting it blindly, since the defaults capture more than most projects actually need. `ts // sentry.client.config.ts import * as Sentry from '@sentry/nextjs'; Sentry.init({ dsn: process.env.NEXT_PUBLIC_SENTRY_DSN, tracesSampleRate: 0.1, environment: process.env.NODE_ENV, }); ` `ts // sentry.server.config.ts import * as Sentry from '@sentry/nextjs'; Sentry.init({ dsn: process.env.NEXT_PUBLIC_SENTRY_DSN, tracesSampleRate: 0.1, }); ` tracesSampleRate: 0.1 matters more than it looks like it should. Setting this to 1.0 captures full performance tracing on every single request, which sounds thorough and quickly becomes expensive and noisy once real traffic shows up. Ten percent is a reasonable starting point for most projects, adjustable once you see actual volume. 2. Connecting It to error.tsx This is the piece that is easy to miss. error.tsx handles the user-facing fallback, but nothing about it reports the error anywhere by default. `tsx // app/dashboard/error.tsx 'use client'; import * as Sentry from '@sentry/nextjs'; import { useEffect } from 'react'; export default function DashboardError({ error, reset, }: { error: Error & { digest?: string }; reset: () => void; }) { useEffect(() => { Sentry.captureException(error); }, [error]); return ( Something went wrong. Try again ); } ` Without this useEffect , the error boundary works perfectly from the user's perspective, and you never find out it