Sentry Monitoring

Next.js

• Three separate init files, and the browser one is instrumentation-client.ts — not sentry.client.config.ts — alongside sentry.server.config.ts and sentry.edge.config.ts. npx @sentry/wizard@latest -i nextjs creates all three and patches next.config.ts.
• Source maps upload only when next.config.ts is wrapped in withSentryConfig() and SENTRY_AUTH_TOKEN (plus SENTRY_ORG / SENTRY_PROJECT) is present at build time, CI included.
• tunnelRoute: '/monitoring' proxies events through your own origin so ad-blockers stop dropping them.
• app/global-error.tsx reports nothing by itself — call Sentry.captureException(error) inside it. Wrap server actions in Sentry.withServerActionInstrumentation('name', fn).

Node / Express

import './instrument' must come before every other import in the process. app.use(Sentry.expressErrorHandler()) must be the last error-handling middleware.

Sampling and context

• tracesSampleRate: 1.0 dev, 0.2–0.5 low-traffic production, 0.05–0.1 high-traffic. Use tracesSampler returning 0 for /health and polling routes, ~0.5 for checkout/auth.
• Sentry.setUser / setTag / setContext persist for the rest of the session; Sentry.withScope is one-off. Re-throw after captureException when the caller still needs the error.
• Override issue grouping with event.fingerprint = [...] in beforeSend.
• Core Web Vitals are captured with no config. Alert thresholds: LCP > 2.5s, CLS > 0.1, INP > 200ms.
• The DSN is safe to expose client-side. sendDefaultPii: true captures IP, user agent, and authenticated user.

Docs: https://docs.sentry.io/