1. Create or access a Sentry account and organization.
2. Create a Sentry project for this Next.js application.
3. Copy the project DSN from the Sentry project settings.
4. Add the required public variables to .env.local. Add the optional private variables only when source-map uploads should run during production builds.

   NEXT_PUBLIC_ENABLE_SENTRY=true
   NEXT_PUBLIC_SENTRY_DSN=https://your-public-dsn@sentry.io/project-id
   
   # Optional: enable source-map uploads for production builds.
   SENTRY_ORG=your-org-slug
   SENTRY_PROJECT=your-project-slug
   SENTRY_AUTH_TOKEN=your-auth-token

5. Restart the dev server or rebuild the app after changing environment variables.
6. Validate the integration in non-production from /internal/sentry-example-page.
7. Keep SENTRY_AUTH_TOKEN secret. Disable Sentry by setting NEXT_PUBLIC_ENABLE_SENTRY=false or leaving NEXT_PUBLIC_SENTRY_DSN empty.

This guide only describes setup. Runtime behavior stays controlled by the existing Sentry configuration in this project.