Next.js 16.2 App Router error boundary architecture. Use when implementing error handling, creating error.tsx/global-error.tsx files, or debugging white-screen failures. Triggers on "error boundary", "white screen", "error.tsx", "global-error.tsx", "next.js error", or "digest hash". Enforces mandatory global-error.tsx, feature-level error.tsx boundaries, external telemetry with error.digest, and hard-navigation escape hatch.
