runtime-debug

Use this skill when reproducing runtime-bundle, module-resolution, or user-bundle inclusion regressions. Set __NEXT_SHOW_IGNORE_LISTED=true to disable the ignore-list filtering in dev server error output. By default, Next.js collapses internal frames to at ignore-listed frames , which hides useful context when debugging framework internals. Defined in packages/next/src/server/patch-error-inspect.ts . When user next build starts bundling internal Node-only helpers unexpectedly: To prove what user bundling includes, emit webpack stats from the app's next.config.js : Then use stats.toJson({ modules: true, chunks: true, reasons: true }) and diff webpack-stats-server.json between modes. This gives concrete inclusion reasons (e.g. which module required node:stream/promises ) and is more reliable than analyzer HTML alone. - Mirror CI env vars when reproducing CI failures. - Key variables: IS_WEBPACK_TEST=1 forces webpack (turbopack is default), NEXT_SKIP_ISOLATE=1 skips packing next.js.