Next.js

Fix: useRouter query undefined on first render

Why Next.js hydrates a dynamic Pages Router page with an empty query object, how router.isReady fixes it, and why the App Router does not have this exact problem.

Fix TransformStream is not defined in Jest

Separate an old Node limitation from a missing Jest global, then verify the stream reads, writes and closes without replacing the Worker runtime.

Fix Auth.js UntrustedHost in Production

A local reproduction separates the host-trust guard from proxy configuration, environment inference and later sign-in failures.

Fix Turbopack Build Errors from a Webpack Config

Find the plugin behind the unexpected webpack hook, choose a compiler deliberately, and verify that the behaviour you need still runs.

Fix Next.js: Unable to Acquire the Dev Server Lock

Find the server that owns .next/dev/lock, distinguish a held lock from a leftover file, and restart without disrupting other Node applications.

Fix Turbopack's Wrong Workspace Root Warning

Trace the lockfile behind an unexpected workspace root, choose the right standalone or monorepo boundary, and separate a reported memory spike from a verified cause.

Fix "changing an uncontrolled input to be controlled"

Why an empty state object makes React treat a text field as uncontrolled, what the React 19 wording looks like, and the react-hook-form variant of the same warning.

Fix: error while hydrating, root switched to client render

Why this error takes down the whole page instead of one component, and the two separate causes behind it: broken DOM nesting and no Suspense boundary above the failure.

React Hook useEffect has a missing dependency: the fix

The three warnings this rule prints for one fetch function, which remedy each one wants, and a measured run showing what silencing it costs when a prop changes.

Fix TS2882: side-effect import of './globals.css'

Why this error appears on unchanged Next.js projects overnight, which TypeScript actually raises it, and the one-line ambient declaration that fixes it under both compilers.

react-chartjs-2 fill property not working: register Filler

Why a line chart ignores fill: true, the console warning that names the cause, the per-chart and chart.js/auto alternatives, and what each one costs in bundle size.

MUI DatePicker readonly in Cypress CI: fix the variant

A wider Cypress viewport does not guarantee the desktop picker. Diagnose the media query first, then test the UI your users actually receive.

React Hook Form: Fix Confirm Password Validation

Block mismatched submissions, display the field error, and catch a confirmation that becomes stale after the user edits the original password.

Fix Next.js Docker: Cannot find module '/app/server.js'

Follow the server entrypoint from the Next.js build into the final image, then check the application and its static files separately.

Fix Unsupported Server Component type: undefined

Keep the page on the server while repairing Container.Window: direct named imports work, and changing to a default export alone does not fix this case.

Create React App's CORS Header Goes on the API, Not the App

Which of this 2017 question's three answers still applies today, the one react-scripts already handles for you by default, and the fix that works for the rest.

Fix: sh: 1: next: not found on Heroku

Three different, unrelated situations produce the exact same Heroku crash — here is how to tell which one is yours before you change anything.

CORS Not Working on Vercel? Fix the vercel.json Headers

Why a CORS header that passes on localhost can still get blocked once Vercel routes the request, and the one-layer fix Vercel documents for it.

Fix: $VARIABLE is not listed as a dependency in turbo.json

Declare the variable once, in env or globalEnv, and both the lint error and the silent runtime drop under Strict Mode disappear.

Fix: Objects Are Not Valid as a React Child

The 2015 bug reproduced today, the exact modern error text, what the production build shows instead, and the one-line fix for every cause.

Adjacent JSX Elements Must Be Wrapped in an Enclosing Tag

The 2015 wording still fires in Babel today, but Next.js shows a different message for the same mistake, and wrapping the tags is not always the whole fix.

Fix: Cannot set property Request of #<Object> getter

Reproduced line by line with Next.js's own polyfill file and abortcontroller-polyfill's published source across Node 16, 17 and 18, plus which of two independent fixes actually applies.

Fix Cannot resolve symbol 'Routes': stale JetBrains typings

Why a JetBrains IDE flags Routes from react-router-dom 6 as unknown while the app builds, how to prove which typings file it reads, and the order of steps that stops the old copy coming back.

Set the request's mode to 'no-cors'? What to do instead

What the browser's no-cors suggestion really does to an authenticated API call, the one case where it is the right answer, and the two fixes that return your data.

Material UI install fails on React 18 or 19 (ERESOLVE): fix

See why npm refuses the old @material-ui packages on a React 18 or 19 project, which packages to install instead, and why --legacy-peer-deps on React 19 only moves the failure to runtime.

Failed to find font override values: next/font/google fix

Why next/font/google warns about font override values for newer Google Fonts, why the popular fix only works on webpack, and how to get the CLS fallback back.

Fix Invariant: attempted to hard navigate to the same URL

Reproduced on Next.js 13.1.0, 13.2.0 and 16.4.3: why a NextResponse.next() middleware broke the 404 page, why the same invariant still fires after a redeploy, and the catch that stops it.

Access to fetch at accounts.google.com blocked by CORS: fix

Why cors() on your Express API cannot fix a Google sign-in started with fetch, and the three navigation patterns that make the error disappear.

Unrecognized feature: 'interest-cohort' on GitHub Pages

Where the interest-cohort warning came from, why the meta-tag fix does nothing, and the base-path change that actually brings a blank GitHub Pages app back.

Fix Error: NEXT_REDIRECT logged in a Route Handler catch

Reproduced on Next.js 16.4.2: why redirect() inside try/catch logs Error: NEXT_REDIRECT, sends users to the wrong URL or returns a 500, and the three fixes that hold.

Next.js 'URL is malformed' error: use only absolute URLs

Reproduced on Next.js 16.4.2: the relative redirect that throws, the absolute redirect that then loops on itself, and the basePath case where new URL quietly drops the prefix.

Next.js favicon not working: app/favicon.ico vs public/

Reproduced on Next.js 16.4.2: with an icon in both app/ and public/, next dev and next start served different files without a warning. Where each icon file must live, and what renaming to icon.ico really changes.

Fix shadcn combobox: item was not found at the registry

Why the combobox is the one component the CLI cannot find in an older shadcn project, reproduced with shadcn 4.22.1, and the one-line change for each Tailwind version.

Fix Export encountered errors on following paths in Next.js

Read the path list as a map back to your own code: /about/undefined, /components/Navbar and /about/[slug] each point at a different bug, rebuilt on Next.js 16.4.2 (and the first on 14.2.35 too).

Next.js app/api 404 vs 405: route.js and named exports

Reproduced on Next.js 16.4.2: why app/api/admin/all.js answers 404, what a 405 means instead, and the static export case that only 404s in production.

SyntaxError: Unexpected end of input with mode: 'no-cors'

The JSON is in DevTools but never reaches your code: see why an opaque response has nothing to parse, and the two fixes that actually return the data.

Fix next-auth /api/auth/error in production: NO_SECRET

Reproduced on next-auth 4.24.15 and Next.js 15.5.28: why sign-in works on localhost but fails after deploy, what a 404 versus a 500 at /api/auth/error tells you, and the env change that fixes it.

Fix: Do Not Use Array Index in Keys (React)

Why key={index} breaks on reorder and removal, how to prove it with an uncontrolled input, and the three ways to get a real key when your data has no id.

Fix "only exports components": Fast Refresh ESLint error

The exact ESLint rule that throws this, the six code paths that produce six different wordings, and the one move that actually silences it.

Fix Vercel 404: NOT_FOUND Deploying an Express App

Why Vercel answers 404: NOT_FOUND for an Express app that runs locally, and the two things to check: the entry file Vercel looks for, and a leftover Build command/Output Directory setting.

Next.js "Failed to load SWC binary": the real fix

Why next dev or next build refuses to start, what actually happens when npm cannot find the right @next/swc binary, and the one reinstall that puts it back — reproduced on Next.js 16.4.2.

Fix Failed to fetch dynamically imported module (Vite)

Reproduce the production-only Vite error in Chromium, see why retrying the same import does nothing, and ship a reload handler that cannot loop.

Fix response data evicted from inspector cache in Chrome

Separate a missing DevTools response body from a failed download, then capture and check the contents without relying on a 200 status or a guessed size limit.

Fix Next.js missing .next/BUILD_ID at server startup

Separate an absent build from the wrong application root, a mismatched output folder and development artifacts, using the file the production server checks.

Fix Next.js Global CSS cannot be imported: Pages Router

A working global Sass entry point, the rename-only trap, and the different rule for App Router projects, checked against current Next.js builds.

Fix: A Route is only ever to be used as the child of Routes

Why v5-style routing code crashes on React Router 6 and 7, the two-step migration that fixes it, and the second error that appears if you only do half of it.

Fix Functions cannot be passed directly to Client Components

Read the caret line to find the exact prop, then keep that function on the client side of the boundary: four reproduced shapes on Next.js 16.4.0, and why "use server" rarely fixes it.

Next.js: Error: only absolute urls are supported (fix)

Why fetch("/api/products") works after a client-side click but throws on refresh, what each fetch implementation prints, and the two fixes that hold in both routers.

Fix react-scripts: Permission denied on npm run build

Find out in two commands whether your react-scripts bin lost its execute bit or lives on a noexec filesystem, then apply the fix that matches, instead of chmod 777 and sudo.

NextAuth login failed: handle CredentialsSignin, v4 and v5

Reproduced on next-auth 4.24.15 and 5.0.0-beta.32: what signIn() returns on a wrong password, why the accepted if (ok) check breaks on v5, and how to get a usable error code.

Fix 'authOptions' is not a valid Route export field

Reproduced on Next.js 13.4.3 (Linux and Windows), 15.4.11 and 15.5.27: why exporting authOptions from the NextAuth route breaks the build only, and the one-file move that fixes it.

Cannot assign to 'current' (read-only): useRef TS2540 fix

Two characters of parentheses decide whether TypeScript hands back a mutable ref or a read-only one. Here is how to read the overloads and fix the ref in place.

Fix Cannot find module 'caniuse-lite/dist/unpacker/agents'

Why npm install, npm ls and update-browserslist-db all report a healthy tree while the error stays, and the one reinstall that actually puts the missing files back.

Fix Cannot read properties of undefined (reading 'apps')

A Firebase v8 tutorial pasted into a project with a current firebase package: why firebase.apps is undefined, the two imports that fix it, and what Turbopack prints instead.

Minified React error #425: Text Mismatch After Deploy

Decode #425 and its companion #423, reproduce both triggers from the Stack Overflow thread on Next.js 12.2.5, and see what React 19 prints instead.

Fix UnhandledSchemeError: Reading from "node:buffer"

Reproduced on Next.js 16.4.0 with webpack: which import triggers the error, why bare "buffer" builds but "node:buffer" does not, and the three fixes that compile.

Super expression must either be null or a function: Next.js

Reproduced on Next.js 16.4.0 and 13.5.11: why the carousel import crashes the App Router, the two-file fix that keeps your page a Server Component, and the error that comes next.

Fix: FetchError request to localhost:1337 ECONNREFUSED ::1

The exact fix for the ECONNREFUSED ::1:1337 error between Next.js and a local Strapi API, and why it depends on your Node version.

NextAuth: Property 'session' does not exist on type '{}'

Reproduced on Next.js 12.3.4, 13.0.0 and 16.4.0: why the session prop broke in _app.tsx, the one-line generic that fixes it, and why the d.ts override only seems to work.

Fix localStorage is not defined after 'use client' (Next.js)

The cookie banner from the Stack Overflow question, rebuilt on Next.js 16.3.8: why 'use client' does not stop the crash, the useEffect fix, and the other errors Node 25 and 26 print.

Fix: "[object Date]" Cannot Be Serialized as JSON

A Date prop cannot go straight from getStaticProps to the page — convert it first, or the page will not build.

Fix Vercel 'Git author must have access to the project'

Work out which of the three access rules blocked your commit, fix the author identity or the team setup, and get pushes deploying again.

Next.js Images Not Loading from public/static Folder: Fix

Which URL serves a file from public/, why next/image answers 400 instead of 404, and what basePath and a production server change.

Can't Import SVG in Next.js: Fix for Turbopack and Webpack

Why <Logo /> fails with "Element type is invalid" or "Module parse failed", and the SVGR setups that build on Next.js 16 with both bundlers.

Fix: blocked by CORS policy from origin localhost:3000

The browser, not your server, is refusing the response — read the exact wording of the console error to know which of three fixes actually applies.

Fix /tmp/chromium libnss3.so Error on Vercel and Lambda

Get headless Chromium launching again in a Vercel Function or on AWS Lambda, and understand why pinning Node 14 was never a real fix.

Postmortem: The Next.js App Router Memory Leak of 2023

In 2023, self-hosted Next.js App Router apps were reported eating memory until the host killed them. Issue #49929 ran three months and 131 comments; it found a high process baseline and one canary-only Node.js fetch() leak.

Why global-error.tsx Doesn't Fire in Next.js Dev Mode

A root layout error boundary that looks broken in development but works fine once deployed. The dev-overlay behavior behind it, and how to verify global-error.tsx before you ever hit production.

Fix: Can't Perform a State Update on an Unmounted Component

Separate the old React warning from a persistent resource leak and from out-of-order responses while the component is still mounted.

Fix: Event handlers cannot be passed to Client props

A Server Component cannot hand a function to a Client Component as a prop — functions are not serializable across the RSC boundary. Where to put "use client" instead, with the three shapes this bug actually takes.

Fix: component needs useState, no Client parent

A hook-using component can inherit a client boundary from an importing module. Choose a small entry point so interactive code does not pull unrelated imports into the client bundle.

Fix: Next.js middleware not triggering

middleware.ts runs with no errors but never fires. The three real causes — wrong file location, a matcher that excludes your route, and Node-only imports on the Edge runtime — checked in the order that finds the bug fastest.

Fix: NextRouter was not mounted

useRouter() throws "NextRouter was not mounted" when it runs outside a Pages Router page tree. The three real causes — tests, Storybook, and App Router migrations — and the fix for each.

Firebase Auth IDBDatabase Transaction Error: 2026 Fix

Firebase Auth stores its session in an IndexedDB database called firebaseLocalStorageDb. When that connection closes mid-session, sign-in throws InvalidStateError. Here is the cause, the SDK version that changed the behaviour, and a Next.js App Router setup that degrades gracefully.

Fix "Default condition should be last one" (Firebase)

One Firebase release put "default" before "browser" in the package.json exports map of 30 packages, and webpack's resolver refuses that. Here is the exact error, the diff that caused it, the release that fixed it, and how to find any other package in node_modules doing the same thing.

Fix: react-dom/server Import Error in Next.js App Router

"You're importing a component that imports react-dom/server" is a compile-time rule of the App Router, not a bug in your code. Here is what the rule protects, which use cases are legitimate, and the fixes verified against Next.js 15.5 and 16.3 with both webpack and Turbopack.

Cross-Origin-Opener-Policy Blocks window.closed: 2026 Fix

The Firebase Google sign-in popup loses window.closed access when a COOP header isolates the opener. Here's the exact header change that restores the popup flow.

FirebaseError: Expected first argument to collection() — Fix

When Firestore throws 'Expected first argument to collection()', it's almost always a missing Firestore instance. Learn the exact fix for Next.js and v9 modular SDK.

Next.js 16 /_not-found Prerender Build Error: The Real Fix

Next.js 16 build crashes prerendering the internal /_not-found route. Here are the three actual causes behind it, how to tell which one is yours, and the fix for each.

Next.js 16 "use cache" Errors: Why Cache Components Break

Next.js 16 replaced implicit caching with the explicit "use cache" directive. Here is what actually breaks when you flip cacheComponents on, and how to fix it without reverting.

Fix barrel_optimize Build Warnings with MUI in Next.js

The __barrel_optimize__ warnings come from Next.js rewriting MUI's barrel file imports. They are usually benign — but they can hide a real bundling problem. Here is how to tell the difference and silence them properly.

Fix Next.js 'Cannot Have a Negative Time Stamp' Error

Turbopack dev servers throw "Failed to execute 'measure' on 'Performance': cannot have a negative time stamp" on notFound(), redirect() and dynamic imports. Here is each cause, its confirmation test, and the workaround.

Next.js "Server Is Running Out of Memory" Fix (2026)

Next.js restarts itself when the Node heap crosses its limit. The message is a symptom, not a cause. Here is how to find the leak, the dev-mode fix (Turbopack), and the production levers that actually lower the floor.

Next.js Scroll Resets When searchParams Change

Next.js App Router resets scroll to the top whenever searchParams update, even on the same page. Here is the root cause and the scroll={false} fix that actually keeps the user's position.

Next.js 16 Removed next lint: ESLint 9 Migration

`next lint` is gone in Next.js 16, `next build` no longer lints, and the `eslint` block in next.config is ignored with a warning. You must run ESLint directly with a flat config. The official codemod does most of it; the rest is scripts, CI, and the few footguns the upgrade guide skips.

useSearchParams Suspense Error: 3 Real Fixes (Next.js 15)

The error only surfaces during the production build — dev mode hides it completely. Here is why, and the three fixes ranked by situation.

Fix: Next.js proxy.js matcher not working for static assets

Without a matcher, proxy.js runs on every request including _next/static and public assets. And Server Functions are not separate routes — a matcher gap silently drops auth coverage.

Fix ChunkLoadError: Loading chunk failed (Next.js, webpack)

"ChunkLoadError: Loading chunk 5760 failed" almost always means a user has an old tab open after you shipped a new deploy. The fix is configuration — deploymentId, build IDs, and CDN headers — not a try/catch.

Fix Dynamic Server Usage Error in Next.js App Router

Next.js throws this when a route it wants to render at build time calls a dynamic function — cookies(), headers(), searchParams, or a no-store fetch. The fix is either opt the route into dynamic rendering, or remove the request-time dependency if it should be static.

Fix next/image Hostname Not Configured in Next.js

next/image strictly allow-lists remote hosts. The fix is images.remotePatterns in next.config — matched exactly on protocol, hostname, port, and pathname. Get one wrong (http vs https, a subdomain, a missing port) and it still blocks.

use client vs use server in Next.js: The Real Difference

The #1 misconception in the App Router: "use server" is not the opposite of "use client". One marks a client boundary in the module graph; the other exposes callable server functions. Server Components are the default — no directive needed.

Next.js Build Passed But Production Broke

A green build only proves the bundle compiled. This postmortem walks through three production-only failures: missing Vercel env vars, Edge runtime imports, and cache behavior that changed after deploy.

Next.js Middleware Not Running on Vercel: 3 Causes

Middleware that works locally can disappear in Vercel production because the matcher never matches, Edge bundles a Node-only import, or auth middleware cannot read the token. This guide gives you the diagnosis order I use before touching app code.

Next.js Pages to App Router Migration Gotchas

The official migration path covers files and APIs. This guide covers the gotchas that break production: cookies timing, removed router events, metadata conflicts, client boundaries, and Edge auth.

How to set the next/image component to 100% height

If your <Image / component ignores height: 100% and appears too small or misaligned, the issue is almost always that the parent container lacks an explicit

Fix Module not found: Can't resolve 'encoding' in Vercel

You see "Module not found: Can't resolve 'encoding'" in your Vercel deployment logs. This guide explains why it happens with cross-fetch/node-fetch and how to fix it permanently.

Next.js Query String Params: searchParams + useRouter

If `router.query` examples keep breaking on you, the problem is usually that you're mixing App Router and Pages Router APIs. Here is the exact fix for each case.

Next.js Redirect from / to another page

If your redirect works only after render, flickers, or fires in the wrong place, you are probably using the wrong redirect API for the job. Here is the exact mapping.

How to Access Route Parameter Inside getServerSideProps

Learn why your dynamic route parameter appears as undefined in getServerSideProps and how to correctly extract it from the context object for server-side data fetching.

Fix 'Next.js 15 requires Node.js 18.18' Build Error

Next.js 15 drops support for older Node versions. Here is how to upgrade to Node.js 18.18.0 or later and fix build errors.

Fix "Parsing error: Cannot find module next/babel"

Fix ESLint's 'Cannot find module next/babel' parsing error in Next.js 13+ projects by updating your ESLint config and understanding SWC vs Babel resolution. Works in monorepos too.

Fix useEffect Running Twice in React 18 — Strict Mode

React 18 Strict Mode intentionally runs effects twice in development to catch side effects. Here's how to handle it safely in production.

NextJS Warning: Extra attributes from the server – Fix 2026

A step‑by‑step guide to remove the "Extra attributes from the server" hydration warning in Next.js, covering root cause, fix, and verification.

Window is not defined in Next.js – 2026 Fix for React Apps

Get rid of the 'window is not defined' error in Next.js by moving browser‑only code behind a safe check or using dynamic imports. The guide walks you through the exact changes.

How to Change the Port in Next.js (dev and start)

Change the default Next.js port when it collides with another process, and know why next dev sometimes moves to 3001 on its own while next start crashes.

How to implement LCP end to end

Learn how to instrument Largest Contentful Paint (LCP) in a Next.js project, send the metric to your analytics provider, and verify that the data is accurate.

cookies() Returns a Promise in Next.js 15/16: Fix

Why cookies() became async in Next.js 15, the error it throws, and the exact patterns that fix session reads in the App Router.

Fix "cookies() should be awaited" Error in Next.js 15

Next.js 15 broke synchronous `cookies().get()`. Every server-side call must now `await cookies()` first. Here's the precise migration — App Router pages, route handlers, Server Actions, and Supabase SSR — plus the codemod that fixes 90% of call sites automatically.

Fix Next.js revalidatePath Not Working in Server Actions

Your Server Action mutates data but the page shows stale values until you hard-refresh. `revalidatePath` is one of those APIs that "succeeds" while doing nothing. Here are the six reasons it no-ops, with the exact fix for each — including a URL served through a rewrite and a second page that reads the same tagged data.

Fix next/image Layout Shift (CLS) in Next.js

next/image only prevents layout shift when it can reserve space. Eight fixes for CLS and LCP problems caused by images, each checked against the Next.js and web.dev documentation.

Next.js 15 Middleware: Auth, Rate Limiting & Edge Guide

Middleware patterns for Next.js 15, grounded in the Edge runtime docs: authentication, rate limiting, A/B testing, geolocation, bot blocking, CSP headers, and request logging. Every pattern ships with working code.

Next.js 15 Partial Prerendering: Guide

A practical, production-focused deep dive into Next.js 15 Partial Prerendering — how it actually works, when it wins, the traps nobody warns you about, and how to migrate an existing app without breaking it.

Next.js 15 Caching Explained: Why Data Shows Stale

Upgraded to Next.js 15 and suddenly your data is stale — or refreshing too often? The caching model changed completely. Here is what actually happens and how to control it.

How to Structure Your Next.js App Router Project for Scale

Stop shoving everything into the components folder. Learn the Feature-Sliced Design pattern adapted perfectly for the Next.js App Router.

Offline-First Next.js + Supabase: Sync That Actually Works

A typed Dexie queue, stable sync lifecycle and account-scoped cache, with explicit boundaries for offline edits and mocked failure-path tests.

Next.js Server Actions with Supabase: Complete Guide

Master Next.js Server Actions with Supabase. Build type-safe, progressive forms with validation, error handling, optimistic updates, and production-ready patterns.

Next.js + Supabase Data Fetching: Server Components

Master data fetching in Next.js with Supabase. Learn Server Components, streaming, parallel queries, caching strategies, and performance optimization patterns.

Next.js Webhook Handling and Event-Driven Architecture

Complete guide to webhook handling and event-driven architecture with Next.js and Supabase. Learn webhook security, retry mechanisms, event sourcing, and distributed system patterns.

Next.js Server Actions vs API Routes: When to Use Each

Understand the differences between Server Actions and API Routes in Next.js 15. Learn when to use each approach with real-world examples and performance comparisons.

Next.js + Supabase Performance: 10 Real Fixes

Ten fixes for slow Next.js + Supabase apps, each grounded in the official docs rather than a single unverifiable case-study number — RLS-indexed columns, N+1 joins, the connection-pooler trap on serverless, image transforms, and caching layers.

React Server Components: Complete Deep Dive

Next.js 15 vs 14: Real Benchmarks + Upgrade Verdict (2026)

What Next.js's own release notes actually say changed between 14 and 15 — caching defaults, async APIs, and Turbopack's real (and still-partial) stability status — plus the breaking changes that hurt on upgrade.

Next.js Performance Optimization for Indie Developers

Master Next.js performance optimization techniques. Learn how to achieve perfect Core Web Vitals scores, optimize images, reduce bundle size, and deliver lightning-fast user experiences.

Fix 'Hydration failed' in Next.js: 8 Root Causes (2026)

Hydration mismatch errors breaking your Next.js app? Learn the root causes and 8 proven fixes to eliminate these errors permanently.

Next.js 'Module not found: Can't resolve': 6 Fixes

Module not found errors only in production? Learn why Next.js builds fail after deploy and get 6 proven fixes that work on Vercel, AWS, and other platforms.

Next.js Turbopack Stuck on Compiling? 5 Fixes (2026)

Turbopack stuck on compiling in Next.js 15/16? Learn the exact causes and 5 proven fixes, plus how to disable Turbopack safely with next build --webpack when production builds crash.