Fix · Node, npm and build

Next.js: error about webpack config versus Turbopack

Not checked against the vendor's current screens

What you may see

The build fails saying a webpack configuration exists but Turbopack is the default

Most likely cause

Newer Next versions use Turbopack by default, and a custom webpack setting from an older project or tutorial is not read by it.

Check first (about two minutes)

Check the Next version in package.json and whether next.config has a webpack function.

The fix prompt

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The exact error or what you see

What you did before it happened

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Prompt language

You are a patient senior engineer who knows Node.js, npm and build tools and explains them to people who are not developers. I am not a developer, so explain every step in plain words and tell me exactly which button, menu or command you mean. If you are not sure about something, say so; do not guess.

Menu and button names change over time. If you cannot find a button or page I mention, say so and tell me what to look for instead of guessing.

THE PROBLEM
Next.js: error about webpack config versus Turbopack

THE EXACT ERROR OR WHAT I SEE
[paste the exact error here]

WHAT I DID BEFORE IT HAPPENED
[write in a few words what you did before it happened]

MOST LIKELY CAUSE
Newer Next versions use Turbopack by default, and a custom webpack setting from an older project or tutorial is not read by it.

DO THESE STEPS, IN THIS ORDER
1. Read the exact message and the Next documentation for my version (do not guess options).
2. Find what the webpack function does; replace it with the supported setting if there is one.
3. If it must stay, tell me how to build with webpack for that script, explaining the trade-off.
Stop and tell me if what you see does not match a step. Do not skip ahead.

CHECK THAT IT WORKED
- npm run build passes with the chosen bundler.
Tell me exactly what I should see on the screen when it works.

DO NOT CHANGE
- Do not downgrade Next without telling me.
- Anything I did not ask about: the design, the text, other pages, other settings or the data.
- Do not delete files, data or branches, do not reset or force-push, and do not rewrite history, unless you first show me exactly what would be lost and I say yes.
- Do not paste, print or ask me to paste a password or secret key into this chat. If one is needed, tell me which settings page of the right service to store it in.

WHEN YOU FINISH
Explain in simple words what you changed (file by file or setting by setting), why you changed it, and how I can undo it.

Paste it into Claude, ChatGPT, Gemini or Cursor, then follow what it says.

After you tried it, did it work?

Steps

Read the exact message and the Next documentation for my version (do not guess options).
Find what the webpack function does; replace it with the supported setting if there is one.
If it must stay, tell me how to build with webpack for that script, explaining the trade-off.

Do not do this

Do not copy webpack tweaks from old tutorials.
Do not downgrade Next without telling me.

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