Next.js "Module not found: Can't resolve" - Fix in CI

During next build the bundler could not resolve an import. The package is missing, a paths alias is not honored, or the file casing differs on the Linux runner.

What this error means

The build fails with Module not found: Can't resolve '<module>' referencing the importing file.

Failed to compile.

./app/page.tsx
Module not found: Can't resolve '@/components/Header'

https://nextjs.org/docs/messages/module-not-found

Common causes

Missing dependency

The package is imported but not in package.json, or the lockfile install omitted it.

Alias or case mismatch

A tsconfig paths alias is wrong, or the filename case differs from the import on case-sensitive Linux.

How to fix it

Install the dependency and verify the path

Install the package.
Confirm the file exists with exact casing.

Terminal

npm install <package>
ls -la components/Header.tsx

Confirm tsconfig path aliases

Ensure baseUrl and paths map your alias to a real directory.

tsconfig.json

// tsconfig.json
{ "compilerOptions": { "baseUrl": ".", "paths": { "@/*": ["./*"] } } }

How to prevent it

Commit a lockfile and install with npm ci.
Develop on a case-sensitive filesystem to catch casing bugs before CI.