Node ERR_REQUIRE_ESM "Must use import to load ES Module" - Fix in CI

ERR_REQUIRE_ESM means CommonJS code tried to require() a package that is ESM-only. Many popular packages have gone ESM-only, breaking projects that still use require.

What this error means

A CommonJS project (or compiled-to-CJS output) crashes with ERR_REQUIRE_ESM when loading a dependency that ships only ESM. It often appears right after upgrading such a dependency to a major that dropped CommonJS.

Node output

Error [ERR_REQUIRE_ESM]: require() of ES Module
/app/node_modules/chalk/source/index.js from /app/index.js not supported.
Instead change the require of index.js to a dynamic import() which is
available in all CommonJS modules.

Common causes

The dependency is ESM-only

A package published an ESM-only major (no CommonJS entry). CommonJS require() cannot load it synchronously.

Your project (or its build output) is CommonJS

If your package is CJS - or TS compiles to CJS - a plain require of the ESM package fails.

How to fix it

Move to ESM or use dynamic import

Convert your module to ESM, or load the ESM-only package with await import().

// CJS interop without converting everything:
const chalk = (await import('chalk')).default;

// or make the package ESM:
// package.json -> { "type": "module" }

Pin a CJS-compatible version if you must

If converting is not feasible now, pin the last dependency major that still shipped CommonJS.
Plan the ESM migration (set "type": "module", fix imports) rather than pinning forever.
For TS, target ESM output (NodeNext) to consume ESM-only deps cleanly.

How to prevent it

Migrate projects to ESM as the ecosystem moves.
Use dynamic import() for ESM-only deps in CJS code.
Read release notes before bumping a dep to an ESM-only major.