Bug: ERR_REQUIRE_ESM when using @workflow/world-postgres in Next.js App Router

[rolivegab]

Describe the bug

When using @workflow/world-postgres with the Next.js App Router, the development server crashes with an ERR_REQUIRE_ESM error upon the first API request to a route that uses the workflow library.

Maybe the error occurs because @workflow/world-postgres is an ES Module ("type": "module"), but some part of the Next.js build process (seemingly triggered by the workflow library's internal runtime) attempts to load it using require()?

To Reproduce

1. Create a Next.js App Router project.
2. Install the following packages:
   • next: 15.3.5
   • workflow: 4.0.1-beta.11
   • @workflow/world-postgres: 4.1.0-beta.7
3. Set up a simple API route (/api/test/route.ts) that imports start from workflow/api.
4. Configure instrumentation.ts to initialize the postgres world.
5. Run the development server (next dev) and send a POST request to the API route.

Expected behavior

The API route should execute the workflow without crashing the server.

Error Log

Error: require() of ES Module /path/to/project/node_modules/.pnpm/@workflow+world-postgres@4.1.0-beta.7/.../node_modules/@workflow/world-postgres/dist/index.js from /path/to/project/apps/api2/index.js not supported.
Instead change the require of ... to a dynamic import() which is available in all CommonJS modules.
at createWorld (../../src/runtime/world.ts:47:14)
at getWorldHandlers (../../src/runtime/world.ts:74:17)
...

[pranaygp]

is this happening in next 16 too, or using turbopack in next 15?

[TooTallNate]

What is your Node.js version?

[rolivegab]

My node version is v20.18.3