Uncaught Error" when deploying a producer/consumer

[avioforse]

What versions & operating system are you using?
System:
OS: Linux 6.8 Linux Mint 22.1 (Xia)
CPU: (12) x64 AMD Ryzen 5 4600G with Radeon Graphics
Memory: 7.94 GB / 14.99 GB
Container: Yes
Shell: 5.2.21 - /bin/bash
npmPackages:
wrangler: ^4.119.0 => 4.119.0

Please provide a link to a minimal reproduction
https://github.com/avioforse/producer-worker

Describe the Bug
The code used was taken from the documentation:
https://developers.cloudflare.com/queues/configuration/javascript-apis/
The producer and consumer are launched locally.
However, upon deployment, it crashes with the error "Uncaught Error."

Please provide any relevant error logs
✘ [ERROR] A request to the Cloudflare API (/accounts/a5c6e109ce1ad693e0d3ebf59e31d990/workers/scripts/producer-worker) failed.

Uncaught Error: Dynamic require of "fs" is not supported
at null. (pyodideRuntime-internal:emscriptenSetup:6:9)
at null. (pyodideRuntime-internal:emscriptenSetup:206:16)
at null. (pyodideRuntime-internal:emscriptenSetup:29530:22) in
instantiateEmscriptenModule
at null. (pyodide-internal:python:157:78)
at null. (pyodide-internal:jaeger:12:16) in enterJaegerSpan
at null. (pyodide-internal:python:157:30) in loadPyodide
at null. (pyodide:python-entrypoint-helper:107:35)
at null. (pyodide:python-entrypoint-helper:113:11)
at null. (pyodide-internal:jaeger:12:16) in enterJaegerSpan
at null. (pyodide:python-entrypoint-helper:102:18) in getPyodide
[code: 10021]

[ryanking13]

could you please share your wrangler.jsonc files and, if possible, a minimal reproducer so we can reproduce?

[avioforse]

could you please share your wrangler.jsonc files and, if possible, a minimal reproducer so we can reproduce?

---

src/entry.py

from workers import Response, WorkerEntrypoint


class Default(WorkerEntrypoint):
    async def fetch(self, request):
        await self.env.MY_QUEUE.send("Hello avioforse!")
        return Response("Sent!")

wrangler.jsonc

{
	"$schema": "node_modules/wrangler/config-schema.json",
	"name": "producer-worker",
	"main": "src/entry.py",
	"compatibility_date": "2026-08-06",
	"compatibility_flags": [
		"python_workers"
	],
	"observability": {
		"enabled": true
	},
	"queues": {
		"producers": [
			{
				"queue": "queue-name",
				"binding": "MY_QUEUE"
			}
		]
	}
}

[ryanking13]

Thanks, I was able to reproduce the error. Let me take a look

[ryanking13]

This seems to be related to the incompatibility between nodejs_compat flag and Python worker. We are working on a fix. Meanwhile, you can use one of the following workarounds:

1. Set the compat date before 2026-08-03.

2. Set no_nodejs_compat compat flag in wrangler.jsonc

[dom96]

Looks like this is another way this error can manifest:

  Uncaught TypeError: The argument 'path' The argument must be a file URL object, a file URL string,
  or an absolute path string.. Received 'undefined'
    at null.<anonymous> (node:module:34:15) in createRequire
    at null.<anonymous> (pyodideRuntime-internal:emscriptenSetup:174:20) in _createPyodideModule
   [code: 10021]
  To learn more about this error, visit:
  https://developers.cloudflare.com/workers/observability/errors/#validation-errors-10021

Resolved after using no_nodejs_compat.

[ryanking13]

Yeah, it would show different error depending on the compat date (Python version).