Loader stalls MessagePort since v24

Version

v24.15.0

Platform

Linux lab178 6.18.19-1.qubes.fc37.x86_64 #1 SMP PREEMPT_DYNAMIC Tue Mar 24 01:20:46 GMT 2026 x86_64 GNU/Linux

Subsystem

module

What steps will reproduce the bug?

In an async resolve hook of a custom loader, await a message from a MessagePort. The message never arrives and the promise never resolves.

This repository has a reproduction. It does a simple pong exchange with the main thread. On v23 and before it works. On v24 and later it hangs forever.

https://github.com/cinderflash/loader-stall

$ nvm use v23
Now using node v23.11.1 (npm v10.9.2)
$ node index.mjs
ping
PONG
ping
PONG
ping
PONG
$ nvm use v24
Now using node v24.15.0 (npm v11.12.1)
$ node index.mjs
(STALL FOREVER)
$ nvm use v25
Now using node v25.9.0 (npm v11.12.1)
$ node index.mjs
(STALL FOREVER)

How often does it reproduce? Is there a required condition?

On v24 and v25, 100% of the time.

On prior versions, this never happens.

What is the expected behavior? Why is that the expected behavior?

Ability to perform exchanges with the main thread within a loader hook.

I'd like to use this to acquire information available on the main thread to use in determining how to resolve the specifier.

What do you see instead?

Awaiting a message in a loader hook stalls forever. The message never arrives and the engine never detects an unresolved promise.

Additional information

No response

Commencez par exécuter la reproduction liée du blocage du loader, index.mjs, sur Node.js v23 et v24 afin de confirmer la régression. Étudiez le hook de résolution asynchrone du module loader et son comportement d’échange via MessagePort, puis ajoutez un test de régression montrant que le message arrive et que la promesse est résolue dans les versions actuelles.