Invocable method with callout fails with Callout Loop not allowed""

We think we know the problem, but are looking for confirmation that this isn’t supported…

We have a Skuid page that’s hosted in a Community that runs on the Partner Central template. The page has a button that calls an invocable method in an Apex class - that method makes a callout to a remote system.

This works in Preview mode; but in the Community, it fails with a “Callout Loop not allowed” response.

We’ve noted that the URL called is different in the Community than when run in Preview, so it appears some Skuid proxy is called when running in the Community. Our theory is that this proxy is called as a web service; this tries to call our method which makes a callout, but this is blocked as callouts from callouts are not allowed.

The only thing going against this theory is that the Skuid docs say that calling an invocable method uses an API method - it doesn’t limit this to any particular run time, so I would’ve thought we’d encounter the error even in preview…

We’re looking at if we can move this to a VF page hosting a Skuid component instead, and invoke that from a pop up…