Using external_links in sidekick containers

I was able to successfully use external_links in services to add an alias to a service in a different stack:

 - otherstack/someservice:alias

However, once I mark this container as a sidekick, external_links no longer seem to work (I can still ping “someservice.otherstack”, but I cannot ping “alias” anymore).

Is this a known limitation or potentially a bug?

You are unable to set links on the sidekick (as the UI shows), but you can add the links in the primary service. Even though the link is set at the primary service level, the sidekick will be able to ping the alias.