Is this a bug in VisualEditor, perhaps? Or in Parsoid? Does it happen when editing article pages with VE?

I can't really test, because I'm getting

TypeError: $trigger.data(...).$dialog is undefined load.php:4:588
"Exception in store-localstorage-update:" load.php:177:555
"NS_ERROR_DOM_QUOTA_REACHED: Persistent storage maximum size reached" DOMException >[NS_ERROR_DOM_QUOTA_REACHED: "Persistent storage maximum size reached"
code: 1014
nsresult: 0x805303f6
location: https://pt.wikipedia.org/w/load.php?debug=false&lang=pt-br&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=4%2BsuyLdS:175]

when I access
https://pt.wikipedia.org/w/index.php?title=Usu%C3%A1rio%28a%29:He7d3r/Testes&veaction=edit
using Firefox 38 on linux.

TypeError: $trigger.data(...).$dialog is undefined load.php:4:588

Ouch, that sounds like a local script / user script / Gadget error. It doesn't happen for me; maybe you could try logged-out or using incognito?

Apparently, that comes from

$trigger.data('callout').$dialog.find('li.cx-campaign-translations').replaceWith(getTranslationsItem());

https://github.com/wikimedia/mediawiki-extensions-ContentTranslation/blob/88324ec56bd780ce1d27df70c819a8a165181990/modules/campaigns/ext.cx.campaigns.contributionsmenu.js#L123
because VisualEditor works again if I disable the beta feature on
https://pt.wikipedia.org/wiki/Special:Preferences#mw-prefsection-betafeatures

However, I was able to reproduce the problem reported here, i.e., I saw a working link when I added "en:Test" to my page:
https://pt.wikipedia.org/w/index.php?diff=42517031
As soon as I saved the page, the link disappears (as expected), so VisualEditor is not being good at showing how the page will look like after the edit is saved.

I created T101421: TypeError: $trigger.data(...).$dialog is undefined for that other bug.

https://www.mediawiki.org/w/index.php?title=User:Catrope/Sandbox&diff=1666237&oldid=1656914 shows that this only happens when you try to make an internal link to de:Foo. If you make an external link to http://de.wikipedia.org/wiki/Foo instead, VE correctly produces a link to :de:Foo.

Are this and T103635: Stop the user from adding a langlink when we think they wanted to insert an interwiki instead duplicates of T95850: Parsoid does not escape language prefixes in internal link hrefs, causing html2html round-trip failures?