I'm assuming this was with the visual editor (or the new wikitext editor), correct?

In T168236#3361336, @matmarex wrote:

I'm assuming this was with the visual editor (or the new wikitext editor), correct?

Yes, it was with the new Wikitext editor.

This only happens when you load the page via action=edit

Change 362443 had a related patch set uploaded (by Esanders; owner: Esanders):
[mediawiki/extensions/VisualEditor@master] Regenrate title in all non-view page scenarios

https://gerrit.wikimedia.org/r/362443

Change 362443 merged by jenkins-bot:
[mediawiki/extensions/VisualEditor@master] DesktopArticleTarget: Regenerate title in all non-view page scenarios

https://gerrit.wikimedia.org/r/362443

I fought against the same issue a couple of years ago.

For some browsers the <title> element might get new content.

However, some do not expect changing titles. There it became necessary to remove the <title> entirely from DOM and insert a new one, which I do always after that experience and it worked properly.

From the JS perspective the new text was stored and could be retrieved again, but it was not the same as displayed in the system which kept the old one.

I don’t know how that is implemented right now.

The tab title displaying editing occurs when you first open VE and then switch to source mode make make changes the publish those changes, to its as if the first action of changing the title to editing via VE hasnt been closed down when the switch takes place, I using chrome Version 66.0.3359.181 (Official Build) (64-bit) in windows 10

@Gnangarra Thanks for the report. I'll split it to a separate task rather than reopen this one, if you don't mind. It seems to be a separate issue.