Bug 187685

I started noticing this in Mojave Beta 3, but the use case that brought this on I think may have only happened after B3 came out so not sure if affects earlier versions.

Issue
The issue was when looking at websites the top roughly 50px (didn't measure precisely yet) gets cut off and you can't scroll up to see it. Toggling the bookmark bar on/off allows you to access the top of the site again. After further testing I now know how to reproduce on on other Macs finally so opening this report.

Background, I have thousands of keychain logins I wanted to migrate to 1Password. In Mojave all the scripts to do this automatically are no longer possible currently so decided to do manually, where I put all the urls of sites I want to change from keychain in Numbers.app. I'd then click on a link in numbers and save the new login to 1P in Safari Technology Preview. It involved clicking the Login/Signin on each site which is almost always on the top of the site and noticed it was cut off on each site.

I did more testing to isolate the issue. It doesn't seem to affect normal Safari only the Preview (but not 100% certain of that yet). Definitely happens in Beta 3, but not sure if happened in beta 2 since only started this password changing in Beta 3 I think. If you visit a website normally in Safari Preview by typing it into the URL field the issue does not happen.

If you click on a link in Numbers.app or presumably other apps, I was able to replicate in TextEdit.app as well, the issue is reproducible. If I have no safari tabs open and click on say GitHub.com in Numbers.app the issue happens. If I then clicking on say Yahoo.com it doesn't happen (since a tab is already open). If I close out all the tabs and click on Yahoo.com it does happen. Also was able to reproduce on two Macs 2017 MBP and 2017 iMac both running latest beta 3 and latest safari preview (both logged into accounts associated with my iCloud account).

I haven't done more extensive testing yet but hopefully enough info so you can reproduce on your end. If not let me know and happy to provide anything you need such as videos of it, etc.

How to Reproduce
1. Install latest macOS Beta 3 and latest Safari Technology Preview.
2. Add links such as Yahoo.com, Github.com, etc to an app such as Numbers.app or TextEdit, etc.
3. Close out all Safari Preview windows.
4. Click on a link from Numbers/TextEdit/etc.

Notice the header of site is cut off and unreachable through scrolling. (toggling bookmark bar fixes).

To reproduce again you need to close out the tabs since clicking on addition links will work fine until you do.