Opening New Terminal Tab Moves Window Above Dock This is difficult to explain, so please bear with me.

When I open a new tab in Terminal, the Terminal window moves. This only happens when the window is at the bottom of the screen. The window moves up vertically just enough so that it is not below/beside the dock anymore. It does not move horizontally. It also remains the same size.

No other apps behave this way, only Terminal. I am using version 2.8.

Terminal did not behave this way in macOS 10.12 Sierra. It started behaving this way when I updated to 10.13.1 High Sierra.

Step by step, this is what happens:


Open Terminal.
Move Terminal window to bottom left or right corner of screen (flush with the edges).
Open new tab in Terminal.
Terminal window moves up so that it is higher than the dock.


How do I prevent #4 from happening? How do I prevent the Terminal window from moving by itself when I open a new tab?



Before





After
According to macOS, windows should not be behind the Dock. When the bounds of a window are updated, macOS moves any windows from behind the Dock above the Dock.

The window bounds update when you add a new tab, so macOS looks at those bounds and moves them such that they don't overlap with the Dock section of the screen. There's no way to change this currently.

As for why this happens in High Sierra and not in Sierra, I presume it's because Terminal now uses the unified tabs functionality provided in AppKit.

Terminal has always had tabs, but macOS recently introduced tabs as part of the OS, for any app to use. I believe Terminal now uses this functionality for its tabs, which has caused this. You can test this by opening Terminal with multiple tabs and pressing ⇧⌘\ for Show All Tabs — this is functionality provided system-wide by the OS, not by Terminal, for managing tabs including the tab bar.