Apple - Opening tab in Terminal resizes window
While this is not a full solution but more of a workaround, I still thought it's worth sharing.
Like many on this thread, I noticed that, much to my annoyance, the Terminal window changes size when I add new Tab on El Capitan (10.11.3). I'm also using Spectacle for arranging my windows from the keyboard. I thought it might be an issue with spectacle but the same happens when I quit spectacle and resize Terminal windows with touchpad.
From what I noticed it only happens to me when when the below sequence is followed: 1. Open a new Terminal window 2. Add a new tab 3. Make the window smaller (height or width) 4. Add a new tab, and this one will change the size of the window.
Nothing happens when I make it bigger. I figured through experimentation that each and every tab in the window must be holding it's dimensions form when it was last viewed. In this particular scenario the last new tab in step 4 will change the size of the window to what it was when tab 1 was last viewed.
Now this is most important bit. The new tabs will adjust its dimensions to the biggest tab in the window.
Workaround: When I resize the Terminal window, I use Shift+CMD+Arrows to quickly browse through all the tab in this window. If I do that, new tabs will not affect the size of the window.
While it might be useful to some, I understand that it is not really practical, especially if you have a lot of tabs open. It is my way of dealing with this until a proper solution comes along.
This behavior is due to the Window settings in Terminal. All new terminals open to what is specified under Window (default is 80 x 24). When you open a tab, it resizes the window to the new tab.
I wasn't able to find a solution to this for Terminal.app, however, I've since switched to iTerm 2, and it doesn't suffer from this issue. All new tabs open to the same dimensions as the existing window they're opened into, rather than resizing the window to the default.
You can find iTerm 2 at http://www.iterm2.com/
Open Terminal
Click on Terminal on the menubar, go to Preferences
Select General
Change the option 'New tabs open with' to 'Same Profile'