After upgrading, I noticed my terminal got extremely slow (MBP 2013). There is a noticeable input delay, moving the window or switching to another application lags and skips the animation. I noticed the background needs around 1s to recreate the opacity/blur effect after window switching, so I tried disabling the effect in the settings, which restored previous performance completely.
Is this a known issue? I'd like to have my transparent, blurred background back.
High Sierra – Terminal lags if background opacity is set
high sierraterminal
Related Solutions
It's time to move over to iTerm2. It's highly unlikely a fix will be found in the wild because it doesn't make sense to do so.
It's no longer under active development. From the About page on their website
SIP must be disabled to use. (IMO), disabling SIP to get a non-critical app to function is not a wise path to pursue. SIP adds a layer of protection to your system that isn't worth disabling for a terminal app. From their web page specifically on SIP
System Integrity Protection (SIP) is a new security feature introduced by Apple. That's good, but unfortunately it prevents TotalTerminal from augmenting Terminal. This article will tell you how to configure your machine, so that you can use TotalTerminal. Before you do this, it is important to get informed about what System Integrity Protection is, and what it means to turn it off. Technical details are well covered in SIP review on Ars Technica. Apple also provided some information here.
And finally, the note from the developer himself:
Do you really depend on TotalTerminal workflows so much that you want to possibly lower your system security? Frankly, I'm going to stop TotalTerminal development because I have personally switched to iTerm 2. It offers similar functionality to Visor and comparable features to build-in Terminal.app.
TL;DR
Total Terminal requires you to disable security. It would be counter productive to find/create/bodge a workaround when ultimately you would end up with an insecure system when there are already excellent alternatives (like iTerm2) that don't have this vulnerability/flaw/drawback.
The Terminal settings allow you to escape this hell.
Terminal > Preferences (or Cmd-,) > General:
Second to last item: "Use Cmd-1 through Cmd-9 to switch tabs"
Unselect this option and it all goes back to how it was before!
Best Answer
So, for completeness' sake since there doesn't seem to be a better answer as of yet, I'll add my solution.
If your Terminal.app started showing the behavior outlined in the question and you have modified the blur/opacity settings, turning these off will restore previous performance. To do so, open the terminal settings (⌘ + ,), switch to the Profile tab and click on the background color picker next to color & effects. Here, set the faders for opacity and blur to 100%.
If someone finds a way to enable transparency again without trashing performance, I'll be happy to accept their answer.