Starting somewhere last year, something happened to the terminal on bigsur, on every clean start up it would hang for many seconds until the prompt was there.
There are some people who have found some solutions, I tried all of them until it something worked, so here is a compilation for you to try as well.
For some the problem seemed to be they did not accept the license:
sudo xcodebuild -license accept
Related to this, could be that the command line tools are not properly installed:
In the interest of time this is what seemed to have worked for me
sudo rm -rf /Library/Developer/CommandLineTools sudo xcode-select --install sudo xcode-select -switch /Library/Developer/CommandLineTools
For some the problem seems to be the integrated git version, replace it via brew:
brew install git
Others report that the zsh version that comes with mac is old, replace it with:
brew install zsh
One user reports having a nvm default alias caused the issue for him:
Tried all Google results and nothing works. Eventually, I found it was caused by setting Node.js v8.x as default in nvm, alias default to system will resolve the issue. Although I don’t know why nvm need to run xcodebuild for Node.js v8.x.
Sometimes the slowdown could be caused by some extra step, I had a different problem with one of the apps I use, you can see what happens when you start a zsh session with:
zsh -i -c -x exit
I ended up trying a bunch of things here, disabling some plugins, nvm, trying to lazy load components
Zsh loads a lot of files for configuration, it could be possible (not in my case), that some of this is poorly configured, worth a try if you already tried everything above:
Hopefully this will solve your problem, mine was fixed somewhere between installing zsh via brew and re-installing the xcode-tools