Yep — you can install Oh My Zsh without changing your user’s login shell.

How to do it

1. Make sure zsh is installed macOS already has it. On Linux: sudo apt install zsh (or your distro’s package manager).
2. Run the installer but prevent shell changes/auto-launch

   export CHSH=no RUNZSH=no KEEP_ZSHRC=yes
   sh -c "$(curl -fsSL https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"
   

   • CHSH=no → don’t change your default shell
   • RUNZSH=no → don’t auto-start zsh after install
   • KEEP_ZSHRC=yes → don’t overwrite an existing .zshrc (safe even if you don’t have one yet)
3. Use it only when you want
   • Start a zsh session manually: zsh (or exec zsh to replace the current shell).
   • Or set just one terminal profile / VS Code terminal to run zsh while leaving your system default as bash.

Verify your default shell didn’t change

• Quick check in a new terminal: echo "$SHELL"
• Linux: getent passwd "$USER"
• macOS: dscl . -read /Users/$USER UserShell

Later, if you do want to switch

• Change login shell: chsh -s /bin/zsh (Linux) or chsh -s /bin/zsh on macOS (then log out/in).
• Revert to bash: chsh -s /bin/bash.

That’s it—Oh My Zsh will be installed and ready, but only active when you launch zsh.