Fix slow zsh startup in Git Bash on Windows. Why Oh My Zsh and Powerlevel10k take over a second to load under MSYS2, how to measure it, and safe fixes that cut zsh startup from 719 ms to 243 ms without losing a single plugin.
Keywords: oh my zsh slow startup windows, git bash zsh slow, powerlevel10k git bash windows, msys2 zsh startup time, zsh-defer, compinit slow, zprof, zsh profiling
⚠️ Warning: AI can make mistakes. Everything here changes your shell startup files (~/.zshrc,~/.bashrc, your Oh My Zsh install). One wrong line can leave you without a working terminal. Back up first, read every change before it is applied, and keep a second terminal (for example PowerShell) open so you can roll back. If you use the AI prompts at the end, supervise every step and approve each change yourself.