macbook pro – Extremely slow Terminal startup on macOS Sequoia (M3 Mac Pro)

Problem

On my new M3 Mac Pro (36 GB RAM) running macOS Sequoia 15.3.2, launching a new interactive shell in both the built‑in Terminal.app and the GPU‑accelerated Ghostty takes orders of magnitude longer than on my Linux/Windows boxes. I frequently use tmux, and spawning new panes can take > 1 second, whereas on Linux/Windows it’s < 0.03 s.

What I’ve Tried

1. Stripped-down ~/.zshrc

   • Disabled ALL plugins; still see initial startup ~1.2 s and subsequent ~0.1–0.2 s.

2. Custom timing function:

timezsh () {
  shell=${1-$SHELL}
  for i in $(seq 1 10); do
    /usr/bin/time $shell -i -c exit
  done
}

Results (no plugins):

real 1.24; user 0.10; sys 0.05
real 0.15; user 0.04; sys 0.03
real 0.13; user 0.03; sys 0.03
real 0.14; user 0.03; sys 0.03

With plugins enabled:

3. compinit tweaks & zprof analysis

   • Precompiled cache, removed old dump files, no significant improvement.

4. Homebrew & some cli tools also feel sluggish, suggesting a deeper system issue.

Environment

• macOS: Sequoia 15.3.2
• Hardware: Apple M3 Pro, 36 GB RAM
• Shells tested:
  • /bin/zsh (default)
  • /bin/bash
• Measurement tool: /usr/bin/time and zprof

Questions

Has anyone observed 1-2 second cold startup on an M3 Mac for Zsh, even with minimal config?
Are there known system-wide factors (e.g. Rosetta layers, filesystem checks, notarization delays) that could slow down every new shell instance?
How can I diagnose what’s happening during that 1 second (e.g. tracing dynamic libraries, file-system stalls)?
Any tweaks or workarounds to get terminal/spawn times closer to < 0.1 s?

Thanks in advance for any insights!