James' Growth Diary

Apr 26, 2026 · Backend Development

Fast Path and Parallel Prefetch: The Secret to Sub‑Second CLI Startup

The article dissects Claude Code's sub‑second startup by explaining how a beta header enables Fast Mode, how parallel prefetch of MDM configuration and macOS Keychain is orchestrated with Promise.all in a preAction hook, and how multi‑layer gating and a cooldown mechanism ensure safe, recoverable performance gains.