James' Growth Diary
Jun 9, 2026 · Backend Development
The 12 ms Secret: How Claude Code Optimizes CLI Startup Performance
This article dissects Claude Code’s 12 ms --version response and its 1.1 MB lazy‑loaded footprint, explaining a four‑layer startup chain that uses fast‑path handling, parallel prefetch, selective lazy imports, memoized global initialization, and compile‑time dead‑code elimination to achieve near‑instant CLI launch.
BunCLILazy Loading
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