Claude Code Source Code Breakdown

Earlier today (March 31st, 2026) - Chaofan Shou on X discovered something that Anthropic probably didn’t want the world to see: the entire source code of Claude Code, Anthropic’s official AI coding CLI, was sitting in plain sight on the npm registry via a sourcemap file bundled into the published package. I’ve maintained a backup of that code on GitHub here but that’s not the fun part Let’s dive deep into what’s in it, how the leak happened and most importantly, the things we now know that were never meant to be public. How Did This Even Happen? This is the part that honestly made me go “…really?” When you publish a JavaScript/TypeScript package to npm, the build toolchain often generates source map files (.map files).

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