Claude Code's Source Code Exposed — Every System Explained From Scratch (512K Lines)

Anthropic's Claude Code source just leaked. All 512,000 lines of it. If you've used Claude Code, you know it feels like magic — you type a message, it reads your files, edits your code, runs your tests, and somehow gets it right most of the time. But magic doesn't scale. Engineering does. And let me tell you — after going through this entire codebase, I'm genuinely impressed. Not by any single brilliant algorithm, but by the sheer thoughtfulness of every decision. You can tell this was built by people who've been woken up at 3 AM by production incidents and decided "never again." I've distilled the whole thing into plain-English explanations. No assumptions about your background. If you know what a function is, you can follow this. Let's go. Table of Contents The Query Engine — The Heart of Everything How Conversations Stay Within Limits — 5 Compression Layers Error Recovery — What Happens When Things Go Wrong Tools — How Claude Actually Does Things Permissions — The Safety Net The Sys