What I Learned from Reading Claude Code’s Reconstructed Source

What I Learned from Reading Claude Code’s Reconstructed Source Around March 31, 2026, it became widely known that parts of Claude Code CLI’s implementation could be reconstructed from source maps that had remained in the npm package. A public mirror circulated for a while, but it was not an official open-source release by Anthropic, and it has since turned into a different project. This post is a memo of my own impressions after reading a reconstructed copy of the source that I had saved locally at the time. Rather than discussing the current state of any public mirror, I want to focus on the design characteristics that became visible from actually tracing through the code. My first impression: this is a much larger product codebase than I expected The first thing that surprised me was the sheer size of the codebase. In the reconstructed source I had on hand, there were roughly 1,900 files and about 510,000 lines of code. This is not a small single-purpose CLI. It is a fairly large pro