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Claude Code source map leak via npm package

March 26, 2026Shruti, Rohan Paul, TestingCatalog News

Multiple creators report Anthropic accidentally shipped a huge map file in the Claude Code npm package, exposing roughly 512,000 lines of TypeScript. The leak triggered rapid mirroring, reverse engineering, and security concerns.

Anthropic leaked 512,000 lines of Claude Code source code yesterday.
4 AM. Anthropic pushes an update to npm. Inside the package: their entire codebase. A 60 MB debugging file accidentally bundled in.
Anthropic’s official npm package for Claude Code had accidentally shipped a massive `.map` source map file. Boom — the entire ~512,000-line TypeScript codebase
Anthropic’s official npm package for Claude Code had accidentally shipped a massive `.map` source map file.
Boom — the entire ~512,000-line TypeScript codebase
Anthropic built a whole system called "Undercover Mode" to stop Claude from accidentally leaking internal codenames in git commits. Then shipped the entire source code in the npm package. 512,000 lines.
Shruti
Rohan Paul
TestingCatalog News
Gergely Orosz
Alex Volkov (Thursd/AI)
Min Choi
Wes Roth
Poonam Soni
Bindu Reddy
Carlos E. Perez
claude codenpmleakanthropicclaude codesource codesystem prompt

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