Anthropic AI programming tool Claude Code's npm package leaked full source code

Gate News, March 31, blockchain security company Fuzzland intern researcher Chaofan Shou pointed out on X that the npm package for Anthropic’s AI programming tool Claude Code contains a complete source map file (cli.js.map, about 60MB), from which all TypeScript source code can be reconstructed. Verified: the latest version released today, v2.1.88, still includes this file. It contains the complete code for all 1,906 Claude Code proprietary source files, covering implementation details such as internal API design, an analytics telemetry system, encryption tools, and inter-process communication protocols. A source map is a debugging file used in JavaScript development to map minified code back to the original source code; it should not appear in production release packages. In February 2025, an early version of Claude Code was already exposed for the same issue. At the time, Anthropic removed the old version from npm and deleted the source map, but the problem later reappeared. On GitHub, multiple public repositories have already extracted and organized the reconstructed source code, with ghuntley/claude-code-source-code-deobfuscation receiving nearly a thousand stars. The leaked material is the client implementation code for the Claude Code CLI tool, not model weights or user data, so it poses no direct security risk to ordinary users. However, the continued exposure of the full source code means the internal architecture, security mechanisms, and telemetry logic are completely transparent to the outside world.