Anthropic’s Claude Code Source Exposed Through npm Source Maps
Summary
A report says source maps published with Claude Code on the public npm registry enabled reconstruction of Anthropic’s TypeScript source. Anthropic secured the registry, but reconstructed copies are reportedly circulating publicly.
Key points
- The exposure reportedly resulted from publishing production code with source map files to the public npm registry, allowing reconstruction of the original TypeScript.
- The exposed source reportedly includes a roughly 46,000-line QueryEngine.ts and implementations for more than 40 agent tools.
- The article says the source includes Claude Code’s permission system and feature flags associated with unreleased capabilities.
- The report says Anthropic secured the registry, but reconstructed copies are already being hosted publicly.
- The article says the exposure did not grant access to personal user data; it primarily exposed proprietary code and internal logic.
Article Details
- Victim Organization
- Anthropic
- Incident Type
- Accidental exposure of proprietary source code through source maps published in the public npm registry
- Disclosure Date
- 2026-03-31
- Data Types Exposed
- Proprietary TypeScript source code
- Internal system prompts
- Permission-system logic
- Build-time feature flags and references to unreleased features
- Affected Records
- Not applicable; no personal user data was reported exposed.
- Affected Data Size
- The exposed source included a roughly 46,000-line QueryEngine.ts file and implementations for more than 40 agent tools; total size was not disclosed.
- Operational Impact
- Anthropic secured the registry. The article reports that reconstructed copies of the source were already being hosted publicly; no service disruption was reported.
- Ransom Or Extortion
- Unknown
- Claim Status
- confirmed