On 31 March 2026, developers reported that Anthropic’s Claude Code CLI distribution on npm included a source map that allowed reconstruction of roughly 512,000 lines of TypeScript across a large file count. The episode is best categorized as accidental intellectual-property exposure (proprietary client/tooling source), not a leak of Anthropic customers’ personal data or model weights.
Relation to other March 2026 Anthropic items
This is separate from the Sanity CMS configuration issue that exposed unpublished marketing assets earlier the same week.
Canonical record: Anthropic Claude Code (npm) 2026 on BreachHistory.