Anthropic leaked 500,000 lines of its own source code

Evidence record

Axios March 31 reporting based partly on an Anthropic spokesperson. A routine Claude Code release exposed a debugging/source-map artifact and reference to original code. The company acknowledged human packaging error, said no customer data or credentials were exposed, and denied an intrusion. Scope is Claude Code client/harness source, not model weights.

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Claim-level citations (5)

• supportsClaude Code release exposed proprietary agent harness source through a debugging artifact: Contemporaneous r/ClaudeAI discussion linked a Chaofan Shou X disclosure as the first widely circulated report; the source post and public package were not independently fetched for this dossier.

  Paragraph attributing discovery to Chaofan Shou

• supportsClaude Code release exposed proprietary agent harness source through a debugging artifact: A March 31, 2026 public Claude Code release accidentally included source-revealing debugging material, according to reporting and Anthropic's acknowledgment of packaging error.

  State of play and Anthropic spokesperson statement on packaging error

• supportsClaude Code release exposed proprietary agent harness source through a debugging artifact: The disclosed material was Claude Code application and harness source, described as roughly 500,000 lines across nearly 2,000 files, not a leak of the underlying Claude model weights. Anthropic said no sensitive customer credentials or customer data were involved.

  Opening, file/archive description and spokesperson quotation

• supportsClaude Code release exposed proprietary agent harness source through a debugging artifact: Anthropic attributed the March disclosure to human release-packaging error, denied exposure of sensitive customer data or credentials and said it was rolling out preventive measures; the inspected statements do not document a verified completed long-term prevention rollout.

  What they're saying, Anthropic spokesperson statement beginning Earlier today and follow-up statement This was a release packaging issue

• supportsClaude Code release exposed proprietary agent harness source through a debugging artifact: Axios reports that the publicly shipped debugging artifact pointed to a ZIP archive on Anthropic-owned cloud storage containing nearly 2,000 source files and about 500,000 lines of Claude Code client code. The original package and archive were not independently downloaded in this review.

  State of play, bullet beginning The file, which was quickly discovered, and preceding release paragraph