What caused Anthropic's Claude Code leak?

A missing `*.map` in .npmignore let a massive source map ship publicly, linking to their full codebase ZIP.

How do I prevent source map leaks in my npm packages?

Add `*.map` and `dist/*.map` to .npmignore. Always run `npm pack --dry-run` before publishing.

What secret features were in Anthropic's leaked code?

KAIROS background agent, Undercover Mode for stealth commits, and a hidden Tamagotchi-style Buddy System pet simulator.

One Forgotten Line: How Anthropic Handed Rivals Their $340 Billion AI Crown Jewels

Picture firing up your terminal for the latest AI coding tool — only to accidentally download a company's entire secret playbook. That's what happened when Anthropic's negligence gifted the world their crown jewels.

DevTools Feed Apr 03, 2026 3 min read 17 views

⚡ Key Takeaways

One missing .npmignore line leaked 512K lines of Anthropic's Claude Code, costing billions in IP value. 𝕏
Exposed features include spy agents and CLI pets — signs of rushed, creative chaos. 𝕏
Run `npm pack --dry-run` religiously; AI tool leaks accelerate the open-source agent revolution. 𝕏

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#.npmignore #AI safety fail #Anthropic leak #claude-code #npm source map

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Originally reported by dev.to

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