Claude Code Source Code Leaked via npm Sourcemap — How to Check Your Packages

What this error means

npm package sourcemap exposes full Claude Code source code on registry is a Claude Code failure pattern reported for developers trying to find out if my npm packages are leaking source code via sourcemaps, understand the claude code source leak incident. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

On March 31, 2026, Chaofan Shou (@Fried_rice) discovered the entire source code of Claude Code accessible via sourcemap on the npm registry. A community backup repo was created (github.com/yasasbanukaofficial/claude-code) and a comprehensive analysis synthesized from 26 articles and 7 Hacker News threads (github.com/pankaj28843/understanding-claude-code).

Common causes

• On March 31, 2026, the entire source code of Claude Code was discovered publicly accessible via a sourcemap file in the published npm package. Developers search to understand what was exposed, whether their own packages have similar vulnerabilities, and how to audit npm packages for sourcemap leaks. This is a landmark supply-chain security event affecting all npm publishers.
• On March 31, 2026, Chaofan Shou (@Fried_rice) discovered the entire source code of Claude Code accessible via sourcemap on the npm registry. A community backup repo was created (github.com/yasasbanukaofficial/claude-code) and a comprehensive analysis synthesized from 26 articles and 7 Hacker News threads (github.com/pankaj28843/understanding-claude-code).

Quick fixes

1. Confirm the exact error signature matches npm package sourcemap exposes full Claude Code source code on registry.
2. Check the Claude Code account, local tool state, and provider configuration involved in the failing workflow.
3. Compare the failing environment with a known working setup, then change one configuration value at a time.

Platform/tool-specific checks

• Verify the command, editor, extension, or API client that produced the error.
• Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
• Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

1. Capture the exact error message and the command, editor action, or request that triggered it.
2. Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
3. Review the source evidence below and compare it with your environment.
4. Apply one change at a time and rerun the smallest failing action.
5. Keep the working fix documented for the team or deployment environment.

How to prevent it

• Keep provider/tool configuration documented.
• Record non-secret diagnostics such as tool version, provider name, model name, and command path.
• Add a lightweight check before CI or production workflows depend on the tool.

Sources checked

• https://github.com/yasasbanukaofficial/claude-code
• https://github.com/pankaj28843/understanding-claude-code

Evidence note: On March 31, 2026, Chaofan Shou (@Fried_rice) discovered the entire source code of Claude Code accessible via sourcemap on the npm registry. A community backup repo was created (github.com/yasasbanukaofficial/claude-code) and a comprehensive analysis synthesized from 26 articles and 7 Hacker News threads (github.com/pankaj28843/understanding-claude-code).

Related errors

• npm sourcemap leak prevention best practices
• How to audit npm packages for exposed source code
• Webpack sourcemap production build security

FAQ

What should I check first?

Start with the exact npm package sourcemap exposes full Claude Code source code on registry text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed Claude Code workflow until the root cause is understood.

Is this guaranteed to have one fix?

No. The imported evidence supports the troubleshooting path above, but tool behavior can vary by account, plan, version, provider, and local configuration.

How do I know the fix worked?

Rerun the same command, editor action, or request. The fix is working when that action completes without npm package sourcemap exposes full Claude Code source code on registry.