Fetching NPM Source Code

Uses the opensrc CLI tool to fetch source code for npm packages and GitHub repositories, enabling deeper context for analyzing implementations.

Capabilities

•Fetch npm packages: Download source code for any npm package at the installed version
•Fetch GitHub repositories: Clone source code directly from any public GitHub repo
•Auto-detect versions: Automatically matches installed package versions from lockfiles
•List sources: View all previously fetched packages
•Remove sources: Clean up fetched source code
•Auto-configure: Optionally updates .gitignore, tsconfig.json, and AGENTS.md

Installation

The skill uses opensrc, which must be installed globally:

bash

npm install -g opensrc

Or use with npx (no installation needed):

bash

npx opensrc <package>

Common Workflows

Fetch a Single Package

Get source code for a package at your installed version:

bash

opensrc zod

This stores source in opensrc/zod/ and auto-detects the version from your lockfile.

Fetch Specific Version

bash

opensrc zod@3.22.0

Fetch Multiple Packages

bash

opensrc react react-dom next

Fetch GitHub Repository

bash

# Using shorthand
opensrc facebook/react

# Using full GitHub URL
opensrc https://github.com/colinhacks/zod

# Fetch specific branch or tag
opensrc owner/repo@v1.0.0

GitHub repos are stored as opensrc/owner--repo/.

List All Fetched Sources

bash

opensrc list

Displays all packages with versions and paths. The data is stored in opensrc/sources.json.

Remove a Source

bash

# Remove package
opensrc remove zod

# Remove GitHub repo
opensrc remove owner--repo

File Modifications

On first run, opensrc asks permission to modify:

•.gitignore — adds opensrc/ to ignore list
•tsconfig.json — excludes opensrc/ from compilation
•AGENTS.md — adds section pointing agents to source code

Skip the prompt with:

bash

opensrc zod --modify      # Allow modifications
opensrc zod --modify=false  # Deny modifications

Preferences are saved to opensrc/settings.json.

Output Structure

After fetching, your project contains:

code

opensrc/
├── settings.json       # Your modification preferences
├── sources.json        # Index of fetched packages
└── zod/
    ├── src/
    ├── package.json
    └── ... (all source files)

The sources.json tracks what's available:

json

{
  "packages": [
    { "name": "zod", "version": "3.22.0", "path": "opensrc/zod" }
  ]
}

Use Cases

•Understanding implementation details: When types alone aren't enough
•Reviewing package code: Before relying on a dependency
•Finding examples: See how a package uses internal features
•Debugging: Trace through actual implementations
•Learning: Study well-written open source code