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# Yarn
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Yarn is a fast, reliable, and secure dependency management tool for JavaScript/Node.js projects. It serves as an alternative to npm with enhanced features including offline mode, deterministic installs, network performance optimizations, and flat dependency resolution. Yarn provides comprehensive dependency management capabilities with caching mechanisms, detailed lockfile format for reproducible builds, and integrity verification through checksums.
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## Package Information
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- **Package Name**: yarn
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- **Package Type**: npm
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- **Language**: JavaScript (Node.js)
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- **Installation**: `npm install -g yarn` or download from https://yarnpkg.com/
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- **Binary**: `yarn`, `yarnpkg`
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- **Version**: 1.22.22
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## Core Imports
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Yarn is a command-line tool, so it doesn't use traditional imports. Instead, it's invoked via shell commands:
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```bash
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# Global installation
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npm install -g yarn
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# Usage via npx (no installation required)
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npx yarn <command>
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# Direct binary usage (after global install)
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yarn <command>
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yarnpkg <command>  # Alternative binary name
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```
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## Basic Usage
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Yarn is primarily used as a command-line tool for managing dependencies:
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```bash
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# Install dependencies
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yarn install
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# Add a dependency
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yarn add react
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# Add a dev dependency
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yarn add --dev jest
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# Remove a dependency
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yarn remove lodash
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# Run scripts
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yarn run build
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yarn test
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# Upgrade dependencies
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yarn upgrade
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```
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## Architecture
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Yarn is built around several key components:
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- **CLI Interface**: 30+ commands for complete package management workflow
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- **Configuration System**: RC files, registry management, and workspace support
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- **Lockfile Management**: Deterministic dependency resolution with yarn.lock
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- **Package Resolution**: Multi-registry support with exotic resolvers (Git, GitHub, etc.)
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- **Cache System**: Offline-first architecture with intelligent caching
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- **Workspace Support**: Monorepo management with workspace-aware operations
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- **Integrity Checking**: Checksum verification for security
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## Capabilities
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### Package Management Commands
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Core commands for installing, adding, removing, and upgrading dependencies.
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```bash { .api }
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# Install all dependencies from package.json
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yarn install [--production] [--frozen-lockfile] [--offline]
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# Add dependencies to package.json
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yarn add <package> [--dev] [--peer] [--optional] [--exact] [--tilde]
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# Remove dependencies from package.json
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yarn remove <package>
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# Upgrade dependencies
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yarn upgrade [package] [--latest] [--exact] [--pattern]
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```
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[Package Management](./package-management.md)
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### Project Commands
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Commands for project initialization, script execution, and development workflow.
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```bash { .api }
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# Initialize new project
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yarn init [-y] [--private]
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# Create project from template
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yarn create <starter-kit-package> [args]
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# Run package scripts
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yarn run <script-name> [args]
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yarn <script-name>
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# Execute binaries
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yarn exec <command> [args]
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# Run Node.js
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yarn node [args]
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```
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[Project Management](./project-management.md)
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### Information Commands
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Commands for inspecting packages, dependencies, and project status.
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```bash { .api }
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# Show package information
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yarn info <package> [field]
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# List installed packages
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yarn list [--depth] [--pattern]
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# Show why package is installed
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yarn why <package>
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# Show outdated packages
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yarn outdated [package]
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# Show license information
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yarn licenses list|generate-disclaimer
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# Show binary locations
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yarn bin [package]
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```
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[Information Commands](./information-commands.md)
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### Registry Commands
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Commands for interacting with npm registries and package publishing.
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```bash { .api }
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# Login to registry
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yarn login
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# Logout from registry
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yarn logout
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# Publish package
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yarn publish [--tag] [--access] [--registry]
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# Manage package access
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yarn access public|restricted <package>
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yarn access grant|revoke <read-write|read-only> <scope:team> <package>
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# Manage package ownership
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yarn owner add|remove|list <user> <package>
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# Manage package tags
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yarn tag add|remove|list <package> <tag>
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# Manage organization teams
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yarn team create|destroy <scope:team>
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yarn team add|remove <scope:team> <user>
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yarn team list <scope> [team]
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```
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[Registry Operations](./registry-operations.md)
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### Workspace Commands
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Commands for managing monorepos and workspaces.
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```bash { .api }
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# Run command in all workspaces
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yarn workspaces run <command>
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# Get workspace information
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yarn workspaces info [--json]
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# Run command in specific workspace
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yarn workspace <workspace-name> <command>
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```
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[Workspace Management](./workspace-management.md)
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### Configuration Commands
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Commands for managing yarn configuration and global packages.
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```bash { .api }
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# Manage configuration
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yarn config set <key> <value> [--global]
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yarn config get <key>
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yarn config delete <key>
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yarn config list
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# Manage global packages
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yarn global add <package>
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yarn global remove <package>
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yarn global list
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# Manage symlinks for development
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yarn link [package]
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yarn unlink [package]
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```
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[Configuration](./configuration.md)
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### Cache Commands
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Commands for managing yarn's package cache.
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```bash { .api }
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# Show cache directory
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yarn cache dir
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# List cached packages
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yarn cache list [--pattern]
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# Clean cache
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yarn cache clean [package]
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```
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[Cache Management](./cache-management.md)
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### Utility Commands
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Additional utility commands for package integrity, security, and maintenance.
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```bash { .api }
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# Verify package integrity
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yarn check [--integrity] [--verify-tree]
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# Run security audit
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yarn audit [--level] [--json]
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# Create package tarball
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yarn pack [--filename]
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# Import dependencies from package-lock.json
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yarn import
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# Generate lockfile entry
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yarn generate-lock-entry
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# Clean unnecessary files
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yarn autoclean [--init] [--force]
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# Temporarily unplug Plug'n'Play packages for debugging
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yarn unplug <package> [--clear] [--clear-all]
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# Manage release policies and yarn version
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yarn policies set-version <version>
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# Show help
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yarn help [command]
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# Show version
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yarn version [--new-version] [--major] [--minor] [--patch]
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# Show versions of dependencies
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yarn versions
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```
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[Utility Commands](./utility-commands.md)
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## Types
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```javascript { .api }
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// Command-line options for yarn install
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interface InstallOptions {
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  production?: boolean;          // Install only production dependencies
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  "frozen-lockfile"?: boolean;   // Don't generate lockfile and fail if update needed
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  "pure-lockfile"?: boolean;     // Don't generate lockfile
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  offline?: boolean;             // Use only cached packages
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  "ignore-scripts"?: boolean;    // Don't run lifecycle scripts
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  "ignore-platform"?: boolean;   // Don't check platform compatibility
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  "ignore-engines"?: boolean;    // Don't check engines compatibility
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  "ignore-optional"?: boolean;   // Don't install optional dependencies
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  "force"?: boolean;             // Force re-download of packages
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  "har"?: boolean;               // Save HAR file for network requests
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  "non-interactive"?: boolean;   // Disable interactive prompts
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  "no-bin-links"?: boolean;      // Don't create symlinks for binaries
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  "flat"?: boolean;              // Install all dependencies in root node_modules
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  "focus"?: boolean;             // Focus on workspace dependencies
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  "verbose"?: boolean;           // Show additional logging
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}
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// Command-line options for yarn add
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interface AddOptions {
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  dev?: boolean;                 // Add to devDependencies
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  peer?: boolean;                // Add to peerDependencies  
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  optional?: boolean;            // Add to optionalDependencies
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  exact?: boolean;               // Install exact version
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  tilde?: boolean;               // Install with tilde range
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  "ignore-workspace-root-check"?: boolean; // Allow install on workspace root
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  "audit"?: boolean;             // Run audit after install
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}
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// Configuration values
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interface YarnConfig {
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  registry?: string;             // Package registry URL
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  "cache-folder"?: string;       // Cache directory path
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  "global-folder"?: string;      // Global packages directory
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  "modules-folder"?: string;     // Local node_modules directory name
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  "offline-mirror"?: string;     // Offline mirror directory
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  "disable-self-update-check"?: boolean; // Disable update checks
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  "ignore-engines"?: boolean;    // Ignore engines field
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  "ignore-scripts"?: boolean;    // Don't run lifecycle scripts
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  workspaces?: boolean;          // Enable workspaces
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  "workspace-experimental"?: boolean; // Enable experimental features
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}
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```
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## Exit Codes
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Yarn uses standard exit codes to indicate success or failure:
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- **0**: Success
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- **1**: General error (network issues, package not found, etc.)
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- **2**: Missing or invalid arguments
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- **3**: Permission errors
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- **4**: Network connectivity issues
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- **5**: Package resolution errors
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## Environment Variables
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```bash { .api }
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# Cache directory override
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YARN_CACHE_FOLDER=/path/to/cache
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# Registry override  
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YARN_REGISTRY=https://registry.npmjs.org
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# Disable update checks
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YARN_DISABLE_SELF_UPDATE_CHECK=true
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# Enable offline mode
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YARN_ENABLE_OFFLINE_MODE=true
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# HTTP proxy settings
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HTTP_PROXY=http://proxy.example.com:8080
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HTTPS_PROXY=https://proxy.example.com:8080
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```