Create Package

Create a new self-contained package under src/packages/ with its first module.

Foundational documentation

Read these docs before creating a package — they define the conventions this skill builds on:

• Package Development — Package & module structure, folder conventions, manifest bubbling, public API rules
• Entities — Entity types, entity context, how entityType connects workspaces/trees/actions/routing
• Data Flow — Repository pattern, data sources, stores, worked examples

Naming conventions

• Package names are plural (e.g., data-types, languages, tags, documents, relations)
• Module names are singular (e.g., data-type, language, tag, document, relation)

What you need from the user

1. Package name — The domain name in plural form (e.g., data-types, languages, tags) — kebab-case
2. First module name — The primary module in singular form (e.g., data-type, language, tag)

When to create a package vs. add to core

• New package: Domain-specific CMS features (documents, media, data-type, language). Each package is independent and self-contained.
• Add to core: UI framework infrastructure shared by all packages (modals, routing, extension system). Use the add-core-module skill instead.

Files to create

src/packages/{package-name}/
├── package.json                    # npm workspace package
├── vite.config.ts                  # Build configuration
├── umbraco-package.ts              # Bundle entry point (lazy-loads manifests)
├── manifests.ts                    # Aggregates all module manifests
├── {module-name}/                  # First module
│   ├── index.ts                   # Public API exports
│   ├── manifests.ts               # Module manifest registrations
│   ├── constants.ts               # Module constants
│   └── types.ts                   # Module types

Step 1: Create package.json

Every package is an npm workspace. It needs a minimal package.json:

{
	"name": "@umbraco-backoffice/{package-name}",
	"version": "0.0.0",
	"private": true,
	"type": "module",
	"scripts": {
		"build": "vite build"
	}
}

Step 2: Create vite.config.ts

Non-core packages use the simple default config with three entry points (index.ts, manifests.ts, umbraco-package.ts):

import { defineConfig } from 'vite';
import { rmSync } from 'fs';
import { getDefaultConfig } from '../../vite-config-base';

const dist = '../../../dist-cms/packages/{package-name}';

// delete the unbundled dist folder
rmSync(dist, { recursive: true, force: true });

export default defineConfig({
	...getDefaultConfig({ dist }),
});

Step 3: Create umbraco-package.ts

The bundle entry point that lazy-loads the package's manifests:

export const name = 'Umbraco.Core.{PackageName}';
export const extensions = [
	{
		name: '{PackageName} Bundle',
		alias: 'Umb.Bundle.{PackageName}',
		type: 'bundle',
		js: () => import('./manifests.js'),
	},
];

Convention: name uses Umbraco.Core.{PascalCaseName}, alias uses Umb.Bundle.{PascalCaseName}.

Step 4: Create the package-level manifests.ts

Aggregates all module manifests:

import { manifests as {moduleName}Manifests } from './{module-name}/manifests.js';

export const manifests: Array<UmbExtensionManifest> = [
	...{moduleName}Manifests,
];

As you add more modules, import and spread their manifests here.

Step 5: Create the first module

{module-name}/manifests.ts

export const manifests: Array<UmbExtensionManifest> = [
	// Extension registrations go here as you build features
];

{module-name}/index.ts

// Public API exports — classes, types, constants needed by other packages

{module-name}/constants.ts

// Module constants — aliases, entity types, context tokens

{module-name}/types.ts

// Module type definitions — domain models, config interfaces

Step 6: Register the package

Three registrations are needed to wire the package into the build:

1. Add subpath export to root package.json

In /src/Umbraco.Web.UI.Client/package.json, add to the exports field:

"./{package-name}": "./dist-cms/packages/{package-name}/index.js"

2. Regenerate TypeScript config

npm run generate:tsconfig

This updates tsconfig.json paths so @umbraco-cms/backoffice/{package-name} resolves correctly.

3. Install workspace dependencies

npm install

This registers the new workspace package with npm.

Reference: existing packages to study

• Simple package: src/packages/data-type/ — straightforward entity with CRUD
• Complex package: src/packages/documents/ — multiple modules, rich entity
• Minimal package: src/packages/tags/ — small feature area

Checklist

• package.json created with "type": "module" and build script
• vite.config.ts created using getDefaultConfig()
• umbraco-package.ts created with bundle entry point
• manifests.ts created at package level, aggregating module manifests
• First module has manifests.ts, index.ts, constants.ts, types.ts
• Subpath export added to root package.json
• npm run generate:tsconfig executed
• npm install executed to register the workspace
• Compiles: npm run compile