---
title: Concepts
description: How Twenty apps work — entity model, sandboxing, and the install lifecycle.
icon: "sitemap"
---

Twenty apps are TypeScript packages that extend your workspace with custom objects, logic, UI components, and AI capabilities. They run on the Twenty platform with full sandboxing and permission controls.

## How apps work

An app is a collection of **entities** declared using `defineEntity()` functions from the `twenty-sdk` package. The SDK detects these declarations via AST analysis at build time and produces a **manifest** — a complete description of what your app adds to a workspace. These functions validate your configuration at build time and provide IDE autocompletion and type safety.

```
your-app/
├── src/
│   ├── application-config.ts    ← defineApplication (required, one per app)
│   ├── roles/                   ← defineRole
│   ├── objects/                 ← defineObject
│   ├── fields/                  ← defineField
│   ├── logic-functions/         ← defineLogicFunction
│   ├── front-components/        ← defineFrontComponent
│   ├── skills/                  ← defineSkill
│   ├── agents/                  ← defineAgent
│   ├── views/                   ← defineView
│   ├── navigation-menu-items/   ← defineNavigationMenuItem
│   └── page-layouts/            ← definePageLayout
├── public/                      ← Static assets (images, icons)
└── package.json
```

<Note>
  **File organization is up to you.** Entity detection is AST-based — the SDK finds `export default defineEntity(...)` calls regardless of where the file lives. The folder structure above is a convention, not a requirement.
</Note>

## Entity types

| Entity | Purpose | Docs |
|--------|---------|------|
| **Application** | App identity, default role, variables | [Application Config](/developers/extend/apps/config/application) |
| **Role** | Permission sets on objects and fields | [Roles & Permissions](/developers/extend/apps/config/roles) |
| **Object** | Custom record types with fields | [Objects](/developers/extend/apps/data/objects) |
| **Field** | Add fields to objects from other apps | [Extending Objects](/developers/extend/apps/data/extending-objects) |
| **Relation** | Bidirectional links between objects | [Relations](/developers/extend/apps/data/relations) |
| **Logic Function** | Server-side TypeScript with triggers | [Logic Functions](/developers/extend/apps/logic/logic-functions) |
| **Skill** | Reusable AI agent instructions | [Skills & Agents](/developers/extend/apps/logic/skills-and-agents) |
| **Agent** | AI assistants with custom prompts | [Skills & Agents](/developers/extend/apps/logic/skills-and-agents) |
| **Connection Provider** | OAuth credentials for third-party APIs | [Connections](/developers/extend/apps/logic/connections) |
| **View** | Pre-configured record list views | [Views](/developers/extend/apps/layout/views) |
| **Navigation Menu Item** | Custom sidebar entries | [Navigation Menu Items](/developers/extend/apps/layout/navigation-menu-items) |
| **Page Layout** | Tabs and widgets on a record's detail page | [Page Layouts](/developers/extend/apps/layout/page-layouts) |
| **Front Component** | Sandboxed React UI inside Twenty | [Front Components](/developers/extend/apps/layout/front-components) |
| **Command Menu Item** | Quick actions and Cmd+K entries | [Command Menu Items](/developers/extend/apps/layout/command-menu-items) |

## Sandboxing

- **Logic functions** run in isolated Node.js processes on the server. They only access data through the typed API client, scoped to the app's role permissions.
- **Front components** run in Web Workers using Remote DOM — sandboxed from the main page but rendering native DOM elements (not iframes). They communicate with Twenty via a message-passing host API.
- **Permissions** are enforced at the API level. The runtime token (`TWENTY_APP_ACCESS_TOKEN`) is derived from the role defined in `defineApplication()`.

## App lifecycle

```
┌─────────────────────────────────────────────────────────┐
│ Development                                             │
│   npx create-twenty-app → yarn twenty dev (live sync)   │
├─────────────────────────────────────────────────────────┤
│ Build & Deploy                                          │
│   yarn twenty dev:build → yarn twenty app:publish        │
├─────────────────────────────────────────────────────────┤
│ Install flow                                            │
│   upload → [pre-install] → metadata migration →         │
│   generate SDK → [post-install]                         │
├─────────────────────────────────────────────────────────┤
│ Publish                                                 │
│   npm publish → appears in Twenty marketplace           │
└─────────────────────────────────────────────────────────┘
```

- **`yarn twenty dev`** — watches your source files and live-syncs changes to a connected Twenty server. The typed API client is regenerated automatically when the schema changes.
- **`yarn twenty dev:build`** — compiles TypeScript, bundles logic functions and front components with esbuild, and produces a manifest.
- **Pre/post-install hooks** — optional functions that run during installation. See [Install Hooks](/developers/extend/apps/config/install-hooks) for details.

## Next steps

<CardGroup cols={2}>
  <Card title="Config" icon="screwdriver-wrench" href="/developers/extend/apps/config/overview">
    Application identity, default role, and install hooks.
  </Card>
  <Card title="Data" icon="database" href="/developers/extend/apps/data/overview">
    Objects, fields, and bidirectional relations.
  </Card>
  <Card title="Logic" icon="bolt" href="/developers/extend/apps/logic/overview">
    Logic functions, skills, agents, and OAuth connections.
  </Card>
  <Card title="Layout" icon="table-columns" href="/developers/extend/apps/layout/overview">
    Views, navigation, page layouts, front components.
  </Card>
  <Card title="Operations" icon="rocket" href="/developers/extend/apps/operations/overview">
    CLI, testing, remotes, CI, and publishing your app.
  </Card>
</CardGroup>
