# Introduction

Loopstack is a **TypeScript workflow framework** for building stateful automations, AI agents, and interactive workflows on top of NestJS.

## What You Can Build

- **AI Workflows** — Stateful automations that chain tools, transform data, and route dynamically
- **AI Agents** — AI agent harnesses with tool calling, context management and message history
- **Orchestration Systems** — Compose complex systems by spawning nested agents and workflows
- **Secure Execution** — Run code and access files in isolated sandboxed environments
- **HITL Systems** — Pause workflows for Human-in-the-Loop review, input, or confirmation

...built directly into your NestJS backends.

## How It Works

Loopstack apps are built from three core concepts:

- **Workflows** — TypeScript classes that define a state machine with transitions, guards, and routing
- **Tools** — Reusable logic units called directly in your workflows
- **Documents** — Structured data objects displayed in the Loopstack Studio UI

## Next steps

- [Core Concepts](/docs/learn/core-concepts) — understand workflows, tools, documents, and providers
- [Capabilities](/docs/learn/capabilities) — quick feature matrix to validate your use case
- [Getting Started](/docs/build/getting-started) — set up your first project