# Human‑in‑the‑Loop (HITL) with LangGraph

This repository contains a minimal example of how to implement a **Human‑in‑the‑Loop** interruption in a LangGraph workflow.  
The graph consists of a single node that triggers an interrupt, presents a question to the user via a console menu (`questionary`), receives the answer, and then resumes execution.

---

## 📦 Project Overview

- **Purpose**: Demonstrate how to pause a LangGraph flow for human input and resume it afterward.
- **Key Components**:
  - `main.py`: The only script – builds the graph, defines the interrupt handler, and runs the workflow.
  - Uses **LangGraph** for state management and interruption handling.
  - Uses **questionary** to display a CLI menu and capture user responses.

---

## ⚙️ Prerequisites

| Dependency | Minimum Version |
|------------|-----------------|
| Python     | 3.10+           |
| LangGraph  | Latest (pip install `langgraph`) |
| questionary| Latest (pip install `questionary`) |

> **Note**: No external services (Ollama, Qdrant, etc.) are required for this demo.

---

## 📥 Installation

```bash
# Clone the repository
git clone https://github.com/your-username/hitl-langgraph.git
cd hitl-langgraph

# Create a virtual environment (optional but recommended)
python -m venv .venv
source .venv/bin/activate   # On Windows: .\.venv\Scripts\activate

# Install dependencies
pip install -r requirements.txt
```

`requirements.txt` contains:

```text
langgraph>=0.1.0
questionary>=2.0.0
```

---

## 🚀 Running the Example

The project has a single executable file: `main.py`.

```bash
python main.py
```

### What Happens?

1. The graph starts and immediately triggers an interrupt.
2. A console menu appears:

   ```
   ❓ What is your favorite programming language?
     1) Python
     2) JavaScript
     3) Rust
     4) Go
   ```

3. After you select an option, the workflow resumes and prints a confirmation message.

---

## 📄 Example Output

```text
$ python main.py
❓ What is your favorite programming language?
1) Python
2) JavaScript
3) Rust
4) Go
> 1

You selected: Python
Workflow finished.
```

Feel free to modify the question or options in `main.py` to suit your own use case.

---

## 📚 Further Reading

- [LangGraph Documentation](https://langgraph.org/docs/)
- [questionary Docs](https://github.com/tmbo/questionary)

Happy hacking!