# Human‑in‑the‑Loop Agent with LangGraph

This repository contains a minimal example of a **Human‑in‑the‑Loop** (HITL) agent built on top of [LangGraph](https://github.com/langchain-ai/langgraph).  
The agent pauses whenever it needs to call an external tool, presents the tool output to the user and waits for a decision (`approve` or `reject`). After the decision is made the conversation continues automatically.

> **⚠️ Prerequisites** – The example uses OpenAI‑compatible APIs.  
> Make sure you have an API key set in the environment variable `OPENAI_API_KEY`.

---

## 📦 Installation

```bash
# 1️⃣ Clone the repo (or copy solution.py into a new folder)
git clone https://github.com/your-username/hitl-langgraph.git
cd hitl-langgraph

# 2️⃣ Create and activate a virtual environment (optional but recommended)
python -m venv .venv
source .venv/bin/activate   # Windows: .\.venv\Scripts\activate

# 3️⃣ Install dependencies
pip install --upgrade pip
pip install langchain-openai langgraph langchain-tools
```

> **Tip** – If you want to use a different LLM (e.g., Anthropic, Gemini), replace the `ChatOpenAI` import with the appropriate wrapper and adjust the model name.

---

## 🚀 Running the Agent

The main logic is in `solution.py`.  
Run it directly:

```bash
python solution.py
```

### What Happens?

1. The agent starts a conversation.
2. When it decides to call the `get_weather` tool, the execution pauses.
3. The tool output (e.g., `"Погода в Москва на 2024-05-28: солнечно 25°C."`) is printed to the console.
4. You are prompted to type **approve** or **reject**:
   - `approve`: the agent resumes with the tool result as normal input.
   - `reject`: the agent receives a `ToolMessage` indicating rejection and can decide what to do next.

---

## 🔧 Example Interaction

```text
$ python solution.py
Agent: Какую погоду вы хотите узнать?
User: Москва на 2024-05-28
Agent (calling tool): get_weather(city='Москва', date='2024-05-28')
Tool output: Погода в Москва на 2024-05-28: солнечно 25°C.
Please type 'approve' or 'reject': approve
Agent: Спасибо! Как ещё могу помочь?
```

If you type `reject`, the agent will receive a rejection message and can, for example, ask for clarification.

---

## 📁 Project Structure

| File | Purpose |
|------|---------|
| `solution.py` | Full implementation of the HITL agent. |
| `README.md` | This documentation file. |

---

## 🛠️ Customization

- **Add more tools** – Decorate any function with `@tool` and add it to the `tools=[...]` list.
- **Change prompt** – Edit `system_prompt` in `create_react_agent`.
- **Persist memory** – Replace `MemorySaver()` with a file‑based or database checkpoint if you need persistence across runs.

---

## 📜 License

MIT © 2026. Feel free to fork and adapt for your own projects!