**What was implemented**  
I added the missing dependencies to `requirements.txt` so the project can import the required modules.

**Why it satisfies the requirement**  
The assignment explicitly asks for the packages `langgraph` and `langchain-openai` to be listed in `requirements.txt`. By including them, the environment will install these libraries and the code that imports them will run without `ModuleNotFoundError`.

**Key code excerpts**

```txt
# requirements.txt
langgraph
langchain-openai
```

This file now contains the two packages, matching the reviewer’s feedback.

**Limitations**  
None – the change is straightforward and fully addresses the requested update.