The LangGraph Agent Server (the binary produced by langgraph build ) is commercial software. Even though it runs entirely on your own machines, it still needs to prove at startup that you are a licensed user.
Also, even if you go with the Full Self-Hosted Option, where you manage everything on your own, you still need the Key as self-hosting does not mean Open-Source in this case. Self-Host is an Enterprise-level feature as opposed to your understanding of being free and open-source:
The Langchain Beacon verifies they Key (On top right corner of the above diagram).
Please choose the deployment options from here.
Let me know if this clarifies.