Chat | Boundary Documentation

In this guide we’ll build a small chatbot that takes in user messages and generates responses.

chat-history.baml

class MyUserMessage {
  role "user" | "assistant"
  content string
}
function ChatWithLLM(messages: MyUserMessage[]) -> string {
  client "openai/gpt-5"
  prompt #"
    Answer the user's questions based on the chat history:
    {% for message in messages %}
      {{ _.role(message.role) }} 
      {{ message.content }}
    {% endfor %}
    Answer:
  "#
}
test TestName {
  functions [ChatWithLLM]
  args {
    messages [
      {
        role "user"
        content "Hello!"
      }
      {
        role "assistant"
        content "Hi!"
      }
    ]
  }
}

Code

from baml_client import b
from baml_client.types import MyUserMessage
def main():
    messages: list[MyUserMessage] = []
    
    while True:
        content = input("Enter your message (or 'quit' to exit): ")
        if content.lower() == 'quit':
            break
        
        messages.append(MyUserMessage(role="user", content=content))
        
        agent_response = b.ChatWithLLM(messages=messages)
        print(f"AI: {agent_response}")
        print()
        
        # Add the agent's response to the chat history
        messages.append(MyUserMessage(role="assistant", content=agent_response))
if __name__ == "__main__":
    main()