Behaviour for connecting LangchainPrompt to a Large Language Model.

Implement this behaviour to add support for any LLM provider not covered by the built-in adapters.

Built-in adapters

• LangchainPrompt.Adapters.Langchain — delegates to any elixir-langchain chat model.
• LangchainPrompt.Adapters.Test — in-process adapter for ExUnit tests; records calls and supports on-demand failure simulation.

Custom adapter example

defmodule MyApp.Adapters.OpenAIDirect do
  @behaviour LangchainPrompt.Adapter

  @impl true
  def chat(messages, opts) do
    # build request, call API, return {:ok, %Message{}} or {:error, reason}
  end
end