Behaviour for collection selection in the Agent pipeline.

The selector determines which collections to search based on the question and available collections. This allows for both LLM-based routing (default) and deterministic routing based on user context, metadata, or business logic.

Implementing a Custom Selector

defmodule MyApp.TeamBasedSelector do
  @behaviour Arcana.Agent.Selector

  @impl true
  def select(_question, _collections, opts) do
    case opts[:context][:team] do
      "api" -> {:ok, ["api-reference", "sdk-docs"], "API team routing"}
      "mobile" -> {:ok, ["mobile-docs", "react-native"], "Mobile team routing"}
      _ -> {:ok, ["general"], "Default routing"}
    end
  end
end

Using a Custom Selector

Agent.new(question, repo: repo, llm: llm)
|> Agent.select(
  collections: ["api-reference", "mobile-docs", "general"],
  selector: MyApp.TeamBasedSelector,
  context: %{team: current_user.team}
)

Using an Inline Function

Agent.select(ctx,
  collections: collections,
  selector: fn question, _collections, _opts ->
    if question =~ "API" do
      {:ok, ["api-docs"], "Question mentions API"}
    else
      {:ok, ["general"], "General query"}
    end
  end
)