Behaviour for query decomposition in the Agent pipeline.

The decomposer breaks complex questions into simpler sub-questions that can be searched independently, improving retrieval for multi-faceted queries.

Built-in Implementations

• Arcana.Agent.Decomposer.LLM - Uses your LLM to decompose queries (default)

Implementing a Custom Decomposer

defmodule MyApp.KeywordDecomposer do
  @behaviour Arcana.Agent.Decomposer

  @impl true
  def decompose(question, _opts) do
    # Simple keyword-based decomposition
    sub_questions =
      question
      |> String.split(~r/\s+(and|vs|versus|compared to)\s+/i)
      |> Enum.map(&String.trim/1)
      |> Enum.reject(&(&1 == ""))

    {:ok, sub_questions}
  end
end

Using a Custom Decomposer

Agent.new(question, repo: repo, llm: llm)
|> Agent.decompose(decomposer: MyApp.KeywordDecomposer)
|> Agent.search()

Using an Inline Function

Agent.decompose(ctx,
  decomposer: fn question, _opts ->
    {:ok, [question]}  # No decomposition
  end
)