Behaviour for query rewriting in the Agent pipeline.

The rewriter transforms conversational input into clear search queries by removing filler phrases, greetings, and other noise while preserving the core question and important terms.

Built-in Implementations

• Arcana.Agent.Rewriter.LLM - Uses your LLM to rewrite queries (default)

Implementing a Custom Rewriter

defmodule MyApp.RegexRewriter do
  @behaviour Arcana.Agent.Rewriter

  @impl true
  def rewrite(question, _opts) do
    cleaned =
      question
      |> String.replace(~r/^(hey|hi|hello)[,!]?\s*/i, "")
      |> String.replace(~r/^(can you|could you|please)\s+/i, "")
      |> String.trim()

    {:ok, cleaned}
  end
end

Using a Custom Rewriter

Agent.new(question, repo: repo, llm: llm)
|> Agent.rewrite(rewriter: MyApp.RegexRewriter)
|> Agent.search()

Using an Inline Function

Agent.rewrite(ctx,
  rewriter: fn question, _opts ->
    {:ok, String.downcase(question)}
  end
)