Behaviour for embedding providers used by Arcana.

Arcana accepts any module that implements this behaviour. Built-in implementations are provided for:

• Arcana.Embedder.Local - Local Bumblebee models (e.g., bge-small-en-v1.5)
• Arcana.Embedder.OpenAI - OpenAI embeddings via Req.LLM

Configuration

Configure your embedding provider in config.exs:

# Default: Local Bumblebee with bge-small-en-v1.5 (384 dims)
config :arcana, embedder: :local

# Local with different HuggingFace model
config :arcana, embedder: {:local, model: "BAAI/bge-large-en-v1.5"}

# OpenAI via Req.LLM
config :arcana, embedder: :openai
config :arcana, embedder: {:openai, model: "text-embedding-3-large"}

# Custom function
config :arcana, embedder: fn text -> {:ok, embedding} end

# Custom module implementing this behaviour
config :arcana, embedder: MyApp.CohereEmbedder
config :arcana, embedder: {MyApp.CohereEmbedder, api_key: "..."}

Implementing a Custom Embedder

Create a module that implements this behaviour:

defmodule MyApp.CohereEmbedder do
  @behaviour Arcana.Embedder

  @impl true
  def embed(text, opts) do
    api_key = opts[:api_key] || System.get_env("COHERE_API_KEY")
    # Call Cohere API...
    {:ok, embedding}
  end

  @impl true
  def dimensions(_opts), do: 1024
end

Then configure:

config :arcana, embedder: {MyApp.CohereEmbedder, api_key: "..."}