Configuration management for Arcana.

Handles parsing and resolving configuration for embedders, chunkers, and other pluggable components.

Redacting Sensitive Values

Use Arcana.Config.redact/1 to wrap any config value for safe inspection:

config = Application.get_env(:arcana, :llm)
inspect(Arcana.Config.redact(config))
# => {"zai:glm-4.7", [api_key: "[REDACTED]"]}

Embedder Configuration

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

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

# OpenAI (requires req_llm and OPENAI_API_KEY)
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 Arcana.Embedder behaviour
config :arcana, embedder: MyApp.CohereEmbedder
config :arcana, embedder: {MyApp.CohereEmbedder, api_key: "..."}

Chunker Configuration

# Default: text_chunker-based chunking
config :arcana, chunker: :default

# Default chunker with custom options
config :arcana, chunker: {:default, chunk_size: 512, chunk_overlap: 100}

# Custom function (receives text, opts; returns list of chunk maps)
config :arcana, chunker: fn text, _opts ->
  [%{text: text, chunk_index: 0, token_count: 10}]
end

# Custom module implementing Arcana.Chunker behaviour
config :arcana, chunker: MyApp.SemanticChunker
config :arcana, chunker: {MyApp.SemanticChunker, model: "..."}

PDF Parser Configuration

# Default: poppler's pdftotext
config :arcana, pdf_parser: :poppler

# Custom module implementing Arcana.FileParser.PDF behaviour
config :arcana, pdf_parser: MyApp.PDFParser
config :arcana, pdf_parser: {MyApp.PDFParser, some_option: "value"}

Search Defaults

Set defaults for Arcana.search/2. Per-call options override these. Any option accepted by Arcana.Search.search/2 can be set globally.

config :arcana, search: [
  limit: 10,
  threshold: 0.0,
  mode: :vector,              # :vector | :keyword | :hybrid
  vector_weight: 0.5,         # for hybrid mode
  keyword_weight: 0.5,        # for hybrid mode
  rewriter: &MyApp.rewrite/1, # query rewriter function
  # plus any backend-specific opts (e.g. :hnsw_ef_search for pgvector)
]

Ask Defaults

Set defaults for Arcana.ask/2. Per-call options override these. Any option accepted by Arcana.Ask.ask/2 can be set globally.

config :arcana, ask: [
  limit: 5,
  mode: :semantic,
  threshold: 0.0,
  prompt: &MyApp.custom_prompt/3
]

Reranker Configuration

Set a global reranker that will be applied automatically by Arcana.search/2 and Arcana.ask/2. Per-call :reranker options override this. Pass reranker: false per-call to disable for a single request.

# Global reranker module
config :arcana, reranker: Arcana.Reranker.CrossEncoder

# With options (e.g. over_fetch multiplier, threshold)
config :arcana, reranker: {Arcana.Reranker.CrossEncoder, over_fetch: 3}

# Custom function: fn question, chunks, opts -> {:ok, reranked} end
config :arcana, reranker: &MyApp.rerank/3