@spec instance_default() :: %{
  provider: String.t() | nil,
  model: String.t() | nil,
  adapter: module() | nil,
  endpoint_config: map()
}

Returns the provider the dashboard should preselect in the LLM override form, along with the instance settings that back it.

An instance that already configures a provider — a self-hosted vLLM gateway whose endpoint and API key come from the release's own environment, say — should not make an operator retype those into a dashboard form. Set :default_provider and the override form opens with that adapter selected and the configured model filled in, and treats blank credential fields as "use whatever the instance is already configured with":

config :gettext_translator, GettextTranslator,
  endpoint: MyApp.LLM.ChatVLLM,
  endpoint_model: System.get_env("GETTEXT_TRANSLATOR_MODEL", "gemma-4-26b-a4b-it"),
  default_provider: :vllm

The value may be an atom or a string naming one of the adapters the form offers (:openai, :anthropic, :ollama, :google_ai, :vllm).

:provider is nil when :default_provider is unset, which leaves the override form behaving exactly as it did before this option existed.

@spec known_providers() :: [String.t()]

The provider slugs the dashboard override form offers, which are also the only accepted values of :default_provider.

@spec provider_info() ::
  %{configured: boolean(), adapter_name: String.t(), model: String.t()}
  | %{configured: false}

Returns a summary of the configured LLM provider for display in the dashboard.

Returns %{configured: true, adapter_name: "ChatOpenAI", model: "gpt-4"} when configured, or %{configured: false} otherwise.

@spec provider_label(String.t() | nil) :: String.t() | nil

Human-readable label for a provider slug, or nil if it is not a known one.

"google_ai" is not what anyone wants to read in a form label.

@spec resolve_override(map(), map()) :: %{
  adapter: module(),
  adapter_name: String.t(),
  model: String.t(),
  config: map()
}

Turns the dashboard override form's params into the provider override map the translation chain consumes.

Lives here rather than in the page because it is provider/config resolution rather than view logic, and because the two decisions it makes are worth testing directly:

• Which adapter module. Choosing the provider the instance is configured for uses that instance's own :endpoint module, not the generic LangChain one. For a self-hosted gateway that is the whole point: a module like MyApp.LLM.ChatVLLM resolves its endpoint and bearer token from the release environment, where ChatOpenAI would need the full completions URL typed into the form.

• Which credentials. Blank fields inherit the instance's :endpoint_config, but only when the submitted adapter is the configured one — picking a different provider must not send it another provider's key. Anything actually typed always wins.