Model-call features

Use a feature label for the business operation that makes a provider call. The conversation label can group calls, but it does not have to describe every operation in that conversation.

config = Agentix.Conversation.Config.new(
  model: "your-provider:your-model",
  feature: "chat",
  summary_feature: "workspace_summary",
  model_call_log: :records
)

Agentix.Conversation.send_message(id, message, scope,
  config: config,
  feature: "view_generation"
)

The precedence is:

1. Config.feature is the conversation label and call default.
2. send_message/4 can set feature: for that turn.
3. A sequential pre-hook can call Hook.put_feature/2 for one model call.

Use explicit operation context in the hook. Do not guess a purpose from model output or change a conversation's config during a running call.

Agentix.Hook.pre(:call_purpose, fn turn ->
  feature = MyApp.Operations.feature_for_call(turn)
  {:cont, Agentix.Hook.put_feature(turn, feature)}
end)

The hook runs before each new call in a tool loop. Each call starts from the turn default. A prior hook override does not leak into the next call or turn. Parallel hooks only add context. Post-hooks cannot relabel a completed call.

Agentix saves the selected purpose before dispatch. Provider retries and cancellation retain it. Recovery preserves the turn default and last call selection. Hooks still run for context and authorization during recovery, but cannot relabel a call whose feature was saved before dispatch. The next new logical call can select a new feature.

Background summary calls use Config.summary_feature, which defaults to "conversation_summary". They do not inherit the foreground call label.

Feature values are nonblank strings of 1–255 bytes. A turn or hook can explicitly use nil to omit attribution. Summary features must not be nil. Invalid turn values raise before dispatch; invalid hook values halt the turn before dispatch.

The effective feature is stored in the existing agentix_model_calls.feature column and included in foreground model-call telemetry. No migration or host attempt table is needed. Model-call records require model_call_log: :records or :full.