LemonRouter.ModelSelection (lemon_router v0.1.0)

Resolves model + engine selection independently from profile binding.

This module keeps profile defaults useful (engine, system prompt, tool policy) while allowing model selection to be overridden at request/session layers.

Precedence (highest to lowest):

model: request-level explicit model -> meta model -> session model -> profile model -> history model -> router default model
engine: resume engine -> explicit engine_id -> model-implied engine -> profile default engine

The history_model slot is populated by the router when the routing_feedback feature flag is enabled and sufficient historical performance data exists for the task context. It acts as a soft tie-breaker between the profile default and the router fallback — it never overrides explicit user intent.

If an explicit engine_id conflicts with a model-implied engine, we keep the explicit engine (caller intent wins) and emit a warning.

Summary

Types

t()

Functions

resolve(input)

Types

t()

@type t() :: %{
  model: String.t() | nil,
  engine_id: String.t() | nil,
  model_engine: String.t() | nil,
  warning: String.t() | nil
}

Functions

resolve(input)

@spec resolve(map()) :: t()