Module: Legion::LLM::Router::BodyModelHintPolicy

Extended by:
Legion::Logging::Helper
Defined in:
lib/legion/llm/router/body_model_hint_policy.rb

Overview

The SOLE body-model hint decision (SSOT v3 §17.1 / D19). Given the untrusted request-body model value and any trusted explicit model, it returns one immutable Phase 1 BodyModelHintDecision. It never returns a lane, substitute model, or alias; only a honored decision carries a model constraint. PayloadBuilder/translators/executor may not independently reinterpret body.model — they consume this decision.

X-Legion-Model (the trusted channel) is intentionally EXEMPT from the whitelist/blacklist lists: a nonblank trusted model always supersedes.

Class Method Summary collapse

Class Method Details

.call(body_model:, trusted_model:, settings_snapshot:) ⇒ Object 



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# File 'lib/legion/llm/router/body_model_hint_policy.rb', line 18

def self.call(body_model:, trusted_model:, settings_snapshot:)
  requested = normalize(body_model)
  generation = settings_snapshot.generation

  # 1. missing/blank body model → absent (requested_model carries nil).
  return decision(requested_model: nil, disposition: :absent, settings_generation: generation) if requested.nil?

  # 2. body + trusted explicit model → trusted wins, body is metadata only.
  unless normalize(trusted_model).nil?
    return decision(requested_model: requested, disposition: :superseded_by_explicit_model,
                    settings_generation: generation)
  end

  # 3. auto-routing alias → auto (you-pick intent, no constraint).
  return decision(requested_model: requested, disposition: :auto, settings_generation: generation) if auto_alias?(requested, settings_snapshot.auto_routing_model_aliases)

  # 4. body hints globally disabled → ignored.
  unless settings_snapshot.allow_body_routing_hints
    return decision(requested_model: requested, disposition: :ignored_disabled,
                    settings_generation: generation)
  end

  whitelist = settings_snapshot.body_model_hint_whitelist
  blacklist = settings_snapshot.body_model_hint_blacklist

  # 5. nonempty whitelist with no match → ignored_not_whitelisted.
  if !whitelist.empty? && substring_match(requested, whitelist).nil?
    return decision(requested_model: requested, disposition: :ignored_not_whitelisted,
                    settings_generation: generation)
  end

  # 6. any blacklist match → ignored_blacklisted (blacklist wins over whitelist).
  matched_black = substring_match(requested, blacklist)
  unless matched_black.nil?
    return decision(requested_model: requested, disposition: :ignored_blacklisted,
                    matched_blacklist: matched_black, matched_whitelist: substring_match(requested, whitelist),
                    settings_generation: generation)
  end

  # 7. honored → exact body model becomes the model constraint.
  decision(requested_model: requested, disposition: :honored, model_constraint: requested,
           matched_whitelist: substring_match(requested, whitelist), settings_generation: generation)
end