Opt-in migration consent, enabled by setting consent_settings on the HotSwap or ColdSwap migration strategy.

Before migrating a participating child, the hub asks the process whether it may be moved. :ready migrates it through the regular migration path; :defer (or no reply within :consent_timeout) parks it in the deferred list, retried every :retry_interval and force-migrated after :max_defer_time. ProcessHub.Service.Migration.migration_ready/2 signals readiness early.

Participating processes use this module:

defmodule MyServer do
  use GenServer
  use ProcessHub.Strategy.Migration.MigrationConsent

  # Optional override, defaults to :ready.
  def migration_consent(state), do: if(state.busy?, do: :defer, else: :ready)
end

Consent covers the primary instance only; Replication-managed replicas are unaffected. Detection reads the child spec start module, so processes started through wrapper modules migrate immediately. Forced migration uses the best-effort handover path, so prepare_handover_state should return resumable progress.