@type failure_class() ::
  :policy_denied
  | :route_unresolved
  | :placement_unavailable
  | :launch_failed
  | :transport_failed
  | :protocol_framing_failed
  | :semantic_runtime_failed
  | :approval_expired
  | :lease_expired
  | :attach_mismatch
  | :remote_disconnect
  | :cancellation
  | :timeout

@type metadata_t() :: %{
  primary_owner: atom(),
  retryable?: boolean(),
  durable_truth_relevance: :durable_truth | :raw_fact_only
}