anchor.diff:  maybe_mark_sent_message({message, Message}, Clock, MessageInfo) ->
     #message_event{message = #message{message_id = Id}} = Message,
     ets:update_element(MessageInfo, Id, {?message_sent, Clock});
  -maybe_mark_sent_message(_, _Clock, _MessageI) -> true.
  +maybe_mark_sent_message(Special, Clock, MessageInfo) ->
  +  case is_list(Special) of
  +    false -> true;
  +    true ->
  +      Message = proplists:lookup(message, Special),
  +      maybe_mark_sent_message(Message, Clock, MessageInfo)
  +  end.
   
   plan_more_interleavings([], OldTrace, _SchedulerState) ->
     OldTrace;
  
positive.code: %% Between scheduler and an instrumented process
  %%------------------------------------------------------------------------------
  
  get_next_event_backend(#event{actor = {_Sender, Recipient}} = Event, State) ->
    #scheduler_state{processes = Processes, timeout = _Timeout} = State,
    case ets:lookup(Processes, Recipient) =/= [] of
      true ->
        #event{event_info = EventInfo} = Event,
        #message_event{message = Message, type = Type} = EventInfo,
        %% Message delivery always succeeds
        Recipient ! {Type, Message},
        UpdatedEvent =
          receive
            {trapping, Trapping} ->
              NewEventInfo = EventInfo#message_event{trapping = Trapping},
              Event#event{event_info = NewEventInfo}
          end,
        {ok, UpdatedEvent}
      %% false ->
      %%   %% Sending to system process. Sender must wait for immediate reply!
      %%   Sender ! {system, Event},
      %%   receive
      %%     {system_reply, UpdatedEvent} -> UpdatedEvent
      %%   after
      %%     Timeout -> error(timeout)
      %%   end
    end;
  get_next_event_backend(#event{actor = Pid} = Event, State) when is_pid(Pid) ->
    Pid ! Event,
    get_next_event_backend_loop(Event, State).
  
negative.code:         Next#trace_state{
            active_processes = ordsets:add_element(SpawnedPid, ActiveProcesses)
           },
        State#scheduler_state{trace = [NewNext|Trace]};
      List when is_list(List) ->
        lists:foldl(fun update_special/2, State, Special)
    end.
  
  process_message(MessageEvent, PendingMessages, MessageInfo) ->
  