anchor.diff:  
   -spec build_recon_struct(method(), OldSyncStruct::sync_struct() | {},
                            DestI::intervals:non_empty_interval(), db_chunk(),
  -                         Params::parameters() | {}, FinishRecon::boolean())
  +                         Params::parameters() | {}, BeginSync::boolean())
           -> sync_struct().
   build_recon_struct(bloom, _OldSyncStruct = {}, I, DBItems, _Params, true) ->
       % note: for bloom, parameters don't need to match - use our own
  
positive.code:     Tree = merkle_tree:new(I, DBItems, [{signature_size, SignatureSize},
                                          {branch_factor, BranchFactor},
                                          {bucket_size, BucketSize},
                                          {keep_bucket, not FinishRecon}]),
      if FinishRecon ->
             % no more DB items -> create art struct:
             #art_recon_struct{art = art:new(Tree, get_art_config()),
                               signature_size = SignatureSize,
  
negative.code:               end,
      {BuildTime, SyncStruct} =
          util:tc(fun() -> build_recon_struct(ToBuild, OldSyncStruct, DestI,
                                              DBList, Params, BeginSync)
                  end),
      Stats1 = rr_recon_stats:inc([{build_time, BuildTime}], Stats),
      NewState = State#rr_recon_state{struct = SyncStruct, stats = Stats1},
      if BeginSync ->
             begin_sync(SyncStruct, Params, NewState#rr_recon_state{stage = reconciliation});
         true ->
             NewState % keep stage (at initiator: reconciliation, at other: build_struct)
  