Program: 159685
Project: 159685
Buggy source:
@Override public boolean askToActivateAlternativeCosts(Ability ability,Game game){
  if (ability instanceof SpellAbility) {
    Player player=game.getPlayer(controllerId);
    ProwlWatcher prowlWatcher=(ProwlWatcher)game.getState().getWatchers().get("String_Node_Str");
    Card card=game.getCard(ability.getSourceId());
    if (player == null || prowlWatcher == null || card == null) {
      throw new IllegalArgumentException("String_Node_Str");
    }
    boolean canProwl=false;
    if (prowlWatcher.getDamagingSubtypes(ability.getControllerId()) != null) {
      for (      String subtype : prowlWatcher.getDamagingSubtypes(ability.getControllerId())) {
        if (card.getSubtype().contains(subtype)) {
          canProwl=true;
          break;
        }
      }
    }
    if (canProwl) {
      this.resetProwl();
      for (      AlternativeCost2 prowlCost : prowlCosts) {
        if (prowlCost.canPay(sourceId,controllerId,game) && player.chooseUse(Outcome.Benefit,new StringBuilder("String_Node_Str").append(PROWL_KEYWORD).append("String_Node_Str").append(prowlCost.getText(true)).append("String_Node_Str").toString(),game)) {
          prowlCost.activate();
          ability.getManaCostsToPay().clear();
          ability.getCosts().clear();
          for (Iterator it=((Costs)prowlCost).iterator(); it.hasNext(); ) {
            Cost cost=(Cost)it.next();
            if (cost instanceof ManaCostsImpl) {
              ability.getManaCostsToPay().add((ManaCostsImpl)cost.copy());
            }
 else {
              ability.getCosts().add(cost.copy());
            }
          }
        }
      }
    }
  }
  return isActivated();
}

Fixed version (ground truth):
@Override public boolean askToActivateAlternativeCosts(Ability ability,Game game){
  if (ability instanceof SpellAbility) {
    Player player=game.getPlayer(controllerId);
    ProwlWatcher prowlWatcher=(ProwlWatcher)game.getState().getWatchers().get("String_Node_Str");
    Card card=game.getCard(ability.getSourceId());
    if (player == null || prowlWatcher == null || card == null) {
      throw new IllegalArgumentException("String_Node_Str");
    }
    boolean canProwl=false;
    for (    String subtype : card.getSubtype()) {
      if (prowlWatcher.hasSubtypeMadeCombatDamage(ability.getControllerId(),subtype)) {
        canProwl=true;
        break;
      }
    }
    if (canProwl) {
      this.resetProwl();
      for (      AlternativeCost2 prowlCost : prowlCosts) {
        if (prowlCost.canPay(sourceId,controllerId,game) && player.chooseUse(Outcome.Benefit,new StringBuilder("String_Node_Str").append(PROWL_KEYWORD).append("String_Node_Str").append(prowlCost.getText(true)).append("String_Node_Str").toString(),game)) {
          prowlCost.activate();
          ability.getManaCostsToPay().clear();
          ability.getCosts().clear();
          for (Iterator it=((Costs)prowlCost).iterator(); it.hasNext(); ) {
            Cost cost=(Cost)it.next();
            if (cost instanceof ManaCostsImpl) {
              ability.getManaCostsToPay().add((ManaCostsImpl)cost.copy());
            }
 else {
              ability.getCosts().add(cost.copy());
            }
          }
        }
      }
    }
  }
  return isActivated();
}