# UNDF: UNDF-2026-000000982
--- a/source/glest_game/type_instances/unit.cpp
+++ b/source/glest_game/type_instances/unit.cpp
@@ -2,6 +2,7 @@
 //	unit.cpp
 //

+#include <unordered_set>
 #include "unit.h"

 #include <cassert>
@@ -2576,7 +2577,12 @@
             UnitUpdater *unitUpdater = this->game->getWorld()->getUnitUpdater();

             const AttackBoost *attackBoost = currSkill->getAttackBoost();
             vector<Unit *> candidates = unitUpdater->findUnitsInRange(this, attackBoost->radius);
-            vector<int> candidateValidIdList;
-            candidateValidIdList.reserve(candidates.size());
+            std::unordered_set<int> candidateValidIdSet;
+            candidateValidIdSet.reserve(candidates.size());
+
+            // Build hash set of currently boosted unit IDs for O(1) membership test
+            std::unordered_set<int> boostedIdSet(
+                currentAttackBoostOriginatorEffect.currentAttackBoostUnits.begin(),
+                currentAttackBoostOriginatorEffect.currentAttackBoostUnits.end());

             if (debugBoost)
                 printf("Line: %d candidates unit size: " MG_SIZE_T_SPECIFIER " attackBoost: %s\n", __LINE__, candidates.size(),
@@ -2585,9 +2591,9 @@
             for (unsigned int i = 0; i < candidates.size(); ++i) {
                 Unit *affectedUnit = candidates[i];
-                candidateValidIdList.push_back(affectedUnit->getId());
+                candidateValidIdSet.insert(affectedUnit->getId());

-                std::vector<int>::iterator iterFound = std::find(currentAttackBoostOriginatorEffect.currentAttackBoostUnits.begin(),
-                                                                 currentAttackBoostOriginatorEffect.currentAttackBoostUnits.end(), affectedUnit->getId());
+                bool alreadyBoosted = boostedIdSet.count(affectedUnit->getId()) > 0;

                 if (attackBoost->isAffected(this, affectedUnit) == true) {
-                    if (iterFound == currentAttackBoostOriginatorEffect.currentAttackBoostUnits.end()) {
+                    if (!alreadyBoosted) {
                         if (affectedUnit->applyAttackBoost(attackBoost, this) == true) {
                             currentAttackBoostOriginatorEffect.currentAttackBoostUnits.push_back(affectedUnit->getId());
+                            boostedIdSet.insert(affectedUnit->getId());
                         }
                     }
                 } else {
-                    if (iterFound != currentAttackBoostOriginatorEffect.currentAttackBoostUnits.end()) {
+                    if (alreadyBoosted) {
                         affectedUnit->deapplyAttackBoost(currentAttackBoostOriginatorEffect.skillType->getAttackBoost(), this);
-                        currentAttackBoostOriginatorEffect.currentAttackBoostUnits.erase(iterFound);
+                        auto eraseIt = std::find(currentAttackBoostOriginatorEffect.currentAttackBoostUnits.begin(),
+                                                 currentAttackBoostOriginatorEffect.currentAttackBoostUnits.end(), affectedUnit->getId());
+                        if (eraseIt != currentAttackBoostOriginatorEffect.currentAttackBoostUnits.end()) {
+                            currentAttackBoostOriginatorEffect.currentAttackBoostUnits.erase(eraseIt);
+                        }
+                        boostedIdSet.erase(affectedUnit->getId());
                     }
                 }
             }
@@ -2616,7 +2622,7 @@
             if (currentAttackBoostOriginatorEffect.currentAttackBoostUnits.empty() == false) {
                 for (int i = (int)currentAttackBoostOriginatorEffect.currentAttackBoostUnits.size() - 1; i >= 0; --i) {
                     int findUnitId = currentAttackBoostOriginatorEffect.currentAttackBoostUnits[i];

-                    std::vector<int>::iterator iterFound = std::find(candidateValidIdList.begin(), candidateValidIdList.end(), findUnitId);
-                    if (iterFound == candidateValidIdList.end()) {
+                    if (candidateValidIdSet.count(findUnitId) == 0) {
                         Unit *affectedUnit = game->getWorld()->findUnitById(findUnitId);
                         if (affectedUnit != NULL) {
                             affectedUnit->deapplyAttackBoost(currentAttackBoostOriginatorEffect.skillType->getAttackBoost(), this);