diff --git a/src/main/java/net/javahippie/fitpub/repository/AchievementRepository.java b/src/main/java/net/javahippie/fitpub/repository/AchievementRepository.java
index d06471b..130869c 100644
--- a/src/main/java/net/javahippie/fitpub/repository/AchievementRepository.java
+++ b/src/main/java/net/javahippie/fitpub/repository/AchievementRepository.java
@@ -2,6 +2,7 @@ package net.javahippie.fitpub.repository;
 
 import net.javahippie.fitpub.model.entity.Achievement;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Modifying;
 import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
@@ -40,6 +41,12 @@ public interface AchievementRepository extends JpaRepository<Achievement, UUID>
      */
     long countByUserId(UUID userId);
 
+    /**
+     * Delete all achievements for a user.
+     */
+    @Modifying
+    void deleteByUserId(UUID userId);
+
     /**
      * Get count of achievements earned by a user in a date range.
      */
diff --git a/src/main/java/net/javahippie/fitpub/service/AchievementService.java b/src/main/java/net/javahippie/fitpub/service/AchievementService.java
index d52ed2e..702a581 100644
--- a/src/main/java/net/javahippie/fitpub/service/AchievementService.java
+++ b/src/main/java/net/javahippie/fitpub/service/AchievementService.java
@@ -86,6 +86,31 @@ public class AchievementService {
         return newAchievements;
     }
 
+    /**
+     * Rebuild all achievements for a user from chronological activity history.
+     */
+    @Transactional
+    public List<Achievement> rebuildAchievementsForUser(UUID userId) {
+        if (userId == null) {
+            return List.of();
+        }
+
+        List<Activity> activityHistory = activityRepository.findByUserIdOrderByStartedAtAsc(userId);
+        if (activityHistory.isEmpty()) {
+            achievementRepository.deleteByUserId(userId);
+            return List.of();
+        }
+
+        achievementRepository.deleteByUserId(userId);
+
+        List<Achievement> rebuiltAchievements = new ArrayList<>();
+        for (Activity activity : activityHistory) {
+            rebuiltAchievements.addAll(checkAndAwardAchievements(activity));
+        }
+
+        return rebuiltAchievements;
+    }
+
     /**
      * Check first activity achievements.
      */
diff --git a/src/main/java/net/javahippie/fitpub/service/BatchImportService.java b/src/main/java/net/javahippie/fitpub/service/BatchImportService.java
index ea477cd..b33b10a 100644
--- a/src/main/java/net/javahippie/fitpub/service/BatchImportService.java
+++ b/src/main/java/net/javahippie/fitpub/service/BatchImportService.java
@@ -344,11 +344,9 @@ public class BatchImportService {
                 personalRecordService.checkAndUpdatePersonalRecords(activity);
             }
 
-            // Recalculate achievements for each activity
+            // Recalculate achievements from the full chronological activity history
             log.debug("Recalculating achievements...");
-            for (Activity activity : activities) {
-                achievementService.checkAndAwardAchievements(activity);
-            }
+            achievementService.rebuildAchievementsForUser(job.getUserId());
 
             // Recalculate training load for each activity
             log.debug("Recalculating training load...");
diff --git a/src/test/java/net/javahippie/fitpub/service/AchievementServiceTest.java b/src/test/java/net/javahippie/fitpub/service/AchievementServiceTest.java
index 27d6ac4..a38e05b 100644
--- a/src/test/java/net/javahippie/fitpub/service/AchievementServiceTest.java
+++ b/src/test/java/net/javahippie/fitpub/service/AchievementServiceTest.java
@@ -4,6 +4,7 @@ import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InOrder;
 import org.mockito.InjectMocks;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
@@ -391,6 +392,28 @@ class AchievementServiceTest {
         assertEquals(activity.getId(), distanceAchievement.getActivityId());
     }
 
+    @Test
+    @DisplayName("Should rebuild achievements by deleting existing rows and replaying history")
+    void testRebuildAchievementsForUser() {
+        Activity previous = createActivity(Activity.ActivityType.RUN, 9000L, BigDecimal.ZERO);
+        previous.setStartedAt(LocalDateTime.of(2025, 11, 30, 10, 0));
+        previous.setEndedAt(LocalDateTime.of(2025, 11, 30, 11, 0));
+        Activity activity = createActivity(Activity.ActivityType.RUN, 2000L, BigDecimal.ZERO);
+        activity.setStartedAt(LocalDateTime.of(2025, 12, 1, 7, 15));
+        activity.setEndedAt(LocalDateTime.of(2025, 12, 1, 8, 5));
+
+        stubHistory(previous, activity);
+        when(achievementRepository.save(any(Achievement.class))).thenAnswer(invocation -> invocation.getArgument(0));
+
+        List<Achievement> rebuilt = achievementService.rebuildAchievementsForUser(userId);
+
+        assertTrue(rebuilt.stream().anyMatch(a -> a.getAchievementType() == Achievement.AchievementType.DISTANCE_10K));
+
+        InOrder inOrder = inOrder(achievementRepository);
+        inOrder.verify(achievementRepository).deleteByUserId(userId);
+        inOrder.verify(achievementRepository, atLeastOnce()).save(any(Achievement.class));
+    }
+
     @Test
     @DisplayName("Should get user achievements")
     void testGetUserAchievements() {