diff --git a/pkg/models/kanban_task_bucket.go b/pkg/models/kanban_task_bucket.go
index 108b8a371..58a8bbad3 100644
--- a/pkg/models/kanban_task_bucket.go
+++ b/pkg/models/kanban_task_bucket.go
@@ -148,14 +148,20 @@ func updateTaskBucket(s *xorm.Session, a web.Auth, b *TaskBucket) (err error) {
 				// A repeating task doesn't stay in the done bucket; route
 				// it back to the view's default bucket so the user sees
 				// the next iteration waiting in the "To-Do" column.
-				b.BucketID, err = getDefaultBucketID(s, view)
-				if err != nil {
-					return err
+				// When no default bucket is configured, leave the task in
+				// its current bucket — no update needed.
+				if view.DefaultBucketID != 0 {
+					b.BucketID, err = getDefaultBucketID(s, view)
+					if err != nil {
+						return err
+					}
+				} else {
+					b.BucketID = oldTaskBucket.BucketID
 				}
-				// If the task is already in the default bucket, skip the
-				// upsert — MySQL's UPDATE returns 0 affected rows when
-				// the value is unchanged, which would make upsert fall
-				// through to INSERT and hit the unique constraint.
+				// If the bucket is unchanged, skip the upsert — MySQL's
+				// UPDATE returns 0 affected rows when the value is unchanged,
+				// which would make upsert fall through to INSERT and hit the
+				// unique constraint.
 				if b.BucketID == oldTaskBucket.BucketID {
 					updateBucket = false
 				}
diff --git a/pkg/models/kanban_task_bucket_test.go b/pkg/models/kanban_task_bucket_test.go
index 6d1eb2f24..032da7315 100644
--- a/pkg/models/kanban_task_bucket_test.go
+++ b/pkg/models/kanban_task_bucket_test.go
@@ -226,6 +226,61 @@ func TestTaskBucket_Update(t *testing.T) {
 		})
 	})
 
+	t.Run("moving a repeating task from a non-default bucket when no default bucket is configured preserves the original bucket", func(t *testing.T) {
+		db.LoadAndAssertFixtures(t)
+		s := db.NewSession()
+		defer s.Close()
+
+		u := &user.User{ID: 1}
+
+		// View 4 has default_bucket_id: 1 and done_bucket_id: 3.
+		// Remove the default bucket to test fallback behavior.
+		_, err := s.ID(4).Cols("default_bucket_id").Update(&ProjectView{DefaultBucketID: 0})
+		require.NoError(t, err)
+
+		// Task 28 is a repeating task. Pre-position it in bucket 2
+		// using a raw update so we can bypass the bucket-2 limit check.
+		_, err = s.Where("task_id = ? AND project_view_id = ?", 28, 4).
+			Cols("bucket_id").
+			Update(&TaskBucket{BucketID: 2})
+		require.NoError(t, err)
+
+		tb := &TaskBucket{
+			TaskID:        28,
+			BucketID:      3, // Bucket 3 is the done bucket on view 4
+			ProjectViewID: 4,
+			ProjectID:     1,
+		}
+		err = tb.Update(s, u)
+		require.NoError(t, err)
+		err = s.Commit()
+		require.NoError(t, err)
+
+		// Repeating task should have been re-opened by updateDone...
+		assert.False(t, tb.Task.Done)
+
+		// ...and routed back to the ORIGINAL bucket (2), not the default (1)
+		// and not left in the done bucket (3).
+		assert.Equal(t, int64(2), tb.BucketID)
+
+		db.AssertExists(t, "tasks", map[string]interface{}{
+			"id":   28,
+			"done": false,
+		}, false)
+		db.AssertExists(t, "task_buckets", map[string]interface{}{
+			"task_id":   28,
+			"bucket_id": 2,
+		}, false)
+		db.AssertMissing(t, "task_buckets", map[string]interface{}{
+			"task_id":   28,
+			"bucket_id": 1,
+		})
+		db.AssertMissing(t, "task_buckets", map[string]interface{}{
+			"task_id":   28,
+			"bucket_id": 3,
+		})
+	})
+
 	t.Run("keep done timestamp when moving task between projects", func(t *testing.T) {
 		db.LoadAndAssertFixtures(t)
 		u := &user.User{ID: 1}
diff --git a/pkg/models/tasks.go b/pkg/models/tasks.go
index ee5eda824..a20295f0f 100644
--- a/pkg/models/tasks.go
+++ b/pkg/models/tasks.go
@@ -1535,31 +1535,35 @@ func (t *Task) moveTaskToDoneBuckets(s *xorm.Session, a web.Auth, views []*Proje
 // and is used when a repeating task is marked done: repeating tasks
 // don't stay in the done bucket, so they should be routed back to
 // the default ("To-Do") bucket so the next iteration is visible there.
+// When no explicit default bucket is configured, the task stays in its
+// current bucket — no update needed.
 func (t *Task) moveTaskToDefaultBuckets(s *xorm.Session, a web.Auth, views []*ProjectView) error {
 	for _, view := range views {
-		defaultBucketID, err := getDefaultBucketID(s, view)
-		if err != nil {
-			return err
-		}
+		if view.DefaultBucketID != 0 {
+			defaultBucketID, err := getDefaultBucketID(s, view)
+			if err != nil {
+				return err
+			}
 
-		tb := &TaskBucket{
-			BucketID:      defaultBucketID,
-			TaskID:        t.ID,
-			ProjectViewID: view.ID,
-			ProjectID:     t.ProjectID,
-		}
-		err = updateTaskBucket(s, a, tb)
-		if err != nil {
-			return err
+			tb := &TaskBucket{
+				BucketID:      defaultBucketID,
+				TaskID:        t.ID,
+				ProjectViewID: view.ID,
+				ProjectID:     t.ProjectID,
+			}
+			if err = updateTaskBucket(s, a, tb); err != nil {
+				return err
+			}
 		}
+		// When no default bucket is configured, the task stays in its current
+		// bucket — no bucket update needed.
 
 		tp := TaskPosition{
 			TaskID:        t.ID,
 			ProjectViewID: view.ID,
 			Position:      calculateDefaultPosition(t.Index, t.Position),
 		}
-		err = updateTaskPosition(s, a, &tp)
-		if err != nil {
+		if err := updateTaskPosition(s, a, &tp); err != nil {
 			return err
 		}
 	}