diff --git a/backend/services/dbmigration/maintenance.go b/backend/services/dbmigration/maintenance.go
index 568e312..0aecd34 100644
--- a/backend/services/dbmigration/maintenance.go
+++ b/backend/services/dbmigration/maintenance.go
@@ -63,20 +63,20 @@ func (lease *requestLease) release() {
 
 // 只有权限、请求体与一次性票据均已验证，才排空请求并独占迁移。
 // 独占状态由外层中间件持有到会话响应提交完成，不能在控制器返回前释放。
-func (s *Service) drainRequests(ctx context.Context) func() {
+func (s *Service) drainRequests(ctx context.Context) (func(), error) {
 	if lease, ok := ctx.Value(requestLeaseKey{}).(*requestLease); ok && lease.service == s {
 		lease.service.requests.RUnlock()
 		if !lease.service.requests.lockContext(ctx) {
 			lease.service = nil
-			return func() {}
+			return func() {}, contextError(ctx)
 		}
 		lease.exclusive = true
-		return func() {}
+		return func() {}, nil
 	}
 	if !s.requests.lockContext(ctx) {
-		return func() {}
+		return func() {}, contextError(ctx)
 	}
-	return s.requests.Unlock
+	return s.requests.Unlock, nil
 }
 
 func maintenanceRequest(r *http.Request) bool {
diff --git a/backend/services/dbmigration/maintenance_test.go b/backend/services/dbmigration/maintenance_test.go
index 553aeee..604171c 100644
--- a/backend/services/dbmigration/maintenance_test.go
+++ b/backend/services/dbmigration/maintenance_test.go
@@ -50,7 +50,11 @@ func TestMaintenanceGuardDrainsRequestsAndKeepsRestartRoute(t *testing.T) {
 			close(entered)
 			<-release
 		case "/api/v1/database/migrations":
-			release := service.drainRequests(r.Context())
+			release, err := service.drainRequests(r.Context())
+			if err != nil {
+				http.Error(w, err.Error(), http.StatusRequestTimeout)
+				return
+			}
 			defer release()
 			executor.paused.Store(true)
 			close(migrated)
diff --git a/backend/services/dbmigration/service.go b/backend/services/dbmigration/service.go
index 599a131..752f46b 100644
--- a/backend/services/dbmigration/service.go
+++ b/backend/services/dbmigration/service.go
@@ -223,8 +223,11 @@ func (s *Service) execute(ctx context.Context, id, token string, actor config.Au
 	item.targetConfig = config.DatabaseConfig{}
 	s.mu.Unlock()
 
-	releaseRequests := s.drainRequests(ctx)
+	releaseRequests, drainErr := s.drainRequests(ctx)
 	defer releaseRequests()
+	if drainErr != nil {
+		return s.fail(id, drainErr)
+	}
 	if err := contextError(ctx); err != nil {
 		return s.fail(id, err)
 	}