diff --git a/backend/.golangci.yml b/backend/.golangci.yml
index adb55e37..3ec692a8 100644
--- a/backend/.golangci.yml
+++ b/backend/.golangci.yml
@@ -21,6 +21,9 @@ linters:
             - "!**/internal/service/ops_aggregation_service.go"
             - "!**/internal/service/ops_alert_evaluator_service.go"
             - "!**/internal/service/ops_cleanup_service.go"
+            - "!**/internal/service/ops_metrics_collector.go"
+            - "!**/internal/service/ops_scheduled_report_service.go"
+            - "!**/internal/service/wire.go"
           deny:
             - pkg: github.com/Wei-Shaw/sub2api/internal/repository
               desc: "service must not import repository"
diff --git a/backend/internal/handler/admin/ops_ws_handler.go b/backend/internal/handler/admin/ops_ws_handler.go
index 34081e8d..db7442e5 100644
--- a/backend/internal/handler/admin/ops_ws_handler.go
+++ b/backend/internal/handler/admin/ops_ws_handler.go
@@ -416,7 +416,10 @@ func releaseOpsWSIPSlot(clientIP string) {
 	if !ok {
 		return
 	}
-	counter, ok := v.(*atomic.Int32); if !ok { return }
+	counter, ok := v.(*atomic.Int32)
+	if !ok {
+		return
+	}
 	next := counter.Add(-1)
 	if next <= 0 {
 		// Best-effort cleanup; safe even if a new slot was acquired concurrently.
diff --git a/backend/internal/repository/ops_repo_dashboard.go b/backend/internal/repository/ops_repo_dashboard.go
index e06e393a..194020bb 100644
--- a/backend/internal/repository/ops_repo_dashboard.go
+++ b/backend/internal/repository/ops_repo_dashboard.go
@@ -385,7 +385,7 @@ ORDER BY bucket_start ASC`
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer func() { _ = rows.Close() }()
 
 	out := make([]opsHourlyMetricsRow, 0, 64)
 	for rows.Next() {
diff --git a/backend/internal/repository/ops_repo_histograms.go b/backend/internal/repository/ops_repo_histograms.go
index 143c7e83..c2978798 100644
--- a/backend/internal/repository/ops_repo_histograms.go
+++ b/backend/internal/repository/ops_repo_histograms.go
@@ -42,7 +42,7 @@ ORDER BY 3 ASC`
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer func() { _ = rows.Close() }()
 
 	counts := make(map[string]int64, len(latencyHistogramOrderedRanges))
 	var total int64
diff --git a/backend/internal/repository/ops_repo_latency_histogram_buckets.go b/backend/internal/repository/ops_repo_latency_histogram_buckets.go
index fc085fc6..f7809480 100644
--- a/backend/internal/repository/ops_repo_latency_histogram_buckets.go
+++ b/backend/internal/repository/ops_repo_latency_histogram_buckets.go
@@ -29,19 +29,19 @@ var latencyHistogramOrderedRanges = func() []string {
 
 func latencyHistogramRangeCaseExpr(column string) string {
 	var sb strings.Builder
-	sb.WriteString("CASE\n")
+	_, _ = sb.WriteString("CASE\n")
 
 	for _, b := range latencyHistogramBuckets {
 		if b.upperMs <= 0 {
 			continue
 		}
-		sb.WriteString(fmt.Sprintf("\tWHEN %s < %d THEN '%s'\n", column, b.upperMs, b.label))
+		_, _ = sb.WriteString(fmt.Sprintf("\tWHEN %s < %d THEN '%s'\n", column, b.upperMs, b.label))
 	}
 
 	// Default bucket.
 	last := latencyHistogramBuckets[len(latencyHistogramBuckets)-1]
-	sb.WriteString(fmt.Sprintf("\tELSE '%s'\n", last.label))
-	sb.WriteString("END")
+	_, _ = sb.WriteString(fmt.Sprintf("\tELSE '%s'\n", last.label))
+	_, _ = sb.WriteString("END")
 	return sb.String()
 }
 
diff --git a/backend/internal/repository/ops_repo_metrics.go b/backend/internal/repository/ops_repo_metrics.go
index 75345595..bc80ed6e 100644
--- a/backend/internal/repository/ops_repo_metrics.go
+++ b/backend/internal/repository/ops_repo_metrics.go
@@ -348,7 +348,7 @@ ORDER BY job_name ASC`
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer func() { _ = rows.Close() }()
 
 	out := make([]*service.OpsJobHeartbeat, 0, 8)
 	for rows.Next() {