diff --git a/backend/internal/redispkg/redis.go b/backend/internal/redispkg/redis.go
index e8d8878..abae72e 100644
--- a/backend/internal/redispkg/redis.go
+++ b/backend/internal/redispkg/redis.go
@@ -67,8 +67,12 @@ func (r *R) Lock(ctx context.Context, key string, ttl time.Duration) (func(), bo
 	rand.Read(b)
 	tok := hex.EncodeToString(b)
 	ok, err := r.c.SetNX(ctx, key, tok, ttl).Result()
-	if err != nil || !ok {
-		return noop, false
+	if err != nil { // spec §9: Redis 故障降级放行,锁只做尽力去重
+		log.Printf("redis lock %s: %v (proceeding without lock)", key, err)
+		return noop, true
+	}
+	if !ok {
+		return noop, false // 锁被持有,别的副本在扫
 	}
 	return func() {
 		r.c.Eval(ctx,
diff --git a/backend/internal/redispkg/redis_test.go b/backend/internal/redispkg/redis_test.go
index cfd8486..8d65092 100644
--- a/backend/internal/redispkg/redis_test.go
+++ b/backend/internal/redispkg/redis_test.go
@@ -22,3 +22,12 @@ func TestDisabledIsSafe(t *testing.T) {
 	}
 	un()
 }
+
+func TestDeadRedisLockFailsOpen(t *testing.T) {
+	r := New("redis://127.0.0.1:16399") // 死端口
+	un, ok := r.Lock(context.Background(), "lk", time.Second)
+	if !ok {
+		t.Fatal("Lock on redis error must fail open (spec §9)")
+	}
+	un()
+}