diff --git a/deploy/kubernetes/easyai-ai-gateway-cluster-release b/deploy/kubernetes/easyai-ai-gateway-cluster-release
index a2c115a..59a11bf 100755
--- a/deploy/kubernetes/easyai-ai-gateway-cluster-release
+++ b/deploy/kubernetes/easyai-ai-gateway-cluster-release
@@ -716,7 +716,7 @@ prepare_postgres_single_instance() {
   local source_sha=$1
   local current_instances current_primary primary_node synchronous_enabled
   if ! grep -Eq '^  instances: 1$' "$DESIRED_STATE_DIR/database.yaml" ||
-     ! grep -Eq '^    synchronous: null$' "$DESIRED_STATE_DIR/database.yaml"; then
+     grep -Eq '^[[:space:]]+synchronous:' "$DESIRED_STATE_DIR/database.yaml"; then
     echo 'production PostgreSQL desired state must declare one instance with synchronous replication disabled' >&2
     return 1
   fi
diff --git a/deploy/kubernetes/production/database.yaml b/deploy/kubernetes/production/database.yaml
index d50d7e4..8c77060 100644
--- a/deploy/kubernetes/production/database.yaml
+++ b/deploy/kubernetes/production/database.yaml
@@ -117,9 +117,6 @@ spec:
       cpu: "2"
       memory: 3Gi
   postgresql:
-    # Keep this explicit null so server-side apply atomically removes the old
-    # two-instance synchronous setting during preflight field management.
-    synchronous: null
     parameters:
       # A 16 MiB WAL segment every 60 seconds requires at least 2.24 Mbit/s
       # of continuous cross-region throughput even while the database is idle.
diff --git a/tests/release/manual-release-test.sh b/tests/release/manual-release-test.sh
index f4bfd57..ddf062e 100755
--- a/tests/release/manual-release-test.sh
+++ b/tests/release/manual-release-test.sh
@@ -316,7 +316,10 @@ if grep -Fq 'archive_timeout: 60s' "$root/deploy/kubernetes/production/database.
 fi
 grep -Fq '  instances: 1' "$root/deploy/kubernetes/production/database.yaml"
 grep -Fq '      easyai.io/site: ningbo' "$root/deploy/kubernetes/production/database.yaml"
-grep -Fq '    synchronous: null' "$root/deploy/kubernetes/production/database.yaml"
+if grep -Eq '^[[:space:]]+synchronous:' "$root/deploy/kubernetes/production/database.yaml"; then
+  echo 'production single-instance PostgreSQL must not declare synchronous replication' >&2
+  exit 1
+fi
 grep -Fq 'wal_sender_timeout: 30s' "$root/deploy/kubernetes/production/database.yaml"
 grep -Fq 'wal_receiver_timeout: 30s' "$root/deploy/kubernetes/production/database.yaml"
 bash -n "$root/scripts/cluster/configure-control-plane-io.sh"