diff --git a/infra/lib/foundation-stack.ts b/infra/lib/foundation-stack.ts
index b2fa4ab..c5bb5ef 100644
--- a/infra/lib/foundation-stack.ts
+++ b/infra/lib/foundation-stack.ts
@@ -88,7 +88,11 @@ export class FoundationStack extends cdk.Stack {
     // PR3: replaced the RDS instance + OpenSearch Serverless with Aurora + pgvector
     // (kills the AOSS OCU floor; scales toward 0 ACU when idle). Data API is required
     // by Bedrock Knowledge Bases to query the vector table.
-    const dbCluster = new rds.DatabaseCluster(this, 'Database', {
+    // Construct ID is 'AuroraCluster' (not 'Database') so CloudFormation gets a NEW
+    // logical ID for the cluster — the old RDS DBInstance shared logical ID 'Database*'
+    // and CFN forbids changing a resource's type in place ("Update of resource type is
+    // not permitted"). A distinct ID makes it a clean replace instead.
+    const dbCluster = new rds.DatabaseCluster(this, 'AuroraCluster', {
       clusterIdentifier: `proposal-system-db${config.stackSuffix}`,
       engine: rds.DatabaseClusterEngine.auroraPostgres({
         version: rds.AuroraPostgresEngineVersion.VER_15_4,