diff --git a/.changeset/gentle-news-provide.md b/.changeset/gentle-news-provide.md
new file mode 100644
index 000000000..5e892279f
--- /dev/null
+++ b/.changeset/gentle-news-provide.md
@@ -0,0 +1,5 @@
+---
+"aws-sdk-js-codemod": patch
+---
+
+Do not use spread syntax on accumulators
diff --git a/biome.json b/biome.json
index e81febeb5..9af8d7f22 100644
--- a/biome.json
+++ b/biome.json
@@ -20,9 +20,6 @@
         "noUndeclaredVariables": "error",
         "noUnusedVariables": "error"
       },
-      "performance": {
-        "noAccumulatingSpread": "off"
-      },
       "style": {
         "noNamespace": "error",
         "noNonNullAssertion": "off",
diff --git a/src/transforms/v2-to-v3/client-names/getClientMetadataRecord.ts b/src/transforms/v2-to-v3/client-names/getClientMetadataRecord.ts
index df343f3ef..967297f71 100644
--- a/src/transforms/v2-to-v3/client-names/getClientMetadataRecord.ts
+++ b/src/transforms/v2-to-v3/client-names/getClientMetadataRecord.ts
@@ -7,16 +7,19 @@ export const getClientMetadataRecord = (
 ): ClientMetadataRecord =>
   Object.entries(
     Object.entries(v2ClientNamesRecord).reduce(
-      (acc, [v2ClientName, v2ClientLocalName]) => ({
-        ...acc,
-        [v2ClientName]: {
+      (acc: ClientMetadataRecord, [v2ClientName, v2ClientLocalName]) => {
+        acc[v2ClientName] = {
           v2ClientLocalName,
           v3ClientName: getV3ClientName(v2ClientName),
           v3ClientPackageName: getV3ClientPackageName(v2ClientName),
-        },
-      }),
+        };
+        return acc;
+      },
       {}
-    ) as ClientMetadataRecord
+    )
   )
     .sort(([, { v3ClientPackageName: a }], [, { v3ClientPackageName: b }]) => b.localeCompare(a))
-    .reduce((r, [k, v]) => ({ ...r, [k]: v }), {});
+    .reduce((acc: ClientMetadataRecord, [key, value]) => {
+      acc[key] = value;
+      return acc;
+    }, {});
diff --git a/src/transforms/v2-to-v3/config/CLIENT_NAMES_MAP.ts b/src/transforms/v2-to-v3/config/CLIENT_NAMES_MAP.ts
index 821a61d09..42bdcb1b8 100644
--- a/src/transforms/v2-to-v3/config/CLIENT_NAMES_MAP.ts
+++ b/src/transforms/v2-to-v3/config/CLIENT_NAMES_MAP.ts
@@ -2,7 +2,10 @@ import { CLIENT_NAMES } from "./CLIENT_NAMES";
 
 // The key is the client name in v2, and value is the client name in v3.
 export const CLIENT_NAMES_MAP: Record<string, string> = {
-  ...CLIENT_NAMES.reduce((acc, name) => ({ ...acc, [name]: name }), {}),
+  ...CLIENT_NAMES.reduce((acc: Record<string, string>, name) => {
+    acc[name] = name;
+    return acc;
+  }, {}),
   AugmentedAIRuntime: "SageMakerA2IRuntime",
   CUR: "CostAndUsageReportService",
   CodeArtifact: "Codeartifact",
diff --git a/src/transforms/v2-to-v3/config/CLIENT_PACKAGE_NAMES_MAP.ts b/src/transforms/v2-to-v3/config/CLIENT_PACKAGE_NAMES_MAP.ts
index e75a1564b..24e190acd 100644
--- a/src/transforms/v2-to-v3/config/CLIENT_PACKAGE_NAMES_MAP.ts
+++ b/src/transforms/v2-to-v3/config/CLIENT_PACKAGE_NAMES_MAP.ts
@@ -2,37 +2,34 @@ import { CLIENT_NAMES } from "./CLIENT_NAMES";
 
 // The key is the client name in v2, and value is the client package name in v3.
 export const CLIENT_PACKAGE_NAMES_MAP: Record<string, string> = {
-  ...CLIENT_NAMES.reduce(
-    (acc, name) => ({
-      ...acc,
-      [name]: `client-${name.replace(/([a-z])([A-Z])/g, "$1-$2").toLowerCase()}`
-        .replace("-chime-sdk", "-chime-sdk-")
-        .replace("client-amplify-", "client-amplify")
-        .replace("client-bcmdata-exports", "client-bcm-data-exports")
-        .replace("client-control-catalog", "client-controlcatalog")
-        .replace("client-clean-rooms-ml", "client-cleanroomsml")
-        .replace("client-cloud-", "client-cloud")
-        .replace("client-code-", "client-code")
-        .replace("client-connect-", "client-connect")
-        .replace("client-data-", "client-data")
-        .replace("client-free-tier", "client-freetier")
-        .replace("client-io-t", "client-iot-")
-        .replace("client-iot-fleet-", "client-iotfleet")
-        .replace("client-lookout-", "client-lookout")
-        .replace("client-media-", "client-media")
-        .replace("client-migration-hub-", "client-migrationhub")
-        .replace("client-network-monitor", "client-networkmonitor")
-        .replace("client-pinpoint-sms", "client-pinpoint-sms-")
-        .replace("client-route53", "client-route53-")
-        .replace("client-sage-maker", "client-sagemaker")
-        .replace("client-security-", "client-security")
-        .replace("client-supply-chain", "client-supplychain")
-        .replace("client-timestream-influx-db", "client-timestream-influxdb")
-        .replace("client-trusted-advisor", "client-trustedadvisor")
-        .replace("client-work-", "client-work"),
-    }),
-    {}
-  ),
+  ...CLIENT_NAMES.reduce((acc: Record<string, string>, name) => {
+    acc[name] = `client-${name.replace(/([a-z])([A-Z])/g, "$1-$2").toLowerCase()}`
+      .replace("-chime-sdk", "-chime-sdk-")
+      .replace("client-amplify-", "client-amplify")
+      .replace("client-bcmdata-exports", "client-bcm-data-exports")
+      .replace("client-control-catalog", "client-controlcatalog")
+      .replace("client-clean-rooms-ml", "client-cleanroomsml")
+      .replace("client-cloud-", "client-cloud")
+      .replace("client-code-", "client-code")
+      .replace("client-connect-", "client-connect")
+      .replace("client-data-", "client-data")
+      .replace("client-free-tier", "client-freetier")
+      .replace("client-io-t", "client-iot-")
+      .replace("client-iot-fleet-", "client-iotfleet")
+      .replace("client-lookout-", "client-lookout")
+      .replace("client-media-", "client-media")
+      .replace("client-migration-hub-", "client-migrationhub")
+      .replace("client-network-monitor", "client-networkmonitor")
+      .replace("client-pinpoint-sms", "client-pinpoint-sms-")
+      .replace("client-route53", "client-route53-")
+      .replace("client-sage-maker", "client-sagemaker")
+      .replace("client-security-", "client-security")
+      .replace("client-supply-chain", "client-supplychain")
+      .replace("client-timestream-influx-db", "client-timestream-influxdb")
+      .replace("client-trusted-advisor", "client-trustedadvisor")
+      .replace("client-work-", "client-work");
+    return acc;
+  }, {}),
   AccessAnalyzer: "client-accessanalyzer",
   ACMPCA: "client-acm-pca",
   APIGateway: "client-api-gateway",