diff --git a/src/sync/apply.ts b/src/sync/apply.ts
index 6c5cd28..698f694 100644
--- a/src/sync/apply.ts
+++ b/src/sync/apply.ts
@@ -1,7 +1,14 @@
 import { promises as fs } from 'node:fs';
 import path from 'node:path';
 
-import { deepMerge, parseJsonc, pathExists, stripOverrides, writeJsonFile } from './config.js';
+import {
+  deepMerge,
+  hasOwn,
+  parseJsonc,
+  pathExists,
+  stripOverrides,
+  writeJsonFile,
+} from './config.js';
 import {
   extractMcpSecrets,
   hasOverrides,
@@ -283,7 +290,7 @@ function isDeepEqual(left: unknown, right: unknown): boolean {
     const rightKeys = Object.keys(right as Record<string, unknown>);
     if (leftKeys.length !== rightKeys.length) return false;
     for (const key of leftKeys) {
-      if (!Object.hasOwn(right, key)) return false;
+      if (!hasOwn(right as Record<string, unknown>, key)) return false;
       if (
         !isDeepEqual(
           (left as Record<string, unknown>)[key],
diff --git a/src/sync/config.ts b/src/sync/config.ts
index 4ab9b0f..7cdeb11 100644
--- a/src/sync/config.ts
+++ b/src/sync/config.ts
@@ -178,11 +178,15 @@ export async function writeJsonFile(
   }
 }
 
-function isPlainObject(value: unknown): value is Record<string, unknown> {
+export function isPlainObject(value: unknown): value is Record<string, unknown> {
   if (!value || typeof value !== 'object') return false;
   return Object.getPrototypeOf(value) === Object.prototype;
 }
 
+export function hasOwn(target: Record<string, unknown>, key: string): boolean {
+  return Object.hasOwn(target, key);
+}
+
 function stripJsonComments(input: string): string {
   let output = '';
   let inString = false;
diff --git a/src/sync/mcp-secrets.ts b/src/sync/mcp-secrets.ts
index 0c15b25..72dad4a 100644
--- a/src/sync/mcp-secrets.ts
+++ b/src/sync/mcp-secrets.ts
@@ -1,4 +1,4 @@
-import { deepMerge } from './config.js';
+import { deepMerge, hasOwn, isPlainObject } from './config.js';
 
 export interface McpSecretExtraction {
   sanitizedConfig: Record<string, unknown>;
@@ -106,15 +106,7 @@ function getPlainObject(value: unknown): Record<string, unknown> | null {
   return isPlainObject(value) ? (value as Record<string, unknown>) : null;
 }
 
-function isPlainObject(value: unknown): value is Record<string, unknown> {
-  if (!value || typeof value !== 'object') return false;
-  return Object.getPrototypeOf(value) === Object.prototype;
-}
-
 function cloneConfig(config: Record<string, unknown>): Record<string, unknown> {
-  if (typeof structuredClone === 'function') {
-    return structuredClone(config);
-  }
   return JSON.parse(JSON.stringify(config)) as Record<string, unknown>;
 }
 
@@ -136,7 +128,7 @@ export function stripOverrideKeys(
   const result: Record<string, unknown> = { ...base };
 
   for (const [key, removeValue] of Object.entries(toRemove)) {
-    if (!Object.hasOwn(result, key)) continue;
+    if (!hasOwn(result, key)) continue;
     const currentValue = result[key];
     if (isPlainObject(removeValue) && isPlainObject(currentValue)) {
       const stripped = stripOverrideKeys(