diff --git a/scripts/agents/planner.agent.js b/scripts/agents/planner.agent.js
index fa47abb9..41d83474 100644
--- a/scripts/agents/planner.agent.js
+++ b/scripts/agents/planner.agent.js
@@ -257,12 +257,19 @@ function generatePlan(context) {
 **Confidence:** ${context.projectAssignment.confidence}
 **Reason:** ${context.projectAssignment.reason}
 `;
-    return plan.replace(
-      /---\r?\n\*\*Generated by Planner Agent\*\*.*/,
-      `${projectSection.trimStart()}
----
-**Generated by Planner Agent** <!-- planner-agent-summary -->`,
-    );
+    const marker = "<!-- planner-agent-summary -->";
+    const markerIndex = plan.indexOf(marker);
+    if (markerIndex !== -1) {
+      const footerIndex = plan.lastIndexOf("---", markerIndex);
+      if (footerIndex !== -1) {
+        return (
+          plan.slice(0, footerIndex) +
+          projectSection.trimStart() +
+          "\n" +
+          plan.slice(footerIndex)
+        );
+      }
+    }
   }
 
   return plan;
diff --git a/tests/jest.setup.localstorage.js b/tests/jest.setup.localstorage.js
index 8c07bf7b..4f41e7e8 100644
--- a/tests/jest.setup.localstorage.js
+++ b/tests/jest.setup.localstorage.js
@@ -1,10 +1,10 @@
 /**
- * Jest Setup: localStorage polyfill
- * Provides localStorage mock for jsdom test environment
+ * Jest Setup: Node.js built-ins polyfill
+ * Provides polyfills for Node.js built-ins in jsdom test environment
  *
- * @fileoverview localStorage polyfill for jest/jsdom tests
+ * @fileoverview Built-ins polyfills for jest/jsdom tests
  * @author LightSpeedWP Team
- * @version 1.0.0
+ * @version 1.1.0
  */
 
 // Polyfill TextDecoder and TextEncoder for test environments that don't have them
@@ -24,3 +24,17 @@ if (typeof global.localStorage === "undefined") {
   };
   global.localStorage = localStorageMock;
 }
+
+// Polyfill TextDecoder and TextEncoder for ESM modules using @actions/core
+if (
+  typeof global.TextDecoder === "undefined" ||
+  typeof global.TextEncoder === "undefined"
+) {
+  const { TextDecoder, TextEncoder } = require("util");
+  if (typeof global.TextDecoder === "undefined") {
+    global.TextDecoder = TextDecoder;
+  }
+  if (typeof global.TextEncoder === "undefined") {
+    global.TextEncoder = TextEncoder;
+  }
+}