diff --git a/scripts/modules/task-manager/update-task-by-id.js b/scripts/modules/task-manager/update-task-by-id.js
index b77044fc..19603897 100644
--- a/scripts/modules/task-manager/update-task-by-id.js
+++ b/scripts/modules/task-manager/update-task-by-id.js
@@ -190,8 +190,45 @@ function parseUpdatedTaskFromText(text, expectedTaskId, logFn, isMCP) {
 		throw new Error('Parsed AI response is not a valid JSON object.');
 	}
 
+	// Preprocess the task to ensure subtasks have proper structure
+	const preprocessedTask = {
+		...parsedTask,
+		status: parsedTask.status || 'pending',
+		dependencies: Array.isArray(parsedTask.dependencies)
+			? parsedTask.dependencies
+			: [],
+		details:
+			typeof parsedTask.details === 'string'
+				? parsedTask.details
+				: String(parsedTask.details || ''),
+		testStrategy:
+			typeof parsedTask.testStrategy === 'string'
+				? parsedTask.testStrategy
+				: String(parsedTask.testStrategy || ''),
+		// Ensure subtasks is an array and each subtask has required fields
+		subtasks: Array.isArray(parsedTask.subtasks)
+			? parsedTask.subtasks.map((subtask) => ({
+					...subtask,
+					title: subtask.title || '',
+					description: subtask.description || '',
+					status: subtask.status || 'pending',
+					dependencies: Array.isArray(subtask.dependencies)
+						? subtask.dependencies
+						: [],
+					details:
+						typeof subtask.details === 'string'
+							? subtask.details
+							: String(subtask.details || ''),
+					testStrategy:
+						typeof subtask.testStrategy === 'string'
+							? subtask.testStrategy
+							: String(subtask.testStrategy || '')
+				}))
+			: []
+	};
+
 	// Validate the parsed task object using Zod
-	const validationResult = updatedTaskSchema.safeParse(parsedTask);
+	const validationResult = updatedTaskSchema.safeParse(preprocessedTask);
 	if (!validationResult.success) {
 		report('error', 'Parsed task object failed Zod validation.');
 		validationResult.error.errors.forEach((err) => {
diff --git a/scripts/modules/task-manager/update-tasks.js b/scripts/modules/task-manager/update-tasks.js
index fa048037..43b854b2 100644
--- a/scripts/modules/task-manager/update-tasks.js
+++ b/scripts/modules/task-manager/update-tasks.js
@@ -196,7 +196,18 @@ function parseUpdatedTasksFromText(text, expectedCount, logFn, isMCP) {
 		);
 	}
 
-	const validationResult = updatedTaskArraySchema.safeParse(parsedTasks);
+	// Preprocess tasks to ensure required fields have proper defaults
+	const preprocessedTasks = parsedTasks.map((task) => ({
+		...task,
+		// Ensure subtasks is always an array (not null or undefined)
+		subtasks: Array.isArray(task.subtasks) ? task.subtasks : [],
+		// Ensure status has a default value if missing
+		status: task.status || 'pending',
+		// Ensure dependencies is always an array
+		dependencies: Array.isArray(task.dependencies) ? task.dependencies : []
+	}));
+
+	const validationResult = updatedTaskArraySchema.safeParse(preprocessedTasks);
 	if (!validationResult.success) {
 		report('error', 'Parsed task array failed Zod validation.');
 		validationResult.error.errors.forEach((err) => {
@@ -442,7 +453,17 @@ async function updateTasks(
 			data.tasks.forEach((task, index) => {
 				if (updatedTasksMap.has(task.id)) {
 					// Only update if the task was part of the set sent to AI
-					data.tasks[index] = updatedTasksMap.get(task.id);
+					const updatedTask = updatedTasksMap.get(task.id);
+					// Merge the updated task with the existing one to preserve fields like subtasks
+					data.tasks[index] = {
+						...task, // Keep all existing fields
+						...updatedTask, // Override with updated fields
+						// Ensure subtasks field is preserved if not provided by AI
+						subtasks:
+							updatedTask.subtasks !== undefined
+								? updatedTask.subtasks
+								: task.subtasks
+					};
 					actualUpdateCount++;
 				}
 			});