feat: persist parent-child task relationships across extension reloads

- Add parentTaskId, rootTaskId, and taskHierarchy fields to HistoryItem schema
- Store task IDs alongside object references in Task class
- Update taskMetadata to save parent-child relationship data
- Modify ClineProvider to restore task hierarchy when loading from history
- Implement getTaskHierarchy() method to build hierarchy array

Fixes #6624

packages/types/src/history.ts

@@ -17,6 +17,9 @@ export const historyItemSchema = z.object({
 	size: z.number().optional(),
 	workspace: z.string().optional(),
 	mode: z.string().optional(),
+	parentTaskId: z.string().optional(),
+	rootTaskId: z.string().optional(),
+	taskHierarchy: z.array(z.string()).optional(),
 })
 
 export type HistoryItem = z.infer<typeof historyItemSchema>

src/core/task-persistence/taskMetadata.ts

@@ -19,6 +19,9 @@ export type TaskMetadataOptions = {
 	globalStoragePath: string
 	workspace: string
 	mode?: string
+	parentTaskId?: string
+	rootTaskId?: string
+	taskHierarchy?: string[]
 }
 
 export async function taskMetadata({
@@ -28,6 +31,9 @@ export async function taskMetadata({
 	globalStoragePath,
 	workspace,
 	mode,
+	parentTaskId,
+	rootTaskId,
+	taskHierarchy,
 }: TaskMetadataOptions) {
 	const taskDir = await getTaskDirectoryPath(globalStoragePath, taskId)
 
@@ -95,6 +101,9 @@ export async function taskMetadata({
 		size: taskDirSize,
 		workspace,
 		mode,
+		parentTaskId,
+		rootTaskId,
+		taskHierarchy,
 	}
 
 	return { historyItem, tokenUsage }

src/core/task/Task.ts

@@ -129,6 +129,10 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 	readonly taskNumber: number
 	readonly workspacePath: string
 
+	// Store task IDs for persistence
+	readonly rootTaskId: string | undefined = undefined
+	readonly parentTaskId: string | undefined = undefined
+
 	/**
 	 * The mode associated with this task. Persisted across sessions
 	 * to maintain user context when reopening tasks from history.
@@ -307,6 +311,10 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 		this.parentTask = parentTask
 		this.taskNumber = taskNumber
 
+		// Store task IDs for persistence
+		this.rootTaskId = rootTask?.taskId
+		this.parentTaskId = parentTask?.taskId
+
 		// Store the task's mode when it's created.
 		// For history items, use the stored mode; for new tasks, we'll set it
 		// after getting state.
@@ -582,6 +590,9 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 				globalStoragePath: this.globalStoragePath,
 				workspace: this.cwd,
 				mode: this._taskMode || defaultModeSlug, // Use the task's own mode, not the current provider mode
+				parentTaskId: this.parentTaskId,
+				rootTaskId: this.rootTaskId,
+				taskHierarchy: this.getTaskHierarchy(),
 			})
 
 			this.emit(RooCodeEventName.TaskTokenUsageUpdated, this.taskId, tokenUsage)
@@ -2152,4 +2163,17 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 	public get cwd() {
 		return this.workspacePath
 	}
+
+	// Get task hierarchy for persistence
+	public getTaskHierarchy(): string[] {
+		const hierarchy: string[] = []
+		let currentTask: Task | undefined = this.parentTask
+
+		while (currentTask) {
+			hierarchy.unshift(currentTask.taskId)
+			currentTask = currentTask.parentTask
+		}
+
+		return hierarchy
+	}
 }

src/core/webview/ClineProvider.ts

@@ -740,6 +740,18 @@ export class ClineProvider
 			experiments,
 		} = await this.getState()
 
+		// Restore parent and root tasks if their IDs are stored in the history item
+		let rootTask: Task | undefined = historyItem.rootTask
+		let parentTask: Task | undefined = historyItem.parentTask
+
+		// If we don't have the actual task objects but have their IDs, try to find them in the stack
+		if (!rootTask && historyItem.rootTaskId) {
+			rootTask = this.clineStack.find((task) => task.taskId === historyItem.rootTaskId)
+		}
+		if (!parentTask && historyItem.parentTaskId) {
+			parentTask = this.clineStack.find((task) => task.taskId === historyItem.parentTaskId)
+		}
+
 		const task = new Task({
 			provider: this,
 			apiConfiguration,
@@ -749,8 +761,8 @@ export class ClineProvider
 			consecutiveMistakeLimit: apiConfiguration.consecutiveMistakeLimit,
 			historyItem,
 			experiments,
-			rootTask: historyItem.rootTask,
-			parentTask: historyItem.parentTask,
+			rootTask,
+			parentTask,
 			taskNumber: historyItem.number,
 			onCreated: (instance) => this.emit(RooCodeEventName.TaskCreated, instance),
 		})
@@ -1344,6 +1356,23 @@ export class ClineProvider
 		if (id !== this.getCurrentCline()?.taskId) {
 			// Non-current task.
 			const { historyItem } = await this.getTaskWithId(id)
+
+			// Check if this task has parent/child relationships that need to be restored
+			if (historyItem.taskHierarchy && historyItem.taskHierarchy.length > 0) {
+				// Restore the entire task hierarchy from root to this task
+				const taskHistory = this.getGlobalState("taskHistory") ?? []
+
+				// First, restore all parent tasks in the hierarchy
+				for (const taskId of historyItem.taskHierarchy) {
+					const parentHistoryItem = taskHistory.find((item: HistoryItem) => item.id === taskId)
+					if (parentHistoryItem && !this.clineStack.find((task) => task.taskId === taskId)) {
+						// This parent task is not in the stack, so restore it
+						await this.initClineWithHistoryItem(parentHistoryItem)
+					}
+				}
+			}
+
+			// Now restore the requested task
 			await this.initClineWithHistoryItem(historyItem) // Clears existing task.
 		}