fix: preserve task state when extension host restarts in new window

- Modified ClineProvider.ts to check if tasks exist before clearing them
- Only clear task stack on fresh start, not on webview restoration
- Added logging to indicate when task state is preserved
- Updated webviewMessageHandler to log when restoring active tasks

This fixes the issue where prompts were lost after extension host restart
in a new window.

Fixes #8035

src/core/webview/ClineProvider.ts

@@ -134,6 +134,7 @@ export class ClineProvider
 	private taskCreationCallback: (task: Task) => void
 	private taskEventListeners: WeakMap<Task, Array<() => void>> = new WeakMap()
 	private currentWorkspacePath: string | undefined
+	private isWebviewRestored: boolean = false // Track if webview is being restored after restart
 
 	private recentTasksCache?: string[]
 	private pendingOperations: Map<string, PendingEditOperation> = new Map()
@@ -686,6 +687,9 @@ export class ClineProvider
 	}
 
 	async resolveWebviewView(webviewView: vscode.WebviewView | vscode.WebviewPanel) {
+		// Check if we already have a task stack (indicating a restore after extension host restart)
+		const hasExistingTasks = this.clineStack.length > 0
+
 		this.view = webviewView
 		const inTabMode = "onDidChangeViewState" in webviewView
 
@@ -695,6 +699,9 @@ export class ClineProvider
 			setPanel(webviewView, "sidebar")
 		}
 
+		// Mark that we're restoring if we have existing tasks
+		this.isWebviewRestored = hasExistingTasks
+
 		// Initialize out-of-scope variables that need to receive persistent
 		// global state values.
 		this.getState().then(
@@ -810,8 +817,17 @@ export class ClineProvider
 		})
 		this.webviewDisposables.push(configDisposable)
 
-		// If the extension is starting a new session, clear previous task state.
-		await this.removeClineFromStack()
+		// Only clear task state if this is a fresh start, not when restoring after extension host restart
+		// When the extension host restarts in a new window, we want to preserve the task state
+		if (!hasExistingTasks) {
+			// This is a fresh start, clear any previous task state
+			await this.removeClineFromStack()
+		} else {
+			// We're restoring after an extension host restart, preserve the task state
+			this.log("Preserving task state after extension host restart")
+			// Post the current state to the webview so it can restore the UI
+			await this.postStateToWebview()
+		}
 	}
 
 	public async createTaskWithHistoryItem(historyItem: HistoryItem & { rootTask?: Task; parentTask?: Task }) {

src/core/webview/webviewMessageHandler.ts

@@ -443,6 +443,13 @@ export const webviewMessageHandler = async (
 				provider.postMessageToWebview({ type: "mcpServers", mcpServers: mcpHub.getAllServers() })
 			}
 
+			// If we have an active task (after extension host restart), notify the webview to restore it
+			const activeTask = provider.getCurrentTask()
+			if (activeTask) {
+				provider.log("Restoring active task after extension host restart")
+				// The state will be posted by postStateToWebview() above, which includes the current task
+			}
+
 			provider.providerSettingsManager
 				.listConfig()
 				.then(async (listApiConfig) => {