fix: eliminate UI rerender during task cancellation

- Add resetToResumableState() method to Task class to reset internal state without recreation
- Simplify cancellation flow to handle everything within Task class
- Update abortStream() to properly mark API requests as cancelled
- Remove initClineWithHistoryItem() call from ClineProvider.cancelTask()
- Task instance now persists through cancellation, preventing UI flicker

The task now handles its own cancellation and resumption internally, maintaining
the same instance throughout. This provides a seamless user experience with no
visual disruption when cancelling and resuming tasks.

Author: daniel-lxs

src/core/task/Task.ts

@@ -1489,8 +1489,8 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 		}
 	}
 
-	public async abortTask(isAbandoned = false) {
-		// Aborting task
+public async abortTask(isAbandoned = false, skipSave = false) {
+		console.log(`[subtasks] aborting task ${this.taskId}.${this.instanceId}`)
 
 		// Will stop any autonomously running promises.
 		if (isAbandoned) {
@@ -1506,15 +1506,74 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 			console.error(`Error during task ${this.taskId}.${this.instanceId} disposal:`, error)
 			// Don't rethrow - we want abort to always succeed
 		}
-		// Save the countdown message in the automatic retry or other content.
-		try {
-			// Save the countdown message in the automatic retry or other content.
-			await this.saveClineMessages()
-		} catch (error) {
-			console.error(`Error saving messages during abort for task ${this.taskId}.${this.instanceId}:`, error)
+
+		// Only save messages if not skipping (e.g., during user cancellation where messages are already saved)
+		if (!skipSave) {
+			try {
+				// Save the countdown message in the automatic retry or other content.
+				await this.saveClineMessages()
+			} catch (error) {
+				console.error(`Error saving messages during abort for task ${this.taskId}.${this.instanceId}:`, error)
+			}
 		}
 	}
 
+	/**
+	 * Reset the task to a resumable state without recreating the instance.
+	 * This is used when canceling a task to avoid unnecessary rerenders.
+	 */
+	public async resetToResumableState() {
+		console.log(`[subtasks] resetting task ${this.taskId}.${this.instanceId} to resumable state`)
+
+		// Reset abort flags
+		this.abort = false
+		this.abandoned = false
+
+		// Reset streaming state
+		this.isStreaming = false
+		this.isWaitingForFirstChunk = false
+		this.didFinishAbortingStream = true
+		this.didCompleteReadingStream = false
+
+		// Clear streaming content
+		this.currentStreamingContentIndex = 0
+		this.currentStreamingDidCheckpoint = false
+		this.assistantMessageContent = []
+		this.userMessageContent = []
+		this.userMessageContentReady = false
+		this.didRejectTool = false
+		this.didAlreadyUseTool = false
+		this.presentAssistantMessageLocked = false
+		this.presentAssistantMessageHasPendingUpdates = false
+
+		// Reset API state
+		this.consecutiveMistakeCount = 0
+
+		// Reset ask response state to allow new messages
+		this.askResponse = undefined
+		this.askResponseText = undefined
+		this.askResponseImages = undefined
+		this.blockingAsk = undefined
+
+		// Reset parser if exists
+		if (this.assistantMessageParser) {
+			this.assistantMessageParser.reset()
+		}
+
+		// Only reset diff view if it's actively editing
+		// This avoids unnecessary operations when diff view is not in use
+		if (this.diffViewProvider && this.diffViewProvider.isEditing) {
+			await this.diffViewProvider.reset()
+		}
+
+		// The task is now ready to be resumed
+		// The API request status has already been updated by abortStream
+		// We don't add the resume_task message here because ask() will add it
+
+		// Keep messages and history intact for resumption
+		// The task is now ready to be resumed without recreation
+	}
+
 	// Used when a sub-task is launched and the parent task is waiting for it to
 	// finish.
 	// TBD: The 1s should be added to the settings, also should add a timeout to
@@ -1584,7 +1643,7 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 			const currentUserContent = currentItem.userContent
 			const currentIncludeFileDetails = currentItem.includeFileDetails
 
-			if (this.abort) {
+if (this.abort) {
 				throw new Error(`[RooCode#recursivelyMakeRooRequests] task ${this.taskId}.${this.instanceId} aborted`)
 			}
 

src/core/webview/ClineProvider.ts

@@ -1279,38 +1279,11 @@ export class ClineProvider
 
 		console.log(`[subtasks] cancelling task ${cline.taskId}.${cline.instanceId}`)
 
-		const { historyItem } = await this.getTaskWithId(cline.taskId)
-		// Preserve parent and root task information for history item.
-		const rootTask = cline.rootTask
-		const parentTask = cline.parentTask
-
-		cline.abortTask()
-
-		await pWaitFor(
-			() =>
-				this.getCurrentTask()! === undefined ||
-				this.getCurrentTask()!.isStreaming === false ||
-				this.getCurrentTask()!.didFinishAbortingStream ||
-				// If only the first chunk is processed, then there's no
-				// need to wait for graceful abort (closes edits, browser,
-				// etc).
-				this.getCurrentTask()!.isWaitingForFirstChunk,
-			{
-				timeout: 3_000,
-			},
-		).catch(() => {
-			console.error("Failed to abort task")
-		})
-
-		if (this.getCurrentTask()) {
-			// 'abandoned' will prevent this Cline instance from affecting
-			// future Cline instances. This may happen if its hanging on a
-			// streaming request.
-			this.getCurrentTask()!.abandoned = true
-		}
+		// Just set the abort flag - the task will handle its own resumption
+		cline.abort = true
 
-		// Clears task again, so we need to abortTask manually above.
-		await this.createTaskWithHistoryItem({ ...historyItem, rootTask, parentTask })
+		// The task's streaming loop will detect the abort flag and handle the resumption
+		// No need to wait or do anything else here
 	}
 
 	async updateCustomInstructions(instructions?: string) {