fix: prevent conversation history loss when canceling during response

- Add explicit saveApiConversationHistory() call after adding interrupted message in abortStream
- Reverse order of abortStream/abortTask calls to save state before cleanup
- Add safety check in saveApiMessages to prevent overwriting non-empty history with empty array

Fixes #8153

src/core/task-persistence/apiMessages.ts

@@ -79,5 +79,31 @@ export async function saveApiMessages({
 }) {
 	const taskDir = await getTaskDirectoryPath(globalStoragePath, taskId)
 	const filePath = path.join(taskDir, GlobalFileNames.apiConversationHistory)
+
+	// Safety check: prevent saving an empty array if a non-empty conversation previously existed
+	if (Array.isArray(messages) && messages.length === 0) {
+		// Check if there's an existing non-empty conversation history
+		if (await fileExistsAtPath(filePath)) {
+			try {
+				const existingContent = await fs.readFile(filePath, "utf8")
+				const existingData = JSON.parse(existingContent)
+				if (Array.isArray(existingData) && existingData.length > 0) {
+					console.error(
+						`[Roo-Debug] saveApiMessages: Attempted to save empty array over existing non-empty conversation. ` +
+							`TaskId: ${taskId}, Existing messages count: ${existingData.length}. ` +
+							`Skipping save to prevent data loss.`,
+					)
+					return // Don't save empty array over non-empty conversation
+				}
+			} catch (error) {
+				// If we can't read/parse the existing file, proceed with save
+				console.error(
+					`[Roo-Debug] saveApiMessages: Error checking existing conversation history. ` +
+						`TaskId: ${taskId}, Error: ${error}. Proceeding with save.`,
+				)
+			}
+		}
+	}
+
 	await safeWriteJson(filePath, messages)
 }

src/core/task/Task.ts

@@ -1904,6 +1904,9 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 						],
 					})
 
+					// Explicitly save the API conversation history after adding the interrupted message
+					await this.saveApiConversationHistory()
+
 					// Update `api_req_started` to have cancelled and cost, so that
 					// we can display the cost of the partial stream.
 					updateApiReqMsg(cancelReason, streamingFailedMessage)
@@ -2196,9 +2199,10 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 							? undefined
 							: (error.message ?? JSON.stringify(serializeError(error), null, 2))
 
-						// Now call abortTask after determining the cancel reason.
-						await this.abortTask()
+						// Reverse the order: call abortStream first to properly save the interrupted message
+						// before abortTask cleans up resources
 						await abortStream(cancelReason, streamingFailedMessage)
+						await this.abortTask()
 
 						const history = await provider?.getTaskWithId(this.taskId)