fix: prevent duplicate responses when using native OpenAI tool format

- Fixed issue where text content was being duplicated in responses when using native tool format
- The problem occurred because text was accumulated in both assistantMessage and assistantMessageContent
- Solution: For native protocol with text blocks, use only the text blocks from assistantMessageContent
- For XML protocol or native without text blocks, use the accumulated assistantMessage as before

Fixes #9669

src/core/task/Task.ts

@@ -2924,8 +2924,23 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 					// Build the assistant message content array
 					const assistantContent: Array<Anthropic.TextBlockParam | Anthropic.ToolUseBlockParam> = []
 
-					// Add text content if present
-					if (assistantMessage) {
+					// For native protocol, check if we already have text blocks in assistantMessageContent
+					// to avoid duplication. For XML protocol, use the accumulated assistantMessage.
+					const hasTextBlocks = this.assistantMessageContent.some((block) => block.type === "text")
+
+					if (!shouldUseXmlParser && hasTextBlocks) {
+						// Native protocol with text blocks - use the text blocks from assistantMessageContent
+						const textBlocks = this.assistantMessageContent.filter((block) => block.type === "text")
+						for (const block of textBlocks) {
+							if (block.type === "text" && block.content) {
+								assistantContent.push({
+									type: "text" as const,
+									text: block.content,
+								})
+							}
+						}
+					} else if (assistantMessage) {
+						// XML protocol or native protocol without text blocks - use accumulated assistantMessage
 						assistantContent.push({
 							type: "text" as const,
 							text: assistantMessage,