diff --git a/service/task/worker.go b/service/task/worker.go
index 7bad2ec..20dd537 100644
--- a/service/task/worker.go
+++ b/service/task/worker.go
@@ -277,7 +277,7 @@ func (w *asyncWorker) parseAndRetry(ctx context.Context, body map[string]any, ta
 	return body, nil
 }
 
-// injectErrorMessage 将错误信息拼接到 user 消息中
+// injectErrorMessage 将错误信息插入到最后一个 user 消息之前
 func injectErrorMessage(payload map[string]any, err error) map[string]any {
 	if err == nil {
 		return payload
@@ -288,30 +288,34 @@ func injectErrorMessage(payload map[string]any, err error) map[string]any {
 		return payload
 	}
 
-	errMsg := fmt.Sprintf("\n\n【上一轮输出错误，请修正】%s", err.Error())
+	errMsg := fmt.Sprintf("【上一轮输出错误，请修正】%s", err.Error())
 
-	// 找到最后一个 role=user 的消息，追加错误提示
+	// 找到最后一个 user 的位置
+	lastUserIdx := -1
 	for i := len(messages) - 1; i >= 0; i-- {
 		msg, ok := messages[i].(map[string]any)
 		if !ok {
 			continue
 		}
-		if gconv.String(msg["role"]) != "user" {
-			continue
+		if gconv.String(msg["role"]) == "user" {
+			lastUserIdx = i
+			break
 		}
-
-		switch c := msg["content"].(type) {
-		case string:
-			msg["content"] = c + errMsg
-		case []any:
-			msg["content"] = append(c, map[string]any{
-				"type": "text",
-				"text": errMsg,
-			})
-		}
-		break
 	}
 
+	if lastUserIdx == -1 {
+		return payload
+	}
+
+	// 在最后一个 user 之前插入错误消息
+	errMsgObj := map[string]any{
+		"role":    "user",
+		"content": []map[string]any{{"type": "text", "text": errMsg}},
+	}
+
+	// 切片插入
+	messages = append(messages[:lastUserIdx], append([]any{errMsgObj}, messages[lastUserIdx:]...)...)
+	payload["messages"] = messages
 	return payload
 }