diff --git a/backend/internal/ai/llm/openai.go b/backend/internal/ai/llm/openai.go
index 754176c..e421d7e 100644
--- a/backend/internal/ai/llm/openai.go
+++ b/backend/internal/ai/llm/openai.go
@@ -61,7 +61,7 @@ type chatMessage struct {
 
 type contentPart struct {
 	Type     string    `json:"type"`
-	Text     string    `json:"text,omitempty"`
+	Text     string    `json:"text"`
 	ImageURL *imageURL `json:"image_url,omitempty"`
 }
 
@@ -100,6 +100,9 @@ func (o *OpenAIService) ChatStream(ctx context.Context, req Request) (<-chan Chu
 	if err != nil {
 		return nil, fmt.Errorf("llm: marshal request: %w", err)
 	}
+	if err != nil {
+		return nil, fmt.Errorf("llm: marshal request: %w", err)
+	}
 
 	// 创建带超时的 context
 	ctx, cancel := context.WithTimeout(ctx, o.timeout)