diff --git a/src/lib/grading.ts b/src/lib/grading.ts
index ddda366..d724cff 100644
--- a/src/lib/grading.ts
+++ b/src/lib/grading.ts
@@ -15,7 +15,7 @@ export type GradingResult = {
 };
 
 const DEFAULT_BASE_URL =
-  "https://www.chataiapi.com/v1beta/models/gemini-2.5-pro:generateContent";
+  "https://www.chataiapi.com/v1beta/models/gemini-3-pro-preview:generateContent";
 
 export function createGradingPrompt(scoringCriteria: string, studentId: string): string {
   const normalizedStudentId = studentId?.trim() || "未提供";