diff --git a/backend/internal/pkg/antigravity/oauth.go b/backend/internal/pkg/antigravity/oauth.go
index 26b307bbf7..625dcaea69 100644
--- a/backend/internal/pkg/antigravity/oauth.go
+++ b/backend/internal/pkg/antigravity/oauth.go
@@ -34,7 +34,7 @@ const (
 	AntigravityUserAgentVersionEnv = "ANTIGRAVITY_USER_AGENT_VERSION"
 
 	// DefaultUserAgentVersion 是未通过环境变量或后台设置覆盖时使用的默认版本号。
-	DefaultUserAgentVersion = "1.23.2"
+	DefaultUserAgentVersion = "2.9.1"
 
 	// 固定的 redirect_uri（用户需手动复制 code）
 	RedirectURI = "http://localhost:8085/callback"
diff --git a/backend/internal/pkg/antigravity/oauth_test.go b/backend/internal/pkg/antigravity/oauth_test.go
index 7849492c7c..4ebc7e5434 100644
--- a/backend/internal/pkg/antigravity/oauth_test.go
+++ b/backend/internal/pkg/antigravity/oauth_test.go
@@ -693,7 +693,7 @@ func TestConstants_值正确(t *testing.T) {
 	if RedirectURI != "http://localhost:8085/callback" {
 		t.Errorf("RedirectURI 不匹配: got %s", RedirectURI)
 	}
-	if GetUserAgent() != "antigravity/1.23.2 windows/amd64" {
+	if GetUserAgent() != "antigravity/2.9.1 windows/amd64" {
 		t.Errorf("UserAgent 不匹配: got %s", GetUserAgent())
 	}
 	if SessionTTL != 30*time.Minute {