fix(antigravity): route paid accounts to daily endpoint

backend/internal/service/antigravity_gateway_retry.go

@@ -48,17 +48,14 @@ type antigravityRetryLoopResult struct {
 
 // resolveAntigravityForwardBaseURL 解析转发用 base URL。
 //
-// 默认使用生产端点 cloudcode-pa.googleapis.com（antigravity.BaseURLs 的首个地址，
-// 与账号 OAuth 登录/测试连接所用的 antigravity.BaseURL 一致）。
+// 显式环境变量优先。未配置时，LoadCodeAssist 返回 paidTier 的付费账号使用
+// daily 端点，其他账号继续使用生产端点，避免免费账号的 OAuth token 出现 401。
 //
 // 历史上这里改用 ForwardBaseURLs()（把 daily/sandbox 排到首位）并默认取首个地址，
 // 导致网关把带生产 OAuth token 的请求发到 daily-cloudcode-pa.sandbox.googleapis.com，
 // 上游拒绝 → 账号被 401「Invalid bearer token」/502 打入临时不可调度且无法恢复
 // （见 #3611 / #2962）。后台「测试连接」用的是生产端点，所以「测试成功但网关 401」。
-//
-// daily/sandbox 端点仅供内部联调，需显式设置
-// GATEWAY_ANTIGRAVITY_FORWARD_BASE_URL=daily（或 sandbox）才启用。
-func resolveAntigravityForwardBaseURL() string {
+func resolveAntigravityForwardBaseURL(account *Account) string {
 	baseURLs := antigravity.BaseURLs
 	if len(baseURLs) == 0 {
 		return ""
@@ -67,9 +64,28 @@ func resolveAntigravityForwardBaseURL() string {
 	if (mode == "daily" || mode == "sandbox") && len(baseURLs) > 1 {
 		return baseURLs[1]
 	}
+	if mode == "" && accountHasAntigravityPaidTier(account) && len(baseURLs) > 1 {
+		return baseURLs[1]
+	}
 	return baseURLs[0]
 }
 
+func accountHasAntigravityPaidTier(account *Account) bool {
+	if account == nil || account.Credentials == nil {
+		return false
+	}
+	planType, ok := account.Credentials["plan_type"].(string)
+	if !ok {
+		return false
+	}
+	switch strings.ToLower(strings.TrimSpace(planType)) {
+	case "pro", "ultra":
+		return true
+	default:
+		return false
+	}
+}
+
 // smartRetryAction 智能重试的处理结果
 type smartRetryAction int
 
@@ -488,7 +504,7 @@ func (s *AntigravityGatewayService) antigravityRetryLoop(p antigravityRetryLoopP
 		}
 	}
 
-	baseURL := resolveAntigravityForwardBaseURL()
+	baseURL := resolveAntigravityForwardBaseURL(p.account)
 	if baseURL == "" {
 		return nil, errors.New("no antigravity forward base url configured")
 	}

backend/internal/service/antigravity_rate_limit_test.go

@@ -1009,9 +1009,7 @@ func TestIsAntigravityAccountSwitchError(t *testing.T) {
 	}
 }
 
-func TestResolveAntigravityForwardBaseURL_DefaultDaily(t *testing.T) {
-	t.Setenv(antigravityForwardBaseURLEnv, "")
-
+func TestResolveAntigravityForwardBaseURL(t *testing.T) {
 	oldBaseURLs := append([]string(nil), antigravity.BaseURLs...)
 	defer func() {
 		antigravity.BaseURLs = oldBaseURLs
@@ -1019,10 +1017,46 @@ func TestResolveAntigravityForwardBaseURL_DefaultDaily(t *testing.T) {
 
 	prodURL := "https://prod.test"
 	dailyURL := "https://daily.test"
-	antigravity.BaseURLs = []string{dailyURL, prodURL}
+	antigravity.BaseURLs = []string{prodURL, dailyURL}
 
-	resolved := resolveAntigravityForwardBaseURL()
-	require.Equal(t, dailyURL, resolved)
+	tests := []struct {
+		name    string
+		env     string
+		account *Account
+		want    string
+	}{
+		{
+			name: "pro defaults to daily", account: &Account{Credentials: map[string]any{"plan_type": " Pro "}},
+			want: dailyURL,
+		},
+		{
+			name: "ultra defaults to daily", account: &Account{Credentials: map[string]any{"plan_type": "ULTRA"}},
+			want: dailyURL,
+		},
+		{name: "free defaults to prod", account: &Account{Credentials: map[string]any{"plan_type": "free"}}, want: prodURL},
+		{name: "abnormal defaults to prod", account: &Account{Credentials: map[string]any{"plan_type": "Abnormal"}}, want: prodURL},
+		{name: "unknown defaults to prod", account: &Account{Credentials: map[string]any{"plan_type": "enterprise"}}, want: prodURL},
+		{name: "malformed defaults to prod", account: &Account{Credentials: map[string]any{"plan_type": map[string]any{"name": "pro"}}}, want: prodURL},
+		{name: "missing defaults to prod", account: &Account{Credentials: map[string]any{}}, want: prodURL},
+		{name: "nil account defaults to prod", account: nil, want: prodURL},
+		{
+			name: "daily override wins for free tier", env: " daily ",
+			account: &Account{Credentials: map[string]any{"plan_type": "free"}},
+			want:    dailyURL,
+		},
+		{
+			name: "prod override wins for paid tier", env: " PROD ",
+			account: &Account{Credentials: map[string]any{"plan_type": "pro"}},
+			want:    prodURL,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Setenv(antigravityForwardBaseURLEnv, tt.env)
+			require.Equal(t, tt.want, resolveAntigravityForwardBaseURL(tt.account))
+		})
+	}
 }
 
 func TestAntigravityAccountSwitchError_Error(t *testing.T) {