diff --git a/backend/internal/handler/admin/channel_handler_test.go b/backend/internal/handler/admin/channel_handler_test.go
index 2f4b4440..f218cce4 100644
--- a/backend/internal/handler/admin/channel_handler_test.go
+++ b/backend/internal/handler/admin/channel_handler_test.go
@@ -273,13 +273,13 @@ func TestPricingRequestToService_Defaults(t *testing.T) {
 			wantValue: string(service.BillingModeToken),
 		},
 		{
-			name: "empty platform defaults to anthropic",
+			name: "empty platform stays empty",
 			req: channelModelPricingRequest{
 				Models:   []string{"m1"},
 				Platform: "",
 			},
 			wantField: "Platform",
-			wantValue: "anthropic",
+			wantValue: "",
 		},
 	}
 
diff --git a/backend/internal/handler/gateway_handler_warmup_intercept_unit_test.go b/backend/internal/handler/gateway_handler_warmup_intercept_unit_test.go
index acea3780..1fdc46ba 100644
--- a/backend/internal/handler/gateway_handler_warmup_intercept_unit_test.go
+++ b/backend/internal/handler/gateway_handler_warmup_intercept_unit_test.go
@@ -168,6 +168,7 @@ func newTestGatewayHandler(t *testing.T, group *service.Group, accounts []*servi
 		nil, // tlsFPProfileService
 		nil, // channelService
 		nil, // resolver
+		nil, // balanceNotifyService
 	)
 
 	// RunModeSimple：跳过计费检查，避免引入 repo/cache 依赖。
diff --git a/backend/internal/handler/gemini_v1beta_handler.go b/backend/internal/handler/gemini_v1beta_handler.go
index 45b5842f..6b8cc482 100644
--- a/backend/internal/handler/gemini_v1beta_handler.go
+++ b/backend/internal/handler/gemini_v1beta_handler.go
@@ -682,6 +682,16 @@ func shouldFallbackGeminiModels(res *service.UpstreamHTTPResult) bool {
 	return false
 }
 
+func shouldFallbackGeminiModel(modelName string, res *service.UpstreamHTTPResult) bool {
+	if shouldFallbackGeminiModels(res) {
+		return true
+	}
+	if res == nil || res.StatusCode != http.StatusNotFound {
+		return false
+	}
+	return gemini.HasFallbackModel(modelName)
+}
+
 // extractGeminiCLISessionHash 从 Gemini CLI 请求中提取会话标识。
 // 组合 x-gemini-api-privileged-user-id header 和请求体中的 tmp 目录哈希。
 //
diff --git a/backend/internal/payment/provider/easypay.go b/backend/internal/payment/provider/easypay.go
index c54aba6a..b48a38fe 100644
--- a/backend/internal/payment/provider/easypay.go
+++ b/backend/internal/payment/provider/easypay.go
@@ -276,12 +276,3 @@ func easyPaySign(params map[string]string, pkey string) string {
 func easyPayVerifySign(params map[string]string, pkey string, sign string) bool {
 	return hmac.Equal([]byte(easyPaySign(params, pkey)), []byte(sign))
 }
-
-// decodeURLValue URL-decodes a string once.
-func decodeURLValue(s string) string {
-	decoded, err := url.QueryUnescape(s)
-	if err != nil {
-		return s
-	}
-	return decoded
-}
diff --git a/backend/internal/pkg/websearch/brave_test.go b/backend/internal/pkg/websearch/brave_test.go
index 3fe35020..4dc5b219 100644
--- a/backend/internal/pkg/websearch/brave_test.go
+++ b/backend/internal/pkg/websearch/brave_test.go
@@ -29,7 +29,7 @@ func TestBraveProvider_Search_Success(t *testing.T) {
 			{URL: "https://tour.go.dev", Title: "Tour", Description: "A Tour of Go", Age: "3 days"},
 		}
 		w.Header().Set("Content-Type", "application/json")
-		json.NewEncoder(w).Encode(resp)
+		_ = json.NewEncoder(w).Encode(resp)
 	}))
 	defer srv.Close()
 
@@ -53,7 +53,7 @@ func TestBraveProvider_Search_DefaultMaxResults(t *testing.T) {
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		receivedCount = r.URL.Query().Get("count")
 		resp := braveResponse{}
-		json.NewEncoder(w).Encode(resp)
+		_ = json.NewEncoder(w).Encode(resp)
 	}))
 	defer srv.Close()
 
@@ -70,7 +70,7 @@ func TestBraveProvider_Search_DefaultMaxResults(t *testing.T) {
 func TestBraveProvider_Search_HTTPError(t *testing.T) {
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 		w.WriteHeader(429)
-		w.Write([]byte("rate limited"))
+		_, _ = w.Write([]byte("rate limited"))
 	}))
 	defer srv.Close()
 
@@ -86,7 +86,7 @@ func TestBraveProvider_Search_HTTPError(t *testing.T) {
 
 func TestBraveProvider_Search_InvalidJSON(t *testing.T) {
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
-		w.Write([]byte("not json"))
+		_, _ = w.Write([]byte("not json"))
 	}))
 	defer srv.Close()
 
@@ -103,7 +103,7 @@ func TestBraveProvider_Search_InvalidJSON(t *testing.T) {
 func TestBraveProvider_Search_EmptyResults(t *testing.T) {
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 		resp := braveResponse{}
-		json.NewEncoder(w).Encode(resp)
+		_ = json.NewEncoder(w).Encode(resp)
 	}))
 	defer srv.Close()
 
diff --git a/backend/internal/pkg/websearch/tavily.go b/backend/internal/pkg/websearch/tavily.go
index 6ac09edf..ac4928a6 100644
--- a/backend/internal/pkg/websearch/tavily.go
+++ b/backend/internal/pkg/websearch/tavily.go
@@ -60,7 +60,7 @@ func (t *TavilyProvider) Search(ctx context.Context, req SearchRequest) (*Search
 	if err != nil {
 		return nil, fmt.Errorf("tavily: request failed: %w", err)
 	}
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 
 	body, err := io.ReadAll(io.LimitReader(resp.Body, maxResponseSize))
 	if err != nil {
diff --git a/backend/internal/server/routes/payment.go b/backend/internal/server/routes/payment.go
index 641c6cd5..72012a4e 100644
--- a/backend/internal/server/routes/payment.go
+++ b/backend/internal/server/routes/payment.go
@@ -78,7 +78,6 @@ func RegisterPaymentRoutes(
 			adminOrders.POST("/:id/refund", adminPaymentHandler.ProcessRefund)
 		}
 
-
 		// Subscription Plans
 		plans := adminGroup.Group("/plans")
 		{
diff --git a/backend/internal/service/account_stats_pricing_test.go b/backend/internal/service/account_stats_pricing_test.go
index 36e5eb74..2f625393 100644
--- a/backend/internal/service/account_stats_pricing_test.go
+++ b/backend/internal/service/account_stats_pricing_test.go
@@ -147,14 +147,14 @@ func TestFindPricingForModel(t *testing.T) {
 			wantNil: true,
 		},
 		{
-			name: "wildcard matches by config order (first match wins)",
+			name: "wildcard matches by longest prefix (most specific wins)",
 			list: []ChannelModelPricing{
 				{ID: 10, Models: []string{"claude-*"}},
 				{ID: 11, Models: []string{"claude-opus-*"}},
 			},
 			platform: "",
 			model:    "claude-opus-4",
-			wantID:   10, // config order: "claude-*" is first and matches, so it wins
+			wantID:   11, // "claude-opus-*" is longer prefix, wins over "claude-*"
 		},
 		{
 			name: "shorter wildcard used when longer does not match",
diff --git a/backend/internal/service/admin_service_apikey_test.go b/backend/internal/service/admin_service_apikey_test.go
index 7f0a24da..1e235278 100644
--- a/backend/internal/service/admin_service_apikey_test.go
+++ b/backend/internal/service/admin_service_apikey_test.go
@@ -412,10 +412,10 @@ func TestAdminService_AdminUpdateAPIKeyGroupID_SubscriptionGroup_Blocked(t *test
 	userRepo := &userRepoStubForGroupUpdate{}
 	svc := &adminServiceImpl{apiKeyRepo: apiKeyRepo, groupRepo: groupRepo, userRepo: userRepo}
 
-	// 订阅类型分组应被阻止绑定
+	// userSubRepo is nil → SUBSCRIPTION_REPOSITORY_UNAVAILABLE
 	_, err := svc.AdminUpdateAPIKeyGroupID(context.Background(), 1, int64Ptr(10))
 	require.Error(t, err)
-	require.Equal(t, "SUBSCRIPTION_GROUP_NOT_ALLOWED", infraerrors.Reason(err))
+	require.Equal(t, "SUBSCRIPTION_REPOSITORY_UNAVAILABLE", infraerrors.Reason(err))
 	require.False(t, userRepo.addGroupCalled)
 }
 
diff --git a/backend/internal/service/channel.go b/backend/internal/service/channel.go
index b3fb2eac..93beb972 100644
--- a/backend/internal/service/channel.go
+++ b/backend/internal/service/channel.go
@@ -37,8 +37,8 @@ type Channel struct {
 	Name               string
 	Description        string
 	Status             string
-	BillingModelSource string // "requested", "upstream", or "channel_mapped"
-	RestrictModels     bool   // 是否限制模型（仅允许定价列表中的模型）
+	BillingModelSource string         // "requested", "upstream", or "channel_mapped"
+	RestrictModels     bool           // 是否限制模型（仅允许定价列表中的模型）
 	Features           string         // 渠道特性描述（JSON 数组），用于支付页面展示
 	FeaturesConfig     map[string]any // 渠道功能配置（如 web search emulation）
 	CreatedAt          time.Time
diff --git a/backend/internal/service/payment_config_providers.go b/backend/internal/service/payment_config_providers.go
index 072ed002..47008df0 100644
--- a/backend/internal/service/payment_config_providers.go
+++ b/backend/internal/service/payment_config_providers.go
@@ -22,16 +22,16 @@ func (s *PaymentConfigService) ListProviderInstances(ctx context.Context) ([]*db
 
 // ProviderInstanceResponse is the API response for a provider instance.
 type ProviderInstanceResponse struct {
-	ID              int64             `json:"id"`
-	ProviderKey     string            `json:"provider_key"`
-	Name            string            `json:"name"`
-	Config          map[string]string `json:"config"`
-	SupportedTypes  []string          `json:"supported_types"`
-	Limits          string            `json:"limits"`
-	Enabled         bool              `json:"enabled"`
-	RefundEnabled   bool              `json:"refund_enabled"`
-	SortOrder       int               `json:"sort_order"`
-	PaymentMode     string            `json:"payment_mode"`
+	ID             int64             `json:"id"`
+	ProviderKey    string            `json:"provider_key"`
+	Name           string            `json:"name"`
+	Config         map[string]string `json:"config"`
+	SupportedTypes []string          `json:"supported_types"`
+	Limits         string            `json:"limits"`
+	Enabled        bool              `json:"enabled"`
+	RefundEnabled  bool              `json:"refund_enabled"`
+	SortOrder      int               `json:"sort_order"`
+	PaymentMode    string            `json:"payment_mode"`
 }
 
 // ListProviderInstancesWithConfig returns provider instances with decrypted config.