perf(网关): 复用分组上下文减少热路径查询

新增 GetByIDLite 并在网关与 Gemini 选择流程复用上下文 group，避免 COUNT 触发
更新 API key 中间件注入 group 上下文，减少重复查库
补充 gateway/gemini 中间件与仓库层回归测试

测试: make test

backend/internal/pkg/ctxkey/ctxkey.go

@@ -9,4 +9,6 @@ const (
 	ForcePlatform Key = "ctx_force_platform"
 	// IsClaudeCodeClient 是否为 Claude Code 客户端，由中间件设置
 	IsClaudeCodeClient Key = "ctx_is_claude_code_client"
+	// Group 认证后的分组信息，由 API Key 认证中间件设置
+	Group Key = "ctx_group"
 )

backend/internal/repository/group_repo.go

@@ -60,6 +60,16 @@ func (r *groupRepository) Create(ctx context.Context, groupIn *service.Group) er
 }
 
 func (r *groupRepository) GetByID(ctx context.Context, id int64) (*service.Group, error) {
+	out, err := r.GetByIDLite(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	count, _ := r.GetAccountCount(ctx, out.ID)
+	out.AccountCount = count
+	return out, nil
+}
+
+func (r *groupRepository) GetByIDLite(ctx context.Context, id int64) (*service.Group, error) {
 	m, err := r.client.Group.Query().
 		Where(group.IDEQ(id)).
 		Only(ctx)
@@ -67,10 +77,7 @@ func (r *groupRepository) GetByID(ctx context.Context, id int64) (*service.Group
 		return nil, translatePersistenceError(err, service.ErrGroupNotFound, nil)
 	}
 
-	out := groupEntityToService(m)
-	count, _ := r.GetAccountCount(ctx, out.ID)
-	out.AccountCount = count
-	return out, nil
+	return groupEntityToService(m), nil
 }
 
 func (r *groupRepository) Update(ctx context.Context, groupIn *service.Group) error {

backend/internal/repository/group_repo_integration_test.go

@@ -4,6 +4,8 @@ package repository
 
 import (
 	"context"
+	"database/sql"
+	"errors"
 	"testing"
 
 	dbent "github.com/Wei-Shaw/sub2api/ent"
@@ -19,6 +21,20 @@ type GroupRepoSuite struct {
 	repo *groupRepository
 }
 
+type forbidSQLExecutor struct {
+	called bool
+}
+
+func (s *forbidSQLExecutor) ExecContext(ctx context.Context, query string, args ...any) (sql.Result, error) {
+	s.called = true
+	return nil, errors.New("unexpected sql exec")
+}
+
+func (s *forbidSQLExecutor) QueryContext(ctx context.Context, query string, args ...any) (*sql.Rows, error) {
+	s.called = true
+	return nil, errors.New("unexpected sql query")
+}
+
 func (s *GroupRepoSuite) SetupTest() {
 	s.ctx = context.Background()
 	tx := testEntTx(s.T())
@@ -57,6 +73,26 @@ func (s *GroupRepoSuite) TestGetByID_NotFound() {
 	s.Require().ErrorIs(err, service.ErrGroupNotFound)
 }
 
+func (s *GroupRepoSuite) TestGetByIDLite_DoesNotUseAccountCount() {
+	group := &service.Group{
+		Name:             "lite-group",
+		Platform:         service.PlatformAnthropic,
+		RateMultiplier:   1.0,
+		IsExclusive:      false,
+		Status:           service.StatusActive,
+		SubscriptionType: service.SubscriptionTypeStandard,
+	}
+	s.Require().NoError(s.repo.Create(s.ctx, group))
+
+	spy := &forbidSQLExecutor{}
+	repo := newGroupRepositoryWithSQL(s.tx.Client(), spy)
+
+	got, err := repo.GetByIDLite(s.ctx, group.ID)
+	s.Require().NoError(err)
+	s.Require().Equal(group.ID, got.ID)
+	s.Require().False(spy.called, "expected no direct sql executor usage")
+}
+
 func (s *GroupRepoSuite) TestUpdate() {
 	group := &service.Group{
 		Name:             "original",

backend/internal/server/api_contract_test.go

@@ -567,6 +567,10 @@ func (stubGroupRepo) GetByID(ctx context.Context, id int64) (*service.Group, err
 	return nil, service.ErrGroupNotFound
 }
 
+func (stubGroupRepo) GetByIDLite(ctx context.Context, id int64) (*service.Group, error) {
+	return nil, service.ErrGroupNotFound
+}
+
 func (stubGroupRepo) Update(ctx context.Context, group *service.Group) error {
 	return errors.New("not implemented")
 }

backend/internal/server/middleware/api_key_auth.go

 package middleware
 
 import (
+	"context"
 	"errors"
 	"log"
 	"strings"
 
 	"github.com/Wei-Shaw/sub2api/internal/config"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/ctxkey"
 	"github.com/Wei-Shaw/sub2api/internal/service"
 
 	"github.com/gin-gonic/gin"
@@ -91,6 +93,7 @@ func apiKeyAuthWithSubscription(apiKeyService *service.APIKeyService, subscripti
 				Concurrency: apiKey.User.Concurrency,
 			})
 			c.Set(string(ContextKeyUserRole), apiKey.User.Role)
+			setGroupContext(c, apiKey.Group)
 			c.Next()
 			return
 		}
@@ -149,6 +152,7 @@ func apiKeyAuthWithSubscription(apiKeyService *service.APIKeyService, subscripti
 			Concurrency: apiKey.User.Concurrency,
 		})
 		c.Set(string(ContextKeyUserRole), apiKey.User.Role)
+		setGroupContext(c, apiKey.Group)
 
 		c.Next()
 	}
@@ -173,3 +177,14 @@ func GetSubscriptionFromContext(c *gin.Context) (*service.UserSubscription, bool
 	subscription, ok := value.(*service.UserSubscription)
 	return subscription, ok
 }
+
+func setGroupContext(c *gin.Context, group *service.Group) {
+	if group == nil {
+		return
+	}
+	if existing, ok := c.Request.Context().Value(ctxkey.Group).(*service.Group); ok && existing != nil && existing.ID == group.ID {
+		return
+	}
+	ctx := context.WithValue(c.Request.Context(), ctxkey.Group, group)
+	c.Request = c.Request.WithContext(ctx)
+}

backend/internal/server/middleware/api_key_auth_google.go

@@ -63,6 +63,7 @@ func APIKeyAuthWithSubscriptionGoogle(apiKeyService *service.APIKeyService, subs
 				Concurrency: apiKey.User.Concurrency,
 			})
 			c.Set(string(ContextKeyUserRole), apiKey.User.Role)
+			setGroupContext(c, apiKey.Group)
 			c.Next()
 			return
 		}
@@ -102,6 +103,7 @@ func APIKeyAuthWithSubscriptionGoogle(apiKeyService *service.APIKeyService, subs
 			Concurrency: apiKey.User.Concurrency,
 		})
 		c.Set(string(ContextKeyUserRole), apiKey.User.Role)
+		setGroupContext(c, apiKey.Group)
 		c.Next()
 	}
 }

backend/internal/server/middleware/api_key_auth_google_test.go

@@ -9,6 +9,7 @@ import (
 	"testing"
 
 	"github.com/Wei-Shaw/sub2api/internal/config"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/ctxkey"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/pagination"
 	"github.com/Wei-Shaw/sub2api/internal/service"
 
@@ -133,6 +134,69 @@ func TestApiKeyAuthWithSubscriptionGoogle_QueryApiKeyRejected(t *testing.T) {
 	require.Equal(t, "INVALID_ARGUMENT", resp.Error.Status)
 }
 
+func TestApiKeyAuthWithSubscriptionGoogleSetsGroupContext(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	group := &service.Group{
+		ID:       99,
+		Name:     "g1",
+		Status:   service.StatusActive,
+		Platform: service.PlatformGemini,
+	}
+	user := &service.User{
+		ID:          7,
+		Role:        service.RoleUser,
+		Status:      service.StatusActive,
+		Balance:     10,
+		Concurrency: 3,
+	}
+	apiKey := &service.APIKey{
+		ID:     100,
+		UserID: user.ID,
+		Key:    "test-key",
+		Status: service.StatusActive,
+		User:   user,
+		Group:  group,
+	}
+	apiKey.GroupID = &group.ID
+
+	apiKeyService := service.NewAPIKeyService(
+		fakeAPIKeyRepo{
+			getByKey: func(ctx context.Context, key string) (*service.APIKey, error) {
+				if key != apiKey.Key {
+					return nil, service.ErrAPIKeyNotFound
+				}
+				clone := *apiKey
+				return &clone, nil
+			},
+		},
+		nil,
+		nil,
+		nil,
+		nil,
+		&config.Config{RunMode: config.RunModeSimple},
+	)
+
+	cfg := &config.Config{RunMode: config.RunModeSimple}
+	r := gin.New()
+	r.Use(APIKeyAuthWithSubscriptionGoogle(apiKeyService, nil, cfg))
+	r.GET("/v1beta/test", func(c *gin.Context) {
+		groupFromCtx, ok := c.Request.Context().Value(ctxkey.Group).(*service.Group)
+		if !ok || groupFromCtx == nil || groupFromCtx.ID != group.ID {
+			c.JSON(http.StatusInternalServerError, gin.H{"ok": false})
+			return
+		}
+		c.JSON(http.StatusOK, gin.H{"ok": true})
+	})
+
+	req := httptest.NewRequest(http.MethodGet, "/v1beta/test", nil)
+	req.Header.Set("x-api-key", apiKey.Key)
+	rec := httptest.NewRecorder()
+	r.ServeHTTP(rec, req)
+
+	require.Equal(t, http.StatusOK, rec.Code)
+}
+
 func TestApiKeyAuthWithSubscriptionGoogle_QueryKeyAllowedOnV1Beta(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 

backend/internal/server/middleware/api_key_auth_test.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/Wei-Shaw/sub2api/internal/config"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/ctxkey"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/pagination"
 	"github.com/Wei-Shaw/sub2api/internal/service"
 	"github.com/gin-gonic/gin"
@@ -110,6 +111,63 @@ func TestSimpleModeBypassesQuotaCheck(t *testing.T) {
 	})
 }
 
+func TestAPIKeyAuthSetsGroupContext(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	group := &service.Group{
+		ID:       101,
+		Name:     "g1",
+		Status:   service.StatusActive,
+		Platform: service.PlatformAnthropic,
+	}
+	user := &service.User{
+		ID:          7,
+		Role:        service.RoleUser,
+		Status:      service.StatusActive,
+		Balance:     10,
+		Concurrency: 3,
+	}
+	apiKey := &service.APIKey{
+		ID:     100,
+		UserID: user.ID,
+		Key:    "test-key",
+		Status: service.StatusActive,
+		User:   user,
+		Group:  group,
+	}
+	apiKey.GroupID = &group.ID
+
+	apiKeyRepo := &stubApiKeyRepo{
+		getByKey: func(ctx context.Context, key string) (*service.APIKey, error) {
+			if key != apiKey.Key {
+				return nil, service.ErrAPIKeyNotFound
+			}
+			clone := *apiKey
+			return &clone, nil
+		},
+	}
+
+	cfg := &config.Config{RunMode: config.RunModeSimple}
+	apiKeyService := service.NewAPIKeyService(apiKeyRepo, nil, nil, nil, nil, cfg)
+	router := gin.New()
+	router.Use(gin.HandlerFunc(NewAPIKeyAuthMiddleware(apiKeyService, nil, cfg)))
+	router.GET("/t", func(c *gin.Context) {
+		groupFromCtx, ok := c.Request.Context().Value(ctxkey.Group).(*service.Group)
+		if !ok || groupFromCtx == nil || groupFromCtx.ID != group.ID {
+			c.JSON(http.StatusInternalServerError, gin.H{"ok": false})
+			return
+		}
+		c.JSON(http.StatusOK, gin.H{"ok": true})
+	})
+
+	w := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/t", nil)
+	req.Header.Set("x-api-key", apiKey.Key)
+	router.ServeHTTP(w, req)
+
+	require.Equal(t, http.StatusOK, w.Code)
+}
+
 func newAuthTestRouter(apiKeyService *service.APIKeyService, subscriptionService *service.SubscriptionService, cfg *config.Config) *gin.Engine {
 	router := gin.New()
 	router.Use(gin.HandlerFunc(NewAPIKeyAuthMiddleware(apiKeyService, subscriptionService, cfg)))

backend/internal/service/admin_service_delete_test.go

@@ -107,6 +107,10 @@ func (s *groupRepoStub) GetByID(ctx context.Context, id int64) (*Group, error) {
 	panic("unexpected GetByID call")
 }
 
+func (s *groupRepoStub) GetByIDLite(ctx context.Context, id int64) (*Group, error) {
+	panic("unexpected GetByIDLite call")
+}
+
 func (s *groupRepoStub) Update(ctx context.Context, group *Group) error {
 	panic("unexpected Update call")
 }

backend/internal/service/admin_service_group_test.go

@@ -35,6 +35,13 @@ func (s *groupRepoStubForAdmin) GetByID(_ context.Context, _ int64) (*Group, err
 	return s.getByID, nil
 }
 
+func (s *groupRepoStubForAdmin) GetByIDLite(_ context.Context, _ int64) (*Group, error) {
+	if s.getErr != nil {
+		return nil, s.getErr
+	}
+	return s.getByID, nil
+}
+
 func (s *groupRepoStubForAdmin) Delete(_ context.Context, _ int64) error {
 	panic("unexpected Delete call")
 }

backend/internal/service/gateway_multiplatform_test.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/Wei-Shaw/sub2api/internal/config"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/ctxkey"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/pagination"
 	"github.com/stretchr/testify/require"
 )
@@ -185,6 +186,56 @@ func (m *mockGatewayCacheForPlatform) RefreshSessionTTL(ctx context.Context, gro
 	return nil
 }
 
+type mockGroupRepoForGateway struct {
+	groups           map[int64]*Group
+	getByIDCalls     int
+	getByIDLiteCalls int
+}
+
+func (m *mockGroupRepoForGateway) GetByID(ctx context.Context, id int64) (*Group, error) {
+	m.getByIDCalls++
+	if g, ok := m.groups[id]; ok {
+		return g, nil
+	}
+	return nil, ErrGroupNotFound
+}
+
+func (m *mockGroupRepoForGateway) GetByIDLite(ctx context.Context, id int64) (*Group, error) {
+	m.getByIDLiteCalls++
+	if g, ok := m.groups[id]; ok {
+		return g, nil
+	}
+	return nil, ErrGroupNotFound
+}
+
+func (m *mockGroupRepoForGateway) Create(ctx context.Context, group *Group) error { return nil }
+func (m *mockGroupRepoForGateway) Update(ctx context.Context, group *Group) error { return nil }
+func (m *mockGroupRepoForGateway) Delete(ctx context.Context, id int64) error     { return nil }
+func (m *mockGroupRepoForGateway) DeleteCascade(ctx context.Context, id int64) ([]int64, error) {
+	return nil, nil
+}
+func (m *mockGroupRepoForGateway) List(ctx context.Context, params pagination.PaginationParams) ([]Group, *pagination.PaginationResult, error) {
+	return nil, nil, nil
+}
+func (m *mockGroupRepoForGateway) ListWithFilters(ctx context.Context, params pagination.PaginationParams, platform, status string, isExclusive *bool) ([]Group, *pagination.PaginationResult, error) {
+	return nil, nil, nil
+}
+func (m *mockGroupRepoForGateway) ListActive(ctx context.Context) ([]Group, error) {
+	return nil, nil
+}
+func (m *mockGroupRepoForGateway) ListActiveByPlatform(ctx context.Context, platform string) ([]Group, error) {
+	return nil, nil
+}
+func (m *mockGroupRepoForGateway) ExistsByName(ctx context.Context, name string) (bool, error) {
+	return false, nil
+}
+func (m *mockGroupRepoForGateway) GetAccountCount(ctx context.Context, groupID int64) (int64, error) {
+	return 0, nil
+}
+func (m *mockGroupRepoForGateway) DeleteAccountGroupsByGroupID(ctx context.Context, groupID int64) (int64, error) {
+	return 0, nil
+}
+
 func ptr[T any](v T) *T {
 	return &v
 }
@@ -1013,3 +1064,85 @@ func TestGatewayService_SelectAccountWithLoadAwareness(t *testing.T) {
 		require.Contains(t, err.Error(), "no available accounts")
 	})
 }
+
+func TestGatewayService_GroupResolution_ReusesContextGroup(t *testing.T) {
+	ctx := context.Background()
+	groupID := int64(42)
+	group := &Group{
+		ID:       groupID,
+		Platform: PlatformAnthropic,
+		Status:   StatusActive,
+	}
+	ctx = context.WithValue(ctx, ctxkey.Group, group)
+
+	repo := &mockAccountRepoForPlatform{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformAnthropic, Priority: 1, Status: StatusActive, Schedulable: true},
+		},
+		accountsByID: map[int64]*Account{},
+	}
+	for i := range repo.accounts {
+		repo.accountsByID[repo.accounts[i].ID] = &repo.accounts[i]
+	}
+
+	groupRepo := &mockGroupRepoForGateway{
+		groups: map[int64]*Group{groupID: group},
+	}
+
+	svc := &GatewayService{
+		accountRepo: repo,
+		groupRepo:   groupRepo,
+		cfg:         testConfig(),
+	}
+
+	account, err := svc.SelectAccountForModelWithExclusions(ctx, &groupID, "", "claude-3-5-sonnet-20241022", nil)
+	require.NoError(t, err)
+	require.NotNil(t, account)
+	require.Equal(t, 0, groupRepo.getByIDCalls)
+	require.Equal(t, 0, groupRepo.getByIDLiteCalls)
+}
+
+func TestGatewayService_GroupResolution_FallbackUsesLiteOnce(t *testing.T) {
+	ctx := context.Background()
+	groupID := int64(10)
+	fallbackID := int64(11)
+	group := &Group{
+		ID:              groupID,
+		Platform:        PlatformAnthropic,
+		Status:          StatusActive,
+		ClaudeCodeOnly:  true,
+		FallbackGroupID: &fallbackID,
+	}
+	fallbackGroup := &Group{
+		ID:       fallbackID,
+		Platform: PlatformAnthropic,
+		Status:   StatusActive,
+	}
+	ctx = context.WithValue(ctx, ctxkey.Group, group)
+
+	repo := &mockAccountRepoForPlatform{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformAnthropic, Priority: 1, Status: StatusActive, Schedulable: true},
+		},
+		accountsByID: map[int64]*Account{},
+	}
+	for i := range repo.accounts {
+		repo.accountsByID[repo.accounts[i].ID] = &repo.accounts[i]
+	}
+
+	groupRepo := &mockGroupRepoForGateway{
+		groups: map[int64]*Group{fallbackID: fallbackGroup},
+	}
+
+	svc := &GatewayService{
+		accountRepo: repo,
+		groupRepo:   groupRepo,
+		cfg:         testConfig(),
+	}
+
+	account, err := svc.SelectAccountForModelWithExclusions(ctx, &groupID, "", "claude-3-5-sonnet-20241022", nil)
+	require.NoError(t, err)
+	require.NotNil(t, account)
+	require.Equal(t, 0, groupRepo.getByIDCalls)
+	require.Equal(t, 1, groupRepo.getByIDLiteCalls)
+}

backend/internal/service/gateway_service.go

@@ -361,27 +361,13 @@ func (s *GatewayService) SelectAccountForModelWithExclusions(ctx context.Context
 	if hasForcePlatform && forcePlatform != "" {
 		platform = forcePlatform
 	} else if groupID != nil {
-		// 根据分组 platform 决定查询哪种账号
-		group, err := s.groupRepo.GetByID(ctx, *groupID)
+		group, resolvedGroupID, err := s.resolveGatewayGroup(ctx, groupID)
 		if err != nil {
-			return nil, fmt.Errorf("get group failed: %w", err)
+			return nil, err
 		}
+		groupID = resolvedGroupID
+		ctx = s.withGroupContext(ctx, group)
 		platform = group.Platform
-
-		// 检查 Claude Code 客户端限制
-		if group.ClaudeCodeOnly {
-			isClaudeCode := IsClaudeCodeClient(ctx)
-			if !isClaudeCode {
-				// 非 Claude Code 客户端，检查是否有降级分组
-				if group.FallbackGroupID != nil {
-					// 使用降级分组重新调度
-					fallbackGroupID := *group.FallbackGroupID
-					return s.SelectAccountForModelWithExclusions(ctx, &fallbackGroupID, sessionHash, requestedModel, excludedIDs)
-				}
-				// 无降级分组，拒绝访问
-				return nil, ErrClaudeCodeOnly
-			}
-		}
 	} else {
 		// 无分组时只使用原生 anthropic 平台
 		platform = PlatformAnthropic
@@ -409,10 +395,11 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 	}
 
 	// 检查 Claude Code 客户端限制（可能会替换 groupID 为降级分组）
-	groupID, err := s.checkClaudeCodeRestriction(ctx, groupID)
+	group, groupID, err := s.checkClaudeCodeRestriction(ctx, groupID)
 	if err != nil {
 		return nil, err
 	}
+	ctx = s.withGroupContext(ctx, group)
 
 	if s.concurrencyService == nil || !cfg.LoadBatchEnabled {
 		account, err := s.SelectAccountForModelWithExclusions(ctx, groupID, sessionHash, requestedModel, excludedIDs)
@@ -452,7 +439,7 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 		}, nil
 	}
 
-	platform, hasForcePlatform, err := s.resolvePlatform(ctx, groupID)
+	platform, hasForcePlatform, err := s.resolvePlatform(ctx, groupID, group)
 	if err != nil {
 		return nil, err
 	}
@@ -652,51 +639,91 @@ func (s *GatewayService) schedulingConfig() config.GatewaySchedulingConfig {
 	}
 }
 
-// checkClaudeCodeRestriction 检查分组的 Claude Code 客户端限制
-// 如果分组启用了 claude_code_only 且请求不是来自 Claude Code 客户端：
-//   - 有降级分组：返回降级分组的 ID
-//   - 无降级分组：返回 ErrClaudeCodeOnly 错误
-func (s *GatewayService) checkClaudeCodeRestriction(ctx context.Context, groupID *int64) (*int64, error) {
-	if groupID == nil {
-		return groupID, nil
+func (s *GatewayService) withGroupContext(ctx context.Context, group *Group) context.Context {
+	if group == nil {
+		return ctx
 	}
+	if existing, ok := ctx.Value(ctxkey.Group).(*Group); ok && existing != nil && existing.ID == group.ID {
+		return ctx
+	}
+	return context.WithValue(ctx, ctxkey.Group, group)
+}
 
-	// 强制平台模式不检查 Claude Code 限制
-	if _, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string); hasForcePlatform {
-		return groupID, nil
+func (s *GatewayService) groupFromContext(ctx context.Context, groupID int64) *Group {
+	if group, ok := ctx.Value(ctxkey.Group).(*Group); ok && group != nil && group.ID == groupID {
+		return group
 	}
+	return nil
+}
 
-	group, err := s.groupRepo.GetByID(ctx, *groupID)
+func (s *GatewayService) resolveGroupByID(ctx context.Context, groupID int64) (*Group, error) {
+	if group := s.groupFromContext(ctx, groupID); group != nil {
+		return group, nil
+	}
+	group, err := s.groupRepo.GetByIDLite(ctx, groupID)
 	if err != nil {
 		return nil, fmt.Errorf("get group failed: %w", err)
 	}
+	return group, nil
+}
+
+func (s *GatewayService) resolveGatewayGroup(ctx context.Context, groupID *int64) (*Group, *int64, error) {
+	if groupID == nil {
+		return nil, nil, nil
+	}
 
-	if !group.ClaudeCodeOnly {
-		return groupID, nil
+	currentID := *groupID
+	for {
+		group, err := s.resolveGroupByID(ctx, currentID)
+		if err != nil {
+			return nil, nil, err
 		}
 
-	// 分组启用了 Claude Code 限制
-	if IsClaudeCodeClient(ctx) {
-		return groupID, nil
+		if !group.ClaudeCodeOnly || IsClaudeCodeClient(ctx) {
+			return group, &currentID, nil
 		}
 
-	// 非 Claude Code 客户端，检查降级分组
-	if group.FallbackGroupID != nil {
-		return group.FallbackGroupID, nil
+		if group.FallbackGroupID == nil {
+			return nil, nil, ErrClaudeCodeOnly
 		}
+		currentID = *group.FallbackGroupID
+	}
+}
 
-	return nil, ErrClaudeCodeOnly
+// checkClaudeCodeRestriction 检查分组的 Claude Code 客户端限制
+// 如果分组启用了 claude_code_only 且请求不是来自 Claude Code 客户端：
+//   - 有降级分组：返回降级分组的 ID
+//   - 无降级分组：返回 ErrClaudeCodeOnly 错误
+func (s *GatewayService) checkClaudeCodeRestriction(ctx context.Context, groupID *int64) (*Group, *int64, error) {
+	if groupID == nil {
+		return nil, groupID, nil
+	}
+
+	// 强制平台模式不检查 Claude Code 限制
+	if _, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string); hasForcePlatform {
+		return nil, groupID, nil
+	}
+
+	group, resolvedID, err := s.resolveGatewayGroup(ctx, groupID)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return group, resolvedID, nil
 }
 
-func (s *GatewayService) resolvePlatform(ctx context.Context, groupID *int64) (string, bool, error) {
+func (s *GatewayService) resolvePlatform(ctx context.Context, groupID *int64, group *Group) (string, bool, error) {
 	forcePlatform, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string)
 	if hasForcePlatform && forcePlatform != "" {
 		return forcePlatform, true, nil
 	}
+	if group != nil {
+		return group.Platform, false, nil
+	}
 	if groupID != nil {
-		group, err := s.groupRepo.GetByID(ctx, *groupID)
+		group, err := s.resolveGroupByID(ctx, *groupID)
 		if err != nil {
-			return "", false, fmt.Errorf("get group failed: %w", err)
+			return "", false, err
 		}
 		return group.Platform, false, nil
 	}

backend/internal/service/gemini_messages_compat_service.go

@@ -86,10 +86,16 @@ func (s *GeminiMessagesCompatService) SelectAccountForModelWithExclusions(ctx co
 		platform = forcePlatform
 	} else if groupID != nil {
 		// 根据分组 platform 决定查询哪种账号
-		group, err := s.groupRepo.GetByID(ctx, *groupID)
+		var group *Group
+		if ctxGroup, ok := ctx.Value(ctxkey.Group).(*Group); ok && ctxGroup != nil && ctxGroup.ID == *groupID {
+			group = ctxGroup
+		} else {
+			var err error
+			group, err = s.groupRepo.GetByIDLite(ctx, *groupID)
 			if err != nil {
 				return nil, fmt.Errorf("get group failed: %w", err)
 			}
+		}
 		platform = group.Platform
 	} else {
 		// 无分组时只使用原生 gemini 平台

backend/internal/service/gemini_multiplatform_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/Wei-Shaw/sub2api/internal/pkg/ctxkey"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/pagination"
 	"github.com/stretchr/testify/require"
 )
@@ -147,9 +148,20 @@ var _ AccountRepository = (*mockAccountRepoForGemini)(nil)
 // mockGroupRepoForGemini Gemini 测试用的 group repo mock
 type mockGroupRepoForGemini struct {
 	groups           map[int64]*Group
+	getByIDCalls     int
+	getByIDLiteCalls int
 }
 
 func (m *mockGroupRepoForGemini) GetByID(ctx context.Context, id int64) (*Group, error) {
+	m.getByIDCalls++
+	if g, ok := m.groups[id]; ok {
+		return g, nil
+	}
+	return nil, errors.New("group not found")
+}
+
+func (m *mockGroupRepoForGemini) GetByIDLite(ctx context.Context, id int64) (*Group, error) {
+	m.getByIDLiteCalls++
 	if g, ok := m.groups[id]; ok {
 		return g, nil
 	}
@@ -242,6 +254,76 @@ func TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_GeminiP
 	require.Equal(t, PlatformGemini, acc.Platform, "无分组时应只返回 gemini 平台账户")
 }
 
+func TestGeminiMessagesCompatService_GroupResolution_ReusesContextGroup(t *testing.T) {
+	ctx := context.Background()
+	groupID := int64(7)
+	group := &Group{
+		ID:       groupID,
+		Platform: PlatformGemini,
+		Status:   StatusActive,
+	}
+	ctx = context.WithValue(ctx, ctxkey.Group, group)
+
+	repo := &mockAccountRepoForGemini{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformGemini, Priority: 1, Status: StatusActive, Schedulable: true},
+		},
+		accountsByID: map[int64]*Account{},
+	}
+	for i := range repo.accounts {
+		repo.accountsByID[repo.accounts[i].ID] = &repo.accounts[i]
+	}
+
+	cache := &mockGatewayCacheForGemini{}
+	groupRepo := &mockGroupRepoForGemini{groups: map[int64]*Group{}}
+
+	svc := &GeminiMessagesCompatService{
+		accountRepo: repo,
+		groupRepo:   groupRepo,
+		cache:       cache,
+	}
+
+	acc, err := svc.SelectAccountForModelWithExclusions(ctx, &groupID, "", "gemini-2.5-flash", nil)
+	require.NoError(t, err)
+	require.NotNil(t, acc)
+	require.Equal(t, 0, groupRepo.getByIDCalls)
+	require.Equal(t, 0, groupRepo.getByIDLiteCalls)
+}
+
+func TestGeminiMessagesCompatService_GroupResolution_UsesLiteFetch(t *testing.T) {
+	ctx := context.Background()
+	groupID := int64(7)
+
+	repo := &mockAccountRepoForGemini{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformGemini, Priority: 1, Status: StatusActive, Schedulable: true},
+		},
+		accountsByID: map[int64]*Account{},
+	}
+	for i := range repo.accounts {
+		repo.accountsByID[repo.accounts[i].ID] = &repo.accounts[i]
+	}
+
+	cache := &mockGatewayCacheForGemini{}
+	groupRepo := &mockGroupRepoForGemini{
+		groups: map[int64]*Group{
+			groupID: {ID: groupID, Platform: PlatformGemini},
+		},
+	}
+
+	svc := &GeminiMessagesCompatService{
+		accountRepo: repo,
+		groupRepo:   groupRepo,
+		cache:       cache,
+	}
+
+	acc, err := svc.SelectAccountForModelWithExclusions(ctx, &groupID, "", "gemini-2.5-flash", nil)
+	require.NoError(t, err)
+	require.NotNil(t, acc)
+	require.Equal(t, 0, groupRepo.getByIDCalls)
+	require.Equal(t, 1, groupRepo.getByIDLiteCalls)
+}
+
 // TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_AntigravityGroup 测试 antigravity 分组
 func TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_AntigravityGroup(t *testing.T) {
 	ctx := context.Background()

backend/internal/service/group_service.go

@@ -16,6 +16,7 @@ var (
 type GroupRepository interface {
 	Create(ctx context.Context, group *Group) error
 	GetByID(ctx context.Context, id int64) (*Group, error)
+	GetByIDLite(ctx context.Context, id int64) (*Group, error)
 	Update(ctx context.Context, group *Group) error
 	Delete(ctx context.Context, id int64) error
 	DeleteCascade(ctx context.Context, id int64) ([]int64, error)