fix(分组): 防止降级环并校验上下文分组

- 增加降级链路环检测并拦截配置

- 仅复用合法分组上下文并必要时回退查询

- 标注 GetByIDLite 轻量语义并补充测试

backend/internal/repository/group_repo.go

@@ -70,6 +70,7 @@ func (r *groupRepository) GetByID(ctx context.Context, id int64) (*service.Group
 }
 
 func (r *groupRepository) GetByIDLite(ctx context.Context, id int64) (*service.Group, error) {
+	// AccountCount is intentionally not loaded here; use GetByID when needed.
 	m, err := r.client.Group.Query().
 		Where(group.IDEQ(id)).
 		Only(ctx)

backend/internal/server/middleware/api_key_auth.go

@@ -179,7 +179,7 @@ func GetSubscriptionFromContext(c *gin.Context) (*service.UserSubscription, bool
 }
 
 func setGroupContext(c *gin.Context, group *service.Group) {
-	if group == nil {
+	if !service.IsGroupContextValid(group) {
 		return
 	}
 	if existing, ok := c.Request.Context().Value(ctxkey.Group).(*service.Group); ok && existing != nil && existing.ID == group.ID {

backend/internal/service/admin_service.go

@@ -575,18 +575,33 @@ func (s *adminServiceImpl) validateFallbackGroup(ctx context.Context, currentGro
 		return fmt.Errorf("cannot set self as fallback group")
 	}
 
+	visited := map[int64]struct{}{}
+	nextID := fallbackGroupID
+	for {
+		if _, seen := visited[nextID]; seen {
+			return fmt.Errorf("fallback group cycle detected")
+		}
+		visited[nextID] = struct{}{}
+		if currentGroupID > 0 && nextID == currentGroupID {
+			return fmt.Errorf("fallback group cycle detected")
+		}
+
 		// 检查降级分组是否存在
-	fallbackGroup, err := s.groupRepo.GetByID(ctx, fallbackGroupID)
+		fallbackGroup, err := s.groupRepo.GetByIDLite(ctx, nextID)
 		if err != nil {
 			return fmt.Errorf("fallback group not found: %w", err)
 		}
 
 		// 降级分组不能启用 claude_code_only，否则会造成死循环
-	if fallbackGroup.ClaudeCodeOnly {
+		if nextID == fallbackGroupID && fallbackGroup.ClaudeCodeOnly {
 			return fmt.Errorf("fallback group cannot have claude_code_only enabled")
 		}
 
+		if fallbackGroup.FallbackGroupID == nil {
 			return nil
+		}
+		nextID = *fallbackGroup.FallbackGroupID
+	}
 }
 
 func (s *adminServiceImpl) UpdateGroup(ctx context.Context, id int64, input *UpdateGroupInput) (*Group, error) {

backend/internal/service/admin_service_group_test.go

@@ -202,3 +202,84 @@ func TestAdminService_UpdateGroup_PartialImagePricing(t *testing.T) {
 	require.InDelta(t, 0.15, *repo.updated.ImagePrice2K, 0.0001) // 原值保持
 	require.Nil(t, repo.updated.ImagePrice4K)
 }
+
+func TestAdminService_ValidateFallbackGroup_DetectsCycle(t *testing.T) {
+	groupID := int64(1)
+	fallbackID := int64(2)
+	repo := &groupRepoStubForFallbackCycle{
+		groups: map[int64]*Group{
+			groupID: {
+				ID:              groupID,
+				FallbackGroupID: &fallbackID,
+			},
+			fallbackID: {
+				ID:              fallbackID,
+				FallbackGroupID: &groupID,
+			},
+		},
+	}
+	svc := &adminServiceImpl{groupRepo: repo}
+
+	err := svc.validateFallbackGroup(context.Background(), groupID, fallbackID)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "fallback group cycle")
+}
+
+type groupRepoStubForFallbackCycle struct {
+	groups map[int64]*Group
+}
+
+func (s *groupRepoStubForFallbackCycle) Create(_ context.Context, _ *Group) error {
+	panic("unexpected Create call")
+}
+
+func (s *groupRepoStubForFallbackCycle) Update(_ context.Context, _ *Group) error {
+	panic("unexpected Update call")
+}
+
+func (s *groupRepoStubForFallbackCycle) GetByID(ctx context.Context, id int64) (*Group, error) {
+	return s.GetByIDLite(ctx, id)
+}
+
+func (s *groupRepoStubForFallbackCycle) GetByIDLite(_ context.Context, id int64) (*Group, error) {
+	if g, ok := s.groups[id]; ok {
+		return g, nil
+	}
+	return nil, ErrGroupNotFound
+}
+
+func (s *groupRepoStubForFallbackCycle) Delete(_ context.Context, _ int64) error {
+	panic("unexpected Delete call")
+}
+
+func (s *groupRepoStubForFallbackCycle) DeleteCascade(_ context.Context, _ int64) ([]int64, error) {
+	panic("unexpected DeleteCascade call")
+}
+
+func (s *groupRepoStubForFallbackCycle) List(_ context.Context, _ pagination.PaginationParams) ([]Group, *pagination.PaginationResult, error) {
+	panic("unexpected List call")
+}
+
+func (s *groupRepoStubForFallbackCycle) ListWithFilters(_ context.Context, _ pagination.PaginationParams, _, _ string, _ *bool) ([]Group, *pagination.PaginationResult, error) {
+	panic("unexpected ListWithFilters call")
+}
+
+func (s *groupRepoStubForFallbackCycle) ListActive(_ context.Context) ([]Group, error) {
+	panic("unexpected ListActive call")
+}
+
+func (s *groupRepoStubForFallbackCycle) ListActiveByPlatform(_ context.Context, _ string) ([]Group, error) {
+	panic("unexpected ListActiveByPlatform call")
+}
+
+func (s *groupRepoStubForFallbackCycle) ExistsByName(_ context.Context, _ string) (bool, error) {
+	panic("unexpected ExistsByName call")
+}
+
+func (s *groupRepoStubForFallbackCycle) GetAccountCount(_ context.Context, _ int64) (int64, error) {
+	panic("unexpected GetAccountCount call")
+}
+
+func (s *groupRepoStubForFallbackCycle) DeleteAccountGroupsByGroupID(_ context.Context, _ int64) (int64, error) {
+	panic("unexpected DeleteAccountGroupsByGroupID call")
+}

backend/internal/service/gateway_multiplatform_test.go

@@ -1102,6 +1102,47 @@ func TestGatewayService_GroupResolution_ReusesContextGroup(t *testing.T) {
 	require.Equal(t, 0, groupRepo.getByIDLiteCalls)
 }
 
+func TestGatewayService_GroupResolution_IgnoresInvalidContextGroup(t *testing.T) {
+	ctx := context.Background()
+	groupID := int64(42)
+	ctxGroup := &Group{
+		ID:     groupID,
+		Status: StatusActive,
+	}
+	ctx = context.WithValue(ctx, ctxkey.Group, ctxGroup)
+
+	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]
+	}
+
+	group := &Group{
+		ID:       groupID,
+		Platform: PlatformAnthropic,
+		Status:   StatusActive,
+	}
+	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, 1, groupRepo.getByIDLiteCalls)
+}
+
 func TestGatewayService_GroupResolution_FallbackUsesLiteOnce(t *testing.T) {
 	ctx := context.Background()
 	groupID := int64(10)
@@ -1146,3 +1187,41 @@ func TestGatewayService_GroupResolution_FallbackUsesLiteOnce(t *testing.T) {
 	require.Equal(t, 0, groupRepo.getByIDCalls)
 	require.Equal(t, 1, groupRepo.getByIDLiteCalls)
 }
+
+func TestGatewayService_ResolveGatewayGroup_DetectsFallbackCycle(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,
+		ClaudeCodeOnly:  true,
+		FallbackGroupID: &groupID,
+	}
+
+	groupRepo := &mockGroupRepoForGateway{
+		groups: map[int64]*Group{
+			groupID:    group,
+			fallbackID: fallbackGroup,
+		},
+	}
+
+	svc := &GatewayService{
+		groupRepo: groupRepo,
+	}
+
+	gotGroup, gotID, err := svc.resolveGatewayGroup(ctx, &groupID)
+	require.Error(t, err)
+	require.Nil(t, gotGroup)
+	require.Nil(t, gotID)
+	require.Contains(t, err.Error(), "fallback group cycle")
+}

backend/internal/service/gateway_service.go

@@ -640,7 +640,7 @@ func (s *GatewayService) schedulingConfig() config.GatewaySchedulingConfig {
 }
 
 func (s *GatewayService) withGroupContext(ctx context.Context, group *Group) context.Context {
-	if group == nil {
+	if !IsGroupContextValid(group) {
 		return ctx
 	}
 	if existing, ok := ctx.Value(ctxkey.Group).(*Group); ok && existing != nil && existing.ID == group.ID {
@@ -650,7 +650,7 @@ func (s *GatewayService) withGroupContext(ctx context.Context, group *Group) con
 }
 
 func (s *GatewayService) groupFromContext(ctx context.Context, groupID int64) *Group {
-	if group, ok := ctx.Value(ctxkey.Group).(*Group); ok && group != nil && group.ID == groupID {
+	if group, ok := ctx.Value(ctxkey.Group).(*Group); ok && IsGroupContextValid(group) && group.ID == groupID {
 		return group
 	}
 	return nil
@@ -673,7 +673,13 @@ func (s *GatewayService) resolveGatewayGroup(ctx context.Context, groupID *int64
 	}
 
 	currentID := *groupID
+	visited := map[int64]struct{}{}
 	for {
+		if _, seen := visited[currentID]; seen {
+			return nil, nil, fmt.Errorf("fallback group cycle detected")
+		}
+		visited[currentID] = struct{}{}
+
 		group, err := s.resolveGroupByID(ctx, currentID)
 		if err != nil {
 			return nil, nil, err

backend/internal/service/gemini_messages_compat_service.go

@@ -87,7 +87,7 @@ func (s *GeminiMessagesCompatService) SelectAccountForModelWithExclusions(ctx co
 	} else if groupID != nil {
 		// 根据分组 platform 决定查询哪种账号
 		var group *Group
-		if ctxGroup, ok := ctx.Value(ctxkey.Group).(*Group); ok && ctxGroup != nil && ctxGroup.ID == *groupID {
+		if ctxGroup, ok := ctx.Value(ctxkey.Group).(*Group); ok && IsGroupContextValid(ctxGroup) && ctxGroup.ID == *groupID {
 			group = ctxGroup
 		} else {
 			var err error

backend/internal/service/group.go

@@ -72,3 +72,17 @@ func (g *Group) GetImagePrice(imageSize string) *float64 {
 		return g.ImagePrice2K
 	}
 }
+
+// IsGroupContextValid reports whether a group from context has the fields required for routing decisions.
+func IsGroupContextValid(group *Group) bool {
+	if group == nil {
+		return false
+	}
+	if group.ID <= 0 {
+		return false
+	}
+	if group.Platform == "" || group.Status == "" {
+		return false
+	}
+	return true
+}