feat: 添加5h窗口费用控制和会话数量限制

- 支持Anthropic OAuth/SetupToken账号的5h窗口费用阈值控制
- 支持账号级别的并发会话数量限制
- 使用Redis缓存窗口费用(30秒TTL)减少数据库压力
- 费用计算基于标准费用(不含账号倍率)

backend/internal/service/account.go

@@ -557,3 +557,141 @@ func (a *Account) IsMixedSchedulingEnabled() bool {
 	}
 	return false
 }
+
+// WindowCostSchedulability 窗口费用调度状态
+type WindowCostSchedulability int
+
+const (
+	// WindowCostSchedulable 可正常调度
+	WindowCostSchedulable WindowCostSchedulability = iota
+	// WindowCostStickyOnly 仅允许粘性会话
+	WindowCostStickyOnly
+	// WindowCostNotSchedulable 完全不可调度
+	WindowCostNotSchedulable
+)
+
+// IsAnthropicOAuthOrSetupToken 判断是否为 Anthropic OAuth 或 SetupToken 类型账号
+// 仅这两类账号支持 5h 窗口额度控制和会话数量控制
+func (a *Account) IsAnthropicOAuthOrSetupToken() bool {
+	return a.Platform == PlatformAnthropic && (a.Type == AccountTypeOAuth || a.Type == AccountTypeSetupToken)
+}
+
+// GetWindowCostLimit 获取 5h 窗口费用阈值（美元）
+// 返回 0 表示未启用
+func (a *Account) GetWindowCostLimit() float64 {
+	if a.Extra == nil {
+		return 0
+	}
+	if v, ok := a.Extra["window_cost_limit"]; ok {
+		return parseExtraFloat64(v)
+	}
+	return 0
+}
+
+// GetWindowCostStickyReserve 获取粘性会话预留额度（美元）
+// 默认值为 10
+func (a *Account) GetWindowCostStickyReserve() float64 {
+	if a.Extra == nil {
+		return 10.0
+	}
+	if v, ok := a.Extra["window_cost_sticky_reserve"]; ok {
+		val := parseExtraFloat64(v)
+		if val > 0 {
+			return val
+		}
+	}
+	return 10.0
+}
+
+// GetMaxSessions 获取最大并发会话数
+// 返回 0 表示未启用
+func (a *Account) GetMaxSessions() int {
+	if a.Extra == nil {
+		return 0
+	}
+	if v, ok := a.Extra["max_sessions"]; ok {
+		return parseExtraInt(v)
+	}
+	return 0
+}
+
+// GetSessionIdleTimeoutMinutes 获取会话空闲超时分钟数
+// 默认值为 5 分钟
+func (a *Account) GetSessionIdleTimeoutMinutes() int {
+	if a.Extra == nil {
+		return 5
+	}
+	if v, ok := a.Extra["session_idle_timeout_minutes"]; ok {
+		val := parseExtraInt(v)
+		if val > 0 {
+			return val
+		}
+	}
+	return 5
+}
+
+// CheckWindowCostSchedulability 根据当前窗口费用检查调度状态
+// - 费用 < 阈值: WindowCostSchedulable（可正常调度）
+// - 费用 >= 阈值 且 < 阈值+预留: WindowCostStickyOnly（仅粘性会话）
+// - 费用 >= 阈值+预留: WindowCostNotSchedulable（不可调度）
+func (a *Account) CheckWindowCostSchedulability(currentWindowCost float64) WindowCostSchedulability {
+	limit := a.GetWindowCostLimit()
+	if limit <= 0 {
+		return WindowCostSchedulable
+	}
+
+	if currentWindowCost < limit {
+		return WindowCostSchedulable
+	}
+
+	stickyReserve := a.GetWindowCostStickyReserve()
+	if currentWindowCost < limit+stickyReserve {
+		return WindowCostStickyOnly
+	}
+
+	return WindowCostNotSchedulable
+}
+
+// parseExtraFloat64 从 extra 字段解析 float64 值
+func parseExtraFloat64(value any) float64 {
+	switch v := value.(type) {
+	case float64:
+		return v
+	case float32:
+		return float64(v)
+	case int:
+		return float64(v)
+	case int64:
+		return float64(v)
+	case json.Number:
+		if f, err := v.Float64(); err == nil {
+			return f
+		}
+	case string:
+		if f, err := strconv.ParseFloat(strings.TrimSpace(v), 64); err == nil {
+			return f
+		}
+	}
+	return 0
+}
+
+// parseExtraInt 从 extra 字段解析 int 值
+func parseExtraInt(value any) int {
+	switch v := value.(type) {
+	case int:
+		return v
+	case int64:
+		return int(v)
+	case float64:
+		return int(v)
+	case json.Number:
+		if i, err := v.Int64(); err == nil {
+			return int(i)
+		}
+	case string:
+		if i, err := strconv.Atoi(strings.TrimSpace(v)); err == nil {
+			return i
+		}
+	}
+	return 0
+}

backend/internal/service/account_usage_service.go

@@ -575,3 +575,9 @@ func buildGeminiUsageProgress(used, limit int64, resetAt time.Time, tokens int64
 		},
 	}
 }
+
+// GetAccountWindowStats 获取账号在指定时间窗口内的使用统计
+// 用于账号列表页面显示当前窗口费用
+func (s *AccountUsageService) GetAccountWindowStats(ctx context.Context, accountID int64, startTime time.Time) (*usagestats.AccountStats, error) {
+	return s.usageLogRepo.GetAccountWindowStats(ctx, accountID, startTime)
+}

backend/internal/service/gateway_multiplatform_test.go

@@ -1052,7 +1052,7 @@ func TestGatewayService_SelectAccountWithLoadAwareness(t *testing.T) {
 			concurrencyService: nil, // No concurrency service
 		}
 
-		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "", "claude-3-5-sonnet-20241022", nil)
+		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "", "claude-3-5-sonnet-20241022", nil, "")
 		require.NoError(t, err)
 		require.NotNil(t, result)
 		require.NotNil(t, result.Account)
@@ -1105,7 +1105,7 @@ func TestGatewayService_SelectAccountWithLoadAwareness(t *testing.T) {
 			concurrencyService: nil, // legacy path
 		}
 
-		result, err := svc.SelectAccountWithLoadAwareness(ctx, &groupID, sessionHash, "claude-b", nil)
+		result, err := svc.SelectAccountWithLoadAwareness(ctx, &groupID, sessionHash, "claude-b", nil, "")
 		require.NoError(t, err)
 		require.NotNil(t, result)
 		require.NotNil(t, result.Account)
@@ -1137,7 +1137,7 @@ func TestGatewayService_SelectAccountWithLoadAwareness(t *testing.T) {
 			concurrencyService: nil,
 		}
 
-		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "", "claude-3-5-sonnet-20241022", nil)
+		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "", "claude-3-5-sonnet-20241022", nil, "")
 		require.NoError(t, err)
 		require.NotNil(t, result)
 		require.NotNil(t, result.Account)
@@ -1169,7 +1169,7 @@ func TestGatewayService_SelectAccountWithLoadAwareness(t *testing.T) {
 		}
 
 		excludedIDs := map[int64]struct{}{1: {}}
-		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "", "claude-3-5-sonnet-20241022", excludedIDs)
+		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "", "claude-3-5-sonnet-20241022", excludedIDs, "")
 		require.NoError(t, err)
 		require.NotNil(t, result)
 		require.NotNil(t, result.Account)
@@ -1203,7 +1203,7 @@ func TestGatewayService_SelectAccountWithLoadAwareness(t *testing.T) {
 			concurrencyService: NewConcurrencyService(concurrencyCache),
 		}
 
-		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "sticky", "claude-3-5-sonnet-20241022", nil)
+		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "sticky", "claude-3-5-sonnet-20241022", nil, "")
 		require.NoError(t, err)
 		require.NotNil(t, result)
 		require.NotNil(t, result.Account)
@@ -1239,7 +1239,7 @@ func TestGatewayService_SelectAccountWithLoadAwareness(t *testing.T) {
 			concurrencyService: NewConcurrencyService(concurrencyCache),
 		}
 
-		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "sticky", "claude-3-5-sonnet-20241022", nil)
+		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "sticky", "claude-3-5-sonnet-20241022", nil, "")
 		require.NoError(t, err)
 		require.NotNil(t, result)
 		require.NotNil(t, result.Account)
@@ -1266,7 +1266,7 @@ func TestGatewayService_SelectAccountWithLoadAwareness(t *testing.T) {
 			concurrencyService: nil,
 		}
 
-		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "", "claude-3-5-sonnet-20241022", nil)
+		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "", "claude-3-5-sonnet-20241022", nil, "")
 		require.Error(t, err)
 		require.Nil(t, result)
 		require.Contains(t, err.Error(), "no available accounts")
@@ -1298,7 +1298,7 @@ func TestGatewayService_SelectAccountWithLoadAwareness(t *testing.T) {
 			concurrencyService: nil,
 		}
 
-		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "", "claude-3-5-sonnet-20241022", nil)
+		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "", "claude-3-5-sonnet-20241022", nil, "")
 		require.NoError(t, err)
 		require.NotNil(t, result)
 		require.NotNil(t, result.Account)
@@ -1331,7 +1331,7 @@ func TestGatewayService_SelectAccountWithLoadAwareness(t *testing.T) {
 			concurrencyService: nil,
 		}
 
-		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "", "claude-3-5-sonnet-20241022", nil)
+		result, err := svc.SelectAccountWithLoadAwareness(ctx, nil, "", "claude-3-5-sonnet-20241022", nil, "")
 		require.NoError(t, err)
 		require.NotNil(t, result)
 		require.NotNil(t, result.Account)

backend/internal/service/gateway_service.go

@@ -176,6 +176,7 @@ type GatewayService struct {
 	deferredService     *DeferredService
 	concurrencyService  *ConcurrencyService
 	claudeTokenProvider *ClaudeTokenProvider
+	sessionLimitCache   SessionLimitCache // 会话数量限制缓存（仅 Anthropic OAuth/SetupToken）
 }
 
 // NewGatewayService creates a new GatewayService
@@ -196,6 +197,7 @@ func NewGatewayService(
 	httpUpstream HTTPUpstream,
 	deferredService *DeferredService,
 	claudeTokenProvider *ClaudeTokenProvider,
+	sessionLimitCache SessionLimitCache,
 ) *GatewayService {
 	return &GatewayService{
 		accountRepo:         accountRepo,
@@ -214,6 +216,7 @@ func NewGatewayService(
 		httpUpstream:        httpUpstream,
 		deferredService:     deferredService,
 		claudeTokenProvider: claudeTokenProvider,
+		sessionLimitCache:   sessionLimitCache,
 	}
 }
 
@@ -407,8 +410,12 @@ func (s *GatewayService) SelectAccountForModelWithExclusions(ctx context.Context
 }
 
 // SelectAccountWithLoadAwareness selects account with load-awareness and wait plan.
-func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}) (*AccountSelectionResult, error) {
+// metadataUserID: 原始 metadata.user_id 字段（用于提取会话 UUID 进行会话数量限制）
+func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}, metadataUserID string) (*AccountSelectionResult, error) {
 	cfg := s.schedulingConfig()
+	// 提取会话 UUID（用于会话数量限制）
+	sessionUUID := extractSessionUUID(metadataUserID)
+
 	var stickyAccountID int64
 	if sessionHash != "" && s.cache != nil {
 		if accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), sessionHash); err == nil {
@@ -527,7 +534,7 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 	if len(routingAccountIDs) > 0 && s.concurrencyService != nil {
 		// 1. 过滤出路由列表中可调度的账号
 		var routingCandidates []*Account
-		var filteredExcluded, filteredMissing, filteredUnsched, filteredPlatform, filteredModelScope, filteredModelMapping int
+		var filteredExcluded, filteredMissing, filteredUnsched, filteredPlatform, filteredModelScope, filteredModelMapping, filteredWindowCost int
 		for _, routingAccountID := range routingAccountIDs {
 			if isExcluded(routingAccountID) {
 				filteredExcluded++
@@ -554,13 +561,18 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 				filteredModelMapping++
 				continue
 			}
+			// 窗口费用检查（非粘性会话路径）
+			if !s.isAccountSchedulableForWindowCost(ctx, account, false) {
+				filteredWindowCost++
+				continue
+			}
 			routingCandidates = append(routingCandidates, account)
 		}
 
 		if s.debugModelRoutingEnabled() {
-			log.Printf("[ModelRoutingDebug] routed candidates: group_id=%v model=%s routed=%d candidates=%d filtered(excluded=%d missing=%d unsched=%d platform=%d model_scope=%d model_mapping=%d)",
+			log.Printf("[ModelRoutingDebug] routed candidates: group_id=%v model=%s routed=%d candidates=%d filtered(excluded=%d missing=%d unsched=%d platform=%d model_scope=%d model_mapping=%d window_cost=%d)",
 				derefGroupID(groupID), requestedModel, len(routingAccountIDs), len(routingCandidates),
-				filteredExcluded, filteredMissing, filteredUnsched, filteredPlatform, filteredModelScope, filteredModelMapping)
+				filteredExcluded, filteredMissing, filteredUnsched, filteredPlatform, filteredModelScope, filteredModelMapping, filteredWindowCost)
 		}
 
 		if len(routingCandidates) > 0 {
@@ -573,18 +585,25 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 						if stickyAccount.IsSchedulable() &&
 							s.isAccountAllowedForPlatform(stickyAccount, platform, useMixed) &&
 							stickyAccount.IsSchedulableForModel(requestedModel) &&
-							(requestedModel == "" || s.isModelSupportedByAccount(stickyAccount, requestedModel)) {
+							(requestedModel == "" || s.isModelSupportedByAccount(stickyAccount, requestedModel)) &&
+							s.isAccountSchedulableForWindowCost(ctx, stickyAccount, true) { // 粘性会话窗口费用检查
 							result, err := s.tryAcquireAccountSlot(ctx, stickyAccountID, stickyAccount.Concurrency)
 							if err == nil && result.Acquired {
-								_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL)
-								if s.debugModelRoutingEnabled() {
-									log.Printf("[ModelRoutingDebug] routed sticky hit: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), stickyAccountID)
+								// 会话数量限制检查
+								if !s.checkAndRegisterSession(ctx, stickyAccount, sessionUUID) {
+									result.ReleaseFunc() // 释放槽位
+									// 继续到负载感知选择
+								} else {
+									_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL)
+									if s.debugModelRoutingEnabled() {
+										log.Printf("[ModelRoutingDebug] routed sticky hit: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), stickyAccountID)
+									}
+									return &AccountSelectionResult{
+										Account:     stickyAccount,
+										Acquired:    true,
+										ReleaseFunc: result.ReleaseFunc,
+									}, nil
 								}
-								return &AccountSelectionResult{
-									Account:     stickyAccount,
-									Acquired:    true,
-									ReleaseFunc: result.ReleaseFunc,
-								}, nil
 							}
 
 							waitingCount, _ := s.concurrencyService.GetAccountWaitingCount(ctx, stickyAccountID)
@@ -657,6 +676,11 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 				for _, item := range routingAvailable {
 					result, err := s.tryAcquireAccountSlot(ctx, item.account.ID, item.account.Concurrency)
 					if err == nil && result.Acquired {
+						// 会话数量限制检查
+						if !s.checkAndRegisterSession(ctx, item.account, sessionUUID) {
+							result.ReleaseFunc() // 释放槽位，继续尝试下一个账号
+							continue
+						}
 						if sessionHash != "" && s.cache != nil {
 							_ = s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, item.account.ID, stickySessionTTL)
 						}
@@ -699,15 +723,21 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 			if ok && s.isAccountInGroup(account, groupID) &&
 				s.isAccountAllowedForPlatform(account, platform, useMixed) &&
 				account.IsSchedulableForModel(requestedModel) &&
-				(requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) {
+				(requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) &&
+				s.isAccountSchedulableForWindowCost(ctx, account, true) { // 粘性会话窗口费用检查
 				result, err := s.tryAcquireAccountSlot(ctx, accountID, account.Concurrency)
 				if err == nil && result.Acquired {
-					_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL)
-					return &AccountSelectionResult{
-						Account:     account,
-						Acquired:    true,
-						ReleaseFunc: result.ReleaseFunc,
-					}, nil
+					// 会话数量限制检查
+					if !s.checkAndRegisterSession(ctx, account, sessionUUID) {
+						result.ReleaseFunc() // 释放槽位，继续到 Layer 2
+					} else {
+						_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL)
+						return &AccountSelectionResult{
+							Account:     account,
+							Acquired:    true,
+							ReleaseFunc: result.ReleaseFunc,
+						}, nil
+					}
 				}
 
 				waitingCount, _ := s.concurrencyService.GetAccountWaitingCount(ctx, accountID)
@@ -748,6 +778,10 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 		if requestedModel != "" && !s.isModelSupportedByAccount(acc, requestedModel) {
 			continue
 		}
+		// 窗口费用检查（非粘性会话路径）
+		if !s.isAccountSchedulableForWindowCost(ctx, acc, false) {
+			continue
+		}
 		candidates = append(candidates, acc)
 	}
 
@@ -765,7 +799,7 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 
 	loadMap, err := s.concurrencyService.GetAccountsLoadBatch(ctx, accountLoads)
 	if err != nil {
-		if result, ok := s.tryAcquireByLegacyOrder(ctx, candidates, groupID, sessionHash, preferOAuth); ok {
+		if result, ok := s.tryAcquireByLegacyOrder(ctx, candidates, groupID, sessionHash, preferOAuth, sessionUUID); ok {
 			return result, nil
 		}
 	} else {
@@ -814,6 +848,11 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 			for _, item := range available {
 				result, err := s.tryAcquireAccountSlot(ctx, item.account.ID, item.account.Concurrency)
 				if err == nil && result.Acquired {
+					// 会话数量限制检查
+					if !s.checkAndRegisterSession(ctx, item.account, sessionUUID) {
+						result.ReleaseFunc() // 释放槽位，继续尝试下一个账号
+						continue
+					}
 					if sessionHash != "" && s.cache != nil {
 						_ = s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, item.account.ID, stickySessionTTL)
 					}
@@ -843,13 +882,18 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 	return nil, errors.New("no available accounts")
 }
 
-func (s *GatewayService) tryAcquireByLegacyOrder(ctx context.Context, candidates []*Account, groupID *int64, sessionHash string, preferOAuth bool) (*AccountSelectionResult, bool) {
+func (s *GatewayService) tryAcquireByLegacyOrder(ctx context.Context, candidates []*Account, groupID *int64, sessionHash string, preferOAuth bool, sessionUUID string) (*AccountSelectionResult, bool) {
 	ordered := append([]*Account(nil), candidates...)
 	sortAccountsByPriorityAndLastUsed(ordered, preferOAuth)
 
 	for _, acc := range ordered {
 		result, err := s.tryAcquireAccountSlot(ctx, acc.ID, acc.Concurrency)
 		if err == nil && result.Acquired {
+			// 会话数量限制检查
+			if !s.checkAndRegisterSession(ctx, acc, sessionUUID) {
+				result.ReleaseFunc() // 释放槽位，继续尝试下一个账号
+				continue
+			}
 			if sessionHash != "" && s.cache != nil {
 				_ = s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, acc.ID, stickySessionTTL)
 			}
@@ -1081,6 +1125,107 @@ func (s *GatewayService) tryAcquireAccountSlot(ctx context.Context, accountID in
 	return s.concurrencyService.AcquireAccountSlot(ctx, accountID, maxConcurrency)
 }
 
+// isAccountSchedulableForWindowCost 检查账号是否可根据窗口费用进行调度
+// 仅适用于 Anthropic OAuth/SetupToken 账号
+// 返回 true 表示可调度，false 表示不可调度
+func (s *GatewayService) isAccountSchedulableForWindowCost(ctx context.Context, account *Account, isSticky bool) bool {
+	// 只检查 Anthropic OAuth/SetupToken 账号
+	if !account.IsAnthropicOAuthOrSetupToken() {
+		return true
+	}
+
+	limit := account.GetWindowCostLimit()
+	if limit <= 0 {
+		return true // 未启用窗口费用限制
+	}
+
+	// 尝试从缓存获取窗口费用
+	var currentCost float64
+	if s.sessionLimitCache != nil {
+		if cost, hit, err := s.sessionLimitCache.GetWindowCost(ctx, account.ID); err == nil && hit {
+			currentCost = cost
+			goto checkSchedulability
+		}
+	}
+
+	// 缓存未命中，从数据库查询
+	{
+		var startTime time.Time
+		if account.SessionWindowStart != nil {
+			startTime = *account.SessionWindowStart
+		} else {
+			startTime = time.Now().Add(-5 * time.Hour)
+		}
+
+		stats, err := s.usageLogRepo.GetAccountWindowStats(ctx, account.ID, startTime)
+		if err != nil {
+			// 失败开放：查询失败时允许调度
+			return true
+		}
+
+		// 使用标准费用（不含账号倍率）
+		currentCost = stats.StandardCost
+
+		// 设置缓存（忽略错误）
+		if s.sessionLimitCache != nil {
+			_ = s.sessionLimitCache.SetWindowCost(ctx, account.ID, currentCost)
+		}
+	}
+
+checkSchedulability:
+	schedulability := account.CheckWindowCostSchedulability(currentCost)
+
+	switch schedulability {
+	case WindowCostSchedulable:
+		return true
+	case WindowCostStickyOnly:
+		return isSticky
+	case WindowCostNotSchedulable:
+		return false
+	}
+	return true
+}
+
+// checkAndRegisterSession 检查并注册会话，用于会话数量限制
+// 仅适用于 Anthropic OAuth/SetupToken 账号
+// 返回 true 表示允许（在限制内或会话已存在），false 表示拒绝（超出限制且是新会话）
+func (s *GatewayService) checkAndRegisterSession(ctx context.Context, account *Account, sessionUUID string) bool {
+	// 只检查 Anthropic OAuth/SetupToken 账号
+	if !account.IsAnthropicOAuthOrSetupToken() {
+		return true
+	}
+
+	maxSessions := account.GetMaxSessions()
+	if maxSessions <= 0 || sessionUUID == "" {
+		return true // 未启用会话限制或无会话ID
+	}
+
+	if s.sessionLimitCache == nil {
+		return true // 缓存不可用时允许通过
+	}
+
+	idleTimeout := time.Duration(account.GetSessionIdleTimeoutMinutes()) * time.Minute
+
+	allowed, err := s.sessionLimitCache.RegisterSession(ctx, account.ID, sessionUUID, maxSessions, idleTimeout)
+	if err != nil {
+		// 失败开放：缓存错误时允许通过
+		return true
+	}
+	return allowed
+}
+
+// extractSessionUUID 从 metadata.user_id 中提取会话 UUID
+// 格式: user_{64位hex}_account__session_{uuid}
+func extractSessionUUID(metadataUserID string) string {
+	if metadataUserID == "" {
+		return ""
+	}
+	if match := sessionIDRegex.FindStringSubmatch(metadataUserID); len(match) > 1 {
+		return match[1]
+	}
+	return ""
+}
+
 func (s *GatewayService) getSchedulableAccount(ctx context.Context, accountID int64) (*Account, error) {
 	if s.schedulerSnapshot != nil {
 		return s.schedulerSnapshot.GetAccount(ctx, accountID)

backend/internal/service/ops_retry.go

@@ -514,7 +514,7 @@ func (s *OpsService) selectAccountForRetry(ctx context.Context, reqType opsRetry
 		if s.gatewayService == nil {
 			return nil, fmt.Errorf("gateway service not available")
 		}
-		return s.gatewayService.SelectAccountWithLoadAwareness(ctx, groupID, "", model, excludedIDs)
+		return s.gatewayService.SelectAccountWithLoadAwareness(ctx, groupID, "", model, excludedIDs, "") // 重试不使用会话限制
 	default:
 		return nil, fmt.Errorf("unsupported retry type: %s", reqType)
 	}

backend/internal/service/session_limit_cache.go

@@ -0,0 +1,63 @@
+package service
+
+import (
+	"context"
+	"time"
+)
+
+// SessionLimitCache 管理账号级别的活跃会话跟踪
+// 用于 Anthropic OAuth/SetupToken 账号的会话数量限制
+//
+// Key 格式: session_limit:account:{accountID}
+// 数据结构: Sorted Set (member=sessionUUID, score=timestamp)
+//
+// 会话在空闲超时后自动过期，无需手动清理
+type SessionLimitCache interface {
+	// RegisterSession 注册会话活动
+	// - 如果会话已存在，刷新其时间戳并返回 true
+	// - 如果会话不存在且活跃会话数 < maxSessions，添加新会话并返回 true
+	// - 如果会话不存在且活跃会话数 >= maxSessions，返回 false（拒绝）
+	//
+	// 参数:
+	//   accountID: 账号 ID
+	//   sessionUUID: 从 metadata.user_id 中提取的会话 UUID
+	//   maxSessions: 最大并发会话数限制
+	//   idleTimeout: 会话空闲超时时间
+	//
+	// 返回:
+	//   allowed: true 表示允许（在限制内或会话已存在），false 表示拒绝（超出限制且是新会话）
+	//   error: 操作错误
+	RegisterSession(ctx context.Context, accountID int64, sessionUUID string, maxSessions int, idleTimeout time.Duration) (allowed bool, err error)
+
+	// RefreshSession 刷新现有会话的时间戳
+	// 用于活跃会话保持活动状态
+	RefreshSession(ctx context.Context, accountID int64, sessionUUID string, idleTimeout time.Duration) error
+
+	// GetActiveSessionCount 获取当前活跃会话数
+	// 返回未过期的会话数量
+	GetActiveSessionCount(ctx context.Context, accountID int64) (int, error)
+
+	// GetActiveSessionCountBatch 批量获取多个账号的活跃会话数
+	// 返回 map[accountID]count，查询失败的账号不在 map 中
+	GetActiveSessionCountBatch(ctx context.Context, accountIDs []int64) (map[int64]int, error)
+
+	// IsSessionActive 检查特定会话是否活跃（未过期）
+	IsSessionActive(ctx context.Context, accountID int64, sessionUUID string) (bool, error)
+
+	// ========== 5h窗口费用缓存 ==========
+	// Key 格式: window_cost:account:{accountID}
+	// 用于缓存账号在当前5h窗口内的标准费用，减少数据库聚合查询压力
+
+	// GetWindowCost 获取缓存的窗口费用
+	// 返回 (cost, true, nil) 如果缓存命中
+	// 返回 (0, false, nil) 如果缓存未命中
+	// 返回 (0, false, err) 如果发生错误
+	GetWindowCost(ctx context.Context, accountID int64) (cost float64, hit bool, err error)
+
+	// SetWindowCost 设置窗口费用缓存
+	SetWindowCost(ctx context.Context, accountID int64, cost float64) error
+
+	// GetWindowCostBatch 批量获取窗口费用缓存
+	// 返回 map[accountID]cost，缓存未命中的账号不在 map 中
+	GetWindowCostBatch(ctx context.Context, accountIDs []int64) (map[int64]float64, error)
+}