Merge branch 'main' of github.com:Wei-Shaw/sub2api

backend/internal/service/auth_service.go

@@ -153,8 +153,8 @@ func (s *AuthService) RegisterWithVerification(ctx context.Context, email, passw
 		return "", nil, ErrServiceUnavailable
 	}
 
-	// 应用优惠码（如果提供）
-	if promoCode != "" && s.promoService != nil {
+	// 应用优惠码（如果提供且功能已启用）
+	if promoCode != "" && s.promoService != nil && s.settingService != nil && s.settingService.IsPromoCodeEnabled(ctx) {
 		if err := s.promoService.ApplyPromoCode(ctx, user.ID, promoCode); err != nil {
 			// 优惠码应用失败不影响注册，只记录日志
 			log.Printf("[Auth] Failed to apply promo code for user %d: %v", user.ID, err)

backend/internal/service/domain_constants.go

@@ -71,6 +71,7 @@ const (
 	// 注册设置
 	SettingKeyRegistrationEnabled = "registration_enabled" // 是否开放注册
 	SettingKeyEmailVerifyEnabled  = "email_verify_enabled" // 是否开启邮件验证
+	SettingKeyPromoCodeEnabled    = "promo_code_enabled"   // 是否启用优惠码功能
 
 	// 邮件服务设置
 	SettingKeySMTPHost     = "smtp_host"      // SMTP服务器地址

backend/internal/service/gateway_service.go

@@ -136,11 +136,24 @@ var allowedHeaders = map[string]bool{
 	"content-type":                              true,
 }
 
-// GatewayCache defines cache operations for gateway service
+// GatewayCache 定义网关服务的缓存操作接口。
+// 提供粘性会话（Sticky Session）的存储、查询、刷新和删除功能。
+//
+// GatewayCache defines cache operations for gateway service.
+// Provides sticky session storage, retrieval, refresh and deletion capabilities.
 type GatewayCache interface {
+	// GetSessionAccountID 获取粘性会话绑定的账号 ID
+	// Get the account ID bound to a sticky session
 	GetSessionAccountID(ctx context.Context, groupID int64, sessionHash string) (int64, error)
+	// SetSessionAccountID 设置粘性会话与账号的绑定关系
+	// Set the binding between sticky session and account
 	SetSessionAccountID(ctx context.Context, groupID int64, sessionHash string, accountID int64, ttl time.Duration) error
+	// RefreshSessionTTL 刷新粘性会话的过期时间
+	// Refresh the expiration time of a sticky session
 	RefreshSessionTTL(ctx context.Context, groupID int64, sessionHash string, ttl time.Duration) error
+	// DeleteSessionAccountID 删除粘性会话绑定，用于账号不可用时主动清理
+	// Delete sticky session binding, used to proactively clean up when account becomes unavailable
+	DeleteSessionAccountID(ctx context.Context, groupID int64, sessionHash string) error
 }
 
 // derefGroupID safely dereferences *int64 to int64, returning 0 if nil
@@ -151,6 +164,28 @@ func derefGroupID(groupID *int64) int64 {
 	return *groupID
 }
 
+// shouldClearStickySession 检查账号是否处于不可调度状态，需要清理粘性会话绑定。
+// 当账号状态为错误、禁用、不可调度，或处于临时不可调度期间时，返回 true。
+// 这确保后续请求不会继续使用不可用的账号。
+//
+// shouldClearStickySession checks if an account is in an unschedulable state
+// and the sticky session binding should be cleared.
+// Returns true when account status is error/disabled, schedulable is false,
+// or within temporary unschedulable period.
+// This ensures subsequent requests won't continue using unavailable accounts.
+func shouldClearStickySession(account *Account) bool {
+	if account == nil {
+		return false
+	}
+	if account.Status == StatusError || account.Status == StatusDisabled || !account.Schedulable {
+		return true
+	}
+	if account.TempUnschedulableUntil != nil && time.Now().Before(*account.TempUnschedulableUntil) {
+		return true
+	}
+	return false
+}
+
 type AccountWaitPlan struct {
 	AccountID      int64
 	MaxConcurrency int
@@ -1067,6 +1102,8 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 							}
 							// 粘性账号槽位满且等待队列已满，继续使用负载感知选择
 						}
+					} else {
+						_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
 					}
 				}
 			}
@@ -1173,41 +1210,52 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 		accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
 		if err == nil && accountID > 0 && !isExcluded(accountID) {
 			account, ok := accountByID[accountID]
-			if ok && s.isAccountInGroup(account, groupID) &&
-				s.isAccountAllowedForPlatform(account, platform, useMixed) &&
-				account.IsSchedulableForModel(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 {
-					// 会话数量限制检查
-					if !s.checkAndRegisterSession(ctx, account, sessionHash) {
-						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
-					}
+			if ok {
+				// 检查账户是否需要清理粘性会话绑定
+				// Check if the account needs sticky session cleanup
+				clearSticky := shouldClearStickySession(account)
+				if clearSticky {
+					_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
 				}
+				if !clearSticky && s.isAccountInGroup(account, groupID) &&
+					s.isAccountAllowedForPlatform(account, platform, useMixed) &&
+					account.IsSchedulableForModel(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 {
+						// 会话数量限制检查
+						// Session count limit check
+						if !s.checkAndRegisterSession(ctx, account, sessionHash) {
+							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)
-				if waitingCount < cfg.StickySessionMaxWaiting {
-					// 会话数量限制检查（等待计划也需要占用会话配额）
-					if !s.checkAndRegisterSession(ctx, account, sessionHash) {
-						// 会话限制已满，继续到 Layer 2
-					} else {
-						return &AccountSelectionResult{
-							Account: account,
-							WaitPlan: &AccountWaitPlan{
-								AccountID:      accountID,
-								MaxConcurrency: account.Concurrency,
-								Timeout:        cfg.StickySessionWaitTimeout,
-								MaxWaiting:     cfg.StickySessionMaxWaiting,
-							},
-						}, nil
+					waitingCount, _ := s.concurrencyService.GetAccountWaitingCount(ctx, accountID)
+					if waitingCount < cfg.StickySessionMaxWaiting {
+						// 会话数量限制检查（等待计划也需要占用会话配额）
+						// Session count limit check (wait plan also requires session quota)
+						if !s.checkAndRegisterSession(ctx, account, sessionHash) {
+							// 会话限制已满，继续到 Layer 2
+							// Session limit full, continue to Layer 2
+						} else {
+							return &AccountSelectionResult{
+								Account: account,
+								WaitPlan: &AccountWaitPlan{
+									AccountID:      accountID,
+									MaxConcurrency: account.Concurrency,
+									Timeout:        cfg.StickySessionWaitTimeout,
+									MaxWaiting:     cfg.StickySessionMaxWaiting,
+								},
+							}, nil
+						}
 					}
 				}
 			}
@@ -1827,14 +1875,20 @@ func (s *GatewayService) selectAccountForModelWithPlatform(ctx context.Context,
 				if _, excluded := excludedIDs[accountID]; !excluded {
 					account, err := s.getSchedulableAccount(ctx, accountID)
 					// 检查账号分组归属和平台匹配（确保粘性会话不会跨分组或跨平台）
-					if err == nil && s.isAccountInGroup(account, groupID) && account.Platform == platform && account.IsSchedulableForModel(requestedModel) && (requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) {
-						if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
-							log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
+					if err == nil {
+						clearSticky := shouldClearStickySession(account)
+						if clearSticky {
+							_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
 						}
-						if s.debugModelRoutingEnabled() {
-							log.Printf("[ModelRoutingDebug] legacy routed sticky hit: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), accountID)
+						if !clearSticky && s.isAccountInGroup(account, groupID) && account.Platform == platform && account.IsSchedulableForModel(requestedModel) && (requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) {
+							if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
+								log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
+							}
+							if s.debugModelRoutingEnabled() {
+								log.Printf("[ModelRoutingDebug] legacy routed sticky hit: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), accountID)
+							}
+							return account, nil
 						}
-						return account, nil
 					}
 				}
 			}
@@ -1924,11 +1978,17 @@ func (s *GatewayService) selectAccountForModelWithPlatform(ctx context.Context,
 			if _, excluded := excludedIDs[accountID]; !excluded {
 				account, err := s.getSchedulableAccount(ctx, accountID)
 				// 检查账号分组归属和平台匹配（确保粘性会话不会跨分组或跨平台）
-				if err == nil && s.isAccountInGroup(account, groupID) && account.Platform == platform && account.IsSchedulableForModel(requestedModel) && (requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) {
-					if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
-						log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
+				if err == nil {
+					clearSticky := shouldClearStickySession(account)
+					if clearSticky {
+						_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
+					}
+					if !clearSticky && s.isAccountInGroup(account, groupID) && account.Platform == platform && account.IsSchedulableForModel(requestedModel) && (requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) {
+						if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
+							log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
+						}
+						return account, nil
 					}
-					return account, nil
 				}
 			}
 		}
@@ -2028,15 +2088,21 @@ func (s *GatewayService) selectAccountWithMixedScheduling(ctx context.Context, g
 				if _, excluded := excludedIDs[accountID]; !excluded {
 					account, err := s.getSchedulableAccount(ctx, accountID)
 					// 检查账号分组归属和有效性：原生平台直接匹配，antigravity 需要启用混合调度
-					if err == nil && s.isAccountInGroup(account, groupID) && account.IsSchedulableForModel(requestedModel) && (requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) {
-						if account.Platform == nativePlatform || (account.Platform == PlatformAntigravity && account.IsMixedSchedulingEnabled()) {
-							if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
-								log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
+					if err == nil {
+						clearSticky := shouldClearStickySession(account)
+						if clearSticky {
+							_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
+						}
+						if !clearSticky && s.isAccountInGroup(account, groupID) && account.IsSchedulableForModel(requestedModel) && (requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) {
+							if account.Platform == nativePlatform || (account.Platform == PlatformAntigravity && account.IsMixedSchedulingEnabled()) {
+								if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
+									log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
+								}
+								if s.debugModelRoutingEnabled() {
+									log.Printf("[ModelRoutingDebug] legacy mixed routed sticky hit: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), accountID)
+								}
+								return account, nil
 							}
-							if s.debugModelRoutingEnabled() {
-								log.Printf("[ModelRoutingDebug] legacy mixed routed sticky hit: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), accountID)
-							}
-							return account, nil
 						}
 					}
 				}
@@ -2127,12 +2193,18 @@ func (s *GatewayService) selectAccountWithMixedScheduling(ctx context.Context, g
 			if _, excluded := excludedIDs[accountID]; !excluded {
 				account, err := s.getSchedulableAccount(ctx, accountID)
 				// 检查账号分组归属和有效性：原生平台直接匹配，antigravity 需要启用混合调度
-				if err == nil && s.isAccountInGroup(account, groupID) && account.IsSchedulableForModel(requestedModel) && (requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) {
-					if account.Platform == nativePlatform || (account.Platform == PlatformAntigravity && account.IsMixedSchedulingEnabled()) {
-						if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
-							log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
+				if err == nil {
+					clearSticky := shouldClearStickySession(account)
+					if clearSticky {
+						_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
+					}
+					if !clearSticky && s.isAccountInGroup(account, groupID) && account.IsSchedulableForModel(requestedModel) && (requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) {
+						if account.Platform == nativePlatform || (account.Platform == PlatformAntigravity && account.IsMixedSchedulingEnabled()) {
+							if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
+								log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
+							}
+							return account, nil
 						}
-						return account, nil
 					}
 				}
 			}

backend/internal/service/gemini_messages_compat_service.go

@@ -82,70 +82,23 @@ func (s *GeminiMessagesCompatService) SelectAccountForModel(ctx context.Context,
 }
 
 func (s *GeminiMessagesCompatService) SelectAccountForModelWithExclusions(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}) (*Account, error) {
-	// 优先检查 context 中的强制平台（/antigravity 路由）
-	var platform string
-	forcePlatform, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string)
-	if hasForcePlatform && forcePlatform != "" {
-		platform = forcePlatform
-	} 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 && IsGroupContextValid(ctxGroup) && 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
-		platform = PlatformGemini
+	// 1. 确定目标平台和调度模式
+	// Determine target platform and scheduling mode
+	platform, useMixedScheduling, hasForcePlatform, err := s.resolvePlatformAndSchedulingMode(ctx, groupID)
+	if err != nil {
+		return nil, err
 	}
 
-	// gemini 分组支持混合调度（包含启用了 mixed_scheduling 的 antigravity 账户）
-	// 注意：强制平台模式不走混合调度
-	useMixedScheduling := platform == PlatformGemini && !hasForcePlatform
-
 	cacheKey := "gemini:" + sessionHash
 
-	if sessionHash != "" {
-		accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), cacheKey)
-		if err == nil && accountID > 0 {
-			if _, excluded := excludedIDs[accountID]; !excluded {
-				account, err := s.getSchedulableAccount(ctx, accountID)
-				// 检查账号是否有效：原生平台直接匹配，antigravity 需要启用混合调度
-				if err == nil && account.IsSchedulableForModel(requestedModel) && (requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) {
-					valid := false
-					if account.Platform == platform {
-						valid = true
-					} else if useMixedScheduling && account.Platform == PlatformAntigravity && account.IsMixedSchedulingEnabled() {
-						valid = true
-					}
-					if valid {
-						usable := true
-						if s.rateLimitService != nil && requestedModel != "" {
-							ok, err := s.rateLimitService.PreCheckUsage(ctx, account, requestedModel)
-							if err != nil {
-								log.Printf("[Gemini PreCheck] Account %d precheck error: %v", account.ID, err)
-							}
-							if !ok {
-								usable = false
-							}
-						}
-						if usable {
-							_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), cacheKey, geminiStickySessionTTL)
-							return account, nil
-						}
-					}
-				}
-			}
-		}
+	// 2. 尝试粘性会话命中
+	// Try sticky session hit
+	if account := s.tryStickySessionHit(ctx, groupID, sessionHash, cacheKey, requestedModel, excludedIDs, platform, useMixedScheduling); account != nil {
+		return account, nil
 	}
 
-	// 查询可调度账户（强制平台模式：优先按分组查找，找不到再查全部）
+	// 3. 查询可调度账户（强制平台模式：优先按分组查找，找不到再查全部）
+	// Query schedulable accounts (force platform mode: try group first, fallback to all)
 	accounts, err := s.listSchedulableAccountsOnce(ctx, groupID, platform, hasForcePlatform)
 	if err != nil {
 		return nil, fmt.Errorf("query accounts failed: %w", err)
@@ -158,56 +111,9 @@ func (s *GeminiMessagesCompatService) SelectAccountForModelWithExclusions(ctx co
 		}
 	}
 
-	var selected *Account
-	for i := range accounts {
-		acc := &accounts[i]
-		if _, excluded := excludedIDs[acc.ID]; excluded {
-			continue
-		}
-		// 混合调度模式下：原生平台直接通过，antigravity 需要启用 mixed_scheduling
-		// 非混合调度模式（antigravity 分组）：不需要过滤
-		if useMixedScheduling && acc.Platform == PlatformAntigravity && !acc.IsMixedSchedulingEnabled() {
-			continue
-		}
-		if !acc.IsSchedulableForModel(requestedModel) {
-			continue
-		}
-		if requestedModel != "" && !s.isModelSupportedByAccount(acc, requestedModel) {
-			continue
-		}
-		if s.rateLimitService != nil && requestedModel != "" {
-			ok, err := s.rateLimitService.PreCheckUsage(ctx, acc, requestedModel)
-			if err != nil {
-				log.Printf("[Gemini PreCheck] Account %d precheck error: %v", acc.ID, err)
-			}
-			if !ok {
-				continue
-			}
-		}
-		if selected == nil {
-			selected = acc
-			continue
-		}
-		if acc.Priority < selected.Priority {
-			selected = acc
-		} else if acc.Priority == selected.Priority {
-			switch {
-			case acc.LastUsedAt == nil && selected.LastUsedAt != nil:
-				selected = acc
-			case acc.LastUsedAt != nil && selected.LastUsedAt == nil:
-				// keep selected (never used is preferred)
-			case acc.LastUsedAt == nil && selected.LastUsedAt == nil:
-				// Prefer OAuth accounts when both are unused (more compatible for Code Assist flows).
-				if acc.Type == AccountTypeOAuth && selected.Type != AccountTypeOAuth {
-					selected = acc
-				}
-			default:
-				if acc.LastUsedAt.Before(*selected.LastUsedAt) {
-					selected = acc
-				}
-			}
-		}
-	}
+	// 4. 按优先级 + LRU 选择最佳账号
+	// Select best account by priority + LRU
+	selected := s.selectBestGeminiAccount(ctx, accounts, requestedModel, excludedIDs, platform, useMixedScheduling)
 
 	if selected == nil {
 		if requestedModel != "" {
@@ -216,6 +122,8 @@ func (s *GeminiMessagesCompatService) SelectAccountForModelWithExclusions(ctx co
 		return nil, errors.New("no available Gemini accounts")
 	}
 
+	// 5. 设置粘性会话绑定
+	// Set sticky session binding
 	if sessionHash != "" {
 		_ = s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), cacheKey, selected.ID, geminiStickySessionTTL)
 	}
@@ -223,6 +131,229 @@ func (s *GeminiMessagesCompatService) SelectAccountForModelWithExclusions(ctx co
 	return selected, nil
 }
 
+// resolvePlatformAndSchedulingMode 解析目标平台和调度模式。
+// 返回：平台名称、是否使用混合调度、是否强制平台、错误。
+//
+// resolvePlatformAndSchedulingMode resolves target platform and scheduling mode.
+// Returns: platform name, whether to use mixed scheduling, whether force platform, error.
+func (s *GeminiMessagesCompatService) resolvePlatformAndSchedulingMode(ctx context.Context, groupID *int64) (platform string, useMixedScheduling bool, hasForcePlatform bool, err error) {
+	// 优先检查 context 中的强制平台（/antigravity 路由）
+	forcePlatform, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string)
+	if hasForcePlatform && forcePlatform != "" {
+		return forcePlatform, false, true, nil
+	}
+
+	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 && IsGroupContextValid(ctxGroup) && ctxGroup.ID == *groupID {
+			group = ctxGroup
+		} else {
+			group, err = s.groupRepo.GetByIDLite(ctx, *groupID)
+			if err != nil {
+				return "", false, false, fmt.Errorf("get group failed: %w", err)
+			}
+		}
+		// gemini 分组支持混合调度（包含启用了 mixed_scheduling 的 antigravity 账户）
+		return group.Platform, group.Platform == PlatformGemini, false, nil
+	}
+
+	// 无分组时只使用原生 gemini 平台
+	return PlatformGemini, true, false, nil
+}
+
+// tryStickySessionHit 尝试从粘性会话获取账号。
+// 如果命中且账号可用则返回账号；如果账号不可用则清理会话并返回 nil。
+//
+// tryStickySessionHit attempts to get account from sticky session.
+// Returns account if hit and usable; clears session and returns nil if account unavailable.
+func (s *GeminiMessagesCompatService) tryStickySessionHit(
+	ctx context.Context,
+	groupID *int64,
+	sessionHash, cacheKey, requestedModel string,
+	excludedIDs map[int64]struct{},
+	platform string,
+	useMixedScheduling bool,
+) *Account {
+	if sessionHash == "" {
+		return nil
+	}
+
+	accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), cacheKey)
+	if err != nil || accountID <= 0 {
+		return nil
+	}
+
+	if _, excluded := excludedIDs[accountID]; excluded {
+		return nil
+	}
+
+	account, err := s.getSchedulableAccount(ctx, accountID)
+	if err != nil {
+		return nil
+	}
+
+	// 检查账号是否需要清理粘性会话
+	// Check if sticky session should be cleared
+	if shouldClearStickySession(account) {
+		_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), cacheKey)
+		return nil
+	}
+
+	// 验证账号是否可用于当前请求
+	// Verify account is usable for current request
+	if !s.isAccountUsableForRequest(ctx, account, requestedModel, platform, useMixedScheduling) {
+		return nil
+	}
+
+	// 刷新会话 TTL 并返回账号
+	// Refresh session TTL and return account
+	_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), cacheKey, geminiStickySessionTTL)
+	return account
+}
+
+// isAccountUsableForRequest 检查账号是否可用于当前请求。
+// 验证：模型调度、模型支持、平台匹配、速率限制预检。
+//
+// isAccountUsableForRequest checks if account is usable for current request.
+// Validates: model scheduling, model support, platform matching, rate limit precheck.
+func (s *GeminiMessagesCompatService) isAccountUsableForRequest(
+	ctx context.Context,
+	account *Account,
+	requestedModel, platform string,
+	useMixedScheduling bool,
+) bool {
+	// 检查模型调度能力
+	// Check model scheduling capability
+	if !account.IsSchedulableForModel(requestedModel) {
+		return false
+	}
+
+	// 检查模型支持
+	// Check model support
+	if requestedModel != "" && !s.isModelSupportedByAccount(account, requestedModel) {
+		return false
+	}
+
+	// 检查平台匹配
+	// Check platform matching
+	if !s.isAccountValidForPlatform(account, platform, useMixedScheduling) {
+		return false
+	}
+
+	// 速率限制预检
+	// Rate limit precheck
+	if !s.passesRateLimitPreCheck(ctx, account, requestedModel) {
+		return false
+	}
+
+	return true
+}
+
+// isAccountValidForPlatform 检查账号是否匹配目标平台。
+// 原生平台直接匹配；混合调度模式下 antigravity 需要启用 mixed_scheduling。
+//
+// isAccountValidForPlatform checks if account matches target platform.
+// Native platform matches directly; mixed scheduling mode requires antigravity to enable mixed_scheduling.
+func (s *GeminiMessagesCompatService) isAccountValidForPlatform(account *Account, platform string, useMixedScheduling bool) bool {
+	if account.Platform == platform {
+		return true
+	}
+	if useMixedScheduling && account.Platform == PlatformAntigravity && account.IsMixedSchedulingEnabled() {
+		return true
+	}
+	return false
+}
+
+// passesRateLimitPreCheck 执行速率限制预检。
+// 返回 true 表示通过预检或无需预检。
+//
+// passesRateLimitPreCheck performs rate limit precheck.
+// Returns true if passed or precheck not required.
+func (s *GeminiMessagesCompatService) passesRateLimitPreCheck(ctx context.Context, account *Account, requestedModel string) bool {
+	if s.rateLimitService == nil || requestedModel == "" {
+		return true
+	}
+	ok, err := s.rateLimitService.PreCheckUsage(ctx, account, requestedModel)
+	if err != nil {
+		log.Printf("[Gemini PreCheck] Account %d precheck error: %v", account.ID, err)
+	}
+	return ok
+}
+
+// selectBestGeminiAccount 从候选账号中选择最佳账号（优先级 + LRU + OAuth 优先）。
+// 返回 nil 表示无可用账号。
+//
+// selectBestGeminiAccount selects best account from candidates (priority + LRU + OAuth preferred).
+// Returns nil if no available account.
+func (s *GeminiMessagesCompatService) selectBestGeminiAccount(
+	ctx context.Context,
+	accounts []Account,
+	requestedModel string,
+	excludedIDs map[int64]struct{},
+	platform string,
+	useMixedScheduling bool,
+) *Account {
+	var selected *Account
+
+	for i := range accounts {
+		acc := &accounts[i]
+
+		// 跳过被排除的账号
+		if _, excluded := excludedIDs[acc.ID]; excluded {
+			continue
+		}
+
+		// 检查账号是否可用于当前请求
+		if !s.isAccountUsableForRequest(ctx, acc, requestedModel, platform, useMixedScheduling) {
+			continue
+		}
+
+		// 选择最佳账号
+		if selected == nil {
+			selected = acc
+			continue
+		}
+
+		if s.isBetterGeminiAccount(acc, selected) {
+			selected = acc
+		}
+	}
+
+	return selected
+}
+
+// isBetterGeminiAccount 判断 candidate 是否比 current 更优。
+// 规则：优先级更高（数值更小）优先；同优先级时，未使用过的优先（OAuth > 非 OAuth），其次是最久未使用的。
+//
+// isBetterGeminiAccount checks if candidate is better than current.
+// Rules: higher priority (lower value) wins; same priority: never used (OAuth > non-OAuth) > least recently used.
+func (s *GeminiMessagesCompatService) isBetterGeminiAccount(candidate, current *Account) bool {
+	// 优先级更高（数值更小）
+	if candidate.Priority < current.Priority {
+		return true
+	}
+	if candidate.Priority > current.Priority {
+		return false
+	}
+
+	// 同优先级，比较最后使用时间
+	switch {
+	case candidate.LastUsedAt == nil && current.LastUsedAt != nil:
+		// candidate 从未使用，优先
+		return true
+	case candidate.LastUsedAt != nil && current.LastUsedAt == nil:
+		// current 从未使用，保持
+		return false
+	case candidate.LastUsedAt == nil && current.LastUsedAt == nil:
+		// 都未使用，优先选择 OAuth 账号（更兼容 Code Assist 流程）
+		return candidate.Type == AccountTypeOAuth && current.Type != AccountTypeOAuth
+	default:
+		// 都使用过，选择最久未使用的
+		return candidate.LastUsedAt.Before(*current.LastUsedAt)
+	}
+}
+
 // isModelSupportedByAccount 根据账户平台检查模型支持
 func (s *GeminiMessagesCompatService) isModelSupportedByAccount(account *Account, requestedModel string) bool {
 	if account.Platform == PlatformAntigravity {

backend/internal/service/gemini_multiplatform_test.go

@@ -15,8 +15,10 @@ import (
 
 // mockAccountRepoForGemini Gemini 测试用的 mock
 type mockAccountRepoForGemini struct {
-	accounts     []Account
-	accountsByID map[int64]*Account
+	accounts           []Account
+	accountsByID       map[int64]*Account
+	listByGroupFunc    func(ctx context.Context, groupID int64, platforms []string) ([]Account, error)
+	listByPlatformFunc func(ctx context.Context, platforms []string) ([]Account, error)
 }
 
 func (m *mockAccountRepoForGemini) GetByID(ctx context.Context, id int64) (*Account, error) {
@@ -107,6 +109,9 @@ func (m *mockAccountRepoForGemini) ListSchedulableByGroupID(ctx context.Context,
 	return nil, nil
 }
 func (m *mockAccountRepoForGemini) ListSchedulableByPlatforms(ctx context.Context, platforms []string) ([]Account, error) {
+	if m.listByPlatformFunc != nil {
+		return m.listByPlatformFunc(ctx, platforms)
+	}
 	var result []Account
 	platformSet := make(map[string]bool)
 	for _, p := range platforms {
@@ -120,6 +125,9 @@ func (m *mockAccountRepoForGemini) ListSchedulableByPlatforms(ctx context.Contex
 	return result, nil
 }
 func (m *mockAccountRepoForGemini) ListSchedulableByGroupIDAndPlatforms(ctx context.Context, groupID int64, platforms []string) ([]Account, error) {
+	if m.listByGroupFunc != nil {
+		return m.listByGroupFunc(ctx, groupID, platforms)
+	}
 	return m.ListSchedulableByPlatforms(ctx, platforms)
 }
 func (m *mockAccountRepoForGemini) SetRateLimited(ctx context.Context, id int64, resetAt time.Time) error {
@@ -215,6 +223,7 @@ var _ GroupRepository = (*mockGroupRepoForGemini)(nil)
 // mockGatewayCacheForGemini Gemini 测试用的 cache mock
 type mockGatewayCacheForGemini struct {
 	sessionBindings map[string]int64
+	deletedSessions map[string]int
 }
 
 func (m *mockGatewayCacheForGemini) GetSessionAccountID(ctx context.Context, groupID int64, sessionHash string) (int64, error) {
@@ -236,6 +245,18 @@ func (m *mockGatewayCacheForGemini) RefreshSessionTTL(ctx context.Context, group
 	return nil
 }
 
+func (m *mockGatewayCacheForGemini) DeleteSessionAccountID(ctx context.Context, groupID int64, sessionHash string) error {
+	if m.sessionBindings == nil {
+		return nil
+	}
+	if m.deletedSessions == nil {
+		m.deletedSessions = make(map[string]int)
+	}
+	m.deletedSessions[sessionHash]++
+	delete(m.sessionBindings, sessionHash)
+	return nil
+}
+
 // TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_GeminiPlatform 测试 Gemini 单平台选择
 func TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_GeminiPlatform(t *testing.T) {
 	ctx := context.Background()
@@ -526,6 +547,274 @@ func TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_StickyS
 		// 粘性会话未命中，按优先级选择
 		require.Equal(t, int64(2), acc.ID, "粘性会话未命中，应按优先级选择")
 	})
+
+	t.Run("粘性会话不可调度-清理并回退选择", func(t *testing.T) {
+		repo := &mockAccountRepoForGemini{
+			accounts: []Account{
+				{ID: 1, Platform: PlatformGemini, Priority: 2, Status: StatusDisabled, Schedulable: true},
+				{ID: 2, 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{
+			sessionBindings: map[string]int64{"gemini:session-123": 1},
+		}
+		groupRepo := &mockGroupRepoForGemini{groups: map[int64]*Group{}}
+
+		svc := &GeminiMessagesCompatService{
+			accountRepo: repo,
+			groupRepo:   groupRepo,
+			cache:       cache,
+		}
+
+		acc, err := svc.SelectAccountForModelWithExclusions(ctx, nil, "session-123", "gemini-2.5-flash", nil)
+		require.NoError(t, err)
+		require.NotNil(t, acc)
+		require.Equal(t, int64(2), acc.ID)
+		require.Equal(t, 1, cache.deletedSessions["gemini:session-123"])
+		require.Equal(t, int64(2), cache.sessionBindings["gemini:session-123"])
+	})
+}
+
+func TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_ForcePlatformFallback(t *testing.T) {
+	ctx := context.Background()
+	groupID := int64(9)
+	ctx = context.WithValue(ctx, ctxkey.ForcePlatform, PlatformAntigravity)
+
+	repo := &mockAccountRepoForGemini{
+		listByGroupFunc: func(ctx context.Context, groupID int64, platforms []string) ([]Account, error) {
+			return nil, nil
+		},
+		listByPlatformFunc: func(ctx context.Context, platforms []string) ([]Account, error) {
+			return []Account{
+				{ID: 1, Platform: PlatformAntigravity, Priority: 1, Status: StatusActive, Schedulable: true},
+			}, nil
+		},
+		accountsByID: map[int64]*Account{
+			1: {ID: 1, Platform: PlatformAntigravity, Priority: 1, Status: StatusActive, Schedulable: true},
+		},
+	}
+
+	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, int64(1), acc.ID)
+}
+
+func TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_NoModelSupport(t *testing.T) {
+	ctx := context.Background()
+
+	repo := &mockAccountRepoForGemini{
+		accounts: []Account{
+			{
+				ID:          1,
+				Platform:    PlatformGemini,
+				Priority:    1,
+				Status:      StatusActive,
+				Schedulable: true,
+				Credentials: map[string]any{"model_mapping": map[string]any{"gemini-1.0-pro": "gemini-1.0-pro"}},
+			},
+		},
+		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, nil, "", "gemini-2.5-flash", nil)
+	require.Error(t, err)
+	require.Nil(t, acc)
+	require.Contains(t, err.Error(), "supporting model")
+}
+
+func TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_StickyMixedScheduling(t *testing.T) {
+	ctx := context.Background()
+	repo := &mockAccountRepoForGemini{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformAntigravity, Priority: 1, Status: StatusActive, Schedulable: true, Extra: map[string]any{"mixed_scheduling": true}},
+			{ID: 2, Platform: PlatformGemini, Priority: 2, Status: StatusActive, Schedulable: true},
+		},
+		accountsByID: map[int64]*Account{},
+	}
+	for i := range repo.accounts {
+		repo.accountsByID[repo.accounts[i].ID] = &repo.accounts[i]
+	}
+
+	cache := &mockGatewayCacheForGemini{
+		sessionBindings: map[string]int64{"gemini:session-999": 1},
+	}
+	groupRepo := &mockGroupRepoForGemini{groups: map[int64]*Group{}}
+
+	svc := &GeminiMessagesCompatService{
+		accountRepo: repo,
+		groupRepo:   groupRepo,
+		cache:       cache,
+	}
+
+	acc, err := svc.SelectAccountForModelWithExclusions(ctx, nil, "session-999", "gemini-2.5-flash", nil)
+	require.NoError(t, err)
+	require.NotNil(t, acc)
+	require.Equal(t, int64(1), acc.ID)
+}
+
+func TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_SkipDisabledMixedScheduling(t *testing.T) {
+	ctx := context.Background()
+	repo := &mockAccountRepoForGemini{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformAntigravity, Priority: 1, Status: StatusActive, Schedulable: true},
+			{ID: 2, Platform: PlatformGemini, Priority: 2, 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, nil, "", "gemini-2.5-flash", nil)
+	require.NoError(t, err)
+	require.NotNil(t, acc)
+	require.Equal(t, int64(2), acc.ID)
+}
+
+func TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_ExcludedAccount(t *testing.T) {
+	ctx := context.Background()
+	repo := &mockAccountRepoForGemini{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformGemini, Priority: 1, Status: StatusActive, Schedulable: true},
+			{ID: 2, Platform: PlatformGemini, Priority: 2, 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,
+	}
+
+	excluded := map[int64]struct{}{1: {}}
+	acc, err := svc.SelectAccountForModelWithExclusions(ctx, nil, "", "gemini-2.5-flash", excluded)
+	require.NoError(t, err)
+	require.NotNil(t, acc)
+	require.Equal(t, int64(2), acc.ID)
+}
+
+func TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_ListError(t *testing.T) {
+	ctx := context.Background()
+	repo := &mockAccountRepoForGemini{
+		listByPlatformFunc: func(ctx context.Context, platforms []string) ([]Account, error) {
+			return nil, errors.New("query failed")
+		},
+	}
+
+	cache := &mockGatewayCacheForGemini{}
+	groupRepo := &mockGroupRepoForGemini{groups: map[int64]*Group{}}
+
+	svc := &GeminiMessagesCompatService{
+		accountRepo: repo,
+		groupRepo:   groupRepo,
+		cache:       cache,
+	}
+
+	acc, err := svc.SelectAccountForModelWithExclusions(ctx, nil, "", "gemini-2.5-flash", nil)
+	require.Error(t, err)
+	require.Nil(t, acc)
+	require.Contains(t, err.Error(), "query accounts failed")
+}
+
+func TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_PreferOAuth(t *testing.T) {
+	ctx := context.Background()
+	repo := &mockAccountRepoForGemini{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformGemini, Priority: 1, Status: StatusActive, Schedulable: true, Type: AccountTypeAPIKey},
+			{ID: 2, Platform: PlatformGemini, Priority: 1, Status: StatusActive, Schedulable: true, Type: AccountTypeOAuth},
+		},
+		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, nil, "", "gemini-2.5-pro", nil)
+	require.NoError(t, err)
+	require.NotNil(t, acc)
+	require.Equal(t, int64(2), acc.ID)
+}
+
+func TestGeminiMessagesCompatService_SelectAccountForModelWithExclusions_PreferLeastRecentlyUsed(t *testing.T) {
+	ctx := context.Background()
+	oldTime := time.Now().Add(-2 * time.Hour)
+	newTime := time.Now().Add(-1 * time.Hour)
+	repo := &mockAccountRepoForGemini{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformGemini, Priority: 1, Status: StatusActive, Schedulable: true, LastUsedAt: &newTime},
+			{ID: 2, Platform: PlatformGemini, Priority: 1, Status: StatusActive, Schedulable: true, LastUsedAt: &oldTime},
+		},
+		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, nil, "", "gemini-2.5-pro", nil)
+	require.NoError(t, err)
+	require.NotNil(t, acc)
+	require.Equal(t, int64(2), acc.ID)
 }
 
 // TestGeminiPlatformRouting_DocumentRouteDecision 测试平台路由决策逻辑

backend/internal/service/openai_gateway_service.go

@@ -180,67 +180,26 @@ func (s *OpenAIGatewayService) SelectAccountForModel(ctx context.Context, groupI
 }
 
 // SelectAccountForModelWithExclusions selects an account supporting the requested model while excluding specified accounts.
+// SelectAccountForModelWithExclusions 选择支持指定模型的账号，同时排除指定的账号。
 func (s *OpenAIGatewayService) SelectAccountForModelWithExclusions(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}) (*Account, error) {
-	// 1. Check sticky session
-	if sessionHash != "" {
-		accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), "openai:"+sessionHash)
-		if err == nil && accountID > 0 {
-			if _, excluded := excludedIDs[accountID]; !excluded {
-				account, err := s.getSchedulableAccount(ctx, accountID)
-				if err == nil && account.IsSchedulable() && account.IsOpenAI() && (requestedModel == "" || account.IsModelSupported(requestedModel)) {
-					// Refresh sticky session TTL
-					_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), "openai:"+sessionHash, openaiStickySessionTTL)
-					return account, nil
-				}
-			}
-		}
+	cacheKey := "openai:" + sessionHash
+
+	// 1. 尝试粘性会话命中
+	// Try sticky session hit
+	if account := s.tryStickySessionHit(ctx, groupID, sessionHash, cacheKey, requestedModel, excludedIDs); account != nil {
+		return account, nil
 	}
 
-	// 2. Get schedulable OpenAI accounts
+	// 2. 获取可调度的 OpenAI 账号
+	// Get schedulable OpenAI accounts
 	accounts, err := s.listSchedulableAccounts(ctx, groupID)
 	if err != nil {
 		return nil, fmt.Errorf("query accounts failed: %w", err)
 	}
 
-	// 3. Select by priority + LRU
-	var selected *Account
-	for i := range accounts {
-		acc := &accounts[i]
-		if _, excluded := excludedIDs[acc.ID]; excluded {
-			continue
-		}
-		// Scheduler snapshots can be temporarily stale; re-check schedulability here to
-		// avoid selecting accounts that were recently rate-limited/overloaded.
-		if !acc.IsSchedulable() {
-			continue
-		}
-		// Check model support
-		if requestedModel != "" && !acc.IsModelSupported(requestedModel) {
-			continue
-		}
-		if selected == nil {
-			selected = acc
-			continue
-		}
-		// Lower priority value means higher priority
-		if acc.Priority < selected.Priority {
-			selected = acc
-		} else if acc.Priority == selected.Priority {
-			switch {
-			case acc.LastUsedAt == nil && selected.LastUsedAt != nil:
-				selected = acc
-			case acc.LastUsedAt != nil && selected.LastUsedAt == nil:
-				// keep selected (never used is preferred)
-			case acc.LastUsedAt == nil && selected.LastUsedAt == nil:
-				// keep selected (both never used)
-			default:
-				// Same priority, select least recently used
-				if acc.LastUsedAt.Before(*selected.LastUsedAt) {
-					selected = acc
-				}
-			}
-		}
-	}
+	// 3. 按优先级 + LRU 选择最佳账号
+	// Select by priority + LRU
+	selected := s.selectBestAccount(accounts, requestedModel, excludedIDs)
 
 	if selected == nil {
 		if requestedModel != "" {
@@ -249,14 +208,138 @@ func (s *OpenAIGatewayService) SelectAccountForModelWithExclusions(ctx context.C
 		return nil, errors.New("no available OpenAI accounts")
 	}
 
-	// 4. Set sticky session
+	// 4. 设置粘性会话绑定
+	// Set sticky session binding
 	if sessionHash != "" {
-		_ = s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), "openai:"+sessionHash, selected.ID, openaiStickySessionTTL)
+		_ = s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), cacheKey, selected.ID, openaiStickySessionTTL)
 	}
 
 	return selected, nil
 }
 
+// tryStickySessionHit 尝试从粘性会话获取账号。
+// 如果命中且账号可用则返回账号；如果账号不可用则清理会话并返回 nil。
+//
+// tryStickySessionHit attempts to get account from sticky session.
+// Returns account if hit and usable; clears session and returns nil if account is unavailable.
+func (s *OpenAIGatewayService) tryStickySessionHit(ctx context.Context, groupID *int64, sessionHash, cacheKey, requestedModel string, excludedIDs map[int64]struct{}) *Account {
+	if sessionHash == "" {
+		return nil
+	}
+
+	accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), cacheKey)
+	if err != nil || accountID <= 0 {
+		return nil
+	}
+
+	if _, excluded := excludedIDs[accountID]; excluded {
+		return nil
+	}
+
+	account, err := s.getSchedulableAccount(ctx, accountID)
+	if err != nil {
+		return nil
+	}
+
+	// 检查账号是否需要清理粘性会话
+	// Check if sticky session should be cleared
+	if shouldClearStickySession(account) {
+		_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), cacheKey)
+		return nil
+	}
+
+	// 验证账号是否可用于当前请求
+	// Verify account is usable for current request
+	if !account.IsSchedulable() || !account.IsOpenAI() {
+		return nil
+	}
+	if requestedModel != "" && !account.IsModelSupported(requestedModel) {
+		return nil
+	}
+
+	// 刷新会话 TTL 并返回账号
+	// Refresh session TTL and return account
+	_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), cacheKey, openaiStickySessionTTL)
+	return account
+}
+
+// selectBestAccount 从候选账号中选择最佳账号（优先级 + LRU）。
+// 返回 nil 表示无可用账号。
+//
+// selectBestAccount selects the best account from candidates (priority + LRU).
+// Returns nil if no available account.
+func (s *OpenAIGatewayService) selectBestAccount(accounts []Account, requestedModel string, excludedIDs map[int64]struct{}) *Account {
+	var selected *Account
+
+	for i := range accounts {
+		acc := &accounts[i]
+
+		// 跳过被排除的账号
+		// Skip excluded accounts
+		if _, excluded := excludedIDs[acc.ID]; excluded {
+			continue
+		}
+
+		// 调度器快照可能暂时过时，这里重新检查可调度性和平台
+		// Scheduler snapshots can be temporarily stale; re-check schedulability and platform
+		if !acc.IsSchedulable() || !acc.IsOpenAI() {
+			continue
+		}
+
+		// 检查模型支持
+		// Check model support
+		if requestedModel != "" && !acc.IsModelSupported(requestedModel) {
+			continue
+		}
+
+		// 选择优先级最高且最久未使用的账号
+		// Select highest priority and least recently used
+		if selected == nil {
+			selected = acc
+			continue
+		}
+
+		if s.isBetterAccount(acc, selected) {
+			selected = acc
+		}
+	}
+
+	return selected
+}
+
+// isBetterAccount 判断 candidate 是否比 current 更优。
+// 规则：优先级更高（数值更小）优先；同优先级时，未使用过的优先，其次是最久未使用的。
+//
+// isBetterAccount checks if candidate is better than current.
+// Rules: higher priority (lower value) wins; same priority: never used > least recently used.
+func (s *OpenAIGatewayService) isBetterAccount(candidate, current *Account) bool {
+	// 优先级更高（数值更小）
+	// Higher priority (lower value)
+	if candidate.Priority < current.Priority {
+		return true
+	}
+	if candidate.Priority > current.Priority {
+		return false
+	}
+
+	// 同优先级，比较最后使用时间
+	// Same priority, compare last used time
+	switch {
+	case candidate.LastUsedAt == nil && current.LastUsedAt != nil:
+		// candidate 从未使用，优先
+		return true
+	case candidate.LastUsedAt != nil && current.LastUsedAt == nil:
+		// current 从未使用，保持
+		return false
+	case candidate.LastUsedAt == nil && current.LastUsedAt == nil:
+		// 都未使用，保持
+		return false
+	default:
+		// 都使用过，选择最久未使用的
+		return candidate.LastUsedAt.Before(*current.LastUsedAt)
+	}
+}
+
 // SelectAccountWithLoadAwareness selects an account with load-awareness and wait plan.
 func (s *OpenAIGatewayService) SelectAccountWithLoadAwareness(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}) (*AccountSelectionResult, error) {
 	cfg := s.schedulingConfig()
@@ -325,29 +408,35 @@ func (s *OpenAIGatewayService) SelectAccountWithLoadAwareness(ctx context.Contex
 		accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), "openai:"+sessionHash)
 		if err == nil && accountID > 0 && !isExcluded(accountID) {
 			account, err := s.getSchedulableAccount(ctx, accountID)
-			if err == nil && account.IsSchedulable() && account.IsOpenAI() &&
-				(requestedModel == "" || account.IsModelSupported(requestedModel)) {
-				result, err := s.tryAcquireAccountSlot(ctx, accountID, account.Concurrency)
-				if err == nil && result.Acquired {
-					_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), "openai:"+sessionHash, openaiStickySessionTTL)
-					return &AccountSelectionResult{
-						Account:     account,
-						Acquired:    true,
-						ReleaseFunc: result.ReleaseFunc,
-					}, nil
+			if err == nil {
+				clearSticky := shouldClearStickySession(account)
+				if clearSticky {
+					_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), "openai:"+sessionHash)
 				}
+				if !clearSticky && account.IsSchedulable() && account.IsOpenAI() &&
+					(requestedModel == "" || account.IsModelSupported(requestedModel)) {
+					result, err := s.tryAcquireAccountSlot(ctx, accountID, account.Concurrency)
+					if err == nil && result.Acquired {
+						_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), "openai:"+sessionHash, openaiStickySessionTTL)
+						return &AccountSelectionResult{
+							Account:     account,
+							Acquired:    true,
+							ReleaseFunc: result.ReleaseFunc,
+						}, nil
+					}
 
-				waitingCount, _ := s.concurrencyService.GetAccountWaitingCount(ctx, accountID)
-				if waitingCount < cfg.StickySessionMaxWaiting {
-					return &AccountSelectionResult{
-						Account: account,
-						WaitPlan: &AccountWaitPlan{
-							AccountID:      accountID,
-							MaxConcurrency: account.Concurrency,
-							Timeout:        cfg.StickySessionWaitTimeout,
-							MaxWaiting:     cfg.StickySessionMaxWaiting,
-						},
-					}, nil
+					waitingCount, _ := s.concurrencyService.GetAccountWaitingCount(ctx, accountID)
+					if waitingCount < cfg.StickySessionMaxWaiting {
+						return &AccountSelectionResult{
+							Account: account,
+							WaitPlan: &AccountWaitPlan{
+								AccountID:      accountID,
+								MaxConcurrency: account.Concurrency,
+								Timeout:        cfg.StickySessionWaitTimeout,
+								MaxWaiting:     cfg.StickySessionMaxWaiting,
+							},
+						}, nil
+					}
 				}
 			}
 		}

backend/internal/service/openai_gateway_service_test.go

@@ -21,16 +21,42 @@ type stubOpenAIAccountRepo struct {
 	accounts []Account
 }
 
+func (r stubOpenAIAccountRepo) GetByID(ctx context.Context, id int64) (*Account, error) {
+	for i := range r.accounts {
+		if r.accounts[i].ID == id {
+			return &r.accounts[i], nil
+		}
+	}
+	return nil, errors.New("account not found")
+}
+
 func (r stubOpenAIAccountRepo) ListSchedulableByGroupIDAndPlatform(ctx context.Context, groupID int64, platform string) ([]Account, error) {
-	return append([]Account(nil), r.accounts...), nil
+	var result []Account
+	for _, acc := range r.accounts {
+		if acc.Platform == platform {
+			result = append(result, acc)
+		}
+	}
+	return result, nil
 }
 
 func (r stubOpenAIAccountRepo) ListSchedulableByPlatform(ctx context.Context, platform string) ([]Account, error) {
-	return append([]Account(nil), r.accounts...), nil
+	var result []Account
+	for _, acc := range r.accounts {
+		if acc.Platform == platform {
+			result = append(result, acc)
+		}
+	}
+	return result, nil
 }
 
 type stubConcurrencyCache struct {
 	ConcurrencyCache
+	loadBatchErr    error
+	loadMap         map[int64]*AccountLoadInfo
+	acquireResults  map[int64]bool
+	waitCounts      map[int64]int
+	skipDefaultLoad bool
 }
 
 type cancelReadCloser struct{}
@@ -53,6 +79,11 @@ func (w *failingGinWriter) Write(p []byte) (int, error) {
 }
 
 func (c stubConcurrencyCache) AcquireAccountSlot(ctx context.Context, accountID int64, maxConcurrency int, requestID string) (bool, error) {
+	if c.acquireResults != nil {
+		if result, ok := c.acquireResults[accountID]; ok {
+			return result, nil
+		}
+	}
 	return true, nil
 }
 
@@ -61,8 +92,25 @@ func (c stubConcurrencyCache) ReleaseAccountSlot(ctx context.Context, accountID
 }
 
 func (c stubConcurrencyCache) GetAccountsLoadBatch(ctx context.Context, accounts []AccountWithConcurrency) (map[int64]*AccountLoadInfo, error) {
+	if c.loadBatchErr != nil {
+		return nil, c.loadBatchErr
+	}
 	out := make(map[int64]*AccountLoadInfo, len(accounts))
+	if c.skipDefaultLoad && c.loadMap != nil {
+		for _, acc := range accounts {
+			if load, ok := c.loadMap[acc.ID]; ok {
+				out[acc.ID] = load
+			}
+		}
+		return out, nil
+	}
 	for _, acc := range accounts {
+		if c.loadMap != nil {
+			if load, ok := c.loadMap[acc.ID]; ok {
+				out[acc.ID] = load
+				continue
+			}
+		}
 		out[acc.ID] = &AccountLoadInfo{AccountID: acc.ID, LoadRate: 0}
 	}
 	return out, nil
@@ -111,6 +159,51 @@ func TestOpenAIGatewayService_GenerateSessionHash_Priority(t *testing.T) {
 	}
 }
 
+func (c stubConcurrencyCache) GetAccountWaitingCount(ctx context.Context, accountID int64) (int, error) {
+	if c.waitCounts != nil {
+		if count, ok := c.waitCounts[accountID]; ok {
+			return count, nil
+		}
+	}
+	return 0, nil
+}
+
+type stubGatewayCache struct {
+	sessionBindings map[string]int64
+	deletedSessions map[string]int
+}
+
+func (c *stubGatewayCache) GetSessionAccountID(ctx context.Context, groupID int64, sessionHash string) (int64, error) {
+	if id, ok := c.sessionBindings[sessionHash]; ok {
+		return id, nil
+	}
+	return 0, errors.New("not found")
+}
+
+func (c *stubGatewayCache) SetSessionAccountID(ctx context.Context, groupID int64, sessionHash string, accountID int64, ttl time.Duration) error {
+	if c.sessionBindings == nil {
+		c.sessionBindings = make(map[string]int64)
+	}
+	c.sessionBindings[sessionHash] = accountID
+	return nil
+}
+
+func (c *stubGatewayCache) RefreshSessionTTL(ctx context.Context, groupID int64, sessionHash string, ttl time.Duration) error {
+	return nil
+}
+
+func (c *stubGatewayCache) DeleteSessionAccountID(ctx context.Context, groupID int64, sessionHash string) error {
+	if c.sessionBindings == nil {
+		return nil
+	}
+	if c.deletedSessions == nil {
+		c.deletedSessions = make(map[string]int)
+	}
+	c.deletedSessions[sessionHash]++
+	delete(c.sessionBindings, sessionHash)
+	return nil
+}
+
 func TestOpenAISelectAccountWithLoadAwareness_FiltersUnschedulable(t *testing.T) {
 	now := time.Now()
 	resetAt := now.Add(10 * time.Minute)
@@ -201,6 +294,515 @@ func TestOpenAISelectAccountWithLoadAwareness_FiltersUnschedulableWhenNoConcurre
 	}
 }
 
+func TestOpenAISelectAccountForModelWithExclusions_StickyUnschedulableClearsSession(t *testing.T) {
+	sessionHash := "session-1"
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusDisabled, Schedulable: true, Concurrency: 1},
+			{ID: 2, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1},
+		},
+	}
+	cache := &stubGatewayCache{
+		sessionBindings: map[string]int64{"openai:" + sessionHash: 1},
+	}
+
+	svc := &OpenAIGatewayService{
+		accountRepo: repo,
+		cache:       cache,
+	}
+
+	acc, err := svc.SelectAccountForModelWithExclusions(context.Background(), nil, sessionHash, "gpt-4", nil)
+	if err != nil {
+		t.Fatalf("SelectAccountForModelWithExclusions error: %v", err)
+	}
+	if acc == nil || acc.ID != 2 {
+		t.Fatalf("expected account 2, got %+v", acc)
+	}
+	if cache.deletedSessions["openai:"+sessionHash] != 1 {
+		t.Fatalf("expected sticky session to be deleted")
+	}
+	if cache.sessionBindings["openai:"+sessionHash] != 2 {
+		t.Fatalf("expected sticky session to bind to account 2")
+	}
+}
+
+func TestOpenAISelectAccountWithLoadAwareness_StickyUnschedulableClearsSession(t *testing.T) {
+	sessionHash := "session-2"
+	groupID := int64(1)
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusDisabled, Schedulable: true, Concurrency: 1},
+			{ID: 2, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1},
+		},
+	}
+	cache := &stubGatewayCache{
+		sessionBindings: map[string]int64{"openai:" + sessionHash: 1},
+	}
+
+	svc := &OpenAIGatewayService{
+		accountRepo:        repo,
+		cache:              cache,
+		concurrencyService: NewConcurrencyService(stubConcurrencyCache{}),
+	}
+
+	selection, err := svc.SelectAccountWithLoadAwareness(context.Background(), &groupID, sessionHash, "gpt-4", nil)
+	if err != nil {
+		t.Fatalf("SelectAccountWithLoadAwareness error: %v", err)
+	}
+	if selection == nil || selection.Account == nil || selection.Account.ID != 2 {
+		t.Fatalf("expected account 2, got %+v", selection)
+	}
+	if cache.deletedSessions["openai:"+sessionHash] != 1 {
+		t.Fatalf("expected sticky session to be deleted")
+	}
+	if cache.sessionBindings["openai:"+sessionHash] != 2 {
+		t.Fatalf("expected sticky session to bind to account 2")
+	}
+	if selection.ReleaseFunc != nil {
+		selection.ReleaseFunc()
+	}
+}
+
+func TestOpenAISelectAccountForModelWithExclusions_NoModelSupport(t *testing.T) {
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{
+				ID:          1,
+				Platform:    PlatformOpenAI,
+				Status:      StatusActive,
+				Schedulable: true,
+				Credentials: map[string]any{"model_mapping": map[string]any{"gpt-3.5-turbo": "gpt-3.5-turbo"}},
+			},
+		},
+	}
+	cache := &stubGatewayCache{}
+
+	svc := &OpenAIGatewayService{
+		accountRepo: repo,
+		cache:       cache,
+	}
+
+	acc, err := svc.SelectAccountForModelWithExclusions(context.Background(), nil, "", "gpt-4", nil)
+	if err == nil {
+		t.Fatalf("expected error for unsupported model")
+	}
+	if acc != nil {
+		t.Fatalf("expected nil account for unsupported model")
+	}
+	if !strings.Contains(err.Error(), "supporting model") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestOpenAISelectAccountWithLoadAwareness_LoadBatchErrorFallback(t *testing.T) {
+	groupID := int64(1)
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 2},
+			{ID: 2, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1},
+		},
+	}
+	cache := &stubGatewayCache{}
+	concurrencyCache := stubConcurrencyCache{
+		loadBatchErr: errors.New("load batch failed"),
+	}
+
+	svc := &OpenAIGatewayService{
+		accountRepo:        repo,
+		cache:              cache,
+		concurrencyService: NewConcurrencyService(concurrencyCache),
+	}
+
+	selection, err := svc.SelectAccountWithLoadAwareness(context.Background(), &groupID, "fallback", "gpt-4", nil)
+	if err != nil {
+		t.Fatalf("SelectAccountWithLoadAwareness error: %v", err)
+	}
+	if selection == nil || selection.Account == nil {
+		t.Fatalf("expected selection")
+	}
+	if selection.Account.ID != 2 {
+		t.Fatalf("expected account 2, got %d", selection.Account.ID)
+	}
+	if cache.sessionBindings["openai:fallback"] != 2 {
+		t.Fatalf("expected sticky session updated")
+	}
+	if selection.ReleaseFunc != nil {
+		selection.ReleaseFunc()
+	}
+}
+
+func TestOpenAISelectAccountWithLoadAwareness_NoSlotFallbackWait(t *testing.T) {
+	groupID := int64(1)
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1},
+		},
+	}
+	cache := &stubGatewayCache{}
+	concurrencyCache := stubConcurrencyCache{
+		acquireResults: map[int64]bool{1: false},
+		loadMap: map[int64]*AccountLoadInfo{
+			1: {AccountID: 1, LoadRate: 10},
+		},
+	}
+
+	svc := &OpenAIGatewayService{
+		accountRepo:        repo,
+		cache:              cache,
+		concurrencyService: NewConcurrencyService(concurrencyCache),
+	}
+
+	selection, err := svc.SelectAccountWithLoadAwareness(context.Background(), &groupID, "", "gpt-4", nil)
+	if err != nil {
+		t.Fatalf("SelectAccountWithLoadAwareness error: %v", err)
+	}
+	if selection == nil || selection.WaitPlan == nil {
+		t.Fatalf("expected wait plan fallback")
+	}
+	if selection.Account == nil || selection.Account.ID != 1 {
+		t.Fatalf("expected account 1")
+	}
+}
+
+func TestOpenAISelectAccountForModelWithExclusions_SetsStickyBinding(t *testing.T) {
+	sessionHash := "bind"
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1},
+		},
+	}
+	cache := &stubGatewayCache{}
+
+	svc := &OpenAIGatewayService{
+		accountRepo: repo,
+		cache:       cache,
+	}
+
+	acc, err := svc.SelectAccountForModelWithExclusions(context.Background(), nil, sessionHash, "gpt-4", nil)
+	if err != nil {
+		t.Fatalf("SelectAccountForModelWithExclusions error: %v", err)
+	}
+	if acc == nil || acc.ID != 1 {
+		t.Fatalf("expected account 1")
+	}
+	if cache.sessionBindings["openai:"+sessionHash] != 1 {
+		t.Fatalf("expected sticky session binding")
+	}
+}
+
+func TestOpenAISelectAccountWithLoadAwareness_StickyWaitPlan(t *testing.T) {
+	sessionHash := "sticky-wait"
+	groupID := int64(1)
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1},
+		},
+	}
+	cache := &stubGatewayCache{
+		sessionBindings: map[string]int64{"openai:" + sessionHash: 1},
+	}
+	concurrencyCache := stubConcurrencyCache{
+		acquireResults: map[int64]bool{1: false},
+		waitCounts:     map[int64]int{1: 0},
+	}
+
+	svc := &OpenAIGatewayService{
+		accountRepo:        repo,
+		cache:              cache,
+		concurrencyService: NewConcurrencyService(concurrencyCache),
+	}
+
+	selection, err := svc.SelectAccountWithLoadAwareness(context.Background(), &groupID, sessionHash, "gpt-4", nil)
+	if err != nil {
+		t.Fatalf("SelectAccountWithLoadAwareness error: %v", err)
+	}
+	if selection == nil || selection.WaitPlan == nil {
+		t.Fatalf("expected sticky wait plan")
+	}
+	if selection.Account == nil || selection.Account.ID != 1 {
+		t.Fatalf("expected account 1")
+	}
+}
+
+func TestOpenAISelectAccountWithLoadAwareness_PrefersLowerLoad(t *testing.T) {
+	groupID := int64(1)
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1},
+			{ID: 2, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1},
+		},
+	}
+	cache := &stubGatewayCache{}
+	concurrencyCache := stubConcurrencyCache{
+		loadMap: map[int64]*AccountLoadInfo{
+			1: {AccountID: 1, LoadRate: 80},
+			2: {AccountID: 2, LoadRate: 10},
+		},
+	}
+
+	svc := &OpenAIGatewayService{
+		accountRepo:        repo,
+		cache:              cache,
+		concurrencyService: NewConcurrencyService(concurrencyCache),
+	}
+
+	selection, err := svc.SelectAccountWithLoadAwareness(context.Background(), &groupID, "load", "gpt-4", nil)
+	if err != nil {
+		t.Fatalf("SelectAccountWithLoadAwareness error: %v", err)
+	}
+	if selection == nil || selection.Account == nil || selection.Account.ID != 2 {
+		t.Fatalf("expected account 2")
+	}
+	if cache.sessionBindings["openai:load"] != 2 {
+		t.Fatalf("expected sticky session updated")
+	}
+}
+
+func TestOpenAISelectAccountForModelWithExclusions_StickyExcludedFallback(t *testing.T) {
+	sessionHash := "excluded"
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1},
+			{ID: 2, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 2},
+		},
+	}
+	cache := &stubGatewayCache{
+		sessionBindings: map[string]int64{"openai:" + sessionHash: 1},
+	}
+
+	svc := &OpenAIGatewayService{
+		accountRepo: repo,
+		cache:       cache,
+	}
+
+	excluded := map[int64]struct{}{1: {}}
+	acc, err := svc.SelectAccountForModelWithExclusions(context.Background(), nil, sessionHash, "gpt-4", excluded)
+	if err != nil {
+		t.Fatalf("SelectAccountForModelWithExclusions error: %v", err)
+	}
+	if acc == nil || acc.ID != 2 {
+		t.Fatalf("expected account 2")
+	}
+}
+
+func TestOpenAISelectAccountForModelWithExclusions_StickyNonOpenAI(t *testing.T) {
+	sessionHash := "non-openai"
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformAnthropic, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1},
+			{ID: 2, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 2},
+		},
+	}
+	cache := &stubGatewayCache{
+		sessionBindings: map[string]int64{"openai:" + sessionHash: 1},
+	}
+
+	svc := &OpenAIGatewayService{
+		accountRepo: repo,
+		cache:       cache,
+	}
+
+	acc, err := svc.SelectAccountForModelWithExclusions(context.Background(), nil, sessionHash, "gpt-4", nil)
+	if err != nil {
+		t.Fatalf("SelectAccountForModelWithExclusions error: %v", err)
+	}
+	if acc == nil || acc.ID != 2 {
+		t.Fatalf("expected account 2")
+	}
+}
+
+func TestOpenAISelectAccountForModelWithExclusions_NoAccounts(t *testing.T) {
+	repo := stubOpenAIAccountRepo{accounts: []Account{}}
+	cache := &stubGatewayCache{}
+
+	svc := &OpenAIGatewayService{
+		accountRepo: repo,
+		cache:       cache,
+	}
+
+	acc, err := svc.SelectAccountForModelWithExclusions(context.Background(), nil, "", "", nil)
+	if err == nil {
+		t.Fatalf("expected error for no accounts")
+	}
+	if acc != nil {
+		t.Fatalf("expected nil account")
+	}
+	if !strings.Contains(err.Error(), "no available OpenAI accounts") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestOpenAISelectAccountWithLoadAwareness_NoCandidates(t *testing.T) {
+	groupID := int64(1)
+	resetAt := time.Now().Add(1 * time.Hour)
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1, RateLimitResetAt: &resetAt},
+		},
+	}
+	cache := &stubGatewayCache{}
+	concurrencyCache := stubConcurrencyCache{}
+
+	svc := &OpenAIGatewayService{
+		accountRepo:        repo,
+		cache:              cache,
+		concurrencyService: NewConcurrencyService(concurrencyCache),
+	}
+
+	selection, err := svc.SelectAccountWithLoadAwareness(context.Background(), &groupID, "", "gpt-4", nil)
+	if err == nil {
+		t.Fatalf("expected error for no candidates")
+	}
+	if selection != nil {
+		t.Fatalf("expected nil selection")
+	}
+}
+
+func TestOpenAISelectAccountWithLoadAwareness_AllFullWaitPlan(t *testing.T) {
+	groupID := int64(1)
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1},
+		},
+	}
+	cache := &stubGatewayCache{}
+	concurrencyCache := stubConcurrencyCache{
+		loadMap: map[int64]*AccountLoadInfo{
+			1: {AccountID: 1, LoadRate: 100},
+		},
+	}
+
+	svc := &OpenAIGatewayService{
+		accountRepo:        repo,
+		cache:              cache,
+		concurrencyService: NewConcurrencyService(concurrencyCache),
+	}
+
+	selection, err := svc.SelectAccountWithLoadAwareness(context.Background(), &groupID, "", "gpt-4", nil)
+	if err != nil {
+		t.Fatalf("SelectAccountWithLoadAwareness error: %v", err)
+	}
+	if selection == nil || selection.WaitPlan == nil {
+		t.Fatalf("expected wait plan")
+	}
+}
+
+func TestOpenAISelectAccountWithLoadAwareness_LoadBatchErrorNoAcquire(t *testing.T) {
+	groupID := int64(1)
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1},
+		},
+	}
+	cache := &stubGatewayCache{}
+	concurrencyCache := stubConcurrencyCache{
+		loadBatchErr:   errors.New("load batch failed"),
+		acquireResults: map[int64]bool{1: false},
+	}
+
+	svc := &OpenAIGatewayService{
+		accountRepo:        repo,
+		cache:              cache,
+		concurrencyService: NewConcurrencyService(concurrencyCache),
+	}
+
+	selection, err := svc.SelectAccountWithLoadAwareness(context.Background(), &groupID, "", "gpt-4", nil)
+	if err != nil {
+		t.Fatalf("SelectAccountWithLoadAwareness error: %v", err)
+	}
+	if selection == nil || selection.WaitPlan == nil {
+		t.Fatalf("expected wait plan")
+	}
+}
+
+func TestOpenAISelectAccountWithLoadAwareness_MissingLoadInfo(t *testing.T) {
+	groupID := int64(1)
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1},
+			{ID: 2, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1},
+		},
+	}
+	cache := &stubGatewayCache{}
+	concurrencyCache := stubConcurrencyCache{
+		loadMap: map[int64]*AccountLoadInfo{
+			1: {AccountID: 1, LoadRate: 50},
+		},
+		skipDefaultLoad: true,
+	}
+
+	svc := &OpenAIGatewayService{
+		accountRepo:        repo,
+		cache:              cache,
+		concurrencyService: NewConcurrencyService(concurrencyCache),
+	}
+
+	selection, err := svc.SelectAccountWithLoadAwareness(context.Background(), &groupID, "", "gpt-4", nil)
+	if err != nil {
+		t.Fatalf("SelectAccountWithLoadAwareness error: %v", err)
+	}
+	if selection == nil || selection.Account == nil || selection.Account.ID != 2 {
+		t.Fatalf("expected account 2")
+	}
+}
+
+func TestOpenAISelectAccountForModelWithExclusions_LeastRecentlyUsed(t *testing.T) {
+	oldTime := time.Now().Add(-2 * time.Hour)
+	newTime := time.Now().Add(-1 * time.Hour)
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Priority: 1, LastUsedAt: &newTime},
+			{ID: 2, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Priority: 1, LastUsedAt: &oldTime},
+		},
+	}
+	cache := &stubGatewayCache{}
+
+	svc := &OpenAIGatewayService{
+		accountRepo: repo,
+		cache:       cache,
+	}
+
+	acc, err := svc.SelectAccountForModelWithExclusions(context.Background(), nil, "", "gpt-4", nil)
+	if err != nil {
+		t.Fatalf("SelectAccountForModelWithExclusions error: %v", err)
+	}
+	if acc == nil || acc.ID != 2 {
+		t.Fatalf("expected account 2")
+	}
+}
+
+func TestOpenAISelectAccountWithLoadAwareness_PreferNeverUsed(t *testing.T) {
+	groupID := int64(1)
+	lastUsed := time.Now().Add(-1 * time.Hour)
+	repo := stubOpenAIAccountRepo{
+		accounts: []Account{
+			{ID: 1, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1, LastUsedAt: &lastUsed},
+			{ID: 2, Platform: PlatformOpenAI, Status: StatusActive, Schedulable: true, Concurrency: 1, Priority: 1},
+		},
+	}
+	cache := &stubGatewayCache{}
+	concurrencyCache := stubConcurrencyCache{
+		loadMap: map[int64]*AccountLoadInfo{
+			1: {AccountID: 1, LoadRate: 10},
+			2: {AccountID: 2, LoadRate: 10},
+		},
+	}
+
+	svc := &OpenAIGatewayService{
+		accountRepo:        repo,
+		cache:              cache,
+		concurrencyService: NewConcurrencyService(concurrencyCache),
+	}
+
+	selection, err := svc.SelectAccountWithLoadAwareness(context.Background(), &groupID, "", "gpt-4", nil)
+	if err != nil {
+		t.Fatalf("SelectAccountWithLoadAwareness error: %v", err)
+	}
+	if selection == nil || selection.Account == nil || selection.Account.ID != 2 {
+		t.Fatalf("expected account 2")
+	}
+}
+
 func TestOpenAIStreamingTimeout(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 	cfg := &config.Config{

backend/internal/service/setting_service.go

@@ -60,6 +60,7 @@ func (s *SettingService) GetPublicSettings(ctx context.Context) (*PublicSettings
 	keys := []string{
 		SettingKeyRegistrationEnabled,
 		SettingKeyEmailVerifyEnabled,
+		SettingKeyPromoCodeEnabled,
 		SettingKeyTurnstileEnabled,
 		SettingKeyTurnstileSiteKey,
 		SettingKeySiteName,
@@ -88,6 +89,7 @@ func (s *SettingService) GetPublicSettings(ctx context.Context) (*PublicSettings
 	return &PublicSettings{
 		RegistrationEnabled: settings[SettingKeyRegistrationEnabled] == "true",
 		EmailVerifyEnabled:  settings[SettingKeyEmailVerifyEnabled] == "true",
+		PromoCodeEnabled:    settings[SettingKeyPromoCodeEnabled] != "false", // 默认启用
 		TurnstileEnabled:    settings[SettingKeyTurnstileEnabled] == "true",
 		TurnstileSiteKey:    settings[SettingKeyTurnstileSiteKey],
 		SiteName:            s.getStringOrDefault(settings, SettingKeySiteName, "Sub2API"),
@@ -125,6 +127,7 @@ func (s *SettingService) GetPublicSettingsForInjection(ctx context.Context) (any
 	return &struct {
 		RegistrationEnabled bool   `json:"registration_enabled"`
 		EmailVerifyEnabled  bool   `json:"email_verify_enabled"`
+		PromoCodeEnabled    bool   `json:"promo_code_enabled"`
 		TurnstileEnabled    bool   `json:"turnstile_enabled"`
 		TurnstileSiteKey    string `json:"turnstile_site_key,omitempty"`
 		SiteName            string `json:"site_name"`
@@ -140,6 +143,7 @@ func (s *SettingService) GetPublicSettingsForInjection(ctx context.Context) (any
 	}{
 		RegistrationEnabled: settings.RegistrationEnabled,
 		EmailVerifyEnabled:  settings.EmailVerifyEnabled,
+		PromoCodeEnabled:    settings.PromoCodeEnabled,
 		TurnstileEnabled:    settings.TurnstileEnabled,
 		TurnstileSiteKey:    settings.TurnstileSiteKey,
 		SiteName:            settings.SiteName,
@@ -162,6 +166,7 @@ func (s *SettingService) UpdateSettings(ctx context.Context, settings *SystemSet
 	// 注册设置
 	updates[SettingKeyRegistrationEnabled] = strconv.FormatBool(settings.RegistrationEnabled)
 	updates[SettingKeyEmailVerifyEnabled] = strconv.FormatBool(settings.EmailVerifyEnabled)
+	updates[SettingKeyPromoCodeEnabled] = strconv.FormatBool(settings.PromoCodeEnabled)
 
 	// 邮件服务设置（只有非空才更新密码）
 	updates[SettingKeySMTPHost] = settings.SMTPHost
@@ -248,6 +253,15 @@ func (s *SettingService) IsEmailVerifyEnabled(ctx context.Context) bool {
 	return value == "true"
 }
 
+// IsPromoCodeEnabled 检查是否启用优惠码功能
+func (s *SettingService) IsPromoCodeEnabled(ctx context.Context) bool {
+	value, err := s.settingRepo.GetValue(ctx, SettingKeyPromoCodeEnabled)
+	if err != nil {
+		return true // 默认启用
+	}
+	return value != "false"
+}
+
 // GetSiteName 获取网站名称
 func (s *SettingService) GetSiteName(ctx context.Context) string {
 	value, err := s.settingRepo.GetValue(ctx, SettingKeySiteName)
@@ -297,6 +311,7 @@ func (s *SettingService) InitializeDefaultSettings(ctx context.Context) error {
 	defaults := map[string]string{
 		SettingKeyRegistrationEnabled: "true",
 		SettingKeyEmailVerifyEnabled:  "false",
+		SettingKeyPromoCodeEnabled:    "true", // 默认启用优惠码功能
 		SettingKeySiteName:            "Sub2API",
 		SettingKeySiteLogo:            "",
 		SettingKeyDefaultConcurrency:  strconv.Itoa(s.cfg.Default.UserConcurrency),
@@ -328,6 +343,7 @@ func (s *SettingService) parseSettings(settings map[string]string) *SystemSettin
 	result := &SystemSettings{
 		RegistrationEnabled:          settings[SettingKeyRegistrationEnabled] == "true",
 		EmailVerifyEnabled:           settings[SettingKeyEmailVerifyEnabled] == "true",
+		PromoCodeEnabled:             settings[SettingKeyPromoCodeEnabled] != "false", // 默认启用
 		SMTPHost:                     settings[SettingKeySMTPHost],
 		SMTPUsername:                 settings[SettingKeySMTPUsername],
 		SMTPFrom:                     settings[SettingKeySMTPFrom],

backend/internal/service/settings_view.go

@@ -3,6 +3,7 @@ package service
 type SystemSettings struct {
 	RegistrationEnabled bool
 	EmailVerifyEnabled  bool
+	PromoCodeEnabled    bool
 
 	SMTPHost               string
 	SMTPPort               int
@@ -58,6 +59,7 @@ type SystemSettings struct {
 type PublicSettings struct {
 	RegistrationEnabled bool
 	EmailVerifyEnabled  bool
+	PromoCodeEnabled    bool
 	TurnstileEnabled    bool
 	TurnstileSiteKey    string
 	SiteName            string

backend/internal/service/sticky_session_test.go

@@ -0,0 +1,54 @@
+//go:build unit
+
+// Package service 提供 API 网关核心服务。
+// 本文件包含 shouldClearStickySession 函数的单元测试，
+// 验证粘性会话清理逻辑在各种账号状态下的正确行为。
+//
+// This file contains unit tests for the shouldClearStickySession function,
+// verifying correct sticky session clearing behavior under various account states.
+package service
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+// TestShouldClearStickySession 测试粘性会话清理判断逻辑。
+// 验证在以下情况下是否正确判断需要清理粘性会话：
+//   - nil 账号：不清理（返回 false）
+//   - 状态为错误或禁用：清理
+//   - 不可调度：清理
+//   - 临时不可调度且未过期：清理
+//   - 临时不可调度已过期：不清理
+//   - 正常可调度状态：不清理
+//
+// TestShouldClearStickySession tests the sticky session clearing logic.
+// Verifies correct behavior for various account states including:
+// nil account, error/disabled status, unschedulable, temporary unschedulable.
+func TestShouldClearStickySession(t *testing.T) {
+	now := time.Now()
+	future := now.Add(1 * time.Hour)
+	past := now.Add(-1 * time.Hour)
+
+	tests := []struct {
+		name    string
+		account *Account
+		want    bool
+	}{
+		{name: "nil account", account: nil, want: false},
+		{name: "status error", account: &Account{Status: StatusError, Schedulable: true}, want: true},
+		{name: "status disabled", account: &Account{Status: StatusDisabled, Schedulable: true}, want: true},
+		{name: "schedulable false", account: &Account{Status: StatusActive, Schedulable: false}, want: true},
+		{name: "temp unschedulable", account: &Account{Status: StatusActive, Schedulable: true, TempUnschedulableUntil: &future}, want: true},
+		{name: "temp unschedulable expired", account: &Account{Status: StatusActive, Schedulable: true, TempUnschedulableUntil: &past}, want: false},
+		{name: "active schedulable", account: &Account{Status: StatusActive, Schedulable: true}, want: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			require.Equal(t, tt.want, shouldClearStickySession(tt.account))
+		})
+	}
+}

backend/internal/service/usage_cleanup_service_test.go

@@ -345,6 +345,9 @@ func TestUsageCleanupServiceRunOnceSuccess(t *testing.T) {
 	repo.mu.Lock()
 	defer repo.mu.Unlock()
 	require.Len(t, repo.deleteCalls, 3)
+	require.Equal(t, 2, repo.deleteCalls[0].limit)
+	require.True(t, repo.deleteCalls[0].filters.StartTime.Equal(start))
+	require.True(t, repo.deleteCalls[0].filters.EndTime.Equal(end))
 	require.Len(t, repo.markSucceeded, 1)
 	require.Empty(t, repo.markFailed)
 	require.Equal(t, int64(5), repo.markSucceeded[0].taskID)