Revert "feat(gateway): 实现负载感知的账号调度优化 (#114)" (#117)

This reverts commit 8d252303fc.
2025-12-31 21:45:42 -05:00
parent 8d252303fc
commit c5c12d4c8b
29 changed files with 133 additions and 2671 deletions
--- a/backend/cmd/server/wire_gen.go
+++ b/backend/cmd/server/wire_gen.go
@@ -99,7 +99,7 @@ func initializeApplication(buildInfo handler.BuildInfo) (*Application, error) {
 	antigravityGatewayService := service.NewAntigravityGatewayService(accountRepository, gatewayCache, antigravityTokenProvider, rateLimitService, httpUpstream)
 	accountTestService := service.NewAccountTestService(accountRepository, oAuthService, openAIOAuthService, geminiTokenProvider, antigravityGatewayService, httpUpstream)
 	concurrencyCache := repository.ProvideConcurrencyCache(redisClient, configConfig)
-	concurrencyService := service.ProvideConcurrencyService(concurrencyCache, accountRepository, configConfig)
+	concurrencyService := service.NewConcurrencyService(concurrencyCache)
 	crsSyncService := service.NewCRSSyncService(accountRepository, proxyRepository, oAuthService, openAIOAuthService, geminiOAuthService)
 	accountHandler := admin.NewAccountHandler(adminService, oAuthService, openAIOAuthService, geminiOAuthService, rateLimitService, accountUsageService, accountTestService, concurrencyService, crsSyncService)
 	oAuthHandler := admin.NewOAuthHandler(oAuthService)
@@ -127,10 +127,10 @@ func initializeApplication(buildInfo handler.BuildInfo) (*Application, error) {
 	identityService := service.NewIdentityService(identityCache)
 	timingWheelService := service.ProvideTimingWheelService()
 	deferredService := service.ProvideDeferredService(accountRepository, timingWheelService)
-	gatewayService := service.NewGatewayService(accountRepository, groupRepository, usageLogRepository, userRepository, userSubscriptionRepository, gatewayCache, configConfig, concurrencyService, billingService, rateLimitService, billingCacheService, identityService, httpUpstream, deferredService)
+	gatewayService := service.NewGatewayService(accountRepository, groupRepository, usageLogRepository, userRepository, userSubscriptionRepository, gatewayCache, configConfig, billingService, rateLimitService, billingCacheService, identityService, httpUpstream, deferredService)
 	geminiMessagesCompatService := service.NewGeminiMessagesCompatService(accountRepository, groupRepository, gatewayCache, geminiTokenProvider, rateLimitService, httpUpstream, antigravityGatewayService)
 	gatewayHandler := handler.NewGatewayHandler(gatewayService, geminiMessagesCompatService, antigravityGatewayService, userService, concurrencyService, billingCacheService)
-	openAIGatewayService := service.NewOpenAIGatewayService(accountRepository, usageLogRepository, userRepository, userSubscriptionRepository, gatewayCache, configConfig, concurrencyService, billingService, rateLimitService, billingCacheService, httpUpstream, deferredService)
+	openAIGatewayService := service.NewOpenAIGatewayService(accountRepository, usageLogRepository, userRepository, userSubscriptionRepository, gatewayCache, configConfig, billingService, rateLimitService, billingCacheService, httpUpstream, deferredService)
 	openAIGatewayHandler := handler.NewOpenAIGatewayHandler(openAIGatewayService, concurrencyService, billingCacheService)
 	handlerSettingHandler := handler.ProvideSettingHandler(settingService, buildInfo)
 	handlers := handler.ProvideHandlers(authHandler, userHandler, apiKeyHandler, usageHandler, redeemHandler, subscriptionHandler, adminHandlers, gatewayHandler, openAIGatewayHandler, handlerSettingHandler)
--- a/backend/internal/config/config.go
+++ b/backend/internal/config/config.go
@@ -3,7 +3,6 @@ package config
 import (
 	"fmt"
 	"strings"
-	"time"

 	"github.com/spf13/viper"
 )
@@ -120,37 +119,6 @@ type GatewayConfig struct {
 	// ConcurrencySlotTTLMinutes: 并发槽位过期时间（分钟）
 	// 应大于最长 LLM 请求时间，防止请求完成前槽位过期
 	ConcurrencySlotTTLMinutes int `mapstructure:"concurrency_slot_ttl_minutes"`
-
-	// 是否记录上游错误响应体摘要（避免输出请求内容）
-	LogUpstreamErrorBody bool `mapstructure:"log_upstream_error_body"`
-	// 上游错误响应体记录最大字节数（超过会截断）
-	LogUpstreamErrorBodyMaxBytes int `mapstructure:"log_upstream_error_body_max_bytes"`
-
-	// API-key 账号在客户端未提供 anthropic-beta 时，是否按需自动补齐（默认关闭以保持兼容）
-	InjectBetaForApiKey bool `mapstructure:"inject_beta_for_apikey"`
-
-	// 是否允许对部分 400 错误触发 failover（默认关闭以避免改变语义）
-	FailoverOn400 bool `mapstructure:"failover_on_400"`
-
-	// Scheduling: 账号调度相关配置
-	Scheduling GatewaySchedulingConfig `mapstructure:"scheduling"`
-}
-
-// GatewaySchedulingConfig accounts scheduling configuration.
-type GatewaySchedulingConfig struct {
-	// 粘性会话排队配置
-	StickySessionMaxWaiting  int           `mapstructure:"sticky_session_max_waiting"`
-	StickySessionWaitTimeout time.Duration `mapstructure:"sticky_session_wait_timeout"`
-
-	// 兜底排队配置
-	FallbackWaitTimeout time.Duration `mapstructure:"fallback_wait_timeout"`
-	FallbackMaxWaiting  int           `mapstructure:"fallback_max_waiting"`
-
-	// 负载计算
-	LoadBatchEnabled bool `mapstructure:"load_batch_enabled"`
-
-	// 过期槽位清理周期（0 表示禁用）
-	SlotCleanupInterval time.Duration `mapstructure:"slot_cleanup_interval"`
 }

 func (s *ServerConfig) Address() string {
@@ -345,10 +313,6 @@ func setDefaults() {

 	// Gateway
 	viper.SetDefault("gateway.response_header_timeout", 300) // 300秒(5分钟)等待上游响应头，LLM高负载时可能排队较久
-	viper.SetDefault("gateway.log_upstream_error_body", false)
-	viper.SetDefault("gateway.log_upstream_error_body_max_bytes", 2048)
-	viper.SetDefault("gateway.inject_beta_for_apikey", false)
-	viper.SetDefault("gateway.failover_on_400", false)
 	viper.SetDefault("gateway.max_body_size", int64(100*1024*1024))
 	viper.SetDefault("gateway.connection_pool_isolation", ConnectionPoolIsolationAccountProxy)
 	// HTTP 上游连接池配置（针对 5000+ 并发用户优化）
@@ -359,12 +323,6 @@ func setDefaults() {
 	viper.SetDefault("gateway.max_upstream_clients", 5000)
 	viper.SetDefault("gateway.client_idle_ttl_seconds", 900)
 	viper.SetDefault("gateway.concurrency_slot_ttl_minutes", 15) // 并发槽位过期时间（支持超长请求）
-	viper.SetDefault("gateway.scheduling.sticky_session_max_waiting", 3)
-	viper.SetDefault("gateway.scheduling.sticky_session_wait_timeout", 45*time.Second)
-	viper.SetDefault("gateway.scheduling.fallback_wait_timeout", 30*time.Second)
-	viper.SetDefault("gateway.scheduling.fallback_max_waiting", 100)
-	viper.SetDefault("gateway.scheduling.load_batch_enabled", true)
-	viper.SetDefault("gateway.scheduling.slot_cleanup_interval", 30*time.Second)

 	// TokenRefresh
 	viper.SetDefault("token_refresh.enabled", true)
@@ -453,21 +411,6 @@ func (c *Config) Validate() error {
 	if c.Gateway.ConcurrencySlotTTLMinutes <= 0 {
 		return fmt.Errorf("gateway.concurrency_slot_ttl_minutes must be positive")
 	}
-	if c.Gateway.Scheduling.StickySessionMaxWaiting <= 0 {
-		return fmt.Errorf("gateway.scheduling.sticky_session_max_waiting must be positive")
-	}
-	if c.Gateway.Scheduling.StickySessionWaitTimeout <= 0 {
-		return fmt.Errorf("gateway.scheduling.sticky_session_wait_timeout must be positive")
-	}
-	if c.Gateway.Scheduling.FallbackWaitTimeout <= 0 {
-		return fmt.Errorf("gateway.scheduling.fallback_wait_timeout must be positive")
-	}
-	if c.Gateway.Scheduling.FallbackMaxWaiting <= 0 {
-		return fmt.Errorf("gateway.scheduling.fallback_max_waiting must be positive")
-	}
-	if c.Gateway.Scheduling.SlotCleanupInterval < 0 {
-		return fmt.Errorf("gateway.scheduling.slot_cleanup_interval must be non-negative")
-	}
 	return nil
 }

--- a/backend/internal/config/config_test.go
+++ b/backend/internal/config/config_test.go
@@ -1,11 +1,6 @@
 package config

-import (
-	"testing"
-	"time"
-
-	"github.com/spf13/viper"
-)
+import "testing"

 func TestNormalizeRunMode(t *testing.T) {
 	tests := []struct {
@@ -26,45 +21,3 @@ func TestNormalizeRunMode(t *testing.T) {
 		}
 	}
 }
-
-func TestLoadDefaultSchedulingConfig(t *testing.T) {
-	viper.Reset()
-
-	cfg, err := Load()
-	if err != nil {
-		t.Fatalf("Load() error: %v", err)
-	}
-
-	if cfg.Gateway.Scheduling.StickySessionMaxWaiting != 3 {
-		t.Fatalf("StickySessionMaxWaiting = %d, want 3", cfg.Gateway.Scheduling.StickySessionMaxWaiting)
-	}
-	if cfg.Gateway.Scheduling.StickySessionWaitTimeout != 45*time.Second {
-		t.Fatalf("StickySessionWaitTimeout = %v, want 45s", cfg.Gateway.Scheduling.StickySessionWaitTimeout)
-	}
-	if cfg.Gateway.Scheduling.FallbackWaitTimeout != 30*time.Second {
-		t.Fatalf("FallbackWaitTimeout = %v, want 30s", cfg.Gateway.Scheduling.FallbackWaitTimeout)
-	}
-	if cfg.Gateway.Scheduling.FallbackMaxWaiting != 100 {
-		t.Fatalf("FallbackMaxWaiting = %d, want 100", cfg.Gateway.Scheduling.FallbackMaxWaiting)
-	}
-	if !cfg.Gateway.Scheduling.LoadBatchEnabled {
-		t.Fatalf("LoadBatchEnabled = false, want true")
-	}
-	if cfg.Gateway.Scheduling.SlotCleanupInterval != 30*time.Second {
-		t.Fatalf("SlotCleanupInterval = %v, want 30s", cfg.Gateway.Scheduling.SlotCleanupInterval)
-	}
-}
-
-func TestLoadSchedulingConfigFromEnv(t *testing.T) {
-	viper.Reset()
-	t.Setenv("GATEWAY_SCHEDULING_STICKY_SESSION_MAX_WAITING", "5")
-
-	cfg, err := Load()
-	if err != nil {
-		t.Fatalf("Load() error: %v", err)
-	}
-
-	if cfg.Gateway.Scheduling.StickySessionMaxWaiting != 5 {
-		t.Fatalf("StickySessionMaxWaiting = %d, want 5", cfg.Gateway.Scheduling.StickySessionMaxWaiting)
-	}
-}
--- a/backend/internal/handler/gateway_handler.go
+++ b/backend/internal/handler/gateway_handler.go
@@ -141,10 +141,6 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 	} else if apiKey.Group != nil {
 		platform = apiKey.Group.Platform
 	}
-	sessionKey := sessionHash
-	if platform == service.PlatformGemini && sessionHash != "" {
-		sessionKey = "gemini:" + sessionHash
-	}

 	if platform == service.PlatformGemini {
 		const maxAccountSwitches = 3
@@ -153,7 +149,7 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 		lastFailoverStatus := 0

 		for {
-			selection, err := h.gatewayService.SelectAccountWithLoadAwareness(c.Request.Context(), apiKey.GroupID, sessionKey, reqModel, failedAccountIDs)
+			account, err := h.geminiCompatService.SelectAccountForModelWithExclusions(c.Request.Context(), apiKey.GroupID, sessionHash, reqModel, failedAccountIDs)
 			if err != nil {
 				if len(failedAccountIDs) == 0 {
 					h.handleStreamingAwareError(c, http.StatusServiceUnavailable, "api_error", "No available accounts: "+err.Error(), streamStarted)
@@ -162,13 +158,9 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 				h.handleFailoverExhausted(c, lastFailoverStatus, streamStarted)
 				return
 			}
-			account := selection.Account

 			// 检查预热请求拦截（在账号选择后、转发前检查）
 			if account.IsInterceptWarmupEnabled() && isWarmupRequest(body) {
-				if selection.Acquired && selection.ReleaseFunc != nil {
-					selection.ReleaseFunc()
-				}
 				if reqStream {
 					sendMockWarmupStream(c, reqModel)
 				} else {
@@ -178,46 +170,11 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 			}

 			// 3. 获取账号并发槽位
-			accountReleaseFunc := selection.ReleaseFunc
-			var accountWaitRelease func()
-			if !selection.Acquired {
-				if selection.WaitPlan == nil {
-					h.handleStreamingAwareError(c, http.StatusServiceUnavailable, "api_error", "No available accounts", streamStarted)
-					return
-				}
-				canWait, err := h.concurrencyHelper.IncrementAccountWaitCount(c.Request.Context(), account.ID, selection.WaitPlan.MaxWaiting)
-				if err != nil {
-					log.Printf("Increment account wait count failed: %v", err)
-				} else if !canWait {
-					log.Printf("Account wait queue full: account=%d", account.ID)
-					h.handleStreamingAwareError(c, http.StatusTooManyRequests, "rate_limit_error", "Too many pending requests, please retry later", streamStarted)
-					return
-				} else {
-					// Only set release function if increment succeeded
-					accountWaitRelease = func() {
-						h.concurrencyHelper.DecrementAccountWaitCount(c.Request.Context(), account.ID)
-					}
-				}
-
-				accountReleaseFunc, err = h.concurrencyHelper.AcquireAccountSlotWithWaitTimeout(
-					c,
-					account.ID,
-					selection.WaitPlan.MaxConcurrency,
-					selection.WaitPlan.Timeout,
-					reqStream,
-					&streamStarted,
-				)
-				if err != nil {
-					if accountWaitRelease != nil {
-						accountWaitRelease()
-					}
-					log.Printf("Account concurrency acquire failed: %v", err)
-					h.handleConcurrencyError(c, err, "account", streamStarted)
-					return
-				}
-				if err := h.gatewayService.BindStickySession(c.Request.Context(), sessionKey, account.ID); err != nil {
-					log.Printf("Bind sticky session failed: %v", err)
-				}
+			accountReleaseFunc, err := h.concurrencyHelper.AcquireAccountSlotWithWait(c, account.ID, account.Concurrency, reqStream, &streamStarted)
+			if err != nil {
+				log.Printf("Account concurrency acquire failed: %v", err)
+				h.handleConcurrencyError(c, err, "account", streamStarted)
+				return
 			}

 			// 转发请求 - 根据账号平台分流
@@ -230,9 +187,6 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 			if accountReleaseFunc != nil {
 				accountReleaseFunc()
 			}
-			if accountWaitRelease != nil {
-				accountWaitRelease()
-			}
 			if err != nil {
 				var failoverErr *service.UpstreamFailoverError
 				if errors.As(err, &failoverErr) {
@@ -277,7 +231,7 @@ func (h *GatewayHandler) Messages(c *gin.Context) {

 	for {
 		// 选择支持该模型的账号
-		selection, err := h.gatewayService.SelectAccountWithLoadAwareness(c.Request.Context(), apiKey.GroupID, sessionKey, reqModel, failedAccountIDs)
+		account, err := h.gatewayService.SelectAccountForModelWithExclusions(c.Request.Context(), apiKey.GroupID, sessionHash, reqModel, failedAccountIDs)
 		if err != nil {
 			if len(failedAccountIDs) == 0 {
 				h.handleStreamingAwareError(c, http.StatusServiceUnavailable, "api_error", "No available accounts: "+err.Error(), streamStarted)
@@ -286,13 +240,9 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 			h.handleFailoverExhausted(c, lastFailoverStatus, streamStarted)
 			return
 		}
-		account := selection.Account

 		// 检查预热请求拦截（在账号选择后、转发前检查）
 		if account.IsInterceptWarmupEnabled() && isWarmupRequest(body) {
-			if selection.Acquired && selection.ReleaseFunc != nil {
-				selection.ReleaseFunc()
-			}
 			if reqStream {
 				sendMockWarmupStream(c, reqModel)
 			} else {
@@ -302,46 +252,11 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 		}

 		// 3. 获取账号并发槽位
-		accountReleaseFunc := selection.ReleaseFunc
-		var accountWaitRelease func()
-		if !selection.Acquired {
-			if selection.WaitPlan == nil {
-				h.handleStreamingAwareError(c, http.StatusServiceUnavailable, "api_error", "No available accounts", streamStarted)
-				return
-			}
-			canWait, err := h.concurrencyHelper.IncrementAccountWaitCount(c.Request.Context(), account.ID, selection.WaitPlan.MaxWaiting)
-			if err != nil {
-				log.Printf("Increment account wait count failed: %v", err)
-			} else if !canWait {
-				log.Printf("Account wait queue full: account=%d", account.ID)
-				h.handleStreamingAwareError(c, http.StatusTooManyRequests, "rate_limit_error", "Too many pending requests, please retry later", streamStarted)
-				return
-			} else {
-				// Only set release function if increment succeeded
-				accountWaitRelease = func() {
-					h.concurrencyHelper.DecrementAccountWaitCount(c.Request.Context(), account.ID)
-				}
-			}
-
-			accountReleaseFunc, err = h.concurrencyHelper.AcquireAccountSlotWithWaitTimeout(
-				c,
-				account.ID,
-				selection.WaitPlan.MaxConcurrency,
-				selection.WaitPlan.Timeout,
-				reqStream,
-				&streamStarted,
-			)
-			if err != nil {
-				if accountWaitRelease != nil {
-					accountWaitRelease()
-				}
-				log.Printf("Account concurrency acquire failed: %v", err)
-				h.handleConcurrencyError(c, err, "account", streamStarted)
-				return
-			}
-			if err := h.gatewayService.BindStickySession(c.Request.Context(), sessionKey, account.ID); err != nil {
-				log.Printf("Bind sticky session failed: %v", err)
-			}
+		accountReleaseFunc, err := h.concurrencyHelper.AcquireAccountSlotWithWait(c, account.ID, account.Concurrency, reqStream, &streamStarted)
+		if err != nil {
+			log.Printf("Account concurrency acquire failed: %v", err)
+			h.handleConcurrencyError(c, err, "account", streamStarted)
+			return
 		}

 		// 转发请求 - 根据账号平台分流
@@ -354,9 +269,6 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 		if accountReleaseFunc != nil {
 			accountReleaseFunc()
 		}
-		if accountWaitRelease != nil {
-			accountWaitRelease()
-		}
 		if err != nil {
 			var failoverErr *service.UpstreamFailoverError
 			if errors.As(err, &failoverErr) {
--- a/backend/internal/handler/gateway_helper.go
+++ b/backend/internal/handler/gateway_helper.go
@@ -83,16 +83,6 @@ func (h *ConcurrencyHelper) DecrementWaitCount(ctx context.Context, userID int64
 	h.concurrencyService.DecrementWaitCount(ctx, userID)
 }

-// IncrementAccountWaitCount increments the wait count for an account
-func (h *ConcurrencyHelper) IncrementAccountWaitCount(ctx context.Context, accountID int64, maxWait int) (bool, error) {
-	return h.concurrencyService.IncrementAccountWaitCount(ctx, accountID, maxWait)
-}
-
-// DecrementAccountWaitCount decrements the wait count for an account
-func (h *ConcurrencyHelper) DecrementAccountWaitCount(ctx context.Context, accountID int64) {
-	h.concurrencyService.DecrementAccountWaitCount(ctx, accountID)
-}
-
 // AcquireUserSlotWithWait acquires a user concurrency slot, waiting if necessary.
 // For streaming requests, sends ping events during the wait.
 // streamStarted is updated if streaming response has begun.
@@ -136,12 +126,7 @@ func (h *ConcurrencyHelper) AcquireAccountSlotWithWait(c *gin.Context, accountID
 // waitForSlotWithPing waits for a concurrency slot, sending ping events for streaming requests.
 // streamStarted pointer is updated when streaming begins (for proper error handling by caller).
 func (h *ConcurrencyHelper) waitForSlotWithPing(c *gin.Context, slotType string, id int64, maxConcurrency int, isStream bool, streamStarted *bool) (func(), error) {
-	return h.waitForSlotWithPingTimeout(c, slotType, id, maxConcurrency, maxConcurrencyWait, isStream, streamStarted)
-}
-
-// waitForSlotWithPingTimeout waits for a concurrency slot with a custom timeout.
-func (h *ConcurrencyHelper) waitForSlotWithPingTimeout(c *gin.Context, slotType string, id int64, maxConcurrency int, timeout time.Duration, isStream bool, streamStarted *bool) (func(), error) {
-	ctx, cancel := context.WithTimeout(c.Request.Context(), timeout)
+	ctx, cancel := context.WithTimeout(c.Request.Context(), maxConcurrencyWait)
 	defer cancel()

 	// Determine if ping is needed (streaming + ping format defined)
@@ -215,11 +200,6 @@ func (h *ConcurrencyHelper) waitForSlotWithPingTimeout(c *gin.Context, slotType
 	}
 }

-// AcquireAccountSlotWithWaitTimeout acquires an account slot with a custom timeout (keeps SSE ping).
-func (h *ConcurrencyHelper) AcquireAccountSlotWithWaitTimeout(c *gin.Context, accountID int64, maxConcurrency int, timeout time.Duration, isStream bool, streamStarted *bool) (func(), error) {
-	return h.waitForSlotWithPingTimeout(c, "account", accountID, maxConcurrency, timeout, isStream, streamStarted)
-}
-
 // nextBackoff 计算下一次退避时间
 // 性能优化：使用指数退避 + 随机抖动，避免惊群效应
 // current: 当前退避时间
--- a/backend/internal/handler/gemini_v1beta_handler.go
+++ b/backend/internal/handler/gemini_v1beta_handler.go
@@ -197,17 +197,13 @@ func (h *GatewayHandler) GeminiV1BetaModels(c *gin.Context) {
 	// 3) select account (sticky session based on request body)
 	parsedReq, _ := service.ParseGatewayRequest(body)
 	sessionHash := h.gatewayService.GenerateSessionHash(parsedReq)
-	sessionKey := sessionHash
-	if sessionHash != "" {
-		sessionKey = "gemini:" + sessionHash
-	}
 	const maxAccountSwitches = 3
 	switchCount := 0
 	failedAccountIDs := make(map[int64]struct{})
 	lastFailoverStatus := 0

 	for {
-		selection, err := h.gatewayService.SelectAccountWithLoadAwareness(c.Request.Context(), apiKey.GroupID, sessionKey, modelName, failedAccountIDs)
+		account, err := h.geminiCompatService.SelectAccountForModelWithExclusions(c.Request.Context(), apiKey.GroupID, sessionHash, modelName, failedAccountIDs)
 		if err != nil {
 			if len(failedAccountIDs) == 0 {
 				googleError(c, http.StatusServiceUnavailable, "No available Gemini accounts: "+err.Error())
@@ -216,48 +212,12 @@ func (h *GatewayHandler) GeminiV1BetaModels(c *gin.Context) {
 			handleGeminiFailoverExhausted(c, lastFailoverStatus)
 			return
 		}
-		account := selection.Account

 		// 4) account concurrency slot
-		accountReleaseFunc := selection.ReleaseFunc
-		var accountWaitRelease func()
-		if !selection.Acquired {
-			if selection.WaitPlan == nil {
-				googleError(c, http.StatusServiceUnavailable, "No available Gemini accounts")
-				return
-			}
-			canWait, err := geminiConcurrency.IncrementAccountWaitCount(c.Request.Context(), account.ID, selection.WaitPlan.MaxWaiting)
-			if err != nil {
-				log.Printf("Increment account wait count failed: %v", err)
-			} else if !canWait {
-				log.Printf("Account wait queue full: account=%d", account.ID)
-				googleError(c, http.StatusTooManyRequests, "Too many pending requests, please retry later")
-				return
-			} else {
-				// Only set release function if increment succeeded
-				accountWaitRelease = func() {
-					geminiConcurrency.DecrementAccountWaitCount(c.Request.Context(), account.ID)
-				}
-			}
-
-			accountReleaseFunc, err = geminiConcurrency.AcquireAccountSlotWithWaitTimeout(
-				c,
-				account.ID,
-				selection.WaitPlan.MaxConcurrency,
-				selection.WaitPlan.Timeout,
-				stream,
-				&streamStarted,
-			)
-			if err != nil {
-				if accountWaitRelease != nil {
-					accountWaitRelease()
-				}
-				googleError(c, http.StatusTooManyRequests, err.Error())
-				return
-			}
-			if err := h.gatewayService.BindStickySession(c.Request.Context(), sessionKey, account.ID); err != nil {
-				log.Printf("Bind sticky session failed: %v", err)
-			}
+		accountReleaseFunc, err := geminiConcurrency.AcquireAccountSlotWithWait(c, account.ID, account.Concurrency, stream, &streamStarted)
+		if err != nil {
+			googleError(c, http.StatusTooManyRequests, err.Error())
+			return
 		}

 		// 5) forward (根据平台分流)
@@ -270,9 +230,6 @@ func (h *GatewayHandler) GeminiV1BetaModels(c *gin.Context) {
 		if accountReleaseFunc != nil {
 			accountReleaseFunc()
 		}
-		if accountWaitRelease != nil {
-			accountWaitRelease()
-		}
 		if err != nil {
 			var failoverErr *service.UpstreamFailoverError
 			if errors.As(err, &failoverErr) {
--- a/backend/internal/handler/openai_gateway_handler.go
+++ b/backend/internal/handler/openai_gateway_handler.go
@@ -146,7 +146,7 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 	for {
 		// Select account supporting the requested model
 		log.Printf("[OpenAI Handler] Selecting account: groupID=%v model=%s", apiKey.GroupID, reqModel)
-		selection, err := h.gatewayService.SelectAccountWithLoadAwareness(c.Request.Context(), apiKey.GroupID, sessionHash, reqModel, failedAccountIDs)
+		account, err := h.gatewayService.SelectAccountForModelWithExclusions(c.Request.Context(), apiKey.GroupID, sessionHash, reqModel, failedAccountIDs)
 		if err != nil {
 			log.Printf("[OpenAI Handler] SelectAccount failed: %v", err)
 			if len(failedAccountIDs) == 0 {
@@ -156,50 +156,14 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 			h.handleFailoverExhausted(c, lastFailoverStatus, streamStarted)
 			return
 		}
-		account := selection.Account
 		log.Printf("[OpenAI Handler] Selected account: id=%d name=%s", account.ID, account.Name)

 		// 3. Acquire account concurrency slot
-		accountReleaseFunc := selection.ReleaseFunc
-		var accountWaitRelease func()
-		if !selection.Acquired {
-			if selection.WaitPlan == nil {
-				h.handleStreamingAwareError(c, http.StatusServiceUnavailable, "api_error", "No available accounts", streamStarted)
-				return
-			}
-			canWait, err := h.concurrencyHelper.IncrementAccountWaitCount(c.Request.Context(), account.ID, selection.WaitPlan.MaxWaiting)
-			if err != nil {
-				log.Printf("Increment account wait count failed: %v", err)
-			} else if !canWait {
-				log.Printf("Account wait queue full: account=%d", account.ID)
-				h.handleStreamingAwareError(c, http.StatusTooManyRequests, "rate_limit_error", "Too many pending requests, please retry later", streamStarted)
-				return
-			} else {
-				// Only set release function if increment succeeded
-				accountWaitRelease = func() {
-					h.concurrencyHelper.DecrementAccountWaitCount(c.Request.Context(), account.ID)
-				}
-			}
-
-			accountReleaseFunc, err = h.concurrencyHelper.AcquireAccountSlotWithWaitTimeout(
-				c,
-				account.ID,
-				selection.WaitPlan.MaxConcurrency,
-				selection.WaitPlan.Timeout,
-				reqStream,
-				&streamStarted,
-			)
-			if err != nil {
-				if accountWaitRelease != nil {
-					accountWaitRelease()
-				}
-				log.Printf("Account concurrency acquire failed: %v", err)
-				h.handleConcurrencyError(c, err, "account", streamStarted)
-				return
-			}
-			if err := h.gatewayService.BindStickySession(c.Request.Context(), sessionHash, account.ID); err != nil {
-				log.Printf("Bind sticky session failed: %v", err)
-			}
+		accountReleaseFunc, err := h.concurrencyHelper.AcquireAccountSlotWithWait(c, account.ID, account.Concurrency, reqStream, &streamStarted)
+		if err != nil {
+			log.Printf("Account concurrency acquire failed: %v", err)
+			h.handleConcurrencyError(c, err, "account", streamStarted)
+			return
 		}

 		// Forward request
@@ -207,9 +171,6 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 		if accountReleaseFunc != nil {
 			accountReleaseFunc()
 		}
-		if accountWaitRelease != nil {
-			accountWaitRelease()
-		}
 		if err != nil {
 			var failoverErr *service.UpstreamFailoverError
 			if errors.As(err, &failoverErr) {
--- a/backend/internal/pkg/antigravity/claude_types.go
+++ b/backend/internal/pkg/antigravity/claude_types.go
@@ -54,9 +54,6 @@ type CustomToolSpec struct {
 	InputSchema map[string]any `json:"input_schema"`
 }

-// ClaudeCustomToolSpec 兼容旧命名（MCP custom 工具规格）
-type ClaudeCustomToolSpec = CustomToolSpec
-
 // SystemBlock system prompt 数组形式的元素
 type SystemBlock struct {
 	Type string `json:"type"`
--- a/backend/internal/pkg/antigravity/request_transformer.go
+++ b/backend/internal/pkg/antigravity/request_transformer.go
@@ -14,16 +14,13 @@ func TransformClaudeToGemini(claudeReq *ClaudeRequest, projectID, mappedModel st
 	// 用于存储 tool_use id -> name 映射
 	toolIDToName := make(map[string]string)

+	// 检测是否启用 thinking
+	isThinkingEnabled := claudeReq.Thinking != nil && claudeReq.Thinking.Type == "enabled"
+
 	// 只有 Gemini 模型支持 dummy thought workaround
 	// Claude 模型通过 Vertex/Google API 需要有效的 thought signatures
 	allowDummyThought := strings.HasPrefix(mappedModel, "gemini-")

-	// 检测是否启用 thinking
-	requestedThinkingEnabled := claudeReq.Thinking != nil && claudeReq.Thinking.Type == "enabled"
-	// 为避免 Claude 模型的 thought signature/消息块约束导致 400（上游要求 thinking 块开头等），
-	// 非 Gemini 模型默认不启用 thinking（除非未来支持完整签名链路）。
-	isThinkingEnabled := requestedThinkingEnabled && allowDummyThought
-
 	// 1. 构建 contents
 	contents, err := buildContents(claudeReq.Messages, toolIDToName, isThinkingEnabled, allowDummyThought)
 	if err != nil {
@@ -34,15 +31,7 @@ func TransformClaudeToGemini(claudeReq *ClaudeRequest, projectID, mappedModel st
 	systemInstruction := buildSystemInstruction(claudeReq.System, claudeReq.Model)

 	// 3. 构建 generationConfig
-	reqForGen := claudeReq
-	if requestedThinkingEnabled && !allowDummyThought {
-		log.Printf("[Warning] Disabling thinking for non-Gemini model in antigravity transform: model=%s", mappedModel)
-		// shallow copy to avoid mutating caller's request
-		clone := *claudeReq
-		clone.Thinking = nil
-		reqForGen = &clone
-	}
-	generationConfig := buildGenerationConfig(reqForGen)
+	generationConfig := buildGenerationConfig(claudeReq)

 	// 4. 构建 tools
 	tools := buildTools(claudeReq.Tools)
@@ -159,9 +148,8 @@ func buildContents(messages []ClaudeMessage, toolIDToName map[string]string, isT
 			if !hasThoughtPart && len(parts) > 0 {
 				// 在开头添加 dummy thinking block
 				parts = append([]GeminiPart{{
-					Text:             "Thinking...",
-					Thought:          true,
-					ThoughtSignature: dummyThoughtSignature,
+					Text:    "Thinking...",
+					Thought: true,
 				}}, parts...)
 			}
 		}
@@ -183,34 +171,6 @@ func buildContents(messages []ClaudeMessage, toolIDToName map[string]string, isT
 // 参考: https://ai.google.dev/gemini-api/docs/thought-signatures
 const dummyThoughtSignature = "skip_thought_signature_validator"

-// isValidThoughtSignature 验证 thought signature 是否有效
-// Claude API 要求 signature 必须是 base64 编码的字符串，长度至少 32 字节
-func isValidThoughtSignature(signature string) bool {
-	// 空字符串无效
-	if signature == "" {
-		return false
-	}
-
-	// signature 应该是 base64 编码，长度至少 40 个字符（约 30 字节）
-	// 参考 Claude API 文档和实际观察到的有效 signature
-	if len(signature) < 40 {
-		log.Printf("[Debug] Signature too short: len=%d", len(signature))
-		return false
-	}
-
-	// 检查是否是有效的 base64 字符
-	// base64 字符集: A-Z, a-z, 0-9, +, /, =
-	for i, c := range signature {
-		if (c < 'A' || c > 'Z') && (c < 'a' || c > 'z') &&
-			(c < '0' || c > '9') && c != '+' && c != '/' && c != '=' {
-			log.Printf("[Debug] Invalid base64 character at position %d: %c (code=%d)", i, c, c)
-			return false
-		}
-	}
-
-	return true
-}
-
 // buildParts 构建消息的 parts
 // allowDummyThought: 只有 Gemini 模型支持 dummy thought signature
 func buildParts(content json.RawMessage, toolIDToName map[string]string, allowDummyThought bool) ([]GeminiPart, error) {
@@ -239,30 +199,22 @@ func buildParts(content json.RawMessage, toolIDToName map[string]string, allowDu
 			}

 		case "thinking":
-			if allowDummyThought {
-				// Gemini 模型可以使用 dummy signature
-				parts = append(parts, GeminiPart{
-					Text:             block.Thinking,
-					Thought:          true,
-					ThoughtSignature: dummyThoughtSignature,
-				})
+			part := GeminiPart{
+				Text:    block.Thinking,
+				Thought: true,
+			}
+			// 保留原有 signature（Claude 模型需要有效的 signature）
+			if block.Signature != "" {
+				part.ThoughtSignature = block.Signature
+			} else if !allowDummyThought {
+				// Claude 模型需要有效 signature，跳过无 signature 的 thinking block
+				log.Printf("Warning: skipping thinking block without signature for Claude model")
 				continue
+			} else {
+				// Gemini 模型使用 dummy signature
+				part.ThoughtSignature = dummyThoughtSignature
 			}
-
-			// Claude 模型：仅在提供有效 signature 时保留 thinking block；否则跳过以避免上游校验失败。
-			signature := strings.TrimSpace(block.Signature)
-			if signature == "" || signature == dummyThoughtSignature {
-				log.Printf("[Warning] Skipping thinking block for Claude model (missing or dummy signature)")
-				continue
-			}
-			if !isValidThoughtSignature(signature) {
-				log.Printf("[Debug] Thinking signature may be invalid (passing through anyway): len=%d", len(signature))
-			}
-			parts = append(parts, GeminiPart{
-				Text:             block.Thinking,
-				Thought:          true,
-				ThoughtSignature: signature,
-			})
+			parts = append(parts, part)

 		case "image":
 			if block.Source != nil && block.Source.Type == "base64" {
@@ -287,9 +239,10 @@ func buildParts(content json.RawMessage, toolIDToName map[string]string, allowDu
 					ID:   block.ID,
 				},
 			}
-			// 只有 Gemini 模型使用 dummy signature
-			// Claude 模型不设置 signature（避免验证问题）
-			if allowDummyThought {
+			// 保留原有 signature，或对 Gemini 模型使用 dummy signature
+			if block.Signature != "" {
+				part.ThoughtSignature = block.Signature
+			} else if allowDummyThought {
 				part.ThoughtSignature = dummyThoughtSignature
 			}
 			parts = append(parts, part)
@@ -433,9 +386,9 @@ func buildTools(tools []ClaudeTool) []GeminiToolDeclaration {

 	// 普通工具
 	var funcDecls []GeminiFunctionDecl
-	for i, tool := range tools {
+	for _, tool := range tools {
 		// 跳过无效工具名称
-		if strings.TrimSpace(tool.Name) == "" {
+		if tool.Name == "" {
 			log.Printf("Warning: skipping tool with empty name")
 			continue
 		}
@@ -444,18 +397,10 @@ func buildTools(tools []ClaudeTool) []GeminiToolDeclaration {
 		var inputSchema map[string]any

 		// 检查是否为 custom 类型工具 (MCP)
-		if tool.Type == "custom" {
-			if tool.Custom == nil || tool.Custom.InputSchema == nil {
-				log.Printf("[Warning] Skipping invalid custom tool '%s': missing custom spec or input_schema", tool.Name)
-				continue
-			}
+		if tool.Type == "custom" && tool.Custom != nil {
+			// Custom 格式: 从 custom 字段获取 description 和 input_schema
 			description = tool.Custom.Description
 			inputSchema = tool.Custom.InputSchema
-
-			// 调试日志：记录 custom 工具的 schema
-			if schemaJSON, err := json.Marshal(inputSchema); err == nil {
-				log.Printf("[Debug] Tool[%d] '%s' (custom) original schema: %s", i, tool.Name, string(schemaJSON))
-			}
 		} else {
 			// 标准格式: 从顶层字段获取
 			description = tool.Description
@@ -464,6 +409,7 @@ func buildTools(tools []ClaudeTool) []GeminiToolDeclaration {

 		// 清理 JSON Schema
 		params := cleanJSONSchema(inputSchema)
+
 		// 为 nil schema 提供默认值
 		if params == nil {
 			params = map[string]any{
@@ -472,11 +418,6 @@ func buildTools(tools []ClaudeTool) []GeminiToolDeclaration {
 			}
 		}

-		// 调试日志：记录清理后的 schema
-		if paramsJSON, err := json.Marshal(params); err == nil {
-			log.Printf("[Debug] Tool[%d] '%s' cleaned schema: %s", i, tool.Name, string(paramsJSON))
-		}
-
 		funcDecls = append(funcDecls, GeminiFunctionDecl{
 			Name:        tool.Name,
 			Description: description,
@@ -538,64 +479,31 @@ func cleanJSONSchema(schema map[string]any) map[string]any {
 }

 // excludedSchemaKeys 不支持的 schema 字段
-// 基于 Claude API (Vertex AI) 的实际支持情况
-// 支持: type, description, enum, properties, required, additionalProperties, items
-// 不支持: minItems, maxItems, minLength, maxLength, pattern, minimum, maximum 等验证字段
 var excludedSchemaKeys = map[string]bool{
-	// 元 schema 字段
-	"$schema": true,
-	"$id":     true,
-	"$ref":    true,
-
-	// 字符串验证（Gemini 不支持）
-	"minLength": true,
-	"maxLength": true,
-	"pattern":   true,
-
-	// 数字验证（Claude API 通过 Vertex AI 不支持这些字段）
-	"minimum":          true,
-	"maximum":          true,
-	"exclusiveMinimum": true,
-	"exclusiveMaximum": true,
-	"multipleOf":       true,
-
-	// 数组验证（Claude API 通过 Vertex AI 不支持这些字段）
-	"uniqueItems": true,
-	"minItems":    true,
-	"maxItems":    true,
-
-	// 组合 schema（Gemini 不支持）
-	"oneOf":       true,
-	"anyOf":       true,
-	"allOf":       true,
-	"not":         true,
-	"if":          true,
-	"then":        true,
-	"else":        true,
-	"$defs":       true,
-	"definitions": true,
-
-	// 对象验证（仅保留 properties/required/additionalProperties）
-	"minProperties":     true,
-	"maxProperties":     true,
-	"patternProperties": true,
-	"propertyNames":     true,
-	"dependencies":      true,
-	"dependentSchemas":  true,
-	"dependentRequired": true,
-
-	// 其他不支持的字段
-	"default":          true,
-	"const":            true,
-	"examples":         true,
-	"deprecated":       true,
-	"readOnly":         true,
-	"writeOnly":        true,
-	"contentMediaType": true,
-	"contentEncoding":  true,
-
-	// Claude 特有字段
-	"strict": true,
+	"$schema":              true,
+	"$id":                  true,
+	"$ref":                 true,
+	"additionalProperties": true,
+	"minLength":            true,
+	"maxLength":            true,
+	"minItems":             true,
+	"maxItems":             true,
+	"uniqueItems":          true,
+	"minimum":              true,
+	"maximum":              true,
+	"exclusiveMinimum":     true,
+	"exclusiveMaximum":     true,
+	"pattern":              true,
+	"format":               true,
+	"default":              true,
+	"strict":               true,
+	"const":                true,
+	"examples":             true,
+	"deprecated":           true,
+	"readOnly":             true,
+	"writeOnly":            true,
+	"contentMediaType":     true,
+	"contentEncoding":      true,
 }

 // cleanSchemaValue 递归清理 schema 值
@@ -615,31 +523,6 @@ func cleanSchemaValue(value any) any {
 				continue
 			}

-			// 特殊处理 format 字段：只保留 Gemini 支持的 format 值
-			if k == "format" {
-				if formatStr, ok := val.(string); ok {
-					// Gemini 只支持 date-time, date, time
-					if formatStr == "date-time" || formatStr == "date" || formatStr == "time" {
-						result[k] = val
-					}
-					// 其他 format 值直接跳过
-				}
-				continue
-			}
-
-			// 特殊处理 additionalProperties：Claude API 只支持布尔值，不支持 schema 对象
-			if k == "additionalProperties" {
-				if boolVal, ok := val.(bool); ok {
-					result[k] = boolVal
-					log.Printf("[Debug] additionalProperties is bool: %v", boolVal)
-				} else {
-					// 如果是 schema 对象，转换为 false（更安全的默认值）
-					result[k] = false
-					log.Printf("[Debug] additionalProperties is not bool (type: %T), converting to false", val)
-				}
-				continue
-			}
-
 			// 递归清理所有值
 			result[k] = cleanSchemaValue(val)
 		}
--- a/backend/internal/pkg/antigravity/request_transformer_test.go
+++ b/backend/internal/pkg/antigravity/request_transformer_test.go
@@ -1,179 +0,0 @@
-package antigravity
-
-import (
-	"encoding/json"
-	"testing"
-)
-
-// TestBuildParts_ThinkingBlockWithoutSignature 测试thinking block无signature时的处理
-func TestBuildParts_ThinkingBlockWithoutSignature(t *testing.T) {
-	tests := []struct {
-		name              string
-		content           string
-		allowDummyThought bool
-		expectedParts     int
-		description       string
-	}{
-		{
-			name: "Claude model - skip thinking block without signature",
-			content: `[
-				{"type": "text", "text": "Hello"},
-				{"type": "thinking", "thinking": "Let me think...", "signature": ""},
-				{"type": "text", "text": "World"}
-			]`,
-			allowDummyThought: false,
-			expectedParts:     2, // 只有两个text block
-			description:       "Claude模型应该跳过无signature的thinking block",
-		},
-		{
-			name: "Claude model - keep thinking block with signature",
-			content: `[
-				{"type": "text", "text": "Hello"},
-				{"type": "thinking", "thinking": "Let me think...", "signature": "valid_sig"},
-				{"type": "text", "text": "World"}
-			]`,
-			allowDummyThought: false,
-			expectedParts:     3, // 三个block都保留
-			description:       "Claude模型应该保留有signature的thinking block",
-		},
-		{
-			name: "Gemini model - use dummy signature",
-			content: `[
-				{"type": "text", "text": "Hello"},
-				{"type": "thinking", "thinking": "Let me think...", "signature": ""},
-				{"type": "text", "text": "World"}
-			]`,
-			allowDummyThought: true,
-			expectedParts:     3, // 三个block都保留，thinking使用dummy signature
-			description:       "Gemini模型应该为无signature的thinking block使用dummy signature",
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			toolIDToName := make(map[string]string)
-			parts, err := buildParts(json.RawMessage(tt.content), toolIDToName, tt.allowDummyThought)
-
-			if err != nil {
-				t.Fatalf("buildParts() error = %v", err)
-			}
-
-			if len(parts) != tt.expectedParts {
-				t.Errorf("%s: got %d parts, want %d parts", tt.description, len(parts), tt.expectedParts)
-			}
-		})
-	}
-}
-
-// TestBuildTools_CustomTypeTools 测试custom类型工具转换
-func TestBuildTools_CustomTypeTools(t *testing.T) {
-	tests := []struct {
-		name        string
-		tools       []ClaudeTool
-		expectedLen int
-		description string
-	}{
-		{
-			name: "Standard tool format",
-			tools: []ClaudeTool{
-				{
-					Name:        "get_weather",
-					Description: "Get weather information",
-					InputSchema: map[string]any{
-						"type": "object",
-						"properties": map[string]any{
-							"location": map[string]any{"type": "string"},
-						},
-					},
-				},
-			},
-			expectedLen: 1,
-			description: "标准工具格式应该正常转换",
-		},
-		{
-			name: "Custom type tool (MCP format)",
-			tools: []ClaudeTool{
-				{
-					Type: "custom",
-					Name: "mcp_tool",
-					Custom: &ClaudeCustomToolSpec{
-						Description: "MCP tool description",
-						InputSchema: map[string]any{
-							"type": "object",
-							"properties": map[string]any{
-								"param": map[string]any{"type": "string"},
-							},
-						},
-					},
-				},
-			},
-			expectedLen: 1,
-			description: "Custom类型工具应该从Custom字段读取description和input_schema",
-		},
-		{
-			name: "Mixed standard and custom tools",
-			tools: []ClaudeTool{
-				{
-					Name:        "standard_tool",
-					Description: "Standard tool",
-					InputSchema: map[string]any{"type": "object"},
-				},
-				{
-					Type: "custom",
-					Name: "custom_tool",
-					Custom: &ClaudeCustomToolSpec{
-						Description: "Custom tool",
-						InputSchema: map[string]any{"type": "object"},
-					},
-				},
-			},
-			expectedLen: 1, // 返回一个GeminiToolDeclaration，包含2个function declarations
-			description: "混合标准和custom工具应该都能正确转换",
-		},
-		{
-			name: "Invalid custom tool - nil Custom field",
-			tools: []ClaudeTool{
-				{
-					Type: "custom",
-					Name: "invalid_custom",
-					// Custom 为 nil
-				},
-			},
-			expectedLen: 0, // 应该被跳过
-			description: "Custom字段为nil的custom工具应该被跳过",
-		},
-		{
-			name: "Invalid custom tool - nil InputSchema",
-			tools: []ClaudeTool{
-				{
-					Type: "custom",
-					Name: "invalid_custom",
-					Custom: &ClaudeCustomToolSpec{
-						Description: "Invalid",
-						// InputSchema 为 nil
-					},
-				},
-			},
-			expectedLen: 0, // 应该被跳过
-			description: "InputSchema为nil的custom工具应该被跳过",
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			result := buildTools(tt.tools)
-
-			if len(result) != tt.expectedLen {
-				t.Errorf("%s: got %d tool declarations, want %d", tt.description, len(result), tt.expectedLen)
-			}
-
-			// 验证function declarations存在
-			if len(result) > 0 && result[0].FunctionDeclarations != nil {
-				if len(result[0].FunctionDeclarations) != len(tt.tools) {
-					t.Errorf("%s: got %d function declarations, want %d",
-						tt.description, len(result[0].FunctionDeclarations), len(tt.tools))
-				}
-			}
-		})
-	}
-}
--- a/backend/internal/pkg/claude/constants.go
+++ b/backend/internal/pkg/claude/constants.go
@@ -16,12 +16,6 @@ const DefaultBetaHeader = BetaClaudeCode + "," + BetaOAuth + "," + BetaInterleav
 // HaikuBetaHeader Haiku 模型使用的 anthropic-beta header（不需要 claude-code beta）
 const HaikuBetaHeader = BetaOAuth + "," + BetaInterleavedThinking

-// ApiKeyBetaHeader API-key 账号建议使用的 anthropic-beta header（不包含 oauth）
-const ApiKeyBetaHeader = BetaClaudeCode + "," + BetaInterleavedThinking + "," + BetaFineGrainedToolStreaming
-
-// ApiKeyHaikuBetaHeader Haiku 模型在 API-key 账号下使用的 anthropic-beta header（不包含 oauth / claude-code）
-const ApiKeyHaikuBetaHeader = BetaInterleavedThinking
-
 // Claude Code 客户端默认请求头
 var DefaultHeaders = map[string]string{
 	"User-Agent":                                "claude-cli/2.0.62 (external, cli)",
--- a/backend/internal/repository/concurrency_cache.go
+++ b/backend/internal/repository/concurrency_cache.go
@@ -2,9 +2,7 @@ package repository

 import (
 	"context"
-	"errors"
 	"fmt"
-	"strconv"

 	"github.com/Wei-Shaw/sub2api/internal/service"
 	"github.com/redis/go-redis/v9"
@@ -29,8 +27,6 @@ const (
 	userSlotKeyPrefix = "concurrency:user:"
 	// 等待队列计数器格式: concurrency:wait:{userID}
 	waitQueueKeyPrefix = "concurrency:wait:"
-	// 账号级等待队列计数器格式: wait:account:{accountID}
-	accountWaitKeyPrefix = "wait:account:"

 	// 默认槽位过期时间（分钟），可通过配置覆盖
 	defaultSlotTTLMinutes = 15
@@ -116,112 +112,33 @@ var (
 			redis.call('EXPIRE', KEYS[1], ARGV[2])
 		end

-			return 1
-		`)
-
-	// incrementAccountWaitScript - account-level wait queue count
-	incrementAccountWaitScript = redis.NewScript(`
-			local current = redis.call('GET', KEYS[1])
-			if current == false then
-				current = 0
-			else
-				current = tonumber(current)
-			end
-
-			if current >= tonumber(ARGV[1]) then
-				return 0
-			end
-
-			local newVal = redis.call('INCR', KEYS[1])
-
-			-- Only set TTL on first creation to avoid refreshing zombie data
-			if newVal == 1 then
-				redis.call('EXPIRE', KEYS[1], ARGV[2])
-			end
-
-			return 1
-		`)
+		return 1
+	`)

 	// decrementWaitScript - same as before
 	decrementWaitScript = redis.NewScript(`
-			local current = redis.call('GET', KEYS[1])
-			if current ~= false and tonumber(current) > 0 then
-				redis.call('DECR', KEYS[1])
-			end
-			return 1
-		`)
-
-	// getAccountsLoadBatchScript - batch load query (read-only)
-	// ARGV[1] = slot TTL (seconds, retained for compatibility)
-	// ARGV[2..n] = accountID1, maxConcurrency1, accountID2, maxConcurrency2, ...
-	getAccountsLoadBatchScript = redis.NewScript(`
-			local result = {}
-
-			local i = 2
-			while i <= #ARGV do
-				local accountID = ARGV[i]
-				local maxConcurrency = tonumber(ARGV[i + 1])
-
-				local slotKey = 'concurrency:account:' .. accountID
-				local currentConcurrency = redis.call('ZCARD', slotKey)
-
-				local waitKey = 'wait:account:' .. accountID
-				local waitingCount = redis.call('GET', waitKey)
-				if waitingCount == false then
-					waitingCount = 0
-				else
-					waitingCount = tonumber(waitingCount)
-				end
-
-				local loadRate = 0
-				if maxConcurrency > 0 then
-					loadRate = math.floor((currentConcurrency + waitingCount) * 100 / maxConcurrency)
-				end
-
-				table.insert(result, accountID)
-				table.insert(result, currentConcurrency)
-				table.insert(result, waitingCount)
-				table.insert(result, loadRate)
-
-				i = i + 2
-			end
-
-			return result
-		`)
-
-	// cleanupExpiredSlotsScript - remove expired slots
-	// KEYS[1] = concurrency:account:{accountID}
-	// ARGV[1] = TTL (seconds)
-	cleanupExpiredSlotsScript = redis.NewScript(`
-			local key = KEYS[1]
-			local ttl = tonumber(ARGV[1])
-			local timeResult = redis.call('TIME')
-			local now = tonumber(timeResult[1])
-			local expireBefore = now - ttl
-			return redis.call('ZREMRANGEBYSCORE', key, '-inf', expireBefore)
-		`)
+		local current = redis.call('GET', KEYS[1])
+		if current ~= false and tonumber(current) > 0 then
+			redis.call('DECR', KEYS[1])
+		end
+		return 1
+	`)
 )

 type concurrencyCache struct {
-	rdb                 *redis.Client
-	slotTTLSeconds      int // 槽位过期时间（秒）
-	waitQueueTTLSeconds int // 等待队列过期时间（秒）
+	rdb            *redis.Client
+	slotTTLSeconds int // 槽位过期时间（秒）
 }

 // NewConcurrencyCache 创建并发控制缓存
 // slotTTLMinutes: 槽位过期时间（分钟），0 或负数使用默认值 15 分钟
-// waitQueueTTLSeconds: 等待队列过期时间（秒），0 或负数使用 slot TTL
-func NewConcurrencyCache(rdb *redis.Client, slotTTLMinutes int, waitQueueTTLSeconds int) service.ConcurrencyCache {
+func NewConcurrencyCache(rdb *redis.Client, slotTTLMinutes int) service.ConcurrencyCache {
 	if slotTTLMinutes <= 0 {
 		slotTTLMinutes = defaultSlotTTLMinutes
 	}
-	if waitQueueTTLSeconds <= 0 {
-		waitQueueTTLSeconds = slotTTLMinutes * 60
-	}
 	return &concurrencyCache{
-		rdb:                 rdb,
-		slotTTLSeconds:      slotTTLMinutes * 60,
-		waitQueueTTLSeconds: waitQueueTTLSeconds,
+		rdb:            rdb,
+		slotTTLSeconds: slotTTLMinutes * 60,
 	}
 }

@@ -238,10 +155,6 @@ func waitQueueKey(userID int64) string {
 	return fmt.Sprintf("%s%d", waitQueueKeyPrefix, userID)
 }

-func accountWaitKey(accountID int64) string {
-	return fmt.Sprintf("%s%d", accountWaitKeyPrefix, accountID)
-}
-
 // Account slot operations

 func (c *concurrencyCache) AcquireAccountSlot(ctx context.Context, accountID int64, maxConcurrency int, requestID string) (bool, error) {
@@ -312,75 +225,3 @@ func (c *concurrencyCache) DecrementWaitCount(ctx context.Context, userID int64)
 	_, err := decrementWaitScript.Run(ctx, c.rdb, []string{key}).Result()
 	return err
 }
-
-// Account wait queue operations
-
-func (c *concurrencyCache) IncrementAccountWaitCount(ctx context.Context, accountID int64, maxWait int) (bool, error) {
-	key := accountWaitKey(accountID)
-	result, err := incrementAccountWaitScript.Run(ctx, c.rdb, []string{key}, maxWait, c.waitQueueTTLSeconds).Int()
-	if err != nil {
-		return false, err
-	}
-	return result == 1, nil
-}
-
-func (c *concurrencyCache) DecrementAccountWaitCount(ctx context.Context, accountID int64) error {
-	key := accountWaitKey(accountID)
-	_, err := decrementWaitScript.Run(ctx, c.rdb, []string{key}).Result()
-	return err
-}
-
-func (c *concurrencyCache) GetAccountWaitingCount(ctx context.Context, accountID int64) (int, error) {
-	key := accountWaitKey(accountID)
-	val, err := c.rdb.Get(ctx, key).Int()
-	if err != nil && !errors.Is(err, redis.Nil) {
-		return 0, err
-	}
-	if errors.Is(err, redis.Nil) {
-		return 0, nil
-	}
-	return val, nil
-}
-
-func (c *concurrencyCache) GetAccountsLoadBatch(ctx context.Context, accounts []service.AccountWithConcurrency) (map[int64]*service.AccountLoadInfo, error) {
-	if len(accounts) == 0 {
-		return map[int64]*service.AccountLoadInfo{}, nil
-	}
-
-	args := []any{c.slotTTLSeconds}
-	for _, acc := range accounts {
-		args = append(args, acc.ID, acc.MaxConcurrency)
-	}
-
-	result, err := getAccountsLoadBatchScript.Run(ctx, c.rdb, []string{}, args...).Slice()
-	if err != nil {
-		return nil, err
-	}
-
-	loadMap := make(map[int64]*service.AccountLoadInfo)
-	for i := 0; i < len(result); i += 4 {
-		if i+3 >= len(result) {
-			break
-		}
-
-		accountID, _ := strconv.ParseInt(fmt.Sprintf("%v", result[i]), 10, 64)
-		currentConcurrency, _ := strconv.Atoi(fmt.Sprintf("%v", result[i+1]))
-		waitingCount, _ := strconv.Atoi(fmt.Sprintf("%v", result[i+2]))
-		loadRate, _ := strconv.Atoi(fmt.Sprintf("%v", result[i+3]))
-
-		loadMap[accountID] = &service.AccountLoadInfo{
-			AccountID:          accountID,
-			CurrentConcurrency: currentConcurrency,
-			WaitingCount:       waitingCount,
-			LoadRate:           loadRate,
-		}
-	}
-
-	return loadMap, nil
-}
-
-func (c *concurrencyCache) CleanupExpiredAccountSlots(ctx context.Context, accountID int64) error {
-	key := accountSlotKey(accountID)
-	_, err := cleanupExpiredSlotsScript.Run(ctx, c.rdb, []string{key}, c.slotTTLSeconds).Result()
-	return err
-}
--- a/backend/internal/repository/concurrency_cache_benchmark_test.go
+++ b/backend/internal/repository/concurrency_cache_benchmark_test.go
@@ -22,7 +22,7 @@ func BenchmarkAccountConcurrency(b *testing.B) {
 		_ = rdb.Close()
 	}()

-	cache, _ := NewConcurrencyCache(rdb, benchSlotTTLMinutes, int(benchSlotTTL.Seconds())).(*concurrencyCache)
+	cache, _ := NewConcurrencyCache(rdb, benchSlotTTLMinutes).(*concurrencyCache)
 	ctx := context.Background()

 	for _, size := range []int{10, 100, 1000} {
--- a/backend/internal/repository/concurrency_cache_integration_test.go
+++ b/backend/internal/repository/concurrency_cache_integration_test.go
@@ -27,7 +27,7 @@ type ConcurrencyCacheSuite struct {

 func (s *ConcurrencyCacheSuite) SetupTest() {
 	s.IntegrationRedisSuite.SetupTest()
-	s.cache = NewConcurrencyCache(s.rdb, testSlotTTLMinutes, int(testSlotTTL.Seconds()))
+	s.cache = NewConcurrencyCache(s.rdb, testSlotTTLMinutes)
 }

 func (s *ConcurrencyCacheSuite) TestAccountSlot_AcquireAndRelease() {
@@ -218,48 +218,6 @@ func (s *ConcurrencyCacheSuite) TestWaitQueue_DecrementNoNegative() {
 	require.GreaterOrEqual(s.T(), val, 0, "expected non-negative wait count")
 }

-func (s *ConcurrencyCacheSuite) TestAccountWaitQueue_IncrementAndDecrement() {
-	accountID := int64(30)
-	waitKey := fmt.Sprintf("%s%d", accountWaitKeyPrefix, accountID)
-
-	ok, err := s.cache.IncrementAccountWaitCount(s.ctx, accountID, 2)
-	require.NoError(s.T(), err, "IncrementAccountWaitCount 1")
-	require.True(s.T(), ok)
-
-	ok, err = s.cache.IncrementAccountWaitCount(s.ctx, accountID, 2)
-	require.NoError(s.T(), err, "IncrementAccountWaitCount 2")
-	require.True(s.T(), ok)
-
-	ok, err = s.cache.IncrementAccountWaitCount(s.ctx, accountID, 2)
-	require.NoError(s.T(), err, "IncrementAccountWaitCount 3")
-	require.False(s.T(), ok, "expected account wait increment over max to fail")
-
-	ttl, err := s.rdb.TTL(s.ctx, waitKey).Result()
-	require.NoError(s.T(), err, "TTL account waitKey")
-	s.AssertTTLWithin(ttl, 1*time.Second, testSlotTTL)
-
-	require.NoError(s.T(), s.cache.DecrementAccountWaitCount(s.ctx, accountID), "DecrementAccountWaitCount")
-
-	val, err := s.rdb.Get(s.ctx, waitKey).Int()
-	if !errors.Is(err, redis.Nil) {
-		require.NoError(s.T(), err, "Get waitKey")
-	}
-	require.Equal(s.T(), 1, val, "expected account wait count 1")
-}
-
-func (s *ConcurrencyCacheSuite) TestAccountWaitQueue_DecrementNoNegative() {
-	accountID := int64(301)
-	waitKey := fmt.Sprintf("%s%d", accountWaitKeyPrefix, accountID)
-
-	require.NoError(s.T(), s.cache.DecrementAccountWaitCount(s.ctx, accountID), "DecrementAccountWaitCount on non-existent key")
-
-	val, err := s.rdb.Get(s.ctx, waitKey).Int()
-	if !errors.Is(err, redis.Nil) {
-		require.NoError(s.T(), err, "Get waitKey")
-	}
-	require.GreaterOrEqual(s.T(), val, 0, "expected non-negative account wait count after decrement on empty")
-}
-
 func (s *ConcurrencyCacheSuite) TestGetAccountConcurrency_Missing() {
 	// When no slots exist, GetAccountConcurrency should return 0
 	cur, err := s.cache.GetAccountConcurrency(s.ctx, 999)
@@ -274,139 +232,6 @@ func (s *ConcurrencyCacheSuite) TestGetUserConcurrency_Missing() {
 	require.Equal(s.T(), 0, cur)
 }

-func (s *ConcurrencyCacheSuite) TestGetAccountsLoadBatch() {
-	s.T().Skip("TODO: Fix this test - CurrentConcurrency returns 0 instead of expected value in CI")
-	// Setup: Create accounts with different load states
-	account1 := int64(100)
-	account2 := int64(101)
-	account3 := int64(102)
-
-	// Account 1: 2/3 slots used, 1 waiting
-	ok, err := s.cache.AcquireAccountSlot(s.ctx, account1, 3, "req1")
-	require.NoError(s.T(), err)
-	require.True(s.T(), ok)
-	ok, err = s.cache.AcquireAccountSlot(s.ctx, account1, 3, "req2")
-	require.NoError(s.T(), err)
-	require.True(s.T(), ok)
-	ok, err = s.cache.IncrementAccountWaitCount(s.ctx, account1, 5)
-	require.NoError(s.T(), err)
-	require.True(s.T(), ok)
-
-	// Account 2: 1/2 slots used, 0 waiting
-	ok, err = s.cache.AcquireAccountSlot(s.ctx, account2, 2, "req3")
-	require.NoError(s.T(), err)
-	require.True(s.T(), ok)
-
-	// Account 3: 0/1 slots used, 0 waiting (idle)
-
-	// Query batch load
-	accounts := []service.AccountWithConcurrency{
-		{ID: account1, MaxConcurrency: 3},
-		{ID: account2, MaxConcurrency: 2},
-		{ID: account3, MaxConcurrency: 1},
-	}
-
-	loadMap, err := s.cache.GetAccountsLoadBatch(s.ctx, accounts)
-	require.NoError(s.T(), err)
-	require.Len(s.T(), loadMap, 3)
-
-	// Verify account1: (2 + 1) / 3 = 100%
-	load1 := loadMap[account1]
-	require.NotNil(s.T(), load1)
-	require.Equal(s.T(), account1, load1.AccountID)
-	require.Equal(s.T(), 2, load1.CurrentConcurrency)
-	require.Equal(s.T(), 1, load1.WaitingCount)
-	require.Equal(s.T(), 100, load1.LoadRate)
-
-	// Verify account2: (1 + 0) / 2 = 50%
-	load2 := loadMap[account2]
-	require.NotNil(s.T(), load2)
-	require.Equal(s.T(), account2, load2.AccountID)
-	require.Equal(s.T(), 1, load2.CurrentConcurrency)
-	require.Equal(s.T(), 0, load2.WaitingCount)
-	require.Equal(s.T(), 50, load2.LoadRate)
-
-	// Verify account3: (0 + 0) / 1 = 0%
-	load3 := loadMap[account3]
-	require.NotNil(s.T(), load3)
-	require.Equal(s.T(), account3, load3.AccountID)
-	require.Equal(s.T(), 0, load3.CurrentConcurrency)
-	require.Equal(s.T(), 0, load3.WaitingCount)
-	require.Equal(s.T(), 0, load3.LoadRate)
-}
-
-func (s *ConcurrencyCacheSuite) TestGetAccountsLoadBatch_Empty() {
-	// Test with empty account list
-	loadMap, err := s.cache.GetAccountsLoadBatch(s.ctx, []service.AccountWithConcurrency{})
-	require.NoError(s.T(), err)
-	require.Empty(s.T(), loadMap)
-}
-
-func (s *ConcurrencyCacheSuite) TestCleanupExpiredAccountSlots() {
-	accountID := int64(200)
-	slotKey := fmt.Sprintf("%s%d", accountSlotKeyPrefix, accountID)
-
-	// Acquire 3 slots
-	ok, err := s.cache.AcquireAccountSlot(s.ctx, accountID, 5, "req1")
-	require.NoError(s.T(), err)
-	require.True(s.T(), ok)
-	ok, err = s.cache.AcquireAccountSlot(s.ctx, accountID, 5, "req2")
-	require.NoError(s.T(), err)
-	require.True(s.T(), ok)
-	ok, err = s.cache.AcquireAccountSlot(s.ctx, accountID, 5, "req3")
-	require.NoError(s.T(), err)
-	require.True(s.T(), ok)
-
-	// Verify 3 slots exist
-	cur, err := s.cache.GetAccountConcurrency(s.ctx, accountID)
-	require.NoError(s.T(), err)
-	require.Equal(s.T(), 3, cur)
-
-	// Manually set old timestamps for req1 and req2 (simulate expired slots)
-	now := time.Now().Unix()
-	expiredTime := now - int64(testSlotTTL.Seconds()) - 10 // 10 seconds past TTL
-	err = s.rdb.ZAdd(s.ctx, slotKey, redis.Z{Score: float64(expiredTime), Member: "req1"}).Err()
-	require.NoError(s.T(), err)
-	err = s.rdb.ZAdd(s.ctx, slotKey, redis.Z{Score: float64(expiredTime), Member: "req2"}).Err()
-	require.NoError(s.T(), err)
-
-	// Run cleanup
-	err = s.cache.CleanupExpiredAccountSlots(s.ctx, accountID)
-	require.NoError(s.T(), err)
-
-	// Verify only 1 slot remains (req3)
-	cur, err = s.cache.GetAccountConcurrency(s.ctx, accountID)
-	require.NoError(s.T(), err)
-	require.Equal(s.T(), 1, cur)
-
-	// Verify req3 still exists
-	members, err := s.rdb.ZRange(s.ctx, slotKey, 0, -1).Result()
-	require.NoError(s.T(), err)
-	require.Len(s.T(), members, 1)
-	require.Equal(s.T(), "req3", members[0])
-}
-
-func (s *ConcurrencyCacheSuite) TestCleanupExpiredAccountSlots_NoExpired() {
-	accountID := int64(201)
-
-	// Acquire 2 fresh slots
-	ok, err := s.cache.AcquireAccountSlot(s.ctx, accountID, 5, "req1")
-	require.NoError(s.T(), err)
-	require.True(s.T(), ok)
-	ok, err = s.cache.AcquireAccountSlot(s.ctx, accountID, 5, "req2")
-	require.NoError(s.T(), err)
-	require.True(s.T(), ok)
-
-	// Run cleanup (should not remove anything)
-	err = s.cache.CleanupExpiredAccountSlots(s.ctx, accountID)
-	require.NoError(s.T(), err)
-
-	// Verify both slots still exist
-	cur, err := s.cache.GetAccountConcurrency(s.ctx, accountID)
-	require.NoError(s.T(), err)
-	require.Equal(s.T(), 2, cur)
-}
-
 func TestConcurrencyCacheSuite(t *testing.T) {
 	suite.Run(t, new(ConcurrencyCacheSuite))
 }
--- a/backend/internal/repository/wire.go
+++ b/backend/internal/repository/wire.go
@@ -15,14 +15,7 @@ import (
 // ProvideConcurrencyCache 创建并发控制缓存，从配置读取 TTL 参数
 // 性能优化：TTL 可配置，支持长时间运行的 LLM 请求场景
 func ProvideConcurrencyCache(rdb *redis.Client, cfg *config.Config) service.ConcurrencyCache {
-	waitTTLSeconds := int(cfg.Gateway.Scheduling.StickySessionWaitTimeout.Seconds())
-	if cfg.Gateway.Scheduling.FallbackWaitTimeout > cfg.Gateway.Scheduling.StickySessionWaitTimeout {
-		waitTTLSeconds = int(cfg.Gateway.Scheduling.FallbackWaitTimeout.Seconds())
-	}
-	if waitTTLSeconds <= 0 {
-		waitTTLSeconds = cfg.Gateway.ConcurrencySlotTTLMinutes * 60
-	}
-	return NewConcurrencyCache(rdb, cfg.Gateway.ConcurrencySlotTTLMinutes, waitTTLSeconds)
+	return NewConcurrencyCache(rdb, cfg.Gateway.ConcurrencySlotTTLMinutes)
 }

 // ProviderSet is the Wire provider set for all repositories
--- a/backend/internal/service/antigravity_gateway_service.go
+++ b/backend/internal/service/antigravity_gateway_service.go
@@ -358,15 +358,6 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 		return nil, fmt.Errorf("transform request: %w", err)
 	}

-	// 调试：记录转换后的请求体（仅记录前 2000 字符）
-	if bodyJSON, err := json.Marshal(geminiBody); err == nil {
-		truncated := string(bodyJSON)
-		if len(truncated) > 2000 {
-			truncated = truncated[:2000] + "..."
-		}
-		log.Printf("[Debug] Transformed Gemini request: %s", truncated)
-	}
-
 	// 构建上游 action
 	action := "generateContent"
 	if claudeReq.Stream {
--- a/backend/internal/service/concurrency_service.go
+++ b/backend/internal/service/concurrency_service.go
@@ -18,11 +18,6 @@ type ConcurrencyCache interface {
 	ReleaseAccountSlot(ctx context.Context, accountID int64, requestID string) error
 	GetAccountConcurrency(ctx context.Context, accountID int64) (int, error)

-	// 账号等待队列（账号级）
-	IncrementAccountWaitCount(ctx context.Context, accountID int64, maxWait int) (bool, error)
-	DecrementAccountWaitCount(ctx context.Context, accountID int64) error
-	GetAccountWaitingCount(ctx context.Context, accountID int64) (int, error)
-
 	// 用户槽位管理
 	// 键格式: concurrency:user:{userID}（有序集合，成员为 requestID）
 	AcquireUserSlot(ctx context.Context, userID int64, maxConcurrency int, requestID string) (bool, error)
@@ -32,12 +27,6 @@ type ConcurrencyCache interface {
 	// 等待队列计数（只在首次创建时设置 TTL）
 	IncrementWaitCount(ctx context.Context, userID int64, maxWait int) (bool, error)
 	DecrementWaitCount(ctx context.Context, userID int64) error
-
-	// 批量负载查询（只读）
-	GetAccountsLoadBatch(ctx context.Context, accounts []AccountWithConcurrency) (map[int64]*AccountLoadInfo, error)
-
-	// 清理过期槽位（后台任务）
-	CleanupExpiredAccountSlots(ctx context.Context, accountID int64) error
 }

 // generateRequestID generates a unique request ID for concurrency slot tracking
@@ -72,18 +61,6 @@ type AcquireResult struct {
 	ReleaseFunc func() // Must be called when done (typically via defer)
 }

-type AccountWithConcurrency struct {
-	ID             int64
-	MaxConcurrency int
-}
-
-type AccountLoadInfo struct {
-	AccountID          int64
-	CurrentConcurrency int
-	WaitingCount       int
-	LoadRate           int // 0-100+ (percent)
-}
-
 // AcquireAccountSlot attempts to acquire a concurrency slot for an account.
 // If the account is at max concurrency, it waits until a slot is available or timeout.
 // Returns a release function that MUST be called when the request completes.
@@ -200,42 +177,6 @@ func (s *ConcurrencyService) DecrementWaitCount(ctx context.Context, userID int6
 	}
 }

-// IncrementAccountWaitCount increments the wait queue counter for an account.
-func (s *ConcurrencyService) IncrementAccountWaitCount(ctx context.Context, accountID int64, maxWait int) (bool, error) {
-	if s.cache == nil {
-		return true, nil
-	}
-
-	result, err := s.cache.IncrementAccountWaitCount(ctx, accountID, maxWait)
-	if err != nil {
-		log.Printf("Warning: increment wait count failed for account %d: %v", accountID, err)
-		return true, nil
-	}
-	return result, nil
-}
-
-// DecrementAccountWaitCount decrements the wait queue counter for an account.
-func (s *ConcurrencyService) DecrementAccountWaitCount(ctx context.Context, accountID int64) {
-	if s.cache == nil {
-		return
-	}
-
-	bgCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-	defer cancel()
-
-	if err := s.cache.DecrementAccountWaitCount(bgCtx, accountID); err != nil {
-		log.Printf("Warning: decrement wait count failed for account %d: %v", accountID, err)
-	}
-}
-
-// GetAccountWaitingCount gets current wait queue count for an account.
-func (s *ConcurrencyService) GetAccountWaitingCount(ctx context.Context, accountID int64) (int, error) {
-	if s.cache == nil {
-		return 0, nil
-	}
-	return s.cache.GetAccountWaitingCount(ctx, accountID)
-}
-
 // CalculateMaxWait calculates the maximum wait queue size for a user
 // maxWait = userConcurrency + defaultExtraWaitSlots
 func CalculateMaxWait(userConcurrency int) int {
@@ -245,57 +186,6 @@ func CalculateMaxWait(userConcurrency int) int {
 	return userConcurrency + defaultExtraWaitSlots
 }

-// GetAccountsLoadBatch returns load info for multiple accounts.
-func (s *ConcurrencyService) GetAccountsLoadBatch(ctx context.Context, accounts []AccountWithConcurrency) (map[int64]*AccountLoadInfo, error) {
-	if s.cache == nil {
-		return map[int64]*AccountLoadInfo{}, nil
-	}
-	return s.cache.GetAccountsLoadBatch(ctx, accounts)
-}
-
-// CleanupExpiredAccountSlots removes expired slots for one account (background task).
-func (s *ConcurrencyService) CleanupExpiredAccountSlots(ctx context.Context, accountID int64) error {
-	if s.cache == nil {
-		return nil
-	}
-	return s.cache.CleanupExpiredAccountSlots(ctx, accountID)
-}
-
-// StartSlotCleanupWorker starts a background cleanup worker for expired account slots.
-func (s *ConcurrencyService) StartSlotCleanupWorker(accountRepo AccountRepository, interval time.Duration) {
-	if s == nil || s.cache == nil || accountRepo == nil || interval <= 0 {
-		return
-	}
-
-	runCleanup := func() {
-		listCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-		accounts, err := accountRepo.ListSchedulable(listCtx)
-		cancel()
-		if err != nil {
-			log.Printf("Warning: list schedulable accounts failed: %v", err)
-			return
-		}
-		for _, account := range accounts {
-			accountCtx, accountCancel := context.WithTimeout(context.Background(), 2*time.Second)
-			err := s.cache.CleanupExpiredAccountSlots(accountCtx, account.ID)
-			accountCancel()
-			if err != nil {
-				log.Printf("Warning: cleanup expired slots failed for account %d: %v", account.ID, err)
-			}
-		}
-	}
-
-	go func() {
-		ticker := time.NewTicker(interval)
-		defer ticker.Stop()
-
-		runCleanup()
-		for range ticker.C {
-			runCleanup()
-		}
-	}()
-}
-
 // GetAccountConcurrencyBatch gets current concurrency counts for multiple accounts
 // Returns a map of accountID -> current concurrency count
 func (s *ConcurrencyService) GetAccountConcurrencyBatch(ctx context.Context, accountIDs []int64) (map[int64]int, error) {
--- a/backend/internal/service/gateway_multiplatform_test.go
+++ b/backend/internal/service/gateway_multiplatform_test.go
@@ -261,34 +261,6 @@ func TestGatewayService_SelectAccountForModelWithPlatform_PriorityAndLastUsed(t
 	require.Equal(t, int64(2), acc.ID, "同优先级应选择最久未用的账户")
 }

-func TestGatewayService_SelectAccountForModelWithPlatform_GeminiOAuthPreference(t *testing.T) {
-	ctx := context.Background()
-
-	repo := &mockAccountRepoForPlatform{
-		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 := &mockGatewayCacheForPlatform{}
-
-	svc := &GatewayService{
-		accountRepo: repo,
-		cache:       cache,
-		cfg:         testConfig(),
-	}
-
-	acc, err := svc.selectAccountForModelWithPlatform(ctx, nil, "", "gemini-2.5-pro", nil, PlatformGemini)
-	require.NoError(t, err)
-	require.NotNil(t, acc)
-	require.Equal(t, int64(2), acc.ID, "同优先级且未使用时应优先选择OAuth账户")
-}
-
 // TestGatewayService_SelectAccountForModelWithPlatform_NoAvailableAccounts 测试无可用账户
 func TestGatewayService_SelectAccountForModelWithPlatform_NoAvailableAccounts(t *testing.T) {
 	ctx := context.Background()
@@ -604,32 +576,6 @@ func TestGatewayService_isModelSupportedByAccount(t *testing.T) {
 func TestGatewayService_selectAccountWithMixedScheduling(t *testing.T) {
 	ctx := context.Background()

-	t.Run("混合调度-Gemini优先选择OAuth账户", func(t *testing.T) {
-		repo := &mockAccountRepoForPlatform{
-			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 := &mockGatewayCacheForPlatform{}
-
-		svc := &GatewayService{
-			accountRepo: repo,
-			cache:       cache,
-			cfg:         testConfig(),
-		}
-
-		acc, err := svc.selectAccountWithMixedScheduling(ctx, nil, "", "gemini-2.5-pro", nil, PlatformGemini)
-		require.NoError(t, err)
-		require.NotNil(t, acc)
-		require.Equal(t, int64(2), acc.ID, "同优先级且未使用时应优先选择OAuth账户")
-	})
-
 	t.Run("混合调度-包含启用mixed_scheduling的antigravity账户", func(t *testing.T) {
 		repo := &mockAccountRepoForPlatform{
 			accounts: []Account{
@@ -837,160 +783,3 @@ func TestAccount_IsMixedSchedulingEnabled(t *testing.T) {
 		})
 	}
 }
-
-// mockConcurrencyService for testing
-type mockConcurrencyService struct {
-	accountLoads      map[int64]*AccountLoadInfo
-	accountWaitCounts map[int64]int
-	acquireResults    map[int64]bool
-}
-
-func (m *mockConcurrencyService) GetAccountsLoadBatch(ctx context.Context, accounts []AccountWithConcurrency) (map[int64]*AccountLoadInfo, error) {
-	if m.accountLoads == nil {
-		return map[int64]*AccountLoadInfo{}, nil
-	}
-	result := make(map[int64]*AccountLoadInfo)
-	for _, acc := range accounts {
-		if load, ok := m.accountLoads[acc.ID]; ok {
-			result[acc.ID] = load
-		} else {
-			result[acc.ID] = &AccountLoadInfo{
-				AccountID:          acc.ID,
-				CurrentConcurrency: 0,
-				WaitingCount:       0,
-				LoadRate:           0,
-			}
-		}
-	}
-	return result, nil
-}
-
-func (m *mockConcurrencyService) GetAccountWaitingCount(ctx context.Context, accountID int64) (int, error) {
-	if m.accountWaitCounts == nil {
-		return 0, nil
-	}
-	return m.accountWaitCounts[accountID], nil
-}
-
-// TestGatewayService_SelectAccountWithLoadAwareness tests load-aware account selection
-func TestGatewayService_SelectAccountWithLoadAwareness(t *testing.T) {
-	ctx := context.Background()
-
-	t.Run("禁用负载批量查询-降级到传统选择", func(t *testing.T) {
-		repo := &mockAccountRepoForPlatform{
-			accounts: []Account{
-				{ID: 1, Platform: PlatformAnthropic, Priority: 1, Status: StatusActive, Schedulable: true, Concurrency: 5},
-				{ID: 2, Platform: PlatformAnthropic, Priority: 2, Status: StatusActive, Schedulable: true, Concurrency: 5},
-			},
-			accountsByID: map[int64]*Account{},
-		}
-		for i := range repo.accounts {
-			repo.accountsByID[repo.accounts[i].ID] = &repo.accounts[i]
-		}
-
-		cache := &mockGatewayCacheForPlatform{}
-
-		cfg := testConfig()
-		cfg.Gateway.Scheduling.LoadBatchEnabled = false
-
-		svc := &GatewayService{
-			accountRepo:        repo,
-			cache:              cache,
-			cfg:                cfg,
-			concurrencyService: nil, // No concurrency service
-		}
-
-		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)
-		require.Equal(t, int64(1), result.Account.ID, "应选择优先级最高的账号")
-	})
-
-	t.Run("无ConcurrencyService-降级到传统选择", func(t *testing.T) {
-		repo := &mockAccountRepoForPlatform{
-			accounts: []Account{
-				{ID: 1, Platform: PlatformAnthropic, Priority: 2, Status: StatusActive, Schedulable: true, Concurrency: 5},
-				{ID: 2, Platform: PlatformAnthropic, Priority: 1, Status: StatusActive, Schedulable: true, Concurrency: 5},
-			},
-			accountsByID: map[int64]*Account{},
-		}
-		for i := range repo.accounts {
-			repo.accountsByID[repo.accounts[i].ID] = &repo.accounts[i]
-		}
-
-		cache := &mockGatewayCacheForPlatform{}
-
-		cfg := testConfig()
-		cfg.Gateway.Scheduling.LoadBatchEnabled = true
-
-		svc := &GatewayService{
-			accountRepo:        repo,
-			cache:              cache,
-			cfg:                cfg,
-			concurrencyService: 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)
-		require.Equal(t, int64(2), result.Account.ID, "应选择优先级最高的账号")
-	})
-
-	t.Run("排除账号-不选择被排除的账号", func(t *testing.T) {
-		repo := &mockAccountRepoForPlatform{
-			accounts: []Account{
-				{ID: 1, Platform: PlatformAnthropic, Priority: 1, Status: StatusActive, Schedulable: true, Concurrency: 5},
-				{ID: 2, Platform: PlatformAnthropic, Priority: 2, Status: StatusActive, Schedulable: true, Concurrency: 5},
-			},
-			accountsByID: map[int64]*Account{},
-		}
-		for i := range repo.accounts {
-			repo.accountsByID[repo.accounts[i].ID] = &repo.accounts[i]
-		}
-
-		cache := &mockGatewayCacheForPlatform{}
-
-		cfg := testConfig()
-		cfg.Gateway.Scheduling.LoadBatchEnabled = false
-
-		svc := &GatewayService{
-			accountRepo:        repo,
-			cache:              cache,
-			cfg:                cfg,
-			concurrencyService: nil,
-		}
-
-		excludedIDs := map[int64]struct{}{1: {}}
-		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)
-		require.Equal(t, int64(2), result.Account.ID, "不应选择被排除的账号")
-	})
-
-	t.Run("无可用账号-返回错误", func(t *testing.T) {
-		repo := &mockAccountRepoForPlatform{
-			accounts:     []Account{},
-			accountsByID: map[int64]*Account{},
-		}
-
-		cache := &mockGatewayCacheForPlatform{}
-
-		cfg := testConfig()
-		cfg.Gateway.Scheduling.LoadBatchEnabled = false
-
-		svc := &GatewayService{
-			accountRepo:        repo,
-			cache:              cache,
-			cfg:                cfg,
-			concurrencyService: 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")
-	})
-}
--- a/backend/internal/service/gateway_service.go
+++ b/backend/internal/service/gateway_service.go
@@ -13,14 +13,12 @@ import (
 	"log"
 	"net/http"
 	"regexp"
-	"sort"
 	"strings"
 	"time"

 	"github.com/Wei-Shaw/sub2api/internal/config"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/claude"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/ctxkey"
-	"github.com/tidwall/gjson"
 	"github.com/tidwall/sjson"

 	"github.com/gin-gonic/gin"
@@ -68,20 +66,6 @@ type GatewayCache interface {
 	RefreshSessionTTL(ctx context.Context, sessionHash string, ttl time.Duration) error
 }

-type AccountWaitPlan struct {
-	AccountID      int64
-	MaxConcurrency int
-	Timeout        time.Duration
-	MaxWaiting     int
-}
-
-type AccountSelectionResult struct {
-	Account     *Account
-	Acquired    bool
-	ReleaseFunc func()
-	WaitPlan    *AccountWaitPlan // nil means no wait allowed
-}
-
 // ClaudeUsage 表示Claude API返回的usage信息
 type ClaudeUsage struct {
 	InputTokens              int `json:"input_tokens"`
@@ -124,7 +108,6 @@ type GatewayService struct {
 	identityService     *IdentityService
 	httpUpstream        HTTPUpstream
 	deferredService     *DeferredService
-	concurrencyService  *ConcurrencyService
 }

 // NewGatewayService creates a new GatewayService
@@ -136,7 +119,6 @@ func NewGatewayService(
 	userSubRepo UserSubscriptionRepository,
 	cache GatewayCache,
 	cfg *config.Config,
-	concurrencyService *ConcurrencyService,
 	billingService *BillingService,
 	rateLimitService *RateLimitService,
 	billingCacheService *BillingCacheService,
@@ -152,7 +134,6 @@ func NewGatewayService(
 		userSubRepo:         userSubRepo,
 		cache:               cache,
 		cfg:                 cfg,
-		concurrencyService:  concurrencyService,
 		billingService:      billingService,
 		rateLimitService:    rateLimitService,
 		billingCacheService: billingCacheService,
@@ -202,14 +183,6 @@ func (s *GatewayService) GenerateSessionHash(parsed *ParsedRequest) string {
 	return ""
 }

-// BindStickySession sets session -> account binding with standard TTL.
-func (s *GatewayService) BindStickySession(ctx context.Context, sessionHash string, accountID int64) error {
-	if sessionHash == "" || accountID <= 0 {
-		return nil
-	}
-	return s.cache.SetSessionAccountID(ctx, sessionHash, accountID, stickySessionTTL)
-}
-
 func (s *GatewayService) extractCacheableContent(parsed *ParsedRequest) string {
 	if parsed == nil {
 		return ""
@@ -359,354 +332,8 @@ func (s *GatewayService) SelectAccountForModelWithExclusions(ctx context.Context
 	return s.selectAccountForModelWithPlatform(ctx, groupID, sessionHash, requestedModel, excludedIDs, platform)
 }

-// 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) {
-	cfg := s.schedulingConfig()
-	var stickyAccountID int64
-	if sessionHash != "" && s.cache != nil {
-		if accountID, err := s.cache.GetSessionAccountID(ctx, sessionHash); err == nil {
-			stickyAccountID = accountID
-		}
-	}
-	if s.concurrencyService == nil || !cfg.LoadBatchEnabled {
-		account, err := s.SelectAccountForModelWithExclusions(ctx, groupID, sessionHash, requestedModel, excludedIDs)
-		if err != nil {
-			return nil, err
-		}
-		result, err := s.tryAcquireAccountSlot(ctx, account.ID, account.Concurrency)
-		if err == nil && result.Acquired {
-			return &AccountSelectionResult{
-				Account:     account,
-				Acquired:    true,
-				ReleaseFunc: result.ReleaseFunc,
-			}, nil
-		}
-		if stickyAccountID > 0 && stickyAccountID == account.ID && s.concurrencyService != nil {
-			waitingCount, _ := s.concurrencyService.GetAccountWaitingCount(ctx, account.ID)
-			if waitingCount < cfg.StickySessionMaxWaiting {
-				return &AccountSelectionResult{
-					Account: account,
-					WaitPlan: &AccountWaitPlan{
-						AccountID:      account.ID,
-						MaxConcurrency: account.Concurrency,
-						Timeout:        cfg.StickySessionWaitTimeout,
-						MaxWaiting:     cfg.StickySessionMaxWaiting,
-					},
-				}, nil
-			}
-		}
-		return &AccountSelectionResult{
-			Account: account,
-			WaitPlan: &AccountWaitPlan{
-				AccountID:      account.ID,
-				MaxConcurrency: account.Concurrency,
-				Timeout:        cfg.FallbackWaitTimeout,
-				MaxWaiting:     cfg.FallbackMaxWaiting,
-			},
-		}, nil
-	}
-
-	platform, hasForcePlatform, err := s.resolvePlatform(ctx, groupID)
-	if err != nil {
-		return nil, err
-	}
-	preferOAuth := platform == PlatformGemini
-
-	accounts, useMixed, err := s.listSchedulableAccounts(ctx, groupID, platform, hasForcePlatform)
-	if err != nil {
-		return nil, err
-	}
-	if len(accounts) == 0 {
-		return nil, errors.New("no available accounts")
-	}
-
-	isExcluded := func(accountID int64) bool {
-		if excludedIDs == nil {
-			return false
-		}
-		_, excluded := excludedIDs[accountID]
-		return excluded
-	}
-
-	// ============ Layer 1: 粘性会话优先 ============
-	if sessionHash != "" {
-		accountID, err := s.cache.GetSessionAccountID(ctx, sessionHash)
-		if err == nil && accountID > 0 && !isExcluded(accountID) {
-			account, err := s.accountRepo.GetByID(ctx, accountID)
-			if err == nil && s.isAccountAllowedForPlatform(account, platform, useMixed) &&
-				account.IsSchedulable() &&
-				(requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) {
-				result, err := s.tryAcquireAccountSlot(ctx, accountID, account.Concurrency)
-				if err == nil && result.Acquired {
-					_ = s.cache.RefreshSessionTTL(ctx, sessionHash, stickySessionTTL)
-					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
-				}
-			}
-		}
-	}
-
-	// ============ Layer 2: 负载感知选择 ============
-	candidates := make([]*Account, 0, len(accounts))
-	for i := range accounts {
-		acc := &accounts[i]
-		if isExcluded(acc.ID) {
-			continue
-		}
-		if !s.isAccountAllowedForPlatform(acc, platform, useMixed) {
-			continue
-		}
-		if requestedModel != "" && !s.isModelSupportedByAccount(acc, requestedModel) {
-			continue
-		}
-		candidates = append(candidates, acc)
-	}
-
-	if len(candidates) == 0 {
-		return nil, errors.New("no available accounts")
-	}
-
-	accountLoads := make([]AccountWithConcurrency, 0, len(candidates))
-	for _, acc := range candidates {
-		accountLoads = append(accountLoads, AccountWithConcurrency{
-			ID:             acc.ID,
-			MaxConcurrency: acc.Concurrency,
-		})
-	}
-
-	loadMap, err := s.concurrencyService.GetAccountsLoadBatch(ctx, accountLoads)
-	if err != nil {
-		if result, ok := s.tryAcquireByLegacyOrder(ctx, candidates, sessionHash, preferOAuth); ok {
-			return result, nil
-		}
-	} else {
-		type accountWithLoad struct {
-			account  *Account
-			loadInfo *AccountLoadInfo
-		}
-		var available []accountWithLoad
-		for _, acc := range candidates {
-			loadInfo := loadMap[acc.ID]
-			if loadInfo == nil {
-				loadInfo = &AccountLoadInfo{AccountID: acc.ID}
-			}
-			if loadInfo.LoadRate < 100 {
-				available = append(available, accountWithLoad{
-					account:  acc,
-					loadInfo: loadInfo,
-				})
-			}
-		}
-
-		if len(available) > 0 {
-			sort.SliceStable(available, func(i, j int) bool {
-				a, b := available[i], available[j]
-				if a.account.Priority != b.account.Priority {
-					return a.account.Priority < b.account.Priority
-				}
-				if a.loadInfo.LoadRate != b.loadInfo.LoadRate {
-					return a.loadInfo.LoadRate < b.loadInfo.LoadRate
-				}
-				switch {
-				case a.account.LastUsedAt == nil && b.account.LastUsedAt != nil:
-					return true
-				case a.account.LastUsedAt != nil && b.account.LastUsedAt == nil:
-					return false
-				case a.account.LastUsedAt == nil && b.account.LastUsedAt == nil:
-					if preferOAuth && a.account.Type != b.account.Type {
-						return a.account.Type == AccountTypeOAuth
-					}
-					return false
-				default:
-					return a.account.LastUsedAt.Before(*b.account.LastUsedAt)
-				}
-			})
-
-			for _, item := range available {
-				result, err := s.tryAcquireAccountSlot(ctx, item.account.ID, item.account.Concurrency)
-				if err == nil && result.Acquired {
-					if sessionHash != "" {
-						_ = s.cache.SetSessionAccountID(ctx, sessionHash, item.account.ID, stickySessionTTL)
-					}
-					return &AccountSelectionResult{
-						Account:     item.account,
-						Acquired:    true,
-						ReleaseFunc: result.ReleaseFunc,
-					}, nil
-				}
-			}
-		}
-	}
-
-	// ============ Layer 3: 兜底排队 ============
-	sortAccountsByPriorityAndLastUsed(candidates, preferOAuth)
-	for _, acc := range candidates {
-		return &AccountSelectionResult{
-			Account: acc,
-			WaitPlan: &AccountWaitPlan{
-				AccountID:      acc.ID,
-				MaxConcurrency: acc.Concurrency,
-				Timeout:        cfg.FallbackWaitTimeout,
-				MaxWaiting:     cfg.FallbackMaxWaiting,
-			},
-		}, nil
-	}
-	return nil, errors.New("no available accounts")
-}
-
-func (s *GatewayService) tryAcquireByLegacyOrder(ctx context.Context, candidates []*Account, sessionHash string, preferOAuth bool) (*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 {
-			if sessionHash != "" {
-				_ = s.cache.SetSessionAccountID(ctx, sessionHash, acc.ID, stickySessionTTL)
-			}
-			return &AccountSelectionResult{
-				Account:     acc,
-				Acquired:    true,
-				ReleaseFunc: result.ReleaseFunc,
-			}, true
-		}
-	}
-
-	return nil, false
-}
-
-func (s *GatewayService) schedulingConfig() config.GatewaySchedulingConfig {
-	if s.cfg != nil {
-		return s.cfg.Gateway.Scheduling
-	}
-	return config.GatewaySchedulingConfig{
-		StickySessionMaxWaiting:  3,
-		StickySessionWaitTimeout: 45 * time.Second,
-		FallbackWaitTimeout:      30 * time.Second,
-		FallbackMaxWaiting:       100,
-		LoadBatchEnabled:         true,
-		SlotCleanupInterval:      30 * time.Second,
-	}
-}
-
-func (s *GatewayService) resolvePlatform(ctx context.Context, groupID *int64) (string, bool, error) {
-	forcePlatform, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string)
-	if hasForcePlatform && forcePlatform != "" {
-		return forcePlatform, true, nil
-	}
-	if groupID != nil {
-		group, err := s.groupRepo.GetByID(ctx, *groupID)
-		if err != nil {
-			return "", false, fmt.Errorf("get group failed: %w", err)
-		}
-		return group.Platform, false, nil
-	}
-	return PlatformAnthropic, false, nil
-}
-
-func (s *GatewayService) listSchedulableAccounts(ctx context.Context, groupID *int64, platform string, hasForcePlatform bool) ([]Account, bool, error) {
-	useMixed := (platform == PlatformAnthropic || platform == PlatformGemini) && !hasForcePlatform
-	if useMixed {
-		platforms := []string{platform, PlatformAntigravity}
-		var accounts []Account
-		var err error
-		if groupID != nil {
-			accounts, err = s.accountRepo.ListSchedulableByGroupIDAndPlatforms(ctx, *groupID, platforms)
-		} else {
-			accounts, err = s.accountRepo.ListSchedulableByPlatforms(ctx, platforms)
-		}
-		if err != nil {
-			return nil, useMixed, err
-		}
-		filtered := make([]Account, 0, len(accounts))
-		for _, acc := range accounts {
-			if acc.Platform == PlatformAntigravity && !acc.IsMixedSchedulingEnabled() {
-				continue
-			}
-			filtered = append(filtered, acc)
-		}
-		return filtered, useMixed, nil
-	}
-
-	var accounts []Account
-	var err error
-	if s.cfg != nil && s.cfg.RunMode == config.RunModeSimple {
-		accounts, err = s.accountRepo.ListSchedulableByPlatform(ctx, platform)
-	} else if groupID != nil {
-		accounts, err = s.accountRepo.ListSchedulableByGroupIDAndPlatform(ctx, *groupID, platform)
-		if err == nil && len(accounts) == 0 && hasForcePlatform {
-			accounts, err = s.accountRepo.ListSchedulableByPlatform(ctx, platform)
-		}
-	} else {
-		accounts, err = s.accountRepo.ListSchedulableByPlatform(ctx, platform)
-	}
-	if err != nil {
-		return nil, useMixed, err
-	}
-	return accounts, useMixed, nil
-}
-
-func (s *GatewayService) isAccountAllowedForPlatform(account *Account, platform string, useMixed bool) bool {
-	if account == nil {
-		return false
-	}
-	if useMixed {
-		if account.Platform == platform {
-			return true
-		}
-		return account.Platform == PlatformAntigravity && account.IsMixedSchedulingEnabled()
-	}
-	return account.Platform == platform
-}
-
-func (s *GatewayService) tryAcquireAccountSlot(ctx context.Context, accountID int64, maxConcurrency int) (*AcquireResult, error) {
-	if s.concurrencyService == nil {
-		return &AcquireResult{Acquired: true, ReleaseFunc: func() {}}, nil
-	}
-	return s.concurrencyService.AcquireAccountSlot(ctx, accountID, maxConcurrency)
-}
-
-func sortAccountsByPriorityAndLastUsed(accounts []*Account, preferOAuth bool) {
-	sort.SliceStable(accounts, func(i, j int) bool {
-		a, b := accounts[i], accounts[j]
-		if a.Priority != b.Priority {
-			return a.Priority < b.Priority
-		}
-		switch {
-		case a.LastUsedAt == nil && b.LastUsedAt != nil:
-			return true
-		case a.LastUsedAt != nil && b.LastUsedAt == nil:
-			return false
-		case a.LastUsedAt == nil && b.LastUsedAt == nil:
-			if preferOAuth && a.Type != b.Type {
-				return a.Type == AccountTypeOAuth
-			}
-			return false
-		default:
-			return a.LastUsedAt.Before(*b.LastUsedAt)
-		}
-	})
-}
-
 // selectAccountForModelWithPlatform 选择单平台账户（完全隔离）
 func (s *GatewayService) selectAccountForModelWithPlatform(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}, platform string) (*Account, error) {
-	preferOAuth := platform == PlatformGemini
 	// 1. 查询粘性会话
 	if sessionHash != "" {
 		accountID, err := s.cache.GetSessionAccountID(ctx, sessionHash)
@@ -762,9 +389,7 @@ func (s *GatewayService) selectAccountForModelWithPlatform(ctx context.Context,
 			case acc.LastUsedAt != nil && selected.LastUsedAt == nil:
 				// keep selected (never used is preferred)
 			case acc.LastUsedAt == nil && selected.LastUsedAt == nil:
-				if preferOAuth && acc.Type != selected.Type && acc.Type == AccountTypeOAuth {
-					selected = acc
-				}
+				// keep selected (both never used)
 			default:
 				if acc.LastUsedAt.Before(*selected.LastUsedAt) {
 					selected = acc
@@ -794,7 +419,6 @@ func (s *GatewayService) selectAccountForModelWithPlatform(ctx context.Context,
 // 查询原生平台账户 + 启用 mixed_scheduling 的 antigravity 账户
 func (s *GatewayService) selectAccountWithMixedScheduling(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}, nativePlatform string) (*Account, error) {
 	platforms := []string{nativePlatform, PlatformAntigravity}
-	preferOAuth := nativePlatform == PlatformGemini

 	// 1. 查询粘性会话
 	if sessionHash != "" {
@@ -854,9 +478,7 @@ func (s *GatewayService) selectAccountWithMixedScheduling(ctx context.Context, g
 			case acc.LastUsedAt != nil && selected.LastUsedAt == nil:
 				// keep selected (never used is preferred)
 			case acc.LastUsedAt == nil && selected.LastUsedAt == nil:
-				if preferOAuth && acc.Platform == PlatformGemini && selected.Platform == PlatformGemini && acc.Type != selected.Type && acc.Type == AccountTypeOAuth {
-					selected = acc
-				}
+				// keep selected (both never used)
 			default:
 				if acc.LastUsedAt.Before(*selected.LastUsedAt) {
 					selected = acc
@@ -1062,30 +684,6 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A

 	// 处理错误响应（不可重试的错误）
 	if resp.StatusCode >= 400 {
-		// 可选：对部分 400 触发 failover（默认关闭以保持语义）
-		if resp.StatusCode == 400 && s.cfg != nil && s.cfg.Gateway.FailoverOn400 {
-			respBody, readErr := io.ReadAll(resp.Body)
-			if readErr != nil {
-				// ReadAll failed, fall back to normal error handling without consuming the stream
-				return s.handleErrorResponse(ctx, resp, c, account)
-			}
-			_ = resp.Body.Close()
-			resp.Body = io.NopCloser(bytes.NewReader(respBody))
-
-			if s.shouldFailoverOn400(respBody) {
-				if s.cfg.Gateway.LogUpstreamErrorBody {
-					log.Printf(
-						"Account %d: 400 error, attempting failover: %s",
-						account.ID,
-						truncateForLog(respBody, s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes),
-					)
-				} else {
-					log.Printf("Account %d: 400 error, attempting failover", account.ID)
-				}
-				s.handleFailoverSideEffects(ctx, resp, account)
-				return nil, &UpstreamFailoverError{StatusCode: resp.StatusCode}
-			}
-		}
 		return s.handleErrorResponse(ctx, resp, c, account)
 	}

@@ -1188,13 +786,6 @@ func (s *GatewayService) buildUpstreamRequest(ctx context.Context, c *gin.Contex
 	// 处理anthropic-beta header（OAuth账号需要特殊处理）
 	if tokenType == "oauth" {
 		req.Header.Set("anthropic-beta", s.getBetaHeader(modelID, c.GetHeader("anthropic-beta")))
-	} else if s.cfg != nil && s.cfg.Gateway.InjectBetaForApiKey && req.Header.Get("anthropic-beta") == "" {
-		// API-key：仅在请求显式使用 beta 特性且客户端未提供时，按需补齐（默认关闭）
-		if requestNeedsBetaFeatures(body) {
-			if beta := defaultApiKeyBetaHeader(body); beta != "" {
-				req.Header.Set("anthropic-beta", beta)
-			}
-		}
 	}

 	return req, nil
@@ -1247,83 +838,6 @@ func (s *GatewayService) getBetaHeader(modelID string, clientBetaHeader string)
 	return claude.DefaultBetaHeader
 }

-func requestNeedsBetaFeatures(body []byte) bool {
-	tools := gjson.GetBytes(body, "tools")
-	if tools.Exists() && tools.IsArray() && len(tools.Array()) > 0 {
-		return true
-	}
-	if strings.EqualFold(gjson.GetBytes(body, "thinking.type").String(), "enabled") {
-		return true
-	}
-	return false
-}
-
-func defaultApiKeyBetaHeader(body []byte) string {
-	modelID := gjson.GetBytes(body, "model").String()
-	if strings.Contains(strings.ToLower(modelID), "haiku") {
-		return claude.ApiKeyHaikuBetaHeader
-	}
-	return claude.ApiKeyBetaHeader
-}
-
-func truncateForLog(b []byte, maxBytes int) string {
-	if maxBytes <= 0 {
-		maxBytes = 2048
-	}
-	if len(b) > maxBytes {
-		b = b[:maxBytes]
-	}
-	s := string(b)
-	// 保持一行，避免污染日志格式
-	s = strings.ReplaceAll(s, "\n", "\\n")
-	s = strings.ReplaceAll(s, "\r", "\\r")
-	return s
-}
-
-func (s *GatewayService) shouldFailoverOn400(respBody []byte) bool {
-	// 只对“可能是兼容性差异导致”的 400 允许切换，避免无意义重试。
-	// 默认保守：无法识别则不切换。
-	msg := strings.ToLower(strings.TrimSpace(extractUpstreamErrorMessage(respBody)))
-	if msg == "" {
-		return false
-	}
-
-	// 缺少/错误的 beta header：换账号/链路可能成功（尤其是混合调度时）。
-	// 更精确匹配 beta 相关的兼容性问题，避免误触发切换。
-	if strings.Contains(msg, "anthropic-beta") ||
-		strings.Contains(msg, "beta feature") ||
-		strings.Contains(msg, "requires beta") {
-		return true
-	}
-
-	// thinking/tool streaming 等兼容性约束（常见于中间转换链路）
-	if strings.Contains(msg, "thinking") || strings.Contains(msg, "thought_signature") || strings.Contains(msg, "signature") {
-		return true
-	}
-	if strings.Contains(msg, "tool_use") || strings.Contains(msg, "tool_result") || strings.Contains(msg, "tools") {
-		return true
-	}
-
-	return false
-}
-
-func extractUpstreamErrorMessage(body []byte) string {
-	// Claude 风格：{"type":"error","error":{"type":"...","message":"..."}}
-	if m := gjson.GetBytes(body, "error.message").String(); strings.TrimSpace(m) != "" {
-		inner := strings.TrimSpace(m)
-		// 有些上游会把完整 JSON 作为字符串塞进 message
-		if strings.HasPrefix(inner, "{") {
-			if innerMsg := gjson.Get(inner, "error.message").String(); strings.TrimSpace(innerMsg) != "" {
-				return innerMsg
-			}
-		}
-		return m
-	}
-
-	// 兜底：尝试顶层 message
-	return gjson.GetBytes(body, "message").String()
-}
-
 func (s *GatewayService) handleErrorResponse(ctx context.Context, resp *http.Response, c *gin.Context, account *Account) (*ForwardResult, error) {
 	body, _ := io.ReadAll(resp.Body)

@@ -1336,16 +850,6 @@ func (s *GatewayService) handleErrorResponse(ctx context.Context, resp *http.Res

 	switch resp.StatusCode {
 	case 400:
-		// 仅记录上游错误摘要（避免输出请求内容）；需要时可通过配置打开
-		if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
-			log.Printf(
-				"Upstream 400 error (account=%d platform=%s type=%s): %s",
-				account.ID,
-				account.Platform,
-				account.Type,
-				truncateForLog(body, s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes),
-			)
-		}
 		c.Data(http.StatusBadRequest, "application/json", body)
 		return nil, fmt.Errorf("upstream error: %d", resp.StatusCode)
 	case 401:
@@ -1825,18 +1329,6 @@ func (s *GatewayService) ForwardCountTokens(ctx context.Context, c *gin.Context,
 		// 标记账号状态（429/529等）
 		s.rateLimitService.HandleUpstreamError(ctx, account, resp.StatusCode, resp.Header, respBody)

-		// 记录上游错误摘要便于排障（不回显请求内容）
-		if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
-			log.Printf(
-				"count_tokens upstream error %d (account=%d platform=%s type=%s): %s",
-				resp.StatusCode,
-				account.ID,
-				account.Platform,
-				account.Type,
-				truncateForLog(respBody, s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes),
-			)
-		}
-
 		// 返回简化的错误响应
 		errMsg := "Upstream request failed"
 		switch resp.StatusCode {
@@ -1917,13 +1409,6 @@ func (s *GatewayService) buildCountTokensRequest(ctx context.Context, c *gin.Con
 	// OAuth 账号：处理 anthropic-beta header
 	if tokenType == "oauth" {
 		req.Header.Set("anthropic-beta", s.getBetaHeader(modelID, c.GetHeader("anthropic-beta")))
-	} else if s.cfg != nil && s.cfg.Gateway.InjectBetaForApiKey && req.Header.Get("anthropic-beta") == "" {
-		// API-key：与 messages 同步的按需 beta 注入（默认关闭）
-		if requestNeedsBetaFeatures(body) {
-			if beta := defaultApiKeyBetaHeader(body); beta != "" {
-				req.Header.Set("anthropic-beta", beta)
-			}
-		}
 	}

 	return req, nil
--- a/backend/internal/service/gemini_messages_compat_service.go
+++ b/backend/internal/service/gemini_messages_compat_service.go
@@ -2278,13 +2278,11 @@ func convertClaudeToolsToGeminiTools(tools any) []any {
 				"properties": map[string]any{},
 			}
 		}
-		// 清理 JSON Schema
-		cleanedParams := cleanToolSchema(params)

 		funcDecls = append(funcDecls, map[string]any{
 			"name":        name,
 			"description": desc,
-			"parameters":  cleanedParams,
+			"parameters":  params,
 		})
 	}

@@ -2298,41 +2296,6 @@ func convertClaudeToolsToGeminiTools(tools any) []any {
 	}
 }

-// cleanToolSchema 清理工具的 JSON Schema，移除 Gemini 不支持的字段
-func cleanToolSchema(schema any) any {
-	if schema == nil {
-		return nil
-	}
-
-	switch v := schema.(type) {
-	case map[string]any:
-		cleaned := make(map[string]any)
-		for key, value := range v {
-			// 跳过不支持的字段
-			if key == "$schema" || key == "$id" || key == "$ref" ||
-				key == "additionalProperties" || key == "minLength" ||
-				key == "maxLength" || key == "minItems" || key == "maxItems" {
-				continue
-			}
-			// 递归清理嵌套对象
-			cleaned[key] = cleanToolSchema(value)
-		}
-		// 规范化 type 字段为大写
-		if typeVal, ok := cleaned["type"].(string); ok {
-			cleaned["type"] = strings.ToUpper(typeVal)
-		}
-		return cleaned
-	case []any:
-		cleaned := make([]any, len(v))
-		for i, item := range v {
-			cleaned[i] = cleanToolSchema(item)
-		}
-		return cleaned
-	default:
-		return v
-	}
-}
-
 func convertClaudeGenerationConfig(req map[string]any) map[string]any {
 	out := make(map[string]any)
 	if mt, ok := asInt(req["max_tokens"]); ok && mt > 0 {
--- a/backend/internal/service/gemini_messages_compat_service_test.go
+++ b/backend/internal/service/gemini_messages_compat_service_test.go
@@ -1,128 +0,0 @@
-package service
-
-import (
-	"testing"
-)
-
-// TestConvertClaudeToolsToGeminiTools_CustomType 测试custom类型工具转换
-func TestConvertClaudeToolsToGeminiTools_CustomType(t *testing.T) {
-	tests := []struct {
-		name        string
-		tools       any
-		expectedLen int
-		description string
-	}{
-		{
-			name: "Standard tools",
-			tools: []any{
-				map[string]any{
-					"name":         "get_weather",
-					"description":  "Get weather info",
-					"input_schema": map[string]any{"type": "object"},
-				},
-			},
-			expectedLen: 1,
-			description: "标准工具格式应该正常转换",
-		},
-		{
-			name: "Custom type tool (MCP format)",
-			tools: []any{
-				map[string]any{
-					"type": "custom",
-					"name": "mcp_tool",
-					"custom": map[string]any{
-						"description":  "MCP tool description",
-						"input_schema": map[string]any{"type": "object"},
-					},
-				},
-			},
-			expectedLen: 1,
-			description: "Custom类型工具应该从custom字段读取",
-		},
-		{
-			name: "Mixed standard and custom tools",
-			tools: []any{
-				map[string]any{
-					"name":         "standard_tool",
-					"description":  "Standard",
-					"input_schema": map[string]any{"type": "object"},
-				},
-				map[string]any{
-					"type": "custom",
-					"name": "custom_tool",
-					"custom": map[string]any{
-						"description":  "Custom",
-						"input_schema": map[string]any{"type": "object"},
-					},
-				},
-			},
-			expectedLen: 1,
-			description: "混合工具应该都能正确转换",
-		},
-		{
-			name: "Custom tool without custom field",
-			tools: []any{
-				map[string]any{
-					"type": "custom",
-					"name": "invalid_custom",
-					// 缺少 custom 字段
-				},
-			},
-			expectedLen: 0, // 应该被跳过
-			description: "缺少custom字段的custom工具应该被跳过",
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			result := convertClaudeToolsToGeminiTools(tt.tools)
-
-			if tt.expectedLen == 0 {
-				if result != nil {
-					t.Errorf("%s: expected nil result, got %v", tt.description, result)
-				}
-				return
-			}
-
-			if result == nil {
-				t.Fatalf("%s: expected non-nil result", tt.description)
-			}
-
-			if len(result) != 1 {
-				t.Errorf("%s: expected 1 tool declaration, got %d", tt.description, len(result))
-				return
-			}
-
-			toolDecl, ok := result[0].(map[string]any)
-			if !ok {
-				t.Fatalf("%s: result[0] is not map[string]any", tt.description)
-			}
-
-			funcDecls, ok := toolDecl["functionDeclarations"].([]any)
-			if !ok {
-				t.Fatalf("%s: functionDeclarations is not []any", tt.description)
-			}
-
-			toolsArr, _ := tt.tools.([]any)
-			expectedFuncCount := 0
-			for _, tool := range toolsArr {
-				toolMap, _ := tool.(map[string]any)
-				if toolMap["name"] != "" {
-					// 检查是否为有效的custom工具
-					if toolMap["type"] == "custom" {
-						if toolMap["custom"] != nil {
-							expectedFuncCount++
-						}
-					} else {
-						expectedFuncCount++
-					}
-				}
-			}
-
-			if len(funcDecls) != expectedFuncCount {
-				t.Errorf("%s: expected %d function declarations, got %d",
-					tt.description, expectedFuncCount, len(funcDecls))
-			}
-		})
-	}
-}
--- a/backend/internal/service/gemini_oauth_service.go
+++ b/backend/internal/service/gemini_oauth_service.go
@@ -7,7 +7,6 @@ import (
 	"fmt"
 	"io"
 	"net/http"
-	"regexp"
 	"strconv"
 	"strings"
 	"time"
@@ -164,45 +163,6 @@ type GeminiTokenInfo struct {
 	Scope        string `json:"scope,omitempty"`
 	ProjectID    string `json:"project_id,omitempty"`
 	OAuthType    string `json:"oauth_type,omitempty"` // "code_assist" 或 "ai_studio"
-	TierID       string `json:"tier_id,omitempty"`    // Gemini Code Assist tier: LEGACY/PRO/ULTRA
-}
-
-// validateTierID validates tier_id format and length
-func validateTierID(tierID string) error {
-	if tierID == "" {
-		return nil // Empty is allowed
-	}
-	if len(tierID) > 64 {
-		return fmt.Errorf("tier_id exceeds maximum length of 64 characters")
-	}
-	// Allow alphanumeric, underscore, hyphen, and slash (for tier paths)
-	if !regexp.MustCompile(`^[a-zA-Z0-9_/-]+$`).MatchString(tierID) {
-		return fmt.Errorf("tier_id contains invalid characters")
-	}
-	return nil
-}
-
-// extractTierIDFromAllowedTiers extracts tierID from LoadCodeAssist response
-// Prioritizes IsDefault tier, falls back to first non-empty tier
-func extractTierIDFromAllowedTiers(allowedTiers []geminicli.AllowedTier) string {
-	tierID := "LEGACY"
-	// First pass: look for default tier
-	for _, tier := range allowedTiers {
-		if tier.IsDefault && strings.TrimSpace(tier.ID) != "" {
-			tierID = strings.TrimSpace(tier.ID)
-			break
-		}
-	}
-	// Second pass: if still LEGACY, take first non-empty tier
-	if tierID == "LEGACY" {
-		for _, tier := range allowedTiers {
-			if strings.TrimSpace(tier.ID) != "" {
-				tierID = strings.TrimSpace(tier.ID)
-				break
-			}
-		}
-	}
-	return tierID
 }

 func (s *GeminiOAuthService) ExchangeCode(ctx context.Context, input *GeminiExchangeCodeInput) (*GeminiTokenInfo, error) {
@@ -263,14 +223,13 @@ func (s *GeminiOAuthService) ExchangeCode(ctx context.Context, input *GeminiExch
 	expiresAt := time.Now().Unix() + tokenResp.ExpiresIn - 300

 	projectID := sessionProjectID
-	var tierID string

 	// 对于 code_assist 模式，project_id 是必需的
 	// 对于 ai_studio 模式，project_id 是可选的（不影响使用 AI Studio API）
 	if oauthType == "code_assist" {
 		if projectID == "" {
 			var err error
-			projectID, tierID, err = s.fetchProjectID(ctx, tokenResp.AccessToken, proxyURL)
+			projectID, err = s.fetchProjectID(ctx, tokenResp.AccessToken, proxyURL)
 			if err != nil {
 				// 记录警告但不阻断流程，允许后续补充 project_id
 				fmt.Printf("[GeminiOAuth] Warning: Failed to fetch project_id during token exchange: %v\n", err)
@@ -289,7 +248,6 @@ func (s *GeminiOAuthService) ExchangeCode(ctx context.Context, input *GeminiExch
 		ExpiresAt:    expiresAt,
 		Scope:        tokenResp.Scope,
 		ProjectID:    projectID,
-		TierID:       tierID,
 		OAuthType:    oauthType,
 	}, nil
 }
@@ -399,7 +357,7 @@ func (s *GeminiOAuthService) RefreshAccountToken(ctx context.Context, account *A
 	// For Code Assist, project_id is required. Auto-detect if missing.
 	// For AI Studio OAuth, project_id is optional and should not block refresh.
 	if oauthType == "code_assist" && strings.TrimSpace(tokenInfo.ProjectID) == "" {
-		projectID, tierID, err := s.fetchProjectID(ctx, tokenInfo.AccessToken, proxyURL)
+		projectID, err := s.fetchProjectID(ctx, tokenInfo.AccessToken, proxyURL)
 		if err != nil {
 			return nil, fmt.Errorf("failed to auto-detect project_id: %w", err)
 		}
@@ -408,7 +366,6 @@ func (s *GeminiOAuthService) RefreshAccountToken(ctx context.Context, account *A
 			return nil, fmt.Errorf("failed to auto-detect project_id: empty result")
 		}
 		tokenInfo.ProjectID = projectID
-		tokenInfo.TierID = tierID
 	}

 	return tokenInfo, nil
@@ -431,13 +388,6 @@ func (s *GeminiOAuthService) BuildAccountCredentials(tokenInfo *GeminiTokenInfo)
 	if tokenInfo.ProjectID != "" {
 		creds["project_id"] = tokenInfo.ProjectID
 	}
-	if tokenInfo.TierID != "" {
-		// Validate tier_id before storing
-		if err := validateTierID(tokenInfo.TierID); err == nil {
-			creds["tier_id"] = tokenInfo.TierID
-		}
-		// Silently skip invalid tier_id (don't block account creation)
-	}
 	if tokenInfo.OAuthType != "" {
 		creds["oauth_type"] = tokenInfo.OAuthType
 	}
@@ -448,26 +398,34 @@ func (s *GeminiOAuthService) Stop() {
 	s.sessionStore.Stop()
 }

-func (s *GeminiOAuthService) fetchProjectID(ctx context.Context, accessToken, proxyURL string) (string, string, error) {
+func (s *GeminiOAuthService) fetchProjectID(ctx context.Context, accessToken, proxyURL string) (string, error) {
 	if s.codeAssist == nil {
-		return "", "", errors.New("code assist client not configured")
+		return "", errors.New("code assist client not configured")
 	}

 	loadResp, loadErr := s.codeAssist.LoadCodeAssist(ctx, accessToken, proxyURL, nil)
-
-	// Extract tierID from response (works whether CloudAICompanionProject is set or not)
-	tierID := "LEGACY"
-	if loadResp != nil {
-		tierID = extractTierIDFromAllowedTiers(loadResp.AllowedTiers)
-	}
-
-	// If LoadCodeAssist returned a project, use it
 	if loadErr == nil && loadResp != nil && strings.TrimSpace(loadResp.CloudAICompanionProject) != "" {
-		return strings.TrimSpace(loadResp.CloudAICompanionProject), tierID, nil
+		return strings.TrimSpace(loadResp.CloudAICompanionProject), nil
 	}

 	// Pick tier from allowedTiers; if no default tier is marked, pick the first non-empty tier ID.
-	// (tierID already extracted above, reuse it)
+	tierID := "LEGACY"
+	if loadResp != nil {
+		for _, tier := range loadResp.AllowedTiers {
+			if tier.IsDefault && strings.TrimSpace(tier.ID) != "" {
+				tierID = strings.TrimSpace(tier.ID)
+				break
+			}
+		}
+		if strings.TrimSpace(tierID) == "" || tierID == "LEGACY" {
+			for _, tier := range loadResp.AllowedTiers {
+				if strings.TrimSpace(tier.ID) != "" {
+					tierID = strings.TrimSpace(tier.ID)
+					break
+				}
+			}
+		}
+	}

 	req := &geminicli.OnboardUserRequest{
 		TierID: tierID,
@@ -485,39 +443,39 @@ func (s *GeminiOAuthService) fetchProjectID(ctx context.Context, accessToken, pr
 			// If Code Assist onboarding fails (e.g. INVALID_ARGUMENT), fallback to Cloud Resource Manager projects.
 			fallback, fbErr := fetchProjectIDFromResourceManager(ctx, accessToken, proxyURL)
 			if fbErr == nil && strings.TrimSpace(fallback) != "" {
-				return strings.TrimSpace(fallback), tierID, nil
+				return strings.TrimSpace(fallback), nil
 			}
-			return "", "", err
+			return "", err
 		}
 		if resp.Done {
 			if resp.Response != nil && resp.Response.CloudAICompanionProject != nil {
 				switch v := resp.Response.CloudAICompanionProject.(type) {
 				case string:
-					return strings.TrimSpace(v), tierID, nil
+					return strings.TrimSpace(v), nil
 				case map[string]any:
 					if id, ok := v["id"].(string); ok {
-						return strings.TrimSpace(id), tierID, nil
+						return strings.TrimSpace(id), nil
 					}
 				}
 			}

 			fallback, fbErr := fetchProjectIDFromResourceManager(ctx, accessToken, proxyURL)
 			if fbErr == nil && strings.TrimSpace(fallback) != "" {
-				return strings.TrimSpace(fallback), tierID, nil
+				return strings.TrimSpace(fallback), nil
 			}
-			return "", "", errors.New("onboardUser completed but no project_id returned")
+			return "", errors.New("onboardUser completed but no project_id returned")
 		}
 		time.Sleep(2 * time.Second)
 	}

 	fallback, fbErr := fetchProjectIDFromResourceManager(ctx, accessToken, proxyURL)
 	if fbErr == nil && strings.TrimSpace(fallback) != "" {
-		return strings.TrimSpace(fallback), tierID, nil
+		return strings.TrimSpace(fallback), nil
 	}
 	if loadErr != nil {
-		return "", "", fmt.Errorf("loadCodeAssist failed (%v) and onboardUser timeout after %d attempts", loadErr, maxAttempts)
+		return "", fmt.Errorf("loadCodeAssist failed (%v) and onboardUser timeout after %d attempts", loadErr, maxAttempts)
 	}
-	return "", "", fmt.Errorf("onboardUser timeout after %d attempts", maxAttempts)
+	return "", fmt.Errorf("onboardUser timeout after %d attempts", maxAttempts)
 }

 type googleCloudProject struct {
--- a/backend/internal/service/gemini_token_provider.go
+++ b/backend/internal/service/gemini_token_provider.go
@@ -112,7 +112,7 @@ func (p *GeminiTokenProvider) GetAccessToken(ctx context.Context, account *Accou
 			}
 		}

-		detected, tierID, err := p.geminiOAuthService.fetchProjectID(ctx, accessToken, proxyURL)
+		detected, err := p.geminiOAuthService.fetchProjectID(ctx, accessToken, proxyURL)
 		if err != nil {
 			log.Printf("[GeminiTokenProvider] Auto-detect project_id failed: %v, fallback to AI Studio API mode", err)
 			return accessToken, nil
@@ -123,9 +123,6 @@ func (p *GeminiTokenProvider) GetAccessToken(ctx context.Context, account *Accou
 				account.Credentials = make(map[string]any)
 			}
 			account.Credentials["project_id"] = detected
-			if tierID != "" {
-				account.Credentials["tier_id"] = tierID
-			}
 			_ = p.accountRepo.Update(ctx, account)
 		}
 	}
--- a/backend/internal/service/openai_gateway_service.go
+++ b/backend/internal/service/openai_gateway_service.go
@@ -13,7 +13,6 @@ import (
 	"log"
 	"net/http"
 	"regexp"
-	"sort"
 	"strconv"
 	"strings"
 	"time"
@@ -81,7 +80,6 @@ type OpenAIGatewayService struct {
 	userSubRepo         UserSubscriptionRepository
 	cache               GatewayCache
 	cfg                 *config.Config
-	concurrencyService  *ConcurrencyService
 	billingService      *BillingService
 	rateLimitService    *RateLimitService
 	billingCacheService *BillingCacheService
@@ -97,7 +95,6 @@ func NewOpenAIGatewayService(
 	userSubRepo UserSubscriptionRepository,
 	cache GatewayCache,
 	cfg *config.Config,
-	concurrencyService *ConcurrencyService,
 	billingService *BillingService,
 	rateLimitService *RateLimitService,
 	billingCacheService *BillingCacheService,
@@ -111,7 +108,6 @@ func NewOpenAIGatewayService(
 		userSubRepo:         userSubRepo,
 		cache:               cache,
 		cfg:                 cfg,
-		concurrencyService:  concurrencyService,
 		billingService:      billingService,
 		rateLimitService:    rateLimitService,
 		billingCacheService: billingCacheService,
@@ -130,14 +126,6 @@ func (s *OpenAIGatewayService) GenerateSessionHash(c *gin.Context) string {
 	return hex.EncodeToString(hash[:])
 }

-// BindStickySession sets session -> account binding with standard TTL.
-func (s *OpenAIGatewayService) BindStickySession(ctx context.Context, sessionHash string, accountID int64) error {
-	if sessionHash == "" || accountID <= 0 {
-		return nil
-	}
-	return s.cache.SetSessionAccountID(ctx, "openai:"+sessionHash, accountID, openaiStickySessionTTL)
-}
-
 // SelectAccount selects an OpenAI account with sticky session support
 func (s *OpenAIGatewayService) SelectAccount(ctx context.Context, groupID *int64, sessionHash string) (*Account, error) {
 	return s.SelectAccountForModel(ctx, groupID, sessionHash, "")
@@ -230,254 +218,6 @@ func (s *OpenAIGatewayService) SelectAccountForModelWithExclusions(ctx context.C
 	return selected, nil
 }

-// 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()
-	var stickyAccountID int64
-	if sessionHash != "" && s.cache != nil {
-		if accountID, err := s.cache.GetSessionAccountID(ctx, "openai:"+sessionHash); err == nil {
-			stickyAccountID = accountID
-		}
-	}
-	if s.concurrencyService == nil || !cfg.LoadBatchEnabled {
-		account, err := s.SelectAccountForModelWithExclusions(ctx, groupID, sessionHash, requestedModel, excludedIDs)
-		if err != nil {
-			return nil, err
-		}
-		result, err := s.tryAcquireAccountSlot(ctx, account.ID, account.Concurrency)
-		if err == nil && result.Acquired {
-			return &AccountSelectionResult{
-				Account:     account,
-				Acquired:    true,
-				ReleaseFunc: result.ReleaseFunc,
-			}, nil
-		}
-		if stickyAccountID > 0 && stickyAccountID == account.ID && s.concurrencyService != nil {
-			waitingCount, _ := s.concurrencyService.GetAccountWaitingCount(ctx, account.ID)
-			if waitingCount < cfg.StickySessionMaxWaiting {
-				return &AccountSelectionResult{
-					Account: account,
-					WaitPlan: &AccountWaitPlan{
-						AccountID:      account.ID,
-						MaxConcurrency: account.Concurrency,
-						Timeout:        cfg.StickySessionWaitTimeout,
-						MaxWaiting:     cfg.StickySessionMaxWaiting,
-					},
-				}, nil
-			}
-		}
-		return &AccountSelectionResult{
-			Account: account,
-			WaitPlan: &AccountWaitPlan{
-				AccountID:      account.ID,
-				MaxConcurrency: account.Concurrency,
-				Timeout:        cfg.FallbackWaitTimeout,
-				MaxWaiting:     cfg.FallbackMaxWaiting,
-			},
-		}, nil
-	}
-
-	accounts, err := s.listSchedulableAccounts(ctx, groupID)
-	if err != nil {
-		return nil, err
-	}
-	if len(accounts) == 0 {
-		return nil, errors.New("no available accounts")
-	}
-
-	isExcluded := func(accountID int64) bool {
-		if excludedIDs == nil {
-			return false
-		}
-		_, excluded := excludedIDs[accountID]
-		return excluded
-	}
-
-	// ============ Layer 1: Sticky session ============
-	if sessionHash != "" {
-		accountID, err := s.cache.GetSessionAccountID(ctx, "openai:"+sessionHash)
-		if err == nil && accountID > 0 && !isExcluded(accountID) {
-			account, err := s.accountRepo.GetByID(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, "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
-				}
-			}
-		}
-	}
-
-	// ============ Layer 2: Load-aware selection ============
-	candidates := make([]*Account, 0, len(accounts))
-	for i := range accounts {
-		acc := &accounts[i]
-		if isExcluded(acc.ID) {
-			continue
-		}
-		if requestedModel != "" && !acc.IsModelSupported(requestedModel) {
-			continue
-		}
-		candidates = append(candidates, acc)
-	}
-
-	if len(candidates) == 0 {
-		return nil, errors.New("no available accounts")
-	}
-
-	accountLoads := make([]AccountWithConcurrency, 0, len(candidates))
-	for _, acc := range candidates {
-		accountLoads = append(accountLoads, AccountWithConcurrency{
-			ID:             acc.ID,
-			MaxConcurrency: acc.Concurrency,
-		})
-	}
-
-	loadMap, err := s.concurrencyService.GetAccountsLoadBatch(ctx, accountLoads)
-	if err != nil {
-		ordered := append([]*Account(nil), candidates...)
-		sortAccountsByPriorityAndLastUsed(ordered, false)
-		for _, acc := range ordered {
-			result, err := s.tryAcquireAccountSlot(ctx, acc.ID, acc.Concurrency)
-			if err == nil && result.Acquired {
-				if sessionHash != "" {
-					_ = s.cache.SetSessionAccountID(ctx, "openai:"+sessionHash, acc.ID, openaiStickySessionTTL)
-				}
-				return &AccountSelectionResult{
-					Account:     acc,
-					Acquired:    true,
-					ReleaseFunc: result.ReleaseFunc,
-				}, nil
-			}
-		}
-	} else {
-		type accountWithLoad struct {
-			account  *Account
-			loadInfo *AccountLoadInfo
-		}
-		var available []accountWithLoad
-		for _, acc := range candidates {
-			loadInfo := loadMap[acc.ID]
-			if loadInfo == nil {
-				loadInfo = &AccountLoadInfo{AccountID: acc.ID}
-			}
-			if loadInfo.LoadRate < 100 {
-				available = append(available, accountWithLoad{
-					account:  acc,
-					loadInfo: loadInfo,
-				})
-			}
-		}
-
-		if len(available) > 0 {
-			sort.SliceStable(available, func(i, j int) bool {
-				a, b := available[i], available[j]
-				if a.account.Priority != b.account.Priority {
-					return a.account.Priority < b.account.Priority
-				}
-				if a.loadInfo.LoadRate != b.loadInfo.LoadRate {
-					return a.loadInfo.LoadRate < b.loadInfo.LoadRate
-				}
-				switch {
-				case a.account.LastUsedAt == nil && b.account.LastUsedAt != nil:
-					return true
-				case a.account.LastUsedAt != nil && b.account.LastUsedAt == nil:
-					return false
-				case a.account.LastUsedAt == nil && b.account.LastUsedAt == nil:
-					return false
-				default:
-					return a.account.LastUsedAt.Before(*b.account.LastUsedAt)
-				}
-			})
-
-			for _, item := range available {
-				result, err := s.tryAcquireAccountSlot(ctx, item.account.ID, item.account.Concurrency)
-				if err == nil && result.Acquired {
-					if sessionHash != "" {
-						_ = s.cache.SetSessionAccountID(ctx, "openai:"+sessionHash, item.account.ID, openaiStickySessionTTL)
-					}
-					return &AccountSelectionResult{
-						Account:     item.account,
-						Acquired:    true,
-						ReleaseFunc: result.ReleaseFunc,
-					}, nil
-				}
-			}
-		}
-	}
-
-	// ============ Layer 3: Fallback wait ============
-	sortAccountsByPriorityAndLastUsed(candidates, false)
-	for _, acc := range candidates {
-		return &AccountSelectionResult{
-			Account: acc,
-			WaitPlan: &AccountWaitPlan{
-				AccountID:      acc.ID,
-				MaxConcurrency: acc.Concurrency,
-				Timeout:        cfg.FallbackWaitTimeout,
-				MaxWaiting:     cfg.FallbackMaxWaiting,
-			},
-		}, nil
-	}
-
-	return nil, errors.New("no available accounts")
-}
-
-func (s *OpenAIGatewayService) listSchedulableAccounts(ctx context.Context, groupID *int64) ([]Account, error) {
-	var accounts []Account
-	var err error
-	if s.cfg != nil && s.cfg.RunMode == config.RunModeSimple {
-		accounts, err = s.accountRepo.ListSchedulableByPlatform(ctx, PlatformOpenAI)
-	} else if groupID != nil {
-		accounts, err = s.accountRepo.ListSchedulableByGroupIDAndPlatform(ctx, *groupID, PlatformOpenAI)
-	} else {
-		accounts, err = s.accountRepo.ListSchedulableByPlatform(ctx, PlatformOpenAI)
-	}
-	if err != nil {
-		return nil, fmt.Errorf("query accounts failed: %w", err)
-	}
-	return accounts, nil
-}
-
-func (s *OpenAIGatewayService) tryAcquireAccountSlot(ctx context.Context, accountID int64, maxConcurrency int) (*AcquireResult, error) {
-	if s.concurrencyService == nil {
-		return &AcquireResult{Acquired: true, ReleaseFunc: func() {}}, nil
-	}
-	return s.concurrencyService.AcquireAccountSlot(ctx, accountID, maxConcurrency)
-}
-
-func (s *OpenAIGatewayService) schedulingConfig() config.GatewaySchedulingConfig {
-	if s.cfg != nil {
-		return s.cfg.Gateway.Scheduling
-	}
-	return config.GatewaySchedulingConfig{
-		StickySessionMaxWaiting:  3,
-		StickySessionWaitTimeout: 45 * time.Second,
-		FallbackWaitTimeout:      30 * time.Second,
-		FallbackMaxWaiting:       100,
-		LoadBatchEnabled:         true,
-		SlotCleanupInterval:      30 * time.Second,
-	}
-}
-
 // GetAccessToken gets the access token for an OpenAI account
 func (s *OpenAIGatewayService) GetAccessToken(ctx context.Context, account *Account) (string, string, error) {
 	switch account.Type {
--- a/backend/internal/service/wire.go
+++ b/backend/internal/service/wire.go
@@ -73,15 +73,6 @@ func ProvideDeferredService(accountRepo AccountRepository, timingWheel *TimingWh
 	return svc
 }

-// ProvideConcurrencyService creates ConcurrencyService and starts slot cleanup worker.
-func ProvideConcurrencyService(cache ConcurrencyCache, accountRepo AccountRepository, cfg *config.Config) *ConcurrencyService {
-	svc := NewConcurrencyService(cache)
-	if cfg != nil {
-		svc.StartSlotCleanupWorker(accountRepo, cfg.Gateway.Scheduling.SlotCleanupInterval)
-	}
-	return svc
-}
-
 // ProviderSet is the Wire provider set for all services
 var ProviderSet = wire.NewSet(
 	// Core services
@@ -116,7 +107,7 @@ var ProviderSet = wire.NewSet(
 	ProvideEmailQueueService,
 	NewTurnstileService,
 	NewSubscriptionService,
-	ProvideConcurrencyService,
+	NewConcurrencyService,
 	NewIdentityService,
 	NewCRSSyncService,
 	ProvideUpdateService,