Merge branch 'main' of https://github.com/mt21625457/aicodex2api

backend/internal/service/gateway_service.go

@@ -5,7 +5,6 @@ import (
 	"bytes"
 	"context"
 	"crypto/sha256"
-	"encoding/hex"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -17,6 +16,7 @@ import (
 	"os"
 	"regexp"
 	"sort"
+	"strconv"
 	"strings"
 	"sync/atomic"
 	"time"
@@ -26,6 +26,7 @@ import (
 	"github.com/Wei-Shaw/sub2api/internal/pkg/ctxkey"
 	"github.com/Wei-Shaw/sub2api/internal/util/responseheaders"
 	"github.com/Wei-Shaw/sub2api/internal/util/urlvalidator"
+	"github.com/cespare/xxhash/v2"
 	"github.com/google/uuid"
 	"github.com/tidwall/gjson"
 	"github.com/tidwall/sjson"
@@ -245,9 +246,6 @@ var (
 // ErrClaudeCodeOnly 表示分组仅允许 Claude Code 客户端访问
 var ErrClaudeCodeOnly = errors.New("this group only allows Claude Code clients")
 
-// ErrModelScopeNotSupported 表示请求的模型系列不在分组支持的范围内
-var ErrModelScopeNotSupported = errors.New("model scope not supported by this group")
-
 // allowedHeaders 白名单headers（参考CRS项目）
 var allowedHeaders = map[string]bool{
 	"accept":                                    true,
@@ -273,13 +271,6 @@ var allowedHeaders = map[string]bool{
 // GatewayCache 定义网关服务的缓存操作接口。
 // 提供粘性会话（Sticky Session）的存储、查询、刷新和删除功能。
 //
-// ModelLoadInfo 模型负载信息（用于 Antigravity 调度）
-// Model load info for Antigravity scheduling
-type ModelLoadInfo struct {
-	CallCount  int64     // 当前分钟调用次数 / Call count in current minute
-	LastUsedAt time.Time // 最后调度时间（零值表示未调度过）/ Last scheduling time (zero means never scheduled)
-}
-
 // GatewayCache defines cache operations for gateway service.
 // Provides sticky session storage, retrieval, refresh and deletion capabilities.
 type GatewayCache interface {
@@ -295,24 +286,6 @@ type GatewayCache interface {
 	// DeleteSessionAccountID 删除粘性会话绑定，用于账号不可用时主动清理
 	// Delete sticky session binding, used to proactively clean up when account becomes unavailable
 	DeleteSessionAccountID(ctx context.Context, groupID int64, sessionHash string) error
-
-	// IncrModelCallCount 增加模型调用次数并更新最后调度时间（Antigravity 专用）
-	// Increment model call count and update last scheduling time (Antigravity only)
-	// 返回更新后的调用次数
-	IncrModelCallCount(ctx context.Context, accountID int64, model string) (int64, error)
-
-	// GetModelLoadBatch 批量获取账号的模型负载信息（Antigravity 专用）
-	// Batch get model load info for accounts (Antigravity only)
-	GetModelLoadBatch(ctx context.Context, accountIDs []int64, model string) (map[int64]*ModelLoadInfo, error)
-
-	// FindGeminiSession 查找 Gemini 会话（MGET 倒序匹配）
-	// Find Gemini session using MGET reverse order matching
-	// 返回最长匹配的会话信息（uuid, accountID）
-	FindGeminiSession(ctx context.Context, groupID int64, prefixHash, digestChain string) (uuid string, accountID int64, found bool)
-
-	// SaveGeminiSession 保存 Gemini 会话
-	// Save Gemini session binding
-	SaveGeminiSession(ctx context.Context, groupID int64, prefixHash, digestChain, uuid string, accountID int64) error
 }
 
 // derefGroupID safely dereferences *int64 to int64, returning 0 if nil
@@ -323,21 +296,15 @@ func derefGroupID(groupID *int64) int64 {
 	return *groupID
 }
 
-// stickySessionRateLimitThreshold 定义清除粘性会话的限流时间阈值。
-// 当账号限流剩余时间超过此阈值时，清除粘性会话以便切换到其他账号。
-// 低于此阈值时保持粘性会话，等待短暂限流结束。
-const stickySessionRateLimitThreshold = 10 * time.Second
-
 // shouldClearStickySession 检查账号是否处于不可调度状态，需要清理粘性会话绑定。
 // 当账号状态为错误、禁用、不可调度、处于临时不可调度期间，
-// 或模型限流剩余时间超过 stickySessionRateLimitThreshold 时，返回 true。
+// 或请求的模型处于限流状态时，返回 true。
 // 这确保后续请求不会继续使用不可用的账号。
 //
 // shouldClearStickySession checks if an account is in an unschedulable state
 // and the sticky session binding should be cleared.
 // Returns true when account status is error/disabled, schedulable is false,
-// within temporary unschedulable period, or model rate limit remaining time
-// exceeds stickySessionRateLimitThreshold.
+// within temporary unschedulable period, or the requested model is rate-limited.
 // This ensures subsequent requests won't continue using unavailable accounts.
 func shouldClearStickySession(account *Account, requestedModel string) bool {
 	if account == nil {
@@ -349,8 +316,8 @@ func shouldClearStickySession(account *Account, requestedModel string) bool {
 	if account.TempUnschedulableUntil != nil && time.Now().Before(*account.TempUnschedulableUntil) {
 		return true
 	}
-	// 检查模型限流和 scope 限流，只在超过阈值时清除粘性会话
-	if remaining := account.GetRateLimitRemainingTimeWithContext(context.Background(), requestedModel); remaining > stickySessionRateLimitThreshold {
+	// 检查模型限流和 scope 限流，有限流即清除粘性会话
+	if remaining := account.GetRateLimitRemainingTimeWithContext(context.Background(), requestedModel); remaining > 0 {
 		return true
 	}
 	return false
@@ -413,6 +380,7 @@ type GatewayService struct {
 	userSubRepo         UserSubscriptionRepository
 	userGroupRateRepo   UserGroupRateRepository
 	cache               GatewayCache
+	digestStore         *DigestSessionStore
 	cfg                 *config.Config
 	schedulerSnapshot   *SchedulerSnapshotService
 	billingService      *BillingService
@@ -446,6 +414,7 @@ func NewGatewayService(
 	deferredService *DeferredService,
 	claudeTokenProvider *ClaudeTokenProvider,
 	sessionLimitCache SessionLimitCache,
+	digestStore *DigestSessionStore,
 ) *GatewayService {
 	return &GatewayService{
 		accountRepo:         accountRepo,
@@ -455,6 +424,7 @@ func NewGatewayService(
 		userSubRepo:         userSubRepo,
 		userGroupRateRepo:   userGroupRateRepo,
 		cache:               cache,
+		digestStore:         digestStore,
 		cfg:                 cfg,
 		schedulerSnapshot:   schedulerSnapshot,
 		concurrencyService:  concurrencyService,
@@ -488,23 +458,45 @@ func (s *GatewayService) GenerateSessionHash(parsed *ParsedRequest) string {
 		return s.hashContent(cacheableContent)
 	}
 
-	// 3. Fallback: 使用 system 内容
+	// 3. 最后 fallback: 使用 session上下文 + system + 所有消息的完整摘要串
+	var combined strings.Builder
+	// 混入请求上下文区分因子，避免不同用户相同消息产生相同 hash
+	if parsed.SessionContext != nil {
+		_, _ = combined.WriteString(parsed.SessionContext.ClientIP)
+		_, _ = combined.WriteString(":")
+		_, _ = combined.WriteString(parsed.SessionContext.UserAgent)
+		_, _ = combined.WriteString(":")
+		_, _ = combined.WriteString(strconv.FormatInt(parsed.SessionContext.APIKeyID, 10))
+		_, _ = combined.WriteString("|")
+	}
 	if parsed.System != nil {
 		systemText := s.extractTextFromSystem(parsed.System)
 		if systemText != "" {
-			return s.hashContent(systemText)
+			_, _ = combined.WriteString(systemText)
 		}
 	}
-
-	// 4. 最后 fallback: 使用第一条消息
-	if len(parsed.Messages) > 0 {
-		if firstMsg, ok := parsed.Messages[0].(map[string]any); ok {
-			msgText := s.extractTextFromContent(firstMsg["content"])
-			if msgText != "" {
-				return s.hashContent(msgText)
+	for _, msg := range parsed.Messages {
+		if m, ok := msg.(map[string]any); ok {
+			if content, exists := m["content"]; exists {
+				// Anthropic: messages[].content
+				if msgText := s.extractTextFromContent(content); msgText != "" {
+					_, _ = combined.WriteString(msgText)
+				}
+			} else if parts, ok := m["parts"].([]any); ok {
+				// Gemini: contents[].parts[].text
+				for _, part := range parts {
+					if partMap, ok := part.(map[string]any); ok {
+						if text, ok := partMap["text"].(string); ok {
+							_, _ = combined.WriteString(text)
+						}
+					}
+				}
 			}
 		}
 	}
+	if combined.Len() > 0 {
+		return s.hashContent(combined.String())
+	}
 
 	return ""
 }
@@ -532,19 +524,37 @@ func (s *GatewayService) GetCachedSessionAccountID(ctx context.Context, groupID
 
 // FindGeminiSession 查找 Gemini 会话（基于内容摘要链的 Fallback 匹配）
 // 返回最长匹配的会话信息（uuid, accountID）
-func (s *GatewayService) FindGeminiSession(ctx context.Context, groupID int64, prefixHash, digestChain string) (uuid string, accountID int64, found bool) {
-	if digestChain == "" || s.cache == nil {
-		return "", 0, false
+func (s *GatewayService) FindGeminiSession(_ context.Context, groupID int64, prefixHash, digestChain string) (uuid string, accountID int64, matchedChain string, found bool) {
+	if digestChain == "" || s.digestStore == nil {
+		return "", 0, "", false
 	}
-	return s.cache.FindGeminiSession(ctx, groupID, prefixHash, digestChain)
+	return s.digestStore.Find(groupID, prefixHash, digestChain)
 }
 
-// SaveGeminiSession 保存 Gemini 会话
-func (s *GatewayService) SaveGeminiSession(ctx context.Context, groupID int64, prefixHash, digestChain, uuid string, accountID int64) error {
-	if digestChain == "" || s.cache == nil {
+// SaveGeminiSession 保存 Gemini 会话。oldDigestChain 为 Find 返回的 matchedChain，用于删旧 key。
+func (s *GatewayService) SaveGeminiSession(_ context.Context, groupID int64, prefixHash, digestChain, uuid string, accountID int64, oldDigestChain string) error {
+	if digestChain == "" || s.digestStore == nil {
 		return nil
 	}
-	return s.cache.SaveGeminiSession(ctx, groupID, prefixHash, digestChain, uuid, accountID)
+	s.digestStore.Save(groupID, prefixHash, digestChain, uuid, accountID, oldDigestChain)
+	return nil
+}
+
+// FindAnthropicSession 查找 Anthropic 会话（基于内容摘要链的 Fallback 匹配）
+func (s *GatewayService) FindAnthropicSession(_ context.Context, groupID int64, prefixHash, digestChain string) (uuid string, accountID int64, matchedChain string, found bool) {
+	if digestChain == "" || s.digestStore == nil {
+		return "", 0, "", false
+	}
+	return s.digestStore.Find(groupID, prefixHash, digestChain)
+}
+
+// SaveAnthropicSession 保存 Anthropic 会话
+func (s *GatewayService) SaveAnthropicSession(_ context.Context, groupID int64, prefixHash, digestChain, uuid string, accountID int64, oldDigestChain string) error {
+	if digestChain == "" || s.digestStore == nil {
+		return nil
+	}
+	s.digestStore.Save(groupID, prefixHash, digestChain, uuid, accountID, oldDigestChain)
+	return nil
 }
 
 func (s *GatewayService) extractCacheableContent(parsed *ParsedRequest) string {
@@ -629,8 +639,8 @@ func (s *GatewayService) extractTextFromContent(content any) string {
 }
 
 func (s *GatewayService) hashContent(content string) string {
-	hash := sha256.Sum256([]byte(content))
-	return hex.EncodeToString(hash[:16]) // 32字符
+	h := xxhash.Sum64String(content)
+	return strconv.FormatUint(h, 36)
 }
 
 // replaceModelInBody 替换请求体中的model字段
@@ -989,13 +999,6 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 		log.Printf("[ModelRoutingDebug] load-aware enabled: group_id=%v model=%s session=%s platform=%s", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), platform)
 	}
 
-	// Antigravity 模型系列检查（在账号选择前检查，确保所有代码路径都经过此检查）
-	if platform == PlatformAntigravity && groupID != nil && requestedModel != "" {
-		if err := s.checkAntigravityModelScope(ctx, *groupID, requestedModel); err != nil {
-			return nil, err
-		}
-	}
-
 	accounts, useMixed, err := s.listSchedulableAccounts(ctx, groupID, platform, hasForcePlatform)
 	if err != nil {
 		return nil, err
@@ -1110,7 +1113,6 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 									result.ReleaseFunc() // 释放槽位
 									// 继续到负载感知选择
 								} else {
-									_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL)
 									if s.debugModelRoutingEnabled() {
 										log.Printf("[ModelRoutingDebug] routed sticky hit: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), stickyAccountID)
 									}
@@ -1190,6 +1192,7 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 						return a.account.LastUsedAt.Before(*b.account.LastUsedAt)
 					}
 				})
+				shuffleWithinSortGroups(routingAvailable)
 
 				// 4. 尝试获取槽位
 				for _, item := range routingAvailable {
@@ -1264,7 +1267,6 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 						if !s.checkAndRegisterSession(ctx, account, sessionHash) {
 							result.ReleaseFunc() // 释放槽位，继续到 Layer 2
 						} else {
-							_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL)
 							return &AccountSelectionResult{
 								Account:     account,
 								Acquired:    true,
@@ -1344,10 +1346,6 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 			return result, nil
 		}
 	} else {
-		// Antigravity 平台：获取模型负载信息
-		var modelLoadMap map[int64]*ModelLoadInfo
-		isAntigravity := platform == PlatformAntigravity
-
 		var available []accountWithLoad
 		for _, acc := range candidates {
 			loadInfo := loadMap[acc.ID]
@@ -1362,109 +1360,44 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 			}
 		}
 
-		// Antigravity 平台：按账号实际映射后的模型名获取模型负载（与 Forward 的统计保持一致）
-		if isAntigravity && requestedModel != "" && s.cache != nil && len(available) > 0 {
-			modelLoadMap = make(map[int64]*ModelLoadInfo, len(available))
-			modelToAccountIDs := make(map[string][]int64)
-			for _, item := range available {
-				mappedModel := mapAntigravityModel(item.account, requestedModel)
-				if mappedModel == "" {
-					continue
-				}
-				modelToAccountIDs[mappedModel] = append(modelToAccountIDs[mappedModel], item.account.ID)
+		// 分层过滤选择：优先级 → 负载率 → LRU
+		for len(available) > 0 {
+			// 1. 取优先级最小的集合
+			candidates := filterByMinPriority(available)
+			// 2. 取负载率最低的集合
+			candidates = filterByMinLoadRate(candidates)
+			// 3. LRU 选择最久未用的账号
+			selected := selectByLRU(candidates, preferOAuth)
+			if selected == nil {
+				break
 			}
-			for model, ids := range modelToAccountIDs {
-				batch, err := s.cache.GetModelLoadBatch(ctx, ids, model)
-				if err != nil {
-					continue
-				}
-				for id, info := range batch {
-					modelLoadMap[id] = info
-				}
-			}
-			if len(modelLoadMap) == 0 {
-				modelLoadMap = nil
-			}
-		}
 
-		// Antigravity 平台：优先级硬过滤 →（同优先级内）按调用次数选择（最少优先，新账号用平均值）
-		// 其他平台：分层过滤选择：优先级 → 负载率 → LRU
-		if isAntigravity {
-			for len(available) > 0 {
-				// 1. 取优先级最小的集合（硬过滤）
-				candidates := filterByMinPriority(available)
-				// 2. 同优先级内按调用次数选择（调用次数最少优先，新账号使用平均值）
-				selected := selectByCallCount(candidates, modelLoadMap, preferOAuth)
-				if selected == nil {
-					break
-				}
-
-				result, err := s.tryAcquireAccountSlot(ctx, selected.account.ID, selected.account.Concurrency)
-				if err == nil && result.Acquired {
-					// 会话数量限制检查
-					if !s.checkAndRegisterSession(ctx, selected.account, sessionHash) {
-						result.ReleaseFunc() // 释放槽位，继续尝试下一个账号
-					} else {
-						if sessionHash != "" && s.cache != nil {
-							_ = s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, selected.account.ID, stickySessionTTL)
-						}
-						return &AccountSelectionResult{
-							Account:     selected.account,
-							Acquired:    true,
-							ReleaseFunc: result.ReleaseFunc,
-						}, nil
+			result, err := s.tryAcquireAccountSlot(ctx, selected.account.ID, selected.account.Concurrency)
+			if err == nil && result.Acquired {
+				// 会话数量限制检查
+				if !s.checkAndRegisterSession(ctx, selected.account, sessionHash) {
+					result.ReleaseFunc() // 释放槽位，继续尝试下一个账号
+				} else {
+					if sessionHash != "" && s.cache != nil {
+						_ = s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, selected.account.ID, stickySessionTTL)
 					}
+					return &AccountSelectionResult{
+						Account:     selected.account,
+						Acquired:    true,
+						ReleaseFunc: result.ReleaseFunc,
+					}, nil
 				}
-
-				// 移除已尝试的账号，重新选择
-				selectedID := selected.account.ID
-				newAvailable := make([]accountWithLoad, 0, len(available)-1)
-				for _, acc := range available {
-					if acc.account.ID != selectedID {
-						newAvailable = append(newAvailable, acc)
-					}
-				}
-				available = newAvailable
 			}
-		} else {
-			for len(available) > 0 {
-				// 1. 取优先级最小的集合
-				candidates := filterByMinPriority(available)
-				// 2. 取负载率最低的集合
-				candidates = filterByMinLoadRate(candidates)
-				// 3. LRU 选择最久未用的账号
-				selected := selectByLRU(candidates, preferOAuth)
-				if selected == nil {
-					break
-				}
 
-				result, err := s.tryAcquireAccountSlot(ctx, selected.account.ID, selected.account.Concurrency)
-				if err == nil && result.Acquired {
-					// 会话数量限制检查
-					if !s.checkAndRegisterSession(ctx, selected.account, sessionHash) {
-						result.ReleaseFunc() // 释放槽位，继续尝试下一个账号
-					} else {
-						if sessionHash != "" && s.cache != nil {
-							_ = s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, selected.account.ID, stickySessionTTL)
-						}
-						return &AccountSelectionResult{
-							Account:     selected.account,
-							Acquired:    true,
-							ReleaseFunc: result.ReleaseFunc,
-						}, nil
-					}
+			// 移除已尝试的账号，重新进行分层过滤
+			selectedID := selected.account.ID
+			newAvailable := make([]accountWithLoad, 0, len(available)-1)
+			for _, acc := range available {
+				if acc.account.ID != selectedID {
+					newAvailable = append(newAvailable, acc)
 				}
-
-				// 移除已尝试的账号，重新进行分层过滤
-				selectedID := selected.account.ID
-				newAvailable := make([]accountWithLoad, 0, len(available)-1)
-				for _, acc := range available {
-					if acc.account.ID != selectedID {
-						newAvailable = append(newAvailable, acc)
-					}
-				}
-				available = newAvailable
 			}
+			available = newAvailable
 		}
 	}
 
@@ -2000,87 +1933,79 @@ func sortAccountsByPriorityAndLastUsed(accounts []*Account, preferOAuth bool) {
 			return a.LastUsedAt.Before(*b.LastUsedAt)
 		}
 	})
+	shuffleWithinPriorityAndLastUsed(accounts)
 }
 
-// selectByCallCount 从候选账号中选择调用次数最少的账号（Antigravity 专用）
-// 新账号（CallCount=0）使用平均调用次数作为虚拟值，避免冷启动被猛调
-// 如果有多个账号具有相同的最小调用次数，则随机选择一个
-func selectByCallCount(accounts []accountWithLoad, modelLoadMap map[int64]*ModelLoadInfo, preferOAuth bool) *accountWithLoad {
-	if len(accounts) == 0 {
-		return nil
+// shuffleWithinSortGroups 对排序后的 accountWithLoad 切片，按 (Priority, LoadRate, LastUsedAt) 分组后组内随机打乱。
+// 防止并发请求读取同一快照时，确定性排序导致所有请求命中相同账号。
+func shuffleWithinSortGroups(accounts []accountWithLoad) {
+	if len(accounts) <= 1 {
+		return
 	}
-	if len(accounts) == 1 {
-		return &accounts[0]
-	}
-
-	// 如果没有负载信息，回退到 LRU
-	if modelLoadMap == nil {
-		return selectByLRU(accounts, preferOAuth)
-	}
-
-	// 1. 计算平均调用次数（用于新账号冷启动）
-	var totalCallCount int64
-	var countWithCalls int
-	for _, acc := range accounts {
-		if info := modelLoadMap[acc.account.ID]; info != nil && info.CallCount > 0 {
-			totalCallCount += info.CallCount
-			countWithCalls++
+	i := 0
+	for i < len(accounts) {
+		j := i + 1
+		for j < len(accounts) && sameAccountWithLoadGroup(accounts[i], accounts[j]) {
+			j++
 		}
-	}
-
-	var avgCallCount int64
-	if countWithCalls > 0 {
-		avgCallCount = totalCallCount / int64(countWithCalls)
-	}
-
-	// 2. 获取每个账号的有效调用次数
-	getEffectiveCallCount := func(acc accountWithLoad) int64 {
-		if acc.account == nil {
-			return 0
+		if j-i > 1 {
+			mathrand.Shuffle(j-i, func(a, b int) {
+				accounts[i+a], accounts[i+b] = accounts[i+b], accounts[i+a]
+			})
 		}
-		info := modelLoadMap[acc.account.ID]
-		if info == nil || info.CallCount == 0 {
-			return avgCallCount // 新账号使用平均值
-		}
-		return info.CallCount
+		i = j
 	}
+}
 
-	// 3. 找到最小调用次数
-	minCount := getEffectiveCallCount(accounts[0])
-	for _, acc := range accounts[1:] {
-		if c := getEffectiveCallCount(acc); c < minCount {
-			minCount = c
-		}
+// sameAccountWithLoadGroup 判断两个 accountWithLoad 是否属于同一排序组
+func sameAccountWithLoadGroup(a, b accountWithLoad) bool {
+	if a.account.Priority != b.account.Priority {
+		return false
 	}
-
-	// 4. 收集所有具有最小调用次数的账号
-	var candidateIdxs []int
-	for i, acc := range accounts {
-		if getEffectiveCallCount(acc) == minCount {
-			candidateIdxs = append(candidateIdxs, i)
-		}
+	if a.loadInfo.LoadRate != b.loadInfo.LoadRate {
+		return false
 	}
+	return sameLastUsedAt(a.account.LastUsedAt, b.account.LastUsedAt)
+}
 
-	// 5. 如果只有一个候选，直接返回
-	if len(candidateIdxs) == 1 {
-		return &accounts[candidateIdxs[0]]
+// shuffleWithinPriorityAndLastUsed 对排序后的 []*Account 切片，按 (Priority, LastUsedAt) 分组后组内随机打乱。
+func shuffleWithinPriorityAndLastUsed(accounts []*Account) {
+	if len(accounts) <= 1 {
+		return
 	}
-
-	// 6. preferOAuth 处理
-	if preferOAuth {
-		var oauthIdxs []int
-		for _, idx := range candidateIdxs {
-			if accounts[idx].account.Type == AccountTypeOAuth {
-				oauthIdxs = append(oauthIdxs, idx)
-			}
+	i := 0
+	for i < len(accounts) {
+		j := i + 1
+		for j < len(accounts) && sameAccountGroup(accounts[i], accounts[j]) {
+			j++
 		}
-		if len(oauthIdxs) > 0 {
-			candidateIdxs = oauthIdxs
+		if j-i > 1 {
+			mathrand.Shuffle(j-i, func(a, b int) {
+				accounts[i+a], accounts[i+b] = accounts[i+b], accounts[i+a]
+			})
 		}
+		i = j
 	}
+}
 
-	// 7. 随机选择
-	return &accounts[candidateIdxs[mathrand.Intn(len(candidateIdxs))]]
+// sameAccountGroup 判断两个 Account 是否属于同一排序组（Priority + LastUsedAt）
+func sameAccountGroup(a, b *Account) bool {
+	if a.Priority != b.Priority {
+		return false
+	}
+	return sameLastUsedAt(a.LastUsedAt, b.LastUsedAt)
+}
+
+// sameLastUsedAt 判断两个 LastUsedAt 是否相同（精度到秒）
+func sameLastUsedAt(a, b *time.Time) bool {
+	switch {
+	case a == nil && b == nil:
+		return true
+	case a == nil || b == nil:
+		return false
+	default:
+		return a.Unix() == b.Unix()
+	}
 }
 
 // sortCandidatesForFallback 根据配置选择排序策略
@@ -2135,13 +2060,6 @@ func shuffleWithinPriority(accounts []*Account) {
 
 // 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) {
-	// 对 Antigravity 平台，检查请求的模型系列是否在分组支持范围内
-	if platform == PlatformAntigravity && groupID != nil && requestedModel != "" {
-		if err := s.checkAntigravityModelScope(ctx, *groupID, requestedModel); err != nil {
-			return nil, err
-		}
-	}
-
 	preferOAuth := platform == PlatformGemini
 	routingAccountIDs := s.routingAccountIDsForRequest(ctx, groupID, requestedModel, platform)
 
@@ -2169,9 +2087,6 @@ func (s *GatewayService) selectAccountForModelWithPlatform(ctx context.Context,
 							_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
 						}
 						if !clearSticky && s.isAccountInGroup(account, groupID) && account.Platform == platform && (requestedModel == "" || s.isModelSupportedByAccountWithContext(ctx, account, requestedModel)) && account.IsSchedulableForModelWithContext(ctx, requestedModel) {
-							if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
-								log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
-							}
 							if s.debugModelRoutingEnabled() {
 								log.Printf("[ModelRoutingDebug] legacy routed sticky hit: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), accountID)
 							}
@@ -2272,9 +2187,6 @@ func (s *GatewayService) selectAccountForModelWithPlatform(ctx context.Context,
 						_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
 					}
 					if !clearSticky && s.isAccountInGroup(account, groupID) && account.Platform == platform && (requestedModel == "" || s.isModelSupportedByAccountWithContext(ctx, account, requestedModel)) && account.IsSchedulableForModelWithContext(ctx, requestedModel) {
-						if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
-							log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
-						}
 						return account, nil
 					}
 				}
@@ -2383,9 +2295,6 @@ func (s *GatewayService) selectAccountWithMixedScheduling(ctx context.Context, g
 						}
 						if !clearSticky && s.isAccountInGroup(account, groupID) && (requestedModel == "" || s.isModelSupportedByAccountWithContext(ctx, account, requestedModel)) && account.IsSchedulableForModelWithContext(ctx, requestedModel) {
 							if account.Platform == nativePlatform || (account.Platform == PlatformAntigravity && account.IsMixedSchedulingEnabled()) {
-								if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
-									log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
-								}
 								if s.debugModelRoutingEnabled() {
 									log.Printf("[ModelRoutingDebug] legacy mixed routed sticky hit: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), accountID)
 								}
@@ -2488,9 +2397,6 @@ func (s *GatewayService) selectAccountWithMixedScheduling(ctx context.Context, g
 					}
 					if !clearSticky && s.isAccountInGroup(account, groupID) && (requestedModel == "" || s.isModelSupportedByAccountWithContext(ctx, account, requestedModel)) && account.IsSchedulableForModelWithContext(ctx, requestedModel) {
 						if account.Platform == nativePlatform || (account.Platform == PlatformAntigravity && account.IsMixedSchedulingEnabled()) {
-							if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
-								log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
-							}
 							return account, nil
 						}
 					}
@@ -5159,27 +5065,6 @@ func (s *GatewayService) validateUpstreamBaseURL(raw string) (string, error) {
 	return normalized, nil
 }
 
-// checkAntigravityModelScope 检查 Antigravity 平台的模型系列是否在分组支持范围内
-func (s *GatewayService) checkAntigravityModelScope(ctx context.Context, groupID int64, requestedModel string) error {
-	scope, ok := ResolveAntigravityQuotaScope(requestedModel)
-	if !ok {
-		return nil // 无法解析 scope，跳过检查
-	}
-
-	group, err := s.resolveGroupByID(ctx, groupID)
-	if err != nil {
-		return nil // 查询失败时放行
-	}
-	if group == nil {
-		return nil // 分组不存在时放行
-	}
-
-	if !IsScopeSupported(group.SupportedModelScopes, scope) {
-		return ErrModelScopeNotSupported
-	}
-	return nil
-}
-
 // GetAvailableModels returns the list of models available for a group
 // It aggregates model_mapping keys from all schedulable accounts in the group
 func (s *GatewayService) GetAvailableModels(ctx context.Context, groupID *int64, platform string) []string {